Study On Technology Of Laser Induced Dieless Forming Of Stainless Steel Sheet

The bend forming of metal sheet is one of the most common techniques in the industry, which is achieved with the aid of a mold. In order to reduce the cycle of the mold design and the cost of manufacture, that needs to form without a die. Laser induced dieless forming is one of the new forming techniques without a die. Laser induced dieless forming of metal sheet is the thermal stress natural plastic forming, which is base of the performance of flatulence due to heat and shrink, using the laser induce the internal stress. The high accuracy and flexibility of laser provide the unique advance for applying this technique in the practical manufacturing. The forming of the part needs to layout the path to scan several times in the special zones. There are important to research the laws of different laser induced dieless forming and the influence laws of the rate of deformation by the temperature field and stress field. On the base of correlative research work in the world, this paper analysis the influence laws between the laser pulse parameters and the bending angles. And the 3D laser induced dieless forming curved surfaces of metal sheet are achieved by the different scanning strategies. On the time, the forming mechanism is investigated in the paper, which is the square sheet transform to the spherical dome by laser induced dieless forming with spider scanning path. The research works provide the substantial theoretical basis for the accurately forecast of the 3D shape by laser induced dieless forming, and the improvement of the efficient and accuracy of laser induced dieless forming.The paper analyzes the thermal elastic-plastic constitutive model and builds the thermal-stress coupled mathematical model of 3D laser induced dieless forming. In the simulation of the square sheet transform to the spherical dome with spider scanning strategies by laser induced dieless forming, the technique is applied that are the methods of dividing the zone, flux and flow density to deal with the element load, and of following the load to treat with the boundary conditions in every analysis step. In laser heating, the temperature gradient between the upper and bottom surface is the key influential factor of sheet's deformation. The plastic deformation is relative to the temperature gradient. The inertial elastic-plastic stress waves influence the motion state of the particle of sheet directly. The paper illustrates the calculations of stress-strain state and kinematics parameters of the sheet in laser forming process. And that is the base of optimizing the processing parameters for laser induced dieless forming in the future work.In this paper, the 2D and 3D experimental system of Nd:YAG laser induced dieless forming with different scanning strategies are set up. And it illustrates the relationship that the bending angles are influenced by the laser energy, sheet geometry and the material factors. The scanning strategy is proved to be the main influencing factor of 3D sheet laser forming. The cross spider from outer to the center scanning transform the square and circle sheet into a spherical dome, and radial line from center to the outer scanning transform rectangle sheet into a saddle shape. In spite of the symmetry of the whole scanning pattern, the processed lines at any time during the process are not in symmetry, and this makes it difficult to achieve the symmetry of a spherical dome by using square sheet. The height of formed square sheet firstly decreases with the laser scanning velocity increasing and begins to decrease at a certain processing parameters by cross spider strategy, in which the circle sheet is opposite with the square sheet, and in which the rectangle sheet is decreases with speed increasing. The whole height of the formed shape has an increscent trend with the laser power increasing and also increases with the scanning number.This paper shows the specific characters of the pulse laser action and explores the relativity between the formed shape and the laser parameters. The research results show that the bending angles firstly increase quickly as the laser pulse rate increases and begin to decrease slowly at a certain processing parameters. The bending angles have an approximately trend to increase with the pulse width increasing, and the bending angle firstly increases with the laser pulse energy and begins to decrease at certain laser pulse energy, as there is a certain pulse energy parameter resulting in a maximum bending angle for a certain material and processing parameters. The microstructure of heat affected zones of pulse laser scanned is layered, and the micro-hardness, the wear resistance and the acid corrosion resistance are improved than that in the basal body. At last, the paper analyzes the accuracy of the formed shape of 3D laser induced dieless forming, and explores the reasons of the errors by laser induced dieless forming. Give the experimental research on the 3D shape of laser induced dieless forming. On the base of that, the paper discusses the applications in the industry of laser induced dieless forming in the future.