JP2001099770A - Heat cycle testing device for shape memory alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform in a short time heat cycle tests of a shape memory alloy member repeated a multiplicity of times. SOLUTION: This device has a holding means 2 holding a shape memory alloy member 1 which is a measurement objective and an energized heating control means 3 directly energizing the shape memory alloy member 1 itself. Furthermore, an electric resistance of the shape memory alloy member 1 changed by energized heating is measured by a resistance measuring means 6 and sent to the energized heating control means 3 as a signal E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for testing a heat cycle of a shape memory alloy.

[0002]

2. Description of the Related Art A test for measuring how much force a shape memory alloy generates or moves when heat is applied to the shape memory alloy. The thermal cycle test ”has been performed from the aspect of quality assurance of operability of shape memory alloys and the like.

Conventionally, a heat cycle test of such a shape memory alloy is generally performed by externally applying heat.
For example, as shown in FIG. 3, a method of immersing a shape memory alloy member 31 as a measurement target in hot water 32 and cold water in a storage container 33 alternately to raise and lower the temperature of the shape memory alloy member 31,
Alternatively, a method has been used in which a shape memory alloy member is placed in a constant temperature bath to raise and lower the temperature in the bath.

[0004]

However, the above-mentioned conventional thermal cycle test apparatus has a problem that one cycle of measurement requires a long time. In particular, it is not suitable to be used for a repeated test of several thousand to several hundred thousand times (for example, a characteristic deterioration test or a life test).

The present invention enables the above-described one cycle to be performed within, for example, a few seconds, and is used as an auxiliary device of a high-precision resistance measuring device such as a thermomechanical analyzer (TMA) many times (for example, several thousand times to several times). It is an object of the present invention to provide a test apparatus capable of executing 100,000 heating / cooling cycles.

[0006]

SUMMARY OF THE INVENTION Therefore, a heat cycle test apparatus for a shape memory alloy according to the present invention comprises: holding means for holding a shape memory alloy member to be measured; Heating control means for heating; and resistance measuring means for measuring an electric resistance value of the shape memory alloy member changed by the heating by the current supply and sending a signal to the current control means.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments.

In FIG. 1, reference numeral 1 denotes a shape memory alloy member to be measured, and in the present invention, a correlation is shown between the generated force (or deformation) and the electric resistance value. A shape memory alloy member that undergoes a phase transformation is an object to be measured.

Reference numeral 2 denotes holding means for detachably attaching and holding the shape memory alloy member 1. For example, a U-shaped attachment main body 2 a and both ends of the shape memory alloy member 1 are attached to each other at the time of attachment. (Fixed portions 2b, 2b) which are fixed so as to be adjustable (by screwing back and forth of the screw portion).

Reference numeral 3 denotes an energization heating control means for energizing and heating the shape memory alloy member itself, and is electrically connected to both ends of the shape memory alloy member 1 via wires 4 and 5. For example,
In a shape memory alloy that causes martensitic transformation, the heating control means 3 has a heating capacity capable of causing a phase transformation from a martensitic phase to a parent phase.

Reference numeral 6 denotes a resistance value measuring means for measuring an electric resistance value of the shape memory alloy member 1 which changes due to the heating by the above-described electric current and sending a signal E to the electric heating control means 3. This resistance value measuring means 6 includes a resistance value measuring device 6a
And wires 7 and 8 electrically connected to both ends of the shape memory alloy member 1, and an electric heating control means 3 for transmitting the signal E.
And a wiring 9 connected thereto.

In the embodiment shown in FIG. 1, the holding means 2 is configured to hold the dimensions of the shape memory alloy member 1 once fixed. Therefore, the generated force changes (increases or decreases) with the temperature change of the shape memory alloy member 1. In the present invention, since the correlation between this generated force and the electric resistance value is known, the correlation data is used. Based on this, the operability of the shape memory alloy member can be found by watching the electrical resistance value without measuring the generated force itself.

For example, in the case where the shape memory alloy member 1 is a coil whose shape is stored in a compressed state, if the characteristic that the electric resistance value of this coil decreases with compression is known in advance, the actual coil Even without measuring the force (deformation amount), the generated force (deformation amount) of this coil can be estimated.

In this way, the electric resistance value of the shape memory alloy is measured by the resistance value measuring means 6 and transmitted as a signal E to the energization heating control means 3, and the shape memory alloy member is 1 by ON / OFF control (and cooling control by cooling at a low temperature or cooling by blowing air) of the shape memory alloy member 1 (or in the embodiment shown in FIG. 2 to be described later). (Deformation amount) can be feedback controlled.

Moreover, the object to be measured (shape memory alloy member 1)
Since the self-heating is carried out directly by itself, one cycle can be performed within several seconds, which is suitable for measurement of thousands to hundreds of thousands of life tests.

In the present invention, since the resistance value is measured during the test, the object to be measured (shape memory alloy member 1) can be simplified.
(It can be treated as normal if the electrical resistance value reaches a predetermined value) (this was not possible with the conventional thermal cycle test apparatus as shown in FIG. 3).

Next, FIG. 2 shows another embodiment of the present invention. An electric heating control means 3 for energizing and heating the shape memory alloy member 1 itself, and a resistance for sending a signal E to the electric heating control means 3 by measuring an electric resistance value of the shape memory alloy member 1 changed by the electric heating. The point including the value measuring means 6 is the same as that of the above-described embodiment. However, in FIG. 2, the holding means 2 for holding the shape memory alloy member 1 to be measured is different.

That is, the holding means 2 comprises the shape memory alloy member 1
Is a structure for holding the both ends of the body freely (without fixing) so as to be able to freely expand and contract. And a restoring actuator 12 for shortening (or extending) the shape memory alloy member 1 in the opposite direction.

The shape memory alloy member 1 can be applied to a member that undergoes a phase transformation that shows a correlation between the deformation amount and the electric resistance value.

As the restoring actuator 12, an electrically operated reciprocating mechanism is preferable.
As indicated by the two-dot chain line, the measuring device 6 of the resistance value measuring means 6
It is desirable to send the signal G from a to perform the restoration operation.

In the test apparatus having the structure as shown in FIG. 2, when the shape memory alloy member 1 is energized by the electric heating means 3, the temperature rises and the mounting length of the shape memory alloy member 1 increases. (Or decrease). Since the correlation between the mounting length of the shape memory alloy member 1 and the electric resistance value is known, the electric resistance value can be calculated based on the correlation data without measuring the length dimension (increase / decrease). The operability of the shape memory alloy member 1 can be found by watching.

In this way, the electric resistance value of the shape memory alloy is measured by the resistance value measuring means 6, transmitted to the electric heating control means 3 as a signal E, and the amount of deformation is determined based on the correlation data. ON / O the energization of the shape memory alloy member 1
FF control and a cooling fan 13 as illustrated in FIG.
The cooling amount is controlled by air blowing or the like, whereby the deformation amount of the shape memory alloy member 1 can be feedback controlled.

Moreover, the object to be measured (shape memory alloy member 1)
Since the self-heating is carried out directly by itself, one cycle can be performed within several seconds, which is suitable for measurement of thousands to hundreds of thousands of life tests. Since the resistance value is measured during the test, the characteristics of the shape memory alloy member 1 can be easily evaluated.

Note that, in FIG.
Instead of 12, it is also possible to use a weight (constant load) or use a variable load to perform a heat cycle test that deforms the shape memory alloy member 1.

[0025]

According to the present invention, it is possible to shorten the measurement time of one cycle to a short time by the above configuration. 2.) Multiple repetitive tests (heating / cooling cycle tests) can be performed in a short period of time. For example, thousands to hundreds of thousands of life tests and operability confirmation tests can be performed in a short period of time. Further, characteristic evaluation during the test can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention.

FIG. 2 is a configuration explanatory view showing another embodiment.

FIG. 3 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shape memory alloy member 2 Holding means 3 Electric heating control means 6 Resistance measuring means E signal

Claims (1)

[Claims] 1. A holding means for holding a shape memory alloy member to be measured, an energization heating control means for energizing and heating the shape memory alloy member itself, and the shape memory alloy member changed by heating by the energization. And a resistance value measuring means for measuring the electric resistance value and sending a signal to the electric heating control means.