Shot peening a spring wire improves its:
A) Aesthetic appearance
B) Fatigue resistance
C) Electrical conductivity
D) Color under stress
The correct answer and explanation is:
The correct answer is B) Fatigue resistance.
Shot peening is a mechanical process used to improve the durability and performance of materials, particularly in components like spring wires. During this process, small spherical media (often called “shots”) are blasted at the surface of the material. This creates small indentations or dimples on the surface of the wire, which induce compressive residual stresses.
These compressive stresses are important because they counteract the tensile stresses that typically occur during loading. Tensile stresses can lead to crack formation and propagation, especially in cyclic loading conditions, such as the repeated bending or twisting that a spring experiences. By introducing compressive stresses, shot peening helps to delay the onset of fatigue cracks and increases the overall fatigue resistance of the wire.
Fatigue resistance refers to a material’s ability to withstand repeated loading and unloading without failure. In the case of spring wires, which undergo cyclical stress and strain, fatigue resistance is a critical property. Without sufficient fatigue resistance, a spring might fail prematurely, compromising the performance of the device or system that relies on it.
While shot peening can have some minor effects on a spring’s appearance, it does not improve the wire’s aesthetic appeal (answer A). It also does not directly affect the wire’s electrical conductivity (answer C) or color under stress (answer D). Therefore, the key benefit of shot peening in spring wires is its enhancement of fatigue resistance, allowing them to last longer and perform more reliably under repetitive mechanical stress.