Defect detection device and defect detection method
In a defect detection device ( 10 ), an exciter ( 11 ) gives a test object (S) a vibration with a variable frequency. A vibration state measurer ( 15, 163 ) performs a measurement of the vibration state of the surface of the test object by an optical means while the vibration is given to the test object, and determines, for each position on the surface, a numerical value representing the vibration state based on a result of the measurement. A judgment-index-value determiner ( 164 ) determines a judgment index value by Fourier transform based on the numerical value representing the vibration state at each position, where the judgment index value is a numerical value representing a strength of the vibration for each wavenumber. A wavenumber-wavelength determiner ( 165 ) determines, based on the judgment index value determined for each wavenumber, a wavenumber or wavelength of an elastic wave induced in the test object by the vibration.
1 . A defect detection device, comprising:
an exciter configured to give a test object a vibration of a predetermined frequency;
a vibration state measurer configured to perform a measurement of a vibration state of a measurement area on a surface of the test object by an optical means while the vibration is given to the test object, and to determine, for each position on the surface, a numerical value representing the vibration state based on a result of the measurement;
a judgment-index-value determiner configured to determine a judgment index value by performing Fourier transform on an entire area of the measurement area based on the numerical value representing the vibration state at each position, where the judgment index value is a numerical value representing a strength of the vibration for each wavenumber; and
a frequency controller configured to set the predetermined frequency,
wherein a wavenumber or wavelength of an elastic wave induced within the entire area of the measurement area in the test object by the vibration given to the test object is determined based on a comparison of each of the judgment index value determined for each wavenumber,
wherein the frequency controller changes the predetermined frequency based on the determined wavenumber or wavelength.
2 . The defect detection device according to claim 1 , wherein the judgment-index-value determiner is configured to determine the judgment index value for each scalar-valued wavenumber.
3 . The defect detection device according to claim 1 , further comprising:
a display device configured to display an image showing the vibration state, based on the numerical value representing the vibration state determined for each position on the surface; and
a wavelength determination target area setter configured to set a wavelength determination target area within the image displayed by the display device,
wherein the judgment-index-value determiner is configured to perform the Fourier transform based on the numerical value representing the vibration state at each position within the wavelength determination target area.
4 . The defect detection device according to claim 1 , wherein the determined wavenumber or wavelength includes not only a wavenumber or wavelength at which the judgment index value has a largest value, but also another wavenumber or wavelength at which the judgment index value has a local maximum.
5 . A defect detection method, comprising:
a vibration-giving process for giving a test object a vibration of a predetermined frequency;
a vibration state measurement process for performing a measurement of a vibration state of a measurement area on a surface of the test object by an optical means while the vibration is given to the test object, and for determining, for each position on the surface, a numerical value representing the vibration state based on a result of the measurement;
a judgment-index-value determination process for determining a judgment index value by performing Fourier transform on an entire area of the measurement area based on the numerical value representing the vibration state at each position, where the judgment index value is a numerical value representing a strength of the vibration of each wavenumber;
a wavenumber-wavelength determination process for determining, based on a comparison of each of the judgment index value determined for each wavenumber, a wavenumber or wavelength of an elastic wave induced within the entire area of the measurement area in the test object by the vibration given to the test object; and
a determination process for determining whether or not the wavenumber or wavelength determined in the wavenumber-wavelength determination process is within a predetermined range, based on the wavenumber or wavelength as well as a size of a defect expected to be present in the test object,
wherein, when it is determined in the determination process that the wavenumber or wavelength is not within the predetermined range, the aforementioned processes are once more performed after the predetermined frequency is changed.