A volumetric heat source finite element model is proposed to simulate the key hole effect during the Nd:YAG pulse laser welding. The measured data has been used to correlate the volumetric model parameters and the laser parameters. The laser power distributed in the beam cross area is in a Gaussian type. Two heat transfer models are employed in the fusion area, i.e the surface absorption heat transfer model in the low power intensity region and the keyhole heat transfer model in the high power intensity region. An experimentally measured critical power intensity is introduced to identify the occurrence of keyhole effect. The value of critical power intensity is dependent on the welding material. A series of MARC finite element simulations based on the proposed single pulse model are performed to investigate the feasibility and accuracy of this proposed pulse laser welding model. Different power and welding duration pulse laser have used to weld the S304L specimens. The results indicate a good agreement between the simulated and measured shape and size of the weld pool with different laser energy intensities. The validity of the proposed model is confirmed for the S304L steel. The temperature and residual stress distributions around the welding pool in a continuous pulse welding and two sheet overlap welding have also been studied by using the proposal model. The numerical results indicate that the pulse energy, duration and dwell period may affect the residual stress distribution and post-weld deformation significantly. All these results reveal that the proposed volumetric heat source finite element model is a feasible model to analyze the welding phenomena during the pulse laser welding. The results indicate that the pulse dwell period increase in dual pulse laser welding the residual stress decrease on the top of the weld spot surface. The results also show the lower residual stress in multi spots pulse laser welding with smaller weld spots center pitch and weld spot dwell period.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0608112-155652 |
| Date | 08 June 2012 |
| Creators | Hung, Tsung-Pin |
| Contributors | Chi-Hui Chien, Der-Min Tsay, Ying-Chien Tsai, Jao-Hwa Kuang, Ming-Hua Jen, Yung-Chuan Chen, Shyh-Chour Huang, Bo-Wen Huang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0608112-155652 |
| Rights | unrestricted, Copyright information available at source archive |
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