Measuring and testing – Vibration – By mechanical waves
Patent
1989-03-30
1991-04-09
Chapman, John
Measuring and testing
Vibration
By mechanical waves
73620, G01N 2904
Patent
active
050054201
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an ultrasonic method for measurement of the depth of any surface opening flaw possibly existent in a solid mass.
The term "surface opening flaw" in a solid mass used herein refers not only to a flaw developed as an opening on the surface of parts or members of whatever the height, composing, for example, electrical, mechanical equipment or installations, etc. in various industrial fields, but to a flaw not actually opening but existent very closely to the surface. More particularly, the surface opening flaws or open-on-surface flaws include a variety of cracks such as weld cracking in a welded portion, quench cracks caused during a heat treatment, grinding cracks produced during grinding, stress corrosion cracking, etc. and fatigue cracks, etc. in materials, to all of which the present invention is applicable. Also, the term "solid mass" described herein refers to a mass of a metal as well as a mass of a nonmetal such as glass, ceramics, synthetic resin, rubber, etc. through which ultrasonic waves can be propagated.
The "depth of surface opening flaw" as used herein means the vertical distance from the surface of a solid mass from which the flaw opens to the end of the depth in the solid mass.
BACKGROUND ART
For an ultrasonic measurement of the depth of a flaw opened on the surface of a solid mass, such as weld cracking in a welded portion, a fatigue crack in a member portion in which stresses concentrate, etc., various methods have recently been studied because of the necessity for the measured information, and the results from the studies have been reported. For example, (1) the measurement of the fatigue-crack depth by the end peak echo method is reported in the "Nondestructive Inspection" Vol. 31, No. 9, September, 1982, pp. 690-691, (2) a method for inspection for cracks using scattered ultrasonic waves is disclosed in the "Nondestructive Inspection" Vol. 29, No. 2, February, 1980, pp. 136-137, (3) the measurement of the height of incomplete penetration in a welded portion of steel plates is disclosed in the "Non-destructive Inspection" Vol. 34, No. 2, February, 1985, pp. 112-113, and (4) the accuracy of measurement of the notch depth based on time lapse of ultrasonic wave is described in the "Nondestructive Inspection" Vol. 29, No. 2, February, 1980, pp. 130-131.
In the measurement disclosed in the report (1), a spot-focusing type longitudinal wave angle probe is used to measure the relation between the beam path and various kinds of depth of slits formed axially in the inner wall of the bend of a pipe from the outer circumference of the pipe by the end peak echo method, thereby determining the crack depth from a calibration curve prepared based on the measured beam path. In the method for crack measurement using scattered ultrasonic waves in the above report (2), a probe is used which has arrayed therein an ultrasound transmitting transducer and a receiving transducer arrayed symmetrically with respect to a partition sheet. When ultrasonic waves are radiated from the transmitting transducer toward an object immersed in water, and a difference in time .DELTA.t of the reception of scattered waves by the receiving transducer between when the object has a flaw when the object has no flaw is measured. Utilizing the correlation between the time difference .DELTA.t and the flaw depth d, the flaw depth d is determined. In the method described in the above report (3), a two-transducer vertical-type probe is used and placed on the one-side butt joint of a plate finished smooth and having a thickness t (9 to 12 mm in the report). The depth of penetration d in the welded portion is directly read from the time base of the ultrasonic flaw detector and compared with the plate thickness, thereby measuring the height of incomplete penetration h= (t-d). In the method disclosed in the above report (4), an ultrasonic flaw detector permitting measurement of the time of ultrasound propagation with a high accuracy is used to determine the notch depth based on the propag
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patent: 3776026 (1973-12-01), Adler et al.
patent: 4274288 (1981-06-01), Tittmann et al.
patent: 4759221 (1988-07-01), Ortlieb et al.
patent: 4785667 (1988-11-01), Miyajima et al.
Arana Louis M.
Chapman John
Hitachi Construction Machinery Co. Ltd.
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