Dynamic Collapse Simulation of Flexible Multibody Systems with Plasticity Effects

Abstract eng:
In this paper, a method for modelling the dynamic collapse of flexible multibody systems using a non-linear finite element method is presented. The flexible multibody system is assembled by Reissner’s geometrically exact beam elements and mass elements [1]. The primary interest is to model and simulate hydraulic-driven multibody systems under oversized load causing a failure. These collapse simulations can be utilized in the accident analyses or the detection of the device in the extreme conditions that could advise in design. The hydraulic system, and especially hydraulic cylinder, is modelled by a length controlled bar element [1]. In order to model the failure, an elasto- plastic material model is required. Since plastic material model should be robust to utilize the material model in simulations, a stress resultant formulation is introduced. In the plane case, the Reissner’s beam element has three stress resultants: normal and shear force vectors and a bending moment. The stress resultant formulation avoids the through-thickness integration. However, the yield surface depends on the shape of the cross-section. In this paper, the study is restricted to rectangular hollow cross-sections and a stress resultant formulation for elasto-plastic material is introduced. In addition, the stress resultant formulation is verified by a through-thickness integration procedure. The governing equations of motion in the dynamic case are solved by using the implicit Newmark time integration method. A numerical example considering the hydro-mechanical flexible multibody system is presented where a heavy load with sudden stop of hydraulic cylinder causes the collapse of the system. In this example, dynamic effects in the limit load are evident.

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