On Prediction of Passive Contact Forces of Workpiece-Fixture Systems

2003 ◽  
Author(s):  
Cai-Hua Xiongand ◽  
You-Lun Xiong ◽  
Michael Yu Wang
Keyword(s):  
Rigid Body ◽  
Nonlinear Equations ◽  
Contact Point ◽  
Contact Forces ◽  
Contact Model ◽  
System Of Nonlinear Equations ◽  
Elastic Contact ◽  
Elastic Deformations ◽  
Determinate System ◽  
Fixture System

Prediction of passive forces in a frictional workpiece-fixture system is an important problem, since the contact forces have a strong influence on clamp design and on workpiece accuracy during machining. This paper presents a general method for the computation of the contact forces. First, based on the rigid-body kinematics, an indeterminate system of static equilibrium is defined, in which the passive, frictional contact forces cannot be determined arbitrarily as in an actively controlled robotic multi-finger grasp. Then, we define a locally elastic contact model to describe the nonlinear coupling between the contact forces and elastic deformations at the contact point. This model captures the essence of the passive contact. Further, a set of “compatibility” equations are given so that the elastic deformations among all passive contacts in the workpiece-fixture system result in a consistent set of rigid-body displacement of the workpiece in its global system. Finally, combining the locally elastic contact model and the “compatibility” conditions, we transform the force computation problem into a determinate system of nonlinear equations governing all of the elastic deformations at all of the passive contacts. By solving the resulting nonlinear equations with frictional constraints, we can accurately predict all contact forces in the frictional workpiece-fixtures system. This method is illustrated with example cases. The method presented here may also have an application to other passive, indeterminate problems such as power grasps in robotics.

On the prediction of passive contact forces of workpiece-fixture systems

2005 ◽  
Vol 219 (3) ◽  
pp. 309-324 ◽  
Author(s):  
Cai-Hua Xiong ◽  
Michael Yu Wang ◽  
Yong Tang ◽  
You-Lun Xiong
Keyword(s):  
Contact Point ◽  
Linear Equations ◽  
Contact Forces ◽  
Contact Model ◽  
Elastic Contact ◽  
Elastic Deformations ◽  
Non Linear ◽  
Determinate System ◽  
Fixture System ◽  
Non Linear Equations

The prediction of passive forces in a frictional workpiece-fixture system is an important problem, since the contact forces have a strong influence on clamp design and on workpiece accuracy during machining. This paper presents a general method for the computation of passive contact forces. Firstly, an indeterminate system of static equilibrium is defined, in which the passive, frictional contact forces cannot be determined arbitrarily as in an actively controlled robotic multifinger grasp. Then, a locally elastic contact model is used to describe the non-linear coupling between the contact forces and elastic deformations at the contact point. This model captures the essence of the passive contact. Further, a set of ‘compatibility’ equations is given so that the relationship can be developed between the elastic deformations at all contacts and the displacement of the workpiece. Finally, combining the force equilibrium, the locally elastic contact model and the ‘compatibility’ conditions, the passive force computation problem is transformed into a determinate system of non-linear equations governing all of the elastic deformations at all of the passive contacts. By solving the resulting non-linear equations, all passive contact forces can be accurately predicted in the frictional workpiece-fixture system. This method is illustrated with example cases. The method presented here may also have an application to other passive, indeterminate problems such as power grasps in robotics.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

Wheel-Rail Multi-Point Contact Method for Railway Turnouts

2011 ◽  
Vol 97-98 ◽  
pp. 378-381
Author(s):  
Zhi Wei Chen ◽  
Linan Li ◽  
Shi Gang Sun ◽  
Jun Long Zhou
Keyword(s):  
Calculation Method ◽  
Normal Force ◽  
Contact Point ◽  
Point Contact ◽  
Contact Model ◽  
Contact Method ◽  
Elastic Contact ◽  
Simulation Calculation ◽  
Acute Change

A calculation method of wheel-rail multi-point contact based on the elastic contact model is introduced. Moreover, the simulation calculation of vehicles passing through branch lines of No.18 turnouts is carried out. The result showed that the acute change of wheel-rail normal force caused by the transfers of wheel-rail contact point between two rails can be avoid by wheel-rail multi-point contact method, and the transfers of wheel-rail normal force between two rails is smoother. The validity of wheel-rail multi-point contact method is verified.

Distributed Contact Model for Indeterminate Grasp Force Analysis towards Heavy-Duty Manipulation

2011 ◽  
Vol 383-390 ◽  
pp. 4837-4842
Author(s):  
Jin Cheng Mao ◽  
Wen Yu Yang
Keyword(s):  
Contact Forces ◽  
Contact Model ◽  
Elastic Contact ◽  
Three Dimension ◽  
Force Analysis ◽  
Heavy Duty ◽  
Linear Elastic ◽  
Grasp Force ◽  
The Relationship

This paper presents a new contact model to describe the contact constraints for heavy-duty manipulation. This contact model considers the contact area as a surface, which can translate three-dimension forces and torques. The contact deformations which are resulting from the large contact forces cannot be ignored. Distributed linear elastic contact model is adopted to describe the relationship between contact force and contact deformation. A case study is carried out in this paper based on this contact model for the grasp force analysis of heavy-duty manipulators.

An Elastic Contact Model for the Prediction of Workpiece-Fixture Contact Forces in Clamping

1999 ◽  
Vol 121 (3) ◽  
pp. 485-493 ◽  
Author(s):  
B. Li ◽  
S. N. Melkote
Keyword(s):  
Normal Force ◽  
Contact Region ◽  
Contact Forces ◽  
Contact Model ◽  
Quadratic Program ◽  
Elastic Contact ◽  
Complementary Energy ◽  
Elastic Bodies ◽  
Good Agreement ◽  
Tangential Friction

The design and evaluation of machining fixture performance requires accurate knowledge of workpiece-fixture contact forces since they strongly impact workpiece accuracy during clamping and machining. This paper presents an elastic contact model for the prediction of workpiece-fixture contact forces due to clamping. The fixture and workpiece are considered to be elastic bodies in the vicinity of the contact region. The model is formulated as a constrained quadratic program by applying the principle of minimum total complementary energy. The model predicts the normal force, and the magnitude and direction of the tangential (friction) force at each workpiece-fixture contact due to clamping forces. Experimental verification of the model under different clamping loads shows good agreement between predicted and measured normal and tangential contact forces. The model can be used to analyze fixture performance in terms of the contact forces and contact region deformation.

Wedge Damper Modeling and Forced Response Prediction of Frictionally Constrained Blades

2007 ◽  
Author(s):  
Ender Cigeroglu ◽  
Ning An ◽  
Chia-Hsiang Menq
Keyword(s):  
Rigid Body ◽  
Relative Motion ◽  
Harmonic Balance ◽  
Contact Stiffness ◽  
Contact Point ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Contact Forces ◽  
Contact Points ◽  
Contact Surfaces

In this paper, an improved wedge damper model is presented, based on which the effects of wedge dampers on the forced response of frictionally constrained blades are investigated. In the analysis, while the blade is modeled as a constrained structure, the damper is considered as an unconstrained structure. The model of the damper includes six rigid body modes and several elastic modes, the number of which depends on the excitation frequency. In other words, the motion of the damper is not artificially constrained. When modeling the contact surfaces of the wedge damper, discrete contact points along with contact stiffness are evenly distributed on the two contact surfaces. At each contact point, contact stiffness is determined and employed in order to take into account the effects of higher frequency modes that are omitted in the dynamic analysis. Depending on the engine rpm, quasi-static contact analysis is initially employed to determine the contact area as well as the initial preload or gap at each contact point due to the centrifugal force. A friction model is employed to determine the three-dimensional nonlinear contact forces and the relationship between the contact forces and the relative motion is utilized by the Harmonic Balance method. As the relative motion is expressed as a modal superposition, the unknown variables, and thus the resulting nonlinear algebraic equations, in the Harmonic Balance method is in proportion to the number of modes employed, and therefore the number of contact points used is irrelevant. The developed method is applied to tuned bladed disk system and the effects of normal load on the rigid body motion of the damper are investigated. It is shown that, the effect of rotational motion is significant, particularly for the in-phase vibration modes.

Influence of rail flexibility in a wheel/rail wear prediction model

2016 ◽  
Vol 231 (1) ◽  
pp. 57-74 ◽  
Author(s):  
Javier F Aceituno ◽  
Pu Wang ◽  
Liang Wang ◽  
Ahmed A Shabana
Keyword(s):  
Prediction Model ◽  
Rigid Body ◽  
Contact Point ◽  
Three Dimensional ◽  
Contact Forces ◽  
Wear Model ◽  
Material Loss ◽  
Wear Prediction ◽  
Contact Points ◽  
Rail Wear

The aim of this paper is to study the influence of rail flexibility when a wheel/rail wear prediction model that computes the material loss based on an energy approach is used. The wheel/rail wear model used in this investigation is a simplified combined wear hypothesis that is based on the frictional energy loss in the contact patch. In order to account for wear and its distribution in a profiled wheel surface, the contact forces, creepages and location of the wheel/rail contact points are first calculated using a fully nonlinear multibody system (MBS) and three-dimensional contact formulations that account for the rail flexibility. The contact forces, creepages and contact point locations are defined as nonlinear functions of the rail deformations. These nonlinear expressions are used in the wear calculations. The wear distribution is considered to be proportional to the normal force in the contact area. Numerical simulations are first performed in order to compare between the results obtained using the simplified wheel/rail wear model and the results obtained using Archard’s wear model with a focus on sliding when the track is modeled as a rigid body. This simplified wear model is then used in the simulation of the MBS vehicle model in the case of a flexible body track, in which the rails are modeled using the finite element floating frame of reference approach and modal reduction techniques. The effect of the rail deformation on the wear results are examined by comparing these results with those obtained using the rigid-body track model.

A Contact Force Solution for Non-Colliding Contact Dynamics Simulation

2006 ◽  
Author(s):  
Inna Sharf ◽  
Yuning Zhang
Keyword(s):  
Rigid Body ◽  
Contact Force ◽  
Contact Point ◽  
Closed Form Solution ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Contact Dynamics ◽  
Dynamics Simulation ◽  
Friction Forces ◽  
Contact Points

Rigid-body impact modeling remains an intensive area of research spurred on by new applications in robotics, biomechanics, and more generally multibody systems. By contrast, the modeling of non-colliding contact dynamics has attracted significantly less attention. The existing approaches to solve non-colliding contact problems include compliant approaches in which the contact force between objects is defined explicitly as a function of local deformation, and complementarity formulations in which unilateral constraints are employed to compute contact interactions (impulses or forces) to enforce the impenetrability of the contacting objects. In this article, the authors develop a novel approach to solve the non-colliding contact problem for objects of arbitrary geometry in contact at multiple points. Similarly to the complementarity formulation, the solution is based on rigid-body dynamics and enforces contact kinematics constraints at the acceleration level. Differently, it leads to an explicit closed-form solution for the normal forces at the contact points. Integral to the proposed formulation is the treatment of tangential contact forces, in particular the static friction. These friction forces must be calculated as a function of microslip velocity or displacement at the contact point. Numerical results are presented for three test cases: 1) a thin rod sliding down a stationary wedge; 2) a cube rotating off the stationary wedge under application of an external moment and 3) the cube and the wedge both moving under application of a moment. To ascertain validity and correctness, the solutions to frictionless and frictional scenarios obtained with the proposed formulation are compared to those generated by using a commercial simulation tool MSC ADAMS.

Minimum contact stress modification for profile curve design defects in the beam-spring-cone docking mechanism

2021 ◽  
pp. 095440622110036
Author(s):  
Weibin Lan ◽  
Shouwen Fan ◽  
Shuai Fan
Keyword(s):  
Contact Stress ◽  
Elliptic Integral ◽  
Contact Point ◽  
Contact Problems ◽  
Contact Model ◽  
Elastic Contact ◽  
Profile Curve ◽  
Curve Design ◽  
Docking Mechanism ◽  
Design Defects

A minimum contact stress modification method for profile curve design defects in a beam-spring-cone docking mechanism (BSCDM) based on genetic algorithm is presented in this paper, the profile curve and contact position of BSCDM are optimized. Under low-speed conditions, an improved elastic contact model of semi-space elastic bodies is established to modify and optimize the elliptic profile envelope curve based on Hertz contact theory and two kinds of complete elliptic integral, the improved contact model is used to solve elastic contact problems with the geometric characteristics of the ellipse surface, the optimal profile curve of the docking joint and the optimal docking contact point position are obtained. The results of numerical simulation and the experiment demonstrate the feasibility and validity of above models and methods.

Solving System of Nonlinear Equations using Genetic Algorithm

2019 ◽  
Vol 10 (4) ◽  
pp. 877-886 ◽  
Author(s):  
Chhavi Mangla ◽  
Musheer Ahmad ◽  
Moin Uddin
Keyword(s):  
Genetic Algorithm ◽  
Nonlinear Equations ◽  
System Of Nonlinear Equations
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