鋼筋混凝土為當今土木工程不可或缺之營建材料，當混凝土負載過重或發生材料劣化時，往往造成環境中不良因子透過混凝土開裂路徑接觸內部鋼筋，造成鋼筋銹蝕等損傷情況，降低鋼筋混凝土安全性。以非破壞性檢測鋼筋表面銹蝕對鋼筋應力波傳遞行為之影響，有助於對已銹蝕鋼筋混凝土構造物提出妥善修護策略，延長構造物使用年限。
本研究應用超音波脈衝反射檢測方法，探討超音波於有刻痕竹節鋼筋及光面鋼棒傳遞過程之行為。以車床技術在鋼筋/鋼棒上刻鑿出刻痕，試驗變數包括刻痕距離(300 mm、600 mm、900 mm)、深度(鋼筋直徑 10%、20%、40%)、長度(5 mm、10 mm、30 mm、50 mm、100 mm)、斷面形狀(矩形和圓弧)、鋼筋在粗細粒料體積比為1:1 (RC1)、1:2 (RC2)及1:3 (RC3)等三種不同混凝土之相同50 mm保護層厚度時，各別在養護時間為7天、14天、28天進行超音波檢測，並利用有限元素法模擬裸露光面鋼棒在各試驗變數之波傳行為。
研究結果顯示：(1)超音波脈衝檢測法在檢測距離方面非常優異，平均誤差僅1.73%；(2)反射回波振幅隨著深度增加有顯著上升趨勢，但竹節鋼筋在深度10%時，因訊號隱沒於因圓圍邊界反射引致雜訊中，故不論刻痕距離遠近都無法獲取末端反射回波；(3)刻痕長度反射訊號易受邊界與刻痕深度干擾，使結果難以總結趨勢；(4)圓弧刻痕形成之回波振幅平均小於垂直平面刻痕約2.42 mV；(5)鋼筋在RC2披覆混凝土於養護天數28天時，可獲得最小之振幅，比7天與14天養護時間低9.80%到22.44%之間；(6)當RC2混凝土保護層處在面乾內飽和狀態時，與鋼筋間具有較佳鍵結狀狀態，因此，埋設鋼筋在三個養護時間所測得振幅值最小。
數值模擬發現：(1)刻痕位置300 mm到 600 mm的反射波振幅平均降低13.41μm，而振幅由刻痕位置600 mm到 900 mm則平均降低159.82 μm，意即振幅隨刻痕位置越遠而降低；(2)刻痕深度越深，頻率域之回波振幅越大，當刻痕深度10%到20%以及深度20%到40%振幅分別平均增加42.83 μm、510.31 μm；(3) 圓弧刻痕之振幅值平均低於相同深度之方形刻痕45.41 μm。

Reinforced concrete (RC) is current an indispensable construction material in civil engineering. Once the RC is subjected to excessive load or has material deterioration, it often leads to the deleterious factors from environment being reacted with the interior reinforcing bars via the path of concrete cracking to cause the corrosion of reinforcing bars and reduce the safety of RC structure. By using the non-destructive testing to examine the effects of surface corrosion of reinforcing bar on the propagation behavior by stress wave, it is helpful to propose a proper maintenance strategy for corroded RC structure, and extend the its service life.
This study uses the ultrasonic pulse-echo detection methods to explore the behavior of ultrasonic wave propagation of deformed and plain bars with notches. With the lathe technology, the deformed and plain bars were engraved with carved inscription. Test parameters include notch distances (300 mm, 600 mm, 900 mm), notch depths (percentage of diameter 10% , 20%, 40%), notch lengths (5 mm , 10 mm, 30 mm, 50 mm, 100 mm), sectional shapes (square and arc) as well as the ultrasonic examination on deformed bars with embedded depth of 50 mm of concrete cover having three types of volumetric ratios of coarse to fine aggregate of 1 : 1 (RC1)、1 : 2 (RC2)、1 : 3 (RC3), respectively, cured at ages of 7、14、28 days. In the meantime, the Finite-Element method was used to simulate the wave propagating behavior of plain steel rods with various variables.
Experimental results show that (1) the ultrasonic pulse method to detect the notch distances is very well with an average error of only 1.73%; (2) the significant ascending trend of echo amplitude being increases with the increasing depth is observed, however, due to the signal immersed in the noise caused by reflected wave signal from circumferential boundary, the deformed bars with a 10% notch depth of 10% is hard to detect wave reflection form its end regardless of the distances of notches ; (3) it is hard to summarize the general trend of reflected waves with different notch lengths due to the interference resulting of boundaries and notch depths; (4) the amplitudes of reflected signal from arc notches are in average less than those of vertical notches by about 2.42 mV; (5) the reinforcing bar with RC2 cover concrete at curing age of 28 days has the minimum amplitude, which is less than those of 7 days and 14 days by between 9.80% and 22.44%; (6) The RC2 concrete cover at the state of saturated surface dry (SSD) obtains better bond with the deformed bar, such that its amplitudes are minimum among three curing times.
The results of numerical simulation show that (1) The reflected wave amplitudes decrease by 13.41μm in average with notch positions varying from 300 mm to 300 mm, and decrease by 159.82μm in average from 600 mm to 900 mm; (2) the deeper the notch depth is, the larger the amplitude will be in the frequency domain. The reflected wave amplitudes increase by 42.83μm and 510.31μm respectively when the notch depths increase from 10% to 20%, and from 20% to 40%, respectively; (3) the reflected wave amplitudes of arc notches are lower than those of notch with rectangular notch at same depth by about 45.41μm.

1.林莉、李喜孟，超聲波頻譜分析技術及其應用，機械工業出版社，2009.
2.陳永增、鄧惠源，非破壞檢測，第四版，全華圖書出版，2011.
3.Achenbach, J., “Wave Propagation on Elastic Solids,” The Netherlands: North-Holland Publishing Company, 1973.
4.Krautkrämer, J. and H. Krautkrämer, “Ultrasonic Testing of Materials, 4th revised Edition,” Berlin, Germany, 1990.
5.Neville, A. M., “Properties of Concrete, 4th edition,” Longman Group, Limited, Essex, U.K., 1995.
6.Bungey, J. H. and S. G. Millard, “Testing of Concrete in Structures, 3rd edition,” U.K.: Blackie Academic and Professional, pp. 47-74, 1996.
7.甘嘉偉，「超音波檢測技術評估水泥漿體之凝結特性」，碩士論文，國立臺灣科技大學營建工程系，2009.
8.Naik, T. R., V. M. Malhotra and J. S. Popovics, “The Ultrasonic Pulse Velocity Method in CRC Handbook on Nondestructive of Concrete,” CRC Press, pp. 8-1~8-19, 2004.
9.Carino, N. J., “Stress Wave Propagation Methods in CRC Handbook on Nondestructive of Concrete,” CRC Press, pp. 14-1~14-23, 2004.
10.Malhotra, V. M., and V. Sivasundaram, “Resonant Frequency Methods in CRC Handbook on Nondestructive of Concrete,” CRC Press, 2004.
11.ASTM C 215-97 Standard Test Method for Fundamental Transverse, Longitudinal, and Torsional Resonant Frequencies of Concrete Specimens, Annual Book of ASTM Standard, West Conshohocken, 2000.
12.Blitz, J. and G. Simpson , “Ultrasonic Methods of Non-destructive Testing,” 1996.
13.Shih, J. and L. Chen, “Application of Concrete Nondestructive Techniques on Construction Engineering,” The 2nd Taiwan Formosa Enterprises Engineering and Technology Conference, Editor. 2002: Taipei, Taiwan.
14.Reinhardt, H. W. and C. U. Grosse, “Setting and Hardening of Concrete Continuously Monitoring by Elastic Waves,” Proc. of the Int. RILEM Conf. Prod. methods and workability of concrete, Paisley/Schottland, pp. 415-425, 1996.
15.Uchikawa, H., S. Hanehara, and H. Hirao, “Influence of Microstructural Change under Stress on the Strength-Related Properties of Hardened cement Mortar and Paste,” Advanced Cement Based Materials, Vol. 6. No. 3-4, pp. 87-89, 1997.
16.Öztürk, T., J. Rapoport, J. S. Popovics, and S. P. Shah, “Monitoring the setting and hardening of cement-based materials with ultrasound,” Concrete Science and Engineering, Vol. 1, No. 2, pp. 83–91, 1999.
17.Popovics, S., “Analysis of the Concrete Strength versus Ultrasonic Pulse Velocity Relationship,” Materials Evaluation, Vol. 59. pp. 123-130, 2001.
18.Chotard, T., N. Gimet-Breart, A. Smith, D. Fargeot, J.P. Bonnet, and C. Gault, “Application of Ultrasonic Testing to Describe the Hydration of Calcium Aluminate Cement at Early Age,” Cement and Concrete Research, Vol. 30. No. 3, pp. 405-412, 2001.
19.Reis, H., B. L. Ervin, ,D. A. Kuchma and J. T. Bernhard, “Estimation of Corrosion Damage in Steel Reinforced Mortar Using Guided Waves,” J. Pressure Vessel Technology, Vol. 127, No. 3, pp. 255-261, 2005.
20.Sharma, S., “Longitudinal Guided Waves for Monitoring Chloride Corrosion in Reinforcing Bars in Concrete,” Structural Health Monitoring, Vol. 9, No. 6, pp. 555-567, 2010.
21.Liang, M. T., R. Huang and C. M. Jiang, “Nondestructive testing of the corrosive damage of reinforced concrete structures using ultrasonic method,” J. of Marine Science and Technology, Vol. 4, No. 1, pp. 29-34.
22.Li, R., T. Natsuki and Q.-Q. Ni, “A novel dynamic stress analysis in bimaterial composite with defect using ultrasonic wave propagation,” Composite Structures, Vol. 132. pp. 255-264, 2015.
23.Guo, X. and Y. Mao, “Defect identification based on parameter estimation of histogram in ultrasonic IR thermography,” Mechanical Systems and Signal Processing,” Vol. 58-59, pp.218-227, 2015.
24.Gao, S., N. Wang, L. Wang and J. Han, “Application of an ultrasonic wave propagation field in the quantitative identification of cavity defect of log disc,” Computers and Electronics in Agriculture, Vol. 108, pp. 123-129, 2014.
25.Shakibi, B., F. Honarvar, M. D. C. Moles, J. Caldwell and A.y N. Sinclair, “Resolution enhancement of ultrasonic defect signals for crack sizing,” NDT&E International, Vol. 52, pp. 37-50, 2012.
26. Graff, K. F., “Wave Motion in Elastic Solids,” Chapter 8, 1991.
27.Valsamos, G., F. Casadei and G. Solomos, “A numerical study of wave dispersion curves in cylindrical rods with circular cross-section,” Applied and Computational Mechanics, Vol. 7, pp. 99-114, 2013
28.ABAQUS User’s Manual (6.12), P.2-15.