Abstract

Wind turbines must endure a high number of load cycles during their service lifetime. Therefore, the fatigue strength verification plays an important role. Butt-welded joints are one of the most common structural details in the tower structure of wind turbines. In general, the nominal stress method is used for their fatigue verification. The Eurocode 3 part 1–9 is the current design standard for this field of application and defines the fatigue resistance by pre-defined FAT-classes. This paper presents recent results of fatigue tests on small-scaled specimens and large components with transverse butt welds to discuss the validity of the FAT-class. In addition, results from numerical simulations for the verification with the effective notch stress and the crack propagation approach are used for comparison. For this purpose, macroscopic measurements of the weld seam geometry and a 3D scan were used for a realistic consideration of the notch effect in the simulation. Based on the consistency between the numerical results and the fatigue tests, the influence of the seam geometry on the fatigue resistance was worked out. Furthermore, a prediction of the fatigue strength of butt-welded joints with plate thicknesses up to 80 mm was carried out.

中文翻译：

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风力涡轮机塔架对接焊缝的抗疲劳性评估——小规模和组件试验的实验研究以及基于数值的方法与局部概念的比较

摘要

风力涡轮机在其使用寿命期间必须承受大量的负载循环。因此，疲劳强度验证起着重要的作用。对焊接头是风力发电机塔架结构中最常见的结构细节之一。一般而言，疲劳验证采用标称应力法。欧洲规范 3 第 1-9 部分是该应用领域的当前设计标准，并通过预定义的 FAT 等级定义了抗疲劳性。本文介绍了小尺寸样本和带有横向对接焊缝的大型部件的疲劳试验的最新结果，以讨论 FAT 等级的有效性。此外，还使用有效缺口应力和裂纹扩展方法进行验证的数值模拟结果进行比较。为此，使用焊缝几何形状的宏观测量和 3D 扫描来真实考虑模拟中的缺口效应。基于数值结果与疲劳试验的一致性，计算出焊缝几何形状对疲劳强度的影响。此外，还对板厚最大为 80 mm 的对接焊缝的疲劳强度进行了预测。