Advanced Materials Research Vols. 472-475

Abstract: In this note, an adaptive repetitive control scheme is presented for a class of nonlinearly parameterized systems based on fuzzy basis function networks (FBFNs). The parameters of the fuzzy rules are tuned with adaptive schemes. The adaptive repetitive control law is derived by using Lyapunov synthesis method to guarantee the closed-loop stability and the tracking performance. By means of FBFNs, the controller singularity problem is solved as it avoids the nonlinear parameterization from entering into the adaptive control and repetitive control. The proposed approach has the added advantage that it does not require an exact structure of the system dynamics. The proposed controller is applied to control a model of permanent-magnet linear synchronous motor (PMLSM) subject to significant disturbances and parameter uncertainties. The simulation results demonstrate the effectiveness of the proposed method in terms of significant reduction in chattering while maintaining asymptotic convergence.

Abstract: In this study, orthogonal turning experiments are performed to analyze the machinability of Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17), a β-rich, α+β type alloy. PVD TiAlN coated carbide tool inserts are applied, because they are used widely for machining this material. The cutting forces and cutting temperatures are examined under different cutting conditions, which the cutting speeds are varied from 44m/min to 123m/min, the feed rates are 0.06mm/r, 0.08mm/r, 0.10mm/r and 0.12mm/r,respectively.There are some different varying trends of both the cutting force and the thrust force with the change of cutting speed. The cutting temperatures are found to increase with cutting speeds as well as feed rates.

Abstract: Although the progress has been achieved in conductive Nanoparticle/Polymer Composites(NPC), but there are many problems to be solved before their commercial application in a large scale, especially on their processing technology. The barriers include the dispersion of nanoparticle, the effect of nanoparticle concentration and interface on the overall properties of materials. In order to improve the application of NPC, the microstructural effect of injection molded NPC on its resistivity was investigated to build the relationship between the processing conditions and the properties in this paper. Composites used in the experiment were carbon black(CB)/polypropylene(PP). The microstructures of the injection molded parts at different positions were investigated with Scanning Electrical Microscope, and corresponsive properties were tested. The results showed that the distribution of CB nanoparticles changed with the injection pressure and had significant effect on the conductivity of the part. With the increase of injection pressure CB particles strongly oriented towards the flow direction of the polymer and thickness of oriented layer increased, which improve conductivity of the composites. The results also showed that crystallization was enhanced because of existence of nanoparticles, which should have increased the mechanical properties of the composite and decreased its resistivity because of the interfacial action between CB particles and polymer matrix.

Abstract: A model for the design of symmetrical gradient ceramic nozzles is presented. The purpose is to form compressive residual stresses at the entry and exit of the ceramic nozzle, and to reduce the erosion wear at these areas during abrasive air-jet machining. A SiC/(W,Ti)C ceramic nozzle with symmetrical gradient structure at its entry and exit was produced by hot pressing. The residual stresses inside this layered nozzle in the fabricating process were calculated by means of the FEM. The mechanical properties at individual layers were measured, the microstructure was examined. The erosion wear of this symmetrical gradient ceramic nozzle was investigated and compared with an unstressed reference nozzle. The production of symmetrical gradient structures with compressive residual stresses within the entry and exit of the nozzle has been proved to be a suitable way to obtain ceramic nozzles with superior erosion resistance.

Abstract: SiC ceramics is very promising to be widely applied due to the excellent physical and chemical properties.However, the very difficult process of SiC ceramics hinders its application. In this paper, the nano-cutting of SiC ceramics is simulated based on molecular dynamics. The influences of the tool rake and cutting depth on the cutting force, the kinetic energy and potential are analyzed. The results show that the cutting force, system kinetic energy and potential energy increase firstly,reach the maximum, and then decrease in the process; with the increase of the tool rake, the cutting force and the kinetic energy decrease; with the increase of the cutting depth, the cutting force increases, and the kinetic energy and the potential energy decreases. These results are very helpful to understanding the process mechanism of SiC ceramics and increasing its process efficiency

Abstract: There are many benchmark problems which have exact solutions or experiment data to gauge the simulation of aeroacoustic problems. Annular duct acoustic modes are good benchmark problems of this kind. The waves propagated along the duct can be considered as the summation of infinite Fourier modes. The energy relations of a single Fourier mode are deduced from governing equations in this paper. To investigate the properties of acoustic wave propagating along the duct, it’s necessary to decompose acoustic waves in the duct into multiple Fourier modes; the decomposition methods are presented.

Abstract: The genetic algorithm converges faster compared with the traditional optimization algorithm, the global optimal solution can be quickly obtained and it is very effective for multi-peak function optimization. A milling process parameter optimization model is established for titanium based on genetic algorithm in this paper, the relevant constraints is considered and the optional titanium milling parameters is achieved based on the targets of maximum production efficiency and minimum cost, utilizing MATLAB optimization software to program, the best combination of cutting parameters is got finally. Experimental results show that the cutting efficiency and production costs are significantly improved with the optimized cutting parameters, so that the defects of low efficiency in CNC machining resulting in relying on experienced cutting parameters is overcome.

Abstract: Electric pulse current (EPC) was employed to treat ZA27 alloy cast in the sand mould during the solidification. The experiment results indicated that the shrinkage cavity and the porosity in the ZA27 alloy was apparently reduced. And correspondingly, the mechanical properties of the castings were certainly improved. The current pulse applied in the initial stage of the solidification produced a better treatment result. The density of the casting ZA27 alloy treated with EPC in initial stage and later stage increased by 4.1 and 1.6 percent than that without EPC, respectively.

Abstract: The purpose of this investigation is to examine the machining behavior of cemented carbide tools in dry hard milling of cellular aluminium alloy (6N01) by experiments and finite-element analysis. From the machining point of view, Cellular aluminium alloy are often considered as poor machinability materials. Milling tests were carried out by using a three-head milling machine and a milling force measuring device. For this purpose, both microscopic and microstructural aspects of the tools were taken into consideration. Meanwhile, the cutting forces and the noise intensity are also considered in the experiment. Results show that cutting forces vary greatly with the experimental cutting parameters. Additionally, the noise field intensity increased greatly as the feed rate increased. Analysis indicated that the major tool wear mechanisms observed in the machining tests involve adhesive wear and abrasion wear.

Abstract: The work investigates the structure parameters of adjustable subatmospheric pumping scraps device and oil feeder, which have extremely significant impacts on double feeder system in the deep-hole drilling process. Equations for subatmospheric zone pressure are derived herein using the siphon principle, and experiments are performed the trends of pressure on the single factor condition, which provide reasonable structure parameters for adjustable subatmospheric pumping scraps device. Oil feeder is studied based on the Euler column theory, and it can be optimized that is intermediate support, pilot bushing as well as sealing. The universal finite element software is used to design the structure of adjustable subatmospheric pumping scraps device and oil feeder, also reasonable structure design scheme of double feeder system core components is given.