Description

Short technical description: Overview The Federal Highway Administration (FHWA) Nondestructive Evaluation (NDE) Laboratory was established in 1998. The objective of the FHWA NDE Laboratory is to improve the state of the practice for highway bridge inspection. The laboratory is designed to act as a resource for state transportation agencies, industry, and academia concerned with the development and testing of innovative NDE technologies. The laboratory provides independent evaluation of NDE technologies, develops new NDE technologies, and provides technical assistance to States exploring the use of these advanced technologies. The NDE Laboratory utilizes a series of unique resources to evaluate and assess the factors affecting the reliability and performance of NDE systems. To supplement the capabilities of the NDE laboratory facilities, a series of field–test bridges located in Northern Virginia and southern Pennsylvania are utilized to conduct field studies. In addition, a collection of component test specimens are used in various test programs. NDE Laboratory Facilities The NDE Laboratory provides a facility for the development and testing of NDE technologies. The laboratory includes a structural loading floor for constructing mock–ups of field conditions, a radiological facility used for creating X–ray images of defects, a computed tomography facility for characterizing materials, and an instrumentation facility used for manufacturing prototypes and developing new NDE tools. The component specimens provide a realistic testbed for the development of new NDE technologies. Component specimens at the NDE Laboratory include sections of bridge deck containing delaminations, welded details containing cracks, cracked bridge pins, prestressed box beams containing corroded and broken strands, cracked sign supports, and other specimens with characteristic forms of deterioration. Decommissioned highway bridges are used to evaluate NDE methods under realistic environmental conditions. Two steel bridges that are open to traffic and fully instrumented are used to test NDE methods associated with live loading, such as new instrumentation for global bridge monitoring. These bridges are critical to evaluating the effect of restricted access, structure geometry, surface conditions, platform stability, and human factors on the application of NDE methods during normal bridge inspections. These test bridges provide the NDE Laboratory with a unique ability to evaluate NDE technologies under the same conditions that normal bridge inspections are typically conducted, providing a powerful tool in the evaluation process. Unique features: Equipment The NDE Laboratory includes an 11.8 m by 3.6 m structural loading floor used to construct mock–ups of field conditions and produce component specimens. The laboratory also acts as a staging area for research conducted at the test bridges. The laboratory space is equipped with storage areas and test set–up areas. An x–ray computed tomography and digital radiography imaging system was built according to specific specifications for the laboratory. The system consists of dual–focus 420–kV and microfocus 160–kV continuous x–ray sources. It includes two digital detectors, with a 512–channel linear array detector for tomographic imaging and a tri–field image intensifier with a digital camera for both real–time radiography and microtomography. The system can benefit many industrial and scientific applications, including materials research, nondestructive testing, core sample characterization, weld inspection, failure analysis, and reverse engineering. It is suitable for x–ray inspection of metallic and non–metallic items over a wide range of densities. The system produces cross–sectional computed tomography (CT) images, in–motion real–time radiography (RTR) images, and digitized radiographed (DR) images. In addition to density mapping, CT provides complete 3D morphology of parts with highly accurate dimensioning capability. The CT data sets can be converted to line drawings and exported as splines for solid modeling and comparison to Computer–Aided Design (CAD) drawings. Computed tomography also provides superior flaw detection capability of extremely small cracks, porosities, and voids that are normally not visible with film radiography inspection. The system can provide spatial resolution of up to 20 lines per millimeter or 25–microns. In addition, sample sizes up to a weight of 200–kg and a length of 100–cm can be accomodated. The system has been used by researchers at the NDE Laboratory to conduct projects such as determination of air void parameters, crack propagation, and internal structure characterization of portland cement concrete and asphalt concrete structures. Specified type of facility: nondestructive evaluation and testing

Keywords

nondestructive evaluation and testing

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