Effect of T6 Treatment on Low-Cycle Fatigue Properties of Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc Alloy

2014 ◽  
Vol 664 ◽  
pp. 28-33
Author(s):  
Ying Lan ◽  
Li Jia Chen ◽  
Xin Che ◽  
Feng Li
Keyword(s):  
Strain Hardening ◽  
Low Cycle Fatigue ◽  
Aging Treatment ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Fatigue Properties ◽  
Strain Hardening Exponent ◽  
Cycle Fatigue ◽  
Linear Behavior

The low-cycle fatigue behaviors of as-extruded and T6 treated Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloys at room temperature have been investigated under those total-strain amplitudes ranged from 0.3% to 1.0%, and the influence of T6 treatment on the low-cycle fatigue properties of Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloy was clarified. The experimental results show that during fatigue deformation, the significant cyclic strain hardening and stable cyclic stress response can be noted for both as-extruded and T6 treated Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloys. The fatigue life of as-extruded Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloy at all strain amplitudes is longer than that of the alloy subjected to T6 aging treatment. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively. The T6 treatment can significantly increase the cyclic strain hardening exponent and cyclic strength coefficient of extruded Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloy.

Low Cycle Fatigue of Cast γ-TiAl Based Alloys at High Temperature

2010 ◽  
Vol 452-453 ◽  
pp. 421-424 ◽  
Author(s):  
Martin Petrenec ◽  
Miroslav Šmíd ◽  
Tomáš Kruml ◽  
Karel Obrtlík ◽  
Jaroslav Polák
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Surface Region ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Nb Content ◽  
Cyclic Straining

The low-cycle fatigue properties of cast nearly lamellar TiAl alloys with diverse Nb content at room temperature and 750°C were compared. Monotonic tensile curves, cyclic stress-strain curves (CSSC) and combined fatigue life curves were obtained at both temperatures. After cyclic straining the surface relief and the fracture surfaces were observed using scanning electron microscopy. The increase in Nb content significantly improves tensile properties and CSSCs at both temperatures. The combined fatigue life curves especially at 750 °C are shifted to higher fatigue lives. The effect o Nb content on the tensile and cyclic strength is discussed in relation to the thickness of the lamellae. Persistent slip markings formed along interlamellar interfaces were predominant locations for fatigue cracks. At both temperatures and materials showed similar crack initiation and propagation behavior. The cracks initiated at surface or in sub-surface region creating smooth flat areas corresponding to the persistent slip bands.

Evaluation of Fatigue Failure of S960QL Steel in the Conditions of Plastic Strain

2016 ◽  
Vol 250 ◽  
pp. 175-181 ◽  
Author(s):  
Tomasz Slezak ◽  
Lucjan Sniezek ◽  
Janusz Torzewski ◽  
Volodymyr Hutsaylyuk
Keyword(s):  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Strain ◽  
High Strength ◽  
Strain Ratio ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Strain Hardening Exponent ◽  
Total Strain Amplitude ◽  
Cyclic Strength Coefficient

The article presents the results of research on low cycle fatigue strength of high-strength structural steel S960QL. During the tests, controlled force was applied using the different total strain amplitude εac and strain ratio Rε = 0.1. The obtained results allowed to determine the value of the cyclic strain hardening exponent n' and the cyclic strength coefficient K' and to draw the cyclic stress-strain curve. Analysis was also carried out of fatigue life based on the Manson-Coffin-Basquin equation. Fatigue values were also determined. Fractographic tests of fatigue fractures allowed to identify the causes of crack initiation and the course of their propagation.

scholarly journals Evaluation of Low Cycle Fatigue Performance of Selective Laser Melted Titanium Alloy Ti–6Al–4V

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1041 ◽  
Author(s):  
Peng Zhang ◽  
Allen Naihui He ◽  
Fei Liu ◽  
Kaifei Zhang ◽  
Junjie Jiang ◽  
...  
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Cyclic Stress ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Low Carbon ◽  
Specific Strength ◽  
Material Fatigue ◽  
Lower Strain ◽  
High Degree

The material of Ti–6Al–4V has been widely applied in various industries, such as automobile, aerospace, and medical due to its high specific strength, superior thermal stability and strong corrosion resistance. In the recent decades, selective laser melting (SLM) has become an attractive method to fabricate Ti–6Al–4V parts, thanks to its significant advantages in low material consumption, the high degree of freedom in design, low carbon footprint, etc. Predictability of SLM material fatigue properties is especially important for the safety-critical structures under dynamic load cases. The present research is aimed at evaluating the low cycle fatigue (LCF) performance of SLM Ti–6Al–4V under high loading states. LCF tests were performed for as-built and annealed SLM Ti–6Al–4V. Comparison between LCF properties of SLM Ti–6Al–4V and the wrought Ti–6Al–4V was also made. It was found that as-built SLM Ti–6Al–4V demonstrated a comparable LCF performance with the wrought material. The LCF life of as-built SLM Ti–6Al–4V was longer than that of wrought Ti–6Al–4V at lower strain amplitudes. However, the wrought Ti–6Al–4V had better LCF performance at higher strain amplitudes. The results revealed that the porosity in the as-built SLM material exerted much more impact on the degradation of the material at high strain amplitudes. Annealing deteriorated the LCF performance of SLM Ti–6Al–4V material due to the formation of coarser grains. The cyclic Ramberg–Osgood and the Basquin–Coffin–Manson models were fitted to depict the cyclic stress–strain and the strain–life curves for the SLM Ti–6Al–4V, based on which the LCF performance parameters were determined. In addition, the fatigue fracture surfaces were observed by using scanning electron microscopy (SEM), and the results indicated that fatigue cracks originated from the surface or subsurface defects.

Cyclic Plastic Deformation of a Circular Plate With Work Hardening

1984 ◽  
Vol 106 (4) ◽  
pp. 336-341
Author(s):  
R. Winter
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Nonlinear Behavior ◽  
Strain Curve ◽  
Strain Range ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Element Analysis

An experimental and theoretical study was performed of the nonlinear behavior of a simply supported flat circular aluminum plate under reversed cyclic central load. The application is for the analysis of cyclic stress and strain of structural components in the plastic range for predicting low-cycle fatigue life. The main purpose was to determine the relative accuracy of an elastic-plastic large deformation finite element analysis when the material properties input data are derived from monotonic (noncyclic) stress-strain curves versus that derived from cyclic stress-strain curves. The results showed that large errors could be induced in the theoretical prediction of cyclic strain range when using the monotonic stress-strain curve, which could lead to large errors in predicting low-cycle fatigue life. The use of cyclic stress-strain curves, according to the model developed by Morrow, et al., proved to be accurate and convenient.

Strain Hardening by High Density SISFs During Low Cycle Fatigue in Ni3(Al,Zr) Single Crystal

1994 ◽  
Vol 364 ◽  
Author(s):  
Yuefeng Gu ◽  
Yi Liu ◽  
Jianting Guo ◽  
Dongliang Lin
Keyword(s):  
Electron Microscope ◽  
Single Crystal ◽  
Strain Hardening ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Stacking Faults ◽  
Cyclic Strain ◽  
Cycle Fatigue ◽  
Transmission Electron ◽  
Stress Asymmetry

AbstractStress response and its correlation with dislocation substructures in Ni3(Al,Zr) single crystal fatigued at room temperature have been studied. Cyclic strain hardening was found to be asymmetric and increased with increasing applied cyclic strain. Transmission Electron Microscope (TEM) observation showed that there are a profusion superlattic intrinsic stacking faults (SISFs) in fatigued Ni3(Al,Zr) single crystal samples. The cyclic strain hardening and stress asymmetry are explained by the movement of the SISF.

Influence of Heat Treatment on Low-Cycle Fatigue Behavior of AZ61 Magnesium Alloy

2011 ◽  
Vol 287-290 ◽  
pp. 883-887
Author(s):  
Shu Ying Yin ◽  
Li Jia Chen ◽  
Xin Wang
Keyword(s):  
Solid Solution ◽  
Magnesium Alloy ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Aging Treatment ◽  
Cyclic Stress ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Az61 Magnesium Alloy ◽  
Az61 Alloy

In order to identify the influence of solid solution, aging and solid solution plus aging treatments on the low-cycle fatigue behavior of the extruded AZ61 magnesium alloy, the low-cycle fatigue tests were performed at room temperature for the extruded AZ61 magnesium alloy with different treating states. The results indicate that the cyclic stress response behavior of the extruded AZ61 magnesium alloy exhibits both cyclic strain hardening and stability. The solid solution, aging and solid solution plus aging treatments tend to decrease the cyclic deformation resistance of the extruded AZ61 alloy in most conditions. The solid solution treatment can enhance the fatigue lives of the extruded AZ61 alloy at medium total strain amplitudes. In addition, the aging treatment can prolong the low-cycle fatigue lives of the AZ61 alloy at most total strain amplitudes, while the case for the solid solution plus aging treatment is just contrary. For the extruded AZ61 alloy with different treating states, a linear relationship between cyclic stress amplitude and plastic strain amplitude is noted.

High Strain Low Cycle Fatigue and Anti-Seismic Behavior of HRB400 QST Reinforced Steel Bars

2011 ◽  
Vol 250-253 ◽  
pp. 1128-1133 ◽  
Author(s):  
Yu Kun Lv ◽  
Guang Min Sheng ◽  
Hao Fei Xue
Keyword(s):  
High Strain ◽  
Low Cycle Fatigue ◽  
Hardened Layer ◽  
Cyclic Stress ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Steel Bars ◽  
Reinforced Steel ◽  
Surface Scan ◽  
The Relationship

Based on the failure model of building structural steels under earthquake loading, High strain low cycle fatigue properties of HRB400QST (yield strength grade 400MPa, Quenched and Self Tempered) reinforced steel bars with diameters of 20mm and 16mm(unmachined) and HRB400V-N MA(microalloying)with diameters of 16mm (unmachined) were investigated. Based on the tests of total strain controlling, cycle strain response character of three kinds of steel bars and the relationship between cyclic stress and strain were researched. Hollomon and Coffin-Manson formulas were used to induce fatigue life formulas of three kinds of steel bars, and then the values of σa·Δεt were gained when Nf =100, calculated results show that the high strain low cycle fatigue properties of HRB400V-N MA rebars tested are much better than HRB400QST steel bars. Rupture surface scan reveals that surface hardened layer will reduce the cyclic toughness, and is bad for the anti-seismic performance.

Continuum damage mechanics-based ductile behavior and fatigue life estimation of low carbon steels: AISI 1020 and AISI 1030

2019 ◽  
Vol 233 (10) ◽  
pp. 2057-2071
Author(s):  
Abhinav Gautam ◽  
Prabir Kumar Sarkar
Keyword(s):  
Fatigue Life ◽  
Strain Hardening ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Continuum Damage Mechanics ◽  
Strain Hardening Exponent ◽  
Cycle Fatigue ◽  
Ductile Flow ◽  
Ductile Behavior

This paper presents an experimental estimation of the ductile behavior and low-cycle fatigue life for widely used structural steels AISI 1020 and AISI 1030 based on continuum damage mechanics approach. This method identifies the deterioration in stiffness of a material arising from micromechanisms of formation, growth, and coalescence of microvoids. This helps the characterization of the ductile flow behavior of metals through a damage variable D, evaluated via load–unload cyclic tensile test. The influence of strain hardening exponent, commonly treated as a constant in ductile flow characterization, is also explored in the current investigation. Its determination uses the Hollomon constitutive relation. Estimated D at different strain levels defines the corresponding effective stress. Application of this stress to the strain equivalence theory then enables the prediction of the stress–strain curve. The model-based results closely approximate the experimental stress–strain curve up to the onset of necking. The agreement of experimental results for fatigue life of the materials from low-cycle fatigue tests with damage-based low-cycle fatigue model demonstrates the correctness of the experimental findings. The damage-based model additionally helps in the prediction of microcrack nucleation and crack propagation life separately. Fractographic examinations of test specimen exhibit usually observed morphology of involved failure mechanisms. The present study emphasizes the experimental means of damage-based ductile flow assessment involving strain hardening exponent term and also the low-cycle fatigue life estimation. The significance of varying strain hardening exponent is further expressed in terms of the corresponding damage magnitude. The material data obtained from this study depicts the damage state at different levels of plastic strain that may serve as a useful information for metal-forming process design.

Low Cycle Fatigue Behaviors of TI-6AL-4V Alloy Controlled by Strain and Stress

2012 ◽  
Vol 525-526 ◽  
pp. 441-444
Author(s):  
Rui Feng Wang ◽  
You Tang Li ◽  
Hu Ping An
Keyword(s):  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Cyclic Strain ◽  
Cyclic Creep ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Compressive Stresses ◽  
Initial Stage ◽  
Main Factor

The low cycle fatigue behaviors of TI-6AL-4V alloy controlled by strain were investigated by experiment. The fatigue tests were performed at room temperature, and cyclic strain and stress ratio are 0.1 with triangle load wave. The results show that TI-6AL-4V alloy is soften rapidly under the cyclic tensile stresses and it is harden rapidly under the cyclic compressive stresses during the initial-stage of strain controlled fatigue, and the rates of cyclic soften and cyclic harden are decreased with the fatigue progress. The soften rate is related to the cyclic strain but little to the cyclic stress during the overall fatigue progress. The change of cyclic stress is related to the macro friction stresses. The results of experiment show that obvious cyclic creep occurs under the stress controlled low cycle fatigue conditions, and the magnitude of cyclic creep strain is related to the maximum cyclic stress. The softening of tensile friction stresses is the main factor of cyclic creep.

Estimation of Cyclic Strain Hardening Exponent and Cyclic Strength Coefficient of Steels by Artificial Neural Networks

2008 ◽  
Author(s):  
R. Ghajar ◽  
J. Alizadeh K. ◽  
N. Naserifar
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Strain Hardening ◽  
Cyclic Strain ◽  
Cyclic Strength ◽  
True Stress ◽  
Strain Hardening Exponent ◽  
Strength Coefficient ◽  
Cyclic Strength Coefficient ◽  
Artificial Neural

The objective of this paper is to demonstrate the applicability of artificial neural networks on estimation of the cyclic strain hardening exponent and cyclic strength coefficient of steels on the basis of monotonic tensile tests properties. In order to demonstrate this applicability, steels tensile data was extracted from the literatures and two separate neural networks was conducted. One set of data was used for training networks and remaining of data for testing them. The regression analysis was used to check the system accuracy for training and test data at the end of learning. Comparing results of neural networks with values obtained from direct fitting of experimental data was indicated that cyclic strain hardening exponent and cyclic strength coefficient, which characterize the stable curves of true stress amplitude versus true plastic strain amplitude, were predicted reasonable. It was concluded that predicted stable cyclic true stress-strain curve properties by trained neural network are more accurate compared to approximate relations based on low-cycle fatigue properties.

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