October 25, 2024

We will have the first technical talk this Friday. Thijs Masmeijer, a PhD Candidate from Prof. Ed Harbtpur’s group, will give a talk on his latest work on “Directional DIC with automatic feature selection“.

📅 Date: Friday Oct 25
🕕 Time: 12:30PM – 1:30PM(ish)

🏛️ Location: SIG 224
💻 Zoom: Zoom LinkBio:
Thijs is a PhD candidate at Ed Habtour’s Illimited Lab in our department. The Illimited lab is a structural vibration lab guided by bio-inspiration. Thijs’ dissertation is on the signaling properties of spider webs. Spiders localize prey in their webs based on vibration cues. The spider’s approach to signaling provides valuable information on designing engineering sensing systems.Title: Directional DIC with automatic feature selection

Abstract:
Using displacement identification via high-speed cameras is a non-contact, full-field technique for characterizing the dynamic properties of engineered structures. Achieving reliable measurements of structural deformation through conventional Digital Image Correlation (DIC) requires a well-defined spatial gradient in two orthogonal directions within an image subset of pixels. However, DIC is susceptible to the aperture problem, which leads to an ill-conditioned optimization problem. An example of such a case is cable systems on which no speckle patterns can be applied. This study proposes Directional DIC (D-DIC) as an alternative technique to overcome the limitations posed by the aperture problem in conventional DIC methods. Directional DIC assumes the local direction of motion, which is often a valid assumption in structural vibration tests, as individual vibration shapes are often unidirectional at localized parts of the structure. This alleviates some restrictions on trackable image subsets, enabling more trackable locations. A parameter for quantifying expected tracking performance for D-DIC is introduced. The parameter enables automatic feature selection for D-DIC, making optical methods more accessible for displacement identification on structures where no speckle patterns can be applied. A flexible spider web-like structure to validate the D-DIC method and compare it to the conventional DIC. The experimental findings show that the Directional DIC method allows for measuring displacements at significantly more locations than conventional DIC. Additionally, Direct DIC provides less noisy frequency response functions, more retrieved stable poles, and more fitted vibrational modes. Unlike conventional DIC, DDIC appears to be less hindered by the aperture problem, even when small subsets are used.