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    Numerical investigation of plastic strain homogeneity during equal-channel angular pressing of a Cu-Zr Alloy
    (2021-12-01)
    Wongsa-Ngam, Jittraporn
    ;
    Noraphaiphipaksa, Nitikorn
    ;
    Kanchanomai, Chaosuan
    ;
    Langdon, Terence G.
    A three-dimensional finite element method (3D FEM) simulation was carried out using ABAQUS/Explicit software to simulate multi-pass processing by equal-channel angular pressing (ECAP) of a circular cross-sectional workpiece of a Cu-Zr alloy. The effective plastic strain distri-bution, the strain homogeneity and the occurrence of a steady-state zone in the workpiece were investigated during ECAP processing for up to eight passes. The simulation results show that a strain inhomogeneity was developed in ECAP after one pass due to the formation of a corner gap in the outer corner of the die. The calculations show that the average effective plastic strain and the degree of homogeneity both increase with the number of ECAP passes. Based on the coefficient of variance, a steady-state zone was identified in the middle section of the ECAP workpiece, and this was numerically evaluated as extending over a length of approximately 40 mm along the longitudinal axis for the Cu-Zr alloy.
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    The boundary condition of a 3D continuum model for a quasi 2D plane strain condition
    (2021-06-01)
    Chaiyaput, Salisa Fern
    ;
    Sugimoto, M.
    The half-model has been used in the finite element analysis, based on the symmetric condition against the tunnel’s longitudinal, vertical plane, but this design concept cannot apply to a staggered lining. Therefore, the authors have proposed a multi-ring model to present the segmental lining behavior of a 3D continuum ground model in the case of staggered building, but the proposed 12-ring model shows the different axial force distributions in circumferential directions between the center of the model and the end of the model, especially in cases of soft soil. Accordingly, to make clear, the mechanism of the above difference and to establish the analysis condition of the proposed model for quasi 2D plane strain condition, this paper evaluates the influence of boundary condition on the transverse cross section at the end of the segmental lining on the segmental lining behavior, based on the analyzed axial force and bending moment in soft and stiff ground conditions using both the 2-ring model and a 12-ring model. As a result, it was confirmed that the proposed 2-ring model could simulate the segmental lining behavior under quasi 2D plane strain condition.
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    Reconfirmation of Skempton-Bjerrum 2D to 3D settlement conversion using FEM of full scale embankments
    (2018-06-01)
    Chaiyaput, S.
    ;
    Bergado, D. T.
    The soil is a production of natural process, which is highly variable with very complex properties, and soil behavior can be difficult to calculate. Numerical Simulation can be applied to deal with the numerous aspects of complex geotechnical structures. The 3D FEM simulation model can present the conditions of the geotechnical project in details and assumptions, which are similar to actual situations, but the process of running the 3D FEM analysis takes longer computer time. Therefore, 2D FEM simulation model is proposed to reduce calculation time, but the prediction results are usually overestimated. Accordingly, this paper re-analyzed the 2D analysis to represent the performance of 3D analysis based on Skempton-Bjerrum method. The simulated 2D and 3D FEM settlement results had been carried out and compared with the measured data of two full scale embankments including the dissipation of the excess pore pressure. Consequently, it was confirmed that predicted result of 2D and 3D FEM numerical simulation agreed with the correction of Skempton-Bjerrum method that can be applied to predict the final settlements in 3D conditions.
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    Tunneling simulation in soft ground using shell elements and grouting layer
    (2017-01-01)
    Lueprasert, Prateep
    ;
    Jonpradist, Pornkasem
    ;
    Suwansawat, Suchatvee
    With the advancement of computer sciences and researches on tunneling simulation in the past, the 3D finite element analysis of tunnel excavation by Tunnel Boring Machines (TBMs) has been extensively used over the last decade. Due to that the complicated construction sequences and relevant loads can be taken into account, complex interaction problems can then be performed. Many simulation techniques have been proposed depending on the assumptions used in the modeling. For modeling the tunnel lining, solid elements are commonly used due to the ratio between the width and thickness of the lining is not large. In addition, most studies focused on the ground deformation, not the lining forces. In the circumstance that the lining forces are essentially observed, the structural elements that directly provide the values are preferred. Therefore, this research attempts to propose the shell elements as tunnel lining together with the grouting layer in the analysis. The analysis results from the proposed method and the conventional one are compared and discussed in terms of ground deformation and lining forces together with the field measurement data. The results reveal that the simulation by the proposed method is sufficient and can reasonably reproduce the soil and lining responses.
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    Influence of process parameters on shape quality and area fraction in round-to-hexagonal composite wire drawing
    (2008-07-18)
    Norasethasopon, Somchai
    This research paper shows how three of the main process parameters, the composite wire yield-stress (S), the cross-sectional area reduction (Re) and die-half-angle (α), influenced drawing stress, area fraction of the core and shape quality in the round-to-hexagonal composite wire drawing by FEM and experiment. The FEM and experimental round-to-hexagonal composite-wire drawing were conducted and compared using two metallic materials types. The Re, α, and S strongly influenced the shape quality. The Re, α, and S slightly influenced change in area fraction of core. The increasing of the area fraction of core was found by experiment. Both increasing and decreasing of the area fraction of core were found by FEM. The change in area fraction of core, which equals to zero, was obtained at a value of α and this α value increased as S increased. The Re, α, and S strongly influenced drawing stress. The Re and S directly strongly and inversely influenced optimal die-half-angle, respectively. © 2007 Elsevier B.V. All rights reserved.