JPH0533334B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a stress imaging system that uses thermoelastic effects to maintain an optimal phase even if a beat occurs between the scan frequency of load detection and the frequency of the load signal. This invention relates to an automatic phase adjustment method that can be adjusted to

[Conventional technology]

When conducting a metal fatigue test, etc., a stress measurement device is used that applies a compressive load or tensile load to a sample, detects infrared rays from the sample surface, and measures the stress distribution of the sample in a non-contact manner. This method focuses on the thermoelastic effect in which the surface temperature of the stress concentration area of a sample increases when subjected to a compressive load, and decreases when subjected to a tensile load. This stress measurement device that uses thermoelastic effects applies a load to the sample periodically and detects infrared rays from the sample surface that correspond to the temperature of the sample. A signal is obtained by subtracting the temperature when no load is applied or when a load is applied in the opposite direction, and a temperature distribution image of the sample, that is, a stress distribution image is obtained based on this difference signal.

FIG. 3 is a diagram showing the overall configuration of the stress imaging system, FIG. 4 is a diagram showing the specific configuration of the system generation circuit, and FIG. 5 is a diagram for explaining the operation of the timing generation circuit shown in FIG. 4. FIG. In the figure,
11 is a sample, 12 is a load shaker, 13 is an infrared camera, 14 is a signal processing circuit, 15 is an A/D converter, 16 is a timing generation circuit, 17 is a data processing device (computer), 21 is an amplifier, 22 is a comparator , 23, 24, 37 and 38 are differentiating circuits, 25 is an oscillation circuit, 26, 27 and 30 are counters, 28 and 29 are monomulti, 31 is a latch circuit, 32 is a NAND circuit, 33 to 35 are FF (flip-flop circuits) ), 36 is an AND circuit, 39
41 to 41 indicate the I/O interface of the CPU.

In FIG. 3, a load shaker 12 applies an alternating load to the sample 11 by repeatedly applying a compressive load and a tensile load. The infrared camera 13 two-dimensionally scans and detects infrared rays generated from the sample 11 by applying an alternating load.
This infrared detection signal is transmitted to the signal processing circuit 14 and the A/
The data is sent to the data processing device 17 through the D converter 15. Further, the timing generation circuit 16 generates a timing signal for sampling the infrared detection signal based on the load waveform obtained from the load shaker 12, and sends it to the data processing device 17. The data processing device 17 consists of an arithmetic processing section, a storage section, a display section, etc., and takes in the infrared detection signal according to the timing signal supplied from the timing generation circuit 16, performs stress integration and other predetermined processing, and stores it in the storage section. The stress image is stored and further displayed on the display section.

The timing generation circuit 16 uses the load signal as a synchronization signal, as shown in FIG. 4 for its specific circuit configuration and FIG. 5 for the waveforms of its main signals.
From this synchronization signal, a compression side start signal is obtained by a rising differentiation, and a tension side start signal is obtained by a falling differentiation, through a comparator 22 and differentiating circuits 23 and 24. Using one of these signals, a counter 30 counts one cycle of clocks to obtain cycle data. The data processing device is the CPU
This one-cycle data T _S is read through the I/O interface 39 of the CPU, and the phase data T _D T _D = T _S ×N/N _S is calculated and sent to the I/O interface 40 of the CPU.
Set to . In the above formula, N _S is the number of divisions of one cycle, and N is 0 to N _S . The compression counter 26 and the tension counter 27 are loaded with phase data T _D using the compression side start signal or the tension side start signal. Then, the compression counter 26 receives the phase data.
After presetting T _D , the clock is subtracted, and when the count value reaches 0, an underflow signal is sent. This underflow signal sets the FF 33 to make it a compressed signal, and also takes the timing of the timing signal HBL during the horizontal scanning period to create an effective HBL on the compression side. Only this effective HBL data is used as stress data to detect and integrate data on the compression side.

The tension counter 27 similarly sends out an underflow signal, which resets the FF 33 and inverts the compression signal to become a tension signal. Similarly, an effective HBL on the tension side is created, and data on the tension side of stress is detected and integrated.

With the above configuration, the phase data is set from the data processing device, the compression side temperature and the tension side temperature are detected, and the stress value at that time is determined from "compression side temperature - tension side temperature".

The phase data is set as follows. First, the operator sets the cursor on a portion of the displayed stress image where the stress value is high. This setting advances the V scan of the scanner unit to the V position of the cursor. The scanner then performs a line scan at the specified position of the cursor. Thereafter, the number of divisions N _i is set to 0, stress integration and difference calculation are performed for several points near the cursor cross point, and the average value S _i for these several points is determined. This is to improve the S/N through averaging.
Next, N is changed in order up to N _S /2 (N _S is the number of sections in one cycle), and the average value S of each stress value is determined. Thereafter, the maximum value S _nax of the average value S is determined, and the number of sections N _nax corresponding to that position is determined. Thereby, phase data T _D is calculated using the formula T _D = T _S ×N _nax /N _S.

[Problem that the invention seeks to solve]

As mentioned above, in the stress imaging system using the thermoelastic effect, it is necessary to match the detected phase with the load signal, but the stress signal due to the thermoelastic effect is extremely small and has a frequency of 1 to 50 Hz.
Due to the low degree of phasing, it was extremely difficult to perform this phase matching manually. Additionally, when automating and setting this phase using a computer, the line scan or frame scan type generates a beat when the frequency of the scan signal and the frequency that is an integer multiple of the frequency of the load signal approach each other. It may not be possible to match the correct phase.

The present invention is based on the above considerations, and includes:
The purpose of this invention is to provide an automatic phase adjustment method for a stress imaging system that can match the optimum phase even if the frequency of a scan signal and a frequency obtained by multiplying the frequency of a load signal by an integer are close to each other and a beat occurs. be.

[Means for solving problems]

Therefore, the automatic phase adjustment method of the stress imaging system of the present invention includes a period detection circuit that determines the period of the load signal, a delay circuit that generates a signal delayed by a specified delay time on the compression side and the tension side of the load signal, and In a stress imaging system equipped with a data processing device that detects and integrates stress using circuit signals, displays a stress image, and automatically adjusts the detection phase by specifying the delay time, the data processing device includes:
The stress value is integrated a predetermined number of times for each step that divides the half cycle of the load signal, and the process is repeated multiple times to find the step at which the stress value is maximum, and the specified delay time is calculated from this step. It is characterized by being configured as desired.

[Effect]

In the automatic phase adjustment method of the stress imaging system of the present invention, stress values are first accumulated for each step a predetermined number of times, and this is repeated, so that the exact maximum value can be found for each stress accumulation value. . In other words, if the frequency of the scan signal and the frequency obtained by multiplying the frequency of the load signal by an integer are close to each other, even if you simply repeat stress integration the same number of times as in the method of the present invention, the integrated value near the maximum value is in a beat state, making it difficult to find the exact position of the maximum value.However, in the method of the present invention, since the stress integration is not repeated uniformly, it is possible to search for the exact maximum value. Since the phase is matched according to the search result of this maximum value, it is possible to match the phase to the optimum phase for stress detection.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of an automatic phase adjustment method of a stress imaging system according to the present invention.

In the automatic phase adjustment method of the stress image system according to the present invention, a cursor is set on the screen displaying the stress image, and the vertical direction is stopped on the horizontal line of the cursor to perform a line scan. Then, the half cycle of the load signal is divided into a predetermined number S, and stress integration is performed for each step. In this stress integration, in order to avoid a beat between the load signal and the horizontal scan, the first integration is performed a predetermined number of times N for each step. This is further performed a predetermined number of times M as a second integration.
is repeated for a total of N×M times. The maximum value of the stress values of the S step obtained through the integration is detected, and phase data is generated based on the point of the detected maximum value. Figure 1 shows an example of the process flow described above, in which a half cycle is divided into 6 parts, the first integration is performed eight times, and the second integration is performed eight times.
16 times, that is, S=16, N=8, and M=16. This will be explained below.

Read the cycle data of the load signal. Perform the following processing.

One-line stress integration is roughly performed, and the average value of the data around the cross point (for example, 5 points) specified on the screen by the cursor is determined. Perform the following processing.

The total loop integration, ie, the number of times M of the secondary integration described above, is set to "1". Perform the following processing.

Step S for performing stress integration is set to "0". In other words, in this case, the steps S for performing stress integration are 16 steps from "0" to "15". Perform the following processing.

Stress integration (first integration) in step S is 8
Implemented twice. Perform the following processing.

Check whether step S of the first integration has reached "15".

If YES, perform the process; if NO, perform the process.

Raise step S by one step. Return to next process.

Check whether the number of times M of secondary integration has reached "16".

If YES, perform the process; if NO, perform the process.

The number M of secondary integration is added by one. Return to next process.

Find the value of step S that maximizes the average value (integrated value) around the cross point. Then, phase data is generated based on this value.

Note that if the S/N is good, you can leave it as is, but if the S/N is poor, that is, there is not much difference between the maximum value and the surrounding values, and the maximum value does not stand out, then change the maximum value. For example, the process may be returned to the above process for the vicinity of , for example, five points, and the same process may be repeated to find the maximum value again.

In the stress imaging system to which the present invention is applied, the number of delay clocks is determined from the value of step S determined by the above-described processing, and this is set as phase data.

FIG. 2 is a diagram showing an example of a configuration of functional blocks of a phase adjustment section according to the present invention, in which 1 is a step control section, 2 is a stress integration section, 3 is a maximum value detector, and 4 is a phase setting section. In the configuration shown in FIG. 2, the step control section 1 sets the step for performing stress integration in the phase setting section 4, and causes the stress integration section 2 to execute stress integration. When the stress integration is completed, the maximum value detection section 3 determines the point where the integrated stress value is maximum, and the phase setting section 4 sets optimal phase data based on the result.

Note that the present invention is not limited to the above embodiments, and the number of half-cycle divisions, the number of primary integrations, the number of secondary integrations, etc. may vary depending on the stress detection frequency, the load signal frequency, the system An appropriate value may be selected depending on the situation. It goes without saying that various other modifications are possible.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, primary stress integration is performed a predetermined number of times at each step of a half cycle, and this is repeated multiple times by secondary integration to obtain the maximum value. Therefore, the frequency of the scan signal and the frequency obtained by multiplying the frequency of the load signal by an integer become close to each other, and even if a beat occurs, it is possible to match the optimum phase.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of the automatic phase adjustment method of the stress imaging system according to the present invention, FIG. Figure 4 shows the overall configuration of the stress imaging system, Figure 4 shows the specific configuration of the timing generation circuit, and Figure 5 is a waveform diagram for explaining the operation of the timing generation circuit shown in Figure 3. It is. DESCRIPTION OF SYMBOLS 1... Step control part, 2... Stress integration part, 3... Maximum value detection part, 4... Phase setting part, 11... Sample, 12
...Load shaker, 13...Infrared camera, 14...Signal processing circuit, 15...A/D converter, 16...Timing generation circuit, 17...Data processing device (computer), 21...Amplifier, 22...Comparator, 23,
24, 37 and 38... Differential circuit, 25... Transmission circuit,
26, 27 and 30...counter, 28 and 29...mono multi, 31...latch circuit, 32...Nand circuit,
33 to 35...FF (flip-flop circuit),
36...AND circuit, 39 to 41...CPU I/O interface.

Claims (1)

[Claims] 1. A period detection circuit that determines the period of the load signal, a delay circuit that generates a signal delayed by a specified delay time on the compression side and the tension side of the load signal, and stress detection based on the signal of the delay circuit. In a stress imaging system equipped with a data processing device that performs integration and displays a stress image and automatically adjusts the detection phase by specifying the delay time, the data processing device performs integration and displays a stress image, and the data processing device calculates a plurality of steps for dividing a half cycle of a load signal. Stress characterized by a structure in which a stress value is integrated a predetermined number of times, the process is repeated a plurality of times to find a step at which the stress value is maximum, and a specified delay time is found from the step. Automatic phase adjustment method for imaging systems. 2. The automatic phase adjustment method for a stress imaging system according to claim 1, wherein the number of repetitions is adjusted according to a difference between a maximum stress value and a value around the maximum stress value.