A mesh objective continuum damage model for quasi-brittle crack modelling and finite element implementation

2019 ◽  
Vol 28 (9) ◽  
pp. 1299-1322 ◽  
Author(s):  
Xiaole Li ◽  
Weicheng Gao ◽  
Wei Liu
Keyword(s):  
Finite Element ◽  
Strain Field ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Tracking Algorithm ◽  
Continuum Damage ◽  
Brittle Crack ◽  
Proposed Model ◽  
Failure Evolution ◽  
Non Local

In the framework of continuum damage mechanics, a computational model for quasi-brittle crack modelling is proposed. The proposed model has significant mesh-objectivity and accuracy advantages over existing methods for modeling quasi-brittle crack. These stem from the combination of the local crack tracking algorithm, the new calculation of crack bandwidth and the non-local treatment regarding strain field. Resorting to the implementation of local crack tracking algorithm, it is desirable that the spurious dependence of conventional continuum damage mechanics-based model on mesh bias can be effectively addressed. The new estimation of the real-time crack bandwidth can be not only depending on the element size and pattern, but also on the physical crack path within each consolidate cracked element. Thus, the energy dissipation during crack propagation can be characterized in a more accurate, physically based manner. The non-local averaging regarding the strain field in the course of failure evolution is carried out within an elliptical domain, the configuration of which is related to finite element and crack trajectory obtained by the local crack track algorithm. With this combined technique, it is expected that a more accurate crack evolution course can be achieved numerically, which allows engineers to adopt relatively coarse unstructured discretizations without sacrificing solution accuracy. By numerical examples, the proposed model, empowered by the combined techniques, demonstrates significant improvements in the prediction of crack propagating of quasi-brittle materials. This model may provide engineers a more reliable tool in practical application of computational material failure.

Fatigue Life of the Human Teeth: A Continuum Damage Approach

2019 ◽  
Vol 43 ◽  
pp. 1-19
Author(s):  
Theddeus Tochukwu Akano
Keyword(s):  
Fatigue Life ◽  
Damage Mechanics ◽  
Stress Amplitude ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Elastoplastic Model ◽  
Human Teeth ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Cycles To Failure

Normal oral food ingestion processes such as mastication would not have been possible without the teeth. The human teeth are subjected to many cyclic loadings per day. This, in turn, exerts forces on the teeth just like an engineering material undergoing the same cyclic loading. Over a period, there will be the creation of microcracks on the teeth that might not be visible ab initio. The constant formation of these microcracks weakens the teeth structure and foundation that result in its fracture. Therefore, the need to predict the fatigue life for human teeth is essential. In this paper, a continuum damage mechanics (CDM) based model is employed to evaluate the fatigue life of the human teeth. The material characteristic of the teeth is captured within the framework of the elastoplastic model. By applying the damage evolution equivalence, a mathematical formula is developed that describes the fatigue life in terms of the stress amplitude. Existing experimental data served as a guide as to the completeness of the proposed model. Results as a function of age and tubule orientation are presented. The outcomes produced by the current study have substantial agreement with the experimental results when plotted on the same axes. There is a notable difference in the number of cycles to failure as the tubule orientation increases. It is also revealed that the developed model could forecast for any tubule orientation and be adopted for both young and old teeth.

Finite Element Simulation of the Creep Behavior of 2.25Cr-1Mo-0.25V Steel Based on Continuum Damage Mechanics

2015 ◽  
Vol 750 ◽  
pp. 266-271 ◽  
Author(s):  
Yu Zhou ◽  
Xue Dong Chen ◽  
Zhi Chao Fan ◽  
Yi Chun Han
Keyword(s):  
Genetic Algorithm ◽  
Finite Element ◽  
Creep Behavior ◽  
Constitutive Equations ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Element Simulation

The creep behavior of 2.25Cr-1Mo-0.25V ferritic steel was investigated using a set of physically-based creep damage constitutive equations. The material constants were determined according to the creep experimental data, using an efficient genetic algorithm. The user-defined subroutine for creep damage evolution was developed based on the commercial finite element software ANSYS and its user programmable features (UPFs), and the numerical simulation of the stress distribution and the damage evolution of the semi V-type notched specimen during creep were studied. The results showed that the genetic algorithm is a very efficient optimization approach for the parameter identification of the creep damage constitutive equations, and finite element simulation based on continuum damage mechanics can be used to analyze and predict the creep damage evolution under multi-axial stress states.

scholarly journals Failure Analysis of Composite Pinned Joints Based on Continuum Damage Mechanics

2018 ◽  
Vol 36 (5) ◽  
pp. 848-855
Author(s):  
Hongliang Tuo ◽  
Xiaoping Ma ◽  
Zhixian Lu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Element Model ◽  
Fracture Plane ◽  
Continuum Damage ◽  
Bearing Strength ◽  
Matrix Damage ◽  
Pinned Joints

The paper conducted bearing tests on composite pinned joints with four different stacking sequences. The bearing strength and bearing chord stiffness were obtained. The influence of stacking sequences on failure modes, bearing strength and bearing chord stiffness was discussed. Based on continuum damage mechanics, a three-dimensional finite element model of composite pinned joint under bearing load was built, where the maximum strain criterion was employed for initiation and bi-liner damage constitutive relation for revolution of fiber damage, while the physical-based Puck criterion was used for matrix damage initiation, and matrix damage revolution depended on the effective strain on the fracture plane. The failure mode, bearing strength and bearing chord stiffness of composite pinned joint were discussed with this model under which the non-linear shear behavior and in-situ strength effects were considered. Good agreements between test results and numerical simulations validates the accuracy and applicability of the finite element model.

A review of continuum damage and plasticity in concrete: Part II – Numerical framework

2021 ◽  
pp. 105678952110632 ◽  
Author(s):  
George Z Voyiadjis ◽  
Bilal Ahmed ◽  
Taehyo Park
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Numerical Algorithms ◽  
Continuum Damage Mechanics ◽  
Future Research ◽  
Continuum Damage ◽  
Iterative Schemes ◽  
Rate Dependent ◽  
Concrete Damage ◽  
Open Issues

In this part II, companion article, we present the numerical review of continuum damage mechanics and plasticity in the context of finite element. The numerical advancements in local, nonlocal, and rate-dependent models are presented. The numerical algorithms, type of elements utilized in numerical analysis, the commercial software’s or in-house codes used for the analysis, iterative schemes, explicit or implicit approaches to solving finite element equations, and degree of continuity of element are discussed in this part. Lastly, some open issues in concrete damage modeling and future research needed are also discussed.

Finite Element Simulation of Damage in Dynamically Loaded Weldments

2000 ◽  
Author(s):  
Ricardo Moraes ◽  
David Nicholson
Keyword(s):  
Finite Element ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Thermal Softening ◽  
Impulsive Loading ◽  
Published Data ◽  
Continuum Damage ◽  
Explicit Finite Element ◽  
Projectile Impact ◽  
Welded Structure

Abstract The main goal of the current investigation is to accommodate combined damage softening and thermal softening in structures that experience ductile fracture [1] due to an impulsive loading. A constitutive model first introduced by Johnson-Cook [2], which is sensitive to strain rate effects and temperature softening, is extended to explain the proposed idea. Equations are derived through continuum mechanics theory. Continuum Damage Mechanics (CDM) was first introduced by Kachanov [3] during the fifties. Since then, the topic has been under development by many authors. Numerical simulations are performed in the explicit finite element impact code LS-DYNA [4]. Constitutive equations for a viscoplastic model with damage and thermal softening are implemented in the code using a User Defined Subroutine UMAT. The Continuum Damage Mechanics (CDM) model is based on the Bonora formulation [5]. The combined material model, named UMAT 41, is added to the program static library using Digital Visual Fortran (FORTRAN 90). Using the User Defined Material, the solution of an explosive charge and of projectile impact applied to a ring-stiffened welded structure is analyzed to predict fracture. Ring-stiffened structures are widely used in ships, submarines and aircraft, which are subject to explosive or projectile attack. Results obtained using models with and without damage softening agree very well with previously published data with respect to crack paths. However, the time histories and thresholds are sensitive to the model used [6]. Projectile impact is also presented in this work.

scholarly journals Creep crack simulations using continuum damage mechanics and extended finite element method

2017 ◽  
Vol 28 (1) ◽  
pp. 3-34 ◽  
Author(s):  
VB Pandey ◽  
I V Singh ◽  
BK Mishra ◽  
S Ahmad ◽  
AV Rao ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Growth ◽  
Damage Mechanics ◽  
Extended Finite Element Method ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Extended Finite Element ◽  
Creep Crack ◽  
Element Method

In the present work, elasto-plastic creep crack growth simulations are performed using continuum damage mechanics and extended finite element method. Liu–Murakami creep damage model and explicit time integration scheme are used to evaluate the creep strain and damage variable for various materials at different temperatures. Compact tension and C-shaped tension specimens are selected for the simulation of crack growth analysis. For damage evaluation, both local and nonlocal approaches are employed. The accuracy of the extended finite element method solutions is checked by comparing with experimental results and finite element solutions. These results show that the extended finite element method requires a much coarser mesh to effectively model crack propagation. It is also shown that mesh independent results can be achieved by using nonlocal implementation.

Sign in / Sign up

Export Citation Format

Share Document