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Aaron Goh's picture

Mechanical vs Rheological Properties

What are the differences between "mechanical" and "rheological" properties?

Are "mechanical" properties a subset of "rheological" properties or vice versa? Or do they merely overlap?


Double effective stress of porous media (by Li chuanliang)

At present, the concept of effective stress has undergone three periods:

1. Terzaghi's effective stress         

            σeff= σ-p

 2. Biot’s effective stress

              σeff= σ-αp

 3. Double effective stress

A comments wordle

I was hoping to see Abaqus or Ansys as the top words. Instead I see help, thanks, stress and incident.

Zhigang Suo's picture

Report of the Chair, The Applied Mechanics Division, 2010

This report will appear in the 2010 Newsletter of the Applied Mechanics Division, of the American Society of Mechanical Engineers.

SN curve(s) of an anisotropic material


     I was just wondering how many S-N curves would i need to  define the fatigue properties of an anisotropic material. For an isotropic material we just use 1-curve. Would that also  be enough  for an anisotropic material? We need 21 elastic constants to define anisotropic material. Would the number of SN curves be similar or be somehow related to the number or would the number of S-N curves required would be probabilistic in nature. i.e. we find the S-N curves along several planes and get a some sort of probabilistic distibution. 


Atul Jain

Manjesh's picture


Hi everybody,

          Can anybody tell me what is the difference between these two field outputs in ABAQUS?? First one is CPRESS and the other one is PRESSURE which comes under stress output??? Actually I want to know normal pressure for my work. Which one of these two will give me Normal pressure??? Thanks..

Mubeen's picture

Crystal Plasticity- overview

I read this article today, perhaps other beginners like me can also get some benefit from this:

Title: Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling: Theory, experiments, applications.  

Teng Li's picture

Number of registered users of iMechanica exceeds 20,000

As of 11 May 2010, the number of registered users of iMechanica exceeded 20,000 , the total number of posts is 8191, the total number of comments is 14557.  The growth of iMechanica community remains steady since its launch.

Founded in September 2006, iMechanica aims

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?




Mario J. Juha

Temesgen Markos's picture


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.

I was just wondering if a similar thing is possible in applied mechanics. imechania seems ideally suited for that. 

dileepade's picture

ansys command using IRLF,1



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..


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

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

Choose a channel featured in the header of iMechanica: 

   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


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.



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

Choose a channel featured in the header of iMechanica: 

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)?



higher order shell theories and finite elements

Choose a channel featured in the header of iMechanica: 



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


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


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


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