SPR Die Geometry for Crack-Resistant Magnesium Alloy Joining
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Solution Overview
Problem
Self-piercing riveting technologies face challenges when joining magnesium alloys due to their reduced ductility and formability, leading to structural integrity issues and cracking during the rivet installation process.
Innovation Solution
A specially designed self-piercing riveting die with a unique geometry, including a recessed area and a rivet with a reduced web thickness, is used to control deformation and reduce the risk of cracking, by selecting the die and rivet based on material properties and volume displacement to ensure a robust mechanical interlock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If existing SPR technologies are used to join magnesium alloys, then weight reduction is achieved, but the structural integrity is reduced and cracking occurs due to reduced formability
Solution Approach 1:
The patent modifies critical parameters of the SPR process including die geometry (cavity shape, radius, depth), rivet dimensions (diameter, length, web thickness), and process variables (upset force, displacement rate) to accommodate the reduced formability of magnesium alloys while maintaining structural integrity
Solution Approach 2:
The patent applies localized quality improvements by using a specially designed die cavity with specific radius and shape at the rivet upset location, and by controlling the local deformation zone to prevent cracking while achieving reliable joints in magnesium alloys
2Productivity
If SPR process is applied to magnesium alloys, then fastening speed is maintained, but material damage occurs during rivet installation
Solution Approach 1:
The patent optimizes process parameters including upset force magnitude, displacement rate, and die geometry to reduce material damage while preserving the high-speed capability of SPR for magnesium alloy fastening
Solution Approach 2:
The patent employs dynamic control of the rivet upset process, adjusting force and displacement rates during installation to adapt to the specific formability characteristics of magnesium alloys, thereby preventing damage while maintaining productivity
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 effectively reduces the risk of cracking and enhances the structural integrity of magnesium alloy castings by controlling deformation and material displacement during the riveting process, allowing for the successful joining of magnesium alloys using existing SPR devices.
Implementation Method 1
pressing an SPR rivet through the stack toward the SPR die... to deform the upper layer into an interior cavity defined by the rivet
Data Source
AI summary
A self-piercing riveting (SPR) die includes a die body including an outer surface, a lower surface that is parallel to and offset from the outer surface, and a side surface that circumscribes the lower surface. A distance between the lower surface and the outer surface is within a range between approximately 0.4 mm to 1.2 mm. An angle between the side surface and the lower surface is within a range between approximately 55 to 80 degrees. An inner diameter of the outer surface is within a range between approximately 13 to 18 mm.