Two methods for determining impact-force history on elastic plates

Two methods are presented to detect the impact-force history on elastic plates. The first method involves construction of a Greens function to relate the strain responses to an impact force acting axisymmetrically on a circular plate. The classical plate theory and a series of Bessel functions were used to obtain the Greens functions in the time domain. The gradient projection method was employed to search for the optimal force history. Examples using circular plates with free and fixed boundary conditions are demonstrated. On the other hand, the second method is purely experiment-based and involves no Greens function. Thus, this method can be applied to structures of various geometries, boundary conditions and material properties. The very satisfactory agreement between the measured and the detected force histories using both methods shows that they are reliable for impact-force determination purposes.