離岸風力機塔架在正常發電下之非共平面疲勞裂縫成長分析;Analysis of Non-Coplanar Fatigue Crack Growth in Offshore Wind Turbine Tower under Normal Power Production

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題名:	離岸風力機塔架在正常發電下之非共平面疲勞裂縫成長分析;Analysis of Non-Coplanar Fatigue Crack Growth in Offshore Wind Turbine Tower under Normal Power Production
作者:	劉冠宏;Liu, Guan-Hong
貢獻者:	機械工程學系
關鍵詞:	離岸風力機;非共平面裂縫;疲勞裂縫成長;等效應力法;Offshore Wind Turbine;Non-Coplanar Cracks;Ansys SMART Crack Growth;Fatigue Crack Growth;Equivalent Stress Method
日期:	2025-07-24
上傳時間:	2025-10-17 13:07:07 (UTC+8)
出版者:	國立中央大學
摘要:	本研究探討5 MW離岸風力機塔架在正常發電工況(DLC 1.2)下，塔架所承受之風浪耦合負載對結構應力的影響，並針對在塔架具有非共平面裂縫時之疲勞裂縫成長行為。研究方法整合GH-Bladed、Ansys和Matlab等軟體以進行分析。研究內容分為兩個部分。第一部分考量規範IEC 61400-3之DLC 1.2設計工況，探討離岸風力機在正常發電運轉下之塔架應力大小與其分布狀況。第二部分為在Ansys SMART Crack Growth 建立非共平面橢圓裂縫，並討論非共平面表面裂縫之間，因為裂縫成長產生相互作用影響而引起的屏蔽或增強效應，並探討疲勞裂裂縫成長壽命預測。研究結果顯示在正常發電運轉下，從切入風速至額定風速，離岸風力機塔架最大正向應力會逐漸上升，當超過額定風速後會因為葉片節距角作動而改變，使得最大正向應力呈現下降趨勢。並且在額定風速為10.88 m/s時，風力機塔架最大應力位於下塔架底部上方0.2 m的迎風面處。若在該位置建立非共平面雙橢圓裂縫，裂縫會在最大正向應力處發展成主要裂縫，該裂縫的成長模式與單裂縫情況相近，並且裂縫之間會因為屏蔽效應的影響，致使另一裂縫形成次要裂縫，並減緩甚至停止裂縫成長。在不同裂縫幾何尺寸下，兩條等長裂縫之裂縫尖端在達到任一條裂縫的垂直平分線投影位置時，會有最大的屏蔽效應。當兩條裂縫的水平間距等於裂縫的兩倍長度時，會有最大增強效應。兩條裂縫長度之比值會影響非共平面裂縫成長，裂縫長度比越小，屏蔽效應越明顯。在疲勞裂縫成長壽命預測分析結果方面，不同幾何尺寸的非共平面雙裂縫，疲勞裂縫成長因為屏蔽效應的影響，其疲勞損傷不一定會大於單裂縫所造成疲勞損傷，而是取決於二條裂縫的相對位置。 ;This study investigates the influence of the wind-wave coupling load on the fatigue crack growth of the wind turbine tower which has non-coplanar cracks. A NREL 5MW OWT wind turbine was taken as the object, and DLC 1.2 normal power production conditions in IEC 61400-3 were considered. The research method was to integrate software such as GH-Bladed, Ansys and Matlab for analysis. The content is divided into two parts. The first part explores the magnitude and distribution of tower stress under normal power production operation. The second part is to establish non-coplanar elliptical cracks in Ansys SMART Crack Growth, explore the shielding or enhancement effects caused by the interaction between non-coplanar cracks, and discuss the fatigue crack growth life. The results show that under normal power production operation, from the cut-in wind speed to the rated wind speed, the maximum normal stress of the wind turbine tower gradually increases. When the wind speed exceeds the rated wind speed, due to the change of the blade pitch angle, the maximum normal stress shows a downward trend. Under the rated wind speed, the maximum stress of the wind turbine tower is located at 0.2 m above the bottom of the lower tower on the windward side. If a non- coplanar double elliptical crack is established at this position, the crack will develop into the primary crack at the maximum normal stress. The growth pattern of this crack is similar to that of a single crack. Moreover, due to the influence of the shielding effect, the other crack will form a secondary crack, which will slow down or even stop the growth of the crack. Under different crack geometric dimensions, when the crack tips of two equal - length cracks reach the projection position of the vertical bisector of either crack, the maximum shielding effect occurs. The greatest enhancement effect will occur when the horizontal distance between the two cracks is equal to twice the crack length. The ratio of the lengths of the two cracks will affect the growth of non-coplanar cracks. The smaller the ratio of the crack lengths, the more obvious the shielding effect. In terms of the analysis results of the fatigue crack growth life, for non-coplanar double cracks of different geometric dimensions, due to the influence of the shielding effect, the fatigue damage caused by the fatigue crack growth is not necessarily greater than that caused by a single crack, but depends on the relative positions of the two cracks.
顯示於類別:	[機械工程研究所] 博碩士論文

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