Asymmetric Thread Form for Tubular Composites
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Solution Overview
Problem
Existing thread forms for tubular composites in oil and gas wellbore applications are not suited for high load conditions due to their design based on isotropic materials, leading to interlaminar shear failure and inadequate strength in anisotropic composite materials.
Innovation Solution
A thread form with a smaller load bearing flank angle, reducing interlaminar stresses by orienting loads more radially and decreasing axial stresses, allowing for higher load capacity and designed for composite-to-composite and metal-to-composite connections with an elastomeric seal for pressure retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional thread forms designed for isotropic materials are used in tubular composites, then manufacturing is simplified, but interlaminar shear failure occurs and strength is insufficient
Solution Approach 1:
The patent modifies the thread geometry parameters, specifically reducing the load bearing flank angle from traditional values (e.g., 30 degrees in Acme threads) to a smaller angle (e.g., 15 degrees). This parameter change redirects the load path to be more perpendicular to the laminate layers, reducing interlaminar shear stresses and preventing failure while maintaining connection strength
Solution Approach 2:
The thread form introduces asymmetry in the flank angles, with the load bearing flank having a smaller angle compared to traditional symmetric thread forms. This asymmetric design optimizes the stress distribution in the anisotropic composite material, directing loads away from the weak interlaminar regions
2Force
If thread forms with larger load bearing flank angles are used, then load capacity increases, but interlaminar shear stresses increase causing failure
Solution Approach 1:
By changing the load bearing flank angle parameter to a smaller value, the patent simultaneously achieves both objectives: the thread geometry is optimized to carry axial loads effectively while the load path is redirected to minimize shear stresses in the interlaminar regions, solving the contradiction between load capacity and stress reduction
3Strength
If thread forms are optimized for anisotropic materials, then strength and reliability improve, but design complexity increases
Solution Approach 1:
The patent applies a systematic parameter change approach, modifying only the critical load bearing flank angle while maintaining other standard thread parameters. This focused optimization achieves significant strength improvements without requiring complete redesign of the entire thread form, thus limiting the increase in design complexity
Data Source
AI summary
Herein disclosed is a mechanism for providing high load capabilities in downhole locations. The mechanism comprises tubulars, at least one of which is constructed from composite; and the tubular composite being for high load capabilities in connecting the tubulars. In some cases, there are at least two tubulars in the mechanism. In some cases, the mechanism comprises a thread form, which thread form is mounted to translate an axially directed force into a radially directed force. In some cases, the high load capabilities include a load bearing flank angle of 15° to 50° as measured from the axis of said tubular. In some cases, the high load capabilities include a clearance flank angle of 15° or less as measured perpendicular to the axis of said tubular. In some cases, at least one of the tubulars includes a thread pitch, having from 2 to 12 threads per inch.