JPH0559291U - Fatigue crack initiation position detection device for test piece - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a device for detecting a fatigue crack initiation position of a test piece. [Structure] Test piece 3 from light source 1 through first polarizing plate 2
The incident light IL is radiated on the upper side, and the reflected light RL from the test piece 3 is secondly irradiated.
Before the start of the test, an image is taken by the camera 5 through the polarizing plate 4 of the above, the analog image signal from the camera 5 is converted into a digital image signal by the analog / digital converter 6, and the image is processed by the image processor 7. Alternatively, the crack occurrence position in the fatigue test of the test piece 3 can be detected by calculating the lightness change position by comparing with the image signal immediately after that.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a fatigue crack initiation position detecting device for a test piece used in a fatigue test of a material.

[0002]

[Prior Art]

 Conventionally, when a material fatigue test is performed, the fatigue cracks that occur in the test piece are generally confirmed by human eyes directly or through a microscope or a television camera.

[0003]

[Problems to be solved by the device]

 However, such a conventional method is problematic because it requires constant observation of the test piece during the test, which requires a great deal of time and labor. It is an object of the present invention to provide a fatigue crack generation position detecting device for a test piece that solves the above problems.

[0004]

[Means for Solving the Problems]

 The present invention provides a light source that irradiates a test piece with incident light through a first polarizing plate, a camera that captures reflected light from the test piece through a second polarizing plate, and an analog image from this camera. The analog / digital converter that converts the signal into a digital image signal and the digital image signal from this analog / digital converter are image processed and compared with the image signal before or immediately after the start of the test to determine the change position of the brightness. An apparatus for detecting a fatigue crack occurrence position of a test piece, comprising: an image processing unit to be obtained. The first polarizing plate and the second polarizing plate may be replaced with a single polarizing plate.

[0005]

[Work]

 According to the present invention, the incident light emitted from the light source passes through the first polarizing plate, so that only the light in a certain direction hits the test piece. On the other hand, the reflected light from the test piece enters the camera through the second polarizing plate. At this time, if the surface of the test piece, that is, the reflection surface of the light does not change, each of the test pieces entering the camera. The brightness of the position will not change.

However, when a crack is generated on the surface of the test piece, the light is scattered there, so that the reflection direction changes and the amount of light also changes, so that the brightness of the crack generation position changes. Therefore, by digitizing the image signal (brightness) entering the camera and comparing it with the image signal (brightness) before the test start or immediately after the test start, and obtaining the position where the brightness has changed, that position can be determined. It can be determined as a crack generation position. Furthermore, by recording the image processing results with respect to time, it is possible to determine the time when a crack occurs or the number of fatigue repetitions. From the viewpoint of measurement accuracy, it is preferable that the amount of light is large, and therefore the surface of the test piece, that is, the reflecting surface is preferably polished.

[0007]

【Example】

 FIG. 1 is a schematic diagram showing an embodiment of the present invention. The incident light IL emitted from the light source 1 is polarized by the first polarizing plate 2 and then reflected on the surface of the plate-shaped test piece 3, for example, and the reflected light RL passes through the second polarizing plate 4. An image is captured as an analog image signal by the camera 5, and the analog image signal is converted into a digital image signal by the analog / digital converter 6. This digital image signal is compared in the image processing unit 7 with the image signal captured before or immediately after the start of the test, and the position where the brightness changes is determined, and that position is determined as the crack generation position. R. Furthermore, if the digital image signal is recorded in a recorder 8 such as an XY recorder, the time when the brightness changes can be determined, and this time and the frequency characteristic obtained in the fatigue test can be determined. The number of repeated cracks can be determined from

Although the test piece 3 is described as having a plate shape in the above embodiment, the present invention is not limited to this, and a rod-shaped or compact (CT) test piece may be used. .. Further, although the polarization of the incident light IL and the reflected light RL is described as using the two polarizing plates of the first polarizing plate 2 and the second polarizing plate 4, the incident light IL and the reflected light RL are simultaneously polarized. One polarizing plate may be shared as long as it has a characteristic. Further, the type of the camera 5 may be any type such as one that operates continuously or one that operates intermittently.

[0009]

[Effect of the device]

 According to the fatigue crack generation position detection device of the present invention, the crack generation position can be automatically determined by performing image processing on the change in the brightness of the reflected light in the fatigue test. This eliminates the need to constantly observe the test piece, which can save labor.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing an embodiment of the present invention.

[Explanation of symbols]

 1 Light Source 2 First Polarizing Plate 3 Test Piece 4 Second Polarizing Plate 5 Camera 6 Analog / Digital Converter 7 Image Processor 8 Recorder IL Incident Light RL Reflected Light

Claims (2)

[Scope of utility model registration request] 1. A light source for irradiating a test piece with incident light through a first polarizing plate, a camera for imaging reflected light from the test piece through a second polarizing plate, and an analog from this camera. An analog / digital converter that converts an image signal into a digital image signal, and a position where the lightness of the digital image signal from the analog / digital converter is changed by comparing the image signal before or immediately after the image processing. An image processing unit for obtaining a fatigue crack occurrence position detecting device for a test piece. 2. The first polarizing plate and the second polarizing plate
The fatigue crack generation position detecting device for a test piece according to claim 1, wherein the device is replaced with one polarizing plate.