试件尺寸对金属材料Hopkinson拉杆实验结果的影响研究

Study on the Specimen Size-Effect of Hopkinson Tensile Bar Experiments

  • 摘要: 分离式Hopkinson拉杆是当前进行材料高应变率加载条件下力学行为的主要研究手段.受加载条件的限制,往往采用小尺寸的试件开展实验.因此,试件在加工过程中的加工硬化对实验结果会产生一定的影响,从而不能完全反映真实材料的力学性能.为研究这一效应的影响,首先利用微纳米压痕法测量了小尺寸不锈钢试件沿表面厚度方向的维氏硬度变化规律,得到了加工硬化层的厚度及其对材料性能的影响.在此基础上,通过理论分析研究了加工硬化对试件拉伸试验结果的影响,并结合不同尺寸试件的准静态拉伸试验结果,给出了分离式Hopkinson拉杆动态拉伸结果的修正方法.

     

    Abstract: Split Hopkinson Bar (SPHB) is the main method to study the mechanical behaviors of materials under high strain-rate loadings. Restricted by loading conditions, generally only small-sized specimens were used in SPHB experiments. Therefore, work-hardening effect which occurs in the machining process could influence the experiments and the results could not reflect the true mechanical properties of materials. To study this effect, Vickers-hardness variation of the material along the cross-section of small-size stainless steel specimens were measured by indentation experiments, and the work-hardening effects on the properties of materials were obtained. By investigating the influence of work-hardening on the tensile property theoretically, the correction method of dynamic tensile results of split Hopkinson tensile bar was given accounting for the quasi-static tensile test results of specimens with different dimensions.

     

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