Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2000-10-05
2003-04-08
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S612000, C073S614000, C073S625000
Reexamination Certificate
active
06543287
ABSTRACT:
BACKGROUND
The present invention relates to a nondestructive technique or method for the inspection of materials. More specifically, but without limitation, the present invention relates to a nondestructive technique or method for the inspection of materials utilizing a method for acoustic imaging by angle beam. The method helps find various imperfections and discontinuities on a material or test piece.
Nondestructive inspection (“NDI”) is a field which includes all means of evaluating the quality and strength of materials and structures without adversely affecting their quality, strength or usefulness. NDI usually includes methods recognized by the American Society of Nondestructive Testing. These methods include radiography, eddy current testing, dye penetrant testing, ultrasonic testing, leak testing, thermography, and the like. These methods help find cracks, corrosion, weld flaws, rolling or processing flaws, thickness variations and various other imperfections or discontinuities that may affect quality and strength of a material or structure.
Detection of these types of imperfections or discontinuities is difficult even with all the presently available testing methods. Detection of corrosion and small fatigue cracks is difficult and time consuming when only one side of a material or structure is accessible. In addition, the presently available testing methods do not indicate the type of discontinuity or imperfection. Even ultrasonic inspection with a single crystal search unit does not indicate the type of discontinuity or imperfection.
Another method of nondestructive inspection is the real time imaging of ultrasound waves. Real time imaging of ultrasound waves utilizes a modified Charge Coupled Device (“CCD”) camera. The camera provides images with normal television framing rates of 100% of the interior parts. The method utilizes high frequency sound waves instead of ionizing radiation. Sound beams are passed through the work piece being inspected and are partially attenuated by discontinuities and imperfections. The internal volume of the material is therefore imaged as in radiography (volumetric inspection). This then provides a shadowgraph display similar to a real time X-ray except that no ionizing radiation is present. Unlike radiographic (X-ray) methods, sound waves are strongly blocked by cracks, voids and other interfacial discontinuities. This provides higher sensitivity to critical and potentially dangerous discontinuities or imperfections. The real time imaging of ultrasonic waves method either passes the sound beam entirely through the material or structure, or introduces the sound beam from the front of the material or structure (perpendicular to it). It then images the part of the beam reflected back to the camera by internal discontinuities or imperfections. These methods are successful in thick structures or when the beam can be arranged to pass through the structure or material from one side to the other (through transmission). These methods have difficulty inspecting very thin objects or when one side of the material or structure is not accessible.
Thus, there is a need in the art to provide a method for acoustic imaging by angle beam that incorporates the listed benefits without the limitations inherent in present methods. For the foregoing reasons, there is a need for a method of inspection that can quickly inspect thin material for discontinuities or imperfections. In addition, there is also a need for a method of inspection that allows inspection of a material when both sides of the material are not accessible.
SUMMARY
The instant invention is directed to a method for acoustic imaging by angle beam that satisfies the needs enumerated above and below.
The present invention is directed to a technique or method for the inspection of materials, specifically a test piece with a first surface and a second surface. The invention utilizes real time ultrasonic imaging in a new and unique way. An ultrasonic sound wave is introduced at an angle to the first surface of the test piece or piece to be inspected. The wave is at an angle sufficient to cause it to progress through the test piece by bouncing forward consecutively between the first and second surfaces of the test piece. The wave enters the test piece, is refracted, and proceeds to the second surface (the surface furthest from a CCD acoustic imaging camera) at some non-vertical angle and reflects to the first surface (the surface nearest the CCD acoustic imaging camera). Part of the wave refracts through the first surface to the CCD acoustic imaging camera while another part reflects and travels to the second surface. This is repeated and the wave moves down the test piece in a series of bounces between surfaces with a proportion refracting through the first surface at each bounce. The portion of the beam that refracts through the first surface is focused to an imaging area in the CCD acoustic imaging camera, which transmits the wave to a video output. The video output displays the internal volume of the test piece. The video output further displays all the imperfections and discontinuities of the test piece. It allows a user to determine the location and type of imperfection or discontinuity.
It is an object of the invention to provide a method for fast inspection of a thin material. It is also an object of the invention to provide a method where the test piece can be inspected for corrosion and cracks when both surfaces of the thin material are not accessible.
It another object of the invention to provide a method for volumetric or three-dimensional inspection. In addition, it is also an object of the invention to provide a method of inspection that indicates the type of discontinuity or imperfection.
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Glut Mark O.
Larkin Daniel S.
Saint-Surin Jacques M
The United States of America as represented by the Secretary of
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