Experimental Studies On Quality Assurance Of Laser Shock Processing By The Amplitude And Time-of-flight Of The Shock Wave In Air

Laser Shock Processing is an important part of laser processing technology, and its biggest role is to introduce a high depth of compressive residual stress, which can greatly increase the fatigue life of the workpiece. Currently, one of the key problems is how to real time NDE of laser shock processing, which is also called quality assurance of laser shock processing in U. S. Patent, and it has a very important application prospects for the exploration and research of this technology. This article originates from the research status of domestic and foreign of the technology of quality assurance of laser shock processing and then outlines the methods and principles of these technologies. The patent of time-of-flight is selected as the base of this article, and the technology of real time NDE of laser shock processing is studied and theoretically analyzed. The main contents of this article are as follows:Containment layer is removed to fundamentally understand the time-of-flight of the shock wave in air with acoustic emission sensor, and Al foil is used as the target, which is absorption layer in the technology of laser shock processing. The laser used in the experiment delivers Gaussian pulses of nearly 10 ns full width at half-maximum, and its output energy is 50mJ-1000mJ with its spot diameters of 1mm. The experimental results are analyzed by reference to Taylor solution, and the empirical formula of the energy of the shock wave and the energy of the laser beam is proposed in this paper, which notes that it is feasible to real time NDE of laser shock processing by the method of time-of-flight.The technology of quality assurance of laser shock processing by the amplitude and time-of-flight of the shock wave is studied. The laser used in this experiment delivers Gaussian pulses of nearly 23 ns full width at half-maximum, and its output energy is 5J-15J with its spot diameters of 7mm. The workpiece is 45 steel, the absorption layer is Al foil, and the confinement layer is fluid overlays. The results show that with laser intensities increases, time-of-flight of the shock wave in air decreases nonlinearly, and the amplitude of the shock wave in air and workpiece increases nonlinearly, and the compressive residual stress closes to saturation. Finally, the empirical formulas for the amplitude of the shock wave in air and the amplitude in the workpiece, and for time of flight of the shock wave in air and the compressive residual stress in the workpiece are established, respectively, which could provide theoretical reference for quality assurance of laser shock processing.