CN104438538B - Three-dimensional curved surface stretch forming method based on surface-changing discrete mould - Google Patents

Abstract

The invention provides a three-dimensional curved surface stretch forming method based on a surface-changing discrete mould, and belongs to the field of metal plastic machining. Nonuniform deformation of a plate in the stretch forming process is the main cause of kinds of defects. According to the method, based on the discrete mould, the forming process of a curved surface is controlled through the change of the mould surface. In the forming process, the plate is kept completely attached to the mould surface all the time, the continuous and uniform change of the mould surface makes the deformation of the plate more and more uniform, the forming defects are avoided, and a high-quality curved-surface part can be obtained through stretch forming. The discrete mould is composed of regularly-arrayed basic body units, and real-time control over the geometrical shape of the surface of the stretch forming mould is achieved by changing the height of the basic body units. Besides, in the stretch forming process, the plate is clamped by a clamp to rotate along with the change of the mould surface, the clamp does not need to move in the horizontal direction or height direction, and therefore a loading structure of stretch forming equipment can be simplified through the forming method.

Description

Three-dimension curved surface method of stretch forming based on modification face discrete type mould

Technical field

The invention belongs to Metal Forming field, relate to a kind of sheet forming method it is adaptable to large-scale three dimensional curved surface The stretch forming of part.

Background technology

Stretch forming is a kind of important processing mode of large-scale curved part.Tradition is pull-shaped to draw using type face is changeless Shape mould, the geometry of die face designs according to curved surface part to be shaped.In forming process, pull-shaped mould is ambilateral Clamp clamps plate two ends, by the motion of clamp, so that plate is come into contact with mould, and formation of finally fitting with mould completely is bent Surface parts.Using traditional fixed pattern face mould tool pull-shaped to easily cause deformation uneven, cause rupture, wrinkling and skid wire, slightly The defects such as crystalline substance, these problems are especially prominent in the material forming of the deflection controlled range very little such as aluminium alloy, titanium alloy.Separately Outward, traditional pull-shaped also presence patch mould difficult problem, for ensureing patch mould, plate must leave the hanging section of sufficient length, lead to Form larger process residue after shaping.For improving deformation distribution, improving the patch mould state of plate, people are in clamp movement locus Optimization design aspect has carried out many research work, but these problems are difficult to thoroughly solve.

Three-dimension curved surface stretch forming is carried out using modification face mould tool, so that plate is protected with die face all the time in forming process Hold and fit completely, it is possible to achieve deformation homogenization, and can solve the problems, such as that patch mould is bad, it is to avoid defect produces, and improves curved surface zero The stretch forming quality of part.

Content of the invention

The purpose of the present invention is：Easily inhomogeneous deformation occurs for traditional fixed pattern face mould tool is pull-shaped, thus causing into The problem of various defects on shape part, the present invention will provide a kind of three-dimension curved surface stretch forming based on modification face discrete type mould Method, by the forming process of the change Control curve of die face, in forming process, plate is complete with die face all the time Laminating, makes the deformation of plate tend to uniform, thus avoiding various forming defectses to produce, obtains high-quality stretch forming curved surface zero Part.

The above-mentioned purpose of the present invention is achieved through the following technical solutions, and is described with reference to the drawings as follows：

A kind of three-dimension curved surface method of stretch forming based on modification face discrete type mould, with the variable discrete type mould in type face 2 and clamp 3 as forming tool it is characterised in that：The method passes through the curve form of die face 1 with discrete type mould 2 Consecutive variations and clamp 3 profile-followed rotation, make clamp 3 clamp plate 4 keep same with what die face 1 was fitted completely When, gradually stretcher strain, eventually form three-dimension curved surface part 5；

Described discrete type mould 2 is made up of the regularly arranged basic body unit 6 of m row n row.In plate 4 stretch forming Cheng Zhong, the change of die face 1 is changed controlling by the relative altitude of each basic body, and the motion of discrete type mould 2 includes discrete In the lifting of formula mould 2 entirety and discrete type mould 2 between each basic body unit 6 short transverse relative motion；

Described clamp 3 clamps plate 4, during stretch forming, rotates with the tangential variations at die face 1 edge, But the position of occurred level and short transverse is not moved；

The rotation of the motion of described discrete type mould 2 and clamp 3 ensure plate 4 in forming process all the time with die face 1 fits completely, makes deformation tend to uniform, obtains high-quality stretch forming curved surface part 5；

The comprising the following steps that of the control forming process of the method：

A. the primary tape face of discrete type mould 2 is adjusted to plane, and clamp 3 clamps plate 4, the initial plane patch with mould Close；

B. the shape according to profile surface, at the uniform velocity risen based on each basic body unit 6 and clamp 3 uniform rotation principle, Determine in the short transverse displacement w of each basic body of the forming process t and hard-over θ of clamp_maxAnd discrete type mould 2 The displacement d in whole height direction；

C. the whole height direction of the short transverse displacement w according to required basic body unit 6 and discrete type mould 2 Displacement d course over time, controls the up and down motion of discrete type mould 2 and each basic body unit 6, carries out three-dimension curved surface Stretch forming.

Wherein, in step b determine discrete type mould each basic body unit 6 the direction displacement of forming process t z and from The detailed process of the overall z direction displacement of scattered formula mould 2 is：

A. extract the coordinate x at basic body unit 6 center of the i-th row jth row_ijAnd y_ij(i=1,2 ..., m；J=1,2 ..., n；Wherein m is the line number of basic body unit 6, and n is the columns of basic body unit 6)；Determine bent at discrete type mould 2 edges at two ends The maximum tangential tilt in face, i.e. the hard-over θ of clamp_max, and determine the surface parameter equation of three-dimension curved surface part 5：

Wherein x, y are the coordinate of horizontal direction, and z is short transverse coordinate；U, v are the parameter coordinate of three-dimension curved surface part 5；

B. solving equation II, calculates the basic body unit 6 of the i-th row jth row and the parameter of the contact point of three-dimension curved surface part 5 Coordinate u_iAnd v_j

Wherein x (u_i,v_j), y (u_i,v_j) be given by profile surface equation I, r is the Probe-radius of basic body unit (6), h For plate 4 thickness, H is the thickness of cushion 7, n_x(u_i,v_j) and n_y(u_i,v_j) divide for normal direction outside the unit of three-dimension curved surface part 5 Amount, is calculated by following formula

Wherein P (u_i,v_j) be given by profile surface equation (I)；

C. the final height at the end of utilizing the basic body that equation IV calculates the i-th row jth row to shape

Wherein z (u_i,v_j) be given by profile surface equation I, the outer normal component n of unit of curved surface_z(u_i,v_j) by equation III Be given；

D. equation V is utilized to calculate the z direction displacement in t for the basic body unit 6 of the i-th row jth row of discrete type mould 2

Wherein z_minThe basic body unit (6) that calculates for equation (IV) final highly in minima, T is stretch forming The total time needing；

Calculate the global displacement in the z direction in t for the discrete mold 2 using equation VI

Wherein l is the distance of die edge to clamp, θ_maxFor the maximum tangential tilt of both mold ends edge curved surface, that is, The hard-over of clamp.

In the method for the invention, described basic body unit 6 is by cell cube 8, basic body adjusting lever 9 and basic body control Unit 10 processed forms, and described basic body control unit 10 includes adjusting shape motor, decelerator and encoder, the height of basic body unit 6 Degree is by basic body control unit 10 real-time control；Regularly arranged m row n arranges basic body unit and fixes structure by fixed plate with base 11 The variable discrete type mould 2 of forming surface.

Further, using cushion 7 between discrete type mould 2 and plate 4, to avoid going out on the curved surface part shaping Existing impression.

Further, described cushion 7 can adopt polyurethane sheet or rubber slab.

Compared with prior art the invention has the beneficial effects as follows：

Because plate and die face are completely attached to by cushion all the time during curve generating, the change of plate can be made Shape tends to uniform, thus the generation of various forming defectses can be avoided, obtains high-quality curved surface part；Additionally, with existing Pull-shaped technology using fixed pattern face mould tool is compared, and improves patch mould state, can substantially reduce technique clout, material-saving；? Afterwards, during stretch forming, clamp clamping plate rotates with the change of die face, and clamp does not need levelness and height side To motion, thus this manufacturing process can also simplify the loading structure of pull-shaped equipment.

Brief description

Fig. 1 is modification face of the present invention discrete type mould structure schematic diagram；

Fig. 2 is modification face of the present invention discrete type mould Stretch Forming Process schematic diagram；

Fig. 3 is basic body cellular construction schematic diagram；

Fig. 4 is clamp corner, hanging section length and discrete type mould global displacement schematic diagram；

Fig. 5 is t the i-th row jth row basic body cell height direction displacement diagram；

Fig. 6 is the sphere drip molding equivalent strain scattergram pull-shaped using modification face discrete type mould；

Fig. 7 is the sphere drip molding equivalent strain scattergram pull-shaped using traditional fixed pattern face mould tool；

Fig. 8 is the strain contrast that the pull-shaped sphere drip molding pull-shaped with tradition in modification face is distributed along along draw direction axis of symmetry Figure；

Fig. 9 is the strain that the pull-shaped sphere drip molding pull-shaped with tradition in modification face is distributed along along the axis of symmetry of stretched vertically direction Comparison diagram.

In figure：

1. die face, 2. discrete type mould, 3. pulling-in dog, 4. plate, 5. three-dimension curved surface part, 6. basic body unit, 7. cushion, 8. cell cube, 9. basic body adjusting lever, 10. basic body control unit, 11. fixed plates and base.

The whole height direction amount of movement of d- discrete type mould

θ-clamp the anglec of rotation

z_min- basic body unit final highly in minima

L- die edge is to the distance of clamp

z_ijThe final height of the basic body unit of the-the i-th row jth column position

R- basic body unit Probe-radius

Specific embodiment

Further illustrate detailed content and its specific embodiment of the present invention with reference to Figure of description：

As depicted in figs. 1 and 2, the discrete type mould 2 of stretch forming is by 6 groups regularly arranged of the basic body unit of m row n row Become.During the stretch forming of plate 4, the change of die face 1 is changed to control by the relative altitude of each basic body, discrete The motion of formula mould 2 includes the phase in the lifting of discrete type mould 2 entirety and discrete type mould 2 between each basic body unit 6 To motion.

As shown in Figure 2 and Figure 4, clamp 3 clamping plate 4, during stretch forming, tangential with die face 1 edge Change and rotate, but the position of occurred level and short transverse is not moved.

As shown in Figure 2 and Figure 4, ensure plate 4 in forming process by the rotation of the motion of discrete type mould 2 and clamp 3 In fit completely with die face 1 all the time, make deformation tend to uniform, obtain high-quality stretch forming three-dimension curved surface part 5.

As shown in Fig. 2 the control forming process of three-dimension curved surface method of stretch forming based on modification face discrete type mould Comprise the following steps that：

A. the primary tape face of discrete type mould 2 is adjusted to plane, clamp 3 clamps plate 4, first with discrete type mould 2 Beginning plane is fitted, and is set as the initial time of forming process this moment；

B. the shape according to three-dimension curved surface part 5, is at the uniform velocity risen based on each basic body unit 6 and clamp 3 uniform rotation Principle, determines the hard-over θ of the short transverse displacement w in each basic body unit 6 of forming process t and clamp 3_maxAnd The whole height direction displacement d of discrete type mould 2；

C. according to required basic body unit 6 displacement w and discrete type mould 2 whole height direction displacement d in time Change course, controls the motion of discrete type mould 2 and each basic body unit 6, carries out the stretch forming of three-dimension curved surface.

As shown in Figure 4 and Figure 5, determine each basic body unit 6 of discrete mold in the direction displacement of forming process t z and Mould entirety the displacement of z direction detailed process be：

A. determine the coordinate x in x, y direction for each basic body center_ijAnd y_ijI=1,2 ..., m；J=1,2 ..., n；Wherein m Be basic body line number n be basic body columns；Determine the maximum tangential tilt of both mold ends edge curved surface, that is, clamp is Big corner θ_max, and determine the parametric equation of three-dimension curved surface part 5：

Wherein u, v are the parameter coordinate of curved surface.

B. solving equation II, calculates the basic body of the i-th row jth row and the parameter of the contact point of target three-dimension curved surface part 5 Coordinate u_iAnd v_j

Wherein x (u_i,v_j), y (u_i,v_j) be given by profile surface equation I, r is basic body Probe-radius, and h is that plate 4 is thick Degree, H is the thickness of cushion 7, n_x(u_i,v_j) and n_y(u_i,v_j) it is normal component outside the unit of curved surface, calculated by following formula

C. the final height at the end of utilizing the basic body that equation IV calculates the i-th row jth row to shape

Wherein z (u_i,v_j) be given by profile surface equation I, the outer normal component n of unit of curved surface_z(u_i,v_j) by equation III Be given.

D. equation V is utilized to calculate the z direction displacement in t for the basic body of the i-th row jth row of discrete mold 2

Calculate the global displacement in the z direction in t for the discrete mold 2 using equation VI

Wherein z_minThe basic body that calculates for equation IV final highly in minima, T for stretch forming need total when Between, l is the distance of die edge to clamp, θ_maxFor the maximum tangential tilt of both mold ends edge curved surface, the i.e. maximum of clamp Corner.

As shown in figure 3, the basic body unit 6 of discrete type mould 2 is by cell cube 8, basic body adjusting lever 9 and basic body control Unit 10 processed forms, and basic body control unit 10 includes adjusting shape motor, decelerator and encoder, and the height of basic body is by basic Body control unit 10 real-time control.Regularly arranged m row n arranges basic body unit can by the fixing structure forming surface of fixed plate and base 11 The discrete type mould 2 becoming.

As shown in Figure 2 and Figure 4, cushion 7 should be used between discrete mold 2 and plate 4, to avoid in the curved surface shaping On part, impression occurs, and cushion 7 can adopt polyurethane sheet or rubber slab.

Specific embodiment

Plate 4 is 400mm × 240mm, thickness h=1mm；The target surface of three-dimension curved surface part 5 is the ball of radius 360mm Face, it is 250mm × 250mm that discrete type mould 2 shapes area；Discrete type mould 2 is made up of 10 × 10 basic body units 6, base The size of body is 25mm × 25mm, basic body unit 6 Probe-radius r=15mm；Discrete type mould 2 edge to clamp 3 away from From for l=45mm, cushion 7 is the polyurethane sheet of thickness H=30mm.

The concretely comprising the following steps of the control forming process of the three-dimension curved surface method of stretch forming based on modification face discrete type mould：

The first step：The primary tape face of discrete type mould 2 is adjusted to plane, clamp 3 clamping plate 4 is initially put down with mould Fit in face；

Second step：Determine the coordinate x in x, y direction for the center of each basic body unit 6 of discrete type mould 2_ijAnd y_ij：

Determine the maximum tangential tilt of curved surface at discrete type mould 2 edges at two ends, that is, the hard-over of clamp is θ_max= 19.47 °, and determine the parametric equation of profile surface：

Wherein R=360mm is the radius of sphere,With θ for profile surface parameter coordinate (i.e. in equation Iv =θ).

3rd step：According to equation II, by basic body unit 6 and the target profile surface of following equation solution the i-th row jth row The parameter coordinate of contact pointAnd θ_j

Wherein spherical radius R=360mm, the Probe-radius r=15mm of basic body unit 6, sheet thickness h=1mm, elasticity Mat thickness H=30mm,WithThe outer normal component of unit for profile surface；

4th step：According to equation IV, at the end of being shaped by the basic body unit 6 of following Equation for Calculating the i-th row jth row Height eventually

WhereinThe outer normal component of unit for profile surface；

5th step：The basic body unit 6 of the i-th row jth row calculating discrete type mould 2 according to equation V is in the z side of t To displacement

Calculate the global displacement in the z direction in t for the discrete type mould 2 according to equation VI

Wherein z_minFor basic body unit 6 final highly in minima, the total time that T needs for stretch forming, discrete type Mould 2 edge to the maximum tangential tilt of clamp curved surface at l=45mm, discrete type mould 2 edges at two ends, i.e. clamp Hard-over θ_max=19.47 °.

Become using the sphere that the three-dimension curved surface method of stretch forming of modification face discrete type mould is shaped with traditional pull-shaped mode The numerical simulation result of the draw direction stress distribution of shape part is given by Fig. 6, Fig. 7, the strain longitudinally and on lateral symmetry axis Distribution is given by Fig. 8, Fig. 9, and the longitudinal direction of spherical parts is as follows with the maximum of strain, minima contrast on lateral symmetry axis：

Compared with traditional pull-shaped mode, under its plastic strain amplitude of curved surface of modification face discrete type mould pull-shaped method shaping is notable Fall, stress distribution degree of irregularity is greatly improved.Should using the maximum on the pull-shaped method longitudinal axis of modification face discrete type mould Become and have dropped 11.6%, maximum strain and minimum strain difference have dropped 72%；Maximum strain on axis of pitch have dropped 11.6%, minimum strain have dropped 18%.

Claims (6)

1. a kind of three-dimension curved surface method of stretch forming based on modification face discrete type mould, with discrete type mould (2) and clamp (3) As forming tool it is characterised in that：The method passes through the company with discrete type mould (2) for the curve form of die face (1) Continue the profile-followed rotation of change and clamp (3) and change, make the plate (4) that clamp (3) clamps keep complete with die face (1) While full laminating, gradually stretcher strain, eventually form three-dimension curved surface part (5)；

Described discrete type mould (2) is made up of the regularly arranged basic body unit (6) of m row n row, in plate (4) stretch forming During, the change of die face (1) is changed to control by the relative altitude of each basic body, the sports bag of discrete type mould (2) Include in the overall lifting of discrete type mould (2) and discrete type mould (2) the relative of short transverse between each basic body unit (6) Motion；

Described clamp (3) clamping plate (4), during stretch forming, turns with the tangential variations at die face (1) edge Dynamic, but the position of occurred level and short transverse is not moved；

The rotation of the motion of described discrete type mould (2) and clamp (3) ensure plate (4) in forming process all the time with mould type Fitting completely in face (1), makes deformation tend to uniform, obtains high-quality stretch forming curved surface part (5).

2. a kind of three-dimension curved surface method of stretch forming based on modification face discrete type mould as claimed in claim 1, the method Control comprising the following steps that of forming process：

A. the primary tape face of discrete type mould (2) is adjusted to plane, clamp (3) clamping plate (4), the initial plane patch with mould Close；

B. the shape according to profile surface, at the uniform velocity risen based on each basic body unit (6) and clamp (3) uniform rotation principle, Determine in the short transverse displacement w of each basic body of the forming process t and hard-over θ of clamp_maxAnd discrete type mould (2) the displacement d in whole height direction；

C. the position in the short transverse displacement w according to required basic body unit (6) and discrete type mould (2) whole height direction Move d course over time, control the up and down motion of discrete type mould (2) and each basic body unit (6), carry out three-dimension curved surface Stretch forming.

3. a kind of three-dimension curved surface method of stretch forming based on modification face discrete type mould according to claim 2, its feature It is, each basic body unit (6) determining discrete type mould in step b is in forming process t short transverse displacement and discrete The detailed process of formula mould (2) whole height direction displacement is：

A. extract the coordinate x at basic body unit (6) center of the i-th row jth row_ijAnd yi_j(i=1,2 ..., m；J=1,2 ..., n； Wherein m is total line number of basic body unit (6), and n is total columns of basic body unit (6))；Determine discrete type mould (2) two ends The maximum tangential tilt of edge's curved surface, i.e. the hard-over θ of clamp_max, and determine the Surface Parameters of three-dimension curved surface part (5) Equation：

$P(u,v)=\left\{\begin{array}{c}x(u,v)\\ y(u,v)\\ z(u,v)\end{array}\right\}---\left(I\right)$

Wherein x, y are the coordinate of horizontal direction, and z is short transverse coordinate；U, v are the parameter coordinate of three-dimension curved surface part (5)；

B. solving equation (II), calculates the basic body unit (6) of the i-th row jth row and the ginseng of the contact point of three-dimension curved surface part (5) Number coordinate u_iAnd v_j

$\left\{\begin{array}{c}x(u_i,v_j)-(r+H+\frac{h}{2})n_x(u_i,v_j)=x_{ij}\\ y(u_i,v_j)-(r+H+\frac{h}{2})n_y(u_i,v_j)=y_{ij}\end{array}\right.,(i=1,2,\mathrm{...},m;j=1,2,\mathrm{...},n)---\left(II\right)$

Wherein x (u_i,v_j), y (u_i,v_j) be given by profile surface equation (I), r is the Probe-radius of basic body unit (6), and h is plate Material (4) thickness, H is the thickness of cushion (7), n_x(u_i,v_j) and n_y(u_i,v_j) it is normal direction outside the unit of three-dimension curved surface part (5) Component, is calculated by following formula

$n(u_i,v_j)=\left\{\begin{array}{c}{n}_x(u_i,v_j)\\ n_y(u_i,v_j)\\ n_z(u_i,v_j)\end{array}\right\}=\frac{\frac{\∂P(u_i,v_j)}{\∂u}\×\frac{\∂P(u_i,v_j)}{\∂v}}{\left|\frac{\∂P(u_i,v_j)}{\∂u}\×\frac{\∂P(u_i,v_j)}{\∂v}\right|}---\left(III\right)$

Wherein P (u_i,v_j) be given by profile surface equation (I)；

C. the final height at the end of utilizing the basic body that equation (IV) calculates the i-th row jth row to shape

${z^f}_{ij}=z(u_i,v_{\stackrel{\·}{j}})-(r+H+\frac{h}{2})n_z(u_i,v_j)+r,(i=1,2,...,m;j=1,2,...,n)---\left(IV\right)$

Wherein z (u_i,v_j) be given by surface equation (I), the outer normal component n of unit of curved surface_z(u_i,v_j) be given by equation (III)；

D. equation (V) is utilized to calculate the basic body unit (6) of the i-th row jth row of discrete type mould (2) in the z direction position of t Move

$w_{ij}\left(t\right)=({z^f}_{ij}-z_{min})\frac{t}{T},(i=1,2,...,m;j=1,2,...,n)---\left(V\right)$

Wherein z_minThe basic body unit (6) that calculates for equation (IV) final highly in minima, T is stretch forming needs Total time；

Calculate the global displacement in the z direction in t for the discrete mold (2) using equation (VI)

$d\left(t\right)=\frac{{\mathrm{l\θ}}_{max}}{T}t---\left(VI\right)$

Wherein l is the distance of die edge to clamp, θ_maxFor the maximum tangential tilt of both mold ends edge curved surface, i.e. clamp Hard-over.

4. a kind of three-dimension curved surface stretch forming side based on modification face discrete type mould according to any one of claim 1-3 Method is it is characterised in that described basic body unit (6) controls list by cell cube (8), basic body adjusting lever (9) and basic body First (10) composition, described basic body control unit (10) includes adjusting shape motor, decelerator and encoder, basic body unit (6) Height is by basic body control unit (10) real-time control；Regularly arranged m row n arranges basic body unit by fixed plate and base (11) The variable discrete type mould (2) of fixing structure forming surface.

5. a kind of three-dimension curved surface stretch forming side based on modification face discrete type mould according to any one of claim 1-3 Method it is characterised in that using cushion (7) between discrete type mould (2) and plate (4), to avoid in the curved surface zero shaping Impression is occurred on part.

6. a kind of three-dimension curved surface method of stretch forming based on modification face discrete type mould according to claim 3, its feature It is, described cushion (7) can adopt polyurethane sheet or rubber slab.