A method and device for analyzing torsional stiffness of a bus body frame

Abstract

The present invention discloses a method and device for analyzing the torsional stiffness of a bus body frame. The method comprises: establishing a finite element model of the bus body frame based on a three-dimensional model of the bus body frame; establishing a simplified finite element suspension model; establishing boundary conditions to impose constraints on the finite element model of the bus body frame and the simplified finite element suspension model; establishing load conditions to apply loads to the simplified finite element suspension model and determine torque; performing a mechanical solution on the finite element model of the bus body frame to obtain displacements of measurement points and relative torsion angles of the bus body frame under torque; obtaining the torsional stiffness of the bus body frame based on the relative torsion angles, and detecting whether the bus body frame design scheme meets torsional stiffness requirements based on the torsional stiffness. The present invention can efficiently, accurately, and cost-effectively analyze the torsional stiffness of the bus body frame, while also enabling optimization of multiple design schemes and verification of their effectiveness.

Description

Technical Field

[0001] The invention belongs to the technical field of bus body structures, and in particular relates to a method and device for analyzing the torsional stiffness of a bus body frame. Background Art

[0002] The body frame is the primary structure of the passenger compartment of a bus. The design of the body frame must ensure sufficient torsional rigidity to resist torsional deformation. Insufficient torsional rigidity in the body frame will significantly reduce the bus's load-bearing capacity, increasing the likelihood of structural strength failure and fatigue damage and increasing the chance of window frame glass breakage. Furthermore, insufficient torsional rigidity in the body frame will reduce the body's modal properties, thereby reducing the bus's NVH (Noise, Vibration, Harshness) performance. Therefore, strict control of the bus body frame's torsional rigidity is necessary in the early stages of design to avoid the cost and time associated with optimization and rectification due to insufficient basic performance in the later stages of product development and during use.

[0003] In the existing technology, the torsional stiffness analysis of bus body frames usually adopts the empirical evaluation method. The accuracy of the torsional stiffness value is affected by the experience level of the designer. A universal analysis and evaluation system has not been formed in the early stage of design, and it cannot be guaranteed that the body frame has the required torsional stiffness during the design, development and actual production process. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for analyzing the torsional stiffness of a bus body frame, so as to solve the problem in the prior art that the torsional stiffness of the bus body frame is evaluated by empirical evaluation methods, and the accuracy of the torsional stiffness is affected by the experience level of the designer.

[0005] Based on the above objectives, in a first aspect, the present invention provides a method for analyzing the torsional stiffness of a bus body frame, comprising:

[0006] Establish a finite element model of the bus body frame based on the three-dimensional model of the bus body frame;

[0007] Establish a simple finite element suspension model;

[0008] Establishing boundary conditions, and applying constraints on the bus body frame finite element model and the finite element suspension simplified model respectively according to the boundary conditions;

[0009] establishing load conditions, applying loads to the simplified finite element suspension model according to the load conditions, and determining torque;

[0010] Performing mechanical solution on the finite element model of the bus body frame to obtain the displacement of the measuring point, and obtaining the relative torsion angle of the bus body frame under the action of the torque according to the displacement of the measuring point;

[0011] The torsional stiffness of the bus body frame is acquired according to the relative torsion angle, and whether the bus body frame design scheme meets the torsional stiffness requirement is detected according to the torsional stiffness of the bus body frame.

[0012] Preferably, the establishing of a simplified finite element suspension model includes:

[0013] Obtain the general arrangement drawing of the bus;

[0014] Obtaining a node set under different suspension states according to a general arrangement diagram of the bus;

[0015] The nodes in the node set are connected through one-dimensional units to complete the establishment of the finite element suspension simple model.

[0016] Preferably, the suspension state is a leaf spring state; and obtaining a node set in different suspension states according to the general layout diagram of the bus includes:

[0017] The node set is generated by determining the front axle left wheel center, the front axle right wheel center, the intersection point of the front axle and the left leaf spring, the intersection point of the front axle and the right leaf spring, and the midpoint of the intersection point of the front axle and the left and right leaf springs in the general layout diagram of the bus.

[0018] Preferably, the suspension state is an airbag state; and obtaining a node set in different suspension states according to the general layout diagram of the bus includes:

[0019] In the general layout diagram of the bus, the left wheel center of the front axle, the left wheel center of the front axle, the intersection point of the front axle and the left airbag, the intersection point of the front axle and the right airbag, and the midpoint of the intersection point of the front axle and the left and right airbags are determined to generate the node set.

[0020] Preferably, the establishing of boundary conditions and applying constraints on the bus body frame finite element model according to the boundary conditions include:

[0021] The center of the left side frame main longitudinal beam section corresponding to the rear axle in the bus body skeleton finite element model is marked as the first constraint point, and translational freedom constraints in the front-back, left-right, and up-down directions are applied at the first constraint point; and the center of the right side frame main longitudinal beam section corresponding to the rear axle is marked as the second constraint point, and translational freedom constraints in the front-back and up-down directions are applied at the second constraint point.

[0022] Preferably, the establishing of boundary conditions and applying constraints on the finite element suspension simplified model according to the boundary conditions include:

[0023] The midpoint of the intersection of the front axle and the left and right leaf springs or the front axle and the left and right airbags in the simple finite element suspension model is marked as a suspension constraint point, and a translational freedom constraint in the up and down directions is applied to the suspension constraint point.

[0024] Preferably, establishing the load condition, applying the load on the finite element suspension simplified model according to the load condition, and determining the torque includes:

[0025] Marking the front axle left wheel center and the front axle right wheel center in the finite element suspension simplified model as preset loading points;

[0026] Applying a first load and a second load to the left wheel center of the front axle and the right wheel center of the front axle respectively;

[0027] A torque applied to the front axle is obtained based on the first load and the second load.

[0028] Preferably, the calculation formula of the torque T is:

[0029]

[0030]

[0031] Wherein, T is the torque; F f is the first load applied in the vertical direction at the left wheel center of the front axle, F r is the second load applied to the right wheel center of the front axle in the vertical direction, and the first load and the second load are in opposite directions; L is the lateral distance between the left wheel center of the front axle and the right wheel center of the front axle; M f is the fully loaded axle weight of the front axle; g is the acceleration due to gravity.

[0032] Preferably, the calculation formula of the relative torsion angle is:

[0033]

[0034] Among them, α is the relative torsion angle of the bus body frame under the action of the torque; ΔZ1 is the absolute value of the vertical displacement of the left wheel center of the front axle as the test point; ΔZ2 is the absolute value of the vertical displacement of the right wheel center of the front axle as the test point; k is the torsion constant.

[0035] In a second aspect, the present invention provides a bus body frame torsional stiffness analysis device, comprising a processor, a memory, and a bus body frame torsional stiffness analysis program stored in the memory and runnable on the processor. When the processor executes the bus body frame torsional stiffness analysis program, the bus body frame torsional stiffness analysis method of the first aspect is implemented.

[0036] The present invention provides a bus body frame torsional stiffness analysis method and device. After establishing a bus body frame three-dimensional model and a finite element suspension simplified model, the bus body frame finite element model and the finite element suspension simplified model are first constrained according to boundary conditions, and the finite element suspension simplified model is loaded according to load conditions, and torque is determined to complete overall constraint and overall loading. Then, the bus body frame finite element model associated with the bus body frame three-dimensional model is solved to obtain the displacement of the measurement point, and the relative torsion angle of the bus body frame under the action of torque is obtained based on the displacement of the measurement point, thereby calculating the torsional stiffness. Finally, the torsional stiffness is used to detect whether the bus body frame design meets the torsional stiffness requirements. The present invention can analyze the torsional stiffness of the bus body frame efficiently, accurately, and at low cost. At the same time, it can realize the optimization of multiple design solutions and the verification of the effectiveness of the design solutions, ensuring that the bus body frame design solution is produced and manufactured under the premise of meeting the torsional stiffness design target, thereby avoiding the use of physical verification and optimization, and reducing the time cost of design and development, physical verification, and manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 Flowchart of a bus body frame torsional stiffness analysis method according to one embodiment of the present invention;

[0039] Figure 2 A schematic diagram of a three-dimensional model of a bus body skeleton in one embodiment of the present invention;

[0040] Figure 3 A schematic diagram of a simplified finite element suspension model in one embodiment of the invention;

[0041] Figure 4 A schematic diagram of the frame restraint position in one embodiment of the invention;

[0042] Figure 5 Flowchart of step S40 of the bus body frame torsional stiffness analysis method according to one embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0044] like Figure 1 As shown, in one embodiment, a method for analyzing the torsional stiffness of a bus body frame is provided, comprising the following steps:

[0045] Step S10: establishing a finite element model of the bus body frame based on the three-dimensional model of the bus body frame.

[0046] In this embodiment, the bus body skeleton 3D model includes a front 3D model, a rear 3D model, left and right side 3D models, a roof 3D model, and a frame and floor 3D model.

[0047] Specifically, by presetting 3D drawing software such as PROE, establish Figure 2 The bus body skeleton three-dimensional model is shown, and the bus body skeleton three-dimensional model is imported into a preset finite element software such as HyperMesh, and the bus body skeleton three-dimensional model is processed by geometric cleaning and mesh division to obtain the bus body skeleton finite element model, that is, the three-dimensional model data is converted from geometric data to finite element model data for finite element analysis.

[0048] Step S20: establishing a simple finite element suspension model.

[0049] In this embodiment, the simplified finite element front suspension model is composed of multiple nodes connected by one-dimensional elements, wherein the one-dimensional elements can be RBE2 elements (Rigid Body Element 2) or BEAM elements.

[0050] Specifically, a bus general layout diagram is obtained. Based on this diagram, a node set under different suspension states is obtained. Each node in the node set is connected using one-dimensional elements to simplify the suspension into a simple finite element suspension model. The bus general layout diagram includes information such as the overall dimensions of the bus, the installation locations of various functional components, and the relative positional relationships between these components.

[0051] As a preference, Figure 3 The simple finite element suspension model shown ( Figure 3 In the middle, the left and right sides correspond to the leaf spring state and the airbag state respectively), obtaining the node set in different suspension states according to the general layout diagram of the bus may include the following steps:

[0052] When the suspension state is the leaf spring state, the front axle left wheel center 1, the front axle right wheel center 2, the intersection point 3 of the front axle and the left leaf spring, the intersection point 4 of the front axle and the right leaf spring, and the midpoint 5 of the intersection point of the front axle and the left and right leaf springs are determined in the general layout diagram of the bus to generate a node set.

[0053] When the suspension state is the airbag state, the front axle left wheel center 1, the front axle right wheel center 2, the intersection point 3 of the front axle and the left airbag, the intersection point 4 of the front axle and the right airbag, and the midpoint 5 of the intersection point of the front axle and the left and right airbags are determined in the general layout diagram of the bus to generate a node set.

[0054] That is, in the general layout diagram, determine the front axle left wheel center 1, the front axle right wheel center 2, the intersection point 3 of the front axle and the left leaf spring or the left airbag, the intersection point 4 of the front axle and the right leaf spring or the right airbag, and the midpoint 5 of the intersection of the front axle and the left and right leaf springs or the front axle and the left and right airbags, and connect the aforementioned nodes through one-dimensional units to simplify the suspension into a simple finite element suspension model.

[0055] It is understandable that this embodiment proposes a suspension simplification method, which reduces the difficulty of suspension modeling while reflecting the suspension's functional characteristics. At the same time, the node positions are derived from the actual general layout information, ensuring that the simplified structure of the suspension conforms to the actual situation.

[0056] Step S30 : establishing boundary conditions, and applying constraints on the bus body frame finite element model and the finite element suspension simplified model respectively according to the boundary conditions.

[0057] In this embodiment, the boundary conditions are to impose a translational freedom constraint in at least one direction on the skeleton constraint points (including the first constraint point and the second constraint point) of the bus body skeleton three-dimensional model, and to impose a translational freedom constraint in at least one direction on the suspension constraint points of the finite element suspension simple model. Figure 4 As shown in the schematic diagram of the frame constraint position, applying constraints on the bus body frame finite element model means marking the center 6 of the left side frame main longitudinal beam section corresponding to the rear axle in the bus body frame finite element model as the first constraint point, and applying translational freedom constraints in the front-to-back, left-to-right, and up-to-down directions at the first constraint point; and marking the center 7 of the right side frame main longitudinal beam section corresponding to the rear axle as the second constraint point, and applying translational freedom constraints in the front-to-back and up-to-down directions at the second constraint point.

[0058] Applying constraints on the simple finite element suspension model means marking the midpoint 5 of the intersection of the front axle and the left and right leaf springs or the left and right airbags in the simple finite element suspension model as a suspension constraint point, and applying a translational degree of freedom constraint in the up and down directions at the suspension constraint point.

[0059] It can be understood that this embodiment stipulates the grasping range of the main longitudinal beam corresponding to the rear axle, and stipulates the constraint freedom on the left and right sides of the main longitudinal beam corresponding to the rear axle. These regulations allow the vehicle body frame to fully participate in the deformation under the action of torsion without adding any additional stiffness, thereby making the stiffness value obtained from the analysis more realistic.

[0060] In other embodiments, the boundary conditions may include an MPC constraint (Multiple Points Constraint) between the left and right wheel centers of the finite element suspension simple model. In this case, applying constraints on the finite element suspension simple model means applying MPC constraints in the up and down directions between the left and right wheel centers of the front axle in the finite element suspension simple model.

[0061] Step S40 : establishing a load condition, applying a load to the finite element suspension simplified model according to the load condition, and determining the torque T.

[0062] It can be understood that the bus body frame is part of the entire bus and is the overall load-bearing structure. It is installed on the chassis and driven by the chassis, while the suspension is part of the chassis. The power of the chassis is transmitted to the body through the suspension, and drives the body forward and brakes, etc., so that the load borne by the body frame is first transmitted to the suspension, and then from the suspension to the body frame. Therefore, when analyzing the torsional stiffness of the body frame, the load is loaded on the suspension.

[0063] In this embodiment, the loading condition is to apply the first load F to the preset loading points of the finite element suspension simple model. f and the second load F r , where the first load F f With the second load F r The magnitudes are equal and the directions are opposite. Figure 5 As shown, step S40 includes the following steps:

[0064] Step S401: Mark the front axle left wheel center 1 and the front axle right wheel center 2 in the finite element suspension simplified model as preset loading points.

[0065] Step S402: Apply a first load F to the front axle left wheel center 1 and the front axle right wheel center 2 respectively. f and the second load F r .

[0066] Step S403: According to the first load F f and the second load F r The torque T applied to the front axle is obtained, where the calculation formula of the torque T can be expressed as:

[0067]

[0068]

[0069] In formula (1), F f is the first load applied in the vertical direction at the left wheel center 1 of the front axle, F r is the second load applied vertically to the right wheel center 2 of the front axle, and the first load and the second load are in opposite directions, that is, if the first load is in an upward direction, the corresponding second load is in a downward direction, and if the first load is in a downward direction, the corresponding second load is in an upward direction; L is the lateral distance between the left wheel center 1 and the right wheel center 2 of the front axle; M f is the fully loaded axle weight of the front axle; g is the acceleration due to gravity.

[0070] It can be understood that this embodiment proposes an analysis method for the front axle torque load, using the unilateral front axle load under actual full-load conditions as the unilateral load input, avoiding the arbitrariness brought about by artificially defined loads, making the load loading realistic and traceable.

[0071] Step S50 , performing mechanical solution on the finite element model of the bus body frame to obtain the displacement of the measuring point, and obtaining the relative torsion angle α of the bus body frame under the action of the torque T according to the displacement of the measuring point.

[0072] The calculation formula of the relative torsion angle can be expressed as:

[0073]

[0074] In formula (2), α is the relative torsion angle of the bus body frame under the action of torque T; ΔZ1 is the absolute value of the vertical displacement of the left wheel center 1 of the front axle as the test point; ΔZ2 is the absolute value of the vertical displacement of the right wheel center 2 of the front axle as the test point; k is the torsion constant, and k = 57.3.

[0075] It can be understood that the constraints applied to the finite element model of the bus body frame, as well as the constraints and loads applied to the finite element suspension simple model, are ultimately transferred to the nodes of the finite element model of the bus body frame. In step S40, the load is applied using the front axle left wheel center 1 and the front axle right wheel center 2 in the finite element suspension simple model as loading points. In the corresponding step S50, the front axle left wheel center 1 and the front axle right wheel center 2 are used as test points for solving. After obtaining the displacement of the measurement point, the relative torsion angle α of the bus body frame under the action of the torque T is calculated by formula (2).

[0076] Step S60: Obtain the torsional stiffness K of the bus body frame according to the relative torsion angle α, and detect whether the bus body frame design scheme meets the torsional stiffness requirements based on the torsional stiffness of the bus body frame. The calculation formula of the torsional stiffness is:

[0077]

[0078] In this embodiment, the torsional stiffness K of the bus body frame is calculated by formula (3), and the torsional stiffness K of the bus body frame is compared with the target value G K Compare and determine whether the body frame design meets the torsional stiffness requirements. When the torsional stiffness K of the bus body frame reaches (greater than or equal to) the target value G K When the torsional stiffness K of the bus body frame does not reach (is less than) the target value G K When the vehicle body frame design does not meet the torsional stiffness requirements, the vehicle body frame design is determined to be non-compliant with the torsional stiffness requirements and a test result indicating that the design does not meet the requirements is issued. Furthermore, the design scheme validity is verified and multiple design schemes are optimized based on the test result. It is understood that the torsional stiffness of this embodiment refers to the front end torsional state.

[0079] In summary, the bus body frame torsional stiffness analysis method of this embodiment, after establishing a bus body frame three-dimensional model and a finite element suspension simplified model, first constrains the bus body frame finite element model and the finite element suspension simplified model according to boundary conditions, and loads the finite element suspension simplified model according to load conditions, and determines the torque to complete the overall constraint and overall loading. Then, the bus body frame finite element model associated with the bus body frame three-dimensional model is solved to obtain the displacement of the measurement point, and the relative torsion angle of the bus body frame under the action of torque is obtained based on the displacement of the measurement point, thereby calculating the torsional stiffness. Finally, the bus body frame design scheme is tested based on the torsional stiffness to determine whether it meets the torsional stiffness requirements. The bus body frame torsional stiffness analysis method of this embodiment can efficiently, accurately, and cost-effectively analyze the torsional stiffness of the bus body frame, and can also realize the optimization of multiple design schemes and the verification of the effectiveness of the design schemes, ensuring that the bus body frame design scheme is produced and manufactured under the premise of meeting the torsional stiffness design target, thereby avoiding the use of physical verification and optimization, and reducing the time cost of design and development, the cost of physical verification and manufacturing, etc.

[0080] In addition, in one embodiment, a bus body frame torsional stiffness analysis device is provided, comprising a processor, a memory, and a bus body frame torsional stiffness analysis program stored in the memory and executable on the processor. When the processor executes the bus body frame torsional stiffness analysis program, the steps of the bus body frame torsional stiffness analysis method in any of the above-mentioned embodiments are implemented.

[0081] Those skilled in the art will understand that the discussion of any of the above embodiments is merely illustrative and is not intended to limit the scope of the present disclosure (including the claims) to these examples. Within the spirit of the present invention, the technical features of the above embodiments or different embodiments may be combined, and there are many other variations of the various aspects of the present invention described above, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the torsional stiffness of a bus body frame, characterized in that: include: Establish a finite element model of the bus body frame based on the three-dimensional model of the bus body frame; Establish a simple finite element suspension model; Establishing boundary conditions, and applying constraints on the bus body frame finite element model and the finite element suspension simplified model respectively according to the boundary conditions; establishing load conditions, applying loads to the simplified finite element suspension model according to the load conditions, and determining torque; Performing mechanical solution on the finite element model of the bus body frame to obtain the displacement of the measuring point, and obtaining the relative torsion angle of the bus body frame under the action of the torque according to the displacement of the measuring point; Obtaining the torsional stiffness of the bus body frame according to the relative torsion angle, and detecting whether the bus body frame design scheme meets the torsional stiffness requirements according to the torsional stiffness of the bus body frame; The method of establishing a simple finite element suspension model includes: Obtain the general arrangement drawing of the bus; Obtaining a node set under different suspension states according to a general arrangement diagram of the bus; Connecting each node in the node set through a one-dimensional unit to simplify the bus suspension into a simple finite element suspension model; The suspension state is an airbag state; The acquiring of node sets in different suspension states according to the general layout diagram of the bus includes: Determining the left wheel center of the front axle, the left wheel center of the front axle, the intersection point of the front axle and the left airbag, the intersection point of the front axle and the right airbag, and the midpoint of the intersection points of the front axle and the left and right airbags in the general layout diagram of the bus to generate the node set; The torque The calculation formula is: ， ； in, is the torque; is the first load applied in the vertical direction at the left wheel center of the front axle, A second load applied in the vertical direction at the right wheel center of the front axle, wherein the first load and the second load are in opposite directions; is the lateral distance between the left wheel center of the front axle and the right wheel center of the front axle; The fully loaded axle weight of the front axle; is the acceleration due to gravity.

2. The bus body frame torsional stiffness analysis method according to claim 1, characterized in that: The suspension state is a leaf spring state; The acquiring of node sets in different suspension states according to the general layout diagram of the bus includes: The node set is generated by determining the front axle left wheel center, the front axle right wheel center, the intersection point of the front axle and the left leaf spring, the intersection point of the front axle and the right leaf spring, and the midpoint of the intersection point of the front axle and the left and right leaf springs in the general layout diagram of the bus.

3. The bus body frame torsional stiffness analysis method according to claim 1, wherein: The establishing of boundary conditions and applying constraints on the bus body frame finite element model according to the boundary conditions include: The center of the left side frame main longitudinal beam section corresponding to the rear axle in the bus body skeleton finite element model is marked as a first constraint point, and translational freedom constraints in the front-back, left-right, and up-down directions are applied at the first constraint point; and the center of the right side frame main longitudinal beam section corresponding to the rear axle is marked as a second constraint point, and translational freedom constraints in the front-back and up-down directions are applied at the second constraint point.

4. The bus body frame torsional stiffness analysis method according to claim 1, wherein: The establishing of boundary conditions and applying constraints on the finite element suspension simplified model according to the boundary conditions include: The midpoint of the intersection of the front axle and the left and right leaf springs or the front axle and the left and right airbags in the simple finite element suspension model is marked as a suspension constraint point, and a translational freedom constraint in the up and down directions is applied to the suspension constraint point.

5. The bus body frame torsional stiffness analysis method according to claim 1, wherein: The establishing of the load condition, applying the load on the finite element suspension simplified model according to the load condition, and determining the torque includes: Marking the front axle left wheel center and the front axle right wheel center in the finite element suspension simplified model as preset loading points; Applying a first load and a second load to the left wheel center of the front axle and the right wheel center of the front axle respectively; A torque applied to the front axle is obtained based on the first load and the second load.

6. The bus body frame torsional stiffness analysis method according to claim 1, characterized in that: The calculation formula of the relative torsion angle is: ； in, is the relative torsion angle of the bus body frame under the action of the torque; The absolute value of the vertical displacement of the left wheel center of the front axle is used as the test point; The absolute value of the vertical displacement of the right wheel center of the front axle as the test point; is the torsion constant.

7. A bus body frame torsional stiffness analysis device, characterized in that: The invention comprises a processor, a memory and a bus body frame torsional stiffness analysis program stored in the memory and executable on the processor. When the processor executes the bus body frame torsional stiffness analysis program, the bus body frame torsional stiffness analysis method as claimed in any one of claims 1 to 6 is implemented.

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