Problem 3 Select a group of candidate materials for energy s

Problem 3: Select a group of candidate materials for energy storing flywheel using Ashby chart. Following information is available:

Flywheel is a solid disk with radius R and thickness t, rotating with angular velocity w. The energy stored is given by:

U = ½ (/2rR⁴t) w²

The quantity to be maximized is the KE / unit mass. The maximum centrifugal stress in spinning disk is given by:

_max = (3 + v/8) rR²w²

Solution

There are several charts for selection of materials:

Want to maximise KE/Unit mass

Notice that KE goes as R^2, energy stored as R^4

These are the main parameters.

We want to accomodate these within the material strength limits. Since angular velocity is not given, assume as high as possible. Then need to go to upper end of the chart.

SELECT Specific modulus vs Specific weight ==E/rho / Sigmaf/rho

The chart is appended

It may be seen that composites glass, and ceramics have highets ratingdue to their specific properties