ES2278482B1

ES2278482B1 - Measuring device for direct measurement of magnetostriction volume of magnetic materials, comprises container holder with tight closing except for capillary section, where holder is filled with liquid

Info

Publication number: ES2278482B1
Application number: ES200402858A
Authority: ES
Inventors: Guillermo Rivero Rodriguez; Marta Multigner Dominguez; Javier Valdes Tamames
Original assignee: Universidad Complutense de Madrid
Current assignee: Universidad Complutense de Madrid
Priority date: 2004-11-26
Filing date: 2004-11-26
Publication date: 2008-06-16
Anticipated expiration: 2024-11-26
Also published as: ES2278482A1

Abstract

The device comprises a container holder with a tight closing except for a capillary section. The holder is filled with a harmless liquid after the sample is placed in the interior. The level of external magnetic fluid in the capillary varies, when the sample undergoes a change in volume due to a field of action. A computer program that controls the position of a digital camera mounted on a rigid vertical arm records this variation. The arm is moved by a motor, which conforms to the meniscus that the liquid forms in the capillary tangent with respect to the electronic monitor that produces the digital camera image. The capillary section is obtained by knowing the distance between the positions in the level of liquid in before and after applying magnetic field. The value of the magnetostriction volume represents the variation volume with respect to the relative intensity of the field.

Description

Dispositivo para la medida directa de la magnetostricción de volumen de materiales magnéticos.Device for direct measurement of the volume magnetostriction of magnetic materials.

Object of the invention

La presente invención se refiere a un sistema para medir magnetostricción de volumen de los materiales magnéticos con dos ventajas notables. En primer lugar se trata de una medida directa, y en segundo lugar permite la medida de esta propiedad en materiales con morfología muy variada.The present invention relates to a system to measure volume magnetostriction of magnetic materials With two notable advantages. First of all it is a measure direct, and secondly it allows the measurement of this property in materials with very varied morphology.

La invención se encuadra en el campo técnico de la medida de propiedades magnéticas de materiales.The invention falls within the technical field of the measurement of magnetic properties of materials.

Background of the invention

Existen diversos métodos para medir la magnetostricción lineal de los materiales, como por ejemplo mediante el uso de galgas extensiométricas, el método de ángulo bajo o del cantilever (P.T. Squire, Meas. Sci. Technol., 5, (1994)). Actualmente la magnetostricción de volumen se obtiene de modo indirecto a través de la medida de la magnetostricción lineal en las direcciones perpendicular y transversal al campo magnético aplicado (E. du Trémolet de Lacheisserie, Magnetostriction Theory and Applications of Magnetoelasticity, CRC Press Inc., Boca Raton (1993)). Además, existe la limitación de no poderse realizar este tipo de medidas sobre muestras en forma de polvo ya que las técnicas mencionadas anteriormente no son aplicables a este tipo de muestras.There are several methods to measure the linear magnetostriction of materials, such as by using strain gauges, the low angle or cantilever method (PT Squire, Meas. Sci. Technol., 5, (1994)). Currently, volume magnetostriction is obtained indirectly through the measurement of linear magnetostriction in the directions perpendicular and transverse to the applied magnetic field (E. du Trémolet de Lacheisserie, Magnetostriction Theory and Applications of Magnetoelasticity , CRC Press Inc., Boca Mouse (1993)). In addition, there is a limitation of not being able to perform this type of measurement on samples in powder form since the techniques mentioned above are not applicable to this type of samples.

Hasta donde nuestro conocimiento alcanza no existe ningún método de medida de la magnetostricción que sea directo y aplicable sobre cualquier tipo de muestra sólida. Con el fin de solventar estas limitaciones se ha ideado la presente invención.As far as our knowledge reaches not There is no method of measuring magnetostriction that is Direct and applicable on any type of solid sample. With the In order to solve these limitations, the present invention.

Description of the invention

El objeto de la presente invención es obtener el valor la magnetostricción de volumen de muestras de material sólido mediante la medida directa de la variación de volumen que experimenta la muestra al aplicarle un campo magnético. El método que se propone en la presente invención consiste en colocar la muestra en un recipiente portamuestras, rellenar el espacio libre restante con un líquido inerte y medir el volumen de líquido que es desplazado al dilatarse o contraerse la muestra. La magnetostricción de volumen es una magnitud relativa que toma valores típicos entre 10^{-7} y 10^{-5}. En el caso de nuevos materiales lo habitual es disponer de poco volumen de muestra, así por ejemplo una muestra con un volumen de 10 cm^{3}, podría variar su volumen al aplicarle un campo magnético entre 10^{-6} y 10^{-4} cm^{3}. Para poder medir una variación de volumen tan pequeña lo que se hace en este invento es obligar a que el desplazamiento del líquido ya mencionado solo pueda producirse por un capilar de sección conocida y pequeña, del orden de 5\cdot10^{-4} cm^{2}. De este modo la variación en el nivel del líquido del capilar es proporcional a la variación del volumen de la muestra. Así, con el ejemplo cuantitativo con el que estamos ilustrando la descripción, para una variación de volumen de 10^{-6} cm^{3} por un capilar de 5\cdot10^{-4} cm^{2} de sección tendríamos una variación en el nivel del líquido de 0,1 cm. La medida de esta variación de nivel se realiza enfocando una cámara digital sobre el menisco del líquido, cuya imagen se recibe en un monitor. Dicha cámara está montada sobre un brazo rígido que se desplaza verticalmente sobre un tornillo sin fin gracias a un motor paso a paso, que a su vez está controlado con un ordenador. Siguiendo el nivel del líquido en el capilar con la cámara y conociendo el paso mínimo del motor y el número de pasos, se obtiene la medida de la variación del nivel, y como la sección del capilar es conocida, multiplicando la sección de capilar por la variación del nivel se obtiene el valor de la variación de volumen experimentada por la muestra.The object of the present invention is to obtain the volume magnetostriction value of solid material samples by direct measurement of the volume variation that Experience the sample by applying a magnetic field. The method which is proposed in the present invention is to place the Sample in a sample holder, fill in the free space remaining with an inert liquid and measure the volume of liquid that is displaced when the sample is dilated or contracted. The volume magnetostriction is a relative magnitude that takes typical values between 10-7 and 10-5. In the case of new materials the usual thing is to have a small sample volume, as well for example a sample with a volume of 10 cm3, could vary its volume by applying a magnetic field between 10-6 and 10-4 cm3. In order to measure such a variation in volume small what is done in this invention is to force the displacement of the aforementioned liquid can only be produced by a capillary of known and small section, of the order of 5 · 10-4 cm2. Thus the variation in the level of capillary fluid is proportional to volume variation of the sample. Thus, with the quantitative example with which we are illustrating the description, for a variation in volume of 10-6 cm3 for a capillary of 5 · 10-4 cm2 of section we would have a variation in the liquid level of 0.1 cm. The measurement of this level variation is done by focusing a camera digital on the meniscus of the liquid, whose image is received in a monitor. Said camera is mounted on a rigid arm that is moves vertically on an endless screw thanks to a motor step by step, which in turn is controlled with a computer. Following the level of the liquid in the capillary with the chamber and knowing the minimum engine step and the number of steps, get the measure of the level variation, and as the section of the capillary is known, multiplying the capillary section by the level variation you get the value of the volume variation Experienced by the sample.

Description of the drawings

La invención se ilustra con los siguientes dibujos: \bullet La figura 1 muestra un esquema general de todo el sistema de medida con todos sus componentes:The invention is illustrated with the following Drawings: Figure 1 shows a general outline of the entire measuring system with all its components:

1.one.: recipiente portamuestrassample holder

2.2.: capilarcapillary

3.3.: piezas polares del electroimánpolar electromagnet parts

4.Four.: cámara digitaldigital camera

5.5.: monitormonitor

6.6.: brazo soporte de la cámara digitalarm digital camera support

7.7.: tornillo sin finendless screw

8.8.: motor "paso a paso"engine "Step by Step"

9.9.: ordenador personalpersonal computer

10.10.: nivel de referencia electrónicoreference level electronic

11.eleven.: bases móvilesmobile bases

12.12.: control electrónico del motor "paso a paso"electronic motor control "step Step"

13.13.: pie telescópicofoot telescopic

\bullet La figura 2 muestra un esquema del recipiente portamuestras 1:Figure 2 shows a diagram of the sample holder 1:

1414: tubo de entrada de líquidotube liquid inlet

15fifteen: tubo de purga de burbujastube bubble purge

16.16.: llave de pasostopcock

17.17.: llave de pasostopcock

18.18.: cuerpo cilíndricocylindrical body

19.19.: tapa roscadatop threaded

20.twenty.: tapa de cuarzo transparentetop transparent quartz

21.twenty-one.: tubo-soporte del capilarsupport tube capillary

22.22: extremo del pie telescópicotelescopic foot end

Embodiment of the invention

En una realización preferente del invento, el sistema consta de un recipiente portamuestras (1) estanco cerrado a excepción de un capilar (2) de 0.8 mm de diámetro. Este capilar es el único canal por el que se puede desplazar el líquido y es por tanto donde se controla el nivel del mismo. Se procede del siguiente modo: se coloca la muestra en el recipiente portamuestras (1) que se cierra con una tapa roscada (19) provista de una junta estanca y se rellena con un líquido por el tubo (14), asegurándose de que no queden burbujas de aire (que escapan por el tubo (15)), hasta que se detecta el menisco en el capilar (2) y se cierran las laves de paso (16, 17).In a preferred embodiment of the invention, the system consists of a sample holder (1) sealed closed to except for a capillary (2) of 0.8 mm in diameter. This capillary is the only channel through which the liquid can move and is by both where the level of it is controlled. It comes from the following mode: the sample is placed in the sample holder (1) that it closes with a threaded cover (19) provided with a seal and it is filled with a liquid through the tube (14), making sure that no air bubbles remain (escaping through the tube (15)), until the meniscus is detected in the capillary (2) and the laves are closed step (16, 17).

La verificación de que no quedan burbujas se realiza gracias a la tapa de cuarzo transparente (20). El recipiente portamuestras (1) se coloca entre las piezas polares de un electroimán (3) de modo que el capilar quede visible ajustando la altura del extremo del pie telescópico (22). Los materiales de las distintas piezas, preferentemente acero inoxidable no magnético, latón y pyrex, han sido elegidos para que no se vean afectados por el campo magnético externo. Con una cámara digital, provista de un objetivo óptico (4) se enfoca el menisco del líquido en el capilar (2) y se obtiene la imagen aumentada en un monitor (5). La cámara está montada sobre un brazo rígido (6) que se puede desplazar verticalmente sobre un tornillo sin fin (7).Verification that no bubbles remain performed thanks to the transparent quartz cover (20). He sample holder (1) is placed between the polar pieces of an electromagnet (3) so that the capillary is visible by adjusting the height of the telescopic foot end (22). The materials of the different parts, preferably non-magnetic stainless steel, brass and pyrex, have been chosen so that they are not affected by The external magnetic field. With a digital camera, provided with a Optical objective (4) focuses the meniscus of the liquid in the capillary (2) and the enlarged image is obtained on a monitor (5). The camera It is mounted on a rigid arm (6) that can be moved vertically on an endless screw (7).

Mediante un motor paso a paso (8), controlado a través del ordenador (9), se consigue un paso mínimo de 3.75 \mum. Se ha introducido una línea de referencia electrónica (10) en el monitor. De este modo, se ajusta la posición del menisco con la referencia electrónica antes de aplicar el campo y si la muestra posee propiedades de magnetostricción de volumen, al aplicar el campo magnético se detectan variaciones en la posición del menisco. El reajuste de la posición del menisco respecto a la referencia electrónica (10) se realiza desplazando la cámara (4), verticalmente, sobre el brazo rígido (6), mediante el giro del motor paso a paso (8) que transmite el movimiento al tornillo sin fin (7). La distancia entre las posiciones inicial y final de la cámara (4) se obtiene multiplicando el número de pasos del motor (8), necesario para reajustar la posición del menisco, por el cociente entre el paso de la hélice del tornillo sin fin (7) y el número de pasos por vuelta del motor (8). Esta distancia nos da la medida de la variación de la altura del líquido en el capilar (2), de sección conocida, y por lo tanto la variación de volumen que ha sufrido la muestra.Through a stepper motor (8), controlled by through the computer (9), a minimum step of 3.75 is achieved \ mum. An electronic reference line has been introduced (10) on the monitor In this way, the meniscus position is adjusted with the electronic reference before applying the field and if the sample it has volume magnetostricting properties, when applying the magnetic field variations in the position of the meniscus are detected. The readjustment of the meniscus position with respect to the reference electronics (10) is done by moving the camera (4), vertically, on the rigid arm (6), by turning the stepper motor (8) that transmits movement to the screw without end (7). The distance between the initial and final positions of the chamber (4) is obtained by multiplying the number of motor steps (8), necessary to readjust the meniscus position, by quotient between the pitch of the worm screw propeller (7) and the number of steps per engine turn (8). This distance gives us the measurement of the variation in the height of the liquid in the capillary (2), of known section, and therefore the volume variation that has suffered the sample.

Tanto el pie (11) del portamuestras (1) como el del tornillo sin fin (7) por el que se desplaza la cámara (4), se nivelan mediante tres tornillos regulables, situados en los vértices de un triángulo imaginario, que hacen las veces de puntos de apoyo de la misma, y que mediante un nivel unido a dicha plataforma permiten colocarla en posición horizontal, con el fin de ajustar el paralelismo entre ambos. También se ha dispuesto un termopar para controlar la temperatura, la cual debe ser constante durante la medida para evitar efectos de la dilatación del líquido.Both the foot (11) of the sample holder (1) and the of the worm screw (7) through which the chamber (4) moves, it level with three adjustable screws, located in the vertices of an imaginary triangle, which serve as points support thereof, and that through a level attached to said platform allow to place it in a horizontal position, in order to Adjust the parallelism between them. It has also arranged a thermocouple to control the temperature, which must be constant during the measurement to avoid effects of dilation of the liquid.

Si se tiene en cuenta que en esta descripción preferente el volumen del portamuestras (1) es 9,7 .10^{4} mm^{3} y la distancia mínima que se puede apreciar ópticamente en el monitor, 3,75 .10^{-2} mm (un orden de magnitud mayor que el paso mínimo), la mínima variación relativa de volumen que se puede medir en este sistema es \DeltaV/V= 4 .10^{-7}.If you consider that in this description Preferably, the volume of the sample holder (1) is 9.7 .10 4 mm3 and the minimum distance that can be seen optically in the monitor, 3.75 .10-2 mm (an order of magnitude greater than the minimum step), the minimum relative volume variation that can be measure in this system is ΔV / V = 4 .10-7.

Claims

1. Device for direct measurement of the volume magnetostriction of samples of magnetic materials, whatever their shape and in particular for samples in the form of dust, characterized in that it is formed by: A sample holder with the possibility of a tight seal except for an orifice connected to a capillary, which is the channel that allows to move a liquid contained in it, when the volume of the sample increases or decreases due to the application of an external magnetic field. A digital camera, which is fixed to a support, attached to the mechanism of a vertical endless screw supported on a mobile platform, which rotates regulates the height of said camera and allows to observe and follow in real time the level of the liquid in the capillary (meniscus) and whose output signal is sent to a monitor, provided with a horizontal reference level generated by an electronic circuit. A stepper motor, whose axis transmits the turning movement to the worm, controlled by an electronic circuit, which allows the step-by-step turning movement in opposite directions. The movement is controlled by an electronic circuit and a computer program, which records the steps performed by the engine. A telescopic foot that allows to regulate the height of the sample holder on its base, constituted by a mobile platform normal to said foot.

2. Device for direct measurement of the magnetostriction of the volume of magnetic materials, according to the preceding claim, characterized in that the sample holder is formed by:

A rigid container, made of non-material ferromagnetic, with a screw cap, provided with a gasket watertight

Two tubes, which communicate inside the container with the outside, made of non-material ferromagnetic, provided with stopcocks, attached to the container by welding and / or adhesives and allowing the injection of liquid and the evacuation of air from inside the container.

A third tube, which communicates inside the container with the outside, made of non-ferromagnetic material provided at its end with a transparent glass capillary, of uniform inside diameter, attached to the vessel by welding and / or adhesives.

3. Procedure for direct measurement of the magnetostriction of the volume of samples of magnetic materials, according to previous claims, characterized in that the sample is placed in the sample holder and filled with a liquid until the meniscus is detected in the capillary. The sample holder is placed between the polar parts of an electromagnet so that the capillary is visible. The height of the digital camera is varied, using a computer program that controls the steps of the motor that moves the worm, until the meniscus, which forms the liquid in the capillary, is tangent to the reference level of the monitor. The position of the camera is registered in the computer program. Then the external magnetic field is applied and if there is a variation of the height of the meniscus of the liquid in the capillary, the height of the digital camera is varied by the steps of the motor, which moves the worm, until said meniscus It is again tangent to the electronic reference level on the monitor. The steps taken by the engine to adjust the meniscus of the liquid in the capillary to the electronic reference level, are recorded by the computer control program, allowing, from the relationship between the passage of the motor and the passage of the screw without Finally, measure the variation of the height of said meniscus.

4. Procedure for the direct measurement of the volume magnetostriction of samples of magnetic materials, according to the preceding claim, characterized in that the measurement of the variation of the height of the meniscus of the liquid in the capillary of uniform internal diameter, allows to obtain a direct measurement of the variation in volume of the sample or samples contained in the container.

The measure of the volume variations of the sample or samples contained in the container, to which it is applied an external magnetic field, depending on the magnetic field applied, gives the direct measure of volume magnetostriction of said samples.