In this work, piezoelectric energy harvesting performance via friction-induced vibration is investigated numerically. A one-degree-of-freedom friction system with a piezoelectric element is proposed, to study the piezoelectric energy harvesting via friction-induced stick-slip vibration. Subsequently, a two-degree-of-freedom friction system with two piezoelectric elements is proposed, to investigate the piezoelectric energy harvesting via model coupling vibration. Results show that regardless of the friction systems, it is feasible to convert friction-induced vibration energy to electrical energy when the friction system is operating in the unstable vibration region. Parametrical analysis indicates that for the one-degree-of-freedom friction system, when the normal load increases from 5 N to 30 N, the stick-slip motion becomes more intense, and the friction system will generate more electric energy. While for the two-degree-of-freedom friction system, with the normal load increase from 20 N to 120 N, there is a critical normal load value for the generation of the strongest vibration and the highest voltage output. When the velocity of the belt increases from 0.5 m/s to 2 m/s, the amplitudes of vibration and output voltage become larger. While with the velocity further increasing, the stick-slip motion and generated electric energy disappear. For both friction systems, the external electric resistance has no effect on the dynamic behaviour of the friction system; however, it can modify the output voltage amplitudes within limits. It is also found that when the force factor of piezoelectric element increases from 3.1 × 10−5 N/V to 3.1 × 10−3 N/V, the vibration and harvested energy gradually increase. When the force factor further increases to 3.1 × 10−2 N/V, the vibration reduces drastically and the corresponding output voltages reduce significantly, which proves that a piezoelectric element with an appropriated force factor can give the highest harvested energy and conversion efficiency.

In this work, piezoelectric energy harvesting (PEH) performance via friction-induced vibration (FIV) is studied numerically. A nonlinear two-degree-of-freedom friction system (mass-on-belt) with piezoelectric elements, which simultaneously considers the stick-slip motion, model coupling instability, separation, and reattachment between the mass and belt, is proposed. Both complex eigenvalue analyses and transient dynamic analysis of this nonlinear system are carried out. Results show that it is feasible to convert FIV energy to electrical energy when the friction system is operating in the unstable vibration region. There exists a critical friction coefficient (μc) for the system to generate FIV and output visible voltage. The friction coefficient plays a significant role in affecting the dynamics and PEH performance of the friction system. The friction system is able to generate stronger vibration and higher voltage in the case that both the kinetic friction coefficient and static friction coefficient are larger than μc. Moreover, it is seen that the separation behavior between contact pair can result in overestimating or underestimating the vibration magnitude and output voltage amplitude, and the overestimate or underestimate phenomenon is determined by the located range of friction coefficient. Furthermore, it is confirmed that an appropriate value of external resistance is beneficial for the friction system to achieve the highest output voltage. The obtained results will be beneficial for the design of PEH device by means of FIV.