Towards approximate models of coulomb frictional moments in: I) revolute pin joints and II) spherical-socket ball joints (original) (raw)

Influence of the contact–impact force model on the dynamic response of multi-body systems

Proceedings of the …, 2006

This work deals with contact -impact force models for both spherical and cylindrical contact surfaces. The incorporation of the friction phenomenon, based on the Coulomb friction law, is also discussed together with an effective computational strategy, which includes the automatic step size selection procedure. Impacts within a revolute clearance joint in a basic slider -crank mechanism are used as an example to compare the different contact force models. The collision is a prominent phenomenon in many multi-body systems such as mechanisms with intermittent motion, kinematic discontinuities, and clearance joints. As a result of an impact, the values of the system state variables change very fast, eventually looking like discontinuities in the system velocities and accelerations. The impact is characterized by large forces that are applied and removed in a short time period. The knowledge of the peak forces developed in the impact process is very important for the dynamic analysis of multibody systems and it has consequences in the design process. The model for the contactimpact force must consider the material and geometric properties of the colliding surfaces, consider information on the impact velocity, contribute to an efficient integration, and account for some level of energy dissipation. These characteristics are ensured with a continuous contact force model, in which the deformation and contact forces are considered as continuous functions.

Analysis of rigid-body dynamic models for simulation of systems with frictional contacts

… -AMERICAN SOCIETY OF …, 2001

The use of Coulomb's friction law with the principles of classical rigid body dynamics introduces mathematical inconsistencies. Speci cally, the forward dynamics problem can have no solutions or multiple solutions. In these situations, compliant contact models, while increasing the dimensionality of the state vector, can resolve these problems. The simplicity and e ciency of rigid body models, however, provide strong motivation for their use during those portions of a simulation when the rigid body solution is unique and stable.

A Study on the Dynamics of Spatial Mechanisms with Frictional Spherical Clearance Joints

Journal of Computational and Nonlinear Dynamics, 2017

An investigation on the dynamic modeling and analysis of spatial mechanisms with spherical clearance joints including friction is presented. For this purpose, the ball and the socket, which compose a spherical joint, are modeled as two individual colliding components. The normal contact-impact forces that develop at the spherical clearance joint are determined by using a continuous force model. A continuous analysis approach is used here with a Hertzian-based contact force model, which includes a dissipative term representing the energy dissipation during the contact process. The pseudopenetration that occurs between the potential contact points of the ball and the socket surface, as well as the indentation rate play a crucial role in the evaluation of the normal contact forces. In addition, several different friction force models based on the Coulomb's law are revisited in this work. The friction models utilized here can accommodate the various friction regimens and phenomena t...

Friction Forces in Numerical Simulations of Kinematical Joints of Mechanical Systems

2021

The paper presents a way of estimation, by simulation, of friction forces that occur in the kinematical joints of mechanical systems. Friction forces between planar surfaces, in revolute joints, and in spherical joints are computed, and the results are compared with the values achieved from simulation. SolidWorks software is used for the simulation process.

Multibody dynamics simulation of planar linkages with Dahl friction

Multibody System Dynamics, 2007

It is well known that classical Coulomb dry friction model does not portrays important physical phenomena occurring in the contact between mating surfaces. Moreover, the discontinuity of force at zero velocity has many drawbacks during numerical simulations. In the attempt of exploring alternatives to Coulomb friction model, this paper present the application of the Dahl friction model in a multibody dynamics formulation. The analysis herein presented includes also the modeling of friction forces in lower pairs and some hints on the efficient computation of Lagrange parameters during the fixed-point iteration process. Two numerical examples are offered.

Contact Conditions for Cylindrical, Prismatic, and Screw Joints in Flexible Multibody Systems

Multibody System Dynamics, 2001

This paper focuses on the modeling of the contact conditions associated with cylindrical, prismatic, and screw joints in flexible multibody systems. In the classical formulation these joints are developed for rigid bodies, and kinematic constraints are enforced between the kinematic variables of the two bodies. These constraints express the conditions for relative translation and rotation of the two bodies along and about a body-fixed axis, and imply the relative sliding and rotation of the two bodies which remain in constant contact with each other. However, these kinematic constraints no longer imply relative sliding with contact when one of the bodies is flexible. To remedy this situation, a sliding joint and a sliding screw joint are proposed that involves kinematic constraints at the instantaneous point of contact between the sliding bodies. For sliding screw joints, additional constraints are added on the relative rotation of the contacting bodies. Various numerical examples are presented that demonstrate the dramatically different behavior of cylindrical, prismatic, or screw joints and of the proposed sliding and sliding screw joints in the presence of elastic bodies, and the usefulness of these constraint elements in the modeling of complex mechanical systems.

Modeling of frictional contact parameters of mechanical systems” Int

2020

It is well recognized that the contact stiffness, true contact area, and the contact force are among the key features in the study of friction system behavior. This paper presents the development of formulae for the mechanical component of dry-friction at the interface of two microscopic rough surfaces. Elastic deformation under the influence of the contact forces is considered. The elastic contact model formulation between interacting asperities is not assumed to occur only at asperity peaks, thus allowing the possibility of oblique contacts wherein the local contact surfaces are no longer parallel to the mean planes of the mating surfaces. It is shown that the approach enables the separation of the contact area into its normal and tangential projections and the contact force into its normal and tangential components. The mathematical model of contact is utilized to develop formulae for normal and tangential contact stiffness. The analytical method is used to estimate contact stiff...

Spatial Joints with Clearance: Dry Contact Models

2008

This paper presents a new technique for assessing the influence that clearance of spatial joints has on the kinematics and dynamics of multi-body systems. The technique is developed for the revolute joint in which the basic elements are the journal and bearing. Under certain working conditions, these two mechanical elements collide with each other being the contact treated as coupled forces. The forces between each pair of contacting bodies are equal and opposite, and the magnitude and direction are calculated based on the positions and velocities of the bodies, as well as on the geometry of the joint. A continuous contact force model is used to evaluate the contact-impact force. The proposed methodology is developed in the framework of the multi-body systems formulation; therefore, the forces developed during the contact between the joint elements are introduced into the systems' equations of motion as external forces. A double pendulum is used as a numerical example to show the application of the proposed methodology, being the efficiency of the developed methodologies discussed in the process of the results obtained.

Dynamic response of multibody systems with multiple clearance joints

Journal of Computational and Nonlinear Dynamics, 2012

A general methodology for the dynamic modeling and analysis of planar multibody systems with multiple clearance joints is presented. The interconnecting bodies that constitute a real physical mechanical joint are modeled as colliding components, whose dynamic behavior is influenced by the geometric, physical and mechanical properties of the contacting surfaces. A continuous contact force model, based on the elastic Hertz theory, together with a dissipative term associated with the internal damping, is utilized to evaluate the intra-joint normal contact forces. The incorporation of the friction phenomenon, based on the classical Coulomb's friction law, is also included in this study. The suitable contact force models are embedded into the dynamic equations of motion for the multibody systems. In the sequel of this process, the fundamental methods to deal with contact-impact events in mechanical systems are presented. Finally, two planar mechanisms with multiple revolute clearance joints are used to demonstrate the accuracy and efficiency of the presented approach and to discuss the main assumptions and procedures adopted. The effects of single versus multiple clearance revolute joints are discussed.