scholarly journals Thermodynamic entropy as a marker of high‐cycle fatigue damage accumulation: Example for normalized SAE 1045 steel

2020 ◽  
Vol 43 (12) ◽  
pp. 2854-2866
Author(s):  
Zhenjie Teng ◽  
Haoran Wu ◽  
Christian Boller ◽  
Peter Starke
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Thermodynamic Entropy ◽  
Fatigue Damage Accumulation ◽  
1045 Steel

scholarly journals MODELING FATIGUE LIFE OF POLYCRYSTALLINE STRUCTURAL ALLOYS UNDER A COMBINED EFFECT OF LOW- AND HIGH-CYCLE FATIGUE MECHANISMS

2019 ◽  
Vol 81 (3) ◽  
pp. 305-323
Author(s):  
I.A. Volkov ◽  
L.A. Igumnov ◽  
S.N. Sikaryov ◽  
D.N. Shishulin ◽  
A.I. Volkov
Keyword(s):  
Plastic Deformation ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
High Cycle Fatigue ◽  
Strength Criterion ◽  
Combined Effect ◽  
Evolutionary Equation ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation ◽  
Main Effects

Processes of fatigue life of polycrystalline structural alloys under a combined effect of low- and high-cycle fatigue are considered. In the framework of mechanics of damaged media (MDM), a mathematical model is developed, which describes processes of plastic deformation and fatigue damage accumulation. The MDM model consists of three interrelated parts: relations defining cyclic elastoplastic behavior of the material, accounting for its dependence on the failure process; equations describing fatigue damage accumulation kinetics; a strength criterion of the damaged material. The version of defining relations of elastoplasticity is based on the notion of yield surface and the principle of orthogonality of the plastic strain rate vector to the yield surface at the loading point. This version of equations of state reflects the main effects of the cyclic plastic deformation process of the material for arbitrarily complex loading trajectories. The version of kinetic equations of damage accumulation is based on introducing a scalar parameter of damage degree. The construction uses energy-based principles and accounts for the main effects of the process of nucleation, growth and merging of microdefects under arbitrarily complex multiaxial loading regimes. A combined form of the evolutionary equation of fatigue damage accumulation in the regions of low-cycle (LCF) and high-cycle (HCF) fatigue is proposed. It is shown that, under regular cyclic loading of the material, the stress amplitude of the cycle decreases by degrees during the transition from LCF to HCF and depends on the physical interaction of these mechanisms in the transition zone. The condition when the damage degree attains its critical value is taken as the strength criterion of the damaged material. A methodology of numerically determining parameters of the evolutionary equation of fatigue damage accumulation in the conditions of HCF is presented. To assess the reliability and the limits of applicability of the defining relations of MDM, processes of plastic deformation and fatigue damage accumulation in a number of structural alloys in cyclic tests have been numerically studied, and the obtained numerical results have been compared with the data of full-scale experiments. The results of comparison of the numerical and experimental data reveal that the developed model of mechanics of damaged media adequately describes durability of structures subjected to a combined effect of low- and high-cycle fatigue mechanisms. It is shown that the introduced MDM model qualitatively and, accurately enough for practical engineering purposes, quantitatively describes the main effects of the processes of plastic deformation and fatigue damage accumulation in structural alloys under cyclic loading.

scholarly journals High-cycle fatigue damage accumulation in paper

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Yoon Joo Na ◽  
Sarah A. Paluskiewicz ◽  
Christopher L. Muhlstein
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
High Cycle Fatigue ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation

scholarly journals Damage accumulation near the cold-expanded hole due to high-cycle fatigue by crack compliance method

2021 ◽  
Vol 16 (59) ◽  
pp. 115-128
Author(s):  
Sviatoslav Eleonsky ◽  
Yuri Matvienko ◽  
Vladimir Pisarev ◽  
Michael Zajtsev
Keyword(s):  
Residual Stress ◽  
Fracture Mechanics ◽  
Damage Accumulation ◽  
High Cycle Fatigue ◽  
Initial Point ◽  
Displacement Component ◽  
Electronic Speckle Pattern Interferometry ◽  
Cycle Fatigue ◽  
Fatigue Damage Accumulation ◽  
Plane Displacement

The novel destructive method is implemented for quantitative assessment of fatigue damage accumulation in the stress concentration zone accompanied by residual stress due to cold expansion of the through-thickness hole. Damage accumulation is reached by preliminary cyclic loading of plane specimens with cold-expanded holes. Narrow notches, emanating from the hole edge at different stages of high-cycle fatigue, serve to manifest a damage level. These notches are inserted without applying external load. Deformation response to local material removing, caused by pure residual stress influence, is measured by electronic speckle pattern interferometry (ESPI) in terms of in-plane displacement components. Normalized values of the notch mouth open displacement (NMOD), in-plane displacement component at the initial point of the notch acting in the notch direction (U0), in-plane displacement component at the final point of the notch acting in the notch direction (U1) and the stress intensity factor (SIF) are used as current damage indicators. Numerical integration of curves, describing an evolution of each fracture mechanics parameter over lifetime, produces the damage accumulation function in an explicit form. It is established that all four fracture mechanics parameters give very close results.

Prediction of Nonlinear Evolution of Fatigue Damage Accumulation From an Energy-Based Model

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
M.-H. Herman Shen ◽  
Sajedur R. Akanda
Keyword(s):  
Experimental Data ◽  
Fatigue Damage ◽  
Applied Stress ◽  
Damage Accumulation ◽  
Nonlinear Evolution ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Welded Steel ◽  
Fatigue Damage Accumulation ◽  
Energy History

An energy-based framework is developed for welded steel and AL6061-T6 for assessment of nonlinear evolution of fatigue damage accumulation along fatigue life. The framework involves interrogation at continuum using a newly developed experimental procedure to determine the cyclic damaging energy to reveal that the accumulated fatigue damage evolves nonlinearly along cycle in case of low cycle fatigue but has somewhat linear relationship with cycle in case of high cycle fatigue. The accumulated fatigue damage is defined as the ratio of the accumulated cyclic damaging energy to the fatigue toughness, a material property and hence remains the same at all applied stress ranges. Based on the experimental data, a model is developed in order to predict cyclic damaging energy history at any applied stress range. The predicted fatigue damage evolution from the energy-based model are found to agree well with the experimental data.

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