Hi
I see the formula function in the RMB drop down from Solutions in the tree; please give me a hint on how to translate orthogonal stresses into cylindrical stresses.
I've searched around for a means to create a new coordinate system (rect or cyl), is this possible? Can solver results be translated to a cylindrical system that is not at the global origin, i.e. offset, if there were several cylindrical features for which cylindrical results were of interest?
Tim
Comments
I have experience with TRANSFORM, but not paired with the NODAL FILE / LOCAL.
Regards
Thank you for your suggestion; I was working directly in Mecway but yes see that I could work in CCX and certainly view the results in CGX. I should try to read the .frd with cylindrical results (using *TRANSFORM) back into Mecway.
I'm keen to explore the post-processing, between coordinate systems, within Mecway.
Regards, Tim
What is the reason to choose that kind of results?
I'm looking at a ring beam so the stresses of interest are on planes that run radially from the axis that passes through the ring centre and is normal to the plane of the ring. I have calculated the transverse shear force, bending moment and twisting moment within the ring (annular) beam, that is supported in 6 places, equi-spaced; loading is a constant line load around the ring centreline. The direct and shear stresses calculated are in the radial plane (that is also perpendicular to the tangent of the circular centreline of the ring beam). I would like to reconcile these hand calculations with the FEA testcase before moving on to a more complex geometry. The hand calculation is important in sizing of the ring beam cross-section (a more desirable situation than adjusting the FEA cross-section multiple times in the search for a near optimal design).
Tim
The formula for rotating the stress tensor is well documented, such as:
http://www2.mae.ufl.edu/haftka/adv-elast/lectures/Section2-4.pdf
http://web.mit.edu/course/3/3.11/www/modules/trans.pdf
Thank you for the stress tensor links.
The radial component is defined as (x*u.x + y*u.y) / sqrt(x^2+y^2) in the manual. My poor transformation skill leads to ur = (u.x^2+u.y^2)^0.5 but this losses the sign (sense) of the displacement whereas your transformation succeeds.
What is the corresponding transformation for the theta component of displacement?
(it's not atan(u.y/u.x))
Can the option of a cylindrical coordinate system be considered as an enhancement?
An arbitrary coordinate system in space may not be necessary but a cylindrical coordinate system positioned at the origin would perhaps be in keeping with the Mecway workflow.
An alternative enhancement would be include the solution results derived in the cylindrical coordinate system. This avoids dealing with BCs and loading on a cylindrical basis, only post-processing.
Tim
I would imagine you can do the same for the tangential component - dot product of displacement with the unit tangential vector (r^ cross z^ ?), or start from the rotation matrix formula and expand it into scalar terms.
Cylindrical coordinates come up form time to time, which was part of the intention behind the formula tool, but it's not very convenient still being limited to scalars. I may have to add a special cylindrical stress option.
stress_rr = ( x^2*s.xx + 2*x*y*s.xy + y^2*s.yy ) / ( x^2+y^2 )
stress_tt = ( y^2*s.xx - 2*x*y*s.xy + x^2*s.yy ) / ( x^2+y^2 )
Attached is an example of a uniform ring with hoop stress. You can see the formulas match the XX and YY components at locations where they are X and Y axes are aligned with the radial and tangential axes.
I still have to do more thorough validation, then I'll include the formulas in the manual.
Thanks much for including the two pdf files above. I have some studying to do....
What program do I need to open the .liml file you posted on March12, above?
Thanks for you efforts.