JP2017163119A - Composite reinforced type magnetostrictive composite material and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a composite reinforced type magnetostrictive composite material which can be spread in many fields as an "independent power generation type" smart material having a light weight, a robust, high strength, a large generation power, and durability against a stress load; and a method for manufacturing the magnetostrictive composite material.SOLUTION: A magnetostrictive fiber reinforced type composite material having a high generation power with a residual tensile stress included therein is manufactured by the steps of: mixing a base material with a hardening agent in certain proportions; arraying FeCo fibers in one direction in a mold; pouring the resultant base material into the mold in a state in which a stress is loaded on the fibers by a weight, followed by hardening at a room temperature for 24 hours; and further, putting the resultant hardened FeCo fiber-reinforced composite material in a thermostatic oven to keep heating the composite material at 80°C for three hours for causing the post-hardening of the composite material. A magnetostrictive fiber reinforced type composite material with a higher performance can be manufactured by performing a thermal treatment on the FeCo fibers. In addition, the composite material can be optimized in combination of a theoretical analysis.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a composite reinforced magnetostrictive composite material and a method for manufacturing the same, and more particularly, a self-powered smart composite reinforced magnetostrictive composite having a robust and light weight embedded with a magnetostrictive alloy filler. The present invention relates to a material and a manufacturing method thereof.

  The principle of its function is that when a magnetostrictive alloy receives an external force (stress), the strain energy reaches inside the material, and the micro magnetic moment region in the crystal (hereinafter referred to as magnetic domain or magnetic domain) The so-called “reverse magnetostriction phenomenon” is used in which leakage flux is generated in a form corresponding to the stress from the sample surface.

  A magnetostrictive alloy with such a function is processed into a thin plate or thin wire, and is appropriately embedded in a matrix (matrix) made of polymer, metal, or ceramics to enhance the inverse magnetostriction effect (leakage flux phenomenon) at the same time as composite reinforcement. Therefore, it is intended to provide a composite functional and smart composite material with enhanced external force sensor and vibration power generation functions.

  Since the new material according to the present invention mainly uses an iron-based new magnetostrictive FeCo excess type alloy, it has higher strength, durability and corrosion resistance than conventional magnetostrictive alloys made of rare earths or rare metals. Since the ratio of the filler (filler) embedded in can be reduced, the composite material product can be flexible and lightweight.

  In addition, due to the inverse magnetostrictive effect of the magnetostrictive alloy filler, the corresponding leakage flux is generated (released) outside the surface of the bulk composite material in response to external forces. Under heavy load, it is possible to extract vibration power by attaching a coil.

  The FeCo magnetostrictive alloy used in the development of this material and embedded in the base material has elongation and freedom of molding and integration with the base material side, so the applicability to product applications can be greatly expanded. It becomes possible.

  That is, from the above, as a magnetostrictive composite bulk material that can withstand light weight, robust high strength, large electric power, stress load, sports products, cars (body / tire), aerospace equipment parts, infrastructure structure materials, It can be applied to medical and welfare equipment members, and in the future, to micro battery functions for wearable IoT devices, and may be the first new material inside and outside of the “self-sustaining power generation” smart material.

  The Internet has more than 2 billion users worldwide and has the potential to further improve user experience and quality of life by communicating between various devices. “Internet of things“ IoT ”” is a technology that makes it possible to provide long-awaited applications and business opportunities such as robots, healthcare, and real-time monitoring [Non-Patent Document 1]. On the other hand, energy harvesting is a technology that has recently been attracting attention as an alternative to power for wireless communication nodes, and many studies have been conducted with the aim of directly recovering energy from vibration and motion.

  In order to enable energy recovery, magnetostrictive materials have high magnetostrictive characteristics, can be mass-produced, and are low-cost materials [Non-Patent Document 2]. Terfenol-D, which consists of terbium, dysprosium and iron, is recognized as an important magnetostrictive material due to its huge magnetostriction (800-1600ppm) and low magnetic anisotropy [Non-Patent Document 3]. For this reason, Davino et al. [Non-Patent Document 4] studied the magnetostriction and magnetic properties of Terfenol-D rods under various stresses and magnetic fields, and achieved the maximum magnetoelastic constant with relatively low compression prestress and bias magnetic field. It shows what you can do. A design method for Terfenol-D power generators that recover energy from traffic has been proposed by Viola et al. [Non Patent Literature 5].

  Furthermore, Mori et al. [Non-Patent Document 6] are conducting research on the dynamic bending and energy harvesting characteristics of cantilevers with a resonance adjustment function using Terfenol-D plates, both theoretically and experimentally. Terfenol-D is a promising energy harvesting material, but its use as an alternative to piezoelectric materials is limited by several issues, including brittleness and the generation of high eddy currents that limit the effective frequency range .

  These problems have led to studies to solve the above problems using composite materials. Recently, a magnetostrictive composite material in which Terfenol-D particles are dispersed in a polymer matrix has attracted attention because of its high tensile strength and small eddy current loss [Non-Patent Document 7-9]. Kubicka et al. [Non-Patent Documents 10 and 11] clarified the influence of the amount and size of Terfenol-D particles dispersed on the stress-induced magnetic flux density of Terfenol-D particle-dispersed epoxy resin. Yoffe et al. [Non-Patent Document 12] proposed a new model of the external force-induced magnetic field of Terfenol-D particle-dispersed epoxy composites.

  The Fe-Ga alloy known as Galfenol exhibits a magnetostriction of 400 ppm, and some researchers have studied the energy harvesting characteristics of Galfenol oscillating power generators [13, 14]. However, they also have drawbacks such as difficulty in production and processing, high costs, etc., and they are incomplete as full-scale energy harvesting materials, have few timely cases, and have not yet been commercialized.

From the above, the problems and limits of use of the two conventional magnetostrictive alloy materials (rare metal FeGa (Galenol), rare earth Terfenol-D) made in the United States (patent) are as follows.
1) The casting material was brittle, difficult to process, and secondary processing (wire material, plate material strong processing (rolling, wire drawing) was “impossible”.
2) The rigidity of these two types of magnetostrictive alloys is less than half that of iron-based alloys and is soft, and with secondary processing (strong processing), the inside (crystal orientation change, internal defects (crack, dislocation density inhomogeneity) (Internal stress inhomogeneity) occurs, and the magnetic / magnetostrictive properties are greatly reduced.Therefore, it is impossible to obtain rolled thin plates and narrowed wires obtained from secondary processed materials. There were no industrial products.

On the other hand, recently (2011), Fe _1-x Co _x magnetostrictive (x = 50-90 at%) alloys have been developed by forging and cold working, and the effects of various alloy compositions and heat treatments have been studied. [15]. The effects of heat treatment on Fe-Co alloys with high Co content have also been studied [16]. The Fe—Co alloy exhibits high strength, ductility, and excellent workability, and an Fe—Co alloy fiber can be easily produced.

  Magnetostrictive continuous Fe-Co alloy fibers with a high aspect ratio exhibit various characteristics (low demagnetizing factor, strong magnetocrystalline anisotropy, etc.), so high magnetostrictive properties can be obtained by dispersing Fe-Co fibers in the polymer. The development of composite materials with Furthermore, the polymer composite material is lightweight, and a high-quality composite material design that makes use of the characteristics of the Fe-Co fiber, such as providing a pre-restressing effect at the time of production, becomes possible.

C. Han, J. M. Jornet, E. Fadel, I. F. Akyildiz, Comput. Networks 57,622-633 (2013). L. Wang, F. G. Yuan, Smart Mater.Struct.17,045009 (2008). A. E. Clark, B. F. De Savage, R. Bozorth, Phys. Rev. 138, A216-A224 (1965). D. Davino, A. Giustiniani, C. Visone, Phys. B407, 1427-1432 (2012). A. Viola, V. Franzitta, G. Cipriani, V. D. Dio, F. M. Raimondi, M. Trapanese, IEEE Trans. Mag. 51, 8208404 (2015). K. Mori, T. Horibe, S. Ishikawa, Y. Shindo, F. Narita, Smart Mater.Struct. 24, 125032 (2015). T. A. Duenasa, G. P. Carman, J. Appl. Phys. 90, 2433-2439 (2001). X. Dong, J. Ou, X. Guan, M. Qi, J. Mag. Mag, Mater. 322, 3648-3652 (2010). J. Kaleta, D. Lewandowski, R. Mech, Arch. Civil Mech. Eng., In press. M. Kubicka, T. Mahrholz, A. Kuhn, P. Wierach, M. Sinapius, J. Mater.Sci. 47,5752-5759 (2012). M. Kubicka, T. Mahrholz, A. Kuhn, P. Wierach, M. Sinapius, J. Mater.Sci. 48, 6578-6584 (2013). A. Yoffe, Y. Weber, D. Shilo, J. Mech. Phys. Solids 85, 203-218 (2015). B. Rezaeealam, T. Ueno, S. Yamada, IEEE Tran. Magnetics 48, 3977-3980 (2010). S. Kita, T. Ueno, S. Yamada, J. Appl. Phys. 117, 17B508 (2015). S. Yamaura, T. Nakajima, T. Satoh, T. Ebata, Y. Furuya, Mater. Sci. Eng. B 193, 121-129 (2015). N. Kimura, T. Kubota, T. Yamamoto, S. Fukuoka, Y. Furuya, J. JapanInst. Met. Mater. 79, 441-446 (2015). : Masaki Yokoyama, Shinichi Yamaura, Ken Kubota, Atsuko Okazaki, Kazuhiko Sunagawa, Munekatsu Shimada, Yasufumi Furuya, “Characteristics of High Magnetostrictive Fe-Co-V Alloys as Magnetostrictive Ring Type Torque Sensor Elements”, Materials Science and Engineering, 50,32-37 (2013).) K. Mori, Y. Shindo, F. Narita, Smart Mater.Struct. 21, 115003 (2012). Z. Jia, W. Liu, Y. Zhang, F. Wang, D. Guo, Sens. Actuators A 128, 158-164 (2006). Z. G. Zhang, T. Ueno, T. Yamazaki, T. Higuchi, IEEE Tran. Magnetics 46, 1641-1644 (2010). Y. Wan, D. Fang, K.-C. Hwang, Int. J. Non-Linear Mech. 38,1053-1065 (2003). H. Hauser, J. Appl. Phys. 96,2753-2767 (2004). M. Karsten, Probleme der Technischen Magnetisierungskurve, Springer, Berlin, 1938. Y. Furuya, J. Jp. Welding Soc. 64, 120-125 (1995).

JP 2014-84484 A JP 2013-177664 A

  In the present invention, a magnetostrictive fiber reinforced composite material utilizing the characteristics of the newly developed FeCo excess filler fiber is developed, and an optimum design technique for the magnetostrictive power generation composite material is provided from both theoretical and experimental viewpoints. Then, by measuring the strength of the magnetic flux leakage from the specimen under repeated loading and extracting the power with a coil installed around the specimen, the theoretical analysis and the experimental data were compared and examined, and the vibration power generation material By clarifying the load conditions, we aim to apply energy harvesting devices using smart composite materials with high output energy harvesting characteristics.

  When designing and prototyping a fiber reinforced composite material, a filler (filler) in the form of a thin plate or wire embedded in the base material (matrix) side is required. However, two conventional magnetostrictive alloy materials made in the United States (patent), that is, rare metal FeGa2 element (Galfenol) and rare earth terfenol-D, are brittle and difficult to process, and secondary processing (rolling, drawing) ) The strong processing of thin plate materials and thin wire materials by (3) was virtually impossible.

  To solve this problem, the filler (filler) used in the present invention is aimed at solving the problem by adopting an iron-based FeCo-rich alloy recently developed in Japan. In other words, it is possible to reduce the thickness to 1 mm or less by secondary processing and to make it thinner. Due to the reforming effect associated with the subsequent heat treatment, it is superior in strength, durability, and corrosion resistance compared to conventional magnetostrictive alloys made of rare earth or rare metals, and the filler (filler) ratio embedded in the base material side It can be reduced.

The composite material product has flexibility and light weight, and has a degree of freedom of molding and integration with the base material side, so that the applicability to product application can be greatly expanded. In other words, it can be the first new material in Japan and overseas as a “self-sustaining power generation” smart material that can withstand light weight, robust high strength, large power generation, and stress load, and can be developed in various fields as an industrial material.
The present invention provides a composite reinforced vibration power generation material that can be developed in various fields as a “self-supporting power generation” smart material that can withstand light weight, robust high strength, large power generation, and stress load, and a method for manufacturing the same. Objective.

The invention according to claim 1 is a composite reinforced magnetostrictive composite material in which a wire and / or thin plate made of an iron-based magnetostrictive alloy and having a residual stress is embedded in a base material (matrix) as a filler.
The invention according to claim 2 is the magnetostrictive composite material according to claim 1, wherein the iron-based magnetostrictive alloy is a magnetostrictive alloy having a Co-rich composition (Co = 69-79 at%).
Since the magnetostriction amount exceeds 100 ppm in the range of Co = 69-79 at%, this range is preferable.
FeGa-based (Galfenol, rare earth-based Terfenol-D), which is a magnetostrictive alloy material, is difficult to perform secondary processing on post-cast wire and plate materials. Defects in the controlled crystal structure (crystal orientation, internal defects (cracking, dislocation density inhomogeneity, internal stress inhomogeneity)) occur, and the magnetic / magnetostrictive characteristics are greatly reduced.
On the other hand, a magnetostrictive alloy having a Co-rich composition is particularly preferable because it can be strongly processed.
Further, when Co = 69-79 at%, since the magnetostriction amount exceeds 100 ppm, it is more preferable to set Co within this range.
The invention according to claim 3 is the magnetostrictive composite material according to any one of claims 1 to 3, wherein the filler has a tensile residual stress, and the base material has a compressive residual stress.
By generating a residual stress on the base material and filler side, a magnetostrictive composite material in which strength and the inverse magnetostriction effect (leakage magnetic flux phenomenon) are further enhanced can be obtained.
The invention according to claim 4 is the magnetostrictive composite material according to any one of claims 1 to 3, wherein the filler is a secondary processed product obtained by drawing or rolling a forged material.
The invention according to claim 5 is the magnetostrictive composite material according to any one of claims 1 to 4, wherein the base material is a polymer, metal, or ceramic.
The invention according to claim 6 is the magnetostrictive composite material according to claim 5, wherein the polymer is an epoxy resin.
When an epoxy resin is used as a base material, a higher residual stress can be obtained than when ceramic or metal is used as a base material.
The invention according to claim 7 is a method for manufacturing a magnetostrictive composite material, in which a filler made of an iron-based magnetostrictive alloy is manufactured by a process of casting a base material while applying a prestress.
The invention according to claim 8 is the method for producing a magnetostrictive composite material according to claim 7, wherein the iron-based magnetostrictive alloy is a magnetostrictive alloy having a Co-rich composition (Co = 69-79 at%).
The invention according to claim 9 is the method for producing a magnetostrictive composite material according to claim 7 or 8, wherein the filler before casting is subjected to a blunt heat treatment at 400 to 600 ° C.
When the pre-cast filler is annealed, the magnetic and magnetostrictive characteristics are improved as compared with the case of as drawn or as rolled. In particular, this tendency appears at an annealing temperature of 400 to 600 ° C.
The invention according to claim 10 is the method for producing a magnetostrictive composite material according to any one of claims 7 to 9, wherein the filler is a secondary processed product obtained by drawing or rolling a forged material.
The invention according to claim 11 is the method for producing a magnetostrictive composite material according to any one of claims 7 to 10, wherein the base material is a polymer, a metal, or ceramics.
The invention according to claim 12 is the method for producing a magnetostrictive composite material according to claim 11, wherein the polymer is an epoxy resin.
The invention according to claim 13 is the electromagnetic induction in which the leakage magnetic flux (inverse magnetostriction effect) from the magnetostrictive filler at the time of stress loading is installed outside the main body surface portion of the composite material according to any one of claims 1 to 7. This is a power generation device that detects vibrations and generates vibrational power.

According to the present invention, the following various effects can be obtained.
According to the present invention, the magnetostriction susceptibility dm increases. That is, the rising gradient of the magnetostrictive curve, dm = magnetostriction (λ) / applied magnetic field strength (H)) increases. The filler of the present invention is linear and has a high aspect ratio (length / diameter).
for that reason,
a) The demagnetizing factor decreases, the magnetic flux density remaining inside increases, and the magnetic flux leakage increases. As a result, an increase in vibration power can be expected.
b) Increase in remanent domain; crystal orientation occurs in the longitudinal direction (size ratio large) by secondary processing. In particular, the number of residual magnetic domains increases due to internal residual stress, dislocation density, and precipitation phase distribution that are easily magnetized, strengthen the iron-based <100> orientation, are easily magnetized, and are accompanied by strong processing, and leakage flux It is considered that power generation can be increased.
In the present invention, the filler has prestress (internal residual stress).
In the FeCo fiber reinforced composite material (composite), in the manufacturing process, the fiber is cast and solidified in an epoxy base material with a tensile prestress applied to the fiber. Therefore, residual compressive stress is generated on the matrix (base material) side, and tensile residual stress is generated on the fiber side. It is considered that this fiber-side residual stress promotes the movement of the magnetic domain, the domain wall movement frequently occurs, the amount of leakage magnetic flux increases, and the vibration power generation increases.
In the present invention, there is a large “strain rate (spot speed) dependency”, and therefore a large power generation is obtained.
The FeCo excess type alloy filler obtained by carrying out strong processing in the secondary processing step generates discontinuous distribution of crystal grains and large residual stress heterogeneity inside. The FeCo alloy is a hard material having a stiffness (Young's modulus) of 200 GPa, twice that of FeGa, four times that of Terefnol-D rare earth, and twice as strong as the strength. Therefore, from the dynamic theory of the magnetic domain, the barrier energy of the domain wall is high, and in order to move the magnetic domain and promote the magnetization, a large stress load is required in the initial stage. However, once this high level domain wall barrier is exceeded, a large dynamic domain behavior occurs due to the inhomogeneity of the internal structure, and a strong magnetic flux is emitted to the outside. Therefore, the FeCo fiber reinforced composite was able to generate a large power generation due to a large “strain rate (spot speed) dependency”.

Internal magnetic domain when the magnetostrictive alloy is loaded (SN pole change) Explanation of leakage flux generation due to rearrangement (inverse magnetostrictive effect) Magnetic parameters related to magnetostriction and inverse magnetostriction effect (magnetization curve of magnetic material) Comparison of magnetostriction characteristics of FeCo processed wire and melt cast material Magnetization curve (FeCo processed wire, melt casting) Procedure for manufacturing composite materials (a) Test jig, coil and load condition, (Relationship between load / output voltage and time) Relationship between output voltage density and average load stress and stress rate: (a) Comparison between composite and galphenol, (b) Effect of residual tensile stress Of effective magnetostriction constant by analysis (A) Strain-field curve magnetization curve, (b) Dynamic domain model

The principle and operation of the present invention will be described below together with embodiments for carrying out the present invention.
When an external magnetic field is applied to a ferromagnetic material such as iron or cobalt, it is distorted in the direction of the magnetic field. This is called a magnetostriction effect (or “Joule effect”, “magnetostriction effect”). The length change (distortion) is not large, but the ratio change (ΔL / L)
Is around 10-6 to 10-5, but the response speed is as fast as MHz, so it is used as an element for ultrasonic oscillators. On the other hand, when an external stress (compressive force or tensile force) is applied to a magnetic material, its dimensions change, and at the same time, its internal magnetization state (electron spin state, magnetic domain structure, magnetic permeability, etc.) Since it changes, a leakage magnetic flux is generated around it. This phenomenon is called inverse magnetostriction effect. By utilizing this phenomenon, it can be applied to a sensor for evaluating the magnitude and strain of a load stress (external force) applied to a magnetostrictive material.

  Recently, the possibility of an inverse magnetostrictive element for micro-environmental power generation that obtains electric power by installing a coil that captures a leakage magnetic flux generated when mechanical vibration is applied to the magnetostrictive material itself has been studied. Fig. 1 conceptually shows the principles and applications of the magnetostrictive effect and inverse magnetostrictive effect. When a magnetostrictive alloy is loaded, internal magnetic domains (SN pole change) and leakage flux generation (reverse magnetostriction effect) accompanying rearrangement occur. A material that exhibits an appropriate inverse magnetostrictive effect used in the present invention is a newly developed iron-based magnetostrictive alloy (FeCo, FeGa series, etc.) [Patent Document 1], which leaks from its surface from a small stress level. It is a material that can generate magnetic flux (magnetism) and can be a highly sensitive stress (strain) sensor.

  For this purpose, the following material properties were found to be important. As can be seen from the magnetic parameters on the magnetization curve of the magnetic material related to the magnetostriction / inverse magnetostriction effect shown in FIG. 2, (1) the magnetostriction amount (λ) is large, and (2) the magnetostriction susceptibility (gradient: dm = Dλ / dH), (3) large residual magnetic flux density (Br) in the magnetization curve (hysteresis curve), medium coercive force (Hc), (4) crystal anisotropy, It is effective to make the iron easy magnetization axis <100> oriented strong material. The effectiveness of magnetic characteristic factors (parameters) in these magnetostrictive materials has been confirmed from the results of a magnetostrictive ring type torque sensor based on the inverse magnetostrictive effect [Non-patent Document 17]. More recently, in connection with this, even in a vibration power generation element which is one of devices using inverse magnetostriction, a larger leakage magnetic flux (= torque sensor sensitivity) is obtained in the FeCo system than in the conventional FeGa system (US patent). Proven with vibration power generation output [Patent Document 2].

  In order to aim for the application of energy harvesting devices using smart magnetostrictive composite materials with high output energy harvesting characteristics, first of all, high-sensitivity FeCo-based magnetostrictive materials and their magnetic properties (reverse magnetostriction phenomenon, magnetic parameters) Selection is important. As shown in the previous section, as an example of selecting a magnetostrictive material that has a large inverse magnetostriction effect and can be a high-sensitivity sensor, FIG. 3 shows a comparison between a processed wire with a Co-rich composition (Co = 71 wt%) and a molten cast material. A comparison of magnetostriction characteristics is shown. In the processed wire, as can be seen from the X-ray crystal diffraction results, the crystal orientation is aligned in the longitudinal direction and the crystal anisotropy is strong, so the amount of magnetostriction (λ) is increased compared to the melted material of random orientation crystal. Yes. In addition, the magnetostriction phenomenon occurs with less magnetic field strength (H), which can be said to be a highly sensitive material.

  Next, Table 1 shows magnetostriction and magnetostriction susceptibility of the FeCo processed wire and the melted (melted casting) material. It can be seen that the processed wire has a magnetostriction (λ) increased 1.36 times and a magnetostriction susceptibility (dm) increased 1.65 times. FIG. 4 shows the magnetization curves of both (FeCo processed wire and melted cast material). From the enlarged view near the origin (= H = 0), it is understood that the coercive force (Hc) and the residual magnetic flux density (Br) are high as well as the sharp rise (permeability and magnetic susceptibility) of the processed wire. Table 2 shows a comparison of magnetization parameters between the processed wire and the molten cast material. The residual magnetic flux density (Br) and the coercive force (Hc), both of which have a strong effect on the strength of the leakage magnetic flux (φ) from the magnetostrictive material, are both higher in the processed wire, Br = 5.23 times, Hc = 3 0.03 times, and it can be seen that a strong rolling process and a drawn material are more advantageous as an inverse magnetostrictive sensor.

  The cause of the increase in leakage flux was investigated from the X-ray diffraction of the FeCo processed wire. From the cross section of the wire and the peak intensity of the crystal diffraction plane in the longitudinal direction of the drawing, the face centered cubic (fcc) phase cannot be confirmed, and only the body centered cubic (bcc) phase is confirmed. Due to the difference in longitudinal section, the presence of crystal orientation was confirmed in this processed wire.

  In order to improve the magnetic / magnetostrictive characteristics, the thin wire material and the thin plate material after the secondary processing are subjected to an appropriate annealing heat treatment in the middle temperature range (400 ° C.) to be modified. The characteristic improvement is seen rather than the secondary processed wire.

Next, an example of the manufacturing method of the FeCo fiber reinforced composite material of this invention is demonstrated. Fig. 5 shows the characteristics of the composite material and the manufacturing procedure. The base material was bisphenol-F epoxy resin, the curing agent was polyamine, and the base material was prepared so that the mixing ratio was 100: 55. Then, Fe _1-x Co _x (x = 71 wt%) FeCo fibers with a diameter of 1 mm and a length of l = 15 to 19 mm are arranged in one direction in the mold, and are approximately 0, 12.5, 25, and 50 MPa by weight. The epoxy base material was poured into the mold while stress was applied.
Thereafter, it was cured at room temperature for 24 hours. Next, the cured FeCo fiber reinforced composite material was placed in a constant temperature furnace and heated at 80 ° C. and held for 3 hours for post-curing. Table 3 shows predicted values of the final shape of the sample (cross-sectional area A, length l), fiber volume containing vf, and tensile residual stress σ ₀ . For comparison, Galfenol made by Etrema (USA) having the dimensions shown in Table 3 was also prepared. Table 4 shows the elastic compliance s ₃₃ , the piezomagnetic constant d ₃₃ , the secondary magnetoelastic coefficient m, and the magnetic permeability μ ₃₃ of each material.

An impact compression test was performed using the samples shown in Table 3. The test was performed using Autograph (SHIMAZU AG-50kNXD), and as shown in FIG. 6A, a 5-cycle compression load with a minimum load P _min = 50 N and a maximum load P _max = 550 N was applied. The crosshead speeds at this time are dδ / dt = 0.25, 0.50, 0.75, 1.0, 2.0, and 3.0 mm / s (δ is the crosshead displacement). During the test, the sample was loaded with a bias magnetic field B ₀ = 62 mT using a permanent magnet. The output voltage Vout was measured using a coil (FIG. 6A) having a cross-sectional area of about 113 mm ² , 2500 turns, a length of 36 mm, and a resistance of 106Ω and a data logger. FIG. 6 (b) shows the relationship between the output voltage _Vout and the load P of the Fe ₂₉ Co ₇₁ fiber / polymer composite material and the time t. Dδ / dt = 3 mm / s, P _min = 50 N, P _This is the case when _max = 550N. The output voltage differs between loading and unloading, and it will be evaluated in the future at the load value.

Ｆｅ_２９Ｃｏ_７１繊維，熱処理（８５０°Ｃで５時間後急冷）されたFe₂₉Co₇₁繊維，Galfenol [非特許文献２０]とエポキシの物性を表IIに示す。逆磁歪効果（ビラリ効果）によって誘起される磁束密度がバイアス磁場Ｈ_０＝Ｂ_０／μ_０（μ_０＝１．２×１０^−６Ｈ／ｍは自由空間の透磁率）に比べ小さいと仮定すると，Ｆｅ-Ｃｏ繊維の応力と磁束密度は次のように得られる。

また，エポキシマトリックスのひずみと磁束密度は，上添え字mを用いて，次のように与えられる。

ここで，Nはコイル巻き数、Ａ^ｆはFe-Co繊維の断面積，

は試験片に作用する平均応力，tは時間である。2次の磁気弾性係数は，

と表すことができる（ここで，m^fは単位磁場当たりの磁歪を意味する定数，r^fは単位プレストレス・単位磁場当たりの磁歪を意味する定数、σ₀はプレストレスである）[非特許文献２１]。 A theoretical analysis was also performed. To add a theoretical study to the experimental results, consider a representative volume element (RVE) model in which a single circular cross-section Fe-Co fiber is fully bonded to an epoxy matrix cylinder. The ratio of the radius of the Fe-Co fiber to the epoxy cylinder is (v ^f ) ^1/2, and the fiber volume content of RVE is v ^f , which is equivalent to the fiber volume content of the specimen. Non-patent document 18 shows the basic formula in the rectangular coordinate system Ox ₁ x ₂ x ₃ . The axis of easy magnetization of the Fe-Co fibers and x ₃ direction. Considering that the length of the composite material is much larger than other dimensions (width and thickness, or diameter) and that the easy axis of magnetization coincides with the length direction (easy axis), the longitudinal 33 magnetostriction deformation mode is dominant. Therefore, it can be assumed that the magnetoelastic constant d ′ ₃₃ depends on the x ₃ direction component (H ₃ ) of the magnetic field strength vector [Non-patent Document 19]. Here, the superscript f indicates a fiber. Considering the one-dimensional problem, the constitutive equation of Fe-Co fiber is given as follows.

Fe ₂₉ Co ₇₁ fibers show a heat treatment (850 ° C in a quench after 5 hours) has been Fe ₂₉ Co ₇₁ fibers, the properties of epoxy and Galfenol [Non-Patent Document 20] in Table II. It is assumed that the magnetic flux density induced by the inverse magnetostriction effect (biliary effect) is smaller than the bias magnetic field H ₀ = B ₀ / μ ₀ (μ ₀ = 1.2 × 10 ⁻⁶ H / m is the permeability of free space). Then, the stress and magnetic flux density of the Fe—Co fiber can be obtained as follows.

The strain and magnetic flux density of the epoxy matrix are given as follows using the superscript m.

Where N is the number of coil turns, A ^f is the cross-sectional area of the Fe-Co fiber,

Is the average stress acting on the specimen and t is the time. The secondary magnetoelastic coefficient is

Where m ^f is a constant indicating magnetostriction per unit magnetic field, r ^f is a constant indicating unit prestress / magnetostriction per unit magnetic field, and σ ₀ is prestress. Reference 21].

ここに、M_sは飽和磁化、lは粒径に関連する磁壁ジャンプ長さ（金属微細構造の不均質分布パラメータサイズ），Aは磁歪感受率や磁壁の数に関連する定数である。Kersten[非特許文献２３]によって検討されるように，式(8)のμ_０Ｍ_ｓも内部応力に依存する。さらに，純鉄の磁化中磁束漏れによるバルクハウゼンノイズ電圧（V_BHN）が粒度の逆平方根（すなわちｇ_ｇ ^−１／２）に比例するという報告もある[非特許文献２４]。 For the magnetic domain behavior model, the calculated value of Equation (7) is almost the same as the actual value in the case of Galfenol, but not in the case of the composite material. In this study, as shown by the following formula, a large magnetic domain wall velocity v _w For Fe-Co fibers are thought to induce a large magnetic flux density varies locally [Non-Patent Document 22].

Here, M _s is saturation magnetization, l is domain wall jump length related to grain size (heterogeneous distribution parameter size of metal microstructure), and A is a constant related to magnetostriction susceptibility and the number of domain walls. Kersten As discussed by [Non-Patent Document 23], μ ₀ M _s of formula (8) also depends on the internal stress. Furthermore, there is a report that the Barkhausen noise voltage (V _BHN ) due to magnetic flux leakage during magnetization of pure iron is proportional to the inverse square root of the grain size (ie, g _g ^−1/2 ) [Non-patent Document 24].

The results obtained are shown below. FIG. 7 shows the relationship between the output voltage density Vout / Alvf, the stress rate (dσ ⁰ ₃₃ ) / dt, and the maximum average stress σ _max of the Fe ₂₉ Co ₇₁ fiber / polymer composite material. For comparison, Galfenol results are also shown. In the region where the output voltage density of the composite material is large and the load speed is large, the value is about twice that of galphenol (Fig. 7 (a)). In addition, the output voltage density of the composite material changed depending on the load speed, and increased as the load speed increased. On the other hand, the output voltage density of Galfenol increases with increasing load speed, but tends to saturate. FIG. 7 (b) shows the residual stress dependence of the curve of output voltage density-load speed and output voltage density-maximum average stress, and the slope of the curve becomes maximum at residual stress σ ₀ = 2.8 MPa. Results were obtained. As a result, it is expected that there is an optimum value for the residual stress that maximizes the output voltage. Figure 8 predicts the effective magnetoelastic constant of Fe ₂₉ Co ₇₁ fiber / polymer composite, and for comparison also shows the results of a composite made using Galfenol and Fe ₂₉ Co ₇₁ fiber heat treatment. . The effective magnetoelastic constant of the composite material using Fe ₂₉ Co ₇₁ fiber was larger than that of Galfenol. Moreover, the effective magnetoelastic constant tended to improve dramatically by changing the volume content and the bias magnetic field. The predicted values are shown in Table 5.

FIG. 9 (a), it shows the measurement result of the length 15 mm, width 5 mm, distortion due to Fe ₂₉ Co ₇₁ magnetic field of the bulk and Galfenol thickness 3 mm (magnetostriction), the magnetostrictive characteristic of Galfenol is Fe ₂₉ Co ₇₁ Larger than bulk. Since Galfenol has coarse grains, the output voltage becomes relatively large at low load speed and stress level. On the other hand, the fine Fe ₂₉ Co ₇₁ bulk has discontinuous distribution of crystal grains and inhomogeneity of residual stress inside, and the energy of the domain wall is large, and it is necessary to promote the magnetization by moving the magnetic domain ( In the case of the composite material shown in FIG. 9 (b)), this can be easily achieved, and the dynamic magnetic domain behavior easily occurs to obtain a large output voltage. In FIG. 9 (a), the predicted results of the magnetostrictive characteristics of the magnetostrictive composite material are also shown by broken lines.

The conclusion is summarized from theoretical analysis and experimental results. In this study, we succeeded in developing a new magnetostrictive composite material that makes the best use of the characteristics of Fe ₂₉ Co ₇₁ fiber. In the manufacturing process, high crystallinity and magnetic anisotropy are imparted to the material, and the influence of the demagnetizing factor can be effectively reduced by the high aspect ratio of the fiber, increasing the inverse magnetostrictive effect of the magnetostrictive composite material. Is possible. In addition, the output voltage of the new composite material increased with the domain wall motion as the loading speed increased, and the results exceeded those of Galfenol.

Proposal of a model for dynamic domain behavior enables the identification of phenomenological factors peculiar to heterogeneous microstructures of polycrystalline Fe-Co, and the physics of magnetostriction observed in Fe ₂₉ Co ₇₁ fiber / polymer composites. Behavior was clarified. It was also shown that the output voltage could be further increased when heat-treated or thinner fibers were used. In addition, the magnetostriction constant d ₃₃ showed for the first time that the mutual interference between magnetic domain migration and heterogeneous grain distribution dominates the energy harvesting characteristics of Fe ₂₉ Co ₇₁ fiber / polymer composites. Future advances and developments in energy harvesting are expected by optimizing magnetostrictive composites that take advantage of the characteristics of Fe-Co fibers. Fe-Co has high strength and can withstand high temperatures, and can be a promising material not only for energy harvesting devices but also for sensors and actuators for extreme environments.

  The new material according to the present invention has strength (flexibility) and ultra-light weight, and also has a degree of freedom of molding and integration. Functional parts in the field of machinery and structures, for example, sports products (racquets) , Spikes, etc.), cars (vehicle bodies, tires, etc.), aerospace equipment (moving blade durbin, etc.), medical and welfare equipment, and in the future, can be applied to micro battery functions for wearable IoT devices. It is.

Claims (13)

A composite reinforced magnetostrictive composite material, which is made of an iron-based magnetostrictive alloy and has a residual stress and / or a thin plate embedded in a base material (matrix) as a filler. 2. The magnetostrictive composite material according to claim 1, wherein the iron-based magnetostrictive alloy is a magnetostrictive alloy having a Co-rich composition (Co = 69-79 at%). The magnetostrictive composite material according to claim 1, wherein the filler has a tensile residual stress, and the base material has a compressive residual stress. The magnetostrictive composite material according to any one of claims 1 to 3, wherein the filler is a secondary processed product obtained by drawing or rolling a forged material. The magnetostrictive composite material according to claim 1, wherein the base material is a polymer, a metal, or a ceramic. The magnetostrictive composite material according to claim 5, wherein the polymer is an epoxy resin. A method for manufacturing a magnetostrictive composite material, wherein a filler made of an iron-based magnetostrictive alloy is manufactured by a process of casting a base material while applying a prestress. 8. The method for producing a magnetostrictive composite material according to claim 7, wherein the iron-based magnetostrictive alloy is a magnetostrictive alloy having a Co-excess type composition (Co = 69-79 at%). The method for producing a magnetostrictive composite material according to claim 7 or 8, wherein the filler before the casting is subjected to a blunt heat treatment at 400 to 600 ° C. The method for producing a magnetostrictive composite material according to claim 7, wherein the filler is a secondary processed product obtained by drawing or rolling a forged material. The method for producing a magnetostrictive composite material according to claim 7, wherein the base material is a polymer, a metal, or a ceramic. The method for producing a magnetostrictive composite material according to claim 11, wherein the polymer is an epoxy resin. A leakage magnetic flux (inverse magnetostrictive effect) from a magnetostrictive filler during stress loading is detected by an electromagnetic induction coil installed outside the surface of the main body of the composite material according to any one of claims 1 to 6, and vibration power generation A power generation device designed to gain power.

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