Research is currently being conducted on the feasibility of hydroforming extruded magnesium tubes to integrate multiple parts into a single hydroformed section. Among other advantages, such sections would reduce the weight of both cars and planes, particularly when used in the vehicle frame. This would lead to either reduced fuel costs, or the ability to carry an increased payload. Magnesium generally has limited ductility, which in the case of the current extruded tubes is even further reduced at the extrusion seams. These are locations where the material flow separates and rejoins during extrusion and are unavoidable when a hollow profile die is used. When the tubes are stressed in a circumferential direction by hydroforming, tube ruptures consistently occur along the extrusion seams of the tubes. This has led to the current project, an inquiry into the exact cause of failure at these locations. An overview of the nature of magnesium, including deformation systems is presented and the creation of irregularities at the longitudinal seams of the tube is discussed. The sources of these irregularities are considered together with their roles in producing the failures. The experimental results of cone wedge testing at various temperatures and compression rates are presented and compared to the results of certain free expansion hydroforming trials. Several possible means of improving the magnesium tubes during production are included. The results are summarized and the most fruitful directions for future work are outlined.
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