JP3040288B2 - Infrared stress imaging system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared stress imaging system and, more particularly, to an infrared stress imaging system in which a sample is subjected to repeated compressive / tensile loads to detect the stress of the sample.

[0002]

2. Description of the Related Art Measuring the magnitude of a stress generated in each part of an object is a complete and accurate method for designing a machine or a structure by selecting the shape of each part, the dimensions of the material used, the material, and the like. It is crucial to enable economical design. Therefore, conventionally, a strain gauge has been attached to an object to be measured, and strain generated in the object to be measured has been detected to measure a stress distribution.

[0003] However, there is a problem that it is troublesome to attach the strain gauge to the object to be measured, and it takes much time for the measurement. On the other hand, if a compressive / tensile load is repeatedly applied to an object, heat generation and heat absorption appear, and if this heat generation and heat absorption are repeated in a relatively short cycle, diffusion of heat to the surroundings or interruption of heat from the surroundings is interrupted. With the insulation insulated
The surface temperature at the stress concentration portion changes, and there is a proportional relationship between the temperature change amount and the stress change, and it has been proposed to use this to measure the stress distribution (Japanese Patent Publication No. Sho 62-1204).
No., JP-B-62-1205, JP-B-63-7333
No., Japanese Patent Application No. 4-178376). According to such a stress distribution measuring method, non-contact measurement can be performed quickly and easily as compared with a conventional measuring method using a strain gauge or the like.

FIG. 3 is a timing chart of a conventional apparatus for displaying an image of a stress distribution based on temperature data obtained by horizontally and vertically scanning an image spot of an infrared detector on an object to which a load is periodically applied. a chart, vibration signal f _in the camera HB signal multiplied by the repeated load to a subject such as tensile and compression: not synchronized with the (camera scan infrared data acquisition signal signals of one scan line of the infrared image) taken . Conventionally, as shown in FIG. 3, the positive trigger occurs when the phase of the stress is maximized with respect to excitation signal f _in, the (diagram generates negative trigger when the phase of stress is minimized, pressurized plus trigger when Fushingo f _in is maximum, because when the minimum has occurred a negative trigger stress phase applied to the subject is necessarily displaced without matching excitation signal f _in, the actual A plus trigger and a minus trigger are generated when the stress becomes maximum and minimum, respectively.) The first camera HB signal is taken as plus temperature data for the plus trigger, and the first camera HB signal is taken as minus temperature data for the minus trigger. By taking the difference between the plus data and minus data for the entire screen, temperature change distribution data is obtained and can be used as stress distribution data. The plus data and the minus data can be added during a half cycle of the excitation signal fin _in order to improve the S / N ratio (two times in the case of the figure).

[0005]

[SUMMARY OF THE INVENTION Incidentally, as shown in FIG. 3, when the frequency of the excitation signal f _in smaller than the horizontal scanning frequency of the camera (usually about 400Hz) (70~80Hz) is , the time t _p comes the first camera HB signal to the positive trigger, the time t _m which comes first camera HB signal to the negative trigger is relatively small with respect to the period of the excitation signal f _in, pressurizing each camera HB signal during one period of Fushingo f _in at least one is susceptible uptake, the frequency of the excitation signal f _in relatively large as _{(200~300Hz), t p, t} m There may become relatively large with respect to the period of the excitation signal f _in, necessarily no longer be captured each camera HB signal during one period of the excitation signal f _in. Therefore, stress distribution data cannot be obtained. In this case, the frequency of the excitation signal f _in is the fraction less degree limit of the frequency of the camera HB signals.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object the object of the present invention even in a high state in which the subject excitation signal frequency approaches the line scanning frequency of an infrared camera. An object of the present invention is to provide an infrared stress imaging system capable of reliably detecting a temperature change distribution and detecting a stress distribution.

[0007]

In order to achieve the above object, an infrared stress imaging system according to the present invention applies a load to a subject periodically, and detects a temperature change of a sample surface due to heat generation and heat absorption by an infrared ray. In an infrared stress imaging system that detects by a camera and detects a stress distribution based on a temperature change distribution, an image signal from the infrared camera is input within a predetermined time width when the stress applied to the subject becomes substantially maximum. Only when the image signal is taken as plus temperature distribution data, and only when an image signal from the infrared camera is input within a predetermined time width when the stress applied to the subject is substantially minimized, the image signal is taken as minus temperature distribution data. The temperature change distribution is obtained by taking the difference between the plus temperature distribution data and the minus temperature distribution data. The one in which the features.

[0008]

According to the present invention, only when an image signal is input from an infrared camera within a predetermined time width when the stress applied to the subject becomes substantially maximum, the image signal is taken in as plus temperature distribution data and is applied to the subject. Only when an image signal from the infrared camera is input within a predetermined time width when the applied stress is substantially minimized, the image signal is captured as minus temperature distribution data, and the captured plus temperature distribution data and minus temperature distribution data are compared. Since the temperature change distribution is obtained by taking the difference, the temperature change distribution can be ensured even when the vibration frequency of the subject approaches the vibration frequency more than several minutes of the scanning frequency of the infrared camera. Can be detected to detect the stress distribution.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of an infrared stress imaging system according to the present invention will be described below with reference to the drawings. FIG.
5 is a timing chart for explaining the principle of the infrared stress imaging system according to the present invention, in which the vibration of the subject and the scanning of the infrared camera are not synchronized. It is to subject, as excitation signal f _in, e.g., cyclic loading of the tensile and compression is applied. Then, the positive trigger occurs when stress on the excitation signal f _in is the phase of maximum,
Stress generates negative trigger when the phase of a minimum (in the figure, a positive triggered when excitation signal f _in is maximum,
While generating a negative trigger at a minimum, since the stress applied to the object phase is always shifted without matching excitation signal f _in, respectively plus triggered when the actual stress is maximum, the minimum, A negative trigger is generated. ). A plus trigger gate signal having a time width t _{Gp is formed by} the plus trigger, and a minus trigger gate signal having a time width t _{Gm is formed by} the minus trigger. A camera HB signal (camera scan) having a rising portion during the gate period is generated. Infrared data capture signal: Only one scan line signal of an infrared image) is used as valid data for detecting a temperature change, and each camera HB signal is captured as plus temperature data and minus temperature data. That is, only when the camera HB signal rises while t _Gp is “H”, the data is valid and taken in as plus temperature data. Next, only when the camera HB signal rises while t _Gm is “H”, the data is taken in as valid as minus temperature data. Excitation signal f _in
In one cycle of the above, at least one of the plus temperature data and the minus temperature data cannot always be taken in. However, by repeating the above taking in many cycles, plus temperature data and minus temperature data can always be taken. Thereafter, as in the conventional case, the difference between the plus data and the minus data is obtained for the entire screen to obtain temperature change distribution data, which can be used as stress distribution data.

[0010] Incidentally, the positive trigger gate signal t _Gp, negative trigger gate signal t _Gm, it is necessary to change the respective time widths by the frequency of the excitation signal f _in. The higher the frequency of the excitation signal f _in, to shorten.

As described above, it is possible to detect stress distribution data of a subject having a higher excitation frequency than the conventional system described with reference to FIG.

Next, FIG. 2 is a block diagram showing one embodiment of the infrared stress imaging system of the present invention based on the above principle. This system includes a vibrator 1 for vibrating a subject S
And an infrared camera 2 for capturing an image of the subject S that is repeatedly subjected to a load by the vibrator 1.
Plus trigger generating circuit 3, minus trigger generating circuit 4,
Frequency detection circuit 5, plus trigger gate generation circuit 6, minus trigger gate generation circuit 7, synchronization determination circuits 8, 9,
Arithmetic control circuit 10, plus data memory 11,
It comprises a minus data memory 12, a difference data memory 13, and a display device 14.

[0013] The operation is positive trigger generating circuit 3, a negative trigger generating circuit 4, respectively, at the frequency detection circuit 5 receives the excitation signal f _in, as shown from the vibrator 1 in FIG. 1. Plus trigger generating circuit 3, a negative trigger generating circuit 4, the positive trigger at maximum becomes the phase position of the respective stress to excitation signal f _in, generates negative trigger at smallest phase position. At the same time, it detects the frequency of the excitation signal f _in the frequency detecting circuit 5.

[0014] frequency of the excitation signal f _in from the positive trigger and frequency detection circuit 5 from the positive trigger generating circuit 3 is input to the positive trigger gate generating circuit 6, negative trigger a frequency detection circuit from the negative trigger generating circuit 4 frequency of vibration signal f _in from 5 is input to the negative trigger gate generating circuit 7, respectively generate positive trigger gate signal and the minus trigger gate signal having a predetermined time width t _Gp, t _Gm.

A camera HB signal repeatedly input for a horizontal scanning line at a predetermined vertical position from the infrared camera 2 and a positive trigger gate signal generated by the positive trigger gate generating circuit 6 are input to one cycle discriminating circuit 8 and Only when it is determined that a rising portion of any camera HB signal is included in the “H” of the trigger gate signal, the camera HB signal of that cycle is taken into the plus data memory 11 and the camera HB signal and the negative trigger Only when the negative trigger gate signal generated by the gate generating circuit 7 is input to the other cycle determining circuit 9 and it is determined that any of the camera HB signal rising portions is included in the negative trigger gate signal “H”. , The camera HB signal of that cycle is taken into the minus data memory 12.

The plus temperature data and minus temperature data taken into the plus data memory 11 and minus data memory 12 are sent to a difference data memory 13 under the control of the arithmetic control circuit 10, and the difference between them is taken. It is stored in the difference data memory 13.

In this manner, temperature change distribution data for one horizontal scanning line is obtained. Next, the horizontal scanning position of the infrared camera 2 is advanced to the next scanning line based on a signal from the difference data memory 13, for example. The temperature change distribution data of the scanning line is similarly obtained, and the same is performed for the entire screen, thereby obtaining the two-dimensional temperature change distribution data of the subject S. The temperature change distribution data stored in the difference data memory 13 is displayed as an image on, for example, the display device 14 to determine the stress distribution of the subject S.

When the temperature data is integrated, the addition is performed in the plus data memory 11 and the minus data memory 12, the result is divided by the number of times of integration, and the difference data is stored in the difference data memory 13.
Can also be entered.

Although the infrared stress imaging system of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments, and various modifications are possible.

[0020]

As is apparent from the above description, according to the infrared stress imaging system of the present invention, an image signal from the infrared camera is input within a predetermined time width when the stress applied to the subject becomes substantially maximum. Only when the image signal is taken as plus temperature distribution data, and only when an image signal from the infrared camera is input within a predetermined time width when the stress applied to the subject is substantially minimized, the image signal is taken as minus temperature distribution data. The temperature change distribution is obtained by taking the difference between the taken plus temperature distribution data and the taken minus temperature distribution data, so if the vibration frequency of the subject is more than several minutes of the scanning frequency of the infrared camera, Even in a high state approaching the excitation frequency, the temperature distribution can be reliably detected to detect the stress distribution.

[Brief description of the drawings]

FIG. 1 is a timing chart for explaining the principle of an infrared stress imaging system according to the present invention.

FIG. 2 is a block diagram of one embodiment of the infrared stress imaging system of the present invention.

FIG. 3 is a timing chart for explaining a conventional infrared stress imaging system.

[Explanation of symbols]

 S: subject 1: exciter 2: infrared camera 3: plus trigger generation circuit 4: minus trigger generation circuit 5: frequency detection circuit 6: plus trigger gate generation circuit 7: minus trigger gate generation circuit 8, 9: synchronization determination Circuit 10 Operation control circuit 11 Plus data memory 12 Minus data memory 13 Difference data memory 14 Display device

Claims (1)

(57) [Claims] 1. A method in which a load is periodically applied to a subject to generate heat,
In the infrared stress imaging system that detects the temperature change of the sample surface based on the endothermic effect with an infrared camera and detects the stress distribution based on the temperature change distribution, a predetermined time width when the stress applied to the subject becomes substantially maximum Only when the image signal from the infrared camera is input into the camera, the image signal is captured as plus temperature distribution data, and the image signal from the infrared camera is input within a predetermined time width when the stress applied to the subject is substantially minimized. An infrared stress imaging system characterized in that the image signal is fetched only as a negative temperature distribution data and the temperature change distribution is obtained by taking the difference between the fetched positive temperature distribution data and the negative temperature distribution data.