Internal Bending-Beam Strain-Gage Wind Tunnel Balances

摘要

The relative load-carrying capacity of three types of internal balances was compared using information in the literature. The bending-beam balance is superior, when D is less than 35 mm. The capacity of task-balances is equal at larger diameters and the two-shell balance is a competitor, when D is greater than 50 mm. A strength computation model of the bending-beam balance of the Rollab type based on simple engineering theories is presented. The strength of available types of high alloy steels is discussed as well as the expected relations between mechanical stresses and electrical signals. It is shown during the calculation of the 30 mm balance, that the angle deflection of the sting at maximum load is very large, and that it is very beneficial to have access to a sting material with higher modulus of elasticity than steel. The influence of the numerical value of the diameter on the load carrying capacity at constant stress of the current type of balance is discussed, and task and two-shell balances are compared. A mathematical model of 2nd degree, which combines the force system loading the balance with the balance signals is described. This model can be used during calibration and wind-tunnel testing.