I want to implement a new user element using the UEL subroutine. To simulate dynamic cases, one has to define the mass, damping and stiffness matrix then build the RHS and AMATRIX as defined by abaqus.
The stiffness matrix K is obtained by integrating the material tangent matrxis (DDSDDE) over the element’s volume.
My questions are the following:
-UEL having no argument for stress and strain (STRESS,STRAN…Dstran), do i have to define them my self? (by derivative of the displacements U,DU ?
-The tangent material matrix (DDSDDE) being strain and stress dependent, i need to define the stresses and strains in the UEL, then i need to call the UMAT to return DDSDDE. Do i also have to perform Newton raphson itterations to correct for non linearity? (in umat this would have been done by abaqus itself, but when i call umat inside uel i am not sure…)