한국해양대학교

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핫스탬핑강의 너트 프로젝션 용접 시 너트 재질이 용접부 파단모드 변화에 미치는 영향

Title
핫스탬핑강의 너트 프로젝션 용접 시 너트 재질이 용접부 파단모드 변화에 미치는 영향
Author(s)
임성상
Keyword
Nut projection welding, Hot stamped steel, Carbon steel nut, Boron steel nut, Failure mode, Shrinkage cavity
Publication Year
2017
Publisher
한국해양대학교 조선기자재공학과
URI
http://repository.kmou.ac.kr/handle/2014.oak/11374
http://kmou.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002330830
Abstract
The use of materials for modern lightweight auto-bodies is becoming more complex than hitherto assemblies. The high strength materials nowadays frequently used for more specific fields such as the front and rear sub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It is desirable to use nuts attached to the assembled sheets by projection welding to decrease the number of loose parts which improves the quality. In this study nut projection welding was carried out between a nut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the joints were characterized by optical and scanning electron microscope. The mechanical properties of the joints were evaluated by microhardness measurements and pull-out test. An indigenously designed sample fixture set-up was used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed the dominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity and small size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardness of HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengths and superior weldability. Hence the fracture load and failure mode characteristics can be considered as an indication of the weldability of materials in nut projection welding.
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기계공학과 > Thesis
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핫스탬핑강의 너트 프로젝션 용접 시 너트 재질이 용접부 파단모드 변화에 미치는 영향.pdf Download

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