cryogenic Charpy

JHOLLAND1 · Jul 7, 2019

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

JHOLLAND1 · Jul 7, 2019

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

cyanidekid · Jul 8, 2019

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

DDoug · Jul 8, 2019

JHOLLAND1 said:
fracture force varied from 21 to 100 lb-ft of these 9 coupons

What material held on to 100 ft/lbs at -40 c ?

Rewt · Jul 8, 2019

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

I saw that and thought, very nice lab table

4GSR · Jul 8, 2019

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.

L Vanice · Jul 8, 2019

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

Nmbmxer · Jul 8, 2019

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

SCILOGEX DILVAC Portable Dry Ice Maker |
Scilogex

Mark Rand · Jul 8, 2019

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.

DocsMachine · Jul 10, 2019

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.

muckalee · Jul 10, 2019

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

9100 · Jul 15, 2019

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

Trboatworks · Jul 19, 2019

“...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/cha...hallenges-07-00020.pdf?filename=&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-Under-Perilous-N/dp/1585742406

northernsinger · Jul 20, 2019

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?

L Vanice · Jul 20, 2019

northernsinger said:
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/uploads/2/6/2/0/26200212/charpy_impact_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/literature-library/corporate/2005/02/history-of-satec.pdf?la=en See page 8 for the SI Charpy machine.

Larry

northernsinger · Jul 20, 2019

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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