Conical Tool Research Articles

Friction drilling of cast metals

This study investigates the friction drilling process, a nontraditional hole-making technique, for cast metals. In friction drilling, a rotating conical tool is applied to penetrate work-material and create a bushing in a single step without generating chip. The cast aluminum and magnesium alloys, two materials studied, are brittle compared to the ductile metal workpiece material used in previous friction drilling research. The technical challenge is to generate a cylindrical shaped bushing without significant radial fracture or petal formation. Two ideas of pre-heating the workpiece and high speed friction drilling are proposed. Effects of workpiece temperature, spindle speed, and feed rate on experimentally measured thrust force, torque, and bushing shape were analyzed. The thrust force and torque decreased and the bushing shape was improved with increased workpiece temperature. Varying spindle speed shows mixed results in bushing formation of two different work-materials. The energy, average power, and peak power required for friction drilling were calculated and analyzed to demonstrate quantitatively the benefits of workpiece pre-heating and high spindle speed in friction drilling.

Flank milling of a ruled surface with conical tools—an optimization approach

In this paper, machining a ruled surface with a conical tool is discussed. The main goal of our method (the spatial tangent points shift method) is to minimize the error between the given surface and the machined surface. A three-step-optimization is applied. In each step, the cutting tool is tangential to two guiding rails. The guiding rails can be located anywhere within the ruled surface. The first step is to initialize the tool position and find the point with the biggest deviation; the second step tries to minimize the surface error by moving the guiding rails towards the point with the largest deviation along the ruling line, which reduces the surface error to nearly half of its original value; the third step is to shift the tool position along the feed direction to further reduce the error between the given surface and the machined surface. We test the effect of various tool parameters on our method, and we compare our method to other methods of milling with a conical tool. Finally, we used our method to machine a test part and the accuracy of the assessment was verified experimentally.

Optimal response of conical tool semi angle in ductile metal sheets indentation and its governing mechanics

The nonlinear dependence aspect of various conical tool indentation parameters leading to an optimum tool semi angle value for easiest perforation is plotted and discussed explicitly in this work with the conclusion that tool angle has an optimum response towards most of the indentation parameters. Around this optimum angle, the aluminium sheets showed minimum fracture toughness as well as minimum work input to overcome the offered resistance. At the end, the mechanism leading to this phenomenon is presented with the conclusion that plastic flow dominates as the dimple semi cone angle reaches 35 and both pre and post plastic flow perforations lead the tool semi cone angle value towards this dimple cone semi angle of plastic flow initiation for its optimum performance. It is also concluded that specimen material failure is solely under tensile hoop stress and hence results into radial cracks initiation and propagation.

Finite element analysis of tube flaring process with a conical tool

The extended r min technique is incorporated into an incrementally updated Lagrangian formulation (ULF) of an elasto-plastic finite element computer code in order to handle contact boundary conditions to analyse the axisymmetric tube flaring process with a conical tool. A modified Coulomb friction law was adopted to calculate the influence of the friction coefficient on the tube flaring process. The effects of size and mechanical properties of tubes, as well as lubricants and tool semi-angle on flaring load were studied. It was found that good lubrication is effective in reducing flaring load. An optimum tool semi-angle (tool load is lower) in flaring is determined by frictional and bending activity at the tool inlet. In addition, the forming behaviour of the tube end is investigated to understand whether outward curling takes place and how much influence the tool semi-angle and tube size (initial thickness/initial mean diameter of tube) have on outward curling mode.

An Elasto-Plastic Finite Element Analysis of the Axisymmetrical Tube-Nosing Process with a Conical Tool

An Elasto-Plastic Finite Element Analysis of the Axisymmetrical Tube-Nosing Process with a Conical Tool

An approximate upper bound approach for the single-grit rotating scratch with a conical tool on pure metal

An upper bound model has been proposed for the single-grit rotating scratch with a conical tool on a rigid perfectly-plastic material. The model was validated experimentally with a newly-developed technique to make scratches on annealed pure titanium. It has been realized that the built-up edge (BUE) governs the material removal process of the rotating scratch. The current model makes use of the modification of BUE to the tool configuration so that the discretization of plastic region in the vicinity of the tool becomes feasible. The features of side-ridge and front-ridge, BUE and sub-layer plastic zone have been found to be evolving in different ways during the rotating scratch. Three material removal mechanisms were uncovered to be involved with the rotating scratch process, namely, plastic (shear) deformation, contact friction and ductile fracture. In the first-half of the scratch, the first two mechanisms dominate the process, while in the second-half, the ductile fracture plays an active role as evidenced by the extensive tearing along the both banks of scratch.

Five-axis NC milling of ruled surfaces: Optimal geometry of a conical tool

The Side milling of ruled surfaces using a conical milling cutter was studied. This is a field that has largely been ignored by research scientists, but it is much used in industry, especially to machine turbine blades. In this study, we first suggest an improved positioning with respect to the directrices of the ruled surface. As compared with the methods already developed for the cylindrical cutter, this positioning enables the error between the cutter and the work-piece to be reduced. An algorithm is then introduced to calculate error so one can determine the cutter dimensions (cone radius and angle) in order to respect the tolerance interval imposed by the design office. This study provides an opportunity to determine cutters with greater dimensions, thus alleviating bending problems during milling.

Mechanics of mixed-mode ductile material removal with a conical tool and the size dependence of the specific energy

The mechanics of material removal during a single-grit rotating scratch has been investigated both analytically and experimentally. The models for cutting, plowing and mixed modes of material removal are analyzed based on the pressure and the frictional resistance. The mixed-mode model takes into account the contribution of built-up edge (BUE) ahead of the tool. To validate the model, single-grit rotating scratch experiments were conducted with a conical diamond tool on pure titanium. It was noticed that the adhesion between the tool and the deformed material, and the hardening properties of material play active roles in the scratching process and provide a driving force to the formation of the BUE. The overall frictional coefficient was found to oscillate strongly on both ends of the scratch but increases steadily over the central span of the scratch length. It is shown that the mixed-mode model captures the salient features of material removal and the size dependence of specific energy during the formation of a rotating scratch. The size dependence of specific energy may be attributed to the size effect of the yield pressure in titanium.

Characteristics of single-grit rotating scratch with a conical tool on pure titanium

Single-grit rotating scratch tests have been conducted with a conical diamond tool on pure titanium. The force profiles during the scratch event were captured using high frequency force transducers. The mechanisms of material removal have been characterized by optical and scanning electron microscopes. It was observed that the adhesion between the tool and the deformed material and the hardening properties of material play active roles in the scratching process. Adiabatic shear band (ASB) formation followed by cracking was observed to be responsible for the material removal during scratching. The overall frictional coefficient (OFC) was found to oscillate strongly at the beginning and at the end of the scratch, but increased steadily in the middle of the scratch. The size dependence of overall specific energy was observed and was mainly attributed to the competition between hardening and softening during the scratching process. Instantaneous specific energy and instantaneous scratch hardness have been introduced to characterize the process. These parameters were found to be sensitive to the depth of cut, thus validating the close correlation to the size effect of overall specific energy.

Response of Ductile Metal Sheet Parameters to the Cone Angle of Indenting Conical Tool and Fracture Toughness Evaluation

The indentation and perforation of ductile metal sheet with a conical tool is accompanied by elastoplastic bending, stretching, plastic flow, and crack initiation and propagation. This ultimately results in material fracture in the form of petals. It has been observed that the perforation process is dependent upon the angle of the conical tool. Fracture toughness, crack initiation, work input before and after crack initiation, number of petals, and sheet and petal bending angles all depend on the tool angle. Crack initiation has resulted at minimum tool displacement for a tool angle α=45°, while minimum work input before and after the crack initiation is observed when the tool has an angle α=35°. The optimum range of tool angles for the indentation process is α=22.5 to 50°. In this range, the aluminum sheets showed minimum fracture toughness as well as minimum work input to overcome the offered resistance.

Analysis of conical tool perforation of ductile metal sheets

The perforation of a ductile metal sheet with a conical tool is accompanied by elasto–plastic bending, stretching, plastic flow and perforation initiation and propagation and ultimately it results in material fracture in the form of petals. The number and size of petals depends on the sheet thickness, material properties, tool angle, anisotropy in the material and indentation speed. In this work the mathematical relations for the fracture mechanism has been developed to analyze different parameters’ response and evaluate fracture toughness of the metal sheets of various thickness using computer code based on this analysis.

Indentation fracture and soft impresser fatigue in sapphire and polycrystalline alumina

The soft impresser technique has many advantages compared with conventional diamond pyramid indentation for studying the deformation and fracture of materials that would normally be considered ‘brittle’. In particular, as utilised in this study, it can be used to study the evolution of deformation and crack initiation and propagation under contact fatigue conditions. Alumina, both in its sintered polycrystalline form and as single crystals (sapphire), has been investigated because of its many uses in engineering load-bearing applications. Intially conical tool steel impressers were used to subject the flat ceramic surfaces to mean pressures of 5.2 ± 2.4 GPa for up to 7.5 × 10 6 cycles. Plastic deformation in the polycrystalline alumina was observed after only 10 3 loadings, followed by cracking at the edge of the contact zone and subsequent crack interlinking and radial extension. The sapphire showed no signs of deformation or cracking under these conditions, but did deform and crack after only one cycle when a harder WC/Co impresser was used.

Cooling Characteristics of Cutting Grain in Grinding

The temperature of a cutting grain when cutting has been completed is investigated experimentally and theoretically. As the model of the cutting grain, a conical tool of ceramic is used. The temperature of the grain at various times after cutting is measured using an infrared radiation pyrometer with an optical fiber. The cooling process of the cutting grain during air cutting is analyzed by reference to unsteady-state heat transfer theory. The cooling of the grain is extremely rapid, that is, the temperature of the grain decreases to one fourth of the maximum temperature in 1 ms after cutting. The maximum temperature of the cutting grain reached at the end of cutting is estimated to be the melting point of the work material.

Thermal Behaviour of Cutting Grain in Grinding

Temperature at the interface between the cutting grain and a workpiece is measured using a two-color pyrometer with a fused fiber coupler. For the cutting grain, a conical tool of translucent alumina is used. The infrared rays radiated from the interface and transmitted through the conical tool are accepted by a fused fiber coupler and led to two infrared detectors of different spectral sensitivity. The temperature increases rapidly and reaches a saturated value after a short time (about 0.1 ms). The saturated temperature measured increases with the increase in the cutting speed up to the melting point of the work material.

微小切削における切りくず生成温度(第1報)

A temperature at the tip of a conical cutting tool is measured immediately after micro chip forming using an infrared radiation pyrometer with an optical fiber. The fundamental structure of this pyrometer is that the infrared flux radiated from the tip of the conical cutting tool after cutting is accepted and transmitted to an infrared detector InSb by an optical fiber. The measurement accurancy when applying the pyrometer to the experiment is investigated theoretically. The temperature at the tip of the conical tool at various cooling times after cutting is measured using this pyrometer. A carbon steel and a tungsten are used as workpieces. A cooling characteristic of the tool is analyzed by heat transfer theory. Applying the theoretical results to the experimental results, the temperature of the tip of the conical tool just after cutting is estimated to be 1500°C for carbon steel and 2400°C for tungsten; 1500°C is almost equal to the melting point of carbon steel.

Improving Method of Flaring Limit of Thin Walled Circular Tubes by Orbital Rotary Forming with a Cylindrical Tool.

Orbital rotary flaring of thin walled copper tubes with a cylindrical tool has been experimentally investigated to improve the flaring limit of the tubes. The results are summarized as follows: (1) Flaring limits were determined by the onset of necking and two kind of bucklings. (2) The flaring limit of hard tube is higher than that of both press forming and orbital rotary forming with a conical tool. Heigher flaring limit is obtainable with a cylindrical tool having smaller diameters and higher feed speeds. (3) A modified inclination method is introduced to prevent the necking and the buckling at tool inlet. Then, it is found that the buckling and necking modes are prevented under the proposed preventing condition.

Scraping with conical tools—a brief review

A study of the mechanics of the scraping action of conical tools is applicable to grinding or abrasive theories and the frictional contact of mating surfaces. The mechanics of wedge indentation in the simulation of conical tools are carefully reviewed. Adhesion, friction forces and stress conditions during the sliding of conical tools are discussed. Material flow, ridge formation and surface changes caused by scraping with conical tools are outlined.

Principles of soil-tool interaction

The paper analyses the process of borehole forming in soil through penetration by a conical tool under periodically repeated load impulses. Tests were carried out in the laboratory and in the field, on disturbed and undisturbed soil respectively, under quasi-static and dynamic loading. These tests yielded relationships between the frontal resistance force of the soil and the toll displacement, and also between the cone resistance on the one hand and the cross-sectional area of the tool and its velocity of penetration on the other. It was found that as the frontal resistance force increases in the loading stage, both recoverable and nonrecoverable deformations are produced; moreover, the tool displacement in the loading stage considerably exceeds its counterpart in the unloading stage, as the restoring force of the soil decreases. Results indicate that the variation pattern of the frontal resistance force is practically unaffected by the cyclic character of the process, and that the soils studied fall under the category of cyclically ideal materials. Analysis and generalization of the results of the present study, and of others, yielded a set of mechanical characteristics representing the actual properties of the soil. These characteristics in turn yielded a piecewise-linear relationship between the frontal resistance force and the tool displacement—an approximation which can serve as a basis for minimization of the energy consumption of the cyclic borehole forming process, and eventually for mathematical description of the soil-tool interaction in general.

切りくず生成機構に及ぼす切削速度の影響

In order to clarify the effect of the cutting velocity magnified up to a actual range and a simulated tool in the shape of square pyramid on the mechanism of chip formation in a single grit grinding was practiced. Cutting action was arrested by a quick-stop device. The behavior of material in front of tool face during cutting was observed minutely on the cross-section along the cutting direction of a groove. In addition, these present results were compared with previous ones used a single grit simulated conical tool. A stagnating region beneath the tool face was found, it served as a kind of tool, and was apt to form the chip. It was clear that the stagnating region formed by a simulated square pyramid tool was more extensive than that made by a simulated conical tool.

Deformation work in abrasive cutting

In order to investigate the complicated behavior of material beneath the groove formed by abrasive grain cutting, and single grit cutting test was performed with a modified cutting tool which was determined statistically. In the experiment a conical tool having an apex angle of 90° –160° was used. To observe the deformed zone beneath the groove, the cross section of the work material beneath the groove was obtained by using a micro-cutter. Then the hardness of the deformed zone was measured in three directions, i.e. at the surface, at the cross section along the cutting direction and at the cross section perpendicular to the cutting direction. Besides, a compression test was performed and taking the relations between stress-strain and strain-hardness into consideration, the deformation work beneath the groove was obtained. Then the deformation work was compared with the total work necessary to form a groove which was calculated from cutting force. As a result it was found that there were two types of deformed zone, i.e. cutting type and compression type as well as in the case of indentation test. The ratio of deformation work to the total work expended in forming a groove with conical tool depends on the apex angle of the tool and the ratio reaches 0.2–0.7 in this experiment.