A new composite friction energy-absorbing structure and design method

Abstract

The application discloses a novel composite friction energy-absorbing structure and a design method, and belongs to the technical field of collision energy-absorbing, and comprises a novel composite friction energy-absorbing structure (HFEAS) which is composed of a bearing bush, a climbing-preventing device, a pre-tightening bolt, a friction plate and a friction tube, one end of the friction tube is bonded with an inner tube iron, the outer side of the friction tube is provided with the friction plate through the bearing bush, and the other end of the friction tube is provided with the climbing-preventing device. The novel composite friction energy-absorbing structure and the design method are adopted, the high strength, the high rigidity and the tribological characteristics of the composite material are combined, and a new direction is provided for the energy level active control, the repeated utilization, the iterative upgrading and the development of the energy-absorbing structure.

Description

Technical Field

[0001] The present invention relates to the technical field of collision energy absorption, and in particular to a novel composite friction energy absorption structure and a design method thereof. Background Art

[0002] In recent years, a large number of scholars have conducted extensive research on energy-absorbing structures such as thin-walled structures and columnar structures. Traditional circular, square and honeycomb tube structures are widely used in energy absorbers due to their simple structural configuration, easy processing and low cost. At present, the energy-absorbing structures in the railway industry mainly include expansion type, contraction type, split type, cutting type and collapse type. In 2018, Li et al. combined experimental and numerical methods to study the energy absorption behavior of contraction tubes under quasi-static loads. The results show that the force-displacement curve is greatly affected by the cone angle and tube size, while the friction coefficient has little effect on it; in 2020, Guan et al. used theoretical, experimental and numerical methods to study the energy absorption behavior of split multi-circular tubes.

[0003] With the high level of social and economic development and the political pressure to reduce fuel combustion and carbon emissions, the supervision of the railway, aviation, automobile and maritime industries is gradually increasing, and the lightweight design of collision-resistant energy-absorbing structures has been proposed. At present, the research on new materials mainly includes: aluminum alloys, high-strength steel, composite materials, polymers and sponge rubber. In 2021, Liu et al. proposed an energy-absorbing structure based on the combination of functional gradient and fractal honeycomb. In 2014, Kathiresan et al. studied the quasi-static axial compression capacity of thin-walled e-type glass fiber / epoxy resin reinforced (GFRP) composite conical shells, studied the buckling mode and fracture area of ​​GFRP composite conical shells, and determined the thin collapse mechanism. In 2017, Sun et al. used finite element simulation analysis methods to study the collision characteristics of traditional square tubes and cross tubes in aluminum structures through experiments and numerical analysis. In 2014, Xu et al. studied the strength enhancement of honeycomb metals such as foam aluminum and honeycomb under dynamic compression. In 2020, Xu et al. designed and compared the collision performance of axisymmetric rectangular tube (ART) and uniform thickness tube (UTT) under offset load.

[0004] Due to the advantages of composite materials, such as light weight and high energy absorption ratio, many researchers have used them in the design of energy-absorbing structures. However, most of these methods are aimed at energy-absorbing structures that collapse and cannot be repaired, and they cannot achieve active control and energy level matching of the energy-absorbing structures. At the same time, few researchers have studied the friction properties of composite materials to design reusable friction energy-absorbing structures and to investigate their application effects in energy-absorbing structures.

[0005] Passive safety protection is provided by energy-absorbing structures at the ends of rail vehicles, the last line of defense for passengers in collision accidents. Currently, most energy-absorbing structures absorb energy through plastic deformation and collapse, which cannot be reused and matched with active energy level control. The development of high-quality, efficient, and environmentally friendly energy-absorbing structures that are reusable and can achieve active energy level control has become a research hotspot. Summary of the Invention

[0006] The purpose of this invention is to provide a new type of composite friction energy absorption structure and design method, which combines the high strength, high stiffness and tribological properties of composite materials, and provides a new direction for the active control, reuse, iterative upgrading and development of energy levels of energy absorption structures.

[0007] To achieve the above objectives, the present invention provides a novel composite friction energy absorption structure, including a friction tube, one end of which is bonded with an inner tube iron, a friction plate is installed on the outside of the friction tube through a bearing shell, and the other end of the friction tube is provided with an anti-climbing device.

[0008] Preferably, the friction tube is a metal friction tube or a CFRP friction tube.

[0009] Preferably, the outer side of the friction tube is bonded to the inner tube iron, the bearing bush and the friction plate using methacrylate structural adhesive.

[0010] Preferably, the bearing is mounted on the outer side of the friction tube by pre-tightening bolts, and the magnitude of the friction force is controlled by adjusting the pre-tightening pressure, thereby achieving collision resistance performance level matching and active control of the energy-absorbing structure.

[0011] A design method for a novel composite friction energy absorption structure includes the following steps:

[0012] Step 1: Prepare carbon fiber raw materials. The carbon fiber material is prefabricated from carbon fiber and epoxy resin film.

[0013] Step 2: Clean the raw materials with acetone;

[0014] Step 3: Cut the raw materials, splice the carbon fiber layers at 0° and 90° angles, wrap them with high-strength BOPP tape and PET tape, and spin-form them at high temperature for every 2mm wall thickness;

[0015] Step 4: Set the winding machine to 300 rpm to shape the carbon fibers into corresponding friction tubes and friction plates;

[0016] Step 5: Cut the special-shaped CFRP into special-shaped round tubes and round tiles of corresponding lengths using a water jet cutting process;

[0017] Step 6: Establish and verify the finite element model of HFEAS;

[0018] Step 7: Perform parameter analysis and multi-objective optimization on the energy-absorbing structure.

[0019] Preferably, the verification in step six is ​​specifically as follows:

[0020] In order to evaluate the crashworthiness of energy-absorbing structures, four indicators are used: energy absorption EA, initial peak impact force IPIF, impact force efficiency IFE, and specific energy absorption SEA. Their mathematical expressions are as follows:

[0021]

[0022] Where, S is the relative displacement during the collision; F is the impact force during the collision;

[0023] IPIF=max(F);

[0024] Where F is the impact force during the collision;

[0025]

[0026] Where F mean is the average force during the collision, F max is the overall maximum force during the collision, and the IFE describes the uniformity of the force-displacement response;

[0027]

[0028] Where m is the mass of the energy-absorbing structure, and SEA represents the collision energy absorbed per unit mass;

[0029] The calculation method of the specific component failure criterion is as follows:

[0030] For stretched fiber mode:

[0031]

[0032] For compressed fiber mode:

[0033]

[0034] For Stretch Matrix mode:

[0035]

[0036] For compressed matrix mode:

[0037]

[0038] Where σ aa and σ bb are the stresses in directions 1 and 2 respectively; X c 、Xt 、Y c and Y t Represent the ultimate stresses of longitudinal compression, longitudinal tension, transverse compression and transverse tension respectively; S c is the shear strength, τ ab is the shear stress; β represents the weight factor of the shear contribution to the tensile fiber mode, which is a nonlinear factor.

[0039] Therefore, the present invention adopts the above-mentioned new composite friction energy absorption structure and design method, combining the high strength, high stiffness and tribological properties of composite materials, and provides a new direction for the active control, reuse, iterative upgrading and development of energy levels of energy absorption structures.

[0040] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the HFEAS structure of an embodiment of a novel composite friction energy absorption structure and design method of the present invention;

[0042] Figure 2 This is a finite element model diagram of HFEAS of an embodiment of a novel composite friction energy absorbing structure and design method of the present invention;

[0043] Figure 3 Schematic diagram of the stress direction of CFRP in the verification of an embodiment of a novel composite friction energy absorption structure and design method of the present invention;

[0044] Figure 4 This is a comparison diagram of the experiment and simulation of a novel composite friction energy absorption structure and design method embodiment of the present invention, wherein Figure 4 (a) is the force-displacement curve of the experiment and finite element simulation. Figure 4 (b) is the time-energy curve of the experiment and finite element simulation;

[0045] Figure 5 It is a multi-objective optimization process of an embodiment of a novel composite friction energy absorption structure and design method of the present invention;

[0046] Figure 6 It is a Pareto solution diagram of an embodiment of a novel composite friction energy absorption structure and design method of the present invention;

[0047] Figure 7 It is a radar chart of various crashworthiness indicators of an embodiment of a novel composite friction energy absorption structure and design method of the present invention.

[0048] Reference numerals

[0049] 1. Bearing; 2. Pre-tightening bolt; 3. Friction plate; 4. Friction tube; 5. Anti-climbing device. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0051] Unless otherwise defined, technical or scientific terms used herein shall have the same meaning as those generally understood by persons of ordinary skill in the art to which the present invention pertains. Terms such as "connect" or "connected" as used herein are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0052] Example 1

[0053] The present invention provides a novel composite friction energy absorbing structure (HFEAS) and its design method, which consists of a bearing 1, an anti-climbing device 5, a pre-tightening bolt 2, an inner iron tube, a friction tube 4 and a friction plate 3. The schematic diagram of the HFEAS structure is shown in FIG. Figure 1 As shown, one end of the friction tube 4 is bonded to the inner iron tube. Friction tube 4 is made of metal or CFRP. The outer surface of friction tube 4 is bonded to the inner iron tube, bearing shell 1, and friction plate 3 using methacrylate structural adhesive to ensure overall structural stability. An anti-climbing device 5 is installed at the other end of friction tube 4 to prevent passengers or others from walking or climbing on the contact rail, ensuring normal train operation.

[0054] The bearing shell 1 secures the friction plate 3 to the outer side of the friction tube 4 via pre-tightening bolts 2. The friction tube 4 is tightly surrounded by the friction plate 3. The mutual compression between the friction plate 3 and the friction tube 4 generates corresponding axial pressure and normal force, which in turn generates annular resistance that blocks the friction tube 4. This can replace the intermediate energy-absorbing structure of existing high-speed train couplers and can be widely used in various types of subways, locomotives, and high-speed trains, eliminating the need for separate design.

[0055] By adjusting the preload force, the coupler can achieve a wide range of safety thresholds. The platform force of the coupler collision process can be accurately and freely controlled to achieve high-efficiency energy level matching, and the safe speed of the high-speed train coupling is increased from 7km / h to 14km / h, greatly improving the train coupling safety threshold and coupling efficiency, and providing new ideas for the rapid dispatch and precise control of high-speed trains.

[0056] After the friction plate 3 and the friction tube 4 are squeezed against each other, the structure can be used again by adjusting the pre-tightening bolt 2 again. In this way, the structure can be reused, greatly reducing the cost of use and providing effective guarantees for the pedigree design of the train's crashworthiness and energy absorption structure and the correlation analysis of structural parameters.

[0057] The preload bolt 2 has a strength grade of 8.8 and a bolt hole size of M10 mm. The bearing bushing is secured with bolts and washers. Preload is applied to the bearing bushing using a digital torque wrench to ensure consistent preload across all four bolts. The diameters of the bearing shell 1, friction plate 3, friction tube 4, and inner iron tube are 40 mm, 30 mm, 20 mm, and 5 mm, respectively. The ring angles of the bearing shell 1 and friction plate 3 are both 160°. The thickness of the bearing shell 1, friction plate 3, friction tube 4, and inner iron tube are all consistent, at 5 mm.

[0058] The HFEAS manufacturing process is complex, requiring separate processing of carbon fiber and steel materials during testing. Currently, carbon fiber types include CFRP (carbon fiber reinforced plastic) and other FRP (fiber reinforced plastic). CFRP offers excellent specific strength and stiffness. The CFRP reinforcements comprise 24k in volume, representing a 60% volume fraction, and epoxy resin is used as the carbon fiber matrix. Due to the high level of impurities on the Q345 surface, simply bonding the CFRP to the material can easily cause it to fall apart.

[0059] To improve the performance of the CFRP-steel joint, the outer surfaces of the joint were polished using a sander. Methacrylate structural adhesive was then applied to the gap between the outer surfaces of the steel and CFRP joints. A vacuum pump was then used to create a pressure of 0.02 MPa, which was then turned off and held for 5 minutes. After vacuuming, the specimens were clamped and placed in an oven for processing. The specimens were preheated to 100°C, cured at 150°C for 1 hour, then at 120°C for 30 minutes, and then removed after cooling to 50°C. A pressure of 0.02 MPa was maintained throughout the entire process.

[0060] The finite element model of HFEAS is as follows Figure 2 As shown, the accuracy of the finite element simulation is verified. The experimental and simulation parameter settings are as follows: the outer diameter of the friction tube is set to 20 mm, the thickness of the inner tube iron and the bearing is set to 5 mm, the pre-contact length is set to 50 mm, and the thickness of the friction tube and the fiber tube is set to 2 mm.

[0061] The force-displacement curves and time-energy curves of the experiment and finite element simulation are shown in Figure 2. Figure 4 (a) and Figure 4 (b) is shown. Figure 4 As can be seen from (a), the simulation curve has certain fluctuations compared with the experimental curve. The simulation curve oscillates around the experimental curve, and the overall difference is not large. Figure 4 (b) shows that the energy value of the simulation curve is slightly larger than that of the test curve at the beginning and slightly smaller than that of the test curve at the end. Overall, the simulation curve fluctuates around the test curve, and the change process is basically the same.

[0062] Multi-objective optimization:

[0063] In the event of a train collision, the HFEAS should be designed to absorb as much energy as possible to prevent passenger injuries. Comparison revealed that the friction tube diameter D, bolt preload P_F, and inner tube iron thickness S_t significantly impact the structure's crashworthiness. Therefore, referring to the bolt preload standard and the train energy absorption tube diameter design reference, the values ​​of D and P_F are set to [20, 140] and [1000, 49000], respectively. The multi-objective problem of the HFEAS is expressed as follows:

[0064]

[0065] The sampling method for DOE is an important prerequisite for multi-objective optimization. The main sampling methods include the Hammersley method, the Full Factorial method, the Box Behnken method, and the Latin Hypercube method. Compared with traditional sampling methods, the Hammersley method reduces the number of samples by a factor of two, making it suitable for highly nonlinear response surfaces. It reduces time and unit cost while maintaining the same level of accuracy. Therefore, the Hammersley sampling method was used to fit an accurate candidate model using 100 levels. The generated sampling points and their corresponding responses are shown in Table 1.

[0066] Table 1 Sampling results of finite element models with different structural parameters based on Hammersely

[0067] No. D(mm) P_F(N) S_t(mm) PCF(kN) EA(kJ) SEA (kg / kJ) 1 20.4 11000 3.7 78.4 11.8 3.60 2 21.3 6000 5.3 42.0 6.1 1.46 3 22.1 16000 2.6 121.0 17.7 6.15 4 22.9 3500 4.2 24.6 3.7 0.96 5 23.8 13500 5.9 92.4 14.1 2.91 6 24.6 8500 3.1 62.3 9.5 2.80 7 25.4 18500 4.8 127.0 19.4 4.35 8 26.3 2250 6.4 25.5 2.3 0.41 9 27.1 2250 2.2 95.1 13.8 4.57 10 27.9 250 3.9 52.9 7.9 1.88 11 28.8 17250 5.5 124.1 18.5 3.44 12 29.6 4750 2.7 35.1 5.2 1.45 13 30.4 14750 4.4 109.8 16.1 3.33 14 31.3 9750 6.1 69.5 10.1 1.65 15 32.1 19750 3.3 152.0 21.1 5.02 16 32.9 1625 5.0 27.9 1.8 0.32 17 33.8 11625 6.6 82.0 12.0 1.72 18 34.6 6625 2.4 50.5 7.7 2.12 19 35.4 16625 4.0 125.2 18.5 3.62 20 36.3 4125 5.7 36.9 4.4 0.66 ... ... ... ... ... ... ... 100 39.6 2875 3.5 27.3 3.2 0.64

[0068] Surrogate model and error analysis:

[0069] Since high-speed train collision is a mechanical problem involving highly nonlinear responses and large deformations, it is usually difficult to derive the objective functions of its response indicators EA, PCF and SEA using traditional mathematical methods. In order to obtain efficient and accurate optimization results, alternative modeling technology has become an effective method to solve this complex problem. Currently, widely used alternative models include least squares regression (LSR), moving least squares method (MLSM), radial basis function (RBF) and polynomial response surface (PRS) models, which have been proven to be particularly effective in crashworthiness design. Using MLSM, a cubic polynomial model is obtained as shown below:

[0070] PCF=-2.12+1.89*D+0.0052*P_F-6.76*S_t-0.026*D 2 +0.58*S_t 2 ;

[0071] EA=2.17-0.092*D+0.001*P_F-0.47*S_t+0.002*D2 +0.031*S_t 2 ;

[0072] SEA=7.47-0.16*D+0.00023*P_F-1.35*S_t+0.0016*D 2 +0.098*S_t 2 ;

[0073] To further ensure the accuracy and stability of the proxy model, the relative average absolute error (RAAE), root mean square error (RMSE) and coefficient of determination (R 2 ) is used to describe the accuracy of the model, and the evaluation indicators are defined as follows:

[0074]

[0075]

[0076]

[0077] Where y i 、 and are the true value, predicted value and average value of the sample points respectively, and n is the number of sample points.

[0078] The corresponding values ​​are shown in Table 2, which shows that EA, PCF and SEA have higher accuracy. 2 The values ​​of are 0.989, 0.997, and 0.953, respectively, with an error within 10%. The RAAE values ​​are all very small, less than 0.1. The RMSE value is higher. Overall, the prediction formula is highly accurate and can be used to predict the performance of hybrid friction energy-absorbing structures.

[0079] Table 2 Error analysis results

[0080] Target <![CDATA[R 2 ]]> RAAE RMSE PCF 0.989 0.085 43.36 EA 0.997 0.034 28.94 SEA 0.953 0.089 23.89

[0081] The number of multi-objective optimization objects is 3, and the objectives are not a simple linear relationship. Therefore, the G-CBW method is used to find the optimal Pareto solution set and obtain the weight ratio and optimal solution of the corresponding objectives.

[0082] The Gain Matrix-Cloud Model Best Worst (G-CBW) method is proposed to determine the Pareto solution set obtained by multi-objective optimization and obtain the optimal solution through the following steps: determining the target decision variables corresponding to the decision criterion; clarifying the best and worst decision objectives; determining the priority of the best decision objective and the worst decision objective relative to other decision objectives; finding the optimal weights, determining the gain matrix and the gain weight matrix; and finding the most satisfactory solution.

[0083] The G-CBW method combines all objectives into a single cost function through weighted averaging, emphasizing their relative importance. It is suitable for practical engineering applications and provides a reasonable means for optimizing decisions. In order to find the optimal solution from the Pareto solution set, the Pareto solution set can be multiplied by the transpose matrix of the gain weight matrix to obtain the corresponding decision target matrix. Then, by summing each row of the decision target, the corresponding Pareto solution with the largest sum is the optimal solution. The calculation formula is as follows. The multi-objective optimization technology route of HFEAS is as follows: Figure 5 shown.

[0084]

[0085] Where L is the decision target matrix; Y = [y ij ] mxn represents the Pareto solution set; C k (k=1,2,...,m) represents the kth solution of the Pareto solution set; D i (1,2,...,m) represents the i-th decision goal.

[0086] Optimization results:

[0087] Common optimization algorithms include the GRSM adaptive response surface method, the GRSM global response method, the genetic algorithm, and the MOGA multi-objective algorithm. The GRSM global response method can generate a response surface based on very few data points. Unlike other algorithms, which stop calculations after reaching a convergence criterion, it only stops optimization when the optimal value is reached. The GRSM method was used for multi-objective optimization, and the method parameters during the calculation are shown in Table 3.

[0088] Table 3 Parameters of GRSM algorithm

[0089]

[0090] Based on the GRSM algorithm for multi-objective optimization, the optimal performance of the Pareto solution set of EA, PCF and SEA is as follows: Figure 6 The optimal weights obtained from solving the model are (0.65, 0.25, 0.1), and the gain weights are (0.65, -0.25, 0.1). The gain decision matrix can be used to find the optimal solution for multi-objective optimization. The results show that when D = 118.1 mm, P_F = 49000 N, and S_t = 2 mm, the optimal solution is PCF = 357.52 kN, EA = 54.91 kJ, and SEA = 12.10 kJ / kg.

[0091] To illustrate the improvement in crashworthiness after optimization, Figure 7A radar plot of various crashworthiness metrics is presented, comparing the optimized structure's crashworthiness performance with that of the experimental sample. The radar plot clearly shows that the experimental results are completely matched by the optimized design. Although the PCF of the simulated results is larger than that of the experimental sample, all other crashworthiness metrics show significant improvements. Therefore, the optimized structure's overall crashworthiness performance has been enhanced.

[0092] Therefore, the present invention adopts the above-mentioned new composite friction energy absorption structure and design method, combining the high strength, high stiffness and tribological properties of composite materials, and provides a new direction for the active control of energy levels, reusability, iterative upgrading and development of energy absorption structures.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A design method for a novel composite friction energy absorption structure, characterized in that: The new composite friction energy absorption structure includes a friction tube, one end of which is bonded with an inner iron tube, a friction plate is installed on the outside of the friction tube through a bearing bush, and the other end of the friction tube is provided with an anti-climbing device; The friction tube is a metal friction tube or a CFRP friction tube; the outer side of the friction tube is bonded with the inner tube iron, the bearing bush and the friction plate using methacrylate structural adhesive; The design method includes the following steps: Step 1: Prepare carbon fiber raw materials. The carbon fiber material is prefabricated from carbon fiber and epoxy resin film. Step 2: Clean the raw materials with acetone; Step 3: Cut the raw materials, splice the carbon fiber layers at 0° and 90° angles, wrap them with high-strength BOPP tape and PET tape, and spin-form them at high temperature for every 2 mm wall thickness; Step 4: Set the winding machine to 300 rpm to shape the carbon fibers into corresponding friction tubes and friction plates; Step 5: Cut the special-shaped CFRP into special-shaped round tubes and round tiles of corresponding lengths using a water jet cutting process; Step 6: Establish and verify the finite element model of HFEAS; Step 7: Perform parameter analysis and multi-objective optimization on the energy-absorbing structure.

2. The design method of a novel composite friction energy absorption structure according to claim 1, characterized in that: The bearing bushing mounts the friction plate on the outside of the friction tube via pre-tightening bolts, and the friction force is controlled by adjusting the pre-tightening pressure, thereby achieving crash resistance performance level matching and active control of the energy-absorbing structure.

3. The design method of a novel composite friction energy absorption structure according to claim 1, characterized in that: The verification in step six is ​​specifically as follows: In order to evaluate the crashworthiness of energy-absorbing structures, the energy absorption EA , initial peak impact force IPIF , impact efficiency IFE and specific energy absorption SEA The mathematical expressions of the four indicators are: ； Where, S is the relative displacement during the collision process; F is the impact force during the collision; ； Where, F is the impact force during the collision; ； In the formula is the average force during the collision, is the overall maximum force during the collision, IFE describes the uniformity of the force-displacement response; ； Where, is the mass of the energy-absorbing structure, SEA It represents the collision energy absorbed per unit mass; The calculation method of the specific component failure criterion is as follows: For stretched fiber mode: ； For compressed fiber mode: For Stretch Matrix mode: ； For compressed matrix mode: In the formula and are the stresses in directions 1 and 2 respectively; 、 、 and represent the ultimate stresses of longitudinal compression, longitudinal tension, transverse compression, and transverse tension, respectively; is the shear strength, is the shear stress; The weighting factor representing the contribution of shear to the tensile fiber mode is a nonlinear factor.

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