Thickened Bottom Sheet for Crack-Free Magnesium Riveting
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Solution Overview
Problem
The challenge in the automotive industry is to join brittle materials like magnesium in vehicle manufacturing without cracking, which occurs due to the thinness and brittleness of the materials used in self-piercing rivet technology, leading to compromised joint integrity and increased production costs.
Innovation Solution
Increasing the thickness of the lower layer in material stack-ups to at least 4.0 mm, particularly in areas where mechanical fasteners are inserted, to reduce strain and prevent cracking during the riveting process, allowing for the use of self-piercing rivets and other fasteners without heating the magnesium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-piercing rivet technology is used to join magnesium and other brittle materials, then production efficiency is improved, but cracking occurs in the rivet button due to material thinness and brittleness
Solution Approach 1:
The patent applies local quality by increasing the thickness of the lower layer specifically in the area where the mechanical fastener is inserted (the rivet button area), while other areas can maintain their original thickness. This localized thickening to at least 4.0 mm provides the necessary material volume to prevent cracking during the riveting process, resolving the contradiction between using efficient self-piercing rivet technology and maintaining joint integrity in brittle materials.
2Reliability
If the thickness of the lower layer is increased to prevent cracking, then joint durability is improved, but material usage and manufacturing complexity increase
Solution Approach 1:
Rather than increasing the thickness of the entire lower layer, the patent implements localized thickening only in the specific area where the mechanical fastener is inserted. This approach maintains joint durability by ensuring sufficient material thickness (at least 4.0 mm) at the critical rivet button location, while avoiding the unnecessary material usage and manufacturing complexity that would result from uniformly increasing the entire layer's thickness.
Data Source
AI summary
A system for attaching material stack-up layers of at least two layers together using mechanical fasteners is disclosed. The material stack-up comprises at least an upper layer and a lower layer. The lower layer has a relatively constant thickness equal to or greater than 4.0 mm or may have alternating thick and thin areas in which the thickness of the thick area is equal to or greater than 4.0 mm. A mechanical fastener attaches the upper layer and the lower layer and is inserted at least partially into the lower layer. The fastener is inserted into the thick area of the embodiment having alternating thick and thin areas. The lower layer may be any of a variety of materials, including magnesium or any other brittle material. The lower layer may also be a casting, such as a magnesium casting. The mechanical fastener may be any of fasteners, screws or bolts.