CN101782445B - Rapid measurement method of internal stress distribution based on wedge structure and error correction method thereof - Google Patents
Rapid measurement method of internal stress distribution based on wedge structure and error correction method thereof Download PDFInfo
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- CN101782445B CN101782445B CN2010190261053A CN201019026105A CN101782445B CN 101782445 B CN101782445 B CN 101782445B CN 2010190261053 A CN2010190261053 A CN 2010190261053A CN 201019026105 A CN201019026105 A CN 201019026105A CN 101782445 B CN101782445 B CN 101782445B
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Abstract
The invention discloses a rapid measurement method of internal stress distribution based on wedge structure and an error correction method, belonging to the technical field of measurement. The rapid measurement method comprises the following steps of processing a blank into the wedge structure, then measuring a deformation curve of the lower surface, and finally, calculating the internal stress distribution of the blank according to the deformation curve. The error correction is carried out on the rapid measurement method by a numerical method, so that higher measurement precision can be obtained.
Description
Technical field
The present invention relates to a kind of rapid measurement method of internal stress distribution and error correcting method thereof, belong to field of measuring technique based on wedge structure.
Background technology
The blank internal stress cuts in the process of part the internal stress imbalance that will discharge gradually and produce along with the continuous excision of material at blank, causes processing the back part thus and deforms.Must measure the internal stress of blank in order to study and control machining deformation, obtain the blank internal stress and distribute.The method of existing multiple measurement unrelieved stress can be divided into two big classes according to the measuring principle difference: based on the measuring method of Material Physics attribute and the measuring method of removing based on material.The former comprises x rays method, supercritical ultrasonics technology, method of magnetic and photoelastic method etc.The latter comprises orifice method, successively method and crackle flexibility method etc.X rays method, supercritical ultrasonics technology and method of magnetic only energy measurement object top layer are counted the interior stress mean value of micrometer range, though photoelastic method energy measurement interior of articles stress distribution is only applicable to transparent substance, are not suitable for opaque metal blank.Orifice method can be measured drill hole more exactly and count stress mean value in the mm depth scope, but it fathoms and also only limits in the several millimeters scopes.Successively method and crackle flexibility method can be measured the distribution of blank internal stress along its thickness direction, are applicable to measure the uniform stress field.For the blank of types such as aluminum alloy pretensioning plate, its internal stress only changes along the blank thickness direction usually, and variation is less in the layer of same thickness, is similar to even distribution.Need measure when utilizing method successively or crackle flexibility method to measure the blank stress distribution that sample successively excises along with material or crackle increases the strain of generation gradually, normally build electric bridge and finish, require operating personnel to have higher technical merit by the stickup foil gauge.Simultaneously, these two kinds of methods require every excision layer of material or strengthen crack depth all to discharge anchor clamps one time, and then write down strain data one time, and operation steps is many, and efficient is not high.Simultaneously, successively method gained stress distribution data break equals each material bed thickness that is excised, and is same, and crackle flexibility method gained stress distribution data break equals the poor of twice crack depth that link to each other.For thickness is tens of millimeters blank, consider that the material thickness of the each excision of efficiency of measurement or the degree of depth of increasing are generally 2 millimeter, so both resolution is lower.
Summary of the invention
Problems such as the measuring operation that the present invention is directed to the distribution of the blank homogeneous state of stress is loaded down with trivial details, efficient is low, data resolution is low, a kind of rapid measurement method of internal stress distribution and error correcting method thereof based on wedge structure proposed, have simple to operate, efficiency of measurement is high and data resolution can reach advantages such as tens of microns, is suitable for the quick measurement of blank internal stress
The present invention adopts following technical scheme for achieving the above object:
The present invention is based on the rapid measurement method of internal stress distribution method of wedge structure, intercept two samples respectively from the length and the Width of block blank, the wedge structure that then two samples is cut into two consistent size is respectively also measured the deformation curve of two wedge bottom surfaces respectively, utilizes the wedge algorithm to calculate the distribution of the normal stress of blank length and Width along the blank thickness direction respectively by these two deformation curves again; Wherein said sample is a rectangular parallelepiped, and thickness is consistent with blank thickness, and sample is cut into inclined wedge-shaped, its bottom surface along its length before cutting into wedge structure first preprocessing go out a deformation measurement band.
The ratio range of described specimen width and thickness can be 1 to 10, and the ratio range of length and width can be 2 to 5.
Described wedge maximum ga(u)ge equals sample thickness, and the wedge minimum thickness is zero, and the length of wedge and width equal the length and the width of sample respectively, and the wedge bottom surface is same bottom surface with the bottom surface of cutting the preceding processed deformation measurement band of sample.
The measurement band of the described sample rectangular surfaces parallel with the sample bottom surface is smooth straight, and this rectangular surfaces length equals specimen length, and width is 1 to 5 millimeter, and is positioned at the centre position of sample bottom width direction, 0.1 to 0.2 millimeter of test coupon bottom surface.
When sample cuts into wedge, under the internal stress effect, measure and be with the deflection that bends to measure the curve that strip length direction changes along it; The measuring method of described deformation curve is as follows: with the wedge bottom surface up, utilize fixed contactless laser displacement sensor to locating tab assembly band middle position, wedge is moved horizontally with the relative motion of laser displacement sensor formation along its length direction finish bottom surface deformation curve scanning, the space length of double sampling point is less than 0.05 millimeter in the scanning.
Described wedge algorithm is as follows: calculate the distribution of the normal stress of wedge intercepting direction along thickness direction according to deformation curve, the wedge length direction is an X-axis, and thickness direction is the Z axle, and then concrete computing method are seen formula (1):
Wherein: σ (z) is the variation function of normal stress along thickness direction,
E is the elastic modulus of sample material, and μ is the Poisson ratio of sample material, and L is a specimen length, and H is a specimen height, and x is the X-axis coordinate figure; A summit of getting on the face of the maximum bottom of wedge thickness is a true origin, and span is 0 to L, ρ
CxFor deformation curve is the radius-of-curvature function at x place at coordinate; L
xFor after wedge is the cross section bending at x place at coordinate, the distance function in the bending neutral layer in cross section and the centre position in cross section; Described centre position is meant the centre position of cross section along the wedge thickness direction, and it can be solved by formula (2):
A
xL
x+B
xL′
x+C
x＝0 (2)
Wherein: parameter A
x=2L ρ
Cx', parameter
Parameter
And ρ
Cx' be radius-of-curvature function ρ
CxExponent number at the x place, L '
xBe function L
xFirst order derivative at the x place, L
xValue at border x=0 place is
Error correcting method based on the rapid measurement method of internal stress distribution method of wedge structure comprises the steps: at first, the material parameter of setting up two numerical models and giving sample according to specimen size; Then, giving two initial internal stresss of model respectively distributes; Again, utilize numerical method to calculate the bottom surface additional deformation curve that two mould processing become wedge respectively; At last, described deformation curve is deducted corresponding additional deformation curve obtain new deformation curve, the stress distribution result who utilizes the wedge algorithm computation to make new advances based on described new deformation curve.
For the sample of described length and Width, size is consistent with corresponding sample respectively for described two numerical models.
The initial internal stress of described two models distributes, and the normal stress of the model of representing blank length direction sample only being given the blank Width distributes, and the normal stress of the model of representing blank Width sample only being given the blank length direction distributes; The normal stress of blank Width distributes and the normal stress distribution of blank length direction gets by the wedge algorithm computation.
In described additional deformation curve, when the model that contains primary stress was cut into wedge in numerical simulation, the distortion that the bottom surface takes place was along with the change curve of wedge length direction.
The present invention has following effect: 1, can measure the distribution of blank internal stress along the blank thickness direction.2, sample directly is processed into wedge, and repeatedly release clip is only measured wedge bottom surface deformation curve one time, so the efficiency of measurement height.3, replace measuring strain with non-contacting laser displacement sensor scanning bottom surface deformation curve, simplified the measurement operation.4, deformation curve when scanning sampled point is at interval less than 0.05 millimeter, make stress along the spaced far of thickness direction distributed data less than 0.05 millimeter, resolution improves greatly.
Description of drawings
Fig. 1 is of the present invention based on the rapid measurement method of internal stress distribution of wedge structure and a preferable implementing procedure figure of error correcting method thereof.
Fig. 2-Fig. 5 be followed successively by of the present invention based on wedge structure rapid measurement method of internal stress distribution and four of error correcting method implement view.
Label title: 101-115, method implementation step among Fig. 1-Fig. 5,1, blank flat, 11, the blank flat length direction, 12, the blank flat Width, 2, blank length direction sample, 21, wedge 1,22, wedge 2,3, blank Width sample, 4, sample or tiltedly carve the bottom surface, 5, measure band, 6, specimen length direction normal stress is along the distribution of thickness direction, 7, laser displacement sensor.
Embodiment
Be elaborated below in conjunction with the technical scheme of accompanying drawing to invention:
The present invention relates to a kind of rapid measurement method of internal stress distribution and error correcting method thereof based on wedge structure, measure its bottom surface deformation curve after blank being processed into wedge structure, the internal stress that is calculated blank by this deformation curve distributes.By numerical method this method is carried out error correction, can obtain than high measurement accuracy.The now concrete specific embodiments of introducing the method that the present invention relates to.
Fig. 1 is of the present invention based on the rapid measurement method of internal stress distribution of wedge structure and a preferable implementing procedure of error correcting method thereof.
Step 101: as shown in Figure 2, from blank flat 1 intercepting blank length direction sample 2 and blank Width sample 3, the length direction of blank length direction sample 2 is consistent with blank length direction 11, the length direction of blank Width sample 3 is consistent with blank Width 12, and the consistent size of length direction sample 2 and blank Width sample 3, both thickness and blank 1 consistency of thickness, both width are got 5 times of blank 1 thickness, and both length are got 10 times of blank 1 thickness.
Step 102: as shown in Figure 3, with the bottom surface 4 of blank length direction sample 2 up and process and run through the specimen length direction, width is 5 millimeters, and the degree of depth is about 0.1 millimeter measurement and is with 5.Measurement is relevant with the flatness of sample bottom surface 4 with 5 the degree of depth, as very out-of-flatness of sample bottom surface 4, adds and should adopt materials with smaller excision thickness man-hour, as 0.05 millimeter, successively removes until measuring the band face parallel with the bottom surface straight.Blank Width sample 3 is carried out same operation.
Step 103: as shown in Figure 4, blank length direction sample 2 is cut into wedge 1---21 and wedge 2---22 along the diagonal line of the rectangular surfaces at its length and thickness place.As adopt the method for line cutting to cut, can obtain above-mentioned two wedges.As the method that adopts milling then should guarantee to obtain the wedge 1---21 of full-size, and therefore wedge 2---22 then can not be obtained by chopping.Subsequent calculations only needs the bottom surface deformation data of wedge 1---21, so two kinds of methods all can satisfy measurement requirement.Blank Width sample 3 is carried out same operation.
Step 104: as shown in Figure 5, the measurement of wedge bottom surface 4 deformation curves can be carried out on platforms such as three-coordinate measuring machine or Three Degree Of Freedom lathe, laser displacement sensor 7 is fixed in the platform top, make its laser beam emission downwards and, wedge bottom surface 4 is fixed on the parts that can do tangential movement on the platform up perpendicular to the direction of motion of platform.Along with platform motion parts level is at the uniform velocity mobile, wedge bottom surface 4 relatively-stationary laser displacement sensors 7 move, and carry out deformation curve scanning.Because the measurement on the wedge bottom surface 4 deforms after being with 5 processing, along with relative displacements take place for each measured point and the laser displacement sensor 7 measured with 5 that scan, displacement is gathered and is preserved by laser displacement sensor 7.It is 300 mm/min that translational speed can be set, and the sampling interval of laser displacement sensor 7 is 10 milliseconds, and then adjacent two data point spacings are 0.05 millimeter.The position that high order end on the wedge bottom surface 4 is set simultaneously is that the initial point of X-axis is with reference to zero-bit, and along with scanning is carried out, the displacement data of subsequent acquisition constitutes the machining deformation curve of wedge bottom surface 4.The wedge that 3 processing obtain to blank Width sample carries out same deformation curve operation.Obtain two deformation curves of two wedges altogether.
Step 105: calculate radius-of-curvature everywhere on two deformation curves.
Step 106: the Lx that calculates blank length and Width according to formula (2) respectively.
Step 107: calculate the normal stress distribution of blank length direction and the normal stress distribution of Width respectively according to formula (1).
Step 108: judge whether to be first result of calculation.When step 105-step 107 is first chi result of calculation by the result after carrying out successively for the first time, change step 109 over to, otherwise change step 114 over to.
Step 109: in finite element software, set up the numerical model of blank length direction sample 2 and blank Width sample 3 respectively, and give and blank material identical materials parameter.
Step 110: the numerical model of blank Width sample 3 being given blank length direction sample 2 by the stress distribution of step 107 calculating gained.Blank length direction sample 2 is given the numerical model of blank Width sample 3 by the stress distribution of step 107 calculating gained.
Step 111: in simulation software, carry out the wedge machining simulation, obtain a wedge, obtain the another one wedge by the numerical model of blank Width sample 3 by the numerical model of blank length direction sample 2.
Step 112: read respectively machining simulation the bottom surface deformation curve of two wedges, be called the additional deformation curve.
Step 113: the bottom surface deformation curve of the actual processing gained wedge of blank length direction sample 2 is deducted the bottom surface deformation curve of the numerical model machining simulation gained wedge of blank length direction sample 2, obtain the new bottom surface deformation curve of this direction sample.Blank Width sample 3 is done same operation also can obtain a new bottom surface deformation curve.Obtain two new deformation curves altogether.
Utilize two new deformation curves, obtain new stress distribution result of calculation behind the repeating step 105-108.From this process of step 109-105-108 is the error correction process, and revises and to enter step 114 after finishing.
Step 114: revised new stress distribution is compared with result of calculation last time, set the threshold value of both differences.When being lower than the threshold value of setting, precision is qualified, enters step 115, otherwise reenters step 110, carries out error correction once more.
Step 115: measure and to finish, obtained of the distribution of the normal stress of the normal stress of blank length direction and Width along its thickness direction.
The above only is a better embodiment of a kind of rapid measurement method of internal stress distribution and the error correcting method thereof based on wedge structure that the present invention relates to, but practical range of the present invention is not limited thereto example.
Claims (5)
1. rapid measurement method of internal stress distribution method based on wedge structure, it is characterized in that: intercept two samples respectively from the length and the Width of block blank, the wedge structure that then two samples is cut into two consistent size is respectively also measured the deformation curve of two wedge bottom surfaces respectively, utilizes the wedge algorithm to calculate the distribution of the internal stress of blank length and Width along the blank thickness direction respectively by these two deformation curves again; Wherein said sample is a rectangular parallelepiped, and thickness is consistent with blank thickness, and sample is cut into inclined wedge-shaped, its bottom surface along its length before cutting into wedge structure first preprocessing go out a deformation measurement band;
The ratio range of described specimen width and thickness can be 1 to 10, and the ratio range of length and width can be 2 to 5;
Described wedge maximum ga(u)ge equals sample thickness, and the wedge minimum thickness is zero, and the length of wedge and width equal the length and the width of sample respectively, and the wedge bottom surface is same bottom surface with the bottom surface of cutting the preceding processed deformation measurement band of sample;
The measurement band of the described sample rectangular surfaces parallel with the sample bottom surface is smooth straight, and this rectangular surfaces length equals specimen length, and width is 1 to 5 millimeter, and is positioned at the centre position of sample bottom width direction, 0.1 to 0.2 millimeter of test coupon bottom surface;
When sample cuts into wedge, under the internal stress effect, measure and be with the deflection that bends to measure the curve that strip length direction changes along it; The measuring method of described deformation curve is as follows: with the wedge bottom surface up, utilize fixed contactless laser displacement sensor to locating tab assembly band middle position, wedge is moved horizontally with the relative motion of laser displacement sensor formation along its length direction finish bottom surface deformation curve scanning, the space length of double sampling point is less than 0.05 millimeter in the scanning;
Described wedge algorithm is as follows: calculate the distribution of the internal stress of wedge intercepting direction along thickness direction according to deformation curve, the wedge length direction is an X-axis, and thickness direction is the Z axle, and then concrete computing method are seen formula (1):
Wherein: σ (z) is the variation function of internal stress along thickness direction,
E is the elastic modulus of sample material, and μ is the Poisson ratio of sample material, and L is a specimen length, and H is a specimen height, and x is the X-axis coordinate figure; A summit of getting on the face of the maximum bottom of wedge thickness is a true origin, and span is 0 to L, ρ
CxFor deformation curve is the radius-of-curvature function at x place at coordinate; L
xFor after wedge is the cross section bending at x place at coordinate, the distance function in the bending neutral layer in cross section and the centre position in cross section; Described centre position is meant the centre position of cross section along the wedge thickness direction, and it can be solved by formula (2):
A
xL
x+B
xL′
x+C
x＝0 (2)
Wherein: parameter A
x=2L ρ
Cx', parameter
Parameter
And ρ
Cx' be radius-of-curvature function ρ
CxExponent number at the x place, L '
xBe function L
xFirst order derivative at the x place, L
xValue at border x=0 place is
2. the error correcting method based on the described rapid measurement method of internal stress distribution method based on wedge structure of claim 1 is characterized in that comprising the steps: at first, the material parameter of setting up two numerical models and giving sample according to specimen size; Then, giving two initial internal stresss of model respectively distributes; Again, utilize numerical method to calculate the bottom surface additional deformation curve that two mould processing become wedge respectively; At last, described deformation curve is deducted corresponding additional deformation curve obtain new deformation curve, the stress distribution result who utilizes the wedge algorithm computation to make new advances based on described new deformation curve.
3. the error correcting method of the rapid measurement method of internal stress distribution method based on wedge structure according to claim 2 is characterized in that described two numerical models represent the sample of described length and Width respectively, and size is consistent with corresponding sample.
4. the error correcting method of the rapid measurement method of internal stress distribution method based on wedge structure according to claim 2, it is characterized in that the initial internal stress of described two models distributes, the internal stress of the model of representing blank length direction sample only being given the blank Width distributes, and the internal stress of the model of representing blank Width sample only being given the blank length direction distributes; The internal stress of blank Width distributes and the internal stress distribution of blank length direction gets by the wedge algorithm computation.
5. the error correcting method of the rapid measurement method of internal stress distribution method based on wedge structure according to claim 2, it is characterized in that described additional deformation curve, when the model that contains primary stress was cut into wedge in numerical simulation, the distortion that the bottom surface takes place changed along with the change curve of wedge length direction.
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