Dual-stage precision actuation system for thermomechanical measurements with expanded displacement range

A thermomechanical analyzer (TMA) comprising a hybrid drive designed to significantly enhance the measurement range while reducing complexity is presented. The hybrid drive integrates a coarse (motor spindle) and a fine (piezoelectric) positioning stage, actuated simultaneously and controlled by a unified feedback system. Besides a much larger displacement range this approach foregoes the need of complex cooling for moving components. The force transducer used to maintain a constant load can resolve forces below 1 mN, while the sample expansion or shrinkage is measured optically via a frictionless encoder with 2 nm resolution. The performance of the positioning system is validated first with a simulated sample (using a piezo walking leg motor) and the TMA capabilities with a CuZn39Pb3 brass sample, which reveals a length change associated with lead melting within the brass matrix upon heating.