A review on the rotary ultrasonic machining of advanced ceramics

Advanced ceramics are likely candidates for many industrial applications due to their superior properties. However, their high machining costs lead to limited applications. Rotary ultrasonic machining (RUM) is one of the cost-effective machining processes available for drilling holes in advanced ceramics. This paper reports on investigations in the last few years on RUM process of advanced ceramics. Emphasis is given on the effect of RUM process parameters (such as applied static load, rotational speed, ultrasonic power and vibration amplitude, abrasive grit size and coolant) on machinability parameters (such as material removal rate, tool wear and surface roughness). Results on tool wear and edge chipping are also reported

Precision Grinding of Hard and Brittle Materials

Two novel techniques were used to study the formation of ductile mode streaks during diamond grinding (primary process) of germanium, silicon, and glass that aid the secondary process of polishing. In the first technique asph~ric surfaces were generated on Ge and Si at conventional speeds (5000 rpm). In the second technique high speed grinding (100,000 rpm) of plano surfaces on glass and Si surfaces was carried out Form accuracy, surface finish and ductile mode grinding streaks are discussed in this paper. It was found that resinoid diamond wheels gave more ductile streaks than metal-bonded wheels but better form accuracy was obtained with the latter. Transparent ground surfaces were obtained more easily with Pyrex rather than with BK 7 glass, thus necessitating very little time for polishing. Ductile streaks appeared in abundance on germanium rather than silicon. Both the novel grinding techniques were used on CNC machining centres

Determination of energy consumption during turning of hardened stainless steel using resultant cutting force

Downsizing energy consumption during the machining of metals is vital for sustainable manufacturing. As a prerequisite, energy consumption should be determined, through direct or indirect measurement. The manufacturing process of interest is the finish turning which has been explored to generate (near) net shapes, particularly for hardened steels. In this paper, we propose using measured cutting forces to calculate the electrical energy consumption during the finish turning process of metals where typically the depth of cut is lower than the cutting tool nose radius. In this approach, the resultant cutting force should be used for calculating the energy consumption, instead of only the main (tangential) cutting force as used in the conventional approach. A case study was carried out where a hardened stainless steel (AISI 420, hardness of 47–48 HRC) was turned using a coated carbide tool, with a nose radius of 0.8 mm, without cutting fluid, and at 0.4 mm depth of cut. The experimental design varied the cutting speed (100, 130, and 170 m/min) and feed (0.10, 0.125, and 0.16 mm) while other parameters were kept constant. The results indicate that the electrical energy consumption during the particular dry turning of hardened steel can be calculated using cutting force data as proposed. This generally means machining studies that measure cutting forces can also present energy consumption during the finish or hard turning of metals, without specifically measuring the power consumption of the machining process. For this particular dry turning of hardened stainless steel, cutting parameters optimization in terms of machining responses (i.e., low surface roughness, long tool life, low cutting force, and low energy consumption) was also determined to provide an insight on how energy consumption can be integrated with other machining responses towards sustainable machining process of metals

GIS multi-criteria analysis by orderedweighted averaging (OWA): Toward an integrated citrus management strategy

This study proposes a site location assessment model for citrus cropland using multi-criteria evaluation (MCE) and the combination of a set of factors for suitability mapping and delineating the suitable areas for citrus production in Ramsar, Iran. It defines an incorporated method for the suitability mapping of the most appropriate sites for citrus cultivars with an emphasis on the multi-criteria decision analysis (MCDA) process. The combination of geographic information system (GIS) and a modified version of the analytic hierarchy process (AHP) based on the ordered weighted averaging (OWA) technique is also emphasized. The OWA is based on two principles, namely: the weights of relative criterion significance and the order weights. Therefore, the participatory technique was employed to outline the set of standards and the important criterion. The results derived from the GIS-OWA technique indicate that the cultivation of citrus is feasible only in limited areas, which make up 6.7% of the total area near the Caspian Sea. This investigation has shown that the GIS-OWA model can be integrated into MCDA to select the optimal site for citrus production. The present research highlights how multi-criteria in GIS can play a considerable role in decision making for evaluating the suitability of selected sites for citrus production

The Effect of PLA/HA Coating Thickness on Crack Formation and Corrosion Performance

Surface modification of metallic implants is often required to facilitate positive interaction between the implant and the surrounding hard tissue. In this study, a polymer-ceramic composite coating of polylactic acid/hydroxyapatite (PLA/HA) was successfully deposited on a Co–Cr–Mo alloy by the dip coating method in chloroform suspension at room temperature. The effect of various PLA/HA dipping layers was studied and the dip coating process parameters were optimized in order to obtain a homogeneous, crack free, densely packed and adhesive coating. It is found that PLA/HA-coated substrate with 3 dipping layers were denser and less crack sensitive compared to 6 dipping layers. Although it is hypothesized that a coarser coated surface helps to facilitate ingrowth of osseous tissue in human body, but current findings show opposite manners due to the fact that a higher corrosion rate was obtained. The coated substrate with 6 dipping layers also were found more profound to micro-cracks and delamination with a lower microhardness value compared to coated substrate with 3 dipping layers

Review of the Nanostructuring and Doping Strategies for High-Performance ZnO Thermoelectric Materials

Unique properties of thermoelectric materials enable the conversion of waste heat to electrical energies. Among the reported materials, Zinc oxide (ZnO) gained attention due to its superior thermoelectric performance. In this review, we attempt to oversee the approaches to improve the thermoelectric properties of ZnO, where nanostructuring and doping methods will be assessed. The outcomes of the reviewed studies are analysed and benchmarked to obtain a preliminary understanding of the parameters involved in improving the thermoelectric properties of Zn

Study on adhesion strength of tin coated biomedical ti-13zr-13nb alloy

One of the crucial factors which determine the success of coated implantation and stability in the long run is the strength of adhesion between the coating and substrate. After implantation, a weakly adhered coating may delaminate and this might seriously restrict the implant’s effectiveness and longevity. Based on past studies, the quality of TiN coating is directly influenced by the process parameters. The objective of this research is to evaluate the effect of N2 gas flow rate on adhesion strength of biomedical grade Ti-13Zr-13Nb alloy. In this research, N2 gas flow rate of 100, 200 and 300 sccm were varied while the other parameters (substrate temperature and bias voltage) were fixed. The scratch testing method was used to examine the adhesion strength of the TiN coating. This research used the calibrated optical images to verify the total coating failures on the scratched coated samples. The results indicated that the micro droplet form on the TiN coating decreases as the flow rate of the N2 gas increases. In contrast, the TiN coating’s adhesion strength increases with the increase of N2 gas flow rate. It can be concluded that N2 gas flow rate was significant factor in improving the coating properties of TiN on Ti-13Zr-13Nb alloy

Thermal oxidation promotes growth of nanocrystalline diamond on biomedical grade Co Cr mo alloy

Diamond coatings are employed to yield significant benefits in applications such as for cutting tools, optical lenses, biomedical components, microelectronics, engineering and thermal management systems. Although there are many research reporting the successful of diamond coating on titanium, tungsten carbide and steel alloys but there are still lacking of research on the cobalt based alloy as the substrate. In order to coat diamond on these metals substrate, chemical vapor deposition (CVD) technique is commonly used. This paper reports on investigations of nano-crystalline diamond (NCD) coating on different carbon content of cobalt based alloys. Emphasis is given to achieve good adhesion of NCD coating on high and low carbon content of cobalt-chromium-molybdenum (Co-Cr-Mo) alloys using two different processes of surface pretreatment such as mechanical roughening the sample surface (≈0.3µm) and by using thermal oxidation to create oxide interlayer. The results revealed that most of the coating on samples was peel-off on roughened surface. However, there were small portion of NCD coating that still intact on sample with oxide interlayer. The thickness NCD coating obtained was approximately 5µm. Since the adhesion strength of the diamond coatings were very poor and easily delaminated, scratch test could not be performed on both sample conditions. Surface morphology and characterization of diamond coatings were investigated by Scanning Electron Microscopy (SEM) and X-ray diffraction respectively

Improving biocompatibility of cobalt based alloy using chemical etching and mechanical treatment

Biomedical grade of cobalt based alloy have found a plethora of applications as medical devices especially in dental and articulation joints like in total ankle, knee and hip arthroplasty. However, the long-term performance of this material is highly dependent on their ability to withstand in harsh aqueous environment effects such as corrosion and wear once they are used inside a human body. Loss of surface integrity and subsequent leaching of toxic metal ions as well as particles to the surrounding tissues may undermine biocompatibility of metallic implants, also potentially causing untimely loss of mechanical function and device failure. In this study, a biomedical grade of Co-Cr-Mo alloy surface was treated with various surface modification techniques such as chemical etching and mechanical roughening in order to improve its biocompatibility. Investigation was done to study which techniques possesses the positive effect in cell growth and excellent cell response on the treated surface of Co-Cr-Mo alloy. In-vitro study showed that human osteoblast cells grown with good adherence and spread out with an intimate contact on the chemical etched surface after 14 days of incubation. It is believed that porous structure with grooves owned by chemical etched surface helps in anchoring the cells to the substrate surface and facilitates cells growth since more protein molecules expected to have more sites on CT surface. On mechanical roughened surface, the cells appeared to show slightly less extended cell membranes and remained rounded

Research progress of sol-gel ceramic coating : A review

The sol-gel method is a simple and low-cost technique that requires low temperature for the reaction process. Sol-gels can be made from a wide variety of ceramic materials, including alumina, chromium, silica, and zirconium. This technique has been used in a variety of applications, including corrosion prevention, biomedical applications, and electronic devices. The sol-gel technique has made significant progress in a variety of fabrication applications. Numerous papers have reported on the incorporation of ceramic materials with other materials to increase the performance of sol-gel coating. The ceramic sol-gel coating increased the corrosion resistance and thermal properties of the coated materials while remaining a low-cost approach. This paper highlights current reports on the various applications of sol-gel ceramic coatings