181–190 of 196 posts
I imagine extremely large construction and digging. Kilometer-tall buildings and deep large tunnels.
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That makes sense, if I don't rip open a bag on the first try it'll just stretch and never open
Stretch it in one direction, then grab in the middle of the stretched area and pull sideways, and it pops open like nothing.
Now I wonder if that is how these "magic cut" wasabi and ginger sachets work.
If you're reading this article, you may wish to know that arguably a "counterpart" to heavy press forging is explosive forming [1] in which a chemical high explosive is used to force a template material against a template. The overpressure generated by the explosive can be equivalent or maybe even greater than heavy press forgings (a 50,000 US short ton force press exerts ≈500 MN force; peak overpressure close to det…
Example: In a shell and tube heat exchanger, the tubes might have some really reactive stuff in it so you might make the tube side out of indium , titanium, nickel, or even an expensive stainless steel like S32205/S31803. The shell side might just have river water for cooling, and can just be painted and have a sacrificial anode somewhere inside.
The bulkhead where all the tubes penetrate (the "tubesheet") might be 6' (180cm) in diameter and 4-8 inches (10-20cm) thick - an extraordinarily expensive hunk of material (or possibly not even available in the thickness needed) when made 100% of the more exotic materials; easily in the 6 figure range.
Sometimes this problem is solved by having a welder coat the entire surface with weld metal that's good enough to withstand the corrosion characteristics of the process stream, but with larger parts this can take _days_; with some metallurgies (e.g. brass) it's not even possible.
Instead, the practice was to explosion bond a "thin" layer (1/4" (6mm) or so) of the expensive stuff to a more standard carbon steel forging. The tubes are usually very thin walled and welded/brazed to the cladding.
What's cool is the interface layer between the two metals looks like when two liquids meet with swirls and whorls of the two materials interleaving, but frozen solid.
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annealing, which resets the grain structure, happens at a lower temperature than melting or sintering.
Doesn't annealing take hours, particularly at the lower range of temperatures? Perhaps the additive process can keep the metal hot for a much shorter time. Granted, this also means stresses from the manufacturing process will not be removed.
> Forgings have the added advantage of variable grain direction which generally can be tailored to the stress patterns of a specific design. This is a super underappreciated fact! It's often repeated that forging is just stronger, but just squishing steel does NOT make it stronger. Forging a part is so much more than just smashing it into a shape. Steel cable is made of pretty ordinary steel which is stretched 100s o…
I have had this question in my mind for decades: > "Can you forge metals in a highly controlled and directed magnetic field where you can orient the grain/alignment of atoms/fields in whatever direction you want. Further, if true, what happens when you make damascus from varying plated that have particular alignments/grains - and what are the features of this material?
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I have had this question in my mind for decades: > "Can you forge metals in a highly controlled and directed magnetic field where you can orient the grain/alignment of atoms/fields in whatever direction you want. Further, if true, what happens when you make damascus from varying plated that have particular alignments/grains - and what are the features of this material?
Electromagnetic stirring is used in continuous casting for grain refinement. It’s also used sometimes in welding.
If you're reading this article, you may wish to know that arguably a "counterpart" to heavy press forging is explosive forming [1] in which a chemical high explosive is used to force a template material against a template. The overpressure generated by the explosive can be equivalent or maybe even greater than heavy press forgings (a 50,000 US short ton force press exerts ≈500 MN force; peak overpressure close to det…
I used to work as a design engineer for a pressure vessel manufacturer - we used explosion bonding all the time to bond more expensive corrosion resistant layers to carbon steel backing parts. Example: In a shell and tube heat exchanger, the tubes might have some really reactive stuff in it so you might make the tube side out of indium , titanium, nickel, or even an expensive stainless steel like S32205/S31803. The s…
Earlier quoted context omitted.
The best evidence for grain flow on a really atomic scale comes from what is called texture analysis in X-ray or electron-beam crystallography (or related techniques): you get a deviation in the distribution of Bragg peaks due to the fact that you have a non uniform distribution over the orientation of the unit cells within the crystallites in the bulk material. You can fit this in a spherical harmonic basis and quit…
I'm not saying grain flow doesn't exist. My claim is that I can't find any support for the idea that grain flow results in superior strength characteristics in the grain direction.
This paper [1] has some good data in it:
"The experiments in this study were developed to verify the influence of the grain-flow orientation on fatigue life and its impact on the anisotropic properties of a mechanical component. To this end, steel specimens were made, and their fiber was oriented by machining and hot forging. Subsequently, they were subjected to flexo-rotational fatigue tests in a piece of specific equipment to determine their fatigue life."
(...) They then describe three parts: A, properly forged, B, improperly forged, and C, machined. (...)
"The results showed that specimens of configuration A achieved a much longer fatigue life than configurations B and C, actually doubling it. The results indicated a similar fatigue life behavior between configurations B and C. It is important to emphasize that this similar behavior between these two configurations is valid for this case analyzed (...)"
Earlier quoted context omitted.
I used to work as a design engineer for a pressure vessel manufacturer - we used explosion bonding all the time to bond more expensive corrosion resistant layers to carbon steel backing parts. Example: In a shell and tube heat exchanger, the tubes might have some really reactive stuff in it so you might make the tube side out of indium , titanium, nickel, or even an expensive stainless steel like S32205/S31803. The s…
That sounds amazingly fun -- thank you for sharing, and for including si units! Do you have any pictures of the whorls? (I'm imagining something like damask steel)