Inverse Load Determination from Propeller Strain Measurements
Abstract
Classical problems in structural mechanics solve for the strain field of a structure given a knownloading. However, there are a variety of practical situations in which it would be more desirableto infer the loading on a structure given a set of corresponding strain measurements. Thisso-called ~inverse problem~ is challenging because it can result in systems of equations that areill-conditioned (i.e., small measurement errors can lead to unacceptably large errors in the calculatedloads). Motivated by the planned sea trial of an advanced material propeller, the Navyrequires a robust method for measuring and conditioning strain gauge data such that the loadingon the propeller blades can be reliably reconstructed. Here we propose the development of such amethod. This method will enable the use of strain data as valuable experimental evidence of fluidloading on propellers during operation. The calculated loads can also be used as experimentalvalidation of computational fluid dynamics (CFD) propeller simulations.Previous work has focused on the optimization of strain gauge placement through the globalminimization of the condition number of the system matrix. The proposed effort will have fourprimary objectives. 1) Draw from and expand upon previous research to inform the optimal placementand orientation of strain gauges in the upcoming sea trial. 2) Perform select noise filteringmethods to reduce measurement error prior to attempting the inverse calculation. 3) Implementa number of matrix regularization strategies and compare their effectiveness in improving thecondition number of the system matrix. 4) Use system identification methods to estimate loadingconditions without the need to perform an inverse calculation. The different strategies applied inthese four areas will be used with existing propeller strain gauge data to determine their relativeeffectiveness at calculating accurate unsteady loads. Ultimately, an overall calculation approachthat includes a combination of the most effective strategies will be determined.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 03, 2017
- Source ID
- N000141712292
Entities
People
- Robert F Davis
Organizations
- Office of Naval Research
- The University of Georgia
- United States Navy