gidge348
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Post by gidge348 on Apr 7, 2016 5:10:35 GMT -5
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greazy
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Post by greazy on Apr 8, 2016 21:44:54 GMT -5
it never occurred to me to look on ebay of all things haha the supplier im talking to also have 720 udimet material they are doing a bit of looking around for me so if they come up blank ill go the ebay road
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greazy
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Post by greazy on Apr 9, 2016 6:31:53 GMT -5
dose anyone know if udimet material is ok for model jet blisks? they use it for the large gas turbine im working on at work but its for blades only i think the disk is waspaloy 718. i have only heard of people using 718 for model jet blisks. could be because its easily cast.
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Post by finiteparts on Apr 9, 2016 12:29:31 GMT -5
Hi greazy, U720 is a very capable material for a homemade turbine disk...my guess is that the cost will be quite scary though! The roll off of material tensile capabilities occurs at a higher temperature for the U720 material than for Inconel 718 or 713c, so it's more capable with respect to pull loads at temperature. It has a slightly lower density than the Inconels so for a given geometry, the pull loads due to the blades will be slightly lower. A quick look at the material properties seems to indicate that it is a better material choice...but, they do say it work hardens during machining, so it may be really tough to work with. See the links below for material properties... www.specialmetals.com/documents/Inconel%20alloy%20718.pdfwww.specialmetals.com/documents/Udimet%20alloy%20720.pdfwww.nickelinstitute.org/~/media/Files/TechnicalLiterature/Alloy713C_337_.ashxThe other thing to notice about U720 and Inco 718 is that the material properties are really dependent on the strengthening processes that the material gets. The use of solutioning, aging and heat treatments are selected to set the material internal grain size which controls the mechanical properties of these metals...so don't assume that a purchased blank of U720 has the material properties shown in the link about. You have to ask how it was strengthened... solutioned? Aged? Heat treated? That is what determines it capability. Just a quick correction...Waspaloly is a different alloy than Inconel 718...I think you might have inadvertently combined them above when you said "...but its for blades only i think the disk is waspaloy 718." Also, most turbochargers are cast from Inconel 713c, not Inconel 718, so that is why I provide the above link to the Inco713c. Inconel 713c is easier to cast and can be use in the "as cast" state, were Inconel 718 requires some strengthening processes, usually solution and heat treatment, so it is more expensive and thus not as common. Inco 718 does exhibit an increase in tensile capability, so sometimes the extra cost is worth it. As an example, if we look at the 0.2% yield strength of the three materials at around 1000 F, we see: Inconel 713c ~ 105 ksi Inconel 718 ~ 150 ksi Udimet 720 ~ 175 ksi (all values pulled from the above linked documents) so, the gain in tensile capability is easily seen...but when you look at the graphs of yield or ultimate tensile strength vs temperature, you see that the strengths of each of the above materials starts to fall off very quickly at elevated temperatures. Inconel 718 falls off first at around 1400 F, with the Inconel 713c going just a bit higher at around 1450 F and finally the U720 holding well up to 1600 F. The ability to maintain strength as the temperature rises is an obvious benefit, so the higher cost of U720 may be justified in some situations. Good luck on your project! Chris
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greazy
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Post by greazy on Apr 9, 2016 19:00:30 GMT -5
cheers chris, yea i meant waspaloy or 718. so in theory as long as i can machine/grind it's the better choice. the blanks on ebay (as posted in above comments) seem fairly priced but the supplier im talking to has access to 720 so I'll probably get it from him as I'll know exactly what I'm getting.
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greazy
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Post by greazy on Apr 13, 2016 8:35:03 GMT -5
i emailed the ebay 720 seller posted above asking exactly what state the material is in he replied
((we don't have certs for this material but should be in annealed condition. We've had customers machine this material without any complaints.))
dose that mean it needs heat treatment after grinding to shape? it says its precipitation hardened from what i understand that means it has already been heat treated...
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Post by finiteparts on Apr 18, 2016 22:31:27 GMT -5
Hi greazy, It sounds to me like the statements about precipitation hardening, would be more correct to say that it "can be" PH'ed. By the seller stating that it is likely in an annealed condition, it will still need to be heat treated. Without the certs, you have absolutely no idea what condition the material is in. That being said, it is probably still a very capable alloy even in the annealed condition, but I am unable to find any material data on it in the annealed state. Here are several articles that talk about the heat treats...you could also check with some of the companies out there, if they do a run were they heat treat U720 material, it might not cost much to have them throw it in the furnace with the larger batch. www.tms.org/superalloys/10.7449/1984/Superalloys_1984_573_580.pdfwww.azom.com/article.aspx?ArticleID=7741Good luck, Chris
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greazy
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Post by greazy on Apr 19, 2016 8:59:46 GMT -5
well this just arrived in the post. the misses cant understand how this "pointy metal disk" makes me so excited... some people will just never get it! the supplier im talking with can't get any more inconel untill their yearly order for BHP in a few months time so if i want it from them I'll have to wait. on the other hand the ebay U720 disk has dropped some $$ since i last looked on ebay. I want to use the 720 if i can get it treated for a small enough cost so thats the next quest for now. ryan, Attachments:
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Post by racket on Apr 19, 2016 15:04:33 GMT -5
Hi Ryan
Shes a nice bit of alloy :-)
Cheers John
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greazy
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Post by greazy on Apr 29, 2016 7:30:07 GMT -5
i was mucking around a bit with calculations with the x831 compressor wheel and came up with the idea PR is essentially how much the compressor squeezes an amount of air into an area if it halves the area it doubles the pr. so would it be right to assume a theoretical PR of 3.82 before efficency and gap losses with the compressor inlet area and outlet area as with the picture above? I'm positive its just a coincidence referencing johns calcs he came up with 3.6 to 3.8 thats why I feel it may be something. however if you use the squared area inlet /outlet it comes to 1.8 ish cheers ryan, Attachments:
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Post by racket on Apr 29, 2016 16:27:21 GMT -5
Hi Ryan
LOL............maybe just a coincidence .
I ended up with a radial air velocity of 500 ft/sec out of the exducer , density 0.1194 lbs/cu ft - 8.375 cu ft/lb , area 0.0612 sq ft , mass flow 3.65 lbs/sec , whirl of 1200 ft/sec , tangential 1300 ft/sec for an angle of ~22.5 degrees .
Cheers John
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greazy
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Post by greazy on May 18, 2016 4:43:54 GMT -5
i think i have found some suitable bearings for my build and need to calculate the critical rotation to suss out and design my shaft length and thickness. im using the kamps book page 70 but i have no idea how to punch it into the calculator... can anyone help please?? im trying to replicate the books demonstration calcs first to get the hang of it. the shaft size in the book is 14mm. the parts underlined in red are the numbers i have no clue how to enter into the calculator T.I.A
ryan
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greazy
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Post by greazy on May 18, 2016 4:46:13 GMT -5
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Post by racket on May 19, 2016 4:15:13 GMT -5
Hi Ryan
On my calculator theres a yx key , if I hit 10 then yx then 9 , I get 1.00000 09, then if I multiply by the 1.886 , I get 1.88600 09 , if I divide by 1,000,000, I end up with 1886, which is correct ........I think :-)
Or you could go the old fashioned way and use 1,000,000,000 instead of 10 to the 9th power ..................LOL, its been 50 years since I did this sort of stuff at school , so don't take my comments as gospel.
Cheers John
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greazy
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Post by greazy on May 19, 2016 20:22:51 GMT -5
ahh so its times 10 to the power of 9. not to the power of negative 9 like i was entering it... the dash before it in the book is deceiving i thought it was creating a decimal not a huge number.
thanks john
ryan
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