August 1, 2014.
This project will investigate the local buckling induced fracture behavior of round steel tubes subjected to axial compressive loads, representative of observed failures in buried pipelines during seismic events. Nine initial tests will be conducted across three lengths of round steel tube: 8”, 12”, and 20”. Another twelve tests will be conducted on the lengths of 12” and 20” to test varying initial compressive force upon the round steel tubes. Three D/t ratios will be considered for each length of round steel tube: 52.6, 78.9, and 121.2. To verify the material properties of the test specimens an ancillary tensile coupon test will be conducted. Nine tensile coupons will be taken from the specimens, three from each D/t ratio. The coupons will be tested for hardness, ductility, stress capacity, and strain capacity. While the pipe experiments are designed to provide relationships between the geometrical parameters and the cyclic ductility to fracture initiation, the results of these tests will also inform the critical buckling capacity, and its relationship to the D/t ratio, specimen length and material properties. It is expected the study will result in empirical equations for fracture ductility, critical buckling strain, and the buckling wavelength as a function of the D/t ratio and length. The experimental results will be used to inform a physics-based fracture model utilizing stress and plastic strain demands from finite element analyses.
California State University, Sacramento (Sac State)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013 and Grant No. 0833353. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).