24-10-2012, 01:35 PM
Study and Analyses on the Structural Performance of a Balance
ABSTRACT
Strain-gauge balances for use in wind tunnels have been designed at Langley Research Center (LaRC) since its inception.
Currently Langley has more than 300 balances available for its researchers. A force balance is inherently a critically stressed
component due to the requirements of measurement sensitivity. The strain-gauge balances have been used in Langley s wind
tunnels for a wide variety of aerodynamic tests, and the designs encompass a large array of sizes, loads, and environmental
effects. There are six degrees of freedom that a balance has to measure. The balance s task to measure these six degrees of
freedom has introduced challenging work in transducer development technology areas. As the emphasis increases on
improving aerodynamic performance of all types of aircraft and spacecraft, the demand for improved balances is at the
forefront. Force balance stress analysis and acceptance criteria are under review due to LaRC wind tunnel operational safety
requirements. This paper presents some of the analyses and research done at LaRC that influence structural integrity of the
balances. The analyses are helpful in understanding the overall behavior of existing balances and can be used in the design
of new balances to enhance performance. Initially, a maximum load combination was used for a linear structural analysis.
When nonlinear effects were encountered, the analysis was extended to include nonlinearities using MSC.Nastran . Because
most of the balances are designed using Pro/Mechanica , it is desirable and efficient to use Pro/Mechanica for stress analysis.
However, Pro/Mechanica is limited to linear analysis. Both Pro/Mechanica and MSC.Nastran are used for analyses in the
present work. The structural integrity of balances and the possibility of modifying existing balances to enhance structural
integrity are investigated.