Applied Mechanics and Materials Vols. 110-116

Abstract: Aiming at improving the Q-factor and simplifying the fabricating process of the cupped solid-state wave Gyroscope, a novel cupped solid-state wave gyroscope based on piezoelectric effect is presented in this paper. The sensor has a novel cupped metallic resonator comprises of a cone shell and eight thin flat beams. The working principle of the gyroscope is validated by FEM. Compared with conventional solid-stated gyroscopes, the novel structural features improve the Q-factor and simplify the fabricating process of the gyroscope. The prototypal gyroscope is fabricated and tested, the work mode frequency is about 3979Hz, and the Q-factor is over 8000 in atmosphere. The side-lobes in the output signal’s FFT curve validate the novel design scheme.

Abstract: Powder mixed electrical discharge machining (PMEDM) is one of the recent innovations for the enhancement of the capabilities of EDM process. In this study, the effects of powder addition on the surface modification of mild steel were investigated. Copper tungsten electrode was used in the machining. Two different powders namely TiC and Al2O3 were used in the study with kerosene as the dielectric medium. The powder types and currents were manipulated to study their effects on the machined surface. The results show that increasing the current leads to increase in recast layer thickness, and the cracks. The Al2O3 powder gave higher layer thickness than TiC powder. TiC Powder addition also produced higher hardness, more tool material and carbon depositions on the work surface than Al2O3 powder.

Abstract: Fly ash and a mixture of alkaline activators namely sodium silicate (Waterglass) and sodium hydroxide (NaOH) solution were used for preparing geopolymer. The aim of this research is to determine the optimum value of the alkaline activator/fly ash ratio. The effect of the oxide molar ratios of SiO2/Al2O3, water content of the alkaline activator and the Waterglass% content were studied for each Alkaline activator/fly ash ratio. The geopolymers were synthesized by the activation of fly ash with alkaline solution at three different alkaline activator/fly ash ratios which were 0.3, 0.35, and 0.4 at a specific constant ratio of waterglass/NaOH solution of 1.00. The geopolymers were cured at 70°C for 24 h and cured to room temperature. Results revealed that the alkaline activator/fly ash ratio of 0.4 has the optimum amount of alkaline liquid, which shows the highest rate of geopolymerization compared to other ratios. A high strength of 8.61 MPa was achieved with 0.4 of activator/fly ash ratio and 14% of waterglass content.

Abstract: This paper demonstrates, theoretically and experimentally, the feasibility of utilizing Shape Memory Alloy (SMA) as an actuator in controlling the flexural vibrations of a flexible cantilevered beam. The shape memory alloy used in this study is merely a straight wire which is made of nickel titanium alloy called Nitinol. Acting as tendons, these SMAs undergo phase transformation, to the austenitic phase, producing significant forces and displacement capabilities as well as low power consumption. This actuator unit is composed of a SMA wire attached to a spring in series. After being set-up with a load cell the transfer functions of the actuator are measured. Considering the uncertainty of the actuator unit performance the H-infinity optimal controllers are designed and installed into the control system. By integrating the thermal and dynamic characteristics of the SMA into beam dynamical model the composite beam-actuators system can now be developed. The robust stability performance of the designed controller is evaluated through vibrational test on the cantilever and the result is shown to be adequately attenuated.

Abstract: Manufacturers around the world constantly strive for lower cost solutions in order to maintain their competitiveness on machined components and manufactured goods. Globally, part quality has been found to be at acceptable levels and it continues to improve, while the pressure for part piece cost is enormous and is constantly being influenced downward by competition and buyer strategies. In machining processes, it is necessary to attain the desired surface quality in order to produce parts providing the required functioning. The surface quality is influenced by various cutting parameters (cutting speed, feed, depth of cut) and sometimes some other parameters. The objective of this paper is to review the effect of cutting parameters on surface integrity (surface roughness and residual stress) in hard turning.

Abstract: Austenitic stainless steel type AISI 316LN (316LN SS) material has been nitrided by three different nitride techniques such as Sursulf, Gas and Plasma nitriding. The 316LN SS samples have been prepared with two different surface roughnesses. The effects of surface roughness on nitriding with respect to formation of coating, case depth, increase in surface hardness and coating adhesion strength have been evaluated. The coating thickness was high for mirror polished samples than ground samples for all nitriding techniques. The coating thickness was very high (76.5µm) for plasma nitrided (PN) mirror polished sample and thin (22.5µm) & uneven for Sursulf Nitrided (SSN) ground sample. However, the SSN sample produces high surface hardness and good adhesion strength than PN. The Gas nitided (GN) sample produces the moderate result between SSN and PN.

Abstract: The existence of Surface Plasmons (SPs) is possible only if the metal have a negative dielectric constant at the corresponding optical frequency. In this paper the propagation characteristics of Surface Plasmon Waves (SPWs) which exists on noble metals like gold (Au) and silver (Ag) due to the formation of Surface Plasmon Polaritons (SPPs), have been evaluated theoretically and simulated with the help of MATLAB programming language. The variation of the propagation constant (PC), the attenuation coefficient (AC) and the penetration depth (PD) inside the metals and the dielectric has been determined. It has been found that highly conducting metals Au and Ag provide a strong confinement to the SPWs at optical frequencies.

Abstract: The present paper deals with the study of Rayleigh-Taylor instability at the cylindrical interface using viscous potential flow theory. In the inviscid potential flow theory, the viscous term in Navier-Stokes equation vanishes as viscosity is zero. In viscous potential flow, the viscous term in Navier-Stokes equation vanishes as vorticity is zero but viscosity is not zero. Viscosity enters through normal stress balance in viscous potential flow theory and tangential stresses are not considered. A dispersion relation is derived and stability is discussed in terms of various parameters such as Ohnesorge number, density ratio etc. A condition for neutral stability is obtained and it is given in terms of critical value of the wave number. It is observed that the Ohnesorge number has destabilizing effect while inner fluid fraction has stabilizing effect on the stability of the system.

Abstract: Granular materials have widespread use in the industry. The flow of granular media requires careful studies through experiments to understand the rheology of these complex materials. The present work determines the surface profile of dense granular media subjected to cylindrical Couette flow. A translation stage is used to obtain measurement of depth varying with radial distance. A depth gauge attached to the translation stage is used to measure the surface profile. Glass beads (average diameter 0.8-1 mm) and mustard seeds (average diameter 1.2-1.4 mm) are used as model granular materials. Two different Couette gaps are used (4cm and 3cm). Cylinders with smooth surfaces, as well as coated with emery paper are used. The surface profile varies with material, surface roughness of the cylinders, and the gap between the two cylinders. The comparison of the various cases has been done by graphical representation. The probable reasons for the development of such a surface profile are given.

Abstract: The computational analysis was performed of self-sustained oscillatory flow over the open cavity driven by a shear layer at flight Mach 5.0 condition with the solution of the Reynolds-averaged Navier-Stokes equations with a two-equation turbulence model. The self-sustained oscillation cycle of the open ramp cavity was got by simulation. It is found that the self-sustained oscillation feature of the cavity was complex flow. The shear layer rolls up and forms a vortex that grows in strength as the fluid enters the cavity. The amplitude of the pressure oscillation on the aft wall is much higher than that at the other wall due to the mass entrainment and ejection mechanism along the aft wall. This periodic mass addition and expulsion could be critical to the fuel and air mixing and flame-holding in the scramjet engine applications.