Principles and validation of strain gauge shunt design for large dynamic strain measurement

• Shunt structure is proposed to reduce large strain proportionally to a manageable level.
• Fatigue failure by large dynamic strain can be avoided by this shunt structure.
• Working principles of strain shunt are derived theoretically from 1D model.
• The design of the strain shunt structure is experimentally validated by loading test.
• The dynamic response of the shunt structure is studied by FEA.

In order to eliminate the fatigue failure of metallic thin film strain gauges under large alternating strain condition, a mechanical structure reducing the large strain on the target surface proportionally to a safe level is proposed as strain shunt in this study. The working principles of the strain shunt structure are illustrated and the shunt ratio of strain reduction is derived theoretically from a simplified one dimensional model. The prototype strain shunt is validated by tensile load test experiments which confirm the repeatability and linearity. Moreover, the usability of the strain shunt structure under alternating loads, the stability of shunt ratio under the combined stress conditions, and the dynamic response of the strain shunt structure are investigated by finite element analysis.