Laser Shock Peening Fluid Confinement Layer for Energy Delivery
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Solution Overview
Problem
Existing Laser Shock Peening (LSP) processes face limitations due to air breakdown and size constraints, particularly with thin water layers and submersion methods, which affect energy delivery and component treatability.
Innovation Solution
A system that uses a thick fluid layer with a constant thickness to induce a secondary shock event through cavitation, eliminating air-fluid interfaces and allowing direct fluid contact with the target, while measuring the first bubble oscillation period for diagnostic energy transfer monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thin water layer is used in conventional LSP, then the process can be applied to larger components, but air breakdown occurs and energy delivery becomes unreliable
Solution Approach 1:
The patent introduces a thick fluid layer (typically water) as an intermediary medium between the laser beam and the target component. This fluid layer eliminates air breakdown by replacing the air medium with a non-combustible fluid, while still allowing laser energy to transmit through to the target. The fluid layer thickness is specifically controlled (typically 1-10 mm) to prevent air breakdown while maintaining component accessibility.
Solution Approach 2:
The patent changes the physical parameter of the confinement medium from air to a liquid fluid (typically water). This parameter change eliminates the combustion issue inherent in air, allowing reliable energy delivery. The fluid's optical properties are selected to maintain laser transmission while providing the necessary confinement for shock wave generation.
2Reliability
If a thick fluid layer is used to prevent air breakdown, then energy delivery repeatability improves, but the system complexity increases
Solution Approach 1:
The thick fluid layer serves as a simple intermediary that prevents air breakdown without requiring complex additional components. The fluid can be delivered through straightforward mechanisms such as pumps, nozzles, or spray systems, avoiding the need for complex vacuum chambers or atmospheric control systems.
Solution Approach 2:
The patent employs hydraulic principles by using a liquid fluid (typically water) under controlled flow to create the confinement layer. This approach leverages well-understood fluid delivery mechanisms, keeping the system relatively simple while achieving reliable energy delivery through the elimination of air breakdown.
3Ease of manufacture
If conventional SP is used, then the process is simple and well-established, but the affected depth of the plastically deformed region is shallow
Solution Approach 1:
The patent replaces the mechanical impacting system of conventional shot peening with a laser-based system. Instead of mechanically propelling particles at the target, a high-power laser generates a shock wave through a fluid medium, which then induces plastic deformation. This substitution enables much greater penetration depth while maintaining process control.
Solution Approach 2:
The laser pulse induces rapid phase transitions in the target material surface, creating a high-pressure plasma state that generates a shock wave. This phase transition mechanism allows energy to be delivered deep into the material, overcoming the shallow penetration limitation of mechanical shot peening.
4Length of moving object
If LSP is used to increase affected depth, then compressive residual stresses are introduced to greater depth, but plasma breakdown may occur
Solution Approach 1:
The patent uses a liquid fluid (typically water) as an inert confinement medium that prevents plasma breakdown. The fluid's high dielectric strength and lack of combustibility create an environment where laser-induced plasma cannot sustain itself, eliminating the harmful breakdown effect while still allowing the desired shock wave generation and deep penetration.
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 enhances energy delivery repeatability, reduces plasma breakdown, and allows for higher frequency laser pulses, improving the depth and uniformity of compressive residual stress induction in metal components.
Implementation Method 1
An intense pulsed laser beam irradiates a target at power intensities in the range of 1 to 10 GW/cm2. The incident high intensity irradiation results in vaporisation of the target surface which expands rapidly as a partially ionised gas, which is also referred to as plasma
Implementation Method 2
a second shock event through cavitation in the fluid layer occurs upon the collapse of a plasma/vapour bubble generated after the laser pulse striking the target
Implementation Method 3
The rapid pressure pulse due to the plasma expansion generates a shockwave that propagates through the metallic target, resulting in a uniaxial dynamic strain and plastic deformation
Data Source
AI summary
The invention is concerned with a system for performing Laser Shock Peeing on a target (100). The system includes a device (10) for generating and transmitting a laser pulse to the target (100) and a fluid source for supplying a fluid into a fluid flow path arranged between an inlet (20) and an outlet (22.1, 22.2). A solid medium (14), which is transparent to incident laser light (12), is located in the laser path so as to allow the laser pulse to pass through it. In use, the fluid flow path is sandwiched between the solid medium (14) and the target (100) during the laser shock peening process so that the fluid is in direct contact with the solid medium (14) and the target (100), thereby eliminating any air-fluid interface in the travel path of the laser pulse. The fluid is also supplied into the fluid flow path having a constant thickness such that a second shock event through cavitation in the fluid layer occurs upon the collapse of a plasmalvapor bubble generated after the laser pulse striking the target. The invention also concerns a method of performing Laser Shock Peeing using the system in accordance with the invention and, in particular, the use of the first bubble oscillation period to determine the amount of energy being delivered to the target (100). The monitoring of the energy being delivered to the target (100) provides for process diagnostics during the LSP procedure.