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The autofrettaged thick-walled tube containing semi-elliptical crack is investigated. To study the variation of stress intensity factor on crack front, at first, two dimensional weight function is extracted. Stress intensity factor of all points on crack front can be calculate using proposed weight function, also, the complicated loading on crack faces including the loads due to axial gradient pressure in short cylinder and open-end tubes can be considered. Results show that, opposite of the cylinder subjected to uniform pressure, in pipes under gradient pressure, the maximum stress intensity factor are not necessarily on deepest point and surface points. The maximum stress intensity factor occurs on non-surface points in autofrettaged tubes. The results obtained from two dimensional weight function method have a good accuracy with the results obtained from finite element method. Prediction of fatigue crack configuration using two dimensional weight function can be more accurate than those obtained from one dimensional weight function.

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A family of rotating disks used in Iranian turbine and compressor industry is investigated. Mechanical and thermal loads due to working condition would lead to the crack initiation in the inner surface of the disk. The aim of this paper is the development of the two-dimensional weight function for the rotating disks containing semi-elliptical longitudinal cracks. The general form of the two-dimensional weight function is related to the proposed weight functions for embedded cracked domain in literature. In order to determine the unknown coefficient of the weight function, the reference stress intensity factors for cracked geometry subjected to reference loads are calculated. The analysis indicated that the results are independent of the number of terms in proposed weight function expansion. Extracting the weight function for disks with from 90 to 420 mm thickness enables one to predict the stress intensity factor for cracks in the structure subjected to arbitrary loading. The stress intensity factor for each point on the crack front subjecting to one or two dimensional loads would be calculated using the derived weight function. The results reveal that the increasing of the height to thickness ratio in rotating disks leads to the increase of the stress intensity factor for high depth ratio crack ones. Results show that the configuration of the disk sections affects the stress intensity factors of the same aspect ratio cracks in the structures. The comparison of the results obtained from the weight function method and those obtained with FEM are in good agreement.

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In this paper, the static stiffness and strength as well as fatigue life of adhesively bonded single lap joint (SLJ) are numerically studied using the cohesive zone model (CZM). In order to simulation of the SLJ using mixed-mode bi-linear CZM, the failure behavior of adhesive in modes II and III is considered the same. Fatigue damage propagation is simulated through scripting USDFLD Subroutine in ABAQUS/Standard. Static stiffness and strength and fatigue life obtained in this study are consistent with experimental results available in literature. Then, the effect of geometric parameters including overlap length, substrate thickness, and tapered substrates are investigated. The obtained results reveal that the increase of the overlap length would lead to increase the static strength and fatigue life prediction. While increasing substrate thickness results improved fatigue life, there are no a known relation between the static strength and substrate thickness due to the changes of the loading modes. Tapered substrates have also positive effect on the strength and fatigue life because of more compatible rotations. Therefore, to improve the strength and fatigue life of a SLJ, authors suggest greater overlap length and thickness along with tapered substrates.

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In this paper, the constrained groove pressing (CGP) process of Al 5052 sheets are experimentally and numerically studied. The CGP process produces the micro-grained-size sheets to enriched strength nano-grained-size ones. The goal of this investigation is the development of an algorithm for the mechanical behavior (Strength and Hardness) prediction of the sheets fabricated by the process. The algorithm enables one to evaluate the die geometry and pressing pass definition effects on mechanical behavior of the fabricated sheet. The proposed algorithm is based on the available relation in literature between the macroscopic behavior and the grain size in metal sheets and between the hardness and the strength properties of metal sheets. The Al 5052 samples are fabricated by two passes of the CGP process. The yield strength and the Vickers hardness of the annealed, the one and two pass CGPed samples are experimentally obtained. The predicted results by the developed algorithm are in good agreement with the experimental data. The comparison of the predicted results by the algorithm with available experimental data for the mechanical behavior of the CGPed pure aluminum sheets with different dies reveals the good accuracy of the proposed algorithm. The algorithm enables one to economical save from the time-consuming experimental evaluation of groove geometry effects on the fabricated sheets and optimum die selection. The effects of the die groove angle on the yield strength and the hardness of the CGPed Al 5052 sheets are estimated using the developed algorithm.