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Study of fatigue loads in spot weld joints for a side impact beam
2007 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Gestamp HardTech develops and produces press-hardened safety components in boron steel for the passenger car industry. During door slam testing performed by a car manufacturer, the front door is opened and closed 100 000 times. If the spot welds joining the Side impact beam with the inner panel receive too high stress levels during this test, fatigue fracture will occur. Today, one or two additional weld tabs are often applied to the rear joining position to handle the fatigue loads. The drawback with this design is that the shear tabs are driving the blank size. There are also manufacturing difficulties associated to the shear tab design. The purpose of this thesis is to, by simulation loops, find a design of the rear end of the Side impact beam, including positions- and number of welds, that provides equal or better fatigue resistance as a “shear tab” design. The fatigue life is evaluated through FE-simulations of the door slam where the fatigue parameter called Equivalent structural stress is determined for each spot weld. This parameter is analytically calculated from the spot weld forces during Post-processing. The thesis has also included fatigue testing of spot welded specimens for determination of material data used in the formation of Equivalent structural stress. The results show that by changing the placements of the welds and by minor changes of the Side impact beam, the Equivalent structural stress in the most critical weld is reduced to the same level as when a shear tab is present.

Place, publisher, year, edition, pages
Keyword [en]
Keyword [sv]
URN: urn:nbn:se:ltu:diva-46772ISRN: LTU-EX--07/110--SELocal ID: 46435185-e9ba-49c2-8529-63032634f5c1OAI: diva2:1020087
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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