JPS6197566A - Detection for generation of crack in brittle material - Google Patents

Abstract

PURPOSE:To detect a possible defect due to the generation of a microscopic crack, by applying an acoustic emission detecting method to a lightweight aerated concrete being cured with an autoclave to monitor. CONSTITUTION:Brittle material S to be inspected is arranged in a container 2 supported with a base 1. The container 2 has a heater 3, which is connected to a controller 12 and a recorder 11 and further to a thermocouple 4 to heat and control the inside of the container 2 to a required temperature. In addition, a waveguide rod 5 is provided piercing the wall of the container 2 and the tip thereof is stuck into a lightweight aerated concrete material S while the other end thereof is mounted on an acoustic emission transducer 6 outside the container 2. An acoustic emission signal in the material S is inputted into a personal computer 9 and a data recorder 10 via an amplifier 7. In this manner, the material S in the container 2 is cured adequately under the required curing conditions and a microscopic crack can be observed as generated during the curing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for detecting the occurrence of cracks in brittle materials such as lightweight cellular concrete, cement concrete, and ceramics.

Conventional technology The quality of the product depends on the microcracks that occur during curing in an autoclave, which is a high-temperature, high-pressure steam pot, during the final step of the manufacturing process for light aerated concrete. In other words, the porous green cake, which is a foam-cured molded product, is cut into plates and kept in an autoclave for over ten hours at a temperature of about /f O'(!).
The product is cured under a pressure of 100 cm/cm, but during this curing, the microcracks may deteriorate and a phenomenon called explosion may sometimes develop into a fatal defect, resulting in a defective product. However, such defects are only visible when the autoclave is removed from the autoclave after curing, and there is no suitable means to understand the mechanism of microcracks occurring during the curing process inside the autoclave, which is a sealed pressure vessel, and a strain meter is used. It's just an attempt. However, in this method of using strain gauges, it is necessary to attach a large number of strain gauges to the brittle material, but all of the strain gauges do not operate smoothly, resulting in high running costs. Although it is suitable for measuring within the elastic region, such as changes in the elastic modulus of
Disadvantages include that it is particularly unsuitable for materials whose physical properties change, such as in the curing of lightweight cellular concrete.

In general, plastic deformation in solid materials varies depending on the material, but in fragile materials such as cellular concrete, cement concrete, and ceramics, there is a transition from elastic deformation to heavy deformation under loading conditions, and at this time The generation of sound due to friction or slip between the constituent materials is called acoustic emissions.
sion), and is the first generation of microcracks. Furthermore, when the load is increased, microcracks connect with each other and occur, eventually forming a fracture.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to solve the problems in the use of conventional strain meters by applying an acoustic emission detection method to lightweight cellular concrete being cured in an autoclave for monitoring. An object of the present invention is to provide a method for detecting the occurrence of cracks in brittle materials, which is characterized by detecting the occurrence of defects based on the occurrence of cracks.

According to the present invention, the ability to detect crank occurrence of brittle materials;
In this method, the tip of a waveguide rod that passes through the wall of the container is hermetically sealed and secured to a brittle material installed in a sealed heated pressure vessel, and the other end of the waveguide rod is attached to the outside of the vessel. It is characterized by the fact that it is equipped with an acoustic emission transducer and detects the occurrence of cracks in brittle materials via a waveguide rod and transducer.

Other objects, features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate an apparatus for carrying out the method of the invention.

Embodiment of the Invention An example of a detection device for carrying out the method of detecting the occurrence of cracks in brittle materials according to the present invention is shown in FIG. comprising a container,
In this container λ the brittle material to be inspected is placed.

Further, the container is equipped with an appropriate heater 3, so that it can be heated to a required temperature, and the temperature can be measured with a thermocouple. Furthermore, a waveguide rod S is provided to penetrate the wall of the container, and is airtightly attached to the wall of the container using a suitable gasket. The waveguide j is made of stainless steel or other suitable steel material, and in the illustrated embodiment, the tip is sharply pointed so that it can be inserted into the material S of lightweight cellular concrete, and the material to be inspected is In the case of solid materials such as cement concrete, it is designed to adsorb or come into contact with the surface of the material. The other end of the waveguide S is placed outside the container, and an acoustic emission transducer 6 is attached thereto, and is connected to a personal computer 9 and a data recorder 104C via an amplifier and a monitor S. Therefore, the AI (acoustic emission) signal in the material 8 is amplified by the amplifier 7 and input to the personal computer 9 and data recorder io.

In addition, the thermocouple is connected to the recorder//and controller l-
Furthermore, it is connected to a heater 3, so that the inside of the container can be heated to a desired temperature.

In the detection device I configured in this way, the material S to be inspected is a raw material S that is stirred with a mixer, poured into a mold, foamed and hardened, and hardened after a period of time S of pouring. The cake is cut into predetermined plate shapes and placed in a container-circle. The material S placed in the container is subjected to necessary curing under the required conditions for flea growth, and microcracks generated during curing are observed. The relationship between temperature and AE quadrant over time in light air-centered concrete under the required curing conditions considered in this way is shown in Figures 2 and 3, and in both figures, the curved edge A indicates the temperature. The waveform 66 minutes B%C1D shows the AE quadrant. Comparing both figures, we can see that no explosions or cracks were detected in the material deposition trowel shown in Figure 42, and the AI signal was only detected as waveform part B when the temperature dropped, and this level of AFi was detected.
The generation of the signal, ie the microcrank, did not lead to the destruction of the material. In addition, quite a lot of AK signals are observed in the material shown in Figure 3, and they are noticeable during the waiting period at a temperature of about 1000, from the temperature rise section to the early holding period, and during the temperature drop period. After 6 years of use, the material showed large cracks and was destroyed. Therefore, A
The occurrence of a crack can be determined from the detected waveform portion C1D of the E signal.

Of course, the mixing ratio of the ingredients and the autoclave curing conditions can be greatly changed.

Effects of the invention In this way, from the AE multiplication signal observation by the method of this invention,
In the case of destruction in the autoclave, the AI flaw signal is detected from the time of temperature rise to the early stage of holding, and if it does not break, the AI flaw signal is not detected in this area, so such AE multiplied signal detection is required. U during curing in autoclave! The occurrence of cracks in aerated concrete can be detected early and reliably, and the configuration and installation of the detection device are simple and easy to manufacture, and can be manufactured at low cost. This diminishes the effectiveness of testing.

[Brief explanation of the drawing]

=i Figure d shows a detection device for carrying out the method of this invention.
A schematic diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are graphs showing the relationship between time, temperature, and the number of Am-order quadrants in the method of the present invention. In the figure, l: stand, container, J: heater, q: heating pair, s: 4-wave rod, 6: acoustic emission transducer, ri: amplifier, g
: monitor, t: personal computer, lO: data recorder, //: recorder, 12: controller. Patent applicant Onoda Cement Co., Ltd. Figure 1 Figure 2 Death Figure 3 Approximately I'Jl (between IJQ)

Claims (1)

[Claims] In a brittle material placed in a sealed heated pressure vessel,
The tip of a waveguide rod that penetrates the wall of the container is hermetically sealed, and an acoustic emission transducer is attached to the other end of the waveguide rod to guide the generation of cracks in brittle materials. A method for detecting the occurrence of cracks in brittle materials, characterized by detecting through a rod and a transducer.