Set control parameters for springback analysis, as illustrated in Figure 8.3.107.

GENERAL

SHELL WARPING STIFFNESS (BWC): Default is set as 2, i.e. Belytschko-Tsay

ADVANCED: Advanced parameter setting.

Figure 8.3.107  Springback control parameters interface

IMPLICIT ANALYSIS

Allow to user to select approach of springback analysis: single step springback or multiple step springback analysis. Multiple step springback is set as default option. Single step springback analysis usually leads to good result. However, converged result may not be obtained using single step springback analysis for relatively flexible part. The user is recommended to conduct springback analysis using multiple step approach. Detailed descriptions for setting up single or multiple step springback analysis is described in LS-DYNA Keyword User’s Manual.

INITIAL TIME STEP SIZE (DT0): Initial time step size of springback analysis. Default value is 0.001.

NUMBER OF IMPLICIT STEP (NSBS): Number of implicit step. Set to 1 if single step implicit analysis is performed. If the value is greater than 1, multiple implicit analysis is used.

ADVANCED: Sets advanced parameter of implicit analysis. See Figure 8.3.108 for the list of parameters.

Figure 8.3.108  Advanced parameter for Implicit Analysis

COARSENING MESH

Allow the user to use coarsening mesh technique during springback analysis. During drawing simulation, adaptive mesh is adopted to refine blank mesh to capture details on tooling. Adaptive meshing increases model size and poses a challenge to convergence in springback analysis. This option merges the refined mesh in flat regions to reduce model size. It reduces the rate of incidence of convergence problems and shorten the computing time.

ANGLE: Sets the angle criteria for merging neighboring elements. If the angular difference of element normals between adjacent elements is less than the given criteria, these elements are merged. Default angle is 8°.

CHECKING MESH

This function allows the user to check mesh quality during Springback analysis. The user can check adaptive constraints, minimum aspect ratio, minimum and maximum allowable interior angle and minimum element size.

FIXING BAD ELEMENT

This function enables the solver to automatically repair distorted elements and output the relevant information into text file. It helps to increase precision of springback analysis, as well as improving convergence.