Why a hollow shaft is stronger than a solid shaft?
Answers
Why is a hollow shaft better than a solid shaft?
Let me list down a few of the advantages first.
In comparison to a solid shaft, a hollow shaft is of less weight, for a given length and diameter. This is pretty obvious and wont be requiring any further explanation. Moreover it’s a good idea to go ahead with hollow shafts, if we our emphasis is on weight reduction and cost-cutting.
Hollow shafts are much better to take torsional loads compared to solid shafts. As shown in the figure, shear stress in a “shaft subjected to torsion” varies linearly from zero at the center to the maximum at the boundary. Inside a solid shaft, most of the material experiences / carries a shear stress whose value is much below the maximum shear stress [Interior portion of the shaft]. But at the same they are adding to the weight, without contributing much to the capability of the shaft to carry torsional load.
Shear stress at a point in a hollow shaft (τ) is given by , τ=TrIp
where τ=Shear stress in a hollow shaft
T = Torque in shaft (N-m)
r = radial distance from the center to the point of interest (m)
Ip=Polar area moment of inertia (m4)
Average shear stress[ (Min. Shear stress + Max. Shear Stress)/ 2 ] in a hollow shaft will be higher compared to a solid shaft and it’s value is more closer to the maximum shear stress.
Hollow shaft has a greater Strength to weight ratio.