• Geotechnical Engineering
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• v.8 no.4
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• pp.17-30
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• 1992

Constitutive relations for lightly overconsolidated state of clayey soils. as well as normally consolidated state of those, play an important role in the analyses of geotechnical structures in clay deposits. For the practical point of view, a constitutive model applicable to lightly overconsolidated soils should be developed to easily evaluate the model parameters, and to precisely predict the various behavior of OC soils. For that purpose, a constitutive model for the lightly overconsolidated soil behavior has been proposed to rep- resent the undrained behavior which can be normalized using equivalent pressure, p. , Yielding within the initial yield surface is modeled exclusively using the given normally consolidated model parameters only. Furthermore, the proposed model can be applied to consider the effects of overconsolidation, secondary consolidation, and stress relaxation. The measured behavior in undrained triaxial tests has been Predicted easily and precisely in comparison with other models.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.3
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• pp.421-426
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• 2013

We evaluated physical properties such as density, compressive characteristics, irrecoverable work, and stress relaxation of red pepper powder with different particle sizes. The particle sizes showed a normal distribution in size, with a particle size of $150{\sim}600{\mu}m$ accounting for 70.95% of the particles in the Hanbando cultivar and 82.21% in the Cheongyang cultivar. Loose bulk density ranged between 0.34 and $0.45g/cm^3$, while tapped bulk density ranged between 0.43 and $0.56g/cm^3$. The Hausner ratio was highest (1.531) at a particle size below $150{\mu}m$ in the Cheongyang cultivar. The compressibility and compression ratios were 0.001351~0.004383 and 1.0062~1.0265, respectively. Irrecoverable work ranged between 69.16% and 90.24%. The $K_2$ value and stress relaxation characteristics were greatest (1.74 and 44.92%, respectively) at particle sizes of $300{\sim}425{\mu}m$ in the Cheongyang cultivar. The dynamic angle of repose was $32.84-49.84^{\circ}$. Overall, particle sizes below $150{\mu}m$ had the highest compactibility, cohesiveness, and transformation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.4
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• pp.599-605
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• 2011

This study investigated the physical properties of red pepper powders according to cultivation area and variety. Values for density, compressive characteristics, dynamic angle, irrecoverable work, and stress relaxation were analysed. Loose bulk density ranged between 0.40 and 0.50 g/$cm^3$, and tapped bulk density ranged between 0.49 and 0.67 g/$cm^3$. The highest Hausner ratio was 1.369 for PRmanitta cultivated in Eumseong and the lowest value of was 0.194 for Buchon cultivated in Yeongyang. Compressibility ranged between 0.0046 and 0.0092. The highest compression ratio was 1.040 for Myeongjak cultivated in Suwon, and the lowest value was 1.007 for Buchon cultivated in Yeongyang. Dynamic angles ranged between 35.14 and $41.70^{\circ}$. The highest irrecoverable work value was 79.9% for PRmanitta cultivated in Eumseong and the lowest value was 67.9% for Nokgwang cultivated in Suwon. The greatest $k_2$ and relaxation values of stress relaxation characteristics were 1.56 and 42.03%, respectively, for Cheongyang cultivated in Yeongyang.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.103-111
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• 2002

Steady-state creep analysis of power generation turbine blade is carried out considering thermal loads and centrifugal forces. Creep strains and stresses of the turbine blade are calculated for 3-D finite clement model of the turbine blade. From the numerical results, creep life of the turbine blade is predicted. The results of creep analysis during about 200 hours indicate that creep strains of the turbine blade do not reach the rupture strain of GTD111. Creep stresses of the turbine blade are relaxed as time increases. Maximum creep strain occurs at the tip section of the airfoil pressure surface. The maximum creep strain of the turbine blade is expected close to the rupture strain after 50,000 hours approximately. The turbine blade may not have creep damage for the starting procedure of the turbine.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.69-79
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• 2011

Laboratory tests are generally used to determine the input parameters for the selected constitutive models controlling various stress and drainage conditions, but have disadvantages in that the tests are performed on the samples obtained from the bore hole which are prone to be disturbed by various factors such as the tube penetrations, sample preparations and storage. To overcome these disadvantages, it is necessary to understand the effect of disturbance on the stiffness of the sample, especially the normally consolidated clays which are generally considered as soft clays. Therefore, in this study triaxial tests are performed on the normally consolidated kaolinite to evaluate the sample disturbance effects on the stiffness and to determine the field representative input parameters. The stress path results show that the shear and coupling modulus degradation patterns with strain are affected seriously by the disturbance. However, the strengths of the normally consolidated kaolinite are little influenced by the disturbance.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2001.03a
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• pp.118-131
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• 2001

우리 나라의 양수발전소는 지금까지 단일공동을 굴착하였다. 그러나 양양 양수발전소는 두 개의 대공동 즉, 발전소와 주 변전소로 구성된다. 이 경우 공동 구조물의 안정성, 특히 두 공동사이에 형성되는 암주를 영구적으로 안전하게 유지 할 수 있도록 보장되어야 한다. 본 연구에서는 개별요소법을 이용하여 두 공동과 암주의 구조적 안정성을 평가하였으며, 구성모델로 Barton-Bandis의 절리모델을 이용하였다. 현지 암반의 초기응력, 자연절리면의 거칠기계수 불연속면의 공간적 분포 특성과 같은 중요한 요인들은 현지 조사를 통하여 구하였다. 이외에 두 가지 경우 즉, 무보강과 보강의 경우 지보시스템의 최적화를 분석하였으며, 또한 보강효과를 검토하였다. 연구결과 보강의 경우 수평변위와 절리의 전단변위가 감소되었으며 암주내 이완영역 역시 감소됨을 확인하였다. 두 공동사이에 있는 약 36m 두께의 암주에 적절한 보강조치를 취하여 안정성을 확보할 수 있었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.641-646
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• 2001

In early-age concrete, volumetric deformations due to thermal expansion and moisture transfer are restrained by various boundary conditions, and then restraint stresses occur in proportion to developed stiffness. With increase of the age, these stresses are gradually relieved by significant relaxation behavior of early-age concrete. Therefore, it is necessary to consider the stress relaxation in order to analyze the behavior of early-age concrete more accurately. In this paper, we propose a unified algorithm which combines a relaxation model with hydration model, heat conduction model, micropore structure formation model, moisture diffusion model and mechanical properties development model and develop a finite element program based on the algorithm. The program is applied to evaluate stress development if a temperature-stress test machine (TSTM) specimen and a massive concrete structure, and then validity of the program is discussed and evaluated.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.872-877
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• 2004

Welding residual stresses are the main topics of welding research fields. The residual stresses and distortion of structures by welding exert negative effect on the safety of mechanical structures. That is, expansion of material by high temperature and distortion by cooling during welding process are caused by tensile and compressive residual stresses in welding material, and this residual stresses can induce fracture and fatigue problems of welding structures. The accurate prediction of residual stress and relaxation due to mechanical loading of weld zone is very important to improve the quality of weldment. In this study, a finite element modeling technique is developed to simulate the relaxation of residual stresses due to mechanical loading. The effects of load ratio for static and cyclic loading are evaluated based on analytical results.

• Journal of Welding and Joining
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• v.15 no.2
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• pp.81-88
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• 1997

The residual stresses produced by a circumferential weld between axisymmetric cylinders are one of the most important problems concerning buckling strength, fatigue strength, stress corrosion cracking in shell structures, and arc quite different from those due to a butt weld between flat plates. This paper presents experimental studies on weld cylinder models of various heat inputs and thin cylinder diameters by blind hole drilling method. As a result, it is certified that weld residual stress (axial stress and hoop stress) is larger, as heat input and shell cylinder diameter are larger, and that experimental results show good agreement with the result of preceding researchers.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.268-275
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• 1999

The purpose of this study is to propose the method of determining the initial pneumatic membrane structures surface and stresses and displacements. Tension structure such as pneumatic membrane structures is stabilized by their initial prestress and air pressure. The process to find initial structural overall shape of tension structures produced by initial prestress called shape finding. One of the most important factor for the design of membrane structures is to search initial smooth surface, because unlike steel or concrete building elements which resist loads in bending, all tension structure forces are carried within the surface by membrane stress. The result for initial surface of pneumatic membrane element and maximum displacement in large deformation in analysis is compared with well-known nonlinear numerical method such as Newton-raphson method and dynamic relaxation method