This Major Research Instrumentation (MRI) project involves acquisition of a Digital Image Correlation System. The photogrammetric technology provides full-field non-contact measurements of 3D displacements of complex test systems in real-time. The intent is two-fold, (a) to detect and visualize emerging cracks and strain concentrations on test articles without the use of traditional contact measurements such as strain gauges and differential transducers, and (b) to develop an adaptive feed-back signal for controlling the force input in the pre- and post-failure regime. The 3-D DIC measurement system by Trilion Inc. includes four pairs of 12 megapixel digital cameras, the Tritop coordinate measurement system, an image processing workstation and controller, and the Aramis processing software with a real-time interface for control. Each pair of digital cameras is mounted on a tripod with dedicated lighting to provide a series of stereoscopic images of the test article within the field of view. The Aramis processing software tracks the coordinates of 10,000+ facet points. It provides deformation field data for structural materials testing up to and beyond their maximum load resistance, and progressive failure such as crack initiation and propagation in structural components and systems.
The portable instrumentation system will provide new opportunities for undergraduate and graduate students to acquaint themselves with the capabilities of digital image correlation systems and their application to a variety of research projects spanning from testing materials and infrastructural components to biomedical applications. Under the direction of eleven faculty, students in Civil and Mechanical Engineering will be trained in (a) the use of powerful imaging to track emerging failure mechanisms, and (b) the field of servo-controlled testing of materials and structures.
This instrumentation project involved the acquisition of a Digital Image Correlation System which enables the UH user group to acquire full-field 3D non-contact images of deformations and crack measurements in order to visualize progressive failure mechanisms of test specimens in real time. The 3-D DIC measurement system by Trilion Inc. includes four pairs of 12 megapixel digital cameras, the Tritop coordinate measurement system, an image processing workstation and controller, and the ARAMIS processing software with a real-time interface for control. The MRI project provided ample opportunities to under graduate and graduate students to get exposed and acquainted with an innovative imaging and visualization system and to gain insight in the mechanics and failure of materials and structures. The students took also part to two training sessions, provided by Trilion Inc., in order to enable them to use the imaging system for a variety of applications and to integrate the system of eight cameras. The impact due to the acquisition of this system is principally in Structural Mechanics and Materials. The instrumentation has been used to quantify the plastification and cracking around the defects in metals (Figure 1), to observe cracking and delamination in composite subsea pipes (Figure 2), to characterize debonding behavior between shape memory alloys and fiber reinforced polymer composites (Figure 3), to develop a more detailed understanding of the cracking behavior of masonry components and to study buckling behavior of corroded steel bridge piers. The DIC has applicability in multiple fields, including mechanical, aeronautical, automotive, new energy technologies and biomechanics applications. The results have been disseminated through Conferences, Journal Papers and Workshops. The Department of Civil and Environmental Engineering at the University of Houston hosted two workshops in collaboration with Trilion Inc., promoting the dissemination to the industries and interfacing industry and university.
