Applied Mechanics and Materials Vols. 110-116

Abstract: We study the joint effects of viscosity, resistivity and ion-neutral collisions on Alfvén surface waves propagating along a partially ionized plasma - vacuum interface. Applying boundary conditions at plasma-vacuum interface, we obtain the dispersion relation for Alfvén surface waves and solve it numerically. For different values of resistivity and neutral gas friction parameters, the variation of real and imaginary parts of wave number with viscosity parameter are shown graphically. It is found that two-mode structure of Alfvén surface waves results due to the combined effects of resistivity, viscosity and ion-neutral collisions. These results might be useful for studying the behavior of Alfvén surface waves in laboratory and space plasmas.

Abstract: The viscosity of some simple fluids in the wide density and temperature ranges have been calculated by the modified Enskog theory (MET) and with the help of Kaplun equations. The thermal pressure, second virial coefficient and internal energy are calculated from the modified SAFT-BACK EOS. The proposed scheme was further examined for the prediction of the viscosity of some dense fluids, including Ar, N2, O2, CO2, CH4, C2H6, C3H8 and C4H10. A comparison of the calculated and experimental values of the viscosity yields an overall average deviation of 2.16%.

Abstract: The motion of the upper free surface of a liquid column released from rest in a vertical, conical container is analyzed theoretically and experimentally. An inviscid, one-dimensional model, for a slightly expanding pipe's radius, describes how the recently reported super free fall of liquids occurs in liquids of very low viscosity. Experiments agree with the theoretical results.

Abstract: In the present paper, an attempt has been made to discuss the degradation mechanism of bond coat and bond coat/top coat interface in thermal barrier coating system in the presence of corrosive salts such Na2SO4 and V2O5.These salts come from impurities in low grade fuel used in gas turbine industry. Salt mixture of Na2SO4 + V2O5 was prepared and applied on surface of thermal barrier coating (TBC) specimens. The specimens were exposed isothermally to 900oC for 200, 400 and 700 hours. SEM analysis revealed the formation of thermally grown oxide (TGO) in specimens sprayed with corrosive salts. Results revealed that there was no degradation of either bond coat or bond coat/top coat interface up to 200 hours of isothermal exposure .Interface cracking and spallation was observed after 400 hours of isothermal exposure owing to depletion of zirconia stabilizer i.e yttria and phase transformation of tetragonal zirconia to monoclinic zirconia.

Abstract: In this paper a novel L-shape microcantilever that is more sensitive in compare of traditional rectangular microcantilever is proposed. In traditional microcantilever surface stress sensor a slight momentum is induced by distributed area stress lead to a slight deformation. In contrast, the proposed sensor substitution the slight momentum with concentrated point force in lateral direction on the tip of the microcantilever. This lead to, mechanically amplifies of the influence of area stress and more displacement. In addition, it has been theoretically proved that proposed microcantilever sensor with same lateral area in compare with traditional microcantilever surface stress sensor can be 2 to 100 orders more sensitive. The proposed L-shape microcantilever configuration of sensor could be incorporated in most of the microfabrication processes. However in this paper we use a low cost fabrication method based on polymeric microcantilever with metal piezoresistive detection.

Abstract: Compared with the free surface, the ruled surface is a linear set of parameters, and is obtained by a straight line moving in space along the curve trajectory, and tts modern processing methods are all complex and high cost. Spatial linkage mechanism has many features such as simple structure, easily control, sports continuous and so on, and the initiative crank continuous rotating drives the mechanism, at the same time, the rod length, the motion pair length or the twist angle is changed, which the cutter with start position fixed on a point of the rod main moves along the given curve, and feed moves straightly along the rod itself, so, the ruled surface was processed. The method is uncomplicated, and achieves high efficiency and high precision continuous line contact surface parts finishing, operating easily and saving cost.

Abstract: Friction couples are still unsolved problems, and the optimal choice depends on the patient’s age, level of activity and functional requirements. Finite element (FE) study was performed to investigate the contact mechanics and stress/strain distribution of hip resurfacing for different bearing couples. Ceramic-ceramic or ceramic-metal bearing couples reduce adhesive wear that also reduces osteolysis. There is, however, a problem of stem fracture risk of femoral component because of brittle alumina. Stress shielding within the bone tissue, was also found to be the major concern regarding the use of ceramic as an alternative to metallic resurfacing prostheses. All these bearing couples require to be supported by clinical studies to provide surgeons an appropriate choice of bearing materials.

Abstract: This study examines the experimental results of wear and friction characteristics using normal lubricant and jatropha oil (JO) added lubricants. The experiments are performed using a four-ball tribotester with standard test method ASTM D 4172. This simple test consists of a device by means of which a ball bearing is rotated in contact with three fixed ball bearings that are immersed in the sample. Different loads are applied to the balls weights on a load lever that gives a correlative pressure act similar to the one in the piston cylinder frictional zone. The data presented to evaluate friction and wear characteristics are coefficient of friction (μ), wear scar diameter (WSD), flash temperature parameter (FTP) and viscosity index (VI). Each test was conducted for two different loads (15 kg and 40 kg) to observe the variation of above parameters. All tests were carried out at 75 °C and speed 1200 rpm respectively for one hour. The normal lubricant (0% JO) was used for comparison purposes. The test results show that 5% JO added lubricant has over all good influences in reducing wear and friction coefficient. The objective of this investigation is to develop a new lubricant based on biofuel added lubricant (such as jatropha oil), which can also be used for biofuel fueled IC engines. The promising results have been presented with discussions.

Abstract: The author finds that there is outflow during piezoelectric pump sucking process, and a dynamic model combined with hydrodynamics and mechanical vibration is presented for the anlysis of piezoelectric pump sucking process phenomenon. The model is utilized to study the reason of sucking process outflow and the effect of the driving frequency, outlet valve rigidity, the load in inlet and outlet on the sucking process outflow. The result turns out that the flow inertia is the cause of sucking process outflow; the inertial flow also exists during draining process as the sucking process; increasing driving frequency, or outlet valve rigidity, the inertial flow decreases, increasing the load in inlet and outlet has the same effect. The research makes it clear that the pump output flow should include two parts, bulk flow and inertial flow, which will provide theory reference for the precise flow control of piezoelectric pump.

Abstract: This study is focused on vibration analysis of a rectangular plate in partial coupled with a vertical bounded fluid. The fluid displacement potential satisfying the fluid boundary conditions is derived and the wet dynamic modal functions of the plate are expanded in terms of the finite Fourier series for a compatibility requirement along the contacting surface between the plate and the fluid. The natural frequencies of the plate coupled with sloshing fluid modes are calculated using Rayleigh–Ritz method based on minimizing the Rayleigh quotient. The proposed analytical method is verified by comparing the presented results with the results obtained by three–dimensional finite element analysis. Finally, the influence of hydrostatic pressure and fluid depth on the natural frequencies are examined and discussed in details.