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Updated: 23 hours 31 min ago

regarding the modelling

Sun, 2018-07-01 09:21

In reply to Wrapped Concrete

hi sir i am doing my m.tech thesis in strengthening of columns using cfrp so i kindly need a modelling details and procedure in mechanical apdl ansys. so please mail any infirmation and mail to raghuveer190694@gmail.com

NEED A HELP IN UMAT

Thu, 2018-06-28 04:48

In reply to Sharing ABAQUS UMAT and VUMAT subroutines

Hello everyone!

I want to simulate the cracks formation in unsaturated soil using UMAT, does any one can help me to write the codes for that?

 

Thanks

Hi Lagoue

Tue, 2018-06-26 15:24

In reply to Finite element analysis of a Euler Bernoulli Beam: calculations of natural frequencies with MATLAB

Hi Lagoue

why have you put the young's modulus in mN/mm^2 (206e+6) instead of N/mm^2 (206e+3), is this just a mistake?

 

Jamie

Postdoctoral Associate

Tue, 2018-06-26 15:15

In reply to Job - Postdoctoral Associate University of Notre Dame

Postdoctoral Associate

The University of Notre Dame, Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM), is seeking a highly qualified candidate for the postdoctoral associate position in the area of computational mechanics/physics with emphasis on chemically reactive solids. C-SWARM is center of excellence established by National Nuclear Security Administration (NNSA) whose primary focus is on the emerging field of predictive science. The main mission of C-SWARM is to predict shock conditions under which new materials can be synthesized using predictive computational models that are verified and validated with quantified uncertainty on future high-performance Exascale computer platforms.

The successful candidates will be a key part of a team that is developing and implementing adaptive, multiscale, high-performance (parallel) computational algorithms for numerical solutions of chemo-thermo-mechanical PDE’s with emphasis on complex heterogeneous materials, such as heterogeneous reactive composites, etc.

 

Qualifications:

•    Ph.D. in Mechanical Engineering, Theoretical and Applied Mechanics, Applied Mathematics, Physics or related engineering or sciencediscipline

•    Knowledge of computational nonlinear solid/fluid mechanics and/or chemical kinetics and solid-solid phasetransformations

•    Knowledge of numerical methods for solution of nonlinearPDEs

•    Knowledge of C/C++ and UNIX operating system isrequired

•    Experience in parallelprogramming

Close Date:

Review of applications will begin immediately and continue until the position is filled.

 

Salary:

Salary will commensurate with qualifications and experience.

 

Contact:

Interested applicants should send a CV with a cover letter, names of at least three references, and a summary of recent work. All applications should be submitted electronically (paperless process) as a single PDF documentto:

 

C-SWARM Program Manager

Department of Aerospace and Mechanical Engineering University of Notre Dame

117M Cushing Hall Notre Dame, IN 46556 574-631-3957

cswarm@nd.edu www.cswarm.nd.edu

 

The University of Notre Dame is an Affirmative Action, Equal Opportunity Employer.

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Women and minorities are encouraged to apply.

estimating master curves

Mon, 2018-06-25 14:18

In reply to Generate master curve for viscoelasticity

I can provide a recently written Matlab code (without extensive testing) for estimating a master curve from a discrete family of curves making use of fmincon. JG

estimating master curves

Mon, 2018-06-25 14:16

In reply to Generate master curve for viscoelasticity

I can provide a recently written Matlab code for esitmating a master curve from a set of curves that makes use of fmincon. Joe Goddard

You see a random microstructure.

Sun, 2018-06-24 21:41

In reply to You see a random microstructure.

43 years ago I took a special course (for 10-12 students) of Continuum Mechanics taught by Professor Barenblatt in Moscow State University. The course was structured more as a collection of problems united by his charisma and scientific interests, rather than a classical systematic course. Up to now I remember in details his facial expression, gestures, voice, and glance when he demonstrated an album of reproductions of van Gogh (it was a first album of van Gogh’s reproductions which I saw). Grigory Isaakovich explained the essence of material microstructure by the words “Look on these reproductions of van Gogh in my hands. And now look at the same pictures in your hands. You see a random microstructure.” It was a performance of the theater of one genius actor. I was shocked, impressed and encouraged. I did not could not estimate enough at that time who was Barenblatt, but I felt the God’s thoughts.

Only in a few years after graduation I began to work in micromechanics. From that time at each moment when I consider heterogeneous material a trigger is switched on in my mind “I see the random microstructure. It is myne.” The next paper is ready.

   The ideas of Grigory Barenblatt, his creativity, vision of similarity of different problems and their generalization, and his ability (that is most important) to generate absolutely unexpected points of view on any classical problem are with us forever.

Valeriy Buryachenko

You see a random microstructure.

Sun, 2018-06-24 21:38

In reply to Barenblatt died, age 90

<p class="MsoNormal" style="margin-bottom: .0001pt; text-align: justify; text-justify: inter-ideograph; line-height: normal; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 12.0pt; font-family: 'Times New Roman',serif; mso-fareast-font-family: 'Times New Roman'; color: #26282a;">43 years ago I took a special course (for 10-12 students) of Continuum Mechanics taught by Professor Barenblatt in Moscow State University. The course was structured more as a collection of problems united by his charisma and scientific interests, rather than a classical systematic course. Up to now I remember in details his facial expression, gestures, voice, and glance when he demonstrated an album of reproductions of van Gogh (it was a first album of van Gogh’s reproductions which I saw). Grigory Isaakovich explained the essence of material microstructure by the words “Look on these reproductions of van Gogh in my hands. And now look at the same pictures in your hands. You see a random microstructure.” It was a performance of the theater of one genius actor. I was shocked, impressed and encouraged. I did not could not estimate enough at that time who was Barenblatt, but I felt the God’s thoughts. </span></p>
<p class="MsoNormal" style="margin-bottom: .0001pt; text-align: justify; text-justify: inter-ideograph; line-height: normal; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 12.0pt; font-family: 'Times New Roman',serif; mso-fareast-font-family: 'Times New Roman'; color: #26282a;">Only in a few years after graduation I began to work in micromechanics. From that time at each moment when I consider heterogeneous material a trigger is switched on in my mind “I see the random microstructure. It is myne.” The next paper is ready. </span></p>
<p class="MsoNormal" style="margin-bottom: .0001pt; text-align: justify; text-justify: inter-ideograph; line-height: normal; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 12.0pt; font-family: 'Times New Roman',serif; mso-fareast-font-family: 'Times New Roman'; color: #26282a;"><span style="mso-spacerun: yes;">&nbsp;&nbsp; </span>The ideas of Grigory Barenblatt, his creativity, vision of similarity of different problems and their generalization, and his ability (that is most important) to generate absolutely unexpected points of view on any classical problem are with us forever.</span></p>
<p class="MsoNormal" style="margin-bottom: .0001pt; text-align: justify; text-justify: inter-ideograph; line-height: normal; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 12.0pt; font-family: 'Times New Roman',serif;">Valeriy Buryachenko</span></p>

What he offered was

Sun, 2018-06-24 14:37

In reply to Barenblatt died, age 90

What he offered was tantamount to removing the singularity at the crack-tip.

Thanks for showing us a way (and for loving mechanics, just the way we do), and R.I.P.

Best regards,

--Ajit

 

Postdoctoral Fellow Position in Chemistry

Sun, 2018-06-24 09:47

In reply to 3-Year Postdoctoral Fellow: Green Chemistry/Materials Chemistry

Postdoctoral Fellow Position in Chemistry

Dear Ill,

Fri, 2018-06-22 05:58

In reply to Re:How to bridge MD with DD

Dear Ill,

Thank you very much for your detailed explanations, which provide important insights to multiscale modelling. The hierarchical coupling you suggested might be effective for bridging between DD and MD, which would advance the understanding of plasticity from atomic level to dislocation level.

<p class="MsoNormal" style=

Fri, 2018-06-22 03:57

In reply to CEMEF PhD thesis 2018 : Numerical modeling of thin products forming under complex loads

<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><em style="mso-bidi-font-style: normal;"><span style="color: black; mso-ansi-language: EN-US;" lang="EN-US">Presentation of the establishment and the laboratory of reception:</span></em></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span style="mso-ansi-language: EN-GB;" lang="EN-GB">CEMEF, which stands for Centre de Mise en Forme des Matériaux, or Centre for Material Forming, is a leading research centre in the field of material forming. It was created in 1974 and is located in the Sophia Antipolis science park, near Nice in the south of France. It is a research laboratory of Mines ParisTech and has been associated with CNRS, the French National Science Foundation since 1979.<br /> CEMEF develops global approaches in material forming (polymers, bio-polymers, elastomers, metals, alloys...), combining physics, physical chemistry, mechanics, thermics, modelling, numerical simulation (finite element methods, meshing, fluid-structure coupling...). The scientific developments are applied to forming processes: injection molding, extrusion, forging, machining, rolling, welding... It has about 160 people, including 70 PhD students.</span></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><em style="mso-bidi-font-style: normal;"><span style="mso-ansi-language: EN-GB;" lang="EN-GB"><span style="color: #000000;"><em style="mso-bidi-font-style: normal;"><span style="font-size: 10pt; font-family: 'Calibri','sans-serif'; letter-spacing: -0.2pt;" lang="EN-GB">Global objective of work</span></em></span>: </span></em></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span lang="EN-GB"><span lang="EN-US">The main purpose of this thesis is to improve the capabilities of Forge to model thin products. The first challenge to rise will be related to the development of constitutive laws adapted to reproduce the anisotropy of materials under complex non-proportional loading paths</span></span><span style="font-size: small;" lang="EN-GB"><span lang="EN-US">.</span></span></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span lang="EN-GB"><span lang="EN-US">More infos on :</span></span></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span lang="EN-GB"><span lang="EN-US">http://www.cemef.mines-paristech.fr/sections/formations/doctorats/pour-p...
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;">&nbsp;</p>
<p>&nbsp;</p>

<p class="MsoNormal" style=

Fri, 2018-06-22 03:57

In reply to CEMEF PhD thesis 2018 : Numerical modeling of thin products forming under complex loads

<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><em style="mso-bidi-font-style: normal;"><span style="color: black; mso-ansi-language: EN-US;" lang="EN-US">Presentation of the establishment and the laboratory of reception:</span></em></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span style="mso-ansi-language: EN-GB;" lang="EN-GB">CEMEF, which stands for Centre de Mise en Forme des Matériaux, or Centre for Material Forming, is a leading research centre in the field of material forming. It was created in 1974 and is located in the Sophia Antipolis science park, near Nice in the south of France. It is a research laboratory of Mines ParisTech and has been associated with CNRS, the French National Science Foundation since 1979.<br /> CEMEF develops global approaches in material forming (polymers, bio-polymers, elastomers, metals, alloys...), combining physics, physical chemistry, mechanics, thermics, modelling, numerical simulation (finite element methods, meshing, fluid-structure coupling...). The scientific developments are applied to forming processes: injection molding, extrusion, forging, machining, rolling, welding... It has about 160 people, including 70 PhD students.</span></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><em style="mso-bidi-font-style: normal;"><span style="mso-ansi-language: EN-GB;" lang="EN-GB"><span style="color: #000000;"><em style="mso-bidi-font-style: normal;"><span style="font-size: 10pt; font-family: 'Calibri','sans-serif'; letter-spacing: -0.2pt;" lang="EN-GB">Global objective of work</span></em></span>: </span></em></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span lang="EN-GB"><span lang="EN-US">The main purpose of this thesis is to improve the capabilities of Forge to model thin products. The first challenge to rise will be related to the development of constitutive laws adapted to reproduce the anisotropy of materials under complex non-proportional loading paths</span></span><span style="font-size: small;" lang="EN-GB"><span lang="EN-US">.</span></span></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span lang="EN-GB"><span lang="EN-US">More infos on :</span></span></p>
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;"><span lang="EN-GB"><span lang="EN-US">http://www.cemef.mines-paristech.fr/sections/formations/doctorats/pour-p...
<p class="MsoNormal" style="mso-layout-grid-align: none; text-autospace: none;">&nbsp;</p>
<p>&nbsp;</p>

Re:time scale bridging in MD

Fri, 2018-06-22 00:22

In reply to time scale bridging in MD

Dear Harold

Thank for your comment and sharing very relevant papers. The strain rate in MD is a long-stranding challenge and many efforts have been made to resolve this limitations. It is very intereting to see your recent work and others, which could achieve physically reasonable time duration in MD modeling. 

Another interesting approach to resolve the time step in MD is found from developing special purpose supercomputer for biomolecular simulation designed and constructed by D. E. Shaw Research (DESRES). Without develiping a new algorithm for time-step, they could perform MD simulation for long timespan (https://www.nature.com/articles/nphys3553), which allow us to investigate detailed motion of molecules without losing "jiggling and wiggling" motions of atoms, said Richard Feynman in his seminal 1963 Lectures on Physics. 

Center for Shock Wave

Thu, 2018-06-21 13:14

In reply to Job - Postdoctoral Associate University of Notre Dame

Center for Shock Wave-processing of Advanced Reactive Materials 

time scale bridging in MD

Thu, 2018-06-21 08:34

In reply to Re:How to bridge MD with DD

Dear Ill:

Thanks for bringing up this interesting journal club.  Since you mention the well-known time scale issues with MD, I wanted to mention some recent work that has been done in this area with regards to metal plasticity.  Specifically, we recently showed that, using potential energy landscape exploration techniques, we can both capture experimentally-observed rate-dependent ductile-to-brittle transitions in bicrystalline metal nanowires:

https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b04972

while also predicting new superplastic creep behavior in single crystal metal nanowires that emerges at timescales inaccessible to MD:  

https://pubs.acs.org/doi/abs/10.1021/acsnano.8b02199

There are also other groups doing excellent, related work on predictive modeling of different material systems using similar time scale bridging techniques.  For example Sid Yip and collaborators on amorphous solids (http://www.pnas.org/content/114/52/13631), and Pradeep Sharma working on a variety of material systems (batteries, metals, etc, i.e. https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.1.055401).

Re:How to bridge MD with DD

Thu, 2018-06-21 01:30

In reply to Journal Club for June 2018: Modeling dislocation mediated plasticity using meso-scale discrete dislocation dynamics

Thanks for your comments. It is very interesting to get the very similar dislocation structures in DD with MD, with a simple nucleation based on max. resolved shear stress in different oriented micropillars. However, the dislocation network in DD is not exactly the same as MD result. For example, in <100> oriented pillars, MD shows a rectangular network, but DD shows cross-shaped dislocations. I believe both models has limitations to get the “real” structures. That is to say, very high strain rate in MD would localize dislocation activity on a single slip plane, and the dislocation microstructure in DD results from a nucleation rule. I believe it would be needed to perform in-Situ TEM experiments to see the real dislocation structures, but it is also challenging to do torsion experiment in this scale. I look forward to see the experimental proof on anisotropic dislocation microstructures.

Regarding the different time scale in MD and DD, DD results could give rise to very similar stress-strain relations with steady-state experiments via a modified loading condition(so called cut-off plastic strain rate method), while MD has an intrinsic limitation on high strain rate. DD model is required to have atomistic input, in order to characterize individual dislocation mobility and mutual interaction mechanism. Therefore, the scaling bridging between MD and DD would be handled by hierarchical coupling, rather than concurrent approach due to different time scale.

Re: Modeling boundaries

Thu, 2018-06-21 01:08

In reply to Modeling boundaries

To answer your first question regarding difficulty in developing a set of rules for such interactions, it mainly results from the fact that there are many parameters to characterize grain boundaries and dislocations. Specifically, the geometry of a grain boundary can be characterized by 5 degrees of freedom (dof): 3 for the relative misorientation between the two grains, and 2 for the direction of the grain boundary plane normal. Likewise, it also require 5 dof for dislocations: 3 Burgers vector and 2 for the direction. In addition, intrinsic material properties would be also involved, such as the core structure and stacking fault energy and others. We also need to consider the effect of incidence angle.

As a result, there are many factors to affect the interaction mechanisms, so that it is very challenging to draw a simple rule to determine the various types of interactions.

There has been many trials to characterize interaction mechanisms from analytical and computational approach, but there still lacks of a general rule. I expect stochasticity would also play a role, but I am not aware of much in detail about it. Other opinion/suggestions on stochasticity will be highly appreciated.

Secondly, I do agree that concurrent modeling approach to model interface would be a good idea to deal with complex interactions, because continuum approach will be helpful to consider large deformation(including rotation) and also give rise to accurate far-field stress calculations. However, it still required a “rule”, which I believe, only comes from atomistic modeling with proper potentials.

How to bridge MD with DD

Thu, 2018-06-21 00:11

In reply to Journal Club for June 2018: Modeling dislocation mediated plasticity using meso-scale discrete dislocation dynamics

Dear Ill,

Thank you very much for your posting such impressive topics. As shown in Fig. 4, the deformation mechanisms revealed by DD simulations is very similar to that indicated by MD simulations. But there exists an apparent difference in the length scale between DD and MD simulations. Has there been any method to bridge MD with DD?

Best,

Xiaoyan

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