Rivet Die Cavity Geometry for Crack-Free Fastener Insertion
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Solution Overview
Problem
Low ductility materials, such as cast aluminium, are prone to cracking during self-piercing rivet setting operations, leading to potential corrosion and joint failure due to fluid ingress.
Innovation Solution
A rivet die with a specific cavity design that provides central support and controlled compression to the workpiece, reducing the likelihood of cracking by ensuring even stress distribution and minimizing contact with less supportive areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rivet setting operation is used on low ductility materials, then the rivet can be inserted into the workpiece, but cracks are likely to form in the workpiece during the operation
Solution Approach 1:
The die cavity geometry is modified by introducing a groove at a specific radial position and depth, creating different support zones (first portion with greater support, second portion with lesser support). This geometric parameter change alters the stress distribution in the workpiece during rivet setting, ensuring compressive stress predominates to prevent cracking in low ductility materials.
2Strength
If the die cavity provides uniform support to the workpiece, then the workpiece is well supported during rivet insertion, but tensile stresses may still cause cracking in low ductility materials
Solution Approach 1:
The die cavity is designed with non-uniform support characteristics: the first portion (closer to the central axis) provides greater support while the second portion (radially outward) provides lesser support. This local differentiation in support quality creates a controlled stress gradient that ensures compressive stress dominates in the critical central region where cracks are most likely to form.
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 die design significantly reduces the likelihood of cracking during rivet setting, enhancing joint integrity and preventing corrosion by maintaining compressive stress and minimizing tensile forces.
Implementation Method 1
the material of the workpiece deflects such that it is supported by the first portion of the base surface
Implementation Method 2
the workpiece is subjected to compressive stress throughout the rivet setting operation
Implementation Method 3
the material of the workpiece deforms into the groove, which compresses the material that is received within the groove
Data Source
AI summary
There is disclosed a rivet die (13) for a rivet setting tool (2). The rivet die (13) comprises a main body (20) that defines an upper surface (39). The rivet die (13) further comprises a die cavity (21) that is formed in the upper surface (39). The die cavity (21) is defined at least in part by a base surface (42). The base surface (42) comprises a groove (50) that extends at least partly around a central axis C, a first portion (46) through which the central axis C extends, and a second portion (48). The groove (50) is disposed radially outwards of the first portion (46). The second portion (48) is disposed radially outwards of the groove (50). The groove (50) and the second portion 48 border one another at an interface (56). The first portion (46) defines a first portion depth d1 in a direction along the central axis C. The interface (56) defines an interface depth d5 in a direction along the central axis C. The first portion depth dl is less than the interface depth d5.