• 대한기계학회논문집A
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• 제36권8호
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• pp.857-863
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• 2012

본 연구에서는 승객의 안전성을 확보하기 위하여 상부 고강도강 SABC1470, 하부 냉간 압연강 SPFH590과 SPFC980으로 경량화를 위하여 레이저 TWB 용접하였다. TWB 이종재료 시험편은 열처리에 의하여 SABC1470 재료에 고강도화 하였다. 수냉까지 대기 시간에 따르는 인장강도와 센터필라와 같은 부정 조건에 의한 고속 굽힘의 변형 거동을 평가하였다. 동일 온도에서 열처리 된 TWB 시험편은 수냉까지 대기 시간에 따라서 인장강도와 굽힘강도가 감소하였다. $850^{\circ}C$에서 열처리한 SABC1470 + SPFH590 TWB 시험편은 추돌에 의해 차체 파손시 파괴거동을 유도하여 승객을 보호할 수 있는 적절한 조건이었다. 사고에 의한 승객의 안전을 고려하면, 센터필라는 상부재로서 SABC1470, 하부재료로 SPFH590을 사용하는 것이 안전하다.

• 한국레이저가공학회지
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• 제18권2호
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• pp.5-10
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• 2015

A tailor welded blank (TWB) is a welded blank comprised of two or more sheets with different properties - thickness, strengths or formabilities. TWBs are applied to the body panels to reduce weight and cost of the part. In this research, ultra high strength steel and high ductility steel were joined and laser tailor welded blanks were implemented. Yb:YAG laser welding tests were conducted with various welding conditions, and mechanical and geometrical characteristics of weldments were evaluated.

• Journal of Welding and Joining
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• 제33권6호
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• pp.36-41
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• 2015

In the automotive industry, TWB hot stamping process is broadly adapted to reduce weight of the car and improve fuel efficiency. However, the process faces a problem of weakened strength of the welded zone after hot stamping process, due to the fact that Al-Si elements of the coating layer penetrating the welded zone. In this study, filler wires with high percentages of carbon and manganese is adapted during laser welding process to secure the strength of the fusion zone. In addition, wire feeding speed and laser welding speed are optimized by sample test.

• 소성∙가공
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• 제20권5호
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• pp.362-368
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• 2011

For the purpose of improving crashworthiness qualities and maximizing weight saving efficiency, TWB's(tailor welded blanks) of quench-hardenable boron steel sheet formed by hot stamping processes has been used for automotive BIW (body in white) applications. In this work, the flow behaviors of TWB of quench-hardenable boron steel sheet were investigated in uniaxial tension tests at elevated temperature. TWB's having a uniform thickness of 1.4mm were fabricated by laser welding. Specimens with two weld line directions were used to test the mechanical property and reliability of the weld zone. After heating at $950^{\circ}C$ for 5min, the specimens were subjected to tension test at 650, 700 and $800^{\circ}C$ with a strain rate of 0.01 /s and at $700^{\circ}C$ with strain rates of 0.01, 0.1 and 1/s. The ultimate strength of the weld zones was higher than that of the base materials at 650 and $700^{\circ}C$, but was similar to the base metal at $800^{\circ}C$. Fracture occurred at the base material at 650 and $700^{\circ}C$, but at the weld zone at $800^{\circ}C$.

• 한국생산제조학회지
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• 제9권5호
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• pp.80-86
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• 2000

The Tailor Welded Blanks(TWB) are using various materials (different thickness, strength and different materials) can be welded together prior to the forming process. Therefore, TWB applications have become little by little important in automobile industries, because it has more light weight and process reduction. A burnish area is very important for TWB using laser welding. In this paper, evaluated failure criterion, effect of clearance and distance of between pad and punch by computer simulation. We used element separation method for fracture. And applied a plastic strain to failure criterion. According to the analysis results, we obtain failure criterion, when plastic strain is 2.0. The burnish area and clearance were inverse proportional.

• 소성∙가공
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• 제18권1호
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• pp.73-79
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• 2009

In order to investigate the formability of friction stir welded(FSW) tailor welded blanks(TWB) with respect to the base material's directional combination, aluminum alloy AA6111-T4 sheets were welded with three different conjoining types: RD-RD, TD-RD and TD-TD. Here, RD and TD represent rolling and transverse directions, respectively. For experimental formability study, three tests with gradual complexity were performed: the simple tension test with various weld line directions for uni-axial elongation, the hemisphere dome stretching test for biaxial stretching and the cylindrical cup deep drawing test. As a result, all three forming tests showed that RD-RD type samples exhibited the best formability, while TD-TD type sheets showed the least formability performance.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.151-155
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• 2001

The purpose of this study is to investigate the weldline movement of the laser welded sheets during the warm deep drawing process. For this investigation, Five steps of temperature ranges, from room temperature to $200^{\circ}C$, and two kinds of thickness combination, 0.8 mm${\times}$1.2 mm and 0.8 mm${\times}$1.6 mm SCP1 material sheets, were adopted. Also, the numerical analysis using the PAM-STAMP has been carried out with the same models as the specimens. As a result the higher temperature was adopted, the less weld-line movement was observed.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.573-578
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• 2000

Recently, Tailor Welded Blanks(TWB) is widely used in automotive industry since the transformation characteristics of its material can be changed. However, clearance between welding surface becomes the important factor which affect the quality of the laser weld, causing difficulties in preparing the sheet. The objective of this paper is to systematically evaluate the effects of previously presented fracture criterion and shearing condition on precise mechanical shearing simulation result. Also predict the optimum shearing condition, effect of shearing condition such as clearance and punch radius on the shear plane shape was evaluated.

• 열처리공학회지
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• 제25권6호
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• pp.283-291
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• 2012

In order to increase the anti-oxidation property during the tailor welding blanked hot press forming process for a high strength boron steel sheet, we performed a different coating method on the boron-steel sheet such as 87% Al - 13% Si and Fe - 8.87 Zn dipping plating procedure. However, during laser welding process, the Al-Si coated steel sheet has showed a low tensile strength and about half value of elongation than the original boron-steel sheet. Aluminum and silicon, elements of coating layer were diffused into the boron-steel matrix and have shown a low strength result than non-coated specimen. On the other hand, Zinc-coated boron-steel has expectedly showed a excellent tensile strength and micro-harness value in the welded area like original boron-steel.

• 대한기계학회논문집A
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• 제36권8호
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• pp.929-934
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• 2012

본 연구에서는 레이저 TWB로 용접된 이종재료의 동적 특성에 대한 해석이 수행되었다. 해석프로그램은 Hyper works 10.0으로 Solver는 LS-DYNA v.971, 모델링 요소는 2D-Shell, 요소 수는 35,641개, 노드 수는 36,561개이다. 충격속도는 10 km/h이다. 상 하부의 용접선 높이에 따르는 영향을 연구하기 위하여, 하부의 길이를 300 mm와 400 mm로 하였다. 얻어진 결론은 다음과 같다. 길이 300 mm인 하부 재료 SPFC980의 변형은 가장 작고, 충돌 흡수 에너지는 가장 크다. 하부 냉연강 기준으로 TWB의 위치가 짧을수록 성능이 우수하게 나타났다. 즉, 상대적으로 상부 고강도강인 SABC1470 재료가 차지하는 비율에 따라 성능이 좌우되었다. 하부 재료 SPFH590은 큰 변형이 나타났고, 충돌성능은 SPFC980보다 현저히 떨어졌다. 따라서 충돌 성능 해석 결과에서 하부 재료 SPFC980인 길이 300 mm가 가장 우수한 것으로 나타났다.