NODAL FORCE BASED FINITE ELEMENT METHOD AND ITS APPLICATION IN DURABILITY ANALYSIS

摘要

In the conventional finite element methods, the stresses are obtained from the computed nodal displacements and are thus a derived quantity, which is not accurate. Additionally, equilibrium of resulted element stresses is, in general, not satisfied at every point in the conventional finite element solutions, which is one of the major reasons for severe mesh-sensitivity in stress or strain results. However, the equilibrium of nodal force is always guaranteed in all finite element solutions regardless of mesh sizes. This equilibrium of nodal force provides a good way to recovering stress with improved accuracy, and various methods, including the currently widely used structural stress procedure for fatigue life assessment, have been proposed with varying degrees of complexity and success. In this paper, a new post-processing procedure is proposed to calculate surface traction stress for 3-D solid elements in terms of nodal forces from the conventional commercial finite element analysis software, such as Abaqus and Nastran. The applicability and limitation of the nodal force based method is demonstrated by applying it to two-dimensional and three-dimensional linear elastic continuum solid elements. Finally, its application in durability analysis such as fatigue and creep life assessments is discussed.