最近模拟木材受力问题，把材性输进去一运算就报错，下面是报错内容：
The stress-strain matrix of material 1 is not positive definite, which
is required for real materials. Being positive definite means that
1.0 - NUXY**2*EX/EY - NUYZ**2*EY/EZ - NUXZ**2*EX/EZ -
2.0*NUXY*NUYZ*NUXZ*EX/EZ must be positive, but is equal to -5.8046.
Consider reducing the Poisson's ratios.

EX = 1.22E+10 EY = 1.22E+09 EZ = 610000000
NUXY = 0.2 NUYZ = 0.43 NUXZ = 0.47
GXY = 915000000 GYZ = 219000000 GXZ = 732000000.
请问高手这是什么原因？材性是别人用过的，应该不会错，高分求救!