Rounding Radius Research Articles

Improving the technology for manufacturing hollow cylindrical parts for vehicles by refining technological estimation dependences

This paper shows that the technological preparation of production accounts for 20‒70 % of the total labor intensity of technical preparation. An important role belongs to the applied programs of finite-element modeling. However, such software packages often cannot be purchased by small-scale industrial enterprises for various reasons. Therefore, special empirical and analytical calculation models are used, which have proved to be quite effective in typical metal processing processes. Drawing a cylindrical hollow part was used as an example of the improved analytical dependence to calculate meridional tensile stresses. Existing analytical models of the process accounted for the bending moment through additional stresses. However, this approach only roughly described the deformation process. It was possible to refine the existing analytical dependences by introducing a term into the differential equilibrium equations that takes into consideration the bending moment that acts in the meridional direction when a workpiece passes the rounding on the matrix edge. Analysis of the obtained expression revealed that the bending of a workpiece gives rise to the stretching meridional stresses, which depend on the ratio of the squares of the thickness of the workpiece and the radius of the matrix rounding. The results of the estimation data from the numerical and theoretical models coincided for small values of the radius of the matrix rounding of 1‒2 mm, which confirms the adequacy of the analytical solution. In the numerical model, there is an extreme point where the tensile stresses have a minimum and, after it, begin to increase; this corresponds to the matrix rounding radius of 5 mm

Experimental and Numerical Studies of Tool Wear Processes in the Nibbling Process.

The work concerns an analysis of the wear mechanisms of punches in the nibbling process. The nibbling process is the multiple punching of holes or external contours using circular punches, the diameter of which is much smaller than the size of the punched shapes. Analytical, numerical and experimental studies were carried out. In the analytical solution, formulas for determining the pressures in the contact zone were developed, thus enabling a simple estimation of the designed nibbling tools. In numerical studies, the influence of the punch rounding radius on the fatigue wear was investigated. It has been shown that the change in the punch cutting edge radius from r = 0 mm to r = 0.5 mm enables a seven-fold increase in the fatigue wear resistance. It was found that the change in the punch cutting edge rounding radius has an impact on the quality of the product (the greater the radius r, the worse the technological quality of the product). In experimental studies, the abrasive wear process was primarily investigated. For this purpose, the nibbling process was tested on S235JR + AR steel sheets with tools made of NC11LV/1.2379 steel without any coating and with an AlCrTiN layer. It was found that the special AlCrTiN layer used allowed for an increase in the resistance to abrasive wear, and thus increased the service life by approx. three times. The last element of the work is an assessment of the technological quality of the product after nibbling depending on the degree and type of stamp wear (quantitative and qualitative assessment).

Исследование сил при съеме тонких слоев строганием и фрезерованием

The problem of machining structural elements with removal of metal layers with thickness less than 0.01 mm by carbide tools, when the conditional radius of the blade rounding is less than or equal to the thickness of the cut layer, is considered. These cutting conditions can be considered constricted which requires research into cutting forces and chip shape. The problem of recording and measuring small cutting forces arising during blade machining of small grooves that serve for gas drainage in the manufacture of rubber products is solved. To measure forces, a lever fixed in a universal dynamometer, which has a supporting support with small friction, is used. Value of force moment measured with dynamometer can be used for optimization of cutting conditions, selection of tool geometry when processing small relief elements. Dependences of lever system cutting forces and displacements on the use of lubricant-cooling liquids, values of front angles during planing and milling with small-size tools are investigated. Experimental discrepancies between theoretical calculations of cutting forces according to classical and modern reference data and fixed results with the use of cutting liquids during cutting with small values of feed for carbide tools are found

Experimental analysis and design strength models adopted by international guides for FRP-confined concrete columns subjected to axial compression

Carbon fiber jacketing is an efficient technique for increasing the strength and strain capacity of concrete circular and square section columns subjected to axial load, although confinement efficiency decreases for rectangular cross-section members. The research project BIA 2016-80310-P includes an experimental program on intermediate-size plain concrete specimens strengthened with carbon fiber jackets, mostly with square and rectangular cross-sections. The results, alongside others with similar characteristics from two databases published, are compared to predictions of four international guides. The incidence of the key parameters in the experimental results is analyzed, such as the aspect ratio of the section, the effective strain in FRP jacket attained at failure or the rounded corner radius. As a result, two efficiency strain factors are proposed, one for circular and another for rectangular specimens. The predictions contained in certain guides, based on a simple linear design-model, are improved by using the proposed efficiency strain factor for rectangular sections.

Influence of structural parameters on the modal characteristics of a Francis runner

The modal characteristics are important issues of a Francis turbine runner. It is prone to cause excessive vibration even resonance of turbine if the natural frequency is close to the excitation frequency. Thus, in the runner design and optimization processes, not only hydraulic characteristics but also dynamic characteristics should be considered to ensure the safe and stable operation of the unit. The modal analysis of hydrofoil NACA0009 is calculated by means of coupled acoustic fluid–structure model to verify the feasibility of the method and the results show good agreement with the experimental results. Then the effect of gap and structure parameters are discussed. Results show that the effect of fluid in the crown gap and seal on natural frequency and added mass is small, but the effect of fluid in the band gap and seal is considerable. The mode shapes are similar under different structural parameters, but the natural frequency and added mass factor are different. The effect of root rounding radius is more obvious than that of blade thickness and band thickness. Besides, the effect mechanism of band thickness on modal characteristics is quite complex, the lower-order frequency decreases while the higher-order frequency increases with the increase of the band thickness. The results in this paper are helpful to avoid the typical resonance frequency such as rotor–stator interaction frequency in the design and optimization processes.

SELECTION OF THE EXTERNAL WALL ROUNDING ANGLE OPTIMAL RADIUS

The article analyzes one of the ways to increase the heat-protective properties of thebuilding corner - rounding the outer surface of the outer wall the corner . The walls of houses nearthe outer corner, due to their configuration, have less heat-insulating properties than the walls inother areas. This is due to the fact that the area of heat flow perception on the inner surface of thewalls at an angle less than the area of heat transfer on the outer surface. Convective heat exchangenear the inner surface of the corner, due to the inhibition of air movement is less than in other areas,so the amount of heat coming from the indoor air to the wall surface is less. For climatic conditionsof Poltava region the research of temperature fields of calculated sections of the wall (withoutrounding of a corner, with rounding of a wall of various radius an external surface) with definitionof a heat stream size, the minimum temperature on an internal surface of a wall and the resulted heattransfer resistance is carried out. The dependences of the rounding radius of the wall outer surfaceon the heat flow passing through the design area of the wall outer corner, brick consumption withinthe design area, insulation consumption within the design area, the amount of room area reductiondue to rounding the wall for five design schemes. The analysis of dependences the constructed graphsshowed that the intensive reduction of the heat flux passing through the calculated section occurs ata radius of the wall outer surface rounding of 0.9 m and more; a slight decrease in the area of theroom due to the rounding of the wall occurs to a radius of curvature of 1.4 m; intensive reduction ofbrick volume within the calculated area occurs when the radius of curvature is more than 0.8 m,similarly to mineral wool up to 0.7 m. It is determined that the optimal radius of curvature of theouter wall is 0.8 m, it will increase the thermal properties of the angle and reduce the heat transfercoefficient by the transmission of the external enclosing structure of the building as a whole.

On the Use of an Inflatable Rubber Lip to Improve the Reverse Thrust Flow Field in a Variable Pitch Fan

Abstract The installed variable pitch fan (VPF) reverse thrust flow field is obtained from the flow solution of an integrated airframe-engine research model for the complete reverser engagement regime during the aircraft landing run from 140 knots to 40 knots. The model includes a twin-engine airframe, complete flow path representation of a future 40 000 lbf high bypass ratio geared turbofan engine, and a bespoke reverse flow-capable VPF design. The reverse thrust flow field, at all speeds, indicates that the reverse flow out of the nacelle inlet is washed downstream by the freestream toward the engine exit regions. Consequently, reverse flow enters the engine through the bypass nozzle from a 180 deg turn of the washed-down stream. This results in a region of circumferentially varying separated flow at the nozzle lip that acts as a blockage to the reverse flow entry into the engine. To mitigate the blockage issue, smooth guidance of the reverse flow into the engine to avoid separation can be achieved by using an inflatable rubber lip that would define a bell-mouth-like geometric feature with a round radius at the nacelle exit region. In nominal engine operation, the rubber lip would be stowed flush within the contours of the optimized nacelle surface. The design space of the rubber lip is studied by considering different rounding radii and locations of the turn radius with respect to the nacelle trailing edge. The choices of the design parameters are chosen by considering the nacelle edge thickness, inflation air volume requirement, weight, and thickness of support structures. The effect of these designs on the reverse thrust flow field is studied by incorporating the designs into the integrated model, with realistic installation-related restrictions. It is observed that a rounding radius of 0.1× nacelle length is sufficient to reduce the blockage and increase the ingested reverse flow by 47% to 18% in the 140–40 knots landing speed range. The inflatable rubber lip represents a design modification that can aid in the improvement of VPF reverse thrust operation, in cases where an augmentation of reverse thrust capability over the baseline is desired.

Research of strength properties of half-finished products

The article covers experimental study of knives with different sharpening angles to determine the strength properties of molded half-finished product and associated energy consumption for cutting. Determination of the values of the limiting shear stress of products depending on moisture content of the dough and the radius of rounding of the knife.

DEFORMATION BEHAVIOR MATHEMATICAL MODELING OF A POLYMER MATERIAL LAYER WITH TECHNOLOGICAL HOLE FOR A LUBRICANT

Mathematical modeling of the flat layer of a polymeric material deformation behavior with a polished steel plate within the framework frictional contact was carried out of this work. The influence of the technological groove geometric configuration for the lubricant on the contact unit deformation is considered. The lubricant volume in the calculation scheme does not take into account that does not correspond to the favorable occasion of lack of lubrication in the recess. The parameterized model creation of a polymer layer portion with one technological recess with a different base rounding radius from 0.5 to 2 mm with a step of 0.25 mm is done. The technological recess geometrical influence on the deformation of its profile at loads from 5 to 90 MPa was established within the framework of the study. Changes in the cross-sectional area of the recess, the maximum level of the plastic deformations intensity, contact pressure, contact tangential stress and the contact interaction area from the load and the rounding radius are established. The contact zone parameters redistribution due to an increase in the contact interaction area for all rounding versions for the technological recess base for the lubricant occurs at loads of more than 40-50 MPa. The design with a rounding radius of 2 mm has a number of advantages: minimum deformation of the technological recess area, the minimum level of the maximum plastic deformations intensity, the maximum contact interaction area, etc.

Theory of Formation of Edge’s Surface Roughness Finished by Radial Polymer-Abrasive Brushes

Formation of roughness during treatment by polymer-abrasive brushes occurred as a result of interaction of cutting micro-relief with processed surface. The cutting micro-relief of abrasive instrument is described in the form of random process with normal distributional law. When calculation of roughness, the depths of penetration of cutting lugs in processed material as well as regularity of changing of radial radius of rounding of peaks of cutting lugs from modes of treatment are taken into consideration. Set are relations of roughness of processed edge from modes of treatment (deformations of instrument, cutting velocities, feeding) as well as from constituent cutting force. It is proved that usage of polymer-abrasive brushes for rounding of edges faces all requirements of aviation industry on roughness of processed edges.

Study of the External Inverting Process of the Mild Steel Thin-walled Tube

The invertube is an ideal energy absorber to improve the crashworthiness of the vehicle skeleton body structure, but the low cost mild steel thin-walled tube often suffers some serious tearing phenomena in the external inverting process on the forming die. In order to investigate the interference factors of external inverting deformation, the optimum parameter of die structure design and the axial resistance force level of thin-walled tube in the external inverting process, a nonlinear finite element explicit dynamic codes were adapted to simulate the plastic inverting process of a mild steel thin-walled tube. The tube has the outer diameter of 60mm and the wall thickness of 2.0mm. The external inverting processes were conducted upon two kinds of round corner dies. Based on the results of previous theoretical analysis, the radius range of the corresponding die were obtained by theoretical calculation. The two die section forms and a series of dies with different round corner radii were also designed to build finite element simulation models. The inverting simulation results show that the optimal induced radii of the dies are within the range of 10.5-11.0mm. Meanwhile, it can be seen that the mild steel thin-walled tube has good formability in the early stage, which is convenient for the subsequent fine shaping of the invertube end. Moreover, the die bears less axial extrusion force, which is conducive to the improvement of the working life of the die. In the last, an ideal alloy steel die with the optimal rounded radius of 10.7mm was manufactured and used to verify the feasibility to finish the invertube manufacturing using mild steel thin-walled tubes. It provides a good simulation technology reference for the die structure design to realize the external inverting of the mild steel thin-walled tube.

Research of weight and linear wear from resource indicators of cultivator paws hardened by combined method

The article presents the results of theoretical and experimental studies of weight and linear wear from resource indicators of cultivator paws hardened by the combined method. It is established that in order to achieve an increased resource of cultivator legs, world manufacturers use special alloying materials, design features and technological methods of hardening, namely heat treatment, application of wear-resistant materials. The most commonly used methods for strengthening the working surfaces of parts are conventional hardening of medium-carbon, high-carbon and alloy steels. The hardness of the metal can be obtained in the range of 45 HRC for steel 45 and up to 65 HRC for steel 65G and alloy steels. To determine the change in the geometric parameters of the blades of cultivator legs during production tests recorded linear wear, weight wear and the radius of rounding of the cutting edge of the working bodies with an operating time of 8, 23, 42 and 54 ha. According to the results of linear wear of the wings of experimental cultivator paws during production tests, the materials that provide the best performance against abrasive wear were determined. As a result of the analysis of cultivator paws with a yield of 54 ha, it was found that the working bodies do not have visible damage and extreme wear and are suitable for further use. At the same time, measurements showed that the amount of wear on the width of the blade is 5.3–11.9 mm.

Кинематический расчет и построение графиков высоты подъема и скорости толкателя тангенциальных кулачков с использованием программы MATHCAD

The article shows the design features of tangential cams with a rounded top, provides a method for determining the lifting height and speed of the pusher when the roller is rolling in a straight line and in contact with the actual profile of the cam. The formulas for the kinematic calculation of the tangential cam are refined taking into account the radius of the initial circumference of the shaft, the radius of the rounding of the cam tip and the value of the radius of the pusher roller. Calculations are given to determine the stroke and speed of the pusher when the roller is rolling on the sections of the straight and arc-shaped surface of tangential cams with a radius of rounding of 6 and 10 mm. Formulas are proposed for determining the lift of the pusher in the rolling section of the roller along the radius of the cam tip at a constant coefficient λ = 1 and λ = 1,5. Using the Mathcad program calculations are performed and combined graphs of the pusher lift and the change in its speed are constructed for two types of tangential cams

МЕТОДИКА РАСЧЕТА ШЕРОХОВАТОСТИ ПОВЕРХНОСТИ ПРИ ОБРАБОТКЕ АБРАЗИВНЫМ ИНСТРУМЕНТОМ ИЗ СВС МАТЕРИАЛОВ

In the article, studies of the surface roughness during grinding with an abrasive tool made of SHS materials were carried out. Studies have shown that the surface roughness when grinding with SHS KR wheels increases in proportion to the increase in the radius of rounding of the grain top, plunge feed and inversely proportional to the speed of rotation of the wheel and workpiece, as well as the hardness of the material being processed.

Turbulent Mixing Process of a Round Jet With Slot Lobes

Abstract Turbulent mixing in the near region of a round jet with three slot lobes is examined via mean velocity and turbulent statistics and structures at a Reynolds number of 15,000. The design utilizes separate flow motivations upstream of each geometric feature, deviating from conventional nozzles or orifice plates. Immediate outlet velocity profiles are heavily influenced by opposing pressure gradients between the neighboring round and slot streams. Spanwise mean velocity profiles reveal the majority of the convective exchange between a given slot and the round center occurs in the immediate near field, but has lasting effects on the axial centerline profiles downstream. This is also reflected by the velocity half-widths, exhibiting asymmetry across the entirety of available measurements. Centerline turbulence intensities exhibit strong and short-lived isotropy. The increasingly anisotropic intensities found downstream are lower than similar geometries from the literature, implying that mixing development is inhibited. Reynolds stresses at the round-slot interface are significantly smaller than the round-stagnant exchange, but achieve a symmetric condition at x/D ≅ 4. Two-point spatial correlations of the fluctuating streamwise velocity exhibit stronger dependence toward the axial centerline at the round-slot interface in comparison to the nominal round radius. In contrast, spanwise velocity fluctuations exhibit nearly identical, localized behaviors on each side of the jet. Corresponding differences in streamwise integral length scale peak in the range 1.0 ≤ x/D ≤ 1.5, and so too do the turbulent structures in this area, as a result of the collated jet geometry.

Research of the mechanics of the microcutting process and the formation of a stagnant zone

Investigations of the parameters of the processes of chips and the treated surface formation, taking into account the rounding radius of the cutting blade, made it possible to determine the beginning of the separation of the stagnant zone material. According to the developed model of separation of the processed material, the minimum possible thickness of the chips during cutting is determined. Keywords: microcutting, blade curvature radius, separation, stagnant zone. rechenko-denis@mail.ru.

Effective heat transfer surfaces of tubes and plates with spiral vortex generators – inclined oval-trench dimples

Numerical simulation of laminar heat transfer enhancement at the hydrodynamic stabilization length of the tube with 8 inclined longitudinal oval-trench dimples (OTDs) in the transformer oil flow has revealed an optimal inclination angle of dimples, at which a value of thermal and hydraulic performance (THP) is achieved. Heat transfer of a dimpled tube increases by a factor of 28 in comparison with a smooth tube at practically invariable hydraulic losses. Heat transfer enhancement is calculated in turbulent air flow around a flat plate with a package of 16 one-row dimples inclined at an angle of 60° on the longitudinal section of 40 in length and 4 in width under the symmetry conditions at the side boundaries of the plate section and at a dimple step of 2.4. The dimple is 1 in width, 4.5 in length, and 0.2 in depth. Its rounding radius is 0.3. The boundary layer thickness at the section inlet is 0.175. The effect of abnormal separated flow intensification and heat transfer enhancement in dimples has been confirmed. (f/f pl )min=-3, (Nu/Nu pl )max = 4. Relative heat transfer grows by a factor of 1.43 in comparison with the smooth plate and the drag coefficient increases by a factor of 2.08. However the thermal and hydraulic performance defined in terms of heat load growth is 1.12.

Расчет сил и момента резания при фрезеровании концевыми фрезами

This paper presents a computational sequence for calculating the components of the cutting force and torque when milling with carbide end mills. The calculation algorithm includes the transition from the tangential and radial components of the force to the force components in the machine coordinate system. On the helical cutting edge, two parts are highlighted: one on the cylindrical (peripheral) surface and the other one on the arc of the rounded tip of the tooth. These parts of the cutting edge are divided into sections where the calculation is performed, followed by summation of the force components along the axes of the machine co-ordinate system and the moment relative to the axis of the cutter. An analysis of the components of the force and torque depending on the depth of cutting, feed, number of teeth of the cutter, blade wear and radius of the tip rounding is performed. The ratio of forces and moments for various milling conditions of structural carbon steel and aluminum alloys is shown. The developed algorithm is applied in a computational program that can be used to perform operational calculations of forces and torque for various milling conditions. The calculated parameters can be used as technological limiters in optimization problems, as well as for strength calculations of tools, milling equipment, and the selection of components of milling machine drives.

Deformation of an Isotropic Plate with Periodic System of Curvilinear Holes and Plasticity Bands

By the method of singular integral equations, we solve a plane elastoplastic problem of fracture mechanics for an isotropic plane with an infinite series of curvilinear holes and plasticity bands at their tips. We study the influence of the shapes of smooth holes and the radii of rounding of the contours at their tips on the opening displacements and lengths of the plasticity bands. The solutions of the corresponding problems for semiinfinite bilateral rounded notches whose tips serve as the origins of plasticity bands are obtained by the limit transition in the case where the relative distance between the holes tends to zero. On the basis of the deformation criterion of fracture and solutions of the periodic elastoplastic problem, we approximately determine the strength of rectangular specimens with bilateral U-shaped notches.

Separating Loss in Axial-Flow-Turbine Cascades

The use of a system of basic hydrogasdynamic equations, which was written for the portion of contraction of the flow at entry into a cascade of axial-flow turbine profiles at large angles of reattachment to the walls of a blade passage, has enabled the authors to obtain analytical dependences (characteristics) of the loss on the angles of entry of the flow into the cascade. The obtained procedure of calculating the loss permits taking account of the radius of rounding of the profiles at entry, on which the region of insensitivity to the angle of attack is dependent, and also determining relevant flow-entry angles limiting the insensitivity region. The authors have proposed variants of the procedure for both an incompressible-fluid model and a compressible gas, where use is made of the gasdynamic functions of the reduced velocity. The calculated characteristics of the turbine cascades are in good agreement with the existing experimental data in a wide range of angles of attack and radii of rounding of the profiles′ leading edges. The influence of the flow compressibility on the loss has been shown. To test the procedure under the conditions of pulsed flow through the turbine where the angles of attack are particularly large, the authors carried out investigations whose results are also in good agreement with the results of corresponding calculations.