EXPERIMENTAL STUDY OF A MECHANICAL SYSTEM CONTAINING A LOCAL CONTINUOUS STIFFNESS NON-LINEARITY UNDER PERIODIC EXCITATION AND A STATIC LOAD
✍ Scribed by T.J. Royston; R. Singh
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 330 KB
- Volume
- 198
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
Local stiffness non-linearities under dynamic (periodic) and static (time-invariant) loads exist in many complex mechanical systems, oftentimes at the junctions of assembled components. Unlike in linear systems, a static load may significantly alter the nature of the non-linearity and dynamic response, in terms of amplitude, frequency content and stability. To examine such phenomena, a controlled laboratory experiment with a local continuous stiffness non-linearity has been designed, fabricated, instrumented and analyzed. It consists of a flexible support structure in the form of a simply supported beam and a rigid body mounted on the support structure by a multi-dimensional non-linear ''hardening'' spring element. The non-linear elastic element is made of a very thin beam clamped between tapered ends. Multi-harmonic, amplitude-dependent, frequency-sweepdirection-dependent periodic responses to slowly swept harmonic excitation were measured by using order tracking with a dynamic signal analyzer. It was found that the static load induces the ''hardening'' stiffness element to behave like a ''softening'' spring under certain conditions. The cause of this is explained via theoretical studies of a simple single-degree-of-freedom non-linear oscillator and a more complex model of the experimental system itself. Experimental and theoretical studies of the multi-degree-offreedom, multi-dimensional test system also showed that the local non-linearity has a broad spectral and spatial influence on the dynamic behavior of the overall system. For instance, it alters the characteristics of several system resonances and modes.