Background technology
In current civil engineering industry, strain measurement is widely used in the knots such as building, railway, bridge, traffic, dam
On structure.The stress-strain test of structure is that engineering staff understands structural stress state, ensures structural safety and carry out structure and set
The important link that meter optimizes.Such as at work progress and the Long Period Health Monitoring of operation process of Longspan Bridge
In, the ess-strain in crucial cross section is monitored, for bridge construction, operate, offer foundation be provided, it is ensured that structural safety is
One requisite link of bridge construction.
Common strain testing method has fiber grating method, vibrating string type strain method of testing, draws secondary meter or digital display dial gauge
Method, resistance-type stain measuring technology etc..It is big etc. that fiber grating method has electromagnetism interference, preferable insulating properties, transmission capacity
Advantage, shortcoming is that sensor processing technique is complicated, relatively costly, and required ancillary equipment is more, apparatus expensive, safeguards Replacement procedure
Complicated, relatively costly, limit large-scale promotion and application;Vibrating string type strain method of testing directly exports the natural frequency of vibration of vibratory string
Signal, reflects the strain size of tested component by the change of frequency, although vibrating string type strain test has capacity of resisting disturbance
By force, the feature such as zero drift is little, temperature influence is little, long-time stability are good, at present for relatively in civil engineering strain testing
For extensively, but only it is suitable for static strain testing, is not suitable for dynamic strain test;Draw secondary meter or digital display dial gauge method is long by gauge length
Degree and the restriction installed, use fewer in Experiments of Machanics;The sensing used of resistance-type stain measuring technology is also called resistance should
Become meter, be called for short foil gauge or resistor disc, utilize resistor disc that non electrical quantity is converted to electricity, then be amplified through electronic machine, show
Show and record, so higher amplification can be obtained, thus reach higher sensitivity, have be easily achieved digitized, from
Dynamicization, with low cost, operating technology is required the advantage such as relatively low, be the strain testing method being most widely used at present, carry out
Long term monitoring it is applicable to after encapsulation process.
Owing to dynamic under Vehicle Load of bridge should be less, general three axle load automobiles cause about 10
Bridge moving strains, and the dynamic strain that station wagon causes is less;External environmental interference, as variations in temperature, wind etc. can draw 1-2 bridge
The fluctuation of dynamic strain;But, current resistor straining testing precision is universal 1 strain, and this is by current circuit amplification system
Technical merit determines, because of wiring technique and the difference of instrument hardware quality, circuit amplification system the most often can cause 0-2 strain
Noise signal;In this context, to precisely test bridge moving strain, overcome environment and instrument system noise to become the most tired
Difficult.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of high-resolution strain detection testing device, and this device can realize higher
Test accuracy, be widely used in Test on Bridge Loading, health monitoring and based on the technology such as dynamic strain identification traveling load neck
Territory.
For solve above-mentioned technical problem, the present invention by the following technical solutions: high-resolution strain testing method, at bridge
Component surface parallel strain direction steel planting or 2 bases that welding center distance is L, penetrate the top of base by transmission lever
Perforate, and use nut transmission lever to be tightened in the both sides of base top perforate;At the induction rod two that perforate centre-to-centre spacing in two ends is l
Difference adhering resistance formula foil gauge at the symmetry of side, and use protective material by resistance strain plate and to be pasted with resistance strain plate
Induction rod portion envelops protection;Abutting end two transmission levers uses bolt induction rod and transmission lever to be connected and tightens admittedly
Fixed;Resistance strain plate accesses strain acquirement cabinet according to double foil gauge connections, adjusts nut and makes base, transmission lever and induction rod
Fully stress, the actual measurement strain reading induction rod is ε ';By formulaCalculate and obtain bridge member
Surface strain to be measured is ε;Wherein, S, E, SE are respectively the area of section of transmission lever, elasticity modulus of materials, axial deformation rigidity;
S, e, se are respectively the area of section of induction rod, elasticity modulus of materials, axial deformation rigidity;L is the perforate of induction rod both ends
Centre distance, L is base center distance.
After induction rod adhering resistance formula foil gauge, put into the drying baker that temperature is 120 DEG C-150 DEG C and be no less than 3 hours, take
Protective material parcel protection is used immediately after going out.
Induction rod and the axial rigidity ratio of transmission leverλ is less than 0.01;Centre distance l of induction rod both ends perforate with
Base center distance L ratioβ is less than 0.1;Formula isDefinition
ξ is and transmission lever and the material of induction rod, size, the relevant characteristic coefficient of cut-in method of foil gauge, the material chosen and
λ and β that size draws, makes ξ be less than 0.1.
High-resolution strain detection testing device, is mainly made up of base, induction rod, transmission lever and resistance strain plate;At the bottom of 2
The center distance of seat is L, and the top perforate of each base is also respectively interposed a transmission lever, uses in perforate both sides that nut is fixing to be passed
Pass bar;Being provided with perforate centre-to-centre spacing in two ends between two transmission lever adjacent both ends is that the induction rod of l, transmission lever and induction rod pass through spiral shell
Bolt is fixed;Difference adhering resistance formula foil gauge at induction rod lateral symmetry, resistance strain plate is according to double foil gauge connections and answers
Become and gather cabinet and connect, resistance strain plate and post the induction rod part of resistance strain plate by protective material covering protection.
The area of section of induction rod is preferably less than 5mm2, in the middle of its perforate, gap length is generally less than 20mm;Cutting of transmission lever
Face area is preferably greater than 105mm2, single effective length should be greater than 100mm.
Induction rod cross sectional shape is rectangle, and its long limit is more than 5 with the ratio of minor face.
Induction rod typically chooses the elastic modelling quantity alloy metal material less than 150GPa;Transmission lever is chosen elastic modelling quantity and is more than
The alloy metal material of 200GPa, ceramic material, carbon fiber bar etc.;Protective material is epoxy resin mortar polymer.
Induction rod typically chooses magnalium;It is fine that transmission lever chooses the high model carbon that elastic modelling quantity is 300GPa, 450GPa
Tie up or superelevation model carbon fiber, or elastic modelling quantity is the ceramic SiC etc. of 450GPa.
For the problem of the test accuracy deficiency that existing strain testing method exists, inventor establishes a kind of high-resolution
Rate strain testing method, this method uses the connection combination that different-stiffness necessarily constructs than two kinds of parts with length ratio, logical
Cross mechanics principle the deformation in coverage to be concentrated on a certain parts, play the effect of mechan-amplifier bridge strain.Accordingly,
Inventor has also designed and produced corresponding test device.Use this method of testing and test device, in conjunction with inventor through the mechanics of materials
And high accuracy based on parameters of operating part ratio of rigidity, the length ratio strain solution formula that structural mechanics method is derived, to realize relatively
High test accuracy, reaches 0.01 μ ε the highest (accuracy of conventional strain testing method is only 1 μ ε), is broadly applicable
In Test on Bridge Loading, health monitoring and based on technical fields such as dynamic strain identification traveling loads.Compared with prior art, this
Bright outstanding advantage is:
(1) by mechan-amplifier, by strain amplification decades of times to hundreds times, even thousand times, improve the identification of small strain
Rate and accurate testing degree;
(2) amplification has highlighted the numerical value of structural strain, and Test System Noise does not changes, and is equivalent to reduce test system
Noise jamming;
(3) test device instrument is simple, with low cost, it is easy to change;
(4) bridge Modal testing and analysis based on bridge moving strain can be realized.
Detailed description of the invention
The ultimate principle of high-resolution strain testing method of the present invention
1. operating procedure
As depicted in figs. 1 and 2, bridge member surface parallel strain direction steel planting or welding center distance be the 2 of L
Individual base, penetrates transmission lever the top perforate of base, and uses nut transmission lever to be tightened in the both sides of base top perforate;
It is difference adhering resistance formula foil gauge at the induction rod lateral symmetry of l in two ends perforate centre-to-centre spacing, and uses protective material by electricity
Resistive foil gauge and the induction rod portion envelops protection being pasted with resistance strain plate;Abutting end two transmission levers uses spiral shell
Induction rod and transmission lever connection are tightened fixing by bolt;Resistance strain plate accesses strain acquirement cabinet according to double foil gauge connections,
Adjusting nut and make the abundant stress of base, transmission lever and induction rod, the actual measurement strain reading induction rod is ε ';By formulaCalculate and obtain bridge member surface strain stress to be measured;Wherein, S, E, SE are respectively cutting of transmission lever
Face area, elasticity modulus of materials, axial deformation rigidity;S, e, se are respectively the area of section of induction rod, elasticity modulus of materials, axle
To deformation rigidity;L is the centre distance of induction rod both ends perforate, and L is base center distance.
Wherein, after induction rod adhering resistance formula foil gauge, put into the drying baker that temperature is 120 DEG C-150 DEG C little no less than 3
Time, use protective material (epoxy resin mortar polymer) parcel protection after taking-up immediately.
2. the derivation of equation
As it is shown on figure 3, under the effect of two ends axial force F, induction rod and transmission lever strain are respectively ε, ε ', and axle power is
F, the length of induction rod, area of section and elastic modelling quantity be respectively l, s, e, the length of transmission lever, area of section and elastic modelling quantity
It is respectively l ', S, E.Thus can obtain formula (1)
Se ε=F, SE ε '=F, be i.e.
Se ε=SE ε ' (1)
The ratio of strain stress, ε ' can be obtained, order by formula (1)See formula (2)
Component total length is L, L=l+2l ', and under axial force F effect, total Zhongchang amount Δ L is formula (3)
L ε+2l ' ε '=Δ L (3)
Formula (3) both sides, with divided by L, can obtain formula (4)
OrderFormula (2) is brought into formula (4) and obtains formula (5)
Mean strain in induction rod and transmission lever length range is the strain of structure, makes this mean strain numerical value be
It is i.e.Formula (6) is obtained after formula (5) abbreviation
When resistance strain plate accesses strain acquirement cabinet according to double foil gauge connections, actual measurement strain is induction rod strain
2 times, then have formula (7)
This seasonξ is relevant to induction rod and transmission lever area of section, length and elastic modelling quantity
Characteristic coefficient.
The strain of structure in formula (6)For a certain value, when induction rod and transmission lever area of section, length and elastic modelling quantity ginseng
Array is closed when meeting particular kind of relationship so that when characteristic coefficient ξ is less than 1, must haveAnd induction rod and transmission lever area of section,
When length and elastic modelling quantity are definite value, characteristic coefficient ξ is also definite value, when characteristic coefficient ξ is 0.1,It it is i.e. induction rod
Strain be 10 times of structural strain;When characteristic coefficient κ is 0.01,Be i.e. the strain of induction rod be structural strain
100 times;The structural strain that structure is less cannot be accurately tested when using existing method of testingTime, use the present invention by
Specific induction rod and the test device of transmission lever combination, adhering resistance formula foil gauge on induction rod, can record and compare structural strainThe ε of big several times, can be scaled, by characteristic coefficient ξ, the structural strain that conventional method can not accurately obtainIt is the most former
Reason is, by induction rod and the particular combination of transmission lever, utilizes the principle of deformation consistency of structural mechanics and the mechanics of materials, namely
The method of machinery is presented on distinctive parts after several times are amplified in less strain, more accurate by characteristic coefficient ξ inverse
Structural strainGenerally, when using milimeter scale to go the length measuring 1.31mm, the length data measured is probably
1.0mm or 1.5mm, it is impossible to accurately reflect actual length.But after the magnifier of employing 10 times, 100 times amplifies, then use millimeter
Chi removes the image after measuring and amplifying, and the length data measured is respectively 13.0mm, 131.0m.Now when the amplification knowing magnifier
Multiple is 10 times, 100 times respectively, can try to achieve physical length and be respectively 1.3mm, 1.31mm after inverse).
Application example
Illustrating the present invention below by way of application example, parallel employing traditional method carries out contrast test, wherein applies
Example is carried out with reference to said method operation, and traditional method is as follows:
(1) selecting sticking strength high (shear strength is typically not less than 3-4MPa), electrical insulation capability is good, chemical stability and
The glue of good manufacturability.
(2) select foil gauge, with magnifier, foil gauge is checked, it is ensured that the foil gauge zero defect of selection and breakage.
Select, with batch test chamber, the foil gauge that sensitivity coefficient is identical with resistance, use million to beat up table or circuit tester and its resistance is measured,
Ensure that error is not more than 0.5 Ω;
(3) location, tentatively draws patch location, is polished flat the position of paster with emery cloth or emery wheel, concrete surface
Without laitance, it is coated with primer if desired and processes, the most again polish, accurately draw the longitudinal and transverse of measuring point at the position polished flat
Centrage and the direction of stickup foil gauge;
(4) paster, dips acetone or ethanol with tweezers folder rayon balls and paster is obtained position cleans up.Grasping should
Become sheet lead-out wire, at one layer of glue of its back side uniform application, be then placed on measuring point, adjust the position of foil gauge so that it is can be accurate
Determine position.Foil gauge covers small pieces cellophane finger roll gently, extrusion surplus glue and bubble.It is careful not to make to answer
Become sheet position to move.Gently press 1-2min with finger, after glue primary solidification, can loose one's grip.
(5) weld, check, dry solidification and the protection of foil gauge.
Application example 1
At 2 bases that parallel strain direction, bridge member surface steel planting center distance is 166mm;Diameter 18mm's
Transmission lever penetrates the perforate on the top of base, and uses nut transmission lever to be tightened in the both sides of base top perforate;At two ends
Perforate centre-to-centre spacing is the induction rod lateral symmetry adhering resistance formula foil gauge respectively of 16mm, and induction rod cross section is 6mm × 0.5mm square
Shape;And use protective material by resistance strain plate and the part induction rod parcel protection being pasted with resistance strain plate;Passing
The abutting end passing bar uses bolt to tighten fixing by induction rod and transmission lever connection;Resistance strain plate is according to double foil gauge connections
Access strain acquirement cabinet, adjust nut and make the abundant stress of base, transmission lever and induction rod.The face, cross section of steel material transmission lever
Long-pending, elasticity modulus of materials, axial deformation rigidity are respectively 254.47mm2、200GPa、5.0894×104kN/mm;Aluminum alloy materials
The area of section of induction rod, elasticity modulus of materials, axial deformation rigidity are respectively 3.00mm2、71GPa、2.13×102kN/mm;
Induction rod is 0.0041852 with the axial rigidity ratio of transmission lever, and the centre distance of induction rod both ends perforate is and base center
Gap ratio is 0.09639, sensor characteristics coefficient ξ 0.050084.
Measured result compares and is shown in Table 1.
Table 1 application example 1 and traditional method test result
Class of loading |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
Theoretical strain |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
9.0 |
10.0 |
Conventional actual measurement strain |
1 |
1.5 |
3.0 |
4.5 |
5.0 |
6.5 |
7.5 |
8.0 |
9.0 |
9.5 |
This method is surveyed |
20 |
39 |
61 |
80 |
102 |
120 |
143 |
162 |
182 |
196 |
Actual measurement inverse strain |
1.00 |
1.95 |
3.06 |
4.01 |
5.11 |
6.01 |
7.16 |
8.11 |
9.12 |
9.82 |
Application example 2
At 2 bases that parallel strain direction, bridge member surface steel planting center distance is 520mm;Diameter 23mm's
Transmission lever penetrates the perforate on the top of base, and uses nut transmission lever to be tightened in the both sides of base top perforate;At two ends
Perforate centre-to-centre spacing is the almag induction rod lateral symmetry adhering resistance formula foil gauge respectively of 10mm, and induction rod cross section is 4mm
× 0.5mm rectangle;And use protective material by resistance strain plate and the part induction rod parcel being pasted with resistance strain plate
Protection;Abutting end in transmission lever uses bolt to tighten fixing by induction rod and transmission lever connection;Resistance strain plate is according to double
Foil gauge connection accesses strain acquirement cabinet, adjusts nut and makes the abundant stress of base, transmission lever and induction rod.The cross section of transmission lever
Area, elasticity modulus of materials, axial deformation rigidity are respectively 415.48mm2、210GPa、8.7245×104kN/mm;Induction rod
Area of section, elasticity modulus of materials, axial deformation rigidity are respectively 2.00mm2、40GPa、0.80×102kN/mm;Induction rod with
The axial rigidity ratio of transmission lever is 0.0009169, and the centre distance of induction rod both ends perforate is for base center distance ratio to be
0.019231, sensor characteristics coefficient ξ is 0.01007.Embodiment 2 method compares with traditional method measured result and is shown in Table 2
Table 2 embodiment 2 test result
Class of loading |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
Theoretical strain (μ ε) |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
9.0 |
10.0 |
Conventional actual measurement strain (μ ε) |
1.5 |
2.0 |
3.0 |
4.5 |
5.5 |
6.0 |
6.5 |
8.0 |
9.5 |
11 |
Conventional actual measurement strain error (%) |
50.0 |
0 |
0 |
12.5 |
10.0 |
0.0 |
7.1 |
0 |
5.6 |
10.0 |
This method actual measurement (μ ε) |
102 |
204 |
289 |
393 |
500 |
575 |
698 |
778 |
899 |
1005 |
Actual measurement inverse strain (μ ε) |
1.03 |
2.05 |
2.91 |
3.96 |
5.03 |
5.79 |
7.03 |
7.83 |
9.05 |
10.12 |
Actual measurement inverse strain error (%) |
3.0 |
2.5 |
3.0 |
1.0 |
0.6 |
3.5 |
0.4 |
2.1 |
0.6 |
1.2 |
In Tables 1 and 2, each index parameter implication is as follows:
Theoretical strain: Theoretical Calculation strains, and is i.e. Utopian logarithmic strain.
Conventional actual measurement strain: the test result of conventional adhering resistance formula foil gauge, precision is only capable of reaching 0.5 μ ε.
Conventional actual measurement strain error: | theoretical strain-conventional actual measurement strain | × 100/ theoretical strain
This method is surveyed: uses the device actual measurement strain of this programme, by the method for mechan-amplifier, strain is exaggerated
100 times.
Actual measurement inverse strain: consider the inverse strain after device characteristic value, and the strain of the high accuracy of structure, high precision.
Actual measurement inverse strain error=| theoretical strain-actual measurement inverse strain | × 100/ theoretical strain.