Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Specified electrical sensor or system
Reexamination Certificate
1998-05-18
2001-05-08
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Specified electrical sensor or system
Reexamination Certificate
active
06227057
ABSTRACT:
TECHNICAL FIELD OF INVENTION
This invention relates in general to the field of strain gages and, more particularly, to an apparatus and method for rapid strain measurement.
BACKGROUND OF THE INVENTION
A strain gage is a device used to measure surface strains in structural materials. A type of strain gage most commonly used is an electrical resistance-type strain gage. An electrical resistance-type strain gage includes a metallic foil grid having a number of elongated, laterally-spaced, series-connected grid elements and enlarged terminal regions. The enlarged terminal regions may be attached to external electrical leads. In operation, as a structural material deforms, the foil grid elements change in length. This change in length results in a change in electrical resistance of the grid elements. The change in electrical resistance of the grid elements may be measured to provide a level of strain experienced by the structural material.
Using the strain gage to measure an amount of surface strain in a structural component usually requires securely affixing or bonding the strain gage to the structural component. The process of bonding the strain gage to the structural component usually requires chemically and mechanically preparing a location on the structural component to receive the strain gage, applying a masking material to the structural component to prevent subsequent process materials from migrating onto adjacent areas of the structural component, and bonding the strain gage to the structural component using cements and/or epoxies. Bonding materials may require mixing precise amounts of several different chemicals together and may require elevated temperatures and pressures while curing. After the bonding material has cured and an amount of strain has been measured, the strain gage may be either removed from the structural component, allowed to remain on the structural component, or the structural component may be discarded. If the strain gage is removed from the structural component, residual bonding material may also have to be removed from the structural component.
The above-described process of using a strain gage suffers several disadvantages. For example, the above-described process of applying the strain gage is complex and time-consuming. In addition, removing the strain gage from the structural component may damage the structural component and render the strain gage unusable for repeated use. Also, discarding the structural component or allowing the strain gage to remain on the structural component may be unacceptable alternatives.
SUMMARY OF THE INVENTION
Accordingly, a need has arisen for an apparatus and method for providing rapid strain measurement of structural components.
In accordance with the teachings of the present invention, an apparatus and method for rapid strain gage measurement are provided that address disadvantages and problems associated with prior art strain gages and methods. According to one embodiment of the present invention, a strain gage assembly comprises a mounting substrate having an adhesive surface and a gage surface. The adhesive surface includes an adhesive layer disposed thereon operable to affix the mounting substrate to a component, the adhesive layer further operable to allow ready detachment of the mounting substrate from the component. The mounting substrate also includes a strain gage affixed to the gage surface of the mounting substrate.
According to another embodiment of the invention, a method for fabricating a strain gage assembly comprises providing a mounting substrate having an adhesive surface and a gage surface. The adhesive surface has an adhesive layer disposed thereon operable to affix the substrate to a component, the adhesive layer further operable to allow ready detachment of the mounting substrate from the component. The method also includes affixing a strain gage to the gage surface of the mounting substrate.
Embodiments of the invention provide several technical advantages. For example, one embodiment of the invention provides a strain gage assembly that requires less time and cost to install and remove than conventional strain gage assemblies. Also, an embodiment of the invention provides a strain gage assembly that is reusable. Another embodiment of the invention provides a strain gage assembly that attenuates strain, allowing measurement of large cyclic strains. Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.
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Haas Edwin G.
Papazian John M.
Schwarz Robert C.
Winter Robert
Anderson Terry J.
Hoch, Jr. Karl J.
Noori Max
Northrop Grumman Corporation
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