A simulation method for automobile wheel hub fracture failure

Abstract

The present invention discloses a method for simulating the fracture failure of an automobile wheel hub, comprising the following steps: S1, sampling the rim and spokes of an actual automobile wheel hub and conducting material testing to obtain force-displacement curves under different test conditions; S2, combining the obtained force-displacement curves under different test conditions and applying LS-DYNA finite element analysis software to establish MAT_24 material cards and MAT_ADD_EROSION material cards for the rim and spokes, respectively. The MAT_24 material card for the wheel hub is obtained by scaling the MAT_24 material cards of the rim or spokes, and the MAT_ADD_EROSION material card for the wheel hub is the same as the MAT_ADD_EROSION material card for the spokes; S3, establishing a finite element model of the automobile wheel hub; S4, conducting a static crush test and a dynamic drop test on the wheel hub, assigning the material card established in S2 to the automobile wheel hub finite element model established in S3, and determining the automobile wheel hub simulation model through experimental calibration. The method can accurately simulate the deformation and failure of automobile wheel hubs under collision conditions.

Description

Technical Field

[0001] The invention relates to finite element simulation analysis, and in particular to a method for simulating the fracture failure of an automobile wheel hub. Background Art

[0002] The 25% offset frontal collision, included in the China Insurance Automobile Safety Index (C-IASI), involves a vehicle striking a fixed rigid barrier head-on at 64 km / h with a 25% overlap (driver's side). Due to the small collision area, critical body components such as the longitudinal beam and anti-collision beam are not fully involved in the collision. Therefore, after the collision, the tire assembly acts as a key force transmission path, transmitting the impact force to the cockpit. The most direct impact is deformation of the cockpit, squeezing the driver's living space, and ultimately injuring the driver and passengers. During a collision, the wheel hub will experience varying degrees of fracture failure. Accurately simulating the fracture failure behavior of the wheel hub during a full-vehicle collision is particularly important for vehicle structural design and collision simulation analysis.

[0003] Currently, automobile wheel hubs are not designed to fail in whole-vehicle collision simulation analysis, or simple force failure or time failure is used. This is significantly different from the wheel hub fracture failure during an actual collision, affecting the accuracy of whole-vehicle collision simulation analysis and making it impossible to evaluate and predict the vehicle structure and injuries to the driver and passengers. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for simulating the fracture failure of an automobile wheel hub, which can realize accurate simulation of the deformation and failure of the automobile wheel hub under collision conditions.

[0005] The automobile wheel hub fracture failure simulation method of the present invention comprises the following steps:

[0006] S1, sample the rim and spoke of the actual automobile wheel hub and perform material testing to obtain the force-displacement curves under different test conditions;

[0007] S2. Based on the force-displacement curves under different test conditions obtained in step S1, use LS-DYNA finite element analysis software to establish MAT_24 material cards and MAT_ADD_EROSION material cards for the rim and spoke, respectively. The MAT_24 material card for the wheel center is obtained by scaling the MAT_24 material card for the rim or spoke. The MAT_ADD_EROSION material card for the wheel center is the same as the MAT_ADD_EROSION material card for the spoke.

[0008] S3, establishing a finite element model of an automobile wheel hub, wherein the finite element model of the automobile wheel hub includes three parts: a rim, a spoke, and a wheel center, and the connections between the three parts share a common node;

[0009] S4, conducts a static crush test and a dynamic drop test on the wheel hub, assigns the material card established in S2 to the finite element model of the automobile wheel hub established in S3, and determines the automobile wheel hub simulation model through experimental calibration.

[0010] Furthermore, the material testing tests include unidirectional tensile test, shear test, tension-shear test, R5 notch tensile test, R10 notch tensile test, center hole tensile test, compression test, and perforation test.

[0011] Furthermore, the MAT_24 material card for the rim and spoke is specifically established by obtaining true stress-strain curves of the rim and spoke based on the force-displacement curves obtained under uniaxial tension conditions, extrapolating the true stress-strain curves through a hardening analysis model to obtain a hardening curve for the MAT_24 material card. Other information on the MAT_24 material card is determined based on the material of the automobile hub.

[0012] The establishment of the MAT_ADD_EROSION material card for the rim and spoke is specifically as follows: the GISSMO failure model is used to characterize the fracture failure behavior of the rim and spoke materials, and based on the force-displacement curves under different test conditions obtained from the material testing experiment, a finite element benchmarking model of the test sample is established, and the finite element benchmarking model simulation and the test force-displacement curve are consistent with each other at 90% or above; then, the actual stress triaxiality and equivalent plastic failure strain under different test conditions are obtained through the simulation results of the finite element benchmarking model, and the simulation data obtained under different stress states are data fitted to obtain the fracture failure curve of the MAT_ADD_EROSION material card. Other information of the MAT_ADD_EROSION material card is determined according to the material of the automobile wheel hub.

[0013] Furthermore, other information of the material card MAT_24 includes: material density, elastic modulus E, and Poisson's ratio parameters, which are obtained by looking up the table;

[0014] Other information of the MAT_ADD_EROSION material card includes material instability curve, size effect curve, and stress decay index;

[0015] The material instability curve is a constant value in the range of -2 / 3 compressive stress state to 2 / 3 biaxial tensile stress state, which is the equivalent plastic strain corresponding to the necking of the material in the uniaxial tensile test;

[0016] The size effect curve is obtained by using a uniaxial tensile finite element benchmarking model, and 0.5mm, 1mm, 2mm, 4mm and 8mm finite element models are established for simulation and test benchmarking. Finally, the force-displacement curves under different sizes are obtained with a degree of agreement of more than 90% with the uniaxial tensile test conditions. The equivalent plastic failure strain at 0.5mm is used as the standard for normalization, and the scaling coefficients of the fracture failure curves under different sizes can be obtained, which are the size effect curves.

[0017] The stress decay index is manually input with different values ​​to match the drop in the force-displacement curve after necking occurs in the uniaxial tensile test condition, so that the degree of agreement between the simulation and the test force-displacement curve is 90% or above as the stress decay index value.

[0018] Furthermore, in S3, a finite element model of the automobile wheel hub is established using tetrahedron units.

[0019] Furthermore, the static crushing test in S4 is specifically as follows: the automobile wheel hub is fixed on the base, and the punch is used to statically press the wheel hub at a quasi-static speed, while constraining the punch in other directions except the vertical direction, so that the automobile wheel hub fractures and fails under the action of static pressure, and the simulated maximum force value F1 based on the automobile wheel hub finite element model and the actual test maximum force value F2 based on the actual automobile wheel hub during static crushing are respectively obtained. If the ratio of F1 to F2 is 85~115%, and the simulated fracture failure form of the automobile wheel hub is similar to the actual test fracture failure form, it is determined that the benchmarking accuracy of the automobile wheel hub finite element model meets the requirements; otherwise, it is determined that the benchmarking accuracy does not meet the requirements, and the static crushing test is repeated after returning to S2 to optimize the MAT_24 material card and the MAT_ADD_EROSION material card.

[0020] Furthermore, the dynamic drop test in S4 is specifically as follows: the automobile wheel hub is fixed on the base, and the degrees of freedom of the punch in other directions except the vertical direction are constrained. The speed at which the punch impacts the automobile wheel hub is controlled by adjusting the mass of the punch, so that the automobile wheel hub fractures and fails under the action of the impact force of the punch, and the simulated maximum force value F3 based on the automobile wheel hub finite element model and the actual test maximum force value F4 based on the actual automobile wheel hub during the dynamic drop impact are respectively obtained. If the ratio of F3 to F4 is 85-115%, and the simulated fracture failure form of the automobile wheel hub is similar to the actual test fracture failure form, it is determined that the benchmarking accuracy of the automobile wheel hub finite element model meets the requirements; otherwise, it is determined that the benchmarking accuracy does not meet the requirements, and the dynamic drop test is repeated after returning to step 2 to optimize the MAT_24 material card and the MAT_ADD_EROSION material card.

[0021] Compared with the prior art, the present invention has the following beneficial effects.

[0022] The automotive wheel hub fracture failure simulation method described in this invention takes into account the differences in mechanical properties between different regions of the automotive wheel hub and utilizes pre-processing software for refined modeling. LS-DYNA analysis software is also used to create the MAT_24 material card and the MAT_ADD_EROSION material card. Combined with design verification test benchmarking and optimization, a finite element simulation analysis model of the automotive wheel hub, including fracture failure behavior, is obtained. This truly reflects the mechanical properties of the automotive wheel hub, namely its fracture failure behavior, facilitating design changes to the vehicle structure during the design phase.

[0023] 2. The present invention adopts the GISSMO model to simulate material damage failure, taking into account the failure behavior under different stress states, and truly reflects the fracture failure behavior of automobile wheels under collision conditions, thereby improving the accuracy of vehicle collision simulation analysis and effectively guiding vehicle structural design and body development.

[0024] 3. The automobile wheel hub fracture failure simulation method of the present invention has a simple process and is easy to implement, which provides ideas for the simulation research of the fracture failure behavior of other components. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow chart of the automobile wheel hub fracture failure simulation method of the present invention;

[0026] Figure 2 Schematic diagram of sampling of test samples of the material of the present invention;

[0027] Figure 3 It is a structural schematic diagram of the automobile wheel hub of the present invention;

[0028] Figure 4 2 is a schematic diagram of the fracture failure curve of the present invention;

[0029] Figure 5 is a schematic diagram of a finite element model of the automobile wheel hub of the present invention;

[0030] Figure 6 This is one of the schematic diagrams of the automobile wheel hub static crush verification test according to the present invention;

[0031] Figure 7 This is the second schematic diagram of the automobile wheel hub static crush verification test according to the present invention;

[0032] Figure 8 It is a schematic diagram of the automobile wheel hub dynamic drop verification test of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to the accompanying drawings.

[0034] See also Figure 1, the automobile wheel hub fracture failure simulation method shown includes the following steps:

[0035] S1. Sample the rim and spokes of the actual automobile wheel and conduct material testing. Specifically, the following steps are used: CAD software is used to read the 3D model data of the automobile wheel; based on the test sample size of the material testing test, an area that can be used as a material testing sample is selected in the 3D model of the automobile wheel; see Figure 2 Generally, a relatively flat area on the automobile wheel hub 1, that is, the rim 11 and the spoke 12 area are selected as the sampling area.

[0036] According to the sampling area determined in CAD, test specimens for unidirectional tensile test, shear test, tension-shear test, R5 notch tensile test, R10 notch tensile test, center hole tensile test, compression test, and perforation test are taken out from the actual automobile wheel hub. Then, material testing is carried out on the taken test specimens, namely, material constitutive model testing and material fracture failure testing, to obtain force-displacement curves under different test conditions.

[0037] S2. Combined with the force-displacement curves under different test conditions obtained in step S1, a finite element benchmarking model equivalent to the test sample is established by finite element simulation to develop a hub material fracture failure card. The hub fracture failure card is coupled with the elastic-plastic model by defining the keywords MAT_24 material card and MAT_ADD_EROSION material card in the LS-DYNA finite element analysis software. The MAT_24 material card and MAT_ADD_EROSION material card describe the elastic-plastic behavior and fracture behavior of the material respectively.

[0038] Affected by structural characteristics, see Figure 3 The yield strengths of the rim 11, spokes 12, and wheel center 13 of automobile wheel hub 1 vary. Therefore, LS-DYNA finite element analysis software was used to create MAT_24 and MAT_ADD_EROSION material cards for rim 11 and spokes 12, respectively. Since sampling at wheel center 13 is difficult, the MAT_24 material card for wheel center 13 was scaled by the MAT_24 material cards of rim 11 or spoke 12. The scaling factor was based on empirical amplitudes. The fracture failure mode of wheel center 13 is similar to that of spokes 12, so the MAT_ADD_EROSION material card for wheel center 13 was set to be the same as that of the spokes.

[0039] The establishment of the MAT_24 material card of the rim 11 and the spoke 12 is specifically as follows: based on the force-displacement curve obtained under the unidirectional tensile working condition, the true stress-strain curve of the rim and the spoke is obtained, and the true stress-strain curve is extrapolated through the hardening analysis model to obtain the hardening curve of the MAT_24 material card, and the hardening analysis model includes at least one of Swift, HS and VOCE. A finite element comparison model of the test sample is established, and the simulation and test are compared to make the degree of agreement between the simulation and the test force-displacement curves 90% or above. If the degree of agreement is lower than 90%, the true stress-strain curve is extrapolated again through the hardening analysis model to obtain the hardening curve of the MAT_24 material card. Other information of the MAT_24 material card is determined according to the material of the automobile wheel hub. Specifically, other information of the MAT_24 material card includes: material density, elastic modulus E, Poisson's ratio parameters, which are obtained by table lookup;

[0040] The establishment of the MAT_ADD_EROSION material card of the rim 11 and spoke 12 is specifically as follows: the GISSMO failure model is used to characterize the fracture failure behavior of the rim and spoke materials, and based on the force-displacement curves under different test conditions obtained from the material test, a finite element benchmarking model of the test sample is established, and the finite element benchmarking model simulation and the test force-displacement curve are consistent with each other at 90% or above. If the consistency is lower than 90%, the finite element benchmarking model is re-established until the consistency meets the requirements. Then, the actual stress triaxiality and equivalent plastic failure strain under different test conditions are obtained through the simulation results of the finite element benchmarking model, and the simulation data obtained under different stress states are fitted, see Figure 4 , and obtain the fracture failure curve of the MAT_ADD_EROSION material card. Other information of the MAT_ADD_EROSION material card includes a material instability curve, a size effect curve, and a stress decay index; the material instability curve is obtained by manually entering different values ​​to match the force-displacement curve under the uniaxial tensile test condition with the equivalent plastic strain corresponding to the necking of the material in the uniaxial tensile test, and is a certain value in the range of -2 / 3 compression stress state to 2 / 3 biaxial tensile stress state; the size effect curve is obtained by manually entering different values ​​to match the force-displacement curve under the uniaxial tensile test condition with the drop amplitude of the curve after necking, so that the simulation and experimental force-displacement curves match at least 90% of each other, and the scaling coefficient of the fracture failure curve under different sizes is obtained.

[0041] S3, see Figure 5 , the pre-processing software Hypermesh is used to establish a finite element model of the automobile wheel hub. The finite element model of the automobile wheel hub includes three parts: the rim, the spoke and the wheel center, and the nodes are shared at the connection of the three parts. The finite element model of the automobile wheel hub is modeled using tetrahedron units. Due to the complexity of the automobile wheel hub shape and structure, the unit grid size is controlled at 2-4mm. Since the wheel hub structure is complex and irregular, the mesh division of hexahedron units is difficult, which is not conducive to engineering applications. Tetrahedron units are used for division. By using different unit integration types to compare the calculation results of the hexahedron units, the tetrahedron unit integration type with the smallest difference in the simulation calculation results is selected. At the same time, in order to ensure the accuracy of the simulation analysis results, at least two layers of body grid units are distributed in the thickness direction;

[0042] S4, conducts a static crush test and a dynamic drop test on the wheel hub, assigns the material card established in S2 to the finite element model of the automobile wheel hub established in S3, and determines the automobile wheel hub simulation model through experimental calibration.

[0043] The static crush test specifically includes: establishing a static pressure simulation model of the automobile wheel hub punch, including an automobile wheel hub finite element model, a base finite element model and a punch finite element model with MAT_24 material card and MAT_ADD_EROSION material card. Figure 6 and Figure 7 The automobile wheel hub 1 is fixed on the base 2, and the punch 3 is used to statically press the automobile wheel hub 1 at a quasi-static speed. At the same time, the punch 3 is constrained in all directions except the vertical direction, so that the automobile wheel hub 1 breaks and fails under the action of static pressure. The maximum force value F1 of the simulation based on the automobile wheel hub finite element model during static crushing is 286kN, and the maximum force value F2 of the actual test based on the actual automobile wheel hub is 273kN. The ratio of F1 to F2 is 104.8%, which indicates that the benchmarking accuracy of the automobile wheel hub finite element model meets the requirements.

[0044] See also Figure 5 The static pressure position of the punch 3 is located on the side of the automobile wheel hub 1 close to the spoke 12 and the wheel center 13, and the strength and fracture failure mode of the spoke 12 and the wheel center 13 are compared. Figure 6 The static pressure position of the head 3 is located on the side of the automobile hub 1 away from the spoke 12 and the wheel center 13, and the strength of the rim 11 and the fracture failure mode are aligned.

[0045] The dynamic drop test is specifically as follows: Figure 8The automobile wheel hub 1 is fixed on the base 2, and the punch 3 is constrained in all directions except the vertical direction. The speed at which the punch 3 impacts the automobile wheel hub 1 is controlled by adjusting the mass of the punch 3, so that the automobile wheel hub 1 breaks and fails under the action of the impact force of the punch 3. The maximum force value F3 of the simulation based on the automobile wheel hub finite element model during dynamic drop impact is 365kN, and the maximum force value F4 of the actual test based on the actual automobile wheel hub is 355kN. If the ratio of F3 to F4 is 102.8%, it is determined that the benchmarking accuracy of the automobile wheel hub finite element model meets the requirements; otherwise, it is determined that the benchmarking accuracy does not meet the requirements.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for simulating the fracture failure of an automobile wheel hub, characterized in that: The steps include: S1, sampling the rim and spokes of the actual automobile wheel hub and performing material testing tests to obtain force-displacement curves under different test conditions; the material testing tests include uniaxial tensile test, shear test, tension-shear test, R5 notch tensile test, R10 notch tensile test, center hole tensile test, compression test, and perforation test; S2. Based on the force-displacement curves under different test conditions obtained in step S1, use LS-DYNA finite element analysis software to establish MAT_24 material cards and MAT_ADD_EROSION material cards for the rim and spoke, respectively. The MAT_24 material card for the wheel center is obtained by scaling the MAT_24 material card for the rim or spoke. The MAT_ADD_EROSION material card for the wheel center is the same as the MAT_ADD_EROSION material card for the spoke. The MAT_24 material card for the rim and spoke is specifically established by obtaining a true stress-strain curve for the rim and spoke based on the force-displacement curve obtained under uniaxial tension conditions, and extrapolating the true stress-strain curve using a hardening analysis model to obtain a hardening curve for the MAT_24 material card. Other information on the MAT_24 material card is determined based on the material of the automobile hub. The establishment of the MAT_ADD_EROSION material card of the rim and spoke is specifically as follows: the GISSMO failure model is used to characterize the fracture failure behavior of the rim and spoke materials, and based on the force-displacement curves under different test conditions obtained from the material test, a finite element benchmarking model of the test sample is established, and the degree of agreement between the finite element benchmarking model simulation and the test force-displacement curve is made to be 90% or above; then, the actual stress triaxiality and equivalent plastic failure strain under different test conditions are obtained through the simulation results of the finite element benchmarking model, and the simulation data obtained under different stress states are data fitted to obtain the fracture failure curve of the MAT_ADD_EROSION material card. Other information of the MAT_ADD_EROSION material card is determined according to the test data; Other information on the MAT_24 material card includes: material density, elastic modulus E, and Poisson's ratio parameters, which are obtained by looking up the table; Other information of the MAT_ADD_EROSION material card includes material instability curve, size effect curve, and stress decay index; The material instability curve is a constant value in the range of -2 / 3 compressive stress state to 2 / 3 biaxial tensile stress state, which is the equivalent plastic strain corresponding to the necking of the material in the uniaxial tensile test; The size effect curve is obtained by using a uniaxial tensile finite element benchmarking model, and 0.5mm, 1mm, 2mm, 4mm and 8mm finite element models are established for simulation and test benchmarking. Finally, the force-displacement curves under different sizes are obtained with a degree of agreement of more than 90% with the uniaxial tensile test conditions. The equivalent plastic failure strain at 0.5mm is used as the standard for normalization, and the scaling coefficients of the fracture failure curves under different sizes are obtained, which are the size effect curves. The stress decay index is manually input with different values ​​to match the drop in the force-displacement curve after necking occurs in the uniaxial tensile test condition, so that the degree of agreement between the simulation and test force-displacement curves is 90% or above as the stress decay index value; S3, establishing a finite element model of an automobile wheel hub, wherein the finite element model of the automobile wheel hub includes three parts: a rim, a spoke, and a wheel center, and the connections between the three parts share nodes; the finite element model of the automobile wheel hub is modeled using tetrahedral elements, the mesh size of the tetrahedral elements is 2-4 mm, and at least two layers of volume mesh elements are distributed in the thickness direction of the finite element model of the automobile wheel hub; S4, conducts a static crush test and a dynamic drop test on the wheel hub, assigns the material card established in S2 to the finite element model of the automobile wheel hub established in S3, and determines the automobile wheel hub simulation model through experimental calibration.

2. The automobile wheel hub fracture failure simulation method according to claim 1, characterized in that: The static crushing test in S4 is specifically as follows: the automobile wheel hub is fixed on the base, and the punch is used to statically press the wheel hub at a quasi-static speed, while constraining the punch in all directions except the vertical direction, so that the automobile wheel hub fractures and fails under the action of static pressure, and the simulated maximum force value F1 based on the automobile wheel hub finite element model and the actual test maximum force value F2 based on the actual automobile wheel hub during static crushing are respectively obtained. If the ratio of F1 to F2 is 85-115%, and the simulated fracture failure form of the automobile wheel hub is similar to the actual test fracture failure form, it is determined that the benchmarking accuracy of the automobile wheel hub finite element model meets the requirements; otherwise, it is determined that the benchmarking accuracy does not meet the requirements, and the static crushing test is repeated after returning to step 2 to optimize the MAT_24 material card and the MAT_ADD_EROSION material card.

3. The automobile wheel hub fracture failure simulation method according to claim 1 or 2, characterized in that: The dynamic drop test in S4 is specifically as follows: the automobile wheel hub is fixed on the base, and the degrees of freedom of the punch in other directions except the vertical direction are constrained. The speed at which the punch impacts the automobile wheel hub is controlled by adjusting the mass of the punch, so that the automobile wheel hub fractures and fails under the action of the punch impact force, and the simulated maximum force value F3 based on the automobile wheel hub finite element model and the actual test maximum force value F4 based on the actual automobile wheel hub during the dynamic drop impact are respectively obtained. If the ratio of F3 to F4 is 85-115%, and the simulated fracture failure form of the automobile wheel hub is similar to the actual test fracture failure form, it is determined that the benchmarking accuracy of the automobile wheel hub finite element model meets the requirements; otherwise, it is determined that the benchmarking accuracy does not meet the requirements, and the dynamic drop test is repeated after returning to S2 to optimize the MAT_24 material card and the MAT_ADD_EROSION material card.

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