Running on Straight Rails

Boffins in Austria have been studying railway tracks to better understand the residual stresses that result from straightening them during processing.

Roller straightening is the final step in production of the rails, after hot rolling is performed at around 1000&degree;C cooling (presumably with water spray) results in curvature of the rails. This varies depending on the rail geometry and cooling conditions.
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Results from finite element modelling, and measurement of stresses using the contour method and neutron diffraction were compared. The model matches the trends of the measurements in the vertical plane (possibly the mode important since it has the largest residual stresses). In the paper comparison of neutron results for triaxial stresses shows there are residual stresses in the plane perpendicular to the vertical through the rail tool, although these were not predicted by the FEM model.

Residual Stresses

Residual Stresses along vertical symmetry axis

References

  1. http://phys.org/news/2015-01-rails-straight.html#nRlv
  2. R. Kaiser, M. Stefenelli, T. Hatzenbichler, T. Antretter, J. Keckes and B. Buchmayr (2014) “Experimental characterization and modelling of triaxial residual stresses in straightened railway rails,” The Journal of Strain Analysis for Engineering Design, 1-9 DOI: 10.1177/0309324714560040
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No Highway in the Sky

‘No Highway’ is a book dramatising fatigue in metals, the story was made into the movie ‘No Highway in the Sky’ staring Jimmy Stewart. This is the only movie I know which is about metal fatigue. The book was published in 1948, and the movie appeared in 1951.

The author Nevil Shute Norway, was a pioneer aircraft designer. The story centres around Theodore Honey, a middle-aged widower and boffin at the Royal Aircraft Establishment Farnborough (site of much fundamental work on aircraft and fatigue).

Theodore is sent to investigate a previous air crash, but he realises that his theory applies to the plane he is travelling on, which he forces to land. After inspection of the aircraft on land, the much annoyed pilot is ready to take-off again, leaving Theodore Honey behind. However, Theodore’s conviction in his theory leads him to ground the plane by retracting the landing-gear. Everyone is left perplexed by his actions, except the air-stewardess and an actress aboard the plane who Theodore had convinced.

Therefore, go forth, companion: when you find
No Highway more, no track, all being blind,
The way to go shall glimmer in the mind.

Interestingly the book, in which a new airliner design being subject to mechanical failure due to metal fatigue, came before the failures of the de Havilland Comet airliner just six years later (1954).

James Stewart in No Highway in the Sky

James Stewart in No Highway in the Sky

As well as the book “No Highway” and the movie, there is also the radio play made by CBS. The radio play also stars Jimmy Stewart and Marlene Dietrich.

Part 1

Part 2

Part 3

Part 4

Part 5

Part 6

Making a welded Damascus Knife

John Neeman Tools have posted a beautiful video of manufacturing a welded Damascus patterned knife.

5 layers of 3 different steels were forge-welded, folded, and forged. With each step being repeated 8 times. This produces a patterned with 320 layers. Finally twisting and forging the steel produces a more complex pattern.

Just checking the number of layers, I get their total to be different. My calculation of the number of layers is 5 × 28 = 1280, that is 4 times more than claimed (320 layers should be the result of folding 6 times (6 folds 5 × 26).

With 1280 folds, if we assume the thickness of the knife is 2 mm, that means each layer is 1.6 μm, 320 folds would be 6 μm layers. These are both lower than what can be resolved using the naked eye. It’s very close to the wavelength of visble light — if the metal were folded one more time, or the final thickness of the knife is less than 1 mm you would be there.

Effect of tempering upon the tensile properties of a nanostructured bainitic steel

This paper is now available at http://www.sciencedirect.com/science/article/pii/S0921509314009642 for those with access by science direct. I made final proof corrections last Saturday, so when the final version is released the conclusions will change… in that “hard–nanostructured–bainitic steels” will become “hard nanostructured bainitic steels”.

Periodic Video of Speculum

Prof. Martyn Poliakoff has made a video showing Isaac Newton’s first telescope, which is kept at the Royal Society, in London. As we learned in physics, Isaac Newton used a mirror in his telescope to minimise chromatic aberrations which can occur when using lenses. The mirror was therefore a critical part of the telescope, a special alloy of one-third tin and two-thirds copper and a small amount of arsenic was used, called Speculum.

Adventures in Physical Metallurgy of Steels

During July 2013 I attended Adventures in Physical Metallurgy of Steels hosted by the Phase Transformations and Complex Properties research group of the Department of Materials Science and Metallurgy.

The programme looked like this, videos are appearing on bhadeshia123’s channel on youtube (links). There is also a playlist available.

Programme
Introduction to Adventure. H. Bhadeshia

Architectured Steels, T. Koseki

Magneto-structural coupling. I. Abrikosov

Quench and partitioning. J. Speer

Crystallographic variant selection. S. Kundu

Secondary hardened bainite, J. R. Yang

Welding of high carbon steel, K. Fang

Isotropy and Fatigue: P. Ölund

Atoms in bainite, atomic mechanisms. F. Caballero

Pulsed steels, R. Qin

Fullerenes & buckyballs in steel: I. V. Shchetinin

Boron: Type IV cracking, F. Abe

Low-density steel, H-L. Yi

Friction stirring of steel, T. Debroy

Flash Processing, G. Cola

Reliable first principles calculations for iron: A. Paxton

Steels composites for energy applications, C. Capdevila-Montes

Microstructures without contact, C. Davis

Pop-in deformation, H. N. Han

Plausibility of fine bainite, C. García-Mateo

Reduced Activation, K. Wu

Architectured microstructures, G. Anand

Flash microstructure, S. Babu

Energetic TWIP, D. Dye

Mass production of fine bainite: A. Rose

Voids and 30000 atoms, S. Munetoh

Soft Particles, T. Tsuchiyama

Mechanochemistry, F. Miani

Simplex and Kappa steels, I. Gutierrez-Urrutia

Innoculated high-speed steel, A. Chaus

Non-cubic ferrite, D-W. Suh

Montage of events

Superbainite

Structure of superbainite. Inset is a same-scale image of a carbon nanotube. [1]

Structure of superbainite. Inset is a same-scale image of a carbon nanotube. [1]

According to archaeologists, the Iron Age began in 1300 BC and lasted for around two millennia. Today, steels (alloys of iron and carbon) comprise 95% of global metal consumption and this trend shows no sign of declining.

Glancing at the media, however, one would be forgiven for assuming that steel is now a has-been. We are bombarded with stories of novel materials: carbon nanotubes, metallic glasses, graphene, carbon fibre, nickel superalloys. . . all of which are “stronger than steel”.

“Now we can construct space elevators!” claim the articles. “Let’s build a climbing frame to the moon! We’ll use this stuff to make everything!”

The observant among us, however, will note that most cars, trains and buildings still don’t feature superalloys, metallic glass or magic nanotubes. Neither are they invisible; nor do they fly; nor do they do any of the other things that journalists tend to ‘predict’.

Instead, steels somehow remain the best — and cheapest — materials for the job. Also, they are stronger than steel. This is because ‘steel’ is a vague construct used by sensationalists, with an unspecified strength guaranteed to be less than that of a novel material. Metallurgists rarely refer to ‘steel’, just as the Inuit have fifty words for snow, not one of which is ‘snow’.

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