Elastoplastic Damage Model Research Articles

Elasto-plastic damage model considering cohesive matrix interface layers for composite laminates

A three-dimensional (3D) Finite element (FE)-based progressive damage model, which considers the interface matrix layer between two neighboring laminae as a layer of cohesive elements, is proposed to analyze laminated composite plates. An elasto-plastic damage model is integrated with the FE-based program ABAQUS that uses user-defined material subroutine. The present damage model includes fiber failure, matrix failure, and delamination effects. A cohesive zone model, which is available in ABAQUS and uses cohesive elements, is combined with the proposed model to address the delamination damage in the interface layers. 3D solid brick elements are used to model composite layers, and cohesive zone elements are used in between two composite layers to model the adhesive layers. The proposed model has been applied for the progressive damage simulation of AS4/PEEK composite laminates under in-plane and uniaxial tensile loading.

Progressive Analysis of Bearing Failure in Pin-Loaded Composite Laminates Using an Elasto-Plastic Damage Model

Bearing failure of composite laminate is very complicated due to the complexity of different failure mechanisms and their interactions. In this paper, an elasto-plastic damage model is built up to describe the process of failure in composite laminates subjected to bearing load. Non-linear behavior of composite before failure is taken into consideration by using a modified Sun-Chen one parameter plasticity model. LaRC05 failure criteria are employed to predict the initiation of failure and the evolution of failure is described by a CDM based stiffness degradation model. Both theory and some application issues like parameter determination are discussed according to phenomenon of experiments. The model is firstly validated by several experiment results of unidirectional laminate and then applicated into the progressive analysis of bearing failure in pin-loaded multidirectional laminates, both intralaminar and interlaminar damage are taken into consideration. The result of finite element analysis is compared with experiment results; it shows good agreements in both mechanical response and progress of failure, so the model can be evaluated to be effective and practical in bearing failure analysis of composite laminates.

Fatigue lifetime prediction of structural steel by cohesive-traction embedded elasto-plastic damage model with kinematic hardening

Fatigue lifetime prediction of structural steel by cohesive-traction embedded elasto-plastic damage model with kinematic hardening

An equivalent elastoplastic damage model based on micromechanics for hybrid fiber-reinforced composites under uniaxial tension

A micromechanics-based equivalent elastoplastic damage model for both notch-sensitive and multiple cracking hybrid fiber reinforced composite is proposed in this study. In this model, the elastic modulus, first cracking strength, and ultimate strength are estimated based on micromechanics. To quantify strain after matrix cracks, a novel characteristic length is defined based on the damage mechanics. The effects of the fiber length, diameter and modulus, and interfacial bond stress on the characteristic length of hybrid fiber reinforced composite are presented. In order to avoid the difficulty of determining the traditional damage and plastic potential function, this model is developed from the behavior of single fiber at mesolevel to the response of hybrid fiber reinforced composite at macrolevel. Then the calculated results are verified with several published experimental results of fiber reinforced composites and hybrid fiber reinforced composite, including notch-sensitive cracking fiber reinforced composite, multiple cracking fiber reinforced composite, and multiple cracking hybrid fiber reinforced composite reinforced with two types of fibers (steel fiber and polyethylene fiber). A parametric study has been performed to investigate the effects of the fiber properties, including the fiber volume fraction, length, diameter, and interfacial bond stress, on the tensile performance of hybrid fiber reinforced composite reinforced with steel fiber-like and polyethylene fiber-like fibers. The results indicate that enhancement of the tensile performance can be achieved more effectively by improving the polyethylene fiber-like fiber than steel fiber-like fiber.

Numerical modeling of the elastoplastic damage behavior of dry and saturated concrete targets subjected to rigid projectile penetration

SummaryThe objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts.

Experimental and Modelling Investigations of the Coupled Elastoplastic Damage of a Quasi-brittle Rock

Triaxial compression tests are conducted on a quasi-brittle rock, limestone. The analyses show that elastoplastic deformation is coupled with damage. Based on the experimental investigation, a coupled elastoplastic damage model is developed within the framework of irreversible thermodynamics. The coupling effects between the plastic and damage dissipations are described by introducing an isotropic damage variable into the elastic stiffness and yield criterion. The novelty of the model is in the description of the thermodynamic force associated with damage, which is formulated as a state function of both elastic and plastic strain energies. The latter gives a full consideration on the comprehensive effects of plastic strain and stress changing processes in rock material on the development of damage. The damage criterion and potential are constructed to determine the onset and evolution of damage variable. The return mapping algorithms of the coupled model are deduced for three different inelastic corrections. Comparisons between test data and numerical simulations show that the coupled elastoplastic damage model is capable of describing the main mechanical behaviours of the quasi-brittle rock.

Numerical modelling of long-term stability of the rock joint

This paper is focused on the numerical modelling of long-term stability of the rock joint, which has been performed using the extended finite element method. An elastoplastic damage model is developed for the rock matrix around the joints, while a specially developed interface model has been used for the joints. The proposed model for rock joint is based on the assumptions made on the aperture scale. The simplest exponential degradation law has been proposed for both the residual friction angle and the aperture erosion, for taking into consideration the time effects. The proposed model is then used to simulate some direct shear tests realised on the intact and eroded rock interfaces. Comparison of available test results shows that the proposed model is capable to predict satisfactorily the time-dependant degradation caused by either the residual friction angle decrease and/or interface roughness erosion. Therefore, the time effects is numerically analysed via a parametric study on an academic example. The numerical results show that the degradation caused by the decrease in residual friction angle and erosion on the joint surface reduce dramatically joint’s resistance.

Effects of inclusion stiffness on the cracking of cement-based composites under drying: a numerical study

This paper focuses on the evolution of shrinkage cracking in a geometrically simplified concrete, i.e. a composite made of cement matrix including the glass spheres. In the first part, the laboratory samples at different levels of drying are examined experimentally. In order to identify the occurrence of cracking as well as its evolution in a direct and visual way, a non-destructive method called X-ray microtomography is used. The distribution of cracks is clearly identified, including their location and shape by the observation of cross section of samples. Based on the experimental investigations, a special coupled elastoplastic damage model is proposed to describe the mechanical behaviour of the composite. The obtained results satisfactorily reproduced the stress distribution and evolution in studied composite under drying and gave a better understanding of mechanical mechanism of shrinkage cracking. In order to study the influence of matrix behaviour and inclusion stiffness, a series of parametric studies are also performed by using a hydromechanical coupling code, incorporating the proposed constitutive model. One notices that the crack distribution in the sample depends strongly on the stiffness of inclusion and the mechanical behaviour of cement matrix.

An anisotropic elastoplastic damage constitutive model for 3D needled C/C-SiC composites

This paper established a combined elastoplastic damage model to analyze the nonlinear mechanical behavior of 3D needled C/C-SiC composites. Inelastic deformation and stiffness degradation of the composite were characterized by the plasticity and damage theories. An innovative plastic potential function containing variable parameters was proposed to consider particularly the anisotropy of plastic deformation in each material direction. Based on the Weibull statistical distribution of the material strength, an exponential damage state function was established to characterize stiffness degradation for the composite in each material direction. Parameters of this constitutive model were determined from experiments data. It can be found that the nonlinear stress-strain curves for the composite under off-axis tensile and shear loadings can be accurately described by the model. The yield and damage surfaces of the composite were also studied. Finally, the constitutive model was validated by analyzing the mechanical behavior of a composite plate containing a center-hole subjected to tensile load.

탄-소성 손상모델을 활용한 고망간강의 인장거동 모사에 관한 연구

탄-소성 손상모델을 활용한 고망간강의 인장거동 모사에 관한 연구

Elasto-plastic damage modelling of beams and columns with mechanical degradation

Elasto-plastic damage modelling of beams and columns with mechanical degradation

Effects of frost-damage on mechanical performance of concrete

The aim of this study is to provide the quantificational change laws of strength, stiffness, and deformation capacity of frost-damaged concrete relating to a united index, the data were obtained by different researchers. Then the index of relative compressive strength (RCS) was introduced as the indicator of frost damage and a large number of mechanical performance testing data of frost-damaged concrete were collected and analyzed. By curve fitting, the correlations between RCS and the initial elastic modulus, the strain at peak compressive stress, and biaxial compressive strength, and tensile strength, and the strain at peak tensile stress were established. Thereafter, the analytical stress-strain response of frost-damaged concrete under monotonic loading was presented using RCS and compared with that of the experimental data. Moreover, an isotropic elastoplastic damage model of frost-damaged concrete subjected to repeated loading was established. Finally, we can systematically estimate the effects of frost-damage on the mechanical performance of concrete, which can be provided for the numerical simulation of frost-damaged concrete structures.

A three-invariant cap-plasticity damage model for cementitious materials

We present a new continuum elastoplastic damage model for cementitious materials which captures their distinct behavior in tension and compression due to crack-induced damage and irreversible plastic deformation. It also describes their response under multi-axial loading with low to high confining pressures. A smooth, closed-convex three stress-invariant yield surface is developed which perpendicularly intersects the negative hydrostatic axis and is composed of a shear loading surface and an elliptical cap. It incorporates a plastic internal state variable (ISV) characterizing non-uniform hardening of both shear loading surface and elliptical cap, while the flow rule is considered to have volumetric non-associativity. Damage evolution laws incorporate two ISVs describing crack growth at the macroscale under tensile and compressive stresses separately. Overall damage under multiaxial loading explicitly considers the effect of confining stresses on damage evolution and stiffness recovery effects under cyclic loading. Model predictions are compared against several experimental results on various concretes and also against responses of recently reported models. The proposed model predicts distinctive features of concrete very well including hardening behavior in triaxial-compression and both pre- and post-peak volumetric behavior.

An elasto-plastic damage model for functionally graded plates with in-plane material properties variation: Material model and numerical implementation

The paper presents an elasto-plastic damage model based on irreversible thermodynamics for the analysis of functionally graded (FG) plates with in-plane material properties variations. The model considers a simple power law function to describe the FG plates as continua with smooth variation of material properties, such as Young’s Modulus, yield stress, plastic material constants and damage parameters. By introducing two independent plastic and damage multipliers, the model is applicable to different types of materials. Employing the operator splitting methodology, a three-step predictor/multi-corrector algorithm is developed that includes an elastic predictor, a plastic corrector, and a damage corrector. Then, the damage finite element (FE) solutions are obtained using linear hexahedral solid elements with spatially graded property distribution (at different Gauss points), and subsequently implemented by a user material subroutine (UMAT) in the ABAQUS FE software. Good agreement is shown between the analytical damage models, the FE solutions and experimental results sourced from the literature. Several numerical examples establish that the present model is not only accurate, but provides a simple approach to predicting damage of different types of materials, including those that demonstrate both elastic-brittle damage and elasto-plastic damage behaviours. Moreover, the presented model effectively describes the continuum damage of FG plates, capturing variation of the damage variable throughout the plane of the plate.

Numerical simulation of squat reinforced concrete wall strengthened by FRP composite material

The advanced design rules and the latest known earthquakes, have imposed a strengthening of reinforced concrete structures. Many research works and practical achievements of the application of the external reinforcement by using FRP composite materials have been particularly developed in the recent years. This type of strengthening seems promising for the seismic reinforcement of buildings. Among of the components of structures that could affect the stability of the structure in case of an earthquake is the reinforced concrete walls, which require in many cases a strengthening, especially in case where the diagonal cracks can be developed. The intent of this paper is to present a numerical simulation of squat reinforced concrete wall strengthened by FRP composite material (carbon fiber epoxy). The intent of this study is to perform finite element model to investigate the effects of such reinforcement in the squat reinforced concrete walls. Taking advantage of a commercial finite element package ABAQUS code, three-dimensional numerical simulations were performed, addressing the parameters associated with the squat reinforced concrete walls. An elasto-plastic damage model material is used for concrete, for steel, an elastic-plastic behavior is adopted, and the FRP composite is considered unidirectional and orthotropic. The obtained results in terms of displacements, stresses, damage illustrate clearly the importance of this strengthening strategy.

An elasto-plastic damage model for argillaceous geomaterials

The aim of this paper is to present a new elastoplastic damage model for unsaturated porous media. The proposed model within the context of poromechanics is intended for constitutive modelling of geomaterials which show two (irreversible) dissipative aspects involving plastic flow and damage. Independent stress state variables, namely net stress and suction, are adopted as stress variables of the model. Barcelona Basic Model is extended to a non-isothermal formulation and is coupled to a damage formulation using damage dependent yield surface and damaged stress variables. The stress state variables are transformed into the damaged state through the definition of effective damaged suction and effective damaged net stress in the framework of Continuum Damage Mechanics (CDM). Damage effects on intrinsic permeability and transfer laws are also taken into consideration. The model has been implemented in Θ-STOCK Code and predictive capabilities of the model have been evaluated against experimental results from the literature. The model is validated by comparing the numerical results with experimental results of argillites and results of an elastodamage model. The proposed model is also shown to give satisfactory simulation results which match the experimental data from a heating test on bentonite samples.

Hysteresis behaviour modelling of woven composite using a collaborative elastoplastic damage model with fractional derivatives

The collaborative model is a new tool to represent visco-elastoplastic damaged material behaviour including hysteresis loops for woven composites under cyclic loading. The model consists of two sub-models. The first one describes a material behaviour during loading path. The elastic and the in-elastic strains as well as the in-ply damage are computed. The second part deals with hysteresis modelling during unloading path using a fractional derivative approach. Just a few parameters are required to represent the hysteresis loops. The material strain-rate effect is also taken into account by two sub-models. The parameters identification methodology is presented and the fractional derivative approximations are detailed. The collaborative model is validated for the woven composite with thermoset and thermoplastic matrixes. The precise estimation of the dissipated energy is possible.

Modelling of change in permeability induced by dilatancy for brittle geomaterials

The safety and durability of concrete structures are significantly affected by cracking. This structural disorder provides a preferential path for the penetration of fluids and may accelerate the material deterioration. This study investigates the mechanical damage and permeability interactions in geomaterials subjected to compressive stress inducing cracking. The development reported here is implemented within an elasto-plastic damage model able to compute plastic dilatancy. The model assumes an initial isotropic permeability tensor which becomes anisotropic with non-isotropic expansion. The model capabilities are highlighted by simulating uniaxial and triaxial compression tests. The simulation results are compared with experimental data.

Numerical prediction of springback and ductile damage in rubber-pad forming process of aluminum sheet metal

Rubber forming is a sheet metal forming process using flexible punch or die. In this paper, finite element method is introduced to analyze rubber-pad forming process of aluminum sheet metal. An elasto-plastic constitutive model with J2 yield criterion and mixed non-linear isotropic/kinematic hardening coupled with Lemaitre's ductile damage has been adopted during flexible forming operation. To model rubber material, a Mooney-Rivlin theory is used in the finite element simulation. A stamping of aluminum sheet metal with soft punch is simulated. A fully coupled elasto-plastic damage model is implemented in ABAQUS/Standard software via UMAT subroutine to study the effect of some key process parameters like hardness of rubber, type of rubber on the variation of the thickness, the springback and damage of aluminum sheet metal.

Analyzing the impact of microstructural defects on the failure response of ceramic fiber reinforced aluminum composites

The computational homogenization technique is employed to investigate the effect of pre-existing microstructural voids on the failure response of a ceramic fiber reinforced aluminum composite subjected to loads in transverse to the fiber direction. Automated numerical simulations are carried out using a hierarchical interface-enriched finite element method (HIFEM), which enables the use of simple structured meshes for creating the discretized model. The HIFEM is integrated with a new microstructure quantification algorithm relying on the Random Sequential Adsorption (RSA) and Non-Uniform Rational B-Splines (NURBS) to create realistic periodic unit cells of the composite based on imaging data. A strain-driven homogenization problem is then solved at the microscale to simulate the damage evolution in the aluminum matrix using the Lemaitre elasto-plastic damage model. Six virtual models of the composite microstructure with varying volume fractions and spatial distributions of pre-existing voids are analyzed to determine their failure responses subject to macroscopic normal and shear strains. The outcomes of this study indicate that although for the latter type of loading the impact of small volume fractions of voids on the failure response is negligible, their presence significantly deteriorates the composite mechanical strength subject to uniaxial and equi-biaxial macroscopic normal strains.