Papers by Author: Ji Cai Kuai

Abstract: CoCrMo alloy is widely used in the medical field to make Biomedical prosthesis,But it is difficult to process resulting in the high cost of Biomedical prosthesis, Find an efficient and low-cost processing method has become a problem to be solved. In this paper, CoCrMo alloy Biomedical prosthesis were fabricated by Electrolytic In-process Dressing grinding. We studied the ELID grinding performance, grinding force, surface quality and the formation mechanism of Corrosion-resistant oxide layer of CoCrMo alloy by using dynamometer, roughness tester, XRD and SEM. It is proposed that the ELID grinding method forms an oxide layer on the surface of the prosthesis, which increases the corrosion resistance and biocompatibility of the prosthesis so that it can be better adapt to the biological environment in vivo. It was further confirmed that the ELID grinding method is an effective method for manufacturing CoCrMo Alloy Bioprosthesis.

Abstract: ELID ultra-precision grinding mirror surface can achieve nanometer precision. However, after the grinding wheel passivates the abrasive particles in electrolysis, it is easy to scratch the ultra-precision ELID grinding surface into the grinding process. In order to solve this problem, a non-abrasive grain α-Fe bonded grinding wheel is propose, which contains no abrasive particles. After electrolysis, oxide film is formed on the surface of the wheel. In ultra-precision ELID grinding, there is no abrasive particles involved, only the polishing effect of oxide film. There is no need to worry about the scratching of exfoliated abrasive particles that have been machined on ultra-precision ELID surfaces. Thus achieving extremely high surface accuracy.

Abstract: The formation mechanism of α-Fe2O3 on iron-bonded diamond wheel surface by ELID grinding is presented here. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the compositions of the oxide films. X-ray diffraction analysis demonstrated the existence of the diffraction peak of α-Fe2O3, which was observed in ELID grinding iron-bonded diamond wheel surface. To illustrate the correctness of our theory, X-ray photoelectron spectroscopy analysis was also performed. Results reveal that the characteristic spectrum of oxide film on ELID wheel has coincidence with the standard spectrum of Fe_2p in α-Fe₂O₃. These results suggest the existence of α-Fe₂O₃ in oxide films on the grinding wheel surface. The potentiality that α-Fe₂O₃ can bring polishing effect to ELID grinding process has also been discussed. It helps understand how ELID grinding can achieve excellent surface finish for the workpiece.

Abstract: In this paper we analyze the forming mechanism of composite abrasive grains in oxide film on ELID grinding wheel surface, By using composition information and by taking advantage of microscale structure, we have investigated that abrasive grains surface is covered by a layer of oxide film and the fresh oxide film is loose and porous like turtle shaped crack when crushed and dried. The elements of oxide film consist of α-Fe2O3 with sphere grain of 5-50nm. This phenomena is demonstrated that the composite abrasive grains in oxide film is a compound structure which is centered by abrasive grains, with α-Fe2O3,Fe (OH)3 surrounded.

Abstract: This paper conducted a theoretical study on the generation and transformation mechanism of α-Fe₂O₃ in the oxide film and an experimental verification of the presence of it. Firstly, the electrochemical process of the generation and transformation of α-Fe₂O₃ in the oxide film was analyzed, followed by the measurement of the content of it in the oxide film using X-ray diffractometer.

Abstract: The adhesion property of oxide film has great effects on the grinding quality and efficiency of ELID grinding. In this paper, adhesion strength model of oxide film is established, ELID grinding is conducted to nanometric cemented carbide and ordinary cemented carbide, ELID grinding force is measured, adhesive stress is calculated and the correctness of adhesion model is verified. The results show that the adhesion strength of oxide film is relatively greater, the transition from γ-Fe₂O₃ to α-Fe₂O₃ in the oxide film is relatively fuller and the polishing performance is relatively better while the grinding depth is smaller; with the deepening of grinding, the adhesion strength of oxide film reduces, the composition of the oxide film that transforms into α-Fe₂O₃ is less and the polishing ability reduces. The adhesion model of oxide film well reflects the adhesion property of oxide film, and the application of this model can represent the distribution, shedding and updating of the oxide film on the surface of grinding wheel.

Abstract: Nano cemented carbide is a new style cutter material. Because its grain size is very small, it is superior to common cemented carbide in properties, such as high hardness, fracture toughness, flexural strength and higher abrasion resistance. It is proposed to have wide application prospect to tools and mould manufacturing, machinery manufacturing, geological drilling, mining, oil field development, etc. In this paper, nanocemented carbide tool was ground with ELID technology, and the marble were cut with nanocemented carbide, and the cutting properties of nanocemented carbide were studied. Results imply that the tool life of nanocemented carbide is 0.5-1 times longer than that of common cemented carbide at low cutting speed. Which means the nanocemented carbide is more suitable for machining hard and brittle material than common cemented carbides at low cutting speed. And the microscopic analysis showed, the mechanism of tool wear is the abrasive wear as well as the shedding of WC hard phase within Co phase caused by the hard spots shed from the marble embedding in the internal part of binder phase Co which is located in the hard phase WC.

Abstract: The dynamic changes of the friction properties of the oxide film are characterized by the dynamic changes of the ELID grinding force. The tangential force and normal force are used to represent the friction coefficient in order to obtain the accurate real-time friction coefficient of oxide film. Therefore, the friction coefficient of various grinding wheels with different bonding agents, various grinding parameters, various grinding materials (nano- Al2O3 ceramic, nano ZrO2 ceramic and ordinary ZrO2 ceramic), and ELID grinding and ordinary grinding can be further studied. The results show that: the friction coefficient of the oxide film on the bronze-based grinding wheel is greater than that composed by iron; the friction coefficient of the oxide film decreases with the increase in grinding depth and feeding speed; the friction coefficient of the oxide film and nano-materials is smaller than that of the oxide film and ordinary materials; the transformation from γ-Fe2O3 to α-Fe2O3 in oxide film and the elastic deformation of the oxide film caused by the high-temperature of grinding may make the friction coefficient of ELID grinding greater than that of ordinary grinding, so the oxide film contains better property of friction and polishing. Therefore, excellent surface quality is easier to be obtained by it compared with the ordinary grinding technology.

Abstract: As ELID grinding technology is characterized by simpleness, practicality, low cost and so on, it is wildly used in ultra-precision sharpening, ultra-precision grinding, ultra-precision polishing and some other fields of difficult-to-cut material. ELID grinding technology was applied in the grinding of cutting tool in this paper, and the cutting tools with nano-grained cemented carbide, common cemented carbide, nanoY-TZP ceramics and some other materials were respectively grinded. Then, the surface quality of their anterior and posterior grinding horns and their edge radius were studied and compared with traditional grinding technology of cutting tool. The results show that the surface roughness and edge radius of nano-grained cemented carbide cutting tool are respectively Ra2nm and 0.3μm, the surface roughness and edge radius of common cemented carbide cutting tool are respectively Ra20nm and 1μm and the surface roughness and edge radius of nanoY-TZP ceramic cutting tool are respectively Ra60nm and 0.2μm after grinding by applying ELID grinding technology, which are far better than that from traditional grinding technology; this further proves that the adoption of ELID grinding technology in the grinding of cutting tool is feasible.

Abstract: As the grain size of nano ceramic has reached nanometer grade, it possesses high hardness, high wear resistance and high toughness. Therefore, the scalpel made by nano ceramic has the virtue of high wear resistance, good corrosion resistance, long service life, non-toxic, non-static, sharp edge and so on, but the processing of this kind of scalpel is extremely difficult. This paper prepares the nano-ceramic scalpel by using ELID grinding technology, and also studies the thickness, surface roughness, edge sharpness of scalpel. The research results show that the thickness of prepared scalpel is 0.3 mm, the surface roughness is 6-60 nm and the edge radius is 200 nm, the cutting experiment on suture shows that this scalpel can meet the requirements of international standard for medical scalpel when the cutting force is less than 0.8 N. This further proves that the ELID grinding technology is suitable for the preparation of nano-ceramic scalpel. The preparation technology and technological equipment of nano-ceramic scalpel are proposed on the basis of above achievements, and this technology possesses promising application prospect.