Applied Mechanics and Materials Vols. 365-366

Abstract: Thermoelectric energy harvesting is emerging as a promising alternative energy source to drive wireless sensors in mechanical, civil, and aerospace engineering systems. Typically, the waste heat from spindle units of machine tools creates obvious potential for thermoelectric generation. The structure of heat sinks on a thermoelectric generator has a great effect on the output voltage of the thermoelectric generator due to the temperature difference between hot and cold sides induced by heat transfer, so several typical structures of heat sinks are studied under different rotation speed of the spindle. According to the simulation study, the thermal resistance of heat sinks was presented. In the experiment, the output voltages of a thermoelectric generator were measured under different rotation speed with different structures of heat sinks. Experiment and simulation shows that the two pipes structure of the heat sink can help the generator to produce more power.

Abstract: Use gas-driven light gas gun is one of the techniques extensively used to achieve hypervelocity projectiles. The device was made up of a compressed gas gun as the first-stage drive. A new type high pressure pneumatic injecting system of gas-driven light gas gun for hypervelocity launching is introduced. As a critical component of the injecting system, the high pressure pneumatic valve was designed. Functions of the pneumatic valve were preserved and relevant techniques were discussed. Besides, a high pressure pneumatic mass flow control test-bed using inert medium was built in order to study the dynamic response characteristic of high pressure pneumatic valve in gas-driven light gas gun. To ascertain the response delay time of the valve, several turn-on and turn-off experimental tests of the valve were initiated. The results suggest that: the pressure of pneumatic electromagnetic valve gas supply circuit seriously influenced the properties of high pressure pneumatic valve; the mean delay time of the high pressure pneumatic valve was 190ms approximately at 6.5MPa gas pressure of the pneumatic electromagnetic valve gas supply circuit.

Abstract: The meshing principle of a new kind of parabolic gear is introduced, and the tooth surface equations of parabolic gear are obtained. A tooth contact analysis to simulate meshing and contact is applied. The paper investigates the influence of misalignment on transmission errors and shift of bearing contact. Examples to illustrate the developed approaches are proposed. The research provides the basis for design of new high strength parabolic gears.

Abstract: The model that describes the friction between contact surfaces of motion pair of the feed system has been established use of Stribeck friction theory, it fully reflected the various lubrication conditions. The bifurcation and stability analysis of the model has been done. The experimental methods were used to research the nonlinear dynamics characteristics of the feed system under the external excitation. The influences that friction force to the nonlinear characteristics of the system at the certain parameters condition were analyzed. Utilize the research findings of the dynamical characteristics that caused by friction in the feed system can effectively provide a theoretical basis for designing optimization of complex systems in engineering, fault diagnosis and vibration control.

Abstract: An analysis is conducted and solutions are provided for the dynamic performance of high speed hybrid thrust bearing. By adopting bulk flow theory, the turbulent Reynolds equation is solved numerically with the different orifice diameter and supply pressure. The results show that increasing supply pressure can significantly improve the bearing stiffness and damping, while the orifice diameters make a different effect on the bearing stiffness and damping.

Abstract: Three-dimensional elastic stresses developed in the root fillet of spur gear tooth due to uniform or non-uniform load distribution are analyzed in detail using global-local technique. Results indicate that root stresses distribute always non-uniformly along tooth width, and the maximum critical root stress (CRS) and its position depend on the face width and load distribution form. The maximum CRS is always higher than the corresponding value obtained under plane assumption and the value on the free surface. So, it is dangerous to use the CRSs calculated in practical gear designs. This research provides knowledge of root stresses for engineer to guard against gear failure and to design for increased loading.

Abstract: Abstract. Because of the extraordinary physical properties of engineering ceramics such as high hardness, low thermal expansion, light weight and abrasion resistant, it accommodates very well with the high-speed and precision requirements of spindle-bearing unit. In order to prove the superior dynamic characteristic of the all-ceramic spindle-bearing unit bacause of the application of engineering ceramics in shaft and bearing of spindle system, the natural frequency and modes of the all-ceramic spindle-bearing unit were analyzed. In this study, spindle-bearing model was built and analyzed by the Finite Element Method(FEM) and Hertz theory, comprehensively considering both of the stiffness of bearing and the effect of preload, which was different from the tranditional spindle analysis model. The research results show that all-ceramic spindle-bearing unit has higher natural frequency and better dynamic characteristics compare of traditional steel spindle-bearing unit.

Abstract: Aerostatic dry gas seal has attracted more and more attention because of its advantages with low friction loss, low heat generation, large opening force and high gas film stiffness at low-speed operation situation. The influence of the radial groove width ratio, B_w, on the performance of the aerostatic dry gas seal has been investigated by an analytical method by solving the N-S equation in order to understand the performance of the seal further more. The results show that the effect of the radial groove width ratio, B_w, on the opening force and on the gas film stiffness is obvious. The opening force decreases with the radial groove width ratio, B_w, increasing at the same gas film thickness. The situation of the gas film stiffness is complex. When the gas film thickness is smaller than a critical value, about 6μm as to the example presented in this paper, the gas film stiffness increases with the B_w increasing, but the gas film stiffness decreases with the B_w increasing when thickness is larger than the critical value. With the increasing of B_w, the leakage to the atmosphere, Q₂, increases, but the leakage to the process fluid, Q₁, reduces.

Abstract: Based on the finite element non-linear contact theory, the calculation model of the self-adhesive label printing pressure is achieved, then doing the non-linear contact of this model by using ANSYS. By changing the magnitude of interference between the printing cylinder and the printing platform, printing pressure is achieved in different magnitudes of interference. Contrast to the traditional empirical method, this method make up for the lack of calculating the printing pressure. It turns out help correcting mechanism parameters to achieve the optimal design.

Abstract: In this paper, the object of study is one pair increasing gear with building a two-dimensional plane model in ANSYS. According to the gears meshing theory, considering the gear deformation, solve the static transmission error and the gear mesh stiffness in different conditions. The influence of the centre errors on static transmission error and mesh Stiffness are basis for modal analysis based on the mesh stiffness of gear and unbalanced harmonic response.