CN114112130B - Device and method capable of repeatedly measuring stress intensity factor of crack tip - Google Patents
Device and method capable of repeatedly measuring stress intensity factor of crack tip Download PDFInfo
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- CN114112130B CN114112130B CN202111162787.8A CN202111162787A CN114112130B CN 114112130 B CN114112130 B CN 114112130B CN 202111162787 A CN202111162787 A CN 202111162787A CN 114112130 B CN114112130 B CN 114112130B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/20—Metals
- G01N33/204—Structure thereof, e.g. crystal structure
- G01N33/2045—Defects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a device and a method for repeatedly measuring stress intensity factors of crack tips, wherein the device comprises a base and a pressing fixing device, the base comprises a stress intensity factor strain gauge, a rubber backing plate, a carbon fiber plate, a rubber protection layer and a magnet, the stress intensity factor strain gauge comprises a sensitive grid, a base and a lead wire, holes are formed in the carbon fiber plate, the rubber backing plate and the rubber protection layer, grooves are formed in the carbon fiber plate, and the magnet is arranged in the grooves. According to the invention, the stress intensity factor strain gauge is fixed through the pressing fixing device, the strain gauge is not required to be stuck, the portable type strain gauge is convenient to carry, the portable type strain gauge is proper in protection, can be reused, can rapidly measure stress intensity factors of crack tips of different measuring points, and has a wide application prospect.
Description
Technical Field
The invention relates to the field of fatigue crack stress intensity factor measurement, in particular to a device and a method for repeatedly measuring crack tip stress intensity factors.
Background
The steel box girder is easy to generate fatigue cracks under the cyclic action of vehicle load due to the complex structure, more welding details, adverse effects of factors such as welding defects, residual stress and the like. The stress intensity factor, which is an elastomechanical concept, can be used to describe the severity of stress near the crack tip, predicting the fatigue crack propagation of the structure. In order to deeply study the propagation behavior of fatigue cracks, to obtain the stress field characteristics of the crack tips, it is necessary to accurately measure the stress intensity factors of the crack tips.
The stress intensity factor sheet is a resistance strain sheet for specifically measuring the stress intensity factor of the crack tip, and the stress intensity factor of the crack tip can be directly measured (see JP6222772B2 for details). With the progress of manufacturing technology, the stress intensity factor sheet is finer in working, better in measuring precision and more expensive. The traditional stress intensity factor sheet needs to be stuck at the position of the measuring point, the same stress intensity factor sheet cannot be used at different measuring points, the utilization rate is low, and the measuring cost is high; the lead wires are led out from two sides of the stress intensity factor sheet and are directly exposed in the environment, so that the lead wires are not convenient to protect and are easy to damage in the use process.
Disclosure of Invention
The invention aims to: aiming at the defects, the invention provides a novel device which is small, portable, novel in design, proper in protection and reusable and can be used for measuring the fatigue crack stress intensity factor of the steel box girder.
The technical scheme is as follows:
a device for repeatable measurement of crack tip stress intensity factor, comprising a press fixture and a base, wherein:
the base comprises a stress intensity factor strain gauge, a rubber backing plate, a carbon fiber plate, a rubber protection layer and a magnet, wherein the rubber protection layer, the magnet, the carbon fiber plate, the rubber backing plate and the stress intensity factor strain gauge are sequentially stacked from top to bottom and connected into a whole;
the stress intensity factor strain gauge comprises a substrate, wherein a central hole of the substrate is formed in the middle of the substrate, sensitive grids are respectively arranged on two sides of the central hole of the substrate, and a plurality of leads are uniformly and correspondingly arranged on the sensitive grids on two sides of the central hole of the substrate;
the rubber backing plate is provided with a through backing plate center hole at a position corresponding to the base center hole, and a through backing plate lead hole at a position corresponding to each lead-out position;
the carbon fiber plate is provided with a through fiber plate center hole at a position corresponding to the pad plate center hole, a through fiber plate lead hole is arranged at a position corresponding to the pad plate lead hole, a groove is arranged at the middle position of the upper surface of the carbon fiber plate, and a magnet is embedded in the groove; the rubber protective layer is provided with a through protective layer through hole at a position corresponding to the magnet;
the leads on the substrate uniformly and correspondingly pass through the lead holes of the backing plate and the lead holes of the fiber plate in sequence, are arranged on the upper surface of the carbon fiber plate and extend out from the same side of the carbon fiber plate
The base can be fixed at the crack tip position by pressing by the pressing fixture.
Preferably, the number of leads, pad lead holes and fiberboard lead holes is 8.
Preferably, the inner diameter of each pad pin hole is uniform as well as the inner diameter of each fiberboard pin hole.
Preferably, the inner diameters of the pad plate central hole, the base central hole, the fiber board central hole and the protective layer through hole are consistent.
Preferably, the rubber protection layer is provided with a corresponding lead protection groove for each lead arranged on the carbon fiber board surface on the surface opposite to the carbon fiber board.
Preferably, the pressing fixing device comprises a positioning screw, a pressing block, a magnetic column, a universal rotating ring and a base, wherein a threaded hole is formed in the base;
the magnetic force column is arranged around the base, the universal rotating ring is hung at the middle position of the base through the positioning screw, the pressing block is arranged at the lower end of the universal rotating ring, and the pressing block is enabled to press the base arranged at the tip of the crack through rotating the positioning screw.
Preferably, the universal rotating ring comprises a bolt, a connecting piece, a rotating shaft pressing block and a positioning cone, wherein the positioning cone is arranged below the pressing block, and the radius of the bottom surface of the positioning cone is smaller than the aperture of a central hole of the stress intensity factor sheet;
the number of the connecting pieces is more than one, and two adjacent connecting pieces are connected through the rotating shaft;
the bolt is fitted in the uppermost connecting piece and can be in threaded fit connection with the set screw.
Preferably, the bottom of the positioning screw is connected with the universal rotating ring through a clamping groove.
Another object of the present invention is to provide a method for measuring a crack tip stress intensity factor, which is realized based on the device for repeatedly measuring the crack tip stress intensity factor, comprising the following steps: firstly, determining the position of a crack tip, adjusting the position of a pressing fixing device, enabling the top point of a positioning cone of the pressing fixing device to be aligned with the crack tip, then rotating a positioning screw of the pressing fixing device anticlockwise, driving the positioning cone to rise to the position right below through a universal ring of the pressing fixing device until a base can be placed, then aligning a central hole of the base with the crack tip, initially fixing the base by using a magnet, rotating the positioning screw clockwise, pressing the side, with the pressing block, of the universal rotating ring when the pressing block is fully contacted with a rubber protection layer of the base, screwing the positioning screw until the base is completely pressed on the crack tip, and connecting a lead with signal acquisition equipment, so that the stress intensity factor of the fatigue crack tip can be measured.
Preferably, the handheld universal rotating ring presses the side of the pressing block, so that the pressing block only changes in height, and the base is prevented from being damaged when the pressing block is attached to the base.
The beneficial effects are that: the invention has the following substantial advantages and advances:
1. the lead wires pass through the holes and are arranged on the carbon fiber plate and led out from one side of the carbon fiber plate, and meanwhile, the lead wires are protected by the rubber protection layer, so that the protection effect under the complex environment is enhanced.
2. Need not to paste, use magnet to carry out preliminary fixed to the base, use to press fixing device to carry out final fixed to the base, take off after the measurement and press fixing device and base can continue to use, conveniently carry, repeatedly usable has promoted measurement of efficiency greatly, has reduced test cost.
Therefore, the strain gauge can be used for rapidly and accurately measuring the stress intensity factors of a plurality of measuring points, improves the working efficiency, and is more suitable for the measuring environment and conditions of an actual bridge.
Drawings
FIG. 1 is a schematic diagram of the overall construction design of the present invention;
FIG. 2 is a schematic view of a base structure according to the present invention;
FIG. 3 is a schematic view of the structure of the pressing fixture of the present invention;
FIG. 4 is a schematic diagram of a wire arrangement of the present invention;
FIG. 5 is a schematic diagram of a rubber protective layer design according to the present invention;
fig. 6, 7 and 8 are schematic diagrams of the use method of the present invention.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The invention is further described below with reference to the accompanying drawings and examples:
the invention relates to a device capable of repeatedly measuring a crack tip stress intensity factor, which comprises a base 1 and a pressing fixing device 2, wherein the base 1 can be fixed at the crack tip position by pressing of the pressing fixing device 2, as shown in fig. 1 to 7, wherein:
the base 1 comprises a stress intensity factor strain gauge 11, a rubber backing plate 12, a carbon fiber plate 13, a rubber protection layer 17 and a magnet 16, wherein the rubber protection layer 17, the magnet 16, the carbon fiber plate 13, the rubber backing plate 12 and the stress intensity factor strain gauge 11 are sequentially stacked from top to bottom and connected into a whole; specifically, the stress intensity factor strain gauge 11 includes a substrate 18, a central substrate hole is formed in the middle of the substrate 18, the substrate 18 is respectively provided with sensitive grids 15 on two sides of the central substrate hole, and the sensitive grids 15 on two sides of the central substrate hole are uniformly and correspondingly provided with a plurality of leads 14; the rubber pad 12 is provided with a through pad center hole at a position corresponding to the base center hole, and is provided with a through pad lead hole at a position corresponding to the lead-out position of each lead 14; the carbon fiber plate 13 is provided with a through fiber plate center hole at a position corresponding to the pad plate center hole, a through fiber plate lead hole is arranged at a position corresponding to the pad plate lead hole, a groove is arranged at the middle position of the upper surface of the carbon fiber plate 13, and the magnet 16 is embedded in the groove; the rubber protection layer 17 is provided with a through protection layer through hole at a position corresponding to the magnet 16; after passing through the pad lead holes and the fiber board lead holes in sequence, the leads 14 on the substrate 18 are arranged on the upper surface of the carbon fiber board 13 and extend out from the same side of the carbon fiber board 13.
The carbon fiber plate 13 and the rubber backing plate 12 are provided with central holes (backing plate central holes and fiber plate central holes), the stress intensity factor strain gauge 11 comprises a sensitive grid 15, a substrate 18 and a lead 14, the rubber backing plate 12 is provided with eight small holes (backing plate lead holes) for penetrating the lead 14, a hole (substrate central hole) with the same aperture as the stress intensity factor sheet 11 is formed in the rubber backing plate 12, the carbon fiber plate 13 is provided with a groove, a magnet 16 is embedded in the groove, eight holes (fiber plate lead holes) with the same aperture and function as the rubber backing plate 12 small holes are formed in the groove, and a hole (fiber plate central hole) with the same aperture as the stress intensity factor sheet 11 is formed in the groove. The stress intensity factor sheets 11, the rubber backing plate 12 and the holes with the same aperture of the carbon fiber plate 13 are in one-to-one correspondence and are stuck together to form a whole. The carbon fiber plate 13 is provided with a rubber protective layer 17 on the side where the leads 14 are arranged, and plays a role of covering and protecting the leads 14.
The pressing and fixing device 2 comprises a positioning screw 21, a pressing block 22, a magnetic column 23, a universal rotating ring 24 and a base 25, wherein a threaded hole 28 is formed in the base 25. The magnetic force columns 23 are arranged around the base 25, so that the fixing effect can be achieved, and the positioning screw 21 can be adjusted in height and fixed by using the threaded holes 28. The middle part of the base 25 is suspended with a universal rotating ring 24 through a positioning screw 21, the lower end of the universal rotating ring 24 is provided with a pressing block 22, and the pressing block 22 is driven to press the base arranged at the tip of the crack through rotating the positioning screw 21. The set screw 21 is connected to the universal rotary ring 24 via a clamping groove 26.
The universal rotary ring 24 comprises a bolt 29, a connecting piece 210, a rotating shaft 211, a pressing block 22 and a positioning cone 27. The positioning cone 27 is arranged below the pressing block 22, and the radius of the bottom surface of the positioning cone 27 is smaller than the aperture of the central hole of the stress intensity factor sheet 11; the number of the connecting pieces 210 is more than one, and two adjacent connecting pieces 210 are connected through the rotating shaft 211; the bolt 29 is fitted in the uppermost connector 210 and can be screwed with the set screw 21. When the positioning screw 21 rotates to adjust the height, the hand-held universal rotating ring 24 is provided with the connecting piece 210 at one side of the pressing block 22, so that the pressing block does not rotate and only changes in height, and the pressing block cannot be damaged when being attached to the base.
When the device is used, the accurate position of the tip of the fatigue crack 3 of the steel box girder member is firstly determined, the magnetic column 23 is adsorbed on the surface of steel, the positioning screw 21 is rotated clockwise until the top point of the positioning cone 27 contacts the surface of the steel, and the position of the pressing and fixing device 2 is adjusted so that the top point of the positioning cone 27 is exactly aligned with the tip of the fatigue crack 3. The set screw 21 is then rotated counter-clockwise until the set cone 27 is sufficiently spaced from the tip of the fatigue crack 3 to set down the susceptor 1. The hole of the base 1 is aligned with the tip of the fatigue crack 3, the positioning screw 21 is rotated clockwise until the pressing block 22 is completely contacted with the rubber protection layer 17, the connecting piece 210 on one side of the pressing block 22 of the universal rotating ring 24 is pressed, and the positioning screw 21 is continuously rotated clockwise until the base is completely attached to the surface of steel under the pressing action. And connecting the lead with the acquisition equipment, so as to measure the stress intensity factor of the tip of the fatigue crack 3.
Claims (9)
1. Device for repeatable measurement of crack tip stress intensity factor, characterized by comprising a pressing fixture (2) and a base (1), wherein: the base (1) comprises a stress intensity factor strain gauge (11), a rubber backing plate (12), a carbon fiber plate (13), a rubber protection layer (17) and a magnet (16), wherein the rubber protection layer (17), the magnet (16), the carbon fiber plate (13), the rubber backing plate (12) and the stress intensity factor strain gauge (11) are sequentially stacked from top to bottom and connected into a whole;
the stress intensity factor strain gauge (11) comprises a substrate (18), wherein a central hole of the substrate is formed in the middle of the substrate (18), sensitive grids (15) are respectively arranged on two sides of the central hole of the substrate (18), and a plurality of leads (14) are uniformly and correspondingly arranged on the sensitive grids (15) on two sides of the central hole of the substrate;
the rubber pad (12) is provided with a through pad center hole at a position corresponding to the base center hole, and is provided with a through pad lead hole at a position corresponding to the lead-out position of each lead (14);
the carbon fiber plate (13) is provided with a through fiber plate center hole at a position corresponding to the pad plate center hole, a through fiber plate lead hole is arranged at a position corresponding to the pad plate lead hole, a groove is arranged at the middle position of the upper surface of the carbon fiber plate (13), and the magnet (16) is embedded in the groove; the rubber protection layer (17) is provided with a through protection layer through hole at a position corresponding to the magnet (16);
after passing through the pad lead holes and the fiber board lead holes in sequence, the leads (14) on the substrate (18) are arranged on the upper surface of the carbon fiber board (13) and extend out from the same side of the carbon fiber board (13);
the base (1) can be fixed at the position of the crack tip by pressing the pressing fixing device (2);
the pressing fixing device (2) comprises a positioning screw (21), a pressing block (22), a magnetic column (23), a universal rotating ring (24), a base (25) and a positioning cone (27);
the base (25) is provided with a threaded hole (28); the periphery of the base (25) is provided with the magnetic force column (23), and the middle position of the base (25) is suspended with the universal rotating ring (24) through the positioning screw (21);
the lower end of the universal rotating ring (24) is provided with a pressing block (22); the positioning cone (27) is arranged below the pressing block (22), and the radius of the bottom surface of the positioning cone (27) is smaller than the aperture of the central hole of the stress intensity factor strain gauge (11);
by rotating the set screw (21), the pressing block (22) is urged to press the base (1) placed at the tip of the crack.
2. The device for repeatable crack tip stress intensity factor measurement as claimed in claim 1, wherein the number of leads (14), pad lead holes and fiberboard lead holes is 8.
3. The apparatus for repeatable crack tip stress intensity factor of claim 1, wherein the inner diameter of each pad pin hole is uniform as well as the inner diameter of each fiberboard pin hole.
4. The apparatus for repeatable crack tip stress intensity factor measurement of claim 1, wherein the backing plate central hole, the base central hole, the fiberboard central hole, and the protective layer through hole have uniform inner diameters.
5. The device for repeatedly measuring crack tip stress intensity factor according to claim 1, wherein the rubber protection layer (17) is provided with a corresponding lead protection groove for each lead arranged on the carbon fiber plate (13) plate surface at the plate surface opposite to the carbon fiber plate (13).
6. The device for repeatedly measuring crack tip stress intensity factor as claimed in claim 5, wherein the universal rotary ring (24) comprises a bolt (29), a connecting piece (210), a rotating shaft (211); the number of the connecting pieces (210) is more than one, and two adjacent connecting pieces (210) are connected through the rotating shaft (211); the bolt (29) is fitted in the uppermost connecting piece (210) and can be connected with the positioning screw (21) in a threaded fit.
7. The device for repeatedly measuring crack tip stress intensity factor as claimed in claim 6, wherein the bottom of the set screw (21) is connected with the universal rotating ring (24) through a clamping groove (26).
8. A method of measuring a crack tip stress intensity factor based on the repeatable crack tip stress intensity factor measuring device of claim 1, comprising the steps of: firstly, determining the position of a crack tip, adjusting the position of a pressing fixing device, enabling the top point of a positioning cone of the pressing fixing device to be aligned with the crack tip, then rotating a positioning screw of the pressing fixing device anticlockwise, driving the positioning cone to rise to the position right below through a universal ring of the pressing fixing device until a base can be placed, then aligning a central hole of the base with the crack tip, initially fixing the base by using a magnet, rotating the positioning screw clockwise, pressing the side, with the pressing block, of the universal rotating ring when the pressing block is fully contacted with a rubber protection layer of the base, screwing the positioning screw until the base is completely pressed on the crack tip, and connecting a lead with signal acquisition equipment, so that the stress intensity factor of the fatigue crack tip can be measured.
9. The method of measuring crack tip stress intensity factor as set forth in claim 8, wherein the hand-held gimbal swivel presses the block side such that only the height of the press block changes, avoiding the press block (22) from causing base damage when it has been attached to the base.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111162787.8A CN114112130B (en) | 2021-09-30 | 2021-09-30 | Device and method capable of repeatedly measuring stress intensity factor of crack tip |
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| CN202111162787.8A CN114112130B (en) | 2021-09-30 | 2021-09-30 | Device and method capable of repeatedly measuring stress intensity factor of crack tip |
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| CN114112130A CN114112130A (en) | 2022-03-01 |
| CN114112130B true CN114112130B (en) | 2023-04-21 |
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