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lagrange multiplier and contact elements

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I would like to know how contact elements are different from " general "ie non contact finite elements.

Also I would like to know how Lagrange multiplier method is used in contcat analysis.


My understanding of the Lagrange multiplier is like this: when we have to impose a constraint equation

[C][D]=[Q] as constraint between DOFs, we incude a term Y*{[[C][D]-[Q]} where Y is the Lagrange multiplier ,in the potential energy functional and minimize the functional  to get the algebraic equations.

non linear analysis

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I am trying to learn non linear FEA ( Newton Raphson method)and this is what my understanding is. Kindly advise if you think my understanding is correct.

1) At the beginning of the analysis, I am using a small load step and using the current stiffess matrix ( which I am designating as initial tangent stiffness) I am solving for the initial displacement step for this load.

Here my question is: How this initial  tangent stiffness is calculated?

 The way I look at it:

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Is there a failure criterion/model for brittle spheres?

Hi, everyone

I am a student. I am  dealing with a failure problem of brittle spheres. These have a lot of flaws inside.I did some compression tests. Single spheres are crushed by a pair of parallel plates. I got the crush load distribution (in terms of critical contact force). 

My question is:

is there a failure criterion/model which relates to load(critical contact force), Youngs moduli and Poisson ratios of shpere and plates, radius and friction coefficient?

Interlaminar Stresses

Dear Sir/Madam,

Interlaminar stresses in Composites

I have modelled Plain Stress problem in hypermesh(Input deck is created in Hypermesh to solve in Abaqus).Layup sequence is [0/90/90/0], am getting the Stresses( σ11, σ22, σ12) in top and bottom layers only, but unable to get the stresses at each Interface, If any one knows how to write the code, please reply back.

Hi, I've a doubt in ANSYS

My doubt is in transient dynamic analysis.

take a simple model of 40*2*1 m dimensions.Applying brick45 material. with e=2.069e11N/m2

poissons ratio= .3

density= 7830kg/m3

first performing modal analysis with just arresting displacements in 1 side in subspace method and getting 10 sets of frequencies..

then performing transient dynamic analysis in mode superposition method with dynamic loads.and solve it

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Mahendra Gattu's picture

Concrete tied arch

Respected imehanicians!
                      I am a tackling an important problem about the behavior of concrete tied arch. Each concrete arch rests on two steel I-beams. The steel I-beams are supported at their ends. They are connected at various locations along their length by tie rods. A picture is worth 1000 words  basic figure.pdf.

mold filling simulation with flo3d


I want to simulate mold filling of a bar mold with a semisolid alloy by means of FLOW3D cfd package. but there are some problem. for example when I input a file I encounter an error like "level   1 error in subroutine rdstl: level   1 error in subroutine rdstl"in preprocessor. what can I do? does my .stl file have any faults?

other problem with another project is that when i want to solve the problem I encounter an error like "convective flux exceeded stability limit".repeatedly. is my meshing insufficient? how can I solve that too?

What is the Shore A hardness used for?

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The Shore A and D hardness tests are widely used by the rubber industry.  However, I'm not sure what practical use these numbers can be put to during design.  My current feeling is that Shore hardness numbers can at best give you a feel for the texture of the rubber - a Shore A value of 5 = gummy bear texture, Shore A = 40 implies erasure texture etc.

Can someone explain how Shore hardness values can be used in the design of mechanical components made of rubber?

Thanks in advance,

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Associated Press Writer
posted: 14 July 2008
05:23 pm ET

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Horizontal Vessel Support

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Hellow colleagues

I'm an equipment designer and i need to verify the stresses on the shell of an horizontal vessel over 3 saddles. I don't want to make a FEA analysis because is quite expensive to me.

I ask for your colaboration to find a method, other than Zick's one (only applicable for two saddles), to calculate the stresses on an horizontal vessel over multiple saddle supports.

to model creep behavior in ABAQUS


I have different stress strain curves at different hours (1hr, 10hr, 100hr).  for a constant stress, the strain increases with increase in number of hours(creep)

They look like stress-strain curves at different strain rates.

now I want to define a material card with these curves with above mentioned number of hours.

I kindly request you to suggest me a CARD in ABAQUS which takes care of this behavior.

How to calculate natural frequency of a beam with 3 spans

We are designing a underslung crane with 4 end trucks (3 spans). The crane girder is made of Universal Beam (UB). Can someone help to calculate the first fundamental (natural) frequency of the beam?

Zhigang Suo's picture

Large deformation and instability in gels

I'm attaching slides of a talk that I gave yesterday at the Schlumberger-Doll Research Center.  In preparing the talk, I made liberal use of slides prepared by Wei Hong for his own presentations.  The talk is mainly based on the following papers:


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