Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1986-09-16
1987-12-29
Tokar, Michael J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
73799, H04N 718, G01N 1908
Patent
active
047164590
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fatigue crack position detection apparatus for detecting a distal end position of a crack in a test piece used in a fatigue test for metal material.
BACKGROUND ART
Measurement of fatigue of a metal material uses fatigue test piece 10 in which fatigue crack 12 is formed, as shown in FIG. 2. The shape and size of piece 10 are defined in, e.g., B. S. 5762-1979 (Methods for crack opening displacement testing). Test piece 10 is defined such that crack 12 having a predetermined length is formed from the bottom portion of notch 11 formed in the central portion of piece 10. During formation of crack 12, a load must be applied on test piece 10 while observing the length, i.e., the distal end position of crack 12.
Various conventional methods for detecting the distal end position of crack 12 have been used. Among these methods, noncontact detection methods are preferable. The noncontact detection methods include a method for optically monitoring crack 12 and a method for detecting a magnetic change caused by crack 12 as a change in eddy current, if piece 10 is a magnetic substance. However, in the method using the eddy current, the detection result varies in accordance with the magnetic characteristics of the piece, and a crack position cannot be precisely detected. Therefore, demand has arisen for an apparatus which can precisely and easily detect a crack position by an optical method.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a fatigue crack position detection apparatus which can detect a distal end position of a crack formed in a fatigue test piece in a noncontact manner.
According to the present invention, there is provided a method for automatically measuring a crack distal end position in a fatigue test piece, characterized in that luminance levels are integrated from an image signal obtained by scanning a reference line and a crack formed in a fatigue test piece in the same direction as that of the reference line so as to obtain a reference line position from a maximum luminance level. The image signal is converted into a binary signal to detect a crack distal end position by discriminating continuity of a high-level value, and a distance between the reference line position and the crack distal end position is then calculated.
According to the present invention, there is provided an apparatus for automatically measuring a crack distal end position of a fatigue test piece, characterized by comprising: scanning means for scanning a reference line and a crack in a fatigue test piece with the reference line, for obtaining a crack distal end position within an identical field of view; reference line detection means for integrating luminance levels from a video signal obtained by a scanning operation of the scanning means in the same direction as that of the reference line to obtain a maximum level to detect a reference line position; crack distal end position detection means for binary-coding the luminance levels of the video signal output from the scanning means in a direction perpendicular to a direction of the crack and thereafter discriminating continuity of a high-level value to detect a crack distal end position; and crack distal end position calculating means for calculating a distance between the reference line position obtained by the reference line detection means and the crack distal end position obtained by the crack distal end position detection means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a fatigue crack position detection apparatus according to an embodiment of the present invention;
FIG. 2 is a side view of a fatigue test piece;
FIG. 3 is a perspective view partially showing the apparatus shown in FIG. 1;
FIG. 4(a) is a view of an image of a test piece;
FIG. 4(b) is a graph showing luminance distribution along the vertical direction of a test piece image;
FIGS. 5(a) to 5(d) are views showing a crack detecting operation;
FIGS. 6(a) to 6(c) are views showing a noise removing operati
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patent: 4446481 (1984-05-01), Edamatsu et al.
patent: 4574642 (1986-03-01), Fleischman
patent: 4613234 (1986-09-01), Cruickshank
Inomata Masaichi
Iwai Kenji
Makabe Eiichi
Maruyama Kyusuke
Sano Kazuo
Nippon Kokan Kabushiki Kaisha
Raevis Robert R.
Tokar Michael J.
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