Punch-Riveting Die Geometry for Joining Steel to Cast Aluminum
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Solution Overview
Problem
In vehicle construction, there is a need to join high strength steel or ultra-high strength steel with brittle materials like cast aluminum without cracking and while maintaining a robust joint, as existing self-piercing riveting technologies face challenges in avoiding rivet collapse and ensuring high joining force, especially when dealing with non-deformable brittle materials.
Innovation Solution
A punch-riveting die with a specific geometry, featuring a recess with three annular bases and walls, including a projection and convex flow barriers, is designed to support the self-piercing riveting process, optimizing material flow and reducing stress, allowing for the joining of high strength steel with brittle cast aluminum without cracking and maintaining joint performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional self-piercing riveting is used to join high strength steel with brittle cast aluminum, then joining of different materials is achieved, but cracking occurs in the brittle material or rivet collapse happens
Solution Approach 1:
The die cavity is designed with differentiated zones: a first cavity region with larger volume for receiving material from the upper workpiece, and a second cavity region with smaller volume for forming the rivet base. This local differentiation in cavity geometry allows optimized material flow and stress distribution in different areas, preventing cracking in brittle materials while maintaining joint integrity
Solution Approach 2:
The invention changes the geometric parameters of the die cavity, specifically creating an inclined first base that forms a ramp structure. This parameter change in the die geometry controls the material flow and stress distribution during rivet setting, enabling successful joining of brittle materials without cracking or rivet collapse
2Quantity of substance
If the die cavity volume is increased to accommodate more material flow, then material flow is improved, but the die size and complexity increase
Solution Approach 1:
The die cavity is segmented into distinct functional regions: a first cavity region for material reception and flow, and a second cavity region for base formation. This segmentation allows each region to be optimized independently for its specific function, achieving sufficient material flow without requiring an overall increase in die size or complexity
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 effectively prevents cracking and ensures a robust joint by optimizing material flow and stress reduction, enabling the joining of high strength steel with brittle cast aluminum while maintaining the integrity of the rivet and workpieces.
Implementation Method 1
When driven into the workpiece arrangement, the hollow shank of the rivet widen radially and hereby creates an undercut that results in permanent joining of the workpieces
Implementation Method 2
the first annular base is inclined with respect to the plane defined by the sheet metal support surface. This improves the material intake to avoid cracks
Data Source
Figure 1~2
Figure 3
AI summary
Punch-riveting die (22) for a punch-riveting tool (10) for setting a semi-hollow punch rivet with a rivet shank inner diameter into a punch rivet joint, the punch-riveting die (22) comprising a basic body (24) with a sheet metal support surface (30) and a recess (32) for forming an underside of a punch-rivet joint, the recess being arranged rotationally symmetrically to the central axis of the punch-riveting die (22), the recess (32) having a first annular base (34), a second annular base (36) and a central cavity (38) extending axially below the second base of the recess, wherein a projection (40) is realized in the central part of the cavity (38), and wherein a first annular wall (42) extends between the first base and the sheet metal support surface (30), a second annular wall (44) extends between the first base and the second base, and a third annular wall (46) extends between the second base and the bottom of the cavity (38).