calculation pressure clamping screws bracketing

[Micheletecnospazio]

Hello, everyone. My name is mychele mechanical engineering student. .
I would like to ask you this question. .
there is a way in addition to a finite element analysis to find also rightly with some approximation the tightening force of screws for the tightening on lathe in particular of pieces almost all or ring or cylindrical. . .
pallets have 8 possibilities for handling... Usually 4 external brackets not to fly the rotating piece and 4 internal reactions not to decentralize the blurred piece compared to the brackets of 45 degrees each... so to complete all 360 degrees. .

thanks in advance for your answers

 

[Micheletecnospazio]

I attach a scenario made quickly with nx.(I apologize for quality but I did not understand how to put attachments larger than 19 kb).. in which there are reactions but it will be enough to imagine alternate brackets... In this case you can notice that being the low piece i.e. a ring and not a cylinder in all bolts tightening you can overlook the stinging moment... the arm is too small compared to the diameter. .
Moreover for fatigue considerations I do not think it is useful to make a life safe design... bolts in any case are such as to "live" very long regardless of sinusoidal variations of normal stress cutting and stinging moment. . .

the design according to me therefore is to be made in a static way simply taking into consideration the most stressed part. . .
what is not clear to me though is that while the brackets close to the tool that works will be compressed the brackets on the opposite side will be woven... or vice versa depending on whether the tool in his work cuts particular superior or maybe does gorges or particular "singing" from below to above.. .
So this is my first doubt...

the second big doubt is : once calculated the bolt or set of more stressed bolts and then found the newtons to which they have to resist the tightening force will be equal to this... but how does it translate into tightening? I'll explain. How many laps do I screw the bolts? I must also keep in mind that the materials are normally sweet steels.. only sometimes inconell (which is harder) then excessive tightening pressure can create deformations. . until they are in roughing it is fine but in finishing no...
I hope I have made clear the picture

 

[numero1]

Can this help you?http://www.cad3d.it/forum1/showthread.php?t=22062And this too?http://www.cad3d.it/forum1/showthread.php?p=181817
ciao

 

[Micheletecnospazio]

Can this help you?http://www.cad3d.it/forum1/showthread.php?t=22062And this too?http://www.cad3d.it/forum1/showthread.php?p=181817
ciao

Thank you for your answer. .
So I read both the discussions. . .
interesting and partly similar to my problem which remains of greater complexity. . .
for example the tool cutter in which position creates greater reaction in bolts?
the tool moves externally and internally in the same operation so when working internal diameters creates a system of forces when working externally other
for example when working internal diameters the brackets depending on whether they are close or diametrically opposite are stressed once traction and once compression. . .
Anyway vabbè tomorrow step for the university also and I try to understand if it is possible to simulate the system with some programs... at least to understand what is the most stressed point and make an effective static sizing. .
I have already equipped with the one 10011 actually there are bolts that serve us (m16) and resistance class 8.8... and certainly from the embroidery tables that can withstand maximum effort. . .
the problem finally found the system of forces is to understand: is there a way to understand analytically at least approximate how many threads tighten to have tot tightening force? in fact the problem is not to understand if the bolts resist but to tell the operator how much I have to tighten them without using comparisons etc. to see if you squeal too much the piece and deforms etc... and to tighten the less stressed bolts with less vein because they definitely serve but are not fundamental. . then zero even diseconomies linked to losses of time and dangerous deformations to be resumed in subsequent operations

Ultimately thank you again for your answer and time dedicated to me but the problem is not yet solved... :smile: