Applied Mechanics and Materials Vols. 117-119

Abstract: The parameterized multi-body system dynamics model of the valve train of a diesel engine is built in ADAMS. The spring stiffness, spring force, valve mass and valve stiffness are set as experimental factors, and valve seat force and maximum acceleration are set as responses. Dynamic simulation experiments are carried out using design of experiment (DOE) method, from which the notable factors are obtained. The functions of response surfaces on notable factors are gotten, and then optimization design is implemented based on response surfaces.

Abstract: To more accurately simulate the pressure distribution of the ultra-thin air bearing film, Reynolds equation must be modified to account for the gas rarefaction effect. Starting from a widely used model of Reynolds equation, a new simplified second order model is proposed to simulate the ultra-thin air bearing film in hard disk drives. The new model of Reynolds equation possesses simpler mathematical form than that of the previous model. The new model is solved using a least square finite difference method and the resultant numerical results are compared with those of the previous model. The computational efficiencies of the new model and the previous model are also compared.

Abstract: It has been found that viscoelastic fluid has evident heat transfer enhancement function in macro scale. But in micro scale, viscoelastic fluid’s flow and heat transfer characteristics are still unknown. In this paper, the heat transfer process of viscoelastic fluid in the microchannel is studied by numerical simulation method. The simulation results show that the maximum heat transfer enhancement of viscoelastic fluid is up to 800%, compared with pure viscous fluid. The viscoelastic fluid has such obvious heat transfer enhancement function because of its strong secondary flow. Laminar sub-layer can be damaged by the strong secondary flow, and thus radial flow generates in laminar sub-layer. The radial flow can increase the interference and mixing effect, and enhances fluid’s turbulence and convection which can enhance heat transfer as a result. So the heat transfer enhancement depends on the intensity of secondary flow which is caused by the second normal stress difference, and it will increase with the raise of the flow rate.

Abstract: In the paper a flow stress model based on the dislocation theory in consideration of the recrystallization is shortly presented. The model contains two parts: a classic model of dislocation evolution and recrystallization model. The latter considers different kinds of recrystallization as the same process rooted in nucleation and grain growth. The results of the model parameters identification and the simulation are presented in this paper. Then disadvantages of the model are considered and new proposal for improvement the model are presented. Results of preliminary simulation are presented as well

Abstract: The linear stability of flows confined between two concentric rotating cylinders with wall slip is examined. The curves of marginal stability in the plane of the angular velocities at the walls are obtained as a function of slip coefficient, showing the stabilizing effect of slip on the flow stability. The eigenfunction for the first mode at the onset of instability and the corresponding cell pattern are obtained for different slip coefficients. It is found that the number of cell pattern in the radial direction increases with increasing slip coefficients.

Abstract: An experimental system used for temperature measurement is designed by the K-type thermocouple thermometry to achieve a direct measurement of cutting temperature in high speed orthogonal turning. The general regularity of temperature distribution is concluded, and the corresponding influences of cutting speed and cutting depth on the maximum temperature value are discussed in detail. Experimental data and simulating results are comparative analyzed to demonstrate the feasibility and correctness of Finite Element Method (FEM) model simulation and analytical solution. The verified model of temperature field can be applied to develop an effective non-contact soft-sensing method for high speed cutting temperature.

Abstract: This paper describes the hydrodynamic performance prediction of ship hull with propeller by using CFD techniques. As an attempt in investigating the flow features around ship hull equipped with a rotating propeller, open water test, resistance test, and self-propulsion test were conducted. The paper discusses also the applicability of different turbulence models which are used to predict the hydrodynamic performance of the propeller, the hull, and the interaction hull-propeller. The hydrodynamic performance prediction method was gotten and was validated. The computational results were validated against the existing experimental data.

Abstract: Based on field investigation and lab analysis, litter production and season dynamic in the different ages of Eucalyptus plantation (2006, 2005, 2004, 2003, 2002) were studied in this paper. Based on litter collection during 1 years, the annual litter production was estimated to be 2797 kg•hm-2, 4489 kg•hm-2, 3098 kg•hm-2 and 3692 kg.hm-2 for 2006, 2005, 2004, 2003 and 2002. Variance analysis showed that the difference of the litter production of the eucalyptus plantation between 2006 and 2003, 2005 reached the extremely significantly level (p<0.01). Monthly litter production showed seasonal dynamics to some extent. There were two peaks for 2006 and 2002, with occurring in April, September and, February and April respectively and three peaks for 2004 and 2003, with occurring in in February, April and June. But there was only one peak appearing in June. Synthetically, the litter production of 2006, 2002 achieved maximum in April accounting for 13.50% and 28.09% of the total but 2005, 2004 and 2003 achieved in June accounting for 23.83%, 21.33% and 19.23% respectively. Fallen leaves accounted for 84.86%~90.04% of the total litter, droppings for 5.01%-6.70%, branches for 2.95%-4.52%, barks for 2.64%-3.62%, and fruits for 0.00%-0.55%%.

Abstract: In this paper, the dependance of microstructures on temperature stability of the (Mg_1-xCax)₂SiO₄ (0≤x≤0.5) ceramics prepared by the conventional solid-state route were investigated. The XRD and SEM testing results showed the (Mg_1-xCax)₂SiO₄ ceramics were mainly composed of both forsterite (Mg₂SiO₄) phase and Monticouite (MgCaSiO₄) phase. Significantly, with increasing x, the ceramic temperature coefficients of resonant frequency (τ_f) were strongly correlated to the ceramic crystalline phase compositions and could be adjusted to near zero value through changing the contents of both phases. And its dielectric constants (e_r) were kept in the range of 6.8 to 8.7, and the quality factors (Q×f value) in the range of 18, 080 GHz to 55, 840 GHz at 15GHz.

Abstract: The objective of investigation is to use numerical simulation obtain the effect of three different flexible deformation parameters (the maximum deforming amplitude, the phase difference between the plunging motion and the deformation motion and location of the maximum deforming) on unsteady aerodynamic performance of an airfoil with plunging and pitching motion. It is shown the effect of flexible deformation at low Reynolds number is obvious. The effect of the maximum deforming amplitude and the phase difference on aerodynamic forces is quite significant while the time courses of C_L and C_T don’t almost change with location of the maximum deforming. Different deforming amplitude and the phase difference may be advantageous or disadvantageous for averaged aerodynamic forces. Larger phase difference can produce more thrust and make the forward flight faster. Compared with the rigid airfoil, the appreciate combination of deformation parameters is beneficial in MAV design.