CN1176361C - Method for measuring stressed deformation of cement-base composite material - Google Patents
Method for measuring stressed deformation of cement-base composite material Download PDFInfo
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- CN1176361C CN1176361C CNB021065144A CN02106514A CN1176361C CN 1176361 C CN1176361 C CN 1176361C CN B021065144 A CNB021065144 A CN B021065144A CN 02106514 A CN02106514 A CN 02106514A CN 1176361 C CN1176361 C CN 1176361C
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Abstract
The present invention relates to a detection method for the stress distortion of a cement base composite material. A conducting film as a sensor, which is composed of chopped carbon fibers, graphite powder and an adhesive, is coated on the surface of a sample of a cement base composite material and is combined with a corresponding signal collecting device of a bridge circuit so as to detect the uneven deformation and the cracking of the sample of a cement base composite material under the condition that the sample of a cement base composite material stressed, loaded and impacted. The voltage variation and the current variation which are caused by the resistance variation of the conducting film are detected, and thus, the deformation and the cracking extent of the sample can be reflected.
Description
Technical field
The present invention relates to a kind of detection method of stressed deformation of cement-base composite material, belong to the building material technology category.
Background technology
Cement-base composite material, be by cement, water, sandstone gather materials and a little auxiliary material formulated.Produce gelatination by cement generation hydration reaction, the external phase of formation cement-base composite material is gathered materials sandstone and auxiliary material condense in together, forms firm artificial stone.Be present consumption maximum, most widely used building materials.
According to the difference of gathering materials that adopts, cement-base composite material can be divided into sand-cement slurry and concrete two big classes: it is formulated that sand-cement slurry mainly contains cement, water and fine aggregate (sand); Concrete batching need comprise that also coarse aggregate is the sandstone material.Though the Portland cement based composites have higher Young modulus (10～40GPa), tensile strength low (1～6MPa), failure strain is little by (10
-4～10
-2), almost be hard brittle material (Birchall J D.J Mat Sci Lett, 2,125-126,1982).Deficiency on these physics, the mechanical property is that the defective that the Portland cement based composites is caused in aquation, gelling forming process determines.
The defective that cement-base composite material exists comprises: the crackle that inhomogeneous contraction produced in (1) cement-base composite material process of setting; (2) bubble of bringing into by gathering materials in the cement-base composite material aquation whipping process solidifies formed hole, back at cement-base composite material.When these defectives make cement-base composite material be subjected to stretching, crooked deformation, cause stress to be concentrated to crack tip rapidly, crack the destruction that expansion causes material body.The aging of cement-base composite material quickened in the stripping that these defectives of while make the Portland cement based composites easily produce seepage and soluble-salt.B.Zhang (Cem.Concr.Res.20 (5), 699-771,1998) has carried out systematic research to the intensity of cement-base composite material and the relation of defective, draws the intensity of cement-base composite material and porosity and pore diameter and is negative correlation.
For improving the combination property of cement-base composite material, improve tensile strength, around serviceable life of song, compliance and prolongation cement-base composite material, people have released no gross imperfection (Macro-Defect-Free) MDF cement-base composite material (N.McN.ALFORD, J.Mat.Sci.20,37-45,1985).According to whether adopting the fiber reinforcement technology, be subdivided into MDF cement-base composite material and fiber reinforcement MDF cement-base composite material again; The MDF cement-base composite material is by adding a small amount of superpolymer to remove the gross imperfection of cement-base composite material; Fiber reinforcement MDF cement-base composite material is to add inorganic or polymer fiber, forms three-dimensional interpenetrating polymer network in matrix, comprehensively improves physics, the mechanical property of cement-base composite material.
Up to now, at cement-base composite material, people have done a large amount of research, but inconsistent at the detection method of the part mechanical property of cement-base composite material, make to detect data and lose comparability.
The physics of cement-base composite material, mechanical property test method and defective thereof
Unify the examination criteria except rupture strength, compressive strength have ISO, physics, the mechanical property----impact strength (Impact Energy/ImpactStrength) of all MDF cement based and fiber reinforced cement-based composite material, anti-bending strength, bent toughness (Flexural Toughness), tensile property detect index all and first crackle have the pass.But ISO, ASTM do not set up the detection method of standard as yet to the impact strength (Impact Energy/Impact Strength) of fiber reinforced concrete at present, yardstick to first crackle does not have clear and definite boundary, to one of important performance index of fiber reinforced concrete--the detection of-impact strength, it detects the different comparabilities that lose of the boundary of forever breaking that data cause because of detection method and impact.
CNS GB/T 15231.1～15231.5--94, the glass fiber reinforced cement method for testing performance, the width and the degree of depth (being accurate to 0.02mm) with the vernier caliper measurement impact fracture, and then calculated impact strength, run into the width of the impact fracture under fracture scrambling and the incomplete failure condition and the problems of measurement of the degree of depth equally.
The detection of the tensile property of fiber reinforced concrete and mortar, domestic basic with reference to GB15231.4-94 glass fiber reinforced cement method for testing performance.By pasting the resistance strain gage of test specimen central authorities, detect test specimen corresponding load-strain (stress-strain) curve in drawing process.By load-strain (stress-strain) curve calculation tensile strength and tensile modulus of elasticity, ultimate load when just having begun to leave straight line from load-strain (stress-strain) curve draws tension proportional limit intensity, draw tensile strength by peak load, the tensile property of fiber reinforced concrete is estimated.
The detection method of the anti-bending strength of fiber reinforced cement-based composite material, domestic all with reference to GB15231.4-94 glass fiber reinforced cement method for testing performance.With electronic universal tester (range 50kN, precision 1%),,, and also draw load-sag curve by function record until destruction with the speed loading of 2～5mm/min.Ultimate load when just having begun to leave straight line from load-sag curve draws bending resistance proportional limit intensity, draws bending strength by peak load, and the anti-bending strength of fiber reinforced concrete is estimated.
LOP＝(W
1L/bd
2)×10
3 (1)
MOR＝(W
2L/bd
2)×10
3 (2)
E
b＝(23W
3L
3/108δ
1bd
3)×10
3 (3)
LOP bending resistance proportional limit intensity, MPa
The MOR bending strength, MPa
E
bThe bending resistance elastic modulus, MPa
W
1Bending resistance proportional limit load, KN
W
2The bending resistance peak load, KN
W
32/3rds bending resistance proportional limit loads, KN
The L span, mm
The b specimen width, mm
The d specimen thickness, mm
δ
1W
3The amount of deflection that Shi Jiahe is ordered, mm
Its evaluation index bending resistance proportional limit intensity LOP, bending resistance elastic modulus E
b, all relevant with ultimate load when just having begun to leave straight line on load-sag curve.
Bending strength standard method of test when occurring with the bent toughness (FlexuralToughness) of ASTM C1018-97 fiber reinforced cement-based composite material and first crackle is similar.ASTM C1018-97 adopts three point type electronic sensors to measure the strain of sample in the load process, arranges that along the center line of sample upper surface two sensors place the top of sample two end supports symmetrically, and one is positioned at mid point.The measured strain of point sensor can draw the clean amount of deflection (strain) under the loading condition during the strain mean that records with two end sensors deducted, by load-sag curve, the bending strength the when bent toughness (Flexural Toughness) of evaluation fiber reinforced cement-based composite material and first crackle occur.
But, the load-sag curve of experiment gained, before reaching the bending resistance peak load, linearity can be very not desirable, and spill is arranged, and (figure (1) is a) and convex (scheme (1) b) two classes.No matter be the load-sag curve of spill and convex, to determining that pairing amount of deflection of first crackle (promptly beginning to leave the pairing amount of deflection of point that straight line is on the curve) and bending resistance proportional limit load (promptly beginning to leave the pairing load of point that straight line is on curve) all have the result of the load-sag curve of certain randomness, especially convex.This will cause index that the anti-bending strength of fiber reinforced concrete is estimated--and-bending resistance proportional limit intensity and bending resistance elastic modulus calculate and produce bigger error.
All there is unevenness in all cement-base composite material goods on microtexture and small scale macrostructure, in the GB15231.4-94 glass fiber reinforced cement method for testing performance, the resistance-strain agreement that contracts a film or TV play to an actor or actress of pasting test specimen central authorities is sixths of whole test specimen lifting surface area, can not reflect the nonhomogeneous strain that the fibre reinforced cement goods are subjected under the stretching condition being produced largely.ASTM C1018-97 adopts three point type electronic sensors to measure the strain of sample in the load processes, can not reflect the nonhomogeneous strain that the fibre reinforced cement goods are subjected under the bending condition being produced.
People are to physics, mechanical property----impact strength (Impact Energy/Impact Strength), anti-bending strength, bent toughness (FlexuralToughness), tensile property detection method and the evaluation of MDF cement based and fiber reinforced cement-based composite material, utilize the conducting concrete that adds carbon fiber as sensor, by detecting changes in resistance, can react concrete load-strain and cracking situation more all sidedly, in the dam deformation of patent 98119894.5, the automatic early-warning system that ftractures, be used; B.Glisic (Cement ﹠amp; Concrete Composites, 22,115-119,2000) utilize the optical fiber of identical material and length, with one as reference, another root places plastic tube as pre-buried induction optical fiber, and the phase place and the time of passing through the light of these two optical fiber by detection change to determine the intensity of variation of concrete construction.Distortion, cracking that these methods can only solve the large-sized concrete building detect.For the Performance Detection of determining cement-base composite material,, the MDF cement based of required detection and the character of fiber reinforced cement-based composite material matrix will be changed if add the conducting concrete technology of carbon fiber; Because the carbon fiber that adds plays humidification to cement-base composite material again both as the conduction medium of cement-base composite material, the MDF cement based of required detection and the original physics of fiber reinforced cement-based composite material, mechanical property have been changed.As use optical fiber, also there is similar problem.
Summary of the invention
The purpose of the detection method of a kind of stressed deformation of cement-base composite material of the present invention is to detect the nonhomogeneous strain that unevenness that the cement-base composite material goods exist on microtexture and small scale macrostructure causes, promptly provide the nonhomogeneous strain of cement-base composite material goods, the detection method of irregular cracking under stretching, bending and the impact condition being subjected to.
The enforcement approach of the detection method of a kind of stressed deformation of cement-base composite material of the present invention is, combine firm conducting film with sample as sensor by surface-coated at the cement-base composite material sample of required detection, sensor is connected with corresponding bridge circuit signal picker by pre-buried copper wire electrode or cable guide, sample stretched, crooked and impact the distortion and the cracking that produce and will directly cause conducting film itself to produce distortion and cracking, can reflect the deformation and the cracking degree of sample by detection conducting film changes in resistance.
In conjunction with test findings, just adopt conducting film as sensor, cement-base composite material is stressed by detecting, changes in resistance and changed by the voltage signal that resistance variations causes under the condition that is hit, and estimates the physics of cement-base composite material, the detection method of mechanical property is further elaborated.
(1), adopt conducting film as sensor
1) composition of conducting film
Adopt the tackifier that adds average length 3mm～12mm chopped carbon fiber, dag as conducting resinl, be coated on the cement-base composite material sample, form conducting film.Long dispersion, the too short formation conduction interpenetrating networks that are unfavorable for of being unfavorable for of chopped carbon fiber.
● the ratio of dag and carbon fiber (weight ratio); Dag: carbon fiber=1.0～30: 1
In conducting film, chopped carbon fiber forms interpenetrating networks, constitutes conductive bodies; Add dag and be for chopped carbon fiber being dispersed in the conducting film, making conducting film have uniform conductive, guarantee that conducting film self strain does not under external force produce uneven resistance variations.
Conducting film self thickness is 0.1～0.3mm, and the mechanical property to cement-base composite material does not exert an influence.
The main body of considering cement-base composite material is a silicate systems, and chemical property and glass that it is surperficial are close, and for ease of observation, adopting glass is base material coated with conductive glue, the distribution of chopped carbon fiber in the observation conducting film.Form conducting resinl with chopped carbon fiber, dag, tackifier, chopped carbon fiber is mixed earlier with dag, add tackifier and stir 1 minute mixing, on glass, brush on one side, form conducting film with hairbrush.Solidify the degree of scatter of back chopped carbon fiber in conducting film by microscopic.
Figure (2) is (a weight ratio behind a small amount of dag of interpolation; Dag: carbon fiber=3.5: 1), the distribution photo of chopped carbon fiber in conducting film, enlargement factor is 50; As can be seen from the figure, dag can insert carbon fiber bundle in whipping process, makes to reduce between the carbon fiber monofilament to fetter to be easy to separate, and carbon fiber has tended to into monofilament and evenly distributed, and does not have agglomeration.
Tackifier can adopt phenolics, epoxy resin and acrylate resin.
The ratio of chopped carbon fiber and tackifier (weight ratio):
Chopped carbon fiber: tackifier=0.1～5.0: 100
Specimen preparation, the glass sheet of employing 250mm * 30mm * 3.5mm, two ends are twined copper wire and are constituted electrode, two interelectrode distances are 180mm, evenly coat conducting resinl therebetween and form conducting film, see figure (3), the conducting resinl of coloured part for applying, copper wire electrode and the copper wire lead-in wire of gray line for twining.Brush conducting resinl and should surpass each 5～10mm of two interelectrode distances, guarantee that conducting film and the copper wire electrode that is twined have excellent contact.
Adopt glass sheet as conducting film condition test base material, consider that glass and cement-base composite material have close surface chemical property, the chemical bond power of conducting resinl and base material does not have bigger difference; Glass surface is than cement-base composite material smooth surface, and the mechanical bond force rate of conducting resinl and glass and the mechanical bond power of cement-base composite material are little, can not produce the judgement to the effect of conducting resinl in cement-base composite material; And glass material is more convenient for observing.
As tackifier, add the carbon fiber of varying number with modification acrylate 301,, detect the conductivity L of the conducting film after solidifying by figure (3) preparation conducting film.The conductivity L of conducting film and carbon fiber content W
tGood correlationship is arranged, see figure (4).Figure (4) is the volume conductance μ (ms/cm of conducting film
3) and carbon fiber content W
t(mg) relation.
Can utilize the content that changes carbon fiber in the conducting resinl, be designed to the sensor of different electric conductivities, satisfy different needs.
2), the resistance of conducting film variation characteristic in time
Tackifier is mixed with dag with chopped carbon fiber, stir 1 minute mixing and form conducting resinl, see Table 1.On glass, brush on one side with hairbrush, form conducting film.Detect corresponding resistance value under the different time with universal electric meter.
The full solidification time is that ((180mm * 50mm) is pressed in Jiao Mianshang to the paper slip of the glass sheet of 250mm * 30mm * 3.5mm) under a 70g A4 copy paper is cut out with onesize, in 10 minutes, when taking off paper slip, it is down sticking by the glue face to observe the paper fibers with 5 times magnifieres, and be the full solidification time corresponding room temperature following set time of this moment.
The composition of table 1, conducting resinl
With acrylate as the conducting film resistance of tackifier over time trend see figure (5); The conducting film resistance variations seldom after 10 hours.
Phenolic aldehyde, epoxy resin also have similar results, but set time is slower as the conducting film of tackifier than modification acrylate.
Above-mentioned experimental result can draw:
● modification acrylate is as the conducting film of tackifier, and curing rate is fast, and the resistance of conducting film changes little in time; Comparatively desirable.The preferred modification acrylate that uses is as tackifier.
3), the bonding force of conducting film and breaking elongation
With modification acrylate 301,302, each 20g as tackifier, add carbon fiber 0.150g, the dag 1.50g of average length 6mm, on the PET film of the glass sheet of 250mm * 30mm * 3.5mm and 250mm * 30mm * 0.12mm, brush the preparation conducting film respectively; The PET film is the conducting film preparation reference figure (3) of carrier.Solidify after 10 hours, examination peels the conducting film on the glass sheet and surveys its breaking elongation; The PET film stretches with conducting film as carrier, measures the breaking elongation of conducting film.Adopt the bridge signal collector in the test, the voltage signal sudden change that the monitoring conducting film produces during corresponding to fracture in drawing process; Set rate of extension 100mm/min, on the Shinbch tensilometer, detect its breaking elongation, the results are shown in table (2).
The adhesive effect and the breaking elongation of the conducting film of table (2), different tackifier
Conducting film must guarantee that conducting film and cement-base composite material sample have good bonding force, and the elastic strain of conducting membrane material can not be too wide in the gap with the strain of cement-base composite material as the strain transducer as cement-base composite material.When the cracking strain took place for the conducting film that elasticity is very good, cement-base composite material, itself did not break conducting film, and hop does not take place its resistance changes.Can draw from the result of table (2):
The tackifier that a, modification acrylate are used as the preparation conducting film has good cementability, the strain of reaction water cement-based composite material in time.
B, the formed conducting film of modification acrylate 301,302 systems, its breaking strain exceeds a scalar product than the failure strain (about 0.0005) of cement-base composite material, comparatively approaching with the MDF cement-base composite material, be a kind of comparatively desirable cement-base composite material strain, cracking inductive material.
(4), the resistance variations of glass breakage and conducting film
, mix with dag respectively as tackifier with acrylate 301, stir and be mixed into conducting resinl in 1 minute, by shown in the figure (3), on glass, brush on one side, make conducting film with hairbrush with chopped carbon fiber.
After the full solidification, glass sheet is scribbled one of conducting film face down, place on the smooth desktop, touch the glass sheet stage casing, and break to glass sheet, detect the resistance change of corresponding conducting film before and after each the impact with universal electric meter with the tip iron staff.The experiment discovery, before the glass sheet fracture, conducting film resistance substantially constant; During the glass sheet fracture, resistance variations is bigger.The results are shown in table (3).
The resistance variations of conducting film before and after the composition of table (3), conducting resinl and the glass breakage
As can be seen, its conducting film is before and after the glass cracking from table (3), and resistance value has the variation of scalar product, is suitable for cement-base composite material strain, cracking inductive material.This conclusion can also be behind the glass sheet cracking, and the bonding state of breach place conducting film and glass sheet obtains being close to card, sees figure (6a), (6b).
Figure (6a), acrylate 301 system glass sheet breach microphotos, (glass is up) (enlargement factor: 50).
Figure (6b), acrylate 301 system glass sheet breach microphotos, (conducting film faces up) (enlargement factor: 50)
From figure (6a), (6b) as can be seen, acrylate is the conducting film of tackifier, and its breach position is identical with the position of carrier glass cracking, has reflected that also conducting film combines closely with the glass sheet matrix, to the fracture of the matrix of coating and the response that deformation has sensitivity.
It is conducting film sensor will have sensitivity to the nonhomogeneous strain of cement-base composite material sample reflection.
(2), signal picker
1, signals collecting principle
The bridge circuit signal picker is seen synoptic diagram (7), wherein:
R
1, R
2, fixed resistance, R
1=R
2Ω
R
3, variable resistor, replace Ω with the 10K potentiometer
R
g, galvanometer G resistance Ω
R
x, testing resistance Ω
I
g, galvanometer G electric current A
V
g, galvanometer G the voltage V at two ends
E, dc constant voltage power supply V
D
1, D
2Be light emitting diode
K, contactor
I
g＝(R
2R
3-R
1R
x)E/{(R
1R
2R
3+R
2R
3R
x+R
3R
xR
1
+R
xR
1R
2+R
g(R
1+R
3)(R
2+R
x)} (4)
Get R
1=R
2=R 〉=10R
3, R
3With R
xIn the time of quite, I
gNumerical value and (R
3-R
x) be directly proportional, work as R
xWhen sudden change occurring, pairing galvanometer electric current I
gVoltage V with the galvanometer two ends
gSudden change also will occur, formula (4) can be approximated to be formula (5).
I
g＝(R
3-R
x)RE/{R
2R
3+2RR
3R
x+R
2R
x+R
2R
g} (5)
V
g＝I
gR
g (6)
Get R
1=R
2=R～R
g〉=10R
3, formula (5), formula (6) can be approximated to be formula (7), formula (8) respectively.
I
g＝(R
3-R
x)E/{RR
g} (7)
V
g＝(R
3-R
x)E/R (8)
R
3Known, response signal I
g, V
gDirectly and R
xBe varied to linear relationship.
According to formula (4), (6), (8) as can be known, when open circuit and two kinds of extreme cases of short circuit appearred in the resistance that is detected, voltage direction was opposite;
Open circuit: R
x＞＞R
3, V
g＜0
Short circuit: R
x=0, V
g＞0
Can select light emitting diode D for use
1, D
2In parallel with galvanometer, the optics shows signal during as open circuit and short circuit.
2, the making of signal picker
The bridge diagram signal picker is seen synoptic diagram (7), comprises fixed resistance (R
1, R
2), variable resistor R
3, galvanometer (G), coated with conductive film cement-base composite material sample (testing resistance R
x), light emitting diode (D
1, D
2), dc constant voltage power supply E, contactor K, connect with lead; Wherein:
1), fixed resistance, R
1=R
2=5000～100000 Ω
2), variable resistor R
3, replace with 1K～10K potentiometer
3), the light emitting diode of two different colours being connected with galvanometer G reverse parallel connection, as red, green light emitting diode; R
xShort circuit pipe light-emitting diodes D
2In time, glow, R
xOpen circuit pipe light-emitting diodes D
1The time green light
4), also available voltmeter replaces variation with detectable voltage signals in galvanometer G position
5), adopt cable guide with R
xWith being connected of bridge diagram, being convenient to sample and changing
6), adopt the dc constant voltage power supply E of 4.5～12V, wherein the K switch that is connected of an end and circuit is just connected during test.
Carbon fiber addition in the practical operation, in the control conducting film makes R
x≤ 500 Ω guarantee 10R
x～10R
3≤ R
1=R
2=R～R
g
The detection method of a kind of stressed deformation of cement-base composite material of the present invention, combine firm conducting film with sample as sensor and bridge circuit signal picker by surface-coated at the cement-base composite material sample of required detection, the deformation and the cracking degree that stretched at sample by detecting, the conducting film changes in resistance under bending and the impact condition can reflect sample can accurately detect the nonhomogeneous strain that unevenness that the cement-base composite material goods exist causes on microtexture and small scale macrostructure.
Description of drawings:
Figure (1), load (LOAD)-amount of deflection (DEFLECTION) curve, (figure (1) is a) and the convex that is bent upwards (figure (1) b) curve to reach reclinate spill before the bending resistance peak load.
Figure (2), the distribution photo of chopped carbon fiber in conducting film, enlargement factor is 50 (weight ratio, dags: carbon fiber=3.5: 1).
Figure (3), coated with conductive glue forms the glass sheet of the 250mm * 30mm * 3.5mm of conducting film.
Figure (4), the volume conductance μ (ms/cm of conducting film
3) and carbon fiber content W
t(mg) relation.
Figure (5), acrylate is as the conducting film resistance R (ohm) of the tackifier variation tendency of T (min) in time.
Figure (6a), the electropane sheet breach microphoto of acrylate 301 systems, (glass is up) (enlargement factor: 50).
Figure (6b), the electropane sheet breach microphoto of acrylate 301 systems, (conducting film faces up) (enlargement factor: 50)
Figure (7), bridge circuit signal picker synoptic diagram.
Figure (8), the mortar specimen synoptic diagram of surface-coated conducting film.
Figure (9), simple and easy ball falling impact experimental provision synoptic diagram.
Figure (10), the bruise area S of fine-denier polypropylene staple fibres refinforced cement mortar and change in voltage (V
g-V
G0) relation
Be described further below in conjunction with embodiment.
Embodiment
Embodiment 1:
1, specimen preparation
1), fine-denier polypropylene staple fibres refinforced cement mortar
Ratio: cement: normal sand: water=1: 2.5: 0.44
The fine-denier polypropylene staple fibres volume:
Fine-denier polypropylene staple fibres: sand-cement slurry=1: 1000 (volume ratio)
Mixing time: cement+fiber 1.5min
Cement+fiber+normal sand+water 3min
The vibrations time; 2min
Maintenance is 24 hours in the standard, the demoulding, natural curing 28 days.
2), sample surface-coated conducting film
After the length of time, specimen surface is handled with conducting resinl and is formed conducting film sensor, sees figure (8) in sand-cement slurry and the natural curing of fine-denier polypropylene staple fibres refinforced cement mortar.Figure (8) is the mortar specimen synoptic diagram of surface-coated conducting film.
Copper wire is twined at sample both ends of the surface 20mm place, as electrode.Except lead portion, the copper wire of specimen surface is covered by conducting film.
3), the conducting resinl that forms conducting film is formed
Table (4), conducting resinl are formed
2, the impact experiment of fine-denier polypropylene staple fibres refinforced cement mortar
The test specimen of coated with conductive film is placed by figure (9), regulated the annulus size and guarantee that the steel ball center of Φ 55mm is concordant with the annulus root edge, apart from cement flooring 290mm.The placement location of base, cement-base composite material sample is drawn good graticule on smooth cement flooring, each ball falling impact experiment back guarantees that as being subjected to displacement timely adjustment each impact position does not change.Steel ball quality is 236g.
Its contact conductor is connected with signal picker, energized, regulator potentiometer makes the voltage of universal electric meter approach zero, the record initial voltage.Carry out impact experiment with quality for the 236g steel ball.Every impact once detects crackle width and length in conjunction with 5 times magnifieres with vernier caliper, and the record correspondent voltage, and the signal of observation light emitting diode changes.
3, experimental result
The impact experiment of fine-denier polypropylene staple fibres refinforced cement mortar the results are shown in Table (5) and figure (10).Figure (10) is the bruise area S and the change in voltage (V of fine-denier polypropylene staple fibres refinforced cement mortar
g-V
G0) relation, begin generating region at crackle, the bruise area of fine-denier polypropylene staple fibres refinforced cement mortar becomes good linear relationship with change in voltage.
Table (5), V
G0=12mV, R
X0=70.2 Ω
| Impact number of times | Voltage V g(mV) | Change in voltage (V g-V g0)mV | Crackle (width * length) area S (mm 2) |
| 1 | 53 | 41 | 0.1×40 |
| 2 | 58 | 46 | 0.1×50 |
| 3 | 75 | 63 | 0.1×80 |
| 4 | 110 | 98 | 0.1×100 |
| 5 | 190 | 178 | 0.1×40+0.2×80 |
Embodiment 2:
1, specimen preparation
1), sand-cement slurry
The ratio of a, fine-denier polypropylene staple fibres refinforced cement mortar and fine-denier polypropylene staple fibres volume, mixing time, vibrations time, standard curing time are with embodiment 1.
The ratio of b, conventional cement mortar, mixing time, vibrations time, the same a of maintenance.Do not add fine-denier polypropylene staple fibres.
2), sample surface-coated conducting film is with embodiment 1.
3), the conducting resinl that forms conducting film is formed with embodiment 1.
2, the impact experiment of sand-cement slurry is with embodiment 1.
2. experimental result
Table (6),
| Sample | The natural curing time (my god) | Change in voltage (V g-V g0)mV | Crackle (width * length) area S (mm 2) | ||
| No. | Kind | Measured area | Reference area | ||
| 1 | b | 110 | 34.1 | 0.1×60 | 3.6 |
| 2 | a | 110 | 52.4 | 0.1×70 | 5.6 |
| 3 | a | 83 | 31.3 | 0.1×18 | 3.3 |
| 4 | a | 83 | 71.2 | 0.1×92 | 7.8 |
| 5 | a | 83 | 115.6 | 0.1×40+0.2×40 | 12.5 |
Reference area is according to figure (10) bruise area S and change in voltage (V
g-V
G0) relation, by actual measurement change in voltage (V
g-V
G0) the corresponding bruise area S of calculating.
Claims (5)
1. the detection method of a stressed deformation of cement-base composite material, it is characterized in that described detection method is to adopt the conducting film of chopped carbon fiber, dag, tackifier formation as sensor, detects by the stress and deformation of bridge circuit signal picker to cement-base composite material;
Described conducting film is made of dag, chopped carbon fiber, tackifier, and it consists of: by weight
Dag: chopped carbon fiber=1.0～30: 1
Chopped carbon fiber: tackifier=0.1～5.0: 100
The average length of described chopped carbon fiber is 3mm～12mm;
Galvanometer G reverse parallel connection in the described bridge circuit signal picker connects the light emitting diode of two different colours.
2. the detection method of a kind of stressed deformation of cement-base composite material according to claim 1 is characterized in that used tackifier is phenolics, epoxy resin and acrylate resin.
3. the detection method of a kind of stressed deformation of cement-base composite material according to claim 1 is characterized in that the fixed resistance R of bridge circuit signal picker
1=R
2=5000～100000 Ω.
4. the detection method of a kind of stressed deformation of cement-base composite material according to claim 1 is characterized in that the variable resistor R of bridge circuit signal picker
3It is 1K～10K potentiometer.
5. the detection method of a kind of stressed deformation of cement-base composite material according to claim 1 is characterized in that the bridge circuit signal picker adopts the dc constant voltage power supply of 4.5～12V.
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| CNB021065144A CN1176361C (en) | 2002-02-26 | 2002-02-26 | Method for measuring stressed deformation of cement-base composite material |
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