CN113155648B - A method and system for measuring microscopic deformation of materials based on impact test - Google Patents

Abstract

The invention relates to a material microscopic deformation measuring method and system based on an impact test, wherein the method comprises the following steps: dotting the side surface of the sample to obtain a dot array surface; shooting a point array surface to obtain a first point array surface picture; shooting the point array surface of the sample after impact to obtain a second point array surface picture; processing the first lattice plane picture to obtain a first effective lattice map; calculating the first effective dot matrix graph to obtain a plurality of first dot matrix linear intervals; processing the second lattice plane picture to obtain a second effective lattice plane picture; calculating the second effective dot matrix diagram to obtain a plurality of second dot matrix straight line intervals; subtracting a second dot matrix linear distance corresponding to the first dot matrix linear distance from the first dot matrix linear distance to obtain a plurality of local deformation quantities; and accumulating the plurality of local deformation quantities to obtain a total deformation quantity. The invention replaces the existing manual measuring method of the microscopic deformation of the material, and improves the measuring precision of the local deformation.

Description

A method and system for measuring microscopic deformation of materials based on impact test

technical field

The invention relates to the technical field of material microscopic deformation measurement, in particular to a method and system for measuring material microscopic deformation based on an impact test.

Background technique

Metal or composite materials have a wide range of applications in automotive manufacturing, material handling, marine engineering and aerospace. The impact test is an experiment to study the dynamic load resistance of materials. The dynamic load and static load have different effects. Due to the fast loading speed, the stress in the material suddenly increases, and the deformation speed affects the mechanical properties of the material. Therefore, the performance of the material on the dynamic load another reaction. Materials that tend to be very ductile under static loading will exhibit brittle properties under dynamic loading. Therefore, it is of great practical significance to conduct experimental research on impact properties of metal samples.

At present, most of the existing methods for measuring the deformation of the sample section in the drop weight impact test are manual measurement of the total deformation before and after the impact by means of a helical micrometer after the impact. However, this method cannot accurately measure the local deformation of the section during the impact process, the error is large, and the local deformation of the section and the relationship between the deformation and the number of impacts cannot be obtained. At the same time, the existing method for measuring the deformation of the sample section in the drop weight impact test has higher requirements on the device for preventing the secondary impact of the test bench itself, and the cost of the test bench is also increased accordingly.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and system for measuring the microscopic deformation of a material based on an impact test, so as to solve the problem that the existing method for measuring the microscopic deformation of a material has a large error in measuring the local deformation of a section.

For achieving the above object, the present invention provides the following scheme:

A method for measuring the microscopic deformation of a material based on an impact test, comprising:

Dot the side of the sample to get the lattice surface;

photographing the dot matrix surface to obtain a picture of the first dot matrix surface;

Photograph the lattice surface of the sample after impact to obtain the second lattice surface picture;

processing the first bitmap image to obtain a first valid bitmap;

Calculating the first effective lattice map to obtain a plurality of first lattice line spacings;

processing the second bitmap image to obtain a second valid bitmap;

Calculating the second effective lattice map to obtain a plurality of second lattice line spacings;

subtracting the second lattice line spacing corresponding to the first lattice line spacing from the first lattice line spacing to obtain a plurality of local deformation variables;

A plurality of the local deformation variables are accumulated to obtain a total deformation variable.

Optionally, the side of the sample is dotted to obtain a lattice surface, which specifically includes:

Using an ultraviolet marking machine, a dot matrix with a fixed horizontal and vertical spacing is marked on the side of the sample to obtain a dot matrix surface.

Optionally, the processing of the first bitmap image to obtain a first valid bitmap specifically includes:

Perform filtering processing on the first lattice plane picture to obtain a first lattice plane filtered picture;

performing binarization processing on the first lattice surface filtered picture to obtain a first binarized picture;

Screening of the area and roundness of the first binarized picture is carried out, and the area obtained after screening is used as the first valid point;

A first valid bitmap is determined according to a plurality of the first valid points.

Optionally, the calculation of the first effective lattice map to obtain a plurality of first lattice line spacings specifically includes:

extracting the coordinates of the first valid point in the first valid bitmap;

The least squares method is used to linearly fit the coordinates of the first valid point of each row to obtain a fitted straight line of each row;

The distances between adjacent fitting lines are obtained by using the distance formula between two parallel straight lines, and the distances between a plurality of the first lattice lines are obtained.

Optionally, the screening of the area and roundness of the first binarized picture is performed, and the region obtained after screening is used as the first valid point, which specifically includes:

performing an opening operation on the first binarized picture to obtain a first smooth picture;

Extract the feature of the white area in the first smooth image, and select the area within 1500 to 3500 pixels and the circularity above 0.65 as the first valid point.

Optionally, the processing of the second bitmap image to obtain a second valid bitmap specifically includes:

performing filtering processing on the second lattice surface picture to obtain a second lattice surface filtering picture;

performing binarization processing on the second lattice surface filtered picture to obtain a second binarized picture;

Screening of the area and roundness of the second binarized picture is carried out, and the area obtained after screening is used as the second valid point;

A second valid bitmap is determined according to a plurality of the second valid points.

Optionally, the calculation of the second effective lattice map to obtain a plurality of second lattice line spacings specifically includes:

extracting the coordinates of the second valid point in the second valid bitmap;

The least squares method is used to perform linear fitting on the coordinates of the second valid point of each row to obtain a fitted straight line for each row;

Calculate the slope of the fitted straight line of each row to obtain a plurality of slopes;

averaging a plurality of said slopes to obtain an average slope;

Assign the average slope to the fitted straight line of each row, keep the intercept unchanged, and obtain the fitted straight line with the same slope;

The distances between adjacent fitted straight lines with the same slope are obtained by using the distance formula between two parallel straight lines, and the distances between a plurality of the second lattice straight lines are obtained.

Optionally, the screening of the area and roundness of the second binarized picture is performed, and the area obtained after screening is used as the second valid point, which specifically includes:

performing an opening operation on the second binarized picture to obtain a second smooth picture;

Extract the feature of the white area in the second smooth image, and select the area within 1500 to 3500 pixels and the circularity above 0.65 as the second valid point.

A material microscopic deformation measurement system based on impact test, including:

Dotting module, used to dot the side of the sample to get the dot matrix surface;

a photographing module, used for photographing the dot matrix surface to obtain a picture of the first dot matrix surface; also used for photographing the dot matrix surface of the impacted sample to obtain a second dot matrix surface picture;

The picture processing module is used for processing the first lattice surface picture to obtain a first effective lattice map, and calculating the first effective lattice map to obtain a plurality of first lattice line spacings; for processing the second lattice surface picture to obtain a second effective lattice map, and calculating the second effective lattice map to obtain a plurality of second lattice line spacings;

a local deformation variable calculation module, configured to subtract the second lattice linear spacing corresponding to the first lattice linear spacing from the first lattice linear spacing to obtain a plurality of local deformation variables;

The total shape variable calculation module is used for accumulating a plurality of the local shape variables to obtain the total shape variable.

Optionally, the photographing module is a CCD camera.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

The present invention processes the first lattice plane picture and the second lattice plane picture by acquiring the first lattice plane picture and the second lattice plane picture, and obtains a plurality of first lattice planes and a plurality of second lattice planes. Lattice line spacing, the first lattice line spacing minus the corresponding second lattice line spacing, obtain the deformation variable between each row of the lattice, and obtain multiple local deformation variables; accumulate multiple local deformation variables to obtain total shape variable. By processing the picture, the local deformation of the sample is obtained, which replaces the existing manual measurement method of the microscopic deformation of the material, and improves the measurement accuracy of the local deformation.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a flow chart of a method for measuring the microscopic deformation of a material based on an impact test of the present invention;

Fig. 2 is the dimension drawing of the side surface of the sample and the dot matrix after dotting;

Figure 3 is a picture of the first dot matrix surface;

Fig. 4 is the first lattice plane filtering picture;

Fig. 5 is the first effective bitmap;

Fig. 6 is the linear fitting straight line diagram of the first effective bitmap;

FIG. 7 is a system block diagram of an impact test-based material microscopic deformation measurement system of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a method and system for measuring the microscopic deformation of a material based on an impact test, so as to solve the problem that the existing method for measuring the microscopic deformation of a material has a large error in measuring the local deformation of a section.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

This embodiment provides a method for measuring the microscopic deformation of a material based on an impact test, which measures the cross-sectional deformation of a sample in a drop weight impact test through image processing.

Fig. 1 is a flow chart of a method for measuring the microscopic deformation of a material based on an impact test. As shown in Fig. 1, the method includes: firstly cutting the used test material into multiple samples with the same shape and size. A drop-weight impact test detection device is provided, the position of the sample is guaranteed to be fixed by a fixture, and a high-precision CCD camera installed separately from the drop-weight impact test detection device ensures the same photographing environment before and after the impact. The deformation measurement was carried out on the sample by the following method.

Step 101: Dotting the side of the sample to obtain a lattice surface.

The side of the sample is dotted to obtain a lattice surface, which specifically includes:

Using a UV marking machine, a dot matrix with a fixed horizontal and vertical spacing is printed on the side of the sample to obtain a dot matrix surface, that is, the preparation of the sample is completed. As shown in Figure 2, the horizontal spacing of the dot matrix is 0.4cm, and the vertical spacing is 0.25cm, the height of the sample is 10cm.

Step 102 : photographing the dot matrix surface to obtain a first dot matrix surface picture, as shown in FIG. 3 .

Step 103 : photographing the lattice surface of the impacted sample to obtain a second lattice surface picture.

Specifically, the sample is placed under the impact testing machine to be photographed by a high-precision CCD camera that has been relatively fixed, and then the impact on the sample is started, and stopped at an appropriate time according to the purpose of the test. After stopping, the sample was photographed with a high-precision CCD camera while keeping the foreground depth basically unchanged. The samples were photographed under the same conditions, and the dot matrix images before and after the impact were obtained. If the deformation data under different impact times is required, the sample needs to be photographed according to the above requirements every time the machine is shut down.

Step 104: Process the first bitmap image to obtain a first valid bitmap.

The first effective bitmap is preprocessed, and the noise is removed by Gaussian filtering or median filtering. In the present invention, median filtering is used, and the scale is about 20, as shown in Figure 4, and then the processed The image continues to undergo adaptive binarization. Since the actual samples often have various plaques, it is difficult to completely remove the plaques by filtering. Therefore, it is necessary to binarize the image after removing the noise. After the binarization, the area and roundness need to be screened to obtain A valid bitmap.

The processing of the first lattice plane picture to obtain the first valid lattice picture specifically includes:

Perform filtering processing on the first lattice surface picture to obtain a first lattice surface filtering picture; perform binarization processing on the first lattice surface filtering picture to obtain a first binarized picture; A binarized image is screened for area and roundness, and the area obtained after screening is used as the first valid point; the first valid bitmap is determined according to a plurality of the first valid points, as shown in FIG. 5 .

Wherein, the area and roundness of the first binarized image are screened, and the area obtained after screening is used as the first valid point, which specifically includes:

Perform an opening operation on the first binarized picture to obtain a first smooth picture; extract the features of the white area in the first smooth picture, and screen the area within 1500 to 3500 pixels and the circularity is above 0.65 as the first valid point.

First perform the opening operation, then extract the features of the white area in the picture, delete the areas with too large, too small and too small roundness, that is, the areas with an area of 1500 to 3500 pixels and a roundness above 0.65 are generally regarded as is a valid point. The centroid coordinates are extracted from the remaining white area, and the position of the corresponding points of the centroid coordinates in the lattice can be arranged by using the bubble sort method twice. In this embodiment, the extracted horizontal and vertical coordinates are saved to two In the matrix, it is convenient for the next line fitting and distance calculation.

Step 105: Calculating the first effective lattice map to obtain a plurality of first lattice line spacings.

The calculation of the first effective lattice map to obtain a plurality of first lattice line spacings specifically includes:

Extract the coordinates of the first valid point in the first valid bitmap; use the least squares method to perform linear fitting on the coordinates of the first valid point in each row to obtain a fitted straight line for each row, as shown in Figure 6 ; Use the distance formula between two parallel straight lines to obtain the spacing between adjacent fitted straight lines, and obtain a plurality of the first lattice straight line spacings.

Step 106: Process the second bitmap image to obtain a second valid bitmap.

The processing of the second lattice surface picture to obtain a second effective lattice map specifically includes:

performing filtering processing on the second lattice surface picture to obtain a second lattice surface filtering picture; performing binarization processing on the second lattice surface filtering picture to obtain a second binarizing picture; The binarized image is screened for area and roundness, and the area obtained after screening is used as the second valid point; the second valid bitmap is determined according to a plurality of the second valid points.

Wherein, the area and roundness of the second binarized image are screened, and the area obtained after screening is used as the second valid point, which specifically includes:

Perform an opening operation on the second binarized picture to obtain a second smooth picture; extract the features of the white area in the second smooth picture, and filter the area within 1500 to 3500 pixels and the circularity is above 0.65. as a second valid point.

Step 107: Calculating the second effective lattice map to obtain a plurality of second lattice line spacings.

After obtaining the second valid bitmap, extract the coordinates of the second valid point in the second valid bitmap, and use the least squares method to perform straight line fitting on the coordinates of the second valid point in each row to obtain the fitted straight line, and then The slope of the fitted line is averaged, and the average is reassigned to each line, keeping the intercept unchanged. Next, use the distance formula between two parallel straight lines to obtain the spacing between adjacent fitting straight lines with the same slope. The same processing method is adopted for the effective lattice diagrams before and after the impact. The line spacing of the lattice after the impact corresponding to the line spacing of the lattice before the impact can be subtracted from the line spacing of the lattice before the impact. between the deformation variables, that is, the local deformation variables. The total shape variable can be obtained by accumulating the local shape variables of each row.

The calculation of the second effective lattice map to obtain a plurality of second lattice line spacings specifically includes:

Extract the coordinates of the second valid point in the second valid bitmap; use the least squares method to perform linear fitting on the coordinates of the second valid point in each row to obtain the fitted straight line of each row; calculate all the coordinates of each row The slope of the fitting straight line is obtained to obtain multiple slopes; the average slope is averaged to obtain the average slope; the average slope is assigned to the fitted straight line of each row, keeping the intercept unchanged, and obtaining the same slope The fitted straight line is obtained; the distance between adjacent fitted straight lines with the same slope is obtained by using the distance formula between the two parallel straight lines, and a plurality of the second lattice straight line distances are obtained.

Step 108 : subtract the second lattice line spacing corresponding to the first lattice line spacing from the first lattice line spacing to obtain a plurality of local deformation variables.

Step 109: Accumulate a plurality of the local deformation variables to obtain a total deformation variable.

The obtained local deformation variables are plotted, with the number of impacts as the horizontal axis and the local or total deformation variables as the vertical axis, the relationship between the deformation amount and the number of impacts can be obtained.

The impact test is carried out on samples of the same material with different impact times, and steps 101-109 are repeated.

To sum up, the method of measuring the cross-section deformation of the sample in the drop weight impact test by using image processing proposed by the present invention is a good substitute for the original manual measurement method by mechanical tools, which reduces the workload and improves the data. Acquired precision.

Fig. 7 is a system block diagram of a material microscopic deformation measurement system based on impact test of the present invention, as shown in Fig. 7, including:

The spotting module 201 is used for spotting the side surface of the sample to obtain a dot matrix surface.

The photographing module 202 is used for photographing the lattice surface to obtain a picture of the first lattice surface; and is also used for photographing the lattice surface of the impacted sample to obtain a picture of the second lattice surface. Optionally, the photographing module 202 is a CCD camera.

The picture processing module 203 is configured to process the first lattice surface picture to obtain a first effective lattice map, and calculate the first effective lattice map to obtain a plurality of first lattice line spacings; and It is used for processing the second lattice plane picture to obtain a second effective lattice map, and calculating the second effective lattice map to obtain a plurality of second lattice line spacings.

The local deformation variable calculation module 204 is configured to subtract the second lattice linear spacing corresponding to the first lattice linear spacing from the first lattice linear spacing to obtain a plurality of local deformation variables.

The total deformation variable calculation module 205 is used for accumulating a plurality of the local deformation variables to obtain the total deformation variable.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

The principles and implementations of the present invention are described herein using specific examples. The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. a material microscopic deformation measurement method based on impact test, is characterized in that, comprises: Dot the side of the sample to get the lattice surface; photographing the dot matrix surface to obtain a picture of the first dot matrix surface; Photograph the lattice surface of the sample after impact to obtain the second lattice surface picture; processing the first bitmap image to obtain a first valid bitmap; Calculating the first effective lattice map to obtain a plurality of first lattice line spacings; The calculation of the first effective lattice map to obtain a plurality of first lattice line spacings specifically includes: extracting the coordinates of the first valid point in the first valid bitmap; The least squares method is used to linearly fit the coordinates of the first valid point of each row to obtain a fitted straight line of each row; Use the distance formula between two parallel straight lines to obtain the spacing between adjacent fitted straight lines, and obtain a plurality of the first lattice straight line spacings; processing the second bitmap image to obtain a second valid bitmap; Calculating the second effective lattice map to obtain a plurality of second lattice line spacings; The calculation of the second effective lattice map to obtain a plurality of second lattice line spacings specifically includes: extracting the coordinates of the second valid point in the second valid bitmap; The least squares method is used to perform linear fitting on the coordinates of the second valid point of each row to obtain a fitted straight line for each row; Calculate the slope of the fitted straight line of each row to obtain a plurality of slopes; averaging a plurality of said slopes to obtain an average slope; Assign the average slope to the fitted straight line of each row, keep the intercept unchanged, and obtain the fitted straight line with the same slope; Use the distance formula between two parallel straight lines to obtain the spacing between adjacent fitted straight lines with the same slope, and obtain a plurality of the second lattice straight line spacings; subtracting the second lattice line spacing corresponding to the first lattice line spacing from the first lattice line spacing to obtain a plurality of local deformation variables; A plurality of the local deformation variables are accumulated to obtain a total deformation variable. 2. The method for measuring the microscopic deformation of a material based on an impact test according to claim 1, characterized in that, the side surface of the sample is dotted to obtain a lattice surface, which specifically comprises: Using an ultraviolet marking machine, a dot matrix with a fixed horizontal and vertical spacing is marked on the side of the sample to obtain a dot matrix surface. 3 . The method for measuring the microscopic deformation of a material based on an impact test according to claim 1 , wherein the processing of the first lattice plane picture to obtain the first effective lattice picture, specifically comprising: 4 . : Perform filtering processing on the first lattice plane picture to obtain a first lattice plane filtered picture; performing binarization processing on the first lattice surface filtered picture to obtain a first binarized picture; Screening of the area and roundness of the first binarized picture is carried out, and the area obtained after screening is used as the first valid point; A first valid bitmap is determined according to a plurality of the first valid points. 4. The method for measuring the microscopic deformation of a material based on an impact test according to claim 3, wherein the first binarized picture is screened for area and roundness, and the screened The area is used as the first valid point, which includes: performing an opening operation on the first binarized picture to obtain a first smooth picture; Extract the feature of the white area in the first smooth image, and select the area within 1500 to 3500 pixels and the circularity above 0.65 as the first valid point. 5 . The method for measuring the microscopic deformation of materials based on an impact test according to claim 1 , wherein the processing of the second lattice surface picture to obtain a second effective lattice map, specifically comprising: 6 . : performing filtering processing on the second lattice surface picture to obtain a second lattice surface filtering picture; performing binarization processing on the second lattice surface filtered picture to obtain a second binarized picture; Screening of the area and roundness of the second binarized picture is carried out, and the area obtained after screening is used as the second valid point; A second valid bitmap is determined according to a plurality of the second valid points. 6 . The method for measuring the microscopic deformation of a material based on an impact test according to claim 5 , wherein the second binarized image is screened for area and roundness, and the screen obtained after the screening is performed. 7 . The area is used as the second valid point, including: performing an opening operation on the second binarized picture to obtain a second smooth picture; Extract the feature of the white area in the second smooth image, and select the area within 1500 to 3500 pixels and the circularity above 0.65 as the second valid point. 7. A material microscopic deformation measurement system based on impact test, characterized in that, comprising: Dotting module, used to dot the side of the sample to get the dot matrix surface; a photographing module, used for photographing the dot matrix surface to obtain a picture of the first dot matrix surface; also used for photographing the dot matrix surface of the impacted sample to obtain a second dot matrix surface picture; The picture processing module is used for processing the first lattice surface picture to obtain a first effective lattice map, and calculating the first effective lattice map to obtain a plurality of first lattice line spacings; for processing the second lattice surface picture to obtain a second effective lattice map, and calculating the second effective lattice map to obtain a plurality of second lattice line spacings; The calculation of the first effective lattice map to obtain a plurality of first lattice line spacings specifically includes: extracting the coordinates of the first valid point in the first valid bitmap; The least squares method is used to linearly fit the coordinates of the first valid point of each row to obtain a fitted straight line of each row; Use the distance formula between two parallel straight lines to obtain the spacing between adjacent fitted straight lines, and obtain a plurality of the first lattice straight line spacings; The calculation of the second effective lattice map to obtain a plurality of second lattice line spacings specifically includes: extracting the coordinates of the second valid point in the second valid bitmap; The least squares method is used to perform linear fitting on the coordinates of the second valid point of each row to obtain a fitted straight line for each row; Calculate the slope of the fitted straight line of each row to obtain a plurality of slopes; averaging a plurality of said slopes to obtain an average slope; Assign the average slope to the fitted straight line of each row, keep the intercept unchanged, and obtain the fitted straight line with the same slope; Use the distance formula between two parallel straight lines to obtain the spacing between adjacent fitted straight lines with the same slope, and obtain a plurality of the second lattice straight line spacings; a local deformation variable calculation module, configured to subtract the second lattice linear spacing corresponding to the first lattice linear spacing from the first lattice linear spacing to obtain a plurality of local deformation variables; The total shape variable calculation module is used for accumulating a plurality of the local shape variables to obtain the total shape variable. 8 . The impact test-based material microscopic deformation measurement system according to claim 7 , wherein the photographing module is a CCD camera. 9 .

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