打音法在磁磚黏合完整度偵測之應用

Application of Impact-Acoustics to Detect Tile-Wall Bonding Integrity

張楠(Nan Zhang)

指導教授 ： 劉佩玲

國立臺灣大學/工學院/應用力學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602373

摘要

本研究之主旨在探索打音法於磁磚黏合完整度檢測之應用。打音法係藉由敲擊試體表面使試體產生振動，進而導致週遭空氣之壓力波傳導而產生聲音。對磁磚表面進行打音試驗時，磁磚與結構體有脫黏或無貼黏情況，敲擊所激發之振動模態不同，經由對聲音訊號進行頻譜分析，便可辨識磁磚是否有黏合之現象。
相較先前之研究多以實驗探討磁磚在脫黏狀況下之打音反應，本文以數值模擬對打音法進行參數分析，分析磁磚在各種黏合狀況之聲音響應及其物理現象，並以模型實驗驗證。由數值模擬與模型試驗結果可知，不管磁磚是否有脫黏現象，只要敲擊點位於無脫黏部位，所接收之打音頻率與完全無脫黏之磁磚一致，皆等於敲擊回音公式估算之結構底部回音頻率。磁磚脫黏部位受到敲擊時，會產生薄板撓曲振動，且敲擊脫黏部位之不同位置會激發出不同振動模式。當敲擊點較接近脫黏部位中間，所激發之第一模態能量最大，當敲擊點往脫黏部位邊緣移動，第二或更高模態能量會提高，甚至超越第一模態能量。一般而言，脫黏磁磚之打音頻率低於無脫黏磁磚，但若脫黏面積很小，其打音頻率可能反高於無脫黏磁磚。
傳統打音法係以聲音頻率降低作為脫黏存在之判斷依據，而該聲音頻率應屬打音頻譜中能量最高的尖峰頻率。然根據本研究之試驗結果，該判斷法則似有不足。本文建議改採打音頻譜中第一個尖峰，而非最高尖峰，之頻率作為檢測磁磚黏合完整度之主要依據，檢測流程如下：先以現場採樣或以敲擊回音公式估算無脫黏部位之打音頻率，再對各待測磁磚進行打音試驗。若打音頻譜第一個尖峰頻率與結構底部回音頻率相近，可判定該敲擊點下方無脫黏。若第一個尖峰頻率比結構底部回音頻率高，該敲擊點下方可能有小面積的脫黏存在；若第一個尖峰頻率比結構底部回音頻率低，則脫黏面積較大。對較大面積之脫黏，若要進一步掌握磁磚脫黏部位之面積分佈，可在磁磚表面進行格點式打音試驗，由打音頻譜判斷各格點是落在無脫黏部位、脫黏部位中間、或脫黏部位邊緣，便可描繪出脫黏部位之大略形狀。

關鍵字

打音法 ； 磁磚 ； 單向流固耦合 ； 非破壞性檢測

並列摘要

The objective of this study is to perform impact-acoustics to detect the tile-wall bonding integrity. Impact-acoustics is based on impacting vibration of the object surfaces, making the sounds caused by surrounding pressure of air vibration. We can see the differences between debonded and undebonded tiles and structure when we performing impact-acoustics on the surface of tiles. The differences came from the different vibration modes after impacting the surface of tiles. Therefore, we can analyze the frequency domain from the acoustic signal to recognize if the tile-wall bonding is debonded or not.
Compared to the previous study, most of them use experimental data to get conclusion, we process parameter analysis to impact-acoustics by numerical simulation. We analyzed the response of sounds and physical phenomena from every kind of tile-wall bonding situation, then verified by model experiment. From the results of numerical simulation and model experiment, we found that no matter the tile is debonded or not, as long as the impact location is on the undebonded part, the frequency of undebonded tile is identical with the debonded one. Both of them are equal to the frequency of thickness of structure, which is estimated by the formula of impact-echo. When the debonded part is impacted, flexural vibrations will perform. Different vibration modes will be excited by impacting different debonded location. The closer impacting location to the middle of debonded part, the larger energy of first mode will excited. While changing the impact location to the edge of debonded part, the second mode or the higher mode energy will be excited, even exceed the first mode. Generally, the frequency of debonded tile is lower than undebonded tile, but if the area of debonded is very small, the frequency may even higher than undebonded one.
Traditional impact-acoustics is using the reduction of frequency as a judgment of debonded tile, which belongs to the highest frequency peak on the frequency domain. However, according to the result of this study, the way of judgment is kind of inadequate. This study recommends not to adopt the highest peak on frequency domain, but the first one. The inspection process is as follows: First of all, sampling on site or estimating frequency of undebonded part, then processing impact-acoustics to each test tile. If the first peak on the frequency domain is close to the frequency of structure thickness, we can conclude this impact location of tile is undebonded. If the frequency of first peak is higher than the frequency of structure thickness, the impact location may have a small debonded below. If the frequency of first peak is lower than the frequency of structure thickness, the impact location may have a larger debonded underneath. To further understand the distribution area of debonded parts on the larger tile, performing impact-acoustics experiment with grid on the surface of tile is recommended. Utilizing frequency domain, each point of grid would be judged on the undebonded part, the middle of the debonded part or the edge of debonded part, then we can depict the rough shape of debonded part.

並列關鍵字

Impact-Acoustics ； Tile ； One-Way Fluid-Structure Interaction ； Nondestructive Testing

參考文獻

[16] 葉柏涼,敲擊回音法之時間-頻率域分析與影像法,應用力學研究所,台灣大學,2006.

[3] B.L.Luk,K.P.liu,Z.D.Jiang,F.Tong,Robotic impact-acoustics system for tile-wall bonding integrity inspection,Mechatronics 19(2009)1251-1260.

[4] B.L.Luk,K.P.liu,F.Tong,K.F.Man,Impact-acoustics inspection of tile-wall bonding integrity via wavelet transform and hidden Markov models,Sound and Vibra.329(2010) 1954-1967.

[5] B.L.Luk,K.P.Liu,F.Tong,Rapid evaluation of tile-wall bonding integrity using multiple-head impact acoustic method,NDT&E Int.44(2011)297-304.

[6] F.Tong,S.K.Tso,X.M.XU,Tile-wall bonding integrity inspection based on time-domain features of impact acoustics,Sensors Actuat.A:Phys.132(2006)557-556.