JP2023034074A - Simulation method between mold model and rubber model - Google Patents

Abstract

To provide a simulation method capable of accurately predicting damage of rubber during mold removal.SOLUTION: A simulation method includes: a first step S1 of inputting a mold model and a rubber model in which a vulcanization mold and rubber are modeled with a finite number of elements, respectively, into a computer; a second step S2 of setting a peeling stress on a contact surface between the mold model and the rubber model; a third step S3 of causing the computer to calculate a stress on the contact surface of the rubber model by relatively moving the rubber model from an initial state where the mold model and the rubber model are adhered at the contact surface so as to be away from the vulcanization mold; and a fourth step S4 of causing the computer to determine a sticking state of the contact surface based on the peeling stress and the calculated stress of the rubber model.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to a method of simulating a mold model and a rubber model.

BACKGROUND ART Conventionally, there has been known a technique of forming sipes in tread rubber using a vulcanization mold having protruding blades. The blade may damage the tread rubber during demolding. Therefore, techniques for modifying the shape of the sipe (blade) to suppress damage to the tread rubber have been studied (see, for example, Patent Document 1).

JP 2017-24526 A

In recent years, there has been a demand for a technique for predicting damage to tread rubber during demolding.

The present disclosure has been devised in view of the actual situation as described above, and a main object of the present disclosure is to provide a simulation method capable of accurately predicting rubber damage during demolding.

The present disclosure is a simulation method for simulating how vulcanized rubber vulcanized in a vulcanization mold is removed from the vulcanization mold,
a first step of inputting a mold model and a rubber model obtained by modeling the vulcanization mold and the rubber with a finite number of elements, respectively, into a computer;
a second step of setting a peeling stress on the contact surface between the mold model and the rubber model;
The computer relatively moves the rubber model away from the vulcanization mold from an initial state in which the mold model and the rubber model are fixed at the contact surface, thereby moving the rubber model a third step of calculating the stress at the contact surface of
a fourth step in which the computer determines a sticking state of the contact surface based on the peel stress and the calculated stress of the rubber model;
This is a simulation method for a mold model and a rubber model.

According to the simulation method of the present disclosure, in the third step, the rubber model is moved from the initial state to calculate the stress on the contact surface, and in the fourth step, the peel stress and the stress are calculated. Since the sticking state of the contact surface is determined based on the above, the sticking state of the contact surface is accurately reproduced. This makes it possible to accurately predict damage to the rubber during demolding.

It is a perspective view which shows an example of the computer for performing a simulation method. 1 is a perspective view showing one form of tread rubber of a tire, which is an example of vulcanized rubber preferably calculated by this simulation method; FIG. FIG. 3 is a perspective view showing a vulcanization mold for vulcanizing the tread rubber of FIG. 2 ; It is a flowchart which shows the processing procedure of this simulation method. FIG. 2 is a cross-sectional view showing an example of a mold model and a rubber model that are input to a computer in this simulation method; FIG. 4 is a cross-sectional view showing the rubber model that has been moved relative to the mold model and removed from the mold; FIG. 5 is a flow chart showing an example of a second step in FIG. 4; FIG. It is a figure which shows an example of a test piece. It is the photograph of the part damaged by the tire after demolding. FIG. 4 is a diagram showing the distribution of maximum principal stress calculated by applying this simulation method;

An embodiment of the present disclosure will be described below with reference to the drawings.
In the simulation method of the present embodiment, a computer is used to simulate a state in which vulcanized rubber vulcanized in a vulcanization mold is removed from the vulcanization mold.

FIG. 1 is a perspective view showing an example of a computer for executing the simulation method of this embodiment. A computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c and a display device 1d. The main body 1a is provided with, for example, an arithmetic processing unit (CPU), a ROM, a work memory, a storage device such as a magnetic disk, and disk drive devices 1a1 and 1a2. Software and the like for executing the simulation method of this embodiment are stored in advance in the storage device. Therefore, the computer 1 is configured as a simulation device for calculating how vulcanized rubber is released from a vulcanization mold.

An example of vulcanized rubber that is preferably calculated by this simulation method is tire tread rubber. The vulcanized rubber is not limited to the above tread rubber as long as it is vulcanized using a vulcanization mold.

FIG. 2 shows an example of the tread rubber 10. As shown in FIG. The tread rubber 10 includes sipes (thin grooves) 11 that open to the tread surface. The tread rubber 10 may be in a form that does not include the sipe 11 . A belt member, a carcass, and the like (not shown) are arranged inside the tread rubber 10 in the tire radial direction.

FIG. 3 shows a vulcanization mold 20 for vulcanizing the tread rubber 10 . Vulcanization mold 20 includes blade 21 for forming sipe 11 in tread rubber 10 . The blade 21 protrudes from the tread forming surface 22 into the cavity space.

FIG. 4 shows the processing procedure of this simulation method 100 . The simulation method 100 is a method of simulating a mold model simulating the vulcanization mold 20 and a rubber model simulating vulcanized rubber.

The simulation method 100 includes a first step S1 of inputting a mold model and a rubber model into the computer 1, a second step S2 of setting the peel stress in the computer 1, a third step S2 of calculating the stress in the computer 1, and a computer and a fourth step of determining a stuck condition.

In the first step S1, a mold model and a rubber model are input to the computer 1. As shown in FIG.

FIG. 5 shows an example of the mold model 30 and the rubber model 40. As shown in FIG. The mold model 30 and the rubber model 40 are each modeled with a finite number of elements. The vulcanization mold 20 and the shape of the vulcanized rubber are reproduced by the assembly of each element. For example, the shapes of the tread rubber 10 shown in FIG. 2 and the vulcanization mold 20 shown in FIG. 3 are reproduced. In FIG. 5, a region around the sipe 11 of FIG. 2 and the blade 21 of FIG. 3 is shown enlarged.

The tread rubber 10 and the vulcanization mold 20 may be modeled over their entire circumferences or partially modeled. As an example of the latter, modeling may be performed in units of segments (and tread rubber 10 in corresponding regions) divided into a plurality of segments in the circumferential direction. Further, the modeling may be limited to only the vicinity of the division position of the segment where the tread rubber 10 is likely to be damaged.

Material data of the metal and vulcanized rubber forming the vulcanization mold 20 are applied to each element. For example, physical property data based on measured values such as elastic modulus, Poisson's ratio, and density of each material is applied. The coefficient of friction between the metal forming the vulcanization mold 20 and the vulcanized rubber is applied.

In the second step S2, the peeling stress is set on the contact surfaces 31, 41 between the mold model 30 and the rubber model 40 on the computer 1. FIG. “Peeling stress” means that the vulcanized rubber is separated from the vulcanization mold 20 when the vulcanized rubber is removed from the vulcanization mold 20 (that is, the contact surfaces 31 and 41 are vulcanized). It is the stress generated on the contact surface between the vulcanized rubber and the vulcanization mold 20 when the vulcanized rubber is released from the restraint of the vulcanization mold 20 . For example, at a location where the vulcanized rubber moves parallel to the contact surface with the vulcanization mold 20, the "peel stress" is the shear stress occurring on the contact surface.

In the third step S3, the stress generated in the contact surfaces 31, 41 when the rubber model 40 is moved from the mold model 30 is calculated. In the rubber model 40, the mold model 30 and the rubber model 40 are fixed at their respective contact surfaces 31, 41 (that is, the rubber model 40 is constrained to the mold model 30 at the contact surfaces 31, 41). (present) is relatively moved away from the mold model 30 from the initial state. For example, the fixed surface of the tread rubber 10 of the tire with the belt member, that is, the element (node) corresponding to the inner peripheral surface of the tread rubber 10 is moved away from the mold model 30, and the rubber model 40 is moved. A stress is calculated. As a result, on the computer 1, demolding of the vulcanized rubber from the vulcanization mold 20 is simulated.

FIG. 6 shows the rubber model 40 that has been moved relative to the mold model 30 in the direction of the arrow and demolded.

In the fourth step S4, the adhered state of the contact surfaces 31, 41 is determined based on the peel stress set in the second step S2 and the stress of the rubber model 40 calculated in the third step S3. As a result, the fixed state of the contact surfaces 31 and 41 can be accurately reproduced on the computer 1, and damage to the rubber during demolding can be accurately predicted.

Furthermore, the computer 1 maintains or changes the constraint state on the contact surfaces 31, 41 (steps S10, S11, S12).

That is, when the computer 1 determines in the fourth step S4 that the fixed state is maintained (Y in step S10), the state of restraint at the contact surfaces 31, 41, that is, the rubber model 40 is placed against the mold model 30. The boundary condition that displacement is impossible is maintained (step S11). On the other hand, when the computer 1 determines that the fixed state is released (N in step S10), the contact surfaces 31 and 41 are restrained, i.e., the rubber model 40 can be displaced with respect to the mold model 30. Boundary conditions are changed (step S12).

In the fourth step S4, the adhesion state of the contact surfaces 31, 41 is determined based on the magnitude relationship between the peel stress set in the second step S2 and the stress of the rubber model 40 calculated in the third step S3.

That is, when the calculated stress is less than the peeling stress, the computer 1 determines that the adhered state is maintained (Y in step S10). In this case, the constraint condition at the contact surfaces 31, 41, that is, the boundary condition that the rubber model 40 cannot be displaced with respect to the mold model 30 is maintained (step S11).

On the other hand, if the calculated stress is greater than or equal to the peeling stress, the computer 1 determines that the adhered state is released (N in step S10). In this case, the constraint conditions on the contact surfaces 31 and 41, that is, the boundary conditions are changed so that the rubber model 40 can be displaced with respect to the mold model 30 (step S12). For example, the contact surfaces 31 and 41 are provided with a predetermined friction coefficient (dynamic friction coefficient) input in the first step S1, and the displacement and stress of the rubber model 40 are calculated.

After that, the loop from the third step S3 to step S13 is repeated until the movement amount of the rubber model 40 reaches the preset movement amount (Y in S13). As shown in FIG. 6, before the rubber model 40 is completely separated from the mold model 30, the loop of the third step S3 to step S13 may be exited to terminate the calculation.

FIG. 7 shows an example of the second step S2. The second step S2 includes a step S21 of measuring the peel stress using the vulcanization mold 20 and a test piece containing rubber, and a step S22 of applying the measured peel stress to the contact surfaces 31, 41. is desirable. As a result, the peeling stress actually measured in the second step S2 is applied, so that the adhered state of the contact surfaces 31 and 41 can be accurately reproduced on the computer 1 .

FIG. 8 shows an example of the test piece 50. As shown in FIG. A test piece 50 is prepared by pressing a metal test piece 51 and a rubber test piece 52 together.

The metal test piece 51 is made of the same metal as the vulcanization mold 20 . In the vulcanization mold 20 including the blade 21 for forming the sipe 11 in the tread rubber 10, when measuring the peeling stress of the tread rubber 10 from the blade 21, a metal made of the same material as the blade 21 A test piece 51 is applied.

The rubber test piece 52 is composed of rubber having the same composition as the unvulcanized rubber to be simulated. The test piece 50 is produced by pressing a metal test piece 51 and a rubber test piece 52 together at the vulcanization temperature. As a result, the peeling stress can be measured easily and accurately in the second step S2, so that the determination of the adhered state at the contact surfaces 31 and 41 can be made even more accurately.

Preferably, in the third step S3, the computer 1 calculates at least one of stress and strain occurring in the rubber model 40. FIG. This makes it possible to predict in detail how the vulcanized rubber will be demolded from the vulcanization mold 20 .

Furthermore, the simulation method 100 may further include a prediction step of predicting rubber damage during demolding based on at least one of stress and strain occurring in the rubber model 40 . The prediction step is performed after the third step S3 of calculating stresses and/or strains.

For example, in the prediction step, at least one of stress and strain occurring in the rubber model 40 obtained by calculation is compared with a predetermined threshold value. If the stress or the like is greater than the threshold, it can be determined that there is a high possibility that the rubber will be damaged during demolding. If the stress or the like is smaller than the threshold value, it can be determined that the rubber is unlikely to be damaged during demolding. This makes it possible to accurately and precisely predict rubber damage during demolding.

Although the simulation method of the present disclosure has been described in detail above, the present disclosure is not limited to the above-described specific embodiments, and can be implemented with various modifications. For example, the simulation method 100 is not limited to the tread rubber 10, but can be widely applied to tires and other vulcanized rubbers vulcanized by vulcanization molds other than tires.

This simulation method was applied to calculate the stress generated in the rubber of a tire whose tread rubber was damaged when it was removed from the vulcanization mold, and the locations of damage and stress concentration were compared. . The tire size was 175/65R15, and S-DYNA manufactured by JSOL was used as structural analysis software for calculating stress and the like.

FIG. 9 is a photograph of a damaged portion of the tire after demolding.

FIG. 10 shows the stress distribution calculated by applying this simulation method. Regions of high stress are shown darker.

As is clear from FIGS. 9 and 10, the stress concentration positions predicted by the calculations by this simulation method are in good agreement with the actual damage positions of the rubber after demolding. It was confirmed that it is possible to accurately predict the damage of

[Appendix]
The present disclosure includes the following aspects.

[Present Disclosure 1]
A simulation method for simulating how a vulcanized rubber vulcanized in a vulcanization mold is released from the vulcanization mold,
a first step of inputting a mold model and a rubber model obtained by modeling the vulcanization mold and the rubber with a finite number of elements, respectively, into a computer;
a second step of setting a peeling stress on the contact surface between the mold model and the rubber model;
The computer relatively moves the rubber model away from the mold model from an initial state in which the mold model and the rubber model are fixed on the contact surface, and the rubber model moves away from the mold model. a third step of calculating the stress at the contact surface;
a fourth step in which the computer determines a sticking state of the contact surface based on the peel stress and the calculated stress of the rubber model;
A simulation method for a mold model and a rubber model.
[Disclosure 2]
The fourth step determines that the fixed state is maintained when the calculated stress is less than the peel stress, and determines that the fixed state is maintained when the calculated stress is greater than or equal to the peel stress. The mold model and rubber model simulation method according to the present disclosure 1, wherein it is determined that is released.
[Disclosure 3]
The second step is
a step of measuring the peel stress using a test piece containing the vulcanization mold and the rubber;
and applying the measured peel stress to the contact surface.
[Disclosure 4]
The test piece is prepared by pressing a metal test piece of the same material as the vulcanization mold and a rubber test piece of the same composition as the unvulcanized rubber at the vulcanization temperature. , a method of simulating a mold model and a rubber model according to 3 of the present disclosure.
[Disclosure 5]
5. The method of simulating a mold model and a rubber model according to any one of the present disclosures 1 to 4, wherein the third step includes a step of calculating at least one of stress and strain occurring in the rubber model.
[Disclosure 6]
The metal according to 5 of the present disclosure, further comprising, after the third step, a prediction step of predicting damage to the rubber during demolding based on at least one of the stress and strain occurring in the rubber model. A method of simulating a die model and a rubber model.
[Present Disclosure 7]
7. The method of simulating a mold model and a rubber model according to any one of the present disclosures 1 to 6, wherein the rubber model includes a tread model portion that models tread rubber of a tire.
[Disclosure 8]
The mold model includes a blade model section modeling a blade for forming a sipe in the tread rubber,
The mold model and rubber model simulation method according to the present disclosure 7, wherein the contact surface includes a contact surface between the tread model portion and the blade model portion.

1 computer 10 tread rubber 11 sipe 20 vulcanization mold 21 blade 30 mold model 31 contact surface 40 rubber model 41 contact surface 50 test piece 51 metal test piece 52 rubber test piece 100 simulation method S1 first step S2 second step S3 Third step S4 Fourth step

Claims (8)

A simulation method for simulating how a vulcanized rubber vulcanized in a vulcanization mold is released from the vulcanization mold,
a first step of inputting a mold model and a rubber model obtained by modeling the vulcanization mold and the rubber with a finite number of elements, respectively, into a computer;
a second step of setting a peeling stress on the contact surface between the mold model and the rubber model;
The computer relatively moves the rubber model away from the mold model from an initial state in which the mold model and the rubber model are fixed on the contact surface, and the rubber model moves away from the mold model. a third step of calculating the stress at the contact surface;
a fourth step in which the computer determines a sticking state of the contact surface based on the peel stress and the calculated stress of the rubber model;
A simulation method for a mold model and a rubber model. The fourth step determines that the fixed state is maintained when the calculated stress is less than the peel stress, and determines that the fixed state is maintained when the calculated stress is greater than or equal to the peel stress. 2. The method of simulating a mold model and a rubber model according to claim 1, wherein it is determined that is released. The second step is
a step of measuring the peel stress using a test piece containing the vulcanization mold and the rubber;
and applying the measured peel stress to the contact surface. The test piece is prepared by pressing a metal test piece of the same material as the vulcanization mold and a rubber test piece of the same composition as the unvulcanized rubber at the vulcanization temperature. 4. A simulation method for a mold model and a rubber model according to claim 3. 5. The method of simulating a mold model and a rubber model according to any one of claims 1 to 4, wherein said third step includes a step of calculating at least one of stress and strain occurring in said rubber model. . 6. The metal according to claim 5, further comprising, after the third step, a prediction step of predicting damage to the rubber during demolding based on at least one of stress and strain occurring in the rubber model. A method of simulating a die model and a rubber model. The method of simulating a mold model and a rubber model according to any one of claims 1 to 6, wherein the rubber model includes a tread model portion modeling tread rubber of a tire. The mold model includes a blade model section modeling a blade for forming a sipe in the tread rubber,
8. The method of simulating a mold model and a rubber model according to claim 7, wherein said contact surface includes a contact surface between said tread model portion and said blade model portion.

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