They are not lifed but should be getting inspected every 6 months life will be 20 -30 years

That's interesting, what do they use for inspection?

A visual check for cracks and deformation,no test kit like ultra sound or dye penetrant unless something is noticed if it looks bad the defective the section replaced.

Aw, I thought there was gonna be some fancy hardness/ageing analysis gear then we could use ourselves and get our alloy front and rear subframes back in from the MSA
I don't think they'll let us get by with an inspection from the Mk1 Eyeball 

As for general inspection its always a visual on everything, they only crack test if necessary or specified in an annual test or usage of. 

If it looks f...ed it probably is, if its had a knock or re formed it may need a NDT 

Doesn't help with fatigue though, 's why the MSA/FIA outlawed them, you can't tell visually how good they are for scrutineering.
  I was hoping you'd got some sort of hand held hardness/grain crack tester 

Pnillip you are to be disapointed the only tool used on aluminium alloys is an ultrasonic tester but They are better on the flat surfaces, on complex curve joint welds if they worked the scope display would be hards to interrogate I should think.

Yeah, they use US for scrutineering but just for wall thickness testing on flats and suspect bends.
Only thing I've ever used for assessing fatigue was an SEM but they're not exactly portable, but that was a while ago, maybe smaller now

When you make a roll cage / fabrication of any kind it goes through a test like what i do at work ( if specified by the manufacturer or being used in industry etc ). It is tested to what ever standards its give at that time or what ever the customer wishes. If it passes its good to go. Once passed off depending if its been given a time limit ( use by date ) or a time for inspection i.e 6 - 12 months or a regular inspection time of every time the object is used it is up to the individual to keep to these records. This is for health and safety and insurance purpose.

Like i said before if it been hit miss used etc it will have to go through the testing process again or scrapped. Thickness test etc is usually a given when testing and a written document on equipment and material used for the purpose of life the item will be used for or recommendation of testing there after. Unless its a compress cylinder that has liquid inside or similar that wears the inside of the equipment a thickness test is not necessary unless that object has been dragged or marked in any way and is less than the recommended build quality that item will be assessed there after . 

Yes, but if you're making aluminium roll cages it doesn't matter if it's been hit, misused, etc, etc - it will fatigue over time just sat there under it's own rate. It'll fatigue really fast with vibration from gun firing and an engine, you don't need to mistreat it.

I can only assume whatever you have cages on (what are they by the way?) must have them massively oversized not to have the lifecycled.

They are used on mobile gun platform vehicles.

I've done some work on Snatches and WMIK's before but they both had steel cages.

which helps to make wmik+ 4.5 tonnes gross which is a lot for a rover chassis base.

What cost is safety?

If your going to the effort of building s cage/rollover hoop then why not pay a bit extra to have the right materials?

Get on to your local metal stockist and ask for prices, many do pre fabricated bends to make life easier too just a case of weld together.

Make it look pretty by using some of the new powder coating processes