JPS61124836A - Apparatus for obtaining stress image - Google Patents

Abstract

PURPOSE:To obtain an accurate stress distribution image even if the frequency of load varies, by monitoring the frequency of the load applied to a specimen and obtaining the stress distribution image only by the temp. signal at the time of predetermined frequency. CONSTITUTION:When the frequency of the change in the load applied to a specimen 1 is within a predetermined range, a pulling start pulse signal is supplied to an A/D converter 5 and the image signal from a scanner 3 is sampled at this time as a pulling time signal and converted to a digital signal to be supplied to a data processing apparatus 18. A large number of data, which are based on a large number of times of scannings by the scanner 3, of the surface of the specimen 1 are integrated in memory 9. Thereafter, the data processing apparatus 18 calculates the difference between the signal intensities of a compression time signal and the pulling time signal at every part of the specimen and this difference signal is supplied to an image display apparatus 20 to display the stress distribution of the specimen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for obtaining stress distribution images using thermoelastic effects.

[Prior Art] The stress distribution of a sample is measured in a non-contact manner using the thermoelastic effect. This measurement focuses on the fact that the surface temperature of the stress concentration area of the sample increases when subjected to a compressive load, and conversely decreases when subjected to a tensile load. In other words, in this measurement, a load is applied to the sample periodically, and during that time, infrared rays from the sample surface corresponding to the sample temperature are detected, and the load is calculated from the temperature when the load is applied to each part of the sample. A signal is obtained by subtracting the temperature when no load or reverse load is applied, and a temperature distribution image of the sample, that is, a stress distribution image is obtained based on this difference signal.

[Problems to be Solved by the Invention] Incidentally, in order to obtain a stress distribution image, it is necessary to apply a load periodically to the sample, but if the frequency of this periodic change in load varies, , since the temperature during loading changes accordingly, it is not possible to obtain an accurate stress distribution image.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an apparatus that can obtain an accurate stress distribution image even if the frequency of the load changes.

[Means for Solving the Problems] An apparatus for obtaining a stress image distribution based on the present invention includes a load applying means that applies a periodic load to a sample to be measured, and a load applying means that applies a periodic load to a sample to be measured, and a load applying means that applies a periodic load to a sample to be measured, and means for detecting infrared rays, means for obtaining a signal corresponding to the frequency of the change from a periodic change signal synchronized with the load change applied to the sample, and the frequency of the periodic change falling within a predetermined range. A method for detecting a stress, a means for sampling a video signal from the detection means based on a signal from the detection means, and a data processing means for obtaining a stress image based on the sampled signal. It is characterized by

[Example] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, 1 is a sample to be measured, and a load is applied to the sample 1 from a load application 112, and the sample 1 is subjected to periodic compression and tension. 3 is an infrared scanner;
The infrared scanner 3 sequentially guides infrared rays from the surface of the sample 1 to a detector to obtain a video signal. After the video signal is amplified by an amplifier 4, it is supplied to an A-D converter 5 and converted into a digital signal. The load application device 2 generates a signal corresponding to a change in the load applied to the sample 1, and the signal is amplified by an amplifier 6 and then supplied to a comparator 7.

The signal from the comparator 7 is fed to a first and second monostable multivibrator 8.9, and the pulse signals from the two monostable multivibrators are fed to a counter 1o. The counter 10 generates a clock signal generator 1 in response to pulses from the monostable multivibrator 8.9.
The clock signal is counted from 1 and the value is latched in the latch circuit 12. The value of the latch circuit is supplied to a first and a second comparator 13.14. The output signals of the first and second comparators are supplied to an AND circuit 15, and the output signal of the AND circuit 15 is supplied to an AND circuit 16.1.
7. The AND circuit 16 is also supplied with a signal from the first monostable multivibrator 8, and the AND circuit 17 is also supplied with a signal from the second monostable multivibrator 9. The signals from the AND circuits 16 and 17 are supplied to the A-D converter 5, and the signals from the A-D converter 5 are supplied to the A-D converter 5.
The D converter 5 samples the video signal according to the signal from the AND circuit. The signal from the A/D converter 5 is supplied to a memory 19 via a data processing means 18 such as a computer and stored therein. The data processing means 1
8 performs predetermined processing based on the data stored in the memory, and supplies the result to the display device 20.

In the configuration described above, compressive and tensile loads are periodically applied to the sample 1 by the load applying device 2, and the signal shown in FIG. 2(a) corresponding to this periodic change is generated. It is obtained from the load applying machine 2. FIG. 2(a)
The signal shown in FIG. 2 is amplified and then supplied to the comparator 7 to obtain the signal shown in FIG. 2(b). The output signal of the comparator 7 is supplied to the first and second monostable multivibrators 8°9, and the first monostable multivibrator 8 changes as shown in FIG. 2(C) at the rising edge of the supplied signal. The second monostable multivibrator 9 generates the pulse signal shown in FIG. 2(d) at the falling edge of the supplied signal. The output pulses of the two monostable multivibrators 8.9 are supplied to a counter 10, which is cleared at the same time by the pulses from the first monostable multivibrator 8. Start counting the clock signal and start counting the second clock signal.
The counting is stopped by a pulse signal from the monostable multivibrator 9. The count value of the counter 10 is latched by a latch circuit 12, and the latched count value is 1 of the load from compression to tension.
is the number of clock signals that occur during half the period,
It corresponds to the frequency of the change in the load. The latch circuit 1
The value latched to 2 is supplied to the first and second comparators 13 and 14.

The first comparator 13 compares the value corresponding to the upper limit frequency with the value latched by the launch circuit 12, and when the latched value is less than the value corresponding to the upper limit frequency, the first comparator 13 compares the value corresponding to the upper limit frequency with the value latched by the launch circuit 12. A high level signal shown in FIG. 2(e) is generated.

The second comparator 14 compares the value corresponding to the lower limit frequency with the value latched by the latch circuit 12, and when the latched value is greater than or equal to the value corresponding to the lower limit frequency, the second comparator 14 compares the value corresponding to the lower limit frequency with the value latched by the latch circuit 12. A high level signal shown in FIG. 2(f) is generated.

The signals shown in FIG. 2(e) and FIG. 2(f) are supplied to an AND circuit 15, and the signals shown in FIG. 2(Q) are supplied from the AND circuit 15.
The signal shown is obtained. The signal from the AND circuit 15 is supplied to AND circuits 16 and 17. The AND circuit 16
is also supplied with a pulse signal from the first monostable multivibrator 8, and when a high level signal is supplied from the AND circuit 15, that is, when the frequency of load change is within a predetermined range, compression is performed. A starting pulse signal is supplied to the A-D converter 5, and at this time, the image signals from the scanner 3h1 are sampled as compression signals, converted to digital signals, and supplied to the data processing device. On the other hand, the AND circuit 17 is also supplied with a pulse signal from the second monostable multivibrator 9, and when the high level signal is supplied from the AND circuit 15, that is, the frequency of the load change reaches a predetermined value. When within the range, a pulse signal for starting tension is supplied to the A-D converter 5, and at that time, the video signal from the scanner 3 is sampled as a tension signal, converted to a digital signal, and supplied to the data processing device 18. . The compression signal and the tension signal are stored in one memory according to the position on the sample surface, and a large amount of data based on multiple scans of the sample surface by the scanner 3 is integrated in the memory 19. After completing this predetermined number of integrations, the data processing device 18 determines the difference in signal strength between the compression signal and the tension signal for each part of the sample, and displays this difference signal as a video display bag! 20, the stress distribution of the sample is displayed on the display device.

In this way, in the above-mentioned embodiment, a half-cycle time corresponding to the frequency is detected every cycle of the load change applied to the sample, and when this detection signal is within a predetermined range, the amount temperature of the next cycle is detected. It is configured to perform signal sampling, and can selectively obtain only the temperature signal when a load is applied to the sample at a predetermined frequency, and the display shows an accurate stress distribution image of the sample. is displayed. Note that the present invention is not limited to this embodiment and can be modified in many ways. For example, the temperature signal of a sample is continuously A-D converted and stored in memory along with the time, while the frequency of load changes applied to the sample is detected and the time when the frequency falls within a predetermined frequency range is recorded. After the series of measurements is completed, only the temperature signal at the time when the load change falls within a predetermined frequency range is extracted from all the stored temperature signals, and the desired data processing is performed. It may be configured as follows.

Further, the load applied to the sample is not limited to periodic compression and tension, but may be such that compression and no load, or no load and tension are applied to the sample periodically.

[Effects] As detailed above, in the present invention, the frequency of the load applied to the sample is monitored and a stress distribution image is obtained only from the temperature signal at a predetermined frequency, so that accurate You can (q) an image.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a signal waveform diagram used to explain the operation of the embodiment shown in FIG. 1... Sample 2... Load applying device 3... Scanner 4... Amplifier 5... A-D converter 6... Amplifier 7... Comparator 8.9.
... Monostable multivibrator 10 ... Counter 11 ... Clock signal generator 12 ... Latch circuit 13.14 ... Comparator 15.16.17 ... AND circuit 18 ... Data processing device

Claims (3)

[Claims] (1) A load applying means for applying a periodic load to the sample to be measured, a means for detecting infrared rays from each part of the sample to which the load is applied, and a periodic load application method synchronized with changes in the load applied to the sample means for obtaining a signal corresponding to the frequency of the change from the change signal; means for detecting that the frequency of the periodic change falls within a predetermined range; and the infrared detecting means based on the signal from the detection means. 1. An apparatus for obtaining a stress image, comprising means for sampling a video signal from a source, and data processing means for obtaining a stress image based on the sampled signal. (2) A signal corresponding to the frequency is obtained for each cycle of periodic changes in the load applied to the sample, and if the frequency is within a predetermined range, a video signal is generated in one period of the next periodic change. An apparatus for obtaining a stress image according to claim 1, wherein sampling is performed. (3) The video signal from the detection means is stored in the memory according to the time, and the time when the frequency of the periodic change falls within a predetermined range is also stored, and the data processing means 2. An apparatus for obtaining a stress image according to claim 1, wherein the apparatus is configured to sample necessary data based on both signals obtained.