Arcuate Spring Induction Hardening for Fatigue Life
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Solution Overview
Problem
Current methods for forming arcuate springs are complex, time-consuming, and costly, with existing processes like arc opening being inefficient, leading to high manufacturing costs and internal stresses in the springs.
Innovation Solution
The process involves induction hardening to form arcuate springs by initially forming a straight spring, prestressing it, and then heat treating using induction heating to relieve stresses and create an arcuate shape, significantly reducing manufacturing time and internal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the arc opening process is used to form the arcuate spring, then the arcuate shape is achieved, but the manufacturing time is very time consuming
Solution Approach 1:
The patent applies induction heating to rapidly heat the spring material to austenite transformation temperature, changing the thermal parameters to enable martensitic transformation upon cooling. This thermal parameter change allows the spring to be formed into the arcuate shape during the phase transformation process, achieving the desired shape while dramatically reducing manufacturing time compared to traditional arc opening processes
Solution Approach 2:
The patent utilizes the phase transition of steel from austenite to martensite through induction heating and rapid cooling. The spring material is heated to transform to austenite, then rapidly cooled to transform to martensite, which has different mechanical properties. This phase transition enables the material to be formed into the arcuate shape during transformation while minimizing residual stresses and reducing manufacturing time
2Shape
If traditional arc opening process is used, then the arcuate spring is formed, but internal stresses are generated in the spring
Solution Approach 1:
The patent utilizes controlled phase transition of the spring material from austenite to martensite through induction heating and rapid cooling. This phase transition occurs uniformly throughout the material, allowing the arcuate shape to be established during transformation rather than by forcing a pre-formed spring into shape. This eliminates the generation of internal stresses that would otherwise occur during mechanical forming
Solution Approach 2:
The patent replaces the traditional mechanical arc opening process with an induction heating-based forming method. Instead of mechanically forcing the spring into an arcuate shape (which generates internal stresses), the invention uses thermal energy to transform the material phase and enable shape change during transformation. This substitution of mechanical forming with thermal-phase transformation eliminates harmful internal stresses
3Ease of manufacture
If multiple shorter straight springs are used instead of one long bowed spring, then the assembly is completed, but the device complexity increases
Solution Approach 1:
The patent creates a single arcuate spring that can replace multiple shorter straight springs in the vibration damper assembly. By forming one continuous spring with the desired arcuate geometry through induction heating, the invention eliminates the need for multiple separate spring components, thereby reducing assembly complexity while maintaining the necessary functional segments for vibration damping
Solution Approach 2:
The patent merges multiple separate spring components into a single integrated arcuate spring. By using induction heating to form one continuous spring with the appropriate arcuate shape and dimensions, the invention combines the functions of multiple shorter springs into a single component, reducing the number of parts and simplifying the overall assembly
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 results in springs with improved residual stress rates, increased fatigue life, and reduced manufacturing costs, enabling the production of high-strength arcuate springs with enhanced performance and durability.
Implementation Method 1
heating the spring by induction heating
Implementation Method 2
heat treating the spring by induction heating at elevated temperatures for a sufficient time to relieve stresses in the spring
Implementation Method 3
cooling the arcuate spring to lower (e.g., ambient) temperatures
Data Source
Figure 1~2
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Figure 5
AI summary
An arcuate spring having a plurality of coils which are configured and dimensioned to provide an arcuate shape to the spring and being substantially free of internal stresses which would tend to urge the coils into linear alignment. The spring is designed to function under load conditions while maintaining its natural arcuate shape. The spring is can be heated by use of an induction heating process.