The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Gbadebo Owolabi - One of the best experts on this subject based on the ideXlab platform.
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a new approach to estimating the Fatigue Notch Factor of ti 6al 4v components
International Journal of Fatigue, 2016Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Adewale Olasumboye, Horace WhitworthAbstract:Abstract Titanium alloy is used for airframe components and compressor blades application because of its high strength and fracture toughness at low temperatures and high strength and creep resistance at elevated temperature. This paper extends a recently developed probabilistic mesomechanics based model to Notched titanium alloy components using simulation strategies that capture both the essence of Notch root stress gradient and the complexity of realistic microstructures. The Notch size effects and Notch root and inelastic behavior are combined with probability distributions of microscale stress and small crack initiation to inform minimum life design methods. A new approach which can be applied using crystal plasticity finite element or closed form solution is also proposed as a more robust method for determining the Fatigue Notch Factor than the existing classical methods. The Fatigue Notch Factors predicted using the new probabilistic mesomechanics based model are in good agreements with experimental for Notched titanium alloy specimens subjected to cyclic loads with various stress ratios.
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The effects of Notch size and material microstructure on the Notch sensitivity Factor for Notched components
Engineering Fracture Mechanics, 2015Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Oluwakayode Bamiduro, Adewale Olasumboye, Horace WhitworthAbstract:Abstract Nickel base superalloys are used in hot sections of gas turbine engines due to its high strength and good creep, Fatigue, and corrosion resistance at high temperature. In this paper, a new probabilistic approach based on weakest-link theory that accounts for the effects of the microstructure, Notch size and Notch acuity is described and applied to nickel base superalloy to determine the Fatigue Notch Factor, Notch sensitivity index and the probability of forming microstructurally small crack from the Notch root. The simulation results obtained from this framework are compared with experimental results and results obtained using existing classical methods for Notched polycrystalline nickel base superalloys for the different Notch root radii and acuities considered.
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extension of a probabilistic mesomechanics based model for Fatigue Notch Factor to titanium alloy components
Procedia Materials Science, 2014Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Oluwakayode Bamiduro, Horace WhitworthAbstract:Abstract This paper extends a recently developed probabilistic mesomechaniccs based model for Fatigue Notch Factor to titanium alloy components. The Notch size effects and Notch root and inelastic behaviour are combined with probability distributions of microscale stress-strain gradient and small crack initiation to inform minimum life design methods. The Fatigue Notch Factors predicted using the new model are in good agreements with the experimental results for the Notched titanium alloy specimens.
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On Fatigue Strength Reduction Factor: State of the Art
Volume 8: Mechanics of Solids Structures and Fluids, 2012Co-Authors: Gbadebo Owolabi, Horace Whitworth, Benedict Egboiyi, Olanrewaju AlukoAbstract:Numerous theoretical models have been developed to predict the Fatigue strength reduction Factor (also known as Fatigue Notch Factor), an important parameter in Fatigue life prediction of Notched components. These models include: the classical average stress method, the fracture mechanics method, the stress field intensity method, the strain energy method, and the weakest link method. However, most of these methods do not incorporate explicit sensitivity to materials microstructure. Accordingly, Notch sensitivity remains a highly empirical subject in spite of significant advances in microstructure-sensitive modeling. This paper gives a detailed literature review of these methods and addresses their limitations. It also discusses a recently developed probabilistic method for microstructure-sensitive Fatigue Notch Factor. The probabilistic method provides a very strong physical basis for Fatigue strength reduction and associated Notch sensitivity; thus it can be used to determine the effect of Notches on reduction of Fatigue resistance in a way that directly incorporates microstructure. The results obtained using the new probabilistic framework and other conventional methods are compared with experimental data for Notched components. The probabilistic framework gives better correlation with experimental results for the Notch sensitivity and Notch size effect than the conventional approaches including the Neuber’s, the Peterson, and the fracture mechanics methods.Copyright © 2012 by ASME
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Microstructure-dependent Fatigue damage process zone and Notch sensitivity index
International Journal of Fracture, 2011Co-Authors: Gbadebo Owolabi, Benedict Egboiyi, Horace WhitworthAbstract:The development of simulation methods for calculating Notch root parameters for purposes of estimating the Fatigue life of Notched components is a critical aspect of designing against Fatigue failures. At present, however, treatment of the Notch root stress and plastic strain field gradients, coupled with intrinsic length scales of grains or other material attributes, has yet to be developed. Ultimately, this approach will be necessary to form a predictive basis for Notch size effects in forming and propagating microstructurally small cracks in real structural materials and components. In this study, computational micromechanics is used to clarify and distinguish process zone for crack formation and microstructurally small crack growth, relative to scale of Notch root radius and spatial extent of stress concentration at the Notch. A new nonlocal criterion for the Fatigue damage process zone based on the distribution of a shear-based Fatigue indicator parameter is proposed and used along with a statistical method to obtain a new microstructure-sensitive Fatigue Notch Factor and associated Notch sensitivity index, thereby extending Notch sensitivity to explicitly incorporate microstructure sensitivity and attendant size effects via probabilistic arguments. The Notch sensitivity values obtained for a range of Notch root radii using the new statistical approach presented in this study predict the general trends obtained from experimental results available in literature.
Horace Whitworth - One of the best experts on this subject based on the ideXlab platform.
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a new approach to estimating the Fatigue Notch Factor of ti 6al 4v components
International Journal of Fatigue, 2016Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Adewale Olasumboye, Horace WhitworthAbstract:Abstract Titanium alloy is used for airframe components and compressor blades application because of its high strength and fracture toughness at low temperatures and high strength and creep resistance at elevated temperature. This paper extends a recently developed probabilistic mesomechanics based model to Notched titanium alloy components using simulation strategies that capture both the essence of Notch root stress gradient and the complexity of realistic microstructures. The Notch size effects and Notch root and inelastic behavior are combined with probability distributions of microscale stress and small crack initiation to inform minimum life design methods. A new approach which can be applied using crystal plasticity finite element or closed form solution is also proposed as a more robust method for determining the Fatigue Notch Factor than the existing classical methods. The Fatigue Notch Factors predicted using the new probabilistic mesomechanics based model are in good agreements with experimental for Notched titanium alloy specimens subjected to cyclic loads with various stress ratios.
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The effects of Notch size and material microstructure on the Notch sensitivity Factor for Notched components
Engineering Fracture Mechanics, 2015Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Oluwakayode Bamiduro, Adewale Olasumboye, Horace WhitworthAbstract:Abstract Nickel base superalloys are used in hot sections of gas turbine engines due to its high strength and good creep, Fatigue, and corrosion resistance at high temperature. In this paper, a new probabilistic approach based on weakest-link theory that accounts for the effects of the microstructure, Notch size and Notch acuity is described and applied to nickel base superalloy to determine the Fatigue Notch Factor, Notch sensitivity index and the probability of forming microstructurally small crack from the Notch root. The simulation results obtained from this framework are compared with experimental results and results obtained using existing classical methods for Notched polycrystalline nickel base superalloys for the different Notch root radii and acuities considered.
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extension of a probabilistic mesomechanics based model for Fatigue Notch Factor to titanium alloy components
Procedia Materials Science, 2014Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Oluwakayode Bamiduro, Horace WhitworthAbstract:Abstract This paper extends a recently developed probabilistic mesomechaniccs based model for Fatigue Notch Factor to titanium alloy components. The Notch size effects and Notch root and inelastic behaviour are combined with probability distributions of microscale stress-strain gradient and small crack initiation to inform minimum life design methods. The Fatigue Notch Factors predicted using the new model are in good agreements with the experimental results for the Notched titanium alloy specimens.
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On Fatigue Strength Reduction Factor: State of the Art
Volume 8: Mechanics of Solids Structures and Fluids, 2012Co-Authors: Gbadebo Owolabi, Horace Whitworth, Benedict Egboiyi, Olanrewaju AlukoAbstract:Numerous theoretical models have been developed to predict the Fatigue strength reduction Factor (also known as Fatigue Notch Factor), an important parameter in Fatigue life prediction of Notched components. These models include: the classical average stress method, the fracture mechanics method, the stress field intensity method, the strain energy method, and the weakest link method. However, most of these methods do not incorporate explicit sensitivity to materials microstructure. Accordingly, Notch sensitivity remains a highly empirical subject in spite of significant advances in microstructure-sensitive modeling. This paper gives a detailed literature review of these methods and addresses their limitations. It also discusses a recently developed probabilistic method for microstructure-sensitive Fatigue Notch Factor. The probabilistic method provides a very strong physical basis for Fatigue strength reduction and associated Notch sensitivity; thus it can be used to determine the effect of Notches on reduction of Fatigue resistance in a way that directly incorporates microstructure. The results obtained using the new probabilistic framework and other conventional methods are compared with experimental data for Notched components. The probabilistic framework gives better correlation with experimental results for the Notch sensitivity and Notch size effect than the conventional approaches including the Neuber’s, the Peterson, and the fracture mechanics methods.Copyright © 2012 by ASME
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Microstructure-dependent Fatigue damage process zone and Notch sensitivity index
International Journal of Fracture, 2011Co-Authors: Gbadebo Owolabi, Benedict Egboiyi, Horace WhitworthAbstract:The development of simulation methods for calculating Notch root parameters for purposes of estimating the Fatigue life of Notched components is a critical aspect of designing against Fatigue failures. At present, however, treatment of the Notch root stress and plastic strain field gradients, coupled with intrinsic length scales of grains or other material attributes, has yet to be developed. Ultimately, this approach will be necessary to form a predictive basis for Notch size effects in forming and propagating microstructurally small cracks in real structural materials and components. In this study, computational micromechanics is used to clarify and distinguish process zone for crack formation and microstructurally small crack growth, relative to scale of Notch root radius and spatial extent of stress concentration at the Notch. A new nonlocal criterion for the Fatigue damage process zone based on the distribution of a shear-based Fatigue indicator parameter is proposed and used along with a statistical method to obtain a new microstructure-sensitive Fatigue Notch Factor and associated Notch sensitivity index, thereby extending Notch sensitivity to explicitly incorporate microstructure sensitivity and attendant size effects via probabilistic arguments. The Notch sensitivity values obtained for a range of Notch root radii using the new statistical approach presented in this study predict the general trends obtained from experimental results available in literature.
Dick Arnold - One of the best experts on this subject based on the ideXlab platform.
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the influence of burr formation and feed rate on the Fatigue life of drilled titanium and aluminium alloys used in aircraft manufacture
Cirp Annals-manufacturing Technology, 2018Co-Authors: Ali M Abdelhafeez, David K. Aspinwall, Anthony Dowson, Dick ArnoldAbstract:Abstract Following drilling, Fatigue life trials were performed on as-drilled and deburred specimens made from Ti–6Al–4V, AA7010 and AA2024, with feed rates varied at 2 levels. Deburring dramatically increased the Fatigue performance of the Ti–6Al–4V and AA7010 samples by 69% and 283% respectively, but there was no significant effect on the AA2024 alloy. Fractography showed failure initiated near the exit burrs in Ti–6Al–4V and AA7010 specimens but not in the AA2024 workpieces. Correlation (R2) of Fatigue Notch Factor against the sum of entrance and exit burr height was 0.68 and 0.79 for Ti–6Al–4V and AA7010 respectively, compared to 0.54 for AA2024.
Oluwamayowa Okeyoyin - One of the best experts on this subject based on the ideXlab platform.
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a new approach to estimating the Fatigue Notch Factor of ti 6al 4v components
International Journal of Fatigue, 2016Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Adewale Olasumboye, Horace WhitworthAbstract:Abstract Titanium alloy is used for airframe components and compressor blades application because of its high strength and fracture toughness at low temperatures and high strength and creep resistance at elevated temperature. This paper extends a recently developed probabilistic mesomechanics based model to Notched titanium alloy components using simulation strategies that capture both the essence of Notch root stress gradient and the complexity of realistic microstructures. The Notch size effects and Notch root and inelastic behavior are combined with probability distributions of microscale stress and small crack initiation to inform minimum life design methods. A new approach which can be applied using crystal plasticity finite element or closed form solution is also proposed as a more robust method for determining the Fatigue Notch Factor than the existing classical methods. The Fatigue Notch Factors predicted using the new probabilistic mesomechanics based model are in good agreements with experimental for Notched titanium alloy specimens subjected to cyclic loads with various stress ratios.
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The effects of Notch size and material microstructure on the Notch sensitivity Factor for Notched components
Engineering Fracture Mechanics, 2015Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Oluwakayode Bamiduro, Adewale Olasumboye, Horace WhitworthAbstract:Abstract Nickel base superalloys are used in hot sections of gas turbine engines due to its high strength and good creep, Fatigue, and corrosion resistance at high temperature. In this paper, a new probabilistic approach based on weakest-link theory that accounts for the effects of the microstructure, Notch size and Notch acuity is described and applied to nickel base superalloy to determine the Fatigue Notch Factor, Notch sensitivity index and the probability of forming microstructurally small crack from the Notch root. The simulation results obtained from this framework are compared with experimental results and results obtained using existing classical methods for Notched polycrystalline nickel base superalloys for the different Notch root radii and acuities considered.
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extension of a probabilistic mesomechanics based model for Fatigue Notch Factor to titanium alloy components
Procedia Materials Science, 2014Co-Authors: Gbadebo Owolabi, Oluwamayowa Okeyoyin, Oluwakayode Bamiduro, Horace WhitworthAbstract:Abstract This paper extends a recently developed probabilistic mesomechaniccs based model for Fatigue Notch Factor to titanium alloy components. The Notch size effects and Notch root and inelastic behaviour are combined with probability distributions of microscale stress-strain gradient and small crack initiation to inform minimum life design methods. The Fatigue Notch Factors predicted using the new model are in good agreements with the experimental results for the Notched titanium alloy specimens.
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application of weakest link probabilistic framework for Fatigue Notch Factor to aero engine materials
wjm, 2013Co-Authors: Oluwamayowa OkeyoyinAbstract:This paper is concerned with the extension of a recently developed probabilistic framework based on Weibull’s weakest link and extreme-value statistics to aero-engine materials like titanium alloy and nickel-base super alloys using simulation strategies that capture both the essence of Notch root stress gradient and the complexity of realistic microstructures. In this paper, Notch size effects and Notch root inelastic behavior are combined with probability distributions of microscale stress-strain gradient and small crack initiation to inform minimum life design methods. A new approach which can be applied using crystal plasticity finite element or closed-form solution is also proposed as a more robust approach for determining Fatigue Notch Factor than the existing classical methods. The Fatigue Notch Factors predicted using the new framework are in good agreements with experimental results obtained from literature for Notched titanium alloy specimens subjected to uniaxial cyclic loads with various stress ratio.
Dieter Radaj - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Notch Factor of gaps in welded joints reconsidered
Engineering Fracture Mechanics, 1997Co-Authors: Dieter RadajAbstract:Abstract The Fatigue Notch Factor of short gaps or cracks in welded joints determined by the Notch stress approach with fictitious Notch rounding is modified on the basis of theoretical relations for Notch stresses and stress intensity Factors. The accuracy of the derived correction Factors is proven by application to a cruciform welded joint with short internal gaps.
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Geometrically nonlinear behaviour or spot welded joints in tensile and compressive shear loading
Engineering Fracture Mechanics, 1995Co-Authors: Dieter Radaj, S. ZhangAbstract:Abstract The geometrically nonlinear behaviour of spot welded joints including buckling and gap closure and its influence on local stress parameters at the weld spot edge (structural stresses, Notch stress or Fatigue Notch Factor, stress intensity Factors) are determined by a large displacement analysis of the tensile shear specimen subjected to tensile and compressive loading. The local parameters mentioned are considered decisive for Fatigue crack initiation. A continuous beam model and a plate strip model are used within a simplified procedure. A more sophisticated finite element model is applied on the specimens thereafter. The nonlinear effect is small for steel plates more than 1 mm thick in the medium and high cycle Fatigue range of tensile loading. It may be stronger for compressive loading but is at least partially compensated for in this case by the gap closure effect.
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Notch effect of welded joints subjected to antiplane shear loading
Engineering Fracture Mechanics, 1992Co-Authors: Dieter Radaj, S. ZhangAbstract:Abstract Complementary to existing solutions of the plane problem of Notch stress concentration of welded joints, the antiplane problem is solved using the boundary element method. Typical shape examples of welded joints are considered. Tensile loading is compared with longitudinal shear loading. Based on these solutions, the biaxial and oblique loading is dealt with, taking the cruciform joint and transverse stiffener as examples. The Fatigue Notch Factor is determined based on the microstructural support hypothesis proposed by Neuber.
