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  • Open Access

    ARTICLE

    Research on damage distribution and permeability distribution of coal seam with slotted borehole

    Yi Xue1,2, Feng Gao1,2,3, Xingguang Liu4, Xiru Li2

    CMC-Computers, Materials & Continua, Vol.47, No.2, pp. 127-141, 2015, DOI:10.3970/cmc.2015.047.127

    Abstract In order to study the effect of high pressure water jet cutting technology on the permeability of single coal seam, we use the damage variable to describe the fracture distribution of coal seam, develop the 3-D finite element program based on the damage theory, and then analyze the damage distribution of coal seam after drilling and slotting. Using MTS815 rock mechanics testing system and the permeability test system, we conduct the permeability test and get the relationship between permeability and damage. Based on the damage distribution of coal seam after drilling and slotting and the permeability change law, we analyze… More >

  • Open Access

    ARTICLE

    Identification of Damaged Teeth in Gears using Wavelet Transform Applied to the Angular Vibration Signal

    P.A. Meroño1, F.C. Gómez2, F. Marín1

    CMC-Computers, Materials & Continua, Vol.47, No.2, pp. 107-125, 2015, DOI:10.3970/cmc.2015.047.107

    Abstract This work represents a comparative study of Wavelet Transform of angular vibration signal and the traditional Fourier analysis applied to the signals of angular vibration, in one transmission which involve gears. How it is known, the elastic deformation of the material, together with the superficial irregularities of the teeth due to wear, provoke characteristic angular oscillations, which make it possible to distinguish between the regular functioning of a mechanism in good condition and the angular vibrations provoked by wear and the superficial irregularities of teeth in poor condition. However, the character of the vibrations produced in such circumstances means that… More >

  • Open Access

    ARTICLE

    EvaluatingWater Vapor Permeance Measurement Techniques for Highly Permeable Membranes

    Bui Duc Thuan1,2, Wong Yonghui2, Chua Kian Jon2, Ng Kim Choon2

    CMC-Computers, Materials & Continua, Vol.47, No.2, pp. 89-105, 2015, DOI:10.3970/cmc.2015.047.089

    Abstract The cup method and dynamic moisture permeation cell (DMPC) method are two common techniques used to determine the water vapor permeation properties of a membrane. Often, ignoring the resistance of boundary air layers to the transport of water vapor results in the water vapor permeance of the membrane being underestimated in practical tests. The measurement errors are higher with highly permeable membranes. In this study, the two methods were simulated using COMSOL Multiphysics platform and the extent of the error was evaluated. Initial results showed that the error is equally high in both methods. With the correction for the still… More >

  • Open Access

    ARTICLE

    Static and Dynamic Analysis of Laminated Thick and Thin Plates and Shells by a Very Simple Displacement-based 3-D Hexahedral Element with Over-Integration

    Qifeng Fan1, Yaping Zhang2, Leiting Dong1,3, Shu Li1, Satya N. Atluri4

    CMC-Computers, Materials & Continua, Vol.47, No.2, pp. 65-88, 2015, DOI:10.3970/cmc.2015.047.065

    Abstract A very simple displacement-based hexahedral 32-node element (denoted as DPH32), with over-integration in the thickness direction, is developed in this paper for static and dynamic analyses of laminated composite plates and shells. In contrast to higher-order or layer-wise higher-order plate and shell theories which are widely popularized in the current literature, the proposed method does not develop specific theories of plates and shells with postulated kinematic assumptions, but simply uses the theory of 3-D solid mechanics and the widely-available solid elements. Over-integration is used to evaluate the element stiffness matrices of laminated structures with an arbitrary number of laminae, while… More >

  • Open Access

    ARTICLE

    A New Theory of Strain Hardening and its Consequences for Yield Stress and Failure Stress

    CMC-Computers, Materials & Continua, Vol.47, No.1, pp. 45-63, 2015, DOI:10.3970/cmc.2015.047.045

    Abstract A new theory of strain hardening is developed. Important in its own right, the strain hardening solution is also of decisive use in rigorously defining the historically broad concepts of yield stress and failure stress. Under ideal conditions yield stress is found to represent a 3rd order transition. Failure stress is an explicit "failure of function" criterion rather than just being the primitive notion of breaking into pieces. Computational extensions and opportunities are discussed. More >

  • Open Access

    ARTICLE

    A Macro Element Method to Improve Computational Efficiency in Large-scaled Nonlinear Analysis

    Huan Wang1, Weifeng Yuan2,3, Fei Jia2

    CMC-Computers, Materials & Continua, Vol.47, No.1, pp. 31-43, 2015, DOI:10.3970/cmc.2015.047.031

    Abstract Compared with dealing with a linear system, solving a nonlinear system equation in numerical simulation requires generally more CPU time since iterative approach is usually used in the latter. To cut down the computing cost, a direct way is to reduce the degree of freedoms (DOF) of the problem under investigation. However, this kind of treatment may result in poorer accuracy. In this manuscript, a macro element method is proposed to improve computational efficiency in large-scaled nonlinear analysis. When this concept is incorporated into finite element analysis (FEA), all the members in the linear zones of a structure can be… More >

  • Open Access

    ARTICLE

    Investigation on a Two-dimensional Generalized Thermal Shock Problem with Temperature-dependent Properties

    Tianhu He1,2,3, Yongbin Ma2,3, Shuanhu Shi3

    CMC-Computers, Materials & Continua, Vol.47, No.1, pp. 15-29, 2015, DOI:10.3970/cmc.2015.047.015

    Abstract The dynamic response of a two-dimensional generalized thermoelastic problem with temperature-dependent properties is investigated in the context of generalized thermoelasticity proposed by Lord and Shulman. The governing equations are formulated, and due to the nonlinearity and complexity of the governing equations resulted from the temperature-dependent properties, a numerical method, i.e., finite element method is adopted to solve such problem. By means of virtual displacement principle, the nonlinear finite element equations are derived. To demonstrate the solution process, a thermoelastic half-space subjected to a thermal shock on its bounding surface is considered in detail. The nonlinear finite element equations for this… More >

  • Open Access

    ARTICLE

    Bending Response of Foldcore Composite Sandwich Beams

    Lixin Cong1, Yuguo Sun1,2, Xinzhu Wang3

    CMC-Computers, Materials & Continua, Vol.47, No.1, pp. 1-14, 2015, DOI:10.3970/cmc.2015.047.001

    Abstract In order to solve bending behavior difference of corrugated structure in L andWorientation, bending response for composite sandwich beams with foldcores of three different wall thicknesses were experimentally and numerically investigated. Effect of the cell walls thickness on the strength and failure behavior of the composite sandwich beams with L and W orientations was also examined. The deformation mode was obtained by the numerical method; a constitutive law of laminated material has been incorporated into a finite element (FE) analysis program. Numerical calculations give accurate prediction to the bending response of foldcore composite sandwich beams comparing with experiments. Structural flexural… More >

  • Open Access

    ARTICLE

    Analysis of Local Fracture Strain and Damage Limit of Advanced High Strength Steels using Measured Displacement Fields and FEM

    N. Ma1,2, K. Sato3, K. Takada4

    CMC-Computers, Materials & Continua, Vol.46, No.3, pp. 195-219, 2015, DOI:10.3970/cmc.2015.046.195

    Abstract The local mechanical behaviors of advanced high strength steels undergoing a very large strain from uniform plastic deformation to fracture were investigated with the aid of a measured displacement field and a measurement based FEM. As a measurement method, a digital image grid method (DIGM) was developed and the three-direction transient displacement field on uniaxial tensile test pieces was measured. Combining the measured transient displacement field with the finite element method, a measurement based FEM (M-FEM) was developed for the computation of distribution of the local strains, local stresses and ductile damage accumulation in a tensile test piece. Furthermore, the… More >

  • Open Access

    ARTICLE

    Modeling the Axial Splitting and Curling of Metal Tubes under Crush Loads

    W.Xu1, A.M. Waas2

    CMC-Computers, Materials & Continua, Vol.46, No.3, pp. 165-194, 2015, DOI:10.3970/cmc.2015.046.165

    Abstract Plastic deformation and splitting are two important mechanisms of energy dissipation when metal tubes undergo axial crushing. Isotropic J2 plasticity theory combined with a failure criterion is used to model axial splitting and curling of metal tubes undergoing axial crush. The proposed material model is implemented within a finite element (FE) framework using the user material subroutine VUMAT option available in the commercial code ABAQUS. Experimental results from literature are used to validate the model. The predicted splitting and curling patterns as well as the load-displacement response agree well with the experimental observations. The present material model is also used… More >

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