Doctor of Philosophy (PhD)
Mechanical Engineering Department
The continuing trend of metallic device and product miniaturization has motivated studies on microscale metal forming technologies. A better understanding of materials’ mechanical response and deformation behavior is of importance for the design and operation of micro metal forming processes. In this dissertation, uniaxial compression testing was conducted on Al ring and pillar specimens with characteristic dimensions at meso to micro scales. The experimental data reveal inadequacies of the existing surface layer model and provides a baseline for delineating deformation mechanisms in micro metal forming operations. Microscale reverse extrusion experiment was carried out on Cu and Al rod specimens with varying average grain sizes. Texture assessment on extruded Cu parts showed the texture components formed at tens of microns scale were consistent with those observed in macro scale extrusion. The grain size effect on both the mechanical response and deformation inhomogeneity was demonstrated and was further elucidated by a detailed comparison between the experimental results and the output of crystal plasticity finite element simulations. Another promising micro metal forming operation, namely microscale compression molding, was conducted on single crystal Al, using a series of rectangular double-punch sets with varying punch width and spacing in between. The characteristic molding pressure was observed to exhibit a significant dependence on both the spacing itself and the ratio of the spacing to the punch width. The molded features were characterized and the phenomenon of incomplete filling was observed and discussed. All these experimental results furnish new and basic knowledge for meso/micro scale metal forming technologies, as well as supplying data against which small scale plasticity theories/models can be tested.
Zhang, Bin, "Microscale Metal Forming: Mesoscopic Size Effect, Extrusion and Molding" (2019). LSU Doctoral Dissertations. 4857.