In commonly used analyses where force is used to control loading, the norm of residual force can be used to control convergence. There are four main ANSYS nonlinear convergence criteria: force, displacement, moment, and rotation. In general, when the structure is subjected to force loading or stiffness growth, or when analyzing thin films, the linear search can be turned on with the command LNSRCH.
Linear search can generally achieve convergence in analysis, but the cost is a significant reduction in solving speed, especially for materials with nonlinearity. Linear search can be considered as an alternative to adaptive descent, and both should not be used at the same time. Proper use of adaptive descent factor can also improve the convergence of certain nonlinear elements. Although in general, using the automatic default options will yield the best convergence characteristics, it is not ruled out that other selections may be more effective. When nonlinear convergence is difficult, the default Newton-Raphson options of the program can be adjusted. If convergence fails within a too large time step, this feature can halve the time step, allowing the calculation to continue.Ģ、Adjust Newton-Raphson options and adaptive descent It is worth noting that when the automatic time step is adopted, the bisection method will be automatically activated. Therefore, it is very important to set the initial time step appropriately, which can generally be determined through trial and error. During the nonlinear solution process, if the initial time step is too small, the automatic time step algorithm may cause your running time to be too long on the other hand, if your minimum time step is too large, non-convergence may occur. Opening the automatic time step often requires a relatively small minimum time step (or maximum number of steps, defined using DELTIM or NSUBST). When we encounter convergence difficulties, a very important method is to open the automatic time step. This article summarizes several common adjustment methods for convergence difficulties in nonlinear solutions, for reference only.ĪNSYS uses time as a tracking parameter for all static and transient analyses, regardless of whether the analysis depends on time. When solving geometric non-linear problems using ANSYS, convergence difficulties may occur due to unsuitable parameter settings with the default system configuration.
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