Showing papers in "Mechanical Science and Technology in 2003"

Stress-analysis of a Complex Structure with the ANSYS System

Abstract: Finite element modeling (FEM) of a complex structure is a time consuming work for engineering calculation process. Even though some advanced software systems provide many modeling facilities, a good model still strongly depends on the skill of analyzers. Therefore, this paper presents some modeling skill and experiences in the application of the large scale commercial software ANSYS 5.7 to model a complex joint structure typical to engineering analysis. In section 2, a six step procedure for building FEM with APDL language is proposed, and more details and different modeling methods to simulate a bolt connection are studied.

Theoretical Analysis on Meshing Impact of Involute Gears

Abstract: Based on meshing characteristic of involute gears and theory of mechanical dynamics, a series of relationships among geometric parameters, impact velocity as well as maximal impact force of the gears in the meshing process were established. The impact velocity and impact force in transmission caused by the main factors, such as gear width, transmission ratio, loaded deformation of meshing teeth, work condition, and gear's structure, were analyzed.

Appication of Genetic Algorithm Based on Task Sequences to Assembly Line Balancing

Abstract: In this paper, we present a genetic algorithm based on task sequences for assembly line balancing. Our algorithm scans only in the subspace of those feasible task sequences, and it has high efficiency. At the same time, it keeps the excellent searching capability of common genetic algorithm. The result of a case study with our algorithm is satisfactory.

FEM Simulation of Orthogonal Metal Cutting Process

Abstract: Cutting is an important manufacturing process o f metal. The chip formation in metal cutting is one of the typical large deforma tion problems, which involves material nonlinearity, geometrical nonlinearity an d boundary nonlinearity, and thermal-mechanical coupling. In this paper, a plan e strain model is built to simulate orthogonal cutting, where workpiece is treat ed as elasto-plastic model, and the cutting tool is treated as rigid model. The above FEM model is analyzed by commercial software DEFORM-2D, and some results including the chip formation, temperature distribution, cutting force variable and residual stress were obtained. Simulation results are in agreement with prev ious experiment results.

Analysis of Structural General Reliability of the Loading and Strength Based on Information Entropy

Abstract: We present a new method for analysis of structural general reliability based on information entropy With the method, a fuzziness set can be transformed into a random set Firstly, a membership function for the low, middle, and high strength or load is defined Then, the reliability functions are proposed when the load is a random variable, when the strength is a fuzzy variable, and when the load and the strength are all fuzzy variables After that, a function of the general reliability about the fuzziness state in the structure is presented Finally, the equations of the general reliability of the random fuzzy structural system are given

Key Technology and Prospects on the Electric Vehicles

Abstract: Because of its great advantage over traditional vehicles in environmental protection and energy saving, the electric vehicles will become the main terrestrial vehicles on the urban roads in the 21 st centuries. This paper mainly introduces the significance of developing electric vehicles, the current situation in the development of electric vehicles all over the world, state of the art in every assembly of electric vehicles, and its future prospects.

Knowledge-based Engineering Design: Theory, Method and Practice

Abstract: Engineering design is an innovative process driven by knowledge, and knowledge-based engineering (KBE) is an important approach to promote the intelligence of design In this paper, the definition of KBE is put forward firstly, the difference between KBE and other technologies, such as CAD, expert system (ES), are well analyzed and synthesized The methodology for engineering design based on KBE is proposed, and the tools and methods for knowledge processing are classified based on the geometry-relativity with design knowledge The application of KBE technology is reviewed Finally, taking the design of metal stamping die as an example, we established a system frame for engineering design based on KBE

On Distributed Collaborative Design Environment Supporting Conceptual Design

Abstract: Conceptual design of a complicated product often requires the collaboration among multi disciplinary experts. Based on the blackboard model, this paper proposes a distributed collaborative design framework. Several key technologies supporting this framework, such as shared product information model, distributed modeling method for the design, and a constraint based conflict detection method are first introduced. Then a distributed collaborative modular design environment (DCMDE) is developed by using the proposed technologies and Internet enabling techniques, and it can support collaborative conceptual design of mechanical product by multi disciplinary designers dispersed geographically. A collaborative gearbox design case demonstrates the effectiveness of the system.

Numerical Simulation of Transient Heat Transfer Process for Wet Friction Clutch

Abstract: The formulas of friction heat and heat convection coefficient for wet friction clutch are given. The 3-D heat transfer analysis models of internal and external friction piece are established, and finite element method for transient temperature field problem is employed to solve the heat transfer process of friction piece under idle and combination situation. The idle efficiency and outlet temperature of lubricating oil are also calculated.

Five Methods for Modern Mechanism Creative Design

Abstract: We first analyzed the characteristics of modern mechanisms and its creative design. Then, we present five methods for modern mechanism creative design (MMCD),and they are:(1) by making use of the controllability of drive-elements;(2) by making use of the knowledge bases of computer aided conceptual design;(3) by making use of a few links to accomplish complex motion process;(4) by making use of existing theory on relative disciplines, such as optics, electronics, hydraulic theory, etc;(5) by making use of bond graph theory to make mechanism type transformation.

Research on a Flexible Agent-based Workflow System

Abstract: Aiming at lack of flexibility in current workflow system, we put forward a flexible workflow system model by using agent, so as to enhance the flexibility, autonomy and self-cooperation capacity of the system. By introducing the architecture of the model, we describe each agent in detail. Finally, a prototype based on this model is presented.

High Quality Geometric Modeling of Blade

Abstract: Based on thorough investigation of blade modeling, defections of blade geometry model are found, and they are caused by unsuitable section parameterization. Arithmetic of constructing section middle curve and calculating section thickness are presented for solving the problem, and a new parameterization of section curve is realized which can guarantee high quality blade modeling.

Analysis for the Static Stiffness of a Parallel Guiding Compliant Mechanism

Abstract: Parallel guiding compliant mechanism is a new type of mechanism. Because of its special applications, the parallel guiding compliant mechanism requires very high positioning accuracy, which mainly depends on its static stiffness. To overcome the shortcomings in existing analysis for static stiffness of compliant mechanism, compliance matrix method in structural analysis is applied for the establishment of a new theoretic model. Compared to the result from the finite element analysis, the result by using this method is proved to be valid.

Application of Genetic Algorithm in Blade Arrangement of Engine

Abstract: In Chinese maintenance enterprises, simple m an ual blade-pairing procedures can only satisfy the lower balancing requirement o f Maintenance Manual. For a great number of blades, this arrangement scheme is n ow made out on the support of manufacturers. These processes ask workers for hig h technical ability and also need frequently repeated pairing, adjusting and run -up, which will cause delay in maintenance schedule and increase maintenance co st. We developed a universal intelligent blade arrangement software suitable to any stage blades of different type engines, based on the overall optimization an d fast convergence of Genetic Algorithm(GA). This software will give optimal bla de arrangement sequence to gain least unbalance volume. The blade arrangement pr oblem was reduced to classical assignation problem. The proposed GA scheme has h igher balancing precision, less computing time and simple common feasibility. The GA's intelligent seeking flow and three special operators are upbuilt. The d ifference of blade arrangement for fan, compressor and turbine only reflected to the different construction of GA's adaptability function.The experimental resul ts for fan blades of PW4000 engine indicated the proposed GA scheme was far much better than those given from both the simple pair method and simulation computa tion of Pratt Whitney Company.

Investigation on the Type and Variation of Coupler Curve of Hybrid Five-bar Linkage

Abstract: Based on the analysis of the link length of a planar five-bar, the assemblability of linkage and the sufficient and necessary condition of the existence of full revolvable joint are proposed. Then, the type of the planar five-bar linkage is analyzed. The existence condition of unconditional triple crank, unconditional double crank, unconditional crank-rocker and double rocker are derived. Based on computer mechanism simulation, the coupler curve of a hybrid five-bar linkage with double crank are investigated and some laws of coupler curve are derived for the first time.

Development of Multi-process Conventional Spinning and Research on Roller-Trace

Abstract: Determination of roller-trace is a key problem for realizing multi-process conventional spinning, and has a great effect on success of spinning. In this paper, we summarized the state of the art of determination of roller-trace which mainly employs experimental methods at present, including some roller-trace types commonly used. The development tendency that combine FEM numerical simulation technology with theoretical analysis is evaluated.

An Algorithm for Computing Voronoi Diagrams for Multi-connected Domain

Abstract: Voronoi diagram is widely applied in the field of CAD/CAM. We first studied the wavefront propagation algorithm for computing Voronoi diagrams for single connected domain. Then an algorithm for computing Voronoi diagrams of multi connected domain is proposed. Such an algorithm improves the wavefront propagation algorithm and is suitable for multi connected domain. Two examples of computing Voronoi diagrams for multi connected domain are presented. The results of simulation verified the correctness of the algorithm.

A Gyrobondgraph Method for Analysis of the Dynamic and Static Force of Planar Linkage in Non-inertial Coordinate System

Abstract: A gyrobondgraph method for the dynamic and static force analysis of planar linkage in non-inertial coordinate system is introduced.The general procedure to model planar linkage in non-inertial coordinate system by bond graphs is provided.Based on the basic concept of gyrobondgraph, the unified formulae of balancing moments and constraint forces at joints are derived, they are easily generated on a computer in a complete form. The very difficult algebraic problem caused by differential causality and nonlinear geometric constraints in formulating the unified formulae of balancing moments and constraint forces can be overcome. This procedure is very suitable for systems containing multi-energy domains. By a practical example,the validity of this procedure is illustrated.

Scanning Path Algorithm for Rapid Prototyping(RP) Based on Voronoi Diagrams

Abstract: An algorithm of computing Voronoi diagrams for multi-connected domain is proposed, which improves the wavefront-propagation algorithm. The algorithm of computing Voronoi diagrams for multi-connected domain is implemented with Microsoft Visual C++, and applied to the generation of laser scanning path in stereo lithography.

CBR-based Research on a Rapid Design System of the Decelerator

Abstract: This paper researches rapid design system of the decelerator based on UG software, adopting case based reasoning method, using object oriented modular design. Geometric modeling method is introduced based on knowledge driven method. The key technology of rapid design system of the decelerator is given on the basis of case based reasoning.

Leg Mechanism of a Quadruped Walking Robot and its Stability Gait Control

Abstract: We designed a leg mechanism for a quadruped walking robot. We first analyzed in detail the kinematic relationship between the gait of the quadruped walking robot and the leg mechanism. Based on the analysis, a driver for this kind of leg mechanism is designed.

Investigation on the Wear of the Milling Cutter during Milling Ti-Alloy with Nitrogen Media

Abstract: Based on lots of experiments and research on the milling of Ti-alloy with nitrogen gas media, we analyse the wear characteristics and mechanism of milling cutters. We draw the conclusion that the milling with nitrogen gas media is much better than dry milling

Study of the Workspace of a 3-PTT Parallel Micromanipulator

Abstract: Studied in this paper is the workspace of a 3-PTT parallel micromanipulator. Constraint factors, such as the maximum extension of actuators and the maximum revolving range of flexure hinges, are discussed. A cylinder coordinate numerical search approach is used for workspace determination. At the end of this paper, a computer simulation is presented to show 3 dimensional graphical description of the workspace.

Finite Element Analysis Based on Structural Parametric Design and Its Application

Abstract: For many series of products which has similar structure, it is easy to adjust the geometric model of products by using structure parametric design method. Based on the idea of the structure parametric design method in Finite Element Analysis(FEA), a method for building a parametric FEA Model by using parametric design language is provided. By using this method, the FEA model can be easily create by adjusting several geometric parameters and the process of FEA is automatically executed. The remarkable effect of this method is that it is more convenient for repeated FEA for a simslar model and analysis of series of products. Further more, the efficiency is improved and the time for product design will be shortened greatly. By using the ANSYS Parametric Design Language(APDL), the FEA process including creating FEA model and analysis steps is discussed. A practical parametric FEA model is established and stress analys is done by using our method. The results show that this method is very efficient in FEA of a structure.

Dynamic Behavior of a Rotor with Dry Friction Dampers

Abstract: A model of a dry friction damper is suggested and incorporated into a Jeffcott rotor. Its advantages of damping and stabilizing the vibration of the rotor are revealed by an investigation on the motion of the rotor with dry friction dampers. A boundary limit of the stabilization provided by the dry friction dampers is obtained, which is A lim=2Fμπ|D|s (F-the normal force acting on the friction plane; μ-the friction coefficient; D-the inherent negative damping of the rotor; s-the stiffness of the rotor). It follows that the dry friction damper may be a promising replacement of the squeeze film damper in some circumstances.

A Formula for Accurate Calculation of a Cam′s Pressure Angle

Abstract: The force model of a cam is presented, which considers the factors of different materials, different working loads and the acceleration's magnitude of the follower. A formula for accurate calculation of its pressure angle is also given.

Coupled Electromechanical Dynamic Model of Rotor-Magnetic Bearings System

Abstract: The dynamic model of a rigid rotor active magnetic bearing system is set up completely. It includes the coupled action of thrust magnetic bearing upon the lateral vibration in a rotor system and the coupled action between radial magnetic bearings due to the journal inclination in addition to the gyroscopic action. It also adds the electrical differential equations of control system and the consideration of the mounting of sensors on different positions of magnetic bearings. Such a model can be used for the coupled electromechanical dynamics analysis of rotor system equipped with magnetic bearings.

Parametric Design and Automation of Virtual Assembly Based on UG

Abstract: The secondary development process is introduced to access the parameterized parts with UG/Open API to accomplish the parts' parametric design based on the analysis of the component functions and structural features of the aircraft hard mechanical control system. To overcome the disadvantages during manually assembling complicated systems, such as the trivialities of the operation and the weakness of the repeat property , a method is proposed to assemble the system by automatically placing the parts on the appropriate positions by means of transforming the matrix of the parts' coordinates and record the procedure of the virtual assembly in order to accomplish the automatization of the virtual assembly.

A New Approach to Load Balancing in Web-Based CAD/CAM System

Abstract: The globalization of manufacture brings along the development and research of Web-based CAD/CAM system. Some key techniques are involved, including web server load balancing. This paper analyses traditional load balancing techniques, adopts JavaServlet to design a system, discusses this new technology and presents a new Software-based approach to server load balancing, thus supports the Web-based system to work credibly and efficiently.

The Research on a New Method Based on Wall-Climbing Robot for Measuring the Volume of Oil Tank

Abstract: After a long period of using, the volume of a large oil tank will change because of its deformation. So it is necessary to re measure the volume of the large oil tank when the tank is in use. The traditional methods, such as optical reference method, enclosed ruler method, are hard and dangerous to operator, and their measuring efficiency is low. A new method based on the technology of wall climbing robot is introduced, which is called self moving method. In such a method, a wall climbing robot moves around the oil tank, through the sensors on the robot, the volume of the oil tank can be calculated. This method increases the automation and the efficiency of measurement, and satisfies the measurement precision.