In the current research, the application and capability of electric discharge treatment (EDT) for enhancing the cytocompatibility and tribological properties of medical-grade Co–Cr alloy were investigated. The Co–Cr specimens were treated by copper tungsten (Cu–W) electrode in a deionized water tank (dielectric medium) at different spark energy levels. To examine the cytocompatibility of substrates, the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was performed to evaluate the substrate cell viability. Furthermore, the wear rate and coefficient of friction of the substrates were examined on a pin-on-disc tribometer. In vitro cytocompatibility results revealed that the % viability of the MG-63 cells on EDT sample was approximately two times improved compared with that on the untreated surface. The tribological results showed that the treated samples have better friction reducing properties and four times higher wear resistance compared with unmachined Co–Cr samples. The surface modification at 10 A current and 60 µs pulse on-time and 150 µs off-time were found as significant parameters in both assessments.

Wear and corrosion properties of AM70 magnesium alloy subjected to equal channel angular pressing (ECAP) were investigated using pin-on-disc dry sliding wear test and electrochemical impedance spectroscopy (EIS), respectively. Wear test was conducted with 30 and 40 N loads with sliding distance of 5000 m and at a constant speed of 3 m/s. Reduced coefficient of friction (COF) and wear mass loss of ECAP processed samples showed increased wear resistance. Worn surface analysis by scanning electron microscope (SEM) showed the presence of delamination, wear debris, and plowing. Energy dispersive X-ray spectrometer (EDS) revealed the occurrence of oxidation, and the wear mechanism was identified as abrasion and oxidation wear. EIS plots showed the improvement in corrosion resistance of ECAP processed magnesium alloy compared to initial condition due to grain refinement and homogeneous distribution of secondary particles.

This paper analyses a mobile robot with independently rotating wheels travelling on uneven but smooth ground, including ascending or descending surfaces. We formulate a mathematical expression for the energy cost of the robot's movement. For our analysis, we utilise the principle of virtual work and assume that the robot moves with a fixed arrangement of wheel axes and without using a steering handle. The mathematical model reveals that the coefficient of friction and the payload distribution dominate the wheel behaviour, including slipping and skidding. We minimise the virtual work expression to determine the robot's motion complying with driven wheels. The model also enables us to estimate trajectories for different ground conditions. A hybrid robot, PEOPLER-II, is used to demonstrate the predicted motions, including turns and spins, by following angular velocity control rules. Experimental data verifies that the proposed formulation and minimisation of virtual work are valid techniques for predicting a robot's trajectory. The method described is widely applicable to wheeled robots having independently driven wheels.