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A fatigue driving stress approach to damage and life prediction under variable amplitude loading

INTERNATIONAL JOURNAL OF DAMAGE MECHANICS 2013年第3期22卷 393-404页

作者： Kwofie, Samuel Rahbar, Nima Univ Sci & Technol Dept Mat Engn Kumasi Ghana Univ Massachusetts Dept Civil & Environm Engn N Dartmouth MA 02747 USA

A fatigue driving stress that causes fatigue damage is presented and used to predict residual fatigue life under variable loading. This fatigue driving stress is a function of the applied cyclic stress (sigma), number of loading cycles (n), and the number of cycles to failure (N). It increases with loading cycles until the fatigue strength is reached when fracture occurs. By determining the equivalent number of cycles or life fraction at current load that yields the same fatigue driving stress as the previous loads, the remaining life can be predicted. A new damage model is derived as a function of expended life fraction of applied load, the logarithm life of applied load and the logarithm life of the initial applied load. The derived cumulative damage model indicates that Sigma niNi>1 for low-to-high loading sequence, and Sigma niNi<1, for high-to-low loading. In the case of constant amplitude loading, however, Sigma niNi=1. Life predictions from the present damage model and the Miner model are compared with experimental results from literature. The comparison shows that the present model presents a good estimation of the experimental data. Furthermore life prediction using the present model is found to give better agreement with experimental data than the popular Miner model.

关键词： variable amplitude loading life-fraction fatigue driving stress damage model life prediction

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Fatigue Modeling of a Notched Flat Plate Under variable amplitude loading Supported by Elastoplastic Finite Element Method Analyses

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JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME 2011年第6期133卷 061207页

作者： Pereira, Helder F. S. G. De Jesus, Abilio M. P. Ribeiro, Alfredo S. Fernandes, Antonio A. IDMEC Polo FEUP UCVE P-4200465 Oporto Portugal Univ Tras Os Montes & Alto Douro Sch Sci & Technol UCVE IDMEC P-5001801 Quinta De Prados Vila Real Portugal Univ Porto Fac Engn P-4200465 Oporto Portugal

Although intensive research has been carried out to understand the fatigue behavior of steel notched components, under variable amplitude loading, no definite and general robust models have been derived so far. Therefore, every effort to augment the knowledge in this topic is welcomed. Within this context, existing variable amplitude data, derived by the authors for a notched low carbon pressure vessel steel (P355NL1) flat plate, is used to assess a local approach to fatigue. A linear damage summation framework, supported by elastoplastic finite element analyses, is used. Several variable amplitude loadings were selected and analyzed, using alternative configurations of kinematic hardening plasticity models (e.g., Chaboche's model with distinct constants superposition). The predictions are assessed using available experimental data and data derived with simplified empirical elastoplastic tools. This paper highlights the difficulties of performing such elastoplastic analysis and compares the obtained results with those obtained using more classical tools for elastoplastic analysis (Glinka and Seeger-Heuler). It was found that fatigue predictions based on an elastoplastic finite element analysis, made using the Chaboche's model, were significantly more accurate than predictions based on simplified elastoplastic analysis. These results have important practical relevance. [DOI: 10.1115/1.4004617]

关键词： fatigue notched plate variable amplitude loading finite element method elastoplastic analysis

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Fatigue life and plastic deformation behavior of electrodeposited copper thin film under variable amplitude loading

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INTERNATIONAL JOURNAL OF FATIGUE 2012年 38卷 1-6页

作者： Lee, Do-Young Song, Ji-Ho Korea Adv Inst Sci & Technol Sch Mech Aerosp & Syst Engn Div Mech Engn Taejon 305701 South Korea

As an exploratory study to investigate fatigue behavior of an elecrodeposited copper thin film under variable amplitude loading, repeated two-block loading tests were performed for various loading conditions. Plastic deformation behavior was continuously measured during the tests. Due to the load interaction effect under repeated two-block loading, fatigue life is significantly reduced. A concept is introduced to evaluate the load interaction effect and successfully utilized to predict fatigue life through simulation of the monotonic plastic strain (ratcheting strain) behavior under repeated two-block loading. Effects of load parameters of repeated two-block loading on fatigue life were also discussed. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Electrodeposited copper thin film Fatigue test variable amplitude loading Two-block loading thin film fatigue Miner's rule

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Fatigue crack growth analysis of plasma nitrided AISI 4140 low-alloy steel: Part 2-variable amplitude loading and load interactions

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MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 2016年 672卷 265-275页

作者： Kovaci, H. Yetim, A. F. Baran, O. Celik, A. Ataturk Univ Dept Mech Engn Fac Engn Erzurum Turkey Erzurum Tech Univ Dept Mech Engn Fac Engn & Architecture Erzurum Turkey Erzincan Univ Dept Mech Engn Fac Engn Erzincan Turkey

The effects of plasma nitriding on fatigue crack growth (FCG) properties of AISI 4140 low-alloy steel under variable amplitude loading (VAL) conditions were investigated. The compact tension specimens made of AISI 4140 were plasma nitrided at 400 degrees C, 500 degrees C and 600 degrees C for 1 and 4 h. CT specimens were subjected to fatigue under different VAL conditions including overload (OL), underload (UL), over-load+underload (OL+UL) and underload + overload (UL+ OL). The OL investigations revealed that the FCG life of untreated and plasma nitrided samples increased with respect to constant amplitude loading (CAL). Plasma nitrided samples exhibited less FCG life increase than untreated sample because of decreased crack tip plastic zone size and crack retardation period. In the case of UL, FCG lives of all samples decreased in comparison to CAL. The effect of tensile residual stresses formed after UL was suppressed by the compressive residual stresses produced by plasma nitriding. Also, it was seen that the increasing compound layer thickness and the presence of Braunite phase increased the brittleness of the material regardless of the loading type. The overall results showed that the loding type and mechanical/structural characteristics of nitride layers significantly affected the FCG behavior of the material. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Fatigue crack growth Plasma nitriding variable amplitude loading Overload Underload

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A round robin study of high-frequency mechanical impact (HFMI)-treated welded joints subjected to variable amplitude loading

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WELDING IN THE WORLD 2013年第3期57卷 437-447页

作者： Yildirim, Halid Can Marquis, Gary B. Aalto Univ Dept Appl Mech Aalto 00076 Finland KTH Royal Inst Technol Div Lightweight Struct Dept Aeronaut & Vehicle Engn S-10044 Stockholm Sweden

High-frequency mechanical impact (HFMI) treatment has been significantly developed as a reliable, effective and user-friendly method for post-weld fatigue strength improvement technique for welded structures. The development of an International Institute of Welding best practice guideline for implementing HFMI has been hindered by the lack of directly comparable experimental data for numerous HFMI methods. In this study, nominally identical longitudinal attachments in high-strength steel were manufactured in one welding workshop and distributed to four HFMI equipment manufacturers for treatment. Specimens were fatigue tested on a machine using identical variable amplitude loading histories. HFMI groove measurements were done for each specimen and X-ray diffraction-based residual stress measurements were performed on 10 specimens. The HFMI groove dimensions and the residual stress states showed similarity in general, however small changes were observed. Experimental results indicate that all of the HFMI-improved welds from the HFMI equipment manufacturers satisfied the previously proposed characteristic S-N line based on both the yield strength and the specimen geometry. Results of the study are valuable and promising with respect to the development of a future guideline. The goal of the study has not been to compare treatments, so specific data points are not associated specific HFMI equipment manufacturers.

关键词： High-frequency mechanical impact (HFMI) Weld toe improvement Fatigue improvement High-strength steels variable amplitude loading

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A phenomenological stress-strain model for wrought magnesium alloys under elastoplastic strain-controlled variable amplitude loading

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INTERNATIONAL JOURNAL OF FATIGUE 2015年 80卷 306-323页

作者： Dallmeier, Johannes Denk, Josef Huber, Otto Saage, Holger Eigenfeld, Klaus Univ Appl Sci Landshut Fac Mech Engn Competence Ctr Lightweight Design LLK Freiberg Germany Tech Univ Bergakad Freiberg Foundry Inst Freiberg Germany

Wrought magnesium alloys typically reveal strong basal textures and thus, non-symmetric sigmoidal shaped hysteresis loops within the elastoplastic load range. A detailed description of those hysteresis loops is necessary for numerical fatigue analyses. Therefore, a one-dimensional phenomenological model was developed for elastoplastic strain-controlled constant and variable amplitude loading. The phenomenological model consists of a three-component equation, which considers elastic, plastic, and pseudoelastic strain components with a set of eight material constants. Experimentally and numerically determined hysteresis loops of four different magnesium alloys were compared by means of different examples with constant and variable amplitude. Good correlation is reached and the relevant fatigue parameters like strain energy density were estimated with good accuracy. Applying an energy based fatigue parameter on modelled hysteresis loops, the fatigue life is predicted adequately for constant and variable amplitude loading including mean strain and mean stress effects. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Wrought magnesium alloys Strain-controlled hysteresis loops Phenomenological stress-strain model variable amplitude loading Fatigue modelling

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Fatigue bearing failure of CFRP composite in bolted joints exposed to biaxial variable amplitude loading at elevated temperature

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COMPOSITE STRUCTURES 2016年 142卷 71-77页

作者： Kapidzic, Zlatan Ansell, Hans Schon, Joakim Simonsson, Kjell Saab AB SE-58188 Linkoping Sweden Swedish Def Res Agcy FOI SE-17290 Stockholm Sweden Linkoping Univ Div Solid Mech SE-58183 Linkoping Sweden

Hybrid structures that contain composite-aluminium interfaces tend to develop internal loads at elevated temperatures. In long bolted joints, the thermally induced bolt loads are superimposed onto the mechanically applied load and can induce a biaxial bearing load state. This paper presents an experimental and numerical study of the bearing fatigue failure of carbon-epoxy laminate specimens, exposed to uniaxial and biaxial variable amplitude loading at 90 degrees C. A specifically designed experimental rig was used, where both the mechanical and the thermally induced bolt loads were applied by means of mechanical load actuators. A fatigue model based on the kinetic theory of fracture for polymers, which was previously implemented for constant amplitude loading, is expanded to account for the variable amplitude load history. The results suggest that the biaxial loading gives a longer fatigue life than the uniaxial loading for the same maximum peak resultant force. This result can be utilized as a conservative dimensioning strategy by designing biaxially loaded joints in terms of maximum peak resultant bearing load using uniaxial fatigue data. (c) 2016 Elsevier Ltd. All rights reserved.

关键词： Carbon-epoxy Thermally induced load Fatigue bearing failure variable amplitude loading

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Fatigue life prediction based on crack closure for 6156 Al-alloy laser welded joints under variable amplitude loading

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INTERNATIONAL JOURNAL OF FATIGUE 2015年 72卷 11-18页

作者： Liu, Hu Shang, De-Guang Liu, Jian-Zhong Guo, Zhen-Kun Beijing Univ Technol Coll Mech Engn & Appl Elect Technol Beijing 100124 Peoples R China Beijing Inst Aeronaut Mat Beijing 100095 Peoples R China

A fatigue prediction approach is proposed using fracture mechanics for laser beam welded Al-alloy joints under stationary variable amplitude loading. The proposed approach was based on the constant crack open stress intensity factor in each loading block for stationary variable amplitude loading. The influence of welding residual stress on fatigue life under stationary variable amplitude was taken into account by the change of crack open stress intensity factor in each loading block. The residual stress relaxation coefficient beta = 0.5 was proposed to consider the residual stress relaxation for the laser beam welded Al-alloy joints during the fatigue crack growth process. Fatigue life prediction results showed that a very good agreement between experimental and estimated results was obtained. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Fatigue crack growth Life prediction variable amplitude loading Crack closure Residual stress

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Thermo-mechanical fatigue life prediction method under multiaxial variable amplitude loading

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INTERNATIONAL JOURNAL OF FATIGUE 2019年 127卷 382-394页

作者： Wang, Jin-Jie Shang, De-Guang Sun, Yu-Juan Li, Luo-Jin Li, Dao-Hang Beijing Univ Technol Coll Mech Engn & Appl Elect Technol Beijing 100124 Peoples R China

Based on the Wang-Brown method, a time-dependent multiaxial cycle counting algorithm was proposed under multiaxial thermomechanical variable amplitude loading. By using the proposed multiaxial cycle counting algorithm, a new thermo-mechanical fatigue life prediction method was proposed, in which the pure fatigue damage, creep damage, and the interaction damage taking into account the interaction modulus varying with temperature were calculated for each reversal counted by the cycle counting algorithm. Three types of damage from all the counted reversals for the whole strain-time history were accumulated, and the thermo-mechanical multiaxial fatigue life can be predicted. The thermo-mechanical fatigue experimental data for thin-walled tubular specimen of superalloy GH4169 under multiaxial constant amplitude and variable amplitude loadings were used to verify the proposed method. The results demonstrated that the proposed method can provide very satisfactory prediction results.

关键词： Multiaxial fatigue Thermo-mechanical fatigue variable amplitude loading Life prediction Multiaxial cycle counting

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Fatigue Reliability Evaluation Method of a Gear Transmission System Under variable amplitude loading

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IEEE TRANSACTIONS ON RELIABILITY 2019年第2期68卷 599-608页

作者： Tan, Xiufeng Xie, Liyang Northeastern Univ Minist Educ Mech Engn & Automat Dept Key Lab Vibrat & Control Aeroprop Syst Shenyang 110819 Liaoning Peoples R China

The gear transmission system is a typical time-domain series system, and its fatigue reliability evaluation under variable amplitude loading has long attracted the interests from scholars. The widely used Monte Carlo (MC) method to evaluate the reliability of a system with material and load uncertainties is time consuming, especially when used in combination with a fatigue analysis software. Concerning this problem, this paper proposes a "deterministic damage-random threshold (DDRT)" reliability model. The model converts the randomness from damage to the threshold, thus saving time because only the median damage and the damage for key reliability of each fatigue part are required in reliability evaluation. Based on this model, a reliability calculation flow of a gear transmission system is proposed considering the time-domain characteristic of gears. Finally, the model is verified by numerical examples and the fatigue test data of gears.

关键词： Fatigue reliability gear transmission system Monte Carlo (MC) random threshold variable amplitude loading

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