|
姓名 |
莊偉廉(Wei-Lien Chuang) |
電子郵件信箱 |
E-mail 資料不公開 |
|
畢業系所 |
營建工程系碩士班(Department and Graduate Institute of Constrction
Engineering) |
|
畢業學位 |
碩士(Master) |
畢業時期 |
95學年第2學期 |
|
論文名稱(中) |
混凝土骨材散射效應對暫態彈性波非破壞檢測技術影響之研究 |
|
論文名稱(英) |
The
Investigation on the Scattering Effect of the Aggregates in
Concrete Using the Transient-elastic-wave-based NDT Technologies |
|
檔案 |
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|
論文使用權限 |
校內外完全公開 |
|
論文語文/頁數 |
中文/79 |
|
摘要(中) |
在非破壞的應用中，常會因為混凝土的非均質性影響到應力波的傳遞，尤其是以敲擊式的接收波形更為明顯，使得訊號的判讀受到一些影響。要如何改善此問題，當波長-骨材粒徑比對於敲擊源鋼珠大小的選用，將會變的很重要。當骨材最大粒徑固定時，應選用何種尺寸的鋼珠，才能使訊號變的較為符合檢測方法中均質材料之假設，是此研究之重點。本研究以有限差分法進行數值模擬，針對半無窮域表面位移訊號、音阻抗比對散射效應影響及板型試體散射進行分析，並分別製作不同骨材粒徑之混凝土試體進行實驗與模擬比對，結果可發現數值模擬與實驗之結果趨勢相同。在本研究中可發現實驗的趨勢與模擬相近，因此提供了檢測人員一個參考之依據，當所需檢測訊號較短，也就是說在邊界反射尚未被擷取時，波長-骨材粒徑約6倍以上，可將混凝土視為一均質材料，而當檢測需要用到來回反射訊號時，如板狀試體之檢測、則波長-骨材粒徑約8~9倍以上，才可將混凝土視為均質材料看待。 |
|
摘要(英) |
The
transient-elastic-wave-based nondestructive evaluation
technologies have been successively applied to monitor the
quality of in-situ civil structures. The principle of present
technologies is based on the assumption that concrete is a
homogeneous material. However, the scattering of elastic waves
by the aggregates does affect the analysis of the received
signals when the short-wavelength elastic wave is used to
enhance the resolution of inspection. Finite difference models
were used to simulate the propagation of transient elastic wave
inside concrete structure. The force-time functions of impact
source corresponding to various steel balls were derived from
Hertz contact theory. Surface responses of standard
impact-and-receive operation were obtained based on a
two-material model and a homogeneous model, respectively. The
normalized coherent coefficient of these two received signals
was regarded as the quantitative index of signal distortion
owing to scattering effect. Relations between that coefficient
and key parameters were carefully analyzed. Simulation and
measurement both show that as the ratio of wavelength to
aggregate diameter increases, the scattering effectdecreases.
When the ratio is larger than 6, the normalized coherent
coefficient approaches 0.9 or above. Thus concrete could be
treated as a kind of homogeneous material and then the analysis
assumption of elastic-wave-based NDT principle matches. The
acoustic impedance difference between aggregate and cement paste
seriously affect the normalized coherent coefficient. A proper
elastic wave source for inspecting concrete structures can be
determined according to the estimated wavelength and the maximum
aggregate diameter. |
|
關鍵字(中) |
波長-骨材粒徑比
|
關鍵字(英) |
Scattering Effect of the Aggregates in Concrete
|
|
口試委員 |
童建樺 - 召集委員
李明君 - 委員
楊哲化 - 委員
江支弘 - 指導教授
|
|
口試日期 |
2007-07-18 |
繳交日期 |
2007-08-22 |