• 한국음향학회지
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• 제28권7호
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• pp.646-652
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• 2009

본 논문에서는 점용접 너깃의 피로수명을 고려한 차량 서브프레임의 용접간격 최적화 설계기법이 제안된다. 주파수영역 피로해석기법에 의해 점용접 너깃의 피로수명이 평가된다. 피로해석에서 사용되는 입력 데이터는 벨지안로 프로파일을 통과하는 차량동역학 해석과 차량 서브프레임 유한요소모델의 모드 주파수 해석을 통해 얻는다. 주파수 영역 피로해석으로 부터 얻은 피로수명 결과로부터 용접간격 최적화를 수행 할 설계점들이 선정된다. 점용접 너깃의 피로수명을 최대화시키는 용접간격을 얻기 위하여 4-요인, 3-수준 직교배열 실험계획법이 사용된다. 본 연구를 통하여 최적화된 서브프레임은 초기모델에 비하여 최소 피로수명을 갖는 용접 너깃의 피로수명이 약 65.8 % 증대되는 것을 알 수 있다.

• 오토저널
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• 제13권5호
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• pp.42-50
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• 1991

According as the members and inner and outer plates of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. Therefore, it has been increasingly required to improve the fatigue strength of the spot welded structures. As one of the improving methods for such problem, the author had previously proposed the method of alleviating stress concentration at nugget edge of the spot weld part and improving its fatigue strength [1]. But, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic estimation method of them. In this report, by considering nugget edge of the spot weld part of the spot welded lap joint subjected to tensile load to the ligament crack, fatigue strength of various spot welded lap joints was estimated with the stress intensity factor (S.I.F.) K which is fracture mechanical parameter. It is known that evaluation of fatigue strength of the spot welded lap joint by the stress intensity factor (S.I.F.) K is more effective than the maximum stress $(\sigma_{ymax}$) at edge of the spot weld part on the center line of width of the plate.

• Journal of Welding and Joining
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• 제33권2호
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• pp.47-55
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• 2015

With using adaptive control of the resistance spot welding machine, the advantage on electrode life time for galvanized steels has been addressed. This study was aimed to evaluate the electrode life time of galvanized steels with applying the constant current control and the adaptive control resistance spot welding process for a comparison purpose. The growth in diameter of electrode face was similar for both the constant current and the adaptive control up to 2000 welds. The button diameter was decreased with weld numbers, however, sudden increase in button diameter with use of the adaptive control after 1500 welds was observed. The peak load was continuously decreased with increasing number of welds for both the constant current and the adaptive control. The current compensation during a weld was observed with using the adaptive control after 1800 welds since the ${\beta}$-peak on dynamic resistance curve was detected at later weld time. The current compensation with adaptive control during resistance spot welding enhanced the nugget diameter at the faying interface of steel sheets and improved the penetration to thinner steel sheet.

• Journal of Welding and Joining
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• 제29권2호
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• pp.72-79
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• 2011

The scope of this investigation is to evaluate the effect of joining parameters on the microstructural features and mechanical properties of dissimilar aluminum alloys, 1mm-thickness fixing AA6K31 at the top position and fixing AA5J32 at the bottom position. The friction stir lap welds were studied under various welding conditions, rotation speed of 1000, 1250, 1500rpm and welding speed of 100, 300, 500, 700mm/min, respectively. Mechanical test has been investigated in terms of tensile shear test and hardness test. The results showed that three type nugget shapes such as onion ring, zigzag type, hooking with the void, have been observed with revolutionary pitch. All welding conditions fractured at the HAZ of top plate, A6K31 and also the strength compare with base metal of lap joints were low efficiency, 52~63%. The thickness of fractured position was decreased with the lower heat input conditions. The relationships were excellent due to linear between the effective thickness of fractured position and peak load. The fractured position was the interface between joint area and not joint area. Also the strength efficiency compared with base metal was lower than decreasing rate of thickness because the hardness was decreased at fractured position due to softened material.

• 한국기계가공학회지
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• 제20권12호
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• pp.24-29
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• 2021

Recently, owing to the high demand for eco-friendly cars in the automotive industry, noise and vibrations have become major challenges. The use of laminated damping steel is increasing in response to these demands. Laminated damping steel is primarily used in sound insulation plates. The vibration energy is converted into thermal energy due to the viscoelastic resin being located between two steel sheets and being able to damp the vibrations when an external force, such as, noise or vibration is applied to the steel plate. Laminated damping steel is chiefly applied to dash panels in automotive body parts, and because of its structure, junction technology for bonding with other components is necessary. However, there has not been sufficient research conducted on junctions. In this study, regardless of the electrode shape, in the range of 4.0 ~ 8.0 kA welding current, the same welding force and welding time were applied which were 2.8 kN and 200 m/s (12 cycles) and the tensile shear load and nugget size were analyzed after the resistance spot welding between different materials of laminated damping steel with a thickness of 1.035 mm. The results show that in the range of 5 ~ 8 kA welding current, 1.035 mm laminated damping steel meets the MS181-15 standard, which is the technical standard of Hyundai-Kia Motors.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.30-41
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• 2006

This paper shows mechanical Properties and behaviors of macrostructures for specimens welded by F.S.W according to welding conditions and tool dimensions with $6.35mm_t$ aluminum 7075-T651 alloy plate. It apparently results in defect-free weld zone in case transition speed was changed to 15mm/min 61mm/min and 124mm/min under conditions of tool rotation speed such as 800rpm. 1250rpm and 1600rpm respectively with tool's Pin diameter 40mm and 60mm. The optimum mechanical property, ultimate stress,${\sigma}_Y=470Mpa$ is obtained at the condition of 124mm/min of travel speed with 800rpm of tool rotation speed using full screw type pin. shoulder dia. $20{\phi}mm$ pin dia. $6{\phi}mm$ and pin length 6mm. The full-screw type and the half-screw type pin shows the similar behaviors of weldability. It is found that the size of nugget is depended on tool transition speed and tool dimension by macrostructures of the cross section of weld zone.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.242-249
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• 1999

Spot welding is very important and useful technology in fabrication of an automobile body structure. Because fatigue strength of the spot welding point is however considerably lower than parent metal due to stress concentration at the nugget edge, accurate stress analysis and fatigue stength evaluation of spot welded lap joint are very important to valuate the reliability and durability of automobile body structure and to establish a criterion of long life fatigue design. Many invetigators have studied so far onsystematic fatigue strength evaluation with various methods. It is however necessary to verify their reliability and abailability for practical application to fatigue design of spot welded structure, Thus,in this study, fatigue strength evaluation methods of spot welded lap joint. which are the maximum principal stress method. the fracture and availability with the Weibull probability distribution. From the results, it was found that reliability and availability withe the Weibull probaility distribution. From the results, it was found that reliability and availability of the suggest fatigue strength estimation methods methods were higher than $\Delta$P-$N_f$ relation. However, among them , reliability of the maximum pricipal stress method was the highest.

• Journal of Welding and Joining
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• 제14권2호
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• pp.36-45
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• 1996

Fatigue strength of the spot welded lap joint is considerably influenced by corrosive environments. Particularly, the chloride and the sulfide are most injurious to strength of the spot welded lap joint. Therefore, there is a need to evaluate its effect to corrosion fatigue strength for safe life design of spot welded structures. In order to evaluate their corrosion fatigue strength, corrosion fatigue tests on the spot welded lap joints of the uncoated and the coated high strength steel sheets were conducted in air and in 10% NaCl solution. Corrosion fatigue strength of the uncoated specimens were entirely lower than the coated one in NaCl solution, but those of the coated specimens in NaCl solution were lower than in air. And stress distribution in single spon welded lap joint subjected to tension-shear load was investigated by the finite element method. Using these results, we tried to evaluate corrosion fatgue strength of the various spot welded lap joints with maximum stress $\sigma_{max}$ at edge on loading side of the spot welded lap joint. We could find that corrosion fatigue strength could be quantitatively and systematically rearranged by $\sigma_{max}$.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.348-358
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• 2005

This paper showed mechanical properties and behaviors of macrostructures for specimens welded by F.S.W according to welding conditions and tool with 6.35$mm_t$ aluminum 7075-T651alloy plate. It resulted in defect-free weld zone in case tool rotation speed was 800rpm, 1250rpm and 1600rpm respectively that transition speed was changed to 15mm/min, 61mm/min and 124mm/min with tool's pin diameter 4${\Phi}$mm and 6${\Phi}$mm. The optimum mechanical property, ultimate stress,${\sigma}_Y$=470Mpa was obtained at the condition of 124mm/min of travel speed with 800rpm of tool rotation speed using full screw type pin, shoulder dia. 20${\Phi}$mm, pin dia.6${\Phi}$mm and pin length 6mm. The full-screw type and the half-screw type pin showed the similar behaviors of weldability. It is found that the size of nugget was depended on tool transition speed and tool dimension by macrostructures of the cross section of weld zone.

• Journal of Welding and Joining
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• 제35권2호
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• pp.52-57
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• 2017

In this study, resistance spot weldability of lightweight steel with high Al contents was evaluated using various electrode shapes. The six types of electrode shape were prepared with different electrode face diameter and radius. The tensile shear tests were carried out to investigate the failure behaviors. Also, the nugget size and hardness were measured and compared with various electrode shapes. The experimental results show that the acceptable weld current region for low density lightweight steel could be obtained with 10mm electrode face diameter and 76mm electrode face radius.