WO2011115261A1 - Rubber product inspection method and rubber product inspection device - Google Patents

Rubber product inspection method and rubber product inspection device Download PDF

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Publication number
WO2011115261A1
WO2011115261A1 PCT/JP2011/056607 JP2011056607W WO2011115261A1 WO 2011115261 A1 WO2011115261 A1 WO 2011115261A1 JP 2011056607 W JP2011056607 W JP 2011056607W WO 2011115261 A1 WO2011115261 A1 WO 2011115261A1
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WIPO (PCT)
Prior art keywords
rubber product
rubber
crack
elastic wave
signal
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PCT/JP2011/056607
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French (fr)
Japanese (ja)
Inventor
純一郎 山辺
隆志 松本
伸 西村
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独立行政法人産業技術総合研究所
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Publication of WO2011115261A1 publication Critical patent/WO2011115261A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/14—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object using acoustic emission techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/4409—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison
    • G01N29/4427—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison with stored values, e.g. threshold values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/46—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by spectral analysis, e.g. Fourier analysis or wavelet analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G01N2203/0062—Crack or flaws
    • G01N2203/0066—Propagation of crack
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0235—Plastics; polymers; soft materials, e.g. rubber

Definitions

  • the present invention relates to a rubber product inspection method and a rubber product inspection device. More specifically, the present invention relates to an inspection method and a rubber product inspection device for detecting an elastic wave generated from a rubber product and determining a damaged state or quality of the rubber product from the characteristic of the elastic wave.
  • Rubber seals represented by O-rings are used in a wide range of fields, from home appliances to large machines, precision equipment to construction machinery. Rubber has excellent properties such as plasma resistance, heat resistance, cleanness, non-adhesiveness, chemical resistance, solvent resistance, oil resistance, and has an advantage that it can be easily manufactured into a desired shape.
  • rubber has a long history of rubber production for centuries since it was extracted from natural plants and used for industrial purposes. However, special attention is required for rubber products used in severe environmental conditions such as high temperature, vacuum and high pressure, environments where high airtightness is required, particularly rubber seal materials. For example, when manufacturing the rubber product, the quality control and design requires knowledge and experience and requires great effort and great care. Also, since it is an environment that requires high airtightness when used, knowledge and experience are also required for quality control, and careful attention is paid.
  • Patent Document 1 discloses a method of observing a crack on the surface of a belt after stretching the rubber belt a plurality of times. For this observation, mechanical energy is added to the belt.
  • a method for inspecting a crack inside the rubber product a non-destructive inspection without applying a load to the rubber product is preferable.
  • the acoustic emission (hereinafter referred to as AE) signal is an elastic wave that is emitted when a material is deformed, broken, or cracked. This elastic wave can be detected by a detection element installed on the surface of the material.
  • the AE signal usually has a frequency band of several kHz to several MHz, although it depends on the type of material and the type of deformation, fracture, crack, and the like.
  • an AE signal generated in a metal material is a signal having a frequency of 100 kHz to 1 MHz.
  • a piezoelectric element is generally used as a sensor for detecting an AE signal.
  • the piezoelectric element is brought into close contact with the surface of a material to detect the AE signal.
  • a quality control system for laminated rubber in which an AE sensor attached to a laminated rubber used in a seismic isolation structure detects an AE signal generated from a defect in the laminated rubber (Patent Document 2). 3).
  • the arrival order and time difference of AE signals detected by a plurality of AE sensors are measured, and the position where a defect occurs is specified (see paragraph [0026] in the specification of Patent Document 2).
  • Patent Document 4 discloses a method and an apparatus for estimating a damaged state of a rubber product such as a tire. Install an AE sensor inside the wheel rim of the tire, detect AE waves, compare the degree of change in the cumulative number of AE waves, and the relationship data between the cumulative number of AE waves known in advance and the tire damage status Estimate the damage condition of the tire.
  • the AE signal is composed of elastic waves having a plurality of frequencies that are continuously generated in a short period of time, and the strength and size thereof vary depending on the type of material, the size of a crack, and the like.
  • AE sensor acoustic emission sensor
  • the first method is an event method in which one AE signal is counted as one.
  • an AE signal to be counted is called an AE event count
  • an AE event count number per unit time is called an AE event count rate.
  • This AE event count rate is often used for evaluation of fatigue crack propagation in consideration of the fact that the AE signal generated from a crack that propagates due to repeated stress is basically discrete.
  • the second method is a ring-down method that counts all amplitudes that exceed the defined reference value.
  • An AE signal counted by this ring-down method is called an AE ring-down count
  • an AE ring-down count number per unit time is called an AE ring-down count rate.
  • FIG. 15 illustrates the difference between the event method and the ring-down method.
  • FIG. 15A shows one AE signal.
  • FIGS. 15B and 15C show the difference between the event method and the ring-down method, which are two methods for counting the AE signal.
  • FIG. 15B shows the event method.
  • FIG. 15C shows the ring-down method.
  • the maximum intensity of the AE signal in FIG. 15A is equal to or greater than a set threshold value.
  • the AE signal in FIG. 15A is counted as “1” in the event method.
  • the AE signal in FIG. 15A is counted as “4” in the ring-down method, as shown in FIG. 15C.
  • JP 2005-164499 A Japanese Patent Laid-Open No. 11-64098 Japanese Patent Laid-Open No. 11-64099 JP 2005-337929 A
  • a method for detecting AE waves is known as a non-destructive inspection technique for metal materials.
  • the amplitude of AE waves generated from rubber products is orders of magnitude smaller than that of AE waves generated from metal.
  • the incidence of AE waves generated from rubber products is orders of magnitude less than that of metal.
  • Patent Documents 2 and 3 an AE sensor is used for inspection of a large rubber material used for a building structure. This rubber material is supported by a large pressure from a building structure or the like.
  • those described in Patent Documents 2 and 3 see only the change in the count of the AE signal. Under such circumstances, a technology for inspecting a minute rubber product such as a rubber seal material using an AE sensor has not yet been established.
  • An object of the present invention is to provide a rubber product inspection method and a rubber product inspection device for inspecting a rubber product by nondestructive inspection using AE waves.
  • Another object of the present invention is to provide a rubber product inspection method and a rubber product inspection device for inspecting a rubber seal material by nondestructive inspection using AE waves.
  • Rubber products refers to products, parts, members, etc. that use rubber as a material.
  • the type of rubber is appropriately selected and used according to the use of rubber products, application location, application equipment, and the like.
  • Examples of rubber types include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, chloroprene rubber, nitrile rubber, ethylene propylene rubber, acrylic rubber, epichlorohydrin rubber, hypalon, urethane rubber, silicone rubber, and fluorine rubber. Perfluoro-rubber.
  • EPDM ethylene propylene rubber
  • NBR acrylonitrile butadiene rubber
  • silicone rubber silicone rubber
  • fluorine rubber fluorine rubber and the like
  • carbon black silica and other fillers, anti-aging agents, oils and the like can be used.
  • Crack (Crack in English) is a defect such as a crack, a crack, or a crack generated in a material, in the case of the present invention, in a rubber product.
  • a crack is generated from the surface or inside of the rubber product.
  • the generated crack is repeatedly developed by the load, and eventually the rubber product is destroyed.
  • a load is applied to a material having a crack, a stress concentration with a high load is generated in the crack, particularly in the vicinity of the tip of the crack.
  • AE Acoustic Emission
  • AE Acoustic Emission
  • This elastic wave can be detected by an AE sensor which is an element for detecting an AE signal installed on the surface of the material.
  • the AE sensor is an element for converting an elastic wave into an electric signal and outputting it.
  • the AE sensor is generally composed of a piezoelectric element, detects an AE signal in close contact with the material surface, converts the AE signal into an electrical signal, and outputs the electrical signal.
  • the purpose of the present invention is to inspect a crack generated inside a rubber product and grasp its size and progress.
  • the internal crack condition of the rubber product used in a severe environment such as high pressure can be detected in a slight state, and the use can be stopped before the internal crack reaches the surface.
  • the remarkable effect that the failure avoidance of the apparatus which uses a rubber product, the performance maintenance, and an accident can be prevented beforehand is brought about.
  • the maintenance of the apparatus using the rubber product becomes easy.
  • the rubber product inspection method of the present invention is an inspection of a rubber product for inspecting the damage of the rubber product by detecting an elastic wave (AE) generated from a crack of the rubber product by an elastic wave detecting means (AE sensor). Is the method.
  • the method for inspecting a rubber product includes detecting the elastic wave (AE) generated from the rubber product after decompressing the rubber product in a high-pressure gas atmosphere environment composed of gas, and detecting the elastic wave (AE) From the characteristics of the change over time, the elastic wave is (a) the elastic wave generated when supersaturated gas becomes a bubble from the rubber product, or (b) the bubble It is characterized by inspecting the state of damage of the rubber product by determining whether the elastic wave is generated when a crack is generated starting from the point.
  • the method for inspecting a rubber product according to the present invention presumes that the rubber product is greatly damaged when a change with time of the crack shows an indication that the crack has progressed to the surface of the rubber product. Furthermore, in the method for inspecting a rubber product according to the present invention, the determination is made by comparing the change with time with characteristics of the rubber product whose damage state is known in advance.
  • the rubber product may be an O-ring.
  • the rubber product inspection apparatus of the present invention is for detecting elastic waves (AE).
  • the elastic wave detection means (AE sensor) is fixed to or installed near the rubber product, and the elastic wave detection means (AE).
  • a sensor analyzing the elastic wave (AE) generated from the rubber product, obtaining a change with time, and analyzing the rubber product comprising an analysis means for judging damage of the rubber product. It is a device for inspection.
  • the analysis means obtains a change with time of the elastic wave (AE) detected by an elastic wave detection means (AE sensor) after decompressing the rubber product under a high-pressure gas atmosphere environment, and from the characteristics of the change with time,
  • the elastic wave is (a) the elastic wave generated when a supersaturated gas becomes a bubble from the rubber product, or (b) the elasticity generated when a crack is generated from the bubble.
  • the analysis means determines that the rubber product is damaged, and outputs a signal to that effect. To do.
  • the analyzing means estimates that the rubber product is damaged and outputs a signal to that effect. To do.
  • the analysis means includes comparison means for comparing the change with time with characteristic data of the rubber product whose damage state is known in advance.
  • the rubber product may be an O-ring.
  • the rubber product inspection method and the rubber product inspection apparatus of the present invention can detect AE waves generated from the inside of the rubber products, evaluate the rubber products from the trends of the AE waves, and perform nondestructive inspection. It was.
  • FIG. 1 is a conceptual diagram illustrating an outline of a damage detection system 1 for rubber products according to an embodiment of the present invention.
  • FIG. 2 is a diagram illustrating an example of the O-ring of the sample 3 according to the present embodiment of the present invention.
  • FIG. 2A is a conceptual diagram of the O-ring, and
  • FIG. It is AA sectional drawing of 2 (a).
  • FIG. 3 is a block diagram showing an example of the signal processing unit 5 of the rubber product damage detection system 1 according to the embodiment of the present invention.
  • FIG. 4 is a graph showing the relationship between the AE event count generated in rubber and the AE amplitude.
  • FIG. 5 is a graph showing the relationship between the AE event count generated in rubber and the AE frequency.
  • FIG. 1 is a conceptual diagram illustrating an outline of a damage detection system 1 for rubber products according to an embodiment of the present invention.
  • FIG. 2 is a diagram illustrating an example of the O-ring of the sample 3 according to the present embodiment of the present invention.
  • FIG. 6 is a conceptual diagram showing an outline of Experiment 1 showing a method for comparing attenuation of AE signals in a metal material and a rubber material.
  • FIG. 7 is a graph showing the results of Experiment 1, and is a graph showing the results of measuring the attenuation of AE waves generated in the metal material and the rubber material.
  • FIG. 8 is a conceptual diagram showing the state of measurement in Experiment 2
  • FIG. 8 (a) is a conceptual diagram showing the dimensions of the test piece
  • FIG. 8 (b) is an AE signal when a crack is generated in the test piece. It is a conceptual diagram which shows a mode that it measures.
  • FIG. 9 is a graph showing the results of Experiment 2.
  • FIG. 9A shows the case of copper
  • FIG. 9A shows the case of copper
  • FIG. 9A shows the case of copper
  • FIG. 10 shows the results of Experiment 3 and is a photograph showing a cross section of a rubber test piece.
  • FIG. 10 (a) is a photograph after the test exposed to high-pressure gas is repeated three times.
  • (B) is a photograph after the test exposed to high-pressure gas was repeated five times.
  • FIG. 11 is a graph showing the result of obtaining the event rate by performing signal processing on the detected AE signal after repeated exposure tests.
  • FIG. 12 shows an internal crack occurrence state after decompression of a cylindrical test piece exposed in high-pressure hydrogen gas.
  • FIG. 13 is a graph showing the relationship between the AE event count and the AE amplitude generated from the test piece of FIG. 12,
  • FIG. 13 (a) is a graph showing measurement data, and FIG.
  • FIG. 13 (b) is a graph showing FIG. Is a logarithmic axis.
  • FIG. 14 is a diagram stylistically showing the mechanism of occurrence of cracks and bubbles in a rubber product.
  • FIG. 14 (a) is a state of supersaturation
  • FIG. 14 (b) is the generation of bubbles
  • FIG. 14 (c) illustrates how a crack is generated starting from a bubble.
  • FIG. 15 is a diagram for explaining the types of AE signals to be measured.
  • FIG. 15A shows one AE signal
  • FIG. 15B conceptually shows the event method
  • FIG. 15C shows the ring-down method. It is shown schematically.
  • FIG. 1 is a diagram illustrating an outline of a damage detection system 1 for rubber products.
  • a rubber product damage detection system 1 shown in FIG. 1 is a system for confirming and verifying the damage of a rubber product through experiments. From the pressure device 2, the sample 3, the AE sensor 4, the signal processing unit 5, the computer 6, and the like. It is configured.
  • the pressure device 2 is a device for placing the sample 3 therein, maintaining the pressure of the gas in the interior at a predetermined pressure, and controlling the pressure. That is, the pressure device 2 is a gas supply / exhaust means such as a pump 7, and supplies a gas such as hydrogen gas into the pressure device 2 or exhausts the gas in the pressure device 2 to The gas pressure is adjusted to a predetermined pressure.
  • the sample 3 is a rubber product.
  • the sample 3 is a rubber O-ring that is one of seal parts.
  • FIG. 2 shows an example of an O-ring of sample 3 used in this embodiment. As shown in FIG. 2 (a), this O-ring has a radius R1 on the inside and a radius R2 on the outside, and is a ring made of a rubber material having a circular cross-sectional shape.
  • the AE sensor 4 detects an AE signal generated from the sample 3.
  • the AE sensor 4 can be of any shape and operating principle, but in the present embodiment, the AE sensor 4 is made of a piezoelectric material.
  • the AE sensor 4 converts the detected AE signal into an electrical signal and outputs it as a detection signal. This output is input to a subsequent apparatus connected to the AE sensor 4. In the example shown in FIG. 1, the output signal of the AE sensor 4 is input to the signal processing unit 5.
  • the signal processing unit 5 is for analyzing the detection signal received from the AE sensor 4.
  • FIG. 3 shows a circuit example of the signal processing unit 5 in a block diagram.
  • the signal processing unit 5 includes a memory 11, a CPU 10, an input interface 12, an output interface 13, and the like.
  • the memory 11 stores a control program (not shown) for controlling the signal processing unit 5. When the signal processing unit 5 is activated, this control program is called and operates.
  • the input interface 12 is an interface for inputting the detection signal described above to the signal processing unit 5.
  • the input interface 12 is directly connected to the AE sensor 4 and receives a detection signal output from the AE sensor 4.
  • the received detection signal is stored in the memory 11 and read and processed by the control program.
  • the CPU 10 sequentially executes the instructions of the control program stored in the memory 11 to operate the signal processing unit 5.
  • the output interface 13 is for outputting the result of processing the detection signal by the signal processing unit 5. That is, the result of processing the data that is the detection signal by the control program is output as AE signal data.
  • the output AE signal data is provided to the computer 6.
  • the AE signal data is output in a format that can be confirmed by the operator in the computer 6 and displayed on a display or the like.
  • the system 1 includes a preamplifier 16 for amplifying the AE signal received by the AE sensor 4 and outputting the amplified signal to the signal processing unit 5 as indicated by a broken line in FIG.
  • the signal processing unit 5 has a power interface 15 for supplying power.
  • the power supply interface 15 is connected to a direct current or alternating current power source or the like.
  • the signal processing unit 5 has a built-in power source (not shown) such as a battery, and the power interface 15 is connected to the built-in power source.
  • the signal processing unit 5 shows an outline of processing the detection signal. Processing of the detection signal is performed by a control program. These processes can also be realized by a circuit having the same function as this control program.
  • the signal processing unit 5 stores the detection signal in the memory 11 from the data received from the AE sensor 4. At this time, reception time data indicating the time when the detection signal is received is stored in association with the detection signal. Further, other data related to the internal pressure of the pressure device 2 is also stored in association with this detection signal and / or reception time data.
  • the signal processing unit 5 reads the detection signal and the reception time data stored in the memory 11, processes the data, and calculates the AE event count and the AE amplitude.
  • the quality of the sample 3 is determined by comparing the relationship between the AE event count and the AE amplitude with a preset use limit line (described later).
  • the time course of the crack in sample 3 is presumed that sample 3 is severely damaged when it shows signs that the crack has progressed and progressed to the surface of the rubber product, or when the use limit line is reached.
  • the use limit line can be used as this indication.
  • this time-dependent change is compared with the characteristic of the sample 3 whose damage state is known in advance, the damage of the sample 3 is evaluated, and the quality of the sample 3 can also be determined.
  • the signal processing unit 5 outputs the calculation result of the AE event count and the AE amplitude, the determination result, and / or the contents of the memory 11 from the output interface 13 as output data.
  • the output format and device are graph data and tabular data to be used as data for a display device or a printing device. It can also be output in text format data for processing by other electronic computers. It is also possible to add the latest data to this graph and output it.
  • the signal processing unit 5 includes a pressure measuring device (not shown) and the like for measuring the internal pressure of the pressure device 2.
  • the signal processing unit 5 receives data from the AE sensor 4 continuously, periodically, or at a designated time. Further, the signal processing unit 5 receives data from the AE sensor 4 at the time of an operator's reception request or a data request from a computer 6 or other electronic device connected to the signal processing unit 5.
  • the signal processing unit 5 outputs the calculation result continuously, periodically, or at a designated time.
  • the AE sensor 4 is fixed so as to contact the surface of the sample 4 in the pressure device 2.
  • any method may be used as long as the AE sensor 4 is brought into close contact with the surface of the sample 3 and comes into contact therewith.
  • the internal pressure of the pressure device 2 is preferably measured using a pressure measuring device.
  • the pressure measuring device may be a device included in an apparatus for filling the pressure device 2 with a fluid.
  • the AE sensor 4 is preferably one that adjusts a predetermined detection sensitivity. That is, it is preferable that the AE sensor 4 can adjust the detection sensitivity when detecting the AE signal. This detection sensitivity may be set by the signal processing unit 5.
  • the signal processing unit 5 processes a value greater than a predetermined reference value among signals received from the AE sensor 4 as an AE signal.
  • the signal processing unit 5 can output the data received from the AE sensor 4 as it is from the output interface 13.
  • the signal processing unit 5 filters the data received from the AE sensor 4 by frequency and intensity, performs elementary signal processing, and outputs the result from the output interface 13.
  • the output raw data is processed by the computer 6 connected to the output interface 13.
  • the computer 6 performs processing such as calculation and determination of the AE event count and the AE amplitude described above, which has been processed by the signal processing unit 5.
  • an AE signal having a predetermined frequency is extracted by a filter, and the extracted AE signal is amplified by a main amplifier.
  • the computer 6 is an electronic computer for analyzing the signal output from the signal processing unit 5. Although not shown, the computer 6 is an electronic computer including a CPU, a RAM, a ROM, an auxiliary storage device, an input / output interface, and input / output devices such as a display, a mouse, and a keyboard. The computer 6 can use any electronic computer as long as it can perform the processing described in the present embodiment.
  • the computer 6 analyzes a series of AE signals detected by the AE sensor 4 and performs analysis with reference to a database (not shown).
  • the database is a database that stores data related to the AE signal emitted from the sample 3.
  • the database stores data relating to normal, that is, usable sample 3, data relating to sample 3 that has become unusable, and the like. Data can be updated in the database from the signal processing unit 5 or the computer 6. In addition, an administrator, a user, etc. can update the database manually.
  • the database is stored in the main storage device or auxiliary storage device of the computer 6 or a connected external storage device.
  • the database is installed in or near the computer 6, but may be installed in a remote place accessible by wireless or wired communication means.
  • Analysis by the computer 6 is performed in the following procedure.
  • the result of the analysis by the computer 6 is an evaluation of the quality of the sample 3. For example, when the crack in the sample 3 is not large, that is, when it is determined that the sample 3 can perform its original function, a signal indicating an inspection pass is output.
  • the computer 6 can totalize all the inspection results of the sample 3 including past inspection data, collect them in a visually checkable graph, etc., and display them on the display or print them on the printing device. .
  • FIG. 4 is a schematic diagram showing a change over time in the relationship between the AE event count of the AE signal generated from the O-ring of the sample 3 and the AE amplitude.
  • the AE event count and the AE amplitude have a power relationship regardless of the presence or absence of cracks.
  • the slope m is 4, and the bubbles in the sample 3 are in the state before the crack is generated.
  • the crack is a relatively minor damage.
  • the relationship between the AE event count and the AE amplitude is shifted in the upper right direction as shown by the arrows in FIG. 4 as indicated by the arrows in FIG.
  • the broken line graph in FIG. 4 is an acceptable line (usage limit line) indicating a reference value provided for determining whether the sample 3 is good or bad. If the measured value of the sample 3 is located above the pass line, the sample 3 may be damaged or damaged and cannot be used. When the measured value of the sample 3 is located below the acceptance line, the state of the sample 3 is good and can be used. Data similar to the graph of FIG. 4 is stored in the database. The computer 6 determines the sample 3 by comparing the newly measured AE signal with this data stored in the database. Therefore, the computer 6 can determine the quality of the sample 3 based on the use limit line by comparing the measurement result of the sample 3 with the data of FIG. 4 stored in the database.
  • FIG. 5 is a schematic diagram showing the relationship between the AE event count and the AE frequency obtained by analyzing the AE signal by Fourier change.
  • the frequency of the generated AE signal varies depending on the formation of a bubble and the generation of a crack, and it is possible to extract only the AE signal accompanying the generation of a crack using a bandpass filter. That is, in the example of FIG. 5, it can be seen that the frequency of the AE signal generated when bubbles are formed is lower than the frequency of the AE signal generated when cracks are generated. By filtering and monitoring these frequencies with a band-pass filter, it is possible to monitor whether bubbles are formed or cracks are generated.
  • Experiment 1 AE signals generated by a metal material and a rubber material were measured and their attenuation rates were compared.
  • Experiment 2 receives the AE signal generated by the metal material and the rubber material, and analyzes the difference between the constituent signals.
  • Experiment 3 a rubber sample is placed in a high-pressure gas, the pressure of the gas is increased, and the pressure reduction is repeated one or more times, and then AE is measured.
  • FIG. 6 is a conceptual diagram for measuring the attenuation amount of the AE signal (AE wave) of each frequency component using rubber test pieces having different thicknesses.
  • Three types of cylindrical rubber test pieces having different thicknesses were prepared, and a first AE sensor and a second AE sensor were attached to both ends of the test piece.
  • the dimensions of the test piece were 13 mm in diameter and 2, 6 and 12 mm in thickness.
  • the 1st AE sensor and the 2nd AE sensor are AE sensors AE-900F2 manufactured by NF Circuit Design Block Co., Ltd. (English notation: NF Corporation, location: Yokohama, Kanagawa, Japan). Met.
  • the transmitter was a multi-function generator WF1973 manufactured by NF Circuit Design Block Co., Ltd. (English notation: NF Corporation, location: Yokohama, Kanagawa, Japan).
  • the first AE sensor functioned as a broadband AE signal transmitter.
  • the sine wave transmitted from the first AE sensor and transmitted through the test piece was received by the second AE sensor.
  • the second AE sensor functioned as a receiver for the AE signal.
  • the AE signal received by the second AE sensor was amplified with a preamplifier (Pre-Amplifier 9913, manufactured by NF Circuit Design Block Co., Ltd.), and observed with an oscilloscope (WaveRunner 6060A manufactured by LeCroy (New York City, USA)).
  • Pre-Amplifier 9913 manufactured by NF Circuit Design Block Co., Ltd.
  • oscilloscope WiveRunner 6060A manufactured by LeCroy (New York City, USA)
  • Experiment 1 was conducted in the atmosphere at room temperature.
  • the amplitude reduction of the receiving sine wave with respect to the transmitting sine wave was measured for each thickness of each test piece, and the influence of the frequency on the AE signal attenuation of the rubber material was evaluated.
  • FIG. 7 is a graph showing the experimental results of Experiment 1.
  • the vertical axis of the graph of FIG. 7 is the amplitude A of the AE signal on the reception side with respect to the amplitude A0 of the AE signal on the transmission side, and the horizontal axis is the thickness of the test piece.
  • the attenuation of the AE signal in the rubber material is larger than the attenuation of the AE signal in the metal material.
  • the attenuation amount of the AE signal having a frequency of 1 MHz or less is about 50% even when the thickness of the test piece is 10 mm. Therefore, assuming a rubber test piece having a thickness of about 10 mm, the frequency of the target AE signal should be 1 MHz or less.
  • FIG. 8 shows a state of an experiment for measuring a difference between AE signals generated between a metal material and a rubber material.
  • the test piece is a trouser type test piece. The dimensions of the test piece are illustrated in FIG.
  • the test piece was 100 mm in length, 15 mm in width, and 2 mm in thickness.
  • the notch was 40 mm in the length direction from the end of the test piece.
  • Two types of test pieces, copper and rubber, were used.
  • an AE signal generated in each material of a metal material and a rubber material is received and analyzed, and the difference in the constituent signals of the AE signal is analyzed.
  • the AE sensor was placed in close contact with the test piece. And as shown by the arrow, the test piece was pulled and torn. The elastic waves generated along with the cracks propagating from the notch during tearing were measured. Experiment 2 was performed in air at room temperature. The measurement results are shown in the graph of FIG.
  • the graph shown in FIG. 9A is for copper, and the graph shown in FIG. 9B is for rubber.
  • the horizontal axis of the graphs of FIGS. 9A and 9B shows the elapsed time at the time of measurement.
  • the vertical axis on the right side of the graphs of FIGS. 9A and 9B shows the AE event count rate.
  • the vertical axis on the left side of the graphs of FIGS. 9A and 9B shows the tearing force when tearing the test piece.
  • the crack propagates in the region where the stress becomes flat.
  • an AE signal is generated as the crack progresses.
  • the AE event count rate generated is smaller than that of steel.
  • Experiment 3 Repeated exposure of rubber material to high pressure gas.
  • Experiment 3 is described.
  • a cylindrical rubber test piece was placed in a chamber for high-pressure hydrogen gas, and the pressure of the high-pressure hydrogen gas was repeatedly applied to generate a crack inside the test piece.
  • the test piece had a cylindrical shape with a diameter of 29 mm and a thickness of 12.5 mm.
  • the material of the test piece was unfilled peroxide-crosslinked ethylene propylene rubber.
  • FIG. 10 is a photograph when the surface of the test piece is observed with a microscope after the rubber test piece is repeatedly exposed to gas.
  • FIG. 10 (a) is a photograph of the surface observed with a microscope after repeating the test of exposure to high-pressure gas three times.
  • FIG. 10 (b) is a photograph of the surface observed with a microscope after repeating the test of exposure to high-pressure gas five times.
  • a transparent test piece is observed with an optical microscope, and a crack generated inside the test piece can be clearly observed.
  • the crack is larger and the number of cracks is larger in the case of five times than in the case of three times.
  • FIG. 11 is a graph showing the result of obtaining the event rate by processing the detected AE signal. The vertical axis of this graph indicates the AE event count rate, and the horizontal axis indicates the elapsed time. From this graph, as the number of repeated exposure tests increases, the AE event count rate also increases with crack damage.
  • FIG. 12 is a cross-sectional photograph of a rubber test piece exposed to hydrogen gas for 24 hours and left in the atmosphere at room temperature. Since this rubber test piece is not transparent, the test was cut with a cutter and the cross section was photographed.
  • This rubber test piece was a cylindrical type made from unfilled sulfur vulcanized ethylene propylene rubber, and had a diameter of 29 mm and a thickness of 12.5 mm.
  • the conditions of the hydrogen gas were a pressure of 0.7, 10, 30 MPa, and a temperature of 30 ° C.
  • the test piece was obtained by observing the cross section of the test piece with an optical microscope after cutting the cross section of the test piece with a cutter three days after decompression. When the pressure of hydrogen gas was 0.7 MPa, no crack was generated on the test piece. When the hydrogen gas pressure was 10 MPa and 30 MPa, cracks were observed in the test piece.
  • FIG. 13 is a graph showing the relationship between the AE event count of the AE signal measured after decompression and the AE amplitude.
  • the AE event count and the AE amplitude have a power relationship.
  • m 2 at pressures of 10 MPa and 30 MPa at which cracks were observed.
  • the relationship between the AE event count and the AE amplitude shifted to the upper right in the figure.
  • FIG. 14A illustrates this state in a stylized manner.
  • FIG. 14B illustrates this state in a stylized manner, and bubbles are indicated by arrows.
  • FIG. 14 (c) schematically illustrates this state, and a crack generated from the enlarged bubble is indicated by an arrow.
  • the amount of hydrogen leaking from the sample increases as the crack progresses. And, it is expected that significant cracking can be caused by this hydrogen penetrating the sample.
  • An AE signal is generated both when a bubble is formed and when a crack occurs. However, the characteristics of the generated AE signal differ between the formation of bubbles and the generation of cracks. This situation can be generalized as shown in the graph of FIG. The vertical axis of the graph in FIG. 13B indicates the AE event count.
  • the horizontal axis indicates the amplitude of the AE signal.
  • the graph when bubbles are formed is more gradual than the graph when cracks are generated. Therefore, attention is paid to the relationship between the AE count rate and the amplitude.
  • the relationship between the AE count rate and the amplitude by repetition according to FIG. 13A is shifted to a graph in the upper right direction in the drawing when the pressure increases.
  • the last graph is a graph when there is severe damage. According to the occurrence of cracks and their progress, the slope of the graph is gentler than that during bubble formation.
  • the amplitude of the AE signal at the time of bubble formation is smaller than that at the time of crack occurrence, and the count rate is also small.
  • a use limit line is provided before the point of severe damage, and it is confirmed whether the relationship between the AE count rate and the amplitude has reached this use limit line. Can be judged. Thereby, it can also be determined whether or not there is a crack that causes damage to the surface of the rubber product. Therefore, from the viewpoint of utilization in industry, the use of rubber products that exceed this use limit line should be stopped for the purpose of ensuring safety. This is very useful in the field of machine inspection and the like.
  • the present invention may be used in industrial fields that use rubber products.
  • the present invention is preferably used in a field where a rubber seal material is used.
  • This invention is good to be utilized for the product which needs to detect and prevent the damage by a crack like rubber packing in advance.

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Abstract

Disclosed are a rubber product inspection method and a rubber products inspection device that use AE waves to nondestructively inspect a rubber product. When nondestructively inspecting a rubber product, an AE signal, which is emitted from a break in the rubber product, is sensed with AE sensors (4), and the change over time of the AE signal is derived. From the characteristic of the change over time, a determination is made as to whether the AE signal is emitted from the rubber product when a supersaturated gaseous body forms a bubble, or is emitted when a crack arises with a bubble as a cause. The change over time of the AE signal is also compared against pre-measured data, the progress of the break in the rubber product is assessed, and a determination of the quality of the rubber product is made.

Description

ゴム製品の検査方法及びゴム製品の検査装置Rubber product inspection method and rubber product inspection device
　本発明は、ゴム製品の検査方法及びゴム製品の検査装置に関する。更に詳しくは、ゴム製品から発生する弾性波を検知して、この弾性波の特性からゴム製品の損傷状態又は良否を判定するための検査方法及びゴム製品検査装置に関する。 The present invention relates to a rubber product inspection method and a rubber product inspection device. More specifically, the present invention relates to an inspection method and a rubber product inspection device for detecting an elastic wave generated from a rubber product and determining a damaged state or quality of the rubber product from the characteristic of the elastic wave.
　Ｏリングに代表されるゴム製のシール部材は、家電製品から大型の機械、精密機器から建築機械まで、幅広い分野で使用されている。ゴムは、耐プラズマ性、耐熱性、クリーン性、非固着性、耐薬品性、耐溶剤性、耐油性等の優れた性質を備え、希望の形状に製造し易いという利点がある。また、ゴムは、天然の植物から採取されて工業用に利用されてから何世紀もたち、ゴム製造の歴史は古い。しかしながら、特に高温、真空、高気圧等の厳しい環境条件、高い気密性が求められる環境等で使用されるゴム製品、特にゴム製のシール材料、等に関しては、注意が必要である。例えば、そのゴム製品を製造するとき、その品質管理と設計では、知識と経験が要求され、大変な労力と細心の注意が必要である。また、使用するときも、高い気密性が求められる環境なので、品質管理にも同じく知識と経験が要求され、細心の注意が払われる。 ゴ ム Rubber seals represented by O-rings are used in a wide range of fields, from home appliances to large machines, precision equipment to construction machinery. Rubber has excellent properties such as plasma resistance, heat resistance, cleanness, non-adhesiveness, chemical resistance, solvent resistance, oil resistance, and has an advantage that it can be easily manufactured into a desired shape. In addition, rubber has a long history of rubber production for centuries since it was extracted from natural plants and used for industrial purposes. However, special attention is required for rubber products used in severe environmental conditions such as high temperature, vacuum and high pressure, environments where high airtightness is required, particularly rubber seal materials. For example, when manufacturing the rubber product, the quality control and design requires knowledge and experience and requires great effort and great care. Also, since it is an environment that requires high airtightness when used, knowledge and experience are also required for quality control, and careful attention is paid.
　このようなシール材料は、定期的に交換するか、定期的な検査をしなければならない。ゴム製品の検査は、様々な方法と検知原理が提案され利用されている。例えば、Ｘ線で観察したり、その表面を肉眼や顕微鏡等で観察したりするものである。特許文献１には、ゴム製のベルトを複数回にわたって伸長させた後、ベルトの表面のき裂を観察する方法が開示されている。この観察のためには、ベルトに機械的エネルギー加えている。しかしながら、ゴム製品の内部のき裂を検査する方法としては、ゴム製品に負荷をかけない非破壊検査が好ましい。 ¡Seal materials such as this must be replaced regularly or regularly inspected. For the inspection of rubber products, various methods and detection principles have been proposed and used. For example, it is observed with X-rays or the surface is observed with the naked eye or a microscope. Patent Document 1 discloses a method of observing a crack on the surface of a belt after stretching the rubber belt a plurality of times. For this observation, mechanical energy is added to the belt. However, as a method for inspecting a crack inside the rubber product, a non-destructive inspection without applying a load to the rubber product is preferable.
　非破壊検査する方法の一つは、アコースティックエミッションを用いる方法がある。アコースティックエミッション（以下、ＡＥという。）信号は、材料の変形、破壊又は、き裂発生に伴って放出される弾性波である。この弾性波は、材料の表面に設置した、検出素子で検出することができる。ＡＥ信号は、材料の種類とその変形、破壊やき裂等の種類によるが、通常、数kHz～数MHzに周波数帯域を持っている。例えば、金属材料で発生するＡＥ信号は、主として１００ｋＨｚ～１ＭＨｚの周波数の信号である。 One method of nondestructive inspection is to use acoustic emission. The acoustic emission (hereinafter referred to as AE) signal is an elastic wave that is emitted when a material is deformed, broken, or cracked. This elastic wave can be detected by a detection element installed on the surface of the material. The AE signal usually has a frequency band of several kHz to several MHz, although it depends on the type of material and the type of deformation, fracture, crack, and the like. For example, an AE signal generated in a metal material is a signal having a frequency of 100 kHz to 1 MHz.
　ゴム材料の場合も，金属材料と同様に１ＭＨｚ以下の周波数の信号を対象とする。ＡＥ信号を検出するためのセンサーは、一般的には圧電素子が用いられており、この圧電素子を材料の表面に密着させてＡＥ信号を検出している。この例としては、免震構造物に使用している積層ゴムに取りつけたＡＥセンサーで、積層ゴムの欠陥から発生するＡＥ信号を検知する積層ゴムの品質管理システムが開示されている（特許文献２、３参照）。このシステムでは、複数のＡＥセンサーで検知したＡＥ信号の到達順序や時間差を計測し、欠陥の発生位置を特定している（特許文献２の明細書の段落［００２６］を参照。）。 In the case of rubber materials, signals with a frequency of 1 MHz or less are the same as metal materials. As a sensor for detecting an AE signal, a piezoelectric element is generally used. The piezoelectric element is brought into close contact with the surface of a material to detect the AE signal. As an example of this, a quality control system for laminated rubber is disclosed in which an AE sensor attached to a laminated rubber used in a seismic isolation structure detects an AE signal generated from a defect in the laminated rubber (Patent Document 2). 3). In this system, the arrival order and time difference of AE signals detected by a plurality of AE sensors are measured, and the position where a defect occurs is specified (see paragraph [0026] in the specification of Patent Document 2).
　また、このシステムでは、積層ゴム内のマイクロクラックの発生、進展に伴って発生した超音波を検知している（特許文献２の明細書の段落［００２６］を参照。）。更に、特許文献４には、タイヤ等のゴム製品の破損状態を推定するための方法と装置が開示されている。タイヤのホイルリム部の内側にＡＥセンサーを取り付け、ＡＥ波を検知し、ＡＥ波の累積数の変化の度合いと、事前に分かっているＡＥ波の累積数とタイヤ破損状態の関係データと比較して、タイヤの破損状態を推定している。 Also, in this system, ultrasonic waves generated with the occurrence and development of microcracks in the laminated rubber are detected (see paragraph [0026] of the specification of Patent Document 2). Furthermore, Patent Document 4 discloses a method and an apparatus for estimating a damaged state of a rubber product such as a tire. Install an AE sensor inside the wheel rim of the tire, detect AE waves, compare the degree of change in the cumulative number of AE waves, and the relationship data between the cumulative number of AE waves known in advance and the tire damage status Estimate the damage condition of the tire.
　（イベント法とリングダウン法）
　ＡＥ信号を検出することでは、材料中で発生したクラック発生、そのクラックの進行状態の監視が可能である。ＡＥ信号は、短期間に連続的に発生する複数の周波数の弾性波から構成されており、その強度と大きさは、材料の種類やき裂の大きさ等によって異なる。ＡＥ信号を検出し、電気信号として出力するためのアコースティックエミッションセンサー（以下、ＡＥセンサーという。）に検出される信号を処理する方法として、次の二つの方法がある。ＡＥセンサーで受信されて観察されるＡＥ信号は、性質を異にする２種類に分類できる。 (Event method and ring-down method)
By detecting the AE signal, it is possible to monitor the occurrence of cracks in the material and the progress of the cracks. The AE signal is composed of elastic waves having a plurality of frequencies that are continuously generated in a short period of time, and the strength and size thereof vary depending on the type of material, the size of a crack, and the like. There are the following two methods for processing a signal detected by an acoustic emission sensor (hereinafter referred to as AE sensor) for detecting an AE signal and outputting it as an electrical signal. The AE signals received and observed by the AE sensor can be classified into two types having different properties.
　第１の方法は、１つのＡＥ信号を１つと数えるイベント法である。このイベント法では、計数するＡＥ信号をＡＥイベントカウントと呼び、単位時間当たりのＡＥイベントカウント数をＡＥイベントカウントレートと呼ぶ。このＡＥイベントカウントレートは、応力の繰り返しによって進展するき裂から発生するＡＥ信号が基本的に離散的であることを考慮し、疲労き裂進展の評価に用いることが多い。 The first method is an event method in which one AE signal is counted as one. In this event method, an AE signal to be counted is called an AE event count, and an AE event count number per unit time is called an AE event count rate. This AE event count rate is often used for evaluation of fatigue crack propagation in consideration of the fact that the AE signal generated from a crack that propagates due to repeated stress is basically discrete.
　第２の方法は、定義した基準値以上の振幅を全て数えるリングダウン法である。このリングダウン法で計数するＡＥ信号をＡＥリングダウンカウントと呼び、単位時間当たりのＡＥリングダウンカウント数をＡＥリングダウンカウントレートと呼ぶ。図１５には、イベント法と、リングダウン法の違いを図示している。図１５（ａ）には、１つのＡＥ信号を示している。図１５（ｂ）及び図１５（ｃ）には、このＡＥ信号を計数する２つの方法であるイベント法とリングダウン法の違いを示している。 The second method is a ring-down method that counts all amplitudes that exceed the defined reference value. An AE signal counted by this ring-down method is called an AE ring-down count, and an AE ring-down count number per unit time is called an AE ring-down count rate. FIG. 15 illustrates the difference between the event method and the ring-down method. FIG. 15A shows one AE signal. FIGS. 15B and 15C show the difference between the event method and the ring-down method, which are two methods for counting the AE signal.
　図１５（ｂ）は、イベント法を示している。図１５（ｃ）は、リングダウン法を示している。図１５（ａ）のＡＥ信号の最大強度は、設定した閾値以上である。図１５（ａ）のＡＥ信号は、図１５（ｂ）に示すように、イベント法では、「１」とカウントされる。リングダウン法では、１つのＡＥ信号を構成する複数の弾性波の中で設定した閾値以上の強度のものを全て数える。このために図１５（ａ）のＡＥ信号は、図１５（ｃ）に示すように、リングダウン法では、「４」とカウントされる。 FIG. 15B shows the event method. FIG. 15C shows the ring-down method. The maximum intensity of the AE signal in FIG. 15A is equal to or greater than a set threshold value. As shown in FIG. 15B, the AE signal in FIG. 15A is counted as “1” in the event method. In the ring-down method, all of the plurality of elastic waves constituting one AE signal are counted with an intensity equal to or higher than a set threshold value. For this reason, the AE signal in FIG. 15A is counted as “4” in the ring-down method, as shown in FIG. 15C.
特開２００５－１６４４９９号公報JP 2005-164499 A 特開平１１－６４０９８号公報Japanese Patent Laid-Open No. 11-64098 特開平１１－６４０９９号公報Japanese Patent Laid-Open No. 11-64099 特開２００５－３３７９２９号公報JP 2005-337929 A
　上述のように、肉眼や顕微鏡等でゴム製品の表面を観察する方法では、ゴム製品の表面に出ている損傷は発見できたとしても、内部に発生したき裂等の損傷の発見はできない。また、ＡＥ波を検知する方法は、金属材料の非破壊検査技術として公知である。しかし、ゴム製品から発生するＡＥ波の振幅は、金属から発生するＡＥ波と比べ、桁違いに小さい。同様に、ゴム製品から発生するＡＥ波の発生率も、金属の場合と比べて、桁違いに少ない。 As described above, in the method of observing the surface of a rubber product with the naked eye or a microscope, damage such as a crack generated inside cannot be detected even if damage on the surface of the rubber product can be detected. A method for detecting AE waves is known as a non-destructive inspection technique for metal materials. However, the amplitude of AE waves generated from rubber products is orders of magnitude smaller than that of AE waves generated from metal. Similarly, the incidence of AE waves generated from rubber products is orders of magnitude less than that of metal.
　上述の特許文献２、３には、建築構造物に利用される大きいゴム材料の検査にＡＥセンサーを利用している。このゴム材料は、建築構造物等の大きな圧力を受けて支えるものである。また、特許文献２、３に記載されたものは、ＡＥ信号のカウントの変化のみをみている。このような状況で、ゴム製のシール材料等の微小なゴム製品については、ＡＥセンサーを用いて、その検査を行う技術がまだ確立されていない。 In the above-mentioned Patent Documents 2 and 3, an AE sensor is used for inspection of a large rubber material used for a building structure. This rubber material is supported by a large pressure from a building structure or the like. In addition, those described in Patent Documents 2 and 3 see only the change in the count of the AE signal. Under such circumstances, a technology for inspecting a minute rubber product such as a rubber seal material using an AE sensor has not yet been established.
　本発明は上述のような技術背景のもとになされたものであり、下記の目的を達成する。
　本発明の目的は、ゴム製品を、ＡＥ波を利用した非破壊検査により、検査するゴム製品の検査方法及びゴム製品の検査装置を提供する。
　本発明の他の目的は、ゴム製のシール材料を、ＡＥ波を利用した非破壊検査により、検査するゴム製品の検査方法及びゴム製品の検査装置を提供する。 The present invention has been made based on the technical background as described above, and achieves the following objects.
An object of the present invention is to provide a rubber product inspection method and a rubber product inspection device for inspecting a rubber product by nondestructive inspection using AE waves.
Another object of the present invention is to provide a rubber product inspection method and a rubber product inspection device for inspecting a rubber seal material by nondestructive inspection using AE waves.
　〔用語の定義〕
　本発明において、ゴム製品、き裂、アコースティックエミッション（ＡＥ）は、次に定義される意味で使用する。以下、この用語毎に説明する。 〔Definition of terms〕
In the present invention, rubber products, cracks, and acoustic emission (AE) are used as defined below. Hereinafter, each term will be described.
　「ゴム製品」とは、材料にゴムを利用した製品、部品や部材等を言う。ゴムの種類は、ゴム製品の用途、適用箇所、適用機器等に応じて適宜選択して使用する。ゴムの種類としては、例えば天然ゴム、イソプレンゴム、ブタジエンゴム、スチレンブタジエンゴム、ブチルゴム、クロロプレンゴム、ニトリルゴム、エチレンプロピレンゴム、アクリルゴム、エピクロロヒドリンゴム、ハイパロン、ウレタンゴム、シリコーンゴム、フッ素ゴム、パーフロオロゴムが挙げられる。また、エチレンプロピレンゴム（EPDM）、アクリロニトリルブタジエンゴム（NBR）、水添加NBR、シリコーンゴム、フッ素ゴム等が挙げられる。これらのゴム材料に補強のために、これらに限定しないが、カーボンブラック、シリカ等のフィラー、老化防止剤、オイル等を添加したものも利用できる。 "Rubber products" refers to products, parts, members, etc. that use rubber as a material. The type of rubber is appropriately selected and used according to the use of rubber products, application location, application equipment, and the like. Examples of rubber types include natural rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, chloroprene rubber, nitrile rubber, ethylene propylene rubber, acrylic rubber, epichlorohydrin rubber, hypalon, urethane rubber, silicone rubber, and fluorine rubber. Perfluoro-rubber. Further, ethylene propylene rubber (EPDM), acrylonitrile butadiene rubber (NBR), water-added NBR, silicone rubber, fluorine rubber and the like can be mentioned. In order to reinforce these rubber materials, but not limited thereto, carbon black, silica and other fillers, anti-aging agents, oils and the like can be used.
　「き裂」（英語表記では、Crack。）は、材料に、本発明の場合はゴム製品に、生じたひび割れ、割れ目、裂け目等の欠陥である。ゴム製品が繰り返し負荷や静的な負荷を受けると、き裂は、ゴム製品の表面又は内部から発生する。発生したき裂は繰り返し負荷によって進展して、最終的にはゴム製品が破壊する。き裂を有する材料に負荷を与えると、き裂に、特に、き裂の先端近傍には負荷の高い応力集中が発生する。 "Crack" (Crack in English) is a defect such as a crack, a crack, or a crack generated in a material, in the case of the present invention, in a rubber product. When a rubber product is repeatedly or statically loaded, a crack is generated from the surface or inside of the rubber product. The generated crack is repeatedly developed by the load, and eventually the rubber product is destroyed. When a load is applied to a material having a crack, a stress concentration with a high load is generated in the crack, particularly in the vicinity of the tip of the crack.
　この応力集中が材料の破壊靱性を上回ると、き裂の長さが伸びることでき裂進展が起こる。部材の疲労寿命の８０％程度は、発生したき裂が肉眼で観察可能になるまでに進展するのに費やされる。言い換えると、部材の疲労寿命の８０％程度は、肉眼で観察が困難な１ｍｍ以下のき裂が進展するのに費やされる。よって、部材の破壊を防ぐ、部材の破壊を予測する、部材の破壊の兆候を検知するためには、肉眼で観察することが困難な１ｍｍ以下のき裂を検知する必要がある。 When this stress concentration exceeds the fracture toughness of the material, the crack length can be extended and crack growth occurs. About 80% of the fatigue life of the member is expended to develop until the generated crack can be observed with the naked eye. In other words, about 80% of the fatigue life of the member is spent on the development of a crack of 1 mm or less that is difficult to observe with the naked eye. Therefore, in order to prevent the destruction of the member, to predict the destruction of the member, and to detect the sign of the destruction of the member, it is necessary to detect a crack of 1 mm or less that is difficult to observe with the naked eye.
　「アコースティックエミッション（ＡＥ）」は、材料の変形、破壊又は、き裂の発生に伴って放出される弾性波である。このＡＥは、本発明ではＡＥ波又はＡＥ信号とする。この弾性波は、材料の表面に設置した、ＡＥ信号を検出するための素子であるＡＥセンサーで検出することができる。ＡＥセンサーは、弾性波を電気信号に変換して出力するための素子である。ＡＥセンサーは、一般的には、圧電素子からなり、材料表面に密着させてＡＥ信号を検出し、ＡＥ信号を電気信号に変換して出力する。 “Acoustic Emission (AE)” is an elastic wave that is emitted when a material is deformed, broken or cracked. In the present invention, this AE is an AE wave or an AE signal. This elastic wave can be detected by an AE sensor which is an element for detecting an AE signal installed on the surface of the material. The AE sensor is an element for converting an elastic wave into an electric signal and outputting it. The AE sensor is generally composed of a piezoelectric element, detects an AE signal in close contact with the material surface, converts the AE signal into an electrical signal, and outputs the electrical signal.
　本発明は、ゴム製品の内部に発生したき裂を検査し、その大きさ、進展状況を把握することを目的にするものである。これによって、高圧等の厳しい環境下で利用されるゴム製品の内部き裂状況を、軽微な状態で検知し、内部き裂が表面に達する前に使用を停止することができる。これにより、ゴム製品を使用する装置の故障回避、その性能維持、事故を事前に防止ができるという顕著な効果がもたらされる。無論、ゴム製品の内部き裂状況を軽微な状態で検知できるので、ゴム製品を使用する装置のメンテナンスも容易になる。 The purpose of the present invention is to inspect a crack generated inside a rubber product and grasp its size and progress. As a result, the internal crack condition of the rubber product used in a severe environment such as high pressure can be detected in a slight state, and the use can be stopped before the internal crack reaches the surface. Thereby, the remarkable effect that the failure avoidance of the apparatus which uses a rubber product, the performance maintenance, and an accident can be prevented beforehand is brought about. Of course, since the internal crack condition of the rubber product can be detected in a slight state, the maintenance of the apparatus using the rubber product becomes easy.
　例えば、流体機械の高圧流体のシール、防振等に利用されているゴム製のシール部品の場合を考える。このシール部品の内部で発生したき裂が進展して、表面に達すると、本来の役割である密封性、耐圧力等の働きができなくなる。更に、き裂がシール部品の表面まで進み、破裂すれば、機械事故の原因にもなりえる。そのために、シール部品の内部で発生したき裂をできるだけ速く検知でき、その進展も随時検査できるものが望ましい。また、シール部品の内部で発生したき裂が進展し、表面に達する時期等を予測することも望まれている。 Consider, for example, the case of rubber seal parts used for high-pressure fluid sealing and vibration isolation of fluid machinery. When the crack generated inside the seal component progresses and reaches the surface, the original functions such as sealing performance and pressure resistance cannot be performed. Furthermore, if the crack advances to the surface of the seal part and ruptures, it may cause a mechanical accident. Therefore, it is desirable to be able to detect a crack generated inside the seal component as quickly as possible and to inspect its progress as needed. It is also desired to predict when the crack generated inside the seal part will progress and reach the surface.
　本発明は、前記目的を達成するため、次の手段を採る。
　本発明のゴム製品の検査方法は、ゴム製品のき裂から発生する弾性波（ＡＥ）を弾性波検知手段（ＡＥセンサー）で検知して、ゴム製品の損傷を検査するためのゴム製品の検査方法である。　本発明のゴム製品の検査方法は、気体からなる高圧気体雰囲気環境下で前記ゴム製品を減圧した後、前記ゴム製品から発生する前記弾性波（ＡＥ）を検知して、前記弾性波（ＡＥ）の経時変化を求め、前記経時変化の特性から、前記弾性波が、（ａ）前記ゴム製品から過飽和気体が気泡になったときに発生する前記弾性波であるか、又は、（ｂ）前記気泡を起点としてき裂が発生したときに発生する前記弾性波であるかを判定して、前記ゴム製品の損傷の状態を検査することを特徴とする。 In order to achieve the above object, the present invention employs the following means.
The rubber product inspection method of the present invention is an inspection of a rubber product for inspecting the damage of the rubber product by detecting an elastic wave (AE) generated from a crack of the rubber product by an elastic wave detecting means (AE sensor). Is the method. The method for inspecting a rubber product according to the present invention includes detecting the elastic wave (AE) generated from the rubber product after decompressing the rubber product in a high-pressure gas atmosphere environment composed of gas, and detecting the elastic wave (AE) From the characteristics of the change over time, the elastic wave is (a) the elastic wave generated when supersaturated gas becomes a bubble from the rubber product, or (b) the bubble It is characterized by inspecting the state of damage of the rubber product by determining whether the elastic wave is generated when a crack is generated starting from the point.
　また、本発明のゴム製品の検査方法は、前記き裂の経時変化が、前記き裂が進展してゴム製品の表面に進展する兆候を示すとき、前記ゴム製品は損傷が大きいと推定する。更に、本発明のゴム製品の検査方法は、前記判定は、前記経時変化を、予め損傷状態を分かっている前記ゴム製品の特性と比較して、求められる。前記ゴム製品は、Ｏリングであると良い。 In addition, the method for inspecting a rubber product according to the present invention presumes that the rubber product is greatly damaged when a change with time of the crack shows an indication that the crack has progressed to the surface of the rubber product. Furthermore, in the method for inspecting a rubber product according to the present invention, the determination is made by comparing the change with time with characteristics of the rubber product whose damage state is known in advance. The rubber product may be an O-ring.
　本発明のゴム製品の検査装置は、弾性波（ＡＥ）を検知するためのもので、ゴム製品に固定又は近傍に設置された弾性波検知手段（ＡＥセンサー）と、前記弾性波検知手段（ＡＥセンサー）で検知されたもので、前記ゴム製品のから発生する前記弾性波（ＡＥ）を解析して、経時変化を求め、前記ゴム製品の損傷を判定する解析手段とからなるゴム製品の損傷を検査ための装置である。 The rubber product inspection apparatus of the present invention is for detecting elastic waves (AE). The elastic wave detection means (AE sensor) is fixed to or installed near the rubber product, and the elastic wave detection means (AE). A sensor), analyzing the elastic wave (AE) generated from the rubber product, obtaining a change with time, and analyzing the rubber product comprising an analysis means for judging damage of the rubber product. It is a device for inspection.
　前記解析手段は、高圧ガス雰囲気環境下で前記ゴム製品を減圧した後、弾性波検知手段（ＡＥセンサー）で検知した前記弾性波（ＡＥ）の経時変化を求め、前記経時変化の特性から、前記弾性波が、（ａ）前記ゴム製品から過飽和気体が気泡になったときに発生する前記弾性波であるか、又は、（ｂ）前記気泡を起点としてき裂が発生したときに発生する前記弾性波であるかを判定して、前記解析手段は、前記き裂から発生する前記弾性波の場合は、前記ゴム製品が損傷していると判定し、その旨の信号を出力することを特徴とする。 The analysis means obtains a change with time of the elastic wave (AE) detected by an elastic wave detection means (AE sensor) after decompressing the rubber product under a high-pressure gas atmosphere environment, and from the characteristics of the change with time, The elastic wave is (a) the elastic wave generated when a supersaturated gas becomes a bubble from the rubber product, or (b) the elasticity generated when a crack is generated from the bubble. In the case of the elastic wave generated from the crack, the analysis means determines that the rubber product is damaged, and outputs a signal to that effect. To do.
　前記解析手段は、前記き裂の経時変化が、前記き裂が進展してゴム製品の表面に進展する兆候を示すとき、前記ゴム製品は損傷が大きいと推定して、その旨の信号を出力する。前記解析手段は、前記経時変化を、予め損傷状態を分かっている前記ゴム製品の特性データと比較する比較手段を有する。前記ゴム製品は、Ｏリングであると良い。 When the time-dependent change of the crack indicates that the crack has progressed and progressed to the surface of the rubber product, the analyzing means estimates that the rubber product is damaged and outputs a signal to that effect. To do. The analysis means includes comparison means for comparing the change with time with characteristic data of the rubber product whose damage state is known in advance. The rubber product may be an O-ring.
　本発明のゴム製品の検査方法及びゴム製品の検査装置は、ゴム製品の内部から発生するＡＥ波を検知して、ＡＥ波の動向から、ゴム製品を評価し、非破壊検査ができるようになった。 The rubber product inspection method and the rubber product inspection apparatus of the present invention can detect AE waves generated from the inside of the rubber products, evaluate the rubber products from the trends of the AE waves, and perform nondestructive inspection. It was.
図１は、本発明の実施の形態のゴム製品の損傷検知システム１の概要を図示している概念図である。FIG. 1 is a conceptual diagram illustrating an outline of a damage detection system 1 for rubber products according to an embodiment of the present invention. 図２は、本発明の本実施の形態のサンプル３のＯリングの例を図示している図であり、図２（ａ）は、Ｏリングの概念図で、図２（ｂ）は、図２(ａ)のＡ－Ａ断面図である。FIG. 2 is a diagram illustrating an example of the O-ring of the sample 3 according to the present embodiment of the present invention. FIG. 2A is a conceptual diagram of the O-ring, and FIG. It is AA sectional drawing of 2 (a). 図３は、本発明の実施の形態のゴム製品の損傷検知システム１の信号処理ユニット５の例を示しているブロック図である。FIG. 3 is a block diagram showing an example of the signal processing unit 5 of the rubber product damage detection system 1 according to the embodiment of the present invention. 図４は、ゴム内で発生されるＡＥイベントカウント対ＡＥ振幅の関係を示すグラフである。FIG. 4 is a graph showing the relationship between the AE event count generated in rubber and the AE amplitude. 図５は、ゴム内で発生されるＡＥイベントカウント対ＡＥ周波数の関係を示すグラフである。FIG. 5 is a graph showing the relationship between the AE event count generated in rubber and the AE frequency. 図６は、金属材料とゴム材料におけるＡＥ信号の減衰を比較するための方法を示す実験１の概要を示す概念図である。FIG. 6 is a conceptual diagram showing an outline of Experiment 1 showing a method for comparing attenuation of AE signals in a metal material and a rubber material. 図７は、実験１の結果を示すグラフで、金属材料とゴム材料で発生するＡＥ波の減衰量を測定した結果を示すグラフである。FIG. 7 is a graph showing the results of Experiment 1, and is a graph showing the results of measuring the attenuation of AE waves generated in the metal material and the rubber material. 図８は、実験２の測定の様子を示す概念図であり、図８（ａ）は試験片の寸法を示す概念図で、図８（ｂ）は試験片にき裂を発生させてＡＥ信号を測定する様子を示す概念図である。FIG. 8 is a conceptual diagram showing the state of measurement in Experiment 2, FIG. 8 (a) is a conceptual diagram showing the dimensions of the test piece, and FIG. 8 (b) is an AE signal when a crack is generated in the test piece. It is a conceptual diagram which shows a mode that it measures. 図９は、実験２の結果を示すグラフであり、図９（ａ）は銅の場合であり、図９（ｂ）はゴムの場合である。FIG. 9 is a graph showing the results of Experiment 2. FIG. 9A shows the case of copper, and FIG. 9B shows the case of rubber. 図１０は、実験３の結果を示すもので、ゴム製の試験片の断面を示す写真であり、図１０（ａ）は高圧ガスに暴露する試験を３回繰り返した後の写真で、図１０（ｂ）は高圧ガスに暴露する試験を５回繰り返した後の写真である。FIG. 10 shows the results of Experiment 3 and is a photograph showing a cross section of a rubber test piece. FIG. 10 (a) is a photograph after the test exposed to high-pressure gas is repeated three times. (B) is a photograph after the test exposed to high-pressure gas was repeated five times. 図１１は、繰り返し暴露試験した後、検出されたＡＥ信号を信号処理し、イベントレートを求めた結果を示すグラフである。FIG. 11 is a graph showing the result of obtaining the event rate by performing signal processing on the detected AE signal after repeated exposure tests. 図１２は、高圧水素ガス中で曝露した円柱試験片の減圧後の内部き裂発生状況である。FIG. 12 shows an internal crack occurrence state after decompression of a cylindrical test piece exposed in high-pressure hydrogen gas. 図１３は、図１２の試験片から発生したＡＥイベントカウントとＡＥ振幅の関係を示すグラフであり、図１３（ａ）は測定データを示すグラフであり、図１３（ｂ）は図１３（ａ）を対数軸にしたグラフである。FIG. 13 is a graph showing the relationship between the AE event count and the AE amplitude generated from the test piece of FIG. 12, FIG. 13 (a) is a graph showing measurement data, and FIG. 13 (b) is a graph showing FIG. Is a logarithmic axis. 図１４は、ゴム製品内で気泡とき裂が発生するメカニズムを様式的に示した図であり、図１４（ａ）は過飽和の状態、図１４（ｂ）は気泡の発生、図１４（ｃ）は気泡を起点としてき裂が発生する様子を図示している。FIG. 14 is a diagram stylistically showing the mechanism of occurrence of cracks and bubbles in a rubber product. FIG. 14 (a) is a state of supersaturation, FIG. 14 (b) is the generation of bubbles, and FIG. 14 (c). Fig. 2 illustrates how a crack is generated starting from a bubble. 図１５は、計測されるＡＥ信号の種類を説明した図であり、図１５（ａ）は１つのＡＥ信号を示し、図１５（ｂ）はイベント法、図１５（ｃ）リングダウン法を概念的に図示している。FIG. 15 is a diagram for explaining the types of AE signals to be measured. FIG. 15A shows one AE signal, FIG. 15B conceptually shows the event method, and FIG. 15C shows the ring-down method. It is shown schematically.
　〔ゴム製品の損傷検知システムの全体概要〕
　図１は、ゴム製品の損傷検知システム１の概要を図示している図である。図１に示すゴム製品の損傷検知システム１は、ゴム製品の損傷を実験により確認、検証するためのシステムであり、圧力装置２、サンプル３、ＡＥセンサー４、信号処理ユニット５、コンピュータ６等から構成されている。圧力装置２は、その内部にサンプル３を置き、その内部のガスの圧力を所定圧力に保ち、圧力を制御するための装置である。即ち、圧力装置２は、ポンプ７等のガス供給・排気手段で、圧力装置２内に水素ガス等のガスを供給するか、圧力装置２内のガスを排気して、圧力装置２の内部のガスの圧力を所定圧力に調整する。 [Overview of rubber product damage detection system]
FIG. 1 is a diagram illustrating an outline of a damage detection system 1 for rubber products. A rubber product damage detection system 1 shown in FIG. 1 is a system for confirming and verifying the damage of a rubber product through experiments. From the pressure device 2, the sample 3, the AE sensor 4, the signal processing unit 5, the computer 6, and the like. It is configured. The pressure device 2 is a device for placing the sample 3 therein, maintaining the pressure of the gas in the interior at a predetermined pressure, and controlling the pressure. That is, the pressure device 2 is a gas supply / exhaust means such as a pump 7, and supplies a gas such as hydrogen gas into the pressure device 2 or exhausts the gas in the pressure device 2 to The gas pressure is adjusted to a predetermined pressure.
　高圧ガス中に曝されたゴム製品のゴム材料中に、き裂や巨視的な欠陥が存在する場合を考える。通常では、ゴム材料中にき裂が発生又は発生したき裂が進展しない程度の高圧の圧力でするゴム製品を曝露と、高圧ガスを減圧した後に、このゴム材料中にき裂が発生又は、既に発生したき裂や欠陥が進展する。このようなき裂の発生と進展に伴い、ゴム製品からＡＥ信号が出力される。このＡＥ信号は、ＡＥセンサー等で計測することができる。なお、図１のようにゴム製品を圧力装置２内に入れずに、稼働中のゴム製品に直接、ＡＥセンサーを取り付け、稼働中のゴム製品からのＡＥ信号を計測しても良い。本実施の形態では、サンプル３は、ゴム製品である。本実施の形態においては、サンプル３は、シール部品の一つであるゴム製のＯリング（Ｏ-ring）である。 Suppose that there are cracks and macroscopic defects in the rubber material of rubber products exposed to high-pressure gas. Normally, a rubber product is exposed to a high-pressure pressure at which a crack is generated in the rubber material or a crack that has not occurred, and after the high-pressure gas is depressurized, a crack is generated in the rubber material, or Cracks and defects that have already occurred develop. An AE signal is output from the rubber product as the cracks are generated and propagated. This AE signal can be measured by an AE sensor or the like. In addition, as shown in FIG. 1, an AE sensor may be directly attached to an operating rubber product without measuring the rubber product in the pressure device 2, and an AE signal from the operating rubber product may be measured. In the present embodiment, the sample 3 is a rubber product. In the present embodiment, the sample 3 is a rubber O-ring that is one of seal parts.
　しかし、サンプル３は、シール部品、Ｏリング等に限定するものではなく、ゴム製の部品、製品であれば任意の形状であっても良い。図２には、本実施の形態に用いるサンプル３のＯリングの例を図示している。図２（ａ）に示すように、このＯリングは、その内側の半径Ｒ１と外側の半径Ｒ２を持ち、断面形状が円形でゴム製の材料からできているリングである。図２（ｂ）は、図２(ａ)のＡ－Ａ断面図を示している。この断面は、所定の直径Ｄ（＝Ｒ２－Ｒ１）の円になっている。後述する測定では、断面直径Ｄが３．２３ｍｍ、内側半径Ｒ１が５．９５ｍｍのＯリングを使用した。 However, the sample 3 is not limited to seal parts, O-rings, etc., and may be any shape as long as it is a rubber part or product. FIG. 2 shows an example of an O-ring of sample 3 used in this embodiment. As shown in FIG. 2 (a), this O-ring has a radius R1 on the inside and a radius R2 on the outside, and is a ring made of a rubber material having a circular cross-sectional shape. FIG. 2B shows a cross-sectional view along the line AA in FIG. This cross section is a circle having a predetermined diameter D (= R2-R1). In the measurement described later, an O-ring having a cross-sectional diameter D of 3.23 mm and an inner radius R1 of 5.95 mm was used.
　ＡＥセンサー４は、サンプル３から発生するＡＥ信号を検知するものである。ＡＥセンサー４は、任意の形状、動作原理のものが利用できるが、本実施の形態においては、ＡＥセンサー４は圧電体からなるものである。ＡＥセンサー４は、検知したＡＥ信号を、電気信号に変換して、検出信号として出力する。この出力は、ＡＥセンサー４に接続された後段の装置に入力される。図１に示した例では、ＡＥセンサー４の出力信号は、信号処理ユニット５に入力される。信号処理ユニット５は、ＡＥセンサー４から受信した検出信号を、解析するためのものである。 The AE sensor 4 detects an AE signal generated from the sample 3. The AE sensor 4 can be of any shape and operating principle, but in the present embodiment, the AE sensor 4 is made of a piezoelectric material. The AE sensor 4 converts the detected AE signal into an electrical signal and outputs it as a detection signal. This output is input to a subsequent apparatus connected to the AE sensor 4. In the example shown in FIG. 1, the output signal of the AE sensor 4 is input to the signal processing unit 5. The signal processing unit 5 is for analyzing the detection signal received from the AE sensor 4.
　図３には、信号処理ユニット５の回路例をブロック図で図示したものである。信号処理ユニット５は、メモリ１１、ＣＰＵ１０、入力インターフェース１２、出力インターフェース１３等からなる。メモリ１１には、信号処理ユニット５を制御するための制御プログラム（図示せず。）が格納される。信号処理ユニット５の起動時に、この制御プログラムが呼び出されて動作する。入力インターフェース１２は、上述の検出信号を信号処理ユニット５に入力するためのインターフェースである。入力インターフェース１２は、ＡＥセンサー４に直接接続されていて、ＡＥセンサー４から出力される検出信号を受信する。 FIG. 3 shows a circuit example of the signal processing unit 5 in a block diagram. The signal processing unit 5 includes a memory 11, a CPU 10, an input interface 12, an output interface 13, and the like. The memory 11 stores a control program (not shown) for controlling the signal processing unit 5. When the signal processing unit 5 is activated, this control program is called and operates. The input interface 12 is an interface for inputting the detection signal described above to the signal processing unit 5. The input interface 12 is directly connected to the AE sensor 4 and receives a detection signal output from the AE sensor 4.
　受信された検出信号は、メモリ１１に保存されて、制御プログラムによって読み出されて処理される。ＣＰＵ１０は、メモリ１１に格納されている制御プログラムの命令を順次実行して、信号処理ユニット５を動作させる。出力インターフェース１３は、信号処理ユニット５で検出信号を処理した結果を出力するためのものである。つまり、制御プログラムで検出信号であるデータを処理した結果を、ＡＥ信号データとして、出力する。この出力されたＡＥ信号データは、コンピュータ６に提供される。例えば、このＡＥ信号データは、コンピュータ６では、作業者が確認可能な形式で出力され、ディスプレイ等に表示される。 The received detection signal is stored in the memory 11 and read and processed by the control program. The CPU 10 sequentially executes the instructions of the control program stored in the memory 11 to operate the signal processing unit 5. The output interface 13 is for outputting the result of processing the detection signal by the signal processing unit 5. That is, the result of processing the data that is the detection signal by the control program is output as AE signal data. The output AE signal data is provided to the computer 6. For example, the AE signal data is output in a format that can be confirmed by the operator in the computer 6 and displayed on a display or the like.
　また、出力インターフェース１３に接続された他の電子計算機に提供することも可能である。本実施の形態のシステム１は、図３に破線で示したように、ＡＥセンサー４で受信したＡＥ信号を増幅して、信号処理ユニット５に出力するためのプリアンプ１６を有している。信号処理ユニット５は、電源供給用に電源用インターフェース１５を有する。電源用インターフェース１５は、直流又は交流の電源等に接続されている。例えば、信号処理ユニット５は、バッテリー等の電源（図示せず。）を内蔵し、電源用インターフェース１５はこの内蔵電源に接続さている。 Also, it can be provided to other electronic computers connected to the output interface 13. The system 1 according to the present embodiment includes a preamplifier 16 for amplifying the AE signal received by the AE sensor 4 and outputting the amplified signal to the signal processing unit 5 as indicated by a broken line in FIG. The signal processing unit 5 has a power interface 15 for supplying power. The power supply interface 15 is connected to a direct current or alternating current power source or the like. For example, the signal processing unit 5 has a built-in power source (not shown) such as a battery, and the power interface 15 is connected to the built-in power source.
　次に、信号処理ユニット５は、検出信号を処理する概要を示す。検出信号の処理は、制御プログラムによって行なわれる。これらの処理は、この制御プログラムと同様な機能を持つ回路でも実現できる。信号処理ユニット５は、ＡＥセンサー４から受信したデータから、検出信号をメモリ１１に保存する。このとき、検出信号を受信した時間を示す受信時間データを、検出信号に関連付けて保存する。また、圧力装置２の内圧等に関する他のデータも、同じくこの検出信号及び／又は受信時間データに関連付けて保存する。信号処理ユニット５は、メモリ１１に保存された検出信号と受信時間データを読み出して、データ処理してＡＥイベントカウントとＡＥ振幅を計算する。 Next, the signal processing unit 5 shows an outline of processing the detection signal. Processing of the detection signal is performed by a control program. These processes can also be realized by a circuit having the same function as this control program. The signal processing unit 5 stores the detection signal in the memory 11 from the data received from the AE sensor 4. At this time, reception time data indicating the time when the detection signal is received is stored in association with the detection signal. Further, other data related to the internal pressure of the pressure device 2 is also stored in association with this detection signal and / or reception time data. The signal processing unit 5 reads the detection signal and the reception time data stored in the memory 11, processes the data, and calculates the AE event count and the AE amplitude.
　そして、ＡＥイベントカウントとＡＥ振幅の関係を予め設定した使用限界線（後述する。）と比較して、サンプル３の良否を判定する。サンプル３のき裂の経時変化は、き裂が進展してゴム製品の表面に進展する兆候を示すとき、又は使用限界線に達するとき、サンプル３は損傷が大きいと推定される。この兆候としては、使用限界線を利用することができる。また、この経時変化は、予め損傷状態を分かっているサンプル３の特性と比較され、サンプル３の損傷が評価され、サンプル３の良否を判定することもできる。 Then, the quality of the sample 3 is determined by comparing the relationship between the AE event count and the AE amplitude with a preset use limit line (described later). The time course of the crack in sample 3 is presumed that sample 3 is severely damaged when it shows signs that the crack has progressed and progressed to the surface of the rubber product, or when the use limit line is reached. The use limit line can be used as this indication. Moreover, this time-dependent change is compared with the characteristic of the sample 3 whose damage state is known in advance, the damage of the sample 3 is evaluated, and the quality of the sample 3 can also be determined.
　信号処理ユニット５は、ＡＥイベントカウントとＡＥ振幅の計算結果、判定の結果及び／又はメモリ１１の内容を出力データとして、出力インターフェース１３から出力する。出力形式、装置は、これらのデータをグラフ化、表形式にして、表示装置又は印刷装置用のデータとするものが好ましい。また、テキスト形式のデータにして、他の電子計算機等の処理用に出力するようにもできる。このグラフに、最新のデータを追加して出力することも可能である。 The signal processing unit 5 outputs the calculation result of the AE event count and the AE amplitude, the determination result, and / or the contents of the memory 11 from the output interface 13 as output data. It is preferable that the output format and device are graph data and tabular data to be used as data for a display device or a printing device. It can also be output in text format data for processing by other electronic computers. It is also possible to add the latest data to this graph and output it.
　このようにすると、サンプルの使用者、管理者等は、サンプル４の損傷状態の進展を把握しやすくなる。信号処理ユニット５は、上述のように、圧力装置２の内圧を測定するための、圧力測定器（図示せず。）等を有している。信号処理ユニット５は、ＡＥセンサー４からデータを連続的に、又は定期的に、又は指定時刻に受信する。また、信号処理ユニット５は、操作者の受信要求、信号処理ユニット５に接続されたコンピュータ６や他の電子機器等のデータ要求のときに、ＡＥセンサー４からデータを受信する。 This makes it easier for sample users, managers, etc. to grasp the progress of the damage state of sample 4. As described above, the signal processing unit 5 includes a pressure measuring device (not shown) and the like for measuring the internal pressure of the pressure device 2. The signal processing unit 5 receives data from the AE sensor 4 continuously, periodically, or at a designated time. Further, the signal processing unit 5 receives data from the AE sensor 4 at the time of an operator's reception request or a data request from a computer 6 or other electronic device connected to the signal processing unit 5.
　更に、信号処理ユニット５は、計算結果を連続的に、又は定期的に、又は指定時刻に出力する。ＡＥセンサー４は、圧力装置２内のサンプル４の表面に接触するように固定されている。この固定時の固定手段としては、ＡＥセンサー４をサンプル３の表面に密着させ、接触するようなものであればどのような方法でも良い。図示していないが、圧力装置２の内圧は、圧力測定器を用いて測定されているものが好ましい。圧力測定器は、圧力装置２に流体を充填する装置に含まれるデバイスであるものでも良い。 Furthermore, the signal processing unit 5 outputs the calculation result continuously, periodically, or at a designated time. The AE sensor 4 is fixed so as to contact the surface of the sample 4 in the pressure device 2. As a fixing means at the time of fixing, any method may be used as long as the AE sensor 4 is brought into close contact with the surface of the sample 3 and comes into contact therewith. Although not shown, the internal pressure of the pressure device 2 is preferably measured using a pressure measuring device. The pressure measuring device may be a device included in an apparatus for filling the pressure device 2 with a fluid.
　圧力測定器は、当業者に自明なものであれば、既知の測定手段を含めどんな種類・測定原理のものでも良い。ＡＥセンサー４は、所定の検知感度を調整するものが好ましい。つまり、ＡＥセンサー４は、ＡＥ信号を検知するとき、その検知感度を調整可能なものが好ましい。この検知感度は、信号処理ユニット５で設定しても良い。信号処理ユニット５は、ＡＥセンサー４から受信した信号の内、所定基準値以上の値をＡＥ信号として処理する。信号処理ユニット５は、ＡＥセンサー４から受信したデータをそのまま出力インターフェース１３から出力できる。 Pressure measuring instrument, as long as obvious to those skilled in the art, may be of any type and measurement principle include known measuring means. The AE sensor 4 is preferably one that adjusts a predetermined detection sensitivity. That is, it is preferable that the AE sensor 4 can adjust the detection sensitivity when detecting the AE signal. This detection sensitivity may be set by the signal processing unit 5. The signal processing unit 5 processes a value greater than a predetermined reference value among signals received from the AE sensor 4 as an AE signal. The signal processing unit 5 can output the data received from the AE sensor 4 as it is from the output interface 13.
　通常は、信号処理ユニット５は、ＡＥセンサー４から受信したデータについては、周波数や強度でフィルタリングし、初歩的な信号処理を行って、出力インターフェース１３から出力する。この出力された生のデータは、出力インターフェース１３に接続されたコンピュータ６で処理される。例えば、コンピュータ６は、信号処理ユニット５で処理していた、上述の、ＡＥイベントカウントとＡＥ振幅の計算、判定等の処理を行う。信号処理ユニット５では、フィルタによって所定の周波数のＡＥ信号を抽出し、抽出されたＡＥ信号がメインアンプにて増幅される。 Normally, the signal processing unit 5 filters the data received from the AE sensor 4 by frequency and intensity, performs elementary signal processing, and outputs the result from the output interface 13. The output raw data is processed by the computer 6 connected to the output interface 13. For example, the computer 6 performs processing such as calculation and determination of the AE event count and the AE amplitude described above, which has been processed by the signal processing unit 5. In the signal processing unit 5, an AE signal having a predetermined frequency is extracted by a filter, and the extracted AE signal is amplified by a main amplifier.
　そして、あらかじめ設定したＡＥ振幅値を超えたＡＥ信号の計数、振幅値の計算およびフーリエ変換が行われ、ＡＥイベントカウント、ＡＥ振幅およびＡＥ信号の周波数が計測される。コンピュータ６は、信号処理ユニット５から出力された信号を解析するための電子計算機である。コンピュータ６は、図示していないが、ＣＰＵ、ＲＡＭ、ＲＯＭ、補助記憶装置、入出力インターフェース、及び、ディスプレイ、マウス、キーボード等の入出力デバイス等を備えた電子計算機である。コンピュータ６は、本実施の形態で記述した処理を行うことができるものであれば、任意の電子計算機を使用できる。 AE signal count exceeding the preset AE amplitude value, amplitude value calculation and Fourier transform are performed, and AE event count, AE amplitude and AE signal frequency are measured. The computer 6 is an electronic computer for analyzing the signal output from the signal processing unit 5. Although not shown, the computer 6 is an electronic computer including a CPU, a RAM, a ROM, an auxiliary storage device, an input / output interface, and input / output devices such as a display, a mouse, and a keyboard. The computer 6 can use any electronic computer as long as it can perform the processing described in the present embodiment.
　コンピュータ６は、ＡＥセンサー４で検知した一連のＡＥ信号を解析し、データベース（図示せず。）を参照して、解析を行う。データベースは、サンプル３から発するＡＥ信号に関するデータを格納したデータベースである。データベースには、正常な、つまり、利用可能なサンプル３に関するデータ、使用不可になったサンプル３に関するデータ等が格納される。データベースは、信号処理ユニット５又はコンピュータ６からデータ更新ができる。また、管理者、ユーザ等が、手動で、データベースを更新することができる。 The computer 6 analyzes a series of AE signals detected by the AE sensor 4 and performs analysis with reference to a database (not shown). The database is a database that stores data related to the AE signal emitted from the sample 3. The database stores data relating to normal, that is, usable sample 3, data relating to sample 3 that has become unusable, and the like. Data can be updated in the database from the signal processing unit 5 or the computer 6. In addition, an administrator, a user, etc. can update the database manually.
　データベースは、コンピュータ６の主記憶装置又は補助記憶装置又は接続された外部記憶装置に格納されている。データベースは、コンピュータ６内又はその近くに設置されたものであるが、無線又は有線の通信手段によってアクセスできる遠隔地に設置されたものであっても良い。コンピュータ６での解析は、次の手順で行われる。コンピュータ６での解析の結果は、サンプル３の良否の鑑定になる。例えば、サンプル３内のき裂が大きくないとき、つまり、サンプル３が本来の機能を果たせると判断した時は、検査合格を示す信号を出力する。 The database is stored in the main storage device or auxiliary storage device of the computer 6 or a connected external storage device. The database is installed in or near the computer 6, but may be installed in a remote place accessible by wireless or wired communication means. Analysis by the computer 6 is performed in the following procedure. The result of the analysis by the computer 6 is an evaluation of the quality of the sample 3. For example, when the crack in the sample 3 is not large, that is, when it is determined that the sample 3 can perform its original function, a signal indicating an inspection pass is output.
　サンプル３内のき裂が大きく、つまり、サンプル３が本来の機能を果たせないと判断した時は、検査不合格を示す信号を出力する。無論、き裂が大きくはないが、数が多かったりするときも、検査不合格を示す信号を出力する。コンピュータ６は、サンプル３の検査結果を、過去の検査データも含めて、全て集計して、視覚で確認可能形式のグラフ等にまとめ、そのディスプレイに表示するか、印刷装置に印刷することもできる。 When the crack in the sample 3 is large, that is, when it is determined that the sample 3 cannot perform its original function, a signal indicating an inspection failure is output. Of course, even if the crack is not large but the number is large, a signal indicating failure of inspection is output. The computer 6 can totalize all the inspection results of the sample 3 including past inspection data, collect them in a visually checkable graph, etc., and display them on the display or print them on the printing device. .
　図４は、サンプル３のＯリングから発生するＡＥ信号のＡＥイベントカウントとＡＥ振幅の関係の経時変化の模式図を示す。ＡＥイベントカウントとＡＥ振幅は、き裂発生の有無にかかわらずべき乗の関係がある。き裂が発生していないグラフＡの場合にはその傾きｍが４であり、サンプル３内の気泡は、き裂発生の前段階の状態である。気泡を起点としてき裂が発生するとグラフＢのようにその傾きｍが２となる。このときは、き裂は比較的に軽微な損傷である。そして、き裂損傷が激しくなると、図４の中の矢印で示すように、グラフＢ、Ｃ、及びＤのようにＡＥイベントカウントとＡＥ振幅の関係は、右上方向にシフトしていく。 FIG. 4 is a schematic diagram showing a change over time in the relationship between the AE event count of the AE signal generated from the O-ring of the sample 3 and the AE amplitude. The AE event count and the AE amplitude have a power relationship regardless of the presence or absence of cracks. In the case of the graph A in which no crack is generated, the slope m is 4, and the bubbles in the sample 3 are in the state before the crack is generated. When a crack is generated starting from a bubble, its slope m becomes 2 as shown in graph B. At this time, the crack is a relatively minor damage. When the crack damage becomes severe, the relationship between the AE event count and the AE amplitude is shifted in the upper right direction as shown by the arrows in FIG. 4 as indicated by the arrows in FIG.
　サンプル３がグラフＤの状態だと、サンプル３は、もはや機械等に使用することができない程度に損傷している。図４の中の破線のグラフは、サンプル３の良否の判定をするために設けた基準値を示す合格ライン（使用限界線）である。サンプル３の測定値がこの合格ラインより上側に位置すると、そのサンプル３は破損している又は破損する恐れがあり、使用できない。サンプル３の測定値がこの合格ラインより下側に位置すると、そのサンプル３の状態は良好であり、使用することができる。データベースには、この図４のグラフと同様なデータが格納される。コンピュータ６では、新規に測定したＡＥ信号を、データベースに格納されているこのデータと比較して、サンプル３の判定を行う。よって、コンピュータ６は、サンプル３の測定結果を、データベースに保存されている図４のデータと比較して、使用限界線を元に、サンプル３の良否が判定できる。 When sample 3 is in the state of graph D, sample 3 is damaged to such an extent that it can no longer be used for a machine or the like. The broken line graph in FIG. 4 is an acceptable line (usage limit line) indicating a reference value provided for determining whether the sample 3 is good or bad. If the measured value of the sample 3 is located above the pass line, the sample 3 may be damaged or damaged and cannot be used. When the measured value of the sample 3 is located below the acceptance line, the state of the sample 3 is good and can be used. Data similar to the graph of FIG. 4 is stored in the database. The computer 6 determines the sample 3 by comparing the newly measured AE signal with this data stored in the database. Therefore, the computer 6 can determine the quality of the sample 3 based on the use limit line by comparing the measurement result of the sample 3 with the data of FIG. 4 stored in the database.
　図５は、ＡＥ信号をフーリエ変化して解析したＡＥイベントカウントとＡＥ周波数の関係の模式図である。気泡の形成とき裂の発生により、生じるＡＥ信号の周波数が異なり、バンドパスフィルターを用いてき裂発生に伴うＡＥ信号のみを取り出すことが可能である。つまり、図５の例では、気泡の形成のとき発生するＡＥ信号の周波数は、き裂の発生のときに発生するＡＥ信号の周波数より少ないことが解る。これらの周波数をバンドパスフィルターでフィルタリングして監視することにより、気泡の形成かき裂の発生かを監視することができる。 FIG. 5 is a schematic diagram showing the relationship between the AE event count and the AE frequency obtained by analyzing the AE signal by Fourier change. The frequency of the generated AE signal varies depending on the formation of a bubble and the generation of a crack, and it is possible to extract only the AE signal accompanying the generation of a crack using a bandpass filter. That is, in the example of FIG. 5, it can be seen that the frequency of the AE signal generated when bubbles are formed is lower than the frequency of the AE signal generated when cracks are generated. By filtering and monitoring these frequencies with a band-pass filter, it is possible to monitor whether bubbles are formed or cracks are generated.
　〔実験について〕
　以下、このサンプルの解析を裏付けするいくつかの実験の測定を示す。実験１は、金属材料とゴム材料で発生するＡＥ信号を測定して、その減衰率を比較したものである。実験２は、金属材料とゴム材料で発生するＡＥ信号を受信して、その構成信号の違いを解析したものである。実験３は、ゴム製のサンプルを高圧ガスに配置し、ガスの圧力を高圧にし、減圧する測定を１回もしくは複数回繰り返した後、ＡＥを測定したものである。 [Experiment]
Below are some experimental measurements that support the analysis of this sample. In Experiment 1, AE signals generated by a metal material and a rubber material were measured and their attenuation rates were compared. Experiment 2 receives the AE signal generated by the metal material and the rubber material, and analyzes the difference between the constituent signals. In Experiment 3, a rubber sample is placed in a high-pressure gas, the pressure of the gas is increased, and the pressure reduction is repeated one or more times, and then AE is measured.
〔実験１：　金属材料とゴム材料で発生するＡＥ信号の減衰の比較〕
　まず、実験１について記述する。図６は、厚みの異なるゴムの試験片を用いて、各周波数成分のＡＥ信号（ＡＥ波）の減衰量を測定する概念図である。厚さの異なる３種類の円柱型のゴムの試験片を作製し、試験片の両端に第１ＡＥセンサーと第２ＡＥセンサーを取り付けた。試験片の寸法は、直径が１３ｍｍ、厚さが２、６及び１２ｍｍであった。第１ＡＥセンサーと第２ＡＥセンサーは、株式会社エヌエフ回路設計ブロック（英語表記：NF Corporation、所在地：日本国神奈川県横浜市）製のＡＥセンサーＡＥ－９００Ｆ２で、３００ｋＨｚ～２．２ＭＨｚの広帯域用ＡＥセンサーであった。 [Experiment 1: Comparison of attenuation of AE signal generated by metal material and rubber material]
First, Experiment 1 is described. FIG. 6 is a conceptual diagram for measuring the attenuation amount of the AE signal (AE wave) of each frequency component using rubber test pieces having different thicknesses. Three types of cylindrical rubber test pieces having different thicknesses were prepared, and a first AE sensor and a second AE sensor were attached to both ends of the test piece. The dimensions of the test piece were 13 mm in diameter and 2, 6 and 12 mm in thickness. The 1st AE sensor and the 2nd AE sensor are AE sensors AE-900F2 manufactured by NF Circuit Design Block Co., Ltd. (English notation: NF Corporation, location: Yokohama, Kanagawa, Japan). Met.
　そして、第１ＡＥセンサーに、発信器で生成した正弦波の電気信号を送った。この正弦波は、１００ｋＨｚ～３ＭＨｚの範囲であった。発信器は、株式会社エヌエフ回路設計ブロック（英語表記：NF Corporation、所在地：日本国神奈川県横浜市）製のマルチファンクションジェネレータＷＦ１９７３であった。第１ＡＥセンサーは、広帯域のＡＥ信号の発信器として機能した。第２ＡＥセンサーで、第１ＡＥセンサーから送信され試験片を透過した正弦波を受信した。第２ＡＥセンサーは、ＡＥ信号の受信機として機能した。第２ＡＥセンサーで受信したＡＥ信号をプリアンプ（Pre-Amplifier 9913、株式会社エヌエフ回路設計ブロック製）で増幅し、オシロスコープ（LeCroy社（所在地：米国ニューヨーク市）製のWaveRunner 6030A）で観察した。 And the electric signal of the sine wave generated by the transmitter was sent to the 1st AE sensor. This sine wave was in the range of 100 kHz to 3 MHz. The transmitter was a multi-function generator WF1973 manufactured by NF Circuit Design Block Co., Ltd. (English notation: NF Corporation, location: Yokohama, Kanagawa, Japan). The first AE sensor functioned as a broadband AE signal transmitter. The sine wave transmitted from the first AE sensor and transmitted through the test piece was received by the second AE sensor. The second AE sensor functioned as a receiver for the AE signal. The AE signal received by the second AE sensor was amplified with a preamplifier (Pre-Amplifier 9913, manufactured by NF Circuit Design Block Co., Ltd.), and observed with an oscilloscope (WaveRunner 6060A manufactured by LeCroy (New York City, USA)).
　実験１は、室温で、大気中にて行われた。この実験１によって、送信側の正弦波に対する受信側の正弦波の振幅低下を各試験片の厚さごとに測定して、ゴム材料のＡＥ信号減衰に及ぼす周波数の影響を評価した。図７は、実験１の実験結果を示すグラフである。図７のグラフの縦軸は、送信側のＡＥ信号の振幅Ａ０に対する受信側のＡＥ信号の振幅Ａであり、横軸は試験片の厚さである。ゴム材料でのＡＥ信号の減衰は、金属材料でのＡＥ信号の減衰と比べて大きい。図７に図示されたグラフから明らかなように、１ＭＨｚ以下の周波数のＡＥ信号の減衰量は、試験片の厚さが１０ｍｍでも５０％程度である。よって、厚さ１０ｍｍ程度のゴムの試験片を想定すると、対象とするＡＥ信号の周波数は１ＭＨｚ以下とすべきである。 Experiment 1 was conducted in the atmosphere at room temperature. In Experiment 1, the amplitude reduction of the receiving sine wave with respect to the transmitting sine wave was measured for each thickness of each test piece, and the influence of the frequency on the AE signal attenuation of the rubber material was evaluated. FIG. 7 is a graph showing the experimental results of Experiment 1. The vertical axis of the graph of FIG. 7 is the amplitude A of the AE signal on the reception side with respect to the amplitude A0 of the AE signal on the transmission side, and the horizontal axis is the thickness of the test piece. The attenuation of the AE signal in the rubber material is larger than the attenuation of the AE signal in the metal material. As apparent from the graph shown in FIG. 7, the attenuation amount of the AE signal having a frequency of 1 MHz or less is about 50% even when the thickness of the test piece is 10 mm. Therefore, assuming a rubber test piece having a thickness of about 10 mm, the frequency of the target AE signal should be 1 MHz or less.
〔実験２：　金属材料とゴム材料で発生するＡＥ信号の違い〕
　次に、実験２について、記述する。図８には、金属材料とゴム材料で発生するＡＥ信号の違いを測定する実験の様子を示している。試験片はトラウザ型試験片である。試験片の寸法は、図８（ａ）に図示している。試験片は、長さが１００ｍｍで、幅が１５ｍｍで、厚さが２ｍｍであった。切欠きは、試験片の端から長さ方向に４０ｍｍであった。試験片は、銅とゴムの２種類を利用した。この実験２は、金属材料とゴム材料の各材料内で発生するＡＥ信号を受信して、解析し、このＡＥ信号の構成信号の違いを解析したものである。 [Experiment 2: Difference in AE signal generated between metal material and rubber material]
Next, Experiment 2 will be described. FIG. 8 shows a state of an experiment for measuring a difference between AE signals generated between a metal material and a rubber material. The test piece is a trouser type test piece. The dimensions of the test piece are illustrated in FIG. The test piece was 100 mm in length, 15 mm in width, and 2 mm in thickness. The notch was 40 mm in the length direction from the end of the test piece. Two types of test pieces, copper and rubber, were used. In this experiment 2, an AE signal generated in each material of a metal material and a rubber material is received and analyzed, and the difference in the constituent signals of the AE signal is analyzed.
　図８（ｂ）に図示したように、試験片にＡＥセンサーを密着するよう設置した。そして、矢印で示すように試験片を引っ張って引裂いた。引裂いた際に切欠きから進展するき裂に伴って発生する弾性波を計測した。実験２は室温で大気中にて行われた。この測定結果は、図９のグラフに示している。図９（ａ）に図示したグラフは銅の場合で、図９（ｂ）に図示したグラフはゴムの場合である。図９（ａ）と図９ｂ）のグラフの横軸は、測定時の経過時間を示している。図９（ａ）と図９ｂ）のグラフの右側の縦軸は、ＡＥイベントカウントレートを示している。 As shown in FIG. 8B, the AE sensor was placed in close contact with the test piece. And as shown by the arrow, the test piece was pulled and torn. The elastic waves generated along with the cracks propagating from the notch during tearing were measured. Experiment 2 was performed in air at room temperature. The measurement results are shown in the graph of FIG. The graph shown in FIG. 9A is for copper, and the graph shown in FIG. 9B is for rubber. The horizontal axis of the graphs of FIGS. 9A and 9B shows the elapsed time at the time of measurement. The vertical axis on the right side of the graphs of FIGS. 9A and 9B shows the AE event count rate.
　また、図９（ａ）と図９ｂ）のグラフの左側の縦軸は、試験片を引裂くときの引裂力を示している。図９のグラフから解るように、応力が平坦になる領域において、き裂が進展する。これらのグラフから解るように、ゴムの場合も、銅の場合も、き裂の進展に伴って、ＡＥ信号が発生している。しかし、ゴムの場合、鋼に比べて発生するＡＥイベントカウントレートは少ない。 Also, the vertical axis on the left side of the graphs of FIGS. 9A and 9B shows the tearing force when tearing the test piece. As can be seen from the graph of FIG. 9, the crack propagates in the region where the stress becomes flat. As can be seen from these graphs, in the case of rubber and copper, an AE signal is generated as the crack progresses. However, in the case of rubber, the AE event count rate generated is smaller than that of steel.
〔実験３：　ゴム材料に繰り返し高圧ガスを暴露する試験〕
　実験３について記述する。この実験３では、円柱型のゴムの試験片を高圧水素ガス用のチャンバ内に置き、高圧水素ガスの加減圧を繰返して試験片の内部にき裂を発生させた。試験片の寸法は、直径が２９ｍｍ、厚さが１２．５ｍｍの円柱形状であった。試験片の材料は、未充填過酸化物架橋エチレンプロピレンゴムを使用した。 [Experiment 3: Repeated exposure of rubber material to high pressure gas]
Experiment 3 is described. In Experiment 3, a cylindrical rubber test piece was placed in a chamber for high-pressure hydrogen gas, and the pressure of the high-pressure hydrogen gas was repeatedly applied to generate a crack inside the test piece. The test piece had a cylindrical shape with a diameter of 29 mm and a thickness of 12.5 mm. The material of the test piece was unfilled peroxide-crosslinked ethylene propylene rubber.
　試験片は透明である。試験片は、チャンバ内におき、圧力０．７ＭＰａ、温度２５℃の高圧水素ガスの環境で２４時間曝露した。その後、チャンバ内を減圧して試験片内にき裂を発生させた。試験片は減圧後にチャンバ内から取り出した。そして、試験片の内部き裂の発生状況をマイクロスコープで観察すると共に、試験片の表面にＡＥセンサーを装着し、発生するＡＥ信号を計測した。図１０は、ゴム製の試験片を繰り返し、ガス暴露した後で、試験片の表面を顕微鏡で観察するときの写真である。図１０（ａ）は、高圧ガスに暴露する試験を３回繰り返した後、その表面を顕微鏡で観察した写真である。 Specimen is transparent. The specimen was placed in the chamber and exposed for 24 hours in an environment of high pressure hydrogen gas at a pressure of 0.7 MPa and a temperature of 25 ° C. Thereafter, the inside of the chamber was decompressed to generate a crack in the test piece. The specimen was removed from the chamber after decompression. Then, the occurrence of internal cracks in the test piece was observed with a microscope, and an AE sensor was mounted on the surface of the test piece, and the generated AE signal was measured. FIG. 10 is a photograph when the surface of the test piece is observed with a microscope after the rubber test piece is repeatedly exposed to gas. FIG. 10 (a) is a photograph of the surface observed with a microscope after repeating the test of exposure to high-pressure gas three times.
　図１０（ｂ）は、高圧ガスに暴露する試験を５回繰り返した後、その表面を顕微鏡で観察した写真である。図１０（ａ）と図１０（ｂ）のようには、透明な試験片を光学顕微鏡で観察して、試験片の内部に発生したき裂がはっきりと観察できる。この写真からわかるように、３回の場合に比べて、５回の場合は、き裂が大きくなり、き裂の数も多くなっている。図１１は、検出されたＡＥ信号を信号処理し、イベントレートを求めた結果を示すグラフである。このグラフの縦軸は、ＡＥイベントカウントレートを示し、横軸は経過時間を示している。このグラフからは、暴露試験の繰り返し回数が多くなると、き裂損傷に伴い、ＡＥイベントカウントレートも増加している。 FIG. 10 (b) is a photograph of the surface observed with a microscope after repeating the test of exposure to high-pressure gas five times. As shown in FIGS. 10A and 10B, a transparent test piece is observed with an optical microscope, and a crack generated inside the test piece can be clearly observed. As can be seen from this photograph, the crack is larger and the number of cracks is larger in the case of five times than in the case of three times. FIG. 11 is a graph showing the result of obtaining the event rate by processing the detected AE signal. The vertical axis of this graph indicates the AE event count rate, and the horizontal axis indicates the elapsed time. From this graph, as the number of repeated exposure tests increases, the AE event count rate also increases with crack damage.
　図１２は、ゴムの試験片を、水素ガス中で２４時間曝露後、室温で大気中に放置したときの断面写真である。このゴムの試験片は、透明ではないので、試験をカッタで切断し、その断面を撮影した。このゴムの試験片は、未充填硫黄加硫エチレンプロピレンゴムから作製した円柱型のものであり、直径が２９ｍｍ、厚さが１２．５ｍｍであった。水素ガスの条件は、圧力が０．７、１０、３０ＭＰａ、温度が３０℃であった。試験片は、減圧して３日後に、試験片の断面をカッタにて切断し、この試験片の断面を光学顕微鏡によって観察したものである。水素ガスの圧力が０．７ＭＰａの場合、試験片にはき裂が発生していなかった。水素ガスの圧力が１０ＭＰａ及び３０ＭＰａの場合、試験片には、内部にき裂が観察された。 FIG. 12 is a cross-sectional photograph of a rubber test piece exposed to hydrogen gas for 24 hours and left in the atmosphere at room temperature. Since this rubber test piece is not transparent, the test was cut with a cutter and the cross section was photographed. This rubber test piece was a cylindrical type made from unfilled sulfur vulcanized ethylene propylene rubber, and had a diameter of 29 mm and a thickness of 12.5 mm. The conditions of the hydrogen gas were a pressure of 0.7, 10, 30 MPa, and a temperature of 30 ° C. The test piece was obtained by observing the cross section of the test piece with an optical microscope after cutting the cross section of the test piece with a cutter three days after decompression. When the pressure of hydrogen gas was 0.7 MPa, no crack was generated on the test piece. When the hydrogen gas pressure was 10 MPa and 30 MPa, cracks were observed in the test piece.
　水素ガスの曝露圧力が高いほど、試験片のき裂の損傷が激しくなった。図１２（ａ）の試験片の表面にＡＥセンサーを取り付け、減圧後に生じたＡＥ信号を計測した。図１３は、減圧後に計測されたＡＥ信号のＡＥイベントカウントとＡＥ振幅の関係を示すグラフである。ＡＥイベントカウントとＡＥ振幅はべき乗の関係にある。き裂が発生していない圧力０．７ＭＰａでの傾きはｍ＝４であった。これに対して、き裂が認められた圧力１０ＭＰａ及び３０ＭＰａではｍ＝２であった。また、き裂損傷が激しいほど、ＡＥイベントカウントとＡＥ振幅の関係が図中の右上方向にシフトした。 The higher the hydrogen gas exposure pressure, the more severely cracked the specimen. An AE sensor was attached to the surface of the test piece in FIG. 12 (a), and an AE signal generated after decompression was measured. FIG. 13 is a graph showing the relationship between the AE event count of the AE signal measured after decompression and the AE amplitude. The AE event count and the AE amplitude have a power relationship. The slope at a pressure of 0.7 MPa at which no crack was generated was m = 4. On the other hand, m = 2 at pressures of 10 MPa and 30 MPa at which cracks were observed. In addition, as the crack damage was more severe, the relationship between the AE event count and the AE amplitude shifted to the upper right in the figure.
〔実験データのまとめ〕
　これらの一連の試験からは、ゴム製品の中に次のような挙動があったと推測できる。圧力装置２の中にゴム製のサンプル３を置き、高圧にすると、圧力装置２の水素ガスは過飽和状態になる。図１４（ａ）には、この様子を様式的に図示したものである。そして、圧力装置２から内部のガスを抜きとって減圧にすると、ゴム内の過飽和の水素が、ゴム内に気泡化する。図１４（ｂ）には、この様子を様式的に図示しており、気泡は矢印で示している。そして、更に減圧していくと、この気泡を起点としてき裂が発生する。 [Summary of experimental data]
From these series of tests, it can be inferred that the following behavior was present in rubber products. When the rubber sample 3 is placed in the pressure device 2 and the pressure is increased, the hydrogen gas in the pressure device 2 becomes supersaturated. FIG. 14A illustrates this state in a stylized manner. When the internal gas is extracted from the pressure device 2 to reduce the pressure, supersaturated hydrogen in the rubber is bubbled into the rubber. FIG. 14B illustrates this state in a stylized manner, and bubbles are indicated by arrows. When the pressure is further reduced, a crack is generated starting from this bubble.
　図１４（ｃ）には、この様子を様式的に図示しており、大きくなった気泡から発生するき裂を矢印で示している。き裂の進展によってサンプルから漏れる水素量が増加する。そして、この水素がサンプルを貫通することによって、著しいき裂ができると予想される。気泡が形成されるときと、き裂が発生するときの、両方で、ＡＥ信号が発生する。しかし、気泡の形成と、き裂の発生では、発生されるＡＥ信号の特性が異なる。この様子は、図１３（ｂ）に示すグラフの通り、一般化できる。図１３（ｂ）のグラフの縦軸は、ＡＥのイベントカウントを示している。 FIG. 14 (c) schematically illustrates this state, and a crack generated from the enlarged bubble is indicated by an arrow. The amount of hydrogen leaking from the sample increases as the crack progresses. And, it is expected that significant cracking can be caused by this hydrogen penetrating the sample. An AE signal is generated both when a bubble is formed and when a crack occurs. However, the characteristics of the generated AE signal differ between the formation of bubbles and the generation of cracks. This situation can be generalized as shown in the graph of FIG. The vertical axis of the graph in FIG. 13B indicates the AE event count.
　横軸は、ＡＥ信号の振幅を示している。また、気泡が形成されるときのグラフは、き裂発生のときのグラフより、緩やかである。よって、このＡＥカウントレートと振幅の関係に着目する。上の図１３（ａ）による、繰返しによりＡＥカウントレートと振幅の関係は、圧力が大きくなると図中の右上方向のグラフにシフトしている。そして、最後のグラフは、激しい損傷がある場合のグラフである。き裂の発生、その進展によると、グラフの傾きは、気泡形成時より緩やかになっている。気泡形成時のＡＥ信号の振幅は、き裂発生時より小さくて、カウントレートも小さい。 The horizontal axis indicates the amplitude of the AE signal. Also, the graph when bubbles are formed is more gradual than the graph when cracks are generated. Therefore, attention is paid to the relationship between the AE count rate and the amplitude. The relationship between the AE count rate and the amplitude by repetition according to FIG. 13A is shifted to a graph in the upper right direction in the drawing when the pressure increases. The last graph is a graph when there is severe damage. According to the occurrence of cracks and their progress, the slope of the graph is gentler than that during bubble formation. The amplitude of the AE signal at the time of bubble formation is smaller than that at the time of crack occurrence, and the count rate is also small.
　そこで、ゴム製品の場合は、激しい損傷がある時点より前に使用限界線を設けて、ＡＥカウントレートと振幅の関係がこの使用限界線に達しているか否かを確認し、ゴム製品の良否を判定できる。これにより、ゴム製品に、その表面に損傷を起こすき裂があるか否かも判定できる。よって、産業に利用する視点から言えば、この使用限界線を越えた、ゴム製品は、安全性の確保の意味からその使用を停止すべきである。これは、機械検査等の現場では、おおいに役立つものである。 Therefore, in the case of rubber products, a use limit line is provided before the point of severe damage, and it is confirmed whether the relationship between the AE count rate and the amplitude has reached this use limit line. Can be judged. Thereby, it can also be determined whether or not there is a crack that causes damage to the surface of the rubber product. Therefore, from the viewpoint of utilization in industry, the use of rubber products that exceed this use limit line should be stopped for the purpose of ensuring safety. This is very useful in the field of machine inspection and the like.
　このように、き裂に対するＡＥ信号の経時変化から、ゴム製品、例えばＯリング、の内部から発生したき裂が、その表面を貫通する前に使用を停止する。このシステムにて，内部き裂が表面に達する前に，ゴム製品の損傷を検知することができる。上述の実験１～３では、圧力装置２には、水素を使用したが、ゴム製品に支障がない任意のガス、例えば、ヘリウムや窒素等の不活性ガスも使用できる。 Thus, due to the change over time of the AE signal with respect to the crack, the use of the crack generated from the inside of the rubber product, for example, the O-ring, is stopped before penetrating the surface. This system can detect damage to rubber products before the internal crack reaches the surface. In Experiments 1 to 3 described above, hydrogen is used for the pressure device 2, but any gas that does not interfere with the rubber product, for example, an inert gas such as helium or nitrogen can be used.
　本発明は、ゴム製品を利用する産業分野に利用するとよい。本発明は、ゴム製のシール材料を利用する分野に利用すると良い。本発明は、特に、ゴムパッキンのようなき裂による損傷を事前に検知し防ぐ必要がある製品に利用されると良い。 The present invention may be used in industrial fields that use rubber products. The present invention is preferably used in a field where a rubber seal material is used. Especially this invention is good to be utilized for the product which needs to detect and prevent the damage by a crack like rubber packing in advance.
　１…ゴム製品の損傷検知システム
　２…圧力装置
　３…サンプル（ゴム製品）
　４…ＡＥセンサー
　５…信号処理ユニット
　６…コンピュータ
　１６…プリアンプ 1 ... Rubber product damage detection system 2 ... Pressure device 3 ... Sample (rubber product)
4 ... AE sensor 5 ... Signal processing unit 6 ... Computer 16 ... Preamplifier

Claims (8)

  1. 　ゴム製品のき裂から発生する弾性波（ＡＥ）を弾性波検知手段（ＡＥセンサー）で検知して、ゴム製品の損傷を検査するためのゴム製品の検査方法であって、
    　気体からなる高圧気体雰囲気環境下で前記ゴム製品を減圧した後、前記ゴム製品から発生する前記弾性波（ＡＥ）を検知して、前記弾性波（ＡＥ）の経時変化を求め、
    　前記経時変化の特性から、前記弾性波が、（ａ）前記ゴム製品から過飽和気体が気泡になったときに発生する前記弾性波であるか、又は、（ｂ）前記気泡を起点としてき裂が発生したときに発生する前記弾性波であるかを判定して、前記ゴム製品の損傷の状態を検査する
    　ことを特徴とするゴム製品の検査方法。     A method for inspecting a rubber product to detect damage to the rubber product by detecting an elastic wave (AE) generated from a crack in the rubber product with an elastic wave detecting means (AE sensor),
    After depressurizing the rubber product in a high-pressure gas atmosphere environment consisting of gas, the elastic wave (AE) generated from the rubber product is detected, and the time-dependent change of the elastic wave (AE) is obtained.
    From the characteristics of the change over time, the elastic wave is (a) the elastic wave generated when a supersaturated gas becomes a bubble from the rubber product, or (b) a crack starting from the bubble. A method for inspecting a rubber product, comprising: determining whether the elastic wave is generated when it is generated and inspecting a state of damage to the rubber product.
  2. 　請求項１に記載のゴム製品の検査方法において、
    　前記き裂の経時変化が、前記き裂が進展してゴム製品の表面に進展する兆候を示すとき、前記ゴム製品は損傷が大きいと推定する
    　ことを特徴とするゴム製品の検査方法。     In the rubber product inspection method according to claim 1,
    The method for inspecting a rubber product, wherein the rubber product is presumed to be damaged when the change with time of the crack shows an indication that the crack has progressed to the surface of the rubber product.
  3. 　請求項１に記載のゴム製品の検査方法において、
    　前記判定は、前記経時変化を、予め損傷状態を分かっている前記ゴム製品の特性と比較して、求められる
    　ことを特徴とするゴム製品の検査方法。     In the rubber product inspection method according to claim 1,
    The determination is made by comparing the time-dependent change with the characteristic of the rubber product whose damage state is known in advance.
  4. 　請求項１乃至３の中から選択される１項に記載のゴム製品の検査方法において、
    　前記ゴム製品は、Ｏリングである
    　ことを特徴とするゴム製品の検査方法。     The method for inspecting a rubber product according to claim 1 selected from claims 1 to 3.
    The method for inspecting a rubber product, wherein the rubber product is an O-ring.
  5. 　弾性波（ＡＥ）を検知するためのもので、ゴム製品に固定又は近傍に設置された弾性波検知手段（ＡＥセンサー）と、
    　前記弾性波検知手段（ＡＥセンサー）で検知されたもので、前記ゴム製品のから発生する前記弾性波（ＡＥ）を解析して、経時変化を求め、前記ゴム製品の損傷を判定する解析手段と
    　からなるゴム製品の損傷を検査ためのゴム製品の検査装置であって、
    　前記解析手段は、
    　高圧ガス雰囲気環境下で前記ゴム製品を減圧した後、弾性波検知手段（ＡＥセンサー）で検知した前記弾性波（ＡＥ）の経時変化を求め、
    　前記経時変化の特性から、前記弾性波が、（ａ）前記ゴム製品から過飽和気体が気泡になったときに発生する前記弾性波であるか、又は、（ｂ）前記気泡を起点としてき裂が発生したときに発生する前記弾性波であるかを判定して、
    　前記解析手段は、
    　前記き裂から発生する前記弾性波の場合は、前記ゴム製品が損傷していると判定し、その旨の信号を出力する
    　ことを特徴とするゴム製品の検査装置。     Elastic wave detection means (AE sensor) for detecting elastic waves (AE), fixed to rubber products or installed nearby
    An analysis means which is detected by the elastic wave detection means (AE sensor), analyzes the elastic wave (AE) generated from the rubber product, obtains a change with time, and determines damage of the rubber product; A rubber product inspection device for inspecting a rubber product for damage, comprising:
    The analysis means includes
    After depressurizing the rubber product in a high-pressure gas atmosphere environment, obtain the time-dependent change of the elastic wave (AE) detected by the elastic wave detection means (AE sensor),
    From the characteristics of the change over time, the elastic wave is (a) the elastic wave generated when a supersaturated gas becomes a bubble from the rubber product, or (b) a crack starting from the bubble. Determine whether the elastic wave is generated when it occurs,
    The analysis means includes
    In the case of the elastic wave generated from the crack, it is determined that the rubber product is damaged, and a signal to that effect is output.
  6. 　請求項５に記載のゴム製品の検査装置において、
    　前記解析手段は、前記き裂の経時変化が、前記き裂が進展してゴム製品の表面に進展する兆候を示すとき、前記ゴム製品は損傷が大きいと推定して、その旨の信号を出力する
    　ことを特徴とするゴム製品の検査装置。     In the rubber product inspection apparatus according to claim 5,
    When the time-dependent change of the crack indicates that the crack has progressed and progressed to the surface of the rubber product, the analyzing means estimates that the rubber product is damaged and outputs a signal to that effect. An inspection device for rubber products characterized by
  7. 　請求項５に記載のゴム製品の検査装置において、
    　前記解析手段は、前記経時変化を、予め損傷状態を分かっている前記ゴム製品の特性データと比較する比較手段を有する
    　ことを特徴とするゴム製品の検査装置。     In the rubber product inspection apparatus according to claim 5,
    The analysis unit includes a comparison unit that compares the temporal change with characteristic data of the rubber product whose damage state is known in advance.
  8. 　請求項５乃至７の中から選択される１項に記載のゴム製品の検査装置において、
    　前記ゴム製品は、Ｏリングである
    　ことを特徴とするゴム製品の検査装置。     In the rubber product inspection device according to claim 1, which is selected from claims 5 to 7,
    The rubber product is an O-ring.
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