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As one of the promising micro-manufacturing technologies, micro-forming has economical and ecological advantages in terms of mass and near-net-shape production. However, size effects increasingly affect material performances with scaling down geometry and process parameters and consequently hinder applications of micro-forming. Electrically-assisted (EA) micro-forming may have the potential to minimize the size effects. In order to investigate the size effects in the EA micro-forming, uniaxial tension tests were conducted on miniaturized AZ31 tensile samples with varying grain sizes and geometry sizes at a constant DC current density. It was found that the normalized flow stress reduction, i.e., decreases of flow stresses / flow stresses at room temperature (RT), increased with the decrease of the grain size and with the increase of the geometry size at the

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In this paper, a new piezo-actuated XY parallel compliant mechanism for large workspace nano-positioning with decoupled motions is developed by incorporating a novel Z-shaped flexure hinge (ZFH)-based mechanism into the mirror-symmetrically distributed structure. The bridge-type mechanism and two-stage leverage mechanisms serve as preliminary displacement amplifiers, while further amplification with motion transfer and decoupled output motions are achieved by means of the ZFH mechanism. Based on finite element theory, a high-precision analytical model of the XY compliant mechanism is established by considering all the connecting linkages as flexible components. Through the improved differential evolution algorithm, the optimized compliant mechanism is capable of performing millimeter-scale workspace nano-positioning with decoupled motions. In addition, the input displacement unbalance, resulting from the lateral force which has potential to damage the piezoelectric actuators, is markedly lowered to a negligible value. The performance of the fabricated compliant mechanism with optimized parameters is investigated to well agree with both the analytical model and ANSYS simulation. In addition, based on the inverse kinematics derived from the model and experimental results, different elliptical vibration trajectories are accurately acquired.

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