Fatigue, fracture toughness, and crack propagation tests were performed on five candidate steels for wind tower applications. Normally, these... Show moreFatigue, fracture toughness, and crack propagation tests were performed on five candidate steels for wind tower applications. Normally, these steels are ordered to meet ASTM A572/A709 Grade 50 or EN 10025-2 Grade S355 in the normalized condition. Five steels with varying carbon content and alloy additions focusing on niobium and vanadium content are investigated. Two of the five steels are in the normalized condition to check the EN 10025-2 requirement while the rest are in the as-rolled condition. Fatigue tests were performed to determine the endurance limit using a constant amplitude loading at a constant load ratio. Fracture toughness testing using the J integral method was performed to determine the critical fracture energy, Jc. This value is then converted to the critical plain strain stress intensity factor if requirements are met. Three fracture toughness tests were performed for each material at room temperature using a C(T) specimen. Crack propagation tests were performed to determine the Paris constants using a contoured double cantilever beam specimen. The steels with niobium give better results in fatigue and displayed smaller grain diameters than the steels with vanadium. The fatigue results for the low carbon steel with niobium are comparable to another HPS steel. Overall, the low carbon steel with niobium provides better toughness, fatigue resistance, and weldability than the steels that are normalized to meet the EN 10025-2 requirement for wind tower plates. M.S. in Materials Science and Engineering, July 2011 Show less
