multiaxial fatigue (shaft)

[Domenico Garofalo]

hi guys ...to study the cases of multiaxial fatigue (proportional and not proportional) related to a tree. I don't understand the difference between these two cases, maybe it's my book that sucks slightly.
As I have understood, the proportional case is given when the mom flett is constant, so they will be born in the tree 2 sigma1 and sigma2 proportional tensions between them. In the nonproportional case I also have taw(strength due to the torque moment) not proportional to the 2 tensions sigma1 sigma2. tell me if it's so kindly (I'll attach photos of the topic)

 

[Stan9411]

5 years of mechanical engineering and this definition never heard. or is new or is too old. First of all, if I have a flender moment, I will have a single sigma. I don't see why there should be more than one. the two proportional sigma (one double of the other) are due to the internal pressure to the tube in the figure. are mariot sigma, axial and circumferential, the first half of the second

 

[Stan9411]

the fact that the torque is alternating or constant has nothing to do with the aforementioned sigma. if it is constant does not have an alternating component so it has no effect on fatigue. if it is alternating you will combine it somehow with other components of effort (gough-pollard crackers, sines) and you get an equivalent effort to compare with the fatigue limit or to insert in the woeller curve

 

[meccanicamg]

What's written on your book is a little ambiguous. on the tube that is symmetric does not serve all those menades.
normally you can look for more or other things and using a woheler diagram consider the cumulative damage of the various stresses.
that a pressure tube has tensions as an attachment. then if you add torsion or bending there are definitely additional tensions you need to consider.
then with sinesis you do the test with difficulty identifying the plan where the stresses that compose are maximum. clearly if the actions and therefore the tensions are constant is one thing, if they are buttons or rotating is quite different.

 

[meccanicamg]

I am also looking at various books, but we always talk about circles of more 2d and 3d and equation 3d with ratings of mono or multiaxial states as attached