Effect of laser shock forming on surface roughness of targets

In order to study the effects of laser shock forming on the surface roughness,metal sheet of aluminum and 304 stainless steel of 0.5mm thickness are used as samples of laser shock forming,and laser beams with radius of 0.4mm,wavelength of 1054nm and pulse width of 23ns was applied in laser shock forming,while the energy for aluminum sheet was 15.4J and for 304 stainless steel was 18.92J.The measurement results after laser shock forming show that laser shock forming may improve the surface roughness to two roughness rank.There are two reasons for surface roughness improvement.On the one hand,it will generate a series of trasmission wasves and reflection waves when the stress wave spreads in tiny peak of sheet surface,and the tiny peak would rupture if the strength of reflection tensile wave is beyond the tensile strength of targets.On the other hand,a high pressure zone is formed in the air because of high speed motion of sheet,and plastic deformation of tiny peak would take place if the pressure of air acted on the back of sheet is greater than the dynamic bend intensity.So the altitude of tiny peak is decreased by the rupture and plastic deformation of tiny peak and it results in improvement of the surface roughness.