Boots – shoes – and leggings
Patent
1995-01-26
1997-09-23
Cosimano, Edward
Boots, shoes, and leggings
73600, 73602, 73609, 73610, 73614, 364506, 36455101, 364572, 364574, G01N 2904, G01N 2910
Patent
active
056711549
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an ultrasonic inspection apparatus which transmits an ultrasonic pulse to a target object and analyzes an echo signal detected from the target object to detect a flaw present in the target object and, more particularly, to a signal processing method and signal processing device in which, after a detected high-frequency echo signal is temporarily converted into a digital signal, noise of the digital signal is reduced.
An ultrasonic inspection apparatus is arranged as shown in FIG. 25. An ultrasonic transmit-receive unit 1 transmits a pulse signal at a predetermined period T.sub.0 to a probe 3 provided to a target object 2 such as steel material directly or through a delay material such as water. As shown in FIG. 26, the probe 3 converts the received pulse signal into an ultrasonic pulse a to apply the ultrasonic pulse a to the target object 2. The ultrasonic pulse a applied into the target object 2 is reflected by a bottom surface 2a of the target object 2 and received by the probe 3 again. The probe 3 converts the reflected wave into an electrical signal to transmit the electrical signal to the ultrasonic transmit-receive unit 1. The ultrasonic transmit-receive unit 1 amplifies the electrical signal and transmits the amplified signal to a signal processing device 4 as an echo signal b.
The echo signal b includes a bottom surface (B) echo 5b corresponding to the wave reflected by the bottom surface 2a and a flaw (F) echo 5b caused by a flaw. In addition, a frequency f of the ultrasonic pulse a is determined by the thickness or the like of an ultrasonic vibrator incorporated in the probe 3. The frequency f of the ultrasonic pulse a used for inspection is set to be several MHz to ten and several MHz. Therefore, the frequency range of the signal waveforms of the bottom surface echo 5a and the flaw echo 5b included in the echo signal b is a wide range of 0 Hz to ten and several MHz.
The signal processing device 4 performs various signal processes to the echo signal b received from the ultrasonic transmit-receive unit 1, and the signal processing device 4 displays a signal process result and the presence/absence of a flaw on a display unit 6. In this case, in order to perform a signal process to the echo signal and display the echo signal, a trigger signal S synchronized with the pulse signal is supplied from the ultrasonic transmit-receive unit 1 to the signal processing device 4.
In the flaw inspection apparatus arranged described above, the echo signal a output from the ultrasonic transmit-receive unit 1 includes, in addition to the bottom surface echo 5a and the flaw echo 5b, a larger amount of noise. When an amount of noise included in the ultrasonic pulse a is large, the reliability of an inspection result is considerably degraded. The noise is roughly classified into electrical noise and material noise.
The electrical noise is constituted by external noise caused by mixing an electromagnetic wave into the probe 3, the ultrasonic transmit-receive unit 1, a connection cable, or the like and internal noise generated by an amplifier or the like incorporated in the ultrasonic transmit-receive unit 1.
An ultrasonic wave propagating in the target object 2 is scattered by the crystal grain boundary of a material. This scattered ultrasonic wave is received by the probe 3. The echo signal b output from the probe 3 includes the received scattered ultrasonic wave as a scattered echo. This scattered echo is the material noise described above.
Reduction of the noise included in the echo signal b is very important to perform ultrasonic inspection at high accuracy.
Conventionally, an analog filter is used to reduce noise components included in the echo signal b. For example, a BPF (Bandpass Filter) for causing the frequency component of the ultrasonic echo to pass is used for electrical noise having a wide-frequency component. In addition, an LPF (Low-Pass Filter) or a BPF is used for material noise utilizing that the frequency distribution of the flaw echo 5b is lower than that of a scat
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Horigome Hidekazu
Iizuka Yukinori
Murayama Akira
Nakazawa Shin
Cosimano Edward
NKK Corporation
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