15.02.45 85-160 mm Panzer Plate Sollkurve

[Peasant]

In this thickness range, the 75mm projectile is badly overmatched. Ductile holing will be a common failure mode for pointed projectiles if the projectile manages to stay intact. In order to test vs shock they would have needed a 12.8-15cm blunt target slug projectile, which one may critisize, would have beared little relationship to real world needs. However, projectile break up increases variance and increased variance correlates with reduced relevance of test results, i.e. less desirable from QC point of view. Low hardness armor fails typically by exceeding the resistence to plastic deformation, i.e. the soft armor further reinforces ductile holing events. Keeping the cap in such a case (remember, they tested acceptance quality floors for procurement of armor plate) just reduces a source of error (projectile quality variance).

Thinner gauges were treated to higher hardness and shock resistence to adiabatic shear failure then becomes much more probable failure modes, which needed to be guarded against.

There is a hole in that neat theory of yours, the 3.7cm AP shell did not break up at low-mid obliquity unlike the 5cm shell under similar conditions, probably owning to the lower striking velocity (703m/s vs 866m/s). This does leave a possibility for the weakness to adiabatic shear in that gauge of plate.

I'm gonna say probably something really stupid, but, perhaps this is the reason why the thicknesses near the lower end of the spectrum tested by the 5cm ohne kappe shell required such high obliquity angles to guarantee immunity?

[critical mass]

Interesting. I have little data on the 3.7cm Pzgr. Do You have examples of intact penetrations? Since this calibre would be tested normally vs very hard homo and FH plates, it would surprise me if it could negotiate intact penetration at 700m/s.

[Peasant]

Interesting. I have little data on the 3.7cm Pzgr. Do You have examples of intact penetrations? Since this calibre would be tested normally vs very hard homo and FH plates, it would surprise me if it could negotiate intact penetration at 700m/s.

Hmmm... you're making good point. Since this gauge of plate is even harder than the one tested with 5cm AP, perhaps the decreased striking velocity would not be as effective at keeping the shell intact as I've assumed.

I do not have access to any material that one cannot find on the Internet, so I'm working with circumstantial evidence here. Since the DeMarre K coefficient for striking angles of 90..60° is lower for the plate gauges tested with 3.7cm shell, I assumed that its due to the shell staying intact but this pattern is consistent between 90° and 60° while even if it could remain intact at normal incidence, its much harder to believe that it did at 60°.

There is another possible explanation. Since these are not ballistic test results themselves but minimal acceptance specifications, perhaps they are just more lenient for this gauge because RHA of this hardness is inevitably more susceptible to the type of damage from a blunted penetrator.

The question to ask would be: wouldn't it have been better to temper this gauge to a lower hardness similar to that for plate tested with 5cm AP? But then perhaps it wouldn't be as capable of damaging the lower velocity uncapped shells, resulting in even lower resistance at low obliquity when tested against 3.7cm Pak?

[Thoddy]

the Sollkurve appears as a comparison document for certain steels checked for armor purposes; physical properties and behave under ballistic attack.

With ongoing war Chromium, Nickel and Molybdenum ... Wolfram becam very scarce in Germany, so they looked for lower alloyed steels wich could serve as armor, preferably with best possible ballistic properties as the higher alloy armour grade steels. But that was very difficult. (description is also given in Bericht 166 der Lilienthalgesellschaft) ...typically they increased thickness somewhat to overcome the lower ballistic resistance.

Additionally they tried to replace the standard electric steels(E) by Siemens-Martin-Steel (SM) wich require much lesser energy to produce.

[Peasant]

It appears that I've made a slight error in the formula here, the correct coefficients are as follows:

[Peasant]

In this thickness range, the 75mm projectile is badly overmatched. Ductile holing will be a common failure mode for pointed projectiles if the projectile manages to stay intact. In order to test vs shock they would have needed a 12.8-15cm blunt target slug projectile, which one may critisize, would have beared little relationship to real world needs. However, projectile break up increases variance and increased variance correlates with reduced relevance of test results, i.e. less desirable from QC point of view. Low hardness armor fails typically by exceeding the resistence to plastic deformation, i.e. the soft armor further reinforces ductile holing events. Keeping the cap in such a case (remember, they tested acceptance quality floors for procurement of armor plate) just reduces a source of error (projectile quality variance).

Thinner gauges were treated to higher hardness and shock resistence to adiabatic shear failure then becomes much more probable failure modes, which needed to be guarded against.

I have something to show you:



The disparity of K coefficients between the capped and uncapped shells got me thinking: what if the AP cap works in reverse too? It cushions the impact and reduces the peak force of the projectile, yes, but on the armor as well! So an uncapped AP is more likely to show an insufficient toughness of the armour, reducing the ballistic limit obtained when using the G(s) limit as criteria for defeat.
Is this line of logic correct?

[Thoddy]

Do you have the AD(A) number from this document?


...
What are the weight numbers for the for projectilebody and armour piercing cap for
-37 mm M51 and
-37 mm M74.

[Peasant]

Do you have the AD(A) number from this document?


...
What are the weight numbers for the for projectilebody and armour piercing cap for
-37 mm M51 and
-37 mm M74.

The chart is from AD_830287 "Engineering Design Handbook: Elements of Armament Engineering, Part II: Ballistics" p.203

-37mm M51: 0,753kg body, 0,87kg whole projectile
-37mm M74: 0,87kg whole projectile.

[Thoddy]

-37mm M51: 0,753kg body, 0,87kg whole projectile
-37mm M74: 0,87kg whole projectile.

Then repeat the de Marre caculation for M74 with the same de Marre factor but lower weight of the M51 body.
And plot the results.
I hope
Geometry ( i.e. ogive ) was the same?( except lenght)

The AP-cap is some kind of "death weight" at low obliquity when attacking homogenous armour.
Its weight completely falls out of the calculation.

[Peasant]

-37mm M51: 0,753kg body, 0,87kg whole projectile
-37mm M74: 0,87kg whole projectile.

Then repeat the de Marre caculation for M74 with the same de Marre factor but lower weight of the M51 body.
And plot the results.
I hope
Geometry ( i.e. ogive ) was the same?( except lenght)

The AP-cap is some kind of "death weight" at low obliquity when attacking homogenous armour.
Its weight completely falls out of the calculation.

Why won't *you* do it?

Even better question: why haven't you done it *before* posting your comment?

Because if you had, you would've known that I've already taken into account the smaller body weight of M51 shell.