When you import a solid part, ABAQUS/CAE tries to create a closed solid part. Similarly, when you import a shell part, ABAQUS/CAE tries to create a connected shell part. If the part is imported successfully, the part is considered valid and precise. However, if the precision of the original part is less than the precision used by ABAQUS/CAE, the part may be imprecise or invalid. In most cases you can continue working with an imprecise part; however, you cannot work with an invalid part.
The terms “imprecise” and “invalid” are described in more detail below.
Imprecise
A valid part can be either precise or imprecise. If ABAQUS/CAE must use a looser tolerance in some areas to recreate a closed volume from the imported part, the part is considered imprecise. You can complete most modeling operations with imprecise parts. In addition, parts with imprecise geometry can be meshed with triangles, tetrahedral elements, and quadrilateral elements using the advancing front algorithm.
You should try to work with an imprecise part. If ABAQUS/CAE cannot proceed, you can suppress the imprecise region or use the geometry repair tools to try and make the part precise. However, if the part contains many complex surfaces, the geometry repair tools may not be able to make the part precise and using the tools may be time consuming. If you cannot work with the imprecise part and you cannot make the part precise, you should return to the CAD application that generated the original file and increase the precision.
Invalid
If the errors are so large that ABAQUS/CAE cannot recreate a closed volume from the imported part, the part is considered to be invalid. For example, large gaps between edges cause a part to be invalid. Similarly, points on edges that are far away from an underlying surface cause a part to be invalid.
If the part is invalid, you can use a combination of the Query toolset and the Repair toolset to try to make it valid. In general, a part that cannot be made valid cannot be used by ABAQUS/CAE, and you should return to the CAD application that generated the original file and attempt to fix the geometry. The only way that you can use an invalid part in ABAQUS/CAE is to apply a display body constraint to the part in the Interaction module. A display body is included in the model for display purposes only. If you apply a display body constraint, you do not have to mesh the instance and can continue to analyze your model. For more information, see “Modeling display bodies,” Section 21.5.