CN111272091A

CN111272091A - Automatic identification method for large deformation of welded I-steel based on three-dimensional laser scanning

Info

Publication number: CN111272091A
Application number: CN202010157700.7A
Authority: CN
Inventors: 徐燕; 杨森; 郑宝锋
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2020-03-09
Filing date: 2020-03-09
Publication date: 2020-06-12
Anticipated expiration: 2040-03-09
Also published as: CN111272091B

Abstract

The invention discloses a method for automatically identifying large deformation of a welded I-steel based on three-dimensional laser scanning, which comprises the steps of firstly obtaining point cloud data of a complete component, selecting approximate midpoints of flanges of the upper surface and the lower surface of the component, and establishing an initial coordinate system; separating out scanning points on the upper surface and the lower surface of the component, calculating the central position of a section according to point cloud segmentation and curve linear fitting, and updating a coordinate system; uniformly slicing the point cloud along the Z-axis direction, converting the point cloud data of each layer into binary images, identifying the positions of weld toes with different section heights, segmenting a section curve, performing curve fitting, extracting a connecting line of the intersection point of a flange and a web of the component as a deformed component actual central axis, re-layering the point cloud data, repeating the segmentation and fitting steps, and obtaining the geometric shape of each layered section; the method can quickly and accurately acquire the full-field three-dimensional deformation information of the component, and has accurate measurement and high efficiency.

Description

Automatic identification method for large deformation of welded I-steel based on three-dimensional laser scanning

Technical Field

The invention belongs to the technical field of experimental tests, and particularly relates to a method for automatically identifying large deformation of a welded I-steel based on three-dimensional laser scanning, which can quickly and accurately acquire full-field three-dimensional deformation information of a component.

Background

The accurate description of the buckling deformation of the steel member is a key link for carrying out related theoretical derivation, is one of data which are most commonly used for verifying the numerical analysis result, and is also the basis for carrying out the judgment of the member failure mode and the establishment of a design formula. Therefore, the measurement of the buckling deformation is particularly important in the laboratory test.

In a laboratory, a commonly used method for measuring the buckling deformation is a displacement sensor. However, the displacement sensor has obvious defects in observation, the number of the measuring points is limited, only the deformation of the limited points on the member can be obtained, and accurate three-dimensional deformation data cannot be obtained. Meanwhile, due to the uncertain influence of defect distribution, the buckling position of the steel member has strong discreteness, and the measuring point arrangement of the displacement sensor is possibly not at the optimal observation position, so that data are often lost.

The three-dimensional laser scanning technology is a high and new technology for rapidly acquiring three-dimensional space data with large area and high resolution, which is started in the middle of the nineties of the last century, and establishes a three-dimensional influence model of the surface of a measured object through high-speed laser scanning measurement. The three-dimensional laser scanning has the advantages of rapidness, accuracy, no contact and the like, so that the method has the potential of being applied to full-field three-dimensional deformation measurement of components in a laboratory. Because the welded I-shaped member generates obvious large buckling deformation and member length change after a compression failure experiment, the existing point cloud matching method cannot obtain ideal effect. Therefore, an automatic processing method for three-dimensional scanning point cloud data after large deformation of a welded I-shaped component is needed at present, and full-field three-dimensional deformation information of the component can be rapidly and accurately acquired.

Disclosure of Invention

In order to solve the problems, the invention discloses a method for automatically identifying large deformation of a welded I-steel based on three-dimensional laser scanning, which can quickly and accurately acquire the full-field three-dimensional deformation information of a component.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for automatically identifying large deformation of a welded I-steel based on three-dimensional laser scanning comprises the following specific steps:

s1: placing a welding I-shaped component which is subjected to compression or bending loading failure in an open position in a laboratory, using a commercial handheld laser scanner to obtain three-dimensional point clouds on the surface of the component from different view angles, and obtaining point cloud data of the complete component under a unified coordinate system through point cloud splicing;

S2-S6: establishing a three-dimensional model and deformation information of the welding I-shaped component by analyzing and processing the three-dimensional laser scanning point cloud data;

s2: self-defining a coordinate system and coordinate transformation, namely, defining the coordinate system and the coordinate transformation in two steps, namely, initial definition and precise definition, selecting the central positions of flanges on two sides of the lower surface of a welded I-shaped member, defining the connecting line of the central positions as a Y axis of the initial coordinate system, selecting the central positions of the upper surface and the lower surface of the member and the flange edge of the flank, and defining the connecting line of the central positions as a Z axis of the initial coordinate system; on the basis, finely adjusting a coordinate system, separating scanning points of the upper surface and the lower surface of the component, carrying out point cloud segmentation according to geometric space characteristics, respectively carrying out curve linear fitting on edges of flanges and webs, calculating the central position of a section, and defining a central connecting line of the upper surface and the lower surface as a new Z axis; carrying out coordinate transformation according to newly defined coordinate system information to obtain a new point cloud coordinate;

s3: slicing the point clouds in layers, uniformly slicing the point clouds along the Z-axis direction, wherein the distance between every two adjacent slices is not higher than 1/20 of the length of the component;

s4: section curve segmentation and fitting: the accurate segmentation of a welding line and a flange edge and the accurate segmentation of the welding line and a web edge cannot be finished by directly utilizing the characteristics of point cloud coordinates and normal vectors, so that the point cloud is converted into a binary image, and the positions of welding toes with different section heights are identified by a template matching method based on correlation; dividing the section curve by combining the point cloud coordinates, the point cloud normal vectors and the weld toe coordinates; taking the integral or local buckling, bending and twisting deformation and coupling of flanges and webs of the I-steel into consideration, and selecting Fourier series to perform curve fitting; calculating the center lines of flanges and webs of the cross section of the I-shaped steel by utilizing the fitted curve information, and recording the coordinates of the uniform points on the center lines;

s5: considering that the component may be bent and buckled laterally after being deformed, extracting a connecting line of the intersection point of the flange and the web of the component as an actual central axis of the deformed component, re-layering point cloud data, and repeating S4 to obtain the geometric shape of each layered section;

s6: and summarizing the cross section shapes of the layered components, establishing a three-dimensional model after the components are deformed, comparing the three-dimensional model with the design size information of the components, and acquiring the full-field three-dimensional deformation information of the components.

The invention has the beneficial effects that:

1. the non-contact measurement of the deformation of the welded I-shaped component is realized, the measurement is accurate, the efficiency is high, and the measurement cost is saved;

2. the full-field deformation information visualization is realized, and the method can be used for decomposing the failure mode of the component.

Drawings

FIG. 1 is a flow chart of the method of the present invention;

FIG. 2 is a coordinate system customization of point cloud data;

FIG. 3 illustrates weld toe position identification in each layer of point cloud data;

FIG. 4 is a segmentation and curve fitting of layered point cloud data in a plane;

fig. 5 is a three-dimensional model of a deformed welded i-shaped member.

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.

The case of deformation measurement of an i-shaped member is welded to illustrate embodiments of the present invention.

S1: acquiring point cloud data of the complete component by using a commercial handheld laser scanner, wherein the point cloud data is shown in a figure 2 (a);

s2: selecting approximate midpoints of flanges of the upper surface and the lower surface of the component, such as P1, P2 and P3 in the step (a) of FIG. 2, and establishing an initial coordinate system; and (4) separating scanning points of the upper surface and the lower surface of the component, calculating the central position of the cross section according to point cloud segmentation and curve linear fitting, and updating a coordinate system, wherein the central position is shown as O in the figure 2 (c).

S3: uniformly slicing the point cloud along the Z-axis direction, wherein the distance between every two adjacent slices is 1/100 of the length of the component;

s4: converting the point cloud data of each layer into a binary image, and identifying the positions of the weld toes with different section heights by a template matching method based on correlation, as shown in FIG. 3; the cross-sectional curve is divided, see fig. 4 (a); curve fitting using fourier series, see fig. 4 (b);

s5: extracting a connecting line of the intersection point of the flange and the web of the component as a deformed component actual central axis, re-layering point cloud data, and repeating S4 to obtain the geometric shape of each layered section;

s6: the cross section shapes of the layered components are collected, and the full-field three-dimensional deformation information of the components is obtained, which is shown in figure 5.

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.

Claims

1. A method for automatically identifying large deformation of a welded I-steel based on three-dimensional laser scanning is characterized by comprising the following steps: the specific implementation steps are as follows:

s1: placing a welding I-shaped component which is subjected to compression or bending loading failure in an open position in a laboratory, using a handheld laser scanner to obtain three-dimensional point clouds on the surface of the component from different view angles, and obtaining point cloud data of the complete component under a unified coordinate system through point cloud splicing;

s2: self-defining a coordinate system and coordinate transformation, wherein the self-defining coordinate system and the coordinate transformation are divided into two steps, namely initial definition and accurate definition; selecting the central positions of flanges at two sides of the lower surface of the welded I-shaped component, defining the connecting line of the central positions as a Y axis of an initial coordinate system, selecting the central positions of the upper surface and the lower surface of the component and the flange edge of the side wing, and defining the connecting line of the central positions as a Z axis of the initial coordinate system; on the basis, finely adjusting a coordinate system, separating scanning points of the upper surface and the lower surface of the component, carrying out point cloud segmentation according to geometric space characteristics, respectively carrying out curve linear fitting on edges of flanges and webs, calculating the central position of a section, and defining a central connecting line of the upper surface and the lower surface as a new Z axis; carrying out coordinate transformation according to newly defined coordinate system information to obtain a new point cloud coordinate;

s4: the method comprises the steps of section curve segmentation and fitting, namely firstly converting point cloud into a binary image, and identifying the positions of weld toes with different section heights by a template matching method based on correlation; dividing the section curve by combining the point cloud coordinates, the point cloud normal vectors and the weld toe coordinates; selecting Fourier series to perform curve fitting; calculating the center lines of flanges and webs of the cross section of the I-shaped steel by utilizing the fitted curve information, and recording the coordinates of the uniform points on the center lines;