International Journal of Mechanical and Materials Engineering

The article reports a recent study on heat flux of the top heat mode closed looped oscillating heat pipe with check valves (THMCLOHP/CV). An experimental system was evaluated under normal operating conditions. The THMCLOHP/CV was made of a copper tube with an inside diameter of 2.03 mm. The working fluid was water, ethanol and R123 with a filling ratio of 30%, 50% and 80% with respect to the total volume of the tube. The angles of inclination were 20°, 40°, 60°, 80° and 90° from the horizontal axis. The number of turn was 40 turns and 2 check valves. Three lengths of evaporator investigated were 50, 100 and 150 mm. The operating temperatures were 45°C, 55°C and 65°C. Experimental data showed that the THMCLOHP/CV at evaporator length of 50 mm gave a better heat flux with filling ratio at 50% when using R123 as working fluid and the operating temperature of 65°C at angles of inclination of 90°. It was further found that an evaporator length of 50 mm was superior in heat flux over other length in all experimental conditions under this study. Moreover, the presence of operating temperature had clearly contributed to raise the heat flux of THMCLOHP/CV, but the heat flux had decreased when evaporator length increased.

The principle aim of the present investigation is to study the heat transfer analysis of steady two dimensional flow of conducting dusty fluid over a stretching cylinder immersed in a porous media under the influence of non-uniform source/sink. Governing partial differential equations are reduced into coupled non-linear ordinary differential equations using suitable similarity transformations. The resulting system of equations are then solved Numerically with efficient Runge Kutta Fehlberg-45 Method. Graphical display of the obtained numerical solution is performed to illustrate the influence of various flow controlling parameters like curvature parameter, magnetic parameter, porous parameter, Prandtl number, heat source/sink parameter, fluid-particle interaction parameter on velocity and temperature distributions of both fluid and dust phases. The numerical results for the skin-friction coefficient and Nusselt number are also presented. Finally, the obtained numerical solutions are compared and found to be in good agreement with previously published results under special cases. The velocity within the boundary layer in the case of cylinder is larger than the flat surface and both the magnitude of the skin friction coefficient and heat transfer rate at the surface are higher for cylinder when compared to that of flat plate.

Dissimilar welding of aluminium (Al) and copper (Cu) has many applications in the electric power, electronic and piping industries. The weldments in these applications are highly valued for their corrosion resistance, heat and electricity conducting properties. The Al-Cu joints are lighter, cheaper and have conductivity equal to that of copper alloys. Much research has investigated dissimilar welding of Al-Cu by solid-state welding and fusion welding processes with the aim of optimising the properties and strength of such dissimilar joints. The main aim of the study is to critically review the factors influencing the properties of the Al-Cu joint. The study mainly discusses about the effects of intermetallic compounds (IMC) on the properties of Al-Cu joint and their effect while in service. The effects of joining aluminium alloy 1060 with pure copper by laser welding, friction stir welding and brazing have been reviewed and compared. The review shows that the various intermetallic compound formations in the joint have both beneficial and detrimental effects. The characteristics of these intermetallic compounds vary according to the location of the phase formed. Comparison of processes and parameters for welding of Al 1060 with pure Cu shows that the formation of the intermetallic compounds and their effects on the weld properties are mainly influenced by the welding speed, heat input, the thermal properties of the base metals and the filler metal as well as the dilution between the base metal and filler metal.

Experimental studies have been carried out to establish the possibility of using vibratory machining technology through shock-wave transmission for oxide coating preparation on aluminum-alloyed machine components and also to discuss the technological possibilities of applying vibration mechanochemical solid lubricant coatings based on MoS2 to improve the surface quality and performance properties of machine component parts. The coating characteristics are determined by measuring and comparing certain tribological properties of the samples before processing, after normal coating, and after vibratory coating process. A deeper study with a scanning microscope was made by comparing result of normal and vibratory coating. The vibratory coating shows a reduction of grain sizes, a regular orientation of the grain, and a dense grain structure leading to the formation of a thin layer covered by a film orientated parallel to the surface of friction giving an imparted surface finish. The reduction of microroughness is also accompanied with good performances in terms of increasing in wear resistance and decreasing in coefficient of friction. This reflects the presence of complex influence of mechanical and chemical components in the formation of coating on superficial layers during lower shock-wave vibration giving at the end structured ameliorated state of surface that leads to an increase in the part lifespan and equally shows technological opportunities that can be used to improve surface quality and performance properties of machine component parts.

An ISO standard tooth profile has a symmetric pressure angle of 20°. However, the load capacity can be increased with respect to bending and contact pressure by increasing the pressure angle on the meshing side of an asymmetric tooth. Accordingly, we analyzed the torque transmission capacity of asymmetric gears with various pressure angles. We calculated the deflection and bending stress of teeth by the finite element method and found the root stress taking into account the load-sharing ratio. Hertzian contact stress was calculated with respect to contact pressure. Normal vector load was converted into a torque, and torque capacity was evaluated when the stress reached the allowable stress for each case. Reduced bending stress because of an increase in tooth thickness and decreased transmission torque because of a reduction in the base circle radius work together to maximize the load capacity for bending at a pressure angle of around 30°. Maximum load capacity with respect to contact pressure is achieved when the pressure angle is made 45° by increasing the radius of the contact surface. Both strength with respect to bending and contact pressure are found, and the torque transmission capacity of the gear is determined by the lower value of the two. For low-strength materials such as flame-hardened steel, damage due to contact pressure is expected for all forms of gears and the greatest torque capacity was at a pressure angle of 45°. In the case of assuming 800 Hv and an inclusion size $$ \sqrt{\boldsymbol{A}}=50 $$  μm for a high-strength material, the greatest torque transmission capacity is obtained at a pressure angle of 30°. In the case of assuming a moderate-strength material such as case-hardened steel, an optimal form exists at which strength with respect to bending and strength with respect to contact pressure are equal.

This study was conducted to investigate the synergistic effects of cutting parameters on surface roughness in ball end milling of oxygen-free high conductivity (OFHC) copper and to determine a statistical model that can suitably correlate the experimental results. Firstly, an experimental plan based on a full factorial rotatable central composite design with variable parameters, the cutting feed rate or feed per tooth, axial depth of cut, radial depth of cut, and the cutting speed, was developed. The range for each variable was varied through five different levels. Secondly, a mathematical model was formulated based on the response surface methodology (RSM) for roughness components (Ra and Rz micron). The predicted values from the model were found to be close to the actual experimental values. Finally, for checking the adequacy of the models, analysis of variance (ANOVA) was used to examine the dependence of the process parameters and their interactions. The developed model would assist in selecting the cutting variables for optimization of ball end milling process for a particular material. Based on the results from this study, it is concluded that the step over or radial depth of cut have a higher contribution (45.81%) and thus has a significant influence on the surface roughness of the milled OFHC copper.

This paper deals with the propagation of the plane wave in a nonlocal magneto-thermoelastic semiconductor solid with rotation. The fractional-order three-phase lag theory of thermoelasticity with two temperatures has been applied. When a longitudinal wave is incident on the surface z = 0, four types of reflected coupled longitudinal waves (the coupled longitudinal displacement wave, the coupled thermal wave, coupled carrier density wave, and coupled transverse displacement wave) are identified. The plane wave characteristics such as phase velocities, specific loss, attenuation coefficient, and penetration depth of various reflected waves are computed. The effects of two temperatures, non-local parameter, fractional order parameter, and Hall current on these wave characteristics are illustrated graphically with the use of MATLAB software.

The laminar 2-D blended convection of the nanofluids at different volume fractions has gained interest in the last decade due to an enormous application in technology. The laminar-flow stream system can be further modified by changing the geometry of the channel, adding an external heating source, and changing the initial conditions at which the stream is being influenced. The investigation of this system includes the variation of the geometrical parameters of the channel, Reynolds number, Nusselt number, and type of the nanoparticles used in preparing the nanofluid with water as the base fluid. These parameters constitute a very successful leading to utilize the numerical solutions by using a finite volume method. Regarding heat flow, one side of the channel was supplied by the heat while the temperature of the other side was kept steadily. The upstream walls of the regressive confronting step were considered as adiabatic surfaces. The nanofluids were made by adding aluminum oxide (Al2O3), copper oxide (CuO), silicon dioxide (SiO2), or zinc oxide (ZnO) nanoparticles to various volume fractions in the scope of 1 to 4% and diverse nanoparticle diameters of 25 to 80 nm. The calculations were performed with heat flux, Reynolds numbers (Re), and step height (S) at a range of 100 <  < 600 W/m2, 100 <  Re  < 500, and 3 ≤ S ≤ 5.8, respectively. The numerical study has shown that the nanofluid with SiO2 has the highest value of the Nusselt number (Nu). The distribution area and the Nu increase as Reynolds number increases and diminish as the volume fraction diminishes with the increase of the nanoparticle diameter. The outcome of this paper has shown that assisting flow has shown superiority over the opposing flow when Nu increases.