Helical spring, commonly known as coil spring, is subjected to various stresses when they are loaded.
The major stresses in a helical spring include:
Axial Stress (Tensile or Compressive Stress): When a load is applied along the axis of the spring (either in tension or compression), the spring experiences axial stress. This stress results from the stretching or compressing of the spring material and is responsible for the spring’s ability to store and release mechanical energy.
Shear Stress: Shear stress occurs within the spring due to the torsional or twisting deformation when the spring is wound or unwound. It’s a result of the helical shape of the spring wire. Shear stress is a crucial factor in determining the spring’s shear modulus and its resistance to twisting.
Bearing Stress: Bearing stress occurs at the points where the spring coils make contact with each other or with the mating parts. It’s especially important in the case of compression springs where the adjacent coils touch. Proper design and manufacturing ensure that the bearing stress is distributed evenly to prevent localized damage.
Residual Stress: Residual stresses are internal stresses that remain in the spring material after the manufacturing process. They can result from processes like coiling, heating, or shot peening. Residual stresses can impact the spring’s performance and fatigue life.
Torsional Stress: Torsional stress, also known as twisting stress, arises when a helical spring is subjected to a torque or twisting load. It’s a critical factor in springs used in applications where rotational motion is involved.
Proper design and material selection are essential to ensure that a helical spring can withstand these stresses while maintaining its desired characteristics, such as spring rate, load capacity, and fatigue life. The choice of wire material, wire diameter, coil pitch, number of coils, and the spring’s geometry all play a crucial role in determining how these stresses affect the spring’s performance.
