S/N ratio measuring method in eddy current testing on internal surface of pipe or tube
View Patent ↗A method in accordance with the present invention includes the steps of: separating an eddy current signal into an X-axis component and a Y-axis component to obtain signal waveform data of the respective components; excluding predetermined low-frequency components respectively from the respective signal waveform data thus obtained; calculating a noise voltage value V 1 defined by the following Equation (1) based upon voltage values X(i) and Y(i) of the signal waveform data of the X-axis component and the Y-axis component from which the low-frequency components have been excluded; and calculating an S/N ratio by dividing a voltage value D of an eddy current signal corresponding to a predetermined artificial flaw by the noise voltage value V 1 : V 1 = π / n · ∑ i = 1 n ( X ( i ) 2 + Y ( i ) 2 ) 1 / 2 ( 1 ) where n represents the number of samplings of the signal waveform data.
1. A method for measuring an S/N ratio in an eddy current testing on an internal surface of a pipe or tube comprising the steps of:
using a microprocessor for;
separating an eddy current signal obtained by executing an eddy current testing on the internal surface of a pipe or tube in an axis direction into an X-axis component and a Y-axis component that are different from each other by 90° in the phases thereof to obtain signal waveform data of the X-axis component and signal waveform data of the Y-axis component;
excluding predetermined low-frequency components respectively from the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component thus obtained;
calculating a noise voltage value V 1 defined by the following Equation (1) based upon a voltage value X(i) of the signal waveform data of the X-axis component with the low-frequency component excluded therefrom and a voltage value Y(i) of the signal waveform data of the Y-axis component with the low-frequency component excluded therefrom; and
calculating an S/N ratio defined by the following Equation (2) based upon a voltage value D of an eddy current signal corresponding to a predetermined artificial flaw, obtained by executing an eddy current testing on an internal surface of a pipe or tube with the artificial flaw formed therein, and the noise voltage value V 1 :
V
1
=
π
/
n
·
∑
i
=
1
n
(
X
(
i
)
2
+
Y
(
i
)
2
)
1
/
2
(
1
)
where n represents the number of samplings of the signal waveform data,
S/N ratio= D/V 1 (2).
2. The method for measuring an S/N ratio in an eddy current testing on an internal surface of a pipe or tube according to claim 1 , wherein the step of excluding the predetermined low-frequency components comprises the steps of:
extracting a frequency spectrum by applying a Fourier transform to each of the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component;
excluding the low-frequency component from the frequency spectrum thus extracted; and
applying an Inverse Fourier transform to the frequency spectrum with the low-frequency component excluded therefrom to generate signal waveform data of the X-axis component with the low-frequency component excluded therefrom and signal waveform data of the Y-axis component with the low-frequency component excluded therefrom.
3. A method for measuring an S/N ratio in an eddy current testing on an internal surface of a pipe or tube comprising the steps of:
using a microprocessor for;
separating an eddy current signal obtained by executing an eddy current testing on the internal surface of a pipe or tube in an axis direction into an X-axis component and a Y-axis component that are different from each other by 90° in the phases thereof to obtain signal waveform data of the X-axis component and signal waveform data of the Y-axis component;
excluding predetermined low-frequency components respectively from the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component thus obtained;
dividing the signal waveform data of the X-axis component with the low-frequency component excluded therefrom and the signal waveform data of the Y-axis component with the low-frequency component excluded therefrom respectively into signal waveform data for each of a plurality of sections j (j=1 to N, N: an integer of 2 or more) in the axis direction of the pipe or tube;
calculating a noise voltage value V 2 (j) defined by the following Equation (3) for each of the divided sections j based upon a voltage value X(i, j) of the signal waveform data of the X-axis component with the low-frequency component excluded therefrom and a voltage value Y(i, j) of the signal waveform data of the Y-axis component with the low-frequency component excluded therefrom; and
calculating an S/N ratio defined by the following Equation (4) based upon a voltage value D of an eddy current signal corresponding to a predetermined artificial flaw, obtained by executing an eddy current testing on an internal surface of a pipe or tube with the artificial flaw formed therein, as well as based upon a maximum value V 2 over the entire sections of the noise voltage value V 2 (j) calculated for each of the sections j:
V
2
(
j
)
=
π
/
m
·
∑
i
=
1
m
(
X
(
i
,
j
)
2
+
Y
(
i
,
j
)
2
)
1
/
2
(
3
)
where m represents the number of samplings of the signal waveform data in each section,
S/N ratio= D/V 2 (4).
4. The method for measuring an S/N ratio in an eddy current testing on an internal surface of a pipe or tube according to claim 3 , wherein the step of excluding the predetermined low-frequency components comprises the steps of:
extracting a frequency spectrum by applying a Fourier transform to each of the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component;
excluding the low-frequency component from the frequency spectrum thus extracted; and
applying an Inverse Fourier transform to the frequency spectrum with the low-frequency component excluded therefrom to generate signal waveform data of the X-axis component with the low-frequency component excluded therefrom and signal waveform data of the Y-axis component with the low-frequency component excluded therefrom.
5. A method for measuring an S/N ratio in an eddy current testing on an internal surface of a pipe or tube comprising the steps of:
using a microprocessor for;
separating an eddy current signal obtained by executing an eddy current testing on the internal surface of a pipe or tube in an axis direction into an X-axis component and a Y-axis component that are different from each other by 90° in the phases thereof to obtain signal waveform data of the X-axis component and signal waveform data of the Y-axis component;
dividing the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component thus obtained respectively into signal waveform data for each of a plurality of sections j (j=1 to N, N: an integer of 2 or more) in the axis direction of the pipe or tube;
excluding predetermined low-frequency components respectively from the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component for each of the divided sections j;
calculating a noise voltage value V 2 (j) defined by the following Equation (3) for each of the divided sections j based upon a voltage value X(i, j) of the signal waveform data of the X-axis component with the low-frequency component excluded therefrom and a voltage value Y(i, j) of the signal waveform data of the Y-axis component with the low-frequency component excluded therefrom; and
calculating an S/N ratio defined by the following Equation (4) based upon a voltage value D of an eddy current signal corresponding to a predetermined artificial flaw, obtained by executing an eddy current testing on an internal surface of a pipe or tube with the artificial flaw formed therein, as well as based upon a maximum value V 2 over the entire sections of the noise voltage value V 2 (j) calculated for each of the sections j:
V
2
(
j
)
=
π
/
m
·
∑
i
=
1
m
(
X
(
i
,
j
)
2
+
Y
(
i
,
j
)
2
)
1
/
2
(
3
)
where m represents the number of samplings of the signal waveform data in each section,
S/N ratio= D/V 2 (4).
6. The method for measuring an S/N ratio in an eddy current testing on an internal surface of a pipe or tube according to claim 5 , wherein the step of excluding the predetermined low-frequency components comprises the steps of:
extracting a frequency spectrum by applying a Fourier transform to each of the signal waveform data of the X-axis component and the signal waveform data of the Y-axis component;
excluding the low-frequency component from the frequency spectrum thus extracted; and
applying an Inverse Fourier transform to the frequency spectrum with the low-frequency component excluded therefrom to generate signal waveform data of the X-axis component with the low-frequency component excluded therefrom and signal waveform data of the Y-axis component with the low-frequency component excluded therefrom.