Electro-Pulse Assisted Deep Rolling for Low-Force Surface Strengthening
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Solution Overview
Problem
The deep rolling process for enhancing surface strength and subsurface compressive residual stresses in metallic substrates is limited by the maximum force that can be applied, which restricts its application to certain components and materials, especially those with complex geometries or requiring higher pressures than conventional tooling can generate.
Innovation Solution
A method combining electro-pulsed current with deep rolling using a multi-axis powered machine to apply a roller with a normal force sufficient for plastic deformation, concurrently producing an electroplastic effect that refines the grain structure and increases dislocation sources and tangles, thereby enhancing residual compressive stresses without the need for excessive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional deep rolling process is used to enhance surface strength and compressive residual stresses, then surface strength is improved, but the process is limited by maximum applicable force which restricts use on certain components and materials
Solution Approach 1:
The patent combines conventional deep rolling process with electro-pulse treatment to create a hybrid process. The electro-pulse current is applied simultaneously with the mechanical rolling action, merging two different physical mechanisms (mechanical deformation and electroplastic effect) to achieve enhanced surface strengthening without requiring excessive mechanical force alone.
Solution Approach 2:
The patent introduces electro-pulse parameters (current density, pulse duration, frequency) as additional control variables to the traditional deep rolling process. By changing these electrical parameters, the process can achieve the desired plastic deformation and residual stress state without being constrained by the mechanical force limits of conventional tooling.
2Stress or pressure
If higher rolling force is applied to achieve desired compressive residual stress profile, then residual stress is improved, but component complexity or tooling limitations prevent application of sufficient force
Solution Approach 1:
The patent partially replaces the mechanical force generation system with an electro-pulse system. Instead of relying solely on mechanical rolling force to achieve plastic deformation and residual stresses, the electro-pulse current induces electroplastic effects that assist the mechanical deformation process, reducing the dependency on high mechanical forces that would be difficult to apply to complex geometries.
3Adaptability or versatility
If conventional deep rolling is used on materials with varying mechanical properties, then processing is limited by tool pressure capabilities, but electro-pulse assistance enables processing of diverse materials
Solution Approach 1:
The hybrid deep rolling-electro-pulse process becomes a universal treatment method that can be applied to a wide range of materials with different mechanical properties. The electro-pulse component provides a material-independent mechanism for assisting plastic deformation, making the process adaptable to both soft and hard materials, unlike conventional deep rolling which is constrained by tooling pressure capabilities for each specific material.
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 approach reduces the required normal force for plastic deformation, allows processing of materials with varying mechanical properties, and achieves deeper refinement of grain structure and increased dislocation sources, resulting in enhanced fatigue strength and surface smoothness.
Implementation Method 1
concurrently applying an electro-pulsed current to the workpiece surface in a manner that produces an electroplastic effect at the workpiece surface and a near surface region contiguous with the workpiece surface, the electroplastic effect and the plastic deformation producing a refinement in a grain structure at the workpiece surface and a near surface region and an increase in dislocation sources and tangles within the grain structure
Implementation Method 2
applying the roller of the deep rolling tool against a workpiece surface with a normal force sufficient to plastically deform the workpiece
Implementation Method 3
applying the roller of the deep rolling tool against a workpiece surface with a normal force sufficient to plastically deform the workpiece and translating the roller of the deep rolling tool relative to the workpiece surface; the actuating including applying the roller of the deep rolling tool against a workpiece surface with a normal force sufficient to plastically deform the workpiece and translating the roller of the deep rolling tool relative to the workpiece surface; applying the roller produces compressive residual stress within the workpiece
Data Source
AI summary
A mechanical surface treatment method for a workpiece includes using a multi-axis powered machine to actuate a deep rolling tool having a roller relative to the workpiece. The actuating includes applying the roller against a workpiece surface with a normal force sufficient to plastically deform the workpiece and translating the roller relative to the workpiece surface. The method includes concurrently applying an electrical current to the workpiece surface in a manner that produces an electroplastic effect at the workpiece surface and a near surface region. The electroplastic effect and the plastic deformation produce a refinement in a grain structure at the workpiece surface and near surface region and an increase in dislocation sources and tangles within the grain structure.