Applied Mechanics and Materials Vols. 423-426

Abstract: The carburizing heat treatments of ultrafine-grained WC-Co composites with sub-stoichiometric carbon content were carried out, and the microstructures of ultrafine-grained WC-Co carbides before and after treated were characterized by means of scanning electron microscopy and X-ray diffraction. The results show that the functionally gradient ultrafine-grained WC-Co hardmetals with a Co depleted surface and not comprising the η-phase can be fabricated by carburizing heat treatment. After heat treatment, WC grain sizes in materials are still at the ultrafine grade.

Abstract: A series of (Bi_1-xLa_x)₂Al₄O₉ (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40) ceramics were prepared by sol-gel method with sintering process. Doping dependent investigations were carried out to show the influence of La atom on the structural stability. The products were characterized using X-ray diffraction, scanning electron microscopy. This showed that the second phase is increased gradually by La doping. When the value of La is 0.4, the main phase tends to become LaAlO₃. Details on dielectric properties are reported. The permittivity of as-prepared doped samples increases slightly compared to pure Bi₂Al₄O₉ and excellent frequency stability is exhibited.

Abstract: In order to improve the flow stability when wafer scans at high speed, immersion lithography with small flow-thickness is proposed for the high resolution lithography. By using the three-dimensionally numerical methods, the immersion flow in micro-gap is investigated to analyze the behaviors of liquid flow. Based on the flow characteristics of typical structures with different liquid thickness and scanning speed, the liquid mean-velocity on account of thousand sample points in the exposure area are studied, and the appropriate parameters and method of effective renovation with small thickness are also given.

Abstract: In this paper, six sigma methods were used in bearing ring grinding process improvement. In the improvement, bearing outer ring roundness error was selected as the assessment index, and exsiting problems in grinding process were defined, roundness error of bearing outer ring was measured.One-way analysis of variance was applied to analyze the test results, it indicates that workpiece center height, guide wheel tilt angle and grinding wheel balance are the three main factors that affecting roundness error.According to this analysis, orthogonal experiment was designed. The results show that grinding wheel balance, guide wheel tilt angle and workpiece center height on the impact of roundness error are in descending order. On this basis, a series of measures were carried out to control these three parameters. Uitimately, the grinding process capability index is increased from 0.88 to 1.43, and the target of improvement are achieved.

Abstract: This paper estimates the electrical energy loss on high-temperature plasma processing waste printed circuit boards. Using three plasma torch powers in big output power (60W) and a plasma torch power in relatively small output power (30W), after 4.5 hours of high-temperature plasma incineration, 43 kilograms of waste printed circuit boards was successively fused at high temperature plasma incinerator. After calculating, the total electrical energy loss for four powers was about 1,070 kilowatts hours during sample incineration.

Abstract: In order to study the acoustic emission characteristics of coarse aggregates, improved of large-scale triaxial apparatus is used to do the consolidated undrained triaxial tests of sericite schist coarse aggregates, with the acoustic emission signals monitoring. The test results show that a large number of AE signals of sericite schist coarse aggregates are generated in the initial stage. Before the axial strain reach 10%, AE counts are relatively quiet. But after 10%, they become anomalous and emerge obvious leap values. When the confining pressure up to 200kPa, AE signals are mainly generated by sliding friction. With confining pressure increasing, the proporation of rolling friction and particle breakage is more and more obvious.

Abstract: In order to establish the relation between acoustic emission parameter and rock mechanical damage mechanism, as well as to better figure out landscape limestone damage and deformation influenced by uniaxial compression, MTS815 rock mechanical electro-hydraulic servo test system and 8CHSPCI-2 acoustic emission and detection system are applied to implement a test and research on damage evolution of limestone under uniaxial compression and the corresponding acoustic emission feature. On this basis, the acoustic emission feature of limestone under uniaxial compression is analyzed. Moreover, based on the damage variable of normalized accumulated emission ringing count, the uniaxial compression limestone damage model based on acoustic emission feature is established, and the damage evolution curve and equation of limestone is figured out as well. Shown by the research, acoustic emission information reflects the internal damage of limestone, and is closely related with densification of inner original fracture, as well as emerging, developing, and merging of new fractures. The acoustic emission feature of limestone perfectly describes its deformation and damage evolution.

Abstract: The friction and wear properties of the water lubricated rubber bearing, made of the nitrile butadiene rubber (NBR), were studied in this article. The results showed that adding the appropriate amounts of carbon black and molybdenum disulfide (MoS₂) could reduce the friction coefficient and the abrasion loss to the minimum values. Meanwhile, the general laws of the two parameters with different loads, rotational speeds and lubricant media have been discovered: the values of friction coefficient and abrasion loss of the rubber bearing, lubricated in both water and seawater, increase firstly and then gradually decrease with the increasing loads.When the loads exceed 500N, the values increase drastically. And the values of friction coefficient and abrasion loss decline with the increasing rotating speed. Moreover, the values of these two parameters in seawater were a little bit higher than those in water. The friction and wear mechanisms of water lubricated rubber bearing were also discussed..

Abstract: Electrochemical machining (ECM) is a non tradition process used for the machining of metal matrix composites. Metal matrix composites are used for applications in aero scope, automobile industries and medical field. Determination of optimal process parameter is difficult in ECM machining process for obtaining maximum Material Removal Rate (MRR) and good Surface Roughness (SR).The multiple regression model was used to obtain the relationship between process parameters and output parameters and Weighted Sum Genetic Algorithm (WSGA) optimization was proposed to optimize the ECM process parameter. .The Voltage, Current, Feed Rate and Electrolyte Concentration are considered as decision variables, MRR and SR are the machining parameters used in the proposed work.

Abstract: The numerical simulation on upsetting process of large forgings is conducted by using ANSYS/LS-DYNA. The FEM model is established by determining materials, contacts, constraints and loads. The distributions of strain and stress are calculated and discussed. Drum shape coefficient is defined to measure the nonuniform in deformation. The simulative values of upsetting forces are compared with those in theoretical methods, which gives the same change tendency and consistency. Influences of height-diameter ratio to strain, drum shape, tangential stress and upsetting force are also investigated, which provides basic guidance to determine process parameters in upsetting.