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Poisson's ratio
σ
σ
x
y
z
The cuboid is stretched in the x (axial) direction and contracts in the y, z (lateral) directions
Poisson's ratio
x1
x0
y1
y0
x
y
z
εx = (x1-x0) / x0
εy = (y1-y0) / y0
εz = (z1-z0) / z0
For uniaxial tensile stress in the x direction,
we define the Poisson's ratio as
ν = -εy / εx = -εz / εx
we define the Poisson's ratio as
ν = -εy / εx = -εz / εx
Normal materials with Poisson's ratio 0 - 0.5
Normal materials expand in the axial direction and contract in the lateral directions under uniaxial stress.
σ
σ
Auxetic materials with negative Poisson's ratio
Auxetic materials expand in all directions under uniaxial stress.
σ
σ