abaqus裂纹扩展约束问题？ 50

这是警告信息

***WARNING: SOLVER PROBLEM.  ZERO PIVOT WHEN PROCESSING ELEMENT 777 INSTANCE 

             PART-1-1 INTERNAL NODE 177683 D.O.F. 1

  Typically a zero pivot is associated with an overconstraint in the model. 

 However, Abaqus was not able to identify any chains of constraints that might 

 lead to an overconstraint at this node. This suggests that the model might be 

 insufficiently constrained. Please check the constraints used in this model. 

 ***WARNING: SOLVER PROBLEM.  ZERO PIVOT WHEN PROCESSING ELEMENT 777 INSTANCE 

             PART-1-1 INTERNAL NODE 177683 D.O.F. 2

  Typically a zero pivot is associated with an overconstraint in the model. 

 However, Abaqus was not able to identify any chains of constraints that might 

 lead to an overconstraint at this node. This suggests that the model might be 

 insufficiently constrained. Please check the constraints used in this model. 

我查阅了，警告的单元都是在XFEM预置裂纹的地方，此处在进行仿真的时候是没有施加约束的

这是什么原因？

是模型的原因嘛？还是裂纹预置的不对