Off-road Truck Transport Vibration PSD

[Christo_AU]

Hi All

I am designing a modified shipping container to be transported by truck on both asphalt and dirt roads. This is a defence job, so the design loads are typically obtained from MIL-STD-810.

However, the off-road truck transport vibration PSD from 810 seems extremely conservative (Table 514.8C-VII Category 4 Composite wheeled vehicle vibration exposure). I did some research into how this PSD was compiled, and it does indeed appear to be conservative and based on older trucks (1980's).

Can anyone please recommend an off-road truck transport vibration PSD for fatigue design purposes? This does not have to be defence related, civilian spec is fine.

And also an on-road PSD please?

PS: I know 810 always suggests the use of measured data over the loads in 810. Although I do have some measured data, it's specific to a single truck on a single, high quality, unpaved road.

 

[btrueblood]

"This is a defence job, so the design loads are typically obtained from MIL-STD-810."

Pretty much a full stop, right there. If your container is going to be moved by NATO armed forces personnel and equipment, then you are pretty much going to qual test using the 810 standard.

"I did some research into how this PSD was compiled, and it does indeed appear to be conservative and based on older trucks (1980's)."

I'm not sure there has been that much advancement in shock absorbers and tires, much less road grading and maintenance, to say that the Mil Spec is somehow conservative or obsolete. You might be able to research newer armed forces vehicle developement reports to see if newer equipment somehow delivers smoother rides.

 

[Christo_AU]

Hi btrueblood

Thank you for the feedback. I obviously can't disclose any details, but we do have some freedom with the design loads as this will only be transported by commercial semi-trailers on asphalt and reasonably well maintained dirt roads. We also aren't bound to 810 in the requirements.

I do take your point regarding shock absorbers and tires.

However, I do believe that the composite wheel envelope in 810 is conservative. An article published by the US Army Aberdeen Test Centre where the composite wheeled vibration envelope was developed, explicitly states this. Unfortunately this article has to be bought online else I would share it.

https://meridian.allenpress.com/jie...e-Origin-of-the-Composite-Wheeled-Vehicle-Two

Essentially they measured vibration from many military trucks and trailers, combined into a worst case envelope, and multiplied this by 2 "for conservatism". The tracks used were also pretty severe, used to represent military activity in undeveloped countries.

810 does state that actual measured data can be used. I do have some measured data of a container on a military truck driving on dirt roads. The acceleration RMS is almost 8 times less compared to composite wheeled. However, I think this PSD is underestimated, hence this post. If you do have any vibration PSD's of trucks on dirt roads, I will greatly appreciate it if you could share? (civilian or military is fine)

 

[CWB1]

I would reach out to the heavy equipment manufacturers ie Cat, Cummins, GE, etc. They should be able to provide design guides that include this data for packaging their engines/pumps/generators/etc.

Not sure what they'll provide foreigners, but stateside you might also reach out to TACOM to see if they have any updated guidance. Commercial vehicle tires and suspension systems have come a long way in the past 40 years.

 

[rb1957]

what does your contract say ?

what if the customer says (in a design review) "I thought you'd be using 810" ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[IRstuff]

There are some severe test conditions, such as Perryman, Churchville, washboard, etc. Maybe contact

https://natc-ht.com/about-us/test-courses/

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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http://www.eng-tips.com/forumlist.cfm

 

[Christo_AU]

Hi All

Thank you for all the feedback, much appreciated.

I found the following standards relating to commercial truck/semi-trailer transport. This is only for on-road transport. Might help someone in future.
ISO 13355 (in the latest edition theres 3 PSD's from different countries)
ASTM D4169-16 & D4728-06 (doesn't indicate travel distance associated with test)

Regards