A Fast Identification Method of Yield Strength of Materials Based on Bending Experimental Data

Abstract

Identifying the yield strength of materials quickly and accurately is the key to realizing defect prediction and digital process control on the production line. This paper focuses on identifying the material yield strength based on bending deformation, analyzing the influence of different die fillets, punch fillets, and die spans on the curve shapes, determining the reasonable dimensions of the device, and developing them. Two methods for rapidly extracting the yield load are proposed—the window vector method (WV) and the fitting residual method (FR)—and compared with the double secant line method (CWA) and the one tenth thickness method (t/10). Because there is no direct correspondence between the yield load and the material performance parameters, the relevant equations were fitted using the experimental data. The linear correlation between load and yield strength determined by these four methods was close to 0.99. Finally, four kinds of sheets with high, medium and low yield strength were tested and compared with the observed results. The result shows that when the yield strength is small, the average error and the relevant model dispersion will increase. As the yield strength increases, the biases increase gradually. The prediction errors based on the t/10, WV, and FR methods were all below 4%.

Precision and Flexible Bending Control Strategy Based on Analytical Models and Data Models

“…The data points before yield bending are used to optimize the elastic modulus, and the transition points between elastic and plastic bending are used to optimize the yield strength, while the data points after yield bending are used to optimize the hardening parameters, and the unloading data points are used to optimize the variable modulus parameters. The window method [32] is used to automatically identify the (14)…”