Joining Element Undercut Bonding for Thin Lightweight Components

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Solution Overview

Problem

Existing joining processes for lightweight materials, such as aluminum and fiber composites, face challenges as direct welding or soldering is often not possible, and existing joining aids do not effectively address the need for flexible connections between diverse materials.

Innovation Solution

A method involving a joining aid element with a retaining section is pressed into a through-hole, which is widened by an indentation, forming a force and form-lock connection, allowing material bonding and additional functional sections for diverse materials like aluminum and steel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a joining aid is pressed into a through-hole to connect lightweight materials, then the connection strength is improved, but the component thickness is reduced

Engineering Contradiction:
Improveconnection strengthVSAvoidcomponent thickness
Core Design Contradiction:
StrengthVSLength of moving object

Solution Approach 1:

The patent introduces an indentation feature that creates a radial dimension change in the through-hole geometry. By widening the hole at specific locations through indentation, the joining aid element engages in multiple dimensions (axial pressing + radial engagement), distributing the connection strength across different spatial dimensions rather than relying solely on thickness

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The solution employs a composite joining aid element consisting of a retaining section and a functional section with different materials optimized for specific functions. The retaining section material is selected for optimal pressing and retention characteristics, while the functional section material is chosen for welding or bonding compatibility, creating a composite structure that achieves high connection strength without requiring increased component thickness

Inventive Principle:
Principle #40Composite materials

2Ease of manufacture

If existing joining aids are used for diverse materials, then the joining process is simplified, but the adaptability to different material pairings is reduced

Engineering Contradiction:
Improvejoining process simplicityVSAvoidmaterial pairing flexibility
Core Design Contradiction:
Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The joining aid element is designed with a universal retaining section geometry that can be pressed into standard through-holes across different component types, while the functional section offers multiple material options (weldable material, bondable material, or both) to accommodate diverse material pairings. This multi-functional design maintains process simplicity while enhancing adaptability to aluminum, steel, and composite materials

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent enables adaptability through parameter changes in the functional section material composition and properties. By selecting different materials for the functional section with varying weldability, bondability, and mechanical properties, the same joining aid structure can be adapted to different material pairings without changing the overall joining process flow

Inventive Principle:
Principle #35Parameter changes

3Strength

If the through-hole is widened by indentation, then the force-lock connection is improved, but the manufacturing complexity increases

Engineering Contradiction:
Improveforce-lock connection strengthVSAvoidhole geometry complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The indentation is created as a preliminary action during component manufacturing, before the joining aid is installed. This pre-formed geometric feature prepares the through-hole for optimal joining aid engagement, creating the force-lock connection geometry in advance rather than during the joining process itself, thereby reducing overall manufacturing complexity

Inventive Principle:
Principle #10Preliminary action

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 method achieves high strength connections with reduced component thickness, minimizing hydrogen embrittlement and edge cracking, enabling the joining of lightweight materials using existing welding systems, particularly suitable for thin sheets.

Implementation Method 1

the retaining section of the joining aid element is pressed into the through-hole and is connected to the hole wall by force and/or form locking

Methodology Applied
Scientific EffectForce-fit connection: Mechanical Force

Implementation Method 2

the retaining section of the joining aid element is pressed into the through-hole and is connected to the hole wall by force and/or form locking

Methodology Applied
Scientific EffectForm-fit connection: Deformation

Implementation Method 3

the through hole is widened at at least one edge region by an indentation, wherein the retaining section of the joining aid element is pressed into the through hole and is connected to the hole wall by force and/or form locking, and the retaining section engages in the indentation

Methodology Applied
Scientific EffectUndercut formation: Deformation

Implementation Method 4

forming a material-fit connection by welding, soldering or bonding, wherein the joining aid element is material-fitted to the base material of the second component

Methodology Applied
Scientific EffectWelding: Welding

Implementation Method 5

forming a material-fit connection by welding, soldering or bonding, wherein the joining aid element is material-fitted to the base material of the second component

Methodology Applied
Scientific EffectSoldering: Soldering

Implementation Method 6

forming a material-fit connection by welding, soldering or bonding, wherein the joining aid element is material-fitted to the base material of the second component

Methodology Applied
Scientific EffectBonding: Adhesive

Data Source

PatentEP3568256B1Method for the production of a component bonding of at least two components
Publication Date: 2025.11.05 BAYERISCHE MOTOREN WERKE AG
  • EP3568256B1 patent drawingFigure 1~2
  • EP3568256B1 patent drawingFigure 3~4

AI summary

The invention relates to a component (2) in which, at at least one joint, at which a joining connection to a further component is to be formed later, a joining element (4) having a holding section (7) is pressed into the component, and the joining element (4) also has a functional section (8), by means of which at least one further function can be implemented. According to the invention, the holding section (7) of the joining element (4) is arranged in a passage hole (13), and the passage hole is widened in at least one edge region by an embossing (14), wherein the holding section (7) of the joining element (4) is pressed into the passage hole (4) and is connected to the hole wall in a force-fitting and/or form-fitting manner and engages in the embossing (14). The invention further relates to a component combination of at least two components which are joined at at least one joint, comprising the component (2) according to the invention having a joining element (4), and to a method for producing the component and the component combination.