Applied Mechanics and Materials Vol. 33

Abstract: In semi-solid remelting process, the various stages of reheating temperature and isothermal holding time must be accurately controlled in order to obtain the uniformly distributed and small equiaxed grains microstructure. In this paper, a temperature control program was developed and the remelting process for Al-7Si-2RE aluminum alloy was carried out. The results showed that with the raise of reheating temperature and the extension of isothermal holding time, the liquid fraction increases, α-phase grain grows and becomes rounding in the process of Al-7Si-2RE alloy semi-solid remelting. The most reasonable process parameter of reheating temperature is at 585~590°C and its appropriate isothermal holding time are about 10~15min for the semi-solid Al-7Si-2RE alloy.

Abstract: Through the orthogonal test in which stainless steel 316 was milled with high speed by solid cemented carbide end cutter, the milling force was measured. By multiple linear regression method, the prediction formula of the milling forces of stainless steel 316 was found. In addition, this study validates to significant degree of the formula meeting the actual condition, which can provide a reference to better selection of cutting parameter in advance and the design of high-speed milling cutter.

Abstract: On the basis of manipulability ellipsoid of manipulator, the velocity directional manipulability of three-fingered dexterous robot hand is defined. Under the condition of given position and orientation, taking the velocity directional manipulability as objective function, the optimal velocity transmission direction is presented in this paper. The given example shows the velocity transmission performance of three-fingered dexterous robot hand on a specific position and orientation.

Abstract: Siemens AG SINUMERIK820 is used for high-speed numerical control (NC) grinder, which integers CNC and PLC and is safe and reliable. The mechanism of high speed spindle is that the motor and spindle are combined as one body; rapid feedrate is realized by steep-lead ball screw and increasing feed servo motor rotation speed; the wear particles of wheel are mainly of cubic Boron Nitride and diamonds; and the machine is more stable and reliable.

Abstract: The paper established the mathematical model of plunger-type hydraulic cylinder, founded the simulation model in the SIMULINK environment and solved its unit-step response, gave the hydraulic cylinder design parameter and the medium character’s influence to its unit-step response, summarized the intrinsic relations between parameters and the time domain index, provided the theory basis to optimize the hydraulic cylinder dynamic property. Conducting the research of the hydraulic cylinder system using SIMULINK has the outstanding characters such as the simple programming, the direct-viewing modeling, the highly effective simulation, it may reduce the design cycle greatly, reduce the design cost, enhance the product performance. The research conducted suggests this method may promote to the research of all the hydraulic package and hydraulic system.

Abstract: Malfunction prediction is a trend of NC machine tool malfunction diagnosis development and the diagnosis accuracy is heavily dependent on the real and online acquisition of malfunction parameters. Gear malfunction is one of main mechanical malfunctions, and it is very meaningful to forecast its malfunction. The shock vibration of gear malfunction is non-stationary, so it should be processed by time frequency algorithms. Kalman filtering and Laplace wavelet are time frequency algorithms. Klaman filtering is self-adapting algorithm, and can filter noise in real-time. Laplace wavelet can obtain malfunction parameters by correlation filtering when correlation parameter k is the maximum. The proposed technique features two appealing advantages, which include self-adapting Kalman filter-based time-frequency algorithm and a Laplace wavelet-based parameters extraction. A set of simulating gear vibration data was used for verification. It provides a quantitative and more efficient means for obtaining the malfunction parameters to malfunction forecasting system.

Abstract: This study investigated the adsorption of congo red by activated carbon-attapulgite composite adsorbent (ACA) and zeolite-attapulgite composite adsorbent (ZA) from aqueous solution. All of these two adsorbents have mesopores and macropores structure different from general activated carbon adsorbent with micropores distribution through analysis of mercury porosimeter .The research focused on the effects of adsorption capacity in four aspects: contact time, solution pH, temperature and initial dye concentration. The results indicated that ACA had higher adsorption rate in the first 30 min contact time and ZA had higher removal percentage because of the difference on the pore size and total pore area. There was little difference on removal percentage of ACA and ZA when pH changing from 1 to 13 and the adsorption rate exceeded 94% in all kinds of pH condition. The removal efficiency of congo red on ACA and ZA increased from 92% to 95% with increase of temperature from 293K to323K. The reduction rate of congo red decreased with an increase in the initial congo red concentration for ACA and ZA.These results suggest that all of the two adsorbents is a potential low-cost adsorbent for the dye removal from industrial wastewater.

Abstract: In sheet metal forming, friction condition between sheet metal and mold is a very important problem for it influences the formability and the variation of stress, strain and thickness of sheet metal, and so on. Simulation experiments had been done to measure friction coefficients online at punch and die rounded corners under different process parameters during warm deep forming of magnesium alloy sheet. The results made it clear: temperature shows the greatest effect on friction coefficients, the effect of blank holding force (BHF) secondly, and no significant effect of lubricant on the friction coefficients. The friction coefficients at die rounded corner are larger than those at punch rounded corner. The dynamic changed friction coefficients models with temperature and BHF were fitted by the experimental data respectively, and they were added into simulation software through further development by user subroutine VFRIC using FORTRAN language to improve the accuracy of the numerical simulation.

Abstract: Application of topological graphs to analyze and synthesize planetary gear trains (PGTs) is an effective approach in searching for innovative planetary trains. Two topological graphs of basic structure and three fundamental units of PGTs are established as the basis of topological synthesis. Then combination system of PGTs are summarized based on stratify-cation, which can be classified as four basic type including series, parallel, separate and close. Several kinds of compound combination are also discussed. The variation law of topological graphs are analyzed and sorted as diversification including evolution, regression, decay and recovery and inversion transforming graphs to PGTs. Finally graph library based on variation law is presented as a simple and practical way to create a great number of new PGTs.