JP2010261770A - Accumulated fatigue calculation method, and vibration test method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accumulated fatigue calculation method for accurately calculating the accumulated fatigue even when non-Gaussian vibration is applied to a structure, and easily calculating the accumulated fatigue every frequency. <P>SOLUTION: This accumulated fatigue calculation method for calculating the accumulated fatigue occurring in a transportation article P mounted on a vibration environment, includes a first step of measuring time series waveform data of vibration acceleration of the transportation article P obtained by a second acceleration sensor 5, a second step of sequentially extracting amplitude S<SB>i</SB>contributing to the accumulated fatigue of the varying vibration acceleration by a rain flow method based on the time series waveform data of the measured vibration acceleration, a third step of setting frequency f<SB>n</SB>(where, f<SB>n</SB>=1/T<SB>n</SB>) by measuring the width T<SB>n</SB>of the time axis direction for each amplitude S<SB>i</SB>, and a fourth step of calculating the accumulated fatigue occurring in the structure every frequency f<SB>n</SB>based on the amplitude S<SB>i</SB>and generating frequency N<SB>i</SB>for each size. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an accumulated fatigue calculation method for calculating accumulated fatigue occurring in a structure placed in a vibration environment, and the accumulated fatigue calculated method is loaded on a transportation means such as an automobile or a railway vehicle. The present invention relates to a vibration test method for evaluating durability of a transported product such as a structure against vibration.

  Conventionally, the durability of a structure such as cargo or equipment mounted on a transportation means such as a vehicle, railroad, or aircraft is evaluated by conducting a vibration test in advance. As such a vibration test, for example, a method disclosed in Patent Document 1 is known.

  In the vibration test method described in Patent Document 1, vibration generated by a transportation means such as a vehicle during actual transportation is measured in advance, and the structure is vibrated by reproducing this vibration with a vibration testing machine. Then, the power spectral density (PSD) generated in the structure due to the vibration is measured, the measured PSD is divided for each desired frequency band, and vibration waveform data is derived for each frequency band by inverse Fourier transform. Based on the vibration waveform data, the accumulated fatigue accumulated in the structure during actual transportation is calculated for each frequency band. The calculated accumulated fatigue is set as the target accumulated fatigue, and in the vibration test, vibration having a PSD larger than that at the time of actual transportation is applied to the structure until the accumulated fatigue generated in the structure becomes the target accumulated fatigue. By inspecting whether or not the product is damaged, it is predicted whether or not the structure will be damaged during actual transportation.

JP 2005-181195 A

  However, in the vibration test method described in Patent Document 1, the vibration waveform data for each frequency band derived when calculating accumulated fatigue is assumed to be Gaussian vibration whose probability density function is a normal distribution. ing. That is, in Patent Document 1 described above, when calculating the accumulated fatigue of the structure, it is assumed that the distribution of the peak positions of vibration acceleration of each vibration waveform data follows the Rayleigh distribution, using the following formula (1). The accumulated fatigue is calculated. Α is a value specific to the structure, β is accumulated fatigue, f is the expected frequency, σ is the standard deviation of the probability density function for the instantaneous value of vibration acceleration, T is the actual transport time, and Γ is the gamma Each function is shown.

  However, it is recognized that the vibration generated in the transportation means during actual transportation is a non-Gaussian vibration whose probability density function is not necessarily a normal distribution. Specifically, it has been recognized that the kurtosis of a Gaussian vibration shows 3 whereas the actual vibration shows a kurtosis other than 3. Therefore, the accumulated fatigue calculation method according to the conventional method has a problem that the accumulated fatigue cannot be accurately calculated if non-Gaussian vibration is actually applied to the structure.

  In addition, in the vibration test method described in Patent Document 1 described above, vibration waveform data generated in the structure for each predetermined frequency band is derived, and thereafter, accumulated fatigue is calculated based on the vibration waveform data for each frequency band. Therefore, there is also a problem that it takes much time to calculate the accumulated fatigue for each frequency band.

  The present invention has been made by paying attention to the above-described problem, and even when non-Gaussian vibration is applied to the structure, the accumulated fatigue can be accurately calculated, and the accumulated fatigue for each frequency can be calculated. It is an object of the present invention to provide an accumulated fatigue calculation method that can be easily calculated, and a vibration test method using the accumulated fatigue calculation method.

The accumulated fatigue calculation method according to the present invention is for calculating accumulated fatigue occurring in a structure placed in a vibration environment, and is a method for detecting a vibration detection value of a structure obtained by a sensor that detects vibration of the structure. first steps, based on the time-series waveform data of the vibration detected value measured, the second step of extracting a contributing amplitude S _i to accumulated fatigue of the vibration detection value sequentially varying for measuring the time-series waveform data A third step of setting a frequency f _n (where f _n = 1 / T _n ) by measuring a width T _n in the time axis direction for each amplitude S _{i, and} for each frequency f _n And a fourth step of calculating the accumulated fatigue generated in the structure based on the amplitude S _i and the occurrence frequency N _i for each size. According to this fatigue accumulation method, even if the vibration applied to the structure is a non-Gaussian vibration, the accumulated fatigue caused by the vibration can be calculated for each frequency.

In a preferred embodiment of the present invention, in the second step, the peak of the vibration detection value peak position is sequentially extracted to detect the vibration detection value of each peak, and the valley peak is sequentially extracted. Then, after detecting the vibration detection value of each valley peak, the difference between the vibration detection values of the adjacent peak and valley peaks is calculated, and this difference is set as the amplitude S _i of the vibration detection value, In the third step, the time interval between the adjacent peak and valley peaks is measured, and this time interval is set as the width T _{n in the} time axis direction.

In another preferred embodiment of the present invention, in the second step, a peak position of the vibration detection value and a corresponding bottom position are sequentially extracted based on a rainflow method, and the peak position and the peak position are extracted. The difference between the vibration detection values at the bottom position corresponding to is calculated and this difference is set as the amplitude S _i of the vibration detection value. In the third step, the time interval between the corresponding peak position and the bottom position is measured. to and sets the time interval as the width T _n of the time axis direction. As a method for extracting an amplitude S _i of the vibration detection value, range method, such as range pair method, it is possible to use other cycle counting method.

  The vibration generation method according to the present invention is a vibration test method for evaluating the vibration durability of a structure placed on the vibration body, and is applied to the structure based on the vibration conditions of the vibration generated in the vibration body. A test specification setting step for determining a reference vibration condition for vibration, and accumulated fatigue generated in the structure due to vibration of the reference vibration condition are calculated for each frequency by the above-described accumulated fatigue calculation method, and this is referred to as target accumulated fatigue. A reference value acquisition step, and when a desired test time is set and the structure is vibrated for the test time, accumulation for each frequency generated in the structure within the test time calculated in the same manner as the reference value acquisition step A test condition determining step for determining a vibration condition for a vibration test to be applied to the structure so that the fatigue is the target accumulated fatigue; and the test vibration obtained in the test condition determining step. By vibrating structures based on matter and test time, characterized in that it comprises a vibration applying step of determining the presence or absence of breakage of the structure.

  In the above-described configuration of the present invention, examples of the “vibrating body” include transportation means such as vehicles, railroads, and airplanes that transport equipment, parts, cargo, and the like. It is used to evaluate the vibration durability of a transported product, but is not necessarily limited thereto. For example, the present invention can also be applied to evaluate the vibration durability of devices and parts mounted on devices that are constantly subjected to vibration during operation.

  According to this vibration test method, even if the vibration generated in the vibrating body is a non-Gaussian vibration, it is possible to evaluate the vibration durability of the structure with high accuracy according to the actual transportation environment.

A preferred embodiment of the present invention, in the test condition determining step, by setting the phase angle [Phi _k giving the power spectral density and the frequency components f _k for each frequency component f _k of the vibration to be imparted to the structure appropriately The test vibration condition is determined such that the accumulated fatigue at each frequency generated in the structure within the test time becomes the target accumulated fatigue.

Further preferred embodiments of the present invention, in the test condition determining step, a probability density distribution (although the phase difference .DELTA..PHI representing the delay of the phase angle of each frequency component _{f k (ΔΦ = Φ (k} + 1) -Φ k), 0 ≦ ΔΦ ≦ 2π) was appropriately set, and sets the phase angle [Phi _k of each frequency component f _k to calculate the phase difference .DELTA..PHI between each frequency component based on the probability density distribution.

In another preferred embodiment of the present invention, in the test condition determining step, the phase angle Φ _k of each frequency component f _k is set to an angular frequency ω, an initial phase Φ ₀ (0 ≦ Φ ₀ ≦ 2π), Formula expressed by group delay time t _k calculated using normal random number N (μ, σ ² ) based on mean μ and variance σ ² : Φ _{(k + 1)} = Φ _k + t _{(k + 1)} dω It is characterized by setting.

  According to the accumulated fatigue calculation method of the present invention, even if the vibration applied to the structure is non-Gaussian vibration, the accumulated fatigue can be calculated for each frequency. Further, according to the vibration test method of the present invention, even if the vibration generated in the vibrating body is a non-Gaussian vibration, the structure placed on the vibrating body is highly suitable for the actual transportation environment. Accurate evaluation of vibration durability can be performed.

1 is a schematic configuration diagram of a vibration testing machine that performs a vibration testing method of the present invention. It is a flowchart for demonstrating the outline | summary of the vibration test method of this invention. It is a flowchart for demonstrating a test specification setting step. It is a figure which shows typically an example of the transportation route of actual transportation. It is a flowchart for demonstrating a reference value acquisition step. It is vibration waveform data which shows an example of the vibration which arises in transport goods. It is a figure for demonstrating the extraction method of the amplitude by a rainflow method. It is a figure for demonstrating the calculation method of the magnitude | size of an amplitude and the width | variety of a time-axis direction. It is a figure which shows an example of the target accumulation fatigue which arises in transport goods. It is a figure which shows an example of the target accumulation fatigue which arises in the transportation goods of a stacked state. It is a flowchart for demonstrating a test condition determination step. It is the figure which showed the comparative example of real accumulation fatigue and target accumulation fatigue. It is a flowchart which shows 1st Embodiment of step 33 of FIG. It is a figure which shows an example of probability density distribution of a phase difference. It is a flowchart which shows 2nd Embodiment of step 33 of FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The accumulated fatigue calculation method of the present invention is for calculating accumulated fatigue generated in a structure placed in a vibration environment. In addition, the vibration test method of the present invention determines whether or not the transported goods P loaded on transportation means such as vehicles, railways, and airplanes are damaged by vibration during transportation (hereinafter referred to as “actual vibration”). This is for prediction, and is characterized by using the accumulated fatigue calculation method of the present invention. The transported goods P correspond to structures such as precision instruments, for example, and such transported goods P are usually transported together with cushioning materials in a state of being accommodated in a container such as a box. The cushioning material is formed of foamed material, paper, wood, etc., and is disposed between the inner surface of the container and the transported product P.

  FIG. 1 shows a schematic configuration of a vibration test apparatus 1 used in a vibration test method according to an embodiment of the present invention. The vibration testing apparatus 1 controls the vibration table 2 on which the transported product P is placed, the vibration exciter 3 capable of applying vibration with a predetermined acceleration to the vibration table 2, and the operation of the vibration exciter 3. And a control device 10. The transported goods P are arranged on the vibration table 2 while being supported by the buffer material 6.

  Acceleration sensors 4 and 5 for detecting these vibrations are attached to the vibration table 2 and the transportation product P, respectively. Each acceleration sensor 4, 5 outputs the detected vibration acceleration of the vibration table 2 and the transported item P to the control device 10. The second acceleration sensor 5 attached to the transported product P may be attached to a plurality of parts of the transported product P. In addition, when a plurality of transported goods P are stacked, the second acceleration sensor 5 may be attached to each transported goods P stacked.

  In the present embodiment, vibration acceleration is used as the vibration detection value of the transported product P, but other strains, stresses, loads, and the like generated in the transported product P due to vibration can also be used as the vibration detection value.

  The control device 10 includes a display unit 11, an input unit 12, and a memory unit 16 in addition to a CPU 13 that is a main body of control and calculation, a ROM 14 and a RAM 15 that are storage units, and each is connected via a bus 19. Has been. The control device 10 is configured by an information processing device such as a personal computer, for example, and is connected to the first acceleration sensor 4 and the second acceleration sensor 5 via the A / D converter 17 and is also D / A converted. It is connected to the vibration exciter 3 via a device 18.

  The display unit 11 includes a liquid crystal monitor, a CRT monitor, or the like. The input unit 12 includes a mouse, input keys, a touch panel, and the like. The ROM 14 stores various data in addition to the program executed by the CPU 13. The RAM 15 is used for reading and writing data necessary for executing the program.

  The memory unit 16 stores vibration waveform data of actual vibrations measured in advance for each transportation route by various transportation means, a probability density function for vibration acceleration of actual vibrations calculated based on the vibration waveform data, PSD (Power Spectrum Density: Various information such as power spectral density), kurtosis and skewness is stored. Further, input information from the input unit 12, data of vibration detection values by the first acceleration sensor 4 and the second acceleration sensor 5, a data processing method and calculation formula used when calculating accumulated fatigue by the CPU 13, and its calculation Stores various information such as information.

  The CPU 13 generates vibration waveform data of vibration to be reproduced in the vibration test while reading / writing data from / to the RAM 15 according to the program stored in the ROM 14, and applies the vibration waveform data to the vibration exciter 3 to vibrate the vibration table 2. Then, a vibration test is performed on the transported product P, and its durability is evaluated.

  Next, a vibration test method for the transported goods P using the vibration test apparatus 1 will be described. The general flow of the vibration test method of the present embodiment is as shown in the flowchart in FIG. In the figure, ST is an abbreviation for “STEP”.

  First, based on the vibration conditions of actual vibrations that occur in vehicles such as vehicles during actual transportation, a test specification setting step is performed to determine the reference vibration conditions for vibrations to be given to the transported goods P. Generate (step 1).

  Next, by giving vibrations of the reference vibration condition generated in the test specification setting step to the transported goods P, the accumulated fatigue generated in the transported goods P is determined by the accumulated fatigue calculation method of the present invention (details will be described later). A reference value acquisition step for calculating is performed, and a reference value (target accumulated fatigue) to be used for determining the test conditions of the main test is obtained (step 2).

  Then, a desired test time is set, and when the transportation product P is vibrated during this test time, a vibration test applied to the transportation product P so that the accumulated fatigue occurring in the transportation product P becomes the target accumulated fatigue. The test condition determining step for determining the vibration conditions for the test is performed, and the test conditions (the vibration conditions for the test and the test time) of the main test are determined (step 3).

  Finally, based on the test vibration conditions and the test time determined in the test condition determination step, a vibration applying step for vibrating the transported goods P is performed, and the main test is performed (step 4). Hereinafter, each step will be described in detail.

(1) Test specification setting step (Step 1)
The test specification setting step will be described with reference to the flowchart shown in FIG.

First, in step 10, the CPU 13 performs a process of calculating a PSD for each frequency component f _k by performing Fourier transform on vibration waveform data of a certain period of actual vibration generated in the transportation means (for example, vehicle) during actual transportation. This vibration waveform data is obtained, for example, by actually measuring the vibration acceleration of the placement surface (for example, a vehicle bed) of the article to be transported P during actual transportation with a vibration recorder.

  In addition, processing for calculating kurtosis and skewness, which are parameters representing the characteristics of the vibration waveform data, from the vibration waveform data of the actual vibration is performed. Here, kurtosis is a feature quantity that represents the steepness (degree of sharpness) of the frequency distribution of vibration acceleration, and skewness is a feature quantity that represents the asymmetry of the frequency distribution of vibration acceleration. It is a general index used in science. These data are stored in the memory unit 16. In addition, although the vehicle is mentioned here, vibration waveform data of actual vibrations generated in various transportation means (railway, airplane, carriage, etc.) are measured, and PSD, kurtosis, The skewness and the like are calculated and stored in the memory unit 16 for each transportation means.

In the next step 11, the CPU 13 performs processing for calculating the amplitude X _k for each frequency component f _k using the following formula (2) based on the calculated PSD. In the present specification, k is an index to each frequency component.

Next, in step 12, the CPU 13 executes a process of setting the phase angle Φ _k for each frequency component f _k . Here, the kurtosis and the skewness obtained from the vibration waveform data of the actual vibration are set as target values, and the phase of each frequency component f _k is set so that the kurtosis and the skewness of the generated vibration waveform data match the target values. to set the angle Φ _k. The setting of the phase angle [Phi _k for each frequency component _{f k} can be performed by a method the applicant of the present application has proposed in Japanese Patent Application No. 2009-051940. This patent application is incorporated herein by reference.

In step 13, the CPU 13 generates vibration waveform data by performing inverse Fourier transform on each frequency component f _{k in} which the amplitude D _k and the phase angle Φ _k are set, and supplies the vibration waveform data to the transported product P in the next step. Determine vibration conditions for vibration reference.

  According to this test specification setting step, the generated vibration has the same PSD as the actual vibration PSD generated in the transportation means during actual transportation, and the kurtosis and further the distortion are the vibrations of the actual vibration. It almost matches the kurtosis and skewness obtained from the waveform data. Therefore, according to this test specification setting step, the actual vibration (particularly non-Gaussian vibration) generated in the transportation means during actual transportation can be reproduced with high accuracy, and the transportation product P A vibration test can be performed.

In actual transportation, there are few cases in which the transported goods P are transported only by a single transportation means, and the transportation is generally carried over a plurality of transportation means. Therefore, for example, when the transportation route of actual transportation is constituted by a plurality of scenarios a1 to a5 as shown in FIG. 4, the transportation route is expressed as {a ₁ and (a ₂ or a ₃ ) and a _4} expressed in or a _5, based on the vibration waveform data of the actual vibration corresponding to each scenario a1-a5, it generates vibration waveform data which reproduces the real vibration for each scenario a1-a5, by combining these Then, vibration waveform data corresponding to actual transportation is created, and the vibration condition for reference of vibration to be given to the transported product P is determined.

(2) Reference value acquisition step (step 2)
The reference value acquisition step will be described with reference to the flowchart shown in FIG.

  First, in step 20, the CPU 13 vibrates the vibration table 2 based on the vibration waveform data generated in the test specification setting step, and gives a vibration that reproduces the actual vibration to the transported product P. Then, the second acceleration sensor 5 attached to the transported product P measures time-series waveform data of vibration acceleration generated in the transported product P due to this vibration as shown in FIG. When the transported product P is small and the acceleration sensor cannot be directly attached to the transported product P, the vibration acceleration generated in the transported product P by the first acceleration sensor 4 attached to the vibration table 2. The time-series waveform data may be measured.

  Further, when the transported goods P are transported in a stacked state during actual transportation, the transported goods P are actually placed on the vibrating table 2 in a state of being stacked (for example, in a state of being stacked in two stages) The time-series waveform data of the vibration acceleration generated in the transported goods P is measured by the second acceleration sensor 5 for each stacked transported goods P.

In a next step 21, CPU 13, from the time-series waveform data of the vibration acceleration measured shipment P, it performs a process of sequentially extracting contributes amplitude S _i to accumulated fatigue of the vibration acceleration varies.

In this embodiment, as shown in FIG. 7, the amplitude S _i is extracted by the rainflow method. The vibration waveform shown in FIG. 7 is obtained by extracting a part of the vibration waveform shown in FIG. 6, the horizontal axis is vibration acceleration, and the vertical axis is time.

  In the rainflow method, as shown in FIG. 7, assuming a vibration waveform having a vertical axis as a time axis, a roof structure in which this vibration waveform is multiplexed, the base position (peak position) P1 of each roof. Imagine flowing raindrops in the order of mountain and valley from P2,. Raindrops shall flow and stop when the following three conditions are satisfied.

  Raindrops begin to flow in numerical order from the base of the roof and continue to flow down to the lower roof until the stop condition is met (condition 1). In addition, the raindrops falling from the eaves stop when one of the following two stop conditions is satisfied (condition 2). In the case of a rightward flow, it stops when an eaves of another roof appears on the left side from the starting point of raindrops flowing rightward (stop condition 1). On the other hand, in the case of a leftward flow, when the eaves of another roof appear on the right side from the starting point of raindrops flowing leftward, the flow stops (stop condition 2). For example, raindrops flowing from P7 to P8 shown in FIG. 7 stop at P8 because P9 on the left side of P7 appears. Furthermore, if raindrops have already flowed through a part of the roof, the flow stops (condition 3). For example, the flow from P3 to P4 stops at the same lateral position (P2 ') as P2 in order to hit the flow from P1.

As shown in FIG. 7, the CPU 13 extracts positions where raindrops have stopped from the peak positions P _i (i = 1, 2,...) At the bases of the roofs by the above-described rainflow method. _Are extracted as bottom positions B _i corresponding to the respective peak positions P _i . Then, CPU 13, the horizontal coordinates of each peak position P _i and the bottom position B _i are measured to detect the vibration acceleration of the peak position P _i and the bottom position B _i respectively. Then, as shown in FIG. 8, the absolute value of the difference between the vibration acceleration at each peak position P _{i and} the vibration acceleration at each bottom position B _i corresponding thereto is calculated, and this absolute value is used as the amplitude S _i. These are set (in the illustrated example, the peak position P ₁ and the bottom position B ₁ , and the peak position P ₅ and the bottom position B ₅ are shown).

Then, CPU 13, in step 22, as shown in FIG. 8, the time interval _{t n} between each peak position _{P i} and the bottom position _{B i} corresponding thereto is measured, the time interval _{t n} by setting the width _{T n} in the time axis direction of the amplitude _{S i,} it performs processing for the frequency _{f n (however, f n = 1 / T n} ) for each amplitude _{S i} to set the. Then, the amplitude S _i is distributed for each frequency f _n , and the occurrence frequency (count number) N _i is counted for each magnitude of the amplitude S _i .

Finally, in step 23, the CPU 13 performs a process of calculating the accumulated fatigue β of the transported goods P for each frequency f _n by using the following formula (3) using the fatigue SN curve. As a result, as shown in FIG. 9, the accumulated fatigue β generated in the transported goods P during actual transportation is calculated for each frequency f _n , and the calculated accumulated fatigue is set as the target accumulated fatigue. In the following formula (3), α is an acceleration coefficient and is a value specific to the transported product P.

When the transported goods P are actually vibrated in a stacked state, as shown in FIG. 10, the accumulated fatigue (A), (B) is stored for each frequency f _n for each stacked transported product P. To calculate. Then, the accumulated fatigue (C) including both the calculated accumulated fatigue (A) and (B) is calculated, and this accumulated fatigue (C) is set as the target accumulated fatigue. As a result, even if the goods P are stacked during actual transportation, it is possible to evaluate the durability against the vibration by one-stage loading in the subsequent test.

In addition, as shown in FIG. 3, when the transportation route of actual transportation is configured by a plurality of scenarios a1 to a5, if the accumulated fatigue calculated for each scenario is A1 to A5, the transportation goods in actual transportation The target accumulated fatigue occurring in P is set to max [sum {A ₁ , max (A ₂ , A ₃ ), A ₄ }, A ₅ ] (max: maximum value, sum: sum). Thereby, when a transportation route can be considered in various actual transportations, the necessary minimum accumulated fatigue can be calculated for each frequency, and an over test and an under test can be avoided.

According to this reference value setting step, even if the actual vibration generated in the transportation means during actual transportation is a non-Gaussian vibration whose probability density distribution is not a normal distribution, accumulated fatigue that occurs in the transportation product P is reduced. It is possible to calculate for each frequency f _n . In addition, even if the actual vibration generated in the transportation means during actual transportation is Gaussian vibration, if the vibration actually generated in the transported goods P is non-Gaussian vibration, the accumulated fatigue generated in the transported goods P is reduced. It is possible to calculate for each frequency f _n .

In addition, as in the vibration test method described in Patent Document 1 described in the prior art, it is not necessary to derive a time-series waveform data of the vibration acceleration generated in the structure for each frequency, the frequency f _n by a simple method The accumulated fatigue for each can be calculated.

In the present embodiment, although so as to extract the amplitude S _i by rain flow method, peak count method, the range method, such as range pair method, using other cycle counting method, the accumulated fatigue of vibration acceleration The contributing amplitude S _i may be extracted.

For example, in FIG. 7, of the peak position _{P i} of the vibration waveform, the crest peak _{P 1, P 3, P 5} ··· are sequentially extracted by the respective ridges peak _{P 1, P 3, P 5} ··· Are detected, and the trough peaks P ₂ , P ₄ , P ₆ ... Are sequentially extracted to detect the vibration accelerations of the trough peaks P ₂ , P ₄ , P ₆ . Then, a difference in vibration acceleration between adjacent peak and valley peaks (for example, P ₁ and P ₂ , P ₂ and P _3, etc.) is calculated, and this difference is set as the amplitude S _i . Further, the time interval between the adjacent peak and valley peaks is measured, and this time interval is set as the width T _n of the amplitude S _{i in} the time axis direction, and the frequency f is set for each amplitude S _{i. n} (where f _n = 1 / T _n ) is set. Then, sorting the amplitude S _i for each frequency f _n, on the basis of the amplitude S _i and frequency N _i per its size, to calculate the accumulated fatigue β of shipment P for each frequency f _n May be.

(3) Test condition determination step (Step 3)
The test condition determining step will be described with reference to the flowchart shown in FIG. 11 as appropriate.

  First, in step 30, the test time of the transported goods P that the user desires in this test is input. This input can be performed on a predetermined setting screen displayed on the display unit 11 by the CPU 13. In general, shortening the test time improves the test efficiency because the test is completed in a short time, while the vibration conditions of the actual vibration and the vibration conditions of the main test may deviate and the test accuracy may decrease. Can occur.

Next, the CPU 13 determines a vibration condition for testing when the actual test is actually performed based on the input test time. Specifically, when the transported goods P are vibrated during a desired test time, the accumulated fatigue for each frequency f _n generated in the transported goods P within the test time calculated in the same manner as in the reference value acquiring step. The vibration condition of the vibration applied to the transported product P is determined so as to achieve the target accumulated fatigue.

Here, conventionally, in determining the test vibration conditions, depending on the test time, the user is power spectral density of each frequency component f _k of the vibration given to the shipment P (initial PSD) is set appropriately Further, vibration waveform data is generated by performing inverse Fourier transform by giving a phase angle Φ _k to each frequency component f _k at random. Then, the given generated vibration waveform data to based vibration shipment test time set to P, and calculates the accumulated fatigue for each frequency f _n occurring shipment P This vibration is compared with the target cumulative fatigue. Hereinafter, the fatigue that the transported product P receives due to vibration within the test time is referred to as “actual accumulated fatigue”. Then, the ratio of the target accumulated fatigue with respect to the actual accumulated fatigue due to the vibration due to the initial PSD is calculated, and based on this ratio, the power spectrum density of the vibration applied to the transported goods P is corrected, so that the actual accumulated fatigue becomes the target accumulated fatigue. I try to get tired.

  However, in this conventional method, when determining the vibration conditions for the test described above, since the Gaussian vibration is given to the transported goods P, the actual accumulated fatigue does not match the target accumulated fatigue. As shown in FIG. 12, it is confirmed that the actual accumulated fatigue does not coincide with the target accumulated fatigue in the high frequency region. Therefore, in this test, there is a problem that evaluation accuracy of vibration durability is lowered.

Therefore, in this embodiment, not only the power spectral density of the vibration given to the shipment P, by setting the phase angle [Phi _k given to each frequency component f _k appropriately, giving vibration of non-Gaussian to shipment P Thus, the actual accumulated fatigue generated in the transported goods P within the test time is made to coincide with or substantially coincide with the target accumulated fatigue.

In FIG. 11, in step 31, the power spectral density (PSD) for each frequency component f _{k of} vibration given to the transported product P by the user is appropriately set. Next, in step 32, based on these set PSDs, the CPU 13 performs a process of calculating the amplitude x _k for each frequency component f _k using the above equation (2). Next, in step 33, the CPU 13 executes a process of setting the phase angle φ _k for each frequency component f _k .

FIG. 13 shows a first embodiment of the phase angle setting process in step 33 of FIG. 11, and each phase setting process of the first embodiment will be described with reference to the flowchart shown in FIG. 13 as appropriate. In the first embodiment, the CPU 13 first presets the probability density distribution of the delay (phase difference) Δφ (= φ _{(k + 1)} −φ _k ) of the phase angle φ _k of each frequency component f _k in step 33A. To do. At this time, as shown in FIG. 14, the shape of the probability density distribution of the phase difference Δφ is such that the position of the peak value of the probability density distribution of the phase difference Δφ is, for example, the center of the maximum value 2π of the phase difference and the minimum value 0. The probability density distribution of the phase difference Δφ is created so as to be located at the position of π. The shape of the probability density distribution of the phase difference Δφ can be changed by appropriately adjusting the length L of the base.

Next, in step 33B, the CPU 13 performs a process of calculating the phase difference Δφ between the frequency components using the created probability density distribution of the phase difference Δφ, and finally, the phase of the reference frequency component f ₁ . by setting the angle phi ₁ appropriately, the f _k each respective frequency component, and sets the phase angle phi _k (step 33C).

Returning to FIG. 11, CPU 13 is generated in step 34, by performing inverse Fourier transform on the amplitude D _k and the frequency components f _k the phase angle phi _k is set, a vibration waveform data of the vibration given to the shipment P To do. Then, based on the vibration waveform data, the vibration table 2 is vibrated, and the test article and vibration are given to the transported goods P (step 35).

Next, in step 36, based on the detection value from the second acceleration sensor 5 attached to the transported product P, the test time is calculated by the accumulated fatigue calculation method of the present invention in the same manner as in the reference value acquisition step. The actual accumulated fatigue for each frequency f _n occurring in the transported product P is calculated. Then, the CPU 13 compares this actual accumulated fatigue with the target accumulated fatigue (step 37), and if the actual accumulated fatigue and the target accumulated fatigue do not coincide with each other, step 37 becomes “NO” and the process returns to step 31; Based on the difference, the power spectral density and the phase angle φ _k for each frequency component f _{k of the} vibration applied to the transported product P are corrected so that the actual accumulated fatigue matches the target accumulated fatigue.

  By repeating this operation, if the actual accumulated fatigue coincides with or substantially coincides with the target accumulated fatigue, step 37 becomes “YES” and the process proceeds to step 38, and the CPU 13 sets the obtained vibration condition as the test vibration condition. Set.

  In the first embodiment, the kurtosis of the generated vibration can be controlled. Therefore, according to the first embodiment, the vibration applied to the transported product P can be a non-Gaussian vibration, so that the actual accumulated fatigue matches or substantially matches the target accumulated fatigue (even in the high frequency region). ) Is possible.

FIG. 15 shows a second embodiment of the phase angle setting process in step 33 of FIG. 11. Each phase setting process of the second embodiment will be described with reference to the flowchart shown in FIG. 15 as appropriate. In the second embodiment, a group delay time t is introduced in order to set the phase angle φ _k for each frequency component f _k . Here, the group delay time t is generally obtained by differentiating the delay Δφ (= φ _{(k + 1)} −φ _k ) of the phase angle Φ _k of each component wave subjected to Fourier transform with the angular frequency ω. And is defined by t = dΦ / dω (where ω = 2πf). In this second embodiment, the phase angle phi _k of each frequency component f _k, is set based on the equation below using the group delay time t (4).

Specifically, the method of setting the phase angle Φ _k will be described. First, in step 33D, the CPU 13 assumes that the distribution of the group delay time t _k follows a normal distribution, and the average μ _t (hereinafter referred to as “average group delay time”). μ _t ”) and variance σ _t ² (hereinafter referred to as“ dispersed group delay time σ _t ² ”) are appropriately set, so that the set average group delay time μ _t and variance group delay time σ _t ² can be obtained. Based on this, a normal random number N (μ _t , σ _t ² ) of the group delay time t is generated, and a process of calculating the group delay time t _k for each frequency component f _k is performed (step 33E).

Here, the dispersion group delay time σ _t ² corresponds to the duration of the component wave group. If the average group delay time μ _t is kept constant and the dispersion group delay time σ _t ² is changed, the vibration waveform data generated has a greater degree of vibration impact as the dispersion group delay time σ _t ² increases. Thus, it has been confirmed that the amplitude is reduced and the vibration waveform data is a steady waveform. Therefore, the variance group delay time σ _t ² is a parameter corresponding to the kurtosis of the generated vibration waveform data. By appropriately setting the variance group delay time σ _t ² , the peak of the generated vibration waveform data is obtained. You can control the degree.

In step 33F, the CPU 13 performs a process of appropriately setting the initial phase φ0 between [ ₀ to 2π]. Here, the initial phase φ ₀ corresponds to the vertical symmetry with respect to the time axis of the component wave group. When the dispersion group delay time σ _t ² and the average group delay time μ _t are made constant and the initial phase φ ₀ is changed, the generated oscillation waveform data is vertically symmetrical with respect to the time axis due to the change of the initial phase φ _0. It has been confirmed that the property, that is, the skewness changes. Therefore, the initial phase φ ₀ is a parameter corresponding to the skewness of the generated vibration waveform data, and the skewness of the generated vibration waveform data can be controlled by appropriately setting the initial phase φ _0. it can.

In Step 33D to Step 33F, the CPU 13 appropriately sets the dispersion group delay time σ _t ² and the average group delay time μ _t and the initial phase Φ ₀ . Then, a group delay time t _k is generated for each frequency component f _{k based} on the normal random number N (μ _t , σ _t ² ), and in the next step 33G, each frequency component is used using the above equation (4). A phase angle φ _k is set for f _k .

Then, the CPU 13 performs the inverse Fourier transform on each frequency component f _{k in} which the amplitude D _k and the phase angle φ _k are set (step 34 in FIG. 11), thereby generating vibration waveform data of the vibration to be given to the transported product P. . Then, based on the vibration waveform data, the vibration table 2 is vibrated, and the test article and vibration are given to the transported goods P (step 35). Subsequent steps 36 to 38 are the same as those in the first embodiment described above, and a detailed description thereof will be omitted here.

  In the second embodiment, the kurtosis and distortion of the generated vibration can be controlled. Therefore, according to the second embodiment, the vibration applied to the transported product P can be made closer to a non-Gaussian vibration than in the first embodiment, so that the actual accumulated fatigue matches or substantially matches the target accumulated fatigue. (Even in the high frequency region).

(4) Vibration applying step (step 4)
In this vibration applying step, after the transported product P is placed on the vibration table 2, the vibration table 2 is vibrated by the vibration of the test conditions (test vibration conditions and test time) determined in the test condition determination step. Conduct this test. Then, after a predetermined test time has elapsed, the vibration of the shaking table 2 is stopped and the damage status of the transported goods P is inspected.

  As described above, in the vibration test method of the present embodiment, even if the vibration generated in the transportation means is non-Gaussian vibration, it is highly accurate for the transported goods P and is accurate according to the actual transportation environment. It is possible to evaluate vibration durability.

  In the present embodiment, the transported goods P transported by the transport means have been described. However, the present invention is also applied to devices and parts mounted on devices that are constantly vibrated, such as transport means. Can do.

DESCRIPTION OF SYMBOLS 1 Vibration test apparatus 4 1st acceleration sensor 5 2nd acceleration sensor 10 Control apparatus 13 CPU
14 ROM
15 RAM
16 Memory part P Transportation goods

Claims (7)

An accumulated fatigue calculation method for calculating accumulated fatigue generated in a structure placed in a vibration environment,
A first step of measuring time-series waveform data of a vibration detection value of the structure obtained by a sensor for detecting the vibration of the structure;
A second step of sequentially extracting amplitude S _i that contributes to accumulated fatigue of the vibration detection value that fluctuates based on the measured time-series waveform data of the vibration detection value;
A third step of setting a frequency f _n (where f _n = 1 / T _n ) by measuring a width T _n in the time axis direction for each amplitude S _i ;
The accumulated fatigue calculation comprising: a fourth step of calculating the accumulated fatigue generated in the structure based on the amplitude S _i and the occurrence frequency N _i for each magnitude for each frequency f _n Method. In the second step, the peak of the peak position of the vibration detection value is sequentially extracted to detect the vibration detection value of each peak, and the valley peak is sequentially extracted to detect the vibration of each valley peak. After detecting the value, the difference between the vibration detection values of the adjacent peak and valley peaks is calculated, and this difference is set as the amplitude S _i of the vibration detection value.
2. The method according to claim 1, wherein in the third step, a time interval between adjacent peak and valley peaks is measured, and the time interval is set as a width T _{n in the} time axis direction. Accumulated fatigue calculation method. In the second step, the vibration detection value peak position and the corresponding bottom position are sequentially extracted based on the rainflow method, and the difference between the peak position and the vibration detection value corresponding to the peak position is calculated. This difference is set as the amplitude S _i of the vibration detection value,
2. The accumulated fatigue according to claim 1, wherein in the third step, a time interval between a corresponding peak position and a bottom position is measured, and the time interval is set as a width T _{n in the} time axis direction. Calculation method. A vibration test method for evaluating vibration durability of a structure placed on a vibration body,
A test specification setting step for determining a reference vibration condition for a vibration to be applied to the structure based on a vibration condition of the vibration generated in the vibration body;
A reference value acquisition step of calculating accumulated fatigue generated in the structure by vibration under the reference vibration condition for each frequency by the accumulated fatigue calculating method according to any one of claims 1 to 3, and setting this as target accumulated fatigue When,
When a desired test time is set and the structure is vibrated for the test time, the accumulated fatigue for each frequency generated in the structure within the test time calculated in the same manner as the reference value acquisition step is the target accumulated fatigue. A test condition determining step for determining a vibration condition for vibration test to be applied to the structure,
A vibration test method comprising: a vibration applying step of vibrating the structure based on the test vibration conditions and the test time obtained in the test condition determining step to determine whether the structure is damaged. Wherein in the test condition determining step, by setting the phase angle [Phi _k giving the power spectral density and the frequency components f _k for each frequency component f _k of the vibration to be imparted to the structure as appropriate, structures within the test time The vibration test method according to claim 4, wherein a test vibration condition is determined such that the accumulated fatigue at each frequency occurring in the frequency becomes the target accumulated fatigue. In the test condition determination step, a probability density distribution (where 0 ≦ ΔΦ ≦ 2π) of a phase difference ΔΦ (ΔΦ = Φ _{(k + 1)} −Φ _k ) representing a phase angle delay of each frequency component f _k is appropriately set. , vibration test method according to claim 5, characterized in that setting the phase angle [Phi _k of each frequency component f _k to calculate the phase difference ΔΦ between each frequency component based on the probability density distribution. In the test condition determining step, the phase angle [Phi _k of each frequency component f _k, the angular frequency omega, the initial phase [Phi ₀ and _{(0 ≦ Φ 0 ≦ 2π)} , and the average μ and variance sigma ² based Formula expressed by group delay time t _k calculated using normal random number N (μ, σ ² ):
Φ _{(k + 1)} = Φ _k + t _{(k + 1)} dω
The vibration test method according to claim 5, wherein the vibration test method is set by:

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