Applied Mechanics and Materials Vols. 764-765

Abstract: Most of structures are inevitable for imperfections. In this regards, evaluation of imperfection is more important for sensitive devices such as the resonators for high level of accuracy. In this work, micro ring structure is studied with arbitrarily located point masses. As a model, rotating thin ring is used and heat conduction effects are considered with the thermo-elastic damping effects. Using mode shapes of the ring, analytical model is introduced. For analyzing micro structure, various level of Quality factor (Q-factor) are studied. Furthermore, influences of concentrated random point masses are considered by the split of the natural frequencies.

Abstract: Heave Compensation system minimizes vessel heave motion during drilling operation of drillship. Heave compensator plays a role as damping form heave motion of drillship such as principle spring of car suspension system. The load transfers on the parts of heave compensator. Stress and deformation of all parts is evaluated to diagnose the stability of the compensator. This study makes a decision on the safety of structure by ANSYS 12.0v workbench.

Abstract: The brakes of an automobile are among the most critical components regarding the safety features, and disc brakes are the most common type used in passenger vehicles. In this research, the squeal phenomena of a swirl-vent brake rotor and the thermal analysis of two straight-vent brake rotors, made of cast-iron and aluminum-alloy, are investigated. For the squeal analysis, finite element models are created and analyzed using a prestressed modal analysis with complex eigen-solutions. For the thermal analysis, heat transfer coefficients on the surfaces of a rotor as functions of time are first estimated by CFD simulation, and then imported to a thermal analysis program as the boundary condition. Finally, the temperature distribution of the rotor can be calculated by finite element analysis. The simulation results show that vortices will arise in the vented passages of straight-vent rotors, which means less heat carried away and lower heat transfer coefficients. The swirl-vent brake design is clearly better for thermal ventilation. Furthermore, under the same condition, aluminum-alloy rotors exhibit more uniform temperature distributions with smaller temperature gradients than cast-iron rotors do.

Abstract: Traditionally, the reduction ratio of a spur gear pair is limited to 4 ~ 7. For a spur gear transmission with reduction ratio more than 7, it is necessary to have more than two gear pairs. Consider the cost of production, this paper proposes a helical spur gear reducer with one gear pair having reduction ratio 19.25 to substitute the gear reducer with two gear pairs. Based on the involute theorem, the gear data of helical spur gear pair is obtained. According to the gear data, its corresponding engineering drawing is accomplished. This manuscript verify that one spur gear pair also can have high reduction ratio (20 ~ 30).

Abstract: One stochastic dynamical model of a thin rectangular plate subject to in-plate parametrical narrow band noise excitation is proposed based on elastic theory and Galerkin’s approach. At first the model is simplified applying the multiple scale method and the averaged equation in Ito form is obtained. Secondly, the stochastic moment stability of the steady state responses are analyzed by Floquet theory and the moment method. Finally, the second order moment of the system is obtained, which can be used to estimate the variance of the responses. The numerical results agree with the theatrical analysis.

Abstract: The design method on bicycle’s functional elements proposed by this research is based on analysis on the winning work in the Global Bicycle Design Competition. Via analyzing its creative design on functional elements, our study is aimed to establish a creative design method on bicycle for designers to develop lots of creative ideas at the concept development stage. This research is divided into three stages, including analysis on bicycle’s creative design elements, construction of creative design method flow on bicycle’s functional elements, and case study on design prototype. For analysis on bicycle’s creative design elements, we have come up with a symbol table of bicycle’s creative functional elements (CFEs). As to construction of creative design method flow on bicycle’s functional elements, we first asked the designer to describe his/her design theme, and then picked bicycle’s CFEs according to the contents described. After CFEs were picked, we then conducted the space position arrangement of functional element symbols. Based on designer’s requirements, we produced several kinds of space arrangements on CFEs, and then we designed a new bicycle by referring to the symbol table of bicycle’s CFEs acquired. In the final step, we followed the flowchart of bicycle’s CFEs constructed by this research, and proceeded a case study prototype design.

Abstract: A molecular spring isolator which consists of water and hydrophobic zeolites as working medium is investigated. When the isolator undergoes periodic excitation, water intrudes into hydrophobic pores of zeolites depending on the external pressure and extrudes from the pores as hydraulic pressure decreases. As a result, molecular spring absorbs, releases and dissipates mechanism energy. To obtain the stiffness properties of molecular spring isolator, the mechanics modal of water column intruding into a hydrophobic pore is established utilizing force equilibrium. Subsequently, the process of water infiltrating large numbers of hydrophobic pores is explored. Then the quasi-static experiment is carried out to validate the theoretical modal. It is found that the molecular spring exhibits high static and low dynamic stiffness. Finally, the effect of quantity of zeolites and temperature on stiffness of molecular spring is investigated experimentally.

Abstract: This work experimentally explored the free convection heat transfer characteristics of finned heat sink with sintered-metal-beads layers. It has been proven that the metallic porous media can enhance the forced convection heat transfer efficiently. This work sintered the metal beads to adhere onto the both side surfaces of each radial plate fin of the metallic heat sink, and investigated whether the sintered-metal-beads layers promote the free convection heat transfer or not. The 0.5~0.85mm-diameetr bronze beads were employed. They were sintered smooth with the radial plate fins of the copper heat sink by thin layers at high temperature. The experimental groups were the plate-shape sintered-metal-beads and strip-shape sintered-metal-beads heat sinks. The pure copper finned heat sink was set as the control group. The results demonstrated that the thermal resistances of the experimental groups were separately 20.7% and 11.6% higher than that of the control group at the smaller temperature difference between the heated surface and the ambient (△T≈30°C); while the thermal resistances of the experimental groups were separately 15.3% and 6.9% higher than that of the control group at △T≈60°C. In general, the present sintered-metal-beads layers cannot strengthen the free convection heat transfer.

Abstract: Recently, it is essential to enhance the value of the products to make them more competitive. Therefore, the technical level of the high-precision products is required. Thermal deformation error, which accounts for a significant effect of processing accuracy of machine tools. In order to reduce thermal deformation error such studies the thermal characteristics of the Hydrostatic spindle is required. In this study, we could confirm the reliability of the analysis by assessing the thermal characteristics through measurement of the grinding machine temperature and thermal structural analysis. The temperature of the front bearing 10 °C or more higher than the temperature of the rear bearing, thermal deformation of the spindle, was found to be dependent on the temperature of the hydrostatic bearing. And could identify the thermal characteristics of the hydrostatic spindle.

Abstract: Heat transfer and friction factors of fully developed turbulent flows in the stationary rectangular divergent channel with parallel angled ribbed have been investigated experimentally. Four different parallel angled ribs (α = 30, 45, 60, and 90-deg) are placed to the channel’s two opposite walls as well as to the channel’s one sided wall only, respectively. The ribbed rectangular divergent channel has the inclination angle of 0.72deg at the left and right walls, corresponding to D_ho/D_hi =1.16. The divergent channel has the cross-section of100 x75 mm² at inlet and 100 x 100 mm² at exit. The ribbed walls are manufactured with a fixed rib height (e) =10 mm and the ratio of rib spacing (p) to height (e) = 10.