The rigidity of the bellows refers to the force required to make the bellows produce unit displacement, which is the basis of calculating the elastic thrust of the corrugated expansion joint. For bellows with the same diameter and the same pressure, stiffness is one of the parameters to measure the performance of bellows.
The stiffness of bellows can be divided into axial stiffness, bending stiffness, torsional stiffness and so on according to the different load and displacement properties. Among them, the calculation formulas of axial stiffness of bellows mainly include the following:
Formula 1: K = (3 π r^4Et) / (2L^3), where K represents the stiffness coefficient of the bellows, r represents the inner diameter of the bellows, E represents the Young's modulus of the bellows, t represents the wall thickness of the bellows, and L represents the length of the bellows. In this formula, Et is the product of Young's modulus and wall thickness.
Formula 2: K = (E * h^3) / (12 (1-V^2) L), where K is the ring stiffness of the bellows, E is the elastic modulus of the bellows, h is the thickness of the bellows, v is the Poisson's ratio of the bellows, and L is the corrugation distance of the bellows. This formula shows the relationship between bellows ring stiffness and parameters such as elastic modulus, thickness, Poisson's ratio and corrugation distance of the bellows.
In addition to the above formulas, there are various methods for calculating bellows stiffness, such as energy method, empirical formula, numerical method, EJMA standard stiffness calculation method, Japanese TOYO stiffness calculation method, and American KELLOGG (new method) stiffness calculation method. These methods can give more accurate and suitable calculation results of bellows stiffness according to specific application scenarios and requirements.
In practical application, the rigidity of bellows will be affected by many factors, such as elastic characteristics of materials, size and shape of bellows, manufacturing process of bellows, etc. Therefore, when selecting the bellows, it is necessary to comprehensively consider these factors according to the specific application needs and conditions to ensure that the bellows can meet the use requirements.