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  1. #1
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    Default cryogenic Charpy

    125 years ago Professor Georges Charpy standardized metallic specimen testing

    10 x 10 x 55 mm mini-bars referred to as coupons--are submitted to
    swing hammer impact

    today I dropped by local test lab performing cryogenic Charpy testing
    designated temp -40 deg C
    to achieve this the lab discharged bottled co2 into expansion chamber which in
    two minutes produced cube of solid co2

    shavings from this block were placed into denatured alcohol to lower temp of alcohol bath to -40

    9 Charpy specimens were allowed to soak followed by rapid extraction and swing fracture

    energy was recorded in lb-feet and joules

    fracture force varied from 21 to 100 lb-ft of these 9 coupons


    video

    YouTube
    Attached Thumbnails Attached Thumbnails 100_1169.jpg   100_1170.jpg   100_1172.jpg   100_1173.jpg   100_1176.jpg  


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    this lab uses liquid nitrogen for coupon temps down to -300 F

    the specimens fractured today were obtained from 4140 plate 6x6x2 inches

    the lab keeps specimens indefinitely but photographs --macro--each coupon and
    incorporates the image in one page report per specimen
    Attached Thumbnails Attached Thumbnails 100_1192.jpg   100_1191.jpg   100_1180.jpg   100_1193.jpg   100_1171.jpg  


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    I like the “dry ice” maker on the chair! Cool...

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    Quote Originally Posted by JHOLLAND1 View Post

    fracture force varied from 21 to 100 lb-ft of these 9 coupons
    What material held on to 100 ft/lbs at -40 c ?

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    Quote Originally Posted by cyanidekid View Post
    I like the “dry ice” maker on the chair! Cool...
    I saw that and thought, very nice lab table

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    Anybody in the oilfield surface equipment manufacturing business can tell you how critical Charpy impact values are. Especially for any equipment being used in sub zero environments like the North Sea, Alaska, and Siberia region of Russia. Same goes for world wide ship building business, too.
    There's several testing labs in Houston set up that do Charpy impact testing. Most build a makeshift box out of foam insulation board from a box store, with one side with a flap that is flipped open for the swing arm to enter when ready to test at a given temperature. But to go up to 100 degrees C, that's a whole different ball game.

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    The other impact test is the Izod. Charpy vs. Izod: An Impact Testing Comparison | Element

    These devices test toughness, which many people confuse with tensile strength. Toughness is a combination of tensile strength and ductility A steel file is very strong, but is not at all tough. An annealed copper bar is relatively weak, but is very tough.

    Larry

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    I was "admiring" the dry ice maker so I looked up dry ice makers, I'm in the wrong business:

    capture.jpg

    SCILOGEX DILVAC Portable Dry Ice Maker |
    Scilogex

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    We used the Izod test at work. Not really surprising since Edwin Izod worked at and developed it at Willans and Robinson's Victoria Works in Rugby, which is where I was employed for 34 years. We had his original testing machine in a display area in the Erecting shop. I believe that it has now gone to a museum, since the new owners became less and less interested in the history of their acquisitions.

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    I remember a Popular Mechanics (I think) article from many years ago, where they tested a piece of the Titanic hull- not only a fragment that had been brought up during some of the initial discovery dives, but also on a rivet-hole "slug" that had been kept as a souvenir (and even engraved with the date and time it was punched, as I recall.)

    I don't remember the actual values from the article- if any were even given- but a chunk of mild steel simply bent over when hit by the hammer, while both samples from the ship hull basically snapped off clean and went flying. Nearly as brittle as cast iron, it seemed.

    From that and metallurgical analysis, they determined that the steel had a very high... sulfur, I think, content, which made it brittle. Speculation off of that suggested that the hole caused by the iceberg wasn't a "rip" or gash, as much as it was a gaping hole, when large pieces of the plating actually cracked off and fell away.

    Doc.

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    I may still have a copy of the original report on the Titanic. If any one wants to see it send a Pm

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    A lot of Liberty ships broke in half-

    liberty ship crack - Google Search

    People forgot that salt sea water can get a lot colder than 0C before it freezes.

    Bill

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    “...another important reason for failure associated with welding is the hydrogen embitterment; most of the fractures initiate at deck square hatch corners where there is a stress concentration; and the ship steel has fairly poor Charpy-Impact tested fracture toughness. It has been admitted that, although the numerous catastrophic failures were a painful experience, the failures of the Liberty Ships caused significant progress in the study of fracture mechanics. Considering their effect, the Liberty Ships are still a success.”

    https://res.mdpi.com/challenges/chal...=&attachment=1

    I enjoyed Farley Mowats Grey Seas Under, his account of his WWII service on a ocean tug out of Newfoundland which set out in all weathers to rescue ships.
    Sometimes the odd half Liberty Ship still afloat which was brought to harbor to be knit to a new bow or stern.

    https://www.amazon.com/Grey-Seas-Und.../dp/1585742406

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    Does anyone know the name of the impact tester in the first set of photographs: I don't.

    My father was a mechanical engineer trained at the Towne School at the University of Pennsylvania, in the 1930's. He was a loyal and interested alum (though he didn't practice as an engineer--but I think he kept his license up) and we lived close by the university. When I was a boy he would take me to open houses at the engineering school--I think these were called 'Engineering Day,' and I have early memories of various material testing machinery, though nothing specific.

    Of course Philadelphia did well in the materials testing machine business, with Riehle and Tinius Olsen (the latter still going).

    (I'm not certain it is still going but, after my father's 1994 death, my mother--she's still going, 94 years old--endowed a small scholarship in the engineering school there, in his name, and for years went down to functions there. I think her gift to the University was structured as an annuity and--while the students awarded this and the university have done OK with this, she, by living so long, might have done even better.)

    The testing machine?

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    Quote Originally Posted by northernsinger View Post
    Does anyone know the name of the impact tester in the first set of photographs: I don't. ...The testing machine?
    Picture 3 in post 2 shows the dial and name plate of a Satec Systems Charpy impact tester Model SI-1D. That is the same model used to get data for this study of carbon and stainless steels impact test results at various temperatures:

    https://emanalhajji.weebly.com/uploa...mpact_test.pdf

    Satec is a brand with roots in Baldwin Locomotive, Lima and Warner & Swasey, among other big names in test machines.

    https://www.instron.us/~/media/liter...atec.pdf?la=en See page 8 for the SI Charpy machine.

    Larry

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    Larry, thank you, that is excellent reading for me, who had no idea about most of this. More Philadelphia connections, in Southwark and Weidemann. I appreciate it.


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