JP2743309B2 - Elasticity / viscosity coefficient measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the elastic and viscous coefficients of a substance, and more particularly to a substance which is fluidized by applying vibration to exhibit the properties of a viscoelastic body, for example, concrete, earth and sand, and polymers It is suitable for measuring the elastic modulus and viscosity coefficient of materials and foods.

[0002]

2. Description of the Related Art In order to form "hard concrete" or "ultra-hard concrete" having a unit water amount significantly smaller than that of ordinary concrete, a vibration compaction method of simultaneously applying vibration and an overload is employed. (For example, see JP-B-45-36305, JP-B-57-42635, and JP-A-2-25303). According to this method, since the amount of cement paste can at least reduce the interval between aggregates and increase the adhesive strength, the required strength can be obtained with a small amount of cement, and the quality of the concrete itself can be improved. It is also very advantageous for factory production, such as economy due to immediate demolding, adaptability to diversification of production, and adaptability to automation of production.

Various methods have been proposed for measuring the physical properties of ordinary concrete. For example,
Japanese Patent Publication No. 54-19356 discloses that a test rod having a conical tip and a constant outer diameter is repeatedly penetrated into fresh concrete at different penetration speeds, and the shear stress obtained for each penetration is determined. From the slope φ of a straight line on a graph (representing the penetration speed on the horizontal axis and the shear stress on the vertical axis) on the graph representing the relationship between the velocity v and the shear stress τ, and the value θ at which this straight line intersects the vertical axis (τ axis), The plastic viscosity (viscosity value) η _pl and the yield value (elastic value) γ _f are determined by the following equations.

Η _pl = tan φ / A γ _f = θ / B where A and B are constants determined by the boundary surface between the fresh concrete and the test rod, and are obtained by experiments.

However, according to this, it is impossible to measure the elastic modulus and the viscosity coefficient of concrete during vibration, and therefore, it is naturally impossible to dynamically measure the change over time. Further, in order to increase the measurement accuracy, it is necessary to change the penetration speed of the test rod many times, and the measurement requires time and labor. Furthermore, since the penetration and the removal of the test rod are repeated, the property of the concrete may change as the number of measurements increases.

Conventional methods for measuring the elastic modulus and viscosity coefficient of concrete, including the method described in this publication, are as follows:
This is possible because the fresh concrete itself is in a liquid state from the beginning, which is initially apparently the same as a granular material and does not liquefy unless compacted by vibration. It cannot be applied to “ultra-hardened concrete”. Such hardened or ultra-hardened concrete has little meaning even if its physical properties in the state of powder and granules before vibration compaction are meaningless. Can be grasped. In particular, in order to obtain the desired strength, it is very important to know exactly when the vibration compaction is completed.

[0007] Despite the advantages of hardened or ultra-hardened concrete as described above, there has been no method for measuring the physical properties in the vibration compaction process, particularly the completion time of the vibration compaction. The setting of vibration compaction conditions, the adjustment of blending, and the selection of aggregates have to rely on human experience and intuition, and the development of a method that can measure the completion time of vibration compaction even during molding has been desired.

[0008]

Therefore, the present invention provides:
Focusing on the elastic coefficient and the viscosity coefficient as measurement physical quantities that know the completion time of vibration compaction, the development of the present invention was initiated, and the object of the present invention is to reduce the vibration like hardened or ultra-hardened concrete. The elasticity coefficient and the viscosity coefficient of a substance which is fluidized by giving and exhibits the properties of a viscoelastic body can be measured dynamically and statically, easily and simultaneously, and its temporal change can be continuously measured. It is to provide a method and an apparatus.

[0009]

According to the measuring method of the present invention, a force f ₀ applied to one end of the object to be measured, an acceleration a _{0 of} the vibration, and a force f _h applied to the other end of the object to be measured are vibrated.
The acceleration a _h of vibration measured at the same time as, the measured acceleration a
_The speeds obtained from ₀ and a _h are respectively v ₀ and v _h , the density of the object to be measured is ρ, the distance between both ends of the object to be measured is h,
Assuming that the angular frequency of the vibration applied to the object to be measured is ω, the characteristic impedance is Z ₀ , and the propagation constant is γ, the elastic coefficient E and the viscosity coefficient η are obtained from the following relational expressions.

[0010]

(Equation 4)

[0011]

(Equation 5)

[0012]

(Equation 6)

When the object to be measured is a substance which is fluidized by applying vibration and exhibits the properties of a viscoelastic body,
This substance is put in a container, and the force and acceleration applied to both ends of the substance are simultaneously measured.

As shown in FIG. 1, a measuring apparatus according to the present invention comprises a container 2 for containing a measuring object which is fluidized by applying vibration to exhibit the properties of a viscoelastic body, and which applies vibration to the container 2. A vibrator 3 for applying the force, first force pickup means 4A for detecting a force applied to one end of the object 1 in the container 2, and a first force pickup means for detecting acceleration of vibration at one end of the object 1. Acceleration pickup means 5
A, second force pickup means 4B for detecting a force applied to the other end of the measurement target 1 in the container 2, and the measurement target 1
And second acceleration pickup means 5B for detecting the acceleration of the vibration at the other end.

In consideration of actual molding in which hardened or ultra-hardened concrete is put into a mold and compacted by vibration while being pressed from above, the container 2 is simulated as the mold itself or a mold. The first force pickup means 4A and the first acceleration pickup means 5A are provided on the bottom side of the container 2, and the second force pickup means 4B and the second
The acceleration pickup means 5B is provided on a pressurizing body 6 for pressurizing the upper surface of the measuring object 1 placed in the container 2. When the container (mold) 2 is fixed on the vibration table 7 and vibrated, the first force pickup means 4A and the first acceleration pickup means 5A are provided on the vibration table 7. In FIG. 1, reference numeral 8 denotes a support spring that supports the vibration table 7 on the base 9, reference numeral 10 denotes a dash pot (buffer brake), and reference numeral 11 denotes a suspension spring that suspends the pressurizing body 6.

[0016]

In order to facilitate the understanding of the present invention, before describing its operation and the above-mentioned relational expressions (1), (2) and (3), the present invention and the circumstances leading to the derivation of this relational expression will be described. I do.

Since the concrete in the vibrating formwork is considered to be a viscoelastic body, a basic Voigt model can be adopted as an analysis model of the viscoelastic body. FIG. 2 shows the Voigt model. In this figure, E is an elastic coefficient, η is a viscosity coefficient,
ρ is the density. In this model, the elastic modulus E (P
a) and viscosity coefficient η (Pa · s) and sound velocity c (m / s)
The following equations (4) and (5) are derived from the equivalent circuit of FIG.

[0018]

(Equation 7)

[0019]

(Equation 8)

Here, x = ωη / E. Given the sound velocity and the damping constant, the elastic coefficient E and the viscosity coefficient η are obtained from equations (4) and (5).

Therefore, the present inventors have studied the pulse transmission method, the resonance method, and the acoustic tube method as methods for obtaining the values of the sound speed and the attenuation constant. However, as a result of these experiments, it was found that the sound wave attenuation of concrete during vibration was very large, and it was extremely difficult to measure the sound velocity and damping constant by the resonance method and acoustic tube method using the resonance phenomenon. .
Also, when the pulse transmission method was used, the measurement could be performed, but it was not easy, and the accuracy was not guaranteed. This is because the attenuation of the sound wave in the vibrating concrete is very large, and the vibration of the vibration table acts as a large noise because the mold is fixed on the vibration table and vibrated.

However, since the vibration of the vibration table is very strong, if this vibration can be positively used as a signal, a large S / N ratio (signal-to-noise ratio) should be measured. Therefore, the present inventors have focused on this fact, and from the viewpoint of actively using vibration (vibration of the vibration table) that worked as noise in the acoustic method as a signal, the present invention has It was developed.

In view of the above, according to the present invention, when the side on which vibration is applied to a measuring object such as concrete is the input side and the opposite side is the output side, the output side which has propagated through the measuring object is used. Not only the acceleration and force of the vibration of
The acceleration and the force of the vibration on the input side are also measured, and the elastic coefficient and the viscosity coefficient are obtained from the input / output correlation applying the characteristic analysis method of the transmission path of the electric signal.

That is, when the configuration of FIG. 1 is represented as a system model according to the Voigt model, it is as shown in FIG. In this figure, f ₀ and v ₀ are the forces and velocities on the input side (lower side in FIG. 1), f _{h and} v _h are the forces and velocities on the output side (upper side in FIG. 1), and h is the container 2
Of the object to be measured (concrete) 1 inside, m ₁ and m
₂ is the mass of the vibration table 7 and the pressure body 6, s ₁ and r ₁
Is the spring constant of the support spring 8 and the resistance of the dash pot 10, and s ₂ is the spring constant of the suspension spring 11.

FIG. 4 shows that the input side force f ₀ and speed v _0.
And the output-side force f _h and the speed v _h , the above relational expression (1) is established. Then, assuming that the characteristic impedance is Z ₀ and the propagation constant is γ, the elastic coefficient E and the viscosity coefficient η can be obtained simultaneously from the above equations (2) and (3).

[0026]

FIG. 1 shows a schematic configuration of a measuring apparatus according to the present invention. In this measuring device, the container 1 is fixed on a vibration table 7 on which a pair of vibrators 3 are attached on the lower side, while the pressure body 6 is suspended via a suspension spring 11. The vibration table 7 is horizontally supported on a base 9 via a plurality of dashpots 10 using a plurality of support springs 8 and a pneumatic cushion. When the vibration table 7 is vibrated by the vibrator 3, the container 2 also vibrates integrally therewith. In the case of this example, the container 2 simulates a concrete formwork, has a vertically long cylindrical shape with open upper and lower surfaces, and has a bottom opening closed by the vibration table 7. The pressure body 11 has a thick disk shape and can be freely inserted into the container 2 while being suspended.

On the vibration table 7, an acceleration sensor 5A is attached as first acceleration pickup means for detecting the acceleration of the vibration, and is applied to the lower surface of the measuring object 1 placed in the container 1. In order to detect a force, a piezoelectric sensor 4A is used as first force pickup means.
Is attached. Further, the object to be measured 1 is
An acceleration sensor 5B is attached as second acceleration pickup means to detect the acceleration of the vibration propagating through the inside, and as a second force pickup means to detect the force applied to the upper surface of the measuring object 1 The piezoelectric sensor 4B is attached.

Next, a description will be given of a measurement example in which the present inventors actually measured a prototype of a measuring apparatus according to the configuration shown in FIG. 1 and used the prototype.

<Measurement object> As a measurement object, a super-hard concrete having a water / cement ratio of 38% was used. The compounding weight ratio is as follows: cement 0.3, water 0.38, fine sand 1.27, medium grain sand 1.5.
7, coarse sand 2.94, crushed stone 0.78. The kneading time is
Sand, crushed stone and water were added for 1 minute, and cement was added for 1 minute and 30 seconds. Furthermore, the concrete left for 17 minutes after the kneading is finished is 10 cm in inner diameter and 20 cm in height.
The measurement was started after putting into the container (mold) 2 of the above.

<Measurement Method> The vibration acceleration of the vibrator 3 is kept constant at 12 G, and the vibration frequency is changed in three steps of 70 Hz, 85 Hz and 100 Hz. For each vibration frequency, the lower surface of the concrete 1 is measured by the piezoelectric sensors 4A and 4B. And the force applied to the upper surface,
Further, the vibration table 7 is controlled by the acceleration sensors 5A and 5B.
And the vibration acceleration propagated to the pressurizing body 6 were simultaneously detected as electric signals. FIG. 5 is a block diagram of the measurement system, in which electric signals from each sensor are amplified by an amplifier 12 and then input to a four-channel fast Fourier transform analyzer 13. Each input signal is averaged at regular intervals, and 3
Automatically transfer function a _h / a ₀ , frequency function f for 30 seconds
₀ and f _h were captured on floppy disks. Then, the data is graphed as follows, and the relational expression (1),
The elastic coefficient and the viscosity coefficient were calculated according to (2) and (3).

<Measurement Results> FIG. 6 shows the temporal change of the amplitude ratio | a _h / a ₀ | of the acceleration of the upper end portion relative to the acceleration of the lower end portion of the concrete at each of the vibration frequencies of 70 Hz, 85 Hz, and 100 Hz. FIG. 7 shows the temporal change of Arg (a _h / a ₀ ).
Are shown below. FIG. 8 shows the temporal change of the amplitude ratio | f _h / f ₀ | of the upper end force to the lower end force of the concrete, and FIG. 9 shows the temporal change of the phase difference Arg (f _h / f ₀ ). Shown respectively. Further, the amplitude ratio and the phase difference of such acceleration, and the amplitude ratio of the force and the phase difference were obtained from the measured values,
FIG. 10 shows the distribution of the amplitude of the acceleration and the amplitude of the force in the concrete 150 seconds after the start of the vibration. FIG. 11 shows a temporal change of the elastic coefficient calculated from the measured values of the acceleration and the force, and FIG. 12 shows a temporal change of the viscosity coefficient. In addition,
11 and 12, the results of three experiments (No. 1 to No. 3) are also shown.

<Consideration> According to the measurement results of the elastic modulus, in the case of 70 Hz, variation is observed in three experiments, but it can be seen that the value at 330 seconds is larger than the value after 10 seconds. In the case of 85 Hz, the elastic coefficient increases with time. In the case of 100 Hz, the elastic coefficient decreases at one time during the passage of 50 seconds, but thereafter gradually increases. Looking at the measurement results of the viscosity coefficient, it can be seen that in the case of 70 Hz, there is variation in three experiments, but the variation increases with time. In the case of 85 Hz, the viscosity coefficient rapidly decreases between 10 seconds and 30 seconds, and thereafter gradually increases. Also, 100H
In the case of z, the viscosity coefficient decreases sharply between 10 and 50 seconds and does not change much thereafter.

Although an example of measuring the elastic modulus and the viscosity coefficient of ultra-hard concrete has been described above, the present invention can be applied not only to such super-hard concrete but also to ordinary concrete. .
In fact, the present inventors measured the elastic modulus and the viscosity coefficient of ordinary concrete having a water / cement ratio of 55% by performing the same experiment as above with the vibration frequency of the vibrator set to 60 Hz. FIG. 13 is a graph showing the temporal change of the elastic coefficient in that case, and FIG. 14 is a graph showing the viscosity coefficient.

The present invention is not limited to concrete, but can be applied to other substances which become fluid by application of vibration and exhibit properties of a viscoelastic body. Furthermore, the elastic modulus of a substance (for example, rock) that does not exhibit such properties even when vibration is applied and maintains the current state all the time can be measured by applying vibration. In this case, the container can be omitted.

[0035]

As described above, the present invention has the following effects. Like a hardened or ultra-hardened concrete, it is possible to dynamically and statically and easily measure the elasticity coefficient and the viscosity coefficient of a substance which is fluidized by applying vibration to exhibit the properties of a viscoelastic body. Elasticity coefficient and viscosity coefficient can be measured simultaneously. Since the temporal changes in the elasticity coefficient and the viscosity coefficient can be measured continuously, it is possible to accurately know the completion time of vibration compaction in the formation of hardened or ultra-hardened concrete. Relied on human intuition,
It is possible to accurately design vibration compaction settings, mix adjustments, and selection of aggregates, and to produce concrete products with stable quality. Since the modulus of elasticity and viscosity, and the change over time thereof can be measured even during actual molding, automatic control of the completion time of vibration compaction becomes possible. Not only can it be applied to a wide range of materials that exhibit the properties of a viscoelastic body when fluidized by applying vibration, but also the elastic modulus of a material that does not exhibit such properties even when subjected to vibration and maintains the current state all the time, Can be easily measured by giving

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a measuring device according to the present invention.

FIG. 2 is a Voigt model diagram.

FIG. 3 is an equivalent circuit of the above.

FIG. 4 is a system model diagram of the measuring device of FIG. 1;

FIG. 5 is a system block diagram of the measuring device of FIG. 1;

FIG. 6 is a graph showing the amplitude ratio of acceleration in a measurement example using a super-hardened concrete having a water / cement ratio of 38% as a measurement target.

FIG. 7 is a graph showing a phase difference of acceleration.

FIG. 8 is a graph showing a force amplitude ratio.

FIG. 9 is a graph showing a force phase difference.

FIG. 10 is a graph showing distributions of acceleration amplitude and force amplitude in concrete.

FIG. 11 is a graph showing a temporal change of an elastic coefficient.

FIG. 12 is a graph showing a temporal change of a viscosity coefficient.

FIG. 13 is a graph showing the change over time of the elastic modulus of a measurement example in which ordinary concrete having a water / cement ratio of 55% was measured.

FIG. 14 is a graph showing a temporal change of a viscosity coefficient.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measurement object 2 Container 3 Vibrator 4A 1st force pickup means 4B 2nd force pickup means 5A 1st acceleration pickup means 5B 2nd acceleration pickup means 6 Pressurizing body 7 Vibration table 8 Support spring 9 Base 10 Dashpot 11 Suspension spring 12 Amplifier 13 Fast Fourier transform analyzer

Claims (4)

(57) [Claims] 1. While vibrating an object to be measured, force f ₀ applied to one end and acceleration a _{0 of} vibration, and force f _h applied to the other end and acceleration a _h of vibration are simultaneously measured and measured. The velocities obtained from the accelerations a ₀ and a _h are v ₀ and v
_h , the density of the object to be measured is ρ, the distance between both ends of the object to be measured is h, the angular frequency of vibration applied to the object to be measured is ω, the characteristic impedance is Z ₀ , and the propagation constant is γ, and the elastic modulus is A method for measuring an elastic coefficient and a viscosity coefficient, wherein E and a viscosity coefficient η are determined by the following relational expressions. (Equation 1) (Equation 2) (Equation 3) 2. An object to be measured is a substance which is fluidized by applying vibration and exhibits the properties of a viscoelastic body. This substance is put in a container and the force and acceleration applied to both ends of the substance are measured simultaneously. 2. The method according to claim 1, wherein the elastic modulus and the viscosity coefficient are measured. 3. A container for accommodating an object to be measured which is fluidized by applying vibration and exhibits the properties of a viscoelastic body, a vibrator for applying vibration to the container, and one end of the object to be measured in the container. First force pickup means for detecting an applied force, first acceleration pickup means for detecting an acceleration of vibration at one end of the measurement object, and a force applied to the other end of the measurement object in the container. A second force pickup unit for detecting, and a second acceleration pickup unit for detecting an acceleration of vibration at the other end of the object to be measured, wherein the first force pickup unit and the first acceleration pickup Means is provided on the bottom side of the container, and the second force pickup means and the second acceleration pickup means are provided on a pressurizing body for pressurizing the upper surface of the measurement object placed in the container. Modulus & Viscosity measuring device as. 4. A container for accommodating an object to be measured which is fluidized by applying vibration to exhibit the properties of a viscoelastic body, a vibrator for applying vibration to the container, and one end of the object to be measured in the container. First force pickup means for detecting an applied force, first acceleration pickup means for detecting an acceleration of vibration at one end of the measurement object, and a force applied to the other end of the measurement object in the container. A second force pickup unit for detecting, and a second acceleration pickup unit for detecting acceleration of vibration at the other end of the object to be measured, the first force pickup unit and the first acceleration pickup unit Is provided on a vibration table on which the container is placed,
An elastic modulus / viscosity coefficient measuring device, wherein the second force pickup means and the second acceleration pickup means are provided on a pressurizing body which presses an upper surface of a measurement object placed in a container.