Electrophoretic Deposition: Fundamentals and Applications IV
Material Forming ESAFORM 2012
Micro-Nano Technology XIII
Advances in Manufacturing Systems
Progress in Polymer Processing
Advanced Materials in Microwaves and Optics
Anti-Fatigue Design and Manufacturing Technologies I
Behaviour of Material and Composite Structures
Silicon Science and Advanced Micro-Device Engineering II
Precision Machining VI
Materials and Applications for Sensors and Transducers
Testing and Evaluation of Inorganic Materials II
Anti-Fatigue Design and Manufacturing Technologies I
摘要: In order to reduce manufacturing cost, a methodology of accuracy synthesis for machine tool was recommended by combining both machining cost and Least Square method. Weighted coefficients representing the machining difficulty of manufacturing processes were introduced. 3PRS/UPS redundant parallel kinematic mechanism (3PRS/UPS PKM) was taken as an example, and its component tolerances were derived by the proposed method. Comparing with conventional method, the component tolerances were allocated reasonably. A further tolerance allocation for spherical and rotational joints was studied in detail. And hence, the producibility of component was improved and the manufacturing cost was reduced. The results showed that the proposed method was capable of producing tolerance allocations economically and accurately.
摘要: Particle reinforced metal matrix composites (PMMC) possess many outstanding properties and are increasingly applied in automobile, aerospace, electronics and medical industries. However, PMMC is a typical difficult-to-machining material due to the rapid tool wear rate and excessive machining induced defects. Although large amount of investigations have been done on the conventional machining of PMMC, merely several researchers have dedicated themselves to the study of milling, especially high speed milling of this material. Within the milling studies, most researchers have selected the carbide coated or uncoated solid carbide tools whose tool life was not satisfactory for engineering application. The literatures review indicates that most researchers limited their study to sintering or casting SiCp/Al composites at the low or moderate cutting speed. Material produced by the in-situ reaction method or titanium matrix composites was seldom selected as the research object. The research content was limited to the effect of cutting parameters on the machined surface quality or cutting forces. It is suggested that high-speed milling with PCD tool should be conducted in order to improve the machined surface quality and material removal rate and decrease the machining cost. Tool life modeling, surface roughness prediction, cutting parameters optimization and high-speed milling data base and the expert system should be greatly noticed by the researchers.
摘要: The metal cutting is a complexly dynamic physical process of thermal-mechanical coupling. It is difficult in analyzing the mechanism of machining deformation with the traditional calculation method. The key simulation technologies of the machining process are analyzed by means of finite element method (FEM), such as material constitutive model, chip separation criterion, tool-chip interaction and friction model, thermal control equation. During finite element simulation of the peripheral milling of the thin-walled workpiece, the contact constraints between the tool and workpiece can be effectively simplified. Thus, the tool and workpiece are considered as rigid and elastic bodies, respectively. In sequence, the unit birth and death technology is used to simulate the material removal in the milling process so that the effect of the workpiece size on machining deformation can be researched accurately. The investigation on the theory and application of the above key technologies can not only analyze and predict the deformation of thin-walled parts, but also optimize process parameters to control the machining deformation.
摘要: For great progress in heat pipe technology, a micro heat pipe has become an ideal heat dissipating device in high heat-flux electronic products, and capillary limit is the main factor affecting its heat transfer performance. Based on analyses of capillary limit and currently commonly-used groove structures, this paper built capillary limit models for micro heat pipes with dovetail-groove, rectangular-groove, trapezoidal-groove and V-groove wick structures respectively for theoretical analyses. The analysis results show that better heat transfer performances can be obtained in micro heat pipes with small-angle dovetail (i.e. a sector structure), rectangular and small-angle trapezoidal grooved wick structures when groove depth is 0.2-0.3mm and top-width-to-depth ratio is 1.2-1.5.
摘要: Milling process of jointing blank of 7022 aluminum alloy was simulated by ANSYS. The results show that the maximum residual tensile stress and pressure stress are mainly concentrated in the jointing seam zone when the jointing blank is milled. The milling deformation of jointing blank is shown as “wave” shape. The milling deformation of key eye side is shown upwarp. The jointing initiating terminal is shown downward displacement. The maximum downward displacement is present to the middle of jointing seam central line. In additional, the milling deformation along sheet length direction is shown outward extension.
摘要: Ruthenium (Ru) and ruthernium alloys may be utilized as new copper barrier materials in copper interconnects of ultra-large scale integration (ULSI), and chemical mechanical polish (CMP) can be applied in planarization for ULSI production. In this paper, CMP experiments were done on high purity Ru by using home-made slurry, the effect of oxidizer, complexing agent, polishing downforce, pH value, inhibitor species and inhibitor concentration on the material removal rate (MRR) was investigated. The results revealed that MRR can reach 8.7 nm/min under the following conditions: the main constituents in slurry were 1 wt.% SiO2, 1 wt.% (NH4)2S2O8, 1 wt.% tartaric acid and 3 mM imidazole, the pH value was 8.0, the down force was 2.5 psi (17.24 kPa); the roughness Ra was 7.6 nm under these conditions.
摘要: This paper presented a finite element simulation model for the analysis of AISI D2 orthogonal cutting process using TiAlN coated inserts. Firstly, AISI D2 material constitutive model was built based on power law model, which was used in the FEM codes to describe the effect of strain, strain rate and temperature on the material flow stress. In modeling the chip formation, a damage model was employed to predict the chip separation. Then cutting edge radius and thickness of TiAlN coating of cutting tool were measured by SEM. Friction coefficients of cutting tool against AISI D2 steel were obtained by ball-on-plate friction tests on UMT-2 high speed tribometer. Finally, finite element simulations of AISI D2 orthogonal cutting processes were performed using AdvantedgeTM software. The simulated results of cutting forces and chip morphology showed good agreement with the experimental results, which validated the reliability of the cutting process simulation method.
摘要: Silicon carbide (SiC) is a promising material for fabricating wire compacting dies due to its advantages of light weight and even high wear resistance over the tungsten carbide, which currently is the most popular material used to produce compacting dies. In present study, a layer of CVD diamond film is deposited on the interior-hole surface of compacting dies using the hot filament chemical vapor deposition (HFCVD) method, following by a surface polish process, aiming at further elongating the lifetime of compacting dies and improving the surface quality of produced wires. The characterization of both as-deposited and polished CVD diamond films is employed by scanning electron microscopy (SEM), surface profiler, Raman spectroscopy and X-ray diffraction (XRD) spectroscopy. Furthermore, the performance of as-fabricated CVD diamond coated compacting dies is examined in the real production process. The results exhibit that the as-deposited CVD diamond films are homogeneous and their surface finish is significantly smoothened after the surface polish process. As compared with the conventional compacting dies, the working lifetime of the diamond coated SiC compacting dies can be increased by a factor of above 15 and in the course of processing, copper stranded wires with high surface quality and uniform sectional area can be obtained.
摘要: Rock tunnel boring machine is one of the main machineries and equipments for underground engineering, and the failure of its disc cutter is the main failure form of this machinery. The experiment on the failure and wear of the disc cutter is difficult. In this paper, a rock hob test-bed is designed, and the hydraulic-driven system of its disc cutter of rock hob test-bed is simulated; the effect of load and flow rate of hydraulic oil in this hydraulic system on characteristics of this disc cutter system is analyzed. The results show that the vertical movement speed of disc cutter is directly proportional to the flow rate; the effect of the load on this speed and the vertical pressure can be ignored; the delay time of the movement of the disc cutter to the flow rate of hydraulic oil is proportional to the load. These results are very helpful to the structure optimization of disc cutter system of rock tunnel boring machine and the improvement of working efficiency.