臺灣博碩士論文加值系統

對於所有在高速旋轉狀態下運作的機械而言，機件本身的功能及效率為初始設計時的主要考量，除此之外，機械運轉時的安全性能亦為不可輕忽的一項課題。科技發展愈趨完備。人類依賴機械的程度也愈趨頻繁，為了避免機械在運作的過程中突發性的破壞毀損，而造成使用者的傷害或是預定任務的延遲，因此，如何維持機械性能及可靠度就顯得格外重要。
本研究以直昇機旋翼葉片為例，在旋翼表面具有凹槽 (notch) 的情形之下，以高速旋轉之實驗儀器，模擬直昇機在保持懸停 (hover) 姿態時，受到空氣動力、扭力、旋轉之離心力，以及疲勞 (fatigue)破壞的多重因素影響之下，對於葉片上不同位置的裂紋 (crack) 生成與成長的情形做一歸納探討，並輔之以旋翼葉片空氣動力理論模式佐證實驗之結果，期能建立一套動態旋轉機械表面裂紋成長之資料以供後人參考。

Considerable fracture work has been done on the ductile materials for tensile loading since this mode was thought to be the most dangerous and was also the easiest to test in the laboratory. However, most structures do not experience just one type of loading but combinations of tension and shear. This situation is commonly known as mixed mode loading. The rotating machines such as compressor turbine blades, cooling fans, propellers, and helicopter rotor blades… etc., are easy to sustain such mixed loading and the fracture occur.
In this research, the mixed mode fracture of a pair of highly rotating metallic blades have been investigated at room temperature using single edge notched specimens. A set of 2-bladed rotor is driven by a 220 volt AC motor and the rotating speed is fixed as 850 rpm. The notch is located in various blade positions from blade root to tip. The correlation of notches at blade leading edge and trailing edge are also studied. A simple theoretical model of a flapping Bernoulli-Euler-Beam like rotor blade model is established for analytic study.
The experimental results show that the crack growth for the notched blade at leading edge is faster than the trailing edge notched blade. The near-root notched blade crack occurs earlier than the blade that the notch located near the tip. The cracks grow fast in the case of the rotor blade with higher angle-of-attack. In the analytic study of blade flapping motion, it is found that the aerodynamic force plays an important role in rotating machines. The aerodynamic force lifts the highly rotating blades. Due to the fact from the experimental data, it is shown that the blade flapping bending moment causes the crack occurring at the lower part of the rotating blade with angle-of-attack. It is noted that the aerodynamic force should be included in doing the rotating fracture problems.

第一章 緒論.........................................1
1.1 研究動機....................................1
1.2 文獻回顧....................................2
第二章 理論模式.....................................5
2.1 結構彈性葉片及空氣動力耦合方程..............5
第三章 實驗設計及方法..............................10
3.1 實驗儀器...................................10
3.1.1 旋轉模擬實驗機..........................10
3.1.2 高倍率光學顯微鏡........................14
3.2 實驗步驟...................................23
第四章 結果與討論..................................29
4.1 理論分析...................................29
4.2 實驗結果...................................36
4.2.1 裂紋產生時間分析比較....................36
4.2.2 裂紋產生形式分析比較....................37
第五章 結論........................................68
參考文獻...........................................71
附錄...............................................76
附錄A..............................................76
附錄B..............................................81

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