JPS58210544A - Measurement system of viscoelasticity in audible frequency band - Google Patents

Abstract

PURPOSE:To meaure viscoelasticity precisely by calculating complex modulus with prescribed mechanical impedances from the relation concerning to the plural oscillation states caused by the different phases of the forced oscillations applied on a specimen from boths ends thereof. CONSTITUTION:Two exciters 14', 14'' which have the same characteristic and can be controlled in relative phases are provided at both ends of a specimen 10, and arbitary different oscillation is applied on the specimen; for example, different oscillation state generated by locking the 2nd exciter 14'' and operating only the 1st exciter 14'. The 1st and the 2nd stress detectors 16', 16'' and displacement detectors 18', 18'' are placed between the two exciters 14', 14'' and the specimen 10 to detect the two different oscillation states, and the precise calculation of complex modulus of elasticity is made possible by taking the oscillation distribution detected with the displacement detectors for the two positions in both states into consideration. The viscoelasticity is thus measured precisely.

Description

[Detailed description of the invention]

To control and control dynamic or complex viscoelasticity up to f'L, one end of the sample is fixed via a load cell whose displacement can be ignored, and a displacement detector is applied from the other end to apply vibration. Sample/7'] The samples were measured in rows based on the transverse specific stress, θ' ratio, and phase difference at the other end. However, since the stress detection of a load cell depends on strain, that is, minute displacement ('', it is impossible to detect stress without displacement, and it is performed by displacing an elastic body due to stress. Therefore, the load cell sensing element is connected to an elastic body, that is, a vibration system. Since the vibration of the sample and the vibration of the load cell coexist, it becomes a combined IR (vibration system) and causes an error in detecting the characteristics of the sample itself.This error is less of a problem as long as the applied vibration frequency is low. [Measurement frequency]) The error becomes thicker with the upper row ′fX
Therefore, solving the errors caused by stress detectors has become the biggest challenge in recent viscoelastic measurements. This error prevention is particularly necessary for research in the audio frequency band, which is important for increasing the measurement frequency band, especially for the development of soundproofing materials. Based on these principles, a method of applying forced vibration from one end of the sample has been used to determine the viscoelastic fAn constant at frequencies below several 100 Hz, and waves at frequencies above several 1000 Hz have been determined using ultrasonic absorption methods. Although the audio frequency band in between has become important as mentioned above, there has been little research into it due to the need to consider it as a wave. In order to investigate the viscoelastic properties in the audio frequency band as waves, the present invention applies two forced vibrations from both ends of the sample. changes to change the vibration state of the sample,
This is an attempt to elucidate viscoelasticity by considering it as a wave. That is, when considered as a wave, the amplitude and phase of the vibration are a function not only of time but also of the position within the sample, so it is necessary to measure the displacement and stress at two or more positions, so it is necessary to measure the displacement and stress at two or more positions. A detector is placed at both ends of the sample like a vibrator, and the mechanical impedance changes depending on the different vibration states of the sample, and the viscoelasticity is detected by considering the wave nature. Furthermore, when using such a method, the stress detector, especially the load cell, constitutes one vibration system as mentioned above, so this force mixes with the vibration of the sample and causes errors! If a displacement detector such as an optical displacement detector that consumes constant energy is placed between the three force detectors and the sample, the characteristics of the displacement detector will not be included in the stress detector and the stress of the sample will be reduced. However, the input vibration displacement of the sample, which is the output of the stress detector, is captured and detected by the displacement detector, so the characteristics of the stress detector can be regarded as the characteristics of the exciter. A stress detector can indicate the correct stress being applied to the sample. The relationship between the stress and displacement of the sample, that is, the mechanical impedance, etc., is determined using a method that prevents errors in the stress detector.
According to the present invention, it was discovered that the complex modulus of elasticity can be easily calculated through the mechanical impedance from the relationship between the vibration states of the egg number due to the different phases of forced vibrations applied from both ends, and using this, the complex modulus of the acid 1 The purpose of this is to determine the Preferred embodiments will be described below with reference to the drawings. Figure 1 shows the viscoelastic measurement method in the United States, where 10 is the sample and the hanging device is 16.
The stress σ due to the displacement ξ applied to the first vibrator 14 at
Detected and E°=σ/ξ/1 ・・・・・・−・・・・・・・・・・・・・
... (1) From the amplitude of Eo and the phases of ξ and σ, Eo
is determined by using equation (1), considering that the displacement is negligible since it is located at a large elastic body of 4. However, no matter how small the displacement, it is impossible to detect stress without displacement, and since there is always a displacement, the detector 16 itself is a vibration system, and therefore the sample, which is the vibration system in Figure 1, is The stress detector is a vibration system, and the difference in fixation is small, so the stress detector is not a vibration system (approximated by equation 11, but ω is in the audio frequency range, so ω is in the audio frequency range, so ω is in the audio frequency range). band)
The closer the error is, the larger the error becomes (Equation 11 is used when the correction is insufficient.
Recently, the viscoelastic autopsy of the circumfosal zone has become a problem in the foot (error correction is the greatest). In addition, for viscoelasticity measurement using conventional (C) formula 11, sample l is used.
We can also consider O simply as one spring body, and assume that the displacement is along a straight line, that is, the strain or location in the sample.

[I have been thinking that it is possible to approach Nakasei because it is uniform regardless of C, but I-I- Trial self-shoulder crab 11 displacements in a viscous elastic body with a simple spring (7 samples It is a function of the position in the center, that is, it takes the form of a wave, and therefore the drum is E” == )'-I-i rt 4 ρ-quality t
,,=distance from the first end of the charge, t=waiting time. When vibrational displacement ei011 is applied from one end (first end) of the sample (21 displacement ξage ξ(4t) = (Mco −'Ns+n−χ)eIo
” −= (indicated by ゝ C・ in 315 and determined by M N I”i boundary φ.
---・(41) As shown in the above equation, the displacement ξ in the sample is not uniform, but is a variable and becomes a wave that changes with t, so that the strain at 1 is constant regardless of X. Such assumptions cannot be used, and it is necessary to know the distribution of vibration that changes depending on the boundary conditions. To do this, displacement is detected not only at one end but at one or more at the same time, and first, the vibration distribution is known and the vibration distribution at the excitation end is detected. It is necessary to correct the complex elasticity obtained from the stress and the first order. However, since there is only one vibration state, it is difficult to calculate the correction for the complex elasticity described above, and rather, it is necessary to compare two specific vibration states. It is easier to find the complex modulus of the sample from the relationship between the mechanical impedance at one end and the complex modulus at each time. The exciter 14 has two characteristics that are the same and can control the relative phase.
', 14' indicates different sample vibrations, the digit indicates that the second exciter 14' is locked and only wJ1 exciter 14' is operated, or the first and second exciters are set to different relative phases. Different vibration states are created in the sample by simultaneously moving the actuators at θ. At the same time, between the two vibrators 14', 14' and the sample 10, as shown in FIG.
6'' and a displacement detector 18'. 18'' are placed to detect two different vibration states caused by different operations of the two vibrators 14', 14', and to detect the stress at one end in both conditions. Based on the relationship between the two values of the outputs of the displacement detectors 16' and 18'(G16' and IF1''), the vibration distribution detected by the displacement detectors at two positions is
This makes it possible to temporarily subtract the double ultraviolet ray ratio. However, if a detector with energy consumption close to 0 is used to measure displacement, such as the quality detector 18' or 18'' 1-piece optical type used at this time, the stress required for detector displacement is 0, so stress detection is possible. The outputs of the detectors 16', 16' indicate the stress required for the displacement of the sample 10 only, and since the displacement detector 18'lFt'' is spun directly to the edge of the sample outside the stress detector, the output of the sample 10 is
stress detector 16', which indicates the true displacement of the conventional method;
Although the displacement of 16' is small, it can prevent the error due to the displacement 6'.The first end 12' and the second end 12' of the sample lO are placed on both ends of the specimen as shown in Figure 2. 171st L
The vibration state g when the I vibrator 14' and the second vibrator 14' having the same characteristics are operated at a relative phase angle θ is simplified as 1 below.
I will clarify. (In equation 21, if the second vibrator 14' applies a vibration of e1'JJt, then M=1 and the second vibrator 14' is 6 +
(“-〇), the tth equation (2) is ω (CnS, + N S in −j') e16
'(=eI (0)t-θ)-...-, +31C1 Therefore, it is shown in each case when θ"" Or 'l π. Also, if N when the second end is fixed is Nflx, Nfix when ξCt) = 0 is ωl (-'- On the other hand, the force F( is
. δξ F=-AE”(ko)work=.・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・(9) Mechanical impedance Z as seen from the excitation end Z = F7 (41
)knee.・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・－・・・（1011 Since ix has a double angle cocution relationship, 2z(π)Zfix=z(π)×A2ρE. ,'-E" = (2Zfix-z(π))Z(π)/
Eo can be easily calculated from the relationship ρA2°°°°curve °αJ. At the same time, it is also possible to obtain the complex modulus of elasticity from the relationship between the impedances of special legs such as θ;, -yrtr3, π, and yuπ. According to the method of the present invention, unlike the viscoelasticity at low frequencies in the US where the sample can be considered as a simple spring body with constant strain, the viscoelasticity in the audio frequency range has to be regarded as a wave. To measure the elasticity more precisely, i.e. by taking into account the non-uniform strain distribution and making it controllable by two exciters, through the mechanical impedance in one or more different vibration states. This method makes it possible to precisely measure the complex modulus of elasticity while successfully eliminating the errors of conventional stress measuring instruments. In this text, we have described two ways to use the stress detector, but it goes without saying that one of them can be omitted depending on the test method. 4. Simple explanation of external drawings Figure 1 is an element layout diagram of the conventional forced vibration viscoelastic measurement method in which the sample is vibrated from one end and fixed at the other end, and Figure 2 is the device arrangement of the viscoelasticity measurement method in which the sample is vibrated at both ends of the present invention. Element layout diagram of measurement method. 10 in the figure Samples 12', 12'' First and second sample ends 14 Vibrators 14', 14'' First and second vibrators 16 Stress detectors 16', 16' First and second stress detectors 18 Displacement detector 1B', IR" second displacement detector Stress detection load cell elastic body

Claims (1)

[Claims] l) Two vibrators with the same characteristics and controllable relative phase are provided at both ends of the sample, and the two forced vibrations are relatively controlled to create different vibration states in the sample. An audio frequency band viscoelasticity measurement method characterized by measuring the complex viscoelasticity of the given sample. An audio frequency band viscoelasticity measurement method according to claim 1, characterized in that the complex viscoelasticity of a sample is determined using the method. 3) Connect the measuring devices in the order of the vibrator, stress detector, displacement detector, and sample from the outside, and make the displacement detector a type where the measurement energy can be ignored. 4. The audio frequency band viscoelasticity measuring method according to claim 3, wherein the method for measuring viscoelasticity in an audio frequency band makes it possible to detect a multimodal rate by measuring the following.