Sheet-Metal Bonding and Welding to Prevent Joint-Line Festooning
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Solution Overview
Problem
The existing method of joining sheet metal parts using glue and welds results in a phenomenon called 'festooning', leading to gaps and air bubbles, which deteriorate the bonding quality due to the elastic return of the sheet metal after polymerization of the glue.
Innovation Solution
A method involving partial insertion of self-piercing rivets before applying glue and welds along the joint line, with the rivets positioned to constrain the sheet metal and prevent elastic return, ensuring optimal bonding by using structural adhesives and electric resistance welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sheet metal parts are joined by gluing and welding along a joint line, then mechanical strength and rigidity are improved, but elastic return causes festooning and gaps that deteriorate bonding quality
Solution Approach 1:
Self-piercing rivets are inserted into the sheet metal parts before the gluing operation to pre-constrain the parts and prevent elastic return during and after polymerization. This preliminary mechanical constraint ensures that the joint line remains stable throughout the bonding process, eliminating festooning and gaps that would otherwise deteriorate bonding quality.
Solution Approach 2:
Self-piercing rivets act as intermediary elements between the two sheet metal parts, providing mechanical constraint while allowing the adhesive to bond the parts together. The rivets transfer and distribute stresses between the parts, preventing localized deformation and ensuring uniform bonding across the joint line.
2Stability of the object's composition
If clamping means are used to keep glued parts immobile during polymerization, then bonding stability is improved, but additional equipment and process complexity are required
Solution Approach 1:
The self-piercing rivets provide self-constraint by being mechanically formed into the sheet metal parts during insertion. The rivets create interference fits and deformation zones that automatically constrain the parts without requiring external clamping devices. This self-service mechanism simplifies the overall process by eliminating the need for additional clamping equipment and operations.
3Strength
If multiple weld points are made along the joint line, then mechanical strength is improved, but the festooning phenomenon increases due to elastic return between weld points
Solution Approach 1:
Self-piercing rivets are inserted before welding to pre-constrain the sheet metal parts and prevent elastic return between weld points. The rivets maintain the joint line flatness throughout the welding process by providing continuous mechanical constraint, thereby preventing festooning while allowing multiple weld points to be made for enhanced strength.
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
Prevents the 'festooning' phenomenon, ensuring stable bonding quality by constraining the sheet metal with self-piercing rivets, maintaining the edges under stress until polymerization is complete.
Implementation Method 1
the elastic return of this sheet metal from the edge of the second piece between these two welding points is prevented by the rivet which holds it under stress
Implementation Method 2
the final fixing of the parts is only achieved after the polymerization (hardening) of the glue
Implementation Method 3
making weld points on said superimposed edges of said pieces at the level of the sections of said joint line without glue
Data Source
Figure 1~4
Figure 5~6
AI summary
The invention relates to a method for joining two sheet-metal parts (2, 3) together by adhesive bonding and welding along a join line (4), comprising the following successive steps: - partially inserting at least one self-piercing rivet (5) into an edge (2A) of the first part (2) at the join line, - depositing a plurality of beads of glue (6) discontinuously along the join line at the edge (2A) of the first part (2) and in such a way that each self-piercing rivet is covered by a corresponding bead of glue, - superposing an edge (3A) of the second part (3) on the edge (2A) of the first part (2) and pressing these two edges together, - creating welding spots (7) at the superposed edges of the parts at the portions of the join line that are devoid of glue.