Hi everyone,

I am working buckling analysis of imperfection sensitive cylindrical shell under axial compression my problem is that i want study the effect of buckling and collapse load on the geometric imperfection so initially i carried out the eigen buckling analysis of shell with unit load calculated the buckling load at first mode shape which matched with my analytical equation of shell this is being carried out in model-1 and  i copied the model just changed the step gave static riks i made the analysis to run give that load is buckle load of first mode shape gave imperfection by superimposing 3mode shapes 0.2mm on first mode,0.1,0.5mm scale factor after 100 increments my structure did not collapse but stresses are induced there is no collapse can you please suggest me some idea how to solve this problem.