Stretch molding method and stretch molding apparatus

Abstract

To provide a stretch forming method and a stretch forming device that can perform ideal stretch forming while improving work efficiency.SOLUTION: A stretch forming method is performed to deform, along a metal die, a long workpiece made of a metallic material while applying stretch load to the workpiece in a longitudinal direction thereof. The method executes: a first step of applying the stretch load to the workpiece partially placed on the die, so as to remove deflection of the workpiece in the longitudinal direction; a second step of deforming the workpiece so as to cause the workpiece to conform to the die; and a third step of applying the stretch load to the workpiece fitting along the die so as to plastically deform the workpiece. Therein at least one of the first and second steps applies, to the workpiece, a stretch load equal to or greater than a yield stress of the metallic material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a stretch forming method and a stretch forming apparatus.

Background Art

[0002] Conventionally, as stretch forming, stretch forming using a mold for stretch forming a long workpiece and a second mold smaller than the mold removably installed in the mold is known (for example, see Patent Document 1). In this stretch forming, in order to reduce the strain difference between the central portion and the end portion of the workpiece caused by residual stress, after performing the first-stage stretch forming by bringing the second mold into contact with the central portion of the workpiece, the second mold is removed, and the second-stage stretch forming is performed by bringing the mold into contact with the entire workpiece.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the stretch forming of Patent Document 1, since it is necessary to use the second mold or perform two-stage stretch forming, the work becomes complicated.

[0005] Therefore, an object of the present disclosure is to provide a stretch forming method and a stretch forming apparatus that can perform suitable stretch forming while improving work efficiency.

Means for Solving the Problems

[0006] The stretch forming method of the present disclosure is a stretch forming method in which a long workpiece made of a metal material is deformed along a mold while a stretch load is applied in the longitudinal direction of the workpiece, and the method comprises: a first step of applying the stretch load to remove deflection of the workpiece in the longitudinal direction with a part of the workpiece placed in the mold; a second step of deforming the workpiece to conform to the mold; and a third step of applying the stretch load to the workpiece along the mold to cause plastic deformation, wherein in at least one of the first and second steps, the stretch load applied to the workpiece is greater than or equal to the yield stress of the metal material.

[0007] The stretch forming apparatus of the present disclosure comprises a mold for deforming a workpiece, a load applying unit for applying a stretch load in the longitudinal direction of a long workpiece made of a metal material, and a control unit for controlling the load applying unit. The control unit controls the load applying unit to perform the following steps: a first step of applying the stretch load to remove deflection of the workpiece in the longitudinal direction while a part of the workpiece is placed in the mold; a second step of deforming the workpiece to conform to the mold; and a third step of applying the stretch load to the workpiece along the mold to cause plastic deformation. In at least one of the first and second steps, the stretch load applied to the workpiece is greater than or equal to the yield stress of the metal material. [Effects of the Invention]

[0008] According to this disclosure, suitable stretch molding can be performed while improving work efficiency. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an explanatory diagram of a stretch molding apparatus and stretch molding method according to the first embodiment. [Figure 2] Figure 2 is an explanatory diagram of a stretch molding apparatus and stretch molding method according to the second embodiment. [Modes for carrying out the invention]

[0010] Embodiments relating to this disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit this disclosure. Furthermore, some components in the embodiments described below are substituted or substantially identical to those easily substituted by those skilled in the art. Moreover, the components described below can be combined as appropriate, and if there are multiple embodiments, each embodiment can be combined.

[0011] [First Embodiment] The stretch forming apparatus 10 and stretch forming method according to the first embodiment are an apparatus and method for deforming a long workpiece W made of a metal material along a mold 15 while applying a stretch load in the longitudinal direction of the workpiece W.

[0012] Workpiece W can be, for example, a solution-treated aluminum alloy as the metal material. Workpiece W can be any metal material that is suitable for stretch forming. Workpiece W is a long object with a long longitudinal length and is formed into an arc shape by stretch forming using the mold 15.

[0013] (Stretch molding machine) Next, the stretch molding apparatus 10 will be described with reference to Figure 1. The stretch molding apparatus 10 comprises a mold 15, a load application unit 16, and a control unit 17.

[0014] The mold 15 is a mold material for forming the workpiece W into an arc shape. The mold 15 has an arc-shaped molding surface on its upper surface, which is a curved surface that is convex upwards. When forming the workpiece W, the center of the workpiece W in the longitudinal direction comes into contact with the top of the molding surface of the mold 15.

[0015] The load-applying unit 16 holds both ends of the workpiece W in the longitudinal direction and applies a stretch load by pulling the workpiece W in the longitudinal direction. The load-applying unit 16 is controlled by the control unit 17 to move the workpiece W relative to the mold 15 and apply the stretch load, thereby performing various processes on the workpiece W.

[0016] The control unit 17 includes, for example, an integrated circuit such as a CPU (Central Processing Unit). The control unit 17 controls the load application unit 16 to execute the stretch forming method described below. In the following description, a solution-treated aluminum alloy is used as the metal material for the workpiece W.

[0017] (Stretch molding method) Next, with reference to Figure 1, a stretch forming method performed by the stretch forming apparatus 10 will be described. The stretch forming method includes the steps of removing the deflection of the workpiece W (first step) S1, deforming the workpiece W according to the mold 15 (second step) S2, and applying a stretch load to the workpiece W to form it into an arc shape (third step) S3.

[0018] Step S1 is a pre-stretching process in which a stretch load is applied to the workpiece W in advance. In step S1, the control unit 17, using the load application unit 16, holds both ends of the workpiece W and places the central part of the workpiece W on top of the mold 15. With the central part of the workpiece W placed on top of the mold 15, the control unit 17 applies a stretch load to the workpiece W using the load application unit 16 that is capable of eliminating deflection. At this time, the control unit 17 applies a stretch load that is greater than or equal to the yield stress of the metal material used in the workpiece W. Specifically, if the metal material is an aluminum alloy, the control unit 17 applies a stretch load such that the plastic strain is between 1% and 2%. As a result, in step S1, a stretch load that causes plastic deformation is applied to the workpiece W.

[0019] Step S2 is a wrapping process of winding the work W around the mold 15. In step S2, the control unit 17 reduces the stretch load applied in step S1 and moves the work W in a direction approaching the mold 15, and installs both ends of the work W on the mold 15. As a result, the area of the surface of the work W that contacts the mold 15 in step S2 is larger than that in step S1. In step S2, the stretch load applied to the work W by the control unit 17 is smaller than the yield stress of the metal material used for the work W. Thereby, in step S2, a stretch load that causes elastic deformation is applied to the work W.

[0020] Step S3 is a post-stretch process of applying a stretch load to the work W. In step S3, the control unit 17 increases the stretch load applied in step S2 and applies a stretch load to the work W along the mold 15. In step S3, the stretch load applied to the work W by the control unit 17 is a stretch load equal to or greater than the yield stress of the metal material used for the work W. Thereby, in step S3, a stretch load that causes plastic deformation is applied to the work W.

[0021] [Second Embodiment] Next, referring to FIG. 2, the second embodiment will be described. FIG. 2 is an explanatory diagram of a stretch forming apparatus and a stretch forming method according to the second embodiment. In the second embodiment, in order to avoid redundant description, parts different from the first embodiment will be described, and parts having the same configuration as those in the first embodiment will be described with the same reference numerals.

[0022] (Stretch Forming Method) The stretch forming method of the second embodiment uses the stretch load in step S2 of the first embodiment as the stretch load that causes plastic deformation of the work W.

[0023] Specifically, in step S2A of the stretch forming method of the second embodiment, the control unit 17 moves the workpiece W toward the mold 15 with the same stretch load as applied in step S1, and places both ends of the workpiece W in the mold 15. In other words, in step S2A, the stretch load applied by the control unit 17 to the workpiece W is greater than or equal to the yield stress of the metal material used in the workpiece W. As a result, in step S2A, a stretch load that causes plastic deformation is applied to the workpiece W.

[0024] In the second embodiment, the stretch load in step S2A was the same as in step S1, but it is not particularly limited, and any stretch load that allows for plastic deformation may be used.

[0025] Furthermore, in the second embodiment, a stretch load that allows plastic deformation was applied to the workpiece W in steps S1 and S2A. In this case, the stretch load in step S3 may be a stretch load that allows plastic deformation, but with a lower stretch amount compared to the first embodiment.

[0026] Furthermore, in the second embodiment, a stretch load that allows plastic deformation of the workpiece W is applied in steps S1 and S2A, but in step S1, the workpiece W may be subjected to elastic deformation.

[0027] As described above, the stretch molding method and stretch molding apparatus described in the first and second embodiments can be understood, for example, as follows.

[0028] A stretch forming method according to the first embodiment is a stretch forming method in which a long workpiece W made of a metal material is deformed along a mold 15 while a stretch load is applied in the longitudinal direction of the workpiece W, and the method is performed as follows: a first step S1 in which a part of the workpiece W is placed in the mold 15 and the stretch load is applied to remove the deflection of the workpiece W in the longitudinal direction; a second step S2 in which the workpiece W is deformed to conform to the mold 15; and a third step S3 in which the stretch load is applied to the workpiece W along the mold 15 to cause plastic deformation, wherein in at least one of the first step S1 and the second step S2, the stretch load is applied to the workpiece W to a value greater than or equal to the yield stress of the metal material.

[0029] With this configuration, in at least one of the first step S1 and the second step S2, the workpiece W can be plastically deformed by applying a stretch load greater than or equal to the yield stress of the workpiece W. Therefore, even when the contact area between the mold 15 and the workpiece W is small, plastic strain can be applied to the entire workpiece W, and residual stress in the workpiece W can be suitably removed. Then, in the third step S3, by applying a stretch load to the workpiece W from which residual stress along the mold 15 has been removed, suitable stretch forming can be performed while suppressing deformation of the workpiece W. In addition, since stretch forming is performed using a single mold 15, work efficiency can be improved.

[0030] In a second embodiment, in the stretch forming method according to the first embodiment, the metal material is a solution-treated aluminum alloy, and in at least one of the first step S1 and the second step S2, the stretch load is applied such that the plastic strain is between 1% and 2%.

[0031] This configuration allows for the effective removal of residual stress generated in solution-treated aluminum alloys.

[0032] In a third embodiment, when the stretch load is applied in the first step S1 and the second step S2 to an amount equal to or greater than the yield stress of the metal material, the stretch load in the first step S1 and the stretch load in the second step S2 are the same load.

[0033] With this configuration, when transitioning from step S1 to step S2, the stretch load does not change, thus further improving work efficiency.

[0034] The stretch forming apparatus according to the fourth embodiment comprises a mold 15 for deforming a workpiece W, a load applying unit 16 for applying a stretch load in the longitudinal direction of a long workpiece W made of a metal material, and a control unit 17 for controlling the load applying unit 16. The control unit 17 controls the load applying unit 16 to perform the following steps: a first step S1 in which a stretch load is applied with a part of the workpiece W placed in the mold 15 to remove deflection of the workpiece W in the longitudinal direction; a second step S2 in which the workpiece W is deformed in accordance with the mold 15; and a third step S3 in which the stretch load is applied to the workpiece W along the mold 15 to cause plastic deformation. In at least one of the first step S1 and the second step S2, the stretch load is applied to the workpiece W at a level equal to or greater than the yield stress of the metal material.

[0035] With this configuration, in at least one of the first step S1 and the second step S2, the workpiece W can be plastically deformed by applying a stretch load greater than or equal to the yield stress of the workpiece W. Therefore, even when the contact area between the mold 15 and the workpiece W is small, plastic strain can be applied to the entire workpiece W, and residual stress in the workpiece W can be suitably removed. Then, in the third step S3, by applying a stretch load to the workpiece W from which residual stress along the mold 15 has been removed, suitable stretch forming can be performed while suppressing deformation of the workpiece W. In addition, since stretch forming is performed using a single mold 15, work efficiency can be improved. [Explanation of Symbols]

[0036] 10 Stretch molding machine 15 molds 16 Load-applying section 17 Control Unit

Claims

1. In a stretch forming method in which a long workpiece made of a metal material is deformed along a mold while a stretch load is applied in the longitudinal direction of the workpiece, The first step involves placing a portion of the workpiece in the mold and applying the stretch load that causes plastic deformation to the workpiece to remove the deflection of the workpiece in the longitudinal direction, A second step of deforming the workpiece in accordance with the mold, A third step is performed in which the stretch load is applied to the workpiece along the mold to cause plastic deformation, The first step is a stretch forming method in which a stretch load equal to or greater than the yield stress of the metal material is applied to the workpiece.

2. The aforementioned metal material is a solution-treated aluminum alloy. The stretch molding method according to claim 1, wherein in at least one of the first step and the second step, the stretch load is applied such that the plastic strain is between 1% and 2%.

3. The stretch forming method according to claim 1, wherein, in the first step and the second step, when the stretch load is applied that is greater than or equal to the yield stress of the metal material, the stretch load in the first step and the stretch load in the second step are the same load.

4. A mold that deforms the workpiece, A load-applying unit that applies a stretch load in the longitudinal direction to a long workpiece made of metal material, The system comprises a control unit for controlling the load application unit, The control unit controls the load application unit, The first step involves placing a portion of the workpiece in the mold and applying the stretch load that causes plastic deformation to the workpiece to remove the deflection of the workpiece in the longitudinal direction, A second step of deforming the workpiece in accordance with the mold, The third step involves applying the stretch load to the workpiece along the mold to cause plastic deformation. The first step involves a stretch forming apparatus that applies a stretch load to the workpiece that is greater than or equal to the yield stress of the metal material.

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