Characterization of Nonlinear Joint Stiffness Using Dynamic and Static Experimental Methods

An experimental study was conducted to characterize the nonlinear rotational stiffness of a missile fin control actuation system testbed. Dynamic testing was used to measure the acceleration response of the fin to a sine-sweep input at various force levels. The modal frequency and damping of the rotation mode were tracked as a function of applied force to determine the converged control surface rotation mode. Frequency response functions were generated in order to estimate the dynamic stiffness of the control actuation system joint. Static freeplay and rigidity data were also collected using an applied quasi-static load and measuring the resultant displacements at multiple locations around the fin. The freeplay and rigidity data were used to characterize the degree of nonlinearity in the joint stiffness with respect to applied load.