| 1. |
陳 強, 何超, 王清遠, Very high cycle fatigue strength and failure mechanisms of welded joint（溶接継手の超高サイクル疲労強度と破壊機構）, 日本機械学会九州支部年次大会, 2017.03, Fatigue strength and failure mechanisms of welded joints in high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regime. The effects of welding defect, micro-plasticity and second phase particle on fatigue crack initiation process are discussed based on our recent experimental studies. The results indicate that VHCF behaviors of welded joints showed strong sensitivities to microstructural and mechanical heterogeneities. In addition, we compare the fatigue strength between arc welding, laser-hybrid welding and friction stir welding so as to propose optimizations of welding parameters for fatigue life improvement.. |
| 2. |
N. Kawagoishi, K. Kariya, Y. Maeda, E. Kinoshita, Qiang Chen, M. Goto, Fatigue strength of aluminum cast alloy in plant oil, 12th International Conference on Fracture and Damage Mechanics, FDM 2013, Effect of plant oil on the fatigue strength of a squeeze cast Al-Si-Mg alloy was investigated. Crack growth rate was higher in plant oil than in air, inducing a decrease in fatigue strength. The reason included is explained from the viewpoint of high water absorbency of plant oils, on basis of hydrogen enhanced localized plasticity.. |
| 3. |
Qiang Chen, Qingyuan Wang, Norio Kawagoishi, Kohji Kariya, Yuzo Nakamura, Nu Yan, Effect of aging condition on fatigue strength of maraging steel in long life region, 13th International Conference on Fracture 2013, ICF 2013, A novel aging treatment was proposed to improve the fatigue strength of maraging steel by taking the effects of aging condition and humidity into account. Rotating bending fatigue tests were carried out for a 350 grade of 18% Ni maraging steel in the long life region up to 108 cycles in the relative humidity of 25% and 85%. Aging conditions under investigation included a conventional aging or the so called single aging at 753K, and a two-step aging or double aging by ageing at lower temperature of 473K succeeded to the single aging. Through the double aging, the susceptibility of fatigue strength to humidity was significantly improved without any deleterious effects. The main reasons for the decrease in fatigue strength in high humidity are due to the promotion of crack initiation and the acceleration of small crack propagation. The improvement of fatigue property in high humidity by the double aging was explained from the roles of the additional precipitation of supersaturated Mo atoms during the second lower temperature aging.. |
| 4. |
Qiang Chen, Takanori Nagano, Yuzo Nakamura, Yoshikazu Maeda, Norio Kawagoishi, Initiation and propagation behavior of a fatigue crack of maraging steel in high humidity, 13th International Conference on Fracture 2013, ICF 2013, The effect of humidity on the fatigue properties of 18% Ni maraging steels with different hardness and aging structure was investigated under rotating bending fatigue by varying relatively humidity from 25% to 95%. It was found that the initiation and the early propagation of a fatigue crack were accelerated in high humidity, which caused to a large decrease in fatigue strength of the alloys. In fact, the fatigue strength at 107 cycles obtained in RH 85% was less than a half of that in RH25%. Meanwhile, successive observation on surface fatigue progress and the fractographic analysis of fractured specimens elucidated that anodic dissolution was the main reason for promoting crack initiation whilst hydrogen embrittlement due to cathode reaction was responsible for the acceleration of crack propagation. However, the acceleration of crack propagation was suppressed by the formation of reverted austenite.. |
| 5. |
K. Kariya, N. Kawagoishi, H. Maeda, Qiang Chen, M. Goto, Y. Nu, Fatigue fracture mechanism of extruded Al alloy 7075-T6 in high humidity, 10th International Conference on Fracture and Damage Mechanics, FDM2011, Effect of high humidity on growth mechanism of a fatigue crack was investigated for an extruded bar of an age-hardened Al alloy 7075-T6 which had the marked texture of plane (111). Fracture in high humidity occurred by the growth of a shear mode crack under high stress levels, though a crack propagated in a tensile mode under low stress ones, macroscopically. Many voids and slip planes were observed on the fracture surface yielded by the shear mode crack. Especially most of the fracture surface was occupied by voids where the crack was small. The void percentage decreased with increasing in the crack depth. Fracture surface yielded by the shear mode crack was a plane (100). The growth direction of the shear mode crack to the cross section of specimen was about 55° corresponding to the angle composed by this plane and the texture of plane (111). These results suggest that the shear mode crack was related to microstructure, stress and environment. The growth mechanism of the shear mode crack assisted by hydrogen was proposed based on the results of the acceleration of crack growth and the formation of voids in high humidity.. |
| 6. |
Qiang Chen, N. Kawagoishi, G. Hashiguchi, M. Oki, K. Kusukawa, Fatigue behavior and fracture mechanism of al alloy 7075-t6 under ultrasonic cycling deformation, 17th European Conference on Fracture 2008: Multilevel Approach to Fracture of Materials, Components and Structures, ECF17, To investigate the effects of loading frequency on fatigue crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy 7075-T6 in ambient air and in N2 gas. The results obtained were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending fatigue. This may be caused by the retardation of crack initiation and early crack propagation. In ultrasonic fatigue, the growth direction of cracks changed macroscopically from tensile mode to shear mode with the direction oblique about 35 degrees to the stress axis. Fracture mechanism involved changed from striations featured to transgranular facets and microvoids predominated. Crack growth rate at growth mode transition was ~3x10-9 m/cycle. The relation between applied stress, a, and crack depth, bT, at the transition sites can be approximated as anbT = constant. The results were discussed from viewpoints of crack tip plasticity, time dependent environment effect and the texture microstructure of the alloy.. |
| 7. |
Tatsuo Sakai, Qiang Chen, Ayako Uchiyatna, Akiyoshi Nakagawa, Toshiki Ohnaka, A study on ultra-long life fatigue characteristics of maraging steels with/without aging treatment in rotating bending, 4th International Conference on Very High Cycle Fatigue, VHCF-4, Maraging steel is one of typical high strength steels used for light-weight mechanical structures due to its significantly high strength over 2000 MPa. It was melted in vacuum furnace in order to reduce the contents of unexpected inclusions so that higher mechanical properties can be achieved. After solution treatment, appropriate aging treatments were applied to some specimens to provide the desired strength levels. Ultra-long life fatigue properties were investigated by using both solution treated and aging hardened specimens under rotating bending fatigue. The effects of aging conditions were examined from the viewpoints of fatigue life, strength distribution, fatigue mechanism, and fracture morphology.. |
| 8. |
K. Morino, N. Kawagoishi, Qiang Chen, K. Fukada, E. Kondo, Internal fracture process in fatigue of radical nitrided bearing steel, Sixth International Conference on Computer Methods and Experimental Measurements for Surface Treatment Effects, Surface Treatment VI, 2003.12, Rotating bending fatigue tests were carried out for a radical nitrided bearing steel in order to investigate the initiation and propagation behavior of an internal crack. Surface fracture occurred under high stress levels and fish-eye fracture happened under low stress levels so that the S-N curve appeared in the shape of two-step lines. The depth of the origin of internal fracture was confined in a relatively narrow region near the boundary between the hardened and non-hardened matrix. By two-step loading fatigue tests in the internal fracture region, a circular trace corresponding to the stress change was observed within the fish-eye. In the internal fracture region, a crack was initiated at the early stage of the fatigue process, that is, most of the fatigue life of internal fracture was occupied by the growth life of an internal crack.. |
| 9. |
Q. Y. Wang, N. Kawagoishi, Qiang Chen, R. M. Pidaparti, Probabilistic Modeling of Pitting Corrosion Fatigue Life, Proceedings of the Twelfth (2002) International Offshore and Polar Engineering Conference, Corrosion and fatigue are two types of damages found in aircraft and offshore structures. Corrosion fatigue processes are characterized by randomness due to the random nature of materials, initial defects, loading, and environmental condition. In this study, a mechanistically based probabilistic model for prediction of pitting corrosion fatigue life in aluminum alloys has been developed which captures the effect of the interaction of cyclic load and corrosive environment and all the stages of the corrosion fatigue process. Monte Carlo simulations were performed to define the failure probability distribution. Predicted cumulative distribution functions of fatigue life agreed reasonably well the experimental data.. |
| 10. |
N. Kawagoishi, K. Morino, K. Fukada, Qiang Chen, E. Kondo, On fish-eye fracture of radical nitrided die steel, Fifth International Conference on Computer Methods and Experimental Measurements for Surface Treatment Effects, Surface Treatment V, 2001.12, In order to investigate the effect of radical nitriding on fatigue strength of die steel, rotating bending fatigue tests were carried out at room temperature and 450°C. Fatigue strength was increased by nitriding at both temperatures due to surface hardening and compressive residual stress generated in the surface region. Comparing with the non-nitrided steel in which the fracture origin was at surface slip bands or surface defects, the nitrided steel fractured with the origin at inner inclusions at both temperatures. In the nitrided steel, cracks initiated from inclusions in the non-hardened layer or near the boundary between hardened and non-hardened layers. The difference in fatigue strength between the two temperatures was discussed based on the feature of fish-eye.. |
| 11. |
Qiang Chen, N. Kawagoishi, K. Othubo, E. Kondo, M. Sakai, T. Kizaki, Ultrasonic fatigue strength in Inconel 718, SUPERALLOYS 718, 625, 706 and Various Derivatives, 2001.01, The fatigue strength of a nickel-base superalloy, Inconel 718, was investigated at room temperature under an ultrasonic frequency (19.5 kHz) loading in ambient air environment. The endurance (S-N) data show that fatigue strength was enhanced at ultrasonic frequency as compared to those at conventional frequencies. Small crack initiation and propagation behavior was observed during the fatigue progress at both ultrasonic fatigue and conventional rotary bending fatigue. The effect of frequency on the fatigue fracture mechanism was examined from a microscopic viewpoint.. |
| 12. |
Chao He, Yujuan Wu, Liming Peng, Ning Su, Qiang Chen, Shucheng Yuan, Yongjie Liu, Qingyuan Wang, Effect of microstructure on small fatigue crack initiation and early propagation behavior in Mg-10Gd-3Y-0.3Zr alloy, International Journal of Fatigue, 2019.02, Microstructural cyclic deformation mechanisms and their relation to small fatigue crack initiation and early propagation behavior were experimentally investigated in a rare earth-containing magnesium alloy (Mg-Gd-Y-Zr). The results indicate that basal slip is the dominant deformation mechanism, especially in coarse grains, and eventually leads to fatigue crack initiation. Early crack propagation behavior was strongly influenced by local microstructural heterogeneities in grain size and orientation. Three kinds of microstructures—favorably-oriented coarse grains, fine grain clusters and unfavorably-oriented coarse grains—are discussed in terms of their deformation mechanisms and resistance to crack propagation. These microstructural effects caused highly variable crack propagation rates within the first ∼200 μm of cracks.. |
| 13. |
Chao He, Yongjie Liu, Jiukai Li, Kun Yang, Qingyuan Wang, Qiang Chen, Very-high-cycle fatigue crack initiation and propagation behaviours of magnesium alloy ZK60, Materials Science and Technology (United Kingdom), 2018.04, The aim of this paper is to assess the very-high-cycle fatigue (VHCF) behaviour of a magnesium alloy (ZK60). Results indicate that the fatigue crack initiates from an area consisting of many distributed facets, while the region of early crack propagation is characterised by parallel traces, based on a fractographic analysis. The significant differences in morphology around the crack initiation area result from the interaction between the deformation twinning and the plastic zone at the crack tip. In addition, the fatigue crack propagation rate around the crack initiation site is also estimated based on a modified Murakami model. It is found that the formation stage for the fatigue crack is of great importance to the fatigue failure mechanism in the VHCF regime.. |
| 14. |
仮屋 孝二, 皮籠石 紀雄, 陳 強, 中村 祐三, 王 清遠, GS04 高量度中における7075-T6押出材の疲労き裂伝ぱ特性, M&M材料力学カンファレンス, 2014.07, Effect of humidity on the growth properties of a fatigue crack in an age-hardened Al alloy was investigated in relative humidity of 25% and 85% at loading frequencies of 50 and 6Hz. Macroscopic growth mode of a crack was a tensile one in low humidity, while the mode changed from the shear one to the tensile one with increase in fatigue life in high humidity. The crack in low humidity propagated by forming striation. On the other hand, in high humidity, most of fracture surface was occupied by many slip planes in the shear mode crack, and many granular facets in addition to striations were observed in the tensile mode growth. The difference in growth mechanism was explained by microstructure and cyclic softening behavior of the alloy and hydrogen content.. |
| 15. |
陳 強, WANG Qingyuan, 仮屋 孝二, 皮籠石 紀雄, 後藤 真宏, 3B2 高強度金属材料の超音波疲労におけるき裂伝ぱ機構(耐疲労設計:基礎研究と応用事例3), 日本機械学会九州支部講演論文集, 2013.09. |
| 16. |
皮籠石紀雄, 中村祐三, 仮屋孝二, 陳強, 永野茂憲, 前田義和, マルエージング鋼の疲労特性改善に有効な時効条件, 材料, 2013.12, The effect of aging condition on fatigue properties and the mechanism of decrease in fatigue strength in high humidity in 18% Ni maraging steel of grade 350 were investigated under rotating bending in relative humidity of 25% and 85%. Aging conditions investigated were under-, peak- and over-aging ones at the conventional aging temperature of 753K. In addition, double-aging treatments which were under- peak- and over-aging treatments at 673K and under-aging one at 473K after the peak-aging at 753K were also examined. Both of static and fatigue strengths were increased by the double-aging without any decrease in ductility and fatigue fracture toughness. Fatigue strength was markedly decreased by high humidity in all of the steels, and the decrease in fatigue strength was mainly caused by the accelerations of crack initiation and its growth at the early stage of fatigue process. The decrease in fatigue strength in high humidity was also suppressed by the double aging. A few facets comparable to a grain size of a prior austenite were observed at the fracture origins in high humidity but transgranular cracks by slip deformation were in low humidity. However most of the fracture surfaces were covered with lath boundary cracking regardless of the humidity and aging conditions. River pattern was observed in the facets, suggesting that the acceleration of crack growth in high humidity was a behavior related to hydrogen generated in cathode reaction. Based on the results, new aging treatment for improvement of fatigue properties of maraging steel was proposed. © 2013 The Society of Materials Science, Japan.. |
| 17. |
仮屋孝二, 前田季輝, 皮籠石紀雄, 陳強, 中村祐三, 森野数博, Al合金7075-T6押出し材の疲労き裂伝ぱ挙動に及ぼす湿度の影響, 材料, 2012.08, In order to investigate the effects of humidity change and loading frequency on growth behavior of a fatigue crack of an extruded bar of an age-hardened Al alloy 7075-T6, rotating bending fatigue tests were carried out in relative humidity of 25% and 85% at frequencies of 50Hz and 6Hz. At 50Hz, macroscopic appearances of fractures were a shear mode at high stress levels in high humidity, though those were a tensile mode in other conditions of humidity and stress levels. The crack growth rate was accelerated by high humidity. By changing humidity, both of the growth rate and the growth mode of a crack were immediately changed to those corresponding to the changed humidity. That is, the growth behavior and fatigue life under humidity change may be estimated by those in constant humidity. Fatigue life in high humidity at 6Hz was longer than that at 50Hz in spite of accelerations of both of the crack initiation and its growth rate in the early growth process in high humidity at both frequency, though there was no or little influence of frequency on fatigue life in low humidity. Moreover, the crack propagated in the tensile mode even at high stress levels where the shear mode crack propagated at 50Hz. These results were explained by the effect of hydrogen on the crack growth behavior. © 2012 The Society of Materials Science, Japan.. |
| 18. |
皮籠石紀雄, 東晃広, 陳強, 中村祐三, 森野数博, 高湿度下におけるAl合金2017の疲労特性に及ぼす微視組織の影響, 材料, 2012.06, In order to investigate effects of a texture and a slip characteristic on fatigue properties of Al alloys in high humidity, rotating bending fatigue tests were carried out using plain specimens of an extruded bar and a drawn one of age-hardened Al alloy 2017-T4 and an Al alloy annealed the extruded one in relative humidity of 25% and 85%. The extruded Al alloy and the annealed one had a marked texture of a (111) plane at the cross section of each bar, but a specified orientation was not observed in the drawn one. In addition, the aged-hardened Al alloys show a planar slip property and the annealed alloy shows a wavy one. In the all Al alloys, the obvious retardation of a small crack growth due to blocking effect of a grain boundary was observed in low humidity, though the retardation disappeared in high humidity. Moreover the acceleration of a crack growth was yielded due to the change in growth mechanism of a crack from a tensile mode in low humidity to a shear mode at high stress levels in high humidity in the extruded alloy, though the effect of humidity on the growth mechanism was very small in the drawn Al alloy and the annealed one. In the extruded Al alloy, the fracture surface yielded by the shear mode crack in high humidity was occupied by many slip planes and voids and was a (100) plane, though the fracture surface formed by the growth of the tensile mode crack in low humidity was covered with striations. In the drawn and annealed Al alloys, fracture surfaces were mainly occupied by striations irrespective of humidity and stress levels. © 2012 The Society of Materials Science, Japan.. |
| 19. |
陳 強, 皮籠石 紀雄, 橋口 原, 鈴木 孝明, Tai Y-C, OS1501 パリレンC薄膜の引張特性に及ぼす膜厚の影響(OS15-1 性能の発現と機構,OS-15 微視構造を有する材料の変形と破壊), M&M材料力学カンファレンス, 2011.07, Parylene C is an inert, hydrophobic, flexible and biocompatible polymer coating material, which has recently found broad MEMS and BioMEMS applications including microstructures, micro sensors and actuators. As a result, many researches have been conducted by focusing on the utilization of Parylene C thin films. Little attention, however, was paid to and rare was known about the mechanical properties of the thin films that may subject to severe tension, bending, twisting or the combination of these loading, especially in biomedical implants in which strength reliability must be secured during a reasonable lifetime. The objective of the present study, therefore, is to investigate the tensile properties of Parylene C thin films fabricated by micromachining process in the range of thickness from submicron to tens of microns. The effect of sample thickness is discussed.. |
| 20. |
皮籠石 紀雄, 福留 拓朗, 仮屋 孝二, 陳 強, 後藤 真宏, 高湿度下における時効硬化Al合金押出し材の疲労強度 : 回転曲げ疲労と超音波疲労, 日本機械学会論文集 A編, 2010.12, In order to investigate the availability of ultrasonic fatigue test for the evaluation of fatigue properties under conventional loading frequency, fatigue tests under ultrasonic frequency and rotating bending were carried out using plain specimens of an age-hardened and extruded Al alloy 7075-T6 in 7 kinds of environments of controlled humidity of 25, 50, 70 and 85%, distilled water oxygen gas and nitrogen gas. Although fatigue strength was decreased by high humidity, the decrease by high humidity was very small when the humidity was lower than about 60%～70% and fatigue strength was largely decreased above that humidity under both tests. However, the main reason for the decrease in fatigue strength by high humidity was different between rotating bending fatigue and ultrasonic fatigue. That is, the decrease in fatigue strength was mainly the acceleration of crack growth caused by brittle fracture under rotating bending and the transition to shear mode crack accompanied with glide plane decohesion and void formation under ultrasonic loading, respectively.. |
| 21. |
武智 和洋, 陳 強, 楠川 量啓, 仮谷 宗一郎, 大平 文和, 鈴木 孝明, 209 LP-CVDポリシリコン薄膜の繰返し引張り疲労(材料力学VI), 講演論文集, 2009.02. |
| 22. |
Norio Kawagoishi, Eiji Maemura, Qiang Chen, Masahiro Goto, Kazuhiro Morino, Effect of grain size on ultrasonic fatigue properties of Ni-base super alloy inconel 718, Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2008.07, Ultrasonic fatigue tests of plain specimens with different grain sizes were carried out for Ni-base super alloy, Inconel 718, in ambient air in order to investigate the effect of grain size on fatigue properties. Fatigue strength was increased with decrease in grain size. The increase in fatigue strength by refining grain size was mainly caused by the suppression of crack initiation. That is, the effect of grain size on crack growth rate was hardly recognized, though crack morphology was rougher in the specimen of larger grain, meaning that the crack growth in the large-grained specimens was suppressed by roughness induced crack closure. On the other hand, however, more flat facets caused by twin boundary cracking were observed in the large-grained specimens, which inversely led to crack growth acceleration.. |
| 23. |
皮籠石 紀雄, 前村 英史, 陳 強, 後藤 真宏, 森野 数博, Ni基超合金インコネル718の超音波疲労特性に及ぼす結晶粒径の影響, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2008.07, Ultrasonic fatigue tests of plain specimens with different grain sizes were carried out for Ni-base super alloy, Inconel 718, in ambient air in order to investigate the effect of grain size on fatigue properties. Fatigue strength was increased with decrease in grain size. The increase in fatigue strength by refining grain size was mainly caused by the suppression of crack initiation. That is, the effect of grain size on crack growth rate was hardly recognized, though crack morphology was rougher in the specimen of larger grain, meaning that the crack growth in the large-grained specimens was suppressed by roughness induced crack closure. On the other hand, however, more flat facets caused by twin boundary cracking were observed in the large-grained specimens, which inversely led to crack growth acceleration.. |
| 24. |
前村 英史, 皮籠石 紀雄, 陳 強, 後藤 真宏, 森野 数博, 117 インコネル718の超音波疲労特性に及ぼす微視組織の影響(OS 材料利用・改質に関する実験・数値解析(その3)), 日本機械学会九州支部講演論文集, 2007.10. |
| 25. |
陳 強, 橋口 原, 皮籠石 紀雄, 鈴木 勝順, 楠川 量啓, 酒井 達雄, 村井 正徳, 堀邊 英夫, 506 ナノ・マイクロ材料の超高サイクル疲労信頼性試験装置の開発(OS9-1 粘弾性・疲労・マイクロ,OS9 実験力学における新たな試み), M&M材料力学カンファレンス, 2007.10, A novel strain controlled, free standing tensile fatigue system was developed by using the combined PZT and micromachining technologies in order to conduct in-situ observation and assessment of high cycle fatigue behavior in LP-CVD poly Silicon thin films within a scanning electron microscope (SEM).. |
| 26. |
永野茂憲, 皮籠石紀雄, 森山三千彦, 陳強, 長島悦一, 硬さレベルを変えたマルエージング鋼の疲労強度に及ぼすショットピーニングの影響, 材料, 2007.12, In order to investigate the hardness dependence on the fatigue strengths for surface fracture and internal fracture, rotating bending fatigue tests were carried out for maraging steels using specimens with different hardness obtained by heat-treating at different under-aging conditions. Fatigue limit for surface fracture was evaluated in electro-polished specimens and the one for internal fracture was in shot-peened ones, where fatigue limits were defined as fatigue strengths at 107cycles for surface fracture and 108cycles for internal fracture, respectively. Fatigue limit for internal fracture increased with increase in hardness similar to the one for surface fracture. However, the proportional relationship between the fatigue limit and the hardness existed till higher hardness in the fatigue limit for internal fracture than in the one for surface fracture. This difference in the hardness dependence on fatigue limit was discussed from the viewpoint of the influence of humidity on the fatigue strength. © 2007 The Society of Materials Science.. |
| 27. |
皮籠石 紀雄, 興 雅博, 後藤 真宏, 陳 強, 王 清遠, Al合金7075-T6の超音波疲労におけるき裂伝ぱ挙動, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2006.09, In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T6, in ambient air and in N_2 gas, and the results were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending one. This was caused by the retardation of a crack initiation and its early propagation. In ultrasonic fatigue, the growth direction of a crack changed macroscopically from a tensile mode to a shear one which the direction was about 35 degrees against to the specimen axis, and fracture mechanism also changed from striations to transgranular facets with voids microscopically. Crack growth rate at the transition of crack growth direction was about 3×10^ m/cycle. The relation between an applied stress σ_a and a crack depth at the transition of crack growth direction b_T was expressed by σ^n_ab_T=constant. These results were explained from the time dependent environmental effect and texture of microstructure.. |
| 28. |
Norio Kawagoishi, Masahiro Oki, Masahiro Goto, Qiang Chen, Qingyuan Wang, Crack growth behavior of Al alloy 7075-T6 under ultrasonic fatigue, Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2006.09, In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T 6, in ambient air and in N2 gas, and the results were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending one. This was caused by the retardation of a crack initiation and its early propagation. In ultrasonic fatigue, the growth direction of a crack changed macroscopically from a tensile mode to a shear one which the direction was about 35 degrees against to the specimen axis, and fracture mechanism also changed from striations to transgranular facets with voids microscopically. Crack growth rate at the transition of crack growth direction was about 3×10-9 m/cycle. The relation between an applied stress σa and a crack depth at the transition of crack growth direction bT was expressed by σanbT=constant. These results were explained from the time dependent environmental effect and texture of microstructure.. |
| 29. |
Norio Kawagoishi, Jun Ogawa, Qiang Chen, Masahiro Goto, Kazuhiro Morino, Effect of loading frequency on fatigue strength of Ni-based super alloy, Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2006.10, In order to investigate the growth mechanism of a fatigue crack of Ni-based super alloy at ultrasonic frequency, ultrasonic fatigue and rotating bending fatigue tests were carried out for Inconel 718 in ambient air and in N 2 gas using plain and notched specimens and the results in both tests were compared by focusing on the effects of strain rate and environment. In ambient air, fatigue strength was higher in ultrasonic fatigue than in rotating bending fatigue in plain specimen, while the results in notched specimen were the reverse. Many transgranular cracks and cleavage like cracks were observed on the fracture surface in ultrasonic fatigue in addition to striation and transgranular facets observed in rotating bending fatigue and there was no difference in the fracture mechanism between plain specimen and notched one. Moreover, these effects of frequency on the growth mechanism of a crack in ambient air were nearly the same in N2 gas, though fatigue strength in N2 gas was higher than that in air. The increase in fatigue strength in N2 gas was mainly caused by the retardation of a crack initiation.. |
| 30. |
Q. Y. Wang, N. Kawagoishi, Q. Chen, Fatigue and fracture behaviour of structural Al-alloys up to very long life regimes, International Journal of Fatigue, 2006.11, Very long life fatigue and near-threshold fatigue crack growth behaviour of 7075 and 6061 Al-alloys in T6 condition were investigated using accelerated fatigue testing at 19.5 kHz on a piezoelectric machine. Significant interfacial voids were observed in the two Al-alloys during crack initiation and early fatigue crack growth process. Fatigue failure in Al-alloys could be ascribed to: the formation of a number of fatigue voids, their growth and coalescence, and the subsequent formation and propagation of macroscopic cracks. Moreover, fatigue crack growth rates of small cracks in these alloys were found to be greater than those of large cracks for the same stress intensity factor range. © 2006 Elsevier Ltd. All rights reserved.. |
| 31. |
Q. Y. Wang, M. R. Sriraman, N. Kawagoishi, Q. Chen, Fatigue crack growth of bonded composite repairs in gigacycle regime, International Journal of Fatigue, 2006.10, Fatigue induced from various aeromechanical sources can reach gigacycle regime due to vibratory stress cycles at high frequencies. Composite repairs offer various advantages over mechanical fastening or riveting, including improved long-term durability behavior and reduced corrosion. In this study, by using ultrasonic frequency cyclic loading, fatigue crack growth tests in gigacycle regime were conducted on notched 7075 and 6061 aluminum alloy substrates (in T6 condition) with and without bonded Boron/epoxy patches. A considerable increase in the fatigue life was observed with more number of patch plies. The effect of patch configuration and thickness on enhancing the fatigue strength by orders of magnitude has been demonstrated. © 2006 Elsevier Ltd. All rights reserved.. |
| 32. |
皮籠石 紀雄, 小川 遵, 陳 強, 後藤 真宏, 森野 数博, Ni基超合金の疲労強度に及ぼす繰返し速度の影響, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2006.10, In order to investigate the growth mechanism of a fatigue crack of Ni-based super alloy at ultrasonic frequency, ultrasonic fatigue and rotating bending fatigue tests were carried out for Inconel 718 in ambient air and in N_2 gas using plain and notched specimens and the results in both tests were compared by focusing on the effects of strain rate and environment. In ambient air, fatigue strength was higher in ultrasonic fatigue than in rotating bending fatigue in plain specimen, while the results in notched specimen were the reverse. Many transgranular cracks and cleavage like cracks were observed on the fracture surface in ultrasonic fatigue in addition to striation and transgranular facets observed in rotating bending fatigue and there was no difference in the fracture mechanism between plain specimen and notched one. Moreover, these effects of frequency on the growth mechanism of a crack in ambient air were nearly the same in N_2 gas, though fatigue strength in N_2 gas was higher than that in air. The increase in fatigue strength in N_2 gas was mainly caused by the retardation of a crack initiation.. |
| 33. |
皮籠石 紀雄, 興 雅博, 後藤 真宏, 陳 強, 王 清遠, 107 Al合金の超音波疲労におけるき裂伝ぱ挙動(OS1-2 疲労II,OS1 機能性材料の損傷とその力学的背景), 日本機械学会九州支部講演論文集, 2005.10, In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T6, and the results were compared with those in rotating bending fatigue. Fatigue strength in ultrasonic was higher than that in rotating bending. Growth direction of a crack changed from tensile mode to shear one in ultrasonic. The relation between an applied stress σ_a and a crack length at transition of growth direction b_T was expressed as σ_a ^nb_T=C.. |
| 34. |
皮篭石紀雄, 後藤真宏, 森野数博, 松山芳弘, 陳強, Ni基超合金の中高温疲労強度に及ぼす結晶粒径の影響, 日本材料学会学術講演会講演論文集, 2005.05. |
| 35. |
Q. Chen, N. Kawagoishi, Q. Y. Wang, N. Yan, T. Ono, G. Hashiguchi, Small crack behavior and fracture of nickel-based superalloy under ultrasonic fatigue, International Journal of Fatigue, 2005.10, Fracture and small crack behavior in the very high cycle domain of 10 9 cycles were investigated with a nickel-based superalloy under ultrasonic fatigue in ambient air at room temperature. The influence of ultrasonic frequency is examined by comparing the results with those in conventional low frequency fatigue. It is found that fatigue strength increases as frequency is raised up to 19.5 kHz and the most of fatigue life is consumed in nucleating and propagating small cracks up to 100 μm. Transition of fracture mode from transgranular ductile fracture to cleavage-dominated fracture occurs beyond a critical stress intensity factor range of approximately 21MPam, leading to the catastrophic failure under ultrasonic fatigue. © 2005 Elsevier Ltd. All rights reserved.. |
| 36. |
Q. Y. Wang, N. Kawagoishi, Q. Chen, R. M. Pidaparti, Fatigue life enhancement of defective structures by bonded repairs, Structural Engineering and Mechanics, 2004.09, Defective metallic components and structures are being repaired with bonded composite patches to improve overall mechanical and fatigue properties. In this study, fatigue crack growth tests were conducted on pre-cracked 7075/T6 Aluminum substrates with and without bonded Boron/epoxy patches. A considerable increase in the fatigue life and a decrease in the stress intensity factor (SIF) were observed as the number of patch plies increased. The experimental results demonstrate that the patch configurations and patch thickness can enhance fatigue life by order of magnitude. Quantitative comparisons between analytical and experimental data were made, and the analytical model based on a modified Rose's analytical solution appears to best estimate the fatigue life.. |
| 37. |
Q. Y. Wang, N. Kawagoishi, Q. Chen, Fatigue voids in structural Al-alloys under high-frequency cyclic loading, Journal of Materials Science, 2004.01, The fatigue behavior of 7075/T6 and 6061/T6 aluminum alloys in the very long life regime was investigated by using piezoelectric accelerated fatigue tests at 19.5 KHz. The mechanism of fatigue crack initiation and propagation by void formation and growth was identified using scanning electron microscopy (SEM).. |
| 38. |
Norio Kawagoishi, Qiang Chen, Nu Yan, Qingyuan Wang, Masahiro Goto, Ultrasonic fatigue properties of an age-hardened Al alloy 6061-T6, Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2004.08, In order to investigate the influence of loading frequency on the fatigue properties of Al alloy, ultrasonic fatigue tests were carried out for an age-hardened Al alloy, 6061-T6. The results were compared with those of rotating bending fatigue in view points of initiation and propagation behavior of a crack and fracture mechanism. Fatigue life was longer in ultrasonic fatigue than in rotating bending fatigue, which was mainly caused by the suppression of crack initiation. In ultrasonic fatigue, many fatigue voids and cleavage cracks were observed on the fracture surface in addition to the shear mode cracks, striations and dimples, which were typical fracture modes in rotating bending.. |
| 39. |
皮籠石 紀雄, 陳 強, 燕 怒, 王 清遠, 後藤 真宏, 時効硬化Al合金6061-T6の超音波疲労特性, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2004.08, In order to investigate the influence of loading frequency on the fatigue properties of Al alloy, ultrasonic fatigue tests were carried out for an age-hardened Al alloy, 6061-T6. The results were compared with those of rotating bending fatigue in view points of initiation and propagation behavior of a crack and fracture mechanism. Fatigue life was longer in ultrasonic fatigue than in rotating bending fatigue, which was mainly caused by the suppression of crack initiation. In ultrasonic fatigue, many fatigue voids and cleavage cracks were observed on the fracture surface in addition to the shear mode cracks, striations and dimples, which were typical fracture modes in rotating bending.. |
| 40. |
皮籠石 紀雄, 陳 強, 後藤 真宏, 王 清遠, 西谷 弘信, 206 各種金属材料における超音波疲労特性, 日本機械学会九州支部講演論文集, 2003.10. |
| 41. |
Q. Y. Wang, N. Kawagoishi, Q. Chen, Effect of pitting corrosion on very high cycle fatigue behavior, Scripta Materialia, 2003.10, The effects of pitting corrosion on very high cycle fatigue behavior of aluminum alloys were discussed. The results indicated that the presence of pre-existing corrosion pits, produced by 1-day, 4-day and 7-day immersion in salt water significantly reduces the fatigue life of the alloy by a factor of 10-100. It was also found that the pittings accelerated crack initiation and promoted multiple-site damage.. |
| 42. |
Qingyuan Wang, N. Kawagoishi, Q. Chen, R. M. Pidaparti, Evaluation of the probability distribution of pitting corrosion fatigue life in aircraft materials, Acta Mechanica Sinica/Lixue Xuebao, 2003.06, Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials, loading, and environmental conditions. A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation). The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pitting current, and material properties due to the scatter found in the experimental data. Monte Carlo simulations were performed to define the failure probability distribution. Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data.. |
| 43. |
Q. Chen, VS Deshpande, E Van der Giessen, A Needleman, Friction stress effects on mode I crack growth predictions, SCRIPTA MATERIALIA, 2003.03, The effect of a lattice friction stress on the monotonic growth of a plane strain mode I crack under small-scale yielding conditions is analyzed using discrete dislocation plasticity. When the friction stress is increased from zero to half the dislocation nucleation stress, the crack tip stress field changes from one characteristic of a plastic solid to one characteristic of an elastic solid, and the crack growth resistance decreases substantially. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.. |
| 44. |
陳 強, 皮籠石 紀雄, 西谷 弘信, 大坪 謙一, 王 清遠, 近藤 英二, Ni基超合金の超音波疲労特性, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2003.03, In order to investigate the effect of load frequency on the fatigue strength and fracture mechanism of a nickel-base superalloy, Inconel 718, fatigue tests were carried out under an ultrasonic frequency (19.5kHz) in ambient air environment. The results were compared with those obtained under conventional rotatary bending fatigue at a frequency of 50 Hz. Fatigue strength increased at ultrasonic frequency, which is mainly caused by the suppression of crack initiation and its growth at the early stage. Under both ultrasonic and rotary bending fatigue tests, most of fatigue life consumed in the growth of a crack smaller than 1 mm. In the ultrasonic fatigue, intergranular and cleavage crack propagations were observed in addition to striation, which was a dominant fracture mechanism in the conventional fatigue.. |
| 45. |
Norio Kawagoishi, Qiang Chen, Nu Yan, Qingyuan Wang, Eiji Kondo, Ultrasonic Fatigue Properties of a High Strength Extruded Al Alloy, Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2003.12, In order to investigate the influence of loading frequency on the fatigue strength and fracture mechanism of a high strength Al alloy, ultrasonic fatigue tests were carried out for an extruded Al alloy 7075-T 6 and the results were compared with those of rotating bending fatigue tests. Fatigue strength of ultrasonic was higher than that of rotating bending. The crack initiation and the crack growth rate in ultrasonic fatigue were delayed compared with those of rotating bending fatigue. In case of ultrasonic fatigue, the direction of crack growth changed from tensile mode to shear mode and many voids were observed on the fracture surface in shear mode growth, whereas the crack propagated in tensile mode and striations were observed in rotating bending fatigue.. |
| 46. |
Qiang Chen, Norio Kawagoishi, Hironobu Nisitani, Ken Ichi Otsubo, Qingyuan Wang, Eiji Kondo, Ultrasonic fatigue properties of Ni-base superalloy, Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2003.03, In order to investigate the effect of load frequency on the fatigue strength and fracture mechanism of a nickel-base superalloy, Inconel 718, fatigue tests were carried out under an ultrasonic frequency (19.5 kHz) in ambient air environment. The results were compared with those obtained under conventional rotatary bending fatigue at a frequency of 50 Hz. Fatigue strength increased at ultrasonic frequency, which is mainly caused by the suppression of crack initiation and its growth at the early stage. Under both ultrasonic and rotary bending fatigue tests, most of fatigue life consumed in the growth of a crack smaller than 1 mm. In the ultrasonic fatigue, intergranular and cleavage crack propagations were observed in addition to striation, which was a dominant fracture mechanism in the conventional fatigue.. |
| 47. |
皮籠石 紀雄, 陳 強, 燕 怒, 王 清遠, 近藤 英二, 高強度Al合金押出し材の超音波疲労特性, 日本機械学會論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2003.12, In order to investigate the influence of loading frequency on the fatigue strength and fracture mechanism of a high strength Al alloy, ultrasonic fatigue tests were carried out for an extruded Al alloy 7075-T 6 and the results were compared with those of rotating bending fatigue tests. Fatigue strength of ultrasonic was higher than that of rotating bending. The crack initiation and the crack growth rate in ultrasonic fatigue were delayed compared with those of rotating bending fatigue. In case of ultrasonic fatigue, the direction of crack growth changed from tensile mode to shear mode and many voids were observed on the fracture surface in shear mode growth, whereas the crack propagated in tensile mode and striations were observed in rotating bending fatigue.. |
| 48. |
陳 強, Deshpande V. S, Giessen van der E, Needleman A, 341 モード I き裂伝ぱに及ぼす Peierls 応力の影響, 計算力学講演会講演論文集, 2002.10. |
| 49. |
Q. Y. Wang, C. Bathias, N. Kawagoishi, Q. Chen, Effect of inclusion on subsurface crack initiation and gigacycle fatigue strength, International Journal of Fatigue, 2002.12, The effect of inclusions on crack initiation and propagation in gigacycle fatigue was investigated experimentally and analytically in six high strength low alloy steels. Fatigue testing was performed at very high numbers of cycles through ultrasonic fatigue tests at 20 kHz. Inclusions at subsurface are common sites for fatigue crack nucleation in these alloys when cycles to failure was > 107 cycles. A significant change in the slope of the S-N curve was observed accompanying the transition from surface to subsurface crack initiation. A deterministic model has been developed to predict the total fatigue life, i.e. crack initiation life and crack propagation life, from the measured inclusion sizes. The predicted fatigue strength agreed reasonably well with the experimental results. It is a tendency that smaller inclusions are associated with longer fatigue life. The results demonstrated that the portions of life attributed to subsurface crack initiation between 107 and 109 cycles are > 99%. © 2002 Elsevier Science Ltd. All rights reserved.. |
| 50. |
Norio Kawagoishi, Qiang Chen, Ken Ichi Otsubo, Nu Yan, Eiji Kondo, Qingyuan Wang, Fatigue properties of Ni-base superalloy in long life region at elevated temperature, Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 2002.08, The fatigue properties of a nickel-base superalloy, Inconel 718, in long-life region up to 108 cycles were investigated under rotating bending at room temperature and elevated temperature of 300°C, 500°C and 600°C. S-N curves at 500°C and 600°C showed the stepwise shapes, though those in cases of room temperature and 300°C were the conventional one-step ones. All the fractures originated from the specimen surface at room temperature and 300°C, while the internal fractures occurred in long-life region beyond 107 cycles and the surface fractures at the stress levels over the horizontal line of S-N curves corresponding to the fatigue limit for the surface fracture at 500°C and 600°C. Intergranular cracking were observed at the origin of internal fracture.. |
| 51. |
皮籠石 紀雄, 陳 強, 大坪 謙一, 燕 怒, 近藤 英二, 王 清遠, Ni基超合金の長寿命域における中高温疲労特性, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 2002.08, The fatigue properties of a nickel-base superalloy, Inconel 718, in long-life region up to 108 cycles were investigated under rotating bending at room temperature and elevated temperature of 300°C, 500°C and 600°C. S-N curves at 500°C and 600°C showed the stepwise shapes, though those in cases of room temperature and 300°C were the conventional one-step ones. All the fractures originated from the specimen surface at room temperature and 300°C, while the internal fractures occurred in long-life region beyond 107 cycles and the surface fractures at the stress levels over the horizontal line of S-N curves corresponding to the fatigue limit for the surface fracture at 500°C and 600°C. Intergranular crackings were observed at the origin of internal fracture.. |
| 52. |
大坪 謙一, 陳 強, 燕 怒, 王 清遠, 皮籠石 紀雄, 707 Ni基超合金の超音波疲労強度(G.S. 材料力学 : 疲労), 日本機械学会九州支部講演論文集, 2001.10, The fatigue strength of a nikel-base superalloy, Inconel 718, was investigated at room temperature under an ultrasonic frequency (19.5kHz) loading in ambient air environment. The endurance (S-N) data show that fatigue strength was enhanced at ultrasonic frequency as compared with those at conventional frequencies. Small crack initiation and propagation behavior was observed during the fatigue progress at both ultrasonic fatigue and conventional rotary bending fatigue. The effect of frequency on the fatigue mechanism was examined from a microscope viewpoint.. |
| 53. |
陳 強, Ni基超合金の高温疲労特性に関する研究(学位論文の要旨), 鹿児島大学工学部研究報告, 2000.09. |
| 54. |
陳 強, 皮籠石 紀雄, 近藤 英二, 岩本 竜一, 森田 春美, 1011 Ni基超合金の疲労強度に及ぼす研削加工の影響(O.S.6-3 合金の疲労強度)(オーガナイズドセッション6 : 先進材料の機能と強度特性), 講演論文集, 2000.03. |
| 55. |
廣瀬 仁大, 皮籠石 紀雄, 西谷 弘信, 近藤 英二, 陳 強, 108 Alホイール用鋳物の疲労特性(O.S.1-2 疲労強度)(O.S.1 疲労破壊事故の防止 : 被害の評価と実際問題への応用), 日本機械学会九州支部講演論文集, 2000.06. |
| 56. |
遠矢 良樹, 近藤 英二, 皮籠石 紀雄, 陳 強, 308 振動解析による被削材表面形状のインプロセス同定(生産加工II), 日本機械学会九州支部講演論文集, 2000.03. |
| 57. |
近藤 英二, 皮籠石 紀雄, 中村 正和, 陳 強, 446 AE の発生パターンによる疲労損傷度の推定, Dynamics and Design Conference : 機械力学・計測制御講演論文集 : D & D, 2000.09, Fatigue fracture is a serious problem in high-speed machines and lightened structures. Therefore, it is very important for fully automated machines to predict or estimate fatigue damage of the machines nondestructively. On the other hand, acoustic emission is the phenomenon that elastic waves caused by released elastic deformation energy propagate in materials, and initiation and propagation of cracks can be detected by using the acoustic emission.. Accordingly, fatigue damage of a specimen in plane bending fatigue test was tried to be estimated by using pattern of occurrence of AE per cycle of periodic change of stress. As a result, it was verified that proposal method can estimate fatigue damage, but with a little error.. |
| 58. |
中村 正和, 近藤 英二, 皮籠石 紀雄, 陳 強, 618 AE発生のパターン認識による疲労損傷度の評価(材料力学III), 日本機械学会九州支部講演論文集, 2000.03. |
| 59. |
Q. Chen, N. Kawagoishi, H. Nisitani, Evaluation of fatigue crack growth rate and life prediction of Inconel 718 at room and elevated temperatures, Materials Science and Engineering A, 2000.01, The fatigue crack growth behavior of Inconel 718 was investigated under rotating bending fatigue at room temperature, 300, 500, and 600°C in air. It has been found that the small crack growth rate could be evaluated by the small crack growth law at high stress levels, where the small-scale yielding conditions are exceeded and the Paris law is not applicable, irrespective of the temperature. The fatigue strength of plain specimens increased considerably in the long-life region at the elevated temperatures, because the early growth of a small crack in the range of 20-30 μm was suppressed. However, a crack grew faster at higher temperature after growing beyond about 50 μm due to the decrease of crack growth resistance. The fatigue life in the stable crack growth period can be predicted by the small crack growth law.. |
| 60. |
N. Kawagoishi, Q. Chen, H. Nisitani, Fatigue strength of Inconel 718 at elevated temperatures, Fatigue and Fracture of Engineering Materials and Structures, 2000.03, The strength of Inconel 718 under rotary bending fatigue is investigated at room temperature, 300, 500 and 600 °C in air. It is found that in the long-life region, the fatigue strength of a plain specimen is much higher at elevated temperatures than at room temperature, though the static strength decreases with the increase in temperature. The effect of temperature on the fatigue strength is examined in terms of the initiation and early growth behaviour of a small crack. The results are discussed in relation to the competition between the softening of the nickel matrix (γ phase) and the surface oxidation at elevated temperatures.. |
| 61. |
Qiang Chen, Norio Kawagoishi, Hironobu Nisitani, Evaluation of notched fatigue strength at elevated temperature by linear notch mechanics, International Journal of Fatigue, 1999.10, The notched fatigue strength of nickel-base superalloy Inconel 718 has been investigated under rotating bending loading at room temperature and 500 °C in air. The applicability of linear notch mechanics to the evaluation of notched fatigue strength at elevated temperature was assessed in terms of the fatigue limit for crack initiation and that for crack growth. The effect of temperature on the fatigue strength and notch sensitivity of Inconel 718 was examined. The results were discussed from the viewpoints of the softening of matrix and surface oxidation at elevated temperature.. |
| 62. |
N. Kawagoishi, Q. Chen, E. Kondo, M. Goto, H. Nisitani, Influence of Cubic Boron Nitride Grinding on the Fatigue Strengths of Carbon Steels and a Nickel-Base Superalloy, Journal of Materials Engineering and Performance, 1999.04, The influence of cubic boron nitride (CBN) grinding on fatigue strength was investigated on an annealed carbon steel, a quenched and tempered carbon steel at room temperature, and a nickel-base superalloy, Inconel 718, at room temperature and 500°C. The results were discussed from several viewpoints, including surface roughness, residual stress, and work hardening or softening due to CBN grinding. The fatigue strength increased upon CBN grinding at room temperature, primarily because of the generation of compressive residual stress in the surface region. However, in the case of Inconel 718, this marked increase in the fatigue strength tended to disappear at the elevated temperature due to the release of compressive residual stress and the decrease of crack growth resistance at an elevated temperature.. |
| 63. |
近藤英二, 皮篭石紀雄, 向井原崇, 陳強, 岩本竜一, 切刃の丸味による切削面の弾性回復と切削抵抗, 精密工学会大会学術講演会講演論文集, 1999.03. |
| 64. |
皮籠石 紀雄, 大園 義久, 陳 強, 後藤 真宏, 田中 秀穂, 近藤 英二, Ni 基超合金の疲労き裂発生および初期伝ぱに及ぼす高温酸化膜の影響, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 1998.04, Rotating bending fatigue tests were carried out for Ni base super alloy Inconel 718 at room temperature and elevated temperatures of 300℃, 500℃ and 600℃ in order to investigate the effect of surface oxidation at the elevated temperatures on the fatigue crack initiation and its early growth process. The fatigue strength was higher at the elevated temperatures than at room temperature when stress levels were low. This phenomenon was caused from that the growth of a crack smaller than the size of a few grains was suppresed at the elevated temperatures, though the growth of a larger crack was accelerated. The main reason for the suppression of the early growth of a small crack was a formation of oxide films on the specimen surface at the elevated temperatures.. |
| 65. |
皮籠石 紀雄, 陳 強, 西谷 弘信, 後藤 真宏, 近藤 英二, Ni基超合金の中・高温疲労における切欠感度, 日本機械学会論文集. A編 = Transactions of the Japan Society of Mechanical Engineers. A, 1998.11, Rotating bending fatigue tests were carried out for nickel-base superalloy Inconel 718 in air at room temperature and the elevated temperatures of 300℃, 500℃ and 600℃ using the 60 degree V-grooved specimen in order to investigate the influence of temperature on the notch sensitivity of the alloy. The notch sensitivity was assessed in terms of the limiting stress for crack initiation σ_ and that for crack growth σ_, based on the Linear Notch Mechanics (LNM). It was found that the fatigue limits σ_, σ_ of notched specimen can be evaluated by LMN at each temperature. Although the notch sensitivity of Inconel 718 to the two fatigue limits is relatively low considering its high static strength at all the temperatures, especially to the fatigue limit for crack growth, it becomes more sensitive at the elevated temperatures than at room temperature. The results were discussed with the effect of temperature on the arresting behavior of fatigue crack growth.. |
| 66. |
大隈博輝, 近藤英二, 皮篭石紀雄, 陳強, 動的切削過程の特性値による工具摩耗の検出, 精密工学会九州支部・中国四国支部講演会講演論文集, 1998.11. |
| 67. |
向井原崇, 近藤英二, 皮篭石紀雄, 陳強, 微小切込みにおける切削機構, 精密工学会九州支部・中国四国支部講演会講演論文集, 1998.11. |
| 68. |
皮籠石 紀雄, 藤村 顕世, 陳 強, 有川 俊, 前野 一朗, 田中 秀穂, CBN 研削加工材の疲労強度(炭素鋼およびNi基合金の場合), 日本機械学会論文集. A編, 1997.09, Rotating bending fatigue tests were carried out on carbon steels and a nickel-based super alloy, Inconel 718, for investigation of the effect of CBN wheel grinding on the fatigue strength at room temperature and 500°C. The results are discussed from several view points, including surface roughness, residual stress and work hardening or softening due to grinding. The fatigue strength increased upon CBN wheel grinding at room temperature, primarily because of generation of compressive residual stress due to the CBN wheel grinding. However, this marked increase in the fatigue strength due to CBN wheel grinding tended to disappear at elevated temperature.. |
| 69. |
皮籠石 紀雄, 陳 強, 田中 秀穂, 前野 一朗, 清藤 純一, Ni基超合金の微小き裂伝ぱ特性, 日本機械学会論文集. A編, 1997.07, Rotating bending fatigue tests were carried out for Inconel 718 at room temperature to investigate the growth characteristics of a small crack. It was found that: (1) The crack initiated at the grain boundary and then propagated as a transgranular crack. (2) When the stress level was higher than the fatigue limit, the fatigue life was mainly controlled by the growth life of a crack smaller than 1 mm. (3) The fatigue limit was a limiting stress for the crack propagation. (4) At low stress levels (σa/σ0.20.6), it was determined by the small crack growth law.. |
| 70. |
Norio Kawagoishi, Qiang Chen, Hironobu Nisitani, Masahiro Goto, Hideho Tanaka, Fatigue crack growth resistance in nickel-base superalloy at elevated temperatures, Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 1997.01, Rotating bending fatigue tests were carried out for Inconel 718 at room temperature and elevated temperatures of 300 °C, 500 °C and 600 °C to investigate the influence of temperature on the fatigue crack growth resistance. The crack growth rate can be expressed by the small crack growth law, dl/dN = C1σanl = C2(σa/σB)nl, at all the temperatures, where σB, σaand l are the tensile strength, the stress amplitude and the crack length, and C1, C2and n are constants. Therefore, the resistance to crack growth was evaluated using the small crack growth law. The fatigue crack growth resistance decreased with the increase of temperature.. |
| 71. |
Norio Kawagoishi, Kensei Fujimura, Qiang Chen, Masaru Arikawa, Ichiro Maeno, Hideho Tanaka, Fatigue strength of specimens ground by a CBN wheel (In cases of carbon steels and a nickel-base super alloy), Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, 1997.01, Rotating bending fatigue tests were carried out on carbon steels and a nickel-based super alloy, Inconel 718, for investigation of the effect of CBN wheel grinding on the fatigue strength at room temperature and 500 °C. The results are discussed from several view points, including surface roughness, residual stress and work hardening or softening due to grinding. The fatigue strength increased upon CBN wheel grinding at room temperature, primarily because of generation of compressive residual stress due to the CBN wheel grinding. However, this marked increase in the fatigue strength due to CBN wheel grinding tended to disappear at elevated temperature.. |
| 72. |
皮籠石 紀雄, 陳 強, 田中 秀穂, 前野 一朗, 清藤 純一, Ni基超合金の微小き裂伝ぱ特性, 日本機械学会論文集. A編, 1997.07, Rotating bending fatigue tests were carried out for Inconel 718 at room temperature to investigate the growth characteristics of a small crack. It was found that : (1) The crack initiated at the grain boundary and then propagated as a transgranular crack. (2) When the stress level was higher than the fatigue limit, the fatigue life was mainly controlled by the growth life of a crack smaller than 1mm. (3) The fatigue limit was a limiting stress for the crack propagation. (4) At low stress levels (σa/σ0.2a : stress amplitude, σ0.2 : 0.2% proof stress), the crack growth rate was determined by the stress intensity factor range ΔK ; and at high stress levels (σa/σ0.2>0.6), it was determined by the small crack growth law.. |
| 73. |
皮籠石 紀雄, 陳 強, 西谷 弘信, 後藤 真宏, 田中 秀穂, Ni基超合金の高温における疲労き裂伝ぱ抵抗, 日本機械学会論文集. A編, 1997.11, Rotating bending fatigue tests were carried out for Inconel 718 at room temperature and elevated temperatures of 300℃, 500℃ and 600℃ to investigate the influence of temperature on the fatigue crack growth resistance. The crack growth rate can be expressed by the small crack growth law, dl/dN=C_1σ^n_al=C_2(σ_a/σ_B)^nl, at all the temperatures, where σ_B, σ_a and l are the tensile strength, the stress amplitude and the crack length, and C_1,C_2 and n are constants. Therefore, the resistance to crack growth was evaluated using the small crack growth law. The fatigue crack growth resistance decreased with the increase of temperature.. |
| 74. |
皮篭石 紀雄, 陳 強, 田中 秀穂, 前野 一朗, 清藤 純一, 高温におけるNi基超合金の切欠強度, 日本機械学会論文集. A編, 1996.04, Because of its excellent mechanical properties at elevated temperature, a nickel-base superalloy has been widely used in the aerospace industry and nuclear power plants. In this study, rotating bending fatigue tests were carried out for Inconel 718 at room temperature and elevated temperatures of 300 °C, 400 °C and 500 °C to investigate the notch sensitivity at the elevated temperatures. It was found that the fatigue limits of plain specimens were higher at the elevated temperatures than at room temperature, which might be due to the suppression of the crack initiation at the elevated temperatures, however, the resistance to crack growth became smaller at the elevated temperatures than at room temperature. Therefore, the fatigue strength of a notched specimen, in which a crack initiated easily owing to the stress concentration introduced, was lower at the elevated temperatures than at room temperature. Consequently, the fatigue strength reduction factor was larger at the elevated temperatures than at room temperature.. |
| 75. |
皮篭石 紀雄, 陳 強, 田中 秀穂, 前野 一朗, 清藤 純一, 高温におけるNi基超合金の切欠強度, 日本機械学会論文集. A編, 1996.04, Because of its excellent mechanical properties at elevated temperature, a nickel-base superalloy has been widely used in the aerospace industry and nuclear power plants. In this study, rotating bending fatigue tests were carried out for Inconel 718 at room temperature and elevated temperatures of 300°C, 400°C and 500°C to investigate the notch sensitivity at the elevated temperatures. It was found that the fatigue limits of plain specimens were higher at the elevated temperatures than at room temperature, which might be due to the suppression of the crack initiation at the elevated temperatures, however, the resistance to crack growth became smaller at the elevated temperatures than at room temperature. Therefore, the fatigue strength of a notched specimen, in which a crack initiated easily owing to the stress concentration introduced, was lower at the elevated temperatures than at room temperature. Consequently, the fatigue strength reduction factor was larger at the elevated temperatures than at room temperature.. |
| 76. |
前野一朗, 陳強, 皮篭石紀雄, 田中秀穂, 清藤純一, Ni基超合金の疲労強度に及ぼす研削加工の影響, 精密工学会九州支部地方講演会講演論文集, 1995.11. |
| 77. |
瀬戸洋一, 皮篭石紀雄, 田中秀穂, 陳強, 泊誠, Ni基超合金の研削加工材の高温疲労強度, 精密工学会九州支部地方講演会講演論文集, 1995.11. |
| 78. |
有川俊, 皮篭石紀雄, 田中秀穂, 陳強, 切欠感度の異なる材料における研削加工材の回転曲げ疲労強度, 精密工学会九州支部地方講演会講演論文集, 1995.11. |
| 79. |
Xiaohong Shao, Qiang Chen, Zhen-Zhen Peng, Kazuhiro Kitamura, Xiu-Liang Ma, Deformation-induced redistribution of solute atoms in an Mg-Zn-Y alloy, THERMEC’ 2018, 2018.07. |
| 80. |
N. Kawagoishi, Q. Chen, H. Nisitani, Significance of the small crack growth law and its practical application, Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 2021.08, The effects of microstructure and specimen size on the fatigue crack growth rate of an annealed 0.42 C steel were investigated under uniaxial fatigue loading in air. Although a dramatic fluctuation of crack growth rate was found in the propagation process of microstructurally small cracks, the mean value of crack growth rate can be evaluated by a simple mechanical parameter, σanl (l, crack length; n, constant), under high stress levels where small-scale yielding conditions are exceeded. This parameter is also effective for cracks larger than 1 to 2 mm under high stress levels, as long as the finite boundary effect of a specimen on the driving force of crack propagation is considered. The crack growth rate of the alloy was described as a function of stress amplitude and crack length in terms of two mechanical parameters, σanl and ΔK. The applicable conditions of the two parameters were discussed and manifested.. |
