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【概要描述】Raleigh Spring Elastic Technology Co., Ltd. would like to point out that disc spring fatigue life assessment is an iterative analysis process. It is not possible to set a target fatigue life first and
【概要描述】Raleigh Spring Elastic Technology Co., Ltd. would like to point out that disc spring fatigue life assessment is an iterative analysis process. It is not possible to set a target fatigue life first and
Raleigh Spring Elastic Technology Co., Ltd. would like to point out that disc spring fatigue life assessment is an iterative analysis process. It is not possible to set a target fatigue life first and then derive the disc spring configuration in reverse. The selection and fatigue life verification must be completed step by step according to the proper engineering procedure.
The complete evaluation process is as follows:
Determine the load that the disc spring needs to provide when it is under the minimum compression condition, and identify the minimum-load operating condition of the equipment.
Define the full-load operating condition of the disc spring. This can be determined based on the required travel range or the additional load applied to the disc spring during operation.
Based on the operating conditions, preliminarily select the appropriate disc spring specification. The following key principles should be considered:
A. Select the appropriate disc spring specification and series.
Ensure that the disc spring always retains a minimum preload equivalent to 15%–20% of the rated maximum load under all operating conditions. If this preload cannot be maintained, the upper end of the inner diameter of the disc spring is highly susceptible to alternating tensile stress, which may lead to premature failure.
B. Select the appropriate number of disc springs.
The total number of disc springs must satisfy the required equipment travel. The actual compression of a single disc spring must never exceed the maximum permissible compression specified by the applicable standard.
C. Properly determine the stacking direction and number of disc springs.
Ensure that, under the full-load operating condition, the load carried by each individual disc spring does not exceed its rated limit.
D. Engineering experience from Raleigh Spring Elastic Technology Co., Ltd.:
Under equivalent operating conditions, larger disc springs with moderate load capacity, such as B Series and C Series disc springs, are preferred. Compared with small-size, high-load A-type disc springs, they generally provide better fatigue performance.
For the selected disc spring specification, calculate the deformation at the minimum and maximum compression positions.
If only the load parameters are known, the corresponding compression travel should be calculated using the appropriate formulas.
The deformation values can be obtained either by interpolation from the load-deflection curves in the product catalog or by precise calculation using the formulas specified in DIN EN 16984.
The stress and output force of a disc spring are both determined by its compression deformation.
The critical stress areas of a disc spring are concentrated at two edge locations:
In practical engineering applications, it is recommended to verify both points. The point experiencing the higher stress level will directly determine the fatigue service life of the entire disc spring assembly.
The stress values can be estimated by interpolation from the tables provided in product catalogs.
Raleigh Spring Elastic Technology Co., Ltd. recommends using the established formulas specified in DIN EN 16984 for accurate calculations, as they provide higher data reliability.
Refer to the applicable standard fatigue curve.
Use the minimum stress as the horizontal axis and the maximum stress as the vertical axis. Locate the corresponding intersection region of the two stress values to evaluate the expected fatigue cycle life.
The fundamental design principle is:
Maintain a preload of 15%–20% under the minimum-load operating condition while minimizing the deformation travel of each individual disc spring as much as possible.
The fatigue curves provided in this article represent typical disc spring service-life data obtained under laboratory conditions.
To correctly use the curves for fatigue life assessment, the stress values corresponding to the minimum and maximum deformation positions of the disc spring must first be calculated.
Fatigue failure is primarily governed by tensile stress. At a minimum, the stresses at Points II and III must be verified.
Raleigh Spring Elastic Technology Co., Ltd. recommends calculating both points and using the most severe operating condition as the basis for the design.
The basic fatigue data were obtained through sinusoidal cyclic loading tests using a laboratory fatigue testing machine, with the fatigue life corresponding to a 99% survival probability.
The applicable conditions are:
1. Parallel stacking can significantly reduce fatigue life.
Disc springs stacked in parallel may interfere with one another, resulting in uneven deformation of individual springs, localized stress concentrations, and accelerated damage.
2. Proper lubrication is essential for high-frequency applications.
Friction can generate continuous heat, which may significantly reduce the fatigue cycle life.
3. Structural design should be strengthened for fatigue applications.
The guiding structure of the disc spring assembly, contact surface geometry, and selection of hardened support washers are all critical.
The disc spring assembly must be properly aligned and coaxial to avoid localized point contact, which can cause stress concentration and premature fracture.
The fatigue reference data provided in this article apply only to DIN-standard disc springs manufactured from raw materials that have not undergone shot peening.
Shot peening can improve the fatigue performance of certain disc springs. However, the actual improvement must be verified through dedicated fatigue testing and should not be directly extrapolated from the basic fatigue curves.
