Ki Weon Kang

Structural Integrity of Small Wind Turbine Composite Blade Using Structural Test and Finite Element Analysis

This study deals with structural analysis and testing under loading conditions calculated by computational fluid dynamics for a small composite blade that is utilized in a dual rotor wind turbine system. First, the aerodynamic forces were analyzed at the rated and cutout wind speed to identify the bending moment distribution along the blade length in previous research. Then, full-scale structural tests were conducted according to IEC 61400-2 to evaluate the structural integrity of the composite blade. These results were compared with finite element analysis to identify the accuracy of the structural analysis. Based on these results, it was revealed that the existing blade has a very high safety margin. Then, the layup of the composite blade was redesigned and analyzed using finite element analysis to achieve structural integrity and economic efficiency. § 이 논문은 2012 년도 대한기계학회 신뢰성부문 춘계학술대회 (2012. 4. 5.-6., 영남대학교) 발표논문임. † Corresponding Author, kwkang68@kunsan.ac.kr

Statistical Distribution of Fatigue Life of Composite Materials for Small Wind-Turbine Blades

This paper deals with several statistical distribution functions for the analysis of fatigue life data of composite laminates for small wind-turbine blades. A series of tensile tests was performed on triaxial glass/epoxy laminates for loading directions of , , and . Then, fatigue tests were carried out to determine the fatigue life at the aforementioned loading directions and the fatigue stresses at four levels. Two-parameter Weibull, three-parameter Weibull, normal, and log-normal distributions were used to fit the fatigue life data of the triaxial composite laminates. The three-parameter Weibull distribution most accurately described the fatigue life data measured experimentally for all the cases considered. Furthermore, the variation of fatigue life was simultaneously affected by the loading direction and fatigue stress level.

Development of fatigue stress spectrum and fatigue life prediction of endless winder sheave for wind turbine lift using finite element analysis

This paper aims to develop the fatigue stress spectrum and predicted fatigue life of the endless winder sheave using finite element (FE) analysis, which is utilized in wind turbine lift. First, we identified the fatigue critical location (FCL) of endless winder sheave through a static FE analysis. And the lifting velocity was measured using the non-contact velocity dectector. Based on the measured lifting velocity and compressive loads by traction of endless winder sheave, the compressive load-angle of rotation history at the FCL was determined. According to the compressive load-angle of rotation time history, total 230 FE analyses were performed with the interval of the angle of rotation of 15°, we eventually obtained the fatigue stress spectrum at the FCL. These results were processed using the rainflow cycle counting and the Goodman equation. Finally, the fatigue life of sheave was evaluated using the linear damage cumulative rule.

Probabilistic Analysis of Fatigue Behavior of Induction Hardened Steel

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.