Friction Stir Riveting With Consumable Pin
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Solution Overview
Problem
Existing metal joining methods, such as welding and friction stir welding, face challenges with high melting temperature materials like steel and stainless steel due to solidification defects, residual stresses, and the need for predrilled holes, which increase costs and reduce base metal properties.
Innovation Solution
A friction stir riveting method using a partially consumable pin with a cutting edge that cuts through work pieces and then undergoes plasticization, allowing for diffusion bonding without leaving a hole, utilizing a detachable and multi-segmented pin design for efficient and economical joining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction stir welding is used to join high melting temperature materials, then joining strength is improved, but solidification defects and residual stresses occur
Solution Approach 1:
The patent utilizes controlled phase transitions by heating the work pieces to plasticization temperature (below melting point) and then rapidly cooling them during the friction stir riveting process. This controlled thermal cycling enables solid state bonding while avoiding solidification defects that occur in traditional welding by preventing complete melting and subsequent solidification
Solution Approach 2:
The patent replaces the traditional welding mechanism (fusion joining) with a friction-based solid state joining mechanism. The rotating pin generates frictional heat and mechanical stirring action that plasticizes and bonds the materials without melting, thereby eliminating solidification defects and reducing residual stresses associated with phase transformation
2Ease of manufacture
If predrilled holes are made for fasteners, then mechanical joining is enabled, but base metal properties are reduced and costs increase
Solution Approach 1:
The patent extracts and eliminates the need for predrilled holes by using a consumable pin that is friction-stirred directly into the work pieces during the joining process. The pin itself becomes the fastener, removing the separate hole-drilling operation and preserving base metal integrity
Solution Approach 2:
The patent merges the hole-creation function and the fastening function into a single integrated process. The consumable pin serves both as the tool that creates the joining zone and as the permanent fastener that remains in the work pieces, eliminating the need for separate hole drilling and fastener installation steps
3Strength
If rotational speed is increased for plasticization, then bonding quality is improved, but process time increases
Solution Approach 1:
The patent employs periodic variation in rotational speed during the friction stir riveting process. The tool rotates at high speed to generate frictional heat and plasticize the materials, then rapidly decelerates or stops to enable bonding. This periodic acceleration and deceleration cycle allows rapid processing while achieving high bonding quality
Solution Approach 2:
The patent rushes through the heating and plasticization phases by using high rotational speeds for brief periods, then quickly transitions to the bonding phase by rapid deceleration. This minimizes the time spent in intermediate states and accelerates the overall process while ensuring adequate bonding occurs during the brief decelerated period
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 method enables strong, defect-free bonding of high melting temperature materials with reduced residual stresses and no need for predrilled holes, offering a rapid and cost-effective solid state joining process.
Implementation Method 1
the rotational speed of the tool is changed to cause plasticization of the pin itself, as well as the first and second work piece materials being joined
Implementation Method 2
cause plasticization of the pin itself, as well as the first and second work piece materials being joined
Implementation Method 3
the rotation of the tool is rapidly decelerated or stopped completely to enable the bonding of the pin and the first and second work piece materials
Data Source
AI summary
A friction stir tool is provided to perform friction stir riveting using a partially consumable pin, wherein the pin includes a cutting edge on a bottom surface thereof, wherein the tool is rotated at a first speed to enable cutting by the pin into a first material that is overlapping a second material, wherein after the pin has cut to a sufficient depth, the rotational speed of the tool is increased to thereby enable plasticization of the consumable pin, the first material, and the second material, wherein the tool is then rapidly decelerated until stopped, enabling diffusion bonding between the pin, the first material and the second material.