Papers by Author: Ding Fang Chen

Abstract: A simple FGM object with one gradient direction is easily fabricated by the current technique; However, how to fabricate multiple gradients FGM objects is rarely mentioned by some related papers. This paper proposed a representation and fabrication approach to deal with this problem. This approach, termed as minimum fabrication cell (MFC) or allowance fabrication cell (AFC), focus on fabrication of multiple gradients FGM object. In MFC, an arbitrary 3-D model is adaptively sliced into a series of 2-D layers, and each layer is subdivided into a series of MFC or AFC along toolpath. The three linear interpolation is applied to calculate the material for each MFC or AFC, and gradient contribution ratio (GCR) is applied to calculate the material for each vertex on the MFC or AFC.

Abstract: An adaptive slicing algorithm based on stereo lithography (STL) model was proposed in order to improve the forming precision of product in rapid prototyping. In the algorithm, the topological information of STL model was established, and the relationship between triangle facet and vertexes was constructed. And the adaptive slicing process based on STL model was implemented using the proposed method with combination of intersection points tracking and marking. The slicing thickness was automatically calculated according to the area differential ratio of adjacent slices.

Abstract: Based on fluid mechanics, the filling process of magnesium alloy step-plate casting molten metal was analyzed, and the filling characteristics were studied by numerical simulating. The results show the filling velocity and the wall thickness of casting have a great effect on the filling characteristics of magnesium alloy. When the filling velocity is less than 0.3 m/s, the liquid frontier of molten metal and the fluid level of thick upper surface fluctuate greatly, and the defects of air entrainment and oxide impurities will appear. When the filling velocity is more than 0.58 m/s, the molten metal fills in turbulent way, and the defects of sputter and air entrainment will appear. The correlation between the wall thickness of casting and the critical filling velocity presented in this paper can be used for the optimization of filling velocity.

Abstract: Loss characterization in magnetostrictors is one of the key issues for realizing reliable magnetomechanical transducers. Concerning with the hysteresis minor loop within a relatively linear area of magnetostrictive curve, there are three types of losses, elastic loss, magnetic loss and piezomagnetic coupling loss, similar to the loss mechanism of a piezoelectric (elastic, dielectric and piezoelectric losses) that our group has established recent years. By measuring accurately the mechanical quality factors QA for the resonance and QB for the anti-resonance in the admittance/impedance curve, we can derive these three physical losses. By introducing these losses factors we can characterize magnetostrictive losses using complex parameters.

Abstract: There are three types of losses for magnetostrictors, elastic loss, magnetic loss and piezomagnetic coupling loss, similar to the loss mechanism of a piezoelectric (elastic, dielectric and piezoelectric losses) that our group has established recent years. By introducing these losses factors we can characterize magnetostrictive losses using complex parameters. Here we derived the relationship of mechanical quality factors and losses factor based on admittance spectra expression we have established previously. By measuring accurately the mechanical quality factors QA for the resonance and QB for the anti-resonance in the admittance/impedance curve, we can derive these three physical losses to characterize magnetostrictive hysteresis loss.

Abstract: In Virtual instrument (VI) established for computer based automated test and control, the process with only single thread has limits when developed for acquiring high speed data, analyzing and displaying them the meaning while. Any interference from another task may block the whole running process and cause data missing. In order to increase the throughput, responding time and multi-task processing efficiency of VI, multi-thread programming with the platform LabWindows/CVI is introduced in this paper. Contents include the two strategies to establish multi-thread program, Thread pool and Asynchronous Timer, and how to protect data with multi-thread programming. Finally, a case study showed a multi-thread VI based on Asynchronous Timer method, with the comparison of performance between single thread and multi-thread program.

Abstract: Among all the bulk conveying processes, how to effectively and conveniently put the bulk into the conveying process is regarded as one of the most important problems. This article brings out a brand-new equipment—Screw-gas Bulk Sucking and Taking Equipment for the solution, which applies both the theory of vertical screw conveyor and the theory of pneumatic handling. It constitutes of 3 parts; respectively from bottom to above they are: Centrifugal force Separating Part, Screw Lifting Part and Pneumatic Conveying Part. Particle material is drawn into the equipment in the form of gas-solid two-phase flow by the Atmospheric pressure, and then helically rises in the Centrifugal Force Separating Part which is an inverted cone. The material would be separated from the two-phase flow by the effect of centrifugal force and then be lifted in the Screw Lifting Part. The gas flow with the very little remained material would be drawn into the blower. By thus Screw-gas Bulk Sucking and Taking Equipment could take the material and put it to the next conveying process conveniently and efficiently with the superiorities of low clearing-up, little dust removal, simple construction and convenient maintenance. The article provides the feasibility of the new equipment by experiments on 3 kinds of identical particle.

Abstract: The theoretical derivation of model analysis is elaborated first in the paper. Then combined with the developed micro-feed tool holder, the structure’s first ten order vibration mode is analyzed through the finite element analysis software. From the analysis results, the natural frequency in every mode is finally obtained. After the analysis, an important conclusion is put forward. Based on the conclusion, an improvement measure for the micro-feed tool holder structure is proposed.

Abstract: By combining magnetostrictive actuator with flow valve directly, the flow was precisely controlled due to magnetic materials’ properties of fast response (less than 1μs)and large magnetostrictive strain (up to 1500ppm). The structure was designed based on this theory, and the flow - displacement model of valve was established by analyzing the size of the valve opening in different incentive current. The flow field was analyzed through multi-physics analysis software COMSOL. Simulation results showed that, the continuous adjustment and precision control were realized in a certain range of flow in the valve. Therefore, it could not only adjust the flow in micro amount directly, but also can be a pilot valve for high frequency precision large flow valve.

Abstract: This paper resolves spatial RSSR mechanism in D-H coordinates to obtain its position equations. By extending Roberts-Chebyschev Theorem, it is demonstrated mathematically that RSSR mechanism possesses the same character as planer four-bar linkages in generating cognates. Considering strict requirements of spherical hinges in manufacture and assembly, this paper then addresses substitution methods of spherical hinge in RSSR mechanism, including constraining DOF of spherical pair by specific structural dimensions and replacing high pair by combinations of low pairs, while taking examples of sphere 4R mechanism, spatial orthogonal crank-rocker mechanism and spatial 6R mechanism in dobby machine. Physical kinematic simulation is done in the environment of MSC.ADAMS to validate the feasibility of spherical hinge replacement, providing guidance and reference to future design of complex spatial mechanisms.