skjoex
Structural
- Jul 17, 2007
- 82
Hi
I need to verify a design of automobile lifting device (attached file 01.tif). I have never done such an analysis before and unfortunately I do not have any experience or someone to ask. So I ask YOU to help me with some guidelines.
As you can see there is a runner (diameter of roller bearings is 52mm, width is 18mm) able to move up and down inside of thin-walled beam (thickness of 5mm). Some questions:
1.: how to aplly loads ? First I applied loads in form of pressure on elements in contact region between rollers and wall of the beam. I guessed 18mm x 4mm for each roller as to be contact surface (results are shown on the rest of images)...then I realised that there is something like Hertz formula and this surfaces according to it have to be 18mm x 0.6mm only ! Which means incredible rise of local stresses in region.
2.: Type of analysis ? Since the beam is thin-walled I decided for geometrically and matierial non-linear solution with geometric imperfection included. First I performed linear analyse with prestress ON, then linear buckling analysis to get the first buckling shape and finally non-linear solution. I use shell181 with 8 plies.
Steel grade is S355 with yield stress 355MPa...I do not know what to do with these local stresses. Since they are so high I guess there still be a local plasticity through entire thickness of the plate even if I rise the thickness up to 10mm. Since there is movable runner I do not want to allow plasticity at all. I even do not know what to tell a customer. His design is totally wrong ? He is not going to be happy I guess...
Any help will be appreciated ! Possible advices how to impove the design of the beam itself as well !
With best regards
Lubo
PS.: sorry for my poor english.
I need to verify a design of automobile lifting device (attached file 01.tif). I have never done such an analysis before and unfortunately I do not have any experience or someone to ask. So I ask YOU to help me with some guidelines.
As you can see there is a runner (diameter of roller bearings is 52mm, width is 18mm) able to move up and down inside of thin-walled beam (thickness of 5mm). Some questions:
1.: how to aplly loads ? First I applied loads in form of pressure on elements in contact region between rollers and wall of the beam. I guessed 18mm x 4mm for each roller as to be contact surface (results are shown on the rest of images)...then I realised that there is something like Hertz formula and this surfaces according to it have to be 18mm x 0.6mm only ! Which means incredible rise of local stresses in region.
2.: Type of analysis ? Since the beam is thin-walled I decided for geometrically and matierial non-linear solution with geometric imperfection included. First I performed linear analyse with prestress ON, then linear buckling analysis to get the first buckling shape and finally non-linear solution. I use shell181 with 8 plies.
Steel grade is S355 with yield stress 355MPa...I do not know what to do with these local stresses. Since they are so high I guess there still be a local plasticity through entire thickness of the plate even if I rise the thickness up to 10mm. Since there is movable runner I do not want to allow plasticity at all. I even do not know what to tell a customer. His design is totally wrong ? He is not going to be happy I guess...
Any help will be appreciated ! Possible advices how to impove the design of the beam itself as well !
With best regards
Lubo
PS.: sorry for my poor english.