Curved surface type grouser structure coupling simulation method based on DEM-MBD

Abstract

A curved surface type grouser structure coupling simulation method based on DEM-MBD comprises the steps that firstly, three-dimensional software is used for establishing a caterpillar band single body model with curved surface type grousers, then a caterpillar band model is obtained through a single body array, a driving wheel model, a thrust wheel model and a guide wheel model are established, a vehicle body model is assembled, and a whole vehicle model is obtained; the method comprises the following steps of: constructing a simulation environment by utilizing the cooperation of Recurdyn software and EDEM software, establishing a same crawler-soil coupling simulation model, simultaneously performing simulation coupling in the Recurdyn software and the EDEM software through a step-by-step iteration method, mutually exchanging data between the Recurdyn software and the EDEM software to perform bidirectional coupling calculation, calculating crawler motion stress characteristics by Recurdyn, and calculating the crawler motion stress characteristics by using the EDEM software. The EDEM simulates the mechanical and motion characteristics of the soil bed particles, the EDEM and the soil bed particles exchange data with each other, the simulation calculation process is completed, the accuracy of the simulation result is finally ensured, and powerful support is provided for the structural optimization design of the curved surface type grouser.

Description

Technical Field

[0001] The invention relates to the field of coupled simulation methods of grouser structures, and in particular to a coupled simulation method of curved grouser structures based on DEM-MBD. Background Art

[0002] As the carrier of agricultural equipment under complex terrain conditions, all-terrain engineering vehicles are usually divided into: wheeled, foot-type, crawler-type, etc. Compared with the other two types, tracked all-terrain vehicles have the advantages of small ground contact pressure, strong climbing ability, small turning radius, and strong obstacle crossing ability. They have gradually become the preferred carrier of agricultural intelligent equipment in mountainous and hilly areas. Tracked vehicles are widely used in forestry, agriculture, mining and other fields due to their large contact area with the soil, good passability and good soil adhesion. However, tracked vehicles are prone to slipping due to insufficient adhesion when driving on soft hilly soil, resulting in complex changes in driving performance, which seriously affects their passability. As an important component to enhance the adhesion and friction between the track and the ground, the structure of the spur structure has an extremely important influence on the adhesion performance of the tracked vehicle.

[0003] The existing spur structures are all straight spurs, that is, long rectangular spur structures. Although a variety of design methods are used to improve adhesion, the limitations of the straight spur structure itself still restrict the adhesion of the track. Therefore, a curved spur structure is proposed, which changes the surface of the side where the spur pushes the soil to an arc surface, which can improve the adhesion of the track compared to the existing straight track. However, when designing specific parameters for the curved spurs, it is necessary to simulate and judge the performance of the track through simulation. The existing technology generally adopts a track structure optimization method based on a single finite element analysis. The simulation process is complex, the calculation time is long, and the simulation environment is quite different from the actual working environment of the track, resulting in low accuracy of the simulation results. Summary of the invention

[0004] The purpose of the present invention is to provide a coupled simulation method of a curved grouser structure based on DEM-MBD to improve the simulation accuracy.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a DEM-MBD-based curved spur structure coupling simulation method, comprising the following steps: Step 1, using 3D software to establish a crawler monomer model with curved spurs, including a crawler section and a spur of a long strip structure, the length direction of the spur is parallel to the width direction of the crawler, the two sides of the spur along the thickness direction are a base surface and a bottom surface parallel to each other, the base surface is connected to the surface of the crawler, one side of the spur along the width direction is a back-soil plane away from the movement direction of the spur, the other side of the spur along the width direction is a bulldozer arc surface facing the movement direction of the spur, the back-soil plane and the bottom surface are perpendicular to each other, the axis of the bulldozer arc surface and the bottom surface are located in the same reference plane, and the axis of the bulldozer arc surface is located on the side of the bottom surface away from the back-soil plane along the movement direction of the spur, the axis of the bulldozer arc surface is parallel to the length direction of the spur, and the radius of the bulldozer arc surface is not less than the thickness of the spur; Then, the crawler model is arrayed to obtain a crawler model, and the crawler model is assembled with a driving wheel model, a supporting wheel model and a guide wheel model to obtain a complete vehicle model; Step 2: Use Recurdyn software and EDEM software to build a simulation environment, establish a ground system in Recurdyn software, load the whole vehicle model on the ground system and set the structural parameters; randomly generate soil particle models of different geometric shapes and sizes in EDEM software, use gravity deposition method to pile and bond the soil particle models, establish a soil bed model on the ground system, and make the soil bed model located in front of the whole vehicle model along the X-axis direction, so as to establish the same track-soil coupling simulation model in Recurdyn software and EDEM software; Step 3: Simulate the track-soil coupling simulation model simultaneously in Recurdyn and EDEM software by a step-by-step iteration method. First, set the simulation time in Recurdyn and EDEM software, and set the time step in RecurDyn software to an integer multiple of the time step in EDEM software. Then make the whole vehicle model move along the X-axis direction, and perform coupled simulation of the interaction between the track and the soil through the movement of the whole vehicle model on the soil bed model. Calculate the force characteristics of the track motion through Recurdyn software, and calculate the mechanical and motion characteristics of the soil bed particles through EDEM software. Recurdyn and EDEM software exchange data with each other for two-way coupling calculation. Output the simulation results after the simulation time is reached, and complete the coupled simulation of the curved track structure.

[0006] Preferably, in step 2, the soil particle models are bonded according to the Hertz-Mindlin with Bonding contact model, so that bonding bonds that withstand normal force and tangential force within a predetermined range are formed between the soil particle models.

[0007] According to the above technical solution, the beneficial effects of the present invention are: The present invention utilizes Recurdyn software and EDEM software to build a simulation environment, establishes the same track-soil coupling simulation model in Recurdyn software and EDEM software, and then performs simulation coupling in Recurdyn software and EDEM software simultaneously through a step-by-step iteration method. Recurdyn software and EDEM software exchange data with each other to perform two-way coupling calculation. The DEM method of EDEM software can accurately simulate the interaction between particles and between particles and other objects, and is particularly suitable for the behavior simulation of the track system on complex terrain. The MBD multi-body dynamics of Recurdyn software can simulate the overall motion behavior and dynamic characteristics of the track system. Through the mutual combination of DEM and MBD methods, the interaction between the track and the ground can be accurately simulated at the particle level, and the dynamic response of the entire track system can be captured, thereby ultimately ensuring the accuracy of the simulation result and providing strong support for the structural optimization design of the curved track spur. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of a curved spur; Figure 2 It is a partial schematic diagram of a crawler with curved grouser installed; Figure 3 It is a side view of the curved spur; Figure 4 This is the side view of the spur when the minimum radius is used; Figure 5 This is the force analysis diagram of the sliding soil when the spur pushes the soil; Figure 6 Schematic diagram of differentiating sliding soil.

[0009] Markings in the figure: 1. Spurs, 2. Tracks, 3. Base surface, 4. Bottom surface, 5. Soil-carrying plane, 6. Bulldozer arc surface, 7. Soil, 8. Sliding soil. DETAILED DESCRIPTION

[0010] With reference to the accompanying drawings, the specific implementation is as follows: A coupled simulation method for a curved spur structure based on DEM-MBD includes the following steps: Step 1: Use 3D software to build a single body model of a crawler track 2 with curved spurs, including a crawler track 2 and a long strip-shaped spur 1.

[0011] The structure of the curved spur is as follows: Figure 1-3As shown, the length direction of the spur 1 is parallel to the width direction of the track 2, the two sides of the spur 1 along the thickness direction are a base surface 3 and a bottom surface 4 which are parallel to each other, the base surface 3 is connected to the surface of the track 2, one side of the spur 1 along the width direction is a soil-carrying plane 5 which is away from the movement direction of the spur 1, and the other side of the spur 1 along the width direction is a bulldozer arc surface 6 which is toward the movement direction of the spur 1, the soil-carrying plane 5 and the bottom surface 4 are perpendicular to each other, and the soil-carrying plane 5 extends along the length direction of the spur.

[0012] like Figure 1 , 3 As shown, the axis of the bulldozer arc surface 6 and the bottom surface 4 are located in the same reference plane, and the axis of the bulldozer arc surface 6 is located on the side of the bottom surface 4 away from the back-soil plane 5 along the movement direction of the grouser 1, the axis of the bulldozer arc surface 6 is parallel to the length direction of the grouser 1, and the radius of the bulldozer arc surface 6 is not less than the thickness of the grouser 1. Figure 3 From the side view, the tangent of the bulldozer arc surface 6 at the connection position with the bottom surface 4 is perpendicular to the bottom surface 4 and parallel to the back-soil plane 5, and the position where the other side of the bulldozer arc surface 6 extends to the crawler 2 will change according to the radius of the bulldozer arc surface 6. When the radius of the bulldozer arc surface 6 is the smallest, it is Figure 4 The radius of the bulldozer arc surface 6 shown is equal to the thickness of the spur 1. At this time, the tangent of the bulldozer arc surface 6 at the connection position with the base surface 3 is located on the base surface 3, and the arc angle of the bulldozer arc surface 6 is 90°.

[0013] Then the track monomer model is arrayed to obtain the track model. Figure 2 That is, a partial section of the track model that includes two curved spurs. The track model is assembled with the driving wheel model, the supporting wheel model and the guide wheel model to obtain the whole vehicle model.

[0014] Step 2: Use Recurdyn software and EDEM software to build a simulation environment, establish a ground system in Recurdyn software, load the vehicle model on the ground system and set the structural parameters. Randomly generate soil particle models of different geometric shapes and sizes in EDEM software, and then use the gravity deposition method to stack and bond the soil particle models according to the Hertz-Mindlin with Bonding contact model, and form bonding bonds between the soil particle models that withstand normal and tangential forces within a predetermined range. Finally, establish a soil bed model on the ground system, and make the soil bed model located in front of the vehicle model along the X-axis direction, so as to establish the same track-soil coupling simulation model in Recurdyn software and EDEM software.

[0015] Step 3: Simulate the track-soil coupling simulation model simultaneously in Recurdyn and EDEM software by using a step-by-step iteration method. First, set the simulation time in Recurdyn and EDEM software, and set the time step in RecurDyn software to an integer multiple of the time step in EDEM software. Then, make the whole vehicle model move along the X-axis direction, and perform the coupled simulation of the interaction between the track 2 and the soil 7 through the movement of the whole vehicle model on the soil bed model.

[0016] The Recurdyn software is used to calculate the motion force characteristics of track 2, and the EDEM software is used to calculate the mechanical and motion characteristics of soil bed particles. Recurdyn software and EDEM software exchange data with each other for two-way coupling calculation. After the simulation time is reached, the simulation results are output, and the coupling simulation of the curved spur structure is completed.

[0017] The simulation results can provide support for the structural design of the curved grouser. The specific method is to change the radius of the bulldozer arc surface 6 of the curved grouser, perform multiple simulations on the vehicle model with different radii, calculate the track adhesion according to the multiple simulation results, compare the track adhesion at different radii, and select the radius with the largest adhesion as the radius of the bulldozer arc surface 6, so as to optimize the structure of the curved grouser.

[0018] The force analysis of curved spurs pushing soil is as follows: Figure 5 As shown, the ABC area is the sliding soil body 8 where the soil 7 is pushed and slides, AB represents the bulldozer arc surface 6, AC represents the base surface 3 of the spur 1 and the surface of the soil 7, and BC is the soil sliding surface of the sliding soil body 8. The dFp arrow represents the force of the bulldozer arc surface 6 acting on the sliding soil body 8, and the f arrow represents the friction between the remaining sliding soil body 8 and the remaining soil 7 when sliding occurs.

[0019] The calculation formula for track adhesion is: ; In the above formula, b is the length of the spurs, l is the length of the track shoe in the single-body track model, d is the width of the bottom surface of the spur, R is the radius of the bulldozer arc surface, h is the thickness of the shoe spur, M i is the number of all spurs in the vehicle model.

[0020] z is the soil subsidence, n is the soil deformation index, γ is the soil specific gravity, cis the soil cohesive strength, k c is the soil cohesive deformation modulus, k φ is the soil friction deformation modulus, W Add load in vertical direction.

[0021] δ is the friction angle between soil and spurs, φ is the internal friction angle.

[0022] Among the above parameters, soil cohesion strength c and soil deformation index n Need to be determined based on simulation results, except δ , φ , c and n All other parameters can be set directly or selected by referring to the simulation results. δ and φ The angle will change with the settings of other parameters. δ The essence of the angle is equivalent to differentiating the sliding soil, such as Figure 6 As shown in the figure, a differential trapezoid is generated in the sliding soil. The two bases of the differential trapezoid are parallel to the soil sliding surface BC. One oblique side of the differential trapezoid is located on the AC surface of the sliding soil, and the other oblique side is located on the AB surface where the sliding soil contacts the bulldozer arc surface 6, and is parallel to the AB arc in the soil settlement amount. z The angle between the tangent line and the vertical direction is the friction angle between the soil and the spur. δ .

[0023] It can be seen that as the soil subsidence z The changes of different depth positions δ The angle will also change. To simplify the calculation process and ensure the validity of the calculation results, z The value is z = h , δ The value is δ =arcsin( z / R ).

[0024] φ The value of is determined by first replacing the curved spurs in the track monomer model with the straight spurs of the rectangular structure, the length of the straight spurs is equal to the length of the curved spurs, the thickness of the straight spurs is equal to the thickness of the curved spurs, and the width of the straight spurs is equal to the bottom width of the curved spurs.

[0025] The various parameters of the linear grouser when pushing the soil can be obtained through existing design experience and design methods. Therefore, according to the sliding soil body 8 formed when the linear grouser pushes the soil 7, the angle between the soil sliding surface and the horizontal plane is obtained. θ , and then according to Get the internal friction angle φ The value of .

[0026] This embodiment uses five different spur structures for comparative simulation experiments, among which the four spur structures are curved spurs with a bottom width of 12 mm and a thickness of 12 mm, and the radii are respectively R Ⅰ =12mm, R Ⅱ =15mm, R Ⅲ =18mm and R Ⅳ =24mm, and the other spur structure is a straight spur as a comparative example, the width of the straight spur is 12mm, the thickness is 12mm, and the length is equal to the four curved spurs. After simulation and calculation of adhesion, the results are shown in the following table.

[0027] Table 1 Comparison of average adhesion of tracks with different spur types The actual test results show that under the same working conditions, the adhesion of the curved track is better than that of the straight track, and the improvement ratio of the curved track on adhesion increases with the decrease of the curvature radius of the track. This is because the soil particles have more interaction with the track surface, which can provide a greater reaction force and is beneficial to enhance the adhesion performance between the track and the soil.

[0028] This embodiment jointly adopts the DEM method of EDEM software and the MBD multi-body dynamics method of Recurdyn software, which can accurately simulate the interaction between the track and the ground at the particle level, while capturing the dynamic response of the entire track system, ultimately ensuring the accuracy of the simulation results and providing strong support for the structural optimization design of curved spurs.

Claims

1. A coupled simulation method for curved grouser structure based on DEM-MBD, characterized in that: The following steps are involved: Step 1: Use three-dimensional software to establish a single body model of a crawler (2) with curved spurs, including a crawler (2) and a long strip-shaped spur (1), wherein the length direction of the spur (1) is parallel to the width direction of the crawler (2), and the two sides of the spur (1) along the thickness direction are a base surface (3) and a bottom surface (4) parallel to each other, and the base surface (3) is connected to the surface of the crawler (2), and one side of the spur (1) along the width direction is a back-soil plane (5) away from the movement direction of the spur (1), and the spur (1) along the thickness direction is parallel to the width direction of the crawler (2). The other side in the width direction is a bulldozer arc surface (6) facing the movement direction of the spur (1), the back-soil plane (5) and the bottom surface (4) are perpendicular to each other, the axis of the bulldozer arc surface (6) and the bottom surface (4) are located in the same reference plane, and the axis of the bulldozer arc surface (6) is located on the side of the bottom surface (4) away from the back-soil plane (5) along the movement direction of the spur (1), the axis of the bulldozer arc surface (6) is parallel to the length direction of the spur (1), and the radius of the bulldozer arc surface (6) is not less than the thickness of the spur (1); Then, the crawler model is arrayed to obtain a crawler model, and the crawler model is assembled with a driving wheel model, a supporting wheel model and a guide wheel model to obtain a complete vehicle model; Step 2: Use Recurdyn software and EDEM software to build a simulation environment, establish a ground system in Recurdyn software, load the whole vehicle model on the ground system and set the structural parameters; randomly generate soil particle models of different geometric shapes and sizes in EDEM software, use gravity deposition method to pile and bond the soil particle models, establish a soil bed model on the ground system, and make the soil bed model located in front of the whole vehicle model along the X-axis direction, so as to establish the same track-soil coupling simulation model in Recurdyn software and EDEM software; Step 3: Simulate the coupling of the track-soil coupling simulation model simultaneously in the Recurdyn software and the EDEM software by a step-by-step iteration method. First, set the simulation time in the Recurdyn software and the EDEM software, and set the time step in the RecurDyn software to an integer multiple of the time step in the EDEM software. Then, make the whole vehicle model move along the X-axis direction, and perform the coupling simulation of the interaction between the track (2) and the soil (7) through the movement of the whole vehicle model on the soil bed model. Calculate the force characteristics of the track (2) movement through the Recurdyn software, and calculate the mechanical and motion characteristics of the soil bed particles through the EDEM software. The Recurdyn software and the EDEM software exchange data with each other for two-way coupling calculation. After reaching the simulation time, output the simulation results, and complete the coupling simulation of the curved track structure.

2. The method for coupling simulation of curved grouser structure based on DEM-MBD according to claim 1, characterized in that: In step 2, the soil particle model is bonded according to the Hertz-Mindlin with Bonding contact model, and bonding bonds that withstand normal force and tangential force within a predetermined range are formed between the soil particle models.

Images