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In this paper, an experimental investigation of fatigue crack growth behavior and fatigue life of Coach Peel (CP) specimens is reported. In this investigation, the CP specimens with 1 and 1.5 mm thickness and from mild steel are used. Specimens are tested by a 25 kN capacity INSTRON 8802 servo-hydraulic fatigue test machine under constant amplitude but various level loadings. During loading, the crack length and cycle numbers are measured accurately by a 100X light microscope. Initiation and propagation of spot weld specimens are measured by drawing vertical displacement of the specimen’s vs cycle’s curves. Results show that initiation and propagation of cracks often occur in the plate with less thickness. Also in low level loadings, cracks propagate longtitudinaly, but in high level loadings, usually nugget pull out and joints, fail catastrophically. The crack lengths during propagation, are nearly unique in both plates with the same thickness.

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In this paper, an experimental investigation of fatigue crack growth behavior and fatigue life of Coach Peel (CP) specimens is reported. In this investigation, the CP specimens with 1 and 1.5 mm thickness and from mild steel are used. Specimens are tested by a 25 kN capacity INSTRON 8802 servo-hydraulic fatigue test machine under constant amplitude but various level loadings. During loading, the crack length and cycle numbers are measured accurately by a 100X light microscope. Initiation and propagation of spot weld specimens are measured by drawing vertical displacement of the specimen’s vs cycle’s curves. Results show that initiation and propagation of cracks often occur in the plate with less thickness. Also in low level loadings, cracks propagate longtitudinaly, but in high level loadings, usually nugget pull out and joints, fail catastrophically. The crack lengths during propagation, are nearly unique in both plates with the same thickness.

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In sheet metal forming processes, one of the most important limitations relates to the elastic recovery after punch unloading, which usually leads to spring-back phenomenon. Production of precise parts without spring-back controlling is not possible. Hence, the main aim of the present research is to minimize the amount of spring-back as well as to prevent the crack initiation during bending process of Aluminum A1050-H14 sheet. For this purpose, firstly, the sheet metal bending process was numerically simulated in ABAQUS finite element package. Then, the effect of friction coefficient and punch velocity was investigated on elastic recovery and von Mises stress in order to minimize the spring-back as well as to prevent the crack initiation. In this regard, python programming language was utilized. Then, by linking multi-objective genetic algorithm and finite element method in modeFRONTIER software, the optimum values of the process parameters were determined. It should be mentioned that for validation purposes, the simulation results of the present study were compared with the experimental data available in literature, showing a 3.14% relative error between the numerical and experimental results.