本研究以NREL 5MW OWT風力機塔架為對象，選擇規範IEC 61400-3之DLC 1.2疲勞工況，進行離岸風力機在正常發電時之塔架疲勞分析。風況及海況模擬參數，為採用新竹沿海之資料，並整合GH-Bladed、ANSYS、MATLAB及FAMOS等軟體進行疲勞分析。葉片與塔架模型的準確性以自然頻率分析值與實驗值之比較來驗證。材料疲勞性質的應力-壽命(S-N)線選用Eurocode 3之71 category。疲勞分析方法包括雨流循環計數、Goodman平均應力修正及Miner疲勞損傷累積法則。 研究結果顯示塔架除了塔底管壁內側有較大von-Mises應力外，亦在23 m高度管壁外側出現較大應力。在應力歷程計算方面，可採用單位負載法取代ANSYS動態應力分析，以大幅降低分析時間。在切入風速至切出風速之間，風速愈高，則塔架的疲勞損傷愈大，且大致成線性關係。在海洋參數中，示性波高愈大，塔架疲勞損傷愈大。尖峰週期提高時，塔架底部疲勞損傷會降低。水位的上升，會提高塔架的疲勞損傷值。風浪方向為 -45°時，會比0°時造成較大的塔架損傷。在20年正常發電下各風浪方向觀測位置之疲勞損傷值皆小於1，塔架在此期間不會產生疲勞失效。 ;In this study, the fatigue damage of NREL 5MW OWT wind turbine tower was analyzed under the normal power production based on the DLC 1.2 in IEC 61400-3. Wind and sea conditions were based on the information obtained from the coast of Hsinchu. Software programs including GH-Bladed, ANSYS, MATLAB and FAMOS were integrated. The accuracy of the model was verified by comparing the results of natural frequency analysis with the experimental data. The S-N curve of 71 category in Eurocode 3 was adopted in the fatigue analysis. Fatigue analysis methods included rainflow cycle counting, Goodman mean stress correction, and Miner’s fatigue damage accumulation rule. The results show that the inner wall of the tower bottom had a maximum von Mises stress and the outer wall at a height of 23 m also had high stress. In the aspect of stress history calculation, unit load method can replace ANSYS dynamic stress analysis to greatly reduce the analysis time. The higher the wind speed is, the greater the fatigue damage of the tower is, and the relationship is roughly linear. The higher the indicative significant wave height is, the greater the fatigue damage of the tower is. When the peak period is increased, the fatigue damage at the bottom of the tower will be reduced. The rise of sea level will increase the fatigue damage value of the tower. When the wind wave direction is -45°, the tower damage will be greater than that at 0°. Under 20 years of normal power generation, the fatigue damage of the tower is less than 1, and fatigue failure of the tower will not occur during this period.
