Trouble calculating deflection of a 80x80mm T-Slot

[triumph406]

You are a bit late to the party, this whole exercise was to inform the builders or users of aluminum extrusion, that they have a choice of what grade of aluminum to buy, 6061 T6 or 6063 T5, it would be very hard to find 6063 T6, I would suggest that you get the 2 extrusions of the 2 grades and have it tested

And if the x-section is identical in I (second moment of area) you'll get the same deflection,regardless of aluminum or temper upto yield, it's not any harder than that to understand.

[plasmamatt]

I would have to agree with Triumph406 on this one. The engineering formulas are tried and true. The deflection formula only takes cross section and Young's Modulus into consideration. Knowing that the Young's Modulus is the same for both grades of aluminum would indicate that the deflection is the same. The only way to reduce the deflection would be to go to a larger cross section or completely different material. The yield strength is going to be higher on certain grades of aluminum but that only determines at what point the material will start to permanently deform. On an FEA analysis the higher grade of aluminum will show up as having less stress but stress and deflection are two totally different things.

[mactec54]

And if the x-section is identical in I (second moment of area) you'll get the same deflection,regardless of aluminum or temper upto yield, it's not any harder than that to understand.

All I asked you to do is do a Lab test, regardless of the Tec formula's, there is quite a difference in the deflection result, this being also that the 2 Grades do not have the same E value, if you want to nit pick, and be be technically correct there is ( 1 ) point difference between the ( 2 ) Grades

[mactec54]

I would have to agree with Triumph406 on this one. The engineering formulas are tried and true. The deflection formula only takes cross section and Young's Modulus into consideration. Knowing that the Young's Modulus is the same for both grades of aluminum would indicate that the deflection is the same. The only way to reduce the deflection would be to go to a larger cross section or completely different material. The yield strength is going to be higher on certain grades of aluminum but that only determines at what point the material will start to permanently deform. On an FEA analysis the higher grade of aluminum will show up as having less stress but stress and deflection are two totally different things.

The Young's Modulus is not the same for the 2 different Grades, so there is going to be a different result, most charts and specs, just round the numbers off, that Trumph406 is quoting, if one wants to quote things with accurate results, you need to use the correct numbers for the material you want to test, the composition of the 2 materials is also quite different

[triumph406]

All I asked you to do is do a Lab test,

You ask for a lab test. Do you even know what to “test” for, or how to do it?

Do you realise you could do your own test by either putting a beam across 2 supports, putting a DTI in the middle, and then putting a load on the beam and measuring the deflection?

Or clamping an overhanging beam to a table, again putting a DTI on the end, and then hanging a weight off the end.

And if your really interested you can determine E (young’s modulus) from this test.
We have the equation

Y = (P * l^3) / (48 * E * I)

So if you hang a weight P
Determine the deflection Y
Know the I
You can calculate the E

E = (P * L^3)/ (Y *48 * I)

regardless of the Tec formula's, there is quite a difference in the deflection result, this being also that the 2 Grades do not have the same E value, if you want to nit pick, and be be technically correct there is ( 1 ) point difference between the ( 2 ) Grades

You need to let this one go and admit you don’t know what your doing or talking about!!

Can you give sources that give different E values for 6063/6061 etc? If there are differences, they will be very small, and insignificant. (except to you)

You say

regardless of the Tec formula's

What does that mean? The formulas are wrong? Merely there for guidance? A good start? Or inconvenient for the Mactec54 narrative?

Read some Engineering books (Roarks/Shigleys/Marks etc) learn some engineering, then use it to help rather than mislead.

Buy some pieces of 6061/2024/7075 from Mcmaster, it could be ¼” sq, 12” long.
Have 10” hanging off a table, put a notch at the end to hook a cable over that is the same distance from the edge of the table, put a DTI at the end, hang a weight,and measure the deflection. If each sample has the same height/width you’ll see the same deflection. Smaill differences in I (2nd moment of area) will account for differences in deflection.
I = (bd^3) /12
Where b = width, d= height.

[triumph406]

On an FEA analysis the higher grade of aluminum will show up as having less stress but stress and deflection are two totally different things.

If you have the same x-section properties (I and c), the same loading (moment) the deflection will be the same, therefore the stress will be the same, regardless of the aluminum alloy.

Stress and deflection will go hand in hand. If you double the load, you will double the deflection, and double the stress.

The equation for stress is

Fb = Mc/I

Fb = bending stress.
M = moment
c = distance to neutral axis
I = 2nd moment of area.

If you have a beam/shape of Aluminum/Steel/Stainless, and each material has the same I andc, for the same moment M the stress will be the same. The difference is that the deflection of Aluminum will be approx 3x that of steel/stainless, as the E of steel/stainless is approx 3x higher.

You want to be carefull with FEA, it's easy to get misleading results. for the work I do if you do FEA you also have to do some hand calcs to back up the FEA results.

[mactec54]

You ask for a lab test. Do you even know what to “test” for, or how to do it?

Do you realise you could do your own test by either putting a beam across 2 supports, putting a DTI in the middle, and then putting a load on the beam and measuring the deflection?

Or clamping an overhanging beam to a table, again putting a DTI on the end, and then hanging a weight off the end.

You need to let this one go and admit you don’t know what your doing or talking about!!

Can you give sources that give different E values for 6063/6061 etc? If there are differences, they will be very small, and insignificant. (except to you) .

Yes you can test it with a DTI as most do if they have, or want to

Source NIST Standards Material Measurement Laboratory

Insignificant I don't think so, there are many different grades with in the same series of aluminum that have a slightly different E value

6063 68 Gpa 9.9x10^6 PSI

6061 69 Gpa 10x10^6 PSI

For those that are reading this and want to try to understand what Young's E modulus is all about

Young’s modulus is a measure of the stiffness or rigidity of a material. It only applies to small amounts of elongation or compression which are reversible and do not cause permanent deformation when the exterior applied force is removed. It provides a direct indication of the extent of the distortion that can be expected for a given (small) load. A stiff material has a high Young's modulus and changes its shape only slightly under elastic loads, A flexible material has a low Young's modulus and changes its shape considerably (e.g. rubbers), Without this quantity, comparing the rigidity of any two materials is difficult.

[triumph406]

Insignificant I don't think so, there are many different grades with in the same series of aluminum that have a slightly different E value

6063 68 Gpa 9.9x10^6 PSI
6061 69 Gpa 10x10^6 PSI
.

I don’t know where you sourced that information from, but lets says it’s accurate do you know what that means? There’s 1% difference between the 2 values!

So if 6063 deflects .100” all things being equal 6061 will deflect .099”.

That isn’t a significant difference.

For those that are reading this and want to try to understand what Young's E modulus is all about

Young’s modulus is a measure of the stiffness or rigidity of a material. It only applies to small amounts of elongation or compression which are reversible and do not cause permanent deformation when the exterior applied force is removed. It provides a direct indication of the extent of the distortion that can be expected for a given (small) load. A stiff material has a high Young's modulus and changes its shape only slightly under elastic loads, A flexible material has a low Young's modulus and changes its shape considerably (e.g. rubbers), Without this quantity, comparing the rigidity of any two materials is difficult.

Have you accepted that yield strength has nothing to do with deflection?

[mactec54]

I don’t know where you sourced that information from, but lets says it’s accurate do you know what that means? There’s 1% difference between the 2 values!

So if 6063 deflects .100” all things being equal 6061 will deflect .099”.

That isn’t a significant difference.



Have you accepted that yield strength has nothing to do with deflection?

Young’s modulus is a measure of the stiffness or rigidity of a material.

Read the post I stated where I sourced the information from and have another source to back that up as well

[triumph406]

Young’s modulus is a measure of the stiffness or rigidity of a material.

Read the post I stated where I sourced the information from and have another source to back that up as well

So is 1% difference between 2 values of E significant to your designs? (Assuming there is 1% difference)

If one material would deflect .100", the other .099", tell me how is that significant? It isn't.

[plasmamatt]

If you have the same x-section properties (I and c), the same loading (moment) the deflection will be the same, therefore the stress will be the same, regardless of the aluminum alloy.

100% agree. I said it wrong and didn't catch it until I hit submit. What I meant to say is that in an FEA analysis it will show that the higher grade of aluminum can handle a higher load because of it's higher yield strength. With that said though if all things are equal both grades of aluminum are going to have the same deflection.

I would also agree that care should be used with the use of FEA. It can be potentially dangerous in certain designs. A hand calculation is always the best way to double check things. I have my mechanical engineering degree and actually had a course in FEA about 20 years ago. My professor used the space shuttle Challenger as an example of were FEA was not used properly. One of our design projects was to determine where the mistakes were made and redesign the o-ring location on the booster rockets. I talk to so many "I learned it on the job engineers" using FEA but they don't have any formal education to really understand it.

[triumph406]

I agree, someone as troubled as this gets me responding to how they are posting

You are correct we are talking about the same thing different terms, but some can never accept that, it has to be there way of thinking or it is trash

OK, so at what point do you admit you were wrong?

[wendtmk]

All right. Lets keep this discussion civil with out the heated responses, finger pointing, etc. Any more flareups, this thread will be locked. Stop acting like 8 year olds in the sand box. You're supposed to be adults.

[triumph406]

All right. Lets keep this discussion civil with out the heated responses, finger pointing, etc. Any more flareups, this thread will be locked. Stop acting like 8 year olds in the sand box. You're supposed to be adults.

You miss the point that somebody was providing inaccurate information, based on a lack of understanding of basic engineering principles. Didn't think it was that overheated, I've seen much worse.

Maybe you should spend your time correcting inaccurate information that's being provided by some? That would be better moderation don't you think?

[wendtmk]

No, you're missing the point. There are civil ways of telling someone they're incorrect, and there are uncivil ways. Step back from the keyboard occasionally, take a deep breath, and then think about what you are going to post. Disagreement is always going to happen, facts be damned. How you handle it is the key.

This discussion is starting to get to the monkeys in the cage throwing feces. The warning was for all involved parties. Not singling out anyone, just telling all to calm down. Like it or not, that is what moderators do.

I don't spend my time correcting information in things where my knowledge is more limited than a lot of folks who concentrate in that area. I do try to do that in areas where I have knowledge of the subject. However, I do know when emotional conflicts arise, and we, as moderators step in to try and settle things down. Sometimes we have to lock threads because the involved parties won't take a hint. Sometimes the parties go way overboard and get time outs.

It's up to you folks to control your behavior. It's up to us mods to take action when folks can't or won't.

[mactec54]

The deflection will be the same for any grade of Aluminum, 6061/7075/2024 etc etc. The E (youngs modulus) is similar for all Aluminums (with very small variations) The difference being that the aluminums (and steels) with higher yields will deflect further before yielding.

Did you not post this, will deflect further before yielding

Have you accepted that yield strength has nothing to do with deflection?

The answer is above in what you posted

As I said in the other post, Young’s modulus is a measure of the stiffness or rigidity of a material.

This whole thread was about what material would be best, as an extrusion 6061 is by far the best choice

They don't use 6063 for aircraft parts, but they do use 6061

[triumph406]

Did you not post this, will deflect further before yielding

Yes I did, but what's your point? Explain yourself

As I said in the other post, Young’s modulus is a measure of the stiffness or rigidity of a material.

This whole thread was about what material would be best, as an extrusion 6061 is by far the best choice

They don't use 6063 for aircraft parts, but they do use 6061

It's not by far the best choice, and to say it's better because they use 6061 in aircraft and not 6063 is meaningless.

6061 isn't used in aircraft structural parts like Spars/Ribs/bulkheads etc. It's strength/weight ratio is inferior to 2024/7075. Your not going to use 6061 where strength is critical because if you did you would end up with an overweight aircraft.

The part you don't understand is that for what you guys are doing with the extrusion, ANY aluminum would be acceptable. You shouldn't be getting anywhere close to yield/ultimate stresses, and the ONLY concern should be deflection. But at any deflection you do get, if properly designed the stresses will be low.

I wonder why 8020 and FrameWorld use 6105 for their extrusions, explain that one. Why don't they use 6061?

[triumph406]

Ok Mactec some tech for you


The picture has 2 graphs, one for 6061 and the other 7075 (from Mil Handbook 5)

Left hand picture shows the 6061 yielding at approx 36ksi, with a strain of .0035in/in

Right picture shows for 7075, at a stress of 36ksi, the strain is also .0035in/in. (but not yielding)

Therefore at a stress of 36ksi, 6061 and 7075 will have the same deflection. 7075 will yield at approx 69ksi (longitudinal direction) at a strain of .0065in/in.

You can see that up and till it yields the slope of stress/strain is a straight line for both 6061/7075 and any other aluminum.

Therefore for the same force/moment the deflection will be the same (with minor variations) for any aluminum up to yield.

Per MilHbk 5
Youngs modulus for
7075 = 10.3e6 psi
2024 = 10.5-10.7e6 psi
6061 = 9.9e6 psi
7050 = 10.3e6 psi
so all very similar

[mactec54]

Ok Mactec some tech for you


The picture has 2 graphs, one for 6061 and the other 7075 (from Mil Handbook 5)

Left hand picture shows the 6061 yielding at approx 36ksi, with a strain of .0035in/in

Right picture shows for 7075, at a stress of 36ksi, the strain is also .0035in/in. (but not yielding)

Therefore at a stress of 36ksi, 6061 and 7075 will have the same deflection. 7075 will yield at approx 69ksi (longitudinal direction) at a strain of .0065in/in.

You can see that up and till it yields the slope of stress/strain is a straight line for both 6061/7075 and any other aluminum.

Therefore for the same force/moment the deflection will be the same (with minor variations) for any aluminum up to yield.

Per MilHbk 5
Youngs modulus for
7075 = 10.3e6 psi
2024 = 10.5-10.7e6 psi
6061 = 9.9e6 psi
7050 = 10.3e6 psi
so all very similar

Anyone can get find this information as I have been saying the GPAs are different and the yields are different, with almost every grade of aluminum you have just showed us that with these grades

There is only one material in what you have listed that is used for aluminum extrusion 6061 all the rest you list have higher GPA and also have different higher yield no question about that part

Why are you not using the material 6063 verse's any of the above, this is the material in question, we already know how good these other materials are, and what the difference's are as slight as it may be there is a difference and the benefit's of what you choose to use

May be 6063 it is not listed in your Mil hand book # 5, as I doubt that they would have a use for it with such a low yield

[triumph406]

May be 6063 it is not listed in your Mil hand book # 5, as I doubt that they would have a use for it with such a low yield

Why are you fixated on yield? Do you even know why?

Matweb has 6063-T6 yield at room temp = 31000psi
Matweb has 6063-T832 yield at room temp = 39000psi
Matweb has 6063-T83 yield at room temp = 31000psi
Matweb has 6063-T6 yield at room temp = 40000psi

I got to ask, even for 6063-T6 do you think any design using that material is going to yield? If the loads are so high that an extrusion yields, the issue isn't the material but the poor design. Changing from 6063 to 6061 isn't going to fix the failings in your design is it?