Closed-Section Steel Member Joining 980 MPa Plates Without Welding
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Solution Overview
Problem
High-strength steel plates used in vehicle body structures are difficult to join due to poor workability, making welding and mechanical fastening challenging, and existing solutions do not effectively address the joining of two high-strength steel plates without these methods.
Innovation Solution
A structural member configuration where two high-strength steel plates with tensile strength of at least 980 MPa are joined using hemming bending and an adhesive, with specific geometric and material properties to enhance workability and prevent cracking, such as a λ value of 50% or higher and a curvature radius to thickness ratio of 1.0 or more, allowing for strong bonding without welding or mechanical fastening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength steel plates (tensile strength ≥980 MPa) are used for vehicle body structures, then strength and weight reduction are improved, but workability and ease of joining deteriorate
Solution Approach 1:
The patent replaces traditional mechanical joining methods (welding, mechanical fastening) with adhesive bonding. The adhesive joint is applied to join high-strength steel plates with tensile strength of 980 MPa or more, eliminating the need for welding or mechanical fasteners that are difficult to apply to such high-strength materials.
Solution Approach 2:
The patent specifies precise geometric parameters for the adhesive joint configuration: the width W1 of the adhesive joint application area is set to 0.05 to 0.15 times the plate thickness t, and the length L1 is 0.05 to 0.15 times the plate width W. These parameter optimizations enable effective adhesive bonding of high-strength steel plates while maintaining workability.
2Ease of manufacture
If adhesive bonding is used to join high-strength steel plates, then ease of joining is improved, but joining strength may deteriorate
Solution Approach 1:
The patent optimizes the geometric parameters of the adhesive joint: the width W1 is set to 0.05 to 0.15 times the plate thickness t, and the length L1 is set to 0.05 to 0.15 times the plate width W. These parameter ranges ensure sufficient bonding area and stress distribution, achieving joining strength comparable to or exceeding traditional methods while maintaining ease of application.
Solution Approach 2:
The patent applies adhesive to a specifically designed area on the steel plate surface before assembly. The adhesive joint application area is predetermined with specific dimensions (W1 and L1), ensuring proper adhesive distribution and bonding performance before the components are joined together.
3Strength
If hemming bending is applied to high-strength steel plates, then rigidity is improved, but process defects like cracking may occur
Solution Approach 1:
The patent specifies that the λ value (hole expansion ratio) of the high-strength steel plate material should be 50% or more. This material parameter selection ensures sufficient ductility and formability, allowing hemming bending to be performed without causing cracking or other process defects while achieving the desired rigidity enhancement.
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 configuration enables strong and rigid joining of high-strength steel plates, improving impact absorption and safety performance by suppressing process defects like cracking, while reducing weight and enhancing dimensional accuracy, thus addressing the challenges of joining high-strength steel plates.
Implementation Method 1
the second bonded part held in the first hemming process part and bonded to the first hemming process part by an adhesive
Data Source
AI summary
A structural member is elongated in a longitudinal direction, and includes a first member made of a steel plate and a second member made of a steel plate, the first member and the second member being joined. In the structural member, a closed cross-sectional shape is formed by the first member and the second member in a cross section perpendicular to the longitudinal direction. The first member has a tensile strength of equal to or greater than 980 MPa, and includes a first hemming process part subjected to hemming bending at both end parts in a width direction orthogonal to the longitudinal direction. The second member has a tensile strength of equal to or greater than 980 MPa, and includes a second bonded part held in the first hemming process part at both end parts in the width direction and bonded to the first hemming process part by an adhesive.