This research aims to present a novel approach in magnetic abrasive finishing to improve its potential for creating different finishing patterns in the free-form surface using no special fixtures or tool machines to minimize the complexity of the process. The key point of this idea is that magnetic abrasive particles can move in special patterns by transfer magnetic fields (similar to a magnetic train moving on a magnetic rail) and create the desired polishing patterns on the surface simultaneously. The coils are placed under a thin plate; then, a flexible magnetic path is created by a special arrangement of magnetic coils; after that, the coils are turned on and off in turn, and the magnetic abrasive particles move in the created path and abrasive the surface. The continuous movement of magnetic abrasive particles under the magnetic field will abrade the thin sheets' surface. The tests were performed on copper sheets with a thickness of 1 mm. Experimental parameters include electric current (0.25, 0.5, and 0.75 A), speed of turning on and off of the coils (speed of magnetic abrasive particle movement) (20, 30, and 40 mm/s), and process time (1, 2, and 3 h). The experiments were performed on L-shaped and free-form sheets. The results show that using a transmission magnetic field in the MAF (TMAF) makes it easy to create different surface roughness patterns in different directions simultaneously. While in one part of the L-shape the electric current is 0.25 A, the surface roughness is around 0.90 µm, in the other part, where the electric current is 0.75 A, the surface roughness is around 0.49 µm. Meanwhile, TMAF makes it possible to finish a free-form surface with no special fixtures. Moreover, there is a direct relationship between the change in the surface roughness and the electric current and process time.
The genome inside the eukaryotic cells is guarded by a unique shell structure, called the nuclear envelope (NE), made of lipid membranes. This structure has an ultra torus topology with thousands of torus-shaped holes that imparts the structure a high flexural stiffness. Inspired from this biological design, here we present a novel “torene” architecture to design lightweight shell structures with ultra-stiffness for engineering applications. We perform finite element analyses on classic benchmark problems to investigate the mechanics of torene shells. This study reveals that the torene shells can achieve one order of magnitude or higher flexural stiffness than traditional shells with the same amount of material. This novel geometric strategy opens new avenues to exploit additive manufacturing to design lightweight shell structures for extreme mechanical environments.
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