Usually, end milling operations have been carried out using conventional uniform helix tools with fixed helix angles. Thus, many studies have been conducted to study the effects of these tools on the thermomechanical properties of a milling process. Recently, there have been works that point to the benefits of using harmonic endmills. Harmonic endmills consist of cutting edge profiles that have continuously harmonically varying helix angles. The variation is described using a harmonic function of axial position (elevation) of points on the cutting edge. In this work, a 3D finite element simulation using ABAQUS, is carried out for the complex milling process of Titanium alloy Ti6Al4V. The envelope of the harmonic tool is first generated using a set of MATLAB codes and stored in a Standard Triangle Language (.stl) format. The machine tool is introduced into an FEM program which has been designed to provide for dynamic effects, thermo‐mechanical coupling, material damage law and the criterion for contact associated with the milling process. A Johnson‐Cook material constitutive equation which combines the effects of strain hardening, strain softening, and temperature softening is used. To account for the chip separation criterion, the Johnson Cook damage evolution equation is used. The milling process simulation for Ti6Al4V is then carried out. In the end, the stress distribution and the cutting forces are obtained.
A solar photovoltaic (PV)-driven active crop drying system comprising a solar air heater, a three-tray drying chamber and a data logger was designed and fabricated.Drying system is equipped with three DC fans of 18 W each, powered by 150 W mono-crystalline, solar PV module, and 180 Ah deep cycle battery storage. Purposebuilt data logger constructed with a 60-pin Arduino-mega microcontroller and equipped with a digital dual-display screen was used to acquire real-time data on relative humidity and temperature at vital points in the drying system. Performance evaluation of the dryer was carried out while studying the drying characteristics of plantain chips at three thicknesses of 0.7, 1.0, and 1.5 cm. Drying characteristics were presented in graphs of moisture content (MC db ) versus time, moisture ratio (MR) versus time, and drying rate (DR) versus time for the different trays. Final moisture contents of the plantain chips were 10, 14, and 21% for the 0.7, 1.0, and 1.5 cm, respectively, in the three trays. The higher figures for the 1.0 and 1.5 cm levels of thickness are attributable to case hardening. Results showed that drying proceeded mainly in the falling rate period. Graphs of MR and DR showed that the drying process was more effective as the chips became thinner. Evaluation of 10 thin-layer drying models carried out using the acquired data showed that the Wang and Singh model was the best suited for describing the drying characteristics of plantain.
Practical applicationsThe results of the present work will be very useful to food processing companies producing Plantain chips for local consumption and export. A good knowledge of the best suited thin-layer drying model will help to predict the MR (and hence MC) as a function of drying time. In this way, energy might be saved and product quality guaranteed. In addition to quality assurance applications, the effect of layer thickness on drying characteristic would be very useful in prescribing the optimal thickness of the chips being processed.
The devastating effects of termites on wood and the contribution of termite activities to the rising levels of atmospheric CO2 and CH4 constitute a serious threat to global economy and the ozone layer. In order to stall the contribution of termites to the rising levels of greenhouse gases, this work considers the conversion of termite biomass to activated carbon electrode. The waste termite biomass obtained during the production of termite biodiesel was converted to activated carbon electrode by a one-step carbonization-activation process, using potassium hydroxide as activating agent. The optimal specific surface area of the activated carbon was recorded at 900 oC, 9 h and 3:1 KOH-biomass ratio. The surface morphology and functionalization of the activated carbon were examined using the SEM, TEM, XRD, Raman and XPS characterization techniques. The electrochemical performance of the activated carbon electrode was tested in aqueous (1 M H2SO4) and ionic liquid (1 M EMImBF4) electrolytes. Results obtained from cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance experiments showed that the specific capacitance of the activated carbon electrode was higher in 1 M H2SO4 (78 Fg-1 at 0.5 Ag-1) than in 1 M EMImBF4 (53 Fg-1 at 0.5 Ag-1). However, after completing 10, 000 chare-discharge cycles at 10 Ag-1, the activated carbon electrode lost ~ 5% of its specific capacitance in 1 M H2SO4 and ~ 2% of its capacitance in 1 M EMImBF4. Overall, the results showed that waste termite biomass could be valorised in the production of activated carbon for energy storage in supercapacitors.
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