Thread Forming Screw with Constant Radius Flank for Low Ductility Materials
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Solution Overview
Problem
Conventional thread forming screws fail to provide reliable joints in low ductility materials like magnesium and aluminum alloys due to issues such as slivering, layer eruption, chipped threads, fracturing, and debris creation, which affect the integrity and performance of the fastening system.
Innovation Solution
A thread forming screw with a constant radius thread flank design that deforms the material without cracking, allowing for maximum material displacement and engagement, along with a corresponding thread roll die for manufacturing, which eliminates the need for tapping and enhances torsional strength and reusability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thread forming screws are used in low ductility materials, then the fastening process can be completed, but material fractures, slivering, layer eruption, and chipped threads occur reducing joint reliability
Solution Approach 1:
The thread flank is designed with a constant radius curvature instead of a straight or angular profile. This curved geometry allows the thread to deform the material gradually and uniformly, preventing stress concentration that leads to fractures, slivering, and layer eruption in low ductility materials.
Solution Approach 2:
The invention modifies the geometric parameters of the thread profile, specifically implementing a constant radius thread flank with optimized curvature. This parameter change enables the thread to accommodate the low ductility of materials like magnesium and aluminum alloys by distributing deformation more evenly, thereby preventing material failure while maintaining joint reliability.
2Ease of operation
If tapping is performed to form threads in the material, then the screw can be fastened, but the tapping process creates fractures and disturbances that weaken the fastening
Solution Approach 1:
Instead of cutting or forming threads by removing material or creating grooves (conventional tapping), the invention inverts the approach by using a forming thread that displaces and deforms the material plastically. This inversion eliminates the harmful effects of tapping while achieving secure fastening through material engagement.
Solution Approach 2:
The invention extracts or eliminates the tapping operation entirely from the fastening process. By designing a thread forming screw with constant radius flank that can directly engage and deform the material, the harmful tapping step is removed, preventing fractures and disturbances that would otherwise weaken the fastening integrity.
3Adaptability or versatility
If standard thread bolts are used, then assembly can proceed, but removal and reinsertion weakens and destroys threads creating magnesium powder and contamination
Solution Approach 1:
The constant radius thread flank design creates a more uniform stress distribution during both installation and removal operations. This curved geometry prevents the concentration of stresses that lead to thread destruction and material fragmentation, enabling multiple removal and reinsertion cycles without generating magnesium powder or compromising joint integrity.
4Strength
If conventional screw threads are used, then fastening can be achieved, but torsional strength and resistance to vibration loosening are insufficient
Solution Approach 1:
By changing the geometric parameters of the thread profile to include a constant radius flank, the invention optimizes the stress distribution and material engagement. This parameter modification enhances both torsional strength and resistance to vibration loosening by creating more uniform contact stresses and improving the mechanical interlocking between the thread and the material.
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 solution provides a reliable and efficient joint with high torsional strength, reduced debris, and improved assembly efficiency, minimizing damage to the material and preventing vibration loosening, while being suitable for miniaturization and various material applications.
Implementation Method 1
the threads may be arranged to deform the ductile material without cracking or damaging the surrounding ductile material of the work piece
Data Source
AI summary
A thread forming screw thread fastener and a corresponding thread roll die are disclosed for fastening into a hole of a workpiece composed of low ductility material. More specifically, the thread forming screw thread has smooth radius thread flank which has a capability of deforming low ductile material such as magnesium, soft aluminum, thermoset plastics and other low ductility materials to deform the ductile material efficiently minimizing cracks, debris, low friction during installation and a maximum engagement of the screw with mating parts with the ductile material.