CN103769451B - A kind of method of ultra-thin tubing minor radius bending forming - Google Patents
A kind of method of ultra-thin tubing minor radius bending forming Download PDFInfo
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Abstract
The present invention relates to metal material plastic working manufacturing process.A kind of method of ultra-thin tubing minor radius bending forming, it is characterized in that comprising the steps: 1). adopt steel wire that the position to be bent of tubing is closely wound around parcel, gauge of wire is 1-3 times of tube wall thickness, and the thickness of steel wire parcel can be the 1-4 of tube wall thickness doubly as required; 2). plug is put in the tubing inside after wrapped wire, then adopts conventional numerical-control bending equipment to carry out numerical control bending forming to the tubing after wrapped wire; 3). after bending forming terminates, utilize wrapping machine to take off on the steel wire of parcel, the ultra-thin pipe fitting of small-bend radius can be obtained.The method is by realizing flexural deformation during to the parcel of tubing, an additional potential stress is introduced to tubing, the central core of tubing is made to shift to outside tubing, thus the tension outside reduction tubing, to reduce the Reducing thickness of wall thickness outside tubing, the Instability wrinkling defect of Inner tubing layers when simultaneously also effectively alleviating bending.
Description
Technical field
The present invention relates to metal material plastic working manufacturing process, be specifically related to a kind of new method of ultra-thin tubing minor radius bending forming, belong to Plastic working " technical field.
Background technology
Along with Aero-Space and the lightweight of mechanical transport field, high-performance, the development trend of low cost, also more and more higher to the requirement of elbow member, need radius-thickness ratio (ratio of diameter D and wall thickness t) larger, the bending radius (radius R of pipe fitting bending neutral layer
0with the ratio of pipe diameter D) less higher with forming accuracy.Adopt ultra-thin small curvature radius pipe fitting, not only can loss of weight, realize lightweight, pipe-line system arrangement also can be made compact, cost-saving.But along with the raising of tubing radius-thickness ratio and the reduction of bending radius, the distortion of metal increases, and adopts conventional bending tube forming technique, by overproof for the ovality of the wall thickness reduction that makes outside minor radius bend pipe and cross section, inner side produces wave wrinkle, has a strong impact on bending quality.At present, the traditional manufacturing process of this type of minor radius bending pipe fitting is generally the elbow adopting the welding of punching press metal plate part to prepare small-bend radius, and then and straight tube carry out assemble welding.But the existence of a large amount of weld seam, not only cause production efficiency low, cost is high, and will bear pressure and the percussion of internal flow medium during elbow member work, and weld seam adds potential safety hazard, poor reliability.
Adopt the ultra-thin small-bend radius pipe fitting of seamless pipe monolithic molding, both saved space, and in turn ensure that the loss of weight of reliability of structure and component.But in order to ensure the bending quality of tubing, the radius-thickness ratio of tubing and relative bending radius must control within the specific limits by conventional bending pipes technique.Such as, adopt bend, roll bending and filler bending method time, the limit radius-thickness ratio of pipe fitting is generally all less than 30, and minimum bending radius is also greater than 2d, does not reach the requirement of the ultra-thin tubing bend pipe that is shaped far away.It is 20mm ~ 120mm that push-bending process is applicable to bend diameter, wall thickness 0.8mm ~ 2mm, angle of bend 15 ° ~ 120 °, the sharp bend short tube of bending radius 1 ~ 2d.Because pipe fitting is all by bending die, be not therefore suitable for single elbow member that two ends straightway is longer yet.Outside axial thrust exacerbates axial compression stress inside bend pipe simultaneously, for the thin-wall pipe that radius-thickness ratio is larger, easily produces unstability in bending pipes process, and research shows that push-bending process bends stainless steel 1.2d pipe fitting radius-thickness ratio and is generally less than 35.
At present, for the tubing that above-mentioned ultra-thin minor radius is bending, in order to avoid or reduce the generation of forming defects, engineering adopts solid filler or flexible filler are conventional method as inner support.Conventional solid filler comprises ice, sand, rosin or low-melting alloy etc., but these fillers not only load consuming time, and in supporting, pressure is uncontrollable, also easily cause tubing internal injury, bending quality is poor, and the percentage elongation of low-melting alloy is limited, and bending radius can not be too small.Flexible filler is often referred to gas and liquid, generally carries out Pressure filling with water or wet goods liquid.Owing to adopting liquid as inner filling medium, formation of parts surface quality is good, and inside tube wall, wrinkling tendency is little, and bending forming precision is high, is particularly useful for variable curvature, bending pipes that radius-thickness ratio is large.Wherein relatively more typical application is exactly the liquid filled shear bending method that Hydraulic shaping engineering center of Harbin Institute of Technology proposes, and relies on detrusion to produce material flowing and realizes bending, aluminium alloy and titanium alloy tube joint that the relative bending radius that can be shaped is less than 0.5.But utilize liquid medium to provide interior pressure, need special equipment, performance difficulty, equipment investment is large, and shaping dies is complicated, hydraulic seal difficulty.The fillet size be shaped depends primarily on interior pressure, is difficult to realize accurate fixing quantity.In addition, the raising of interior pressure adds the Normal compressive stress of tube wall, can cause the increase of frictional force between tubing and mould.When shaping fillet is very little, in required shaping, pressure is very large, and rubbing can be more outstanding to the adverse effect of forming accuracy.Table 1 to bend accessible limit radius-thickness ratio for mild steel during differently curved radius and aluminum alloy thin walled pipe topping up.Therefrom visible, limit radius-thickness ratio reduces with bending radius and reduces gradually.When bending radius reaches (2 ~ 3) d, the limit radius-thickness ratio of mild steel and Aluminum Alloy Tube can not more than 40.
Accessible limit radius-thickness ratio under table 1 different materials and bending radius
Numerical-control bending is that tradition is gone for a stroll the advanced tube plastic forming technology of one that technique grows up in conjunction with machine tool industry and Numeric Control Technology.Tubing for three dimensions axis can one-time continuous be shaped, and the conduit CNC tube bending machine of outside more than the 30%-40% of aircraft engine of developed countries bends and forms.Numerical control bending forming contains many group mould constraint Collaborative Control pipe fitting deformational behaviors, can better controlling sections distortion and the defect such as wrinkling, and the increase tube bending forming limit, is suitable for the shaping of light-wall pipe small-bend radius.Generally adopt many balls core, its relative bending radius of numerical-control bending of the certain moduli lamps structure such as wrinkle resistant piece can reach 1.5.But along with the increase of light-wall pipe radius-thickness ratio, the minimum relative bending radius of numerical controlled bending of pipe also constantly improves gradually.External Aviation Enterprise grasps ripe numerical controlled bending of pipe technology, and in maximum diameter thickness rate and minimum relative bending radius, have larger breakthrough, its numerical-control bending technology accessible limit radius-thickness ratio is as shown in table 2.Can see from table, stainless-steel thin-wall pipe radius-thickness ratio is maximum reaches 127, and minimum bending radius can reach 2d.The maximum diameter thickness rate of Aluminum Alloy Tube reaches 77, and minimum bending radius can reach 1.7d.In recent years, domestic numerical control bending forming technology fast development, bends large radius-thickness ratio light-wall pipe ability and external gap reduces gradually, in numerical control bending forming rule and thin-walled tube bending theoretical research etc., achieve many important research achievements.Show stainless-steel thin-wall pipe numerical-control bending experimental studies results, when relative bending radius reaches 1.5, its maximum diameter thickness rate can reach 50.Show aluminum alloy thin walled pipe numerical-control bending experimental studies results, when relative bending radius reaches 1.5 ~ 2, its maximum diameter thickness rate can reach 50; When relative bending radius reaches 1, its maximum diameter thickness rate is reduced to 38.
Above data shows, adopts existing curved super-long structure, and the limit radius-thickness ratio of shapable light-wall pipe is about 100, and relative bending radius is about 2.
The external accessible limit radius-thickness ratio of numerical-control bending of table 2
Conventional bending method, tubing at moment of face M flex under action, as shown in Figure 3.The material outside of bending deformation area is subject to tangential stretching and extends, and inside material shortens by tangential compression.Due to tangential stress σ
θand strain stress
θdistribution along tubing section is continuous, therefore at the end of BENDING PROCESS, drawing zone is transitioned into compressional zone, there is one deck fiber at its intersection, and its length equals the original length of pipe, i.e. this fibrolaminar strain stress
θ=0.This fibrage is called strain neutral layer, and its position in section can represent with radius of curvature ρ.When the material outside in Tube Bending Deformation district is subject to tangential tensile elongation higher than its material percentage elongation, tubing will break, as shown in Figure 3 b; When tubing inside material, by tangential compression, unstability occurs, will occur wrinkling inside tubing, as shown in Figure 3 b.
Summary of the invention
The object of the present invention is to provide a kind of method of ultra-thin tubing minor radius bending forming, the method is by realizing flexural deformation during to the parcel of tubing, an additional potential stress is introduced to tubing, the central core of tubing is made to shift to outside tubing, thus the tension outside reduction tubing, to reduce the Reducing thickness of wall thickness outside tubing, the Instability wrinkling defect of Inner tubing layers when simultaneously also effectively alleviating bending.
For achieving the above object, the technical solution adopted in the present invention is: a kind of method of ultra-thin tubing minor radius bending forming, is characterized in that comprising the steps:
1). adopt steel wire 1 that the position C to be bent of tubing 2 is closely wound around parcel, the 1-3 that gauge of wire (square steel silk is the length of side) is tube wall thickness doubly (i.e. tube wall thickness: gauge of wire=1:1-3), the thickness of steel wire parcel can be the 1-4 of tubing (original tube) wall thickness doubly as required, and the gap between the steel wire of parcel and tubing is about 0.1mm (steel wire of parcel and the outside dimension gap of tubing is at about 0.1mm);
2). the tubing inside after wrapped wire is put into plug (many balls core) 3, then conventional numerical-control bending equipment is adopted to carry out numerical control bending forming [adopt quiet fixture block 4 and wrinkle resistant piece 5, and traditional numerical control bending forming being implemented by dynamic fixture block 6 and bending die 7 pairs of tubing] to the tubing after wrapped wire;
3). after bending forming terminates, utilized by the steel wire of parcel wrapping machine to take off (steel wire that after removing bending forming, tubing wraps up), the ultra-thin pipe fitting of small-bend radius can be obtained.
Described steel wire 1 is square steel silk (band) or round steel wire.
Described tubing 2 is the tubing of large radius-thickness ratio.Radius-thickness ratio refers to the ratio of tube outer diameter and wall thickness.
Ultra-thin pipe (ultra-thin pipe fitting) is greater than the pipe (pipe fitting) of 50 for radius-thickness ratio.Small-bend radius is the tube outer diameter that bending radius is less than 1.5 times.
Adopt the method to carry out tube bending forming, radius-thickness ratio when homogeneous tube bends can be reduced.Introduce a frictional force to tubing when being out of shape by the steel wire bent of tubing outer layer covers simultaneously, tensile stress outside during reduction bending pipes and the compression stress of inner side, make to move outside stress neuter layer, not only inhibit the wall thickness reduction outside tubing, also effectively improve the Instability wrinkling inside tubing, improve the bending forming limit of tubing.
The invention solves existing method to bend the ultra-thin tubing of large radius-thickness ratio and cannot realize the bending difficult problem of minor radius.
The invention has the beneficial effects as follows: the structure of the equipment adopted is simple, convenient, practical, novel, steel wire parcel tubing is simple and easy to do.Because steel wire thickness is 1-4 tube wall thickness doubly, radius-thickness ratio when homogeneous tube bends can be reduced.Introduce a frictional force to tubing when being out of shape by the steel wire bent of tubing outer layer covers simultaneously, the contraction of outer field elongation and internal layer when this frictional force can stop bending pipes, and to producing tangential compression stress outside tubing, to producing tangential elongation stress inside tubing, thus when reducing bending pipes outside drawing stress and the compression stress of inner side, make to move outside stress neuter layer, not only inhibit the wall thickness reduction outside tubing, also effectively improve the Instability wrinkling inside tubing.Therefore, come compared to traditional bending process, this technique effectively can avoid defect, improves the bending forming limit of tubing.
Accompanying drawing explanation
Fig. 1 is the schematic diagram after tubing of the present invention carries out steel wire winding parcel.
Fig. 2 is the schematic diagram (parcel tube bending forming schematic diagram) that the tubing of wrapped wire of the present invention carries out numerical-control bending.
Fig. 3 is force analysis and defect map in traditional piping material BENDING PROCESS; A is bending pipes force diagram; B is bending pipes defect map.
Fig. 4 is force analysis figure in the bending pipes process of wrapped wire of the present invention.
In figure: 1-steel wire, 2-tubing, 3-plug, the quiet fixture block of 4-, wrinkle resistant piece of 5-, 6-moves fixture block, 7-bending die; C in Fig. 1 represents position to be bent (bending section); In Fig. 2, W represents bending die rotary speed; In Fig. 4, F represents that tubing is subject to the support force of plug, and f represents frictional force, and M represents bending moment, σ
θrepresent tangential stress, ε
θrepresent tangential strain.
Detailed description of the invention
Embodiment 1:
A method for ultra-thin tubing minor radius bending forming, comprises the steps:
1). the diameter of tubing 2 is 60mm, and thickness is 0.73mm(and radius-thickness ratio is 82), length is 400mm, and the material of tubing 2 is tubing 201; Described steel wire 1 is round steel wire, steel wire diameter is 1.5mm, concrete parcel one deck is that 1.5mm is thick, bending radius is 90mm, the length of position C to be bent is 200mm, the outside dimension of plug (many balls core) 3 is 57.8mm, and the diameter of the ball comprised is 57.4mm, and the arrangement form of ball is that three balls are connected on plug by hinge; As shown in Figure 1;
Adopt steel wire 1 that the position C to be bent of tubing 2 is closely wound around parcel, the gap between the steel wire of parcel and tubing is about 0.1mm (steel wire of parcel and the outside dimension gap of tubing is at about 0.1mm);
2). the tubing inside after wrapped wire is put into plug (many balls core) 3, then conventional numerical-control bending equipment is adopted to carry out numerical control bending forming [adopt quiet fixture block 4 and wrinkle resistant piece 5, and traditional numerical control bending forming being implemented by dynamic fixture block 6 and bending die 7 pairs of tubing] to the tubing after wrapped wire;
3). after bending forming terminates, utilized by the steel wire of parcel wrapping machine to take off (steel wire that after removing bending forming, tubing wraps up), the ultra-thin pipe fitting of small-bend radius can be obtained.
Described steel wire 1 is round steel wire.
The structure of plug 3 is shown in Fig. 2, and plug is in series with three core balls by hinge, forms many balls core together.But the maximum feature of the present invention is the steel wire wrapped up outside tubing, and it can change Tube Bending Deformation stress characteristic, realizes the minor radius bending forming of ultra-thin tubing, and its basic structure is shown in the three-dimensional CAD figure of Fig. 1, and flexural deformation force analysis is shown in Fig. 4.
Smoothly inside the ultra-thin elbow member finally obtained have no wrinkling, outside also has no defects such as breaking.
Embodiment 2:
A method for ultra-thin tubing minor radius bending forming, comprises the steps:
1). the diameter of tubing 2 is 60mm, and thickness is 0.73mm(and radius-thickness ratio is 82), length is 400mm, and the material of tubing 2 is 201; Described steel wire 1 is square steel silk, square steel silk is equilateral 1.5 × 1.5mm, concrete parcel one deck is that 1.5mm is thick, bending radius is 90mm, the length at position to be bent is 200mm, the outside dimension of plug (many balls core) 3 is 57.8mm, and the diameter of the ball comprised is 57.4mm, and the arrangement form of ball is that three balls are connected on plug by hinge; As shown in Figure 1;
Adopt steel wire 1 that the position C to be bent of tubing 2 is closely wound around parcel, the gap between the steel wire of parcel and tubing is about 0.1mm (steel wire of parcel and the outside dimension gap of tubing is at about 0.1mm);
2). the tubing inside after wrapped wire is put into plug (many balls core) 3, then conventional numerical-control bending equipment is adopted to carry out numerical control bending forming [adopt quiet fixture block 4 and wrinkle resistant piece 5, and traditional numerical control bending forming being implemented by dynamic fixture block 6 and bending die 7 pairs of tubing] to the tubing after wrapped wire;
3). after bending forming terminates, utilized by the steel wire of parcel wrapping machine to take off (steel wire that after removing bending forming, tubing wraps up), the ultra-thin pipe fitting of small-bend radius can be obtained.
Described steel wire 1 is square steel silk.
Smoothly inside the ultra-thin elbow member finally obtained have no wrinkling, outside also has no defects such as breaking.
Claims (3)
1. a method for ultra-thin tubing minor radius bending forming, is characterized in that comprising the steps:
1). adopt steel wire (1) that the position to be bent (C) of tubing (2) is closely wound around parcel, gauge of wire is 1-3 times of tube wall thickness, the thickness of steel wire parcel can be the 1-4 of tube wall thickness doubly as required, and the gap between the steel wire of parcel and tubing is 0.1mm;
2). plug (3) is put in the tubing inside after wrapped wire, then adopts conventional numerical-control bending equipment to carry out numerical control bending forming to the tubing after wrapped wire;
3). after bending forming terminates, utilize wrapping machine to take off on the steel wire of parcel, the ultra-thin pipe fitting of small-bend radius can be obtained; Described ultra-thin pipe fitting is the pipe fitting that radius-thickness ratio is greater than 50, and small-bend radius is the tube outer diameter that bending radius is less than 1.5 times.
2. the method for a kind of ultra-thin tubing minor radius bending forming according to claim 1, is characterized in that: described steel wire (1) is square steel silk or round steel wire.
3. the method for a kind of ultra-thin tubing minor radius bending forming according to claim 1, is characterized in that: the tubing that described tubing (2) is large radius-thickness ratio.
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| CN105618532B (en) * | 2015-12-23 | 2017-11-24 | 中国航空工业集团公司北京航空制造工程研究所 | Gap support unit, gap supporting tool and bending forming method |
| US10507310B2 (en) * | 2016-10-27 | 2019-12-17 | Acclarent, Inc. | Dilation apparatus with malleable feature and apparatus to bend malleable feature |
| CN106391794A (en) * | 2016-11-25 | 2017-02-15 | 沈阳黎明航空发动机(集团)有限责任公司 | Small-curvature-radius forming method for conduit |
| CN106903194B (en) * | 2017-03-09 | 2018-09-14 | 南京航空航天大学 | A method of improving the metal 3 D auto bending forming limit |
| CN107282722B (en) * | 2017-07-03 | 2023-09-26 | 浙江长兴和良智能装备有限公司 | Small R forming method for pipe bent pipe and pipe end forming machine |
| CN107745030A (en) * | 2017-09-27 | 2018-03-02 | 浙江海卓利克液压科技有限公司 | Hydraulic-bend shaped device and bend forming method |
| CN111061219B (en) * | 2019-12-16 | 2021-03-23 | 南京航空航天大学 | Method for rapidly determining forming process parameters |
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