Applied Mechanics and Materials Vols. 190-191

Abstract: Abstract: In order to improve the control precision of the piezoceramic actuator in precision position system, a dynamic modeling of Ultra-precision Positioning System is proposed. A two-step identification strategy is adopted in this paper. Step 1: The linear model was identified based on step input response by least square method. Step 2: According to the step.1 result, the designed nonlinear observer was applied to estimate the output of hysteresis by Fast Tracking Differentiator. The polynomials are used consistently approximate continuous functions of f(.) and g(.) in the Duhem modeling based on the theorem of the Weierstrass polynomial approximation theory. Recursive least square methods are developed to identify α and the coefficients of the polynomials in Duhem model. At last , the simulation results show applicability, rapid convergence velocity and high calculation accuracy of the algorithm.

Abstract: The idea of ontology is introduced into knowledge representation for process planning of mechanical parts to support knowledge sharing and reuse, which means knowledge is expressed abstractly as domain ontology according to the characteristics of process planning of mechanical parts. Process planning domain ontology is an explicit and elaborate description of a conceptualization in the process planning domain, i.e. it is with five elements: concepts, relations, attributes, rules and cases. Domain ontology is constructed by abstracting and describing the five elements from process planning, and is stored within relational database. An example is included to demonstrate the operation of the proposed approach and show effectiveness in knowledge representation for process planning of mechanical parts.

Abstract: In this article, it is studied how to establish and solve the mathematical model of temperature field of hot runner of injection mould, visual numerical simulation analysis for temperature field is realized with computer, and finally corresponding example is cited.

Abstract: For analysis the performance of cluster tools, Stochastic Petri nets model was used to describe the serial process procedure of cluster tools and the operation sequence of the robot. The firing rate of transition represents the frequency of activities. In order to improve the scalability of the model, the modular approach is used to model. Firstly the sub-models of tool’s modules were developed. Then according to the process procedure, all the sub-models were combined to construct a Petri nets model. Finally, the firing rates are added to every transition. Markov process approach was used to analyze model. Some performance measures equation are deduced, such as the throughput, the utilization of process chamber, the utilization of the robot and the wafer residency rate in process chamber. Petri nets models and performance measures equation developed in paper can assist performance analysis and verify the effectiveness of scheduling algorithm.

Abstract: Expansion tube energy absorber is of interest in bumper device on the spacecraft, for example the seat-bumper and its crushing characteristics have shown an excellent performance. This paper contributes to the analysis and investigation of the crushing characteristics of the expansion tube energy absorber, by simulating the response of the 2Al2T4 expansion tube subjected to quasi-static axial compressive loading, using the LS-DYNA finite element code. Corresponding tests were conducted to serve as comparison purpose. Satisfactory level of agreement between simulation and testing results was obtained regarding the main characteristics of the tested expansion tubes such as peak compressive load, energy absorption and the overall compressive response. Formula of the crushing force deduced using plastic mechanic theory was checked. Impact model was also constructed and dynamic simulations were performed to investigate the axial impact response of the expansion tube energy absorber. The simulation results of quasi-static and dynamic compression response of the expansion tube are very similar.

Abstract: Fine blanking, as an effective and economy metal forming process, can be used for the manufacturing of helical gears with inclined forming movement. In the present study, a reliable three-dimensional (3D) rigid-plastic finite element (FE) model is developed on the DEFORM-3D platform for rotational fine blanking of a helical gear. Based on this FE model, distributions of different field variables such as metal flow velocity, mean stress and effective strain are obtained, and cut surface features and punch stroke curve are predicted. The results achieved in this study can not only evaluate the capabilities of the rotational fine blanking process of a helical gear, but also provide valuable guidelines and a better understanding of the deformation mechanism of this process.

Abstract: the noise problem met during sensing-measurement hasn’t been adequately discussed. In this paper, the calculation errors caused by the noises are demonstrated. A practical optical sensing-localization algorithm based on specially organized Genetic Algorithm is proposed, and application-test experiments of this algorithm are described. Moreover, a parallel-operation scheme suited for Cloud-Computing supporting is introduced. Developments of the algorithm mentioned above provide an effective approach for the rapidly growing field, independent-localization, which would benefit the fields such as geographical mapping, navigation, especially when GPS becomes not readily available due to industrial or natural disturbances such as radio or thunder.

Abstract: Stop valves are commonly used as fluid flow control equipments in many engineering applications. A numerical study of a three-dimensional, complex geometry, stop-check valve was performed for model validation and improved understanding of valve flow features. This paper has provided a numerical investigation of the fluid flow inside a stop valve, including the modeling and the simulation of the stop valves. According to the simulation result of original valve structure, two cone valve block shape with different gradient are presented to bring some optimization to the stop-valve. CFD simulations were conducted for different structure of the valve to verify the performance of the valve after redesign the internal flow structure. The simulation results show that the pressure drop vortex strength, maximum velocity and velocity nonuniformity of valve outlet had been reduced obviously. Furthermore, the results of the three-dimensional optimization analysis of valve shape can be used in the design of low noise and high efficiency valve for industry.

Abstract: Because of the large deflection deformation of crane’s main arm, it is difficult to display the real-time shape of the crane’s main arm and also is necessary to display the deformed main arm to increase the realism of the system in the development of a system platform to simulate crane operation in practical situation. There is a few research in this area, therefore the study of the flexural deflection of the main arm of crane modeling method has important practical significance for engineering. This paper first briefly introduces the main arm of crane's deflection numerical calculation theory, then explores the application of OSG through three different ways to establish the occurrence of deformation model of the crane’s main arm, then compares their advantages and disadvantages, and finally finds that the display effect by the wire frame method to establish the occurrence of flexural deformation model of the crane’s main arm is the best, and gives a simple example to illustrate that.

Abstract: In some cases, it’s not enough to consider only the objective function of the global optimal point, but also the character of this point and its nearby area. To this end, the concept of practicably optimal point is introduced in this paper. Further, a novel intelligence method named simulated particle swarm optimization (NSPSO) algorithm is proposed to obtain the practicably optimal points according to different requirements. The optimization results reveal that the NSPSO algorithm has strong convergence and stability, and appears to be an efficient alternative for obtaining the practicably optimal points according to different requirements.