KR102051746B1 - Device for measuring modal damping coefficient and measuring method using the same - Google Patents

Abstract

The present invention relates to a modal attenuation coefficient measuring device and a method for measuring a modal attenuation coefficient using the same. The modal attenuation coefficient measuring device according to the present invention sets a pattern by a test object and a control for calculating a modal attenuation coefficient, and sets An exciting force that applies a physical force to one side of the test object according to an excitation pattern, a sensor that is in contact with the other side of the test object and collects vibration signals generated by the test object by the physical force, and a physical force applied by the exciter A modal attenuation coefficient calculator for converting a signal and the vibration signal collected by the sensor into a frequency domain signal to calculate a frequency response function, and extracting a resonance point based on the frequency response function to calculate a modal attenuation coefficient for the resonance point. Wherein the exciter has a different excitation pattern for the test object. Applying a physical force, the modal attenuation coefficient calculator calculates a frequency response function for each of the excitation patterns based on the vibration signal collected by the sensor, and modal to the resonance point for each of the excitation patterns based on the calculated frequency response function. Calculate the attenuation factor.

Description

DEVICE FOR MEASURING MODAL DAMPING COEFFICIENT AND MEASURING METHOD USING THE SAME}

The present invention relates to a modal attenuation coefficient measuring apparatus and a method for measuring a modal attenuation coefficient using the same, and more particularly, to accurately analyze the physical characteristics of the test object by measuring the modal attenuation coefficient in consideration of temperature and humidity as well as an input excitation pattern. The present invention relates to a modal attenuation coefficient measuring apparatus capable of measuring a modal attenuation coefficient using the same.

The damping action is to offset the external load energy by changing the internal load energy into internal energy by using the inherent characteristics of the material, which increases the structural safety of the material and decreases the response, thereby providing a lot of benefits in terms of durability. Damping Coefficient is used in time domain or frequency domain and is used to physically express the damping action. In order to understand the mechanical properties of the material or system it is very important to accurately measure the value of the attenuation coefficient, and various methods of measuring the value are proposed. In particular, the damping coefficient measured in the frequency domain is called a modal damping coefficient, and the frequency attenuation value at each resonant point is required to measure the modal damping coefficient. A modal test is usually used to obtain the frequency attenuation, but since the physical quantity is vulnerable to external noise, the average value of the values obtained through the repeated test is used.

Existing modal test methods for measuring modal attenuation coefficients are weak to external noise as described above and use approximate values, so that the measurement is performed under limited conditions subject to specific input patterns. There is a problem inevitably have a big error with the actual situation affected by the pattern. In addition, the existing modal test method has a problem that does not consider the effects of other environmental factors at all.

Measuring accurate modal damping coefficient values is very important as a preliminary information to ensure mechanical reliability of the material or system. For example, in the case of automotive parts, lightweight materials (for example, aluminum, magnesium, engineering plastics, CFRP, etc.) are being used more recently than steel materials, and accurate modal damping coefficient values are used to secure reliability of the materials. It has become very important to measure.

Republic of Korea Patent Application Publication No. 10-2015-0061907 (2015.06.05), pages 3 to 4

The present invention provides a modal attenuation coefficient measuring device and modal using the same to reduce the difference from the actual situation affected by various external input patterns and to accurately analyze the physical characteristics of the test object by measuring the modal attenuation coefficient through various input patterns. Provides a method for measuring attenuation coefficients.

The present invention provides a modal damping coefficient measuring device that can accurately analyze the physical characteristics of the test object by measuring the modal attenuation coefficient in consideration of the temperature that affects the test object, as well as the pattern having various inputs and the method of measuring the modal attenuation coefficient using the same To provide.

Modal attenuation coefficient measuring device according to the present invention is a test object for measuring the modal attenuation coefficient, the excitation pattern for setting the excitation pattern by the control, and applying a physical force to one side of the test object according to the set excitation pattern, the test object A sensor that collects the vibration signal generated by the test object by the physical force and a physical force signal applied by the exciter and the vibration signal collected by the sensor into a frequency domain signal And a modal attenuation coefficient calculation unit for extracting a resonance point based on the frequency response function and calculating a modal attenuation coefficient for the resonance point, wherein the exciter applies a physical force to the test object in different excitation patterns, The modal attenuation coefficient calculator is based on the vibration signal collected by the sensor A frequency response function is calculated for each excitation pattern, and a modal attenuation coefficient for a resonance point for each excitation pattern is calculated based on the calculated frequency response function.

In one embodiment, the exciter exerts a physical force in at least three excitation patterns, the excitation pattern comprising a random pattern, a harmonic pattern and an impact pattern, wherein each pattern is the same Has a frequency band.

In one embodiment, the exciter comprises an impact hammer or an electrodynamic shaker.

In one embodiment, the exciter exerts a physical force at least two times for each excitation pattern, and the modal attenuation coefficient calculator calculates a frequency response function by the number of times the physical force is applied to each excitation pattern.

In one embodiment, the modal attenuation coefficient calculator calculates one representative frequency response function for each excitation pattern through curve fitting in a frequency domain after averaging the calculated frequency response functions for each excitation pattern. do.

In one embodiment, the modal attenuation coefficient calculator extracts a resonance point using a peak-picking algorithm based on the frequency response function.

In one embodiment, the modal attenuation coefficient calculator calculates a modal attenuation coefficient using Equations 1 and 2 below.

[Equation 1]

Where R _i ^e is the frequency response function molecular component in the i-th input excitation pattern, M _i is the mass value, C _i is the modal damping coefficient, K _i is the stiffness coefficient, and N is the total number of input excitation patterns

[Equation 2]

Here, w _n is the frequency of the resonance point, w _a and w _b are the frequency of the point (| α | / √2) where the power becomes 1/2 of the power of the resonance point (| α |).

In one embodiment, the modal attenuation coefficient calculator derives Equation 3 from Equation 1 using modal attenuation coefficients calculated for each excitation pattern.

[Equation 3]

Where p _i represents the pattern with the i th input, and C _i , p _i is the modal attenuation coefficient value for the pattern with the i th input

In one embodiment, when a physical force mixed with a plurality of patterns is applied through the exciter, the modal attenuation coefficient calculator calculates a modal attenuation coefficient using Equation 4 below.

[Equation 4]

Here, α, β and γ are linear interpolation coefficients and have values between 0 and 1, respectively. The sum of the linear interpolation coefficients of each item is 1. C _i , p _i is the modal attenuation factor value for the i th input pattern

In one embodiment, the modal attenuation coefficient measuring device further comprises a chamber capable of adjusting the internal temperature, wherein the test object, the object support, the exciter and the sensor is provided in the chamber.

In one embodiment, the chamber adjusts the internal temperature differently to at least one or more temperatures, the exciter exerts a physical force on the test object in different excitation patterns for each of the temperature conditions, and the modal attenuation coefficient calculation unit is A modal attenuation coefficient is calculated by calculating a frequency response function for each temperature condition and each excitation pattern.

In one embodiment, the modal attenuation coefficient calculation unit calculates a modal attenuation coefficient for each temperature condition for a specific excitation pattern, and approximates the modal attenuation coefficient for each temperature condition to a Taylor's series to calculate Equation 6 below. .

[Equation 6]

Where C _i and _Ti are modal attenuation coefficient values calculated at the i th temperature condition, α _i is the Taylor series constant, and T _i is the i th temperature

In one embodiment, the modal attenuation coefficient calculator calculates a modal attenuation coefficient according to temperature based on the condition of Equation 6 and Equation 7 below.

[Equation 7]

Where T _en is the room temperature temperature, C _i , and p _i are the modal attenuation coefficient values for the i th input pattern.

The modal attenuation coefficient measuring method according to the present invention comprises the steps of applying a physical force in the excitation pattern to each side of the test object by the excitation control, the sensor collecting the vibration signal generated by the test object and calculating the modal attenuation coefficient In addition, the frequency response function is calculated by converting the physical force signal applied by the exciter and the vibration signal collected by the sensor into a frequency domain signal, extracting a resonance point based on the frequency response function, and modal attenuation coefficient for the corresponding resonance point. Comprising: calculating the modal attenuation coefficient, the step of calculating the frequency response function for each of the excitation pattern based on the vibration signal collected by the sensor, and based on the calculated frequency response function The modal attenuation coefficient for the resonance point is calculated for each pattern.

In one embodiment, the step of applying a physical force to the exciter is to apply a physical force in at least three or more excitation patterns, wherein the excitation pattern comprises a random pattern, harmonic pattern and impact pattern and each pattern is the same frequency band Have

In one embodiment, the method of measuring the modal attenuation coefficient further comprises differently adjusting the temperature in the chamber to at least one or more temperatures, wherein applying the physical force to the exciter is different for the test object for each of the temperature conditions. Applying a physical force to the excitation pattern, and calculating the modal attenuation coefficient calculates a modal attenuation coefficient by calculating a frequency response function for each temperature condition and each excitation pattern.

As described above, the modal damping coefficient measuring apparatus and the modal damping coefficient measuring method using the same according to the present invention by measuring the modal attenuation coefficient through a variety of input excitation pattern to be different from the actual situation affected by various external input patterns It can reduce and accurately analyze the physical characteristics of the test object.

Modal attenuation coefficient measuring device and a method for measuring modal attenuation coefficient using the same according to the present invention can accurately analyze the physical characteristics of the test object by measuring the modal attenuation coefficient in consideration of the temperature affecting the test object as well as the pattern having various inputs Can be.

Modal attenuation coefficient measuring device according to the present invention and a modal attenuation coefficient measuring method using the same provides a measuring device and a measuring method suitable for the total inspection and automation of the object by simplifying the structure of the device.

1 is a block diagram showing the configuration of a modal attenuation coefficient measuring apparatus according to an embodiment of the present invention
2 shows an example of a test sample.
3 is a view showing an example of fatigue damage measured for the test sample of FIG.
4 is a diagram illustrating an example of a method of extracting a resonance point and measuring modal attenuation coefficients using a peak-picking algorithm.
5 is a diagram illustrating a specific experimental example of an apparatus for measuring modal attenuation coefficients;
6 to 12 show frequency response functions calculated at each sensor position.
FIG. 13 is a diagram illustrating a process of extracting a resonance point from the frequency response function of FIG. 6 and calculating a modal attenuation coefficient of the corresponding resonance point.
14 shows modal attenuation coefficient values measured according to an input excitation pattern.
15 shows modal attenuation coefficient values measured according to temperature conditions.
16 is a flowchart illustrating a method of measuring a modal attenuation coefficient using a modal attenuation coefficient measuring apparatus according to an embodiment of the present invention.

Hereinafter, a detailed description of a modal attenuation coefficient measuring apparatus and a method for measuring a modal attenuation coefficient using the same will be described.

1 is a block diagram showing the configuration of a modal attenuation coefficient measuring apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the modal attenuation coefficient measuring apparatus 100 calculates an exciter 110, a test object 120, a sensor 130, a force sensor 140, a chamber 150, and a modal attenuation coefficient. The unit 160 may be included.

The modal attenuation coefficient measuring apparatus 100 measures the modal attenuation coefficient of the test object 120 by considering not only various input patterns but also temperatures affecting the test object. For example, the modal attenuation coefficient measuring apparatus 100 may add a variety of input excitation patterns to the test object 120 to calculate a frequency response function and measure the modal attenuation coefficient. In addition, the modal attenuation coefficient measuring apparatus 100 may add a pattern having an input to the test object 120 under different temperature conditions, calculate a frequency response function, and measure the modal attenuation coefficient.

The exciter 110 sets an excitation pattern under control, and applies a physical force to one side of the test object 120 according to the set excitation pattern. In one embodiment, the exciter 110 may apply a physical force to the test object 120 in a different excitation pattern. The exciter 110 may include a uniaxial exciter for applying a force in one axis direction, a two-axis exciter for applying a force in the two axis direction, a three-axis exciter for applying a force in the three axis direction, and the like. Hereinafter, it will be described on the assumption that it is used as the exciter having a single axis excitation for convenience of description. For example, the exciter 110 may include an electrodynamic shaker or an actuator that vibrates by applying force in one axial direction.

In another embodiment, it may be used as a machine 110 having a fixed impact device (eg, impact hammer) capable of automatically applying an impact to the test object 120. The impact hammer does not cause physical damage to the test object 120, does not require pre-processing for the test, and may apply the impact to the test object 120 over a wide frequency. In the case of an impact hammer, a tip may be provided at a portion (impact portion) that is to be actually excited. In one embodiment, the tip may be replaced automatically or manually depending on the frequency band required for the input excitation pattern. For example, if a high frequency band input excitation pattern is required, the impact hammer may be a tip of a steel product having a sharp front and a large rigidity. When a low frequency input excitation pattern is required, a small rigid tip such as plastic or rubber may be used for the impact hammer.

The test object 120 is a target object for measuring a modal attenuation coefficient by adding an input excitation pattern. For example, the test object 120 may correspond to an automotive part.

In one embodiment, the test object 120 may be placed on the vibrator 110 via an automatic transfer device (not shown). The test object 120 may be positioned based on the structural features of the object. For example, the test object 120 may be placed on the exciter 110 so that the physical force is applied to the position most efficient for measuring the modal attenuation coefficient according to the test result.

The sensor 130 is in contact with the other side of the test object 120 and collects a signal generated by the test object 120 by the physical force applied by the exciter 110. The type of sensor 130 may vary depending on the type of physical signal to be collected. For example, an acceleration sensor can be used for measuring acceleration vibration, a laser sensor can be used for measuring surface velocity, and photogrammetry for measuring displacement. String pots can be used. Hereinafter, for convenience of description, it will be described on the assumption that the acceleration sensor is used as the sensor 130 to collect the vibration signal. Since the response (vibration) signal according to the input (impact) signal is three-axis acceleration, the acceleration sensor is configured to measure the response of all three axes.

In one embodiment, at least one sensor 130 may be used to collect signals generated by the test object 120. For example, vibration signals of the test object 120 may be collected using three sensors.

In one embodiment, if there is a gap between the test object 120 and the sensor 130 may cause unwanted vibration, the measuring device may further include a close contact portion for close contact with the sensor 130 and the test object 120. have. For example, in order to prevent unwanted vibration, a close contact portion such as a weak rubber may be provided between the test object 120 and the sensor 130.

The force sensor 140 is provided below the exciter 110 to measure the force exerted by the exciter 110. The signal measured by the force sensor 140 may be used as the input signal F (w) in obtaining a frequency response function of the test object 120.

Chamber 150 adjusts the internal temperature differently to at least one or more temperatures. The exciter 110, the test object 120, the sensor 130, and the force sensor 140 may be provided in the chamber 150 to perform an operation according to a set temperature condition. For example, the exciter 110 may add an input excitation pattern to the test object 120 in the chamber 150 according to a set temperature condition.

The modal attenuation coefficient calculator 160 converts the physical force (input excitation pattern) signal applied by the exciter 110 and the vibration signal collected by the sensor 130 into a frequency domain signal to convert the frequency response function. (frequency response function, H (w) = R (w) / F (w), where R (w) is the response signal, F (w) input signal, and w (= 2πf) is the frequency). The modal attenuation coefficient calculator 160 may extract a resonance point based on the calculated frequency response function and calculate a modal attenuation coefficient for the corresponding resonance point.

In one embodiment, the modal attenuation coefficient calculator 160 calculates a frequency response function for each excitation pattern based on the vibration signal collected by the sensor 130, and a resonance point for each excitation pattern based on the calculated frequency response function. The modal attenuation coefficient for can be calculated.

For example, when an input excitation pattern is set in the exciter 110 and a temperature condition is set in the chamber 150, the modal attenuation coefficient calculator 160 may provide a frequency response function for the corresponding temperature condition and the excitation pattern. The modal attenuation coefficient can be calculated. In the above manner, the modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient by calculating a frequency response function for each temperature condition and each excitation pattern.

Hereinafter, a process of measuring the modal attenuation coefficient of the test object 120 using the modal attenuation coefficient measuring apparatus 100 of FIG. 1 will be described in detail.

The most typical phenomenon influenced by the modal damping coefficient value is the magnitude of the response rapidly increasing near the resonance point, and the fatigue damage at the stress concentration site is changed by the difference in magnitude.

FIG. 2 is a diagram illustrating an example of a test sample, and FIG. 3 is a diagram illustrating an example of fatigue damage measured for the test sample of FIG. 2.

Referring to FIG. 2, FIG. 2 (a) is a schematic diagram of the shape of a test object, and FIG. 2 (b) shows acceleration sensors # 1, # 2, # 3, and # 4 on an actual test object. Figure is a view showing an example of the position and attachment method attached. In one embodiment, the test object of FIG. 2 is a component made of S45C, a mild steel with a relatively small modal damping coefficient.

Referring to FIG. 3, FIG. 3A is a diagram illustrating fatigue damage in the 280 hz section as a fatigue damage calculated when a pattern included in the test object of FIG. 2 is added. FIG. 3 (b) is a diagram illustrating fatigue damage in the 1625 hz section as fatigue damage calculated when a pattern included in the test object of FIG. 2 is added. The fatigue damage may be calculated as a normalized log value based on the magnitude value of the frequency response function calculated for the test object.

Referring to FIG. 3, it can be seen that fatigue damage is clearly different according to the type of the excitation pattern applied to the test object of FIG. 2, that is, the random excitation pattern (solid line) and the harmonic excitation pattern (dashed line). Can be. That is, even though the resonance points are the same, the fatigue damage is different because the modal damping coefficients are different according to the input excitation pattern, and the modal damping coefficients differ in the fatigue damage.

The modal attenuation coefficient measuring device according to the present invention can measure the modal attenuation coefficient through various input excitation patterns, thereby reducing the difference from the actual situation affected by various external input patterns and accurately analyzing the physical characteristics of the test object.

Referring back to FIG. 1, the exciter 110 exerts a physical force on the test object 120 in different excitation patterns. For example, the exciter 110 may apply a physical force to the test object 120 in at least three excitation patterns under control. In one embodiment, the excitation pattern includes a random pattern, a harmonic pattern, and an impact pattern, and each pattern may have the same frequency band. The random pattern represents an excitation pattern including an arbitrary plurality of frequency signals, and the harmonic pattern represents an excitation pattern including a sinusoidal signal of a fundamental frequency. The impact pattern represents an excitation pattern that includes an impact signal. In one embodiment, the exciter 110 may sequentially apply the excitation pattern in a predetermined order.

The sensor 130 collects the signal generated by the test object 120, and the modal attenuation coefficient calculator 160 calculates a frequency response function for each excitation pattern based on the vibration signal collected by the sensor. The modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient for the resonance point for each excitation pattern based on the calculated frequency response function.

In one embodiment, the exciter 110 may apply a physical force to the test object 120 at least two times for each excitation pattern. For example, when it is set to apply three times for each excitation pattern (for example, random pattern, harmonic pattern, and impact pattern), the exciter 110 is excited three times with a random pattern, three times with a harmonic pattern It can be excited three times with an impact pattern.

The modal attenuation coefficient calculator 160 calculates a frequency response function by the number of times that a physical force is applied to each excitation pattern. For example, when it is set to apply three times for each excitation pattern, the modal attenuation coefficient calculator 160 may calculate three frequency response functions for each of the random pattern, the harmonic pattern, and the impact pattern.

When the frequency response function is calculated by the number of times the physical force is applied to each excitation pattern, the modal attenuation coefficient calculation unit 160 averages the calculated frequency response functions for each excitation pattern and then curve fitting in the frequency domain. We calculate one representative frequency response function for each excitation pattern. The modal attenuation coefficient calculator 160 may calculate a representative frequency response function using one of various curve fitting algorithms. For example, the modal attenuation coefficient calculator 160 may calculate a representative response function using one of an Algebraic fitting algorithm and a Geometric fitting algorithm.

The modal attenuation coefficient calculator 160 extracts a resonance point using a peak-picking algorithm based on the representative frequency response function calculated for each excitation pattern. For example, to extract the resonance point, one of various known peak peaking algorithms, such as a step peak peaking algorithm or an R-peak peaking algorithm, may be selected and used.

4 is a diagram illustrating an example of a method of extracting resonance points and measuring modal attenuation coefficients using a peak peaking algorithm.

Referring to FIG. 4, the left diagram of FIG. 4 illustrates a representative frequency response function calculated for a specific excitation pattern, and the right diagram of FIG. 4 illustrates that one resonance point is extracted through a peak peaking algorithm.

The modal attenuation coefficient calculation unit 160 may measure the modal attenuation coefficient for each excitation pattern through the representative frequency response function and the extracted resonance point as shown in FIG. 4. For example, the representative frequency response function of FIG. 4 may be represented by Equation 1 below, and the modal attenuation coefficient calculator 160 may measure a modal attenuation coefficient using Equation 2 below.

[Equation 1]

Where R _i ^e is the frequency response function molecular component in the i th input pattern, M _i is the mass value, C _i is the modal attenuation coefficient, K _i is the stiffness coefficient, and N is the total number of input patterns. Indicates.

[Equation 2]

Here, w _n denotes the frequency of the resonance point, w _a and w _b denote the frequency of the point (| α | / √2) at which the power becomes 1/2 of the power (| α |) of the resonance point.

In the same manner as described above, the modal attenuation coefficient calculator 160 may measure the modal attenuation coefficient for each excitation pattern.

5 is a diagram illustrating a specific experimental example of an apparatus for measuring modal attenuation coefficients.

FIG. 5 is configured to collect and analyze signals of an experimental object using seven sensors for experimental purposes. Referring to FIG. 5, it can be seen that seven sensors # 1 to # 7 are attached to the test object.

The following is an example of the case where the two test patterns (random pattern and harmonic pattern) were added to the test object under the conditions shown in Table 1 below.

Pattern with random Harmonic Size with 0.005 (g ² / Hz) 0.5 g Frequency 10 Hz to 500 Hz 10 Hz to 500 Hz

As shown in Table 1, different excitation patterns are used. Excitation frequency bands of excitation patterns are the same and excitation sizes are different. The magnitude of the excitation does not significantly affect the experimental results because it is the process of obtaining the frequency response function.

6 to 12 are diagrams illustrating a frequency response function calculated at each sensor position.

The modal attenuation coefficient calculator 160 calculates a frequency response function based on the vibration signals collected by the sensors # 1 to # 7. The process of calculating the frequency response function depends on the pattern you have. In the case of the random pattern, since several similar frequency response functions are calculated in the process of calculating the frequency response function, the average value of the corresponding frequency response functions is derived as the final frequency response function. In the case of harmonic patterns, the frequency response function for one excitation frequency is continuously measured over time, and the frequency response function at each excitation frequency obtained over time is superimposed to obtain the final frequency response function.

6 shows a frequency response function calculated based on the signal collected at sensor # 1 (position 1), FIG. 7 shows a frequency response function calculated based on the signal collected at sensor # 2 (position 2), 8 shows a frequency response function calculated based on the signals collected at sensor # 3 (position 3), FIG. 9 shows a frequency response function calculated based on the signals collected at sensor # 4 (position 4), FIG. 10 shows a frequency response function calculated based on the signal collected at sensor # 5 (position 5), FIG. 11 shows a frequency response function calculated based on the signal collected at sensor # 6 (position 6), 12 shows the frequency response function calculated based on the signal collected at sensor # 7 (position 7).

FIG. 13 is a diagram illustrating a process of extracting a resonance point from the frequency response function of FIG. 6 and calculating a modal attenuation coefficient of the resonance point.

FIG. 13 illustrates that the resonance point is extracted at around 210 Hz, and Table 2 summarizes the modal attenuation coefficients calculated at the resonance point through the experiment.

Pattern with Resonance point Modal damping coefficient Random pattern 218.6 Hz 0.5 * (227.9-210.4) /218.6 = 4.0% Harmonic pattern 218.6 Hz 0.5 * (229.9-210.5) /218.6 = 4.4%

In the same manner as described above, the resonance point and the modal attenuation coefficient may be calculated for the frequency response function of the sensor # 2 to the sensor # 7.

14 shows modal attenuation coefficient values measured according to an input excitation pattern.

Referring to FIG. 14, it can be seen that different modal attenuation coefficient values are calculated according to the input excitation pattern. In FIG. 5, p _i represents an i th input excitation pattern, and C _i , p _i represents a modal attenuation coefficient value for the i th input excitation pattern. For example, p ₁ represents a random pattern, p ₂ represents a harmonic pattern, p ₃ represents an impact pattern, C _i , p ₁ represents a modal attenuation coefficient value for the random pattern, and C _i , p ₂ represents a modal for the harmonic pattern. The damping coefficient values, C _i , p ₃ , represent modal damping coefficient values for the impact pattern.

Considering that the modal attenuation coefficient value varies according to each of the plurality of input excitation patterns, Equation 1 may be modified as in Equation 3 below. The modal attenuation coefficient calculator 160 may derive Equation 3 from Equation 1 using the modal attenuation coefficients calculated for each excitation pattern.

[Equation 3]

Here, p _i represents a pattern having an i th input, and C _i , p _i represents a modal attenuation coefficient value for the pattern having an i th input.

FIG. 14 is a diagram illustrating modal attenuation coefficient values calculated when a plurality of patterns are not mixed and one excitation pattern is applied to the test object 120 at a time. However, when a physical force mixed with a plurality of excitation patterns is applied to the test object 120 through the exciter 110, a modal attenuation coefficient value that does not coincide with FIG. 14 may be calculated. When a physical force mixed with a plurality of patterns is applied to the test object 120 through the exciter 110, the modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient using Equation 4 below.

[Equation 4]

Here, α, β and γ are linear interpolation coefficients and have values between 0 and 1, respectively. The sum of the linear interpolation coefficients of each item is 1. C _i , p _i represent the modal attenuation coefficient values for the i th input excitation pattern.

For example, when a sine-on-random physical force is applied to the test object 120 through the exciter 110, the modal attenuation coefficient calculating unit 160 may be represented by Equation 5 below. The modal attenuation coefficient can be calculated using.

[Equation 5]

In this way, by measuring the modal attenuation coefficient through various input patterns, the modal attenuation coefficient measuring apparatus 100 reduces the difference with the actual situation affected by various external input patterns and accurately analyzes the physical characteristics of the test object. can do.

In the actual situation, temperature is a factor that greatly affects the physical change of the test object, so it is necessary to calculate and reflect the modal attenuation coefficient value according to the change of temperature.

Referring back to FIG. 1, the chamber 150 may differently adjust the internal temperature to at least one or more temperatures under control. The exciter 110 applies a physical force in a different excitation pattern to the test object 120 for each set temperature condition. The modal attenuation coefficient calculator 160 calculates a modal attenuation coefficient by calculating a frequency response function for each temperature condition set in the chamber 150 and for each excitation pattern applied by the exciter 110. The process of calculating the modal attenuation coefficients is as described above, only the temperature conditions vary.

15 is a diagram illustrating modal attenuation coefficient values measured according to temperature conditions.

Referring to FIG. 15, it can be seen that different modal attenuation coefficient values are calculated according to temperature conditions. In FIG. 15, T _i represents the i-th temperature, and C _i and _Ti represent modal attenuation coefficient values calculated when a specific input excitation pattern is applied under the i-th temperature condition. 15, it can be seen that the modal attenuation coefficient value changes according to the temperature condition.

As shown in FIG. 15, the modal attenuation coefficient calculating unit 160 calculates a modal attenuation coefficient for each temperature condition and approximates the modal attenuation coefficient for each temperature condition to a Taylor's series to calculate Equation 6 below. .

[Equation 6]

Here, C _i , _Ti are modal attenuation coefficient values calculated at the i-th temperature condition, α _i is the Taylor series constant, and T _i is the i-th temperature. That is, according to equation (6), the modal attenuation coefficient value is a function of temperature. In addition, assuming that modal attenuation coefficient values calculated through Equations 3 to 5 are calculated at room temperature T _en , the relationship of Equation 7 to Equation 6 is satisfied.

[Equation 7]

The modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient according to temperature based on the conditions of Equations 6 and 7. That is, when the modal attenuation coefficient curve according to the temperature of Equation 6 is calculated in consideration of the condition of Equation 7, the modal attenuation coefficient calculator 160 calculates the modal attenuation coefficient according to the input excitation pattern. The modal attenuation coefficient of the test object 120 may be calculated using Equation 5 and Equation 6 for calculating the modal attenuation coefficient according to the temperature condition. For example, when a first input excitation pattern is applied at room temperature, the modal attenuation coefficient of the test object 120 may be calculated as C _i , p ₁ (= C _i , T _en ), and at a temperature T ₁ other than room temperature. When the first input excitation pattern is applied, the modal attenuation coefficient of the test object 120 may be C _i , T ₁ calculated through Equation 6 instead of C _i , p ₁ .

In the above manner, by measuring the modal attenuation coefficient according to the temperature condition as well as the input excitation pattern, the modal attenuation coefficient measuring apparatus 100 reduces the difference between the actual situation affected by the temperature as well as the input excitation pattern and Accurately analyze physical properties.

16 is a flowchart illustrating a method of measuring a modal attenuation coefficient using a modal attenuation coefficient measuring apparatus according to an embodiment of the present invention.

Referring to FIG. 16, the exciter 110 applies physical forces in different excitation patterns to one side of the test object 120 under control (step S1610). In one embodiment, the step of applying the physical force by the exciter 110 may apply the physical force in at least three or more excitation patterns, wherein the excitation pattern is a random pattern, a harmonic pattern, and an impact pattern. It may include. In one embodiment, each pattern may have the same frequency band.

The sensor 130 collects the vibration signal generated by the test object 120 (step S1620). The modal attenuation coefficient calculating unit 160 converts the physical force signal applied by the exciter 110 and the vibration signal collected by the sensor 130 into a frequency domain signal to calculate a frequency response function and based on the frequency response function. The resonance point is extracted to calculate a modal attenuation coefficient for the resonance point (step S1630).

In an embodiment, the step of calculating the modal attenuation coefficient by the modal attenuation coefficient calculating unit 160 may calculate a frequency response function for each excitation pattern based on the vibration signal collected by the sensor 130, and calculate the calculated frequency response function. Calculating a modal attenuation coefficient for the resonance point for each of the excitation patterns. By measuring the modal attenuation coefficients through various input excitation patterns, the modal attenuation coefficient calculation unit 160 can accurately analyze physical characteristics of the test object while reducing a difference from the actual situation affected by various external input patterns.

The process of calculating the modal attenuation coefficient by the modal attenuation coefficient calculating unit 160 is as described above. For example, the process of the modal attenuation coefficient calculator 160 calculating the modal attenuation coefficient is as described in Equations 1 to 3 below.

When a physical force mixed with a plurality of patterns is applied to the test object 120 through the exciter 110, the modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient through Equations 4 to 5. .

In one embodiment, the modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient value according to a change in temperature.

The modal attenuation coefficient measuring apparatus 100 differently adjusts the temperature in the chamber 150 to at least one temperature according to the control, and the exciter 110 is physically in a different excitation pattern to the test object 120 for each temperature condition. Apply force. The modal attenuation coefficient calculating unit 160 calculates a modal attenuation coefficient by calculating a frequency response function for each temperature condition and each excitation pattern. In one embodiment, the modal attenuation coefficient calculator 160 calculates a modal attenuation coefficient for each temperature condition with respect to the pattern, and approximates the calculated modal attenuation coefficient for each temperature condition to a Taylor's series. Can be calculated. The modal attenuation coefficient calculator 160 may calculate a modal attenuation coefficient according to temperature based on the conditions of Equations 6 and 7.

The modal attenuation coefficient measuring apparatus and measuring method described with reference to FIGS. 1 to 16 may also be implemented in the form of a recording medium including instructions executable by a computer, such as an application or a module executed by a computer.

Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, computer readable media may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, modules or other data. Communication media typically includes computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transmission mechanism, and includes any information delivery media.

A module may mean hardware capable of performing functions and operations according to each name described in the specification, and may also mean computer program code capable of performing specific functions and operations. It may also mean an electronic recording medium, eg, a processor, on which computer program code capable of performing specific functions and operations is mounted.

Although the embodiments of the present invention have been described above, the technical idea of the present invention is not limited to the above embodiments, and may be implemented by various modal attenuation coefficient measuring devices and measuring methods in a range that does not depart from the technical idea of the present invention.

100: modal damping coefficient measuring device
110: excitation
120: test object
130 sensor
140: force sensor
150: chamber
160: modal attenuation coefficient calculation unit

Claims (16)

A test object for calculating a modal attenuation coefficient;
An exciter for setting an excitation pattern under control and for applying a physical force to one side of the test object according to the set excitation pattern;
A sensor contacting the other side of the test object and collecting vibration signals generated by the test object by the physical force; And
A frequency response function is calculated by converting the physical force signal applied by the exciter and the vibration signal collected by the sensor into a frequency domain signal, and extracting a resonance point based on the frequency response function to obtain a modal attenuation coefficient for the resonance point. Including a modal attenuation coefficient calculator for calculating,
The exciter exerts a physical force on the test object in different excitation patterns,
The modal attenuation coefficient calculator calculates a frequency response function for each of the excitation patterns based on the vibration signal collected by the sensor, and calculates a modal attenuation coefficient for the resonance point for each of the excitation patterns based on the calculated frequency response function. ,
The modal attenuation coefficient calculating unit extracts a resonance point using a peak-picking algorithm based on the frequency response function,
The modal attenuation coefficient calculating unit calculates a modal attenuation coefficient using Equations 1 and 2 below.
Modal damping coefficient measuring device.
[Equation 1]

Where R _i ^e is the frequency response function molecular component in the ith input excitation pattern, M _i is the mass value, C _i is the modal damping coefficient, K _i is the stiffness coefficient, and N is the total number of input excitation patterns
[Equation 2]

Here, w _n is the frequency of the resonance point, w _a and w _b is the frequency of the point (| α | / √2) where the power becomes 1/2 of the power of the resonance point (| α |)
The method of claim 1, wherein the exciter
Exert a physical force in at least three excitation patterns, the excitation pattern comprising a random pattern, a harmonic pattern and an impact pattern, each pattern measuring a modal attenuation coefficient having the same frequency band Device.
The method of claim 1, wherein the exciter
Modal damping coefficient measuring device comprising an electrodynamic shaker or an impact hammer.
The method of claim 2,
The exciter exerts a physical force at least twice per each excitation pattern,
And a modal attenuation coefficient measuring unit calculating a frequency response function by the number of times a physical force is applied to each of the excitation patterns.
The method of claim 4, wherein the modal attenuation coefficient calculation unit
And averaging the calculated frequency response functions for each excitation pattern and calculating one representative frequency response function for each excitation pattern through curve fitting in a frequency domain.
delete delete The apparatus of claim 1, wherein the modal attenuation coefficient calculation unit derives the following Equation 3 from Equation 1 using the modal attenuation coefficients calculated for each excitation pattern.
[Equation 3]

Where p _i represents the pattern with the i th input, and C _i , p _i is the modal attenuation coefficient value for the pattern with the i th input
A test object for calculating a modal attenuation coefficient;
An exciter for setting an excitation pattern under control and for applying a physical force to one side of the test object according to the set excitation pattern;
A sensor contacting the other side of the test object and collecting vibration signals generated by the test object by the physical force; And
A frequency response function is calculated by converting the physical force signal applied by the exciter and the vibration signal collected by the sensor into a frequency domain signal, and extracting a resonance point based on the frequency response function to obtain a modal attenuation coefficient for the resonance point. Including a modal attenuation coefficient calculation unit to calculate,
The exciter exerts a physical force on the test object in different excitation patterns,
The modal attenuation coefficient calculator calculates a frequency response function for each of the excitation patterns based on the vibration signal collected by the sensor, and calculates a modal attenuation coefficient for the resonance point for each of the excitation patterns based on the calculated frequency response function. ,
When a physical force mixed with a plurality of patterns is applied through the exciter,
The modal attenuation coefficient measuring unit calculates a modal attenuation coefficient using the following equation (4).
[Equation 4]

Here, α, β and γ are linear interpolation coefficients and have values between 0 and 1, respectively. The sum of the linear interpolation coefficients of each item is 1. C _i , p _i is the modal attenuation factor value for the i th input pattern
The method of claim 1,
The modal attenuation coefficient measuring device further includes a chamber that can adjust the internal temperature,
And a test object, an exciter, and a sensor are provided in the chamber.
The method of claim 10,
The chamber differently adjusts the internal temperature to at least one temperature,
The exciter exerts a physical force on the test object in different excitation patterns for each of the temperature conditions,
And a modal attenuation coefficient measuring unit calculating a modal attenuation coefficient by calculating a frequency response function for each of the temperature conditions and the respective excitation patterns.
The method of claim 11, wherein the modal attenuation coefficient calculation unit
Calculate modal attenuation coefficients for specific excitation patterns by temperature conditions,
Modal attenuation coefficient measuring device for calculating the following equation (6) by approximating the modal attenuation coefficient for each temperature condition to Taylor's series.
[Equation 6]

Where C _i and _Ti are modal attenuation coefficient values calculated at the i th temperature condition, α _i is the Taylor series constant, and T _i is the i th temperature
The method of claim 12, wherein the modal attenuation coefficient calculation unit
A modal damping coefficient measuring apparatus for calculating a modal attenuation coefficient according to temperature based on the conditions of Equations 6 and 7 below.
[Equation 7]

Where T _en is the room temperature temperature, C _i , and p _i are the modal attenuation coefficient values for the i th input pattern.
Applying a physical force in a different excitation pattern to one side of the test object by controlling the excitation;
Collecting a vibration signal generated by the sensor at the test object; And
The modal attenuation coefficient calculator calculates a frequency response function by converting the physical force signal applied by the exciter and the vibration signal collected by the sensor into a frequency domain signal, extracting a resonance point based on the frequency response function, Calculating a modal attenuation coefficient for
The calculating of the modal attenuation coefficient may include calculating a frequency response function for each excitation pattern based on the vibration signal collected by the sensor, and modal attenuation coefficient for the resonance point for each excitation pattern based on the calculated frequency response function. Yields,
The calculating of the modal attenuation coefficient may include extracting a resonance point using a peak-picking algorithm based on the frequency response function.
The calculating of the modal attenuation coefficient may include calculating a modal attenuation coefficient using Equation 1 and Equation 2 below.
Method for measuring modal damping coefficients.
[Equation 1]

Where R _i ^e is the frequency response function molecular component in the i-th input excitation pattern, M _i is the mass value, C _i is the modal damping coefficient, K _i is the stiffness coefficient, and N is the total number of input excitation patterns
[Equation 2]

Here, w _n is the frequency of the resonance point, w _a and w _b are the frequency of the point (| α | / √2) where the power becomes 1/2 of the power of the resonance point (| α |).
15. The method of claim 14, wherein applying the physical force to the exciter
Applying a physical force to at least three excitation patterns, wherein the excitation pattern comprises a random pattern, a harmonic pattern and an impact pattern, each pattern having the same frequency band.
The method of claim 14, wherein the modal attenuation coefficient measuring method is
Further adjusting the temperature in the chamber to at least one temperature,
The exerting force exerts a physical force
The physical force is applied to the test object in different excitation patterns for each of the temperature conditions,
Computing the modal attenuation coefficient
A modal attenuation coefficient measuring method for calculating a modal attenuation coefficient by calculating a frequency response function for each temperature condition and each excitation pattern.

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