改进Hopkinson拉杆加载CT试样断裂数值模拟

Fracture numerical simulation of CT specimen loaded by improved Hopkinson tensile bar

摘要:

为研究紧凑拉伸(CT)试样的动态断裂性能，将分离式Hopkinson拉杆进行了改进，在入射杆与透射杆的加载端设计了一种夹持装置，实现了CT试样的动态断裂测试.采用ANSYS/LS-DYNA数值分析程序，对拉伸应力波加载下，基于改进后Hopkinson拉杆系统的CT试样动态断裂测试过程进行了数值模拟研究，得出CT试样的动态断裂响应，计算了表征其动态断裂韧性的相关参量.结果表明,试样中应力分布由非对称状态经约80 μs达到对称分布状态，此后试样应力分布云图对称，两端加载点载荷相等，试样达到应力平衡状态，满足了Hopkinson杆断裂韧性测试要求，并讨论了夹头截面突变与销钉直径对应力波传播和试样应力平衡的影响，为后续Hopkinson拉杆装置继续改进与CT试样动态断裂测试提供了依据.

Abstract:

To study the dynamic fracture performance about the compact tension(CT)specimen,the split Hopkinson bar was improved,and a kind of clamping device between the loading point of incident bar and transmission bar was designed to study the dynamic fracture test on the CT specimen. In terms of tensile stress wave propagation,the finite element method based on ANSYS/LS-DYNA had been adopted to realize the dynamic fracture response and calculate the relative parameters about the dynamic fracture toughness. The result shows that,the stress distribution in the CT specimens from the asymmetric state to the symmetric distribution needs about 80 μs,and then stress distribution cloud in the specimen becomes symmetric and the stresses on two points become equal. Thus the CT specimens come to the balance state,meeting the dynamic fracture toughness test requirements. The effect of the chuck section and the pin diameter on the stress wave propagation and stress balance was studied,which will provide the basis for the further research on the Hopkinson tensile bar and the dynamic fracture test on the CT specimens.