OS2129 Accurate Prediction of Fatigue Life in Frequency Domain by Adjusting Probability Density of Stress Amplitude

2012 ◽  
Vol 2012 (0) ◽  
pp. _OS2129-1_-_OS2129-3_
Author(s):  
Norio TAKEDA ◽  
Tomohiro NARUSE
Keyword(s):  
Fatigue Life ◽  
Probability Density ◽  
Frequency Domain ◽  
Stress Amplitude ◽  
Accurate Prediction

Accurate Prediction of Fatigue Life under Random Loading

2014 ◽  
Vol 891-892 ◽  
pp. 1347-1352
Author(s):  
Norio Takeda ◽  
Tomohiro Naruse
Keyword(s):  
Fatigue Life ◽  
Frequency Domain ◽  
Prediction Accuracy ◽  
Life Prediction ◽  
Stress Amplitude ◽  
Fatigue Life Prediction ◽  
Random Loading ◽  
Power Spectral ◽  
Mechanical Products ◽  
As Stress

This study focuses on the method of predicting the fatigue life of materials subjected to random loading. Since random stress caused by random loading is rigorously expressed in the frequency domain as stress power spectral density (PSD), fatigue life should be predicted using stress PSD. We propose two adjustment methods of improving the accuracy of fatigue life prediction using stress PSD in the frequency domain. The method proposed by Dirlik is widely used for predicting the fatigue life in the frequency domain; however, it overestimates fatigue damage caused by large stress amplitude when the slope of the fatigue resistance curve is large. To prevent this overestimation, we applied our two adjustment methods to fatigue life prediction for typical random stresses observed on mechanical products. As a result, the adjustment methods worked well in improving prediction accuracy. Lightweight and reliable products can be therefore designed by applying the proposed methods to the evaluation of fatigue life under random loading.

Fatigue Life of the Human Teeth: A Continuum Damage Approach

2019 ◽  
Vol 43 ◽  
pp. 1-19
Author(s):  
Theddeus Tochukwu Akano
Keyword(s):  
Fatigue Life ◽  
Damage Mechanics ◽  
Stress Amplitude ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Elastoplastic Model ◽  
Human Teeth ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Cycles To Failure

Normal oral food ingestion processes such as mastication would not have been possible without the teeth. The human teeth are subjected to many cyclic loadings per day. This, in turn, exerts forces on the teeth just like an engineering material undergoing the same cyclic loading. Over a period, there will be the creation of microcracks on the teeth that might not be visible ab initio. The constant formation of these microcracks weakens the teeth structure and foundation that result in its fracture. Therefore, the need to predict the fatigue life for human teeth is essential. In this paper, a continuum damage mechanics (CDM) based model is employed to evaluate the fatigue life of the human teeth. The material characteristic of the teeth is captured within the framework of the elastoplastic model. By applying the damage evolution equivalence, a mathematical formula is developed that describes the fatigue life in terms of the stress amplitude. Existing experimental data served as a guide as to the completeness of the proposed model. Results as a function of age and tubule orientation are presented. The outcomes produced by the current study have substantial agreement with the experimental results when plotted on the same axes. There is a notable difference in the number of cycles to failure as the tubule orientation increases. It is also revealed that the developed model could forecast for any tubule orientation and be adopted for both young and old teeth.

Uniaxial Ratcheting and Low-Cycle Fatigue Failure of U75V Rail Steel

2016 ◽  
Vol 853 ◽  
pp. 246-250 ◽  
Author(s):  
Tao Fang ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Rail Steel ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Cyclic Straining

Experiments on U75V rail steel were carried out to investigate the cyclic feature, ratcheting behavior and low-cycle fatigue under both strain- and stress-controlled loadings at room temperature. It was found that U75V rail steel shows strain amplitude dependent cyclic softening feature, i.e., the responded stress amplitude under strain-controlled decreases with the increasing number of cycles and reaches a stable value after about 20th cycle. Ratcheting strain increases with an increasing stress amplitude and mean stress, except for stress ratio, and the ratcheting strain in failure also increases with an increasing stress amplitude, mean stress and stress ratio. The low-cycle fatigue lives under cyclic straining decrease linearly with an increasing strain amplitude, the fatigue lives under cyclic stressing decrease with an increasing mean stress except for zero mean stress, and decrease with an increasing stress amplitude. Ratcheting behavior with a high mean stress reduces fatigue life of rail steel by comparing fatigue lives under stress cycling with those under strain cycling. Research findings are helpful to evaluate fatigue life of U75V rail steel in the railways with passenger and freight traffic.

Investigation on the Probabilistic Distribution of the Stress Range of Net Cage Floater of Fish Cage for Fatigue Life Prediction

2018 ◽  
Author(s):  
Xiao-Dong Bai ◽  
Yun-Peng Zhao ◽  
Guo-Hai Dong ◽  
Chun-Wei Bi
Keyword(s):  
Fatigue Life ◽  
Probability Density ◽  
Limit State ◽  
Frequency Domain Analysis ◽  
Random Wave ◽  
Stress Range ◽  
Fish Farms ◽  
Short Term ◽  
Element Analysis ◽  
Distribution Of Stress

The failure risk of fish cages has increased in the harsher environmental conditions as fish farms have moved into the open sea in recent years. Fatigue failure is an important limit state for the floating system of the fish cage under the long-term action of waves. This study is presented to investigate the applicable probability density function for estimating fatigue life of the high-density polyethylene (HDPE) floating collars. The stress response of the floating collars system in random wave is firstly analyzed based on the finite element analysis combined with a hydrodynamic model. The stress histories of floating collars under each sea state are counted using the rainflow method as a benchmark for fatigue frequency domain analysis. The distribution of stress range was fitted by various probability density functions including Rayleigh, Weibull, Gamma and generalized extreme value (GEV) distributions. Comparisons of the estimated fatigue life using different distributions with rainflow statistic results were performed. Results indicate fatigue estimation based on the GEV and Gamma distributions by removing the negligible low stress range give much more accurate fatigue damage results of the short-term stress range distribution. While Weibull distribution overestimates the fatigue lifetime of the floating collar based on the short-term distribution of stress ranges.

scholarly journals High Cycle Fatigue Appearance of 10wt% cr steel and Dissimilar Metal Weld

2021 ◽  
Vol 9 (VI) ◽  
pp. 2185-2202
Author(s):  
Hilal Ahmad Shah
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Cycle Fatigue ◽  
Crack Initiation And Propagation ◽  
R Ratio ◽  
Initiation And Propagation ◽  
Different Temperatures ◽  
Fracture Surface Analysis ◽  
Metal Weld

The present study deals with the high cycle fatigue (HCF) behavior of a ten wt% Cr steel at ambient also as high temperatures (300–853 K). S–N curves were created at unlike temperatures using an R-ratio of −1. Outcome of mean stress was established over and done with Haigh diagram at 853 K using different R-values. Fatigue life was found to decrease with upsurge in test temperature and stress amplitude. Fatigue life was attempted using Basquin equation. Detailed fracture surface analysis was performed to study the crack initiation and propagation modes towards empathetic the mechanisms of failure at different temperatures.

Effect of Plasticity on Fatigue Life of Welded Nuclear Component With Local Brittle Zone

2003 ◽  
Author(s):  
Jong-Sung Kim ◽  
Se-Hwan Lee ◽  
Tae-Eun Jin
Keyword(s):  
Fatigue Life ◽  
Tensile Properties ◽  
Stress Amplitude ◽  
Low Alloy Steels ◽  
The Finite Element Method ◽  
Fatigue Lifetime ◽  
Nuclear Component ◽  
Alloy Steels ◽  
Brittle Zone ◽  
Produce Strain

The local brittle zone (LBZ), which has lower tensile properties as well as lower fracture toughness than base metal and weldment, can occur on the heat affected zone (HAZ) of some nuclear components made of low alloy steels due to the carbide coarsening by multi-pass welding and post-weld heat treatment. These variations of material strengths across the welds due to the LBZ can produce strain concentrations when the stress amplitude is large enough to cause cyclic plastic flow. But, it is difficult to find the previous researches about a relation between the fatigue life of LBZ on real nuclear components and plasticity. So, in this study, the microstructures and tensile properties of HAZ on nuclear components are predicted by using the semi-analytical method, and the fatigue lifetimes of welds on nuclear components with the LBZ are evaluated by the finite element method considering the local plasticity and the variations of tensile properties, and the fatigue analysis procedure of ASME B&PV Code Sec.III. Finally, the effect of LBZ on nuclear components on fatigue lifetime is reviewed.

Sign in / Sign up

Export Citation Format

Share Document