CN109530521B - Method for determining internal high pressure forming process parameters - Google Patents

Method for determining internal high pressure forming process parameters Download PDF

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CN109530521B
CN109530521B CN201811615193.6A CN201811615193A CN109530521B CN 109530521 B CN109530521 B CN 109530521B CN 201811615193 A CN201811615193 A CN 201811615193A CN 109530521 B CN109530521 B CN 109530521B
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unit
internal pressure
fillet
tube blank
closing stroke
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CN109530521A (en
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张亚歧
高方勇
阮楹妍
刘俊锋
胡文治
周海龙
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Dongfeng Motor Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
    • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
    • B21D26/033—Deforming tubular bodies
    • B21D26/041—Means for controlling fluid parameters, e.g. pressure or temperature

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  • Shaping Metal By Deep-Drawing, Or The Like (AREA)

Abstract

The invention discloses a method for determining internal high pressure forming process parameters, which comprises the steps of analyzing and establishing an internal pressure, a mold closing and a stroke allowable range before a sample is manufactured, obtaining the maximum thinning rate delta, the fillet joint clearance α and the undercut width d of a tubular beam through analysis, and settingThe technical requirements of the sample piece are as follows: the maximum thinning rate delta is not more than delta under the condition of no undercut0And the fillet fit clearance α is not more than α0And the undercut width d is not more than 0, the distribution of the three indexes on an internal pressure-mould closing stroke plane is respectively determined, and the areas of the conditions are subjected to intersection to obtain a reasonable mould closing stroke and internal pressure distribution range.

Description

Method for determining internal high pressure forming process parameters
Technical Field
The invention belongs to the technical field of automobile parts, and particularly relates to a method for determining internal high-pressure forming process parameters.
Background
The existing plate stamping and welding process is not easy to form parts with complex shapes, and assembly errors are difficult to control due to low plate utilization rate and low forming precision. The internal high-pressure forming replaces solid with hollow, and the uniform section with the variable section, and replaces the blocking integrally to realize the integral variable section of the part, and the internal high-pressure forming replaces the solid with hollow, replaces the uniform section with the variable section, and replaces the tailor welding with the integral forming to realize the light weight of the automobile. Indent type tubular beam spare is most common on the car, and indent type tubular beam spare generally adopts preforming + interior high-pressure bulging to realize, to this kind of forming mode, when the terrace die descends, if tubular product is inside not to have mechanical support, die cavity has not flowed into smoothly to die joint department pipe, has produced the shrivelled of mechanical nature at the die joint to the unable meeting requirements of appearance spare. Therefore, it is necessary to determine the relationship between the mold closing stroke (which is the ratio of the descending distance of the upper mold to the entire mold closing height, and hereinafter, the closing stroke is the ratio) and the internal pressure. The relation between the closing stroke and the internal pressure of the die can be given before the sample is manufactured, so that the debugging period of the die can be greatly shortened, and the surface quality and the performance of the sample can be effectively improved. In the die closing process, if the pipe is not mechanically supported, the fillet part of the pipe cannot be attached to a convex die fillet, and the pipe blank at the parting surface cannot smoothly flow into a die cavity due to lack of mechanical support, so that the pipe blank at the parting surface is directly crushed (as shown in fig. 1 and 2), and a sample cannot meet the requirement. Therefore, the maximum reduction rate of the pipe blank, the fillet joint clearance and the undercut width are used as evaluation indexes for successfully completing the die closing, and specific explanations of the three indexes are shown in FIG. 3.
Through analysis, a relation cloud picture between the mold closing stroke and the internal pressure is established, and then the mold closing stroke and the internal pressure combination are determined on the relation cloud picture according to the specific structure characteristics of the product.
Disclosure of Invention
The invention aims to solve the defects of the background technology and provide a method for determining the parameters of an internal high-pressure forming process.
The technical scheme adopted by the invention is as follows: a method for determining internal high pressure forming process parameters comprises the following steps:
(1) before the sample piece is manufactured, the allowable ranges of internal pressure, mold closing and stroke are analyzed, the maximum thinning rate delta of the tubular beam, the fillet attaching gap α and the undercut width d are obtained through analysis, and the technical requirement of the sample piece is set, namely, under the condition that undercut does not occur, the maximum thinning rate delta is not greater than delta0And the fillet fit clearance α is not more than α0And the undercut width d is not more than 0, the distribution of the three indexes on the internal pressure-die closing stroke plane is respectively determined, and the fillet attaching gap α, the maximum reduction rate delta and the undercut width d meet the conditions:
Figure BDA0001925678030000021
δ0、α0specified according to design requirements, e.g. reduction δ0Required to be more than or equal to 8 percent and profile tolerance α0The area under the condition is not more than +/-1.5 mm, and the reasonable distribution range of the mold closing stroke and the internal pressure can be obtained by intersecting the area under the condition;
(2) through analysis, the internal pressure and the mold closing stroke are used as input variables, the undercut width d, the fillet fit clearance α and the maximum thinning rate delta are used as output variables, a plurality of groups of tests are designed to obtain the relation between input and output, three index variable contour maps are obtained on an input plane, and then the allowable range of the mold closing stroke and the internal pressure distribution is determined according to the formula (1).
The formula (1) in the step (1) can be converted into the following formula (2),
Figure BDA0001925678030000031
wherein S is0Is the mold closure height, unit: mm; d0The undercut width of the tube blank after the completion of the forming is expressed by the unit: mm; f is the friction coefficient of the tube blank and the die, and is generally 0.12-0.18; di、liInstantaneous undercut width and instantaneous mould closing stroke, unit: mm; p0Pressure applied inside the lumen, unit: mpa; pbIs the tensile strength of the pipe, unit: mpa; dmaxThe maximum section perimeter after the tube is formed is as follows: mm; d is the initial outer diameter of the tube blank, unit: mm.
In the scheme, the maximum reduction rate delta is (thickness of the formed tube blank-initial tube blank)/thickness of the initial tube blank in unit:%, the fillet joint gap α is the maximum distance between the tube blank at the fillet part and the die after forming in unit of mm, and the undercut width d is the width of the tube blank which does not flow into the cavity of the female die after forming in unit of mm.
The invention completes the pre-forming and the hydraulic bulging of the tubular beam by applying the internal pressure in time in the die closing process, determines the reasonable combination of the internal pressure and the stroke by constructing the contour map of the index variable on the stroke-internal pressure plane, and is helpful for obtaining the technical parameters of the tubular beam.
According to the method, the structural characteristics of the concave pipe beam are fully considered, the undercut width, the fillet fit clearance and the maximum thinning rate are used as evaluation indexes of an internal high-pressure forming result, a cloud chart of the relation between the mold closing stroke and the internal pressure is determined through analysis, and a proper mold closing stroke and internal pressure combination is determined according to the cloud chart.
Drawings
FIG. 1 is a schematic view of the deformation of a tube blank prior to closing of a die in the prior art;
FIG. 2 is a schematic view showing the deformation of a tube blank after the die is closed in the prior art;
FIG. 3 is a paraphrasing graph of the index variables;
FIG. 4 is a cloud view of undercut width distributions;
FIG. 5 is a cloud of maximum reduction distributions;
FIG. 6 is a cloud view of fillet fit gap distribution;
FIG. 7 is a schematic view of the determined mold closing stroke and internal pressure distribution range of the present invention.
In the figure, 1-concave die, 2-convex die, 3-pipe fitting and 4-round corner part.
Detailed Description
The invention will be further described in detail with reference to the following drawings and specific examples, which are not intended to limit the invention, but are for clear understanding.
The invention discloses a method for determining internal high-pressure forming process parameters, which comprises the following steps:
(1) before the sample piece is manufactured, the allowable ranges of internal pressure, mold closing and stroke are analyzed, the maximum thinning rate delta of the tubular beam, the fillet attaching gap α and the undercut width d are obtained through analysis, and the technical requirement of the sample piece is set, namely, under the condition that undercut does not occur, the maximum thinning rate delta is not greater than delta0And the fillet fit clearance α is not more than α0And the undercut width d is not more than 0, the distribution of the three indexes on the internal pressure-die closing stroke plane is respectively determined, and the fillet attaching gap α, the maximum reduction rate delta and the undercut width d meet the conditions:
Figure BDA0001925678030000051
δ0、α0specified according to design requirements, e.g. reduction δ0Required to be more than or equal to 8 percent and profile tolerance α0The area under the condition is not more than +/-1.5 mm, and the reasonable distribution range of the mold closing stroke and the internal pressure can be obtained by intersecting the area under the condition;
(2) through analysis, the internal pressure and the mold closing stroke are used as input variables, the undercut width d, the fillet joint clearance α and the maximum thinning rate delta are used as output variables, a plurality of groups of tests are designed to obtain the relation between input and output, a contour map of three index variables is obtained on an input plane, and the allowable range of the mold closing stroke and the internal pressure distribution is determined according to the formula (1), as shown in fig. 4-7.
The formula (1) in the step (1) can be converted into the following formula (2),
Figure BDA0001925678030000061
wherein S is0Is the mold closure height, unit: mm; d0The undercut width of the tube blank after the completion of the forming is expressed by the unit: mm; f is the friction coefficient of the tube blank and the die, and is generally 0.12-0.18; di、liInstantaneous undercut width and instantaneous mould closing stroke, unit: mm; p0Pressure applied inside the lumen, unit: mpa; pbIs the tensile strength of the pipe, unit: mpa; dmaxThe maximum section perimeter after the tube is formed is as follows: mm; d is the initial outer diameter of the tube blank, unit: mm.
The maximum reduction rate is one of main indexes reflecting the formability of a product, the pipe beam piece generally has performance requirements, and the performance of the pipe beam piece is influenced when the reduction rate is too large or too small, so that the maximum reduction rate is used as a performance evaluation index of internal high pressure forming; the fillet joint clearance mainly reflects the joint degree of the pipe beam piece and a designed product, and the pipe blank can not be jointed to the surface of the die when the internal pressure is too low, so that the fillet joint clearance is used as a size evaluation index; in terms of product appearance reflected by undercut width, if undercut occurs, the product cannot meet the requirement necessarily, and therefore the undercut width is used as an appearance quality evaluation index.
And determining a distribution cloud chart of the evaluation index on a mold closing stroke-internal pressure plane. Firstly, establishing a corresponding mathematical model according to a product digital model, designing a plurality of groups of analysis models by taking the closing stroke and the internal pressure of the mold as combined variables, constructing a contour map of index variables on a mold closing stroke-internal pressure plane according to all analysis results, setting three index variable thresholds of indexes according to the structural characteristics and the technical requirements of the product, and determining a proper mold closing stroke and internal pressure combination on a cloud map.
Those not described in detail in this specification are within the skill of the art.

Claims (2)

1. A method for determining internal high pressure forming process parameters is characterized in that: the method comprises the following steps:
(1) before the sample piece is manufactured, the allowable ranges of the internal pressure and the mold closing stroke are analyzed, the maximum thinning rate delta of the tubular beam, the fillet attaching gap α and the undercut width d are obtained through analysis, and the technical requirement of the sample piece is set that the maximum thinning rate is not more than delta under the condition that undercut does not occur0And the fillet fit clearance is not more than α0And the undercut width d is not more than 0, the distribution of the three indexes on the internal pressure-die closing stroke plane is respectively determined, and the fillet attaching gap α, the maximum reduction rate delta and the undercut width d meet the conditions:
Figure FDA0002438016390000011
δ0、α0the reduction rate delta is specified according to design requirements0Required to be more than or equal to 8 percent and profile tolerance α0The area under the condition is not more than +/-1.5 mm, and the reasonable distribution range of the mold closing stroke and the internal pressure can be obtained by intersecting the area under the condition;
(2) through analysis, the internal pressure and the mold closing stroke are used as input variables, the undercut width d, the fillet fit clearance α and the maximum thinning rate delta are used as output variables, a plurality of groups of tests are designed to obtain the relation between input and output, three index variable contour maps are obtained on an input plane, and then the allowable range of the mold closing stroke and the internal pressure distribution is determined according to the formula (1);
the maximum reduction rate delta is (thickness of the formed tube blank-initial tube blank)/thickness of the initial tube blank in unit percent, the fillet joint clearance α is the maximum distance between the tube blank at the fillet part and the die after forming is finished in unit mm, and the undercut width d is the width of the tube blank which does not flow into the cavity of the female die after forming is finished in unit mm.
2. The method for determining internal high pressure forming process parameters according to claim 1, wherein: the formula (1) in the step (1) can be converted into the following formula (2),
Figure FDA0002438016390000021
wherein S is0Is the mold closure height, unit: mm; d0The undercut width of the tube blank after the completion of the forming is expressed by the unit: mm; f is the friction coefficient of the tube blank and the die, and is generally 0.12-0.18; di、liInstantaneous undercut width and instantaneous mould closing stroke, unit: mm; p0Pressure applied to the inside of the lumen, unit: mpa; pbIs the tensile strength of the pipe, unit: mpa; dmaxThe maximum section perimeter after the tube is formed is as follows: mm; d is the initial outer diameter of the tube blank, unit: mm.
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US4557128A (en) * 1982-01-27 1985-12-10 Costabile John J Apparatus for producing a bulge in thin metal material
CN1644264A (en) * 2005-01-21 2005-07-27 哈尔滨工业大学 High-pressure forming method in tubular member for lowering forming pressure
CN101967619B (en) * 2010-11-01 2012-10-31 成都东丽补强科技有限公司 Method for reinforcement repair of pipeline by using metal hot spraying and fibrous composite
US8978432B2 (en) * 2013-02-12 2015-03-17 Caterpillar Inc. Multi-stage tube hydroforming process
CN105537364A (en) * 2016-01-21 2016-05-04 连云港珍珠河石化管件有限公司 Preparation method for bi-metal composite t-branch pipe

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