Bahman Azarhoushang

Effects of Ultrasonic Assisted Grinding on CBN Grinding Wheels Performance

The effects of ultrasonic assisted grinding on vitrified CBN grinding wheels performance have been investigated. The ultrasonic vibration has been superimposed to the workpiece in feed and cross feed directions and the kinematics of the process in both directions have been discussed. The obtained results show that applying ultrasonic vibration to the grinding process can improve the quality of the workpiece surface, the efficiency of the process and decrease the grinding forces and specific energy considerably.Copyright

Effects of high power ultrasonic vibration on temperature distribution of workpiece in dry creep feed up grinding

Temperature history and distribution of steel workpiece (X20Cr13) was measured by a high tech infrared camera under ultrasonic assisted dry creep feed up grinding. For this purpose, a special experimental setup was designed and fabricated to vibrate only workpiece along two directions by a high power ultrasonic transducer. In this study, ultrasonic effects with respect to grinding parameters including depth of cut (ae), feed speed (vw), and cutting speed (vs) has been investigated. The results indicate that the ultrasonic vibration has considerable effect on reduction of temperature, depth of thermal damage of workpiece and width of temperature contours. Maximum temperature reduction of 25.91% was reported at condition of vs=15m/s, vw=500mm/min, ae=0.4mm in the presence of ultrasonic vibration.

Dressing of CBN grinding wheels with ultrasonic assistance

Though ultrasonic assistance has been successfully used for a long time in different machining processes, the use of its positive effects in dressing of superabrasives grinding tools is rather new, which could have drawn the attention of researchers in the last decade. In ultrasonic-assisted dressing, high-frequency and low-amplitude vibrations are superimposed on the movement of dressing or grinding tool. The experimental investigation carried out at the KSF Institute showed that applying ultrasonic vibration to both a stationary diamond dressing tool and a point crushing roll reduces the grinding forces, causing a reduction of the heat generated at the grinding zone.

Effects of Vibration-Assisted Grinding on Wear Behavior of Vitrified Bond Al2O3 Wheel

The total removal of grinding wheel material includes two main parts. The larger of the two is the result of dressing and truing operation and the other relatively small part is due to the wheel wear which takes place during the actual grinding process. The frequency of dressing and truing operations depends on the cutting conditions, wheel characteristic, etc. However in dry grinding as there is no cutting fluid to transfer the heat from the contact zone, the wheel wear during grinding and the frequency of dressing is much higher due to the higher grinding forces and temperatures. Vibration grinding reduces wear of the grinding wheel during the process considerably and decreases the frequency of dressing operation significantly. Hence it increases the efficiency of the process and reduces the cost. The investigation carried out in the KSF institute shows the improvement on the surface roughness, reduction of the grinding forces, thermal damage of the ground surface and radial wear of the grinding wheel in case of using vibration grinding comparing to conventional grinding. The designed and developed ultrasonically vibrated workpiece holder and the experimental investigation show a decrease of up to 80% of radial wear of the grinding wheel.

Effects of ultrasonic vibration on grinding of 100Cr6

A new grinding method that superimposes ultrasonic vibrations on the workpiece is contrived. An ultrasonic-assisted grinding unit is used for a series of experiments under different vibration and grinding conditions to examine the behaviour of grinding forces and surface roughness. Compared to conventional grinding, a decrease of the thermal damage on the workpiece and a reduction of cutting forces have been achieved. The effects of Ultrasonic-Assisted Grinding on both dry and wet grinding were also examined. It is found that superimposing ultrasonic vibrations, especially in dry grinding, is one of the most effective methods for grinding soft steels.

Developing a special block sonotrode for ultrasonic-assisted grinding process

Despite its known advantages, the ultrasonic-assisted machining process has not been widely introduced into industrial environment. Until the present time, the ultrasonic-assisted machining was only possible for small and light parts, when vibrating the workpiece, or for small and special designed tools, when vibrating the tool. It is demonstrated that due to the changes in mechanical properties of the material, efficiency of the ultrasonic assisted machining is much higher when the vibration is superimposed on the workpiece. Hence, there is an abundant need for development of a proper innovative ultrasonic vibration system which is able to vibrate industrial workpieces of different sizes and weights. To address this requirement, a special designed block sonotrode is invented. The first carried out experiments show that the application of the new ultrasonic system can reduce the grinding forces, surface roughness and thermal damages on the workpiece and increase the G-ratio considerably.

Theoretical and experimental investigation of intermittent grinding of SiC with a segmented grinding wheel

The widespread replacement of metals by the advanced ceramics has been limited by the high manufacturing costs of these materials and the difficulties involved. To meet the increasing demand of advanced ceramics, the current technological constraints should be overcome. One of the main targets in grinding of these materials is increasing the machining efficiency. Utilisation of a segmented grinding wheel can reduce the grinding forces and temperatures and increase the material removal rate. Hence, an especially designed segmented wheel (T-Tool) has been developed in this study. Both theoretical and experimental results illustrate the high performance of the developed grinding wheel. The obtained results show that the application of the T-Tool wheel can increase the G-ratio and decrease the grinding forces considerably. A decrease of up to 35% of grinding forces has been achieved.

Intermittent Grinding of Advanced Ceramic with the T-Tool Grinding Wheel

The application of advanced ceramics in high-tech industries is increasing considerably due to their superior properties. However the difficulties involved and manufacturing costs have been impediments to the widespread replacement of metals by the advanced ceramics. One of the main targets in grinding of these materials is increasing the machining efficiency while preserving the surface integrity. Hence in order to reduce the grinding forces and temperatures and increase the material removal rate, a specially designed segmented wheel (T-Tool) has been developed. Reducing the static cutting edges via segmenting the wheel which automatically leads to reduction of momentarily engaging cutting edges results in a reduction of rubbing and plowing regimes and therefore a decrease in the specific grinding energy. The obtained results show that the application of the T-Tool wheel can increase the G-ratio and decrease the grinding forces considerably. A decrease of up to 35% of grinding forces has been achieved.

Grinding of Soft Steel with Assistance of Ultrasonic Vibrations

Compared to other machining processes, conventional grinding has a low material removal rate and involves high specific energy. A major part of the specific energy in grinding is changed to heat which makes harmful effect on surface quality. A recent and promising method is the use of ultrasonic assistance to increase the material removal rate along with decreasing the thermal damage on the workpiece and reducing cutting forces. The advantages of Ultrasonic Assisted Grinding (UAG) were proved mostly for the brittle material. Our investigations show the improvement on the surface roughness, reduction of the grinding forces and thermal damage in case of using UAG comparing to Conventional Grinding (CG) for a soft material of 100Cr6. The designed and developed ultrasonically vibrated workpiece holder and the experimental investigation show a decrease of up to 40% of normal grinding forces.

Modelling of the micro-grinding process considering the grinding tool topography

The micro topography of the grinding tool has a considerable influence on the cutting forces and temperature as well as the tool wear. This paper addresses an analytical modelling of the micro-grinding process based on the real tool topography and kinematic modelling of the cutting-edgeworkpiece interactions. An approximate shape of the abrasive grains and their distribution is obtained from the confocal images, which are taken from the tool surface - determining the grain height protrusion and the probability density function of the grains. To determine the grinding forces, a transient kinematic approach is developed. In this method, the individual grit interaction with the workpiece is extended to the whole cutting zone in the peripheral flank grinding operation. Hence a predictive model of cutting forces and surface roughness in micro grinding of titanium grade 5 is developed. Finally, the simulated forces and surface roughness are validated by the experimental results.