EP0938671A1 - Procede et appareil permettant de mesurer directement la resistance de cables metalliques - Google Patents

Procede et appareil permettant de mesurer directement la resistance de cables metalliques

Info

Publication number
EP0938671A1
EP0938671A1 EP97942176A EP97942176A EP0938671A1 EP 0938671 A1 EP0938671 A1 EP 0938671A1 EP 97942176 A EP97942176 A EP 97942176A EP 97942176 A EP97942176 A EP 97942176A EP 0938671 A1 EP0938671 A1 EP 0938671A1
Authority
EP
European Patent Office
Prior art keywords
magnetic field
mechanical properties
cable
barkhausen
measuring
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97942176A
Other languages
German (de)
English (en)
Inventor
Mordechai Melamud
Gabriel Kohn
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Case Technologies Ltd
Original Assignee
Case Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Case Technologies Ltd filed Critical Case Technologies Ltd
Publication of EP0938671A1 publication Critical patent/EP0938671A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/725—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables by using magneto-acoustical effects or the Barkhausen effect

Definitions

  • the invention relates to a method and apparatus for measuring the mechanical properties, in particular yield strength, tensile strength and hardness, of metal cables or wires, in particular ferromagnetic cables or wires, during the production process or while in use, for lifting or conveying loads or supporting and transporting loads, for example in cable cars.
  • the method to which the invention relates is also applicable for detecting aging in static applications, such as in pre-tensioned reinforced concrete or controlling the properties of tubular steel products such as pipes, and in all cases in which it is possible to produce relative motion between a control apparatus and the ferromagnetic structure that is being controlled.
  • Barkhausen effect A phenomenon known as the Barkhausen effect has been described extensively in the literature, e.g., in the paper by Swartzendruber et al. (J. Appl. Phys. 67, No. 9, 5469-5471 (1990).
  • This effect consists of the large number of irreversible jumps in magnetization that occur while a ferromagnetic material is subjected to a varying magnetic field.
  • the jumps are due to the unpinning of domain wall structures from defects and impurities in the material.
  • As the applied field increases a wall breaks away from one pinning site and moves rapidly until stopped by another pinning site.
  • the resultant jumps in magnetization which have the characteristic of a noise signal, can be detected by suitable sensors as described, for example, by Swartzendruber and Hich ⁇ in a separate paper (Res. Nondestr. Eval (1993) 5, 41-50). Since the pinning sites of the domain walls, i.e., dislocations and impurities, also affect the mechanical properties of the steel, it is possible to correlate the Barkhausen signal with the mechanical properties of metals. Thus, the art describes the application of the Barkhausen effect to determine properties of metals based on relationships existing between the Barkhausen signals and said properties.
  • the Barkhausen signals are used to determine properties of steeL USP 4,689,558, 4,977,373 and 4,881,030 disclose the determination of residual stress or fatigue limit in steel and like materials, based on the Barkhausen signals.
  • USP 5,313,405 discloses a system for non-destructive evaluation of the surface characteristics of a magnetic material, comEprising probe to a sample of the material for applying an alternating magnetic field at a plurality of frequencies selected to excite Barkhausen domains at different levels, near but below the surface of the sample, means for detecting a complex Barkhausen response of the sample for more than one frequency, and processor means for analyzing the characteristics of said responses to isolate at least frequency and amplitude information from each response for determination of the surface characteristics of the sample.
  • Coercivity can be measured by recording the magnetization of the sample as a function of variable applied magnetic field (hysteresis loop); in this case, the coercivity is determined as the value of applied field at which the magnetization of the measured sample is zero.
  • the coercivity of ferromagnetic steel can also be estimated- hy the measuremeiit of the Barkhausen signal rate (BSR-) as a function of variable applied magnetic field. It can be shown that a maximum in the BSE. occurs near the coercive field as the applied field is changed.
  • metal cables may fail, due to one or more of the following causes: abrasion and crushing, due to contact of the cable with an abrading medium or to its being subjected to severe mechanical pressure; corrosion, due to corrosive environment; broken or cut strands, due to fatigue or mechanical damage, or to a high overload beyond the load-bearing capacity of the cable; shock loading or overroadihg; " and overheating or fatigue.
  • the method of the invention for measuring the mechanical properties, particularly yield strength and tensile strength, of ferromagnetic elongated structures, particularly cables comprises the following steps:
  • Barkhausen signals hereinafter also indicated by "BS"
  • BSR BS rate
  • the mechanical properties of the structure may be determined from the Barkhausen signals by calculation, if a definite functional relationship from said signals and said properties exists and is known. But in many cases this is difficult or even impossible. This may be true, for example, with reference to defects or damages that may affect a structure, and yet axe not related to the numerical value of a specific mechanical property. Therefore, in a preferred embodiment of the invention, the properties of the tested structure are determined by creating a series of reference samples, having the defects or having undergone the damages that are relevant and likely to have occurred in the particular tested structure, depending on the way it has been made, on its use and age, and on its history in general.
  • any tested structure is subjected to same procedure, the diagram referring to it is compared to those of the reference' samples, and ' it is ⁇ et ' ermined. which are the reference samples that are closest to the tested structure. If the diagram of this latter is practically ' the same or very close to that of a reference sample, this provides the required information, as the tested structure can be assumed to have substantially the same relevant properties as that reference samples. Otherwise, if the diagram of the tested structure is intermediate between those of two reference samples, the tested structure can be assumed to have properties intermediate between those of said two samples.
  • the Barkhausen sensor will measure the BSRs as a function of a magnetic field which varies only with time.
  • a device for measuring the field strength e.g., a Hall probe, will be provided and incorporated in the apparatus according to the invention.
  • the driving field is produced by at least an electromagnet fed with an alternating current, at least a sensor is provided" in - -fixed position with respect- t ⁇ " ' the electromagnet, the cable is stationary with respect to the apparatus unit constituted by the electromagnet and the sensor, and the time, with respect to which the BSR is measured, is recorded.
  • the dimensions of the electromagnet and of the sensor are also measured, as they determine the length of the cable element which is subjected to the BSR measurement during the time required to acquire the ⁇ m * ⁇ m ⁇ m needed amount of BS.
  • the relative speed of the cable with respect to said unit is measured, in addition to the dimensions of the electromagnet and of the sensor.
  • the magnetic field is generated by at least an electromagnet fed with an alternating current, and the magnetic field is therefore variable with time
  • at least a BS sensor is provided in a fixed position with respect to the electromagnet - viz. the apparatus unit constituted by the electromagnet and the sensor is the same as in the first form of the invention - but the cable is in motion with respect to said apparatus.
  • the measured BSR therefore, depends both on the instant value of the magnetic field and on the speed of the cable, with respect to the said apparatus unit.
  • the magnetic field is generated by permanent magnets and a string or row of sensors is spaced along the fl-sris of the magnet system,- which coincides with the axis of the cable.
  • the sensors are positioned at points at which the induced magnetic field has differe ⁇ f'values.
  • the applied field values will be pre- calibrated at the position of each sensor, so that it will be possible, though not necessary, to use a field strength measuring device.
  • the cable is in motion with respect to the apparatus constituted by the said magnets and the said string of sensors.
  • the string of sensors will provide, in their various measurements at different times, signals relative to different cable elements, since the cable is in motion along the axis of the apparatus with respect to the sensors.
  • Correct processing will permit to relate the signals to a certain cable element as it travels along the system at the different field values.
  • Processing the sensors'- output at time intervals, which are coordinated with their spacing and with the cable speed, will supply the data as a function of field for each cable element.
  • the same result can be achieved by periodically reading all sensors and rearranging the data by means of a computing unit.
  • the results of the measurements will consist of a set of values of BS at different values of the applied magnetic field.
  • the number of BS per seconds, viz. the BSR occurring at the sensor at a few, at least four, applied field values will be recorded. These will be fitted to a Gaussian type or similar function.
  • the location of the first moment (viz., the average) of this function with respect to the applied field is calculated by a computer.
  • the strength (UTS) or hardness of the tested cable section may be subsequently calculated by comparing the results to those obtained from a similar cable of known mechanical properties; or the other procedures explained hereinbefore may be resorted to.
  • the apparatus according to the invention comprises:
  • the apparatus preferably includes means for measuring its speed relative to the cable, generally for measuring the speed of the cable, if the apparatus is stationary, or that of the apparatus itself, if the cable is stationary.
  • Electromagnets may have a similar or any other convenient structure and shape.
  • each sensor comprises a number of individual sensor elements mounted on an am-mlar support which surrounds he ' traveling cable and is essentially coaxial ith it and several sensors, of such or of a different structure, are preferably positioned along the cable as a "string", at different field intensities.
  • the electromagnets or permanent magnets and the sensors are stationary and placed at any convenient position along the line, towards the end of it. If the invention is applied to a machine or equipment in which only a certain portion of a cable is unrolled from a support and re-rolled on it, such as in a crane, this is the portion that will be tested, preferably by means of a portable apparatus unit, according to the invention, placed in each case in the most suitable position. If the invention is applied to a stationary -cable, an apparatus unit that moves along the cable will be employed. In cable car and some other applications there are two types of cables: a stationary and a moving one. For each type, the appropriate testing apparatus - fixed or movable and of the appropriate shape - will be used.
  • Fig. 1 is a schematic representation in axial cross-section of an apparatus according to a first embodiment of the invention
  • Figs. 2a and 2b are schematic representations, in axial and transverse cross-section along plane A-A, respectively, of an apparatus according to a second embodiment of the invention
  • Figs. 3a, 3b and 3c are schematic representations, in axial and transverse cross-section along plane B-B and in perspective view, respectively, of an apparatus according to a third embodiment of the invention.
  • Fig. 4 is a schematic representation in axial cross-section of an apparatus according to a fourth embodiment of the invention.
  • Figs. 5a and 5b are schematic representations, in axial and transverse cross-section along plane C-C, respectively, of an apparatus according to a fifth embodiment of the invention.
  • Figs. 6a and 6b are schematic representations, in perspective view and transverse cross-section along plane D-D, respectively, of an apparatus according to a sixth embodiment of the invention, and Fig. 6c is a detail of Fig. 6b at an enlarged scale;
  • Figs. 7 to 10 are diagrams representing the BSR as a function of the inducing magnetic field intensity, for different tested structures; and Fig. 11 is a diagram showing a typical relationship of UTS or YS to the BSR peak position.
  • the apparatus comprises a single electromagnet 10, fed with alternating current, encircling the tested cable (not shown). 12 indicates a Barkhausen sensor.
  • the cable is in motion with respect to the apparatus, as ' indicated by arrow 15.
  • The-apparatus includes Relative Cable-Sensor Speed (RCSS) measuring unit 13 and a field strength measuring unit (e.g., Hall probe 14) to measure the magnetic field applied to the cable.
  • RCSS Relative Cable-Sensor Speed
  • Hall probe 14 field strength measuring unit
  • Figs. 2a and 2b illustrate another embodiment of apparatus, comprising a circumferential array of U-shaped AC electromagnets 20.
  • the apparatus includes an RCSS measuring unit 21 and a field strength measuring unit (e.g., Hall probe 22) to measure the magnetic field applied to the cable.
  • This apparatus is designed in such a way that it can be opened (split) in order to encircle an installed cable, as schematically shown in cross- section in Fig. 2b. It comprises at least two, but preferably six, as shown in the drawing, U-shaped electromagnets 20 of the same polarity, applying a homogeneous magnetic field along the cable axis. 23 designates a Barkausen sensor.
  • the apparatus has a casing 24 in two separable halves, for access to its components.
  • a third embodiment of the apparatus according to the invention comprises a number of permanent magnets 30. They are at least two, they fully encircle the cable (not shown) and are magnetized parallel to their axis. These are arranged along the path of the tested cable (not shown) with opposing magnetic poles facing each other, as designated by S and N in the drawing.
  • a few Barkhausen sensors 31 are spaced equally between the ⁇ magnets along the axis of the apparatus, viz. the -tested cable path,- at positions of known (preset) values of the applied magnetic field.
  • the magnets are ' ' spfi su that it is possible to open the apparatus, consisting of two halves 33, in order to encircle the tested cable.
  • a Relative Cable- Sensor Speed (RCSS) measuring unit 34 is placed inside the apparatus housing to measure the speed of the cable relative to the sensor. Both the magnets and sensors are mounted on adjustable mounts so as to fit various cable diameters.
  • FIG. 4 A further embodiment, slightly different from the previous one, of the apparatus of the invention is schematically shown in Fig. 4. It contains at least two DC electromagnets 40, Barkhausen sensors 41 and RCSS 42, mounted on a casing 43. This apparatus cannot be opened so as to be mounted around a cable, and is therefore intended to be used on the production line of wire ropes (not shown), or at least any other installation where the tested wire rope can be inserted through the apparatus.
  • a fifth embodiment of the apparatus of the invention is schematically shown in Figs. 5a and 5b. It comprises at least two circumferential arrays of U-shaped DC electromagnets 50, placed around the cable path and mounted on a casing 54, instead of the electromagnets of Fig. 4.
  • This apparatus can be opened, as it comprises a housing in two halves 51, and placed around an installed cable at any suitable test location. It also comprises Barkhausen sensors 52 and a RCSS 53.
  • Barkhausen Signal sensor units are" described in the Kterature (e.g.rL-J. Swartzendruber and G.E. Hicho, Res. Nondestr. EvaL (1993), 5, 41-50).
  • Each comprises a ferrite core in the shape of a toroid with a coil wound around it.
  • the toroid is ground flat on one side to provide a gap. This is an example of Barkhausen Signal sensor and there are differently built such sensors.
  • a circumferential assemblage sensor can be built of a few Barkhausen signal sensor units arranged on a ring.
  • One such arrangement is schematically shown in Figs. 6a, 6b and 6c, wherein 60 is the apparatus housing and 61 are the sensor xmits, one of which is shown at an enlarged scale in Fig. 6c.
  • An encircling sensor can consist of a coil wound around a cylindrical path in which the tested cable moves, and can be made according to the teaching of the above reference.
  • Fig. 7 shows a typical BSR.
  • the location (e.g., center of peak) of the BSR peak with respect to the applied magnetic field is directly related to the strength (UTS) of the cable or wire.
  • a wire or cable having low UTS will have its peak located at a smaller inducing magnetic field when compared with a similar wire with a higher UTS. This is illustrated in Fig. 8. .
  • The. curve in full .line refers to a metal sample having lower UTS than that of the sample to which the curve in broken lines refers.
  • the location of the center of the BSR peak with respect, to the applied field is linearly related to the strength of the cable, as shown in the diagram of Fig. 11..

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

Cette invention concerne un procédé et un appareil qui permettent de mesurer les propriétés mécaniques de structures allongées et ferromagnétiques, tel que des câbles, en mesurant les signaux de Barkhausen. Ce procédé consiste à générer un champ magnétique qui varie en fonction du temps ou de la position, puis à mesurer la cadence des signaux de Barkhausen en fonction du champ magnétique pour chaque section de la structure que l'on veut tester. Les propriétés mécaniques sont déterminées pour chaque section en fonction des signaux de Barkhausen par rapport ces dernières. Cet appareil comprend un système qui va générer un champ magnétique variable, plusieurs capteurs de signaux de Barkhausen qui sont répartis sur toute la longueur de la structure, ainsi qu'un système qui va comparer les signaux par rapport à chaque section testée.
EP97942176A 1996-11-07 1997-10-06 Procede et appareil permettant de mesurer directement la resistance de cables metalliques Withdrawn EP0938671A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
IL11957996A IL119579A (en) 1996-11-07 1996-11-07 Method and apparatus for the on-line measurement of the strength of metal cables
IL11957996 1996-11-07
PCT/IL1997/000323 WO1998020335A1 (fr) 1996-11-07 1997-10-06 Procede et appareil permettant de mesurer directement la resistance de cables metalliques

Publications (1)

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EP0938671A1 true EP0938671A1 (fr) 1999-09-01

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EP97942176A Withdrawn EP0938671A1 (fr) 1996-11-07 1997-10-06 Procede et appareil permettant de mesurer directement la resistance de cables metalliques

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Country Link
EP (1) EP0938671A1 (fr)
AU (1) AU4395797A (fr)
IL (1) IL119579A (fr)
WO (1) WO1998020335A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6750545B1 (en) 2003-02-28 2004-06-15 Amkor Technology, Inc. Semiconductor package capable of die stacking

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999056122A1 (fr) * 1998-04-27 1999-11-04 Case Technologies Ltd. Procede et appareil non destructifs et en ligne de determination des proprietes mecaniques de cables en acier inoxydable
ES2277751B1 (es) * 2005-07-19 2008-06-16 Fundacion Barredo Equipo para el control permanente y continuo de los cables de acero en instalaciones de transporte o de elevacion de personal y de materiales.

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60247155A (ja) * 1984-05-22 1985-12-06 Sumitomo Metal Ind Ltd 結晶粒度測定方法及び装置
JPS61148364A (ja) * 1984-12-22 1986-07-07 Sumitomo Metal Ind Ltd 材質異常検出方法及び装置
FR2692977B1 (fr) * 1992-06-26 1996-12-06 Aerospatiale Procede de controle non destructif d'une soudure.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9820335A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6750545B1 (en) 2003-02-28 2004-06-15 Amkor Technology, Inc. Semiconductor package capable of die stacking

Also Published As

Publication number Publication date
AU4395797A (en) 1998-05-29
WO1998020335A1 (fr) 1998-05-14
IL119579A0 (en) 1997-02-18
IL119579A (en) 2000-06-01

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