A method for determining the sticking position of a strain gauge for wheel pressure testing

Abstract

A method for determining the pasting position of a strain gauge for wheel pressure testing comprises the following steps: based on the wheel, rail and normal rated load borne by the wheel to be tested, a wheel-rail contact fine finite element model taking into account contact nonlinearity is established; based on the wheel-rail contact fine finite element model, the contact state between the wheel and the rail under load is calculated and analyzed to obtain the wheel-rail contact response; in the wheel-rail contact state: according to the accuracy of the main strain sensor patch, the area with the maximum influence of contact stress on the waist of the rail under contact is selected as the pasting area of ​​the main strain sensor patch; the method uses the finite element analysis method to determine the accurate position of the main strain sensor patch and the temperature compensation strain gauge, which can reduce the uncertainty of the pasting position during wheel pressure monitoring and improve the accuracy of wheel pressure detection.

Description

Technical Field

[0001] The invention relates to the technical field of wheel pressure testing, and in particular to a method for determining a sticking position of a strain gauge for a wheel pressure testing. Background Art

[0002] Stackers and reclaimers and ship loaders are heavy equipment used for continuous mobile bulk material handling. The weight and load of the equipment are evenly dispersed on the running rails through a number of steel running wheel groups and transmitted to the rail foundation. By driving the wheel group to run slowly, the equipment can reach a suitable working position. Wheel pressure is the force exerted on the rail when the wheel contacts the rail, reflecting the wheel load. The balance of wheel pressure of each wheel affects the service life of the wheel and rail, as well as the fatigue strength of the main steel structure, and ultimately determines the stability of the whole machine. In order to ensure the safe and reliable operation of the equipment, the wheel pressure needs to be tested regularly.

[0003] At present, the wheel pressure detection method mostly adopts the rail stress detection method: the main strain gauge and temperature compensation strain gauge for measuring the wheel pressure are pre-pasted on both sides of the waist of the rail located in front of the wheel whose wheel pressure is to be detected, and the stress testing equipment is connected. Then the equipment is driven to make multiple wheels pass through the rail tread above the main strain gauge pasting position in turn. The rail is deformed due to contact with the wheel and the load, and the strain signal generated on the strain gauge is then converted to obtain the wheel pressure of each wheel.

[0004] This method only needs to be carried out during the downtime of the equipment and does not affect the normal operation of the equipment. However, the bottleneck problems are: (1) For accurate detection, the main strain gauge should be pasted at the position in the time domain that experiences the entire process from zero stress change to maximum stress after the rail is loaded; (2) The temperature compensation strain gauge is only used to reduce the influence of temperature on the measurement results of the main strain gauge, but its pasting position is easily affected by deformation; currently, the selection of the pasting position of these two strain gauges depends entirely on the test experience of the test personnel, and the repeatability of each wheel pressure test result is poor and unstable. Therefore, how to accurately determine the pasting position of the main strain gauge and the temperature compensation strain gauge on the waist of the rail before testing is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to propose a method for determining the pasting position of a wheel pressure test strain gauge, which uses finite element analysis to determine the exact position of a main strain sensor patch and a temperature compensation strain gauge, thereby reducing the uncertainty of the pasting position during wheel pressure monitoring.

[0006] The technical solution adopted by the present invention is: a method for determining the pasting position of a wheel pressure test strain gauge, comprising the following steps: Based on the need to detect the parameters of the equipment wheels and rails and the normal rated load borne by the wheels, a detailed finite element model of wheel-rail contact taking into account contact nonlinearity is established; Based on the wheel-rail contact fine finite element model, the contact state between the wheel and the rail under load is calculated and analyzed to obtain the wheel-rail contact response; When the wheel is in contact with the rail: According to the accuracy of the main strain sensor patch, the area with the maximum impact of contact stress on the waist of the rail when it is in contact is selected as the pasting area of ​​the main strain sensor patch; According to the accuracy of the temperature compensation strain gauge, the area outside the maximum deformation influence area of ​​the rail waist under the contact effect is selected as the pasting area of ​​the temperature compensation strain gauge.

[0007] As a preferred solution, the main strain sensor patch and the temperature compensation strain gauge are entirely within their respective pasting areas.

[0008] As a preferred solution, the pasting position of the temperature compensation strain gauge is close to the pasting position of the main strain sensor patch.

[0009] As a preferred solution, the wheel-rail contact response includes the deformation, contact stress and equivalent stress distribution law of the wheel, and the deformation, contact stress and equivalent stress distribution law of the rail; When the wheel is in contact with the rail, the contour map of the area where the contact stress of the rail is most affected by the contact effect and the contour map of the area where the deformation of the rail is most affected by the contact effect are extracted.

[0010] As a preferred solution, the distance from the wheel center to the crest of the contour line of the maximum impact area of ​​the contact stress in the length direction of the rail is taken as the minimum distance when the wheel starts, and the distance between the pasting position of the main strain sensor patch and the position when the wheel starts is greater than the minimum distance.

[0011] As a preferred solution, when the edge of the area with the maximum impact of contact stress in the length direction of the rail presents a multi-wavy profile, the average of the distances from the center of the wheel to each wave crest is taken as the minimum distance when the wheel starts.

[0012] As a preferred solution, the height of the wave crest of the area with the maximum impact of contact stress in the length direction of the rail at the waist of the rail is used as the pasting height of the main strain sensor patch.

[0013] As a preferred solution, when the edge of the area with the maximum impact of contact stress in the length direction of the rail presents a multi-wavy profile, the area between the upper and lower outermost wave peaks in the height direction of the rail waist is used as the pasting area of ​​the main strain sensor patch.

[0014] As a preferred solution, the temperature compensation strain gauge is located directly below the main strain sensor patch.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present method for determining the pasting position of the strain gauge for wheel pressure testing establishes and analyzes the contact nonlinear finite element model between the wheel and the rail, analyzes the contact stress and deformation distribution characteristics of the rail, and provides a basis for effectively determining the pasting position of the main strain gauge and the temperature compensation strain gauge for wheel pressure detection on the waist of the rail. The present invention reduces the measurement uncertainty caused by the empirical determination of the pasting strain gauge, and the prediction method is reliable and stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the contact between the wheel and the rail in an example of the present invention; Figure 2 is a schematic cross-sectional view of a wheel in an example of the present invention; Figure 3 is a schematic cross-sectional view of a rail in an example of the present invention; Figure 4 It is a wheel-rail contact stress distribution cloud diagram in an example of the present invention; Figure 5 This is a distribution cloud diagram of stress areas above 0.1 MPa in the example of the present invention; Figure 6 This is a distribution cloud diagram of deformation areas above 0.01 mm in an example of the present invention.

[0018] Figure numerals: 1. rail, 2. wheel. DETAILED DESCRIPTION

[0019] The present invention is described in detail below by way of exemplary embodiments. However, it should be understood that, without further description, elements, structures and features in one embodiment may also be beneficially combined in other embodiments.

[0020] It should be noted that: unless otherwise defined, the technical terms or scientific terms used in this document shall have the usual meanings understood by people with ordinary skills in the field to which the invention belongs. The words "one", "an" or "the" and the like used in the patent application specification and claims of the present invention do not express quantity restrictions, but indicate the existence of at least one; the words "first", "second" and "third" used in this document shall not be regarded as restrictions on the order of components, but are only used to distinguish different components; words such as "include" or "comprise" and the like indicate that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalents, but do not exclude other elements or objects with the same function.

[0021] In order to describe the determination method more clearly, Figure 1-6 Describe this embodiment: A method for determining a sticking position of a wheel pressure test strain gauge comprises the following steps: Based on the need to detect the normal rated load borne by the wheel 2, the rail 1 and the wheel, a detailed finite element model of the contact between the wheel 2 and the rail 1 is established taking into account the contact nonlinearity; Based on the fine finite element model of the contact between the wheel 2 and the rail 1, the contact state between the wheel 2 and the rail 1 under the load is calculated and analyzed to obtain the contact response between the wheel 2 and the rail 1; When wheel 2 is in contact with rail 1: According to the accuracy of the main strain sensor patch, the area with the maximum impact of contact stress on the waist of the rail 1 when it is subjected to contact is selected as the pasting area of ​​the main strain sensor patch; According to the accuracy of the temperature compensation strain gauge, the area outside the area with the maximum influence of deformation of the waist of the rail 1 when it is subjected to contact is selected as the pasting area of ​​the temperature compensation strain gauge.

[0022] The wheel-rail contact response includes the deformation, contact stress and equivalent stress distribution of the wheel, as well as the deformation, contact stress and equivalent stress distribution of the rail. When the wheel and rail are in contact, the contour map of the area where the contact stress of the rail is most affected by the contact effect and the contour map of the area where the deformation of the rail is most affected by the contact effect are extracted, and the positions of the main strain sensor patch and the temperature compensation strain gauge are determined by the contour map. The location of the main strain sensor patch includes its horizontal position and vertical height on the waist of the rail.

[0023] The edge of the stress area may form an irregular, single-peak or multi-peak envelope profile. The profile formed is related to the load and track model. The contact stress at the peak is obvious, so the vertical height of the principal strain sensor patch can be determined by the peak position of the area with the maximum influence of the contact stress. When the area with the largest impact of contact stress is a single peak, the height of the peak of the area with the largest impact of contact stress in the rail length direction at the waist of the rail is used as the pasting height of the main strain sensor patch; when pasting, the center of the main strain sensor patch is preferably on the wave height line at the level of the peak; When the area with the maximum impact of contact stress presents a multi-wavy profile in the length direction of the rail, the area between the upper and lower outermost wave peaks in the height direction of the rail waist is used as the pasting area of ​​the main strain sensor patch; multiple main strain sensor patches can also be set and pasted respectively at the height position of each wave peak on the rail waist.

[0024] In order to ensure that the main strain sensor patch experiences the whole process from zero stress change to maximum stress after the rail is loaded in the time domain, the distance from the center of the wheel to the peak of the contour line of the maximum impact area of ​​the contact stress in the length direction of the rail is taken as the minimum distance when the wheel starts, and the distance between the pasting position of the main strain sensor patch and the position when the wheel starts is greater than the minimum distance, that is, the position outside the minimum distance in the forward direction of the wheel is selected as the pasting area; When the edge of the area with the maximum impact of contact stress in the length direction of the rail presents a multi-wavy profile, the average of the distances from the wheel center to each wave peak is taken as the minimum distance when the wheel starts to reduce the error.

[0025] The temperature compensation strain gauge is extremely sensitive to temperature changes. Its main function is to correct the impact of temperature on detection. It should be pasted at the position where the track deformation is small to eliminate the impact of track deformation on the compensation strain gauge. Its position meets the following conditions: First, it is outside the area with the greatest influence of deformation when under contact, avoiding interference from rail deformation and improving the accuracy of wheel pressure detection; Second, the temperature compensation strain gauge is close to the main strain sensor patch.

[0026] For the convenience of pasting, the horizontal position and height position of the main strain sensor patch can be determined first, and then the temperature compensation strain gauge can be pasted directly below the main strain sensor patch, and it is ensured that the temperature compensation strain gauge is outside the area with the greatest influence of deformation.

[0027] To ensure the accuracy of detection, the main strain sensor patch and the temperature compensation strain gauge are placed in their respective pasting areas.

[0028] The fine finite element model of wheel-rail contact includes nonlinear fine finite element models of contact between a single wheel, two wheels and multiple wheels and the rail respectively; by analyzing the contact models including a single wheel, two wheels and multiple wheels and the rail respectively, the changes caused by the maximum influence area range on the stress and deformation of the rail due to the simultaneous contact of different numbers of wheels and the rail are determined.

[0029] This method decomposes the contacting structures into a limited number of units through finite element contact analysis, defines the contact surface and boundary conditions, and considers nonlinear behaviors such as friction. It uses mathematical methods to calculate the stress and strain of each unit, and finally accurately predicts the stress and deformation distribution inside and on the surface of the contact area and the contacting structure. The biggest feature of finite element contact analysis is that it can accurately simulate the complex behavior of the contact interface, avoid the limitations of traditional analytical methods, eliminate the uncertainty of contact problems, greatly improve the reliability and efficiency of contact problems in engineering, and reduce the trial and error cost in practical applications.

[0030] The following is a specific example: The target wheel is Figure 2 The double-rim wheel shown has a wheel tread diameter of 630mm and a rim width of 120mm. The rail specification is QU100 rail that meets the "YB / T5055-2014 Crane Rail". Figure 3 shown.

[0031] Material properties: wheel material 42CrMo, rail U71Mn. The fine finite element model of wheel-rail contact assumes that the material is continuous, uniform and isotropic, and the material deformation is within the linear elastic range. The elastic modulus of the wheel and rail are both 2.06×10^5MPa, and the Poisson's ratio is 0.29.

[0032] Meshing: The finite element model uses high-order tetrahedral units and the mesh in the wheel-rail contact area is encrypted.

[0033] Contact relationship: The wheel and rail are in surface-to-surface contact. The penalty function method is used to impose contact constraints. The Coulomb friction model is used to define the friction behavior. The static friction coefficient is 0.15.

[0034] Boundary conditions: The bottom of the rail is fixedly constrained, the normal rated pressure load borne by the wheel center is 40t, and the load direction is perpendicular to the rail tread from the wheel center.

[0035] Calculate the fine finite element model of wheel-rail contact and analyze the wheel-rail contact response in the calculation results: according to Figure 3 As shown in the simulation result cloud map, the contact spot formed by the wheel and the rail is elliptical, the maximum contact stress of the wheel is 1197MPa, and the maximum contact stress of the rail is 1207MPa.

[0036] According to the accuracy requirements of the test equipment, the stress influence area above 0.1MPa is investigated (the area with the maximum contact stress when the waist of the rail is under contact, that is, the red area on the rail). Figure 5As shown, the stress influence area above 0.1MPa is in the shape of "Σ"; in the horizontal direction, the average distance between the two peaks of the "Σ"-shaped contact spot and the center of the wheel is 616mm; in the vertical direction, the distances between the two peaks of the "Σ"-shaped contact spot and the bottom surface of the rail are 44mm and 76mm respectively.

[0037] According to the measurement requirements of temperature compensation strain gauges, the deformation influence area above 0.01mm (the area with the greatest deformation influence when the waist of the rail is under contact, i.e. the blue area on the rail) needs to be paid attention to during simulation calculation. Figure 6 As shown, the deformation affected area above 0.01 mm is "U" shaped; the distance between the bottom of the "U" shaped contact spot and the bottom surface of the rail is 48 mm.

[0038] Based on the above simulation results, the strain gauge pasting position is predicted: In the horizontal direction, the main strain sensor patch position should be more than 616mm from the wheel center, that is, the starting distance of the wheel during the test should be greater than 616mm. In the vertical direction, the strain sensor should be pasted in the area between 44mm and 76mm from the bottom of the rail.

[0039] The temperature compensation strain gauge should be pasted close to the main strain gauge and within the area of ​​0 to 48 mm from the bottom surface of the rail.

[0040] The parts not described in detail in the above embodiments are prior art.

[0041] It should be noted that although the present invention is described by the above embodiments, the present invention may also have other various embodiments. Without departing from the spirit and scope of the present invention, it is obvious that those skilled in the art may make various corresponding changes and deformations to the present invention, but these changes and deformations should all fall within the scope of protection of the appended claims of the present invention and their equivalents.

Claims

1. A method for determining the pasting position of a wheel pressure test strain gauge, characterized in that: The following steps are involved: Based on the need to detect the parameters of the equipment wheels and rails and the normal rated load borne by the wheels, a detailed finite element model of wheel-rail contact taking into account contact nonlinearity is established; Based on the wheel-rail contact fine finite element model, the contact state between the wheel and the rail under load is calculated and analyzed to obtain the wheel-rail contact response; When the wheel is in contact with the rail: According to the accuracy of the main strain sensor patch, the area with the maximum impact of contact stress on the waist of the rail when it is in contact is selected as the pasting area of ​​the main strain sensor patch; According to the accuracy of the temperature compensation strain gauge, the area outside the area with the maximum influence of deformation of the rail waist under contact is selected as the pasting area of ​​the temperature compensation strain gauge.

2. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 1, characterized in that: The main strain sensor patch and the temperature compensation strain gauge are integrally located within their respective pasting areas.

3. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 1, characterized in that: The pasting position of the temperature compensation strain gauge is close to the pasting position of the main strain sensor patch.

4. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 1, characterized in that: The wheel-rail contact response includes the deformation, contact stress and equivalent stress distribution law of the wheel, and the deformation, contact stress and equivalent stress distribution law of the rail; When the wheel is in contact with the rail, the contour map of the area where the contact stress of the rail is most affected by the contact action and the contour map of the area where the deformation of the rail is most affected by the contact action are extracted.

5. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 4, characterized in that: The distance from the wheel center to the peak of the contour line of the maximum impact area of ​​the contact stress in the length direction of the rail is taken as the minimum distance when the wheel starts, and the distance between the pasting position of the main strain sensor patch and the position when the wheel starts is greater than the minimum distance.

6. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 5, characterized in that: When the edge of the area with the maximum impact of contact stress in the length direction of the rail presents a multi-wavy profile, the average of the distances from the wheel center to each wave crest is taken as the minimum distance when the wheel starts.

7. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 4, characterized in that: The height of the wave crest of the area with the maximum impact of contact stress in the length direction of the rail at the waist of the rail is taken as the pasting height of the main strain sensor patch.

8. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 4, characterized in that: When the edge of the area with the maximum impact of contact stress in the length direction of the rail presents a multi-wavy profile, the area between the upper and lower outermost wave peaks in the height direction of the rail waist is used as the pasting area of ​​the main strain sensor patch.

9. The method for determining the sticking position of a wheel pressure test strain gauge according to claim 1, characterized in that: The temperature compensation strain gauge is located directly below the main strain sensor patch.

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