P 5. Solids under stress Flashcards
Hookes law?
(given in data booklet)
but not when u needa state it
F = kx
The force is proportional to the extension of a spring within the limits of proportionality
Within hookes law, define each symbol
F = spring force
k = spring constant
x = spring stretch, or distance?, extension??
Springs in series and parallels?
K if springs in series? = x doubled
K if springs in parallel? = x halved
And finding energy in spring too = ?
E = 1/2k x X^2
How to find spring constant in graph?
Rise/Run
If you know u know lolo
But in general, it’s the same with F = kx, u kinda just re-arrange
How to find tensile stress?
Tell me about it
σ(Nm^-2) = Force(n)/Area(M^2)
Can be pascals (Pa) but that equals Nm^-2 too
The force per unit cross-sectional area
How to find tensile strain?
Tell me about it
ε = extension(m)/length(m)
It’s quite literally just it’s extension divided by it’s total length
CAREFUL OF DIFFERENT UNITS
The extension per unit length
How u find young modulus of a material?
E = σ/ε
= stress/strain
In addition:
E = fl/ax, so know that or u gl finding that equation urself
Sadly and unfortunately, I’m cooked for these material type shit for this part of the topic
Is this enough for the materials?
o7
No, i remember there’s something missing therefore…..
Tell me about stress-strain graphs for ductile materials
Visualise this:
- x axis = strain
- y axis = stress
- Think about like disobeying hooke’s law
- Line goes up and as u keep pulling, there’s like a new arc above
- Then it kinda just breaks
- The point where new arc comes is limit of proportionality (yield strength)
- In addition u can state about elastic limit too
- Afterwards u can say about how u reach its ultimate strength
- Then at the end say it just fractures
The last 2 is the plastic region
KNOW ABOUT NECKING:
The point where the specific area stretches?
What is necking?
The thinning of the cross-sectional are of a material at the weakest point.
Necking is where the cross-sectional area of the metal reduces as it deforms plastically. To keep extending the metal and lower stress is needed shown by the dip in the curve on the stress-strain graph
Tell me about stress-strain graphs for polymeric materials
Rubber elastic material:
Visualise this:
- When stretching, it’s “loading”
- But when u unstretch, it’s “unloading” (recommend just saying “loads” instead of “stretch”)
- The area between loading and unloading is the energy transferred per unit volume
It actually produces heat
How about for a polymer picture summary n shi?:
- Think about it in terms of chemistry analysis
- It’s rubber so it appears that the long chains are coiled up within material allowing for much weaker Van deer Waals bonds to form between adjacent lengths of the coils
- Picture 1 = tangled, rando ass lines
- Picture 2 = straightening, tangled but one part is straight
- Picture 3 = straight, just a line of half hexagons
ik this is obscure, i wish u can just put images in brainscape, too bad it’s paid. But honestly ur best clue here: chemistry, hexagons, kinetic energy.
Order of the stress-strain graphs?
- Limit of proportionality (obeys Hooke’s law)
- Elastic limit
- Yield point
- Ultimate strength
4.5. Necking - Fracture point
3-5. Plastic region
Just missing topics for this one
Okay
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