Abstract: The high-speed metal cutting process is analyzed by finite element (FE) method in order to understand the effects of the cutting speed on the thermomechanical responses of workpiece materials. The reliability of numerical simulation is firstly validated by comparing the simulated cutting force with experimental data. Then a series of FE simulations are carried out to reveal the effects of the cutting speed on three key cutting state variables. The cutting force varies with the cutting speed and shows a minimum inflexion at 10 m/s. The maximum temperature in the secondary deformation zone increases gradually with the cutting speed and finally tends to a steady value. The residual stress decreases with the cutting speed as a whole. Thus high speed cutting can improve surface machining precision of product. Besides, it is found that the high residual stress mainly concentrates in the topmost surface layer with a depth of 0.1 mm and sharply decreases to a low level beyond the layer.
Abstract: A mathematical model has been developed to predict the residual stresses level in pre-stretched aluminum alloy plate. This is based on force balances of the residual stress, theory of plastoelasticity and a new conception of free length. The model is relatively simple because only rolling direction residual stress is taken into account, but provides a clear illustration of stress relief mechanism in stretching process. With this model, residual stress distributions of stretched beam can be determined directly by knowing the specimen dimensions, material properties and the original stress. The model offers an useful tool to show the effect of varying tension ratio on the final residual stress level, thus makes it possible to predict stress relief and control residual stresses. An example of using the model is presented by applying published data while showing mechanism of stress relief during stretching. Analysis indicates that it is stretch-caused convergence of the free lengths of strips in beam that lead to reduction in the residual stresses.
Abstract: Time, cost and quality are three central objectives the manufacturing enterprises seek, but they restrict and affect each other. To analyze the relations among three objectives and achieve their exact optimization during manufacturing are the important problems which are worth researching. Based on the practice investigation and reasoning, the action mechanisms of three objectives are deeply analyzed, and their effect rules and relations are ascertained. The optimization model of time-cost-quality is set up according to their relations. The special program is designed for the integrative optimization model based on the idea of accurate calculation, and is applied to solve the optimization problem. Finally the methods put forward are applied to the instance about car part manufacturing, and a series of optimization result is obtained. Some conclusions which are valuable for the manager in enterprise are summarized by analyzing the optimization result. The instance application indicates that the model and the methods can help to make decision for production.
Abstract: Under the circumstances of 7/24 taper tooling system being widely replaced by 1/10 taper tooling system in the high-speed machining, using 1/10 taper HSK- A63 tools as the research object, this article, adopting the method of finite element method, analyzes the parameters such as clamp force, surplus magnitude and rotary speed which affect the connecting performances of 1/10 taper spindle/ tool-holder. The results of this study provide basic and useful guidance for the parameters’ selection of 1/10 taper tooling system in practical machining.
Abstract: Analyzing a mill’s ability of flatness control has two purposes, one is finding the feather of a mill, and the other is making a judgment that whether a flatness error can be eliminated. But using classical method is hard to form a correct judgment when the error is complicated. Based on applying efficiency function in finding the property of each flatness actuator, a new method is developed to describe a mill’s comprehensive ability of flatness control. And we found the factors which contribute to whether a mill can weaken a certain flatness error. Practical application shows the new method is feasible.
Abstract: Directional solidified turbine blades of Ni-based superalloy are widely used as key parts of the gas turbine engines. The mechanical properties of the blade are greatly influenced by the final microstructure. In this paper, a mathematic model was proposed for the three dimensional simulation of microstructure evolution in directional solidification. Based on the thermo model of heat transfer, the grain growth within the blade and the microstructure morphology were simulated via a Cellular Automaton method. Validation experiments were carried out. The simulated cooling curves and microstructures corresponded well with the experimental results.
Abstract: Thermal errors generally account for as much as 70% of the total errors of CNC machine tools, are the most contributor to the workpiece dimensional precision in precision machining process. Thermal error compensation is an effective way to decreasing thermal errors. Precision mode is a key to thermal error compensation. In this paper thermal error modeling method based on the artificial neural networks (ANN) algorithm is applied for a vertical machining center. Four key temperature points of a vertical machining center were obtained based on the temperature field analysis. A novel genetic algorism-Back propagation neural network (GA-BPN) thermal error model was proposed on the basis of four temperature points. The emulations and experiments prove that there was about a 60% increase in machine tool precision.
Abstract: To study the stability margin sensitivity to the parameters of the geared rotor system is prerequisite to carry on structure optimization design and vibration control. The global dynamic equations of the geared two rotor system are set up through the coupled matrix of the spiral bevel gear pairs, and the stability margin is obtained by analyzing the global dynamic equations. To enhance the damping of the bearings and to enhance the module and mesh damping of the gear pairs can improve the stability margin of the geared rotor system. The method for the stability margin sensitivity analysis of the geared multi-rotor system is feasible. The conclusions from the numerical example are useful to improve the stability margin of the geared multi-rotor systems.
Abstract: Simulation models based on the different structural levitation vortexes were built, the analysis on the flow characteristics of pressure distribution and bearing capacity was conducted by using the RNG κ-ε turbulent model and non-uniform meshing in variable working conditions. At last, the influence factors and variation rules of vortex adsorption negative pressure effect were obtained. The theory and the experiment results indicate that the vortex carrier with symmetrical tangential air supply has the optimal stability, but the optimal negative pressure effect and the great lifting force are obtained by the vortex carrier with tangential single air supply.
Abstract: The Hidden Markov Model (HMM) offers a powerful framework for temporal modeling of features extracted from time varying signals, and the Artificial Neural Network (ANN) has been widely used for pattern recognition, time series prediction, and optimization and forecasting. This paper describes a hybrid HMM/ANN approach which is a very competitive alternative to standard HMM for cutting chatter monitoring both in terms of performances and recognition accuracy. The hybrid HMM/ANN system uses ANN, usually a Multi-layer Perceptron ANN, to integrate the multi-stream inputs as feature transformation, whose goal is to take the advantages from the properties of both HMM and ANN. Experimental results show the efficiency of the hybrid system in monitoring of cutting process.