When purchasing springs, engineers are often best served to consider quality, bespoke solutions for their projects – while these can be slightly more expensive initially, their effectiveness can definitely be seen in their durability, tensile strength, and life expectancy.
However, as with all things, no spring will last forever – engineers should regularly check for durability and fatigue in springs, as overly stressed springs can have a dramatic effect on the overall application to which the spring contributes.
Spring Durability and Performance
When designing springs, it is essential to review the projected durability of the resulting spring – how likely is it to lose force, or shorten under given pressure? Ideally, to ensure your spring continues to perform over time, the stress it is exposed to should never be greater than the strength of the spring material. If applied stress is greater than the spring’s overall strength, the spring’s deflection crosses from ‘elastic’ (i.e. returning to state once released) to ‘plastic’ (i.e. the applied stress creates a permanent deformation in the spring), placing pressure on the spring which will affect performance over time.
What is Spring Fatigue?
Spring fatigue can occur when a spring is subjected to the repeated stress of being loaded and unloaded over time. In particular, this fatigue can be seen in scenarios where the spring is loaded to excess – loading within the spring’s range of elasticity will allow the spring to return to state, but adding additional load could cause stress on the spring. This can create small cracks in the unit’s material, which in turn can increase stress and add to fatigue over time.
An example of this would be a compression spring being loaded with varying loads over time – this will cause the spring to compress and recover repeatedly, slowly reducing the spring’s ability to return to base state.
Spring fatigue is an essential consideration, particularly for springs used in manufacturing or aerospace, as the condition can greatly affect the performance of the overall application making use of the spring.
How to Protect Against Spring Fatigue
As spring fatigue can be caused by excessive stress placed on the spring, reducing the level of stress through creating smaller loads or adding additional springs should help to increase the life expectancy of your spring. Other solutions include:
- Increasing the outer diameter of your spring
- Decreasing the overall diameter of the spring wire
- Increasing the amount of active coils included in the spring
Your spring manufacturer will review all potential causes for fatigue in your spring design, and incorporate solutions to ensure good life expectancy from your resulting spring product.
At SCS, our dedicated team of spring experts have been creating custom, high-performance spring and wire solutions across medical, aerospace, and industrial applications for over 45 years – contact us today to find out how we can help improve your spring performance.