JP5488963B2 - Simulation method for impact performance of wheels with tires - Google Patents

Description

  The present invention relates to a vehicle wheel performance evaluation method, and more particularly to a simulation method capable of accurately predicting the impact performance of a wheel with a tire using a computer.

  Wheels for vehicles are important safety parts. In addition to the mechanical strength of the structure, the impact performance (resistance to resistance) prevents cracks when the vehicle collides with an obstacle such as climbing a curb on a sidewalk or a car stop. Impact) is required. On the other hand, the wheels are also required to be lighter by changing the shape and reducing the wall thickness in order to reduce the unsprung weight and improve ride comfort and running stability, or to improve vehicle fuel efficiency. ing. In order to improve the impact performance, it is conceivable to increase the strength by forming the wheel thick, but there is a problem that hindering the weight reduction of the wheel.

  A wheel manufacturer develops a wheel by conducting a computer-aided design called CAD or CAE at the time of design, preliminarily examining the shape and weight, and performing performance evaluation such as impact tests, rotating bending tests, and drum durability tests. However, studies to satisfy the conflicting demands of strength and weight reduction are mostly based on trial and error, and the long-term development is spent.

  Conventionally, evaluation of the impact performance of a wheel is based on the assumption that the wheel is impacted by an obstacle such as designing the wheel, manufacturing a die, making a prototype, and then riding the vehicle on a curb when driving the vehicle. As a test, for example, evaluation is performed by performing an impact test defined in JIS D4103 “Automotive Parts—Disk Wheel—Performance and Display”. In the impact test of JIS, the disk surface (radial direction) of the wheel on which the tire is mounted is tilted at an angle of 30 ° with respect to the horizontal, and the central hub portion of the wheel is fixed to the support base. Make sure that the weight of the specified mass is dropped and collided at the specified position from the height of the fall, and check that there is no damage to the wheel (harmful cracks) or sudden tire air leakage due to the collision of the weight. The impact performance is evaluated.

  In addition to the test specified in the above JIS, the wheel impact performance evaluation method includes ISO 7141 (Road vehicles-Light alloy wheels-Impact test), and the inclination angle of the wheel radial direction with respect to the horizontal is set to 13 °. There is an ISO system impact test specified as a different test specification, and there is no official standard, but car manufacturers and others have specified their own test specifications and standard values, such as setting the wheel tilt angle to 90 ° to the horizontal. There is an exam.

  FIG. 10 is a schematic diagram of an actual wheel impact test apparatus 20. In the impact test apparatus 20 of FIG. 10, 21 is a wheel, 22 is a tire, 23 is a weight, 23a is a main weight of the weight 23, 23b is a subweight, 23c is a main weight 23a suspended from the subweight 23b. A coil spring 24 to be connected is a support base for fixing the disk surface 21 a of the wheel 21. The impact test apparatus 20 shown in FIG. 10 has tires 22 attached to wheels 21, and the inclination angle θ in the radial direction of the wheel 21 with respect to the horizontal is 90 °, that is, the radial direction of the wheel 21 is vertical. The position of the auxiliary weight 23b with respect to the tire 22 is determined by being fixed to the support base 24 by the method described above, and the weight 23 is dropped from the height H of the fall. The weight 23 is composed of the main weight 23a, the auxiliary weight 23b, and the coil spring 23c in consideration of the impact absorption by the suspension (suspension device) of the vehicle when the vehicle collides with an obstacle. The auxiliary weight 23b is provided with an impact load caused by unsprung parts (tire, wheel, brake system, hub carrier or axle supporting the same) mounted below the vehicle suspension as a boundary. The coil spring 23c simulates a shock absorbing effect that absorbs the impact load by elastic deformation of the suspension.

  However, in order to evaluate the impact performance of the wheel with the impact test apparatus shown in FIG. 10, it takes a great deal of man-hours and costs, and if the impact performance is not sufficient, the design change of the wheel, the die There is a problem that the process of correction, trial manufacture, and impact test must be repeatedly performed, resulting in a long development period. Although it depends on the size and shape of the wheel, the period for evaluating the impact performance of the wheel is after the design of the wheel, that is, excluding the design period from the zero base, and the entity is manufactured through mold production and trial production. Therefore, it takes about 3 months to perform the impact test. In addition, the period required for the partial design change of the wheel, the mold correction, the prototype production / production and the impact test after the mold production is about two weeks.

  On the other hand, in recent years, an attempt has been made to evaluate the performance of a wheel by numerical analysis (simulation) using a computer instead of a test using a real wheel. In the impact test as well, a proposal has been made to speed up product development activities by predicting the impact test result in advance by simulation and using this to take measures such as shape change and wall thickness increase / decrease in advance. .

  For example, in Patent Document 1, as an evaluation method for the impact strength of a wheel, the mechanical properties of the wheel material are examined, and a finite element analysis in which a load acting on the wheel is replaced with a static load is performed to perform physical properties of the wheel with respect to the load. Then, the wheel is replaced with a spring element having a spring characteristic based on the obtained physical property, and the relationship between the wheel and the weight is modeled as a vibration system by the spring element and the weight, and the drop height of the weight with respect to the wheel is determined. An analysis technique is disclosed in which the vibration system model is solved based on the initial conditions, the maximum load acting on the wheel is calculated, and the impact strength of the wheel is estimated from the maximum load and the physical properties of the wheel. According to Patent Document 1, the impact strength of a wheel can be evaluated without actually performing a trial manufacture of a wheel or an impact test.

  Further, in Patent Document 2, as a simulation method of tire / wheel performance, a step of setting an assembly model of a wheel with tires divided by a finite number of elements is set, and the assembly model is subjected to rolling under the set rolling conditions. An analysis technique including a step of performing simulation and a step of acquiring an evaluation value from an assembly model subjected to rolling simulation is disclosed.

  According to this Patent Document 2, various factors in which the tire and the wheel influence each other, for example, a frictional force generated between the tire and the wheel and a factor such as a deviation in the tire circumferential direction between the tire and the wheel are taken into consideration. Since it is possible to perform a rolling simulation while putting it in, it is possible to obtain simulation results that are close to actual vehicle evaluation, such as steering stability, straight running stability, riding comfort, and wear resistance. In Patent Document 2, as an example of rolling simulation showing the effect of the cornering force when the slip angle is set as the rolling condition, the stress distribution of the wheel model during cornering is analyzed. There is a description that a wheel that balances weight reduction and rigidity can be obtained by reinforcing a portion where a large stress is applied and cutting a portion where the stress is small.

Japanese Patent Laid-Open No. 5-99784 JP 2002-350294 A

  However, the conventional impact test simulation has the following problems to be solved. Since the evaluation method for the impact strength of a wheel disclosed in Patent Document 1 models only a single wheel, analysis accuracy cannot be said to be sufficient. In other words, an actual vehicle is composed of wheels made up of tires and wheels, and when a vehicle collides with an obstacle such as a curb during driving, the impact force at the time of the collision is transmitted to the wheel via the tire. The However, Patent Document 1 does not take into account the effects of the presence of the tire, for example, the characteristics of the tire itself, the compression or deformation of the tire due to the air filled in the tire, and the analysis accuracy of the wheel is sufficient. Absent.

  Further, the tire / wheel performance simulation method disclosed in Patent Document 2 has been proposed mainly focusing on the simulation of tire performance, and is exemplified by the analysis of the stress distribution of the wheel model during cornering. A rolling simulation with a small impact force applied to the wheel, such as driving, deceleration and turning, is assumed. For this reason, when the wheel collides with an obstacle such as a curb stone, the behavior when the tire deforms greatly due to a relatively large impact force different from that during normal driving, and the impact performance of the wheel considering it It is difficult to evaluate and predict.

  The present invention has been made in view of the above circumstances, and it is possible to accurately measure the impact performance of a wheel when a relatively large impact force is applied, which is assumed when the vehicle collides with an obstacle such as riding on a curb or a car stop. An object of the present invention is to provide a method for simulating the impact performance of a wheel with a tire that can be predicted well in a short time.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research focusing on the simulation (simulation) of the actual impact test using a computer. By numerically analyzing the behavior when a weight with a predetermined mass is dropped from a predetermined height to a predetermined position on a tire on a wheel with a tire fixed at a predetermined inclination angle, it is simulated and reproduced. The present invention was conceived by obtaining the knowledge that the above-mentioned problems can be solved and the impact performance of the wheel can be evaluated.

That is, according to the method for simulating the impact performance of a wheel with a tire according to the present invention, a step of setting a wheel model (S1), a step of setting a tire model (S2), and aligning the tire model and the wheel model are performed. A step (S3) of setting the attached wheel model, and the main weight, the counterweight, and the spring element with the external dimensions of the main weight and the counterweight smaller than the external dimensions of the main weight and the counterweight used in the physical impact test A step of setting a weight model consisting of (S4), increasing the density of each of the main weight and the counterweight so that the main weight and the counterweight have a predetermined mass, and increasing the density of the wheel model more than 1 time to 500 times scan performed in step (S5) for setting analysis conditions including the setting, the impact simulation of colliding a weight model the wheel model with tires below Tsu and up (S6), and step (S7) from the impact simulation to obtain the stress and / or strain of the wheel, characterized in that it comprises a.

  According to the present invention, the impact performance of a wheel when a relatively large impact force is applied, which is assumed when the vehicle collides with an obstacle such as climbing on a curb or a car stop, can be accurately predicted in a short time. Can do. This is expected to contribute to securing the strength and weight of the wheel, and it is possible to develop the wheel with a small number of prototypes, thereby contributing to shortening the development period and reducing costs.

It is a perspective view which shows an example of the wheel model with a tire of this invention, and a weight model. It is a flowchart which shows an example of the wheel development procedure containing the simulation method of this invention. It is the perspective view which visualized the mode of the collision behavior obtained by the impact simulation of this invention. It is a graph which shows the analysis result of this invention, and the actual measurement result of the impact test of an entity. It is the perspective view which visualized the distribution of the stress which generate | occur | produces when the impact force concerning the wheel model obtained by the impact simulation of this invention is the maximum. It is a figure which shows the site | part in which the crack generate | occur | produced in the impact test of the real wheel. It is a perspective view which shows the wheel model without a tire of a comparative example, and a weight model. It is a graph which shows the analysis result of a comparative example, and the actual measurement result of a physical impact test. It is the perspective view which visualized the distribution of the stress which generate | occur | produces when the impact force concerning the wheel model obtained by the impact simulation of the comparative example is the maximum. It is a schematic diagram of the impact test apparatus of a real wheel. This is an image taken with a high-speed camera of the collision behavior of the actual impact test.

(Embodiment 1)
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of a wheel model with tire 10 and a weight model 13 of the present invention. FIG. 2 is a flowchart showing an example of a wheel development procedure including the simulation method of the present invention. Hereinafter, a description will be given with reference to FIGS. 1 and 2. Note that the specific values such as the weight falling position and the analysis condition set value described below are examples for explaining the embodiment of the present invention, and the present invention is not limited to this. The mass of the weight, the drop height, the drop position on the tire, and the like may be set based on test specifications specified by the car manufacturer. The tire size of this embodiment is exemplified for the case of 225 / 50R18.

  FIG. 1 shows a half model (half model) obtained by cutting a wheel model 10 with a tire on a meridian plane including a rotation axis, and a weight model 13 on a center plane in a longitudinal direction, respectively. Show. The half model is preferable because the number of model elements can be reduced and the calculation time can be shortened. However, instead of the half model, a full model obtained by modeling all the configurations to be simulated may be used.

(S1) Step of setting the wheel model The wheel includes a disc surface fastened to the axle with a bolt through a mounting hole, a rim portion on which a tire is mounted, a spoke portion that connects the disc surface and the rim portion, etc. It consists of elements. The wheel model 11 divides each element of the wheel into finite elements composed of solid elements such as hexahedral elements and tetrahedral elements, and is set as numerical data that can be calculated by a computer.

(S2) Step of setting a tire model A tire is a composite structure composed of elements such as a rubber part, a bead wire, a steel belt, and a carcass. In the tire model 12, each element of the tire is divided into finite elements composed of solid elements, shell elements, etc., and set as numerical data that can be calculated by a computer. In addition, since the impact simulation of the present invention does not perform a rolling simulation that simulates the behavior at the time of rolling in consideration of the running state, it is not necessary to set the tread pattern of the tire rubber part that is important in the rolling simulation, A road surface model is also unnecessary.

  The step (S1) for setting the wheel model 11 and the step (S2) for setting the tire model 12 may be executed in reverse order, and the steps (S1) and (S2) are performed in parallel. May be.

(S3) Tire step establishing a wheel model with tires Next, the wheel model 11 and the tire model 12, similarly to the wheel actually assembled tire, by combining with so I position if on the computer The attached wheel model 10 is set.

  Here, a predetermined inclination angle (θ in FIG. 10) with respect to the horizontal in the wheel radial direction when the weight collides with the tire is set. In the present embodiment, the wheel model 10 with a tire is set by tilting the disk surface 11a of the wheel model 11 at an angle of 90 ° with respect to the horizontal. In the actual impact test, the contact state between the weight, the wheel, and the tire changes when the weight falls depending on the inclination angle θ with respect to the horizontal when the tire-equipped wheel is fixed to the support base. That is, the smaller the angle θ, the easier it is for the dropped weight to come into contact with the wheel. On the other hand, the larger the angle θ, ie, the closer the wheel is from the horizontal to the vertical in the radial direction, the harder it is to touch the wheel. , Easy to contact the tire. In other words, the smaller the inclination angle θ in the wheel radial direction with respect to the horizontal, the smaller the influence of the tire on the impact, and the larger the angle θ, the greater the influence of the tire on the impact. Therefore, from the viewpoint of improving the prediction accuracy of the wheel impact performance in consideration of the influence of the tire included in the problem to be solved by the present invention, the simulation method of the present invention uses the inclination angle of the wheel in the radial direction and the horizontal as a test specification. It is suitable for reproducing the impact test of the tire wheel with the wheel fixed at 90 °.

(S4) A step of setting a weight model composed of the main weight, the counterweight and the spring element by making the outer dimensions of the main weight and the counterweight smaller than the outer dimensions of the main weight and the counterweight used in the physical impact test. Next, a weight model 13 including a main weight 13a, an auxiliary weight 13b, and a spring element 13c therebetween is set. The main weight 13a and the auxiliary weight 13b are divided into finite elements composed of solid elements such as hexahedral elements and tetrahedral elements, and the spring element 13c is divided into finite elements composed of a plurality of beam elements, both of which are calculated by a computer. Set as possible numerical data.

  The external dimensions (sizes) of the main weight 13a and the auxiliary weight 13b used in the physical impact test are relatively large compared to the tire-equipped wheel in order to secure the mass. If the weight model is set with the actual weight size, the number of elements becomes enormous and the calculation time increases. Therefore, the outer dimensions of the main weight 13a and the auxiliary weight 13b are reduced within a range that does not affect the impact simulation, such as securing a larger outer dimension than the contact area between the weight and the tire when the weight is dropped and collided. And set the model. Thereby, the number of elements of the weight model 13 can be reduced and the calculation time can be shortened.

  Further, as a predetermined drop position when the weight collides with the tire, for example, a relative positional relationship between the corner 13d at the lower right corner of the auxiliary weight 13b in FIG. 1 and the tire model 12 is set. In the present embodiment, as the tire axial distance, the corner portion 13d of the auxiliary weight 13b is positioned at, for example, about 1/4 of the total tire width starting from the sidewall end S of the tire on the inner side (inner side) of the vehicle. As described above, the weight model 13 and the wheel model with tire 10 are aligned.

(S5) Setting analysis conditions including increasing the density of the main weight and the counterweight so that the main weight and the counterweight have a predetermined mass and setting the density of the wheel model to more than 1 time and less than 500 times Next, the material constants (longitudinal elastic modulus, Poisson's ratio, density, etc.) of each model, the air pressure of the tire model 12, the friction coefficient of the contact surface between the tire model 12 and the wheel model 11, the initial speed of the weight model 13, etc. The various analysis conditions are set as follows.

(S5-1) Wheel Model Assuming a cast wheel made of an aluminum alloy, the wheel model 11 is an elastic-plastic material and has a longitudinal elastic modulus of 70 GPa, a Poisson's ratio of 0.3, and a density of 2.7 × 10 ⁻⁶ kg / mm ^3. And a stress-strain diagram is set. The density of the wheel model preferably be set to less than 1-fold 500 fold, and more preferably set to 100 times or less 10 times.

(S5-2) Tire Model The rubber part of the tire model 12 sets a transverse elastic modulus of 3.0 MPa of a general rubber material. A bead wire and a steel belt set the longitudinal elastic modulus 206 GPa of steel materials. The carcass generally uses twisted organic fibers (polyester or the like), and sets a longitudinal elastic modulus of 20 GPa.

(S5-3) Wheel Model with Tire In the actual wheel impact test apparatus 20 shown in FIG. 10, since the disk surface 21a of the wheel 21 is fixed to the support 24, the wheel model with tire 10 shown in FIG. In order to prevent the disk surface 11a of the wheel model 11 from moving, a restraint condition is set that fully restrains the nodes in contact with the mounting holes 11b from moving relatively in the XYZ axis directions shown in FIG. In addition, a restraint condition for restraining the behavior in the X-axis direction is set for the nodes of the tire element and the wheel element located on the symmetry plane that is the cut surface of the half model shown in FIG. When the analysis model is a full model, no constraint condition is set for elements located on the symmetry plane.

(S5-4) Weight model The weight model 13 is a rigid body for the main weight 13a and the auxiliary weight 13b, and has a longitudinal elastic modulus of 206 GPa and a Poisson's ratio of 0.3, and a weight of a predetermined mass. Since the weight model 13 is a half model with respect to the main weight 910 kg and the auxiliary weight 100 kg used in the physical impact test, the mass 455 kg of the main weight 13 a and the weight 50 kg of the auxiliary weight 13 b are set as half masses. As for the density of the weight, the outer dimensions (size) of the weight are set to be small in order to shorten the calculation time as described in the above step (S4), so the density of the steel material that is the weight material is set as it is. Then, the above-mentioned predetermined mass cannot be ensured. For this reason, the density of each of the main weight 13a and the auxiliary weight 13b is set large so that the main weight 13a and the auxiliary weight 13b have a predetermined mass (455 kg and 50 kg). Further, in this embodiment, the falling height of the weight model 13 is set to 127 mm (5 inches) as the predetermined falling height of the weight.

  The spring element 13c is composed of a plurality of springs, and 10 elements are set. The combined spring constant of all the spring elements is set to 500 N / mm, and the initial contraction amount is set to 6 mm in accordance with the JIS regulations of the impact test.

  The weight model 13 allows only the relative movement in the falling direction, that is, the Y-axis direction in FIG. 1, and the main weight 13a, the auxiliary weight 13b, and the spring element 13c are constrained in the behavior in the XZ-axis direction. Set constraint conditions for all nodes.

(S5-5) Air pressure, friction coefficient of contact surface, initial speed of weight model, and analysis condition The air pressure of the tire model 12 is 0.26 MPa, which is filled in the impact test of the substance, the wheel model 11 and the tire model 12 The friction coefficient of the contact surface is 0.1 as a constant value, and the initial speed of the weight model 13 is calculated and set as follows from the falling height (H) of the weight in the physical impact test. For example, in the impact test shown in FIG. 10, when the fall height of the weight 23 is (H), the speed (V) of the weight 23 at the moment of hitting the tire 22 is the energy conservation law [V = √ (2 gH) , (G: gravity acceleration 9807 mm / s ² )], the initial speed is set to 1578 mm / s when the fall height of the weight model 13 is 127 mm (5 inches).

(S6) Step of performing an impact simulation in which a weight model collides with a wheel model with a tire Next, an impact analysis software capable of dynamic elasto-plastic analysis by a finite element method (FEM) is used among commercially available application software. Then, an impact simulation in which the weight model 13 collides with the wheel model with tire 10 is performed. That is, based on the various analysis conditions set in the above step (S5), the weight model 13 is dropped and collided with the wheel model with tire 10 in FIG. 1, and the weight model 13 collides with the wheel model 10 with tire. The behavior of the time is reproduced in a computer simulation sequentially, and impact force / acceleration / displacement, etc., are used as evaluation values of the weight model 13, and stress and / or strain of each part of the wheel are used as evaluation values of the wheel model 10. To analyze. The impact analysis process is performed by sequentially calculating the time step every minute time set by the application software, and the evaluation values of the weight model 13 and the wheel model 10 are set at predetermined output time intervals. The data is output and stored, and the calculation ends when the predetermined calculation end time is reached. In this embodiment, the output time interval is set to 0.008 (seconds) and the calculation end time is set to 0.24 (seconds). The output time interval is preferably 0.01 (seconds) or less, more preferably 0.005 (seconds) or less. The calculation end time is preferably 0.1 (seconds) or longer.

(S7) Step of Acquiring Wheel Stress and / or Strain from Impact Simulation Next, a step of acquiring stress and / or strain of each part of the wheel as an evaluation value from the wheel model 10 that has performed the impact simulation is performed. The stress and strain of each part of the wheel obtained in this step is used for pre-examination such as shape change and thickness increase / decrease so as to satisfy strength and weight reduction in wheel development. Each of these evaluation values is preset and output and stored in the impact simulation in step (S6), and is acquired and visualized in step (S7).

  FIG. 3 is a perspective view visualizing the state of the collision behavior obtained by the impact simulation of the present invention. In FIG. 3, (a) is the state (0 (second)) when the weight model 13 contacts the tire model 12, and (b) is 0.064 (second) from the contact between the weight model 13 and the tire model 12. (C) shows a state in which the tire model 12 after the deformation is deformed, and the tire model 12 after 0.176 (seconds) from the contact between the weight model 13 and the tire model 12 is largely crushed and the wheel model 11 is also deformed. It shows the state.

  FIG. 11 is an image taken by a high-speed camera of the collision behavior of the actual impact test. The physical impact test was performed with the same test specifications as in the above-described embodiment. In FIG. 11, (a) is the state when the weight 23 contacts the tire 22 (0 (seconds)), (b) is the tire after 0.06 (seconds) from the contact between the weight 23 and the tire 22. 22 shows a state in which the tire 22 is deformed, and (c) shows a state in which the tire 21 is greatly crushed and the wheel 21 is also deformed after 0.18 (seconds) has elapsed since the contact between the weight 23 and the tire 22. In the actual impact test, the cross section and the inside cannot be visualized as in the simulation, so the evaluation is only within the range observed by the appearance. However, the deformation and collapse of the tire and wheel corresponding to the elapsed time are shown in FIG. The actual impact test and the impact simulation in FIG. 3 agree well. From this, it can be seen that the simulation method of the present invention reproduces the impact test of the actual tire-equipped wheel well.

  FIG. 4 is a graph showing the analysis result of the present invention and the actual measurement result of the impact test of the substance. In FIG. 4, the horizontal axis represents the elapsed time (seconds) starting from the time when the weight contacted the tire (0 (seconds)), and the vertical axis represents the displacement (mm) of the main weight and auxiliary weight (mm) and the weight load. The impact force (kN) on the wheel as an index is shown, and the analysis values of the analysis results of the present invention are as follows: the displacement of the main weight is indicated by a square mark, the displacement of the auxiliary weight is indicated by a triangle mark, and the impact force is indicated by a circle mark. Moreover, the actual measurement value which is the actual measurement result of the impact test of the substance is indicated by a bold solid line.

  Based on the actual measurement value (solid line) in FIG. 4, the behavior of the weight and the change of the load in the impact test of the substance are explained. (1) After the weight contacts the tire, the downward load and displacement of the weight are The tire continues to increase, and the tire is crushed. (2) When the tire is completely crushed in the vicinity of the inner flange (rim) after about 0.064 seconds, the weight load increases rapidly. (3) About 0.08 to 0.12 During the second, the descending (displacement) of the counterweight stops, but the main weight continues to descend (displaces), and during this time, the coil spring between the auxiliary weight and the main weight is compressed and contracted, so the weight load increase is (4) After about 0.12 seconds, the compression of the coil spring stops, the load increases again due to the inertial force of the main weight, and the wheel deforms, so the subweight also descends (displaces) again, (5) About Since the wheel receives the inertial force of the weight around 0.176 seconds, the load and displacement of the weight are maximum (peak ), And (6) about 0.176 seconds after the slide into increased weight has rebounded.

  As shown in FIG. 4, the analysis value (square mark, triangle mark, circle mark) is the lowest point when the displacement of the main weight and the counterweight is about 0.176 (seconds) as in the actual measurement value (solid line). Reaches the maximum, the load on the weight reaches its peak, and the impact force applied to the wheel is maximized. Incidentally, the reproduction diagram of the collision behavior in FIG. 3 (c) shows the state of each model when 0.176 (seconds) when the impact force becomes maximum in FIG. The deformation and the deformation of the wheel model are visualized. As is clear from FIG. 4, both the displacement of the main weight and the counterweight and the impact force on the wheel are in good agreement with the analysis value and the actual measurement value for each elapsed time, and according to the simulation method of the present invention, It can be seen that the impact performance of a wheel with a tire can be accurately predicted.

  FIG. 5 is a perspective view visualizing the distribution of stress generated when the impact force applied to the wheel model 11 obtained by the impact simulation of the present invention is maximum. FIG. 6 is a diagram showing a portion where a crack (K) has occurred in the impact test of the actual wheel. The part where the maximum tensile stress (σmax) is generated in the wheel model 11 in FIG. 5 (solid line circled circle) and the part where the crack (K) occurs in the actual wheel in FIG. 6 (solid line circled circle) It matches well. As is clear from the comparison between FIG. 5 and FIG. 6, the generation site of the maximum tensile stress in the analysis result and the generation site of the crack in the impact test of the substance are in good agreement. According to this, it can be seen that the impact performance of a wheel with a tire can be accurately predicted. In addition, although the site | part shown with the broken-line circle | round | yen of FIG. 5 also has a large stress, since this site | part shows compressive stress and it does not influence crack generation | occurrence | production, it excluded from the object of evaluation.

  By performing the simulation method including the steps (S1) to (S7) described above, the impact performance of the wheel can be accurately predicted. Next, a procedure for securing the strength and reducing the weight by evaluating the wheel performance using the simulation method of the present invention will be described.

(S8) Step of determining whether the impact performance of the wheel has reached the target Next, it is determined whether the impact performance of the wheel has reached the target, and the wheel performance is evaluated. In this step, it is determined whether or not the stress and / or strain applied to the wheel model 11 obtained in the above step (S7) is smaller than the mechanical properties of the wheel set as a target through a material test. For example, the maximum tensile stress (σmax) and / or the maximum strain (%) when the impact force applied to the wheel model 11 is the maximum are based on the tensile strength and / or strain of the wheel set as a target from a material test or the like in advance. If it is small, it is determined that the wheel does not crack even in the impact test of the actual wheel.

(S9) Step of changing the shape and dimensions of the wheel model In the above step (S8), the maximum tensile stress (σmax) and / or maximum strain (%) applied to the wheel model 11 is the target wheel mechanical If the property is exceeded, the shape / dimension of the wheel model 11 is changed, and the wheel model 11 reflecting the shape / dimension change is created again in the step (S1), and the step (S2) including the impact simulation is performed. ) To (S7), and when the wheel model 11 satisfies the step (S8), a real wheel is produced.

  While implementing the simulation method including the procedure of each of the above steps (S1) to (S7), and developing the wheel by the procedure of each of the above steps (S8) and (S9), the performance of the wheel was evaluated. It is expected to contribute to ensuring strength and reducing weight.

  For comparison with the present invention, the impact performance was simulated with a tireless wheel model. FIG. 7 is a perspective view showing a tireless wheel model 11 and a weight model 13 of a comparative example. In the comparative example, the analysis is performed under the same analysis conditions as in the above-described embodiment except that the tire model is deleted. In the comparative example, since there is no tire model, the falling weight model 13 comes into contact with the inner flange (rim) of the wheel model 11 and an impact force acts directly on the wheel model 11.

  FIG. 8 is a graph showing the analysis result of the comparative example and the actual measurement result of the impact test of the substance. In FIG. 8, the horizontal and vertical axes, and the plots and solid lines on the graph are shown in the same manner as in the embodiment. As analysis values of the comparative example, the displacement of the main weight is indicated by square marks, and the displacement of the auxiliary weight is triangular. The impact force is indicated by a circle, and the actual value of the impact test of the substance is indicated by a bold solid line. In addition, about the elapsed time (second) of an analysis value in FIG. 8, the time point when the weight model contacted the wheel model is shown as a starting point (0 (second). As shown in FIG. In the simulation of impact performance, the displacement (mm) with respect to the elapsed time (seconds) of the main weight and the counterweight and the value of the impact force (kN) against the wheel model are significantly different from the actually measured values in the impact test of the actual tire wheel. According to the analysis result of the comparative example, the impact force applied to the wheel is maximum when 0.128 (seconds) has elapsed since the contact between the weight model and the wheel model.

  FIG. 9 is a perspective view visualizing the distribution of stress generated when the impact force applied to the wheel model 11 obtained by the impact simulation of the comparative example is maximum. The maximum tensile stress (σmax) generation site (solid line circle) in the wheel model 11 of the comparative example of FIG. 9 and the crack (K) generation site (solid line circle) in the actual wheel of FIG. Are very different. 8 and 9, it is difficult to accurately predict the impact performance of the wheel even if the impact performance is simulated using a wheel model without a tire as in the comparative example. In addition, although the site | part shown with the broken-line circle | round | yen circle | round | yen of FIG. 9 is also large in stress, since this site | part shows compressive stress and it does not affect crack generation, it excluded from the object of evaluation.

(Embodiment 2)
Hereinafter, an example in which the calculation time is shortened will be described as another embodiment of the present invention. In the second embodiment, the procedure (step), analysis model, analysis conditions, etc. of the simulation method are the same as those in the first embodiment except that the density of the wheel model is changed.

When the wheel model 11 in the first embodiment was implemented at a density of 2.7 × 10 ⁻⁶ kg / mm ³ , the analysis time required about 4.6 days (109.8 Hr). If a computer with high processing capability is used, the calculation time can be shortened, but it requires new capital investment and increases the cost of performance evaluation. Therefore, we examined increasing the density of the wheel model to ensure the prediction accuracy and further reduce the calculation time.

When the analysis is performed using the finite element method of the explicit method, the minute time (Δt) in which the time step is engraved at the time of calculation is determined by the Courant condition represented by the following equation (1).
Δt ≦ L / √ (E / ρ) (1)
Here, Δt is a minute time for ticking time steps, L is an element size of the analysis model, E is an elastic coefficient, and ρ is density. Of these, the element size of the analysis model is the representative length (element length) of the smallest element among the elements constituting the analysis model. Δt in equation (1) is calculated for all elements of the analysis model, and the simulation is performed based on the minimum Δt of these. Therefore, if Δt is small, much time is required for calculation. Moreover, the calculation time of analysis becomes longer as the total number of elements of the analysis model increases. Therefore, in order to shorten the calculation time, it is necessary to increase the minute time Δt for ticking the time step and reduce the total number of elements. From the above equation (1), in order to increase Δt, (b) increase the element size (element length) of the analysis model, (b) decrease the elastic modulus, and (c) increase the density. There are two ways. (B) In the method (b), there is a concern that the analysis error will increase and the prediction accuracy will deteriorate, so the calculation time will be shortened by increasing the density of (c).

  In the present embodiment, the impact simulation was performed according to the steps (S1) to (S7) described above by changing the density of the wheel model to 10 times, 100 times, and 500 times, respectively. Next, from the results of simulation analysis and actual impact test results, find the maximum displacement of the main and secondary weights and the maximum impact force on the wheel when the load and displacement of the weight reach its peak. It was. Further, an error (analysis error (%)) of an analysis value with respect to an actual measurement value for the maximum value of the displacement and impact force is calculated, and a time (calculation time (Hr) required to reach a predetermined calculation end time is set. ))It was confirmed. Table 1 shows the analysis error and calculation time when the density of the wheel model is changed. In Table 1, in the calculation time column for the actual impact test, for comparison, the required time (approximately 3 months) from the mold production until the impact test is performed is also shown. For reference, analysis values, analysis errors, and calculation times in the case of impact simulation without a tire with the wheel model density set to 1 are also shown.

  As shown in Table 1, the analysis error when the wheel model density is 10 times is about 4% as the impact force, but the weight displacement is about 2%, which is equivalent to the analysis error of density 1 time. In addition, the analysis error when the density was increased to 100 times was about 10%, and it was determined that any of them had no problem as the prediction accuracy. In addition, the calculation time is 1/3 (time required 33.3 Hr) at a density of 10 times and 1/10 (time ratio at a density of 100), assuming that the time at a density of 1 (109.8 Hr) is 1. It can be seen that the required time can be significantly reduced to 10.7 Hr). On the other hand, the calculation time when the density of the wheel model is increased to 500 times is 1/23 (required time 4.7 Hr), and the time required for the calculation can be further shortened. Since both the displacement and the impact force increase to about 30%, there is a concern that the prediction accuracy may deteriorate. Therefore, it is desirable to increase the density of the wheel model in order to ensure the prediction accuracy and reduce the calculation time, and when increasing the density, the density of the wheel model may be set to less than 500 times. Preferably, it is more preferably set to 100 times or less.

  From the above, according to the method for simulating the impact performance of a wheel with a tire according to the present invention, the impact performance of the wheel when a relatively large impact force is applied, such as when the vehicle collides with an obstacle such as climbing on a curb or a car stop. Can be predicted with high accuracy and in a short time. By developing the wheel based on the simulation results of this impact performance, it can be expected to contribute to securing the strength and weight reduction of the wheel, and it is possible to develop the wheel with a small number of prototypes, for example, shortening the development period and cost It can also be expected to contribute to reduction.

10: Wheel model with tire 11: Wheel model 11a: Disc surface 11b: Mounting hole 12: Tire model 13: Weight model 13a: Main weight 13b: Subweight 13c: Spring element 20: Impact test device 21: Wheel 21a: Disc Surface 22: Tire 23: Weight 23a: Main weight 23b; Subweight 23c: Coil spring 24: Support base H: Fall height V: Weight speed θ: Tilt angle of wheel

Claims (1)

A step of setting a wheel model, a step of setting a tire model, a step of setting a tire model and a wheel model by aligning the tire model and the wheel model, and an external impact test of the main weight and the counterweight. Setting a weight model composed of a main weight, a counterweight, and a spring element by making it smaller than the outer dimensions of the main weight and the counterweight used in the main weight, and the main weight so that the main weight and the counterweight have a predetermined mass. and a step of setting the analysis conditions includes setting it to increase the density of each of Fukutsumu and the density of Hoirumo del less than 1 fold 500 fold, impact simulation of colliding a weight model the wheel model with tires And obtaining a wheel stress and / or strain from an impact simulation. Simulation method of the impact performance of the per wheel.