Papers by Keyword: Damage Mechanics

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Authors: Qin Dong, Ping Yang, Jun Lin Deng, Hong Wang
Abstract: A low-cycle fatigue damage model for stiffened plates has been derived based on the theory of damage mechanics. The fatigue damage variable equation of the stiffened plate under cyclic loading was introduced into the accumulative plastic strain equation. Then by means of integral transformation, the evolution equation of axial plastic strain was derived under low cyclic loading condition. The analysis results by the presented model compare well with those by the finite element method.
Authors: H.E. Fang, Chi Loong Chow, Fan Yang
Authors: Xue Ren Zhang, Jian Hui Zhao, Keh Chih Hwang
Authors: Min He, Duan Hu Shi, Feng Yang, Ning Zhang, Hua Feng Guo
Abstract: An indentation approach with Berkovich indenter is proposed to determine fracture toughness for ductile materials. With decrease of effective elastic modulus, an approximate linear relationship between logarithmic plastic penetration depth and logarithmic effective elastic modulus, and a quadratic polynomial relationship between the plastic penetration depths and penetration loads are exhibited by indentation investigation with Berkovich indenter. The damage constructive equation of effective elastic modulus is proposed to determine the critical effective elastic modulus at the fracture point, which is the key problem to calculate the indentation energy to fracture. The critical plastic penetration depth is identified after the critical effective elastic modulus can be predicted by conventional mechanical properties. The fracture toughness is calculated according to the equation of penetration load, plastic penetration depth and the critical plastic penetration depth.
Authors: Makoto Imura, Tetsusei Kurashiki, Hiroaki Nakai, Masaru Zako
Abstract: Fiber reinforced composite materials have been applied widely to many structures, because they have some advantages like easy handling, high specific strength, etc. The numerical method like finite element method has been applied to design and to evaluate the material properties and behavior as the development of Computer Aided Engineering. It is very difficult to calculate with accuracy not only in structural scale but also in detail material scale (for example, the order of fiber diameter) by the traditional FEM, becausecompositematerials like woven fabric composites have the geometrical complexityand the large difference between above mentioned scales. The development of multi-scale analysis method is one of the major topics in computational mechanics. Mesh superpositionis one of multi-scale analysis methods and is an effective method to solve the problems which have the large difference between the structure scale and the reinforcement scale. We have expanded the finite element mesh superposition method with 3 scales and have defined as M3 (Macro-Meso-Micro) method. In this paper, we have proposed a new approach method combined with M3 method and homogenized method to obtain the mechanical properties and to simulate the behavior of woven fabric composites. In addition, the elastic-plastic mechanics and the damage mechanics have been introduced into M3 method to investigate the effects of matrix-crack on the structural and material properties. From the numerical results, it is revealed that it is very useful for the evaluation of mechanical properties of composite materials.
Authors: Juan Zhang, Yuan Zhang, Ke Qiang He, Wei Gong Chen
Abstract: As an exploration and extension of load/unload response ratio theory, unload/ load response ratio theory (ULRR for short) is introduced firstly, and the relationship between ULRR (Y′) and elastic modulus (E for short) is obtained. Based on the basic theory of damage mechanics,the relationship between ULRR and damage variable (D for short) is set up and analyzed with the relationship between E and D. The unloading and loading experiments on a two-story structure carried out in the University of Naples in Italy are introduced;and calculated damage variable is compared with that calculated by Zhang Langping who put forward Weibull distribution as random distribution function. The results show that damage variable of the structure keep highly consistent with calculations of these two methods. Therefore, the relationship between Y′and D provides a new approach to a health assessment to catastrophic failure of large-scale structures and prediction of engineering.
Authors: Hu Qi, Yun Gui Li, Xi Lin Lu
Abstract: In this paper, an elastic plastic damage model is presented based on the combined use of elastic plastic constitutive equations along with continuum damage mechanics. A tensile and a compressive damage variable are adopted to describe the different responses of concrete under tension and compression, respectively. The Helmholtz Free Energy is decomposed into hydrostatic stress component and deviatoric stress components. The hydrostatic stress component is neglected and the deviatoric stress component is amended according to stress state, resulting in a more accurate description of the concrete’s response under multi-axial stress state. Finally, through several numerical simulations it is proved that the proposed model has the capability of simulating typical nonlinear performances of concrete material.
Authors: M. Vaz, Pablo A. Muñoz-Rojas, M.R. Lange
Abstract: Mechanical degradation and ductile failure in metal forming operations can be successfully modelled using fully coupled damage models. In addition, it has been largely reported in the literature that temperature variations affect material behaviour, especially thermal softening. This paper presents a numerical discussion of the coupled effects between ductile damage and temperature evolution based on the simulation of tensile tests of notched specimens.
Authors: Michele Buonsanti, Giovanni Leonardi, Francesco Scoppelliti
Abstract: The particles distinct element model has the consistency to model the mechanical behavior of the microscopic structures inside an asphalt mixture. The model assumes that the schematized granular constituents are in a contact point, considering the thin asphalt films as the binding elements. In this paper, we will model (at micro-scale) the damage to a surface in asphalt concrete under an impulsive load, considering binding, interface, viscosity and friction. Our aim is to reproduce the micro-damage due to detachment among the elementary components of the concrete in airports pavements.The proposed approach is mainly from a mechanical point of view, and a general model describing adhesive contact between rigid bodies is proposed. The intensity of adhesion is supposed to decrease under prescribed shear and normal displacement fields and comes by energy reduction, where the viscosity and friction contributes are taken in account.A numerical implementation by finite element procedures has been performed, and the outcome is presented.
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