Resumo em Inglês:

Abstract In this study, stress variations in cylindrical single lap joints under tensile loading were investigated as both elastic and viscoelastic(time-dependent) solutions. Analytical modeling utilized the Pugno-Carpinteri method and the Lubkin-Reissner method, while numerical modeling employed the Abaqus analysis program. The viscoelastic solution was derived from the associated elastic solution application using the Alfrey correspondence principle. Transformed elastic modulus values for the viscoelastic solution were obtained through methodologies proposed by Schapery and the generalized Maxwell-Wiechert model. The analyses revealed that maximum stress occurred at the initiation of loading, with stress values decreasing over time at the adhesive edges, and an increase in stiffness observed in the central region of the adhesive. In single lap joints, it was found that overall in-plane stiffness remained constant independent of the adhesive modulus value.

Resumo em Inglês:

Abstract In this paper, a methodology is proposed to evaluate the optimal design of truss structures considering progressive collapse. This methodology combines Total-Lagrangian formulation for material and geometrical nonlinear analysis, using nodal positions and log-strain measure; the Systematic Reliability-based Approach to Progressive Collapse method; and risk-optimization formulation. Two benchmark examples are analyzed and discussed. The results demonstrate the accuracy, robustness, and efficiency of the proposed methodology in evaluation the optimal design of truss structures subjected to progressive collapse. It is shown that material behavior (elastic, elastoplastic, and hyperelastic) and rate of loading (step and linear load) can lead to different optimal design configurations. In the redundant hyperstatic truss example, the coefficient of vulnerability identifies the most critical bar for each truss configuration. The most vulnerable bars in the reference design become less vulnerable in the optimal design, leading to load redistribution, or alternate load paths, which reduce the probability of occurrence of progressive collapse.

Resumo em Inglês:

Abstract Normal firing of the percussion ignition system is essential to the reliable operation of firearms. Percussion energy, critical dimension, and assembly parameters all have a significant impact on a firearm’s percussion ignition performance. This study was intended to reveal how various factors influenced a firearm’s percussion ignition performance. The percussion ignition process of a small-caliber automatic rifle was simulated in this paper by conducting pressure measurement tests for the entire cartridge to obtain the gas pressure response. A finite element model was built to study the firearm’s percussion ignition performance. The simulation parameters were calibrated based on experimental results, and the accuracy of the simulation model was verified. Local sensitivity analysis was carried out for each influencing factor using the control variable method. Global sensitivity analysis was conducted based on the optimal Latin hypercube design that accounted for coupling effects between the influencing factors. The results show: Hammer’s falling height has the greatest influence on the firing ignition performance. The primer seating depth has the least effect on the firing ignition performance. This article can provide technical support for improving the design of the percussion and ignition system of the firearm and improving the reliability of the percussion and ignition.