Split-Thread Accessory Mounting for Brittle Drill Bit Bodies
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Solution Overview
Problem
Conventional drilling systems face challenges in securely attaching accessories to downhole tools due to stress risers in threaded connections, which can lead to fracture risks in brittle materials.
Innovation Solution
A downhole tool design featuring a body with lateral recesses and a connection member that includes a radially inward taper, allowing for secure attachment of accessories through rotation and pinching, using materials like metal matrix composites and tool steel to enhance strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If threaded connections are used to attach accessories to the bit, then the accessories can be securely attached, but stress risers increase the risk of fracture in brittle materials
Solution Approach 1:
The connection member is divided into multiple segments (first segment with external threads, second segment with radial taper, third segment with transverse groove) that can deform independently. This segmentation allows the connection to distribute stress more evenly and avoid stress concentration at a single point, thereby reducing fracture risk while maintaining attachment strength.
Solution Approach 2:
The connection member undergoes parameter changes through elastic and plastic deformation. The radial taper portion deforms elastically during installation and operation, while the transverse groove allows controlled plastic deformation. These parameter changes enable the connection to absorb energy and reduce stress risers, preventing fracture in brittle bit materials.
2Strength
If high torque is applied to rotate the accessory into the connection member, then secure attachment is achieved, but the risk of fracturing brittle materials increases
Solution Approach 1:
The connection member acts as an intermediary between the accessory and the bit body. It absorbs the high installation torque through its deformable structure (radial taper and transverse groove), protecting the brittle bit material from direct stress. The intermediary connection member fails safely by deforming rather than transmitting full torque to the bit body.
Solution Approach 2:
The connection member is designed with built-in cushioning features (radial taper and transverse groove) that prepare for high torque loads before they occur. These features allow controlled deformation to absorb shock and reduce peak stresses, cushioning the brittle bit material against fracture during the high-torque installation process.
3Ease of operation
If conventional threaded connections are used, then accessories can be attached, but the connection may loosen under high downhole conditions
Solution Approach 1:
The connection member transitions from a rigid static component to a dynamic component that can deform elastically and plastically. The radial taper allows elastic deformation that creates a locking effect, while the transverse groove permits controlled plastic deformation. This dynamic behavior enables the connection to maintain stability under varying downhole conditions while remaining relatively easy to install.
Data Source
AI summary
An accessory is coupled to a body using a connection member inserted into a plurality of lateral recesses of a bore. The accessory includes a complementary connection mechanism to the connection member and is tightened in the bore with a torque. An example accessory is a nozzle for use with a drill bit. The nozzle includes threads and the drill bit includes a nozzle bore with lateral recesses. Partial thread segments are inserted into the lateral recesses, and the nozzle is threaded to the partial thread segments.