Microchannel manufacturing is one of the fastest growing areas in advanced manufacturing with numerous applications, including turbine blade cooling structures, compact microchannel heat exchangers, and electronic cooling devices. Recent development of metallic additive manufacturing (AM) based on direct metal laser sintering technology is capable of fabricating microscale structures with high complexity and design flexibility. However, powder bed laser sintering process produces rough surface characteristics caused by hatch overlaps and particle attachments, leading to channel size reductions and rough surfaces. In this paper, dimensional metrology of cross-sectional views of multirow microchannels made by AM was conducted by a scanning electron microscope (SEM) at different locations along the printing direction. Channel size reduction, surface roughness, and circularity tolerance of the as-printed channels were analyzed based on micrographs captured by SEM. Results showed that both channel sizes and hole pitches affected the printing qualities of microchannels. The as-printed channel sizes reduced by more than 15% compared to the designed values. Two approaches were made in this paper to improve printing qualities. The first one was to redesign channel size in computer-aided design (CAD) model to make the as-printed channel sizes closer to the objective values. Electrochemical polishing (ECP) was then applied as a second way using sulfuric acid solutions. Surface roughness value was reduced by more than 40% after the ECP process.

A finite-layer method (FLM) based on consolidation theory is presented for land subsidence due to groundwater withdrawal. The groundwater flow in aquifer systems and the displacement within soil skeletons are approximated by an integration of the standard finite-element method (FEM) in the vertical direction and analytical techniques in the other two spatial directions. By virtue of the analytical eigenfunctions introduced in the formulation, the FEM-weighted residual equations can be decoupled into small-scale linear subsystems, and the formulas for coefficient matrices and flow vectors can be obtained explicitly. Numerical examples are presented to verify the validity of the presented solution through comparisons with available analytical and experimental results. The study also shows that the compressibility of pore water has a significant influence on the pumping-induced subsidence process. The numerical applications to multilayered aquifer systems and horizontal wells are presented to demonstrate the applicability and efficiency of the present method.

Most analytical and semi-analytical models for pumping-induced land subsidence invoke the simplifying assumptions regarding characteristics of geomaterials, as well as the pattern of drawdown response to pumping. This paper presents an analytical solution for one-dimensional consolidation of the multilayered soil due to groundwater drawdown, in which viscoelastic property and time-dependent drawdown are taken into account. The presented solution is developed by using the boundary transformation techniques. The validity of the proposed solution is verified by comparing with a degenerated case for a single layer, as well as with the numerical solutions and experimental results for a two-layer system. The difference between the average consolidation degree U _p , defined by hydraulic head, and U _s , defined by total settlement, is discussed. Detailed parametric studies are conducted to reveal the effects of viscoelastic properties and drawdown patterns on the consolidation process. It is revealed that while the effect of different drawdown response patterns is significant during the early–intermediate stages of consolidation, the viscoelastic properties may have a more dominant influence on long-term consolidation behaviour, depending on the values of the material parameters, which are reflected in both the deformation process of soil layers and the dissipation of excess pore-water pressure.