A study on the mean stress relaxation behavior of 2124-T851 aluminum alloy during low-cycle fatigue at different strain ratios

2015 ◽  
Vol 67 ◽  
pp. 272-279 ◽  
Author(s):  
Hong Hao ◽  
Duyi Ye ◽  
Yingzhen Chen ◽  
Mi Feng ◽  
Jianzhong Liu
Keyword(s):  
Aluminum Alloy ◽  
Stress Relaxation ◽  
Low Cycle Fatigue ◽  
Relaxation Behavior ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Stress Relaxation Behavior ◽  
The Mean ◽  
Mean Stress Relaxation

Comparative Study of Creep and Stress Relaxation Behavior for 7055 Aluminum Alloy

2011 ◽  
Vol 314-316 ◽  
pp. 772-777 ◽  
Author(s):  
Li Hua Zhan ◽  
Yan Guang Li ◽  
Ming Hui Huang ◽  
Jian Guo Lin
Keyword(s):  
Aluminum Alloy ◽  
Creep Rate ◽  
Stress Relaxation ◽  
Relaxation Rate ◽  
Constitutive Equations ◽  
Relaxation Behavior ◽  
Experimental Results ◽  
Stress Relaxation Behavior ◽  
Creep And Stress Relaxation ◽  
7055 Aluminum Alloy

In order to study the similarities and dissimilarities between creep and stress relaxation behavior of age formed aluminum alloys, both creep ageing and stress relaxation ageing experiments have been conducted with plate shaped 7055 aluminum alloy specimens on the 100 KN tensile testing machine performed at 120 °C for 20 h, under different stress levels from 190.0 to 357.8 MPa. The experimental results show that similar variation trends for creep and stress relaxation behavior were observed. Both creep and stress relaxation curves can be divided into two stages. During the first stage, higher creep rate and stress relaxation rate occur, which increase with stress levels but decrease with ageing time. While during the second stage, both the creep rate and the stress relaxation rate reach its lowest value and keep constant. A set of unified creep ageing constitutive equations has been developed and calibrated from creep experimental data, which can be used to predict the creep strain under age forming conditions perfectly. But the experimental results from stress relaxation ageing tests cannot be predicted with the established creep ageing constitutive equations, which shows that there is not a one-to-one correspondence between creep and stress relaxation, creep deformation is the most important but not the only reason for stress relaxation under age forming condition.

Effect of Mean Stress and of Mean Strain in Low-Cycle Fatigue of A-517 and A-201 Steels

1970 ◽  
Vol 92 (1) ◽  
pp. 35-51 ◽  
Author(s):  
J. Dubuc ◽  
J. R. Vanasse ◽  
A. Biron ◽  
A. Bazergui
Keyword(s):  
Plastic Strain ◽  
Pressure Vessel ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
The Mean ◽  
Mean Strain

A number of low-cycle fatigue tests has been carried out at room temperature on two materials commonly used in pressure vessel fabrication. For strain-controlled tests, the influence of different mean strains is studied; similarly, the effect of varying the mean stress is analyzed for stress-controlled tests. Relations involving elastic and plastic strain ranges, and the variations of strains or stresses during the fatigue tests are discussed.

scholarly journals Study on the Elastic–Plastic Correlation of Low-Cycle Fatigue for Variable Asymmetric Loadings

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2451 ◽  
Author(s):  
Junhong Zhang ◽  
Weidong Li ◽  
Huwei Dai ◽  
Nuohao Liu ◽  
Jiewei Lin
Keyword(s):  
Low Cycle Fatigue ◽  
Strain Ratio ◽  
Stress Effect ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Asymmetric Loading ◽  
Pressure Tubing ◽  
Proposed Model ◽  
The Mean

The mean stress effect in fatigue life varies by material and loading conditions. Therefore, a classical low cycle fatigue (LCF) model based on mean stress correction shows limits in asymmetric loading cases in both accuracy and applicability. In this paper, the effect of strain ratio (R) on LCF life is analyzed and a strain ratio-based model is presented for asymmetric loading cases. Two correction factors are introduced to express correlations between strain ratio and fatigue strength coefficient and between strain ratio and fatigue ductility coefficient. Verifications are conducted through four materials under different strain ratios: high-pressure tubing steel (HPTS), 2124-T851 aluminum alloy, epoxy resin and AZ61A magnesium alloy. Compared with current widely used LCF models, the proposed model shows a better life prediction accuracy and higher potential in implementation in symmetric and asymmetric loading cases for different materials. It is also found that the strain ratio-based correction is able to consider the damage of ratcheting strain that the mean stress-based models cannot.

Experimental and Theoretical Study of the Cyclic Relaxation of Die Cast Magnesium Alloy

2009 ◽  
Vol 610-613 ◽  
pp. 991-998 ◽  
Author(s):  
Shu Sheng Xu ◽  
Xiang Guo Zeng ◽  
Zhan Hua Gao ◽  
Hua Yan Chen ◽  
Jing Hong Fan
Keyword(s):  
Magnesium Alloy ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Fatigue Testing ◽  
Weight Ratio ◽  
Mean Stress ◽  
R Ratio ◽  
The Mean ◽  
Mean Stress Relaxation ◽  
Magnesium Alloy Am60

Magnesium alloys are among the best light-weight structural material with a relatively high strength-to-weight ratio end excellent technological properties. Therefore, magnesium attracts special attention of researchers working in automotive and aircraft industry. This work paid the efforts to the structural components made out of magnesium alloy AM60 such as chassis, transmission case in automotive, where the components are subject to cyclic loading after being pre-loaded. In this study, the cyclic stress-strain behaviors were investigated by strain-controlled fatigue testing. In order to investigate the effects of R-ratio on mean stress relaxation, the R-ratio ranged from 0.1 to 0.7 at the strain amplitude of 0.3%. The experimental results indicate that the mean stress relaxation increases with the increasing R-ratio. A constitutive model was proposed to simulate the mean stress relaxation. The calculation results show that the constitutive model developed in this work is capable of reproducing the stress relaxation behaviors of magnesium alloy AM60 under strain control.

Strain Ratio Effect on the Low Cycle Fatigue Behavior and Microstructure of High-Mn Austenitic Alloy Undergoing the Strain-Induced ε-Martensitic Transformation

2018 ◽  
Vol 941 ◽  
pp. 1065-1070
Author(s):  
Ilya Nikulin ◽  
Takahiro Sawaguchi
Keyword(s):  
Martensitic Transformation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Control Mode ◽  
Total Strain ◽  
Lattice Rotation ◽  
Mean Stress ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
The Mean

The effect of the strain asymmetry on low-cycle fatigue properties and microstructure of Fe–15Mn–10Cr–8Ni–4Si (in. wt. %) alloy undergoing the strain-induced ε-martensitic transformation (ε-MT) were investigated at strain ratios,R, of-1, -0.2, 0.2 and 0.5 under total strain-control mode with total strain amplitude of 0.01. At studied strain ratios the clear asymmetry in tension and compression stress providing tensile mean stress was observed in alloy deformed atRof-0.2, 0.2 and 0.5. The mean stress rapidly decreases to ~ 100 cycles and remain almost zero until failure. It was found that strain-induced ε-martensitic transformation and lattice rotation of austenite provide cyclic hardening of the studied alloy leading to the mean stress relaxation and provides the stability in hysteresis loops behavior at studiedR. As a consequence, the fatigue life,Nf, of the alloy remains on the level of the alloy deformed by LCF atR, of -1 (NfR=-1=9200 cycles). The details of the fatigue behavior, deformation mechanisms and microstructure evolution of the studied alloy are discussed.

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