huangyhg

fatigue strength of vascomax 350
hi,
i need to calculate the fatigue strength of vascomax 350 material.
i have referred machine design hand book, author-shigley
the data provided and example calculation is for material having ultimate strength less than 200ksi.
the ultimate strength of vascomax 350 is 350ksi .
please help me calculating the fatigue strength for the material.
mainly i require the true stress at fracture (σ'f) for the material.
thanks,
ana

if you have to have information for that specific material, you should contact the supplier, allegheny technologies.
you can perform a literature search using the free sites google scholar and scirus.
mil-hdbk-5 has data for maraging steels in the 250 and 280 (300) conditions.
you could pay to have actual testing performed.
regards,
cory
careful ... the fatigue may be acceptable, there may not be much data readily available so yo may need to do your own tests, but beware ... the crack sensivity of ultra high strength steel is notoriously bad.
a simple yahoo for "vascomax" found allvac.com, with a very nice data sheet for these steels, including your 350 alloy, and including a generic fatigue curve.
geez, i wish people would do alittle digging before asking for info that is readily available !
allvac is a division of allegheny technologies. the fatigue data they provide is simple rotating beam. the four-point analysis that paramathma is seeking is more complicated.
regards,
cory
is the op looking for "certification" data, or "design check" data (to be verified by test later) ?
i'd use the available data (cautiously) ... it's enough to make you think about fatigue stresses >120ksi.
thank you.
visited the allvac.com and found the fatigue strength.
they have tested using the "r r moore rotating beam fatigue test".(image attached)
but when we refer mil-hdbk-5, they simply refer s-n curve.
but in here they have mentioned "r r moore rotating beam fatigue test".
i am confused.
please explain

they present an "s-n" curve in their data. they've obtained the results from a rotating beam test (a quick way to biuld up +ve and-ve stress cycles) ... not stunningly representative of our structures, but good enough imho for a design guide.
thank you rb1957.
as you have mentioned that s-n curve provided in the catalogue is based on the "r r moore rotating beam fatigue test".
could you please explain about the curves obtained in mil-hdbk-5 i.e how have they plotted this curve?
thanks,
paramathma
have you even read mil-hdbk-5? it describes how the data are obtained.
regards,
cory
from a manufacturing standpoint only. this material moves at heat treat and will change dramatically after hardening.
i was browsing and found this site about the material. i'll make sure i do my homework before asking a question here. i would say the state the same things as were said when to much info is asked for.

a curve thru data points is just that ... a best fit.
i assume you're building a landing gear, possibly an engine truss. the problem with ultra high strength steel is that whilst fatigue may be acceptable, damage tolerance sucks. landing gear is about the only place you could reasonably expect to utilise this type of steel, due to damage tolerance requirements. possibly you could essentially make the part disposable (long threshold, very short repeat = replace the part after the threshold life) ... operators may not be particularly happy with that approach.
knowing noting more about your problem, you've got enough data to design the part and have some confidence that when you come to fatigue test it it might not blow-up in your face.
you might want to checkout this website, fatigue calculator.
this site is courtesy of metengfff">.

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