What diameter should the driving pulley have on which a rubber belt ru...
Solution:
Given data:
Thickness of the belt, t = 15 mm
Width of the belt, w = 110 mm
Bending stress in belt, σ = 5 N/mm²
Modulus of elasticity of belt material, E = 100 N/mm²
Formula used:
Bending stress in a belt, σ = (M*y)/I
where M = bending moment, y = distance from the neutral axis to the point of interest, and I = moment of inertia of the belt cross-section.
The moment of inertia of a rectangular cross-section is given by I = (t*w³)/12.
The bending moment can be calculated as M = T*D/2, where T is the tension in the belt and D is the diameter of the driving pulley.
Calculation:
Substituting the given values in the formula for the moment of inertia, we get:
I = (15*110³)/12 = 1,113,750 mm⁴
The maximum bending stress in the belt is given as 5 N/mm².
Substituting the values of bending stress, moment of inertia and distance from the neutral axis (which is half the thickness of the belt) in the formula for bending stress in a belt, we get:
5 = (M*(15/2))/(1,113,750/12)
M = 270,312.5 Nmm
The tension in the belt can be calculated as T = σ*A, where A is the cross-sectional area of the belt.
Substituting the given values, we get:
T = 5*(15*110) = 8250 N
Substituting the values of tension and bending moment in the formula for the diameter of the driving pulley, we get:
D = (2*M)/(T) = (2*270,312.5)/8250 = 65.45 mm
Therefore, the diameter of the driving pulley on which a rubber belt runs should be 300 mm to limit the bending stress in the belt to 5 N/mm².