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Arc length factors in Riks method

Submitted by Staszkinson on
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Computational Mechanics Forum
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Riks increment factors arc length

Hello,

It would be grateful if someone could explain me how to calibrate arc length increment factors in Static, Riks method in Abaqus.

For a default input in Static, Riks step I get max LPF factor equal 147(this value is probably correct, expected 147.8). Unfortunately, I'm not satisfied in number of increments(the result of 12 increments). The question is: how to calibrate arc length increment factors(initial, minimum, maxium arc length increment and estimated total arc length) to get more accurate results.

I found something about it, quote:

Reduce dof's in FEM

Submitted by SivaSrinivasKolukula on
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FEM
DOF's
reduce degree's of freedom

Hi 

  I have MDOF equation:

                MX"+CX'+KX = F(t).

 Say the order of each matrix is  nXn. I want to reduce the order of the matrices. 

I will find the eigen vectors and get modal vectors matrix phi. I will pick some dominating frequencies say around 24 modes.

then reducedM = phi'*M*phi.

defining hysteresis energy in abaqus

Submitted by arfaouisamar on
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Fracture Mechanics Forum
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hi all
working on low cycle fatigue and following the manual i have to define hysteresis energy as a damage criterion but in the menu of mechanical i found all other criterion except hysteresis energy.so how can i define this criterion in abaqus 6.10.
waiting for your kind reply  

How to solve Euler-Bernoulli beam for point load?

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I am student and learning beam theory. I am trying to solve Euler-Bernoulli 4th order differential equation to find the deflection of a beam.  The equation is

 

EI v''''(x) = w

where v is the transverse deflection and w is the distributed uniform load on the beam. 

But how would you solve the above if the beam is fixed on both ends, and instead of w, I have a point load P at say distance 'a' from the left end?  For a beam fixed on both ends, I use the following boundary conditions

[FEM] How we are using shell geometry properties in time of calculation?

Submitted by IvanKushnarenko on
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Shell
Geometry
quadratic forms

Hello.

I'm interested in methods and approaches for FEM, that are used for taking into account the shell geometry properties (curvatures, quadratic forms) in time of calculation. I'm not telling about NURBS, the shells are defyned by analytical expressions: sphere, Monge surfaces, Joachimstahl surface. In Zienkewich book they are use the flat elements, but in time of calculation they don't use the shell geometry, only for mesh generation. Maybe someone somehow have used in shape functions the coefficients of quadratic forms...

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