A Four-Parameter Iwan Model for Lap-Type Joints

SEGALMAN, DANIEL J.

Sandia National Laboratories

关键词: Energy Losses;    Joints;    Design;    Simulation;    42 Engineering;   

DOI  :  10.2172/805877
RP-ID  :  SAND2002-3828
RP-ID  :  AC04-94AL85000
RP-ID  :  805877

美国|英语

来源: UNT Digital Library

【 摘 要 】

The constitutive behavior of mechanical joints is largely responsible for the energy dissipation and vibration damping in weapons systems. For reasons arising from the dramatically different length scales associated with those dissipative mechanisms and the length scales characteristic of the overall structure, this physics cannot be captured through direct numerical simulation (DNS) of the contact mechanics within a structural dynamics analysis. The difficulties of DNS manifest themselves either in terms of Courant times that are orders of magnitude smaller than that necessary for structural dynamics analysis or as intractable conditioning problems. The only practical method for accommodating the nonlinear nature of joint mechanisms within structural dynamic analysis is through constitutive models employing degrees of freedom natural to the scale of structural dynamics. In this way, development of constitutive models for joint response is a prerequisite for a predictive structural dynamics capability. A four-parameter model, built on a framework developed by Iwan, is used to reproduce the qualitative and quantitative properties of lap-type joints. In the development presented here, the parameters are deduced by matching experimental values of energy dissipation in harmonic loading and values of the force necessary to initiate macro-slip. (These experiments can be performed on real hardware or virtually via fine-resolution, nonlinear quasi-static finite elements.) The resulting constitutive model can then be used to predict the force/displacement results from arbitrary load histories.