我的计算结果不收敛 怎么回事？

wanghao1118

No convergence,iteration limit reached,automatic time stepping might help



INTERMEDIATE ITERATION RESULTS CAN BE OBTAINED BY
REQUESTING DETAILED ITERATION HISTORY PRINTOUT.

DIFFERENT SOLUTION STRATEGY MAY BE USED TO RERUN
THE ANALYSIS, SEE THE THEORY AND MODELING GUIDE.


  S O L U T I O N   T I M E   L O G (IN SEC)

            FOR PROBLEM

  *** NO HEADING DEFINED ***                                                     




INPUT PHASE  . . . . . . . . . . . . . . . . . .      0.04

SUBSTRUCTURES INPUT PHASE. . . . . . . . . . . .      0.00

INITIALIZATIONS. . . . . . . . . . . . . . . . .      0.00

ASSEMBLAGE OF LINEAR STIFFNESS,EFFECTIVE STIFF-
NESS,MASS MATRICES AND LOAD VECTORS . . . . . .       0.02

FREQUENCY (OR BUCKLING) ANALYSIS . . . . . . . .      0.00

INITIAL CALCULATIONS FOR MODE SUPERPOSITION     
                      ANALYSIS . . . . . . . . .       0.00

TRIANGULARIZATION OF LINEAR (EFFECTIVE)         
                      STIFFNESS MATRIX  . . . . .      0.00


STEP-BY-STEP SOLUTION (         1 TIME STEPS)

   CALCULATION OF EFFECTIVE LOAD VECTORS  . . .        0.00
   UPDATING EFFECTIVE STIFFNESS MATRICES        
   AND RHS VECTOR FOR NONLINEARITIES  . . . . .        0.22
   UPDATING EFFECTIVE STIFFNESS MATRIX FOR      
   CENTRIFUGAL DEFORMATION DEPENDENT LOADING. .        0.00
   MODE SUPERPOSITION . . . . . . . . . . . . .        0.00
   SOLUTION OF EQUATIONS  . . . . . . . . . . .        0.39
   EQUILIBRIUM ITERATIONS (TOTAL) . . . . . . .        0.63
   CALCULATION AND PRINTING OF DISPLACE-        
   MENTS, VELOCITIES, AND ACCELERATIONS . . . .        0.00
   CALCULATION AND PRINTING OF STRESSES . . . .        0.00
   FRACTURE MECHANICS . . . . . . . . . . . . .        0.00

                               STEP-BY-STEP TOTAL. . .       0.67

CALCULATION AND PRINTING OF SUBSTRUCTURE        
                 INTERNAL RESPONSES  . . . . . . . . .       0.00

帮帮我看看怎么回事  谢谢了

tonnyw

There are different ways to check if the solution is convergent.
1. Using smaller load steps
2. Using Full Newton Method instead of Modified Newton Method or BFG method
3. Using Line Search
4. Using ATS

You can use any one of the above or you can combine all of them.

The most conservative way I would suggest for your case is to use smaller load steps plus Full Newton Method plus Line search. If the solution is not convergent, then using ATS plus Full Newton Method plus Line Search with bigger convergence tolerance. If the solution is still not converged, you should not expect converged solution at all for your problem.

minsen83712

其实不收敛的地方很多的，你不能一句话就这么完了。我建议大家以后应该把自己的命令流放在上面啊。因为不收敛有可能是材料本身的问题啊

tonnyw

I think you might need to read my comments again. What I am talking about is the problem of convergence in solving a nonlinear system. I didn't talk about what could be the reasons that might cause the non-convergence.

huahua2005

这种情况如果模型没问题，往往就用ATS解决

wandawei-112

如果用ATS也不行呢，有一种情况就是边界设置是符合物理实际的，但计算往往就很难实现的 ，这个时候考虑的东西真的让人抓狂的

zstqq

ats不行，调一下材料的粘聚力大小，一般变大

naore

7# zstqq
这句有道理

2519200

6# wandawei-112

六楼说得非常有道理，我现在就遇到了流体在墙边界处用ATS计算不收敛的情况，请问六楼遇到这种情况是如何解决的？谢谢！^_^

wild_field

2楼说的既是，不收敛的原因很多，如果以上方法还不能收敛的话，模型自身肯定有问题。

wyx5418

c值加大了，一般能收敛，但是这样就跟工程实际不相符了

wu330324

ATS是什么啊