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Bo Li's picture

Dielectric strength: dependent or independent of stretch?

 Dielectric elastomer can undergo giant deformation, but are susceptive to various failure modes. i.e electrical breakdown.

Some experimental papers (Kofod, Plante, Chen, see the attachment) reported the dielectric strength of VHB material (a kind of dielectric elastomer) under difference pre-stretch, equal bi-axially or unequal bi-axially. And the strength (maximum voltage can be applied before breakdown) has be greatly improved by these mechanical stretches.

 So here comes the question: is the dielectric strength dependent or independent of stretch?

Mario Juha's picture

Is peridynamics a superset of Continuum Mechanics?

Recently, I have found a new theory, called Peridynamics, used to solve, mainly, fracture mechanics problems in materials. But, I am confused about the issue if it is a superset of continuum mechanics or is it a totally new theory that reformulate our previous understanding of continuum mechanics? How do you measure material properties with this theory? Do we need to reformulate our theories to deal with fracture mechanics problems? Is it a totally accepted scientific theory?

 

cordially,

 

Mario J. Juha

Temesgen Markos's picture

super-mechanician?

This month's issue of SIAM news had a beautiful story of how one hard problem in mathematics was solved in less than six weeks using online collaboration. SIAM's story is not online yet, but here is another link to the same story .   SIAM news refers to a "super-mathematician" coming out of several individual mathematician spread all over the world.

dileepade's picture

ansys command using IRLF,1

sir/madam...

 

i m little bit confused about doing inerta relief command analysing free free model...such as aircraft....

i have an quey that.. if command IRLF,1 used in ansys for static analysis... but model is in dynamic ?

what will be the the displacement and stress plot using IRLF,1 command....will these simmulate the correct model??

 

please guide me in this regards..

Dileep 

Today is Pi day and Einstein's birthday, again!

Google's logo is very cute today !  

Today is defined as Pi day, it is also Albert Einstein's birthday. Besides, today is Japaness lover's "white day".

According to Wiki, "In the 1980s the Japanese National Confectionery Industry Association launched a successful campaign to make March 14 a "reply day", where men are expected to return the favour to those who gave them chocolates on Valentine's Day, calling it White Day for the color of the chocolates being offered."

Integrity of Scholarly Publishing under Attack

 

This issue of CAM digest re-published D.N. Arnold's article  "Integrity under Attack - the state of scholarly publishing". The orginal article is available via weblink

http://www.ima.umn.edu/~arnold/siam-columns/integrity-under-attack.pdf

Why we start from honeycombs rather than cocoons.

The study of cellular solids is greatly influenced by the honeycomb. However, the honeycomb is not a component as whole for bees. Instead, the bee only care the shape and mechanical property of the cells, but in the engineering field, a cell of honeycomb is seldom used. We use them as plate, shell and so on. I think we ignore another porous material called cocoons, the protection to the most fragile period of insects. It is always bearing the load as a whole component.

ROPS Analysis

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   Need some help with ROPS analysis and design Criteria  

    I am aware that the (Roll Over Protection Structure) ROPS analysis is an ocean and I have just started to explore it as there is a need of it at my work. As of now, I have more questions and many wrong answers. So kindly bare with me. I will start with a brief introduction of what I know followed  by my question.

How to classify vehicle parts into sprung and unsprung mass?

I am currently working on deriving equations for different vehicle models using Lagrangian and Newtonian methods. I am need of parameters to test few MATLAB models, and in vague to know exactly how to classify the mass into sprung and unsprung. Similarly, how do I obtain the MOI separately for the unsprung mass?

babakp's picture

HyperFoam

Dear all

 

I want to start modeling the Hyper foam behavior in abaqus software, it is very usefull for me to consult with someone who works on that.

Regards

Babak

Dr. Michael Nosonovsky's picture

Green Tribology

Tribology is defined as the science and technology of interacting surfaces in relative motion, which involves friction, wear and lubrication.

The term “tribology” was introduced in the 1960s by Prof. Peter Jost.  In the consequent decades, various aspects of interacting surfaces in relative motion have been the focus of tribology, including, for example, the tribology of automotive applications, microelectromechanical systems, magnetic storage devices, adhesive contact, micro/nanotribology, biotribology.

MichelleLOyen's picture

Twitter and iMechanica

How many iMechanica users are on Twitter?  And how many are on Twitter with professional contacts? 

 I started to use Twitter about 4 months ago in a completely social, non-professional context.  As a personal (expat-focussed) blogger, I started to notice that I was
catching blog posts in my Twitter feed before I would see them in my
feed aggregator (Bloglines).   Twitter has emerged as a different sort
of feed aggregator, as well as a provider of information. 

load blast ls-dyna

Operation of the keyword *load-blast of LS-Dyna

How it works and its various applications in the simulation of an explosion of a mine

why thermal stress is self equilibrating

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Thermal stress does not develop when the free displacement is not constrained. How is this related to the term self equilibrating?

 

Say, I have a plate with the upper and lower surfaces at two different temperatures. The plate is not having any other constraint to prevent themal expansion. Why thermal stresses will not be generated in this case ( because of temperature gradient)?

 

Regards

higher order shell theories and finite elements

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Hello,

 

Recently I faced few questions in a course that I am attending:

 

1) Outline the salient features of different higher order shell theories.

 

2)Explain why some shell theories are not suitable as the basis of element formulation.

 

3) Discuss any limitations of elements being used in relation to their underlying formulation ( e.g use of shallow shell theory or cylindrical shell theory).

 

Stress/Strain calculation

Hello 

what do think why investigators await about 3 decades to calculation of local stress/strain by elastic-plastic fracture mechanics?and basically why elber's discovery[crack closure] was so important and play a key role in numerous articles?

How can i calcualtion the amount of load transfer through the contacting crack faces?

How can i determine the location of it?

 

Thank you

Mario Juha's picture

Why ANSYS not ABAQUS?

I would like to know why ABAQUS is the dominant FEM program (in terms of comments) in this forum? Why do you consider ABAQUS over ANSYS?

I have been using ANSYS for at least 8 years and I am very please with the capabilities of it. But I have not seen ABAQUS or used it. Beside, reading all the comments that are posted in imechanica, I feel like I am using the wrong FEM program. 

Which are the advantage of ABAQUS over ANSYS?

 

Thank you,

 Mario J . Juha

www.eng.usf.edu/~mjuha/

Rui Huang's picture

von Karman plate equations

Many of us (including myself) have used the nonlinear equations for elastic plates, originally proposed by von Karman (1910). I recently came across a book with some interesting comments about the plate equations, which may be of interest to share with others on imechanica. The book's title is "Plates and Junctions in Elastic Multi-Structures", authored by Philippe G. Ciarlet and published by Springer-Verlag in 1990.

Successful people will choose Ed Hardy

The
ed hardy Clothing was getting out to everyone and I noticed, in certain areas, that people were really into this shit. I thought it was a little weird mostly. Why? Because its based on a tattoo artist by the name of Don Ed Hardy. Christian Audigier was pretty much making shirts based of his tattoos. I admit, I do like Don Ed Hardy’s tattoos on people but not on clothes. Don’t get it twisted. I found the tattoo concept interesting. But it only appeals to me it as a coloring book on a shirt.

traditional concrete model VS damage concrete model

In my opioion, the traditional concrete model is taking the smeared cracking concept to deal with the tensile cracking and using the elastoplastic method to deal with the compressive softening.

We can find that recently the CDM based concrete model become a hot research subject.

But what are the advantages of the CDM-based?

Thank you very much!

dileepade's picture

need help in Ansys static analysis

sir ,i ahve some problems in use ansys element CERIG,MPC 184 and RB3 elements....what is difference in transfering loads to slave nodes using MPC184 elements and command CERIG and RBE3 ..

 

and also why mass21 elements are required if u defining coonection usimg CERIg and RBE3 command..

 

plz...advice and clarify my doubts to understand better..

 

thanks and regards..

 

-dileep 

Morteza_Kiani's picture

How can I model a bridge which consits of a small beam of composite that surrounded with ceramic layer

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Hi dear

I am going to model a bridge in dental work which it consists of two parts:

1: a small beam which it is made of composite 5 plys

2: a cramic part which surround the beam.

I want to model it with Abaqus. Please help me if you can. I'd appreciate if you help me and send its steps to my email: kian32m@yahoo.com

 

USNCTAM Address 2009

Check out the talk by Dr. Arden L. Bement, Jr., Director , National Science Foundation 
on TAM 

at  http://www.nsf.gov/news/speeches/bement/09/alb090424_tamsymp.jsp?govDel=USNSF_51

For the proceedings of the 2008 SBE&S workshop go to

Teng Li's picture

President Obama on the Necessity of Science (video)

Obama spoke at the National Academy of Sciences on Apr. 27, 2009, in which he states his commitment to doubling of science funding and stem education. From his speech,

 "At such a difficult moment, there are those who say we cannot afford to invest in science, that support for research is somehow a luxury at moments defined by necessities.  I fundamentally disagree.  Science is more essential for our prosperity, our security, our health, our environment and our quality of life than it has ever been before."

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