lifting attachment

[PIETRO2002]

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

maybe do as sketch to post 32

 

[Fulvio Romano]

[...] 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?

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

maybe do as sketch to post 32

I have thought of a thousand things and the best solution is always and anyway make a threaded hole and put on a normalized gulf. Welding should always be avoided when you can.

This time you can't. The object is done so, I'm not putting it on the market. It is not even a machine within the meaning of 2006/42/ce, so the machine directive does not apply. is not a lifting accessory because it is not placed on the market separately. There is no obligation to certify welding. I simply asked for help in evaluating the mechanical resistance of the ring because different formulas and fem give strongly discordant results.

Now please can we return to structural aspects?

 

[MassiVonWeizen]

maybe do as sketch to post 32

Now please can we return to structural aspects?

I mean something like this.
e mi taccio

 

[PIETRO2002]

I have thought of a thousand things and the best solution is always and anyway make a threaded hole and put on a normalized gulf. Welding should always be avoided when you can.

This time you can't. The object is done so, I'm not putting it on the market. It is not even a machine within the meaning of 2006/42/ce, so the machine directive does not apply. is not a lifting accessory because it is not placed on the market separately. There is no obligation to certify welding. I simply asked for help in evaluating the mechanical resistance of the ring because different formulas and fem give strongly discordant results.

Now please can we return to structural aspects?

Sorry if I disturbed my speech, I just wanted to make a contribution and value to the discussion.

 

[PIETRO2002]

I have thought of a thousand things and the best solution is always and anyway make a threaded hole and put on a normalized gulf. Welding should always be avoided when you can.

This time you can't. The object is done so, I'm not putting it on the market. It is not even a machine within the meaning of 2006/42/ce, so the machine directive does not apply. is not a lifting accessory because it is not placed on the market separately. There is no obligation to certify welding. I simply asked for help in evaluating the mechanical resistance of the ring because different formulas and fem give strongly discordant results.

Now please can we return to structural aspects?

Welding is also part of the structural aspects!

 

[PIETRO2002]

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

is it not considered cutting stress at point a?

 

[PIETRO2002]

supposing to check the ring to a cutting stress, with a tau = 4 kg/mm^, on the section of 25 x 10 = 250 mm^ a force of 1000 kg could be applied, if you smooth the ring, see sketch, with 2 bevels 5 x 45°, the resistant section becomes 5 x 34 x 2 = 340 mm^, then the applicable force , 340 x 4 = 1360 kg

 

[Mattymecc]

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.

I did not understand this reasoning much, if it can help talking about plasticity I did a non-linear analysis with model of elastic-perfectly plastic material (s235). under some result of the last iteration that came to convergence:

Vertical shift:
plasticized regions:
the last iteration corresponds to a load of 18 kn = 1834 kg

 

[PIETRO2002]

I did not understand this reasoning much, if it can help talking about plasticity I did a non-linear analysis with model of elastic-perfectly plastic material (s235). under some result of the last iteration that came to convergence:

Vertical shift:
View attachment 71759plasticized regions:
View attachment 71760the last iteration corresponds to a load of 18 kn = 1834 kg

Why don't you ever refer to cutting efforts in your calculations?

 

[meccanicamg]

I did not understand this reasoning much, if it can help talking about plasticity I did a non-linear analysis with model of elastic-perfectly plastic material (s235). under some result of the last iteration that came to convergence:

Vertical shift:
View attachment 71759plasticized regions:
View attachment 71760the last iteration corresponds to a load of 18 kn = 1834 kg

in fact the load is going up.
seems better truthful.

 

[meccanicamg]

supposing to check the ring to a cutting stress, with a tau = 4 kg/mm^, on the section of 25 x 10 = 250 mm^ a force of 1000 kg could be applied, if you smooth the ring, see sketch, with 2 bevels 5 x 45°, the resistant section becomes 5 x 34 x 2 = 340 mm^, then the applicable force , 340 x 4 = 1360 kg

definitely at the base of the ring make two bevels and make welding full penetration allows to have a greater area to be subjected to traction and therefore avoids the detachment of the ring.

 

[Mattymecc]

Why don't you ever refer to cutting efforts in your calculations?

I have done nothing here... is the program that considers the complex of tensions that act at every point and establishes whether plasticization occurs or not... the second image represents the distribution of the equivalent tension of von mises.

 

[meccanicamg]

to have some time, you could look This is what explanation.

 

[meccanicamg]

that for us means to consider in general:and for traction/compression this:Will we be able to find the voltage according to the load?

 

[Fulvio Romano]

Why don't you ever refer to cutting efforts in your calculations?

because the cutting equivalent sigma is lower than the equivalent sigma from moment on. Moreover the maximum sigma from moment is on the surface, while the equivalent sigma from cutting is at the center of the section, so do not add up.
in the specific case the cutting sigma is equal to rad(3)*3/2* (f/a) and reaches the yield for a force of 3,500kg. should not be considered in hand calculations. the fem however considers it, but it is not among the maximum tensions.

 

[Fulvio Romano]

definitely at the base of the ring make two bevels and make welding full penetration allows to have a greater area to be subjected to traction and therefore avoids the detachment of the ring.

the bevels there are and the welding is full penetration. three overlapping cords were made.

 

[Fulvio Romano]

I did not understand this reasoning much, if it can help talking about plasticity I did a non-linear analysis with model of elastic-perfectly plastic material (s235). under some result of the last iteration that came to convergence:

se tu e @meccanicamg You don't get it, I have to be explained grossly and franticly. I try to explain myself better. we have a ring in carpentry and a normalized link. the two objects have mainly three differences: different material, different section, express load as wll = 1/2.5 times the yield. As geometries are analogous I tried to calculate three scale factors for the three conversions (the ratio between the yields of the two materials, the ratio between the inertia moments of the two sections and... 2.5) so that the product of the three factors gives me the factor of scale between the ring model and the model-link, thus putting them in the same conditions of material, section and test conditions.
the result is that the ring, under the same conditions as the link, should yield to 2270kg instead of 1200kg of the fem (two different models). the explanation is:

1. the fem is wrong for some inscrutable reason
2. the ring and the link differ for some additional aspect besides the three shaped by the scale factor.

assuming that it is true the 2 I launched in a couple of considerations knowing that the wll of the link is not calculated, but it is the result of a test on a real material. and the real materials, especially when laminated, have characteristics even much higher than the precautions of the tables (which typically refer to the fork between casting in source and continuous casting).
other hypothesis, but this easily verifiable to the fem, is that straight traits help the distribution of tensions.

under some result of the last iteration that came to convergence:

Vertical shift:

plasticized regions:

the last iteration corresponds to a load of 18 kn = 1834 kg

Can you help me understand better? 1834 kg if I admit some plasticization? But how much?
and how do I return to a s355jr? We're not on the line, so I can't make a relationship like done until now, right?

 

[PIETRO2002]

but at the end of the fair, what load can the ring bear? can keep on the machine, with what degree of safety?

 

[PIETRO2002]

to have a reference parameter, if it can be useful, I attach a page of a catalog.

 

[meccanicamg]

to have a reference parameter, if it can be useful, I attach a page of a catalog.

as geometry resembles what brings 8t.
steel 35crmo4 has rs≥835mpa and rm≥985mpa.
compared to a s235 has the ratio between the yielding loads of 3.5 times.
grill area is 2.2 times more than ring area.
8t divided 2,2 and divided 3.5 does 1040kg lifting.... always with factor not of 4 because the ratio rm/rs is different but we do that at least 2.5 there is it.
It will be an approximate account but I think it is more truthful than 800kg.

it is definitely different to evaluate the high hertz pressure that incrudes where there is the hook grafted in the ring compared to the bending and cutting tension of the round arc that you flet.
@fulvio Roman was the real lifting test made? What happened?

with the fem you need to simulate the contact area with the hook by delimiting the contact area. In this way intensifying the mesh we could be able to discriminate the compression of hertz which will also be 600mpa down there and the bending tension that will be lower than the break and will be close to the yielding.

Moreover the characteristics of the s235 should be understood because if it is cut from a sheet is one thing....if it was a diameter round 150 turned is like butter.