Lock Mandrel Housing Flexibility for Shear Load Distribution
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Solution Overview
Problem
Existing lock mandrel designs face challenges in distributing shear loads effectively, leading to stress on the housing between dog windows, which can result in reduced strength and increased stress concentrations due to the tradeoff between dog width and housing wall thickness.
Innovation Solution
The implementation of multiple rows of locking dogs with axial flexibility between rows, combined with extensions that transfer loads from the housing to the profile, allowing for load sharing and reduced stress on individual contact points, and the use of shape memory alloys for enhanced flexibility and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the dogs are made wider to hold more shear load, then the shear load capacity is improved, but the housing wall thickness is reduced which reduces the strength to tolerate pressure differential stresses
Solution Approach 1:
The housing is segmented into multiple sections (first section, second section, third section) with different structural characteristics. The first section has increased wall thickness to handle pressure differential stresses, while the second section accommodates the dogs. This segmentation allows the housing to maintain both strength for pressure differentials and capacity for shear loads without requiring uniform wall thickness throughout.
Solution Approach 2:
The housing structure is made non-uniform with varying wall thickness at different locations. The first section has greater wall thickness than the second section to provide localized strength where pressure differential stresses are highest, while the second section is optimized for dog accommodation and shear load transfer. This local quality variation resolves the contradiction by providing strength exactly where needed rather than uniformly throughout.
2Force
If multiple rows of dogs are used to share shear loading, then the shear load distribution is improved, but the housing flexibility required for load sharing may reduce structural integrity
Solution Approach 1:
The housing is divided into multiple sections with the first section providing structural support and the second section providing flexibility for dog movement. This segmentation allows different parts of the housing to have different mechanical properties - the first section maintains structural integrity while the second section allows the necessary flexibility for multiple rows of dogs to share shear loading through independent movement.
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
This solution enables the distribution of shear loads across multiple contact surfaces, reducing stress concentrations and allowing for larger dog sizes without compromising the structural integrity of the housing, thereby improving the tool's ability to handle pressure differentials and maintain well control.
Implementation Method 1
The housing can include segments of shape memory alloy that provide elastic flexibility between the rows of dogs
Implementation Method 2
A ramp 26 leads to a larger diameter portion 28. As seen in FIG. 2 when the ramp 26 is pushed against the dogs 18 the dogs 18 get pushed out through the windows 16
Implementation Method 3
The dogs can also have extensions with a surface that grippingly engages the housing adjacent the window on extension of the dogs such that loads can transfer from the housing into the extension and into the profile
Data Source
AI summary
A plurality of rows of locking dogs are provided with housing flexibility between rows to allow them to share a shear loading while leaving enough structural integrity in the housing to define the windows through which the dogs emerge. The dogs can also have extensions with a surface that grippingly engages the housing adjacent the window on extension of the dogs such that loads can transfer from the housing into the extension and into the profile in which the dog is disposed rather than passing the shear stress through the window edge into the dog that is in the profile. The dog configuration can also share the load on multiple contact surfaces of the housing to reduce stress at each contact location.