Patent ID: 12194519

Reference Signs:1—Die body;11—Die cavity;12—Working belt structure;2—Die cavity geometry;21—Medial axis of symmetrical extrusion die;22—Left contour line of symmetrical extrusion die;23—Right contour line of symmetrical extrusion die;24—Medial axis of the unequal-channel angular self-bending extrusion die;25—Left contour line of the unequal-channel angular self-bending extrusion die;26—Right contour line of the unequal-channel angular self-bending extrusion die;31—Extruded bent profile.

DETAILED DESCRIPTION OF EMBODIMENTS

The technical solutions of the present disclosure will be described below clearly and completely in connection with examples. It is apparent that the examples to be described are some, but not all of the examples of the present disclosure. All the other examples obtained by those of ordinary skill in the art in light of the examples of the present disclosure without inventive efforts will fall within the scope of the present disclosure as claimed.

It should be noted that this embodiment combines a forming process of the profile, in which extrusion and bending is integrated, with a streamlined extrusion die, and proposes a new process of unequal-channel angular self-bending extrusion forming, enabling metal to flow unevenly in the die cavity, so as to directly extrude the bent profile, in a manner of designing a streamlined extrusion die structure with a twisted medial axis.

As shown inFIGS.1to3, the method for designing an unequal-channel angular self-bending extrusion die provided by this embodiment comprises the following steps: designing a symmetrical streamlined extrusion die based on sine function, wherein the wall surfaces of two sides of the die cavity11of the extrusion die are symmetrical streamlined; making the medial axis of the die cavity11of the symmetrical streamlined extrusion die twisted and deformed in a certain plane, to form an arched curve, wherein the arched curve remains symmetrical along the extrusion direction, and has no offset at both ends of the curve and is tangent to the axis; establishing a die cavity11wall surface equation of the unequal-channel angular self-bending extrusion die according to the medial axis of the arched curve; and setting a working belt structure12downstream the die cavity11of the unequal-channel angular self-bending extrusion die, with the wall surface of the working belt structure12parallel to the extrusion direction.

The method for designing an unequal-channel angular self-bending extrusion die provided by this embodiment comprises the following steps: designing a symmetrical streamlined extrusion die based on sine function, wherein the wall surfaces of two sides of the die cavity11of the extrusion die are symmetrical streamlined; making the medial axis of the die cavity11of the symmetrical streamlined extrusion die twisted and deformed in a certain plane, to form an arched curve, wherein the arched curve remains symmetrical along the extrusion direction, and has no offset at both ends of the curve and is tangent to the axis; establishing a die cavity11wall surface equation of the unequal-channel angular self-bending extrusion die according to the medial axis of the arched curve; setting a working belt structure12downstream the die cavity11of the unequal-channel angular self-bending extrusion die, with the wall surface of the working belt structure12parallel to the extrusion direction; designing and forming an unequal-channel angular self-bending extrusion die, wherein after the metal flow passes through the unequal-channel angular self-bending extrusion die, the die cavity11of the unequal-channel angular self-bending extrusion die is used to control the extrusion speed to be linearly distributed, so as to directly form bent parts by extrusion, as a result of which the profile is not subject to lateral moment, thereby cross-sectional deformation is reduced or prevented on the outer side surface of the profile, and the flow of the metal during the extrusion process is smoother than that of the conventional stepped extrusion die, and the extrusion load is reduced, alleviating the technical problems of springback, wrinkling and cross-sectional deformation during bending process of the profile in the prior art, and reducing the load during extrusion.

The specific design steps as shown inFIG.2: in a preferred embodiment of the present disclosure, the designing a symmetrical streamlined extrusion die based on a sine function also comprises: remaining the shape of die cavity11of the extrusion die to be circular along any horizontal section. The boundary curve of the die cavity11of the extrusion die is described by a sine function, with the center of the medial axis21of the symmetric extrusion die as the origin and the z direction as the extrusion direction, wherein the function of the left contour line22of the symmetric extrusion die is:

Line_left=(R-r2)⁢sin⁡(πL·z)⁢R+r2

The function of the right contour line23of the symmetrical extrusion die is:

Line_right=-(R-r2)⁢sin⁡(πL·z)+R+r2where R is the diameter of the inlet die hole, that is, the diameter of the blank; r is the diameter of the outlet die hole, that is, the diameter of the bar, and L is the height of the die cavity11.

In a preferred embodiment of the present disclosure, the making the medial axis of the die cavity11of the symmetrical streamlined extrusion die twisted and deformed in a certain plane further comprises: the Axis_trig of the twisted medial axis Axis is described as follows based on the trigonometric function:

Axis_trig=h2⁢cos⁡(2⁢πL·z)+h2where h is the maximum offset distance of the twisted and deformed medial axis curve;

In a preferred embodiment of the present disclosure, the making the medial axis of the die cavity11of the symmetrical streamlined extrusion die twisted and deformed in a certain plane further comprises:the Axis_gauss of the twisted medial axis Axis is described as follows based on the Gauss-like distribution function:
Axis_gauss0=Aexp(−B·z2)where A, B are undetermined coefficients;wherein the twisted medial axis is the medial axis24of unequal-channel angular self-bending extrusion die.

In a preferred embodiment of the present disclosure, it further comprises a step of:correcting Axis_gauss0 by mathematical transformation, including first calculating the value of Axis_gauss0 at the end point, which is Axis_gauss0 (L/2), wherein the coefficient A is set as h+Axis_gauss0 (L/2), so as to enlarge the curve height by Axis_gauss (L/2) times and then subtracting Axis_gauss0 (L/2) to obtain the corrected medial axis Axis_gauss based on the Gaussian-like distribution function. The equation is described as:
Axis_gauss=(h+Axis_gauss0(L/2))exp(B·z2)−Axis_gauss0(L/2)where the value of the coefficient B is an empirical value, when the value of B is 0.01, the distance from the end point of the curve to the original axis can be controlled within 0.01 mm.

In a preferred embodiment of the present disclosure, the establishing the die cavity11wall surface equation of the unequal-channel angular self-bending extrusion die comprises a step of:describing the wall surface of die cavity11as the curved surface equation of:

(x-Axis)2+y2=(R-r2⁢sin⁡(πL·z)-R+r2)2where Axis is Axis_trig or Axis_gauss, respectively.

As shown inFIG.2, in this embodiment, the steps of the above design method are further explained by using specific values: the designed die is to produce a curved bar with a diameter of D=8 mm, so the radius of the curved bar is r=4 mm, and the original blank is selected as D=40 mm in diameter, so the radius of the original blank is R=20 mm, and the die height is set as L=40 mm based on requirements. According to the designed die cavity geometry2, the boundary curve of the symmetrical streamlined die cavity11is described by a sine function, wherein the origin is the center of the medial axis21of the symmetrical extrusion die, and the z direction is set as the extrusion direction, whereby the function Line_left of the left contour line22of the symmetrical extrusion die is described as:

Lineleft=(2⁢0-42)⁢sin⁡(π4⁢0·z)-2⁢0+42the function Line_right of the right contour line23of the symmetrical extrusion die is described as:

Line_right=-(20-42)⁢sin⁡(π40·z)+20+42where the wall surface equation of the symmetrical streamlined die cavity11is described as:

x2+y2=(2⁢0-42⁢sin⁡(π4⁢0·z)-2⁢0+42)2where the maximum offset height of the medial axis24of the unequal-channel angular self-bending extrusion die is h=10 mm, and the Axis_trig of the medial axis24of the unequal-channel angular self-bending extrusion die is described by trigonometric function as:

Axis_trig=102⁢cos⁡(2⁢π40·z)+102

Another description of Axis_gauss of the medial axis24of the unequal-channel angular self-bending extrusion die based on the Gauss-like distribution function is:
Axis_gauss=(10+0.1832)exp(0.01·z2)−0.1832

After the equation Axis of the medial axis24of the unequal-channel angular self-bending extrusion die is determined, that is, after the medial axis of the symmetrical streamlined die cavity11is twisted and deformed, the other parameters of the die cavity11structure are translated accordingly, that is, the shape of the cavity before the deformation remains circular along a certain horizontal section. After deformation, on a plane perpendicular to the extrusion direction, the distance between each of the points on the wall surface of the die cavity11and the medial axis24of the unequal-channel angular self-bending extrusion die is equal, that is, the section of die cavity11is circular, while the position of the center of the circle is different from the original one, which can determine the curved surface equation of the unequal-channel angular die cavity11wall surface formed by the left contour line25of the unequal-channel angular self-bending extrusion die and the right contour line26of the unequal-channel angular self-bending extrusion die, according to the structure principle of the unequal-channel angular self-bending extrusion die, wherein the curved surface equation formulated by Axis_trig of the unequal-channel angular die cavity11wall surface of the medial axis24of the unequal-channel angular self-bending extrusion die is:

(x-1⁢02⁢cos⁡(2⁢π4⁢0·z)-1⁢02)2+y2=(2⁢0-42⁢sin⁡(π4⁢0·z)-2⁢0+42)2wherein the curved surface equation formulated by Axis_gauss of the unequal-channel angular die cavity11wall surface of the medial axis24of the unequal-channel angular self-bending extrusion die is:

(x-(1⁢0+0.1⁢8⁢3⁢2)⁢exp⁡(0⁢.01·z2)+0.1⁢8⁢3⁢2)2+y2=(2⁢0-42⁢sin⁡(π4⁢0·z)-2⁢0+42)2

Furthermore, upon determination of the unequal-channel angular extrusion die cavity11, a working belt structure12with certain length is set additionally downstream it. The length of the working belt structure12may be selected as t=6 mm. The wall surface of the working belt structure12is parallel to the extrusion direction.

This embodiment provides a method for manufacturing an unequal-channel angular self-bending extrusion die, which is manufactured based on the method for designing the unequal-channel angular self-bending extrusion die; and this embodiment, based on the designing method aforementioned, is manufactured mechanically using the curved surface equation of the unequal-channel angular die cavity11wall surface, thereby an unequal-channel angular self-bending extrusion die can be manufactured.

The present embodiment provides an unequal-channel angular self-bending extrusion die, which is manufactured by the method for manufacturing the unequal-channel angular self-bending extrusion die, comprising: a die body1;wherein the die body1comprises the die cavity11and the working belt structure12, the die cavity11has a self-bending outlet and the working belt structure12extends along the self-bending outlet of the die cavity11, and the working belt structure12is integrally connected with the die cavity11; and the wall surface of the die cavity11is a curved surface equation of:

(x-axis)2+y2=(R-r2⁢sin⁡(πL·z)-R+r2)2where R is the diameter of the inlet die hole of the die cavity11, that is, the diameter of the blank; r is the diameter of the outlet die hole of the die cavity11, that is, the diameter of the bar; L is the height of the die cavity11, and Axis is the equation of the medial axis of the die cavity11.

In the preferred embodiment of the present disclosure, the medial axis equation of the die cavity11is described as follows based on trigonometric function:

Axis_trig=h2⁢cos⁡(2⁢πL·z)+h2where h is the maximum offset distance of the twisted and deformed medial axis curve;or the medial axis equation of the die cavity11is described based on the Gaussian-like distribution function as,
Axis_gauss=(h+Axis_gauss0(L/2))exp(B·z2)−Axis_gauss0(L/2)where the value of the coefficient B is an empirical value, when the value of B is 0.01, the distance from the end point of the curve to the original axis can be controlled within 0.01 mm;where Axis is Axis_trig or Axis_gauss, respectively.

In this embodiment, adding the working belt structure12can extend the deformation coordination of metal, reduce the difference in metal flow speed in the channel of the working belt structure12, and reduce the uneven level of the extrusion speed, hence reducing the degree of bending. Therefore, adding the working belt structure12can be used to design the extrusion of profiles with different bending curvatures.

This embodiment provides an extrusion method based on the unequal-channel angular self-bending extrusion die, which comprises the following steps: placing metal in the die cavity11of the die body1; controlling the speed of extruding the metal at the inlet of the die cavity11; based on the self-bending outlet of the die cavity11and the working belt structure12, extruding metal to form a bent profile with a preset curvature, thereby forming an extruded bent profile31.

In this embodiment, the process parameters of the extrusion method comprise: the material of the blank is AA6063 aluminum alloy, the extrusion ratio λ=25, the extrusion speed v=10 mm/s, the preheating temperature of the blank is 450° C., and the preheating temperature of the extrusion barrel is 470° C., the preheating temperature of the extrusion die is 480° C.; the shear friction model is applied between the blank and the die, with the friction factor being set to 0.7, and the Coulomb friction model is applied between the blank and the working belt, with the friction factor being set to 0.3; according to symmetry, simulation is performed on ½ of the entire model, and all components are divided into tetrahedral elements, the mesh number of blank is 30,000, and the displacement step size is 0.2 mm.

As shown inFIG.3, a mesh diagram for the simulation result of the deformed body when numerical calculation is performed on the extruded bent profile31which is formed by the unequal-channel angular self-bending extrusion die of the embodiment of the present disclosure is shown. During the extrusion process, the metal flow rate at the outlet of the die cavity11is linearly distributed. When the profile is extruded, it will naturally bend to the side with slower flow rate, to allow for the natural bending and forming of bar profile of aluminum alloy, thereby one-time extruding high-quality products with a certain curvature while the extrusion load is lower than that of conventional dies.

As shown inFIG.3, in addition, when metal enters the die, the strain is always greater toward the left on the same horizontal line, that is, the strain of the metal on the convex edge of the die (left side) is greater than that on the concave side of the die (right side). The strain reaches the maximum at the outlet of the die, therefore the deformation on the left is always greater than that on the right. Due to the deformation coordination of metal, the extruded profile bends to the right.

It should be noted that the “left”, “right” and “z direction” mentioned in the present disclosure all relate to the position of the unequal-channel angular self-bending extrusion die when it is working, which is only intended for a smooth description, and shall not impose limitations on the present disclosure.

Finally, it should be noted that the above embodiments are merely intended to illustrate the technical solutions of the present disclosure, but not intended to limit the present disclosure. Although the present disclosure has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that the technical solutions disclosed in the foregoing embodiments may still be modified, or some or all of the technical features therein may be replaced with equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present disclosure.