The goal of this collaborative research project is to investigate a novel electromagnetic peening-assisted laser micromachining process. The research objectives of the project are to understand responses of a workpiece under the simultaneous action of laser beam radiation and compressive forces generated by electromagnetic induction during machining, and to test the hypothesis that, during the electromagnetic peening-assisted laser micromachining process, the application of electromagnetic forces can generate a beneficial peening effect, enhancing the mechanical properties of the workpiece. A physics-based model will be developed based on continuum mechanics and Maxwell's electromagnetic field theory, which can predict and help understand the process mechanism. The model will be tested by comparing with experiments that include both in-situ observations of the electromagnetic peening-assisted laser micromachining process and the characterization of the processed workpieces. The machining rate, microstructures and residual stresses will be characterized using an optical surface profilometer, scanning and transmission electron microscopes and X-ray diffraction respectively. The fatigue properties of machined samples will also be tested.
If successful, this research will provide an improved understanding of material response under laser radiation and electromechanical forces. The electromagnetic peening effect is expected to enhance the mechanical properties of laser-machined workpieces, with a potential to improve product quality. This technology is environmentally friendly as it does not involve harmful chemicals. Better product quality and longer lifetime decrease the need for re-manufacturing and hence imply less energy and material consumption and less waste generation.
During this project, the evolution of plasma produced by intense nanosecond laser ablation of metal in vacuum under an external magnetic field has been studied using a two-stage model. It has been found that under the investigated conditions, due to the presence of the magnetic field, the plasma velocity is reduced, while the plasma overall temperature is increased, and its parameter spatial distributions (e.g., temperature and density) become relatively more uniform. Using a three-dimensional electromagnetic (EM) and mechanical model, theoretical calculations under the simulated conditions have shown that passing a "coil" with an electric current pulse can induce EM forces in an aluminum alloy workpiece placed nearby, and can generate surface compressive residual stress at the bottom of a pre-existing hole in the workpiece, which, however, requires a very high coil current. An EM shot peening process that requires a lower coil current has been experimentally studied. It has been found that under the studied conditions, the EM shot peening process has enhanced the surface morphology quality around the boundary of a laser-machined microhole, and the surface morphology change also suggests that compressive surface plastic deformation has probably occurred around the hole boundary, which may be potentially beneficial to the material mechanical properties. Intelectural metrit: This project 1) leads to fundamental technology advances by bringinghybrid manufacturing into laser materials processing; 2) provide a quantitative understanding of hybrid physical processes through experimental study and multiphysics simulation, and set up a solid science base for EPALM applications; 3) open new ways to obtain enhanced mechanical properties by studying the hybrid nanostructures formed in EPALM. Broader impact: 1) EPALM will increase the manufacturing efficiency and product qualityof industries related to micromachining, such as electronics, automotive, aerospace, medical device, and optics industries. 2) EPALM will benefit sustainability, environmental protection, and energy and material saving. EPALM is environmentally friendly without involving any harmful chemicals. Better product quality and longer lifetime decrease the need of re-manufacturing and hence imply less energy and material consumption and waste generation. 3) This project will meet the challenges of education in manufacturing through (a) integrating interdisciplinary science and advancedmanufacturing programs in research and education; (b) providing multidisciplinary research opportunities for graduate and undergraduate students to promote discovery and understanding of advanced manufacturing process; (c) outreaching for good undergraduate/graduate students and retaining them in science and engineering, especially underrepresented and minority students.
