Stress-Strain Graphs of different materials

[lpettigrew]

Homework Statement

Using labelled axes, draw stress-strain graphs for;
1.Rubber
2.Copper
3.Glass
4.Mild Steel

On the sketch graph for copper mark the following points: a - the limit of proportionality, b- the
elastic limit, c - the yield stress, d - the ultimate tensile stress, e - the breaking point

Relevant Equations

S

Hello, so I am not actually seeking help sketching the stress strain graphs. However, I am rather confused about the last part of the question to comprehensively label the stress-strain graph of copper with the limit of proportionality etc.
Evaluating the graph, it becomes clear that these points are not directly discernible, at least not to the degree of detail specified by he question. Do you think that this is a mistake and that the question meant to ask one to identify these points on the graph for mild steel?

I have just attached two images from online showing an average stress-strain graph for copper and mild-steel to support my thoughts.

Also, I have not sketched them out yet but I have also attached what I think a stress-strain graph for;
1. Rubber looks like. This forms a hysteresis loop.
2. Glass looks like. Materials lacking in mobility like glass are usually brittle rather than ductile. Brittle materials do not have a well-defined yield point, therefore, the ultimate strength and breaking strength are the same. Glass would not usually show any plastic deformation but fail while the deformation is elastic. Thus, an average stress–strain curve for a brittle material will be linear.

 

[lpettigrew]

Hello, sorry to ask but I would still appreciate anyone's thoughts on this problem?

 

[lpettigrew]

Help?

 

[lpettigrew]

Sorry to ask but I am still in need of some help above

 

[haruspex]

No, I don't think it is a mistake. Note that the mild steel has an upper and lower yield point, whereas the question just asks for "yield point ". That fits with the copper curve.
Just mark them as seems appropriate. Post your answer here and I'll take a look.

 

[Sylvain Poudrette]

Hello
Textbook behaviour: Mild steel has a sharp yield point because of its cristallography BCC and carbon content while copper does not, its yield point being measured when strain is offset by 0.2% from initial linear curve. Glass hasperfectly linear behaviour until rupture hence no yield point
Not sure about rubber

 

[lpettigrew]

No, I don't think it is a mistake. Note that the mild steel has an upper and lower yield point, whereas the question just asks for "yield point ". That fits with the copper curve.
Just mark them as seems appropriate. Post your answer here and I'll take a look.

@haruspex Thank you for your reply, I have only just read it. I have labelled diagrams for stress-strain graphs of copper and mild steel to show; the limit of proportionality, the elastic limit, the yield stress, the ultimate tensile stress and the fracture point. Would these positionings and graphs be correct?

 

[lpettigrew]

Hello
Textbook behaviour: Mild steel has a sharp yield point because of its cristallography BCC and carbon content while copper does not, its yield point being measured when strain is offset by 0.2% from initial linear curve. Glass hasperfectly linear behaviour until rupture hence no yield point
Not sure about rubber

Thank you for your reply also. I see from further research myself that the yield stress of copper is measured when strain is 0.2% from the linear curve, thank you for providing this information

 

[Lnewqban]

... Would these positionings and graphs be correct?

I believe those are correct.

 

[lpettigrew]

I believe those are correct.

Thank you for your reply, I appreciate it