Nonlinear Spline Finite Element Method for Ribbing of Cold-Rolled Coils

The ribbing problem has serious influence on the steel product quality, which produces additional shape waves on the surface of uncoiled steel strip on the process of curl. Nonlinear spline finite element method (n-spline FEM) is adopted to establish the relationship between the ribbing height and deflection of additional shape wave, for example, post-buckling deformation. The proposed spline FEM is more effective and convenient than traditional finite element method in the buckling analysis. Using the spline FEM, the shape wave caused by the ribbing is calculated, and then the ribbing values can be obtained which are difficult to measure in practice. At the same time, the judgment rule is also given for estimating the strip quality according to the ribbing value.