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D.Rittel's blog

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A study of hypervelocity glancing collisions

Most of the research carried out on hypervelocity  collisions, of the kind encountered in space, assume that the projectile hits a stationary target. In reality, both the target and the projectile are moving at high velocity in a non-colinear fasion. We present here a study of this  phenomenon and its rfelationship  with oblique impact.  

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A simple question....

There has been a lot of buzz and excitement about "big data" lately, to a point that science in the coming years would be made of and by "big data", not to mention "deep learning", another hot item. Well....I just wonder, how comes that nowadays, in those very tough corona times, haven't we founmd a vaccine, maybe a cure, or at least a sound epidemiologic study with clear outcomes using "deep learning" or "big data"? I will appreciate updates that will help me answering those simple questions.

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BSSM Experimental Mechanics Conference - kind reminder

Final Call for Abstracts 
for the British Society for Strain Measurement's (BSSM)

15th International Conference on Advances in Experimental Mechanics
St Anne's College, University of Oxford, UK
8th - 10th September, 2020
 Submission deadline 28th February, 2020

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Abstract submission reminder for the BSSM's 15th International Conference on Advances in Experimental Mechanics

All invited to submit an abstract to this conference, one of the best in the field, in the long tradition of BSSM Conferences


8th - 10th September 2020, St Anne's College, University of Oxford, UK.

The 15th in a series of conferences organised by the British Society for Strain
Measurement showcasing novel and innovative research in Experimental Mechanics.

Abstract submission deadline 28th February 2020    

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IUTAM Milano: Impact Mechanics and Wave Propagation - deadline approaching

Please don't forget to submit your abstract until Jan. 10th. The deadline is approaching!

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ICTAM 2020 - Thematic Session - Impact Mechanics and Wave Propagation

Dear Colleagues:

As many of you may know, the International Conference on Theoretical and Applied Mechanics (ICTAM) will be held in Milano next year (

Professor Kikuo Kishimoto and I are co-organizing a thematic session on:

SM07 Impact Mechanics and Wave Propagation

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A steel sphere impacting and propagating in water

A small steel sphere is launched at 153 m/s through a water tank. This is a nice visualization of cavity expansion ion a fluid. Note the rebound as the sphere bounces back and hits the water tank again.

The movie exceeds the 20Mb limit, sio it is available on youtube:



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Shock attenuation using methylcellulose gels

Shock attenuation is of prime concerns when bodily organs are involved, such as traumatic brain injury. Most armor systems nowadays are aimed at defeating the threat, such as breaking a projectile using hard ceramic armor. Yet, such solutions do not mitigate the initial acceleration (elastic) wave that is responsible for internal organ damage, although no penetration occurred.

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Reassessment of dynamic thermomechanical conversion in metals by J. C. Nieto-Fuentes, S. Osovski, A. Venkert and D. Rittel

The Taylor-Quinney coefficient is universally understood as a manifestation of the stored energy of cold work, and one therefore assumes a one to one correspoindence between its value and the microstructural state of the deformed material. In the attached letter (to appear in Phys Rev Letters), we question this assumption by bringing new experimental evidence that the thermomechanical conversion is a function of the kinetics of the process and not of the final microstructure only.

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prof. Sol Bodner passed away

The Materials Mechanics Center (Technion) mourns the passing away of our respected colleague and founder of the Materials Mechanics Center, Prof. SOL BODNER. May he rest in peace. Our sincere condolences to his family.

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ICTAM 2020 - SM07 Impact Mechanics and Wave Propagation

The coming ICTAM will be held in Milan, August 23-28, 2020.

Professor K. Kishimoto and myself have been mandated by the Chairs to organize the following  thematic session:

SM07 Impact Mechanics and Wave Propagation

We hereby invite our colleagues to submit their abstract and make this session a real success!

Dany and Kikuo

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Impact energy mitigation characterization of methyl cellulose hydrogels

Aqueousmethylcellulose solutions are fascinating inverse-freezing materials, known to reversibly form gels upon heating. Recently, these materials have been found to undergo this endothermic solidification upon impact. The imapct-induced solidification was shown to occur in the microseconds’ timescale,  setting the path for examining their functionality for shockabsorption purposes.

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ICDT 2020

All invited to attend a promising conference on defence-related topics, in the broad context of the subject:

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About Mechanics-Materials and Dentistry of dental implants

Dental implants are increasingly being placed for edentulous patients worldwide. While the clinical aspects of the implants are extensively investigated, engineering considerations of the implant as a functional structure subjected to ill-defined boundary conditions are less considered. A recent trend is to consider all ceramic implants as an alternative to the classical titanium-based implants.

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I attach a flyer for the coming CISM course in Udine.

All welcome

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Materials Science and Engineering C

Checking upon the status of a submitted paper that has been with the journal for 2 weeks, we received the following response.

I will let you judge.....


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Ballistic penetration and fragmentation of brittle targets

The attached, to appear in I.J. Impact Engng., is an attempt to simplify such very complex calculations using an incubation time concept for defects coalescence, in the spirit of Tuler and Butcher and others.

By comparing the calculations and the experiments, it seems that the approach works nicely, produces realistic results, and most of all does not necessitate complex models with too many parameters of very sophisticated FE formulations.



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the Taylor-Quinney coefficient may depend on the loading mode....

A systematic comparison of dynamic tension, compression and shear....The TQ factor is not necessarily the same for different loading modes, emphasizing the role of the deformation micromechanisms.

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Dynamic crushing of a multi-columnar structure

Experiment realized by Daniel Levy (DFL-technion). We use a Kirana ultra high speed camera and the framing rate is 500,000/second.


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Adiabatic shear-Dynamic recrystallization-Softening

The attached results address the extent to which the presence of a nanograined, dynamically recrystallized phase may soften a material (in that case Ti6Al4V), causing ultimately failure by shear localization.

Comments welcome.

D. Rittel


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Dynamic fracture of transparent ceramic

Captured at 7.5 and 8 million fps with a Kirana camera. This is a one point impact test used to determine the dynamic flexural strength. Courtesy of Dvir Blumer and Eden Promushkin, the Dynamic Fracture Laboratory, Technion, Haifa, Israel.

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About adiabatic shear failure.....

Not too long ago, we identified dynamic recrystallization (DRX) as a potentially softening factor leading to the formation of adiabatic shear bands. However, the exact nature and the extent of the softening effect till remained to be assessed. The link to our new paper provides additional information on this issue.

(the paper is also attached)


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