The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Hiroshi Noguchi - One of the best experts on this subject based on the ideXlab platform.
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Fatigue Strength of Plain and Notched Specimens of Thermoplastics. (In The Case of Polyetheretherketone)
Transactions of the Japan Society of Mechanical Engineers. A, 2016Co-Authors: Hironobu Nisitani, Hiroshi Noguchi, Terutaka YamaguchiAbstract:In this paper, rotating-bending fatigue tests for polyetheretherketone (PEEK) were carried out to investigate the fatigue characteristics of Plain and notched Specimens at room temperature. The results were discussed using linear notch mechanics. In the case of the Plain Specimen, fracture always occurs from defects and the crack growth rate is very high. The fatigue crack initiation of this material is of the point-initiation type and the fatigue strength is very sensitive to a notch. The fatigue strength of an arbitrarily notched Specimen of this material will be estimated from the present results rearranged based on linear notch mechanics.
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fatigue limit of new precipitation hardened aluminium alloy with distinct fatigue crack propagation limit
International Journal of Fatigue, 2012Co-Authors: Lei Zeng, Takahiro Shikama, Yoshimasa Takahashi, Shinji Yoshihara, Tadashi Aiura, Hiroshi NoguchiAbstract:Abstract The goal of this study was to confirm the presence of fatigue limit in a Plain Specimen of a new precipitation-hardened aluminium alloy. The alloy was fabricated by adding 0.53% excess Mg to the standard 6061-T6 aluminium alloy with a balanced Mg 2 Si composition. There were two challenges in this study: verification of the existence of fatigue limit in this new alloy and interpretation of the large scatter in Specimen life at the low stress level amplitude. For the former, the existence of a fatigue limit was confirmed by a coaxing effect test. For the latter, the initiation and growth behaviors of a small fatigue crack at low stress amplitude were observed by plastic replica method not only with an optical microscope but also with a scanning electron microscope (SEM). The study results showed that the large scatter in Specimen fatigue life at the low stress level amplitude was due to the anomalous initiation and growth behaviors of the small fatigue crack, which in turn was strongly influenced by local conditions. Finally, a conservative S – N curve of this new alloy evaluated by using a Plain Specimen could be obtained where a distinct knee point showed at cycles of about 10 6 .
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prediction of fatigue limit reliability of high strength steel with deep notch under mean stress σ m 0
International Journal of Fracture, 2011Co-Authors: Tatsujiro Miyazaki, Hiroshi Noguchi, Masaharu KageAbstract:Because a fatigue limit of high strength steel with Vickers hardness HV > 400 is scattered, it is difficult to predict the fatigue limit for S-N curve experimentally. The authors have proposed a nondestructive method for predicting the fatigue limit reliability of Plain Specimen of the high strength steel by the stress-strength model which consists of “statistical characteristics of hardness of a matrix under a small indentation load” and “statistical characteristics of hardness required for non-propagations of fatigue cracks from microstructural defects in a material”. In this paper, a nondestructive method for predicting the fatigue limit reliability of notched Specimen of the high strength steel with microstructural defects such as non-metallic inclusions and pits from characteristics of a stress field near a notch, statistical characteristics of Vickers hardness and defect size is proposed. Especially, the method is applied to a structure with a deep notch under a mean stress σm = 0. Then, fatigue tests were carried out on the notched Specimens of quenched-tempered 0.5% carbon steels with HV ≃ 600 changing a notch root radius under a constant notch depth, and the validity of the prediction method is examined by comparing predicted results to experimental ones.
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Prediction of fatigue limit reliability of high strength steel with deep notch under mean stress σ _ m = 0
International Journal of Fracture, 2011Co-Authors: Tatsujiro Miyazaki, Hiroshi Noguchi, Masaharu KageAbstract:Because a fatigue limit of high strength steel with Vickers hardness H _ V > 400 is scattered, it is difficult to predict the fatigue limit for S - N curve experimentally. The authors have proposed a nondestructive method for predicting the fatigue limit reliability of Plain Specimen of the high strength steel by the stress-strength model which consists of “statistical characteristics of hardness of a matrix under a small indentation load” and “statistical characteristics of hardness required for non-propagations of fatigue cracks from microstructural defects in a material”. In this paper, a nondestructive method for predicting the fatigue limit reliability of notched Specimen of the high strength steel with microstructural defects such as non-metallic inclusions and pits from characteristics of a stress field near a notch, statistical characteristics of Vickers hardness and defect size is proposed. Especially, the method is applied to a structure with a deep notch under a mean stress σ _ m = 0. Then, fatigue tests were carried out on the notched Specimens of quenched-tempered 0.5% carbon steels with H _ V ≃ 600 changing a notch root radius under a constant notch depth, and the validity of the prediction method is examined by comparing predicted results to experimental ones.
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effects of hydrogen gas environment on fatigue strength at 107 cycles in Plain Specimen of type 316l stainless steel
Journal of Solid Mechanics and Materials Engineering, 2009Co-Authors: Kyohei Kawamoto, Kazuhiko Ochi, Hiroshi NoguchiAbstract:In order to clarify the hydrogen effect on the fatigue strength at 107 cycles in a Plain Specimen of type 316L austenitic stainless steel, rotating bending fatigue tests in laboratory air and plane bending fatigue tests in 1.0 MPa dry hydrogen gas and in air at 313 K were carried out. The main results obtained are as follows. The observed fatigue behavior showed that the fatigue strength at 107 cycles in both environments is determined by the non-propagation of a fatigue crack of the order of the grain size. Also, the strength at 107 cycles in hydrogen gas is slightly higher than that in air. In the region of high-cycle fatigue, the fatigue life in hydrogen gas is longer than that in air, which is mainly caused by the longer crack initiation life in hydrogen gas. The crack propagation life in hydrogen gas is shorter than that in air but has only a small ratio to the fatigue life in this region.
Pramod Padole - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Low Cycle Fatigue Response of 316 LN Stainless Steel in the Presence of Notch
Journal of Materials Engineering and Performance, 2018Co-Authors: Richa Agrawal, J. Veerababu, Sunil Goyal, R. Sandhya, Rashmi Uddanwadiker, Pramod PadoleAbstract:Notches introduced in the Plain Specimen result in the multiaxial state of stress that exists in the actual components due to the presence of flaws and defects. In the present work, low cycle fatigue life estimation of Plain and notched Specimens of 316 LN stainless steel is carried out at room temperature and 823 K. The Plain and notched Specimens with different notch radii were subjected to varying strain amplitudes ranging from ± 0.25 to ± 1.0% at a strain rate of 3 × 10^−3 s^−1. The fatigue life decreased in the presence of notch for all strain amplitudes at both the temperatures. The decrease in fatigue life was found to be more at room temperature than at 823 K. The fatigue life of the notched Specimen decreased by approximately 94.2% compared to Plain Specimen at room temperature. However, at 823 K the decrease in fatigue life for notched Specimen was approximately 84.6%. Low cycle fatigue life of the Plain and notched Specimens was estimated by Neuber’s rule and finite element analysis approach. Neuber’s rule overestimated the fatigue life by maximum factor of 2.6 for Specimens at room temperature and by maximum factor of 5 for Specimens at 823 K. However, it gives closer approximation at higher strain amplitudes at 823 K. Life estimation by finite element analysis at room temperature was within a factor of 1.5 as compared to experimental life, whereas it underestimated the fatigue life within a factor of 6 at high temperature.
Masahiro Goto - One of the best experts on this subject based on the ideXlab platform.
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Growth Rate of Small Surface-Cracks in Age Hardening Cu-Ni-Si Alloy under Cyclic Stressing
Key Engineering Materials, 2019Co-Authors: Masahiro Goto, Takaei Yamamoto, Junichi Kitamura, R. Takanami, Terutoshi YakushijiAbstract:Stress-controlled fatigue tests were conducted on round-bar Specimens to understand the fatigue behavior of precipitate-strengthened Cu–6Ni–1.5Si alloy. The cracks were initiated at the grain boundaries, followed by growth along the crystallographic slip planes in the adjacent grains. The crack growth data of Plain Specimens exhibited a large scatter, resulting in a difficulty of the measurement of crack growth rate. To evaluate the small-crack growth rate of the alloy, the Plain Specimens with a small blind hole as the crack starter were fatigued. The crack growth rate of small cracks from the hole was uniquely determined by a term σanl and the material constant, n, was 5.3. The term σanl with n = 5.3 was applied to the Plain Specimen, showing good applicability of the term to small cracks in the Plain Specimen.
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Behavior of Fatigue Cracks Generated from a Small Artificial-Defect in Plain Specimen of Copper Processed by Equal Channel Angular Pressing
Materials Science Forum, 2018Co-Authors: Masahiro Goto, Takaei Yamamoto, Junichi Kitamura, Takashi Iwamura, Terutoshi YakushijiAbstract:Fatigue tests of ultrafine-grained copper processed by equal channel angular pressing were conducted on the round-bar Specimens with a small artificial-defect. The fatigue crack initiated from the defect at an early fatigue stage. After the crack initiation, the crack grew with a 45° inclination to the loading axis at stress amplitudes above 180 MPa. At the stress less than 160 MPa, however, the crack grew perpendicular to the loading axis. The physical background of deferent crack path directions between high-and low-stresses was discussed from the viewpoint of a morphological feature of damaged traces along the crack path.
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Growth Behavior Of Small Surface Cracks InCoarse And Ultrafine Grained Copper
Computational Methods and Experimental Measurements XIV, 2009Co-Authors: Masahiro Goto, Yoshinori Ando, N. Kawagoishi, N. TeshimaAbstract:Since fatigue life of a Plain Specimen of ductile metals is controlled mainly by the propagation life of a small surface crack, to clarify the growth behavior of a small crack is crucial to the safe design of smooth members. However, little has been reported on the growth behavior of small surface cracks in ultrafine grained (UFG) metals. In the present study, stress-controlled fatigue tests for coarse grained (CG) and UFG copper were conducted. The surface damage evolution during cyclic stressing was observed by optical microscopy, and the growth behavior of a small surface crack was monitored by a plastic replication technique. The physical background of fatigue damage for CG and UFG copper was discussed from the viewpoints of the initiation and growth behavior of small surface cracks.
Ciro Santus - One of the best experts on this subject based on the ideXlab platform.
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Determination of the fatigue critical distance according to the Line and the Point Methods with rounded V-notched Specimen
International Journal of Fatigue, 2017Co-Authors: Ciro Santus, David Taylor, Matteo BenedettiAbstract:Abstract The critical distance length should in principle be deduced from the Plain Specimen fatigue limit and the threshold stress intensity factor range. However, the threshold range is difficult to measure experimentally, hence this length is usually obtained by means of a notched Specimen. The critical distance inverse search, both according to the Line and the Point Methods, is presented in this paper referring to a relatively sharp V-notched Specimen. Precise indications about the geometry parameters are given along with a complete analytical procedure to easily obtain the critical distance. A sensitivity analysis is discussed, providing evidence of a critical distance range for a well-posed inversion problem.
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High Load Ratio Fatigue Strength and Mean Stress Evolution of Quenched and Tempered 42CrMo4 Steel
Journal of Materials Engineering and Performance, 2017Co-Authors: Leonardo Bertini, Ciro Santus, Luca Le Bone, Francesco Chiesi, Leonardo TognarelliAbstract:The fatigue strength at a high number of cycles with initial elastic–plastic behavior was experimentally investigated on quenched and tempered 42CrMo4 steel. Fatigue tests on unnotched Specimens were performed both under load and strain controls, by imposing various levels of amplitude and with several high load ratios. Different ratcheting and relaxation trends, with significant effects on fatigue, are observed and discussed, and then reported in the Haigh diagram, highlighting a clear correlation with the Smith–Watson–Topper model. High load ratio tests were also conducted on notched Specimens with C (blunt) and V (sharp) geometries. A Chaboche model with three parameter couples was proposed by fitting Plain Specimen cyclic and relaxation tests, and then finite element analyses were performed to simulate the notched Specimen test results. A significant stress relaxation at the notch root became clearly evident by reporting the numerical results in the Haigh diagram, thus exPlaining the low mean stress sensitivity of the notched Specimens.
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Physically short crack propagation in metals during high cycle fatigue
International Journal of Fatigue, 2009Co-Authors: Ciro Santus, D. TaylorAbstract:In metals, during high cycle fatigue on Plain Specimens, almost the entire fatigue life is spent as short crack initiation and propagation. The fatigue short crack life can be schematically divided into two subsequent phases: microstructurally short crack and physically short crack. Recently, Chapetti proposed a physically short crack threshold and propagation driving force model [Chapetti MD. Fatigue propagation threshold of short cracks under constant amplitude loading. Int J Fatigue 2003;25(12):1319-1326]. In his model the physically short crack behavior is obtained from the long crack propagation, just introducing the reduced threshold due to unsaturated closure. In the present paper the physically short crack propagation is similarly modeled by means of a driving force equation, but independent from the long crack propagation. In this way, a better description of the short crack behavior is provided, however short crack propagation data is required. Physically short crack propagation model parameters were obtained, by fitting experimental data drawn from the literature, for two aluminum alloys and a titanium alloy at two different heat treatment conditions and load ratios. By calculating the physically short crack plus long crack propagation, and assuming microstructurally short crack as part of the initiation stage, a purer information about crack initiation can be drawn from the S-N curves, and it is shown in the paper for the investigated materials. A precise crack initiation size and the number of cycles just for initiation are then provided. This information is useful to accurately predict fatigue life for blunt notched and for thick components, where the propagation is much higher than in the small Plain Specimen. A validation of the model was obtained by predicting the fatigue life of a notched Specimen. An accurate prediction was obtained both when the initiation was much smaller than propagation and when almost the entire fatigue life was initiation. © 2009 Elsevier Ltd. All rights reserved.
D. Taylor - One of the best experts on this subject based on the ideXlab platform.
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Physically short crack propagation in metals during high cycle fatigue
International Journal of Fatigue, 2009Co-Authors: Ciro Santus, D. TaylorAbstract:In metals, during high cycle fatigue on Plain Specimens, almost the entire fatigue life is spent as short crack initiation and propagation. The fatigue short crack life can be schematically divided into two subsequent phases: microstructurally short crack and physically short crack. Recently, Chapetti proposed a physically short crack threshold and propagation driving force model [Chapetti MD. Fatigue propagation threshold of short cracks under constant amplitude loading. Int J Fatigue 2003;25(12):1319-1326]. In his model the physically short crack behavior is obtained from the long crack propagation, just introducing the reduced threshold due to unsaturated closure. In the present paper the physically short crack propagation is similarly modeled by means of a driving force equation, but independent from the long crack propagation. In this way, a better description of the short crack behavior is provided, however short crack propagation data is required. Physically short crack propagation model parameters were obtained, by fitting experimental data drawn from the literature, for two aluminum alloys and a titanium alloy at two different heat treatment conditions and load ratios. By calculating the physically short crack plus long crack propagation, and assuming microstructurally short crack as part of the initiation stage, a purer information about crack initiation can be drawn from the S-N curves, and it is shown in the paper for the investigated materials. A precise crack initiation size and the number of cycles just for initiation are then provided. This information is useful to accurately predict fatigue life for blunt notched and for thick components, where the propagation is much higher than in the small Plain Specimen. A validation of the model was obtained by predicting the fatigue life of a notched Specimen. An accurate prediction was obtained both when the initiation was much smaller than propagation and when almost the entire fatigue life was initiation. © 2009 Elsevier Ltd. All rights reserved.