动态SCB实验技术的数值模拟研究

Numerical simulation of dynamic SCB testing

采用Ls-Dyna程序对基于分离式Hopkinson压杆(SHPB)装置的动态半圆弯曲(SCB)实验进行了数值模拟。模拟结果表明:最大拉应力始终产生于试样的直边中点;基于静态弹性理论得到的试样最大拉应力误差在13.7%以内;适合采用透射波计算试样最大拉应力,不宜采用三波法;试样顶端采用线加载方式会产生较高的应力集中,该处可能压溃,改用圆弧面加载方式可以确保试样拉伸失效。本文还对巴西圆盘(BD)实验进行了数值模拟,与SCB实验的对比结果表明:SCB实验中试样更容易达到动态力平衡,且加载方式对试样失效形式的影响更小。由此可见,SCB实验更适合脆性材料动态间接拉伸强度的测量。

LS-DYNA commercial software is used in the numerical simulation of dynamic semi-circular bending(SCB) test loaded by the Split Hopkinson Pressure Bar(SHPB) device. Simulation results obtained show that: The maximum tensile stress always appears at the midpoint of the straight side of the specimen; The error of the maximum tensile stress based on the static elasticity theory is within 10%; The transmitted wave is suitable to be used to calculate the maximum tensile stress of specimen, while three-wave method is unsuitable; The stress on the top of the specimen will be highly concentrated by the line loading mode, which may lead to compressive failure. Replaced by the arc surface loading mode can ensure the specimen tensile failure. Simulation results also show that, compared with the Brazil disc(BD) test, SCB test is more suitable for the measurement of dynamic indirect tensile strength of brittle materials. It mainly shows in two aspects: The specimen is easier to achieve dynamic force equilibrium; Influence of loading mode on the failure mode of the specimen is small.