D5
Multibody Dynamics

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08:35
conference time (CEST, Berlin)
Virtual Testing for High Lift Systems: Flexibility in Multibody Simulations – An Alternative to the Modal Neutral File Approach
26/10/2021 08:35 conference time (CEST, Berlin)
Room: D
T. Ulmer (Airbus Operations, DEU)
T. Ulmer (Airbus Operations, DEU)
Airbus High Lift System Test Department at Bremen successfully conducts since several years Virtual Testing (VT). The approach of Virtual Testing by means of computer simulations of physics-based models has been applied for all major aircraft development programmes of the last years since A380. The preferred simulation methodology is multibody simulation (MBS). Depending on the test objective and the mechanism that is simulated, specific parts need to be modelled as flexible bodies. Generally, these flexible bodies are represented by modal neutral files (MNF), derived from existing linear static finite element method (FEM) models. This involves several, time-consuming pre-processing tasks such as extraction of the body under consideration from an integrated FEM model or the assignment of inertias that are not necessarily contained in the linear static FEM. A specific type of high lift kinematics (Fowler kinematics) constitutes a special case that involves a carriage that travels on a flexible track beam. In FEM, this is realized by dedicated models for dedicated positions of the carriage on the track. Implementation is done for instance by changing locations of grids or by GENEL statements with changing parameters. Hence, the mechanism’s effective, position-depending flexibility is correctly modelled. In MBS the default way of modelling is to use a translational joint between the carriage and a rigid track, which in terms is connected to the flexible beam. This connection is effected by a rigid body element (RBE). This leads to a constant, mean effective stiffness of the beam, independent of the actual carriage position. Depending on the ratio between beam flexibility and applied load, this can lead to an unacceptable error. Hence in scope of an R&T project an alternative approach is investigated and demonstrated. The carriage is connected to the track by a multidimensional spring with position-dependent coefficients. The coefficients either can be taken directly from available GENEL parameters or can be derived by simple static FEM analyses (application of unit loads). Position dependency in the MBS model is achieved by spline interpolation. This leads to both, a correct consideration of the position-dependent stiffness as well as a simplification of the pre-processing process. The modelling approach is integrated into a table defined, script-based model creation process which addresses the need for robust, efficient and traceable model creation (cf. Simulation Process Data Management, SPDM).
Virtual Testing, Flexible Multi Body Simulation, Flexible Body Creation, Representation of Flexibility, SPDM, Simulation Process Data Management.
08:55
conference time (CEST, Berlin)
DEMMOW – Detailed Model of a Morphing Wing: Development of Separate Components Models
26/10/2021 08:55 conference time (CEST, Berlin)
Room: D
M. Bruyneel, A. Mawet, (GDTech, BEL); G. Carossa, E. Marinone (Leonardo Aircraft, ITA)
M. Bruyneel, A. Mawet, (GDTech, BEL); G. Carossa, E. Marinone (Leonardo Aircraft, ITA)
High-lift devices like slats and flaps have been used for a long time to improve the performance of the aircraft depending on the flight conditions. Wingtip and winglet have become popular solutions to decrease the drag coming from wing tips vortices and to increase the fuel efficiency. These components are assembled on the wing box structure to form the full wing. Classical high-lift devices are expensive, complex and heavy. They are therefore not acceptable solutions for the current trends on efficient and green aircrafts. Recent developments based on adaptive/morphing structures may overcome the limitations of classical high-lift devices, and so provide better solutions while reaching the objectives in terms of efficiency and environmental impact; furthermore, control laws of wingtip and winglet surfaces may be defined in order to obtain a wing loading control and alleviation system (LC&A technologies). The idea is to adapt the shape of the wing to the flight condition by using morphing techniques. The compliant and/or kinematic mechanisms as well as the actuation system are now inserted in the wing and used to change its shape. Using morphing concepts allows shape change without generation of discontinuities in the flow (no aerodynamic gap). This paper presents the activities undertaken in the DEMMOW project (CleanSky 2, n°755621). The goal of the project was to develop a high fidelity integrated non-linear MBS-FEM model of a morphing wing, including several structural components (composite box, morphing winglet, droop nose and adaptive trailing edge), with kinematic joints and actuators. Multi-body dynamics modelling of the mechanical system is addressed by the finite element method extended to multi-body systems including flexibility and non-linearities related to large displacements and rotations, and to morphing parts that can include compliant structures and non-linear materials, leading to a flexible wing concept. The paper will highlight the development of the finite element models of the separate morphing components (morphing winglet, droop nose and adaptive trailing edge). Comparison to ground test results will be provided.
MBS-FEM, morphing wing
09:15
conference time (CEST, Berlin)
Deployment of Software Tools for Simulation Based Design of Drill Hammers
26/10/2021 09:15 conference time (CEST, Berlin)
Room: D
V. Keppler (CENIT AG, DEU)
V. Keppler (CENIT AG, DEU)
Several development objectives need to be considered when developing drill hammers. Besides achieving the highest possible power-to-weight ratio, the health and safety features of the tools are becoming increasingly important. In particular, it must be ensured that the transmission of vibrations to the operator is minimized or lies within the limits of health and safety regulations. Modelling the vibration behavior of drill hammers, there is a strong interaction between the biomechanical operator, the tool and the application. To enable an appropriate prediction accuracy of the vibration level, both the dynamics of the hammering mechanism as well as the dynamics of the operator model must be understood and modelled correctly. Hereby, the complexity of the hand-arm-models reaches from simple 3-mass-spring systems to detailed biomechanical operator models. The number of required input parameters often increases with the complexity of the models. The goal of this study has been to enhance the system understanding of the various model parameters. For this purpose, the system dynamics have been validated based on measurement data capured for different drill hammers, operator poses and anthropometrics. To simulate complex mechanical systems, the multi-body simulation has proven to be an efficient method. In this study, the software Simpack has been used. The computation time for a system time of two seconds took 15 minutes using a single core solver and can be reduced to four minutes computation time using parallel solving on 4 cores. Due to the high dimension of the parameter space, the interactive parameter identification has shown to be error prone as well as the documentation has been cumbersome and therefore often incomplete or difficult to reproduce. In order to choose a more targeted approach, the simulation process has been extended by the automation tool Isight which is able to perform design of experiments, optimizations and sensitivity analysis. Doing so, a better parameter safety and prediction accuracy could be provided.
Multibody-Simulation, System-Simulation, Simulation Driven Design, Power Tools, Drill Hammer, Operator Models, Parameter, Optimization, Simpack, Isight, SIMULIA
09:35
conference time (CEST, Berlin)
Contact Modelling in Multi Body Simulation for Seat Mechanisms
26/10/2021 09:35 conference time (CEST, Berlin)
Room: D
M. Ben Tkaya, D. Guillaume, A. Page, L. Guerin, (Faurecia Caligny, FRA)
M. Ben Tkaya, D. Guillaume, A. Page, L. Guerin, (Faurecia Caligny, FRA)
Seat mechanisms are the components which enable to adjust seat’s position. Functional simulation aims to reproduce the behaviour of these mechanisms during their normal usages whereas FEA simulations are used for strength prediction. Functional simulation needs a precise description of different components geometry and contact interactions definition between different bodies. The classical approaches by using FEA modelling need a discretization of the geometries. To have a precise representation of the components, the use of fine mesh becomes mandatory for better description of the contact surface. this will lead to a high CPU time and an accuracy issue. Chosen methodology for functional simulation in Faurecia Automotive Seating is multi-body dynamics using Simcenter- 3D Motion software. In this tool two types of contact can be used to define interaction between bodies: analytical contact and 3D contact. The first one is based on Hertzian theory and complicated geometries are approximated by several analytical contacts. Second type of contact is based on a discretization of the real surface by facets. Choice of contact in model can have impact on results. To industrialize the application of Simcenter 3D Motion modelling on different product, a fixed methodology must be defined, specifically, for contact modelling. This work describes the methodology used by Faurecia in multi-body and functional modelling. In the first section a description of different contacts used in Simcenter 3D Motion is presented with a comparison of results between used approaches and the sensitivity of results to different contact settings will be presented. The second section will describe Faurecia methodology and the impact of the contact choice on tracks simulation. The third section presents an application on gear by using different types of contact. A comparison between different approaches is realized. To conclude, some efficiency tools developed using NX Open to automate model preparation based on developed methodology are presented.
Multibody, contact, Simcenter 3D Motion
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