Improving Local Temperature Rise in Rotational Incremental Sheet Forming Process by Modifying Forming Parameters Using Response Surface Method

In rotational incremental sheet forming( RISF) process,the friction heating of rotational tool could lead to local temperature rise of the sheet and cause the improvement of sheet's formability.Lightweight metal,such as magnesium alloy,could be deformed by RISF without additional heating. The objective of this study is to investigate the effects of forming parameters,namely,tool rotational speed,feed-rate,step size and wall angle,on the local temperature rise. Using response surface methodology and central composite design( CCD) experimental design,the significance,sequence of parameters and regression models would be analyzed with AZ31 B as the experimental material,and 3D response surface plots would be shown. Combined with actual processing conditions,the measures to improve the local temperature rise by modifying each parameter would be discussed in the end. The results showed that hierarchy of the parameters with respect to the significance of their effects on the local temperature at the side wall was: feed-rate,step size,and rotational speed,while at the bottom it was: feed-rate,step size,wall angle, and rotational speed, and no significant interaction appeared. It was found that the most significant parameter was not rotational speed,but feed-rate,followed by step size,for both test positions. In addition, the local temperature would increase by elevating step size,wall angle,rotating rate,and bringing down of feed-rate.

3D Casson nanofluid flow over slendering surface in a suspension of gyrotactic microorganisms with Cattaneo-Christov heat flux

A mathematical model is proposed to execute the features of the non-uniform heat source or sink in the chemically reacting magnetohydrodynamic （MHD） Casson fluid across a slendering sheet in the presence of microorganisms and Cattaneo-Christov heat flux. Multiple slips （diffusion, thermal, and momentum slips） are applied in the modeling of the heat and mass transport processes. The Runge-Kutta based shooting method is used to find the solutions. Numerical simulation is carried out for various values of the physical constraints when the Casson index parameter is positive, negative, or infinite with the aid of plots. The coefficients of the skin factors, the local Nusselt number, and the Sherwood number are estimated for different parameters, and discussed for engineering interest. It is found that the gyrotactic microorganisms are greatly encouraged when the dimensionless parameters increase, especially when the Casson fluid parameter is negative. It is worth mentioning that th~ velocity profiles when the Casson fluid parameter is positive are higher than those when the Casson fluid parameter is negative or infinite, whereas the temperature and concentration fields show exactly opposite phenomena.

Research of the use of silver nanowires as a current spreading layer on vertical-cavity surface-emitting lasers

Silver nanowire（AgNW） film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers（VCSELs） with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality.Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm.The performance of VCSELs with and without AgNW film was studied.When the AgNW film was applied to the surface of VCSELs,due to its better current spreading effect,the maximum output optical power increased from 23.4 mW to 24.4 mW,the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA,the differential resistance decreased from 23.95 Ω to 21.13 Ω,and the far field pattern at 50 mA decreased from 21.6° to 19.2°.At the same time,the near field test results showed that the light in the aperture was more uniform,and the far field exhibited a better single peak characteristic.Various results showed that VCSELs with AgNW on the surface showed better beam quality.

Influence of magneto-thermo radiation on heat transfer of a thin nanofluid film with non-uniform heat source/sink

The objective of the present work is to analyze the flow,heat and mass transfer characteristics in a thin nanofluid film over a heated stretched sheet in the presence of a non-uniform heat source/sink and thermal radiation.Similarity variables are used to transform the partial differential equations into a system of ordinary differential equations.The resulting system of nonlinear ordinary differential equations is then solved numerically by using the Runge-Kutta-Fehlberg integration scheme with a shooting technique.The effects of the unsteadiness parameter,the thermal radiation,the non-uniform heat source/sink parameter on flow and heat transfer fields are analyzed.It is found that an increase in the unsteadiness parameter is to increase the velocity and temperature gradient profiles.However,an increase in the thermal radiation parameter affects the nanoparticle temperature gradient of the nanofluid film but the reversed is true with the concentration gradient.