Calibration Modeling of Nonmonolithic Wind-Tunnel Force Balances

Experimental designs and regression models for calibrating nonmonolithic (multiple piece) internal wind-tunnel force balances were investigated through a case study that demonstrated fundamental deficiencies with a typical test schedule. Itwas found that the current calibration point selectionmethod,which swept thedesign space two factors at a time, introduced a degree of correlation among model terms, depending on the model form. While using the statistical design of experiment performancemetrics to analyze the deficiencies in the experimental design, it was also found that there were problems inherent to the model form itself that were independent of the design. An analysis of the calibrationmodel, endorsed by the AIAA recommended practices document for nonmonolithic balances, lead to correlated response model terms due to overparameterization. Four new modeling strategies are proposed to overcome these challenges for nonmonolithic force balances.