[Maurizio D'Angelo]

These are the reference books.
The Knight and the Blast Furnace by dottor Alan Williams
The Great Warbow by Robert Hardy and Matthew Strickland
Weapons & Warfare in Renaissance Europe by Bert Hall

Timo Nieminen, I want to complete your numbers
Table of resistance to the arrows

1mm-- 2mm-- 3mm-- 4mm--
55J--- 175J--- 300J--- 475J--- Normal
66J--- 210J--- 360J--- 570 J--- impact 30°
78J--- 250J--- 425J--- 670 J--- impact 45°


Alan Williams has split the steel bands in each band stemmed from a coefficient W

Quality Steel:
I – Iron (slag 3-4% without carbon)-120-150 KJ/m2, W = 0,5
example: armor of spikes produced in mass 1500

II – Low carbon steel (slag 1%, carbon 0,3%)-180-210 KJ/m2, W = 0,75
example: armor infantry in Nuremberg.

III– Steel with an average level of carbon (slag < 1%, carbonio 0,6%)-240-260 KJ/m2, W = 1,1
example: Milanese armor XV-XVI century, or the beginning of the XVI century, Greenwich

IV – Steel with an average level of carbon, hardened (slag 0,5% circa, carbon 0,6%)-300-500 KJ/m2, W = 1,5
example: armor from Innsbruck, Augsburg, Landshut and Greenwich (after 1560)

what really matters is the resistance to fracture, because without fracture can not even be the penetration. (240-260 KJ/m2, W = 1,1)

decomposition of a vector, perpendicular energy can be obtained by dividing the total energy for the cosine of the angle of impact.
In this way, rounded armor is 20% stronger and gleaned 40%.

armors, grade III and IV is tested against all reasonable doubt, that they were no perforate by longbow so as no to crossbow. A sword had no chance.
In 1600 had the armor thicknesses of 6-7 mm in the vital points.

[Nat Lamb]

Ok, from what I can get from those numbers, an optimal underarm thrust, against a 1mm flat plate (really cheap munition grade perhaps?) would just barely get through, with 8 joules to spare. Any rounding and it is not doable.
An optimal overarm thrust against a flat plate could (by my guestimate as the mid point between the required energies for 1mm and 2mm) got through 1.4mm plate, provided it was a)flat, b)braced, c) dead on angle wise.

What does that indicate? a particularly stiff, acute point might go through poor quality armour if the target was lying still on the ground any other situation and the physics just don't add up. Looking at the thicknesses that Dan listed for various pieces of armour, the only one that was 1.4mm or less was the cuisses, so with an armourpiercing spike, well mounted, against an incapacitated oponent lying prone, you might stab into his thigh on a good day...maybe. Seems pretty straight forward to me, but I might be missing something, I am a philosphy major, not anything usefull

[Maurizio D'Angelo]

I think that if a person is not stupid, keep an open mind. If my ideas are wrong I' m ready to change them.
I say in the first post that a sword could be thrust into the vulnerabilities of an armor. The vulnerabilities are usually not fatal.
To make a logical discourse, I propose not to mix bows, crossbows and swords. I propose also to identify what kind of armor.
You can explain better your thinking? for example: We speak of Milanese armor type, steel grade III, weapon used sword.
If you'd rather start by arrows, the important thing is to specify this.
Is also important to establish whether an armature is considered good if the wearer is not killed, one wounded by 3 cm does not endanger life. Here's what we mean? If you just enter or to kill.
Arrows, in some mail, came in, but not enough to kill.
I read that some soldiers, were walking with so many arrows in the mail, but arrows had not passed the gambeson.
We have said that the mail offered good protection against arrows.

My thoughts.
An arrow is different from a sword.
Gauge pressure is influenced by the mass and velocity. For a sword speed is different than for an arrow. One example is 300 joules on an area of 2mm are different, in terms of penetration of an area of 20mm. For this, I think it is wrong to take the data provided for the arrows and move them to a sword. This just to begin to clarify. Correct me if I'm wrong.
In the meantime, I look for information on swords, it is clear that these data, are averages, a sword with a spiked tip is different from one with a rounded tip. I do not know if they were made differences.

[Maurizio D'Angelo]

Using the search function (I found much on this site) but I think that every time something can be usefully added.
Before considering the details of the swords, I want to emphasize that the kinetic energy is different depending on the mass and velocity, for the purpose of penetration is also important in the shape of the object that has to hit the target and its hardness. Contains data of those arrows with projectiles, notice how different is the kinetic energy that is used to perforate the same thing.
from this we can understand that different from an arrow and a projectile or a sword.

Table of resistance to the arrows
1mm-- 2mm-- 3mm-- 4mm--
55J--- 175J--- 300J--- 475J--- Normal
66J--- 210J--- 360J--- 570J--- impact 30°
78J--- 250J--- 425J--- 670J--- impact 45°

Table of Resistance to Projectiles (ball 20mm)
1mm-- 2mm-- 3mm-- 4mm--
155J--- 750J--- 1700J---3400J---Normal
186J--- 900J--- 2000J---4000J---impact 30°
217J--- 1050J-- 2300J---4700J---impact 45°

To thrust swords, I have found no data between the texts cited. I found an Italian author, with regard to the mail, are all in agreement with the article by Dan.
For armor and arrows, in agreement with that said here.
He stated that a sword thrust, with a peak relatively thin, it cannot pierce a sheet of 1.9 mm, because it breaks, and also because it is impossible to give a push in kinetic energy useful to pierce armor. Remains a sword cut. With a cut since the areas concerned will be at least 8 cm, we would need a kinetic energy of about 380J, impossible even with a sword in both hands. Maximus, a very strong man with a great sword will give 190J. Recall that the part is 8 cm.

Although it has no value, today I tried to break through an iron plate of 2.5 mm with a makeshift sword, soldered the sockets for your hands to push more effectively, I had a very sharp peak, width 40 mm thickness 5 mm, wheit 3 kg. I did that a bump, no cutting, but only see the thickness, suggests a lot. Perhaps not everyone has in mind what is 2.5 mm in a slab of iron. See a real plate means understanding more than the numbers given here.
One last thing. I believe that the thickness Dan says here, they refer to a Milanese armor. Armor made with grade I and II had greater thickness. Keep in mind that, the double thickness, the energy required is triples, no proportional.
If the data refer to a armor of grade I, a tip of the sword (as estoc?) can penetrate a thickness of about 1.3-1.4 mm with 80-100J of force, could not break his sword, it penetrates the armor, perhaps 4 cm, the rear leg. A hypothesis that I can not exclude
Here a photo,
this tests (more reliable than my ) were done in agreement with Alan Williams data from an engineer with this machine.

[Nat Lamb]

Maurizio, when you say "you" I am not sure if you are refering to my post, but I will assume you are. I think that we are agreeing very loudly with each other, but that due to language diferences it might seem like disagreement. The diferences here being Italian to English translation on one side and "Humanities student trying to talk about engineering and physics" language problems on my end

What I was trying to say was much the same as what you said in your post, except you said it much better. Namely that there is nowhere that it is theoretically possible to thrust through an plate armour that will actually cause real injury to the wearer. Closest you get is with a overarm downward stab to the the thigh, with a narrow spike, which could not be called a "fatal" injury. I was thinking of type II steel, in a flat plate, 1.5mm thick, and braced agains something solid (in my exhample, the ground). The point that I was making is that that is about the worst "plate" armour a person could possibly wear onto a battlefield, and it would stop anything but the most optimal thrusting/piercing attack, and even then the penetration would be minor.

[Timo Nieminen]

Nat, I think your conclusions are sound.

As for the energy required by a sword thrust or cut to penetrate, it'll be more than a bodkin. A pyramid tip - like the bodkin - is optimal, and the more acute the angle, the better, up to when the pyramid breaks/bends rather than penetrating. If the sword blade is wider than the bodkin, it'll take more energy. Cuts will be even worse. Very much worse, because they'll typically achieve little cutting into the target after cutting into the (light) armour. See the famous Japanese helmet-cutting tests,

http://www.shinkendo.com/kabuto.html

where the record-breaking cuts would not have reached the head inside the helmet, had there been a head inside the helmet. Note that Japanese helmets (kabuto, hence helmet-cutting = kabutowari) ranged from lacquered beer cans through to bullet-proof. The ones used for tests like these look to be towards the lower end of the scale - in one photo I saw, the (modern) helmet crumpled from the blow (which did save it from being cut through).