Pipe-to-Flange Joined Body Using Spring-Back Material Mismatch
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Solution Overview
Problem
Existing methods for joining dissimilar metals like steel and aluminum, such as those described in JP S51-133170 A and JP H9-192760 A, lack sufficient examination of material properties, resulting in suboptimal joining strength.
Innovation Solution
A joined body configuration where a pipe-shaped first member is inserted into a plate-shaped second member with a cylindrical flange portion, featuring a larger spring-back amount, is used, allowing for improved contact area and pressure distribution through elastic deformation, enhancing joining strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If dissimilar metals (steel and aluminum) are joined using conventional press-fitting methods, then multi-materialization is achieved, but joining strength is insufficient due to inadequate material property examination
Solution Approach 1:
The invention changes the material parameter selection criterion from conventional properties to spring-back amount. Specifically, it requires that the spring-back amount of the second member be larger than that of the first member (spring-back amount relationship: second member > first member). This parameter change enables optimized joining strength through elastic deformation control during press-fitting, resolving the contradiction between achieving strong joints and maintaining manufacturing simplicity.
2Strength
If high tension steel is used to reduce weight and improve safety, then vehicle safety and weight reduction are achieved, but formability decreases and forming load increases
Solution Approach 1:
The invention employs composite material construction by joining dissimilar metals (steel first member and aluminum second member) with different mechanical properties. The steel member provides high strength for safety-critical functions, while the aluminum member offers lighter weight and better formability for body panels. This composite approach resolves the contradiction by allowing each material to perform its optimal function.
3Weight of moving object
If aluminum parts are used to reduce weight, then specific gravity is reduced, but joining difficulty with steel parts increases due to dissimilar metal properties
Solution Approach 1:
The invention changes the joining approach by utilizing spring-back amount differences between materials rather than relying on conventional joining parameters. By selecting materials where the aluminum member (second member) has a larger spring-back amount than the steel member (first member), the joining process benefits from elastic deformation that enhances interference fit and joining strength, thereby reducing joining difficulty despite dissimilar metal properties.
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
The method improves joining strength and durability by defining material properties based on spring-back amounts, reducing thermal strain and maintaining high dimensional accuracy compared to traditional welding methods.
Implementation Method 1
A material of the second member is larger than a material of the first member in a spring-back amount
Implementation Method 2
the curved surface portion having a protruding shape abuts on the outer circumferential surface of the first member. Therefore, the contact area between the first member and the second member increases. Due to the increase in the contact area, the contact pressure between the first member and the second member when a load is applied to the joined body can be reduced
Data Source
AI summary
A joined body includes: a first member having a pipe shape; and a second member including a wall portion having a plate shape, and a flange portion having a cylinder shape provided with an insertion hole through which the first member is inserted. In a state where the first member is inserted into the insertion hole of the flange portion of the second member, the first member and the second member are joined with the first member pipe-expanded. A material of the second member is larger than a material of the first member in a spring-back amount.