• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.7
• /
• pp.643-651
• /
• 2011

An experimental study on the failure of aluminum sandwich joints under shear loading was conducted. A total of 60 specimens including three different insert types and two different potting types were fabricated and tested. The test results showed that the through-clearance type of joint fails at the highest load among insert type joints. The failure load of the potted joints with the dimple washer increased by 10% compared to the simple potted joints. As expected, the shear failure load became higher in accordance with the face thickness increase. It was also found that the upper face in contact with the loading tool is more dominant over the failure load.

• Journal of the Korean Society for Railway
• /
• v.19 no.6
• /
• pp.777-784
• /
• 2016

In this study, regulation of the performance test load of a vibration-proof fastening system used in urban railways was established through evaluation of the loads that it bears in the field. In order to investigate the range of the dynamic stiffness of the vibration-proof fastening system, dynamic stiffness tests were carried out for three types of vibration-proof fastening system that can be domestically supplied. Train and track interaction analyses in the frequency domain were carried out to evaluate the dynamic wheel loads. The track irregularity, which is a very important input factor in train and track interaction analysis, was considered as a PSD (Power Spectral Density) function, which was derived based on the measured data. The loads on the vibration-proof rail fastening system were evaluated considering various operating conditions in the urban railway. Regulation of the performance test load of the vibration-proof rail fastening system was established based on the evaluated loads.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.9
• /
• pp.841-850
• /
• 2008

Strength and failure of composite-to-aluminum rivetted, bonded, and rivet/bonding hybrid single-lap joints were investigated by experiment. A total of 82 joint specimens were tested with 3 different overlap lengths and 2 types of stacking sequence. FM73m adhesive film and NAS9308-4-03 rivet were used for hybrid joints. While failure loads of the bonded and hybrid joints increased as the overlap length increased, failure loads of the rivetted joints were not affected by the overlap length. Effect of the stacking sequence was not remarkable in the simple bonded or rivetted joints. Failure loads of the hybrid joints, however, showed the maximum of 30% difference depending on the stacking sequence. Major failure mode of the bonded and hybrid joints was the delamination of the composite adherend and failure mode of riveted joints was the rivet failure with local bearing.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1996.11a
• /
• pp.15-24
• /
• 1996

로켓모타의 연소관은 구조적인 편의성 및 경량화를 위하여 도옴-실린더부와 실린더-노즐부에 나사체결방법을 많이 적용하고 있는데, 나사의 골부위에 집중응력이 발생하여 인장강도를 넘는 응력이 발생하는 경우가 있다. 본 연구에서는 나사의 골부위의 응력수준을 좀 더 정확히 예측하기 위하여 나사체결시 작용하는 조립 토오크에 의한 초기하중을 고려한 구조해석을 수행하였으며, 나사부위에 발생하는 응력이 항복강도를 초과하므로 정확한 해석을 위하여 탄소성해석을 수행하였다. 조립 토오크에 의한 초기하중은 나사체결 멈춤부에 음(-)의 접촉 간극을 부여하여 모델링하였으며, 조립 토오크의 크기는 나사체결 근접부에서 변형률을 측정하여 모사하였다. 해석결과 초기하중을 고려하여 구조해석을 수행하면 최대예상 작동압력에서 초기하중의 영향은 거의 나타나지 않았으며, 마찰계수를 감소시키면 최대응력이 감소하여 구조적 안전성이 증가할 것으로 판단된다.

• Journal of the Korean Society for Railway
• /
• v.20 no.4
• /
• pp.521-528
• /
• 2017

In this study, vertical loading tests were conducted to investigate the nonlinear behaviors of the fastening systems that have generally been used in the concrete track of domestic railway lines. Nonlinear load-displacement curve models were derived based on the test results. The uplift forces generated in the fastening systems were evaluated by applying the derived nonlinear models as well as the existing linear models. The influence of the factors on the maximum uplift force of the fastening system was analyzed through a parameter study on the distance between neighboring sleepers, the horizontal distance between the center of the bearing and the nearest fastening system from the deck end, and the height of the bridge girder. From the evaluation results it is known that, for economical track and bridge design, due to deck end deformation, it is necessary to consider the nonlinear behavior of the fastening system in the calculation of the uplift force of the fastening systems.

• Composites Research
• /
• v.27 no.6
• /
• pp.213-218
• /
• 2014

This paper predicted the strength of mechanical joint of composites under bending load by means of the characteristic curve method. The method has been employed only for tensile and compression load conditions, but in this study, this method was extended to the bending load condition. For the finite element analysis (FEA), the nonlinear analysis was conducted considering the contact and friction effects between composite material and pin. The failure strength and mode on characteristic curve were evaluate with Tsai-Wu failure theory. To validate the results of FEA, the experiments were conducted to find out the failure load by applying bending moment on the composite specimens. The results showed reasonable agreements with theoretical results. These results lead to a conclusion that the characteristic curve method can be applied to predict the bending strength of mechanical joint of composites.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.1
• /
• pp.25-33
• /
• 2003

The failure load and mode of the unidirectional and fabric hybrid composite laminate joints are studied by test and finite element analysis. Test is conducted for the specimens with nine various geometries under pin loading. Finite element analysis is performed considering the contact and friction effects between the pin and laminate by MSC/NASTRAN. Failure is estimated by Tsai-Wu and Yamada-Sun criteria on the characteristic curve. While the failure of the specimens with the small width and edge length are much affected by the joint geometry, the geometry effects are negligible in the specimens with large width and edge length. Finite element analysis based on the characteristic length method reasonably predicts the failure load and mode of the joints.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 1997.11a
• /
• pp.29-29
• /
• 1997

각광 받는 구조재료인 섬유강화 복합적층재에 대한 기계적 체결 거동은 본질적인 재료의 이방성에 의해서 파단강도가 파단 모우드와 매우 밀접한 관련을 갖는 것으로 알려져 있다. 따라서, 복합적층판 체결부의 정밀 구조 설계에서는 단순화에 따른 오차를 줄이고 정밀해에 의한 설계 및 해석이 요청된다. 특히, 층간응력 성분을 무시할 수 없는 두께를 갖는 복합적층 판의 기계적 체결부 해석이나 실제 구조물의 체결부에서 발생하는 굽힘이나 비틀림과 같은 하중 상태를 묘사하기 위해서도 정밀한 3차원 응력 해석은 필요하다. 하지만, 지금까지 기계적 체결부의 거동에 관한 연구는 층간응력 성분들을 어느정도 무시할 수 있는 얇은 평판에 대한 2차원 응력해석에 주로 국한되어 왔으며, 일부 수행된 체결부에 대한 3차원 응력 해석의 경우 여러 단점을 갖는 3차원 연속체 요소에 의한 유한요소 해석이 수행되었을 뿐이다.본 연구는 층간응력 성분들을 무시할 수 없는 두께를 갖는 복합적층판의 기계적 체결부 해석에 지금까지 사용되어온 3차원 연속체 요소에 의한 유한요소 방법이 갖는 단점들을 개선한 Layerwise 유한요소법을 이용하여 3차원 응력해석을 수행하였다. 특히, 선형상보성원리에 근거한 최적설계 기법을 응용하여, 기계적 체결시 핀과 적층판의 홀 사이에 발생하는 하중 전달 과정을 모사하고, 접촉력에 의한 홀 주위의 복잡하고 국부적인 응력 집중현상을 규명하여본다.

• Composites Research
• /
• v.30 no.6
• /
• pp.384-392
• /
• 2017

Sandwich panels with three different joint configurations were tested to design a novel sandwich joint structure that can effectively support both the tensile and compressive loads. The sandwich core was mainly aluminum flex honeycomb but the PMI foam core was limitedly applied to the ramp area which is transition part from sandwich to solid laminate. The face of sandwich panel was made of carbon fiber composite. For configuration 1, the composite flange and the sandwich panel were cocured. For configurations 2 and 3, an aluminum flange was fastened to the solid laminate by HI-LOK pins and adhesive. The average compressive failure loads of configurations 1, 2, and 3 were 295, 226, and 291 kN, respectively, and the average tensile failure loads were 47.3 (delamination), 83.7 (bolt failure), and 291 (fixture damage) kN, respectively. Considering the compressive failure loads only, both the configurations 1 and 3 showed good performance. However, the configuration 1 showed delamination in the corner of the composite flange under tension at early stage of loading. Therefore, it was confirmed that the structure that can effectively support tension and compressive loads at the same time is the configuration 3 which used a mechanically fastened aluminum flange so that there is no risk of delamination at the corner.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.39-45
• /
• 2008

A levitation rail is placed on the top of track structure to operate Maglev vehicles and a part of track that link up with a sleeper is applied repeated load in Maglev vehicles operation. This paper aimed to verify validity of design for levitation rail, through the fatigue analysis about load which is applied to levitation rail in Maglev vehicles operation and impact load occurring in an emergency landing. Load conditions applied design load(23kN/m) in normal operation and skid drop load(24kN/m) in vehicle drop. And boundary conditions are consider bolt fixing and welding. Through static analysis, weak point and maximum stress of levitation rail could be obtained. S-N(stress-life) method was used in oder to predict fatigue life, and Goodman relationship was applied to consider a effect of mean stress. Also damage was calculated by using Miner's. As a result of fatigue analysis, levitation rail had a fatigue life which was more than requirement ($10^6$cycle) in all analysis conditions. Assumption that $10^8{\sim}10^9$cycles is infinite life, all analysis conditions had infinite life except a case under drop load and bolt fixing($1.21{\times}10^6$).