基于SHPB技术测试典型金属动态压缩性能的尺寸效应分析

Study on size effect analysis of dynamic compression properties of typical metals based on SHPB technique

为探究金属材料在SHPB动态测试中的尺寸效应问题,该文选用3种具有典型晶体结构的金属材料2A12铝合金(面心立方,FCC)、45钢(体心立方,BBC)以及TC4钛合金(密排六方,HCP),分别加工成具有相同长径比(0.8)、不同尺寸(Φ10 mm×8 mm,Φ5 mm×4 mm,Φ2 mm×1.6 mm)的圆柱形压缩试样,并采用三组不同杆径的SHPB装置(杆径分别为Φ19 mm、Φ12.7 mm、Φ5 mm)进行动态力学性能测试。结果表明:在金属材料的动态压缩力学性能测试中,所用试样的尺寸在满足一定要求时方可获得其稳定的塑性流动应力,对于绝大多数金属建议采用直径大于5 mm的试样进行测试;采用微型SHPB装置配合小尺寸试样所测得材料的塑性流动应力偏低;对应变率敏感的材料,其尺寸效应也更为显著;被测试样的塑性流动应力或与试样的应力三轴度(即一维应力程度)相关。该文意在分析SHPB测试中的尺寸问题以期对相关学者和工程技术人员准确地获取金属材料的动态实验数据提供参考。

In order to investigate the size effect of metallic material in dynamic test conducted on split Hopkinson pressure bar(SHPB).Three typical metallic materials,i.e.,2A12 aluminum alloy(FCC),45 steel(BBC),and TC4 titanium alloy(HCP) were selected and processed into the specimens which are of same aspect ratio(0.8) but of different sizes(Φ10 mm×8 mm,Φ5 mm×4 mm,Φ2 mm×1.6 mm).These specimens were loaded respectively by three sets of SHPB devices with different bar diameters(Φ19 mm,Φ12.7 mm,Φ 5mm).The test results show that:1) For dynamic compression mechanical property testing,the size of specimen should meet certain requirements to obtain the stable plastic flow stress of material.For the vast majority of metals,it is recommended to use the specimens with a diameter greater than 5 mm.The plastic flow stress of the small size specimen measured by the miniature SHPB device is relatively low.2) The size effect is more obvious for the materials sensitive to strain rate.3) The plastic flow stress of the specimen is supposed to be related to its triaxial stress(i.e.,one-dimensional stress degree).This study aims to provide a reference for relevant researchers and engineers to accurately obtain the dynamic experimental data of metal materials.