Young’s modulus, E
Note:

E measures the stiffness of the material. The higher the E, the less it strains under the same stress.

E is usually constant for the same material (e.g. E_{steel} = 200 GPa), so if we know the σ we can find ε using E, and viceversa

The magnitude of E is usually very large, and GPa (10^{9}) is commonly used.

In experiments, stress is usually obtained by measuring strain using strain rosettes, and then converted to stress via E.
Poisson’s ratio, ν
Have you ever noticed that, when you stretch anything (say a rubber block), part of the material actually thins or necks? That’s because the material needs to be redistributed to allow it to stretch. The degree at which this occurs is governed by the Poisson’s ratio.
Note:

There is a –ve sign because ε_{lat} usually has an opposite sign to ε_{long}, so the –ve sign makes the ratio +ve.

Very important property when we look at generalised Hooke’s law.
Shear modulus, G
Basically the same as Young’s modulus E, but for shear conditions:
Note:

G measures the shear stiffness of the material. The higher the G, the less it “tilts” under the same shear loading.

Also usually very large in magnitude, and is normally prescribed in GPa.
Great! You've completed Chapter 1. Let’s look at C2: Axial Load now.
Young’s modulus, E
Note:

E measures the stiffness of the material. The higher the E, the less it strains under the same stress.

E is usually constant for the same material (e.g. E_{steel} = 200 GPa), so if we know the σ we can find ε using E, and viceversa

The magnitude of E is usually very large, and GPa (10^{9}) is commonly used.

In experiments, stress is usually obtained by measuring strain using strain rosettes, and then converted to stress via E.
Poisson’s ratio, ν
Have you ever noticed that, when you stretch anything (say a rubber block), part of the material actually thins or necks? That’s because the material needs to be redistributed to allow it to stretch. The degree at which this occurs is governed by the Poisson’s ratio.
Note:

There is a –ve sign because ε_{lat} usually has an opposite sign to ε_{long}, so the –ve sign makes the ratio +ve.

Very important property when we look at generalised Hooke’s law.
Shear modulus, G
Basically the same as Young’s modulus E, but for shear conditions:
Note:

G measures the shear stiffness of the material. The higher the G, the less it “tilts” under the same shear loading.

Also usually very large in magnitude, and is normally prescribed in GPa.
Great! You've completed Chapter 1. Let’s look at C2: Axial Load now.