Figure 1: Extent of creep cavity at various stresses and strains (a,c,e,g,i,k) – 50 MPa and (b,d,f,h,j,l) – 68 MPa for the top tube. True strain at (a)1.187,(c)0.897,(e) 0.626, (g) 0.525,(i) 0.398 and (k) 0.359.(b) 0.781,(d) 0.652,(f) 0.565,(h) 0.40,(j) 0.244 and (l) 0.149 [14].