abaqus提示错误？ improperly defined surface(s).？ 200

4 improperly defined surface(s). Please check your surface definitions. Make sure that all surface normals point outward.

Abaqus/Explicit Packager exited with an error - Please see the  status file for possible error messages if the file exists.

这种错误应该从哪下手解决呢？怎么在abaqus里面查看surface normals？谢谢