轴向冲击作用下杆的弹塑性动态屈曲准则

Elastic-plastic dynamic buckling criterion of rods under axial impact

为了提出一种不仅满足梁杆结构工程需要,而且涉及的物理量测量简便的动态屈曲准则。以轴向重物冲击下微弓形扁长金属杆的弹塑性动态屈曲为例,采用显式动力学有限元仿真分析方法,分析了不同重物冲击速度下扁长杆的动态响应,归纳了在轴向冲击作用下杆的弹塑性动态屈曲准则,应用此准则进一步研究了扁长杆的初始条件参数(材料屈服应力、预制弓形幅值和截面尺寸等)与临界冲击速度关系,验证了此准则的一般性和有效性。经过研究,提出了在轴向冲击作用下杆的动态屈曲准则——加载分离准则:重物对杆的轴向加载过程中,杆的加载端与重物发生明显的分离;加载分离准则可以满足工程需要,与基于载荷-响应曲线的B-R(Budiansky-Roth)运动准则相比,涉及的物理量测量更为简便;与提高扁长杆的材料强度和加工精度相比,增大截面尺寸是提高其动态屈曲强度的较有效方法。

In order to propose an elastic-plastic dynamic buckling criterion for satisfying engineering requirements of beam and rod structures and simplifying measurement method,taking elastic-plastic dynamic buckling of a micro-bow flat long metal rod under axial weight impact as an example,dynamic responses of the rod under different axial impact velocities were analyzed with the explicit dynamic finite element simulation analysis method to generalize an elastic-plastic dynamic buckling criterion.Using this criterion,relations among initial condition parameters of the flat long rod including material yield stress,deflection and cross-section size of prefabricated micro-bow shape,etc.and critical impact velocity were further studied to verify the universality and effectiveness of the criterion.After investigation,the rod dynamic buckling criterion under action of axial impacts,i.e.,the loading-separation criterion was proposed,it was described that if a rod is loaded by weights in axial direction,as soon as an obvious separation between its loaded end and weights happens,it enters dynamic buckling.It was shown that the loading-separation criterion can satisfy engineering requirements;compared with Budiansky-Roth(BR)motion criterion based on load-response curve,the measurements for physical variables involved to this criterion are easier and simpler;compared with enhancing material strength and improving machining accuracy of the flat long rod,increase in its cross-section size is more effective to lift its dynamic buckling strength.