Development of a methodology for non-contacting strain measurements in fluid environments using computer vision

Using first order, ray optics theory, a method has been developed and experimentally verified for measurement of surface strains on structures immersed in fluid environments. The methodology utilizes an imaging system that is contained within an air environment and separated from the fluid media by an optical quality, transparent window. Theoretical considerations demonstrate that non-contacting strain measurements in fluid systems are somewhat sensitive to the relative orientation of the transparent window, providing insight into the system setup required to make accurate strain measurements in fluid environments. Underwater experimental measurements using a laboratory-based system arc in excellent agreement with theoretical predictions, demonstrating that the proposed methodology is both viable and capable of measuring strains accurately.