65 results on '"Y.J. Xie"'
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2. Cold spray additive manufacturing of Invar 36 alloy: microstructure, thermal expansion and mechanical properties
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Jiang Wang, Longtao Liu, Shanqing Li, Renzhong Huang, Y.J. Xie, Hanlin Liao, Zhongming Ren, Chaoyue Chen, Ruixin Zhao, and Xiaoli Jin
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Materials science ,Polymers and Plastics ,Annealing (metallurgy) ,Mechanical Engineering ,Metals and Alloys ,Gas dynamic cold spray ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Grain growth ,Mechanics of Materials ,Residual stress ,Materials Chemistry ,Ceramics and Composites ,engineering ,Composite material ,0210 nano-technology ,Invar ,Tensile testing - Abstract
In this work, the Invar 36 alloys were manufactured using cold spray (CS) additive manufacturing technique. The systematic investigations were made on the microstructural evolution, thermal expansion and mechanical properties under as-sprayed (AS) and heat-treated (HT) conditions. XRD (X-ray diffraction) and ICP-AES (inductively coupled plasma atomic emission spectroscopy) analyses show that no phase transformation, oxidation, nor element content change have occurred. The X-ray computed tomography (XCT) exhibited a near fully dense structure with a porosity of 0.025% in the helium-produced sample under as-sprayed condition, whereas the nitrogen-produced samples produced at 5 MPa and 800 °C show more irregular pore defects. He-AS sample shows a more prominent grain refinement than that of nitrogen samples due to the more extensive plastic deformation. The post heat-treatment exhibited a promoted grain growth, inter-particle diffusion, as well as the formation of annealing twins. Between 25 °C and 200 °C, the nitrogen samples possessed lower CTE (coefficient of thermal expansion) values (1.53 × 10-6/°C) compared with those produced by casting and laser additive manufacturing. The He-AS samples exhibited a noticeable negative CTE value between 25 °C and 200 °C, which may due to the significant compressive residual stress (-272 MPa) compensating its displacement with temperature increase during CTE test. The N2-HT and He-HT Invar 36 samples present a notable balance between strength and ductility. In conclusion, the CS technique can be considered as a potential method to produce the Invar 36 component with high thermal and mechanical performance.
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- 2021
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3. A tale of two genera: Exotic Eucalyptus and Acacia species in China. 2. Plantation resource development
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R. J. Arnold, S.J. Midgley, H.R. Wang, J.Z. Luo, and Y.J. Xie
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Ecology ,biology ,Agroforestry ,Geography, Planning and Development ,Foundation (engineering) ,Acacia ,Climate change ,Forestry ,biology.organism_classification ,Eucalyptus ,Geography ,Resource development ,Wood processing ,Domestication ,China - Abstract
In China a substantial plantation industry involving 5.4 M ha of exotic eucalypts and up to 50 000 ha of exotic acacias, has been built on a foundation of collaborative R&D sponsored by both China and Australia over the past 40 years. Germplasm derived from some of the early collaboration still provides the majority of trees deployed in current eucalypt plantations in China. But, whilst the past 2 decades has been the best of times for plantation eucalypts in China, the past decade has simultaneously been the worst of times for plantation acacias. Improved plantation productivities achieved through R&D programs coupled with innovations in processing markedly increased the profitability of young eucalypt plantations; this provided strong market pull for expansion of these plantations. For exotic acacias though, plantation areas in China have declined over the past decade. Factors that have contributed to the contrasting fates of these species in China, along with their future outlooks, are reviewed in this report.
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- 2020
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4. A tale of two genera: exotic Eucalyptus and Acacia species in China. 1. Domestication and research
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R. J. Arnold, S.J. Midgley, J.Z. Luo, Y.J. Xie, and H.R. Wang
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Germplasm ,Ecology ,biology ,Agroforestry ,Geography, Planning and Development ,Acacia ,Forestry ,biology.organism_classification ,Eucalyptus ,Geography ,Southern china ,Genetic resources ,China ,Domestication ,Silviculture - Abstract
In China a substantial plantation industry, including 5.4 M ha of eucalypts and up to 50,000 ha of acacias, has been built on a foundation of R&D and germplasm acquisition for exotic eucalypt and acacia species over the past 40 years. From the 1980s through to the early 2000s a suite of Chinese-Australian collaborative R&D projects made major contributions to domestication, genetic improvement, silviculture and other aspects of plantation eucalypts and acacias in southern China. Even today, germplasm derived from earlier projects still provides the majority of planting stock deployed in China's current eucalypt plantations. For eucalypts, improvements in plantation productivities have been achieved through solid, well managed R&D programs. For acacias, despite work done in past decades to develop breeding populations and production capacities for improved seeds, genetic resources of acacias in China have deteriorated greatly in recent years. Factors affecting domestication and genetic improvement of both genera in China are reviewed in this report along with the research undertaken for both genera over the past 40 years.
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- 2020
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5. The effects of fabrication atmosphere condition on the microstructural and mechanical properties of laser direct manufactured stainless steel 17-4 PH
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Xuejun Chen, Y.J. Xie, Yulong Li, Chi Changtai, Wuyou Wang, Muqin Wang, Duoming Wang, Zhongjun Chen, and Cheng Xiangping
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Austenite ,Materials science ,Fabrication ,Polymers and Plastics ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Nitrogen ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Phase (matter) ,Ultimate tensile strength ,Materials Chemistry ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Dispersion (chemistry) ,Porosity - Abstract
The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4PH components fabricated by laser direct manufacturing (LDM) were investigated through measurements on phase constitution, porosity, tensile strength, fracture morphology, hardness and evolution of substrate temperature. Results showed that the samples produced in air atmosphere condition possessed higher tensile strength and hardness for both as-deposited and heat-treated states than that in Ar chamber condition, due to dispersion strengthening effect of amorphous oxide particles and nitrogen solution strengthening as a result of higher content of oxygen and nitrogen. The temperature of substrate heat accumulation was higher in Ar chamber condition, leading to dramatically lower porosity and more reverse austenite, which also contributed to the lower strength and hardness.
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- 2019
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6. Underlying fracture trends and triggering on Mode-II crack branching and kinking for quasi-brittle solids
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J. Li, Y.M. Cai, Y.J. Xie, and X.Y. Zheng
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Strain energy release rate ,Conservation law ,Materials science ,Mechanical Engineering ,0211 other engineering and technologies ,02 engineering and technology ,Mechanics ,Computer Science::Computational Geometry ,Physics::Classical Physics ,Instability ,Physics::Geophysics ,Condensed Matter::Materials Science ,020303 mechanical engineering & transports ,Fracture toughness ,0203 mechanical engineering ,Mechanics of Materials ,Fracture (geology) ,General Materials Science ,Brittle solids ,Fracture configurations ,021101 geological & geomatics engineering - Abstract
A geometrical model on multiple cracks initiation from boundary with singular stress fields has been proposed for the fracture analysis of Mode-II crack. The conservation law has been explored utilizing a partial integral path, from which an analytical solution of the energy release rate for multiple cracks initiation from a crack tip has been established. Some underlying fracture trends of cracks initiation from a crack tip, including crack side-branching and crack kinking, for quasi-static Mode-II deformation have been theoretically investigated, which implies actually some degree of instability for Mode-II fracture. The K-based criterions and fracture toughness for Mode-II crack side-branching and kinking have been defined. The fracture configurations of crack side-branching and kinking under Mode-II loading and corresponding fracture toughness predicted by the present modelling agree well with the experimental observations on the rock fracture reported in the literatures.
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- 2019
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7. A computational method of stress intensity factor for flat-oval cross-section thin-walled pipe
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Z.Y. Hu, C. Li, H.F. Zhao, B.F. Zhao, Y.J. Xie, Wei Yin, and L.Y. Xie
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0209 industrial biotechnology ,Materials science ,Mechanical Engineering ,Fracture mechanics ,02 engineering and technology ,Mechanics ,Bending ,Stress field ,Cross section (physics) ,020303 mechanical engineering & transports ,020901 industrial engineering & automation ,0203 mechanical engineering ,Mechanics of Materials ,Fracture (geology) ,General Materials Science ,Stress intensity factor ,Intensity (heat transfer) ,Parametric statistics - Abstract
As an important parameter of fracture criterion, stress intensity factor (SIF) is considered to be one metric of the singular stress field intensity near the crack tip, also a main parametric in fracture mechanics. Therefore, solving technique on the stress intensity factor takes an important role in engineering applications. In view of typical three-dimensional features of flat-oval thin-walled pipes, it is relatively tough to obtain the stress intensity factors for the special-shaped shells with multi-transverse cracks by classical methods. In this paper, a very simple method based on J2-integral and bending theory is proposed to calculate the SIFs. Examples demonstrate that this technique is feasible, especially, that, suitable for the determination of the stress intensity factors of three-dimensional complicated structures. And the results show that not only the solution process is simple and available, but also the closed-form solutions can be derived effectively.
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- 2019
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8. Mode-I stress intensity factors for cracked special-shaped shells under bending
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Y.J. Xie, H. Yuan, and W.J. Liu
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Conservation law ,Materials science ,Mechanical Engineering ,0211 other engineering and technologies ,Mode (statistics) ,Shell (structure) ,02 engineering and technology ,Bending ,Mechanics ,Finite element method ,Stress (mechanics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,General Materials Science ,Beam (structure) ,Stress intensity factor ,021101 geological & geomatics engineering - Abstract
The slender special-shaped shells possess both shell and beam characteristics, which are widely used in practical engineering. A slender special-shaped shell under bending with some complex cracks, such as a frost flower-shaped crack and circumferential periodic cracks in a pipeline, is actually a typical three-dimensional complex crack problem with many different singular stress fields and stress intensity factors. In the present article, a very simple and practical technique based on the elementary mechanics and the concept of the conservation law is proposed to determine the stress intensity factors. The results from present method are shown to agree well with available solutions and FEM. In particular, the present method can also be easily applied to the other similar cracked structural shells.
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- 2019
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9. Windows to trigger crack branching for cracked solids under mixed Mode-I/II loading
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W.J. Yuan, Y.J. Xie, and H. Yuan
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Mechanics of Materials ,Applied Mathematics ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Condensed Matter Physics - Published
- 2022
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10. Synthesis of carbon nanotube reinforced Al matrix composite coatings via cold spray deposition
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Hongjian Wu, Xingchen Yan, Zhanqiu Tan, Zhiqiang Li, Xinliang Xie, Hanlin Liao, Y.J. Xie, Shuohong Gao, Gang Ji, Chaoyue Chen, Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), Université de Technologie de Belfort-Montbeliard (UTBM)-Université de Bourgogne (UB)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS), Institute of Mechanics, Materials and Civil Engineering [Louvain] (IMMC), Université Catholique de Louvain = Catholic University of Louvain (UCL), Unité Matériaux et Transformations - UMR 8207 (UMET), Centrale Lille-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Shanghai Jiao Tong University [Shanghai], University of Shanghai [Shanghai], Laboratoire Interdisciplinaire Carnot de Bourgogne [Dijon] (LICB), Université de Bourgogne (UB)-Université de Technologie de Belfort-Montbeliard (UTBM)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centrale Lille Institut (CLIL), UCL - SST/IMMC/IMAP - Materials and process engineering, Univ. Bourgogne Franche-Comté - ICB UMR 6303, CNRS, Univ. Lille - Unité Matériaux et Transformations, Shanghai Jiao Tong University - State Key Laboratory of Metal Matrix Composites, Shanghai University - State Key Laboratory of Advanced Special Steels, and Guangdong Academy of Sciences - National Engineering Laboratory for Modern Materials Surface Engineering Technology
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Materials science ,Composite number ,Gas dynamic cold spray ,02 engineering and technology ,Carbon nanotube ,engineering.material ,Carbon nanotube reinforced ,01 natural sciences ,law.invention ,Coating ,law ,0103 physical sciences ,Materials Chemistry ,Composite material ,Plastic deformation ,Ball mill ,Mechanical property ,010302 applied physics ,Al matrix composite ,Cold spray ,Surfaces and Interfaces ,General Chemistry ,[CHIM.MATE]Chemical Sciences/Material chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Surfaces, Coatings and Films ,engineering ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Particle ,0210 nano-technology ,Metallic bonding - Abstract
International audience; For the fabrication of high-strength carbon nanotube (CNT) reinforced Al matrix composites, the uniform dispersion, strong interface bonding and high structural integrity of CNTs have been regarded as the three most important issues. In this work, two distinct approaches, namely high shear dispersion (HSD) and shift-speed ball milling (SSBM), were applied to disperse CNTs (1.5 wt%) into pure Al powders. These two kinds of CNT/Al composite powders as well as the pure Al powder (as a comparison) were deposited onto stainless steel plates by cold spraying using different processing parameters. The velocity and the temperature of the particle prior to impact was simulated by the commercial code of Fluent. The deposition efficiency, microstructure evolution, as well as the distribution and structural integrity of CNTs in the composite coatings produced from different starting powders were comparatively investigated in terms of X-ray diffraction (XRD), Raman spectra, and electron back scanning diffraction (EBSD). According to the XRD and Raman analysis, no new phases such as oxides or brittle Al4C3 were detectable in both CNT/Al composite coatings. Some structural damages of CNTs were found in both composite coatings, especially the one fabricated from HSD composite powder. The dispersion of CNTs onto Al particle surfaces by HSD approach did not achieve a significant strengthening effect on the composite coatings, but adversely affected the metallic bonding of the particles and the substrate. The microhardness of the CNT/Al composite coating produced from SSBM powders reached around ~115 HV0.1, showing a significant improvement compared to the pure Al coating mainly due to the grain refinement and CNTs strengthening.
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- 2021
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11. Geometrical effect of a notch tip on fracture toughness test
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W.J. Yuan and Y.J. Xie
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Applied Mathematics ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
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12. Disturbance effect of weak Mode-II loading on the fracture of Mode-I crack
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H. Yuan, Y.J. Xie, and W. Wang
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2022
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13. Instability of cracks initiation from a mixed-mode crack tip with iso-stress intensity factors KI and KII
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Y.J. Xie, W.J. Yuan, X.W. Cui, X.Y. Zheng, Y. Wang, and X.H. Li
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Strain energy release rate ,Materials science ,Applied Mathematics ,Mechanical Engineering ,0211 other engineering and technologies ,02 engineering and technology ,Mechanics ,Condensed Matter Physics ,Mixed mode ,Instability ,Intensity (physics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Present method ,Critical energy ,Fracture (geology) ,General Materials Science ,Stress intensity factor ,021101 geological & geomatics engineering - Abstract
For a special case of mixed-mode crack with iso-stress intensity factors KI and KII, the instability of cracks initiation from a crack tip has been investigated based on the principle of the energy-based driving force. By using the J i -integrals over the crack boundary, the fracture modelling and relevant energy release rate on the multiple-crack initiation have been formulized. It has been found that when stress intensity factors KI and KII close to each other, more possible forms of multiple-cracks initiation from a crack tip may occur theoretically including the crack side-branching and kinking, which is remarkable and conducive to better understand the complex fractural phenomena in engineering and fracture tests. By using the present method, which part of the crack tip boundary fracture can be identified and the relevant critical energy release rate can be found.
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- 2018
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14. Influence of Cr addition on the interface purification of vacuum brazed NiCr-Cr 3 C 2 coatings on single crystal superalloy
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Y.J. Xie, Wenqin Wang, Xiuwen Han, Muqin Wang, Chi Changtai, Xuejun Chen, and Duoming Wang
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010302 applied physics ,Materials science ,Diffusion ,Metallurgy ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Surfaces, Coatings and Films ,Coating ,Phase (matter) ,0103 physical sciences ,Materials Chemistry ,engineering ,Brazing ,Nichrome ,0210 nano-technology ,Base metal ,Layer (electronics) - Abstract
In order to improve the high temperature wear- and oxidation resistance of single crystal superalloy, NiCr-Cr3C2 coatings were vacuum brazed on the surface. Different weight ratios of Cr were added into the coatings to control the diffusion of Si and C into the base metal, which would be harmful to the base metal stability. The results show that, when no Cr was added into the coatings, a layer of Ni3Si phase at the interface and MC precipitates in base metal were produced. With the increase of the Cr addition, the coating/base metal interface was gradually purified. The Ni3Si layer and the MC precipitates disappeared when the Cr addition increased to 30 wt% and an interface was clearly presented with the γ′ phases on both sides epitaxially growing on some extent. After 200 thermal fatigue cycles, the total crack lengths were measured, which decreased with increasing Cr addition, indicating that the thermal fatigue resistance was improved.
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- 2017
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15. Tribological and corrosion behaviors of Zr-doped graphite-like carbon nanostructured coatings on Ti6Al4V alloy
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W.Q. Bai, Li Lingling, X.L. Wang, Y.J. Xie, J.P. Tu, and C.D. Gu
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Corrosion ,symbols.namesake ,Materials Chemistry ,Graphite ,Composite material ,Nanocomposite ,Metallurgy ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,Tribology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry ,symbols ,0210 nano-technology ,Raman spectroscopy ,Carbon - Abstract
Biomedical Ti6Al4V alloy exhibits excellent mechanical and anti-corrosion properties but poor wear resistance. In order to improve the combination performance of Ti6Al4V alloy, Zr-doped graphite-like carbon (GLC) nanomultilayer and nanocomposite coatings are deposited by magnetron sputtering. The microstructures of the coatings are characterized by transmission electron microscopy (TEM) and Raman spectroscopy. The Zr-doped GLC nanomultilayer shows low friction coefficient and wear rate at applied loads of 1 N and 3 N in Hank's solution. In addition, both the Zr-doped GLC nanomultilayer and nanocomposite coatings present high corrosion resistance, which results from the corrosion-resistant GLC and zirconium oxide. Compared to the Zr-doped GLC nanocomposite, the nanomultilayer is more promising in the applications under simultaneously tribological and corrosive conditions.
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- 2017
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16. Adhesion and tribological properties of gradient designed a-C film on ultrahigh molecular weight polyethylene
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X.L. Wang, G. Jin, W.Q. Bai, Y.J. Xie, Li Lingling, and J.P. Tu
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010302 applied physics ,Equiaxed crystals ,Materials science ,Metals and Alloys ,Biasing ,02 engineering and technology ,Surfaces and Interfaces ,Sputter deposition ,Tribology ,Nanoindentation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Film coating ,Amorphous carbon ,0103 physical sciences ,Materials Chemistry ,Composite material ,0210 nano-technology ,Tribometer - Abstract
Amorphous carbon (a-C) film is deposited with a gradient designed bias voltage on the ultrahigh molecular weight polyethylene (UHMWPE) substrates and Si3N4 balls via a closed field unbalanced magnetron sputtering. The designed bias voltage continuously increases from − 40 V to − 80 V with two different increasing rate. The film with a thickness of approximately 1000 nm is made up of equiaxed grains with size of around 20 nm. Nanoindentation tests show that the hardness of the UHMWPE increases from 44 MPa to 2.16 GPa after deposition of a-C film with gradient designed bias voltage. The wear rate and friction coefficient of the a-C film sliding against a-C films coated on Si3N4 balls is tested in air and Hank's solution by means of a reciprocating tribometer. The a-C film deposited with gradient bias voltage exhibits superior adhesion and tribological performance, compared with those deposited with balanced bias voltage. The a-C film wearing against Si3N4 balls with a-C film coating shows a lower wear rate, compared with a-C films wearing against uncoated balls, decreasing from 1.95 × 10− 15 m3 N− 1 m− 1 to 1.23 × 10− 15 m3 N− 1 m− 1. There is a further enhancement of the anti-wear performance in Hank's solution.
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- 2017
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17. Corrosion and tribocorrosion performance of M (M Ta, Ti) doped amorphous carbon multilayers in Hank's solution
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Y.J. Xie, J.P. Tu, G. Jin, Li Lingling, X.L. Wang, Liu Dongguang, and W.Q. Bai
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010302 applied physics ,Materials science ,Tribocorrosion ,Metallurgy ,Doping ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Surfaces, Coatings and Films ,Corrosion ,Amorphous carbon ,Breakage ,Residual stress ,0103 physical sciences ,Materials Chemistry ,Artificial joints ,0210 nano-technology - Abstract
Amorphous carbon (a-C) and Ta- or Ti-doped a-C multilayer films are deposited onto Ti6Al4V alloy by an industrial closed field unbalanced magnetron sputtering. The corrosion and tribocorrosion performances of these films are investigated in Hank's solution at 37 °C. The a-C film exhibits enhanced wear and corrosion resistance compared with the bare Ti6Al4V alloy, but the cracks propagate during the tribocorrosion process, which leads to serious breakage. Interestingly, the tribocorrosion resistance of a-C film is improved by introducing Ta- or Ti-doped multilayered structure. The high mechanical properties (high hardness and low residual stress), good corrosion, and wear resistance of Ta- and Ti-doped a-C multilayer films make them excellent protective materials for artificial joints.
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- 2016
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18. Developing new microstructure through laser melting of electrospark layer of precipitation hardened nickel based superalloy
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Hamid Reza Shahverdi, Y.J. Xie, M. Ebrahimnia, and F. Malek Ghaini
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Materials science ,Alloy ,Metallurgy ,Laser beam welding ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Grain size ,020501 mining & metallurgy ,Superalloy ,Precipitation hardening ,0205 materials engineering ,engineering ,General Materials Science ,0210 nano-technology ,Electrospark deposition ,Layer (electronics) - Abstract
Highly oriented fine microstructure was achieved through laser melting of electrospark layer of a precipitation hardened nickel based superalloy. Using electron back scattered diffraction analysis, it was found that the new layer has preferred orientation toward the surface. This microstructure grows epitaxially on the electrospark layer, which consists of very fine grains. Having lower elemental segregation and finer grain size, this new modified microstructure has higher hot cracking resistance compared to the conventional autogenous laser weld microstructure on cast alloy.
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- 2016
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19. An integrated statistical and data-driven framework for supporting flood risk analysis under climate change
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Xiaosheng Qin, Y.J. Xie, and Yan Lu
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010504 meteorology & atmospheric sciences ,Flood myth ,Meteorology ,Hydrological modelling ,0208 environmental biotechnology ,Climate change ,02 engineering and technology ,01 natural sciences ,020801 environmental engineering ,HadCM3 ,Climatology ,100-year flood ,Generalized extreme value distribution ,Range (statistics) ,Environmental science ,0105 earth and related environmental sciences ,Water Science and Technology ,Downscaling - Abstract
Summary An integrated statistical and data-driven (ISD) framework was proposed for analyzing river flows and flood frequencies in the Duhe River Basin, China, under climate change. The proposed framework involved four major components: (i) a hybrid model based on ASD (Automated regression-based Statistical Downscaling tool) and KNN (K-nearest neighbor) was used for downscaling rainfall and CDEN (Conditional Density Estimate Network) was applied for downscaling minimum temperature and relative humidity from global circulation models (GCMs) to local weather stations; (ii) Bayesian neural network (BNN) was used for simulating monthly river flows based on projected weather information; (iii) KNN was applied for converting monthly flow to daily time series; (iv) Generalized Extreme Value (GEV) distribution was adopted for flood frequency analysis. In this study, the variables from CGCM3 A2 and HadCM3 A2 scenarios were employed as the large-scale predictors. The results indicated that the maximum monthly and annual runoffs would both increase under CGCM3 and HadCM3 A2 emission scenarios at the middle and end of this century. The flood risk in the study area would generally increase with a widening uncertainty range. Compared with traditional approaches, the proposed framework takes the full advantages of a series of statistical and data-driven methods and offers a parsimonious way of projecting flood risks under climatic change conditions.
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- 2016
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20. Enhancement of adhesion by a transition layer: Deposition of a-C film on ultrahigh molecular weight polyethylene (UHMWPE) by magnetron sputtering
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Li Lingling, J.P. Tu, W.Q. Bai, Y.J. Xie, F.F. He, X.L. Wang, and G. Jin
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Materials science ,General Physics and Astronomy ,Biasing ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Adhesion ,Substrate (electronics) ,Tribology ,Sputter deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Amorphous carbon ,Composite material ,0210 nano-technology ,Deposition (law) ,Tribometer - Abstract
An amorphous carbon (a-C) film is deposited on the plasma-treated UHMWPE substrate using a closed field unbalanced magnetron sputtering to improve its tribological properties. During the plasma treatment period, a transition layer is prepared by high energy ion bombardment at a bias voltage of −500 V to enhance the adhesion between the a-C film and the substrate. The mechanical and tribological properties of the a-C film were evaluated by nano-indentation and ball-on-disk tribometer. After deposition of a-C film with a thickness 900 nm, the nano-hardness of UHMWPE significantly increases from 47 MPa to 720 MPa and the wear rate decreases from 9.82 × 10 −15 m 3 N −1 m −1 to 4.78 × 10 −15 m 3 N −1 m −1 in bovine calf serum solution. The formation of the transition layer is believed to be the reason why the vertical adhesion between the a-C film and the UHMWPE substrate is enhanced.
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- 2016
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21. Disturbance effects of weak Mode-II loading on K-based Mode-I fracture toughness test
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Y.J. Xie and H. Yuan
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Disturbance (geology) ,Materials science ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Work (physics) ,Mode (statistics) ,Experimental data ,Structural engineering ,Condensed Matter Physics ,Experimental data processing ,Fracture toughness ,Fracture (geology) ,General Materials Science ,business - Abstract
It is well known that making of specimens, experimental set up, fixtures and testing procedure could inevitably affect the experimental accuracy, which will actually induce the disturbance from weak Mode-II loading on the specimen in K-based Mode-I fracture toughness tests. How to quantitatively analyse the disturbance effects is quite interesting and challenging work. In present article, an energy-based modelling on multiple underlying cracks initiation from a crack tip has been suggested to capture and quantify the disturbance effects. Conventional experimental data processing will lead to higher Mode-I fracture toughness values, which would affect the accuracy of fracture assessment, and cannot truly reflect the fracture property of materials. The current investigation has revealed that three theoretical predictable values of K-based Mode-I fracture toughness may be measured in tests if weak Mode-II loading acting on the specimen is inevitable, which is helpful to identify the real value of the fracture toughness and better understand scattered experimental data.
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- 2020
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22. Calculation of characteristic size and fatigue life of structural members with blunt notches
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Xianbing Xu, S.L. Liu, C. Li, L.Y. Xie, T. Mu, and Y.J. Xie
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Stress gradient ,Critical distance ,Characteristic length ,business.industry ,Mechanical Engineering ,0211 other engineering and technologies ,Fatigue testing ,02 engineering and technology ,Unified Model ,Structural engineering ,Fatigue limit ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Crack size ,General Materials Science ,business ,021101 geological & geomatics engineering ,Mathematics - Abstract
In order to evaluate notch effects and size effects on fatigue performances, smooth specimens without stress gradient and a group of notched specimens particularly designed are investigated in this paper. From the perspective of probability, the statistical size effect of the latter is worth studying for bodies weakened by notches. A unified model of combination of the improved theory of critical distance (TCD), along with the concept of highly-stressed-volume (CHSV) is established to identify the initiation crack size, evaluate the fatigue strength, and determine the fatigue lifetime of notched members, and even similar large-scale components in high cycle fatigue regime. The predicted results are compared with the experimental data sets taken from literatures. Fortunately, we find that, the novel model not only inherits the generality of existing methods, such as TCD, but also provides necessary support for predictions of characteristic length and fatigue lifetime of components containing any blunt-notch geometries.
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- 2020
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23. Surface hardening of laser melting deposited 12CrNi2 alloy steel by enhanced plasma carburizing via hollow cathode discharge
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Zhang Dong, H.W. Kang, Y.J. Xie, X. Peng, M. Ebrahimnia, and Wei Zhang
- Subjects
010302 applied physics ,Materials science ,Metallurgy ,Alloy steel ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Indentation hardness ,Cathode ,Surfaces, Coatings and Films ,Carburizing ,law.invention ,law ,Martensite ,0103 physical sciences ,Volume fraction ,Materials Chemistry ,engineering ,0210 nano-technology ,Layer (electronics) - Abstract
Plasma carburizing of 12CrNi2 alloy steel fabricated by laser melting deposition was carried out in a propane-containing atmosphere at temperature of 930 °C with and without hollow cathode discharge (HCD). The generation of the HCD in the carburizing process was achieved by adding an auxiliary cathode opposite the alloy steel sample. The carburized samples were characterized by analysis of microstructure, microhardness and wear performance. The assistance of HCD increased the carbon concentration in the carburized layer and the case depth without changing the carburizing atmosphere and discharge voltage, indicating the improvement of carburizing kinetics. This leads to an increased volume fraction of acicular martensite and an increased the microhardness of the carburized layer as well as the improvement of the wear resistance of alloy steel.
- Published
- 2020
- Full Text
- View/download PDF
24. Potential fracture paths for cracked rocks under compressive-shear loading
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H. Yuan, Y.L. Duo, and Y.J. Xie
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Strain energy release rate ,Conservation law ,Materials science ,0211 other engineering and technologies ,Complex fracture ,02 engineering and technology ,Geotechnical Engineering and Engineering Geology ,Instability ,Compressive load ,Fracture toughness ,Shear (geology) ,Composite material ,021102 mining & metallurgy ,021101 geological & geomatics engineering - Abstract
An energy-based model on multiple cracks initiation from a crack tip has been proposed to capture the physical process of fracture, which can be used to predict and analyse the fracture behaviours of cracked rocks and rock-model materials under compressive-shear loading. The conservation law has been explored utilizing a partial integral path, from which an analytical solution of the energy release rate for multiple cracks initiation from a crack tip has been founded. Some underlying fracture behaviours on cracks initiation from a crack tip, including the crack kinking, side-branching, branching and tri-branching, have been theoretically investigated, which implies actually a degree of instability on a cracked rock under compressive-shear loading. The K-based criteria and fracture toughness for crack kinking, side-branching, branching and tri-branching have been defined. The predictions based on present modelling should help to refresh the understanding of some important experimental observations, such as so called wing cracks and secondary cracks observed in the experiments of cracked rock under compressive loading. As an alternative solution, the energy-based driving mechanism behind complex fracture phenomenon have been suggested.
- Published
- 2020
- Full Text
- View/download PDF
25. Underlying fracture trends on Mode-I crack multiple-branching
- Author
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W. Wang, H. Yuan, and Y.J. Xie
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Strain energy release rate ,Fracture toughness ,Materials science ,Mechanics of Materials ,Mechanical Engineering ,Crack initiation ,General Materials Science ,Fracture configurations ,Mechanics ,Impulse (physics) ,Branching (polymer chemistry) ,Instability - Abstract
An energy-based modelling has been proposed to capture the physical process of multiple cracks initiation from a Mode-I crack tip. The underlying fracture trends and instability on crack tri-branching, symmetric branching and side-branching induced by dominant Mode-I loading are formulized. The solutions of the energy release rate, crack initiation angles and K-based fracture criterion for multiple cracks initiation have been investigated. The upper limit on the number of possible crack initiation is given for a Mode-I crack. The discussions in present article indicate that some underlying fracture configurations for Mode-I crack can be triggered by using impulse loading. Many fracture behaviours for a Mode-I crack can be better explained and understanding based on the present theoretical modelling. The fracture toughness predicted by the present modelling and Griffith’s criterion agree well with experimental results.
- Published
- 2020
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26. Down-regulation of miR-1246 in cervical cancer tissues and its clinical significance
- Author
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Y. Yang, Y.J. Xie, Qian Xu, Yi Zhang, J.X. Chen, and Nianchun Shan
- Subjects
Pathology ,medicine.medical_specialty ,Colorectal cancer ,Down-Regulation ,Uterine Cervical Neoplasms ,Protein Serine-Threonine Kinases ,Transfection ,medicine.disease_cause ,Cell Line, Tumor ,microRNA ,medicine ,Humans ,Clinical significance ,Lung cancer ,Neoplasm Staging ,Cervical cancer ,Human papillomavirus 16 ,business.industry ,Papillomavirus Infections ,Obstetrics and Gynecology ,Oncogene Proteins, Viral ,Middle Aged ,Protein-Tyrosine Kinases ,Prognosis ,medicine.disease ,Gene Expression Regulation, Neoplastic ,Repressor Proteins ,MicroRNAs ,Real-time polymerase chain reaction ,Oncology ,Cancer research ,Female ,business ,Liver cancer ,Carcinogenesis ,HeLa Cells - Abstract
Objective MicroRNAs (miRNAs) are non-coding RNAs that regulate the expression of mRNAs by binding to their 3′-untranslated regions (UTRs). Accumulating evidences show that miRNAs are involved in tumorigenesis such as lung cancer, liver cancer, colon cancer, and cervical cancer. In this study, we focused on the expression of miR-1246 in clinical cervical cancer tissues as well as the relationship between miR-1246 and HPV16E6 infection status. Methods Real-time quantitative polymerase chain reaction technology was used to detect the expression of miR-1246 in 68 cervical cancer tissues and 52 normal tissues. The expression of miR-1246 also was tested in HPV16E6 negative cervical cell line (SiHa) or HPV16E6 positive cell line (C33A). Western blot was performed to detect the expression of DYRK1A after knocking down HPV16E6. Results Our data showed that the expression of miR-1246 was dramatically decreased in cervical cancer tissue, compared with normal control group (p=0.0012), and miR-1246 was negatively correlated with clinical stage and HPV16E6 infected status (p=0.0410), but no correlation was observed with age, tumor diameter, cervical invasion depth, lymph node metastasis, or vascular invasion (p>0.05). Knock down of HPV16E6 significantly raised DYRK1A protein expression targeted by miR-1246. Conclusions The expression of miR-1246 is negatively correlated with cervical cancer procedure as well as HPV16E6 infection status and the miR-1246 may act as a diagnostic biomarker for cervical cancer. In addition, HPV16E6 infection may be a major reason leading to decrease the expression of miR-1246 in cervical cancer. This finding contributes to deep understanding of the miR-1246 function in cervical carcinogenesis.
- Published
- 2015
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27. Fracture-based model of periodic-arrayed indentation for rock cutting
- Author
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Xiaozhi Hu, X. Z. Zhu, X. H. Wang, and Y.J. Xie
- Subjects
Stress (mechanics) ,Stress field ,Cracking ,Materials science ,Breakage ,Indentation ,Fracture (geology) ,Geotechnical engineering ,Fracture mechanics ,Composite material ,Geotechnical Engineering and Engineering Geology ,Stress intensity factor - Abstract
Periodic singular stress fields and K-dominant regions arise adjacent to sharp 90° indenter edges if an elastic substrate is subject to indentation with rigid, flat-ended and periodic indenters. The concept of indentation stress intensity factor Kind is convenient to describe such a singular indentation stress field, which is mathematically similar to that of a Mode-I crack. The singular indentation stress field is sufficient to induce surface cracking even if the substrate surface is free of any micro-cracks. This surface cracking mechanism generated from the flat-ended indentation potentially can play a significant role in damage analysis of rock cutting. During the rock-cutting processing, those periodic singular-stress fields will move along the rock surface, leading to continuous rock surface fracture. In this study, a fracture mechanics model is proposed for rock breakage by using an energy-based approach. The indentation stress intensity factor Kind and indentation cracking equation for rock-cutting/breakage have thus been formulated analytically.
- Published
- 2015
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28. Microstructural characteristics of the built up layer of a precipitation hardened nickel based superalloy by electrospark deposition
- Author
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Hamid Reza Shahverdi, M. Ebrahimnia, F. Malek Ghaini, and Y.J. Xie
- Subjects
Materials science ,Metallurgy ,Nucleation ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,Condensed Matter Physics ,Microstructure ,Surfaces, Coatings and Films ,Superalloy ,Precipitation hardening ,Coating ,Materials Chemistry ,engineering ,Texture (crystalline) ,Electrospark deposition ,Layer (electronics) - Abstract
Buildup of precipitation hardened nickel base superalloys by electro spark deposition due to the low heat input of the process has many attractions. Characterization of the microstructure of the ESD built up layer of IN738LC over an as-cast base metal is accomplished in this work. The grain structure and solidification texture of the coating are investigated by orientation imaging microscopy (OIM), optical and scanning electron microscopy. It is shown that the deposited layer is formed mainly through epitaxial nucleation and growth on the base metal structure while discontinuities acting as nucleation sites produce fine grains with independent orientations. It is shown that such independent grains can have a significant role in improving the integrity of the ESD built up layer, since they can act as crack arrest sites and make the coating more resistant to the propagation of liquation and solidification fissures. Moreover, it is found that nanosized γ′ precipitates exist in the coating indicating the high tendency of γ′ for precipitation even in the extremely high cooling rates involved in the ESD process. Hardness measurements indicated a higher hardness for the built up layer which is attributable to the finer microstructure of the coating.
- Published
- 2014
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29. Prediction of pregnancy outcomes with combined ultrasound scanning of yolk sacs and serum CA 125 determinations in early threatened abortion
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S.J. Chen, M. Chen, and Y.J. Xie
- Subjects
Reproductive Medicine ,Obstetrics and Gynecology - Published
- 2014
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30. Modelling of multiple crack-branching from Mode-I crack-tip in isotropic solids
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M. Cai, Y.J. Xie, W. Wang, Xiao Hu, X.H. Wang, and J. Li
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Strain energy release rate ,Conservation law ,Materials science ,Mechanical Engineering ,Isotropy ,Crack tip opening displacement ,Mode (statistics) ,Mechanics ,Physics::Classical Physics ,Crack growth resistance curve ,Physics::Geophysics ,Condensed Matter::Materials Science ,Cracking ,Crack closure ,Mechanics of Materials ,General Materials Science ,Composite material - Abstract
An energy-based fracture model for multiple crack-branching, or crack-tip shattering, has been proposed and formulized for the Mode-I crack-tip condition in isotropic solids. An analytical solution of the energy release rate for multiple crack-branching from a Mode-I crack tip has been established. The cracking angles have also been analytically derived. It shows that the Griffith’s theorem and conservation law can be applied to both the conventional Mode I crack extension and multiple crack-branching. The multiple crack-branching phenomena predicted by the present model are in good agreement with the experimental observations reported in the literature.
- Published
- 2013
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31. Emergence and rise of eucalypt veneer production in China
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S.J. Midgley, X.F. Chen, J.Z. Luo, R. J. Arnold, and Y.J. Xie
- Subjects
Geography ,Small diameter ,Ecology ,medicine.medical_treatment ,Geography, Planning and Development ,medicine ,Forestry ,Veneer ,China - Abstract
SUMMARY China's plywood production grew rapidly over the past 15 years from around 9 Mm3 yr-1 in the mid 1990s to over 55 M m3 yr-1 by 2011. Associated with this has been a proliferation of small-scale eucalypt veneer mills processing young (≤ 5 yrs) small diameter logs (mostly ≤ 12 cm small end diameter); by 2011 there were over 5000 such mills in China with a collective capacity to process well over 15.0 M m3 yr-1 of logs. We review key characteristics of this eucalypt veneer industry with special focus on three key regions for eucalypt veneer production in China. Factors that have spurred and facilitated the rapid growth of this industry are reviewed along with future challenges likely to emerge for China's eucalypt veneer industry.
- Published
- 2013
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32. Quasibrittle fracture beneath a flat bearing surface
- Author
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D.A. Hills and Y.J. Xie
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Bearing (mechanical) ,Materials science ,Fissure ,business.industry ,Mechanical Engineering ,Structural engineering ,Strength of materials ,law.invention ,medicine.anatomical_structure ,Fracture toughness ,Brittleness ,Mechanics of Materials ,law ,Indentation ,medicine ,Fracture (geology) ,General Materials Science ,Material properties ,business - Abstract
The problem of fracture of the quasibrittle and brittle material such as glass when subject to indentation by a relatively rigid, square-ended uniform punch is considered, using classical energy principles. The strain energy needed to form a crack adjacent to the punch edge is found, and from this the load needed to initiate fracture given. The calculation is of practical interest in the design rating of bearing blocks supporting structural glass. Additionally, it implies also the potential possibility to set up a very simple and practical technique for evaluating some strength-related properties of materials such as the fracture toughness using specimens without macro-pre-existing cracks.
- Published
- 2016
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- View/download PDF
33. Frictional contact induced crack initiation in incompressible substrate
- Author
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Xiao Hu, Y.J. Xie, and X.H. Wang
- Subjects
Strain energy release rate ,Materials science ,Critical load ,business.industry ,Mechanical Engineering ,Crack tip opening displacement ,Fracture mechanics ,Fretting ,Structural engineering ,Mechanics ,Physics::Classical Physics ,Crack growth resistance curve ,Physics::Geophysics ,Stress field ,Condensed Matter::Materials Science ,Crack closure ,Mechanics of Materials ,General Materials Science ,business - Abstract
Surface crack initiation in an incompressible substrate induced through frictional fretting contact is analyzed using an energy-based fracture mechanics model. A closed-form energy release rate for surface crack initiation at the contact boundary has been derived with the crack growth angle determined by the mixed mode singular stress field at the contact edge. The driving forces in the form of Ji-integral, the critical energy release rate and the critical load for crack initiation from the crack free surface have been formulated. The relations between the friction coefficient and crack initiation angle, critical load have been specified.
- Published
- 2011
- Full Text
- View/download PDF
34. Micro-indentation fracture from flat-ended cylindrical indenter
- Author
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Xiao Hu, J. Chen, K.Y. Lee, and Y.J. Xie
- Subjects
Materials science ,business.industry ,Mechanical Engineering ,Fracture mechanics ,Structural engineering ,Stress field ,Brittleness ,Contact mechanics ,Fracture toughness ,Mechanics of Materials ,Indentation ,Fracture (geology) ,General Materials Science ,Composite material ,business ,Stress intensity factor - Abstract
Unlike a Hertzian ring crack induced by a spherical indenter in absence of a singular stress field, a ring crack generated by a rigid flat cylindrical indenter can be explicitly linked to a K-dominant singular stress field at the perimeter of the flat indenter. This means microcrack initiation induced by a flat indenter and relevant properties such as the critical indentation load and fracture toughness can be formulated explicitly using the fracture mechanics approach. It is shown in this paper that the indentation stress intensity factor, K i I , for such a stress field is similar to that of a mode I crack. Based on the energy-releasing rate and the Griffith's theorem, a flat indentation cracking model has been proposed; the critical load and critical cracking angle for crack initiation are derived. A new concept of fracture toughness for negative mode I singular stress field,K i IC , has been defined and a relationship between K i and the traditional K IC has been derived. The experimental investigation validates the existence of such K i ,f rom which theK IC value of the glass had been determined to be 0.772 ± 0.003 MPa m 1/2 , agreeing well with the literature data. This analysis for indentation fracture or crack initiation due to surface contact of a flat indenter is particularly useful in determining K IC of brittle materials with dimensions in micro/nanoscales, e.g. thin films and other microstructures as flat micro/nano-indenters are available and can be used on various nano-indentation machines.
- Published
- 2011
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- View/download PDF
35. Study on Stress Intensity Factors for Circumferential Cracked Elliptical Pipes under Tension
- Author
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Wen Guang Wang, Y. M. Cai, and Y.J. Xie
- Subjects
Materials science ,business.industry ,Tension (physics) ,General Engineering ,Fracture (geology) ,Fracture mechanics ,Structural engineering ,Bending ,Virtual work ,business ,Finite element method ,Stress intensity factor - Abstract
Stress intensity factor is one of the most important parameters in fracture mechanics. Based on the principle of virtual work and bending theory, this paper proposes a method to estimate the stress intensity factor for circumferential cracked elliptical pipes and derive the expression of the stress intensity factor for circumferential cracked elliptical pipes under tension. The compare of the result of this method and finite element method shows this method is credible and convenient.
- Published
- 2011
- Full Text
- View/download PDF
36. A theoretical note on mode-I crack branching and kinking
- Author
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J. Chen, Xiao Hu, Y.J. Xie, Kang Y. Lee, and X.H. Wang
- Subjects
Strain energy release rate ,Conservation law ,Toughness ,Materials science ,Mechanical Engineering ,Mode (statistics) ,Crack tip opening displacement ,Mechanics ,Physics::Classical Physics ,Crack growth resistance curve ,Branching (polymer chemistry) ,Physics::Geophysics ,Condensed Matter::Materials Science ,Crack closure ,Mechanics of Materials ,High Energy Physics::Experiment ,General Materials Science ,Composite material - Abstract
An energy-based fracture mode has been derived for the mode-I crack branching and kinking. The classic J i -integral has been further explored by a new partial integral path and the analytical solution of the energy release rate for crack branching and kinking from a mode-I crack tip has been established. The crack branching/kinking angle has also been analytically derived. It shows that the Griffith’s theorem and conservation law can be applied to both mode-I crack extension and mode-I crack branching and kinking. The branching mechanism for quasi-static mode-I crack has been theoretically investigated. The branching toughness and the K-based criterion for crack branching have been defined. The crack branching phenomena predicted by the present model are in well agreement with the experimental observations reported in the literatures.
- Published
- 2011
- Full Text
- View/download PDF
37. A Theoretical Note on Mode I Crack Kinking and Branching
- Author
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Xiaozhi Hu, Y.J. Xie, and X.H. Wang
- Subjects
Strain energy release rate ,Toughness ,Conservation law ,Materials science ,General Engineering ,Crack tip opening displacement ,Mode (statistics) ,Mechanics ,Physics::Classical Physics ,Crack growth resistance curve ,Branching (polymer chemistry) ,Physics::Geophysics ,Condensed Matter::Materials Science ,Crack closure ,High Energy Physics::Experiment ,Composite material - Abstract
An energy-based fracture mode has been derived for the mode I crack kinking and branching. The classic -integral has been further explored by a new partial integral path and the analytical solution of the energy release rate for crack kinking and branching from a mode-I crack tip has been established. The crack kinking/branching angle has also been analytically derived. It shows that the Griffith’s theorem and conservation law can be applied to both model I crack extension and model I crack kinking and branching. The branching mechanism for quasi-static mode-I crack has been theoretically investigated. The branching toughness and the K-based criterion for crack branching have been defined. The crack branching phenomena predicted by the present model are in well agreement with the experimental observations reported in the literatures.
- Published
- 2010
- Full Text
- View/download PDF
38. Applications of conservation integral to indentation with a rigid punch
- Author
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Xiaozhi Hu, Kang Yong Lee, Y.J. Xie, and Y.M. Cai
- Subjects
Conservation law ,Materials science ,business.industry ,Mechanical Engineering ,Numerical analysis ,Structural engineering ,Mechanics ,Stress (mechanics) ,Stress field ,Singularity ,Brittleness ,Mechanics of Materials ,Indentation ,General Materials Science ,business ,Stress intensity factor - Abstract
When a substrate of the brittle material is indented by a relatively rigid, square-ended punch, a singular stress field and K-dominant region will arise at the near-surface adjacent to the punch corners. The singularity of this stress field is identical with the mode I crack. The stress intensity factor in this case represents the intensification of the stress fields induced by indentation. In present article, a new method to determine the stress intensity factors of the indentation problems is developed based on the conservation law. The physical meanings of the proposed method and some numerical analysis have been investigated.
- Published
- 2009
- Full Text
- View/download PDF
39. Stress intensity factors for cracked homogeneous and composite multi-channel beams
- Author
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Y.J. Xie, X.H. Wang, and Y.Y. Wang
- Subjects
T-beam ,Strain energy release rate ,Cracks ,Materials science ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Surface integral ,Boundary problem ,Composite number ,Structural engineering ,Condensed Matter Physics ,Fracture ,Materials Science(all) ,Mechanics of Materials ,Modelling and Simulation ,Modeling and Simulation ,Structural channel beams ,Fracture (geology) ,General Materials Science ,Virtual work ,business ,Stress intensity factor - Abstract
The homogeneous and composite multi-channel beams are a typical three-dimensional infinite boundary problem. For the cracks in such structures, a very simple method to determine the stress intensity factors has been proposed by using a new concept of the crack surface widening energy release rate and the principle of virtual work. This kind of the energy release rate can be defined by the curved surface integral and the work done by the external loads. From the present discussions a series of the stress intensity factors are derived for the channel and multi-channel beams. Additionally, the stress intensity factor for the cracked T beam can be evolved from the present results for multi-channel beams.
- Published
- 2007
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- View/download PDF
40. A Study of the Relationships Between Lexical Richness and Writing Quality: Taking the English Majors at Guangxi University as an Example
- Author
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Y. Shen and Y.J. Xie
- Subjects
Lexical density ,Computer science ,media_common.quotation_subject ,Quality (business) ,Species richness ,Writing quality ,English vocabulary ,Sophistication ,Linguistics ,media_common - Abstract
The present paper aims to investigate the correlation of lexical richness with writing quality by measuring lexical richness in EFL English writing. The research was performed by measuring timed compositions of 56 senior English majors with four indices of lexical richness, including text length, high frequency words, lexical density, and lexical sophistication. The finding of this study is that lexical richness is indeed taken into consideration in scoring the quality of English writing. The measure of the four indices of lexical richness can distinguish between the higher-scoring compositions and lower-scoring compositions, which shows, to a statistically significant extent, that lexical richness correlates with the quality of English writing. It is hoped that the findings of the present study will be useful for improving the teaching and learning of English vocabulary. KEYWORD: lexical richness; writing Quality; English majors
- Published
- 2015
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41. Stress intensity factor for cracked submarine pipeline with concrete cover
- Author
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Y.J. Xie and W. Tang
- Subjects
Strain energy release rate ,Engineering ,Environmental Engineering ,business.industry ,Pipeline (computing) ,Submarine ,Ocean Engineering ,Fracture mechanics ,Structural engineering ,Pipeline transport ,Submarine pipeline ,Geotechnical engineering ,business ,Stress intensity factor ,Concrete cover - Abstract
For the cracked submarine pipeline with concrete cover, a new method to estimate the stress intensity factor has been proposed based on the concept of the crack surface widening energy release rate. Unlike the classical crack extension energy release rate, the crack surface widening energy release rate can be expressed by the G*-integral and the elementary strength theory of materials for the submarine concrete-covered pipeline with the cracks. In present discussions, a series of solutions of the stress intensity factors in the closed form are derived for cracked pipeline. Analytical results show that the concrete layer covering the pipe is beneficial to the safety of the pipeline. The present method can also be applied to other form of submarine pipeline such as the cracked pipe-in-pipe pipeline.
- Published
- 2006
- Full Text
- View/download PDF
42. An analytical method on circumferential cracked submarine pipe-in-pipe system
- Author
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W. Tang and Y.J. Xie
- Subjects
Strain energy release rate ,Surface (mathematics) ,Engineering ,Series (mathematics) ,business.industry ,Surface integral ,Boundary (topology) ,Submarine ,Ocean Engineering ,Virtual work ,Structural engineering ,business ,Stress intensity factor - Abstract
For cracked submarine pipe-in-pipe system, as a typical three-dimensional finite boundary composite structure, a new and very simple method to determine the stress intensity factors has been proposed by using a new concept of crack surface widening energy release rate and the principle of virtual work. This kind of energy release rate can be defined by the curved surface integral and the work done by the external loads. From the present discussions a series of stress intensity factors are derived for the circumferential cracked pipeline. The practical examples show schematically that uncracked inner pipe may delay failure for the pipe-in-pipe structures.
- Published
- 2005
- Full Text
- View/download PDF
43. Application of -integral on cracked structural beams
- Author
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Y.J. Xie and X.H. Wang
- Subjects
Strain energy release rate ,Surface (mathematics) ,Materials science ,Series (mathematics) ,business.industry ,Metals and Alloys ,Strength theory ,Building and Construction ,Structural engineering ,Mechanics of Materials ,Present method ,Fracture (geology) ,business ,Stress intensity factor ,Civil and Structural Engineering - Abstract
For cracked engineering structural beams, a simple method to determine the stress intensity factors has been proposed based on a new concept of crack surface widening energy release rate. Unlike the classical crack extension energy release rate, the crack surface widening energy release rate can be expressed by the G ∗ -integral and elementary strength theory of materials for slender cracked three-dimensional structures. From present discussions, a series of exact solutions of stress intensity factors are derived for cracked structural T and I beams. The present method can also be applied to other cracked structural beams.
- Published
- 2004
- Full Text
- View/download PDF
44. Stress intensity factors for cracked rectangular cross-section thin-walled tubes
- Author
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X.H. Wang, Y.C. Lin, and Y.J. Xie
- Subjects
Surface (mathematics) ,Strain energy release rate ,Materials science ,Series (mathematics) ,business.industry ,Mechanical Engineering ,Thin walled ,Structural engineering ,Square (algebra) ,Cross section (physics) ,Mechanics of Materials ,mental disorders ,Polygon ,General Materials Science ,Composite material ,business ,Stress intensity factor - Abstract
For cracked structural rectangular thin-walled tubes, an exact and very simple method to determine the stress intensity factors has been proposed based on a new concept of crack surface widening energy release rate. Unlike the classical crack extension energy release rate, the crack surface widening energy release rate can be expressed by the G*-integral and elementary strength theory of materials for slender cracked structures. From present discussions, a series of new and exact solutions of stress intensity factors are derived for cracked rectangular and square tubes. The present method can also be applied to cracked polygon thin-walled tubes.
- Published
- 2004
- Full Text
- View/download PDF
45. Interaction of an electron bunch with a laser pulse in vacuum
- Author
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Q.S. Wang, Y.J. Xie, Zhigang Chen, N. Cao, L. Shao, Y.K. Ho, J. Pang, and Qing Kong
- Subjects
Physics ,Quantum optics ,Beam diameter ,Physics and Astronomy (miscellaneous) ,Scattering ,General Engineering ,General Physics and Astronomy ,Pulse duration ,Electron ,Laser ,law.invention ,Particle acceleration ,law ,Physics::Accelerator Physics ,Thermal emittance ,Atomic physics - Abstract
The output properties of electrons accelerated by the vacuum laser acceleration scheme CAS (capture and acceleration scenario) are addressed. The transport process of the electron bunch, the fraction of the CAS electrons of the incident electrons, the correlation of electron energy with position and scattering angle, the energy spectrum and angular distributions as well as the emittance of the outgoing electrons are studied at a laser intensity of a0=10. In addition, the effects of the laser intensity, beam width, and pulse duration on the properties of the output electrons are also examined. Physical explanations of those output characteristics are presented based on the mechanism behind the CAS scheme. The feasibility of CAS to become a realistic laser accelerator scheme is explored.
- Published
- 2004
- Full Text
- View/download PDF
46. Probabilistic fracture failure analysis of nuclear piping containing defects using R6 method
- Author
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Y.J. Xie, Y.C. Lin, and X.H. Wang
- Subjects
Nuclear and High Energy Physics ,Engineering ,Piping ,business.industry ,Mechanical Engineering ,Probabilistic logic ,Torsion (mechanics) ,Structural engineering ,Nuclear reactor ,law.invention ,Fracture toughness ,Nuclear Energy and Engineering ,law ,Nuclear power plant ,Bending moment ,General Materials Science ,Safety, Risk, Reliability and Quality ,business ,Waste Management and Disposal ,Stress intensity factor - Abstract
Failure analysis of in-service nuclear piping containing defects is an important subject in the nuclear power plants. Considering the uncertainties in various internal operating loadings and external forces, including earthquake and wind, flaw sizes, material fracture toughness and flow stress, this paper presents a probabilistic assessment methodology for in-service nuclear piping containing defects, which is especially designed for programming. A general sampling computation method of the stress intensity factor (SIF), in the form of the relationship between the SIF and the axial force, bending moment and torsion, is adopted in the probabilistic assessment methodology. This relationship has been successfully used in developing the software, Safety Assessment System of In-service Pressure Piping Containing Flaws (SAPP-2003), based on a well-known engineering safety assessment procedure R6. A numerical example is given to show the application of the SAPP-2003 software. The failure probabilities of each defect and the whole piping can be obtained by this software.
- Published
- 2004
- Full Text
- View/download PDF
47. Risk analysis of in-service pressure piping containing defects
- Author
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Yong-Cheng Lin, H Luo, X.H. Wang, and Y.J. Xie
- Subjects
Engineering ,Piping ,business.industry ,Mechanical Engineering ,Monte Carlo method ,Probabilistic logic ,Torsion (mechanics) ,Structural engineering ,Flow stress ,Fracture toughness ,Mechanics of Materials ,Bending moment ,General Materials Science ,business ,Stress intensity factor - Abstract
The reliability of pressure piping containing defects is important in engineering. The failure probability of pressure piping containing defects may be used as a guide to the most economic deployment of resources on maintenance, inspection and repair. This paper presents a probabilistic assessment methodology for in-service pressure piping containing defects, which is especially designed for programming. It is based on three assessment codes, BS 7910, R6 and SAPV-99, considering uncertainties in operating loadings, flaw sizes, material fracture toughness and flow stress. A general sampling computation method of stress intensity factor (SIF), in the form of the relationship between SIF and axial force and bending moment and torsion, is adopted. This relationship has been successfully used in developing software, Safety Assessment System of In-service Pressure Piping Containing Flaws (SAPP-2003), to assess planar and non-planar flaws. A numerical example is presented to illustrate the application of SAPP-2003 for calculating the failure probabilities of separate defects and for the assessed pressure piping.
- Published
- 2004
- Full Text
- View/download PDF
48. Subluminous phase velocity regions of an accurately described Gaussian laser field and laser-driven acceleration
- Author
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J.R. Liu, Z. Chen, Y.K. Ho, N. Cao, Shengxing Zhang, Y.J. Xie, L. Shao, and J. Pang
- Subjects
Physics ,Beam diameter ,business.industry ,General Physics and Astronomy ,Optics ,Thermal velocity ,Dispersion relation ,Physics::Accelerator Physics ,Group velocity ,M squared ,Laser beam quality ,Phase velocity ,business ,Gaussian beam - Abstract
By taking account of the high-order corrections to the paraxial approximation of a Gaussian beam, it has been verified that for a focused laser beam propagating in vacuum, there indeed exists a subluminous wave phase velocity region surrounding the laser beam axis. The magnitude of the phase velocity scales as V ϕm ∼ c (1+ b /( kw 0 ) 2 ), where V ϕm is the phase velocity of the wave, c is the speed of light in vacuum, w 0 is the beam width at focus. This feature gives a reasonable explanation for the mechanism of capture and acceleration scenario.
- Published
- 2003
- Full Text
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49. Crack initiation at contact surface
- Author
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David A. Hills and Y.J. Xie
- Subjects
Surface (mathematics) ,Materials science ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Fretting ,Mechanics ,Structural engineering ,Edge (geometry) ,Condensed Matter Physics ,Stress field ,Crack closure ,Substrate (building) ,Fracture (geology) ,General Materials Science ,business ,Stress concentration - Abstract
By using the S-theory, the crack initiation angle from the contact surface of rectangular rigid punch and flat-surface substrate has been investigated. The coefficient of friction at the edge of contact, which characterizes the asymptotic stress field, is considered as the controlling parameter in the analysis. The predicted results are in agreement with the experimental observations. The information gained may lend insight into the different stages of damage associated with the complex process of fretting fatigue.
- Published
- 2003
- Full Text
- View/download PDF
50. Crack initiation and direction for circumferential periodic cracks in pipe under tension and torsion
- Author
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X.H. Wang and Y.J. Xie
- Subjects
Materials science ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Crack tip opening displacement ,Torsion (mechanics) ,Fracture mechanics ,Mechanics ,Structural engineering ,Condensed Matter Physics ,Crack growth resistance curve ,Crack closure ,Fracture toughness ,General Materials Science ,business ,Stress intensity factor ,Stress concentration - Abstract
The S-theory is applied to determine crack initiation angle and critical load of circumferential periodic cracks in pipe. A technique for determining mode II stress intensity factor is proposed by using G ∗ path independent integral. The method applies also to single-edge crack, double-edge crack and center crack cylindrical panel configurations.
- Published
- 2003
- Full Text
- View/download PDF
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