Composite Elastic Press-Fit Joining for Dissimilar Metal Tubes

Solution Overview

Problem

Existing methods for joining dissimilar metals, such as steel and aluminum, using an elastic body can result in local deformation, permanent strain, or cracking, leading to unfirm joining due to limited pressing force and uneven deformation.

Innovation Solution

A method involving a composite elastic body with different hardness levels, where a harder elastic body is used at stress-bearing areas and a softer elastic body is used at frictional contact areas, allowing for uniform deformation and increased pressing force without local deformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a uniform elastic body is pressed to join dissimilar metals, then the joining process can be simplified, but local deformation, permanent strain, or cracking occurs at the end of the elastic body

Engineering Contradiction:

Improveelastic body structureVSAvoidjoining firmness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The elastic body is constructed with a hardness gradient, where the hardness varies continuously from the center to the surface. The center portion has higher hardness to maintain structural integrity and resist deformation, while the surface portion has lower hardness to reduce friction and prevent local deformation and cracking during pressing. This local quality variation resolves the contradiction by allowing the elastic body to be pressed sufficiently without causing harmful local deformation.

Inventive Principle:

Principle #3Local quality

2Strength

If the elastic body is pressed with high force to achieve firm joining, then the joining strength improves, but the pressing force is not uniformly transmitted due to large frictional force

Engineering Contradiction:

Improvejoining strengthVSAvoiddeformation uniformity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The elastic body's hardness parameter is varied spatially to optimize both force transmission and deformation control. The hardness gradient allows the material to exhibit different mechanical properties at different locations, enabling uniform deformation while maintaining high joining strength. This parameter change resolves the contradiction between achieving high joining strength and maintaining deformation uniformity.

Inventive Principle:

Principle #35Parameter changes

3Strength

If the tube expansion amount is increased to improve joining firmness, then the joining strength improves, but the elastic body undergoes permanent strain or cracking

Engineering Contradiction:

Improvejoining firmnessVSAvoidpermanent strain and cracking

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The elastic body is constructed with a hardness gradient, where the hardness varies continuously from the center to the surface. The center portion has higher hardness to maintain structural integrity and resist deformation, while the surface portion has lower hardness to reduce friction and prevent local deformation and cracking during pressing. This local quality variation resolves the contradiction by allowing the elastic body to be pressed sufficiently without causing harmful local deformation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The elastic body is formed as a composite material with varying composition and hardness throughout its structure. This composite structure combines the benefits of hard material (structural integrity) and soft material (friction reduction) within a single component, enabling the elastic body to withstand high pressing forces without permanent strain or cracking while still achieving firm joining.

Inventive Principle:

Principle #40Composite materials

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 enables firm joining of dissimilar metals by preventing local deformation and allowing for increased bulge amounts of the second member, thereby enhancing the structural integrity of the joined components.

Implementation Method 1

pressing the composite elastic body to cause the second member to bulge out

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the pressing force is not uniformly transmitted to the entire region of the elastic body, which may cause uneven deformation

Methodology Applied

Scientific EffectForce transmission: Mechanical Force

Data Source

PatentUS12202028B2Method for joining members, and composite elastic body used in said method

Publication Date: 2025.01.21 KOBE STEEL LTD

AI summary

A first member provided with a hole, a second member having a tubular shape, and a composite elastic body obtained by combining at least two types of elastic bodies having different hardness are prepared, the second member is inserted into the hole of the first member, the composite elastic body is inserted into the second member, and the composite elastic body is pressed to cause the second member to bulge out, thereby joining the first member and the second member by press-fitting.