Page 248 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
226
10 Jelaska, D. (2012). Gears and Gear Drives, 1e. New York: Wiley.
11 Gere, J.M. and Timoshenko, S.P. (1996). Mechanics of Materials, 4e. CL Engineering.
12 Qiu, X.H. (1997). Mechanical Design, 4e. Beijing: Higher Education Press.
13 Huang, X.K. and Zheng, W.W. Theory of Machines and Mechanisms. Beijing: People’s
Education Press.
14 ISO 6336–2:2006 Calculation of load capacity of spur and helical gears. Part 2: Cal-
culation of surface durability (pittings). Switzerland: International Organization for
Standards, 2006.
15 ISO 6336–3:2006 Calculation of load capacity of spur and helical gears. Part 3:
Calculation of tooth bending strength. Switzerland: International Organization for
Standards, 2006.
16 ISO 6336–5:2003 Calculation of load capacity of spur and helical gears. Part 5:
Strength and quality of materials. International Organization for Standards, 2003.

Problems

Review Questions

1 Discuss the main failure modes of gear drives, the failing mechanism, location and
prevention measures.

2 Which factors affect the face load factor K ? How could one improve uneven load

distribution along the face width?
3 What are the main variables to be decided in gear design and how should one select
them?

4 For a pair of gears, how could one decide which gear is prone to fail due to pitting
and which gear is prone to fail because of tooth breakage?

5 How could one increase the contact strength and bending strength of a cylindrical
gear?

Objective Questions

1 In a gear drive, both the pinion and gear are made of medium carbon steel. The
pinion is heat treated by quenching and tempering and the gear by normalizing. The
contact stress on the tooth surface of the pinion and gear is___.
(a) >
H1 H2
(b) =
H1 H2
(c) H1 < H2
(d) hard to decide
2 Assuming the pitch diameter is constant in a spur gear drive, the larger the _____,
the higher the bending strength of the gear.