TY - JOUR JF - mdrsjrns JO - Modares Mechanical Engineering VL - 15 IS - 4 PY - 2015 Y1 - 2015/6/01 TI - Study the effect of autofrettaging of functionally graded cylinder on the surface crack parameters using numerical discretizing of stress fields TT - بررسی تاثیر فرآیند اتوفرتاژ در استوانه با مواد تابعی مدرج روی پارامترهای ترک سطحی با استفاده از گسسته سازی عددی میدان تنش N2 - In this paper, the variations of the stress intensity factor and energy release rate have been investigated based on the displacement correlation and modified crack closure integral methods for external surface cracks in the autofrettaged functionally graded cylinder (FGC). Mechanical properties vary in the radial direction according to the desired function. Isotropic material behavior and bilinear elastoplastic stress-strain relationship are considered for the FGC. Autofrettage process induces the tensile residual stresses in the outer parts of the cylinder wall, which causing the undesirable effects on the external surface cracks. Many variables affect the distribution of tensile residual stresses. Effects of autofrettage ratio, volume fraction of material and cylinder thickness on the residual stress changes and addition, changes in the size and direction of surface cracks on the stress intensity factor and energy release rate are studied. The results show that the volume fraction has the greatest effects on both crack parameters. The axial cracks are critical in compared with circumferential and angled cracks. The principle of superposition can be used to determine the combinational effects of the residual stresses and applied loads on the behavior of cracks in the graded materials. SP - 255 EP - 264 AU - Seifi, Rahman AU - Dejam, AliReza AD - KW - Autofrettage KW - Residual Stress KW - Stress Intensity Factor KW - energy release rate KW - external surface crack UR - http://mme.modares.ac.ir/article-15-6446-en.html ER -