Calculate buckling of a hydraulic cylinder
Calculate buckling of a hydraulic cylinder
(OP)
I am attempting to calculate the buckling strength of a hydraulic cylinder and have a question. My book shows that I should use the weakest moment of Inertia section bu8t it would seem that that would be inaccurate. The rod inertia is about 1/4 of the tube. So the question is, do I figure the cylinder as the full length being of the rod and pinned at both ends. Or do I just calculate the buckling strength of the rod and figure the tube end is fixed knowing that the tube is much stiffer than the rod? Or is there a better option. I plan to run a solid-doesn't-Works simulation as well, but I would like to make my mind work a little as well and compare.
Thanks
Jim
Thanks
Jim





RE: Calculate buckling of a hydraulic cylinder
The most dangerous point is the rod at maximum height from the cylinder, right?
Thus, you have a hollow cylinder (figure out the actual collapse strength of that cylinder as if it were a true hollow cylinder, not as if it were filled with a pressurized oil.)
Then, the rod is NOT fixed in the cylinder, but is a supported-but-collapsible-thin rod restrained only by the oil seal around the piston head and oil-filled opening in one end of the cylinder, and by the rod itself and its oil seal. So, it will act as a hinged thin rod about the oil seals - which are themselves NOT a rigid sliding structural device. They are mobile mechanical devices.
So your thin rod will most likely collapse at the middle of the total length - which, unfortunately, is also at the point of highest stress for an eccentric load and the lowest resistance to overturning and the point of maximum flexibility.
RE: Calculate buckling of a hydraulic cylinder
Go to page 16 of this link
http://www.boschrexroth-us.com/country_units/ameri...
RE: Calculate buckling of a hydraulic cylinder
RE: Calculate buckling of a hydraulic cylinder
https://exchange.dnv.com/publishing/downloadPDF.as...
The structural guy's at our work suggested buckling calcs were 'classically' performed by modelling the cylinder as a cylindrical rod, with the effective length being the distance between clevis pins (if the cylinder was clevis-pin mounted at each end, not sure how conservative the method is for trunnion mounts and other types).
That DNV link is a good method that I found to compare to other methods suggested and get a feel for the results, such as the Parker catalogue above.
RE: Calculate buckling of a hydraulic cylinder
RE: Calculate buckling of a hydraulic cylinder
RE: Calculate buckling of a hydraulic cylinder
`Roark's Formulas for Stress & Strain` has a formula for buckling which takes account of the cylinder and rod inertias.