基于数字散斑应变测量法的薄板各向异性力学性能研究

系统地说明了采用数字散斑相关法研究薄板各向异性的实验方法和数据处理方法,进而对SPCC钢板和AA6061铝板的各向异性及其演化规律进行了研究。结果表明:散斑应变测量法是一种获取薄板力学性能的有效手段,其最大优点在于能够获得变形过程中的整体应变场,这是研究复杂加载条件下材料力学性能的关键;对于SPCC钢板,其流动应力的各向异性并不严重,但全量和增量形式的Lankford系数(r值和r′值)均表现出了明显的各向异性,且其值随着变形的增加而逐渐降低,这与传统的采用引伸计进行应变测量时只能获得恒定的Lankford系数不同;对于AA6061铝板,其流动应力和r值的各向异性均不明显,但与轧制方向成不同角度试样的伸长率表现出了明显的差异,并且流动应力的加工硬化速率和r′值在拉伸真实应变处于0.15～0.20时出现了剧烈的波动;随着变形的增加,两种薄板应变的各向异性都逐渐增强,SPCC钢板增强得更为明显。

Anisotropy Study of Thin Metallic Sheets with Strain Measurement of Digital Speckle Correlation

Method of experiment and data processing using digital speckle correlation method to investigate sheet’s anisotropy was systematically introduced,then the anisotropy and its evolution of SPCC steel sheet and AA6061 aluminum sheet were researched.The results show that: the speckle strain measuring method is an effective tool to obtain the mechanical properties of sheets,whose greatest advantage is its capability to capture the whole strain field during deformation,and this is key to study mechanical properties of materials under complex loading conditions;for the SPCC steel sheet,the anisotropy of flow stress is not distinct,while the total and incremental Lankford coefficient(r values and r′ values) show obvious anisotropy,moreover its values decrease with the increasing of deformation,which is different with the constant Lankford coefficient by traditional strain measuring using extensometer;for the AA6061 aluminum sheet,the anisotropy of flow stress and r value are not obvious,however,the elongations of specimens in different directions to rolling show an distinct anisotropy,and the working hardening rate of flow stress and r′ value appear a sharp fluctuation when the true tensile strain is between 0.15 and 0.20;the anisotropy of the two sheet’s strain increases gradually with the increasing of deformation,especially for SPCC steel sheet.