Thesis
Study on fatigue life and fracture toughness of sheet metal after laser forming
Washington State University
Master of Science (MS), Washington State University
2003
Handle:
https://hdl.handle.net/2376/132
Abstract
Laser forming (LF) is a highly flexible rapid prototyping and low-volume manufacturing process, which uses laser-induced thermal distortion to shape sheet metal parts without hard tooling or external forces. Analysis of LF process has been focused on geometry change, microstructure change and yield strength in the past. For LF to become a practical rapid prototyping tool, it is critical to study materials’ mechanical properties after laser forming. This project studies fatigue life and fracture toughness of sheet metal after LF. Laser forming differs from other manufacturing processes in that significantly high heating and cooling rates are involved. The results are inhomogeneous microstructure instead of homogeneous microstructure, and at the same time, residual stresses and residual strains are left in the material due to the large thermal gradient through the thickness. These will influence materials’ fatigue life and fracture toughness. However, the current models cannot predict the fatigue life after LF accurately because of differences in assumptions. This work presents a model to predict fatigue life of sheet metal after LF. Results from microstructure integrated finite element modeling of LF are incorporated in the fatigue life model. Low carbon steel is used in this work to validate the model. It is shown that the proposed model can predict the fatigue life of sheet metal after LF with good accuracy. The predictions from the model are consistent with experimental results. Effects of LF conditions on fatigue life of sheet metal are under investigation. After the study on fatigue life, an integrated model to study fracture toughness of sheet metal after LF will be presented. Microstructure, distribution of residual stresses and geometry of sheet metal specimen are considered in the model. Results of residual stress from microstructure integrated finite element modeling of LF are incorporated in the model. The results from the fracture toughness study are found consistent with microstructure analysis
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Details
- Title
- Study on fatigue life and fracture toughness of sheet metal after laser forming
- Creators
- Jun Zhang
- Contributors
- Gary J. Cheng (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525110601842
- Language
- English
- Resource Type
- Thesis