A corroded steel analysis method based on pit fusion and its application

Abstract

The present invention discloses a method for analyzing rusted steel and its application based on pit fusion, belonging to the technical field of steel structures. The technical key points are as follows: First, select a part of the actual rusted steel and investigate the situation of its corrosion pits; through statistics, obtain the statistical parameters of the corrosion pits and the mass loss rate η0 of this area; then, determine the number of corrosion pits of the entire steel member; finally, create a finite element model considering the corrosion pits. By using the method of the present application, the bearing capacity and deformation of the corroded steel beam, steel column or steel support can be calculated better.

Description

Technical Field

[0001] The present invention relates to the field of construction engineering, and in particular to a corroded steel material analysis method based on corrosion pit fusion and application thereof. Background Art

[0002] With the increase in steel production and the increasing maturity of steel structure design theory, the number and scale of steel structure projects in China have increased year by year. However, steel structures have poor durability and are prone to corrosion problems in corrosive environments such as the ocean and industrial atmosphere for a long time.

[0003] Corrosion of steel structures causes damage and performance degradation of steel under environmental influences. The corrosion is destructive, causing the bearing capacity of the building to decline and may even cause collapse, resulting in huge loss of life and property.

[0004] The common method to evaluate the bearing capacity of corroded steel is to conduct an axial tensile test, but the axial tensile test is a destructive test, and the specimen will not be able to continue to serve after the test. Therefore, how to conduct non-destructive safety assessment of corroded steel structures has become an important research topic for scholars from various countries.

[0005] Many researchers have attempted to study the properties of materials after corrosion through experiments, such as:

[0006] Reference 1: "Y. Garbatov, C. Guedes Soares, J. Parunov, J. Kodvanj. Tensile strength assessment of corroded small scale specimens. Corros. Sci. 85 (2014) 296-303", monotonic tensile tests were conducted on steel specimens sampled from structures corroded in actual seawater environments. The results showed that the yield strength showed a nonlinear decrease trend due to local corrosion and stress concentration.

[0007] Reference 2: "Huiyun Chen, Hongbo Liu, Zhihua Chen, Residual behavior of corroded welded hollow spherical joints subjected to eccentric loads. J. Constr. Steel Res. 182 (2021) 106661.", which studies the mechanical properties of corroded welded hollow spherical joints under eccentric loads and points out that uniform corrosion is the main indicator affecting corrosion and load-bearing characteristics.

[0008] Reference 3: "Muhammet Cerit. Corrosion pit-induced stress concentration in spherical pressure vessel. Thin Wall. Struct. 136 (2019) 106-112", studied that the stress concentration factor caused by the elliptical corrosion pit increases with the increase of the corrosion pit depth, but decreases with the increase of the corrosion pit width. Then it is proved that the corrosion pit has an important influence on the mechanical properties of the specimen. Therefore, it is necessary to count the number of corrosion specimens and describe their shapes.

[0009] Reference 4: "Haiying Wu, Honggang Lei, Y. Frank Chen, Junyi Qiao. Comparison on corrosion behavior and mechanical properties of structural steel exposed between urban industrial atmosphere and laboratory simulated environment. Constr. Build. Mater. 211 (2019) 228-243", analyzed the distribution of corrosion pits on the surface of steel samples under accelerated corrosion and atmospheric corrosion conditions, and found that in both cases, the depth of the corrosion pits obeyed the Gaussian distribution, and the thickness loss caused by corrosion increased with time in a power function. In addition, some scholars also used the finite element model (FEM) to analyze the strength degradation caused by corrosion.

[0010] To date, most corrosion tests have focused on accelerated corrosion due to the short test time. However, due to the complexity of the natural environment, accelerated corrosion tests cannot be completely equivalent to natural corrosion. Therefore, mechanical tests must be performed on atmospheric corrosion components.

[0011] In addition, although many researchers have studied the effects of corrosion pits using the finite element method, the corrosion pit parameters used in their models are not obtained through the actual corrosion morphology. This may lead to a huge deviation between the simulated strength degradation and the experimental results. However, the application of inverse reconstruction techniques based on real corrosion is limited due to the time-varying nature of the surface. Therefore, it is necessary to develop a new method to simulate random pits in finite elements and reveal the relationship between mechanical degradation and pits in other steel components.

[0012] There are two main problems with finite element simulation:

[0013] 1) The actual number of pits in structural components is generally in the order of tens of thousands or hundreds of thousands, and it is difficult to obtain the distribution and shape of the above pits.

[0014] 2) Even if a lot of money and time are spent to obtain the actual distribution and shape of the pits in the structural components, finite element modeling completely in accordance with the actual distribution and shape of the pits is also very time-consuming, requiring several months or even years to establish.

[0015] However, no relevant methods have been proposed in existing research to solve the above problems. Summary of the invention

[0016] The purpose of the present invention is to provide a corroded steel material analysis method based on pit fusion and its application, so as to overcome the shortcomings of the prior art.

[0017] The scheme of this application is as follows:

[0018] A corroded steel material analysis method based on pit fusion comprises the following steps:

[0019] Step 1, select a part of the actual corroded steel area and investigate the situation of the rust pits; after statistics, obtain the statistical parameters of the rust pits and the mass loss rate η0 of the area;

[0020] The statistical parameters of the rust pits are: the average value of the corrosion depth variance Aspect ratio.

[0021] Step 2, determining the number of pits in the entire steel component;

[0022] Step 3, create a finite element model considering corrosion pits:

[0023] A finite element model with random pitting distribution was established using ABAQUS software, and the statistical parameters of the rust pits obtained in step 1, the number of pits of the entire steel component obtained in step 2, and the positions of the surface pits were randomly and evenly distributed;

[0024] When a steel component has two exposed faces, corrosion pits should be provided on both surfaces of the component, consistent with actual corrosion;

[0025] When one side of the steel component is exposed (for example, a box-type steel beam), corrosion pits only need to be arranged on the exposed side of the steel component.

[0026] Further, step 1 includes the following sub-steps:

[0027] Step 1-1, using a 3D topography scanner to scan a representative area of ​​the steel structure to obtain a 3D topography of the corrosion surface;

[0028] Step 1-2, select several cross sections where corrosion pits can be observed from the three-dimensional morphology obtained in step 1, and obtain the corrosion pit set characteristic parameter matrix A based on the 2D plane:

[0029]

[0030] According to matrix A, we get matrix B

[0031]

[0032] Among them, for any i-th row c 3,i , use the following formula to solve:

[0033]

[0034] For data: h1, h2, …, h i ,…h m Calculate the average corrosion depth and variance

[0035] For data: c 3，1 , c 3,2 , …, c 3,i , …c 3,m , calculate its average value and variance

[0036] Will As the aspect ratio.

[0037] Further, in step 1-2, for any 2D cross section: firstly, mark the upper and lower endpoints of all the etch pits, and the marked upper and lower endpoints are expressed in the order of: "upper endpoint, lower endpoint, upper endpoint" ... "upper endpoint, lower endpoint, upper endpoint" ... "upper endpoint, lower endpoint, upper endpoint";

[0038] Let the combination of "upper endpoint, lower endpoint, upper endpoint" be called an erosion pit feature point group, and the number of the erosion pit feature point groups is g;

[0039] Take the horizontal direction of the 2D cross section as the X-axis, the positive direction from left to right as the X-axis, the vertical direction downward as the Y-axis, and the upper left corner of the initial edge of the 2D cross section as the origin (i.e. the uncorroded surface is: y=0), and record the coordinates of each endpoint;

[0040] S1, for the first pit, extract a 1，1 ,h1,c 2，1

[0041] h1=y 第1个蚀坑特征点组的下端点 ;

[0042] When 第1个蚀坑特征点组的左侧上端点 ≤y第1个蚀坑特征点组的右侧上端点 hour:

[0043] a 1，1 =(y 第1个蚀坑特征点组的下端点 -y 第1个蚀坑特征点组的左侧上端点 )

[0044] c 2，1 =(x 第1个蚀坑特征点组的下端点 -x 第1个蚀坑特征点组的左侧上端点 )

[0045] When 第1个蚀坑特征点组的左侧上端点 >y 第1个蚀坑特征点组的右侧上端点 hour:

[0046] a 1，1 =(y 第1个蚀坑特征点组的下端点 -y 第1个蚀坑特征点组的右侧上端点 )

[0047] c 2，1 =(x 第1个蚀坑特征点组的右侧上端点 -x 第1个蚀坑特征点组的下端点 )

[0048] S2, for the second pit, extract a 1，2 ,h2,c 2，2

[0049] h2=y 第2个蚀坑特征点组的下端点 ;

[0050] When 第2个蚀坑特征点组的左侧上端点 ≤y 第2个蚀坑特征点组的右侧上端点 hour:

[0051] a 1，2 =(y 第2个蚀坑特征点组的下端点 -y 第2个蚀坑特征点组的左侧上端点 )

[0052] c 2，2 =(x 第2个蚀坑特征点组的下端点 -x 第2个蚀坑特征点组的左侧上端点 )

[0053] When 第2个蚀坑特征点组的左侧上端点 >y 第2个蚀坑特征点组的右侧上端点 hour:

[0054] a 1，2 =(y 第2个蚀坑特征点组的下端点 -y 第2个蚀坑特征点组的右侧上端点 )

[0055] c 2，2 =(x 第2个蚀坑特征点组的右侧上端点 -x 第2个蚀坑特征点组的下端点 )

[0056] …

[0057] Sg, for the g-th etch pit, extract a 1，g ,h g ,c 2，g

[0058] H g =y 第g个蚀坑特征点组的下端点 ;

[0059] When 第g个蚀坑特征点组的左侧上端点 ≤y 第g个蚀坑特征点组的右侧上端点 hour:

[0060] a 1，g =(y 第g个蚀坑特征点组的下端点 -y 第g个蚀坑特征点组的左侧上端点 )

[0061] c 2，g =(x 第g个蚀坑特征点组的下端点 -x 第g个蚀坑特征点组的左侧上端点 )

[0062] When 第g个蚀坑特征点组的左侧上端点 >y 第g个蚀坑特征点组的右侧上端点 hour:

[0063] a 1，g =(y 第g个蚀坑特征点组的下端点 -y 第g个蚀坑特征点组的右侧上端点 )

[0064] c 2，g =(x 第g个蚀坑特征点组的右侧上端点 -x 第g个蚀坑特征点组的下端点 ).

[0065] Further, in step 2, the following method is used in the calculation:

[0066] First calculation:

[0067] First, assume that the number of pits in the entire steel component is n1;

[0068] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η1 of the finite element model is calculated;

[0069] If |(η0-η1) / η0|<5%, the total number of assumed pits n1 is considered to be the number of pits of the entire steel component, and the calculation is stopped;

[0070] If |(η0-η1) / η0|>5%, perform a second calculation;

[0071] Second calculation:

[0072] First, assume that the number of pits in the entire steel component is n2 (n1 is not equal to n2);

[0073] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η2 of the finite element model is calculated;

[0074] If |(η0-η2) / η0|<5%, the total number of assumed pits n2 is considered to be the number of pits in the entire steel component, and the calculation is stopped;

[0075] If |(η0-η2) / η0|>5%, perform the third calculation;

[0076] …

[0077] The kth calculation:

[0078] First, assume that the number of pits in the entire steel component is n k ;

[0079] Secondly, based on the statistical parameters of the rust pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η of the finite element model is calculated. k ;

[0080] If |(η0-η k ) / η0|<5%, that is, the total number of assumed pits n k The number of pits for the entire steel component is stopped;

[0081] If |(η0-η2) / η0|>5%, perform the k+1th calculation

[0082] …….

[0083] Further, in step 2, the following method is used in the calculation:

[0084] Initially, select L different values: n1...n L ;

[0085] First calculation:

[0086] First, assume that the number of pits in the entire steel component is n1;

[0087] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η1 of the finite element model is calculated;

[0088] Second calculation:

[0089] First, assume that the number of pits in the entire steel component is n2;

[0090] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η2 of the finite element model is calculated;

[0091] …

[0092] Lth calculation:

[0093] First, assume that the number of pits in the entire steel component is n L ;

[0094] Secondly, based on the statistical parameters of the rust pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η of the finite element model is calculated. L ;

[0095] That is, multiple sets of "pit number-mass loss rate" data are calculated. Based on this, through data fitting, we can know: the relationship between pit number and mass loss rate, according to the research;

[0096] The relationship between the number of pits n and the mass loss rate η obeys:

[0097]

[0098] In the above formula, d1, d2, d3, d4, d5 are related parameters; T is the thickness of the component;

[0099] According to the above formula, we can solve n 实际 :

[0100]

[0101] An application of a corroded steel material analysis method based on pit fusion, using the aforementioned method to analyze the bearing capacity and deformation of steel beams, steel columns or steel supports.

[0102] Beneficial effects of the present invention:

[0103] First, the basic concept of the present invention is to provide a method for finite element simulation of actual steel components, that is, how to establish a finite element model to analyze the bearing capacity and deformation of corroded steel. Specifically, it combines refined reverse modeling numerical simulation technology and calls Python's NumPy function library to realize the true distribution of corrosion pits, truly simulate the mechanical properties of steel after corrosion, and realize non-destructive evaluation of its remaining mechanical properties.

[0104] The framework of this application method is:

[0105] Step 1, select a part of the corroded steel area and investigate the condition of the rust pits; after statistics, obtain the statistical parameters of the rust pits and the mass loss rate η0 of the area;

[0106] The statistical parameters of the rust pits are: the average value and variance of the corrosion depth h; the average value and variance of the corrosion width c;

[0107] Step 2, determining the number of pits in the entire steel component;

[0108] Step 3, create a finite element model considering corrosion pits:

[0109] A finite element model with random pitting distribution is established using ABAQUS software: according to the statistical parameters of the rust pits obtained in step 1 and the number of pits of the entire steel component obtained in step 2, the pits are randomly and evenly distributed on the steel surface on the finite element model;

[0110] When a steel component has two exposed faces, corrosion pits should be provided on both surfaces of the component, consistent with actual corrosion;

[0111] When one side of the steel component is exposed (e.g. box-type steel beam), corrosion pits only need to be arranged on the exposed side of the steel component;

[0112] Step 4: By calculating the finite element model, the stress and strain information of the corroded steel can be obtained.

[0113] Second, the second inventive point of the present invention is that it proposes a method for determining the number of pits in the entire steel component; the determined calculation method: estimating the number of pits in the entire steel component based on the mass loss rate is the core point of this application.

[0114] However, how to estimate the number of corrosion pits in the entire steel component based on the mass loss rate is a major challenge in actual modeling.

[0115] This application proposes: calculating multiple sets of "pit number-mass loss rate" and then finding the law between the two through data fitting. Through trial calculations of various actual components, the relationship between the pit number n and the mass loss rate η obeys the following relationship:

[0116]

[0117] In the above formula, d1, d2, d3, d4, d5 are related parameters; T is the thickness of the component.

[0118] According to the above formula, we can solve n 实际 :

[0119]

[0120] Thirdly, the third inventive point of the present invention is to consider the influence of pit fusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0121] The present application is further described in detail below in conjunction with the embodiments in the accompanying drawings, but does not constitute any limitation to the present application.

[0122] Figure 1 This is a schematic diagram of the simplified method.

[0123] Figure 2 It is a schematic diagram of the three-dimensional morphology of the corroded surface.

[0124] Figure 3 It is a schematic diagram of the extraction pit depth and lateral or longitudinal diameter.

[0125] Figure 4 is a schematic diagram of the method of the present application.

[0126] Figure 5 Schematic diagram of the cross section of the statistical model of the method of the present application (for the etch pit A2).

[0127] Figure 6 This is the ac relationship diagram of this application (for Fig.12 Instances of ).

[0128] Figure 7 This is a schematic diagram of the distribution of the depth-frequency of corrosion pits (for Fig.12 Instances of ).

[0129] Figure 8 This is a schematic diagram of the distribution of the depth-to-diameter ratio of the corrosion pits (for Fig.12 Instances of ).

[0130] Fig. 9 is a schematic diagram of the relationship between the average mass loss rate and the number of pits (for Fig.12 Instances of ).

[0131] Fig.10 It is a schematic diagram of the finite element model of this application.

[0132] Fig.11 It is a flow chart of the method of this application.

[0133] Fig.12 This is a picture of actual corroded steel parts.

[0134] Fig.13 It is a comparison diagram of the "stress-strain curve" calculated by the method of the present application and the actual test. DETAILED DESCRIPTION

[0135] <Example 1: Corroded steel bearing capacity analysis method based on pit fusion>

[0136] Combined with Fig.11 As shown, the method for analyzing the bearing capacity of corroded steel based on pit fusion proposed in this application includes the following steps:

[0137] Step 1, select a part of the actual corroded steel area and investigate the situation of the rust pits; after statistics, obtain the statistical parameters of the rust pits and the mass loss rate η0 of the area;

[0138] The statistical parameters of the rust pits are: the average value and variance of the corrosion depth h; the average value and variance of the corrosion width c;

[0139] Step 2, determining the number of pits in the entire steel component;

[0140] Step 3, create a finite element model considering corrosion pits:

[0141] A finite element model with random pitting distribution was established using ABAQUS software, and the statistical parameters of the rust pits obtained in step 1, the number of pits of the entire steel component obtained in step 2, and the positions of the surface pits were randomly and evenly distributed;

[0142] When a steel component has two exposed faces, corrosion pits should be simulated on both surfaces of the component to match the actual corrosion;

[0143] When one side of the steel component is exposed (for example, a box-type steel beam), corrosion pits only need to be arranged on the exposed side of the steel component.

[0144] Fig.10 The established finite element model is given, from which the fusion phenomenon of corrosion pits can be clearly seen.

[0145] Step 4: Repeat step 3 and perform multiple simulations to avoid random errors caused by a single random simulation.

[0146] <Example 2: Determining the number of pits in the entire steel component; Determining>

[0147] There are two ways to perform step 2 of the first embodiment.

[0148] First way:

[0149] First calculation:

[0150] First, assume that the number of pits in the entire steel component is n1;

[0151] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η1 of the finite element model is calculated;

[0152] If |(η0-η1) / η0|<5%, the total number of assumed pits n1 is considered to be the number of pits of the entire steel component, and the calculation is stopped;

[0153] If |(η0-η1) / η0|>5%, perform a second calculation;

[0154] Second calculation:

[0155] First, assume that the number of pits in the entire steel component is n2 (n1 is not equal to n2);

[0156] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η2 of the finite element model is calculated;

[0157] If |(η0-η2) / η0|<5%, the total number of assumed pits n2 is considered to be the number of pits in the entire steel component, and the calculation is stopped;

[0158] If |(η0-η2) / η0|>5%, perform the third calculation;

[0159] …

[0160] The kth calculation:

[0161] First, assume that the number of pits in the entire steel component is n k ;

[0162] Secondly, based on the statistical parameters of the rust pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η of the finite element model is calculated. k ;

[0163] If |(η0-η k ) / η0|<5%, that is, the total number of assumed pits n k The number of pits for the entire steel component is stopped;

[0164] If |(η0-η2) / η0|>5%, perform the k+1th calculation

[0165] …….

[0166] The above method is suitable for the case where the number of etch pits is small.

[0167] The second method: When the number of pits is large, the first method is actually very inconvenient. In this regard, the following method is proposed:

[0168] Initially, select L different values: n1...n L ;

[0169] First calculation:

[0170] First, assume that the number of pits in the entire steel component is n1;

[0171] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η1 of the finite element model is calculated;

[0172] Second calculation:

[0173] First, assume that the number of pits in the entire steel component is n2;

[0174] Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η2 of the finite element model is calculated;

[0175] …

[0176] Lth calculation:

[0177] First, assume that the number of pits in the entire steel component is n L ;

[0178] Secondly, based on the statistical parameters of the rust pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η of the finite element model is calculated. L ;

[0179] That is, multiple sets of "pit number-mass loss rate" data are calculated. Based on this, through data fitting, we can know: the relationship between pit number and mass loss rate, according to the research;

[0180] The relationship between the number of pits n and the mass loss rate η obeys:

[0181]

[0182] In the above formula, d1, d2, d3, d4, d5 are related parameters; T is the thickness of the component.

[0183] According to the above formula, we can solve n 实际 :

[0184]

[0185] like Fig. 9 As shown, it is a steel component ( Fig.12 ) of the η-n relationship curve, which conforms to the above formula:

[0186]

[0187] It is particularly important to note that the inventors have also modeled other components and found that the above relationship between the number of corrosion pits n and the mass loss rate η is also applicable.

[0188] <Example 3: Statistical method of pit parameters>

[0189] Another big problem of Example 1 is how to count the pit parameters. Its significance lies in that for steel structures, the statistical method of the pit parameters of corroded steel is one of the most basic and critical issues. The evolution of pits is a process from independent pitting to uniform corrosion. Since pitting causes local weakening, stress concentration is prone to occur at the pitting location, which has a significant impact on the mechanical properties of steel. Therefore, accurate statistics of pits are of great significance to the study of steel corrosion.

[0190] There are two analysis methods for the statistics of pit parameters:

[0191] 1) Consider the method of pit fusion:

[0192] Step 1, using a 3D topography scanner to scan a representative area of ​​the steel structure to obtain a 3D topography of the corrosion surface;

[0193] Step 2, selecting a cross section where corrosion pits can be clearly observed from the three-dimensional morphology obtained in step 1, and obtaining a characteristic parameter matrix A of the corrosion pit set based on the 2D plane;

[0194]

[0195] According to matrix A, we get matrix B

[0196]

[0197] Among them, for any i-th row c 3,i , use the following formula to solve:

[0198]

[0199] For data: h1, h2, …, h i ,…h m Calculate the average And the variance V h :

[0200] For data: c 3，1 , c 3,2 , …, c 3,i , …c 3,m , calculate its average value and variance

[0201] Will Depth of corrosion as a collection of pits;

[0202] Will As the aspect ratio ( Figure 6 a / c is used to represent the aspect ratio).

[0203] 2) Simplified method:

[0204] Step 1, using a 3D topography scanner to scan a representative area of ​​the steel structure to obtain a 3D topography of the corrosion surface;

[0205] Step 2, selecting a cross section where the corrosion pits can be clearly observed from the three-dimensional morphology obtained in step 1, and obtaining a characteristic parameter matrix B of the corrosion pit set based on the 2D plane;

[0206]

[0207] For data: z 1，1 , z1,2 ,…,z 1,i , …z 1,j Calculate the average and variance

[0208] For data: U 1，1 , U 1,2 ,…,U 1,i , …U 1,j , calculate its average value and variance

[0209] Will Depth of corrosion as a collection of pits;

[0210] Will As the aspect ratio ( Figure 6 a / c is used to represent the aspect ratio).

[0211] From the above, we can know the main differences between the two methods of considering merging pits and simplifying methods:

[0212] 1) As attached Figure 1 As shown in the figure, the fused pit A1 is regarded as the whole pit with enlarged diameter and pit depth (Z1 represents the depth of the merged pit, 2U1 represents the width of the merged pit), that is, the pit is regarded as a whole, and the fusion phenomenon is ignored. However, in the actual corrosion process, the fusion phenomenon of pits is inevitable, so the use of simplified methods for the statistics of corrosion pits will cause a large error between the pit parameters and the actual situation.

[0213] 2) The number of rows of the matrix B counted by the above two methods is also different, and the simplified method is smaller than the method considering pit fusion.

[0214] The following is a further explanation of the method of considering pit fusion:

[0215] like Figure 5 As shown,

[0216] Take point AE in the figure as an example to explain how to extract the characteristic parameter matrix A of the pit set when considering pit fusion;

[0217]

[0218] h i represents the i-th corrosion depth, that is, the height from the global reference surface to the corrosion endpoint of the pit, a 1,i Indicates the height between the upper end point of the pit and the corrosion end point of the pit, c 2,i It represents the projection length of the upper endpoint of the pit from the corrosion endpoint of the pit on the horizontal plane.

[0219] Specifically, the instructions are as follows:

[0220] like Figure 5 As shown, establish the XY axis: take the horizontal direction of the 2D section as the X axis (the direction from point A to point E is the positive direction of the X axis), take the vertical downward direction as the Y axis, take the lower left corner of the initial side of the 2D section as the origin, and record the coordinates of each endpoint;

[0221] Let the coordinates of point A be (X A ,Y A ),B(X B ,Y B ),…,E(X E ,Y E ).

[0222] Therefore, the depth of AE is Y A , …, Y E .

[0223] Here are the steps:

[0224] First, use the three points AC to determine the pit A2:

[0225] 1. Compare Y A With Y C The size of y A <y C ,a1=(y B -y A ),c2=(x B -x A ); On the contrary, a1=(y B -y C ),c2=(x C -x B );

[0226] h1=y B ;

[0227] Secondly, use the three CE points to determine the pit B2:

[0228] 2. Compare Y C With Y E The size of Y C >Y E , then a1=(Y E -Y D ),c2=(X E -X D ); On the contrary, a1=(Y E -Y C ),c2=(X D -X C );

[0229] h1=y D ;

[0230] The advantage of this determination is that the two pits can be related through point C.

[0231] For any 2D cross section: First, the researchers mark the upper and lower endpoints. The order of the marked upper and lower endpoints is expressed as: "upper endpoint, lower endpoint, upper endpoint" ... "upper endpoint, lower endpoint, upper endpoint" ... "upper endpoint, lower endpoint, upper endpoint";

[0232] Let the combination of "upper endpoint, lower endpoint, upper endpoint" be called a pit feature point group (essentially a pit), and the number of the pit feature point groups is g;

[0233] Take the horizontal direction of the 2D cross section as the X-axis, the positive direction from left to right as the X-axis, the vertical direction downward as the Y-axis, and the upper left corner of the initial edge of the 2D cross section as the origin (i.e. the uncorroded surface is: y=0), and record the coordinates of each endpoint;

[0234] S1, for the first pit, extract a 1，1 ,h1,c 2，1

[0235] h1=y 第1个蚀坑特征点组的下端点 ;

[0236] When 第1个蚀坑特征点组的左侧上端点 ≤y 第1个蚀坑特征点组的右侧上端点 hour:

[0237] a 1，1 =(y 第1个蚀坑特征点组的下端点 -y 第1个蚀坑特征点组的左侧上端点 )

[0238] c 2，1 =(x 第1个蚀坑特征点组的下端点 -x 第1个蚀坑特征点组的左侧上端点 )

[0239] When 第1个蚀坑特征点组的左侧上端点 >y 第1个蚀坑特征点组的右侧上端点 hour:

[0240] a 1，1 =(y 第1个蚀坑特征点组的下端点 -y 第1个蚀坑特征点组的右侧上端点 )

[0241] c 2，1 =(x 第1个蚀坑特征点组的右侧上端点 -x 第1个蚀坑特征点组的下端点 )

[0242] S2, for the second pit, extract a 1，2 ,h2,c 2，2

[0243] h2=y 第2个蚀坑特征点组的下端点 ;

[0244] When第2个蚀坑特征点组的左侧上端点 ≤y 第2个蚀坑特征点组的右侧上端点 hour:

[0245] a 1，2 =(y 第2个蚀坑特征点组的下端点 -y 第2个蚀坑特征点组的左侧上端点 )

[0246] c 2，2 =(x 第2个蚀坑特征点组的下端点 -x 第2个蚀坑特征点组的左侧上端点 )

[0247] When 第2个蚀坑特征点组的左侧上端点 >y 第2个蚀坑特征点组的右侧上端点 hour:

[0248] a 1，2 =(y 第2个蚀坑特征点组的下端点 -y 第2个蚀坑特征点组的右侧上端点 )

[0249] c 2，2 =(x 第2个蚀坑特征点组的右侧上端点 -x 第2个蚀坑特征点组的下端点 )

[0250] …

[0251] Sg, for the g-th etch pit, extract a 1，g ,h g ,c 2，g

[0252] h g =y 第g个蚀坑特征点组的下端点 ;

[0253] When 第g个蚀坑特征点组的左侧上端点 ≤y 第g个蚀坑特征点组的右侧上端点 hour:

[0254] a 1，g =(y 第g个蚀坑特征点组的下端点 -y 第g个蚀坑特征点组的左侧上端点 )

[0255] c 2，g =(x 第g个蚀坑特征点组的下端点 -x 第g个蚀坑特征点组的左侧上端点 )

[0256] When 第g个蚀坑特征点组的左侧上端点 >y 第g个蚀坑特征点组的右侧上端点 hour:

[0257] a 1，g =(y 第g个蚀坑特征点组的下端点 -y 第g个蚀坑特征点组的右侧上端点 )

[0258] c 2，g =(x 第g个蚀坑特征点组的右侧上端点 -x 第g个蚀坑特征点组的下端点 )

[0259] Parameter explanation:

[0260] Global reference plane: the plane where the highest point of the corrosion surface of the steel plate is located (the plane where the highest point of the 3D topography scanning result is located. If the specimen has an uncorroded surface (a surface with no corrosion at all), it is taken as uncorroded; the position of this plane is determined as the plane where the highest point of the 3D topography scanning result is located or the plane where the uncorroded surface is located).

[0261] Reference surface b1: The plane where the depths of the left end point and the right end point of the erosion pit are higher.

[0262] Z1 represents the depth of the etch pit A1.

[0263] Z represents the corrosion depth of the etch pit A1.

[0264] 2U1 represents the corrosion width of the etch pit A1.

[0265] a1 represents the depth of the etch pit A2 or the etch pit A1.

[0266] a2 represents the local uniform corrosion depth of the etch pit A2.

[0267] h represents the corrosion depth of the etch pit A2.

[0268] a represents the depth of the etch pit obtained according to etch pit A2 / B2.

[0269] c represents the radius of the pit obtained based on pit A2 / B2.

[0270] l1 means Figure 5 The height difference between points AB in .

[0271] l2 represents Figure 5 The height difference of the CB point in .

[0272] l4 means Figure 5 The height difference between points DE in .

[0273] <Test Comparison>

[0274] Fig.12 is a corroded steel part, and the finite element model established for it is Fig.10 ( Figure 6-9 The statistical results are for Fig.12 The actual corrosion statistics of steel parts).

[0275] The corroded steel parts were subjected to tension test to obtain the actual stress-strain curve. The above process was simulated by finite element method to obtain the actual simulated stress-strain curve.

[0276] Fig.13 Middle: The solid black line represents the test, and the five dashed lines represent the results of five finite element simulations (the random distribution of pits is different each time, so more simulations are required); Fig.13It can be seen that the results of this application are consistent with the actual results and are feasible.

[0277] The above embodiments are preferred implementation modes of the present invention and are only used to facilitate the description of the present invention. They are not intended to limit the present invention in any form. Any person with ordinary knowledge in the relevant technical field, if they do not depart from the scope of the technical features of the present invention, can make equivalent embodiments by partial changes or modifications to the technical contents disclosed in the present invention, and they still fall within the scope of the technical features of the present invention without departing from the technical features of the present invention.

Claims

1. A corroded steel material analysis method based on pit fusion, characterized in that: The steps include: Step 1, select a part of the actual corroded steel area and investigate the situation of the rust pits; after statistics, obtain the statistical parameters of the rust pits and the mass loss rate η0 of the area; The statistical parameters of the rust pits are: the average value of the corrosion depth variance Aspect ratio; Step 2, determining the number of pits in the entire steel component; Step 3, create a finite element model considering corrosion pits: A finite element model with random pitting distribution was established using ABAQUS software, and the statistical parameters of the rust pits obtained in step 1, the number of pits of the entire steel component obtained in step 2, and the positions of the surface pits were randomly and evenly distributed; When a steel component has two exposed faces, corrosion pits should be provided on both surfaces of the component, consistent with actual corrosion; When one side of the steel component is exposed, the corrosion pit only needs to be arranged on the exposed side of the steel component; Step 2: When calculating, use the following method: First calculation: First, assume that the number of pits in the entire steel component is n1; Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η1 of the finite element model is calculated; If |(η0-η1) / η0|<5%, the total number of assumed pits n1 is considered to be the number of pits of the entire steel component, and the calculation is stopped; If |(η0-η1) / η0|>5%, perform a second calculation; Second calculation: First, assume that the number of pits in the entire steel component is n2, and n1 is not equal to n2; Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η2 of the finite element model is calculated; If |(η0-η2) / η0|<5%, the total number of assumed pits n2 is considered to be the number of pits in the entire steel component, and the calculation is stopped; If |(η0-η2) / η0|>5%, perform the third calculation; The kth calculation: First, assume that the number of pits in the entire steel component is n k ; Secondly, based on the statistical parameters of the rust pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η of the finite element model is calculated. k ; If |(η0-η k ) / η0|<5%, that is, the total number of assumed pits n k The number of pits for the entire steel component is stopped; If |(η0-η2) / η0|>5%, perform the k+1th calculation.

2. A corroded steel material analysis method based on pit fusion, characterized in that: The steps include: Step 1, select a part of the actual corroded steel area and investigate the situation of the rust pits; after statistics, obtain the statistical parameters of the rust pits and the mass loss rate η0 of the area; The statistical parameters of the rust pits are: the average value of the corrosion depth variance Aspect ratio; Step 2, determining the number of pits in the entire steel component; Step 3, create a finite element model considering corrosion pits: A finite element model with random pitting distribution was established using ABAQUS software, and the statistical parameters of the rust pits obtained in step 1, the number of pits of the entire steel component obtained in step 2, and the positions of the surface pits were randomly and evenly distributed; When a steel component has two exposed faces, corrosion pits should be provided on both surfaces of the component, consistent with actual corrosion; When one side of the steel component is exposed, the corrosion pit only needs to be arranged on the exposed side of the steel component; Step 2: When calculating, use the following method: Initially, select L different values: n1...n L ; First calculation: First, assume that the number of pits in the entire steel component is n1; Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η1 of the finite element model is calculated; Second calculation: First, assume that the number of pits in the entire steel component is n2; Secondly, based on the statistical parameters of the corrosion pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η2 of the finite element model is calculated; Lth calculation: First, assume that the number of pits in the entire steel component is n L ; Secondly, based on the statistical parameters of the rust pits obtained in step 1, a finite element model of the entire steel component is established, and the mass loss rate η of the finite element model is calculated. L ; That is, multiple sets of "pit number-mass loss rate" data are calculated. Based on this, through data fitting, we can know: the relationship between pit number and mass loss rate, according to the research; The relationship between the number of pits n and the mass loss rate η obeys: In the above formula, d1, d2, d3, d4, d5 are related parameters; T is the thickness of the component; According to the above formula, we can solve n 实际 :

3. A corroded steel material analysis method based on pit fusion according to claim 1 or 2, characterized in that: For step 1, it includes the following sub-steps: Step 1-1, using a 3D topography scanner to scan a representative area of ​​the steel structure to obtain a 3D topography of the corrosion surface; Step 1-2, select several cross sections where corrosion pits can be observed from the three-dimensional morphology obtained in step 1, and obtain the corrosion pit set characteristic parameter matrix A based on the 2D plane: According to matrix A, we get matrix B Among them, for any i-th row c 3,i , solve it using the following formula: For data: h1, h2,…, h i ,…h m Calculate the average corrosion depth and variance For data: c 3，1 , c 3,2 , …, c 3,i , …c 3,m , calculate its average value and variance Will As the aspect ratio.

4. The method for analyzing corroded steel based on pit fusion according to claim 3, characterized in that: In step 1-2, for any 2D cross section: first mark the upper and lower endpoints of all the etch pits, and the marked upper and lower endpoints are expressed in the order of "upper endpoint, lower endpoint, upper endpoint" ... "upper endpoint, lower endpoint, upper endpoint" ... "upper endpoint, lower endpoint, upper endpoint"; Let the combination of "upper endpoint, lower endpoint, upper endpoint" be called an erosion pit feature point group, and the number of the erosion pit feature point groups is g; Take the horizontal direction of the 2D section as the X-axis, the positive direction from left to right as the X-axis, the vertical direction downward as the Y-axis, and the upper left corner of the initial edge of the 2D section as the origin, that is, the uncorroded surface is: y = 0, and record the coordinates of each endpoint; S1, for the first pit, extract a 1，1 ,h1,c 2，1 h1=y 第1个蚀坑特征点组的下端点 ; When 第1个蚀坑特征点组的左侧上端点 ≤y 第1个蚀坑特征点组的右侧上端点 hour: to 1，1 (and 第1个蚀坑特征点组的下端点 -and 第1个蚀坑特征点组的左侧上端点 ) c 2，1 =(x 第1个蚀坑特征点组的下端点 -x 第1个蚀坑特征点组的左侧上端点 ) When 第1个蚀坑特征点组的左侧上端点 >y 第1个蚀坑特征点组的右侧上端点 hour: to 1，1 (and 第1个蚀坑特征点组的下端点 -and 第1个蚀坑特征点组的右侧上端点 ) c 2，1 =(x 第1个蚀坑特征点组的右侧上端点 -x 第1个蚀坑特征点组的下端点 ) S2, for the second pit, extract a 1，2 ,h2,c 2，2 h2=y 第2个蚀坑特征点组的下端点 ; When 第2个蚀坑特征点组的左侧上端点 ≤y 第2个蚀坑特征点组的右侧上端点 hour: to 1，2 (and 第2个蚀坑特征点组的下端点 -and 第2个蚀坑特征点组的左侧上端点 ) c 2，2 =(x 第2个蚀坑特征点组的下端点 -x 第2个蚀坑特征点组的左侧上端点 ) When 第2个蚀坑特征点组的左侧上端点 >y 第2个蚀坑特征点组的右侧上端点 hour: to 1，2 (and 第2个蚀坑特征点组的下端点 -and 第2个蚀坑特征点组的右侧上端点 ) c 2，2 =(x 第2个蚀坑特征点组的右侧上端点 -x 第2个蚀坑特征点组的下端点 ) Sg, for the g-th etch pit, extract a 1，g ,h g ,c 2，g H g =y 第g个蚀坑特征点组的下端点 ; When 第g个蚀坑特征点组的左侧上端点 ≤y 第g个蚀坑特征点组的右侧上端点 hour: to 1，g (and 第g个蚀坑特征点组的下端点 -and 第g个蚀坑特征点组的左侧上端点 ) c 2，g =(x 第g个蚀坑特征点组的下端点 -x 第g个蚀坑特征点组的左侧上端点 ) When 第g个蚀坑特征点组的左侧上端点 >y 第g个蚀坑特征点组的右侧上端点 hour: to 1，g (and 第g个蚀坑特征点组的下端点 -and 第g个蚀坑特征点组的右侧上端点 ) c 2，g =(x 第g个蚀坑特征点组的右侧上端点 -x 第g个蚀坑特征点组的下端点 )。 5. An application of a corroded steel material analysis method based on pit fusion, characterized in that: The method as claimed in claim 1 or 2 is used to analyze the bearing capacity of a steel beam, steel column or steel support.

6. An application of a corroded steel material analysis method based on pit fusion, characterized in that: The method according to claim 1 or 2 is used to analyze the deformation of a steel beam, a steel column or a steel support.

Images