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Multibody System Dynamics - Science topic

Multibody System Dynamics, approaches to compute equations of motion of an multibody system, MR.
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Hello all,
I am working on a thermal model in Ansys Fluent 2019 R3, with the geometries of 4 cylinders of different lengths. Three cylinders form an inner tube and one cylinder as an outer tube.
All are considered as a single part.
It is a multiphase model with one material in the inner tubes and another material in the outer tube. I have chosen inner tubes as one cell zone and outer tube as another cell zone. When I gave inlets with a certain velocity and the heat boundary condition on one wall of the inner tubes (mostly first or second tube). I cannot see any heat flow. Moreover, I see a phase distribution issue even after mentioning different cell zones.
Could anyone suggest to me or help me, what could be the reasons for these issues? I have revised many videos and multiple papers regarding the problem. But, I see no useful information.
Any sought of help is highly appreciated.
Thank you
Rajesh
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It would be better if u could attach the geometry of your problem with boundaries you had applied on walls.
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I am looking for an open source software to carry out generic multibody simulations.
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I have a SIMPACK model (.SPCK file).
Is there an open source solver available?
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A mechanism is moving in a particular pattern. There is a real time video of the same with red color markers are stick to each links. Is there any image processing tool or software which can capture the movement of links and give its change in position, velocity and acceleration? So that the results can be used to co relate rigid body/ multibody dynamic model results.
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Hi Subhash,
You are looking for an object tracker / feature matcher. Here below a few tools I remember of:
1) https://physlets.org/tracker/ -> it's manual, quick and dirty for analysing a small quantity of data.
3) http://www.mousemotorlab.org/deeplabcut -> this tool seems promising enough, but computationally heavy.
Keep it simple if you can.
Best,
Andrea
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I have started a research on the modeling of multibody systems dynamics, and since dynamics mean to determine the Differential Equations of Motion, i am called to make the resolution of these OEM.
I need to know how to do so, so i started working on an easy example, but i find it difficult because i have no background on mathematics especially numerical integration.
My question is how to proceed to solve a DAE numerically using one of these methods ; Runge kutta, Adams - Bashford or Moulton, Central differences or Gaussian method?
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Actually, I was reading Shabana’s Book: Computational dynamics, John Wiley & Sons. 2010. As I'm investigating the dynamics of a multi-body system (having rigid and flexible structures). This code was introduced in chapter 9 of Shabana's book with some demonstrations of different parts of the code and it's usage. Yet, to my best knowledge, it was not mentioned from where to get this code. I would like to know where may I find this code, and/or other alternatives with similar or more capabilities?
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To obtain SAMS/2000 you have to reach out to Professor Shabana directly, I would suggest you getting his contact information from University of Illinois at Chicago's website. I strongly believe that SAMS/2000 should be the reference for all other commercial codes. SAMS/2000 is carefully developed by a pioneer professor in the field of computational multi body dynamics for rigid and flexible bodies. It took more than 35 years of research by professor Shabana and hundreds of his Phd students to develop the code!
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Hi,
I built a Simulink vehicle model with Dugoff's tire model that requires two parameters to calculate Fx and Fy; namely, the longitudinal stiffness and the cornering stiffness. Now I would like to verify my Simulink model by comparing the results with MSC ADAMS. ADAMS does not have Dugoff's tire model. How can I get these two parameters from ADAMS ?
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yes i do it several times, so you can see my researches
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why we prefer sliding joints in bridges?
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Valuable submission by Dr. Amjad Albayati and Dr. Victor Nazimko.
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Hi everyone.
I try to find some simple method to measure body-posture. We know a lot of them, but they are either low objective (aspect-based methods) or very difficult and expensive (Formetric 4D). Some advice...?
I know about nice resarch from Australia (https://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-9-113), but I miss some more informations and all my attempts to contact authors ended up failing.
Thanks in advance, Lenka
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I agree with your statement.  All the tools and programs are expensive so I have used a combination of many evaluations on children to come to conclusions.  Here is a couple of guides we have used to train resident on:
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what are the implications behind choosing Extraction and Rotation methods while doing EFA?
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Dear Shinaj,
of course I would say that reading the recommended literature above is inevitable, however I think that it is possible to break down the answer on few core considerations after which you may find through the specific case you have.
1) Principal component  (PCA) vs. factor (axis) analysis (FA). When you want to reduce the data-set (lots of items) to few variables (e.g. summed factor scores for participants that cover the data best), then you choose principal component analysis. In other words, the goal is describing the participants data in the least possible numbers of variables. These then would be the sum scores of the items which belong to the components (at least if it makes apparent sense putting the found items together, and be carefull, explaining all variance also means that this includes binning 'item specific' variance and systematic (factor explained) variance together, which inflates the overall amount of explained variance. Example: You measure response time for each item in a questionnaire and PCA will find a component, which explains the 'longer' reading time, which is due to the length of the given questions the participants read. This will not happen that easily in FA which seeks to separate the item specific variance and the 'meaningful' covariance between items). Hence, when you believe that there is a fine-grained factor structure behind the data, and this is the only thing you want to know, then choose an axis analysis, which is more sensitive to this (usually simply termed factor analysis).
2) Rotation.First, rotation means that you optimize the solution by rotating the (hypothetical) factors in the space of observations such that as much as variance can be explained by the factors, and to further differentiate the factor loadings on the items. When you perform PCA, rotation is futile, because the analysis by definition searches for othogonal components that explain most of the variance (highest factor loadings). Hence, rotation will only give you (nearly) the same results. When using FA rotation makes sense, because FA searches for the structure in the first place, but not maximum variance explanation. After conducting a rotation, which again optimizes factor loadings, you can more easily see which item belongs to each factor. The basic choice further is between orthogonal and oblique rotation, e.g. varimax rotation, which assumes that factors are independent (orthogonal), and promax rotation, which assumes that factors are dependent (oblique/correlated). Last one is to be preferred in EFA, because it is exploratory..., and when the factors are in fact indepented, the promax will give the same solution as the varimax.
There are more points, but I hope this helps priming the indepth reading into the complex topic :)
Best, René
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Applications of Differential-Algebraic Equations: Examples and Benchmarks
Editors:
Steve Campbell, Achim Ilchmann, Volker Mehrmann, and Timo Reis
 The  planned volume in the DAE-FORUM series will encompass prototypical, innovative and emerging examples and benchmarks of DAEs such as electrical networks, chemical reactors, multibody systems, multiphysics models, to name but a few.  Applications may be to a particular problem or to another area of mathematics or science.
Each article (15-40 pages) should start with a modelling section explaining whether the model is prototypical and for which applications it is used, followed by a  mathematical analysis, and - if appropriate - a discussion of the numerical aspects including simulation. Benchmark examples are welcome. All chapters in this upcoming issue of DAE-F will be published “OnlineFirst” with an individual DOI, i.e. contributions are visible and citable already before completion of the book.
We have a number of authors already, but we are open to consideration of additional contributors, especially in new applications. If you would like to suggest any names for our consideration, please feel free to suggest them along with their area of application.
If you are interested in contributing, you may submit your manuscript directly via the link http://www.editorialmanager.com/daef/default.aspx  until August 1, 2017, choosing the article type “Special Issue: Benchmarks in DAEs” from the drop down menu in the submission system. If you would like to discuss your project with us, please feel free to contact any of the four editors.
Note: If the Springer link is not active yet it will be very soon?
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Yes, that sounds interesting.
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I am looking for a software which will help me analyse simple to complex mechanisms with ease. It will be advantageous such software also support co-simulations.
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Hello, I develop the opensource software openmeca : https://gitlab.com/damien.andre/openmeca available for Windows, Mac OsX and Linux. OpenMeca is a standalone program designed for educational mechanics. OpenMeca does not support cosimulation. Its usage is very easy but it does not gives realistic drawing of system because openmeca uses symbols instead of real parts with complex geometries.    Some examples are available on youtube.
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Hello.
I have a mechanical system that can inflate a rubber film by air (in real). My rubber film is not uniform and when inflated it deforms differently based on the thickness. Now, I need to model how the deformed shaped will look during inflation and the active pressure of different area on the rubber surface.
Any idea?
Thanks in advance!
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Thank you very much.
However, I was hoping for (some) more simple and graphical presentation (3D) using any simulation software!
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Except John Sterman Book entitled “Business Dynamics: Systems Thinking and Modeling for a Complex World” that I use it as a master Reference in our class, what books are useful for teaching Purposes?
Do you know a book with many Teaching Examples and Exercises of Model that has Hierarchy of complexity for Student?
In your University what books are as a main references and basis of content?
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In my view, "Introduction to System Dynamics Modeling" written by George P. Richardson, Alexander L.Pugh III, is a quite easy and helpful reference for teaching the system dynamics methodology in graduate level courses. The book is firstly useful for practical managers and analysts, but on the other hand it is highly recommended as a basic introduction to system dynamics while it will also go over some non-technical examples of computer implementation of this methodology. 
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Having a family of vector fields (non-linear, 2d), depending on several control parameters with degenerate fixed points for some values of these, how can we determine the bifurcation type from the normal form?
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Bifurcations have specific normal forms. In that sense, you do not traditionally find bifurcations using the normal form, you find the normal form of the bifurcation (close to the singularity.) From here you can find the specifics of the bifurcation, but everything rests on knowing the eigenvalues of the system linearized about a certain equilibrium.
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I have intrinsic yaw-pitch-roll data for the initial and final position of a rigid body and I want to find the yaw-pitch-roll values halfway. Can I just linearly interpolate the yaw-pitch-roll values?
I would imagine this is done quite often in robotics, 3D graphics, gait analysis and other multibody mechanics applications, so any insight would be appreciated.
Thanks.
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It depends on how you want the rigid body to move. 
If you interpolate the yaw-pitch-roll angles, the interpolated orientation trajectory can be counter-intuitive.  The trajecotry also depends on the frame in which you describe the orientation of the rigid body. You can also express the end orientation with respect to the start orientation using yaw-pitch-roll angles and interpolate these. This is sometimes called three-axis interpolation. 
The orientation trajectory can also be interpolated along one rotation axis, with a constant rotational velocity.   This is sometimes a one-axis interpolation or a SLERP, this can be computed geometrically or using quaternions.  This motion is what most people find most intuitive. 
However, these motions only correspond to the natural motion of rigid bodies with specific inertia properties.  If you'll need a motion corresponding to a free floating rigid body, you'll need the Euler equations for the dynamics of rigid bodies.
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I want to model a cart with wheels in MATLAB SimMechanics and it is important for me that use wheels, not a prismatic joint instead of wheels.
And then I can apply torque by a DC motor to wheels.
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hi mr mostafa
prismatic or revolute joint?
i tried different times (about 1 month) to model the wheels in SimMechanic, ADAMS and working model softwares. but i couldn't model it. after consultation with some of my friends in other univ, i concluded that we don't know a good software to model the wheel behavior on terrain. 
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Looking for subroutine to separate coordinate into depended and in-depended in the case of multibody analysis field. 
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thank you for your helping 
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I would like to transfer transient analysis results from Finite Element Analysis Tool to MultiBody Dynamic Tool.
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I guess that you mean the "Modal Neutral File"?
Actually this is a binary file format used by MSC Adams that contains the data of a flexible body. It can contain information like the invariants of the inertia matrix, the mode shapes and frequencies of the modal base derived from fixed boundary eigenmodes and constaint modes (through orthonormalization, Craig-Bampton modal synthesis) and the position of the chosen interface nodes and maybe other nodes (for graphical representation).
This data is obtained from a linear FE analysis (eigenmode analysis, substructuring) and the major commercially available FE-solvers can write this file ready for import in Adams.
The 'reduced' modal representation of the deformable body contains much less degrees of freedom than the original nodal representation as tze higher frequency modes are usually truncated.
To 'transfer' a transient analysis, you might have to build an analog model to the FE-model in MBS-software and apply the same time dependent loads at the same interface nodes. If you get similar results will mostly depend on a proper choice of the modal basis.
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What is the difference between Prismatic (linear) joint and screw joint in both kinematic and dynamic? Could I use the prismatic joint to get the same behavior of screw joint?
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Prismatic joints have only translation dofs, but screw joints provide both translation as well as rotation together. For a 3D-rigid body, screw motion is the shortest way to get to another point.
You could use prismatic joint to get the same behavior of screw joint by breaking down the rotation part to infinitely small translations.