Analyses of Interfacial Failure

1990 ◽  
Vol 43 (5S) ◽  
pp. S274-S275 ◽  
Author(s):  
A. Needleman
Keyword(s):  
Cohesive Zone ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Interfacial Strength ◽  
Finite Geometry ◽  
Complete Separation ◽  
Type Model ◽  
Interfacial Failure ◽  
Unified Framework ◽  
Full Account

A cohesive zone type model, taking full account of finite geometry changes, is used to provide a unified framework for describing the process of interfacial decohesion from initial debonding through complete separation. Constitutive relations are specified independently for material phases and for the interface. This model permits the prediction of interfacial decohesion without the necessity of introducing some additional failure criterion. Also, since the mechanical response of the interface is specified in terms of both a critical interfacial strength and the work of separation per unit area, dimensional considerations introduce a characteristic length. Various issues associated with the analysis of interfacial failure phenomena within this framework will be discussed.

A Continuum Model for Void Nucleation by Inclusion Debonding

1987 ◽  
Vol 54 (3) ◽  
pp. 525-531 ◽  
Author(s):  
A. Needleman
Keyword(s):  
Cohesive Zone ◽  
Continuum Model ◽  
Cohesive Zone Model ◽  
Characteristic Length ◽  
Void Nucleation ◽  
Finite Geometry ◽  
Zone Model ◽  
Unified Framework ◽  
Full Account ◽  
Spherical Inclusions

A cohesive zone model, taking full account of finite geometry changes, is used to provide a unified framework for describing the process of void nucleation from initial debonding through complete decohesion. A boundary value problem simulating a periodic array of rigid spherical inclusions in an isotropically hardening elastic-viscoplastic matrix is analyzed. Dimensional considerations introduce a characteristic length into the formulation and, depending on the ratio of this characteristic length to the inclusion radius, decohesion occurs either in a “ductile” or “brittle” manner. The effect of the triaxiality of the imposed stress state on nucleation is studied and the numerical results are related to the description of void nucleation within a phenomenological constitutive framework for progressively cavitating solids.

scholarly journals Simulation of Cyclic Loading on Pipe Elbows Using Advanced Plane-Stress Elastoplasticity Models1

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Konstantinos Chatziioannou ◽  
Yuner Huang ◽  
Spyros A. Karamanos
Keyword(s):  
Cyclic Loading ◽  
Large Scale ◽  
Mechanical Response ◽  
Low Cycle Fatigue ◽  
Constitutive Relations ◽  
Cyclic Plasticity ◽  
Integration Scheme ◽  
Repeated Loading ◽  
Finite Element Software ◽  
Hardening Models

Abstract This work investigates the response of industrial steel pipe elbows subjected to severe cyclic loading (e.g., seismic or shutdown/startup conditions), associated with the development of significant inelastic strain amplitudes of alternate sign, which may lead to low-cycle fatigue. To model this response, three cyclic-plasticity hardening models are employed for the numerical analysis of large-scale experiments on elbows reported elsewhere. The constitutive relations of the material model follow the context of von Mises cyclic elasto-plasticity, and the hardening models are implemented in a user subroutine, developed by the authors, which employs a robust numerical integration scheme, and is inserted in a general-purpose finite element software. The three hardening models are evaluated in terms of their ability to predict the strain range at critical locations, and in particular, strain accumulation over the load cycles, a phenomenon called “ratcheting.” The overall good comparison between numerical and experimental results demonstrates that the proposed numerical methodology can be used for simulating accurately the mechanical response of pipe elbows under severe inelastic repeated loading. Finally, this paper highlights some limitations of conventional hardening rules in simulating multi-axial material ratcheting.

A Comparative Study of the Response of Double Shearing and Hypoplastic Models

2002 ◽  
Author(s):  
Huaning Zhu ◽  
Morteza M. Mehrabadi ◽  
Mehrdad Massoudi
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Constitutive Models ◽  
Shear Loading ◽  
Biaxial Compression ◽  
Finite Element Program ◽  
Cyclic Shear ◽  
Hypoplastic Model ◽  
Element Program

The principal objective of this paper is to compare the mechanical response of a double shearing model with that of a hypoplastic model under biaxial compression and under cyclic shear loading. As the origins and nature of these two models are completely different, it is interesting to compare the predictions of these two models. The constitutive relations of the double shearing and the hypoplastic models are implemented in the finite element program ABACUS/Explicit. It is found that the hypoplastic and the double shearing constitutive models both show strong capability in capturing the essential behavior of granular materials. In particular, under the condition of non-cyclic loading, the stress ratio and void ratio predictions of the double shearing and the hypoplastic models are relatively close, while under the condition of cyclic loading, the predictions of these models are quite different. It is important to note that in the double shearing model employed in this comparison the shear rates on the two slip systems are assumed to be equal. Hence, the conclusions derived in this comparison pertain only to this particular double shearing model. Similarly, the hypoplasticity model considered here is that proposed by Wu, et al. [30] and the conclusions reached here pertain only to this particular hypoplasticity model.

The Time Dependent Behavior of Linear Viscoelastic Polymers

2011 ◽  
Vol 675-677 ◽  
pp. 435-438
Author(s):  
Wei Xiang Zhang ◽  
Xing Shao ◽  
Zhao Ran Xiao
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Characteristics ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Time Dependent ◽  
Numerical Examples ◽  
General Methodology ◽  
Inverse Transform ◽  
Dependent Behavior ◽  
Linear Viscoelastic

Polymers have been proved to have attractive mechanical characteristics, which made it desirable to choose these materials over traditional materials for numerous types of applications. As the uses of polymers increase, a thorough understanding of the mechanical behavior of these materials becomes vital in order to perform innovative and economical designs of various components. The main objective of this paper is to develop an effective method with the use of the Laplace inverse transform to describe the time dependent mechanical response of viscoelastic polymers. This general methodology is based on differential constitutive relations for viscoelastic polymers, avoiding the use of relaxation integral functions. As its application, the creep and relaxation properties of the materials are exhibited in the numerical examples.

On the Nonlinear Behavior of Piezoelectric Actuators

2004 ◽  
Vol 10 (3) ◽  
pp. 387-398 ◽  
Author(s):  
M. Arafa ◽  
A. Baz
Keyword(s):  
Harmonic Balance ◽  
Linear Models ◽  
Mechanical Response ◽  
Piezoelectric Materials ◽  
Constitutive Relations ◽  
Primary Resonance ◽  
Nonlinear Behavior ◽  
Piezoelectric Actuators ◽  
Electrical Excitation ◽  
Lumped Parameter

In this paper we present a theoretical and experimental study of the nonlinear behavior of piezoelectric actuators. The nonlinearities are introduced as quadratic terms in the piezoelectric constitutive relations. These relations are employed, together with supporting experimental results, to establish an engineering description of the nonlinearities present in piezoelectric materials. We present a lumped-parameter representation of a system consisting of a piezoactuator driving a mass. The representation is valid in the vicinity of the primary resonance. The resulting nonlinear differential equation of motion is analyzed by the method of harmonic balance to study the effects of nonlinearities on the dynamics of forced vibrations. Experimental measurements of the steady-state mechanical response to harmonic electrical excitation over a range of excitation frequencies and amplitudes quantify the nature and level of nonlinear behavior. The nonlinear behavior, which is mainly evident around the resonant frequency, is shown to be of the softening type and becomes more pronounced at higher drive voltage levels. Numerical simulations based on the developed nonlinear model have shown significant improvement over previous linear models in predicting the experimental behavior of piezoelectric materials at the vicinity of primary resonance.

The Introduction and Application of Cohesive Zone Model on Asphalt Concrete Fracture Behavior

2015 ◽  
Vol 744-746 ◽  
pp. 1320-1323
Author(s):  
Hua Zhang ◽  
Hai Wei Zhang ◽  
Feng Su
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Constitutive Relations ◽  
Ceramic Materials ◽  
Zone Model ◽  
Concrete Fracture ◽  
Future Directions ◽  
Bituminous Mixtures ◽  
Pavement Structures ◽  
Fragmentation Processes

The cohesive zone model (CZM) is being increasingly used to simulate fracture and fragmentation processes in metallic, polymeric, and ceramic materials and their composites. The CZM regards fracture as a gradual phenomenon in which separation takes place across an extended crack tip. This paper introduces the concept of CZM, the constitutive relations of CZM, the influence of the shape of the interface law and up-to-date applications of CZM to bituminous mixtures and pavement structures. Furthermore, some current challenges and the future directions to the modeling of fracture in bituminous materials and pavements are briefly discussed.

Continuum Models for the Mechanical Response of Paper and Paper Composites: Past, Present, and Future

1990 ◽  
Vol 197 ◽  
Author(s):  
Jeffrey C. Suhling
Keyword(s):  
Mechanical Response ◽  
Constitutive Relations ◽  
Paper Industry ◽  
Theoretical Models ◽  
Material Behavior ◽  
Continuum Models ◽  
Future Research ◽  
Fiber Network ◽  
Structural Configurations ◽  
Paper Composites

ABSTRACTPaper and paper composites are utilized in applications where they are subjected to multiaxial stress states and changing environmental conditions. Such materials exhibit nonlinear anisotropic material behavior which is time dependent and affected adversely by slight changes in moisture content and temperature. At present, lack of adequate theoretical models often hampers the design and development of structurally optimized paper products. Therefore, it has been common practice in the pulp and paper industry to use trial and error, and empirical approaches. Accurate continuum models for the mechanical behavior of paper and paper composites are needed to guide the paper product design process.In this work, a limited review of the existing methods for modeling the mechanical response of paper and paper composites is given. At first, a brief overview of the goals of current modeling techniques based on hydrogen bond, fiber network, and continuum approaches is presented. The governing equations and capabilities of current continuum models are then discussed in greater detail. Theories which include linear elastic (generalized Hooke's Law), nonlinear elastic (hyperelastic), linear viscoelastic, nonlinear viscoelastic, and inelastic constitutive relations are addressed. Finally, applications of existing continuum theories to the analysis of paper materials in structural configurations are presented. After these discussions, the limitations of the available continuum models are assessed and future research needs are suggested.

Interfacial Debonding and Stress Field Analysis on a Single Fiber Composite Using FEM

2008 ◽  
Author(s):  
Yi Pan ◽  
Assimina A. Pelegri
Keyword(s):  
Stress Field ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Fiber Composite ◽  
Interfacial Strength ◽  
Interfacial Debonding ◽  
Field Analysis ◽  
Zone Model ◽  
Linear Elastic ◽  
Bonded Composite

Fiber debonding in a bundled fiber reinforced polymer composite is investigated by using finite element method and cohesive zone model. Fiber and matrix are modeled as isotropic and linear elastic materials. Fiber/matrix interface is represented by a cohesive zone model governed by the traction-separation law. Effects of interfacial strength on interfacial debonding and stress field in the bundled fiber composite are examined. The stress field of the debonding composite is compared to that of perfectly bonded composite.

scholarly journals Hyperelastic modelling of arterial layers with distributed collagen fibre orientations

2005 ◽  
Vol 3 (6) ◽  
pp. 15-35 ◽  
Author(s):  
T. Christian Gasser ◽  
Ray W Ogden ◽  
Gerhard A Holzapfel
Keyword(s):  
Structural Model ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Polarized Light ◽  
Collagen Fibre ◽  
Middle Layer ◽  
Biological Tissues ◽  
Free Energy Function ◽  
Collagen Fibres ◽  
Small Pitch

Constitutive relations are fundamental to the solution of problems in continuum mechanics, and are required in the study of, for example, mechanically dominated clinical interventions involving soft biological tissues. Structural continuum constitutive models of arterial layers integrate information about the tissue morphology and therefore allow investigation of the interrelation between structure and function in response to mechanical loading. Collagen fibres are key ingredients in the structure of arteries. In the media (the middle layer of the artery wall) they are arranged in two helically distributed families with a small pitch and very little dispersion in their orientation (i.e. they are aligned quite close to the circumferential direction). By contrast, in the adventitial and intimal layers, the orientation of the collagen fibres is dispersed, as shown by polarized light microscopy of stained arterial tissue. As a result, continuum models that do not account for the dispersion are not able to capture accurately the stress–strain response of these layers. The purpose of this paper, therefore, is to develop a structural continuum framework that is able to represent the dispersion of the collagen fibre orientation. This then allows the development of a new hyperelastic free-energy function that is particularly suited for representing the anisotropic elastic properties of adventitial and intimal layers of arterial walls, and is a generalization of the fibre-reinforced structural model introduced by Holzapfel & Gasser (Holzapfel & Gasser 2001 Comput. Meth. Appl. Mech. Eng . 190 , 4379–4403) and Holzapfel et al . (Holzapfel et al . 2000 J. Elast . 61 , 1–48). The model incorporates an additional scalar structure parameter that characterizes the dispersed collagen orientation. An efficient finite element implementation of the model is then presented and numerical examples show that the dispersion of the orientation of collagen fibres in the adventitia of human iliac arteries has a significant effect on their mechanical response.

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