Advanced Materials - 230411

Question 1

Bauschinger effect

Answer 1

Yield stress under tension is higher than when having a previous compression and then tension.
Also called kinematic hardening.

Question 2

Uniaxial tensile test

Answer 2

Detection of flow stress only possible before necking

Question 3

What is a flow curve?

Answer 3

Flow stress vs True or logarithmic strain. Increasing stress will require more and more stress, which is shown by the curve.
This is called the strain hardening.

Question 4

What’s the use of Hydraulic Bulge Test?

Answer 4

Determination of flow curve experimentally. Another option would be to extrapolate/approximate mathematically.

Question 5

Mathematical description of flow curve

Answer 5

Kf = C * φ n: strain hardening coefficient.
Flow curve extrapolation, Ludwik – Hollomon, Hockett-Sherby, a combination of both approaches would yield the best results.

Question 6

Strain path

Answer 6

It has an influence on the failure behavior. In reality most of the strain paths are not linear.

Question 7

Forming limit curve

Answer 7

10% below the FLC would be a good rule of thumb for the limit.

Question 8

What is φ1 and φ2?

Answer 8

φ1: major strain and φ2: minor strain

Question 9

How many FLC’s do we have for one material?

Answer 9

Infinite. They depend on the strain path.