• Title, Summary, Keyword: modified drucker-prager model

Search Result 15, Processing Time 0.117 seconds

Constitutive Modeling of AZ31B Magnesium Alloys (AZ31B 마그네슘 합금 판재의 구성식 개발)

  • Lee, M.G.;Chung, K.;Kim, H.Y.
    • Transactions of Materials Processing
    • /
    • v.16 no.4
    • /
    • pp.234-238
    • /
    • 2007
  • Magnesium alloy sheets in room temperature have unusual mechanical properties such as high in-plane anisotropy/asymmetry of yield stress and hardening behavior. In this paper, the continuum plasticity models considering the plastic behavior of AZ31B Mg alloy sheet were derived. A new hardening law based on modified two-surface model was developed to consider the general stress-strain response of metals including Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. To include the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified by adding anisotropic constants.

Densification Analysis for SiC Powder under Cold Compaction (냉간압축 하에서 실리콘 카바이드 분말의 치밀화해석)

  • Park, Hwan;Kim, Ki-Tae
    • Journal of the Korean Ceramic Society
    • /
    • v.37 no.6
    • /
    • pp.589-595
    • /
    • 2000
  • Densification behavior of SiC powder was investigated under cold compaction. A special form of the Cap model was proposed from experimental data of SiC powder under triaxial compression. To compare with experimental data of SiC powder under cold compaction, the proposed constitutive model was implemented into a finite element program (ABAQUS). Finite element calculations from the Cam-Clay model and the modified Drucker-Prager model were also compared with experimental data of SiC powder. The agreements between experimental data and finite element results obtained from the proposed constitutive model are reasonably good. In die pressing, finite element results obtained from the Cam-Clay model and the modified Drucker-Prager model, however, show lower average density of SiC powder compacts compared to experimental data.

  • PDF

Quantitative impact response analysis of reinforced concrete beam using the Smoothed Particle Hydrodynamics (SPH) method

  • Mokhatar, S.N.;Sonoda, Y.;Kueh, A.B.H.;Jaini, Z.M.
    • Structural Engineering and Mechanics
    • /
    • v.56 no.6
    • /
    • pp.917-938
    • /
    • 2015
  • The nonlinear numerical analysis of the impact response of reinforced concrete/mortar beam incorporated with the updated Lagrangian method, namely the Smoothed Particle Hydrodynamics (SPH) is carried out in this study. The analysis includes the simulation of the effects of high mass low velocity impact load falling on beam structures. Three material models to describe the localized failure of structural elements are: (1) linear pressure-sensitive yield criteria (Drucker-Prager type) in the pre-peak regime for the concrete/mortar meanwhile, the shear strain energy criterion (Von Mises) is applied for the steel reinforcement (2) nonlinear hardening law by means of modified linear Drucker-Prager envelope by employing the plane cap surface to simulate the irreversible plastic behavior of concrete/mortar (3) implementation of linear and nonlinear softening in tension and compression regions, respectively, to express the complex behavior of concrete material during short time loading condition. Validation upon existing experimental test results is conducted, from which the impact behavior of concrete beams are best described using the SPH model adopting an average velocity and erosion algorithm, where instability in terms of numerical fragmentation is reduced considerably.

Dynamic Characteristics of Railway Structures under High-Speed Train Loading (고속열차 주행 시 동적하중을 받는 철도구조물의 진동 특성)

  • Rhee, Inkyu;Kim, Jae Min
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.33 no.2
    • /
    • pp.121-128
    • /
    • 2020
  • The purpose of this study is to investigate the distribution patterns of displacement and acceleration fields in a nonlinear soil ground based on the interaction of high-speed train, wheel, rail, and ground. For this purpose, a high-speed train in motion was modeled as the actual wheel, and the vertical contact of wheel and rail and the lateral contact, caused by meandering motion, were simulated; this simulation was based on the moving mass analysis. The soil ground part was given the nonlinear behavior of the upper ground part by using the modified the Drucker-Prager model, and the changes in displacement and acceleration were compared with the behavior of the elastic and inelastic grounds. Using this analysis, the displacement and acceleration ranges close to the actual ground behavior were addressed. Additionally, the von-Mises stress and equivalent plastic strain at the ground were examined. Further, the equivalent plastic and total volumetric strains at each failure surface were examined. The variation in stresses, such as vertical stress, transverse pressure, and longitudinal restraint pressure of wheel-rail contact, with the time history was investigated using moving mass. In the case of nonlinear ground model, the displacement difference obtained based on the train travel is not large when compared to that of the elastic ground model, while the acceleration is caused to generate a large decrease.

Constitutive Modeling of Magnesium Alloy Sheets (마그네슘 합금 판재의 비선형 항복.경화거동 모델링)

  • Lee, M.G.;Wagoner, R.H.;Lee, J.K.;Chung, K.;Kim, H.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • /
    • pp.298-301
    • /
    • 2007
  • Magnesium alloy sheets have unique mechanical properties such as high in-plane anisotropy/asymmetry of yield stress and hardening response. The unusual mechanical behavior of magnesium alloys has been understood by the limited symmetry crystal structure of HCP metals or by deformation twinning. In the present study, the continuum plasticity models considering the unusual plastic behavior of magnesium alloy sheet were derived for a finite element analysis. A new hardening law based on two-surface model was developed to consider the general stress-strain response of metal sheets such as Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. In terms of the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified to include the anisotropy of magnesium alloys.

  • PDF

Closed-die Compaction of AZO Powder for FE Simulation of Powder Compaction (압분공정의 유한요소 해석을 위한 AZO 분말의 Closed-die Compaction 실험)

  • Kim, Y.B.;Lee, J.S.;Lee, S.M.;Park, H.J.;Lee, G.A.
    • Transactions of Materials Processing
    • /
    • v.21 no.4
    • /
    • pp.228-233
    • /
    • 2012
  • In this study, powder compaction of AZO (alumina doped zinc oxide) powder was performed with a MTS 810 test system using a cylindrical die having a diameter of 10mm. Pressure-density curves were measured based on the load cell and displacement of the punch. The AZO powder compacts with various densities were formed to investigate the mechanical properties such as fracture stress of the AZO powder as a function of the compact density. Two types of compression tests were conducted in order to estimate the fracture stress using different loading paths: a diameteral compression test and a uniaxial compression test. The pressure-density curves of the AZO powder were obtained and the fracture stress of the compacted powders with various densities was estimated. The results show that the compact pressure dramatically increases as the density increases. Based on the experimental results, calibration of the modified Drucker-Prager/Cap model of the AZO powder for use in FE simulations was developed.

Seismic Response Analysis of Lightly Reinforced Concrete Shear Walls

  • Rhee, In-Kyu
    • International Journal of Railway
    • /
    • v.3 no.2
    • /
    • pp.73-82
    • /
    • 2010
  • Global and local behaviors of a lightly RC shear walls are investigated in this paper. For the sake of cyclic behaviors, nominal ground accelerations of 0.15 g, 0.40 g and 0.55 g which associated with natural periods of the walls are applied as listed in French CAMUS-2000 shake table test. Modified Kent & Park model, Drucker-Prager model for concrete material and $Giufr\acute{e}$-Menegotto-Pinto model for rebar are used for time history analyses using fiber/solids elements respectively. Alternatively, Eulerian beam analysis are discussed by imposing inelastic hinges at the most possible plastic hinge location using modified Takeda's trilinear model with stiffness reduction. Relative displacements, base shears, bending moments of 5-story shear building with 36-tons of mass under bi-lateral seismic excitation are extracted and compared with EC-8, PS-92 and KBC-09 provisions. Multi-scaled degradation process; material damage, elemental fracture and structural failure in turn is discussed in the view of numerical accuracy, efficiency and limitation depending on three different model-based analyses.

  • PDF

Constitutive Model for a Confined Concrete Cylinder with an Unbonded External Steel Jacket

  • Roh, Young-Sook
    • Architectural research
    • /
    • v.17 no.1
    • /
    • pp.41-48
    • /
    • 2015
  • Early investigations focused mainly on manipulating the confinement effect to develop a reinforced concrete column with lateral hoops. Based on this legacy model, Li's model incorporated the additional confinement effect of a steel jacket. However, recent experiments on plain concrete cylinders with steel jackets revealed relatively large discrepancies in the estimates of strength enhancement and the post-peak behavior. Here, we describe a modified constitutive law for confined concrete with an unbonded external steel jacket in terms of three regions for the loading stage. We used a two-phase heterogeneous concrete model to simulate the uniaxial compression test of a $150mm{\times}300mm$ concrete cylinder with three thicknesses of steel jackets: 1.0 mm, 1.5 mm, and 2.0 mm. The proposed constitutive model was verified by a series of finite element analyses using a finite element program. The damaged plasticity model and extended Drucker-Prager model were applied and compared in terms of the level of pressure sensitivity for confinement in 3D. The proposed model yielded results that were in close agreement with the experimental results.

Nonlinear Finite Element Analysis of Containment Vessel by Considering the Tension stiffening Effect

  • Lee, Hong-Pyo;Choun, Young-Sun;Seo, Jeong-Moon;Shin, Jae-Chul
    • Nuclear Engineering and Technology
    • /
    • v.36 no.6
    • /
    • pp.512-527
    • /
    • 2004
  • This paper describes the finite element (FE) analysis results of a 1/4 scale model of a prestressed concrete containment vessel (PCCV) by considering the tension stiffening effect, which is a result of the bond effect between the concrete and the steel. The tension stiffening model is assumed to be an exponential form based on the relationship between the average stress and the average strain of the concrete. The objective of the present FE analysis is to evaluate the ultimate internal pressure capacity of the PCCV, as well as its failure mechanism, when the PCCV model is subjected to a monotonous internal pressure beyond is design pressure capacity. With the commercial code ABAQUS, the FE analysis used two concrete failure criteria: a 2-dimensional axi-symmetric model with modified Drucker-Prager failure criteria and a 3-dimensional model with a damaged plasticity mod디. The results of our FE analysis on the ultimate pressure capacity and failure modes of PCCV have a good agreement with the experimental data.

Damage analysis of arch dam under blast loading

  • Xue, Xinhua;Yang, Xingguo;Zhang, Wohua
    • Computers and Concrete
    • /
    • v.12 no.1
    • /
    • pp.65-77
    • /
    • 2013
  • This paper examines the dynamic response of an arch dam subjected to blast loading. A damage model is developed for three dimensional analysis of arch dams. The modified Drucker-Prager criterion is adopted as the failure criteria of the damage evolution in concrete. Then, Xiluodu arch dam serves as an example to simulate the failure behaviors of structures with the proposed model. The results obtained using the proposed model can reveal the reliability degree of the safe operation level of the high arch dam system as well as the degree of potential failure, providing a reliable basis for risk assessment and risk control.