bluuebunny/crossref_metadata_2025 huggingface dataset:
The Security Study of an EC Protocol Based on Casper/FDR2
Authors: Wang Fang
Published: October 2014

Researchers have proposed several security protocols to protect the electronic commerce security in these years; however, not all of them are secure enough. This article extends model checking method with Casper/FDR2 to model and analyze a new electronic protocol. Attacks are found in the protocol and their mechanisms are discussed. A variety of solutions are given to different security flaws. The improved protocol is proven to be robust and secure.
Wireless Sensor Network Routing Optimization Based on Improved Shuffled Frog Leaping Algorithm
Authors: Ma Yong Chun , Shao Hua Gang
Published: October 2014

Against path optimization problem for wireless sensor network, this paper proposes a path optimization strategy for wireless sensor network based on improved shuffled frog leaping algorithm. The shuffled frog leaping algorithm was used as wireless sensor network path optimization main frame, gauss mutation and opposition-based learning were used to overcome the defects of easily trapping into local optimum and low accuracy computation. Simulation results show that the route optimization mechanism can effectively prolongs the network lifetime,reduces energy consumption, and improves the overall network performance.
A Constraint-Based Approach for Multi-Skilled Project Scheduling Problem
Authors: Li Yan , Xiao Zhi Run
Published: October 2014

The problem of multi-skilled project scheduling (MSPSP) is a complex problem of task scheduling and resource assignment that comes up in the daily management of many software company. In this paper we present a constraint programming (CP) approach for the MSPSP. We extend the project scheduling literature by developing a project scheduling model that accounts for differing skills among workers. The computational results for the MSPSP show that the constraint programming approach increases the performance of the model solving processes. The results for the MSPSP is effective in solving the proposed problem.
Development of Smart Remote Local Information Embedded System Using Global Positioning System
Authors: Choi Won Hyuck , Jie Min Seok
Published: October 2014

In case of existing localization system, it usually depends on video information by camera. Therefore, the camera has to be operated 24 hours a day. For the special region of interest, position recognition is available, however, for the most cases, once the camera is out of observed extent, the position recognition is not available. In order to back up these disadvantages, the Wireless Sensor Network, by using GPS and various sensors, can detect and monitoring the data up to the area which the image information cannot detect. For this, the thesis suggests the efficient monitoring system using GPS and human body detecting sensor.
Component Detection Method for Measuring Precision
Authors: Yi Bing , Zhang Xiao Ming , Wang Xi Jun , Chen Zhan Fang
Published: October 2014

The infrared theodolite is unable to realize the practical problems of star school, put forward a set of indirect detection method for measuring accuracy of photoelectric theodolite, This method not only solves the infrared theodolite test precision,but also can be convenient for full visual field and a full range of accuracy evaluation of equipment.
Detection of Seismic Wave with Laser Interferometer
Authors: Lee Woo Ram , Oh Eun Hwan , Lim Min Woo , You Kwan Ho
Published: October 2014

In this paper, we propose a seismic wave detection process using a laser interferometer as a seismometer. The laser interferometer system is an important equipment with its remarkable accurate capability for displacement measurement. During the process of the seismic wave measurement, however, environmental and nonlinearity error are occurred in a heterodyne laser interferometer. Through the extended Kalman filter compensation, the distortion is reduced. With a recursive STA/LTA algorithm, the PS-time of the seismic wave is determined and then the epicenter distance can be derived. Through some simulations, it is demonstrated that the proposed algorithm can reduce error factors and improve the measurement accuracy of a seismometer.
Analysis of Pressure Wave Model Predictions Considering Diesel Fuel Properties
Authors: Qaisar Hayat , Fan Li Yun , Song En Zhe , Ma Xiu Zhen , Tian Bing Qi , Farouk Naeim
Published: October 2014

Diesel fuel pressure wave inside Combination Electronic Unit Pump (CEUP) pipeline has been investigated using a 1D viscous damped mathematical model considering the effect of four key fuel properties including density, viscosity, acoustic wave speed and bulk modulus. Wave equation (WE) based mathematical model has been developed in MATLAB using finite difference method. Mathematical model results at various operating conditions of diesel engine have been verified by comparing with those of AMESim numerical model of CEUP and quantified through Root Mean Square Errors (RMSE) and Index of Agreements (IA). Dynamic variations of these fuel properties during fuel injection cycles have also been incorporated in mathematical model by utilizing empirical formulas. Predicted results show that simulated results which consider fuel properties dynamic variations as a function of pressure are more coherent to AMESim numerical model results.
Development of Real Time Harmful Gas Detecting Embedded System
Authors: Choi Won Hyuck , Jie Min Seok
Published: October 2014

In this paper, with the development of Information technology, application service between IT and traditional industry has been on the rise. And there are many on-going discussions actively regarding the Air quality system based on wireless sensor network which monitors and control the industrial environment automatically and manually with the application service of detecting harmful gas. In this thesis, operation program constitute the administrator monitoring device, which collects data from sensor node of wireless sensor network and sensor node and transmits environment information to display and server. Also for remote monitoring, user operation program constitutes based on PC/Smartphone Under this, the harmful gas which is made in daily life is measured. Real time monitoring system based on wireless sensor network is designed and realized.
A Study of Flexible Force Control Method on Robotic Assembly for Spacecraft
Authors: Zhang Li Jian , Hu Rui Qin , Yi Wang Min , Fu Hao , Tang Lai Ying
Published: October 2014

For complex spacecraft assembly conditions, how to play effective and flexible robotic characteristics, and improve production efficiency, is the problem needed to solve.this paper presents a flexible force control method on robotic assembly: a 6-axis force/torque sensor is mounted between tools and the end of robots, the operator operates the load by hands directly, and the system can obtain the force/torque information caused by operator’s hands through gravity compensation algorithm, then the force/torque information is used as input parameters to control the robots moving with the hands. The detailed scheme and algorithms are presented in this paper.
Mobile Robot Powered by Solar Cells
Authors: Patic Paul Ciprian , Pascale Lucia , Măntescu Gabriela
Published: October 2014

Generally, robots are a class of technical systems which imitate or substitute driver or human intellectual functions. This is achieved by the combination of various types of handling equipment or locomotors system, causing the anthropomorphic robot character, the different types of computer equipment, or logical, which determines the intellectual functions thereof. The robots operate in a specific environment, the characteristics of which may remain constant or variable over time. While battery technology is of great interest for mobile robots, but it is not reliable in the time, there are several strategies for the storage of energy (fuel cells and the micro-fuel cell), as well as strategies for harvesting energy from the environment in various ways and energy management using sophisticated control techniques to improve power supply costs. One of these strategies is to use solar energy to power mobile robots. The solar cells appearance is due to the need to supply power spacecraft since not require maintenance for a period of time.
Phase Transformation in Multicomponent Ni3 (Mn,Ti) Alloys
Authors: Gribov Yurii , Klopotov Аnatoliy A. , Potekaev Aleksandr I.
Published: October 2014

The paper presents neutron diffraction analysis and X-ray investigation of ordered alloys Ni3(Mn,Ti) within the concentration range from 0 to 12.5 at.% Ti. The significant effect of the third alloying element Ti on the atomic long-range order was observed in superstructure L12 of alloy Ni3Mn. Experimental study has showed that a rapid quenching in ice water does not provide disordered Ni3(Mn,Ti) alloys. The two-phase region of internmetallic bonds was detected in compounds L12 and D024. The paper presents results estimation of electrical resistivity, normal and abnormal values of hall coefficient, Nernst–Ettingshausen effect, thermal electromotive force, and average atomic magnetic moment in quenched and annealed Ni3(Mn,Ti) alloys. Positive values of abnormal hall coefficient and Nernst–Ettingshausen effect were detected that confirms the predominant contribution of antiparallel spin 3d holes in conductivity. It is shown that in 2.2 at.% annealed Ti alloys ordering promotes 3d electron localization.
Mechanical Properties of Calcium Phosphate Coatings Produced by Method of RF-Magnetron Sputtering on Bioinert Alloys
Authors: Kulyashova Kseniya , Sharkeev Yuriy , Sainova Aizhan
Published: October 2014

Results of research of mechanical properties of calciumphosphate coatings produced by the method radio frequency magnetron sputtering on bioinert alloys of titanium, zirconium and were presented. Calcium phosphate coatings show high value of adhesion strength to bioinert metal surface. Calcium phosphate coating on titanium-niobium alloy surface shows the highest value of adhesion strength. Mechanical properties of a composite material based on bioinert alloy and calcium phosphate coating are higher than properties of the components of composite material separately.
Structure of Zr-Y-O Layer in Zr Y O / Si Al N-Based Multilayer Coatings
Authors: Fedorischeva Marina , Sergeev Viktor , Kalashnikov Mark P. , Voronov Andrew , Popova Natal'ya
Published: October 2014

TEM research of the structure of multilayered coatings consisting of alternating layers Si-Al-N and Zr-Y-O of equal thickness was carried out. It was shown that boundaries between different layers were the sharp enough, and the chemical composition in each layer was homogeneous. The phase composition of the layers on the basis of Zr-Y-O contained basically nanocrystalline ZrO2 and the layers on the basis of Si-Al-N, contained partially amorphous, and partially nanocrystalline Si3N4.
Modeling of Orientation Dependence of Critical Resolved Shear Stress and Deformation Mechanisms on Yield Point of Austenitic Stainless Steels Hardened by Interstitial and Substitution Atoms
Authors: Ivanova Olga , Kireeva Irina , Chumlyakov Yuriy
Published: October 2014

The proposed dislocation model describes the orientation dependence of the critical resolved shear stress (CRSS) and deformation mechanisms on the yield point in single crystals of austenitic stainless steel with nitrogen impurities. The model takes into account the following: the change of the interstitial atom position in the lattice from octahedral interstice to tetrahedral site owing to passage of a leading Shockley’s partial dislocation; the change in the separation width between two partial dislocation in external stress field; the relationship between the width of the extended dislocation and the elastic interaction of the extended dislocation with the impurity atoms.
Influence of Crystal Orientation on Ni3Fe Dislocation Structure Evolution
Authors: Teplyakova Ludmila A. , Kunitsyna Tatyana , Koneva Nina
Published: October 2014

The dislocation structure and mechanical properties of Ni3Fe single crystals with the short range order were investigated. The laws of the dislocation structure evolution of single crystals at different deformation axis orientations were analysed. Correlation of the dislocation structure evolution with the deformation stages for the single crystals with the deformation axis orientations [001], [11], [011] and [1.8.12] was established. The role of the slipping plane numbers in the substructure evolution was revealed.
Plastic Deformation Localization of Low Carbon Steel: Hydrogen Effect
Authors: Barannikova Svetlana , Ivanov Yurii F. , Kosinov Dmitriy , Konovalov Sergey , Stolboushkina Оksana , Gromov Victor
Published: October 2014

In the present study, the features of plastic strain localization and structure of polycrystalline low carbon steel Fe-0.07%C were investigated after hot rolling and electrolytic hydrogen saturation. The method of double-exposure speckle photographyhave been used for identification of main types and parameters of plastic flow localization at different stages of strain hardening.Shown the effect of hydrogen on changing of defect substructure and cementite morphology by using optical and electron microscopy.
Relationship between Parameters of Solid Solution and Grain Boundary Ensemble in Pd3Fe Ordered Alloy with L12 Superstructure
Authors: Perevalova Olga , Konovalova Elena , Koneva Nina , Ivanov Konstantin V. , Kozlov Eduard
Published: October 2014

By X-ray diffraction and scanning electron microscopy using the method of back-scattered electrons the parameters of the solid solution (the lattice parameter and the mean-square displacement of atoms) and the grain boundary ensembles in the alloy Pd3Fe with the superstructure L12 have been investigated depending on the degree of the long-range atomic order. The relationship between the proportion of the twins Σ3 in the spectrum of special boundaries and the mean-square displacement of atoms was detected.
Closed-Loop Temperature Control of Material Plasticisation during Friction Stir Welding
Authors: Hattingh D.G. , van Niekerk Theo I. , Pothier Raymond
Published: October 2014

This research presents the potential for improved joint integrity of friction stir welding by controlling the plasticisation temperature in the weld nugget. During a typical FSW, temperature fluctuates with position along the length of the weld. Working from a basis that for all material and tool geometries, there is an Optimal Plasticisation Temperature (OPT), this paper provides a strategy for maintaining this optimal weld temperature by adjusting selected weld input parameters ensuring consistent joint quality, irrespective of component geometry or clamp configuration. This proposed methodology can also be used to determine the OPT for different FSW tool geometries and material combinations. Advanced monitoring and control strategies are essential to ensure that FSW can be made a more robust industrial process that can keep pace with the modern demand for more consistent production and reliability of welded structures. The potential lies in the possibility for an operator to now select an OPT point for a specific approved welding program and allow the welding platform to maintain the OPT via closed-loop temperature control which adjusts tool rotation and or tool traverse speed. This paper further reports on the potential of integration of a closed-loop temperature control algorithm for FSW. The system measures the temperature inside the FSW tool using thermocouple sensors (creating the feedback signal). The controller then applies a PID algorithm which in turn drives the spindle speed (and if necessary, tool traverse speed) in order to change the energy input rate to the weld for controlling plasticisation temperature.
High Quality Non-Ferrous Die Castings Dependence on Die Design – A Review of the Use of Die Filling and Casting Solidification Simulation Results for Successful, Effective and Practical Die Designs
Authors: Reinhardt Carl J. , Murray Morris , Bohlken Isaac
Published: October 2014

High Quality Cost Effective Die Castings rely to a large extent on successful, effective and practical die design. A review is carried out of some runner and gate designs which resulted in successful high quality castings. Some High Pressure and Gravity cast casting are evaluated. Simulation results for evaluating the impact on the flow during filling due to Runner Geometries, Gate Geometries and positions as well as venting, overflows or risers are discussed. Thermal intervention through the use of internal thermal channels are also evaluated through the use of simulation results. The paper centres on a discussion of analysis of simulation results, predicting defects which impact on some aspects of surface finish and porosity. A case study is presented showing the value of following and taking heed of lessons learnt from simulation results, to carry out die designs with reduced reliance on simulation. Index Terms: South African Foundries, High Pressure Die Casting, Computerised Fluid Dynamics Simulation, Die Design, Defect Reduction.
Operational Cost Analysis of a Typical South African High Pressure Die-Casting Business
Authors: Pereira Filipe
Published: October 2014

This paper looks at the issue and influence of the die cost on a typical Aluminium die casting business. High pressure die casting (HPDC) is a manufacturing process used to produce components in a near finished shape with a reasonable good surface aspect, dimensionally accurate and within a short period off time or production cycle. The die is at the heart of the HPDC business and is unique to each component to be produced. A full business analysis was done and the full die cost share was extracted as part of a life cycle inventory of the HPDC manufacturing process. The inventory accounted for the energy metal and other inputs flows through the foundry. Die casting uses significant quantities of energy, as well as materials like oil-based lubricants and cooling water. Costs associated with part finishing are also considered due to the direct link between die manufacture and design and resulting finishing operations required.
Fundamental Differences between Magnesium and Alkali Metal Electrowinning
Authors: van Vuuren D.S. , Swanepoel Eugene
Published: October 2014

In the Kroll and Hunter processes to produce titanium from TiCl4, magnesium and sodium are used respectively as reducing agents. These processes are slow and very energy intensive and consequently much work was done over the years to improve the economics of producing these metals. In this regard, more success has been achieved with improving the economics of magnesium electrowinning than with alkali metal electrowinning. Magnesium electrowinning cells generally have electrodes with a planar shape and alkali metal electrolysis cells have electrodes with a cylindrical shape. Furthermore, recent advances in magnesium electrolysis allowed the introduction of bipolar electrodes, whereas such electrodes have not been introduced in alkali metal electrowinning cells. It is conceptually possible to replicate the advances in the construction of magnesium electrowinning cells to improve sodium or other alkali metal electrowinning cells. However, there are underlying fundamental reasons why it would be difficult to do so.In this paper the technologies for magnesium and alkali metal electrowinning cells are briefly reviewed. The reasons why it would be difficult to copy the improvements made in magnesium electrowinning technology to alkali metal electrowinning technology are then explained in terms of the implications of the underlying chemical and physical properties of the chemicals involved in the processes.
The Additive Manufacturing (AM) of Titanium Alloys
Authors: Froes F.H. , Dutta B.
Published: October 2014

High cost is the major reason that there is not more wide-spread use of titanium alloys. Powder Metallurgy (P/M) represents one cost effective approach to fabrication of titanium components and Additive Manufacturing (AM) is an emerging attractive PM Technique . In this paper AM is discussed with the emphasis on the “work horse” titanium alloy Ti-6Al-4V. The various approaches to AM are presented and discussed, followed by some examples of components produced by AM. The microstructures and mechanical properties of Ti-6Al-4V produced by AM are listed and shown to compare very well with cast and wrought product. Finally, the economic advantages to be gained using the AM technique compared to conventionally processed material are presented. Key words: Additive Manufacturing (AM), 3D Printing, CAD, CAM, Laser, Electron beam, near net shape, remanufacturing, Powder Bed Fusion (PBF), Direct Energy Deposition (DED)
A Study of Solvent Debinding Variables on Ti6Al4V Green Bodies
Authors: Seerane Mandy , Chikwanda Hilda , Focke Walter , Machaka Ronald
Published: October 2014

Debinding is one of the most critical and time consuming stage in metal injection moulding (MIM). German and Bose (1997) reported that early debinding practice relied on thermal binder degradation, requiring up to 300 hours for complete binder removal. Today multi-stage debinding techniques are introduced cutting down the debinding time to as little as 2 hours. This work investigates solvent debinding variables prior to thermal debinding. Solvent debinding is carried out in n-heptane. Wax and stearic acid are the target binder components being leached out from the green bodies, with wax as the major constituent in the binder formulation. Debinding is conducted at 50, 55, 60 and 65°C for 1-4 hours at each temperature. Weight loss measurements were done. For porosity and surface appearance, scanning electron microscope (SEM) analysis and visual inspection were done. Samples de-bound at 65°C showed an appreciable amount of mass loss; however, surface cracks and warping were observed. A 60°C temperature and time of 4 hours demonstrated best results i.e. a satisfactory mass loss, absence of surface cracks and no warping. Mass loss is directly proportional to temperature and time. SEM results are discussed in the paper.
Influence of Powder Particle Size Distribution on the Properties of Press-and-Sintered Titanium and Ti-6Al-4V Preforms
Authors: Bosman Hendrik L. , Blaine Deborah C.
Published: October 2014

The potential to control the final properties, as measured by density, strength and microstructure, of press-and-sintered titanium and master alloy Ti-6Al-4V is investigated by designing and evaluating bimodal particle size distributions of the relevant powders. Ratios of 1/3, 2/3 and 1/1 by volume of coarse to fine powders, as determined by particle size peaks, were blended from -200 and -100 mesh commercially pure titanium powders and -200 mesh 60Al-40V master alloy powder, in the case of Ti-6Al-4V. The powder blends were uniaxially compacted at 350, 400 and 450 MPa, and the green specimens were sintered under high vacuum for two hours at 1300°C. The results support theoretical prediction of green and sintered density based on the ratio of the volume percentage of coarse to fine powder; green density increases as the ratio of coarse powder increases for both the pure and alloy titanium, while the sinter density similarly decreases for the pure titanium. Microstructural observations of the sintered specimens show that the pore size decreases, and the pore shape becomes more rounded, as the ratio of fine powder increases. In order to extend the study to find the optimal packing ratio, and potentially the optimal blend for densification, further refinement of the initial powder particle size distributions is needed.
Preparation of Titanium Alloy Rods by Powder Compact Extrusion
Authors: Yang Fei , Gabbitas Brian , Mukhtar Aamir , Downing Warwick
Published: October 2014

Titanium alloys have a number of features which make them attractive for use in aerospace, marine and chemical engineering, biological engineering, etc., due to their advantage of low density, high strength, and excellent corrosion resistance and biocompatibility. In this paper, Ti-6Al-4V (Ti-64) rods were prepared by vacuum sintering titanium alloy powder compacts at 1300°C for 2h and then hot extruding the as-sintered Ti-64 alloy billets at 1150°C in air. The microstructure and property changes, after vacuum sintering and hot extrusion, were investigated. The results showed clear evidence of porosity and a coarse lamellar microstructure in as-sintered Ti-64 alloy billets. Tensile testing of as-sintered material gave yield strength, ultimate tensile strength and ductility values of 850MPa, 985MPa and 2%, respectively. After extrusion at 1150°C, no obvious pores could be seen in the microstructure of as-extruded Ti-64 alloy rods and the lamellar microstructure was significantly refined, and the mechanical properties were significantly improved. The yield strength, ultimate tensile strength and the ductility reached 1130MPa, 1245MPa and 4.5%, respectively. Compared with the mechanical properties of Ti-64 alloy rod prepared by extruding a hot pressed Ti-64 alloy billet (1300°C for 5min, argon protective atmosphere) in air, the ductility of the Ti-64 alloy rod studied here is lower. The fracture characteristics of as-sintered and as-extruded Ti-64 alloy rods have also been investigated.
Opportunities for the South African Foundry Industry in the Global Automotive Supply Chain
Authors: Krieg Mark , Cunningham Shawn
Published: October 2014

Two rapid assessments of foundries in the automotive supply chain were conducted in 2012 and 2013 on behalf of the National Foundry Technology Network (NFTN), an initiative of the Department of Trade and Industry (dti). The investigation was not an academic or econometric study; but to identify areas where assistance was required by the foundries, and opportunities for growth. There are both Tier 1 and Tier 2 foundries that are qualified to, and do, supply the automotive sector. Castings, components and sub-assemblies are produced in South Africa for the majority of passenger vehicle manufactures. There has been an increase in volumes supplied by smaller, often Tier 2 & 3 foundries, however, drive train castings are largely imported. Furthermore, there was little evidence of supply contracts for the next model ranges. Local castings were said to be 10% to 30% more expensive than imported parts. Typically, sourcing discussions are made outside of the country, and price and security of supply are main considerations. Original Equipment Manufacturers (OEM’s) have committed to local sourcing, but it was clear that a significant intervention was required to change the downward trend. This would be outside the scope of both the Aluminium Federation of South Africa (AFSA) and the NFTN. It was recommended that a Competitive Improvement Initiative (CII) be launched by the NFTN. This was subsequently approved by the NFTN/dti.

 
Friction Hydro Pillar Riveting – Alternative Joining Technique for 3.17mm Ti-6Al-4V Sheet
Authors: Hattingh D.G. , Tsikayi D.S.
Published: October 2014

This paper reports on preliminary results obtained during exploratory research, investigating the feasibility of employing Friction Hydro Pillar Processing principles as an alternative technique for producing riveted joints in 3.17mm Ti-6Al-4V sheets. Influence of process parameters was investigated to understand material flow during the plasticisation phase. An understanding of joint performance from a macrostructural and hardness point of view was established and forms part of the data presented. Process energy was quantified in relation to rotational speed. The data presented will assist in guiding the overall research objective to determine the feasibility of Friction Hydro Pillar Riveting as a suitable alternative high integrity joining process for the Aerospace industry.
Cost Effective Forging of Titanium Alloy Parts and their Mechanical Properties
Authors: Gabbitas Brian , Yang Fei , Raynova Stella , Jia Ming Tu
Published: October 2014

Both open die and closed die powder compact forging can be used for the consolidation of Ti and pre-alloyed Ti 6Al 4V powders produced by a hydride-dehydride (HDH) process. The approach used is initial cold or warm compaction into cylindrical shapes, or into a specific pre-form shape appropriate for achieving a particular final forged shape. The economic benefit is near net-shape processing with minimum machining required after forging. Manufacturing costs are also minimised by forging a compact, with a sufficiently high enough density, in air, without a protective atmosphere. The challenge, from a manufacturing point of view, is the operation of a manufacturing route which gives rapid and qualified compaction to meet production demands and batch sintering to achieve a high enough density prior to final forging to shape. In addition to this the final product has to have the right level of mechanical properties. This paper reviews some key findings from powder compact production, through to sintering and forging. These will be presented in terms of alpha-beta phase distribution in the microstructure, the degree of porosity, heat treatment and their effects on mechanical properties.
The Influence of Initial Grain Size and Strain Sequence of Slab Hot Rolling on the Austenite Evolution of Peritectic Microalloyed Plate Steels
Authors: Maubane Rorisang , Banks Kevin , Stumpf Waldo , Siyasiya Charles , Tuling Alison
Published: October 2014

The influence of the strain sequence during slab hot rolling (also known as “roughing”) on the evolution of austenite in plain carbon, C-Mn-V and C-Mn-Nb-Ti-V steels was investigated. Reheating and roughing simulations were conducted in a Bähr deformation dilatometer using a constant austenitising temperature, constant soaking time and various heating rates and roughing strain sequences. Stress analysis was used to quantify the austenite softening behaviour and the prior austenite grain size was measured from quenched specimens. The austenite grains of the plain carbon steel were coarser than those of both microalloyed steels, with the C-Mn-Nb-Ti-V grade being the finest due to effective pinning of the grain boundaries. Pass strains greater than 0.2 were sufficient for initiation of dynamic recrystallisation (DRX) for the C-Mn and C-Mn-V steels and led to uniform austenite microstructure with austenite grain sizes less than 40µm after the roughing stage.
Development of VC-Ni Eutectic Alloys for Wear Resistance
Authors: Apata O.A. , Muobeleni T.N. , Fabuyide A.A. , Ogunmuyiwa E.N. , Rading G.O. , Jain P.K. , Witcomb M.J. , Cornish L.A.
Published: October 2014

Vanadium carbide is less dense, harder and tougher than tungsten carbide, and nickel is more corrosion resistant that cobalt. Replacing the binder with Ni should improve the corrosion resistance. Since there are eutectics with a wide range of compositions in the C-Ni-V system, this system has potential for wear resistant alloys with ~VC as the discrete hard phase and the nickel solid solution as the binder. The aim of this work was to ascertain if eutectic microstructures with vanadium carbides could be beneficial to wear resistance. Phase studies confirmed the wide range of the eutectic alloys, with VC + (Ni), VC + σ′, VC + (V) and graphite + (Ni) and different morphologies. Preliminary wear tests showed results comparable to WC-Co alloys.
Magnesium Metal Production with Least CO2 Emission
Authors: Neelameggham Neale Ramaswami , Brown R.E.
Published: October 2014

Magnesium metal is one of the few metals with multiple raw material sources. These are either from the hydrosphere of the ocean and saline lakes or from the lithosphere from ores and natural evaporites. This paper will describe CO2emission from both the chemical process stand-point as well as the physical process energy requirements. Present processes of electrolytic as well as the thermal reduction will be described along with their carbon dioxide emissions. Novel methods will be introduced as to how the carbon emission in the production of this light metal can be minimized in a cost effective fashion.
Temperature Dependence and Martensitic Transformation of Ti50Pt50 Shape Memory Alloys
Authors: Mashamaite M.P. , Chauke Hasani Rich , Mahlangu Rosinah , Ngoepe P.E.
Published: October 2014

Shape memory alloys (SMAs) are a fascinating group of metals that have two remarkable properties, the shape memory effect and superelasticity. The TiPt structure with the B2 phase has been reported to undergo a reversible displacive transformation to B19 martensite at about 1200K. However, this system could serve in principle as the basis of high-temperature shape memory alloys. Molecular dynamics study of martensitic transformation in platinum titanium alloys was performed to investigate the effect of temperature dependence on B2 and B19 structures at 50 at.%Pt. The NPT ensemble was used to determine the properties of these systems and we found good comparisons with recent experimental work. The temperature dependence of TiPt shows potential martensitic change when B19 is heated to extreme high temperatures of 273K up to 1573K.
Martensitic Transformation Behaviour of Ti50Pt50-xCox Shape Memory Alloys
Authors: Mahlangu Rosinah , Chauke Hasani Rich , Ngoepe P.E.
Published: October 2014

The supercell approach method was used to investigate the effect of partial substitution of Pt with Co on the TiPt potential shape memory alloy. The first-principles calculations were carried out within the generalized gradient approximation to determine the stability of the Ti50Pt50-xCoxfor x=6.25, 18.75 and 25. We found that the calculated heats of formation and density of states predicted the 6.25 at. % Co to be the most stable structures compared. The elastic properties, thermal coefficient of linear expansion and the density of states results suggest that the partial substitution of Pt with Co decreases the Ms of TiPt with the softening of the Cʹ shear moduli.
Redetermination of the Niobium(V) Precursor, [NbCl5(NCCH3)]
Authors: Herbst Leandra , Visser Hendrik G. , Roodt Andreas
Published: October 2014

The monomeric coordination compound pentachloro(acetonitrile)niobium(V), [NbCl5(NCCH3)], (NCCH3= acetonitrile) has been prepared under aerobic conditions and characterized by single-crystal X-ray diffraction. [NbCl5(NCCH3)] crystallized in the monoclinic spacegroupP21/cwitha= 5.964 (3),b= 9.888 (5),c= 15.448 (9) and β = 98.224 (2). Comparison is made to a previously published isomorphous complex that was prepared under unaerobic conditions.
The Coordination of Novel, Hard Ligand Systems to Tantalum(V) and Niobium(V) Metal Centres
Authors: Koen Renier , Roodt Andreas , Visser Hendrik
Published: October 2014

The formation reaction of acetylacetone to solvated tantalum pentachloride ([TaCl5]2) in methanol, is defined by limiting kinetic behaviour and is indicative of a two-step process. This involves the rapid formation of an intermediate, possiblytrans-[TaCl2(OMe)3(η1-acacH)]) with the stability constant,K1, equal to 2.4 ± 0.3 x 103M-1at 25 °C. The second order rate constant,k1, at 25 °C was determined as 3.1 ± 0.1 x 102M-1s-1. A fit of the data obtained from the UV-Vis study, and describing the total reaction, yielded a value of 1.7 ± 0.2 x 103M-1s-1forK1, which is in agreement with the value obtained earlier. Comparison ofk1andk2indicates that the first reaction is roughly six orders of magnitude (106) faster than the second rate determining step.
Age-Hardening of Rheo-High Pressure Die Cast Al-Alloy 6066
Authors: Taute Carlien , Möller Heinrich
Published: October 2014

Al-Mg-Si-Cu alloy 6066 is a heat-treatable wrought alloy that is commonly used in high performance bicycle frames. Wrought alloys are difficult to cast using conventional liquid casting techniques, as hot tearing can occur. However, a method that effectively reduces that risk is rheo-high pressure die casting (R-HPDC). Casting alloy 6066 using semi-solid metal processing makes it possible to be used for near-net shape forming of components. This study investigates the age-hardening response of R-HPDC alloy 6066. The effects of different solution heat treatments, natural pre-ageing and artificial ageing are studied. The different solution heat treatments investigated are a one-step and a two-step solution treatment. The one-step treatment was performed at 530°C only and the two-step treatment at 530°C followed by 550°C. It is shown that natural pre-ageing has a detrimental effect on the T6 properties and that the longer two-step solution heat treatment is justified due to an increase in hardness and prevention of incipient melting. The Vickers hardness in different temper conditions (F, T4, T5 and T6) were determined and compared to the typical hardness values of the alloy in the wrought condition.
Laser Beam Welding of Semi-Solid Rheocast Aluminium Alloy 2139
Authors: Gilbert C.R.
Published: October 2014

NASA developed aluminium alloy 2139 for use in airframe structural applications as the requirement for higher strength, corrosion resistant, aluminium alloys is increasing, however the need to weld ‘unweldable alloys’ is also becoming apparent. 2139 is seen to be in this class. Semi-solid rheocast aluminium plates (Al-Cu-Mg-Ag) were cast in high pressure die casts. In total 27 welds were fabricated in experimentation, 3 on each plate to avoid distortion by using a continuous wave Nd:YAG. The weldability of this Al-Cu alloy was assessed by optical microscopy to indicate the quality and geometry of the passes. Comparisons were made with As-Cast (F) tempers. Laser power parameters ranged from 3 kW to 4 kW and weld speeds from 4 m/min to 6 m/min. Welds were allowed to cool naturally. The results show that by varying speed and power, when combined with heat treatments, produce diverse results for this unweldable alloy.
Numerical Investigation of Cross-Section on Aluminum A6063 Thin-Walled Structures under Low-Velocity Impact Loading
Authors: Taherkhani Ali , Alavi Nia Ali
Published: October 2014

In this study, the energy absorption capacity and crush strength of cylindrical thin-walled structures is investigated using nonlinear Finite Elements code LS-DYNA. For the thin-walled structure, Aluminum A6063 is used and its behaviour is modeled using power-law equation. In order to better investigate the performance of tubes, the simulation was also carried out on structures with other types of cross-sections such as triangle, square, rectangle, and hexagonal, and their results, namely, energy absorption, crush strength, peak load, and the displacement at the end of tubes was compared to each other. It was seen that the circular cross-section has the highest energy absorption capacity and crush strength, while they are the lowest for the triangular cross-section. It was concluded that increasing the number of sides increases the energy absorption capacity and the crush strength. On the other hand, by comparing the results between the square and rectangular cross-sections, it can be found out that eliminating the symmetry of the cross-section decreases the energy absorption capacity and the crush strength. The crush behaviour of the structure was also studied by changing the mass and the velocity of the striker, simultaneously while its total kinetic energy is kept constant. It was seen that the energy absorption of the structure is more sensitive to the striker velocity than its mass.
Research on the Laws of Wear Rate of Grinding Block in Grinding SiC
Authors: Lu Guo Dong , Zhang Fei Hu , Liu Li Fei
Published: October 2014

Silicon carbide ceramics with its excellent physical and mechanical properties have become the preferred material of space large diameter mirror. But because of its higher hardness, diamond wheel would appear some wear form and wear rate in the mechanical processing process, wear form is an important factor to effect surface and subsurface quality, wear rate effects the surface shape accuracy, so the research on the laws of wear rate of grinding wheel has an important role in grinding. But, because of the particularity of wheel structure, wheel wear form and wear rate changes with time going, which limits the wheel wear research. By the grinding process experiment, the author found the relationship between diamond grinding block wear rate and wheel feeding, and got the laws of wear rate with time. With the laws of wear rate, we can predict the surface accuracy and guide the compensation of wheel feeding.
Experimental Study on Removal Characteristics of Ceramic Materials in Ultrasonic Aided High Efficiency Lapping
Authors: Zhang Chang Juan , Jiao Feng , Zhao Bo
Published: October 2014

In order to clarify the material removal characteristics of Al2O3 engineering ceramics in ultrasonic aided high efficiency lapping, a series of ultrasonic and conventional lapping contrast experiments were carried out on precision lathe with self-made ultrasonic lapping device. The research results show that the value of material removal rate in ultrasonic aided lapping is about 2~4 times that in conventional lapping, especially in ultrasonic axial lapping. In ultrasonic aided lapping, the better removal characteristics can not be obtained by adopting too high or too low lapping parameters, and there are optimum lapping parameters from which a higher material removal rate value can be achieved.
In Situ Measurement and Compensation Turning Technique of Deep MgF2 Conformal Dome
Authors: Zhu Deng Chao , Dai Yi Fan , Guan Chao Liang , Wang Gui Lin , Tie Gui Peng
Published: October 2014

The adoption of conformal optics system can evidently improve the synthetical performance of infrared missiles. Hot-pressing poly-crystal magnesium fluoride (MgF2) is an ideal material for conformal optics dome. But many problems about machining and surface test of deep aspheric surface have not been solved at present, and there is not much research about the machining characteristics of MgF2 material. In this paper, in-situ measurement system is designed, so positional errors that introduced by repeating installation can be avoided. Then, machining process of MgF2 material by single point diamond turning is studied, and optimized diamond turning process is proposed by experiments in order to obtain low surface roughness. Furthermore, surface accuracy is tested by on-machine measurement system. Based on the result, error compensation process of conformal dome is carried out. Finally, the shape error of the dome is less than 0.8μm PV.
Experimental Study of SiC Ceramic Grinding Subsurface Cracks
Authors: Liu Min Hui , Zhang Fei Hu , Lu Guo Dong
Published: October 2014

Silicon carbide ceramics with its excellent physical and mechanical properties have become the preferred material for space large diameter mirror. Diamond wheel grinding is the main way of SiC ceramics forming processing. Subsurface cracks is generated due to the high hardness and brittleness of the material after grinding. In order to remove the impact of cracks, poishing processing with very low efficiency is applied, so it is significant to control the depth of silicon carbide ceramic grinding subsurface cracks and shorten the processing cycle.In this paper grinding experiment of SiC ceramic is conducted. The method of cross-section polishing combined with scanning electron microscope observation is used to research grinding subsurface cracks. The depth of broken surface layer and the maximum depth of sub-surface cracks were proposed to evaluate the grinding subsurface cracks. The result show broken surface layer depth and the maximum depth of sub-surface cracks increase with the decreasement of spindle speed, and increasement of feed rate and grinding depth.
Design and Test of Piezoelectric Tool Actuator on Ultra-Precision Machine Tool for KDP Crystals
Authors: Zhang Chao , Zhang Fei Hu , Zhang Qiang
Published: October 2014

In order to improve the positioning resolution of the tool adapter on ultra-precision machine tool for KDP crystals, this paper presents a new piezo tool actuator. First, a new flexible membrane structure is designed after considering the characteristics of the machine tool for KDP crystals. Then, its detailed structural dimension is determined by finite element method. Finally, the piezo tool actuator is machined based on designs and its performance data is obtained by experiments. Experimental results indicate that its positioning resolution is superior to 0.5μm and its stroke reaches 4.7μm, which can meet the requirements of ultra-precision machine tool for KDP crystals.
Analysis on the Influence of Oxidant in CMP of Ultra-Thin Stainless Steel
Authors: Su Jian Xiu , Chen Jia Peng , Cheng Hai Feng , Fan Song Zhan
Published: October 2014

In chemical mechanical polishing (CMP) of ultra-thin stainless steel, the oxidant of polishing slurry determines the material removal rate (MRR). In this paper, the influences of oxidant in slurry on MRR and surface roughness have been studied in CMP of ultra-thin 304 stainless steel based on alumina (Al2O3) abrasive. The research results show that, in the same conditions, the MRR increases with the increase of the oxidant C and the oxidant B, the MRR decreases with the increase of the oxidant A and the MRR is max with the oxidant C. It indicated that the oxidant C has a large effect on MRR in CMP of the 304 stainless steel. The research results can provide the reference for studying the slurry in CMP of ultra-thin stainless steel.
Introduction of Premixed Micro-Abrasive Water Jet Technology for Deburring
Authors: Qiu Chun Lin , Wang Cheng Yong , Song Yue Xian
Published: October 2014

Micro-abrasive water jet technology for deburring is a new type of removing burrs technics with advantages of high productivity, high flexibility, no cutter damage and less residual damage etc, which is applied more and more extensively. This paper introduces the difference of premixed micro-abrasive water jet and post-mixed micro-abrasive water jet on jet formation, the difference of system principles and applications. This paper also provides the formula that how to quantitatively calculate the impact force of water jet. The principles and factors which influence on deburring and some application examples are also described in this paper.
Analysis of the Main Factors Affecting the Surface Morphology of FSJ Joint
Authors: Deng Yong Fang , Zuo Dun Wen , Song Bo
Published: October 2014

An attempt is made here to analyze the effect of the process parameter and shoulder of tool on the surface topography of FSJ (friction stir joining) joint. It is found that, it is a linear relationship between the feed speed and arc lines spacing, and the slope decreases as feed speed increasing. As the rotational speed increasing, the arc line spacing reduces. While FSJ processes completed at different parameters contain the same ratio between the feed speed and the rotation speed, the arc line spacing of the joint surfaces is the same. The shoulder of tool can increase the width of joint lines, refine arc lines structure, reduce the flash in the retreating side, but increase the flash in the advancing side.
Micro-Nano Burr Removing Mechanism of Precision Ceramics Surface
Authors: Xue Jin Xue , Wang Guo Hu , Gao Guo Fu
Published: October 2014

The micro and nano burr removing mechanism of precision surface of the nano-ZrO2 ceramics were investigated. The ultrasonic vibration finishing experiments showed that the critical ductility finishing depth of the ceramics was 3μm by conventional finishing, but the increment of the critical ductility finishing depth was 50 percent by ultrasonic finishing. The critical ductility finishing depth increased to 6μm. Analyzed by means of SEM, it was transgranular cracking during the micro-nano burr removing process. The nano-ZrO2 ceramics have high toughness so the critical ductility finishing depth increased. The shape, length, width and thickness of the finishing differed greatly from that obtained by conventional finishing.