Laser Processing Distance Measurement via Water Jet Acoustic Interface
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Solution Overview
Problem
Existing laser peening technologies face challenges in accurately measuring the distance between the processing point and the sound sensor in air environments, particularly when using a water stream, due to differences in sound velocity between liquids and air, and issues with liquid splash affecting sensor accuracy.
Innovation Solution
A laser processing apparatus that includes a sound sensor fixed to a water nozzle, a timer to measure the time width of the shock wave, and a calculator to calculate the distance based on the propagation time, ensuring stable distance measurement by accounting for the liquid-air interface and minimizing the impact of water splash on the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a sound sensor is used to measure distance in air environment during laser peening, then the measurement can be performed in air without water immersion, but the sound velocity difference between liquid and air causes measurement inaccuracy
Solution Approach 1:
The patent introduces water as an intermediary medium by jetting water to the workpiece surface during laser peening in air. This creates a localized water environment at the processing point that serves as a consistent acoustic medium for shock wave propagation, enabling accurate distance measurement while maintaining overall air environment processing flexibility.
Solution Approach 2:
The patent changes the acoustic medium parameter from pure air to a water-a air interface environment. By controlling water jetting to create a stable water layer at the processing point, the system establishes a known and consistent acoustic propagation path through water and air, allowing for accurate distance calculation despite the interface complexity.
2Adaptability or versatility
If water is jetted to the workpiece to create local watertight condition, then the laser peening can be performed in air environment, but liquid splash affects the sound sensor accuracy
Solution Approach 1:
The water jet serves as an intermediary that creates a controlled acoustic environment. By directing water precisely to the processing point and managing the water stream geometry, the system achieves plasma confinement without allowing uncontrolled splash to reach the sound sensor, thus maintaining both air environment processing and sensor reliability.
Solution Approach 2:
The patent applies water jetting locally only at the processing point rather than immersing the entire workpiece or sensor. This localized application creates the necessary watertight condition for plasma confinement while minimizing water dispersion and splash effects on surrounding components including the sound sensor.
3Measurement precision
If the sound sensor is positioned closer to the processing point to improve measurement resolution, then the distance measurement precision improves, but the liquid splash impact on the sensor increases
Solution Approach 1:
The system preliminarily establishes a controlled water jet structure before laser irradiation occurs. By pre-positioning the water stream and controlling its geometry and flow characteristics, the system creates a stable acoustic path that allows the sound sensor to be positioned optimally close to the processing point while the pre-established water structure protects against splash interference.
Solution Approach 2:
The patent employs dynamic control of the water jet parameters (flow rate, pressure, angle) to adapt to different processing conditions. This dynamic adjustment allows the system to maintain optimal water layer thickness for acoustic measurement while preventing excessive water dispersion that would splash onto the sound sensor, even when the sensor is positioned close to the processing point.
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
Enables precise and stable measurement of the distance between the processing point and the sound sensor during laser peening in air environments, improving the accuracy and reliability of the laser processing method.
Implementation Method 1
A laser light 11a having a pulse width of about several ns is collected on a spot having a diameter of about 1 mm by a light collector 12 to be irradiated onto a workpiece 1. Then, a surface of the workpiece 1 absorbs energy and is turned into a plasma.
Implementation Method 2
In this event, a strong shock wave 7 occurs in the workpiece 1 and the liquid 6. The shock wave propagates in the workpiece to cause plastic deformation and to change a residual stress at a processing point 2 into a compressive residual stress.
Implementation Method 3
a sound sensor 10 configured to detect the shock wave generated at the processing point 2
Data Source
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AI summary
According to an embodiment, a laser processing apparatus (100) has: a laser light source (11); a light collector (12); a water nozzle (5); a sound sensor (10); a timer; and a distance calculator. The light collector (12) collects the laser light (11a) on a workpiece. The water nozzle (5) supplies a water stream to a surface to be treated of the workpiece. The sound sensor (10) is provided at a predetermined position relative to at least one of the water nozzle (5) and the light collector (12), and receives a sound coming from the surface to be treated. The timer detects a detected time width from a reference time point to a time point when the sound sensor (10) receives the sound. The distance calculator calculates a distance from one of the water nozzle (5) and the light collector (12) to the surface to be processed.