Plate Spring Residual Stress Profile for Fatigue and Sagging Resistance
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Solution Overview
Problem
Plate spring members require improved sagging resistance in addition to fatigue strength, as existing technologies do not effectively address settling resistance and durability simultaneously.
Innovation Solution
A plate spring member with a compressive residual stress distribution where a compressive residual stress of at least 500 MPa is imparted within 50 μm from the surface, and less than 500 MPa beyond 50 μm, along with specific residual stress gradients, to enhance fatigue strength and prevent sagging resistance deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large compressive residual stress is imparted to the deep portion of the plate spring member, then the fatigue strength increases, but the sagging resistance deteriorates
Solution Approach 1:
The patent applies different compressive residual stress levels to different depth regions of the plate spring member. The surface layer (0-50 μm depth) receives high compressive residual stress (≥500 MPa) to improve fatigue strength, while the deeper portions (>50 μm depth) maintain lower compressive residual stress (<500 MPa) to preserve sagging resistance. This spatial differentiation of stress characteristics resolves the contradiction between fatigue strength and sagging resistance.
Solution Approach 2:
The patent segments the plate spring member into two distinct depth zones based on compressive residual stress characteristics: a surface zone (0-50 μm) with high compressive residual stress for fatigue strength enhancement, and a deep zone (>50 μm) with lower compressive residual stress for maintaining sagging resistance. This segmentation allows independent optimization of fatigue strength and sagging resistance in different regions.
2Strength
If shot peening is performed to generate compressive residual stress on the surface, then the fatigue strength improves, but the sagging resistance deteriorates
Solution Approach 1:
The patent modifies the conventional shot peening approach by controlling the compressive residual stress distribution to be localized within the surface layer (0-50 μm depth) with stress magnitude ≥500 MPa, while ensuring that deeper portions (>50 μm depth) maintain stress <500 MPa. This localized stress distribution achieves fatigue strength improvement without the sagging resistance deterioration that occurs with uniform deep compressive stress.
Solution Approach 2:
The patent changes the parameter distribution of compressive residual stress by depth, creating a specific stress profile where the magnitude and depth distribution are precisely controlled. By setting the threshold depth at 50 μm and stress threshold at 500 MPa, the patent optimizes the balance between fatigue strength (improved by compressive stress) and sagging resistance (deteriorated by excessive deep compressive stress).
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 solution improves settling resistance and durability by maintaining high fatigue strength while controlling compressive residual stress to prevent sagging, with the compressive residual stress gradient effectively managed within the plate spring member.
Implementation Method 1
a compressive residual stress distribution in which a compressive residual stress of at least part of a portion within a depth of 50 μm from a surface is 500 MPa or more, and a compressive residual stress of a portion exceeding a depth of 50 μm from the surface is less than 500 MPa
Data Source
AI summary
A plate spring member having a compressive residual stress distribution in which a compressive residual stress of at least part of a portion having a depth from a surface within 50 μm is 500 MPa or more, and the compressive residual stress of a portion having a depth from the surface exceeding 50 μm is less than 500 MPa.