CN108280290B - Concrete aggregate numerical model reconstruction method - Google Patents

Concrete aggregate numerical model reconstruction method Download PDF

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CN108280290B
CN108280290B CN201810059964.1A CN201810059964A CN108280290B CN 108280290 B CN108280290 B CN 108280290B CN 201810059964 A CN201810059964 A CN 201810059964A CN 108280290 B CN108280290 B CN 108280290B
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aggregate
images
continuous
image
test piece
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CN108280290A (en
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范宏
赵铁军
张鹏
万小梅
刘树明
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青岛理工大学
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    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00Computer-aided design [CAD]
    • G06F30/20Design optimisation, verification or simulation
    • G06F30/23Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00Computer-aided design [CAD]
    • G06F30/20Design optimisation, verification or simulation

Abstract

The invention belongs to the technical field of concrete numerical simulation research, and relates to a method for reconstructing a concrete aggregate numerical model, polishing and photographing a test piece containing monomer aggregate or a test piece containing group aggregate to obtain a continuous section image of aggregate, establishing an aggregate model based on the continuous section image, an aggregate model database is established according to aggregate models, a plurality of aggregate models can be established simultaneously by containing aggregate test pieces, the problem that CT scanning equipment is expensive and inconvenient to implement can be solved, and three-dimensional reconstruction is carried out based on real concrete aggregate particles, the appearance characteristics of the real aggregate are simulated to the maximum extent, the established aggregate model is stored in a grid form, creating conditions for establishing a real aggregate model database, and exchanging formats with CAD software or FEA finite element simulation software, so as to facilitate numerical simulation research on the mechanical properties of concrete; the image acquisition mode is simple and quick, and the acquired image sequence has small interlayer spacing, high alignment degree and complete information quantity.

Description

Concrete aggregate numerical model reconstruction method

The technical field is as follows:

the invention belongs to the technical field of concrete numerical simulation research, and relates to a concrete aggregate numerical model reconstruction method which can quickly and accurately acquire multi-phase material small-space continuous section images.

Background art:

concrete (concrete for short) is a general term for engineering composite materials formed by cementing aggregate into a whole by cementing materials, and generally, concrete is composed of coarse aggregate, fine aggregate, cement hydrate, unhydrated cement particles, pores, cracks and the like; the cement concrete, also called as common concrete, is obtained by mixing with water (which may contain additives and admixtures) according to a certain proportion and stirring, and is widely applied to civil engineering. At present, the research on concrete is only limited to a macroscopic level, along with the continuous development of computer technology, the research on the aspect of concrete mesomechanics is increasingly emphasized by people, the damage forms of aggregate, mortar and an interface layer between the aggregate and the mortar in the concrete can be researched after the concrete is subjected to numerical simulation, a finite element geometric model of a concrete material mesostructure is established on the premise of adopting numerical method analysis, and the performance of the concrete has a great relation with the shape, the gradation and the like of the aggregate, so the generation of the concrete aggregate model shape becomes an important subject for the concrete numerical simulation.

The mesoscopic numerical simulation can replace part of experiments under the conditions that a theoretical model is reasonable and the characteristic data of each phase of concrete material are accurate enough, can avoid the objective limit of experimental conditions and the influence of human factors on the result, adopts a plurality of assumptions for the establishment of the concrete mesoscopic model, and has certain errors: for example, the key problem of concrete numerical simulation is the simulation of the shape of concrete aggregate, in the past research, for two-dimensional concrete aggregate, circular or elliptical simulated pebble or gravel aggregate is mostly used, broken stone aggregate is simulated by convex polygon, pebble or gravel aggregate is simulated by spherical or elliptical shape in most three dimensions, and broken stone aggregate is simulated by convex polygon; the simplified modes are feasible on the method, but the morphological characteristics of real concrete aggregate particles cannot be accurately expressed, although the two-dimensional simulation is simple and convenient to calculate, the defects of the two-dimensional simulation are obvious, the spatial distribution and grading characteristics of the concrete aggregate cannot be really restored, and the damage characteristics of the concrete cannot be expressed; in the three-dimensional simulation, the random placement of the spherical, the ellipsoidal and the convex polyhedrons can simulate the spatial distribution form of concrete aggregate, can not completely replace the shape of real aggregate, and has defects in the research aspect of aggregate and mortar interface layers. In order to obtain a more realistic concrete structure and failure characteristics, it is necessary to simulate real concrete aggregates in a more efficient way.

The scanning of the concrete section slices is realized by utilizing an industrial CT scanning technology, then the reconstruction of the concrete model is carried out by using three-dimensional reconstruction software, a concrete numerical model based on a real shape is obtained, and then the analysis is carried out on the basis of the numerical model, so that a better effect can be obtained. However, the application of the CT scanning technology in the concrete field also has disadvantages, when the resolution of the CT scanning image is improved, the density resolution is reduced, which results in insufficient information content, and meanwhile, because the CT scanning technology is greatly influenced by the scanning equipment, noise and artifact interference are easily generated, which causes the reconstructed model to be inaccurate, and the CT scanning equipment is expensive, which is not beneficial to the wide application of the CT scanning technology in the concrete field, the CT scanning technology has certain limitations for the real concrete mesoscopic structure three-dimensional reconstruction.

Chinese patent 201510801544.2 discloses a concrete aggregate structural feature pickup method based on a section shaping method, which is characterized in that an oil sludge module is made of a concrete material for three-dimensional reconstruction, the made oil sludge module is cut and scanned, an obtained scanned image of the oil sludge module is subjected to image processing, a three-dimensional space model of a concrete particle structure is reconstructed, and finally the obtained three-dimensional space model of the concrete particle structure is randomly distributed in direction and position to realize the pickup of the concrete aggregate structural feature; the method for three-dimensional reconstruction of a concrete CT image disclosed in Chinese patent 201210015951.7 includes firstly carrying out tomography scanning on a concrete sample by using a CT machine, secondly carrying out three-dimensional reconstruction on a concrete C T image by using a ray projection algorithm to obtain real images of aggregates, mortar and holes, and finally carrying out three-dimensional reconstruction on the concrete CT image by using a visualization tool VTK.

Based on the reasons, a more accurate and convenient concrete aggregate numerical model reconstruction method is needed to be found, an aggregate model database based on the real concrete aggregate shape is further established by using the numerical model, and aggregates are conveniently and quickly extracted from the model database and randomly put in the model database in the numerical simulation research of concrete.

The invention content is as follows:

the invention aims to overcome the defects in the prior art, develops and designs a method for carrying out model reconstruction on the basis of continuous sectional images obtained by polishing real concrete aggregate layer by layer, and further generates an aggregate model database by utilizing an aggregate model established by the method. To increase the effectiveness of the numerical simulation of the concrete.

In order to achieve the aim, the concrete aggregate numerical model reconstruction method comprises six steps of manufacturing a polishing test piece containing target aggregate, obtaining an aggregate continuous section image, calibrating and preprocessing the continuous section image, generating an aggregate model, calculating aggregate model parameters, performing format conversion and establishing an aggregate model database:

preparing a grinding test piece containing a target aggregate: manufacturing a test piece containing a monomer aggregate or a test piece containing a group aggregate according to the requirements established by the aggregate model database; the manufacturing process of the single aggregate-containing test piece is to wrap a single aggregate in a cementing material to manufacture a polishing test piece, the cementing material is a quick-hardening material convenient for polishing, the quick-hardening material comprises cement mortar and building gypsum, and the single aggregate-containing test piece is convenient for the convenient extraction of the aggregate and the reconstruction of a three-dimensional model; the manufacturing process of the test piece containing the group aggregate is the same as that of the common concrete test piece, and the aggregates containing the group aggregate test piece are adhered and need to be segmented and extracted;

(II) acquiring an aggregate continuous section image: fix the aggregate test piece of polishing on grinding equipment, the bistrique is polished the test piece and is carried out the successive layer dry grinding to the aggregate with the same interval of polishing along the Z axle direction of aggregate test piece of polishing, and the interval of polishing of section is controlled through the feed of bistrique, and the minimum interval of polishing is 0.01mm, and every layer of section is polished and is accomplished the back, uses digital camera to shoot the section, acquires aggregate continuous section image:

(III) calibrating and preprocessing continuous section images: the method comprises the steps of calibrating aggregate continuous section images by adopting a three-anchor point alignment method, wherein when an aggregate grinding test piece is ground in a layered mode, the photographed section images of each layer cannot be registered among layers, because the images are influenced by various factors such as the angle, the distance and the direction of a camera, the movement of the position of an object and other factors when being photographed, the images need to be registered, three control points close to a multiphase material test piece on a test piece clamping mechanism are selected as reference points, the three reference points are not on the same straight line, when the continuous section images are imaged, each section image comprises the three reference points, one standard image is selected as a reference image, the rest section images are to-be-registered images, the standard images are images with the angles, the distances, the directions and the position of the object in the continuous section images meeting the set requirements, and the image registration is a process of seeking one-to-one mapping between the to-be-registered images and the standard images, linking points corresponding to the same spatial position in two images, superposing three control points in an image to be registered with three reference points in a reference image, calculating a spatial mapping relation according to the positions of the control points, carrying out geometric transformation on the image to be registered by using the spatial mapping relation, and carrying out Z-axis direction registration on a continuous section image by using a cpselect function interactive tool in an MATLAB (matrix laboratory) to obtain a registration result; the method comprises the steps of shooting anchor points which do not belong to section images of the porous concrete sample, uniformly cutting the registered continuous section images by utilizing Photoshop (image processing software) and image processing (image analysis software), cutting useless areas including the anchor points around the continuous section images, reserving the continuous section images of the concrete sample polishing area to be analyzed, carrying out gray-scale processing on the cut continuous section images and converting the cut continuous section images into binary images, wherein the white area is aggregate, the black area is gel material, and completing calibration and pretreatment of the continuous section images;

based on the fact that the continuous section images are panoramic images, the imaging equipment parameters for shooting and storing the images are different, and the relative positions and angles of the imaging equipment and the sections of the porous concrete sample are different, so that position deviation exists among the section images of each layer, and the obtained continuous section images need to be subjected to standardization processing to meet the requirements of experimental analysis;

(IV) generating an aggregate model:

(1) in order to ensure that the proportion of image pixels (pixels) to the real aggregate size is consistent, conversion calculation of the image pixels and the real aggregate size is carried out on a continuous sectional image, the scanning resolution of an X axis, a Y axis and a Z axis is input in the process of importing a Mimics (medical image control system) three-dimensional reconstruction software into the continuous sectional image, point coordinates (X ', Y') on the image correspond to corresponding point coordinates (X, Y) on a real slice, the scanning resolution of the X axis and the Y axis is the image real size corresponding to each pixel, and the scanning resolution of the Z axis is the interlayer spacing d of the continuous sectional image;

(2) threshold segmentation, wherein white aggregate areas are extracted to generate aggregate masks, white areas are directly extracted from single aggregate samples, a group of aggregate samples need to judge whether the white areas in different two-dimensional images are from the same aggregate or not, the judgment process is realized through software programming, the centroid distance of any amount of aggregates is compared with the maximum radius of the two aggregates, the centroid distance of the two aggregates is smaller than the radius of any one aggregate to judge that the two aggregates are from the same aggregate, the white areas of the same aggregate are extracted by adopting a method of combining gray value range definition and manual drawing and are stored as the same mask, and the masks of the adhered parts of the different aggregates in the continuous sectional images are manually trimmed and segmented through mask editing operation;

(3) 3D computing the aggregate mask extracted from the single aggregate test piece in the step (2) to generate an initial aggregate surface grid data model, respectively performing 3D computing on different aggregate masks extracted from aggregate test pieces of a group, and simultaneously generating a plurality of initial aggregate surface grid data models, wherein the generated aggregate surface grid data model is a coarse primary model due to the influence of the interlayer spacing of the continuous section images of the aggregate test pieces on the Z-axis resolution;

(4) carrying out fairing, meshing and wrapping treatment on the primary aggregate surface mesh data model generated in the step (3) to obtain an accurate aggregate surface mesh data model, and filling the accurate aggregate surface mesh data model to obtain a real aggregate-based volume mesh data model;

the principle of three-dimensional reconstruction software of the Mimics (medical image control system) for reversely reconstructing the aggregate particle model is as follows: on the basis of three-dimensional information of an unknown object contained in the continuous section images, a digital three-dimensional model of the object outline is reconstructed in a computer, wherein coordinate values (X, Y) of a point P on the unknown object outline on an X axis and a Y axis are determined by the position on a horizontal section of the unknown object outline, and the coordinate value (Z) of the point P on a Z axis is determined by the relation between the cutting distance (d) and the section sequence (n): z is determined as d × n;

and (V) calculating aggregate model parameters and carrying out format conversion: the geometric parameters directly extracted from the aggregate grid data model reconstructed by the Mimics software comprise model volume, surface area, long-axis distance and short-axis distance in the X-axis direction, the Y-axis direction and the Z-axis direction and mass barycentric coordinates determined based on a model coordinate frame, the aggregate model indirect shape parameters including aggregate shape factor, roundness, needle degree and flatness can be calculated through the directly extracted geometric parameters, further, the aggregate grid data model can be converted into a format which is convenient for storing an aggregate model database and is dxf, stl, inp and igs through corresponding interfaces of various application design software provided by the Mimics software, and the aggregate model format is convenient for putting and researching;

and (VI) establishing an aggregate model database: and (5) establishing aggregate grid data models with different sizes and types by utilizing the steps from (I) to (V), carrying out aggregate model parameter statistics and classification integration on the aggregate grid data models with different sizes and types, establishing an aggregate model database, and selecting and putting aggregates in subsequent numerical simulation research.

The interlayer spacing of the aggregate continuous section image related to the step (one) influences the resolution of the aggregate model reconstruction result in the Z-axis direction, and the smaller the interlayer spacing of the aggregate continuous section image is, the more accurate the fitting effect of the external form of the real concrete aggregate model is; the aggregate continuous section image obtained in the step (one) has high resolution and complete contained information, a multiphase and multi-scale numerical model can be reconstructed, different levels of research are facilitated, and the three-dimensional reconstruction of the concrete microstructure based on the aggregate continuous section image is endowed with great flexibility; the aggregate model database established in the step (six) has the characteristics of high degree of reality and convenient and quick aggregate selection, and provides a solid foundation for numerical simulation research of concrete aggregates.

Compared with the prior art, the method has the advantages that the test pieces containing the monomer aggregate or the group aggregate are polished and photographed to obtain the continuous section images of the aggregate, the aggregate model is built based on the continuous section images, the aggregate model database is built according to the aggregate model, a plurality of aggregate models can be built simultaneously for the test pieces containing the group aggregate, the problem that the CT scanning equipment is expensive and inconvenient to implement can be solved, the three-dimensional reconstruction is carried out based on real concrete aggregate particles, the appearance characteristics of the real aggregate are simulated to the maximum extent, the built aggregate model is stored in a grid form, conditions are created for building the real aggregate model database, the format exchange can be carried out with CAD software or FEA finite element simulation software, and the numerical simulation research on the mechanical property of the concrete is facilitated; the method has the advantages of simple and quick image acquisition mode, low image acquisition cost, small interlayer spacing of the acquired image sequence, high alignment degree and complete information quantity, and the established aggregate model database has the characteristics of reality and reliability and is convenient to apply and popularize.

Description of the drawings:

FIG. 1 is a block diagram of the process flow of the present invention.

Fig. 2 is a sectional image before binarization according to step (iii) of embodiment 1 of the present invention.

Fig. 3 is a binarized sectional image obtained in step (iii) of example 1 of the present invention.

FIG. 4 is a diagram showing an aggregate primary structure model according to step (IV) in example 1 of the present invention.

FIG. 5 is a schematic diagram of an aggregate surface mesh pattern according to step (IV) in example 1 of the present invention.

Fig. 6 is a model diagram of an aggregate mesh according to step (iv) in example 1 of the present invention.

FIG. 7 is a model diagram of a transformed CAD aggregate according to step (V) of example 1 of the present invention.

FIG. 8 is a schematic representation of an aggregate having a shape described as biased toward a flat type according to example 2 of the present invention.

FIG. 9 is a schematic representation of an aggregate having a shape described as somewhat flattened according to example 2 of the present invention.

FIG. 10 is a schematic representation of an aggregate having a shape described as a somewhat needle-like shape according to example 2 of the present invention.

FIG. 11 is a schematic representation of an aggregate having a shape described as biased toward acicular according to example 2 of the present invention.

The specific implementation mode is as follows:

the invention is further illustrated by the following examples in conjunction with the accompanying drawings.

Example 1:

the concrete aggregate numerical model reconstruction method related to the embodiment comprises five steps of manufacturing a grinding test piece containing target aggregate, obtaining an aggregate continuous section image, calibrating and preprocessing the continuous section image, generating an aggregate model, calculating parameters of the aggregate model and carrying out format conversion:

preparing a grinding test piece containing a target aggregate: casting a cubic concrete test block of 100mm multiplied by 100mm in situ, and placing the cubic concrete test block in a standard curing room for curing for 7 days to obtain a concrete test piece containing group aggregate;

(II) acquiring an aggregate continuous section image: fix the aggregate test piece of polishing on grinding equipment, the bistrique is polished the test piece and is carried out the successive layer dry grinding with the interval of polishing of 1mm to the aggregate along the Z axle direction of aggregate test piece of polishing, and the interval of polishing of section is controlled through the feeding of bistrique, and every layer section is polished and is accomplished the back, uses digital camera to shoot the section, acquires the interval and is the aggregate continuous section image of 1 mm:

(III) calibrating and preprocessing continuous section images: the method comprises the steps of calibrating aggregate continuous section images by adopting a three-anchor point alignment method, wherein when an aggregate grinding test piece is ground in a layered mode, the photographed section images of each layer cannot be registered among layers, because the images are influenced by various factors such as the angle, the distance and the direction of a camera, the movement of the position of an object and other factors when being photographed, the images need to be registered, three control points close to a multiphase material test piece on a test piece clamping mechanism are selected as reference points, the three reference points are not on the same straight line, when the continuous section images are imaged, each section image comprises the three reference points, one standard image is selected as a reference image, the rest section images are to-be-registered images, the standard images are images with the angles, the distances, the directions and the position of the object in the continuous section images meeting the set requirements, and the image registration is a process of seeking one-to-one mapping between the to-be-registered images and the standard images, linking points corresponding to the same spatial position in two images, superposing three control points in an image to be registered with three reference points in a reference image, calculating a spatial mapping relation according to the positions of the control points, carrying out geometric transformation on the image to be registered by using the spatial mapping relation, and carrying out Z-axis direction registration on a continuous section image by using a cpselect function interactive tool in an MATLAB (matrix laboratory) to obtain a registration result; the method comprises the steps of shooting anchor points which do not belong to section images of the porous concrete sample, uniformly cutting the registered continuous section images by utilizing Photoshop (image processing software) and image processing (image analysis software), cutting useless areas including the anchor points around the continuous section images, reserving the continuous section images of the concrete sample polishing area to be analyzed, carrying out gray-scale processing on the cut continuous section images and converting the cut continuous section images into binary images, wherein the white area is aggregate, the black area is gel material, and completing calibration and pretreatment of the continuous section images;

(IV) generating an aggregate model:

(1) in order to ensure that the proportion of image pixels (pixels) to the real aggregate size is consistent, conversion calculation of the sizes of the image pixels and the real aggregate is carried out on continuous sectional images, the scanning resolutions of an X axis, a Y axis and a Z axis are input in the process of importing the continuous sectional images into Mimics (medical image control system) three-dimensional reconstruction software, point coordinates (X ', Y') on the images correspond to corresponding point coordinates (X, Y) on real slices, and the calculation formula is used for calculating the ratio of the image pixels (pixels) to the real aggregate size according to the scanning resolutions of the X axis, the YAndcalculating to obtain x being 0.25mm and y being 0.25mm, wherein the calculation result represents the image size contained in each pixel of the image, the scanning resolution of the x axis and the y axis is 0.25mm, and the scanning resolution of the z axis is the interval of 1mm of the section images;

(2) threshold segmentation, wherein white aggregate areas are extracted to generate aggregate masks, white areas are directly extracted from single aggregate samples, a group of aggregate samples need to judge whether the white areas in different two-dimensional images are from the same aggregate or not, the judgment process is realized through software programming, the centroid distance of any amount of aggregates is compared with the maximum radius of the two aggregates, the centroid distance of the two aggregates is smaller than the radius of any one aggregate to judge that the two aggregates are from the same aggregate, the white areas of the same aggregate are extracted by adopting a method of combining gray value range definition and manual drawing and are stored as the same mask, and the masks of the adhered parts of the different aggregates in the continuous sectional images are manually trimmed and segmented through mask editing operation;

(3) respectively carrying out 3D calculation on different masks, fitting the aggregate region boundaries under the same mask into a matrix type primary three-dimensional data model, and taking the primary three-dimensional data model generated by fitting as an initial aggregate surface grid data model;

(4) carrying out fairing, meshing and wrapping treatment on the primary aggregate surface mesh data model generated in the step (3) to obtain an accurate aggregate surface mesh data model, and filling the accurate aggregate surface mesh data model to obtain a real aggregate-based volume mesh data model;

and (V) calculating aggregate model parameters and carrying out format conversion: the aggregate grid data model is converted into a dxf format under CAD through a CAD computer aided drawing software interface provided by the Mimics software so as to be convenient for application of an aggregate model database, or the aggregate grid data model is converted into a format required by finite element analysis through an FEA finite element analysis software interface provided by the Mimics software so as to analyze the mechanical property of the aggregate.

Example 2:

in this embodiment, the aggregate model constructed in example 1 is subjected to extraction of geometric parameters of short axial distance, long axial distance, volume, surface area and mass barycentric coordinates determined based on a model coordinate frame, such as those in X-axis direction, Y-axis direction and Z-axis direction, and the results are shown in table 1 (mm):

indirect shape parameters of aggregate shape factor, roundness, conicity and flatness were calculated from the extracted geometric parameters, and the results are shown in table 2:

description of shape Deflection flat type Slightly flat class Slightly acicular class Biased acicular species Form factor -0.70 0.70-1.00 1.00-1.40 1.40- Roundness degree -0.88 0.88-1.00 1.00-1.12 1.12- Degree of penetration 1.43-2.09 1.24-1.91 1.60-2.30 1.80-2.57 Flatness of 0.13-0.45 0.36-0.58 0.45-0.98 0.45-0.88

Integrating, classifying and judging the shape characteristics of the aggregate by the indirect shape parameters; classifying and integrating the aggregate model parameters in the table 1 and the table 2, and establishing a real concrete aggregate model database by the method for randomly putting concrete aggregates and establishing a concrete numerical model, thereby providing beneficial help for numerical simulation research of concrete.

Claims (1)

1. A concrete aggregate numerical model reconstruction method is characterized in that the concrete technological process comprises six steps of manufacturing a polishing test piece containing target aggregate, obtaining aggregate continuous section images, calibrating and preprocessing the continuous section images, generating an aggregate model, calculating aggregate model parameters, carrying out format conversion and establishing an aggregate model database:
preparing a grinding test piece containing a target aggregate: manufacturing a test piece containing a monomer aggregate or a test piece containing a group aggregate according to the requirements established by the aggregate model database; the manufacturing process of the single aggregate-containing test piece is to wrap a single aggregate in a cementing material to manufacture a polishing test piece, the cementing material is a quick-hardening material convenient for polishing, the quick-hardening material comprises cement mortar and building gypsum, and the single aggregate-containing test piece is convenient for the convenient extraction of the aggregate and the reconstruction of a three-dimensional model; the manufacturing process of the test piece containing the group aggregate is the same as that of the common concrete test piece, and the aggregates containing the group aggregate test piece are adhered and need to be segmented and extracted;
(II) acquiring an aggregate continuous section image: fix the aggregate test piece of polishing on grinding equipment, the bistrique is polished the test piece and is carried out the successive layer dry grinding to the aggregate with the same interval of polishing along the Z axle direction of aggregate test piece of polishing, and the interval of polishing of section is controlled through the feed of bistrique, and the minimum interval of polishing is 0.01mm, and every layer of section is polished and is accomplished the back, uses digital camera to shoot the section, acquires aggregate continuous section image:
(III) calibrating and preprocessing continuous section images: the method comprises the steps of calibrating aggregate continuous section images by adopting a three-anchor point alignment method, wherein when an aggregate grinding test piece is ground in a layered mode, the photographed section images of each layer cannot be registered between layers, the images have errors due to the influence of various factors when the images are photographed, the images need to be registered, three control points close to a multiphase material test piece on a test piece clamping mechanism are selected as reference points, the three reference points are not on the same straight line, when the continuous section images are imaged, each section image comprises the three reference points, one standard image is selected as a reference image, the rest section images are images to be registered, the standard images are images with the angles, distances, directions and object positions in the continuous section images meeting the set requirements, the image registration is a process of seeking one-to-one mapping between the images to be registered and the standard images, and is a point corresponding to the same position in space in the two images is connected, three control points in the image to be registered and three reference points in the reference image are coincided, a spatial mapping relation is calculated according to the positions of the control points, geometric transformation is carried out on the image to be registered by using the spatial mapping relation, and in MATLAB, a cpselect function interactive tool is used for carrying out Z-axis direction registration on the continuous section image to obtain a registration result; the method comprises the steps of shooting anchor points which do not belong to section images of the porous concrete sample, uniformly cutting the registered continuous section images by utilizing Photoshop and image plus, cutting useless areas including the anchor points around the continuous section images, reserving the continuous section images of the concrete sample polishing area to be analyzed, carrying out gray-scale processing on the cut continuous section images and converting the cut continuous section images into binary images, wherein the white area is aggregate, the black area is gel material, and completing calibration and pretreatment of the continuous section images;
(IV) generating an aggregate model:
(1) in order to ensure that the proportion of image pixels to the real aggregate dimension is consistent, conversion calculation of the image pixels to the real aggregate dimension is carried out on a continuous sectional image, scanning resolutions of an X axis, a Y axis and a Z axis are input in the process of importing the continuous sectional image into Mimics three-dimensional reconstruction software, point coordinates (X ', Y') on the image correspond to corresponding point coordinates (X, Y) on a real slice, the scanning resolutions of the X axis and the Y axis are the image real dimension corresponding to each pixel, and the scanning resolution of the Z axis is the interlayer spacing d of the continuous sectional image;
(2) threshold segmentation, wherein white aggregate areas are extracted to generate aggregate masks, white areas are directly extracted from single aggregate samples, a group of aggregate samples need to judge whether the white areas in different two-dimensional images are from the same aggregate or not, the judgment process is realized through software programming, the centroid distance of any amount of aggregates is compared with the maximum radius of the two aggregates, the centroid distance of the two aggregates is smaller than the radius of any one aggregate to judge that the two aggregates are from the same aggregate, the white areas of the same aggregate are extracted by adopting a method of combining gray value range definition and manual drawing and are stored as the same mask, and the masks of the adhered parts of the different aggregates in the continuous sectional images are manually trimmed and segmented through mask editing operation;
(3) 3D computing the aggregate mask extracted from the single aggregate test piece in the step (2) to generate an initial aggregate surface grid data model, respectively performing 3D computing on different aggregate masks extracted from aggregate test pieces of a group, and simultaneously generating a plurality of initial aggregate surface grid data models, wherein the generated aggregate surface grid data model is a coarse primary model due to the influence of the interlayer spacing of the continuous section images of the aggregate test pieces on the Z-axis resolution;
(4) carrying out fairing, meshing and wrapping treatment on the primary aggregate surface mesh data model generated in the step (3) to obtain an accurate aggregate surface mesh data model, and filling the accurate aggregate surface mesh data model to obtain a real aggregate-based volume mesh data model;
and (V) calculating aggregate model parameters and carrying out format conversion: the geometric parameters directly extracted from the aggregate grid data model reconstructed by the Mimics software comprise model volume, surface area, long-axis distance and short-axis distance in the X-axis direction, the Y-axis direction and the Z-axis direction and mass barycentric coordinates determined based on a model coordinate frame, the aggregate model indirect shape parameters including aggregate shape factor, roundness, needle degree and flatness can be calculated through the directly extracted geometric parameters, further, the aggregate grid data model can be converted into a format which is convenient for storing an aggregate model database and is dxf, stl, inp and igs through corresponding interfaces of various application design software provided by the Mimics software, and the aggregate model format is convenient for putting and researching;
and (VI) establishing an aggregate model database: and (5) establishing aggregate grid data models with different sizes and types by utilizing the steps from (I) to (V), carrying out aggregate model parameter statistics and classification integration on the aggregate grid data models with different sizes and types, establishing an aggregate model database, and selecting and putting aggregates in subsequent numerical simulation research.
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