Downloaded from https://www.everyspec.com APPENDIX C MIL-STD-31000A C.7.2.8. Degenerate surface corner (G-SU-DP). Definition: One or more corners of a surface meet at a sharp or tangent angle below acceptable minimums. Measurement: angle between tangents of adjacent surface boundaries at the common endpoint, Δθ Effects of condition on CAD data quality: Design or drafting: May be acceptable if normal vectors at the surface corners are well defined. Undefined normal vectors may inhibit cross sections, offset surfaces, 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 corner, producing unsatisfactory results. Recommended correction: Divide the surface into three or create an oversized surface and trim to the required dimensions. C.7.2.9. Indistinct surface knots (G-SU-IK). Definition: Two or more knot points on a spline curve positioned too close to each other. Measurement: distance between knot points, Δu and Δv Effects of condition on CAD data quality: Design and drafting: Cross-sections, offset surfaces, fillets, and rounds may fail. 96