Influence of acoustoelastic coefficient on wave time of flight in stress measurement in piezoelectric self-excited system

• The new type of piezoelectric self-excited system can measure stress in materials.
• The system allowed stress monitoring in a beam made of metal and marble.
• Influence of acoustoelastic coefficient on time of flight was modeled.
• Simulation data were verified experimentally.
• The measurement system may replace classical strain gauge methods.

This paper presents the Self-excited Acoustical System (SAS) in elastic construction stress change measurement. The system is based on the acoustical autoresonance phenomena and enables an indirect measurement of the construction effort level. The essence of the SAS system is to use a piezoelectric vibration emitter and a piezoelectric vibration receiver placed at a distance, which are coupled with a proper power amplifier, and which are operating in a closed loop with a positive feedback. This causes the excitation of the system. The change of the velocity of wave propagation, which is associated with the change of the resonance frequency in the system is caused by the stress change in the examined material. A variable, which determines the change of the acoustic wave velocity, is called an acoustoelastic coefficient β. Such a coefficient allows to determine the absolute stress value in the tested material.