Geometrical-Physical-Mechanical-Challenge

[vlehner]

Hi!

I have a solving problem with the numerical solver.

As you can see in the sketch, i have a heavy tube which is held with two steel-strings. The fixing point of the tube is not in the middle.

Now I'm searching for the forces, angles, and the length change of the strings accounting the hooke's Law, the geometrical relations and static equilibrium.

So far, so good.

When changing the guess-values of the angles i get different results, what should not be.

What is going wrong here?

Any help is appreciated.

Thank you, best regards, Volker

I'm working with MP4.

[-MFra-]

Hi Volker!

with dimensionless variables, mathcad 15 gives the results.

[vlehner]

Hi!

Thank you, but there is the same problem in MC15 like i have in MP4.

Changing the Guess-Values lead to different results.

See attachement please.

[Fred_Kohlhepp · Accepted solution]

Reformulate your solve block, tighten your initial guesses

[vlehner]

Thanks Fred.

I arranged it again, added some equations and i got stable results for a maximum allowed tensile stress of 100N/mm².

(The wires may not have more than 100N/mm² because of security-factor-Prescribed maximum tensile stress)

You hit the nails head with a biiiiiiig Hammer!!!

[vlehner]

Maybe there is a solution with the energy-method for mechanical stress situations.

Has anybody solved something like that with this method?

Maybe we have to add (replace) an equation with an equation based on this method.

[-MFra-]

Hi Volker,

I see you asked me what my nickname, but I no longer find where it is written.

We do not use nicknames.

I would like to know how is born this question in  your mind.

These (nicknames) are things that are used among mafiosi or delinquents or for animals.

I've been always a very strict dr. engineer and teacher, and since, in this case, it may happen some pupils poorly educated and not very, or not at all, respectful, just me I suppose, I have given rise to the emergence of various nicknames.  With all the respect I have for you and all the community members, I would like to say, about nicknames,  that "When you put your feet in the "-s-h-i-t-" (sometimes, to live, it can happen ...),  something stays attached to you. There you can find it."

[vlehner]

Hi F.M,

The only reason for my question is, that the abbreviation "F.M" looked a bit strange for me. Nothing special.

For your reasons to use it, it's ok and i can understand it now.

Best, Volker

[-MFra-]

F. M. are the initials of my first and last name (abbreviation). I do not consider it a nickname.