mechanical principles question help

can anyone help me with this only question I have gotten stuck on all year.



A thick walled hydraulic cylinder is to be made of internal diameter of 80 mm and its function will be to lift a platform of mass 9000 kg. Determine the required wall thickness, if its cylinder’s wall steel chosen has a U.T.S. of 400 MN/m² and a factor of safety of 7∙5 to 1 is to be employed.


Also calculate the new internal diameter when pressurised, given that the steels Poisson’s ratio is quoted as n = 0∙35 and Young’s Modulus is E = 200 GN/m²

Don't know about the 2nd bit, I'm 1st year HND n haven't had strength of materials advanced yet. I think the wall thickness could be 12.2mm
Divide your UTS by 7.5 to get your max permissible. The force required to lift 9000kg is 88290N (m * g) From that the area of contact required can be calculated as 1.655x10^-3m^2
Cross sectional area is given by pi*(outside^2-inside^2)/4 transpose that and I got an outside diameter of 92mm. Subtract 80mm inside dia and you get your 12.2mm thickness.
Again, I'm just 1st year of HND so if I'm wrong I'm sorry but I think what I've done is good there.....

A thick walled hydraulic cylinder is to be made of internal diameter of 80 mm and its function will be to lift a platform of mass 9000 kg. Determine the required wall thickness, if its cylinder’s wall steel chosen has a U.T.S. of 400 MN/m² and a factor of safety of 7∙5 to 1 is to be employed.


Also calculate the new internal diameter when pressurised, given that the steels Poisson’s ratio is quoted as n = 0∙35 and Young’s Modulus is E = 200 GN/m²

You have started out on the right foot although to fully answer this question you'd need to use thick walled vessel theory. You'd need to calculate the required fluid pressure (which you are close to doing) to calculate the internal pressure, assume that the external pressure is zero, and work out how thick the wall needs to be to contain said pressure.

Ok well that's the extent of my strength of materials knowledge so far. Does the rest of that theory come with the advanced module?

I'm not sure how the HND is structured, but with the degree generally yes, it'll be taught after the more basic strength of materials stuff.

Thin walled vessels might be taught with the earlier strength of materials stuff, or it might wait until later alongside thick walled theory.

If you want to read more about thick walled theory, there are lots of links on the internet, but so far I like this one:

http://www.roymech.co.uk/Useful_Tables/Mechanics/Cylinders.html

and the site as a whole for mechanical engineering stuff. But it's best to understand thin walled theory first before moving onto thick walled, if you haven't already done that.

Actually as far as I know, none of the stuff we've done has been geared towards pressure vessels. It's been about cutting sheet metal, tensile loads in UJs and differences in length of components when under load. Simple stress and strain. There's another module of strength of materials, might be doing it after January, that'll probably where pressure vessels comes into it.
RGU in a year n a half I'm hoping!

At RGU you'll do pressure vessels in third year, both thin and thick walled, although not much on thin walled as it's overall much less complex.

Post your working so far, so we can offer assistance.

i have no current workings due to no clue about how to do the question. my tutor has not covered it yet set this task and we are told to get on with it am very lost on how to do it only question that has stumped me during this hnc