Papers by Author: Zheng Qiang Yao

Abstract: This paper presents a theoretical transfer matrix method for the modal analysis of nuclear coolant pump, and base on certain similarity law, a scaled rotor system is designed so as to simulate the characteristics of the real nuclear coolant pump, especially the vibration characteristics. Following that, the finite element method is used to verify the accuracy of the above theoretical method since there are a few simplifications in theoretical method compared with the finite element method. Finally the natural vibration frequencies and vibration modes of both nuclear coolant pump and the designed scaled rotor system are attained, which have high similarity with each other, and which confirm the accuracy of the two methods that are used in this article.

Abstract: In the laser forming of metal plates, there is a substantial waiting time required for cooling down the workpiece so that a steep temperature gradient can be reestablished during the next scan. Currently, there are no standard techniques that can be used to reduce this waiting time. This paper discusses the possibility of using non-natural cooling systems to cool down the workpiece. A numerical model of thermo-mechanical analyses with moving boundary conditions to simulate the traveling of laser beam and moving forced water cooling system is presented. Based on the proposed model, cooling effects under different laser powers and scanning velocities with various cooling conditions are investigated. The results show that the forced water cooling can significantly reduce the temperature with no adverse effect on the forming of plates.

Abstract: Laser interference micro-structuring is a relatively efficient and cost-effective technique for fabricating periodical micro-nano-structuring surfaces. The direct fabrication of sub-micron sized dot array on silicon was performed by four interfering nanosecond laser beams with a diffractive beam splitter. The mechanism to form the dot array was analyzed and it was found that the obtained conical dot array had a negative shape of the interference pattern of four laser beams. A second-order peak between two first-order peaks also occurred due to the liquid-solid expansion.

Abstract: Based on static analysis, this paper investigates the effects of interference fit and axial preload on the performance of the low-speed angular contact ball bearing. The results show the bearing with heavy preload and large radial clearance has big contact angle and high axial stiffness. Besides, large interference could result in small contact angle but high axial stiffness. When the bearing has large interference the axial stiffness increases rapidly due to the effect of interference on the axial stiffness stronger than that of contact angle. And the stiffness formula in the paper could provide boundary conditions for the finite element analysis of spindle-bearing system.

Abstract: A significant amount of research has been performed to explore the result of components tolerances on assembly quality. The paper analyzes the geometrical error sources which affect spindle rotation accuracy of turntable. Then it predicts the spindle rotation accuracy using vector dimension chain which is the most proper method to analyze assembly quality. The method is validated by tests and it could afford theory reference for spindle rotation accuracy analysis. And the computed value suggests the bearings’ rotary precision could be lower to save cost.

Abstract: Laser forming of a micro-structural element involves a complex thermoplastic process. Numerous efforts had been made on the mechanisms of laser forming for macro-size elements, such as temperature gradient mechanism, buckling mechanism and upsetting mechanism, etc. It is found that the three mechanisms cannot depict fully the process of deformation in the macro-size element forming, let alone meet the needs of the micro-size one. Considering the laser inducing thermal stresses with size factors differing from the conventional analysis, it is essential to reveal the mechanisms dominating the forming process to accurately control the bending angle of a tiny plate. By studying the thermal transfer and elastic-plastic deformation of micro-structural element laser forming, the forming mechanism is explained within the micro size. The finite element model for laser bending is constructed for simulation. The stimulation results are agreement with the experimental data.

Abstract: In order to obtain the total cutting energy and the ratios of the three parts of the total energy during cutting off the rubber, a test method was proposed and a test apparatus was constructed to perform the rubber cutting experiment. In the test, the friction force and the cutting force were obtained. Through the analysis of the test results, the friction work, the deformation energy, the surface fracture energy in cutting different thickness of the rubber were calculated. This work originally proposed a test method to acquire the friction force, the friction work between the cutter and workpiece during punching process.

Abstract: Predicting the precision of grinding process, especially correlating surface functionality generation to grinding conditions, would be of great significance to improve grinding accuracy of the end precision product. Huang developed a very promising revolutionary spectral data analysis technique based on the Hilbert transform. The concrete methods of the EMD, the local Hilbert spectrum are introduced. An artificial neural network (ANN) based on back propagation is developed to predict surface roughness Ra. An accelerometer is employed as in-process surface recognition sensor during grinding process to collect the vibration as input neurons. Changing the grinding condition, training and testing within the artificial neural networks to retrieve the weightings, the experimental results show that the proposed ANN surface recognition model is economical, efficient and the model has a high accuracy rate for predicting surface roughness.

Abstract: End mills are very widely used in machining metal. In this paper, based on analysis of three different end milling indexable inserts with 3-D chip breaker, the influence of different chip breaker on cutting force, chip deformation and machined accuracy are studied by comparative experiments. The results show that the cutting effect of end mills with indexable inserts can be improved by optimization of 3-D chip breaker and suitable for different machining condition.

Abstract: The surface roughness is evaluated by decomposing micro-errors from irregular surface image. The wave of surface is designated as signals including high-frequency, mid-frequency, and low-frequency signal, that denote roughness, waveness and the geometry shape error. Hilbert-Huang transform is a promising revolutionary technique for spectral data analysis, which is used to extract roughness from surface. It overcomes the imprecise result of the traditional surface roughness calculation and avoids the complication of the Wavelet analysis. Theory of Empirical Mode Decomposition (EMD) is given in the paper. This method is initially applied in picking up surface roughness, and it is proved to be of very high efficiency and simplicity.