Applied Mechanics and Materials Vol. 784

Abstract: The heterogeneous lattice model is presented to simulate the behaviors of concrete, in which the concrete is regarded as random medium and the stochastic damage constitutive model is proposed. The parameters of the stochastic damage constitutive is identified compared with the experiment results of concrete under uniaxial tension and uniaxial compression.

Abstract: The aim of this paper is to propose the impact failure analysis of reinforced concrete beam using tensile softening technique based on the damage mechanics. In general, tensile crack is the most dominant factor for concrete and it is not appropriate to evaluate their effect by theory of plasticity. Thus mechanical failure of concrete is considered by not only conventional plastic theory but also damage mechanics. In the analysis to calculate the plastic deformation, Drucker-Prager yield surface model is employed, on the other hand Von-Mises yield surface model is applied for the reinforcing bar. Besides, mechanical influence of tensile crack in the concrete is also considered as the decrease of effective cross-section area using anisotropic damage variable. Several impact tests of RC beam are reviewed and their impact response are simulated by proposed analysis method. As a result, it is confirmed that proposed method can simulate impact response of RC beam and it could predict precise failure condition such as the distribution of concrete crack using anisotropic damage model.

Abstract: The ductile failure of metallic alloys is characterized by the long plateau of the stress-strain response during plastic deformation. In aluminium alloys this complex process is principally mediated by crystal slip associated with dislocation nucleation, motion, interaction, and locking. This results in hardening, i.e. the increase in the flow stress and progressive exhaustion of ductility, eventually leading to damage. Therefore, in the advanced stages of deformation the strength increase at the material level competes with overall stiffness and strength decrease due to effective cross-section reduction by decohesion and voiding. Capturing the complex hierarchical failure of these materials requires developing sophisticated concurrent constitutive descriptions of both plastic deformation and damage at different stages of failure. In the present study the modelling of aluminium alloy failure is accomplished using a plasticity-based model with nonlinear hardening coupled with isotropic damage in a thermodynamically consistent framework. The model developed in this way is enhanced with nonlocal regularization to deal with material instabilities issues due to softening. Emphasis is placed on the correspondence between experimental measurements of the essential work of fracture and the non-essential work of fracture, and both local and spatial sets of model parameters. This approach is the key to assuring a constitutive response consistent with experimental observations, an issue usually overlooked in nonlocal constitutive modelling. Numerical examples are used to demonstrate the features of the new approach.

Abstract: This paper provides an overview of recent developments in the modeling of progressive damage in fiber-reinforced composite laminates. Some insights into modeling the size effects of open-hole composite laminates under in-plane tension and compression, the significance of ply-blocking and delamination are discussed. Recent interest in the interaction and migration of matrix cracks and delamination, resulting in development of integrated XFEM-CE and floating node methods will also be presented.

Abstract: A method to simulate concrete structures (quasi-brittle material) with localized nonlinearities is presented. Based on Guyan’s condensation, it consists in replacing the elastic zones of the structure by their equivalent rigidities (super-elements). The nonlinear computation is then performed only on the zones of interest (ie, damaged). As new damaged zones may appear, the proposed method monitors the evolution of the system and re-integrates previously condensed areas if necessary. This method, applied on different tests cases, allows a substantial computation economy.

Abstract: In this work, two time integration algorithms for the anisotropic damage model proposed by Lemaitre et al. (2000) are compared. Specifically, the standard implicit Euler scheme is compared to an algorithm which implicitly solves the elasto-plastic evolution equations and explicitly computes the damage update. To this end, a three dimensional bending example is solved using the finite element method and the results of the two algorithms are compared for different time step sizes.

Abstract: A damage model for thin adhesively bonded joints is presented, which predicts the time to creep-fatigue failure of the joint subjected to combined static and cyclic sustained loadings with constant or variable amplitudes. The influences of particular model parameters on the predicted lifetime are elaborated suggesting the proposed stepwise parameter identification strategy by means of creep and Wöhler fatigue tests until rupture. The parameters are identified and computationally optimized. As a conclusion, the model prediction is verified and validated.

Abstract: In this paper, cycles jumping scheme integration is used to numerically integrate fully coupled constitutive equations in order to predict the low cycle fatigue life under cyclic loading. This procedure avoids the calculation of the full loading cycles (some millions of loading cycles) while considering the transient stages due to the hardening (at the beginning) and the high damage-induced softening during the last tens of loading cycles. The model parameters have been identified using the results obtained from a 316L steel cylindrical specimen subject to symmetric tension-compression loading path. The effects of the specimen size as well as the mesh size on the fatigue life prediction are investigated.

Abstract: The failure of a discrete elastic-damage axial system is investigated using both a discrete and anequivalent continuum approach. The discrete damage mechanics (DDM) approach is based on amicrostructured model composed of a series of periodic elastic-damage springs (axial DDM latticesystem). Such a damage discrete system can be associated with the finite difference formulation of aContinuum Damage Mechanics (CDM) evolution problem.The nonlocal CDM models considered in this paper are mainly built from a continualizationprocedure applied to centered finite difference schemes. A comparison of the discrete and thecontinuous problems for the chains shows the effectiveness of the new micromechanics-basednonlocal Continuum Damage modeling, especially for capturing scale effects.

Abstract: A damage modelization is proposed based on a continuous transition from undamaged to damaged material. The evolution of damage is associated with a moving layer of finite thickness $l_c$, then initiation and propagation of damage can be unified in the same constitutive law. The driving force associated to the layer motion is a generalized release rate of energy. Using a normality rule based on this force the solution of the rate boundary value problem of propagation and displacement satisfies a variational inequation. Applications of the model are proposed.