• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.25-30
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• 2001

The stress intensity factors for edge cracks located at the bonding interface between the semiconductor chip and the adhesive layer subjected to a uniform transverse tensile strain are investigated. Such cracks might be generated due to a stress singularity in the vicinity of the free surface. The boundary element method (BEM) is employed to investigate the behavior of interface stresses. The amplitude of complex stress intensity factor depends on the crack length, but it has a constant value at large crack lengths. The rapid propagation of interface crack is expected if the transverse tensile strain reaches a critical value.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.135-140
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• 2004

Wear mechanisms may be briefly classified by mechanical, chemical and thermal wear. A plane strain finite element method is used with a new material stress and temperature fields to simulate orthogonal machining with continuous chip formation. Deformation of the workpiece material is healed as elastic-viscoplastic with isotropic strain hardening and the numerical solution accounts for coupling between plastic deformation and the temperature field, including treatment of temperature-dependent material properties. Effect of the uncertainty in the constitutive model on the distributions of strait stress and temperature around the shear zone are presented, and the model is validated by comparing average values of the predicted stress, strain, and temperature at the shear zone with experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.299-302
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• 2011

본 논문에서는 보 구조물의 응력 변화에 따른 구조역학적 임피던스의 특성을 분석하였다. 이를 위해 다음과 같은 연구가 수행되었다. 먼저 외팔보 형식의 알루미늄 보에 PZT센서와 strain gage를 부착하고, 하중을 단계적으로 증가시키면서 임피던스를 계측하였다. 다음으로 strain gage에서 계측된 변형률과 PZT로 부터 계측된 임피던스 사이의 관계를 분석하였다. 마지막으로 수치해석을 통해 변형률과 임피던스의 관계를 분석하여, 실험결과와 비교하였다.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.47-51
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• 2012

In this study, the deformation behavior stability of sealing rings with three different cross sectional areas has been presented using a FEM technique. To investigate the deformation behavior stability, the initial compression rate of 25% has been applied to the sealing ring, which is molded with a nitrile butadiene rubber. The maximum strain, maximum stress, and maximum contact normal stress have been analyzed for the working fluid pressure of $25kgf/cm^2$. The FEM results show that the maximum strain of a hollow o-ring and a hollow rectangular ring with a hollow space in the center of a sealing ring is higher than that of a conventional o-ring, but the maximum stress and the maximum contact normal stress are low. In these results, the sealing rings with a hollow space in the center of the cross sectional area is recommended to increase an extended endurance stability of sealing rings. But, the solid sealing ring is designed to guarantee the sealing safety of a contact sealing ring.

• Journal of the Korea Convergence Society
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• v.5 no.1
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• pp.23-27
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• 2014

In case eccentric load is applied at compact tension specimen, the propagation behavior due to existence or nonexistence of hole, numbers and positions of holes near crack is investigated in this study. Strain energy, displacement and stress happened in specimen are examined through simulation analysis. And stress intensity factor is obtained by the basis of strain energy and deformation. When defect or hole exists in structure, the possibility of fracture can be thought to be verified by using the study result.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.18-21
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• 2009

The life of components under high thermal load is typically shorter than other components. The turbopump turbine of liquid rocket is operated under these environments like high temperature and high centrifugal dorce due to high rotating velocity during operating time. These conditions may often cause low-cycle fatigue problem in the turbopump turbine. First of all, to analyze heat stress, ABAQUS/CAE is used and Coffin-manson's equation is used to consider elasticity and plasticity strain. S.W.T's method is used to consider the mean stress effect, using strain history, low-cycle fatigue analysis is done for turbopump turbine which may have FCL(fracture critical location). In this paper, strain life method is applied to analyze low-cycle fatigue.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.17-28
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• 1999

In order to analyze effects of strain rate on consolidation of natural clay, this paper presents a nonlinear elasto viscoplastic model in which viscoplastic behavior is modeled by a unique effective stress-strain-strain rate relationship (equation omitted). The predicted values using numerical analysis are compared with measured ones in several laboratory tests such as creep test, multistage load test, and relaxation test for Berthierville clay. It is possible to estimate consolidation behavior of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.

• Journal of the KSME
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• v.29 no.3
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• pp.231-243
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• 1989

복합재료의 탄성 문제를 정리하면 다음과 같다. 복합재료와 등방성 재료의 탄성학적 차이는 재료의 탄성계수에 기인하며 이것은 각각 다른 형태의 응력-변형률관계를 갖게 한다. 한편 응 력-변형률 관계식을 제외한 탄성학의 지배방정식은 재료의 종류에 관계없이 성립한다. 복합적 층판의 Stiffness와 응력 등은 Lamination 이론을 사용하여 구할 수 있다. 판이론은 평형식을 z방향으로 적분한 식, 즉 합력(resultant force)와 모멘트로 나타낸 평형식을 사용하는데 이 때 처짐 방정식을 구하기 위해 합력. 모멘트-곡률. 변형률 관계식을 이용하는데 이 관계식이 복합 재료와 등방성재료가 상이하다. 결과로 복합재료는 커플링 효과를 갖게 되며, 복합적층판을 대 칭으로 쌓으면 이 효과를 상쇄시킬 수 있다. 복합적층 보의 이론은 유효 굽힘 계수를 도입하면 등방체 보 이론을 사용하여 보의 처짐을 해석할 수 있다. 복합적층 보의 경우 굽힘 응력의 최 대치는 등방체와는 달리 보의 표면에서만 일어나지 않고 내부에서도 일어날 수 있다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.557-568
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• 2016

Squeezing is a phenomenon that may occur in deep tunneling and could bring about a large plastic deformation, tunnel closure and collapse of tunnel supports. Therefore, quantitative estimations of deformation and stress from squeezing and its possibility are necessary for establishment of a rational tunneling method. This study carried out three dimensional numerical analyses using a strain softening model in order to simulate the behaviour of squeezing and to estimate deformation and yield area around tunnels quantitatively. Numerical analyses were performed for 42 cases of various stress and strength conditions. As a result, the maximum tangential stress and strength of rock mass ratio could estimate plastic deformation and yield depth around tunnels and equations of relations between them were proposed.

• Geotechnical Engineering
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• v.13 no.2
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• pp.29-38
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• 1997

Strain softening is observed for geomaterials such as rocks when they are sheared. The proper computational modelling for strain softening is very important because this behavior is closely related to failure in geotechnical problems. In this paper, we have investigated the proper FEM techniques for modelling strain softening in order to simulate failure behavior numerically. In showing numerical examples, the effects of element shape, mesh pattern and of imperfection and the difference between small and large deformation theories, of displacement control and pressure control after peak have been discussed.