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EXPERIMENTAL AND THEORETICAL STUDY ON NUMERICAL DENSITY EVOLUTION OF SHORT FATIGUE CRACKS 被引量:2
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作者 方飙 洪友士 白以龙 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1995年第2期144-152,共9页
Fatigue testing was performed using a kind of triangular shaped specimen to obtain the characteristics of numerical density evolution for short cracks at the primary stage of fatigue damage. The material concerned is ... Fatigue testing was performed using a kind of triangular shaped specimen to obtain the characteristics of numerical density evolution for short cracks at the primary stage of fatigue damage. The material concerned is a structural alloy steel. The experimental results show that the numerical density of short cracks reaches the maximum value when crack length is slightly less than the average grain diameter, indicating grain boundary is the main barrier for short crack extension. Based on the experimental observations and related theory, the expressions for growth velocity and nucleation rate of short cracks have been proposed. With the solution to phase space conservation equation, the theoretical results of numerical density evolution for short cracks were obtained, which were in agreement with our experimental measurements. 展开更多
关键词 short fatigue cracks CRACK NUMERICAL DENSITY fatigue DAMAGE EVOLUTION
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GROWTH BEHAVIOR OF SHORT FATIGUE CRACKS FOR ALUMINUM- LITHIUM ALLOY 8090 被引量:1
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作者 Chen Zheng Northwestern Polytechnical University 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 1991年第4期380-385,共6页
The growth behaviors of short through cracks (0.2 < △a < 2.2mm) and long cracks are compared using CT type specimens in aluminum-lithium alloy 8090 T651. It is found that the short cracks grow much more than lo... The growth behaviors of short through cracks (0.2 < △a < 2.2mm) and long cracks are compared using CT type specimens in aluminum-lithium alloy 8090 T651. It is found that the short cracks grow much more than long ones and are observed to grow at the stress intensity ranges far below the long crack threshold. The distinction of growth bahavior between short and long cracks is attributed to the difference of their crack closure effect. The growth behavior of short cracks can be rationalized with that of long ones in terms of effective stress intensity ranges. The upper demarcation value of short through cracks for aluminum-lithium alloy 8090 is presented. 展开更多
关键词 this FIGURE LITHIUM ALLOY 8090 GROWTH BEHAVIOR OF short fatigue cracks FOR ALUMINUM
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Size Evolution of the Surface Short Fatigue Cracks of 1Cr18Ni9Ti Weld Metal
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作者 Yongxiang ZHAO 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2003年第2期129-132,共4页
Size evolution of the surface short fatigue cracks of lCrl8Ni'9Ti weld metal was investigated. A local viewpoint is applied to be agreement with a so-called 'effectively short fatigue crack criterion'. Att... Size evolution of the surface short fatigue cracks of lCrl8Ni'9Ti weld metal was investigated. A local viewpoint is applied to be agreement with a so-called 'effectively short fatigue crack criterion'. Attention was paid to the dominant effectively short fatigue crack (DESFC) initiation zone and the zones ahead of the DESFC tips. The results revealed that the evolutionary size shows a significant character of microstructural short crack (MSC) and physical short crack (PSC) stages. In the MSC stage, fatigue damage is due to mainly the initiation and irregular growth of the effectively short fatigue cracks (ESFCs). In the PSC stage, the damage is conversely due to mainly the DESFC growth and partially, the growth of the ESFCs and the coalescence of the ESFCs themselves with the DESFC. The process involves from a non-ordered/chaotic state in the initiation of MSC stage, gradually to an independently random state at the transition point between the MSC and PSC stages and then, to an ordered/history-dependent random state. Interactive effect of the collective cracks is stronger and shows an increase in the MSC stage, it reaches a maximum value at the transition point and then, tends to a decrease in the PSC stage. The DESFC acts as a result of the interactive cracks and thus, is deemed suitable to describe the behaviour of collective cracks. 展开更多
关键词 short fatigue crack Damage evolution ICrl8Ni9Ti steel Weld metal
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GROWTH OF SHORT CRACKS OF A537CLI STEEL UNDER FATIGUE LOADING IN 3.5% NaCl SOLUTION
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《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1989年第9期167-171,共5页
The effects of environmental media,both in atmosphere and in 3.5% NaCl aqueous solution, on the growth of short cracks in comparison with the long ones have been investigated under fatigue loading on the specimens of ... The effects of environmental media,both in atmosphere and in 3.5% NaCl aqueous solution, on the growth of short cracks in comparison with the long ones have been investigated under fatigue loading on the specimens of single-edge crack about 0.05—0.15 mm for A537CLI steel.The growth rate of short cracks is faster than those of long ones around the threshoht stress intensity.The threshold stress intensity for short crack growth decreases with de- creasing crack length.The acceleration effect of the salt water,as compared with atmosphere environment,on the growth of short cracks under fatigue is much greater than that on the growth of long cracks. 展开更多
关键词 short fatigue crack offshore platform steel environment medium threshold stress intensity
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Influence of Rare Earth Element on Short Fatigue Crack Threshold for Al-Li Alloy 2090 被引量:2
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作者 陈铮 倪永峰 何明 《Journal of Rare Earths》 SCIE EI CAS CSCD 1994年第4期268-273,共6页
Curves of △Kth vs.△ath and △Kcl·th vs.△ath for aluminum-lithium alloy 2090 have been determined and compared with those for traditional aluminum alloy 2024.The growth resistance of short fatigue cracks for al... Curves of △Kth vs.△ath and △Kcl·th vs.△ath for aluminum-lithium alloy 2090 have been determined and compared with those for traditional aluminum alloy 2024.The growth resistance of short fatigue cracks for aluminum-lithium alloy 2090 is quantitatively evaluated.The essential reason resulting in stronger short cracks effect has been ascertained.Influence of cerium on the growth behavior of short fatigue cracks for aluminum-lithium alloy 2090 was investigated.The results show that by adding cerium into this alloy a significant improvement in △Ki can be achieved and at the same time △Kcl·th is increased.Consequently,the essential factor resulting in lower growth resistance of short fatigue cracks for this alloy is removed and the growth resistance of long and short fatigue cracks is increased. 展开更多
关键词 Aluminum-lithium alloy CERIUM short fatigue crack THRESHOLD
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SHORT FATIGUE CRACK BEHAVIOUR IN ISO-STRESS SPECIMENS 被引量:1
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作者 HOGN Youshi LU Yonghua ZHENG Zhemin Institute of Mechanics,Academia Sinica,Beijing,China Institute of Mechanics,Academia Sinica,Beijing 100080,China 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1990年第4期276-281,共6页
Fatigue tests were made on a vibration machine using specially designed specimens to investi- gate the initiation and propagation features of short fatigue cracks in a weld metal.The spec- imens were triangular in sha... Fatigue tests were made on a vibration machine using specially designed specimens to investi- gate the initiation and propagation features of short fatigue cracks in a weld metal.The spec- imens were triangular in shape so that when loaded as a cantilever beam the surface tensile stress is constant.Test results show that short fatigue cracks mainly originate from slip bands within ferrite grains.The development of short fatigue cracks is marked by a gradual increase in crack density with fatigue cycles.Coalescence of short cracks leads to crack propagation and the crack path is predominantly transgranular. 展开更多
关键词 iso—stress specimen short fatigue crack weld metal
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Influence Mechanism of Cerium on the Threshold of Short Fatigue Crack for Aluminum-lithium Alloy 2090
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作者 Zheng Chen, Yongxin Wang, Bing Liu, Xiaoling Li, Qilong Wei (School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China) 《Rare Metals》 SCIE EI CAS CSCD 2001年第1期32-37,共6页
The thresholds of short fatigue cracks for aluminum-lithium alloys 2090 and 2090+Ce are quantitatively evaluated. The essential reason resulting in stronger short crack effect has been ascertained. Influence of cerium... The thresholds of short fatigue cracks for aluminum-lithium alloys 2090 and 2090+Ce are quantitatively evaluated. The essential reason resulting in stronger short crack effect has been ascertained. Influence of cerium on the threshold of short fatigue cracks for aluminum-lithium alloy 2090 was investigated. The results show that, by adding Ce into this alloy, DeltaK(i) and DeltaK(Cl.th) are increased. The influence mechanism of Ce on the threshold of short fatigue crack for alloy 2090 was explored fi om the bound energy, T, phase, the energy of anti-phase boundary, the energy of super-lattice intrinsic stacking fault and the electron bonds. By adding Ce into alloy 2090, the bound energy of Cu atom in this alloy is increased; the effect of thinning and dispersing T, phase is obtained; the effect of increasing the energy of anti-phase boundary and decreasing the energy of super-lattice intrinsic stacking fault for delta ' phase can be achieved. 展开更多
关键词 aluminum-lithium alloy CE short fatigue crack bound energy fault energy
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THRESHOLD OF SHORT FATIGUE CRACK FOR Al-Li ALLOY 8090
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作者 CHEN Zheng Northwestern Polytechnical University,Xi′an,China Lab.No.401,Northwestern Polytechnical University,Xi′an 710072 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1991年第2期135-138,共4页
Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack... Threshold of fatigue for short through cracks for Al-Li alloy 8090 was evaluated to be lower than that of long cracks,and to decrease with the shortening of the crack length.The correla- tion among the threshold,crack wake,and crack tip shielding of the short fatigue cracks was discussed.The super demarcation length and lowest theoretical threshold of short through fa- tigue cracks were presented. 展开更多
关键词 Al-Li alloy short fatigue crack THRESHOLD crack closure effect crack tip shielding
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Nonequilibrium Statistical Modeling of Fatigue Crack Growth Behaviour
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作者 胡海云 邢修三 《Journal of Beijing Institute of Technology》 EI CAS 2001年第3期240-245,共6页
In order to study the influence of microstructural texture on the growth of short fatigue cracks in metals, the nonequilibrium statistical theory of fatigue fracture correlating a microscopic mechanism with the macros... In order to study the influence of microstructural texture on the growth of short fatigue cracks in metals, the nonequilibrium statistical theory of fatigue fracture correlating a microscopic mechanism with the macroscopic properties is modified to take into consideration the microstructural features of a material, thereby allowing a rationalisation of the experimental data of short fatigue crack growth and long fatigue crack growth. The nonequilibrium statistical theory thus developed relates the growth of cracks with a dislocation mechanism to simulate short fatigue crack growth with the long fatigue crack growth behaviour and predicts the fatigue crack growth rates throughout the fatigue lifetime. The results is finally compared with that of other fatigue theories. 展开更多
关键词 short fatigue crack long fatigue crack fluctuation growth rate nonequilibrium statistical theory
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Optimization of Preventive Grinding of Backup Roll against Contact Fatigue Cracking 被引量:3
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作者 DOUPeng LIYou-guo LIANGKai-ming BAIBing-zhe 《Journal of Iron and Steel Research International》 SCIE CAS CSCD 2005年第3期28-33,45,共7页
In order to optimize the current grinding procedure of the backup roll of 2050 continuously variable crown (CVC) mills, the behavior of rolling contact fatigue (RCF) cracking was investigated. Two RCF short cracks, in... In order to optimize the current grinding procedure of the backup roll of 2050 continuously variable crown (CVC) mills, the behavior of rolling contact fatigue (RCF) cracking was investigated. Two RCF short cracks, including vertical short crack and ratcheting short crack initiated from ratcheting, were observed. The behavior of both RCF cracks was analyzed in detail. Then a modified grinding procedure was proposed according to the behavior of RCF cracks and the preventive grinding strategy. 展开更多
关键词 rolling contact fatigue short crack vertical short crack ratcheting short crack 2050 CVC hot rolling mill preventive grinding
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Theoretical study on Manson-Coffin equation for physically short cracks and lifetime prediction 被引量:15
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作者 HU YanDong HU ZhiZhong CAO ShuZhen 《Science China(Technological Sciences)》 SCIE EI CAS 2012年第1期34-42,共9页
The Manson-Coffin equation has been widely applied to the prediction of fatigue lifetime.But this equation does not explicitly express the relation between the fatigue lifetime and the crack length.The present paper p... The Manson-Coffin equation has been widely applied to the prediction of fatigue lifetime.But this equation does not explicitly express the relation between the fatigue lifetime and the crack length.The present paper proposes that the grain size can be re-placed by the maximum non-damaging crack length.Thus,the growth rate will decrease to zero when the crack reaches this size.Combining with the theory of the fatigue short crack propagation,we derived the relations between physically short crack's initiation-propagation rates and material's mechanical properties,as well as crack length,stress and strain.With the derived relations,fatigue lifetime of short cracks can be successfully predicted by basic mechanical properties.Similar to the format of Manson-Coffin equation,our relations uncover the essence of Manson-Coffin equation which may reveal the short crack's initiation-propagation mechanism.Predictions of fatigue lifetime using our relations were compared with the results of well-known experiments.Good agreement is found in many aspects,such as coefficients,exponents,as well as fatigue life-times,especially for short cracks around 10 micrometers.Predictions on the short crack propagation rates are also compared for 16 types of carbon steels.Satisfactory consistency shows that our relations have wide applicability. 展开更多
关键词 fatigue short crack crack initiation lifetime prediction mechanical properties
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