An Empirical Relationship for Extrapolating Sparse Experimental Lap Joint Data

Correctly incorporating the influence of mechanical joints in built-up mechanical systems is a critical element for model development for structural dynamics predictions. Quality experimental data are often difficult to obtain and is rarely sufficient to determine fully parameters for relevant mathematical models. On the other hand, fine-mesh finite element (FMFE) modeling facilitates innumerable numerical experiments at modest cost. Detailed FMFE analysis of built-up structures with frictional interfaces reproduces trends among problem parameters found experimentally, but there are qualitative differences. Those differences are currently ascribed to the very approximate nature of the friction model available in most finite element codes. Though numerical simulations are insufficient to produce qualitatively correct behavior of joints, some relations, developed here through observations of a multitude of numerical experiments, suggest interesting relationships among joint properties measured under different loading conditions. These relationships can be generalized into forms consistent with data from physical experiments. One such relationship, developed here, expresses the rate of energy dissipation per cycle within the joint under various combinations of extensional and clamping load in terms of dissipation under other load conditions. The use of this relationship—though not exact—is demonstrated for the purpose of extrapolating a representative set of experimental data to span the range of variability observed from real data.