Shock Wave Surface Treatment for Deeper Fatigue Strengthening
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Solution Overview
Problem
Current surface treatment methods do not adequately enhance the fatigue strength of workpieces, particularly in suppressing crack progression and initiation.
Innovation Solution
A surface treatment method involving a combination of applying a plane wave-shaped shock wave for high-density transition and subsequent plastic deformation using a spherical wave-shaped shock wave or physical contact, which induces residual compressive stress and deformation-induced martensite transformation, effectively reducing the likelihood of crack occurrence and progression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If only shot peening treatment is performed, then compressive residual stress is applied to the surface, but the effective processing depth is limited and fatigue strength cannot be further improved
Solution Approach 1:
The surface treatment is divided into two distinct steps: first applying a plane wave-shaped shock wave for high-density transition at deeper layers, then applying a spherical wave-shaped shock wave or physical contact for plastic deformation at the surface. This segmentation allows each step to target specific depth zones, achieving both deep residual compressive stress and surface crack suppression without the depth limitations of conventional single-step methods
Solution Approach 2:
The invention transitions from conventional single-dimensional surface treatment to multi-dimensional treatment by combining two different shock wave propagation patterns (plane wave for depth, spherical wave for surface) and optionally physical contact. This dimensional approach enables simultaneous effective treatment at different depths, with the plane wave reaching deeper positions (0.3mm or greater) while the spherical wave and physical contact address the surface layer (50μm or less)
2Reliability
If conventional surface treatment methods are used, then some crack suppression is achieved, but crack initiation points cannot be reliably eliminated
Solution Approach 1:
The first step of applying plane wave-shaped shock wave for high-density transition is performed as a preliminary action before the second step of plastic deformation. This preliminary treatment creates a dense material structure that suppresses crack progression, while the subsequent plastic deformation step eliminates crack initiation points. The sequential preliminary action ensures both crack suppression and fatigue strength improvement
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 significantly improves the fatigue strength of workpieces by applying residual compressive stress to a deeper surface layer and reducing the starting point for cracks, outperforming existing methods like shot peening.
Implementation Method 1
a plane wave-shaped shock wave is applied to a workpiece to cause high-density transition to occur in a material structure of a workpiece
Implementation Method 2
the workpiece after the first step is subjected to plastic deformation. This plastic deformation is performed by applying a spherical wave-shaped shock wave or a pressure due to physical contact to the workpiece
Implementation Method 3
In the second step, the material structure of the workpiece may be subjected to deformation-induced martensite transformation. In this case, volume expansion occurs in a metal structure, and strain is caused to occur in a parent phase
Implementation Method 4
a compressive residual stress can be applied to a surface of the steel part. Accordingly, even when a crack occurs on a surface when the steel part is used, progress of the crack is suppressed
Data Source
AI summary
A surface treatment method includes: a first step of applying a plane wave-shaped shock wave to a workpiece to cause high-density transition to occur in a material structure of the workpiece; and a second step of applying a spherical wave-shaped shock wave or a pressure due to physical contact to the workpiece after the first step for plastic deformation of the workpiece.