Development of an Integrated Joule Heating based Tensile Testing System forThermo-Mechanical Characterization of Shape Memory Alloy Springs

This work presents the development of a tensile testing system for the thermo-mechanical characterization of shape memory alloy springs, which synchronizes electrical heating with force–displacement. The benchtop frame provides a stiff, reconfigurable load path ideal for small specimens and moderate forces. Force is measured using a full-bridge S-type load cell (mV/V output), and displacement is recorded with a 0–10 V laser displacement sensor. Joule heating is applied directly to the specimen, enabling rapid and uniform temperature control during testing. All data are acquired through a NI-DAQ platform for subsequent analysis.

Calibration of the system is carried out to ensure the accuracy of each measurement channel. The load cell was calibrated with known weights, while displacement was verified using gauge blocks. The electrical heating unit was characterised by recording the applied electrical power to a known resistive element. Validation tests conducted on a standard universal testing machine (UTM) confirmed that the combined system exhibits good repeatability, linearity, and stable performance under the test conditions. The system was demonstrated on NiTi shape-memory alloy (SMA) springs, capturing the coupled thermal and mechanical responses associated with phase transformation and recovery behaviour.

The main contributions of this work are: (i) an integrated thermomechanical–electrical test platform that fits on a laboratory bench; (ii) an open, data pipeline for synchronised sensing and data archiving; and (iii) a calibration and validation methodology transferable to other small-scale thermomechanical tests. This instrument provides a flexible foundation for future stress–strain–temperature experiments.