Determining the force formulas while orthogonal shaped turning by tools with convex radial cutting edge

Orthogonal shaped turning is a non-free cutting process, because the main geometric and force parameters are variable while radial infeed of a tool: side cutting edge angle (SCEA), width and thickness of cut, rake angle and flank angle etc.. In this regard, the existing force dependencies, which are used for stationary conditions of cutting, are not applicable. Analytical dependences for calculating variable cutting forces while orthogonal turning are obtained on the basis of experimental studies in this work. This approach takes into account the cutting areas and corresponding specific pressures using correction coefficients for changing cutting conditions during machining. The obtained calculated dependences are universal and can be used for a free cutting process, i.e. while cutting with a constant value of radial infeed. The obtained analytical dependences make it possible to calculate the energy parameters in the cutting process: power, torque and work in conditions of orthogonal shaped turning

Estimation of triboelectric properties of high-speed steels

Introduction. The paper is devoted to forecasting the operational properties of the existing and newly developed high speed steels depending on their chemical composition by the investigation of thermodynamic processes in the friction zone under cutting, and by receiving analytical dependences for evaluating friction and wear characteristics. The work objective is the prediction of wear resistance of high speed steels on the base of the structural sensitive parameters of the absolute or relative thermo-EMF and entropy of the material which can be calculated by the additivity rule at the known chemical composition. Materials and Methods . The theoretical relationship between the change in entropy of steels and their thermo-EMF is obtained. According to it, a smaller value of the absolute thermo-EMF corresponds to a larger value of the material entropy. This theoretical relationship is experimentally tested on various compositions of high speed steels. Research Results. To determine the relationship between entropy as a thermoelectric characteristic of high speed steels and their wear resistance, experimental tests on friction for the cylindrical samples of high speed steels of different types, and study on the wear properties of drills under steels machining are carried out. Measurements of relative thermo-EMF of these samples are performed; and their absolute values are calculated. The results of these tests show maximum wear resistance of high-speed steels having high values of entropy and low values of the absolute (relative) thermo-EMF. Discussion and Conclusions . The relationship between the wear resistance parameters of high speed steels and their structurally-sensitive characteristics at the micro-level - entropy and absolute thermo-EMF, is established. To reduce wear during friction and cutting, it is necessary to apply the types of high speed steels with maximal entropy and minimal thermo-EMF. Entropy, which with ease can be calculated on the known chemical composition of the material, can be used to assess the operating properties and to predict the wear resistance of both existing and newly developed compositions of high speed steels

Modeling of the temperature field on the rake surface of the lathe cutter taking into account the evolution of cutting forces

This paper is devoted to modeling the temperature field on the rake surface of the hard alloy lathe cutter when turning the work piece from structural steel 30 for a given value of the operating time of the cutting system. The assessment of the thermal state is made taking into account the change in cutting forces during machining. To do this, a model of the evolution of the radial and axial components of the cutting force was built, taking into account its growth in time and the influence of irregular kinematic vibrational perturbations. The calculation of the average temperature values for each section of the rake surface was made on the basis of the scientific approach described earlier, according to which the heating of the contact occurs due to the viscous dissipation of the friction energy in the surface plastically deformed micro layers of the chip. The calculation of the temperature values along the rake surface was carried out by the finite element method on a solid-state model of a fragment of the cutting part of the tool, as a result of which temperature values for the control planes were obtained. The results of digital modeling demonstrate a good correspondence of the calculated temperature values to the experimental data obtained by the semi artificial thermocouple method. The error of modeling the temperature field without taking into account heat exchange with the environment was 7.7-8.6%

Thermodynamic foundations of the rational cutting modes choice under conditions of machining

Durability and tribological tests of standard grades of high-speed steels and experimental single-carbide hard alloys with modified cobalt binder, created on the basis of the standard VK8 grade, under conditions of friction and turning of structural steels 45 and 12Х18Н10Т were carried out. The experiments were carried out for various cutting speeds and friction in order to determine the dependence of the optimal modes from the point of view of reducing the wear rate for cutting materials with different structural and thermodynamic characteristics. It has been experimentally established that high-speed steels with high values of thermal entropy have greater wear resistance in comparison with low-entropy grades, and cutting (sliding) speeds corresponding to minimal wear rates are higher for them. For experimental hard alloys grades characterized by greater thermal entropy values of the binder lower wear rates at optimal cutting speeds compared to the base alloy were also recorded; the values of the optimal cutting speeds for these materials are also higher. Thus, high-entropy cutting materials allow machining at higher speeds, while reducing the wear intensity

Tribological properties of high-entropy high-speed steels under conditions of friction on stainless steel 12H18N9T

This paper is devoted to the study of tribological characteristics of standard grades of high-speed steels (HSS) under conditions of friction on stainless steel 12H18N9T without the use of a lubricant. The grades of HSS selected for research differ in the value of thermal entropy, which is considered as an integral characteristic of their chemical composition. The tests were carried out according to the "pin-disk" friction scheme. The following differences in the characteristics of the friction process have been experimentally established, depending on the value of the thermal entropy of the HSS. Frictional interaction of high-entropy HSS was characterized by increasing the thickness of dissipative structures over time. The forming intermediate layer has a shielding effect, protecting the surfaces of rubbing bodies from destruction, but at the same time it has a large shear resistance, due to which higher coefficients of friction were recorded. The process of friction of HSS grades with low values of thermal entropy is characterized by the convergence of contacting bodies over time. For this group of materials, lower coefficients of friction were recorded against the background of a significant change in the surface micro relief relative to the initial state