The numerical method based on thermal viscoelastic contact theory was studied.It provided a convenient method to judge whether interface debond occured or not.A solid motor grain structure was taken as an example

and contact arithmetic was applied to simulate multilayer complicated boundary of solid motor grain structure.Strain field was computed under flight condition

and distribution rule of interface stress between case and insulation was researched.Results show that strain field contour agrees with the fact.Interface between case and insulation is ideal and is unable to debond.