Ask iMechanica

I recently encountered the research of Phil Attard and others, in which the contact problem is solved, relaxing the restrictions of the traditional contact models (Hertz, JKR, DMT) and solving based on a formulation where the governing equations are derived using finite-range surface forces and calculated numerically, self-consistently.

Hello all,

I have created a 3-d dynamic model in ABAQUS using shell elements.  When I run the analysis I get several warning messages indicating that I have zero pivot nodes.  When I locate where these nodes are, I find that they are in the middle of my beam (modeled with shell elements) away from any boundary conditions.  Does anyone know why ABAQUS is indicating these inconsistent overconstraints in the middle of my model???  The analysis fails to converge when NLGEOM=yes but has no problems converging when NLGEOM is removed.

Thanks in advance

I am trying, quite unsuccessfully, to model a composite steel frame under dynamic loads.  The problem is nonconvergence brought upon by the concrete tensile strains (i think).  Apparently ABAQUS kills the analysis once cracks form in the concrete.  Has anyone had any success using the "Concrete damaged plasticity model" under cyclic loads and large strains.  I have found that researchers use many different concrete properties to get convergence, but I am more interested in a better concrete representation.

Any help on this would be greatly appreciated.

Hello, a simple question about the Lagrangian and Eulerian descriptions of fluid flow.

When is the Lagrangian (particle point of view) useful? It seems
that the Eulerian is always the right one, since velocity and pressure
are fields.....

thanks !

influx

Hi everyone!

I'm brand new of this website, but I'm already very excited about it - it's really helpful.

hi, i am currently working on using abaqus software for solving sintering problems . i just want to know how i can introduce new parameters into abaqus so that by giving some eqns for those i can solve the values of final porosity, shrinkage etc that are not pre-determined in the abaqus . i want to know the porosity distribution  and shrinkage rate in a particular given problem as outputs . please help me out . thnq

Hello everybody,

 In the implementation of nonlinear FEM, there are two ways, namely the Voigt notation and the full matrix notation. Obviously, using Voigt notation, one only stores vector instead of matrix. So, by using the symmetry of the Cauchy and second Piola Kirchhoff stress tensors, it is always possible to implement nonlinear FEM using Voigt notation. 

 So, my question is why the full matrix implementation still exists? It is mentioned in the famous book of Ted Belytschko. Only due to historical reason or there are some advantages? 

Hello all,

I'm modeling the railways track system, in which the rail wil be  affixed to the cross tie by Fastening to against the vertical force. 

Now instead of modeling the Fastening, I would like to model the contact between Rail and cross Tie in ABAQUS. I have try surface to surface; surface to node and also tie constrains, but somehow  the results are not reasonable (not agree to experiment result). I thinks the problem is contact properties.

So are there any one can helo me on the problem?