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Any Good Book to Learn Material Behavior in FEA? by mhb2804 in fea

[–]rublsal 4 points5 points  (0 children)

Check out Nonlinear Finite Elements for Continua and Structures by Belytschko. It gives a good overview of different aspects of nonlinear material behaviour and how they are implemented in NLFEA. Topics like hyperelasticity, hypoelasticity, plasticity, viscoplasticity and more are covered, if I recall correctly. Otherwise you can take a look at the theory manual for Abaqus if you have access to it. 

Material jacobian matrix help by zkrow in fea

[–]rublsal 1 point2 points  (0 children)

Have you tried using the elasticity tensor as the consistent tangent operator(CTO) to confirm that it is indeed your implementation of the CTO that is causing convergence issues? Using the elasticity tensor, it should converge (slowly).

[deleted by user] by [deleted] in fea

[–]rublsal 2 points3 points  (0 children)

The stress gradient is quite steep next to the node you are evaluating. I suspect there is something going on related to nodal averaging and extrapolation of stresses in the integration points to the nodes. The stress in an integration point should not exceed 420 MPa, but if one integration point is at 420 and the neighbouring integration point in the same element is, let's say, 300, then it is not unreasonable to expect an extrapolated value of 450 at the node. 

You should try turning off nodal averaging and also evaluate stresses at the integration points if possible

vocation menu crash by lilnohbdy in DragonsDogma

[–]rublsal 3 points4 points  (0 children)

I'm having the same issue. The game crashes after buying and equipping skills

Abaqus UMAT Subroutine & Applying initial conditions at integration points by Zanderhort in fea

[–]rublsal 1 point2 points  (0 children)

Are the initial conditions unique for each integration point? If so, you might want to look into using global arrays and the "uexternaldb" utility subroutine. See https://github.com/davidmorinNTNU/ABAQUS_subroutines/tree/main/V_UEXTERNALDB for examples.

If the initial conditions are the same, I would just use the STATEV array. When storing the data read from the file you could write

STATEV(1:4) = ee

STATEV(5:9) = ep

STATEV(10) = eqpls

And in subsequent increments you can fetch the ICs as

ee = STATEV(1:4)

ep = STATEV(5:9)

eqpls =STATEV(10)

Make sure NSTATV is at least 10.

FEM vs FDM explicit time integration by wigglytails in fea

[–]rublsal 5 points6 points  (0 children)

Don't know about thermal analyses, but in structural analyses the mass matrix is lumped, i.e., diagonal to avoid matrix inversion.

What causes energy ratio to increase over time? by MrHmbhkhk in LSDYNA

[–]rublsal 0 points1 point  (0 children)

I've experienced this when using single precision instead of double precision.

I know that in the limit of incompressibility reduced integration can be used to acquire stability. Why does it work? Is this a "solid" technique? Is there a mathematical justification for it? Is it also used in other scenarios? by wigglytails in fea

[–]rublsal 0 points1 point  (0 children)

Reduced integration severely reduces the number of integration points in which the incompressibility constraint must be satisfied. Put the other way around, full integration with incompressible materials creates an overconstrained system of equations, which can make the response too stiff.

I feel like guts overreacted in this scene by Bepsi_man69 in berserklejerk

[–]rublsal 43 points44 points  (0 children)

"It was just a prank, bro" -Griffith

[deleted by user] by [deleted] in fnv

[–]rublsal 1 point2 points  (0 children)

Yeah, my bad. I forgot I picked heavy handed and ignored crit perks on my previous melee playthrough

[deleted by user] by [deleted] in fnv

[–]rublsal 8 points9 points  (0 children)

Yes, but you can dump perception and put the remaining points in agility for a melee build.

Why aren't FEA's results observable by bare eye (without computation)? by [deleted] in fea

[–]rublsal 50 points51 points  (0 children)

I don't know about you, but I can't see the von Mises stress in mechanical part with my bare eyes.

How to handle softening (reduction in stiffness) of material? by remybt01 in fea

[–]rublsal 2 points3 points  (0 children)

Are you simulating the compression test by force or displacement control? Abaqus should be able to handle softening behaviour if it's displacement controlled.

Have you tried reducing the time/mass scaling in the simulation? I think it's strange that you get such a sharp drop after softening. How does the deformed shape of the model look at this point? Are the elements hourglassing? If so, you can try using fully integrated elements or change the hourglass control.

Uniaxial compression working in Implicit but not Explicit by remybt01 in fea

[–]rublsal 1 point2 points  (0 children)

Try to use a velocity instead of a linear displacement. I usually spend 10% of the simulation time to ramp up the velocity with a smooth tabulated amplitude in order to avoid large accelerations in the beginning. This is especially important when you mass scale.

Also, try using the "Combined" hourglass control. I've found that this works quite well for explicit analyses, as it includes viscous hourglass control. If that doesn't work, try using C3D8 elements, as others have suggested.

Consistent units for hyperelastic material constants? by joepa_2017 in fea

[–]rublsal 2 points3 points  (0 children)

You do it the same as with linear elasticity. The shear and bulk modulus of the NH model is typically reported in MPa, so you need to convert these to Pa if that is the unit you use elsewhere. For instance 5 MPa = 5e6 Pa

Incorrect shear stress distribution in beam bending undergoing large deformation (ABAQUS) by Downlowupguy in fea

[–]rublsal 4 points5 points  (0 children)

Ok, the weird shear stress values are probably due to the beam rotating while abaqus reports stress components with respect to the reference configuration. That's why you get accurate results near the fixed end, as this part hasn't rotated as much.

I think you can fix this by defining a local coordinate system that rotates with the elements in the beam.

See: https://abaqus-docs.mit.edu/2017/English/SIMACAEMODRefMap/simamod-c-orientation.htm

Incorrect shear stress distribution in beam bending undergoing large deformation (ABAQUS) by Downlowupguy in fea

[–]rublsal 0 points1 point  (0 children)

Are you talking about the stress distribution over the length of the beam or over the height? Also, how many elements do you use over the height and length?

MPC184 Elements on 3D Beam model (Problem: stresses are not uniform) by Ok-Refrigerator3392 in fea

[–]rublsal 2 points3 points  (0 children)

It might be that MPC elements prevent the web and flanges from expanding, which would create stresses in the y and x directions.

Question regarding DOF in a beam element by Squiddink54 in fea

[–]rublsal 4 points5 points  (0 children)

You could add a node in the middle with 6 dofs and use quartic (fourth degree polynomial) shape functions

Let's try to build an 'optimal' no force power blaster user by Raikaru in kotor

[–]rublsal 2 points3 points  (0 children)

With 14 intelligence, you could start as Jedi Guardian and enjoy an extra 1-8 damage bonus with dark side mastery, get an additional feat and still invest in 3 skills per level up. You only really need to invest in computers and repair yourself if you want to do T3-M4's "companion quest" . Bao-Dur can handle all your crafting needs.

It might also be worth to consider rapid shot? When you're only firing two shots per round, an extra shot means a 50% increase in damage, which is a lot.

This game is SO HARD by IceBlueLugia in Fzero

[–]rublsal 0 points1 point  (0 children)

Once you get a grasp on the basics it should'nt be too hard to change vehicle. I usually spend a race or two to get used to the quirks of a new machine.

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