Laminated steel question

[fishbulb]

I have never owned or handled a laminated (san mai?) steel blade, but I have a question about the concept.

As I understand it, the harder than average core provides the cutting power, and the softer than average sides allow the balde to flex without breaking.

This is a good idea, but I don't see how it works.

Intuitively, it would seem that the inner core would fracture at the same point regardless of what was on the sides. To use an extreme example, a plastic/glass windshield can't flex any more than an all glass one, it just stays together after it shatters. However soft you make the sides the middle should still reach the fracture point at the same flex.

Does a laminated blade actually end up as a number of fractured core pieces just held together by the sides? If not, why?

 

[Jeff Clark]

If you take something like a bar of metal and bend it you stretch the "backside" of the bar and compress the "inner side" of the bar. The center line is neither stretched nor compressed it is simply curved. Hardened steel is most vulnerable to cracking where it is stretched. Likewise the outside of a blade is under much higher stress than the core.

Another way to look at it is how flexible thin material is. Paper is in many ways similar to masonite hardboard only much thinner. You can bend paper without cracking it, but masonite will break if bent very far. If you stretch paper it will still tear however. A thin piece of hardened steel will bend pretty far since the surface stresses from bending are proportional to thickness. So put your hard steel in the middle where it won't be stretched and your soft steel on the outside to stretch harmlessly.