Chapter 6: Mechanical Properties Flashcards
what is the formula σ = 𝐹/𝐴𝑜
σ = tensile stress,
Ft = force of tension
Ao = original cross-sectional area before loading
what is the formula τ = Fs/Ao
τ = shear stress
Ft = force of shear
Ao = original cross-sectional area before loading
what is the formula ε = δ/Lo
ε = tensile strian
δ = change in length
Lo = original length
what is the formula εL = -δL/wo
εL = lateral strain
δL = lateral change
wo = original with
what is the formula γ = Δx/y = tan θ
γ = Shear strain
Δx = change in direction
y = other direction
tan θ
what are the units for stress?
N/m^2
What is elastic deformation?
reversible strain
what is the formula σ = E ε?
σ = tensile stress
E = Modulus of Elasticity (different for every substance)
Do stronger or weaker bonds lead to a larger Young’s modulus?
Stronger
Does elastic modulus vary with direction?
yes
what is the formula 𝜈 =−𝜀𝑋/𝜀𝑍 =−𝜀𝑌/𝜀𝑍
ν = Poisson’s Ratio
𝜀𝑋 = strain perpendicular to stress
𝜀Z = strain parallel to stress
what is the formula τ = G γ
τ = Shear stress
G = shear modulus
γ = shear strain
when does noticeable plastic deformation occur?
when εp = 0.002
what is uts?
the maximum stress on stress-strain curve
list the relative strength of the common material groups
Metals > Ceramics > polymers> Composite/fibers
what is the formula %EL = (Lf - Lo) / Lo x 100
%EL = percent elongation
Lf = Length final
Lo = Length initial
What is the formula %RA = Ao - Af / Ao
RA% = percent reduction in area
Ao = Area initial
Af = Area final
what is toughness?
The ability of a material to absorb energy and plastically deform before fracturing.
What is resilience?
The ability of a material to store energy
what is the formula σT = F/Ai?
σT = True Stress
F = Force
Ai = Area instantaneous
what is the formula σT = σ(1+ε)?
σT = True Stress
σ = engineering stress
ε = engineering strain
what is the formula εT = ln(1+ε)?
εT = True strain
ε = engineering strain
what is the formula εT =ln( ℓi / ℓo)
εT = True strain
ℓi = instantaneous length
ℓo = original length
what is the formula σT = k(εT)^n?
σT = True Stress
k and n (stain hardening exponent) are constants
εT = true strain
What is hardness?
a measure of resistance to surface plastic deformation—dent or scratch.
what is this formula 𝜎𝑑 =𝑁𝜎𝑐
𝜎𝑑 = design stress
𝑁 = safety factor
𝜎𝑐 = calculated stress
how do you find the modulus of elasticity?
the slope of the linear curve
How to find the proportional limit?
The end of the linear part of the stress curve
How to find the yield strength on a graph
you take the 0.002 stress and take the slope of elasticity up to the point on the curve.
How to find tensile straingth on a graph?
Maximum point
