Displacement and life of bellows produced by the Krah machine

The quality of the Krah machine bellows and the other two factors are closely related to displacement and life. In the production of the Krah machine bellows, these two factors affect the performance of the bellows as endogenous variables.

Here is the content list:

l Allowable displacement

l Influence factors of allowable displacement

l Service life

Allowable displacement

For the Krah machine bellows working in compression state, its maximum compression displacement is: the maximum displacement of the Krah machine bellows when the bellows are compressed to contact each other under pressure, also known as the maximum allowable displacement of the structure, which is equal to the difference between the free length and the maximum compression length of the Krah machine bellows.

The maximum displacement of the Krah machine bellows without plastic deformation is called the allowable displacement of the Krah machine bellows.

The Krah machine bellows will produce residual deformation in the actual working process, which is also called permanent deformation or plastic deformation. The Krah machine bellows will produce deformation under the action of force or pressure. When the force or pressure is removed, the Krah machine bellows will not return to its original state, which is called residual deformation, Residual deformation is usually expressed by the amount that the Krah machine bellows does not return to the original position, also known as zero offsets.

The relationship between the displacement of the Krah machine bellows and the zero displacements, whether tensile or compressive displacement, in the initial stage of the displacement of the Krah machine bellows, its residual deformation is very small, generally less than the allowable zero displacement value specified in the Krah machine bellows standard. However, when the tensile (or compressive) displacement gradually increases to more than a certain displacement value, it will cause a sudden increase in the zero offset value, which means that the Krah machine bellows produce relatively large residual deformation. After that, if the displacement is increased a little, the residual deformation will increase significantly. Therefore, the Krah machine bellows generally should not exceed this displacement, otherwise, it will seriously reduce the accuracy, stability, reliability, and service life of the Krah machine bellows.

The allowable compression displacement of the Krah machine bellows under compression is larger than that under tension, so the Krah machine bellows should be designed to work under compression as much as possible.

Influence factors of allowable displacement

It is found that the allowable compression displacement of the Krah machine bellows of the same material and specification is 1.5 times the allowable tensile displacement.

The allowable displacement is related to the geometric parameters and material properties of the Krah machine bellows. In general, the allowable displacement of the Krah machine bellows is directly proportional to the square of the material's yield strength and outer diameter, and inversely proportional to the elastic modulus of the material and the wall thickness of the Krah machine bellows. At the same time, relative wave depth and wave thickness also have some influence on it.

Service life

The service life of the Krah machine bellows is the shortest working period or the number of cycles that can ensure normal operation under working conditions. The elastic sealing system composed of the Krah machine bellows often works under the condition of more cycles of variable load and larger displacement. Therefore, it is of great significance to determine the service life of the Krah machine bellows. Because the function of the Krah machine bellows is different, the requirements for its service life are also different.

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