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This paper undertakes theoretical and experimental investigations of a stacked magnetic modulation harvester with frequency up-conversion for maximum harvesting of energy from swing motion. The harvester includes stacked rings including coils, an energy harvesting magnetic ring, a ferromagnetic ring, and a frequency up-conversion magnetic ring with proof mass, which are axially designed in the same rotating axis to increase the rotation speed of the magnetic field due to swing excitations from human motion. The magnetic flux density produced by frequency up-conversion mechanisms are calculated to derive the governing theoretical model for harvester performance prediction. The rotation speeds and inductive voltages of theoretical results show good agreement with the experimental results at a range of rotational speeds. A range of motion speeds tests on a treadmill are performed to demonstrate the advantage of the stacked electromagnetic harvesters on harvested energy from human motion. The average output power improves from approximately 1.5mW to 11.8mW when walking speed increases from 4km/h to 8km/h; the maximum power density under human motion is 61.9μW•g -1 , with total weight of 190.7g.

Self-healing dielectric elastomers are promising for bioinspired actuator and generator applications due to their unique characteristics, such as their lightweight nature, low cost, ease of processing, extended durability, and operational reliability. [1] For example, dielectric elastomer actuators are required to undergo cyclic mechanical deformation when subjected to high electric fields; [2] therefore, they need both high mechanical elasticity and high dielectric permittivity to ensure a high efficiency. In addition, self-healable dielectric elastomers are promising materials for the design of high-performance musclelike actuators. [3] Due to the low Young's modulus, silicone-based elastomers have been widely investigated for actuators and soft systems [4] capable of providing a smooth expansion and contraction at high levels of strain. Recent advances in self-healing technologies have provided a route to create more durable silicone-based soft devices. [5] Bao et al. reported a self-healing polydimethylsiloxane that was crosslinked by coordination complexes to provide high strain, high dielectric strength, and large actuation levels. [6] The materials expanded by 3.6% under a high applied electric potential of 11 kV when used for artificial muscle

In the present work, mode I and mode II tests were carried out on two low alloyed high strength steels. An asymmetrical four point bend specimen and Jn-integral vs. crack growth resistance curve technique were used for determining the mode II elastic-plastic fracture toughness, Ji~ • Jn-integral expression of the specimen was calibrated by finite element method. The results indicate that the present procedure for determining the Jn, values is easy to use. Moreover, the mode I fracture toughness Jt, is very sensitive to the rolling direction of the test steels, but the mode H fracture toughness Ji~ is completely insensitive to the rolling direction of the steels, and the Ja~/Ji, ratio is not a constant for the two steels, including the same steel with different orientations. Finally, the difference of the fracture toughness between the mode I and mode II is discussed with consideration of the different fracture mechanisms.