mesh merge后运行出现错误，需要定义实体截面属性。如何改?

mesh merge后运行出现错误：ELEMENT SET ASSEMBLY_B_SET-13-MERGE REQUIRES A *SOLID SECTION PROPERTY DEFINITION IN ADDITION TO THE *RIGID BODY PROPERTY DEFINITION。可是merge后的part中定义了SOLID SECTION PROPERTY ，见图。小白一枚，求大家指正。谢谢！