GB2068123A - Measuring changes of length of an elongate sample due to linear thermal expansion - Google Patents
Measuring changes of length of an elongate sample due to linear thermal expansion Download PDFInfo
- Publication number
- GB2068123A GB2068123A GB8002613A GB8002613A GB2068123A GB 2068123 A GB2068123 A GB 2068123A GB 8002613 A GB8002613 A GB 8002613A GB 8002613 A GB8002613 A GB 8002613A GB 2068123 A GB2068123 A GB 2068123A
- Authority
- GB
- United Kingdom
- Prior art keywords
- sample
- twin coil
- arrangement
- thermal expansion
- clamping
- 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.)
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/16—Investigating or analyzing materials by the use of thermal means by investigating thermal coefficient of expansion
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
Abstract
The device comprises a first clamping means 2 for clamping one end of the sample 1, and a pick-up head 4, 5, 6 containing a differential transformer, with a micrometer arrangement 6, 13 for adjusting the position of the differential transformer together with a clamp, closed by screw 12, for fixing it in the adjusted position. A mobile part includes a second clamping means 18 for clamping the other end of the sample 1 and causes support means 7, 17 having at its end a ferrite core 16, the ferrite core being situated within the differential transformer and movable therethrough as a consequence of linear thermal expansion of the sample, producing signals indicative of the amount of expansion. <IMAGE>
Description
SPECIFICATION
Arrangement for measuring and recording changes
of length of an elongate sample during an electrochemical process
The invention relates to an arrangement for
measuring and recording changes of length of an
elongate sample during an electrochemical process, for instance during galvanic metallizing or during
hydrogenation of metals.
It bases on a dilatometric method, the principle of which consists in that a coating is deposited on a strip-shaped orwire-shaped sample, or the sample
is exposed to hydrogenation, and its elongation or shortening is measured or automatically recorded in the course of these operations. The character and extent of the internal stress of the deposited coating or the intensity of penetration of hydrogen into the examined sample are determined from these longitudinal changes.As the internal stress of both the coatings and due to hydrogenation frequently rather impairs the original mechanical properties of the base material, the measuring of these values is not only important for the improvement of the quality of the proper coacting systems, but also for increasing the durability of metallized components and parts and of parts, where in the course of their manufacture or in operation a hydrogenation takes place.
A known arrangement for measuring and recording changes of length of elongate samples in electrochemical processes comprises a clamping frame for clamping the sample at its stable end, a stressing device acting on the mobile end of the measured sample by a constant prestress and a head enclosing an electric indicator of longitudinal changes of the sample. The mobile part of the electric indicator is firmly connected with the mobile end of the measured sample, the stable part of the indicator is connected to a nut of a micrometric screw and an axial rolling-contact bearing is provided between the stable part of the electric indicator and the nut of the micro metric screw. This known device with an electric indicator of deformations has a high sensitivity, but when measuring very fine deformations of the sample, the results are burdened by errors which are difficult to define.This is primarily due to its dependability on small changes of temperature causing harmful heat dilatations of parts of the apparatus. In addition it is solved so, that even in case of a very accurate manufacture it is impossible to achieve the required coaxiality of the mobile and stable part of the electric indicator. A further source of errors is that in the course of measuring the vertical position of the stable part of the indicator is fixed by pressure of a spring on a flange of the indicator case, which rests on an axial roller bearing of a micrometric nut. Slight inaccuracies of the screw connection of the roller bearing and of face parts of springs are causing even at slight vibrations of the apparatus unwelcomed slight shiftings of the stable part of the indicator.
Finally, further errors difficult to define are caused if the measured sample is not complely submerged in the measured bath. A consequence thereof is, that a part of the sample in the atmosphere above the level of the bath is subject to parasitic heat dilatations generated by slight changes of the temperature of this atmosphere. The possibility of utilizing the high sensitivity of the electric indicator is therefore at the known apparatus limited and the apparatus needs an elaborate tempering requiring long time.
It is an object of this invention to substantially reduce these drawbacks of arrangements for measuring and recording changes of length of an elongate sample during electrochemical operations by the provision of an arrangement comprising a clamping frame for clamping the stable end of the measured sample, a stressing device acting on the mobile end of the measured sample by a constant prestress and a head enclosing an electric indicator of changes of length of the sample including a twin coil, the mobile part of the electric indicator being connected to a micrometric nut, an axial rolling bearing being situated between the stable part of the electric indicator and the nut, to the supporting part of the arrangement at the centre of the twin coil fixing means for the twin coil are provided, and a relief spring is inserted between a stable case of the electric indicator and the axial bearing of the micrometric nut, the supporting parts and the mobile parts of the arrangement transmitting changes of length of the sample to the electric indicator being made of the same material with a coefficient of thermal expansion from 1 x10 7 to 5x10-6 C 1, It is advantageous if the shank on which the mobile part of the electric indicator is fixed, is made of molten quartz, as thus unwelcomed axial shifts of the core due to thermal expansion of the shank are prevented.
In order to protect against sudden changes of temperature and against corrosive influence of the ambient atmosphere it is advantageous if the supporting stand and the cylindrical support of the arrangement are provided with a protective cover.
The invention will be explained in more detail, by way of example, with reference to the accompanying diagrammatic drawing, in which:
Fig. 1 is an overall elevational view of the whole dilatometric arrangement, where as electric indicator an induction pick-up device is provided,
Fig. 2 is a sectional elevation of the head of the arrangement, and
Fig. 3 is a cross-section through this head.
The illustrated arrangement for measuring a sample 1 comprises a clamping frame 2, 3, supporting parts 4,5,6 and an internal mobile part 7, which is partly shown in broken lines. An accurate coaxiality is secured by the cylindrical arrangement of the supporting and mobile parts, and the disturbing influence of variations of temperature is suppressed in that all parts are made of the same material with a low coefficient of thermal expansion, for instance of an alloy "Invar". Variations of temperature in the course of the measuring cause therefore only small changes of length of supporting parts 4,5,6 and of
the mobile part 7 and as their working length is
approximately equal, these dilatations are mutually
compensated.
Fig. 2 shows a pick-up head of the apparatus. The twin coil 8 of the pick-up device is fixed in a case 9 which must be made of non-magnetic material, for
instance of brass. The case 9 is therefore subject to substantial thermal expansion. In order to suppress the disturbing effect of this thermal expansion, the fixing of the initial vertical position of the twin coil 8 with respect to the supporting stand 4 is according to this invention solved by means of arrestment. The solution consists in that the upper part of the stand 4 is arranged as a clamp 10, enabling clamping of the case 9 by means of a resilient clamp 11 and by an arrestment screw 12. The clamp 11 is situated at the centre of the twin coil 8 of the pick-up device.By clamping the clamp a firm connection of the case 9 with its supporting part 4 is established solely at the place of the twin coil 8, whereas the lower and upper part of the case 9 can expand freely. When the micrometric nut 13 is released, the whole mechanical transmission from the supporting part 6 by way of its thread connection withtns ake micrometric nut 13, of the axial bal bearing 14to ahe case 9, releaved by the spring 15 is disconnec sd, slirninating thus unwelcomed fine snifEings of tile twin coil 8, due to imperfections of threads end owt the bail bearing 14 and also by thermal expansion of the whole system and of the brass case 9, which can be defined with difficulties. The micrnmetrc nut 13 serves here therefore solely for calibration of the apparatus orto determine the linear limits of the used pick-up device and in addition for an accurate adjustmentofthe vertical zero position of the twin coil 8 of the pick-up device with respect to its ferrite core 16.
A shank 17 supporting the ferrite core 16 of the pick-up device is fixed coaxially on the upper end of the mobile part7 of the apparatus. For principal reasons this shank 17 is also made of non-magnetic material, similarly as the case 9 of the pick-up device.
Non-magnetic metal materials have always a substantial thermal expansion and the use of a metallic shank 17 for the ferrite core 16 would cause unwelcomed axial shifts of the core 16 due to thermal expansion of the shank 17. The shank 17 is therefore according to this invention made in the shape of a ground cylinder of molten quartz, the coefficient of thermal expansion of which is even lower than that ofthe alloy "lnvar".
Actually occuring measuring errors, caused by an
incomplete submerging of the clamped sample in the
measured bath are according to this invention eliminated by perfect insulation of the upper clamping device 18. It consists in that the upper part of the clamping device is fixed in a coaxial insulating sleeve and the space between both parts is filled with insulating material, for instance with dentacryl.
After clamping of the sample by means of a clamp of
stainless steel, the clamp is insulated by application
of a teflon cover. This method enables complete
submerging of the sample even into a very aggres
sive bath.
The outlets 21 of the twin coil 8 are connected by
means of flexible insulating conductors 19 with the contacts of a connector 20 fixed on the cylindrical support 5. In order to eliminate errors due to sudden changes oftemperature of the laboratory or working atmosphere, the upper part of the apparatus is according to this invention protected by a cover 22 of transparent material, for instance of perspex. The cover 22 is applied to the apparatus just prior to the proper measuring and serves as heat insulation of parts of the apparatus and as protection against the effects of the ambient atmosphere which, in most cases, is aggressive.
The clamping frame 2,3 is made to be easily exchangeable, the material of the suspension rods 3, insulated by teflon tubes being selected according to the scope of the measurement. For current measurements, particularly for control measurements of operation, the suspension rods 3 are made of the same material as the measured sample 1, in which case variations of the temperature of the examined bath can be neglected as the disturbing thermal expansion of the sample 1 and of the suspension rods 3 are mutually compensated.For accurate measurements the suspension rods 3 are made of a material with a low coefficient of therma expansion; in that case the temperature of the examined bath is in the course of measurements controlled and when evaluating results correction is made due to different thermal expansion of the sample 1 and of the suspension rods 3.
Afinal condition for the elimination of actually occurring errors at measurements is an exactly coaxial fixing of the ferrite core 16 on its shank 17 of molten quartz. A simple assembling appliance is used according to this invention for this purpose, which is not shown in the drawing and which enables accurate coaxial glueing of the ferrite core 16 on the shank 17 of molten quartz directly in the apparatus.
The glueing is performed prior to assembling of the upper part of the apparatus and prior to fixing of the twin coil 8 of the pick-up device in the internal space of the case 9. The assembling appliance is substantially a piston, the external diameter of which is equal to the bore of the case 9. A blind opening of a diameter equal to the diameter of the ferrite core 16 is made in the lower face part of the piston. The depth of the opening is such that after inserting the core 16 into this opening, the core 16 extends by about 1 mm above the face of the piston. A screw is screwed into the upper face of the piston, which pas sesfreelythroughthe upperopening ofthe case 9.
When assembling, a thin film of glue is applied on the upper face of the shank 17 and on the extending face wall of the core 16 which is inserted into the piston, the piston with the core 16 is introduced into the case 9 and the case 9 together with the piston is carefully inserted into the bore of the clamp 10 until the coaxially situated core 16 reaches the shank 17.
After complete hardening of the glue the case 9 with the piston are carefully removed.
The device for initial auxiliary prestressing of a strip-shaped or wire-shaped sample 1 is similar to that used in a known apparatus. Only the prestressing nut 23 and in broken lines the guiding piston with the guiding rod 7 are shown in Fig. 1 for information. The prestress is here also first adjusted by means of the prestressing nut 23, which compresses a calibrated compression spring situated below the guiding piston. The strip-shaped orwire-shaped sample 1 is thereafter coaxially clamped between the upper clamp 18 and the lower clamp 2 and after release of the nut 23 the apparatus is prepared for neasuring.
The arrangement according to this invention operates as follows:
Prior to the proper measurement a heat adjustment of the apparatus to the temperature of the measured medium, for instance of a galvanic bath, is made. According to the kind of the bath eithertempering outside the bath or directly in the bath is used, while the whole clamped sample 1 is submerged in the bath. The outlet 21 of the twin coil 8 is connected to an amplifier operating with a carrier frequency 5 to 8 kHz, on the output of which a measuring or recording device is connected, for instance a coordinate recorder. By turning the micrometric nut 13, the zero position of the twin coil 8 with respect to a microampermeter is adjusted.A perfect tempering of the apparatus is achieved if this position remains stable even if the amplifier is switched overto its highest sensitivity. The impedance bridge of the amplifer is thereafter balanced, the position of the twin coil 8 of the pick-up device is stabilized by the arrestment screw 12, the micrometric nut 13 is loosened and the insulating cover 22 is put in place. Thus the whole arrangement is prepared for automatic recording of the time course of deformations of the sample.
The high sensitivity and stability of the measurement of the apparatus according to this invention enlarges the possibilities of its utilization. The apparatus can be used for the measurement of internal stresses of all kinds of galvanic coatings in the course of their deposition on different base materials, for coating of not only currently used or large thicknesses, but also of very thin coatings below 1 ,am. The possibility of utilizing the apparatus is extended also for measurements of internal stresses of oxide coatings formed for instance during electrolytic oxidation of aluminium and of its alloys. Of practical importance is the possibility of continuous measurements of internal stresses and changes of volumes of galvanic, oxide and organic coatings and changes of volume of different materials occurring in the course of their ageing.The extent of application of the apparatus according to this invention is furthermore increased for continuous measurements of the intensity of hydrogenation of metals proceeding particularly in the course of different treatments, for instance at pickling, cathodic degreasing and in the course of the proper creation of coatings and measurements of absorption of hydrogen from hydrogenated metal in the course of the dehydrogenation process or in the course of ageing.
The apparatus can therefore be used for operational checking of pickling, degreasing and galvanizing baths either directly after preparation and also in the course of their ageing in operation; it is also of importance for the determination of the causes of formation of defective coatings and forthe determination of the highest permissible internal stress in individual concrete cases.
In research it is indispensible for the formulation of new types of baths, particularly for the determina- tion of the influence of functional admixtures and pollutions and of the influence of working conditions. It is applicable in addition to present research methods aiming at widening the knowledge e.g.
about the mechanism of hydrogenic embrittlement of metals, about the influence of different inhibitors and promoters of hydrogenation, and about the influence of galvanic metallizing on mechanical properties of metallized parts. As the apparatus according to this invention is actually a top apparatus of its kind, its additional possibilities of application will be more apparent after it has been more widely used in research.
Claims (8)
1. An arrangement for sensing changes of length due to thermal expansion of an elongate sample subjected to an electrochemical process, the arrangement comprising a first clamping means for clamping one end ofthe sample, a pick-up head containing a twin coil including two coaxial axially spaced coils, means for the adjustment of the twin coil, means for arresting the twin coil in the adjusted position, and a mobile part including a second clamping means for clamping the other end of the sample, support means carried by the second clamping means, and a ferrite core carried by the support means, the ferrite core being situated within the twin coil and movable therethrough as a consequence of linear thermal expansion of the sample, the arrangement including a prestressing device acting on said other end of the sample to keep the same taut, wherein the clamping means, the pick-up head and the support means are made of material having a thermal coefficient of linear expansion between 1x10-7 and 5x106 'C1.
2. An arrangement according to Claim 1 wherein the means for the adjustment of the twin coil include a threaded sleeve carrying an adjustment nut, an axial bearing biased by a spring and a case containing the twin coil.
3. An arrangement according to Claim 1 or 2 wherein the means for arresting the twin coil include an arresting ring controlled by an arresting screw.
4. An arrangement according to any one of the preceding claims wherein the core is carried by a shank made of molten quartz, which forms part of the support means.
5. An arrangement according to any one of the preceding claims wherein the pick-up head is provided with a protective cover.
6. An arrangement for sensing changes of length due to thermal expansion of an elongate sample subjected to an electrochemical process, the arrangement being constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawing.
7. A device for measuring and/or recording changes of length due to thermal expansion of an elongate sample subjected to an electrochemical process, the device comprising an arrangement according to any one of the preceding claims and including an amplifierthe inputofwhich is connected to the outout of the twin coil, and the output of which is connected to the input of a measuring and/or recording device.
8. A device according to Claim 7 constructed, arranged and adapted to operate substantially as herein described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8002613A GB2068123A (en) | 1980-01-25 | 1980-01-25 | Measuring changes of length of an elongate sample due to linear thermal expansion |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8002613A GB2068123A (en) | 1980-01-25 | 1980-01-25 | Measuring changes of length of an elongate sample due to linear thermal expansion |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2068123A true GB2068123A (en) | 1981-08-05 |
Family
ID=10510900
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8002613A Withdrawn GB2068123A (en) | 1980-01-25 | 1980-01-25 | Measuring changes of length of an elongate sample due to linear thermal expansion |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2068123A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4811601A (en) * | 1983-10-11 | 1989-03-14 | Tolan Peter J | Method and apparatus for measuring the change in volume with change in temperature of liquid in tanks |
| US5248200A (en) * | 1992-10-16 | 1993-09-28 | The United States Of America As Represented By The Secretary Of The Army | Portable asphalt stress and strain measuring device |
| US5826983A (en) * | 1995-07-11 | 1998-10-27 | Seiko Instruments Inc. | Thermomechanical analyzer equipped with a thermogravimetry function |
| US6672759B2 (en) * | 1997-07-11 | 2004-01-06 | International Business Machines Corporation | Method for accounting for clamp expansion in a coefficient of thermal expansion measurement |
| US7104680B2 (en) * | 2003-10-31 | 2006-09-12 | Sii Nanotechnology Inc. | Thermal analyzer with gas mixing chamber |
| CN101261214B (en) * | 2007-03-09 | 2011-07-20 | 崔兆星 | High-temperature high pressure dilatometer |
| DE102012212759B4 (en) | 2012-07-20 | 2022-04-28 | Dr. Johannes Heidenhain Gmbh | Device for measuring the linear dimension of a sample |
-
1980
- 1980-01-25 GB GB8002613A patent/GB2068123A/en not_active Withdrawn
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4811601A (en) * | 1983-10-11 | 1989-03-14 | Tolan Peter J | Method and apparatus for measuring the change in volume with change in temperature of liquid in tanks |
| US5248200A (en) * | 1992-10-16 | 1993-09-28 | The United States Of America As Represented By The Secretary Of The Army | Portable asphalt stress and strain measuring device |
| US5826983A (en) * | 1995-07-11 | 1998-10-27 | Seiko Instruments Inc. | Thermomechanical analyzer equipped with a thermogravimetry function |
| US6672759B2 (en) * | 1997-07-11 | 2004-01-06 | International Business Machines Corporation | Method for accounting for clamp expansion in a coefficient of thermal expansion measurement |
| US7104680B2 (en) * | 2003-10-31 | 2006-09-12 | Sii Nanotechnology Inc. | Thermal analyzer with gas mixing chamber |
| CN101261214B (en) * | 2007-03-09 | 2011-07-20 | 崔兆星 | High-temperature high pressure dilatometer |
| DE102012212759B4 (en) | 2012-07-20 | 2022-04-28 | Dr. Johannes Heidenhain Gmbh | Device for measuring the linear dimension of a sample |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |