Application Of The High-Speed Video Technique To Materials Research In Civil Engineering

Abstract

In the field of investigations and research on materials, as we shall see, the highspeed video observation technique is especially well suited to the gathering of visual information. Investigations of such structural materials as concrete and steel are generally based on the results of tests that are most often destructive. Since the phenomena preceding failure, and the failure itself, are rapid, little visual information is available other than that yielded by a preliminary examination of the materials and a check of their appearance after failure. Since the phenomena cannot be observed directly, we must have recourse to observation by means of images taken at4high speed. Moreover, with tests of this type it is not possible to determine the instant of failure, in advance, to within ten seconds or so, and this uncertainty must be overcome by a sufficiently long observation time. An SP 2000 system was used for the high-speed video recording of the tests shown, These tests consisted of compressing a series of cylindrical concrete test specimens at their edges and observing the formation and propagation of the cracks induced by the applied force. These observations were made possible by the speed and capacity of the SP 2000 system, which also offers a new and very real convenience of use, since the high-speed video technique provides real-time access to the information, both during the preparation of the test, in the form of a display on the monitor, and during the processing and interpretation of the data taken from the recorded images. Moreover, since this type of laboratory test is easily repeated, it becomes possible to conduct a parametric investigation of the phenomenon by crushing test specimens having dif-ferent consistencies in terms of type of cement and aggregate site and by varying, say, the loading rate, with the advantage of being able to alter a test according to the results of the last one, if necessary, thanks to the real-time availability of the information.