Identification and Validation of a Low Cycle Fatigue Damage Model for Al 7075-T6 Alloy

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Saeed Masih ◽  
Mohammad Mashayekhi ◽  
Noushin Torabian
Keyword(s):  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Crack Initiation ◽  
Life Time ◽  
Continuum Damage Mechanics ◽  
Material Behavior ◽  
Cycle Fatigue ◽  
Explicit Finite Element ◽  
Al 7075

In this paper, the behavior of 7075-T6 aluminum alloy under low cycle fatigue (LCF) loading is experimentally and numerically investigated using continuum damage mechanics (CDM). An experimental procedure is established to identify the damage parameters for Al 7075-T6. A damage-coupled explicit finite element code is developed using the experimentally extracted damage parameters to study the material behavior under LCF loading. Moreover, fractographic examinations are conducted to identify the fatigue crack initiation locations and propagation mechanisms. The model is employed for life-time assessment of stringer-skin connection of a fuselage and the results are compared with the data available in the literature.

CDM Approach Applied to Crack Initiation and Propagation under Variable Amplitude

2016 ◽  
Vol 829 ◽  
pp. 55-60
Author(s):  
Jin Yang Chu ◽  
Jian Xing Mao
Keyword(s):  
Crack Initiation ◽  
Damage Accumulation ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Continuum Damage Mechanics ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Crack Initiation Life ◽  
Initiation Stage

In this paper, the low cycle fatigue crack initiation life was regarded as a process of damage accumulation and a damage accumulation model was established based on the Continuum Damage Mechanics. By the model, we analyzed how the variable amplitude applied at the crack initiation stage influenced the low cycle fatigue life of high temperature materials. With the parameters of GQGH4169 alloy at room temperature, we determined the specific values of damage parameters by finite element method and numerical analysis method. Then, the crack initiation life predictions were carried out. The results show that using this approach can not only predict the crack initiation life of CT specimen accurately, but also reflect a definite influence of variable amplitude on the crack propagation life combining with the Paris Law, and the test costs reduced consequently.

Effect of Low Cycle Fatigue Damage on Ultimate Strength of Aged Ship Structures

2011 ◽  
Author(s):  
Yu Tian ◽  
Zhuo-shang Ji
Keyword(s):  
Ultimate Strength ◽  
Fatigue Damage ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Simple Procedure ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Strength Reduction ◽  
Cycle Fatigue ◽  
Theoretical Results

The main objective of this paper is to study the effects of general low cycle fatigue (LCF) damage on ultimate strength of unstiffened ship plates under uniaxial compression. A nonlinear LCF damage model has been derived on basis of continuum damage mechanics (CDM) coupled with plastic mechanics in order to define the deterioration of materials. The theoretical results show that the damage variable D can be measured by a simple procedure and it can be related to the mechanical property of material directly. Formulae predicting ultimate strength reduction have been proposed based on amended Faulkner’s simple and useful expression. Nonlinear finite element analyses (FEA) of panels with various material damages have been carried out. The results indicate that the deterioration of materials is important factors determining the amount of strength reduction. It was also found that the proposed formulae can accurately predict the residual ultimate strength of unstiffened plate with general fatigue damage.

Short fatigue crack initiation and growth modeling in aluminum 7075-T6

2014 ◽  
Vol 229 (7) ◽  
pp. 1206-1214 ◽  
Author(s):  
M Amiri ◽  
M Modarres
Keyword(s):  
Crack Initiation ◽  
Damage Mechanics ◽  
Fatigue Crack Initiation ◽  
Estimation Method ◽  
Continuum Damage Mechanics ◽  
Fatigue Tests ◽  
Short Cracks ◽  
Al 7075 ◽  
Edge Notch ◽  
Aluminum 7075

A series of fatigue tests is carried out to investigate the behavior of microcrack initiation and propagation in Al 7075-T6. Plate specimens with semi-circular single edge notch are tested under uniaxial loading at different load amplitudes. Optical microscopy is used to detect the initiation and growth of short cracks. Continuum damage mechanics is used to model the crack initiation. After the initiation, crack growth is studied using fracture mechanics models. For both regions of crack initiation and growth, Bayesian estimation method is used to account for uncertainties in the parameters of the model. Results of the entire fatigue life, including initiation and growth, are compared with experiments. Good agreement is observed.

Fatigue Crack Modeling and Simulation Based on Continuum Damage Mechanics

2006 ◽  
Vol 129 (1) ◽  
pp. 96-102 ◽  
Author(s):  
Masakazu Takagaki ◽  
Toshiya Nakamura
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Present Theory ◽  
Continuum Damage ◽  
Cycle Fatigue

Numerical simulation of fatigue crack propagation based on fracture mechanics and the conventional finite element method requires a huge amount of computational resources when the cracked structure shows a complicated condition such as the multiple site damage or thermal fatigue. The objective of the present study is to develop a simulation technique for fatigue crack propagation that can be applied to complex situations by employing the continuum damage mechanics (CDM). An anisotropic damage tensor is defined to model a macroscopic fatigue crack. The validity of the present theory is examined by comparing the elastic stress distributions around the crack tip with those obtained by a conventional method. Combined with a nonlinear elasto-plastic constitutive equation, numerical simulations are conducted for low cycle fatigue crack propagation in a plate with one or two cracks. The results show good agreement with the experiments. Finally, propagations of multiply distributed cracks under low cycle fatigue loading are simulated to demonstrate the potential application of the present method.

CONTINUUM DAMAGE MECHANICS ANALYSIS OF THIN-WALLED TUBE UNDER CYCLIC BENDING AND INTERNAL CONSTANT PRESSURE

2013 ◽  
Vol 05 (04) ◽  
pp. 1350038 ◽  
Author(s):  
H. YAZDANI ◽  
A. NAYEBI
Keyword(s):  
Internal Pressure ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Cyclic Bending ◽  
Thin Walled Tube ◽  
Thin Walled

Ratcheting and fatigue damage of thin-walled tube under cyclic bending and steady internal pressure is studied. Chaboche's nonlinear kinematic hardening model extended by considering the effect of continuum damage mechanics employed to predict ratcheting. Lemaitre damage model [Lemaitre, J. and Desmorat, R. [2005] Engineering Damage Mechanics (Springer-Verlag, Berlin)] which is appropriate for low cyclic loading is used. Also the evolution features of whole-life ratcheting behavior and low cycle fatigue (LCF) damage of the tube are discussed. A simplified method related to the thin-walled tube under bending and internal pressure is used and compared well with experimental results. Bree's interaction diagram with boundaries between shakedown and ratcheting zone is determined. Whole-life ratcheting of thin-walled tube reduces obviously with increase of internal pressure.

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