iMechanica - Comments

I think people here might

Bin Liu — Thu, 23 Feb 2012 01:45:34 -0500

I think people here might be interested in our robust and efficient FEM algorithm for buckling simulation. Please see the following link.

http://imechanica.org/node/4124

do you mean the result is not trustable

Lihua Jin — Wed, 22 Feb 2012 20:36:22 -0500

Thanks a lot for your answer! So do you mean the result is not trustable? If the quasi-static method helps the convergence of the simualation, but the result is not trustable, why do we bother to use it?

Harnessing instabilities: what's next?

Biswajit Banerjee — Wed, 22 Feb 2012 20:13:45 -0500

I have the good fortune of interacting with people from a number of industries.

One particular problem comes to mind at this stage - the problem of air transport of frozen fish.

Frozen fish are usually transported in styrofoam containers that are leak proof, thermally insulating, and structurally stable enough that they hold their shape during transport. The flip side of having these desirable properties is that they occupy a lot of space and, once delivered to a destination country, are essentially wasted because it is not cost effective to return them to their countries of origin. Go to any major fish market to see the millions of styrofoam containers that have been discarded.

One solution is to make biodegradable containers. Another is to make containers that are foldable (but still leakproof and insulating and antifouling/easily cleaned) and reusable. Instabilities are one way of achieving such a foldable structure (think, for example, of windshield light reflectors or even umbrellas).

But more than solid mechanics has to go into the design of these structures.

-- Biswajit

hr(nh1 + ...)

Sanjay Govindjee — Wed, 22 Feb 2012 17:12:29 -0500

The previous Time_n values are located at hr(nh1 + k) for k=0,1,2,...,number_hist_var_in_element

You need to write the new Time_n+1 values to hr(nh2 + k) for k=0,1,2,...,number_hist_var_in_element

nh1 and nh2 are set for you and are located in hdata.h. After you set the values, FEAP copies them to a global array. When you go to the next time step FEAP automatically moves the time_n+1 values into the time_n locations.

My FEAP site has an example (viscoelastic element) but it is (a) in C so it is not easy to read due to Fortran-C interfacing issues and (b) it is for a much older version of FEAP so some of it is rather outdated.

Prof. Dr. Sanjay Govindjee
University of California, Berkeley

Thank you so much for

queenlebron86 — Wed, 22 Feb 2012 16:02:51 -0500

Thank you so much for sharing ABAQUS tutorials, its learning and examples. I am writing research paper on ABAQUS. I need your help if you could provide some more information, otherwise I will have to go for online custom research paper writing service, which can be expensive.

I was asked question in my

queenlebron86 — Wed, 22 Feb 2012 15:51:25 -0500

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Sir, you have shared an

queenlebron86 — Wed, 22 Feb 2012 15:20:46 -0500

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Also in another report / BOEING are even less obvious problems!

Mike Ciavarella — Wed, 22 Feb 2012 10:37:27 -0500

Boeing says flaw could affect 55 Dreamliners

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Cracks also on Boeing 787 !!!

Mike Ciavarella — Wed, 22 Feb 2012 10:35:47 -0500

Michele C

Boeing to inspect all completed 787s for cracks

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Boeing will inspect all 55 completed Dreamliners for cracks in the composite plastic. (Roslyn Rahman/AFP/Getty Images)

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Reuters

8:10 a.m. CST, February 22, 2012

About 55 of Boeing Co.'s 787 Dreamliner jets could have a recently discovered flaw in the fuselage, the company said on Wednesday, while reiterating that the world's first carbon-plastic passenger plane is safe to fly.

Boeing this month reported signs of "delamination" on a support structure in the rear fuselage, the latest in a series of glitches in developing the revolutionary jet.

Albaugh said the problem was "very fixable."

"We are in the process of fixing the airplanes that are in the (production) flow," he said. "There is no safety or flight issue on the airplanes that we have delivered."

Though composite parts have been in use for years, the 787 is the first airliner built mainly out of the new materials, which help airlines to save fuel by reducing aircraft weight.

Albaugh said the inspections might affect delivery of the aircraft to customers in the short term, but the company still expects to meet its target for this year.

The first six aircraft produced are generally test models.

Sticking to the plans, Boeing expects to boost monthly output to 3.5 in the second quarter and to five by year-end.

Boeing has so far delivered five of the aircraft to Japan's All Nippon Airways, which put the plane into regular passenger service starting on Dec. 1. Due to production problems, that was three years later than originally planned.

ANA said Boeing had contacted the airline to say there were no safety issues involved in shimming and to give a general indication of the inspection procedure.

Boeing has promised to deliver a detailed procedure, which ANA expects to get soon. Meanwhile, all of its five Dreamliners are operating normally, the airline said.

Japan Airlines has already said it no longer expected its first Dreamliner by the end of February as a result of the manufacturing glitch.

The 787 problem comes as Boeing rival Airbus investigates the cause of cracks in part of the wings of its A380 superjumbo. It also insists its jets are safe.

Boeing will decide whether to go ahead with plans to produce a stretched, or longer, version of the 787 Dreamliner by the end of this year, Albaugh said.

Most aircraft analysts expected Boeing to push ahead with the 787-10, which would carry around 320 people, 40 more than the longest 787 version currently on offer, the 787-9.

The 787 and A350 address the mid-sized segment of the market, which is expected to number several thousand aircraft in coming decades as airlines renew fleets to save fuel and open up new routes.

Airbus took the lead last year with strong sales of its A320neo, but Boeing is redressing the balance with its 737 MAX.

"If there really is a softening in the economy, you could see some deferrals, you could see some people cancelling and you could see fewer orders," Albaugh said.

Underlining concerns about the economy, Singapore Airlines said on Wednesday that it was cutting cargo capacity by 20 percent because of weak demand and high fuel pricesiavarella, Politecnico di BARI - Italy, Rector's delegate. http://poliba.academia.edu/micheleciavarella

Yes, the results will be

lizheng619 — Wed, 22 Feb 2012 09:06:52 -0500

Yes, the results will be influenced a lot if using Quasi-static method, especially you have defined damping in you model. The model will have double damping, and therefore too damped.

I have compared the solution will experiment data, it indeed affect a lot.

FSI in gas pipeline

alinia — Wed, 22 Feb 2012 09:02:11 -0500

What's Next?

Douglas P Holmes — Wed, 22 Feb 2012 08:01:11 -0500

With a week remaining in February, allow me to pose the following question: Where do you see this field going in the future?

We have spent a lot of time talking about specific instabilities that perform specific functions, but it would be beneficial to generate a long-range vision. I'd be interested to hear everyone's thoughts.

anisotropic plasticity

Frank Richter — Wed, 22 Feb 2012 06:58:24 -0500

------------------------------------------
Ruhr-University
Bochum
Germany

How to identify the damage model

Johnson G — Wed, 22 Feb 2012 03:42:27 -0500

How to identify the J-C damage model parameters D1-D5 by the tests??

http://www.guardian.co.uk/business/2012/feb/15/airbus-a380-crack

Mike Ciavarella — Wed, 22 Feb 2012 01:13:12 -0500

Michele Ciavarella, Politecnico di BARI - Italy, Rector's delegate.
http://poliba.academia.edu/micheleciavarella