structure dimension
structure dimension
(OP)
could some one tell me how to work out the minimum wall thickness that can be used without causing any deformation. please refer to the file attached for furthur info.
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RE: structure dimension
RE: structure dimension
RE: structure dimension
When you talk about deformation, are you talking about permanent deformation? Or are you looking for something that doesn't deflect at all? (If so, then you you should use a tempered alloy that was quenched in unicorn tinkle.)
Without looking at your model, you probably need to look at h
I assume you have some sort of tube (rectangular, round or square) that is holding *something* and you need to know how thick to make the wall. If that's the case, then you really need to contact someone in your organization that is capable of doing this. Even consider an outside consultant. Nothing wrong with asking, but I think you will find a lot of people responding to your post with the very wise advice of seeking professional help on this one. My big concern for this is that you're talking about a manipulator which can/may(?) impose some very serious dynamic loads on whatever type of base that you're trying to design. Merely taking into account weights and offset loads can end up killing people. That means YOU go to jail.
As I said, I didn't look at your file, but I think you are in over your head. Get someone to help you on this.
Engineering is not the science behind building. It is the science behind not building.
RE: structure dimension
ISZ
RE: structure dimension
i have included a jpeg file with this so you can have a look at it. what i need to find is permanent deformation and the fixture will only have 200 kg resting on top of it in any case. thanx again for your time
RE: structure dimension
In the detail you show there, it appears that the upper horizontal member is butted up against the two vertical members and furthermore, the two vertical members extend higher than the horizontal support.
Because of this, you do not have an adequate moment connection between the members. If you assumed this as having restrained ends, you would get a certain amount of fixity between the two parts, but in reality, the vertical member would "oilcan" *out* at the upper weld and *in* at the lower weld of the connection of the horizontal support. So, unless you change that portion of the detail, you should probably calculate it as a simply supported beam with a load in the center.
What kind of steel are you making this out of? If it is 40mm sq tubing, then you're probably building this in Europe. If that's the case, then assume a simply supported beam, add any torsion due to offset of load, determine your required section modulus (including the correct safety factor) and find your corresponding tube size from the tables here:
http://
The tubes you can obtain most easily in western Europe should conform to EN 10210:S355.
Engineering is not the science behind building. It is the science behind not building.
RE: structure dimension
RE: structure dimension
After you get the wall thickness, you can use beam formula to calculate displacement under the force. You can get all formula from an engineering handbook, or from the web.
RE: structure dimension
Are you intending to make the whole frame out of plate and fabricate box sections?
How do you attach your device to the structure assuming its all fabricated box section?
I would suggest if you want to fabricate sections then fabricate small "I" beams see attached sketch.
Analyse as a simple beam and you can take proportions of plate thickness for flanges and webs from standard beam sections found at this site:-
h
also you can calculate the stresses from the beam theory from the same site but a different link:-
h
Your going to have to guess a size for your "I" beam in terms of depth and width and run some calculations, if it doesn't work try again with a different section.
I suppose one difficulty might be the 40mm width unless you can change it.
RE: structure dimension
desertfox, there will be no welding on this. What you see in the .jpg is just a single piece of 40mm plate, cut out on a cnc. The term "wall thickness" should actually be "member depth."
ash1982, I would suggest you look around a parking lot at the rear bumpers of a lot of larger vehicles. You will see 50mm x 50mm square tube being used as the structural member of receiver hitches. I have attached a picture. It's the part in black.
Look at that picture, remember that these items are designed to pull 5000 pounds and handle heavy acceleration, braking, potholes, overloaded trailer tongue weights and severe abuse by a generally uninformed public and still hold up. This is a 50mm x 50mm section that is hollow in the middle. Take that for what it is -- an observation -- and try to extrapolate it into your application.
Beyond that, I don't think I can help.
Engineering is not the science behind building. It is the science behind not building.
RE: structure dimension
Is this just a frame (base) to hold single column manipulator?
If not the above and just looking at initial and subsequent sketches, I think the use of the phrase welding manipulator is misapplied as the frame depicted would be more suitable for a welding positioner. All welding manipulators that I'm acquainted with are composed of single column with a radial arm or gantry to carry the welding head. If this is indeed for a positioner the loadings would be very high and complex.
Welding manipulators>
http://w
RE: structure dimension
RE: structure dimension
dhenger i'm not looking for a structure that does not deflect when loaded, i'm looking for a mimiumum structure that can take the vertical load without any permenant deformation (Plasticity) thanx for you concern anyway.
RE: structure dimension
It would help if you can tell us exactly what this frame is going to have attached to it.
A 40mm wide structure as we see it doesn't look very stable on its own.
Can you tell us how the frame will be held vertical and why its only 40mm wide, also how do you intend to fasten anything to it.
We are trying to point you in the right direction is there anyone you work with that could help you also?
desertfox
RE: structure dimension
RE: structure dimension
Thanks for the pic it does help but how is the frame attached to the other parts ie bolted, welded?
Also the geen coloured structure that rests on the frames are the attached in anyway and are they running at the centre of the frame or to either side of centre.
desertfox
RE: structure dimension
RE: structure dimension
Think about this for a second: when you stand on a diving board, the support next to the pool is in compression and the support farthest from the pool is in tension. Apply that to your model: one of your supports is likely to be loaded to well over 400kg and the other one will probably be in tension. You need to figure out the center of gravity of your boom and apply that information to your structure.
Furthermore, it appears that a portion of the assembly rotates. Is that correct? Does it rotate about the axis of the centers of the two supports? This fact makes it much more complicated than you first stated. What happens when you turn the boom through a few degrees and the loading is now bending your "vertical" members? Are you sure that the base is fixed to the ground well enough to prevent overturning of the entire assembly?
You ABSOLUTELY MUST call an outside consultant.
Engineering is not the science behind building. It is the science behind not building.
RE: structure dimension
RE: structure dimension
Assume a simply support beam loaded on mid-span with a concentrate load:
L = beam length between center of verticals (say 300 mm)
P = applied load (200 kg + assumed/estimated beam weight)
b = frame/member width (40 mm)
h = member depth to be determined
va = allowable shear stress (0.4*fy, fy = yield strength, mpa)
fa = allowable flexural stress (0.6*fy)
From above we derive two relationships:
P <= 2*va*b*h
--> h >= P/(2*b*va) (1)
M = P*L/4
S = section modulus = b*h^2/6
M <= fa*S
--> h >= [6*M/(fa*b)]^0.5 (2)
The larger h from above satisfys strength requirement. Now check performance of service:
D = deflection
E = modulus of elasticity
I = moment of inertia (b*h^3/12)
D (max) = P*L^3/(48*E*I), at center of the beam
Select a bigger size beam if deflection is too large, and repeat the steps. The result would be conservative for a statically loaded beam.
You may wish to check the vertical members:
1. Assume column simply supported on both ends, k=1.
2. Find allowable stress for respective k*L/r
L = column length
r = radius of gyration (of the weak axis)
3. Check compression stress (P/(2*b*h)) against the allowable. Repeat steps 2 & 3 if necessary.
Finally, check the bottom beam use the same approach as for the top beam. However, P = 200 kg + weight of all 4 members. So the bottom member shall be bigger than the top as the result.
Check my formulations for correctness. Good luck.
RE: structure dimension
I have uploaded a file which gives a formula for the depth of the top member making the assumption that the top member is a simply supported beam in truth of course its far from it but it might get you started.
I got the formula by manipulating the standard bending stress formula ie
σ= M*y/(I) I= b*d^3/12
y = d/2
where b= beam width 40mm
M= bending moment
I = second moment of area
You need to check the vertical legs as suggested cntw1953.
Also if your profiling this plate I would put large radius on all the internal edges, square corners as you have them in your model will give rise to large stress concentrations which might cause you problems.
Seriously you need to get some help from someone your working with as we cannot see or know all the issues.
Personally I would do some ballpark calculations and ask the stress guys to model it to finalise the design.
RE: structure dimension
Is there going to be any rotation of the manipulator once the boom is placed inside it?
RE: structure dimension
"I came, I saw, I made it better."
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RE: structure dimension
1. You need to come up with a free-body-diagram to solve for the weight distribution (which will include finding the CG). If parts can move, you may have to consider several different orientations. You may also need to think about other possible loads on your parts.
2. Determine exactly what material you will be using and what it's properties and capabilities are - then knock the capabilities down at least by half (you should probably have an even larger factor of safety for something like this - it looks like something that might end up being beat to crud)
3. Once you know the weight distribution and the material specifications, you'll have to look at buckling and yielding in your structure for your worst case load condition. If there's any question about which case is the worst case, you should calculate it for all the cases that look like they might be the worst. Pay special attention to stress concentrations in areas such as holes, fillets, and larges changes in net section. Welds are an area of special concern because the material properties of a weld are often lower than that of the parent material. In addition, welds are often at the same locations as stress concentrations. Check literature for information on analyzing weld joints (Shigley's Mechanical Engineering Design is good for basic analyses)
4. You'll have to determine what an acceptable deflection for your part is and make sure the cross section of your supports. You should calculate the deflection your parts under worst case loading. If there's any question about what is the worst case, calculate all cases in question.
5. If your structure fails to meet your requirements in any of the calculations you performed, change your geometry (or material) and iterate until you have a design that works.
If you don't have experience with the types of analysis that I mentioned above, you may need to go get outside help. It looks like you're dealing with some pretty heavy parts, and that a failure could end up hurting someone. You could always try your own hand at an analysis, then hire a consultant to check your work.
RE: structure dimension
RE: structure dimension
can you solve the reactions of a beam ? that's what the green arm looks like to me. if you can, consider the two extremes on position of the arm. this will give you the load into the grey frames (that you're designing). hint, if someelse is designing the green arm, you could ask for their reactions.)
once you've got the load applied, the frame divides into beams and columns; each can be analyzed in turn.
point to ponder ... consider lateral load, what looks to be your x-direction, along the green arm ... the grey supports are not very effective in this direction.
each of your frames will be supporting something like 200 kg (mass, i assume) = 2000N ... not a heck of a lot. what safety factor will you apply ? 2?, 4??
btw ... rant removed ('cause i couldn't be bothered to type it a 2nd time)
RE: structure dimension
I agree with EngineerTex. If you have to ask questions like this, you should not be doing the job. Even if we do provide useful help on your wall thickness, that is not the only thing that might cause a catastrophic failure.
Even if people are not hurt, you could still be producing something that will not work. Your company will be embarrassed. You will be embarrassed. Your customer will be pissed off.