JPH0820343B2 - Method and apparatus for measuring elastic modulus of solid material by impact sound - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring an elastic coefficient of a material in a high temperature or a low temperature by an impact sound generated from the material.

[Conventional technology]

In the conventional method of measuring the elastic coefficient of a material in high temperature or low temperature, the test piece is hung by two hanging threads, and the upper end of one hanging thread is connected to a driver to vibrate, and the other A resonance method in which a hanging thread is connected to a detector to measure the resonance frequency of bending vibration or torsional vibration of a test piece, and ultrasonic pulses of high frequency are generated using a longitudinal wave transducer and a transverse wave transducer. There is an ultrasonic pulse method that accurately measures the speed of sound when excited and an ultrasonic pulse propagates in a test piece.

[Problems to be Solved by the Invention]

However, in the above resonance method, the vibration from the driver is not sufficiently transmitted to the test piece due to the compliance of the hanging thread, and thus the vibration of the test piece is not sufficiently transmitted to the detector.

Further, in the above ultrasonic pulse method, if the vibrator is directly bonded to the test piece, it is difficult to measure at high temperature and low temperature. If the waveguide rod is bonded and interposed, sufficient accuracy cannot be obtained for measuring the ultrasonic velocity.

Therefore, the present invention is intended to measure the elastic modulus of a material at high and low temperatures with high accuracy.

[Means for solving the problem]

The method for measuring the elastic coefficient of a solid material by impact sound according to the present invention is to suspend a test piece of the material to be measured with a heat resistant thread or a cold resistant thread in a high temperature heating furnace or a low temperature cooler and maintain it at a predetermined temperature. A sphere inserted from the outside of the heating furnace or low-temperature cooler is dropped toward the test piece, collides with the test piece to generate an impact sound, and is output to the outside of the high-temperature heating furnace or low-temperature cooler through the impact sound detection port. The natural frequency of bending vibration and torsional vibration of the test piece up to the higher order modes is detected by detecting the impact sound generated and detecting the Fourier spectrum of the original waveform of the radiated sound pressure of the impact sound using the fast Fourier transform. , The elastic coefficient of the material to be measured is calculated and measured based on the natural frequency.

According to the present invention, an apparatus for measuring an elastic coefficient of an immobilization material by an impact sound is provided in a cooling chamber of a high temperature heating furnace or a low temperature cooler, a furnace chamber of a high temperature heating furnace or a low temperature cooler having an impact sound detecting port and an impact ball dropping port. Two heat-resistant or cold-resistant yarns for suspending the test piece of the material to be measured hung at intervals, a sphere dropped toward the test piece, and the impact sound of the sphere on the test piece to a high-temperature heating furnace or low-pitched sound. Means for detecting through impact sound detection port formed in the cooler, natural vibration up to higher modes of bending vibration and torsional vibration of the test piece by frequency analysis of the original waveform of radiated sound pressure of the collision sound by fast Fourier transform method It is composed of an analyzer for detecting the number and an arithmetic unit for calculating the elastic coefficient of the material to be measured based on its natural frequency.

[Action]

In the above measuring device, both ends of the test piece are suspended in a high temperature heating furnace (low temperature cooler) by heat resistant yarn (cold resistant yarn).

Then, the high temperature heating furnace (low temperature cooler) is heated (cooled) by the control means while measuring the temperature of the test piece. Then, the test piece in the high temperature heating furnace (low temperature cooler) is heated (cooled) and maintained at a predetermined temperature.

In that state, put the sphere into the furnace chamber of the high-temperature heating furnace or the cooling chamber of the low-temperature cooler from the impact sphere drop port, drop it toward the test piece, and collide the sphere with the test piece. By detecting the original waveform of the radiated sound pressure of the impact sound using a fast Fourier transform to obtain the Fourier spectrum, the natural frequency up to the higher modes of bending and torsional vibration of the test piece is detected, and Based on the natural frequency, the elastic modulus of the material to be measured at the predetermined temperature, that is, the longitudinal elastic modulus, the lateral elastic modulus, and the Poisson's ratio are simultaneously calculated by the arithmetic unit.

〔Example〕

 Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an overview of the device according to the invention for carrying out the method of the invention.

First, the case of a device for measuring the elastic coefficient of a material at high temperature will be described.

A hollow furnace chamber 2 is formed in the infrared image furnace 1,
The upper and lower sides of the furnace chamber 2 are shielded by an upper heat insulating plate 3 and a lower heat insulating plate 4, respectively. The upper heat insulating plate 3 has a rod-shaped test piece T.
A long hole 5 through which (for example, a ceramics test piece) can pass is formed, and a circular hole 7 through which an impact body, for example, a steel ball 6 can pass is formed in the center of the long hole 5. Lower heat insulating plate 4
A temperature / impact sound detection hole 8 is formed in the.

The upper part of the infrared image furnace 1 is covered with a heat insulating substrate 9 fixed at intervals, and the upper heat insulating plate 3 is attached to the substrate 9.
Opening holes 10 corresponding to the long holes 5 and the circular holes 7 are formed.

On the substrate 9, the columns 11, 11 and the guide rods 1 supported by them are provided.
A gate-shaped stand composed of 2 and 12 and another column 13 are provided. Sliding blocks 14 and 14 are independently mounted on the guide rods 12 and 12 so that their horizontal positions can be adjusted. A suspension rod 15 is attached to the above so that the position thereof can be adjusted in the vertical direction.

Ceramic fiber threads or metal wires, that is, heat resistant threads 16 and 16 are coupled to the lower ends of the hanging bars 15 and 15, and a proper short distance vertically is provided at the lower end of each heat resistant thread 16. A test piece bearing ring is formed by opening the test piece T on the upper test piece bearing ring.
Of the test piece T is supported at both ends or in the vicinity of both ends of the test piece T, and the lower test piece bearing ring is provided with a sub-test piece Ta for temperature detection which is the same as the test piece T. Is supported in the same manner as. One end of the thermocouple 18 is fixed to the sub test piece Ta.

A steel ball guide tube 17 is attached to the support column 12 with an inclination, and the lower end of the steel ball guide tube 17 corresponds to the circular hole 7 of the upper heat insulating plate 3 just above the opening 10 of the substrate 9. Located in position.
A microphone 19 for impact noise detection is provided outside the furnace chamber 2 close to the temperature / impact noise detection hole 8.

As shown in FIG. 2, the thermocouple 18, the thermometer 20, and the temperature controller 21 are sequentially connected, and the microphone 19, the measurement amplifier 22, the oscilloscope 23, the filter 24, and the spectrum analyzer 25 are sequentially connected, and the temperature The controller 21 and the spectrum analyzer 25 are connected to a microcomputer 26, respectively.

The furnace chamber temperature (cooling chamber temperature) is controlled by the temperature controller 21.

In the case of the device for measuring the elastic modulus of a material at low temperature, in the above device, the infrared image furnace 1 having the furnace chamber 2 and the low temperature cooler 101 having the cooling chamber 102 in place of the heat resistant yarn 16 and the cold resistance are used. Thread 116 is used.

Further, in the above embodiment, the lateral impact is applied to the test piece T, but the longitudinal impact may be applied.

In this case, the steel ball 6 is replaced with heat-resistant yarn 16,16 (cold-resistant yarn 116,1
16) is suspended in the furnace chamber 2 (cooling chamber 102) so that the steel ball 6 having a pendulum motion collides with one end surface of the test piece T.

A method of measuring the elastic coefficient of a solid by impact sound in the embodiment of the present invention will be described.

In the above measuring device, first, the sliding blocks 14,14
By adjusting the position of the heat-resistant yarns 16 and 16 (cold-resistant yarns 116 and 116) to correspond to the lengths of the test piece T and the sub-test piece Ta, and the hanging position of the test piece T and the sub-test piece Ta is on the upper side. Long hole 5 of heat insulating plate 3
Therefore, it is preferable that the position slightly deviated from the center of gravity of the test piece is located immediately below the lower end of the steel ball guide tube 17.

Next, the heat-resistant yarns 16 and 16 are respectively set at both ends of the test piece T or in the vicinity of both ends thereof, preferably at the node positions of the primary bending vibration of the test piece T, respectively.
On the upper test piece bearing ring of (cold resistant thread 116,116), the sub test piece T
Both ends of a are supported by lower test piece bearing wheels of heat-resistant threads 16 and 16 (cold-resistant threads 116 and 116), respectively, and the test piece T and the sub-test piece Ta are passed through the openings 10 and in the substrate 9 and the furnace chamber. 2 (cooling room 102)
Suspend horizontally inside. At that time, the test piece T and the sub-test piece
The positions of the suspension rods 15 and 15 are adjusted so that Ta is located at the center of the furnace chamber 2 (cooling chamber 102).

Both ends of the test piece T and the sub-test piece Ta may be tied to the heat resistant thread instead of being supported by the bearing wheels of the heat resistant thread.

The temperature detecting thermocouple 18 fixed to the sub test piece Ta is drawn out from the furnace chamber 2 (cooling chamber 102) through the temperature / impact sound detecting hole 8 of the lower heat insulating plate 4 and connected to the thermometer 20. It

Then, the furnace chamber 2 (cooling chamber 102) of the infrared image furnace 1 (low temperature cooler 101) is heated (cooled) by a heating (cooling) means (not shown). Then, the furnace chamber 2 (cooling chamber 10
The test piece T and the sub-test piece Ta in 2) are also heated (cooled).

At that time, the temperature of the sub test piece Ta is detected by the thermometer 20 via the thermocouple 18. To get an accurate free frequency,
In order to avoid restraining the vibration of the test piece T, the thermocouple 18 is attached to the sub-test piece Ta instead of the test piece T, and the temperature of the sub-test piece Ta is detected. It has been confirmed by preliminary experiments that the test piece T and the sub-test piece Ta have the same temperature and that the presence of the sub-test piece Ta does not affect the natural frequency of the test piece T. Therefore, the temperature of the sub test piece Ta is the temperature of the test piece T.

Therefore, the temperature detected by the thermometer 20 is input to the temperature controller 21, and the temperature controller 21 heats (cools) not shown so that the temperature is maintained at a desired high temperature (low temperature).
The heating (cooling) operation of the means is controlled.

Thus, the test piece T and the sub-test piece Ta are maintained at the set temperature, and the elastic constant of the test piece T under the set temperature of high temperature (low temperature) can be obtained. Then, the measured set temperature is input to and stored in the microcomputer 26.

In that state, when the steel ball 6 is dropped from the upper end opening of the steel ball guide tube 17, the steel ball 6 rolls down in the steel ball guide tube 17,
Further, from the lower end thereof, it passes through the opening 10 of the substrate 9 and the circular hole 7 of the upper heat insulating plate 3 and falls into the furnace chamber 2 (cooling chamber 102), and hits the test piece T to exert an impact force.

At that time, the generated impact sound is detected by the microphone 19, the radiated sound pressure signal of the impact sound is amplified by the measurement amplifier 22, and then input to the oscilloscope 23 to detect and display the original waveform (see FIG. 3). At the same time, the original waveform signal is input to the spectrum analyzer 25 after the low frequency region and the high frequency region that become noise in measurement are removed by the filter 24. In the spectrum analyzer 25, a Fourier spectrum as shown in FIG. 4 is obtained, and the natural frequencies ω ₁ , ω of the bending modes of the first, second, third, ... ₂ , ω ₃ ... And natural frequencies ω _T1 , ω _T2 , ω _T3 ... Of the torsion modes of the first, second, third, ...

Their natural frequencies ω ₁ , obtained in this way,
Based on ω ₂ , ω ₃ ...; ω _T1 , ω _T2 , ω _T3 ..., the longitudinal elastic constant E, the transverse elastic constant G, and the Poisson's ratio ν are calculated in the microcomputer 26 and stored as follows. The longitudinal elastic constant E, the lateral elastic constant G, and the Poisson's ratio ν of the material of the test piece at the set temperature are determined at the same time.

In general, the bending natural frequency in the case of a beam with both ends freely supported such as the above-mentioned test piece is as follows when analyzed using the theory of Timoshenko beam.

Where E: longitudinal elastic constant G: lateral elastic constant ρ: density A: cross-sectional area I: second moment of area λ_n: Euler beam eigenvalue (λ₁= 4.730, λ₂= 7.835, λ ＝ 10.966) κ ′: A factor indicating the effect of shear stress due to the cross-sectional shape of the test piece
It is a number (κ ′ = 2/3 for a rectangle).

or, Is.

Here, h _n (x) is a mode function of free vibration at both ends of the Euler-Bernoulli beam, and “″” is the second derivative with respect to x,
l represents the length of each beam.

_{h n (x) = cosλ n} · sinλ n (x / l) -coshλ n · sinλ n (x / l) + cosλ n · sinhλ n (x / l) -coshλ n · sinhλ n (x / l) -sinλ _{n · cosλ n (x / l} ) + sinhλ n · cosλ n (x / l) -sinλ n · coshλ n (x / l) + sinhλ n · coshλ n (x / l) or, in general, as in the above test piece The natural frequency of torsion in the case of a free-supporting beam with both ends is as shown in the following equation when analyzed using Saint-Venant's theory of torsional vibration of a rod having a rectangular cross section.

here, a: cross section width b: cross section height G = E / {2 (1 + ν)} Therefore, the Poisson's ratio ν is calculated from the above equation.

When the material is an anisotropic material, the anisotropic elastic modulus can be obtained by using three rectangular rod-shaped test pieces taken from three directions.

〔The invention's effect〕

According to the present invention, the elastic modulus of a material at a high temperature or a low temperature, that is, the longitudinal elastic modulus, the lateral elastic modulus, and the Poisson's ratio can be simultaneously and accurately measured in one impact test by a simple method and apparatus.

In particular, since the impact pair is a falling sphere, the impact surface of the test piece is always impacted by the spherical contact, so that the generated sound pressure level and spectrum can be measured stably, and the impact Since the sphere falls from the outside of the heating furnace / cooler, there is no need to install a special device in the furnace / cooling chamber, which is environmentally and spatially restricted, as an impact means, and it is an extremely simple means. Is.

Further, since the impact sound detection port is formed, it is actually difficult to install the impact sound detection microphone in an environmentally severe place such as a furnace chamber / cooling chamber. Since it can be installed outside, the impact sound generated from high and low temperature test pieces can be measured with a microphone.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view of a main part of an elastic coefficient measuring device according to an embodiment of the present invention, FIG. 2 is a block diagram of the elastic coefficient measuring device according to an embodiment of the present invention, and FIG. FIG. 4 is an original waveform diagram of radiated sound pressure of impact sound obtained in the embodiment of the invention, and FIG. 4 is a Fourier spectrum diagram obtained from the original waveform of radiated sound pressure of impact sound of FIG. 1: Infrared image furnace, 101: Low temperature cooler, 2: Furnace chamber 102: Cooling chamber, 3: Upper heat insulating plate, 4: Lower heat insulating plate 5: Long hole, 6: Steel ball, 7: Circular hole 8: Temperature・ Impact sound detection hole, 9: substrate, 10: hole 11, 13: strut, 12: guide rod, 14: sliding block 15: suspension rod, 16: heat resistant thread, 116: cold resistant thread 17: steel ball Guide tube, 18: Thermocouple, 19: Microphone, 20: Thermometer, 21: Temperature controller, 22: Measurement amplifier, 24: Filter 25: Spectrum analyzer, 26: Microcomputer T: Test piece, Ta: Sub-test piece

Claims (2)

[Claims] 1. A test piece of a material to be measured is hung with a heat resistant thread or a cold resistant thread in a high temperature heating furnace or a low temperature cooler,
A sphere kept inside a high-temperature heating furnace or low-temperature cooler, which is maintained at a predetermined temperature, drops toward the test piece and collides with the test piece to generate an impact sound. Or, by detecting the impact sound that comes out of the low-frequency cooler and determining the Fourier spectrum of the original waveform of the radiated sound pressure of the impact sound by using the fast Fourier transform, the bending vibration and the torsional vibration of the test piece up to the higher modes A method for measuring the elastic coefficient of a fixed material by impact sound, in which the natural frequency of the material is detected and the elastic coefficient of the material to be measured is calculated and measured based on the natural frequency. 2. A high temperature heating furnace or a low temperature cooler having an impact sound detecting port and a ball dropping port for impact, a material to be measured suspended in a furnace chamber of a high temperature heating furnace or a cooling chamber of a low temperature cooler at intervals. Two heat-resistant or cold-resistant yarns for hanging the test piece, a sphere dropped toward the test piece, and the impact sound of the sphere on the test piece through the impact sound detection port formed in the high-temperature heating furnace or low-temperature cooler. A means for detecting, an analyzer for detecting natural frequencies up to higher modes of bending vibration and torsional vibration of a test piece by frequency analysis of the original waveform of radiated sound pressure of the collision sound by a fast Fourier transform method, and its natural frequency A device for measuring the elastic coefficient of a fixed material by an impact sound, which comprises an arithmetic device for calculating the elastic coefficient of a material to be measured based on.