Question

In the idealized helical geometry of twisted filament yarn, which assumption is wrong?

• A. yarn is assumed to be circular in cross-section
• B. centre fibre is straight and the fibre in subsequent layers assume helical path of same radius
• C. yarn contains large number of fibres
• D. fibres migrate from their original position

Hint:

Idealized = Perfect. Real = Migrating. If the model says fibers stay in their neat little layers, it's idealized.

Answer 1

The Correct Option is D

Concept: Mathematical models of yarn geometry, like the Idealized Helical Model, simplify the complex structure of yarn to make calculations possible.

Step 1: Reviewing Idealized Assumptions.
The standard idealized model assumes:
• The yarn is a cylinder with a circular cross-section.
• Each fiber follows a perfect helix around the central axis.
• The radius of a fiber's helix remains constant (it stays in its "layer").

Step 2: Identifying the Incorrect Statement.
The assumption that fibres migrate from their original position is actually the definition of a Real yarn, not an Idealized one. In a real yarn, fibers move from the core to the surface and back (migration) due to tension differences. The idealized model explicitly assumes no migration to keep the geometry simple.