Time-dependent Co-ordinate System 4

[Matthew_19]

Hi Everyone,

I am a novice modeller looking to seek help using ABAQUS. I currently have a FORTRAN subroutine that models the laser heat source but I am struggling to move the source to exact locations across the surface, a colleague mentioned to me about using an excel spreadsheet that had time-dependent coordinates that ABAQUS could read, maybe implemented into the subroutine and the laser would move to each location via reading the coordinates file previously written in excel or similiar. Can anybody recommend tutorials or help with how to move a heat source across a surface/body based on X, Y and Z coordinates and how to make sure ABAQUS reads the file?

I would want the laser to start at a location, travel along the z-axis then move slightly down the x-axis by a known distance then repeat the scan? Etc and so on.

Many thanks

 

[FEA way]

Recent versions of Abaqus have built-in functionalities for additive manufacturing simulation. One of them is moving heat source. This capability, together with toolpath-mesh intersection, allows you to define laser path as so called event series using coordinates of arbitrary points (they can be located anywhere inside finite elements) and time when each of these points is reached by laser. There’s no need to write subroutines for this anymore. You just have to include proper keywords in the input file. What’s more, there’s a special plug-in (AM plug-in) that allows you to define that directly in Abaqus/CAE.

These functionalities are described in the documentation (see the chapter titled "Thermomechanical analysis of powder bed-type additive manufacturing processes"). And there’s an example in Example Problem Guide titled "Sequential thermomechanical analysis of a laser powder bed fusion build".

 

[Matthew_19]

Thanks very much @FEA way

The version of ABAQUS I have is 2018 and I am unsure if I have downloaded the plug-in required. Would you be able to point me in the direction of where to find all these functionalities? Or how to find the plug-ins available?

Sorry I am a complete novice with ABAQUS. I cannot seem to find the Title (Thermomechanical analysis of powder bed-type additive manufacturing processes) in the AM plugin 2018.

 

[Matthew_19]

I have currently only found this plug-in available:

https://www.3ds.com/products-services/simulia/trends/digital-additive-manufacturing/

I am unable to locate the plug-in available for the functionalities you mention. Apologies.

 

[FEA way]

To find AM plug-in search for "Dassault Systemes print to perform" or "Dassault Systemes digital additive manufacturing", open first link and locate Download section. I don’t provide URL here because this website may be moved to a different address or renamed in a near future (it already happened recently). Besided that you can’t download the plug-in directly from this website - you have to complete a short form first and then you will be redirected to actual download.

When it comes to the titles of documentation chapters that I’ve mentioned in my previous post, both of them are part of Abaqus documentation. So you have to sign in to your 3ds profile and then open software’s online documentation.

 

[Matthew_19]

I have been able to download the files and now have a bunch of lecture presentations and AM modelling section which is filed with python intel. Do you think it would be easier to call in an excel script for moving the laser given my lack of experience or would you recommend using the functionalities of abaqus?

 

[FEA way]

Your post with link appeared when I was writing my reply so I’ve noticed it when I’ve finished. Yes, currently that’s the correct address of this website.

Among the files that you’ve downloaded there should be a folder named "AMModeler". Place it in abaqus_plugins folder in your working directory. When you run CAE you should be able to find the plug-in in Plug-ins —> AM Modeler(Show/Hide). When you click this button AM modeler menu will appear on the left (where Model and Results trees are located). The rest is really easy and you can use training materials provided with the plug-in to learn how to configure such analysis. That’s the easiest way of doing it.

 

[Matthew_19]

I've extracted the AM folder to the ABAQUS CAE plug ins, but I am unsure if this is right as I can't seem to find it when I go through ABAQUS CAE > Plug-ins? Have I saved it in the wrong place? Thank you very much and hopefully when it works I'll be able to manage

 

[Matthew_19]

I now have the plug in available, however I am still struggling to understand what exactly the AM modelling package defines? I have a CAE model ready but unsure what the plug-in is asking me to do?

 

[FEA way]

You should define all general features of the analysis (geometry, mesh, materials, steps, boundary conditions, interactions, output requests and so on) in the Model tree, as normally done. Then switch to AM Modeler to add features related to AM simulation. Select "Create AM Model" first. Add new Event Series, select from file and read text file that containts laser path data in the following format:

t, x, y, z, P

where: t - time, (x,y,z) - coordinates of point reached by laser at time t, P - laser power.

Create new Table Collections. Select "ABQ_AM.AbsorptionCoeff" Property Table and specify absorption coefficient. Pick "ABQ_AM.MovingHeatSource" as well. In "Laser Event Series (string)" select previously defined laser event series. For "Energy Distribution (string)" choose Concentrated. Then in the Simulation Setup tab you should set Heating - just choose proper Table Collection.

This plug-in, apart from moving heat source, defines another features necessary for AM simulations (such as progressive element activation and progressive cooling). It simply adds proper keywords to input file so the same can be done manually.

Keep in mind that all these built-in functionalities are meant to be used in simulations of selected AM processes. Check the description of these features in the documentation to make sure that they fit the process you want to simulate. For example if you want to model welding then you should use Abaqus Welding Interface (AWI) instead of this plug-in. All other kinds of analyses that can't be done with AM plug-in require the use of subroutines.

 

[Matthew_19]

That's brilliant thank you very much FEA way. I shall try and work it out from there and see what I can do by using this plug-in. The deposition process I am wanting to replicate is the laser metal deposition process and this is available in the plug in. Does this plug in also work as the element birth and death technique or atleast the quiet technique where it can kill all elements then activate them as the heat source passes the corresponding global coordinate system? Reading from the second part of your post that's what I can relate it to.

Do you know of any examples to follow? This seems much easier than doing time-dependent coordinates and modal change for element activation.

 

[Matthew_19]

I want to use the Goldak Moving heat source, there is a function selected that I can use. However, I am unsure of how to actually string the coordinates, would you select the heat source that you want from the model tree area and edit? Or create own? And how do you define the laser path? Sorry, you seem to know what to do and I am completely unsure?

 

[FEA way]

Laser Metal Deposition (LMD) belongs to the group of Directed Energy Deposition (DED) techniques. It just so happens that there examples of DED process simulations both in Abaqus documentation (Example Problems Guide —> "Sequential thermomechanical analysis of a directed energy deposition build") and in workshop attached to AM plug-in. And they use Goldak model. If you follow the description of these examples you should be able to complete your task. The definition of Goldak model is described in Analysis Guide paragraph "Specifying a moving heat source with a Goldak distribution". Generally you have to define laser path in the same way as it is done for concentrated heat source and the only dofference is that additional parameters have to be specified to describe the heat source distribution around the laser spot.

AM simulations use so called progressive element activation. This technique makes elements inactive at the beginning of the simulation and activates them when material is deposited at their location by AM machine. You can choose from partial and full activation. The use of this functionality in DED simulations is described in the Analysis Guide chapter titled "Thermomechanical analysis of FDM- and LDED-type additive manufacturing processes" (paragraph "Specifying progressive element activation").

Note that both of these referenced documentation paragraphs describe manual (keywords) set up of what is done automatically by AM plug-in. However the documentation will help you find out the meaning of various settings available in AM Modeler.

P.S. On a side note, previously I said that for welding simulations you should use AWI. However this plug-in is not available for newer versions and it’s possible to simulate welding using the same techniques as those utilized for DED process analyses.

 

[Matthew_19]

Thank you very much FEAWAY. I think it will be a case of reading through the documentation and trying to relate my problem to the examples given in documentation. Currently trying to define the laser path which is proving difficult as I don't quite understand where to input the variables but I am sure with more reading it can be resolved. I have found the examples so hoping that it'll teach me.

 

[FEA way]

For this kind of AM process you will need just a single text file to be used in event series. This file should contain data in previously mentioned format:

t, x, y, z, P

Of course the software will connect these points to make a toolpath. There is an assmuption that both nozzle velocity and laser power are constant between two specified points. Detailed description can be found in the documentation but also in Dassault Systemes Konwledge Base article "Toolpath-Mesh Intersection Module and Built-in User Subroutines for Additive Manufacturing Process Simulation".

When you have this file prepared you should create two Event Series. One of the "ABQ_AM.MaterialDeposition" type and the other of the "ABQ_AM.PowerMagnitude" type. Select the same file for both of them but name these Event Series differently (for example MaterialPath and PowerPath). Then create two Table Collections (for each of the even series). The rest of the set up is rather easy and you can follow the LDED workshop instruction attached to plug-in. Just remember to switch "Deposition Process" to Bead in table collection used for material deposition.

 

[Matthew_19]

Although the plug in looks very helpful and your explanations have been very useful, I'm not quite grasping the matter for a simple deposition line. , I would still like to see how the time-dependent coordinate system worked..

Would you have any experience with such?

 

[Matthew_19]

The file I create should contain:

T, X, Y, Z as it states on the tables or include power as well?

I will try to configure this way, the task is very simple therefore trying to workout the easiest way for me

 

[FEA way]

Even for the simplest cases it will be easiest to use built-in AM functionalities. Either via plug-in or manually - by specifying proper keywords in the input file. These keywords invoke specific subroutines (including UMDFLUX), utility routines and toolpath-mesh intersection module. The same workflow is used in both cases (you have to define event series, table collections and so on).

The file should contain power values as well. If you don’t have detailed data you can assume constant power over the entire analysis time. But be careful with units.

 

[Matthew_19]

Can I just use the plug-in to set up everything? Without having to write many different subroutines?

If I were to send you my .CAE file would you be able to show what you mean by having event series, table collections and so on?

In the material deposition event series, there are only 4 variables - doesn't include power

 

[Matthew_19]

How do you run an AM model simulation to get the odb?