Impact Dynamics

This scientific area includes the study of transient mechanical processes in which both inertia and rate dependent material properties must be considered. Our interest is primarily directed towards modelling of rate dependent materials. At both deliberate (forming) and accidental (collisions) loading of material and components, deformation rates can become large and therefore rate dependent material models have to be used in simulation of such processes.

Experiments are needed to determine the mechanical properties of a material and at high deformation rates equipment and methods have to be carefully chosen in order to get sufficient accuracy in measured quantities like force and deformation. One method that is used in high-rate experiments is the Split Hopkinson Pressure Bar (or Klsky bar) which is based on measurement of elastic waves in bars. Force and deformation of a specimen placed between two bars loaded by an impact can be determined with this method. Also a specially designed hydraulic machine is sometimes used for high-rate testing. Specially adapted optical methods are used for deformation measurements.

It is sometimes desired to characterise material at combinations of high temperature and high deformation rate because both these components may be present in technical processes. In these cases even higher difficulties regarding measurement techniques are at hand due to the fact that high temperatures raise problems in optical measurements. Development of methods for testing and measurement under these conditions is important for us in this research area.