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Soft Flange B-pillar
2014 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This report is a master thesis conducted at Gestamp HardTech in Luleå. Gestamp HardTech has invented and developed the press hardening technique, which enables the manufacture of ultra high strength steel components. The products that are produced are used for the high demanding safety components of cars, where both low weight and high strength are desired.In this thesis a B-pillar is analysed, which is one part of a cars safety structure. The B-pillar is located in the middle of the car, between the front- and passenger door, and its main function is to protect and minimize injuries at a side impact. As the passengers sit relatively close to the side structures of a car, not much intrusion can be allowed before there is a risk of injury. As of this, B-pillars are made very strong and are many times reinforced. A stiff structure does however increase the risk for cracks, which are not tolerable as they will drastically reduce the load carrying ability of the component, resulting in an unsafe car. Spot welds are areas where cracks are most likely to be seen, as their properties cause strain localization, ultimately leading to material failure.The purpose of this master thesis is to investigate how cracks at the welds can be eliminated with the use of a heat treatment method named “soft zones”. As the name suggests the method implies that specific zones are heated up around the welds, decreasing the hardness. This changes the microstructure of the steel and prohibits strain localization. Various designs of these soft zones have been simulated and the results from this report show that soft zones can be used to eliminate the risk for cracks. Depending on the size of the zone, the resistance against cracks can be determined. Large zones will eliminate cracks completely, but will also decrease the load carrying ability of the B-pillar. However, simulations also show that if the zones are made smaller it is possible to increase the resistance against cracks, without losing any significant performance.

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URN: urn:nbn:se:ltu:diva-52673Local ID: 9c661423-8c74-4b6e-a73a-895c35918600OAI: diva2:1026044
External cooperation
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20140731 (global_studentproject_submitter)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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