JPH04191636A - Apparatus for measuring propagation of crack - Google Patents

Abstract

PURPOSE:To process data as the development quantity of a crack by moving a low-power magnifier observing the crack generated in a test piece matching with the development quantity of the crack and detecting this moving quantity. CONSTITUTION:A test piece 11 is set to a fatigue tester and a low-power magnifier 12 for observing a crack is set to a holding device 13. Next, the magnifier 12 is moved up and down, before and behind or left and right by a moving apparatus 14 to match the focus thereof with the surface of the test piece 11. Then, load of constant stress is repeatedly applied to the test piece 11. At this time, the magnifier 12 is aligned with the leading end of the crack through the moving apparatus 14 and the moving quantity of the magnifier 12 at this time is detected by a dial gauge 15 to be inputted to a CPU 18 through a data logger 16. At the same time, the repeated number of times of stress is inputted to the CPU 18 through a fatigue tester control apparatus 17. By this method, data of high measuring accuracy can be obtained within a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crack propagation measuring system that facilitates the measurement of crack propagation, which is applied to crack propagation analysis of metal materials.

[Prior Art] A crack is a thin fissure that occurs in a material. Generally, for analysis of this crack, d
The relationship value for a/d N-Δ is used. da/
dN represents the crack propagation speed inherent to the material. Δ represents the stress intensity factor at the crack tip.

Conventionally, in a test to determine the relational value of d a / d N - Δ, a load of constant stress was repeatedly applied to a testing board on which a scale of 1 mm pitch was printed in advance, and the amount of crack growth at that time was measured at a low magnification. Measurements were taken with a magnifying glass.

This measurement method will be specifically explained with reference to FIG. In other words, conventionally, after printing or marking scales with a pitch of 1 mm on both sides of the initial crack starter of the testing station 1, a fatigue testing machine was used to apply a constant stress load to the testing station 1, and the cracks at that time were measured. Progress amount (al, a2)
was measured with a looper 2, and the measured value was recorded on a sheet 3 along with the number of repetitions (N) of the stress. Thereafter, the data recorded on the paper 3 was input into a computer, and the computer determined the value related to the above-mentioned d a / d N - Δ.

[Problems to be Solved by the Invention] As mentioned above, conventionally, when testing the crack propagation speed, it is necessary to print a scale with a pitch of 1 mm on the test station in advance, and the crack propagation rate corresponding to the number of repeated stress After sequentially measuring and recording the amount using a looper, it was necessary to input the data into a computer to obtain the relationship value of da/dN-Δ.

Therefore, there were problems in that the test was extremely troublesome, time-consuming, and had low reliability.

The present invention was developed in view of the above points, and it is possible to conduct a highly reliable crack propagation speed test without requiring the printing of a scale by a testing agency or reading or recording data. The purpose of this invention is to provide a crack propagation measurement system that enables shortening of test preparation and test measurement time.

[Means for Solving the Problems] The crack propagation old system according to the present invention measures the amount of progress of cracks occurring in the test center while applying a constant stress load to the test center using a fatigue testing machine, and measures the progress of the crack. In a crack propagation measurement system that determines the relationship between the amount of stress and the number of repetitions of the stress, a low-magnification magnifying glass is used to observe the crack that occurs in the testing agency, and this low-magnification magnifying glass is moved in accordance with the amount of crack development. a moving means, a moving amount detecting means for detecting the moving amount of the low magnification magnifying glass by the moving means, and a moving amount detecting means for detecting the moving amount of the low magnifying glass detected by the moving amount detecting means, and directly detecting the moving amount of the low magnifying glass as the amount of crack growth. The device is equipped with data processing means for directly inputting the number of repetitions of the stress and determining the relationship between the two.

[Function] In the crack propagation measurement system configured as described above, the test center is not provided with 1 mm pitch scales,
The relationship between the amount of crack growth and the number of stress repetitions can be easily determined by simply setting it in a fatigue testing machine and using a moving means to align a low-magnification magnifying glass with the tip of the crack.

Therefore, it is possible to perform measurements quickly without the troublesome measurement work such as printing scales and reading and recording data from the testing agency as in the past.

[Example] Hereinafter, a crack propagation measurement system according to an example of the present invention will be described with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a side view showing the configuration of a crack propagation measuring device according to the first embodiment, and FIG. 2 is a diagram showing the configuration of a measuring system using the same crack propagation measuring device. In the first embodiment, a center cracked type (CCT) having a notch in the center is used.
Type) Test Agency 11 was set in the fatigue testing machine,
While a constant stress load is applied to the test center 11 by the control device 17, the amount of crack growth (crack length) that develops from the notch in the center of the test center 11 and the number of stress repetitions at that time are measured. .

Here, although the testing agency 11 has conventionally printed a scale with a pitch of 1 mm, in this embodiment, it is not necessary to do so, and it is sufficient to simply set it in the fatigue testing machine. Then, a low magnification magnifying glass (louper) 12 for observing cracks occurring in the test center 11 is set on the holder 13, and a rack and pinion type moving device 14 is used to move the low magnification magnifying glass 12 up and down, back and forth, and so on.
Move it left and right until it is in focus with the surface of Testing Agency 11.

In this state, a constant stress load is repeatedly applied to the testing station 11. At that time, the moving device 14 moves the low magnification magnifying glass 1
2 is aligned with the tip of the crack, and the amount of movement of the low magnification magnifying glass 12 at that time is detected by a strain gauge type dial gauge 15. The amount of movement of the low magnification magnifying glass 12 is directly input as the amount of crack growth (crack length 1) to the CPU 18 in the personal computer, for example, via the data logger 16. At the same time, the number of stress repetitions (n) obtained by the control device 17 of the fatigue testing machine is also directly input to the CPU 18.

Such a test is carried out until the test station 11 breaks.

Finally, the CPU 18 calculates the relationship between the amount of crack growth and the number of stress repetitions (the relationship between d a / d N - Δ).
to calculate the crack propagation velocity and output its graph and data values.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a side view showing the configuration of a crack propagation measuring device according to the second embodiment, and FIG. 4 is a diagram showing the configuration of a measuring system using the same crack propagation measuring device. In the second embodiment, a compact type (CT: C
A test chamber 21 of ompaCt Type) is set in a fatigue testing machine, and while a constant stress load is applied to the test chamber 21, the amount of crack growth that develops as the number of repetitions of the stress increases is measured using the moving device 14. Low magnification magnifier 12
It is calculated based on the amount of movement of Then, this is repeated as appropriate, and the relationship between the amount of crack growth and the number of stress repetitions is determined by the CPU 1g.

In this case, similar to the first embodiment above, the Examination Agency 21 has the following information:
There is no need to print a 1 mm pitch scale. In addition, the amount of movement of the low magnification magnifying glass 12 detected by the strain gauge type dial gauge 15, that is, the amount of crack development, is recorded in the data logger.
16 directly to the CPU 1g. at the same time,
The number of stress repetitions is determined by the CPU 1 of the control device 17 of the fatigue testing machine.
8 is input directly.

[Effects of the Invention] As described above, according to the crack propagation measurement system of the present invention, there is no need to print scales with a pitch of 1 mm on the testing station, and the system can be set in a fatigue testing machine as is. Therefore, the trouble of preparing for the exam can be saved.

In addition, after the start of the test, the amount of progress of fatigue cracks due to stress loading is measured by using a dial gauge to detect the amount of movement when a low-magnification magnifying glass (loupe) is aligned with the tip of the crack using a moving device, and by using a data logger. For example, it may be directly imported into the CPU of a personal computer. At this time, the number of repetitions of stress can also be taken into the CPU from the control device of the fatigue testing machine. Therefore, there is no need to read or record data as in the past, and data can be quickly and easily read and recorded.
/ d The relationship between N-Δ is found. This improves crack measurement accuracy.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the configuration of a crack propagation measuring device according to the first embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a measurement system using the same crack propagation measuring device, and FIG. A side view showing the configuration of a crack propagation measuring device according to a second embodiment of the invention, FIG. 4 is a diagram showing the configuration of a measurement system using the same crack propagation measuring device, and FIG. 5 is a conventional crack propagation measuring method. FIG. 11... Center notch type testing station, 12... Low magnification magnifying glass (loupe), 13... Holder, 14... Rack and pinion type moving device, 15-mount strain gauge type dial gauge, 16 ...Data logger-117...Fatigue testing machine control device, 18...CPU, 21...Compact type testing agency. Applicant's agent Patent attorney Takehiko Suzue ΔK N Figure 5

Claims (1)

[Scope of Claims] While applying a constant stress load to the testing agency using a fatigue testing machine, the amount of growth of cracks occurring in the testing agency is measured,
In a crack propagation measurement system that determines the relationship between the amount of crack growth and the number of repetitions of the stress, a low magnification magnifying glass is used to observe the crack that occurs in the testing agency, and this low magnification magnifying glass is used to adjust the amount of crack growth to a moving means for moving; a moving amount detecting means for detecting the moving amount of the low magnification magnifying glass by the moving means; and a moving amount of the low magnifying glass detected by the moving amount detecting means as an amount of crack development. A crack propagation measurement system characterized by comprising data processing means for directly inputting the stress repetition number and for calculating the relationship between the two.