CN114528739A - Simulation method for automobile hub fracture failure - Google Patents

Abstract

The invention discloses a true simulation method for automobile hub fracture failure simulation, which comprises the following steps: s1, sampling the rim and the spoke of the automobile hub real object and carrying out a material test to obtain a force-displacement curve under different test working conditions; s2, combining the obtained force-displacement curves under different test working conditions, applying LS-DYNA finite element analysis software, and respectively establishing an MAT _24 material card and an MAT _ ADD _ EROSION material card of a rim and a spoke, wherein the MAT _24 material card of the wheel center is obtained by zooming the MAT _24 material card of the rim or the spoke, and the MAT _ ADD _ EROSION material card of the wheel center is the same as the MAT _ ADD _ EROSION material card of the spoke; s3, establishing a finite element model of the automobile hub; and S4, performing a static crushing test and a dynamic drop test of the hub, endowing the material card established in S2 to the automobile hub finite element model established in S3, and determining an automobile hub simulation model through test calibration. The accurate simulation of deformation and failure of the automobile hub under the collision working condition can be realized.

Description

A simulation method of automobile wheel hub fracture failure model

technical field

The invention relates to finite element simulation analysis, in particular to a simulation method for a fracture failure model of an automobile wheel hub.

Background technique

The frontal 25% offset collision included in the China Insurance Automobile Safety Index (C-IASI) is the frontal collision of the vehicle with a fixed rigid barrier at a speed of 64KM/h and a 25% overlap rate (driver side). Due to the small collision area, the body The important parts of the body such as longitudinal beams and anti-collision beams are not fully involved in the collision process. Therefore, after the vehicle collides, the tire assembly acts as an important force transmission path to transmit the collision force to the cockpit. The most direct impact is It will cause deformation of the cockpit, squeeze the driver's living space, and eventually cause injury to the driver and passenger. In the process of collision, the wheel hub of the car will break and fail to varying degrees. How to accurately simulate the fracture failure behavior of the wheel hub during the collision of the vehicle is particularly important for the structural design of the vehicle and the analysis of the collision simulation.

At present, the vehicle wheel hub is not designed to fail in the vehicle crash simulation analysis, or simple force failure or time failure is used, which is quite different from the wheel hub fracture failure during the actual collision process, which affects the accuracy of the vehicle crash simulation analysis, and cannot be used for vehicle structure and driving. Occupant injury assessment and prediction.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simulation method for a fracture failure model of an automobile wheel hub, which can realize accurate simulation of the deformation and failure of the automobile wheel hub in a collision condition.

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

S1, sample the rims and spokes of the actual automobile wheel hubs and conduct material tests to obtain the force-displacement curves under different test conditions;

S2, combined with the force-displacement curves under different test conditions obtained from the test in step S1, the LS-DYNA finite element analysis software is used to establish the MAT_24 material card and MAT_ADD_EROSION material card for the rim and the spoke respectively, and the MAT_24 material card for the wheel center. Obtained by scaling the MAT_24 material card of the rim or spoke, the MAT_ADD_EROSION material card of the wheel center is the same as the MAT_ADD_EROSION material card of the spoke;

S3, establishing a finite element model of an automobile hub, the finite element model of the automobile hub includes three parts, a rim, a spoke and a wheel center, and the joints of the three parts share a node;

S4, carry out the static crush test and dynamic drop test of the wheel hub, assign the material card established by S2 to the finite element model of the automobile wheel hub established by S3, and determine the simulation model of the automobile wheel hub through test calibration.

Further, the material testing test includes uniaxial tensile test, shear test, tensile shear test, R5 notched tensile test, R10 notched tensile test, central hole tensile test, compression test, and perforation test.

Further, the establishment of the MAT_24 material card of the rim and the spoke is specifically: based on the obtained force-displacement curve under the uniaxial tensile condition, the true stress-strain curve of the rim and the spoke is obtained, and the true stress-strain curve is analyzed by hardening. The model is extrapolated to obtain the hardening curve of the MAT_24 material card, and other information of the MAT_24 material card is determined according to the material of the automobile wheel hub;

The establishment of the MAT_ADD_EROSION material card of the rim and the spoke is as follows: the GISSMO failure model is used to characterize the fracture failure behavior of the rim and the spoke material, and based on the force-displacement curves under different test conditions obtained from the material test test, the finite limit of the test sample is established. Then, through the simulation results of the finite element benchmarking model, the actual stress triaxiality and so on under different test conditions can be obtained. The plastic failure strain is calculated, and the simulation data obtained under different stress states are fitted to the data 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.

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

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

The material instability curve is a certain value in the range of -2/3 compression stress state to 2/3 biaxial tensile stress state through the equivalent plastic strain corresponding to the necking of the material in the uniaxial tensile test;

The size effect curve is compared with the unidirectional tensile finite element model, and the 0.5mm, 1mm, 2mm, 4mm and 8mm finite element models are established for simulation and test benchmarking, and finally obtained under different sizes. The fit degree of the force-displacement curve under the tensile test condition is more than 90%, and the equivalent plastic failure strain under 0.5mm is used for normalization, and the scaling factor of the fracture failure curve under different sizes can be obtained, which is size effect curve;

The stress decay exponent is used to manually input different values to benchmark the force-displacement curve under the uniaxial tensile test condition with the magnitude of the curve falling off after necking occurs, so that the simulation and test force-displacement curve are in 90% agreement. and above as the stress decay index value.

Further, in S3, a tetrahedral element is used to establish a finite element model of the automobile wheel hub.

Further, the static crushing test in the S4 is specifically as follows: fixing the automobile wheel hub on the base, the punch presses the wheel hub statically at a quasi-static speed, and constrains the punch in other directions except the vertical and outward degrees of freedom, so that the automobile The wheel hub fractures and fails under the action of static pressure, and the simulated maximum force value F ₁ based on the finite element model of the automobile wheel hub and the actual test maximum force value F ₂ based on the actual automobile wheel hub during static crushing are obtained respectively. If F ₁ and F ₂ The ratio is 85 to 115%, and the simulation fracture failure mode of the automobile hub is similar to the actual test fracture failure mode, then it is determined that the benchmarking accuracy of the finite element model of the automobile hub meets the requirements, otherwise it is determined that the benchmarking accuracy does not meet the requirements, and return to S2 to optimize MAT_24 No. material card and MAT_ADD_EROSION material card and re-run static crush test.

Further, the dynamic drop test in the S4 is specifically as follows: fixing the car wheel hub on the base, constraining the punch in other directions of freedom except vertical and outward, and the speed of the punch impacting the car wheel hub is controlled by adjusting the punch quality, so that The car wheel breaks and fails under the impact force of the punch, and the simulated maximum force value F ₃ based on the finite element model of the car wheel hub and the actual test maximum force value F ₄ based on the real car wheel hub during the dynamic drop impact are obtained respectively. If F ₃ The ratio of F ₄ to 85% to 115%, and the simulation fracture failure mode of the automobile wheel hub is similar to the actual test fracture failure mode, then it is judged that the benchmarking accuracy of the finite element model of the automobile wheel hub meets the requirements, otherwise, it is determined that the benchmarking accuracy does not meet the requirements, return Step 2: After optimizing the MAT_24 material card and the MAT_ADD_EROSION material card, perform the static crush test again.

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

1. The automobile wheel hub fracture failure simulation simulation method of the present invention takes into account the differences in mechanical properties of different regions of the automobile wheel hub, and uses preprocessing software to carry out refined modeling. At the same time, the LS-DYNA analysis software was used to establish the MAT_24 material card and the MAT_ADD_EROSION material card. Combined with the design verification test benchmarking optimization, the finite element simulation analysis model of the automobile wheel hub with fracture failure behavior was obtained, which truly reflected the mechanical characteristics of the automobile wheel hub, namely fracture. Failure behavior to facilitate design changes to the vehicle structure during the design phase.

2. The present invention uses the GISSMO model to simulate material damage and failure, considers the failure behavior under different stress states, truly reflects the fracture failure behavior of the automobile wheel hub under the collision condition, improves the accuracy of the vehicle collision simulation analysis, and can Effectively guide the vehicle structure design and body development.

3. The method for simulating the fracture failure of the automobile wheel hub according to the present invention has a simple process and is convenient to implement, and provides an idea for the simulation study of the fracture failure behavior of other parts.

Description of drawings

Fig. 1 is the schematic flow chart of the simulation simulation method of automobile wheel hub fracture failure according to the present invention;

Fig. 2 is the sampling schematic diagram of the material test sample of the present invention;

Fig. 3 is the structural representation of the automobile wheel hub of the present invention;

Fig. 4 is the schematic diagram of fracture failure curve of the present invention;

Fig. 5 is the finite element model schematic diagram of the automobile wheel hub of the present invention;

6 is one of the schematic diagrams of the static crush verification test of the automobile wheel hub according to the present invention;

7 is the second schematic diagram of the static crush verification test of the automobile wheel hub according to the present invention;

FIG. 8 is a schematic diagram of the dynamic drop verification test of the automobile wheel hub according to the present invention.

Detailed ways

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

Referring to Fig. 1, the shown simulation method for simulating failure of automobile wheel hub includes the following steps:

S1, sample the rims and spokes of the actual automobile wheel hub and conduct material testing tests, specifically: using CAD software to read the three-dimensional model data of the automobile wheel hub, and according to the test sample size of the material test test, select the materials that can be used as the material in the three-dimensional model of the automobile wheel hub. For the area of the test sample, see FIG. 2 , generally a relatively flat area on the automobile wheel hub 1 is selected, that is, the position of the rim 11 and the spoke 12 area is taken as the sampling area.

According to the sampling area determined in CAD, take out from the real vehicle hub including uniaxial tensile test, shear test, tensile shear test, R5 notched tensile test, R10 notched tensile test, central hole tensile test, compression test , test samples for perforation test, and then carry out the material test test on the test sample taken out, that is, carry out the material constitutive model test test and the material fracture failure test test, and obtain the force-displacement curve under different test conditions.

S2, combined with the force-displacement curves under different test conditions obtained in the test in step S1, the finite element simulation method is used to establish an equivalent finite element benchmark model of the test sample, and the development of the hub material fracture failure card is carried out, and the hub fracture failure The card is used by coupling the elastoplastic model with the keywords MAT_24 material card and MAT_ADD_EROSION material card defined 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.

Affected by structural characteristics, see Figure 3, there are differences in the yield strength of rim 11, spoke 12 and wheel center 13 in automobile hub 1. Therefore, the LS-DYNA finite element analysis software is used to establish MAT_24 material cards for rim 11 and spoke 12 respectively. and MAT_ADD_EROSION material card. Since it is difficult to take samples at the wheel center 13, the MAT_24 material card of the wheel center 13 is obtained by scaling the MAT_24 material card of the rim 11 or the spoke 12. The scaling factor is based on the empirical amplitude. The fracture failure modes are similar, so the MAT_ADD_EROSION material card of the wheel center 13 is set to be the same as the MAT_ADD_EROSION material card of the spokes.

The establishment of the MAT_24 material card of the rim 11 and the spoke 12 is as follows: based on the obtained force-displacement curve under the uniaxial tensile condition, the true stress-strain curve of the rim and the spoke is obtained, and the true stress-strain curve is analyzed by hardening. The model is extrapolated to obtain the hardening curve of the material card No. MAT_24, and the hardening analysis model includes at least one of Swift, HS and VOCE. The finite element comparison model of the test sample is established, and the simulation and test are compared, so that the force-displacement curve of the simulation and the test agrees with 90% or more. The stress-strain curve was extrapolated to obtain the hardening curve of the MAT_24 material card. The other information of the MAT_24 material card is determined according to the material of the automobile wheel hub. Specifically, the other information of the MAT_24 material card includes: material density, elastic modulus E, and Poisson's ratio parameters, which are obtained by looking up the table;

The establishment of the MAT_ADD_EROSION material card of the rim 11 and the spoke 12 is as follows: the GISSMO failure model is used to characterize the fracture failure behavior of the rim and the spoke material, and the test sample is established based on the force-displacement curve under different test conditions obtained from the material test test. The finite element benchmarking model is established, and the fit of the finite element benchmarking model and the test force-displacement curve is 90% or above. If the fit is less than 90%, the finite element benchmarking model is re-established until the fit 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 to the data, as shown in Figure 4, to obtain the MAT_ADD_EROSION material card The fracture failure curve. Other information of the MAT_ADD_EROSION material card includes material buckling curve, size effect curve, and stress decay index; the material buckling curve is the equivalent plastic strain corresponding to the necking of the material in the uniaxial tensile test, at -2 /3 compressive stress state to 2/3 biaxial tensile stress state is a certain value; the size effect curve is based on the uniaxial tensile finite element model, and the 0.5mm, 1mm, 2mm, 4mm and 8mm finite element models are established respectively. The model is compared with the simulation and test, and finally the force-displacement curves of different sizes and the uniaxial tensile test conditions are obtained to be more than 90% consistent, and the equivalent plastic failure strain under 0.5mm shall prevail. By normalizing, the scaling factor of the fracture failure curve under different sizes can be obtained, that is, the size effect curve; the stress decay index can be compared with the force-displacement curve under the uniaxial tensile test condition by manually entering different values. The magnitude of the curve drop after necking occurs in the middle, so that the fit between the simulation and the test force-displacement curve is 90% and above as the stress decay index value.

S3, referring to FIG. 5, the preprocessing software Hypermesh is used to establish a finite element model of an automobile wheel hub. The finite element model of the automobile wheel hub includes three parts, a rim, a spoke and a wheel center, and the joints of the three parts share a node. The finite element model of the automobile wheel hub The model is modeled with tetrahedral elements. Due to the complexity of the shape and structure of the automobile wheel hub, the mesh size of the element is controlled at 2-4mm. Due to the complex and irregular structure of the hub, the meshing of hexahedral elements is difficult, which is not conducive to engineering applications. Tetrahedral elements are used for division, and the calculation results of hexahedral elements are compared by using different element integration types, and the simulation results are selected to compare the differences. The smallest tetrahedral element integration type. At the same time, in order to ensure the accuracy of the simulation analysis results, at least two layers of volume mesh elements are distributed in the thickness direction;

S4, carry out the static crush test and dynamic drop test of the wheel hub, assign the material card established by S2 to the finite element model of the automobile wheel hub established by S3, and determine the simulation model of the automobile wheel hub through test calibration.

The static crush test is specifically: establishing a static pressure simulation model of an 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 cards and MAT_ADD_EROSION material cards. Referring to Figure 6 and Figure 7, the automobile wheel hub 1 is fixed on the base 2, and the punch 3 statically presses the automobile wheel hub 1 at a quasi-static speed, while constraining the punch 3 in other directions except the vertical and outward degrees of freedom, so that the automobile wheel hub 1 Fracture failure occurs under the action of static pressure, and the simulation maximum force value F ₁ = 286kN based on the finite element model of the automobile wheel hub and the actual test maximum force value F _{2 =} 273kN based on the actual automobile wheel hub during static crushing are obtained. The ratio of F 2 and F ₂ is 104.8%, and it is judged that the benchmarking accuracy of the finite element model of the automobile wheel hub meets the requirements.

Referring to FIG. 5 , the static pressure position of the punch 3 is located on the side of the automobile wheel hub 1 close to the wheel spokes 12 and the wheel center 13 . Referring to FIG. 6 , the static pressure position of the head 3 is located on the side of the automobile wheel hub 1 away from the spoke 12 and the wheel center 13 , and the rim 11 strength benchmarking and fracture failure mode benchmarking are performed.

The dynamic drop test is specifically as follows: referring to FIG. 8 , the automobile wheel hub 1 is fixed on the base 2, the freedom of the punch 3 is restricted in other directions except the vertical direction, and the speed of the punch 3 impacting the automobile wheel hub 1 is adjusted by adjusting the punch 3. To control the quality, the automobile hub 1 breaks and fails under the impact force of the punch 3, and the simulated maximum force value F ₃ = 365kN based on the finite element model of the automobile hub during dynamic drop impact and the actual test based on the actual automobile hub are obtained respectively. The maximum force value F ₄ =355kN, if the ratio of F ₃ and F ₄ is 102.8%, it is determined that the benchmarking accuracy of the finite element model of the automobile wheel hub meets the requirements, otherwise it is determined that the benchmarking accuracy does not meet the requirements.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (7)

1. An automobile hub fracture failure simulation method is characterized by comprising the following steps:

s1, sampling the rim and the spoke of the automobile hub object and performing a material test to obtain force-displacement curves under different test working conditions;

s2, combining the force-displacement curves under different test conditions obtained by the test of the step S1, applying LS-DYNA finite element analysis software, and respectively establishing an MAT _24 material card and an MAT _ ADD _ EROSION material card of a rim and a spoke, wherein the MAT _24 material card of the wheel center is obtained by scaling the MAT _24 material card of the rim or the spoke, and the MAT _ ADD _ EROSION material card of the wheel center is the same as the MAT _ ADD _ EROSION material card of the spoke;

s3, establishing an automobile hub finite element model, wherein the automobile hub finite element model comprises a rim, a spoke and a wheel center, and joints of the three parts share a node;

and S4, performing a static crushing test and a dynamic drop test on the hub, endowing the material card established in S2 to the automobile hub finite element model established in S3, and determining an automobile hub simulation model through test calibration.

2. The automobile hub fracture failure simulation method according to claim 1, characterized in that: the material test comprises a unidirectional tensile test, a shear test, a tensile-shear test, an R5 notch tensile test, an R10 notch tensile test, a center hole tensile test, a compression test and a perforation test.

3. The automobile hub fracture failure simulation method of claim 2, wherein the establishment of the MAT _24 material cards of the rim and the spoke specifically comprises the following steps: obtaining a real stress-strain curve of a rim and a spoke based on the obtained force-displacement curve under the unidirectional tension working condition, extrapolating the real stress-strain curve through a hardening analysis model to obtain a hardening curve of the MAT _24 material card, and determining other information of the MAT _24 material card according to the automobile hub material;

the establishment of the MAT _ ADD _ EROSION material card of the rim and the spoke is specifically as follows: adopting a GISSMO failure model to represent the fracture failure behavior of rim and spoke materials, establishing a finite element benchmarking model of a test sample based on force-displacement curves under different test working conditions obtained by a material test, and enabling the fit degree of the finite element benchmarking model simulation and the test force-displacement curve to be 90% or more; and then obtaining the three-axis degree of actual stress and equivalent plastic failure strain under different test working conditions through a finite element standard model simulation result, performing data fitting on simulation data obtained under different stress conditions to obtain a fracture failure curve of the MAT _ ADD _ EROSION material card, and determining other information of the MAT _ ADD _ EROSION material card according to the test data.

4. The automobile hub fracture failure simulation method according to claim 3, characterized in that: the MAT _24 material card comprises other information: the material density, the elastic modulus E and the Poisson ratio parameters are obtained by looking up a table;

other information of the MAT _ ADD _ EROSION material card comprises a material instability curve, a size effect curve and a stress decay index;

the material instability curve passes through corresponding equivalent plastic strain when the material is necked in a uniaxial tension test, and is a certain value in a range from a-2/3 compressive stress state to a 2/3 biaxial tension stress state;

the size effect curve is subjected to simulation and test benchmarking by respectively establishing 0.5mm, 1mm, 2mm, 4mm and 8mm finite element benchmarking models through a unidirectional stretching finite element benchmarking model, finally, the matching degree of force-displacement curves which can be matched with the unidirectional stretching test under the working condition under different sizes is respectively obtained to be more than 90%, normalization processing is carried out by taking equivalent plastic failure strain under 0.5mm as a reference, and the scaling coefficient of fracture failure curves under different sizes can be obtained, namely the size effect curve;

the stress attenuation index is characterized in that different values are manually input to compare the falling amplitude of a curve after necking in a force-displacement curve under the working condition of a standard unidirectional tensile test, so that the coincidence degree of simulation and test force-displacement curves is 90% or more and is used as the stress attenuation index value.

5. The automobile hub fracture failure simulation method according to claim 1 or 2, characterized in that: and in the step S3, a finite element model of the automobile hub is established by adopting tetrahedral units.

6. The automobile hub fracture failure simulation method according to claim 1 or 2, wherein the static crushing test in the S4 is specifically as follows: the automobile hub is fixed on the base, the punch is used for carrying out static pressure on the hub at a quasi-static speed, and meanwhile, the freedom degrees of the punch in other directions except the vertical direction are restrained, so that the automobile hub is broken and fails under the action of static pressure, and the simulation maximum force value F based on the automobile hub finite element model is obtained when static crushing is respectively obtained₁And practical test maximum force value F based on automobile hub real object₂If F is₁And F₂The ratio of the automobile hub simulation fracture failure mode to the standard precision is 85-115%, if the automobile hub simulation fracture failure mode is similar to the actual test fracture failure mode, the standard precision is judged to meet the requirement, otherwise, the standard precision is judged not to meet the requirement, and the static crushing test is carried out again after the MAT _24 material card and the MAT _ ADD _ EROSION material card are optimized in the second step.

7. The automobile hub fracture failure simulation method according to claim 1 or 2, wherein the dynamic drop test in the S4 specifically comprises: on being fixed in the base with automobile wheel hub, restraint drift other direction degrees of freedom except vertical, the speed that the drift impacted automobile wheel hub is controlled through adjustment drift quality for automobile wheel hub is dashing towardsThe head is broken and failed under the action of impact force, and the simulation maximum force value F based on the finite element model of the automobile hub during dynamic falling impact is respectively obtained₃And practical test maximum force value F based on automobile hub real object₄If F is₃And F₄The ratio of the automobile hub simulation fracture failure mode to the actual test fracture failure mode is 85-115%, if the automobile hub simulation fracture failure mode is similar to the actual test fracture failure mode, the standard alignment precision of the automobile hub finite element model is judged to meet the requirement, otherwise, the standard alignment precision is judged not to meet the requirement, and the automobile hub simulation fracture failure mode returns to S2 to optimize the MAT _24 material card and the MAT _ ADD _ EROSION material card and then the static crushing test is carried out again.

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