The presence of residual stresses in a spring wire is most likely to:
A) Improve the spring’s electrical conductivity
B) Change the spring’s color under UV light
C) Affect the spring’s fatigue life
D) Make the spring glow in the dark
The correct answer and explanation is:
The correct answer is C) Affect the spring’s fatigue life.
Residual stresses are internal forces that remain in a material after it has been manufactured or processed. These stresses are often created during processes like cooling, forming, or surface treatments. In the case of a spring, residual stresses are typically developed when the spring wire is coiled, stretched, or treated thermally.
These stresses can have a significant impact on the fatigue life of the spring. Fatigue refers to the failure of a material due to repeated or fluctuating stresses, which eventually lead to the formation of cracks. When a spring experiences cyclic loading, such as being compressed and stretched repeatedly, the residual stresses in the material can either amplify or mitigate the effects of these loading cycles. In some cases, compressive residual stresses on the surface of the spring can help resist crack initiation, thereby improving its fatigue resistance. However, tensile residual stresses can have the opposite effect, making the spring more prone to crack formation and premature failure.
The effect on fatigue life is crucial because springs are often subjected to repeated loading, and a spring’s ability to withstand this without failure is essential for its performance and longevity. If the residual stresses are not managed properly, the spring may fail much sooner than expected.
In contrast, residual stresses are unlikely to have a noticeable effect on the spring’s electrical conductivity, color under UV light, or whether it glows in the dark. These properties are influenced by the material’s composition and treatment rather than internal stresses.