Influence of Tool Plunge Depth During Friction Stir Spot Welding of AA5052-H32/HDPE/AA5052-H32 Sandwich Sheets
Metal/polymer/metal multi-layered materials have shown promising properties because of lightweight characteristics in automotive industries. Joining of these materials is difficult by conventional methods due to large difference in their physical and chemical properties. In the present work Friction Stir Spot Welding (FSSW) of AA5052-H32/HDPE/AA5052-H32 sandwich sheet is done. The objective is to analyse the influence of tool plunge depth on the joint behaviour. This is accomplished through joint characterization by evaluating mechanical performance, hook and flash formation, grain size, temperature measurement, and hardness distribution. Lap shear test, cross-tension test, peel test, and uni-axial tensile tests are conducted. A comparison between bimetallic and sandwich sheet has also been done. First, for joining sandwich sheets, the optimum plunge depth is 3.6 mm and greater. Adequate joint strength and extension at failure are obtained in this range. The joint strength does not depend on hook geometry, rather it depends on bond width and joint hardness. Second, though the joint strength of sandwich sheets is reduced as compared to bimetallic, the flash formed is minimised in sandwich sheets. The deformed material gets accommodated in the core layer region to reduce the flash formation. Finer grains are seen in sandwich sheet due to lesser peak temperature. Nugget pull out failure is commonly seen after testing and is independent of test method and the plunge depth.
KeywordsSandwich sheets Spot welding Joint strength Hook Temperature Mechanical tests
Authors thank CIF, IIT Guwahati for extending the universal testing machine facility for testing the joints. The authors also thank Department of Science and Technology, India for funding a FIST project (ETII-244/2008) by which the infrared camera was procured and used for temperature measurement. The present work is not funded by any funding organisation
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