Conical Die Research Articles

1303 円筒の反転塑性変形を利用したエレベータ用緩衝器の実用化の検討(安全・安心・セキュリティ・防災,OS5 安全・安心・セキュリティ・防災)

The final goal of this study is to apply the mechanism of inversion plastic deformation of an aluminum tube to the buffer for an elevator instead of an oil-buffer. In this paper, first, an annealed aluminum tube compressed on a conical die is shown to cause stable inversion plastic deformation under some experimental condition which has an ideal load-displacement curve as a shock absorber for various kinds of elevators. Secondly, two kinds of deformations, namely progressive buckling and Euler buckling however, appear under the other conditions. It is explained that the boundary between progressive buckling and Euler buckling is depended on the slenderness ratio. Finally, the relation map among three deformation modes is clarified and the limit of inversion plastic deformation is explored.

Wrinkling behaviour of different grades of annealed commercially pure aluminium sheets when drawing through a conical die

This paper deals with the deep drawing of circular blanks of three different grades of annealed, commercially pure aluminium sheets of different grades, namely ISS 19000, ISS 19600 and ISS 19660, having a thickness of 2.00 mm, into cylindrical cups through Conical die using a flat bottomed punch. It is well established that the use of a Conical die can enhance the limiting draw ratio compared with that obtainable in a conventional drawing operation. When a Conical die is employed, the need for a hold down or clamping ring is eliminated. However, this enhances the propensity of the blank to fail by wrinkling or buckling, particularly in the early stages of a drawing process in which thin sheet blanks are used. For the present work, annealed aluminium sheets of different diameters are drawn through a conical die under dry lubrication condition, until the appearance of a first stage wrinkle. Here, an attempt is made to relate the percentage amount of draw obtainable in the drawing process with the initial diameter of the blank. It is also shown that the onset of wrinkling takes place when the percentage change in thickness reaches a critical value, this value being found to be generally different for both air cooled and furnace cooled aluminium sheets.

Free deformation mechanism and change of forming mode in tube inversion under conical die

Free deformation and the change in forming mode have an important effect on the realization of tube inversion with a conical die, particularly on the size and degree of precision of the formed part. Based on a mechanical model, the mechanism of free deformation and characteristic behavior of forming mode are investigated by an FE system combined with analytical analysis, which permits the condition to realize change in forming mode and inversion to be determined. The results show that for the given tube blank there exists a critical die conical angle αcr, above which the tube will curl to form a double-walled tube; αcr is determined mainly by the tube material parameters, while the geometric parameters have very little effect; the larger the material hardening exponent the smaller the αcr value.

Constitutive model development and hot extrusion simulation for AZ61 magnesium alloy

Compression tests for the AZ61 magnesium alloy have been carried out at temperatures ranging from 200 to 400°C and with different strain rates from 10−3 to 5 s−1. The flow stress–strain curves show that the flow stress reaches a peak value and then decreases to a steady value. This steady value decreases with rising temperature and decreasing strain rate. A new constitutive model is developed to describe flow stress as a function of temperature T, strain rate ϵ, strain ϵ, and strain softening coefficient which is introduced into the simulation (final element method) of hot bar extrusion. The simulation results show that stress is relatively high around the entrance of the conical die, while the highest temperature and the largest strain appear near the exit of conical die. By comparing the simulation and experiment result, successful extrusion temperature and speed are 300°C and 10 mm s−1 respectively.

The effect of strain hardening in the extrusion of bimetallic tubes of porous internal layer

The effect of strain-hardening features of porous materials treated by cold extrusion through a conical die is studied theoretically in the present paper. The theoretical model developed by using the fundamentals of the Plasticity Theory of Real Porous Materials investigates all technological parameters affected in the case of extruding bimetallic tubes with a porous internal layer. Comparative analysis between strain-hardened and ideally plastic materials used in the fabrication of bimetallic tubular components, as far as their effect on various technological extrusion parameters is concerned, such as variation of porosity, applied load, level of total deformation, etc., has been conducted successfully, providing, in this manner, with useful concluding remarks from engineering point of view.

2225 非軸対称ダイスを用いた円管の口絞り加工(S31-1 最新のチューブフォーミングとその動向(1),S31 最新のチューブフォーミングとその動向)

2225 非軸対称ダイスを用いた円管の口絞り加工(S31-1 最新のチューブフォーミングとその動向(1),S31 最新のチューブフォーミングとその動向)

Estimation of Entry Pressure Drop during Conical Die Flow of Carbon Black-Filled Rubber Compound

The flow behavior of polymer melts in a conical die extrusion was discussed in the present paper. On the basis of simplified suppositions, a mathematical model for estimation of entry pressure drop was established by using a tensor analysis method. The rheological properties of rubber compound, such as flow curves, viscosity, entry pressure drop, and extrudate swell, were measured by employing a capillary rheometer in a temperature range of 90–130° C and apparent shear rates varied from 50 to 103 s-1. It was found that the shear flow for the sample obeyed the Power law, and the first normal stress difference increased with increasing shear rates at the channel wall as an exponential function. Furthermore, the entry pressure drop during extrusion of the samples was estimated by using this model. The results showed that the predictions of entry pressure drop were basically consistent with the measured data from the experiments of the sample.

The Direct Extrusion of Copper Clad Aluminum Composite Materials by Using the Conical Dies

This paper describes experimental investigations in the direct extrusion of copper clad aluminum rods through conical dies. Composite materials consist of two or more different material layers. Copper clad aluminum composite materials are being used fur economic and structural purposes and the development of an efficient production method of copper clad aluminum composite material rods by extrusion is very important, It is necessary to know the conditions in which successful uniform extrusion ,and sound cladding may be carried out without any defects in the direct extrusion. There are several variables that have an influence on determining a sound clad extrusion. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios and semi-cone angles of die. Subsequently, the microscopic inspection of interface bonding is carried out for extruded products. By measuring hardness, along extrusion way of products, a variation of hardness has been discussed. Proportional flow state has been considered by measuring radius ratio of Cu sleeve and Al core before and after extrusion.

PREDICTIONGS ON WRINKLING STRENGTH AND LIMITING DRAWING RATION FOR CUP DEEP-DRAWING WITHOUT BOLANKHOLDER THROUGH A CONICAL DIE

PREDICTIONGS ON WRINKLING STRENGTH AND LIMITING DRAWING RATION FOR CUP DEEP-DRAWING WITHOUT BOLANKHOLDER THROUGH A CONICAL DIE

The curling characteristics of static inside-out inversion of metal tubes

The curling behavior of quasi-static inside-out inversion of tubes was analyzed using an energy method technique based on the critical condition for more precise design. (1) The first part is to derive the critical bending radius ρ ̄ c as a curling criterion to distinguish between curling and flaring on a conical die, in which the strain hardening exponent n and half-apex angle of die α have very marked effects on ρ ̄ c theoretically; however, the friction coefficient μ-dependence is not as great as the n. As a result, a much more satisfactory correlation between prediction and experiment is obtained and Kitazawa's study is a special case of this work. (2) The second part is to theoretically find the range of semicircular curling ( ρ ̄ min o < ρ ̄ o < ρ ̄ max o ) and the compressing load P of inversion in tube inversion with a quarter circle die. It appears that the material properties of the aluminum tubes used have little effect on the curling behavior of inversion. It is noted that factors μ and n obviously affect the position of semicircular curling of inversion but not its range size. On the other hand, n in contrast to μ affects significantly the compressing load. Good agreement between the theoretical prediction and experimental results is obtained for the compressing load, except in the case of the sharp fillet die radius for the strictly bending effect to be ignored in the prediction.

Measuring the development of fibre orientation during the melt extrusion of short glass fibre reinforced polypropylene

Abstract In this paper we describe an investigation into the development of fibre orientation during melt extrusion through two convergent dies: a conical die and a slit die. The material used was a short glass fibre (aspect ratio = 24) reinforced polypropylene at two fibre weight fractions, 20% and 30%. The development of fibre orientation through the two convergent zones was measured in detail using sophisticated image analysis facilities developed in-house. It was found that the ‘pseudo-affine’ deformation model predicted the development of fibre orientation very well for both die configurations, in terms of the applied macroscopic elongational strains. The addition of a breaker plate placed in the barrel of the extruder, between the extruder screw and the convergent flow zones, was shown to produce the highest degree of fibre alignment in the extrudates, by introducing additional pre-orientation of the fibres. Mechanical measurements on the extrudates showed that for the very high degrees of fibre alignment attained, the bending modulus in the extrusion direction reached 90% of the theoretical maximum for the fibre aspect ratio used, and the crack resistance parallel to the preferred fibre direction remained high.

Upper-bound and finite-element analysis of axisymmetric hot extrusion

In hot extrusion, knowledge of the temperature distribution and the extrusion power is very important for the determination of the optimal process conditions. In this paper, the combined upper-bound method and finite-element method (FEM) for the optimal design of axisymmetric dies is presented. The billet material during plastic deformation process is modelled as a visco-plastic rate-sensitive material. The material flow stress is considered to be strain-rate and temperature dependent. In the upper-bound analysis, a stream-function form which produces a kinematically admissible velocity field is assumed. The Galerkin FEM is used to solve the axisymmetric heat-conduction equation with convective terms to obtain the temperature distribution in the deformation zone. The combined upper bound method/FEM is applied to analyse four different die shapes, namely, stream-lined, cosine, hyperbolic and conical. From the study it is observed that the optimal die length decreases with friction factor and increases with reduction ratio and ram velocity. The extrusion power required is lowest for the stream-lined die with cosine die following closely behind. The hyperbolic die is, however, better than the conical die at lower reduction ratios, whilst the conical die is superior at greater reduction ratios.

Mathematical model of the solid-phase extrusion of polymeric composite materials

A mathematical model of the deformation of a structurally inhomogeneous material in a conical die is developed. The model accounts for the possibility of the material's compaction and loosening during extrusion. It is demonstrated that both a monotonic decrease, and extremal variation in microporosity are possible with increasing degree of drawing, depending on the character of the composite and deforming tool. Computed results are compared with experimental data obtained for superhigh-molecular polyethylene-based composites filled by polymerization. Good correspondence is established between theory and experiment.

Comparison of extrusion strains produced by cosine and conical dies

Visioplastic analysis is used to compare strain fields produced in cylindrical aluminum billets extruded at elevated temperature through axially symmetric dies that have either a cosine or a conical profile. The visioplastic method consists of computing strain rates from changes experienced in a flow function as a billet passes through the extrusion die. The flow function is constructed using a grid that is stamped on an axial plane of the billet before extrusion. After the partially extruded billet is removed from the die numerical methods are used to determine the strain rates from the deformed grid. The state of strain over the extrusion region is computed using transformation and then integration of the strain rates. Results show that, unlike the conical die, the cosine die does not produce strains of reversed sign in the die entry region. The consequent benefits of using cosine dies for extrusion of powder metals are discussed.

Wrinkling of sheet metals when drawing through a conical die

This paper deals with the deep drawing of circular blanks into cylindrical cups through a conical die using flat-bottomed and hemispherical-ended punches. It is well established that the use of a conical die can enhance the limiting drawing ratio compared with that obtainable in a conventional drawing operation. When a conical die is employed, the need for a hold-down or clamping ring is eliminated. However, this enhances the propensity of the blank to fail by wrinkling or buckling, particularly in the early stages of a drawing process in which thin sheet blanks are used. An attempt is made to rank the properties that appear to suppress wrinkling. The wrinkling modes that develop during the different stages of drawing are identified. It is shown also that the onset of wrinkling takes place when the ratio of the plastic strain increment ( dϵ r/ dϵ θ ) reaches a critical value. This value, which is determined experimentally, compares favourably with the results of theoretical analysis.

Development of a New Burr-Free Shearing Process Utilizing Necking Deformation.

Removal of burrs is necessary because they cause several problems during service. However, neither deburring processes nor existing burr-free shearing processes have been applied succesfully to thin sheet metals. In order to solve this problem, a new burr-free shearing method is proposed. It is based on the idea that the burr-side edge will roll over by necking deformation when the partially sheared material is pulled apart. This paper describes realization of this principle and its application to thin steel sheets. Three methods were attempted for 0.2-mm-thick alminium sheets and 0.14-mm-thick steel sheets. Deformation behavior, application range, and quality of the sheared edge were investigated. As a result, it was found that the method utilizing stretching by a conical die is the most desirable one for practical use.

The effect of work-hardening on deep-drawing through a conical die

An experimental study of the deep-drawing of ten sheet metals through a conical die is described. This is an important process in its own right and also as thefirst stage of a drawing and multiple ironing process. It is shown that the optimum die angle depends on whether the drawing process fails by fracture or by flange wrinkling. If the mode of failure is fracture then a high R-value is beneficial; if the mode of failure is flange wrinkling then the most important variable is the n-value. In the latter case a semi-empirical approach is adopted to demonstrate the relationships between blank diameter, punch diameter, punch profile-radius, sheet thickness and n-value.

Nosing of thin-walled tubes by circular curved dies

Experiments into the nosing of thin-walled aluminum tubes have been carried out in order to clarify the characteristics of nosing by a circular curved die. Comparing the results with those for a conical die, the advantages of a circular curved die are discussed in detail. It is established that a circular curved die is effective in reducing the nosing load, restraining unfavourable deformation, and improving the nosing limit for tubular materials, which buckle at the cylindrical part in conical nosing. It is suggested that it is of advantage to introduce a circular curved part into the inlet of a conical die. Further to the above, numerical analysis is performed on the optimum die radius and die contact pressure, upon which the effect of the die profile is examined.

Erratum: “The Study of Distorted Grid Patterns for Flow-Through Conical Converging Dies by the Multi-triangular Velocity Field” (Journal of Engineering for Industry, 1984, 106, pp. 150–160), “Tool Fracture Probability Under Steady State Cutting Conditions” (Journal of Engineering for Industry, 1984, 106, pp. 161–167), “Tool Fracture Probability of Cutting Tools Under Different Exiting Conditions” (Journal of Engineering for Industry, 1984, 106,

Erratum: “The Study of Distorted Grid Patterns for Flow-Through Conical Converging Dies by the Multi-triangular Velocity Field” (Journal of Engineering for Industry, 1984, 106, pp. 150–160), “Tool Fracture Probability Under Steady State Cutting Conditions” (Journal of Engineering for Industry, 1984, 106, pp. 161–167), “Tool Fracture Probability of Cutting Tools Under Different Exiting Conditions” (Journal of Engineering for Industry, 1984, 106,

The Study of Distorted Grid Patterns for Flow-Through Conical Converging Dies by the Multi-triangular Velocity Field

A variety of velocity fields may be used to analyze the intermediate and final distorted grids for the so-called “flow-through” metal forming processes such as wire drawing, rolling, extrusion, etc. In this paper the triangular velocity field describes the flow of homogeneous, perfectly plastic Mises’ material through a conical converging die. The traditional triangular velocity field was treated and the solution extended. The shape of the distorted grids was uniquely determined by the minimization of the power (drawing or extrusion stresses) required to cause its distortion for a given set of independent process parameters, i.e., process geometry-reduction in area and semi-cone angle, and friction. Actual power (forming stress requirements) was estimated by the upper-bound technique. For the unitriangular velocity field, the power was minimized with respect to the shape of the workpiece (the shape of the triangle). For the multitriangular velocity field, the power was minimized with respect to the shape and the number of triangles. Further, the number of triangles was treated as a real number. Thus, the accurate lower upper-bound was found and the reasonable solution in predicting real distortion grid patterns was then obtained. The analysis determines the severity of the distortion as a function of process geometry and friction.