基于立体视觉的板料塑性应变比测量

Determining Plastic Strain Ratio of Sheet Metal Based on Stereo Vision

提出一种测定板料塑性应变比的新方法。在对双相机进行离线标定以后,利用双相机动态采集板料在单向拉伸时表面变形过程的数字图像,获取在时间轴上相同步的两套图像序列;对这些图像采用立体视觉技术和数字图像相关方法重建各个变形时刻板料表面三维外形;并根据有限应变理论计算局部最大最小主应变;最后利用均匀塑性变形期间相同变形时刻局部应变近似相等的性质,换算出长度与宽度方向的应变,进而计算出板料的塑性应变比。在GB/T 5027-2007标准规定的实验条件下完成了对深冲铝板6016T4PD,硬铝2A12-T4,2A12-O等的塑性应变比测量。结果显示本文方法快速、准确。

A new technique for determining the plastic strain ratio of sheet metal is proposed.After off-line calibration of the two cameras,digital images of the process of sheet metal surface deformation were temporally taken by the cameras so that two sets of time-synchronization image serial were obtained,the 3D shapes of sheet metal surfaces at different deformation time were reconstructed by using stereo vision and digital image correlation methods consequently.Local major and minor strains were then evaluated in terms of finite strain theory.By exploiting the approximate equality of local strains at the same moment during uniform plastic deformation,the major and minor strain were converted into the strains in length and width directions,from which r value can finally be determined.Under the experimental conditions prescribed in GB/T 5027-2007,r values of AA6016T4PD,2A12-T4 2 and 2A12-O were determined,and the results demonstrated the proposed technique was accurate and rapid.