Energy harvesting technologies have been explored by researchers for more than two decades as an alternative to conventional power sources (e.g. batteries) for small-sized and low-power electronic devices. The limited life-time and necessity for periodic recharging or replacement of batteries has been a consistent issue in portable, remote, and implantable devices. Ambient energy can usually be found in the form of solar energy, thermal energy, and vibration energy. Amongst these energy sources, vibration energy presents a persistent presence in nature and manmade structures. Various materials and transduction mechanisms have the ability to convert vibratory energy to useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Piezoelectric transducers, with their inherent electromechanical coupling and high power density compared to electromagnetic and electrostatic transducers, have been widely explored to generate power from vibration energy sources. A topical review of piezoelectric energy harvesting methods was carried out and published in this journal by the authors in 2007. Since 2007, countless researchers have introduced novel materials, transduction mechanisms, electrical circuits, and analytical models to improve various aspects of piezoelectric energy harvesting devices. Additionally, many researchers have also reported novel applications of piezoelectric energy harvesting technology in the past decade. While the body of literature in the field of piezoelectric energy harvesting has grown significantly since 2007, this paper presents an update to the authors' previous review paper by summarizing the notable developments in the field of piezoelectric energy harvesting through the past decade.

https://iopscience.iop.org/article/10.1088/1361-665X/ab36e4/pdf

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

An experimental study of surface and sub-surface damage in pulsed water-jet breakage of rocks

Drop impacts are difficult to characterize due to their transient, non-stationary nature. We discuss the force generated during such impacts, a key quantity for animals, plants, roofs or soil erosion. Although a millimetric drop has a modest weight, it can generate collision forces on the order of thousand times this weight. We measure and discuss this amplification, considering natural parameters such as drop radius and density, impact speed and response time of the substrate. We finally imagine two kinds of devices allowing us to deduce the size of the raindrop from impact forces.

The force of impacting rain

Effects of pulsating water jet impact on aluminium surface

Impact force of low velocity liquid droplets measured using piezoelectric PVDF film

A new peening process for introducing compressive residual stresses with less erosion and good surface finish using a high pressure oil jet was developed. Aluminium alloy, AA 6063 was peened with an oil pressure of 50 MPa at different stand-off-distances. Residual stresses measured using X-ray diffraction indicated the induction of about 50 MPa (compressive) residual stresses on the surface. The depth of compressive residual stress developed was about 250 μm. The surface roughness of the oil jet peened surface depends on the stand-off-distance. Significant work hardening was observed at low stand-off-distances. The temperature rise during the process was marginal and doesn't contribute to stress relaxation. Erosion during the process was also reported based on the mass loss rate measured.

A novel surface modification technique for the introduction of compressive residual stress and preliminary studies on Al alloy AA6063

Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4: Part 2: Surface morphology, erosion, and mass loss

Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4: Residual stress and hardness

A new surface modification process was developed to introduce compressive residual stresses at the surface of components In this process, instead of oil droplets a high-velocity cavitation jet (cloud of oil bubbles) impinges on the surface of the component to be peened The impact pressure generated during implosion of cavitation bubbles causes severe plastic deformation at the surface Consequently, beneficial compressive stresses are developed at the surface In order to find the potential of this process, aluminum alloy AA6063-T6 specimens were peened at a constant cavitation number with various nozzle-traveling velocities Residual stress induced by oil jet cavitation peening was measured using X-ray diffraction Oil cavitation jet peening results in a smooth and hard surface The developed compressive residual stresses at the peened surface are about 52%, 42%, and 35% of yield strength in samples for peened at nozzle traveling velocities of 005 mm/s, 010 mm/s, and 015 mm/s, respectively

A. Sahaya Grinspan

Papers

Impact force of low velocity liquid droplets measured using piezoelectric PVDF film

A novel surface modification technique for the introduction of compressive residual stress and preliminary studies on Al alloy AA6063

Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4: Part 2: Surface morphology, erosion, and mass loss

Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4: Residual stress and hardness

Effect of Nozzle-Traveling Velocity on Oil Cavitation Jet Peening of Aluminum Alloy, AA 6063-T6