• 한국항공우주학회지
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• 제41권12호
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• pp.967-974
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• 2013

저자는 최근 산업체 생산 현장에서 Z-피닝 복합재 구조물을 간편하게 제작할 수 있는 Z-피닝 패치 개념을 제안하였고, 이를 적용하여 복합재 단일-겹침 전단 접합시편을 제작하였으며, 정적시험을 통하여 54~68%의 접합강도의 향상을 발표하였다. 본 연구는 상기 연구의 후속으로서, 반복하중에 대한 접합강도의 향상을 측정하기 위하여 피로시험을 수행하였다. 사용된 Z-핀은 스테인레스강 핀이며, 복합재료와의 결합력을 증가시키기 위하여 표면을 요철 형상으로 가공하였으며, 화학적으로 부식시켰다. 반복하중 조건에서 접합강도는 약 98~125% 향상되었다.

• Journal of Welding and Joining
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• 제29권4호
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• pp.54-60
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• 2011

Adhesive bonding is one of the most promising joining methods which may substitute for conventional metallurgical joining processes, such as welding, brazing and soldering. Curing behavior and mechanical properties of adhesive joint are largely dependent on the curing agent including hardener and catalyst. In this study, effects of curing system on the curing behavior and single-lap shear strength of epoxy adhesive joint are investigated. Dihydrazide, anhydride and dicyandiamide(DICY) were chosen as hardener and imidazole and triphenylphosphine(TPP) were chosen as catalyst. In curing behavior, TPP showed the delay of the curing rate for DICY and ADH at $160^{\circ}C$, compared to imidazole catalyst due to the high curing onset/peak temperature. DICY seemed to be most beneficial in the joint strength for both steel and Al adherends, although the type of adherends affected the shear strength of epoxy adhesive joint.

• 한국레이저가공학회지
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• 제15권1호
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• pp.1-5
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• 2012

Recently ultra high strength steels(UHSS) has been widely applied to the structural or safety components in the automotive industry. Specially, hot stamping boron steel 22MnB5 has shown the crash-resistant characteristics when applying to bumpers and pillars. Lap joint Laser welding of the hot stamped and die quenched sheets of Boron steel was carried out using 3kW Nd/YAG laser. The appropriate Lap joint laser welding conditions were founded separately for four lap joint combinations. The lower sheest is a hot stamped sheet in common and the upper sheet is selected among the hot stamped steel and high strength steels such as SPCC, 370MPa, and 590MPa grade high strength steels. Cross bead sections and local hardening and softening were observed as well as tensile-shear test results.

• 대한기계학회논문집A
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• 제22권4호
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• pp.905-915
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• 1998

Static tensile tests using adhesive-bonded single-lap joints of aluminum alloy were conducted to investigate the effect of geometric factor, overlap length, adherend thickness, adhesive thickness and material composition of adherend/adhesive on the strength of adhesive joint. The average applied shear stress at joint fracture decreased with increasing lap length. However increasing the adherend thickness resulted in a higher joint strength. Higher yield strength of adherend and lower elastic modulus of adhesive is advantageous to the adhesive joint. Newly proposed modified joint factor could be well evaluated the influence of lap length, adherend thickness and adhesive thickness on the bond strength for adhesive joints.

• Journal of Welding and Joining
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• 제15권2호
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• pp.36-42
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• 1997

In this paper, stability of initial strength at solder joint with lead free solders, such as Sn-In (52-48%) and Sn-Ag (96.5-3.5wt%) was studied. To obtain at solder joint with high quality, it is very important to control the temperature at the interface of solder joints. It is found that the thermal EMF (electro motive force) occurs betwee lead frame and copper pad on a substrate during reflow soldering process using heated tip. As a result of control the temperature at interface of solder joints, variation of initial strength at solder joint decreases from about $\pm40%$ to $\pm20%$, and it is realized Pb free soldering process using Sn/In and Sn-Ag solder paste.

• Journal of Welding and Joining
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• 제6권1호
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• pp.28-34
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• 1988

The fatigue test was carried out to evaluate the fatigue characteristics of the accelerated cooled (ACC) TMCP steel and its welded joint. From this study, it was confirmed that ACC TMCP steel has higher fatigue strength than conventional steels. After welding, however, the fatigue strength of ACC TMCP steel was deteriorated associated with HAZ softening when weld reinforcement was removed. On the other hand, with weld reinforcement, there is no effect of HAZ softening on the fatigue strength of welded joint because it is strongly dependant on the detail weld geometry i.e., stress concentration factor. Accordingly the fatigue strength of actual welded joint increases with decreasing the stress concentration factor of welded joint, regardless of HAZ softening.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.709-713
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• 1996

The ceramic has such high qualities as light weight, abrasion resistance, heat resistance compared with metal, but since it is breakable, it can't be used as structural material and it is desirable to joining metal which is full of toughness, but, according as the ceramic/metal joint is executed at high temperature, the joint residual stress develops near the joint sides in the process of cooling the high temperature down to the suitable temperature due to difference of the thermal expansion coefficient between ceramic and metal, and the joint residualstress lowers the fracture strength. In this study, to ensure security and improvement of bending strength, 1 studies on see distribution shape of residual stress according to high thermal cycle, and the influnence of theraml cycle and distribution shape of residual stess on joint-strength.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.103-108
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• 2000

Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.

• 소성∙가공
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• 제18권5호
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• pp.385-391
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• 2009

An adhesively bonded power steering cylinder with a steel tube and an aluminum bracket was developed to reduce the weight of steering systems. To achieve the joint strength between the steel tube and of the aluminum bracket, the shape aluminum bracket re-designed by using the FE-analysis. Fracture behavior of the adhesive layer was considered by a cohesive zone model(CZM), which is based on the two-parameter fracture phenomenon with critical stress and fracture toughness. From the result of FE-analysis with CZM, re-designed power steering cylinder satisfied the desired joint strength for axial and torsion modes. And its joint strength was verified by the fracture test in each mode.

• Journal of Welding and Joining
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• 제14권3호
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• pp.86-92
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• 1996

This paper presents the investigations on the initial strength and its variation of Sn-Pb solder joint using different lead frames, such as are 42 alloy lead and Cu alloy lead. As the result of the lack of initial strength at solder joints, whose pitch is from 0.3 to 0.4mm, short circuit often occured at the solder joint by thermal shock or external impact. Therefore, in this paper investigations were performed on the initial strength and its variation of Sn-Pb solder joint as well as fractured mode with using different lead frames.