Page 419 - Analysis and Design of Machine Elements

Figure 14.11 Characteristic curve of Springs 397
a helical compression spring.

H , and the deflection is . When the spring carries an operating load F ,the spring
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operating length is H , and the deflection is .Theforce varies between F and F ,for a
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reciprocating spring, the working distance is h = − . When the load increases to the
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maximum load F , the correspond spring length is solid length H and the deflection is
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. This is the shortest possible length that the spring can have and the internal stress
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reaches the elastic limit of spring wire. Springs should avoid to be compressed to the
solid length during operation. For a constant pitch compression spring, this load and
deflection satisfies
F F
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= =… …= const (14.5)

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The preload F is usually selected as F = (0.1–0.5) F . The maximum operating F is
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usually decided by the working condition, satisfying F ≤ 0.8 F [10].
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