Lap Joint Overlap Recesses to Prevent Hole-Induced Fracture
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Solution Overview
Problem
In lap joint structures formed by mechanical joining or friction joining, strain concentration at holes leads to premature breaking of sheet members under tensile deformation, particularly when using blind rivets or friction stir spot joining.
Innovation Solution
The introduction of cutaway recessed parts between adjacent joined parts in sheet members, positioned away from the end of the overlapping parts, disperses strain and prevents fracture by absorbing deformation, thereby enhancing the joint's tensile strength and elongation capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical joining means or friction stir spot joining is used to join overlapping sheet members, then the materials can be joined without melting (suitable for high strength steel and different material combinations), but holes are formed at the joined parts which cause strain concentration and lead to premature breaking under tensile deformation
Solution Approach 1:
The patent applies local quality by creating cutaway recessed parts at specific locations (between adjacent joined parts) where strain concentration occurs. This local structural modification changes the stress distribution characteristics only in the critical regions, allowing the majority of the joint to maintain its original strong configuration while preventing fracture at vulnerable points.
Solution Approach 2:
The cutaway recessed parts segment the continuous sheet material into distinct regions, creating a stepped configuration that interrupts the direct stress path through the holes. This segmentation divides the tensile load into multiple load paths, preventing concentration of strain at any single hole location.
2Ease of manufacture
If holes are formed for mechanical joining or friction stir spot joining, then the sheet members can be joined together, but strain concentrates at the holes causing the sheet members to break starting from the holes under tensile deformation
Solution Approach 1:
The cutaway recessed parts are strategically positioned at locations where strain concentration occurs (between adjacent joined parts), creating local structural modifications that prevent fracture. This approach maintains the simplicity of the overall joining process while adding targeted fracture prevention features only where needed.
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
This design effectively prevents the lap joint member from breaking at the holes, improving its tensile strength and deformation resistance, ensuring higher performance and safety in collision scenarios, such as in automotive applications.
Implementation Method 1
by forming cutaway recessed parts at the overlapping parts of sheet members between adjacent joined parts in the direction from the end parts of the overlapping parts to the joined part sides, the structure becomes one dispersing strain due a tensile load and fracture of the lap joint member starting from the holes is suppressed
Data Source
AI summary
The present invention provides an overlapping bonded structure in which breaking of a bonded section at holes formed during bonding can be prevented when an overlapping section formed by overlapping a plurality of meal plate members is bonded by means of a mechanical bonding means or a friction stir spot-welding means. This overlapping bonded structure, in which overlapping portions of a plurality of plate members are spot-welded at a plurality of bonded sections by means of a mechanical bonding means or a friction stir spot-welding means, and in the bonded sections a hole into which the mechanical bonding means is inserted or a hole formed during the spot-welding by the friction stir spot-welding means exists in at least one plate member, is characterized in that a cutout recess is formed between adjacent bonded sections, from an end portion of the overlapping section in the bonded-section direction, in the overlapping section of at least one of the plate sections, and when the inner diameter of the hole is K, an inside bottom portion of the cutout recess is formed at a position having a depth of K or greater from the end portion of the overlapping section.