Bolted Joint Representation in LS-DYNA to Model Bolt Pre-Stress and Bolt Failure Characteristics in Crash Simulations

During the vehicle crash event (especially vehicles involving light and heavy commercial vehicles where bolted connections are predominantly used) bolted joints behavior, in terms of deformation and failure, play significant role in detecting the level of occupant protection offered by the vehicle structure. The current FE modeling techniques, for bolted joint representation in crash FE models, pose various limitations in terms of simulating the real life bolted joint behavior with explicit codes like LS-DYNA. The present bolt modeling techniques do not address the important aspects of bolted joint like • pre-load/pre-stress representation in the bolt, • bearing stresses between bolt shank and clamped plates, clamping forces between plates • Friction between bolts and plates and failure modeling of bolting joints. This paper describes FE modeling methodology, for bolted joint representation in crash FE models, for crash simulations using LS-DYNA. Two alternative options are proposed for modeling of bolted joint, either with beam element or with solid hexa elements so as to address the above mentioned aspects of bolted joint in crash simulations. The proposed FE modeling methodology is validated with theoretical calculations and experimental test results. The proposed bolt modeling methodology will help to achieve accurate prediction of structural behavior in crash load cases where bolted joints are predominantly used in crash load paths, such as cabin structure assessment with pendulum impacts, assessment of under run protections devices etc.