Applying a Stepwise Load for Calculation of the S-N Curve for Trabecular Bone Based on the Linear Hypothesis for Fatigue Damage Accumulation

2012 ◽  
Vol 726 ◽  
pp. 39-42 ◽  
Author(s):  
Tomasz Topoliński ◽  
Artur Cichański ◽  
Adam Mazurkiewicz ◽  
Krzysztof Nowicki
Keyword(s):  
Trabecular Bone ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Applied Load ◽  
Fatigue Tests ◽  
Bone Sample ◽  
Linear Hypothesis ◽  
Fatigue Damage Accumulation

In this work were presented calculated fatigue curves based on fatigue tests of trabecular bone under stepwise load with the application of a linear hypothesis accumulation of fatigue damage. The investigation was performed on 61 cylindrical bone samples obtained from the neck of different femur heads. The bone sample fatigue tests were carried out under compression with stepwise increases of the applied load. The fatigue calculation assumed the Palmgren-Miner (P-M) linear hypothesis accumulation of fatigue damage and the associated modified formulae. The obtained mean fatigue curves were based on the modified stress σ/E0 (E0 – initial stiffnes) for the assumed rule-determined slope or y-intercept. The highest agreement with the literature was obtained for Σn/N=10.

Method of Determining the Initial Stiffness Modulus for Trabecular Bone under Stepwise Load

2012 ◽  
Vol 726 ◽  
pp. 84-89 ◽  
Author(s):  
Tomasz Topoliński ◽  
Artur Cichański ◽  
Adam Mazurkiewicz ◽  
Krzysztof Nowicki
Keyword(s):  
Trabecular Bone ◽  
Damage Accumulation ◽  
Applied Load ◽  
Bone Structure ◽  
Fatigue Tests ◽  
Statistical Relationship ◽  
Initial Stiffness ◽  
Stiffness Modulus ◽  
Unsuccessful Attempt ◽  
Fatigue Damage Accumulation

In this work was presented method of initial stiffness modulus E0 calculation based on fatigue tests of trabecular bone under stepwise load. The investigation was performed on 61 cylindrical bone samples obtained from the neck of different femur heads. The bone sample fatigue tests were carried out under compression with stepwise increases of the applied load. The obtained values of the initial stiffness modulus E0 were consistent with literature data and can be used to determine the S-N curve for trabecular bone using the hypotheses of fatigue damage accumulation. It was also an unsuccessful attempt to find a statistical relationship between the values of the initial stiffness modulus E0 and indices of bone structure.

scholarly journals Nonlinear Fatigue Damage Accumulation

2015 ◽  
Vol 2015 (7) ◽  
pp. 18-23
Author(s):  
Daniel Krzysztof Dębski
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Mutual Influence ◽  
Complex Form ◽  
Linear Hypothesis ◽  
Load History ◽  
Fatigue Load ◽  
Computing Power ◽  
Fatigue Damage Accumulation ◽  
Mutual Relations

Abstract One important element of any computational fatigue analysis is the adoption of a hypothesis of fatigue damage accumulation. The most commonly used is the hypothesis of linear accumulation of fatigue damage called the Palmgren-Miner hypothesis. This linear hypothesis does not take into account a factor of great importance: the mutual influence of consecutive fatigue load sequences on each other. In the presented paper, only two consecutive load sequences linked by mutual relations have been analyzed and the results of the analysis have been shown. A more complex form which takes into account the full load history would create complex formula difficult to use. Perhaps, we should go in this direction, especially that today we have enormous computing power at our disposal.

Cyclic and Fatigue Behavior of the P355NL1 Steel Under Block Loading

2007 ◽  
Author(s):  
He´lder F. S. G. Pereira ◽  
Abi´lio M. P. De Jesus ◽  
Anto´nio A. Fernandes ◽  
Alfredo S. Ribeiro
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Pressure Vessels ◽  
Cumulative Damage ◽  
Sequential Effects ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Life Predictions

Current fatigue analyses of metallic structures undergoing variable amplitude loading, including pressure vessels, are mostly based on linear cumulative damage concepts, as proposed by Palmgren and Miner. This type of analysis neglects any sequential effects of the loading history. Several studies have shown that linear cumulative damage theories can produce inconsistent fatigue life predictions. In this paper, both fatigue damage accumulation and cyclic elastoplastic behaviors of the P355NL1 steel are characterized, using block loading fatigue tests. The loading is composed by blocks of constant strain-controlled amplitudes, applied according to two and multiple alternate blocks sequences. Also, loading composed by blocks of variable strain-controlled amplitudes are investigated. The block loading illustrates that fatigue damage evolves nonlinearly with the number of load cycles, as a function of the block strain amplitudes. These observations suggest a nonlinear damage accumulation rule with load sequential effects for the P355NL1 steel. However, the damage accumulation nonlinearity and load sequential effects are more evident for the two block loading rather than for multiple alternate block sequences, which suggests that the linear Palmgren-Miner’s rule tend to produce better results for more irregular loading histories. Some phenomenological interpretations for the observed trends are discussed under a fracture mechanics framework.

Cyclic and Fatigue Behavior of the P355NL1 Steel Under Block Loading

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Hélder F. S. G. Pereira ◽  
Abílio M. P. De Jesus ◽  
Alfredo S. Ribeiro ◽  
António A. Fernandes
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Pressure Vessels ◽  
Cumulative Damage ◽  
Sequential Effects ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Life Predictions

Current fatigue analyses of metallic structures undergoing variable amplitude loading, including pressure vessels, are mostly based on linear cumulative damage concepts, as proposed by Palmgren and Miner. This type of analysis neglects any sequential effects of the loading history. Several studies have shown that linear cumulative damage theories can produce inconsistent fatigue life predictions. In this paper, both fatigue damage accumulation and cyclic elastoplastic behaviors of the P355NL1 steel are characterized using block loading fatigue tests. The loading is composed of blocks of constant strain-controlled amplitudes, applied according to two and multiple alternate blocks sequences. Also, loading composed by blocks of variable strain-controlled amplitudes are investigated. The block loading illustrates that fatigue damage evolves nonlinearly with the number of load cycles, as a function of the block strain amplitudes. These observations suggest a nonlinear damage accumulation rule with load sequential effects for the P355NL1 steel. However, the damage accumulation nonlinearity and load sequential effects are more evident for the two block loading rather than for multiple alternate block sequences, which suggests that the linear Palmgren–Miner rule tends to produce better results for more irregular loading histories. Some phenomenological interpretations for the observed trends are discussed under a fracture mechanics framework.

Fatigue damage accumulation around notches

2004 ◽  
Vol 46 (6) ◽  
pp. 309-313
Author(s):  
Yutaka Iino ◽  
Hideo Yano
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Fatigue Damage Accumulation

Different Fatigue Dynamics Under Statistically and Spectrally Similar Deterministic and Stochastic Excitations

2013 ◽  
Vol 81 (4) ◽  
Author(s):  
Son Hai Nguyen ◽  
Mike Falco ◽  
Ming Liu ◽  
David Chelidze
Keyword(s):  
Crack Growth ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Growth Dynamics ◽  
Experimental System ◽  
Counting Method ◽  
Random Loading ◽  
Stochastic Excitations ◽  
Fatigue Damage Accumulation ◽  
System Coupling

Estimating and tracking crack growth dynamics is essential for fatigue failure prediction. A new experimental system—coupling structural and crack growth dynamics—was used to show fatigue damage accumulation is different under chaotic (i.e., deterministic) and stochastic (i.e., random) loading, even when both excitations possess the same spectral and statistical signatures. Furthermore, the conventional rain-flow counting method considerably overestimates damage in case of chaotic forcing. Important nonlinear loading characteristics, which can explain the observed discrepancies, are identified and suggested to be included as loading parameters in new macroscopic fatigue models.

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