Papers by Keyword: Cutting

Abstract: Physical phenomena in a nanometric machining process were studied by molecular dynamics simulations. A cylindrical tool was indented and then moved laterally on an initially flat workpiece. The focus of the study is on the effect of lubrication on the nanoscale. Therefore, the indentation and the scratching were studied both in vacuum and submersed in a lubricant. All materials were modeled by Lennard-Jones truncated and shifted potential sites. It is observed, that in the lubricated case, a substantial part of the cutting edge of the tool is in dry contact with the workpiece. Nevertheless, compared to the dry scenario, the lubrication lowers the coefficient of friction. However, the work which is needed for the indentation and the scratching is not reduced. The processed surface is found to be smoother in the lubricated case. As expected, the lubrication has an important influence on the temperature field observed in the simulation.

Abstract: This paper deals with hobbing and finish-hobbing that considers the machine environment when using various hard hob materials. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results are summarized as follows. (1) Under the condition of hobbing with TiN-coated tools in dry cutting and with a minimal quantity of lubricant (MQL) system, P20 and P30 hob materials as the substrate show stable cutting and do not cause tool failure. The flank wear obtained with P30 is less than that obtained with P10 and P20 in the case of the coated TiAlN film tool. The MQL system shows flank wear reduction compared with dry cutting. (2) Under the condition of finish-hobbing, when using the TiN-coated tool, the flank wear obtained with dry cutting is smaller than that obtained with the MQL system. The flank wear increases in the order of P10, P20 and P30 hob materials, and the P10 hob material is effective. The TiAlN-coated P30 tool decreases flank wear and is suitable for finish-hobbing in dry cutting and with the MQL system. (3) Under the condition of hobbing, the finished surface roughness obtained with the MQL system when using TiN-and TiAlN-coated tools is smaller than that obtained by dry cutting. (4) Under the condition of finish-hobbing, the finished surface roughness obtained with TiN-and TiAlN-coated P30 is small in dry cutting and with the MQL system.

Abstract: This study examined the influence of cutting speed, cutting fluid, and pre-impregnated carbon fiber orientation on tool wear and finished surface roughness during turning of carbon fiber reinforced plastic (CFRP) pipes. In the dry cutting process, the tool wear decreased as the cutting speed was increased. An average cutting speed of 92 m/min or higher was found to be acceptable with respect to tool wear. The use of mineral oil resulted in a reduction of tool wear when compared with that in the case of dry cutting. The tool wear with water was lower than that with mineral oil. It was assumed that cooling by water was more effective than lubrication by mineral oil. The results clearly indicated that the tool wear and the finished surface roughness were affected by the carbon fiber orientation.

Abstract: The results of experimental studies of the different machinability group materials’ characteristics, including tool steel DIN C125W, heat-resistant steel (C - 0.1%, Si - 0.6%, Cu - 0.3%, W - 0.1%, Mn - 0.4%, Ni - 23%, P - 0.01%, Cr - 12%, S - 0.01%, V - 0.01, Mo - 1.5%, Ti - 3%, V - 0.001%, Al - 0.6), nickel-based superalloy (Fe - 4%, C - 0.1%, Si - 0.6%, Mn - 0.5%, S - 0.01%, P - 0.01%, Cr - 15%, Ce - 0.01%, Mo - 4%, W - 6%, V - 0.3%, Ti - 2%, Al - 2%, B - 0.01%), the changes in the minimum surface wear, maximum cutting path, and cutting temperature in the processing of these materials, as well as the experimental data analysis showed that the extreme values of changes in the materials’ physical and mechanical properties under the temperature impact can be defined as the minimum surface wear temperature and maximum cutting path temperature, that is, the conditions corresponding to the maximum workability of the materials. It is possible to use the materials physical and mechanical property dependence on temperature for defining the maximum material workability temperature when processing it by cutting. The article suggests a method to define the maximum material workability temperature.

Abstract: The article seals with the study of hard alloy (WC-Co) crack resistance (fracture toughness), depending on the temperature. Three representatives of one-carbide hard alloys (WC 94% Co 6% (fine grain); WC 92%, Co 8%; and WC 85%, Co 15% alloys) were chosen to determine the temperature influence on the stress intensity factor. During the obtained dependences’ analysis, we revealed that the hard alloy maximum performance temperature could be determined by the maximum value of stress intensity factor K_IC. The relation between the temperature of hard alloy (WC-Co) maximum crack resistance (fracture toughness) and the temperature of these materials’ maximum performance, is shown here as a result of experimental study of the dependence of impact resistance from temperature. In addition, the hard alloys’ maximum performance temperature determination technique is developed.

Abstract: It is a well-known fact that thermoelectric currents, reaching even the scale of ampere, develop during chip formation in the workpiece-tool-chip-machine system. The impact of these currents on tool wear in continuous cutting was examined with a qualitative mathematical model, in which wear is described by an autonomous non-linear differential equation.The constants of the model were tailored to wear curves determined by experiments conducted with a P20 carbide tool on a C45 quality steel workpiece. The differences among the tool isolation measurement results obtained by various researchers may be justified by simulation calculations.According to the model, the thermoelectric system behaves in a chaotic way in certain cases. Further research is necessary to decide if this is only a special characteristic of the model or the model shows the actual processes.

Abstract: This research work was carried out aiming to investigate the cutting characteristics of a soft metallic sheet subjected to the wedge blade indentation. The indentation of a lead alloy worksheet was conducted, experimentally using a center bevel blade in order to reveal the experimental background of the indentation. In addition, to investigate the effects of the blade tip geometry, the bevel angle of the wedge blade, on the cutting characteristics of the worksheet, the finite element method (FEM) analysis was conducted. By varying the bevel angle, the critical levels of stresses for the necking of the worksheet were detected. Also, it was found that the bevel angle affected the cutting load resistance, the necking of the worksheet and the final feature of the wedged edge.

Abstract: Defects in glassware are unacceptable in terms of product strength and aesthetics. The unsmooth cut rim of glassware can often be found in the laser trimming of excessive part after blow molding process. Such defect is basically not safe to use and has to be rejected from the production, thereby inevitably increasing the manufacturing cost and time. Hence, this research aims to reduce the defect in glassware rim induced by the laser cutting process. A wine glass was used as a workpiece sample in this study. Laser power, laser cutting time and workpiece rotational speed were tested and optimized to reduce the defects by using the response surface methodology. The optimum condition for the laser cutting of wine glass was found to be 225-W laser power, 2.4-s cutting duration and 335-rpm rotational speed.

Abstract: The use of higher laser powers in laser cutting of CFRP results in both an increase of productivity and in a growth of the heat affected zone at the cut edge. This thermal damage was related to a loss of the static strength due to the reduce load bearing cross section in various studies. In contrast, the thermal damage caused an increase of the average number of load cycles and to a significant reduction of the deviation among the repetitions of each parameter during dynamic open hole tensile testing in recent studies. To explain this positive influence of laser cutting on the fatigue behaviour of CFRP, an analytical model of the load concentration in a plate with a circular notch could be adapted and modified. The orthotropic property of the material is considered in the model. The static strength of thermally treated CFRP was determined in experiments and applied to the model. By inserting the measured temperature-dependent values of the Young´s modulus, the critical tension at the notch could be determined related to the dimensions of the heat affected zone.

Abstract: This paper presents conducted field tests of cyclic loading for railway subgrade. These tests studied the influences of subgrade structure forms of embankment and cutting on the dynamic responses of railway subgrade. The considered dynamic responses included the distribution of dynamic stress in railway subgrade, and the elastic deformation, dynamic stiffness, and cumulative plastic deformation on subgrade surface. The number of cyclic loading in testing was separately about two millions for an embankment and a cutting. The dynamic deviator stress applied on subgrade surface was 92kPa to simulate the maximum stress induced by moving train for the designed railway. Gathered data showed that the dynamic stiffness on subgrade surface for a cutting was approximately a half of the one for an embankment. However, the cumulative plastic deformation was essentially the same for the two forms of subgrade (i.e. the embankment and the cutting). These results provide references for the design of railway subgrade.