Finite element analysis of structures with ablating boundaries

An algorithm has been developed which automatically calculates the time-dependent positions of points on the ablating boundaries of two-dimensional continuum structures with geometrically complex shapes. The boundary may consist of ablating and nonablating parts. The initial ablating and nonablating boundaries are defined by the disjoint union of piecewise linear arcs passing through a finite set of nodal points on the boundary, each defined by a pair of rectangular cartesian coordinates. For a specified ablation rate, the algorithm calculates successive positions of the boundary points at times specified by the user. The algorithm is designed such that it may be easily incorporated, along with an automated mesh generation procedure, into existing finite element codes for transient thermal or stress analysis of structures with ablating boundaries. Two examples are presented from the field of solid rocket analysis.