Monitoring the thermal deformation of steel beams via vision metrology

The multi-epoch deformation monitoring of a series of super-hot steel beams by digital close-range photogrammetry is reported. An on-line configuration of three CCD cameras was established to measure both stable reference points and targets subject to positional displacement. Measurements for each beam were conducted at 70-80 epochs over 2 h as the steel cooled from 1100 degreesC to near room temperature. Special targeting was required to accommodate the changing colour of the beams from white-hot to brown as they cooled and ensure target survival through a large temperature range. A computational approach was employed whereby the photogrammetric triangulation process for any given recording epoch utilised an images obtained up until that lime. The paper discusses all aspects of the project in which seven beams were monitored to a dimensional tolerance of close to 1 mm (RMS 1-sigma). (C) 2000 Elsevier Science B.V. All rights reserved.