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Achieving superior mechanical properties in friction lap joints of copper to carbon-fiber-reinforced plastic by tool offsetting

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Journal of Materials Science & Technology 2018年第9期34卷 1628-1637页

作者： L.H.Wu k.Nagatsuka k.Nakata Joining and Welding Research Institute Osaka University

It is a challenge to achieve a sound welded metal/carbon-fiber-reinforced thermoplastic（CFRTP） joint with high strength and few bubbles. In this study, sound lap joints of Cu and CFRTP were obtained by friction lap joining（FLJ） directly at rotation rates of 600-2000 rpm, with the welding tool at the joint center and offsetting the tool 7 mm away from the center toward the retreating side, respectively. Tool offsetting reduced the non-uniform temperature distribution in the lap joints resulting from the high conductivity of Cu, which not only enhanced the tensile shear force from 0.89-2.25 kN to 1.71-3.54 kN,with the maximum increasing rate of 135%, but also reduced the bubble area to only 19% of the original level of 2000 rpm. It is the first time to report a high-quality Cu/CFRTP joint with a high strength and few bubbles. The large increase of the strength after tool offsetting was attributed to the increase of the joining area, the decrease of bubbles and the decrease of the CFRTP degradation. The details on the generation,quantitative distribution and expulsion of the bubbles in the FLJ joints were discussed.

关键词： Hybrid joining Plastic Metal Carbon-fiber-reinforced plastic Properties

A discrete model for prediction of radon flux from fractured rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第5期10卷 879-892页

作者： k.M. Ajayi k. Shahbazi R Tukkaraja k. katzenstein Department of Mechanical Engineering South Dakota School of Mines and Technology Rapid City SD 57701 USA b Department of Mining Engineering and Management South Dakota School of Mines and Technology Rapid City SD 57701 USA Department of Geology and Geological Engineering South Dakota School of Mines and Technology Rapid City SD 57701 USA

Prediction of radon flux from the fractured zone of a propagating cave mine is basically associated with uncertainty and complexity. For instance, there is restricted access to these zones for field measure- ments, and it is quite difficult to replicate the complex nature of both natural and induced fractures in these zones in laboratory studies. Hence, a technique for predicting radon flux from a fractured rock using a discrete fracture network （DFN） model is developed to address these difficulties. This model quantifies the contribution of fractures to the total radon flux, and estimates the fracture density from a measured radon flux considering the effects of advection, diffusion, as well as radon generation and decay. Radon generation and decay are classified as reaction processes. Therefore, the equation solved is termed as the advection-diffusion-reaction equation （ADRE）. Peclet number （Pe）, a conventional dimensionless parameter that indicates the ratio of mass transport by advection to diffusion, is used to classify the transport regimes. The results show that the proposed model effectively predicts radon flux from a fractured rock. An increase in fracture density for a rock sample with uniformly distributed radon generation rate can elevate radon flux significantly compared with another rock sample with an equivalent increase in radon generation rate. In addition to Pe, two other independent dimensionless parameters （derived for radon transport through fractures） significantly affect radon dimensionless flux. Findings provide insight into radon transport through fractured rocks and can be used to improve radon control measures for proactive mitigation.

关键词： Radon mass flux Radon dimensionless flux Stochastic model Discrete fracture network (DFN) Caving mining method Fractured rocks

Effect of (Ba_(0.6)Sr_(0.4))TiO_3(BST) Doping on Dielectric Properties of CaCu_3Ti_4O_(12)(CCTO)

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Journal of Materials Science & Technology 2012年第12期28卷 1137-1144页

作者： I. Norezan A.k. Yahya M.k. Talari Faculty of Applied Sciences Universiti Teknologi MARAShah Alam Selangor Malaysia

The effect of （Ba（0.6）Sr（0.4））TiO3（BST） addition on dielectric properties of CaCu3Ti4O（12）（CCTO） ceramic was investigated. Ceramic samples with the chemical formula （1-x）CaCu3Ti4O（12）＋ x（Ba（0.6）,Sr（0.4））TiO3 （x=0, 0.05, 0.1, and 0.2） were synthesized from high purity oxide powders by the conventional solid-state synthesis method. X-ray diffraction （XRD） analysis showed the existence of BST as a secondary phase alongside CCTO. Scanning electron microscopy （SEM） investigation showed a slight decrease in grain size of doped CCTO samples. Density measurements showed that porosity content increased with increasing BST addition indicating low densification due to high melting point secondary phase addition. Dielectric constant of undoped CCTO （x=0） showed lack of stability with frequency which dropped drastically between 104 and 105Hz and accompanied by high dielectric loss. Addition of BST into CCTO caused the dielectric constant to slightly decrease but improved stability with frequency compared to the undoped sample. The decrease in dielectric constant of doped CCTO samples was suggested to be partly due to the decrease in average grain size and increase in porosity with BST addition. Nevertheless, a high value of dielectric constant was still maintained around ～104 range for all doped samples. The dielectric loss （tanδ） of all BST-doped samples was lower than that of pure CCTO sample at the frequency range of 103 to 105 Hz probably due to the increase of grains boundary resistivity. The activation energy of grains boundary （E（gb）） showed higher values as compared to the activation energy of grains （Eg ） for all samples and conforms to the internal barrier layer capacitor （IBLC） model.

关键词： CaCu3Ti4O(12)(CCTO) Dielectric properties (Ba(0.6)Sr(0.4))TiO3(BST)

Elimination of boundary effect for laminated overburden model in pillar stability analysis

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Journal of Central South University 2016年第6期23卷 1468-1473页

作者：张鹏 k. A. Heasley Carlson Software Watertown MA 02472 USA Department of Mining Engineering West Virginia University WV 26505 USA

The laminated overburden model(La Model)has been widely used for pillar design and stability *** a boundary element program,the La Model program is sensitive to the boundary condition,which should be considered before creating the *** eliminate the boundary effect in a La Model pillar stability analysis,a suitable boundary buffer zone is needed around the model *** radius of influence(R)and the abutment load extent(D)are two major factors that affect the stresses and displacements calculated in LaM *** determine the optimum buffer zone extent,a database of case histories was analyzed using the La Model *** for R and D were varied until a buffer zone having negligible influence on the pillar stability factor(SF)of the active mining zone(AMZ)was determined.

关键词： pillar stability boundary effect LaModel numerical simulation room-and-pillar

Improvement of warm formability of Al-Mg sheet alloys containing coarse second-phase particles

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Science China(Technological Sciences) 2009年第1期52卷 41-45页

作者： Arne k DAHLE Amit k GHOSH Materials Engineering University of Queensland Department of Materials Science and Engineering University of Michigan

Several alloying elements involving Zr, Cu, Zn and Sc were added to Al-Mg sheet alloys in order to obtain an excellent combination of high strength and good high-temperature formability. Microstruc-tural examination showed that coarse intermetallic particles were formed in the microstructure and their amounts changed with variations of the alloying elements. During warm rolling of thermome-chanical treatments prior to warm deformation, the coarse particles initiated cracks, decreasing the warm formability. For healing the crack damage and further improving the warm formability, a process of hot isothermal press was developed and optimized to the sheet alloys. With this process, the biaxial stretch formability at 350℃ was improved by 22% for an aluminum alloy containing a large amount of coarse particles.

关键词： aluminum alloy microstructure second-phase particle hot isothermal press high-temperature formability

A CASE FOR SUSTAINABLE SECURITY SYSTEMS ENGINEERING:INTEGRATING NATIONAL,HUMAN,ENERGY AND ENVIRONMENTAL SECURITY

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Journal of Systems Science and Systems Engineering 2009年第4期18卷 385-402页

作者： Jason k. LEVY L. Douglas Wilder School of Government and Public Affairs Virginia Commonwealth University

In the wake of the September 11,2001 terrorist attacks, there is a growing sense of insecurity felt by many citizens around the world. Sustainable security, with roots in the sustainable development and human security literature, seeks positive transformations for the co-evolving and mutually dependent human-environmental condition by integrating （and subsuming） national, human, environmental, and energy security concems and capitalizing on opportunities provided by human creativity, diplomatic openings, modernization and environmental change. The field of Sustainable Security Systems Engineering is proposed for protecting, restoring, designing, and implementing a set of integrated natural and man-made processes that equitably and responsibly meet the biophysical needs of human communities, while maintaining long-term security, respecting financial constraints, meeting ecological limits, and improving institutional arrangements for transparent and effective governance. Scenario planning is shown to help promote sustainable security by identifying the preconditions of instability and helping to proactively address them in an increasingly complex and uncertain world. The six papers published in this featured collection cross policy domains, geographic, political, and sectoral boundaries and were discussed at forums sponsored by the Systems Engineering and Global Policy group. Collectively, they demonstrate the quality, breadth and depth of systems engineering methodologies that are used to promote sustainable security.

关键词： Sustainable security systems engineering national security human security environment and energy scenario planning

Sensorless control for hysteresis compensation of AFM scanner by modified Rayleigh model

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Journal of Central South University 2010年第6期17卷 1243-1246页

作者： PARk J k MOON W k Department of Mechanical Engineering Changwon National UniversityChangwon 641-773Korea Department of Mechanical Engineering Pohang Unive rsity of Science and TechnologyPohang 790-784Korea

A novel modified Rayleigh model was developed for compensating hysteresis problem of an atomic force microscope(AFM) *** high driving fields,piezoelectric actuators that integrated a scanner have severe hysteresis,which can cause serious displacement *** hysteresis is from various origins including movement of defects,grain boundary effects,and displacement of ***,because its characteristic is stochastic,it is almost impossible to predict the piezoelectric hysteresis ***,it was predicted phenomenologically,which means that the relationship between inputs and outputs is *** typical phenomenological approach is the Rayleigh ***,the model has the discrepancy with experiment result as the fields *** overcome the demerit of the Rayleigh model,a modified Rayleigh model was *** the modified Rayleigh model,each coefficient should be defined differently according to the field direction due to the increase of the asymmetry in the high *** applying an inverse form of this modified Rayleigh model to an AFM scanner,it is proved that hysteresis can be compensated to a position error of less than 5%.This model has the merits of reducing complicated fitting procedures and saving computation time compared with the Preisach model.

关键词： piezoelectric stack actuator hysteresis compensation Rayleigh model atomic force microscopy

Susceptibility to Hot Cracking and Weldment Heat Treatment of Haynes 230 Superalloy

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Journal of Materials Science & Technology 2006年第5期22卷 685-690页

作者： I.k.Lee Department of Mechatronic Technology National Taiwan Normal University TaipeiTaiwanChina

This study investigates the susceptibility of hot cracking and weldment heat treatment of Haynes 230 superalloy. The Varestriant test was conducted to evaluate this susceptibility. Welding was performed by gas tungsten arc welding （GTAW） and plasma arc welding （PAW） with stress relief heat treatment and solid solution heat treatment. A tensile test is then performed to measure the changes in the mechanical properties of the heattreated material. The results indicate that the number of thermal cycles does not affect the susceptibility of Haynes 230 superalloy to hot cracking. However, it does increase the strain. In weldment of heat treatment, stress relief annealing increases the yield strength and tensile strength of the welded parts. The section of the tensile specimens shows fibrous fractures on the welded parts, regardless of whether they are heat-treated.

关键词： Haynes 230 super alloy Varestriant test Hot cracking Susceptibility Stress relief annealing

Hydrogen Production by Selective Photo-dissociation of Water in Aqueous Colloidal Nano-particles of Doped Iron (Ⅲ) Oxides Semiconductors

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Journal of Materials Science & Technology 2010年第7期26卷 619-624页

作者： kasem k.kasem Natural Information and Mathematical Sciences Department School of Art and SciencesIndiana University KokomoKokomoIN 46904USA

Homogenous and heterogeneous production of hydrogen via photo-dissociation of water has been achieved with visible range solar radiation without any external potential at room temperature. Potassium ferrocyanide as a solvated-electron supplier and electron exchanger in basic buffers was used as a homogenous media for hydrogen production. Aqueous colloidal solutions of p-type Fe2O3 doped with MgO （Fe1.8Mg0.2O3） or with ZnO （Fe1.9Zn0.1O3） suspensions in ferrocyanide solutions were used as heterogeneous media for hydrogen generation by reduction of ferricyanide. The effects of the hole-scavengers such as oxo-anions and solvated-electron- suppliers were investigated. Results showed that Fe2O3 doped with ZnO was more efficient than that doped with MgO. The studies also showed that the aqueous nano-systems we used retained their stability as indicated by the reproducibility of their photocatalytic activities. Solar radiated assemblies of doped Fe2O3/[Fe（CN）6]4^- sustained cyclic systems for continuous hydrogen production.

关键词： Hydrogen production Photo-dissociation Nanoparticles Semiconductors