JP2004333306A - Method for detecting damage position of shape memory alloy, self-sensing type heating control method, self-repairing method, panel made of composite material and shape memory alloy covered with insulating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rationalize a heating current or a heating time, without receiving the effects of the circumferential temperature or the like by determining the damage position of a panel by measuring the resistances of SMAs shape memory alloys (hereinafter to be referred to as SMAs) anytime, to calculate the time differentiation of the resistances, allowing a pulse current to flow to the SMA of which the damage is detected not only to heat the SMA, but also to measure the resistance of the SMA and cutting off the pulse current from the differentiation of the resistances in a panel, wherein SMAs covered with an insulating film are embedded in a composite material in a lattice-like state. <P>SOLUTION: In the panel wherein the SMA covered with the insulating film are embedded in the composite material in a lattice-like state, the damage position of the panel is decided from a time differentiation tolerance limit, by measuring the resistances of the SMAs at anytime and calculating the time differentiation of the resistances. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention measures the damage by detecting the transformation from martensite phase to austenite phase by measuring the resistance change of the SMA, detecting the damage position from the time differential value of the resistance, and performing the electric heating control on the SMA. Specifically, the present invention relates to a method for detecting a damage position of a shape memory alloy, a self-sensing heating control method and a self-repair method, a composite material panel, and a shape memory alloy covered with an insulating film.
[0002]
[Prior art]
Due to the unique physical properties of SMA (shape memory alloy), strong force / weight ratio, and the convenience of easy heating control, many fields (mechanical, electric, automotive engineering, aerospace industry, medical equipment, etc.) Usage is being found, and in particular, smart materials in which SMA is embedded as a sensor or actuator have recently been receiving attention.
The reason is that the smart material can be used as an active observation device by simple control, or can adapt itself to the environment. From such a point, many reports have been made on how to use the method for self-repair of structures, active vibration suppression, noise control, parts of robots, and the like.
[0003]
Conventionally, as a damage detection method using SMA, there has been proposed a method of measuring the resistance of SMA embedded in a composite material and detecting damage from a change in electric resistance (see Patent Document 1). In this method, the resistance value changes due to the environment around the composite material panel, especially the change in temperature, so the accuracy of detecting damage is poor, and the location of the damage is unknown even if it is known that the damage has occurred. is there.
Further, as a method of easily performing the heat cycle test many times for the shape memory alloy member in a short period of time, a method of electrically heating the shape memory alloy member has been proposed. In this case, an attempt is made to determine the amount of deformation by measuring the resistance value (see Patent Document 2).
[0004]
Usually, the transformation of the SMA is caused by self-heating (hereinafter, heating). In this case, the SMA is heated above the critical temperature and transforms from the martensite phase to the austenite phase. At this time, the initially applied inelastic strain is removed, and the shape returns to the original shape set at a higher temperature.
When SMA is used in applications such as self-healing of structures, it is necessary to cause the transformation as soon as possible, for which a large current must be applied.
However, when a large current is applied, overheating occurs, and the shape memory ability is lost, abnormal deformation or SMA peeling occurs, and in severe cases, the surroundings may burn. In particular, when the state of ambient temperature, convection, and radiant heat is unknown, it is extremely difficult to determine an accurate heating time with a predetermined heating current.
[0005]
[Patent Document 1]
JP-A-8-15208 [Patent Document 2]
JP 2001-99770 A
[Problems to be solved by the invention]
The present invention relates to a panel in which an SMA covered with an insulating film is embedded in a grid in a composite material, and determines the damage position and direction of the panel. The pulse current is applied to the SMA that has detected the damage, the SMA is heated, and the resistance is measured. The pulse current is cut off from the time derivative of the resistance, so that the heating current and the heating time are not affected by the ambient temperature and the like. The method for detecting the damage position of the shape memory alloy, the self-sensing type heating control method and the self-healing method, and the composite material panel and the insulating film which can prevent the propagation of damage at high speed and without overheating It is an object to provide a covered shape memory alloy.
[0007]
[Means for Solving the Problems]
The present invention detects and controls the transformation from a martensite phase to an austenite phase by measuring the resistance change of an SMA, detecting the damage position and direction from the time differential value of the resistance, and performing electric heating control on the SMA. And found that the damage could be prevented from spreading.
The present invention is based on this finding,
1. In a panel in which SMA covered with an insulating film is embedded in a grid in a composite material, the damage position and direction of the panel are measured at any time by measuring the resistance of the SMA, and the time derivative of the resistance is determined. 1. A method for detecting a damaged position of a shape memory alloy, characterized by performing Measure the SMA resistance change during the damage detection process, calculate the time derivative of the specific resistance, and confirm the damage position and direction of the smart composite material from the allowable time differential limit regardless of the presence or absence of the SMA R phase. 2. The method for detecting a damaged position of a shape memory alloy according to the above item 1, In a panel in which SMA covered with an insulating film is embedded in a grid in a composite material, the damage position of the panel is measured at any time, and the time derivative of the resistance is obtained. 3. A self-restoration method for a shape memory alloy, characterized in that a pulse current is applied to the SMA in which the damage is detected, and the SMA is heated to repair the damage. The feature is to measure the change of resistance of SMA in the damage location detection process, calculate the time derivative of specific resistance by calculation, and confirm the damage location of the smart composite material from the allowable time derivative limit regardless of the presence or absence of the SMA R phase. 4. The method for self-healing a shape memory alloy according to the above item 3. In a panel in which SMA covered with an insulating film is embedded in a grid in a composite material, the damage position and direction of the panel can be determined by measuring the resistance of the SMA at any time and determining the time derivative of the resistance. Judgment is made, a pulse current is applied to the SMA that has detected damage, high-speed heating of the SMA is performed, and resistance measurement is performed simultaneously. The time derivative of the specific resistance is obtained, and the transformation of the SMA is performed regardless of the presence or absence of the R phase of the SMA. 5. Self-sensing heating control method for shape memory alloy characterized by judging start / end In a panel in which SMA covered with an insulating film is embedded in a grid in a composite material, the damage position and direction of the panel can be determined by measuring the resistance of the SMA at any time and determining the time derivative of the resistance. Make a judgment, apply a pulse current to the SMA that has detected damage, perform high-speed heating of the SMA, measure the resistance at the same time, find the time differential of the specific resistance, and cut off the pulse current when it falls within the specified time differential value 6. A self-repairing method for a shape memory alloy, wherein the repair by damage heating is terminated without overheating by performing the heating. 7. The shape memory as described in (6) above, wherein the heating of the SMA and the resistance measurement are performed at the same time, the time differential of the specific resistance is obtained, and the transformation start / end of the SMA is determined regardless of the presence or absence of the R phase of the SMA. Provide a method for self-healing alloys.
[0008]
Further, the present invention
8. A pulse current is applied to the SMA during the heating process, the SMA is heated and the resistance is measured, and the pulse current is cut off when the time differential value of the resistance exceeds the specified time differential value. 8. Self-sensing heating control method or self-healing method for shape memory alloy according to 9. 9. The damage detection position of the shape memory alloy according to any one of 1 to 8 above, wherein the time differential allowable limit of the resistance is determined within 0.9% of the time differential value of the specific resistance. 9. Method, self-sensing heating control method and self-healing method 9. The method according to any one of claims 1 to 8, wherein the time derivative allowable limit of the resistance is obtained by calculating a time differential value of the specific resistance and setting the value within 0.5% of the value. 10. Self-sensing heating control method and self-healing method The self-sensing type heating of the shape memory alloy according to any one of the above items 6 to 10, wherein the specified value of the time differential of the resistance is obtained by calculating the time differential of the specific resistance and setting it within a range of ± 60% of the value. 11. Control method and self-healing method The self-sensing type heating of the shape memory alloy according to any one of the above items 6 to 10, wherein the specified value of the time differential of the resistance is obtained by calculating the time differential of the specific resistance and setting it within a range of ± 30% of the value. 12. Control method and self-healing method 13. The shape memory alloy damage position detecting method, the self-sensing type heating control method, and the self-detecting method according to any one of the above items 1 to 12, wherein the composite material panel is formed from a carbon fiber composite material or a glass fiber material. 13. Composite material panels used for restoration methods 14. A method for detecting a damage position of a shape memory alloy according to any one of the above items 1 to 13, wherein a polyimide / polyetherimide / fluororesin made of a thermoplastic resin is used as the insulating film. And a shape memory alloy covered with an insulating film for use in a self-healing method.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Conventionally, SMA damage detection and heating control are performed independently. Although this is a simple method, it cannot be said that the SMA material is effectively used.
FIG. 1 shows a schematic diagram of a smart material, composite panel 1 in which SMA wires 2 are embedded. The two orthogonal SMA wires 2 are arranged so as not to contact each other, and the SMA wires 2 and the composite panel 1 are fixed with glue. When a crack is formed on the panel surface of the smart material shown in FIG. 1, that is, when a crack 3 is formed in a panel in which an SMA wire is embedded as shown in FIG. 2 (a), the SMA wire 2 near the crack 3 is quickly changed. A large current must be applied to the SMA wire in order to prevent the crack 3 from growing by heat shrinkage (self-repair).
Therefore, unless the damage position is accurately grasped, the SMA wire 2 near the damage cannot be heated and shrunk. In addition, if the heating current and heating time are set excessively, the SMA may be overheated, resulting in loss of shape memory capability, abnormal deformation or SMA peeling, or fire. is there.
[0010]
In general, the state of the ambient temperature, convection, and radiant heat of the SMA wire is often unknown, so it is extremely difficult to determine an accurate heating time with a predetermined heating current.
Therefore, there is a need for a heating control method for accurately grasping the damage position and quickly transforming and terminating the transformation by high-speed heating of the SMA wire without overheating.
SMA differs in many physical properties such as Young's modulus, damping, specific heat, etc. depending on its metal phase. Due to its structural features, the resistance of SMA as it changes from the martensitic phase to the austenitic phase is highly dependent on the volume ratio of these two phases.
Therefore, by measuring the resistance value of the SMA, the volume ratio, that is, the transformation process can be known. FIG. 2B shows a state in which the SMA wires of EW2 and NS3 are heated and shrunk according to the present invention, and the width of the crack is reduced by the phase transformation of the SMA wires.
However, the resistance value depends not only on the temperature but also on the heat treatment, and further, the resistance value changes as the number of transformations increases.
[0011]
As an example, FIG. 3 shows typical temperature-resistivity characteristics of a Ti—Ni alloy. Such a change is also caused by a change in stress applied to the SMA.
Further, it can be seen from FIG. 3 that the change in the specific resistance is greater when the R phase intervening in the martensite phase is present than when it is not present. The presence or absence of the R phase depends on the heat treatment. When the R phase is present, the reproducibility of the specific resistance becomes worse as the number of transformations increases, and the resistance value does not change uniformly with temperature.
However, as can be seen from FIG. 3, there is a clear inflection point at the beginning and end of the transformation, regardless of the presence or absence of the R phase.
FIG. 4 shows the calculated value and the measured value of the time derivative of the resistivity with respect to the time for determining the start and end of the SMA transformation. The time derivative of the resistivity changes from the minimum value to the maximum value between the start and the end of the transformation, and again changes to the minimum value.
[0012]
On the other hand, as shown in FIG. 5, since the change in resistivity when heating is continued is not so clear as compared with the time derivative, it is more effective for control to use the time derivative of the resistivity, It is possible to exclude the fluctuation of the surrounding environment by finding the derivative of the resistivity with respect to time, instead of looking at the derivative with respect to temperature, and to clearly detect the resistance change value corresponding to the start and end of the transformation. A control method and control circuit for predicting the start and end were devised.
[0013]
The resistance value of the SMA embedded in a lattice is sequentially measured, and the time differential value of the specific resistance is calculated. When an external stress is applied to the SMA, the time differential value of the specific resistance greatly changes.
Therefore, by monitoring the behavior of the time derivative of the SMA, comparing the time derivative of each of the embedded SMAs, and determining the SMA subjected to the stress, the damage position can be accurately detected.
The resistance value is measured while applying a heating current to the SMA wire where the time differential value of the specific resistance has changed greatly, and the time differential value of the specific resistance is calculated. When the value starts to increase, it passes through the inflection point and the transformation starts. When the temperature decreases and stabilizes, it is determined that the transformation is completed, and the heating current is cut off to complete the self-repair.
This makes it possible to determine the damage position without being affected by the ambient temperature and the like, to optimize the heating current and the heating time, appropriately perform the transformation of the SMA, and prevent the damage from progressing. In addition, overheating can be suppressed, loss of shape memory capability, abnormal deformation and peeling can be suppressed, and fire can be prevented.
Next, examples of the present invention will be described. It should be noted that these examples and the like are for the purpose of facilitating understanding of the present invention and its effects, and the present invention is not limited to these descriptions. Therefore, all modifications, modes, and other examples based on the technical concept of the present invention are included in the present invention.
[0015]
(Example)
Self-healing test of damage using a panel in which a shape memory alloy covered with an insulating film made of thermoplastic resin polyimide, polyetherimide, and fluorine resin is embedded in a grid pattern in a carbon fiber composite material or glass fiber material. Was done.
Fig. 6 shows an experiment in which a pre-crack 4 was inserted into the composite material panel 1, a tensile load was applied to propagate the crack 4, the damage position and direction were detected by a self-healing system, heating was controlled, and self-healing was confirmed. FIG.
FIG. 7 is a schematic diagram of the control circuit 5 of the present embodiment.
[0016]
The outline procedure of the experiment is as follows. The SW is opened by the command of the digital I / O, and the current flowing through the SMA is read by the A / D converter while selecting the SMA one after another by the scanner, and the time differential value of the specific resistance is calculated based on the current.
2. If the time differential value of the specific resistance of two orthogonal SMAs exceeds the set permissible limit, it means that the orthogonal point has been damaged. In this case, step 3. go to. If not, proceed as follows: Return to
3. When the time derivative of the resistivity of the SMA corresponding to (x-1 to x + 1, y-1 to y + 1) around the orthogonal point (where the coordinates are (x, y)) is compared, the damage is greater due to the magnitude. Since the direction is known, the heating control is applied to the SMA having the larger damage and the SMA corresponding to (x, y).
At this time, the heating current flows by closing the SW. If the transformation of the SMA has already been completed, the next part is heated. After completion of the transformation, Return to
[0017]
That is, the voltages Vtst and Vsmp of the SMA line are taken into a personal computer through an A / D converter, the resistance value of the SMA line is measured from Rs, Vtst, and Vsmp, and the time derivative of the specific resistance is calculated. By monitoring and comparing with the time derivative allowable limit value, the SMA wire to be subjected to the heating control is determined while determining the damage position and direction, and the heating and resistance value of the determined SMA wire are measured and the time of the specific resistance is determined. The differentiation was calculated, and self-healing was performed by repeating the sensing of the heating resistance of the SMA wire until the time differentiation specified value was reached.
[0018]
FIG. 8 is an example showing a result of monitoring a behavior in which the SMA undergoes a stress fluctuation due to the propagation of a crack from the pre-crack 4 of the composite material panel 5 and the time differential value of the specific resistance greatly changes.
The time derivative allowable limit value is set to 0.5%, the resistance value of the SMA embedded in a lattice is sequentially measured, the time derivative value of the specific resistance is calculated, the behavior of the time derivative value is monitored, and the embedded individual is monitored. By comparing the SMA with the time derivative allowable limit value, the position and direction of minute damage could be detected.
When the time derivative allowable limit value is 0.6 to 0.9%, the damage is enlarged, but it becomes easier to recognize the position of the damage.
[0019]
Further, when the time differential limit value is 1% or more, the crack of the composite material panel progresses and breaks. The specified value of the time differential is set within the range of ± 30%, the resistance value of the SMA embedded in a lattice is measured sequentially, the time differential value of the specific resistance is calculated, the behavior of the time differential value is monitored, and the embedded individual is monitored. By comparing the SMAs of the composite material panels, the damage position could be accurately detected, and a heating current was applied to the SMA at the damaged portion of the composite material panel to perform heating control without overheating, thereby preventing the development of damage.
[0020]
However, when the time derivative specified value is in the range of -40 to -60%, slight overheating is observed. At + 70% or more, self-healing is incomplete while transformation is not completed, and -70% or more. Was overheating leading to loss of shape memory ability, abnormal deformation, and peeling.
FIG. 9 shows the relationship of the transformation end time when the energizing heating current of the heating control is changed. When the energizing heating current is large, the transformation end time is shortened. When the temperature exceeds 62 ° C., which is the SMA transformation end temperature in this example, the heating current is automatically cut off and the self-healing is completed.
In the experiment, the heating period was set to 0.1 second. However, if it is desired to shorten the transformation end time, the heating current should be increased and the heating time should be determined according to the accuracy.
Thus, the ability to freely select the heating current and the heating time is one of the points showing the effectiveness of the present method.
[0021]
【The invention's effect】
The present invention relates to a panel in which an SMA covered with an insulating film is embedded in a composite material in a lattice shape, and the damage position of the panel is measured at any time with respect to the resistance of the SMA, and the time derivative of the resistance is determined to determine the damage position and the like. By applying a pulse current to the SMA that has detected damage, heating and measuring the resistance of the SMA, and cutting off the pulse current from the time derivative of the resistance, the heating current and heating time can be measured without being affected by the ambient temperature. It has a remarkable effect that can be optimized.
Further, according to the present invention, it is possible to prevent the development of damage at high speed without overheating. Therefore, loss of shape memory capability, abnormal deformation, and peeling can be suppressed, and an excellent effect of preventing fire can be obtained.
Furthermore, when the control method and control circuit of the present invention are used, the state of the SMA phase transformation can be automatically detected even when the state of the ambient temperature, convection, and radiant heat is unknown. Since it can be set freely according to the application, it can be used in a wide range of applications, and can be applied to all SMAs that want to transform SMA according to the purpose.
[Brief description of the drawings]
FIG. 1 is a schematic view of a smart material and a composite panel in which an SMA wire is embedded.
FIG. 2 shows a case in which a crack is formed in a panel in which an SMA wire is embedded (a), and a case in which the SMA wire of EW2 and NS3 is heated and shrunk, and the width of the crack is reduced by phase transformation of the SMA wire (b). It is a schematic diagram.
FIG. 3 is a graph showing typical temperature-resistivity characteristics of a Ti—Ni alloy.
FIG. 4 is a view showing a calculated value and a measured value of a time derivative of specific resistance.
FIG. 5 is a diagram showing a time derivative of the specific resistance and a change in the specific resistance.
FIG. 6 is a schematic explanatory view of an experiment in which a pre-crack is applied to a composite material panel, a tensile load is applied, a crack is propagated, a damage position is detected by a self-healing system, heating is controlled, and self-healing is confirmed. It is.
FIG. 7 is a schematic diagram of a control circuit of the present embodiment.
FIG. 8 is a diagram showing an example of monitoring the time derivative when a crack occurs.
FIG. 9 is a diagram showing a transformation end time when a heating current is changed.
[Explanation of symbols]
1. Composite panel 2. 2. SMA wire Crack 4. Pre-crack5. Control circuit

Claims (14)

For a panel in which a shape memory alloy (hereinafter referred to as SMA) covered with an insulating film is embedded in a grid in a composite material, the damage position of the panel can be measured from time to time by measuring the resistance of the SMA, and the time derivative of the resistance can be calculated from the allowable limit of time differentiation. A method for detecting a damaged position of a shape memory alloy, comprising determining a damaged position or the like. The resistance change of the SMA is measured in the process of detecting the damage position, the time derivative of the specific resistance is calculated by calculation, and the damage of the smart composite material is determined from the allowable limit of the time derivative regardless of the presence or absence of the rhombohedral phase (hereinafter referred to as R phase) of the SMA. The method according to claim 1, wherein the position is confirmed. In a panel in which SMA covered with an insulating film is embedded in a grid in a composite material, the damage position of the panel is measured at any time, and the time derivative of the resistance is obtained. A self-repairing method for a shape memory alloy, wherein a pulse current is applied to the SMA in which the damage is detected, and the SMA is heated to repair the damage. The feature is to measure the change of resistance of SMA in the damage location detection process, calculate the time derivative of specific resistance by calculation, and confirm the damage location of the smart composite material from the allowable time derivative limit regardless of the presence or absence of the SMA R phase. The method for self-healing a shape memory alloy according to claim 3. In a panel in which the SMA covered with an insulating film is embedded in a grid in a composite material, the damage position of the panel is measured at any time, and the time derivative of the resistance is measured as needed to determine the damage position, etc. from the allowable time derivative limit. Performs high-speed heating of the SMA by applying a pulse current to the SMA that has detected damage, and simultaneously performs resistance measurement to determine the time derivative of the specific resistance, and starts and ends the transformation of the SMA regardless of the presence or absence of the R phase. A self-sensing heating control method for a shape memory alloy, characterized by determining. In a panel in which the SMA covered with an insulating film is embedded in a grid in a composite material, the damage position of the panel is measured at any time, and the resistance of the SMA is measured from time to time, and the time derivative of the resistance is determined to determine the damage position, etc. from the allowable limit of time differentiation. Performing high-speed heating of the SMA by applying a pulse current to the SMA that has detected damage, and simultaneously measuring the resistance, determining the time derivative of the specific resistance, and interrupting the pulse current when the specific value falls within the specified range of the time derivative. A method for self-healing a shape memory alloy, comprising: terminating repair of damage by heating without overheating by heating. 7. The shape according to claim 6, wherein the resistance of the SMA is measured at the same time as the heating of the SMA, and the time differentiation of the specific resistance is determined to determine the start / end of the transformation of the SMA regardless of the presence or absence of the R phase of the SMA. Self-healing method of memory alloy. 8. The method according to claim 3, wherein a pulse current is supplied to the SMA during the heating process, the SMA is heated and the resistance is measured, and the pulse current is cut off when a time differential value of the resistance exceeds a specified time differential value. Or a self-repairing method for a shape memory alloy. 9. The damage position of the shape memory alloy according to claim 1, wherein a time differential allowable limit of the resistance is obtained by calculating a time differential value of the specific resistance and within 0.9% of the value. Detection method, self-sensing heating control method and self-healing method. 9. The damage position detection of a shape memory alloy according to claim 1, wherein the time differential allowable limit of the resistance is obtained by calculating the time differential value of the specific resistance and setting it within 0.5% of the value. Method, self-sensing heating control method and self-healing method. The self-sensing shape memory alloy according to any one of claims 6 to 10, wherein the specified value of the time differential of the resistance is obtained by calculating the time differential of the specific resistance and within a range of ± 60% of the value. Heat control method and self-healing method. The self-sensing shape memory alloy according to any one of claims 6 to 10, wherein the prescribed time differential value of the resistance is obtained by calculating the time differential value of the specific resistance and setting it within a range of ± 30% of the value. Heat control method and self-healing method. 13. A method for detecting a damage position of a shape memory alloy according to claim 1, wherein the composite material panel is formed from a carbon fiber-based composite material or a glass fiber-based material. Composite panels used for self-healing methods. 14. The method for detecting a damage position of a shape memory alloy according to claim 1, wherein the insulating film is made of a polyimide / polyetherimide / fluorine resin made of a thermoplastic resin. Memory alloy covered with an insulating film used in the self-healing method and the self-healing method.

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