Influence of Stress Bar Length on the Response of a Stress Wave Force Balance Using Finite Element Analysis

The stress wave force balance is used to measure forces in aerodynamic facilities like shock tunnels and wind tunnels. For accurate measurement of forces, the shape and size of the model and the balance are of importance. The dimensions of the balance mounted inside the model (internal balance) depend on the internal diameter of the model. However, the effect of the length of the stress bar is independent of the model dimensions. This paper describes the variation in transient strain responses at various locations of the stress bar with the variation of the length of the stress bar. Impulse force of 10 N magnitude with 1 ms duration was applied at the tip of a hemispherical model, and the strain responses were observed at various locations along the stress bar. Impulse forces of various magnitudes were applied at the tip of the model, and the strain responses were observed. From the simulation results, it was observed that as the length of the stress bar increases, the strain increases. The strain response was also found to be steady with the increase in length of the stress bar.