Nonlinear Finite-Element Modeling of HF2V Lead Extrusion Damping Devices: Generic Design Tool

Abstract

Supplemental energy-dissipation devices are increasingly used to protect structures, limiting loads transferred to structures and absorbing significant response energy without sacrificial structural damage. The displacement of the bulged shaft plastically deforms lead in the high force to volume (HF2V) device, dissipating significant energy. HF2V devices are currently designed using limited precision models, so there is variability in force prediction. Further, although the outcome force is predicted, the knowledge of the exact internal mechanisms resulting in these device forces is lacking, limiting insight and predictive accuracy in device design. This study develops a generic finite-element (FEM) model using commercially available software to better understand force generation and aid in precision device design, thus speeding up the overall design and implementation process for uptake and use. The model is applied to 17 experimental HF2V devices of various sizes. The highly nonlinear analysis is run using the software with automatic increments to balance higher accuracy and computational time. The total force output is sum of the friction forces between lead and steel and the contact pressure forces acting between moving shaft and displaced lead. FEM forces and plots of the 17 devices are compared with experimental device forces and test plots. The errors from force comparison for all 17 devices range from −8% (overprediction) to +39% (underprediction) with a mean absolute error of 7.6% and a signed average error of 4.7%, indicating most errors were small. In particular, the standard error (SE) in manufacturing is SE=±14%. Overall, 13 of 17 devices (76%) are within ±1 SE of 14%; 3 of 17 devices (18%) are within ±2 SE (±28%), and the last has −39% error, which is within ±3 SE=±42%. These results show low errors and a distribution of errors compared with experimental results that are within experimental device construction variability. The overall modeling methodology is objective and repeatable, and thus generalizable. The results validate the overall approach with relatively very low error, providing a general modeling methodology for accurate design of HF2V devices.