3D digital speckle analysis system for dynamic strain measurement in sheet deformation

To avoid the shortcomings of traditional strain detection in sheet deformation,digital speckle correlation method,computer binocular vision theory and mechanics theory of materials were introduced to trace the motion of specimen surface geometric points dynamically by analyzing the speckle images of the sample surfaces before and after deformation.According to the motion of geometric points on the foundations of getting the 3D displacement field,the 3D strain field could be calculated.Based on this principle,the 3D digital speckle analysis system for dynamic strain measurement(XJTUDIC) was developed.Perforated aluminum workpiece was used for uniaxial tension test.It is found that the system can reflect the 3D strain state well in sheet deformation,reconstruct the 3D profile of the specimen surfaces vividly and reproduce the deformation field,the strain field and the forming limit diagram of the workpiece surfaces intuitively.For critical points,the system can also track their trajectory and calculate their strain at any time and arbitrary displacement.Furthermore the system can be utilized to various mechanical sites.