Foam material parameter calibration method for polyurethane curing ballast bed

Abstract

The invention discloses a foam material parameter calibration method for a polyurethane cured ballast bed, which comprises the following steps: establishing a rock-polyurethane model, and determining material parameters to be calibrated; the method comprises the following steps: manufacturing a plurality of rock-polyurethane bonding samples with different polyurethane thicknesses, and respectively carrying out tensile tests to obtain a true force-displacement curve; based on all true force-displacement curves, initial values of material parameters are determined, and a calibration force-displacement curve is determined; and designing a calibration scheme based on the initial value of each key parameter, substituting the calibration scheme into the rock-polyurethane model, simulating a tensile test, and calibrating the value of each material parameter based on a calibration force-displacement curve. The invention provides a foam material parameter calibration method for a polyurethane curing ballast bed, and aims to solve the problem that mechanical parameters of polyurethane foam are difficult to characterize in the prior art and realize calibration of main microscopic mechanical parameters of the polyurethane foam. And a scientific and reasonable basis is provided for discrete element modeling of the polyurethane curing ballast bed.

Description

Technical Field

[0001] The invention relates to the field of polyurethane-cured ballasts, and in particular to a method for calibrating foam material parameters of polyurethane-cured ballasts. Background Art

[0002] As a new type of track structure, the core of polyurethane-cured ballast bed is the use of two-component foamed polyurethane material. This environmentally friendly, safe and fast-reacting material is injected into the loose ballast bed of the ballasted track after pressurized mixing. It uses its rapid expansion and curing characteristics to fully fill and cure the gaps between the ballast particles, thereby building a stable and tight overall structure. The polyurethane-cured ballast bed cleverly avoids the hard contact, dislocation and slippage problems that may occur between traditional ballasts, effectively suppresses the powdering and deterioration process of the ballast, and significantly enhances the stability and durability of the ballast bed structure; at the same time, the polyurethane-cured ballast bed also cleverly combines the easy adjustability of ballasted track with the low maintenance and high stability advantages of ballastless track, becoming a new and efficient solution in the field of track construction.

[0003] In the existing technology, the traditional method is generally to study the performance of polyurethane cured roadbed through indoor tests, but this method has the disadvantage that the test conditions and samples cannot be accurately replicated, which will lead to unnecessary errors. The use of numerical simulation methods to study the performance of polyurethane has gradually become the mainstream method.

[0004] Since numerical simulation has the advantages of low cost and easy repeatability, it is often a good supplement to physical research and theoretical analysis. Compared with the traditional finite element method, the particle discrete element method can accurately control the external stress conditions while ensuring the reproducibility of the sample, which is very suitable for the study of the mechanical properties of polyurethane-cured roadbed. The particle discrete element simulation method regards the sphere as the basic unit of numerical calculation, and the spherical particles are given different properties according to the different test simulation objects. The polyurethane-cured roadbed has strong discontinuity, non-uniformity and randomness in the mechanical transfer mechanism, which makes the action mechanism of the already complex gravel ballast particles more complicated, and it is difficult to simulate using the traditional continuous medium finite element method.

[0005] In polyurethane-cured ballast, polyurethane foam, as a key engineering material, not only plays an important role in gap filling and bonding positioning, but also greatly reduces the sliding and displacement of ballast when trains pass through its soft properties, disperses the forces between ballasts, reduces the loss and pulverization of ballast, and thus reduces the cumulative residual deformation of the ballast, improving the overall performance and stability of the gravel ballast. However, there is currently no definite method for mechanical characterization of polyurethane foam, a complex engineering material, and it is impossible to obtain scientific and reasonable mechanical parameters, making it difficult to provide basic data for discrete element modeling research on polyurethane-cured ballast. Summary of the invention

[0006] The present invention provides a method for calibrating the foam material parameters of a polyurethane cured ballast, so as to solve the problem that it is difficult to characterize the mechanical parameters of the polyurethane foam in the prior art, achieve the purpose of calibrating the main microscopic mechanical parameters of the polyurethane foam, and provide a scientific and reasonable basis for discrete element modeling of the polyurethane cured ballast.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for calibrating parameters of a foam material of a polyurethane-cured ballast comprises the following steps:

[0009] S1. Establish a rock-polyurethane model and determine the material parameters to be calibrated;

[0010] S2. Prepare several rock-polyurethane bonding specimens with different polyurethane thicknesses, conduct tensile tests on them respectively and obtain true force-displacement curves;

[0011] S3. Based on all the real force-displacement curves, determine the initial values ​​of the material parameters and determine the calibration force-displacement curve;

[0012] S4. Design a calibration scheme based on the initial values ​​of each key parameter, substitute the scheme into the rock-polyurethane model, simulate the tensile test, and calibrate the value of each material parameter based on the calibration force-displacement curve.

[0013] In view of the problem that it is difficult to characterize the mechanical parameters of polyurethane foam in the prior art, the present invention proposes a method for calibrating the foam material parameters of polyurethane cured ballast. The method first establishes a rock-polyurethane model, and determines the material parameters to be calibrated based on the established model; then, a sample is made for tensile test to obtain several real force-displacement curves, and based on this, the initial values ​​of some or all material parameters are determined; at the same time, the real force-displacement curve is used as a reference to obtain a calibrated force-displacement curve for subsequent calibration. Based on the initial values ​​of the material parameters determined in the above steps, different calibration schemes are designed, substituted into the rock-polyurethane model for simulation of tensile test, and based on the trial and error method, the simulated force-displacement curve is as close as possible to the calibration force-displacement curve, and the calibrated values ​​of each material parameter are obtained.

[0014] It can be seen that this method can calibrate the main micromechanical parameters of polyurethane foam through the data obtained from the tensile test, filling the gap in the existing technology and providing scientific and reasonable basic data for the discrete element modeling of polyurethane cured roadbed, which is conducive to broadening the research ideas of polyurethane cured roadbed.

[0015] Furthermore, the method for establishing the rock-polyurethane model includes: establishing a contact model of two rocks using a linear parallel bonding model; and connecting the two rocks via a bond to simulate the bonding of polyurethane.

[0016] The linear parallel bond model is a model structure built into existing discrete element software (called linearpbond in some commands). It is a linear-based model that can be installed between ball-ball and ball-surface contacts. The linear parallel bond model is a contact surface between particles. Particles can transmit force and bending moment at the same time. It can be used to simulate bonding materials with high tensile strength. Therefore, it can be used to simulate the mechanical behavior of polyurethane foam in polyurethane cured roadbed. This scheme selects the bond key in the linear parallel bond model to simulate the bonding effect of polyurethane materials.

[0017] Therefore, in this application, the material parameters to be calibrated should be related to the mechanical properties of the bond. The material parameters to be calibrated determined in this scheme include: parallel bond stiffness, ultimate tensile strength and parallel bond friction angle.

[0018] Further, the method for preparing a plurality of rock-polyurethane bonding samples with different polyurethane thicknesses includes:

[0019] S201, drilling and coring the ballast parent rock to obtain a number of cylindrical cores;

[0020] S202, aligning the cylindrical cores in groups of two, and setting different spacings for the cores in each group;

[0021] S203, wrapping tape between each group of cores to bond them together, and reserving injection holes on the tape;

[0022] S204, pouring polyurethane material into the pouring hole, and removing the tape after the polyurethane solidifies.

[0023] In this scheme, the cylindrical cores are aligned in pairs, which means that the two cores in the same group are in a state where the axes are colinear and the end faces are opposite. Among the several groups of cores set up, the distance between the cores in any two groups is different, and the purpose is to eliminate the influence of the macro factor of different polyurethane thickness. Wrapping tape between each group of cores means that at least one circle of tape is wrapped in an annular manner between the two cores in the same group, and the two ends of the tape along the axial direction are respectively bonded to the surfaces of the two cores in the same group. In addition, the amount of polyurethane material poured in this scheme can be calculated based on the distance and core size.

[0024] The sample preparation method of this scheme is conducive to the preparation of small-sized samples, and has obvious advantages in improving test efficiency, reducing costs and manpower consumption, etc.

[0025] Further, the method for determining the initial value of the material parameter includes:

[0026] S301, finding the peak tensile force in each true force-displacement curve, and calculating the polyurethane bonding stiffness corresponding to each true force-displacement curve;

[0027] S302, averaging all peak tensile forces to obtain an average peak tensile force; averaging all polyurethane bonding stiffnesses to obtain an average bonding stiffness;

[0028] S303, taking the average bonding stiffness as the initial value of the parallel bonding stiffness, and taking the average peak tension as the initial value of the ultimate tensile strength.

[0029] The pulling process of the rock-polyurethane specimen is mainly divided into two stages. In the first stage, the stress and deformation of the polyurethane are basically linearly increased. When the peak tension is reached, the bond between the polyurethane and the rock gradually breaks, and the second stage begins. The polyurethane bonding force drops sharply until the bond between the polyurethane and the rock breaks. Therefore, the peak tension is the tension corresponding to the position of the obvious inflection point in the true force-displacement curve. This scheme clearly defines the method for determining the initial value of the parallel bond stiffness and the initial value of the ultimate tensile strength, providing sufficient basis for subsequent accurate calibration.

[0030] Furthermore, the method for calculating the polyurethane bonding stiffness corresponding to each true force-displacement curve is as follows: the peak tension value is divided by the displacement value corresponding to the point where the peak tension is located in the true force-displacement curve, and the result is the polyurethane bonding stiffness corresponding to the current true force-displacement curve.

[0031] In this scheme, the ratio of the ultimate tensile strength to the elongation at break when the sample is destroyed is used as the polyurethane bonding stiffness, which can also be understood as the tensile stress under unit elongation of polyurethane being used as the polyurethane bonding stiffness.

[0032] Furthermore, the method for determining the calibration force-displacement curve includes: fitting the calibration force-displacement curve based on the average peak tension and the average bond stiffness.

[0033] Preferably, the calibration force-displacement curve is fitted with a parabolic equation in the first stage and with a straight line in the second stage.

[0034] Furthermore, step S4 specifically includes:

[0035] S401. Keep the ultimate tensile strength as the initial value, design several different calibration schemes, and calibrate the parallel bond stiffness;

[0036] S402. Based on the calibrated parallel bond stiffness, design several different calibration schemes to calibrate the parallel bond friction angle.

[0037] Preferably, step S401 specifically includes:

[0038] S4011. Designing a number of different parallel bond stiffness values ​​within a set range near an initial value of the parallel bond stiffness;

[0039] S4012. Based on the empirical method, design several different values ​​of parallel bond friction angle;

[0040] S4013. Based on several different values ​​of parallel bond stiffness and several different values ​​of parallel bond friction angle, several preliminary bid schemes for key parameters are obtained;

[0041] S4014, substituting the preliminary standard schemes of each key parameter into the rock-polyurethane model, simulating the tensile test, and obtaining the preliminary standard force-displacement curve;

[0042] S4015. Compare each preliminary calibration force-displacement curve with the calibration force-displacement curve to find the key parameter preliminary calibration scheme with the highest degree of consistency, and use the parallel bonding stiffness therein as the parallel bonding stiffness after calibration.

[0043] Preferably, step S402 specifically includes:

[0044] S4021. Designing a number of different values ​​of the parallel adhesion friction angle within a set range near the parallel adhesion friction angle in the initial bid scheme of the key parameter with the highest degree of fit;

[0045] S4022, based on the initial value of the ultimate tensile strength, the calibrated parallel bond stiffness, and the several different values ​​of the parallel bond friction angles, obtain several key parameter precision calibration schemes;

[0046] S4023, substituting the precise calibration scheme of each key parameter into the rock-polyurethane model, simulating the tensile test, and obtaining the precise calibration force-displacement curve;

[0047] S4024. Compare each precision-calibrated force-displacement curve with the calibration force-displacement curve to find the key parameter precision-calibration scheme with the highest degree of agreement, and use the parallel adhesion friction angle therein as the calibrated parallel adhesion friction angle.

[0048] The "setting range" in this application can be flexibly determined according to actual needs, such as within the range of ±10%, ±20%, etc.

[0049] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0050] 1. The present invention provides a method for calibrating foam material parameters of a polyurethane cured ballast bed. The method calibrates the main microscopic mechanical parameters of the polyurethane foam through the data obtained from the tensile test, which fills the gap in the prior art and provides scientific and reasonable basic data for discrete element modeling of the polyurethane cured ballast bed, which is conducive to broadening the research ideas of the polyurethane cured ballast bed.

[0051] 2. The present invention provides a method for calibrating foam material parameters of a polyurethane-cured ballast, which uses parallel bonding stiffness, ultimate tensile strength and parallel bonding friction angle as material parameters to be calibrated, thereby achieving effective quantitative calibration of the material parameters to be calibrated.

[0052] 3. The method for calibrating the parameters of the foam material of the polyurethane-cured ballast of the present invention prepares small-sized samples for indoor testing, which has obvious advantages in improving test efficiency, reducing costs and manpower consumption, etc.

[0053] 4. The method for calibrating the parameters of the foam material of the polyurethane-cured ballast of the present invention clearly defines the method for determining the initial value of the parallel bonding stiffness and the initial value of the ultimate tensile strength, providing a sufficient basis for subsequent accurate calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0055] Figure 1 It is a schematic diagram of a flow chart of a specific embodiment of the present invention;

[0056] Figure 2 This is a physical picture of a rock-polyurethane bonding sample in a specific embodiment of the present invention;

[0057] Figure 3 It is a schematic diagram of a real force-displacement curve in a specific embodiment of the present invention;

[0058] Figure 4 It is a comparison diagram of each initial calibration force-displacement curve and the calibration curve in the specific embodiment of the present invention;

[0059] Figure 5 It is a comparison diagram of each precision-calibrated force-displacement curve and the calibration curve in a specific embodiment of the present invention;

[0060] Figure 6 The force-displacement curves at different loading rates in a specific embodiment of the present invention;

[0061] Figure 7 is a cross-sectional view of two clamps in a specific embodiment of the present invention;

[0062] Figure 8It is a structural schematic diagram of a positioning block in a specific embodiment of the present invention;

[0063] Fig. 9 It is a schematic diagram of the structure of the convex block in a specific embodiment of the present invention.

[0064] Marks and corresponding parts names in the attached drawings:

[0065] 1-cylindrical core, 2-polyurethane, 3-base, 4-positioning block, 5-convex groove, 6-convex block, 7-panel, 8-first clamping piece, 9-second clamping piece, 10-bolt, 11-slide rail. DETAILED DESCRIPTION

[0066] In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the examples and the accompanying drawings. The schematic embodiments of the present invention and the description thereof are only used to explain the present invention and are not intended to limit the present invention. In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inside", "outside", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application.

[0067] Embodiment 1:

[0068] like Figure 1 A method for calibrating foam material parameters of a polyurethane-cured ballast is shown, comprising:

[0069] Step 1: Establish a rock-polyurethane model and determine the material parameters to be calibrated. Specifically:

[0070] The contact model of two rocks was established using the linear parallel bonding model as the rock-polyurethane model; the two rock models were connected using the bond in the linear parallel bonding model to simulate the bonding of polyurethane.

[0071] The bond can bear force and torque. In this embodiment, the material parameters to be calibrated are: parallel bond stiffness, ultimate tensile strength, and parallel bond friction angle.

[0072] Step 2: Prepare several rock-polyurethane bonding samples with different polyurethane thicknesses. Figure 2 As shown in Figure 1, tensile tests were performed on each sample and true force-displacement curves were obtained. One of the true force-displacement curves is shown in Figure 1. Figure 3 shown.

[0073] Step 3: Based on all the real force-displacement curves, determine the initial values ​​of the material parameters and the calibration force-displacement curves.

[0074] Find the peak tensile force in each true force-displacement curve, and calculate the polyurethane bonding stiffness corresponding to each true force-displacement curve: divide the peak tensile force value by the displacement value corresponding to the point where the peak tensile force is located in the true force-displacement curve to obtain the polyurethane bonding stiffness corresponding to the current true force-displacement curve;

[0075] The average peak tensile force is calculated by averaging all the peak tensile forces, and the average bond stiffness of all polyurethanes is calculated by averaging all the bond stiffness of polyurethanes.

[0076] The average bonding stiffness is taken as the initial value of the parallel bonding stiffness, and the average peak tensile force is taken as the initial value of the ultimate tensile strength.

[0077] In this embodiment, the initial value of the parallel bond stiffness = average peak tension = 2.43341e7 Pa / m;

[0078] In this embodiment, the initial value of the ultimate tensile strength = average peak tensile force = 3.30835734e5 Pa.

[0079] In this embodiment, the initial value of the parallel bond friction angle is obtained from experience.

[0080] The calibration force-displacement curve in this embodiment can be any real force-displacement curve; or the calibration force-displacement curve can be fitted based on the average peak tension and the average bonding stiffness.

[0081] Step 4: Design a calibration scheme based on the initial values ​​of each key parameter, substitute it into the rock-polyurethane model, simulate the tensile test, and calibrate the values ​​of each material parameter based on the calibration force-displacement curve. Specifically:

[0082] (I) Keeping the ultimate tensile strength as the initial value, design several different calibration schemes to calibrate the parallel bond stiffness:

[0083] (1) Designing several different values ​​of parallel bond stiffness within a set range near the initial value of the parallel bond stiffness;

[0084] (2) Based on the empirical method, several different values ​​of parallel bond friction angle are designed;

[0085] (3) Based on several different values ​​of parallel bond stiffness and several different values ​​of parallel bond friction angle, several preliminary bid schemes for key parameters are obtained as shown in Table 1:

[0086] Table 1 Preliminary bid for key parameters

[0087]

[0088]

[0089] (4) Substituting the preliminary calibration schemes of each key parameter into the rock-polyurethane model, simulating the tensile test, and obtaining the preliminary calibration force-displacement curve;

[0090] (5) Compare the initial force-displacement curves with the calibrated force-displacement curves; find the initial calibration scheme with the highest degree of agreement, and use the parallel bond stiffness in it as the parallel bond stiffness after calibration.

[0091] like Figure 4 As shown, in this embodiment, Scheme 5 has the highest degree of agreement with the calibration curve, so the calibrated parallel bond stiffness is determined to be 17616944.93 Pa / m.

[0092] (ii) Based on the calibrated parallel bond stiffness, several different calibration schemes are designed to calibrate the parallel bond friction angle:

[0093] (1) designing a number of different values ​​of the parallel adhesion friction angle within a setting range near the parallel adhesion friction angle in the initial bid scheme of the key parameter with the highest degree of agreement;

[0094] (2) Based on the initial value of the ultimate tensile strength, the calibrated parallel bond stiffness, and the several different values ​​of the parallel bond friction angles, several key parameter precision calibration schemes are obtained as shown in Table 2:

[0095] Table 2 Key parameter precision calibration scheme

[0096] Solution No. Parallel bond stiffness (Pa / m) Parallel bond friction angle (°) 6 17616944.93 50 7 17616944.93 49.5 8 17616944.93 49.8

[0097] (3) Substituting the precise calibration scheme of each key parameter into the rock-polyurethane model, simulating the tensile test, and obtaining the precise calibration force-displacement curve;

[0098] S4024. Compare each precision-calibrated force-displacement curve with the calibration force-displacement curve to find the key parameter precision-calibration scheme with the highest degree of agreement, and use the parallel adhesion friction angle therein as the calibrated parallel adhesion friction angle.

[0099] like Figure 5 As shown, in this embodiment, Scheme 8 has the highest degree of agreement with the calibration curve, so the parallel bonding friction angle after calibration is determined to be 49.8°.

[0100] Therefore, the final calibration results of this embodiment are: parallel bonding stiffness = 17616944.93 Pa / m, ultimate tensile strength = 3.30835734e5 Pa, parallel bonding friction angle = 49.8°.

[0101] It should be noted that Figure 4 and Figure 5 The “calibration curve” in the figure represents the calibration force-displacement curve in this application.

[0102] Embodiment 2:

[0103] A method for calibrating foam material parameters of a polyurethane-cured ballast bed. Based on Example 1, this example prepares rock-polyurethane bonding samples with different polyurethane thicknesses by the following method:

[0104] The ballast parent rock is drilled and cored to obtain a number of cylindrical cores; the cylindrical cores obtained in this embodiment have a diameter of 50 mm and a thickness of 25 mm.

[0105] The cylindrical cores are grouped and aligned in pairs, and different spacings are set for each group of cores; in this embodiment, at least three groups of cores are included, with spacings of 10 mm, 15 mm, and 20 mm, respectively.

[0106] Wrapping tape between each group of cores to bond them together, and reserving injection holes on the tape;

[0107] The polyurethane material is poured into the injection hole, and the tape is removed after the polyurethane is solidified; wherein the injection volume V of the polyurethane material is: V=A×h; wherein A is the diameter of the cylindrical core, and h is the core spacing.

[0108] In addition, this embodiment performs a tensile test on each sample by the following method:

[0109] The cores at both ends of the rock-polyurethane bonding specimen were clamped with a clamp;

[0110] The cores on both sides of the rock-polyurethane bonding specimen were pulled out at a rate of 10 mm / min until the polyurethane was completely broken, and the force-displacement curve during the pulling process was recorded.

[0111] Embodiment 3:

[0112] A method for calibrating foam material parameters of a polyurethane-cured ballast bed. Based on Example 2, in this example, a clamp for clamping the cores at both ends of a rock-polyurethane bonding sample is as follows: Figures 7 to 9 As shown, there are two clamps, which are distributed up and down and are respectively used to connect to the two ends of the tensile testing machine.

[0113] Specifically, the clamp includes a base 3 for connecting to the tensile testing machine, a positioning block 4 fixedly connected to the base 3, a convex groove 5 is provided on the positioning block 4, the convex groove 5 penetrates the positioning block 4 from the side, and the convex groove 5 is open on the side away from the base 3; it also includes a convex block 6 matching the convex groove 5, a panel 7 is arranged on the top of the convex block 6, and a first clamping member 8 and a second clamping member 9 are provided on the panel, the first clamping member 8 and the second clamping member 9 both have arc clamping parts, and the first clamping member 8 and the second clamping member 9 can be locked by a bolt 10.

[0114] In a more preferred embodiment, the first clamping member 8 is fixed on the panel 7, and the second clamping member 9 is slidably fitted on the panel 7 via a slide rail 11, and the direction of the slide rail 11 can make the second clamping member 9 approach and move away from the first clamping member 8.

[0115] The clamp in this embodiment is particularly suitable for tensile tests of small-sized samples, and can overcome the problem that traditional fixing methods cannot fix small-sized core samples on the testing machine.

[0116] Embodiment 4:

[0117] A method for calibrating parameters of foam material of polyurethane cured roadbed. Based on any of the above embodiments, before conducting a simulated tensile test, this embodiment further performs a sensitivity analysis on the loading rate. The specific analysis method includes:

[0118] Several rock-polyurethane bonding specimens with the same polyurethane thickness were made, and tensile tests were carried out at different loading rates to obtain force-displacement curves at different loading rates.

[0119] According to the deviation range of the force-displacement curve at different loading rates, it is judged whether the sample is sensitive to the loading rate:

[0120] If it is not sensitive, the effect of loading rate on the simulation will not be considered, and any loading rate can be used when conducting the simulated tensile test;

[0121] If it is sensitive, the loading rate will be taken as one of the parameters to be calibrated, and the influence of the loading rate needs to be considered in the subsequent design of the calibration scheme.

[0122] In this embodiment, tensile tests were carried out at loading rates of 10 m / s, 20 m / s, 30 m / s, 40 m / s, and 50 m / s, and the force-displacement curves at different loading rates were as follows: Figure 6 As shown. Figure 6 It can be seen that at different loading rates, the force-displacement curves of the specimens of this embodiment are basically the same, indicating that the loading rate has little effect on the macroscopic mechanical behavior of the model of this embodiment. Therefore, the loading rate can be uniformly set to 10 m / s in the subsequent simulation process.

[0123] It should be noted that Figure 6 The V in it represents the loading rate.

[0124] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0125] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In addition, the term "connected" used in this article can be directly connected or indirectly connected via other components without special explanation.

Claims

1. A method for calibrating foam material parameters of a polyurethane-cured ballast bed, characterized in that: The following steps are involved: S1. Establish a rock-polyurethane model and determine the material parameters to be calibrated; S2. Prepare several rock-polyurethane bonding specimens with different polyurethane thicknesses, conduct tensile tests on them respectively and obtain true force-displacement curves; S3. Based on all the real force-displacement curves, determine the initial values ​​of the material parameters and determine the calibration force-displacement curve; S4. Design a calibration scheme based on the initial values ​​of each key parameter, substitute the initial values ​​into the rock-polyurethane model, simulate the tensile test, and calibrate the values ​​of each material parameter based on the calibration force-displacement curve.

2. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 1, characterized in that: The method for establishing a rock-polyurethane model includes: establishing a contact model of two rocks using a linear parallel bonding model; and connecting the two rocks via a bond to simulate the bonding of polyurethane.

3. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 1, characterized in that: The material parameters to be calibrated include: parallel bond stiffness, ultimate tensile strength and parallel bond friction angle.

4. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 1, characterized in that: The method for preparing several rock-polyurethane bonding specimens with different polyurethane thicknesses includes: S201, drilling and coring the ballast parent rock to obtain a number of cylindrical cores; S202, aligning the cylindrical cores in groups of two, and setting different spacings for the cores in each group; S203, wrapping tape between each group of cores to bond them together, and reserving injection holes on the tape; S204, pouring polyurethane material into the pouring hole, and removing the tape after the polyurethane solidifies.

5. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 3, characterized in that: Methods for determining initial values ​​of material parameters include: S301, finding the peak tensile force in each true force-displacement curve, and calculating the polyurethane bonding stiffness corresponding to each true force-displacement curve; S302, averaging all peak tensile forces to obtain an average peak tensile force; averaging all polyurethane bonding stiffnesses to obtain an average bonding stiffness; S303, taking the average bonding stiffness as the initial value of the parallel bonding stiffness, and taking the average peak tension as the initial value of the ultimate tensile strength.

6. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 5, characterized in that: The method for calculating the polyurethane bond stiffness corresponding to each true force-displacement curve is: The peak tensile force value is divided by the displacement value corresponding to the point where the peak tensile force is located in the true force-displacement curve to obtain the polyurethane bonding stiffness corresponding to the current true force-displacement curve.

7. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 5, characterized in that: The method for determining the calibration force-displacement curve includes: fitting the calibration force-displacement curve based on the average peak tension and the average bond stiffness.

8. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 5, characterized in that: Step S4 specifically includes: S401. Keep the ultimate tensile strength as the initial value, design several different calibration schemes, and calibrate the parallel bond stiffness; S402. Based on the calibrated parallel bond stiffness, design several different calibration schemes to calibrate the parallel bond friction angle.

9. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 8, characterized in that: Step S401 specifically includes: S4011. Designing a number of different parallel bond stiffness values ​​within a set range near an initial value of the parallel bond stiffness; S4012. Based on the empirical method, design several different values ​​of parallel bond friction angle; S4013. Based on several different values ​​of parallel bond stiffness and several different values ​​of parallel bond friction angle, several preliminary bid schemes for key parameters are obtained; S4014, substituting the preliminary standard schemes of each key parameter into the rock-polyurethane model, simulating the tensile test, and obtaining the preliminary standard force-displacement curve; S4015. Compare each preliminary calibration force-displacement curve with the calibration force-displacement curve to find the key parameter preliminary calibration scheme with the highest degree of consistency, and use the parallel bonding stiffness therein as the parallel bonding stiffness after calibration.

10. The method for calibrating foam material parameters of a polyurethane-cured ballast according to claim 9, characterized in that: Step S402 specifically includes: S4021. Designing a number of different values ​​of the parallel adhesion friction angle within a set range near the parallel adhesion friction angle in the initial bid scheme of the key parameter with the highest degree of fit; S4022, based on the initial value of the ultimate tensile strength, the calibrated parallel bond stiffness, and the several different values ​​of the parallel bond friction angles, obtain several key parameter precision calibration schemes; S4023, substituting the precise calibration scheme of each key parameter into the rock-polyurethane model, simulating the tensile test, and obtaining the precise calibration force-displacement curve; S4024. Compare each precision-calibrated force-displacement curve with the calibration force-displacement curve to find the key parameter precision-calibration scheme with the highest degree of agreement, and use the parallel adhesion friction angle therein as the calibrated parallel adhesion friction angle.

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