JP6950477B2 - Simulation method of viscoelastic material - Google Patents

Description

The present invention relates to a simulation method for calculating the flow of a viscoelastic material, such as a plastic material such as unvulcanized rubber, using a computer.

Conventionally, a simulation method for calculating the flow of a plastic material having viscoelasticity has been proposed. In this type of simulation, the plastic material is modeled into numerically computable elements and flow conditions are applied to it to calculate the flow of each element from moment to moment.

In the material model, for example, it is conceivable to define both the viscosity and elasticity of the plastic material. However, in the simulation using such a material model, there is a problem that it is difficult to focus the flow calculation. Therefore, in the simulation method of Patent Document 1 below, a material model in which only the viscosity of the plastic material is defined is used.

Japanese Unexamined Patent Publication No. 2013-184637

However, since the simulation method of Patent Document 1 cannot consider the elasticity of the plastic material, there is room for further improvement in improving the accuracy of the flow calculation.

As a result of intensive research, the inventors include a viscosity region in which the viscosity defined in the material model increases as the strain rate increases when the strain rate is larger than a predetermined threshold. Therefore, it was found that the rapid increase in force, which is a characteristic of elasticity, can be expressed only by viscosity.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a simulation method capable of calculating the flow of a material having viscoelasticity with high accuracy.

The present invention is a simulation method for calculating the flow of a material having viscoelasticity using a computer, wherein the material is defined in the computer by using a viscosity model that does not consider elasticity, and the above. The step of defining the viscosity model includes the step of adapting the viscosity model to predetermined flow conditions and calculating the flow state of the viscosity model, and the step of defining the viscosity model defines the relationship between the viscosity of the viscosity model and the strain rate. Including the step, the relationship is that, when the strain rate is from zero to a predetermined threshold, the first viscosity region in which the viscosity becomes constant and / or decreases as the strain rate increases, and the strain rate When it is larger than the threshold value, it has a second viscosity region in which the viscosity increases as the strain rate increases.

In the method for simulating a viscoelastic material according to the present invention, the step of defining a relationship is based on a plurality of viscosity values measured by gradually increasing the strain rate from zero with respect to the material. May be specified.

In the method for simulating a viscoelastic material according to the present invention, the step of defining the relationship may include a step of measuring the extensional viscosity of the material.

In the method for simulating the viscoelastic material according to the present invention, the step of defining the relationship is a first approximate straight line approximated to a portion of the viscosity measurement result in which the viscosity decreases as the strain rate increases. And, the strain rate at the intersection with the second approximate straight line approximated to the portion where the viscosity increases as the strain rate increases may be defined as the threshold value.

ここで、
η：材料の粘度
γ：材料のひずみ速度
ｎ：０より大きい実数 In the method for simulating a viscoelastic material according to the present invention, the first approximate straight line and the second approximate straight line may be defined by the following equation (1).

here,
η: Material viscosity γ: Material strain rate n: Real number greater than 0

The method for simulating a viscoelastic material of the present invention is a step of defining a material having viscoelasticity in a computer using a viscous model that does not consider elasticity, and adapting the viscous model to predetermined flow conditions. It includes a step of calculating the flow state of the viscosity model. In such a simulation method, since the viscosity model that does not consider the elasticity is used, it is possible to prevent the calculation of the flow state from diverging. Therefore, the simulation method of the present invention can stably calculate the flow state of the viscosity model.

The step of defining the viscosity model includes a step of defining the relationship between the viscosity of the viscosity model and the strain rate. The relationship is that when the strain rate is from zero to a predetermined threshold, the first viscosity region where the viscosity becomes constant and / or decreases as the strain rate increases, and the strain rate becomes higher than the threshold. When it is large, it has a second viscosity region in which the viscosity increases as the strain rate increases. With such a second viscosity region, the viscosity model can express a sharp increase in force, which is a characteristic of the elasticity. Therefore, in the simulation method of the present invention, the flow of the material having viscoelasticity can be calculated with high accuracy even if the viscosity model that does not consider the elasticity is used.

It is a perspective view which shows an example of the computer for executing the simulation method of a viscoelastic material. It is sectional drawing which shows an example of the flow path through which a material flows. It is a perspective view which shows an example of a flow path. It is a flowchart which shows an example of the simulation method of a viscoelastic material. It is a flowchart which shows an example of a viscosity model definition process. It is a graph which shows an example of the relationship between viscosity and strain rate of a viscosity model. It is a flowchart which shows an example of the processing procedure of the relation definition process of this embodiment. It is a graph which shows an example of the relationship between a shear viscosity and an extensional viscosity, and a strain rate. It is a flowchart which shows an example of the processing procedure of the flow condition definition process. It is a conceptual diagram which shows an example of a flow path model. It is a graph which shows the relationship between the viscosity and the strain rate of the viscosity model of another embodiment of this invention. It is a graph which shows the relationship between the viscosity of the viscosity model of the comparative example, and the strain rate. It is a graph which shows the relationship between the flow velocity of a viscosity model, and the position in the width direction of a discharge port.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the method for simulating a viscoelastic material of the present embodiment (hereinafter, may be simply referred to as a "simulation method"), a flow of a material having viscoelasticity is calculated using a computer.

FIG. 1 is a perspective view showing an example of a computer for executing the simulation method of the present embodiment. The 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, a storage device such as an arithmetic processing unit (CPU), a ROM, a work memory, and a magnetic disk, and disk drive devices 1a1 and 1a2. Further, the storage device stores in advance software or the like for executing the simulation method of the present embodiment.

The material of this embodiment is a well-kneaded rubber material before cross-linking. However, in addition to such a rubber material, a resin material, an elastomer, or the like may have viscoelasticity. Further, in the present invention, it is premised that the material is in a state where it is sufficiently kneaded and can be regarded as a stable flow state (fluid). For example, in the case of an unvulcanized rubber material, a state in which the material is sufficiently kneaded and the temperature is raised to about 80 ° C. corresponds to this state.

FIG. 2 is a cross-sectional view showing an example of a flow path through which a material flows. FIG. 3 is a perspective view showing an example of the flow path. The flow path 2 of the present embodiment is formed in a cylindrical shape and is connected to the downstream side of the screw type extruder 3. A supply port 5 connected to the extruder 3 is provided at one end of the flow path 2. The material is supplied to the supply port 5 from the extruder 3. As shown in FIG. 3, the supply port 5 is formed in a circular shape in front view.

On the other hand, at the other end of the flow path 2, a discharge port 6 from which the material is extruded is provided. The discharge port 6 of the present embodiment is formed in a triangular shape when viewed from the front. Therefore, the cross-sectional area of the flow path 2 gradually decreases from the upstream side to the downstream side (that is, from the supply port 5 side to the discharge port 9 side).

In the simulation method of the present embodiment, a computer 1 simulates how a material (not shown) flowing through the flow path 2 is pushed out from the discharge port 6. FIG. 4 is a flowchart showing an example of a method for simulating a viscoelastic material.

In the simulation method of the present embodiment, first, the material is defined in the computer 1 by using a viscosity model that does not consider elasticity (viscosity model definition step S1). The viscosity model is for incorporating the material flowing in the flow path 2 (shown in FIGS. 2 and 3) into the numerical calculation by the computer 1. The viscosity model is arranged on the element e (shown in FIG. 10) of the flow path model 7 described later. FIG. 5 is a flowchart showing an example of the viscosity model definition step S1.

In the viscosity model definition step S1 of the present embodiment, first, the specific heat and thermal conductivity of the material are defined (step S11). The specific heat is measured from the material to be analyzed by, for example, an adiabatic continuous method (@ 25 ° C.). The thermal conductivity is measured from the material to be analyzed by, for example, the hot wire method (@ 25 ° C.). The specific heat and thermal conductivity are stored in the computer 1.

Next, in the viscosity model definition step S1 of the present embodiment, the relationship between the viscosity of the viscosity model and the strain rate is defined (relationship definition step S12). FIG. 6 is a graph showing an example of the relationship between the viscosity of the viscosity model and the strain rate. FIG. 6 shows the relationship 10 between the logarithm of viscosity and the logarithm of strain rate. The relationship between the viscosity of the viscosity model and the strain rate (hereinafter, may be simply referred to as “relationship”) 10 is a value of a plurality of viscosities η measured by gradually increasing the strain rate from zero with respect to the material. Identified based on. The relationship 10 of the present embodiment includes a first viscosity region 11 and a second viscosity region 12.

In the first viscosity region 11, when the strain rate is from zero to a predetermined threshold value T, the viscosity η tends to be constant and / or decrease as the strain rate γ increases (in the present embodiment, it tends to decrease). There is. The viscosity η of such a first viscosity region 11 is based on the shear viscosity of the material.

On the other hand, in the second viscosity region 12, when the strain rate is larger than the threshold value T, the viscosity η increases as the strain rate γ increases. The viscosity η of the second viscosity region 12 is based on the extensional viscosity of the material. In such an extensional viscosity, as the strain rate γ increases, the molecular chains constituting the material are fully extended, so that the viscosity η tends to increase.

The relationship 10 of the present embodiment can express the characteristic of viscosity in which the relaxation time of stress relaxation is small by the first viscosity region 11. On the other hand, the relationship 10 can express a rapid increase in force, which is a characteristic of elasticity, due to the second viscosity region 12. Therefore, in relation 10, the characteristic of the viscous elasticity of the material can be expressed only by the viscosity by the first viscosity region 11 and the second viscosity region 12. FIG. 7 is a flowchart showing an example of the processing procedure of the relationship definition step S12 of the present embodiment.

In the relationship definition step S12 of the present embodiment, first, the shear viscosity of the material is measured (step S16). For the measurement of shear viscosity, for example, an ARES rotary rheometer is used. In step S16, a plurality of shear viscosity values are measured by gradually increasing the strain rate from zero for a sufficiently kneaded material (not shown). FIG. 8 is a graph showing an example of the relationship between the shear viscosity and the extensional viscosity and the strain rate.

As shown in FIG. 8, in the measurement result of step S16, the viscosity η (shear viscosity) decreases as the strain rate γ increases. The measurement conditions for shear viscosity can be set as appropriate. The measurement result of the shear viscosity is stored in the computer 1.

Next, in the relationship definition step S12 of the present embodiment, the extensional viscosity of the material is measured (step S17). For example, a capillary rheometer is used to measure the extensional viscosity. In step S17, a plurality of extensional viscosity values are measured by gradually increasing the strain rate from zero with respect to a sufficiently kneaded material (not shown).

As shown in FIG. 8, in the measurement result of step S17, the viscosity η (extensional viscosity) increases as the strain rate γ increases. The measurement conditions for the extensional viscosity can be set as appropriate. The measurement result of the extensional viscosity is stored in the computer 1.

Next, in the relationship definition step S12 of the present embodiment, the relationship between the viscosity of the viscosity model and the strain rate is defined (step S18). In step S18, the relationship 10 shown in FIG. 6 is based on the shear viscosity of the material measured in step S16 (shown in FIG. 8) and the extensional viscosity of the material measured in step S17 (shown in FIG. 8). Is defined.

As described above, the shear viscosity of the material (shown in FIG. 8) measured in step S16 corresponds to the value of the viscosity in the first viscosity region 11 (shown in FIG. 6). On the other hand, the extensional viscosity of the material (shown in FIG. 8) measured in step S17 corresponds to the viscosity of the second viscosity region 12. By plotting these plurality of viscosity values (that is, the measurement result of the shear viscosity of the material and the measurement result of the extensional viscosity of the material), a graph showing the relationship 10 shown in FIG. 6 can be obtained.

In step S18 of the present embodiment, a first approximate straight line 17 that is approximated to a portion of the viscosity measurement result in which the viscosity decreases as the strain rate increases (that is, the first viscosity region 11) is obtained. Next, in step S18, a second approximate straight line 18 that is approximated to a portion where the viscosity increases as the strain rate increases (that is, the second viscosity region 12) is obtained. The first approximate straight line 17 and the second approximate straight line 18 of the present embodiment are defined by the following equation (1).

ここで、
η：材料の粘度
γ：材料のひずみ速度
ｎ：０より大きい実数

here,
η: Material viscosity γ: Material strain rate n: Real number greater than 0

The above equation (1) is based on the power law. The real number (power) n in the above equation (1) indicates the slope between the logarithm of the viscosity η of the material and the logarithm of the strain rate γ of the material. The real number n of the first approximate straight line 17 is a negative value. On the other hand, the real number n of the second approximate straight line 18 is a positive value. Such a straight line approximation can be performed, for example, based on the least squares method.

Next, in step S18 of the present embodiment, the strain rate γ at the intersection 14 of the first approximate straight line 17 and the second approximate straight line 18 is obtained. The strain rate γ at the intersection 14 is specified as a threshold value T between the first viscosity region 11 and the second viscosity region 12. The first viscosity region 11 and the second viscosity region 12 can be separated by such a threshold value T.

In the relationship definition step S12 of the present embodiment, the relationship 10 having the first viscosity region 11 and the second viscosity region 12 can be defined by the first approximate straight line 17, the second approximate straight line 18, and the threshold value T. ..

In the above relationship 10, for example, when the strain rate γ with respect to the material is equal to or less than the threshold value T, the strain rate γ is substituted into the first approximate straight line 17. Thereby, the viscosity η in the first viscosity region 11 corresponding to the strain rate γ can be obtained. This viscosity η is based on the shear viscosity.

On the other hand, when the strain rate γ with respect to the material is larger than the threshold value T, the strain rate γ is substituted into the second approximate straight line 18. Thereby, the viscosity η in the second viscosity region 12 corresponding to the strain rate γ can be obtained. This viscosity η is based on the extensional viscosity.

With such a relationship 10, the viscosity model can express the characteristics of the viscoelasticity of the material only by the viscosity. The relationship 10 is stored in the computer 1. In the present embodiment, as shown in FIG. 8, the first approximate straight line 17 and the second approximate straight line 18 based on the power law are used to approximate the measurement result of the viscosity, but the present invention is not limited to such an embodiment. As long as it can be approximated to the measurement result of viscosity, it is not limited to the power law.

Next, in the simulation method of the present embodiment, the predetermined flow conditions of the viscosity model are input to the computer 1 (flow condition definition step S2). The flow conditions can be appropriately set according to the calculated material flow. As the flow conditions of the present embodiment, conditions for flowing the material into the flow path 2 are set. FIG. 9 is a flowchart showing an example of the processing procedure of the flow condition definition step S2.

In the flow condition definition step S2 of the present embodiment, first, a flow path model 7 that models the flow path 2 is set (step S21). FIG. 10 is a conceptual diagram showing an example of the flow path model 7.

The flow path model 7 is a model (discretized) of the three-dimensional space of the flow path 2 (shown in FIGS. 2 and 3) with a finite number of elements e. At one end of the flow path model 7, there is a supply port 8 to which the viscosity model is supplied. The supply port 8 is set in a circular shape in front view based on the supply port 5 of the flow path 2 shown in FIG.

On the other hand, the other end of the flow path model 7 has a discharge port 9 from which the viscosity model is extruded. The discharge port 9 is set in a triangular shape in front view based on the discharge port 6 of the flow path 2 shown in FIG. Therefore, in the cross section of the flow path model 7, the cross-sectional area gradually decreases from the upstream side to the downstream side (that is, from the supply port 8 side to the discharge port 9 side) as in the flow path 2.

In the flow path model 7, as shown in a partially enlarged view of FIG. 10, the space through which the viscosity model flows is divided (discretized) by a plurality of elements e. The element division is performed by a three-dimensional element such as a polyhedron cell (polyhedral grid) in addition to a tetrahedron and a hexahedron, and in the present embodiment, it is modeled by an Euler element. In each element e, physical quantities such as pressure, temperature and velocity of the viscosity model are calculated. The flow path model 7 is stored in the computer 1.

Next, in the flow condition definition step S2 of the present embodiment, the boundary conditions for calculating the flow of the viscosity model are input to the computer 1 (step S22). As the boundary conditions of the present embodiment, the flow velocity and temperature of the viscosity model supplied to the supply port 8 of the flow path model 7, and the pressure (= 0) of the discharge port 9 of the flow path model 7 are given. The flow velocity and temperature of the viscosity model can be set, for example, by appropriately measuring the flow path 2 to be analyzed and referring to the values. Further, a temperature is applied to the wall surface of the flow path model 7. In this embodiment, a constant temperature is given.

Further, a flow velocity boundary condition is set on the wall surface 7w of the flow path model 7. As the flow velocity boundary condition, the wall surface no-slip condition or the wall surface slip condition can be set as in Patent Document 1, and either of them is adopted depending on the application of the simulation, the required calculation accuracy, and the like. In the present embodiment, the wall surface no-slip condition is set as in Patent Document 1.

Other boundary conditions include a time step of flow calculation (simulation), the number of iterations of iteration in internal processing, and a calculation end time. These conditions are arbitrarily determined according to the purpose of the simulation and the like. The boundary conditions are stored in the computer 1.

Next, in the simulation method of the present embodiment, the computer 1 calculates the flow state of the viscosity model (step S3). In step S3, the viscosity model is applied to predetermined flow conditions, and the flow state of the viscosity model is calculated. In step S3 of the present embodiment, the viscosity model is arranged in the flow path model 7, and the flow calculation is performed so that the viscosity model flows from the supply port 8 to the discharge port 9.

In step S3, at the position of each element e of the flow path model 7, the velocity components in the three directions (x, y, z) that specify the motion state of the viscosity model and the internal state of the viscosity model are calculated by the flow calculation of the viscosity model. Pressure and temperature, which are unknown quantities that identify, are calculated. In other words, these five unknowns should be solved. In the flow calculation of this embodiment, the Navier-Stoks equation in the case of an incompressible flow is used, and the density of the viscosity model is constant.

In this embodiment, the viscosity model is treated as a fluid over the entire temperature range. Therefore, the fluid equations (Navier-Stoks equations, mass conservation equations, and energy equations) will be solved. Further, in the present embodiment, since it is necessary to handle a mixed phase of a plurality of types of viscosity models having different shear viscosities, the VOF (Volume of Fluid) method used in the calculation of the flow at the free interface is used. In the VOF method, instead of directly calculating the movement of the interface between two fluids (viscosity models) with different shear viscosities, etc., the filling rate of the viscosity model in the volume of each element (sometimes called a "cell") ( That is, the body integration rate) is defined and the free interface is averaged and expressed. Details of the governing equation and the like are as described in Patent Document 1 above.

In step S3 of the present embodiment, the calculation is performed until the flow of the viscosity model becomes stable (that is, until it is focused). The flow calculation is performed in the same processing procedure as in steps S100 to S110 described in paragraphs "0041" to "0051" of the specification of Patent Document 1 and FIG. 7. This makes it possible to obtain the stable state of the viscosity model.

In the simulation method of the present embodiment, since a viscosity model that does not consider elasticity is used, it is possible to prevent the calculation of the flow state from diverging. Therefore, the simulation method of the present embodiment can stably calculate the flow state of the viscosity model.

The viscosity of the viscosity model is calculated based on the relationship 10 shown in FIG. Relationship 10 has a second viscosity region 12 in which the viscosity η increases as the strain rate γ increases when the strain rate γ is larger than the threshold value T. The second viscosity region 12 allows the viscosity model to represent the sharp rise in force that is characteristic of elasticity. Therefore, the simulation method of the present embodiment can calculate the flow of a material having viscoelasticity with high accuracy even if a viscosity model that does not consider elasticity is used.

Since the relationship 10 is defined by the first approximate straight line 17, the second approximate straight line 18, and the threshold value T, the viscosity η of the material corresponding to the strain rate γ with respect to the material can be easily and uniquely specified. Therefore, in the simulation method of the present embodiment, it is possible to prevent an increase in calculation cost.

Next, in the simulation method of the present embodiment, the computer 1 acquires the physical quantity of the viscosity model (step S4). In step S4, the physical quantity of the viscosity model having a flow in a stable state is acquired. Examples of the physical quantity include the velocity, pressure and temperature of the viscosity model obtained by the flow calculation. In the present embodiment, the physical quantity of the viscosity model is acquired at the discharge port 9 of the flow path model 7 shown in FIG.

Next, in the simulation method of the present embodiment, the computer 1 determines whether or not the physical quantity of the viscosity model is good (step S5). In step S5, it is determined whether or not the physical quantity of the viscosity model extruded from the discharge port 9 is good. The quality of the viscosity model is appropriately determined based on, for example, the flow velocity distribution at the discharge port 9, the temperature distribution of the viscosity model, and the like.

When it is determined in step S5 that the physical quantity is good (“Y” in step S5), the flow path 2 (shown in FIG. 2) is designed based on the flow path model 7 (shown in FIG. 10). (Step S6). On the other hand, when it is determined that the physical quantity is not good (“N” in step S5), the flow path model 7 is reset (step S7), and steps S1 to S5 are performed again. As a result, it is possible to reliably design the flow path 2 in which the material flow is good.

As shown in FIG. 6, the first viscosity region 11 of the present embodiment is exemplified in that the viscosity decreases as the strain rate increases from zero to a predetermined threshold value T. However, the present invention is not limited to such an embodiment. The first viscosity region 11 may include a portion where the viscosity becomes constant as the strain rate increases. FIG. 11 is a graph showing the relationship between the viscosity and the strain rate of the viscosity model of another embodiment of the present invention. In this embodiment, the same configurations as those in the previous embodiments may be designated by the same reference numerals and description thereof may be omitted.

The relationship 10 of this embodiment is a portion in the first viscosity region 11 in which the viscosity η is constant from zero to a predetermined second threshold value T2 even if the strain rate γ increases (hereinafter, simply “). Between 21 and the second threshold value T2 to the threshold value T, the viscosity η decreases as the strain rate γ increases (hereinafter, simply referred to as a “gradual decrease portion”). Includes 22 and. The fixed portion 21 of the present embodiment indicates the upper limit value of the viscosity η of the viscosity model in the relationship 10.

Due to such a constant portion 21, the relation 10 increases the viscosity η of the viscosity model to be equal to or higher than the viscosity η of the constant portion 21 (that is, the upper limit of the viscosity η) even when the strain rate γ of the viscosity model approaches zero. You can prevent it from happening. Thereby, in the simulation method of this embodiment, it is possible to surely prevent the calculation of the flow state of the viscosity model from diverging.

The second threshold value T2 and the upper limit value of the viscosity η (that is, the viscosity η of the fixed portion 21) can be appropriately set. It is desirable that the second threshold value T2 and the upper limit of the viscosity η are set in consideration of the stability of the calculation based on, for example, the result of calculating the flow state of the viscosity model in advance.

Although the particularly preferable embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be modified into various embodiments.

A simulation was carried out in which the flow of the material having viscoelasticity was calculated using a computer (Example, Comparative Example). In the examples and comparative examples, the materials were defined using a viscosity model that did not consider elasticity according to the processing procedure shown in FIG.

As shown in FIG. 6, the relationship between the viscosity of the viscosity model of the example and the strain rate is as follows:, when the strain rate is between zero and a predetermined threshold, the viscosity decreases as the strain rate increases. It has a viscosity region and a second viscosity region in which the viscosity increases as the strain rate increases when the strain rate is larger than the threshold value.

FIG. 12 is a graph showing the relationship between the viscosity of the viscosity model of the comparative example and the strain rate. The relationship between the viscosity of the viscosity model of the comparative example and the strain rate is that the viscosity becomes constant or decreases as the strain rate increases.

Then, a step of applying the viscosity models of Examples and Comparative Examples to predetermined flow conditions and calculating the flow state of the viscosity model is carried out, and the viscosity is carried out at each position in the width direction of the discharge port of the flow path model. The flow velocities of each model were calculated. The common specifications are as follows, and the flow conditions, etc. are as described in the specification.
Material: Rubber material before cross-linking Example:
Real number n in the first viscosity region: −0.86
Real number n in the second viscosity region: 0.86
Threshold strain rate: 10 (sec ^-1 )
Comparative example:
Real number n: -0.86

FIG. 13 is a graph showing the relationship between the flow velocity of the viscosity model and the position of the discharge port in the width direction. The position in the width direction of the discharge port is in the width direction of the discharge port with reference to one end t (shown in FIG. 3) where the height of the discharge port is the largest (that is, the distance in the width direction of the discharge port is 0). Specified as a distance.

As shown in FIG. 13, in the embodiment, the smaller the height of the discharge port (that is, the larger the position in the width direction), the smaller the flow velocity of the viscosity model. This is because the force (viscosity) of the viscous model increases and the flow velocity decreases due to the increase in the strain rate of the viscous model in the portion where the height (cross-sectional area) of the discharge port decreases. This approximates the tendency of the flow velocity of the actual material with viscoelasticity.

On the other hand, in the comparative example, the smaller the height of the discharge port (that is, the larger the position in the width direction), the larger the flow velocity of the viscosity model. This is because the force (viscosity) of the viscous model decreased and the flow velocity increased due to the increase in the strain rate of the viscous model in the portion where the height (cross-sectional area) of the discharge port decreased. This deviates from the tendency of the flow velocity of the actual material having viscoelasticity.

Therefore, in the examples, even if a viscosity model that does not consider elasticity was used, the flow of the material having viscoelasticity could be calculated with high accuracy as compared with the comparative example.

10 Relationship between viscosity and strain rate of viscosity model 11 1st viscosity region 12 2nd viscosity region

Claims (5)

A simulation method for calculating the flow of viscoelastic material using a computer.
A process of defining the material in the computer using a viscosity model that does not consider elasticity.
Including a step of adapting the viscosity model to predetermined flow conditions and calculating the flow state of the viscosity model.
The step of defining the viscosity model includes a step of defining the relationship between the viscosity of the viscosity model and the strain rate.
The relationship is that when the strain rate is from zero to a predetermined threshold, the first viscosity region where the viscosity becomes constant and / or decreases as the strain rate increases.
When the strain rate is larger than the threshold value, it has a second viscosity region in which the viscosity increases as the strain rate increases.
Simulation method for viscoelastic materials. The viscoelastic material according to claim 1, wherein the step of defining the relationship specifies the relationship with respect to the material based on a plurality of viscosity values measured by gradually increasing the strain rate from zero. Simulation method. The method for simulating a viscoelastic material according to claim 2, wherein the step of defining the relationship includes a step of measuring the extensional viscosity of the material. In the step of defining the relationship, the first approximate straight line approximated to the portion of the measurement result of the viscosity in which the viscosity decreases as the strain rate increases, and the viscosity increases as the strain rate increases. The method for simulating a viscoelastic material according to claim 2 or 3, wherein the strain rate at the intersection with the second approximate straight line approximated to the portion is defined as the threshold value. The method for simulating a viscoelastic material according to claim 4, wherein the first approximate straight line and the second approximate straight line are defined by the following formula (1).

here,
η: Material viscosity γ: Material strain rate n: Real number greater than 0

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