scholarly journals Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
Hualiang Wan ◽  
Qizhi Wang ◽  
Zheng Zhang
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Damage Evolution ◽  
Present Method ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Damage Evolution Equation ◽  
Material Parameters ◽  
Elastoplastic Damage

New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing further development on the ANSYS platform, the anisotropic elastoplastic damage mechanics-finite element method is developed. The fatigue crack propagation life of satellite structure is predicted using the present method and the computational results comply with the experimental data very well.

The Effect of Lack-of-Fusion Porosity on Fatigue Behavior of Additive Manufactured Titanium Alloy

2016 ◽  
Vol 723 ◽  
pp. 44-50
Author(s):  
Hua Liang Wan ◽  
Qi Zhi Wang ◽  
Hui Xing Lin
Keyword(s):  
Experimental Data ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Present Method ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Performance ◽  
Additive Manufacture ◽  
Damage Evolution Equation ◽  
Lack Of Fusion

As we know, the fatigue performance of AM materials is highly associated with the microstructure. The fatigue performance of additive manufacture alloy materials of Ti-6Al-4V is investigated in this study. Considering the hysteresis energy, a damage evolution equation has been advanced. The material parameters in damage evolution equation are obtained with fatigue experimental data. A homogenizing model with reflecting microstructures is established. Two types of defects, gas porosity and lack-of-fusion porosity, are discussed. The mean fatigue crack initiation lives of additive manufactured Ti6Al4V with different orientations are predicted by the present method. The computational results are agreement well with the experimental data. The effect of lack-of-fusion porosity density on the fatigue performance of AM materials is studied. The fatigue lives of AM materials with different lack-of-fusion porosity size are evaluated. This present method represents the effect of the microdefect on the fatigue performance, with the effect of anisotropic damage and strain.

Study on Anisotropic Fatigue Damage Model of Metal Component

2011 ◽  
Vol 21 (4) ◽  
pp. 599-620 ◽  
Author(s):  
Zhang Miao ◽  
Meng Qingchun ◽  
Hu Weiping ◽  
Zhang Xing
Keyword(s):  
Fatigue Life ◽  
Damage Evolution ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Evolution Equations ◽  
Prediction Method ◽  
Volume Element ◽  
Fatigue Life Prediction ◽  
Repeated Loading ◽  
Damage Evolution Equation

First of all, the boom–panel model is constructed to describe the anisotropic damage evolution of continuum volume element. The constitutive relation of continuum volume element is represented by damage extent of the booms and panels. Furthermore, based on irreversible thermodynamics, damage evolution equations of boom and panel are constructed. The fatigue life prediction method for smooth specimen under the repeated loading with constant strain amplitude is constructed. By the theory of conservative integral in damage mechanics, the fatigue life prediction method for notched specimen under the repeated loading with constant amplitude is obtained. Using these methods, the material parameters of LC4CS aluminum alloy in the damage evolution equation can be obtained by the mean values of experimental fatigue curves of standard specimens with KT = 1, K T = 3, and K T = 5. The computational results are in accordance with the experiment data.

scholarly journals An Experimental Study on Low-Cycle Fatigue Crack Initiation Life Prediction of Powder Superalloy FGH96 Based on the Manson-Coffin and Damage Mechanics Methods

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 489
Author(s):  
Yuanming Xu ◽  
Hao Chen ◽  
Shuming Zhang ◽  
Tianpeng He ◽  
Xuerong Liu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Prediction Models ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Life Cycles ◽  
Cycle Fatigue ◽  
Element Analysis

The applicability of both prediction methods for low-cycle fatigue life of powder superalloy based on the Manson-Coffin equation and damage mechanics were addressed. Both fatigue life prediction models were evaluated by low-cycle fatigue experimental data of powder superalloy FGH96 with non-destructive standard parts and those with inclusions. Due to the characteristics of high strength and low plasticity of powder superalloy FGH96, errors in calculating the plastic strain amplitude deviate severely the prediction outcomes when using Manson-Coffin method. Meanwhile, by introducing the damage variable which characterizes the material damage, the damage evolution equation can be built by fitting the experimental data of standard parts and also applied to powder superalloy specimens containing inclusion. It is indispensable to accurately calculate the damage characterization parameter through finite element analysis in local stress concentration around the inclusion. The applicability of the prediction model was verified by the test life cycles of experimental specimens with different types and sizes of inclusions subsequently. Testing and simulation work showed much better prediction accuracies globally for the damage mechanics approach.

scholarly journals Analysis of Fatigue Life of PMMA at Different Frequencies Based on a New Damage Mechanics Model

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Aifeng Huang ◽  
Weixing Yao ◽  
Fang Chen
Keyword(s):  
Fatigue Life ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Low Frequency ◽  
Creep Damage ◽  
Cyclic Creep ◽  
Continuum Damage Mechanics ◽  
Creep Tests ◽  
Damage Evolution Equation ◽  
Load Rate

Low-cycle fatigue tests at different frequencies and creep tests under different stress levels of Plexiglas Resist 45 were conducted. Correspondingly, the creep fracture time,S-Ncurves, cyclic creep, and hysteresis loop were obtained. These results showed that the fatigue life increases with frequency at low frequency domain. After analysis, it was found that fatigue life is dependent on the load rate and is affected by the creep damage. In addition, a new continuum damage mechanics (CDM) model was established to analyze creep-fatigue life, where the damage increment nonlinear summation rule was proposed and the frequency modification was made on the fatigue damage evolution equation. Differential evolution (DE) algorithm was employed to determine the parameters within the model. The proposed model described fatigue life under different frequencies, and the calculated results agreed well with the experimental results.

Continuum damage mechanics application in low-cycle thermal fatigue

2012 ◽  
Vol 22 (2) ◽  
pp. 285-300 ◽  
Author(s):  
M Mashayekhi ◽  
A Taghipour ◽  
A Askari ◽  
M Farzin
Keyword(s):  
Fatigue Life ◽  
Thermal Fatigue ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Isothermal Condition ◽  
Continuum Damage Mechanics ◽  
Life Assessment ◽  
Continuum Damage ◽  
Fatigue Damage Accumulation

In this article, a fatigue model for low-cycle thermal fatigue formulated in a continuum damage mechanics framework is presented. The model is based on a unified damage law presented by Lemaitre for low-cycle fatigue, which has been extended to low-cycle thermal fatigue. The temperature dependencies of material parameters are considered in the damage evolution integration to take the non-isothermal condition of loading into account. This model considers the stress triaxiality and non-linearity of damage evolution, and it is developed to a fatigue damage accumulation rule in which the load sequence effect is also included. The stabilized structural response under thermomechanical loading motivates the use of uncoupled analysis approach making the model a fast tool suitable for design purposes in the costly and time-consuming field of thermomechanical fatigue life assessment. To demonstrate the capability and ease of use of this model for real industrial applications, the low-cycle thermal fatigue life of a stainless steel engine exhaust manifold which is in an early stage of design is assessed.

Damage Analysis of Medium Carbon Steel in Low Cycle Fatigue

2007 ◽  
Vol 353-358 ◽  
pp. 1141-1144
Author(s):  
Zhi Yuan Rui ◽  
Chun Peng Lu ◽  
Emin Li ◽  
Wu Yin Jin
Keyword(s):  
Experimental Data ◽  
Carbon Steel ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Medium Carbon Steel ◽  
Damage Analysis ◽  
Cycle Fatigue ◽  
Medium Carbon ◽  
Life Estimation

By the test of rotational bending for bar of 45 steel with V notch in low cycle fatigue, the bar’s fatigue life is studied under strain-controlled condition. The characteristics of several kinds of specimens' crack propagations are analyzed. The accumulative effect of crack propagation is discussed to find the appropriate load for quick fracture. Based on the theory of continuum medium damage mechanics, the damage evolution model in low cycle fatigue is obtained. The predicted curves and strain-life curves agree with experimental data for medium carbon steel well in this work. These results are very important for the life estimation of medium carbon steel.

A Continuum Damage Mechanics Approach for Fatigue Life Prediction of Open-Hole Metallic Plate

2014 ◽  
Vol 670-671 ◽  
pp. 1060-1067
Author(s):  
Xian Min Chen ◽  
Qin Sun ◽  
Di Guan ◽  
Feng Ping Yang
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Damage Evolution ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Life Prediction ◽  
Cycle Fatigue ◽  
Damage Initiation ◽  
Open Hole

A damage evolution model is presented for fatigue life prediction of metallic structures. This model is formulated based on damage mechanics and the irreversible thermodynamics framework developed by LEMAITRE and CHABOCHE. Using this model, the fatigue lifetime can be predicted both in the high cycle fatigue (HCF) regime and the low cycle fatigue (LCF) regime. Based on the energy theory and material fatigue test data, the plastic strain threshold for damage initiation was modified for HCF and LCF respectively. The damage evolution parameters were determined according to the fatigue test results of standard specimens. A damage mechanics-finite element full-couple method was adopted to simulate the process of fatigue damage evolution. The numerical simulation of fatigue lives were compared with the fatigue tests of 2A12-T4 open-hole plates and good agreement was obtained.

Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

2018 ◽  
Vol 763 ◽  
pp. 867-874
Author(s):  
Yu Shu Liu ◽  
Ke Peng Chen ◽  
Guo Qiang Li ◽  
Fei Fei Sun
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Structural Reliability ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Buckling Restrained Braces ◽  
Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

scholarly journals Low-Cycle Fatigue Crack Initiation Simulation and Life Prediction of Powder Superalloy Considering Inclusion-Matrix Interface Debonding

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4018
Author(s):  
Shuming Zhang ◽  
Yuanming Xu ◽  
Hao Fu ◽  
Yaowei Wen ◽  
Yibing Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Interface Debonding ◽  
Damage Evolution Equation ◽  
Finite Element Software

From the perspective of damage mechanics, the damage parameters were introduced as the characterizing quantity of the decrease in the mechanical properties of powder superalloy material FGH96 under fatigue loading. By deriving a damage evolution equation, a fatigue life prediction model of powder superalloy containing inclusions was constructed based on damage mechanics. The specimens containing elliptical subsurface inclusions and semielliptical surface inclusions were considered. The CONTA172 and TARGE169 elements of finite element software (ANSYS) were used to simulate the interfacial debonding between the inclusions and matrix, and the interface crack initiation life was calculated. Through finite element modeling, the stress field evolution during the interface debonding was traced by simulation. Finally, the effect of the position and shape size of inclusions on interface debonding was explored.

Damage Analysis of Concrete Subjected to Freeze-Thaw Cycles and Chloride Ion Erosion

2011 ◽  
Vol 488-489 ◽  
pp. 464-467
Author(s):  
Ji Ze Mao ◽  
Zhi Yuan Zhang ◽  
Zong Min Liu ◽  
Chao Sun
Keyword(s):  
Constitutive Equation ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Chloride Ion ◽  
Offshore Structures ◽  
Damage Evolution Equation ◽  
Freeze Thaw ◽  
Concrete Materials ◽  
Ion Erosion

With the development of damage mechanics, many researchers have used it to analyze the constitutive equation of concrete. Since the special environment in the cold marine regions, the offshore structures are common to subject to the comprehensive effects of freeze-thaw action and chloride erosion. This might cause concrete materials degradation and reduce the mechanical performance of concrete seriously. In this paper, based on the analysis and mechanical experiments of concrete materials under the comprehensive effects of freeze-thaw action and chloride ion erosion, the damage evolution equation of concrete elastic modulus along with the freeze-thaw cycles and chloride ion contents was established. The effects of chloride ion were investigated during the process of concrete degradation. According to the damage evolution equation, a new constitutive equation of concrete under freeze-thaw action and chloride erosion was established. And then, by means of the element simulation analysis of concrete beams when subjected to the comprehensive actions, the feasibility and applicability of the equation was examined and discussed. In this equation, both the freeze-thaw action and chloride ion erosion were considered together. It will be more suitable for analyzing the durability of concrete structures in the real cold marine regions. It will also provide some references for concrete constitutive theory.

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