• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.864-872
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• 1992

Two double-exposure holograms are made in the different view angle at the same time, using laser, by overlapping before and after the static deformation. These images are transfered to the computer. The fringe patterns of holograms are recognized by image processing and each component of the displacement and strain at each point of the specimen is obtained by vector analysis, and the results were presented in the graphical form. For the verification of all the ment process, the two experimental cases, the in-plane displacement by tension load and the out-of-plane displacement by bending load, are measured. These results are compared with the exact solution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.721-724
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• 2016

Because of the inherent uncertainties caused by the manufacturing process variations, future loading conditions, and incomplete damage models, the lifetimes of mechanical structures under field conditions are significantly different from the results obtained in the laboratories. In this study, a dual sensor was developed to prognosticate the fatigue failure of structures under these uncertain conditions, and its effectiveness was demonstrated on a rectangular columnar structure under repeated uni-axial loading. The dual sensor is a slightly weaker structure embedded in the target structure, so that failure occurs in the sensor earlier than in the target structure. From the signal differences in the strain gauges in the embedded dual sensor, it is possible to differentiate between the normal status and warning status, even under variable loads.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.17-26
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• 2010

Pb-Sn solder is rapidly being replaced by lead-free solder for board-level interconnection in microelectronic package assemblies due to the environmental protection requirement. There is a general lack of mechanical reliability information available on the lead-free solder. In this study, thermo-mechanical behaviors of wire-bond plastic ball grid array (WB-PBGA) package assemblies are characterized by high-sensitivity moire interferometry. Experiments are conducted for two types of WB-PBGA packages that have Pb-Sn solder and lead-free solder as joint interconnections. Using real-time moire setup, fringe patterns are recorded and analyzed for several temperatures. Bending deformations of the assemblies and average strains of the solder balls are investigated and compared for the two type of WB-PBGA package assemblies. Results show that shear strain in #3 solder ball located near the chip shadow boundary is dominant for the failure of the package with Pb-Sn solder, while normal strain in #7 most outer solder ball is dominant for that with lead-free solder. It is also shown that the package with lead-free solder has much larger bending deformation and 10% larger maximum effective strain than the package with Pb-Sn solder at same temperature level.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1461-1469
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• 2011

Using three-dimensional (3-D) FE analyses, this paper provides a method for analyzing the effects on stresses and strains produced by angular and concentric misalignment of a test specimen for a torsion test. To quantitativele compare of the FE results, the average bending strain for the angular, concentric, and combined misalignment was proposed. To verify the effects of axial misalignment of the test specimens, we used both circular and tubular specimens. From the FE results, we proposed general predictions for the effects caused by the various types of axial misalignment and its direction. In addition, we confirmed the effect of initial yielding moment based on the initial yielding condition for axial misalignment of specimens in torsion tests.

• Elastomers and Composites
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• v.42 no.1
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• pp.32-46
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• 2007

Mechanical properties of rubber material are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the material test and accelerated heat aging test were carried out. In order to investigate the effects of heat-aging on the material properties, hardness, elongation, stress-strain curves and dynamic characteristics were obtained from various test conditions. Also, rubber material coefficients were determined by both the uniaxical and equi-biaxial tensile tests.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.329-334
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• 2005

The use of Polymer Concrete (PC) is growing very rapidly in many structural and construction applications such as box culverts, hazardous waste containers, trench lines, floor drains and the repair and overlay of damaged cement concrete surfaces in pavements, bridges, etc. However, PC has a defect economically because resin which be used for binder is expensive. Therefore the latest research is being progressed to replace existing resin with new resin which can reduce the high cost. Here, Polymer concrete using the recycled PET(polyethylene terephthalate) has some merits such as decrease of environmental destruction, decrease of environmental pollution and development of new construction materials. The variables of this study are amount of resin, curing condition and maximum size of coarse aggregate to find out mechanic properties of this. Stress-strain curve was obtained using MTS equipment by strain control. The results indicated that modulus of elasticity was increased gradually in an ascending branch of curve, as an increase of resin content. Compressive strength was the highest for resin content of $13\%$. And Compressive strength was increased as maximum size of coarse aggregate increases. The strain at maximum stress increases with an increase of resin content and size of coarse aggregate. For the descending branch of stress-strain curve the brittle fracture was decreased when it was cured at the room temperature compared to high temperature.

• Composites Research
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• v.25 no.1
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• pp.9-13
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• 2012

In this research, biomechanical characteristics of the bone tissue are experimentally investigated. By using specimens of the bovine bone, the mechanical properties are obtained through tension and shear tests. In experiments, non-homogeneous and anisotropic properties with respect to longitudinal and transversal directions are observed. Moreover, the viscoelastic behavior in which modulus and strength properties are dependent on strain rates is analyzed. It is expected that a numerical damage model of the bone be efficiently established based on the results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.4
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• pp.477-486
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• 1986

본 연구에서는 SM20C를 모재로 하여 입경의 크기가 다른 3종의 복합조직강을 제작 동일한 분위기에서 저 및 고사이클 전영역에 걸쳐 피로특성을 검토하고져 한다. 제일보는 그 중 저사이클특성에 대한 보고이다. 일반적으로 저사이클 피로현상은 재 료가 탄소성 상태하에서 전위, 미소크랙, 보이드(void) 등의 인자가 복합적으로 작용 하여 발생함으로 변형률속도, 제어파형, 온도, 시험방법 및 분위기에 따라 많은 영향 을 받는다. 따라서 본 연구에서는 두가지 실험방법을 사용, 응력-변형율거동을 검토 복합조직강의 피로특성과 입경크기가 피로거동 및 강도에 미치는 영향을 비교 고찰하 였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.911-920
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• 1989

It this study, beam-type bend specimen is used to evaluate the interlaminar fracture toughness of laminated composite under mixed-mode deformations. The specimen is loaded under three-point bending and hence produced mixed-mode deformations in the vicinity of the crack tip according to the variation of the thickness ratio on delamination plane. Total energy release rate is obtained by elementary beam theory considering the effect of shear deformation. The partitioning of total value into mode-I and mode-II components is also performed. The mixed-mode interlaminar fracture toughness is evaluated by experiments on specimens with several thickness ratios of delamination plane. As the part of delamination plane is thicker, the effect of shear deformation on total energy release rate is increased. Beam-type bend specimen men may be applied to obtain informations on the mixed-mode interlaminar fracture behavior of laminated composites.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1161-1171
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• 1993

Model materials are developed to achieve similarity of flow patterns for mild steels in forming processes at high temperatures. The model materials consist of pure plasticine and one or two additives such as resin and lanolin. To verify the similarity of flow patterns between physical modeling and compression of mild steels at high temperatures, ring and compression tests have been carried out with the developed-model materials at various strain rates, temperatures and lubricants. The test results are in good agreement with the flow patterns obtained from upsetting of a mild steel at high temperatures.