ESDU 09006:2011

This Item is concerned with material damping, a type of damping
which is intrinsic in a structure in vibration. The emphasis is on
materials which have engineering applications. Small amounts of
damping at low stress levels can arise in all materials from
thermoelasticity, which is amplitude-independent and
frequency-dependent. With high applied stress, the damping is
nonlinear. Nonlinear damping in metals and alloys is
amplitude-dependent and frequency-independent. The main mechanisms
responsible for nonlinear damping are associated with
amplitude-dependent dislocations, magnetostriction, the
heterogeneous structure of materials and phase transformations, all
of which can give rise to relatively high damping with SDC values
above 10%. In the case of composites, where fibres are embedded in
a matrix, the damping is associated with damping within the matrix,
as well as that which originates from relative slipping between the
matrix and the fibre reinforcement. Metallic materials with high
damping and good engineering properties are referred to as Hidamets
and have specific damping capacities in excess of 10%. The damping
of different materials has been compared in the Item. Composites
have SDC values from 0.5 to 15%. The damping of steels has a wide
range of SDC values from 0.05 to 5%, with the higher values
occurring because of magnetomechanical damping. Hidamets include
cast irons with a coarse flake structure and alloys of manganese
with copper.