JP2004351478A - Tube hydroforming loading path determination method, tube hydroforming apparatus, and method for manufacturing metal member using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for deciding a loading path for tube hydroforming by which the optimum loading path for tube hydroforming can be decided, and a tube hydroforming device and a method for manufacturing a metal member using them. <P>SOLUTION: When the loading path for tube hydroforming is decided, this method is performed with an FEM (finite element method) simulation, and a surface area S and a volume V in the remarked range at each analyzing step, are calculated and the loading path is corrected so that ratio v of V<SP>1/3</SP>and S<SP>1/2</SP>(ν=V<SP>1/3</SP>/S<SP>1/2</SP>) becomes not less than a threshold value, and the loading path is decided by repeating this correction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２９】
【発明の効果】
本発明によれば、最適なチューブハイドロフォーミング用ローディングパスを決定することができる。
なお、本発明を実現するためのチューブハイドロフォーミング装置を用いれば、副次的な効果として、従来のチューブハイドロフォーミング装置は作業者がローディングパスデータを制御盤に手で入力するケースが多く、該データの入力ミスが起こりうるところ、入力ミスも防げる。
【図面の簡単な説明】
【図１】シワが発生したチューブハイドロフォーミング成形後製品の外観を示す図である。
【図２】（ａ）は図１の場合と同じ金型を用い、図１の場合とわずかに異なるローディングパスをとったチューブハイドロフォーミングでシワが発生しなかった成形後製品の外観を示す図であり、（ｂ）は（ａ）の成形について成形圧力と減肉率の関係をＦＥＭシミュレーションと実験とで比較して示した図である。
【図３】ＦＥＭシミュレーション結果から注目領域の体積Ｖを算出する方法の説明図である。
【図４】本発明によるローディングパス決定方法の一例を示す流れ図である。
【図５】ローディングパスの好適な修正方法の説明図である。
【図６】２種類のパラメータＶ／ＳおよびＶ^１／３ ／Ｓ^１／２ の、シワ発生の有無を予測する指標としての有用性を比較して示した図である。
【図７】本発明によるローディングパスと従来のものとを比較して示した図である。
【図８】本発明を実現するためのチューブハイドロフォーミング装置の全体を示す図である。
【符号の説明】
１ 管（金属パイプまたは金属チューブ）
２ 注目領域
３ 仮想領域
５ 金型
１０ 計算機
２０ 防塵用カバー
３０ 制御盤
４０ 電磁弁
５０ 液圧シリンダ
６０ 絞り弁
７０ リリーフ弁
１００ ハイドロフォーミング装置
Ｅ 伝送径路
Ｆ 伝送径路
Ｇ 伝送径路
Ｐ 液圧の供給源（ポンプ）
Ｔ タンク（液体の戻り）
ＰＴ 圧力センサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for determining a loading path of tube hydroforming, a method for manufacturing a tube hydroforming apparatus, and a method for manufacturing a metal member. For example, a member represented by an automobile part or the like is formed by forming a metal tube by tube hydroforming. In manufacturing, a method of determining a loading path of tube hydroforming capable of optimally determining a loading path which is an application schedule of an axial pressing amount and a molding pressure, a tube hydroforming apparatus, and a method of manufacturing a metal member by tube hydroforming using the same. About the method.
[0002]
[Prior art]
Automobile parts, for example, in the frame of an automobile body, a front side frame and a subframe which is one of the underbody parts are examples, and the structure of an automobile, an electric appliance, an industrial machine, a plant, etc. is included. A metal member obtained by hydroforming a pipe (metal pipe) may be used as the member. Tube hydroforming (abbreviation HF), that is, tube hydroforming (abbreviation THF), is a method in which a tube is charged into a mold having a desired shape, and both ends (hereinafter, referred to as "axial") of a metal tube to be formed. A method of forming a desired shape by applying pressure (forming pressure) to the liquid (water, oil, etc.) placed inside the tube while applying force with an axial pushing punch from the end of the tube. is there.
[0003]
In THF, when the pressure applied to the liquid is too small, the tube cannot be formed sufficiently to the shape along the mold. Insufficient molding may occur, or the axial pushing amount may be too small, the wall thickness of the tube may increase, and the tube may break. In order to prevent the buckling of the tube due to excessive pressing or excessive axial pushing, and to complete the molding successfully, the axial pushing amount, which is two process parameters contributing to the molding, is required. It is important that the change in time is consistent with the molding pressure. That is, it is important to select the most suitable combination of the temporal changes of these two process parameters. However, it is not easy to find the optimal combination, and since it is currently determined by skilled workers based on experience, it takes a lot of time and effort to find the optimal combination, and efficiency is high. In some cases, the loading path that is considered optimal is not always optimal. Here, the loading path is an application schedule of the axial pressing amount and the molding pressure, that is, a temporal change, and is represented by a formula (formula, diagram, table, or the like) that defines the temporal change of these process parameters. .
[0004]
In addition, the FEM (finite element method) simulation of tube hydroforming finds a loading path that does not cause insufficient molding or buckling as described above, and searches for an optimal loading path by actually applying the method to metal pipe molding. Attempts to save time and effort have been made, but searching for an optimal loading path by FEM simulation requires the experience of a skilled worker, as in a production site, and is still not efficient.
[0005]
Therefore, Prof. Altan of Ohio State University (abbreviation: OSU) has developed and announced a method of searching for an optimal loading path called adaptive simulation (abbreviation: AS) (see Non-Patent Document 1). In this method, the following processing is performed on an area S and a volume V of a designated region of a tube being formed in an FEM simulation.
(1) First, V_fcIs the volume inside the tube in the designated region, and S is the surface area of the tube in the designated region, and a FEM simulation is performed by a method called a self-feeding method, and V_fcAnd S are the functions V of time τ, respectively._fc ^self(Τ), S^self(Τ), then V_fc ^self(Τ) and S^selfFrom the relationship (τ), the function S^self(V_fc).
(2) Next, when determining the loading path, the above-described AS is performed,
V (τ) = (V_fc(Τ) -V_fc ^self(Τ₀)) / (V_fc ^self(Τ_f) -V_fc ^self(Τ₀)) ‥‥ (1)
τ₀: Start time, τ_f: End time
, A time function V (τ) indicating the volume as a dimensionless index is obtained, and S (V) is obtained from this V (τ) and S (τ) separately obtained. It is an indicator of wrinkles that can occur in pipes,
W (V) = (S (V) / S^self(V) -1) × 100 ‥‥ (2)
Is calculated, and a series of processes of adjusting the loading path so that wrinkles do not occur by making W (V) fall within a certain range are repeated.
[0006]
[Non-patent document 1]
Annals of 51st CIRP, Nancy (France), agosto 2001.
[0007]
[Problems to be solved by the invention]
In the actual tube hydroforming and the FEM simulation, if the axial pressing amount is too large, wrinkles are generated or the metal tube to be formed buckles and the desired shape cannot be obtained. If is too small, the wall thickness of the pipe becomes too large and breaks. Therefore, a loading path that performs tube hydroforming while increasing the axial pressing amount as much as possible so that wrinkles do not occur or even if wrinkles eventually disappear is optimal. Therefore, the point is how to quantitatively capture and monitor wrinkles that may occur by FEM simulation.
[0008]
In view of this point, the AS method of Non-Patent Document 1 is very effective, but there is a problem that if the tuning parameters cannot be set well, it is difficult to investigate the cause because the formula is complicated. . It was even more so for use at production sites. Further, in recent years, the situation has become more difficult, such as the use of more difficult-to-mold tubes, especially for automotive parts.
[0009]
An object of the present invention is to solve the above-described problems and provide a method for determining a loading path of tube hydroforming that can easily determine an optimal loading path, a tube hydroforming apparatus, and a method for manufacturing a metal member using them. It is in.
[0010]
[Means for Solving the Problems]
As a result of repeated studies with reference to the AS method of Non-Patent Document 1, the present inventors have found a simpler method of quantifying wrinkles, and have accomplished the present invention. That is, the present invention is as follows.
(1) In determining the loading path of tube hydroforming, an FEM simulation is performed, and the surface area S and volume V of the region of interest of the tube are calculated for each analysis step.^1/3And S^1/2Ratio ν = V^1/3/ S^1/2A loading path determination method for tube hydroforming, wherein the loading path is corrected so that is equal to or larger than a predetermined threshold value, and the loading path is determined by repeating the correction.
(2) The method for determining a loading path for tube hydroforming according to (1), wherein the threshold value is changed when the maximum thinning amount calculated by the FEM simulation exceeds a limit value.
(3) a mold; hydraulic cylinders disposed at both ends in the axial direction of the mold, which operate in the axial direction of the metal tube to be formed inside the mold; and an electromagnetic valve for switching the operating direction of the hydraulic cylinder. A liquid pressure supply source for supplying liquid to the solenoid valve, a computer having a function of determining a loading path therein, and a control panel for controlling a molding pressure and an axial pressing amount by a command from the computer. A tube hydroforming apparatus characterized by the above-mentioned.
(4) A method for manufacturing a metal member, comprising: manufacturing a metal member by tube hydroforming according to the loading path determined by the method for determining a tube hydroforming loading path according to (1) or (2).
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
1 and 2 show the results of FEM simulations when an experiment was conducted in which a subframe, which is one of the undercarriage parts of an automobile, was formed by tube hydroforming. FIG. 1 shows the appearance of the molded product when wrinkles occurred, and FIG. 2A shows the appearance of the molded product when wrinkles did not occur. Both loading paths are very close, with only slight differences leading to wrinkling. FIG. 2B shows the relationship between the molding pressure and the wall thinning rate in the case where no wrinkles are generated by comparing the results of the FEM simulation with the results of the experiment. In the drawings, experimental data during molding was obtained by measuring the wall thickness of a sample in which molding was stopped halfway. The results of the FEM simulation and the results of the experiment are in good agreement, and it can be said that the accuracy of the FEM simulation is sufficient.
[0012]
In FIG. 1, a region of a pipe where a wrinkle occurs is defined as a region of interest in the present invention. In this region, the case where the wrinkle is generated and the case where the wrinkle is not generated, the FEM simulation results of both loading paths are used. The time-dependent changes in the surface area S (surface area of the space surrounded by the outer circumference of the pipe) and the volume V (volume of the space surrounded by the outer circumference of the pipe) were sequentially captured. The surface area S was defined as the sum of the surface areas of the elements in the region of interest. As shown in FIG. 3, for example, as shown in FIG. 3, in a virtual area 3 (a cubic or rectangular parallelepiped having a volume Vc) including a target area 2 of a pipe, a point group having a total number N is virtually stored in a computer using random numbers. Generated, and whether or not the point group is inside the region of interest is determined by FEM simulation performed in the computer, and the number C of points determined to be inside is determined by the following equation.
V = C / N × Vc ‥‥ (3)
Was calculated. The vertical and horizontal scales of the point cloud plot on the right side of FIG. 3 are positional coordinates used in the FEM simulation.
[0013]
When wrinkles occur, the volume V decreases and the surface area S increases. Therefore, by using a parameter that combines V and S, it is possible to quantitatively capture and predict wrinkles and determine whether or not wrinkles have occurred. Initially, the inventors have newly added V / S in addition to V / S, which has been often used in the past.^1/3/ S^1/2We decided to try two types. This is because the latter is considered to be a better parameter because it is dimensionless. This point is determined by the V / S and V using the surface area S and the volume V of the attention area calculated by the FEM simulation in each of the case of FIG. 1 (wrinkle generation) and the case of FIG. 2A (no wrinkle generation).^1/3/ S^1/2As a result of reproducing and showing the temporal change of V, as shown in FIG.^1/3/ S^1/2Is supported by the fact that the case where wrinkles occur and the case where no wrinkles occur can be more clearly distinguished above and below the threshold. Therefore, in the present invention, as an index for predicting the presence or absence of wrinkles in tube hydroforming, the ratio of the volume V and the surface area S in one dimension is used.
ν = V^1/3/ S^1/2                ‥‥ (4)
It was adopted.
[0014]
For example, in the case of FIG. 6, a threshold value of ν at which the generation of wrinkles is suppressed (a boundary value between wrinkles and no wrinkles) ν_limitFor example, at a stage after the tube and the mold partially contact each other, for example, 0.491, and at a stage before the contact, for example, an initial value (a value before molding) of 0.485 can be adopted. . ν is the threshold ν_limitIn other words, if ν is the threshold ν_limitIf the time is changed as described above, it means that no wrinkles are generated. Note that ν_limitIs not limited to these values. For example, at the stage after the former tube and the mold partially come into contact with each other, they can be set anywhere within the hatched area shown in the lower part of FIG. Since it is preferable to set a threshold value near the center for safety against some disturbance, the value is set as described above. In the latter case, the area is relatively narrow, but the same is true.
[0015]
As described above, the provisional threshold value ν which will be described later with reference to FIG._limitBy setting as, even when the actual tube hydroforming is performed at the same time as the FEM simulation, the problem of wrinkles is practically avoided. Actually, when a vibration occurs due to a disturbance such as a variation in the strength of a tube as a material or a hydraulic pressure fluctuation of a molding pressure, ν <ν_limitHowever, the actual problem is that the FEM simulation is performed for each analysis step, and the maximum wall thickness reduction th is_maxEven if there is a larger analysis step, the threshold ν_limitBecause it works to lower the wrinkles, it is not easy to actually develop wrinkles.
[0016]
The above can be said in the case of the same pipe material and dimensions when the threshold value is found from the case of wrinkle occurrence and the case of no wrinkle occurrence, but when performing hydroforming on pipes of different materials and dimensions, First, try only the FEM simulation (in the process, ν <ν_limit), The optimal loading path (where ν ≧ ν for this optimal loading path)_limitThere is no problem if the actual tube hydroforming is performed at the same time as the FEM simulation at the same time. In this case, of course, a threshold value obtained by performing only the FEM simulation is provisionally set.
[0017]
In addition, the inventors performed FEM simulations on parts having various shapes, and as a result, ν in a state where the tube and the mold were in contact with each other._limitIs obtained from the volume V and the surface area S calculated for the portion corresponding to the region of interest of the tube using the shape data of the mold instead of the tube, and ν of the formula (4) is obtained. It has also been found that a product multiplied by the coefficient can be adopted. The coefficient is set at several levels between 0.99 and 1.00, and the optimum value is set (the optimum value is obtained by performing the FEM simulation with each coefficient, the visual shape of the molded pipe based on the simulation result, and It is possible to select a pipe whose wall thinning rate best matches those of the tubes after the actual molding.) In fact, a sufficiently good result can be obtained by experimenting with about three levels of this coefficient.
[0018]
In addition, it is necessary to select a place where wrinkles are likely to occur as a region of interest of the pipe. Since it is known from experience that the locations that are easy to be bent are limited to some extent, such as inside the bend, it is better to select such locations. It should be noted that the size of the region of interest is preferably as small as possible because the smaller the size of the region of interest, the more clearly the presence or absence of wrinkles can be determined by the parameter ν.
[0019]
An example of the loading path determination method of the present invention using the above parameter ν will be described with reference to the flowchart shown in FIG. This includes a virtual case in which only the FEM simulation is performed and a case in which actual tube hydroforming is performed simultaneously with the FEM simulation.
First, the provisional loading path and the threshold ν_limitIs temporarily set, and the dimensions (outer diameter D, wall thickness t) of the metal tube as the material are₀) And yield stress σ_yPlastic deformation start pressure p calculated from_iIncrease the molding pressure without pushing the shaft up to. Next, analysis of wrinkles is performed by FEM simulation. Here, a parameter ν is calculated from V and S of the attention area, and a preset threshold ν_limitIf it is less than this, only the molding pressure is increased by Δp without axial pressing, and if it is more than that, the molding pressure is maintained and the axial pushing amount (length) is virtually increased by Δd.
[0020]
Next, the maximum thinning amount th in the attention area is calculated, and th is the thinning amount limit value th._maxIf greater, the threshold ν_limitIs preferably changed (reduced) so that it returns to the beginning and starts the calculation again. th is the thickness reduction limit th_maxIf it is less than or equal to the above, when the actual tube hydroforming is performed simultaneously, Δp or Δd is actually increased, and the contact ratio α between the tube and the mold is calculated. Returning to the beginning of the analysis of ν, ν for ν after the virtual increase of Δp or Δd_limitCompare with. If it exceeds 90%, the increment of the axial pushing amount is_fThe molding pressure is fixed virtually or actually to the maximum molding pressure p._maxUp virtually or actually. Maximum molding pressure p_maxIs the maximum value in the specifications of the tube hydroforming equipment. In order to form the tube firmly along the mold to the R part of the corner after molding, it is necessary to increase the molding pressure to this maximum molding pressure. is there. Also, Δd_fAs the tube is finally molded along the mold, push both shaft ends in as far as it will not be excessive, so that it will follow the deformation of the tube so as to shorten it. It is a value that is found from experience and is preferably about 0 to 10 mm, although it depends on the shape of the product after molding.
[0021]
Then the maximum molding pressure p_maxThe maximum thinning amount th is calculated, and the th is the thinning amount limit value th_maxIf greater, the threshold ν_limitIs changed (reduced), and the process returns to the beginning and starts the calculation again; otherwise, the calculation ends.
If the above is considered as one step, and it is considered as one step for the analysis of the FEM simulation and also for the tube hydroforming when the actual tube hydroforming is performed in parallel, the calculation is performed for each analysis step of the FEM simulation in this way. Ν and threshold ν_limitIn order to predict whether or not wrinkles have occurred or to perform actual tube hydroforming in parallel, the data relating to the axial pushing amount by a Silnac sensor or the like and the measurement value output from the pressure sensor PT are used in the FEM simulation. Ν and ν calculated by reflecting each analysis step_limitIn the case where wrinkles occur, the loading path is corrected, and only when no wrinkles occur, it is determined whether or not the maximum thinning amount does not exceed the limit value._limitTo change. The reason for this is that whether or not the pipe is sufficiently molded up to the shape along the mold, that is, the wrinkle is higher than the wall thinning as a priority for determining the formability (if wrinkles occur, Molding immediately fails, but thinning has a relatively large allowable range). By repeating the above steps, the loading path is gradually corrected and determined. In the loading path determined in this way, ν calculated for each analysis step is a threshold ν_limitThat is all.
[0022]
Now, the loading path obtained by the present invention may be actually used for tube hydroforming as it is, but as shown by the dotted line in FIG. It is preferable to use a step-like loading path that is connected to each vertex and corrected as shown by a solid line.
FIG. 7 shows the result of actually applying the loading path obtained by the present invention to tube hydroforming (example of the present invention), the loading path empirically optimized by experiment (conventional example A; no wrinkle generation) and The results are shown in comparison with a loading path (conventional example B) in which wrinkles occur as a result of an experiment. In the example of the present invention, the final axial pressing amount is smaller than that of the conventional examples A and B, and the molding pressure corresponding to the same axial pressing amount is shifted to a higher pressure side than the conventional examples A and B. This means that the molding was conventionally performed by assisting the low molding pressure with the axial pressing, and the loading path which tends to cause excessive amount of axial pressing, that is, buckling of the pipe, generation of local wrinkles, etc. Means that hydroforming was performed. In this regard, the present invention has been able to perform hydroforming with a better loading path. When the maximum wall thinning rate was measured, it was 26.7% in the conventional example A, but was reduced to 24.3% in the example of the present invention, and the effect of the present invention was confirmed.
[0023]
In addition, as described above, thinning is usually a problem when the shaft pushing is too small.However, even if correcting the excessive shaft pushing here, the decrease in the wall thinning is due to excessive shaft pushing. It is presumed that this was due to the fact that there was no longer a place where the wall thickness was abnormally large at a smaller place because the abnormal deformation called buckling of the pipe was about to occur.
[0024]
Next, a hydroforming apparatus for actually realizing the loading path determination method according to the present invention will be described with reference to FIG. The computer 10 for performing the FEM simulation preferably has a personal computer covered with a dust-proof cover 20. As the FEM simulation software, any of a dynamic explicit method, a static explicit method, and a static implicit method is preferably used. From the viewpoint of reducing the time required for the FEM simulation and the accuracy, the inventors consider that the dynamic explicit method is optimal. The loading path obtained by the present invention is stored in the above-described computer 10 as table data relating to, for example, [time]-[forming pressure] and [time]-[axial pressing amount], and the transmission path E is stored. Then, it is transmitted to the control panel 30 of the tube hydroforming apparatus. The table data may be stored in a text format (ASCII format) or in a format of a commonly used spreadsheet software.
[0025]
A command from the control panel 30 is received via the transmission path F, and the solenoid valve indicated by 40 in FIG. 8 switches the hydraulic cylinder of the liquid sent from a supply source P (pump) of hydraulic pressure such as hydraulic oil. It controls so that the supply to 50 may be adjusted. The hydraulic cylinder 50 is configured to transmit data relating to the axial pushing amount to the control panel 30 via the transmission path G by using, for example, an embedded cylinder (not shown) in which a silnack sensor is embedded (for example, a rod). The control is performed so that the axial pushing amount becomes the same as the table data of the loading path. It is desirable to provide a mechanism that makes the rod of the hydraulic cylinder difficult to move. If the solenoid valve 40 is switched in a state where the rod is difficult to move, the molding pressure can be easily adjusted. It is preferable to perform the control with the goal of achieving the data. In the example shown in FIG. 8, a DS3P (Double Solenoid 3 Position) type solenoid valve is used, but a servo valve may be used.
[0026]
The mechanism for making the rod of the hydraulic cylinder difficult to move can be realized, for example, as follows. A throttle valve 60 is provided on the hydraulic cylinder 50 side of the electromagnetic valve 40. If the pressure is reduced, even if the same liquid pressure is applied, the flow rate is reduced because the flow path is restricted, but the pressure of the liquid supplied to the hydraulic cylinder can be increased since the flow path is not closed. However, since the flow rate of the liquid supplied from the supply source of the hydraulic pressure is constant, the surplus returns to the tank T via the relief valve 70. This relief valve is a valve having a mechanism in which a flow path opens when a certain pressure called a cracking pressure is exceeded. Both the throttle of the throttle valve 60 and the cracking pressure of the relief valve 70 are adjusted by an actuator (not shown) by a command from the control panel 30 via a transmission path (not shown).
[0027]
【Example】
A steel pipe (dimensions: φ35 mm × 2.3 mmt × 1000 mmL) equivalent to JIS STKM12A was used as a material, and as an example, 10000 according to the loading path determined by the present invention example (the above-described method), and as a comparative example, as in Conventional Example A The same number of materials were subjected to tube hydroforming using a mold corresponding to the shape of the product after molding in FIG. 2 (a) according to a loading path empirically determined by an experiment. The average value of the results of measuring the minimum wall thickness of 100 pieces, each of which was randomly extracted from 10,000 pieces of each product after molding, and the number of breaks or wrinkles, and 10,000 pieces after molding were investigated. Table 1 shows the results. As shown in the same table, in the example, the number of wrinkles was less than in the comparative example, the average minimum thickness was large, and the method of manufacturing a metal member by the loading path determination method of the present invention was superior to the conventional method. Moldability was shown.
[0028]
[Table 1]

[0029]
【The invention's effect】
According to the present invention, an optimal tube hydroforming loading path can be determined.
Incidentally, if a tube hydroforming device for realizing the present invention is used, as a secondary effect, in the conventional tube hydroforming device, an operator often inputs loading path data to a control panel by hand. Where data input errors can occur, input errors can also be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing the appearance of a tube hydroformed molded product having wrinkles.
FIG. 2 (a) is a view showing the appearance of a molded product in which no wrinkles are generated by tube hydroforming using a slightly different loading path from the case of FIG. 1 using the same mold as in FIG. (B) is a diagram showing the relationship between the molding pressure and the wall thinning rate in the molding of (a) by comparing the results with FEM simulations and experiments.
FIG. 3 is an explanatory diagram of a method of calculating a volume V of a region of interest from an FEM simulation result.
FIG. 4 is a flowchart illustrating an example of a loading path determination method according to the present invention.
FIG. 5 is an explanatory diagram of a preferred method of correcting a loading path.
FIG. 6 shows two types of parameters V / S and V^1/3/ S^1/2FIG. 3 is a diagram comparing and showing the usefulness as an index for predicting the occurrence of wrinkles.
FIG. 7 is a diagram showing a comparison between a loading path according to the present invention and a conventional one.
FIG. 8 is a diagram showing an entire tube hydroforming apparatus for realizing the present invention.
[Explanation of symbols]
1 pipe (metal pipe or metal tube)
2 Attention area
3 virtual area
5 Mold
10 Computer
20 Dustproof cover
30 Control panel
40 solenoid valve
50 hydraulic cylinder
60 Throttle valve
70 Relief valve
100 Hydroforming device
E Transmission path
F Transmission path
G transmission path
P hydraulic pressure source (pump)
T tank (return of liquid)
PT pressure sensor

Claims (4)

In determining the loading path of tube hydroforming, FEM simulation is performed, and the surface area S and volume V of the region of interest of the tube are calculated for each analysis step, and the ratio ν = V ¹ between V ^1/3 and S ^1/2. A loading path determination method for tube hydroforming, wherein the loading path is corrected so that ^{/ 3} / S1 / ² is equal to or greater than a predetermined threshold value, and the loading path is determined by repeating the correction. The method for determining a loading path for tube hydroforming according to claim 1, wherein the threshold value is changed when the maximum thinning amount calculated by the FEM simulation exceeds a limit value. A mold, hydraulic cylinders disposed at both ends of the mold in the axial direction of the mold to operate in the mold in the axial direction inside the mold, an electromagnetic valve for switching an operation direction of the hydraulic cylinder, A liquid pressure supply source for supplying liquid to the valve, a computer having a function for determining a loading path therein, and a control panel for controlling a molding pressure and an axial pressing amount by a command from the computer are provided. Tube hydroforming equipment. A method for manufacturing a metal member, comprising: manufacturing a metal member by tube hydroforming according to the loading path determined by the method for determining a loading path for tube hydroforming according to claim 1.

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