How to calculate the fatigue life of disc springs? Analysis of national standards from stress ratio to preload

The fatigue life of disc springs serves as the core metric for evaluating their dynamic reliability. This lifespan is not a fixed value but a complex function determined by material properties, manufacturing processes, spring design, operating conditions, and environmental factors. Jiangsu Sunzo Spring, strictly adhering to the national standard GB/T 1972 for disc springs, will provide a systematic analysis of scientifically predicting and enhancing spring lifespan through standardized methodologies.

1、The decisive factor for lifespan: the stress ratio (σmin/σmax)

In disc spring design, service life primarily depends on the stress ratio (σmin/σmax). The national standard classifies common disc springs into three groups based on thickness (t), specifying maximum allowable values for their calculated reference stresses (σⅡ, σⅢ), which provides a foundation for high-life-cycle design.

I Group (t ≤ 1.25 mm): Maximum stress = 1300 MPa

II Group (1.25 <t ≤ 6 mm): Maximum stress = 1250 MPa

III Group (6 <t ≤ 14 mm): Maximum stress = 1200 MPa

2、How to query the expected life from the national standard curve?

The 'Disc Spring National Standard' GB/T 1972-2005 provides authoritative fatigue life curves (Figures C.9 to C.11) in its appendix. Engineers can easily estimate service life using these curves.

1. Load/displacement: Determine the maximum and minimum load (or displacement) of the disc spring according to the actual working conditions.

2. Calculate working stress: Determine the minimum stress (σr min) and maximum stress (σr max) based on the load or displacement.

3. Chart Query: In the standard curve plot, locate the point with σr min on the x-axis and σr max on the y-axis.

4. Life determination: The area of the point in the chart directly corresponds to its expected fatigue life (such as 2 million times, 500,000 times, etc.).

3、The design and use of high life disc spring

To ensure that the disc spring reaches the ideal fatigue life, the application of disc spring technology is crucial:

Apply preload: The preload displacement should be at least 0.15 to 0.2 times the free height (0.15h₀ to 0.2h₀) to optimize the stress state and avoid unfavorable stress zones.

Controlled travel: The maximum working displacement should not exceed 0.75h₀. This is not only the benchmark of national standard testing, but also the key to ensure that the stress level does not exceed the standard and thus obtain a long life.

Choose Jiangsu Sunzo for reliable solutions based on deep life analysis. We not only provide standard products compliant with national standards, but also offer customized life simulation and design to ensure your equipment operates stably under dynamic loads.