• 한국압력기기공학회 논문집
• /
• 제11권1호
• /
• pp.12-19
• /
• 2015

As a measure of improving the mechanical properties of a diffusion bonded joint of a ferritic/martensitic steel (FMS), the post-bonding heat treatment (PBHT) is applied. In the temperature range of normalizing condition ($950-1,050^{\circ}C$), diffusion bonding is employed with compressive stress (6 MPa). Due to the martensite structure distributed in the matrix, Vicker's hardness values of the as-bonded are much higher than those of the as-received. Through the PBHT for 1 h at $720^{\circ}C$, hardness values are recovered to as low as those of the as-received condition. Also, tensile properties of PBHT are similar to those of the as-received at up to the test temperature of $550^{\circ}C$, when the diffusion bonding is carried out over $1,000^{\circ}C$. Based on the creep-rupture testing performed at $650^{\circ}C$ in air environment, the joint efficiency of the PBHTed specimens is about 80% in, which is higher than that of the as-bonded specimens.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 춘계학술대회 논문집
• /
• pp.655-659
• /
• 1997

The analysis of cracks at the interface between dissimilar materilar has received a great deal of attention in recent years. In this paper we conducted the static tensile test for the aluminum bonded single lap-joint with the interface edge crack. Comparing this results, that is ultimate load and strain value of aluminum adherend by strain gauge with the fracture mechanics parameters, compliance and stress intensity factors acquied from the boundary element analysis, we concluded that there are critical value of crack length to provoke the interface fracture.

• Journal of Welding and Joining
• /
• 제15권6호
• /
• pp.32-40
• /
• 1997

Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 춘계학술대회 논문집
• /
• pp.517-520
• /
• 2008

Recently, use of adhesive bonding technology is increased to achieve the multi-material design for lightweight structure in automobile industry. In this paper, the fracture strength of adhesive has been studied with the single lap shear test conducted at different temperatures. The joint specimens are made from Al 5052 and SPRC 440 bonded with structural epoxy adhesive. The operating temperature has been considered up to $150[^{\circ}C]$ and the single lap shear test has been conducted with 5mm/min tensile rate. Fracture strength of adhesive bonded joint has been decreased with increase of operating temperature. The fracture strength at the $100[^{\circ}C]$ was shown about half of that at room temperature.

• Composites Research
• /
• 제24권4호
• /
• pp.48-54
• /
• 2011

본 연구에서는 탄소/에폭시 복합재 단일겹침 접착체결부의 염수 수분율이 체결부의 강도 및 파손모드에 미치는 영향을 연구하였다. 시편은 이차접착 방식으로 제작하였고, $71^{\circ}C$, 3.5% 염수환경에서 수분율 0, 0.2, 0.5, 1.0, 2.0%(포화상태)를 갖도록 노출시켰다. 수분율별 시편은 각 8개씩이고, 두 종류의 시험환경을 고려하여 총 80개의 시편에 대한 시험을 수행하였다. 시험결과 복합재 체결부의 강도는 수분율이 2%(포화상태)에 도달하면 감소하지만 그 이전 과도상태(약 1% 근처까지)에서는 오히려 증가하는 것으로 나타났다. 또한 수분율 1%까지는 고온 환경에서의 강도가 상온 강도보다 2~5% 가량 높게 나타났다. 그러나 수분 포화된 고온 환경 체결부의 강도는 상온 강도 대비 약 5% 가량 저하되는 것으로 나타났다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.172-175
• /
• 2001

The co-cured Joining method, which is regarded as an adhesively bonded Joining method, is an efficient joining technique because both curing and bonding processes for the composite structures can be achieved simultaneously. It requires neither surface treatment onto the composite adherend nor an additional adhesive joining process because the excess resin, which is extracted from composite materials during consolidation, accomplishes the co-cured Joining process. Since the adhesive of the co-cured joint is the same material as the resin of the composite adherend, the analysis and design of the co-cured joint for composite structures are simpler than those of an adhesively bonded joint, which uses an additional adhesive. In this paper, effects of the manufacturing parameters, namely surface roughness, stacking sequence of the composite adherend, and manufacturing pressure in the autoclave during curing process, on the tensile load bearing capacity of the co-cured single lap joint will be experimentally investigated.

• 대한기계학회논문집A
• /
• 제35권3호
• /
• pp.333-340
• /
• 2011

본 연구에서는 복합소재 단일겹치기 조인트의 접착부재 형상 및 필렛 유무에 따른 응력집중 완화 효과를 평가하였다. 이를 위해 6가지 서로 다른 끝단부 형상에 대해 비선형 유한요소 해석을 수행하였다. 또한, 복합재 접착부재와 접착제의 다양한 강성비에 따른 6가지 모델의 최대 전단 및 수직응력의 변화를 고찰하였다. 접착부재가 순방향 테이퍼를 갖는 모델의 경우에는 가장 높은 응력값을 보여 조인트의 접합강도가 가장 취약할 것으로 예상되었다. 이에 반해, 접착부재가 역방향 테이퍼를 갖고 필렛이 존재할 경우 가장 낮은 응력값을 보였다. 접착부재와 접착제의 강성변화에 따른 최대응력 변화를 고찰한 결과 접착부재의 강성은 클수록, 접착제 강성은 낮을수록 응력집중은 완화되었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.370-376
• /
• 2001

When an adhesive joint is exposed to high environmental temperature, the tensile load capability of the adhesive joint decreases because the elastic modulus and failure strength of structural adhesive decrease. The thermo-mechanical properties of structural adhesive can be improved by addition of fillers to the adhesive. In this paper, the elastic modulus and failure strength of adhesives as well as the tensile load capability of tubular single lap adhesive joints were experimentally and theoretically investigated with respect to the volume fraction of filler (alumina) and the environmental temperature. Also the tensile modulus of the fille containing epoxy adhesive was predicted using a new equation which considers filler shape, filler content and environmental temperature. The tensile load capability of the adhesive joint was predicted by using the effective strain obtained from the finite element analysis and a new failure model, from which the relation between the bonding length and the crack length was developed with respect to the volume fraction of filler.

• 대한기계학회논문집A
• /
• 제20권7호
• /
• pp.2087-2096
• /
• 1996

Recentrly advantages in composite and light weight material techniques have led to the increased use of bonded dissimilar materials such as ceramics/metal bonded joints, IC package, brazing, coating and soldering in the various industries. It is required to analyze the evaluation method of fracture strength and design methodology of bonded joints in dissimilar materials. Stress singularity according to changes of scarf angles for bonded scarf joints in dissimilar materials was investigated by the boundary element method and static experiments. In this paper, effect of the stress singularity factors at the interface edges of scarf joints on various dissmilar materials combinations were investigated by analysis of its stress and stress singularity index using 2-dimensional elastic program of boundary element method. And the variations of stress singularity index by changes for Young's modulus ratios of materials and scarf angles were investigated. Also, it is found that stress singularities at bonded interface edges are disappeared for certain combination of scarf angle in a pair of bonded dissimilar materials. As the results, it is proposed that the strength evaluation by using stress singularity factors, $\Gamma$, considering stress singularity at the interface edges of bonded dissimilar materials, is very useful.

• International Journal of Automotive Technology
• /
• 제3권4호
• /
• pp.157-163
• /
• 2002

It is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing (NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam (DCB). An optimal condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated and discussed. The experimental values are in good agreement with the computed results by boundary element method (BEM) and Ripling's equation.