Original question

Assumption:

• i made several swords with different cross sections (lenticular, single broad fuller as in viking swords, diamond, hollow ground diamond)
• the blades are made using the same steel and have no taper
• i chose the width for each blade in such a way that all my swords have equal stiffness (producing equal degree of bending requires equal force for each sword)

Question:

• which sword would be less likely to break on impact along the blade’s edge?
• which sword would be less likely to break on impact on the flat of the blade?

Additional illustrations:

Edit:

I found an article on quora which suggests that the “broad fuller” sword blade design is similar to I-beam used in construction: Link

This is actually very helpful because comparing sword geometries can be replaced with comparing different beam shapes which is a lot more widespread topic with a lot of information available

Basically the question boils down to:

• you have an I-beam and a rectangular beam of same mass
• deforming both beams along the weak axis (horizontal on the photo) requires equal amounts of strength

• which beam would require more stress to break it along the strong axis?
• which beam would require more stress to break it along weak axis?

i assume the second question it still valid despite both beams having same strength along the weak axis because their yield points might still be different