Hello everyone, I'm planning some work on an aicraft model, in particulare the skin is made of resin impregnated carbon fiber layers. Is there any way to optimize the number of layers based on the local stress, so i can reduce weight?

Hello, I have some doubts about some concepts, maybe very basic, but I hope you can help me.

I know that hot spot is a method to eliminate peak stress, normally from the weld toe to evaluate fatigue in S-N curves that do not require this component, but I have also seen this method used in shell geometries for, for example, bolt holes. Is this correct?

It is my understanding that in shell elements there is no peak stress, since they linearize the stresses directly through the thickness, so a method like the one described in ASME Sec VIII Div 2 does not make sense to eliminate this stress component. But what about the hot spot method, which linearizes in the meridional or hoop direction? Obviously the stress distribution will not be linear if we apply this method in a bolt hole for example, where there will be a stress concentration. Is it correct to assume in that case that the stress above the linearized maximum stress at the edge of the hole is a peak stress, and therefore should be eliminated for fatigue analyses that require them?

Thanks in advance

Hello,

This is really weird but my company is super tight on their license usage with abacus, which they only allow their “super users” to do FEA

Im only a lowly senior engineer but have 3 years ANSYS experience and want to validate small designs I do with abacus but apparently not good enough for a license to use.

I have picked up using Calculix with freecad on my off time and have been fairly impressed with the outputs - my only caveat is the meshing options are not nearly as refined as the big name software. Luckily, with today’s hardware, I can really just brute force an unnecessarily large mesh in 1% of the time it took me a decade ago.

How do I go about trying to bring up alternative free options? Of course we need to validate but these are very mature programs at this point. Any output will be determined by the input conditions and mesh quality.

Any advice appreciated. Thanks

https://preview.redd.it/3c6xiga9to5e1.png?width=1911&format=png&auto=webp&s=8dcaf393a1ca43cd64790f6f9c5800cf6669a0d8

https://preview.redd.it/juxpvla9to5e1.png?width=1864&format=png&auto=webp&s=80397324c88fe0692677d361f67e3bf05b1e4336

Im trying to get the real eigenvalues of this system. Its essentially just a vertical plate with a pendulum attached to it. Ive constrained the baseplate to be rigid, Ive constrained the vertical plate to the baseplate, and ive constrained the cylinder that the pendulum will rotate around to the vertical plate. Ive constrained the pendulum to the cylinder using a surface to surface constraint. I need the pendulum to rotate around the cylinder freely in the simulation, but every time I run it, the pendulum just acts on its own, and doesnt obey the surface to surface contact constraint I've set on it. I really need some help bc I cannot figure it out. Thanks

Hi. When I use space claim to extract geometry of a chassis I made I use the combine tool to combine all the parts but when I go on mechanical and assign the material eg Aluminium it goes to 90kg. Whereas it should be around 50kg

If I don’t extract geometry and just share the beams on mechanical it gives 50kg

I have no clue but it’s been 2 days and constant hours and I’m losing my mind

I'm trying to simulate a DIY electrostatic "speaker" I made to try and see how it produces pressure waves in the air. I also want to observe its electrostatic behaviour in action too but I can't seem to find an FEA tool out there that... fits my budget that can do it. So far I found simulators specifically for acoustic behaviour analysis but they dont seem to have anything for measuring electrostatic behaviour. Does anyone know a good FEA tool for this?

Hi all, I'm currently working as Senior CAE Engineer in Automotive Chassis primarily on Durability studies. I'm planning to write series of blogs on engineering topics relevant to CAE Engineers. More like interview preparation materials, short books to introduce concepts and develop intuition. I'm planning to cover below topics. Suggest me to add or delete any other subjects.

1. Engineering Mechanics - Statics
2. Engineering Mechanics - Dynamics
3. Mechanics of Materials
4. Practical Introduction to FEA
5. Practical Introduction to Durability Analysis
6. Systems Engineering/New Product Development.

Also suggest me whether to write about Math and Physics related to above subjects to be included as I go or seperate blogs on Engineering Mathematics, University Physics.

I'm completely new to hypermesh, but very experienced with FEMAP. A big tool for me was organizing elements and nodes in groups in FEMAP. Hypermesh seems to operate differently, is there an equivalent "group" function in this tool? I was to just be able to organize elements/nodes in a group an be able to export the EIDs/NIDs to a list.

Are you guys using it? What for? Do you use the paid version?

During our course we analyzed just a plate with tension stress and for the exams we have to design a plate of composite material also with a project on femap, but I'm a bit confused about how I should add the shear.

So part of my university final project in FEA is to compare the performances of different element types to the analytical solution and see which elements converges the closest.

Now for my project it’s relatively simple where I can dumb it down to like a pressure vessel and can easily do hand calcs.

But this got me thinking, for more complex parts where I think hand calcs would be difficult to do ( such as a ribbed sheet metal as a part of a cars crash structure), how exactly is the process of choosing element types performed?

I feel a bit overwhelmed by the variety of element types out there

I have a a large box having a length of 100 cm, and width and height of 60 cm, that contains soil, and it's under a pressure of Q = 50 kPa in the top surface. So when I model the box in Plaxis 2D, I choose Plane strain model and in the model, the length over x direction is 1m, height over y direction is 0.6m. My question is that if Plaxis assumes the out-of-plane depth (z) has a width segment of 1m, then in my case B =0.6m I should scale the pressure Q (distributed line load at the top) down instead of applying the full value?

Because the force in the top is: F_real​=Q⋅A=50kPa⋅0.6m2=30kN, meanwhile in Plaxis: F_Plaxis​=Q⋅width=50kPa⋅1m2=50kN.

Therefore, Q_Plaxis​=50kPa⋅10.6​=30kPa to reflect the real depth. Is this correct or am I mistaken?

Hi guys, how can I define tie break contact between 2 layers in a axisymmetric model in ls dyna. Surface to surface tie break doesn't work with axisymmetric model. Only 2D type contacts can be assigned(as per my understanding).

Can how I define tie break contact? Can I use some other kind of contact in its place?

Hey guys,

I wanted to create a structural simulation of an artillery shell being fired from the barrel.

I have a model of the shell with the charge + few other items.

I want to check whether the shell that I have designed would fail during the acceleration.

The shell might go from stand still to Mach 2+ within a second.

I'm not sure about what boundary conditions or which analysis to use.

I want a simple action.

one harder cylinder (Deformable solid) comes at a velocity and hits a very thin layered wall of soft tissue (Deformable solid) and deforms it

but there is always an error. mostly, the wall tries to stay rigid and rather than deforming, has its mesh distorted. as in, rather than the middle of shape bending backwards,it stays firm and the mesh of the contact surface get deformed and eventually pierce one another

I used explicit dynamic step

I used a contact type interaction property. interactions are: 1. general contact and 2.surface to surface contact

mesh are hex and they seem fine enough. standard linear for cylinder and explicit linear for wall

errors are often:

The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element.

mesh element is distorted

Is there a way to append (i.e. add or remove nodes/elements into) an existing node set or an element set in Prepomax. Whenever I try to edit the set, either removes the previously saved nodes (inspite using shift) or throws an error. Thanks in advance.

I have a strong background in structural engineering but do not have applied FEA/FEM skills.

How can I learn the nuanced details of FEA/FEM without on the job training like: contact, plasticity, impact, creep load step, modeling connections, meshing, buckling, nonlinear statics, transient response, etc...

I am trying to run a simulation in Hypermesh; I am pretty familiar with the software and have been using it for quite some time; however, for a simulation I am doing, I need to constraint one axis in a direction that is tilted with respect to the global reference system.
The only option that makes sense to do this is to create a local coordinate system with the "System" command, and then assign it to the desired constraint, in the tab of the image. This works well with loads, but when I apply it to a constraint, there is no confirmation screen or way I can check if this has been succesfully done, and the simulations are not working as expected (the constrained direction is still in global coordinates. Is this a bug? Am I doing something wrong? Thank you in advance; this operation seems way more obvious in previous versions of the software

https://preview.redd.it/y6b7yxu84a4e1.png?width=1920&format=png&auto=webp&s=3248506841a4553cd30d14aabaf5d8bf3c1698d5

New beginners video on how to create a ply based model on https://www.youtube.com/@learncarbonfiber THANK TOU👍

It may sound silly, but I’m slightly confused. I have a component that needs to be tested in frequency response. The component will be tested on a shaker table.

Bcs The component is in contact with the shaker table through four brackets. Now while modelling this in Hypermesh optistruct , I create 4 RBE2 elements, all on the bottom surface of the bracket and excite it.

Question

1. Since I am applying load through four points, each of those load get summed up as it is applied on the component. That means if I apply the same load on each of RBE2 element that would multiply the load four times. is it okay to do that, or should I create just one RBE2 element that connects to the bottom face of the four brackets.

Which one of the two method is more accurate in describing the actual boundary condition?

So right now I have quite a lot of experience in mechanical FEA and CFD.

Since there are now several powerful tools available for free (OpenFOAM, FreeCAD, SALOME etc..) I was thinking to start freelancing as a side hustle, and maybe in the future making it become a full-time job.

Any of you guys did this and wants to share their experience or have any tips on how to start?

I was thinking one of those freelancing sites like fiver or something, I still didn't really look into it.

I only have access to static software, with no chance to purchase better software from the company.

Is there a way or trick to approx rubber materal in a static? Can i do something to linear properties? I wanted to use a mooney-rivlin model but once i started i only then realised the software says no. And i had prepares for a nonlinear analysis. Damn.

Hello everyone! I really need to perform topological optimization under the action of contact stresses in the teeth of two gears. But my teacher said that usually topological optimization is not performed on contact. Is this so and why?

I planing to buy a new laptop (not that expensive) for my personal use(to run toy peoblem) and to run some software

1. Matlab
2. Adams
3. Hyperworks suite

So, is this configuration enough of I need something else

[Ps it's a thinkpad]

Hi everyone, so I recently posted in regard to a fatigue analysis I was studying.

Since I didn't have the stress vs cycles data I was trying to run cycles to simulate it. Anyway, wrong method, not feasible, etc...

So, I recently got the complete experimental data for the material I'm analyzing (I did not have it at that moment) so I decided to doing it this way

I stayed with my 1C, 3C and 5C, two reversals per cycle, and got the max LE logarithmic strain as 0.001297 in all this analysis.

So I took this value and my understanding is that this is the (delta strain/2) value so there is no need to divide that strain between two.

So when I run the iterations (on the formula) to get the amount of cycles I get 9.05x10^7 cycles for that LE.

Now, my simulation max stress is 247 MPa, which is bellow the yield strength point 310 MPa, so it remains on the elastic zone.

I understand that (sigma'f/E)(2Ni)^b belongs to the elastic zone and (epsilon'f)(2Nf)^c belongs to the plastic zone.

For what I got on the simulation, I would understand that the LE I got it only belongs to the elastic strain (probably a plastic strain too but insignificant value, right?)

So, the dumb question here is, when I'm looking for the cycles through this method it should be taking in count the plastic segment of the formula even if there is no plastic strain?

Hello, good morning,

For a project, I have made an explicit simulation of a longitudinal crash member. Extracting the following force curve from the RigidWall-Crash member contact. The red one is the force as it comes out, and the black one is filtered with a Low Pass Filter at 180 Hz.

Now I want to design the joint at the base of the crash member, and I had thought about extracting this force to calculate, analytically, the number of screws needed and their tightening torque.

My question is, should I use the peak value of the contact or can I use the peak of the filtered signal?

Thanks

https://preview.redd.it/3m5c9xdsvf3e1.png?width=817&format=png&auto=webp&s=11b0b4b59d1106a6e3a21807efb9dae260fb3312

Hello, I want to build a simulation model with more components. I don’t want to use the glue function because it just makes problems. So I decided to use multiple parts, unite them to one solid and then mesh them all together so that the edges are clean. But know I want to give three different material properties to the different parts and have to select them properly. But Flood and Association didn’t work since I have just one meshed solid. Is there a way to maybe define user boxes with the shape of the particular solid bodies so that I can select every element inside the box and then give the material properties? Thank you very much in advance!