Commercial dual-phase (DP) steel in sheet form and comprised of ferrite, martensite, and bainite was subjected to uniaxial tension up to fracture. The damage characteristics were studied through extensive quantitative metallography and scanning electron microscope (SEM) observations of polished sections and fracture surfaces of failed specimens. The observed void nucleation mechanisms include nucleation at the martensite/ferrite interface or triple junction (most predominant), nucleation due to the cracking of martensite particles, and nucleation at the inclusions. The void characteristics in terms of area fraction, void density, void size ranges, and void orientations were analyzed as a function of thickness strain from various regions of the different uniaxial tensile test specimens taken to fracture. The damage analysis suggests that the void nucleation occurs during the entire deformation process with an almost constant rate and this rate reduces before fracture. A nucleation strain of 0.15 has been estimated for this material.
We present a symmetric five-bar compliant mechanism for the displacement amplification of mechanical vibration. When the proposed mechanism is connected to an energy harvester, amplification of the input excitation vibration amplitude leads to an increase in the harvested power. Displacements in the compliant mechanism are caused by deflections in its flexure hinges. The flexure hinges we use are either of the right-circular, or the corner-filleted types. The mechanism is analyzed using energy methods. The displacement amplification was verified analytically and numerically using a finite element model. Through our model we present relations governing the displacement amplification in terms of the design parameters, such as the geometry of the mechanism, the flexure hinges dimensions, in addition to the load caused by the harvester. The effects of the flexure hinge dimensions on displacement amplification, are also presented.
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