iMechanica - ES 242r - Comments

"I have taken a class that

Steve Mccallion — Fri, 05 Dec 2008 11:51:52 -0500

"I have taken a class that the professor made slides with some missing
information that you add in as the lecture progresses. This definitely
keeps you following the lectures."

I like this format of lecturing, for the same reasons as stated. Also, some lecturer's suffer from a terrible case of can't-write-very-neatly-itis. This is not a personal attack on any lecturers (I know there are many here!), it's just a fact of life that not everyone has legible hand writing. Leaving spaces to be filled in definitely helps keep the students' attention, and reduces the hand work required by the lecturer.

I am definitely not in favour of lectures that are conducted solely on power point. First of all, something ALWAYS go wrong. Also, with chalk/pen in hand the lecture tends to become more dynamic, particularly when the lecturer has developed a class to ask many questions, afterall a picture is worth a thousand words.

A larger history can be displayed over several boards, allowing several 'slides' to be in the viewing range of the students. The lecturer also retains the ability to quickly jump back to prior board work when a student asks a question, which is particularly important with many students puzzling over a question for a minute or so before making themselves heard.

I could criticise powerpoints for quite some time, but they do of course have some fantastic advantages when used effectively. I'm about to complete a masters level course in material mechanics with a strong focus on the computational aspects of the subject. My lecturer has created some excellent presentation modules in mathematica which were invaluable for showing the effects of hardening in a much clearer manner than he could have done by hand (perhaps he just downloaded those modules, I know wolfram makes a lot of stuff freely available).

My friends keep talking of

johannabartley — Mon, 10 Nov 2008 12:22:50 -0500

My friends keep talking of COD's and CTOD's and though they learn at the Ohio Dominican University they couldn't tell me the difference between the two notions. Thanks for asking and thanks to all of you who answered.

my test

Manfred H Ulz — Mon, 10 Nov 2008 05:27:17 -0500

Thank you for the hint.

Blogging with LaTeX!!

HsiaoYing Shadow Huang — Thu, 21 Aug 2008 17:20:09 -0400

Hi Alex,

Thanks for this info. Finally I am able to type math entries in the blogs. I've tried it out and it worked perfectly.

Thanks again!!

Comprehensive Distance Education

Noel M. Dioyan — Fri, 11 Apr 2008 09:56:43 -0400

That is very interesting idea sir,if imechanica can provide a distance education from all field of engineering mechanics.The whole world is watching all the comments and suggestion in this site. Maybe, We here from asia can be benefited in your great proposal " Education without boundary" reagardless of distance,races,ethnics and culture..

Hi aswani kumar i am

Ravitej K — Sat, 03 Nov 2007 00:24:44 -0400

Hi aswani kumar

i am ravitej, doing my mtech in IIT kanpur. from ur posting i can guess that u had great knowlwdge in theoritical concepts of strength of materials.i want to ask a doubt regading strength of materials.

i want the mid point deflection in case of "four point bend test" on a
specimen of length 140mm, width of 40mm and thickness of 10mm.

Problem is that, beam theory is valid if the cross-sectional
dimensions are less than axial dimensions. Here this condition is
violated. i had modeled the specimen in Abaqus and the diffection at
mid point is almost double that of the actual diffection calculated
from beam theory.

how can i find the theoritical difflection at mid point in this case?

i had one option, using timoshenko beam theory and applying larger
deflection theory. will it be a reasonable approximation in this case?

please help me in this aspect.

Ravitej Kommana
IIT Kanpur
INDIA.

hi Jamilla

prashant sharma — Wed, 03 Oct 2007 14:27:33 -0400

i am MSc. Engineering by research student with mechancis.

my research works include. study of aero engine turbine disk for protential instabilty using ABAQUS, i have to perform analysis to simulate and predict the bursting phenomenon of disk for which i have to do elastic-plastic analysis and finally bursting of disk in which crack initiation and finally frature have to taken in to account.

so i was wondering if i have some tips regarding the Fracture mechanics particualy crack intiation phenomenon using Cohesive zone model techique from you.

thanks

prashant sharma

prashantsharma8@gmail.com

COD and CTOD:

Gopinath Venkatesan — Mon, 23 Jul 2007 17:18:48 -0400

To my knowledge, COD is first introduced by Boyle [1962] for measuring cracklength directly (I mean without measuring from microscope readings). This is essentially a strain gage reading for compliance (inverse of stiffness, COD/Load). I thought CTOD is the displacement of the crack tip and is different from COD. All these days, I convinced myself that CTOD is developed for elastoplastic while COD can take care of LEFM area but now confused. I will go through the references cited by Wu. Thanks.

Gopinath

COD & CTOD (Reply to Ling Zhu)--Fracture Mechanics class

Xiangfa Wu — Mon, 23 Jul 2007 15:34:02 -0400

Dear Ling, COD as a criterion is used for crack growth in elastoplastic materials, for which the K-criterion does not hold due to the finite plastic zone near crack tip. However, within the framework of SSY, COD-criterion is equivalent to K-criterion (Kanninen and Popelar, 1985). COD-criterion is considered as a supplementary fracture criterion for elastoplastic materials before the evaluation of J-integral (A.A. Wells, 1979) to be discussed in this class. The typical definition of CTOD for cracking in ductile materials can be found in the following link: http://www.efunda.com/formulae/solid_mechanics/fracture_mechanics/fm_epfm_CTOD.cfm

Based on my understanding, COD and CTOD indicate the same term though they may have a little difference in literature here and there. For example, the COD-criterion was discussed in detail in the classic textbook: Advanced Fracture Mechanics (Kanninen and Popelar, 1985), in which the term COD is actually also the CTOD. While in the textbook Cracks and Fracture (Broberg, 1999, pp. 575), it says that COD and COA (crack opening angle) are often written as CTOD (crack tip opening displacement) and CTOA (crack tip opening angle). Also, in some literature, it says that COD is the total displacement at crack tip (usually mixed-mode crack), while CTOD indicates the crack tip opening displacement due to pure mode I loading [e.g. Sha et al., Int. J. Fracture 104 (2000) 409-423]. There may be many others. Therefore, when we use COD or CTOD, we need to take care of the definition used in context. Hope this would make it clear.

thanx for the lecture notes

Zoeb Kaizar Lakdawala — Thu, 14 Jun 2007 09:15:52 -0400

Respected Sir,

I am a M. Tech Student doing my dissertation on Coding on fracture mechanics your lecture notes proves to be exceptional for the begineers like me. Please keep doing the good work for the future aspirants like me

Regards

Zoeb Lakdawala

Lectures online

John W. Hutchinson — Tue, 01 May 2007 15:39:06 -0400

Lee-

You are too kind! I recall the response Eli Sternberg once gave to someone who remarked that he kept his desk very orderly and free of paper. Eli replied that whenever anything accumulated on his desk he published it. In my case, I have to apply a much tighter filter. Most of my old lectures should probably end in the circular file. I have posted some of my old lecture notes on my website at

www.seas.harvard.edu/hutchinson

Thanks for your comments.

JOHN

Thank you, Pro. Hutchinson,

Ying Li — Tue, 01 May 2007 12:22:17 -0400

Thank you for your notes, which give us a help to study in related fields. Since I have seen you at Tsinghua last year, I still remember what you said at your presentation. May I give you a suggestion? I think you have given many presentations at many places. If you can collect them and offer them online, I think it may also very useful as your notes given here.

Lee

Powerpoint Lectures

Karla Polivka — Tue, 10 Apr 2007 15:56:16 -0400

I have taken numerous classes which have used powerpoint slides. I find that it is much easier to follow along and not get lost on something a professor may have said since most of what he/she is presenting is already down on the slides. With that said, having the slides available to print out before the lecture is a very vital part of utilizing the slides effectively and also so one can add their additional notes as one sees fit.

I have just been using the supplemental papers and notes available on imechanica.

I feel that the lectures have been going pretty well here in Nebraska. We do have an issue with the resolution when things are presented on the blackboard. I believe it is the way the camera is angled most of the time since it has a hard time picking what to focus on. However, the resolution on the graphics is pretty good or well enough since we have the slides to follow along with.

Hope this helps!!

Karla

Opportunity in the field of 'Fracture mechanics' with MNC R&Ds

rajbhatts — Fri, 06 Apr 2007 09:30:51 -0400

Opportunity in the field of 'Fracture mechanics' with MNC R&Ds, Bangalore, India

Brief Job Description:

The position requires the specialist to have experience in fatigue, fracture and damage tolerance utilizing customary hand analysis as well as commercially available software codes such as NASGRO, AFGROW, CRKGRO, BEASY, FRANC2D/3D. The specialist must be able to carry out structural analysis and dynamic analysis utilizing advanced methods and software codes to conduct linear and non-linear analysis of metallic and composite rotorcraft and tiltrotors components. Knowledge of Finite Element and Boundary Element Methods and new emerging procedures such as meshless methods is required. The specialist must have experience in research work in the areas such as Fracture Mechanics and course work in Elasticity, Plasticity, Structural Dynamics, Finite Element Methods, Boundary Element Methods and Experimental Methods. The candidate should have experience with solving fracture mechanics problems, and developing working software to solve structural problems that can be demonstrated by his/her results (papers, theses, reports, etc.).

If you're interested in pursuing opportunities based in MNC R&D's in Bangalore, India, Pl fwd your CV and also ask your friends and alumni to fwd their resumes to: phani.raj@adecco.co.in or rajbhatts@gmail.com.

Thanks & regards,
Phaniraj

Power Point Lectures Research

Nachiket Gokhale — Wed, 04 Apr 2007 11:21:37 -0400

http://www.smh.com.au/articles/2007/04/03/1175366240499.html

"The use of the PowerPoint presentation has been a disaster," Professor Sweller said. "It should be ditched."