FEM and EFG Quasi-Static Explicit Buckling Analysis for Thin-Walled Members

The quasi-static explicit finite element method (FEM) and element free Galerkin (EFG) method are applied to trace the post-buckling equilibrium path of thin-walled members in this paper. The factors that primarily control the explicit buckling solutions, such as the computation time, loading function and dynamic relaxation, are investigated and suggested for the buckling analysis of thin-walled members. Three examples of different buckling modes, namely snap-through, overall and local buckling, are studied based on the implicit FEM, quasi-static explicit FEM and EFG method via the commercial software LS-DYNA. The convergence rate and accuracy of the explicit methods are compared with the conventional implicit arc-length method. It is drawn that EFG quasi-static explicit buckling analysis presents the same accurate results as implicit finite element solution, but is without convergence problem and of less-consumption of computing time than FEM.

复杂变截面压杆屈曲载荷计算的传递矩阵法

从楔形和锥形压杆的微分方程出发 ,推得了楔形和锥形压杆的传递矩阵。其中 ,锥形杆的传递矩阵是解析解 ,仅用初等函数来表示 ;楔形杆的传递矩阵是半解析解 ,用贝塞尔函数来表示。这些传递矩阵可用于计算具有圆形和矩形截面的楔形和锥形压杆的屈曲载荷。用传递矩阵法对复杂变截面压杆屈曲载荷的实例计算结果表明 ,本文公式正确。该方法具有精确度高、力学概念清晰及简便易行的优点 。

变截面薄壁构件斜向碰撞性能分析

采用有限元软件LS-DYNA进行数值模拟计算,得到圆锥形和方锥形薄壁构件在不同倾斜载荷角冲击下的碰撞响应,并对两种薄壁构件变形模式、吸能特性和最大峰值冲击载荷进行了比较。数值计算结果表明,圆锥形薄壁构件在斜向冲击下的抗撞性能优于方锥形薄壁构件。

早寒武世西乡生物群四方塔形壳锥体类型及内部结构初探

早寒武世早期"西乡生物群"以盛产不同生长阶段四方塔形壳Quadrapyrgites及大量形态各异的微骨骼化石为特色。在数百枚Quadrapyrgites化石中发现3种不同锥体类型,并对Quadrapyrgites内部结构作初步研究。陕南西乡生物群中Quadrapyrgites化石材料的大量获得,为研究真后生动物起源演化、体型构建提供了丰富材料。