Application of Neural Network Models with Ultra-Small Samples to Optimize the Ultrasonic Consolidation Parameters for 'PEI Adherend/Prepreg (CF-PEI Fabric)/PEI Adherend' Lap Joints

The aim of this study was to optimize the ultrasonic consolidation (USC) parameters for 'PEI adherend/Prepreg (CF-PEI fabric)/PEI adherend' lap joints. For this purpose, artificial neural network (ANN) simulation was carried out. Two ANNs were trained using an ultra-small data sample, which did not provide acceptable predictive accuracy for the applied simulation methods. To solve this issue, it was proposed to artificially increase the learning sample by including additional data synthesized according to the knowledge and experience of experts. As a result, a relationship between the USC parameters and the functional characteristics of the lap joints was determined. The results of ANN simulation were successfully verified; the developed USC procedures were able to form a laminate with an even regular structure characterized by a minimum number of discontinuities and minimal damage to the consolidated components.

Formability of Ultrasonically Additive Manufactured Ti-Al Thin Foil Laminates

This study investigates the effect of strain rates and temperatures on the mechanical behavior of ultrasonically consolidated Titanium–Aluminum thin foils to understand and characterize their formability. To this goal, laminated composite samples with a distinct number of layers were bonded using ultrasonic consolidation. Then, tensile and biaxial hydraulic bulge tests at different strain rates and temperature conditions were conducted. The effect of the sample orientation on the mechanical response was also examined. Tensile and hydraulic bulge tests results were compared to observe differences in ultimate tensile strength and strain levels under uniaxial and biaxial loading conditions. The effects of loading condition, strain rate, and temperature on the material response were analyzed and discussed on the basis of test results. In general, it was concluded that the maximum elongation values attained were higher for the samples subtracted along the sonotrode movement direction compared to those obtained from the normal to sonotrode movement direction. The elongation was obtained as high as 46% for seven bi-layered samples at high-temperature ranges of 200–300 °C. Hydraulic bulge test results showed that elongation improved as the number of bi-layers increased, yet the ultimate strength values did not change significantly indicating an expansion of the formability window.

Effects of interaction volume on X-ray line-scans across an ultrasonically consolidated aluminum/copper interface

Diffusion as a bonding mechanism for ultrasonic consolidation of metals is widely debated due to the short weld times and low processing temperatures. To quantify interdiffusion coefficients, X-ray energy dispersive spectroscopy (XEDS) line-scans were performed across an Al-Cu interface using the Scanning Electron Microscope (SEM) with accelerating voltages ranging from 6 to 22 KeV in increments of 2 KeV and a step size of 0.05 microns. Higher accelerating voltages resulted in broader concentration profiles, indicating higher apparent interdiffusion coefficients when scanned at the same location of the same sample. This error due to the interaction volume interference was quantified using Monte Carlo simulations. It was found that an accelerating voltage of 22 KeV and diffusion distance less than 5 microns resulted in at least 50% error. Even at a smaller accelerating voltage of 6 KeV, the percent error in calculation of the interdiffusion coefficient for a diffusion distance of 0.5 microns is expected to be 15-20%. An approximate diffusion distance and apparent interdiffusion coefficient for ultrasonically consolidated Al-Cu were 0.503 microns and 0.013 um(2) /s, respectively. In this study, a methodology is presented that allows one to estimate the error in the calculation of an interdiffusion coefficient from the accelerating voltage used and the diffusion distance measured by the SEM XEDS at that accelerating voltage.