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Luca Susmel - One of the best experts on this subject based on the ideXlab platform.
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four stress analysis strategies to use the modified wohler curve method to perform the Fatigue Assessment of weldments subjected to constant and variable amplitude multiaxial Fatigue loading
International Journal of Fatigue, 2014Co-Authors: Luca SusmelAbstract:Abstract The present paper investigates the different ways of using the Modified Wohler Curve Method (MWCM) to perform the Fatigue Assessment of steel and aluminium welded joints subjected to in-service variable amplitude (VA) multiaxial load histories. Thanks to its specific features, the above critical plane approach can efficiently be applied in terms of both nominal, hot-spot, and local quantities, that is, by using any of the stress analysis strategies suggested by the Design Recommendations of the International Institute of Welding (IIW). The MWCM can efficiently be used also along with the so-called Theory of Critical Distances applied in the form of the Point Method (PM). The accuracy of the different formalisations of the MWCM investigated in the present paper was systematically checked against a large number of experimental results taken from the literature and generated by testing, under VA biaxial nominal loading, welded samples having different geometries. Such a systematic validation exercise allowed us to prove that our multiaxial Fatigue criterion is successful in designing welded joints against VA multiaxial Fatigue, this holding true independently from both definition adopted to calculate the necessary stress quantities and complexity of the assessed load history.
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modified wohler curve method and multiaxial Fatigue Assessment of thin welded joints
International Journal of Fatigue, 2012Co-Authors: Luca Susmel, Harm AskesAbstract:Abstract The present paper is concerned with the use of the Modified Wohler Curve Method to estimate Fatigue lifetime of thin welded joints of both steel and aluminium subjected to in-phase and out-of-phase multiaxial Fatigue loading. The Modified Wohler Curve Method postulates that, in welded connections subjected to in-service complex time-variable loading, Fatigue damage reaches its maximum value on that material plane experiencing the maximum range of the shear stress amplitude, such a stress quantity being calculated according to the Maximum Variance concept. The most important peculiarity of the above multiaxial Fatigue criterion is that it can be applied by performing the stress analysis in terms of both nominal and local quantities, where in the latter case the relevant stress state at the assumed critical locations can be estimated according to either the reference radius concept or the Theory of Critical Distances. The accuracy and reliability of our multiaxial Fatigue criterion was systematically checked through several experimental results taken from the literature and generated by testing, under in-phase and out-of-phase biaxial loading, welded joints of both steel and aluminium having thickness of the main tube lower than 5 mm. Such a systematic validation exercise allowed us to prove that the Modified Wohler Curve Method is a powerful tool suitable for performing the Fatigue Assessment of thin welded joints, this holding true independently of the strategy adopted to perform the stress analysis. Finally, a microstructural motivation of the length scales included in the Theory of Critical Distances can be established by linking this technique to gradient mechanics, as we will argue.
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multiaxial notch Fatigue from nominal to local stress strain quantities
2009Co-Authors: Luca SusmelAbstract:Useful stress quantities used in Fatigue problems Fundamentals of Fatigue Assessment The modified Wohler curve method in Fatigue Assessment Fatigue Assessment of notched components according to the modified Wohler curve method Multiaxial Fatigue Assessment of welded structures The modified Wohler curve method and metallic materials cracking behaviour under Fatigue loading The modified Manson-Coffin curve method in Fatigue Assessment Multiaxial Fatigue of composite materials.
Gary Marquis - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Assessment of high frequency mechanical impact hfmi treated welded joints subjected to high mean stresses and spectrum loading
Fatigue & Fracture of Engineering Materials & Structures, 2015Co-Authors: Eeva Mikkola, Gary Marquis, Matthew Dore, Mansoor KhurshidAbstract:The Fatigue strength of welded joints can be improved with various post-weld treatment methods. High-frequency mechanical impact treatment is a residual stress modification technique that creates compressive residual stresses at the weld toe. However, these beneficial residual stresses may relax under certain loading conditions. In this paper, previously published Fatigue data for butt and fillet welded joints subjected to high stress ratios and variable amplitude cyclic stresses were evaluated in relation to the current International Institute of Welding (IIW) recommendations on Fatigue strength improvement and a proposed IIW design guideline for high-frequency mechanical impact-treated welded joints. The evaluation showed that the current IIW recommendations resulted in both non-conservative and overly conservative Fatigue strength estimations depending on the applied stress level, whereas the proposed Fatigue Assessment guideline fitted the current data well.
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Fatigue Assessment of high frequency mechanical impact hfmi improved fillet welds by local approaches
International Journal of Fatigue, 2013Co-Authors: Halid Can Yildirim, Gary Marquis, Zuheir BarsoumAbstract:Local Fatigue Assessment methods like the structural hot spot stress and effective notch stress methods as defined by the International Institute of Welding are widely used by design engineers and researchers to assess the Fatigue strength of welded components. This paper provides a comprehensive evaluation of published data for welded joints which had been improved using high frequency mechanical impact (HFMI) treatment. All of the published data for HFMI-treated welds are presented in terms of nominal stress. The goal of the current paper is to establish local Fatigue Assessment procedures for improved fillet welds. In total, 160 published experimental results for longitudinal and cruciform welds subjected to R = 0.1 axial loading are evaluated. Local stress quantities for each joint were assessed based on the finite element analyses and reported nominal stress values. A correction procedure for yield strength that was previously verified for nominal stress-based Fatigue Assessment is also applied to the local stress methods studied in this paper. For both the structural hot spot stress and effective notch stress methods, sets of characteristic Fatigue strength curves as functions of yield strength are proposed and verified. The structural hot spot stress method includes one set of Fatigue strength curves for load-carrying welds and a second set for non-load carrying welds. The effective notch stress method includes a single set of curves for all welds. All of the design curves proposed in this study are conservative with respect to available Fatigue test data.
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An aging aircraft's wing under complex multiaxial spectrum loading: Fatigue Assessment and repairing
International Journal of Fatigue, 2005Co-Authors: Keijo Koski, Jarkko Tikka, Mika Bäckström, Aslak Siljander, Sauli Liukkonen, Gary MarquisAbstract:The structural responses of an aging aircraft's wing due to operational loading cycles are determined using flight measurement. The stressing in the crack initiation locations in the chemically milled wing skin is a combination of compression, tension and shear. The uniaxial Fatigue Assessment and observed cracking behaviour indicates that the Fatigue Assessment should include the multiaxial loading effects. In this paper, the multiaxial Fatigue effects are considered by combining the flight measurement results with FE method and engineering judgement. To avoid or repair the cracking of the chemically milled wing skin composite patching is presented for the reconstructive action.
Zuheir Barsoum - One of the best experts on this subject based on the ideXlab platform.
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Fatigue strength improvement of steel structures by high-frequency mechanical impact: proposed Fatigue Assessment guidelines
Welding in the World, 2013Co-Authors: Gary B. Marquis, Halid Can Yildirim, Eeva Mikkola, Zuheir BarsoumAbstract:In the past decade, high-frequency mechanical impact (HFMI) has significantly developed as a reliable, effective, and user-friendly method for post-weld Fatigue strength improvement technique for welded structures. During this time, period 46 documents on HFMI technology or Fatigue improvements have been presented within Commission XIII of the International Institute of Welding. This paper presents one possible approach to Fatigue Assessment for HFMI-improved joints. Stress analysis methods based on nominal stress, structural hot spot stress, and effective notch stress are all discussed. The document considered the observed extra benefit that has been experimentally observed for HFMI-treated high-strength steels. Some observations and proposals on the effect of loading conditions like high mean stress Fatigue cycles, variable amplitude loading, and large amplitude/low cycle Fatigue cycles are given. Special considerations for low stress concentration details are also given. Several Fatigue Assessment examples are provided in an appendix. A companion paper has also been prepared concerning HFMI equipment, proper procedures, safety, training, quality control measures, and documentation has also been prepared. It is hoped that these guidelines will provide stimulus to researchers working in the field to test and constructively criticize the proposals made with the goal of developing international guidelines relevant to a variety of HFMI technologies and applicable to many industrial sectors. The proposal can also be used as a means of verifying the effectiveness of new equipment as it comes to the market.
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Fatigue Assessment of high frequency mechanical impact hfmi improved fillet welds by local approaches
International Journal of Fatigue, 2013Co-Authors: Halid Can Yildirim, Gary Marquis, Zuheir BarsoumAbstract:Local Fatigue Assessment methods like the structural hot spot stress and effective notch stress methods as defined by the International Institute of Welding are widely used by design engineers and researchers to assess the Fatigue strength of welded components. This paper provides a comprehensive evaluation of published data for welded joints which had been improved using high frequency mechanical impact (HFMI) treatment. All of the published data for HFMI-treated welds are presented in terms of nominal stress. The goal of the current paper is to establish local Fatigue Assessment procedures for improved fillet welds. In total, 160 published experimental results for longitudinal and cruciform welds subjected to R = 0.1 axial loading are evaluated. Local stress quantities for each joint were assessed based on the finite element analyses and reported nominal stress values. A correction procedure for yield strength that was previously verified for nominal stress-based Fatigue Assessment is also applied to the local stress methods studied in this paper. For both the structural hot spot stress and effective notch stress methods, sets of characteristic Fatigue strength curves as functions of yield strength are proposed and verified. The structural hot spot stress method includes one set of Fatigue strength curves for load-carrying welds and a second set for non-load carrying welds. The effective notch stress method includes a single set of curves for all welds. All of the design curves proposed in this study are conservative with respect to available Fatigue test data.
Dongpo Wang - One of the best experts on this subject based on the ideXlab platform.
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Numerical implementation for Fatigue Assessment of butt joint improved by high frequency mechanical impact treatment: A structural hot spot stress approach
International Journal of Fatigue, 2016Co-Authors: Caiyan Deng, Yong Liu, Baoming Gong, Dongpo WangAbstract:Abstract In the study, three-dimensional finite element modelling of high frequency mechanical impact (HFMI) treatment is presented for butt joints of four strength grade materials (Q235B, AISI 1006, 45 Steel and AISI 2205). The Fatigue Assessment of butt joints by HFMI is implemented by structural hot spot stress approaches, i.e., linear surface extrapolation (LSE) and through thickness at the weld toe (TTWT). The effective structural hot spot stress concentration factors for HFMI-treated joints are determined, and the dependence of HFMI improvement on material strength and external stress is well captured by TTWT method. Following structural hot spot stress S-N curves for as-welded joints recommended by IIW, the structural hot spot stress S-N curves for HFMI-treated joints are suggested if the slope m of S-N curves for HFMI-treated joints is designated to vary from 5 to 10, inversely proportional to material strength. At final, the characteristic Fatigue strength (FAT) has been determined and verified with the available experimental data.
Halid Can Yildirim - One of the best experts on this subject based on the ideXlab platform.
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Fatigue strength improvement of steel structures by high-frequency mechanical impact: proposed Fatigue Assessment guidelines
Welding in the World, 2013Co-Authors: Gary B. Marquis, Halid Can Yildirim, Eeva Mikkola, Zuheir BarsoumAbstract:In the past decade, high-frequency mechanical impact (HFMI) has significantly developed as a reliable, effective, and user-friendly method for post-weld Fatigue strength improvement technique for welded structures. During this time, period 46 documents on HFMI technology or Fatigue improvements have been presented within Commission XIII of the International Institute of Welding. This paper presents one possible approach to Fatigue Assessment for HFMI-improved joints. Stress analysis methods based on nominal stress, structural hot spot stress, and effective notch stress are all discussed. The document considered the observed extra benefit that has been experimentally observed for HFMI-treated high-strength steels. Some observations and proposals on the effect of loading conditions like high mean stress Fatigue cycles, variable amplitude loading, and large amplitude/low cycle Fatigue cycles are given. Special considerations for low stress concentration details are also given. Several Fatigue Assessment examples are provided in an appendix. A companion paper has also been prepared concerning HFMI equipment, proper procedures, safety, training, quality control measures, and documentation has also been prepared. It is hoped that these guidelines will provide stimulus to researchers working in the field to test and constructively criticize the proposals made with the goal of developing international guidelines relevant to a variety of HFMI technologies and applicable to many industrial sectors. The proposal can also be used as a means of verifying the effectiveness of new equipment as it comes to the market.
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Fatigue Assessment of high frequency mechanical impact hfmi improved fillet welds by local approaches
International Journal of Fatigue, 2013Co-Authors: Halid Can Yildirim, Gary Marquis, Zuheir BarsoumAbstract:Local Fatigue Assessment methods like the structural hot spot stress and effective notch stress methods as defined by the International Institute of Welding are widely used by design engineers and researchers to assess the Fatigue strength of welded components. This paper provides a comprehensive evaluation of published data for welded joints which had been improved using high frequency mechanical impact (HFMI) treatment. All of the published data for HFMI-treated welds are presented in terms of nominal stress. The goal of the current paper is to establish local Fatigue Assessment procedures for improved fillet welds. In total, 160 published experimental results for longitudinal and cruciform welds subjected to R = 0.1 axial loading are evaluated. Local stress quantities for each joint were assessed based on the finite element analyses and reported nominal stress values. A correction procedure for yield strength that was previously verified for nominal stress-based Fatigue Assessment is also applied to the local stress methods studied in this paper. For both the structural hot spot stress and effective notch stress methods, sets of characteristic Fatigue strength curves as functions of yield strength are proposed and verified. The structural hot spot stress method includes one set of Fatigue strength curves for load-carrying welds and a second set for non-load carrying welds. The effective notch stress method includes a single set of curves for all welds. All of the design curves proposed in this study are conservative with respect to available Fatigue test data.
