SWAP-9, 1-D Stress Analysis for Hydrostatic and Elastic Plastic Materials

1 - Description of problem or function: SWAP9 is a computer program for solving stress-wave problems in one-dimensional strain. It handles both hydrostatic and elastic-plastic materials, can incorporate such effects as work hardening, changes in elastic constants, and yield strength with pressure and internal energy, and spall at a given tensile stress. SWAP9 can also treat detonations, gases, and vaporization of solids resulting from radiant energy deposition. 2 - Method of solution: SWAP9 uses the method of characteristics approach to the solution of hyperbolic partial differential equations which represents all wave shapes by a series of shock waves. The program is given a set of initial conditions consisting of a mathematical description of all lines existing on the x,t plane plus the equations of state of the materials involved. One line must be specified for each shock, interface, and free-surface. After solving the initial interaction, the program modifies its picture of the x,t plane to fit the new conditions, then solves for the next interaction in the time sequence, etc. The equations for solving the various interactions are derived from the conservation equations for mass, momentum, and energy across an one-dimensional shock front. 3 - Restrictions on the complexity of the problem: The basic assumptions about the nature of the problem to be solved are: (a) Only one dimensional motion in rectilinear coordinates is present, i.e., the components of material velocity in the lateral direction are zero at all times. (b) The materials of the problem are strain-rate independent. (c) The materials obey either hydrodynamic or elastic-plastic theory, assuming either Von Mises' or Tresca's yield criterion. These criteria are identical under one dimensional strain conditions. A maxima or 25 different materials is allowed with up to 50 constants for each material. The maximum number of lines active on x,t plane at any given time is 300