dimensioning problem. . .

[-Mc-]

Hello everyone!
I have a semlpic motlo problem to solve but that is putting in my head several doubts;

I have a 80mm diameter tree loaded with uniformly distributed load not fixed but on two constraints;
I have to find the load with which it breaks under bending (it breaks by cutting);
how would you proceed?
I used the various formulas on the manuals and continue to come out different results. . .
the maetrial is 39nicrmo (among other you what rupture load you use? );
Thank you so much!

p.s. hope not to be off topic.. .

 

[Fulvio Romano]

How do you say it breaks by cutting?

Maybe it's better if you put a pattern, but I'd swear otherwise.

However, the procedure is quite simple:

- evaluated if the de saint venant hypothesis is corrected (otherwise everything falls, this is the most trivial error you usually make)
- solve the elastic line, and find the most stressed cutting and bending sections
- solve with cauchy the bending, finding the main tensions
- solve with jourawsky the cut, finding the main tensions (if vale de saint venant at 99.99% the cut is negligible)
- calculations the equivalent sigma of von mises (if it is steel, otherwise use other constitutive links)
- evaluate the results

 

[meccanicamg]

without pattern you understand very little. how does a uniformly distributed load lie on two constraints? the bond is dotted, so it is a force.

Either way, you have to put constraints and calculate binding reactions. then draw the normal action diagrams, cutting, bending moment and twist. identify the most stressed section and analyze the state of effort with von mises or equivalent method.

evaluate the admissible or comparison emission and compare it to the maximum actual voltage value.

Moreover it is difficult to check if the stress has dynamic components, that is if it is a static load does not serve, if the shaft rotates and the stresses are rotating or alternating you will have the fatigue.

attention: fatigue stresses can lead to a strong and premature death of the piece