應用非線性超音波技術評估鋼疲勞損傷

Assessment steel fatigue damage by nonlinear ultrasonic technique

吳善硯(Shan-Yan Wu)

指導教授 ： 楊哲化

國立臺北科技大學/機電學院/製造科技研究所/碩士(2014年)

https://doi.org/10.6841/NTUT.2014.00755

摘要

隨著科技的進步，以及商業化的競爭，傳統的破壞力學、材料力學所設計的產品已經無法同時兼顧高品質、高可靠度卻低成本，而這些高科技產品往往伴隨著後續高維修成本，所以如何使產品擁有較低的生產成本，又可以發揮材料高效能，以及高安全性，非破壞檢測技術是不可或缺。而影響這些尖端產品表現的原因，往往在於製造方面就已經出了問題，隨著精度之提高，傳統超音波技術已經無法檢測出製造前材料本身之微小缺陷或使用中產品之初步破壞跡象，因此之後有非線性超音波技術的應用。
其中又以減少結構使用中之維護成本以及安全性最為重要，因此本研究主要利用非線性超音波量測系統，產生高能量的波入射鋼材，透過穿透法在另一端接收其二倍頻訊號，再依二倍頻振幅與基頻振幅平方之比值計算鋼材的非線性因子。由於二倍頻訊號遠比基頻訊號小，因此如何得到材料本身微小變化所產生的二倍頻訊號也是本文之重點。然後依上述方法對鋼材在不同疲勞週期下量測其非線性因子，藉由不同疲勞週期與其非線性因子之關係，可以繪製材料非線性因子與循環應力次數曲線。最後結果顯示，隨著施加循環應力次數的增加，非線性因子也有增加的趨勢，因此利用非線性超音波技術可以用來評估鋼的疲勞壽命。

關鍵字

鋼CNS SS400 ； 不銹鋼SUS 304 ； 疲勞損傷 ； 非線性超音波技術

並列摘要

With the progress of technology, and commercialized competition, products which were designed by the concept of traditional fracture mechanics and mechanics of materials don’t have simultaneously both high-quality, high-reliability, but low-cost, and these high-tech products are often accompanied by a subsequent high maintenance costs, so how to make products with lower production costs, but also can play a high-performance, as well as high security, non-destructive test is indispensable. And the reasons which influence of these highly sophisticated products performance often lie in manufacturing process, with the improvement of the manufacturing accuracy, conventional ultrasound technique has been unable to detect micro-defect of the material itself, therefore there is nonlinear ultrasound technique.
Among them, the reduction in the use of structural maintenance costs, and safety is most important, so this study is using nonlinear ultrasonic measurement system to produce high energy wave to steel, and through penetration method receiving the second harmonic signal at the sample other side, then following the ratio of second harmonic amplitude and the square of fundamental amplitude can obtain the nonlinearity of steel. Due to the second harmonic signal is much smaller than the fundamental signal, so how to get second harmonic signals generated by small changes in the material itself is also the focus of this article. Then according to the above method can drawn the relationship between nonlinearity and fatigue cycles curve by measuring the nonlinearity of steel at different fatigue cycles. Finally, the results show that with the increase in the number of fatigue cycle, the nonlinearity also have an increasing trend, thus using nonlinear ultrasound technique can be used to assess the fatigue life of steel.

並列關鍵字

steel CNS SS400 ； stainless steel SUS 304 ； fatigue damage ； nonlinear ultrasound technique

參考文獻

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