JP2018179730A - Stress measurement device and stress measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stress measurement device and a stress measurement method capable of calculating more accurate temperature fluctuation quantity and searching for more accurate stress distribution in consideration of heat loss by a stress measurement device which calculates a stress distribution from a temperature fluctuation quantity at each position of a measurement subject based on temperature distribution and measuring a temperature distribution using infrared thermography, giving periodic load to a measurement subject.SOLUTION: A calculation device includes a temperature-fluctuation-quantity calculation part which calculates the temperature fluctuation quantity at each position of the surface of a measurement subject based on the temperature distribution by thermometry equipment, a heat-loss calculation part which calculates the thermal-diffusion loss information about the loss of the heat by diffusion of the heat on the surface of a measurement subject according to the cycle or frequency of the load given by the load giving equipment, an amount calculation part of the corrected temperature fluctuation quantity based on heat-diffusion loss information, and a stress calculation part which calculates the stress distribution of the surface of the measurement subject according to the load based on the amount of the corrected temperature change.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a stress measurement device and a stress measurement method.

  In recent years, in order to further improve the fuel consumption of a vehicle, weight reduction and miniaturization of various parts mounted on the vehicle are desired. For example, a relatively heavy part (object) requiring high rigidity and made of metal such as iron leaves a thickness of a portion requiring rigidity and a thickness of a portion not requiring much rigidity Can make a great contribution to weight reduction. Therefore, various stress measuring devices and stress measuring methods have been disclosed in order to recognize which position and how much stress is applied when an object is loaded.

  For example, in Patent Document 1, a rotating device such as a constant velocity joint is used as an object to be measured, load fluctuation is repeatedly generated on the object to be measured, temperature distribution of the object to be measured is measured by infrared thermography, There is disclosed a stress measurement method for obtaining a stress distribution based on temperature variations. In Patent Document 1, after measuring the initial temperature of the measurement object, repeated load fluctuation is caused, and a first cycle including a first one cycle in a cycle of the load fluctuation and a second cycle including a second cycle Two cycles are set, and the first average temperature in the first cycle and the second average temperature in the second cycle are obtained. Then, using the temperature characteristics determined from the initial temperature, the first average temperature, and the second average temperature, the temperature distribution measured by infrared thermography is corrected, and the stress distribution is determined from the corrected temperature distribution.

JP 2012-103124 A

In the stress measurement method described in Patent Document 1, when cyclic load fluctuation is caused (when cyclic load is applied), the measurement object has (periodical) temperature fluctuation corresponding to load fluctuation. Although it generate | occur | produces, the whole temperature of a measurement object will rise gradually according to progress of time from the start time of load fluctuation. The temperature rise is corrected to obtain a more accurate temperature distribution and a more accurate stress distribution. In addition, when calculating | requiring the stress of each position from the temperature fluctuation amount of each position in temperature distribution, it is generally calculated | required from the following (Formula 1). In Equation (1), ΔT is the amount of temperature change, k is the material constant (thermoelastic coefficient) specific to the material constituting the measurement object, T is the absolute temperature of the material, and Δσ is the amount of stress change .
ΔT = −kTΔσ (Expression 1)

  The above (Equation 1) is an equation that holds under the adiabatic condition. However, in actuality, it is impossible to make each position (each position to which stress is applied) of the object to be measured adiabatically, and heat propagates to the periphery to generate heat loss. Therefore, the measured temperature fluctuation is lower than the actual temperature fluctuation by the amount of heat loss. That is, the calculated stress fluctuation amount is lower than the actual stress fluctuation amount.

  The present invention has been made in view of such a point, and measures the temperature distribution using infrared thermography while periodically applying a load to the measurement object, and measures each of the measurement objects based on the temperature distribution. Stress measurement apparatus and stress measurement method capable of obtaining more accurate temperature variation and more accurate stress distribution in consideration of heat loss in a stress measurement apparatus for obtaining stress distribution from temperature variation of position Intended to be provided.

  In order to solve the above problems, according to a first aspect of the present invention, there is provided a load applying device for applying a load that periodically changes to a measurement object of stress, and the load application device applies the load to the measurement object. The temperature measurement device for measuring the temperature distribution of the surface of the measurement object using infrared thermography while giving the above, the load applied from the load application device, and the temperature distribution by the temperature measurement device. In a stress measuring device having a computing device for obtaining a stress distribution on the surface of the measurement object, the computing device is characterized in that the temperature fluctuation of each position of the surface of the measurement object is based on the temperature distribution by the temperature measuring device. Heat loss due to diffusion of heat on the surface of the object to be measured according to the temperature fluctuation computing unit for obtaining the amount and the period or frequency of the load applied from the load applying device; A heat loss calculation unit for obtaining heat diffusion loss information, a correction temperature change amount calculation unit for obtaining a correction temperature change amount obtained by correcting the temperature change amount based on the heat diffusion loss information, and And a stress calculation unit for obtaining a stress distribution on the surface of the measurement object according to the load.

  A second invention of the present invention is the stress measurement device according to the first invention, wherein the temperature correction characteristic is stored in the arithmetic device, and the temperature correction characteristic is caused by the load. The thermal diffusion loss information corresponding to area-related information on the size of a stress generation area which is an area in which stress is generated and the period or frequency of the load is included, and the arithmetic device is configured to The heat loss calculation unit extracts the stress generation area, which is an area having a large temperature fluctuation compared to the surroundings in the temperature distribution, and the extracted area related information of the stress generation area and the period of the load Or, based on the frequency and the temperature correction characteristic, the generation area thermal diffusion loss information which is the thermal diffusion loss information corresponding to the stress generation area is determined, and the correction temperature variation calculation unit calculates the stress generation area Before The variation with temperature, on the basis of the said generation region thermal diffusion loss information corresponding to the stress generating areas to correct, obtaining the correction temperature variation in the stress generated region, a stress measuring apparatus.

  Next, a third invention of the present invention is the stress measurement device according to the second invention, wherein m is an integer of 1 or more, and the temperature correction characteristic includes m regions extending from the stress generation region. The thermal diffusion loss information corresponding to first to mth peripheral related information regarding the width of each of the first to mth stress peripheral areas, and the period or frequency of the load; The arithmetic unit extracts the first to m-th stress peripheral regions in the heat loss arithmetic unit, and extracts the first to m-th corresponding to the extracted first to m-th stress peripheral regions. The first to m-th heat diffusion loss information corresponding to the 1st to m-th stress peripheral regions on the basis of peripheral related information, the period or frequency of the load, and the temperature correction characteristic. The thermal diffusion loss information is obtained, and the first to m-th The respective temperature fluctuation amounts in the force peripheral region are corrected on the basis of the first to m th thermal diffusion loss information corresponding to the first to m th stress peripheral regions, respectively. It is a stress measurement device which calculates | requires each said correction | amendment temperature fluctuation amount of the said stress periphery area | region.

   Next, according to a fourth aspect of the present invention, in the stress measurement device according to the third aspect, the first to m-th stress peripheral regions extend concentrically with respect to the stress generation region. It is a stress measurement device which is an area of individual donuts.

  Next, according to a fifth aspect of the present invention, there is provided the stress measurement device according to any one of the first to fourth aspects, wherein the arithmetic device comprises the temperature fluctuation amount calculation unit. It is a stress measurement device which calculates the said temperature fluctuation amount of each position on the surface of the said measurement object using lock-in processing based on the load given from the load giving device and the temperature distribution.

  Next, according to a sixth aspect of the present invention, the temperature of the surface of the measurement object is measured using infrared thermography while applying a load that periodically changes to the measurement object of stress using a load applying device. A stress measurement method of measuring a distribution and determining a stress distribution of a surface of the measurement object based on the applied load and the measured temperature distribution using an arithmetic device, the arithmetic device being used The temperature fluctuation amount calculating step for obtaining the temperature fluctuation amount of each position of the surface of the measurement object based on the temperature distribution, and the measurement according to the cycle or frequency of the load using the arithmetic device A heat loss calculating step for obtaining heat diffusion loss information on heat loss due to heat diffusion on the surface of the object, and the temperature change amount corrected based on the heat diffusion loss information using the arithmetic device, a corrected temperature A corrected temperature fluctuation amount calculating step for obtaining a fluctuation amount; and a stress calculating step for calculating a stress distribution of the surface of the measurement object according to the load based on the corrected temperature fluctuation amount using the arithmetic device. It is a stress measurement method.

  A seventh invention of the present invention is the stress measurement method according to the sixth invention, wherein the temperature correction characteristic is stored in the arithmetic device, and the temperature correction characteristic is caused by the load. The heat diffusion loss information corresponding to the region related information on the width of the stress generation region which is a region in which stress is generated and the cycle or frequency of the load is included, and in the heat loss calculating step Extracting the stress generation area which is an area having a large temperature fluctuation compared to the surroundings in the temperature distribution, the area related information of the stress generation area extracted, the period or frequency of the load, and the temperature The thermal diffusion loss information as the thermal diffusion loss information corresponding to the stress generation area is determined based on the correction characteristic, and the correction temperature fluctuation amount calculating step calculates the thermal diffusion loss information in the stress generation area. The temperature variation, the stress is corrected on the basis of the generation region thermal diffusion loss information corresponding to the generating region, obtaining the correction temperature variation in the stress generated region, a stress measurement method.

  An eighth invention of the present invention is the stress measurement method according to the seventh invention, wherein m is an integer of 1 or more, and the temperature correction characteristics are m areas extending from the stress generation area. The thermal diffusion loss information corresponding to first to mth peripheral related information regarding the width of each of the first to mth stress peripheral areas, and the period or frequency of the load; In the heat loss calculating step, first to m-th peripheral related information extracted, and extracted first to m-th peripheral related information corresponding to the extracted first to m-th stress peripheral region; Based on the period or frequency of the load and the temperature correction characteristic, the first to m th thermal diffusion loss information corresponding to the 1 st to m th stress peripheral region is determined The correction temperature variation calculation step, the first to the m-th The respective temperature fluctuation amounts in the stress peripheral region are corrected based on the first to m th thermal diffusion loss information corresponding to the first to m th stress peripheral regions, respectively. In the stress measuring method, the corrected temperature fluctuation amount of each of the stress peripheral region is calculated.

   Next, according to a ninth aspect of the present invention, in the stress measurement method according to the eighth aspect, the first to m-th stress peripheral regions extend concentrically with respect to the stress generation region. It is a stress measurement method which is an area of individual donuts.

  Next, a tenth invention of the present invention is the stress measurement method according to any one of the sixth invention to the ninth invention, wherein the temperature fluctuation amount calculation step is performed on the measurement object. It is a stress measurement method which calculates | requires the said temperature fluctuation amount of each position of the surface of the said measurement object using a lock-in process based on the said load and the said temperature distribution.

  According to the first invention and the sixth invention, the thermal diffusion loss information on the surface of the measurement object is determined according to the cycle or frequency of the load, and the temperature fluctuation amount is corrected based on the thermal diffusion loss information. To obtain the corrected temperature fluctuation amount. Then, the stress distribution is determined based on the corrected temperature fluctuation amount. In this way, in a stress measurement device that measures the temperature distribution using infrared thermography while applying cyclical load to the measurement object, and obtains the stress distribution from the temperature fluctuation amount of each position of the measurement object based on the temperature distribution, In consideration of heat loss, more accurate temperature variation can be determined, and more accurate stress distribution can be determined.

  According to the second invention and the seventh invention, the temperature correction characteristic having the thermal diffusion loss information corresponding to the extracted region related information of the stress generation region and the period or frequency of the load is stored in advance. Thus, appropriate heat diffusion loss information in the stress generation region can be obtained. Therefore, it is possible to appropriately determine the correction temperature fluctuation amount in the stress generation region, and to obtain a more accurate stress distribution in the stress generation region relatively easily.

  According to the third invention and the eighth invention, it is possible to obtain appropriate heat diffusion loss information about the stress peripheral area around the stress generation area as in the stress generation area. Therefore, it is possible to appropriately determine the correction temperature fluctuation amount in the stress peripheral region, and to obtain a more accurate stress distribution in the stress peripheral region relatively easily.

  According to the fourth invention and the ninth invention, the position and the shape of the stress peripheral area can be appropriately determined, and the correction temperature fluctuation amount of each stress peripheral area can be appropriately determined.

  According to the fifth invention and the tenth invention, by using the lock-in process, it is possible to improve the temperature resolution and obtain a temperature fluctuation amount with higher resolution, and a stress distribution with higher resolution. You can get it. Therefore, more accurate stress distribution can be determined.

It is a figure explaining the whole structure of a stress measurement device. FIG. 1 is a view for explaining an example of the internal configuration of a computing device in a stress measurement device. It is a flowchart explaining the example of the processing procedure of an arithmetic unit. It is a figure explaining the example of the load which changes to a measurement object from a load giving device, and which changes periodically. It is a figure explaining an example of temperature distribution information acquired with a temperature measurement device. It is a figure explaining the example of the temperature fluctuation amount corresponding to each stress generation area | region and its surrounding pixel. It is a figure explaining the example of a temperature correction characteristic. It is a figure explaining the example which extracts the stress generating area in a measurement subject. It is the figure seen from the IX arrow direction in FIG. 8, and is a figure explaining the example of a stress generation area | region. It is a figure explaining the load given to the measurement object, the example of the temperature fluctuation amount in the predetermined position in the stress generating area of the measurement object, and the correction temperature fluctuation amount. FIG. 8 is a diagram for explaining an example of a corrected temperature fluctuation amount corresponding to a stress generation region and each pixel around the stress generation region. It is a figure explaining the example of the stress generation area | region and the stress corresponding to each pixel of the periphery. It is a figure explaining the example of stress distribution of a measurement subject.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the present embodiment, an example in which the constant velocity joint 80 is used as the measurement object will be described, but the measurement object is not limited to the constant velocity joint, and various objects can be used as the measurement object.

● [Overall configuration of stress measuring device 1 (FIG. 1) and internal configuration of arithmetic device (FIG. 2)]
FIG. 1 shows an example of the overall configuration of a stress measuring device 1 according to the present invention and an appearance of a constant velocity joint 80 which is an object to be measured. The stress measurement device 1 includes a load application device 10, a temperature measurement device 20, an arithmetic device 40, and the like.

  First, the configuration of a constant velocity joint 80 which is an example of a measurement object will be described. The constant velocity joint 80 described in the present embodiment is a so-called fixed constant velocity joint, and has an outer race 81, a ball cage 82, an inner race 83, a ball 84, an outer shaft 85, and an inner shaft 86. .

  The outer race 81 has a hemispherical shape in which the inside is hollow, and six guide grooves along the longitudinal direction of the outer shaft 85 are formed on the inner wall. Further, an outer shaft hole for inserting and fixing the outer shaft 85 is formed in the outer race 81. In the present embodiment, a stress distribution which is a distribution of stress generated on the surface of the outer race 81 is determined. Moreover, in order to make the emissivity from the surface of the outer race 81 about 1.0 in temperature measurement, it is preferable that the matte black coating (black body coating) is carried out.

  The inner race 83 has a spherical shape, and six guide grooves along the longitudinal direction of the inner shaft 86 are formed on the outer peripheral surface, and the inner race 83 is accommodated in the outer race 81. Further, in the inner race 83, an inner shaft hole for inserting and fixing the inner shaft 86 is formed.

  The balls 84 are disposed between the guide grooves of the inner wall of the outer race 81 and the guide grooves formed on the outer peripheral surface of the inner race 83, and are in contact with the respective guide grooves. Further, between the outer peripheral surface of the inner race 83 and the inner wall of the outer race 81, a ball cage 82 for holding each ball 84 is provided. The ball cage 82 has a spherical plate shape, and holes are formed at positions corresponding to the balls 84.

  The outer shaft 85 is inserted into and fixed to an outer shaft hole formed in the outer race 81. The inner shaft 86 is inserted into and fixed to an inner shaft hole formed in the inner race 83. The inner shaft 86 transmits rotational power to the inner race 83 when rotational power around the inner shaft axis 86J is input. When the rotational power is transmitted to the inner race 83, the rotational power of the inner race 83 is transmitted to the outer race 81 via the ball 84 to rotate the outer shaft 85 around the outer shaft axis 85J.

  The load applying device 10 swings the inner shaft 86 to change periodically such that the inclination angle θ of the inner shaft axis 86J with respect to the outer shaft axis 85J changes within a range of 0 degrees to a predetermined angle ( Load)). This load is given to repeat between zero load and maximum load Fmax at a predetermined cycle (see FIG. 4). In the zero load state, the outer shaft axis 85J and the inner shaft axis 86J coincide with each other, and at the maximum load Fmax, the inclination angle θ of the inner shaft axis 86J with respect to the outer shaft axis 85J is maximum. The maximum load Fmax is set to an appropriate value from the load acquired from the constant velocity joint 80 attached to the actual vehicle, the load obtained by simulation, and the like. Also, for example, when the load frequency f [Hz], the maximum load Fmax [MPa], and the start of operation are instructed from the arithmetic device 40, the load application device 10 periodically changes from zero load to the maximum load Fmax. Load is applied to the constant velocity joint 80 at a frequency f [Hz] (see FIG. 4). Then, the load application device 10 outputs a load signal (see FIG. 4) regarding the magnitude of the load which is fluctuated with the passage of time to the arithmetic device 40.

  The temperature measurement device 20 is, for example, an infrared camera, and measures the temperature distribution on the surface of the outer race 81 (object to be measured) of the constant velocity joint 80 using infrared thermography. For example, the temperature measurement device 20 has a plurality of pixels arranged in a two-dimensional manner, and creates temperature distribution images (see FIG. 5) in which the temperature information is made to correspond to each pixel one after another. Are output to the arithmetic unit 40 one after another. Further, the temperature measuring device 20 may receive, for example, the imaging speed (200 fps), the imaging time, and the instructed imaging speed at the instructed imaging speed when instructed to start the operation from the arithmetic device 40, for example. In the meantime, the temperature distribution image is created one after another, and the created temperature distribution image is output to the computing device 40. The “temperature distribution image” corresponds to the “temperature distribution”.

  The arithmetic device 40 is, for example, a personal computer, and includes arithmetic means such as a CPU. Then, a load signal is input from the load application device 10 to the arithmetic device 40, and a temperature distribution image is input from the temperature measurement device 20. Then, the computing device 40 obtains and displays the stress distribution of the constant velocity joint 80 (measurement object) based on the load signal and the temperature distribution image. Although FIG. 1 shows an example in which the computing device 40 has (includes) a lock-in function for performing so-called lock-in processing, the lock-in device for performing lock-in processing It may be provided outside. In the description of the present embodiment, an example in which the function of lock-in processing is included in the arithmetic device 40 will be described. The lock-in process is an existing process, externally applies load fluctuation (load fluctuation), calculates only the temperature change synchronized with the load signal, and eliminates other irregular ambient temperature changes. It is a thing. By using this lock-in process, for example, even in the case of a temperature distribution image measured by an infrared camera, the temperature resolution can be made about 0.0001 [° C.]. For example, in the case of a lock-in amplifier having an existing lock-in function, two of a measurement signal (in this case, a temperature distribution image) and a reference signal (in this case, a periodically repeating load signal) are input Multiplication is performed by a Phase Sensitive Detector, and then an LPF (Low Pass Filter) is used to obtain an output signal having an intensity component of a target signal (in this case, a signal of a temperature fluctuation amount). A signal (the target signal) having the same frequency as the reference signal is converted to a direct current component by multiplication with the PSD and extracted through the LPF. Also, noise is removed by the LPF in order to retain frequency components.

  In addition, as shown in FIG. 2, the arithmetic device 40 is, as shown in FIG. 2, a load application device drive instruction unit 41A, a temperature measurement device drive instruction unit 41B, an information acquisition unit 41C, a temperature fluctuation amount operation unit 41D, a heat loss operation unit 41E, and a correction temperature It has a fluctuation amount calculation unit 41F, a stress calculation unit 41G, an input unit 42A (a keyboard, a mouse, etc.), a display unit 42B (a liquid crystal monitor, etc.), a storage unit 42C (Hard Disk Drive, etc.) and the like.

[[Processing procedure of the computing device 40 (FIG. 3) and outline of each processing (FIG. 4 to 13)]]
Arithmetic device 40 starts the process shown in the flowchart of FIG. 3 when instructed by the operator to start the operation.

  In step S10, the computing device 40 outputs operation start information to the load applying device 10, causes the constant velocity joint 80 to apply a periodically fluctuating load from the load applying device 10, and gives the state of the applied load. The load signal shown is output, and the process proceeds to step S20. For example, the operation start information to the load application device 10 includes the frequency f [Hz] of the load input from the operator, the maximum load Fmax [Mpa], a command for starting the operation, and the like. The computing means (CPU) of the computing device 40 executing this step S10 functions as a load applying device drive instructing unit 41A shown in FIG.

  In step S20, the arithmetic device 40 outputs setting information to the temperature measurement device 20, performs setting of the temperature measurement device 20, and proceeds to step S30. For example, the setting information for the temperature measurement device 20 includes a shooting speed (200 [fps] or the like), a shooting time, and the like input from the operator.

  In step S30, the arithmetic device 40 acquires a load signal as shown in the example of FIG. 4 from the load application device 10 in real time. FIG. 4 shows an example in which the load signal input to the arithmetic unit 40 is graphed, and at a frequency f [Hz], the load from zero load to the maximum load Fmax [MPa] is constant velocity joint 80 It shows that it is given to. Then, the arithmetic device 40 instructs the operation of the temperature measurement device 20 in synchronization with the phase of the load signal. For example, when it is detected that the phase of the acquired load signal is a predetermined phase, the arithmetic device 40 outputs the operation information to the temperature measurement device 20. The operation information includes a command for generating a temperature distribution image at a set imaging speed and for a set time, and outputting the generated temperature distribution image to the arithmetic device 40. When the arithmetic device 40 acquires a temperature distribution image for a predetermined time or a predetermined cycle, the processing proceeds to step S40. FIG. 5 shows temperature distribution images of time [t1] (load = 0), time [t2] (load = F1), time [t3] (load = Fmax) in FIG. An example is shown, where darker parts indicate higher temperatures. The computing means (CPU) of the computing device 40 executing steps S20 and S30 functions as a temperature measurement device drive instruction unit 41B shown in FIG. The computing means (CPU) of the computing device 40 executing step S30 functions as an information acquisition unit 41C (see FIG. 2) for acquiring load signals and temperature distribution information.

  In step S40, the arithmetic unit 40 obtains the temperature fluctuation amount based on the temperature distribution image using lock-in processing, and proceeds to step S60. In the temperature distribution image, temperature information is stored corresponding to a plurality of pixels arranged in a two-dimensional manner. The arithmetic unit 40 uses lock-in processing to obtain minute temperature fluctuations excluding noise components, such as the influence of environmental temperature and the influence of frictional heat, corresponding to each pixel. Then, the arithmetic unit 40 obtains the temperature fluctuation amount corresponding to each pixel (that is, corresponding to the position of the surface of the constant velocity joint corresponding to each pixel). Thereby, the resolution of the infrared thermography is improved by an order of magnitude, the resolution is high, and more accurate temperature fluctuation is determined. FIG. 6 shows images of the regions A1 to A3 in FIG. 5 and surrounding pixels, and an example of the temperature variation obtained corresponding to each pixel. The amount of temperature change is stored in correspondence with each of the pixels G (u, v) arranged in a two-dimensional manner. FIG. 6 shows that, for example, the amount of temperature change stored corresponding to the pixel G (u5, v5) in the area A1 is Δt [G (u5, v5)]. The process of step S40 corresponds to a temperature fluctuation calculation step of calculating the temperature fluctuation based on the temperature distribution image. The computing means (CPU) of the computing device 40 executing step S40 functions as a temperature fluctuation amount computing unit 41D shown in FIG.

In step S60, the arithmetic unit 40 extracts a stress generation area which is a circular area having a large amount of temperature fluctuation in the temperature distribution image compared to the surroundings. In the example of FIG. 6, a region A1 in which the amount of temperature fluctuation is larger than that of the surroundings is extracted as a stress generation region. The example of FIG. 6 is an image for explanation, and although the area A1 is not circular because it is composed of four pixels, the area A1 is actually composed of a large number of pixels and is circular. Become. In addition, although the example of the following (1), (2), and (3) is shown as a method of extracting the area | region where temperature variation is large compared with circumference | surroundings, it is not limited to this example.
(1) A region including a pixel having a temperature variation amount equal to or more than the appropriately set first threshold value is extracted as a stress generation region.
(2) As shown in the example of FIG. 5, areas B1, B2 and B3 including the ball 84 are set in advance, and the maximum temperature fluctuation amount ΔTmax is determined in each of the areas B1, B2 and B3. Then, for example, a region including a pixel having a temperature fluctuation amount of 0.8 * ΔTmax or more is extracted as a stress generation region.
(3) As shown in the example of FIG. 8, the stress generation region is the contact surface S between the ball 84 and the outer race 81. As shown in FIG. 9, the ball 84 is in contact with the inner wall of the outer race 81. Assuming that this contact surface is S1, the contact surface S shown in FIG. 8 has the contact surface S1 shown in FIG. It is a plane projected on the surface of 81. The contact surface S shown in FIG. 8 can be measured in advance. Therefore, the area of the contact surface S measured in advance is extracted as a stress generation area.

  The arithmetic unit 40 corresponds to the stress generation area based on the area related information on the width of the stress generation area, the frequency (or period) of the load, and the temperature correction characteristic stored in advance in the storage means. The generation area heat diffusion loss information which is the heat diffusion loss information is determined. In addition, the stress generation area | region extracted in said procedure is circular, and area | region relevant information is a diameter of a circular stress generation area | region, for example.

  The temperature correction characteristic is the characteristic shown in the example of FIG. 7, the horizontal axis is the frequency of the load, and the vertical axis is the relative temperature (heat diffusion loss information, in this case, a value of 0 to 1.0). It is a characteristic unique to the material of the object. “Relative temperature” indicates a ratio of how much the temperature is reduced by the loss of heat due to the diffusion of heat actually generated to the ideal adiabatic state. For example, when the area related information is “diameter D1” and the load frequency is “f [Hz]”, in the example of FIG. 7, the thermal diffusion loss information which is the relative temperature (generation area) is K1 (D1, f) It can be asked that there is. In this case, the arithmetic unit 40 determines that the heat generation area heat diffusion loss information corresponding to the stress generation area is K1 (D1, f), and proceeds to step S65.

In step S65, the arithmetic unit 40 corrects the temperature fluctuation amount of the stress generation region based on the heat generation loss information of the generation region, obtains the correction temperature fluctuation amount of the stress generation region, and proceeds to step S70. For example, in the example of FIG. 6, the temperature variation of the pixel G (u5, v5) in the stress generation area (area A1) is .DELTA.t [G (u5, v5)], and the generation area thermal diffusion information is K1 ( In the case of D1, f), assuming that the correction temperature fluctuation amount is ΔT [G (u5, v5)], the following (Expression 2) is satisfied. The corrected temperature fluctuation amount ΔT [G (u5, v5)] can be obtained by (Expression 3) which rearranges this (Expression 2). Arithmetic unit 40 obtains a corrected temperature change amount obtained by correcting the temperature change amount for each pixel in the stress generation region. The relationship between the load, the temperature fluctuation amount, and the correction temperature fluctuation amount is as shown in FIG. Fluctuations in the + (positive) direction in the load indicate a pull, and during pull the temperature fluctuates to the falling side. In addition, fluctuation in the negative (-) direction in the load indicates compression, and during compression, it fluctuates to the side where the temperature rises.
ΔT [G (u5, v5)] * K1 (D1, f) = Δt [G (u5, v5)] (Expression 2)
ΔT [G (u5, v5)] = Δt [G (u5, v5)] * (1 / K1 (D1, f)) (Expression 3)

Note that the temperature correction characteristic shown in FIG. 7 may be created from, for example, the following (Equation 4), (Equation 5), (Equation 6), or may be created using simulation etc. Good. In equation (4), c is the specific heat of the object to be measured, ρ is the density of the object to be measured, (∂u / ∂t) is the time partial derivative of temperature, k is the thermal conductivity of the object to be measured, r is The radius of energy (in this case, the radius of the contact surface between the ball and the outer race), (∂ ² u / ∂r ² ) is the acceleration at which the temperature spreads radially, and (∂u / ∂r) is the temperature The radially spreading velocity, q, is the input energy. Further, in (Equation 5) and (Equation 6), q is the input energy, r is the radius giving the energy (in this case, the radius of the contact surface between the ball and the outer race), b is the size of the energy, a is The diameter of the circular surface giving energy, ω = 2πf (f is the loading frequency). In the present embodiment, although the input energy q is in the form of Asin ωt, the input energy q is not limited to the form of Asin ωt, and various types of input energy can be given. For example, the input energy q may be given in a Gaussian distribution.
cρ (∂u / ∂t) -k [ (∂ 2 u / ∂r 2) + (1 / r) (∂u / ∂r)] = q (r, t) ( Equation 4)
q (r, t) = [(− (b / a) r + b) sin ωt (where 0 ≦ ωt ≦ π) (Equation 5)
q (r, t) = 0 (where π <ωt) (Equation 6)

In step S70, the arithmetic unit 40 extracts first to m-th stress peripheral regions which are m doughnut-shaped regions concentrically extending with respect to the stress generation region. Here, m is an integer of 1 or more. FIG. 6 shows an example in which m is set to 2 and shows an example in which the region A2 is extracted as a first stress peripheral region and the region A3 is extracted as a second stress peripheral region. Hereinafter, an example in which m is set to 2 will be described. The example of FIG. 6 is an image for explanation, and although both the area A2 and the area A3 are not circular, an area A1 and an area A2 are actually configured by a large number of pixels and become circular. In addition, although the example of the following (a) and (b) is shown as a method of determining the diameter of area | region A2 and A3 which extend concentrically with respect to a stress generation area | region (area A1 in the example of FIG. 6), this example It is not limited to
(A) The first threshold, the second threshold, and the third threshold (first threshold> second threshold> third threshold (first threshold>...> M + 1th threshold)) are appropriately set. As described above, the region including the pixel having the temperature fluctuation amount equal to or more than the first threshold is extracted as the stress generation region (region A1). An area including a pixel having a temperature fluctuation amount smaller than the first threshold and equal to or larger than the second threshold is extracted as a first stress peripheral area (area A2). A region including a pixel having a temperature fluctuation amount smaller than the second threshold and equal to or larger than the third threshold is extracted as a second stress peripheral region (region A3).
(B) A first stress peripheral region (a region having a donut shape of concentric inner diameter D1 + ΔDa (ΔDa is appropriately set) and an inner diameter D1 with respect to a circular stress generation region (region A1) having a diameter D1 Extract as A2). Similarly, a doughnut-shaped area having an outer diameter D1 + ΔDa + ΔDb (ΔDb is appropriately set) and an inner diameter D1 + ΔDa is extracted as a second stress peripheral area (area A2) (m donut-shaped stress peripheral areas are extracted).

  The computing device 40 stores first to second (m-th) peripheral related information related to the width of the first to second (m-th) stress peripheral area, the frequency (or period) of the load, and storage means in advance. The first to second (mth) thermal diffusion loss information, which is the thermal diffusion loss information corresponding to the first to second (mth) stress peripheral region, based on the temperature correction characteristics stored in Ask for The first and second (m-th) stress peripheral regions extracted according to the above procedure are donut-shaped, and, for example, the first peripheral related information is the outer diameter of the first stress peripheral region (region A2) The second peripheral related information is the outer diameter of the second stress peripheral region (region A3).

  Since both the stress generation region and the stress peripheral region are part of the outer race 81 of the same material, the temperature correction characteristics are the same as the temperature correction characteristics shown in the example of FIG. 7 described in the stress generation region. For example, when the first peripheral related information is "outside diameter D2", the outside diameter D2 is considered as "diameter D2", and when the load frequency is "f [Hz]", in the example of FIG. The first heat diffusion loss information can be determined as K2 (D2, f). When the second peripheral related information is "outside diameter D3", the outside diameter D3 is considered as "diameter D3", and when the load frequency is "f [Hz]", the relative temperature is in the example of FIG. The second heat diffusion loss information can be determined as K3 (D3, f). In this case, the first to second (mth) thermal diffusion loss information corresponding to the first to second (mth) stress peripheral regions are K2 (D2, f), K3 ( Since it is D3, f), the process proceeds to step S75.

  The processes of steps S60 and S70 correspond to a heat loss calculation step of obtaining heat diffusion loss information according to the frequency (or period) of the load. The computing means (CPU) of the computing device 40 executing steps S60 and S70 functions as the heat loss computing unit 41E shown in FIG.

In step S75, the arithmetic unit 40 corrects each temperature fluctuation amount of the first to second (m-th) stress peripheral region based on the first to second (m-th) thermal diffusion loss information. The corrected temperature fluctuation amount of each of the first to second (m-th) stress peripheral regions is determined, and the process proceeds to step S80. For example, in the example of FIG. 6, the temperature variation of the pixel G (u3, v3) in the first stress peripheral region (region A2) is Δt [G (u3, v3)], and the first thermal diffusion is When the information is K2 (D2, f), the following (Equation 7) is satisfied, assuming that the correction temperature fluctuation amount is ΔT [G (u3, v3)]. The corrected temperature fluctuation amount ΔT [G (u3, v3)] can be obtained by (Expression 8) which rearranges (Expression 7). Further, for example, in the example of FIG. 6, the temperature variation of the pixel G (u7, v6) in the second stress peripheral region (region A3) is Δt [G (u7, v6)], and the second In the case where the thermal diffusion information is K3 (D3, f), assuming that the correction temperature fluctuation amount is ΔT [G (u7, v6)], the following (Expression 9) is satisfied. The corrected temperature fluctuation amount ΔT [G (u7, v6)] can be obtained by (Expression 10) in which this (Expression 9) is arranged. Arithmetic unit 40 obtains a corrected temperature change amount obtained by correcting the temperature change amount for each pixel in the first and second stress peripheral regions. FIG. 11 shows an example of the corrected temperature change amount obtained by correcting the temperature change amount shown in FIG.
ΔT [G (u3, v3)] * K2 (D2, f) = Δt [G (u3, v3)] (Equation 7)
ΔT [G (u3, v3)] = Δt [G (u3, v3)] * (1 / K2 (D2, f)) (Equation 8)
ΔT [G (u7, v6)] * K3 (D3, f) = Δt [G (u7, v6)] (Equation 9)
ΔT [G (u7, v6)] = Δt [G (u7, v6)] * (1 / K3 (D3, f)) (Equation 10)

  The processes of steps S65 and S75 correspond to a correction temperature fluctuation amount calculation step of correcting the temperature fluctuation amount with the thermal diffusion loss information to obtain a correction temperature fluctuation amount. The computing means (CPU) of the computing device 40 executing steps S65 and S75 functions as a correction temperature fluctuation amount computing unit 41F shown in FIG.

In step S80, the arithmetic unit 40 obtains a stress distribution based on the corrected temperature fluctuation amount, and proceeds to step S90. In addition, about the stress generation | occurence | production area | region and stress periphery area | region, as above-mentioned, each corrected temperature fluctuation amount corresponding to each pixel was calculated | required. However, since the region excluding the stress generation region and the stress peripheral region is originally a region where there is almost no temperature variation, there is no need to particularly correct the temperature variation, and temperature variation may be regarded as the correction temperature variation. . The arithmetic unit 40 obtains the stress fluctuation amount Δσ corresponding to the pixel using the following (Equation 11), using the correction temperature fluctuation amount ΔT corresponding to the pixel for each pixel. Since the load is given between zero load and the maximum load Fmax, Δσ is a variation from zero. Therefore, Δσ corresponding to a pixel is the maximum stress corresponding to that pixel. In equation (11), ΔT is a correction temperature fluctuation amount, k is a material constant (thermoelastic coefficient) inherent to the material constituting the measurement object, T is an absolute temperature of the material, and Δσ is a stress fluctuation amount. is there. FIG. 12 shows an example of the stress fluctuation (maximum stress) obtained from the corrected temperature fluctuation shown in FIG.
ΔT = −kTΔσ (Equation 11)

  The process of step S80 corresponds to a stress calculation step of obtaining a stress distribution based on the corrected temperature fluctuation amount. The computing means (CPU) of the computing device 40 executing step S80 functions as a stress computing unit 41G shown in FIG.

  In step S90, the arithmetic unit 40 displays the stress fluctuation amount Δσ (that is, the maximum stress for each pixel) obtained for each pixel as a stress distribution on the display means, and proceeds to step S95. FIG. 13 shows an example of the stress distribution displayed on the display means of the arithmetic device 40. By confirming this stress distribution, the operator can appropriately determine where the thickness should be increased to ensure the rigidity and where the rigidity is not so required. Therefore, it is possible to contribute to reducing the thickness and reducing the weight of a portion which does not require much rigidity.

  In step S95, the arithmetic device 40 determines the presence / absence of the termination instruction, and when the termination instruction is input (Yes), the processing is terminated, and when the termination instruction is not input (No), the processing returns to step S90. Maintain an indication of stress distribution.

● [Effect of this application]
As described above, the stress measurement device and the stress measurement method described in the present embodiment are more accurate stress distributions obtained from more accurate (corrected) temperature fluctuation amounts in consideration of heat loss. Therefore, the operator can appropriately and more accurately determine where stiffness is required and where stiffness is not required. Also, in the prior art in which the heat loss was not taken into consideration, the temperature fluctuation amount lower than the actual temperature fluctuation amount was measured (the temperature is lowered by the heat loss), so the stress fluctuation amount lower than the actual stress fluctuation amount Was seeking. On the other hand, in the present embodiment, in consideration of the heat loss, the low measured temperature fluctuation amount is corrected to the high side to become the actual temperature fluctuation amount, and the stress is corrected to the high side. Insufficient rigidity against stress can be prevented.

  The structure, configuration, shape, appearance, etc. of the stress measuring device of the present invention, and the processing of the stress measuring method of the present invention, processing procedure, etc. can be variously changed, added, deleted without departing from the scope of the present invention. is there. For example, the temperature distribution image is not limited to the image as shown in the example of FIG. 5, and the stress distribution displayed on the display means is not limited to the example of FIG. Also, the processing procedure is not limited to the flowchart shown in FIG.

  In the description of the present embodiment, an example in which the temperature fluctuation amount, the correction temperature fluctuation amount, and the stress fluctuation amount (stress) are obtained for each individual pixel has been described, but a plurality of pixel groups in which a plurality of adjacent pixels are put together The (average) temperature variation, the (average) corrected temperature variation, and the (average) stress variation (stress) may be determined for each pixel group.

  In the present embodiment, the constant velocity joint 80 has been described as an example of the measurement object, but the stress measurement device and the stress measurement method described in the present embodiment are not limited to the constant velocity joint, and various devices It can be applied to the measurement of stress distribution of

  In the present embodiment, as an example of the first to m-th stress peripheral regions, m donut-shaped regions that extend concentrically with respect to the stress generation region are used. It does not have to be in the form. That is, the first to m-th stress peripheral regions may be m regions extending from the stress generation region, and the position and the shape are not limited.

1 Stress Measurement Device 10 Load Application Device 20 Temperature Measurement Device 40 Arithmetic Device 80 Constant Velocity Joint (Measurement Object)
81 outer race 82 ball cage 83 inner race 84 ball 85 outer shaft 85 J outer shaft axis 86 inner shaft 86 J inner shaft axis A 1 area (stress generation area)
A2 area (area around the first stress)
A3 area (area around the second stress)
G (u, v) pixels

Claims (10)

A load applying device that applies a periodically varying load to a measurement object of stress;
A temperature measurement device that measures the temperature distribution on the surface of the measurement object using infrared thermography while applying the load to the measurement object with the load application device;
An arithmetic device for obtaining a stress distribution on the surface of the measurement object based on the load given from the load application device and the temperature distribution according to the temperature measurement device;
In a stress measuring device having
The arithmetic device is
A temperature fluctuation amount calculation unit which calculates a temperature fluctuation amount at each position of the surface of the measurement object based on the temperature distribution by the temperature measurement device;
A heat loss calculation unit for obtaining heat diffusion loss information on heat loss due to heat diffusion on the surface of the measurement object according to the load cycle or frequency given from the load application device;
A correction temperature fluctuation amount calculation unit for calculating a correction temperature fluctuation amount, in which the temperature fluctuation amount is corrected based on the thermal diffusion loss information;
A stress calculation unit for obtaining a stress distribution on the surface of the measurement object according to the load based on the correction temperature fluctuation amount;
Have
Stress measuring device. The stress measurement device according to claim 1, wherein
A temperature correction characteristic is stored in the arithmetic unit, and the temperature correction characteristic is area related information related to the size of a stress generation area which is an area in which a stress is generated due to the load, a cycle of the load or The heat diffusion loss information corresponding to the frequency,
The arithmetic device is
The heat loss calculation unit extracts the stress generation area, which is an area having a large temperature fluctuation compared to the surroundings in the temperature distribution, and the extracted area related information of the stress generation area and the load Based on the period or frequency and the temperature correction characteristic, generation area heat diffusion loss information, which is the heat diffusion loss information corresponding to the stress generation area, is determined
The correction temperature fluctuation calculation unit corrects the temperature fluctuation amount in the stress generation area based on the heat generation area heat diffusion loss information corresponding to the stress generation area, and the correction temperature fluctuation in the stress generation area. Determine the quantity,
Stress measuring device. The stress measurement device according to claim 2, wherein
Let m be an integer greater than or equal to 1,
The temperature correction characteristic includes first to mth peripheral related information regarding the width of each of the first to mth stress peripheral regions which are m regions extending from the stress generation region, and the period or frequency of the load And the heat diffusion loss information corresponding to
The arithmetic unit is
The heat loss calculation unit extracts the first to m-th stress peripheral regions, and extracts the first to m-th peripheral related information corresponding to the extracted first to m-th stress peripheral regions, and Based on the period or frequency of the load and the temperature correction characteristic, the first to m th thermal diffusion loss information corresponding to the 1 st to m th stress peripheral region is determined ,
In the correction temperature fluctuation amount calculation unit, each of the temperature fluctuation amounts in the first to m-th stress peripheral regions corresponds to each of the first to m-th stress peripheral regions. The correction is made on the basis of the thermal diffusion loss information, and the correction temperature fluctuation amount of each of the first to m-th stress peripheral regions is determined.
Stress measuring device. The stress measurement device according to claim 3, wherein
The first to m-th stress peripheral regions are m donut-shaped regions concentrically extending with respect to the stress generation region,
Stress measuring device. It is a stress measurement device according to any one of claims 1 to 4,
The arithmetic device is
The temperature fluctuation amount calculation unit calculates the temperature fluctuation amount of each position on the surface of the measurement object using lock-in processing based on the load applied from the load application device and the temperature distribution. Ask,
Stress measuring device. Using a load applying device, while applying a cyclically varying load to a measurement object of stress,
Measuring the temperature distribution of the surface of the measurement object using infrared thermography;
A stress measurement method for determining a stress distribution on a surface of the measurement object based on the applied load and the measured temperature distribution using an arithmetic device,
A temperature fluctuation amount calculating step of calculating a temperature fluctuation amount at each position of the surface of the measurement object based on the temperature distribution using the arithmetic device;
A heat loss calculating step of obtaining heat diffusion loss information on heat loss due to heat diffusion on the surface of the measurement object according to the load cycle or frequency using the calculation device;
A corrected temperature fluctuation amount calculating step of calculating a corrected temperature fluctuation amount by correcting the temperature fluctuation amount based on the thermal diffusion loss information using the arithmetic device;
A stress calculation step of obtaining a stress distribution on the surface of the measurement object according to the load based on the corrected temperature fluctuation amount using the calculation device;
Have
Stress measurement method. The stress measurement method according to claim 6, wherein
A temperature correction characteristic is stored in the arithmetic unit, and the temperature correction characteristic is area related information related to the size of a stress generation area which is an area in which a stress is generated due to the load, a cycle of the load or The heat diffusion loss information corresponding to the frequency,
In the heat loss calculating step, the stress generation area, which is an area having a large temperature fluctuation compared to the surroundings in the temperature distribution, is extracted, and the area related information of the stress generation area extracted, and the period of the load Or generating region heat diffusion loss information which is the heat diffusion loss information corresponding to the stress generation region based on a frequency and the temperature correction characteristic,
In the correction temperature change amount calculation step, the temperature change amount in the stress generation area is corrected based on the heat generation area heat diffusion loss information corresponding to the stress generation area, and the correction temperature change amount in the stress generation area Ask for
Stress measurement method. The stress measurement method according to claim 7, wherein
Let m be an integer greater than or equal to 1,
The temperature correction characteristic includes first to mth peripheral related information regarding the width of each of the first to mth stress peripheral regions which are m regions extending from the stress generation region, and the period or frequency of the load And the heat diffusion loss information corresponding to
In the heat loss calculating step, the first to m-th peripheral related information corresponding to the extracted first to m-th stress peripheral region is extracted and the load is extracted. The first to m th thermal diffusion loss information, which is the thermal diffusion loss information corresponding to the 1 st to m th stress peripheral region, is determined based on the period or the frequency of the and the temperature correction characteristic,
In the correction temperature fluctuation amount calculating step, each of the temperature fluctuation amounts in the first to m-th stress peripheral regions corresponds to the first to m-th corresponding to each of the first to m-th stress peripheral regions. The correction is made based on the thermal diffusion loss information, and the correction temperature fluctuation amount of each of the first to m-th stress peripheral regions is obtained.
Stress measurement method. The stress measurement method according to claim 8, wherein
The first to m-th stress peripheral regions are m donut-shaped regions concentrically extending with respect to the stress generation region,
Stress measurement method. The stress measurement method according to any one of claims 6 to 9, wherein
In the temperature variation calculation step, the temperature variation of each position of the surface of the measurement object is determined using lock-in processing based on the load applied to the measurement object and the temperature distribution. ,
Stress measurement method.

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