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    A Comparative Study on Fatigue Life Prediction of Spot Welded Coach Peel (CP) and Modified Coach Peel (MCP) Type Test Specimens
    (Springer Science and Business Media Deutschland GmbH, 2021) Akbulut, M.; Ertaş, Ahmet Hanifi
    Besides friction, ultrasonic and laser welding, resistance spot welding is extensively employed for joining sheet metal panels in automotive, railroad and aerospace industry as a reliable, cost-effective, and flexible manufacturing process. Structural panels attached through the spot welding usually undergo cyclic loadings in service, which cause fatigue fracture damage. In order to predict and prevent this type of failure, an in-depth assessment of the fatigue phenomenon is inevitable. In this study, a strain based model known, as Coffin-Manson is adapted to estimate the S–N diagram of various materials, for the first time, on Coach Peel (CP) and Modified Coach Peel (MCP) Type Test Specimens. The strain values used in the model are computed through the FEM analysis. The results obtained in the present work are compared with those of alternative models and experimental data available in literature. Consistencies and discrepancies among the results are presented and interpreted. © 2021, Springer Nature Singapore Pte Ltd.
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    An Experimental Investigation into the Fatigue Behavior of Spot Welded Tensile Shear (TS) Specimens
    (Springer Science and Business Media Deutschland GmbH, 2021) Ertaş, Ahmet Hanifi; Akbulut, M.
    The resistance spot welds (RSWs) are extensively used in many industries especially automotive industry as a joining process of sheet metals due to its flexibility and adaptability to automation. In addition to easy automation capability, there are many more advantages that this joining process offers in the attachments of thin sheet body components, such as effectiveness, low cost and reliability. Despite all the favorable properties of this manufacturing process, the spot welded sheet metals are prone to mechanical fatigue failure especially under cyclic sinusoidal loadings. Therefore, understanding and elucidating the fatigue phenomenon of the RSWs are crucial during the design phase, in terms of estimating and preventing undesired failure conditions. However, in the design procedure, there exist considerable amount of challenges to be overcome to analysis and accordingly predict the fatigue failure in the sheet metals connected by spot welds, among them it can be counted electrode wear-down, non-uniform sheet metal forms, defected or incomplete weld nuggets. Many of these faults cause non-uniform stress distributions inside the sheet metal and make it difficult to estimate fatigue failure. Thereof experimental work, in most cases, shines as a viable option in the fatigue analysis. Within the scope of this work, an attempt is made to examine the fatigue phenomenon of the spot welded sheet metals experimentally. For this purpose, tensile shear (TS) type spot welded test specimens were utilized. A series of fatigue life tests were conducted on the previously prepared samples and the deformed test specimens were examined. The experimental results were compared with those of similar research studies available in the literature. It was observed that the outcomes of the present work are reasonably consistent with the literature results. © 2021, Springer Nature Singapore Pte Ltd.
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    A Fatigue–Reliability Analysis of Spot Welded Modified Tensile Shear (MTS) Specimens
    (Springer Science and Business Media Deutschland GmbH, 2021) Ertaş, Ahmet Hanifi; Akbulut, M.
    In sheet metal structures, generally the resistance spot welds (RSWs) are used as a joining method especially for its adaptability to automation, effectiveness, robustness and low cost. On the other hand, the spot-welded sheet metals operate, most of the time, under cyclic loading conditions, which lead to fatigue fracture in the structure. In order to predict and prevent fatigue damage in the spot-welded sheets properly, many factors which affect the quality of welds in the design phase are to be considered such as arbitrary shapes of the sheet metal, missing or incomplete spot welds, and abrasion of the welding electrodes etc. All these disadvantages cause deviations in the stress analysis and make it very hard to obtain uniform stress distributions. Hence deterministic computational approaches, even pure experimental investigations of spot welded structures, do not always result in reliable outputs. In that case, probabilistic approach appears to be a feasible alternative in the fatigue assessment of RSWs. In this study, a probabilistic fatigue analysis is carried out on spot welded modified tensile-shear (MTS) test specimens. In the probabilistic analysis a g-function was introduced for each case study. The results obtained through aforementioned method were shown to be in good agreement with the related studies in literature. © 2021, Springer Nature Singapore Pte Ltd.