GB2037430A - Method of indirect measurement of bolt or screw pre- stressing - Google Patents
Method of indirect measurement of bolt or screw pre- stressing Download PDFInfo
- Publication number
- GB2037430A GB2037430A GB7943180A GB7943180A GB2037430A GB 2037430 A GB2037430 A GB 2037430A GB 7943180 A GB7943180 A GB 7943180A GB 7943180 A GB7943180 A GB 7943180A GB 2037430 A GB2037430 A GB 2037430A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bolt
- screw
- ultrasonic
- probe
- stressing
- 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- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
- B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
- B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
- B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
- B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
- B25B23/142—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for hand operated wrenches or screwdrivers
- B25B23/1422—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for hand operated wrenches or screwdrivers torque indicators or adjustable torque limiters
- B25B23/1425—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for hand operated wrenches or screwdrivers torque indicators or adjustable torque limiters by electrical means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/24—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed
- G01L5/246—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed using acoustic waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02827—Elastic parameters, strength or force
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/26—Scanned objects
- G01N2291/269—Various geometry objects
- G01N2291/2691—Bolts, screws, heads
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- General Physics & Mathematics (AREA)
- Force Measurement Appropriate To Specific Purposes (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The pre-stressing of a bolt or screw (3) is measured by determining ultrasonically the expansion of the bolt or screw caused by stressing. The change of length is determined in a computer (9) from the time difference for the pulse before and after tightening of the bolt or screw. This change of length is compared with a test bolt or screw subject to the same pre-stressing. An ultrasonic probe 4 5) or an electrodynamic probe may be used, the probe being connected via an ultrasonic unit (8) to the computer (9). <IMAGE>
Description
SPECIFICATION
Method of indirect measurement of bolt or screw pre-stressing
The present invention relates to a method of indirectly measuring bolt or screw pre-stressing by means of ultrasonic pulse echo technique.
Pre-stressing of a bolt or screw (e.g., of cheesehead orfillister-head bolts) is usually determined directly by measuring the tightening torque. This method makes it necessary to accept a scatter range of + 25% which is mainly because the friction coefficient at the underside of the bolt or screw head is a function of external conditions (rust, lubrication etc.). For quantity production, this must be looked upon as an unsatisfactory state of affairs.
An object of the present invention is to provide a method and apparatus permitting faster and much more precise determination of bolt prestressing.
The invention provides a method of indirectly measuring bolt or screw pre-stressing by means of an ultrasonic pulsed echo technique, wherein the length of a test bolt or screw is determined before and after applying a certain pre-stress by means of a tensile machine on the basis of the time delay of an ultrasonic pulse, the change in length is determined by deriving the difference from both lengths, the pre-stressing force of a bolt or screw intended for installation which is of the same type as the test bolt or screw is increased by tightening until the relative change in length determined on the basis of the echo time delay by the ultrasonic pulse is identical with the relative change in length of the test bolt determined in the tensile machine, the ultrasonic unit being calibrated for the sound velocity in the material of the unloaded bolt or screw.
This method makes it possible to narrow down the deviations of the actual pre-stress from the desired pre-stress to a value of + 5% instead of + 25% obtained with conventional methods. This has been made possible by making the method independent of uncertain factors, such as the friction coefficient which tends to vary widely according to the properties of the bolt or screw face. The dependency of the method according to the invention on the sound velocity in the bolt or screw material is avoided by calibrating the ultrasonic equipment for the sound velocity in the bolt or screw in the unloaded state.Afurther advantge of this method is the use of standard full-shank bolts or screws instead of the more expensive elasticated or necked-down bolts or screws because accurate information is provided
on the pre-stress achieved and therefore the user
need not fear any loosening of the bolts or screws due to alternating or cyclic stressing.
The invention further provides apparatus for
carrying out the above-described method and
comprising an ultrasonic probe arranged in a socket interposed between, in use, a bolt or screw
head and a ratchet concentrically arranged with
the socket, the ultrasonic probe being urged in use against the bolt or screw head via a spring with the interposing of a coupling medium, the probe being connected via an ultrasonic unit a with a computer.
Apparatus of this type permits bolts or screws
to be tightened reliably and without any additional time being required so that they are subjected to a
preset pre-stress. This is achieved by measuring the difference in the time it takes for the ultrasonic pulses from the probe to travel through the bolt or screw, these differences being fed after prior amplification to the ultrasonic unit and the computer calculating the elongation of the bolt or screw from which the pre-stress results. In other
words, the operator only has to apply some coupling medium to the bolt or screw head before applying the socket and to tighten the bolt or screw until the computer indicates a certain elongation of the bolt or screw.
Alternatively, an electro-dynamic probe is arranged in a socket interposed between, in use, a bolt or screw head and a ratchet and concentrically arranged with the socket, an air gap being provided, in use, between the probe and the bolt or screw head, the probe being connected via an ultrasonic unit with a computer.
This type of apparatus operates without a coupling medium but otherwise affords the same advantages as the afore-mentioned apparatus. As an additional advantage, it may be used at elevated temperatures (above 330 Kelvin) because only a small air gap is necessary for coupling in place of the heat-sensitive coupling medium.
The invention will now be described with reference to an embodiment shown by way of example in the accompanying drawings, in which
Fig. 1 is a section through a socket and probe placed on a bolt or screw head, and
Fig. 2 is a calibration chart to determine the bolt or screw pre-stressing force.
In Fig. 1 a bolt or screw 3 is tightened by means of a ratchet 1 carrying a socket 2. Inside the socket 2, there is a probe 4 (which in the illustrated embodiment is an ultrasonic probe 5) which is pressed by means of a spring 6 against a head 7 of the bolt or screw 3. When the ultrasonic probe 5 is used, the bolt or screw head 7 would be coated with a coupling medium before the socket is placed thereon. The probe 4 is connected via an ultrasonic unit 8 to a computer 9 which, in quantity production, provides control of the socket and prevents continued tightening of the bolt or screw 3 when a predetermined value is attained.
In more straightforward cases, an ultrasonic unit is sufficient where the elongation of the bolt or screw 3 is indicated and the operator knows by comparing the elongation of a bolt or screw of the same type in a tensile machine when the desired pre-stressing force has been attained.
In place of the ultrasonic probe 5, it is possible to use an electro-dynamic probe employing the principle of megneto-striction where no coupling medium is used but coupling is provided via an air gap with the whole system otherwise remaining unchanged.
Fig. 2 shows a calibration chart where the change Al in the length of the test bolt or screw is plotted against the force F applied by a tensile machine. Calibration is effected in such a manner that a test bolt or screw which is identical with the bolts or screws to be installed in quantity production is clamped in a tensile machine with the same length of constraint as in the installed condition and a load is applied. Now the change in length Al of the bolt or screw is determined as a function of the force F by means of an ultrasonic probe and an ultrasonic unit.The bolt or screw of the same type intended for installation need therefore be subjected only to the elongation Al which can be taken from the calibration chart and measured by means of the apparatus according to the invention during tightening in order to attain a certain pre-stressing force.
For a better understanding of the functioning of the proposed process and apparatus the theoretical background will now be discussed.
The proposed method is based on the fact that, as a bolt or screw is pre-stressed, elongation occurs which according to Hook's law is proportional to the pre-stressing. Measurement of this elongation is by means of ultrasonic waves which are applied tO the bolt or screw head to pass through the bolt or screw and to be reflected at its end. From the time it takes the waves to travel through the bolt or screw, it is possible to determine the length of the bolt or screw, a fact to be borne in mind being that the sound velocity V(T is a function of the stress. Let V0 be the sound velocity in the unstressed state, then Va is obtained by v= VO (1 + a . a)
(1).
In this formula a is also a material constant. If then a bolt or screw of the length 1 is extended by the stress a by an amount of Awl ,then a difference At in elapsed tirhe is obtained as follows:
Basing on Hook's law which in converted form reads:
the approximation formula is obtained:
with a .a 1 and a E. The material constants vO, E occurring in this formula are known or can easily be determined, but not a. The reasons for the change in sound velocity which is a function of Young's modulus, density and Poisson's ratio are difficult to determine in order to calculate a. Therefore, it is better to determined the direct relationship between At and Al by testing. Having regard to usual techniques, it is not At which is relied upon but the shift As is of the echo to be observed on the screen of the ultrasonic unit referred to the pulse emitted. This shift As is proportional to At.
The factor b is an equipment constant of the ultrasonic unit and is the scanning speed of the electronic beam on the lines of the screen.
The factor 2 appearing in the formulae 2, 3, 4 is
usually omitted because the equipment used for ultrasonic testing is arranged so that the factor 2 resulting from double the path which the sound covers on reflection is already incorporated in the unit. For a better understanding of the actual magnitudes occurring, the factor 2 has been included in the formula.
Claims (5)
1. A method of indirectly measuring bolt or screw pre-stressing by means of an ultrasonic pulsed echo technique, wherein the length of a test bolt or screw is determined before and after applying a certain pre-stress by means of a tensile machine on the basis of the time delay of an ultrasonic pulse, the change in length is determined by deriving the difference from both lengths, the pres-stressing force of a bolt or screw intended for installation which is of the same type as the test bolt or screw is increased by tightening until the relative change in length determined on the basis of the echo time delay by the ultrasonic pulse is identical with the relative change in length of the test bolt determined in the tensile machine, the ultrasonic unit being calibrated for the sound velocity in the material of the unloaded bolt or screw.
2. A process for indirect measurement of bolt or screw pre-stressing by means of an ultrasonic pulsed echo technique, substantially as herein described with reference to the accompanying drawing.
3. Apparatus for carrying out the method as claimed in claim 1 or 2, comprising an ultrasonic probe arranged in a socket interposed between, in use, a bolt or screw head and a ratchet concentrically arranged with the socket, the ultrasonic probe being urged in use against the bolt or screw head by a spring with the interposing of a coupling medium, the probe being connected via an ultrasonic unit with a computer.
4. Apparatus for carrying out the method as claimed in claim 1 or 2, wherein an electrodynamic probe is arranged in a socket interposed between, in use, a bolt or screw head and a ratchet and concentrically arranged with the socket, an air gap being provided, in use, between the probe and the bolt or screw head, the probe being connected via an ultrasonic unit with a computer.
5. Apparatus for carrying out the method with reference to the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19782853988 DE2853988A1 (en) | 1978-12-14 | 1978-12-14 | METHOD FOR INDIRECTLY MEASURING THE BOLT TENSION |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2037430A true GB2037430A (en) | 1980-07-09 |
Family
ID=6057171
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7943180A Withdrawn GB2037430A (en) | 1978-12-14 | 1979-12-14 | Method of indirect measurement of bolt or screw pre- stressing |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5582935A (en) |
| AU (1) | AU5380279A (en) |
| DD (1) | DD147642A1 (en) |
| DE (1) | DE2853988A1 (en) |
| DK (1) | DK532079A (en) |
| FR (1) | FR2444267A1 (en) |
| GB (1) | GB2037430A (en) |
| NL (1) | NL7908910A (en) |
| RO (1) | RO81473B (en) |
| SE (1) | SE7910209L (en) |
| ZA (1) | ZA796758B (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2165050A (en) * | 1984-09-26 | 1986-04-03 | Univ City | Non-destructive ultrasonic testing of structures to measure stress |
| US5058439A (en) * | 1990-06-06 | 1991-10-22 | The Babcock & Wilcox Company | Ut socket assembly |
| EP0683394A1 (en) * | 1994-05-18 | 1995-11-22 | Facom | Device for attaching a measuring instrument on a screw head |
| US5589640A (en) * | 1996-04-03 | 1996-12-31 | Butler; Patrick J. | Method for detecting changes in preload on a tie rod installed as part of a core shroud repair in a boiling water reactor |
| EP0967053A2 (en) * | 1998-05-14 | 1999-12-29 | Atlas Copco Tools Ab | Method for determining the axial load in a threaded fastener when tightened above its yield point |
| US6314817B1 (en) | 1998-05-14 | 2001-11-13 | Atlas Copco Tools Ab | Method for tightening a threaded fastener above its yield point |
| GB2370121A (en) * | 2000-08-29 | 2002-06-19 | Fraunhofer Ges Forschung | Ultrasonic monitoring and controlling of a screwing process |
| CN102262021A (en) * | 2010-05-28 | 2011-11-30 | 上海宝冶工程技术有限公司 | Torque force testing device for large-sized bolt |
| EP2806257B1 (en) * | 2013-05-20 | 2020-06-03 | The Boeing Company | Material strain measurement method by means of laser ablation |
| CN117030477A (en) * | 2023-07-28 | 2023-11-10 | 广州华立学院 | Ultrasonic-based detection method for locking force of fixing piece |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3100842A1 (en) * | 1981-01-14 | 1982-08-12 | M.A.N. Maschinenfabrik Augsburg-Nürnberg AG, 8500 Nürnberg | DEVICE FOR MEASURING THE BOLT TENSION |
| JPS5876795A (en) * | 1981-10-31 | 1983-05-09 | Hagiwara Denki Kk | Timing circuit |
| FR2538470B1 (en) * | 1982-12-28 | 1985-06-28 | Prolhac Robert | ULTRASONICALLY CONTROLLED TIGHTENING SCREW AND ITS TARING DEVICE |
| FR2542869B1 (en) * | 1983-03-16 | 1985-08-30 | Centre Techn Ind Mecanique | TIGHTENING AND ULTRASONIC MEASUREMENT OF TIGHTENING VOLTAGES |
| FR2542657B1 (en) * | 1983-03-17 | 1985-11-29 | Facom | DYNAMOMETRIC TIGHTENING APPARATUS |
| FR2561562B1 (en) * | 1984-03-23 | 1988-03-25 | Framatome Sa | TIGHTENING DEVICE OF A SCREWED ASSEMBLY COMPRISING A MEANS OF ULTRASONIC CONTROL OF THE TENSION OF ONE OF THE ELEMENTS OF THIS ASSEMBLY |
| JPH074530Y2 (en) * | 1988-12-07 | 1995-02-01 | 三菱重工業株式会社 | Bolt tightening tool with axial force sensor |
| JPH02274476A (en) * | 1989-04-17 | 1990-11-08 | Hitachi Constr Mach Co Ltd | Bolt fastening device |
| NO2694065T3 (en) * | 2014-12-12 | 2018-05-12 | ||
| CN110579305A (en) * | 2018-06-11 | 2019-12-17 | 北京艾法斯特科技发展有限公司 | Intelligent sleeve system for ultrasonically measuring bolt axial force in real time |
-
1978
- 1978-12-14 DE DE19782853988 patent/DE2853988A1/en not_active Withdrawn
-
1979
- 1979-12-10 FR FR7930190A patent/FR2444267A1/en active Granted
- 1979-12-11 SE SE7910209A patent/SE7910209L/en not_active Application Discontinuation
- 1979-12-11 NL NL7908910A patent/NL7908910A/en not_active Application Discontinuation
- 1979-12-12 DD DD79217601A patent/DD147642A1/en unknown
- 1979-12-13 AU AU53802/79A patent/AU5380279A/en not_active Abandoned
- 1979-12-13 ZA ZA00796758A patent/ZA796758B/en unknown
- 1979-12-13 DK DK532079A patent/DK532079A/en unknown
- 1979-12-14 GB GB7943180A patent/GB2037430A/en not_active Withdrawn
- 1979-12-14 JP JP16266279A patent/JPS5582935A/en active Pending
- 1979-12-14 RO RO99544A patent/RO81473B/en unknown
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2165050A (en) * | 1984-09-26 | 1986-04-03 | Univ City | Non-destructive ultrasonic testing of structures to measure stress |
| US5058439A (en) * | 1990-06-06 | 1991-10-22 | The Babcock & Wilcox Company | Ut socket assembly |
| EP0683394A1 (en) * | 1994-05-18 | 1995-11-22 | Facom | Device for attaching a measuring instrument on a screw head |
| FR2720025A1 (en) * | 1994-05-18 | 1995-11-24 | Facom | Device for attaching an instrument to a drive head of a threaded member, and its application to a dynamometric device. |
| US5721380A (en) * | 1994-05-18 | 1998-02-24 | Facom | Device for fastening an instrument to the drive head of a threaded member, and its application to a dynamometric appliance |
| US5589640A (en) * | 1996-04-03 | 1996-12-31 | Butler; Patrick J. | Method for detecting changes in preload on a tie rod installed as part of a core shroud repair in a boiling water reactor |
| US5809100A (en) * | 1996-04-03 | 1998-09-15 | Mpr Associates, Inc. | Apparatus for detecting changes in preload on a tie rod installed as part of a core shroud repair in a boiling water reactor |
| EP0967053A3 (en) * | 1998-05-14 | 2001-05-30 | Atlas Copco Tools Ab | Method for determining the axial load in a threaded fastener when tightened above its yield point |
| EP0967053A2 (en) * | 1998-05-14 | 1999-12-29 | Atlas Copco Tools Ab | Method for determining the axial load in a threaded fastener when tightened above its yield point |
| US6314817B1 (en) | 1998-05-14 | 2001-11-13 | Atlas Copco Tools Ab | Method for tightening a threaded fastener above its yield point |
| GB2370121A (en) * | 2000-08-29 | 2002-06-19 | Fraunhofer Ges Forschung | Ultrasonic monitoring and controlling of a screwing process |
| GB2370121B (en) * | 2000-08-29 | 2004-02-11 | Fraunhofer Ges Forschung | Method of monitoring and controlling a screwing process |
| CN102262021A (en) * | 2010-05-28 | 2011-11-30 | 上海宝冶工程技术有限公司 | Torque force testing device for large-sized bolt |
| CN102262021B (en) * | 2010-05-28 | 2013-08-21 | 上海宝冶工程技术有限公司 | Torque force testing device for large-sized bolt |
| EP2806257B1 (en) * | 2013-05-20 | 2020-06-03 | The Boeing Company | Material strain measurement method by means of laser ablation |
| CN117030477A (en) * | 2023-07-28 | 2023-11-10 | 广州华立学院 | Ultrasonic-based detection method for locking force of fixing piece |
| CN117030477B (en) * | 2023-07-28 | 2024-05-24 | 广州华立学院 | Ultrasonic-based detection method for locking force of fixing piece |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2444267B3 (en) | 1982-03-12 |
| DE2853988A1 (en) | 1980-07-17 |
| AU5380279A (en) | 1980-07-10 |
| FR2444267A1 (en) | 1980-07-11 |
| JPS5582935A (en) | 1980-06-23 |
| RO81473A (en) | 1983-04-29 |
| SE7910209L (en) | 1980-06-15 |
| ZA796758B (en) | 1980-12-31 |
| DK532079A (en) | 1980-06-15 |
| DD147642A1 (en) | 1981-04-15 |
| RO81473B (en) | 1983-04-30 |
| NL7908910A (en) | 1980-06-17 |
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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) |