### ... and calculation of material characteristics

Test and measurement expert HBM offers the Genesis HighSpeed measurement system that satisfies high demands on dynamics and bandwidth. The modular measurement system offers extremely high sample rates even for systems with high channel counts. Its modularity allows users to optimally adapt the measurement system to their measurement task. For example, corresponding data acquisition cards are available to enable direct connection of the required strain gages in a quarter bridge circuit. Connecting the strain gages is very easy. No additional compensating circuits or preamplifiers are required. Perception software is available for analysis of the acquired signals.

Some prerequisites need to be met to infer the required material characteristics from the acquired signals. Both the incident bar and the transmission bar need to be made from the same material and need to have a great length in comparison to their diameter. In addition, it is essential to know the speed of sound C_{0} at which the pressure waves run through the bars. Provided that the bars' diameter is small, as described above, the speed of sound can easily be calculated from Young's modulus *E* and the density *ρ*:

The above-described strain signals of the pressure wave applied to the incident bar ε_{I}, of the reflected pressure wave ε_{R}, and of the transmitted pressure wave ε_{T} are measured. The resulting material stress is:

with *E* being Young's modulus for the transmission bar and A_{0} the transmission bar's cross-section and *A* the material sample's cross-section. The strain rate of the material sample under test together with the original length* L* of the material sample is:

Forming the integral, the resulting strain is: