Abstract: A system for mapping a surface defect in an electrically-conducting material by measuring a change in the resonance of the material includes a flexible printed circuit board and a two dimensional array of transducers printed on the flexible circuit board, wherein each element of the array includes two transducer coils in a paired arrangement. A receive circuit connected to the coils is tuned to a resonant frequency, and the transducer coils operate in a send/receive mode. In another feature of the invention, there are means for converting a change in measured resonance to a visual display of the depth and width of the surface defect.

Abstract: A system for mapping a surface defect in an electrically-conducting material by measuring a change in the resonance of the material includes a flexible printed circuit board and a two dimensional array of transducers printed on the flexible circuit board, wherein each element of the array includes two transducer coils in a paired arrangement. A receive circuit connected to the coils is tuned to a resonant frequency, and the transducer coils operate in a send/receive mode. In another feature of the invention, there are means for converting a change in measured resonance to a visual display of the depth and width of the surface defect.

Abstract: Axially extending structures having internal forces directed radially outward therefrom may be reinforced by installing bands around the structures. The bands consist of a plurality of elastic convolutions of a composite material which assume a coiled configuration in a relaxed condition. The composite material includes a multiplicity of continuous, high tensile strength filaments encapsulated in a resin matrix and extending codirectionally with one another through the resin matrix. The band is installed around the structure by deflecting portions of the band to an uncoiled configuration and then wrapping these portions of the band around the structure. Adhesive may be used to secure the band tightly around the structure. Particularly useful applications for the composite bands are for reinforcing gas and liquid transmission pipelines and concrete bridge support columns.

Abstract: Spiral bands having a plurality of convolutions of a high tensile strength composite material are formed by feeding a plurality of continuous high tensile strength fibers through an uncured resin to form a web, depositing the web on a release web having at least one substantially flat surface to form a laminate, winding the laminate around the mandrel to form a plurality of overlapping convolutions, curing the resin in the composite web to set the convolutions in a spiral configuration, and then removing the release web from the composite web. The convolutions of the spiral bands in accordance with this process have substantially flat surfaces and an elastic memory. These bands can be used to reinforce axially extending structures having internal forces directed radially outward therefrom by wrapping the band around the structure with a layer of adhesive applied to hold the convolutions in place.

Abstract: In a method for reinforcing defective portions of a pipeline, the defective portions are identified by conventional techniques, soil is excavated from around the pipeline to expose the deteriorated portions, any corrosion protection material is removed and the surface of the pipeline is cleaned. Gouges, dents and corrosion pitting are filled with an uncured filler material and, while the filler material is in an uncured workable state, a plurality of convolutions of a high tensile strength material are wrapped around the defective portion of the pipeline with a layer of a curable adhesive applied between adjacent convolutions. The adhesive then cures to a strongly adhesive state and the filler material cures to a rigid state capable of transferring the fluid pressure load within the pipeline almost instantaneously to the reinforcement band.