CN103499405B - Device and method for detecting residual stress of transparent plastic product - Google Patents
Device and method for detecting residual stress of transparent plastic product Download PDFInfo
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- CN103499405B CN103499405B CN201310479186.9A CN201310479186A CN103499405B CN 103499405 B CN103499405 B CN 103499405B CN 201310479186 A CN201310479186 A CN 201310479186A CN 103499405 B CN103499405 B CN 103499405B
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Abstract
The invention relates to a device and a method for detecting the residual stress of a transparent plastic product. A light source is formed by three single-color LED (Light-Emitting Diode) light sources; an optical system is formed by a plano-convex lens, a polarizer, a 1/4 wave plate set, a polarization analyzer and a lens; an image acquisition and computer processing system is formed by a CCD (Charge Coupled Device) camera and a computer; the plano-convex lens, the polarizer, the 1/4 wave plate set, the polarization analyzer and the lens are sequentially placed behind the light source; a light transmission axis of the polarizer is along an OY direction; a fast axis of the 1/4 wave plate set is along an OX direction; after passing through the plano-convex lens and the lens, the light source is focused on a focus of the CCD camera; and the light source part, the 1/4 wave plate set and the CCD camera are connected with the computer. In the invention, according to three single-color LED light sources with different wavelengths, a stress fringe value under a certain wavelength is calculated by utilizing the characteristic that under the same deviator stress, products of different light wavelengths lambda and a stress fringe value N under the wavelength light are equal. The method and the device have the advantages of large measurement range and high accuracy on detection of the residual stress of the transparent plastic product.
Description
Technical field
The present invention relates to a kind of method and apparatus detecting clear plastic articles unrelieved stress.
Background technology
The orientation and the crystallization that are subject to existing in stronger shear action, processing in process due to plastic melt, melt each position cooling velocity extremely difficulty accomplish that uniformity, melt plastify the reasons such as uneven, article removal is difficult, in the inner generation that all can cause unrelieved stress of plastic products.All can there is unrelieved stress in nearly all plastic products, especially the unrelieved stress of plastic injection goods is more obvious to some extent.The existence of unrelieved stress not only makes plastic products occur buckling deformation and cracking in storage and use procedure, also affects the mechanical property of plastic products, optical property, electric property and presentation quality.Therefore, in the production run of reality, need to detect plastic products stress, to judge that whether these goods are up-to-standard.
Common plastic products, as the material such as polycarbonate, epoxy resin has temporary birefrigent performance.Transparent material noncontact stress measurement device current at present, all adopts photoelastic stress analysis detection method.
Photoelasticity is that some homogeneous clear solid, under effect of stress, birefringent character occurs.Utilize this physical property can pass through observation isochromatic line and isoclinic line under polariscope, the distribution form of quantitative examination stress.Common photoelastic stress analysis method is integer fringe order analytical technology, cannot the size of Measurement accuracy non-integer stripe portion.
In addition, the photoelastic stressed cord level of majority is analyzed, is based on frontier point conditioned disjunction known boundaries point fringe order, infers the progression of whole measured object intra-striate.If do not comprise above-mentioned frontier point in polarization visual field, then cannot determine the progression of each striped in visual field.So for the regional area stress intensity of measured object inside, this type of analytic approach cannot effectively detect.
And wait deviator stress to be less than the material of I level for clear glass flat board, mostly adopt penalty method.Penalty method is exactly that do not putting into measured object, system is in delustring state in linear polarization or circular polarization stress mornitoring optical system; After putting into measured object, delustring state is originally destroyed, now can rotatory polarization sheet, until System recover is to delustring state.The angle that this polaroid rotates is exactly the direct representation to measured object deviator stress.Common penalty method has Sai Nameng (Senarmont) method, clings to than nanotesla (Babinet) method.But penalty method is non-integer fringe analysis technology, the material that cannot be used for being greater than deviator stress I level carries out unrelieved stress detection.
Common plastic products deviator stress is seldom within I level, and at progression higher than the size that also cannot neglect non-integer stripe portion when I level.Thus, how to provide one both can detect multistage stressed cord, accurately can detect again the detection method of the clear plastic articles stress of non-integer stripe portion size simultaneously, become this technical field problem demanding prompt solution.
Summary of the invention
Technology of the present invention is dealt with problems and is: the deficiency overcoming existing stress detection, provides a kind of clear plastic articles unrelieved stress pick-up unit and method.The present invention is swift to operate, to measured object not damaged, can according to measured value, accurately calculate the principle stress difference of measured object size, thus reflect the unrelieved stress size of measured object.
Technical scheme of the present invention is:
A kind of clear plastic articles unrelieved stress pick-up unit, comprises light source, optical system, image acquisition and computer processing system, light source is made up of three kinds of monochromatic LED light source, optical system by plano-convex lens, polarizer, quarter wave plate group, analyzer and lens are formed, and image acquisition and computer processing system are made up of CCD camera, computing machine, place plano-convex lens successively after three kinds of monochromatic LED light source, polarizer, quarter wave plate group, analyzer, lens; The light transmission shaft of polarizer is along OY direction, and the principal direction of stress angle at 45 ° will detected with tested plastic products, the fast axle of quarter wave plate group is along OX direction, light transmission shaft and the OX of analyzer are into θ angle, light source is by Jiao Ji after plano-convex lens and lens in the focus of CCD camera, and the Lights section, quarter wave plate group are connected computing machine with CCD camera.
Three kinds of monochromatic LED light source of light source are respectively: the green light source that the violet source that wavelength is 441.6nm, wavelength are 532, wavelength are the red light source of 670, and are placed in the rotation roulette of light source.
Quarter wave plate group is made up of the quarter wave plate that wavelength is the quarter wave plate of 441.6nm, wavelength is the quarter wave plate of 532nm, wavelength is 441.6nm.
Apply the method that above-mentioned clear plastic articles unrelieved stress pick-up unit detects clear plastic articles unrelieved stress, comprise the following steps:
1) be rotated counterclockwise analyzer, make the CCD camera pixel value collected corresponding to image upper stress check point be minimum, namely light path is in delustring state;
2) obtain respectively under three kinds of colour light sources, θ 1, θ 2, θ 3 jiaos formed by the light transmission shaft of analyzer and OX;
3) calculate on tested plastic products because unrelieved stress causes the optical path difference of this point
If integer variable
, and combination calculates, and chooses
, make
Wherein
,
,
be three kinds of optical source wavelengths;
Unrelieved stress fringe order according to this point on material:
Calculate because unrelieved stress causes the optical path difference of this point on material, thus judge this stress value.
The invention has the beneficial effects as follows:
The present invention compared with prior art, can accurately measure the optical path difference caused by unrelieved stress of clear plastic articles, and achieves the stress mornitoring of the large-scale detection thing regional area based on small field of view.Polarization optics involved by polarized light, diameter is slightly larger, and price increases a lot, and large diameter polaroid and wave plate often cost are high.The present invention can realize detecting by small field of view, significantly can reduce the manufacturing cost of checkout equipment, be beneficial to the popularization on a large scale of unrelieved stress checkout equipment.Meanwhile, this measuring method is equally also applicable to the stress measurement of other transparent materials as aspects such as glass, film and mechanics photoelastic experiments.
Accompanying drawing explanation
Fig. 1 is Cleaning Principle schematic diagram of the present invention;
Fig. 2 is light source rotating disk schematic diagram.
Embodiment
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
As shown in Figure 1, clear plastic articles unrelieved stress pick-up unit of the present invention, is made up of three parts: light source S1, optical system S2, image acquisition and computer processing system S3.
Light source S1 is made up of three kinds of monochromatic LED light source, as accompanying drawing 2, is respectively: the green light source 2 that the violet source 1 that wavelength is 441.6nm, wavelength are 532, wavelength are the red light source 13 of 670, and places the rotation roulette 14 of light source.
Optical system S2 is by plano-convex lens 3, and polarizer 4, quarter wave plate group, analyzer 9 and lens 10 are formed.
Image acquisition and computer processing system S3 are made up of CCD camera 11, computing machine 12.
Quarter wave plate group is made up of the quarter wave plate 8 that wavelength is the quarter wave plate 6 of 441.6nm, wavelength is the quarter wave plate 7 of 532nm, wavelength is 441.6nm.
Plano-convex lens 3 is placed successively, polarizer 4, quarter wave plate group, analyzer 9, lens 10 after three kinds of monochromatic LED light source; The light transmission shaft of polarizer 4 is along OY direction, and the principal direction of stress angle at 45 ° will detected with tested plastic products 5, the fast axle of quarter wave plate group is along OX direction, light transmission shaft and the OX of analyzer 9 are into θ angle, light source S1 is by after plano-convex lens 13 and lens 10, Jiao Ji is in the focus of CCD camera 11, and light source S1, quarter wave plate group are connected computing machine 12 with CCD camera 11.
Choose a wave plate corresponding with optical source wavelength in quarter wave plate group, be placed in light path.The light transmission shaft of polarizer 4 along OY direction, and and on sample study principal direction of stress angle at 45 ° a little, the fast axle of quarter wave plate along OX direction, and the light transmission shaft of analyzer 9 and OX into θ angle.Adjustment plano-convex lens 13 and lens 10, make light source S1 and CCD camera 11 respectively in their focus.
Employing Jones vector carrys out the light vector in calculating optical system.
From the light vector of quarter wave plate outgoing
for
In this formula, W is the Jones matrix of fast axle along the quarter wave plate in OX direction,
for the Jones matrix of the birefringent material 5 of fast axle 45° angle crossing with OX axle,
for the Jones matrix of the linearly polarized light from plane of oscillation polarizer 4 outgoing vertically.
Be δ by expression hysteresis, fast axle becomes the Jones matrix of the line hysteresis device at β angle with OX axle
.For the Jones matrix W of fast axle along the quarter wave plate in OX direction,
, can obtain
For the Jones matrix of the birefringent material 5 of fast axle 45° angle crossing with OX axle
,
, can obtain
So can obtain
Namely be linearly polarized light from the light of quarter wave plate outgoing, its plane of polarization becomes with OY axle
angle.
If by analyzer along counterclockwise rotation
, then its main shaft is perpendicular to the linearly polarized light from quarter wave plate outgoing, so, at discussed some generation frosting phenomenon.On the image that CCD camera 11 can be used to collect, corresponding to the gray value information of the picture point of stress mornitoring point.When the gray-scale value of this point is minimum, delustring this moment can be judged.
Can obtain fringe order is thus
(k is integer, and θ scope is 0 ~ 180 °)
According to two-dimensional stress-optical laws
Wherein
, be cast material fringe value, C is the stress-optical constant of material, and λ is current light source wavelength.
Can be obtained by above three formulas
For the light source of three kinds of wavelength, then have
Simultaneous can obtain
Combination calculates, and it is suitable to choose
, above formula is set up.Then the fringe value of deviator stress is
For polycarbonate commercial production stress mornitoring, as shown in Figure 1, step of the present invention is as follows:
(1) red light source 13 is rotated in light path, open red light source 13, and 670nm wavelength quarter wave plate corresponding for ruddiness is rotated in light path.
(2) adjust each element in light path, make the light transmission shaft of polarizer 4 along OY direction, and and on sample study principal direction of stress angle at 45 ° a little, the fast axle of quarter wave plate along OX direction, and the light transmission shaft of analyzer 9 and OX into θ angle.Adjustment plano-convex lens 13 and lens 10, make light source S1 and CCD camera 11 respectively in their focus.
(3) counterclockwise rotate analyzer 9, stop the rotation when computing machine 12 display analysis point pixel value reaches minimum, and record the anglec of rotation
.
(4) green light source 2 is rotated in light path, open green light source 2, and 532nm wavelength quarter wave plate corresponding for green glow is rotated in light path.Repeat step (2), (3), the record anglec of rotation
.
(5) violet source 1 is rotated in light path, open violet source 1, and 441.6nm wavelength quarter wave plate corresponding for purple light is rotated in light path.Repeat step (2), (3), the record anglec of rotation
.
(6) integer variable is established
, and choose suitable value respectively, make
Namely make
three formulas are closest.Can basis
Calculate because unrelieved stress causes the optical path difference of this point on material, thus judge this stress value.
Claims (1)
1. a clear plastic articles unrelieved stress detection method, the clear plastic articles unrelieved stress pick-up unit adopted, comprise light source (S1), optical system (S2), image acquisition and computer processing system (S3), described light source (S1) is made up of three kinds of monochromatic LED light source, optical system (S2) is by plano-convex lens (3), polarizer (4), quarter wave plate group, analyzer (9) and lens (10) are formed, image acquisition and computer processing system (S3) are by CCD camera (11), computing machine (12) is formed, plano-convex lens (13) is placed successively after three kinds of monochromatic LED light source, polarizer (4), quarter wave plate group, analyzer (9), lens (10), the light transmission shaft of polarizer (4) is along OY direction, and the principal direction of stress angle at 45 ° will detected with tested plastic products (5), the fast axle of quarter wave plate group is along OX direction, light transmission shaft and the OX of analyzer (9) are into θ angle, light source (S1) by plano-convex lens (3) and lens (10) afterwards Jiao Ji in the focus of CCD camera (11), light source (S1), quarter wave plate group are connected computing machine (12) with CCD camera (11), it is characterized in that, comprise the following steps:
1) be rotated counterclockwise analyzer (9), make CCD camera (11) pixel value collected corresponding to image upper stress check point be minimum, namely light path is in delustring state;
2) obtain respectively under three kinds of colour light sources, θ 1, θ 2, θ 3 jiaos formed by the light transmission shaft of analyzer (9) and OX;
3) calculate on tested plastic products (5) because unrelieved stress causes the optical path difference of stress mornitoring point
If integer variable
, and combination calculates, and chooses
, make
Wherein
,
,
be three kinds of optical source wavelengths;
Unrelieved stress fringe order according to material upper stress check point:
Calculate because unrelieved stress causes the optical path difference of stress mornitoring point on material, thus judge this stress value.
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|---|---|---|---|
| CN201310479186.9A CN103499405B (en) | 2013-10-15 | 2013-10-15 | Device and method for detecting residual stress of transparent plastic product |
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|---|---|---|---|
| CN201310479186.9A CN103499405B (en) | 2013-10-15 | 2013-10-15 | Device and method for detecting residual stress of transparent plastic product |
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| CN103499405B true CN103499405B (en) | 2015-07-22 |
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| DE102016218390B3 (en) * | 2016-09-23 | 2018-02-01 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Measuring arrangement and method for measuring mechanical stresses |
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| CN108051443B (en) * | 2017-11-21 | 2020-06-30 | 中国科学院上海光学精密机械研究所 | Device and method for measuring glass stress and defects |
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| CN113063534B (en) * | 2021-03-18 | 2022-03-08 | 中国科学院高能物理研究所 | Nondestructive testing system and method for residual stress of transparent material |
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