Truck driveline vibration modeling using multi-body system

Prediction of NVH parameters of driveline in construction phase is a significant topic nowadays because it can save time and development costs, but requires more complex mathematical models. This paper describes the use of MBS simulation tool for prediction of driveshaft vibration where shaft is modeled as a flexible body. MBS approach can take into account various input parameters, i.e. unbalanced mass of shaft, geometry deviation from ideal shape, mounting points of eccentricity or contact between the shaft and other parts of the driveline. MBS model of driveshaft was verified by measurement on a real vehicle

Computational Dynamics for the Flexible Multi-Body System

Research in computational dynamics has tremendously developed in the recent years because of the demand for analysis and simulation of various multi-body systems in the growing bio-medical, mechanical and aerospace industries. These multi-body systems are made of individual bodies that are interconnected via mechanical joints. Mathematically, these joints that connect the bodies can be described as constraint equations imposed upon the motions of the involved free bodies. This process will result in an equation of motion expressed in the form of a differential-algebraic equation (DAE). This is one of the main difficulties when dealing with the multi-body system because these constraints must be satisfied all the time. The main objective of this dissertation is to develop an efficient and accurate solution algorithm to solve the DAE resulting from flexible multi-body dynamics. The principle of virtual work and D\u27Alembert\u27s principle are used in this dissertation to formulate the equation of motion for a general three dimensional (3D) multi-body dynamic system that involves rigid as well as flexible bodies. The elastic mode shapes and modal coordinates are used to convert the time-variant integrals associated with elastic deformations in the mass matrix into time-invariant ones. In addition, the transient stress distribution is obtained directly in terms of the linear combination of the modal element stress and corresponding modal coordinates solved from DAE. Euler parameters and the matrix exponential method are used to calculate the time-dependent transformation matrix for a general 3D problem. The projection method with constraints correction is proposed in this dissertation to solve the DAE modeling the motion of a constrained multi-body dynamic system. The mixed order technique with the additional Euler parameters method is proposed to solve a general 3D flexible multi-body system. Two examples are studied in this dissertation: a planar slider-crank mechanism and a 3D flexible moving craft in irregular waves. The planar slider-crank mechanism is used in this dissertation to demonstrate the application of the integrals calculated as time-invariants and the proposed projection method with displacement and velocity constraints correction. The flexibility of the connecting rod of the slider-crank mechanism is included in the formulation. The numerical results obtained by the projection method will be compared with those by the commonly used coordinate partitioning method. The results show the validation and efficiency of the proposed constraints correction method. For the 3D flexible craft dynamics, the pressure distribution reconstruction algorithm is carried out to construct the hydrodynamics pressure on the wetted surface based upon the test pressure data. Then the nodal pressure loads are converted to the equivalent nodal force as the external loads for the flexible craft. Both Euler parameters and angular velocities are treated as the generalized coordinates in the equation of motion to model the rotation motion of the craft. Hence, the second order of Euler parameters is not incorporated in the equation of motion. It means that only constraints on first order time derivation of Euler parameter are needed. The results from the proposed Euler parameter methods are compared with the matrix exponential based Newmark method. It shows that the proposed Euler parameter method is non-sensitive to the time steps and has good accuracy. Finally, the least square error optimization method is used to find the Von Mises stress at each node. Thus, the time history nodal stress can be obtained directly from the modal element stress and modal coordinates solved from DAE. Hence, it doesn\u27t need to rerun the dynamic analysis under the nodal displacement to obtain the node stress

An Orbital Stability Study of the Proposed Companions of SW Lyncis

We have investigated the dynamical stability of the proposed companions orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al. 2010). The two candidate companions are of stellar to sub-stellar nature, and were inferred from timing measurements of the system's primary and secondary eclipses. We applied well-tested numerical techniques to accurately integrate the orbits of the two companions and to test for chaotic dynamical behaviour. We carried out the stability analysis within a systematic parameter survey varying both the geometries and orientation of the orbits of the companions, as well as their masses. In all our numerical integrations we found that the proposed SW Lyn multi-body system is highly unstable on time-scales on the order of 1000 years. Our results cast doubt on the interpretation that the timing variations are caused by two companions. This work demonstrates that a straightforward dynamical analysis can help to test whether a best-fit companion-based model is a physically viable explanation for measured eclipse timing variations. We conclude that dynamical considerations reveal that the propsed SW Lyncis multi-body system most likely does not exist or the companions have significantly different orbital properties as conjectured in Kim et al. (2010).Comment: 9 pages, 6 figures, 2 tables. Submitted to and accepted by JASS -- Journal for Astronomy and Space Sciences (using JKAS LaTeX style file

Recent Developments in Smart Adaptive Structures for Solar Sailcraft

The "Smart Adaptive Structures for Solar Sailcraft" development activity at MSFC has investigated issues associated with understanding how to model and scale the subsystem and multi-body system dynamics of a gossamer solar sailcraft with the objective of designing sailcraft attitude control systems. This research and development activity addressed three key tasks that leveraged existing facilities and core competencies of MSFC to investigate dynamics and control issues of solar sails. Key aspects of this effort included modeling and testing of a 30 m deployable boom; modeling of the multi-body system dynamics of a gossamer sailcraft; investigation of control-structures interaction for gossamer sailcraft; and development and experimental demonstration of adaptive control technologies to mitigate control-structures interaction

An advanced 3D multi-body system model for the human lumbar spine

Series : Mechanisms and machine science, ISSN 2211-0984, vol. 24A novel 3D multi-body system model of the human lumbar spine is presented, allowing the dynamic study of the all set but also to access mechanical demands, characteristics and performance under work of the individual intervertebral discs. An advanced FEM analysis was used for the most precise characterization of the disc 6DOF mechanical behavior, in order to build up a tool capable of predicting and assist in the design of disc recovery strategies – namely in the development of replace-ment materials for the degenerated disc nucleus – as well as in the analysis of variations in the me-chanical properties (disorders) at disc level or kinematic structure (e.g. interbody fusion, pedicle fixa-tion, etc.), and its influence in the overall spine dynamics and at motion segments individual level. Preliminary results of the model, at different levels of its development, are presented

Investigation of inner contact and friction conditions of a spherical roller bearing using multi-body simulation

At the Institute of Machine Elements, Gears, and Transmission (MEGT, University of Kaiserslautern) a spherical roller bearing has been modeled in an multi body system (MBS) environment. The use of the commercial MBS (multi-body system) software (MSC ADAMS) allows the development of user-written subroutines for contact recognition and the calculation of contact forces. Those subroutines can help understanding the principles of friction phenomena inside spherical roller bearings, while the measurement of those effects is difficult.Measurements on a friction torque test rig for roller bearings are used to validate the MBS models. Since the sum of all contact forces equals the friction of the bearing, this test stand provides a way for validation of the contact and friction calculations

Linear dynamic modeling of spacecraft with various flexible appendages and on-board angular momentums

We present here a method and some tools developed to build linear models of multi-body systems for space applications (typically satellites). The multi-body system is composed of a main body (hub) fitted with rigid and flexible appendages (solar panels, antennas, propellant tanks,...) and on-board angular momentums (flywheels, control moment gyros). Each appendage can be connected to the hub by a cantilever joint or a pivot joint. More generally, our method can be applied to any open mechanical chain. In our approach, the rigid six degrees of freedom (d.o.f) (three translational and three rotational) are treated all together. That is very convenient to build linear models of complex multi-body systems. Then, the dynamics model used to design AOCS, i.e. the model between forces and torques (applied on the hub) and angular and linear position and velocity of the hub, can be derived very easily. This model can be interpreted using block diagram representation

Soil-structure interaction in resonant railway bridges

Special Issue: José Manuel RoëssetThis paper explores dynamic soil–bridge interaction in high speed railway lines. The analysis was conducted using a general and fully three-dimensional multi-body finite element–boundary element model formulated in the time domain to predict vibrations caused by trains passing over the bridge. The vehicle was modelled as a multi-body system, the track and the bridge were modelled using finite elements and the soil was considered as a half-space by the boundary element method. The dynamic response of bridges to vehicle passage is usually studied using moving force and moving mass models. However, the multi-body system allows to consider the quasi-static and dynamic excitation mechanisms. Soil–structure interaction was taken into account by coupling finite elements and boundary elements. The paper presents the results obtained for a simply supported short span bridge in a resonant regime under different soil stiffness conditions.Ministerio de Ciencia e Innovación BIA2010-14843Centro de Investigación Científica de Andalucía (CICA

Modal Properties of 6-cylinder Tractor Engine Powertrain

Tato diplomová práce uvádí dynamiku klikového mechanismu šestiválcového řadového motoru za účelem návrhu klikového hřídele v CAD programu Pro/Engineer. Následuje popis vibrací klikového mechanismu a analytický výpočet jeho torzních vibrací. Hlavní část diplomové práce se pak zabývá konverzí hřídele do konečno-prvkového modelu v programu ANSYS a jeho importem do prostředí Adams/Engine. V tom je provedena modální analýza klikového ústrojí pro získání vlastních frekvencí a tvarů. Na konec práce je porovnán výstup z analytického řešení a výsledky z multi-body systému.This master’s thesis introduces cranktrain dynamics of the inline 6-cylinder diesel engine in order to design a crankshaft in CAD software Pro/Engineer. Follows a description of cranktrain vibrations and analytical calculation of its torsional vibration. Main part of the master’s thesis deals with conversion of the crankshaft to a finite element model in program ANSYS and its import to Adams/Engine interface. Further, a linear analysis is performed to obtain natural frequencies and inherent shapes of the cranktrain. At the end of the thesis the analytical approach solution and solution from multi-body system are compared.