Wind tunnel test method for erosive wear of wind-sand two-phase flow to galvanized coating of steel member

Abstract

A wind tunnel test method for erosive wear of wind-sand two-phase flow to a galvanized coating of a steel member is characterized by comprising the following steps: step 1, constructing a steel member model with the galvanized coating; 2, performing a wind tunnel test on the steel member model based on the dimensionless wind speed and erosion angle parameters, and constructing a steel member model zinc coating erosion rate calculation model based on the dimensionless wind speed and erosion angle influence; 3, based on the erosion rate calculation model of the zinc coating of the steel member model, performing wind tunnel test on the steel member model under the working conditions of different test piece length-width ratios and test piece distances according to the wind speed and wind sand concentration data of the target area to obtain the optimal test piece length-width ratio and test piece distance of the steel member model; and 4, constructing an optimal steel member suitable for the target area according to the optimal length-width ratio of the test piece and the distance between the test pieces. The method has the effect that the erosion wear of the galvanized coating of the steel member is accurately predicted.

Description

Technical Field

[0001] The invention relates to the technical field of wind-sand erosion and wear, in particular to a wind tunnel test method for erosion and wear of a galvanized coating of a steel component by a two-phase flow of wind and sand. Background Art

[0002] Due to the long-term erosion of steel components in areas with strong sandstorms, their resistance systems have weakened. Existing structural design methods in various countries only meet design requirements under expected loads, ignoring changes in structural performance during operation. Wind and sand erosion damages and destroys the coatings on steel components such as bridges, communication towers, and transmission towers. Furthermore, the harsh natural environment of strong sandstorms leads to accumulated fatigue damage and a gradual decline in performance, which in turn reduces the durability and safety of steel structures.

[0003] Before studying the erosion and wear of steel components by wind-blown sand, it is necessary to distinguish the movement patterns of wind-blown sand. To investigate the motion patterns of wind-blown sand flows, Ryoma Kawamura decomposed the forces acting on the bed into air shear stress and particle shear stress, and proposed a formula for the sand transport rate that includes the critical friction velocity. Under the influence of wind, sand particles undergo three basic motion patterns: creep, saltation, and suspension, which form wind-blown sand flows. The movement patterns of sand particles are related to wind speed and particle size. Suspension and saltation can be distinguished based on particle size, or by the ratio of the terminal settling velocity of the sand particles to the vertical diffusion velocity of the fluid. There are four major dust storm-prone regions worldwide: Central Asia, North America, the Middle East, and Oceania. Central Asian dust storms are primarily located in northwestern and northern China; North American dust storms are primarily found in the western United States and northern Mexico; Middle Eastern dust storms are primarily found along the southern edge of the Sahara Desert in Africa; and Oceanian dust storms are primarily found in western, south-central, and central Australia. The sand particle size distribution mainly ranges from 150μm to 400μm, and the main form of sand movement is saltation. Based on the measured data from the Toksun East observation point, the density of the wind-blown sand flow at different heights was calculated. The results show that the sand concentration at the bottom of the structure is much greater than that at the top, resulting in the lower components being more severely affected by erosion and wear than the upper components.

[0004] The erosion wear theory of particle-eroded materials can be used to analyze the effects of wind and sand on the erosion wear of steel components. Currently, the erosion wear theory of plastic materials mainly involves micro-cutting, deformation wear, and extrusion forging. Research on the factors affecting erosion wear has shown that plastic materials have a significant "particle size effect." The erosion rate increases with increasing particle size within a certain range. When the particle size reaches a certain critical value, the erosion rate changes little. When the particle size is below a certain value, the material does not suffer significant damage but instead exhibits a circumferential flow phenomenon. Furthermore, the hardness and toughness of the material affect the amount of erosion wear at different angles. Erosion wear is also affected by service conditions such as erosion angle, temperature, interference between particle impact and rebound, and particle shape and size. Therefore, erosion wear is a complex process in which multiple factors interact.

[0005] The impact and erosion of sand flow on the surface materials of structural components during movement (wind-sand action) have a complex wind-sand-component coupling effect. Wind tunnel testing is an effective means to deeply study the erosion and wear of components caused by sand. Existing studies have mostly used the airflow sand injection method to carry out local erosion and wear tests of materials under the action of sand. The results show that the erosion mechanical parameters (erosion speed, angle, concentration and time) will affect the erosion and wear resistance of the material.

[0006] The above research has achieved many results in the theory, influencing factors and experiments of wind-sand movement and erosion wear, laying the foundation for conducting wind tunnel tests on the erosion wear of steel components caused by wind-sand two-phase flow.

[0007] Disadvantages of existing technologies: Current experimental studies mostly use the airflow sand injection method, which does not form a uniform wind and sand flow field with a relatively stable wind and sand concentration, resulting in insufficient simulation of flow field parameters; erosion and wear are performed on local rather than overall components, resulting in insufficient representativeness of the test results; and more attention is paid to erosion mechanical parameters while little attention is paid to the study of specimen size effect and spacing effect. Summary of the Invention

[0008] The present invention provides a wind tunnel test method for the erosion and wear of galvanized coatings on steel components caused by two-phase flow of wind and sand. The wind tunnel test studies the erosion and wear laws of galvanized specimens at different erosion angles and wind speeds, as well as different specimen aspect ratios and different specimen spacings, thereby achieving accurate prediction of the erosion and wear of galvanized coatings on steel components.

[0009] To achieve the above-mentioned object, the present invention provides a wind tunnel test method for the erosion and wear of galvanized coatings on steel components caused by two-phase flow of wind and sand, the key of which is to include the following steps:

[0010] Step 1: Build a model of the steel component with galvanized coating;

[0011] Step 2: Conducting a wind tunnel test on the steel component model based on dimensionless wind speed and erosion angle parameters to verify the influence of dimensionless wind speed and erosion angle on the erosion rate of the steel component model, and constructing an erosion rate calculation model for the galvanized layer of the steel component model based on the influence of dimensionless wind speed and erosion angle based on the test data;

[0012] Step 3: Based on the calculation model for the erosion rate of the galvanized layer of the steel component model, wind tunnel tests are conducted on the steel component model under various specimen aspect ratios and specimen spacing conditions according to the wind speed and wind sand concentration data of the target area. The optimal specimen aspect ratio and optimal specimen spacing of the steel component model are obtained through the test.

[0013] Step 4: Construct the optimal steel structure suitable for the target area based on the optimal specimen aspect ratio and optimal specimen spacing.

[0014] Through the above design, the present invention studies the erosion wear law of galvanized specimens under different erosion mechanical parameters (erosion time, erosion angle and wind speed), different specimen aspect ratios and different specimen spacing through wind tunnel tests. The results show that as the erosion angle increases, the erosion rate E of the galvanized coating first increases and then decreases. When the wind direction is 19° to the longitudinal axis of the specimen, that is, when the erosion is 19°, the angle erosion effect is the largest. The E value of the galvanized steel sheet coating decreases with the increase of the aspect ratio. Based on the wind tunnel test, a calculation model for the erosion rate of the galvanized layer of the steel component model under the action of wind and sand was constructed, which can realize the accurate calculation of the erosion rate of the galvanized layer of the steel component under different wind speeds and erosion angles.

[0015] Preferably, the steel component model is divided into angle steel specimens, steel pipe specimens and steel plate specimens according to the cross-sectional form;

[0016] The size and quantity of each specimen are shown in Table 2:

[0017] Table 2

[0018]

[0019] As a preference: In the wind tunnel test, the test condition parameter settings and test data for various specimens are as follows:

[0020] Time conditions were set for the angle steel specimens and steel pipe specimens. The angle steel specimens were arranged at a 45° erosion angle, and the steel pipe specimens were arranged at a 90° erosion angle. The test wind speed for the angle steel specimens and the steel pipe specimens was 33.71 m / s, and the continuous erosion time was 30, 60, 90, 120, 180, 240, and 300 min. After each stage of erosion time, data was collected from the test specimens. After the data collection was completed, the next stage of the test was carried out on the specimen until the end.

[0021] The test data of angle steel specimens under various erosion times are shown in Table 3:

[0022] Table 3

[0023]

[0024] The test data of steel pipe specimens under various erosion times are shown in Table 4:

[0025] Table 4

[0026]

[0027] The diagonal steel specimens and the 200 mm long steel plate specimens were set to erosion angle conditions, with a wind speed of 33.71 m / s, an erosion time of 40 min, an erosion angle of 15° to 90°, and an interval of 15°.

[0028] The test data of angle steel specimens at various erosion angles are shown in Table 5:

[0029] Table 5

[0030]

[0031]

[0032] The test data of steel plate specimens at various erosion angles are shown in Table 6:

[0033] Table 6

[0034]

[0035] The diagonal steel specimens and steel plate specimens were set with dimensionless wind speed conditions, erosion angle of 45°, erosion time of 120 min, and wind speeds of 33.71, 23.16, and 16.43 m / s, respectively;

[0036] The test data of angle steel specimens under various dimensionless wind speeds are shown in Table 7:

[0037] Table 7

[0038]

[0039] The test data of the steel plate specimens under various dimensionless wind speeds are shown in Table 8:

[0040] Table 8

[0041]

[0042] The steel plate specimens were set to the aspect ratio working condition, wind speed 33.71m / s, erosion angle 45°, erosion time 60min, length 50mm~300mm, and interval 50mm;

[0043] The test data of steel plate specimens under various aspect ratios are shown in Table 9:

[0044] Table 9

[0045]

[0046] The maximum spacing that can be set in the high-speed test section is 30d, where d is the outer diameter of the steel pipe. The spacing conditions for the steel pipe specimens are set at a wind speed of 33.71m / s, an erosion angle of 90°, an erosion time of 60min, and spacings of 2, 4, 6, 8, 10, 15, 20, and 30d.

[0047] The test data of steel pipe specimens at various spacings are shown in Table 10:

[0048] Table 10

[0049]

[0050] As a preferred method, the erosion rate calculation model of the galvanized layer of the steel component model based on the influence of dimensionless wind speed and erosion angle is:

[0051] The calculation model of the erosion rate of the galvanized layer of the angle steel specimen is as follows:

[0052]

[0053] The calculation model of the erosion rate of the galvanized layer of the steel plate specimen is as follows:

[0054]

[0055] Where n1 is the first natural frequency of the specimen under the fixed constraints at both ends; L c is the characteristic length of the specimen, which is the thickness of the specimen here; is the impact velocity of the sand particles, is the average wind speed; is the dimensionless wind speed; α is the erosion angle; E is the erosion rate; subscript SA refers to the angle steel specimen; subscript SA refers to the steel plate specimen.

[0056] The wind speed indexes for erosion of galvanized angle steel and steel plate are 2.41 and 2.33, respectively.

[0057] As a preference: in step 3, the aspect ratio data of the steel plate specimen is fitted according to the erosion rate E, and the determination coefficient R is set. 2 =0.834, the erosion rate expression of the steel plate specimen based on the influence of dimensionless wind speed, erosion angle, and aspect ratio is obtained as follows:

[0058]

[0059] E SP (λ ar )=0.77λ ar-0.22

[0060] Among them, λ ar Indicates the aspect ratio.

[0061] The erosion rate of steel plates decreases with increasing aspect ratio and gradually stabilizes. Using an erosion rate expression for steel plate specimens based on wind speed, erosion angle, and aspect ratio, we can calculate the optimal aspect ratio for steel plate products in the target area, thereby reducing the erosion rate of steel plate products when used in the target area and extending the service life of the steel plate.

[0062] Preferably, in step 3, when steel pipe specimens are used in structures in areas with strong wind and sand, the optimal control range of the specimen spacing S / D is (5, 7) d or (14, 16) d.

[0063] As the spacing between the steel pipes increases, the E ratio between the front and rear pipes first decreases, then increases, then decreases again, and then increases again, forming a "W"-shaped distribution. This is likely due to changes in the flow field, vortex shedding, and the interaction between the wake and the downstream pipe. To minimize the impact of wind and sand erosion on galvanized steel components, the spacing between components should be kept around 6 or 15d when designing lattice structures in areas with strong winds and sand.

[0064] Preferably, the wind tunnel used in the wind tunnel test adopts a closed recirculation wind tunnel with an axial flow fan, and the closed recirculation wind tunnel has two test sections, wherein the low-speed test section is 1.5m wide, 0.9m high, and 9.5m long, and the wind speed range is 0m / s to 25m / s; the high-speed test section is 0.71m wide, 0.71m high, and 1.5m long, and the wind speed range is 0m / s to 50m / s;

[0065] The average wind speed corresponding to each gear of the wind tunnel is shown in Table 1:

[0066] Table 1

[0067]

[0068] Wind speed was measured using a Cobra anemometer; concentration was measured using a CCHZ-1000 fully automatic dust concentration meter with a measurement range of 0 to 1000 mg / m3, a resolution of 0.001 mg / m3, and a sampling flow rate of 2 L / min; the analytical balance had a range of 600 g and an accuracy of 1 mg.

[0069] The use of a closed-loop wind tunnel to simulate the environment of a strong sandstorm area can form a uniform flow field with relatively stable sand concentration.

[0070] Preferably, in the wind tunnel test, the erosion rate is defined as the mass loss of the target material caused by a unit mass of particles, that is, the ratio of the mass of the material loss to the mass of the sand particles; the erosion rate index is used to evaluate the erosion resistance of the material. The erosion rate expression is as follows:

[0071]

[0072] Where E is the erosion rate; Δm is the mass lost by the specimen; m s is the cumulative mass of sand particles eroding the specimen; A is the area of ​​the eroded region of the specimen; C is the concentration of sand particles; is the average wind speed; t is the erosion time, and α is the erosion angle.

[0073] The present invention has the following beneficial effects: The erosion and wear of the galvanized coating on steel components under the influence of wind and sand two-phase flow was studied. A closed-loop wind tunnel was used to simulate the environment of a strong sandstorm area, creating a uniform flow field with relatively stable sand concentration. The effects of average wind speed, erosion angle, erosion duration, specimen aspect ratio, and spacing on the erosion rate of galvanized steel components were discussed, and a calculation model for the erosion rate of the galvanized coating was established. The fundamental research results of this invention have scientific significance for ensuring the safe operation of steel structures in strong sandstorm areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 is a flow chart of the present invention;

[0075] Figure 2 The graph of the change of wind sand concentration in the wind tunnel in the embodiment;

[0076] Figure 3 The steel component model size diagram in the embodiment;

[0077] Figure 4 This is a graph showing the effect of erosion time on specimen erosion in the embodiment;

[0078] Figure 5 This is a graph showing the effect of the erosion angle on the erosion rate of the specimen in the embodiment;

[0079] Figure 6 This is a graph showing the effect of wind speed on the erosion rate of the galvanized coating on steel components in the embodiment;

[0080] Figure 7 Graph showing the effect of aspect ratio on erosion rate of galvanized steel sheet in the embodiment;

[0081] Figure 8 This is a curve diagram showing the effect of spacing on the erosion rate of galvanized steel pipes in the embodiment. DETAILED DESCRIPTION

[0082] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The following examples or drawings are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0083] like Figure 1 As shown, a wind tunnel test method for the erosion wear of a galvanized coating on a steel component by a two-phase flow of wind and sand comprises the following steps:

[0084] Step 1: Build a model of the steel component with galvanized coating;

[0085] Step 2: Conducting a wind tunnel test on the steel component model based on dimensionless wind speed and erosion angle parameters to verify the influence of dimensionless wind speed and erosion angle on the erosion rate of the steel component model, and constructing an erosion rate calculation model for the galvanized layer of the steel component model based on the influence of dimensionless wind speed and erosion angle based on the test data;

[0086] Step 3: Based on the calculation model for the erosion rate of the galvanized layer of the steel component model, wind tunnel tests are conducted on the steel component model under various specimen aspect ratios and specimen spacing conditions according to the wind speed and wind sand concentration data of the target area. The optimal specimen aspect ratio and optimal specimen spacing of the steel component model are obtained through the test.

[0087] Step 4: Construct the optimal steel structure suitable for the target area based on the optimal specimen aspect ratio and optimal specimen spacing.

[0088] Next, wind tunnel tests were conducted to study the erosion wear laws of galvanized specimens under different erosion mechanical parameters (erosion time, erosion angle and wind speed), different specimen aspect ratios and different specimen spacing.

[0089] 1. Wind tunnel test design for wind-sand two-phase flow

[0090] 1.1 Experimental equipment

[0091] This embodiment was carried out in the wind tunnel laboratory of the Baoding campus of North China Electric Power University. The wind tunnel is a closed recirculation wind tunnel using axial flow fans, and the tunnel body is an all-steel structure. The wind tunnel has two test sections, of which the low-speed test section is 1.5m wide, 0.9m high, and 9.5m long, with a wind speed range of 0m / s to 25m / s; the high-speed test section is 0.71m wide, 0.71m high, and 1.5m long, with a wind speed range of 0m / s to 50m / s. This embodiment was mainly carried out in the high-speed test section, and a few working conditions were carried out in the low-speed test section. A Cobra anemometer was used for wind speed measurement. The concentration was measured using the CCHZ-1000 fully automatic dust concentration meter, with a measurement range of 0 to 1000mg / m 3 , resolution 0.001mg / m 3 The sampling flow rate is 2 L / min. The analytical balance has a capacity of 600 g and an accuracy of 1 mg.

[0092] 1.2 Wind speed and sand simulation system

[0093] This wind tunnel controls air flow and, in turn, wind speed by rotating the deflector. The deflector controller has seven settings corresponding to seven wind speeds. An anemometer was fixed to the test section, and wind speeds were measured over a 10-minute period. The average wind speeds for settings 3 through 6 were determined by averaging these values ​​(see Table 1). The annual maximum wind speed in strong sandstorm areas can reach 25 to 44 m / s, and the test wind speeds closely simulate those in these areas.

[0094] Table 1 Average wind speed corresponding to each gear of the wind tunnel

[0095]

[0096] In strong sandstorm areas, the majority of sand particles are smaller than 0.25 mm, and their motion patterns include suspension and saltation. To simulate the strong sandstorm environment, a vibrating screen with a 60-mesh screen was used in the wind tunnel laboratory to screen dry, loose, and well-rounded artificial quartz sand with a particle size of less than 0.25 mm. 70 kg of the screened sand was evenly distributed in the test section or at the corners of the wind tunnel.

[0097] Before the test, the sand concentration in the test section should be measured. The fully automatic dust meter is placed in the test section and multiple measurements are performed. Each measurement lasts 5 minutes, and the interval between two adjacent measurements is 15 minutes. Taking the high-speed test section as an example, the measurement results of the change of wind sand concentration over time at 5 wind speeds are as follows: Figure 2 As shown. Figure 2 It can be seen that when the test section was covered with sand, the concentration of wind-blown sand decreased rapidly, and the trend slowed down after 1 hour of continuous blowing, and the concentration tended to be stable after 2 hours of blowing. When the test section was not covered with sand, the sand accumulated at the corner of the wind tunnel served as the source of the wind-blown sand flow, and the concentration of wind-blown sand was relatively stable, with a sand concentration of 40 mg / m 3 ~60 mg / m 3 , which is equivalent to the sand flow concentration at a height of 1m in a strong sandstorm area. When the sand concentration stabilizes, whether the test section is covered with sand or not has little impact on the sand concentration in the test section. Therefore, a period of trial blowing should be carried out before the erosion test, and the test should be carried out after the sand flow concentration stabilizes.

[0098] 1.3 Specimen preparation

[0099] Common cross-sectional forms of steel components include angle steel, steel pipe and steel plate. We purchased hot-dip galvanized equal-edge angle steel, steel pipe and steel plate with strength Q235 produced by Tangshan Iron and Steel Plant and cut them into test specimens of different specifications. The specimen specifications are shown in Table 2. Among them, the length of angle steel and steel pipe is the same, while the length of steel plate is divided into 6 categories. The prepared specimens are as follows Figure 3 shown.

[0100] Table 2 Summary of the size and quantity of specimens of different specifications

[0101]

[0102] 1.4 Test conditions

[0103] This example investigates the erosion wear behavior of galvanized coatings on steel components under various conditions, by varying the erosion time, erosion angle, wind speed, specimen aspect ratio, and specimen spacing. The erosion angle α is the angle between the specimen axis and the incoming wind: one side of the angle steel faces the wind and is eroded, while the other side is parallel to the horizontal plane. When α = 90°, both sides face the wind, and the steel plate thickness is parallel to the horizontal plane. When the angle steel is operating at an angle between 0° and -90°, only one side faces the wind. The test verifies that its erosion wear behavior is similar to that of steel plates; this operating condition is not discussed in this article.

[0104] Time conditions were set for the angle steel and steel pipe specimens. The angle steel was arranged at a 45° erosion angle, and the steel pipe was arranged at a 90° erosion angle. The test wind speed for the angle steel and steel pipe was 33.71 m / s, and the erosion time was 30, 60, 90, 120, 180, 240, and 300 minutes. After each erosion period, data was collected from the test specimens. After the data collection was completed, the next test period was carried out on the specimen until the end.

[0105] The diagonal steel specimens and the 200 mm long steel plate specimens were set to erosion angle conditions with a wind speed of 33.71 m / s, an erosion time of 40 min, an erosion angle of 15° to 90°, and an interval of 15°.

[0106] The diagonal steel specimens were set with wind speed conditions, erosion angle of 45°, erosion time of 120 min, and wind speeds of 33.71, 23.16, and 16.43 m / s, respectively.

[0107] The steel plate specimens were set to the aspect ratio working condition, with a wind speed of 33.71 m / s, an erosion angle of 45°, an erosion time of 60 min, a length of 50 mm to 300 mm, and an interval of 50 mm.

[0108] The maximum spacing that can be set within the high-speed test section is 30d, where d is the outer diameter of the steel pipe (in this example, d = 25mm). The steel pipe specimens were set to spacing conditions with a wind speed of 33.71m / s, an erosion angle of 90°, an erosion time of 60min, and spacings of 2, 4, 6, 8, 10, 15, 20, and 30d.

[0109] 1.5 Test method

[0110] Before the test, wind speed and sand concentration were continuously measured for 5 minutes to ensure that the laboratory's wind and sand environment met the test requirements. Furthermore, the specimen was placed horizontally to ensure that the wind speed and sand concentration were consistent across the specimen during erosion. Before and after erosion, the specimen mass was measured four times using an analytical balance, and the average value was used to calculate the mass loss. The above test method ensured that the wind speed at the same height within the test section was stable, the sand concentration was uniformly distributed, and the wind speed and sand impact velocity were consistent.

[0111] 2. Erosion test results and analysis

[0112] 2.1 Experimental data processing method

[0113] The erosion rate is defined as the mass loss of the target material caused by a unit mass of particles, that is, the ratio of the mass of the material loss to the mass of the sand particles. The erosion rate index is used to evaluate the erosion resistance of the material. The erosion rate expression is as follows:

[0114]

[0115] Where E is the erosion rate; Δm is the mass lost by the specimen; m s is the cumulative mass of sand particles eroding the specimen; A is the area of ​​the eroded region of the specimen; C is the concentration of sand particles; is the average wind speed; t is the erosion time, and α is the erosion angle.

[0116] 2.2 Effect of erosion time on erosion rate

[0117] The two ends of the angle steel are overlapped with the bracket. The erosion area after deducting the obstruction is 240×30mm 2 The connection between the two ends of the steel pipe is not affected by the bracket, and the erosion area is 300×25mm 2 The erosion rate was calculated by formula (1) and (2). The results are summarized in Table 3 and Table 4. The relationship between mass loss and erosion rate over time is shown in Figure 4 The erosion rate of the segmented time and the total time formed by the segmented time are calculated by formula (1) and (2). The calculation results are summarized in Table 3 and Table 4. The relationship between mass loss and erosion rate over time is shown in Figure 4 i represents the i-th time segment, and n represents the total number of time segments. Under the time condition, the conversion of the average sand concentration, mass loss of the specimen, and erosion time data of each stage in Tables 3 and 4 to the overall data is calculated using the following expression:

[0118]

[0119] Among them, n is the erosion stage number of each stage; is the erosion concentration at each stage; t i is the erosion time of each stage; Vm i The mass loss of the specimen at each stage; E i Erosion rate at each stage; m si The cumulative sand mass of the erosion specimen at each stage. When calculating the influence of other working conditions except time condition on erosion rate, t i =t、Vm i =Vm.

[0120] It can be seen from Tables 3 and 4 that the concentration of sand particles changes relatively stably over time. Figure 4 (a) It can be seen that the mass loss of galvanized angle steel and steel pipe is approximately linearly related to the erosion time, and there is no obvious incubation period for mass loss. Figure 4 (b) It can be seen that when the time is 30 and 60 min, the erosion rate of galvanized angle steel is 0.623×10 -3 ~0.663×10 -3 Between 0.600×10 -3 The erosion rate of galvanized steel pipe fluctuates around 1.080×10 -3 ~1.151×10 -3 Between 1.100×10 -3 The erosion rate of the angle steel and the steel pipe decreased at 90 and 180 min. The surface of the specimens was uneven due to the erosion of sand particles, which greatly restricted the diffusion of sand particles. Therefore, a downward section appeared. As the cumulative erosion time increased, the erosion rate did not change much and tended to be stable after 180 min. The stable erosion rate of the galvanized angle steel was 0.624×10 -3 The stable erosion rate of galvanized steel pipe is 1.138×10 -3 This is because continuous erosion by wind and sand particles forms a damage profile on the coating surface. Over time, the coating surface is completely destroyed during this stage, making it difficult to effectively micro-cut and chisel on uneven surfaces. At this point, coating loss is primarily due to fatigue damage caused by the generation and development of microcracks, ultimately forming a stable erosion zone. Therefore, the erosion rate stabilizes between 180 and 300 minutes. The erosion zone area and stable erosion rate of the steel pipe are 1.042 times and 1.824 times those of the angle steel, respectively. The steel pipe contacts the wind and sand flow orthogonally, while the angle steel contacts the wind and sand flow obliquely. When A is the same, the contact area of ​​the former is larger. In addition, the erosion wear of the coating caused by the wind and sand flow includes the combined effects of tangential micro-cutting and normal extrusion deformation, which means that there is a most unfavorable erosion angle between the wind and sand flow and the galvanized coating. The 45° erosion angle of the angle steel is far away from the most unfavorable wind direction angle of 19°, while the angle between the normal line of the steel pipe curved surface and the horizontal plane includes 19° and unfavorable angle ranges. Moreover, the wear of the steel pipe is mainly distributed in the small-angle erosion area, that is, the erosion wear is more severe near the edge of the windward surface of the steel pipe, resulting in more severe erosion wear on the steel pipe. The above factors lead to the erosion rate of the steel pipe being greater than that of the angle steel.

[0121] Table 3 Test data of galvanized angle steel at different erosion times

[0122]

[0123] Table 4 Test data of galvanized steel pipes at different erosion times

[0124]

[0125]

[0126] 2.3 Effect of erosion angle on erosion rate

[0127] The erosion test data of angle steel and steel plate at different erosion angles are shown in Table 5 and Table 6 respectively. It can be seen from Table 5 and Table 6 that at each erosion angle, the mass loss is the largest when α = 30°, and the erosion rate is the largest when α = 15°. In order to obtain the erosion angle function of steel angle and steel plate, the experimental data of different erosion angles are fitted nonlinearly, R 2 are 0.998 and 0.988 respectively. The fitted erosion rate is expressed as:

[0128]

[0129] At all angles, the erosion rate of the angle steel is greater than that of the steel plate. After approximately 19°, the erosion rates of both decrease as the erosion angle increases. This is primarily because as the erosion angle increases, the cutting effect of the sand particles weakens, while the vertical force increases. The continuous impact softens the galvanized coating surface, increasing the proportion of deformation wear. At the same time, the rebounding particles act as a barrier to the incident particles, meeting the requirement for minimal fatigue damage. Furthermore, at high angles of attack, the erosion resistance of the material is primarily determined by its toughness. The specimen coating is a plastic material with high toughness, resulting in minimal erosion, which in turn results in a much lower erosion rate than at lower angles. The two limbs of the angle steel form an angle, and within the erosion angle condition, both limbs face the wind. For the limb parallel to the horizontal plane, the windward side is small (3mm thick), while the horizontal side is large (30mm long). Due to the angle, the incoming sand forms a complex separation and reattachment process on the two inner surfaces, increasing the erosion wear of the angle steel. In this way, the limb parallel to the horizontal plane contributes a certain amount to the mass loss of the specimen, but contributes very little to the projected area of ​​the specimen perpendicular to the downwind direction. Therefore, due to the influence of the limb parallel to the horizontal plane, the increase in the numerator of formulas (8) and (9) will be greater than the denominator, resulting in a larger erosion rate for the angle steel than for the steel plate. According to the fitting curve, the maximum erosion rate of both the angle steel and the steel plate occurs near an erosion angle of 19°, and the decrease in erosion rate slows down after 50°, which is consistent with the typical erosion law of plastic materials.

[0130] Table 5 Test data of galvanized angle steel at different erosion angles

[0131]

[0132] Table 6 Test data of galvanized steel sheets at different erosion angles

[0133]

[0134] 2.4 Effect of wind speed on erosion rate

[0135] The erosion test data of angle steel under wind speed conditions are listed in Table 7. Since the energy required for the peeling of debris from the specimen surface mainly comes from the kinetic energy of the wind-blown sand particles, the kinetic energy of the sand particles will increase as the wind speed increases. Therefore, when the sand particles collide with the galvanized coating of the angle steel, the material surface will absorb more energy from the sand particles, that is, the deformation energy of the coating in the erosion area will also increase, resulting in increased erosion wear. When the average wind speed does not exceed 35m / s, the erosion rate increases with the increase of wind speed. The erosion wear calculation model proposed by Finnie is applicable to most plastic materials and is expressed as follows:

[0136]

[0137] Among them, the parameters k and n are determined by test data, n1 is the first natural frequency of the specimen under the fixed constraints at both ends, L c is the characteristic length of the specimen, here we take the thickness of the specimen, is the impact velocity of the sand particles, assuming

[0138] In this study, formula (10) was used to determine the erosion rate of the galvanized coating on steel angles and steel plates under the action of wind and sand, where the erosion rate is exponentially related to the impact velocity of the sand particles. The test data was fitted by formula (10) to obtain the velocity exponential function of E. For different types of materials, the value range of n is different. For plastic materials, the wind speed index n is generally between 2 and 3. Through calculation, the n1 values ​​of the specimen steel angle and steel plate were determined to be 554.7Hz and 528.4Hz, respectively. The assumption of single parameter analysis in the experiment, that is, the influence of a single parameter on E is independent, can also be used to establish an erosion rate model. Therefore, based on the experimental data, the calculation model for the erosion rate of the galvanized coating on steel angles and steel plates considering the influence of wind speed and erosion angle is determined as:

[0139]

[0140]

[0141] Table 7 Test data of galvanized angle steel at different wind speeds

[0142]

[0143] Table 8 Test data of galvanized steel sheets at different wind speeds

[0144]

[0145] 2.5 Effect of aspect ratio on erosion rate

[0146] The erosion test data of steel plates under aspect ratio conditions are listed in Table 9. The influence of aspect ratio changes on erosion rate is shown in Figure 7 .Depend on Figure 7 It can be seen that when the aspect ratio is 1, the erosion rate is the largest, which is equal to 0.718×10 -3 When the aspect ratio is 6, the erosion rate is the smallest, which is equal to 0.517×10 -3 The erosion rate of the steel plate decreases with the increase of the aspect ratio and gradually tends to be stable. However, when the aspect ratio is 3, the erosion rate is equal to 0.573×10 -3 , which is less than the erosion rate of 0.600×10 when the aspect ratio of the specimen is 4. -3 , anomaly occurs. In general, from the data obtained in Table 9, when the aspect ratio does not exceed 6, the wear resistance of the slender component is better than when the aspect ratio is close to 1. Nonlinear fitting is performed on the experimental data in Table 9 to establish the relationship between E and . Similarly, the assumption of independence between the experimental influencing parameters is adopted. According to E, the aspect ratio data is fitted (R 2 =0.834), the expression of E considering the influence of wind speed, erosion angle, and aspect ratio is obtained as follows:

[0147]

[0148] E SP (λ ar )=0.77λ ar -0.22 (16)

[0149] Formulas (11) and (15) can be used to calculate the erosion rate of the galvanized coating on steel structures with aerodynamic shapes consistent with or close to those of the test specimens in areas with strong wind and sand (sand concentration and particle size similar to those in this study) after being eroded by sand particles.

[0150] Table 9 Test data of galvanized steel sheets at different aspect ratios

[0151]

[0152] 2.6 Effect of spacing on erosion rate

[0153] The steel pipe erosion test data (S / D) under different sample spacing conditions are shown in Table 10, where it is the ratio of the downstream pipe erosion rate to the upstream pipe erosion rate. Figure 8 As shown. Figure 8 (a) It can be seen that the erosion rate of the upstream pipeline is 1.2×10 -3 ~1.5×10 -3Compared with the upstream pipe, the inconsistency of the erosion rate of the downstream pipe with the change of S / D is more obvious. Its erosion rate is within 0.2×10 -3 and 0.9×10 -3 When S / D=2~S / D=30, the effect of spacing on the downstream tube erosion rate is greater than that on the upstream tube erosion rate. Therefore, the distribution shape is mainly controlled by the distribution shape of the downstream tube erosion rate. Figure 8 As shown in (b), with the increase of S / D, it presents a distribution similar to a 'W' shape, and includes four stages. The change in the erosion rate of the series steel pipe body in each stage is mainly affected by the flow field structure, vortex shedding mode and the interaction between the steel pipe bodies. By reviewing the existing literature on flow around a cylinder, the potential internal causes of the changes in each stage when the Reynolds number is 5.7×104 are discussed. In stage 1 (S / D≤6), the wake of the upstream steel pipe body not only strongly interferes with the downstream steel pipe body, but also may cause unstable shedding of the downstream steel pipe body. As S / D gradually increases, the wake interference gradually weakens, the vortex shedding instability decreases, and the resistance of the downstream steel pipe body decreases, resulting in a decrease in its erosion, thus showing a downward trend. In stage 2 (6 Figure 8 In (b), it can also be observed that the minimum value of 0.137 and the next minimum value of 0.167 are reached at S / D = 6 or 15, respectively. To minimize the impact of wind and sand erosion on galvanized steel components, the spacing between components should be kept close to S / D = 6 or 15 when designing lattice structures in areas with strong winds and sand. As the spacing increases, a critical S / D value exists that achieves the same erosion rate for the upstream and downstream steel pipes. Due to laboratory limitations, this critical S / D value was not observed in this experiment, but future experiments could further investigate this issue.

[0154] Table 10 Test data of galvanized steel pipes at different spacings​

[0155]

[0156]

[0157] 3. Conclusion

[0158] 1) The initial placement of the sand significantly affects the rate of change of the wind-blown sand concentration, C, but has a negligible effect on the time it takes for the concentration to reach a relatively stable state. The rate of change is slowest when the sand is concentrated upstream. Therefore, to conduct erosion wear tests on galvanized coatings on steel components under stable wind-blown sand conditions, it is necessary to run the wind tunnel continuously for 120 minutes before the test begins, and then insert the test model without stopping the wind tunnel flow.

[0159] 2) The mass loss of galvanized angle steel and steel pipes shows an approximately linear relationship with corrosion time. The erosion rate (E) of the galvanized coating on both components is not significantly affected by erosion time. At the same erosion duration, the E value when the contact surface between the wind-blown sand and the steel component is curved is significantly higher than when the contact surface is flat.

[0160] 3) According to different erosion angles α and wind speeds and aspect ratio λ ar A calculation model for the E of galvanized coatings was established based on test data from a single specimen. This model can be applied to other galvanized steel components with C, particle size distribution, and component shapes similar to those studied in this study. The model predicted the maximum E value for α = 19° and determined the wind speed index of the galvanized coating on steel angles and steel pipes to be 2.41 and 2.33, respectively. The model also identified the shortcomings of the airflow sandblasting test method in simulating E values ​​and recommended that efforts should be made to increase the α value and adopt slender shapes when using steel components in areas with strong winds and sand. Subsequent research should fully evaluate the shortcomings of the airflow sandblasting method in calculating E.

[0161] 4) For series-connected steel pipes, the spacing S between upstream and downstream pipes has little effect on the E of the upstream pipe, but a greater impact on the E of the downstream pipe. The E ratio between the front and rear pipes exhibits a "W"-shaped distribution as S increases, due to changes in the flow field around the pipes. It is recommended that when using steel pipes in structures in areas with strong sandstorms, the spacing ratio (S / D) should be controlled near 6 or 15 to minimize erosion and wear of the coating. Subsequent research will identify the critical S / D value for achieving the same E values ​​for upstream and downstream pipes.

[0162] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A wind tunnel test method for the erosion and wear of galvanized coatings on steel components by two-phase flow of wind and sand, characterized in that: The following steps are involved: Step 1: Build a model of the steel component with galvanized coating; Step 2: Conducting a wind tunnel test on the steel component model based on dimensionless wind speed and erosion angle parameters to verify the influence of dimensionless wind speed and erosion angle on the erosion rate of the steel component model, and constructing an erosion rate calculation model for the galvanized layer of the steel component model based on the influence of dimensionless wind speed and erosion angle based on the test data; Step 3: Based on the calculation model for the erosion rate of the galvanized layer of the steel component model, wind tunnel tests are conducted on the steel component model under various specimen aspect ratios and specimen spacing conditions according to the wind speed and wind sand concentration data of the target area. The optimal specimen aspect ratio and optimal specimen spacing of the steel component model are obtained through the test. Step 4: Construct the optimal steel structure suitable for the target area based on the optimal specimen aspect ratio and optimal specimen spacing.

2. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 1 is characterized by: The steel component model is divided into angle steel specimens, steel pipe specimens and steel plate specimens according to the cross-sectional form; The size and quantity of each specimen are shown in Table 2: Table 2 3. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 2, characterized in that: In the wind tunnel test, the test parameters and test data for various specimens are as follows: Time conditions were set for the angle steel specimens and steel pipe specimens. The angle steel specimens were arranged at a 45° erosion angle, and the steel pipe specimens were arranged at a 90° erosion angle. The test wind speed for the angle steel specimens and the steel pipe specimens was 33.71 m / s, and the continuous erosion time was 30, 60, 90, 120, 180, 240, and 300 min. After each stage of erosion time, data was collected from the test specimens. After the data collection was completed, the next stage of the test was carried out on the specimen until the end. The test data of angle steel specimens under various erosion times are shown in Table 3: Table 3 The test data of steel pipe specimens under various erosion times are shown in Table 4: Table 4 The diagonal steel specimens and the 200 mm long steel plate specimens were set to erosion angle conditions, with a wind speed of 33.71 m / s, an erosion time of 40 min, an erosion angle of 15° to 90°, and an interval of 15°. The test data of angle steel specimens at various erosion angles are shown in Table 5: Table 5 The test data of steel plate specimens at various erosion angles are shown in Table 6: Table 6 The diagonal steel specimens and steel plate specimens were set with dimensionless wind speed conditions, erosion angle of 45°, erosion time of 120 min, and wind speeds of 33.71, 23.16, and 16.43 m / s, respectively; The test data of angle steel specimens under various dimensionless wind speeds are shown in Table 7: Table 7 The test data of the steel plate specimens under various dimensionless wind speeds are shown in Table 8: Table 8 The steel plate specimens were set to the aspect ratio working condition, wind speed 33.71m / s, erosion angle 45°, erosion time 60min, length 50mm~300mm, and interval 50mm; The test data of steel plate specimens under various aspect ratios are shown in Table 9: Table 9 The maximum spacing that can be set in the high-speed test section is 30d, where d is the outer diameter of the steel pipe. The spacing conditions for the steel pipe specimens are set at a wind speed of 33.71m / s, an erosion angle of 90°, an erosion time of 60min, and spacings of 2, 4, 6, 8, 10, 15, 20, and 30d. The test data of steel pipe specimens at various spacings are shown in Table 10: Table 10 4. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 2, characterized in that: The calculation model of the erosion rate of the galvanized layer of the steel component model based on the influence of dimensionless wind speed and erosion angle is: The calculation model of the erosion rate of the galvanized layer of the angle steel specimen is as follows: The calculation model of the erosion rate of the galvanized layer of the steel plate specimen is as follows: Where n1 is the first natural frequency of the specimen under the fixed constraints at both ends; L c is the characteristic length of the specimen; is the impact velocity of the sand particles, is the average wind speed; is the dimensionless wind speed; α is the erosion angle; E is the erosion rate; subscript SA refers to the angle steel specimen; subscript SA refers to the steel plate specimen.

5. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 4, characterized in that: In step 3, the aspect ratio data of the steel plate specimen is fitted according to the erosion rate E, and the erosion rate expression of the steel plate specimen based on the influence of dimensionless wind speed, erosion angle, and aspect ratio is obtained as follows: E SP (l ar )=0.77l ar -0.22 Among them, λ ar Indicates the aspect ratio.

6. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 3, characterized in that: In step 3, when steel pipe specimens are used in structures in areas with strong wind and sand, the optimal control range of the specimen spacing S / D is (5,7)d or (14,16)d.

7. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 1, characterized in that: The wind tunnel used in the wind tunnel test was a closed recirculation wind tunnel with an axial flow fan. The closed recirculation wind tunnel had two test sections: a low-speed test section with a width of 1.5 m, a height of 0.9 m, and a length of 9.5 m, and a wind speed range of 0 m / s to 25 m / s; and a high-speed test section with a width of 0.71 m, a height of 0.71 m, and a length of 1.5 m, and a wind speed range of 0 m / s to 50 m / s. The average wind speed corresponding to each gear of the wind tunnel is shown in Table 1: Table 1 Wind speed was measured using a Cobra anemometer; concentration was measured using a CCHZ-1000 fully automatic dust concentration meter with a measurement range of 0 to 1000 mg / m3, a resolution of 0.001 mg / m3, and a sampling flow rate of 2 L / min; the analytical balance had a range of 600 g and an accuracy of 1 mg.

8. The wind tunnel test method for erosion wear of galvanized coating on steel components by wind-sand two-phase flow according to claim 1, characterized in that: In wind tunnel tests, the erosion rate is defined as the mass loss of the target material caused by a unit mass of particles, that is, the ratio of the mass of the material loss to the mass of the sand particles. The erosion rate index is used to evaluate the erosion resistance of the material. The erosion rate expression is as follows: Where E is the erosion rate; Δm is the mass lost by the specimen; m s is the cumulative mass of sand particles eroding the specimen; A is the area of ​​the eroded region of the specimen; C is the concentration of sand particles; is the average wind speed; t is the erosion time and α is the erosion angle.

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