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Input variables used in Abaqus UMAT: STRAN, STRESS and DSTRAN

I wonder the mathematical expressions for the variables: STRAN, STRESS, and DSTRAN which are used in UMAT.

What is exactly the 'pressure' of a solid in thermodynamics?

Most literatures on thermodynamics are written or started with the language of 'ideal gas'.

This confuses me a lot when I switch to consider solids. For example, the enthalpy of a system
is defined as H = U + P*V, where P is the pressure of the 'system'. This definition is found to be convenient
when dealing with gas. But in terms of solids, I really doubt if the 'pressure' is meaningful. The volume makes
sense but its relation with energy should be expressed in another way when we consider for example cold-

PBC implementation in equilibrium equation

Hi, guys,

 Do some of you know how Periodical Boundary Condition is implemented in equilibrium equation while using FEM:

div{ C:sym[grad(u)] } = 0 ,where the displacement u is periodical.

Is there any (detailed) documentation about this stuff?


Thank you very much!


software for eigenstrain problem


 Is there some fem code or software that can handle eigenstrain while solving equilibrium equation?




What is the best method now to solve advection equation?

I am solving the advection equation which is hyperbolic. Some basic techniques (shown on the page are either of large oscillation or numerical diffusion.

I am striving to find a method without or with little of these problems. Or is there any post correction method to use?


Thank you all!



What is the best way to numerically solve hyperbolic equation?

What is the best way to numerically solve the transport equation like(the least numerical diffusion phenomenon):

df/dt+v df/dx=0

 Thank you


Is two point tensor a REAL tensor?

Two-point tensor appears in some of continnuum mechanics reference books.

1. In wikipedia, two-point tensor is interperated as:" Two-point tensors, or double vectors, are tensor-like quantities which ... " 

2.Physically speaking, a tensor is a quantity that should not be changed by coordinate transformation while two-point tensor seems to have essential relationship with coordinates.

How to perform surface boundary integration in elasticity fem?

This is a basic question regard to elsticity fem.

How to compute traction boundary integration numerically in elasticity fem under general situation? That is:

\int_{\Gamma} [N][t] d\Gamma,   here [N] is shape function and [t] is surface traction

 My E-mail:

Thanks a lot

fem code for plasticity theory?

Is there any available fem source code for plasticity theory?

 Thanks alot!

Is there any paper/books on the basic idea of crystal plasticity?

what are the books/papers that give the basic idea about dislocation-crystal plasticity theory?

Solve 2d diffusion equation

the problem described by these equations is: at time=0, N particles are dropped onto an infinite plane to diffuse. C(r,t) represents the concentration density of particles

The solution is very simple, but I want to see the procedure.

Thank you very much!

the DEM's solutions for static mechanics seem strange

My own DEM(Discrete Element Method) program's solution for static problem seems strange.

I use my program to calculate the displacement of a cantilever under static pressure:

1. it seems my program shows convergence for static problem as the mesh gets denser. As the mesh grows denser(that means the particle becomes smaller), the displacement(of y direction)  of the free tip becomes smaller.

Is there any computing module which can compute a heap of disk elements in DEM(discrete element method)?

Is there any computing module which can compute a heap of disk elements in DEM(discrete element method)?it'd be better if it is written in matlab or C/C++. I'm doing research on the combined DEM-FEM. I need such module so as to save my time.

Thank you 

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