Peasant Posted May 29 Share Posted May 29 I deeply apologize for resurrecting this venerable topic, but I have something important to add to the discussion: Quote The US 50% Navy limit is ~30m/s below the german G(d) limit, or 96% for plate thickness of 100mm. The difference is due to a combination of a more strict german penetration criteria and softer US plate. For small thickness (T/D ratio) the softer US plate shows a higher ballistic limit, despite being only a 50% limit. Link to comment Share on other sites More sharing options...
Wiedzmin Posted June 19 Share Posted June 19 Ba rh10/73k Link to comment Share on other sites More sharing options...
Peasant Posted June 19 Share Posted June 19 1 hour ago, Wiedzmin said: Ba rh10/73k Of note is that the penetration curve for the Kwk 42 is for the sub-caliber PzGr.40 shell and not AP like the other two. What's the point in comparing apples and oranges, I wonder? Link to comment Share on other sites More sharing options...
Wiedzmin Posted June 19 Share Posted June 19 (edited) Just some random german doc from bundesarchive , available on-line Edited June 19 by Wiedzmin Link to comment Share on other sites More sharing options...
alejandro_ Posted June 26 Share Posted June 26 On 6/19/2024 at 11:16 AM, Wiedzmin said: Just some random german doc from bundesarchive , available on-line Thank you, it shows the advantage in penetration of the 128mm Pak 44 over the 88mm Pak 43. Note vertical axis showing hardness. It is a shame no more data versus different slopes is included, as the 128mm round should have the advantage. Link to comment Share on other sites More sharing options...
alejandro_ Posted June 28 Share Posted June 28 I have put together a table comparing ammunition. For the 88mm I have used PzGr 39/43 (almost identical) as there were more data. With APCBC-HE the 128 mm round has more than twice the energy, and more than 8 times the explosive. Link to comment Share on other sites More sharing options...
Peasant Posted June 28 Share Posted June 28 (edited) Cool, but how is this relevant to this topic? "WWII German Ballistic Penetration Criteria"? Edited June 28 by Peasant Link to comment Share on other sites More sharing options...
sunday Posted June 28 Share Posted June 28 If you are bothered because that, then you should stock some bourbon for the next activation of the loved but fearsome Threadjacker3000™. Link to comment Share on other sites More sharing options...
Peasant Posted June 28 Share Posted June 28 I'm just saying. This not some kind of instant-messaging-social media like Discord where everything that happened over 24 hours ago gets buried forever under new messages. These threads will still be here years, even decades, from now, nourishing the generations to come with knowledge that old farts like us have left them. Link to comment Share on other sites More sharing options...
Peasant Posted July 1 Share Posted July 1 Quote the V/50 penetration criterium is a conformal definition for cross-country comparison. However, I am sure You are aware that the german penetration curves are not Krupp curves. Both Krupp and Rheinmetall had their own penetration curves, seperate form the official ones and based upon the company´s historical samples. While these are primary sources, they are company internal sources and therefore are less reliable than, say WaPrüf´s official penetration curves, tested for on the gouvernmental (speak: independent) prooving ground, not on the company´s one. I have leaked a set of these official penetration curves from my archive to You (and others) a couple of years ago and You´ve used it under Your own term "Datenblatt" since. These are "Durchschlag" curves, in which five out of five tests (no failure allowed) within a narrow velocity range have to completely penetrate a plate of known tensile strength in intact condition (up to ca. 40°) with the failure mode of the plate beeing ductile hole formation. Past 45°,when breakage sets in, the definition was that five out of five tests should result in fragments of the projectile up to and incl. the fwd bourrolet were to be recovered behind the plate. The failure mode of the plate under these conditions was dominated by plugging. The official german "Durchschlag" definition is way more severe than the conformal V/50 and represent a close to 2sigma confidence criterium. Whenever armor penetration is concerned, it´s not enough to know the velocity, obliquity and tensile strength of the plate but also the be able to identify the specific failure mode under which the plate gave way to -or resisted a penetration. That´s why I use to consider only tests, where information of the projectile damage and plate damage is included. This kind of information is not available in the Yugo tests, and this can and will lead people not familar with penetration mechanics to misleading conclusions. Quote J. Sitz comments on practical experiences of the prooving ground work in Lilienthalreport 166(1943) and Hillersleben minutes (1944). The german anti tank projectiles were designed such that the velocity for penetration and the velocity for intact penetration fall together (extreme case: Projectile stuck in plate or even rebound in intact condition with no damage other than stripping of driving bands and nose covers). At obliquities of 40° and above, the variance and the delta between fragmented perforation and intact penetration increased. Also, the type of plate failure enlarged (ductile [slot formation] failure, adiabatic shear failure causing plugs or discs). Notice that they still required a 5 out of 5 success criterium, which is difficult to obtain when break up occurs once in a while. f.e. German official penetration curves give 95mm RHA @ 45° for the 75mm Pzgr 39 at ~960m/s. At the USPG, the projectile was succesful, sometimes at least, against 132mm RHA plate and stayed intact. Quote J. Sitz comments on practical experiences of the prooving ground work in Lilienthalreport 166(1943) and Hillersleben minutes (1944). The german anti tank projectiles were designed such that the velocity for penetration and the velocity for intact penetration fall together (extreme case: Projectile stuck in plate or even rebound in intact condition with no damage other than stripping of driving bands and nose covers). At obliquities of 40° and above, the variance and the delta between fragmented perforation and intact penetration increased. Also, the type of plate failure enlarged (ductile [slot formation] failure, adiabatic shear failure causing plugs or discs). Notice that they still required a 5 out of 5 success criterium, which is difficult to obtain when break up occurs once in a while. f.e. German official penetration curves give 95mm RHA @ 45° for the 75mm Pzgr 39 at ~960m/s. At the USPG, the projectile was succesful, sometimes at least, against 132mm RHA plate and stayed intact. Quote the criteria isn´t described therein, Sitz points out the fact that all projectiles will break up at obliquities larger than 45° (p.112: "..., bei 45° dürfte ein Heilbleiben auch möglich sein und muß angestrebt werden, bei flacheren Winkeln werden die Geschosse zerbrechen.") The "G_D" criterium in use for official penetration curves dates back to the late 1890´s. It wasn´t extra discussed in ww2 as something new. There were three curves used: A) "Grenzkurve" - the velocity at which the projectile depletes all energy and either A1- projectile remians intact but is stuck in plate (not through) A2- projectile completely penetrates but in a broken condition "Durchschlagskurve" defines thee vlocity at which the projectile always completely penetrates (base completely through). The projectile may be broken up or stay intact (similar to A2 but A1 would never be considered "Durchschlag", slight difference) C) "Heilbleibkurve" defines the velocity at which the projectile always penetrates in a condition fit to burst (no damage allowed). was used by the Army, A) and C) by the navy (for homogenious Wh armor, the curves of A- and C fell together for the latest projectiles creating but not for KC). Only for acceptance of armor piercing ammunition, the Army criterium specified at the proofing angle (30°, later increased to 45°) that the projectile has to stay intact (Navy "heilbleib" criterium). For explorative trials to investigate penetration performances, the Army was using the older "Durchschlag" criterium, which is understandable because intact penetration was not obtainable for cal/plate(Krupp trial quality) ratios larger than ~0.8 (for Pzgr39) at 60°. And even if the projectile stayed intact, it cannot be expected do so for five consecutive attempts without failure occuring. In such shots, the limit of the plate is generally taken at that velocity, which insures perforation and the passage of the projectile, whole or in pieces, through the plate in agreement with the requirement for G_Durchschlag. This limit is higher than the theoretical one under conditions, where the projectile does not stay intact because of the energy consumed in the process of projectile break up but it was the only practicable way to secure comparative figures without deviating from the 5/5 requirements. Quote The problem with high obliquity is that mechanics of plate and projectile failure change rapidly. When I come across prooving ground results for high obliquity trials, such as carried out 1942-1944 in BA/MA RH 8/- files, a penetration was counted as "Durchschlag" only if either the whole projectile or fragments up to the forward bourrolet were found behind the plate at 60° and 75°. To identify the original 1890´s defintions of "Durchschlag" would take a couple of weeks in Freiburg, and I am not going to do this, for me it´s sufficient to know how it was done. It is essentially the correct approach because highly oblique impact vs relatively thin (<cal/plate ratio), ductile plate will result in a base first penetration, unless high hardness armor causes sufficient normalization to allow a nose first event (when associated with a lower strain rate in the plate -indicated by adiabatic shear failure rather than ductile slot formation-, this will cause a very substantial reduction of ballistic protection). Base first penetration will, of course mean that fragments of the base will be more commonly encountered behind the plate than fragments of the nose. Stolen from comments under this post: https://www.tankarchives.ca/2017/04/e-50-and-e-75-story-of-failed.html Link to comment Share on other sites More sharing options...
Wiedzmin Posted July 1 Share Posted July 1 2 hours ago, Peasant said: German official penetration curves give 95mm RHA @ 45° for the 75mm Pzgr 39 at ~960m/s. At the USPG, the projectile was succesful, sometimes at least, against 132mm RHA plate and stayed intact. US used same plate quality and hardnes as germans ? Link to comment Share on other sites More sharing options...
Peasant Posted July 1 Share Posted July 1 No, this particular plate was considerably softer, listed as 217 - 230BHN (approximate tensile strength 76 kg/mm^2), compared to German 95 - 105 kg/mm^2 for 80 - 120mm RHA plate. You can see some of the pages from this document here: https://old-forum.warthunder.com/index.php?/topic/426953-misconception-about-german-penetration-criteria/&do=findComment&comment Link to comment Share on other sites More sharing options...
Wiedzmin Posted July 2 Share Posted July 2 Have you seen soviet criteria for comparison btw ? Link to comment Share on other sites More sharing options...
Peasant Posted July 2 Share Posted July 2 1 hour ago, Wiedzmin said: Have you seen soviet criteria for comparison btw ? Funny you should ask, I've just posted this recently: https://forum.axishistory.com/viewtopic.php?p=2539704#p2539704 It's not exactly what you're looking for but it's close. Link to comment Share on other sites More sharing options...
old_goat Posted July 2 Share Posted July 2 16 hours ago, Wiedzmin said: US used same plate quality and hardnes as germans ? Definitely not. American testing plates were softer. They were overconfident at first, and believed there wouldnt be any problems when facing Panthers in normandy. https://worldoftanks.com/en/news/history/chieftains-hatch-us-guns-vs-german-armour-part-1/ Link to comment Share on other sites More sharing options...
Peasant Posted September 15 Share Posted September 15 (edited) 95% probability limit is x1.645 times the SD, so if we take SD of ballistic limit to be 50fps, the velocity where 95% of shots will defeat the armour is 82fps higher than 50% limit used by the US. We can use the relationship of Penetration vs Velocity from DeMarre formula to calculate how much this change in limit velocity alters the thickness defeated: Striking Velocity (fps): 50% penetration thickness (reference): 95% penetration thickness: 5% penetration thickness: 1500 100 93 108 1600 100 93 108 1700 100 93 107 1800 100 94 107 1900 100 94 107 2000 100 94 106 2100 100 95 106 2200 100 95 106 2300 100 95 105 2400 100 95 105 2500 100 95 105 2600 100 96 105 2700 100 96 105 2800 100 96 104 2900 100 96 104 3000 100 96 104 This information can be used in following way: if, let's say, the US 75mm M61 APC round will perforate, with projectile going all the way through, the Tiger I's side armour with 50% probability at exactly 500m, that's the s.v. of 1858fps, which means that it will defeat it on 95% shots at s.v. 82fps higher or 1940fps which is 250m. Edited September 15 by Peasant Link to comment Share on other sites More sharing options...
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