JPH0518877A - Saddle type gage for detecting bending deformation of test - Google Patents

Abstract

PURPOSE:To obtain a gage for bending deformation, which is easily datachable and attachable to a test piece without positional mis-alignment nor coming off from the due position, in an occasion of rupture flexibility test of three points bending test for steel material and so on. CONSTITUTION:To a saddle type gage for bending deformation detection of a test piece, a saddle type supporting table 3 having built-in screws 4 with which the table 3 is fixed to the test piece, a deformation beams 5 which follows deformation of the test piece, and a gage 2 which detects strain of the deformation beam. Accordingly, accurate bending deformation of the test piece can be detected, and an amount of average deformation of the test piece on the whole can be directly and precisely measured, and furthermore the saddle type gage for bending deformation detection does not move out of and come off the due position, even though shocking load is applied to the device during the test.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending deformation detecting gauge in a notched three-point bending tester for determining fracture toughness of steel materials and the like.

[0002]

2. Description of the Related Art The notch three-point bending test is a test method often used as a fracture toughness test for steel materials and the like.
It is also standardized in E399, E992, E1152, etc.

In this test method, a cutout opening is provided in the lower center of a horizontally long rectangular test piece, both ends of the test piece are supported, and a single load or repeated load is applied from the upper center of the test piece to form the cutout opening. The fracture toughness test of the test piece is performed by measuring the state of fracture or crack growth of the part.

Recently, in order to know the toughness of the test piece more precisely, it is often required to measure the state of the above-mentioned notch opening and simultaneously measure the deformation of the entire test piece. Although ASTM standard E1152 does not specify the measurement method for measuring the deformation of the entire test piece, the deformation of the test piece itself is measured directly with the test piece rather than indirectly through the tester. That is recommended.

FIG. 3 is a diagram showing an example of a method of directly measuring the deformation of the test piece itself by the test piece, which is Joice & Hackett.
Method. Conventionally, some other methods have been tried, but of these methods, this method is the most general and practical one. This is done by attaching four tabs 10 to the lateral surface of the test piece when performing the three-point bending test with notch,
The bending beam 9 having the strain gauge 2 is attached to the tabs at both ends of the test piece.
Put on 10. By doing so, the deformation amount of the test piece is transmitted by the tab 10 at the center of the test piece, and the bending beam deforms following the deformation of the test piece under load, so that the deformation amount of the test piece can be measured. However, this method has the following problems.

(1) Since the amount of deformation of the test piece itself is measured from the side surface, it cannot be said that the average amount of deformation of the entire test piece is completely obtained, and there is a problem in accuracy.

(2) The installation of the bending beam is unstable, and especially in the case of an impact load, it often slips off and measurement becomes impossible.

(3) It is troublesome to attach the four-point tabs, which requires a lot of man-hours for processing.

[0009]

DISCLOSURE OF THE INVENTION According to the present invention, in the fracture toughness test of the notched three-point bending test, the deformation of the test piece itself is directly detected by the test piece, and the average bending deformation amount of the entire test piece is accurately measured. A bending deformation detection gauge that can be obtained and will not slip or fall even if a shock load is applied during the test, and that can easily process the test piece and attach the bending deformation detection gauge. The purpose is to provide.

[0010]

The gist of the present invention is, as shown in FIG. 1, a bending deformation detecting gauge to be mounted on the upper portion of a test piece which is subjected to a three-point bending test for determining the fracture toughness of steel materials and the like. There is a downward concave saddle base 3, a downward concave engagement member 11, and a pair of deformed beams 5 connecting the ends of these legs, and the deformed beams include a plurality of strain gauges 2. And a mounting screw 4 for fixing the bending deformation detecting gauge to the upper portion of the test piece at the bottom of the concave portion of the saddle type base 3 for detecting the bending deformation which is deformed in synchronization with the deformation of the test piece. Located on the saddle-shaped gauge.

A description will be given below with reference to the accompanying drawings.

1A and 1B are views showing a saddle type gauge for detecting bending deformation of the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a front view.
(C) is a left side view (A-A arrow view of (a)), (d) is a right side view (A'-A 'arrow view of (a)).

As shown in the drawing, the saddle-type gauge for detecting bending deformation has a saddle-shaped appearance, and the saddle-type gauge for detecting saddle-type bending deformation is provided on the upper side of a horizontally long rectangular test piece to be measured. The mounting saddle type base 3 is fixed to the test piece with mounting screws 4. In addition, a screw hole for fixing the mounting screw 4 at a predetermined position is previously formed in the test piece. A strain gauge 2 is attached to the deformed beam 5 attached to the saddle type base 3 in the vicinity of the saddle type base 3. The saddle type base 3 and the deformed beam 5 are fixed with screws 13. The saddle type gauge for bending deformation detection is attached to the test piece so that the midpoint between the mounting screw 4 and the adjusting screw 12 coincides with the center of the test piece, and the saddle is attached by the mounting screw 4 at that position. The test piece is provided with a screw hole for screwing the mold base 3 and the test piece.

When the saddle gauge for detecting bending deformation is attached to the test piece, an accurate amount of bending deformation cannot be measured if there is a gap between the bottom of the recess of the engaging member 11 and the test piece.

It is necessary that the bottom of the recess of the engaging member 11 and the test piece are in contact with each other at one point, and a sharp adjusting screw 12 for adjusting the clearance is provided at the bottom of the recess of the engaging member 11.

The saddle type base 3 and the engaging member 11 are preferably made of a light and strong material such as aluminum alloy, and the deformed beam 5 is made by bending a thin metal having high elasticity. Strain gauge 2
Is generally used, but it is desirable to perform sufficient coating when testing in a refrigerant.

[0017]

FIG. 2 is a view showing a state in which the saddle type gauge for bending deformation detection of the present invention is attached to a test piece for a three-point bending test, and (a) shows the test piece of the present invention. A plan view when a saddle-type gauge for bending deformation detection is attached, (b) is a front view when a load is applied to the test piece, (c) is a left side view (the view shown by the arrow AA in (a)) ), (D) are right side views (A'-A 'arrow view of (a)).

When the bending deformation of the test piece is detected, it is necessary to calibrate the bending angle of the deformed beam and the output of the strain gauge in advance, and the bending amount d of the test piece in FIG. It is obtained from the bending angle α of the beam and the span S by the following formula.

D = S / 2 × tan α (1) The bending angle α of the deformed beam is the tangent angle of the saddle type base 3 and the engaging member 11 to the deformed beam 5, that is, the screw 13 It coincides with the tangent angle in the arch of the deformed beam 5 caused by the deformation of the test piece with the fixed point as the reference point. Further, this tangent angle matches the deformation angle on both sides of the test piece.

The test piece to be measured is deformed by repeatedly applying a load by the upper ram 7, and the deformed beam 5 and the deformed beam 5 are also deformed in synchronization with each other, and the strain is detected by the strain gauge 2.

As described above, in the fracture toughness test of the three-point bending test, the deformation of the test piece itself can be directly measured from the test piece, and the saddle-type gauge for detecting the bending deformation is dislocated even when an impact load is applied. Therefore, the average amount of bending deformation of the entire test piece can be accurately detected.

Further, since this gauge has a simple mechanism, it can be easily attached and detached and the workability is improved.

[0023]

EXAMPLES Using the saddle type gauge for detecting bending deformation of the present invention, a fracture toughness test of a notched three-point bending test was carried out to determine the amount of deformation of the test piece itself. For comparison with this, the amount of deformation was determined using the same type of test piece by the method of Joice & Hackett in FIG.

The material of the test piece was 60 kg class high-strength steel, and the test condition was that the test piece was repeatedly loaded according to ASTM standard E1152.

FIG. 4 is a diagram showing the relationship between the load detected by the saddle-type bending deformation detecting gauge of the present invention and the bending amount d. The vertical axis is the load applied to the test piece, and the horizontal axis is the above
The bending amount d of the test piece obtained by the equation (1),
Fracture toughness (J-integral value) is calculated from this figure under cyclic loading according to ASTM standard E1152.

FIG. 5 is a diagram showing the fracture toughness (J integral value) obtained based on FIG. 4, and a typical result that the toughness increases linearly as the crack growth length da increases is obtained. Was given. In this figure, the J-integral value on the vertical axis is obtained by the bending amount d detected by the gauge of the present invention. The crack growth length da was calculated from the displacement (COD) of the open end using a separate clip gauge.

FIG. 6 is a diagram showing the fracture toughness (J integral value) obtained by the above-mentioned method of Joice & Hackett. In this test result, no linear relationship portion appeared in the small portion where da value was about 1 mm or less, and the test result was unreliable. This indicates that the bending deformation detection gauge is not firmly fixed to the test piece, and the bending deformation detection gauge shifts during the load-unload process, and an accurate da value cannot be obtained. Is.

[0028]

When a fracture toughness test of a three-point bending test is performed, the saddle-type gauge for bending deformation detection of the present invention is used to detect an accurate bending deformation of the test piece, and the average of the entire test piece is detected. The amount of bending deformation can be measured accurately. In addition, during the test, the saddle-type gauge for detecting bending deformation does not shift or fall off even if an impact load is applied. Further, since the bending deformation detecting gauge of the present invention can be easily attached to and detached from the test piece, the labor of the work can be saved.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a saddle-type gauge for detecting bending deformation.

FIG. 2 is a view in which a saddle-type gauge for detecting bending deformation is attached to a test piece.

FIG. 3 is a diagram showing a conventional method for detecting bending deformation of a test piece.

FIG. 4 is a diagram showing the results of examining the relationship between load and load point displacement using the saddle type gauge of the present invention.

FIG. 5 is a diagram showing the result of examining the relationship between the load integral value and the load point displacement.

FIG. 6 is a diagram showing a result of examining a relation between a load integral value and a load point displacement by a conventional method.

Claims (1)

Claim: What is claimed is: 1. A bending deformation detection gauge to be mounted on the upper part of a test piece for performing a three-point bending test for determining fracture toughness of a material, the saddle type base 3 having a downward concave shape, and The concave engagement member 11 and the pair of deformable beams 5 that connect the ends of these legs.
And a strain gauge 2 attached to these deformed beams, and further has a mounting screw 4 for fixing the bending deformation detection gauge to the upper portion of the test piece at the bottom of the concave portion of the saddle type base. Saddle type gauge for bending deformation detection that deforms with deformation of the.