Ribbed Thermoplastic Profile for Spiral Pipe Stress Reduction
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Solution Overview
Problem
Conventional spirally wound thermoplastic pipes with rectangular cross-section profiles are prone to stress peaks at welded seams and material discontinuities, which can lead to structural failure under internal pressure, especially when used for pressurized applications.
Innovation Solution
A hollow thermoplastic profile with a rectangular cross-section featuring a rib on the inner side, extending along its length, which redistributes stress peaks away from welded seams and towards a continuous extruded section, reducing the risk of crack propagation and enhancing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional hollow profile with uniform wall thickness and rounded edges is used, then the pipe structure is simple to manufacture, but stress peaks occur at welded seams leading to structural failure under internal pressure
Solution Approach 1:
The hollow profile features an asymmetric cross-section with different wall thicknesses: a first wall and second wall with first thickness, and a third wall with second thickness greater than the first thickness. This local variation in wall thickness concentrates material where stress peaks occur (at welded seams) while maintaining structural efficiency, directly resolving the contradiction between strength and manufacturing simplicity.
Solution Approach 2:
The profile employs asymmetric geometry with one wall (third wall) having greater thickness than the other two walls. This asymmetric design strategically places additional material at locations experiencing highest stress during welding and pressurization, eliminating stress concentration problems while preserving manufacturing simplicity through a single extrusion process.
2Reliability
If wall thickness is increased at welded seams to reduce stress peaks, then strength under variable load improves, but material usage and weight increase
Solution Approach 1:
Instead of uniformly increasing wall thickness throughout the profile, the invention applies increased thickness (second thickness) only to the third wall where stress peaks occur during welding. The first and second walls maintain the thinner first thickness, thereby achieving improved reliability under variable load while minimizing material consumption and weight.
Solution Approach 2:
The invention changes the wall thickness parameter locally rather than globally. By varying the thickness parameter from the first thickness to the second thickness at specific locations (third wall), the design achieves optimal stress distribution and reliability while controlling material usage, directly addressing the contradiction between reliability and material quantity.
3Strength
If a rib structure is added to the profile to redistribute stress, then stress concentration at welded seams is reduced, but manufacturing complexity increases
Solution Approach 1:
The asymmetric wall thickness design merges the stress-redistribution function with the basic profile structure. The third wall's increased thickness inherently acts as a stress-distributing element without requiring separate rib structures or additional manufacturing steps, thus improving stress distribution while maintaining ease of manufacture through standard extrusion processes.
Data Source
AI summary
A hollow profile (1) used in the manufacture of a spirally wound double-walled thermo-plastic pipe, which hollow profile has essentially a rectangular cross section, two side walls (5) and an outer wall (3) and an inner wall (4) limiting a cavity (2) within. In the hollow profile the wall that is intended to form the inner wall (4) of the pipe is thicker than the wall (3) of the hollow profile intended to form the outer wall (3) of the pipe. The inner rounding radius (7) of the edges adjacent to the thicker wall (4) of the hollow profile is considerably larger than the rounding radius (6) of the two other edges of the cavity (6) and the inside surface of the thicker wall (4) comprises a rib (8) extending in the hollow cavity of the profile, on the side of the profile forming the inner side of the pipe, in the longitudinal direction of the profile at least essentially along the whole length of the profile.