Dissimilar Metal Joint Bead Structure for Thermal Strain Management
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Solution Overview
Problem
Existing joint structures for dissimilar metals in vehicle components, such as those between steel and aluminum alloy sheets, face challenges in managing thermal expansion strains due to differences in thermal expansion coefficients, particularly in the alignment direction of joined areas, leading to potential deformation and reduced rigidity.
Innovation Solution
A joint structure where a first member (e.g., steel sheet) and a second member (e.g., aluminum alloy sheet) with a higher thermal expansion coefficient are spot-joined at multiple positions in a specific direction, with a bead portion extending orthogonally between these points to absorb thermal expansion, enhancing bending rigidity and suppressing strains in both the alignment and width directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If dissimilar metals (steel and aluminum alloy) are joined together to achieve weight reduction, then weight is reduced, but thermal strain occurs due to different thermal expansion coefficients
Solution Approach 1:
The invention changes the geometric parameters of the aluminum alloy sheet by forming bead portions with specific dimensions (width 5-20mm, height 1-5mm, spacing 10-50mm). These parameter modifications allow the structure to accommodate thermal expansion differences between dissimilar metals while maintaining the weight reduction benefit of using aluminum alloy panels.
Solution Approach 2:
The invention segments the aluminum alloy sheet by forming periodic bead portions along the joined area. This segmentation creates multiple small deformation zones that can independently absorb thermal strain, preventing cumulative stress buildup while maintaining overall structural integrity and weight efficiency.
2Strength
If spot-joining is used to join dissimilar metals at multiple positions, then joining strength is improved, but thermal strain concentration occurs at the joined points
Solution Approach 1:
The bead portions act as intermediary elements between the spot-joined regions. These bead structures serve as transition zones that mediate the thermal expansion differences, distributing and reducing strain concentration at the rigid spot-joined points while maintaining strong mechanical connection between dissimilar metals.
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 effectively reduces thermal strain and enhances bending rigidity in the joined region, maintaining structural integrity and weight reduction while accommodating thermal expansion differences between dissimilar metals.
Implementation Method 1
a thermal strain such as flexure is likely to occur in a joined region due to the difference in thermal expansion coefficient
Implementation Method 2
it is intended to absorb a vehicle width directional strain occurring due to a difference in thermal expansion coefficient between the aluminum roof panel and the roof side rail, by the bead portion formed in the aluminum roof panel
Implementation Method 3
the first member and second member are superimposed on each other and spot-joined together at a plurality of positions in a first direction
Data Source
AI summary
A Joint structure for members of different kinds of metals comprises a first member formed from a metal sheet, and a second member formed from a metal sheet having a coefficient of thermal expansion greater than that of the metal sheet for the first member, wherein the first member and the second member are superimposed on each other and spot-joined together at a plurality of positions in a first direction, and the second member has a bead portion extending along a second direction orthogonal to the first direction, at a position between adjacent ones of the spot-joined points.