Multi-variable Method For Flexible Multibody System Dynamics With Contact/Impact

The problems of multibody system with contact/impact play an importantrole in many ?elds of science and engineering. Undoubtedly, it is a rather im-portant and complex issue of seeking methods with e?ciency and appropriateaccuracy.In recent years, e?orts are made to give considerations to both the e?ciencyand accuracy of simulation. Against this background, multi-variable method isproposed in the thesis to deal with ?exible multibody dynamics with contac-t/impact. Multi-variable method couples the ?oating frame of reference methodand the nonlinear element method to achieve solution e?ciency for the wholesystem and accuracy in contact region. The motion of the non-contact regionis described by the ?oating frame of reference method. Within this framework,modal reduction approaches can be used to achieve e?ciency. Nonlinear FEMmethod is employed for modeling nonlinear and plastic deformation in local con-tact region.MVM has some other advantages: the dynamic equations is consistent inthe periods with and without contact/impact, di?erences lying in appendingand deleting the contact constraints and contact items merely; Nonlinear FEMmethod in the local contact region can deal with contact/impact between arbi-trarily complex interfaces.Dynamic equations of MVM about two multibody systems with contac-t/impact is derived in this thesis. Three forms of dynamic equation are presented:Lagrange multiplier form with position contact constraints, Lagrange multiplierform with velocity contact constraints, tangential complementary form.Moreover, explicit and implicit algorithms of MVM are studied. Merits andshortcomings of these two algorithms are discussed respectively. Some numericalresults are presented, with the e?ciency of the developed method. Veri?cations ofthe numerical results are implemented with Ls-dyna (in the period of impact) andAdams (in the period of non-impact). In addition, experimental investigations using Laser-Doppler Vibrometers are presented. The numerical results solidlyagree with experimental results.At last, the limitation of MVM is presented. MVM is improved to deal withcontact/impact between beams and shells which have large relative rotations.