JP2879245B2 - Dynamic viscoelasticity measurement method - Google Patents

Description

The present invention relates to a method for accurately measuring dynamic viscoelastic properties of a viscoelastic body such as rubber.

[Conventional technology]

As a method of measuring the dynamic viscoelastic properties of a viscoelastic material such as rubber, a method of applying a tensile vibration strain to a columnar test piece (for example, Vibron DD manufactured by Toyo Baldwin Co., Ltd.)
V II). This measurement method gives the initial strain by gripping both ends of the test piece with a chuck and extending it by a certain length,
Based on the state in which the initial strain is applied, the change in stress generated when the vibration strain of a predetermined frequency is applied in the ± direction is measured. On the other hand, rubber containing carbon has a characteristic that dynamic viscoelasticity is greatly changed by initial strain and vibration strain at the time of measurement. For example, as shown in FIG. 4, the tan δ of rubber tends to decrease as the initial strain increases.

However, in the conventional viscoelasticity measuring device, there is a case where the above-mentioned initial strain is not accurately given to the test piece, and there is a problem that the accuracy of the measurement data is reduced. Examining the cause, it was due to the following reasons. That is, when setting the initial strain on the test piece,
As shown in FIG. 3 (a), a pair of chucks 13a, 14a set at an interval L hold both ends of the test piece TP, and then one chuck 14a is moved to a position indicated by a dash-dot line ΔL.
To give the initial distortion. That is, the distortion rate Δ
This will give an initial distortion of L / L. However, when the test piece made of a viscoelastic body is gripped at both ends by the chucks 13a and 14a, as shown in FIG. 3 (b), the test piece is pushed inward by the thickness reduced by the gripping pressure of the chuck. It becomes bent. However, the drawing is exaggerated, and it is common that the bending is hardly recognized by visual inspection. Even if the chuck is moved by ΔL with such a bent state as the point 0, the desired initial strain cannot be applied to the test piece because the value of L at the point 0 is not the true initial length. It had become.

[Problems to be solved by the invention]

The present invention has been made to solve such a conventional problem.When measuring the dynamic viscoelastic properties of a viscoelastic body such as rubber, it is possible to set a highly accurate initial strain on a test piece. An object of the present invention is to provide a dynamic viscoelasticity measuring method that can be used.

[Means for solving the problem]

That is, the dynamic viscoelasticity measurement method of the present invention holds both ends of a test piece made of a viscoelastic body with chucks, and relatively moves both chucks in directions away from each other to give a predetermined initial strain. In a method for measuring a dynamic viscoelastic characteristic by giving a vibration strain of a predetermined frequency with a strain as a reference point, at least one of the chucks is provided with a force detection unit for detecting a tensile load applied to the chuck, After the test piece is gripped by both chucks, the change in the load generated when the test piece is relatively moved is continuously detected, and the initial length of the test piece is determined based on the zero point at which the detected value changes from-to +. In addition to setting the initial distortion, the elongation is further performed until a predetermined initial distortion is obtained.

As described above, the point at which the stress becomes zero is detected by monitoring the stress generated in the test piece by the force detecting unit, and the initial length of the test piece is set and the initial strain is applied based on the time point. Very accurate initial distortion can be set.

Hereinafter, the method of the present invention will be described with reference to a dynamic viscoelasticity measuring apparatus for performing the method.

As shown in FIG. 1, the dynamic viscoelasticity measuring device includes a viscoelasticity measuring unit 1 serving as a measuring body of a test piece TP made of a viscoelastic body such as rubber, a thermocontrol unit 2 attached thereto, and an analog device. It comprises a unit 3, an interface unit 4, a CRT display 6, a computer 7, a printer 8, and the like.

The viscoelasticity measurement unit 1 has an electric shaker 11 installed at one end on a gantry 10 and a force detection unit 19 installed at the other end. The shaft 13 and the force detector 19 attached to the electric shaker 11
Chucks 13a, 14a between the shaft 14 attached to
, Both ends of the test piece TP are gripped. The screw shaft 20 attached to the force detector 19 has a test piece TP
Is extended to the right side of the figure to impart an initial distortion, and by rotating forward and backward, it moves rightward or leftward in the figure. The rotation of the screw shaft 20 is gear 2
This is performed by a servo motor 23 via the first and second motors 22. Also,
The force detector 19 is a load applied to the chuck 14a, that is,
The function of detecting the stress generated in the test piece TP is also performed.

On the other hand, the electric vibration exciter 11 vibrates the shaft 13 at a predetermined frequency and amplitude as shown by the arrow in the figure, and as described above, the elongating vibration strain (dynamic strain) is applied to the test piece TP given the initial strain.
Is given. This elongational vibration strain is caused by the optical strain detector 12 facing the light emitting element 12a fixed to the end of the shaft 13.
Read by.

The test piece TP set as described above is placed in the thermostat 15, and is measured under a constant temperature condition. A gas mixture of air and nitrogen whose temperature has been controlled by the gas mixture temperature control device 9 blows out of the pipe 17 from the thermostatic bath 15 to apply a temperature to the test piece TP. The temperature of the thermostat 15 is detected by a temperature sensor 18 and used for temperature control.

In the figure, the stress generated in the test piece TP
It is detected by a force detector 19 provided on the a side. The detected value is transmitted to the computer 7 via the analog unit 3 and the interface unit 4.

First, at the start of the measurement, the test piece TP is attached to the chucks 13a and 13a.
When attached to a, the test piece TP whose both ends are gripped by the two chucks 13a and 14a is immediately pushed inward by an amount corresponding to the compression of both ends immediately after that, and is bent as shown in FIG. 2 (a). become. However, the figure is drawn exaggerated, and visually,
It is common that bending is hardly known. In the state shown in FIG. 2A, since a compressive stress is generated in the test piece TP, a negative (-) load is detected by the force detector 19. Next, when the servomotor 23 is driven to move the chuck 14a to the right side of the drawing to give a predetermined initial distortion, the test piece TP is switched from the compressed state to the extended state at a position extended by l. The detection value of the detector 19 changes from minus (−) to plus (+) via 0. The distance L + 1 between the two chucks 13a and 14a when the load becomes zero is read by the computer 7 as the initial length of the unstrained test piece TP (see FIG. 2 (b)). ). When the chuck 14a moves further from the zero point, the test piece TP changes so as to be extended, and the detection value of the force detector 19 becomes positive. Then, the chuck 14a is stopped when the chuck 14a is moved by (L + 1) × ΔL / L corresponding to a predetermined initial strain rate (ΔL / L) (see FIG. 2 (c)). By doing so, a desired initial strain is accurately applied to the test piece TP. The above series of operations is controlled by the computer 7.

As described above, when the initial strain is set, the electric shaker 11 operates to apply vibration strain to the test piece TP.

As described above, the analog unit 3, the thermocontrol unit 2, the amplitude control circuit 5, and the like are connected to the computer 7 via the interface unit 4. Therefore, the servomotor 17 and the electric shaker 11 are driven via the analog unit 3 according to the measurement conditions input to the computer 7, and the measurement is performed. Further, a predetermined measurement temperature is maintained via the thermo control unit 2.

The data detected by the force detector 12 is transmitted to the computer 7 via the analog unit 3 and the interface unit 4.
The dynamic viscoelastic characteristics such as the dynamic viscoelastic modulus E ′, the dynamic viscoelastic coefficient E ″, and the loss tangent tan δ are calculated and output to the CRT display 6 and the printer 8.

〔The invention's effect〕

As described above, according to the present invention, in the method for measuring the dynamic viscoelastic properties of a test piece made of a viscoelastic material such as rubber, at least one of the chucks gripping both ends of the test piece is loaded on the chuck. A force detector for detecting a tensile load is provided, and after the test piece is gripped by the two chucks, a change in the load generated when the test piece is relatively moved is continuously detected, and the detected value changes from-to +0. On the basis of the point, and set the initial length of the test piece, since it was further stretched to a predetermined initial strain, it is possible to set a high initial strain on the test piece,
The dynamic viscoelastic properties of a viscoelastic body such as rubber can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a dynamic viscoelasticity measuring apparatus for performing the method of the present invention, and FIGS. 2 (a) to 2 (c) are explanatory views showing a state where an initial strain is applied to a test piece by the method of the present invention. 3 (a) and 3 (b) are explanatory diagrams showing a conventional method for imparting initial distortion, and FIG. 4 is a diagram showing a relationship between amplitude distortion and tan δ. 11: Electric shaker, 19: Force detector, 20: Screw shaft, 23
…… Servo motor, 13a, 14a …… Chuck, TP …… Test piece.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsumi Ishida 5-15-4 Takinogawa, Kita-ku, Tokyo Inside Toyo Seiki Seisakusho Co., Ltd. (56) References JP-A-55-156835 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) G01N 19/00 G01N 3/00-3/62

Claims (1)

(57) [Claims] 1. A test piece made of a viscoelastic body is gripped at both ends by chucks, and both chucks are relatively moved in a direction away from each other to give a predetermined initial strain. In a method for measuring dynamic viscoelastic properties by giving vibration strain, a force detector for detecting a tensile load applied to at least one of the chucks is provided, and a test piece is gripped by both chucks. Then, the change in the load generated when the relative movement is performed is continuously detected, and the initial length of the test piece is determined based on the zero point at which the detected value changes from-to +, and the predetermined length is further determined. Dynamic viscoelasticity measurement method for elongating until the initial strain is reached.