The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Giovanni Meneghetti - One of the best experts on this subject based on the ideXlab platform.
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analysis of crack geometry and location in notched bars by means of a three probe Potential Drop technique
International Journal of Fatigue, 2019Co-Authors: Alberto Campagnolo, Giovanni MeneghettiAbstract:Abstract It is often necessary to define the crack initiation life of a fatigue tested component, generally at a given (short) crack length. The size of an initiated crack can be estimated by employing different experimental Methods, one of which is the direct current Potential Drop (DCPD) technique. In the case of notched bars subjected to fatigue loadings, the crack configuration (i.e. circumferential or semi-elliptical) and location cannot be singled out by means of the Potential Drop Method (PDM) operating with a single Potential probe. In the present contribution, three Potential probes are adopted to overcome this issue. The calibration curves reporting the three Potential Drops as a function of the crack size are derived by means of 3-dimensional electrical FE analyses. Two different crack configurations are analyzed: (i) circumferential and (ii) semi-elliptical surface cracks. The calibration curves have been validated by systematic comparison with experimental results, generated by fatigue testing of sharp as well as blunt notched specimens made of steel and a titanium alloy under pure axial loading. Finally, a procedure to assess the area, the configuration and the location of the initiated fatigue crack starting from the experimentally measured Potential Drops is discussed.
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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, Alberto 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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synthesis of crack initiation life in steel notched specimens under torsional fatigue based on the averaged strain energy density
Procedia structural integrity, 2016Co-Authors: Alberto Campagnolo, Giovanni Meneghetti, Filippo Berto, Keisuke TanakaAbstract:Abstract 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 R 0 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 R 0 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 N A = 2 million loading cycles. (*) A version of the present contribution has already been presented at the 11 th International Conference on Multiaxial Fatigue and Fracture (ICMFF11).
Alberto Campagnolo - One of the best experts on this subject based on the ideXlab platform.
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analysis of crack geometry and location in notched bars by means of a three probe Potential Drop technique
International Journal of Fatigue, 2019Co-Authors: Alberto Campagnolo, Giovanni MeneghettiAbstract:Abstract It is often necessary to define the crack initiation life of a fatigue tested component, generally at a given (short) crack length. The size of an initiated crack can be estimated by employing different experimental Methods, one of which is the direct current Potential Drop (DCPD) technique. In the case of notched bars subjected to fatigue loadings, the crack configuration (i.e. circumferential or semi-elliptical) and location cannot be singled out by means of the Potential Drop Method (PDM) operating with a single Potential probe. In the present contribution, three Potential probes are adopted to overcome this issue. The calibration curves reporting the three Potential Drops as a function of the crack size are derived by means of 3-dimensional electrical FE analyses. Two different crack configurations are analyzed: (i) circumferential and (ii) semi-elliptical surface cracks. The calibration curves have been validated by systematic comparison with experimental results, generated by fatigue testing of sharp as well as blunt notched specimens made of steel and a titanium alloy under pure axial loading. Finally, a procedure to assess the area, the configuration and the location of the initiated fatigue crack starting from the experimentally measured Potential Drops is discussed.
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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, Alberto 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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synthesis of crack initiation life in steel notched specimens under torsional fatigue based on the averaged strain energy density
Procedia structural integrity, 2016Co-Authors: Alberto Campagnolo, Giovanni Meneghetti, Filippo Berto, Keisuke TanakaAbstract:Abstract 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 R 0 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 R 0 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 N A = 2 million loading cycles. (*) A version of the present contribution has already been presented at the 11 th International Conference on Multiaxial Fatigue and Fracture (ICMFF11).
Kenkichi Ishigure - One of the best experts on this subject based on the ideXlab platform.
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effects of hydrogen peroxide on intergranular stress corrosion cracking of stainless steel in high temperature water iii crack growth rates in corrosive environment determined by hydrogen peroxide
Journal of Nuclear Science and Technology, 2000Co-Authors: Yoichi Wada, Atsushi Watanabe, Masahiko Tachibana, Naohito Uetake, Shunsuke Uchida, Kenkichi IshigureAbstract:The stress corrosion cracking (SCC) of structural materials used in boiling water reactors has been studied at relatively low hydrogen peroxide (H 2 O 2 ) concentrations, around 10ppb, which was assumed to be representative of the corrosion environment formed in hydrogen water chemistry (HWC). The 1/4T compact tension specimen was used for measurement of crack growth rates (CGRs) of sensitized type 304 stainless steel in high temperature and high purity water. Crack length was monitored by a reversing direct current Potential Drop Method. Since H 2 O 2 is easily decomposed thermally, a polytetrafluoroethylene-lined autoclave was used to minimize its decomposition on the autoclave surface. The CGR in the H 2 O 2 environment differed from that in the O 2 environment even though the electrochemical corrosion Potential (ECP) for both conditions was the same. The data implied that the ECP could not be used as a common environmental deterministic parameter for SCC behavior at higher Potentials for different oxidant conditions. The corrosion current density was found to play an important role as an environmental index for SCC, which was given as just the current density at the ECP at a specific oxidant concentration. The CGRs were found to be written as CGR = (3.8±0.6)×10 -3 i cor +(1.5±1.6) × 10 -8 mm/s using the calculated corrosion current density i cor below 10 -4 A.cm -2 .
S Pierret - One of the best experts on this subject based on the ideXlab platform.
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optimization of the dcpd technique for monitoring the crack propagation from notch root in localized plasticity
International Journal of Fatigue, 2020Co-Authors: Aurelien Lambourg, Y Nadot, Gilbert Henaff, Stephane Gourdin, Quentin Pujol Dandrebo, S PierretAbstract:Abstract The Direct Current Potential Drop Method is commonly used to monitor the crack growth during fatigue test when optical access to the crack is not possible. The reliability of this Method depends on the calibration curve, which correlates the Potential Drop measurement with the crack length and shape. Using Finite Element Analysis and experimental approaches with heat tints, a procedure for the optimization of the calibration curve has been proposed. The influence of plastic deformation and of the presence of a secondary crack on the calibration curve has been studied. Finally, a test strategy, using two heat tints, has been developed in order to identify the first order parameters for the calculation of calibration curve. This strategy shows higher accuracy of crack length measurement and permit to balance experimental uncertainties out.
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calibration of the Potential Drop Method for monitoring small crack growth from surface anomalies crack front marking technique and finite element simulations
International Journal of Fatigue, 2015Co-Authors: L Doremus, Y Nadot, Gilbert Henaff, Caroline Mary, S PierretAbstract:Abstract The Direct Current Potential Drop Method is one of the possibilities to measure the crack growth during fatigue tests without optical access to the sample. The accuracy of this technique applied to short cracks mainly depends on the calibration curve. In the present work experimental and numerical approaches are proposed to calibrate the Potential Drop measurement. An optimization of the calibration procedure is supported by finite element calculations. The crack front shape and the location of the Potential probes are found to be of great influence. An extensive study is conducted to identify all the mechanisms controlling the Potential Drop measurement. Plastic deformation remains the last parameter which is not directly considered in this study; therefore a calibration strategy is suggested to take into account this effect and achieve a calibration curve with high accuracy. This strategy shows a very good agreement between the obtained calibration curve and the experimental calibration.
Noritaka Yusa - One of the best experts on this subject based on the ideXlab platform.
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assessment of local conductivity distribution in stress corrosion crack region using direct current Potential Drop Method
Corrosion Science, 2017Co-Authors: Wenlu Cai, Shejuan Xie, Zhenmao Chen, Xiaojuan Wang, Cherdpong Jomdecha, Cuixiang Pei, Noritaka YusaAbstract:Abstract As an effort to enhance the precision of quantitative nondestructive evaluation on stress corrosion crack (SCC) sizing with eddy current testing (ECT) technique, the electrical conductivity distribution in the SCC region was investigated in this work through measurement and inversion of the direct current Potential Drop (DCPD) signals with a sliced specimen strategy. An inversion scheme, consisting of an efficient forward DCPD signal simulator and the conjugate gradient optimization algorithm, was proposed and implemented for the reconstruction of the two-dimensional (2D) conductivity distribution inside the SCC. The reasonable reconstruction results from the measured DCPD signals of the practical SCC specimens proved the validity of the proposed scheme. The 2D distribution obtained in this paper shows that the conductivity becomes larger when approaching the crack tip and is the minimum in the crack opening position. The obtained SCC conductivity information gives a good reference to enhance the crack sizing accuracy of ECT.