A device and method for detecting internal stress direction of organic glass

Abstract

The present invention relates to a device and method for detecting the direction of internal stress of organic glass, which belongs to the technical field of internal stress detection and solves the problem of non-destructive detection of the direction of internal stress in the prior art. The device comprises an incident device and a receiving device arranged on both sides of the organic glass to be tested; the dials of the first polarizer frame, the wave plate frame and the second polarizer frame in the incident device and the receiving device are adjusted, and when the amplitude of the overall spectrum curve of the spectrum data collected by the spectrometer is the smallest, the possible direction of the internal stress of the organic glass to be tested is obtained; wherein, the possible direction includes being parallel or perpendicular to the slow axis direction of the wave plate; the dial of the wave plate frame is kept unchanged, the polarizer dial and the analyzer dial are rotated synchronously, and the result of recording the optical path difference of the wave plate and the optical path difference of the organic glass to be tested is determined to determine the direction of the internal stress of the organic glass. The non-destructive detection of the direction of internal stress of the organic glass is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of internal stress detection, and in particular to a device and method for detecting the internal stress direction of organic glass. Background Art

[0002] Among the factors that affect material quality and structural life, stress plays a vital role. Material internal stress refers to the stress that still exists inside the material and maintains self-equilibrium after the external force is eliminated, also known as residual stress. The internal stress in the material is generally divided into thermal stress, structural stress and mechanical stress according to the source. These stresses can cause the material to warp or twist, crack, and even cause material failure. The detection of material internal stress can reflect the state of the material itself and potential problems, so it has very important research and application significance.

[0003] Internal stress detection mainly includes two aspects: internal stress level and internal stress direction. The internal stress level generally refers to the amplitude of internal stress, that is, the size of internal stress. By measuring and calculating the internal stress level of the material and comparing it with the mechanical parameters of the material itself, the structural safety and service life of the material when internal stress exists can be analyzed and predicted; the direction of internal stress is another important aspect. In many cases, the direction of internal stress is worthy of attention and understanding. Accurate detection of the direction of internal stress can help determine the relationship between internal stress and the specific structure of the material, help predict the further development and impact range of the internal stress of the material, and provide a basis and reference for taking effective preventive measures. At present, the detection of internal stress at home and abroad is limited to the detection of internal stress level.

[0004] Accurate detection of the direction of internal stress is full of difficulties and challenges. The ideal detection method is to use non-destructive testing methods for the material to be tested, that is, after the internal stress direction is completed, it will not affect the normal use of the material and will not cause damage to the structure of the material to be tested. In the application fields of transparent materials such as aerospace porthole glass, submersible porthole glass, large organic glass structures, and electronic product screens, there is a strong demand for non-destructive testing of the direction of internal stress. Summary of the invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a device and method for detecting the direction of internal stress in organic glass, so as to solve the problems of limited prior art, low measurement accuracy and non-destructive testing.

[0006] On the one hand, an embodiment of the present invention provides a device for detecting the direction of internal stress in organic glass, comprising an incident device and a receiving device arranged on both sides of the organic glass to be detected;

[0007] The incident device comprises an incident light component and a first polarizing plate frame with a polarizer; the parallel light emitted by the incident light component is incident on the organic glass to be tested through the polarizer;

[0008] The receiving device includes, in sequence along a direction away from the organic glass to be tested, a wave plate frame with a wave plate, a second polarizing plate frame with an analyzer, a receiving light component and a spectrometer;

[0009] Among them, the first polarizer frame, the wave plate frame, and the second polarizer frame are all equipped with dials; the scale values ​​of each dial are adjusted, and the internal stress direction of the organic glass to be tested is obtained based on the scale values ​​of each dial and the corresponding spectral data collected by the spectrometer.

[0010] Optionally, the incident light component includes:

[0011] A light source, a first optical fiber, a collimating lens, a first adapter plate and a first connecting rod; the light emitted by the light source is transmitted to the collimating lens through the first optical fiber; the collimating lens converts the received light into parallel light;

[0012] The first adapter plate is used to fix the collimating lens;

[0013] Two ends of the first connecting rod are respectively connected to the first adapter plate and the first polaroid frame, and are used to support the first adapter plate and the first polaroid frame.

[0014] Optionally, the incident device further comprises a first connecting rod leg and a first leg fixing member;

[0015] The first connecting rod leg is used to support the first connecting rod;

[0016] One end of the first leg fixing piece is fixed on the optical platform, and the other end is used to fix the first connecting rod leg.

[0017] Optionally, the light receiving assembly includes: a second adapter plate, a second connecting rod, and a second optical fiber;

[0018] The wave plate frame, the second polarizing plate frame and the second adapter plate are provided with connecting holes near the edge, and the wave plate frame, the second polarizing plate frame and the second adapter plate are connected in sequence through the second connecting rod;

[0019] The second adapter plate is provided with an adapter structure device, and the adapter structure is used to connect to the second optical fiber;

[0020] The second optical fiber is used to transmit the light output from the switching structure to the spectrometer.

[0021] Optionally, the receiving device further comprises a second connecting rod leg and a second leg fixing member;

[0022] The second connecting rod leg is connected to the second connecting rod and is used to support the second connecting rod;

[0023] One end of the second leg fixing piece is fixed on the optical platform, and the other end is used to fix the second connecting rod leg.

[0024] The embodiment of the present invention also includes a method for detecting the direction of internal stress in organic glass, which specifically includes:

[0025] The parallel light emitted by the incident light component is incident on the organic glass to be tested through the polarizer;

[0026] The parallel light emitted from the organic glass to be tested enters the spectrometer through the wave plate, the analyzer, and the light receiving component; the polarizer, the wave plate, and the analyzer are respectively arranged in the first polarizer frame with a scale plate, the wave plate frame, and the second polarizer frame;

[0027] The scale values ​​of each dial are adjusted, and the internal stress direction of the organic glass to be tested is obtained based on the scale values ​​of each dial and the corresponding spectral data collected by the spectrometer.

[0028] Optionally, adjusting the scale values ​​of each dial, and obtaining the internal stress direction of the organic glass to be tested based on the scale values ​​of each dial and the corresponding spectral data collected by the spectrometer, includes:

[0029] Adjust the dials of the first polarizer frame, the wave plate frame, and the second polarizer frame to obtain the possible direction of the internal stress of the organic glass to be measured when the amplitude of the overall spectrum curve of the spectrum data collected by the spectrometer is the minimum; wherein the possible direction includes parallel or perpendicular to the slow axis direction of the wave plate;

[0030] Keeping the scale plate of the wave plate frame unchanged, rotate the scale plate of the polarizer and the scale plate of the analyzer synchronously, record the superposition result of the optical path difference of the wave plate and the optical path difference of the organic glass to be measured, so as to finally determine the direction of the internal stress of the organic glass.

[0031] Optionally, the dials of the first polarizer frame, the wave plate frame, and the second polarizer frame are adjusted to obtain a possible direction of the internal stress of the organic glass to be measured when the amplitude of the overall spectrum curve of the spectrum data collected by the spectrometer is the smallest, including:

[0032] Adjust the scale values ​​of the polarizer, wave plate and analyzer dials respectively, and keep the sum of the scale values ​​of the polarizer and wave plate dials at 360°, and the sum of the scale values ​​of the polarizer and analyzer dials at 90°, record the spectral data on the spectrometer, and when the amplitude of the collected spectral data curve is the smallest, the possible direction of the internal stress of the organic glass to be measured is obtained to be parallel or perpendicular to the slow axis direction of the wave plate.

[0033] Optionally, the internal stress of the organic glass to be measured corresponds to compressive stress or tensile stress.

[0034] Optionally, the step of keeping the wave plate frame scale plate unchanged, synchronously rotating the polarizer scale plate and the analyzer scale plate, and recording the superposition result of the wave plate optical path difference and the optical path difference of the organic glass to be measured so as to finally determine the direction of the internal stress of the organic glass includes:

[0035] Keep the current wave plate scale value position unchanged, synchronously rotate the polarizer dial and the analyzer dial, and record the spectral data on the spectrometer. At this time, the spectral data is the superposition result of the wave plate optical path difference and the optical path difference of the organic glass to be tested; the superposition result is that the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, or the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested;

[0036] The direction of the internal stress of the organic glass to be tested is finally determined according to the superposition result of the optical path difference of the wave plate and the optical path difference of the organic glass to be tested; when the superposition result is that the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is parallel to the direction of the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is perpendicular to the direction of the slow axis of the wave plate;

[0037] When the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is perpendicular to the direction of the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is parallel to the direction of the slow axis of the wave plate.

[0038] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0039] 1. By setting an incident device and a receiving device on both sides of the organic glass to be tested, and setting a wave plate frame with a wave plate at the receiving device, the direction of the internal stress of the organic glass to be tested is determined by knowing the direction of the slow axis of the wave plate, thereby realizing the detection of the internal stress direction.

[0040] 2. Adjust the scale values ​​of the polarizer, wave plate and analyzer dials respectively, and keep the sum of the scale values ​​of the polarizer and wave plate dials at 360°, and the sum of the scale values ​​of the polarizer and analyzer dials at 90°, record the spectral data on the spectrometer, and when the amplitude of the collected spectral data curve is the smallest, the possible direction of the internal stress of the organic glass to be tested is obtained to be parallel or perpendicular to the slow axis direction of the wave plate, and then finally determine the direction of the internal stress of the organic glass to be tested by superimposing the optical path difference of the wave plate and the optical path difference of the organic glass to be tested.

[0041] Keep the current wave plate scale value position unchanged, rotate the polarizer dial and the analyzer dial synchronously, and record the spectrum data on the spectrometer. At this time, the spectrum data is the superposition result of the wave plate optical path difference and the optical path difference of the organic glass to be tested; when the superposition result is that the optical path difference between the wave plate and the organic glass to be tested is equal to the absolute value of the sum of the optical path difference between the wave plate and the organic glass sample to be tested, the compressive stress direction is parallel to the wave plate slow axis direction, and the tensile stress direction is perpendicular to the wave plate slow axis direction; when the optical path difference between the wave plate and the organic glass to be tested is equal to the absolute value of the difference between the optical path difference between the wave plate and the organic glass sample to be tested, the compressive stress direction is perpendicular to the wave plate slow axis direction, and the tensile stress direction is parallel to the wave plate fast axis direction. Thus, non-destructive detection of the internal stress direction is achieved.

[0042] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0044] Figure 1 A device for detecting the internal stress direction of organic glass in an embodiment of the present invention;

[0045] Figure 2 This is a flow chart of a device and method for detecting the internal stress direction of organic glass in an embodiment of the present invention;

[0046] Figure 3 A polarizing plate frame with a dial in an embodiment of the present invention;

[0047] Figure 4 This is a light path diagram of interference light generated by the photoelasticity of a transparent material in an embodiment of the present invention;

[0048] Figure 5 A component diagram of the light vector in the experimental light path in the embodiment of the present invention in the direction of each device;

[0049] Figure 6 Schematic diagram of the fast and slow axis directions of the wave plate in an embodiment of the present invention;

[0050] Figure 7 It is a schematic diagram of the internal stress direction of the organic glass sample to be tested in the present invention.

[0051] Reference numerals:

[0052] 1-light source; 2-first optical fiber; 3-collimating lens; 4-first adapter plate; 5-first connection; 6-first polarizer frame; 7-first connecting rod leg 8-first leg fixing piece; 9-plexiglass sample to be tested; 10-sample fixing tool; 11-optical platform; 12-wave plate frame; 13-second polarizer frame; 14-second adapter plate; 15-second leg fixing piece; 16-second connecting rod leg; 17-second optical fiber; 18-spectrometer. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0054] The internal stress detection and principle of the material to be tested in the device and method for detecting the internal stress direction of organic glass proposed by the present invention are now described:

[0055] In the embodiment of the present invention, a spectral measurement method is used to detect the direction of internal stress.

[0056] Specifically, when internal stress exists inside a transparent material, it will cause the transparent material to transform from an isotropic material to an anisotropic material, and birefringence will occur when light passes through a transparent material with internal stress. According to the Viertheim stress optics law, the stress (σ x , σ y ) and the relationship between the refractive index can be expressed as:

[0057] n x -n y =C(σ x -σ y ) (1)

[0058] In the above formula, n x 、n y Respectively represent the refractive index in the x and y directions; σ x , σ y It represents the stress in the two principal stress directions of x and y; C represents the stress optical coefficient of the transparent material, which is a physical constant and is only related to the type of transparent material.

[0059] When light passes through a transparent material (anisotropic material) with a thickness of d, the relationship between the optical path difference δ and the refractive index is:

[0060] δ=d(n x -n y ) (2)

[0061] According to equations (1) and (2), the relationship between the residual stress and the optical path difference of a transparent material can be obtained as follows:

[0062]

[0063] From the above formula, we can know that after determining the optical path difference of the transparent material in the two principal stress directions, we can get the stress difference of the transparent material in the two principal stress directions. If the stress value in one of the principal stress directions is close to zero or can be ignored, then the relationship between the internal stress and the optical path difference in this case can be expressed as:

[0064]

[0065] In the embodiment of the present invention, the experimental optical path diagram of the interference light generated by the photoelasticity of the transparent material is shown in FIG3 .

[0066] exist Figure 5 In the figure, the polarization direction of the polarizer is perpendicular to that of the analyzer, and the rectangular block in the middle represents the transparent material specimen. The interface of the incident light of the transparent material is perpendicular to the propagation direction of the linear polarized light passing through the polarizer, and the principal stress direction in the transparent material is parallel to the interface of the incident light of the transparent material. The method of calculating the internal stress of birefringent transparent materials in this way is called the photoelastic method. Look along the direction of light propagation in the optical path and make a component diagram of the light vector in each direction, such as Figure 4 shown.

[0067] Figure 4 The polarization directions of the polarizer and the analyzer are perpendicular to each other, and the two principal stress directions (x, y) in the transparent material are also perpendicular to each other. Let the angle between the polarization direction of the polarizer and one of the principal stress directions in the transparent material be θ. After the light passes through the polarizer, it forms linear polarized light with an amplitude of a. When the linear polarized light generated by the polarizer passes through the inside of the transparent material, birefringence occurs. The vibration directions of the ordinary light and extraordinary light generated by the birefringence are parallel to the two principal stress directions respectively. The amplitudes of the component light vectors of the linear polarized light in the two principal stress directions are:

[0068]

[0069] The amplitudes of these two light vectors are the amplitudes of ordinary light and extraordinary light in the transparent material. After light passes through the transparent material, ordinary light and extraordinary light will produce a certain optical path difference, assuming the optical path difference is δ. When the light vector components in these two directions pass through the analyzer, only the light vector components parallel to the analyzer can pass through the analyzer, so the light vector components in the two principal stress directions are decomposed once more, decomposing them into the polarization direction of the analyzer and the direction perpendicular to the analyzer. From the geometric relationship, it can be seen that the components of the light passing through the analyzer in the two orthogonal directions of the analyzer are:

[0070]

[0071] The two light vector components in the polarization direction of the analyzer have the same vibration direction and a phase difference of Two coherent lights, so the sum vector amplitude of these two light vector components satisfies:

[0072]

[0073] Simplifying the above expression, we can get the square value of the amplitude of the light passing through the analyzer. Because the light intensity I = A 2 , so the light intensity after passing through the polarizer can be expressed as:

[0074]

[0075] In the experiment, for the convenience of analysis, the angle θ between the polarizer and the principal stress is set to 45°, so the above formula can be simplified to:

[0076]

[0077] In the actual measurement process, the light intensity values ​​of each wavelength of the light source are not equal, that is, α is not a constant, but a wavelength-related quantity determined by the light source. Using formula (9) to directly fit the spectral data will produce a large error, so formula (9) is converted to obtain:

[0078]

[0079] Where a(λ) 2 It represents the spectrum corresponding to the light intensity of the light source. For further more accurate measurement and research, the spectrum corresponding to the background light intensity of the natural light environment was also collected before the test and recorded as I BG Considering the influence of the background light intensity of the natural light environment on the experimental process, formula (10) can be further expressed as:

[0080]

[0081] In the optical path design, the angle θ between the polarizer and the principal stress is set to 45°, but in actual adjustment, this angle may have a certain deviation, so the sin in formula (8) 2 The (2θ) value may not be equal to 1, and sin must also be considered when fitting the data. 2 The (2θ) value is considered as a fitting parameter. So formula (11) can be further expressed as:

[0082]

[0083] It is worth pointing out that in the actual test process of "superimposing" the optical path difference between the wave plate and the organic glass material to be tested, the polarizer uses multiple polarization angles for data collection and statistics to obtain more accurate measurement results. The 45° in the above description is only one of several polarization angles. Therefore, sin in formula (12) 2 The introduction of (2θ) is also necessary and reasonable.

[0084] The several test quantities involved in formula (12) are all collected in the form of spectra, which reflects that the spectral measurement method adopted by this patent is an important means in the actual measurement process.

[0085] Based on the above principles, the present invention discloses a device for detecting the direction of internal stress in organic glass. Figure 1 As shown, the device includes an incident device and a receiving device arranged on both sides of the organic glass to be tested;

[0086] The incident device comprises an incident light component and a first polarizing plate frame with a polarizer; the parallel light emitted by the incident light component is incident on the organic glass to be tested through the polarizer;

[0087] The receiving device includes, in sequence along a direction away from the organic glass to be tested, a wave plate frame with a wave plate, a second polarizing plate frame with an analyzer, a receiving light component and a spectrometer;

[0088] Among them, the first polarizer frame, the wave plate frame, and the second polarizer frame are all equipped with dials; the scale values ​​of each dial are adjusted, and the internal stress direction of the organic glass to be tested is obtained based on the scale values ​​of each dial and the corresponding spectral data collected by the spectrometer.

[0089] The incident light component comprises:

[0090] A light source, a first optical fiber, a collimating lens, a first adapter plate and a first connecting rod; the light emitted by the light source is transmitted to the collimating lens through the first optical fiber; the collimating lens converts the received light into parallel light;

[0091] The first adapter plate is used to fix the collimating lens; and a buckle opening is provided in the middle of the first adapter plate, and the collimating lens is screwed into the buckle ring in the middle of the first adapter plate to fix it;

[0092] Two ends of the first connecting rod are respectively connected to the first adapter plate and the first polaroid frame, and are used to support the first adapter plate and the first polaroid frame.

[0093] The incident device also includes a first connecting rod leg and a first leg fixing member;

[0094] The first connecting rod leg is used to support the first connecting rod;

[0095] One end of the first leg fixing piece is fixed on the optical platform, and the other end is used to fix the first connecting rod leg.

[0096] In the receiving device, the receiving optical component includes: a second adapter plate, a second connecting rod, and a second optical fiber;

[0097] The wave plate frame, the second polarizing plate frame and the second adapter plate are provided with connecting holes near the edge, and the wave plate frame, the second polarizing plate frame and the second adapter plate are connected in sequence through the second connecting rod;

[0098] The second adapter plate is provided with an adapter structure device, and the adapter structure is used to connect with the second optical fiber; specifically, PLA plastic fuse is used, and a transition structure is obtained by 3D printing technology, which is used to transmit the parallel light received by the receiving device to the second optical fiber. The transition structure is similar to a funnel in form. The wider end of the transition structure is inserted into the middle through hole of the second adapter plate, and the size is matched; the other narrower end of the transition structure can be inserted into the optical fiber of the spectrometer, and the size is also matched, so as to realize the connection between the second adapter plate and the optical fiber of the spectrometer.

[0099] The second optical fiber is used to transmit the light output from the switching structure to the spectrometer.

[0100] The receiving device also includes a second connecting rod leg and a second leg fixing member;

[0101] The second connecting rod leg is connected to the second connecting rod and is used to support the second connecting rod;

[0102] One end of the second leg fixing piece is fixed on the optical platform, and the other end is used to fix the second connecting rod leg.

[0103] Preferably, in actual measurement, a halogen tungsten light source is used, and for measurement, the working wavelength used is 420-680nm. The core diameter of the optical fiber connected to the light source is selected to be 1mm. One end of the collimating lens is connected to the end of the optical fiber, and the other end is fixed on the adapter plate. The function of the collimating lens is to generate parallel light. The first polarizer frame and the second polarizer frame with a dial are used in the measurement, and the dial is rotatable; the polarization direction of the polarizer can be accurately controlled by reading the dial. For the incident end in the incident device, the polarizer (polarizer) is installed in the first polarizer frame. When the polarization direction of the polarizer is aligned with the 0° of the dial, the snap ring in the middle of the first adapter plate is screwed in and fixed, so that the polarization direction of the polarizer can be always aligned with the 0° of the dial when the dial is rotated. Under this condition, when the dial is rotated to any angle, for example, the dial reads 60° at a certain moment, it can be known that the polarization direction of the current polarizer is at an angle of 60° with the identification line of the dial. In addition, the transmission method is used for detection on the test light path.

[0104] Preferably, the wave plate can be divided into a quarter wave plate, a half wave plate and a full wave plate according to the type. A quarter wave plate is used in the actual test, and its material is quartz crystal, which belongs to a positive crystal. The quarter wave plate made of positive crystal has the following characteristics: the fast axis (Fast) of the positive crystal wave plate is parallel to the vibration direction of the ordinary light (o light) when birefringence occurs; and the slow axis (Slow) perpendicular to the fast axis direction of the positive crystal wave plate is parallel to the vibration direction of the extraordinary light (e light) when birefringence occurs. When the quarter wave plate leaves the factory, it will be installed in a metal ferrule, and the fast axis direction (Fast) will be marked on the ferrule shell, indicating the fast axis direction of the quarter wave plate. During installation, the fast axis direction of the quarter wave plate is always aligned with the 90° scale; since the direction perpendicular to the fast axis direction is the slow axis direction of the wave plate, the installation can ensure that the slow axis direction of the wave plate is always aligned with the 0° scale. In the embodiment of the present invention, we explore the relationship between the stress direction of the organic glass to be tested and the slow axis direction of the wave plate.

[0105] At the receiving end of the receiving device of the internal stress direction detection device, the quarter wave plate is installed in the wave plate frame with a dial. When the fast axis direction of the wave plate is aligned with the 90° of the dial, the retaining ring is screwed in to fix it, so that the fast axis direction of the wave plate is always aligned with the 90° of the dial when the dial is rotated; equivalently, it is also ensured that the slow axis direction of the wave plate is always aligned with the 0° of the dial. In addition, when the quarter wave plate leaves the factory, its optical path difference calibration value is also provided; the optical path difference of the quarter wave plate is "superimposed" with the optical path difference of the organic glass sample to be tested for "superposition" testing and analysis, so as to determine the internal stress direction of the organic glass sample to be tested. The wavelength resolution of the spectrometer used in the actual measurement reaches 0.3nm, with excellent test performance.

[0106] During the test, a standard optical platform is used. By utilizing the positioning holes of the optical platform itself, the optical paths between the incident and receiving ends can be aligned, thus ensuring the accuracy of the test results.

[0107] In order to keep the plexiglass sample still during the test, a sample fixing fixture was designed and manufactured. The plexiglass sample was placed in the fixture slot, and the screws on the side of the fixture were tightened until it just supported the sample, so that the sample could always remain still during the internal stress direction test.

[0108] Preferably, the internal stress of the transparent material test piece to be tested is detected based on the above detection device, such as Figure 2 As shown, it mainly includes the following steps:

[0109] Step S1: the parallel light emitted by the incident light component is incident on the organic glass to be tested through the polarizer;

[0110] The parallel light emitted from the organic glass to be tested enters the spectrometer through the wave plate, the analyzer and the light receiving component; the polarizer, the wave plate and the analyzer are respectively arranged in the first polarizer frame with a scale plate, the wave plate frame and the second polarizer frame.

[0111] Specifically, an incident device, a receiving device and a plexiglass sample are assembled, and an internal stress direction detection device is formed according to the above components.

[0112] Specifically, the incident device, the receiving device and the organic glass sample are installed and fixed according to the organic glass internal stress direction detection device to be tested.

[0113] Step S2: adjusting the scale values ​​of each dial, and obtaining the internal stress direction of the organic glass to be tested based on the scale values ​​of each dial and the corresponding spectrum data collected by the spectrometer.

[0114] The dials of the first polarizer frame, the wave plate frame, and the second polarizer frame are adjusted to obtain the possible direction of the internal stress of the organic glass to be measured when the amplitude of the overall spectrum curve of the spectrum data collected by the spectrometer is minimum; wherein the possible direction includes parallel or perpendicular to the slow axis direction of the wave plate.

[0115] Specifically, first, the scale value of the incident polarizer of the incident device is set to 0°, that is, the 0° of the scale is aligned with the frame identification line. Since the polarization direction of the polarizer is always aligned with the 0° of the scale, the polarization direction of the polarizer is parallel to the frame identification line at the initial moment.

[0116] Then set the wave plate scale value at the receiving end of the receiving device to 0°. Since the slow axis direction of the wave plate is always aligned with the 0° of the scale, the slow axis direction of the wave plate is parallel to the polarization direction of the incident polarizer at the initial moment. Set the polarizer scale value at the receiving end to 90°; after completion, the polarization direction of the analyzer remains orthogonal to the polarization direction of the polarizer.

[0117] Turn on the light source, and it will emit parallel light after passing through the collimating lens, and then enter the receiving end after passing through the organic glass sample. Connect the spectrometer to the computer, start the spectrum acquisition software, set the exposure time (usually set to 20-50ms), and observe the spectrum status in the software interface in real time.

[0118] By gradually increasing the scale value a of the incident end polarizer from a low scale value, the scale value b of the receiving end wave plate and the scale value c of the analyzer are correspondingly gradually reduced; wherein, a+b=360; a+c=90; until the overall spectrum curve collected by the spectrometer reaches the minimum value, it is determined that the stress direction of the organic glass to be tested is parallel or perpendicular to the polarization direction of the polarizer.

[0119] For example, the scale value of the incident end polarizer is set to 10°, the scale value of the receiving end wave plate is set to 350°, and the scale value of the receiving end analyzer is set to 80°, and the spectrum state in the spectrometer acquisition software interface is observed (whether the overall spectrum curve amplitude is enhanced or the overall spectrum curve is weakened). During this operation, the slow axis direction of the wave plate is always parallel to the polarization direction of the polarizer, and the polarization direction of the analyzer is always orthogonal to the polarization direction of the polarizer.

[0120] Then set the scale value of the incident polarizer to 20°, the scale value of the receiving wave plate to 340°, and the scale value of the receiving analyzer to 70°, and observe the spectrum status in the spectrometer acquisition software interface (whether the overall spectrum curve amplitude is enhanced or the overall spectrum curve is weakened). During this operation, the slow axis direction of the wave plate is always parallel to the polarization direction of the polarizer, and the polarization direction of the analyzer is always orthogonal to the polarization direction of the polarizer.

[0121] Similarly, set the scale value of the incident polarizer to 30°, the scale value of the receiving wave plate to 330°, and the scale value of the receiving analyzer to 60°, and observe the spectrum status in the spectrometer acquisition software interface (whether the overall spectrum curve amplitude is enhanced or the overall spectrum curve is weakened). During this operation, the slow axis direction of the wave plate is always parallel to the polarization direction of the polarizer, and the polarization direction of the analyzer is always orthogonal to the polarization direction of the polarizer.

[0122] Specifically, when the scale value of the incident polarizer is at a certain value, such as 50° (the corresponding scale value of the receiving end wave plate is 310°, and the scale value of the receiving end analyzer is 40°), when the overall spectrum curve in the spectrometer acquisition software interface tends to the minimum value (the overall spectrum curve tends to a straight line), then the stress direction of the organic glass to be tested is theoretically parallel to the slow axis direction of the wave plate, or perpendicular to the slow axis direction of the wave plate. The stress direction of the organic glass to be tested should be one of these two situations, according to formula (12)

[0123]

[0124] Where I represents the light intensity passing through the analyzer, I BG is the background light intensity under natural light environment, a(λ) 2 It represents the spectrum corresponding to the light intensity of the light source, δ represents the optical path difference, and λ represents the wavelength.

[0125] If the stress direction of the organic glass to be tested is parallel to the polarization direction of the polarizer (also the slow axis direction of the wave plate), the corresponding value of θ is 0°; then the result on the right side of the equal sign of formula (12) is 0, which also corresponds to the overall spectrum curve amplitude in the spectrometer acquisition software interface tending to the minimum value.

[0126] If the stress direction of the organic glass to be tested is perpendicular to the polarization direction of the polarizer (also the slow axis direction of the wave plate), the corresponding value of θ is 90°; then the result on the right side of the equal sign of formula (12) is also 0, which also corresponds to the overall spectrum curve amplitude in the spectrometer acquisition software interface tending to the minimum value.

[0127] Optionally, the scale value interval of the polarization direction of the polarizer is 10°, which can be adjusted according to specific needs during actual measurement, such as adjusted to 5°. A smaller scale value interval is beneficial to improving the accuracy of detection, but it will increase the detection time.

[0128] At this point, it can be determined that the internal stress direction of the organic glass to be tested has been locked in the two most likely directions, and these two most likely directions are clear - parallel to the slow axis direction of the wave plate, or perpendicular to the slow axis direction of the wave plate, which requires further testing and judgment.

[0129] Step S3: Keeping the wave plate frame scale plate unchanged, synchronously rotate the polarizer scale plate and the analyzer scale plate, record the superposition result of the wave plate optical path difference and the optical path difference of the organic glass to be measured, so as to finally determine the direction of the internal stress of the organic glass.

[0130] Keep the current wave plate scale value position unchanged, rotate the polarizer dial and the analyzer dial synchronously, and record the spectral data on the spectrometer. At this time, the spectral data is the superposition result of the wave plate optical path difference and the optical path difference of the organic glass to be tested; the superposition result is that the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, or the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested;

[0131] In addition, the internal stress of the organic glass is either compressive stress or tensile stress. Before the stress direction detection, it is known in advance whether the internal stress of the organic glass to be tested is compressive stress or tensile stress.

[0132] The direction of the internal stress of the organic glass to be tested is finally determined based on the superposition result of the optical path difference of the wave plate and the optical path difference of the organic glass to be tested; when the superposition result is that the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is parallel to the direction of the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is perpendicular to the direction of the slow axis of the wave plate.

[0133] When the optical path difference between the wave plate and the organic glass to be tested is numerically equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is perpendicular to the direction of the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is parallel to the direction of the slow axis of the wave plate.

[0134] The specific experimental process is: keep the current scale value of the wave plate unchanged, that is, the wave plate scale does not rotate anymore, only rotate the incident end polarizer scale and the receiving end analyzer scale synchronously, and always keep the polarization directions of the polarizer and the analyzer orthogonal. For example, the current scale value of the incident end polarizer is 50°, the scale value of the receiving end wave plate is 310°, and the scale value of the receiving end analyzer is 40°. The scale value of the incident end polarizer is set to 60°, the scale value of the receiving end wave plate remains unchanged, and the scale value of the receiving end analyzer is set to 30°. After the operation is completed, save the spectral data file in the spectrometer acquisition software interface to the specified path, and let the file name be "60°", which means the spectral data corresponding to the polarizer scale value of 60°.

[0135] Then set the scale value of the polarizer at the incident end to 70°, the scale value of the wave plate at the receiving end remains unchanged, and the scale value of the analyzer at the receiving end is set to 20°. After the operation is completed, save the spectral data file in the spectrometer acquisition software interface to the specified path, and name the file "70°", which means the spectral data corresponding to the polarizer scale value of 70°.

[0136] Then set the scale value of the polarizer at the incident end to 80°, the scale value of the wave plate at the receiving end remains unchanged, and the scale value of the analyzer at the receiving end is set to 10°. After the operation is completed, save the spectral data file in the spectrometer acquisition software interface to the specified path, and name the file "80°", which means the spectral data corresponding to the polarizer scale value of 80°.

[0137] The spectral data obtained by the above operation corresponds to I in the numerator on the left side of the equal sign in formula (12).

[0138] Similarly, a certain number of spectral data files can be collected and saved according to the specific needs of the experiment. More data files are beneficial to improving the accuracy of detection, but will increase the detection time.

[0139] The present invention is further described with reference to the following specific embodiments:

[0140] Example 1 Collecting the light intensity spectrum a(λ) of the light source 2 The spectrum I corresponding to the background light intensity of the natural light environment BG , where the light intensity spectrum a(λ) 2 This is done in two steps, including:

[0141] Set the polarizer scale value at the incident end to 0°, and also set the analyzer scale value at the receiving end to 0°, save the spectrum data file in the spectrometer acquisition software interface to the specified path, and name the file "light0"; keep the polarizer scale value at the incident end unchanged, and then set the analyzer scale value at the receiving end to 90°, save the spectrum data file in the spectrometer acquisition software interface to the specified path, and name the file "light90", the light source intensity spectrum a(λ) 2 You can use the "light0-I BG ” and “ light90-I BG "The sum of the two is obtained, that is, a(λ) 2 =(light0-I BG )+(light90-I BG )

[0142] Turn off the light source, save the spectral data file in the spectrometer acquisition software interface to the specified path, and name the file "BG". The corresponding spectrum I is the background light intensity of the natural light environment. BG . I got a clear BG form, which corresponds to a(λ) 2 At this point, the test data required for the internal stress direction of the organic glass to be tested are fully prepared, and the subsequent "superposition" analysis of the optical path difference of the wave plate and the optical path difference of the organic glass to be tested is entered.

[0143] The so-called "superposition" of the optical path difference of the wave plate and the optical path difference of the organic glass to be tested refers to the I and a(λ) obtained under the above conditions. 2 and I BG Data file, calculate the total optical path difference between the wave plate and the organic glass sample to be tested, and then compare it with the wave plate optical path difference (the wave plate optical path difference is known and has been calibrated before leaving the factory), and finally determine the internal stress direction of the organic glass to be tested by judging the relationship between the internal stress direction of the organic glass to be tested and the direction of the wave plate slow axis (is the internal stress direction parallel to the wave plate slow axis direction, or perpendicular to the wave plate slow axis direction). The internal stress direction of the organic glass to be tested is finally determined based on the superposition result of the obtained wave plate optical path difference and the optical path difference of the organic glass to be tested; when the superposition result is that the total optical path difference is numerically equal to the absolute value of the sum of the wave plate optical path difference and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the compressive stress direction is parallel to the wave plate slow axis direction; if the internal stress is tensile stress, the tensile stress direction is perpendicular to the wave plate slow axis direction;

[0144] When the total optical path difference is equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is perpendicular to the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is parallel to the slow axis of the wave plate. The total optical path difference is the superposition result of the optical path difference of the wave plate and the optical path difference of the organic glass to be tested.

[0145] Preferably, the quarter wave plate is a multi-stage quarter wave plate.

[0146] The optical path difference calibration value of the multi-stage quarter-wave plate used in the actual test is 10565nm.

[0147] When the internal stress of the organic glass to be tested is compressive stress, and the direction of the compressive stress is parallel to the direction of the slow axis of the wave plate, the total optical path difference between the wave plate and the organic glass sample to be tested is equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested; when the direction of the compressive stress of the organic glass to be tested is perpendicular to the direction of the slow axis of the wave plate, the total optical path difference between the wave plate and the organic glass sample to be tested is equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested.

[0148] When the internal stress of the organic glass to be tested is tensile stress, and the direction of the tensile stress is perpendicular to the slow axis direction of the wave plate, the total optical path difference between the wave plate and the organic glass sample to be tested is equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested; when the direction of the tensile stress of the organic glass to be tested is parallel to the slow axis direction of the wave plate, the total optical path difference between the wave plate and the organic glass sample to be tested is equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested.

[0149] Example 2 As a verification of the method for detecting the direction of internal stress in organic glass, the laboratory tested and analyzed an organic glass sample (internal stress is compressive stress) with an optical path difference of 5754nm and a clear internal stress direction according to the above complete method and steps. The total optical path difference between the wave plate and the organic glass sample to be tested is calculated by a numerical fitting method, and then compared with the optical path difference of the wave plate to determine the direction of internal stress of the organic glass sample to be tested. Since the test uses an organic glass sample with compressive stress and a clear compressive stress direction, it can help verify whether the internal stress direction detection method in the patent is effective and correct. The details are as follows:

[0150] 1) When the direction of the internal stress (compressive stress) of the organic glass to be measured is parallel to the slow axis direction of the wave plate, such as Figure 6 As shown:

[0151] In this case, the total optical path difference between the wave plate and the organic glass sample to be tested is 16319nm, and 16319=|10565+5754|, indicating that the direction of the internal stress (compressive stress) of the organic glass sample with an optical path difference of 5754nm is parallel to the slow axis direction of the wave plate and perpendicular to the fast axis direction of the wave plate. By observing the receiving end wave plate in the test device, the 0° direction on the wave plate scale is the internal stress direction of the organic glass sample to be tested.

[0152] 2) When the direction of the internal stress (compressive stress) of the organic glass to be measured is perpendicular to the slow axis direction of the wave plate, such as Figure 6 As shown:

[0153] In this case, the total optical path difference between the wave plate and the organic glass sample to be tested is 4811nm, and 4811=|10565-5754|, indicating that the direction of the internal stress (compressive stress) of the organic glass sample with an optical path difference of 5754nm is perpendicular to the slow axis of the wave plate and parallel to the fast axis of the wave plate. By observing the receiving end wave plate in the test device, the 90° direction on the wave plate scale is the internal stress direction of the organic glass sample to be tested, such as Figure 7 shown.

[0154] The tests and analyses of the above two situations have verified the effectiveness and operability of the internal stress direction detection method in the patent, and have been proven that the method in the patent is universal for organic glass materials.

[0155] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0156] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for detecting the direction of internal stress in organic glass, characterized in that: The detection method is implemented based on a preset organic glass internal stress direction detection device, which includes an incident device and a receiving device arranged on both sides of the organic glass to be tested; The incident device comprises an incident light component and a first polarizing plate frame with a polarizer; the parallel light emitted by the incident light component is incident on the organic glass to be tested through the polarizer; The receiving device includes, in sequence along a direction away from the organic glass to be tested, a wave plate frame with a wave plate, a second polarizing plate frame with an analyzer, a receiving light component and a spectrometer; The first polarizer frame, the wave plate frame, and the second polarizer frame are all provided with scale plates; when the scale plates are rotated, the polarization direction of the polarizer is always aligned with 0° of the corresponding scale plate; the polarization direction of the analyzer is always orthogonal to the polarization direction of the polarizer; the wave plate is a quarter wave plate, and the fast axis direction of the wave plate is always aligned with 90° of the corresponding scale plate; The detection method comprises: The parallel light emitted by the incident light component is incident on the organic glass to be tested through the polarizer; The parallel light emitted from the organic glass to be tested enters the spectrometer through the wave plate, the analyzer, and the receiving light component; Adjust the scale values ​​of each dial, and obtain the internal stress direction of the organic glass to be tested based on the scale values ​​of each dial and the corresponding spectral data collected by the spectrometer, including: adjusting the dials of the first polarizer frame, the wave plate frame, and the second polarizer frame in sequence at preset scale value intervals, and keeping the sum of the scale values ​​of the polarizer and the wave plate dials to be 360°, and the sum of the scale values ​​of the polarizer and the analyzer dials to be 90°, and when the amplitude of the overall spectral curve of the spectral data collected by the spectrometer is the minimum, obtaining the possible direction of the internal stress of the organic glass to be tested; wherein, the possible direction includes being parallel to or perpendicular to the slow axis direction of the wave plate; keeping the scale of the wave plate frame unchanged, synchronously rotating the polarizer dial and the analyzer dial, and recording the optical path difference of the wave plate The superposition result of the optical path difference of the organic glass to be tested is used to finally determine the direction of the internal stress of the organic glass, including: when the superposition result is numerically equal to the absolute value of the sum of the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is parallel to the direction of the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is perpendicular to the direction of the slow axis of the wave plate; when the superposition result is numerically equal to the absolute value of the difference between the optical path difference of the wave plate and the optical path difference of the organic glass sample to be tested, if the internal stress of the organic glass is compressive stress, the direction of the compressive stress is perpendicular to the direction of the slow axis of the wave plate; if the internal stress is tensile stress, the direction of the tensile stress is parallel to the direction of the slow axis of the wave plate.

2. The method for detecting the internal stress direction of organic glass according to claim 1, characterized in that: The incident light component comprises: A light source, a first optical fiber, a collimating lens, a first adapter plate and a first connecting rod; the light emitted by the light source is transmitted to the collimating lens through the first optical fiber; the collimating lens converts the received light into parallel light; The first adapter plate is used to fix the collimating lens; Two ends of the first connecting rod are respectively connected to the first adapter plate and the first polaroid frame, and are used to support the first adapter plate and the first polaroid frame.

3. The method for detecting the internal stress direction of organic glass according to claim 2, characterized in that: The incident device also includes a first connecting rod leg and a first leg fixing member; The first connecting rod leg is used to support the first connecting rod; One end of the first leg fixing piece is fixed on the optical platform, and the other end is used to fix the first connecting rod leg.

4. The method for detecting the internal stress direction of organic glass according to any one of claims 1 to 3, characterized in that: The light receiving assembly includes: a second adapter plate, a second connecting rod, and a second optical fiber; The wave plate frame, the second polarizing plate frame and the second adapter plate are provided with connecting holes near the edge, and the wave plate frame, the second polarizing plate frame and the second adapter plate are connected in sequence through the second connecting rod; The second adapter plate is provided with an adapter structure device, and the adapter structure is used to connect to the second optical fiber; The second optical fiber is used to transmit the light output from the switching structure to the spectrometer.

5. The method for detecting the internal stress direction of organic glass according to claim 4, characterized in that: The receiving device also includes a second connecting rod leg and a second leg fixing member; The second connecting rod leg is connected to the second connecting rod and is used to support the second connecting rod; One end of the second leg fixing piece is fixed on the optical platform, and the other end is used to fix the second connecting rod leg.

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