How Chipping of Edges Happens at a Microscopic Level

Larrin,

Great article, thank you for what you do.

I noticed you are hosting your images in your articles, which is excellent. But you do have links to forum posts in some articles. The images in the forum posts are often linked from other sites, and may disappear over time. Also, every forum post will eventually disappear. The forum post you linked in this article already has a lost image in it...

Is there any plan to better preserve the hard work you are doing? It is such a benefit to the community.
 
Randy3000 said:
Larrin,

Great article, thank you for what you do.

I noticed you are hosting your images in your articles, which is excellent. But you do have links to forum posts in some articles. The images in the forum posts are often linked from other sites, and may disappear over time. Also, every forum post will eventually disappear. The forum post you linked in this article already has a lost image in it...

Is there any plan to better preserve the hard work you are doing? It is such a benefit to the community.
Click to expand...
That’s certainly part of what the website is for. Hopefully I won’t let that lapse. A book isn’t out of the question but isn’t in the plan for now. I will be re-writing the forum posts as articles in the future but I am linking to them as necessary when I don’t have an article on the website addressing it.
 
After thinking about the article some more, i have a few questions. I would guess damascus would be more prone to chipping than a mono steel, is that right? When i make slip joint springs now, i test a new design by bending it 90 degrees, and if it doesnt break then that is good for me (there is enough meat around the pivot pin hole, temper is right, etc). After reading the article, i guess what my test is doing is a single fatigue test, and i would suspect if i were to do a repeated fatigue test (use a machine to bend it a normal use amount hundreds of thousands of times) it would also pass.

So i guess what i am wondering is, can one spring pass my 90 degree test but then another spring fail in normal usage due to impurities or due to thin section around the pin or other factors? Is the 90 degree test severe enough i guess is another way to say it. And lastly, is a damascus spring a bad idea?
 
Randy3000 said:
After thinking about the article some more, i have a few questions. I would guess damascus would be more prone to chipping than a mono steel, is that right?
Click to expand...
I'm not sure we have any reason to believe that would be the case. There are some studies on damascus toughness and none of them show poor toughness. Studies on knife edges don't really exist as far as I know.
When i make slip joint springs now, i test a new design by bending it 90 degrees, and if it doesnt break then that is good for me (there is enough meat around the pivot pin hole, temper is right, etc). After reading the article, i guess what my test is doing is a single fatigue test, and i would suspect if i were to do a repeated fatigue test (use a machine to bend it a normal use amount hundreds of thousands of times) it would also pass.

So i guess what i am wondering is, can one spring pass my 90 degree test but then another spring fail in normal usage due to impurities or due to thin section around the pin or other factors? Is the 90 degree test severe enough i guess is another way to say it. And lastly, is a damascus spring a bad idea?
Click to expand...
90 degree bend tests are difficult because they are highly controlled by the cross section; I wrote about this in the flex article: http://knifesteelnerds.com/2018/03/13/why-doesnt-heat-treating-affect-steel-flex/.

However, another method for predicting toughness is with bend fracture strength. A comparison of different Hitachi grades is here: https://www.hitachi-metals.co.jp/e/products/auto/ml/pdf/yss_tool_steels_d.pdf
 
You must log in or register to reply here.
Back
Top