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Keisuke Tanaka - One of the best experts on this subject based on the ideXlab platform.
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notched ti 6al 4v titanium bars under multiaxial fatigue synthesis of Crack Initiation Life based on the averaged strain energy density
Theoretical and Applied Fracture Mechanics, 2018Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:Abstract The fatigue Life of notched components subjected to multiaxial loading conditions may be influenced by extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between Crack surfaces. These extrinsic mechanisms may disrupt the applicability of local approaches, such as that based on the strain energy density (SED) averaged over a structural volume having size R0 and surrounding the Crack Initiation point. In the present contribution, the multiaxial fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, has been analysed. Pure bending, pure torsion and in-phase as well as out-of-phase combined bending-torsion fatigue tests have been carried out on notched specimens characterized by two different root radii, namely 0.1 and 4 mm. Fatigue Crack Initiation and subsequent propagation have been monitored by adopting the direct current potential drop (DCPD) technique. In principle, Crack Initiation Life has been defined when the initiated fatigue Crack fractures the structural volume, which corresponds to a given potential drop increase calibrated by means of electrical finite element (FE) analyses. The structural volume size R0 has been determined by fatigue testing plain and sharp V-notched specimens under pure axial or pure torsion loadings. Finally, the averaged SED approach has been adopted to correlate the experimental fatigue results expressed in terms of Crack Initiation Life, in order to reduce the effect of extrinsic mechanisms.
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Crack Initiation Life in notched steel bars under torsional fatigue synthesis based on the averaged strain energy density approach
International Journal of Fatigue, 2017Co-Authors: A Campagnolo, Giovanni Meneghetti, Filippo Berto, Keisuke TanakaAbstract:Abstract In a recent contribution by Tanaka, the fatigue behaviour of notched bars made of austenitic stainless steel, SUS 316L, and carbon steel, SGV 410, characterized by different values of the notch tip radius was investigated under torsion loading. Tanaka monitored both fatigue Crack Initiation and propagation phases by means of the potential drop technique. The Crack Initiation Life is correlated here to the depth of the initiated fatigue Crack by means of calibration curves derived from electrical finite element (FE) analyses. In the present contribution, the approach based on the strain energy density (SED) averaged over a structural volume embracing the notch tip is employed to re-analyse the original experimental results of each material, by taking into account the Crack Initiation Life, in order to exclude all extrinsic mechanisms acting during the Crack propagation phase, i.e. sliding contact, friction and meshing between Crack mating surfaces.
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Crack Initiation Life in notched ti 6al 4v titanium bars under uniaxial and multiaxial fatigue synthesis based on the averaged strain energy density approach
Fracture and Structural Integrity, 2017Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD) technique. Based on the results obtained from the potential drop technique, the Crack Initiation Life has been defined in correspondence of a relative potential drop increase ?V/?V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED) averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the Crack Initiation Life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests.
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averaged strain energy density based synthesis of Crack Initiation Life in notched steel bars under torsional fatigue
Fracture and Structural Integrity, 2016Co-Authors: Filippo Berto, A Campagnolo, Giovanni Meneghetti, Keisuke TanakaAbstract:The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue Life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the Crack nucleation Life was reduced with increasing stress concentration, on the other hand the Crack propagation Life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED) averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces, Crack Initiation Life has been considered in the present work. In the original paper, Initiation Life was defined in correspondence of a 0.1÷0.4-mm-deep Crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and Cracked specimens at NA = 2 million loading cycles. KEYWORDS. Torsional fatigue; Notch effect; Crack Initiation; Averaged SED; Electrical potential drop
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averaged strain energy density based synthesis of Crack Initiation Life of notched titanium and steel bars under uniaxial and multiaxial fatigue
ECF21, 2016Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, and austenitic stainless steel, AISI 304L, has been analysed. With the aim of investigating the effect of the notch geometry and the loading condition on the fatigue strength of the titanium alloy, pure tension, pure torsion and multiaxial in-phase tension-torsion fatigue tests have been carried out on specimens characterised by two different root radii, namely 0.1 and 4 mm. As regards the notched steel bars, only the notch effect on the torsion fatigue behaviour has been analysed in detail by testing specimens characterised by three different notch tip radii: 0.1, 1 and 4 mm. In all cases, the nominal load ratio R has been kept constant and equal to -1. Crack nucleation and subsequent propagation have been accurately monitored by using the electrical potential drop technique, which allows to define the Crack Initiation Life in correspondence of a Crack depth approximately equal to 0.1÷0.3 mm, according to Tanaka [1]. The experimental fatigue results of each material have been re-analysed using the local strain energy density (SED) averaged over a control volume having radius R 0 surrounding the notch tip [2]. With the aim of excluding all extrinsic mechanisms acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces recently discussed by Tanaka dealing with the torsional fatigue behaviour of notched steel bars [1], the Crack Initiation Life has been considered in the present work. The control radius R 0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated for the two considered materials by imposing the constancy of the averaged SED for both smooth and Cracked specimens at N A = 2 million cycles [2,3]. Therefore, R 0 is seen to depend on two material properties: the plain material fatigue limit (or the high-cycle fatigue strength of smooth specimens) and the threshold value of the stress intensity factor (SIF) range for long Cracks. Finally, the use of the local strain energy density allows to correlate the Crack Initiation Life in a quite narrow scatter-band valid each tested material (Ti-6Al-4V and AISI 304L, respectively), despite the different notch geometries and loading conditions involved in the tests. References [1] Tanaka K. Crack Initiation and propagation in torsional fatigue of circumferentially notched steel bars. Int J Fatigue 2014;58:114–25. [2] Lazzarin P, Zambardi R. A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches. Int J Fract 2001;112:275–98. [3] Lazzarin P, Berto F. From Neuber’s Elementary Volume to Kitagawa and Atzori’s Diagrams: An Interpretation Based on Local Energy. Int J Fract 2005;135:L33–8.
A Campagnolo - One of the best experts on this subject based on the ideXlab platform.
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notched ti 6al 4v titanium bars under multiaxial fatigue synthesis of Crack Initiation Life based on the averaged strain energy density
Theoretical and Applied Fracture Mechanics, 2018Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:Abstract The fatigue Life of notched components subjected to multiaxial loading conditions may be influenced by extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between Crack surfaces. These extrinsic mechanisms may disrupt the applicability of local approaches, such as that based on the strain energy density (SED) averaged over a structural volume having size R0 and surrounding the Crack Initiation point. In the present contribution, the multiaxial fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, has been analysed. Pure bending, pure torsion and in-phase as well as out-of-phase combined bending-torsion fatigue tests have been carried out on notched specimens characterized by two different root radii, namely 0.1 and 4 mm. Fatigue Crack Initiation and subsequent propagation have been monitored by adopting the direct current potential drop (DCPD) technique. In principle, Crack Initiation Life has been defined when the initiated fatigue Crack fractures the structural volume, which corresponds to a given potential drop increase calibrated by means of electrical finite element (FE) analyses. The structural volume size R0 has been determined by fatigue testing plain and sharp V-notched specimens under pure axial or pure torsion loadings. Finally, the averaged SED approach has been adopted to correlate the experimental fatigue results expressed in terms of Crack Initiation Life, in order to reduce the effect of extrinsic mechanisms.
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Crack Initiation Life in notched steel bars under torsional fatigue synthesis based on the averaged strain energy density approach
International Journal of Fatigue, 2017Co-Authors: A Campagnolo, Giovanni Meneghetti, Filippo Berto, Keisuke TanakaAbstract:Abstract In a recent contribution by Tanaka, the fatigue behaviour of notched bars made of austenitic stainless steel, SUS 316L, and carbon steel, SGV 410, characterized by different values of the notch tip radius was investigated under torsion loading. Tanaka monitored both fatigue Crack Initiation and propagation phases by means of the potential drop technique. The Crack Initiation Life is correlated here to the depth of the initiated fatigue Crack by means of calibration curves derived from electrical finite element (FE) analyses. In the present contribution, the approach based on the strain energy density (SED) averaged over a structural volume embracing the notch tip is employed to re-analyse the original experimental results of each material, by taking into account the Crack Initiation Life, in order to exclude all extrinsic mechanisms acting during the Crack propagation phase, i.e. sliding contact, friction and meshing between Crack mating surfaces.
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Crack Initiation Life in notched ti 6al 4v titanium bars under uniaxial and multiaxial fatigue synthesis based on the averaged strain energy density approach
Fracture and Structural Integrity, 2017Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD) technique. Based on the results obtained from the potential drop technique, the Crack Initiation Life has been defined in correspondence of a relative potential drop increase ?V/?V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED) averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the Crack Initiation Life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests.
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averaged strain energy density based synthesis of Crack Initiation Life in notched steel bars under torsional fatigue
Fracture and Structural Integrity, 2016Co-Authors: Filippo Berto, A Campagnolo, Giovanni Meneghetti, Keisuke TanakaAbstract:The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue Life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the Crack nucleation Life was reduced with increasing stress concentration, on the other hand the Crack propagation Life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED) averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces, Crack Initiation Life has been considered in the present work. In the original paper, Initiation Life was defined in correspondence of a 0.1÷0.4-mm-deep Crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and Cracked specimens at NA = 2 million loading cycles. KEYWORDS. Torsional fatigue; Notch effect; Crack Initiation; Averaged SED; Electrical potential drop
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averaged strain energy density based synthesis of Crack Initiation Life of notched titanium and steel bars under uniaxial and multiaxial fatigue
ECF21, 2016Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, and austenitic stainless steel, AISI 304L, has been analysed. With the aim of investigating the effect of the notch geometry and the loading condition on the fatigue strength of the titanium alloy, pure tension, pure torsion and multiaxial in-phase tension-torsion fatigue tests have been carried out on specimens characterised by two different root radii, namely 0.1 and 4 mm. As regards the notched steel bars, only the notch effect on the torsion fatigue behaviour has been analysed in detail by testing specimens characterised by three different notch tip radii: 0.1, 1 and 4 mm. In all cases, the nominal load ratio R has been kept constant and equal to -1. Crack nucleation and subsequent propagation have been accurately monitored by using the electrical potential drop technique, which allows to define the Crack Initiation Life in correspondence of a Crack depth approximately equal to 0.1÷0.3 mm, according to Tanaka [1]. The experimental fatigue results of each material have been re-analysed using the local strain energy density (SED) averaged over a control volume having radius R 0 surrounding the notch tip [2]. With the aim of excluding all extrinsic mechanisms acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces recently discussed by Tanaka dealing with the torsional fatigue behaviour of notched steel bars [1], the Crack Initiation Life has been considered in the present work. The control radius R 0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated for the two considered materials by imposing the constancy of the averaged SED for both smooth and Cracked specimens at N A = 2 million cycles [2,3]. Therefore, R 0 is seen to depend on two material properties: the plain material fatigue limit (or the high-cycle fatigue strength of smooth specimens) and the threshold value of the stress intensity factor (SIF) range for long Cracks. Finally, the use of the local strain energy density allows to correlate the Crack Initiation Life in a quite narrow scatter-band valid each tested material (Ti-6Al-4V and AISI 304L, respectively), despite the different notch geometries and loading conditions involved in the tests. References [1] Tanaka K. Crack Initiation and propagation in torsional fatigue of circumferentially notched steel bars. Int J Fatigue 2014;58:114–25. [2] Lazzarin P, Zambardi R. A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches. Int J Fract 2001;112:275–98. [3] Lazzarin P, Berto F. From Neuber’s Elementary Volume to Kitagawa and Atzori’s Diagrams: An Interpretation Based on Local Energy. Int J Fract 2005;135:L33–8.
Filippo Berto - One of the best experts on this subject based on the ideXlab platform.
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notched ti 6al 4v titanium bars under multiaxial fatigue synthesis of Crack Initiation Life based on the averaged strain energy density
Theoretical and Applied Fracture Mechanics, 2018Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:Abstract The fatigue Life of notched components subjected to multiaxial loading conditions may be influenced by extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between Crack surfaces. These extrinsic mechanisms may disrupt the applicability of local approaches, such as that based on the strain energy density (SED) averaged over a structural volume having size R0 and surrounding the Crack Initiation point. In the present contribution, the multiaxial fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, has been analysed. Pure bending, pure torsion and in-phase as well as out-of-phase combined bending-torsion fatigue tests have been carried out on notched specimens characterized by two different root radii, namely 0.1 and 4 mm. Fatigue Crack Initiation and subsequent propagation have been monitored by adopting the direct current potential drop (DCPD) technique. In principle, Crack Initiation Life has been defined when the initiated fatigue Crack fractures the structural volume, which corresponds to a given potential drop increase calibrated by means of electrical finite element (FE) analyses. The structural volume size R0 has been determined by fatigue testing plain and sharp V-notched specimens under pure axial or pure torsion loadings. Finally, the averaged SED approach has been adopted to correlate the experimental fatigue results expressed in terms of Crack Initiation Life, in order to reduce the effect of extrinsic mechanisms.
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Crack Initiation Life in notched steel bars under torsional fatigue synthesis based on the averaged strain energy density approach
International Journal of Fatigue, 2017Co-Authors: A Campagnolo, Giovanni Meneghetti, Filippo Berto, Keisuke TanakaAbstract:Abstract In a recent contribution by Tanaka, the fatigue behaviour of notched bars made of austenitic stainless steel, SUS 316L, and carbon steel, SGV 410, characterized by different values of the notch tip radius was investigated under torsion loading. Tanaka monitored both fatigue Crack Initiation and propagation phases by means of the potential drop technique. The Crack Initiation Life is correlated here to the depth of the initiated fatigue Crack by means of calibration curves derived from electrical finite element (FE) analyses. In the present contribution, the approach based on the strain energy density (SED) averaged over a structural volume embracing the notch tip is employed to re-analyse the original experimental results of each material, by taking into account the Crack Initiation Life, in order to exclude all extrinsic mechanisms acting during the Crack propagation phase, i.e. sliding contact, friction and meshing between Crack mating surfaces.
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Crack Initiation Life in notched ti 6al 4v titanium bars under uniaxial and multiaxial fatigue synthesis based on the averaged strain energy density approach
Fracture and Structural Integrity, 2017Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD) technique. Based on the results obtained from the potential drop technique, the Crack Initiation Life has been defined in correspondence of a relative potential drop increase ?V/?V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED) averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the Crack Initiation Life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests.
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averaged strain energy density based synthesis of Crack Initiation Life in notched steel bars under torsional fatigue
Fracture and Structural Integrity, 2016Co-Authors: Filippo Berto, A Campagnolo, Giovanni Meneghetti, Keisuke TanakaAbstract:The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue Life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the Crack nucleation Life was reduced with increasing stress concentration, on the other hand the Crack propagation Life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED) averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces, Crack Initiation Life has been considered in the present work. In the original paper, Initiation Life was defined in correspondence of a 0.1÷0.4-mm-deep Crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and Cracked specimens at NA = 2 million loading cycles. KEYWORDS. Torsional fatigue; Notch effect; Crack Initiation; Averaged SED; Electrical potential drop
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averaged strain energy density based synthesis of Crack Initiation Life of notched titanium and steel bars under uniaxial and multiaxial fatigue
ECF21, 2016Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, and austenitic stainless steel, AISI 304L, has been analysed. With the aim of investigating the effect of the notch geometry and the loading condition on the fatigue strength of the titanium alloy, pure tension, pure torsion and multiaxial in-phase tension-torsion fatigue tests have been carried out on specimens characterised by two different root radii, namely 0.1 and 4 mm. As regards the notched steel bars, only the notch effect on the torsion fatigue behaviour has been analysed in detail by testing specimens characterised by three different notch tip radii: 0.1, 1 and 4 mm. In all cases, the nominal load ratio R has been kept constant and equal to -1. Crack nucleation and subsequent propagation have been accurately monitored by using the electrical potential drop technique, which allows to define the Crack Initiation Life in correspondence of a Crack depth approximately equal to 0.1÷0.3 mm, according to Tanaka [1]. The experimental fatigue results of each material have been re-analysed using the local strain energy density (SED) averaged over a control volume having radius R 0 surrounding the notch tip [2]. With the aim of excluding all extrinsic mechanisms acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces recently discussed by Tanaka dealing with the torsional fatigue behaviour of notched steel bars [1], the Crack Initiation Life has been considered in the present work. The control radius R 0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated for the two considered materials by imposing the constancy of the averaged SED for both smooth and Cracked specimens at N A = 2 million cycles [2,3]. Therefore, R 0 is seen to depend on two material properties: the plain material fatigue limit (or the high-cycle fatigue strength of smooth specimens) and the threshold value of the stress intensity factor (SIF) range for long Cracks. Finally, the use of the local strain energy density allows to correlate the Crack Initiation Life in a quite narrow scatter-band valid each tested material (Ti-6Al-4V and AISI 304L, respectively), despite the different notch geometries and loading conditions involved in the tests. References [1] Tanaka K. Crack Initiation and propagation in torsional fatigue of circumferentially notched steel bars. Int J Fatigue 2014;58:114–25. [2] Lazzarin P, Zambardi R. A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches. Int J Fract 2001;112:275–98. [3] Lazzarin P, Berto F. From Neuber’s Elementary Volume to Kitagawa and Atzori’s Diagrams: An Interpretation Based on Local Energy. Int J Fract 2005;135:L33–8.
Giovanni Meneghetti - One of the best experts on this subject based on the ideXlab platform.
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notched ti 6al 4v titanium bars under multiaxial fatigue synthesis of Crack Initiation Life based on the averaged strain energy density
Theoretical and Applied Fracture Mechanics, 2018Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:Abstract The fatigue Life of notched components subjected to multiaxial loading conditions may be influenced by extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between Crack surfaces. These extrinsic mechanisms may disrupt the applicability of local approaches, such as that based on the strain energy density (SED) averaged over a structural volume having size R0 and surrounding the Crack Initiation point. In the present contribution, the multiaxial fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, has been analysed. Pure bending, pure torsion and in-phase as well as out-of-phase combined bending-torsion fatigue tests have been carried out on notched specimens characterized by two different root radii, namely 0.1 and 4 mm. Fatigue Crack Initiation and subsequent propagation have been monitored by adopting the direct current potential drop (DCPD) technique. In principle, Crack Initiation Life has been defined when the initiated fatigue Crack fractures the structural volume, which corresponds to a given potential drop increase calibrated by means of electrical finite element (FE) analyses. The structural volume size R0 has been determined by fatigue testing plain and sharp V-notched specimens under pure axial or pure torsion loadings. Finally, the averaged SED approach has been adopted to correlate the experimental fatigue results expressed in terms of Crack Initiation Life, in order to reduce the effect of extrinsic mechanisms.
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Crack Initiation Life in notched steel bars under torsional fatigue synthesis based on the averaged strain energy density approach
International Journal of Fatigue, 2017Co-Authors: A Campagnolo, Giovanni Meneghetti, Filippo Berto, Keisuke TanakaAbstract:Abstract In a recent contribution by Tanaka, the fatigue behaviour of notched bars made of austenitic stainless steel, SUS 316L, and carbon steel, SGV 410, characterized by different values of the notch tip radius was investigated under torsion loading. Tanaka monitored both fatigue Crack Initiation and propagation phases by means of the potential drop technique. The Crack Initiation Life is correlated here to the depth of the initiated fatigue Crack by means of calibration curves derived from electrical finite element (FE) analyses. In the present contribution, the approach based on the strain energy density (SED) averaged over a structural volume embracing the notch tip is employed to re-analyse the original experimental results of each material, by taking into account the Crack Initiation Life, in order to exclude all extrinsic mechanisms acting during the Crack propagation phase, i.e. sliding contact, friction and meshing between Crack mating surfaces.
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Crack Initiation Life in notched ti 6al 4v titanium bars under uniaxial and multiaxial fatigue synthesis based on the averaged strain energy density approach
Fracture and Structural Integrity, 2017Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD) technique. Based on the results obtained from the potential drop technique, the Crack Initiation Life has been defined in correspondence of a relative potential drop increase ?V/?V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during Crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED) averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the Crack Initiation Life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests.
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averaged strain energy density based synthesis of Crack Initiation Life in notched steel bars under torsional fatigue
Fracture and Structural Integrity, 2016Co-Authors: Filippo Berto, A Campagnolo, Giovanni Meneghetti, Keisuke TanakaAbstract:The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue Life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the Crack nucleation Life was reduced with increasing stress concentration, on the other hand the Crack propagation Life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED) averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces, Crack Initiation Life has been considered in the present work. In the original paper, Initiation Life was defined in correspondence of a 0.1÷0.4-mm-deep Crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and Cracked specimens at NA = 2 million loading cycles. KEYWORDS. Torsional fatigue; Notch effect; Crack Initiation; Averaged SED; Electrical potential drop
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averaged strain energy density based synthesis of Crack Initiation Life of notched titanium and steel bars under uniaxial and multiaxial fatigue
ECF21, 2016Co-Authors: Giovanni Meneghetti, A Campagnolo, Filippo Berto, Keisuke TanakaAbstract:The fatigue behaviour of circumferentially notched specimens made of titanium grade 5 alloy, Ti-6Al-4V, and austenitic stainless steel, AISI 304L, has been analysed. With the aim of investigating the effect of the notch geometry and the loading condition on the fatigue strength of the titanium alloy, pure tension, pure torsion and multiaxial in-phase tension-torsion fatigue tests have been carried out on specimens characterised by two different root radii, namely 0.1 and 4 mm. As regards the notched steel bars, only the notch effect on the torsion fatigue behaviour has been analysed in detail by testing specimens characterised by three different notch tip radii: 0.1, 1 and 4 mm. In all cases, the nominal load ratio R has been kept constant and equal to -1. Crack nucleation and subsequent propagation have been accurately monitored by using the electrical potential drop technique, which allows to define the Crack Initiation Life in correspondence of a Crack depth approximately equal to 0.1÷0.3 mm, according to Tanaka [1]. The experimental fatigue results of each material have been re-analysed using the local strain energy density (SED) averaged over a control volume having radius R 0 surrounding the notch tip [2]. With the aim of excluding all extrinsic mechanisms acting during the fatigue Crack propagation phase, such as sliding contact and/or friction between fracture surfaces recently discussed by Tanaka dealing with the torsional fatigue behaviour of notched steel bars [1], the Crack Initiation Life has been considered in the present work. The control radius R 0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated for the two considered materials by imposing the constancy of the averaged SED for both smooth and Cracked specimens at N A = 2 million cycles [2,3]. Therefore, R 0 is seen to depend on two material properties: the plain material fatigue limit (or the high-cycle fatigue strength of smooth specimens) and the threshold value of the stress intensity factor (SIF) range for long Cracks. Finally, the use of the local strain energy density allows to correlate the Crack Initiation Life in a quite narrow scatter-band valid each tested material (Ti-6Al-4V and AISI 304L, respectively), despite the different notch geometries and loading conditions involved in the tests. References [1] Tanaka K. Crack Initiation and propagation in torsional fatigue of circumferentially notched steel bars. Int J Fatigue 2014;58:114–25. [2] Lazzarin P, Zambardi R. A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches. Int J Fract 2001;112:275–98. [3] Lazzarin P, Berto F. From Neuber’s Elementary Volume to Kitagawa and Atzori’s Diagrams: An Interpretation Based on Local Energy. Int J Fract 2005;135:L33–8.
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application of local stress strain approaches in the prediction of fatigue Crack Initiation Life for cyclically non stabilized and non masing steel
International Journal of Fatigue, 2005Co-Authors: Seonggu HongAbstract:Abstract This study presents a methodology of Life prediction of fatigue Crack Initiation for the cyclically non-stabilized and non-Masing steel. The cyclic behavior of 316L stainless steel was modelled, and the constitutive model was combined with local stress–strain approximations at a notch. The local stress–strain approximation methods were formulated incrementally to get the notch tip stress–strain of the non-Masing material. The local approximations were compared with the FEM results for verification. The prediction of fatigue Crack Initiation Life was carried out by adopting plastic strain energy density (PSED) as a fatigue parameter and all the Life prediction results were within factors of two of the experimental results.
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Application of local stress–strain approaches in the prediction of fatigue Crack Initiation Life for cyclically non-stabilized and non-Masing steel
International Journal of Fatigue, 2005Co-Authors: Seonggu HongAbstract:Abstract This study presents a methodology of Life prediction of fatigue Crack Initiation for the cyclically non-stabilized and non-Masing steel. The cyclic behavior of 316L stainless steel was modelled, and the constitutive model was combined with local stress–strain approximations at a notch. The local stress–strain approximation methods were formulated incrementally to get the notch tip stress–strain of the non-Masing material. The local approximations were compared with the FEM results for verification. The prediction of fatigue Crack Initiation Life was carried out by adopting plastic strain energy density (PSED) as a fatigue parameter and all the Life prediction results were within factors of two of the experimental results.