CN103278268A - Stress testing device and stress concentration testing method based on speckle interference principle - Google Patents

Abstract

The invention relates to a stress testing device and stress concentration testing method based on the speckle interference principle. The stress testing device and stress concentration testing method based on the speckle interference principle solves the problems that according to an existing laser speckle technology, a process for regulation a light path is cockamamie and complex, flexibility is poor, and the existing laser speckle technology can be only used for laboratory measurement analysis and cannot carry out on-site measurement on actual components with large sizes and complex space shapes. Four collimation beam expanding mirrors are adopted in the stress testing device and stress concentration testing method and are arranged on the surface of a tested piece symmetrically, two beams of collimation parallel laser are obtained, a digital CCD camera is used for collecting four speckle field images loaded before and after deformation respectively through control of on-off of four paths of light, and the computer digital picture processing technique is adopted to obtain displacement distribution in two orthogonal directions to further obtain distributed information of stress states of a tested area. The stress testing device and stress concentration testing method is applied to crossing fields of materials science, optics and mechanics.

Description

Stress test device and stress based on the speckle interference principle are concentrated method of testing

Technical field

The present invention relates to materialogy, optics and mechanics crossing domain, be specifically related to concentrate method of testing based on stress test device and the stress of speckle interference principle.

Background technology

The laser speckle interferometry technology is called the electronic speckle pattern interferometry technology again, is a kind of based on nondestructive measurement optics, the whole audience, non-contacting and detection technique.When a branch of coherent light was radiated at smooth coarse reflecting surface, irreflexive light wave mutual superposition will form light and dark mottled distribution, just speckle field.Speckle field is recording the geological information of body surface, utilizes suitable light path and treatment technology, can measure and detect surface displacement, strain, roughness, three-dimensional appearance etc.

Stress measurement means commonly used at present are electrical measuring methods, put up resistance strain gage on the surface of measured body exactly, read strain information at electric wire strain gauge, and recycling mechanics of materials formula calculates the stress value of measured point.The measured result's of this method precision is subjected to foil gauge and puts up the stability of quality, electric wire strain gauge input voltage, the influence of various factors such as power of test environment electromagnetic interference (EMI), can only carry out point-to-point measurement to limited measured point, can not obtain the ess-strain distributed intelligence of the whole audience.And, because this method acquisition is the mean strain value of foil gauge sensitive grid corresponding region, being subjected to the restriction of sensitive grid size, the measuring error under the situation of high gradient strain field is bigger.

Because the laser speckle interferometry measuring technique is a kind of measuring technique of the whole audience, can carry out high-precision measurement to micron-sized little displacement, be used for this technology among the stress measurement and develop corresponding device, will solve problem and difficulty that electrical measuring method is measured ess-strain.But, existing laser speckle method, need to adopt optical mirror slips such as beam splitter, reflective mirror to build space optical path, need special shock insulation platform to arrange required optical element, not only regulate the process very complicated of light path, and very flexible, only can be used for the laboratory measurement analysis, can't actual components huge to size, that spatial form is complicated carry out in-site measurement.

Summary of the invention

The present invention deposits the process very complicated of regulating light path in order to solve existing laser speckle technique, and very flexible, only can be used for the laboratory measurement analysis, can't be huge to size, problem that actual components that spatial form is complicated is carried out in-site measurement.Thereby proposed to concentrate method of testing based on stress test device and the stress of speckle interference principle.

Stress test device based on the speckle interference principle comprises digital CCD camera, four collimator and extender mirrors, single-mode laser, fiber coupler, fiber optic splitter and computing machines,

The laser of described single-mode laser emission is delivered to fiber optic splitter through optical fiber after being coupled by fiber coupler, and fiber optic splitter is divided into four bundle laser with beam of laser, and described four bundle laser are delivered to four collimator and extender mirrors through optical fiber respectively,

Four bundle collimation parallel laser light beam irradiates of four collimator and extender mirror emissions form speckle field on the test specimen surface,

Described four collimator and extender mirrors are symmetrically distributed in twos, four collimator and extender mirrors are divided into two groups, every group comprises two collimator and extender mirrors, the two light beams of two the collimator and extender mirrors emission in every group lay respectively at measured surface normal both sides and described two light beams identical with the angle of normal, described two light beams is thing light and reference light each other, and the camera lens of each collimator and extender mirror equates with the distance on test specimen surface;

Wherein the two light beams and the test specimen surface normal that send of one group of collimator and extender mirror is coplanar in the xoz plane, and two light beams and test specimen surface normal that another group collimator and extender mirror sends are coplanar in the yoz plane; Described xoz plane is vertical mutually with the yoz plane;

Numeral CCD camera is used for taking the speckle field on test specimen surface, and the data output end of digital CCD camera is connected with the data input pin of computing machine.

Described digital CCD camera adopts the industrial camera of 1,300,000 pixels, and the camera lens of this camera is the micro magnifier head.

Single-mode laser is single-mode He-Ne laser.

Fiber optic splitter is one fen four polarization-maintaining beam splitter.

The stress test method of speckle interference principle comprises the steps:

Two bundle collimation parallel laser light beam l of step 1, one group of collimator and extender mirror emission of unlatching ₁And l ₂Be radiated at the test specimen surface and form speckle field x1,

Step 2, gather the speckle field x1 on test specimen surface by digital CCD camera, and this speckle field x1 is sent to computing machine, close this group collimator and extender mirror;

Two bundle collimation parallel laser light beam l of step 3, the other one group of collimator and extender mirror emission of unlatching ₃And l ₄Be radiated at the test specimen surface and form speckle field y1,

Step 4, gather the speckle field y1 on test specimen surface by digital CCD camera, and this speckle field y1 is sent to computing machine, close this group collimator and extender mirror;

Step 5, test specimen is applied a load, make the test specimen surface produce elastic deformation, the speckle field on test specimen surface changes;

Step 6, the described one group of collimator and extender mirror of unlatching step 1, two bundle collimation parallel laser light beam l of this group collimator and extender mirror emission ₁And l ₂Be radiated at the test specimen surface and form speckle field x2, gather the speckle field x2 on test specimen surface by digital CCD camera, and this speckle field x2 is sent to computing machine, close this group collimator and extender mirror;

Step 7, the described one group of collimator and extender mirror of unlatching step 3, two bundle collimation parallel laser light beam l of this group collimator and extender mirror emission ₃And l ₄Be radiated at the test specimen surface and form speckle field y2, gather the speckle field y2 on test specimen surface by digital CCD camera, and this speckle field y2 is sent to computing machine, close this group collimator and extender mirror;

Step 8, computing machine carry out calculation process to speckle field x1 and the speckle field x2 before and after loading, and obtain along light beam l ₁And l ₂The displacement e of direction; In like manner, computing machine carries out calculation process to speckle field y1 and the speckle field y2 before and after loading, and obtains along light beam l ₃And l ₄The displacement c of direction according to displacement e and the c on two mutually orthogonal directions, adopts Elasticity and mechanics of materials formula, obtains the information that stress is concentrated size and location.

Two bundle collimation parallel laser light beam l of one group of collimator and extender mirror emission of the described unlatching of step 1 ₁And l ₂Be radiated at the test specimen surface and form speckle field x1, described two bundle collimation parallel laser light beam l ₁And l ₂Coplanar in the xoz plane with the test specimen surface normal, the optical function I1_x of the speckle field of speckle field x1 correspondence is:

Wherein, the light intensity value at I1_x (r) expression r place, position, u _{1_x}Expression collimation parallel laser light beam l ₁Position r place the light wave amplitude, u _{2_x}Expression collimation parallel laser light beam l ₂Position r place the light wave amplitude,

Expression collimation parallel laser light beam l ₁Position r place the phasing degree,

Expression collimation parallel laser light beam l ₂The phasing degree at position r place.

Step 3 is opened two bundle collimation parallel laser light beam l of other one group of collimator and extender mirror emission ₃And l ₄Be radiated at the test specimen surface and form speckle field y1, described two bundle collimation parallel laser light beam l ₃And l ₄Coplanar in the yoz plane with the test specimen surface normal, the optical function I1_y of the speckle field of speckle field y1 correspondence is:

Wherein, the light intensity value at I1_y (r) expression r place, position, u _{3_y}Expression collimation parallel laser light beam l ₃Amplitude, u _{4_y}Expression collimation parallel laser light beam l ₄Amplitude,

Expression collimation parallel laser light beam l ₃The phasing degree,

Expression collimation parallel laser light beam l ₄The phasing degree.

The optical function I2_x of the speckle field of the described speckle field x2 of step 6 correspondence is:

（3）

Wherein,

Expression collimation parallel laser light beam l ₁Variable quantity at phasing degree, position r place,

Expression collimation parallel laser light beam l ₂Variable quantity at phasing degree, position r place,

The optical function I2_y of the speckle field of the described speckle field y2 of step 7 correspondence is:

（4）

Wherein,

Expression collimation parallel laser light beam l ₃Variable quantity at phasing degree, position r place

Expression collimation parallel laser light beam l ₄Variable quantity at phasing degree, position r place,

The detailed process that obtains the information of test specimen surface stress field distribution state is:

Computing machine carries out calculation process to speckle field x1 and the speckle field x2 before and after loading, and obtains along light beam l ₁And l ₂The detailed process of the displacement e of direction is:

Speckle field x1 and speckle field x2 are carried out the size reduction mode processing, obtain the light intensity difference according to formula (5)

Computing machine carries out calculation process to speckle field y1 and the speckle field y2 before and after loading, and obtains along light beam l ₃And l ₄The detailed process of the displacement c of direction is:

Speckle field y1 and speckle field y2 are carried out the size reduction mode processing, obtain the light intensity difference according to formula (6)

With in formula (5) and (6)

With

Substitution formula (7) and (8) can obtain two displacement e and c on the orthogonal directions respectively:

Wherein, λ represents to collimate the wavelength of parallel laser, θ ₁Expression collimation parallel laser light beam l ₁And l ₂With the angle of test specimen surface normal, θ ₁Expression collimation parallel laser light beam l ₃And l ₄With the angle of test specimen surface normal, e represents to collimate parallel laser light beam l ₁And l ₂The displacement of direction, c represents to collimate parallel laser light beam l ₃And l ₄The displacement of direction;

To collimate parallel laser light beam l ₁And l ₂The displacement e of direction and collimation parallel laser light beam l ₃And l ₄The displacement c substitution Elasticity geometric equation (9) of direction obtains the normal strain ε on two orthogonal directionss _xAnd ε _yAnd shear strain γ _Xy

${\mathrm{\ϵ}}_x=\frac{\∂e}{\∂x}$

${\mathrm{\ϵ}}_y=\frac{\∂c}{\∂y}---\left(9\right)$

${\mathrm{\γ}}_{\mathrm{xy}}=\frac{\∂e}{\∂y}+\frac{\∂c}{\∂x}$

Obtain the stress state of test specimen surface each point according to formula (10):

$\left.\begin{array}{c}{\mathrm{\σ}}_x=\frac{E}{1-v^2}({\mathrm{\ϵ}}_x+{\mathrm{v\ϵ}}_y)\\ {\mathrm{\σ}}_y=\frac{E}{1-v^2}({\mathrm{\ϵ}}_y+{\mathrm{v\ϵ}}_x)\\ {\mathrm{\τ}}_{\mathrm{xy}}=\frac{E}{2(1+v)}{\mathrm{\γ}}_{\mathrm{xy}}\end{array}\right\}---\left(10\right)$

Wherein, E represents the elastic modulus of test specimen material, and ν represents Poisson ratio;

Obtain principle stress and principal direction according to formula (11):

$\left.\begin{array}{c}{\mathrm{\&sigma;}}_1=\frac{{\mathrm{\&sigma;}}_x+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00003285216100011.png,HDA00003285216100031.png"\; state="\{\{state\}\}">y</figure-callout>}}}{2}+\frac{1}{2}\sqrt{{({\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y)}^2+4{\mathrm{\&tau;}}_{\mathrm{<figure-callout\; id="2"\; label="xy"\; filenames="HDA00003285216100011.png,HDA00003285216100031.png"\; state="\{\{state\}\}">xy</figure-callout>}}^2}\\ {\mathrm{\&sigma;}}_2=\frac{{\mathrm{\&sigma;}}_x+{\mathrm{\&sigma;}}_y}{2}-\frac{1}{2}\sqrt{{({\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y)}^2+4{\mathrm{\&tau;}}_{\mathrm{<figure-callout\; id="2"\; label="xy"\; filenames="HDA00003285216100011.png,HDA00003285216100031.png"\; state="\{\{state\}\}">xy</figure-callout>}}^2}\\ {\mathrm{\&theta;}}_P=\frac{1}{2}\arctan (-\frac{{2\mathrm{\&tau;}}_{\mathrm{xy}}}{{\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y})\end{array}\right\}---\left(11\right)$

Wherein, σ ₁The expression first principal stress, σ ₂The expression second principal stress, θ _pExpression principal direction,

Information according to principle stress and principal direction acquisition test specimen surface stress field distribution state realizes the measurement of full field to the structural member stress state.

The space optical path that the present invention adopts single-mode laser and fiber optic splitter to replace catoptron and beam splitter to form, not only saved the loaded down with trivial details work of light path of adjusting, and increased dirigibility and the accessibility of light path system greatly, overcome the difficult problem that classic method can't be applied to large and complex structure spare in-site measurement effectively.This law adopts the computer digital method of testing, has reduced the error that human factor causes measurement result, has reduced more than 30% with conventional art phase ratio error.

Description of drawings

Fig. 1 is the structural representation of the stress test device based on the speckle interference principle of the present invention;

Fig. 2 is the method flow diagram of the stress test method of speckle interference principle,

Fig. 3 is the optical schematic diagram that obtains x direction Displacements Distribution information, and A represents test specimen among the figure.

Embodiment

Embodiment one, specify present embodiment in conjunction with Fig. 1, the described stress test device based on the speckle interference principle of present embodiment comprises digital CCD camera 1, four collimator and extender mirrors 2, single-mode laser 3, fiber coupler 4, fiber optic splitter 5 and computing machines 6

The laser of described single-mode laser 3 emissions is delivered to fiber optic splitter 5 through optical fiber after being coupled by fiber coupler 4, and fiber optic splitter 5 is divided into four bundle laser with beam of laser, and described four bundle laser are delivered to four collimator and extender mirrors 2 through optical fiber respectively,

Four bundle collimation parallel laser light beam irradiates of four collimator and extender mirror 2 emissions form speckle field on the test specimen surface,

Described four collimator and extender mirrors 2 are symmetrically distributed in twos, four collimator and extender mirrors 2 are divided into two groups, every group comprises two collimator and extender mirrors 2, the two light beams of two collimator and extender mirrors 2 emission in every group lay respectively at measured surface normal both sides and described two light beams identical with the angle of normal, described two light beams is thing light and reference light each other, and the camera lens of each collimator and extender mirror 2 equates with the distance on test specimen surface;

Wherein the two light beams and the test specimen surface normal that send of one group of collimator and extender mirror 2 is coplanar in the xoz plane, and two light beams and test specimen surface normal that another group collimator and extender mirror 2 sends are coplanar in the yoz plane; Described xoz plane is vertical mutually with the yoz plane;

Numeral CCD camera 1 is used for taking the speckle field on test specimen surface, and the data output end of digital CCD camera 1 is connected with the data input pin of computing machine 6.

The described optical fiber of present embodiment is single-mode fiber.

The effect of single-mode laser 3 is to produce the laser beam that hot spot is uniform, the coherence is good;

The effect of fiber coupler 4 is that the laser beam that laser instrument sends is coupled among the single-mode fiber, makes laser to propagate in single-mode fiber;

The effect of fiber optic splitter 5 is that the laser with input end evenly is divided into four bundles, and is coupled to respectively among the output single-mode fiber of four collimator and extender mirrors 2;

The effect of collimator and extender mirror 2 is the parallel lasers with laser beam expanding and acquisition collimation; The axis of every group of collimator and extender mirror 2 is coplanar and all perpendicular to the test specimen surface, this group collimator and extender mirror 2 lays respectively at the both sides of measured surface normal, and is identical angle with normal, with the test specimen surface identical distance is arranged.

Numeral CCD camera 1 is used for the digital collection of speckle image;

Computing machine 6 is used for the speckle image that digital CCD camera 1 is gathered is carried out digitized processing, obtains whole audience displacement information, and then draws the strain and stress distributed intelligence of the whole audience.

Present embodiment replaces catoptron by adopting single-mode laser 3, adopt the optical fiber of fiber optic splitter 5 and monotype to replace beam splitter, dirigibility and the accessibility of light path system have been increased greatly, overcome the difficult problem that classic method can't be applied to large and complex structure spare in-site measurement effectively, make this technology of laser speckle walk out the laboratory, the practical structures part is carried out in-site measurement become possibility.

The difference of the described stress test device based on the speckle interference principle of embodiment two, present embodiment and embodiment one is, described digital CCD camera 1 adopts the industrial camera of 1,300,000 pixels, and the camera lens of this camera is the micro magnifier head.

The difference of the described stress test device based on the speckle interference principle of embodiment three, present embodiment and embodiment one is that single-mode laser 3 is single-mode He-Ne lasers.

The described single-mode He-Ne laser of present embodiment is the single-mode He-Ne laser of power 40mW

Embodiment four, specify present embodiment in conjunction with Fig. 2, the difference of the described stress test device based on the speckle interference principle of present embodiment and embodiment one is that fiber optic splitter 5 is one fen four polarization-maintaining beam splitter.

Embodiment five, concentrate method of testing based on the stress of the stress test device of embodiment one described speckle interference principle, comprise the steps:

Two bundle collimation parallel laser light beam l of step 1,2 emissions of one group of collimator and extender mirror of unlatching ₁And l ₂Be radiated at the test specimen surface and form speckle field x1,

Step 2, gather the speckle field x1 on test specimen surface by digital CCD camera 1, and this speckle field x1 is sent to computing machine 6, close this group collimator and extender mirror 2;

Two bundle collimation parallel laser light beam l of step 3, other one group of collimator and extender mirror, 2 emissions of unlatching ₃And l ₄Be radiated at the test specimen surface and form speckle field y1,

Step 4, gather the speckle field y1 on test specimen surface by digital CCD camera 1, and this speckle field y1 is sent to computing machine 6, close this group collimator and extender mirror 2;

Step 5, test specimen is applied a load, make the test specimen surface produce elastic deformation, the speckle field on test specimen surface changes;

Step 6, the described one group of collimator and extender mirror 2 of unlatching step 1, two bundle collimation parallel laser light beam l of these group collimator and extender mirror 2 emissions ₁And l ₂Be radiated at the test specimen surface and form speckle field x2, gather the speckle field x2 on test specimen surface by digital CCD camera 1, and this speckle field x2 is sent to computing machine 6, close this group collimator and extender mirror 2;

Step 7, the described one group of collimator and extender mirror 2 of unlatching step 3, two bundle collimation parallel laser light beam l of these group collimator and extender mirror 2 emissions ₃And l ₄Be radiated at the test specimen surface and form speckle field y2, gather the speckle field y2 on test specimen surface by digital CCD camera 1, and this speckle field y2 is sent to computing machine 6, close this group collimator and extender mirror 2;

Speckle field x1 and speckle field x2 before and after step 8,6 pairs of loadings of computing machine carry out calculation process, obtain along light beam l ₁And l ₂The displacement e of direction; In like manner, speckle field y1 and speckle field y2 before and after 6 pairs of loadings of computing machine carry out calculation process, obtain along light beam l ₃And l ₄The displacement c of direction according to displacement e and the c on two mutually orthogonal directions, adopts Elasticity and mechanics of materials formula, obtains the information of test specimen surface stress field distribution state.

The described loading to test specimen of present embodiment step 5 can adopt simple machinery loading device to carry out mechanical load, the method that also can adopt hydraulic loaded, vacuum load and heat to load.Need select suitable loading method according to the geomery of actual components.

Present embodiment adopts four bundle collimated lights to act on the test specimen surface, can calculate the strain and stress of the whole audience by the displacement on the both direction, and can obtain the size and Orientation of each point principle stress, thereby can judge dangerous point and the hazard level that component stress is concentrated.The method that present embodiment adopts is a kind of whole audience, non-contacting, the non-destructive measuring method that can measure in real time, need not carry out in the darkroom, and is lower to shockproof requirement, and therefore, this method is a kind of high precision, measuring method efficiently.

Concentrate the position that will adjust four collimator and extender mirrors 2 and digital CCD camera 1 before the test beginning at stress in the present embodiment, make four collimator and extender mirrors 2 be symmetrically distributed in twos, digital CCD camera 1 is vertical with the test specimen surface.Adjust aperture, focal length and the enlargement factor of camera lens, make the focal plane of camera lens near the upper surface in tested zone.Connect power supply then, open single-mode laser 3 and computing machine 6, treat that single-mode laser 3 output powers can begin test after stable.

The difference of the stress test method of embodiment six, present embodiment and embodiment five described speckle interference principles is, two bundle collimation parallel laser light beam l of one group of collimator and extender mirror of the described unlatching of step 1,2 emissions ₁And l ₂Be radiated at the test specimen surface and form speckle field x1, described two bundle collimation parallel laser light beam l ₁And l ₂Coplanar in the xoz plane with the test specimen surface normal, the optical function I1_x of the speckle field of speckle field x1 correspondence is:

Wherein, the light intensity value at I1_x (r) expression r place, position, u _{1_x}Expression collimation parallel laser light beam l ₁Position r place the light wave amplitude, u _{2_x}Expression collimation parallel laser light beam l ₂Position r place the light wave amplitude,

Expression collimation parallel laser light beam l ₁Position r place the phasing degree,

Expression collimation parallel laser light beam l ₂The phasing degree at position r place.

The difference of the stress test method of embodiment seven, present embodiment and embodiment five described speckle interference principles is that step 3 is opened two bundle collimation parallel laser light beam l of other one group of collimator and extender mirror, 2 emissions ₃And l ₄Be radiated at the test specimen surface and form speckle field y1, described two bundle collimation parallel laser light beam l ₃And l ₄Coplanar in the yoz plane with the test specimen surface normal, the optical function I1_y of the speckle field of speckle field y1 correspondence is:

Wherein, the light intensity value at I1_y (r) expression r place, position, u _{3_y}Expression collimation parallel laser light beam l ₃Amplitude, u _{4_y}Expression collimation parallel laser light beam l ₄Amplitude,

Expression collimation parallel laser light beam l ₃The phasing degree,

Expression collimation parallel laser light beam l ₄The phasing degree.

The difference of the stress test method of embodiment eight, present embodiment and embodiment five described speckle interference principles is that the optical function I2_x of the speckle field of the described speckle field x2 of step 6 correspondence is:

（3）

Wherein, Expression collimation parallel laser light beam l ₁Variable quantity at phasing degree, position r place, Expression collimation parallel laser light beam l ₂Variable quantity at phasing degree, position r place,

The difference of the stress test method of embodiment nine, present embodiment and embodiment five described speckle interference principles is that the optical function I2_y of the speckle field of the described speckle field y2 of step 7 correspondence is:

（4）

Wherein,

Expression collimation parallel laser light beam l ₃Variable quantity at phasing degree, position r place, Expression collimation parallel laser light beam l ₄Variable quantity at phasing degree, position r place,

The difference of the stress test method of embodiment ten, present embodiment and embodiment five described speckle interference principles is that the detailed process that obtains the information of test specimen surface stress field distribution state is:

Speckle field x1 and speckle field x2 before and after 6 pairs of loadings of computing machine carry out calculation process, obtain along light beam l ₁And l ₂The detailed process of the displacement e of direction is:

Speckle field x1 and speckle field x2 are carried out the size reduction mode processing, obtain the light intensity difference according to formula (5)

Work as phase differential as can be known by formula (5)

During for the odd-multiple of π, this moment then

Obtain maximal value, be presented as bright rays at bar graph; If Be the even-multiple of π, then this moment

Obtain minimum value 0, be presented as dark line at bar graph.And phase differential

Exist linear relationship with the displacement e of measured surface particle on the x direction again, as shown in Figure 3,

Speckle field y1 and speckle field y2 before and after 6 pairs of loadings of computing machine carry out calculation process, obtain along light beam l ₃And l ₄The detailed process of the displacement c of direction is:

Speckle field y1 and speckle field y2 are carried out the size reduction mode processing, obtain the light intensity difference according to formula (6)

With in formula (5) and (6)

With

Substitution formula (7) and (8) can obtain two displacement e and c on the orthogonal directions respectively:

Wherein, λ represents to collimate the wavelength of parallel laser, θ ₁Expression collimation parallel laser light beam l ₁And l ₂With the angle of test specimen surface normal, θ ₁Expression collimation parallel laser light beam l ₃And l ₄With the angle of test specimen surface normal, e represents to collimate parallel laser light beam l ₁And l ₂The displacement of direction, c represents to collimate parallel laser light beam l ₃And l ₄The displacement of direction;

To collimate parallel laser light beam l ₁And l ₂The displacement e of direction and collimation parallel laser light beam l ₃And l ₄The displacement c substitution Elasticity geometric equation (9) of direction obtains the normal strain ε on two orthogonal directionss _xAnd ε _yAnd shear strain γ _Xy

${\mathrm{\&epsiv;}}_x=\frac{\&PartialD;e}{\&PartialD;x}$

${\mathrm{\&epsiv;}}_y=\frac{\&PartialD;c}{\&PartialD;y}---\left(9\right)$

${\mathrm{\&gamma;}}_{\mathrm{xy}}=\frac{\&PartialD;e}{\&PartialD;y}+\frac{\&PartialD;c}{\&PartialD;x}$

Obtain the stress state of test specimen surface each point according to formula (10):

$\left.\begin{array}{c}{\mathrm{\&sigma;}}_x=\frac{E}{1-v^2}({\mathrm{\&epsiv;}}_x+{\mathrm{v\&epsiv;}}_y)\\ {\mathrm{\&sigma;}}_y=\frac{E}{1-v^2}({\mathrm{\&epsiv;}}_y+{\mathrm{v\&epsiv;}}_x)\\ {\mathrm{\&tau;}}_{\mathrm{xy}}=\frac{E}{2(1+v)}{\mathrm{\&gamma;}}_{\mathrm{xy}}\end{array}\right\}---\left(10\right)$

Wherein, E represents the elastic modulus of test specimen material, and ν represents Poisson ratio;

Obtain principle stress and principal direction according to formula (11):

$\left.\begin{array}{c}{\mathrm{\&sigma;}}_1=\frac{{\mathrm{\&sigma;}}_x+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00003285216100011.png,HDA00003285216100031.png"\; state="\{\{state\}\}">y</figure-callout>}}}{2}+\frac{1}{2}\sqrt{{({\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y)}^2+4{\mathrm{\&tau;}}_{\mathrm{<figure-callout\; id="2"\; label="xy"\; filenames="HDA00003285216100011.png,HDA00003285216100031.png"\; state="\{\{state\}\}">xy</figure-callout>}}^2}\\ {\mathrm{\&sigma;}}_2=\frac{{\mathrm{\&sigma;}}_x+{\mathrm{\&sigma;}}_y}{2}-\frac{1}{2}\sqrt{{({\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y)}^2+4{\mathrm{\&tau;}}_{\mathrm{<figure-callout\; id="2"\; label="xy"\; filenames="HDA00003285216100011.png,HDA00003285216100031.png"\; state="\{\{state\}\}">xy</figure-callout>}}^2}\\ {\mathrm{\&theta;}}_P=\frac{1}{2}\arctan (-\frac{{2\mathrm{\&tau;}}_{\mathrm{xy}}}{{\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y})\end{array}\right\}---\left(11\right)$

Wherein, σ ₁The expression first principal stress, σ ₂The expression second principal stress, θ _pExpression principal direction,

Information according to principle stress and principal direction acquisition test specimen surface stress field distribution state realizes the measurement of full field to the structural member stress state.

The present invention not only can be used for the mechanical test research in laboratory, can also be used for the on-the-spot of practical structures part measures in real time, measurement of full field is carried out in distribution to the ess-strain under the structural member loaded state, thereby the position of the dangerous point that counter stress is concentrated and hazard level are analyzed and judged.

Claims (10)

1. based on the stress test device of speckle interference principle, it is characterized in that: it comprises digital CCD camera (1), four collimator and extender mirrors (2), single-mode laser (3), fiber coupler (4), fiber optic splitter (5) and computing machine (6),

After the laser of described single-mode laser (3) emission is coupled by fiber coupler (4), deliver to fiber optic splitter (5) through optical fiber, fiber optic splitter (5) is divided into four bundle laser with beam of laser, and described four bundle laser are delivered to four collimator and extender mirrors (2) through optical fiber respectively

Four bundle collimation parallel laser light beam irradiates of four collimator and extender mirrors (2) emission form speckle field on the test specimen surface,

Described four collimator and extender mirrors (2) are symmetrically distributed in twos, four collimator and extender mirrors (2) are divided into two groups, every group comprises two collimator and extender mirrors (2), the two light beams of two collimator and extender mirrors (2) in every group emission lay respectively at measured surface normal both sides and described two light beams identical with the angle of normal, described two light beams is thing light and reference light each other, and the camera lens of each collimator and extender mirror (2) equates with the distance on test specimen surface;

Wherein the two light beams and the test specimen surface normal that send of one group of collimator and extender mirror (2) is coplanar in the xoz plane, and two light beams and test specimen surface normal that another group collimator and extender mirror (2) sends are coplanar in the yoz plane; Described xoz plane is vertical mutually with the yoz plane;

Numeral CCD camera (1) is used for taking the speckle field on test specimen surface, and the data output end of digital CCD camera (1) is connected with the data input pin of computing machine (6).

2. the stress test device based on the speckle interference principle according to claim 1 is characterized in that: described digital CCD camera (1) adopts the industrial camera of 1,300,000 pixels, and the camera lens of this camera is the micro magnifier head.

3. the stress test device based on the speckle interference principle according to claim 1, it is characterized in that: single-mode laser (3) is single-mode He-Ne laser.

4. the stress test device based on the speckle interference principle according to claim 1, it is characterized in that: fiber optic splitter (5) is one fen four polarization-maintaining beam splitter.

5. concentrate method of testing based on the stress of the stress test device of the described speckle interference principle of claim 1, it is characterized in that: it comprises the steps:

Two bundle collimation parallel laser light beam l of step 1, one group of collimator and extender mirror of unlatching (2) emission ₁And l ₂Be radiated at the test specimen surface and form speckle field x1,

Step 2, gather the speckle field x1 on test specimen surface by digital CCD camera (1), and this speckle field x1 is sent to computing machine (6), close this group collimator and extender mirror (2);

Two bundle collimation parallel laser light beam l of step 3, the other one group of collimator and extender mirror of unlatching (2) emission ₃And l ₄Be radiated at the test specimen surface and form speckle field y1;

Step 4, gather the speckle field y1 on test specimen surface by digital CCD camera (1), and this speckle field y1 is sent to computing machine (6), close this group collimator and extender mirror (2);

Step 5, test specimen is applied a load, make the test specimen surface produce elastic deformation, the speckle field on test specimen surface changes;

Step 6, the unlatching described one group of collimator and extender mirror of step 1 (2), two bundle collimation parallel laser light beam l of this group collimator and extender mirror (2) emission ₁And l ₂Be radiated at the test specimen surface and form speckle field x2, gather the speckle field x2 on test specimen surface by digital CCD camera (1), and this speckle field x2 is sent to computing machine (6), close this group collimator and extender mirror (2);

Step 7, the unlatching described one group of collimator and extender mirror of step 3 (2), two bundle collimation parallel laser light beam l of this group collimator and extender mirror (2) emission ₃And l ₄Be radiated at the test specimen surface and form speckle field y2, gather the speckle field y2 on test specimen surface by digital CCD camera (1), and this speckle field y2 is sent to computing machine (6), close this group collimator and extender mirror (2);

Step 8, computing machine (6) carry out calculation process to speckle field x1 and the speckle field x2 before and after loading, and obtain along light beam l ₁And l ₂The displacement e of direction; In like manner, computing machine (6) carries out calculation process to speckle field y1 and the speckle field y2 before and after loading, and obtains along light beam l ₃And l ₄The displacement c of direction according to displacement e and the c on two mutually orthogonal directions, adopts Elasticity and mechanics of materials formula, obtains the information of test specimen surface stress field distribution state.

6. the stress test method of speckle interference principle according to claim 5 is characterized in that: two bundle collimation parallel laser light beam l of step 1 one group of collimator and extender mirror of described unlatching (2) emission ₁And l ₂Be radiated at the test specimen surface and form speckle field x1, described two bundle collimation parallel laser light beam l ₁And l ₂Coplanar in the xoz plane with the test specimen surface normal, the optical function I1_x of the speckle field of speckle field x1 correspondence is:

Wherein, the light intensity value at I1_x (r) expression r place, position, u _{1_x}Expression collimation parallel laser light beam l ₁Position r place the light wave amplitude, u _{2_x}Expression collimation parallel laser light beam l ₂Position r place the light wave amplitude, Expression collimation parallel laser light beam l ₁Position r place the phasing degree,

Expression collimation parallel laser light beam l ₂The phasing degree at position r place.

7. the stress test method of speckle interference principle according to claim 5 is characterized in that: step 3 is opened two bundle collimation parallel laser light beam l of other one group of collimator and extender mirror (2) emission ₃And l ₄Be radiated at the test specimen surface and form speckle field y1, described two bundle collimation parallel laser light beam l ₃And l ₄Coplanar in the yoz plane with the test specimen surface normal, the optical function I1_y of the speckle field of speckle field y1 correspondence is:

Wherein, the light intensity value at I1_y (r) expression r place, position, u _{3_y}Expression collimation parallel laser light beam l ₃Amplitude, u _{4_y}Expression collimation parallel laser light beam l ₄Amplitude,

Expression collimation parallel laser light beam l ₃The phasing degree,

Expression collimation parallel laser light beam l ₄The phasing degree.

8. the stress test method of speckle interference principle according to claim 5, it is characterized in that: the optical function I2_x of the speckle field of the described speckle field x2 of step 6 correspondence is:

（3）

Wherein, Expression collimation parallel laser light beam l ₁Variable quantity at phasing degree, position r place,

Expression collimation parallel laser light beam l ₂Variable quantity at phasing degree, position r place,

9. the stress test method of speckle interference principle according to claim 5, it is characterized in that: the optical function I2_y of the speckle field of the described speckle field y2 of step 7 correspondence is:

（4）

Wherein,

Expression collimation parallel laser light beam l ₃Variable quantity at phasing degree, position r place,

Expression collimation parallel laser light beam l ₄Variable quantity at phasing degree, position r place,

10. the stress test method of speckle interference principle according to claim 5 is characterized in that: the detailed process that obtains the information of test specimen surface stress field distribution state is:

Computing machine (6) carries out calculation process to speckle field x1 and the speckle field x2 before and after loading, and obtains along light beam l ₁And l ₂The detailed process of the displacement e of direction is:

Speckle field x1 and speckle field x2 are carried out the size reduction mode processing, obtain light intensity difference I_x according to formula (5):

Computing machine (6) carries out calculation process to speckle field y1 and the speckle field y2 before and after loading, and obtains along light beam l ₃And l ₄The detailed process of the displacement c of direction is:

Speckle field y1 and speckle field y2 are carried out the size reduction mode processing, obtain the light intensity difference according to formula (6)

With in formula (5) and (6)

With

Substitution formula (7) and (8) can obtain two displacement e and c on the orthogonal directions respectively:

Wherein, λ represents to collimate the wavelength of parallel laser, θ ₁Expression collimation parallel laser light beam l ₁And l ₂With the angle of test specimen surface normal, θ ₁Expression collimation parallel laser light beam l ₃And l ₄With the angle of test specimen surface normal, e represents to collimate parallel laser light beam l ₁And l ₂The displacement of direction, c represents to collimate parallel laser light beam l ₃And l ₄The displacement of direction;

To collimate parallel laser light beam l ₁And l ₂The displacement e of direction and collimation parallel laser light beam l ₃And l ₄The displacement c substitution Elasticity geometric equation (9) of direction obtains the normal strain ε on two orthogonal directionss _xAnd ε _yAnd shear strain γ _Xy,

${\mathrm{\&epsiv;}}_x=\frac{\&PartialD;e}{\&PartialD;x}$

${\mathrm{\&epsiv;}}_y=\frac{\&PartialD;c}{\&PartialD;y}---\left(9\right)$

${\mathrm{\&gamma;}}_{\mathrm{xy}}=\frac{\&PartialD;e}{\&PartialD;y}+\frac{\&PartialD;c}{\&PartialD;x}$

Obtain the stress state of test specimen surface each point according to formula (10):

$\left.\begin{array}{c}{\mathrm{\&sigma;}}_x=\frac{E}{1-v^2}({\mathrm{\&epsiv;}}_x+{\mathrm{v\&epsiv;}}_y)\\ {\mathrm{\&sigma;}}_y=\frac{E}{1-v^2}({\mathrm{\&epsiv;}}_y+{\mathrm{v\&epsiv;}}_x)\\ {\mathrm{\&tau;}}_{\mathrm{xy}}=\frac{E}{2(1+v)}{\mathrm{\&gamma;}}_{\mathrm{xy}}\end{array}\right\}---\left(10\right)$

Wherein, E represents the elastic modulus of test specimen material, and ν represents Poisson ratio;

Obtain principle stress and principal direction according to formula (11):

$\left.\begin{array}{c}{\mathrm{\&sigma;}}_1=\frac{{\mathrm{\&sigma;}}_x+{\mathrm{\&sigma;}}_y}{2}+\frac{1}{2}\sqrt{{({\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y)}^2+4{\mathrm{\&tau;}}_{\mathrm{xy}}^2}\\ {\mathrm{\&sigma;}}_2=\frac{{\mathrm{\&sigma;}}_x+{\mathrm{\&sigma;}}_y}{2}-\frac{1}{2}\sqrt{{({\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y)}^2+4{\mathrm{\&tau;}}_{\mathrm{xy}}^2}\\ {\mathrm{\&theta;}}_P=\frac{1}{2}\arctan (-\frac{{2\mathrm{\&tau;}}_{\mathrm{xy}}}{{\mathrm{\&sigma;}}_x-{\mathrm{\&sigma;}}_y})\end{array}\right\}---\left(11\right)$

Wherein, σ ₁The expression first principal stress, σ ₂The expression second principal stress, θ _pExpression principal direction,

Information according to principle stress and principal direction acquisition test specimen surface stress field distribution state realizes the measurement of full field to the structural member stress state.

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