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Updated: 7 hours 48 min ago

Veamy v1.1.1 (software for VEM) is out with PDF Manual

Tue, 2017-09-05 22:59

In reply to Veamy: an extensible object-oriented C++ library for the virtual element method

Veamy v1.1.1 is out. 

Download the source code + Veamy Primer v1.1 (PDF Manual):

http://camlab.cl/research/software/veamy/

From Veamy v1.0 to Veamy v1.1.1:

  • Add documentation.
  • Add method to include custom precision for printing output data.
  • Add plane stress material formulation.
  • Update installation instructions.
  • Include more tests and mesh examples.
  • Fix several bugs.

Features:

Free and open source C++ library that implements the virtual element method. The current release of this library allows the solution of 2D linear elastostatic problems.

  • Includes its own mesher based on the computation of the constrained Voronoi diagram. The meshes can be created in arbitrary domains, with or without holes, with procedurally generated points.
  • Meshes can also be read from OFF-style text files (an example can be found in the test folder).
  • Allows easy input of boundary conditions by constraining domain segments and nodes.
  • The results of the computation can be either written into a file or used directly.
  • PolyMesher meshes and boundary conditions can be read straightforwardly in Veamy to solve 2D linear elastostatic problems.

Hi Frank! Thank you for

Tue, 2017-09-05 21:55

In reply to Viscoelastic UMAT: Maxwell and Kelvin

Hi Frank! Thank you for sharing your UMAT code here. I just started working on the viscoelastic material and will need to implement a nonlinear anisotropic viscoelastic material in UMAT. Your code seems to be a great start. You mentioned above the pdf write up for derivation. I was wondering if you may share it and your PhD thesis, the ilnk above doesn't work? My email is sergkuznet@hotmail.com

Thank you!

Dielectric elastomers

Fri, 2017-09-01 23:40

In reply to questions about dielectric elastomers

Questions are welcome.

PhD position in computational solid / fracture mechanics

Fri, 2017-09-01 16:17

In reply to PhD position in computational solid / fracture mechanics

Hello,

I have a PhD position available for a project titled "Asynchronous, Parallel-Adaptive Solution of Extreme Multiscale Problems in Seismology" funded by the U.S. National Science Foundation (NSF). The research involves:

a. Formulation of contact / fracture models (interfacial and/or bulk) for seismic applications, e.g. anisotropic, inhomogeneous rock under dynamic loads.

b. Adaptive spacetime time discontinuous Galerkin formulation for the solution of multiphysics PDEs relevant to this application.

c. High performance computing aspects of the method.

The gradurate research assistantship (GRA) position is for the University of Tennessee Space Institute (UTSI) which is a part of University of Tennessee Knoxville (UTK). This is a collaborative project with the University of Illinois at Urbana-Champaign.

The student should have a strong background and interest in all or most of the following areas:

1. Mathematics: numerical analysis.

2. Computational Solid Mechanics: finite element methods.

3. Computer programming: Proficiency in C++ programming is highly valued. 

4. Fracture Mechanics

This position will be filled very shortly, so please contact me at the earliest possible.

Interested applicants should send an email to rabedi@utk.edu or rabedi@utsi.edu directly describing their background in the four areas mentioned above and attached their CV / resume.

For a general overview of the research projects in my group you can refer to www.rezaabedi.info

 

Dear Mehdi,

Wed, 2017-08-30 20:55

In reply to Hi Vahid,

Dear Mehdi,

It has been quite a long time since I've paid a visit to iMechanica, and I just noticed your reply here. Thanks a lot for the offer. Fortunately, there has been lots of updates from my last visit. I have programmed a Fortran code for the nucleation and growth of grains during solidification in liquid-solid material systems. The code is based on the KKS phase field model. My code also handles the electromigration and elastic effects in materials, and it is coupled with the relative solvers. Here is my early publication, I recently made and the others are on the way:

Phase Field Modeling of Joint Formation During Isothermal Solidification in 3DIC Micro Packaging

https://link.springer.com/article/10.1007/s11669-016-0475-x

 

I am still looking for the opportunities to couple the code with other major solvers like Comsol and expand the whole applicability.

Best

Vahid

 

 

 

 

Computation of Three

Sat, 2017-08-26 12:32

In reply to Computation of Three Dimensional Stresses Based on ESL Theory

Computation of Three Dimensional Stresses Based on the concept of ESL Theory

A new method has been used to accurately compute three dimensional stresses without using equilibrium equations.

There are three ways to accurately calculate transverse normal and shear stresses: The New method, Constitutive law and integration of equilibrium method. This research work uses only the new method and constitutive law.

In this formulation, the continuity conditions of transverse stresses are not imposed at the layer interfaces a priori. There are no additional requirements of computational effort. Further number of unknowns is not increased because of ESL theory.

The transverse shear stress can accurately be calculated only from this new method and the results from the constitutive law are not at all satisfactory . This method gives continuity at the layer interfaces.

The transverse normal stress is calculated either from the new method or constitutive law in this research work. The new method gives continuous transverse normal stress at the layer interfaces whereas computation from the constitutive law gives discontinuous normal stress at the layer interfaces.

The results for thin and moderately thick beams are excellent. Though the accuracy decreases for thick beams (aspect ratio 5), the values of the stresses at the layer interfaces are accurately predicted.

 

This research work shows that three dimensional stresses can accurately be calculated from two dimensional theory (ies).

Computation of Three

Sat, 2017-08-26 12:26

In reply to Computation of Three Dimensional Stresses Based on ESL Theory

Computation of Three Dimensional Stresses Based on the concept of ESL Theory

A new method has been used to accurately compute three dimensional stresses without using equilibrium equations.

There are three ways to accurately calculate transverse normal and shear stresses: The New method, Constitutive law and integration of equilibrium method. This research work uses only the new method and constitutive law.

In this formulation, the continuity conditions of transverse stresses are not imposed at the layer interfaces a priori. There are no additional requirements of computational effort. Further number of unknowns is not increased because of ESL theory.

The transverse shear stress can accurately be calculated only from this new method and the results from the constitutive law are not at all satisfactory . This method gives continuity at the layer interfaces.

The transverse normal stress is calculated either from the new method or constitutive law in this research work. The new method gives continuous transverse normal stress at the layer interfaces whereas computation from the constitutive law gives discontinuous normal stress at the layer interfaces.

The results for thin and moderately thick beams are excellent. Though the accuracy decreases for thick beams (aspect ratio 5), the values of the stresses at the layer interfaces are accurately predicted.

 

This research work shows that three dimensional stresses can accurately be calculated from two dimensional theory (ies).

units

Fri, 2017-08-25 16:13

In reply to Cohesive Density

Dear Jia,
I want to model my part in mm. So what will be the units for these two materials?

First for cohesive: Nominal stress normal-only mode, E or Enn

Second for Engineering constants: E1, G12

Thanks

Results are presented for a

Fri, 2017-08-25 10:18

In reply to Computation of Three Dimensional Stresses Based on ESL Theory

Results are presented for a simply supported laminated composite beams under transverse sinusoidal load applied at the top surface of the beam. The transverse shear stress is computed without imposing continuity condition in the formulatio a priori and constitutive law.   The transverse normal stress is cmputed using constitutive law. The trandverse shear stress is computed with about 5% for yhin and moderately thick beams. For thick beam it is about 6% at the interfaces.

  The trandverse normal stresss is also computed with the above trend

 

This position has been filled. Thank you for the interest.

Thu, 2017-08-24 10:30

In reply to Postdoc Position on computational mechanics of polycrystaline rocks

This position has been filled. Thank you for the interest. 

the position is filled.

Tue, 2017-08-22 11:05

In reply to Postdoc opening in architected materials (or mechanical metamaterials) at Johns Hopkins University

the position is filled. Thank you for your interest.

SHPB

Mon, 2017-08-21 11:30

In reply to split hopkinson pressure bar (SHPB)

The button to upload files does not show in my browser.
Contact me privately.

SHPB

Mon, 2017-08-21 03:21

In reply to SHPB

Dear Mr Frank

thank you very much for your help

 

The inp file available at the above link does not open in Abaqus software. 

Also, the simulation I've done is in 3D.

 

Sincerely yours,

sanaz

SHPB

Sun, 2017-08-20 11:57

position filled

Thu, 2017-08-17 05:36

In reply to Postdoc Position on computational mechanics of polycrystaline rocks

Thank you for the interest. 

It should be A

Wed, 2017-08-16 20:11

In reply to Correct Average of Stress/Strain Microfields

 

You should use A to compare with the experimental results. Theoretically, the average stress over the whole region does not equal the average stress over the top line because the stress on the boundary is not constant. The volume average stress equal the stress on the boundary only when the stress on the boundary is constant. To make an estimation, the value of B stress is smaller than that of A. I hope your results can verify this. Many thanks.

Basic Function & Scope of

Wed, 2017-08-16 19:17

In reply to PhD candidate for finite element developer

Basic Function & Scope of Responsibilities: 

Candidate will be involved in software development of a commercial finite element code (Optistruct) mainly in structural dynamics and acoustic domain. He should have Masters or PhD in Mechanical, Civil or Aerospace engineering with strong knowledge of finite element method in structural dynamics. The candidate will be mainly responsible for writing software in Fortran and C++. It is also desirable from him to be familiar with noise/vibration/harshness (NVH) arena. The candidate must have sound mathematical knowledge and ability to work independently. Responsibilities also would include software testing. Candidate should be a good team player.

 

 Duties & Responsibilities:

  1. To derive mathematical formulation mainly in finite element method.
  2. Must be able to program with Fortran and C++
  3. Handle large code and design code day to day basis.
  4. Debugging code.
  5. Strong organizational skills and ability to multi-task.
  6. Ability to work in small teams with little or no supervision is a must

 

 

Skills:

 

  1. Finite element analysis
  2. Structural dynamics

Nice work

Wed, 2017-08-16 18:12

In reply to Comparing EAM potentials to model slip transfer of sequential mixed character dislocations across two symmetric tilt grain boundaries in Ni

Nice work! Shuozhi. How is our FDM-cac pile-up comparison going? I assume you are very busy the past few months to work on it :) -Xiaohan

The position has been filled.

Wed, 2017-08-16 11:15

In reply to A Post Doc Position to work on Metallic Nanocomposites

The position has been filled. Thank you very much for your interest!

Hi Teng,

Thu, 2017-08-10 13:15

In reply to Heterogeneous material and micro-structure design

Hi Teng,

Excellent points about the heterogeneity and microstructure design! In addition to the biological materials, there are many cases where fillers particles (e.g. silica particles, magnetic particles,...) are added to soft elastomers or gels to tune mechanical properties or to functionalize the material. Understanding the fracture of such soft composite materials are important too, but it may be a challenging task. As for the microstructure design, I think mechanics can can play an important role by providing directions or principles for design, and it may invovle modeling and experimental efforts at multiple scales. Continuum level studies can ellucidate what kind of bulk material behaviors (e.g. nonlinear elasticity, viscoelasticity, ...) and crack tip failure process (e.g. reflected in the traction separation relation in a cohesive zone) are optimal for toughness enhancement, which will set the targets for material design.

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