This study investigates the free vibration behaviors of functionally graded (FGM) plates with a porous structure, resting on a Kerr-type elastic foundation, while accounting for thermal effects and complex material property distributions. Within the framework of higher-order shear deformation theory (HSDT), two novel shape functions are introduced to accurately model transverse shear deformation across the plate thickness without employing shear correction factors. These functions are constructed to satisfy shear stress boundary conditions and capture nonlinear effects induced by material gradation and porosity. A variational formulation is developed to describe the dynamic response of FGM plates in a thermo-mechanical environment, incorporating temperature-dependent material properties and three porosity distributions: uniform, linear, and trigonometric. Numerical solutions are obtained using in-house MATLAB codes, allowing complete control over the formulation and interpretation of the results. The model is validated through detailed comparisons with existing literature, demonstrating high accuracy. The findings reveal that the porosity distribution pattern and gradient intensity significantly influence natural frequencies and mode shapes. The trigonometric porosity distribution exhibits favorable dynamic performance due to preserved stiffness in the surface regions. Additionally, the Kerr-type elastic foundation enables fine tuning of the dynamic response, depending on its specific parameters. The proposed approach provides a reliable and efficient tool for analyzing FGM structures under complex loading conditions and lays the groundwork for future extensions involving nonlinear, time-dependent, and multiphysics analyses.

The influence of various process parameters on the deep drawing process is a current research topic in sheet metal forming technology. Starting from the application of the previously constructed original testing device, an original tribological model was developed based on the process of sheet metal strip sliding between flat contact surfaces under variable pressures. A complex experiment was executed using an Al alloy sheet, tool contact surfaces of different roughness, two types of lubricants and variable contact pressures. The procedure included analytically pre-defined contact pressure functions based on which, for each of the mentioned conditions, the dependencies of the drawing forces and friction coefficients were obtained. The pressure in function P1 constantly decreased from a high initial value until the minimum, while in function P3 the pressure increased until the minimum value at the halfway point of the stroke, after which it increased up to the initial value. On the other hand, the pressure in function P2 constantly increased from the initial minimum value until the maximum value, while in function P4 the pressure increased until reaching the maximum value at the halfway point of the stroke, after which it decreased to the minimum value. This enabled the determination of the influence of tribological factors on the process parameters of intensity of traction (deformation force) and coefficient of friction. The pressure functions starting with decreasing trends produced higher values for the traction forces and the friction coefficient. In addition, it was established that the roughness of the contact surfaces of the tool, especially those with titanium nitride coating, has a significant influence on the process parameters. For surfaces of lower roughness (polished), a tendency of the Al thin sheet to form a glued-on layer was noticed. This was especially prominent for lubrication with MoS₂-based grease under conditions of high contact pressure (functions P1 and P4 at the beginning of the contact).

Influence of the contact pressure in the deep drawing processes is a very actual research topic in the metal forming technology. Within this research the tribological model of the strip sliding in the flat die was developed. The original...

The aim of this paper is to show influence of two elements on plastic strain ratio value, or "r" value. The first element is value of plastic strain, and second is specimen geometry. Extensive experiment was conducted according to appropriate tensile test procedure with 3 materials and 5 different specimen geometries. Steel sheet S235JR, austenitic stainless-steel sheet X5CrNi18-10 and Al alloy sheet AlSi0.9MgMn (i.e. ENAW 6081) were used during the experiments. Nominal thickness for all three sheets was 1 mm. Three out of five specimen geometries had 20 mm width and gage length of 60, 120 and 160 mm while the rest of specimens had width of 15 mm and gage length of 50, 100 mm. All the specimens were laser cut in rolling direction. In preparation part of the experiment, behind material characterization (obtaining base mechanical properties) identification of homogenous deformation field was performed, i.e. plastic strain at the beginning of localization, for each specimen. Related to that strain value 6 degrees of deformation were realized: 75%, 80%, 85%, 90%, 95% and 100%. Results showed expected and significant difference in "r" value for used materials, but influence of specimen geometry and realized plastic strains were low.

The aim of this paper is to show influence of two elements on plastic strain ratio value, or "r" value. The first element is value of plastic strain, and second is specimen geometry. Extensive experiment was conducted according to appropriate tensile test procedure with 3 materials and 5 different specimen geometries. Steel sheet S235JR, austenitic stainless-steel sheet X5CrNi18-10 and Al alloy sheet AlSi0.9MgMn (i.e. ENAW 6081) were used during the experiments. Nominal thickness for all three sheets was 1 mm. Three out of five specimen geometries had 20 mm width and gage length of 60, 120 and 160 mm while the rest of specimens had width of 15 mm and gage length of 50, 100 mm. All the specimens were laser cut in rolling direction. In preparation part of the experiment, behind material characterization (obtaining base mechanical properties) identification of homogenous deformation field was performed, i.e. plastic strain at the beginning of localization, for each specimen. Related to that strain value 6 degrees of deformation were realized: 75%, 80%, 85%, 90%, 95% and 100%. Results showed expected and significant difference in "r" value for used materials, but influence of specimen geometry and realized plastic strains were low.

Despite the development of the new, modern non-metallic materials, the steel materials are largely used in various branches of industry, while in some applications they are still irreplaceable. It is expected that such a trend will remain for certain number of years. This is why the necessity is present for development of the new types of steels, which would possess even better properties. The Chromium-Molybdenum (Cr-Mo) steels, with high vanadium content, belong to the group of newer steels characterized by high values of hardness and toughness. In this research, the tests were performed on samples made from the X180CrMo12-1 steel with varying percentage of vanadium within the limits of 0.5-3%. Vanadium, as a carbide-forming alloying element, creates a carbide network of the M7C3 type around the metal matrix, and finely dispersed carbides of the V6C5 type within the metal matrix. This research was focused on determining the carbides’ composition, observing the shape of metal grains and carbide network, testing the material’s resistance to friction and wear, including the electrochemical characterization, as well. The objective was to determine the carbides microstructure and morphology, as well as to evaluate their impact on the material's characteristics. The experimental investigation was performed using the scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and X-ray diffractometric analysis (XRD). Examination of the carbide composition confirmed that it was the M7C3 carbide.