CN108931562B - Nondestructive testing method for dielectric constant of large-size uneven mixture - Google Patents
Nondestructive testing method for dielectric constant of large-size uneven mixture Download PDFInfo
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Abstract
The invention discloses a nondestructive testing method for the dielectric constant of a large-size uneven mixture. Preparing a large-size uneven cuboid mixture; measuring the length, width and height, and recording data; dividing two surfaces with the largest area by using a grid of 60mm multiplied by 60mm, and drawing a grid by using a marker pen; measuring by using a dielectric constant instrument Percometer; averaging the dielectric constant values of each grid; establishing a 30 multiplied by 5 three-dimensional grid model by simulating a track plate in MATLAB, and introducing dielectric constant values obtained by measuring the upper surface and the lower surface into the model; and fitting the dielectric constant values of the middle three layers of the three-dimensional grid model by using a linear equation to obtain 4500 dielectric constant values of each position of the mixture, and finally obtaining the overall dielectric constant value of the mixture by using a calculation method of average value statistics.
Description
Technical Field
The invention belongs to the field of road engineering, and relates to a nondestructive testing method for the dielectric constant of a large-size uneven mixture.
Background
With the passing of the highway construction peak period in China, a large number of roads need to be maintained. Most of the expressway and the common expressway at present usually adopt asphalt pavement as the main pavement form, the quality detection of the road generally adopts a core drilling sampling method, a large amount of manpower and material resources are consumed, the road is damaged, in addition, the problems of low detection efficiency, incomplete detection and the like always trouble the road maintenance workers at present. Therefore, the ground penetrating radar detection method which is started in recent years has wide acceptance on the road surface detection potential due to the advantages of high efficiency, comprehensiveness and no damage.
As is known, the detection principle of ground penetrating radar depends on the difference in dielectric properties of the pavement materials, and only basic information such as pavement thickness can be read from the appearance of reflected waves, and further research on the dielectric properties of the pavement is needed to detect indexes such as compactness, water content, asphalt content and the like of the pavement, so that it is important to accurately measure the dielectric constant of the pavement. The current methods for measuring the dielectric constant of a dielectric material are various, including a resonance method, a transmission reflection method, a time domain measurement method, a free space method and the like, wherein the resonance method and the classical transmission reflection method both need to prepare a special mold and a sample, or carry out core drilling and cutting on a sample to obtain a required size, and both belong to destructive measurement. The time domain measurement method is mainly used for measuring ultrathin materials due to the fact that the measurement point is single, the test result can only represent the dielectric constant of a uniform medium in a certain extremely small range, and the time domain measurement method does not have the function of measuring the dielectric constant of a large-size heterogeneous mixture. In summary, most of the existing dielectric constant measurement methods belong to destructive measurement or measurement aiming at small-size uniform media, and cannot well meet the actual road engineering, while nondestructive measurement aiming at the dielectric constant of large-size non-uniform mixture is beneficial to improving the detection precision of ground penetrating radar and is more fit with the actual road, but the conventional method is difficult to measure the dielectric constant of the mixture due to the large size and the non-uniformity of the mixture.
Therefore, a nondestructive measurement method capable of ensuring the sample under the conditions of large-size, non-uniform medium and incomplete contact measurement is urgently needed at present, and the overall dielectric property of a large-size mixture can be completely measured, so that the paving uniformity of an actual engineering road and the dielectric property of a composite material of an asphalt pavement mixture can be better reflected, and the detection precision and the engineering application range of the ground penetrating radar are improved.
Disclosure of Invention
The invention aims to provide a test method for detecting the dielectric constant of a large-size uneven mixture, which can completely measure the overall dielectric constant of the large-size mixture, thereby reflecting the paving uniformity of an actual engineering road and the dielectric characteristic of a composite material of an asphalt pavement mixture and providing a theoretical basis for the accuracy of ground penetrating radar for detecting the road quality and various road engineering indexes.
In order to achieve the purpose, the technical scheme is as follows:
a method for detecting the dielectric constant of a large-size inhomogeneous mixture comprises the following steps:
1) preparing a large-size uneven cuboid mixture; measuring the length, width and height, and recording data;
2) dividing two surfaces with the largest area by using a grid of 60mm multiplied by 60mm, and drawing a grid by using a marker pen;
3) measuring by using a Percometer (PM for short) dielectric constant instrument, and selecting a proper probe and a probe mode; measuring air (namely calibrating PM), and preheating PM for 1-2 minutes after calibration is finished;
4) four times of measurement with the rotation angle of 90 degrees are carried out on each grid, the dielectric constant value and the measurement temperature are recorded, and the dielectric constant value of each grid is averaged;
5) establishing a 30 x 5 three-dimensional grid model by simulating a rut plate in MATLAB, and introducing dielectric constant values obtained by measuring the upper surface and the lower surface (two surfaces with the largest area) into the model, wherein the average dielectric constant value of each grid represents 36 numerical values of two 30 x 30 grids on the top layer and the bottom layer in the model (namely, 900 data are respectively introduced into the upper layer and the lower layer);
6) calculating in MATLAB, fitting the dielectric constant values of the middle three layers of the three-dimensional grid model by using a linear equation to obtain 4500 dielectric constant values of each position of the mixture, and finally obtaining the overall dielectric constant value of the mixture by using a calculation method of average value statistics.
According to the scheme, the length and the width of the largest surface of the mixture in the step 1 are both larger than 60 mm.
According to the scheme, the grid area in the step 2 completely covers the measurement area; if the covering is not complete, the dielectric constant of the uncovered part is determined to be the value of the dielectric constant of the nearest grid.
According to the scheme, before the measurement in the step 4, the probe is lifted and placed at a position 5-10cm above the test piece, and the index E of the PM is 1.0, so that the normal work of the PM is determined.
According to the scheme, the linear equation in the step 6 is fitted as follows:
An＝A1+(A1-A5)*(n-1)/4
in the formula, n is the number of model layers; a. thenIs the dielectric constant data of the nth layer; a. the1Dielectric constant data of the top layer of the three-dimensional grid model; a. the5Dielectric constant data underlying the three-dimensional mesh model.
The invention uses the measurable small-area dielectric constant value to carry out integral division on the large-scale mixture by a grid division method, and uses MATLAB software to analyze a fitting data result to obtain the integral dielectric constant value of the mixture, so that the dielectric constant of the large-scale non-uniform mixture can be directly measured, and the method has great progress in the rationality, the test precision and the experiment time of the test method, and specifically comprises the following steps:
(1) can realize the measurement of the dielectric constant of the large-size inhomogeneous mixture under indoor conditions
The test method adopts a free space method and uses a PM instrument as a new method for measuring the dielectric constant of the indoor mixture, can measure the overall dielectric constant of the large-size uneven mixture, and more effectively simulates the dielectric property of the composite material of the actual engineering asphalt pavement compared with the traditional single-point small-range measurement.
(2) The test course is carried out in free space to effectively accelerate the test progress and shorten the test time
The test method can be used for testing the target test body without test consumables, the whole test process is simple, the time consumed by the whole dielectric constant measurement test is extremely short, only 1 hour is needed for a track plate with the length and width of 300mm and the thickness of 50mm, and the conventional dielectric constant test system needs to cut the original test piece drill core into small test pieces meeting the measurement size, and the average time consumed is more than 1 day.
(3) The test result has high precision and strong reliability
The original method needs to drill a large test piece and cut the large test piece into a plurality of small test pieces for dielectric constant measurement, the small test pieces are too small in size, the test pieces can be abraded in the process of drilling and cutting, the test precision is low, the new method adopts a free space method to measure the dielectric constant of the indoor mixture by using PM, the original test pieces do not need to be damaged, the MATLAB is used for three-dimensionally fitting the structural size of the mixture, the overall dielectric constant of the mixture is calculated, and the precision and the reliability of the test result are improved.
Drawings
FIG. 1: a large-area grid division diagram of the asphalt mixture of the rut plate;
FIG. 2 is a drawing: MATLAB simulation diagrams.
Detailed Description
In order to clarify the method for testing the dielectric constant of the large-size heterogeneous mixture, a typical test is used as an example to further illustrate the technical solution of the present invention, but the present invention is not limited to the scope of the present invention.
Preparation of test samples of asphalt mixture
The test adopts a rut forming instrument to form a rut plate asphalt mixture, wherein the used asphalt is SBS modified asphalt provided by the innovative and high-new material stocks Co., Ltd, in the North lake, the aggregate is basalt produced by a certain stone factory in Ohio, Hubei, and the formed rut plate has the length and the width of 300mm and the thickness of 50 mm.
Gridding mixed material
Since the maximum surface of the asphalt mixture of the rut plate in the test is 300mm × 300mm, and the length and the width are integral multiples of 60mm, the rut plate is divided into 25 squares of 5 × 5, each square is 60mm × 60mm, and marked by a marker pen, and the same work is performed on the reverse surface, as shown in fig. 1.
Debugging PM
Selecting a probe SF169 with the diameter of 60mm to be connected with a PM host, opening the PM, and selecting a correct measurement mode according to the model of the probe, wherein the correct setting is shown in H169C on the upper left of a display screen; and then calibrating the PM, placing the probe in the air, displaying the E of 1.0 on a screen at the moment, namely successfully calibrating, and starting to measure after preheating for 1-2 minutes.
Start measurement
Vertically placing the probe in the drawn small square grid, enabling the edge of the probe to be tangent to the side length of the small square grid, displaying the value of E on the PM screen at the moment, and recording after data are stable; the other three 90 ° rotations were performed, four measurements were performed, and the remaining 24 squares were measured according to the same procedure, and the dielectric constant data of the front surface of the rut plate are summarized in table 1 below.
TABLE 1
The dielectric constant data for the back of the rut plate is summarized in table 2 below.
TABLE 2
Building three-dimensional models in MATLAB
Establishing a 30 multiplied by 5 three-dimensional grid model by simulating a rutting plate in the MATLAB, simulating the structural size of the rutting plate, introducing dielectric constant values of an upper grid and a lower grid into the model, and representing 36 numerical values of a 6 multiplied by 6 three-dimensional grid in the MATLAB by using the dielectric constant value of each grid in actual division, namely introducing 900 data into the upper layer and the lower layer respectively;
data processing
Calculations were performed in MATLAB to fit the dielectric constant values of the middle three layers with the following formula (1),
An＝A1+(A1-A5)*(n-1)/4
in the formula, n is the number of model layers; a. thenIs the dielectric constant data of the nth layer; a. the1Dielectric constant data for the top layer of the model; a. the5The dielectric constant data of the bottom layer of the model.
The rut plate simulation diagram shown in fig. 2, wherein dark color represents a small value of dielectric constant and light color represents a large value of dielectric constant; the color data corresponds to a bar, black corresponds to a dielectric constant value of 3.2 and white corresponds to 5.7. 4500 dielectric constant values of each position of the mixture are obtained after expansion, and finally the dielectric constant value of the whole mixture is 4.6499 by adopting a calculation method of average value statistics.
Claims (4)
1. A method for detecting the dielectric constant of a large-size inhomogeneous mixture is characterized by comprising the following steps:
1) preparing a large-size uneven cuboid mixture; measuring the length, width and height, and recording data;
2) dividing two surfaces with the largest area by using a grid of 60mm multiplied by 60mm, and drawing a grid by using a marker pen;
3) measuring by using a dielectric constant instrument Percometer, and selecting a proper probe and a probe mode; measuring air, and preheating PM for 1-2 minutes after calibration is finished;
4) four times of measurement with the rotation angle of 90 degrees are carried out on each grid, the dielectric constant value and the measurement temperature are recorded, and the dielectric constant value of each grid is averaged;
5) establishing a 30 x 5 three-dimensional grid model by simulating a rut plate in MATLAB, and introducing dielectric constant values measured from the upper surface and the lower surface into the model, wherein the average dielectric constant value of each grid represents 36 values of 6 x 6 grids on the top layer and the bottom layer of two 30 x 30 grids in the model;
6) calculating in MATLAB, fitting dielectric constant values of the middle three layers of the three-dimensional grid model by using a linear equation to obtain 4500 dielectric constant values of each position of the mixture, and finally obtaining the overall dielectric constant value of the mixture by using a calculation method of average value statistics; the linear equation fits as follows:
An＝A1+(A1-A5)*(n-1)/4
in the formula, n is the number of model layers; a. thenIs the dielectric constant data of the nth layer; a. the1Dielectric constant data of the top layer of the three-dimensional grid model; a. the5Dielectric constant data underlying the three-dimensional mesh model.
2. The method for detecting the dielectric constant of the large-size inhomogeneous mixed material according to claim 1, wherein the length and width of the largest surface of the mixed material in step 1 are both greater than 60 mm.
3. The method for detecting the dielectric constant of the large-size inhomogeneous mixed material according to claim 1, wherein step 2, the grid area completely covers the measurement area; if the covering is not complete, the dielectric constant of the uncovered part is determined to be the value of the dielectric constant of the nearest grid.
4. The method for detecting the dielectric constant of the large-size inhomogeneous mixture according to claim 1, wherein the normal operation of PM is determined by raising the probe to 5-10cm over the test specimen before the measurement in step 4, and the index E of PM is 1.0.
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| CN110927222A (en) * | 2019-11-28 | 2020-03-27 | 武汉理工大学 | Asphalt mixture quality evaluation method for quantifying temperature and frequency influence factors |
| CN111487296B (en) * | 2020-04-21 | 2022-11-01 | 郑州星驰智能科技有限公司 | Method for detecting mixing uniformity of powdery material |
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