TANGENT STIFFNESS PROPERTIES OF FINITE-ELEMENTS

Original tangent stiffness matrices have been developed explicitly for a triangular and rectangular finite element, by which both the speed of computations and the degree of accuracy are increased. The new tang ent stiffness matrices developed in this study represent the final con ditions of the material, such as the most recent deformed geometry, th e current total stress level, the amount of plastic strains present, a s well as the current material constants in the form of either the tan gent or secant modulus of elasticity. The method of development is so general that the comprehensive tangent stiffness matrices may be devel oped for any other finite element type, such as arbitrary quadrilatera ls, prisms, curvilinear elements, etc.