Issue 48

M. Laredj et alii, Frattura ed Integrità Strutturale, 48 (2019) 193-207; DOI: 10.3221/IGF-ESIS.48.21 203 maintain value of the degree of expansion between 3 and 4%, the thickness between 3 and 6 mm and to keep the yield strength between 345 and 430 MPa. Figure 12 : prediction of maximum compressive residual stress as a function of the three factors In the last of interaction analysis, we focus on the compressive residual stress zone variation according to the three factors as shown in figure (13). The results clearly show that the increase of the degree of expansion and the thickness cause to a larger area of the CRSZ. However the reduction of the yield strength leads to an increase of this zone. Figure 13 : prediction of the compressive residual stresses zone. By introducing the results in the MODDE 5.0 software to examine the different effects, the results given in FIGS. 14 and 15 corresponding respectively to the maximum compressive residual stress and the compressive residual stress zone were obtained. The effects of factors are presented using a bar graph. This diagram gives the effects in descending order of their importance in absolute value. Figure 14 : Effects of factors on MCRS. The analysis of these figures shows that the classification of dominant factors on the maximum compressive residual stresses is as the following: (Ys), (t) and (Ce). On the other hand, for the case of the compressive residual stresses zone and the other points of the residual stress profile, the order of dominant factors are as following: (Ce), (Ys) and (t).