CN110672478A - Testing method and device for analyzing shape of machined sand particles based on image processing technology - Google Patents
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Abstract
The invention discloses a machine-made sand particle shape measuring method and device based on an image processing technology, wherein the machine-made sand particle shape has great influence on the concrete mixing water consumption, and the mechanical property and the durability of the hardened concrete are further influenced. The invention provides a new method based on the shape indexes (circularity, sphericity, length-width ratio and width-height ratio) of the machine-made sand particles. The use of the present measurement method includes: (1) sampling, (2) sample preparation, (3) image acquisition, (4) image processing, and (5) shape index calculation. The invention is characterized in that: according to the mutual relation of three views of the object, the calculation of the three-dimensional size of the machine-made sand particles is completed, and the direct acquisition of the three-dimensional size of the particles based on the image processing technology is realized for the first time; the determination method is simple to operate, accurate in calculation result and strong in applicability.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to a method and a device for testing the shape of machine-made sand particles based on an image processing technology analysis.
Background
As a limited resource, natural sand cannot be regenerated in a short time, and the distribution of the natural sand shows regional differences, so that the requirement of the construction market on fine aggregates cannot be completely met; the machine-made sand is rock particles with the particle size of less than 4.75mm obtained by mechanical crushing, is rich in reserve and can be used as a natural sand substitute resource; compared with natural sand, the machine-made sand obtained by mechanical crushing has rough surface and irregular particles, is in the shapes of a polygon corner, a plurality of sheets and a rod, and the properties of the machine-made sand concrete and the natural sand concrete are different.
At present, China does not strictly regulate the shape of machine-made sand particles, and the machine-made sand particles are mainly evaluated by visual inspection, and the fine aggregate particle shape measurement methods in literature data mainly comprise the following two types:
indirect measurement method: the physical and chemical indexes which are related to the particle shape and convenient to measure are established to indirectly reflect the particle shape information, and the following 4 types are mainly adopted:
(1) the method of clearance ratio: the method is characterized in that the method is specified in the current standard of China, Highway engineering aggregate test regulation JTG E42-2005, the clearance rate of a certain amount of fine aggregate which passes through a standard funnel and is filled into a standard container is measured, namely the angularity of the fine aggregate is expressed by percentage, the method indirectly reflects the shape of fine aggregate particles, and the subjectivity is high when the relative density of the volume of machine-made sand wool is measured, so that the calculation result is influenced.
(2) Flow time method: the method is simple to operate, but a pipe blockage phenomenon is easy to occur when the flowing time of machine-made sand is measured, and misunderstanding is caused.
(3) Strip-shaped hole screening method: song minority and the like customize long-hole sieves with different hole diameters, calculate the content of flaky particles by using screening results, and further process the sand shape by a reactor, but the method can only distinguish spherical particles from flaky particles, and can not well distinguish rod-shaped particles.
(4) Methylene blue solution method: drying the machine-made sand cleaning solution to obtain the content of the stone powder, carrying out a methylene blue marking test on the stone powder, and recording the volume of the dropwise added methylene blue solution when light blue color halo appears around a precipitate deposited on the filter paper to describe the shape of the machine-made sand particles.
Direct measurement: the shape of the fine aggregate particles is directly obtained through image processing and three-dimensional reconstruction, and then shape indexes are established for description, wherein the shape indexes mainly comprise the following 4 types:
x-ray CT technique: garboczi utilizes the X-ray CT technology to obtain the three-dimensional shape of fine aggregate particles, stores the three-dimensional shape in a spherical harmonic function, obtains a particle entity through three-dimensional reconstruction, and can calculate the three-dimensional size, the surface area and the volume of the particles.
Laser scanning technology: komba utilizes a laser scanning technology to obtain three-dimensional size, surface area and volume information of aggregate particles, establishes shape indexes such as length-width ratio, width-height ratio, sphericity and the like, and for analysis of the shape of fine aggregate particles, high resolution is often needed, so that the detection cost is improved, and the application of the laser scanning technology in measurement of the shape of sand-making particles is limited.
Manual measurement: in the American Standard Standard Test Method for Flat Particles, Elongated Particles, or Flat Elongated Particles in Coarse Aggregate, a special proportional caliper is used for manually measuring the proportional relation of the length and the width of the Particles in ASTM D4791-10 to further judge that the Particles belong to a sheet shape or a rod shape.
Image analysis method: with the development of computer technology, image analysis methods are gradually applied to particle shape characterization, and the existing technology mainly obtains information such as particle perimeter, area, length and width by analyzing a plane graph and establishes indexes of circularity and length-width ratio to describe particle shape.
Disclosure of Invention
The invention aims to overcome the defects in the machine-made sand particle shape representation in the prior art and provides a machine-made sand particle shape measuring method and device which are convenient and quick in measuring process and accurate and objective in measuring result.
The technical scheme of the invention is as follows:
a machine-made sand particle shape measuring method based on an image processing technology comprises the following steps:
(1) sampling: uniformly sampling from a material pile, weighing about 2kg of samples to be measured, shoveling the surface of a sampling part before sampling, and randomly extracting 8 parts of machine-made sand with approximately equal quantity from different parts to form a group of samples.
(2) Preparing a sample: drying the sample in a 105 ℃ blast drying oven until the weight is constant, screening the sample, respectively collecting about 100g of machine-made sand particles with the particle size ranges of 1.18-2.36mm and 2.36-4.75mm, washing the collected machine-made sand particles with water to remove fine powder adsorbed on the surfaces of the machine-made sand particles, finally, placing the washed sample in a 105 ℃ blast drying oven for drying, and finishing sample preparation to be measured.
(3) Image acquisition: the machine-made sand particles are arranged on the LED lamp panel (4) in a straight line and are parallel to the LED lamp panel (3) so as to ensure that the particles are not connected and shielded when the images are collected, and a digital camera backlight method is used for shooting and collecting the particle main view and the top view.
(4) Image preprocessing: the first step of processing image extraction information by a computer is to realize image segmentation and identify a target object, so that a graythresh function in a Matlab function library can be directly called to calculate the gray value of an acquired image, then an im2bw function is called to segment the image so that the gray value of target particles is 0 and the background gray value is 1, then a medfilt2 function is called to perform median filtering on the image so as to eliminate optical noise in the image, then a bwearopen function is called to eliminate non-target objects such as dust and the like in the image, and finally an imfill function is called to eliminate bright spots possibly generated by reflected light in a target object area so that the target area becomes a complete connected body.
In the method, for improving the calculation efficiency of the shape of the machine-made sand particles, a bwleabel function is called to mark the particles, so that simultaneous calculation of a plurality of particles in a picture is realized.
(5) Extracting image information: and processing the acquired image by using Matlab software, and calculating to obtain size information including the projection area and the projection perimeter of the particle surface and the length, width and height of the particle. The particle shape description indexes of the particle circularity (R), the aspect ratio (E), the aspect ratio (F) and the sphericity (S) are defined by the following calculation formula:
wherein R represents the circularity of the particle, and A represents the projected area of the particle.
In Matlab software, the total number of pixel points with the gray value of 0 in a preprocessed picture is calculated by calling a length function, C represents the projection perimeter of the particle, and the chain code surrounding the pixel points of the particle can be obtained through 8-chain code thought.
In the formula, E represents the aspect ratio of the particles, length represents the length of the particles, and width represents the width of the particles.
In Matlab, the length and width of a rectangle surrounding a particle is calculated as the nominal size length 'and width' by rotating this rectangle of variable size until the smallest rectangle is found; then calculating the projection length of the target object in the horizontal direction as d1The system is used for length scale transformation caused by different acquisition distances when the height of the particles in the main view is calculated; because the front view and the top view are respectively shot by different cameras, the number of the occupied pixel points of the same size and different views is different, and the pixel points need to be normalized in the length proportion of the same view.
d1＝xmax-xmin
In top view, d1Is the projected length of the particle in the horizontal direction, and the maximum coordinate value x of the particle projected in the horizontal directionmaxThe minimum coordinate value is xmin。
In the formula, F represents the aspect ratio of the particles, width represents the width of the particles, and thickness represents the height of the particles.
Calculating the projection length of the particles in the vertical direction in the front view as h, and calculating the projection length of the particles in the horizontal direction as d2Then, the length ratio RST (ratio for size transition) between the top view and the main view can be obtained, and the nominal height of the granule (thickness') under the size of the main view can be further obtained, and finally, the length is set according to the nominal three-dimensional size>width>And (4) sorting and re-assigning the particle sizes to obtain the real particle sizes.
h=ymax-ymin
In the front view, h is the projection length of the particle in the vertical direction, and the maximum coordinate value y of the projection of the particle in the vertical directionmaxThe minimum coordinate value is ymin。
d2＝xmax-xmin
In the front view, d2 is the projection length of the particle in the horizontal direction, and the maximum coordinate value x of the particle projection in the horizontal directionmaxThe minimum coordinate value is xmin。
Where RST is a scale factor used to program the main view length into the main view, d1 and d2 are described as [0026] and [0030 ].
thickness′=RST×h
Wherein, thickness' is the nominal height of the particle in the length scale of the top view.
Wherein S represents sphericity, and length, width and thickness are as defined above.
The invention also discloses a device of the machine-made sand particle shape measuring method based on the image processing technology, wherein the transpose comprises a digital camera, an LED lamp panel and a bracket, and the LED lamp panel is vertically connected with the LED lamp panel; the LED lamp panel is horizontally arranged, the LED lamp panel is vertically arranged, the edge joint of the LED lamp panel and the LED lamp panel is fixed by screws, the digital camera is fixed on the upper portion of the support, the digital camera is perpendicular to the horizontal LED lamp panel, the distance between the digital camera and the LED lamp panel is 30cm, the digital camera is fixed on the lower portion of the support, the digital camera is perpendicular to the vertical LED lamp panel, and the distance between the digital camera and the LED lamp panel is 30 cm.
The invention has the beneficial effects that: mainly aims at the production and quality control of concrete machine-made sand, and provides technical basis for producing and designing concrete and understanding and controlling the concrete quality. The machine-made sand particles are conveniently, quickly, accurately and objectively measured and evaluated by a computer image processing technology and Matlab software, so that the method is high in practicability and worthy of popularization.
Drawings
FIG. 1 is a schematic view of a machine-made sand particle shape measuring device according to the present invention;
FIG. 2 is a schematic two-dimensional projection of the shape of a machined sand particle of the present invention;
FIG. 3 is a schematic view of a cuboid with minimal encirclement of machined sand particles according to the present invention;
FIG. 4 is a graph showing the results of the measurement of the shape of fine aggregate particles by the present method;
FIG. 5 is a result graph of the method for testing the influence of the random orientation of the machine-made sand on the measurement result;
FIG. 6 is a graph showing the results of the susceptibility test of the evaluation results of the present method to the number of samples collected.
Detailed Description
The present invention will be further illustrated with reference to the accompanying drawings and specific embodiments, which are to be understood as merely illustrative of the invention and not as limiting the scope of the invention.
As shown in fig. 1 to 3, a method for measuring the shape of machine-made sand particles based on image processing technology comprises the following steps:
(1) sampling: uniformly sampling from a material pile, weighing about 2kg of samples to be measured, shoveling the surface of a sampling part before sampling, and randomly extracting 8 parts of machine-made sand with approximately equal quantity from different parts to form a group of samples.
(2) Preparing a sample: drying the sample in a 105 ℃ air blast drying box until the weight is constant, screening the sample, respectively collecting about 100g of machine-made sand particles with the particle size ranges of 1.18-2.36mm and 2.36-4.75mm, washing the collected machine-made sand particles with water, removing fine powder adsorbed on the surfaces of the machine-made sand particles, finally, placing the washed sample in the 105 ℃ air blast drying box for drying, and finishing sample preparation to be measured.
(3) Image acquisition: the machine-made sand particles are arranged on the LED lamp panel (4) in a straight line and are parallel to the LED lamp panel (3) so as to ensure that the particles are not connected and shielded when the images are collected, and a digital camera backlight method is used for shooting and collecting the particle main view and the top view.
(4) Image preprocessing: the first step of processing image extraction information by a computer is to realize image segmentation and identify a target object, so that a graythresh function in a Matlab function library can be directly called to calculate the gray value of an acquired image, then an im2bw function is called to segment the image so that the gray value of target particles is 0 and the background gray value is 1, then a medfilt2 function is called to perform median filtering on the image so as to eliminate noise points in the image, then a bwearopen function is called to eliminate non-target objects in the image, such as dust and the like, and finally an imfill function is called to eliminate bright points possibly generated by optical reflection in a target object region so that the target region becomes a complete connected body.
In the method, for improving the calculation efficiency of the shape of the machine-made sand particles, a bwleabel function is called to mark the particles, so that simultaneous calculation of a plurality of particles in a picture is realized.
(5) Extracting image information: and processing the acquired image by using Matlab software, and calculating to obtain size information including the projection area and the projection perimeter of the particle surface and the length, width and height of the particle. The particle shape description indexes of the particle circularity (R), the aspect ratio (E), the aspect ratio (F) and the sphericity (S) are defined by the following calculation formula:
wherein R represents the circularity of the particle, and A represents the projected area of the particle.
In Matlab software, the total number of pixel points with the gray value of 0 in a preprocessed picture is calculated by calling a length function, C represents the projection perimeter of the particle, and the chain code surrounding the pixel points of the particle can be obtained through 8-chain code thought.
In the formula, E represents the aspect ratio of the particles, length represents the length of the particles, and width represents the width of the particles.
In Matlab, the length and width of a rectangle surrounding a particle is calculated as the nominal size length 'and width' by rotating this rectangle of variable size until the smallest rectangle is found; calculating the projection length of the target object in the horizontal direction as d1, wherein the projection length is used for length scale transformation caused by different acquisition distances during particle height calculation in the main view; because the front view and the top view are respectively shot by different cameras, the number of the occupied pixel points of the same size and different views is different, and the pixel points need to be normalized in the length proportion of the same view.
d1＝xmax-xmin
In the top view, d1 is the projection length of the particle in the horizontal direction, and the maximum coordinate value x of the particle projection in the horizontal directionmaxThe minimum coordinate value is xmin。
In the formula, F represents the aspect ratio of the particles, width represents the width of the particles, and thickness represents the height of the particles.
Calculating the projection length of the particles in the vertical direction in the front view as h, and calculating the projection length of the particles in the horizontal direction as d2Then, the length ratio RST (ratio for size transition) between the top view and the main view can be obtained, and the nominal height of the granule (thickness') under the size of the main view can be further obtained, and finally, the length is set according to the nominal three-dimensional size>width>And (4) sorting and re-assigning the particle sizes to obtain the real particle sizes.
h=ymax-ymin
In the front view, h is the projection length of the particle in the vertical direction, and the maximum coordinate value y of the projection of the particle in the vertical directionmaxThe minimum coordinate value is ymin。
d2＝xmax-xmin
In the front view, d2The maximum coordinate value x of the projection of the particle in the horizontal direction is the projection length of the particle in the horizontal directionmaxThe minimum coordinate value is xmin。
Where RST is a scaling factor used to normalize the main view length into the main view, d1And d2As described above.
thickness′＝RST×h
Wherein, thickness' is the nominal height of the particle in the length scale of the top view.
Wherein S represents sphericity, and length, width and thickness are as defined above.
As shown in fig. 1, the device of the machine-made sand particle shape measurement method based on the image processing technology is adopted for the measurement, the transposition comprises a digital camera (1), a digital camera (2), an LED lamp panel (3), an LED lamp panel (4) and a bracket (5), and the LED lamp panel (3) is vertically connected with the LED lamp panel (4); LED lamp plate (3) level is placed, and LED lamp plate (4) are vertical to be placed, LED lamp plate (3) and the edge of LED lamp plate (4) meet the department and use the screw fixation mutually, digital camera (1) is fixed on support (5) upper portion, digital camera (1) perpendicular to horizontal LED lamp plate (3), digital camera (1) is apart from LED lamp plate (3)30cm, digital camera (2) are fixed in support (5) lower part, vertical LED lamp plate (4) of digital camera (2) perpendicular to, digital camera (2) are apart from LED lamp plate (4)30 cm.
The following examples were tested using the methods and settings described above.
Example 1
The circularity calculation is carried out on a regular cuboid with known size (50.02 multiplied by 40.77 multiplied by 40.18mm), and the accuracy of the measurement result of the method is verified; when the circularity of the rectangular parallelepiped is measured, the circularity is calculated by image analysis based on a plan view (40.77 × 40.18 mm): r0.7850, equal to its true value R0.7850, within a selected accuracy range, so the method can be considered accurate for evaluating object circularity; the three-dimensional sizes of the cuboid obtained by image analysis are respectively as follows: length is 749.34, width is 609.99, and thickness is 606.71 (unit is 1, which represents the number of pixels), calculated according to the definition: the aspect ratio E is 1.2284, the aspect ratio F is 1.0054, and the actual values are E1.2269 and F1.0147, respectively, the relative error of the aspect ratio is 0.12% and the relative error of the aspect ratio is 0.92%, and the relative errors can be found to be less than 1% by analyzing the relative errors of the aspect ratio and the aspect ratio, so that the method can be considered to be accurate for measuring the aspect ratio and the aspect ratio of the object; meanwhile, the sphericity S of the object is calculated to be 0.6591, the true value S is 0.6547, and the relative error is 0.67%, and it can be found by analyzing the relative error of the sphericity that the method has sufficient accuracy for evaluating the sphericity of the object, so that the method can be considered to be accurate for measuring the sphericity of the object.
Example 2: measuring the shapes of the 300 multi-grain machine-made sand particles and the natural sand particles, and calculating the result as shown in figure 4; comparing fig. 4(a) and (b) it can be seen that the machine-made sand is less rounded than the natural sand, indicating that the machine-made sand particles are more angular and less smooth than the natural sand surface; comparing fig. 4(c) and (d), it can be seen that the aspect ratio and aspect ratio of the machine-made sand are both greater than those of the natural sand, which indicates that the machine-made sand particles tend to be more pin-like and plate-like, while the natural sand particles are less different in three-dimensional size and more regular in shape; comparing fig. 4(e) and (f), it can be found that the sphericity index of the natural sand is large, and the dispersion of the sphericity is small, which indicates that the natural sand is closer to a sphere and the particle shape is more uniform; the particle shape evaluation of the natural sand and the machine-made sand by the three shape indexes shows that the natural sand has smooth surface and small edge angle compared with the machine-made sand, is closer to a sphere and accords with general cognition; meanwhile, the method is pioneering in measuring the aspect ratio of the fine aggregate, and compared with the prior art, the method firstly realizes the purpose of obtaining the height of the particles through an image processing technology and further obtains the description of the aspect ratio of the particle suit.
Example 3: and (3) checking the influence of manual operation on the shape result of the machined sand particles measured by the method: in order to check the influence of the machine-made sand particle orientation on the shape calculation result caused by manual placement, 10 random placement tests are carried out on the same batch of particles, and the machine-made sand shape parameters of each random placement are respectively calculated, wherein the calculation result is shown in fig. 5; as can be seen from fig. 5, the change of the position and orientation of the particles due to random 10-time arrangement has little influence on the circularity, aspect ratio and sphericity, and the measurement results of the method on the circularity, aspect ratio and sphericity of the machine-made sand particles can be considered to be not influenced by the arrangement position and orientation of the particles within an error range.
Example 4: because the amount of the machine-made sand used in the concrete is large, the evaluation of the shape of a single particle cannot reflect the influence of the overall shape on the performance of the concrete, so the method has significance on the measurement of the shape of the machine-made sand particle on a statistical level, and the sensitivity study of the measurement result of the shape of the machine-made sand particle on the number of particles is carried out, and the result is shown in FIG. 6; as can be seen from fig. 6, when the shape of the machine-made sand particle is characterized, the measurement result is affected by the number of collected samples, so that a large sample measurement is required, the particle shape index of the machine-made sand particle is statistically analyzed, if the number of samples is too small, the overall shape information of the reaction-made sand cannot be obtained, and if the number of samples is too large, the workload is increased, which causes waste of manpower and resources.
The technical means disclosed in the invention scheme are not limited to the technical means disclosed in the above embodiments, but also include the technical scheme formed by any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and such improvements and modifications are also considered to be within the scope of the present invention.
Claims (5)
1. A machine-made sand particle shape measuring method based on an image processing technology is characterized in that: the method specifically comprises the following steps of,
(1) sampling: uniformly sampling from the material pile;
(2) preparing a sample: drying the sample until the weight is constant, then screening the sample, and respectively collecting machine-made sand particles with the particle size ranges of 1.18-2.36mm and 2.36-4.75 mm; washing the collected machine-made sand particles with water to remove fine powder adsorbed on the surfaces of the machine-made sand particles, and finally drying the washed sample to finish sample preparation to be measured;
(3) image acquisition: arranging machine-made sand particles on an LED lamp panel in a straight line, and shooting and collecting a particle front view and a particle top view by using a digital camera backlight method;
(4) image processing: and processing the acquired image by using Matlab software, and calculating to obtain size information including the projection area and the projection perimeter of the particle surface and the length, width and height of the particle.
2. The method for measuring the shape of the machined sand particles based on the image processing technology as claimed in claim 1, wherein: firstly, before sampling, the surface of a sampling part is firstly removed, and then 8 parts of machine-made sand with approximately equal quantity are randomly extracted from different parts to form a group of samples.
3. The method for measuring the shape of the machined sand particles based on the image processing technology as claimed in claim 1, wherein: the fourth step; image preprocessing: the method comprises the steps of processing image extraction information by a computer, directly calling a graythresh function in a Matlab function library to calculate a gray value of an acquired image, calling an im2bw function to segment the image to enable the gray value of target particles to be 0 and the background gray value to be 1, calling a medfilt2 function to perform median filtering on the image to remove noise points in the image, calling a bwearopen function to eliminate non-target objects in the image, and calling an imfil function to eliminate bright points possibly generated due to optical reflection in a target object region to enable the target region to be a complete connected body.
4. The method for measuring the shape of the machine-made sand particles based on the image processing technology as claimed in claim 1 or 3, wherein: the particle shape description indexes of the particle circularity R, the aspect ratio E, the aspect ratio F and the sphericity S are defined, and the calculation formula is as follows:
wherein R represents the circularity of the particle, and A represents the projected area of the particle;
wherein E represents the aspect ratio of the particles, length represents the length of the particles, and width represents the width of the particles;
d1＝xmax-xmin
in top view, d1Is the projected length of the particle in the horizontal direction, and the maximum coordinate value x of the particle projected in the horizontal directionmaxThe minimum coordinate value is xmin
Wherein F represents the aspect ratio of the particles, width represents the width of the particles, and thickness represents the height of the particles;
h＝ymax-ymin
in the front view, h is the projection length of the particle in the vertical direction, and the maximum coordinate value y of the projection of the particle in the vertical directionmaxThe minimum coordinate value is ymin
d2＝xmax-xmin
In the front view, d2The maximum coordinate value x of the projection of the particle in the horizontal direction is the projection length of the particle in the horizontal directionmaxThe minimum coordinate value is xmin；
In the equation, RST is a scaling factor for planning the main view length into the main view, and "thickness" is RST × h
thickness' is the nominal height of the particle in the top view length scale;
s represents sphericity.
5. A machine-made sand particle shape measurement method based on an image processing technology is characterized in that: the transposing device comprises a digital camera (1), a digital camera (2), an LED lamp panel (3), an LED lamp panel (4) and a bracket (5), wherein the LED lamp panel (3) is vertically connected with the LED lamp panel (4); LED lamp plate (3) level is placed, and LED lamp plate (4) are vertical to be placed, LED lamp plate (3) and the edge of LED lamp plate (4) meet the department and use the screw fixation mutually, digital camera (1) is fixed on support (5) upper portion, digital camera (1) perpendicular to horizontal LED lamp plate (3), digital camera (1) is apart from LED lamp plate (3)30cm, digital camera (2) are fixed in support (5) lower part, vertical LED lamp plate (4) of digital camera (2) perpendicular to, digital camera (2) are apart from LED lamp plate (4)30 cm.
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