Interference Impact Analysis of Multibody Systems

1999 ◽  
Vol 121 (1) ◽  
pp. 128-135 ◽  
Author(s):  
D. Wang ◽  
C. Conti ◽  
D. Beale
Keyword(s):  
Impact Analysis ◽  
Initial Conditions ◽  
The Body ◽  
Contact Joint ◽  
Joint Coordinates ◽  
Computer Aided Analysis ◽  
Constrained Multibody System ◽  
Impact Problems ◽  
The Impact ◽  
Two Bodies

A new computer aided analysis method for frictionless impact problems due to interference between two bodies in a constrained multibody system is presented in this paper. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities and rebounds. The interference surfaces can be described by the joint coordinates of the virtual contact joint, which are very useful for determining the impact time, the types and positions of two impact surfaces and impact initial conditions when an interference happens between two bodies.

Motion Design by Interference Analysis of Multibody Systems

1999 ◽  
Author(s):  
Deming Wang ◽  
David Beale
Keyword(s):  
Multibody Systems ◽  
Impact Analysis ◽  
Multibody System ◽  
The Body ◽  
Interference Analysis ◽  
Contact Joint ◽  
Impact Problems ◽  
Point Line ◽  
Two Bodies ◽  
Motion Design

Abstract A new computer aided analysis method for frictionless interference impact problems between two bodies in a constrained multibody system is presented in the paper, which can be used to perform interference analysis and motion design of multibody systems. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities, rebounds and system motion after the interference impact analysis. The interference surfaces can be any geometric element, such as point, line segment, are and circle described by the joint coordinates of the virtual contact joint. The method are very useful to predict and determine the interference time, the types and positions of two impact surfaces. System motion after the interference can be controlled by changing some dynamic parameters in the multibody system.

Frictional Impact Analysis in Constrained Multibody Systems

1996 ◽  
Author(s):  
Shakil Ahmed ◽  
Hamid M. Lankarani ◽  
Manual F. O. S. Pereira
Keyword(s):  
Impact Velocity ◽  
Canonical Form ◽  
Multibody Systems ◽  
Impact Analysis ◽  
Classical Problem ◽  
Double Pendulum ◽  
Joint Coordinates ◽  
Impact Problems ◽  
Energy Gains ◽  
The Impact

Abstract Analysis of impact problem in the presence of any tangential component of impact velocity requires a friction model capable of correct detection of the impact modes such as sliding, sticking, and reverse sliding. A survery of literature has shown that studies on the impact analysis of multibody systems have either been limited to the direct impact type with only a normal component of impact velocity (no frictional effect) or the ones that include friction have shown energy gains in the results due to the inherent problem in the use of Newton’s hypothesis. This paper presents a formulation for the analysis of impact problems with friction in constrained multibody mechanical systems. The formulation recognizes the correct mode of impact, i.e., sliding, sticking, and reverse sliding. The Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of Newton’s hypothesis are avoided. The formulation is developed by using a canonical form of the system equation of motion using joint coordinates and joint momenta. The use of canonical formulation is a natural way of balancing the momenta for impact problems. The joint coordinates reduces the equations of motion to a minimal set, and eliminate the complications arised from the kinematic constraint equations. The canonical form of equations are solved for the change in joint momenta using Routh’s graphical method. The velocity jumps are then calculated balancing the accumulated momenta of the system during the impact process. The impact cases are classified based on the pre-impact positions and velocities, and mass properties of the impacting systems. Analytical expressions for normal and tangential impulse are derived for each impact case. The classical problem of impact of a falling rod with the ground (a single object impact) is solved with the developed formulation, and the results are compared and verified by the solution from other studies. Another classical problem of a double pendulum striking the ground (a multibody impact) is also solved. The results obtained for the double pendulum problem confirms that the energy gain in impact analysis can be avoided by considering the correct mode of impact and using Poisson’s instead of Newton’s hypothesis.

A representation for planar point contact joints in the multibody mechanical bond graph library

1998 ◽  
Vol 212 (4) ◽  
pp. 305-313 ◽  
Author(s):  
W Favre ◽  
S Scavarda
Keyword(s):  
Point Contact ◽  
Bond Graph ◽  
The Body ◽  
Graph Representation ◽  
Kinematic Constraints ◽  
Contact Joint ◽  
Cam Follower ◽  
Mechanical Bond ◽  
Junction Structure ◽  
Two Bodies

In this paper a bond graph representation of the point contact joint between two bodies with any outline curves and in planar motion is proposed. The body geometry and frames are described, the kinematic constraints attached to the point contact joint are identified and the bond graph junction structure is deduced. The example of an elliptic cam-follower is used to illustrate the bond graph representation. In particular this shows the need for the simulation to add strong damping and very stiff elements to the system.

scholarly journals What goes up must come down Biomechanical impact analysis of jumping locusts

2017 ◽  
Author(s):  
Simon V. Reichel ◽  
Susanna Labisch ◽  
Jan-Henning Dirks
Keyword(s):  
Impact Analysis ◽  
Schistocerca Gregaria ◽  
Impact Damage ◽  
Landing Site ◽  
The Body ◽  
Adhesive Pads ◽  
Degree Of Control ◽  
Free Falling ◽  
The Impact

AbstractMany insects are able to precisely control their jumping movements. Previous studies have shown that many falling insects have some degree of control of their landing-orientation, indicating a possible significant biomechanical role of the exoskeleton in air righting mechanisms. Once in the air, the properties of the actual landing site are almost impossible to predict. Falling insects thus have to cope mostly with the situation at impact. What exactly happens at the impact? Do locusts actively ‘prepare for landing’ while falling, or do they just ‘crash’ into the substrate?Detailed impact analyses of free falling Schistocerca gregaria locusts show that most insects typically crashed onto the substrate. There was no notable impact-reducing behaviour (protrusion of legs, etc.). Independent of dropping angle, both warm and cooled locusts mostly fell onto head and thorax first. Our results also show that alive warm locusts fell significantly faster than inactive or dead locusts. This indicates a possible tradeoff between active control vs. reduced speed. Looking at the morphology of the head-thorax connection in locusts, we propose that the anterior margin of the pronotum might function as a ‘toby collar’ structure, reducing the risk of impact damage to the neck joint. Interestingly, at impact alive insects also tended to perform a bending movement of the body.This biomechanical adaptation might reduce the rebound and shorten the time to recover. The adhesive pads also play an important role to reduce the time to recover by anchoring the insect to the substrate.

A Static Change Impact Analysis Approach based on Metrics and Visualizations to Support the Evolution of Workflow Repositories

2016 ◽  
Vol 13 (2) ◽  
pp. 74-101
Author(s):  
Gustavo Ansaldi Oliva ◽  
Marco Aurélio Gerosa ◽  
Fabio Kon ◽  
Virginia Smith ◽  
Dejan Milojicic
Keyword(s):  
Impact Analysis ◽  
New Technology ◽  
Workflow Management ◽  
The Body ◽  
Analysis Approach ◽  
Tool Support ◽  
Change Impact Analysis ◽  
Support Organizations ◽  
Change Impact ◽  
The Impact

In ever-changing business environments, organizations continuously refine their processes to benefit from and meet the constraints of new technology, new business rules, and new market requirements. Workflow management systems (WFMSs) support organizations in evolving their processes by providing them with technological mechanisms to design, enact, and monitor workflows. However, workflows repositories often grow and start to encompass a variety of interdependent workflows. Without appropriate tool support, keeping track of such interdependencies and staying aware of the impact of a change in a workflow schema becomes hard. Workflow designers are often blindsided by changes that end up inducing side- and ripple-effects. This poses threats to the reliability of the workflows and ultimately hampers the evolvability of the workflow repository as a whole. In this paper, the authors introduce a change impact analysis approach based on metrics and visualizations to support the evolution of workflow repositories. They implemented the approach and later integrated it as a module in the HP Operations Orchestration (HP OO) WFMS. The authors conducted an exploratory study in which they thoroughly analyzed the workflow repositories of 8 HP OO customers. They characterized the customer repositories from a change impact perspective and compared them against each other. The authors were able to spot the workflows with high change impact among thousands of workflows in each repository. They also found that while the out-of-the-box repository included in HP OO had 10 workflows with high change impact, customer repositories included 11 (+10%) to 35 (+250%) workflows with this same characteristic. This result indicates the extent to which customers should put additional effort in evolving their repositories. The authors' approach contributes to the body of knowledge on static workflow evolution and complements existing dynamic workflow evolution approaches. Their techniques also aim to help organizations build more flexible and reliable workflow repositories.

scholarly journals Introducing pre-impact air-cushioning effects into the Wagner model of impact theory

2021 ◽  
Vol 129 (1) ◽  
Author(s):  
Matthew R. Moore
Keyword(s):  
Impact Analysis ◽  
Initial Conditions ◽  
Liquid Pool ◽  
Wagner Model ◽  
Viscous Forces ◽  
Effective Contact ◽  
Impact Theory ◽  
General Power ◽  
Post Impact ◽  
The Impact

AbstractIn this analysis, we consider the effects of non-quiescent initial conditions driven by pre-impact air–water interactions on the classical Wagner model of impact theory. We consider the problem of a rigid, solid impactor moving vertically towards a liquid pool. Prior to impact, viscous forces in the air act to deform the liquid free surface, inducing a flow in the pool. These interactions are then incorporated as initial conditions in the post-impact analysis. We derive expressions for the size of the effective contact set, the leading-order pressure and force on the impactor, and the speed and thickness of the jet at its base. In all cases, we show that the effect of the pre-impact behaviour is to cushion the impactor, reducing the size of the effective contact set and, hence, the force on the impactor. Small- and large-time asymptotic solutions are derived for general power-law impactors, and we show that the effects of the air die away as the impact progresses, so that we approach the classical Wagner solution.

A Poisson-Based Formulation for Frictional Impact Analysis of Open and Closed-Loop Multibody Mechanical Systems

1999 ◽  
Author(s):  
Hamid M. Lankarani ◽  
Murthy Ayyagari
Keyword(s):  
Impact Analysis ◽  
Closed Loop ◽  
Mechanical Systems ◽  
Friction Model ◽  
Momentum Balance ◽  
Contact Period ◽  
Double Pendulum ◽  
Canonical Momentum ◽  
Impact Problems ◽  
The Impact

Abstract Frictional impact analysis requires a friction model capable of correct detection of all possible impact modes such as sliding, sticking, and reverse sliding. Conventional methods for frictional impact analysis have either shown energy gain or not developed for jointed mechanical system, and especially not for closed-chain multibody systems. This paper presents a general formulation for the analysis of impact problems with friction in both open- and closed-loop multibody mechanical systems. The Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of the Newton’s hypothesis are avoided. A canonical form of the system equations of motion using Cartesian coordinates and Cartesian momenta is utilized. The canonical momentum-balance equations are formulated and solved for the change in the system Cartesian momenta using an extension of Routh’s graphical method for the normal and tangential impulses. The velocity jumps are calculated by balancing the accumulated system momenta during the contact period. The formulation is shown to recognize all modes of impact; i.e., sliding, sticking, and reverse sliding. The impact problems are classified into seven cases, and based on the pre-impact system configuration and velocities, expressions for the normal and tangential impulses are derived for each impact case. Examples including the impact of a falling rod on the ground, the tip of a double pendulum impacting the ground, and the impact of the rear wheel and suspension system of an automobile executing a very stiff bump are analyzed with the developed formulation.

Frictional Impact Analysis in Open-Loop Multibody Mechanical Systems

1999 ◽  
Vol 121 (1) ◽  
pp. 119-127 ◽  
Author(s):  
S. Ahmed ◽  
H. M. Lankarani ◽  
M. F. O. S. Pereira
Keyword(s):  
Impact Analysis ◽  
Mechanical Systems ◽  
Classical Problem ◽  
Open Loop ◽  
Tangential Component ◽  
Momentum Balance ◽  
Double Pendulum ◽  
Canonical Momentum ◽  
Impact Problems ◽  
The Impact

Analysis of impact problems in the presence of any tangential component of impact velocity requires a friction model capable of correct detection of the impact modes. This paper presents a formulation for the analysis of impact problems with friction in open-loop multibody mechanical systems. The formulation recognizes the correct mode of impact; i.e., sliding, sticking, and reverse sliding. Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of the Newton’s hypothesis are avoided. The formulation is developed by using a canonical form of the system equations of motion using joint coordinates and joint momenta. The canonical momentum-balance equations are solved for the change in joint momenta using Routh’s graphical method. The velocity jumps are calculated balancing the accumulated momenta of the system during the impact process. The impact cases are classified based on the pre-impact positions and velocities, and inertia properties of the impacting systems, and expressions for the normal and tangential impulse are derived for each impact case. The classical problem of impact of a falling rod with the ground (a single object impact) is solved with the developed formulation and verified. Another classical problem of a double pendulum striking the ground (a multibody system impact) is also presented. The results obtained for the double pendulum problem confirms that the energy gain in impact analysis can be avoided by considering the correct mode of impact and using the Poisson’s instead of the Newton’s hypothesis.

A Poisson-Based Formulation for Frictional Impact Analysis of Multibody Mechanical Systems With Open or Closed Kinematic Chains

1999 ◽  
Vol 122 (4) ◽  
pp. 489-497 ◽  
Author(s):  
Hamid M. Lankarani
Keyword(s):  
Mechanical System ◽  
Impact Analysis ◽  
Mechanical Systems ◽  
Friction Model ◽  
Momentum Balance ◽  
Contact Period ◽  
Double Pendulum ◽  
Canonical Momentum ◽  
Impact Problems ◽  
The Impact

Analysis of frictional impact in a multibody mechanical system requires a friction model capable of correct detection of all possible impact modes such as sliding, sticking, and reverse sliding. Conventional methods for frictional impact analysis have either shown energy gain or not developed for jointed mechanical system, and especially not for closed-chain multibody systems. This paper presents a general formulation for the analysis of impact problems with friction in both open- and closed-loop multibody mechanical systems. Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of Newton’s hypothesis are avoided. A canonical form of the system equations of motion using Cartesian coordinates and Cartesian momenta is utilized. The canonical momentum-balance equations are formulated and solved for the change in the system Cartesian momenta using an extension of Routh’s graphical method for the normal and tangential impulses. The velocity jumps are calculated by balancing the accumulated system momenta during the contact period. The formulation is shown to recognize all modes of impact; i.e., sliding, sticking, and reverse sliding. The impact problems are classified into seven types, and based on the pre-impact system configuration and velocities, expressions for the normal and tangential impulses are derived for each impact type. Examples including the tip of a double pendulum impacting the ground with some experimental verification, and the impact of the rear wheel and suspension system of an automobile executing a very stiff bump are analyzed with the developed formulation. [S1050-0472(00)02304-7]

scholarly journals COVID-19 Measures and Human Dignity in Colombia: Restrictions of Fundamental Rights in Bogotá and Valle de Aburrá during the March-June 2020 Period

2020 ◽  
Vol 19 (40) ◽  
pp. 551-578
Author(s):  
Gladis Cecilia Villegas Arias
Keyword(s):  
Human Dignity ◽  
Local Governments ◽  
Impact Analysis ◽  
Secondary Data ◽  
Fundamental Rights ◽  
The Body ◽  
World Health ◽  
Regulatory Impact Analysis ◽  
Study Results ◽  
The Impact

The goal of this article is to analyze the impact that the regulations issued under the national lockdown declared by the Colombian government during the crisis caused by COVID-19 had on human dignity. A qualitative analysis inspired on the methodology of regulatory impact analysis was applied to secondary data extracted from publications by the World Health Organization (WHO); the national government of Colombia; the local governments of Bogota and the municipalities included in the Metropolitan Area of the Aburra Valley; as well as to news published in relevant newspapers of the country during the episode under study. Results indicated that perceptions of legitimacy of institutions, ability to make decisions, sources of material life, social interactions, social controls, relationships to space, mental health, and controls over the body, were aspects of human dignity negatively impacted by the ruling during this episode. The main conclusion of this article is that citizens of Colombia under the ruling of biology lost many rights that the species had gained for protecting human dignity.

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