KR101997993B1 - Crack inspection device and crack inspecting method using the same - Google Patents

Abstract

The present invention relates to a microcracks inspection apparatus and a microcracks inspection method using the same. The microcracks inspection apparatus according to the present invention is an object support unit for supporting a test object placed at a predetermined position, and physically connected to one side of the test object by control. A force exerting force, a sensor in contact with the other side of the test object and collecting vibration signals 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 A first frequency response function is calculated by converting the signal into a frequency domain signal, and the presence of the minute crack exists in the test object by comparing the resonance point extracted from the first frequency response function with the resonance point of the second frequency response function of the reference object. Micro crack detection unit for detecting the.

Description

Micro crack inspection device and micro crack inspection method using same {CRACK INSPECTION DEVICE AND CRACK INSPECTING METHOD USING THE SAME}

The present invention relates to a microcracks inspection apparatus and a microcracks inspection method using the same, and more particularly, microcracks can be indirectly detected by comparing a resonance point of a target object and a resonance point of a reference object that can be obtained through a frequency response function. The present invention relates to a micro crack inspection apparatus and a micro crack inspection method using the same.

Cold forging is one of the mechanical manufacturing methods and is used in many industrial fields, including the manufacturing of rigid automotive parts. Micro cracks in an object are one of the inevitable side effects of cold forging. Because microcracks have a serious impact on the durability of the object during operation, finished goods manufacturers, such as automotive companies, have strict standards on the tolerance of microcracks during manufacturing. For example, in the case of a park gear used for an automobile transmission, there is a reference value for a crack length of about 100 μm, and the automobile company determines whether a part is defective based on the reference value. Typically, automakers use the eddy current sensor to determine whether the corresponding part is passed. However, in the case of the inspection method using the eddy current sensor, there is a problem that the micro crack of 100 μm or less cannot be detected. In addition, in the case of non-destructive inspection methods other than the inspection method using the eddy current sensor, there is a problem that the inspection equipment is expensive using a special sensor.

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

The present invention provides a microcracks inspection apparatus capable of detecting microcracks indirectly by comparing a resonance point of a target object obtainable through a frequency response function and a resonance point of a reference object, and a microcracks inspection method using the same.

The present invention provides a microcracks inspection apparatus and microcracks using the same, which can effectively determine whether a microcracks, which are very difficult to measure directly, exceed a reference value, by using a physical phenomenon in which the number of resonance points increases with the depth of the microcracks. Provide a test method.

The present invention provides a micro crack inspection apparatus suitable for the entire inspection of an object and automation of inspection by simplifying the structure of the inspection apparatus, and a micro crack inspection method using the same.

The micro-crack inspection apparatus according to the present invention includes an object support unit for supporting a test object placed at a predetermined position, an exciter for applying a physical force to one side of the test object under control, and contacting the other side of the test object, And converting the physical force signal applied by the sensor and the excitation device and the vibration signal collected by the sensor into a frequency domain signal to calculate a first frequency response function, and calculating the first frequency response function. And a small crack detector configured to detect whether the test object is present by comparing the resonance point extracted from the frequency response function with the resonance point of the second frequency response function of the reference object.

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

In one embodiment, the impact hammer is provided with a tip (tip) in the part having, the tip can be replaced according to the frequency band required for detecting the presence of the micro crack.

In one embodiment, the test object may be positioned based on the structural features of the object.

In one embodiment, the test object may be positioned such that the direction in which cracks occur frequently in the object and the direction in which the physical force is applied by the exciter are perpendicular to each other.

In one embodiment, the sensor comprises an acceleration sensor that measures acceleration vibration.

In one embodiment, the micro-crack inspection apparatus further includes an adhesion part for closely contacting the sensor and the test object.

The micro crack detector extracts a first frequency region of interest from a resonance point of the first frequency response function, and the second micro crack detector extracts a first frequency region of interest from a resonance point of the previously measured second object. The frequency of interest is extracted to calculate a coherence value between the value of the first frequency of interest and the value of the second frequency of interest.

In one embodiment, the first region of interest and the second region of interest may be between 0.9 × N (Hz) and 1.1 × N (Hz) in the corresponding frequency response function, respectively. Where N is the resonance point frequency (Hz)

In one embodiment, the micro crack detector detects the presence of micro cracks by calculating a test index through Equation 1 below.

[Equation 1]

Where C (i) is the coherence value at frequency i (Hz).

In an exemplary embodiment, the micro crack detection unit may determine a test object satisfying Equation 2 below as a normal object having no micro crack.

[Equation 2]

Where Inspection is the inspection index and α is the correction factor.

The micro crack inspection method according to the present invention includes the steps of applying a physical force to one side of the test object by the excitation control, a sensor to collect the vibration signal generated by the test object, the physical crack applied by the micro crack detection unit Converting the force signal and the vibration signal collected by the sensor into a frequency domain signal to calculate a first frequency response function, extracting a resonance point from the first frequency response function, and the minute crack detector by the first frequency response function And detecting the presence of micro cracks in the test object by comparing the resonance point extracted from the resonance point extracted from the second frequency response function of the reference object.

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

In one embodiment, the sensor comprises an acceleration sensor that measures acceleration vibration.

The detecting of the presence of the minute cracks may include extracting a first frequency region of interest from a resonance point of the first frequency response function, and extracting a first frequency region of interest from the resonance point of the second frequency response function of the reference object. Extracting a frequency of interest region and calculating a coherence value of the value of the first frequency region of interest and the value of the second frequency region of interest.

In one embodiment, the first region of interest and the second region of interest may be between 0.9 × N (Hz) and 1.1 × N (Hz) in the corresponding frequency response function, respectively. Where N is the resonance point frequency (Hz)

In an embodiment, the detecting of the presence of the micro cracks may further include calculating an inspection index through Equation 1 below.

[Equation 1]

Where C (i) is the coherence value at frequency i (Hz).

In an exemplary embodiment, the detecting of the presence of the micro crack may further include determining whether the test object is a normal object based on Equation 2 below, wherein the micro crack of the test object satisfies Equation 2 below. Determine this as a normal object that does not exist.

[Equation 2]

Where Inspection is the inspection index and α is the correction factor.

As described above, the microcracks inspection apparatus according to the present invention and the microcracks inspection method using the same can detect the microcracks indirectly by comparing the resonance point of the target object and the resonance point of the reference object obtainable through the frequency response function. .

The microcracks inspection apparatus and the microcracks inspection method using the same according to the present invention effectively utilizes a physical phenomenon in which the number of resonance points increases with the depth of the microcracks, effectively determining whether or not the microcracks, which are very difficult to measure directly, exceed a reference value. You can judge.

The micro-crack inspection apparatus and the micro-crack inspection method using the same according to the present invention simplify the structure of the inspection apparatus and provide an inspection apparatus and an inspection method suitable for the whole inspection of an object and automation of inspection.

1 is a configuration diagram showing the configuration of a micro crack inspection apparatus according to an embodiment of the present invention
2 shows an example of a test sample.
3 shows an example of a frequency response function measured for the test sample of FIG.
4 is a diagram illustrating an example of coherence values near a resonance point;
5 is a flowchart illustrating a method for inspecting a minute crack using the apparatus for inspecting a minute crack according to an embodiment of the present invention.

Hereinafter, a detailed description for carrying out the micro crack inspection apparatus and the micro crack inspection method using the same according to the present invention will be described.

1 is a block diagram showing the configuration of a micro crack inspection apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the microcracks inspection apparatus 100 includes an object support 110, a test object 120, an exciter 130, a tip 140, a sensor 150, and a microcracks detector 160. ) May be included.

The microcracks inspection apparatus 100 indirectly detects microcracks formed in the test object 120 using a physical phenomenon in which the number of resonance points increases with the depth of the microcracks. For example, the microcracks inspection apparatus 100 may detect the presence or absence of microcracks formed in the test object 120 by comparing the resonance point of the test object 120 and the reference object that can be obtained through the frequency response function. .

The object supporter 110 supports the test object 120 placed at a predetermined position. The test object 120 is a target object for determining whether or not the normal state by detecting the presence of a small crack. In one embodiment, the test object 120 may be placed on the object support 110 through an automatic transport device (not shown). The test object 120 may be positioned based on the structural features of the object.

For example, in the case of a park gear used for an automobile transmission, there are statistically a large number of cracks in the Y-axis direction of the annular gear teeth. Therefore, when the test object 120 is a park gear used for an automobile transmission, the test object 120 has a vertical direction in which a physical force is applied by the exciter 130 and a direction in which cracks frequently occur in the object. May be placed on the object support 110. That is, the test object 120 may be placed on the object support 110 so that a physical force is applied in the X axis direction of the annular gear tooth. In another embodiment, according to the position of the test object 120 placed on the object support 110, the exciter 130 may move and move a position to apply a physical force to the test object 120. That is, the exciter 130 can move the position so that the physical force can be applied in the X-axis direction of the annular gear teeth.

The exciter 130 applies a physical force to one side of the test object under control. The exciter 130 may utilize a fixed impact device capable of automatically applying an impact to the test object 120. In one embodiment, the exciter 130 may include an impact hammer or an electrodynamic shaker or the like. Hereinafter, for convenience of explanation, it will be described on the assumption that it is used as an impact hammer. 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 140 may be provided at a portion (impact portion) that becomes an actual excitation. In one embodiment, the tip 140 may be replaced automatically or manually according to the frequency band required for detecting the presence of micro cracks in the test object 120. For example, when a high frequency band is required for measuring the resonance point of the test object 120, the tip of the steel product having a sharp front and a large rigidity may be used for the exciter 130. When a low frequency band is required, the tip of the exciter 130 may have a small rigidity such as plastic or rubber.

The sensor 150 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 130. The type of sensor 150 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 150 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.

During the full inspection of the object, it is not suitable to repeatedly attach and detach the sensor 150. Therefore, the sensor 150 is provided in the object support 110 of the inspection apparatus and integrated, and then configures the apparatus to measure the response by placing the test object 120 above the sensor 150 during the inspection. In one embodiment, when there is a gap between the test object 120 and the sensor 150 may cause unwanted vibration, the inspection apparatus further includes a close contact portion for close contact between the sensor 150 and the test object 120. Can be. For example, an adhesion part such as rubber having a weak rigidity may be provided above the sensor 150 to prevent unwanted vibration.

The micro crack detector 160 converts the physical force signal applied by the exciter 130 and the vibration signal collected by the sensor 150 into a frequency domain signal to calculate a frequency response function, and extracts it from the converted frequency domain signal. The presence of the small crack of the test object is detected by comparing the measured resonance point and the resonance point of the frequency domain signal of the previously measured reference object. In one embodiment, the reference object may correspond to a defect-free object having no microcracks in the object.

The minute crack detector 160 calculates a frequency response function H (jw) based on the input (impact) signal induced by the exciter 130 and the response (vibration) signal measured by the sensor 150. (H (jw) = Y (jw) / X (jw), where Y (jw) is the response signal, X (jw) input signal, w is the frequency)

2 is a diagram illustrating an example of a test sample, and FIG. 3 is a diagram illustrating an example of a frequency response function measured for the test sample of FIG. 2.

Referring to FIG. 2, (a) of FIG. 2 is an image of a test object having a crack length of 200 μm using CT equipment, and FIG. 2 (b) shows a test object of a crack length of 230 μm. It is a video.

3 is a frequency response function H (jw) based on the input (impact) signal induced by the exciter 130 and the response (vibration) signal measured by the sensor 150 for each test object of FIG. 2. It shows the result of calculating. Specimen 1 shows the frequency response function of Fig. 2A (test object with a crack length of 200 μm), and Specimen 2 shows the frequency response function of Fig. 2B (test object with a crack length of 230 μm). Indicates. Looking at the enlarged view of the vicinity of the resonance point on the right, it can be seen that the number of resonance points increased according to the depth of the microcracks. That is, in the case of Specimen 2, it can be seen that the phenomenon of branching to two resonance points occurs in the peak period. In the case of the existing inspection apparatus and inspection method, the inspection limit is at least 100 μm, while the micro crack inspection apparatus and the inspection method of the present invention can detect the micro cracks within 30 μm using the same.

Referring back to FIG. 1, the micro crack detector 160 extracts a first frequency region of interest from the resonance point of the first frequency response function calculated by the test object 120, and then measures the second frequency response function of the reference object. A second frequency region of interest is extracted at the resonance point of, and a coherence value of the value of the first frequency region of interest and the value of the second frequency region of interest is calculated. The minute crack detection unit 160 calculates a coherence value through a predefined coherence function using the values of the first frequency region of interest and the values of the second frequency region of interest as the first input value and the second input value, respectively. do. If the calculated coherence value is 1, the two input values are completely correlated; if the coherence value is 0, the two input values are not correlated.

In one embodiment, the first region of interest and the second region of interest may correspond to between 0.9 × N (Hz) and 1.1 × N (Hz) in the corresponding frequency response function, respectively. Here, N represents the resonance point frequency (Hz). Depending on the frequency response function of the test object, the range of the frequency region of interest may be changed.

In the case of the frequency response function, the coherence value is calculated to be near 1 (maximum is 1) near the resonance point due to the magnitude characteristic of the signal, and the signal is weak and easily exposed to the noise signal in the parts far away from the resonance point. A relatively low value is calculated. Therefore, the micro-crack detection unit 160 of the present invention assumes that the frequency of the resonance point is N (Hz), and utilizes only a value between the 0.9 * N (Hz) and 1.1 * N (Hz) frequency bands and uses a coherence value. By calculating, the reliability of the micro crack inspection can be increased.

4 is a diagram illustrating an example of a coherence value near a resonance point.

Referring to FIG. 4, Case 1 shows a result of calculating a coherence value near a resonance point using the frequency response function measured twice for Specimen 2 of FIG. 3. Case 2 and Case 3 show the results of calculating the coherence value near the resonance point using the frequency response function of Specimen 1 and the frequency response function of Specimen 2 measured twice. As discussed in Case 1, when the cracks have the same depth, the value of the coherence value near the resonance point is almost close to 1. On the other hand, if there is a difference in the depth of the cracks, such as case 2 and case 3, it can be seen that the coherence value around the resonance point is significantly lower than the value of 1. 4, it can be seen that the coherence value near the resonance point responds very sensitively to the difference in crack length of about 30 μm.

Referring back to FIG. 1, when the coherence value is calculated using the frequency response function of the test object 120 and the frequency response function of the reference object, the micro crack detection unit 160 checks the index through Equation 1 below. Calculate (Inspection)

[Equation 1]

Here, Inspection is an inspection index and C (i) is a coherence value at a frequency i (Hz).

In the case where the test object 120 without cracks is a normal object, all of the test objects 120 have a value near 1 in the section near the resonance point, and thus the test index is determined by the number of frequencies M of the analyzed regions (0.9 * N to 1.1 * N). Proximity values can be calculated. When the crack lengths of the test object 120 and the reference object are different, the test index may be significantly smaller than the frequency number (M).

After calculating the inspection index, the micro crack detection unit 160 determines whether the test object 120 is a normal object based on Equation 2 below. In an embodiment, the micro crack detector 160 may determine a test object satisfying Equation 2 as a normal object in which no micro crack exists.

[Equation 2]

Where Inspection is the inspection index and α is the correction factor.

The correction coefficient α may vary according to the type of object and may be preset to a value calculated through experiments. When the crack lengths of the test object 120 and the reference object differ by more than a predetermined length, since the value of the test index is significantly smaller than M, Equation 2 is not satisfied. Accordingly, the micro crack detection unit 160 may determine a test object satisfying Equation 2 as a normal object, and determine a test object not satisfying Equation 2 as a defective object.

5 is a flowchart illustrating a micro crack inspection method using the micro crack inspection apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the exciter 130 of the micro crack inspection apparatus applies a physical force to one side of the test object under control (step S510). In one embodiment, the exciter 130 may comprise an impact hammer or an electrodynamic shaker.

The test object 120 is a target object for detecting the presence of micro cracks and determines whether it is normal. The test object 120 may be placed on the object support 110 through an automatic transfer device (not shown). The exciter 130 exerts a physical force on the test object 120 placed on the object support 110. The test object 120 may be positioned based on the structural features of the object.

When a physical force is applied to the test object 120, the sensor 150 collects the vibration signal generated by the test object (step S520). In one embodiment, the sensor 150 may include an acceleration sensor that measures acceleration vibration.

The micro crack detector 160 converts the physical force signal applied by the exciter 130 and the vibration signal collected by the sensor 150 into a frequency domain signal to calculate a first frequency response function, and then calculates a first frequency response function. The resonance point is extracted at step S530.

The micro crack detection unit 160 detects the presence of the micro crack in the test object 120 by comparing the resonance point extracted from the first frequency response function with the resonance point extracted from the second frequency response function of the reference object. S540). In one embodiment, the micro crack detection unit 160 extracts the first frequency region of interest from the resonance point of the first frequency response function calculated by the test object 120, and the resonance point of the second frequency response function of the reference object previously measured. The coherence value of the value of the first frequency region of interest and the value of the second frequency region of interest may be calculated by extracting a second frequency region of interest from.

In one embodiment, the first region of interest and the second region of interest may correspond to between 0.9 × N (Hz) and 1.1 × N (Hz) in the corresponding frequency response function, respectively. Here, N represents the resonance point frequency (Hz). Depending on the frequency response function of the test object, the range of the frequency region of interest may be changed.

When the coherence value is calculated by using the frequency response function of the test object 120 and the frequency response function of the reference object, the micro crack detector 160 calculates an inspection index through Equation 1 below.

[Equation 1]

Here, Inspection is an inspection index and C (i) is a coherence value at a frequency i (Hz).

After calculating the inspection index, the micro crack detection unit 160 determines whether the test object 120 is a normal object based on Equation 2 below. In an embodiment, the micro crack detector 160 may determine a test object satisfying Equation 2 as a normal object in which no micro crack exists.

[Equation 2]

Where Inspection is the inspection index and α is the correction factor.

The disclosed micro crack inspection apparatus and inspection method using the same require only an exciter (for example, an impact hammer) and a sensor (for example, an acceleration sensor) for measuring a response signal. This has a simple advantage. In addition, the frequency coherence function and the coherence function required in the calculation process when detecting the presence of the micro cracks are not complicated functions that require a large amount of calculation time, and thus, there is an advantage in that fast operation is possible. Therefore, the disclosed micro crack inspection apparatus and the inspection method using the same have an advantage that is suitable for the entire inspection of mass-produced products.

The inspection apparatus and inspection method described with reference to FIGS. 1 to 5 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 inspection devices and test methods in a range that does not depart from the technical idea of the present invention.

100: micro crack inspection device
110: object support
120: test object
130: excitation
140: tips
150 sensor
160: micro crack detection unit

Claims (18)

An object supporter supporting an object placed at a predetermined position;
An exciter for applying a physical force to one side of the test object under control;
A sensor contacting the other side of a test object and collecting a vibration signal generated by the test object by the physical force; And
Converting the physical force signal applied by the exciter and the vibration signal collected by the sensor to a frequency domain signal to calculate a first frequency response function, the resonance point extracted from the first frequency response function and the measured of the reference object A micro crack detection unit for detecting the presence of micro cracks in the test object by comparing resonance points of a second frequency response function;
The micro crack detector extracts a first region of interest from the resonance point of the first frequency response function, extracts a second region of interest from the resonance point of the second frequency response function of the reference object, and the first frequency response function. And a value of the frequency region of interest and a value of the second frequency region of interest calculate a coherence value. The method of claim 1,
The exciter is a micro crack inspection device including an impact hammer or an electrodynamic shaker.
The method of claim 2,
The impact hammer is provided with a tip (tip) on the part having, the tip is a micro crack inspection device that can be replaced according to the frequency band required for detecting the presence of the micro crack.
The method of claim 1,
And the test object is positioned on the basis of the structural characteristics of the object.
The method of claim 4, wherein
And the test object is positioned such that the direction in which the crack frequently occurs in the object and the direction in which the physical force is applied by the exciter are perpendicular to each other.
The method of claim 1,
The sensor is a micro crack inspection device including an acceleration sensor for measuring acceleration vibration (acceleration vibration).
The method of claim 1,
The micro crack inspection apparatus further comprises a close contact portion for closely contacting the sensor and the test object.
delete The method of claim 1,
And the first frequency region of interest and the second frequency region of interest are each between 0.9 x N (Hz) and 1.1 x N (Hz) in a corresponding frequency response function.
Where N is the resonance point frequency (Hz)
The method of claim 1,
The micro crack detection unit detects the presence of micro cracks by calculating an inspection index through Equation 1 below.
[Equation 1]

Here, Inspection is an inspection index and C (i) is a coherence value at a frequency i (Hz).
The method of claim 10,
The micro crack detection unit is a micro crack inspection apparatus for determining a test object that satisfies the following equation (2) as a normal object does not exist.
[Equation 2]

Where Inspection is the inspection index and α is the correction factor.
An exciter exerting a physical force on one side of the test object under control;
Collecting a vibration signal generated by the sensor at the test object;
A minute crack detection unit converting the physical force signal applied by the exciter and the vibration signal collected by the sensor into a frequency domain signal to calculate a first frequency response function, and extracting a resonance point from the first frequency response function; And
And detecting, by the micro crack detection unit, whether there is a micro crack present in the test object by comparing the resonance point extracted from the first frequency response function with the resonance point extracted from the second frequency response function of the reference object.
Detecting the presence of the micro cracks is
Extracting a first frequency region of interest at a resonance point of the first frequency response function;
Extracting a second frequency region of interest from a resonance point of the second frequency response function of the previously measured reference object; And
And calculating a coherence value between the value of the first frequency region of interest and the value of the second frequency region of interest.
The method of claim 12,
The exciter includes an impact hammer or an electrodynamic shaker.
The method of claim 12,
The sensor comprises a micro crack inspection method for measuring the acceleration vibration (acceleration vibration).
delete The method of claim 12,
And the first frequency region of interest and the second frequency region of interest are each between 0.9 x N (Hz) and 1.1 x N (Hz) in a corresponding frequency response function.
Where N is the resonance point frequency (Hz)
The method of claim 12, wherein detecting the presence of the micro cracks
The micro crack test method further comprises the step of calculating the test index through the following equation (1).
[Equation 1]

Here, Inspection is an inspection index and C (i) is a coherence value at a frequency i (Hz).
18. The method of claim 17, wherein detecting the presence of the micro cracks
The method may further include determining whether the test object is a normal object based on Equation 2 below, wherein the test object satisfying Equation 2 is determined as a normal object in which no micro crack exists.
[Equation 2]

Where Inspection is the inspection index and α is the correction factor.

Images