lifting attachment

[meccanicamg]

traction area if the ring was an oval (100-80)*25=500mm2.
♪
s=f/a from which f=s•a=137'500n≈13,7t
if you consider the formula of post 9.....f*=f/4,2=3,2t
Try to see the numbers again....I don't think I was wrong. . ..perme so calculated 3t raises.
weld must be certified. You still need a fem.

 

[Fulvio Romano]

traction area if the ring was an oval (100-80)*25=500mm2.
♪
s=f/a from which f=s•a=137'500n≈13,7t
if you consider the formula of post 9.....f*=f/4,2=3,2t
Try to see the numbers again....I don't think I was wrong. . ..perme so calculated 3t raises.
weld must be certified. You still need a fem.

Hello, thank you.
correct 13.7t to yield a s275. I have made the calculation on a s235 to admissible sigma with safety factor 5, here is that the 2800kg return. so we did the same calculation even if the results appear different.

what terrifies me is that the first method and the second method have a discard of an order of magnitude. and from the image below I fear that behavior is as follows:

if the ring is infinitely rigid, points b have a tensile stress and the calculation is the one done above. Okay.
if, however, the ring is deformable and under force in the point to be ovalized, and then b continues to have traction effort but which becomes negligible compared to the bending in point a.

 

[meccanicamg]

Hello, thank you.
correct 13.7t to yield a s275. I have made the calculation on a s235 to admissible sigma with safety factor 5, here is that the 2800kg return. so we did the same calculation even if the results appear different.

what terrifies me is that the first method and the second method have a discard of an order of magnitude. and from the image below I fear that behavior is as follows:

if the ring is infinitely rigid, points b have a tensile stress and the calculation is the one done above. Okay.
if, however, the ring is deformable and under force in the point to be ovalized, and then b continues to have traction effort but which becomes negligible compared to the bending in point a.

View attachment 71726

I think that's right. You should make two accounts to see the numbers or the fem what he tells us.

 

[Fulvio Romano]

the fem tells me it breaks right up there and breaks at 840 kg.

 

[meccanicamg]

the fem tells me it breaks right up there and breaks at 840 kg.
View attachment 71747

It seems to me a little low the load value that can bring the ring.
Did you fem with freecad? Linear analysis elastic or elasto nonlinear plastic?

 

[Fulvio Romano]

It seems to me a little low the load value that can bring the ring.
Did you fem with freecad? Linear analysis elastic or elasto nonlinear plastic?

Linear elastic analysis with freecad. 0.5mm arrow, I'd say it's there.
that is the force that brings the tension to that point at 235 mpa.
1200 for a 355 mpa.

 

[Mattymecc]

I made a two-dimensional model with trave type elements on strand 7, I bound the ring by imposing that the knots below, which are located along a 60° arc, do not transline or ruotine, for a force of 1 kn you have a voltage of von mises equal to about 30 mpa, therefore the maximum load that can hold a ring in s235 is pairs to 235/30 = 7,83 kn

I opted for a model with beam elements so that in the model the local effects due to force are not taken (the peak voltage that is seen in the models above).

 

[meccanicamg]

therefore according to two different methods of fem we still have that tensions are double compared to the theoretical formulas that are used on curved beams.
It would be interesting to understand why the theory does not follow the fem. Moreover it would be interesting to pull the ring strongly known and see what happens.

 

[meccanicamg]

you can think of making a comparison with the oval rings that sell. allego data sheet.
the smallest that could be our 1,6t port with ks=4 therefore 5,2t and the material g80 has a yield of 930mpa against our 235mpa ...ky=3,9 times less.
coarsely ks≈ky here must bring at least 1,6t.
I think the fem is not giving us the right values. should be compared with the model of a ring of these lifting to see if it provides us with similar values or if we have to think of doing a nonlinear analysis elasto plastic, with the assessment that the pressure of hertz may not be a problem.

 

[meccanicamg]

the area of the unregulated ring is 10x25 for two = 500mm2 while the smaller one at table is π•132/4 for two 265mm2 which is half of our ring....so also from this reasoning we see that the fem is not giving us just results. we have more area and can not bring so much less.

 

[Mattymecc]

therefore according to two different methods of fem we still have that tensions are double compared to the theoretical formulas that are used on curved beams.

The theoretical formulas you used above are referred to an "open chain link" not a ring, change the boundary conditions, this is a circular ring.

I think the fem is not giving us the right values. should be compared with the model of a ring of these lifting to see if it provides us with similar values or if we have to think of doing a nonlinear analysis elasto plastic, with the assessment that the pressure of hertz may not be a problem.

I find myself only partially in agreement, in the sense that in my opinion it is not wrong the result provided by the fem, we conducted two different analyses that lead practically to the same result: about 800 kg to yield the ring.
What if I consider an elastoplasty material?? ? this can lead to different conclusions, higher loads but also permanent deformations of the ring... I'll try. . .

 

[PIETRO2002]

Perhaps I go out the subject, you are rightly considering the resistance of the ring, but how do you consider the resistance of the welding? In theory the ring rests on the lower sheet only at one point, what resistant area will the welding have? Will it be at the discretion of what the welding will do? In these cases, isn't it better to make lifting ears like an attached sketch?

 

[Fulvio Romano]

Perhaps I go out the subject, you are rightly considering the resistance of the ring, but how do you consider the resistance of the welding? In theory the ring rests on the lower sheet only at one point, what resistant area will the welding have? Will it be at the discretion of what the welding will do? In these cases, isn't it better to make lifting ears like an attached sketch?

Yes, much better, but I'm checking a structure already realized, I'm not planning one.
welding is from both sides, z5 x 45mm long. resists more than the ring, even if it is counterintuitive.

 

[PIETRO2002]

Yes, much better, but I'm checking a structure already realized, I'm not planning one.
welding is from both sides, z5 x 45mm long. resists more than the ring, even if it is counterintuitive.

As a lifting organ, weld must also be certified, how will you indicate it on the design? As I can see, the strong aera will depend on the welder, which scares a little!

 

[Fulvio Romano]

the area of the unregulated ring is 10x25 for two = 500mm2 while the smaller one at table is π•132/4 for two 265mm2 which is half of our ring....so also from this reasoning we see that the fem is not giving us just results. we have more area and can not bring so much less.

you do not have to consider the area twice, but once the moment of inertia. the most stressed point is to bending, not to traction.

the difference of inertia between a rectangle 10x25 and a tondo d13 is 1,5. wll is the load that leaves a small (I don't remember how much) residual plastic deformation, we make it coincides with y for simplicity. the coefficient ks = 4 is also calculated on the break, not on the yield, so it does not have to do with the calculation that we are doing. to return to y we know that it is 2.5 times the kll reported.
If we go to report in a table the three differences with the various reports, the wll of the link to 1,600kg would coincide with the yielding of the ring to 2.270 kg. then a ton of difference compared to the fem.
Why?
in my opinion the fem says right, and the difference is given by the constructive methodology of the link that is improved in two respects:

1. is probably made of pierced steel and the relative door y closer to r than is found in the characteristics tables of steel
2. It's oval. Amplifying the movements in the fem is seen that the central part of the ring tends to crush, effect that worsens the bending in the upper point and that would be reduced by the straight traits of the oval.

Can you at least convince yourself?

 

[Fulvio Romano]

As a lifting organ, weld must also be certified, how will you indicate it on the design? As I can see, the strong aera will depend on the welder, which scares a little!

If we speak of legislation, it is not a lifting organ. is welded to the structure of the machine, it is part of it and is not removable. therefore does not go (obligatoryly) certified neither the object, nor the welding. Of course. @gerod It could detail the matter, but I'm pretty sure.

 

[gerod]

@fulvio RomanCall me and I answer (adr)!
Meanwhile it would be a lifting accessory, not an organ.
If someone sells it separately to the machine (I buy it from one who builds them - es gulfaro to weld that is marked c) then it must be marked according to the machine directive. If you do it with the car, then you don't need it. however, it is necessary to ensure the mechanical resistance of the object.
just to understand the thing, go see the guideline of the directive to the point where we talk about lifting accessories.

 

[PIETRO2002]

If we speak of legislation, it is not a lifting organ. is welded to the structure of the machine, it is part of it and is not removable. therefore does not go (obligatoryly) certified neither the object, nor the welding. Of course. @gerod It could detail the matter, but I'm pretty sure.

Maybe I'm wrong with the terms, it's not gonna be a lifting organ, but at that ring, you attack us a hook and pick up a machine. rightly you are assessing in detail the resistance of the ring, my observation goes on the welding part. Let us put the case, that the soldering does not hold and there is the accident, read all the newspapers, daily there are dead and wounded in the workplace, to whom do we put responsibility? to the welder who did not manage with the electrode to merge the material of the ring, side thickness 25 to understand, put the responsibility to the designer who made a madonarle error or to the engineer strutturista who validated the project? If I were to validate, I would categorically refuse to sign, I don't know you. At least, if you want to keep the solution with the ring, I would make a plan and run the 2 cyanphrines to accommodate the welding, at least this serves for a calculation and verification basis of the object.

 

[meccanicamg]

you do not have to consider the area twice, but once the moment of inertia. the most stressed point is to bending, not to traction.

the difference of inertia between a rectangle 10x25 and a tondo d13 is 1,5. wll is the load that leaves a small (I don't remember how much) residual plastic deformation, we make it coincides with y for simplicity. the coefficient ks = 4 is also calculated on the break, not on the yield, so it does not have to do with the calculation that we are doing. to return to y we know that it is 2.5 times the kll reported.
If we go to report in a table the three differences with the various reports, the wll of the link to 1,600kg would coincide with the yielding of the ring to 2.270 kg. then a ton of difference compared to the fem.
View attachment 71753Why?
in my opinion the fem says right, and the difference is given by the constructive methodology of the link that is improved in two respects:

1. is probably made of pierced steel and the relative door y closer to r than is found in the characteristics tables of steel
2. It's oval. Amplifying the movements in the fem is seen that the central part of the ring tends to crush, effect that worsens the bending in the upper point and that would be reduced by the straight traits of the oval.

Can you at least convince yourself?

if you look at the link has two thinnings in the vertical tract....which can certainly not increase the seal.
I read several times, but I lost. That's because you're saying we have a more ton of load... so your ring brings more than we've calculated.
the truth? When you raise, tell us what's going on.

 

[MassiVonWeizen]

you have thought to put two side handkerchiefs that help the ring not to ovalize and increase the welded area