I’m working on a “thermal shock” analysis of piping to investigate the transient stress through the pipe wall when severe convection loads are applied to the inside surface. In this case the stresses vary in the radial direction, but not in the circumferential direction (axisymmetric, assuming convection load htc does not vary around the pipe)). For the axial direction, the pipe is considered to be long. so that it can grow/shrink axially, but a plane cutting through the pipe cross section would remain planar (ie, axial strain is constant but non-zero). This fits the definition of generalized plane strain in the axial direction.
If I analyze this by considering a pie-shaped 3D section of some length in the axial direction (ie a segment of a ring of pipe), the boundary conditions on the circumferential planes are essentially symmetric and is easily done. However, with the boundary conditions available in simscale, I’m having some trouble implementing the axial generalized plane strain condition. Note the direct strain must be constant across the section, so the z displacement of each node on that face must be the same. However, the magnitude of that displacement is not known in advance so a fixed boundary condition is not applicable.
How would one implement appropriate boundary conditions for this scenario?