NAFEMS Benchmarks for Plastic Collapse of Square Metal Plates

Benchmark problems with either known theoretical solutions or, alternatively, numerical solutions of sound provenance are of importance to the practising engineer. They are used to verify the finite element system that the engineer is using and also enable him/her to determine the level of mesh refinement required to capture the structural response to the level of accuracy required. NAFEMS offers a range of benchmark problems in their publications together with finite element solutions to the problems. In checking NAFEMS benchmark problems for the plastic collapse of metallic plates, the author found that not only were the reference solutions incorrect but also the finite element solutions provided were insufficiently converged. The reasons behind these issues are explored in this article and provide an interesting illustration of the level of care required when preparing and publishing benchmark problems. The author is a member of the Education & Training Working Group at NAFEMS and has informed the organisation of the errors in their benchmark. NAFEMS will reference this publication in an updated version of the publication containing this benchmark.