scholarly journals Correlations between crack initiation and crack propagation lives of notched specimens under constant and variable amplitude loading

2021 ◽  
Author(s):  
Melanie Fiedler ◽  
Michael Vormwald
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Growth ◽  
Plastic Material ◽  
Local Strain ◽  
Failure Criteria ◽  
Research Association ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Total Fracture

This paper starts with an overview of the application of the three guidelines (GL) of the German Research Association of Mechanical Engineers (FKM). Each of these provides algorithms for calculating fatigue lives of components under constant or variable amplitude loading, however, with underlying different failure criteria, i.e. technical crack initiation life (GL-nonlinear), fatigue crack growth life (GL-fracture mechanics), and total fracture life (GL-linear). This paper introduces the U-Concept which has been evaluated from a large structural durability database. The U-Concept is a small add-on to the Local Strain Approach (LSA) which is the backbone of the GL-nonlinear. It enables 1) to directly calculate the fatigue life to total fracture based on elastic-plastic material behaviour according to the LSA, or 2) to estimate the remaining fatigue life from crack initiation to fracture without a crack growth simulation.

Observing Load Sequence Effects on Simulated and Experimental Fatigue Crack Growth Occurrence

2011 ◽  
Vol 462-463 ◽  
pp. 489-494 ◽  
Author(s):  
S.M. Beden ◽  
Shahrum Abdullah ◽  
Ahmad Kamal Ariffin ◽  
Nawar A. Kadhim
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Test Data ◽  
Growth Models ◽  
Load Cycle ◽  
Engineering Structures ◽  
Variable Amplitude Loading ◽  
Variable Amplitude

Load cycle interactions can have a significant effect in fatigue crack growth (FCG) under variable amplitude loading. Studying of FCG and fatigue life calculation under spectrum loading is important for the reliable life prediction of engineering structures. Many models have been proposed, but yet no universal model exists. In this paper, a fatigue life predicted under various load spectra, using three different fatigue crack growth models namely, the Austen, modified Forman and NASGRO models. These models are validated with fatigue crack growth test data under various amplitude loadings. This application is performed with aids of three-point bend specimens of ASTM A533 steel material. The results clearly show the load sequences effect and the predicted results agree with some discrepancies between the different models as well as with the test data. Thus, neglecting the effect of cycle interaction in fatigue calculations under variable amplitude loading can lead to invalid life predictions.

Predicting Fatigue Crack Growth and Fatigue Life Under Variable Amplitude Loading

2010 ◽  
Vol 2010 (2) ◽  
pp. 37-51
Author(s):  
Michal Jasztal ◽  
Dorota Kocanda ◽  
Henryk Tomaszek
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Probabilistic Approach ◽  
Alloy Sheet ◽  
Load Spectrum ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Fatigue Life Estimation

Predicting Fatigue Crack Growth and Fatigue Life Under Variable Amplitude Loading A probabilistic approach to the description of fatigue crack growth and fatigue life estimation of a component subjected to variable amplitude loading is presented in the paper. The core of the model is a differential equation originated from the Paris formula. In order to consider the influence of overload-underload cycles existing in an exploitive load spectrum on crack growth rate for an aeronautical aluminum alloy sheet, the modified Willenborg retardation model was applied.

Application of the Strip Yield Model to Crack Growth Predictions for Structural Steel

2010 ◽  
Vol 57 (1) ◽  
pp. 1-20
Author(s):  
Małgorzata Skorupa ◽  
Tomasz Machniewicz
Keyword(s):  
Structural Steel ◽  
Crack Growth ◽  
Model Calibration ◽  
Load History ◽  
Yield Model ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Constraint Factors ◽  
Strip Yield Model ◽  
Closure Mechanism

Application of the Strip Yield Model to Crack Growth Predictions for Structural SteelA strip yield model implementation by the present authors is applied to predict fatigue crack growth observed in structural steel specimens under various constant and variable amplitude loading conditions. Attention is paid to the model calibration using the constraint factors in view of the dependence of both the crack closure mechanism and the material stress-strain response on the load history. Prediction capabilities of the model are considered in the context of the incompatibility between the crack growth resistance for constant and variable amplitude loading.

Effect of Processing Layer on Fatigue Strength of Extruded AZ61 Magnesium Alloy

2013 ◽  
Vol 577-578 ◽  
pp. 429-432 ◽  
Author(s):  
Yukio Miyashita ◽  
Kyohei Kushihata ◽  
Toshifumi Kakiuchi ◽  
Mitsuhiro Kiyohara
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Magnesium Alloy ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Crack Growth Resistance ◽  
Az61 Magnesium Alloy

Fatigue Property of an Extruded AZ61 Magnesium Alloy with the Processing Layer Introduced by Machining was Investigated. Rotating Bending Fatigue Tests were Carried out with the Specimen with and without the Processing Layer. According to Results of the Fatigue Tests, Fatigue Life Significantly Increased by Introducing the Processing Layer to the Specimen Surface. Fatigue Crack Initiation and Propagation Behaviors were Observed by Replication Technique during the Fatigue Test. Fatigue Crack Initiation Life of the Specimen with the Processing Layer was Slightly Longer than that of the Specimen without the Processing Layer. Higher Fatigue Crack Growth Resistance was also Observed when the Fatigue Crack was Growing in the Processing Layer in the Specimen with the Processing Layer. the Longer Fatigue Life Observed in the Fatigue Test in the Specimen with the Processing Layer could be Mainly due to the Higher Crack Growth Resistance. it is Speculated that the Fatigue Strength can be Controlled by Change in Condition of Machining Process. it could be Effective way in Industry to Improved Fatigue Strength only by the Cutting Process without Additional Surface Treatment Process.

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