Applied Mechanics and Materials Vol. 274

Abstract: In order to analysis the nonlinear characteristics of vibration signal in the milling chatter process, this article uses Lyapunov Exponent and Approximate Entropy to analysis vibration signal of stable milling, vibration signal of chatter development and vibration signal of chatter in varied cutting-depth milling process. Plot the relationship curves of milling parameters with Lyapunov Exponent and Approximate Entropy respectively. The results showed that vibration signal had strong chaos characteristics when the milling chatter developed and occurred, and chaos characteristics of the vibration signal can be regarded as an effective method to identify the development and occurrence of chatter, and it also has guiding function for choosing milling parameter.

Abstract: With heavy NC machine tool is widely used in many oil pad round guide hydrostatic bearing as the research object, in the under condition of variable viscosity, establish oil film viscosity-temperature equation. Adopt finite volume method, simulation the hydrostatic bearing internal fluid temperature field under different flow rates on the speed of 6R / min. Numerical simulation hydrostatic thrust bearing oil film temperature field, can find a general high temperature region, and then take effective control temperature. It can achieve the hydrostatic thrust bearing oil film temperature field prediction for engineering practical oil chamber structure, offer the theoretical foundation for optimization design.

Abstract: In this paper, modal analysis of ball end mills is modeled by finite element to work out natural frequency and chatter model in tooling system and to calculate the limit curve of stability in single degree freedom system. The effect of cutter flute length and cutter tooth number on maching stability area is also discussed. The results of research show that steady critical cutting depth of milling system declines while the cutter flute length increases, but the trend is not linear, which shows increase partly. An engineering optimization design is made on milling cutter geometrical parameters based on this conclusion.

Abstract: To test the feasibility of proposed double-loop force loading control structure for the integrated testing system for high-speed train end relationship, it established the co-dynamics model of Stewart parallel manipulator and transfixion and developed the PID force controller. The sine force tracking simulation test was carried out in Simulink environment. The results show that, whether the input is in single dof or in 6 dofs, the output can meet the demand of amplitude attenuation and phase lag . This proved that this system has a good performance in force loading and the proposed control structure is feasible for the force loading test of transfixion.

Abstract: This paper put forward the method to calculate screw holding capability for micron wood fiber molded products. First, the mechanical model of screw holding capability has been established. Second, the function of force distributing to the threads has been deduced. Finally, the equation of screw holding capability was put forward. Using this method, we can calculate the screw holding capability of micron wood fiber molded products for screws of various geometric parameters by means of computer rapidly. The strength safety can be estimate for screw joints in micron wood fiber molded products accurately.

Abstract: This paper analyses distribution of the total speed ratio of two-stage helical gear reducer. On the minimum mass and contact strength condition , the optimum speed ratio equation is derived. By means of the least square method, the fitting formula of calculating optimum speed ratio on minimum mass candition is obtained. Using this formula, the optimum speed ratio of two-stage helical gear reducer having minimum mass can be found quickly and accurately.

Abstract: Layer system subdivision and adjustment is applied in oilfield development to ease the contradiction in inner-layer and interlayer and implement separated layer water flooding well, which is a major adjustment measure to improve developing effects. YSL is a typical low-permeability oil field, whose petrophysics is poor, and which exist many problems, such as apparent contradictions between layers, and poor development effects through separated zone water injection and so on. In this article, the thickness of barriers, injection profile, permeability contrast and remaining oil distribution are analyzed comprehensively. So a reasonable method is also proposed. Much weakness that factors are not comprehensive in adjustment method and that the problems in the development process are not accurately reflected is overcome, which exists in the past methods. The adjustment means can utilize poor thin layers better, reduce invalid water injection and ease the contradictions between layer, and oilfield development effects are improved eventually. It is a reference and guidance for other blocks or oilfield which exist the same problems.

Abstract: According to the requirements of the machined workpiece and the actual cutting conditions, the four cemented carbide face milling cutters with equal pitch are selected, using orthogonal test method, the four factors are studyed ,including spindle speed ,feed per tooth ,axial depth of cutting,radial cutting width, and determining the optimal cutting parameters of the milling tool under the condition of different cutting parameters, to improve processing efficiency and surface quality.

Abstract: Feature selection is an preprocessing step in pattern analysis and machine learning. In this paper, we design a algorithm for feature subset. We present L1-norm regularization technique for sparse feature weight. Margin loss are introduced to evaluate features, and we employs gradient descent to search the optimal solution to maximize margin. The proposed technique is tested on UCI data sets. Compared with four margin based loss functions for SVM, the proposed technique is effective and efficient.

Abstract: The study on forming helical tooth shaft processes in cross wedge rolling can contribute to the advantages of material-saving and efficient. Die tooth profile is an important process parameter of cross wedge rolling helical tooth shaft. Three kinds of forming process of die helical teeth were simulated by DEFORM-3D finite element analysis software to analyze three different die helical tooth. According to the tooth forming characteristics, the effects of three kinds of die tooth profile on forming of a polled piece were analyzed. When rolling a polled piece using the die with the same addendum width, it is convenient for die processing and the effect of polled piece forming is better; when using the die with the narrow front and gradually wider rear, the defects of uneven tooth bottom and larger pitch may happen. The rolling experiment was made by using the die with the same width at the tooth bottom. The results are in good agreement with the simulation. Therefore, we should use the die with unchanged addendum width, tooth height and the sidewall proportional increased when designing the die.