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Research Papers

Modal Selection Through Effective Interface Mass With Application to Flexible Multibody Cranktrain Dynamics

[+] Author and Article Information
S. Ricci

Ducati Motor Holding S.p.A.,
Via A. Cavalieri Ducati 3,
Bologna I-40132, Italy
e-mail: stefano.ricci@ducati.com

M. Troncossi

e-mail:  marco.troncossi@unibo.it

A. Rivola

e-mail:  alessandro.rivola@unibo.it
DIN—Department of Engineering for Industry,
University of Bologna,
Via Fontanelle 40,
Forlì I-47121, Italy

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS. Manuscript received November 30, 2012; final manuscript received May 27, 2013; published online September 25, 2013. Assoc. Editor: Aki Mikkola.

J. Comput. Nonlinear Dynam 9(1), 011002 (Sep 25, 2013) (10 pages) Paper No: CND-12-1213; doi: 10.1115/1.4025280 History: Received November 30, 2012; Revised May 27, 2013

The development of a multibody model of a motorbike L-twin engine cranktrain is presented in this work. The need for an accurate evaluation of the loads acting on the main engine components at high rotational speed makes it necessary to take element flexibility into account in order to capture elastodynamic effects, which might have a major impact on the dynamics of the system. Starting from finite element descriptions of both the crankshaft and the connecting rod, the classical Craig–Bampton (CB) technique is employed to obtain reduced models, which are suitable for the subsequent multibody analysis. A particular component mode selection procedure is implemented based on the concept of effective interface mass, allowing an assessment of the accuracy of the reduced model prior to the nonlinear simulation phase. Bearing dynamics also plays an important role in such a high-speed engine application: angular contact ball bearings are modeled according to a 5DOF nonlinear scheme in order to grasp the main bearings behavior while an impedance-based hydrodynamic bearing model is implemented providing an enhanced operation prediction at big end locations. The assembled cranktrain model is simulated using a commercial multibody software platform. Numerical results demonstrate the effectiveness of the procedure implemented for the flexible component model reduction. The advantages of this technique over the traditional mode truncation approach are discussed.

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References

Figures

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Fig. 1

Functional schematic of the cranktrain under study

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Fig. 2

EIM values (a) and EIM cumulative sum curves (b) related to the fixed-interface normal modes of the conrod model

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Fig. 3

Conrod deformation shapes associated with the second and the seventh fixed-interface normal mode

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Fig. 4

EIM values (a) and EIM cumulative sum curves (b) related to the fixed-interface normal modes of the crankshaft model

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Fig. 5

Crankshaft deformation shapes associated with the 1st and 19th fixed-interface normal modes

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Fig. 6

(a) The multibody model implemented in adams (the flywheel and the pinions are modeled as lumped inertias, but they are shown for reference); (b) combustion force magnitudes acting on the two pistons (values are normalized for data confidentiality)

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Fig. 7

(a) Force magnitude trend at the central main bearing 1 as computed for model A; (b) relative deviation of the results provided by model B, C, D, and E with respect to model A

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Fig. 8

(a) Minimum oil film thickness (normalized over radial clearance) at the big end bearing of conrod 1; (b) relative deviation of the results provided by model B, C, D, and E with respect to model A

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Fig. 9

Force magnitude at the central main bearing 1 as computed for model A and model 0, normalized over the peak load value of model A

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