请问这个是什么原因造成的？There are 5972 small equation solver pivot term

*** WARNING *** CP = 16.047 TIME= 18:54:39
There are 5972 small equation solver pivot terms.
*** WARNING *** CP = 19.703 TIME= 18:54:42
There are 9836 small equation solver pivot terms.
*** WARNING *** CP = 23.453 TIME= 18:54:44
There are 5202 small equation solver pivot terms.
*** FATAL *** CP = 25.078 TIME= 18:54:46
The supplied nonlinear material properties produced an incorrect
material tangent matrix. Please check your TB input carefully. A
very small yield stress may cause this failure.
计算的时候出现这些错误，请高手解释一下为什么？多谢！