0
6.3kviews
For circular rod, find elongation, change in the diameter and change in volume of the rod.

A 30mm dia. Solid circular aluminum rod 3m long, is subject to an axial pull of 100 KN. Taking E=70 GN/m^2 and Poisson’s Ratio =1/3, determine the elongation, change in the diameter and change in volume of the rod. Also, find the bulk modulus.

1 Answer
2
316views

Given data:

diameter d=30mm

Length L=3mm=3000mm

Force F=100KN

Modulus of elasticity (E)=70GN/m2=70103N/mm2

Poisson's ratio μ=13

Now, σstress=forceoraxialpullareaofcrosssection= 100103π302N/mm2

Stress=141.47N/mm2

Now, modulus of elasticity=stress(σ)strain(ϵ)

70103=141.47ϵ

ϵ=2.021103

ϵ=changeinlengthoriginallength

2.021103=Δ3000

ΔL=6.063

Now, Poisson's ratio σ=lateralstrainlongitudinalstrain

13=δddΔL= δd306.0633000

Δd=0.02021mm

Now,E=3K(12μ)orE=2G(1+μ)

Using first equation as bulk modulus is asked, not modulus of rigidity

70103=3K(1213

70103=3K(323

K=70103N/mm2or70KN/mm2

Now, bulkmodulus=stressvolumetricstrain

70103=141.47ϵv

ϵv=2.021103

ϵv=changeinvolumeoriginalvolume

2.021103=Δvπ4d2L

2.021103=Δvπ43023000

Changeinvolume(ΔV)=4285.68mm3

Please log in to add an answer.