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Engineering ToolBox > Bolt Stretching
Bolt stretching according Hook's Law can be expressed as
dl = F L / E A (1)
where
dl = change in length of bolt (inches, mm)
F = applied tensile load (lb, kN)
L = effective length of bolt where tensile strength is applied (inches, mm)
E = Young's Modulus of Elasticity (psi, N/mm2)
A = tensile stress area of bolt (square inches, mm2)
Tensile stress area can be expressed as
A = 0.7854 (d - 0.9743/n)2 (2)
where
d = nominal diameter of bolt (inches, mm)
n = number of threads per inch (pitch)
Tensile stress area can be calculated as
A = 0.7854 (7/8 - 0.9743/9)2
= 0.46 (in2)
Change in length of bolt can be calculated as
dl = 10000 (lb) 5 (in) / (30 106 (psi) 0.46 (in2))
= 0.0036 (inches)