Modelling of contact between stiff bodies in automotive transmission systems

in Fisette, Paul; Samin, Jean-Claude (Eds.) Multibody Dynamics: Computational Methods and Applications (2013)

Many transmission components contain moving parts, which can come into in contact. For example, the TORSEN differentials aremainly composed of gear pairs and thrust washers. The friction involved by ... [more ▼]

Many transmission components contain moving parts, which can come into in contact. For example, the TORSEN differentials aremainly composed of gear pairs and thrust washers. The friction involved by contacts between these two parts is essential in the working principle of such differentials. In this chapter, two different contact models are presented and exploited for the modelling of differentials. The former uses an augmented Lagrangian technique or a penalty method and is defined between two flexible bodies or between a rigid body and a flexible structure. The second contact formulation is a continuous impact modelling based on a restitution coefficient. [less ▲]

Investigations on a Level Set based approach for the optimization of flexible components in multibody systems with a fixed mesh grid

in Proceedings of The 6th Asian Conference on Multibody Dynamics: Shanghai (China), 26-30 aout 2012 (2012, August)

This paper considers the optimization of flexible components in mechanical systems thanks to a "fully integrated" optimization method which includes a flexible multibody system simulation based on ... [more ▼]

This paper considers the optimization of flexible components in mechanical systems thanks to a "fully integrated" optimization method which includes a flexible multibody system simulation based on nonlinear finite elements. This approach permits to better capture the effects of dynamic loading under service conditions. This process is challenging because most state-of-the-art studies in structural optimization have been conducted under (quasi-)static loading conditions or vibration design criteria and also because this ``fully integrated" optimization method is not a simple extension of static optimization techniques. The present paper proposes an approach based on a Level Set description of the geometry. This method leads to an intermediate level between shape and topology optimizations. Gradient-based optimization methods are adopted for their convergence speed. Numerical applications are conducted on the optimization of a connecting rod of a reciprocating engine with cyclic dynamic loading to show the feasibility and the promising results of this approach. [less ▲]

A Newmark-type integrator for flexible systems considering nonsmooth unilateral constraints

in Proceedings of the First Joint International Conference on Multibody System Dynamics (2012, June)

Mechanical systems are usually subjected not only to bilateral constraints but also to unilateral constraints. Inspired by the HHT time integration method for smooth flexible multibody dynamics, this ... [more ▼]

Mechanical systems are usually subjected not only to bilateral constraints but also to unilateral constraints. Inspired by the HHT time integration method for smooth flexible multibody dynamics, this paper presents a Newmark-type integrator, denoted by nonsmooth HHT method, to include the nonsmooth property of unilateral constraints. Through numerical examples accounting for both rigid and flexible body models, a bunch of methods are compared with the unilateral constraints on both velocity level and position level. Results show that the presented nonsmooth HHT method benefits from the accuracy and stability property of the classical HHT method with controllable numerical damping. In particular, when it comes to the analysis of flexible systems, the nonsmooth HHT method shows much better accuracy property than that of the other methods, including the Moreau–Jean time-stepping method and the fully implicit Newmark methods. [less ▲]

Modelling of frictional unilateral contact in automotive differentials

Conference (2011, November 14)

Modeling of contact between stiff bodies in automotive transmission systems

in Samin, Jean-Claude; Fisette, Paul (Eds.) Proceedings of MULTIBODY DYNAMICS 2011, ECCOMAS Thematic Conference (2011, July 05)

Many transmission components contain moving parts which can enter in contact. The TORSEN differentials are mainly composed of gear pairs and thrust washers. The friction involved by contacts between these ... [more ▼]

Many transmission components contain moving parts which can enter in contact. The TORSEN differentials are mainly composed of gear pairs and thrust washers. The friction involved by contacts between these two kind of parts is essential in the working principle of such differentials. In this paper, two different contact model are presented. The former uses an augmented Lagrangian technique and is defined between a rigid body and a flexible structure. The second contact formulation is a continuous impact modeling based on a restitution coefficient. [less ▲]

Advances in optimization of flexible components in mutlibody systems: Application to robot-arms design

in Proceedings of the 5th Asian Conference on Multibody Dynamics (2010, August)

The paper considers the optimization of the flexible components of mechanical systems modeled as multibody systems. This approach aims at considering as precisely as possible the dynamic loading of the ... [more ▼]

The paper considers the optimization of the flexible components of mechanical systems modeled as multibody systems. This approach aims at considering as precisely as possible the dynamic loading of the structural components under service conditions in their mechanical systems. While most of the structural optimization developments have been conducted under static or quasi static conditions, the approach is clearly a challenge. Naïve applications of this approach generally lead to fragile and unstable results. To elaborate a robust and reliable approach, we investigate and compare several formulations of the optimization problem. Different optimization algorithms are also tested. To explain the efficiency of the various solution approaches, the complex nature of the design space is investigated. The developments are illustrated using the test-case of the structural design of the links of a two-arm robot subject to a trajectory tracking constraint. [less ▲]

Recent developments in optimization of flexible components of multibody systems

Conference (2010, May)

Recently mechanical engineering has extended from a component to a system oriented approach. The structural analysis of components is now completed by the whole mechanical system simulation using ... [more ▼]

Recently mechanical engineering has extended from a component to a system oriented approach. The structural analysis of components is now completed by the whole mechanical system simulation using multibody system analysis. This evolution aims at capturing better the real loading conditions accounting for the component interaction and couplings in the system. Structural optimization is continuing along the same tracks. Recent works in structural optimization have tried to optimize components with respect to loadings conditions defined through dynamic loading coming from multibody system dynamic analysis. Generally, optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-static load cases to mimic the complex loadings in service. In contrast, we have shown in previous works devoted to topology optimization that an optimization directly based on the dynamic response of the flexible multibody system leads to a more integrated approach. In order to overcome the limitations of some previous approaches, a more integrated optimization technique is proposed here, based on the nonlinear finite element approach for flexible multibody systems. The non linear finite element formalism accounts for both large rigid-body motions and elastic deflection of the structural components. In previous work, the optimal design of components was realized as an optimal truss / beam layout. The present communication investigates the optimal design of components considered as a continuum medium. We study first sizing optimal design of structural components and we later extend the method to optimal material distribution approach to address their lay out optimization. The continuum domain is discretized into finite elements. For sizing optimization, the design variables are wall-thickness and lumped element variables. For topology optimization the design variables are classically density-like parameters associated to a power law interpolation of effective material properties for intermediate densities, also known as Simply Isotropic Material with Penalization (SIMP). This study assesses the feasibility of this approach, which extends optimization techniques to continuum flexible bodies included in MBS. The numerical implementation is conducted in SAMCEF MECANO for the flexible MBS analysis and BOSS Quattro for the optimization shell. The nonlinear equations of motion are solved using a generalized-a time integration scheme while the sensitivity analysis of mechanical responses is based on a direct differentiation method or finite differences. For sizing and parametric optimization the paper investigates and compares several optimization approaches methods such as classical gradient-based methods (SQP, Augmented lagrangian), sequential convex programming methods (CONLIN, MMA), but also surrogate-based optimization method (with Neural Networks) combined with genetic algorithms. The formulation of the problem is also discussed, and its influence on the convergence history is illustrated. Optimal sizing, shape and topology optimization of a simple model of a robot are addressed. The optimization approach is illustrated on numerical applications of sizing optimization of robot arms during trajectory tracking and lightweight layout optimal design of automotive components. [less ▲]