Punch-Riveting Die Geometry for Crack-Free Steel-Aluminum Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing self-piercing riveting (SPR) technologies face challenges in joining high strength or ultra-high strength steel with brittle materials like cast aluminum without cracking or altering the joint's performance.
Innovation Solution
A punch-riveting die with a specific geometry, including a recess with three annular bases and a central cavity with a projection, is designed to support the joining process. This die geometry minimizes rivet compression, forms a sufficient undercut, and includes features like inclined and curved annular bases to manage material flow and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SPR processes are used to join high strength steel with brittle cast aluminum, then the joining process can be completed, but cracks occur within the rivet or the brittle material workpiece
Solution Approach 1:
The patent modifies the geometric parameters of the die cavity, specifically introducing a multi-level cavity structure with different depths and a projection element. This changes the compression parameters and material flow characteristics during riveting, reducing peak stresses that cause cracking in brittle materials like cast aluminum when joining with high strength steel.
Solution Approach 2:
The die cavity is designed with non-uniform depth zones (first, second, and third levels) and a central projection, creating localized regions with different compression characteristics. This allows differential control of material flow in different areas, preventing stress concentration that would lead to cracks in the brittle workpiece material.
2Manufacturing precision
If conventional die geometries are used, then the riveting process is simple, but the rivet compresses excessively and cannot form a sufficient undercut
Solution Approach 1:
The die cavity is segmented into multiple levels (first, second, and third levels) with a central projection, creating distinct zones that control material flow at different stages of compression. This segmentation allows precise control over undercut formation while managing overall die complexity through a systematic multi-level structure.
3Stress or pressure
If uniform die cavity depth is used, then the die structure is simple, but material flow is not properly controlled causing stress concentration
Solution Approach 1:
The die cavity employs local quality variation through its multi-level structure, where different regions have different depths (first level at sheet metal support surface, second level deeper, third level with projection). This creates localized compression zones that distribute stress more evenly throughout the workpiece, preventing stress concentration while maintaining structural integrity.
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 joins high strength or ultra-high strength steel with brittle cast aluminum without cracking, maintaining the joint's performance and integrity by controlling material flow and stress distribution.
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 die plays an important role in the formation of a robust joint. The lowermost workpiece layer is supported at a die.
Data Source
AI summary
A punch-riveting die for a punch-riveting tool for setting a semi-hollow punch rivet into a punch rivet joint. The die comprising a basic body with a sheet metal support surface and a recess for forming an underside of a punch-rivet joint. The recess is arranged rotationally symmetrically to the central axis of the punch-riveting die. The recess having a first annular base, a lower second annular base, and a lowest central cavity extending axially below the second base. A projection rises axially in the central part of the cavity. A first annular wall extends between the first annular base and the sheet metal support surface. A second annular wall extends between the first annular base and the second annular base. A third annular wall extends between the second annular base and the bottom of the cavity.