JPH02143158A - Material deterioration detecting method - Google Patents

Abstract

PURPOSE:To find the degree of deterioration in a material quantitatively by determining the position by finding the ultrasonic wave attenuation factor of an extremely small element by using an ultrasonic wave oscillator and detectors which are installed opposite each other across a measurement position. CONSTITUTION:A probe 8 is swung to move a cylinder 9 straight in parallel to a measured surface and the external shape of the measured surface is found from the swing angle of the probe 8 and the displacement position of the cylinder 9 and stored in a measuring instrument 5. The ultrasonic wave oscillator 2 and detectors 3 are installed across the measurement position and the installation position is known from the external shape information in the device 5. The oscillator 2 sends an ultrasonic wave of constant intensity and the opposite detectors 3 detect it. The detected intensity is the product of ultrasonic wave intensity values attenuated in extremely small elements determined by the positions of the oscillator and detectors. The oscillator is shifted in position and (n) detected intensity values are measured by the N detectors to find the attenuation factor R of each extremely small element, thereby calculating creep damage from the attenuation factor and also diagnose the life.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a material deterioration detection method for measuring the degree of deterioration over time of high-temperature parts such as a steam turbine and diagnosing their lifespan.

(Conventional technology) Generally, turbine rotors, casings, piping, etc.
When metal materials are used under high stress for long periods of time, they deteriorate, resulting in cracks, deformation, and ultimately destruction. In order to ensure the safety and reliability of such structures, it is necessary to detect the deterioration of metal materials over time during use to determine when to replace them.

The conventional method for detecting metal material deterioration is to cut test pieces from actual machine parts and conduct destructive tests.
Since this method involves cutting the actual machine parts, it is difficult to detect the degree of deterioration over time.

Examples of methods for nondestructively detecting deterioration include Japanese Patent Application Laid-Open No. 113360/1983 and "Basic Study on Nondestructive Diagnosis of Creep Damage in Low Alloy Steel" (Materials, Vol. 33, 3).
No. 71, page 137). As shown in Fig. 5, this method is a method that determines the deterioration of actual machine parts, especially creep damage, and changes in electrical resistivity. This is a method to measure the degree of deterioration. However, with these dimensions, as shown in FIG. 6, the change in electrical resistance ratio ΔRρ is the creep damage φ. Although there is not necessarily a one-to-one relationship with φc and increases linearly up to 0.5, it tends to decrease when φc>O,S.

In order to correct this relationship, a method has been proposed that uses measured values of materials that are only subjected to heating, but in either method, the overall average of the measurement member or the average degree of deterioration only near the surface is measured. The measurement accuracy is low because it performs a lifespan diagnosis, and is insufficient to ensure reliability and safety.

(Issues to be Solved by the Invention As mentioned above, in the conventional deterioration measurement method for high-temperature parts, the degree of deterioration inside the member can be accurately measured only by the destructive needle 81g method, while the non-destructive measurement method It is only possible to measure the average degree of deterioration, and it is impossible to measure the position inside one member.

However, the material deterioration of high-temperature parts is not uniform between the inside and the surface, and each part receives a different history of temperature and stress. Good detection of the degree of deterioration is essential.

In addition, recent findings indicate that voids that occur due to creep damage are located several liters from the surface, rather than from the surface of the stress concentration area.
There are also cases where a large amount of deterioration is found in the parts inside l1, which shows the importance of detecting the degree of deterioration inside a single member. Furthermore, conventionally, cast steel parts such as steam turbine casings exhibit a material change called decarburization in areas where the casting surface remains.
Conventional methods have problems such as being able to measure deterioration only after removing the decarburized layer.

The present invention has been made in response to such conventional circumstances,
It is an object of the present invention to provide a material deterioration detection method for determining the position and detecting deterioration inside a high-temperature component and diagnosing the life of the component.

[Structure of the invention]

(Means for Solving Problem 111) The present invention measures and stores the external dimensions of a subject in advance, and then attaches an ultrasonic transmitter and a detector to the subject based on the measurement results. tfli! ! L. The degree of material deterioration is determined from the attenuation rate of the ultrasonic waves sent from the ultrasonic detector to the subject.

(Function) In the present invention, the external shape of the measurement site is determined accurately so that the installation positions of the ultrasonic oscillator and the ultrasonic detector can be obtained with high precision.

Next, the ultrasonic oscillator and ultrasonic detector are placed facing each other across the measurement site. The ultralong wave emitted from the ultrasonic oscillator weakens its intensity while passing through the high-temperature member, and the intensity of the ultralong wave obtained by the detector is determined depending on the transmission distance and material. The ultrasonic oscillator moves by small distances and performs multiple measurements.

The measured value obtained by the detector is the product of the ultrasonic attenuation coefficients of each part on each ultrasonic path, and conversely, the ultrasonic attenuation coefficient of each part inside the material is found as a solution of these equations. be able to.

In the laboratory, ultrasonic attenuation rate and material deterioration degree 1, for example, creep damage φ. Since there is a one-to-one functional relationship with melting, creep damage φ can be calculated from the ultrasonic attenuation rate of each part.

can be obtained, and the creep damage φC inside one member can be understood as a lifetime distribution.

(Example) Hereinafter, one example of the present invention will be described based on FIGS. 1 to 4.

Figure @1 shows a main part of an embodiment of the present invention, and shows a state in which a measurement device is attached to a test object 1 such as a high-temperature component, and the degree of deterioration is measured non-destructively.

That is, the ultrasonic oscillator 2 and the detector 3 are installed on opposite sides surrounding the measurement site of the subject 1 . The ultrasonic oscillator 2 and the detector 3 are connected to an ultralong wave range attenuation rate measuring device 4 that controls them and measures the intensity of the ultrasonic waves. The attenuation rate measuring device 4 also uses an external shape needle 41 that stores the external shape of the measurement site in advance.
It is also connected to the g device 5, and the ultrasonic oscillator 2 and detector 3
By accurately determining the installation position of the oscillator 2 and each detector 3, the mutual distance between the oscillator 2 and each detector 3 and the transmission path of the ultrasonic waves can be determined with high accuracy. The attenuation rate measuring device 4 works in conjunction with the deterioration degree detector 6 to determine the degree of deterioration, such as creep damage φ, from the ultrasonic attenuation rate of each part. Calculate. The obtained deterioration degree damage distribution is displayed as a damage distribution on a display 7 connected to the deterioration degree detector 6, and the lifespan of the measured portion is diagnosed.

FIG. 2 shows the configuration for measuring the external shape before measuring the degree of deterioration. The external shape detector consists of a stylus 8 that moves along the surface on which the ultrasonic oscillator 2 and detector 3 of the measurement site are installed, and a cylinder 9 that moves the stylus directly in the direction of the measurement surface, and is controlled by the external measuring device controller 10. At the same time, it is connected to the external shape measuring device 5 in order to obtain data on the external shape of the measurement site determined from the movements of the stylus 8 and the cylinder 9.

Next, the operation of this embodiment will be explained.

First, to accurately obtain the external shape of the measurement site.

In FIG. 2, in which the external shape is measured, the stylus 8 swings around the supporting part, and the entire supporting part of the stylus 8 moves straight by the cylinder 9, so the cylinder 9
The outer shape of the measurement surface can be determined from the deflection angle of the stylus 8 and the amount of displacement of the cylinder 9 by moving the probe straight approximately parallel to the measurement surface.

The operation of the cylinder 9 is controlled by the external shape measuring device controller 10, and the obtained external shape signal data is sent to the external shape measuring device 5.
is stored in

Next, place the ultrasonic oscillator 2 at the opposite position across the measurement site.
and detector 3 is installed. Although it is possible to measure with a single ultrasonic detector 3, in this case the detector 3 must be moved, and in this case, errors are likely to occur due to differences in the properties of the installation surface, so multiple detectors 3 are used. A more accurate value can be obtained by installing it in a fixed manner. The installation position of the ultrasonic oscillator 2 and detector 3 is the external measurement device! ! It can be accurately obtained using the external shape data of No. 5. An ultrasonic oscillator 2 emits ultrasonic waves with a constant intensity, and a plurality of facing ultrasonic detectors 3 detect ultrasonic waves whose intensity has attenuated after passing through the inside of the member. Assuming that the detection site is a collection of microelements virtually divided into many vertical and horizontal sections, the intensity of the ultrasonic waves obtained by each detector 3 is determined from the positions of the oscillator 2 and the detector 3 within the plurality of microelements. It is the product of the ultrasonic intensity attenuated by . That is, the detection intensity Si of the i-th detector, the intensity s0 of the ultrasonic oscillator. J
Assuming that the attenuation rate of the th minute element is Rj, the following N equations are obtained from N detectors.

5i=S0x (Rjx・-xhl [
i = 1-N) By moving the position of the oscillator and performing n measurements, n×N equations are obtained, and from these equations, the attenuation rate Rj,...R, can be found.

In the laboratory, there is a one-to-one functional relationship between the degree of material deterioration, such as creep damage, and the ultrasonic attenuation rate, as shown in Figure 3. Direct calculation of creep damage becomes possible.

From this result, it is possible to draw an equal creep damage distribution map at the measurement site as shown in FIG. 4 as a distribution map of the degree of material deterioration, thereby understanding the damage state of the five members and making it possible to diagnose the service life.

Test objects such as high-temperature parts often have defects during manufacturing, but these defects have different ultrasonic attenuation characteristics compared to the base material, so it is difficult to clearly understand changes in attenuation rate due to material deterioration. Measures the test object from the initial state of use,
It is necessary to distinguish the defect site from the base material site and perform measurements at regular intervals over time.

Therefore, according to this example, it is possible to non-destructively measure the deterioration of a member used at high temperatures by determining the internal position using ultrasonic waves. Compared to the method of taking samples and destructively measuring the degree of deterioration, lifespan diagnosis can be performed in a shorter time and with higher accuracy.

Another embodiment is a method that uses the dependence of the ultrasonic velocity on the degree of deterioration instead of using the characteristic of the attenuation rate of the ultrasonic wave, and the ultrasonic wave oscillated from the ultrasonic oscillator 2 is applied to the detector 3. By measuring the arrival time and similarly determining the sound speed within each microelement from the distance between the ultrasonic oscillator 2 and the detector 3 and the microelements passing through, it is possible to further calculate the degree of deterioration.

〔Effect of the invention〕

As explained above, the present invention uses an ultrasonic oscillator and a detector placed opposite each other to sandwich the measurement area in order to measure the material deterioration over time of components used at high temperatures. This method non-destructively measures the degree of deterioration at each position within the measurement area based on the relationship between the degree of deterioration obtained in the laboratory by determining the acoustic attenuation rate, and is faster and more accurate than conventional destructive testing methods. The present invention has great effects, such as being able to measure and quantitatively determine the degree of deterioration inside a material by determining its position, which was impossible with conventional non-destructive methods. Furthermore, by measuring from the initial state of the part, it is also possible to measure the defect position and size at the same time.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the deterioration detection device according to the present invention, Fig. 2 is a diagram explaining the behavior of the external shape measuring device shown in Fig. 1, and Fig. 3 is a diagram showing the ultrasonic attenuation rate and creep damage. A graph showing the relationship, FIG. 4 is a diagram displaying the deterioration degree detection results as a creep damage distribution map. FIG. 5 is a diagram showing an example of a conventional non-destructive deterioration detection result, and FIG. 6 is a graph showing an example of a conventional non-destructive deterioration detection result. 1... Subject. 3...Detector, 5...Outline measuring device. 7...Display device. 2...Ultrasonic transmitter, 4...Attenuation rate measuring device, 6...Degradation degree detector, Agent Patent attorney Rule Yudo Chika Nori Daishimaru Ken shoes - 7° Zuichi product diagram

Claims (1)

[Claims] The external dimensions of the object to be examined are measured and memorized in advance, and based on the measurement results, an ultrasound transmitter and a detector are installed on the object, and the ultrasonic waves are transmitted from the ultrasound transmitter to the object. A method for detecting material deterioration, characterized in that the degree of material deterioration is determined from the attenuation rate of ultrasonic waves.