Establishment of sheet metal forming wrinkling limit diagram (WLD) and research on the consistency of WLDs in different processes

With the actual demand for lightweight and high strength of metal parts, wrinkling has become one of the main problems restricting the overall forming of thin-wall members. Therefore, the efficient and accurate prediction and control of it have actual significance. In this work, a critical principal strain analytic model for plate and shell wrinkling was set up with the combination of energy method theory and plastic flow law of material. And a numerical procedure of establishing the wrinkling limit diagram (WLD) was developed based on the finite element method and the critical principal strain analytic model. With the sidewall wrinkling in deep drawing process of the conical cup and the wrinkling of square plate in the Yoshida bucking test (YBT) as the analysis object, the morphology and the characteristics of the WLD under different forming processes were studied, and the effect of loading conditions and stress loading history on the WLD was investigated, it is observed that the WLD is different under the same sheet material but different loading conditions, and indicated the WLD is dependent on the loading conditions.