Evaluation method

Abstract

To provide an evaluation method capable of appropriately evaluating strength of a truck frame for a railroad vehicle.SOLUTION: An evaluation method includes: a process (S1) of applying a load to a truck frame (10) under multiple kinds of load conditions, and acquiring multiple kinds of stresses occurring in the truck frame (10) in accordance with the load conditions, respectively; a process (S2) of calculating an average stress and a fluctuating stress; and a process (S3) of evaluating the strength of the truck frame (10) on the basis of the average stress and the fluctuating stress. The multiple stresses include a main motor in-phase stress generated by a main motor in-phase load, and a main motor inverse-phase stress generated by the main motor in-phase load. The main motor in-phase load is applied to a first main motor (20a) and a second main motor (20b) in the same direction in a vertical direction. The main motor inverse-phase load is applied to the first main motor (20a) and the second main motor (20b) in the opposite direction in the vertical direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an evaluation method, and more particularly to an evaluation method for evaluating the strength of a bogie frame for a railway vehicle.

Background Art

[0002] A bogie for a railway vehicle includes a bogie frame and front and rear axles attached to the bogie frame. The bogie frame is the main structural frame that constitutes the bogie and supports the car body. The bogie frame includes a pair of side bars, a cross bar connecting the side bars, and front and rear main motor seats. The main motor is attached to the bogie frame via each of the main motor seats.

[0003] Conventionally, the strength of the bogie frame has been evaluated in accordance with the general rules for bogie frame strength design specified in JIS E 4207:2019 and the static load test method specified in JIS E 4208-1:2021. In the static load test, a load is applied to the bogie frame according to a plurality of types of load conditions, and for example, the stress for each load condition is measured by strain gauges attached to each part of the bogie frame. Then, the average stress and the fluctuating stress are calculated from the measured stress according to the general rules for bogie frame strength design, and the strength of the bogie frame is evaluated based on the average stress and the fluctuating stress.

[0004] Patent Document 1 discloses a method for evaluating the strength of a bogie frame using analysis by the finite element method (FEM). In Patent Document 1, first, for the bogie frame to be evaluated, an FEM model divided into meshes of a predetermined coarseness is created. Then, virtual strain gauges are defined at all nodes on the FEM model, and the stress generated for each single load (load condition) is obtained. The single loads include, for example, the vertical load, the front-rear load, the left-right load, the brake load, the torsional load, the main motor (motor) load, the drive device load, etc. specified in JIS E 4208-1:2021.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] By the way, in JIS E 4207:2019 and JIS E 4208-1:2021, regarding the main motor load, it is not particularly specified whether to load the in-phase load or the reverse-phase load. That is, it is not specified whether to load the same-direction load (in-phase load) or the opposite-direction load (reverse-phase load) in the vertical direction with respect to the front and rear main motors. However, depending on the part of the bogie frame, the magnitude of the stress generated when the in-phase main motor load is applied may be different from that when the reverse-phase main motor load is applied. Therefore, if the stress is measured only under the condition of either the in-phase or the reverse-phase regarding the main motor load, it may not be possible to properly evaluate the strength of the bogie frame.

[0007] An object of the present disclosure is to provide an evaluation method capable of properly evaluating the strength of a bogie frame for a railway vehicle.

MEANS FOR SOLVING THE PROBLEMS

[0008] The evaluation method according to the present disclosure evaluates the strength of a bogie frame for a railway vehicle. The evaluation method includes a step of applying loads to the bogie frame under a plurality of types of load conditions and acquiring a plurality of stresses generated in the bogie frame corresponding to each of the load conditions, a step of calculating an average stress and a fluctuating stress, and a step of evaluating the strength of the bogie frame based on the average stress and the fluctuating stress. The bogie frame includes a pair of side sills, a cross sill, a first main motor seat for mounting a first main motor, and a second main motor seat for mounting a second main motor. The cross sill connects the side sills to each other. The average stress is the algebraic sum of the stresses generated by the static load among the plurality of stresses. The static load is the force applied to the bogie frame when the railway vehicle is stationary. The fluctuating stress is the square root of the sum of the squares of the stresses generated by the dynamic load among the plurality of stresses. The dynamic load is the force applied to the bogie frame when the railway vehicle is running. The plurality of stresses includes a main motor in-phase stress generated by a main motor in-phase load and a main motor out-of-phase stress generated by a main motor out-of-phase load. The main motor in-phase load is applied in the same direction in the vertical direction with respect to the first main motor and the second main motor. The main motor out-of-phase load is applied in the opposite direction in the vertical direction between the first main motor and the second main motor.

Effect of the Invention

[0009] According to the present disclosure, the strength of a bogie frame for a railway vehicle can be appropriately evaluated.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0011] As described above, in JIS E 4207:2019 and JIS E 4208-1:2021, regarding the main motor load, it is not defined whether to apply the in-phase load or the reverse-phase load. Therefore, conventionally, when evaluating the strength of the bogie frame, only one of the in-phase load and the reverse-phase load has been applied to the bogie frame as the main motor load. However, as confirmed by the inventors, it has been found that both the in-phase load and the reverse-phase load are generated in the bogie frame as the main motor load during the actual running of railway vehicles. Furthermore, the inventors have discovered that depending on the part of the bogie frame, the magnitude of the stress is different between the case where the in-phase main motor load is applied and the case where the reverse-phase main motor load is applied. Therefore, the inventors have considered evaluating the strength of the bogie frame by taking into account not only one of the in-phase main motor load and the reverse-phase main motor load but also both of them, and have completed the evaluation method according to the embodiment.

[0012] The evaluation method according to the embodiment evaluates the strength of a bogie frame for a railway vehicle. The evaluation method includes a step of applying loads to the bogie frame under a plurality of types of load conditions and acquiring a plurality of stresses generated in the bogie frame corresponding to each of the load conditions, a step of calculating an average stress and a fluctuating stress, and a step of evaluating the strength of the bogie frame based on the average stress and the fluctuating stress. The bogie frame includes a pair of side sills, a cross sill, a first main motor seat for mounting a first main motor, and a second main motor seat for mounting a second main motor. The cross sill connects the side sills to each other. The average stress is the algebraic sum of the stresses generated by the static load among the plurality of stresses. The static load is the force applied to the bogie frame when the railway vehicle is stationary. The fluctuating stress is the square root of the sum of the squares of the stresses generated by the dynamic load among the plurality of stresses. The dynamic load is the force applied to the bogie frame when the railway vehicle is running. The plurality of stresses includes a main motor in-phase stress generated by a main motor in-phase load and a main motor anti-phase stress generated by a main motor anti-phase load. The main motor in-phase load is applied in the same direction in the vertical direction with respect to the first main motor and the second main motor. The main motor anti-phase load is applied in the opposite direction in the vertical direction between the first main motor and the second main motor (first configuration).

[0013] The main motor load is classified as a dynamic load, which is the force applied to the bogie frame when the railway vehicle is running. In JIS E 4207:2019 and JIS E 4208-1:2021, the weight L p of each main motor attached to the main motor seat is multiplied by 3 to 10 times as the main motor load, and it is to be loaded vertically at the center of gravity position of each main motor. p Conventionally, since only one of the main motor in-phase load and the main motor anti-phase load was applied to the bogie frame to acquire the stress, for example, when the main motor load was 8L p equivalent stress was generated at each part of the bogie frame, and the fluctuating stress based on the main motor load was sqrt((8L p equivalent stress) 2) On the other hand, in the evaluation method according to the first configuration, the fluctuating stress is calculated using both the in-phase load of the main motor and the reverse-phase load of the main motor. Thereby, as will be described below, the strength of the bogie frame can be evaluated more appropriately.

[0014] According to the study by the present inventors, when the in-phase load of the main motor and the reverse-phase load of the main motor are equal, in the two main motor seats (the first and second main motor seats) existing on the bogie frame, the stress generated by the in-phase load of the main motor and the stress generated by the reverse-phase load of the main motor are equivalent. Therefore, in the evaluation method according to the first configuration, for example, when each of the in-phase load of the main motor and the reverse-phase load of the main motor is 6L p in the main motor seat, a stress equivalent to 6L p (main motor in-phase stress) is generated by the in-phase load of the main motor, and a stress equivalent to 6L p (main motor reverse-phase stress) is also generated by the reverse-phase load of the main motor. Thus, the fluctuating stress based on the main motor load becomes the square root of the sum of the squares of the main motor in-phase stress and the main motor reverse-phase stress, and is approximately 8.5L p equivalent (= sqrt((6L p equivalent stress) 2 + (6L p equivalent stress) 2 ))). Therefore, even if the coefficient multiplied by the weight L p of the main motor is changed from 8 to 6 to apply a smaller main motor load, it is possible to ensure a magnitude equal to or greater than that of the conventional case (when the coefficient is 8) for the fluctuating stress at the main motor seat. Therefore, when evaluating the strength of the bogie frame based on the average stress and the fluctuating stress, it is possible to evaluate the main motor seat on the safe side. That is, the main motor seat can be designed to withstand a main motor load of 8.5L p larger than the conventional 8L p .

[0015] According to the inventors' study, even if the main motor in-phase load and the main motor negative-phase load are equal, the stress generated by the main motor in-phase load and the stress generated by the main motor negative-phase load may differ in parts other than the main motor seat. In some parts of the bogie frame, such as the joints between each side beam and the cross beam, the main motor load is limited to only one of the in-phase and negative-phase as in the conventional case, and the main motor load is set to, for example, 8L. p When the load is applied to the bogie frame, excessive high stress is generated, and the evaluation and design of the strength of the bogie frame may be overly conservative. In other words, even if the impact of the main motor load is small and high stress due to the main motor load is unlikely to occur in a part of the bogie frame, the 8L p In contrast, in the first configuration, in the evaluation of the strength of the bogie frame, both the main motor in-phase load and the main motor negative-phase load are applied to the bogie frame, so that an appropriate evaluation can be performed according to the part of the bogie frame. Specifically, as described above, the main motor in-phase load and the main motor negative-phase load are each set to 6L. p In this case, in areas other than the main motor seat, that is, areas that were previously over-evaluated (designed), the load applied to either the main motor in-phase load or the main motor reverse-phase load is, for example, 6L p A considerable stress is generated. On the other hand, the other of the main motor in-phase load and main motor negative-phase load generates only a smaller stress. If the stress generated by the other of the main motor in-phase load and main motor negative-phase load is, for example, 1 / 3 of the stress generated by one of the main motor in-phase load and main motor negative-phase load, the fluctuating stress based on the main motor load is approximately 6.3L, since it is the square root of the sum of the squares of the main motor in-phase stress and main motor negative-phase stress. p Equivalent (=sqrt((6L p equivalent stress) 2 +(2L p equivalent stress) 2 )). Therefore, the fluctuating stress in parts other than the traction motor seat can be set to a smaller value than before (when the coefficient is 8), and when evaluating the strength of the bogie frame based on the average stress and fluctuating stress, it is possible to perform an appropriate evaluation according to the part. In other words, for parts that are less affected by the traction motor load, the conventional 8L pIt is possible to adopt a design corresponding to a smaller main motor load.

[0016] Thus, in the evaluation method according to the first configuration, among the bogie frames, the strength can be evaluated with a fluctuating stress equal to or greater than that of the conventional one at each main motor seat, while at the parts other than the main motor seats, that is, the parts where the influence of the main motor load is relatively small, the fluctuating stress can be reduced compared to the conventional one, making it less likely to cause over-evaluation and over-design. Therefore, according to the evaluation method according to the first configuration, the strength of the bogie frame for railway vehicles can be accurately evaluated.

[0017] In the evaluation method according to the first configuration, the load value of the main motor reverse-phase load may be equal to or less than the load value of the main motor in-phase load (second configuration).

[0018] During the running of a railway vehicle, the bogie frame vibrates in a state where a plurality of natural vibration modes are superimposed. "Yoshiyuki Shimokawa, et al., 'Development of a Bogie Frame Fatigue Prediction System - Fourth Report - Factor Analysis of Natural Vibration Modes Affecting the Generated Stress of the Bogie Frame and Consideration of the Static Load Test Conditions of the Bogie Frame Based on the Results -', The 29th Railway Technology Consortium Symposium (J-RAIL2022), 2022, S6-1-3, p216-219" lists six vibration modes with a high contribution rate to the stress at the main motor seat. The stress generated at the main motor seat is the superposition of these six vibration modes.

[0019] The six vibration modes include the rigid pitch mode in which the bogie frame performs pitching motion and the mode in which the front and rear main motors vibrate in opposite phases vertically and the bogie frame performs pitching motion simultaneously. These modes are vibration modes corresponding to the main motor reverse-phase load. According to the above paper, the stress due to the vibration mode corresponding to the main motor reverse-phase load is less than half of the stress generated at the main motor seat (the stress obtained by superimposing the six vibration modes). That is, assuming that the stress generated at the main motor seat is mainly the main motor in-phase stress and the main motor reverse-phase stress, during the running of the railway vehicle, the main motor reverse-phase stress at the main motor seat is less than or equal to the main motor in-phase stress.

[0020] Therefore, in the second configuration, the load value of the main motor reverse-phase load is set to be equal to or less than the load value of the main motor in-phase load. In this case, when evaluating the strength of the bogie frame by the evaluation method according to the embodiment, at each of the first and second main motor seats, a main motor reverse-phase stress equal to or less than the main motor in-phase stress can be generated. Therefore, the strength of the bogie frame can be evaluated in accordance with the actual running of the railway vehicle.

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each figure, the same or corresponding components are denoted by the same reference numerals, and the same description will not be repeated.

[0022] [Bogie Frame] FIG. 1 is an example of a bogie frame 10 of a railway vehicle bogie. Referring to FIG. 1, the bogie frame 10 includes a pair of side bars 11, at least one cross bar 12, a first main motor seat 13a, and a second main motor seat 13b.

[0023] The pair of side bars 11 are arranged at intervals in the width direction (left-right direction) of the bogie frame 10. Each of the side bars 11 extends in the longitudinal direction (front-rear direction) of the bogie frame 10. The side bar 11 includes, for example, a plurality of internal ribs 111. The internal ribs 111 are provided inside the side bar 11. The internal ribs 111 are arranged in the longitudinal direction of the side bar 11. The internal ribs 111 may be joined to the inner surface of the side bar 11 by, for example, welding or the like.

[0024] The cross bar 12 extends in the width direction of the bogie frame 10. The cross bar 12 connects the side bars 11 to each other. One longitudinal end of the cross bar 12 is joined to one side bar 11 by, for example, welding. The other longitudinal end of the cross bar 12 is joined to the other side bar 11 by, for example, welding.

[0025] The first main motor support seat 13a is for attaching the first main motor 20a to the bogie frame 10. The first main motor support seat 13a is arranged on one side in the longitudinal direction of the bogie frame 10 with respect to the cross bar 12. The first main motor support seat 13a is provided on the cross bar 12. The first main motor support seat 13a may be joined to the cross bar 12 by welding or the like, or may be integrally formed with the cross bar 12. The first main motor 20a is attached to the cross bar 12 via the first main motor support seat 13a.

[0026] The second main motor support seat 13b is for attaching the second main motor 20b to the bogie frame 10. The second main motor support seat 13b is arranged on the opposite side of the first main motor support seat 13a in the longitudinal direction of the bogie frame 10 with respect to the cross bar 12. The second main motor support seat 13b is arranged with a position shift from the first main motor support seat 13a in the width direction of the bogie frame 10. The second main motor support seat 13b, like the first main motor support seat 13a, is provided on the cross bar 12. The second main motor support seat 13b may be joined to the cross bar 12 by welding or the like, or may be integrally formed with the cross bar 12. The second main motor 20b is attached to the cross bar 12 via the second main motor support seat 13b.

[0027] [Evaluation method] Next, the evaluation method according to this embodiment will be described with reference to FIG. 2 as well. FIG. 2 is a flowchart of the evaluation method. In this evaluation method, the strength of the bogie frame 10 for a railway vehicle is evaluated. As shown in FIG. 2, the evaluation method includes an acquisition step S1, a calculation step S2, and an evaluation step S3.

[0028] [Acquisition step] In the acquisition step S1, a load is applied to the bogie frame 10 under a plurality of types of load conditions, and a plurality of stresses generated in the bogie frame 10 corresponding to the load conditions are acquired.

[0029] In the evaluation method according to this embodiment, both the in-phase load condition of the main motors and the reverse-phase load condition of the main motors are used as load conditions. That is, the load conditions include the in-phase load condition of the main motors and the reverse-phase load condition of the main motors. The in-phase load condition of the main motors is a condition in which the in-phase load of the main motors is applied to the bogie frame 10. The in-phase load of the main motors refers to a load applied in the same direction in the vertical direction with respect to the first main motor 20a and the second main motor 20b. The reverse-phase load condition of the main motors is a condition in which the reverse-phase load of the main motors is applied to the bogie frame 10. The reverse-phase load of the main motors refers to a load applied in the opposite direction in the vertical direction between the first main motor 20a and the second main motor 20b. The load conditions can further include an up-down load condition, a left-right load condition, a front-back load condition, a torsional load condition, a drive device load condition, and a brake load condition. Each load condition includes a load value and a load direction.

[0030] Figure 3 is a schematic diagram for explaining the in-phase load condition of the main motors. Referring to Figure 3, in the case of the in-phase load condition of the main motors, loads in the same direction are applied to the center-of-gravity positions of the front and rear main motors 20a, 20b (Figure 1). In the example of Figure 3, downward loads are applied to the center-of-gravity positions of both the main motors 20a and 20b. However, in the in-phase load condition of the main motors, upward loads may be applied to the center-of-gravity positions of both the main motors 20a and 20b.

[0031] The load value (kN) applied to the center-of-gravity position of each of the main motors 20a, 20b (Figure 1) can be 3 to 10 times the respective weight L of the main motors 20a, 20b in accordance with JIS E 4207:2019. p The main motor load value can be determined, for example, by agreement between the parties involved in the delivery of the bogie frame 10. The load value of the in-phase load of the main motors in the evaluation method according to this embodiment may be a value greater than 1 / √2 times the load value determined by agreement.

[0032] FIG. 4 is a schematic diagram for explaining the main motor reverse-phase load condition. Referring to FIG. 4, in the case of the main motor reverse-phase load condition, a reverse load is applied to the center-of-gravity positions of the front and rear main motors 20a and 20b (FIG. 1). In the example of FIG. 4, an upward load is applied to the center-of-gravity position of the first main motor 20a, while a downward load is applied to the center-of-gravity position of the second main motor 20b. However, conversely, a downward load may be applied to the center-of-gravity position of the first main motor 20a, while an upward load may be applied to the center-of-gravity position of the second main motor 20b.

[0033] The load value of the main motor reverse-phase load in the evaluation method according to the present embodiment may also be a value greater than 1 / √2 times the load value determined by agreement between the transfer parties, similar to the main motor in-phase load. The load value of the main motor reverse-phase load may be equal to or less than the load value of the main motor in-phase load. The load value of the main motor reverse-phase load is, for example, 60% or more of the load value of the main motor in-phase load.

[0034] Each of the up-and-down load condition, left-and-right load condition, front-and-rear load condition, torsional load condition, drive device load condition, and brake load condition can be determined in accordance with JIS E 4207:2019 and JIS E 4208-1:2021 as in the prior art.

[0035] The stress corresponding to each load condition can be measured, for example, using a strain gauge attached to the bogie frame 10. The strain gauge is attached to the part of the bogie frame 10 that is the evaluation target. The strain gauge is attached, for example, to the main motor seats 13a and 13b, the joints between each side sill 11 and the cross sill 12, the internal ribs 111 of each side sill 11, etc. At each part, the stress can be obtained by integrating the Young's modulus with the strain measured by the strain gauge.

[0036] The stress of the bogie frame 10 is obtained for each load condition and for each part to be evaluated. That is, under the main motor in-phase load condition, for each part to be evaluated, the main motor in-phase stress generated by the main motor in-phase load is obtained. Under the main motor reverse-phase load condition, for each part to be evaluated, the main motor reverse-phase stress generated by the main motor reverse-phase load is obtained. Also for other load conditions, for each part to be evaluated, the stress corresponding to the load condition is obtained.

[0037] (Calculation step) In the calculation step S2, the average stress and the fluctuating stress are calculated from the stress obtained in the acquisition step S1. The average stress and the fluctuating stress are calculated for each part to be evaluated of the bogie frame 10.

[0038] The average stress is obtained for each part to be evaluated as the algebraic sum of the stresses generated by the static load among the stresses obtained in the acquisition step S1. The static load is the force applied to the bogie frame 10 when the railway vehicle is stationary. The average stress is calculated according to the stress calculation method specified in JIS E 4207:2019.

[0039] The fluctuating stress is obtained for each part to be evaluated as the square root of the sum of the squares of the stresses generated by the dynamic load among the stresses obtained in the acquisition step S1. The dynamic load is the force applied to the bogie frame 10 when the railway vehicle is running. The main motor in-phase load and the main motor reverse-phase load are included in the dynamic load. The fluctuating stress is calculated according to the stress calculation method specified in JIS E 4207:2019. However, in this embodiment, the main motor in-phase stress corresponding to the main motor in-phase load and the main motor reverse-phase stress corresponding to the main motor reverse-phase load are used in the calculation of the fluctuating stress. For example, the stress [MPa] generated by the main motor in-phase load is σ X and the stress [MPa] generated by the main motor reverse-phase load is σ Y and the stresses [MPa] generated by other dynamic loads are σ1, σ2, ···, σ n (n ≧ 2), when the fluctuating stress σ a is calculated by the following formula (1).

[0040] [Number]

[0041] As described in JIS E 4207:2019, when there is a dynamic load that causes single-sided vibration, the average stress is the value obtained by adding half of the stress due to the dynamic load to the algebraic sum of the stress due to the static load. Also, when there is a stress due to a dynamic load that causes single-sided vibration, the variable stress σ a is synthesized using half of that stress. When there are stresses that occur synchronously with respect to the dynamic load, for these stresses, the square of their algebraic sum shall be used in Equation (1).

[0042] (Evaluation Step) In the evaluation step S3, the strength of the bogie frame 10 is evaluated based on the average stress and the variable stress calculated in the calculation step S2. For example, the strength of the bogie frame 10 can be evaluated using the stress limit diagram described in JIS E 4207:2019. An example of the stress limit diagram is shown in FIG. 5. As shown in FIG. 5, the stress limit diagram is a graph with the average stress on the horizontal axis and the variable stress on the vertical axis. In the stress limit diagram shown in FIG. 5, the lines 31 and 32 are the lines indicating the yield limit of the material, and the line 33 is the line indicating the fatigue limit of the material. In FIG. 5, σ0 is the allowable stress with respect to the yield of the material.

[0043] The stress limit diagram can be prepared for each material. The material here refers to the base material as it is, Gr (ground) finish, and As-Weld (as-welded). In the stress limit diagram shown in FIG. 5, σ W1 is the fatigue allowable stress in the state of the base material as it is, σ W2 is the fatigue allowable stress in the Gr finish state, σ W3 is the fatigue allowable stress in the As-Weld state. The point where the extension line of the fatigue limit line 33 passing through the fatigue allowable stresses σ W1 ~σ W3 intersects the horizontal axis is the tensile strength σ B of the material.

[0044] In the stress limit diagram, the yield limit lines 31 and 32, the fatigue limit line 33, and the region A surrounded by the horizontal axis are the allowable stress ranges.

[0045] In the evaluation step S3, the average stress and the fluctuating stress of the part to be evaluated of the bogie frame 10 are plotted on the stress limit diagram. When the average stress and the fluctuating stress are within the allowable stress region A, the part to be evaluated is evaluated as satisfying the strength requirement. When the average stress and the fluctuating stress are outside the allowable stress region A, the part to be evaluated is evaluated as not satisfying the strength requirement.

[0046] [Effect] According to the evaluation method according to the present embodiment, the strength of the bogie frame 10 for railway vehicles can be appropriately evaluated as compared with the conventional evaluation method. This will be specifically described below.

[0047] In the conventional evaluation method, the fluctuating stress is calculated using only the stress corresponding to the in-phase load of the main motor or only the stress corresponding to the reverse-phase load of the main motor. Using only either the in-phase or the reverse-phase as the main motor load, and multiplying each weight L of the main motors 20a and 20b p by, for example, a coefficient 8 to obtain a value 8L p as the load value, examples of the average stress and the fluctuating stress are shown in FIG. 6. In the stress limit diagram of FIG. 6, for the conventional evaluation method, the plots of the average stress and the fluctuating stress at the main motor seats 13a and 13b and the plots of the average stress and the fluctuating stress at the parts other than the main motor seats 13a and 13b are shown. The parts other than the main motor seats 13a and 13b are, for example, the joints between the respective side bars 11 and the cross bar 12. The parts other than the main motor seats 13a and 13b may be, for example, the internal ribs 111 of each side bar 11. The parts other than the main motor seats 13a and 13b are parts that are less affected by the main motor load.

[0048] In contrast, in the evaluation method according to the present embodiment, the fluctuating stress is calculated using both the stress corresponding to the in-phase load of the main motor and the stress corresponding to the reverse-phase load of the main motor. As a result, the strength of the bogie frame 10 can be evaluated with a smaller main motor load than before. For example, using both the in-phase load and the reverse-phase load of the main motor, for each weight L of the main motors 20a and 20b p the value B×L obtained by multiplying by a coefficient B (B < 8, for example, B = 6) p is used as the load value, and the average stress and the fluctuating stress are shown together in FIG. 6. In the stress limit diagram of FIG. 6, for the evaluation method according to the present embodiment, the plots of the average stress and the fluctuating stress at the main motor seats 13a and 13b and the plots of the average stress and the fluctuating stress at the parts other than the main motor seats 13a and 13b are shown.

[0049] As shown in FIG. 6, regarding the main motor seats 13a and 13b, the fluctuating stress obtained by the evaluation method of the present embodiment is equal to or greater than the fluctuating stress obtained by the conventional evaluation method. For example, in the conventional evaluation method, when the main motor load value is 8L p the fluctuating stress based on the main motor load for the main motor seats 13a and 13b is sqrt((8L p equivalent stress) 2 ). On the other hand, in the evaluation method of the present embodiment, by using both the in-phase load and the reverse-phase load of the main motor, the fluctuating stress based on the main motor load for the main motor seats 13a and 13b is sqrt(2(B×L p equivalent stress) 2 ). Assuming B = 6, in the evaluation method of the present embodiment, a fluctuating stress equivalent to approximately 8.5L p is generated at the main motor seats 13a and 13b, that is, a stress equal to or greater than that of the conventional evaluation method. Therefore, regarding the strength of the main motor seats 13a and 13b, an evaluation equivalent to or safer than the conventional one can be performed.

[0050] As shown in FIG. 6, with respect to the parts other than the main motor seats 13a and 13b, the fluctuating stress obtained by the evaluation method of the present embodiment is smaller than the fluctuating stress obtained by the conventional evaluation method. For example, in the conventional evaluation method, when the main motor load value is 8L p in the case of, for the parts other than the main motor seats 13a and 13b, the fluctuating stress based on the main motor load is sqrt((8L p equivalent stress) 2 ). However, in the case of a part that is less affected by the main motor load, with a main motor load of 8L p , high stress may be generated more than necessary, leading to overdesign. In contrast, in the evaluation method of the present embodiment, both the main motor in-phase load and the main motor reverse-phase load are used. In the parts other than the main motor seats 13a and 13b, since the stress generated by the main motor in-phase load and the stress generated by the main motor reverse-phase load are different, the fluctuating stress based on the main motor load is less than sqrt(2(B×L p equivalent stress) 2 ). For example, when B = 6 and one of the main motor in-phase stress and the main motor reverse-phase stress is set as the stress equivalent to 6L p , the other of the main motor in-phase stress and the main motor reverse-phase stress is smaller than this (for example, 1 / 3 of the main motor in-phase stress). In the case of a part that is less affected by the main motor load, as shown in FIG. 6, since one of the main motor in-phase stress and the main motor reverse-phase stress is significantly smaller than the other, the fluctuating stress is reduced compared to the conventional evaluation method. Therefore, for example, the plate thickness of the part can be reduced, or the welding amount can be reduced to reduce the weight of the carriage frame 10.

[0051] Thus, in the evaluation method according to the present embodiment, for the carriage frame 10, the strength can be evaluated with a fluctuating stress equal to or higher than the conventional one at the main motor seats 13a and 13b, while in the parts other than the main motor seats 13a and 13b, the fluctuating stress can be reduced compared to the conventional one, making it less likely to cause overevaluation and overdesign. According to the evaluation method according to the present embodiment, an appropriate strength evaluation can be performed according to the parts of the carriage frame 10.

[0052] In the evaluation method according to this embodiment, the load value of the main motor reverse-phase load is preferably equal to or less than the load value of the main motor in-phase load. In this case, similar to when the railway vehicle actually runs, the main motor reverse-phase stress generated at the main motor seats 13a and 13b is respectively equal to or less than the main motor in-phase stress generated at the main motor seats 13a and 13b. Therefore, in line with the actual running of the railway vehicle, the strength of the bogie frame 10 can be evaluated more accurately.

[0053] As described above, the embodiments according to the present disclosure have been described. However, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof.

[0054] In the above embodiment, an example of evaluating the strength using the actual bogie frame 10 has been described. However, the strength of the bogie frame 10 can also be evaluated by analysis using the finite element method (FEM analysis). When evaluating the strength of the bogie frame 10 by FEM analysis, the evaluation method can further include a step of creating an FEM model of the bogie frame 10. In the acquisition step S1, various stresses are acquired for the created FEM model. The creation of the FEM model and the acquisition of stresses can be carried out in the same manner as the evaluation method described in Patent Document 1. However, even when using FEM analysis, similar to the above embodiment, the strength of the bogie frame 10 is evaluated using both the main motor in-phase load and the main motor reverse-phase load.

[0055] The strength design and evaluation of the bogie frame 10 are typically carried out in the order of strength design using material mechanics or the finite element method (FEM), fabrication of the bogie frame 10, and static load test. That is, the evaluation method according to the above embodiment may be used in the strength design before the fabrication of the bogie frame 10 or in the static load test after the fabrication of the bogie frame 10.

Description of Reference Numerals

[0056] 10: Bogie frame 11: Side sway 12: Cross sway 13a: First main motor seat 13b: Second main motor seat 20a: First main motor 20b: Second main motor

Claims

1. An evaluation method for evaluating the strength of a bogie frame for a railway vehicle, for a bogie frame including a pair of side sills, a cross sill connecting the side sills, a first main motor seat for mounting a first main motor, and a second main motor seat for mounting a second main motor, loading a load under a plurality of types of load conditions, and obtaining a plurality of stresses generated in the bogie frame corresponding to each of the load conditions; calculating an average stress, which is the algebraic sum of the stresses generated by a static load, which is the force applied to the bogie frame when the railway vehicle is stationary, among the plurality of stresses, and a variable stress, which is the square root of the sum of the squares of the stresses generated by a dynamic load, which is the force applied to the bogie frame when the railway vehicle is running, among the plurality of stresses; evaluating the strength of the bogie frame based on the average stress and the variable stress; comprising: The plurality of stresses include a main motor in-phase stress generated by a main motor in-phase load loaded in the same direction in the vertical direction with respect to the first main motor and the second main motor, and a main motor out-of-phase stress generated by a main motor out-of-phase load loaded in the opposite direction in the vertical direction between the first main motor and the second main motor. Evaluation method.

2. The evaluation method according to claim 1, wherein the load value of the main motor out-of-phase load is equal to or less than the load value of the main motor in-phase load. Evaluation method.

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