JPH08114533A - Platen working method for metal test piece - Google Patents

Abstract

PURPOSE: To simply and accurately give the required compression plastic distortion quantity to a test piece by previously obtaining the relation of hardness of a metal test piece, dimension of chips, compression plastic distortion quantity, and load to be applied to the chips, and continuously measuring the load during the platen working. CONSTITUTION: In the case of the platen working of a test piece 1 made of the material to be used for a large special steel structure, diameter of an upper and a lower chips 10, 11 are decided, and the compression plastic distortion quantity to be given is obtained on the basis of the plate thickness of the test piece 1, and the compression plastic distortion quantity is input with the hardness of the test piece to a compression plastic distortion quantity computing unit 12. The computing unit 12 obtains the load to be applied to the chips 10, 11 in response to the distortion quantity on the basis of the selected working curve. A driving device 7 is driven so as to elevate an upper dies 6 and a compressing member 8 in the arrow A direction, and the test piece 1 provided with a notch 2 is inserted into a space between the chips 10, 11, and set so as to coincide with the position of the chips 10, 11. In this condition, the compression part of the test piece 1 is compressed by the chips 10, 11. The computing unit 12 continues the compression till the computed load obtained on the basis of the working curve coincides with the measured load input from the load cell 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a platen processing method which is carried out prior to a fracture toughness test of a metal test piece.

[0002]

2. Description of the Related Art Conventionally, in the design of large structures such as ships, offshore structures, or onshore tanks, which are made by welding, in order to enhance the safety against brittle fracture, the welded portion is crack opening displacement based on fracture mechanics. (Crack o
Penning displacement (hereinafter abbreviated as COD)) is being conducted to clarify its value. Therefore, it is necessary to carry out a COD test in order to develop materials and evaluate brittleness of new products.

Generally, in the COD test, it is usual to make a notch in a metal test piece for a fatigue test, and the position of the notch is generally a welded portion which is considered to have poor toughness. Many. However,
Residual stress exists in the welded part, which often makes it impossible to make fatigue cracks uniform. Therefore, in order to remove the residual stress caused by welding and to make the fatigue crack uniform, the area where the notch is formed is locally 0.3 to the thickness of the test piece.
Platen processing that gives a compressive plastic strain of about 1% is performed.

This platen processing is carried out, for example, according to actual fair 2-4.
There is a proposed method in Japanese Patent No. 5800, which will be described with reference to FIGS. Although FIG. 1 is a front view of a platen processing apparatus for carrying out the method of the present invention, the parts described in the following description are the same as those of the prior art. FIG. 2 is a perspective view of the test piece, which is the same as the present invention and the prior art. First, a notch 2 is formed on one side of a welded portion of a test piece 1, and the notch 2 is provided between the tips 10 and 11 having a truncated cone shape, at least near the tip of the notch 2 to be compressed 3.
After that, the driving device 7 is driven to apply a load to the compression member 8 through the upper die 6 to press down the test piece 1 and apply a compressive plastic strain to the portion. is there.

[0005]

However, the compressive plastic strain amount (depression amount) in this platen processing is
It depends on the plate thickness. Furthermore, the chip to be used 10,
Since the diameter of 11 differs depending on the structure (ship, marine structure, land tank, etc.) in which the base material of the test piece is used, in the method proposed in Japanese Utility Model Publication No. 2-45800, "Test piece" is used. Set-Platen Processing-
Repeat the test piece removal-compression plastic strain amount measurement several times,
The platen processing was completed when the compressive plastic strain amount reached the target amount. For this reason, this platen processing requires a lot of time and labor, and its processing accuracy is poor. Furthermore, the compressive plastic strain is 1 mm at the deepest.
Since it is a degree, it requires a great deal of skill to actually measure it. An object of the present invention is to give a required amount of compressive plastic strain to a test piece simply and accurately without requiring skill.

[0006]

Means for Solving the Problems The present invention is to solve the above-mentioned problems. The means is to sandwich a metal test piece for a crack opening displacement test between upper and lower chips and apply a load to the chips. According to the platen processing method of giving a local compressive plastic strain to the metal test piece, the relationship between the hardness of the metal test piece, the size of the tip, the amount of compressive plastic strain, and the load to be applied to the tip is obtained in advance. Based on the relationship, the hardness of the metal test piece to be tested, the size of the chip to be used, the load applied to the chip from the required amount of compressive plastic strain is determined, and the load applied to the chip during platen processing is continuously determined. Is measured and the load is applied to the chip until the measured load reaches the determined load.

[0007]

The present inventors have conducted various experiments and studies to automatically obtain a desired amount of compressive plastic strain without taking out a test piece during platen processing as in the past and actually measuring it. As a result, we found the following facts. (1) The amount of compressive plastic strain applied to a test piece is 0.3 to 1% of the plate thickness of the test piece, and the amount varies depending on the plate thickness of the test piece, so it is necessary to apply a corresponding load to the chip. There is. (2) In order to give a predetermined amount of compressive plastic strain to the test piece, it is necessary to apply a load according to the hardness of the test piece to the chip. (3) Since the diameter of the chip used for platen processing differs depending on the test piece (the diameter of the chip is determined by the application of the material used for the test piece, that is, the structure in which the material is used), A corresponding load needs to be applied to the tip.

From this, as shown in the graph of FIG. 3, the relationship between the load applied to the tip and the amount of compressive plastic strain generated in the test piece was obtained in advance as a calibration curve corresponding to the hardness of the test piece and the diameter of the tip. Every time, the required load is calculated from the amount of compressive plastic strain (determined from the plate thickness of the test piece), hardness, and chip diameter of the test piece to be platen processed this time, and the load applied to the chip during platen processing is continuously measured. By stopping the processing when the measured load reaches the load obtained from the calibration curve, a desired amount of compressive plastic strain can be obtained with high accuracy.

[0009]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a front view of a platen processing apparatus for carrying out the method of the present invention. In the figure, 4 is a column erected on a pedestal 5, 6 is an upper die that is vertically movable on the column 4, and 7 is a column. Drive device provided on top of the upper die 6, 8
Is a compression member provided below the upper die 6 via a load cell 9, 10 is a cylindrical upper chip detachably provided at the lower end of the compression member 8, and 11 is a pedestal so that its central axis coincides with that of the upper chip 10. 5, a lower chip detachably provided on the upper part 12,
Is a compressive plastic strain amount calculation unit for calculating the compressive plastic strain amount in the platen processing, and as shown in FIG. 3, the Vickers hardness of the test piece 2 to be platen processed and the chips 10, 1
A calibration curve showing the relationship between the load applied to the test piece 1 and the amount of compressive plastic strain for each diameter of 1 is stored and set. Reference numeral 13 is a display device using a cathode ray tube.

Next, the case where the test piece 1 of the material used for the large special steel structure is platen-processed will be described. (1) First, since the test piece 1 is a material used for a large-scale special steel structure as described above, the upper and lower chips 10,
Determine the diameter R of 11. (2) Further, the compressive plastic strain amount h applied to the test piece 1 is obtained from the plate thickness H of the test piece 1 (the compressive plastic strain amount h is 1% of the plate thickness H). (3) The calculated diameter R of the upper and lower chips 10 and 11, the compressive plastic strain amount h, and the hardness TS of the test piece 1 are input to the compressive plastic strain amount calculation unit 12.

(4) As a result, the compressive plastic strain amount calculation unit 1
In 2, the calibration curve used this time is selected based on the input diameter R of the upper and lower chips 10 and 11 and the hardness TS of the test piece 1. Then, the load Q applied to the chips 10 and 11 is obtained based on the selected calibration curve and the input compressive plastic strain amount h, and is output to the compressive plastic strain amount calculating unit 12 and the display device 13.

(5) Next, the operator drives the driving device 7 to raise the upper die 6 and the compression member 8 in the direction of arrow A to form a space between the upper chip 10 and the lower chip 11. (6) Further, insert the test piece 1 provided with the notch 2 in the space between the upper tip 10 and the lower tip 11 so that the position of the compressed portion 3 coincides with the positions of the upper tip 10 and the lower tip 11. Set to.

(7) In this state, the drive unit 7 has the above (5)
By driving in reverse, the upper die 6 and the compression member 8
Is lowered in the direction of arrow B, and the compressed portion 3 of the test piece 1 is compressed by the upper tip 10 and the lower tip 11. (8) During this period, the load Q _O applied to the compressed portion 3 of the test piece 1
Is measured by the load cell 9, and the measurement signal is output to the compressive plastic strain amount calculation unit 12 and the display device 13.

(9) As a result, the compressive plastic strain amount calculation unit 12
Drives the driving device 7 until the calculated load Q obtained from the calibration curve and the measured load Q _O input from the load cell 9 match. (10) When the calculated load Q and the measured load Q _O match, the drive of the drive device 7 is stopped and the platen processing is completed.

Further, the confirmation of the operation load Q and the measured load Q _O are coincident with the driving device 7 is stopped operator carried out by the display device 13. The stopping operation of the driving device 7 is automatically performed by the compressive plastic strain amount calculating unit 12 as described above, but the present invention is not limited to this, and may be performed while the operator observes the display device 13.

[0016]

As described above, according to the present invention, the load to be applied to the test piece is obtained in advance, and the load is applied to the chip until the load is reached. Since it is not necessary to take out a piece and measure the amount of compressive plastic strain, platen machining can be performed easily and accurately in a short time without requiring skill, and automation is also possible, which is a great effect in this field.

[Brief description of drawings]

FIG. 1 is a front view of a platen processing apparatus for carrying out the method of the present invention.

FIG. 2 is a perspective view of a test piece.

[Fig. 3] Graph of calibration curve

[Explanation of symbols]

 1 Test piece 2 Notch 3 Compressed part 4 Column 5 Stand 6 Upper die 7 Drive device 8 Compressing member 9 Load cell 10 Upper chip 11 Lower chip 12 Compressive plastic strain amount calculation part 13 Display device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Minami No. 1 Nishinosu, Oita-shi, Oita Prefecture Nippon Steel Co., Ltd. Oita Works

Claims (1)

[Claims] 1. A platen working method in which a metal test piece to be subjected to a crack opening displacement test is sandwiched between upper and lower chips, and a load is applied to the chip to give a local compressive plastic strain to the metal test piece. Hardness, the size of the tip, the amount of compressive plastic strain, the relationship between the load applied to the tip, the hardness of the metal test piece to be tested based on this relationship, the size of the tip to be used , Calculate the load to be applied to the chip from the required amount of compressive plastic strain, and continuously measure the load applied to the chip during platen processing, and apply the load to the chip until the measured load reaches the calculated load. A platen processing method for a metal test piece, comprising: