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Fatigue performance of welded joints made of high-strength steel under variable amplitude loading conditions and varying mean stress

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WELDING IN THE WORLD 2025年 1-16页

作者： Gronlund, Kiia Ahola, Antti Lipiainen, Kalle Pesonen, Tero Bjork, Timo Moshtaghi, Masoud Lappeenranta Lahti Univ Technol LUT Lab Steel Struct POB 20 Lappeenranta 53851 Finland

The study experimentally and analytically investigates the effects of variable amplitude (VA) load sequence and varying mean stress on the fatigue strength of welded joints made of high-strength steel. The variable amplitude load spectra were constructed according to a Gaussian normal distribution, and the test series of increasing mean stress (constant maximum stress of the VA load) and decreasing mean stress (constant minimum stress) with identical equivalent stresses were implemented. The applied load spectra incorporated a high peak stress in the beginning of the block to further study the overload and residual stress relaxation effects. In addition, a notch-based fatigue assessment approach, the 4R method, was applied to these load cases. Analyses were conducted with the 4R method to analytically compute local elastic-plastic behavior, and the sequential effect of VA load cycles were considered in the mean stress correction. The fatigue test results showed that the mean stress had a significant impact on the fatigue strength of the welded joints in spite of identical equivalent loads. The difference between the mean fatigue strengths (Delta sigma c,50% = 130 MPa and Delta sigma c,50% = 80 MPa) of the two-test series was approximately 63% with the higher fatigue strength corresponding to low mean stress loading conditions.

关键词： Fatigue strength High-strength steel variable amplitude loading Welded joints 4R method

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A novel experimental method to evaluate the fatigue behaviour and damage evolution of bi-directional composites under variable amplitude loading

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INTERNATIONAL JOURNAL OF FATIGUE 2025年 198卷

作者： Khan, Ateeb Ahmad Singh, Indra Vir Mishra, Bhanu Kumar Chennamsetti, Ramadas IIT Roorkee Dept Mech & Ind Engn Roorkee India Aligarh Muslim Univ Dept Mech Engn Aligarh India DRDO Composites Res Ctr R&DE E Pune India

This study presents a novel experimental approach to evaluate the fatigue performance of bi-directional glass fiber-reinforced polymer (GFRP) composites under variable amplitude sequential block loading conditions. The proposed method incorporates advanced loading protocols to simulate realistic service conditions, capturing the complex nonlinear stress interactions and damage progression unique to composite materials. The experimental setup ensures precise control over load sequences and stress blocks, facilitating a comprehensive understanding of fatigue performance and failure mechanisms based on fatigue life, stiffness degradation and thermal response. Results demonstrate a significant influence of load sequence, cycle mixing and stress level on fatigue behaviour, providing critical insights into material performance and damage evolution. Key findings highlight the pronounced effect of high-to-low (H-L) compared to low-to-high (L-H) loading regimes on fatigue performance, showing up to 38 % reduced fatigue life. The study also demonstrates the influence of crack initiation and propagation rates on fatigue performance under both loading regimes. A load sequence sensitive damage law has been proposed to capture the nonlinear damage accumulation under variable loading conditions. This work provides a robust framework for improving the design and reliability of GFRP composites subjected to variable amplitude loading in engineering applications.

关键词： variable amplitude loading Bi-directional composites Stiffness Degradation Damage Mechanism Modified Miner's Rule

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variable amplitude loading of Al 2024-T351 at different load ratios using ultrasonic equipment

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INTERNATIONAL JOURNAL OF FATIGUE 2014年 60卷 34-42页

作者： Mayer, H. Fitzka, M. Schuller, R. BOKU Inst Phys & Mat Sci A-1190 Vienna Austria

Ultrasonic fatigue tests with variable amplitude are performed for the first time at positive load ratios. The method utilising ultrasonic equipment, a servo-hydraulic or electromechanical load frame and computer control is described. Aluminium alloy 2024-T351 is tested at approximately 20 kHz with variable amplitude in the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regime at load ratios R= -1,R= 0.1 and R= 0.5. Constant amplitude data are available and are used for Miner damage accumulation calculations. For load ratio R= -1, the mean damage sum decreases from 0.5 to 0.3 when lifetimes increase from the HCF regime to 10(9) cycles, and increases at higher numbers of cycles. For load ratio R = 0.1, the mean damage sum decreases from 1.1 to 0.2 when lifetimes increase from HCF to VHCF. At load ratio R= 0.5, the mean damage sum is approximately 0.1 in the VHCF regime. Cracks leading to VHCF failures start at broken constituent particles, probably Al7Cu2(Fe,Mn), or at agglomerations of fractured particles. Crack initiation occurs at the surface or less frequently in the interior. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Very high cycle fatigue variable amplitude loading 2024 Aluminium alloy Ultrasonic fatigue Damage accumulation

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The influence of variable amplitude loading on crack closure and notch fatigue behaviour

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INTERNATIONAL JOURNAL OF FATIGUE 1997年第5期19卷 389-400页

作者： MacDougall, C Topper, TH Department of Civil Engineering University of Waterloo Waterloo Ontario Canada

Smooth and notched 1045 steel specimens were tested under constant amplitude, R = -1 loading and under a variable amplitude load history consisting of periodic overloads followed by high R-ratio small cycles. The notched specimens exhibited a notch size effect under constant amplitude loading, but the effect was reduced in the long life region (defined as a fatigue life > 10(7) cycles) under the variable amplitude load history. A crack growth model that followed crack closure changes on a cycle-by-cycle basis adequately predicted fatigue life for the periodically overloaded notched specimens. (C) 1997 Elsevier Science Ltd.

关键词： fatigue notch fatigue crack closure variable amplitude loading crack growth

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Strip yield modelling of fatigue crack under variable amplitude loading

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JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY 2011年第12期25卷 3025-3036页

作者： Singh, Konjengbam Darunkumar Xu, Yigeng Sinclair, Ian Indian Inst Technol Guwahati Dept Civil Engn Gauhati India Univ Hertfordshire Sch Aerosp Automot & Design Engn Hatfield AL10 9AB Herts England Univ Southampton Mat Res Grp Sch Engn Sci Southampton Hants England

The results from 'strip yield' approach of the FASTRAN type models of plasticity induced crack closure effects of fatigue cracks subjected to variable amplitude loadings are presented. The strip yield results are compared with authors' finite element (FE) and experimental results. It has been observed that the strip yield model is seen to be fundamentally limited by choice of alpha (constraint factor) and corresponding to treat baseline closure effects. Double overload closure behavior is functionally similar for both strip yield and FE models. Under multiple overloads, an important functional difference is seen between FE and strip yield models. This has been linked to the absence of in-plane constraint in the strip yield model, which is seen to have a distinct decreasing influence on on-going closure effects.

关键词： Fatigue variable amplitude loading Strip yield modelling Finite element modelling

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Investigation of fatigue damage to welded joints under variable amplitude loading spectra

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INTERNATIONAL JOURNAL OF FATIGUE 2009年第1期31卷 138-152页

作者： Zhang, Yan-Hui Maddox, S. J. TWI Ltd Struct Integr Technol Grp Cambridge CB1 6AL England

The paper presents the results of the investigation on the effect of loading spectra with different mean stresses on the validity of Miner's rule, and the effect of stresses below the constant amplitude fatigue limit (CAFL) on the fatigue performance of two types of weld joint. In support of understanding the mechanism for any deficiency to Miner's rule, fracture mechanics analysis was carried out by measuring and predicting the crack growth in specimens tested under both constant amplitude and variable amplitude loading. The experimental results showed that, although Miner's rule would predict the same fatigue life for each type of specimens tested under the same spectrum, in fact the actual value of Sigma(n/N) at failure strongly depended on the sequence applied. The influence of the loading sequence on Sigma(n/N) was in agreement with that on crack growth rates. The deficiency in Miner's rule was attributed primarily to the stress interaction effects resulting from the type of loading sequence used. The experimental results also showed that, under certain circumstances, stress ranges well below the fatigue limit were found to be as damaging as implied by the S-N curve extrapolated beyond the CAFL without changing the slope. The value of the minimum fully damaging stress range was found to depend on the basic fatigue strength of the weld joint. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： variable amplitude loading Miner's rule Welded joint Fatigue limit Crack growth

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Closure effects on fatigue crack growth rates at constant and variable amplitude loading

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ENGINEERING FRACTURE MECHANICS 2004年第9-10期71卷 1273-1288页

作者： Månsson, T Öberg, H Nilsson, F Royal Inst Technol KTH Dept Solid Mech SE-10044 Stockholm Sweden

Accurate measurements of fatigue propagation rates after single and during repetitive overloads were performed. It was shown that plastic deformations in the crack tip region and in the crack wake cause crack closure that is of major importance for crack growth rates. The consequences of this for methods to determine certain material properties are discussed. An improved method to measure closure free propagation rate data was utilised. The possibilities and shortcomings of compliance methods to determine crack closure levels are pointed out. The relevance of using DeltaK(I,eff) = K-I,K-max - K-I,K-lim, where K-I,K-lim possibly could be interpreted as the crack closure level was investigated and is discussed. A method to predict average crack propagation rates at block loadings consisting of well-defined load cycles of different amplitudes and R-factors was suggested. Three-dimensional effects after overloads were observed. These observations confirmed that the crack closure behaviour also depends on geometry of the specimen. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： crack closure fatigue crack growth variable amplitude loading

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A critical plane approach for life prediction of high cycle fatigue under multiaxial variable amplitude loading

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INTERNATIONAL JOURNAL OF FATIGUE 2000年第2期22卷 101-119页

作者： Morel, F ENSMA Mecan & Phys Mat Lab F-86960 Chasseneuil Poitou Futuroscope France

In this paper, a new life prediction method for high cycle multiaxial fatigue of metallic materials is presented. It is based on a local approach introduced by Dang Van and developed by Papadopoulos, where accumulated plastic strain due to external loading is estimated at a scale of the order of a few grains. Its evaluation requires the use of a critical plane type fatigue criterion. As soon as the accumulated plastic mesostrain, considered as the damage variable, reaches a critical value, a crack is considered to be initiated. The complex and combined cases of loading (multiaxial and variable amplitude loading) can be analysed with this new method. In particular, attention is given to a description of the damaging effect of the loading path shape on fatigue strength. The application of hardening plasticity laws at the local scale allows one to estimate and sum the damage caused by elementary loading events like transitions. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： high cycle fatigue multiaxial fatigue life prediction variable amplitude loading

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Fatigue testing and analysis of peened highway bridge welds under in-service variable amplitude loading conditions

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INTERNATIONAL JOURNAL OF FATIGUE 2011年第3期33卷 300-312页

作者： Ghahremani, Kasra Walbridge, Scott Univ Waterloo Dept Civil & Environm Engn Waterloo ON N2L 3G1 Canada

A laboratory study is presented wherein needle peened structural steel weld specimens are fatigue tested under simulated in-service loading histories typical of highway bridges A strain-based fracture mechanics model is then validated by comparison with the test results and used to perform additional studies wherein similar welds are analyzed under loading histories encompassing a wider range of Influence lines and bridge spans It is concluded that the employed model is well suited for studying the effects of peening on the fatigue performance of highway bridge welds under in-service loading conditions The consideration of tensile dead load stresses and periodic overload trucks is seen to decrease the predicted benefit of peening This benefit can still be substantial however for a wide range of loading conditions likely to be seen in highway bridges (C) 2010 Elsevier Ltd All rights reserved

关键词： Fatigue Fracture mechanics Needle peening Steel bridges variable amplitude loading

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Elastic-plastic fatigue crack growth analysis under variable amplitude loading spectra

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INTERNATIONAL JOURNAL OF FATIGUE 2009年第11-12期31卷 1828-1836页

作者： Mikheevskiy, S. Glinka, G. Univ Waterloo Dept Mech Engn Waterloo ON N2L 3G1 Canada

Most fatigue loaded components or structures experience a variety of stress histories under typical operating loading conditions. In the case of constant amplitude loading the fatigue crack growth depends only on the component geometry, applied loading and material properties. In the case of variable amplitude loading the fatigue crack growth depends also on the preceding cyclic loading history. Various load sequences may induce different load-interaction effects which can cause either acceleration or deceleration of fatigue crack growth. The recently modified two-parameter fatigue crack growth model based on the local stress-strain material behaviour at the crack tip [1,2] was used to account for the variable amplitude loading effects. The experimental verification of the proposed model was performed using 7075-T6 aluminum alloy, Ti-17 titanium alloy, and 350WT steel. The good agreement between theoretical and experimental data shows the ability of the model to predict the fatigue life under different types of variable amplitude loading spectra. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： UniGrow variable amplitude loading Residual stress

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