Variable Fluence Laser Shock Peening for Thin Airfoils
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser shock peening methods face challenges in efficiently processing small, thin components like gas turbine engine airfoils, as they are prone to delamination, which requires costly 100% inspection and reduces the effectiveness of compressive residual stresses.
Innovation Solution
A variable surface fluence laser shock peening method that adjusts the laser beam's pulse fluence based on the thickness of the article, using a constant volumetric fluence factor of 1200J/cm3 to 1800J/cm3, particularly 1500 J/cm3, to minimize delamination by varying the laser energy for each spot or in groups of spots, allowing for efficient processing of thin sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional laser shock peening is used on thin articles with varying thickness, then compressive residual stresses are produced, but delamination occurs due to excessive energy on thin sections
Solution Approach 1:
The patent applies local quality by varying the laser pulse fluence according to the local thickness of the article. Different regions receive different fluence levels - thinner sections receive lower fluence while thicker sections receive higher fluence, optimizing the compressive stress generation while preventing delamination in thin areas.
Solution Approach 2:
The patent implements dynamics by making the laser fluence adjustable and variable during the processing operation. The system dynamically adapts the fluence level based on real-time or pre-programmed thickness information, allowing the process parameters to change continuously across different zones of the workpiece.
2Strength
If uniform high fluence is applied across the entire surface, then deep compressive stresses are achieved in thick sections, but thin sections suffer delamination
Solution Approach 1:
The patent divides the processing area into zones with different fluence requirements based on local thickness. Each zone receives a customized fluence level, ensuring that thick sections get sufficient energy for deep compressive stresses while thin sections receive reduced energy to maintain structural integrity and avoid delamination.
3Object-affected harmful factors
If variable fluence is applied to prevent delamination, then thin sections are protected, but processing time increases due to individual spot adjustment
Solution Approach 1:
The patent segments the workpiece surface into discrete zones or regions with similar thickness characteristics. Instead of adjusting every single spot individually, the system applies fluence variations at the zone level, which reduces the number of adjustments needed while still preventing delamination across the entire surface.
Solution Approach 2:
The patent uses pre-programmed fluence profiles based on predetermined thickness information of the workpiece. The variable fluence parameters are calculated and stored before processing begins, allowing the system to automatically select appropriate fluence levels without real-time calculation delays, thus maintaining processing efficiency.
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 effectively reduces delamination in thin gas turbine engine airfoils by optimizing the laser pulse fluence according to thickness, enhancing the processing efficiency and maintaining the beneficial compressive residual stresses without the need for extensive inspection.
Implementation Method 1
producing an explosive force at the impingement point of the laser beam by an instantaneous ablation or vaporization of a thin layer of that surface or of a coating (such as tape or paint) on that surface which forms a plasma
Implementation Method 2
producing an explosive force at the impingement point of the laser beam by an instantaneous ablation or vaporization of a thin layer of that surface
Implementation Method 3
The pressure pulse from the rapidly expanding plasma imparts a traveling shockwave into the component. This compressive shockwave initiated by the laser pulse results in deep plastic compressive strains in the component.
Implementation Method 4
This medium enables the plasma to rapidly achieve shockwave pressures that produce the plastic deformation and associated residual stress patterns that constitute the LSP effect. The curtain of water provides a confining medium, to confine and redirect the process generated shockwaves into the bulk of the material of a component being LSP'd
Data Source
AI summary
A method for laser shock peening an article, such as a gas turbine engine airfoil, with varying thickness by varying a surface fluence of a laser beam over a laser shock peening surface as a function of the thickness beneath a laser shock peened spot formed by the beam on the surface. The fluence may be equal to the thickness multiplied by a volumetric fluence factor, the volumetric fluence factor being held constant over the laser shock peening surface. The volumetric fluence factor may be in a range of about 1200 J/cm3 to 1800 J/cm3 and more particularly about 1500 J/cm3. The method may include varying energy in the laser beam using a computer program controlling firing of the laser beam. A device such as an optical attenuator external to a laser performing firing may be used to vary the energy.