Physics - Classical Mechanics - Elasticity and Plasticity of Common Materials

in #physics4 years ago

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Introduction

    Hey it's a me again @drifter1! I took a break from posting, so that I could dedicate myself to the Master's Degree in Computer Science. I needed a break after the Bachelor thesis and then the Master and COVID-19 quarantine stuff etc. happened and so I never got the time to start posting again. Either way, I am still studying, but there is more free time and so I thought of getting into Steemit and the new fork "Hive" again. I will start out by posting in both platforms, but later I might go Hive-only. Today we continue with Physics and more specifically the branch "Classical Mechanics" to continue with the chapter of Equilibrium and Elasticity. In this article we will get into the Elasticity and Plasticity of Common Materials. Its the last part of the chapter, that should have been done 10 months ago! So, without further ado, let's dive straight into it!


Elasticity

    Elasticity is the tendency of solid objects and materials to return to their original shape after some external force caused them to deform. The elasticity of a material is defined through its elastic modulus and elastic limit. High elastic modulus materials are harder to deform, whilst low elastic modulus materials are easier to deform. After a specific elastic limit of stress (force over area) is reached, a material no longer behaves elastically and becomes permanently deformed. For example, a rubber band has low elastic modulus (easily deformed), but a high elastic limit (difficult to permanently deform).

Plasticity

    For stresses beyond the elastic limit, a material behaves plastically. Plasticity is the state in which the deformation is irreversible. In the so called plastic region the material can no longer return to its original shape and size, even if the load is removed. As the stress increases, a material becomes harder and harder to deform, until it reaches the fracture point where it breaks.

Stress-Strain Diagram

    The relationship between the stress and strain can be represented on a stress-strain diagram. Each material has its own characteristic curve. On most typical materials as the load increases the relationship is linear up to a elastic linearity point, which means that Hooke's law is directly obeyed. From their the relationship becomes non-linear. Its worth noting that the behavior is still elastic after the non-linear point is reached. The non-linear point occurs before the elastic limit is reached.

For example:

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Fracture

    There are two types of fractures that can occur on materials after the fracture point of stress is reached. There are fractures that can occur "without warning" causing major damage and are called Brittle Fractures. Then there is Ductile Fracture, which gives some kind of warning that failure is imminent. All fractures involve two steps, the crack formation and the propagation. During a tensile test, Ductile materials show a ultimate strength that is lower than the ultimate tensile strength (UTS) value, whereas in Brittle materials the fracture strength is equal to the UTS. This so called Ductility of Ductile materials allows the material to be alongated in tension, causing them to deform (elongate) more than Brittle materials. Therefore a Ductile fracture is better than a Brittle fracture, as the tension is slowly propagated and absorped before the fracture occurs. In Brittle materials no plastic deformation takes place before the Brittle fracture, which means that the cracks in Brittle Materials are highly unstable and propagating rapidly.

Common Materials

The following table shows the Typical properties of Annealed elements.



From Wikipedia remade using quicklatex

RESOURCES:

References

  1. https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_University_Physics_(OpenStax)/Map%3A_University_Physics_I_-_Mechanics_Sound_Oscillations_and_Waves_(OpenStax)/12%3A_Static_Equilibrium_and_Elasticity/12.06%3A_Elasticity_and_Plasticity
  2. https://courses.lumenlearning.com/boundless-physics/chapter/elasticity-stress-strain-and-fracture/
  3. https://www.nuclear-power.net/nuclear-engineering/materials-science/material-properties/toughness/fracture-of-material-fracture-mechanics/#:~:text=In%20the%20tensile%20test%2C%20the,ultimate%20strength%20at%20this%20point.
  4. https://en.wikipedia.org/wiki/Ultimate_tensile_strength

Images

  1. https://en.wikipedia.org/wiki/File:Stress-strain1.png
  2. https://courses.lumenlearning.com/boundless-physics/chapter/elasticity-stress-strain-and-fracture

Mathematical equations used in this article, where made using quicklatex.


Previous articles of the series

Rectlinear motion

Plane motion

Newton's laws and Applications

Work and Energy

Momentum and Impulse

Angular Motion

Equilibrium and Elasticity


Final words | Next up

And this is actually it for today's post!

Next time we will start getting into Newtonian Gravity...

See ya!

Keep on drifting!