JPH042954A - Apparatus for material evaluation - Google Patents

Abstract

PURPOSE:To three-dimensionally observe a destructed state inside a material by means of X-ray CT technology by providing a load testing device, an X-ray detector, an X-ray controller, a load testing device controller, a data processor and an image display unit. CONSTITUTION:A load testing device 11 comprises rotating motors which are respectively connected to upper and lower test piece holding parts so as to apply rotation to a test piece 12 around a loading axis, a load applying motor for applying load to the test piece 12 and a load cell for measuring the load functioning to the test piece 12. An X-ray source 14 and an X-ray detector 17 are placed oppositely on a line with the testing device 11 interposed, while an X-ray controller 15 controls operation of the X-ray source 14. A load testing device controller 13 controls driving of the testing device 11. A data processor 19 sends instructions to the X-ray controller 15 and the testing device controller 13 as well as records data from the X-ray detector 17 via a data acquisition unit 18 to reconstruct and calculate an X-ray CT image. An image display unit 20 outputs the results of the data processing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for observing and evaluating the internal deformation of various materials under load conditions using X-ray CT (X-ray tomography). .

[Prior Art] For new materials such as ceramics and composite materials, knowing the internal fracture process of the material is particularly important for material development and quality assurance. Therefore, research using the acoustic emission (AE) method, which only dynamically detects the destruction process, is being actively conducted.
43 to 248 introduce an example in which the AE method is applied to a tensile test of fiber reinforced metal (FRM), and the timing of the start of fracture of reinforcing fibers is estimated based on the amplitude and rise time of the detected AE waveform. has been done.

By the way, the above-mentioned characteristics of the AE waveform and various types of fractures in composite materials (fiber breakage, dissociation of fibers and matrix, etc.)
Matrix cracking, delamination, etc.) can be detected by estimating the order in which various types of fracture occurred inside the material from observation of the fracture surface of the sample and changes in the stress-strain curve. , the characteristics of the 8Es that occurred from time to time are compared with individual destructions.

However, this method requires advanced knowledge of fracture mechanics and is indirect, so it lacks reliability.

Therefore, many researchers are trying to solve this problem by applying other nondestructive inspection methods simultaneously with AE measurement.

For example, when applying the AE method to the tensile test of GFRI (graphite fiber reinforced plastic), Awerbuch et al. used a Telnovi camera to observe the progress of damage on the surface of the test piece, and also used ultrasonic waves to inspect the inside of the test piece before and after the test. We investigate using the deep method and X-ray deep wound method, and correlate the obtained AE results with the type of fracture (Mater
At the same time, the AE method is applied to the fatigue test of ial evaluation/43/reinforced plus deck), and at the same time, the test is interrupted and X-ray 1 shadow is performed to correlate the delamination and the results of 8E (Del, eminat+on). a
nd Debonding of Materi
al, s 顯此thbee, ASTM 5TP876
．． 1985, p448-p464).

Other examples have been reported in which the electrical resistance of CF RP under load is measured and fractures of the carbon fibers are detected from changes in electrical resistance, and the results of HaE are interpreted.

[Means for solving the problem] Various attempts have been made since then, but TV cameras provide only two-dimensional information and three-dimensional information such as the size, shape, and position of the fracture in the thickness direction. Neither method is sufficient because the situation is unknown, and electrical resistance can only detect breaks in conductive fibers.

On the other hand, X-ray tomography is a method that has been widely used in recent years to inspect the interior of materials three-dimensionally.
As the T device, a so-called third generation X-ray CT device in which an X-ray tube and an X-ray detector rotate at the same time is often used.

This third generation X-ray C'F device is
As shown in Publication No. 53 and Japanese Utility Model Publication No. 1-84609, etc., [a) an X-ray source and a large number of arcuate arrays arranged opposite to the X-ray source across the space in which the subject is placed; A method in which an arc-shaped X-ray detector having a channel is rotated integrally around the subject described in -F, or (b) a method in which the X-ray source and X-ray detector are fixed and the subject is rotated. Yes (Iron and Copper, No. 14, 19
85, p]24-p13],).

Mainly (a) is used for medical purposes, and (b) is used for industrial purposes, but in either case, in order to obtain a tomographic image with high resolution in detail, it is necessary to It is necessary to collect line projection data.

However, when applying the X-ray CT method to a specimen undergoing a tensile test, method (a) above places the X-ray source and X-ray detector inside the rock frame of the testing machine and rotates around the specimen. This requires a tensile testing machine with a complicated structure and a considerably large space, and the cost is therefore enormous.

Alternatively, the method described in section 2 (b) (the JX-ray source and the It is necessary to make one rotation of 80° or more without applying stress.

The present invention has been made in consideration of the above points, and provides a material evaluation device that three-dimensionally observes the fracture state inside a material during a tensile test using an X-ray CT method.

[Means to solve the problem] Two rotating motors connected to the upper and lower specimen gripping parts to impart motion, a load-bearing motor that applies a load to the specimen, and a load that acts on the specimen. a load test device equipped with a load cell that measures the load, an X-ray source J3 and an X-ray detector arranged in a straight line facing each other across the load test device, and an X-ray control that controls the operation of the X-ray source. a test equipment control unit that controls the driving of the load testing equipment, an X-ray control unit, and a test equipment control unit that issues instructions to the X-ray detector and records data from the X-ray detector via a data collection unit. X-ray C
The present invention is characterized in that it is comprised of a data processing section that performs reconstruction calculations on a T image, and an image display device that outputs the results of the data processing.

[Operation] The details of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of the load testing device that constitutes the present invention.
1 is a motor for applying a load, 2 is a screw shaft connected to the motor shaft, and 3 is a member having a female thread cut on the upper part to fit with the screw shaft 2, and the member has a mechanism that allows it to move up and down without rotating. Bearings 4a and 4b are fixed to guide the movement. Also 5a
, 5b is a motor for rotating the test piece, and the motor 5a for rotating the upper part is
A test piece gripping section 6a is connected to the shaft of the lower rotating motor 5b, and a test piece gripping section 6b is connected via a load cell 7 to the shaft of the lower rotation motor 5b. 8a.

8b is a guide shaft for sliding the member 3 in the tensile direction; 9
is the test piece.

FIG. 2 is a block diagram showing the entire structure of the present invention, in which reference numeral 11 shows the load test device shown in FIG. 1, and 12 shows a cross section of the test piece 9. 13 is the control unit of the load test device, 14 is the X-ray source, 15 is the X-ray control unit, 16 is the fan-shaped X-ray beam, 17 is the X-ray detector, 18 is the data collection unit, and 19 is the data collected by the above 18. A data processing unit 20 is an image display device that stores X-ray projection data and performs CT image reconstruction calculations, as well as controls the control units 13 and 15.

Next, a measurement method using this device will be explained.

First, in FIG. 1, the test piece 9 is held at the test piece gripping portions 6a, 6.
After setting the test specimen 9 to the position b, the member 3 is moved in the bowing direction by rotating the load applying motor 1 and the screw shaft 2, and tension is applied to the test piece 9. The tension is measured by a load cell 7, and when the tension reaches a preset value, the motor 1 is stopped. Then, in order to perform X-ray tomography of the test piece 9 with the tension constant, the X-ray source 14 is activated, and the step angle θ=0°.
Collect X-ray projection data at. Next, the upper and lower rotating motors 5a and 5b rotate the test piece at a predetermined step angle Δθ (for example, 1°) about the axis in the tensile direction.
After rotating the motors 5a and 5b, the motors 5a and 5b are stopped and
Collect X-ray projection data at Δθ.

In this way, X-ray projection data at each angle is collected every Δθ until the rotation angle of the test piece reaches the angle required for image reconstruction, and then the motors 5a, 5b are reversed. , θ-0° and return the test piece. Note that the rotation motor 5
A and 5b each have a built-in high-resolution encoder, and by comparing the number of pulses from the encoder, both motors are rotated synchronously, using a method that does not apply torsional stress due to rotation to the test piece. are doing.

The data processing section 19 in FIG. 2 includes the X-ray control section 15. It controls the load test device control section 13 and the like, records X-ray projection data from the data collection section 18, performs CT and CT image reconstruction calculations, and outputs the results to the image display device 20.

As described above, a tomographic image of a specific cross section can be obtained under a certain tension, but if we take a tomographic image when the tension is increased, the load motor 1 is
may be moved again, and a tomographic image under the desired tension may be measured by the above-mentioned means. In addition, when obtaining a tomographic image at a different position, for example in the longitudinal direction of the test piece, the test piece 12 and the X-ray source 14 are
It is necessary to change the relative position of the load test device 11 and the X-ray detector 17. To do this, place the load test device 11 on a Z-axis stage (not shown), move the test device up and down, and obtain a tomographic image at a predetermined position. It can be measured using a similar method.

[Example] An embodiment of the present invention will be described below.

As a test piece, the length of the parallel part is 20 mm, the width is 3 mm,
The plate thickness was 1.5 mm, and the material used was an aluminum matrix composite material with silicon carbide as reinforcing fibers. After setting this test piece in the grip part, we performed X-ray tomography in advance with no load. As a result, a matrix crack with a length of approximately 50LLm and a width of 2011m extending in the width direction of the test piece was found in the center of the test piece. Ta. When we performed tomography of this test piece while changing the tensile stress in a step-by-step manner, we found that the crack progressed and expanded, and that the tip of the crack reached the reinforcing fibers.
IF fracture was observed from the X-ray CT tomogram.

Furthermore, by attaching an AE transducer to a test piece and performing AE measurements at the same time, it was found that characteristic 8E was released as matrix cracks progressed and fibers broke.

[Effects of the Invention] As explained below, according to the present invention, there is provided a load testing device capable of rotating a test piece by 80 degrees or more in a loaded state, and an X-ray source and an By arranging a detector and performing X-ray tomography, it is possible to observe with high resolution the state of destruction inside the material during the bow string test. In all of the above explanations, the load on the test piece was assumed to be a tensile load, but by reversing the rotation direction of the load-bearing mok, it is possible to observe a compressive load state, and even change the rotation angle of the upper and lower rotation motors. By rotating the upper and lower rotation motors synchronously to maintain a constant torsional load after applying a torsional load to the test piece, it is also possible to observe the failure state in a torsional state. .

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the structure of a load testing device constituting the present invention, and FIG. 2 is a configuration diagram showing the entirety of the present invention. ]... Load loading motor, 2... Screw shaft, 3... Structure part A, 4a, 4b-bearing 1rf, 5 a,
, 5b-J: part and lower part rotation motor, 6a
, 6b... Upper and lower gripping parts, 7... Low mill cell, 8a, 8b... Guide shaft, 9... Test piece, 11. Load test device, 12. Test piece (only cross section shown), 13.
Load test device control section,] 4.. X-ray source, 15. X-ray control section, 16. Fan-shaped X-ray beam, 17..
- Data collection unit, 19... Deku processing unit, 20... Image display device. Agent: Patent attorney Masamitsu Akizawa and 1 other person

Claims (1)

[Claims] Two rotating motors connected to the upper and lower specimen gripping parts to rotate the specimen by more than 180° around the axis in the loading direction, a load motor that applies the load to the specimen, and the specimen. a load test device equipped with a load cell that measures the load acting on the load test device; an X-ray source and an X-ray detector arranged in a straight line facing each other across the load test device; and an X-ray detector that controls the operation of the X-ray source. A ray control section, a test device control section that controls the drive of the load testing device, an X-ray control section, a test device control section that issues instructions to the X-ray control section, and a test device control section that sends data from the X-ray detector through a data collection section. A material evaluation device comprising: a data processing unit that performs reconstruction calculations on recorded X-ray CT images; and an image display device that outputs the results of data processing.