iMechanica - solid mechanics - Comments

Comment on Project

John M. Kolinski — Tue, 02 Dec 2008 11:14:42 -0500

Dear Pawel,

Your project is a neat one, and one about which I've given a bit of thought. I think it will be more about the fluid mechanics than about fluid solid interactions, but it would be neat to simulate this in the low-modulus limit of the cup, where some of the inertial energy in the fluid goes into elastic deformation of the container.

An alternative approach would be to change the container geometry, to see if you can mitigate the formation of the waves. It appears as though the wavelength in a coffee cup is proportional to its diameter; perhaps by making something like a soda bottle, with a narrow top, the sloshing will stop. Alternatively, you could try to divert the waves, by reflecting them off of an angled surface.

Good luck!

John

Why FEM is not used in CFD

Edwin Vollebregt — Sat, 22 Nov 2008 03:46:33 -0500

I just came across this nice discussion, even though it was posted a long time ago.

In my opinion you are quite critical with respect to the "complex geometry" advantage of FEM. FEM is very good at handling complex geometries because it can handle triangles. FDM is very awkward with triangles. FDM can handle complex geometries by using generalized curvilinear/boundary fitted coordinates, by variable grid sizes and by local grid refinement, but none of these are easy to do.

Then why is FEM not used in CFD? Simply because directional derivatives are difficult on an unstructured grid. This concerns transport phenomena: advection processes. Advection is discretised much easier on a structured (i.e. locally orthogonal) grid, particularly when you want high accuracy and be able to capture shocks as well (e.g. using flux limiters). Probably FEM-people have found appropriate ways to deal with advection too, but not as powerful and simple as it is done in FDM.

FVM methods are somewhere in between and combine some of the advantages and disadvantages of both. You can use rectangular volumes in large parts of the domain and polygonal volumes near boundaries or internal interfaces. At the expense of complex administration and complex approximation schemes, you may get flexibility *and* accuracy.

Thank you

Maurice — Thu, 20 Nov 2008 05:02:05 -0500

thank you It will help me for my studies

One Quick Note

Matt Pharr — Tue, 18 Nov 2008 23:39:38 -0500

I was reviewing Pawel's project and found something that might pertain to yours as well. If you are going to try to model the 300-400% volume strain, you may want to try using an Eulerian approach. If you look in the ABAQUS 6.8 documentation under Abaqus Analysis User's Manual in Analysis Techniques and then Section 13.1.1, it states that an Eulerian approach may be used to effectively handle large deformations. I believe this feature may not be available in Version 6.6 (it is not in the 6.6 documentation) but should be available in version 6.8 (if you can find access to it . . . ). So, I would suggest looking into this feature. Anyways, I am not going to waste your time posting some review article since you have probably already read it because I know you are doing this for your research. So, just this one suggestion.

http://www.hlrs.de/organization/aw/services/cae/app/abaqus/Documentation/docs/v6.8/books/usb/default.htm

-Matt

"Contents are Hot"

Matt Pharr — Tue, 18 Nov 2008 23:30:47 -0500

Hot coffee is a serious problem with much work being done on it in terms of legality

http://64.233.169.132/search?q=cache:GbYEBcPI-x0J:www.okbar.org/public/judges/mcdonaldsoutline.pdf+warning+contents+hot+coffee&hl=en&ct=clnk&cd=4&gl=us

and design

http://www.gizmodo.com.au/2007/06/because_contents_are_hot_warni.html

Actually in all seriousness I have found this topic (sloshing of a fliud) interesting since I did a problem on a partially filled milk tanker in introductory fluid mechanics. One thing that you might want to think about though is how ABAQUS will handle this problem. I looked through the documentation and initially found that solving this problem might not be possible to do in ABAQUS. If you look in the ABAQUS 6.8 documentation under Abaqus Analysis User's Manual in Analysis Techniques and then Section 11.5.1, one can see that it is very easy to model a fluid-filled cavity in Abaqus. However, it mentions in this section that the technique used to do so cannot be extended to a partially-filled container; it even directly says that this cannot be applied to sloshing. However, upon further investigation, I found that in Section 13.1.1 that an Eulerian approach can effectively handle liquid sloshing. So, this will be very important to your project. I have also found that this section was not included in the 6.6 documentation, so this feature may not be available in that version. You should definitely look into this and see if you need to find access to Version 6.8.

http://www.hlrs.de/organization/aw/services/cae/app/abaqus/Documentation/docs/v6.8/books/usb/default.htm

Also, I have found an article that may be of interest to you. It gives an overview of different numerical techniques (11 of them) that are used to model sloshing of liquid cargo in ship tanks. Here is the link

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V41-3XRG6T9-5&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=33b663f98abf83a045e45543293e0e1f

-Matt

Interesting project about an important issue of microelectronics

Sung Hoon Kang — Tue, 18 Nov 2008 11:12:59 -0500

Normal
0

false
false
false

MicrosoftInternetExplorer4

st1\:*{behavior:url(#ieooui) }st2\:*{behavior:url(#ieooui) }

/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-parent:"";
mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-para-margin:0in;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
mso-ansi-language:#0400;
mso-fareast-language:#0400;
mso-bidi-language:#0400;}

It’s an interesting project that studies one of the
important issues of microelectronic devices. It would be great to see how the
thermal stress profile will appear with temperature change during operation. I
have a couple of comments from one of the reference in the proposal [1] and
would like to suggest two potentially interesting references [2-3].

According to the paper by Prof. Tu, electromigration is
enhanced by tension but retarded by compression at the cathode and it is vice
versa at the anode. So, he suggests that “a favorable condition should be the
electron current entering the joint from the compression region and leaving
from the tension region.” [1] Thus, it would be interesting to find the tension
and compression regions at both cathode and anodes from the numerical
calculation which can be potentially useful for utilizing the effects that the
author mentioned. In addition, as the author mentioned, it would be also
interesting how the back stress, which can be built up in a flip chip solder
joint for the case of underfill, may interact with thermal shear stress.

As I search literatures about thermal stress in
solder-joint, I found two papers which can be helpful references. Wu et al. studied
the thermal stress in a Sn3.5AgCu half-bump solder joint under a
current stressing [2]. They reported substantial thermal stress accumulation around
the Al-to-solder interface, with a maximum stress of 138 MPa and the stress
gradient in the Ni layer of 1.67´1013 Pa/m resulting in a
stress migration force of 1.82´10−16 N, which is
comparable to the electromigration force, 2.82´10−16 N. In addition, Liu
et al. did 3D modeling of electromigration in IC device and solder joint (SnPb and SnAgCu lead-free solder materials) under the
combination of high current density, thermal load and mechanical load [3]. They
calculated the temperature, stress, atomic flux distribution in a packaging and
predicted void formation.

As a last comment, after doing thermal stress calculation, if
possible, it would be great to compare the numerical analysis result with the
experimental result for better understanding of the phenomena happening in the
flip-chip solder bumps during operation.

References

[1] K. N. Tu, “Recent advances on
electromigration in very-large-scale integration of interconnects”, J. Appl.
Phys. 94, 5451 (2003).

[2] B. Y. Wu, Y. C.
Chan, and H. W. Zhong, M. O. Alam, J. K. L. Lai, “Study of the thermal stress in a Pb-free half-bump solder joint under
current stressing”, Appl. Phys. Lett. 90, 232112 (2007).

[3] Y. Liu, L. Liang, S. Irving, T. Luk “3D Modeling of electromigration
combined with thermal–mechanical effect for IC device and package”,
Microelectron. Reliab. 48, 811 (2008).

Why Man Created The Travel Mug...

milnes — Mon, 17 Nov 2008 23:17:01 -0500

Pawel,

I nearly spill my coffee all the time too.

This is an interesting topic, and one that is fairly important to many areas of mechanical engineering. Espescially important to vehicle dynamics, violent sloshing can radiaclly change a vehicle's performance envelope in dynamic circumstances.

I found an interesting article on Google Scholar that talks about seismically-excited sloshing. It might be a good reference for dealing with multiple simultaneous forcing functions; it's linked below.

-Tom

http://doi.wiley.com/10.1002/(SICI)1096-9845(199607)25:7%3C653::AID-EQE513%3E3.0.CO;2-H

Great Idea

milnes — Mon, 17 Nov 2008 23:07:14 -0500

Matt,

This sounds very interesting; I wasn't aware that this sort of force was generated in traces. While I know relatively little about the area, you may benefit from the following two experimental papers. You could try to reproduce their results numerically if you want to perform a sanity check on your results. It might be valuable to vet your approach with real-world results.

-Tom

http://link.aip.org/link/?JAPIAU/73/3790/1

http://link.aip.org/link/?APPLAB/74/2945/1

thanks

özkan özcan — Sat, 15 Nov 2008 18:14:57 -0500

Teşekkür ederim Barış & thanks a lot Nanshu Lu.

Best Regards

Özkan Özcan

You could use Abaqus CAE to

Yuhang Hu — Wed, 12 Nov 2008 11:25:59 -0500

You could use Abaqus CAE to view it.

In the lab you should run Abaqus CAE and command seperately.

When you are using Abaqus command, you have to close Abaqus CAE window.

ABAQUS/Viewer License Problem

milnes — Tue, 11 Nov 2008 22:13:04 -0500

When I try to run ABAQUS/Viewer from any of the lab computers, I get the following error. Is there an easy way to correct this?

Thanks,

Tom

Neither feature "viewer" nor feature "cae" is available.
License server does not support this feature
Feature: cae
License path: 27006@lab-lm.fas.harvard.edu;27003@140.247.55.24
FLEXlm error: -18,147
For further information, refer to the ABAQUS Installation and Licensing Guide,
or contact your ABAQUS Inc. representative.
ABAQUS Error: ABAQUS/CAE Kernel exited with an error.
ABAQUS Error: ABAQUS/Viewer exited with an error
Press any key to continue . . .

Yuhang - Yes, I will

bjordan555 — Mon, 27 Oct 2008 10:15:31 -0400

Yuhang -

Yes, I will explain the differences, and will include this in my project report.

eigenvalue , eigensolver , eigenfrequensy , eigenmode

ho1mo — Fri, 24 Oct 2008 04:03:42 -0400

Can every body explain me about "eigenvalue , eigensolver , eigenfrequensy , eigenmode"?

Thanks in Advanced

Ho1mo

Actually the displacement

Yuhang Hu — Tue, 21 Oct 2008 21:16:54 -0400

Actually the displacement condition in the hint is consistent with the traction boundary condition. The displacement condition w=τy/μ is derived from the traction condition if ignoring the exist of the hole.

Yes! You can use PDF

Yuhang Hu — Tue, 21 Oct 2008 09:23:33 -0400

Yes! You can use PDF version.