Page 438 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
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Problems
Review Questions

1 What is the characteristic curve of a spring? Give examples of springs correspond-
ing to different types of characteristic curves.

2 What factors affect the strength, rigidity and stability of a spring? What measures
can be taken to improve the strength, rigidity and stability of a spring?

3 What are the requirements for spring wire materials? List commonly used spring
materials.

4 How should one decide on the allowable stress of spring wires?

5 Two cylindrical helical springs have a number of active coils of n and n ,and
A
B
n = 2n . Other specifications are the same.
A
B
(a) If the maximum stress in spring A under load F is , what is the maximum stress
in spring B under the same load?
(b) If the deflection of spring A under the load F is , what is the deflection of spring
B under the same load?
(c) If thespringrateofspring A is k ,whatisthe spring rate of spring B?
A
Objective Questions
1 If spring index C is selected as too small, the spring will _______.
(a) have low rigidity and easily vibrate
(b) be difficult to wind
(c) easily cause instability
(d) have large dimensions

2 The spring wire diameter of a cylindrical helical spring is calculated by _______ anal-
ysis and the number of active coils is calculated by _______ analysis.
(a) strength
(b) stability
(c) rigidity
(d) structure

3 While calculate stress at the cross section of a spring wire, Wahl factor is introduced
to consider _______.
(a) inner stress generated during spring wind
(b) possible defects on the spring wire surface
(c) stress concentration on the wire close to the spring axis
(d) the effect of rising angle and coil curvature on stress

4 Shot peening on spring wires is for the purpose of improving _______.
(a) static strength
(b) fatigue strength