小尺寸低碳钢试件吕德斯效应的三维数字图像相关测量

MEASUREMENT OF LDERS BAND IN SMALL SIZE LOW CARBON STEEL SPECIMEN BY 3D DIGITAL IMAGE CORRELATION METHOD

吕德斯效应是多种金属和合金材料由于屈服阶段的不均匀变形而在材料表面产生条带状褶皱的现象,它会使冲压件表面质量降低.为了防止它的出现,对吕德斯效应进行研究变得非常重要.采用小视场(15 mm×15 mm)下三维数字图像相关方法对小尺寸低碳钢试件在单轴拉伸载荷作用下的变形场进行测量,实际观测了小尺寸试件的吕德斯效应,结合理论模型解释了其形成机理,并分析了吕德斯带传播过程中应变及应变率的变化规律.实验研究表明,运用三维数字图像相关方法测量试件表面变形场,实现了对小尺寸低碳钢试件的吕德斯带演化过程以及颈缩、断裂等细观力学行为的观测,该方法是研究材料变形细观机理的一种有效测量手段.

Lders band is phenomenon of stripped fold on material surface which is caused by the inhomogeneous deformation during the yield stage. It can reduce the quality of stamped parts' surface so that it is important to study the Lders band in order to prevent it from appearing. To complete the observation and analysis of Lders band in small size low carbon steel specimen, the 3D digital image correlation method under small view field(15 mm×15 mm) was used to realize the deformation measurement. The formation mechanism of Lders band was studied and the change of strain and strain rate during the propagation of Lders band was analyzed. Experimental study demonstrates that the 3D digital image correlation method is able to carry on the observation of meso-mechanical behavior like Lders band and necking fracture. It provides an effective means for studying meso-mechanism of deformation.