CN203249815U - Device for measuring early-stage elasticity modulus of cement-based material - Google Patents

Abstract

The utility model discloses a device for measuring an early-stage elasticity modulus of a cement-based material. The device comprises a uniform-section hollow straight pipe, two supporting knife edges and a vibration measurement device, wherein the uniform-section hollow straight pipe is used for filling the to-be-measured cement-based material; the two supporting knife edges are arranged on positions which are 0.224l and 0.776l from the hollow straight pipe respectively, and l is the length of the hollow straight pipe; the two supporting knife edges are used for supporting the hollow straight pipe, so that a combined free beam formed by the to-be-measured cement-based material and the hollow straight pipe is formed; and the vibration measurement device comprises a vibration sensor arranged at a mid-point of the combined free beam and a vibration signal collecting and processing device connected with the vibration sensor. The device can continuously monitor a process in which the early-stage elasticity modulus of the cement-based material changes along with the age at different curing temperatures after the cement-based material enters a mold and isn't demolded; and the structure is simple, and the cost is low.

Description

The early stage elastic modulus measurement mechanism of a kind of cement-based material

Technical field

The utility model relates to a kind of proving installation of Mechanical Properties of Cement-based Materials, relates in particular to the early stage elastic modulus measurement mechanism of a kind of cement-based material.

Background technology

The question synthesis that the early stage cracking of xoncrete structure relates to and complexity have contained the every aspect of the early stage calorifics of cement-based material, mechanics and deformation performance, and mineral admixture and additive are used the complicacy that has also greatly increased its early stage performance.The researcher has carried out a large amount of experimental studies to the early stage macro property of concrete both at home and abroad, attempts to illustrate the early stage Cracking Mechanism of concrete, early stage performance variation law and technical parameter problems of value.Wherein early stage elastic modulus is one of hot issue of being concerned about of researchist with the development and change process in the length of time, but traditional pass through the method that load-deformation is tried to achieve elastic modulus, at least to after test specimen is built form removal in a day, carry out, therefore be difficult to record the more early stage elastic modulus of cement-based material by traditional method.But early the length of time, elastic modulus was extremely important with contraction estimation, Crack Control etc. for its early stage stress for cement-based material, therefore how to make things convenient for, accurately measured units such as becoming design, construction, scientific research and be concerned about one of emphasis.

The utility model content

Technical problem to be solved in the utility model is to overcome the deficiencies in the prior art, the early stage elastic modulus measuring method of a kind of cement-based material and measurement mechanism are provided, can be implemented in from entering mould to the commitment of sclerosis, nondestructively the elastic modulus of cement-based material carried out continuous monitoring with development of age, thereby provide accurately elastic modulus parameter for the research of the early stage mechanics of cement-based material, deformation performance and Numerical Simulation Analysis.

The utility model specifically solves the problems of the technologies described above by the following technical solutions:

The early stage elastic modulus measuring method of a kind of cement-based material, the cement-based material to be measured that at first will mix and stir are full of and are packaged in prismatic hollow straight tube; Then should lie in a horizontal plane on two fulcrums by hollow straight tube, the combination free beam that formation is comprised of cement-based material to be measured and hollow straight tube, two fulcrums are arranged at respectively the hollow straight tube of distance wherein an end 0.224l place and 0.776l place, and l is the length of described hollow straight tube; By being arranged at the vibration transducer of described combination free beam midpoint, continue to monitor first natural frequency of vibration of combination free beam; Calculate the elastic modulus of cement-based material to be measured when be t the length of time by following formula:

$E_c\left(t\right)=[\mathrm{EI}\left(t\right)-E_a{I}_a]\frac{64}{\mathrm{\π}{d}_i^4}$

In the formula, E _cThe elastic modulus of the cement-based material to be measured when (t) representing to be t the length of time; E _aI _aRigidity for described hollow straight tube; d _iBe described hollow straight tube internal diameter; The rigidity of combination free beam when EI (t) represents to be t the length of time obtains by finding the solution following equation:

$\mathrm{EI}\left(t\right)=0.0788\stackrel{\&OverBar;}{m}{l}^4{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">f</figure-callout>}}^2$

Wherein,

Uniform quality for the combination free beam of unit length; L is the length of combination free beam; F is first natural frequency of vibration of combination free beam during t in the length of time, and t watered from cement-based material and counted after being filled with hollow straight tube the length of time.

Further, the method also comprises by adjusting the early stage elastic modulus of described hollow straight tube temperature survey cement-based material to be measured under different curing.Thereby realize providing accurately elastic modulus parameter to early stage mechanics, deformation performance research and the Numerical Simulation Analysis of cement-based material under different curing.

The cement-based material to be measured that mixes and stirs for the ease of perfusion, but described hollow straight tube can be at one end or two ends lid or the plug of folding and sealing are set; Also but both ends open seals an end with the tube sealing cock body first, more hollow straight tube is filled the cement-based material to be measured that mixes and stirs after, utilize the tube sealing cock body with the sealing of another openend.

The early stage elastic modulus measurement mechanism of a kind of cement-based material comprises:

Prismatic hollow straight tube is used for pouring into cement-based material to be measured;

Two bearing edges are arranged at respectively the hollow straight tube of distance wherein an end 0.224l place and 0.776l place, and l is the length of described hollow straight tube, is used for supporting described hollow straight tube, forms the combination free beam that is comprised of cement-based material to be measured and hollow straight tube;

Vibration measurement device comprises the vibration transducer that is arranged at described combination free beam midpoint, and the vibration signals collecting treating apparatus that is connected with vibration transducer.

Preferably, described measurement mechanism also comprises be used to the temperature control equipment of adjusting described hollow straight tube temperature.

Preferably, the cross section of described hollow straight tube is circle or rectangle.The cross sectional dimensions of described hollow straight tube is less than 150mm, and length is 400-1000mm.The material of described hollow straight tube is plastics or or macromolecular material or alloy material.

Compared to existing technology, the utlity model has following beneficial effect:

One, the utility model is the nondestructive test method, and test is before can advance to initial set the length of time.Because also not fully sclerosis before cement-based material condenses, be difficult to carry out load test by form removal and obtain elastic modulus, the utility model method does not need form removal, therefore can behind the device installation in position, namely can test, and mixture pouring and the whole process of device installation can be finished in 15 minutes.

Two, the utility model is a kind of monitoring method that initiatively receives signal, do not need artificial excitation, whole observation process is automatic and continuous, simultaneously can set curing temperature, the process that can be after the device installation namely can the early stage elastic modulus of continuous monitoring different curing cement-based material changes with the length of time.

Three, the utility model apparatus structure is simple, and is with low cost, and measuring method is easy to implement.

Description of drawings

Fig. 1 is the structural representation of the early stage elastic modulus measurement mechanism of the utility model cement-based material in the embodiment; Among the figure, 1 is hollow straight tube, and 2 is bearing edge, and 3 is vibration transducer, and 4 is data collecting instrument, and 5 is computing machine, and 6 is worktable, and 7 is the tube sealing cock body, and 8 is power supply, and 9 is power regulating switch;

Fig. 2 is the single order mode curve of free beam;

Fig. 3 is that water cement ratio is 0.35, curing temperature is 25.0 ℃ cement paste elastic modulus progress curve.

Embodiment

Below in conjunction with accompanying drawing the technical solution of the utility model is elaborated:

Thinking of the present utility model is that cement-based material to be measured and hollow straight tube are formed the combination free beam, by being arranged at the vibration transducer of combination free beam midpoint, continue to monitor the natural frequency of vibration of combination free beam, then try to achieve the elastic modulus in length of time morning of cement-based material to be measured according to the mechanical characteristic of combination free beam.

The early stage elastic modulus measurement mechanism of cement-based material of the present utility model as shown in Figure 1, comprises hollow straight tube 1, two bearing edges 2, vibration transducer 3 and the data collecting instruments 4 that are connected successively with vibration transducer 3, computing machine 5.The utility model measurement mechanism also comprises be used to the temperature control equipment of adjusting described hollow straight tube 1 temperature, adopted a kind of easy hollow straight tube temperature control equipment in this embodiment: the tube wall of hollow straight tube 1 is wound with resistive heater outward, outer parcel one layer of heat preservation material, resistive heater is connected with power supply 8 by power regulating switch 9, by regulating power switch 9, can make the tube wall of hollow straight tube 1 be heated to predetermined curing temperature behind the plugged 8.In this embodiment, the xsect of hollow straight tube 1 is circular, both ends open, and cross-sectional diameter is no more than 100mm, the preferred plastics of material (for example polystyrene) or alloy material, length is 600-1000mm.Vibration transducer 3 can adopt the sensors such as accelerometer or strainometer, and data collecting instrument 4 is with the adaptive data acquiring and recording equipment of sensor 3.

When carrying out the early stage elastic modulus of cement-based material, specifically in accordance with the following methods:

Step 1, according to test needs regulating power switch 9, hollow straight tube 1 is heated to predetermined curing temperature;

Step 2, according to test objective according to match ratio mix cement mixture;

Step 3, with the end sealing with hollow straight tube 1 of tube sealing cock body 7, the mixture that stirs is poured in the hollow straight tube 1, pouring is slight concussion simultaneously, bubble in the vent pipe;

Step 4, when cement mixture is about to fill, stop, leaving highly casting cement mixture not of about 10mm, with hollow straight tube 1 another openend wiped clean, use tube sealing cock body 7 that cement mixture is enclosed in the hollow straight tube 1;

Step 5, filling is had the hollow straight tube 1 of cement mixture to be placed horizontally to be fixed on two bearing edges 2 on the worktable 6, the position of two bearing edges 2 is respectively the hollow straight tube 1 of distance wherein an end 0.224l place and 0.776l place, l is the length of hollow straight tube 1, thereby forms the combination free girder construction that is comprised of cement mixture and hollow straight tube 1;

Step 6, in the midpoint of hollow straight tube 1 sensor 3 that gathers vibration signal is installed, and is connected with data collecting instrument 4;

Step 7, log-on data Acquisition Instrument 4 by the sensor 3 continuous collecting combination free beams vibration signal under the environmental interference around, and are preserved by data collecting instrument 4 records;

The vibration signal of step 8,5 pairs of data Acquisition Instruments of computing machine 4 records obtains the natural frequency of vibration of combination free beam through time domain and frequency domain conversion process, and according to the first calculation of natural vibration frequency combination free beam rigidity.Wherein, from vibration signal, extract the natural frequency of vibration and be existing mature technology, such as the DH5922 dynamic signalling analysis system of east, Jiangsu magnificent measuring technology incorporated company etc.The rigidity of combination free beam can obtain by finding the solution following equation:

$\mathrm{EI}\left(t\right)=0.0788\stackrel{\&OverBar;}{m}{l}^4{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">f</figure-callout>}}^2$

Wherein, Uniform quality for unit length combination free beam; L is the length of combination free beam; F is first natural frequency of vibration of the combination free beam when being t the length of time, and t watered from cement-based material and counted after being filled with hollow straight tube the length of time;

Step 9, calculate cement mixture elastic modulus in different length of time by following formula:

$E_c\left(t\right)=[\mathrm{EI}\left(t\right)-E_a{I}_a]\frac{64}{\mathrm{\&pi;}{d}_i^4}$

In the formula, E _cThe elastic modulus of the cement-based material to be measured when (t) representing to be t the length of time; E _aI _aRigidity for hollow straight tube 1;

d _iInternal diameter for hollow straight tube 1; The rigidity of combination free beam when EI (t) represents to be t the length of time;

Step 10, draw the early stage elastic modulus progress curve of cement-based material by result of calculation;

Step 11, the additive that adopts different match ratio, admixture variety classes and volume and the cement mixture of mineral admixture, repeating step 2～step 10 obtains different mixture ratio and admixture cement-based material elastic modulus progress curve under this curing temperature; By adjusting different curing temperatures, can obtain different mixture ratio and admixture cement-based material elastic modulus progress curve under the different curing.

In order to make the public further understand technical solutions of the utility model, the below provide technical solutions of the utility model theoretical derivation:

The beam Free Transverse differential equation is shown in (1):

$\mathrm{EI}\left(t\right)\frac{{\&PartialD;}^{4}y(x,t)}{\&PartialD;x^4}+\stackrel{\&OverBar;}{m}\frac{{\&PartialD;}^{2}y(x,t)}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">t</figure-callout>}}^2}=0---\left(1\right)$

In the formula, EI (t) is free beam rigidity, is the function of t in the length of time; Y (x, t) is the amount of deflection of beam, be about beam length direction x and the length of time t function;

Be the free beam linear mass.

For the beam Free Transverse differential equation that (1) formula is described, taking into account system has the vibration shape with time-independent, namely adopts the separation of variable to find the solution, and is the product of spatial function Y (x) and function of time T (t) with the beam vibration function decomposition.

So establish the solution of equation (1) be

y(x,t)=Y(x)T(t) （2）

In the formula, Y (x) is model function of vibration, characterizes whole vibration of beam form; T (t) is the function of time, characterizes the vibration regularity of putting on the beam.Formula (2) substitution equation (1) is got

$\mathrm{EI}\left(t\right)\frac{{\&PartialD;}^4\left[y\left(x\right)T\left(t\right)\right]}{\&PartialD;x^4}+\stackrel{\&OverBar;}{m}\frac{{\&PartialD;}^2\left[Y\left(x\right)T\left(t\right)\right]}{\&PartialD;{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">t</figure-callout>}}^2}=0$

Variables separation gets

$\frac{1}{T\left(t\right)}\frac{d^{2}T\left(t\right)}{\mathrm{<figure-callout\; id="2"\; label="d\; t"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">d</figure-callout>}{t}^{}{}^2}=-\frac{1}{Y\left(x\right)}\frac{\mathrm{EI}\left(t\right)}{\stackrel{\&OverBar;}{m}}\frac{d^{4}Y\left(x\right)}{{\mathrm{<figure-callout\; id="4"\; label="dx"\; filenames="130401145146.png,130401145152.png"\; state="\{\{state\}\}">dx</figure-callout>}}^4}$

The following formula equal sign left side and t are irrelevant, and equal sign the right is irrelevant with x, and then the both sides of equation must equal same constant, establish this constant and are-ω ², order $a^2=\frac{\mathrm{EI}}{\stackrel{\&OverBar;}{m}},$ ${\mathrm{\&beta;}}^4=\frac{{\mathrm{\&omega;}}^2}{a^2}$

Then obtain two second order ordinary differential equations

$\frac{d^{2}T\left(t\right)}{\mathrm{<figure-callout\; id="2"\; label="d\; t"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">d</figure-callout>}{t}^{}{}^2}+{\mathrm{\&omega;}}^{2}T=0---\left(3\right)$

$\frac{d^{4}Y\left(x\right)}{d{x}^4}-{\mathrm{\&beta;}}^{4}Y=0---\left(4\right)$

The solution of formula (3), (4) is respectively

Y(x)=C ₁cosβx+C ₂sinβx+C ₃coshβx+C ₄sinhβx （6）

The principal oscillation that gets beam is

Constant C in the formula ₁, C ₂, C ₃, C ₄And natural frequency ω is definite by boundary condition, constant b, Determined by starting condition.

For free beam, two ends are free, and namely bending and shearing equals zero, namely

$\mathrm{EI}\left(t\right)\frac{d^{2}Y\left(x\right)}{d{x}^2}=0,$ $\frac{d}{\mathrm{dx}}\left(\mathrm{EI}\left(t\right)\frac{d^{2}Y\left(x\right)}{{\mathrm{dx}}^2}\right)=0$ (x=0 or l)

Namely

Y''(0)=0，Y'''(0)=0

Y''(l)=0，Y'''(l)=0

The boundary condition substitution (6) at x=0 place is got

C ₂=C ₄，C ₁=C ₃

The boundary condition substitution (6) at x=l place is got

(sinhβl-sinβl)C ₁+(coshβl-cosβl)C ₂=0

(coshβl-cosβl)C ₁+(sinhβl+sinβl)C ₂=0

If following formula is set up and C ₁, C ₂Untrivialo solution is arranged, then have

$\left|\begin{array}{cc}\sinh \mathrm{\&beta;l}-\sin \mathrm{\&beta;l}& \cosh \mathrm{\&beta;l}-\cos \mathrm{\&beta;l}\\ \cosh \mathrm{\&beta;l}-\cos \mathrm{\&beta;l}& \sinh \mathrm{\&beta;l}+\sin \mathrm{\&beta;l}\end{array}\right|=0$

Find the solution this determinant, obtain frequency equation

coshβlcosβl=1

The root that solves the first first order mode is β l=1.506 π.

The single order inherent circular frequency that gets thus free beam is

$\mathrm{\&omega;}={\mathrm{\&beta;}}^{2}a={\left(\mathrm{\&beta;l}\right)}^{\text{2}}\sqrt{\frac{\mathrm{EI}}{\stackrel{\&OverBar;}{m}{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="130401145146.png,130401145152.png"\; state="\{\{state\}\}">l</figure-callout>}}^4}}=22.385\sqrt{\frac{\mathrm{EI}}{\stackrel{\&OverBar;}{m}{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="130401145146.png,130401145152.png"\; state="\{\{state\}\}">l</figure-callout>}}^4}}=\mathrm{\&xi;}\sqrt{\frac{\mathrm{EI}}{\stackrel{\&OverBar;}{m}{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="130401145146.png,130401145152.png"\; state="\{\{state\}\}">l</figure-callout>}}^4}}$

ξ in the formula=22.385 are called the first first order mode coefficient of free beam.

Order $r=\frac{C_1}{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="130401145146.png,130401145157.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}=\frac{\sin \mathrm{\&beta;l}-\sinh \mathrm{\&beta;l}}{\cos \mathrm{\&beta;l}+\cosh \mathrm{\&beta;l}}$

Then corresponding principal mode is

Y(x)=C ₁[cosβx-coshβx+r(sinβx-sinhβx)]

Get the first first order mode curve, as shown in Figure 2.As seen from the figure, under this state, beam has two nodes, make Y (x)=0 can get two node locations respectively at 0.224l and 0.776l place from test specimen one side end face, therefore, two edges of a knife that support free beam are located at respectively 0.224l and 0.776l place, first natural frequency of vibration that can more accurate mensuration combination beam.

According to following formula, get the computing formula of elastic modulus:

$\mathrm{EI}\left(t\right)=\frac{\stackrel{\&OverBar;}{m}{\mathrm{<figure-callout\; id="4"\; label="l"\; filenames="130401145146.png,130401145152.png"\; state="\{\{state\}\}">l</figure-callout>}}^4}{{\mathrm{\&xi;}}^2}{\mathrm{\&omega;}}^2$

ξ=22.385 and ω=2 π f substitutions are got

$\mathrm{EI}\left(t\right)=0.0788\stackrel{\&OverBar;}{m}{l}^4{f}^2---\left(8\right)$

Again

$\mathrm{EI}\left(t\right)=E_a{I}_a+E_c{I}_c\left(t\right)=E_a{I}_a+E_c\left(t\right)\frac{\mathrm{\&pi;}{\mathrm{<figure-callout\; id="4"\; label="d\; i"\; filenames="130401145146.png,130401145152.png"\; state="\{\{state\}\}">d</figure-callout>}}_i^{}}{64}---\left(9\right)$

In the formula, E _aI _aBe hollow straight tube rigidity; E _cI _cRigidity when (t) being t the length of time for cement-based material to be measured; E _cElastic modulus when (t) being t the length of time for water material; d _iInternal diameter for hollow straight tube.

Elastic modulus when therefore, cement-based material is t the length of time is:

$E_c\left(t\right)=[\mathrm{EI}\left(t\right)-E_a{I}_a]\frac{64}{\mathrm{\&pi;}{d}_i^4}---\left(10\right)$

Fig. 3 has shown that the water cement ratio that utilizes the utility model to obtain is 0.35, curing temperature is 25.0 ℃ cement paste elastic modulus progress curve.

Claims (5)

1. the early stage elastic modulus measurement mechanism of cement-based material is characterized in that, comprising:

Prismatic hollow straight tube is used for pouring into cement-based material to be measured;

Two bearing edges are arranged at respectively a wherein end 0.224 of the hollow straight tube of distance lPlace and 0.776 lThe place, lBe the length of described hollow straight tube, be used for supporting described hollow straight tube, form the combination free beam that is formed by cement-based material to be measured and hollow straight tube;

Vibration measurement device comprises the vibration transducer that is arranged at described combination free beam midpoint, and the vibration signals collecting treating apparatus that is connected with vibration transducer.

2. the early stage elastic modulus measurement mechanism of cement-based material as claimed in claim 1 is characterized in that, also comprises be used to the temperature control equipment of adjusting described hollow straight tube temperature.

3. the early stage elastic modulus measurement mechanism of cement-based material as claimed in claim 1 is characterized in that, the cross section of described hollow straight tube is circular.

4. the early stage elastic modulus measurement mechanism of cement-based material as claimed in claim 1 is characterized in that the cross sectional dimensions of described hollow straight tube is less than 150mm, and length is 400-1000mm.

5. the early stage elastic modulus measurement mechanism of cement-based material as claimed in claim 1 is characterized in that the material of described hollow straight tube is macromolecular material or alloy material.

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