Rock Drill Shank Adaptor Flushing Hole Geometry for Fracture Resistance
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Solution Overview
Problem
Existing rock drilling shank adaptors are prone to fracture due to compressive and tensile stresses generated by percussive piston impacts, leading to crack initiation and failure, particularly exacerbated by cavitational damage in underground applications, resulting in costly machine downtime.
Innovation Solution
A rock drilling shank adaptor with a flushing hole featuring non-curved, straight sections at the forward and rearward regions and smooth transitions via curved sections, reducing tensile stresses and minimizing stress concentrations, thereby enhancing the adaptor's service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flushing hole with curved or arced end regions is used, then the hole can be easily manufactured, but stress concentrations occur at the curved regions leading to crack initiation and adaptor fracture
Solution Approach 1:
The patent inverts the conventional approach by using straight sections instead of curved sections at the forward and rearward ends of the flushing hole. This inversion eliminates the stress concentrations that occur at curved regions, thereby preventing crack initiation while maintaining manufacturability through standard drilling techniques.
Solution Approach 2:
The patent changes the geometric parameters of the flushing hole by specifying straight sections with defined lengths (e.g., 0.5-2 times the hole diameter) at the forward and rearward ends. This parameter modification transforms the stress distribution pattern, reducing stress concentrations and improving reliability without compromising ease of manufacture.
2Reliability
If the flushing hole has straight sections at the forward and rearward regions, then tensile stresses are reduced and fracture likelihood decreases, but the hole geometry becomes more complex
Solution Approach 1:
The flushing hole is segmented into distinct regions: straight sections at the forward and rearward ends, and curved transition sections in the middle. This segmentation allows each region to serve its specific function - the straight sections reduce stress concentrations while the curved sections provide smooth transitions, achieving reliability without excessive overall complexity.
Solution Approach 2:
The patent applies local quality by giving different geometric characteristics to different parts of the flushing hole. The forward and rearward regions have straight sections to minimize stress concentrations, while the intermediate regions have curved sections for smooth transitions. This localized differentiation achieves the desired stress distribution without making the entire hole geometry complex.
3Ease of manufacture
If curved or arced end regions are used in the flushing hole, then the hole can be formed with standard tools, but stress concentrations occur leading to adaptor failure under percussive loading
Solution Approach 1:
The patent inverts the conventional design by employing straight sections instead of curved sections at the critical forward and rearward ends of the flushing hole. This inversion eliminates the stress concentrations that occur at curved regions, thereby preventing crack initiation and improving strength while maintaining ease of manufacture through standard drilling operations.
Solution Approach 2:
The patent modifies the geometric parameters by specifying straight sections with particular length ratios (0.5-2 times the hole diameter) at the forward and rearward ends. This parameter change fundamentally alters the stress distribution pattern, reducing stress concentrations and improving strength without sacrificing manufacturability.
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 novel shape configuration significantly reduces the likelihood of fracture, increasing the service life of the shank adaptor by distributing stresses uniformly and reducing fatigue, as demonstrated by a 15% stress reduction and improved operational lifetime under high-cycle fatigue conditions.
Implementation Method 1
the forwardmost and rearwardmost regions of the edge comprise straight sections, each straight section bordered at each end by a respective curved section... significantly reduce the tensile stresses at these regions without increasing stresses at other hole regions
Implementation Method 2
minimise stress and stress concentrations at the region of the hole... significantly reduce the tensile stresses at these regions without increasing stresses at other hole regions
Implementation Method 3
each curve is formed from multiple radii of curvature so as to provide a smooth and gradual transition from the forward and rearward sections to respective side sections of the hole... distributing stresses uniformly
Implementation Method 4
compressive and tensile stresses generated by the percussive piston and in particular the shock wave that is transmitted through the adaptor
Implementation Method 5
compressive and tensile stresses generated by the percussive piston and in particular the shock wave that is transmitted through the adaptor
Implementation Method 6
The flushing fluid acts to both cool the tool and to expel drill cuttings and fines from the bore hole
Implementation Method 7
The piston strike on the adaptor creates a stress (or shock) wave that propagates through the drill string and ultimately to the borehole rock bottom
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A rock drilling shank adaptor comprising an elongate body having an internal flushing bore and an entry hole through the sidewall of the adaptor in fluid communication with the internal bore. The flushing hole is optimised to reduce the likelihood of fracture at the wall of the adaptor and in particular comprises straight sections at axially forward and rearwardmost regions of the hole.