Experimental and Numerical Investigation of Dynamic Damage and Load Transfer of PBX Substitute Material under Low Velocity Impact

The accidental initiation of explosives under mechanical loads has caused numerous catastrophic events. Therefore, the dynamic damage behavior of confined polymer-bonded explosives (PBXs) must be assessed to improve their practical applicability. In this study, polymer-bonded sugar (PBS) materials were prepared using a novel agglomerate to develop a PBX substitute material with enhanced experimental safety. The mechanical properties of the PBS shell were evaluated using a dynamic compression test, which revealed that the compression response of the shell was affected by the strain rate. A low-velocity impact experiment was performed to investigate the dynamic damage and load transfer characteristics of the PBX substitute. A constitutive model was developed to characterize the mechanical response of PBS subjected to high strain rates, and implementing this model in ABAQUS ensured successful prediction of the damage evolution process associated with PBS. Simulation results indicated that the PBS specimen was primarily damaged around its center while sliding friction was dominant near the center during pressure application. Notably, different stress states result in distinct crack growth velocity histories along the axial direction, with the damage ratio progressively decreasing toward regions closer to the impact surface.

Investigation of Microstructure, Oxides, Cracks, and Mechanical Properties of Ti-4Al-2V Joints Prepared Using Underwater Wet Laser Welding

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys.

Influence of an Engineered Notch on the Electromagnetic Radiation Performance of NiTi Shape Memory Alloy

This work explores the influence of a pre-engineered notch on the electromagnetic radiation (EMR) parameters in NiTi shape memory alloy (SMA) during tensile tests. The test data showed that the EMR signal fluctuated between oscillatory and exponential, signifying that the specimen's viscosity damping coefficient changes during strain hardening. The EMR parameters, maximum EMR amplitude, and average EMR energy release rate remained constant initially but rose sharply with the plastic zone radius with progressive loading. It was postulated that new Frank-Read sources permit dislocation multiplication and increase the number of edge dislocations participating in EMR emissions, leading to a rise in the value of EMR parameters. The study of the correlation between EMR emission parameters and the plastic zone radius before the crack tip is a vital crack growth monitoring tool. An analysis of the interrelationship of the EMR energy release rate at fracture with the elastic strain energy release rate would help develop an innovative approach to assess fracture toughness, a critical parameter for the design and safety of metals. The microstructural analysis of tensile fractures and the interrelation between deformation behaviours concerning the EMR parameters offers a novel and real-time approach to improve the extant understanding of the behaviour of metallic materials.

Crack Formation and Control in an AlCoCrFeNi High Entropy Alloy Fabricated by Selective Laser Melting

The equiatomic AlCoCrFeNi high entropy alloy (HEA) is prone to cracking during the additive manufacturing process due to the high cooling rates observed, which limits its application to a large extent. In this study, the selective laser melting (SLM) technique was adopted to fabricate the alloy and the mechanism of crack formation was revealed. Most importantly, a new design strategy was proposed to suppress the generation of cracks, and the optimization of the preparation process was also studied in detail. It is found that the interlaminar crack is related to the heat input at the edge of the specimen, and the internal cracks are formed by solidification cracks. Alloys without interlaminar crack can be prepared by means of combination of the side inclination angle and the process parameters. Side inclination angle optimization provides a possibility for the preparation of crack-free AlCoCrFeNi HEA by SLM.

Preventing Overdoses Involving Stimulants: The POINTS Study Protocol

Background

In recent years, overdoses involving illicit cocaine, methamphetamine, and other stimulants have increased in the U.S. The unintentional consumption of stimulants containing illicit fentanyl is a major risk factor for overdoses, particularly in Massachusetts and Rhode Island. Understanding the drug use patterns and strategies used by people who use stimulants (PWUS) to prevent overdose is necessary to identify risk and protective factors for stimulant-involved overdoses. Mixed-methods research with people who distribute drugs (PWDD) can also provide critical information into the mechanisms through which fentanyl may enter the stimulant supply, and the testing of drug samples can further triangulate PWUS and PWDD perspectives regarding the potency and adulteration of the drug supply. These epidemiological methods can inform collaborative intervention development efforts with community leaders to identify feasible, acceptable, and scalable strategies to prevent fatal and non-fatal overdoses in high-risk communities.

Methods

Our overall objective is to reduce stimulant and opioid-involved overdoses in regions disproportionately affected by the overdose epidemic. To meet this long-term objective, we employ a multi-pronged approach to identify risk and protective factors for unintentional stimulant and opioid-involved overdoses among PWUS, and use these findings to develop a package of locally tailored intervention strategies that can be swiftly implemented to prevent overdoses. Specifically, this study aims to [1] Carry out mixed-methods research with incarcerated and non-incarcerated people who use or distribute illicit stimulants to identify risk and protective factors for stimulant and opioid-involved overdoses; [2] Conduct drug checking to examine the presence and relative quantity of fentanyl and other adulterants in the stimulant supply; and [3] Convene a series of working groups with community stakeholders involved in primary and secondary overdose prevention in Massachusetts and Rhode Island to contextualize our mixed-methods findings and identify multilevel intervention strategies to prevent stimulant-involved overdoses.

Discussion

Completion of this study will yield a rich understanding of the social epidemiology of stimulant and opioid-involved overdoses in addition to community-derived intervention strategies that can be readily implemented and scaled to prevent such overdoses in two states disproportionately impacted by the opioid and overdose crises: Massachusetts and Rhode Island.

PCTC-Net: A Crack Segmentation Network with Parallel Dual Encoder Network Fusing Pre-Conv-Based Transformers and Convolutional Neural Networks

Cracks are common defects that occur on the surfaces of objects and structures. Crack detection is a critical maintenance task that traditionally requires manual labor. Large-scale manual inspections are expensive. Research has been conducted to replace expensive human labor with cheaper computing resources. Recently, crack segmentation based on convolutional neural networks (CNNs) and transformers has been actively investigated for local and global information. However, the transformer is data-intensive owing to its weak inductive bias. Existing labeled datasets for crack segmentation are relatively small. Additionally, a limited amount of fine-grained crack data is available. To address this data-intensive problem, we propose a parallel dual encoder network fusing Pre-Conv-based Transformers and convolutional neural networks (PCTC-Net). The Pre-Conv module automatically optimizes each color channel with a small spatial kernel before the input of the transformer. The proposed model, PCTC-Net, was tested with the DeepCrack, Crack500, and Crackseg9k datasets. The experimental results showed that our model achieved higher generalization performance, stability, and F1 scores than the SOTA model DTrC-Net.

Numerical Study of Crack Prediction and Growth in Automotive Wheel Rims

Finite element analysis has become an essential tool for simulating and understanding crack growth. This technique holds significant importance in the field of mechanical engineering, where it finds wide application in the design and optimization of structural components and material properties. This work began with the identification of critical zones and estimated the number of load life repeats through fatigue analysis, specifically applied to automotive rims utilizing innovative finite element methods. To investigate crack behavior, we are used the Extended Finite Element Method (XFEM) with the volumetric approach to compute the Stress Intensity Factor (SIF). The results obtained by our study align closely with experimental tests in terms of detecting the critical zone where a crack can appear. Our findings contribute to the understanding of fatigue behavior in automotive rims, offering new insights into their structural integrity and performance under various load conditions.

Size-Dependent Electrochemical Performance Mediated by Stress-Induced Cracking in Zn2SnO4 Electrodes

Correlating the microscopic structural characteristics with the macroscopic electrochemical performance in electrode materials is critical for developing excellent-performance lithium-ion batteries, which however remains largely unexplored. Here, we show that the Zn2SnO4 (ZTO) nanowires (NWs) with smaller diameters (d < 5 nm) exhibit slower capacity fade rate and better cycling stability, as compared with the NWs with larger diameters ranging from tens to hundreds of nanometers. By applying in situ transmission electron microscopy (TEM), we discover a strong correlation of cracking behavior with the NW diameter. Upon the first lithiation, there exists a critical diameter of ∼80 nm, below which the NWs neither crack nor fracture, and above which the cracks could easily nucleate and propagate along the specific planes, resulting in the deteriorated cycling stability in larger sized electrodes. Further theoretical calculations based on the finite element model and the climbing image nudged elastic band method faithfully predict the size-dependent cracking behaviors, which may result from the synergistic effect of axial stress evolution as well as preferential Li-ion migration directions during the first lithiation. This work provides a real-time tracking of the tempo-spatial structural evolution of a single ZTO NW, which facilitates a fundamental understanding of how the sample size affects the electrochemical behavior and thus offers a reference for future battery design and application strategy.

Semantic Segmentation of Surface Cracks in Urban Comprehensive Pipe Galleries Based on Global Attention

Cracks inside urban underground comprehensive pipe galleries are small and their characteristics are not obvious. Due to low lighting and large shadow areas, the differentiation between the cracks and background in an image is low. Most current semantic segmentation methods focus on overall segmentation and have a large perceptual range. However, for urban underground comprehensive pipe gallery crack segmentation tasks, it is difficult to pay attention to the detailed features of local edges to obtain accurate segmentation results. A Global Attention Segmentation Network (GA-SegNet) is proposed in this paper. The GA-SegNet is designed to perform semantic segmentation by incorporating global attention mechanisms. In order to perform precise pixel classification in the image, a residual separable convolution attention model is employed in an encoder to extract features at multiple scales. A global attention upsample model (GAM) is utilized in a decoder to enhance the connection between shallow-level features and deep abstract features, which could increase the attention of the network towards small cracks. By employing a balanced loss function, the contribution of crack pixels is increased while reducing the focus on background pixels in the overall loss. This approach aims to improve the segmentation accuracy of cracks. The comparative experimental results with other classic models show that the GA SegNet model proposed in this study has better segmentation performance and multiple evaluation indicators, and has advantages in segmentation accuracy and efficiency.

Detecting Multiple Damages in UHPFRC Beams through Modal Curvature Analysis

Curvature-based damage detection has been previously applied to identify damage in concrete structures, but little attention has been given to the capacity of this method to identify distributed damage in multiple damage zones. This study aims to apply for the first time an enhanced existing method based on modal curvature analysis combined with wavelet transform curvature (WTC) to identify zones and highlight the damage zones of a beam made of ultra-high-performance fiber-reinforced concrete (UHPFRC), a construction material that is emerging worldwide for its outstanding performance and durability. First, three beams with a 2 m span of UHPFRC material were cast, and damaged zones were created by sawing. A reference beam without cracks was also cast. The free vibration responses were measured by 12 accelerometers and calculated by operational modal analysis. Moreover, for the sake of comparison, a finite element model (FEM) was also applied to two identical beams to generate numerical acceleration without noise. Second, the modal curvature was calculated for different modes for both experimental and FEM-simulated acceleration after applying cubic spline interpolation. Finally, two damage identification methods were considered: (i) the damage index (DI), based on averaging the quadratic difference of the local curvature with respect to the reference beam, and (ii) the WTC method, applied to the quadratic difference of the local curvature with respect the reference beam. The results indicate that the developed coupled modal curvature WTC method can better identify the damaged zones of UHPFRC beams.

Exposure to ammonia solution due to substance use: a retrospective study from the French poison centres database (2009-2018)

INTRODUCTION

Ammonia solution (ammonium hydroxide) is used to convert cocaine hydrochloride to freebase cocaine. Due to its causticity, unintentional exposure to ammonia in a substance use context can result in injury. The objective of this study was to describe the characteristics of unintentional oral and buccal ammonia solution exposure in a substance use context.

METHODS

A retrospective study was conducted using the French poison centres database over a 10-year period (2009-2018).

RESULTS

A total of 1,546 files were extracted, and 263 substance users were included. There was a significant increase in the number of these exposures between 2009 and 2018. Unintentional ingestion of ammonia solution was linked to product decanting in 89 per cent of cases. Substance use prior to the exposure and a festive context, such as free parties or teknivals, were identified in 25 per cent and 21 per cent of cases, respectively. Patients received a hospital examination in 87 per cent of cases. The severity of intoxication in substance users was graded as moderate (33 per cent) or severe (15 per cent) using the Poisoning Severity Score.

DISCUSSION

The increased number of ammonia solution cases reported was consistent with an increase in the number of crack users in Europe in the same period. Ammonia solution exposure can suggest the possibility of substance use disorders. In such cases, patients can be referred to receive appropriate treatment and support. This study had some limitations, such as the lack of available information due to the retrospective nature of the study and the non-standardized questions asked by the poison centre during the medical phone interviews.

CONCLUSION

Oral and buccal ammonia solution exposure in known substance users in France increased between 2009 and 2018. These users were mostly young men. A festive context and decanting were frequent. Patients were mainly referred to emergency departments to receive clinical examination and care. The potential severity of oral or buccal ammonia solution exposure in substance users requires increased vigilance among all healthcare professionals involved in the management of these intoxication cases.

Endovascular Treatment of Acute Lower Limb Ischemia Associated with Cocaine Use: A Scoping Review

The endovascular treatment of acute lower limb ischemia associated with cocaine use is an underexplored topic. This scoping review aims to map existing information and point out potential knowledge gaps for future research. We searched databases with a strategy of terms and keywords (Cocaine, Acute, Lower Limb, and Ischemia) for articles related to acute ischemia in the lower limbs and cocaine use. We established eligibility and exclusion criteria and searched without restrictions on language or date of publication. We obtained five case reports published between 2004 and 2015. Most of the patients were men with an average age of 38 years. Treatments were heterogeneous. Most patients showed improvement after surgical thrombectomy. The sample size and variety of interventions limit the generalizability of the results, so it is necessary to do more studies with robust methodologies to standardize treatments and improve the understanding of the condition.

Photo-oxidative Crack Propagation in Transition Metal Dichalcogenides

Monolayered transition-metal dichalcogenides (TMDs) are easily exposed to air, and their crystal quality can often be degraded via oxidation, leading to poor electronic and optical device performance. The degradation becomes more severe in the presence of defects, grain boundaries, and residues. Here, we report crack propagation in pristine TMD monolayers grown by chemical vapor deposition under ambient conditions and light illumination. Under a high relative humidity (RH) of ∼60% and white light illumination, the cracks appear randomly. Photo-oxidative cracks gradually propagated along the grain boundaries of the TMD monolayers. In contrast, under low RH conditions of ∼2%, cracks were scarcely observed. Crack propagation is predominantly attributed to the accumulation of water underneath the TMD monolayers, which is preferentially absorbed by hygroscopic alkali metal-based precursor residues. Crack propagation is further accelerated by the cyclic process of photo-oxidation in a basic medium, leading to localized tensile strain. We also found that such crack propagation is prevented after the removal of alkali metals via the transfer of the sample to other substrates.

Unified Failure Criterion Based on Stress and Stress Gradient Conditions

Specimens made of various materials with different geometric features were investigated to predict the failure loads using the recently proposed criterion comprised of both stress and stress gradient conditions. The notch types were cracks and holes, and the materials were brittle, ductile, isotropic, orthotropic, or fibrous composites. The predicted failure stresses or loads were compared to experimental results, and both experimental and theoretically predicted results agreed well for all the different cases. This suggests that the stress and stress-gradient-based failure criterion is both versatile and accurate in predicting the failure of various materials and geometric features.

Highly Stretchable and Fluorescent Visualizable Thermoplastic Polyurethane/Tetraphenylethylene Plied Yarn Strain Sensor with Heterogeneous and Cracked Structure for Human Health Monitoring

Smart wearable technology has been more and more widely used in monitoring and prewarning of human health and safety, while flexible yarn-based strain sensors have attracted extensive research interest due to their ability to withstand greater external strain and their significant application potential in real-time monitoring of human motion and health signals. Although several strain sensors based on yarn structures have been reported, it remains challenging to strike a balance between high sensitivity and wide strain ranges. At the same time, visual signal sensing is expected to be used in strain sensors thanks to its intuitiveness. In this work, thermoplastic polyurethane (TPU) and tetraphenylethylene (TPE) were wet-spun to fabricate flexible fluorescent fibers used as the substrate of the sensor, followed by the drop addition of polydimethylsiloxane (PDMS) beads and curing to produce a heterogeneous structure, which were further twisted into a plied yarn. Finally, a visualizable flexible yarn strain sensor based on solidified liquid beads and crack structure was obtained by loading polydopamine (PDA) and polypyrrole (PPy) in situ. The sensor exhibited high sensitivity (the GF value was 58.9 at the strain range of 143-184%), a wide working strain range (0-184%), a low monitoring limit (<0.1%), a fast response (58.82 ms), reliable responses at different frequencies, and excellent cycle durability (over 2000 cycles). At the same time, the yarn strain sensor also had excellent photothermal characteristics and a fluorescence crack visualization effect. These attractive advantages enabled yarn strain sensors to accurately monitor various human activities, showing great application potential in health monitoring, personalized medical diagnosis, and other aspects.

Predicting Stress Intensity Factor for Aluminum 6062 T6 Material in L-Shaped Lower Control Arm (LCA) Design Using Extended Finite Element Analysis

The aim of this study is to solve a practical problem encountered in the automotive industry, especially the failure of a cracked lower control arm made of al 6062 T6 material during static and crash physical tests, and to characterize the behavior of cracked parts made of aluminum materials using the fracture mechanics parameters. As a first step, we carried out a numerical study and simulation using Abaqus/CAE 2020 software and the finite element method to determine the stress concentration and load limit capacity for different car weight cases. The von Mises stress variation shows crack initiation and propagation to be in the area of the lower control arm's attachment to the vehicle platform, where stress is concentrated. These numerical results are consistent with the experimental test results found by automotive manufacturers. Also, we find that the mechanical load that can support this part is below 4900 N for good performance. In the second step, we use the results of the first section to simulate the failure of a lower control arm with a crack defect. This paper investigates the stress intensity factor KI in mode I for different lengths (L) and depths (a) of the crack in the lower control arm using the extended finite element method (XFEM) under Abaqus/CAE. For crack failure initiation and progression, we relied on the traction separation law, specifically the maximum principal stress (MAXPS) criterion. The KI factor was evaluated for the materials steel and Al 6062 T6. The results obtained from the variation of the KI coefficient as a function of crack depth (a) and the thickness (t) show that the crack remains stable even when a depth ratio (a/t = 0.8) is reached for the steel material. However, the crack in the Aluminum 6062 T6 material becomes unstable at depth (a/t = 0.6), with a high risk of total failure of the lower control arm.

Comparison and Three-Dimensional Fluorescence Spectrum Analysis of Activated Sludge Treatment with Fenton and UV-Fenton

This study investigated the effects of single Fenton and Fenton and UV combined processes on the cracking degree of anaerobic sludge under the same conditions. The optimal experimental conditions were obtained by repeated determination of Fe2+ dosage, H2O2 dosage and reaction time, so as to achieve the maximum cracking of sludge. In addition, this study applied three-dimensional fluorescence spectrum analysis technology to analyze the organic matter leached from the treated sludge, and different regions of the three-dimensional fluorescence spectra were analyzed and compared for each treatment condition. Repeated experiments showed that the optimal conditions for Fenton are a pH of 3, reaction time of 40 min, 1.4 g/L of Fe2+ and 9 g/L of H2O2. The Fenton process cracking yielded a protein concentration of 0.66 mg/L and sCOD of 5489 mg/L, and the UV-Fenton pretreatment yielded a protein concentration of 0.74 mg/L and sCOD of 5856 mg/L. The sludge particle size was reduced from the original 54.52 mm to 40.30 mm and 36.37 mm, respectively. In addition to these parameters, it was also demonstrated that the Fenton process has a strong cracking effect on sludge by indicators such as the SEM and sludge water content and that UV irradiation can play a role in assisting and helping sludge cracking.

Failure Analysis of Cracked P110 Repaired Tubing Used for Gas Transmission

With green and low-carbon developments in oil fields, an increasing amount of repaired oil tubing is being used as oil and gas transmission pipelines in China. However, due to differences in manufacturing standards between oil tubing and transmission pipelines, there are inevitably some issues during their use. This paper investigates a case of cracking failure in repaired oil tubing used as a gathering and transportation pipeline. The failure occurred after eight months of operation and was characterized by a circumferential crack at the male thread end of the tubing joint. To determine the root cause of the failure, a series of experiments were conducted on the oil tubing. The experiments included visual inspection, chemical composition analysis, mechanical properties testing, hardness testing, metallographic examination, and microstructure analysis. The results revealed that the thread of the cracked tubing was not tightened to the specified position; the connection between the tubing and the coupling was welded in a circumferential direction; and cracks occurred in the heat-affected zone of the weld. Chemical composition, tensile performance, and the Charpy impact of the tubing meet the requirements of API 5CT for P110 material, and no abnormalities were found in the metallographic structure. The microstructure at the weld toe of the fracture is martensite, and the hardness is 476 HV10. Based on the thermal simulation verification test, when the material of the tubing cools from 1200 °C, which is located in the coarse HAZ temperature zone, the base metal transforms into martensite with a little granular bainite, exhibiting its highest hardness value at 371 HV10, which is higher than the allowable hardness for carbon steel and indicates the material has poor weldability. The reasons for the cracking and failure of the tubing are that the P110 repaired tubing has a high carbon equivalent and poor weldability. During the welding process, martensitic structure was formed at the weld toe, and cold cracks appeared in the heat-affected zone, resulting in failure. To avoid the reoccurrence of such failure, recommendations are proposed.

Trench Formation under the Tunable Nanogap: Its Depth Depends on Maximum Strain and Periodicity

Metallic nanogaps have been studied for many years in the context of a significant amount of field enhancements. Nanogaps of macroscopic lengths for long-wave applications have attracted much interest, and recently one dimensional tunable nanogaps have been demonstrated using flexible PET substrates. For nanogaps on flexible substrates with applied tensile strain, large stress is expected in the vicinity of the gap, and it has been confirmed that several hundred nanometer-deep trenches form beneath the position of the nanogap because of this stress singularity. Here, we studied trench formation under nanogap structures using COMSOL Multiphysics 6.1. We constructed a 2D nanogap unit cell, consisting of gold film with a crack on a PDMS substrate containing a trench beneath the crack. Then, we calculated the von Mises stress at the bottom of the trench for various depths and spatial periods. Based on it, we derived the dependence of the trench depth on the strain and periodicity for various yield strengths. It was revealed that as the maximum tensile strain increases, the trench deepens and then diverges. Moreover, longer periods lead to larger depths for the given maximum strain and larger gap widths. These results could be applied to roughly estimate achievable gap widths and trench depths for stretchable zerogap devices.

The Effect of Transcranial Direct Current Stimulation (tDCS) on Cocaine Addiction: A Narrative Review

Cocaine addiction is a significant problem worldwide. The development of addiction involves a reward system, which consists of certain brain regions like the ventral tegmental area, nucleus accumbens, and prefrontal cortex. Currently, there are no approved medications for treating cocaine dependence, so researchers are actively searching for effective treatments that can impact the brain. One potential treatment under investigation is transcranial direct current stimulation (tDCS), a non-invasive method of stimulating the brain to modulate its activity. In this review, we explore the use of tDCS in treating cocaine addiction. We found nine relevant articles via a literature search, and the results indicate that applying tDCS to the right dorsolateral prefrontal cortex (DLPFC) holds promise for reducing drug cravings in individuals with cocaine addiction. The review also discusses the possible mechanisms by which tDCS works and provides recommendations for future research in this field.

Comparative Analysis of Engineering Carbonation Model Extensions to Account for Pre-Existing Cracks

Cracks in reinforced concrete structures can accelerate the local depassivation of reinforcement due to carbonation. Different approaches have been proposed to account for pre-existing cracks within engineering models to predict the carbonation depth. In this study, we provide a detailed comparative analysis of different extensions available for the fib carbonation model to account for cracks, viz., crack influence factor (CIF) approaches, a diffusion-based model and the crack depth adaption. The model extensions are first validated against a dataset of lab data collected from the literature and additional experiments performed as the part of this study. The CIF approaches achieved the highest accuracy for the carbonation depth prediction when compared against lab data. The diffusion-based model was inaccurate for low CO2 concentrations. The crack depth adaption provides overly conservative results. No model was found to be best performing, and large scatter was observed between predicted and experimental values. This emphasizes the need for more detailed multi-physics-based models to achieve accurate predictions. For further comparison, service life predictions were conducted for two structural scales, viz., the whole structure and the cracked area. It is concluded that the choice of model extension and the structural scale of analysis have a large influence on predicted probability of failure.

A Study on the Influence of Process Parameters on the Workpiece Surface Quality in the Cutting of Hard and Brittle Materials with Trepanning Drill

Hard and brittle materials have excellent physical and mechanical properties and are widely used in the fields of microelectronics and optoelectronics. However, due to their high hardness and brittleness, the machining quality of a workpiece struggles to meet the requirements of practical applications. In order to improve the surface quality of deep-hole machining of hard and brittle materials, this article analyzes the formation mechanism of surface roughness and the exit-chipping width during the drilling machining of hard and brittle materials and establishes a mathematical prediction model for the surface roughness and the exit-chipping width of hard and brittle materials using a trepanning cutter. The experimental study on K9 optical glass machining shows that the surface roughness of the workpiece and the exit-chipping width increase with the increase in feed rate, and decrease with the increase in rotational speed. Through comparison and verification between theoretical and experimental values, the average errors of workpiece surface roughness and the exit-chipping width are 13.15% and 6.73%, respectively. This article analyzes the reasons for the errors. The results indicate that the theoretical model proposed in this article can be used to predict the surface roughness and the exit-chipping width of hard and brittle materials processed under the same conditions, providing a theoretical basis to optimize process parameters to improve the surface quality of the workpiece.

The Effects of Crystalline Admixture on the Self-Healing Performance and Mechanical Properties of Mortar with Internally Added Superabsorbent Polymer

Crystalline admixture (CA) can be incorporated into concrete to achieve self-healing of concrete cracks. In this study, both CA and superabsorbent polymer (SAP) were used as self-healing agents to investigate the effects of CA on the self-healing performance and mechanical properties of mortar with internally added SAP at different self-healing ages. The healing effect of cracks in mortar is assessed by crack observation and impermeability. The structure and composition of the filler in the cracks were analyzed by microscopic experiment. The experimental results indicate that CA enhances the healing of cracks in mortar specimens. The chemical reactions of CA primarily contribute to significantly improving the early-age crack-healing ability of the specimens, and the water absorption and expansion ability as well as the internal curing effect of SAP also facilitate the crack-healing process. Increasing the CA content leads to an increase in the Ca/Si ratio of C-S-H, causing a transition from a layered structure to a more compact needle-like structure. When 4% CA was added to the mortar, it resulted in an adequate formation of needle-like C-S-H structures, which eventually penetrate and fill the pits formed by SAP, compensating for the strength loss caused by SAP.

An Evolutionary Strategy for Spawning Habitat Selection by Pseudopungtungia tenuicorpa

In this study, we hypothesized that the limited geographical distribution of Pseudopungtungia tenuicorpa in South Korea is closely related to the local abundance of their preferred spawning habitats. Eggs of P. tenuicorpa were most frequently observed in cracks smaller than 5 cm, followed by the nests of other fish, such as Coreoperca herzi. Although eggs of P. tenuicorpa were also found in cracks larger than 6 cm, most of them were consumed or damaged by other fish. However, the number of P. tenuicorpa eggs spawned in cracks smaller than 5 cm remained similar to the number of eggs at the time of initial spawning, even after 9 days. The strong preference of P. tenuicorpa for cracks smaller than 5 cm was found to influence the geographical distribution of P. tenuicorpa in South Korea. In the upper reaches of the Han River, the ratio of cracks smaller than 5 cm is higher than that in the Geum River and in the Nakdong River, which contributes to the stable population growth of P. tenuicorpa there. In the future, management strategies to maintain/restore cracks smaller than 5 cm should be reviewed for the preservation of this endemic fish in South Korea.

Rock Crack Recognition Technology Based on Deep Learning

The changes in cracks on the surface of rock mass reflect the development of geological disasters, so cracks on the surface of rock mass are early signs of geological disasters such as landslides, collapses, and debris flows. To research geological disasters, it is crucial to swiftly and precisely gather crack information on the surface of rock masses. Drone videography surveys can effectively avoid the limitations of the terrain. This has become an essential method in disaster investigation. This manuscript proposes rock crack recognition technology based on deep learning. First, images of cracks on the surface of a rock mass obtained by a drone were cut into small pictures of 640 × 640. Next, a VOC dataset was produced for crack object detection by enhancing the data with data augmentation techniques, labeling the image using Labelimg. Then, we divided the data into test sets and training sets in a ratio of 2:8. Then, the YOLOv7 model was improved by combining different attention mechanisms. This study is the first to combine YOLOv7 and an attention mechanism for rock crack detection. Finally, the rock crack recognition technology was obtained through comparative analysis. The results show that the precision of the improved model using the SimAM attention mechanism can reach 100%, the recall rate can achieve 75%, the AP can reach 96.89%, and the processing time per 100 images is 10 s, which is the optimal model compared with the other five models. The improvement is relative to the original model, in which the precision was improved by 1.67%, the recall by 1.25%, and the AP by 1.45%, with no decrease in running speed. This proves that rock crack recognition technology based on deep learning can achieve rapid and precise results. It provides a new research direction for identifying early signs of geological hazards.

Nearly Perfect Transmission of Lamé Modes in a Rectangular Beam with Part and Through-Thickness Vertical Cracks

The guided waves in the uniform waveguide of rectangular cross-section exhibit complicated propagation and scattering characteristics due to the diversity of vibration modes. This paper focuses on the mode conversion of the lowest Lamé mode at a part-through or through-thickness crack. Firstly, the Floquet periodicity boundary condition is applied to derive the dispersion curves in the rectangular beam, which relates the axial wavenumber to the frequency. On this basis, the frequency domain analysis is conducted to investigate the interaction between the fundamental longitudinal mode in the vicinity of the first Lamé frequency and a part-through or through-thickness vertical or inclined crack. Finally, the nearly perfect transmission frequency is evaluated by extracting displacement and stress harmonic fields throughout the cross-section. It is shown that this frequency originates from the first Lamé frequency, increases with the crack depth, and decreases with the crack width. Between them, the crack depth plays a major role in the frequency variation. In addition, the nearly perfect transmission frequency is negligibly affected by the beam thickness, and such a phenomenon is not observed for inclined cracks. The nearly perfect transmission may have potential applications in the quantitative evaluation of crack size.

Mapping the Evidence for Opioid-Mediated Changes in Malignancy and Chemotherapeutic Efficacy: Protocol for a Scoping Review

BACKGROUND

Numerous reports contend opioids can augment or inhibit malignancy. At present, there is no consensus on the risk or benefit posed by opioids on malignancy or chemotherapeutic activity. Distinguishing the consequences of opioid use from pain and its management is challenging. Additionally, opioid concentration data is often lacking in clinical studies. A scoping review approach inclusive of preclinical and clinical data will improve our understanding of the risk-benefit relationship concerning commonly prescribed opioids and cancer and cancer treatment.

OBJECTIVE

The aim of the study is to map diverse studies spanning from preclinical to clinical regarding opioids with malignancy and its treatment.

METHODS

This scoping review will use the Arksey six stages framework to (1) identify the research question; (2) identify relevant studies; (3) select studies meeting criteria; (4) extract and chart data; (5) collate, summarize, and report results; and (6) conduct expert consultation. An initial pilot study was undertaken to (1) parameterize the extent and scale of existing data for an evidence review, (2) identify key factors to be extracted in systematic charting efforts, and (3) assess opioid concentration as a variable for its relevance to the central hypothesis. Six databases will be searched with no filters: MEDLINE, Embase, CINAHL Complete, Cochrane Library, Biological Sciences Collection, and International Pharmaceutical Abstracts. Trial registries will include ClinicalTrials.gov, Cochrane CENTRAL, International Standard Randomised Controlled Trial Number Registry, European Union Clinical Trials Register, and World Health Organization International Clinical Trials Registry. Eligibility criteria will include preclinical and clinical study data on opioids effects on tumor growth or survival, or alteration on the antineoplastic activity of chemotherapeutics. We will chart data on (1) opioid concentration from human subjects with cancer, yielding a "physiologic range" to better interpret available preclinical data; (2) patterns of opioid exposure with disease and treatment-related patient outcomes; and (3) the influence of opioids on cancer cell survival, as well as opioid-related changes to cancer cell susceptibility for chemotherapeutics.

RESULTS

This scoping review will present results in narrative forms as well as with the use of tables and diagrams. Initiated in February 2021 at the University of Utah, this protocol is anticipated to generate a scoping review by August 2023. The results of the scoping review will be disseminated through scientific conference proceedings and presentations, stakeholder meetings, and by publication in a peer-reviewed journal.

CONCLUSIONS

The findings of this scoping review will provide a comprehensive description of the consequences of prescription opioids on malignancy and its treatment. By incorporating preclinical and clinical data, this scoping review will invite novel comparisons across study types that could inform new basic, translational, and clinical studies regarding risks and benefits of opioid use among patients with cancer.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/38167.

Cracking Behavior and Deflections in Recycled-Aggregate Beams Reinforced with Waste Fibers Subjected to Long-Term Constant Loading

This report presents the results of long-term tests on concrete beams reinforced with steel cord. In this study, natural aggregate was wholly replaced with waste sand or with wastes from the production of ceramic products and ceramic hollow bricks. The amounts of individual fractions used were determined in accordance with guidelines for reference concrete. A total of eight mixtures were tested; these differed in terms of the type of waste aggregate used. Elements with various fiber-reinforcement ratios were made for each mixture. Steel fibers and waste fibers were used in amounts of 0.0%, 0.5%, and 1.0%. Compressive strength and modulus of elasticity were determined experimentally for each mixture. The main test was a four-point beam bending test. Beams with dimensions of 100 mm × 200 mm × 2900 mm were tested on a stand, which was specially prepared so that three beams could be tested simultaneously. Fiber-reinforcement ratios were 0.5% and 1.0%. Long-term studies were conducted for 1000 days. During the testing period, beam deflections and cracks were measured. The obtained results were compared with values calculated using several methods, considering the influence of dispersed reinforcement. The results enabled the best methods for calculating individual values for mixtures with different types of waste materials to be determined.

A French study of cocaine intoxication/exposure in children (2010-2020)

BACKGROUND AND OBJECTIVE

In the European Union, the record of cocaine-related seizures indicates an expanding supply. The purity has also been increasing. The health impact of these trends remains poorly documented, in particular, the changes and clinical manifestations of intoxication in young children. We attempted to evaluate the trend in French pediatric admissions for cocaine intoxication/exposure over an 11-year period (2010-2020).

METHODS

A retrospective, national, multicenter, study of a pediatric cohort. All children less than 15 years of age admitted to a tertiary-level pediatric emergency unit for proven cocaine intoxication (compatible symptoms and positive toxicological screening) during the reference period were included.

RESULTS

Seventy-four children were included. Forty-six percent were less than 6 years old. Annual admissions increased by a factor of 8 over 11 years (+700%) and 57% of all cases were admitted in the last two years. The main clinical signs were neurologic (59%) followed by cardiovascular symptoms (34%). Twelve patients were transferred to the pediatric intensive care unit. Factors significantly associated with the risk of being transferred to the pediatric intensive care unit were initial admission to the pediatric resuscitation area (P < 0.001), respiratory impairment (P < 0.01), mydriasis (P < 0.01), cardiovascular symptoms (P = 0.014), age of less than 2 years (P = 0.014). Blood and/or urine toxicological screening isolated eighteen other substances besides cocaine in 46 children (66%).

CONCLUSION

Children are collateral victims of the changing trends in cocaine availability, use and purity. Admissions of intoxicated children to pediatric emergency departments are more frequent and there is an increase in severe presentations. Therefore, this is a growing public health concern.

The Incidence of Optic Cracks or Fractures During a Foldable AcrySof or Acriva BB Acrylic Monofocal Intraocular Lens Implantation via the Manual Monarch Injector System With the Cartridge in Phacoemulsification Surgery

PURPOSE

To evaluate the incidence of optic cracks and/or fractures during foldable acrylic intraocular lens (IOL) implantation via the manual Monarch delivery system with the cartridge and to determine factors that help to avoid such complications.

METHODS

Small-incision phacoemulsification surgery was performed in 702 eyes with visually significant cataract formation. A foldable acrylic soft IOL (AcrySof^â MA60BM/MA30BA, Alcon, Fort Worth, TX, USA) or a single-piece acrylic soft IOL (Acriva BB^â, VSY Biotechnology, Amsterdam, The Netherlands) was inserted in all eyes using a cartridge and viscoelastic agents (sodium hyaluronate, Healon^®, Advanced Medical Optics, Santa Ana, CA, USA).

RESULTS

Postoperative central, paracentral, or peripheral optic cracks or fractures were encountered in a total of six of 702 eyes (0.85%). Four of six lenses (0.57%) had optic cracks within the IOL substance, whereas two of 702 cases (0.28%) had full-thickness IOL fractures in the substance in multiple locations. Three of the four lenses with optic cracks were noted to be handled by tying forceps during the cartridge insertion, and one of them was the complication of holding forceps. Two IOLs with full-thickness optic fractures were encountered during the insertion of the IOLs in the capsular bag as a result of direct trauma to the lens optic by the plunger of the injector system overriding the lens optic during cartridge passage. None of the patients suffered from glare or other visual disturbances postoperatively, and, therefore, none of the six eyes required lens replacement.

CONCLUSION

The unintentional extensive pressure effect of the forceps during the holding process of the IOL or the direct trauma to the lens optic by the plunger of injector systems may cause optic cracks or fractures. Physicians should continue to monitor the eyes postoperatively regularly and must determine the benefits and risks to be derived from lens replacement, if such patients complain of significant glare, image degradation, and visual disturbances. We recommend the use of preloaded lenses, which have their own delivery systems and cartridges, to minimize the risk of such complications.

Study on Microstructure and Mechanical Properties at Constant Electromigration Temperature of Sn2.5Ag0.7Cu0.1RE0.05Ni-GNSs/Cu Solder Joints

To solve the electromigration problem of micro-electronic connection solder joints, an ideal electromigration tester was designed, and the thickness of the intermetallic compounds (IMCs), average void diameter, grain orientation, failure, shear strength, and fracture path of Sn2.5Ag0.7Cu0.1RE0.05Ni-GNSs/Cu solder joints under constant-temperature electromigration were studied. The results indicate that the solder joints show evidence of typical electromigration polarity in the asymmetric growth of interfacial IMCs on the anode and cathode sides under the conditions of a current density ≥7 × 10³ A/cm² and an included angle between the c-axis of the β-Sn grains and the current direction θ ≤ 53.2°. The anode-side interfacial IMC is dominated by a Cu₆Sn₅ phase with a gradually increasing thickness, forming a Cu₃Sn phase and showing evidence of microcracks. The Cu₆Sn₅ phase of the cathode-side interfacial IMC is gradually completely dissolved, and the growth of the Cu₃Sn phase is accompanied by the formation of Kirkendall voids. The anisotropic diffusion of Cu atoms in the β-Sn of the micro-solder joints causes increased solder joint resistance and reduced shear strength. The shear fracture path of the solder joints moves from the cathode side near the IMC solder seam to the Cu₃Sn interface. The shear fracture mechanism changes from ductile transgranular fracture dominated by β-Sn dimples to brittle fracture dominated by interfacial IMC cleavage and slip steps.

Towards Automatic Crack Size Estimation with iFEM for Structural Health Monitoring

The inverse finite element method (iFEM) is a model-based technique to compute the displacement (and then the strain) field of a structure from strain measurements and a geometrical discretization of the same. Different literature works exploit the error between the numerically reconstructed strains and the experimental measurements to perform damage identification in a structural health monitoring framework. However, only damage detection and localization are performed, without attempting a proper damage size estimation. The latter could be based on machine learning techniques; however, an a priori definition of the damage conditions would be required. To overcome these limitations, the present work proposes a new approach in which the damage is systematically introduced in the iFEM model to minimize its discrepancy with respect to the physical structure. This is performed with a maximum likelihood estimation framework, where the most accurate damage scenario is selected among a series of different models. The proposed approach was experimentally verified on an aluminum plate subjected to fatigue crack propagation, which enables the creation of a digital twin of the structure itself. The strain field fed to the iFEM routine was experimentally measured with an optical backscatter reflectometry fiber and the methodology was validated with independent observations of lasers and the digital image correlation.

Crack deflection in laminates with graded stiffness-lessons from biology

A crack propagating through a laminate can cause severe structural failure, which may be avoided by deflecting or arresting the crack before it deepens. Inspired by the biology of the scorpion exoskeleton, this study shows how crack deflection can be achieved by gradually varying the stiffness and thickness of the laminate layers. A new generalized multi-layer, multi-material analytical model is proposed, using linear elastic fracture mechanics. The condition for deflection is modeled by comparing the applied stress causing a cohesive failure, resulting in crack propagation, to that causing an adhesive failure, resulting in delamination between layers. We show that a crack propagating in a direction of progressively decreasing elastic moduli is likely to deflect sooner than when the moduli are uniform or increasing. The model is applied to the scorpion cuticle, the laminated structure of which is composed of layers of helical units (Bouligands) with inward decreasing moduli and thickness, interleaved with stiff unidirectional fibrous layers (interlayers). The decreasing moduli act to deflect cracks, whereas the stiff interlayers serve as crack arrestors, making the cuticle less vulnerable to external defects induced by its exposure to harsh living conditions. These concepts may be applied in the design of synthetic laminated structures to improve their damage tolerance and resilience.

The Mechanical Characteristics of High-Strength Self-Compacting Concrete with Toughening Materials Based on Digital Image Correlation Technology

Brittle fracture is a typical mechanical characteristic of high-strength self-compacting concrete, and the research on its toughening modification remains the highlight in the engineering field. To understand the effect of toughening materials (including polymer latex powders, rubber particles, and polyethylene fibers) on the mechanical behavior of C80 high-strength self-compacting concrete under static loading, the failure mode, mechanical strength, strain field, and crack opening displacement (COD) of prepared high-strength self-compacting concrete under compressive, splitting, and flexural loads were studied based on digital image technology (DIC). The corresponding mechanism is also discussed. The results show that the hybrid of polymer latex powders, rubber particles, and polyethylene fibers can increase the crack path and inhibit the development of macrocracks in concrete, thus turning the fracture behavior of concrete from brittle to ductile. The addition of toughening materials reduced the compressive and flexural strengths of high-strength self-compacting concrete, but it increased the splitting strength. DIC showed that the incorporation of toughening materials promoted the redistribution of strain and reduced the degree of strain concentration in high-strength self-compacting concrete. The evolution of COD in high-strength self-compacting concrete can be divided into two stages, including the linear growth stage and the plastic yield stage. The linear growth stage can be extended by incorporating toughening materials. The COD and energy absorption capacity of concrete were enhanced with the addition of toughening materials, and the best enhancement was observed with the hybrid of polymer latex powders, rubber particles, and polyethylene fibers. Overall, this research provides a reference for exploring effective technical measures to improve the toughness of high-strength self-compacting concrete.

Qualitative SEM analysis of fracture surfaces for dental ceramics and polymers broken by flexural strength testing and crown compression

PURPOSE

To perform qualitative analysis using scanning electron microscopy (SEM) of fracture surfaces for ceramic and polymeric dental materials broken via standardized flexural and crunch-the-crown (CTC) tests.

MATERIALS AND METHODS

Zirconia, glass-ceramic, and polymeric (Trilor; TRI, Juvora; JUV, Pekkton; PEK) materials were loaded using crowns for CTC tests, discs (zirconia and glass-ceramics) for piston-on-3 ball tests, bars (polymer) for 3-point bend tests, and bars (zirconia, glass-ceramics) for 4-point bend tests. SEM was used to characterize the fracture surfaces and identify fracture surface features (e.g., origin, mist, hackle, and the direction of crack propagation [DCP]). Electron dispersive spectroscopy was used to identify the local chemistry.

RESULTS

Fracture surface features were found to be less visually apparent for glass-ceramics than zirconia. For zirconia bars, fractures originated roughly midway between the corner and center for processing defects related to sintering. Fractures originated at the bottom corners of glass-ceramic bars (void or surface flaw) and PEK bars (surface flaw). TRI bar failures exposed glassy fibers. Fracture features were generally less discernable for discs compared to bars for zirconia and glass-ceramics. Ceramic crowns fractured into 2 to 3 pieces, with fractures originating at the occlusal surface and clear evidence for the DCP. Failures of TRI and JUV specimens (bars and crowns) were less catastrophic than for the ceramics, with exposed fibers (TRI) and surface cracks (JUV). PEK crown and bar fractures presented dimple (ductile) features formed due to microvoid coalescence followed by brittle crack propagation.

CONCLUSIONS

The critical flaws responsible for failure initiation were a function of material composition and test configuration. Fractographic analysis can reveal problems associated with the manufacturing of materials, their handling, grinding and finishing/polishing procedures, the structural design and choice of material, and the quality of the final laboratory-delivered restoration.

The energy release rate for non-penetrating crack in poroelastic body by fluid-driven fracture

A new class of constrained variational problems, which describe fluid-driven cracks (that are pressurized fractures created by pumping fracturing fluids), is considered within the nonlinear theory of coupled poroelastic models stated in the incremental form. The two-phase medium is constituted by solid particles and fluid-saturated pores; it contains a crack subjected to non-penetration condition between the opposite crack faces. The inequality-constrained optimization is expressed as a saddle-point problem with respect to the unknown solid phase displacement, pore pressure, and contact force. Applying the Lagrange multiplier approach and the Delfour-Zolésio theorem, the shape derivative for the corresponding Lagrangian function is derived using rigorous asymptotic methods. The resulting formula describes the energy release rate under irreversible crack perturbations, which is useful for application of the Griffith criterion of quasi-static fracture.

Study on the Dynamic Evolution Behavior and Failure Mechanism of Burn-Through Instability during In-Service Welding by Combining In-Situ Observation and Failure Analysis

There remains a lack of systematic understanding of burn-through instability, which also restricts the development of evaluation criteria. Based on the designed test device, the dynamic evolution behavior and failure mechanism of burn-through instability were investigated by combining in-situ CCD observation and failure analysis. In the initial stage of burn-through instability, the penetrating defect initiated beneath the molten pool bulge and propagated toward the arc. Finally, the weld centerline cracks or pinholes contributed to the pipeline failure. Based on in-situ observation, the burn-through pinhole was found to be forming in the overheating zone. Cracks and pinholes were found simultaneously in the burn-through instability zone and played an essential role in the burn-through instability. It could be concluded that a major burn-through hole was mainly developed from the fusion line to the inner wall surface along the wall thickness. According to the failure behavior and phenomena, the in-service burn-through instability area was divided into four parts, which were the damage failure (DF) zone, burn-through instability (BTI) zone, propagation (P) zone, and secondary burn-through zone (BT2). The failure mechanisms of the damage failure (DF) zone and burn-through instability (BTI) zone were significantly affected by the high temperature and plastic strain. The failure behavior of the propagation (P) zone was influenced considerably by the DF and BTI zones. The secondary burn-through zone was mainly affected by the high temperature. The uneven distribution of chemical elements showed an important influence on defect initiation.

Highly Sensitive, Stretchable, and Robust Strain Sensor Based on Crack Propagation and Opening

Soft and stretchable strain sensors have been attracting significant attention. However, the trade-off between the sensitivity (gauge factor) and the sensing range has been a major challenge. In this work, we report a soft stretchable resistive strain sensor with an unusual combination of high sensitivity, large sensing range, and high robustness. The sensor is made of a silver nanowire network embedded below the surface of an elastomeric matrix (e.g., poly(dimethylsiloxane)). Periodic mechanical cuts are applied to the top surface of the sensor, changing the current flow from uniformly across the sensor to along the conducting path defined by the open cracks. Both experiment and finite element analysis are conducted to study the effect of the slit depth, slit length, and pitch between the slits. The stretchable strain sensor can be integrated into wearable systems for monitoring physiological functions and body motions associated with different levels of strain, such as blood pressure and lower back health. Finally, a soft three-dimensional (3D) touch sensor that tracks both normal and shear stresses is developed for human-machine interfaces and tactile sensing for robotics.

Crack Width Evaluation of Cracked Mortar Specimen Using Gas Diffusion Characteristics

Several methods have been proposed currently for evaluating the crack width of a mortar specimen. Among these, the water permeability test is widely used to estimate crack width because water permeability is directly related to the average crack width of a specimen through which water passes. However, the viscosity of water makes precise crack width measurement challenging. The possible inflow (outflow) of foreign (healing) substances could affect the test results. To circumvent this limitation, this study proposes a gas diffusion test using oxygen rather than water as the medium. The proposed method includes a process that could compensate for gas diffusion from specimen parts other than the crack, allowing for a more precise estimation of crack width. The crack width can indeed be estimated with an error of 4% or less.

An Experimental Study on the Healing Performance of Complex Capsules Using Multiphase Inorganic Materials for Crack Self-Healing of Cement Mortars

Recently, a self-healing technique capable of repairing cracks in structures has emerged. Among various self-healing technologies, self-healing capsules can be largely classified into two types, depending on the phase of the core material: solid capsules, in which the core material is a powder; and microcapsules, in which the core material is a liquid. Solid capsules and microcapsules have different mechanisms, and their capsule sizes are also distinctly different. This suggests that each has advantages and disadvantages. Most of the studies known to date have utilized single capsules. However, if one uses a mixture of the two types of capsules, it is possible to highlight the strengths of each capsule and compensate for the weaknesses. Therefore, in this study, the first research on complex capsules that mixed solid capsules and microcapsules was attempted. As a result of the experiment, the complex capsule slightly reduced the fluidity of the mortar, but the effect was not significant. Moreover, the complex capsule tended to reduce the compressive strength of the mortar. In particular, it was found that the effect of solid capsules on the reduction in compressive strength among complex capsules was greater than that of microcapsules. Conversely, the healing performance increased when the ratio of solid capsules in the complex capsules was large.

Effect of the Transverse Functional Gradient of the Thin Interfacial Inclusion Material on the Stress Distribution of the Bimaterial under Longitudinal Shear

The effect of a functional gradient in the cross-section material (FGM) of a thin ribbon-like interfacial deformable inclusion on the stress-strain state of a piecewise homogeneous linear-elastic matrix under longitudinal shear conditions is considered. Based on the equations of elasticity theory, a mathematical model of such an FGM inclusion is constructed. An analytic-numerical analysis of the stress fields for some typical cases of the continuous functional gradient dependence of the mechanical properties of the inclusion material is performed. It is proposed to apply the constructed solutions to select the functional gradient properties of the inclusion material to optimize the stress-strain state in its vicinity under the given stresses. The derived equations are suitable with minor modifications for the description of micro-, meso- and nanoscale inclusions. Moreover, the conclusions and calculation results are easily transferable to similar problems of thermal conductivity and thermoelasticity with possible frictional heat dissipation.

Junction problem for thin elastic and volume rigid inclusions in elastic body

The article concerns a junction problem for two-dimensional elastic body with a thin elastic inclusion and a volume rigid inclusion. It is assumed that the inclusions have a common point. A delamination of the thin inclusion from the surrounding elastic body is assumed thus forming an interfacial crack. Constraint-type boundary conditions are imposed at the crack faces to prevent interpenetration between the faces. Moreover, a connection between the crack faces is characterized by a positive damage parameter. Limit transitions are justified as the damage parameter tends to infinity and to zero. In addition to this, a transition to limit is analysed as a rigidity parameter of the thin inclusion tends to infinity. Limit models are investigated. In particular, junction conditions at the common point are found for all cases considered. This article is part of the theme issue 'Non-smooth variational problems and applications'.

Equilibrium problem for a thermoelastic Kirchhoff-Love plate with a delaminated flat rigid inclusion

A new mathematical model describing an equilibrium of a thermoelastic heterogeneous Kirchhoff-Love plate is considered. A corresponding nonlinear variational problem is formulated with respect to a two-dimensional domain with a cut. This cut corresponds to an interfacial crack located on a given part of the boundary of a flat rigid inclusion. The flat inclusion is described by a cylindrical surface. Due to the presence of the flat rigid inclusion in the plate, restrictions of the functions describing displacements to the corresponding curves satisfy special constraints having a linear form. Displacement boundary conditions of an inequality type are set on the crack faces that ensure a mutual non-penetration of opposite crack faces. Solvability of the problem is proved. Under the assumption that the solution of the variational problem is smooth enough, an equivalent differential formulation is found. This article is part of the theme issue 'Non-smooth variational problems and applications'.

Thermo-Mechanical Reliability Study of Through Glass Vias in 3D Interconnection

Three-dimensional (3D) interconnection technology based on glass through vias (TGVs) has been used to integrate passive devices, and optoelectronic devices due to its superior electrical qualities, outstanding mechanical stability, and lower cost. Nevertheless, the performance and reliability of the device will be impacted by the thermal stress brought on by the mismatch of the coefficient of thermal expansion among multi-material structures and the complicated structure of TGV. This paper focuses on thermal stress evolution in different geometric and material parameters and the development of a controlled method for filling polymers in TGV interconnected structures. In addition, a numerical study based on the finite element (FE) model has been conducted to analyze the stress distribution of the different thicknesses of TGV-Cu. Additionally, a TGV interconnected structure model with a polymer buffer layer is given to solve the crack problem appearing at the edge of RDL. Meanwhile, after practical verification, in comparison to the experimental results, the FE model was shown to be highly effective and accurate for predicting the evolution of stress, and several recommendations were made to alleviate stress-related reliability concerns. An improved manufacturing process flow for the TGV interconnected structure was proposed and verified as feasible to address the RDL crack issue based on the aforementioned research. It provides helpful information for the creation of highly reliable TGV connection structures.

New Self-Repairing System for Brittle Matrix Composites Using Corrosion-Induced Intelligent Fiber

Brittle matrix composites such as concrete are susceptible to damage in the form of cracks. Most of the current self-repair and self-healing techniques have repair limits on crack widths or high costs of an external stimulator, or have an unfavorable effect on the composite’s strength. This paper proposes a new concept of corrosion-induced intelligent fiber (CIF) and a new self-repairing system that uses the CIFs to close cracks in brittle matrix composites within a corrosive environment without external help, and without compromising the strength. The CIF comprises an inner core fiber and an outer corrodible coating that are in equilibrium, with the core fiber in tension and the corrodible coating in compression. The preparation steps and shape recovery mechanism of the CIF and the self-repair mechanism of the CIF composites are explained. Based on these concepts, this paper also describes several mechanical models built to predict the magnitude of pre-stress stored in the core fiber, and the maximum pre-stress released to the matrix composites, and the minimum length of the reliable anchor ends of CIF. The sample calculation results show that the recovery strain was 0.5% for the CIF with the steel core fiber and 12.7% for the CIF with the nylon core fiber; the maximum crack closing force provided by the CIF to concrete can be increased by increasing the amount of the CIFs in concrete and the initial tensile stress of the core fiber. This paper provides some suggestions for enhancing the self-repair capability of brittle composites in complex working environments.

Machine Vision-Based Fatigue Crack Propagation System

This paper introduces a machine vision-based system promising low-cost solution for detecting a fatigue crack propagation caused by alternating mechanical stresses. The fatigue crack in technical components usually starts on surfaces at stress concentration points. The presented system was designed to substitute a strain gauge sensor-based measurement using an industrial camera in cooperation with branding software. This paper presents implementation of a machine vision system and algorithm outputs taking on fatigue crack propagation samples.

Localization of Cracks in Concrete Structures Using an Unmanned Aerial Vehicle

Active research on crack detection technology for structures based on unmanned aerial vehicles (UAVs) has attracted considerable attention. Most of the existing research on localization of cracks using UAVs mounted the Global Positioning System (GPS)/Inertial Measurement Unit (IMU) on the UAVs to obtain location information. When such absolute position information is used, several studies confirmed that positioning errors of the UAVs were reflected and were in the order of a few meters. To address these limitations, in this study, without using the absolute position information, localization of cracks was defined using relative position between objects in UAV-captured images to significantly reduce the error level. Through aerial photography, a total of 97 images were acquired. Using the point cloud technique, image stitching, and homography matrix algorithm, 5 cracks and 3 reference objects were defined. Importantly, the comparative analysis of estimated relative position values and ground truth values through field measurement revealed that errors in the range 24-84 mm and 8-48 mm were obtained on the x- and y-directions, respectively. Also, RMSE errors of 37.95-91.24 mm were confirmed. In the future, the proposed methodology can be utilized for supplementing and improving the conventional methods for visual inspection of infrastructures and facilities.

Recovery Behavior of the Macro-Cracks in Elevated Temperature-Damaged Concrete after Post-Fire Curing

Studying the recovery of fire-damaged concrete is of huge economic and environmental significance. The recovery of thermal-induced cracks of fire-damaged concrete leads to the recovery of strength after post-fire curing. To identify the crack recovery behavior of fire-damaged concrete after post-fire curing and its relationship with the recovery of strength, in this study, concrete samples exposed to 400, 600, and 800 °C were treated with the post-fire curing process. The compressive strength recovery was investigated, as well as the crack recovery in terms of the crack length. Moreover, the recovery of the cracks was studied and divided into the categories of mortar cracks and mortar-aggregate interfacial cracks. The results indicate that, after being exposed to high temperatures, the interfacial crack was the main type of crack, and it could clearly be recovered by post-fire curing. The recovery of compressive strength mainly resulted from the recovery of interfacial cracks. The findings of this study can provide practical guidance for the application of post-fire curing to the recovery of fire-damaged concrete structures.

[Effects of attapulgite addition on soil evaporation and crack characteristics]

Water is one of the most important factors limiting vegetation recovery and agricultural development in arid and semi-arid areas. The reduction of ineffective soil evaporation can improve soil water use efficiency. As a kind of clay mineral, attapulgite (ATP) plays a critical role in limiting soil evaporation due to its hydrophilicity and adsorption. In this study, three typical soils with different textures (dark loessial soil, cultivated loess soil, and sandy soil) were selected from the arid and semi-arid area of the Loess Plateau, and five ATP additions (0%, 1%, 2%, 3% and 4%) were set for conducting soil evaporation experiments under natural conditions using micro-evaporators to investigate the effects of ATP addition on different soil evaporation processes and the characteristics of evaporation surface cracks. The results showed that the cumulative evaporation and evaporation loss ratio of the same soil decreased with the increases of ATP addition when the ATP addition was <3%. When ATP was added at 3%, the cumulative evaporation and evaporation loss ratio of dark loessial soil and sandy soil decreased, while those of cultivated loess soil increased. When ATP was added at 4%, the cumulative evaporation decreased and the evaporation loss ratio increased for dark loessial soil, the cumulative evaporation increased and the evaporation loss ratio decreased for sandy soil, and the cumulative evaporation and evaporation loss ratio decreased for cultivated loess soil. The average cumulative evaporation of different soils followed an order of dark loessial soil > cultivated loess soil > sandy soil. Soil water content of ATP treatment was consistently higher than that of control throughout the whole evaporation process in the same soil. Simulations of cumulative evaporation versus the square root of time indicated that the amount of water released from the ATP-treated soil samples at the end of evaporation was higher than that of the control. After the addition of ATP, the crack area density of dark loessial soil and cultivated loess soil increased significantly, and the crack area density of sandy soil increased with the increase of ATP addition. The crack area density of all three soils reached the maximum at 4% of ATP addition. In summary, ATP addition of 3% could minimize the ineffective evaporation of soil water.

Research on the Mechanism and Prevention Methods of the Drying Shrinkage Effect of Earthen Sites

In view of the fact that it is easy for the ancient city soil site of Cai Kingdom to expand and crack when encountering water, this paper explores the methods to improve the expansion and shrinkage deformation, dry shrinkage cracks and easy water absorption characteristics of the expanded site soil based on a lime and silicone hydrophobic agent. In this paper, the expansive clay in the old city site of Cai Kingdom in Zhumadian was taken as the research object, and the dry-shrinkage fissure test of saturated expansive soil was carried out, to study the influencing factors of the dry-shrinkage cracking of expansive soil in this area. The site soil was modified with lime and glue powder, and the fissure image was quantitatively analyzed by MATLAB. The test shows that the smaller the particle size, the faster the evaporation of water and the smaller the surface fissure rate; the thicker the thickness of the soil sample, the greater the surface fissure rate and the greater the crack width; and with the increase in the number of drying and wetting cycles, the surface fissure rate of the soil sample increases. In this paper, lime and waterproof materials are used to improve the expansive soil. This not only reduces the dry shrinkage crack rate, but also improves the waterproof performance and durability of expansive soil.