Basic characterisation of the mechanical behaviour of materials is performed through quasistatic tensile testing.
In order to obtain dynamic material properties, several tensile tests at different strain rate have to be conducted, obtaining as a result a set of stress - strain curves at different velocities. It is desirable to use these tests to cover the whole range of rates expected to reach in component service conditions.
The main problem associated with material dynamic characterisation is mass influence from both sample and testing devices. In dynamic testing the governing equation of the behaviour or the whole system contains inertial terms, whose importance increases with the velocity. Under these conditions, mechanical ringing effects resulting from the sample and testing machine masses are present and, as a consequence, errors are introduced in the obtained measurement.
Curves obtained from tensile tests performed at different rates (5 mm/min, 1 m/s, 7.8 m/s) are presented. It is easy to note that when test velocity is increased, then the response curves measured at the machine load cell show higher oscillations due to inertia effects. If the load measurement is done directly on the sample by means of strain gauges, these oscillations are not observed.