|Title:||Numerical study on damage detection of high speed train axle|
Hong Kong Polytechnic University -- Dissertations
|Department:||Faculty of Engineering|
|Pages:||xiv, 174 leaves : ill. (some col.) ; 30 cm.|
|Abstract:||Engineering structure as an assembly constructed by engineering materials to bearing loads and other forces is widely used in civil construction, transportation, urban infrastructure construction etc. However, accidents have been emerging in endlessly due to engineering structure failures, mastering the real time health status of the structures become one of the hotspot in scientific researches. Structural Health Monitoring as a newly emerging online inspection method in engineering structure, its highly effectiveness of directly assessing the structural health status by detecting on the presence and extent of structural damage greatly raised up the interests in technical research on transportation area, such as aerospace structures and railway structures. Among varieties of SHM methods, Structural Health Monitoring based on wave propagation method in basis of the low attenuation, high detection accuracy and long propagation distance is highly valued nowadays. Whereas, most researches using the guided wave propagation based method were applied on simple structures as plane, beam, shell, tube, etc., not structures with complex shapes. To realize guided wave propagation based SHM in complex engineering structures, investigation on the wave propagation mechanism in complex structures becomes the fundamental step. As experimental method requires too much experiment specimen causing unnecessary waste, it is no longer suitable for wave propagation research. Here, simulation with ABAQUS software based on Finite Element Analysis (FEA) method was adopted in this thesis. According to the properties of FEA method and guided wave propagating properties, appropriate setting of corresponding parameters as excitation frequency, excitation amplitude, step intervals and unit sizes etc. in FEA simulation software could insure the accuracy of the simulation result, which not only simplified the needless process in experiment but also increased the precision in wave propagation analysis.|
This thesis started a research on high speed train axle from simplified structure, thick wall hollow cylinder with/without variable cross-section, to real high speed train axle model based on FEA method with ABAQUS software, illustrating wave propagation properties in thick-wall hollow cylinder structure with single cross-section and wave propagating regulation as a result of variable cross-section effect in hollow cylinder structures. Based on the guided wave propagation mechanism and introducing damage in simulation model, a new detection method of inspecting circumferential displacement response signals was raised in axially symmetric hollow cylinder structure as high speed train axle. This new method used axially symmetric excitation to actuate axially symmetric guided wave modes propagating in axially symmetric structures, and structural damage broke the wave propagation symmetry and aroused node vibration in circumferential direction. Detection on circumferential displacement change enabled the damage identification if circumferential displacement response changed from zero to a relatively large scale. This detection method is very sensitive to tiny damages without the necessity of considering the influence by variable cross-section and thickness of hollow cylinder structure. In actual application, manufacturing and assembly accuracy might affect the excitation symmetry, which was required to be in an error range varied from one PZT wafer to three PZT wafers, all in 1 mm offset/ 1-degree angular deflection.
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