A new ductile damage evolution model

In this paper, the evolution of a ductile damage in the 7075-T6 aluminum alloy is considered based on stress state parameters with a special focus on pre-mechanical working dependency. Uniaxial stress–strain curves are investigated experimentally for two conditions; specimens with shock loaded pre-mechanical working and without it. This kind of loading is applied in order to find out impulsive pressure effects of damage variation procedure. Some experiments are done to take different stress states. Applying two fracture initiations criteria, i.e., Hosford–Coulomb and Xue models, two types of fracture locus of Al-7075-T6 are predicted in terms of plastic strains and stress state parameters under above conditions. By considering experimental data, a new ductile damage evolution model is proposed among plastic behavior. It is introduced by explicating an uncoupled plasticity and related to initial rate dependent stress state. By using both fracture models, our damage evolution model is implemented, phenomenologically as well as the Xue damage model, to compare results.

Download Full-text

Mechanistically based fatigue-damage evolution model for brittle matrix fibre-reinforced composites

Journal of Materials Science ◽

10.1007/bf00367835 ◽

1993 ◽

Vol 28 (20) ◽

pp. 5592-5602 ◽

Cited By ~ 26

Author(s):

V. Ramakrishnan ◽

N. Jayaraman

Keyword(s):

Fatigue Damage ◽

Damage Evolution ◽

Evolution Model ◽

Reinforced Composites ◽

Brittle Matrix ◽

Fibre Reinforced Composites

Download Full-text

A Strain Rate-Dependent Damage Evolution Model for Concrete Based on Experimental Results

Advances in Civil Engineering ◽

10.1155/2021/6643263 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Bin Xu ◽

Xiaoyan Lei ◽

P. Wang ◽

Hui Song

Keyword(s):

Strain Rate ◽

Uniaxial Compression ◽

Damage Evolution ◽

Damage Model ◽

Evolution Model ◽

Experimental Results ◽

Strain Rates ◽

Compression Tests ◽

Stress Strain ◽

Actual Damage

There are various definitions of damage variables from the existing damage models. The calculated damage value by the current methods still could not well correspond to the actual damage value. Therefore, it is necessary to establish a damage evolution model corresponding to the actual damage evolution. In this paper, a strain rate-sensitive isotropic damage model for plain concrete is proposed to describe its nonlinear behavior. Cyclic uniaxial compression tests were conducted on concrete samples at three strain rates of 10−3s−1, 10−4s−1, and 10−5s−1, respectively, and ultrasonic wave measurements were made at specified strain values during the loading progress. A damage variable was defined using the secant and initial moduli, and concrete damage evolution was then studied using the experimental results of the cyclic uniaxial compression tests conducted at the different strain rates. A viscoelastic stress-strain relationship, which considered the proposed damage evolution model, was presented according to the principles of irreversible thermodynamics. The model results agreed well with the experiment and indicated that the proposed damage evolution model can accurately characterize the development of macroscopic mechanical weakening of concrete. A damage-coupled viscoelastic constitutive relationship of concrete was recommended. It was concluded that the model could not only characterize the stress-strain response of materials under one-dimensional compressive load but also truly reflect the degradation law of the macromechanical properties of materials. The proposed damage model will advance the understanding of the failure process of concrete materials.

Download Full-text

Partitioned Cyclic Fatigue Damage Evolution Model for PB-Free Solder Materials

Volume 9: Eighth International Conference on Creep and Fatigue at Elevated Temperatures ◽

10.1115/creep2007-26306 ◽

2007 ◽

Author(s):

Leila J. Ladani ◽

A. Dasgupta

Keyword(s):

Fatigue Damage ◽

Creep Deformation ◽

Damage Evolution ◽

Evolution Model ◽

Micro Scale ◽

Elastic Plastic ◽

Constitutive Properties ◽

Free Solder ◽

Cyclic Damage ◽

Creep Deformations

This study presents an approach to predict the degree of material degradation and the resulting changes in constitutive properties during cyclic loading in viscoplastic materials in micro-scale applications. The objective in the modeling approach is to address the initiation and growth of distributed micro-damage, in the form of micro-cracks and micro-voids, as a result of cyclic, plastic and creep deformations of material. This study extends an existing micromechanics-based approach, developed for unified viscoplastic models [Wen, et al, 2001], which uses dislocation mechanics to predict damage due to distributed micro-scale fatigue crack initiation [Mura and Nakasone, 1990]. In the present study, the approach is extended to a partitioned viscoplastic framework, because the micro-scale mechanisms of deformation and damage are different for plastic and creep deformation. In this approach, the model constants for estimating cyclic damage evolution are allowed to be different for creep and plastic deformations. A partitioned viscoplastic constitutive model is coupled with an energy partitioning (E-P) damage model [Oyan and Dasgupta, 1992] to assess fatigue damage evolution due to cyclic elastic, plastic and creep deformations. Wen’s damage evolution model is extended to include damage evolution due to both plastic and creep deformations. The resulting progressive degradation of elastic, plastic and creep constitutive properties are continuously assessed and updated. The approach is implemented on a viscoplastic Pb-free solder. Dominant deformation modes in this material are dislocation slip for plasticity and diffusion-assisted dislocation climb/glide for creep. The material’s behavior shows a good correlation with the proposed damage evolution model. Damage evolution constants for plastic and creep deformation were obtained for this Pb-free solder from load drop data collected from the mechanical cycling experiments at different temperatures. The amount of cyclic damage is evaluated and compared with experiment.

Download Full-text