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ABOUT Work done by a pressure applied to a system

Submitted by Lianhua Ma on
research
Work done by a pressure

I have one question  about work done by a pressure applied to a system.  The book of Thermodynamics often always present pdV (where dV is the change in the volume of the system. )but never Vdp, Why is that? Is it because we don't treat p as a variable? In a grand canonical ensemble is pressure constant for any system?

Acording to Thermodynamics first law,  du=dq-dw , where dw denotes work done by pressure and external force.  dw=pdv+dw' .   dq=Tds (Thermodynamics second law)

so, dU=TdS-Pdv-dw' 

Is imechanica evolving into mechanics.craigslits?

Submitted by Temesgen Markos on
opinion

Lately I am feeling like imechanica is becoming a craigslist for mechanics than a forum. Most recent blogs are simply ads that do not generate any discussion. Neither do questions from people get any reply, not any where near to what it used to be.

The last journal club had about five or so replies and the current one has no comment with two days to end.

Is it just me or does any body else feel the same too? I feel we have to think about how we can have a community here than just a repository of mechanics related stuff.  

Tsai-Wu criteria on ANSYS

Submitted by filipe_pedro on
education

Hello everyone.

I'm trying to apply the Tsai-Wu criteria to a composite plate in ANSYS. I'm using the SHELL99 element.

However, when I input the data for the criteria an error occours and ANSYS won't show me any results on the criteria.

Can someone help me? How do I use this criteria and what data should I use?

Thanks in advance 

hi everybody,

Submitted by suren on
education

 i'm studying M.S(materials science) and i"m interested in knowing how to do a project work in indenting and extracting mechanical properties of materials using ABAQUS software or using MATLAB. suggest any idea thanks a lot in advance. have a nice time.

Material model for high cycle fatigue

Submitted by Chali Alindunesiy on
research
finite element analysis
Fatigue
numerical simulation

In fatigue analysis, it is common to use S-N curve from database for spesific material, and some time for spesific way of loading. Is there any way to predict fatigue from direct simulation? For example, giving cyclic loading (10^5 times) and the material will suffer damage and eventually failed. In some FEM codes (MARC, LSDYNA, etc) there is Lemaitre-Chaboche model used to analyze material behavior under low cycle cyclic loading.

 Thanks in advance

Chali

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