# Stress on Materials

1. Nov 23, 2014

### oxon88

1. The problem statement, all variables and given/known data
Two identical sized specimens of materials A and B are made from materials which produce stress v strain graphs as shown below.

The specimens are arranged in a press, the press moves uniformly, which of the specimens would be under the greatest stress?

2. Relevant equations
stress = force / area

3. The attempt at a solution

Would they both be under the same stress, they are the same size (area) and both subject to the same force?

2. Nov 23, 2014

### Bystander

What are the definitions of "stress" and of "strain?"

3. Nov 23, 2014

### Staff: Mentor

Your answer is correct of the specimens are placed on top of one another. But what if they are placed next to one another.

Chet

4. Nov 24, 2014

### oxon88

There is a small diagram which I omitted. It shows that the two samples are placed next to each other in the press.

Stress is a measure of the internal force an object is experiencing per unit cross sectional area. Stress = force / area

Strain is a measure of how much an object is being stretched . Strain, ε = Δl / l0

So I guess as the press is putting force onto the samples, sample A will be under less stress because it will deform more than sample B? Meaning sample A will then have a larger area so the amount of stress will be less?

5. Nov 24, 2014

### Staff: Mentor

The strains in the two materials will be exactly the same because this is determined by how much the press moves down. The areas will be the same also. What does that tell you about the stresses?

Chet

6. Nov 26, 2014

### oxon88

Ok so if the 2 materials are under the same amount of strain I guess the stress will be greater in material A, because as we see from the graph, for any value of strain, the stress in material A is always greater.

Am I correct?

7. Nov 26, 2014

Exactly.

8. Jan 6, 2015

### Faisal Nazir

(b) Under identical loads, which material will deflect the most?

(c) The specimens are arranged in a press as shown below, the press moves uniformly, which of the specimens would be under the greatest stress?

9. Jan 6, 2015

### Staff: Mentor

See response #6.

10. Feb 19, 2016

### darin khan

this might be silly but im still confused about Q.b under identical loads, which material will deflect the most then?? please someone let me know ASAP

11. Feb 19, 2016