Nondestructive estimation of remaining fatigue life without the loading history

2019 ◽  
Vol 29 (3) ◽  
pp. 482-502 ◽  
Author(s):  
JY Jang ◽  
M Mehdizadeh ◽  
MM Khonsari
Keyword(s):  
Fatigue Life ◽  
Damage Parameter ◽  
Nondestructive Method ◽  
Loading History ◽  
Number Of Cycles ◽  
Life Predictions ◽  
Short Time ◽  
Remaining Fatigue Life ◽  
Nondestructive Estimation ◽  
Good Agreement

A new nondestructive method to estimate the remaining fatigue life of a fatigue specimen with unknown knowledge of the loading history is presented. It requires only one short-time excitation test. The method utilizes the concept of damage parameter and the temperature rise to reliably predict the remaining number of cycles before fracture. A generalized procedure and numerous experimentally verified examples are presented. It is shown that the method can be applied to both constant and variable stress levels. Extensive laboratory tests reveal that the results of the remaining fatigue life predictions are in very good agreement with measurements.

scholarly journals S-N Curve Characterisation for Composite Materials and Prediction of Remaining Fatigue Life Using Damage Function

2021 ◽  
Vol 5 (3) ◽  
pp. 76
Author(s):  
Ho Sung Kim ◽  
Saijie Huang
Keyword(s):  
Fatigue Life ◽  
Composite Materials ◽  
Loading Rate ◽  
Theoretical Method ◽  
Damage Function ◽  
Simple Method ◽  
Arbitrary Choice ◽  
Number Of Cycles ◽  
First Time ◽  
Remaining Fatigue Life

S-N curve characterisation and prediction of remaining fatigue life are studied using polyethylene terephthalate glycol-modified (PETG). A new simple method for finding a data point at the lowest number of cycles for the Kim and Zhang S-N curve model is proposed to avoid the arbitrary choice of loading rate for tensile testing. It was demonstrated that the arbitrary choice of loading rate may likely lead to an erroneous characterisation for the prediction of the remaining fatigue life. The previously proposed theoretical method for predicting the remaining fatigue life of composite materials involving the damage function was verified at a stress ratio of 0.4 for the first time. Both high to low and low to high loadings were conducted for predicting the remaining fatigue lives and a good agreement between predictions and experimental results was found. Fatigue damage consisting of cracks and whitening is described.

In-Phase and Out-of-Phase Multiaxial Fatigue

1991 ◽  
Vol 113 (1) ◽  
pp. 112-118 ◽  
Author(s):  
F. Ellyin ◽  
K. Golos ◽  
Z. Xia
Keyword(s):  
External Pressure ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Pressure Vessel Steel ◽  
Proportional Loading ◽  
Vessel Steel ◽  
Total Strain Energy Density ◽  
Number Of Cycles ◽  
Life Predictions ◽  
Cycles To Failure

In this investigation, thin-walled circular cylindrical specimens fabricated from a low alloy pressure vessel steel (ASTM A-516 Gr. 70) were subjected to various multiaxial loading conditions. The tests were conducted under strain-controlled condition, and loading was provided through an axial actuator and internal and external pressure across the specimen wall. Four in-plane strain ratios (ρ = Δεt/Δεa) were tested, and the most damaging case was the equi-biaxial in-plane straining, ρ = 1. For the latter condition, 90 deg out-of-phase loading was also investigated. These tests indicated a dramatic decrease in the number of cycles to failure, Nf, as a result of out-of-phase loading. The influence of the plastic strain path on life is thus clearly demonstrated. It is shown that the total strain energy density, ΔWt = ΔWe+ + ΔWp, correlates with both the in-phase and out-of-phase cyclic tests, and therefore is a proper damage parameter to be used for life predictions. A brief description of how ΔWt can be calculated is given for the case of proportional loading. The predicted results are compared with the experimental data, and the agreement is found to be very good indeed.

Total Fatigue Life Prediction under Constant Amplitude Loading

2011 ◽  
Vol 704-705 ◽  
pp. 636-640
Author(s):  
Yu Ting He ◽  
Wen Jun Shu ◽  
Rong Hong Cui ◽  
Li Ming Wu ◽  
Jin Qiang Du
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Life Prediction ◽  
Fatigue Life Prediction ◽  
Constant Amplitude ◽  
Naturally Occurring ◽  
Small Cracks ◽  
Fatigue Crack Propagation Life ◽  
Life Predictions ◽  
Good Agreement

This paper applies the fracture-mechanics-based analysis and the crack-closure concept to naturally occurring small cracks and large crack growth, and to make total fatigue life predictions solely based on crack growth from the assumed initial materials defect. The equation of total fatigue crack propagation life under constant amplitude loading is presented. And the total fatigue propagation lives of LY12-BCZYU aluminium alloy SENT specimens by this equation and validated by experimental results. Validation against calculations by the model and experimental data shows a good agreement.

Fatigue Life Prediction Investigation on Steel Honeycomb Sandwich Beams at High-Temperature

2011 ◽  
Vol 488-489 ◽  
pp. 698-701
Author(s):  
Jie Lu ◽  
Guang Ping Zou ◽  
Yang Cao
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Deformation Monitoring ◽  
Sandwich Beams ◽  
Three Point Bending ◽  
Time Deformation ◽  
Stiffness Reduction ◽  
Honeycomb Sandwich ◽  
Number Of Cycles ◽  
Good Agreement

The aim of this work is to investigate the fatigue behaviors of the steel honeycomb sandwich beams at 400°C through three point bending experiments. A stiffness reduction approach was adopted which was further based on the interpolation by the empirical functions of experimental results. For load control fatigue experiments, the evolution relations between number of cycles and displacement were obtained through real-time deformation monitoring of the specimens. A method based on exponential function fit was adopted in the further analysis, whose coefficients depended on the material properties, loading levels and high temperature conditions. This approach allowed us to predict the high temperature fatigue life of specimens while avoiding a large number of experiments. The results showed that experimental and prediction results were in a good agreement.

New strain energy-based critical plane approach for multiaxial fatigue life prediction

2019 ◽  
Vol 54 (5-6) ◽  
pp. 310-319
Author(s):  
Meng-Fei Hao ◽  
Shun-Peng Zhu ◽  
Ding Liao
Keyword(s):  
Fatigue Life ◽  
Strain Energy ◽  
Equivalent Stress ◽  
Equivalent Strain ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Critical Plane ◽  
Critical Plane Approach ◽  
Energy Aspect ◽  
Life Predictions

Based on critical plane approach, this article develops a new damage parameter through combing the equivalent strain energy aspect for multiaxial fatigue analysis, which includes no additional fitted parameters and overcomes the deficiency of using only equivalent stress/strain criterion separately under multiaxial loadings. Then, experimental data of GH4169, TC4, Al 7050-T7451 alloys under different loading conditions are applied for model validation and comparison with other four models. Results indicate that the proposed damage parameter yields better multiaxial fatigue life predictions than others.

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