阅读说明：本技术 一种降低管状零件回弹的工艺方法 (Process method for reducing resilience of tubular part ) 是由 初冠南 苑世剑 林才渊 于 2019-10-17 设计创作，主要内容包括：一种降低管状零件回弹的工艺方法,本发明涉及管状零件加工技术领域,选取直管坯,进行初步弯曲得到预成形零件；将预成形零件放入终成形模具中的下模内的终成形模腔中；对预成形零件的内腔施加内压支撑,压力值为0-500MPa；将终成形模具进行合模,对预成形零件进行截面压缩,并使材料发生塑性变形,在压缩过程中预成形零件在内压的支撑作用下贴紧终成形模腔；撤掉内压支撑,即得到少甚至无回弹的中空零件。实效性好,能克服高强钢中空零件成形精度差的不足,而且消除回弹的工序可嵌在终成形工序中,实用性更强。(the invention discloses a process method for reducing the resilience of a tubular part, which relates to the technical field of tubular part processing, and comprises the following steps of selecting a straight pipe blank, and preliminarily bending the straight pipe blank to obtain a preformed part; placing the preformed part into a final forming die cavity in a lower die in a final forming die; applying internal pressure support to the inner cavity of the preformed part, wherein the pressure value is 0-500 MPa; closing the final forming die, compressing the section of the preformed part, enabling the material to generate plastic deformation, and enabling the preformed part to be tightly attached to the final forming die cavity under the supporting action of internal pressure in the compression process; and removing the internal pressure support to obtain the hollow part with little or no resilience. The method has good effectiveness, can overcome the defect of poor forming precision of the high-strength steel hollow part, can embed the process of eliminating springback in the final forming process, and has stronger practicability.)

1. a process method for reducing the resilience of a tubular part is characterized by comprising the following steps: the method comprises the following steps:

(1) Selecting a straight pipe blank, and carrying out primary bending to obtain a preformed part;

(2) Placing the preformed part into a final forming die cavity in a lower die in a final forming die, wherein the outline of the final forming die cavity is completely the same as the outline of the finally obtained springback-free hollow part;

(3) Applying internal pressure support to the inner cavity of the preformed part, wherein the pressure value is 0-500 MPa;

(4) closing the final forming die, namely buckling an upper die and a lower die, compressing the section of the preformed part, and enabling the material to generate plastic deformation, wherein the deformation amount reaches 0.1% -50%, and meanwhile, the preformed part is tightly attached to the final forming die cavity under the action of internal pressure support in the compression process;

(5) and removing the internal pressure support to obtain the hollow part with little or no resilience.

2. A process for reducing the springback of a tubular element as claimed in claim 1, wherein: in the step (1), the pre-bent target of the straight pipe blank can be placed into a final forming die as a preformed part.

3. A process for reducing the springback of a tubular element as claimed in claim 1, wherein: in the step (1), the stress components of each point on the preformed part are marked as follows: stress in the tangential direction of the cross-sectional profile is σ_θstress in the tangential direction of the axis is σ_zstress in thickness direction is much smaller than sigma_θand σ_zAnd is therefore ignored; axial stress neutral layer (i.e. sigma) during bending deformation_z0) σ of the outer material_zGreater than 0, namely the sigma of the material at the inner side of the tensile stress neutral layer_z< 0, i.e. compressive stress, and similarly, the tangential stress of the profile also exists at the outer side σ_θ> 0, inner σ_θ＜0Therefore, after the die constraint is removed, the spring back deformation occurs.

4. A process for reducing the springback of a tubular element as claimed in claim 1, wherein: in the step (4), the material is subjected to interface compression, and according to the yield criterion of the Torrelsa, the sigma at each position of the preformed part reaches the yield deformation_θAre all equal to the flow stress σ of the material_iKnowing σ for in-plane strain states_z＝0.5σ_θSo that after compressive deformation, the stress of the materials on both sides of the neutral layer along the tangential direction of the axis is equal to 0.5 sigma_iThat is, the difference in stresses on the inner and outer sides formed or left in the step (1) is eliminated by the compression deformation, so that the spring-back deformation does not occur even after the mold constraint is removed.

5. A process for reducing the springback of a tubular element as claimed in claim 1, wherein: the straight pipe blank is a metal straight pipe blank.

6. A process for reducing the springback of a tubular element as claimed in claim 1, wherein: the straight pipe blank is a high-strength steel straight pipe blank.

7. A process for reducing the springback of a tubular element as claimed in claim 1, wherein: the straight pipe blank is a low-plasticity straight pipe blank.

Technical Field

The invention relates to the technical field of tubular part machining, in particular to a process method for reducing the resilience of a tubular part. .

Background

The hollow part can give full play to the bending modulus and the torsional modulus of the material, achieves the effect of structure weight reduction, is a structural form which is inclined to be adopted by the current vehicles, and is widely applied to automobile chassis and frames in particular. However, the materials used on the chassis and the frame of the automobile at present are high-strength steel, the yield strength fluctuation of the materials is large, and in addition, the transformation of super-cooled austenite in the forming process causes the materials to have serious rebound and irregular rebound amount. The shape precision of the formed part is reduced, and the subsequent assembly welding difficulty is increased. Particularly, the rebound quantity is irregularly found, and the traditional rebound compensation technology cannot avoid the rebound. These difficulties have hindered the widespread use of hollow parts, particularly high strength steel hollow parts. An effective springback control method for the hollow part is urgently needed to be found.

disclosure of Invention

The invention aims to provide a process method for reducing the springback of a tubular part, which is reasonable in design, simple and easy to implement, has good effectiveness, can overcome the defect of poor forming precision of high-strength steel hollow parts, can eliminate the springback process step and can be embedded in a final forming process step, and has stronger practicability.

In order to achieve the purpose, the invention adopts the following technical scheme: the method comprises the following steps:

1. Selecting a straight pipe blank, and carrying out primary bending to obtain a preformed part;

2. Placing the preformed part into a final forming die cavity in a lower die in a final forming die, wherein the outline of the final forming die cavity is completely the same as the outline of the finally obtained springback-free hollow part;

3. Applying internal pressure support to the inner cavity of the preformed part, wherein the pressure value is 0-500MPa, and the standard is that no instability occurs in the next step;

4. Closing the final forming die, namely buckling an upper die and a lower die, compressing the section of the preformed part, and enabling the material to generate plastic deformation, wherein the deformation amount reaches 0.1% -50%, and meanwhile, the preformed part is tightly attached to the final forming die cavity under the supporting action of internal pressure in the compression process;

5. And removing the internal pressure support to obtain the hollow part with little or no resilience.

further, in the step 1, the pre-bent object of the straight pipe blank can be placed into a final forming die as a pre-formed part.

Further, in the step 1The stress components at each point on the preformed part are labeled as follows: stress in the tangential direction of the cross-sectional profile is σ_θstress in the tangential direction of the axis is σ_zStress in thickness direction is much smaller than sigma_θAnd σ_zAnd is therefore ignored; axial stress neutral layer (i.e. sigma) during bending deformation_z0) σ of the outer material_zgreater than 0, namely the sigma of the material at the inner side of the tensile stress neutral layer_z< 0, i.e. compressive stress, and similarly, the tangential stress of the profile also exists at the outer side σ_θ> 0, inner σ_θ< 0, so that after the mold constraint is removed, the spring back deformation occurs.

Further, in the step 4, the material is subjected to interface compression, and according to the yield criterion of the Torressan, the sigma at each position of the preformed part when the preformed part achieves yield deformation_θare all equal to the flow stress σ of the material_iknowing σ for in-plane strain states_z＝0.5σ_θSo that after compressive deformation, the stress of the materials on both sides of the neutral layer along the tangential direction of the axis is equal to 0.5 sigma_iThat is, the difference between the internal and external stresses formed or left in step 1 is eliminated by the compressive deformation, so that the spring-back deformation does not occur even after the mold constraint is removed.

Further, the straight pipe blank 1 is a metal straight pipe blank.

Further, the straight pipe blank 1 is a high-strength steel straight pipe blank.

Further, the straight pipe blank 1 is a low-plasticity straight pipe blank.

After adopting the structure, the invention has the beneficial effects that: the invention provides a process method for reducing the springback of a tubular part, which reduces or eliminates the best time of springback in the stages of product design and die development, so that the springback quantity is accurately predicted by means of analysis, the product design and process are optimized, the springback is reduced by utilizing the product shape, process and compensation, the process method is simple and easy to implement, has good effectiveness, can overcome the defect of poor forming precision of high-strength steel hollow parts, and has stronger practicability because the procedure of eliminating the springback can be embedded in the final forming procedure.

Description of the drawings:

fig. 1 is a schematic view of the structure of a straight tube blank in the present invention.

FIG. 2 is a schematic view of the construction of a preformed part of the present invention.

FIG. 3 is a schematic illustration of the position of the preformed part and the final forming die of the present invention.

Description of reference numerals:

The forming die comprises a straight pipe blank 1, a preformed part 2, a final forming die 3, an upper die 3-2, a lower die 3-1 and a final forming die cavity 4.

the specific implementation mode is as follows:

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

as shown in fig. 1 to fig. 3, the following technical solutions are adopted in the present embodiment: the method comprises the following steps:

1. Selecting a straight pipe blank 1 made of a metal material, carrying out primary bending to obtain a preformed part 2, wherein the pre-bending target of the straight pipe blank 1 is based on that the preformed part 2 can be placed into a final forming die 3, and the stress components of each point on the preformed part 2 are marked as follows: stress in the tangential direction of the cross-sectional profile is σ_θStress in the tangential direction of the axis is σ_zStress in thickness direction is much smaller than sigma_θand σ_zAnd is therefore ignored; axial stress neutral layer (i.e. sigma) during bending deformation_z0) σ of the outer material_zGreater than 0, namely the sigma of the material at the inner side of the tensile stress neutral layer_z< 0, i.e. compressive stress, and similarly, the tangential stress of the profile also exists at the outer side σ_θ> 0, inner σ_θLess than 0, so that after the constraint of the die is removed, the die generates rebound deformation;

2. placing the preformed part 2 into a final forming die cavity 4 in a lower die 3-1 in a final forming die 3, wherein the outline of the final forming die cavity 4 is completely the same as the outline of the finally obtained hollow part without springback;

3. Applying internal pressure support to the inner cavity of the preformed part 2, wherein the pressure value is 0-500MPa, and the standard is that no instability occurs in the next step;

4. closing the final forming die 3, namely buckling an upper die 3-2 and a lower die 3-1, compressing the section of the preformed part 2, and enabling the material to generate plastic deformation, wherein the deformation amount reaches 0.1% -50%; σ everywhere the preformed part 2 reaches yield deformation according to the Lorentaska yield criterion_θAre all equal to the flow stress σ of the material_iFor the plane strain state, σ z is known to be 0.5 σ_θSo that after compressive deformation, the stress of the materials on both sides of the neutral layer along the tangential direction of the axis is equal to 0.5 sigma_iNamely, the stress difference between the inner side and the outer side formed or left in the step 1 is eliminated by compression deformation, so that the rebound deformation does not occur after the constraint of the die is removed; meanwhile, the preformed part 2 is tightly attached to the final forming die cavity 4 under the supporting action of internal pressure in the compression process;

5. And removing the internal pressure support to obtain the hollow part with little or no resilience.

After adopting above-mentioned structure, this embodiment's beneficial effect is as follows:

1. the rebound effect is eliminated, the influence of material yield strength fluctuation and transformation of super-cooled austenite is avoided, and the problem of the rebound of high-strength steel can be solved;

2. The resilience is eliminated by compression, and the resilience can be placed at the forming finishing moment, namely embedded in the finishing forming process, so that the method is simple and easy to implement;

3. The material is used for yielding to eliminate the springback, so that the shape precision can reach about 0.1 mm.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.