CN101975555B - Strain measurement method based on light transmission measuring technology and device thereof - Google Patents

Strain measurement method based on light transmission measuring technology and device thereof Download PDF

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CN101975555B
CN101975555B CN2010102914964A CN201010291496A CN101975555B CN 101975555 B CN101975555 B CN 101975555B CN 2010102914964 A CN2010102914964 A CN 2010102914964A CN 201010291496 A CN201010291496 A CN 201010291496A CN 101975555 B CN101975555 B CN 101975555B
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test section
pin
rigidity
specimen test
strain
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CN101975555A (en
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姚磊江
郑翔
童小燕
曾垂宽
赵凯
胡国镇
魏佩佳
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Northwestern Polytechnical University
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Northwestern Polytechnical University
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Abstract

The invention provides a strain measurement method based on a light transmission measuring technology and a device thereof. The method is characterized by comprising the following steps: fixing two parallel rigid pins at both sides of a sample test section, wherein each rigid pin is perpendicular to the central axis in the stretching direction of the sample test section, and the length of each rigid pin is greater than the width of the sample test section; using a light transmission type digital micrometer to measure the initial distance between the two rigid pins, the real-time distance between the two rigid pins in the stretching process and the ultimate distance between the two rigid pins after the stretching operation; and calculating to obtain the real-time strain and the ultimate strain of the sample test section, wherein the measuring points of the micrometer are positioned at both sides of the sample test section and have the equal distance with the central axis in the stretching direction of the sample test section. By using the light transmission measuring technology to measure changes in the distance between the rigid pins in the stretching process, the invention realizes fast and convenient strain measurement of small-test area materials, flexible materials and large-deformation conditions. Besides, the invention overcomes the defects of the traditional measurement methods and well makes up the blind area of the application of various methods.

Description

A kind of strain measurement method and device thereof based on the light transmission measuring technique
Technical field
The invention belongs to strain measurement method and measurement mechanism in the mechanical field, be specially a kind of strain measurement method and device thereof based on the light transmission measuring technique.
Background technology
Strain measurement method in the mechanical field mainly contains the resistance-strain method at present, uses the mechanical electronic extensometer, and adopts holographic interferometry technique or the like.But in the resistance-strain method owing to receive the influence of foil gauge self area; It is often inapplicable when the less sample of surface area is measured; And foil gauge self also has intensity restriction, and when needs carry out large deformation when measuring, the resistance-strain method is often also inapplicable; And when using the mechanical electronic extensometer, need be clipped on the sample, tested surface is too little or too mostly inapplicable, and institute measure and monitor the growth of standing timber the rigidity of material must be enough greatly, otherwise material receives the strain of extensometer effect generation will influence the strain of material self; Equipment is expensive in the holographic interferometry technique, and when detecting, receives the interference of mechanical vibration, acoustic vibration (like neighbourhood noise) and surround lighting etc. big or the like, therefore need in the darkroom of quiet, cleaning, detect, and is very high to environmental requirement.These methods all are not suitable for being applied in the quick and convenient measurement of small test area material, flexible material and the strain of large deformation situation.
Summary of the invention
The technical matters that solves
Be not suitable for being applied to the technical matters in the quick and convenient measurement of small test area material, flexible material and the strain of large deformation situation for solving existing method, the present invention proposes a kind of strain measurement method and device thereof based on the light transmission measuring technique.
Technical scheme
Described a kind of strain measurement method based on the light transmission measuring technique is characterized in that: may further comprise the steps:
Step 1, fixing two rigidity that are parallel to each other are drawn pin in specimen test section both sides, and it is vertical with the central axis of specimen test section draw direction that rigidity is drawn pin, and rigidity is drawn the width of pin length greater than the specimen test section;
Step 2, adopt light pass through the formula digital micrometer measure two rigidity draw between pin apart from S lAnd S r, with S lAnd S rMean distance S=(S l+ S r)/2 are as the initial length S of specimen test section, wherein S lAnd S rThe measuring position be positioned at specimen test section both sides, and equate with the distance of specimen test section draw direction central axis;
Step 3, tensile sample, adopt light pass through the formula digital micrometer measure in real time two rigidity draw between pin apart from S ' lAnd S ' r, the measuring position is identical in measuring position and the step 2, with S ' lAnd S ' rMean distance S '=(S ' l+ S ' r)/2 are as the length S ' of specimen test section, through formula ε '=(S-S ')/S obtain in real time the strain stress of specimen test section ';
Step 4, when reaching the tensile force of setting, stop tensile sample, adopt light pass through the formula digital micrometer measure two rigidity draw between pin apart from S " tAnd S " r, the measuring position is identical in measuring position and the step 2, with S " lAnd S " rMean distance S "=(S " l+ S " r)/2 are as the final lengths S of specimen test section ", and through formula ε "=(S-S ")/S obtain the final strain stress of specimen test section ".
The method for optimizing of a kind of strain measurement method based on the light transmission measuring technique according to the invention is characterized in that: when sample material is metal material, use soldering fixedly rigidity draw pin; When sample material was nonmetallic materials, use viscose glue fixedly rigidity drew pin.
The method for optimizing of a kind of strain measurement method based on the light transmission measuring technique according to the invention is characterized in that: it is that the cylinder of even thickness draws pin that rigidity is drawn pin, and hardness reaches 45HRC at least.
A kind of device of realizing a kind of strain measurement method based on the light transmission measuring technique according to the invention; It is characterized in that: comprise that metallographictest platform and light pass through the formula digital micrometer; The metallographictest platform is fixed on the testing machine platform through the hole clipping of bottom, and two micrometer mounting grooves are arranged at metallographictest platform top, is symmetrical mark between two micrometer mounting grooves; There is the centering groove symmetry mark top, and the centering groove overlaps with symmetrical mark longitudinal center axis; Light passes through the formula digital micrometer and is placed in the micrometer mounting groove, and is close on the symmetrical mark; When having rigidity and draw the sample of pin and be installed on the testing machine, through the centering groove with sample centering.
Beneficial effect
The present invention measures rigidity through the light transmission measuring technique and draws the variable in distance of pin in drawing process, has realized the quick and convenient measurement to small test area material and strain of large deformation situation and stress.Overcome the defective of existing measuring method, remedied the blind area that several method is used preferably.
Description of drawings
Fig. 1: structural representation of the present invention;
Fig. 2: metallographictest platform structural representation;
Fig. 3: testing machine platform synoptic diagram;
Fig. 4: light passes through formula digital micrometer measuring principle figure;
Fig. 5: the synoptic diagram of dog bone shape sample;
Wherein: 1, metallographictest platform; 2, light passes through the formula digital micrometer; 3, sample; 4, rigidity is drawn pin; 5, testing machine platform; 6, micrometer mounting groove; 7, symmetrical mark; 8, centering groove; 9, lightening hole; 10, hole clipping; 11, testing machine platform base; 12, testing machine platform mounting boss; 13, light passes through formula digital micrometer transmitting terminal; 14, light passes through formula digital micrometer receiving end.
Embodiment
Specify the present invention below in conjunction with embodiment:
With reference to accompanying drawing 1, accompanying drawing 2 and accompanying drawing 3, the strain gauge means based on the light transmission measuring technique according to the invention comprises that metallographictest platform 1 and light pass through formula digital micrometer 2, and metallographictest platform 1 is fixed on the testing machine platform 5 through the hole clipping 10 of bottom; It is symmetrical mark 7 that metallographictest platform 1 top has between 6, two micrometer mounting grooves 6 of two micrometer mounting grooves, and there is centering groove 8 symmetrical mark 7 tops, and centering groove 8 overlaps with symmetrical mark 7 longitudinal center's axis; Light passes through formula digital micrometer 2 and is placed in the micrometer mounting groove 6, and is close on the symmetrical mark 7, and it is fixing with metallographictest platform 1 to use the micrometer jig that light is passed through formula digital micrometer 2; Have rigidity and draw the sample 3 of pin 4 and be installed on the testing machine, and specimen test section central axis aligns with centering groove 8, guarantee that measuring position that two light pass through formula digital micrometer 2 equates apart from the distance of specimen test section central axis.
In the present embodiment; Adopt above-mentioned strain gauge means that rectangle pure copper samples and dog bone shape pure copper samples (having provided the shape figure of dog bone form appearance in the accompanying drawing 5) have been carried out strain measurement; Use therein light passes through the LS-7010 of the model of formula digital micrometer 2 for the production of KEYENCE company; The rectangle pure copper samples is of a size of 16 * 1 * 9 (mm), and dog bone shape pure copper samples semipilot section section is of a size of 6 * 1 * 6 (mm).
At first; Adopt fixing two rigidity that are parallel to each other of soldering method to draw pin 4 in the test section both sides of rectangle pure copper samples and dog bone shape pure copper samples; It is vertical with the central axis of specimen test section draw direction that rigidity is drawn pin, and rigidity is drawn the width of the length of pin 4 greater than the specimen test section; The rigidity of using is drawn pin 4 and is drawn pin as the column type of even thickness, and hardness reaches 45HRC.
Secondly, draw the style 3 of pin 4 and be installed on the testing machine being fixed with rigidity, and specimen test section central axis aligns with centering groove 8, it is equal apart from the distance of specimen test section central axis to guarantee that two light pass through the measuring position of formula digital micrometer 2.Adopt light pass through formula digital micrometer 2 measure two rigidity draw between pin apart from S tAnd S r, S lBe the distance that measure measuring position, specimen test section left side, S rThe distance of measuring for measuring position, specimen test section right side is with S lAnd S rMean distance S=(S l+ S r)/2 are as the initial length S of specimen test section.
Next, the starting characteristics test machine, tensile sample, adopt light pass through formula digital micrometer 2 measure in real time two rigidity draw 4 on pin apart from S ' lAnd S ' r, with S ' lAnd S ' rMean distance S '=(S ' l+ S ' r)/2 are as the length S ' of specimen test section, through formula ε '=(S-S ')/S obtain in real time the strain stress of specimen test section '.And the style strain value that will obtain in real time combines with the stress value that drawing machine provides, and draws out stress-strain diagram.
At last, when testing machine reaches the tensile force of setting, stop tensile sample, adopt light pass through formula digital micrometer 2 measure two rigidity draw 4 on pin apart from S " lAnd S " r, with S " lAnd S " rMean distance S "=(S " l+ S " r)/2 are as the final lengths S of specimen test section ", and through formula ε "=(S-S ")/S obtain the final strain stress of specimen test section ".
Wherein, At the initial length S that obtains the specimen test section and the final lengths S of specimen test section " time; adopted following disposal route: under static force, make and use up formula digital micrometer 2 and carry out data acquisition with 2400 times/second frequency, continuous collecting data 10 seconds; thus the working majority certificate obtained, with measurement S lBe example, establish to gather and obtained S in 10 seconds altogether l24000 data be χ 1～χ 24000, obtain average and be:
χ ‾ = 1 24000 Σ i = 1 24000 χ i
Standard deviation is:
σ = Σ i = 1 24000 ( χ i - χ ‾ ) 2 23999
Use the La Yida criterion, reject gross error, promptly get rid of
Figure BSA00000282644000043
Outside value, ask again with remaining data once to obtain average
Figure BSA00000282644000044
Get
Figure BSA00000282644000045
All the other S r, S " lAnd S " rIn kind obtain.
Strain measurement measurement result of this method and resistance-strain method, the total body strain that records through drawing machine and the comparing result between the calculated value have been provided under 700N and 1400N tensile force below.Wherein owing under the 1400N tensile force, foil gauge is broken, thus there is not the resistance-strain method result under this condition, and under the 1400N tensile force, get into the plastic yield stage, there is not theoretical model yet.In addition, the total body strain that records through drawing machine is mainly used in the contrast of rectangle style, and this is that dog bone form appearance is quite different because total body strain of rectangle style should be identical with local train.In addition, in theory is calculated, because dog bone shape style out-of-shape can't calculate theoretical value.
Figure BSA00000282644000051
Result from table can find out that to small test area and large deformation sample, traditional resistance-strain method not only has limitation very much on measurement range, and the measurement result in tolerance range also exists than mistake; And that result that native system actual measurement strain obtains and theoretical value and drawing machine record total body strain is all more approaching, and measurement range is very big, but practice.

Claims (4)

1. strain measurement method based on the light transmission measuring technique is characterized in that: may further comprise the steps:
Step 1, fixing two rigidity that are parallel to each other are drawn pin in specimen test section both sides, and it is vertical with the central axis of specimen test section draw direction that rigidity is drawn pin, and rigidity is drawn the width of pin length greater than the specimen test section;
Step 2, adopt light pass through the formula digital micrometer measure two rigidity draw between pin apart from S lAnd S r, S lBe the distance that measure measuring position, specimen test section left side, S rThe distance of measuring for measuring position, specimen test section right side is with S lAnd S rMean distance S=(S l+ S r)/2 are as the initial length S of specimen test section, wherein S lAnd S rThe measuring position be positioned at specimen test section both sides, and equate with the distance of specimen test section draw direction central axis;
Step 3, tensile sample, adopt light pass through the formula digital micrometer measure in real time two rigidity draw between pin apart from S ' lAnd S ' r, the measuring position is identical in measuring position and the step 2, with S ' lAnd S ' rMean distance S '=(S ' l+ S ' r)/2 are as the length S ' of specimen test section, through formula ε '=(S-S ')/S obtain in real time the strain stress of specimen test section ';
Step 4, when reaching the tensile force of setting, stop tensile sample, adopt light pass through the formula digital micrometer measure two rigidity draw between pin apart from S " lAnd S " r, the measuring position is identical in measuring position and the step 2, with S " lAnd S " rMean distance S "=(S " l+ S " r)/2 are as the final lengths S of specimen test section ", and through formula ε "=(S-S ")/S obtain the final strain stress of specimen test section ".
2. a kind of strain measurement method based on the light transmission measuring technique according to claim 1 is characterized in that:
When sample material was metal material, pin was drawn in use soldering fixedly rigidity; When sample material was nonmetallic materials, use viscose glue fixedly rigidity drew pin.
3. a kind of strain measurement method based on the light transmission measuring technique according to claim 1 is characterized in that: it is that the cylinder of even thickness draws pin that rigidity is drawn pin, and hardness reaches 45HRC at least.
4. device of realizing the said strain measurement method based on the light transmission measuring technique of claim 1; It is characterized in that: comprise that metallographictest platform and two light pass through the formula digital micrometer; The metallographictest platform is fixed on the testing machine platform through the hole clipping of bottom, and two micrometer mounting grooves are arranged at metallographictest platform top, is symmetrical mark between two micrometer mounting grooves; There is the centering groove symmetry mark top, and the centering groove overlaps with symmetrical mark longitudinal center axis; Light passes through the formula digital micrometer and is placed in the micrometer mounting groove, and is close on the symmetrical mark; When having rigidity and draw the sample of pin and be installed on the testing machine, through the centering groove with sample centering.
CN2010102914964A 2010-09-25 2010-09-25 Strain measurement method based on light transmission measuring technology and device thereof Expired - Fee Related CN101975555B (en)

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