Finite element analysis of a dual-layer substrate sandwiched bridge piezoelectric transducer for harvesting energy from asphalt pavement

Harvesting energy from ambient environment such as vehicle vibration in asphalt pavement holds great potential in powering up the wireless sensor networks along the roadway. Hence, this paper presents a dual-layer substrate sandwiched bridge piezoelectric transducer which converts the mechanical energy into useful electricity to achieve a reliable power source. A dual-layer of thin substrate is added in order to shift away and reduce the stress concentration in the piezoelectric material as high stress concentration will lead to a mechanical failure of transducer such as cracking of piezoelectric plate or distorted end-cap structure. A coupled piezoelectric-circuit finite element model (CPC-FEM) was developed to predict the electric power output and stress concentration of the transducer. The optimum end-cap thickness and suitable material used are determined first within the failure stress criteria. Then, the CPC-FEM was used to study the effect of presence of substrate in reducing the stress concentration and the efficiency of substrate in increasing the load capacity as well as electric power output. The FEA results show that the voltage produced by the transducer is about 132 V with 0.4 mm thickness of titanium alloy end-caps and 0.3 mm stainless steel substrates, which could result in 0.18 mJ of electrical energy and about 3.56 mW potential power output at 20 Hz under the loading pressure of 0.7 MPa.