Measuring and testing – Vibration – Resonance – frequency – or amplitude study
Reexamination Certificate
2003-03-25
2004-01-06
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
Resonance, frequency, or amplitude study
C073S597000, C073S598000, C073S602000, C073S628000
Reexamination Certificate
active
06672162
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ultrasonic detection apparatuses to be employed such as for detecting internal defects or the like of concrete materials by means of ultrasonic waves and an ultrasonic detection method that employs the apparatus. More particularly, the present invention relates to an ultrasonic detection apparatus which provides accurate and high-speed detection of reinforcing bars arranged inside a concrete material, the depth of a crack, the thickness of concrete, gaps and the like, and to an ultrasonic detection method that employs the apparatus.
BACKGROUND ART
A concrete material is a composite structure of cement and coarse aggregates of 1 to 3 mm in diameter. Ultrasonic waves traveling through a concrete material are scattered while being reflected, refracted, and changed in mode repeatedly at the interface between the coarse aggregate and the cement.
This causes readily the ultrasonic waves to be diffused in the concrete material and significantly attenuated in strength in the orientation direction of the ultrasonic waves. The level of the attenuation would be acceleratingly increased as the ultrasonic waves have higher frequencies.
In addition, when longitudinal or transverse ultrasonic waves are input into a concrete material from a surface thereof, longitudinal or transverse ultrasonic waves and direct waves, each having a relatively large amount of energy, coexist with the longitudinal or transverse ultrasonic waves input to the inside of the concrete material. In addition, surface waves having a large amount of energy are generated at the surface of the concrete material.
These phenomena have conventionally made it difficult to detect the inside such as of a concrete material or a porous material by means of ultrasonic waves.
However, recent years have seen an improvement of internal detection methods employing ultrasonic waves. Thus, in some cases, with various conditions being satisfied, it is possible to measure the thickness of a concrete plate or detect gaps or the like therein within a detection depth range of about 20 to 50 cm. The conditions of the detection are shown below.
First, it is necessary to use ultrasonic wave transmitting and receiving transducers having a resonant frequency of about 100 to 500 kHz. Secondly, it is necessary to use transducers having an oscillator as large as about 50 to 70 mm in diameter. Thirdly, it is necessary to apply a stepped voltage to a ceramic oscillator or the like in the transducer instead of the pulsed voltage, which has been conventionally employed.
FIG.
68
(
a
) is a graph showing a pulsed voltage, (b) being a graph showing the spectrum of the pulsed voltage, and (c) being a graph showing a time series waveform of the pulsed voltage. On the other hand, FIG.
69
(
a
) is a graph showing a stepped voltage, (b) being a graph showing the spectrum of the stepped voltage, and (c) being a graph showing a time series waveform of the stepped voltage. The graphs represent pulsed and stepped voltages having values of 50 to 500 V. Differences are found in the spectrum and time series waveform between the pulsed and stepped voltages. Incidentally, the peak frequencies of FIGS.
68
(
b
) and
69
(
b
) are resonant frequencies of oscillators, while FIGS.
68
(
c
) and
69
(
c
) show time series transmit ultrasonic waves.
Now, a conventional method for measuring a concrete material will be explained in which the stepped voltage shown in FIG.
69
(
a
) is applied to the concrete material by using an ultrasonic transducer having an oscillator 56 mm in diameter whose resonant frequency is 1 MHz.
FIG. 70
is a schematic view illustrating a concrete plate as a material to be detected. The concrete plate
41
as a material to be detected has a thickness of 20 cm and contains fine stones about 2 mm in diameter as coarse aggregate. In addition, the concrete plate
41
has a relatively small number of bubbles therein. Furthermore, it should be understood that this measuring method works as a method for making a measurement with one transducer, in which a transducer
42
functions as receiving and transmitting transducers.
FIG. 71
is a graph illustrating a reflected wave obtained under the aforementioned conditions, with the horizontal axis representing the time and the vertical axis representing the amplitude.
Referring to
FIG. 71
, a peak
43
a
shows a longitudinal reflected wave
43
from the bottom surface of the concrete plate. The peak
43
a
is noticeable, showing that it is possible to measure the thickness of the concrete plate under the aforementioned conditions.
Suppose that like the concrete plate
41
, the thickness is relatively thin when compared with the surface area. In this case, according to various types of measurement examples, since a corner-reflected wave
44
from a corner portion and a reflected wave of a surface wave
45
are generally small in amplitude, it is made possible to measure the thickness of a plate as thick as about down to 50 cm under the aforementioned conditions.
However, for a concrete plate having been subjected to aging, it is often difficult to confirm the generation of a reflected wave from the bottom surface thereof. Likewise, when a concrete plate is not a planar one, and great amounts of reflected waves from the corner portions and from surface waves are provided and lots of bubbles are contained in the concrete plate, it is also difficult in many cases to confirm the generation of a reflected wave from the bottom surface.
For example, the following cases make it difficult to measure thickness.
FIG. 72
is a view illustrating a concrete pillar or a material to be detected, (a) being a schematic view thereof before being cut apart and (b) being a schematic view thereof after having been cut apart.
Here, such a concrete pillar
51
was made that has a side of length 30 cm and another side of length 50 cm in a cross section perpendicular to the longitudinal direction. Inside the concrete pillar
51
, there is present a large number of bubbles about 1 to 10 mm in diameter. In addition, contained in the concrete pillar are 30 wt % of coarse aggregates having diameters greater than 5 mm and less than 1 cm, 40 wt % of coarse aggregates having diameters greater than 1 cm and less than 2 cm, and 40 wt % of coarse aggregates having diameters greater than 2 cm. In addition, a concrete material
51
a
having a height of 50 cm was cut from the concrete pillar
51
.
Such a case is explained below in which a transducer
52
is placed at the center A of a plane having a width of 50 cm for measuring the thickness.
FIG. 73
is a schematic view illustrating waves produced when the thickness is measured with the transducer
52
being placed at the center A.
When longitudinal ultrasonic waves are input into the concrete material
51
a
from a surface thereof directly downwards with the transducer
52
being placed at the center A, as shown in
FIG. 73
, a corner-reflected wave
54
, a direct wave
55
, a surface wave
56
, and a longitudinal wave
57
low in strength as well as a reflected wave
53
from the bottom surface return to the center A. Accordingly, the received wave at the center A is a superimposed wave of the waves
53
-
57
, making it difficult to determine the peak of the reflected wave from the bottom surface as shown in FIG.
71
.
Various types of oscillators were actually used for the application of a stepped voltage of 500 V for measurement, with the results being illustrated. FIG.
74
(
a
) is a graph illustrating a time series waveform obtained by a measurement with a transmitting transducer having an oscillator of resonant frequency 2.5 MHz and 20 mm in diameter, (b) being a graph illustrating a time series waveform obtained by a measurement with a transmitting transducer having an oscillator of resonant frequency 500 kHz and 40 mm in diameter, and (c) being a graph illustrating a time series waveform obtained by a measurement with a transmitting transducer having an oscillator of resonant frequency 500 kHz and 70 mm in diameter. Incidentally, the rec
H & B System Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Saint-Surin Jacques
Williams Hezron
LandOfFree
Ultrasonic detection apparatus and ultrasonic detection... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultrasonic detection apparatus and ultrasonic detection..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrasonic detection apparatus and ultrasonic detection... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3192425