2026-09-20T23:12:00Zhttps://dspace.mit.edu/server/oai/request

oai:dspace.mit.edu:1721.1/343462022-01-13T07:54:36Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023

Taiqing Qiu. Kuo, Long-Sheng, 1969- Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Massachusetts Institute of Technology. Department of Mechanical Engineering 2006-11-06T18:15:21Z 2006-11-06T18:15:21Z 2001 2001 http://hdl.handle.net/1721.1/34346 49014623 Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. Includes bibliographical references (leaves 55-57). Laser interactions with metals involve absorption of photon energy by electrons, energy coupling between electrons and the lattice, and energy transport by diffusion of electrons and lattice vibrations. During picosecond laser irradiation of metal films, electrons and the lattice are not in thermal equilibrium. On the other hand, rapid laser heating produces a large degree of superheating and undercooling during melting and solidification. First, this work investigates experimentally non-equilibrium heating processes during intense picosecond laser heating of metal films. Results show excellent agreement with predictions of the two-step radiation heating model. Second, this work develops a general model to characterize both non-equilibrium energy deposition and phase change processes. The predictions show that the non-equilibrium heating processes significantly increase the laser melting threshold, enlarge the thermal-affected region, reduce the lattice temperature rise, prolong the phase change duration, and reduce the solidification speed. These results are important for materials processing using ultrashort pulsed lasers. by Long-Sheng Kuo. S.M. 57 leaves 2020346 bytes 2022639 bytes application/pdf application/pdf eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Mechanical Engineering. Non-equilibrium energy transfer and phase change during intense picosecond laser-metal interactions Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="04aab058-f6f1-41b9-ba73-dc6179dc1cba"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Non-equilibrium energy transfer and phase change during intense picosecond laser-metal interactions</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2001</PublicationDate> <Authors> <Author> <DisplayName>Kuo, Long-Sheng, 1969-</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Mechanical Engineering.</Keyword> <Abstract>Laser interactions with metals involve absorption of photon energy by electrons, energy coupling between electrons and the lattice, and energy transport by diffusion of electrons and lattice vibrations. During picosecond laser irradiation of metal films, electrons and the lattice are not in thermal equilibrium. On the other hand, rapid laser heating produces a large degree of superheating and undercooling during melting and solidification. First, this work investigates experimentally non-equilibrium heating processes during intense picosecond laser heating of metal films. Results show excellent agreement with predictions of the two-step radiation heating model. Second, this work develops a general model to characterize both non-equilibrium energy deposition and phase change processes. The predictions show that the non-equilibrium heating processes significantly increase the laser melting threshold, enlarge the thermal-affected region, reduce the lattice temperature rise, prolong the phase change duration, and reduce the solidification speed. These results are important for materials processing using ultrashort pulsed lasers.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>