Abstract: In this paper, in order to avoid aggregate of nanodiamonds and reduce the damage problem caused by the hard abrasives during polishing, a kind of ultra-fine nanodiamond abrasive polishing pad was fabricated by means of sol-gel technology. The polishing pad was then used to polish silicon wafer on a nano-polishing machine. The surface morphologies and roughness were measured by both optical microscope and atomic force microscope (AFM). It is found that it was easy to machine the silicon wafer to mirror surface after polishing with the nanodiamond pad. And the surface roughness of the silicon wafer was reduced to 0.402 nm.
Abstract: In order to obtain the effective depth of cut on the ground surface, a new grinding process model taking into account thermal expansions of the grinding wheel and the workpiece, elastic deformations of the grinding machine, the grinding wheel and the workpiece and the wheel wear was proposed. Using proposed model, the effective depth of cut was calculated using measured results of the applied depth of cut and the normal grinding force.
Abstract: The scale of influence of the single crystal sapphire crystallographic plane orientation and grinding conditions on the material removal rate, surface finish and the state of sub-surface layer have been studied under Low-Temperature Precision Grinding (LPG). The schemes of forming partial spherical heads for human hip joints endoprostheses are considered and elaborated. The possible versions of forming the spherical heads of endoprosthesis based on the novelties in kinematics and the mode of material removal are discussed.
Abstract: This paper presents further results in addressing this issue and builds upon the results obtained within the project GACR No. 101/07/0751 (research was supported by Czech Grant Agency), and the findings and information obtained from grant project GACR No. 101/05/2562. The problems are oriented to the production and sharpening of rotary tools, especially because all the know-how is owned by foreign companies. The main chapter is devoted to "Solution of the dependance of undercutting of the helical grooves on the grinding wheel diameter, its thickness and depth of the cut" at zero thickness of the grinding wheel. This method is an original analytical method for calculating the undercutting and is a part of the theoretical studies of the grinding helix slot. Then follows a passage, which defines the actual width of the spiral groove profiles at various grinding wheels. The present article summarizes only part of a broad range of problems in the area.
Abstract: This paper deals with study of surface quality changes of hardened steels that grounded with given cutting conditions. The samples of hardened steels are in corrosion chamber dynamic loaded by dynamic force and we observed changes of surface quality in parameters of surface roughness, residual stresses and material portion of profile. Aim of this experiment is evaluate of surface quality in depend on influence of corrosion surrounding and using different cutting conditions during grinding of hardened steels samples.
Abstract: The interest in laser material processing of Carbon Fibre Reinforced Plastic (CFRP) over the past few years has increased, especially in the aerospace industry. A number of different laser groups around the world are investigating different laser sources for the express reason of developing a laser material processing centre for machining CFRP for the aerospace and automotive industry. This paper reports on the work of two such groups, in the UK and Germany, who are using fibre laser technology and a diode pumped solid state laser system. The initial results from the two studies are reported and show that these two very different laser systems offer processing capability with respect to machining CFRP.
Abstract: A study concerning the application of fiber laser to perforate thermoplastic pre-pregs is presented. An IPG fiber laser was used to drill arrays of holes in PEKK carbon-fiber composite pre-preg material. Perforated holes were of the order of 100μm. The effects of laser perforation process parameters including the number of pulses on the geometry of the resultant holes and the thermal damage to the matrix and fibres have been investigated. Dimensional analysis and experimental results have been used to construct the laser perforation process model. Keywords: Laser perforation; Fibre laser; Process modelling; Polymer matrix composites.
Abstract: This paper aims to develop a laser assisted grinding process capable of manufacturing micro features in high strength materials. A diode laser with wavelength 808 nm was set on a precision grinding machine. Micro grooves were fabricated on high strength materials including silicon nitride and aluminium oxide by using the laser assisted grinding process, i.e. laser pre-heat workpiece flowed by micro grinding. The experimental results showed that the laser assisted grinding process resulted in deeper grooves due to thermal expansion of workpiece materials caused by laser heating. However, the machined surface roughness was more consistently better than that obtained using solo grinding process and applying coolant. No subsurface damage was observed in the SEM images of cross sections of the machined workpieces when laser assisted grinding process was used.
Abstract: Abstract: Formation of electrical conducting channels with paramagnetic properties on the surface of three type polymer plates (phenol-formaldehyde and epoxy resins, polyacrylonitrile) under influence of CO2 laser irradiation at the presence of air have been studied. It is shown that the magnitude of surface resistance of the investigated polymers depends on polymer type and irradiation energy. The appearance of electrical conducting regions in the polymer materials is due to laser-chemical transformations of macromolecular physical and chemical structures near the polymer plate surfaces, leading to formation of double conjugated bonds. These structures are characterized also with paramagnetic properties- by method of ESR the free radicals are discovered in the transformed regions of polymers. The obtained results practically are analogous to ones obtained in such polymers after thermal treatment at high temperatures. However there are some advantages: in the latter case for obtaining of conducting materials on the base of dielectric polymers it is necessary to use a high vacuum. Besides of such method does not allow the formation of conducting channels with desired square and configuration on the surface of polymer plates in very short time (about several seconds) at present of air.