JPS6119932B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an extensometer having a novel calculation mechanism suitable for measuring large displacements.

To accurately measure the elongation properties of rubber and other stretchable materials, it is not enough to statically detect the relationship between load and elongation; it is also necessary to record the corresponding change in elongation while increasing or decreasing the load. method is taken.
A gauge tracking type extensometer sets a pair of gauges near both ends of the sample for this elongation measurement, and has a tracking movement amount of a pair of pick-ups that automatically tracks each gauge displacement during the test. This indicates the gauge length elongation of the sample. These pick-ups have a fulcrum that is movably supported in the direction of elongation displacement of the specimen (e.g., vertically), and that respond to the inclination from the current position caused by the displacement of the free end engaged with the gage. The fulcrum itself is driven by a servo mechanism that generates an inclination signal and operates in response to this signal, thereby performing tracking movement of the entire pickup.

However, this elongation detection mechanism is
Since the tracking movement of the pick-up is accompanied by an inevitable response delay to the displacement of the gauge, a measurement error regarding the delay distance will occur. That is, for tracking movement, there must be an inclination of the pick-up (e.g., with respect to the horizontal position) that should generate an inclination signal, and therefore a tracking delay, which determines the speed at which the specimen's elongation displacement progresses or recovers. This is often further exacerbated by the relationship with the response speed of the servo mechanism, and measurement errors in such cases become extremely large.

The present invention aims to eliminate the above-mentioned causes of error in gauge tracking extensometers by converting the inclination angle of the pick-up from the reference angle into the delay distance of the tracking movement, and converting this into a delay distance of the tracking movement of the entire pick-up. The purpose of the present invention is to provide an extensometer suitable for measuring large displacements, which measures elongation displacement by adding .
Note that the delay distance described above is positive when it is taken in the direction of elongation displacement.

In the present invention, when a pair of gauge points are defined on a sample, it is clear that the difference in the above-mentioned summed values (measured in the same coordinate system) for each gauge point is taken as the elongation of the sample. .

Further, in the present invention, the signal representing the pick-up inclination angle from the reference angle is also used as a drive deviation signal for the tracking control system including the servo mechanism.

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

FIG. 1 schematically shows the mechanical configuration and measurement circuit of the extensometer of the present invention, which is similar to the conventional extensometer as far as the mechanical configuration is concerned. In FIG. 1, a sample 1 is held at both ends so that a tensile load can be applied thereto, and reference points 2 and 3 are defined near both ends of the substantial part that expands and contracts. Markers 2, 3
The tips of the pick-ups represented by arrows 4 and 5 are respectively engaged, but only the mechanism related to the upper pick-up 4 is shown in the figure. However, it should be noted that the associated mechanism of the lower pickup 5 is also the same. The pick-up 4 is tiltably supported at a supporting end of a base 7 at a fulcrum 6, and supports a magnetic core 9 at the other end 8. The base 7 supports the detection coil 10 that surrounds the core 9 without restraining it, so when the pick-up 4 tilts, the other end 8 displaces up and down with respect to the fulcrum 6, and the core 9 is also detected. It is designed to move freely up and down with respect to the coil 10.

The base 7 is fixed at one end to a carriage 11, which is slidably held by a guide 12 parallel to the sample, and by pulleys 13, 14.
This guide 12 is connected by a wire 15 stretched between
It is designed to be driven along the wire 1
The pulley 14 driving the drive unit 5 is driven by a servo motor 17 via the shaft of a potentiometer 16. That is, a tracking mechanism is constituted by a series of mechanisms that drive the carriage 11 via the servo motor 17 and move the pick 4. The potentiometer 16 is electrically connected to the arithmetic circuit 18,
The elongation value calculated by this circuit 18 is the indicator recorder 1
It is now recorded by 9. The servo motor 17 is driven by a signal generated by the detection coil 10 due to a change in the relative position between the core 9 and the detection coil 10 based on the tilting of the pickup 4.

Note that the positional relationship between the core 9 and the coil 10 may be reversed, and various other displacement response means may be employed.

According to the present invention, this detection signal is supplied not only to the servo motor 17 but also to the arithmetic circuit 18. FIG. 2 is a block diagram showing the calculation mechanism.

In FIG. 2, the inclination signal Vθ ₁₀ and the reference inclination signal Vθ ₀₁ are both related to the upper pickup 4 in FIG. "The angle that the pick-up 4 has with respect to a certain reference plane such as a sample or a horizontal plane." The tilt angle signal Vθ ₁₀ is a voltage corresponding to a signal generated by the detection coil 10 according to the angle of the pickup 4, and is the reference tilt angle signal Vθ.
θ ₀₁ is when the pick-up 4 occupies the reference angle of inclination,
This is a constant voltage so that Vθ ₁₀ −Vθ ₀₁ =0. That is, the inclination signal Vθ ₁₀ is subtracted from the reference inclination signal Vθ ₀₁ by an appropriate circuit, and Vθ ₁ =Vθ ₁₀ -Vθ ₀₁ corresponding to the actual tracking delay is supplied to the servo amplifier 20 and the arithmetic circuit 18. The value of _Vθ1 is positive or negative depending on whether the pick-up tilt angle is larger or smaller than the reference tilt angle, so the rotation direction of the servo motor 17 driven via the servo amplifier 20 is determined by the sign, and the potentiometer The base 7 is moved either up or down in FIG. 1 via the shaft of the meter 16. The rotation of the axis of the potentiometer 16 produces a corresponding terminal voltage V _pM1 , which naturally corresponds to the amount of tracking movement of the pickup.

In the arithmetic circuit 18, the delay signal Vθ ₁ =Vθ
₁₀ -Vθ ₀₁ and potentiometer voltage (tracking movement amount) V _pM1 are applied to the addition input, and Vθ ₁ +V _p
M1 = _V1 is calculated. This V ₁ is nothing but the actual displacement of the gauge point 2. Regarding the lower pickup 5 in FIG.
₂ and the tracking movement voltage V _pM2 , and add these together. Subtract the above V ₁ from this added value V ₂ and calculate the elongation displacement between gauge points 2 and 3 by V ₂ - _{V 1} = V. is calculated. Recorder 19 is this V
By recording =V ₂ -V ₁ , an accurate elongation curve can be drawn.

Figures 3 and 4 are graphs showing the relationship between elongation measurements of the same sample and time using the conventional method and the calculation method of the present invention, respectively, where an upward slope represents an increase in the tensile load, and a downward slope represents a decrease. is instructing.
In Fig. 3, the depression in the ascending slope at the start of the test indicates a significant tracking delay at the start of the pick-up, and there is a reversal of the elongation displacement as the load increases and decreases, and a reversal as the load increases from decrease to decrease. Similarly, the reversal from decrease to increase is rounded. In view of this, the graph in FIG. 4 shows an accurate acute angle change that corresponds almost to the increase or decrease in load, since the elongation value is added with a value corresponding to the tracking delay according to the present invention.

5 and 6 are load vs. elongation hysteresis curves corresponding to the graphs of FIGS. 3 and 4, respectively; again, the graph of FIG. 6 according to the present invention shows an acute reversal, and It can be seen that this approximately represents the elongation displacement of .

As described above, the present invention enables accurate elongation measurement, and has the advantage that a tilt angle signal for correction can also be used as a drive signal for a servo motor. However, the operation of the tracking mechanism is simply delayed,
It is also possible to separately generate only a signal representing the presence of (±) and track it using this signal.

Also, while the elongation displacement (gage point displacement) of the sample is extremely small, the servo motor 17 is not driven, and the tracking mechanism is not moved for tracking, and the inclination signal Vθ ₁ and V
It may be preferable to measure this elongation displacement using only θ ₂ as V=Vθ ₂ −Vθ ₁ . Therefore, the threshold value of such a minute elongation displacement (the limit above which the tracking mechanism is driven) is set to be the threshold value (±) of the drive input of the servo motor, and this elongation displacement Tracking displacement can only be performed when the distance is reached. In other words, the rotational position of the servo motor when starting due to a small input is unstable, and in this case, as long as the tilt angle signal (deviation value) from the pick-up can cover the gauge displacement,
This is because it is thought that using only this will enable more accurate measurement of elongation displacement.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the tracking mechanism of the extensometer of the present invention, Fig. 2 is a block diagram illustrating its function,
3 and 4 are graphs showing elongation measurement curves using a conventional extensometer and an extensometer according to the present invention, respectively, and FIGS.
3 is a graph showing a load versus elongation history curve corresponding to the measurement results shown in the figure. 1... Sample, 2, 3... Gauge, 4, 5... Pickup for gage tracking, 9... Magnetic core, 10...
Detection coil, 11...carriage, 16...potentiometer, 17...servo motor, 18...
Arithmetic circuit.

Claims (1)

[Scope of Claims] 1. In an extensometer that is provided with a tracking mechanism that tracks the displacement of a gauge by automatic control and extracts a signal corresponding to the amount of tracking, the deviation of the tracking displacement position of the tracking mechanism from the gauge A mechanism that detects the value and generates a signal corresponding to the deviation value, and an arithmetic circuit that calculates the displacement of the gauge by adding the signal corresponding to the deviation value to the signal corresponding to the tracking amount of the tracking mechanism. Characteristic extensometer. 2. Claim 1, characterized in that the arithmetic circuit includes a calculation part for calculating the difference between the gauge point displacements calculated for a pair of gauge points set near both ends of the sample to obtain the total amount of elongation. The extensometer described in Section 1. 3. A mechanism that detects a deviation value of the tracking displacement position of the tracking mechanism with respect to the reference point and generates a signal corresponding to the deviation value is used as a detection error signal for an automatic control system of the tracking mechanism. An extensometer according to claim 1 or 2. 4. The extensometer according to claim 1, 2, or 3, wherein the tracking mechanism is not driven while the gauge displacement of the sample is minute, and the gauge displacement is determined only by the deviation value. . 5. The extensometer according to claim 4, wherein the tracking displacement of the tracking mechanism is caused when the gauge displacement exceeds a minute threshold.