Pulsed Laser With Underwater Metal Targets The Interaction Of The Mechanical Effects Of Experimental Research

The interaction of pulsed laser and underwater target will cause shockwave and the cavitation phenomenon, laser-induced shockwave and cavitation bubble collapse jet impact on target will produce mechanical effect, this is an important basis of laser liquid processing and laser eye medical surgery. Mainly from the angle of experiment, this article measure and analysis the pulse signal produced by interaction of laser pulse and underwater metal material.The basic mechanism of mechanical effect produced by the interaction of laser pulse and underwater metal material is analyzed; Present a point load model of mechanics effect by laser irradiation target, point out the elastic deformation measuring mechanism. Based on the coupling of light intensity of light deflection, build the optical fiber mechanical quantity sensor. With target, it is a field measurment system, the linear range and conditions of how to reduce sensor measuring error are discussed.The mechanical signal of copper target in air and water is measured. Identify laser ablation force (plasma shock wave force) and two jet wallop, According to the ablation force peak'a'and the first jet peak'b''s time interval, we get cavitation bubble collapse cycle of 30mJ pulse. Experiment find that the underwater ablation force peak is 3.72 times that of air when pulse energy is 30mJ; Measure mechanical signal of underwater copper target with different energy laser pulse, the result show the target receive laser ablation force and two jet wallop. The ablation and jet wallop both have threshold energy, three pulse force peaks amplitude all rise and then fall with laser energy's changes, mainly water's threshold is the influence. The laser ablation force depends on the pulse energy, while jet wallop's appear and the amplitude of the impact based on two factors of nondimensional parameters y and pulse energy; Measure the mechanical signal of underwater copper target when there is a constrained cylinder cavity for cavitation bubble. The experiment show that, under constrained mode, jet wallop peak b and c are increasing compared with unconstrained cavity, the more smaller diameter and bigger height of cavity, the more jet wallop increase. While the laser ablation force peak change little, mainly because the constraints of cylinder affect the formation mechanism of jet which is of no effect to ablation force.