• Title/Summary/Keyword: Visco-Plastic

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On Vibration Characteristics Study of Thermo-Visco-Plastic Material Under Periodic Thermal Loading (반복적 열하중을 받는 열탄점소성 구조물의 진동 특성 연구)

  • 김덕관;김승조
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.49-54
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    • 1997
  • In this paper, vibration characteristics are considered about thermo-visco-plastic material under periodic thermal loading. When in high temperature region, thermo-visco-plastic structure has a periodic thermal loading, it is very important in an accumulated structure like a spacestation to investigate vibration characteristic, stress-strain characteristic is considered in various 2-D model by finite element method.

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DEVELOPMENT OF NUMERICAL MODEL FOR THE VISCO-PLASTIC BEHAVIOUR OF THE JOINTED ROCK MASS REINFORCED BY ROCKBOLTS (록볼트로 보강한 절리암반의 점소성거동에 관한 수치해석 모델 개발)

  • Lee, Yeon-Gyu;Lee, Jeong-In;Jo, Tae-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • 1994.09a
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    • pp.149-157
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    • 1994
  • In this study two dimensional visco-plastic finite element model capable of handling the multi-step excavation was developed for investigating the effect of excavation support sequences on the behavior of underground openings in the jointed rock mass. First, the finite element model which is capable of handling the multi-step excavation is developed and verified. And then the model is combined with visco-plastic joint model. Ubiquitous joint pattern was considered in the model and joint properties in cach set were assumed to be indentical. Passive, full-grouted rockbolts were cosidered in the numerical model. The visco-plastic deformations of joints and rockbolts were assumed to be governed by Mohr-Conlomb and von Mises yield criteria, respectively. With the ability of removing elements, the model can simulate the multi-step excavation-suppport sequences. The reliability and applicability of the model to the stability analysis for the underground excavation in pratice was checked by simulating the behavior of underground crude oil storage caverns under construction.

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Structural analysis of liquid rocket thrust chamber regenerative cooling channel using visco-plastic model (점소성 모델을 이용한 액체로켓 연소기 재생냉각 채널 구조해석)

  • Ryu Chul-Sung;Choi Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.05a
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    • pp.151-155
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    • 2006
  • Elastic-viscoplastic structural analysis is performed for regenerative cooling chamber of liquid rocket thrust chamber using Bodner-Partom visco-plastic model. Strain rate test was also conducted for a copper alloy at various temperatures in order to get material constants of visco-plastic model used in the structural analysis. Material constants of visco-plastic model were obtained from strain rate test results and visco-plsstic model was incorporated into finite element program, Marc, by means of user subroutine. The structural analysis results indicate that the deformation of cooling channel is mostly caused by thermal loading rather than pressure loading and confirmed structural stability of the cooling channel under operating condition.

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Numerical Analysis of the Visco-plastic Behavior of Rock Mass Considering Continuum Joints and Rock Bolt Elements (연속체 절리와 록볼트 요소를 고려한 암반의 점소성 거동에 관한 수치해석)

  • 노승환;이정인;이연규
    • Tunnel and Underground Space
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    • v.14 no.3
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    • pp.215-228
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    • 2004
  • Rock mass contains discontinuities such as faults and joints, and their mechanical properties and spatial distribution dominate the stability of rock mass. Because the deformation of rock mass occurs discontinuities in many cases. However in the case of poor quality rock mass under high stresses, the deformation along intact rock can also influence the structure's stability. In this study, two dimensional finite element program was developed with a rheological model to analyze the stability of the structure excavated in jointed rock mass. The “equivalent material” approach was used assuming intact rock, joints and rock bolts as visco-plastic materials. The program was verified by analysing an intact rock model, a jointed rock mass model and a reinforced jointed rock mass model. The displacement was examined in each model with changing the intact rock behaviour as elastic and visco-plastic. In the case of poor quality rock mass under high stresses, e assumption of visco-plastic behaviour of intact rock resulted in larger displacement than when assuming elastic behaviour for intact rock. Therefore it is recommended to add intact rock's visco-plastic behaviour to the existing model, which only assumes visco-plastic behaviour of joints and rock bolts.

A Study of Localization with Al7075 By Using Rigid-Plastic Finite Element Method (강소성 유한요소법을 이용한 알루미늄 7075합금강의 국부화 현상에 대한 연구)

  • 이병섭
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2000.04a
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    • pp.9-12
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    • 2000
  • The importance of the role of plastic spin in the rate-dependent response of materials at large deformations is the main objective of this work. After a brief presentation of a general consitutive framework for visco-rigid plasticity at large strains an isotropic/kinematic hardening and a visco-rigid plastic model are used to analyze the stress-strain response under simple shear. A clear understanding of the role of plastic spin is achieved by obtaining numerical analyzed results for different stress values in which the plastic spin consititutive parameters interrelaste with the strain rate and other more conventional model constants, Especially this paper is concerned with introducing behaviors of Al7075

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Model for Flow Analysis of Fresh Concrete Using Particle Method with Visco-Plastic Flow Formulation (점소성 유동 입자법에 의한 굳지 않은 콘크리트의 유동해석 모델)

  • Cho, Chang-Geun;Kim, Wha-Jung;Choi, Yeol
    • Journal of the Korea Concrete Institute
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    • v.20 no.3
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    • pp.317-323
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    • 2008
  • In the current study, A model for the flow analysis of fresh and highly flowable concrete has been developed using a particle method, the moving particle semi-implicit (MPS) method. The phenomena on the flow of concrete has been considered as a visco-plastic flow problem, and the basic governing equation of concrete particle dynamics has been based on the Navier-Stokes equation in Lagrangian form and the conservation of mass. In order to formulate a visco-plastic flow constitutive law of fresh concrete, concrete is modeled as a highly viscous material in the state of non-flow and as a visco-plastic material in the state of flow after reaching the yield stress of fresh concrete. A flow test of fresh concrete in the L-box was simulated and the predicted flow was well matched with the experimental result. The developed method was well showed the flow motion of concrete particles because it was formulated to be based on the motion of visco-plastic fluid dynamics.

Structural Analysis of Liquid Rocket Thrust Chamber Regenerative Cooling Channel using Bodner-Partom Viscoplastic Model (Bodner-Partom 점소성 모델을 이용한 액체로켓 연소기 재생냉각 채널 구조해석)

  • Ryu, Chul-Sung;Baek, Un-Bong;Choi, Hwan-Seok
    • Journal of the Korean Society of Propulsion Engineers
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    • v.10 no.4
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    • pp.69-76
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    • 2006
  • Elastic-viscoplastic structural analysis has been performed for regenerative cooling chamber of liquid rocket thrust chamber using Bodner-Partom visco-plastic model. Strain rate test was conducted for a copper alloy at various temperatures in order to get material constants of visco-plastic model used in the structural analysis. Material constants of visco-plastic model were obtained from strain rate test results and visco-plastic model was incorporated into finite element program, Marc, by means of a user subroutine. The structural analysis results indicated that the deformation of cooling channel is mostly caused by thermal loading rather than pressure loading and confirmed structural stability of the cooling channel under the operating condition.

Numerical analysis of vertical drains accelerated consolidation considering combined soil disturbance and visco-plastic behaviour

  • Azari, Babak;Fatahi, Behzad;Khabbaz, Hadi
    • Geomechanics and Engineering
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    • v.8 no.2
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    • pp.187-220
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    • 2015
  • Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.

Comparison between 2D FEM Analysis using Elastic (visco)-plastic model and In-situ Behavior (성토가 주변지반에 미치는 영향에 대한 해석적 검증과 실측치의 비교분석)

  • 황성춘;김승렬
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.02a
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    • pp.79-92
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    • 2000
  • In this paper, comparison of the observed and the predicted ground deformations due to the construction of road embankment with peck drain near the construction site was made. Measurement of the ground deformation at the gasoline stand due to the construction of road embankment was made and it was compared with the predicted deformation results of Finite Element Method analysis made with Elasto-plastic and Elastic visco-plastic models. A well agreement was obtained between the measured and predicted ground deformations.

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Characteristics of Long-Term Settlement in the Soft Ground of Nakdong River by Numerical Analysis (수치해석에 의한 낙동강 하구 연약지반의 장기침하특성)

  • Park, Choon-Sik;Ryu, Mean-Young
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.3
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    • pp.55-67
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    • 2019
  • Deep soft ground in mouth of Nackdong river requires to be analysed with prediction method concerning characteristics of secondary consolidation from the beginning because it causes excessive settlement due to time-dependant secondary consolidation characteristics. This study investigated characteristics of extended settlement by conducting one-dimensional theory, elasto-plastic model and visco-elasto-plastic model as well as analyzing long-term measuring data observed over 2,000 days. According to one-dimensional theory and elasto-plastic model, there is not definite correlation between height of embankment and depth of soft ground while visco-elasto-plastic model showed similar result of settlement to that of long-term measuring data. Consequently it is suggested that applying visco-elasto-plastic model to developing deep underground place as studied area on predicting extended settlement before construction prevents economic loss and delay during process by preparing secondary consolidation characteristics.