Resumo em Inglês:

Abstract This study presents an enhanced finite element method (FEM) integrated with the improved first-order shear deformation theory (i-FSDT) for analyzing the natural frequencies of functionally graded sandwich (FGSW) plates resting on a variable elastic foundation (VEF) with uncertain input parameters. The FGSW plates are composed of two functionally graded (FG) face layers and a homogeneous or FG core layer. The proposed method is validated by comparing it with existing benchmark solutions to ensure its accuracy and reliability. In addition, the study explores the effects of geometric configurations, material properties, foundation types, and boundary conditions (BCs) on the natural frequencies of FGSW plates. To address uncertainty in input parameters, Monte Carlo simulation (MCS) is employed to determine the probabilistic range of natural frequencies. The numerical and graphical results show that the uncertainties of the input parameters interact to greatly affect the natural frequency of sandwich plates.

Resumo em Inglês:

Abstract High entropy alloys (HEAs) have attracted widespread attention from researchers as emerging materials. Among them, refractory high entropy alloys (RHEAs) have shown potential for application in high-temperature environments due to their excellent high-temperature mechanical properties. This study mainly focuses on TiAlVZrNb RHEAs, conducting quasi-static and dynamic mechanical experiments, and fitting Johnson Cook constitutive equation parameters. In addition, the formation and aftereffect of the jets are studied through experiments. The temperature and yield strength distribution of the jets are studied through numerical simulation. The results indicate that under quasi-static loading, TiAlVZrNb RHEAs exhibit high yield strength and excellent ductility. The cohesiveness of the jet is discussed by combining the theoretical and mechanical properties. The burn marks on the quilt and oil tank behind the target also confirm the strong aftereffect of TiAlVZrNb RHEAs jet. This study can provide a reference for the application and design of RHEAs liner.

Resumo em Inglês:

Abstract To investigate the influence of spaced targets with large angle of obliquity on the penetration performance of tungsten alloy long rod projectiles with large length-diameter ratio, this study conducted experiments and numerical simulations on the penetration of 93W long rod projectiles into oblique spaced targets. By experiments, the fracture morphology of the long rod projectile after penetrating the target was successfully captured. The recovered cores and were systematically analyzed by scanning electron microscopy (SEM). The results indicate that the fracture mode of the long rod projectile was mainly manifested as transgranular fracture of tungsten grains. In addition, the J-C constitutive parameters of 93W were determined. The mechanism of action for long rod projectiles penetrating spaced targets with large angle of obliquity was ballistic deflection and the fracture of long rod projectiles. By altering structure of the long rod projectiles, the penetration effectiveness against oblique spaced targets could be significantly enhanced.