Method for analyzing structural performance of frame of pure electric mixer truck

Abstract

The invention discloses a pure electric mixer truck frame structure performance analysis method, belongs to the technical field of new energy automobiles, and aims to solve the problem of low precision of an existing electric mixer truck simulation model, and the method comprises the following steps: establishing a mixer truck preliminary finite element analysis model according to a whole vehicle real vehicle state, and calculating the performance of a pure electric mixer truck frame structure based on wheel loads of a pure electric mixer truck under different working conditions; a finite element analysis model under the whole vehicle transportation working condition and a finite element analysis model under the unloading working condition with different stirring tank eccentric distances are obtained, modal analysis calculation, vehicle frame rigidity calculation and strength calculation are conducted on the finite element analysis models, and a vehicle frame modal analysis result, a vehicle frame rigidity analysis result and a strength analysis result are obtained; and further obtaining a performance analysis result of the frame assembly of the pure electric mixer truck. According to the method, the road condition, the working condition and the whole vehicle state can be considered to construct a high-precision analysis model, and a mixer truck performance analysis result with reference significance is provided.

Description

Technical Field

[0001] The present invention relates to an analysis method for the frame structure performance of a pure electric mixer truck, belonging to the technical field of new energy commercial vehicles. Background Art

[0002] The frame of a pure electric mixer truck serves as the load-bearing backbone of the whole vehicle. Main components such as the body, upper mounting, battery pack and its bracket assembly, power assembly, and suspension are directly installed on the frame. In addition, the frame is also subject to torques transmitted from uneven road surfaces through tires - axles - leaf springs, and the load is relatively harsh. Once reliability problems occur, not only are more maintenance costs required, but also a greater impact is caused to the product image. Therefore, it is necessary to focus on evaluating its structural performance. Traditional analysis methods for fuel vehicles do not consider the supporting effects of the body assembly, battery pack brackets spanning both ends of the frame, etc. on the frame, do not consider the eccentric mass of the mixing tank, do not consider the limit of the suspension, the simplified method of bolts results in poor stress evaluation effect, and the strength of the mixer truck during unloading conditions is not investigated, etc., resulting in certain deviations between the frame strength calculation and the actual vehicle operating conditions, and the analysis results cannot verify the actual application situation, etc. Summary of the Invention

[0003] The purpose of the present invention is to provide an analysis method for the frame structure performance of a pure electric mixer truck, which can solve the problems that when modeling the existing pure electric mixer truck, the road conditions, operating conditions, and the overall vehicle transportation state, as well as the mutual loads between various components such as the frame, upper mounting, and axle, are not fully considered, resulting in low simulation, accuracy, and practicality of the analysis model, and realize providing a reference-worthy analysis result for the frame structure of the pure electric mixer truck.

[0004] To solve the above technical problems, the present invention is implemented by adopting the following technical solutions.

[0005] An analysis method for the frame structure performance of a pure electric mixer truck includes:

[0006] Collect the wheel loads, vehicle road condition loads, and the overall vehicle actual state of the pure electric mixer truck under different operating conditions;

[0007] Build an overall vehicle finite element analysis model according to the overall vehicle actual state to obtain a preliminary finite element analysis model of the mixer truck;

[0008] Based on the wheel loads of the pure electric mixer truck under different operating conditions, adjust the eccentric distance of the mixing tank of the preliminary finite element analysis model of the mixer truck to obtain a finite element analysis model under the overall vehicle transportation condition and a finite element analysis model under the overall vehicle unloading condition with different eccentric distances of the mixing tank;

[0009] Perform frame modal analysis and frame stiffness analysis based on the finite element analysis model under the vehicle's full-load transportation condition, and perform strength analysis based on the finite element analysis model under the vehicle's full-load transportation condition and the finite element analysis model under the vehicle's unloading condition respectively according to the vehicle road condition load.

[0010] Optionally, the vehicle road condition load includes: the maximum value of the vehicle's vertical acceleration, the maximum value of the longitudinal acceleration, the maximum value of the lateral acceleration, the maximum value of the displacement of each leaf spring, and the gravity load under the unloading condition;

[0011] The acquisition method of the vehicle road condition load includes:

[0012] Collect the vehicle's vertical, longitudinal, and lateral acceleration signals and the displacement signals of each leaf spring;

[0013] Perform filtering, deburring, and zero-drift removal processing on the vehicle's vertical, longitudinal, and lateral acceleration signals and the displacement signals of each leaf spring in sequence to obtain the processed acceleration signals and displacement signals;

[0014] Extract the maximum value of the vehicle's vertical acceleration, the maximum value of the longitudinal acceleration, the maximum value of the lateral acceleration, and the maximum value of the displacement of each leaf spring based on the processed acceleration signals and displacement signals;

[0015] Apply a gravitational acceleration of one time vertically downward to the vehicle under the unloading condition to obtain the gravity load under the unloading condition.

[0016] Optionally, the actual vehicle state of the vehicle includes: the geometric shapes, materials, connection methods, masses of each component of the vehicle, and the assembly relationships between each component;

[0017] The method of building a vehicle finite element analysis model according to the actual vehicle state of the vehicle to obtain a preliminary finite element analysis model of the mixer truck includes:

[0018] Establish finite element analysis models of each component of the vehicle according to the geometric shapes, materials, connection methods, and masses of each component of the vehicle;

[0019] Connect the finite element analysis models of each component of the vehicle according to the assembly relationships between each component to obtain a preliminary finite element analysis model of the mixer truck;

[0020] Among them, each component includes: the body assembly, the frame assembly, the battery assembly, the mixer truck superstructure, the axle, the tire, the power assembly, and each leaf spring.

[0021] Optionally, establishing finite element analysis models of each component of the vehicle according to the geometric shapes, materials, connection methods, and masses of each component of the vehicle includes:

[0022] When establishing the finite element analysis model of the body assembly, finite element simulations are respectively carried out on uniform sheet metal parts, casting structures such as mount brackets, solder joints, weld seams, bolts, and interior components;

[0023] When establishing the finite element analysis model of the frame assembly, finite element simulations are respectively carried out on uniform sheet metal parts, casting structures such as leaf spring brackets, solder joints, weld seams, and bolts;

[0024] When establishing the finite element analysis model of the powertrain, finite element simulations are respectively carried out on power components and the mounting system;

[0025] When establishing the finite element analysis model of the battery assembly, finite element simulations are respectively carried out on uniform sheet metal parts, casting structures, solder joints, weld seams, battery packs, and battery pack brackets;

[0026] When establishing the finite element analysis model of the upper structure of the mixer truck, finite element simulations are respectively carried out on uniform sheet metal parts, casting structures, mixing tanks, support brackets corresponding to the front and rear of the mixing tank, and U-bolts;

[0027] When establishing the finite element analysis model of the leaf spring, the leaf spring is simulated by two-dimensional shell elements, and the connection pairs between the leaf spring and its mounting components are set based on the assembly relationship between physical objects;

[0028] When establishing the finite element analysis model of the axle, finite element simulation of the solid axle is carried out according to the outer contour of the axle;

[0029] When establishing the finite element analysis model of the tire, finite element simulation of the stiffness parameters of the tire is carried out.

[0030] In this embodiment, when carrying out finite element simulation on the body assembly, it includes: the uniform sheet metal parts are discretely set with two-dimensional shell elements, the casting structures such as mount brackets are discretely arranged with tetrahedral elements, the solder joints and weld seam elements are simulated by the method of solid + flexible elements, and the bolts are simulated by stiffness elements and beam elements; the interior components are attached to the corresponding mounting holes with mass points and flexible elements; among them, the two-dimensional shell element mesh parameter of the uniform sheet metal parts is 8 mm, the tetrahedral element mesh parameter of the casting structures such as mount brackets is 5 mm, the diameter of the beam element is the diameter of the bolt, and the outer diameter of the rigid element is the flange diameter of the bolt / nut, so as to make the mass, centroid of the finite element analysis model of the body assembly consistent with the physical object.

[0031] When performing a solid finite element simulation on the frame assembly in this embodiment, it includes: uniformly discretizing sheet metal parts using two-dimensional shell elements, discretely arranging cast parts such as leaf spring brackets using tetrahedral elements, simulating solder joints and weld elements through the method of solid + flexible elements, and simulating bolts using stiffness elements and beam elements; among them, the mesh parameter of the two-dimensional shell elements of the uniformly sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the cast parts such as leaf spring brackets is 5 mm, the diameter of the beam element is the diameter of the bolt, and the outer diameter of the rigid element is the diameter of the bolt flange surface.

[0032] When performing a solid finite element simulation on the powertrain in this embodiment, it includes: attaching the electric motor, transmission, and other powertrain components to the suspension springs of the suspension system using mass points and rigid elements, and assigning moment of inertia parameters to the electric motor, transmission, and other powertrain components; the suspension system is predetermined to have stiffness parameters with six degrees of freedom.

[0033] When performing a solid finite element simulation on the battery assembly in this embodiment, it includes: uniformly discretizing sheet metal parts using two-dimensional shell elements, discretely arranging cast structures using tetrahedral elements, simulating solder joints and weld elements through the method of solid + flexible elements, designing the battery pack and the battery pack bracket as structural members spanning both ends of the frame and modeling them using hexahedral elements; among them, the mesh parameter of the two-dimensional shell elements of the uniformly sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the cast structures is 5 mm, and the model sizes of the battery pack and the battery pack bracket refer to the physical objects, which are used to make the centroid and mass of the finite element analysis model of the battery pack and the battery pack bracket consistent with the physical objects.

[0034] When performing a solid finite element simulation on the upper structure of the mixer truck in this embodiment, it includes: uniformly discretizing sheet metal parts using two-dimensional shell elements, discretely arranging cast structures using tetrahedral elements, simulating solder joints and weld elements through the method of solid + flexible elements, modeling the mixing tank using solid elements, modeling the U-bolt using solid elements, and setting the kinematic pair relationship for the support brackets corresponding to the front and rear of the mixing tank according to the assembly relationship between the physical objects;

[0035] Among them, the mesh parameter of the two-dimensional shell elements of the uniformly sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the cast structures is 5 mm, and the total mass of the mixing tank is the sum of the mass of the tank body and the concrete under the full-load state.

[0036] When establishing the finite element analysis model of the leaf spring in this embodiment, the leaf spring is simulated using two-dimensional shell elements, and the connection pair between the leaf spring and its mounting components is set based on the assembly relationship between the physical objects; among them, the thickness of the two-dimensional shell elements is adjusted according to the leaf spring stiffness; and the density of the leaf spring elements is adjusted according to the mass of the leaf spring, so that the mass of the leaf spring finite element analysis model is consistent with the physical object;

[0037] The expression for the leaf spring thickness is:

[0038]

[0039] In the formula, is the thickness of the leaf spring, is the stiffness of the leaf spring, is the effective length of the leaf spring, b is the width of the leaf spring, is the elastic modulus of the leaf spring.

[0040] When establishing the finite element analysis model of the axle in this embodiment, finite element simulation of the solid element axle is carried out according to the outer contour of the axle.

[0041] When establishing the finite element analysis model of the tire in this embodiment, finite element simulation of the tire element is carried out. The expression of the tire element is:

[0042]

[0043] In the formula, A is the cross-sectional area of the tire element, and the cross-section is circular. is the static radius of the tire, that is, the length of the tire element. is the vertical stiffness of the tire. is the elastic modulus of the tire.

[0044] Optionally, the wheel loads of the pure electric mixer truck under different working conditions include: the wheel loads of each wheel under the condition that the whole vehicle is fully loaded and the mixing tank rotates normally, and the wheel loads of each wheel at the initial state of unloading of the whole vehicle.

[0045] Based on the wheel loads of the pure electric mixer truck under different working conditions, adjusting the eccentric distance of the mixing tank of the preliminary finite element analysis model of the mixer truck to obtain the finite element model under the vehicle transportation condition and the finite element analysis model under the vehicle unloading condition with different eccentric distances of the mixing tank, including:

[0046] Based on the preliminary finite element analysis model of the mixer truck, set the sliding friction coefficient between the plate parts of the frame assembly, and conduct a leaf spring bench test to obtain the displacement of the leaf spring corresponding to the load when the leaf spring contacts the limit block at the limit.

[0047] Set the displacement of the leaf spring corresponding to the load when the leaf spring contacts the limit block at the limit as the initial distance of the contact relationship between the leaf spring and the frame limit in the preliminary finite element analysis model of the mixer truck.

[0048] After setting the initial distance, according to the wheel loads of each wheel under the condition that the whole vehicle is fully loaded and the mixing tank rotates normally and the wheel loads of each wheel at the initial state of unloading of the whole vehicle, adjust the left and right eccentric distances of the mixing tank finite element model respectively to obtain the finite element analysis model under the vehicle transportation condition and the finite element analysis model under the vehicle unloading condition with different eccentric distances of the mixing tank.

[0049] Optionally, perform a frame modal analysis based on the finite element analysis model under the vehicle transportation condition, including:

[0050] Set the modal extraction frequency of the finite element analysis model under the vehicle transportation condition to 0 - 100 Hz, and perform the vehicle modal analysis calculation to obtain the modal frequencies and vibration modes of each order of the vehicle;

[0051] According to the modal frequencies and vibration modes of each order of the vehicle, find the first-order torsional vibration mode of the frame assembly and determine the frequency associated with the torsional vibration mode;

[0052] If the frequency associated with the torsional vibration mode is lower than the torsional frequency of the benchmark vehicle, the analysis result of the frame modal analysis does not meet the modal performance requirements; otherwise, the analysis result of the frame modal analysis meets the modal performance requirements.

[0053] Optionally, perform a frame stiffness analysis based on the finite element analysis model under the vehicle transportation condition, including:

[0054] Extract the finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly respectively according to the finite element analysis model under the vehicle transportation condition;

[0055] Apply the constraint settings of some components to the extracted finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly respectively, and solve the frame stiffness of the finite element analysis model after applying the vertical load and two reverse acting forces to the frame assembly to obtain the bending stiffness and torsional stiffness of the frame assembly;

[0056] If both the bending stiffness and torsional stiffness of the frame assembly are higher than the stiffness threshold of the benchmark vehicle, the analysis result of the frame stiffness analysis meets the stiffness performance;

[0057] If either the bending stiffness or the torsional stiffness of the frame assembly is lower than the stiffness threshold of the benchmark vehicle, the analysis result of the frame stiffness analysis does not meet the stiffness performance.

[0058] Optionally, apply the constraint settings of some components to the extracted finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly respectively, and solve the frame stiffness of the finite element analysis model after applying the vertical load and two reverse acting forces to the frame assembly to obtain the bending stiffness and torsional stiffness of the frame assembly, including:

[0059] According to the finite element analysis models of the frame assembly and the battery assembly, constrain the vertical movement degrees of freedom on the left and right sides of the frame corresponding to the front axle, constrain the vertical, longitudinal and lateral movement degrees of freedom at the center position of the left balance suspension, and constrain the vertical and longitudinal movement degrees of freedom at the center position of the right balance suspension. Then apply a vertical load at the middle position between the front axle and the center position of the rear balance suspension, solve the finite element analysis models of the frame assembly and the battery assembly, and obtain the maximum vertical displacement of the frame longitudinal beam;

[0060] According to the ratio of the vertical load to the maximum vertical displacement, obtain the bending stiffness of the frame assembly;

[0061] According to the finite element analysis models of the frame assembly and the battery assembly, constrain the vertical movement degree of freedom at the center position of the front crossbeam of the frame, constrain the vertical, longitudinal and lateral movement degrees of freedom at the center of the left balance suspension, and constrain the vertical and longitudinal movement degrees of freedom at the center of the right balance suspension. Then apply forces with equal magnitudes and opposite directions on the left and right sides of the frame corresponding directly above the front axle, solve the finite element analysis models of the frame assembly and the battery assembly, obtain the acting moment and the torsion angles at all longitudinal positions of the frame longitudinal beam, and extract the maximum torsion angle;

[0062] According to the ratio of the acting moment to the maximum torsion angle, obtain the torsional stiffness of the frame assembly.

[0063] Optionally, perform strength analysis on the finite element analysis models under the vehicle's whole - vehicle transportation condition and the whole - vehicle unloading condition respectively according to the vehicle road condition loads, including:

[0064] Perform strength calculations for the frame bending, braking, steering and torsion conditions on the finite element analysis model under the whole - vehicle transportation condition according to the maximum vertical acceleration, maximum longitudinal acceleration, maximum lateral acceleration of the whole vehicle and the maximum displacement of each leaf spring, and respectively obtain the maximum stresses of the frame assembly under each condition;

[0065] Perform strength calculations under the gravity load on the finite element analysis model under the whole - vehicle unloading condition according to the gravity load under the unloading condition, and respectively obtain the maximum stresses of the frame assembly under the unloading condition;

[0066] According to the ratio of the yield strength of the pre - set frame assembly material to the maximum stress of the frame assembly under each condition, obtain the safety factor of the frame strength under each condition;

[0067] Judge whether the frame strength meets the strength performance requirements according to the comparison results between the pre - set safety factor threshold and the safety factors of the frame strength under each condition, and obtain the strength analysis result;

[0068] Among them, if the safety factor of the frame strength under each working condition is not less than the preset safety factor threshold, the strength analysis result meets the strength performance requirements;

[0069] If there is a situation where the safety factor of the frame strength under each working condition is less than the preset safety factor threshold, the strength analysis result does not meet the strength performance requirements.

[0070] Optionally, if there is a situation where the safety factor of the frame strength under each working condition is less than the preset safety factor threshold, the strength analysis result does not meet the strength performance requirements, and it further includes:

[0071] Define the position corresponding to the safety factor of the frame strength under each working condition being less than the preset safety factor threshold as the stress over - standard position;

[0072] Based on the stress over - standard position, judge whether it is near the bolt hole; if it is near the bolt hole position, then re - model the bolt and nut, and solve the stress field and the maximum stress of each working condition after re - modeling the stress over - standard position, which is used for calculating the safety factor of the re - modeled stress over - standard position and judging the strength analysis result;

[0073] If it is not near the bolt hole position, the strength analysis result does not meet the strength performance requirements.

[0074] Optionally, if it is near the bolt hole position, then re - model the bolt and nut, and solve the stress field and the maximum stress of each working condition after re - modeling the stress over - standard position, including:

[0075] Use solid - element modeling to replace the original bolt and nut modeled by stiffness elements and beam elements, obtain the re - modeled bolt and nut, and the bolt and nut elements are discretely set using 2 - mm second - order tetrahedral elements;

[0076] Based on the re - modeled bolt and nut, establish a pre - tightening force load at the bolt section;

[0077] According to the re - modeled bolt and nut, establish a pre - tightening force calculation working condition, and solve to obtain the stress field of the frame containing only the pre - tightening load and the stress analysis result of the pre - tightening force working condition;

[0078] Substitute the stress analysis result of the pre - tightening force working condition back into the strength calculation of each working condition to obtain the maximum stress around the re - modeled position under each working condition;

[0079] According to the ratio of the yield strength of the preset frame assembly material to the maximum stress around the re - modeled position under each working condition, obtain the safety factor of the re - modeled position under each working condition;

[0080] If the safety factor at the rebuilt model positions under each working condition is still less than the preset safety factor threshold, it does not meet the strength performance requirements, and the strength analysis result is that it does not meet the strength performance requirements.

[0081] If the safety factor is greater than or equal to the preset safety factor threshold, and the safety factors at all stress-exceeding positions are greater than or equal to the preset safety factor threshold, then the strength analysis result is that it meets the strength performance requirements.

[0082] Compared with the prior art, the technical effects achieved by the present invention are as follows:

[0083] 1. The present invention collects the wheel loads of the whole vehicle and the acceleration and displacement signals of the user's road conditions, establishes a finite element analysis model of the whole vehicle including the vehicle body, battery pack and bracket, superstructure, leaf spring, axle and tire, and conducts wheel load calibration to establish a high-precision finite element analysis model under different working conditions. Combining the calibration of the eccentric mass during the full load, unloading of the mixing tank and the dynamic rotation of the mixing tank makes the analysis model closer to the actual state under different working conditions and road conditions.

[0084] 2. The present invention conducts a whole vehicle modal analysis on the high-precision finite element analysis model under different working conditions, extracts the frame modes and conducts performance analysis, which can fully consider the interaction loads between the frame and the directly mounted components of the frame, ensuring the accuracy of the analysis model. Considering the influence of the suspension limit and tire stiffness on the analysis results, it can accurately transmit the loads under the spring, improving the accuracy of the simulation analysis.

[0085] 3. The present invention also conducts frame stiffness analysis and performance evaluation; combines typical strength and unloading special working conditions such as bending, braking, steering and torsion according to the user's road conditions to conduct quasi-static strength calculation of the whole vehicle. For the strength performance, conducts an overall analysis of the comprehensive performance of the frame by combining the modal, stiffness and strength calculation results. At the same time, combines two modeling methods of simplified and refined calculation of bolts, which not only ensures the modeling calculation efficiency but also can accurately evaluate the frame strength of the bolt hole accessories with large loads.

[0086] 4. Through the above comprehensive modal, stiffness and strength analysis of the pure electric mixer truck, a comprehensive performance analysis of the pure electric mixer truck can be carried out, which can reduce the deviation between the pure electric mixer truck and the actual vehicle when facing road conditions, working conditions, the overall transportation state of the whole vehicle, and the interaction relationships between various components such as the frame, superstructure and axle, etc., and obtain practical analysis results. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 The figure shows a flowchart of the analysis method for the frame structure performance of the pure electric mixer truck of the present invention;

[0088] Figure 2 The figure shows the schematic diagram of the whole vehicle structure of the pure electric mixer truck of the present invention;

[0089] Figure 3 The figure shows a schematic diagram of the calculation of the bending stiffness of the frame of the present invention and the setting of constraints;

[0090] Figure 4 The figure shows the constraints and loading for the calculation of the torsional stiffness of the frame of the present invention.

[0091] Reference numerals: 1 - vehicle body assembly, 2 - frame assembly, 3 - battery assembly, 4 - upper structure of the mixer truck, 5 - axle, 6 - tire, 8 - each leaf spring. Detailed implementation manners

[0092] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the protection scope of the present invention.

[0093] Embodiment 1

[0094] This embodiment provides an analysis method for the structural performance of the frame of a pure electric mixer truck, as Figure 1 shown including:

[0095] Step a: Collect the wheel loads, vehicle road condition loads, and the actual vehicle state of the pure electric mixer truck under different working conditions;

[0096] Step b: Build a whole vehicle finite element analysis model based on the actual vehicle state of the whole vehicle to obtain a preliminary finite element analysis model of the mixer truck;

[0097] Step c: Based on the wheel loads of the pure electric mixer truck under different working conditions, adjust the eccentric distance of the mixing tank of the preliminary finite element analysis model of the mixer truck to obtain a finite element analysis model under the whole vehicle transportation condition and a finite element analysis model under the whole vehicle unloading condition with different eccentric distances of the mixing tank;

[0098] Step d: Perform frame modal analysis and frame stiffness analysis based on the finite element analysis model under the whole vehicle transportation condition, and perform strength analysis based on the finite element analysis model under the whole vehicle transportation condition and the finite element analysis model under the whole vehicle unloading condition respectively according to the vehicle road condition loads.

[0099] Optionally, the vehicle road condition loads include: the maximum value of the vertical acceleration of the whole vehicle, the maximum value of the longitudinal acceleration, the maximum value of the lateral acceleration, the maximum displacement of each leaf spring 8, and the gravity load under the unloading condition;

[0100] The acquisition method of the vehicle road condition loads includes:

[0101] Collect the vertical, longitudinal, and lateral acceleration signals of the whole vehicle and the displacement signals of each leaf spring 8;

[0102] For the vertical, longitudinal, and lateral acceleration signals of the entire vehicle and the displacement signals of each leaf spring 8, perform filtering, deburring, and zero-drift removal processing in sequence to obtain the processed acceleration signals and displacement signals;

[0103] Based on the processed acceleration signals and displacement signals, extract the maximum vertical acceleration, maximum longitudinal acceleration, maximum lateral acceleration of the entire vehicle, and the maximum displacement of each leaf spring 8;

[0104] Under the unloading condition, apply a gravitational acceleration of one times vertically downward to the entire vehicle to obtain the gravitational load under the unloading condition.

[0105] Optionally, the actual vehicle state of the entire vehicle includes: the geometric shape, material, connection method, mass of each component of the entire vehicle, and the assembly relationship between each component;

[0106] Building a finite element analysis model of the entire vehicle according to the actual vehicle state of the entire vehicle to obtain a preliminary finite element analysis model of the mixer truck, including:

[0107] Establish finite element analysis models for each component of the entire vehicle according to the geometric shape, material, connection method, and mass of each component of the entire vehicle;

[0108] According to the assembly relationship between each component, connect the finite element analysis models of each component of the entire vehicle to obtain a preliminary finite element analysis model of the mixer truck;

[0109] Among them, each component includes: body assembly 1, frame assembly 2, battery assembly 3, mixer truck superstructure 4, axle 5, tire 6, power assembly, and each leaf spring 8.

[0110] Optionally, establishing finite element analysis models for each component of the entire vehicle according to the geometric shape, material, connection method, and mass of each component of the entire vehicle includes:

[0111] When establishing the finite element analysis model of the body assembly 1, perform finite element simulations on uniform sheet metal parts, suspension bracket casting structures, solder joints, welds, bolts, and interior components respectively;

[0112] When establishing the finite element analysis model of the frame assembly 2, perform finite element simulations on uniform sheet metal parts, leaf spring bracket casting structures, solder joints, welds, and bolts respectively;

[0113] When establishing the finite element analysis model of the power assembly, perform finite element simulations on power components and the suspension system respectively;

[0114] When establishing the finite element analysis model of the battery assembly 3, perform finite element simulations on uniform sheet metal parts, casting structures, solder joints, welds, battery packs, and battery pack brackets respectively;

[0115] When establishing the finite element analysis model of the upper structure 4 of the mixer truck, finite element simulations are respectively carried out on the uniform sheet metal parts, casting structures, mixing tank, support brackets corresponding to the front and rear of the mixing tank, and U-bolts;

[0116] When establishing the finite element analysis model of the leaf spring, the leaf spring is simulated by two-dimensional shell elements, and the connection pairs between the leaf spring and its installation components are set based on the assembly relationship between the physical objects;

[0117] When establishing the finite element analysis model of the axle 5, finite element simulation of the solid axle 5 is carried out according to the outer contour of the axle 5;

[0118] When establishing the finite element analysis model of the tire 6, finite element simulation is carried out on the stiffness parameters of the tire 6.

[0119] In this embodiment, when carrying out finite element simulation on the body assembly 1, it includes: the uniform sheet metal parts are discretely set by two-dimensional shell elements, the casting structures of the suspension brackets are discretely arranged by tetrahedral elements, the solder joints and weld elements are simulated by the method of solid + flexible elements, and the bolts are simulated by stiffness elements and beam elements; the interior trim parts are attached to the corresponding mounting holes by mass points and flexible elements; among them, the mesh parameter of the two-dimensional shell elements of the uniform sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the casting structures of the suspension brackets is 5 mm, the diameter of the beam element is the diameter of the bolt, and the outer diameter of the rigid element is the flange diameter of the bolt / nut, so as to make the mass and centroid of the finite element analysis model of the body assembly 1 consistent with the physical object.

[0120] In this embodiment, when carrying out solid finite element simulation on the frame assembly 2, it includes: the uniform sheet metal parts are discretely set by two-dimensional shell elements, the casting structures of the leaf spring brackets are discretely arranged by tetrahedral elements, the solder joints and weld elements are simulated by the method of solid + flexible elements, and the bolts are simulated by stiffness elements and beam elements; among them, the mesh parameter of the two-dimensional shell elements of the uniform sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the casting structures of the leaf spring brackets is 5 mm, the diameter of the beam element is the diameter of the bolt, and the outer diameter of the rigid element is the flange diameter of the bolt.

[0121] In this embodiment, when carrying out solid finite element simulation on the power assembly, it includes: the motor, transmission and other power components are attached to the suspension springs of the suspension system by mass points and rigid elements, and the motor, transmission and other power components are given the moment of inertia parameters; the suspension system is predetermined to have the stiffness parameters with six degrees of freedom.

[0122] When performing a finite element simulation of the physical battery assembly 3 in this embodiment, it includes: discretely setting the uniform sheet metal parts with two-dimensional shell elements, discretely arranging the casting-like structures with tetrahedral elements, simulating the solder joints and weld elements by the method of solid + flexible elements, designing the battery pack and the battery pack bracket as structural parts spanning both ends of the vehicle frame and modeling them with hexahedral elements; among them, the mesh parameter of the two-dimensional shell elements of the uniform sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the casting-like structures is 5 mm, and the model sizes of the battery pack and the battery pack bracket refer to the physical objects, which are used to make the centroid and mass of the finite element analysis models of the battery pack and the battery pack bracket consistent with the physical objects.

[0123] When performing a finite element simulation of the physical upper structure 4 of the mixer truck in this embodiment, it includes: discretely setting the uniform sheet metal parts with two-dimensional shell elements, discretely arranging the casting-like structures with tetrahedral elements, simulating the solder joints and weld elements by the method of solid + flexible elements, modeling the mixing tank with solid elements, modeling the U-bolt with solid elements, and setting the kinematic pair relationship for the support brackets corresponding to the front and rear of the mixing tank according to the assembly relationship between the physical objects;

[0124] Among them, the mesh parameter of the two-dimensional shell elements of the uniform sheet metal parts is 8 mm, the mesh parameter of the tetrahedral elements of the casting-like structures is 5 mm, and the total mass of the mixing tank is the sum of the mass of the tank body and the concrete in the fully loaded state.

[0125] When establishing the finite element analysis model of the leaf spring in this embodiment, the leaf spring is simulated by two-dimensional shell elements, and the connection pair between the leaf spring and its installation components is set based on the assembly relationship between the physical objects; among them, the thickness of the two-dimensional shell elements is adjusted according to the leaf spring stiffness; and the density of the leaf spring elements is adjusted according to the mass of the leaf spring, so that the mass of the leaf spring finite element analysis model is consistent with the physical object;

[0126] The expression for the leaf spring thickness is:

[0127]

[0128] In the formula, is the leaf spring thickness, is the leaf spring stiffness, is the effective length of the leaf spring, b is the leaf spring width, is the elastic modulus of the leaf spring.

[0129] When establishing the finite element analysis model of the axle 5 in this embodiment, a finite element simulation of the solid axle is performed according to the outer contour of the axle 5.

[0130] When establishing the finite element analysis model of the tire 6 in this embodiment, a finite element simulation of the tire 6 elements is performed, and the expression of the tire 6 elements is:

[0131]

[0132] Wherein, A is the cross-sectional area of the tire 6 unit, and the cross-section is circular. is the static radius of the tire 6, which is the length of the tire 6 unit. is the vertical stiffness of the tire 6. is the elastic modulus of the tire 6.

[0133] Optionally, the wheel loads of the pure electric mixer truck under different working conditions include: the wheel loads of each wheel under the condition that the whole vehicle is fully loaded and the mixing tank rotates normally, and the wheel loads of each wheel at the initial state of unloading of the whole vehicle.

[0134] Based on the wheel loads of the pure electric mixer truck under different working conditions, adjusting the eccentric distance of the mixing tank of the preliminary finite element analysis model of the mixer truck to obtain finite element models under the vehicle transportation condition and finite element analysis models under the vehicle unloading condition with different eccentric distances of the mixing tank, including:

[0135] Based on the preliminary finite element analysis model of the mixer truck, set the sliding friction coefficient between the plates of the frame assembly 2, and conduct a leaf spring bench test to obtain the displacement of the leaf spring corresponding to the load F when the leaf spring contacts the limit block at the limit.

[0136] Take the displacement of the leaf spring corresponding to the load F when the leaf spring contacts the limit block at the limit as the initial distance of the contact relationship between the leaf spring and the frame limit in the preliminary finite element analysis model of the mixer truck.

[0137] After setting the initial distance, according to the wheel loads of each wheel under the condition that the whole vehicle is fully loaded and the mixing tank rotates normally and the wheel loads of each wheel at the initial state of unloading of the whole vehicle, adjust the left and right eccentric distances of the mixing tank finite element analysis model respectively to obtain finite element analysis models under the vehicle transportation condition and finite element analysis models under the vehicle unloading condition with different eccentric distances of the mixing tank.

[0138] In this embodiment, the contact between the plates of the frame assembly 2 is established, and the sliding friction coefficient is set to 0.15; a leaf spring bench test is carried out, and the displacement of the leaf spring corresponding to the load F when the leaf spring contacts the limit block at the limit is measured, and the displacement is taken as the initial distance of the contact relationship established between the leaf spring and the frame limit in the finite element analysis model. According to the wheel loads measured in A under the condition of normal transportation with the whole vehicle fully loaded and stationary and the wheel loads at the initial state of unloading, adjust the left and right eccentric distances of the mixing tank finite element analysis model, so that the error between the finite element wheel loads of the whole vehicle and the measured value is less than 2%, obtain the eccentric distance of the mixing tank under the normal operation condition of the whole vehicle and the eccentric distance of the mixing tank at the initial state of unloading, and obtain the finite element analysis models under the vehicle transportation condition and finite element analysis models under the vehicle unloading condition according to different eccentric distances of the mixing tank.

[0139] Optionally, perform a frame modal analysis based on the finite element analysis model under the vehicle transportation condition, including:

[0140] Set the modal extraction frequency of the finite element analysis model under the vehicle transportation condition to 0 - 100 Hz, and perform the vehicle modal analysis calculation to obtain the modal frequencies and vibration modes of each order of the vehicle;

[0141] According to the modal frequencies and vibration modes of each order of the vehicle, find the first-order torsional vibration mode of the frame assembly 2 and record the frequency associated with the torsional vibration mode;

[0142] Based on the comparison result between the torsional frequency of the benchmark vehicle and the recorded frequency, judge whether the frame assembly 2 meets the modal performance requirements, and obtain the frame modal analysis result;

[0143] Among them, when the recorded frequency is lower than the torsional frequency of the benchmark vehicle, the frame modal analysis result is that it does not meet the modal performance requirements;

[0144] When the recorded frequency is higher than the torsional frequency of the benchmark vehicle, the frame modal analysis result is that it meets the modal performance requirements.

[0145] Optionally, perform frame stiffness analysis based on the finite element analysis model under the vehicle transportation condition, including:

[0146] Extract the finite element analysis model of the frame assembly 2 and the finite element analysis model of the battery assembly 3 respectively according to the finite element analysis model under the vehicle transportation condition;

[0147] Apply the constraint settings of some components to the extracted finite element analysis model of the frame assembly 2 and the finite element analysis model of the battery assembly 3 respectively, and solve the frame stiffness of the finite element analysis model after applying vertical load and two reverse acting forces to the frame assembly 2 to obtain the bending stiffness and torsional stiffness of the frame assembly 2;

[0148] If both the bending stiffness and torsional stiffness of the frame assembly 2 are higher than the stiffness threshold of the benchmark vehicle, the frame stiffness analysis result is that it meets the stiffness performance;

[0149] If either the bending stiffness or torsional stiffness of the frame assembly 2 is lower than the stiffness threshold of the benchmark vehicle, the frame stiffness analysis result is that it does not meet the stiffness performance.

[0150] Optionally, apply the constraint settings of some components to the extracted finite element analysis model of the frame assembly 2 and the finite element analysis model of the battery assembly 3 respectively, and solve the frame stiffness of the finite element analysis model after applying vertical load and two reverse acting forces to the frame assembly 2 to obtain the bending stiffness and torsional stiffness of the frame assembly 2, including:

[0151] According to the finite element analysis model of the frame assembly 2 and the finite element analysis model of the battery assembly 3, such as Figure 3Restrict the vertical movement degrees of freedom on both the left and right sides of the frame corresponding to the shown constrained front axle, restrict the vertical, longitudinal, and lateral movement degrees of freedom at the center position of the left balance suspension, restrict the vertical and longitudinal movement degrees of freedom at the center position of the right balance suspension, and then apply a vertical load at the intermediate position between the front axle and the center position of the rear balance suspension. Solve the finite element analysis models of the frame assembly 2 and the battery assembly 3 to obtain the maximum vertical displacement l of the frame longitudinal beam;

[0152] According to the ratio of the vertical load to the maximum vertical displacement l, obtain the bending stiffness of the frame assembly 2;

[0153] According to the finite element analysis models of the frame assembly 2 and the battery assembly 3, as Figure 4 shown, restrict the vertical movement degree of freedom at the center position of the front crossbeam of the frame, restrict the vertical, longitudinal, and lateral movement degrees of freedom at the center of the left balance suspension, restrict the vertical and longitudinal movement degrees of freedom at the center of the right balance suspension, and then apply equal and opposite forces on both the left and right sides of the frame corresponding to directly above the front axle. Solve the finite element analysis models of the frame assembly 2 and the battery assembly 3 to obtain the acting moment M and the torsion angles of the frame longitudinal beam at all longitudinal positions and extract the maximum torsion angle δ;

[0154] According to the ratio of the acting moment M to the maximum torsion angle δ, obtain the torsional stiffness of the frame assembly 2.

[0155] Optionally, perform strength analysis on the finite element analysis models under the vehicle's whole - vehicle transportation condition and the whole - vehicle unloading condition respectively according to the vehicle road condition loads, including:

[0156] According to the maximum vertical acceleration value, maximum longitudinal acceleration value, maximum lateral acceleration value of the whole vehicle and the maximum displacement values of each leaf spring 8, perform strength calculations for the frame bending, braking, steering, and torsion conditions on the finite element analysis model under the whole - vehicle transportation condition, and respectively obtain the maximum stresses of the frame assembly 2 under each condition;

[0157] According to the gravity load under the unloading condition, perform strength calculations for the finite element analysis model under the whole - vehicle unloading condition under the gravity load, and respectively obtain the maximum stresses of the frame assembly 2 under the unloading condition;

[0158] According to the ratio of the yield strength of the pre - set material of the frame assembly 2 to the maximum stresses of the frame assembly 2 under each condition, obtain the safety factors of the frame strength under each condition;

[0159] According to the comparison results between the pre - set safety factor threshold 1.2 and the safety factors of the frame strength under each condition, judge whether the frame strength meets the strength performance requirements and obtain the strength analysis results;

[0160] Among them, if the safety factor of the frame strength under each working condition is not less than the preset safety factor threshold of 1.2, the strength analysis result meets the strength performance requirements;

[0161] If there is a situation where the safety factor of the frame strength under each working condition is less than the preset safety factor threshold of 1.2, the strength analysis result does not meet the strength performance requirements.

[0162] Optionally, if there is a situation where the safety factor of the frame strength under each working condition is less than the preset safety factor threshold of 1.2, the strength analysis result does not meet the strength performance requirements, and it further includes:

[0163] Define the position corresponding to the safety factor of the frame strength under each working condition being less than the preset safety factor threshold of 1.2 as the stress exceeding position;

[0164] Based on the stress exceeding position, judge whether it is near the bolt hole; if it is near the bolt hole position, then re - model the bolt and nut, and solve the stress fields and the maximum stress of each working condition after re - modeling the stress exceeding position, for calculating the safety factor of the stress exceeding position after re - modeling and judging the strength analysis result;

[0165] If it is not near the bolt hole position, the strength analysis result does not meet the strength performance requirements.

[0166] Optionally, if it is near the bolt hole position, then re - model the bolt and nut, and solve the stress fields and the maximum stress of each working condition after re - modeling the stress exceeding position, including:

[0167] Use solid - element modeling to replace the original bolt and nut modeled by stiffness elements and beam elements, obtain the re - modeled bolt and nut, and the bolt and nut elements are discretely set using 2 - mm second - order tetrahedral elements;

[0168] Based on the re - modeled bolt and nut, establish a pre - tightening force load at the bolt section;

[0169] According to the re - modeled bolt and nut, establish a pre - tightening force calculation working condition, and solve to obtain the stress field of the frame containing only the pre - tightening load and the stress analysis result of the pre - tightening force working condition;

[0170] Substitute the stress analysis result of the pre - tightening force working condition back into the strength calculation of each working condition to obtain the maximum stress around the re - modeled position under each working condition;

[0171] According to the ratio of the yield strength of the preset frame assembly 2 material to the maximum stress around the re - modeled position under each working condition, obtain the safety factor of the re - modeled position under each working condition;

[0172] If the safety factor of the reconstructed model position under each working condition is still less than the preset safety factor threshold of 1.2, it does not meet the strength performance requirements, and the strength analysis result is that it does not meet the strength performance requirements.

[0173] If the safety factor is greater than or equal to the preset safety factor threshold of 1.2, and the safety factors of all stress exceeding positions are greater than or equal to the preset safety factor threshold, then the strength analysis result is that it meets the strength performance requirements.

[0174] The present invention collects the wheel load of the whole vehicle and the acceleration and displacement signals of the user's road conditions, establishes a finite element analysis model of the whole vehicle including the vehicle body, battery pack and bracket, superstructure, leaf spring, axle 5 and tire 6, and performs wheel load calibration to establish a high-precision finite element analysis model under different working conditions. Combining the calibration of the eccentric mass during the full load, unloading and dynamic rotation of the mixing tank makes the analysis model closer to the physical state under different working conditions and road conditions. Secondly, the whole vehicle modal analysis is carried out on the high-precision finite element analysis model under different working conditions, and the frame mode is extracted and the performance is analyzed, which can fully consider the interaction loads between the frame and the directly mounted components of the frame, ensuring the accuracy of the analysis model, and combining the influence of the suspension limit and the stiffness of the tire 6 on the analysis result, which can accurately transfer the load under the spring and improve the accuracy of the simulation analysis.

[0175] Combined with the user's road conditions, typical strength and unloading special working conditions such as bending, braking, steering and torsion are set, and the quasi-static strength calculation of the whole vehicle is carried out. For the strength performance, the comprehensive performance of the frame is analyzed in combination with the modal, stiffness and strength calculation results. At the same time, two modeling methods of simplified and refined calculation of bolts are combined, which not only ensures the modeling calculation efficiency, but also can accurately evaluate the frame strength of the bolt hole accessories with large loads. To sum up, the present invention comprehensively analyzes the performance of the pure electric mixer truck in terms of modal, stiffness and strength, which can reduce the deviation between the pure electric mixer truck and the actual vehicle when facing road conditions, working conditions, the whole vehicle transportation state, and the interaction relationship between various components such as the frame, superstructure and axle 5, etc., and obtains practical analysis results.

[0176] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0177] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and combinations of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to produce a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in the flow Figure 1 one or more flows and / or blocks Figure 1 means for implementing the functions specified in one or more blocks or multiple blocks.

[0178] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in the flow Figure 1 one or more flows and / or blocks Figure 1 means for implementing the functions specified in one or more blocks or multiple blocks.

[0179] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in the flow Figure 1 one or more flows and / or blocks Figure 1 means for implementing the functions specified in one or more blocks or multiple blocks.

[0180] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the present invention and the claims. All of these are within the protection scope of the present invention.

Claims

1. A method for analyzing the structural performance of a pure electric mixer truck frame, characterized in that: include: Collect wheel load, vehicle road load and vehicle status of pure electric mixer truck under different working conditions; Build a finite element analysis model of the whole vehicle according to the actual vehicle status, and obtain a preliminary finite element analysis model of the mixer truck; Based on the wheel load of pure electric mixer truck under different working conditions, the eccentric distance of the mixing tank of the preliminary finite element analysis model of the mixer truck is adjusted to obtain the finite element analysis model under the whole vehicle transportation condition with different eccentric distances of the mixing tank and the finite element analysis model under the whole vehicle unloading condition; Based on the finite element analysis model under the whole vehicle transportation condition, the frame modal analysis and frame stiffness analysis are performed, and according to the vehicle road condition load, the strength analysis is performed based on the finite element analysis model under the whole vehicle transportation condition and the finite element analysis model under the whole vehicle unloading condition.

2. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 1 is characterized in that: The vehicle road load includes: the maximum vertical acceleration of the vehicle, the maximum longitudinal acceleration, the maximum lateral acceleration, the maximum displacement of each leaf spring and the gravity load under unloading conditions; The method for collecting vehicle road condition load includes: Collect the vertical, longitudinal, and lateral acceleration signals of the vehicle and the displacement signals of each leaf spring; The vertical, longitudinal and lateral acceleration signals of the vehicle and the displacement signals of each leaf spring are filtered, deburred and de-zeroed in turn to obtain the processed acceleration signals and displacement signals; Based on the processed acceleration signal and displacement signal, the maximum vertical acceleration, maximum longitudinal acceleration, maximum lateral acceleration and maximum displacement of each leaf spring of the vehicle are extracted; Under the unloading condition, a vertical downward gravity acceleration of one times is applied to the vehicle to obtain the gravity load under the unloading condition.

3. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 1 is characterized in that: The actual vehicle status includes: the geometric shape, material, connection method, quality of each component of the vehicle and the assembly relationship between the components; The method of building a finite element analysis model of the whole vehicle according to the actual vehicle state and obtaining a preliminary finite element analysis model of the mixer truck includes: Establish finite element analysis models of each vehicle component according to its geometric shape, material, connection method and quality; According to the assembly relationship between the components, the finite element analysis models of the components of the whole vehicle are connected to obtain a preliminary finite element analysis model of the mixer truck; Among them, the various components include: body assembly, frame assembly, battery assembly, mixer truck upper structure, axle, tire, powertrain and leaf springs.

4. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 3 is characterized in that: The finite element analysis model of each component of the vehicle is established according to the geometric shape, material, connection method and mass of each component of the vehicle, including: When establishing the finite element analysis model of the body assembly, finite element simulations are performed on uniform sheet metal parts, suspension bracket casting structures, welding points, welds, bolts and interior parts; When establishing the finite element analysis model of the frame assembly, finite element simulations are performed on uniform sheet metal parts, leaf spring bracket casting structures, welding points, welds, and bolts; When establishing the finite element analysis model of the powertrain, finite element simulations are performed on the power components and the suspension system respectively; When establishing the finite element analysis model of the battery assembly, finite element simulations are performed on uniform sheet metal parts, casting structures, welding points, welding seams, battery packs, and battery pack brackets; When establishing the finite element analysis model of the mixer truck superstructure, finite element simulations were performed on the uniform sheet metal parts, casting structures, mixing tanks, supporting brackets corresponding to the front and rear of the mixing tanks, and U-bolts; When establishing the finite element analysis model of the leaf spring, the leaf spring is simulated by two-dimensional shell elements, and the connection pair between the leaf spring and its mounting components is set based on the assembly relationship between the real objects; When establishing the finite element analysis model of the axle, the finite element simulation of the solid unit axle is performed according to the outer contour of the axle; When establishing the finite element analysis model of the tire, the finite element simulation of the tire stiffness parameters is performed.

5. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 1 is characterized in that: The wheel loads of the pure electric mixer truck under different working conditions include: the wheel loads of each wheel under the working condition that the whole vehicle is fully loaded and the mixing tank rotates normally, and the wheel loads of each wheel under the initial state of unloading the whole vehicle; The method adjusts the eccentric distance of the mixing tank of the preliminary finite element analysis model of the mixer truck based on the wheel load under different working conditions, and obtains the finite element analysis model under the whole vehicle transportation working condition with different eccentric distances of the mixing tank and the finite element analysis model under the whole vehicle unloading working condition, including: Based on the preliminary finite element analysis model of the mixer truck, the sliding friction coefficient between the plates of the frame assembly is set, and a leaf spring bench test is carried out to obtain the displacement of the leaf spring corresponding to the load when the leaf spring contacts the limit block; The displacement of the leaf spring corresponding to the load when the leaf spring contacts the limit block is set as the initial distance of the contact relationship between the leaf spring and the frame limit in the preliminary finite element analysis model of the mixer truck; After the initial distance is set, the left and right eccentric distances of the finite element analysis model of the mixing tank are adjusted according to the wheel loads when the vehicle is fully loaded and the mixing tank rotates normally and the wheel loads when the vehicle is unloading in the initial state, and the finite element analysis models under the vehicle transportation condition and the finite element analysis models under the vehicle unloading condition with different eccentric distances of the mixing tank are obtained.

6. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 5 is characterized in that: The frame modal analysis is performed based on the finite element analysis model under the whole vehicle transportation condition, including: The modal extraction frequency of the finite element analysis model under the whole vehicle transportation condition is set to 0-100Hz, and the whole vehicle modal analysis calculation is performed to obtain the modal frequencies and vibration shapes of each order of the whole vehicle; According to the modal frequencies and vibration modes of the vehicle, find out the first-order torsional vibration mode of the frame assembly and determine the frequency associated with the torsional vibration mode; If the frequency associated with the torsional vibration mode is lower than the torsional frequency of the benchmark vehicle, the analysis result of the frame modal analysis does not meet the modal performance requirements; otherwise, the analysis result of the frame modal analysis meets the modal performance requirements.

7. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 1 is characterized in that: The frame stiffness analysis is performed based on the finite element analysis model under the whole vehicle transportation condition, including: According to the finite element analysis model under the whole vehicle transportation condition, the finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly are extracted respectively; The constraints of some components are loaded on the extracted finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly, and the frame stiffness of the finite element analysis model is solved after applying the vertical load and two reverse forces to the frame assembly to obtain the bending stiffness and torsional stiffness of the frame assembly; If the bending stiffness and torsional stiffness of the frame assembly are both higher than the benchmark vehicle stiffness threshold, the analysis result of the frame stiffness analysis is that the stiffness performance is met; If any of the bending stiffness and torsional stiffness of the frame assembly is lower than the benchmark vehicle stiffness threshold, the analysis result of the frame stiffness analysis is that the stiffness performance is not met.

8. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 7 is characterized in that: The constraints of some components are loaded on the extracted finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly, and the frame stiffness of the finite element analysis model is solved after applying the vertical load and two reverse forces to the frame assembly to obtain the bending stiffness and torsional stiffness of the frame assembly, including: According to the finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly, the vertical movement freedom of the left and right sides of the frame corresponding to the front axle is constrained, the vertical, longitudinal and lateral movement freedom of the center position of the left balancing suspension is constrained, and the vertical and longitudinal movement freedom of the center position of the right balancing suspension is constrained. Then, a vertical load is applied at the middle position between the front axle and the center position of the rear balancing suspension, and the finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly are solved to obtain the maximum vertical displacement of the frame longitudinal beam; According to the ratio of vertical load to maximum vertical displacement, the bending stiffness of the frame assembly is obtained; According to the finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly, the vertical movement freedom at the center of the front end crossbeam of the frame is constrained, the vertical, longitudinal and lateral movement freedom at the center of the left balance suspension is constrained, and the vertical and longitudinal movement freedom at the center of the right balance suspension is constrained. Then, equal and opposite forces are applied to the left and right sides of the frame corresponding to the front axle, and the finite element analysis model of the frame assembly and the finite element analysis model of the battery assembly are solved to obtain the acting torque and the torsion angle of the frame longitudinal beam at all longitudinal positions and extract the maximum torsion angle; The torsional stiffness of the frame assembly is obtained based on the ratio of the applied torque to the maximum torsion angle.

9. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 1 is characterized in that: According to the vehicle road load, the finite element analysis model under the whole vehicle transportation condition and the finite element analysis model under the whole vehicle unloading condition are respectively subjected to strength analysis, including: According to the maximum vertical acceleration, maximum longitudinal acceleration, maximum lateral acceleration and maximum displacement of each leaf spring of the whole vehicle, the finite element analysis model under the whole vehicle transportation condition is used to calculate the strength of the frame under bending, braking, steering and torsion conditions, and the maximum stress of the frame assembly under each condition is obtained respectively; According to the gravity load under the unloading condition, the strength of the finite element analysis model of the whole vehicle under the unloading condition is calculated under the gravity load, and the maximum stress of the frame assembly under the unloading condition is obtained respectively; According to the ratio of the preset yield strength of the frame assembly material to the maximum stress of the frame assembly under each working condition, the safety factor of the frame strength under each working condition is obtained; According to the comparison result of the preset safety factor threshold and the safety factor of the frame strength under various working conditions, it is judged whether the frame strength meets the strength performance requirements, and the strength analysis result is obtained; Among them, if the safety factor of the frame strength under each working condition is not less than the preset safety factor threshold, the strength analysis result meets the strength performance requirements; If the safety factor of the frame strength under various working conditions is less than the preset safety factor threshold, the strength analysis result will be that the strength performance requirements are not met.

10. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 9 is characterized in that: If the safety factor of the frame strength under each working condition is less than the preset safety factor threshold, the strength analysis result is considered to fail to meet the strength performance requirements, and also includes: The position where the safety factor of the frame strength under each working condition is less than the preset safety factor threshold is defined as the stress exceeding position; Based on the location where the stress exceeds the standard, determine whether it is near the bolt hole; if it is near the bolt hole, remodel the bolts and nuts, and solve the stress field and maximum stress of each working condition after the remodeling of the location where the stress exceeds the standard, which is used to calculate the safety factor of the location where the stress exceeds the standard after the remodeling and determine the strength analysis results; If it is not near the bolt hole, the strength analysis result will not meet the strength performance requirements.

11. The method for analyzing the structural performance of a pure electric mixer truck frame according to claim 10, characterized in that: If it is near the bolt hole, the bolt and nut are remodeled, and the stress field and maximum stress of each working condition after the remodeling of the stress exceeding the standard position are solved, including: The bolts and nuts modeled by the original stiffness unit and beam unit are replaced by solid unit modeling to obtain remodeled bolts and nuts. The bolt and nut units are discretely set using 2mm second-order tetrahedron units. Based on the remodeled bolts and nuts, a preload is established at the bolt section; The preload calculation condition is established based on the remodeled bolts and nuts, and the stress field of the frame containing only the preload and the stress analysis results of the preload condition are obtained; The stress analysis results of the preload condition are brought back into the strength calculation of each condition to obtain the maximum stress around the remodeled position under each condition; The safety factor of the remodeling position under each working condition is obtained according to the ratio of the preset yield strength of the frame assembly material to the maximum stress around the remodeling position under each working condition; If the safety factor of the remodeled position under each working condition is still less than the preset safety factor threshold, the strength performance requirement is not met, and the strength analysis result is that the strength performance requirement is not met; If the safety factor is greater than or equal to the preset safety factor threshold, and if the safety factors of all stress-exceeding locations are greater than or equal to the preset safety factor threshold, the strength analysis result meets the strength performance requirements.

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