Ford Motor Company: Including Bolt PreTension Effects in Durability Analyses

Durability is one of the trickiest analyses to perform in CAE. In the automotive industry, several parts are made of stamped steel and then assembled together using welded joints or threaded joints. For simplicity, over the years, threaded joints have been modeled as rigid attachments between components, not taking into account the effects of torque tightening of bolts. The sheet metal around the head of the bolt and nut have an initial deformation and stress because of local compression that directly affects the durability results.   In this study, Abaqus is used to generate an FE model for sheet metal parts attached by bar elements that represent the bolts. These are pre-tensioned to apply an initial condition of local stress. Then, the durability analysis takes into account the deformed structure for modal analysis and the calculation of modal participation factors, as well as an initial stress that can directly shift the local mean stress.  Modal participation factors are calculated for the model and then converted in nCode software into time series, that can be applied to recreate a dynamic analysis for durability using standard EN glyphs. 

Presenter: Daniel Ramos, Ford Motor Company (Mexico) Originally presented on May 14, 2014 at the 2014 HBM-nCode Products User Group Meeting in Livonia, Michigan (USA).