In Situ Measurements of Contact Pressure for Jointed Interfaces During Dynamic Loading Experiments

Abstract

One of the greatest challenges for developing and validating models for the dynamics of jointed interfaces is measuring and characterizing the contact pressure within a joint. Previous approaches have focused on static measurements, typically taken separately from the dynamic testing of a jointed system. In this research, an electrical contact pressure measurement system is used to measure the contact pressures within a jointed interface during dynamic testing of the jointed system. These experiments invalidate a previously held modeling assumption: that the static pressure distribution is representative of the contact pressure during service of a jointed interface. In fact, for the measurements reported, the extent and magnitude of contact pressures dramatically change across the interface during sinusoidal excitation of the jointed system with more than a quarter of the interface oscillating between being in and out of contact during each period of excitation. While preliminary and scoping in nature, these experiments corroborate recent numerical studies that predict that the contact pressures across an interface significantly change over time as a function of the applied loading. The ramifications of these results are that the energy dissipation mechanisms within a jointed interface significantly evolve over time, resulting in more energy being dissipated in the interface away from the bolts than previously anticipated. This, in turn, necessitates a new constitutive modeling approach for reduced order modeling representations of joints in which the local kinematics are not regularized (such as in traditional Iwan models) and the normal contact forces are directly modeled and allowed to vary with load (contrary to most of the current modeling approaches).