A reconstruction method to determine crack length based on virtual extensometers

Abstract

The laboratory measurement accuracy of crack length has an influence on the study of material properties and behaviors. There are some defects in the existing methods for determining crack length, such as strong subjectivity, complex experimental process and difficult data processing. To solve the above problems, based on the surface deformation data recorded by DIC, a method of reconstructing the virtual extensometers and measuring the crack length is proposed by fixing the virtual extensometers along the crack growth path. The fracture process is analyzed based on the plastic hinge hypothesis, and the whole deformation data of the specimen is obtained by analyzing the length change of the virtual extensometers. The rigid components of virtual extensometers deformation along the crack growth path are reconstructed and compared with the original elongation curve to determine the crack length. It shows that the reconstruction method has a high reliability to compare the prediction results with those of the curvature method, the direct-reading method and the Martinelli-Venzi model method. The characteristic of virtual extensometers fixed after experiment and programming design of analysis process are applied to simplify the experiment and data processing. On the basis, the influence of the initial length of the virtual extensometer and the decomposition process on the results is discussed. The results show that reconstruction method has good adaptability to tunneling effect, and it is expected to realize automatic data collection and processing based on this method.