# Lianhua Ma's blog

## Some problem concerning the position of increment in ABAQUS subroutines.

Dear all,

I have a puzzling question.

As we know, the positions of a increment in a FEM analysis ( in abaqus) include :

1.  the start of the increment    2.    the end of the increment   3.     the current increment     etc

## Deduction of derivatives of free-energy density function in ABAQUS UHYPER

Dear xuanhe and all,

I have reviewed the paper "Method to analyze programmable deformation of dielectric elastomer layers". (Xuanhe zhao, Zhigang Suo)

It is very insteresting.

## ABOUT Work done by a pressure applied to a system

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'

finally, dG=vdp-sdT-dw'

## Cell mechanics-----Soft Tissue (MICROSCOPIC BIOMECHANICS )

The cells of our bodies represent a very large class of systems whose structural components often are both comlex and soft. Most cells have a complex internal structure of biological rods,ropes and sheets.

cell mechanics is vital to tissue formation!

I need some introductory materials to be familiar with cell mechanics and soft tissues in biomechanics. I will appreciate your help and guidance!

Best

Marc

## continuity e.q.,equilibrium e.q. ,N-S , constitutive e.q. for elastic solid and compressible fluid in the space-frequency domain

continuity e.q.,equilibrium e.q. ,N-S , constitutive e.q. for elastic solid and compressible fluid in the space-frequency domain, as shown in the following Fig.

i don't understand how can this author deduce? why v=iwu? is this assumption?  why is this necessary?    thanks for your help and guidance!