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Experimental Study on Wear and spalling Behaviors of Railway Wheel

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1243-1249页

作者： WANG Wenjian GUO Jun LIU Qiyue Tribology Research Institute Southwest Jiaotong University

The current researches of the wear and spalling behaviors of wheel/rail materials focus on the field investigation rather than the mechanism. However, it is necessary and significant for clarifying the mechanism and relationship between the wear and spalling damage of railway wheel to test and reproduce the wheel damages in laboratory. The objective of this paper is to investigate the wear and spalling damage behaviors of railway wheel using a JD-1 wheel/rail simulation facility, which consists of a small wheel serving as rolling stock wheel, and a larger wheel serving as rail. The damage process of wheel roller is explored in terms of the creep ratio, axle load, and carbon content by means of various microscopic examinations. The experimental results show that the wear volume growth of wheel roller is proved to be proportional to the increase of the creep ratio and normal load between simulating wheel and rail. The increase of carbon content of wheel material causes a linear reduction in the wear volume. The microscopic examinations indicate that the rolling wear mechanism transfers from abrasive wear to adhesive and fatigue wear with an increase of tangential friction force, which results in the initiation of fatigue crack, and then aggravates spalling damage on the wheel roller surface. The surface hardness of material depends strongly upon its carbon content. The decrease of the carbon content of wheel material may alleviate spalling damage, but can cause a significant growth in the wear volume of wheel roller. Therefore, there is a competitive relationship between the wear and spalling damage of wheel material. This research proposes an important measure for alleviating or preventing the wear and spalling damage of railway wheel material.

关键词： wear spalling content carbon railway wheel wear mechanism

Experimental simulation investigation of influence of depth on spalling characteristics in circular hard rock tunnel

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Journal of Central South University 2020年第3期27卷 891-910页

作者： LUO Yong GONG Feng-qiang LI Xi-bing WANG Shan-yong School of Resources Environment and Safety Engineering University of South ChinaHengyang 421001China School of Resources and Safety Engineering Central South UniversityChangsha 410083China School of Civil Engineering Southeast UniversityNanjing 211189China ARC Centre of Excellence for Geotechnical Science and Engineering Faculty of Engineering and Built EnvironmentThe University of NewcastleCallaghanNSW 2238Australia

A series of true-triaxial compression tests were performed on red sandstone cubic specimens with a circular hole to investigate the influence of depth on induced spalling in *** failure process of the hole sidewalls was monitored and recorded in real-time by a micro-video monitoring *** general failure evolution processes of the hole sidewall at different initial depths(500 m,1000 m and 1500 m)during the adjustment of vertical stress were *** results show that the hole sidewall all formed spalling before resulting in strain rockburst,and ultimately forming a V-shaped *** far-field principal stress for the initial failure of the tunnel shows a good positive linear correlation with the *** the depth increases,the stress required for the initial failure of the tunnels clearly increased,the spalling became more intense;the size and mass of the rock fragments and depth and width of the V-shaped notches increased,and the range of the failure zone extends along the hole sidewall from the local area to the entire ***,as the depth increases,the support area around the tunnel should be increased accordingly to prevent spalling.

关键词： deep underground engineering circular tunnels spalling strain rockburst true-triaxial loading V-shaped notch

Crystal Plasticity-Based spalling Damage Model for Ductile Metals

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Acta Mechanica Solida Sinica 2023年第1期36卷 76-85页

作者： Chen Li Hai-Ying Wang Lan-Hong Dai State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

spalling is a typical tensile failure that results from the coupling evolution of microstructure and microdamage under high strain-rate *** understand the spalling damage behavior of polycrystalline materials at mesoscale,this paper develops a spalling model by integrating the crystal plasticity theory and the microvoid growth *** model is implemented in ABAQUS simulation via the VUMAT subroutine to simulate a planar impact process of copper,and the results are compared with experimental *** to the inhomogeneity of crystal plastic slip,the local stress fluctuates severely near the grain ***,without introducing the fluctuation in the threshold stress for microdamage evolution,this model can simulate the heterogeneous feature of microvoid nucleation,growth,and coalescence in *** results show that microvoids tend to nucleate at 25°–50°misorientation angle grain boundaries,which undergo a high probability of stress fluctuation.

关键词： spalling Crystal plasticity Microvoid nucleation and growth Grain boundary Finite element method

An investigation on micro pore structures and the vapor pressure mechanism of explosive spalling of RPC exposed to high temperature

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Science China(Technological Sciences) 2013年第2期56卷 458-470页

作者： JU Yang LIU HongBin TIAN KaiPei LIU JinHui WANG Li GE ZhiShun State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete China University of Mining and Technology School of Mechanics and Civil Engineering China University of Mining and Technology

Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling. Applying mercury intrusion po- rosimetry （MIP） and scanning electron microscopy （SEM） techniques, the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350~C. The pore characteristics such as specific pore volume, threshold pore size and most probable pore size varying with temperatures were investigated. A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures. A thin-wall spherical pore model was proposed to ana- lyze the thermo-mechanical mechanism of spalling, by which the stresses varying with the vapor pressure q（T） and the character- istic size of wall （K） at any point of interest were determined. It is shown that the pore characteristics including specific pore volume, average pore size, threshold pore size and most probable pore size rise significantly with the increasing temperature. 200~C appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically. The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores. The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to thin-wall sphere domain where the vapor pressure governs the the rapid accumulation of high vapor pressures as well. The spalling is bounded through the pore model.

关键词： reactive powder concrete (RPC) high temperature spalling pore structure vapor pressure microstructures mercuryintrusion porosimetry (MIP)

spalling MECHANISM OF NITRIDED LAYER OF AUSTENITIC STEEL 4Cr14Ni14W2Mo

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Acta Metallurgica Sinica(English Letters) 1989年第5期2卷 374-376页

作者： SUN Xudong LI Jian Northeast University of Technology,Shenyang,China Lecturer,Dept.of Materials Science and Engineering,Northeast University of Technology,Shenyang,China

The tendency of spalling of the nitrided layer of the hot rolled austenitic steel 4Cr14Ni14W2Mo exhibits close relation to the nitrided surface orientation relative to the rol- led steel *** is found that the dislocations in the imperfectly recrystalized steel align as parallel dislocation walls in macroscopic extent,and the thickness of the“white sublayer”in the nitrided layer is much larger at the surface which is parallel to the dislocation *** such surface the spalling of the nitrided layer happens often.

关键词： nitriding spalling heat resistant steel

Residual Mechanical Properties and Explosive spalling Behavior of Ultra-High-Strength Concrete Exposed to High Temperature

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Journal of Harbin Institute of Technology(New Series) 2017年第4期24卷 62-70页

作者： Gaifei Peng Juan Yang Faculty of Civil Engineering Beijing Jiaotong University

In order to explore the characteristics of ultra-high-strength concrete exposed to high temperature,residual mechanical properties and explosive spalling behavior of ultra-high-strength concrete( UHSC) and high strength concrete( HSC) exposed to high temperatures ranging from 20 ℃ to 800 ℃ were determined. The microstructure of the specimens after exposure to elevated temperature was analyzed by means of scanning electron microscope( SEM) and mercury intrusion porosimetry( MIP). The residual compressive strengths of UHSC and HSC were first increased and then decreased as temperature increased. After exposure to 800 ℃,the compressive strengths of UHSC and HSC were 24. 2 % and 22. 3 % of their original strengths at 20 ℃,respectively. The residual splitting tensile strengths of both UHSC and HSC were consistently decreased with the temperature increasing and were approximately 20% of their original strengths after 800 ℃. However,the residual fracture energies of both concretes tended to ascend even at 600 ℃. The explosive spalling of UHSC was more serious than that of HSC. Moisture content of the specimens governs the explosive spalling of both concretes with a positive correlations,and it is more pronounced in UHSC. These results suggest that UHSC suffers a substantial loss in load-bearing capacity and is highly prone to explosive spalling due to high temperature. The changes in compressive strength are due to the changes in the density and the pore structure of concrete. The probability and severity of explosive spalling of UHSC are much higher than those of HSC due to the higher pore volume in HSC.

关键词： ultra-high-strength concrete high strength concrete residual mechanical properties explosive spalling

spalling OF NITRIDED LAYER OF AUSTENITIC 4Cr14Ni14W2Mo STEEL

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Acta Metallurgica Sinica(English Letters) 1988年 54-58页

作者： LI Jian SUN Xudong LI Zhaixian LI Chunsheng Northeast University of Technology,Shenyang,China Professor,Department of Materials Science,Northeast University of Technology,Shenyang,China

The tendency of spalling of nitrided layer of an austenitic heat resistant steel4Cr14Ni14W2Mo has been studied *** was found that the residualdeformation retained in the rolled steel is the root that causes the spalling of nitridedlayer of the *** the work hardening state is removed by a suitable heat treatment be-fore nitriding,the spalling of nitrided layer can be completely avoided.

关键词： nitriding spalling heat resistant steel

Investigation of stress-induced progressive failure of mine pillars using a Voronoi grain-based breakable block model

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International Journal of Mining Science and Technology 2024年第5期34卷 713-729页

作者： Shili Qiu Shirui Zhang Quan Jiang Shaojun Li Hao Zhang Qiankuan Wang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China

The Voronoi grain-based breakable block model(VGBBM)based on the combined finite-discrete element method(FDEM)was proposed to explicitly characterize the failure mechanism and predict the deformation behavior of hard-rock mine *** influence of the microscopic parameters on the macroscopic mechanical behavior was investigated using laboratory-scale *** field-scale pillar models(width-to-height,W/H=1,2 and 3)were calibrated based on the empirically predicted stress-strain curves of Creighton mine *** results indicated that as the W/H ratios increased,the VGBBM effectively predicted the transition from strain-softening to pseudo-ductile behavior in pillars,and explicitly captured the separated rock slabs and the V-shaped damage zones on both sides of pillars and conjugate shear bands in core zones of *** volumetric strain field revealed significant compressional deformation in core zones of *** the peak strains of W/H=1 and 2 pillars were relatively consistent,there were significant differences in the strain energy storage and release mechanism.W/H was the primary factor influencing the deformation and strain energy in the pillar *** friction coefficient of the structural plane was also an important factor affecting the pillar strength and the weakest discontinuity *** fracture surface was controlled by the discontinuity angle and the friction *** study demonstrated the capability of the VGBBM in predicting the strengths and deformation behavior of hard-rock pillars in deep mine design.

关键词： Pillar strength FDEM Voronoi tessellation spalling Bulking

Role of Wetting Front in Dewetting of Liquid Solder Drop on Cu Thin Films

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Journal of Materials Science & Technology 2010年第3期26卷 200-205页

作者： Wei Liu Lei Zhang J.K. Shang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana IL 61801 USA

The thermodynamic conditions for dewetting of a liquid solder drop on copper thin films were examined under a hot-stage optical microscope in a flowing protective *** of liquid solder was found to depend strongly on the copper film thickness and preceded by spalling of Cu 6 Sn 5 intermetallic ***,the loss of interfacial bonding by spalling was not sufficient to cause immediate dewetting of solder drops if the wetting tip was still strongly bonded to the copper *** introducing a pinning force on the wetting front,a sufficient condition was found from a force balance analysis for dewetting of the liquid solder drop,in general agreement with the experimental results.

关键词： Dewetting Solder spalling Film thickness