JPH03225256A - Dynamic elastic modulus measuring method - Google Patents

Abstract

PURPOSE:To make it possible to directly use a comparatively small-sized parts as a sample without working or destructing it and to measure the dynamic elastic modulus of the sample by press-contacting a hard ball with the sample to elastically deform the sample and oscillating the hard ball in the press-contact direction to apply variation load to the sample. CONSTITUTION:A supporting board 4 is vertically moved in accordance with the size of the sample 15 set up on a sample board 12, the hard ball 10 is allowed to come into contact with the surface of the sample 15 and the supporting board 4 is moved down by a prescribed length to allow the hard ball 16 to vertically come into contact with the surface of the sample 15, so that the intending elastic deformation of the sample is applied only by depth l. When an AC signal is applied from a low frequency oscillator to an exciting device 9 through a coil 8, the movement of its sine wave is transmitted to a rod 6, the rod 6 is vertically moved, the hard ball 10 is oscillated with amplitude (h) in the press-contact direction, so that variation load DELTAp is applied to the sample 15. The dynamic elastic modulus of the sample 15 is found out from the deformation of the hard ball 10 and the phase difference delta of the variation load DELTAp based upon Hertz's law. Thereby, the comparatively small-sized parts can be directly used as a sample without working or destructing it and its dynamic elastic modulus can be measured.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention is a method for measuring the dynamic elastic modulus of small-sized parts made of rubber, polymeric materials, etc., such as oil seals, O-rings, etc. Regarding.

(Prior art) The conventional method of measuring dynamic elastic modulus is to cut out a material into a predetermined size or mold it using a mold, and dynamically deform it using a testing machine. In general, the dynamic elastic modulus is calculated by measuring the phase difference between deformation and load as well as the deformation and load.

(Problem to be solved by the invention) However, the sample must have a certain size in order to be subjected to a testing machine, and samples must be taken from parts with small cross-sectional dimensions such as oil seals, O-rings, etc. That was difficult.

In addition, sealing devices such as oil seals and O-rings come into contact with rotating shafts, etc., so the characteristics of the contact surfaces are an issue, but testing using actual objects is not possible, so in reality, parts must be cut. The rate of deterioration of the polymer material is measured by measuring the hardness of the part closest to the surface in contact with the rotating shaft.

However, in the case of interlocking seals where the load on the contact surface changes dynamically due to vibrations of the rotating shaft, pressure of the sealing fluid, etc., followability to mating parts such as the rotating shaft is a problem.
Static properties such as hardness cannot meet needs.

This invention is intended to solve the above problems, and it is possible to use relatively small parts such as oil seals and O-rings as samples without machining or destroying them, and measure their dynamic elastic modulus. The purpose of this study is to provide a method for measuring dynamic elastic modulus that is possible.

(Means for Solving the Problem) In order to achieve the above object, the present invention presses a probe having an arcuate curved surface against the surface of a sample to elastically deform the sample, and then vibrates the probe in the pressure contact direction. The dynamic elastic modulus of the sample was determined using Hertz's theory from the phase difference between the displacement of the probe and the variable load applied to the sample.

Further, it is desirable that the measuring head is spherical.

(Function) In the present invention based on the above configuration, a variable load is applied to the sample due to the vibration of the probe. From the phase difference between the displacement of the probe and the fluctuating load applied to the sample, the dynamic elastic modulus of the sample can be determined using Hertz's theory.

Furthermore, when the probe is removed from the sample, the sample returns to its original shape.

(Example) Next, the present invention will be explained based on the accompanying drawings.

FIG. 6 shows a measuring device 1 used in the present invention.

The fixed base 2 is provided with a support 3, and the support 3 is provided with a support 4 that is movable up and down by a fine movement mechanism (not shown). A differential transformer 5 is provided within the support base 4, and a port 6 that passes through the hollow portion of the differential transformer 5 is provided vertically. This rod 6 is supported by the support base 4 via a plurality of temporary springs 7 provided in the length direction. An electrodynamic vibration device 9 is provided at the upper end of the londolo. This vibration device 9 is connected via a coil 8 to a low frequency oscillator (not shown). On the other hand, a hard ball 10 as a measuring element is attached to the lower end of the rod 6.
is provided. The radius of this hard ball 10, Poisson's ratio 2
A known elastic modulus is used.

A load cell 11 is provided on the fixed table 2 at a position directly below the rod 6, and a stage 12 is provided on the load cell 11.

By the way, the load cell 11 is connected to a computer 13 and a monitor (pen writing oscilloscope, electromagnetic oscilloscope, synchroscope, etc.) 14. Further, the differential transformer 5 is also connected to the computer 13 and monitor 14 in the same manner.

Next, the operation of the measuring device I and the method of measuring the dynamic elastic modulus using the same will be explained.

First, the support table 4 is moved up and down according to the size of the sample 15, such as an oil seal (made of rubber or polymeric material) placed on the stage 12 (fixed by means not shown).
As shown in the figure, the hard ball 10 is brought into contact with the surface of the sample 15, and the support base 4 is lowered by a predetermined amount, and the hard ball 10 is pressed perpendicularly to the surface of the sample 15 as shown in Fig. 2, and pushed by a depth l and elastically deformed. (within the elastic limit of sample 15).

When an AC signal is applied from a low frequency oscillator (not shown) to the vibration device 9 via the coil 8, the sinusoidal movement is transmitted to the rod 6 and moves up and down, causing the hard ball lO to move in the pressing direction (vertically). It vibrates with varying amplitude.

Here, the amplitude of the hard ball lO is set to a value such that h<z. In this way, a variable load (compressive stress) is applied to the sample 15 due to the vibration of the hard ball 10. In this case, the relationship between stress and displacement is given by the Hertz equation of elastic mechanics. Now, R: Radius of the hard ball νA: Poisson's ratio of the sample El: Dynamic elastic modulus of the sample El: Elastic modulus of the hard ball ν1: Poisson's ratio of the hard ball ΔP: Assuming a variable load applied to the hard ball, the amplitude applied to the hard ball 10 is It is given by the following formula.

In the case of polymer sample 15 in question here, E
, >) Since E a, the second term of equation (1) can be ignored, so the equation becomes as follows.

Transforming this formula, we get becomes.

Here, there are two unknowns, E and ν, which cannot be determined directly, but assuming ν1, the elastic modulus can be determined from equation (3).

The Poisson's ratio of the materials we commonly use is approximately 0.2 ~
It is 0.3. Assuming Poisson's ratio, the influence on accuracy is that the values of (l~ν2)2 are 0.92 and 0.83 at sea 0.2 and 0.3, respectively, and the error is treated as sea 0.25. Also, the error is within ±5%.

In the case of rubber, it is treated as sea 0.5, so formula (3)%
Equation % (4) The dynamic elastic modulus E'' measured in this way is expressed as a complex number as shown in FIG.

On the other hand, during the above-mentioned action, the vertical movement of the rod 6, that is, the hard ball 6
The vibration of the sample 1 is detected by the differential transformer 5 (or the strain gauge (not shown) attached to the leaf spring 7).
The fluctuating load movement applied to the load cell 5 is detected by the load cell 11. Here, since the sample 15 is a viscoelastic material such as rubber or polymeric material, the displacement of the hard ball 10 (solid line), which appears as an analog quantity on the monitor 14 as shown in FIG. A phase difference (time delay) δ occurs with the variable load (dotted line) ΔP.

Therefore, the dynamic elastic modulus E0 mentioned above is is required.

The computer 13 applies the measured values of the amplitude, the variable load ΔP2, and the phase difference δ to equations (4) and (5), and calculates E'' and E'E''.

In the above embodiment, since the characteristics of the viscoelastic sample 15 such as a polymeric material change depending on the vibration frequency, amount of strain, and temperature, the frequency of the low frequency oscillator may be made variable if necessary.

In this way, in the present invention, after the hard ball 10 is brought into contact with the sample 15, the sample 10 is elastically deformed by being pushed in (pressure contact) by a predetermined depth 2, and the hard ball IO is vibrated in the pressure contact direction to cause the sample 10 to change. A load ΔP is applied, and the dynamic elastic modulus of the sample is determined from the displacement of the hard ball 10 and the phase difference δ of the fluctuating load ΔP using Hertz's theory. Therefore, relatively small parts such as oil seals and O-rings made of rubber or polymeric materials can be used as samples without being processed or destroyed, and their dynamic elastic modulus can be measured.

FIG. 7 shows a case where the dynamic elastic modulus of the inner circumferential surface side of the annular sample 16 (for example, the surface of an O-ring or the like that contacts the rotating shaft) is measured. In this case, if a rod 6 with a bent tip end is used, measurement can be performed in the same manner as described above.

(Effects of the Invention) Since the present invention is configured as described above, the hard ball is pressed against the sample to elastically deform the sample, and the hard ball is vibrated in the pressure direction to apply a variable load to the sample. The dynamic elastic modulus of the sample is calculated from the phase difference of displacement and fluctuating load using Hertz's theory.

Therefore, oil seals made of rubber, polymeric materials.

This method has the advantage that a relatively small-sized component such as an O-ring can be used as a sample without being processed or destroyed, and its dynamic elastic modulus can be measured.

[Brief explanation of drawings]

The attached drawings show examples of the present invention, and Figures 1 to 3 are explanatory diagrams showing the process from bringing the hard ball into contact with the sample to applying a variable load, and Figure 4 shows the displacement of the hard ball and the addition to the sample. Figure 5 is a graph showing the relationship between the variable load and the dynamic elastic modulus.
Real part of complex modulus. An explanatory diagram showing the relationship between the imaginary part of the complex modulus of elasticity, Fig. 6 is a diagram showing an example of the configuration of the measuring device used in the present invention, and Fig. 7 is a diagram showing the dynamic elastic modulus of the inner circumferential surface of an annular sample. It is a figure showing a case. Explanation of symbols 10...Hard ball (measuring head) 15...Sample δ...
Displacement difference ΔP...Fluctuating load E...Dynamic elastic modulus

Claims (2)

[Claims] (1) After pressing the contact point with an arc-shaped curved surface against the surface of the sample to elastically deform the sample, the contact point is vibrated in the pressure direction to apply a variable load to the sample, and the displacement of the contact point and the sample are A dynamic elastic modulus measurement method characterized by determining the dynamic elastic modulus of a sample using Hertz's theory from the phase difference with the applied fluctuating load. (2) The method for measuring a dynamic elastic modulus according to claim 1, wherein the measuring element is a sphere.