Views: 86 Author: Site Editor Publish Time: 2025-10-13 Origin: Site
Interpretation of disc spring load displacement curve: Why is 0.75h₀ selected as the detection point in the national standard?
In the world of elastic components, disc springs are renowned for their unique nonlinear stiffness characteristics. A thorough understanding of their load-displacement (Pf) curves is crucial for proper design and selection of disc springs. As a professional manufacturer of disc springs, Jiangsu Sanzhong Elastic will guide you through the scientific principles behind these curves and reveal the rationale behind key inspection points in national standards.
Different from the cylindrical helical spring which follows Hook's law, the Pf curve of disc spring is not a straight line, and its shape is mainly determined by the cross-sectional coefficient of disc spring (ho/t, that is, the ratio of deformation to thickness under pressure). This is the core of disc spring technology.
A Series (ho/t ≈ 0.4): The curve is approximately straight, providing nearly linear stiffness.
B Series (ho/t ≈ 0.75): shows a typical "decreasing" curve, stiffness decreases slightly with increasing deformation.
C Series (ho/t ≈ 1.3): This configuration exhibits pronounced nonlinear characteristics. It should be noted that when the ho/t ratio exceeds 1.3, the disc spring's stress state becomes unstable, making it prone to "flipping" during high-pressure testing or operation, which can cause abrupt curve changes. Higher ho/t values may even generate zero or negative stiffness zones, making this design suitable for specific cushioning or constant-force applications.
In the national standard GB/T 1972 of disc springs, it is stipulated that the detection point of load P is set at the deformation f = 0.75h₀. This implies a profound engineering rigor:
1. The optimal alignment between theoretical models and experimental measurements: The standard recommended theoretical calculation formula shows minor deviations from the actual performance of leaf springs. As illustrated in Figure (3), the theoretical values align most closely with measured results only within the range of f = 0.6h₀ to f = 0.8h₀. Deviations increase significantly when falling below or exceeding this interval.
2. Safety boundary to ensure fatigue life: For disc springs subjected to alternating loads, the working stroke should not exceed 0.75h₀ to ensure their long fatigue life. This point is set as the detection benchmark to ensure the performance and safety of disc springs under most working conditions.
Therefore, Pf=0.75h₀ is taken as the unified detection point of the national standard of disc spring, which perfectly balances the accuracy of theoretical calculation and the safety and reliability of practical application.
When checking the load of the leaf spring group (series, parallel or composite combination), special pressing tools must be used. Jiangsu Sanzhong strictly implements the standards in the quality inspection process to ensure that the pressing tools meet:
Guidance precision: the unilateral gap between the guide and the disc spring should strictly comply with the standard to prevent bias load during the test.
Hardness and finish: The surface hardness of the guide should not be lower than 55HRC, and the roughness Ra should be less than 3.2μm, so as to ensure wear resistance and avoid scratching products.
At Jiangsu Sanzhong Elastic, we firmly believe that exceptional disc spring performance stems from profound understanding and precise control of core parameters such as Pf curves and ho/t ratios. While strictly adhering to national standards for disc springs, we are dedicated to providing clients with in-depth technical insights into spring design and application. This enables precise prediction of elastic component performance during equipment R&D, ultimately optimizing designs and enhancing reliability.
If you need to obtain the analysis of disc spring stiffness curve under specific working conditions or technical selection support, our technical team will provide you with professional assistance at any time.
SUNZO has it’s own researching and development team and test center, has participate in rule-making of the latest national industry standards and the international ISO standards for disc springs.
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