CN106197342A - Fracture width change dynamic monitor based on strain sensing - Google Patents

Abstract

The invention discloses a kind of fracture width change dynamic monitor based on strain sensing, mainly it is made up of base support, induction rod, transmission spring and strain sensor, the connection combination that the transmission spring of its certain rigidity of employing and induction rod necessarily construct, use strain sensor test strain variation value on induction rod, calculated the changing value of fracture width by mechanics and materialogy principle, thus realize the dynamic monitoring of fracture width change.Accordingly, inventor has also designed and produced corresponding monitoring method.Use this monitoring method and device, the rigidity based on spring derived through the mechanics of materials and structural mechanics method in conjunction with inventor, the high accuracy fracture width change solution formula of the physical characteristic of induction rod, change Dynamic Recognition and the monitoring of fracture width can be realized, reduce labor intensity and the testing cost of people, be widely portable to identification and the monitoring of the fracture width changes such as dam, building construction, bridge structure.

Description

Fracture width change dynamic monitor based on strain sensing

Technical field

The invention belongs to fracture width change identify and monitoring technical field, particularly relate to a kind of based on splitting that strain senses Seam change width dynamic monitor.

Background technology

In current civil engineering industry, the xoncrete structure such as building construction, railway, bridge, dam due to material, execute Work, temperature, external load are equal to reason, and in work progress or after building up during operation, crack often occurs in body structure surface.Have A little cracks do not affect structural safety, only the durability that structure is long-term are had certain adverse effect；Some crack but directly affects Structural safety, is one of structural safety whether important symbol.For this reason, it may be necessary to body structure surface crack progressing situation is carried out in time Identification, monitoring, if fracture length and width sustainable development, then be necessary to take to reinforce or other measures, to reduce because of structure Damage or collapse the property loss caused and personal safety threat.The identification of fracture length change easily and simply, can be adopted By labelling, sign or direct repetitive measurement fracture length data, through comparing the length situation of change that can accurately determine crack； Though the change of some fracture length is inconspicuous, but the minimum change of fracture width is unsatisfactory for using predictive of structural-load-carrying capacity and wants Ask or dangerous.

But, owing to structural cracks width is less, (general crack minimum can recognize that width 0.04mm, and maximum crack width can Reach 60mm), the change of its fracture width is the least, and the change of general structure fracture width increases with load or the time changes linearly Or during non-linear acceleration cracking, i.e. think that ratio more serious disease or defect occurs in works, it is unsuitable for continuing carrying and makes a reservation for Function, or need to promptly reinforce disposal.The change of existing fracture width identifies that common method has image amplifying method, pastes fragile material Method, stickup strain gauge method etc..Wherein, image amplifying method is to use magnifying video image, judges fracture width according to benchmark scale, Repeatedly observing fracture width and ask it poor, determining fracture width variable quantity, but after image amplifies, edge of crack obscures, reading has relatively Big error, and repeatedly observation is difficult to ensure that the same position that can be directed at crack, the crack width tried to achieve after causing repeatedly observation Degree variation error is bigger.Pasting fragile material in fracture faces, such as paraffin paper, thin glass etc., fracture width change increases to certain After degree, fragile material can be torn or come off, and represents that fracture width has certain change, but it cannot realize quantitatively, also with regard to nothing Method accurately judges fracture width variable quantity.Pasting strain gauge method is vertically to paste foil gauge across crack, testing strain variation feelings Condition, when fracture width is unchanged, foil gauge produces without strain, and foil gauge changes and represents that fracture width also changes when producing, Similar with pasting fragile material method, this method can only identify whether fracture width changes, but cannot fracture change width enter Row is quantitatively..

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of measures crack based on strain sensing accurate, with low cost Change width dynamic monitor, to realize identifying dynamically, exactly the change of fracture width, is widely portable to dam, room The identification of the fracture width changes such as room building, bridge structure and monitoring.

For solve above-mentioned technical problem, the present invention by the following technical solutions:

Fracture width change dynamic monitor based on strain sensing, mainly by base support, induction rod, transmission spring Form with strain sensor；The center distance of 2 base supports is L, and the top perforate of one of them base support also interts One induction rod, uses nut to fix induction rod one end in perforate both sides, the top of another base support and transmission spring one end Connecting, the other end of induction rod is connected with the transmission spring other end；Strain sensor, strain sensor is adhered on induction rod Being connected with strain acquirement cabinet, the induction rod part of strain sensor and adhesion strain sensor is anti-by protective material parcel Protect.

The material of 2 base supports, equivalently-sized.

Strain sensor is steel chord type, resistance-strain chip or raster pattern.

The area of section of induction rod is not less than 30mm², length is not less than 9 with the radius ratio of the circle of cross section equivalent area, material Material elastic modelling quantity is between 40GPa～210GPa, and the rigidity of transmission spring is more than 2000N/mm.

For problems such as existing fracture width change test accuracy are not enough, inventor establishes a kind of based on strain sensing Fracture width change dynamic monitoring method, this method uses transmission spring and the company that necessarily constructs of induction rod of certain rigidity Connect combination, use strain sensor test strain variation value on induction rod, calculated by mechanics and materialogy principle and split The changing value of seam width, thus realize the dynamic monitoring of fracture width change.Accordingly, inventor has also designed and produced corresponding monitoring Device.Use this monitoring method and device, in conjunction with inventor through the mechanics of materials and structural mechanics method derive based on spring Rigidity, induction rod physical characteristic high accuracy fracture width change solution formula, it is possible to achieve the change of fracture width move State identification and monitoring, reduce labor intensity and the testing cost of people, be widely portable to dam, building construction, bridge structure etc. The identification of fracture width change and monitoring.Compared with prior art, the outstanding advantage of the present invention is:

(1) know-why is different from additive method, is converted into spring internal force by the change of fracture width, is transferred to sensing Bar, identifies induction rod internal force by strain, determines the variable quantity of fracture width, physics through the derivation of the mechanics of materials and structural mechanics Amount transmission is simple, clearly；

(2) test device instrument is simple, with low cost, it is easy to repair and replacement.

(3) fracture width change accuracy of identification is high, for the change accuracy of identification of fracture width up to 0.001mm；

Accompanying drawing explanation

Fig. 1 is use state diagram and the monitoring thereof of present invention fracture width based on strain sensing change dynamic monitoring method The structural representation (being perpendicular to induction rod and transmission spring) of device.

Fig. 2 is present invention fracture width based on strain sensing change dynamic monitoring method and the mechanics principle signal of device Figure.

In figure: 1 body structure surface, 2 cracks, 3 base supports, 4 induction rods, 5 resistance strain plates, 6 transmission springs, 7 nuts.

Detailed description of the invention

Present invention fracture width based on strain sensing change dynamic monitoring method and the ultimate principle of device

1. operating procedure

As depicted in figs. 1 and 2, at the body structure surface (such as body structure surface 1) of both sides, crack, vertical fracture 2 direction is bored respectively Hole bar planting or welding center distance are 2 materials of L, equivalently-sized base support 3；One end of induction rod 4 is penetrated wherein The top perforate of one base support, the other end of induction rod with transmission spring 6 one end is connected, transmit the spring other end and another Base support top is connected；On induction rod, (or other strain detection testing devices, such as string wire frequency for Adhesion resistance formula foil gauge 5 Method or fibre grating method), and wrap up preventative resistance formula foil gauge and the induction rod portion of Adhesion resistance formula foil gauge with protective material Point；Resistance strain plate is connected with strain acquirement cabinet, and uses nut 7 will sense in the both sides of base support top perforate Bar is tightened, and makes the abundant stress of transmission spring, induction rod and base support；The actual measurement strain of induction rod is read in variable interval or timing(i.e. indicating value strain)；By formulaCalculate the changing value obtaining fracture width；Wherein, the length of induction rod Degree, elasticity modulus of materials, area of section are respectively l_g, A and E, transmission spring rigidity be k.

2. the derivation of equation

As in figure 2 it is shown, the length of induction rod, elasticity modulus of materials, area of section are divided into l_g, A and E, transmission spring firm Degree is k, and under the effect of power F, the Zhongchang amount of transmission spring and induction rod is respectively Δ l_c、Δl_g, by transmission spring and induction rod Axial force equal, can obtain formula (1):

$F={\mathrm{\Δl}}_{c}k=\frac{{\mathrm{\Δl}}_{g}EA}{l_g}---\left(1\right)$

After formula (1) abbreviation formula (2):

$\frac{{\mathrm{\Δl}}_c}{{\mathrm{\Δl}}_g}=\frac{EA}{{\mathrm{kl}}_g}---\left(2\right)$

Total Zhongchang amount of order transmission spring and induction rod is Δ L, and total Zhongchang amount Δ L is the variable quantity of fracture width, then There is a formula (3):

Δ L=Δ l_c+Δl_g (3)

Formula (2) brings after formula (3) to obtain formula (4) into:

$\mathrm{\Δ}L=\frac{EA}{{\mathrm{kl}}_g}{\mathrm{\Δl}}_g+{\mathrm{\Δl}}_g---\left(4\right)$

OrderAnd bring formula (4) into,For induction rod indicating value strain, after abbreviation formula (5):

$\mathrm{\Δ}L=\frac{EA}{k}\stackrel{\‾}{\mathrm{\ϵ}}+\stackrel{\‾}{\mathrm{\ϵ}}{l}_g=(\frac{EA}{k}+l_g)\stackrel{\‾}{\mathrm{\ϵ}}---\left(5\right)$

Now, orderCan obtain formula (6):

$\mathrm{\Δ}L=\mathrm{\χ}\stackrel{\‾}{\mathrm{\ϵ}}---\left(6\right)$

χ is the characteristic coefficient relevant to induction rod and transmission spring area of section, length and elastic modelling quantity.Knot in formula (6) The strain of structureFor a certain value, when known induction rod area of section, length and elastic modelling quantity and and during transmission spring rate, Try to achieve the width variation in crack.

When the material maximum linear of induction rod strains as ε_e, then the fracture width maximum variable quantity that can identify, i.e. the amount of being Cheng WeiThe fracture width minimum change that this method can identify is

3. application example

Application preceding method and device, wherein, the length of induction rod, elasticity modulus of materials, area of section are respectively l_g= 40mm, A=30mm²And E=90GPa, the rigidity of transmission spring is k=2000N/mm, and the strain of induction rod material maximum linear is ε_e =1000, then the precision of the monitoring method trying to achieve this fracture width variable quantity is 0.000167mm, and fracture width variable quantity is tested Range is 1.66mm.

Claims (4)

1. a fracture width change dynamic monitor based on strain sensing, it is characterised in that main by base support, sense Answer bar, transmission spring and strain sensor composition；The center distance of 2 base supports is L, the top of one of them base support End perforate and intert an induction rod, perforate both sides use nut fix induction rod one end, the top of another base support and Transmission spring one end connects, and the other end of induction rod is connected with the transmission spring other end；Strain sensor is adhered on induction rod, Strain sensor is connected with strain acquirement cabinet, and the induction rod part of strain sensor and adhesion strain sensor is by preventing Protective material parcel protection.

Fracture width change dynamic monitor based on strain sensing the most according to claim 1, it is characterised in that: institute State the material of 2 base supports, equivalently-sized.

Fracture width change dynamic monitor based on strain sensing the most according to claim 1, it is characterised in that: institute Stating strain sensor is steel chord type, resistance-strain chip or raster pattern.

Fracture width change dynamic monitor based on strain sensing the most according to claim 1, it is characterised in that: institute State the area of section of induction rod not less than 30mm², length is not less than 9 with the radius ratio of the circle of cross section equivalent area, elastic properties of materials Modulus is between 40GPa～210GPa, and the rigidity of described transmission spring is more than 2000N/mm.