Reflections on nonlinear dynamics of machines and structures

In this short note a comparison is made between the methodology of nonlinea r analysis in machine systems versus structural systems. Because of strong nonlinearities in machines with parts in relative motion, chaotic-like dyna mics are more likely to occur in complex multi-body machines than in struct ural systems. Furthermore, it is conjectured that well designed machines ha ve evolved to where a small amount of chaos is always present and is someti mes desired.