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A numerical simulation technique was implemented to automatically optimize the plunger velocity to reduce the defects occurring during die-casting by considering the number of free surfaces and potential energy of the molten metal. In pressure die-casting, the most common defect is porosity that is formed by air entrapment in the following two stages - the first is the injection of the molten metal into shot sleeve, and the second is the filling of the molten metal into the cavity. The latter phenomenon has been investigated in detail by various numerical simulation codes, but there is limited information concerning the former. In order to the simulate flow pattern in the shot sleeve, a moving boundary method is incorporated into the conventional filling simulation system. In addition, the plunger speed and the acceleration time for the various pre-filled levels of molten metal in the sleeve are determined by automatic optimization.

Friction Stir Spot Welding (FSSW) is an emerging joining technique that has seen some successful automotive applications in the past few years. One of the most significant factors that influence the joint strength of a friction stir spot weld is the tool geometry. The tool geometry used in FSSW has been traditionally derived from friction stir linear welding and there has not been much focus on developing tool geometries specifically for FSSW. The main objective of this paper is to evaluate different pin geometries that are specifically catered towards maximizing the strength of friction stir spot welds. In order to evaluate the effect of only the pin, all tools considered had flat shoulders. Four different pin shapes were evaluated - baseline, thick, tapered and inverse tapered pins. Three different pin lengths were considered for each pin shape - 1.0, 1.2 and 1.4mm.

Experiments were carried out to study the effect of thermal expansion of the tool during Friction Stir Spot Welding (FSSW) of large commercial automotive grade aluminum sheets. The objective of this study was to evaluate the tool “growth” using both experimental and numerical techniques and to see its effect on the weld quality (measured in terms of static strength). Two hundred friction stir spot welds were made over 25 Al sheets (A6022-T4) with a specific time interval between each sheet, thereby trying to simulate the welding conditions/sequence on a production line. An Infrared (IR) camera was used to monitor the temperature gradient on the tool during the welds. In addition, finite element analysis was run to predict the thermal expansion of the tool based on the temperature boundary conditions obtained from the IR camera during the experiment.

Friction stir linear welding (FSLW) is widely used in joining lightweight materials including aluminum alloys and magnesium alloys. However, fatigue life prediction method for FSLW is not well developed yet for vehicle structure applications. This paper is tried to use two different methods for the prediction of fatigue life of FSLW in vehicle structures. FSLW is represented with 2-D shell elements for the structural stress approach and is represented with TIE contact for the maximum principal stress approach in finite element (FE) models. S-N curves were developed from coupon specimen test results for both the approaches. These S-N curves were used to predict fatigue life of FSLW of a front shock tower structure that was constructed by joining AM60 to AZ31 and AM60 to AM30. The fatigue life prediction results were then correlated with test results of the front shock tower structures.

Lightweight metals such as Al and Mg alloys have been increasingly used for reducing mass in both structural and non-structural applications in transportation industries. Joining these lightweight materials using traditional fusion welding techniques is a critical challenge for achieving optimum mechanical performance, due to degradation of the constituent materials properties during the process. Friction stir welding (FSW), a solid-state joining technique, has emerged as a promising method for joining these lightweight materials. In particular, high joining efficiency has been achieved for FSW of various Al alloys and Mg alloys separately. Recent work on FSW of dissimilar lightweight materials also show encouraging results based on quasi-static shear performance. However, coach-peel performance of such joints has not been sufficiently examined.

We characterize the cyclic behavior of an AM30 extruded magnesium alloy. The micromechanisms of cyclic damage were studied by means of strain controlled experiments in both the extruded and transverse directions. A scanning electron microscope (SEM) analysis of the microstructure revealed that second phase particles were present in the Mg alloy that nucleated the cracks. However, crack initiation sites were observed to occur due to profuse twinning. Low cycle fatigue parameters were determined, and a microstructure-sensitive MultiStage Fatigue (MSF) model, which is able to capture mechanical and microstructure properties, was implemented to predict fatigue behavior and failure.