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D.Rittel's blog

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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:

 

https://www.youtube.com/watch?v=Ihgmp9mlUc8&list=PLTzO8_nj5CcIKB0Qc1ssHH...

 

 

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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:

http://www.icdt-conf.com/?page=%2Fevent%2F1864384&

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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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DAMAGe AND FAILURe OF MATERIALS UNDER EXTREME CONDITIONS

hello:

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.

 

Enjoy

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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.

 

https://authors.elsevier.com/a/1VMDY57ZjlaZD

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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.

https://www.youtube.com/watch?v=LNWh9JDDepY&feature=youtu.be

 

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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.

https://www.youtube.com/watch?v=mhce_sEyk60&feature=youtu.be

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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.

http://www.nature.com/articles/srep37226

(the paper is also attached)

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A new concept of fast vessel

When one introduces hydrodynamic concept together with protective polyurea coating into the design of fast planning boats, this is the result. Enjoy!

https://www.youtube.com/watch?v=P4_CSaDYMVQ&feature=youtu.be

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phd position H2020 Marie Slodowska Curie ITN/ETN program

We are offering a PhD position to start this coming september at technion, Haifa, Israel, as advertised in the attached file.

To qualify, the candidates should hold an M.Sc. with thesis in mechanical/materials engineering and have passed the GRE with a grade of 85% or more.

The research will be experimental and numerical in character.

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phd position H2020 Marie Slodowska Curie ITN/ETN program

We are offering a PhD position within the franework of OUTCOME consortium (see attached).

The subject of the reserach is adiabatic shear banding of metallic alloys subjected to impact loading and the reserach will combine experimental and numerical work.

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PhD position in D. Rittel's group - OUTCOME collaborative project - ITN-ETN

We are looking for a highly motivated individual with a strong background in materials science and mechanics, to sudy dynamic shear failure of metallic materials. Experience with numerical modeling required. Previous exposure to experimental work will be considered as an advantage.

Additional information can be found in the atatched description of the planned research.

Contact email:  merittel@technion.ac.il

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ICEM 17 - Dynamic behavior of metals under impact and blast

The attached is an invitation to submit your work to the session Prof. P.Chen (BIT) and I are coorganizing at ICEM 17.
We hope to see you there!

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Dental implants: facts one should know

The sad news is that a large percentage of implants contain cracks which have the potential of causing fracture after fatigue growth. This is the outcome of the present study in which a 100 implants were examined, all apparently intact, having been extracted for various reasons, most likely biological but definitely not mechanical.

It seems that the whole field of dental implants, which is growing very fast, needs a serious mechanical re-assessment, from the design stage all the way up to surface roughening.

Comments are welcome

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