An eight-node 24-DOF nonconforming brick element is developed. It contains nine internal modes, including quadratic and cubic forms, wherein each local coordinate component is at most quadratic. The reverse adjustment to patch test is applied to quadratic modes to eliminate shear locking. To rectify the ill-condition of the element stiffness matrix caused by irregular element shape such as large aspect ratio, a modified regularization method is introduced. It is based on Riley's series expansion of the solution to the ill-conditioned linear system and is coupled in the condensation procedure of the internal degrees of freedom. With the regularization parameter = 10 −3 , the first three terms are enough, which are achieved by two additional refinements in addition to the initial value. To validate the accuracy and robustness, a variety of linear benchmark tests is conducted on solid, beam, plate, and shell structures. The results are in good agreement with the reference solutions, provided the mesh is not too coarse or distorted. The overall performance implies that the new element is competitive with almost all the elements cited, including solid, solid-shell, and shell elements, and is a potential one-size-fits-all solution to linear structure problems.
KEYWORDSill-conditioned linear system, nonconforming element, regularization, reverse adjustment Int J Numer Methods Eng. 2019;119:361-382.wileyonlinelibrary.com/journal/nme