JP2002181678A - Shape freezability evaluation method for plastic working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape freezability evaluation method evaluating a shape freezability in plastic working of a structure control type new material aimed at function enhancement as a basic material characteristic. SOLUTION: This shape freezability evaluation method for plastic working is characterized by that a material piece 2 to be measured is mounted on a die 1 in an unconstrained state, the material piece is pressed by a punch 3, a difference Δθ between a bending angle of the material piece at this point and a bending angle of the material piece when the pressing force is released afterwards is used as a spring back amount, and the spring back amount is compared with a spring back amount of a known material determined beforehand in the same condition as the spring back amount to evaluate the shape freezability of the material piece.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape freezing property evaluation method for evaluating shape freezing property as a basic material property at the time of plastic working of a structure control type new material for high performance.

[0002]

2. Description of the Related Art Heretofore, macroscopic parameters such as yield stress, tensile strength and elongation obtained from a tensile test have been used as indices when evaluating the shape freezing property of a material. However, in the case of a new material in which the influence of the microstructure is remarkable in the material properties, for example, a composite structure steel, it is difficult to predict the formability from macro parameters. In addition, since the formability of each part is evaluated individually at the manufacturing site, the effects of the shape of the part, material restraint by the mold, load pressure, etc. are all mixed, and the formability unique to the material is separated.・ It is impossible to extract and evaluate.

[0003] In the automotive industry and the like, the use of tough composite structure steels for the purpose of reducing the weight of a vehicle body and improving collision safety has been increasing. In addition, with the increase in the strength of steel, a processing method has been developed in which the rigidity of the material itself is utilized to eliminate constraints during processing and increase the degree of freedom. However, on the other hand, there is a problem that machining accuracy is likely to be poor due to relatively loose constraint conditions, and it is important to accurately grasp the shape freezing property of the material in order to perform accurate machining with that in mind It is. However, at the present stage, there is no basic shape freezing evaluation method for evaluating shape freezing as a material property.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a new shape freezing evaluation method for evaluating the material properties from the influence of the microstructure of the material in toughened composite structure steel, general structural materials, and the like. Accordingly, an object of the present invention is to solve the above problem. The present invention specifies the shape freezing property of a material by measuring the amount of elastic recovery (spring-back amount) after performing unrestricted bending without providing a support by a die in response to pressing by a punch. This evaluation method enables the separation and extraction of influential factors (material microstructure, mold, processing conditions, etc.) that were not possible with the conventional product-level evaluation, and the material's inherent freezing shape Can be accurately evaluated.

[0005]

For this purpose, a technical solution adopted by the present invention is to place a material to be measured on a die in an unconstrained state and press the material to be measured with a punch, and The bending angle of the measured material piece at the time, and then, the difference Δθ between the bending angle of the measured material piece when the pressing force is released is defined as the springback amount, and a known springback amount is obtained in advance under the same conditions as the springback amount. This is a shape freezing evaluation method for plastic working, which comprises comparing the amount of springback of a material and evaluating the shape freezing of a material piece to be measured. Also,
A method for evaluating the shape freezing property of plastic working, wherein the material to be measured is V-bent by a punch.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for evaluating the shape freezing property of plastic working according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of the method for evaluating the shape freezing property of the present invention, and FIG. FIG. 3 is an explanatory view of a method of measuring the amount of springback, FIG. 4 is a front view of a die, FIG. 5 is a front view of a punch, (a) is a tip having a radius of curvature of R = 2 mm, (b) Has a radius of curvature of R = 20 mm at the tip. FIG. 6 is a graph showing the measurement results.

In FIG. 1, reference numeral 1 denotes a die. As shown in FIG. 1, the die has a width larger than at least the width of a material 2 which is a piece of a material to be measured. Is formed. Reference numeral 2 denotes a material as a material to be measured, which is processed as a predetermined material to be measured 2. Reference numeral 3 denotes a punch for pushing the material, which has a width at least larger than the width of the material 2 which is the material piece to be measured, and has a semicircular shape at the tip of the punch 3 as shown in FIGS. Have been. The radius of curvature of the tip is not limited to R = 2 and R = 20 as shown in the figure, but may be a shape having another radius of curvature.

A method for evaluating the shape freezing property of plastic working of a material to be measured by using the die 1 and the punch 3 will be described. First, as shown in FIG. 1, a material piece to be measured is placed on a die in an unconstrained state.
Push in using two things. The pushing amount at this time can be freely set. For example, as shown in FIG. 2, the pushing is performed by changing the pushing amount so that the bending angle of the material piece is 60 °, 90 °, and 120 °. Then, the springback amount for each pushing amount is measured. This springback amount is shown in FIG.
As shown in (2), the bending angle when the material piece is bent with the punch 3 pushed in by a predetermined amount and the bending angle of the material piece when the load by the punch is released are measured, and the difference between them is measured by the springback amount. And For example, as shown in FIG. 2, the bending angle of the material piece by the punch is 60 °, 90 °, 120 °.
Measure the amount of springback at °.

FIG. 6 shows the relationship between the amount of springback and the bending angle. The determined springback amount is measured in advance under the same conditions as described above, and the shape freezing property of the material to be measured is evaluated by comparing the springback amount with various known materials whose shape freezing properties are evaluated. That is, it is evaluated that the shape freezing property of the material piece to be measured has the same degree of shape freezing property as the material having the closest springback amount to the material piece to be measured among the known materials. The amount of springback is a processing error, and the smaller the amount is, the better the shape freezing property is.

Embodiments Embodiments of the present invention will be described below.
The material to be measured has a length of 150 mm, a width of 30 mm, and a thickness of 1.6.
mm steel plate (composite structure steel) was used. There are five types of steel (homogeneous structure steel and composite structure steel), and three types of bending angles (60 degrees, 90 degrees, and 120 degrees) are prepared using the apparatus shown in FIG. Was subjected to a V-bending test to evaluate the shape freezing property. From the measurement results shown in FIG. 6, the composite structure steel has better shape freezing property than the homogeneous structure steel having the same strength, and has the same shape freezing property as the homogeneous steel having the strength one level lower (under 100 MPa). I knew I was doing it.

Although the embodiment of the present invention has been described above, the symmetrical material of the present invention can be widely symmetrical, such as a toughened composite structure steel or a general structural material. Further, the present invention is not limited to the above embodiment, and the present invention can be implemented in any other form without departing from the spirit or main features. Therefore, the above-described embodiment is merely an example in every aspect and should not be interpreted in a limited manner.

[0012]

As described in detail above, according to the present invention, it is possible to correctly evaluate the shape freezing property of a new material having a complicated structure, and it is possible to perform plastic working on a high-strength material which was originally difficult. The technology can be expected to improve dramatically. In addition, it is applicable to the evaluation of formability of all metal materials including non-ferrous metals such as Al and Ti as well as the composite structure represented by Dual Phase steel (PD steel). Further, in the case of iron and steel materials, excellent effects such as the ability to accurately evaluate the freezing property of a composite structure steel having a soft phase and a hard phase can be exhibited.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a shape freezing property evaluation method of the present invention.

FIG. 2 is an explanatory diagram of a state where a piece of a material to be measured is pushed by a punch.

FIG. 3 is an explanatory diagram of a method of measuring a springback amount.

FIG. 4 is a front view of a die.

5A is a front view of the punch, in which the radius of curvature of the tip is R = 2, and FIG. 5B is that in which the radius of curvature of the tip is R = 20.

FIG. 6 is a graph showing measurement results.

[Explanation of symbols]

 1 Die 2 Material to be measured 3 Punch

Claims (2)

[Claims] An object piece to be measured is placed on a die in an unconstrained state, and the material piece to be measured is pressed by a punch, and the bending angle of the material piece to be measured at that time and the pressing force are released. The difference Δθ of the bending angle of the material piece to be measured at the time is defined as a springback amount, and the springback amount is compared with the springback amount of a known material which has been obtained in advance under the same conditions.
A shape freezing evaluation method for plastic working, which comprises evaluating the shape freezing of a material piece to be measured. 2. The method according to claim 1, wherein the material piece to be measured is V-bent by a punch.