Electrochemical machining operations are performed with tungsten as the tool, and copper and aluminum as two different workpiece materials. Properties of copper and aluminum are given in the table below.
$$ \begin{array}{|c|c|c|c|} \hline \text { Material } & \begin{array}{l} \text { Atomic mass } \\ \text { (amu) } \end{array} & \text { Valency } & \text { Density }\left(\mathrm{g} / \mathrm{cm}^3\right) \\ \hline \text { Copper } & 63 & 2 & 9 \\ \hline \text { Aluminum } & 27 & 3 & 2.7 \\ \hline \end{array} $$Ignore overpotentials, and assume that current efficiency is 100% for both the
workpiece materials. Under identical conditions, if the material removal rate (MRR) of copper is 100 mg/s, the MRR of aluminum will be ________________ mg/s (round-off to two decimal places).
A 4 mm thick aluminum sheet of width w = 100 mm is rolled in a two-roll mill of roll diameter 200 mm each. The workpiece is lubricated with a mineral oil, which gives a coefficient of friction, μ = 0.1. The flow stress (σ) of the material in MPa is σ = 207 + 414 𝜀, where 𝜀 is the true strain. Assuming rolling to be a plane strain deformation process, the roll separation force (F) for maximum permissible draft (thickness reduction) is _________ kN (round off to the nearest integer).
Use:
$F = 1.15 \barσ \left( 1 + \frac{\mu L}{2 \bar h} \right)$ wL, where $\bar \sigma$ is average flow stress, L is roll-workpiece contact length, and $\bar h$ is the average sheet thickness