CN113063356B - Method for measuring directional deformation out-of-plane displacement of material - Google Patents
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Abstract
The invention relates to a method for measuring directional deformation out-of-plane displacement of a material, which comprises the following steps: respectively obtaining an orthographic projection image before material deformation and an orthographic projection image after material deformation; obtaining an in-plane displacement field between two images before and after deformation by using a digital image correlation algorithm; and obtaining an off-plane displacement scalar field of the material deformation from the in-plane displacement field according to the mathematical relationship of the inclined plane. The method can complete measurement by only shooting two images by one camera, the test is not required to be carried out in a darkroom or a shading environment, an interference light path is not required, the applicability to the test environment is high, the measurement can be completed under the natural illumination condition, and the method is suitable for industrial detection. Meanwhile, the method does not need to be converted into a frequency domain or perform phase unwrapping operation, can greatly reduce measurement errors, has higher measurement precision, and is suitable for dynamic measurement.
Description
Technical Field
The invention relates to the technical field of industrial detection, in particular to a method for measuring directional deformation out-of-plane displacement of a material, and in particular relates to a method for measuring directional deformation out-of-plane displacement of an optical fiber image transmission material by utilizing a digital image correlation algorithm.
Background
The optical fiber image transmission material (such as an optical fiber panel, an image inverter, a microchannel plate and the like) is easy to generate various deformations after being subjected to physical, chemical and other physical and chemical actions in the production process. While the deformation is generally small in scale, typically on the order of micrometers, it has a significant impact on the properties of the material. Deformation detection and monitoring of optical fiber image transmission materials are generally realized under high-power microscope. The magnification principle of a microscope can be divided into two types, optical magnification and electronic magnification. The optical magnification refers to a lens combination which is completely magnified by an optical principle, the magnification is limited by the processing technology level of the lens, the magnification is generally tens times, the magnification effect is good, and the accurate morphological information of an object can be obtained; the electronic amplification is an amplification technology based on photoelectric conversion, interpolation and other technologies, and the amplification factor can be 400 times or higher, but the amplification effect is poorer than the definition of an image and the optical amplification. No matter which magnification principle is adopted, only a two-dimensional plan view (namely a plane formed by x and y directions) of the object can be directly obtained under a microscope, the deformation condition of the object in the z-axis direction can not be known, and the development of the micro-scale deformation detection technology of the material is restricted. In general, deformation measurement in the z-axis direction is detected by an atomic force microscope in a point scanning manner, and the method has high measurement accuracy, but related information can be obtained by point-by-point scanning, so that the method has the disadvantages of large workload, long time consumption, high detection cost, and inapplicability to industrial detection because a 1000 x 1000 pixel area array needs several hours or even one day.
The digital image correlation algorithm is an algorithm for estimating in-plane displacement based on block matching motion. The main principle of the method is that an image is divided into a plurality of sub-areas by a window with a fixed size, whether the two sub-areas are matched or not is determined by calculating the correlation coefficient of the sub-areas of the image before and after deformation, the displacement of the sub-area with the highest correlation coefficient in the x direction and the y direction is calculated, and finally the displacement field of each pixel point in the plane (x and y directions), namely the in-plane displacement, is obtained. However, this method is insensitive to out-of-plane displacement of the object and is not suitable for measuring deformations in the z-axis direction. Aiming at the problem, a plurality of researchers put forward binocular, multi-view and interference digital image related algorithms to realize detection of out-of-plane displacement, and good research results are obtained, but most of the algorithms have high requirements on environment, are not suitable for detecting deformation of objects in industrial environments, and are especially not suitable for detecting micron-scale deformation of optical fiber image transmission materials in industrial environments.
Disclosure of Invention
The invention mainly aims to provide a method for measuring directional deformation out-of-plane displacement of a material, and aims to solve the technical problem that the directional deformation out-of-plane displacement of the material, especially the micrometer-scale deformation out-of-plane displacement of an optical fiber image transmission material is difficult to measure in the prior art.
The aim and the technical problems of the invention are realized by adopting the following technical proposal. The invention provides a method for measuring directional deformation out-of-plane displacement of a material, which comprises the following steps:
respectively obtaining an orthographic projection image before material deformation and an orthographic projection image after material deformation;
obtaining an in-plane displacement field between two images before and after deformation by using a digital image correlation algorithm;
and obtaining an off-plane displacement scalar field of the material deformation from the in-plane displacement field according to the mathematical relationship of the inclined plane.
The aim and the technical problems of the invention can be further realized by adopting the following technical measures.
Preferably, in the method for measuring directional deformation off-plane displacement of a material, an in-plane displacement field between two images before and after deformation is obtained by using a digital image correlation algorithm, and an off-plane displacement scalar field of the material deformation is obtained from the in-plane displacement field according to the mathematical relationship of inclined planes; the method specifically comprises the following steps:
the in-plane displacement field between the two images before and after deformation is calculated by the formula (1):
in the formula (1), d is total in-plane displacement before and after deformation; u and v are respectively in-plane displacements of each point on the image in the x direction and the y direction, and u=deltau+u ', v=deltav+v' are obtained by utilizing a digital image correlation algorithm, wherein deltau and deltav are respectively integral pixel displacements of each point on the image in the x direction and the y direction, and u 'and v' are respectively sub-pixel displacements of each point on the image in the x direction and the y direction; r is the image width; alpha is a deformation angle;
defining the deformation of the material as the deformation of the inclined plane, and calculating out-of-plane displacement w of the deformation of the material according to the mathematical relationship of the inclined plane by the formula (2):
w＝Rsinα (2)
in the formula (2), R is the image width; alpha is a deformation angle calculated from formula (1).
Preferably, in the method for measuring directional deformation out-of-plane displacement of a material, deformation of all points in two images before and after deformation of the material is micro-nano deformation.
Preferably, the method for measuring the directional deformation out-of-plane displacement of the material includes respectively acquiring an orthographic projection image before the material is deformed and an orthographic projection image after the material is deformed, and specifically includes:
the method comprises the steps of starting a light source, placing a material on a three-dimensional light-transmitting object stage above the light source, adjusting the magnification of an objective lens of a microscope and the focal length of an industrial camera, enabling an image on the upper surface of the material to be clearly shot by the industrial camera, shooting forward projection images before deformation of the material, setting shooting time intervals according to the speed of deformation, and shooting the forward projection images after deformation of the material.
Preferably, the method for measuring the directional deformation out-of-plane displacement of the material, wherein the out-of-plane displacement unit is converted from a pixel unit to a length unit according to the magnification of a microscope, so as to obtain the out-of-plane displacement height.
Preferably, the method for measuring the directional deformation out-of-plane displacement of the material, wherein the dimensions of the two images before and after the material deformation are between 256×256 pixels and 1024×1024 pixels.
Preferably, in the method for measuring directional deformation out-of-plane displacement of a material, the window size of the digital image correlation algorithm is between 40×40 pixels and 60×60 pixels, so that in-plane displacement of all points in two images before and after deformation is between 3 pixels and 30 pixels.
Preferably, the method for measuring directional deformation out-of-plane displacement of the material further comprises the following steps:
judging the vector direction of the out-of-plane displacement scalar field; if the material is subjected to expansion deformation, the vector direction of the out-of-plane displacement is upward convex; if the material is deformed by shrinkage, the vector direction of the out-of-plane displacement is concave.
Preferably, the method for measuring the directional deformation off-plane displacement of the material, wherein the vector direction of the off-plane displacement scalar field is judged by macroscopic observation of whether the deformation characteristic of the material is expansion type or contraction type; or (b)
Judging the vector direction of the out-of-plane displacement scalar field by an a priori method: the material expands and deforms under the action of heat or high pressure; the material undergoes shrinkage deformation under the action of cold or corrosion.
Preferably, the method for measuring the directional deformation out-of-plane displacement of the material is carried out by Matlab software.
By means of the technical scheme, the method for measuring the directional deformation out-of-plane displacement of the material has at least the following advantages:
1. according to the method, all material deformation in a certain range is regarded as inclined plane deformation, the out-of-plane displacement scalar field of deformation can be obtained by the in-plane displacement field according to the mathematical relationship of the inclined plane, and the in-plane displacement field between two images before and after the material deformation can be obtained by a digital image correlation algorithm; therefore, the method only needs to obtain the orthographic projection image before the deformation of the material and the orthographic projection image after the deformation, and the out-of-plane displacement scalar field of the deformation of the material can be obtained through calculation.
2. The method can complete measurement by only shooting two images by one camera, the test is not required to be carried out in a darkroom or a shading environment, an interference light path is not required, the applicability to the test environment is high, the measurement can be completed under the natural illumination condition, and the method is suitable for industrial detection. Meanwhile, the method does not need to be converted into a frequency domain or perform phase unwrapping operation, can greatly reduce measurement errors, has higher measurement precision, and is suitable for dynamic measurement.
3. The method can be used for measuring the out-of-plane displacement of large-size deformation of a material and also can be used for measuring the out-of-plane displacement of micro-nano deformation of the material. In order to ensure the calculation time and the measurement precision, the size of an image is set to be in the range of (512-1024) ×512-1024, the window size of a digital image correlation algorithm is set to be between 40×40 pixels and 60×60 pixels, the in-plane displacement fields of the two images are subjected to pre-test, and the in-plane displacement of all points in the two images before and after deformation is ensured to be between 3 pixels and 30 pixels.
4. The method can also judge the direction of the out-of-plane displacement (vector field) according to the type of deformation, and if the generated deformation is expansion type, namely the deformation under the action of heat and high pressure, the direction of the out-of-plane displacement is convex upwards; if the generated deformation is shrinkage type deformation, namely cold and corrosion type deformation, the direction of off-plane displacement is concave.
5. The method can be used for measuring the out-of-plane displacement of the qualitative deformation of the material, can also be used for measuring the uniformity of the deformation of the material, has the characteristics of high measuring speed, high measuring precision, good repeatability and the like, can realize dynamic measurement, and also proves the feasibility of measuring the micro-nano deformation of the material.
6. The method realizes the detection of the out-of-plane deformation of the optical fiber image transmission element in the industrial environment, and provides an out-of-plane displacement extraction algorithm based on the correlation of digital images, wherein the in-plane displacement range of each pixel point of the two images before and after the deformation is proper is 3-30 pixels.
The foregoing description is only an overview of the present invention, and is intended to provide a better understanding of the present invention, as it is embodied in the following description, with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a flow chart of a method for measuring directional deformation out-of-plane displacement of a material in accordance with one embodiment of the present invention;
FIG. 2 shows a schematic representation of in-plane displacement as proposed by one embodiment of the present invention;
FIG. 3 shows a schematic representation of out-of-plane displacement as proposed by one embodiment of the present invention;
FIG. 4a shows a schematic representation of the expansion deformation under a microscope according to an embodiment of the present invention;
FIG. 4b shows a schematic representation of the microscopic shrinkage deformation according to an embodiment of the present invention;
FIG. 5 is a schematic diagram showing the principle of measurement of in-plane displacement extraction out-of-plane displacement according to an embodiment of the present invention;
FIG. 6 shows a schematic structural diagram of a measuring device according to an embodiment of the present invention;
FIG. 7a shows a photomicrograph of a material prior to deformation as proposed by an embodiment of the invention;
FIG. 7b shows a photomicrograph of a deformed material in accordance with an embodiment of the invention;
fig. 8 shows a graph of the measurement result of the out-of-plane displacement scalar field of the material deformation proposed by the embodiment of the present invention.
Detailed Description
In order to further describe the technical means and effects adopted by the invention to achieve the preset aim, the following detailed description refers to the specific implementation, structure, characteristics and effects of the method for measuring the directional deformation out-of-plane displacement of the material according to the invention by combining the attached drawings and the preferred embodiment. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.
As shown in fig. 1, a method for measuring directional deformation out-of-plane displacement of a material according to an embodiment of the present invention specifically includes the following steps:
s101, respectively acquiring an orthographic projection image before material deformation and an orthographic projection image after material deformation;
the method can be used for measuring the out-of-plane displacement of large-size deformation of the material and also can be used for measuring the out-of-plane displacement of micro-nano deformation of the material, and when measuring the out-of-plane displacement of the micro-nano deformation of the material, the method provided by the invention adopts a microscope with proper multiple to shoot the micro-nano deformation, and the specific steps are as follows:
starting a light source, placing a material to be measured on a three-dimensional light-transmitting object stage above the light source, placing an industrial camera above an ocular of a microscope, adjusting the magnification of the microscope and the focal length of the industrial camera, enabling an image on the upper surface of the material to be clearly shot by the industrial camera, setting a shooting time interval according to the speed of deformation, and respectively shooting an orthographic projection two-dimensional image before deformation and an orthographic projection two-dimensional image after deformation of the material;
in this step, the centerlines of the light source, material, microscope and industrial camera are collinear. As shown in fig. 6, the measuring device in this step is shown, wherein 1 is a light source, 2 is a three-dimensional light-transmitting stage, 3 is a material to be measured, 4 is an objective lens of a microscope, 5 is an eyepiece of the microscope, 6 is an industrial camera, and 7 is a computer. The operation process is as follows: and (3) turning on the light source, adjusting the position of the three-dimensional light-transmitting object stage, the magnification of the microscope and the focal length of the industrial camera, so that the image of the upper surface of the material to be measured can be clearly shot by the industrial camera. The method comprises the steps of firstly obtaining orthographic projection images before deformation, setting shooting time intervals according to deformation speed, obtaining orthographic projection images after deformation, and further obtaining two images before and after deformation.
In order to ensure the image quality and contrast, the adopted microscope is a pure optical amplification microscope, and the image is not obtained in an electronic amplification mode. The unit of out-of-plane displacement can be converted from pixel unit to length unit according to the magnification of microscope to obtain actual out-of-plane displacement height.
In this step, the material is a solid material, such as an optical fiber image transmission element, and in principle, the solid material is not specifically limited, the degree of deformation of the material selects the magnification of the microscope, the magnification of the material with large deformation is small, and the magnification of the material with small deformation is large. For the accuracy of measurement, the material is made into an object whose detection surface is planar and made parallel to the three-dimensional light-transmitting stage, and preferably made into a cube.
To ensure calculation time and measurement accuracy, the size of the image is set in the range of (256-1024) ×256-1024.
Step S102, obtaining an in-plane displacement field between two images before and after deformation by using a digital image correlation algorithm:
in step S102, the window size of the digital image correlation algorithm is set between 40×40 pixels and 60×60 pixels, and the in-plane displacement fields of the two images before and after deformation are pre-tested, so that the in-plane displacement of all points in the two images is guaranteed to be between 3 pixels and 30 pixels, preferably between 5 pixels and 20 pixels, and when the in-plane displacement exceeds 40% or less than 3 pixels of the window size, the measurement accuracy is reduced, therefore, the in-plane displacement between the two images before and after deformation is preferably between 3-30 pixels, and good measurement results can be obtained for the two images within the range, and on the basis, all deformation can be regarded as inclined deformation under a microscope.
And step 103, obtaining an off-plane displacement scalar field of the material deformation from the in-plane displacement field according to the mathematical relationship of the inclined plane.
The specific measurement principle is as follows:
when a material is deformed, its displacement in the x-axis direction is defined as in-plane displacement u, its displacement in the y-axis direction is defined as in-plane displacement v, and its displacement in the z-axis direction is defined as out-of-plane displacement w.
1. In-plane displacement (In-plane Displacement): when a material moves in a two-dimensional plane (xy-plane), each pixel moves in the x-direction and y-direction by a vector, generally the in-plane displacement in the x-direction is referred to as u, and the in-plane displacement in the y-direction is referred to as v, as shown in fig. 2.
2. Out-of-plane displacement (Out-plane displacement): if the material is deformed in the z-direction (which may be considered to be raised or lowered by a height value), the displacement in the z-direction is referred to as out-of-plane displacement, and its directions are two, i.e., upward and downward, with the upward direction being shown in fig. 3.
3. Directional deformation: directional deformation refers to deformation that can determine the direction of out-of-plane displacement in a priori manner. If the out-of-plane displacement generated by the heated and expanded material is convex, namely expansion type deformation, according to the principle of thermal expansion and contraction, as shown in fig. 4 a; the direction of out-of-plane displacement upon cold shrinkage is concave, i.e. shrinkage deformation, as shown in fig. 4 b.
4. Digital image correlation algorithm: the geometric points on the surface of the material before and after deformation generate in-plane displacement, and the images before and after deformation are related, so that the corresponding geometric points before and after the material deformation can be determined through a related algorithm, and the in-plane deformation field can be directly obtained. The most commonly used calculation correlation formula is formula (4), wherein formula (4) represents that the correlation coefficient C is calculated by taking sub-regions with the size of m x m on the image before and after deformation, and u and v which are the maximum values of C can be the displacement of the center of the sub-region.
In the formula (4), f (x, y) is an image before deformation, g (x, y) is an image after deformation,
and->
The average value of gray scales of the image subareas is respectively calculated, u and v are respectively the in-plane displacement of each point on the image in the x direction and the y direction, and Deltau and Deltav are respectively the whole pixel displacement of each point on the image in the x direction and the y direction.
The whole pixel displacement values of the two images can be determined by the expression (4). However, the actual displacement value is not generally exactly an integer. In order to improve the measurement accuracy, it is necessary to further calculate the sub-pixel displacement based on the whole pixel result. The correlation coefficient calculation formula selected in the gradient-based subpixel correlation algorithm is formula (5):
in equation (5), u 'and v' are sub-pixel displacements in the x-direction and y-direction, respectively, for each point on the image.
Will be
Taylor expansion, taking a first approximation and letting +.>
Formula (6) is available:
in the formula (6), the amino acid sequence of the compound,
in the above formula, the partial derivatives of x and y are expressed by using x and y as subscripts.
When the differential in the formula (6) is calculated, a Barron gradient operator is selected, and the calculation method is as follows, so that the formula (7) is obtained:
the required motion fields u=Δu+u 'and v=Δv+v' between two consecutive images can be found from equation (7).
5. The test principle of in-plane displacement extraction out-of-plane displacement (bevel relationship): according to the method, all deformation under a microscope is regarded as inclined plane deformation, and an off-plane displacement scalar field of the deformation can be obtained from an in-plane displacement field according to the mathematical relationship of the inclined plane; the deformation of the material is defined as the deformation of the slope and the deformation angle is defined as α, i.e. the change in angle caused by deformation of the upper surface of the material, as shown in fig. 5, where oa=oa 1 When seen downwards from the vertical direction, the point a moves to the point a ', the off-plane displacement generated in the vertical direction is w, the total in-plane displacement before and after deformation is d=aa', and R is the distance from the point a to the fulcrum O on the image.
Defining the deformation of the material as the deformation of the inclined plane, and calculating out-of-plane displacement w of the deformation of the material according to the mathematical relationship of the inclined plane by the formula (2):
w＝Rsinα (2)
in the formula (2), R is the image width and is known; alpha is the deformation angle, which is calculated from formula (1), and (1) is the in-plane displacement field between the two images before and after deformation:
in the formula (1), d is total in-plane displacement before and after deformation; u and v are respectively in-plane displacements of each point on the image in the x direction and the y direction, and u=deltau+u ', v=deltav+v' are obtained by utilizing a digital image correlation algorithm, wherein deltau and deltav are respectively integral pixel displacements of each point on the image in the x direction and the y direction, and u 'and v' are respectively sub-pixel displacements of each point on the image in the x direction and the y direction; r is the image width; α is a deformation angle represented by formula (3), which is obtained by deformation according to formula (1):
6. working principle: the measurement device shown in fig. 6 is adopted, a shooting time interval is set according to the deformation speed, two images before and after deformation are obtained, and in order to ensure calculation time and measurement accuracy, the sizes of the images are set in a range of (256-1024) ×256-1024. The window size of the digital image correlation algorithm is set between 40 x 40 pixels and 60 x 60 pixels, and the in-plane displacement fields of the two images are pre-tested, so that the in-plane displacement of all points between the two images is ensured to be between 3 pixels and 30 pixels. The in-plane displacement field between the two images is obtained by utilizing a digital image correlation algorithm, and as all deformation can be regarded as inclined plane deformation under a microscope, the out-of-plane displacement scalar field of the deformation can be obtained by the in-plane displacement field according to the mathematical relationship of the inclined plane.
The method for measuring the directional deformation out-of-plane displacement of the material can be processed by Matlab software.
Further, the method for measuring the directional deformation out-of-plane displacement of the material further comprises the following steps:
and step S104, judging the vector direction (vector field) of the out-of-plane displacement scalar field by macroscopic observation of whether the deformation characteristic of the material is expansion type or contraction type, wherein the out-of-plane displacement vector direction of expansion deformation is convex upwards, and the out-of-plane displacement vector direction of contraction deformation is concave downwards.
Or,
judging the vector direction (vector field) of the out-of-plane displacement scalar field by an a priori method: the material can expand and deform under the action of heat or high pressure, and the direction of off-plane displacement is convex upwards; the material can shrink and deform under the action of cooling or corrosion, and the direction of off-plane displacement is concave.
The invention provides a method for measuring out-of-plane displacement of directional deformation of a material (such as an optical fiber image transmission material) under a microscope by utilizing a digital image correlation algorithm. The method mainly comprises the following steps: the material which is undergoing deformation after being subjected to physical and chemical effects is placed on a stage of a microscope, and an industrial camera is placed above an eyepiece of the microscope to obtain a deformation image of the magnified material under microscopic conditions. Because the deformation scale is smaller, generally the micrometer scale deformation, the two-dimensional images before and after the deformation have certain correlation, the method adopts a digital image correlation algorithm to directly obtain the in-plane displacement of the material, simultaneously the deformation of the material obtained by observation under a microscope is regarded as inclined plane deformation, the out-of-plane displacement scalar field (namely the size of the out-of-plane displacement) of the material can be obtained by the in-plane displacement of the material according to an inclined plane mathematical relation, and the out-of-plane deformation is directional deformation, namely the deformation direction can only have an upward direction and a downward direction, so the out-of-plane displacement vector direction can be determined by observing the deformation type. According to the method, only one camera is required to shoot two images to finish measurement, the measurement can be performed in a laboratory or under natural illumination conditions, the measurement is not required to be performed in a darkroom or under a shading environment, an interference light path is not required, the applicability to the testing environment is high, and the method is suitable for industrial detection. Meanwhile, the method does not need to be converted into a frequency domain or phase unwrapping operation, can greatly reduce measurement errors, has higher measurement precision, and is suitable for industrial production deformation detection and dynamic measurement.
The measuring method designed by the invention is specially provided for the out-of-plane displacement measurement of materials (such as optical fiber image transmission materials) under a microscope, and the displacement calculation can be processed by Matlab software.
The invention will be further described with reference to specific examples, which are not to be construed as limiting the scope of the invention, but rather as falling within the scope of the invention, since numerous insubstantial modifications and adaptations of the invention will now occur to those skilled in the art in light of the foregoing disclosure.
Example 1
The method for measuring the directional deformation out-of-plane displacement of the optical fiber image transmission material by utilizing a digital image correlation method specifically comprises the following steps:
analysis of results: as shown in fig. 8, for the displacement w in the off-plane z-axis direction measured by the method according to the present invention, as can be seen from fig. 8, the maximum value of the off-plane displacement is 26.6 μm, and compared with the actual measurement value, the average error of the off-plane displacement measured by the method according to the present embodiment is 4.11%, the calculation time is only 15 seconds, so that the detection efficiency is greatly improved.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "horizontal", "vertical", etc. are based on the methods or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.
The present invention is not limited to the above-mentioned embodiments, but is intended to be limited to the following embodiments, and any modifications, equivalents and modifications can be made to the above-mentioned embodiments without departing from the scope of the invention.
Claims (8)
1. A method of measuring directional deformation out-of-plane displacement of a material, comprising:
respectively obtaining an orthographic projection image before material deformation and an orthographic projection image after material deformation;
obtaining an in-plane displacement field between two images before and after deformation by using a digital image correlation algorithm;
obtaining an off-plane displacement scalar field of material deformation from the in-plane displacement field according to the mathematical relationship of the inclined plane;
the method for respectively obtaining the orthographic projection image before material deformation and the orthographic projection image after material deformation specifically comprises the following steps:
starting a light source, placing a material on a three-dimensional light-transmitting object stage above the light source, adjusting the magnification of an objective lens of a microscope and the focal length of an industrial camera, enabling an image on the upper surface of the material to be clearly shot by the industrial camera, shooting forward projection images before deformation of the material, setting shooting time intervals according to the speed of deformation, and shooting the forward projection images after deformation of the material;
the size of the two images before and after the deformation of the material is between 256 and 1024 pixels;
the window size of the digital image correlation algorithm is between 40 and 60 x 40 pixels, so that the in-plane displacement of all points in the two images before and after deformation is between 3 and 30 pixels; the method comprises the steps of obtaining an in-plane displacement field between two images before and after deformation by using a digital image correlation algorithm, and obtaining an out-of-plane displacement scalar field of material deformation from the in-plane displacement field according to the mathematical relationship of inclined planes; the method specifically comprises the following steps:
the in-plane displacement field between the two images before and after deformation is calculated by the formula (1):
in the formula (1), d is total in-plane displacement before and after deformation; u and v are respectively in-plane displacements of each point on the image in the x direction and the y direction, and u=deltau+u ', v=deltav+v' are obtained by utilizing a digital image correlation algorithm, wherein deltau and deltav are respectively integral pixel displacements of each point on the image in the x direction and the y direction, and u 'and v' are respectively sub-pixel displacements of each point on the image in the x direction and the y direction; r is the image width; alpha is a deformation angle;
defining the deformation of the material as the deformation of the inclined plane, and calculating out-of-plane displacement w of the deformation of the material according to the mathematical relationship of the inclined plane by the formula (2):
w＝Rsinα (2)
in the formula (2), R is the image width; alpha is a deformation angle calculated from formula (1).
2. The method for measuring directional deformation out-of-plane displacement of a material according to claim 1, wherein deformation of all points in two images before and after deformation of the material is micro-nano deformation.
3. The method for measuring the directional deformation out-of-plane displacement of a material according to claim 1, wherein the out-of-plane displacement unit is converted from a pixel unit to a length unit according to the magnification of a microscope, and the out-of-plane displacement height is obtained.
4. The method of measuring directional deformation out-of-plane displacement of a material according to claim 1, wherein the two images before and after deformation of the material are between 512 x 512 pixels and 1024 x 1024 pixels in size.
5. The method of measuring directional deformation out-of-plane displacement of a material of claim 1, further comprising:
judging the vector direction of the out-of-plane displacement scalar field; if the material is subjected to expansion deformation, the vector direction of the out-of-plane displacement is upward convex; if the material is deformed by shrinkage, the vector direction of the out-of-plane displacement is concave.
6. The method of measuring directional deformation off-plane displacement of a material according to claim 5, wherein the vector direction of the off-plane displacement scalar field is determined by whether the macroscopic deformation characteristic of the observed material is of the expansion type or the contraction type; or (b)
Judging the vector direction of the out-of-plane displacement scalar field by an a priori method: the material expands and deforms under the action of heat or high pressure; the material undergoes shrinkage deformation under the action of cold or corrosion.
7. The method for measuring the directional deformation out-of-plane displacement of the material according to claim 1, wherein the method for measuring the directional deformation out-of-plane displacement of the material is processed by Matlab software.
8. The method for measuring directional deformation out-of-plane displacement of a material according to claim 1, comprising the steps of:
1) The method comprises the steps of starting a light source, placing an optical fiber image transmission material on a light-transmitting objective table above the light source, and adjusting the magnification of an objective lens of a microscope and the focal length of an industrial camera, so that an image of the upper surface of the optical fiber image transmission material can be clearly shot by the industrial camera;
using piezoelectric ceramics to enable the optical fiber image transmission material to incline, wherein the incline height is 25 mu m, the direction is upward, the image size is 400 x 400 pixels, the size of each pixel is 0.08 mu m, and the two-dimensional images before deformation and after deformation are respectively shot under a 50-time optical magnification microscope;
2) Setting a shooting time interval according to the deformation speed to obtain two images before and after deformation, setting the size of the images at 1024 x 1024 pixels, setting the window size of a digital image correlation algorithm at 50 x 50 pixels, pre-testing the in-plane displacement field of the two images, and ensuring that the in-plane displacement of all points between the two images is between 5 pixels and 20 pixels;
3) Firstly, an in-plane displacement field between two images is obtained by using a digital image correlation algorithm, and a deformed off-plane displacement scalar field can be obtained from the in-plane displacement field according to the mathematical relationship of the inclined plane;
4) Judging the direction of the out-of-plane displacement according to the type of deformation, and if the generated deformation is expansion type, namely the deformation under the action of heat and high pressure, the direction of the out-of-plane displacement is convex upwards; if the generated deformation is shrinkage type deformation, namely cold and corrosion type deformation, the direction of off-plane displacement is concave.
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