Elastic Electrofusion Joint With Low-Modulus Weld Zone
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Solution Overview
Problem
Conventional electrofusion fittings for thermoplastic pipes require surface peeling to prevent brittle fractures due to high stress buildup, which is not always feasible and leads to inadequate material bonding, resulting in brittle welds under load.
Innovation Solution
Surrounding the heating element with a thermoplastic material having a lower modulus of elasticity than the base body plastic, allowing for increased flexibility and reduced stress in the weld zone, thereby preventing brittle fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pipe surface is not peeled before welding, then the welding process is simpler and faster, but the welded connection becomes brittle and prone to fracture due to high stress buildup
Solution Approach 1:
The invention changes the material parameter (modulus of elasticity) of the plastic surrounding the heating element to be lower than that of the base body plastic. This parameter change allows the welding zone to be more elastic and flexible, reducing stress concentration at the pipe-socket interface and preventing brittle fracture, thereby maintaining weld reliability without requiring surface peeling
Solution Approach 2:
The invention applies local quality by creating a zone with different material properties around the heating element. The plastic surrounding the heating element has a lower modulus of elasticity (more elastic) compared to the base body plastic, creating a localized elastic zone that absorbs stress and prevents brittle failure at the welding interface
2Strength
If a plastic with lower modulus of elasticity surrounds the heating element, then the stress in the weld zone is reduced and ductile failure occurs, but the structural rigidity of the base body is compromised
Solution Approach 1:
The patent applies local quality by creating a zone with different material properties around the heating element. The plastic surrounding the heating element has a lower modulus of elasticity (more elastic) compared to the base body plastic, creating a localized elastic zone that absorbs stress and prevents brittle failure at the welding interface
Solution Approach 2:
The invention uses composite material structure with two different plastics having different moduli of elasticity. The base body plastic provides structural rigidity, while the surrounding plastic provides elasticity and stress absorption, creating a composite structure that optimizes both strength and stress resistance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of a more elastic plastic surrounding the heating element reduces stress in the weld zone, enabling ductile failure under load and maintaining connection integrity under external forces like bending or tensile loads.
Implementation Method 1
a heating element, preferably a heating wire winding which generates a sufficient amount of heat by supplying electrical energy
Data Source
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AI summary
Electro-welding fitting (1) in particular for joining or connecting pipe ends (3) made of thermoplastic material comprising a base body (2) made of thermoplastic or other weldable plastics (7) with a modulus of elasticity E2 and at least one heating element, preferably a heating wire winding (5) with several turns (6) for heating the plastic, wherein the heating element preferably the heating wire winding (5) is wholly or partially surrounded by a plastic (4) which does not correspond to the plastic (7) of the base body (2) or is a different plastic (4) than that of the base body (2) or has other properties, in particular a different modulus of elasticity.