Pipe Coupling Groove Geometry for Fatigue-Resistant Joints
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Solution Overview
Problem
Polymeric pipe elements are prone to failure at joints due to stress concentrations at groove corners caused by mechanical couplings with arcuate projections, exacerbated by manufacturing tolerances, leading to fatigue and ultimate failure under cyclic or high loads.
Innovation Solution
A coupling design with arcuate projections featuring clearance relief regions of increasing radius of curvature and relief grooves, which reduce stress concentrations by providing clearance and accommodating manufacturing tolerances, ensuring a consistent fit and increased bending rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If arcuate projections with sharp corners are used to engage circumferential grooves, then the coupling can effectively transfer forces and stresses across the joint, but stress concentrations are formed at the groove corners leading to fatigue failure
Solution Approach 1:
The patent applies curvature by replacing the sharp corner geometry at the groove engagement point with a rounded or filleted transition. This curvature eliminates the stress concentration that occurs at sharp corners when arcuate projections engage the groove, thereby improving fatigue resistance while maintaining force transfer capability through the smoothed stress distribution.
2Stress or pressure
If the groove depth is minimized to reduce stress, then the engagement height between keys and groove sides must be increased, but this increases the complexity of maintaining proper geometry under manufacturing tolerances
Solution Approach 1:
The patent modifies the geometric parameters of the groove and arcuate projection interface. By changing the groove profile to include rounded corners and optimizing the engagement geometry, the design achieves stress reduction while creating a more tolerant interface that accommodates manufacturing variations without compromising geometric consistency.
3Reliability
If clearance relief regions with increasing radius of curvature are added to arcuate projections, then stress concentrations are reduced and manufacturing tolerances are accommodated, but the device complexity increases
Solution Approach 1:
The clearance relief regions incorporate curved surfaces with increasing radius of curvature that smoothly transition from the arcuate projection. This curvature design reduces stress concentrations by distributing contact pressures more evenly while accommodating manufacturing tolerances through the gradual geometric transition, rather than using sharp edges or complex multi-faceted surfaces.
Data Source
AI summary
Pipe elements have circumferential grooves. The grooves have a first side surface contiguous with a first floor surface. The first side surface and the first floor surface together subtend a first 90° circular arc when viewed in cross section. The grooves also have a second side surface contiguous with a second floor surface. The second side surface is in spaced relation to and in facing relation with the first side surface. The second side surface and the second floor surface together subtend a second 90° circular arc when viewed in cross section. A third floor surface is contiguous with both the first and second floor surfaces and is a flat surface. A coupling used to connect the pipe elements has arcuate projections which engage the grooves of the pipe elements. The arcuate projections have a semi-circular cross section. Relief grooves are positioned adjacent to each arcuate projection.