Broken full flat ground during batoning

shinyedges said:
You're missing the point, a poorly cut feature that isn't radiused properly can and does cause catastrophic failure. A proper radius all but makes that failure a statistically insignificant decimal place. It's why machinists use radiuses lol
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This is what it must feel for lawyers when random people try to explain the law to them.
 
SharpBits said:
Being a bit of an armor junky, I had to look up 12560. Cool link from one of the mills that makes it. https://www.cliftonsteel.com/steel-products/steel-armor-plate/mil-a-12560
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I have bumper pieces to mraps in my garage 😅 when general dynamics doesn't pick up its material that's been scrapped it eventually gets tossed. I'd patiently wait for that moment so I could use them on my range. I have some THICK large chunks. Enough to make hawks or whatever out of. Also some .5 plates and .25 plates. I tested them out with a boat load of calibers. 46100 as well.
 
J. Doyle said:
In ESEE's case, dumbing down the heat treat so bad that it's stupid soft and overly thick helps mitigate any stress risers that might pop up. ;)😁
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But seriously, though- you’re spot on. The full flat grind isnt optimal for strength, and jimping isn’t optimal for strength, but if you make the blade wide enough, thick enough, and soft enough you can make it just as strong. Now whether or not it’s what anyone actually wants by the end of it is a different story.
 
Nvm, it's all good. Not worth arguing over. I know what a radius is used for as I make them. No point in trying to convince someone of their purpose.
 
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EngrSorenson said:
… listen, I don’t know what parts you’re talking about, or their application, but let’s not over complicate anything. You put a round semicircle of any radius into the edge of a piece of bar stock and you didn’t make it stronger, I promise you that. There’s no cut you can make into a bar of steel that doesn’t reduce the strength in bending, period.
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With respect, Shiny is absolutely correct about radiuses being stronger than hard angles. In any application of steel parts, for any purpose. He's not saying taking semi-circular chunks out of bar stock is going to make anything stronger. Only that it's better to radius a cut out than to leave right angles. It's the old KA-BAR tang conversation again. Are you deliberately taking him out of context or am I stupidly missing some larger point here?
 
The True North said:
With respect, Shiny is absolutely correct about radiuses being stronger than hard angles. In any application of steel parts, for any purpose. He's not saying taking semi-circular chunks out of bar stock is going to make anything stronger. Only that it's better to radius a cut out than to leave right angles. It's the old KA-BAR tang conversation again. Are you deliberately taking him out of context or am I stupidly missing some larger point here?
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I had to go back and re-read what Chris wrote, initially.
A5xfCA0.jpeg

No argument that how jimping is cut matters, but there is no practical radius for jimping that eliminates the stress concentration. Nothing I’ve said above is incorrect, and there’s nothing to argue with.
 
shinyedges said:
Nvm, it's all good. Not worth arguing over. I know what a radius is used for as I make them. No point in trying to convince someone of their purpose.
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I know you deleted the rant, but if you want to know my qualifications, I’m a Mechanical Engineer by education, and machine design is a 3rd year course. Shigley’s “Mechanical Engineering Design” text is widely considered an authority on the subject. I happen to have it right here:

j7FNPh8.jpeg


But peace, brother. Ain’t nothing worth getting upset over. Besides, I don’t have any tables that cover a good approximation of what we’re talking about, since it’s all derived empirically, which makes it hard to talk numbers; the only thing that would really satisfy the discussion.

The one thing I’ll note is that the K factor never goes to 1.0, and therefore never becomes completely negligible, looks like it’s probably a 20% increase, cutting the result in half. The only remaining question is if there’s enough cross sectional area to hold it together.

But to get back on topic, a full flat grind is probably not the sole reason for the OP’s failure, and I’m sure it’s a confluence of design weaknesses, possibly down to the material and heat treat.
 
Most breaks I’ve seen here have been grain irregularities, totally different from relief cuts.
 
EngrSorenson said:
I know you deleted the rant, but if you want to know my qualifications, I’m a Mechanical Engineer by education, and machine design is a 3rd year course. Shigley’s “Mechanical Engineering Design” text is widely considered an authority on the subject. I happen to have it right here:

j7FNPh8.jpeg


But peace, brother. Ain’t nothing worth getting upset over. Besides, I don’t have any tables that cover a good approximation of what we’re talking about, since it’s all derived empirically, which makes it hard to talk numbers; the only thing that would really satisfy the discussion.

The one thing I’ll note is that the K factor never goes to 1.0, and therefore never becomes completely negligible, looks like it’s probably a 20% increase, cutting the result in half. The only remaining question is if there’s enough cross sectional area to hold it together.

But to get back on topic, a full flat grind is probably not the sole reason for the OP’s failure, and I’m sure it’s a confluence of design weaknesses, possibly down to the material and heat treat.
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I think the purpose of the radius has eluded you lol all good though. When a metal is milled and a radius chosen over a sharp angle, it is for preventing stress from causing a failure. You can argue against that all day if you'd like, you still won't be right lol
 
EngrSorenson said:
True or false- every radius cut in metal causes a stress concentration.
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The question is flawed, a radius reduces stress concentration when compared to a sharp edge angle. Hence the point of radiusing to increase resistance of cracks propagating.

Which one of these will have a higher concentration of stress and fail first?20241021_215744.jpg

Night Dan!
 
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shinyedges said:
The question is flawed, a radius reduces stress concentration when compared to a sharp edge angle. Hence the point of radiusing to increase resistance of cracks propagating.

Which one of these will have a higher concentration of stress and fail first?View attachment 2691801

Night Dan!
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that’s the problem. You’re stuck on how radius can mitigate some of the stress concentration. I’m saying jimping can only increase stress concentration when compared to no jimping. Both of these statements are facts, and apparently we’ve been talking past each other.
 
EngrSorenson said:
that’s the problem. You’re stuck on how radius can mitigate some of the stress concentration. I’m saying jimping can only increase stress concentration when compared to no jimping. Both of these statements are facts, and apparently we’ve been talking past each other.
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Agreed, well, we've wasted more time on less important crap before 🤣
 
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