Key Engineering Materials Vols. 392-394

Abstract: Within a shipyard, designers have their own design objectives and moreover apply different software on heterogeneous hardware platforms; nevertheless requested collabtive operation still remains in the comple design circumstance. The paper presents a data hub model to sovle this problem and improve effectiveness and efficiency for ship design. The model is simulation-driven and consists of two main parts, including data management and integrated simulation environment. The data management processes the simulation-based design data storage, access and transformation. The integrated simulation environment bridges the gap among the multidisciplinary domain including CAD geometry, CAE, virtual navigation, kinematics and dynamics simulation. In addition, an application is developed to evaluate the validity of data hub model for ship design.

Abstract: Cracking of blade dovetails occurred in a governing stage of a 50MW steam turbines twice within 5 months. To find out the failure mechanism and measures to avoid the failure accident, one of the cracked blades has been inspected by the metallography and a scanning electronic microscope. The inspection results show that the cracking of the blade is caused by the high cycle fatigue. When governing stage blades are in operation, the vibration of blades can extend to platform or even to dovetail parts over radial supporting surfaces depending on temperature, centrifugal force and assembly tolerance. The calculated results by FEM show that not only natural frequencies of blades in operating are smaller than that in stationary but also the modal order shifts when the blade runs from stationary to operation states. The effect of mode shift on the failure was investigated. According to the conclusion, the blades have been retrofitted by increasing neck of dovetail to avoid dangerous resonance, and the blades have been operating in healthy condition for two years after the modification. Contrarily, if the phenomenon of mode shift were ignored, it would be difficult to find out the right reason of resonance and ways to retrofit the damaged blades.

Abstract: In order to improve the modeling efficiency of the industrial robot dynamics control, the recursive dynamics is studied based on the Spatial Operator Algebra (SOA) theory, and the procedure realization is built in the environment of Matahematica6.0 software. The high effective recursive forward and reward dynamics for the SOA theory, has a simple math expression and a clear physical meaning. The software structure of the forward and inverse dynamics is built and the industrial robot dynamics simulation model is realized based on the integrated procedure VB.NET and Mathematica 6.0. According to the analysis, the example of PUMA560 robot forward and inverse dynamics is studied, and correctness and validity is verified by computed examples.

Abstract: In this paper, a detailed elastic-plastic finite element analysis of the effect of the compressive loading on crack tip plasticity is studied based on the material’s kinematic hardening model. Five centre-cracked panel specimens with different crack lengths are analyzed. The analysis shows that in a tension-compression loading the maximum spread of the crack tip reverse plastic zone increases with the increase of the compressive stress and the near crack tip opening displacement decreases with the increase of the compressive stress at the same nominal stress intensity factor. The applied compressive stress is the main factor controlling the near crack tip parameters.

Abstract: Ant colony algorithm (ACA) is employed and improved in routing protocol of information acquisition of manufacturing process based on wireless networks. Weighting factor for paths selection is defined as an exponential variable in adaptive ACA. In this way, it prevents the weighting factor from excess increasing or rapid reducing to 0 which results in local optimum. This approach can dynamically adjust paths selection and improve global search ability by optimizing global policy. Adaptive ACA consumes the least time in the process of searching the most optimized paths and searches the shortest paths under the same of iterative loops. Under the same condition of the information heuristic factor and the expected heuristic factor, the algorithm shows good adaptation, realizes the load balancing between paths and resolves the dynamic adjustment problem.

Abstract: Tool wear during high speed machining process plays an important role in machining cost and efficiency. The purpose of this study is to examine the impact of tribological properties of coatings on cutting performance. Finite element methods (FEM) were used to model the effect of coated and uncoated cutting tools (K10) on the machinability of the aluminum alloy 7050T7451. Uncoated, Single coated, such as TiC, TiN and Al2O3 and multi-coated tool were studied. All finite element models were assumed to be plane strain. To achieve constitutive model of Al7050T7451 under conditions of machining that high strain rate, high strain and high temperature occur, high speed impact experiment and material drawing experiment were done. Comparison of FEM results shows that the highest temperatures in tools, the temperature change rates of different tools from surface to its bulk material, and the temperatures in chips are changed greatly. It also shows that the cutting temperature of coated tool is lower than uncoated tools, but cutting forces change very little. All these results show that coatings can be used to reduce adhesion between a tool and a workpiece material. The wear resistance of coated tool can be improved effectively and tool life is increased correspondingly.

Abstract: The target movement range of planar five-bar parallel robot is decided by the length of each bar and swinging angle. In general designs are bound by the single-objective optimization. Scope of the overall movement is considered as the goal of optimization. Although this method may seek all the possible movement scope completely, but has actually neglected the restraint of mechanical hinge structure. To determine the length in this way there are interference and stuck phenomenon. To address this issue in this paper the bounds of mechanical structure are added in. A new set of optimization algorithms is established. Analytical method is used to establish the algorithm of planar five-bar parallel robot’s positive solution. Then MATLAB is used to obtain the positive solutions of target movement range. Generally under unconstrained circumstances, we found that there are two positive solutions and mutual symmetry on the x-axis. After adding in the restriction of swinging angle, we succeed in finding the optimal solutions. Finally we use an example to explain how it works. MATLAB is used to determine the length of each bar and found a 200 x 150 mm of the target movement range. Through the diagram has been plotted by MATLAB, we find that the second solution is the optimal solution. This method can be used to optimize the length of planar five-bar parallel robot.

Abstract: This paper analyzes the measure principle of flexible joint stiffness and constructs the measuring system of flexible joint stiffness. It achieves the measurement of flexible joint’s torque-rotation angle stiffness through designing the measuring appliance and translocating clamp. The result shows that it is efficient to develop the measuring system and repeatability error is better than 1%.

Abstract: This paper adopts the parameterized designing method of feature assembled and feature unit. For the feature of non-conventional parts, such as welding box and bearer, using the Visual C++ and AutoCAD as soft tools, the system successfully carries out the basic function of feature assembling, the processing of two-dimensional figure, the building of three-dimensional feature, the automatic producing of technical papers, and so on. The integration idea and design methods of this system can be served as the preference to CAD/CAPP integration for other non-conventional parts.

Abstract: In this paper, the system of brain-computer interface driving neural prosthesis hand is designed using EEG signal as the control signal source. First, a whole design scheme of the system of BCI driving neural prosthesis hand is constructed and the method of EEG detection and recognition is introduced. Then, on the basis of prosthesis hand wildly used by amputees, a three-degree of freedom prosthesis hand is chosen as the control object through rebuilt according to system requirement. The serial communication channel is constructed and the recognition result of hand action is sent to the prosthesis hand controller through serial signal protocol. A prosthesis hand controller is designed using single-chip computer as its core, and the driving method of start-stop and steering of prosthesis hand motor is studied. At last, the purpose of the control of prosthesis hand is achieved by EEG recognition result from hand action.