Fabrication of micro-flow channels on graphite composite bipolar plates using microplaning

A new method of manufacturing micro-flow channels on graphite composite bipolar plate(GCBPP) microplaning using specially designed multi-tooth tool is proposed. In this method, several or even dozens of parallel micro-flow channels ranging from 100 μm to 500 μm in width can be produced simultaneously. But, edge chippings easily occur on the rib surface of GCBPP during microplaning due to brittleness of graphite composites. Experimental results show that edge chippings result in the increase of contact resistance between bipolar plate and carbon paper at low compaction force. While the edge chippings scarcely exert influence on the contact resistance at high compaction force. Contrary to conventional view, the edge chippings can significantly improve performance of microfuel cell and big edge chippings outperform small edge chippings. In addition, the influence of technical parameters on edge chippings was investigated in order to obtain big, but not oversized edge chippings.

Modeling Notch Wear of Ceramic Tool in High Speed Machining of Nickel-based Superalloy

On the basis of theoretical analyses and calculations of high speed continuous impact force and tool notch surface temperature acted upon by burr and serrated chip edge, a notch wear model of low stress value and temperature impact fatigue was established. Saw-tooth-shaped burr and fin-shaped chip edge continuously impacts the rake face and flank face at high speed and high fre-quency, which results in a V-shaped notch wear. An experiment was done to validate that the saw-tooth-shaped burr does affect the notch wear. This model can be utilized to solve reasonably many problems that cannot be explained by any other theoretical assumptions.

Compaction analysis and optimisation of convex-faced pharmaceutical tablets using numerical techniques

Capping failure,edge chipping,and non-uniform mechanical properties of convex-faced pharmaceutical tablets are common problems in the pharma industry.In this paper,the finite element method(FEM)and design of experiment techniques are used to determine the optimal shape of convex-faced(CF)pharmaceutical tablet which has more uniform mechanical properties and less capping and chipping tendency.The effects of different geometrical parameters and friction on the compaction responses of convex-faced pharmaceutical tablets were first identified and analysed.An FEM model of the tabletting process was generated using the implicit code ABAQUS and validated against experimental measurements.Response surface methodology was used to establish the relationship between the design variables,represented by the geometrical parameters and friction coefficient,and compaction responses of interest including residual die pressure,relative density variation within a tablet,and relative shear stress at the edge of a tablet.A statistical-based optimisation approach was then used to optimise the shape of CF tablets.The obtained results demonstrated how the geometrical parameters and friction coefficient of CF pharmaceutical tablets strongly affect their compaction behaviour and quality.