Fatigue Behavior of Vertical Axis Wind Turbine Airfoils with Two Weld Configurations.

摘要

Sandia National Laboratories contracted with Rockwell International Science Center to perform a series of narrowband, pseudo-random cyclic fatigue tests on sections of 6063-T651 aluminum, Darrius-type, vertical axis wind turbine (VAWT) airfoils. We designed and constructed a load member that was mounted within the frame of a rigid 200-kip servohydraulic, closed-loop test system to hold the VAWT section and permit cantilever bending along the shear centerline of the beam. A computer program was developed to synthesize a narrow band, pseudo-random load history with fixed root mean square (RMS) stress levels at a given bandwidth and central frequency. Six specimens each of two different weld configurations at the flange mounting plate were tested at several RMS stress levels with failure defined as visual observation of a 3-inch-long crack in the VAWT. In order to test at as great a frequency as possible, a 20-kip hydraulic ram with a 10-GPM servovalve was employed with a 20-GPM pump. Tests were performed from 2 to 1.3 ksi RMS on the two-weld configurations. The conclusions are obvious that the fillet-weld design is far superior to the butt-weld design in the range of variables used in this program. 1 ref., 13 figs.