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GPGPU-parallelised hybrid finite-discrete element modelling of rock chipping and fragmentation process in mechanical cutting

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第2期12卷 310-325页

作者： Mojtaba Mohammadnejad Sevda Dehkhoda Daisuke Fukuda Hongyuan Liu Andrew Chan School of Engineering College of Science and EngineeringUniversity of TasmaniaHobartTAS7001Australia CSIRO Minerals Resources Business UnitQCAT 1 Technology CourtPullenvaleQLD4069Australia Hatch BrisbaneQLD4000Australia Division of Sustainable Resources Engineering Faculty of EngineeringHokkaido UniversityHokkaidoJapan

Mechanical cutting provides one of the most flexible and environmentally friendly excavation *** has attracted numerous efforts to model the rock chipping and fragmentation process,especially using the explicit finite element method(FEM) and bonded particle model(BPM),in order to improve cutting *** study investigates the application of a general-purpose graphic-processing-unit parallelised hybrid finite-discrete element method(FDEM) which enjoys the advantages of both explicit FEM and BPM,in modelling the rock chipping and fragmentation process in the rock scratch test of mechanical rock *** input parameters of FDEM are determined through a calibration procedure of modelling conventional Brazilian tensile and uniaxial compressive tests of limestone,A series of scratch tests with various cutting velocities,cutter rake angles and cutting depths is then modelled using FDEM with calibrated input parameters.A few cycles of cutter/rock interactions,including their engagement and detachment process,are modelled for each case,which is conducted for the first time to the best knowledge of the authors,thanks to the general purpose graphic processing units(GPGPU) *** failure mechanism,cutting force,chipping morphology and effect of various factors on them are discussed on the basis of the modelled ***,it is concluded that GPGPU-parallelised FDEM provides a powerful tool to further study rock cutting and improve cutting efficiencies since it can explicitly capture different fracture mechanisms contributing to the rock chipping as well as chip formation and the separation process in mechanical ***,it is concluded that chipping is mostly owed to the mix-mode Ⅰ-Ⅱ fracture in all cases although mode Ⅱ cracks and mode Ⅰ cracks are the dominant failures in rock cutting with shallow and deep cutting depths,*** chip morphology is found to be a function of cutter velocdty,cutting depth and cutter rake angl

关键词： Numerical simulation Finite-discrete element method(FDEM) Rock cutting chipping Cracking

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chipping 切杆,不用怕

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世界高尔夫 2016年第7期 34-35页

果岭边有各种复杂棘手的球路等着你面对,但是不必害怕,你只要信任你的挥杆,将球打到洞边。安全第一这一球最关键的就是扎实的击球。如果没有好的击球,你会像一个不折不扣的傻瓜一样将球打进沙坑,平白给自己多增加两杆。为确保扎实的击球... 详细信息

果岭边有各种复杂棘手的球路等着你面对,但是不必害怕,你只要信任你的挥杆,将球打到洞边。安全第一这一球最关键的就是扎实的击球。如果没有好的击球,你会像一个不折不扣的傻瓜一样将球打进沙坑,平白给自己多增加两杆。为确保扎实的击球,设定站姿时让身体更靠近球,握杆握短点,球位往后放更靠近右脚,重心要放在身体左侧在身体很靠近球的情况下,球头跟部会离开地面,这样会使得你用杆头的趾部击球（下图）。这也许看起来不正常或者感觉不舒服,

关键词：果岭握杆跟部趾部安全第一 chipping 球头站姿球后为高

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Tool Failure Analysis in High Speed Milling of Titanium Alloys

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武汉理工大学学报 2006年第S1期28卷 137-142页

作者： MEYER Kevin YU Cindy S M Wu Manufacturing Research Center University of MichiganAnn ArborMIUSA48109

In high speed milling of titanium alloys the high rate of tool failure is the main reason for its high manufacturing cost. In this study,fractured tools which were used in a titanium alloys 5-axis milling process have been observed both in the macro scale using a PG-1000 light microscope and in the micro scale using a Scanning Electron Microscope (SEM) respectively. These observations indicate that most of these tool fractures are the result of tool chipping. Further analysis of each chipping event has shown that beachmarks emanate from points on the cutting edge. This visual evidence indicates that the cutting edge is failing in fatigue due to cyclical mechanical and/or thermal stresses. Initial analyses explaining some of the outlying conditions for this phenomenon are discussed. Future analysis regarding determining the underlying causes of the fatigue phenomenon is then outlined.

关键词： titanium alloys high speed milling cutting edge chipping tool failure analysis

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The Effects of Forest Thinning Practices and Altered Nutrient Supply on Soil Trace Gas Fluxes in Colorado

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Open Journal of Forestry 2014年第3期4卷 278-289页

作者： Mark A. Gathany Ingrid C. Burke Department of Science & Mathematics Cedarville University Cedarville USA Haub School of Environment and Natural Resources University of Wyoming Laramie USA

Increases in wildfire activity in the western United States have prompted land managers to reevaluate management practices. In the Colorado Front Range, where population density is high, there is often a great concern regarding wildfire which leads to efforts that will reduce fire hazard. The most common method of achieving this goal is to thin the forest of small diameter trees. Oftentimes these practices are undertaken with little knowledge of the ecological consequences of such treatments. We investigated the effect(s) of three treatments (control, thinning-only and broadcast chipping) on trace gas fluxes (CO2, CH4, and N2O), litter mass, and soil carbon and nitrogen. In a small plot study, we used a 2 × 3 × 3 randomized complete block design to determine the influence of nutrient amendments (woodchips, nitrogen, and phosphorus availability) on trace gas fluxes. The stand-management study revealed that neither thinning-only nor broadcast chipping significantly affected soil carbon or nitrogen, while thinning-only significantly reduced the amount of forest floor litter. Each trace gas flux was significantly affected by the date of sampling (June or August). CO2 and N2O fluxes each had a significant interaction between treatment and sampling date. We attribute this to a difference in moisture availability between the sampling times. In the plot study we found that only the interaction between woodchip addition and phosphorus availability significantly affected CO2 flux. Nitrous oxide fluxes were not significantly affected by any combination, however, methane uptake was found to respond significantly to different nitrogen and phosphorus levels.

关键词： Forest Restoration chipping Nutrient Supply Greenhouse Gases

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Basic properties and types of zirconia: An overview

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World Journal of Stomatology 2013年第3期2卷 40-47页

作者： Serkan Saridag Onjen Tak Gamze Alniacik Department of Prosthodontics Faculty of Dentistry Kocaeli University 41700 Kocaeli Turkey

This paper describes types and characteristics of zirconia materials in relation to their applications in dentistry. The zirconia material typically used today by most manufacturers is a tetragonal polycrystalline zirconia, partially stabilized with yttrium oxide. The mechanical properties of zirconia have been extensively investigated in the scientific literature and zirconia clearly measures up to any other equivalent manufactured material. The biocompatibility of zirconia has also been extensively evaluated and no local or systemic adverse reactions or cytotoxic effects have been found in relation to it. However, ceramic bonding, ageing, light transmission and manufacturing processes are all factors that need to be further evaluated in order to guide the successful use of zirconia as a prosthetic restorative material. Milling zirconia to full-contour might be an alternative to traditionally veneered restorations. A potential adhesion mechanism appears to be the combination of air abrasion with aluminum oxide particles(silanated or not), followed by sintering with materials containing special reactive monomers. Changes in zirconia properties before and after the sintering process have also been investigated. It was found that after sintering, surface roughness was greater, and micro hardness was slightly reduced; however, accurate precision of fitwas not affected by the sintering process. Currently, zirconia restorations are manufactured by either soft or hard-milling processes, with the manufacturer of each claiming advantages over the other. chipping of the veneering porcelain is reported as a common problem and has been labeled as its main clinical setback. As zirconia has demonstrated good mechanical and biological performance, future technology is attempting to improve esthetics and minimize veneer fracture, aiming to create confidence in the dental community towards this all-ceramic system. Milling zirconia to full-contour might be an alternative to traditio

关键词： Zirconia Biocompatibility Porcelain chipping Mechanical properties

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