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Updated: 22 hours 33 min ago

Yong, 

Wed, 2016-02-10 19:25

In reply to Journal Club Theme of February 2016: Deformation Mechanics of Granular Materials: Local Deformation of Polymer-bonded Sugar at High Strain Rate Loading

Yong, 

You are right recently DIC is receiving high interest for dynamic deformations measurement, and in my opinion, there are two driving factors.

1)      The current improvement and capability of high speed imaging. Currently, there are cameras that can take images at a framing rate above 1 million per second and at a spatial resolution of 400×250 pixel2. . At this speed, a high-quality deformation can be measured. For example, in Hopkinson bar experiment, where the loading duration is in the order of 100 µs, we can get above 100 high-quality images for DIC analysis.

The main challenge as far as DIC as high rate loading is, measuring small deformation/strain. Small deformation is still challenging at quasi-static loading conditions, but by image averaging the data/noise ratio can be improved. Since there will be no time to take multiple images at the same loading, during high strain rate loading, noise reduction by averaging is difficult  and accurate deformation/strain measurement using DIC is challenging. In the case of large deformation, the limit was the imaging system but it is improving year by year.

A detail information regarding high-speed DIC can be obtained in the paper by F. Pierron · M.A. Sutton · V. Tiwari, Experimental Mechanics (2011) 51:537–563 http://link.springer.com/article/10.1007%2Fs11340-010-9402-y#/page-1  

2)      Another reason for recent increase interest in high-speed DIC is the need for understanding failure mechanisms in materials at meso-scale (between Nano and macro) including at high strain rate condition. Heterogeneous materials, like granular materials, even polycrystalline metal at mesoscale, required a full field method to capture the local deformation.

As far as I know, the first high-speed DIC based on ultrafast/high-speed X-ray is by Lu, et al (http://scitation.aip.org/content/aip/journal/rsi/85/7/10.1063/1.4887343). Using PCI/radiograph x-ray and DIC they quantitatively the 3D strain fields in materials with strain noise error in the order of 10-3. Based on an optical system, I think the first high magnification DIC work is by Bodelot et al (http://www.sciencedirect.com/science/article/pii/S0749641915000984). Using a high-speed camera, HPV-2, and Infinity K2 long-distance microscope they could map the deformation field in a copper. They achieved a spatial resolution of 15.2 μm/pixel at 500, 000 frames/sec. Recently we used HPVX-2 with Navitar lens and achieved a spatial resolution of 10.2 μm/pixel at 1 million frames/sec (http://link.springer.com/article/10.1007/s40870-016-0051-9).

 There are some challenges such as, getting the right speckle size, lighting issue and depth of field of the cameras as you go higher magnification, otherwise full field local deformation can be measured even at higher resolution. 

 I would like to hear from others working in the field. 

Abaqus mailing list

Wed, 2016-02-10 16:11

In reply to Abaqus Hetval Subroutine

Subscribe to and seek assistance from the
ABAQUS mailing list
https://groups.yahoo.com/group/ABAQUS
Search the archive before posting.

Good luck

Frank

high-speed DIC

Wed, 2016-02-10 09:32

In reply to Journal Club Theme of February 2016: Deformation Mechanics of Granular Materials: Local Deformation of Polymer-bonded Sugar at High Strain Rate Loading

Hi Addis,

Thanks for leading the discussion on this interesting topic in experimental mechanics. As we know, digitial image correlation (DIC) has been widely used now in measuring full-field deformation and strain from 2D to 3D. Recently I have seen that DIC is receiving increasing interest for dynamic measurements. Could you give us an update on the recent advances in high-speed DIC such as capabilities (e.g., tempo/spatial resolutions), challenges and representative applications? Thanks.

 

phase transformation

Wed, 2016-02-10 08:11

In reply to Abaqus Hetval Subroutine

Thank you. I have red this PDF. I want to use hetval for phase transformation analysis, but I don't know how I should define e.g. (SVAR, PREDEF,...)?

Read this PDF document

Wed, 2016-02-10 07:31

In reply to Abaqus Hetval Subroutine

Google Search "writing user subroutines with abaqus". The PDF file available is best to read and start with. Gradually it can be complex as per your requirements

Plasticity

Tue, 2016-02-09 00:27

In reply to Please suggest self study book for continuum plasticity theory

The following book is also a very good reference on plasticity:

S. Nemat-Nasser, Plasticity - A Treatise on Finite Deformation of Heterogeous Inelastic Materials, Cambridge Press, 2009

Mohsen

Plasticity Modeling & Computation

Mon, 2016-02-08 13:15

In reply to Please suggest self study book for continuum plasticity theory

I would also recommend Plasticity Modeling & Computation by R.I. Borja. It's concise and includes all the essential elements. 

Johnson Cook parameter

Mon, 2016-02-08 05:58

In reply to Johnson Cook failure model

Hi

can Anyone help me to find johnson-cook failure model damage parameters(d1, d2, d3, d4) for modified 9Cr-1Mo steel?

Good books on plasticity

Thu, 2016-02-04 19:09

In reply to Please suggest self study book for continuum plasticity theory

I found these books helpful for me. 

 

  • Bathe, K. J., Kojic, M. Inelastic analysis of solids and structures. 
  • P.M. Dixit, U.S. Dixit, Plasticity: Fundamentals and Applications
  • Khan, A. S., Huang, S. Continuum theory of plasticity
  • de Souza Neto, E. A., Peric, D., & Owen, D. R. J. Computational methods for plasticity: theory and applications.
  • Simo, J. C., Hughes, T. J. Computational inelasticity

 

Simo and Hughes book deals with computational aspects. If you have regorous mathematics background then you may find this book good. Bathe and Kojic book discuss numerical and continuum aspects of plasticity. Dixit's book discusses a lot of priliminary information and plasticity, damage mechanics, etc. Reader may find Khan and Huang's book a good reference. 

 

 

 

more on Neo-Hookean

Thu, 2016-02-04 15:53

In reply to Material Jacobian in UMAT

Surf to
https://web.njit.edu/~sac3/Software.html
a website run by Prof. David Henann, Brown University,

and contact me privately to get a file
"A large deformation Neo–Hookean user material in ANSYS.pdf",
listing a code. I cannot find the button to upload it.

Good luck

Frank

explain this code please

Thu, 2016-02-04 07:57

In reply to strain rate in VUMAT

dear HAIBIN ZHU

could you please the theory of your code please?

Dear Afallah,

Thu, 2016-02-04 07:54

In reply to Hyperelastic Material Jacobian in UMAT

Dear Afallah,

 

thank you very much for your support. This paper helped a lot!

 

Regards

 

Christof

Hyperelastic Material Jacobian in UMAT

Thu, 2016-02-04 01:27

In reply to Material Jacobian in UMAT

Dear Christof

You can find the complete process of material Jacobian computation in the following paper:

"A FINITE ELEMENT IMPLEMENTATION OF KNOWLES STORED-ENERGY FUNCTION: THEORY, CODING AND APPLICATIONS"

You can easily google it and download it freely. Furtheremore, in case of anisotropic hyper elastic material you can use my recenty published paper. My paper link is :

http://www.sciencedirect.com/science/article/pii/S1751616115005032

Best regards.

 

 

Hi I have the same issue

Thu, 2016-02-04 00:30

In reply to Modeling crack propagation with ABAQUS X-FEM

Hi, I am also having the same issue. My statusxfem shows 1 for many elements but crack does not show up. My PHILSM is called. Also, allow crack growth option is given too. Can you please help me on what you had done to see the cracks.

I have another question, can I delete the failed elements ? I have also selected element deletion = YES. But still no element gets deleted.

Thank you so much.

Best Regards!!

Excellent work, check out more in JDBM

Wed, 2016-02-03 22:43

In reply to Journal Club Theme of February 2016: Deformation Mechanics of Granular Materials: Local Deformation of Polymer-bonded Sugar at High Strain Rate Loading

More on this work is available free in the Journal of Dynamic Behavior of Materials upcoming Special Issue http://link.springer.com/article/10.1007/s40870-016-0051-9.  JDBM is now accepting papers for consideration for the second issue of 2016.

Hey, To model ballast and

Wed, 2016-02-03 01:41

In reply to Elasto Plastic model for ballast material

Hey, To model ballast and subgrade in abaqus you should use Drucker prager plasticity model. It's a model that you can use to model granular frictional materials.

 

I don't know have you made literature search about it but this reference is gonna work.

 

http://www.diva-portal.org/smash/get/diva2:467217/FULLTEXT01.pdf

Abaqus mailing list

Tue, 2016-02-02 16:14

In reply to How to Assign Initial Solution-dependent State Variable to VUMAT

Subscribe to and seek assistance from the
ABAQUS mailing list
https://groups.yahoo.com/group/ABAQUS
Search the archive before posting.

Good luck

Frank

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