| 摘要 | 第6-7页 |
| Abstract | 第7-8页 |
| Chapter 1.Introduction | 第14-23页 |
| 1.1 Motivation | 第14-15页 |
| 1.2 The definition of spot weld | 第15-17页 |
| 1.3 Previous Work in Evaluation spot weld | 第17-21页 |
| 1.3.1 Destructive testing method | 第17-19页 |
| 1.3.2 Non-destructive testing method | 第19-21页 |
| 1.4 Theoretical objectives | 第21-23页 |
| Chapter 2.Basic Principles of air-coupled guided waves testing spot welds | 第23-28页 |
| 2.1 The definition of guided waves | 第23-24页 |
| 2.2 Impedance mismatch | 第24页 |
| 2.3 Leaky guided wave | 第24页 |
| 2.4 Boundary condition between air and solid plate | 第24-25页 |
| 2.5 Air coupled ultrasonic guided wave to detect spot welds | 第25-28页 |
| Chapter 3.Simulations | 第28-47页 |
| 3.1 Introduction of simulation software | 第28-29页 |
| 3.2 Parameter selection in Multiphysics COMSOL | 第29页 |
| 3.3 Geometries of simulation models | 第29-33页 |
| 3.4 Simulation the influence of different factors | 第33-40页 |
| 3.4.1 Intensity at different incidence angles | 第35-36页 |
| 3.4.2 Transducer-plate air gap reflections | 第36-37页 |
| 3.4.3 Distance between sender and receiver | 第37-38页 |
| 3.4.4 Different position of transducers | 第38-40页 |
| 3.5 Simulation to inspect spot weld | 第40-47页 |
| 3.5.1 Detection spot weld with 280kHz unfocused transducer | 第40-44页 |
| 3.5.2 Detection spot weld with 500kHz focused transducer | 第44-47页 |
| Chapter 4.Experiments | 第47-58页 |
| 4.1 Experiment set-up | 第47-48页 |
| 4.2 Validation the influence of different parameters | 第48-52页 |
| 4.2.1 Intensity at different incidence angles | 第48-49页 |
| 4.2.2 Transducer-plate air gap reflections | 第49-50页 |
| 4.2.3 The influence of distance between transducers | 第50-51页 |
| 4.2.4 The influence of transducers position | 第51-52页 |
| 4.3 Validation the simulation result when inspecting spot weld | 第52-56页 |
| 4.3.1 Detection spot weld with 280kHz unfocused transducer | 第52-54页 |
| 4.3.2 Detection spot weld with 500kHz focused transducer | 第54-56页 |
| 4.4 Comparison between simulation and experiment | 第56-58页 |
| General Conclusion | 第58-59页 |
| Recommendations for Future Research | 第59-60页 |
| Acknowledgements | 第60-61页 |
| References | 第61-65页 |
| 攻读硕士学位期间发表的论文及科研成果 | 第65页 |
