Research on stress and strain of the Flange Bolts Connection of Wind Turbine based on Finite Element Analysis Jianping Liu 1a , Teng Han 1 , Derui Su 1 , Changguo Ji 1 , Junping Chen 1 1 Department of Electrical Engineering and Automation, Luoyang Institute of Science and Technology, Luoyang, 471023, China a email: liujianping1415@163.com Keywords: stress and strain；bolt；Wind Turbine；Finite Element Analysis Abstract. Wind energy as an inexhaustible green energy is the development trend of the future. Wind turbine bolts play an important role for the service safety of wind turbine, and have become the new promising product of the fastener industry in the world. But because of the high strength bolt connection failure caused by a tower pour accident, caused the attention of the scientific research workers, and put forward to improve reliability, high strength bolt connection to ensure that the wind turbine operation research problems. The rigid strength, toughness and hardenability requirements of the wind turbine bolt steels are really challenging work. In order to study the mechanism of high strength bolt connection failure, the stress and strain of the high strength bolts of a MW wind turbine was researched by finite element analysis. Introduction Wind energy as an inexhaustible green energy is the development trend of the future. But because of the high strength bolt connection failure caused by a tower pour accident, caused the attention of the scientific research workers, and put forward to improve reliability, high strength bolt connection to ensure that the wind turbine operation research problems. In order to study the mechanism of high strength bolt connection failure, the high strength bolts of a MW wind turbine as an example, to study the influence of micro crack on stress of bolt and different preload of bolt fatigue strength. The use of wind power, a form of renewable energy, is soaring in the 21 st century. World wind generation capacity has doubled about every three years between 2000 and 2006. The World Wind Energy Association forecast that, by 2010, over 200 GW of capacity will have been installed worldwide, predicting another impressive 30% yearly growth rate from 2006 to 2010. A wind turbine is a rotary device that extracts energy from the wind. Horizontal-axis wind turbines, the most popular ones, generally consist of a foundation, tower, nacelle and blades. With the vast growth world-wide in the construction of wind farms in recent years, wind turbine bolts have become a new promising product for the Taiwan fastener industry, one of the leading fastener export countries in the world. Wind turbine bolts for nacelles and blades, like all bolts for aerospace use, have higher standards than other bolts as shown in Fig.1. The rigid strength, toughness and hardenability requirements of the wind turbine bolt steels are challenging work for a steel manufacturing company (1-2). Screws and bolts are made from a wide range of materials, with steel being perhaps the most common, in many varieties. ISO 898.1 specification is the primary specification used in wind turbine bolt produc-tion. Some other specific requirements may be negotiated between buyers and suppliers. Tables 1 and 2 show the requirements of material, chemical composition, and mechanical and physical properties in ISO 898.1 Steel bolts usually have a hexagonal head with an ISO strength rating (called the property class) stamped on the head. The property classes most often used are 5.8, 8.8, 10.9, and 12.9. High-strength steel bolts have property classes of 8.8 or above, and wind turbine bolts have property classes of 10.9 or above. For the materials with property classes of 8.8 and above, there must be a sufficient hardenability to ensure a structure consisting of approximately 90% martensite in the core of the threaded sections for the fasteners in the “as-hardened” condition 2nd Workshop on Advanced Research and Technology in Industry Applications (WARTIA 2016) © 2016. The authors - Published by Atlantis Press 441