Laser Peening Stress Patterning to Suppress Metal Workpiece Bending
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Solution Overview
Problem
The laser peening process for metal workpieces often results in plastic deformation, leading to compressive residual stress and metal flow, which causes bending and reduces surface strength.
Innovation Solution
A method involving the selective application of tensile and compressive residual stresses using a laser beam to create separated regions on the workpiece surface, where tensile stress regions are isolated by compressive stress regions, and metal flow regions are made to overlap to enhance compressive stress and reduce bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plastic deformation is applied to improve surface strength, then compressive residual stress is generated, but metal flow occurs causing bending
Solution Approach 1:
The laser beam irradiation is segmented into multiple discrete irradiation points arranged in a matrix pattern, creating separated first regions (tensile stress) and second regions (compressive stress) along the surface. This segmentation prevents continuous metal flow that causes bending while maintaining surface strength improvement through distributed compressive stress zones.
Solution Approach 2:
Different regions of the workpiece surface are given different stress characteristics: first regions receive tensile residual stress at isolated points, while second regions receive compressive residual stress in the areas between irradiation points. This local differentiation of stress quality improves surface strength through compressive stress while the isolated tensile stress regions minimize bending influence.
2Strength
If compressive residual stress is applied to improve surface strength, then surface strength is improved, but the process complexity increases
Solution Approach 1:
A single laser beam performs multiple functions: it creates both first regions (tensile stress) at irradiation points and second regions (compressive stress) in between, simultaneously generates plastic deformation and metal flow, and processes multiple areas through matrix arrangement. This multi-functionality achieves surface strength improvement without requiring additional processing equipment or steps.
Solution Approach 2:
The laser beam parameters (irradiation points arrangement, interval, and pattern) are optimized to control the distribution and ratio of first and second regions. By adjusting these parameters, the process achieves desired surface strength improvement while managing process complexity through controlled variable optimization.
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 improves surface strength while suppressing bending, particularly in titanium and titanium alloys, by balancing the ratio of tensile to compressive stress regions and optimizing metal flow patterns.
Implementation Method 1
a laser peening process for processing a surface of a workpiece containing metal is known (for example, Patent Literature 1). In Patent Literature 1, a compressive residual stress is applied to the workpiece by irradiating the surface of the workpiece with a laser beam.
Implementation Method 2
Plastic deformation can occur in the workpiece by irradiating the workpiece with the laser beam. This plastic deformation applies a compressive residual stress to the workpiece.
Implementation Method 3
When plastic deformation occurs in the workpiece, a metal flow occurs in the periphery of a region in which plastic deformation occurs.
Data Source
AI summary
A processed product manufacturing method includes preparing a workpiece containing metal and forming a plurality of first regions and a second region along a surface of the workpiece by the irradiation of a laser beam. The first regions are applied with a tensile residual stress. In the second region applied with a compressive residual stress, a plurality of irradiation points separated from each other in the surface of the workpiece are irradiated with the laser beam. The first regions are formed to be separated from each other and each of the first regions is surrounded by the second region when viewed from a direction orthogonal to the surface.