Page 250 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
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Answer the following questions:
(a) Which gear is more likely to fail because of pitting? And which gear is more likely
to fail because of tooth breakage?
(b) Decide the value of face width factor .
d
(c) If the load factor is K = 1.3, calculate the maximum torque to be transmitted by
tooth bending strength analysis.
(d) If the load factor is K = 1.3, elastic coefficient Z = 189.8 MPa 1/2 and zone fac-
E
tor Z = 2.5, calculate the maximum torque to be transmitted by tooth contact
H
strength analysis.
3 The variables of a pair of gears are listed here:
z = 20, z = 40, m = 2mm, b = 40 mm, Y = 2.97, Y = 2.35, Y = 1.52,
1 2 Fa1 Fa2 Sa1
1/2
Y = 1.68, Z = 2.5, Z = 189.8(MPa) , K = K = 1.3, [ ] = 500 MPa,
Sa2 H E 1 2 H1
[ ] = 470 MPa, [ ] =390 MPa, [ ] = 370 MPa. Please do the following:
H2 F1 F2
a) Compare the contact strength and bending strength of two gears and predict the
failure modes of each gear.
b) Calculate the maximum torque that can be transmitted by this pair of gears.
4 In the gear box in Figure P8.1, the variables for the first pair of spur gears are: z = 20,
1
z = 100, m = 2.5 mm and b = 45 mm; The variables for the second pair of spur
2 1 2
gears are: z = 23, z = 77, m = 3mm and b = 60 mm. For the two pairs of gears,
3 4 3 4
theallowablestressesofthe pinionsare [ ] = [ ] = 500 MPa and the allowable
H1 H3
stresses of the gears are [ ] = [ ] = 420 MPa. Select load factor K = 1.3 and
H2
H4
1/2
elastic coefficient Z = 189.8 MPa . Determine:
E
Figure P8.1 Illustration for Calculation
Question 4.
Z 1
I X T in
n 1
Z 3
II X X

Z 2

T out X III

Z 4