A Cumulative Damage Rule Based on the Knee Point of the S-N Curve

1976 ◽  
Vol 98 (4) ◽  
pp. 316-321 ◽  
Author(s):  
S. Subramanyan
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Step Test ◽  
Rule Based ◽  
Bending Tests ◽  
Variable Amplitude ◽  
Knee Point ◽  
Life Predictions ◽  
Damage Rule ◽  
35 Steel

Making use of a set of isodamage lines, a fresh concept for predicting the fatigue life, under variable amplitude loading, is presented. It is assumed that all isodamage lines converge at the knee point of a S-log N diagram. The life predictions based on this concept are closer to the experimental data than given by Miner’s linear damage rule. The concept is verified with the step-test data obtained on unnotched C-35 steel specimens in rotary bending. Several other reported experimental data in rotary bending tests also confirm the reliability of this simple damage rule.

scholarly journals Variable Amplitude Fatigue Life in VHCF and Probabilistic Life Predictions

2015 ◽  
Vol 114 ◽  
pp. 574-582 ◽  
Author(s):  
Attilio Arcari ◽  
Nicole Apetre ◽  
Norman Dowling ◽  
Martin Meischel ◽  
Stefanie Stanzl-Tschegg ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Variable Amplitude ◽  
Life Predictions ◽  
Variable Amplitude Fatigue

Use of Fine Aggregate Matrix Experimental Data in Improving Reliability of Fatigue Life Prediction of Asphalt Concrete: Sensitivity of This Approach to Variation in Input Parameters

2017 ◽  
Vol 2631 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Padmini P. Gudipudi ◽  
B. Shane Underwood
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Asphalt Concrete ◽  
Failure Criteria ◽  
Fine Aggregate ◽  
Performance Predictions ◽  
Input Parameters ◽  
Fine Aggregate Matrix ◽  
Input Variables ◽  
Life Predictions

Asphalt concrete (AC) material performance has been assessed by numerous mechanistic models over the years. Often these models are purported to enable more accurate prediction of the pavement service life than existing empirical models. Most of these models use fundamental material properties, which are obtained by performing experiments on the materials, as input variables. However, by introducing more variables, these models create the potential for greater uncertainty because the variables have inherent variability. Variations observed in these input parameters affect the reliability of any resulting performance predictions. In an effort to improve the reliability of fatigue life predictions, experimental data from the fine aggregate matrix (FAM) phase was used in this study for predicting fatigue life. From the comparative assessment, it was observed that the reliability of fatigue life predictions was improved by more than 50% when data from the FAM phase rather than AC data were used. An upscaling procedure was used in predicting the AC material fundamental properties and then in performing a reliability analysis with the predicted data. More reliable fatigue prediction results were also observed when the AC predicted data were used; however, this improvement was not as good as that in the FAM phase. A parametric sensitivity analysis was performed to determine whether variation in any one parameter resulted in a greater impact on the resultant reliability than did variation of other parameters. From the analysis, it was observed that the variation of the modulus parameter affected the reliability predictions more than did the variation of the other input parameters considered in this study, regardless of the model failure criteria used.

scholarly journals Various parameters of the multiaxial variable amplitude loading and their effect on fatigue life and fatigue life computation

2021 ◽  
Author(s):  
J. Papuga ◽  
Matúš Margetin ◽  
Vladimír Chmelko
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Load Path ◽  
Major Focus ◽  
Quality Of Data ◽  
Data Set ◽  
Variable Amplitude ◽  
Shift Effect

The paper discusses various partial solutions used for estimating fatigue life under variable amplitude multiaxial loading in the high-cycle fatigue domain. The concurring effects are treated, and their proposed solutions are commented upon. The major focus is on the categories of the phase shift effect and of cycle counting, and on the scope and quality of data, which support discussed theories. Results of own new experimental data set on specimens from S355 steel are provided. Fatigue life estimates for McDiarmid and Findley multiaxial methods and for two different methods of load path decomposition to cycles are shown to highlight some of the points open for discussion. It is concluded that the available experimental data are not sufficient to substantiate a clear decision to follow a definite algorithm.

scholarly journals Influence of Selected Multiaxial Stress Paths on Fatigue Estimation under Variable Amplitude Loading

2021 ◽  
Author(s):  
Jan Papuga ◽  
Matúš Margetin ◽  
Vladimír Chmelko
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Multiaxial Loading ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Life Estimation ◽  
Fatigue Life Estimation ◽  
Shift Effect ◽  
Fatigue Estimation

The paper discusses solutions used for estimating fatigue life under variable amplitude multiaxial loading in the high-cycle fatigue domain. Various concurring effects are treated, and their proposed solutions are commented upon. The focus is on the categories of the phase shift effect and of cycle counting. It is concluded that the available experimental data are not sufficient to substantiate a clear decision to follow a definite algorithm. An example of own new experimental data is provided, and the fatigue life estimation run to highlight some more points open for discussion.

A Modified Model for Non-Linear Fatigue Damage Accumulation With Load Interaction Effects

2015 ◽  
Author(s):  
Zhaochun Peng ◽  
Hong-Zhong Huang ◽  
Huiying Gao ◽  
Zhiqiang Lv ◽  
Shun-Peng Zhu
Keyword(s):  
Experimental Data ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Interaction Effects ◽  
Variable Amplitude Loading ◽  
Modified Model ◽  
Variable Amplitude ◽  
Fatigue Damage Accumulation ◽  
Non Linear ◽  
Damage Rule

In the case of variable amplitude loading, fatigue damage accumulation theory is closely related to loading histories, such as load sequences, load interactions, and so on. Due to the lack of load histories, there may be a large deviation with the reality for linear damage rule (Miner rule). Although many non-linear fatigue damage accumulation models can deal with the effect of load sequences, load interaction effect cannot be ignored and it plays an important role in damage accumulation behavior. This paper describes the damage evolution behavior based on nonlinear damage rule under variable amplitude loading. A new method to describe the load interaction effects is proposed, it is assumed that the load ratio between adjacent stress levels is used to present this phenomenon. Thereafter, the method is introduced to a non-linear damage model, and a modified model is developed to predict the residual lifetime. Four categories of experimental data sets from literatures are employed to investigate the validity of the proposed model. The results indicate that the modified model shows a good agreement between experimental data and theoretical results. It is also found that the modified model demonstrates an improvement in prediction accuracy over the primary model and Miner rule. Furthermore, the modified model can be easily implemented with the use of Wöhler curve only.

Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

2018 ◽  
Vol 763 ◽  
pp. 867-874
Author(s):  
Yu Shu Liu ◽  
Ke Peng Chen ◽  
Guo Qiang Li ◽  
Fei Fei Sun
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Structural Reliability ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Buckling Restrained Braces ◽  
Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

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