ABAQUS 求解器设置

Abaqus/Standard提供了无数个控制收敛与积分精度的参数设置。通常使用默认的参数值可以处理大多数问题，只有一部分的非线性问题需要用户调整参数，当然用户必须是具有丰富经验的CAE分析师，调整时要格外小心！

在Analysis Manual Documentation 中的7.2章节详细介绍了这些参数的作用及设置方法。

 

7.2.1 Convergence and time integration criteria: overview

Numerous control parameters are associated with the convergence and integration accuracy algorithms in Abaqus/Standard. These parameters are assigned default values that are chosen to optimize the accuracy and efficiency of the solution for a wide spectrum of nonlinear problems. You can change the solution control parameters, as described in the following sections:

A brief synopsis of the more important solution control parameters, together with a description of the circumstances in which they can be used effectively, is provided in “Commonly used control parameters,” Section 7.2.2. This section is likely to be the most useful for the general user and should be read first.

Abaqus/Standard incorporates an empirical algorithm designed to solve the equilibrium equations of nonlinear systems accurately and economically. The criteria used to establish convergence of nonlinear increments and the automatic adjustment of increment size based on the convergence rate are described in “Convergence criteria for nonlinear problems,” Section 7.2.3.

Abaqus/Standard allows you to choose “time integration accuracy parameters” in problems that have a physical time scale. The algorithms that use these parameters for automatically controlling time increment sizes are described in “Time integration accuracy in transient problems,” Section 7.2.4.

 

常用的控制参数

Defining tolerances for field equations

residual control

solution correction control

average flux

initial time average flux

Controlling the time incrementation scheme

the equilibrium iteration for a residual check

the equilibrium iteration for a logarithmic rate of convergence 收敛率对数check

Avoiding premature cutbacks in difficult analyses

Automatically setting the time incrementation parameters

Activating the “line search” algorithm

Defining tolerances for constraint equations

Controlling the solution accuracy in direct cyclic analysis

Imposing the periodicity condition

Defining tolerances for stabilized state and plastic ratchetting detections

 

控制参数调整有两个目的：一是调整非线性方程求解精确度；二是调整时间增量。

Step-Other-General Solution Controls-Edit

会出现罕见的warning对话框，然后才能继续下去。说明对于一般的问题和普通用户，abaqus并不建议调整这些参数。

Abaqus/Standard默认采用牛顿法进行迭代，以利用它的二次收敛速度。接触，或塑性应变变向等行为是严重非连续行为，其收敛相对较难。单元类型对收敛有影响。按容易收敛的排序：简约单元(增强)>简约单元(默认)>普通单元。有时候接触问题很难收敛，此时可以在step步中将（Convert severe discontinuity iterations）打开。如果依然碰到PENETRATION ERROR的问题，可以进一步在step模块other-general solution control-time incrementation中将discontinuous analysis选中（I0=8,IR=10），还可以将每一增量步中所允许的最大缩减次数（IA）增大，以保证不收敛时能有足够小的收敛步长。还可以将Tcont(contact and slip compatibility tolerance)值改大些，但需要检查结果的合理性

另外出现“DISP CORRECTION TOO LARGE COMPARED TO DISP INCREMENT”这类出错信息时，可以采用准牛顿法代替默认的完全牛顿法求解。注意，采用准牛顿法时，之前的分析步的求解方式不能是“接触迭代”（Contact iteration），否则无法求解。

转自公众号——ABAQUS大世界

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