Hammer blow test from MIL-S-901 1

[Tunalover]

Does anyone have correlations that give G-levels produced by the hammer blow test from MIL-S-901?

Bruce aka Tunalover

 

[IRstuff]

They are darn high... ;-)

There's a Navy report by Clements that shows some notional levels. I don't recall if I have a copy or not, but if I do it's at home. My recollection is that the levels are in the 100-300 g range, but there will be attenuation from the surrogate ship structure that you have to mount the UUT to.

TTFN

FAQ731-376

 

[IRstuff]

I guess I should look in by cabinets first. The report is Shipboard Shock and Navy Devices for its Simulation by E.W. Clements, NRL Report 7396. The DTIC acession number is AD746444

Oh, easier than I thought it was:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD746444&Location=U2&doc=GetTRDoc.pdf

Great! I can now get rid of my hardcopy ;-)

TTFN

FAQ731-376

 

[IRstuff]

Some more:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD348861&Location=U2&doc=GetTRDoc.pdf

There's also a NAVSEA Carderock Powerpoint called Representative MIL-S-901D Floating Shock Platform Motions, but that's for the barge test...

Oh, actually, my recollection is that the Navy only accepts barge test quals, but it's been about 8 yrs since I've had anything to do with that.

TTFN

FAQ731-376

 

[capnk]

Clements gives values that are representative of the loading seen on the Medium Weight (MWSM) and Light Weight (LWSM) Machines.

They Navy does accept LWSM and MWSM testing, but it does depend on whether the item is a Princpal Unit or not.

 

[IRstuff]

In our last contract in 2003, we had a non-principal item and was told by our Lakehurst customer that we needed to do a barge test.

TTFN

FAQ731-376

 

[Tunalover]

Thanks for the replies guys!

capnk: where in his report does he give those values? I've looked through the report and brought out of it a whole lot of theory and conjecture but no solid figures!
Thanks in advance.


Bruce aka Tunalover

 

[IRstuff]

Isn't Figure 23 and onward in the NRL 7396 report supposedly actual values for the LW machine?

TTFN

FAQ731-376

 

[spongebob007]

The type of testing really has nothing to do with whether the UUT is considered a principal unit or not. The primary intent of MIL-S-901D testing is to simulate the actual shipboard enviroment the equipment will see. The choice of test type is dictated by several factors. Equipment weight is one consideration. Each shock machine has a combined weight limit for the test fixture and the item being tested. Once you get over 7400 pounds, you have no choice but to go to the barge. The large floating shock platform can handle a payload of up to 400,000 pounds. Another consideration in test types, is how the equipment is mounted aboard the ship. For items that will be attached directly to the hull (internal) or a bulkhead, the LWSM is typically used providing the combined equipment and fixture weight is under 550 pounds. The LWSM is basically for smaller hard mounted equipment.

The MWSM is used for hull and deck mounted equipment, providing the deck mounted equipment is hard mounted or has isolation mounts with less than three inches of deflection.

The class of ship also determines the test type to a degree. For equipment on surface ships such as carriers, the frequencies of the decks are often fairly low. In these cases, the contract may require that the equipment be tested on a barge. The deck frequency may also be specified based on the particular equipment installation. Equipment that uses shock mounts that have a defelction capability greater than three inches must be tested on the barge.

As far as acceleration levels go, the peak values are the highest on the LWSM and are the lowest on the barge test with low frequency decks. The MWSM can produce an input on the order of 100Gs or more.

My advice would be to contact one of the test labs and ask them for actual data.