Electro-Pulse Assisted Deep Rolling With Lower Rolling Force
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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 when conventional tooling and robotic machines are insufficient to generate the required pressure.
Innovation Solution
A method combining multi-axis powered machines with deep rolling tools and electro-pulsed current application to induce plastic deformation and electroplastic effects, refining the grain structure and increasing dislocation sources and tangles, thereby enhancing residual compressive stresses with reduced normal force requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional deep rolling tooling and robotic machines are used to apply force to the workpiece surface, then compressive residual stress can be induced in the near-surface layers, but the maximum force that can be applied is limited, restricting the process to certain components and materials
Solution Approach 1:
The patent combines conventional mechanical deep rolling with electro-pulsed current application in a hybrid process. The electro-pulsed current is applied through the rolling tool to the workpiece surface during the rolling operation, merging two different energy forms (mechanical and electrical) to achieve enhanced plastic deformation at lower mechanical forces, thereby expanding applicability to more components and materials
Solution Approach 2:
The patent partially replaces the mechanical force system with an electro-pulsed current system. Instead of relying solely on high mechanical rolling force to induce plastic deformation, the electro-pulsed current provides an additional mechanism for inducing electroplastic effects that facilitate grain structure refinement and dislocation generation, reducing the dependency on high mechanical forces
2Strength
If higher rolling force is applied to achieve desired compressive residual stress profile, then surface strength and subsurface compressive residual stresses are enhanced, but the tooling and robotic machines may be limited in the amount of tool pressure that can be generated
Solution Approach 1:
The electro-pulsed current acts as an intermediary mechanism that facilitates plastic deformation and grain structure refinement without requiring proportionally high mechanical forces. The electrical energy serves as a mediator that enables the rolling process to achieve enhanced surface strength and compressive residual stresses while operating within the force limitations of conventional tooling
Solution Approach 2:
The patent changes the physical state and properties of the workpiece material by applying electro-pulsed current during rolling. The electroplastic effects induced by the pulsed current alter the material's deformation characteristics, enabling grain structure refinement and increased dislocation density at lower mechanical pressures, thereby achieving enhanced strength without exceeding tooling capabilities
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 allows for the refinement of grain structure and increased dislocation sources deeper into the near-surface region, resulting in enhanced fatigue strength and increased residual compressive stresses, making it possible to process a broader range of materials and components with less normal force than conventional methods, and improving surface smoothness and mechanical properties.
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
The amount of rolling force applied is also significant in terms of whether a process like deep rolling can be used for a given component... producing compressive residual stress within the workpiece
Data Source
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AI summary
A mechanical surface treatment method for a workpiece (22) is provided that includes a) using a multi-axis powered machine (28) to actuate a deep rolling tool (30) having a roller (44) relative to the workpiece (22), the actuating including applying the roller (44) against a workpiece surface with a normal force sufficient to plastically deform the workpiece (22) and translating the roller (44) relative to the workpiece surface; and b) 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 producing 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.