scholarly journals Nonlinear Modal Analysis of Mechanical Systems With Frictionless Contact Interfaces

2009 ◽  
Author(s):  
Denis Laxalde ◽  
Mathias Legrand ◽  
Christophe Pierre
Keyword(s):  
Large Scale ◽  
Augmented Lagrangian ◽  
Mechanical Systems ◽  
Inequality Constraints ◽  
Rayleigh Quotient ◽  
Contact Forces ◽  
Nonlinear Modes ◽  
Frictionless Contact ◽  
Nonlinear Contact ◽  
Nonlinear Modal Analysis

This paper investigates the nonlinear analysis, in the form of nonlinear modes, of mechanical systems undergoing unilateral frictionless contact. The nonlinear eigenproblem is introduced by a Rayleigh quotient minimization with inequality constraints formulated in the frequency domain. An augmented Lagrangian procedure is used for the calculation of the nonlinear contact forces. The efficiency of the proposed method for large-scale mechanical systems involving non-smooth nonlinear terms is shown. An industrial application consisting of a compressor blade in contact with a rigid casing is proposed. Sensitivity of the nonlinear modal parameters to contact is illustrated.

scholarly journals Nonlinear normal modes and their application in structural dynamics

2006 ◽  
Vol 2006 ◽  
pp. 1-15 ◽  
Author(s):  
Christophe Pierre ◽  
Dongying Jiang ◽  
Steven Shaw
Keyword(s):  
Large Scale ◽  
Invariant Manifolds ◽  
Normal Modes ◽  
Nonlinear Normal Modes ◽  
Realistic Model ◽  
Galerkin Projection ◽  
Engineering Structures ◽  
Nonlinear Modes ◽  
Nonlinear Modal Analysis ◽  
Nonlinear Normal

Recent progress in the area of nonlinear modal analysis for structural systems is reported. Systematic methods are developed for generating minimally sized reduced-order models that accurately describe the vibrations of large-scale nonlinear engineering structures. The general approach makes use of nonlinear normal modes that are defined in terms of invariant manifolds in the phase space of the system model. An efficient Galerkin projection method is developed, which allows for the construction of nonlinear modes that are accurate out to large amplitudes of vibration. This approach is successfully extended to the generation of nonlinear modes for systems that are internally resonant and for systems subject to external excitation. The effectiveness of the Galerkin-based construction of the nonlinear normal modes is also demonstrated for a realistic model of a rotating beam.

Modelling Hard Stops and Joint Clearances in Multibody Systems

1995 ◽  
Author(s):  
A. Mehra ◽  
S. Shivaswamy ◽  
H. M. Lankarani
Keyword(s):  
Multibody Systems ◽  
Mechanical Systems ◽  
Contact Forces ◽  
Multiple Impacts ◽  
Continuous Analysis ◽  
Aircraft Landing ◽  
Aircraft Landing Gear ◽  
Short Period ◽  
Nonlinear Contact ◽  
Joint Clearances

Abstract Multibody mechanical systems that have hard stops or joint clearances, encounter changes in the system kinematic structure. Due to the joint clearances or hard stops, internal impacts within the joint geometry occur. As a result of these impacts, nonlinear contact forces of unknown nature are created, which act and disappear over a short period of time. These forces or their corresponding impulses are transmitted throughout the system. In this paper, a methodology for treatment of multibody mechanical systems with hard stops and joint clearances is discussed. The methodology is based on the development of different contact force models that include energy absorption, with which a continuous analysis of the system undergoing internal impact is performed. The concept of effective masses is used to take into account the effect of the entire system rather than the link or the joint that encounters a discontinuous motion. The methodology is more suitable than the conventional impulse / momentum formulation in its treatment of multiple impacts and it guarantees accurate solutions no matter how hard or soft the stops are. The method discussed is applied to a point follower mechanism and an aircraft landing gear latch mechanism.

scholarly journals Modeling and Simulation for Wear Prediction in Planar Mechanical Systems with Multiple Clearance Joints

2021 ◽  
Author(s):  
Bo Li ◽  
Min San Wang ◽  
Charis J Gantes ◽  
Xuan U Tan
Keyword(s):  
Contact Surface ◽  
Mechanical Systems ◽  
Contact Forces ◽  
Force Model ◽  
Wear Depth ◽  
Contact Conditions ◽  
Clearance Joints ◽  
Effective Contact ◽  
Nonlinear Contact ◽  
Driving Condition

Abstract The main goal of this work is to develop a comprehensive methodology for predicting wear in planar mechanical systems with multiple clearance joints and investigating the interaction between the joint clearance, driving condition and wear. In the process, an effective contact surface discretization method together with Lagrangian method are used to establish the dynamic equation of the multibody system. Considering the change of the contact surface, an improved nonlinear contact-force model suitable for the complicated contact conditions is utilized to evaluate the intrajoint forces, and the friction effects between the inter-connecting bodies are discussed using LuGre model. Next, the contact forces developed are integrated into the Archard model to compute the wear depth caused by the relative sliding and the geometry of the bearing is updated. Then, a crank slider mechanism with multiple clearance joints is employed to perform numerical simulations in order to demonstrate the efficiency of the dynamic procedures adopted throughout this work. The correctness of the proposed method is verified by comparing with other literature and simulation results. This study is helpful for predicting joint wear of mechanical systems with clearance and optimize the mechanism’s design.

Modeling of Mechanical Systems Using Rigid Bodies and Transmission Line Joints

1999 ◽  
Vol 121 (4) ◽  
pp. 606-611 ◽  
Author(s):  
Petter Krus
Keyword(s):  
Transmission Line ◽  
Hydraulic System ◽  
Large Scale ◽  
Mechanical Systems ◽  
Rigid Bodies ◽  
Large Scale Systems ◽  
Distributed Parameters ◽  
Transmission Line Modeling ◽  
Integration Algorithms ◽  
Transmission Line Models

Dynamic simulation of systems, where the differential equations of the system are solved numerically, is a very important tool for analysis of the detailed behavior of a system. The main problem when dealing with large complex systems is that most simulation packages rely on centralized integration algorithms. For large scale systems, however, it is an advantage if the system can be partitioned in such a way that the parts can be evaluated with only a minimum of interaction. Using transmission line models, with distributed parameters, physically motivated pure time delays are introduced in the communication between components. These models can be used to represent both lines in a hydraulic system and springs in mechanical systems. As a result, components and subsystems can be simulated more independently of each other. In this paper it is shown how flexible joints based on transmission line modeling (TLM) with distributed parameters can be used to simplify modeling of large mechanical link systems interconnected with other physical domains. Furthermore, it provides a straightforward formulation for parallel processing.

Calculation of Contact Forces of Large-Scale Heavy Forging Manipulator Grippers

2009 ◽  
Vol 419-420 ◽  
pp. 645-648 ◽  
Author(s):  
Qun Ming Li ◽  
Dan Gao ◽  
Hua Deng
Keyword(s):  
Large Scale ◽  
Optimization Method ◽  
Contact Forces ◽  
Robotic Hand ◽  
Closure Condition ◽  
Contact Points ◽  
Robot Hands ◽  
Calculation Results ◽  
Forging Manipulator ◽  
Gripping Force

Different from dexterous robotic hands, the gripper of heavy forging manipulator is an underconstrained mechanism whose tongs are free in a small wiggling range. However, for both a dexterous robotic hand and a heavy gripper, the force closure condition: the force and the torque equilibrium, must be satisfied without exception to maintain the grasping/gripping stability. This paper presents a gripping model for the heavy forging gripper with equivalent friction points, which is similar to a grasp model of multifingered robot hands including four contact points. A gripping force optimization method is proposed for the calculation of contact forces between gripper tongs and forged object. The comparison between the calculation results and the experimental results demonstrates the effectiveness of the proposed calculation method.

Sign in / Sign up

Export Citation Format

Share Document