CN111929307B - On-site nondestructive testing and evaluating method for rust degree of existing steel structural member - Google Patents
- ️Tue May 16 2023
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- CN111929307B CN111929307B CN202010789220.2A CN202010789220A CN111929307B CN 111929307 B CN111929307 B CN 111929307B CN 202010789220 A CN202010789220 A CN 202010789220A CN 111929307 B CN111929307 B CN 111929307B Authority
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- G—PHYSICS
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/02—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
- G01N2021/8854—Grading and classifying of flaws
- G01N2021/8861—Determining coordinates of flaws
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
- G01N2021/8854—Grading and classifying of flaws
- G01N2021/8874—Taking dimensions of defect into account
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
- G01N2021/8887—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques
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Abstract
The invention provides a field nondestructive testing and evaluating method for the rust degree of an existing steel structural member, which comprises the following steps: s1: grading the rust degree of the surface property of the component; s2: judging whether the rust grade of the current component needs quantitative detection and evaluation, if so, continuing the subsequent steps; s3: cleaning the surface of the component; s4: measuring by using an ultrasonic thickness gauge in a region where no etching pit appears to obtain the wall thickness; s5: setting a detection area, and pasting a registration target; s6: setting scanning parameters of the three-dimensional laser scanning equipment; s7: scanning the detection area by using a three-dimensional laser scanning device to obtain point cloud data; s8: simplifying the point cloud data of each plate; s9: and analyzing and processing the point cloud data to obtain quantitative rust degree data and obtain a qualitative evaluation result. The invention discloses a field nondestructive testing and evaluating method for the rust degree of an existing steel structural member, which belongs to the technical field of nondestructive testing and evaluating methods, and is high in testing speed and good in testing precision.
Description
Technical Field
The invention relates to the field of nondestructive testing and evaluation, in particular to a field nondestructive testing and evaluation method for the rust degree of an existing steel structural member.
Background
Rust is an important factor affecting the durability of a steel structure, and for existing steel components, rust not only causes the cross section of the component to be weakened, but also can cause brittle failure of the component to cause structural collapse. Therefore, when detecting existing steel house or components, effective measures are needed to accurately evaluate the rust degree of the components. The existing evaluation method of the rust degree of the steel member mainly comprises a quality evaluation method and a depth evaluation method, wherein the quality evaluation method is used for sampling the rust member and weighing the rust member in a laboratory to calculate the rust rate, but most of existing members do not have the condition of damaging the sampling during field detection, so that the quality evaluation method is not suitable for field detection; the depth evaluation method judges the corrosion degree by measuring the residual thickness of the component or measuring the typical pit depth on site, however, the residual thickness measurement cannot reflect the pitting characteristics, the pit depth on site is measured with larger error, the light condition is often poor during detection, hundreds of pits can exist on the surface of the component, and the maximum pit depth cannot be accurately measured, so the depth evaluation method has great limitation in on-site detection.
The three-dimensional laser scanning obtains a three-dimensional space data source of a target object by measuring the horizontal direction, the inclined distance and the reflection intensity of the surface of the object contacted by the laser point, is a non-contact active detection technology, has the advantages of high sampling rate, high scanning speed, high measurement precision, long measuring distance and the like, and is widely applied to the building mapping industry. In the aspect of defect detection, for point cloud data acquired by laser scanning of an outer elevation, coordinates of a defect area are obviously different from surrounding normal areas, and quantitative identification of the position and the size of the defect can be realized by performing three-dimensional imaging through a signal processing algorithm. As most of the existing steel member rusts are punctiform rusts, the maximum etching pit depth is an important factor for judging the rusting degree of the member, and the etching pit condition on the surface of the member can be rapidly and accurately scanned by a three-dimensional laser scanning technology, thereby realizing rapid nondestructive identification of the maximum etching pit depth and further evaluating the rusting degree of the member. The three-dimensional laser scanning technology is combined with the existing steel member corrosion degree evaluation method to form a set of nondestructive rapid detection evaluation system, so that the rapid detection of the corrosion degree of a large-area member can be realized, the detection precision can meet the engineering requirements, and the method has important application potential in steel structure detection.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a field nondestructive testing and evaluating method for the rust degree of the existing steel structural member, which belongs to the technical field of nondestructive testing, and has the advantages of high testing speed and high testing precision. Including both qualitative and quantitative assessment. Qualitative evaluation refers to rapid qualitative grading of components by using rust characteristics, and directly evaluating the rust degree of the components. The quantitative evaluation refers to quantitative evaluation of the corrosion degree of the component when the mechanical property of the component cannot be directly evaluated according to the qualitative classification result. The quantitative evaluation utilizes a three-dimensional laser scanning device to scan the surface characteristics of the component, utilizes a portable computer to perform post-processing such as registration, denoising, partitioning, analysis, data extraction, digital imaging and the like on point cloud data, and calculates and processes to obtain the results such as the volume corrosion rate, the area corrosion rate, the maximum corrosion depth, the pit distribution image and the like of the component, so that the accurate reflection of the corrosion degree of the component is realized, and a guiding basis is provided for subsequent safety evaluation.
In order to achieve the above object, the present invention provides a method for on-site nondestructive testing and evaluation of the degree of rust of an existing steel structural member, comprising the steps of:
s1: visual inspection is carried out on the member to be detected, and the rust degree of the surface property of the member is initially classified according to a plurality of preset rust grades; part of the rust grades can directly obtain a qualitative evaluation result, and the other part of the rust grades need to be quantitatively detected and evaluated;
s2: judging whether the current rust grade of the component needs quantitative detection and evaluation, if so, continuing the subsequent step, otherwise, ending the step;
s3: cleaning the surface of the component;
s4: measuring the area of the member to be measured, where the etching pit does not appear, by using an ultrasonic thickness gauge to obtain the wall thickness;
s5: setting a detection area in the area where the etching pit appears on the member to be detected, and sticking registration targets on the surface of the member in the detection area at equal intervals;
s6: setting scanning parameters of a three-dimensional laser scanning device;
s7: scanning the detection area by using the three-dimensional laser scanning equipment to obtain point cloud data; registering point clouds generated at three-dimensional laser scanning positions at different positions by using the registration targets based on a nearest point iterative registration method and a coordinate transformation technology to form complete point cloud information of the surface of the component in the detection area;
s8: dividing the components into three plane plates of a web plate, an upper flange and a lower flange according to the types of preset components, dividing and extracting point clouds, denoising by using a k-adjacent point cloud denoising algorithm, resampling the point cloud data according to a detection precision set distance threshold, and simplifying the point cloud data of each plate;
s9: the point cloud data J for the individual plate members i And (3) carrying out analysis treatment to obtain quantitative corrosion degree data of the surface, the plate or the component, and obtaining a qualitative evaluation result according to the quantitative corrosion degree data.
Preferably, in the step S1, the degree of corrosion of the surface property of the member includes six corrosion grades, the corrosion grades including:
the first stage, the anticorrosive paint on the surface of the component is complete;
the second stage, the anticorrosive paint on the surface of the component falls off, but the component is not corroded;
thirdly, the surface of the component is provided with rust, the surface is still smooth, and no obvious pitting corrosion exists;
fourth stage, the surface of the component has pitting corrosion and a certain etching pit, but the etching pit is not connected into a large amount of slices;
a fifth stage, wherein a large number of component pits are connected into pieces, and the surface of the component is corroded and layered; and
a sixth stage in which the member is rusted through, rotted or broken in the thickness direction;
the fourth stage is required to carry out the quantitative detection evaluation; the rest of the rust grades can directly obtain the qualitative assessment result; the first stage, the second stage and the third stage directly obtain the component basically without rust, and the performance of the component can meet the qualitative assessment result of design or specification requirements; the fifth and sixth stages directly achieved severe rust that could not continue as a result of the qualitative assessment of the structural load bearing members.
Preferably, in the step S6, the wavelength, sampling frequency and scanning speed of the three-dimensional laser scanning device are set according to the required detection distance, detection precision and the registration target pitch; the three-dimensional laser scanning device adopts a handheld three-dimensional laser scanning device.
Preferably, the step of analyzing the point cloud data of the single plate in S9 further includes the steps of:
s91: selecting the internal points of the plate as coordinate origins in the point cloud, establishing a local coordinate system, and dividing the point cloud into a front surface and a back surface;
s92: the average z coordinate or r coordinate of the point cloud data of the surface is obtained through average calculation, the average height after rusting is represented, and the average height z of the non-rusted area is obtained through the original design drawing, the component specification table and the actually measured wall thickness i,norm ；
S93: for the plate with both sides being scannable, the average thickness of the plate after rusting
And->
Average coordinates of the front face and the back face, respectively;
for the plate with only one scannable surface, the plate with only one scannable surface comprises a circular tube and double-spliced angle steel, and the average thickness of the plate after corrosion
d represents the thickness of the non-rusted region of the plate;
the volume corrosion rate epsilon of the plate i ＝d i /d；
S94: maximum rust depth h of single-sided point cloud for the plate with only one side capable of scanning i ＝|z i,norm |-|z i,min I, wherein z i,min Representing a minimum value of an absolute value of a z coordinate in the point cloud;
for both sides scannable saidThe plate takes a larger value for the rust depth of the two sides of the plate to obtain the maximum rust depth H of the plate i ；
S95: transforming the single-sided point cloud data, if the single-sided z coordinate value z i ＜z i,norm The point belongs to the pit concave area, and the coordinate of the point is kept unchanged; otherwise, the point belongs to a constant area, the z coordinate of the point is taken as 0, and the transformed point cloud data is stored as a new data set J ia The method comprises the steps of carrying out a first treatment on the surface of the J is subjected to denoising algorithm by using k-nearest neighbor point cloud ia After denoising, performing point cloud imaging by using detection software, respectively representing the positions of a pit concave region and a normal region by using different colors, converting an image into a binary image by using a threshold segmentation principle, and automatically extracting the area A of the pit region by calculating the pixel points of the binary image ia The method comprises the steps of carrying out a first treatment on the surface of the According to the area A of the etching pit area ia Calculating the area corrosion rate eta of the plate i ；
S96: repeating the steps S91-S95 for the rest plates to obtain the volume corrosion rate epsilon of each plate after corrosion i Maximum rust depth H i And area rust rate eta i The method comprises the steps of carrying out a first treatment on the surface of the The corrosion rates of different plates of the same component are weighted and averaged according to the sectional areas of the plates to obtain the overall volume corrosion rate epsilon and the area corrosion rate eta of the component, and the maximum corrosion depth of all the plates is taken as the maximum corrosion depth H of the component; the quantitative rust degree data includes the overall volume rust rate epsilon, the area rust rate eta and the maximum rust depth H of the component.
The invention adopts the technical proposal, which has the following beneficial effects:
(1) And the qualitative detection and the quantitative detection are combined, so that most components without corrosion or with serious corrosion are directly subjected to quick qualitative judgment, quantitative detection is only required for a small part of components with medium corrosion, the detection efficiency is high, the application range is wide, and the method is suitable for detecting large-area components on site.
(2) And the quantitative evaluation is nondestructive detection, so that the mechanical properties of the component are not affected.
(3) The quantitative evaluation can accurately calculate the volume corrosion rate, the area corrosion rate and the maximum corrosion depth, can accurately position the corrosion pit, and has high detection evaluation accuracy.
Drawings
FIG. 1 is a flow chart of a method for in-situ nondestructive testing and evaluation of the degree of rust of an existing steel structural member in accordance with an embodiment of the present invention;
FIG. 2 is a schematic view of a typical H-steel component rust cross-section of an embodiment of the invention;
fig. 3 is a partial enlarged view of a region a of fig. 2.
Detailed Description
The following description of the preferred embodiments of the present invention will be given with reference to fig. 1 to 3, so that the functions and features of the present invention can be better understood.
Referring to fig. 1, a conventional hot rolled H-section steel member 1 is assumed to have a cross-sectional specification of h300×300×10×15. The method for detecting and evaluating the corrosion degree of the existing steel structural member 1 in situ in a nondestructive testing and evaluating manner comprises the following steps:
s1: visual inspection is carried out on the component 1 to be detected, and the rust degree of the surface property of the component 1 is initially classified according to a plurality of preset rust grades; and part of the rust grades can directly obtain a qualitative evaluation result, and the other part of the rust grades need to be quantitatively detected and evaluated.
Preferably, in step S1, the degree of corrosion of the surface profile of the component 1 comprises six corrosion grades, the corrosion grades comprising:
the first stage, the surface anticorrosive paint of the component 1 is complete;
the second stage, the anticorrosive paint on the surface of the component 1 falls off, but the component 1 is not corroded;
thirdly, the surface of the component 1 is provided with rust, the surface is still smooth, and no obvious pitting corrosion exists;
fourth, pitting corrosion exists on the surface of the component 1, a certain etching pit exists, but the etching pit is not connected into a large number of slices;
fifthly, connecting a large number of pits of the component 1 into pieces, wherein the surface of the component 1 is rusted and layered; and
sixth stage, the member 1 is rusted through, rusted or rusted off in the thickness direction;
the fourth stage is required to carry out quantitative detection and evaluation; the other rust grades can directly obtain qualitative evaluation results; the first stage, the second stage and the third stage basically belong to no obvious corrosion, the performance and the section of the component 1 are basically consistent with those of the component 1 which is not corroded, the component 1 is basically rustless, and the performance of the component 1 can meet the qualitative evaluation result required by design or specification; the fifth and sixth serious rusting stages have the existing research results show that the mechanical properties and the residual cross section of the component 1 are greatly reduced at the moment, the component 1 is basically ductile at the moment, the serious rusting is directly obtained, and the component cannot be continuously used as a qualitative evaluation result of the structural bearing component 1. Only the fourth stage requires subsequent detection of pitting of the surface of the component 1.
S2: judging whether the rust grade of the current component 1 needs to be quantitatively detected and evaluated, if so, continuing the subsequent steps, and otherwise, ending the steps.
S3: the surface of the component 1 is cleaned.
S4: and measuring the areas of the flanges and the webs of the member 1 to be measured, which are not provided with etching pits, by using an ultrasonic thickness gauge to obtain the wall thickness.
S5: and setting a detection area in the area where the etching pit appears in the member 1 to be detected, and sticking registration targets on the surface of the member 1 in the detection area at equal intervals.
In the embodiment, a detection area is arranged in a 1000mm area of the midspan of the selection member 1, and a registration target is stuck on the middle surfaces of a web plate and upper and lower flanges in the detection area every 200 mm.
S6: setting scanning parameters of a three-dimensional laser scanning device.
S6, setting the wavelength, sampling frequency and scanning speed of the three-dimensional laser scanning equipment according to the required detection distance, detection precision and registration target distance; the three-dimensional laser scanning device adopts a handheld three-dimensional laser scanning device.
In this embodiment, the portable three-dimensional laser scanning device is set to use green light according to the laser propagation theory, the wavelength is set to 532nm, the scanning speed is set to 200000 points per second, the point spacing is set to 0.05mm, and the detection distance is set to 1m.
S7: scanning the detection area by using a three-dimensional laser scanning device to obtain point cloud data; and registering point clouds generated at three-dimensional laser scanning positions at different positions based on a nearest point iterative registration method and a coordinate transformation technology by using a registration target to form complete point cloud information of the surface of the component 1 in the detection area.
S8: dividing the component 1 into three plane plates of a web plate, an upper flange and a lower flange according to the type of the preset component 1, dividing and extracting point cloud, reducing noise by using a k-adjacent point cloud denoising algorithm, resampling point cloud data according to a detection precision set distance threshold value, and simplifying the point cloud data of each plate;
s9: taking a web as an example, the design section of a web plate in a detection area is 1000 multiplied by 244 multiplied by 10, and the point cloud data J of the web is calculated i And (3) performing analysis treatment to obtain quantitative corrosion degree data of the plate or the component 1, and obtaining a qualitative evaluation result according to the quantitative corrosion degree data.
S9, analyzing and processing the point cloud data of the single plate, and further comprising the steps of:
s91: for a planar plate, selecting an internal point of the plate as an origin of coordinates in the point cloud, establishing a local coordinate system, wherein a z-axis is a thickness direction, so that all z-coordinates of the point clouds on two surfaces in the thickness direction of the plate are respectively more than 0 and less than 0, and dividing the point cloud into J ip Front and back J in The method comprises the steps of carrying out a first treatment on the surface of the For a circular tube, fitting an axis equation and a section curve equation of the outer surface of the circular tube by using a least square method under a global coordinate system, selecting any point on the axis as a coordinate origin, and establishing a local three-dimensional axis coordinate system, wherein an r axis is the thickness direction of the circular tube. Taking a web as an example, selecting a point on the axis of the cross section of the web as a coordinate origin to establish a local coordinate system, and then designing the coordinate z=5mm on the front surface of the web and designing the coordinate z=5mm on the back surface of the web.
S92: the average z coordinate or r coordinate of the point cloud data of the plane (curved surface) is obtained through mean calculation, the average height after rusting is represented, and then the non-rusted area is obtained through the original design drawing, the component specification table and the actually measured wall thicknessAverage height z i,norm ；
Firstly, taking the average value of the z coordinate (r coordinate) to obtain
Extracting the maximum value z of the absolute value of the z coordinate (r coordinate) i,max And define z i,norm ＝z i,max Delta is taken as the z-coordinate (r-coordinate) of the normal surface of the component 1, where delta is a predetermined tolerance to prevent the presence of individual protrusions on the surface of the component 1.
S93: for plates that are both scannable, the average thickness of the plate after rusting
And
average coordinates of the front and back sides respectively;
for the plate with one scannable surface, the plate with one scannable surface comprises a circular tube and double-spliced angle steel, and the average thickness of the plate after being rusted
d represents the thickness of the non-rusted area of the plate; obtained through original design drawing, component specification table or actual measurement;
volume corrosion rate epsilon of plate i ＝d i /d；
S94: maximum rust depth h of single-sided point cloud for plate with only one side capable of scanning i ＝|z i,norm |-|z i,min I, wherein z i,min Representing a minimum value of an absolute value of a z coordinate in the point cloud;
for the plate with both sides being scanned, the rust depth of the two sides of the plate is taken to be a larger value, and the maximum rust depth H of the plate is obtained i ；
S95: transforming the single-sided point cloud data, if the single-sided z coordinate value z i ＜z i,norm The point belongs to the pit concave area, and the coordinate of the point is kept unchanged; otherwise, the point belongs to a constant area, the z coordinate of the point is taken as 0, and the transformed point cloud data is stored as a new data set J ia Representing a recessed portion of the etch pit in the detection region; j is subjected to denoising algorithm by using k-nearest neighbor point cloud ia After denoising, performing point cloud imaging by using detection software, respectively representing the positions of a pit concave region and a normal region by using different colors, converting an image into a binary image by using a threshold segmentation principle, and automatically extracting the area A of the pit region by calculating the pixel points of the binary image ia The method comprises the steps of carrying out a first treatment on the surface of the According to the area A of the etching pit area ia Calculating the area corrosion rate eta of the plate i The method comprises the steps of carrying out a first treatment on the surface of the For each plate, the sum of the areas of the front and back surfaces is taken as the total rust area, and eta is defined i ＝(A iap +A ian ) and/2A is the area corrosion rate of the plate, wherein A is the total area of the single-sided area, A iap Area of the front etching pit area A ian Is the area of the reverse pit area.
S96: repeating the steps S91-S95 on the upper flange and the lower flange to obtain the volume corrosion rate epsilon of each plate after corrosion i Maximum rust depth H i And area rust rate eta i The method comprises the steps of carrying out a first treatment on the surface of the If the corrosion condition of the component 1 needs to be generally evaluated, the corrosion rate of the flange and the web in the detection area is weighted and averaged according to the sectional area of the design specification of the plate to obtain the overall volume corrosion rate epsilon and the area corrosion rate eta of the component 1, and the maximum corrosion depth of all the plates is taken as the maximum corrosion depth H of the component 1; the quantitative rust degree data includes the overall volume rust rate epsilon, the area rust rate eta and the maximum rust depth H of the member 1.
The present invention has been described in detail with reference to the embodiments of the drawings, and those skilled in the art can make various modifications to the invention based on the above description. Accordingly, certain details of the illustrated embodiments are not to be taken as limiting the invention, which is defined by the appended claims.
Claims (3)
1. A field nondestructive testing and evaluating method for the rust degree of an existing steel structural member comprises the following steps:
s1: visual inspection is carried out on the member to be detected, and the rust degree of the surface property of the member is initially classified according to a plurality of preset rust grades; part of the rust grades can directly obtain a qualitative evaluation result, and the other part of the rust grades need to be quantitatively detected and evaluated;
s2: judging whether the current rust grade of the component needs quantitative detection and evaluation, if so, continuing the subsequent step, otherwise, ending the step;
s3: cleaning the surface of the component;
s4: measuring the area of the member to be measured, where the etching pit does not appear, by using an ultrasonic thickness gauge to obtain the wall thickness;
s5: setting a detection area in the area where the etching pit appears on the member to be detected, and sticking registration targets on the surface of the member in the detection area at equal intervals;
s6: setting scanning parameters of a three-dimensional laser scanning device;
s7: scanning the detection area by using the three-dimensional laser scanning equipment to obtain point cloud data; registering point clouds generated at three-dimensional laser scanning positions at different positions by using the registration targets based on a nearest point iterative registration method and a coordinate transformation technology to form complete point cloud information of the surface of the component in the detection area;
s8: dividing the components into three plane plates of a web plate, an upper flange and a lower flange according to the types of preset components, dividing and extracting point clouds, denoising by using a k-adjacent point cloud denoising algorithm, resampling the point cloud data according to a detection precision set distance threshold, and simplifying the point cloud data of each plate;
s9: the point cloud data J for the individual plate members i Analyzing to obtain quantitative corrosion degree data of the surface, the plate or the component, and obtaining a qualitative evaluation result according to the quantitative corrosion degree data;
the step of analyzing and processing the point cloud data of the single plate in S9 further includes the steps of:
s91: selecting the internal points of the plate as coordinate origins in the point cloud, establishing a local coordinate system, and dividing the point cloud into a front surface and a back surface;
s92: the average z coordinate or r coordinate of the point cloud data of the surface is obtained through average calculation, the average height after rusting is represented, and the average height z of the non-rusted area is obtained through the original design drawing, the component specification table and the actually measured wall thickness i,norm ；
S93: for the plate with both sides being scannable, the average thickness of the plate after rusting
And z is the average coordinates of the front face and the back face, respectively;
for the plate with only one scannable surface, the plate with only one scannable surface comprises a circular tube and double-spliced angle steel, and the average thickness of the plate after corrosion
d represents the thickness of the non-rusted region of the plate;
the volume corrosion rate epsilon of the plate i ＝d i /d；
S94: maximum rust depth h of single-sided point cloud for the plate with only one side capable of scanning i ＝|z i,norm |-|z i, min, where z i,min Representing a minimum value of an absolute value of a z coordinate in the point cloud;
for the plate with both sides being scannable, taking a larger value of the rusting depth of the two sides of the plate to obtain the maximum rusting depth H of the plate i ；
S95: transforming the single-sided point cloud data, if the single-sided z coordinate value z i ＜z i,norm The point belongs to the pit depressionThe area, the point coordinates remain unchanged; otherwise, the point belongs to a constant area, the z coordinate of the point is taken as 0, and the transformed point cloud data is stored as a new data set J ia The method comprises the steps of carrying out a first treatment on the surface of the J is subjected to denoising algorithm by using k-nearest neighbor point cloud ia After denoising, performing point cloud imaging by using detection software, respectively representing the positions of a pit concave region and a normal region by using different colors, converting an image into a binary image by using a threshold segmentation principle, and automatically extracting the area A of the pit region by calculating the pixel points of the binary image ia The method comprises the steps of carrying out a first treatment on the surface of the According to the area A of the etching pit area ia Calculating the area corrosion rate eta of the plate i ；
S96: repeating the steps S91-S95 for the rest plates to obtain the volume corrosion rate epsilon of each plate after corrosion i Maximum rust depth H i And area rust rate eta i The method comprises the steps of carrying out a first treatment on the surface of the The corrosion rates of different plates of the same component are weighted and averaged according to the sectional areas of the plates to obtain the overall volume corrosion rate epsilon and the area corrosion rate eta of the component, and the maximum corrosion depth of all the plates is taken as the maximum corrosion depth H of the component; the quantitative rust degree data includes the overall volume rust rate epsilon, the area rust rate eta and the maximum rust depth H of the component.
2. The method for in-situ nondestructive testing evaluation of the degree of corrosion of an existing steel structure member according to claim 1, wherein in the step S1, the degree of corrosion of the member surface property includes six corrosion grades, the corrosion grades including:
the first stage, the anticorrosive paint on the surface of the component is complete;
the second stage, the anticorrosive paint on the surface of the component falls off, but the component is not corroded;
thirdly, the surface of the component is provided with rust, the surface is still smooth, and no obvious pitting corrosion exists;
fourth stage, the surface of the component has pitting corrosion and a certain etching pit, but the etching pit is not connected into a large amount of slices;
a fifth stage, wherein a large number of component pits are connected into pieces, and the surface of the component is corroded and layered; and
a sixth stage in which the member is rusted through, rotted or broken in the thickness direction;
the fourth stage is required to carry out the quantitative detection evaluation; the rest of the rust grades can directly obtain the qualitative assessment result; the first stage, the second stage and the third stage directly obtain the component basically without rust, and the performance of the component can meet the qualitative assessment result of design or specification requirements; the fifth and sixth stages directly achieved severe rust that could not continue as a result of the qualitative assessment of the structural load bearing members.
3. The method for on-site nondestructive testing evaluation of the rust degree of an existing steel structural member according to claim 2, wherein in the step S6, the wavelength, sampling frequency and scanning speed of the three-dimensional laser scanning device are set according to the required detection distance, detection precision and the registration target pitch; the three-dimensional laser scanning device adopts a handheld three-dimensional laser scanning device.
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