Downloaded from https://www.everyspec.com APPENDIX C MIL-STD-31000A Data exchange: No impact on data exchange Finite element analysis: Unwanted mesh elements may be produced, extending solutions times. Numerically controlled manufacturing: No impact Recommended correction: Remove the relatively narrow surface and extend or trim one or both adjacent surfaces to close the gap. C.7.2.7. Degenerate surface boundary (G-SU-DC). Definition: Length of the edge of one surface or patch boundary, L, is below permissible minimum. Some CAD systems define a triangular surface by setting one boundary below a specified limit. Effects of condition on CAD data quality: Design or drafting:
No impact if system supports triangular patches. May produce an undefined normal vector in some systems inhibiting offset surfaces, cross sections, fillets, and rounds. Data exchange: Faces may not trim properly. Finite element analysis: Degenerate mesh elements may be produced. Automatic mesh generation may fail. Numerically controlled milling: Tool paths may converge on degenerate edge, producing unsatisfactory results. Recommended correction: If CAD system does not support three-sided surfaces, create an oversized four-sided surface and trim back to three sides. 95