A 20o full depth involute spur pinion of 4 mm module and 21 teeth is t...
From Lewis equation
Minimum allowable (working stress)
View all questions of this test
A 20o full depth involute spur pinion of 4 mm module and 21 teeth is t...
Problem Statement: To find the minimum allowable stress for the gear material of a 20o full depth involute spur pinion.
Given data:
Module (m) = 4 mm
No. of teeth (N) = 21
Power transmitted (P) = 15 kW
Speed (N) = 960 rpm
Face width (b) = 25 mm
Tooth geometry factor (Y) = 0.32
Combined effect of dynamic load and allied factors intensifying the stress (K) = 1.5
Formula used:
Tangential force (Ft) = (2 × P × 10^3) / (π × N) ---(1)
Pitch diameter (D) = m × N ---(2)
Module factor (Km) = 1 ---(3)
Addendum (ha) = m ---(4)
Dedendum (hf) = 1.25 × m ---(5)
Tooth thickness (s) = π × m / 2 ---(6)
Contact ratio (C) = 1 ---(7)
Velocity factor (Kv) = 1 ---(8)
Dynamic factor (Kv) = ((C × Kv) / (C + Kv - 1))^(1/2) ---(9)
Dynamic load factor (Km) = 1 / (1 + Kf) ---(10)
Tooth load factor (Kf) = Y / (2 × Y - 1) ---(11)
Bending stress (σb) = (Ft × Km × Kv × Ks) / (b × m × Z × Y) ---(12)
Surface stress (σH) = Ft / (b × m × Y) ---(13)
Allowable bending stress (σba) = Sut / K ---(14)
Calculation:
Using equation (1), Ft = (2 × 15 × 10^3) / (π × 960) = 98.17 N
Using equation (2), D = 4 × 21 = 84 mm
Using equation (3), Km = 1
Using equation (4), ha = m = 4 mm
Using equation (5), hf = 1.25 × m = 5 mm
Using equation (6), s = π × m / 2 = 6.28 mm
Using equation (7), C = 1
Using equation (8), Kv = 1
Using equation (9), Kv = ((1 × 1) / (1 + 1 - 1))^(1/2) = 1
Using equation (11), Kf = Y / (2 × Y - 1) = 0.457
Using equation (10), Km = 1 / (1 + 0.457) = 0.686
Using equation (12), σb = (98.17 × 0.686 × 1 × 1) / (25 × 4 × 21 × 0.32) = 166.53 MPa
Using equation (13), σH = 98.17 / (25 × 4 × 0.32) = 30.58 MPa
Using equation (14), σba = Sut
To make sure you are not studying endlessly, EduRev has designed Mechanical Engineering study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Mechanical Engineering.