6 Correlation Analysis of Acoustic Emission Signals …
69
at 50 mm has some little similarity with those at 140, 150, 160 and 170 mm, so the
relevant coefficients have lower values than those at 55, 60 mm and 65 mm. Based on
discussion above, there is no evident relationship between the correlation coefficients
and the AE signal wave features.
6.6 Relation Between Correlation Coefficients and AE
Signal Frequency Components
Amplitude-frequency characteristics of the AE signals discussed in Sect. 6.4 were
obtained with FFT transform, as shown in Fig. 6.5. As described in Fig. 6.5a, the
whole range of frequency components is divided into two evident parts, 0~580 kHz
and 580~1200 kHz. The two parts of AE signal frequencies are respectively presented
in Fig. 6.5b, c. The amplitudes of the lower frequency parts have consistent features,
while the amplitudes of the higher frequency parts have strong fluctuation and
attenuation features with the increase of propagation distances.
Correlation coefficients from frequency components of obtained signals are listed
in Fig. 6.5, divided into three parts. From Fig. 6.5a, coefficients form 15~35 mm
attenuate slowly in the range of 100 mm and fluctuate besides this range. Coefficients
form Fig. 6.6a, b are different form Fig. 6.6a, attenuating and fluctuating sharply in
little rang form the gauge point. The signals have more similarities in the vicinity
(a)0~1200kHz
(b)0~580kHz
(c)580kHz~1200kHz
100 200 300 400 500 600 700 800 900 1000 1100 1200
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Frequency (kHz)
|Y(f)|
Single-Sided Amplitude Spectrum of y(t)(9-14)
50mm
55mm
60mm
65mm
140mm
150mm
160mm
170mm
50
100 150 200 250 300 350 400 450 500 550
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Frequency (kHz)
|Y(f)|
Single-Sided Amplitude Spectrum of y(t)(9-14)
50mm
55mm
60mm
65mm
140mm
150mm
160mm
170mm
600
700
800
900
1000
1100
1200
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Frequency (kHz)
|Y(f)|
Single-Sided Amplitude Spectrum of y(t)(9-14)
50mm
55mm
60mm
65mm
140mm
150mm
160mm
170mm
Fig. 6.5 Frequency distribution of AE signals
(a) coefficients from 15mm~35mm
(b) coefficients from 110mm~170mm
(c) coefficients from 340mm~400mm
0
50
100
150
200
250
300
350
400
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance(mm)
Correlation Coefficient
Correlation Coefficient of AE Signal Frequency
15mm
20mm
30mm
35mm
0
50
100
150
200
250
300
350
400
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance(mm)
Correlation Coefficient
Correlation Coefficient of AE Signal Frequency
140mm
150mm
160mm
170mm
0
50
100
150
200
250
300
350
400
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance(mm)
Correlation Coefficient
Correlation Coefficient of AE Signal Frequency
340mm
360mm
380mm
400mm
Fig. 6.6 Correlation coefficients for frequency components
69
at 50 mm has some little similarity with those at 140, 150, 160 and 170 mm, so the
relevant coefficients have lower values than those at 55, 60 mm and 65 mm. Based on
discussion above, there is no evident relationship between the correlation coefficients
and the AE signal wave features.
6.6 Relation Between Correlation Coefficients and AE
Signal Frequency Components
Amplitude-frequency characteristics of the AE signals discussed in Sect. 6.4 were
obtained with FFT transform, as shown in Fig. 6.5. As described in Fig. 6.5a, the
whole range of frequency components is divided into two evident parts, 0~580 kHz
and 580~1200 kHz. The two parts of AE signal frequencies are respectively presented
in Fig. 6.5b, c. The amplitudes of the lower frequency parts have consistent features,
while the amplitudes of the higher frequency parts have strong fluctuation and
attenuation features with the increase of propagation distances.
Correlation coefficients from frequency components of obtained signals are listed
in Fig. 6.5, divided into three parts. From Fig. 6.5a, coefficients form 15~35 mm
attenuate slowly in the range of 100 mm and fluctuate besides this range. Coefficients
form Fig. 6.6a, b are different form Fig. 6.6a, attenuating and fluctuating sharply in
little rang form the gauge point. The signals have more similarities in the vicinity
(a)0~1200kHz
(b)0~580kHz
(c)580kHz~1200kHz
100 200 300 400 500 600 700 800 900 1000 1100 1200
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Frequency (kHz)
|Y(f)|
Single-Sided Amplitude Spectrum of y(t)(9-14)
50mm
55mm
60mm
65mm
140mm
150mm
160mm
170mm
50
100 150 200 250 300 350 400 450 500 550
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Frequency (kHz)
|Y(f)|
Single-Sided Amplitude Spectrum of y(t)(9-14)
50mm
55mm
60mm
65mm
140mm
150mm
160mm
170mm
600
700
800
900
1000
1100
1200
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Frequency (kHz)
|Y(f)|
Single-Sided Amplitude Spectrum of y(t)(9-14)
50mm
55mm
60mm
65mm
140mm
150mm
160mm
170mm
Fig. 6.5 Frequency distribution of AE signals
(a) coefficients from 15mm~35mm
(b) coefficients from 110mm~170mm
(c) coefficients from 340mm~400mm
0
50
100
150
200
250
300
350
400
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance(mm)
Correlation Coefficient
Correlation Coefficient of AE Signal Frequency
15mm
20mm
30mm
35mm
0
50
100
150
200
250
300
350
400
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance(mm)
Correlation Coefficient
Correlation Coefficient of AE Signal Frequency
140mm
150mm
160mm
170mm
0
50
100
150
200
250
300
350
400
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Distance(mm)
Correlation Coefficient
Correlation Coefficient of AE Signal Frequency
340mm
360mm
380mm
400mm
Fig. 6.6 Correlation coefficients for frequency components