Hardness plywood vs pine

[AndersMalmgren]

Hi, I have a somewhat unusual question about the hardness of plywood vs. pine. I am working on a computer game and gathering information about different types of ammunition penetrating various materials. The problem is that the reference materials I find are different; some shoot at pinewood, often 2 by 4 studs, while others shoot at plywood.

I need to normalize the values. Initially, I thought of just using the density, approximately 410 kg/m3 for pine and weighted against the density of plywood at 680 kg/m3, a factor of 1.66 which matches quite well. A 9mm bullet (124 gr FMJ) goes 100 mm in tightly packed plywood and about 170-190mm in loosely packed 2 by 4 studs (two different references on YouTube).

Yellow pine has a hardness of 870 Janka, but I can't find one for plywood.

 

[Bernieberg]

Conduct a test with a thick piece of pine and a stack of plywood. Use a coarse nail (the closer to your studied caliber, the better). Drive the nail with some form of drop hammer with known mass and drop height. Compare how many blows are needed to penetrate each material to a certain depth. Preferably several attempts.

 

[Bernieberg]

If you are looking for material properties, hardness is probably not the best measure. I would compare the tensile strength of pine across the grain direction with the tensile strength in plywood's weakest direction (probably 45° against the two grain directions). I don't have figures for that, but it's Googleable. "Tensile strength" in English.

 

[AndersMalmgren]

I have a .38 revolver, the problem is that wood is not an approved material to shoot at, so I can't test the hardness that way.

5.56x45 is the smallest caliber we have in the game, but it becomes a big spike I wonder if there will be a large deviation as well. You could try hitting it once and see how far the spike goes in one hit. Take the average of that.

I'll check if I can find yellow pine and plywood specs for it. Thanks

 

[AndersMalmgren]

It wasn't easy to find data on that.

 

[Bernieberg]

I can imagine that it's a bit challenging to find good data. A projectile penetrating a composite is fairly complex, so comparing individual material parameters is probably a bit vague anyway. The uncertainty is probably larger than the difference, so to speak.

An experiment is probably the most beneficial if you want to stick to simple resources and not get a doctorate on the subject. A 6-inch nail is close enough if you want to try, caliber 5 mm on that. You can definitely do the test with just one hit, but you'll probably need to strike quite hard. It's important to ensure you have the same impact energy in repeated attempts. Perhaps a medium-sized sledgehammer on a pendulum might be a reasonable setup.

In younger days, you could always huddle behind a cardboard box when things heated up in an FPS game, can't you survive that anymore?

 

[AndersMalmgren]

I can imagine that it's a bit difficult to find good data. A projectile penetrating a composite is quite complex, so comparing individual material parameters is probably a bit vague anyway. The uncertainty is likely greater than the difference, so to speak.

An experiment is probably what yields the most if you want to stick to simple resources and not pursue a PhD on the matter. A 6-inch nail is close enough if you want to try, caliber 5 mm on that one. You can definitely conduct the test with just one hit, but you probably need to hit it quite hard. It's important to ensure the same impact energy in repeated attempts. Maybe a medium-sized sledgehammer on a pendulum could be a sensible setup.

Yes, maybe I'll test with the widest nail I have. And drop a sledgehammer from the same height. Could provide good repetition And surely the Yanks have worse quality plywood than we do But it will serve as some kind of baseline at least.

In my younger days, you could always crouch behind a cardboard box when things got heated in an FPS game; aren't you supposed to survive that nowadays?

No, in our game, you won't even be able to hide behind a car except for maybe the engine block

 

[Bernieberg]

Looks fantastic! You learned during military service that cover and concealment are not the same, so I'll probably survive a while anyway.

Your clip encouraged some ballistic Googling, this thesis might interest you so you get realistic angle and velocity reduction on the ricochets.

http://www.diva-portal.se/smash/get/diva2:561643/FULLTEXT01.pdf

Regards, video-gaming MÖP physics nerd

 

[AndersMalmgren]

Looks fantastic! You learned during military service that cover and concealment are not the same, so I'll survive for a while anyway.

Your clip encouraged some ballistics googling, this thesis might interest you so you get a realistic angle and velocity reduction on the ricochets.

[link]

Regards from a gaming physics nerd

Cool, I’ll take a look, our recoil model is quite simple at the moment. We have some probability per material type and angle of incidence whether there will be a ricochet or not.

But we have implemented a true ballistic coefficient so the bullets follow the exact trajectory they should, allowing you to shoot straight up and have the bullet come down again

 

[Bernieberg]

Very fun twist in a game!

In the reference I linked to, I saw that there was also a model for penetration depth (eq. 1) where the material is characterized by the material's yield strength (also known as the yield point). However, it probably doesn't help you much, as it is a material property that is difficult to define for wood material.

 

[AndersMalmgren]

Very fun twist in a game!

In the reference I linked, I saw that there was also a model for penetration depth (eq. 1) where the material is characterized by the material's yield strength (also known as yield point). However, it probably helps you little since it is a material property that is difficult to define for wood materials.

Yes, there are some models like Newton’s model, etc. But they are just an estimation. So we have chosen to produce graphs with material depth on one axis and energy transfer on the other. Then through reference materials online, we fill these in for each material and ammo type. We also have some other parameters like the ability of nylans to start tumbling, etc. A 5.56 is designed to start tumbling and therefore doesn't penetrate as many barriers as, for example, a 9mm. However, it penetrates one barrier much better.

 

[Isakare]

Haven't Mythbusters tested it?? They have shot, blown up, and bombed everything there is, it seems like.

 

[AndersMalmgren]

Hasn't Mythbusters tested it ?? They seem to have shot, blown up, and bombed everything that exists.

No Mythbusters have come up when I've googled it actually. Tests like these are good because you can quite accurately calculate how far a bullet goes including tumbling. It's also good if you can find a test in solid material, and that's when you sometimes get different materials in the references.

 

[Isakare]

Have not come across any Mythbusters when I googled actually. Tests like these are good as you can quite accurately calculate how far a bullet travels including tumbling, good if you can also find a test in solid material and that's where you sometimes get different materials on the references.

[media]

Fun to watch, but there wasn't a huge difference.

Dumb question from someone who's never played games where you shoot each other (I drive cars if I'm going to play)
In your game, you can't hide behind just anything, but the material in between and the opponent's weapon are decisive. Did I get it right??

 

[AndersMalmgren]

Fun to watch, but there wasn't a gigantic difference.

Dumb question from someone who has never played games where you shoot each other (I drive cars if I'm going to play)
In your game, you can't hide behind just anything; the material between and the opponent's weapon are crucial. Did I get that right ??

Yes, exactly, you can hide behind a wooden structure, but it's not protection. Not even a steel container is protection against 5.56 or 7.62. In fact, 9mm goes through that type of steel too, but only one side.