To overcome the limitation of honing process, the present work proposes magnetic abrasive honing (MAH) process whereby abrasive stones are replaced by magnetic abrasives. This process is combination of magnetic abrasive finishing (MAF) and honing. MAF which is one of the finishing processes can improve the quality of workpiece surface with various geometries, removing the chips in micrometer scale by magnetic field forces. This study set to apply longitudinal vibration to the tube workpiece in MAF process; hence, this process is called MAH. The effects of rotary speed of workpiece, cross-hatch angle, and mesh number were investigated on the surface roughness of AISI 304. Magnetic abrasives were combination of SiC particles as abrasives and iron particles as ferromagnetic particles in lubricant of SAE 40 oil. The results revealed that the longitudinal movement of workpiece is effective on MAH, as the surface roughness decreased with increasing the cross-hatch angle. Surface roughness decreased with increase of rotary and mesh number. The major changes in surface roughness (58%) were obtained in cross-hatch angle of 45º rotary speed of 800 rpm and mesh size of 400. The microscopic picture showed that three-body wear mechanism is dominant for fine grits. پرونده مقاله

Lapping is one of the most important polishing processes which can be used to fabricate flat and smooth surfaces. In this paper, the effect of lapping characteristics and mesh number of abrasive particles are studied on the surface roughness and flatness for the machining of hardened AISI 52100 rings. The most significant lapping characteristics are pressure, lap plate speed and time. Scanning electron microscopy and optical microscopy are used to investigate micro cracks and surface textures. Results showed that surface roughness increased by rising the lapping pressure and plate speed. Also, reduction of the lapping time and mesh number of abrasive particles led to lower surface roughness. Application of lapping process decreased the flatness to 1.2 µm and surface roughness (Ra) from 0.58 to 0.051 µm. The lapping pressure was a significant factor on the surface roughness; and the lapping time was a significant factor on flatness. However, surface roughness increased with rising of mesh number and lapping time, and increased with decreasing the lapping pressure. The minimum surface roughness was 0.051 μm which was obtained in lapping pressure of 7 kPa, lapping speed of 0.164 m/s, time of 15 min and mesh number of 600.The flatness decreased with lapping speed, and reduced with increasing the pressure, mesh number and lapping time. پرونده مقاله

Barrel finishing is a common technique for surface finishing of industrial parts. Many factors such as working time, abrasive media, initial roughness and machining parameters of rotary barrel affect the final surface roughness of workpieces. Analysing these input parameters in order to obtain the least surface roughness as well as the least working time for barrel finishing of the specific samples, is not possible except by applying Design of Experiments method. Thus, the aim of the present paper is to improve the surface quality of the steel alloy CK45 samples in barrel finishing process, by investigating different combination of three abrasive particles including ceramics, steel balls and aluminium oxide as the abrasive media through design of experiments method. Initial roughness, working time and the combination of abrasive media are the input factors in the designed experiments, while the surface roughness is the output factor. Results show that the best surface roughness and working time have been achieved with the specific combination of steel balls and aluminium oxide particles as the abrasive media. پرونده مقاله

Formation of the burrs in the industrial parts after manufacturing processes such as blanking, punching, machining, cutting and etc. is inevitable. The burring phenomenon decreases the geometrical and dimensional tolerance and makes assembling parts together difficult. Radiusing the corners of workpieces is a common technique to reduce the stress concentrations at corners and also facilitate their assembly. By means of barrel finishing, a number of workpieces undergo deburring and radiusing coincidently in one process. In barrel finishing which is one of the mass finishing techniques, many workpieces with abrasive media are loaded in a rotary barrel. By rotation of the barrel, the parts and abrasive media are collided to each other and rub themselves, resulting in deburring and polishing the workpieces. The working time of this process is normally long. The aim of this study is to decrease the working time by using proper abrasive media. Here, a number of experiments is designed on combination of three abrasive media: steel balls, ceramics and aluminum oxide particles, in different working periods, to achieve appropriate radius and reducing burrs height of CK45 steel alloy samples in reduced working time. پرونده مقاله

Today, germanium single-crystals are used as an infrared and semiconductor material in the manufacturing of infrared optical lenses and windows (thermal vision), gamma-ray detectors, and substrates for optoelectronic and electronic applications. Given that germanium is an optically brittle material with high brittleness and brittle failure that mainly affects the surface integrity of the machined part on this material; In this experimental study, by changing the rake angle and feed rate of the cutting tool, experiments were performed to determine the appropriate rake angles and suitable feed rates and their effects on the surface roughness and texture of the relevant surface for germanium turning in the dry state. The results show that with increasing the rake angle and decreasing the feed rate of the cutting tool, the surface roughness decreases, which reduces the surface damage to a considerable extent. The purpose of this experimental study is to create a surface with the desired quality in the machining process of the germanium optical part using ductile mode machining and to change the parameters of this process to control the configuration and dimensions of microstructures, micro-cracks, micro craters, and Surface pits. پرونده مقاله

Material removal modes in brittle material machining are divided into two categories: ductile modes and brittle modes. Many believe that there is a clear difference between energy costs in these two cases. Spindle speed (SS) and feed rate are the effective parameters in the material machining process. It is tried to conduct experimental studies on the effect of low spindle speeds and high feed rates on the turning of brittle material in this paper. Also, the tool geometry is an important factor in turning brittle materials; so the rake angle of the turning tool was changed for dry machining of a single-crystal workpiece. The results show that the surface roughness decreases by increasing the spindle speed and decreasing the feed rate, which reduces the surface damage significantly. The purpose of this experimental study is to investigate the effect of rotational speed and feed rate on surface roughness and surface texture in the lathe process of the workpiece using the ductile mode of machining and changes in the parameters of this process to control the configuration and dimensions of microstructures (micro craters, Surface pits, and micro-cracks). پرونده مقاله

During the past decade, polymer nanocomposites have emerged relatively as a new and rapidly developing class of composite materials and attracted considerable investment in research and development worldwide.Direct machining of polymers can be an option for personalized products and for manufacturing product samples. To obtain high quality products and reduce machining costs, it is very important to understand the machining conditions so as to achieve enhanced machining performance. The influence of machining parameters (feed rate) and tool type (cemented carbide, HSS and coated HSS) on thrust force in drilling of epoxy, epoxy/clay and epoxy/TiO2nanocomposites are investigated. Variation of input parameters, feed rate and tool type affects the thrust force. The cemented carbide tool creates less thrust force than HSS and coated HSS tools. The thrust force in drilling process of epoxy/TiO2nanocomposite was more significant than epoxy resin and epoxy/nano clay. The minimum thrust force (13 N) was obtained in feed rate of 0.02 mm/tooth in neat epoxy with carbide tool. پرونده مقاله

Conventional material removal of BK7 optical glass will normally result in brittle fracture at thesurface, generating severe subsurface damage and poor surface finish. Subsurface damages inducedby grinding strongly influence the mechanical strength and optical quality of optical glasses.However, through ductile mode grinding it is possible to reduce the surface and subsurface cracks.It is meaningful to evaluate the depth of subsurface cracking through the measurement of surfaceroughness under different grinding parameters. In this research, the surface and subsurface damagesduring micro cup grinding and lapping process of optical glass BK7 are being investigated. In orderto invest the subsurface damages, cross section polishing method is being used and the crosssections are inspected through SEM microscope. The results indicate that number of subsurfacemedian cracks after lapping process are strongly decreased and surface lateral cracks are extendedall over the sample's ground surface. پرونده مقاله

Nowadays the surface texturing has been widely recognized as a usable capability to improve the tribological systems. In this paper, ultrasonic assisted turning (UAT) isperformed to create the micro textures on the flat faces. Micro surface texturing ismade on the Al7075-T6 by the UAT in the face turning process. Then, the influences of cutting speed feed, vibration direction and vibration amplitudeare studied.The effects of process parameterson the friction and wear behaviors of un-textured and textured patterns areinvestigated by the full factorial method. Microscopic images demonstrate the creation of micro dimples on the surfaces.Experimental results showed that textured surfaces can decrease the average friction coefficient and wear rate. The friction coefficient of surfaces generated by the UAT processwasdecreased about 10% in comparison to surfaces generated by conventional face turning.Moreover, because of existence of micro-dimple arrays in surfaces generated by the UAT process, proportion of contact between the pins and textured surfaces reduces. Cutting speed and feed effect on both of the average friction coefficient and wear rate.By increasingofthe cutting speed, feed, vibration amplitude and vibration direction (angle), the average friction coefficient and wear reduce. پرونده مقاله

Surface roughness is a significant parameter which determines the efficiency of optical components. Surface damages induced by grinding strongly influence the mechanical strength and optical quality of optical glasses. It is meaningful to rapid evaluate the surface roughness through the measurement of different grinding parameters. In this study, a cup diamond wheel (D64) is used in grinding process of the specimens made of BK7optical glass to investigate the influences of grinding parameters on the surface roughness. The grinding parameters used in this study are depth of cut, cutting speed, tables speed and feed rate; and effects of these parameters are studied. The dependence of surface roughness on grinding parameters was systematically analyzed. The experimental results indicate that feed rate, depth of cut and cutting speed have the most significant effect on surface roughness, respectively. By increasing feed rate and depth of cut, the surface roughness increases and increasing cutting speed results in a decrease in surface roughness. پرونده مقاله