Introduction To Materials

Question 1

Basic definitions :
Yield stress
UTS
Ductility

Answer 1

Yield stress: elastic limit for materials beyond this it plastically deforms
UTS: max stress value it can take
Ductility = max strain value it can take

Question 2

How to get ductility value and why should be wary

Answer 2

• as the material will have some elastic strain always, must use gradient at breaking point to trace back
• beyond UTS typically the final strain varies with geometry , so not shape independent , so should be used with caution

Question 3

What is ELASTIC STIFFNESS

Answer 3

S= F; delta, where delta is displacement ( either extension or just displacement)

• this can be due to extension, or bending

Question 4

Elastic design what is strength limited and stiffness limited referring too

Answer 4

1) strength limited = you want sigma max < sigma elastic at all times
- the sigma applied will depend on bending or tension or even both

2) stiffness limited - don’t want displacment to exceed max

Question 5

Why are bending tests better than tensile

Answer 5

Because tensile you can’t grip , or damage it while doing test

But bending you can, and then you can find E, sigma y etc better