Maximum Allowable Displacement of  Plastic Corrugated Duct

Maximum Allowable Displacement of  Plastic Corrugated Duct

Summary

The maximum displacement that can be obtained without plastic deformation of the corrugated plastic duct is called the allowable displacement of the plastic duct. The following article introduces the maximum allowable displacement of plastic ducts in various forms.

Plastic corrugated ducts are widely used in automatic control and measuring instruments, vacuum technology, machinery industry, electric power industry, transportation, and the atomic energy industry as sensitive components and shock absorbing components, compensation components, sealing components, valve components, and pipeline connectors.

Different plastic materials are selected for plastic corrugated ducts due to their different uses. Due to the different materials, the performance and use of the processed plastic corrugated duct are also different. When both ends of the plastic corrugated duct are restricted, if the pressure inside the plastic corrugated duct increases to a certain critical value, the plastic corrugated duct will become unstable.

The maximum displacement that can be obtained without plastic deformation of the plastic corrugated duct is called the allowable displacement of the bellows.

Regarding the plastic corrugated duct working in a compressed state, its maximum compression displacement is: under the action of pressure, the plastic corrugated duct can be compressed to the maximum displacement value that can be generated when the corrugations contact each other, also known as the maximum allowable displacement of the structure, It is equal to the difference between the free length of the corrugated duct and the maximum compressed length.

The plastic corrugated duct will produce residual deformation during the theoretical working process. The residual deformation is also called permanent deformation or plastic deformation. 

The corrugated duct will deform under the action of force or pressure. When the force or pressure is removed, the plastic corrugated duct will not return to its original state. The phenomenon of residual deformation is called residual deformation, and the residual deformation is usually expressed by the amount of plastic corrugated duct that does not return to the original position, also known as zero offsets.

The relationship between the displacement of the plastic corrugated duct and the zero offset, no matter the tension or the compression displacement, in the initial stage of the plastic corrugated duct displacement, its residual deformation is very small, generally smaller than the rules in the plastic corrugated duct standard. Zero offset values are allowed. 

However, when the stretching (or shrinking) displacement gradually increases beyond a certain displacement value, it will cause a sudden increase in the zero offset value, which means that the plastic corrugated duct has a relatively large residual deformation. 

Assuming that the displacement is increased a little more, the residual deformation will increase significantly. Therefore, the plastic corrugated duct should generally not exceed this displacement, otherwise, its accuracy, stability, reliability, and service life will be seriously reduced.

The allowable compression displacement of a plastic corrugated duct when working in a compressed state is larger than the allowable tensile displacement when working in a stretched state, so when designing a plastic corrugated duct, the plastic corrugated duct should work in a compressed state as much as possible. 

Through experiments, it is found that under normal circumstances, the allowable compression displacement of the corrugated duct of the same material and the same specification is 1.5 times the allowable tensile displacement.

The allowable displacement is related to the geometric parameters and material properties of the plastic corrugated duct. Under normal circumstances, the allowable displacement of a plastic corrugated duct 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 plastic corrugated duct. At the same time, the relative wave depth and wave thickness also have a certain influence on it.

The above introduces the maximum allowable displacement of the plastic corrugated ducts. If you plan to buy plastic corrugated ducts, please contact us.

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