• Journal of Power System Engineering
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• v.15 no.6
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• pp.5-10
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• 2011

A turbocharger is subjected to rapid temperature changes during thermal cyclic loads. In order to predict the thermo-mechanical failures, it's very important to estimate temperature distributions under the thermal shock test. This paper suggest the finite element techniques with the temperature histories, a constitutive material model and the mechanical constraints to calculate the thermal stresses and plastic strain distributions for the turbine housing. The first step was to develop a simple coupon approach to represent the failure mechanism of the classical design shapes and secondly applied the actual turbocharger to predict and validate the weak locations under the physical engine test.

• Journal of Aerospace System Engineering
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• v.1 no.1
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• pp.45-52
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• 2007

This paper analyzed the extension effects of fatigue life and the application of pre-indentation in aircraft structural material such as aluminum alloys. The test specimen used the thin sheet of aluminum alloy with a single-edged notch. The experiments were conducted after making the pre-crack under a constant amplitude loading. As the fatigue life extension technique, the pre-indentation making an indent on the predicted path of crack propagation was applied. The work presented here discussed about a proper mathematical relation between crack growth rate and the range of stress intensity factor and about the generalization of crack growth mechanism with large retardation effect. A technique to enhance the applicability of pre-indentation if also mentioned.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.28-32
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• 2003

Thermo-mechanical behavior of a ceramic ball grid array(CBGA) package assembly and wire bond ball grid array(WB-PBGA) package assemblies are characterized by high sensitive moire interferometry. Moire fringe patterns are recorded and analyzed at various temperatures in a temperature cycle. Thermal-history dependent analyses of global and local deformations are presented, and bending deformation(warpage) of the package and shear strain in the rightmost solder ball are discussed. A significant non-linear global behavior is documented due to stress relaxation at high temperature. The locations of the critical solder ball in WB-PBGA package assemblies are documented.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.5
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• pp.762-772
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• 2004

Fatigue life of a Piston for large liquid Petroleum liquid injection(LPLi) bus engines is analyzed considering effects of cooling condition parameters : temperature of cooling water, and heat transfer coefficients at oil gallery and bottom surface of piston head. Temperature of the piston is analyzed with varying cooling conditions Stresses of the piston from two load cases of pressure loading. and pressure and thermal loading are analyzed Fatigue life under repeated peak pressure and thermal cycle is analyzed by the strain-life theory. For the two load cases, required loading cycles for engine life are defined, and loading cycles to failure and partial damages are calculated. Based on the resulting accumulated fatigue usage factors, endurance of the piston is evaluated and effects of varying cooling condition Parameters are discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.903-907
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• 1996

Under two level block loading, the carbornitrizing specimen can be expected to show different behavior from other uniform material because the properties of surface layer and inner material are different from each other. In this research, the modified Marco-Starkey cumulative theory, which considers load interaction effect, can predict the life of SCM415 carbornitrizing and original notched and smooth specimen, In the low-high test of carbornitrizing specimen which has long life, however, we may additionally consider the increase of life by means of the stress hardening of inner original material.

• International Journal of Reliability and Applications
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• v.5 no.1
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• pp.15-24
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• 2004

Folder type electronic devices have hinge to support the rotational motion of folder. This hinge is stressed by the rotational inertia moment of folder at the maximum open limit position of folder. This stress is repeated whenever the folder is open, and it is a cause of hinge fracture. In this paper, the reliability evaluation for the hinge fracture in the folder type cellular phone is discussed. For this, the durability testing machine using crank-rocker mechanism is developed to evaluate the life cycle of the hinge, and the degradation after repetitions of opening and shutting is evaluated from the deformation around the hinge, where the deformation is measured by ESPI (electronic speckle pattern interferometer). Experimental results showed that ESPI was able to measure the deformation of hinge precisely, so we could monitor the change of deformation around the hinge as the repetition number of folder open is increased.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.763-768
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• 2004

CWR(Continuous Welded Rail) has many advantage over the conventional jointed rail track. The use of CWR track not only reduces the track maintenance cost, but increase the life cycle of track components. As the use of CWR increases in track structures, derailing disasters associating with track buckling also increase in great numbers due to high compressive thermal stress. Despite the importance, the number of studies relevant to the instability is quite limited. In this paper, It considers the contribution of rail-pad-fastener resistance, uplift of tie and nonlinear analysis. Influence of various track components on CWR track temperature and mode shape were characterized.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.05a
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• pp.88-95
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• 2001

VR(Virtual Reality)의 개념이 제조공학 분야로 확대 적용되면서 설계분야에서의 가상조형 (Virtual Prototyping), 제조분야에서의 가상제조시스템(Virtual Manufacturing System)이라는 새로운 형태의 제조 시스템 및 설계기술이 차세대 제조기술로서 발전해 오고있으며 이런 가상제조방법(Virtual Manufacturing)은 컴퓨터를 이용하며 생산과정에서 제품뿐만이 아니라 유한요소해석을 유용하여, 공정까지도 모의실험을 하며 생산성(manufacturability), 최종 형태(final shape), 잔류 응력(residual stress), 제품 수명 주기(life-cycle)등과 같은 요소들의 최적화 정보를 제공하게 된다. 본 연구에서는 이러한 가상제조방법을 구현하기 위한 기초적 단계로서 가상단조기계를 가상현실기법을 이용하여 모델링하고 Java를 이용하여 모델링된 단조기계를 제어하고 제조되는 단조물에 대한 내부 응력 및 형태변환을 유한 요소법을 이용하여 분석하고 분석된 단조물의 자료를 WEB상을 통하여 닥 수 있게 유한 요소 해석결과를 VRML언어로 변환하는 작업을 수행하였다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.62
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• pp.1-10
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• 2001

The electronics industry is fast growing segment of manufacturing and service industries. It is important that the manufacturer develops a product with adequate life cycle, high quality, and low failure rate in the specified time period. Environmental Stress Screening(ESS) and burn-in are widely used in the electronic industry to assist in the elimination of early failure. In this research, we construct optimal cost model of combined ESS and burn-in under various warranty policy and establish optimal testing times for given environments. Also we conduct sensitivity analysis on various parameter. The results of this study are summarized as follows. Comparing free warranty policy to rebate warranty policy, optimal ESS time is longer under free warranty policy, and optimal burn-in time is longer under rebate warranty policy. Free warranty policy higher than rebate warranty policy in total cost.

• The KSFM Journal of Fluid Machinery
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• v.16 no.4
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• pp.15-21
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• 2013

This study aims to estimate the fatigue resistance of small wind composite blade using the fatigue life estimation formula in the GL guideline. For this, firstly, we estimated a turbine blade's bending moment spectrum by using wind profile wind profile and BEMT. And fatigue tests were performed to obtain the S-N curve of composite materials used in blade. In addition, a finite element analysis was used to identify fatigue critical locations and fatigue stress spectrum. And the fatigue resistance of composite blade were evaluated using the rainflow cycle counting, and Goodman diagram and the fatigue life estimation formula in the GL guideline.