Optics: measuring and testing – Material strain analysis – By light interference detector
Patent
1993-06-18
1996-05-21
Turner, Samuel A.
Optics: measuring and testing
Material strain analysis
By light interference detector
356347, 73802, G01B 9025
Patent
active
055194869
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention concerns the examination of structures using holographic interferometry. It is particularly suitable for the in-situ analysis of riveted, bolted and bonded structures to determine (a) the efficacy of the riveted or bolted joining or the bonding of components and (b) whether fatigue cracks are present in the region of the rivets or bolts. In this application, the invention is especially useful in the examination of the riveted, bolted and bonded connections in the fuselage of an aircraft which can be pressurised or otherwise loaded. Another particularly useful application of the present invention is the in-situ examination of objects constructed from composite materials, to ascertain the presence of damage to the object or the existence of faults as a result of poor construction. A further use of the present invention is the in-situ checking of the efficacy of the application of a composite patch to a damaged composite or aluminium structure or the like. In these last two applications, the present invention is particularly useful for (but is not limited to) the examination of objects made from a composite comprising a resin and fibres of boron, carbon, glass or the like.
BACKGROUND TO THE INVENTION
Structures which use high strength, light weight materials, and which are subject to considerable stress in their normal use, are susceptible to the development of fatigue cracks, particularly in the regions where the sheets of such materials are joined. One example of such a structure is a modern large aircraft, and as the development of the present invention was in part stimulated by the problem of crack detection in the fuselage of a large aircraft, the application of the present invention to this problem will be given some prominence in this specification.
The cause of a significant number of aircraft accidents has been identified as structural failure resulting from the development of fatigue cracks and faulted bonds in the aircraft fuselage, in the vicinity of the riveted connection of the metal sheets forming the fuselage. Thus it is now recognised that the detection of fatigue cracks in aircraft structures, as soon as possible after their formation, is a matter of critical importance, and there has been a considerable commitment of resources to the establishment of a reliable in-situ crack detection technique.
Several commercial crack detection systems are now available. Those systems include eddy current detection techniques, ultrasonic examination techniques and magnetic rubber applications. Unfortunately, each of those techniques is suitable for only a certain limited range of applications, since the sensitivity of each method depends on the geometry of the component being investigated and other factors. Optical techniques for crack analysis using phenomena such as photoelasticity, caustics, moire pattern observations and shearography have also been developed, but those optical techniques (apart from shearography) are laboratory analysis tools and are not readily able to be adapted to in-situ testing of riveted, bolted or bonded structures. Thus there remains a need for a reliable in-situ crack detection system for use in the testing of joins in aircraft fuselage structures.
The present invention, as noted above is also useful in the examination of composite materials, known generally as "composites". Composites comprising resin with fibres of boron, carbon, glass or the like are now being used regularly to construct objects and structures for which the combination of mechanical strength and light weight is desirable. An example of such an object is the rotor blade of a helicopter.
One problem with such objects is that faults in the manufacture of the composite, which may affect the structural strength of the object, are often not visible. Another problem, arising out of the use of such objects, is that, if they receive a substantial blow during their normal use (for example, a bird strike on a helicopter rotor), the structural integrity of the composite material can
REFERENCES:
patent: 3587301 (1971-06-01), Heary
patent: 3828126 (1974-08-01), Ramsey, Jr.
patent: 3860346 (1975-01-01), Kersch et al.
patent: 3911733 (1975-10-01), Bhuta et al.
patent: 4139302 (1979-02-01), Hung et al.
patent: 4464052 (1984-08-01), Neumann
patent: 5065331 (1991-11-01), Vachon et al.
patent: 5257088 (1993-10-01), Tyson, II et al.
Baird John P.
Clark Robert K.
Turner Samuel A.
Unisearch Limited
LandOfFree
Method of creating holographic interferograms for structural exa does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of creating holographic interferograms for structural exa, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of creating holographic interferograms for structural exa will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2042619