@phdthesis{oai:kyutech.repo.nii.ac.jp:00005167,
 author = {Wang,  Zefeng and 王,  澤鋒},
 month = {2017-09-20},
 note = {1 Introduction||2 Extended proportional method and the basic reference problem for the analysis of axisymmetric problems||3 Analysis on Intensity of Singular Stress for Cylinder in Comparison with Bonded Plate||4 Analysis on Intensity of Singular Stress for Bonded Pipe in Comparison with Bonded Plate||5 Analysis on singular stress intensity of ceramic spray coating on hearth roll||6 Conclusion, The bonded axi-symmetric structures have been widely used in the steel and petroleum industries recent years. However, as is known that there is stress singularity at the end of interface for different materials, which may result in the failure of the joint. The intensity of singular stress field （ISSF） was discussed for bonded plate under arbitrary material combination, while few studies are available for the intensity of bonded structures in axi-symmetric problems, and no results with varying material combination. Thus this research focuses on the analysis of ISSF of different axisymmetric problems with arbitrary material combinations, which may contribute to evaluating the strength for axi-symmetric structures. And in addition, the analysis method in this study was applied in the analysis of a practical engineering problem to verify the significance of this study. This thesis is composed of total 6 chapters and organized as follows; Chapter 1 gives an introduction of composites and bonded structures applied to aviation industry, microelectronic packaging, and steel process equipment. Also the applications and importance of bonded axi-symmetric structure are investigated. For example the application in thermal spray coating roll used in continuous annealing furnace and bonded joint of riser pipe in offshore oil equipment. With the extensive application of the technology, structural failure problems are emerging, which requires further study. Then, the issues of the research on singularity in the bonded structures are reviewed, and it is found that there are only few papers focused on the ISSF for bonded axi-symmetric problems. Then, the research purpose of this thesis is introduced, focusing on the analysis of ISSF for bonded axi-symmetric structures. In chapter 2, the proportional method is discussed for axi-symmetric problems. It is known that FEM is not suitable for the solution of bimaterial problems due to the mesh dependence of singular stress near the end of interface. However, FEM is still useful in the analysis of singular stress problems since FEM error can be eliminated by applying the proportional method. This study extends the method to the bonded axisymmetric problems. However, the difference between bonded plane problems and axisymmetric problems makes the application of proportional method quite difficult. This is because non-singular stress appears due to non-zero circumferential strain εθ. Then, non-singular terms are derived explicitly and eliminated from the stress components calculated by FEM to extend this method to axi-symmetric problems. Finally the method is verified by numerical analysis. In chapter 3, the ISSF for the bonded cylinder is first calculated by changing the material combination systematically after extending of the proportional method to axisymmetric problems. Then, the results are compared with that of plane strain problem and the differences are elaborated. It is found that the ISSF of axi-symmetric problem can not be governed by the Dundurs’ parameters, therefore, the maximum and minimum values of the SIFs are considered and shown in tables and charts in the space of Dundurs’ parameters. Chapter 4 mainly focuses on another type of axi-symmetric bonded structure, bonded pipe. The effect of inner radius on ISSF is also discussed. Generally, it is thought that the bonded pipe with an infinite inner diameter is equivalent to the plane strain problem, but it is found that they are quite different. Therefore, the results of bonded pipe with infinite inner diameter are compared with the plane strain problem. As is done in analysis of bonded cylinder in chapter 3, the maximum and minimum values of the ISSF are considered and shown in tables and charts in the space of Dundurs’ parameters. Chapter 5 shows an example of the proposed method applied to a practical engineering problem. By using the aforementioned analysis proposed for bonded axisymmetric structures, a pipe shaped hearth roll used in continuous annealing furnace for producing steel sheet is investigated. Spraying coating is commonly used in the hearth roll. However, after long-term use under high temperature and thermal shock, the spray coating, which is a sandwich bonded structure, will peel off. Thus, Chapter 5 discusses how to improve the strength of the spray coating under thermal shock. It is found that thinner top coating always has better thermal shock resistance. And under fixed top coating thickness, the ISSF takes a minimum value when the coating thickness ratio H/h≅2, which is in accord with the previous research for plane strain state and experimental results in engineering. Here, H and h represent the top coating thickness and bond coating thickness, respectively. In the last chapter of this thesis, chapter 6, main conclusions of this study are summarized for bonded cylinder and boded pipe, and for the optimum design of thermal spray coating., 九州工業大学博士学位論文 学位記番号:工博甲第421号 学位授与年月日:平成28年9月23日, 平成28年度},
 school = {九州工業大学},
 title = {Debonding Strength Evaluation for Bonded Axi-symmetric Bodies in Terms of Intensity of Singular Stress},
 year = {}
}