Models equivalent in damping in experiments for determining the parameters of internal friction in materials

Abstract

The work is devoted to improving the methods of experimental determination of internal friction parameters in materials. The aim of the laboratory experiments is to obtain physical parameters of the material that allow to take into account the damping forces in a uniaxial stress state. The research is focused on the internal friction model, which is based on the use of the generalized Prandtl model, that gives frequency-independent internal friction and allowing for the dependence of internal friction on the level of time-varying stresses. Damped oscillations during pure bending are recorded on a specially made laboratory installation. The description of the installation, the reference points of which coincide with the fixed points of the realized form of natural oscillations, is provided. The algorithm of cameral processing of experimental data is obtained. It is proposed to use a virtual system equivalent in damping. This is a system with one dynamic degree of freedom. The involvement of an imaginary system permits, after performing tests of the sample for pure bending, to acquire data corresponding to stretching - compression. The technique grants the use of long samples, which reduces the negative effect of stress concentration in the anchorages. The damping equivalent scheme makes it possible to use samples with an arbitrary cross-section. The found damping parameters for low-carbon steel are given.

Keywords

• experiment
• parameters of internal friction
• damped oscillations
• numerical step-by-step methods
• dynamics problems
• generalized prandtl diagram
• pure bending
• model equivalent in damping