Fracture toughness is a criterion to determine the resistance of materials against small longitudinal and peripheral cracks, which can be created in the effect of welding or peripheral effects. Therefore, it is extremely important to scrutiny the factors that impress crack treatment and the way that it grows. In this research, fracture toughness was investigated on the peripheral welding zone in gas and oil transfer pipelines made in steel API X65. The fracture toughness is derived by using two different methods. At first, the three-point bending test method was used on samples that made up of the peripheral welding zone. Then, with a numerical simulation it was calculated by ABAQUS software v6/10. The comparison of experimental results and computer simulation results shows good agreement from two methods. The fracture toughness of the welded zone, obtained in this study, was compared with that of the base metal. The results showed that fracture toughness on the welding zone in gas and oil transfer steel pipelines decreased 43% compared to the base metal. This issue shows that peripheral welding on gas and oil transfer pipelines has more talent for crack growth compared to the base metal. Manuscript profile

A model is provided for crack problem in a functionally graded semi-infinite plate under an anti-plane load. The characteristic of material behavior is assumed to change in a linear manner along the plate length. Also the embedded crack is placed in the direction of the material change. The problem is solved using two separate techniques. Primary, by applying Laplace and Fourier transformation, the governing equation for the crack problem is converted to the solution of a singular integral equation system. Then, finite element technique is employed to analyze this problem by considering quadrilateral eight nodded singular element near the crack tips. The effects of material non-homogeneity and crack length on the stress intensity factor are studied and the results of two methods are judged against each other. Manuscript profile

In the present research, the mixed-mode fracture mechanics analysis in a plate with central hole under tensile loading is considered. It is assumed that a plate containing two symmetrical hole-edge cracks is bonded with two dissimilar planes. The stress intensity factors at the crack tips are calculated. The problem is modeled in Casca software and this model is analyzed with Franc software. The effects of various factors such as hole diameter, crack length, angle of crack and material properties of plates have been investigated on stress intensity factors. The stress intensity factors increases with increasing crack length. Also, the stress intensity factors increases with the increase of hole diameter. For a certain amount of for small crack lengths the effect of cracks length on variation of stress intensity factors is more than the hole diameter but for large crack lengths the effect of hole diameter on variation of stress intensity factors is more than the cracks length. Manuscript profile

In the current research work, the problem of fracture mechanics in a plate with a central hole under tensile loading is studied. The stress intensity factors are calculated for a finite plate containing two symmetrical hole-edge cracks. The problem is solved by two different methods, namely the finite element method and the FRANC software analysis. At first the finite element method is used and by writing a program in MATLAB software the stress intensity factors at the crack tips are calculated. The same problem is then reanalyzed with the Franc software and the results are compared. The effects of various factors such as the hole diameter, crack length and crack angle have been investigated on stress intensity factors. The results show that for small crack lengths, the effect of cracks length is more than that of the hole diameter on variation of normalized stress intensity factors, while it is the opposite for large crack lengths, the effect of hole diameter is more than that of the cracks length on variation of normalized stress intensity factors. Manuscript profile

In this research, the failure of a stud bolt was studied. This bolt is under periodic loading, in a multi-stage compressor. The undesired vibration of the system causes vibration load on the bolt. The bolt was modeled in Abaqus software and the generated stress was calculated. To determine the dynamic load on the bolt, the vibration of the system was measured by a digital vibration sensor and this load was simulated in Abaqus software. The boundary condition and loading were considered similar to the real working condition. The failure and fatigue of the bolt was investigated in the periodic loading. The factors such as the shank diameter, chamfer radius and material were changed and the corresponding response of sample and change in stress was studied. The most probable points of the bolt for failure were found and the effected of the reduced shank diameter on its life was considered. In the initial design, the shank diameter was considered 12 mm. The results shown that by decreasing the shank diameter, the stress first decreases and then increases and the minimum of stress occur at the shank with a diameter of 11.47 mm. Also, by increasing the chamfer radius, the stress first increases and then decreases and the minimum of stress occurs at the chamfer radius of 33 mm. Manuscript profile