Analysis of the Degradation of Pearlitic Steel Mechanical Properties Depending on the Stability of the Structural Phases

The paper is focused on analysing the pearlitic steel phase transformations and their influence on the mechanical properties. The intention is to perform a detailed analysis of the heat treatment process using the exact heating temperature and chemical composition to achieve the optimal mechanical properties of the tool. The key area is monitoring and regulating the heat treatment. This technology is constantly undergoing an optimisation process and is an effort to introduce new trends in monitoring phase transformations and processes. The use of non-destructive methods is an adequate tool. The principle is to determine the exact structural phase at a given moment, which can be very difficult when a complex shaped part is heat treated. Which precludes the use of some other methods of phase transformation analysis. Specifically, the determination of the exact moment of finish of the austenitisation process is eminent. The monitoring of these processes will be ensured by both a non-contact pyrometer and also by the AE method with an adequate sensor and waveguide. The resulting structural phases formed after the heat treatment will be evaluated by electron microscopy, followed by the analysis of the mechanical properties of selected steels.

Rheological and Flow Behaviour of Yolk, Albumen and Liquid Whole Egg from Eggs of Six Different Poultry Species

Liquid egg products are one of the basic raw materials for the food industry. Knowledge of their rheological and flow behaviour in real technical elements is absolutely necessary for the selection of suitable technological equipment for their processing. In this article, the rheological properties of liquid egg products were determined. Eggs from six different species of poultry are used: domestic hen (Gallus gallus domesticus) hybrid Hisex Brown; Japanese quail (Coturnix japonica); German carrier goose (Anser anser f. domestica); domestic ducks (Anas platyrhynchos f. domestica); domestic guinea fowl (Numida meleagris f. domestica); and domestic turkeys (Meleagris gallopavo f. domestica). Liquid egg products showed pseudoplastic behaviour in range of shear strain rates from 0.2 up to 200 s⁻¹ and at the temperature of 18 °C. Thus, the flow curves were constructed using the Ostwald-de Waele rheological model, with respect to the pseudoplastic behaviour of liquid egg products. According to the values of the coefficients of determination (R²), the sum of squared estimate of errors (SSE) and the root mean square error (RMSE), this model was appropriately chosen. Using the consistency coefficient K, the flow index n and the adjusted equations for the flow rate of technical and biological fluids in standard pipelines, the 3D velocity profiles of liquid egg products were successfully modelled. The values of the Reynolds number of the individual liquid egg products were calculated, and the type of flow was also determined. A turbulent flow has been detected for some liquid egg products.

Rheological behaviour of chocolate at different temperatures

The rheological behaviour of the chocolate at different temperatures was studied using a concentric cylinder viscometer with precision small samples adapter, temperature sensor and standard spindle. BIO chocolate (100% organic cocoa) has been used for the whole types of experiments. At the first, the range of temperature has been chosen 36 °C, 38 °C, 40 °C, 42 °C, and 44 °C. The shear deformation rate was established from the 0.1 s-1 up to 68 s-1. Rheological behaviour was non-Newtonian (plastic) with inconsiderable yield stress in all temperatures. The chocolate unambiguously demonstrated plastic behaviour and flow curves were fitted by the power law model (Herschel-Bulkley model), Bingham model, and Casson model with taking into account the coefficient of determination R2. The obtained results of rheological behaviour of chocolate can be best described as Casson fluid. Exactly coefficients of models can be used for modelling of flow velocity, volume flow, friction factor, Reynolds number, two dimensional and three dimensional velocity profiles and much more for flow in the real technical elements e.g. pipes, trough, tubes. Finally, temperature dependence of apparent viscosity of chocolate was also continuously measured in the range from 35 °C up to 62 °C. The apparent viscosity decreased in the temperature range. This decrease was fitted using power law equation. The knowledge of the plastic flow behaviour of chocolate is very important, because it is not quite common flow behaviour of foodstuffs.