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numerical simulation of mechanisms of deformation,failure and energy dissipation in porous rock media subjected to wave stresses

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Science China(technological Sciences) 2010年第4期53卷 1098-1113页

作者： JU Yang1,2,WAnG HuiJie1,YAnG YongMing1,HU QinAng3 & PEnG RuiDong1 1 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete,China university of Mining and technology,Beijing 100083,China 2 department of mechanical and manufacturing engineering,university of calgary,calgary,alberta,t2n 1n4,canada 3 School of Environment and Civil engineering,College of engineering,Oklahoma State university,Stillwater,OK 74078,USA State Key Laboratory of Coal Resources and Safe Mining Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete China University of Mining and Technology Beijing China department of mechanical and manufacturing engineering University of Calgary Calgary Canada School of Environment and Civil engineering College of Engineering Oklahoma State University Stillwater USA

the pore characteristics,mineral compositions,physical and mechanical properties of the subarkose sandstones were acquired by means of Ct scan,X-ray diffraction and physical tests.A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were *** 3D finite element models of the rock media with varied porosities were established based on the Ct image processing of the physical models and the MIMICS software *** failure processes of the porous rock media loaded by the split Hopkinson pressure bar(SHPB) were simulated by satisfying the elastic wave propagation *** dynamic responses,stress transition,deformation and failure mechanisms of the porous rock media subjected to the wave stresses were *** is shown that an explicit and quantitative analysis of the stress,strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element *** applied wave stresses of certain amplitude and velocity,no evident pore deformation was observed for the rock media with a porosity less than 15%.the deformation is dominantly the combination of microplasticity(shear strain),cracking(tensile strain) of matrix and coalescence of the cracked regions around *** stresses lead to microplasticity,while tensile stresses result in cracking of the *** and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold *** simulation results of stress wave propagation,deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical *** present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response,stress transit mode,deformation and failure mechanisms and the disaster mechanism

关键词： porous media three-dimensional finite element model rock media stress wave failure mechanism energy dissipation

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Rolling Element Bearing Diagnostics by Combination of Envelope Analysis and Wavelet transform

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Journal of university of Science and technology Beijing 2001年第1期8卷 69-74页

作者： Ying tang, Qiao Sun mechanical engineering School, university of Science and technology Beijing, Beijing 100083, China department of mechanical engineering, university of calgary calgary alberta t2n 1n4, canada mechanical engineering School Univ. of Sci. and Technology Beijing Beijing 100083 China

Rolling element-bearing diagnostics has been studied over the last thirty years, and envelope analysis is widely recognized as being the best approach for detection and diagnosis of rolling element bearing incipient failure. But one of the on-going difficulties with envelope technique is to determine the best frequency band to envelop. Here, wavelet transform technique is introduced into envelope analysis to solve the problem by capturing bearing defects-sensory scales (i.e. frequency bands). A modulated Gaussian function is chosen to be the analytical wavelet because it coincides well with bearing defect-induced vibration signal patterns. Vibration signals measured from railway bearing tests were studied by the proposed method. Cases of bearings with single and multiple defects on inner and outer race under different testing conditions are presented. Experimental results showed that the proposed method allowed a more accurate local description and separation of transient signal part, which were caused by impacts between defects and the mating surfaces in the bearing. the combination method provides an effective signal detection technique for rolling element-bearing diagnostics.

关键词： continuous wavelet transform envelope analysis rolling element bearing diagnostics

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Experimental study of dynamic mechanical properties of reactive powder concrete under high-strain-rate impacts

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Science China(technological Sciences) 2010年第9期53卷 2435-2449页

作者： JU Yang1,2,LIU HongBin1,SHEnG GuoHua1,3 & WAnG HuiJie1 1 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete,China university of Mining and technology,Beijing 100083,China 2 department of mechanical and manufacturing engineering,university of calgary,2500 university Drive,AB t2n 1n4,canada 3 School of Resources and Civil engineering,northeastern university,Shenyang 110004,China State Key Laboratory of Coal Resources and Safe Mining Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete China University of Mining and Technology Beijing China department of mechanical and manufacturing engineering University of Calgary Calgary Canada School of Resources and Civil engineering Northeastern University Shenyang China

the dynamic mechanical properties of reactive powder concrete subjected to compressive impacts with high strain rates ranging from 10 to 1.1×102 s-1 were investigated by means of SHPB (split-Hopkinson-pressure-bar) tests of the cylindrical specimens with five different steel fiber volumetric *** properties of wave stress transmission,failure,strength,and energy consumption of RPC with varied fiber volumes and impact strain rates were *** influences of impact strain rates and fiber volumes on those properties were characterized as *** general forms of the dynamic stress-strain relationships of RPC were modeled based on the experimental *** investigations indicate that for the plain RPC the stress response is greater than the strain response,showing strong brittle *** RPC with a certain volume of fibers sustains higher strain rate impact and exhibits better deformability as compared with the plain *** a constant fiber fraction,the peak compressive strength,corresponding peak strain and the residual strain of the fiber-reinforced RPC rise by varying amounts when the impact strain rate increases,with the residual strain demonstrating the greatest *** the fiber content makes trivial contribution to improving the residual deformability of RPC when the impact strain rate is *** tests also show that the fiber content affects the peak compressive strength and the peak deformability of RPC in a different *** a constant impact strain rate and the fiber fraction less than 1.75%,the peak compressive strength rises with an increasing fiber *** peak compressive strength tends to decrease as the fiber volume exceeds 1.75%.the corresponding peak strain,however,incessantly rises with the increasing fiber *** total energy Edisp that RPC consumed during the period from the beginning of impacts to the time of residual strains elevates with the fiber volume increment as long as the fiber fraction

关键词： impact reactive powder concrete (RPC) high strain rate dynamic strength energy consumption dynamic stress-strain response

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A statistical model for porous structure of rocks

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Science China(technological Sciences) 2008年第11期51卷 2040-2058页

作者： JU Yang1,2, YAnG YongMing1, SOnG ZhenDuo3 & XU WenJing4 1 State Key Laboratory of Coal Resources and Safe Mining, China university of Mining & technology, Beijing 100083, China 2 department of mechanical and manufacturing engineering, the university of calgary, 2500 university Drive nW calgary, AB t2n 1n4, canada 3 China national Coal Mining Equipment Co. Ltd, Beijing 100011, China 4 department of Materials and Metallurgy, the university of Utah, Salt Lake City, Utah 84112, USA State Key Laboratory of Coal Resources and Safe Mining China University of Mining & Technology Beijing China department of mechanical and manufacturing engineering The University of Calgary Calgary Canada China national Coal Mining Equipment Co. Ltd Beijing China department of Materials and Metallurgy The University of Utah Utah USA

the geometric features and the distribution properties of pores in rocks were in- vestigated by means of Ct scanning tests of sandstones. the centroidal coordi- nates of pores, the statistic characterristics of pore distance, quantity, size and their probability density functions were formulated in this paper. the Monte Carlo method and the random number generating algorithm were employed to generate two series of random numbers with the desired statistic characteristics and prob- ability density functions upon which the random distribution of pore position, dis- tance and quantity were determined. A three-dimensional porous structural model of sandstone was constructed based on the FLAC3D program and the information of the pore position and distribution that the series of random numbers defined. On the basis of modelling, the Brazil split tests of rock discs were carried out to ex- amine the stress distribution, the pattern of element failure and the inosculation of failed elements. the simulation indicated that the proposed model was consistent with the realistic porous structure of rock in terms of their statistic properties of pores and geometric similarity. the built-up model disclosed the influence of pores on the stress distribution, failure mode of material elements and the inosculation of failed elements.

关键词： porous structure statistical model random numbers reconstruction rocks

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MICROMACHInInG WItH FEMtOSECOnD LASER

MICROMACHINING WITH FEMTOSECOND LASER

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第七届海内外青年设计与制造科学会议

作者： Yiliu tu and Ming Xia department of mechanical and manufacturing engineering university of calgary calgary AB canada t2n 1n4

＜正＞Femtosecond laser micromachining is a new approach emerging in MEMS area in recent years. Although some applications have been reported, this technology is still not matured and not understood very well. Femtosecond lasers currently show much promise as potential effective tools in micromachining or micro-system applications, which include industrial material processing, biomedicine, photonics, and semiconductors. this paper reviewed femtosecond laser technology with emphasis on mode-locked technology and chirped pulsed amplification （CPA）. We described the most important difference between femtosecond laser and traditional lasers, which is multiphoton absorption during laser material interaction. We introduced the configuration and principle of our femtosecond laser micromachining workstation and the status of micromachining with femtosecond laser pulses in the literature. Some advantages and applications such as processing different materials including transparent materials and creating very fine features （on the order of tens of nm） are presented. Finally, we suggested several future efforts that are parameter selection and optimization of micromachining processing, development of process and tolerance control algorithms, development of sensors and measurement methods, and development of the theory and methods of design for the femtosecond laser micromachining application. to achieve these targets effectively we proposed a "free force" 3D micromachining concept using lasers including femtosecond laser to create micro and nanostructures.

关键词： Laser Micromachining Femtosecond Laser Ultrafast Laser Laser Ablation

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Fundamental Research in Pipeline Corrosion and Stress Corrosion Cracking

Fundamental Research in Pipeline Corrosion and Stress Corros...

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第十三次全国电化学会议

作者： Yufeng Cheng Dept. of mechanical and manufacturing engineering, university of calgary, calgary, AB, t2n 1n4, canada

＜正＞Corrosion and stress corrosion cracking （SCC） have caused significant failures in gas and oil transmission pipelines in canada, resulting in extremely serious consequences in environment, economy and energy transportation. Particularly, SCC-induced pipeline failures are low-probability, high-consequence events. the potential catastrophic effects are evident from the damage caused by the stress corrosion cracking of the transcanada pipeline in 1996, destroying a house 178 metres away as well as nearby power lines, trees, and other vegetation. In addition, millions of cubic feet of natural gas were lost.

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Simple geometrical explanation of Gurtin-Murdoch model of surface elasticity with clarification of its related versions

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Science China(Physics,Mechanics & Astronomy) 2010年第3期53卷 536-544页

作者： Ru C. Q. department of mechanical engineering, university of alberta, Edmonton, alberta, canada t6G 2G8 department of mechanical engineering University of Alberta Edmonton Canada

It is showed that all equations of the linearized Gurtin-Murdoch model of surface elasticity can be derived, in a straightforward way, from a simple second-order expression for the ratio of deformed surface area to initial surface area. this elementary derivation offers a simple explanation for all unique features of the model and its simplified/modified versions, and helps to clarify some misunderstandings of the model already occurring in the literature. Finally, it is demonstrated that, because the Gurtin-Murdoch model is based on a hybrid formulation combining linearized deformation of bulk material with 2nd-order finite deformation of the surface, caution is needed when the original form of this model is applied to bending deformation of thin-walled elastic structures with surface stress.

关键词： surface elasticity surface stress Gurtin-Murdoch model

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CRItERIOn　OF　StOCHAStIC　LAYER　nEAR　A　PLAnAR　HOMOCLInIC　ORBIt　OF　nOnLInEAR　DYnAMICAL　SYStEM

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Journal of Hydrodynamics 1995年第2期7卷 35-50页

作者： Albert C. J. Luo(department of mechanical & Industrial engineering university of Manitoba. Winnipeg, Manitoba, R3t 2n2,canada) Univ of Manitoba Winnipeg Canada

A new analytic method is developed for nonlinear dynamical system, to investigate the mathematical structure and physical characteristics of the stochastic layer near a homoclinic or heteroclinic orbit. this method is based on the subharmonic resonant condition and an energy increment along the separatrix of the system. the critical conditions for the disappearance of stochastic layer are presented, which are associated with all control parameters of the system including initial conditions, excitation frequencies excitatiom amplitudes ***, using this method, we analyze two simple nonlinear dynamical systems, namely,Duffing-Holmes's equation and a forced planar pendulum. As their stochastic layers begin to disappear, their critical amplitudes are also obtained for the given excitation frequency and other chosen parameters. By means of these conditions, we carry out numerical simulations for the two simple models. their stochastic layer will be shown using Poincare mapping section. Our theoretical results are subeequently shown to be in a good agreement with numerical simulations.

关键词： nonlinear dynamical system stochastic layer numerical simulation

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Preparation of MWnts/Al_2O_3 composites and their mechanical and electrical properties

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Science China(technological Sciences) 2005年第6期48卷 622-631页

作者： FAn Jinpeng1,2, ZHAO Daqing1,2, XU Zening1,2 & WU Minsheng1,2 1. department of mechanical engineering, tsinghua university, Beijing 100084, China 2. Key Laboratory for Advanced manufacturing by Materials Processing technology, tsinghua university, Beijing 100084, China department of mechanical engineering Tsinghua University Beijing China Key Laboratory for Advanced manufacturing by Materials Processing technology Tsinghua University Beijing China

the mechanical and electrical properties of MWnts/Al2O3 composite prepared fabricated by hot pressing are investigated. the relation between properties and microstructure of composites is also discussed. With 4wt% MWnts as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1/2, which is 80% higher than that of pure Al2O3 obtained in the same conditions. the main toughening mechanism is Cnts’ pinning alumina grain boundaries, and the pullout of Cnts takes effect also. through adding 2wt% MWnts and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10?3 ?·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. the function of Cnts in composite is related to the distribution state of Cnts in composite, and the distribution state of Cnts in matrix is dependent on preparation procedures.

关键词： MWnts, alumina, composite, fracture toughness, electrical properties.

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Influence of modulation ratio on structure and properties of nanoscale ZrB_2/ZrAln multilayered coatings

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Science China(technological Sciences) 2010年第3期53卷 772-775页

作者： LI DeJun 1,KAnG YuanBin 1,DOnG Lei 1,DEnG XiangYun 1,LIU Hao 2 &SUn XueLiang 2 1College of Physics and Electronic Information Science,tianjin normal university,tianjin 300387,China 2 department of mechanical&Materials engineering,university of Western Ontario,London On,canada College of Physics and Electronic Information Science Tianjin Normal University Tianjin China department of mechanical & Materials engineering University of Western Ontario London Canada

ZrB2/ZrAln multilayered coatings with various modulation ratios(t ZrB2:t ZrAln)and constant modulation periods were prepared by magnetron sputtering system at room ***,XRD,surface profiler and nano-indenter were employed to investigate the influences of tZ rB 2:tZrAlnon the microstructure and mechanical properties of the *** interfaces and nanoscale multilayered modulation were confirmed by *** multilayer with modulation period of 40 nm and ratio of 3:1 displayed the highest hardness(36.4 GPa)and critical fracture load(76.477 mn)with lower *** polycrystalline structure and multilayered modulate structure were directly responsible for the enhanced mechanical properties.

关键词： ZrB2/ZrAln multilayered coating magnetron sputtering modulation ratio nanoscale

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