The Large Displacement that The Hydraulic Bellows Can Obtain without Plastic Deformation is Called the Allowable Displacement of The Bellows
For a bellows hose working in a compressed state, its large compression displacement is: under pressure, the hydraulic bellows compresses to the large displacement value that the corrugations can produce when the corrugations are in contact with each other. It is also called the structural allowable large displacement. Equal to the difference between the free length of the bellows and the maximum compression length.
The large displacement that the hydraulic bellows can obtain without plastic deformation is called the allowable displacement of the bellows.
The bellows will produce residual deformation in the actual working process. Residual deformation is also called permanent deformation or plastic deformation. The bellows deforms under the action of force or pressure. When the force or pressure is removed, the bellows does not return to its original state. Residual deformation, the residual deformation is usually expressed by the amount of the bellows that does not return to the original position, also known as zero offset.
The relationship between the displacement of the bellows and the zero offset, regardless of the tensile or compression displacement, at the initial stage of the bellows displacement, its residual deformation is very small, generally less than the allowable zero specified in the bellows standard The offset value. However, when the tension (or compression) displacement gradually increases to exceed a certain displacement value, it will cause the zero offset value to increase suddenly, which means that the bellows has a relatively large residual deformation, after this. If you increase the displacement a little bit, the residual deformation will increase significantly. Therefore, the bellows should generally not exceed this displacement, otherwise it will seriously reduce its accuracy, stability, reliability and service life.
The allowable compression displacement of the bellows when working under compression is larger than the allowable tensile displacement when working under tension. Therefore, when designing the bellows, the bellows should be designed to work under compression as much as possible. It is found through experiments that, in general, the allowable compression displacement of the same material and the same specification of the bellows is 1.5 times the allowable tensile displacement.
The allowable displacement is related to the geometrical parameters and material properties of the bellows. In general, the allowable displacement of the bellows is proportional to the yield strength of the material and the square of the outer diameter, and inversely proportional to the elastic modulus of the material and the wall thickness of the bellows. At the same time, the relative wave depth and wave thickness also have a certain influence on it.
