Optimum Design of Internal Strain-Gage Balances: An Example of Three-Dimensional Shape Optimization

Abstract

Internal strain-gage balances are often applied to measure the aerodynamic loads acting on the aircraft model in the wind-tunnel test. The balance system consists essentially of one main body and two shoulders elastically interconnected by multibar cages. Designing the cross-sectional geometry of such a multibar cage balance to improve the accuracy of load measurement is an important task for a balance engineer. The study presents an initial attempt to carry out such a design task in a systematic and automated manner. This is achieved by considering two aspects. One is to establish a mathematical model to analyze the stress distribution in the elastic cage and the other is to adopt a three-dimensional shape optimization scheme to design the cross-sectional geometry of the internal strain-gage balance. The design procedure has been completely automated in a computer program. Numerical examples shows that the proposed numerical scheme performs very well.