局部应力差异对压杆弹性稳定的影响

Influence of Local Stress Variance on Elastic Stability of Compression Bar

为研究在不同形式荷载作用下局部应力差异对加载端自由压杆弹性稳定的影响,基于有限元理论探讨了在点加载及面加载情况下压杆的弹性稳定性能.以平面梁单元为例,通过对荷载作用端附近单元的几何刚度矩阵进行调整,模拟了加载形式对加载区局部应力的影响,并通过特征值求解,研究了其对压杆弹性稳定的影响.研究结果表明：加载形式的不同会显著影响加载端自由压杆的稳定临界载荷,但不会影响加载端受约束方向上的稳定临界载荷;长细比介于50～280范围内的一端固定、一端自由的受压圆柱,面加载情况下的弹性稳定临界载荷约为点加载情况下弹性稳定临界载荷的2.14倍。

To discuss how the elastic stability of compression bar is affected by local stress variances with different loading patterns,the finite element（ FE） method was adopted to study the stability performance of compression under the single-point loading and surface loading. A 2-D plane beam was taken as an example and the influence of loading pattern on the local stress variance in the beam element was studied by adjusting the elements near the loading end in the geometric stiffness matrix,and eigenvalue equation was then solved. The results show that different loading patterns notably affect the critical elastic stability loads of compression bar with one end free,but has less effect on the critical loads for the constrained direction of loading end. For the compression bar with one end fixed and one end free and the slenderness ratio from 50 to 280,the critical load under surface loading is 2. 14 times higher than that under singe-point loading.