Prime Example of Fatigue Failure...

[M.D. Holloway]

and a leopard print one I wear when I'm feeling frisky!

[masraum]

Materials was one of the more interesting classes I remember from college, too bad I didn't finish it (I don't think)

[sammyg2]

Originally Posted by LubeMaster77

hint...

Looks like E-3 to me

[sammyg2]

Originally Posted by masraum

Materials was one of the more interesting classes I remember from college, too bad I didn't finish it (I don't think)

LOL many moons ago I was going back to college for about the gazillionth time. I had requested and recieved a copy of my transcripts and it said I took an introductory and advanced metallurgy class at Fullerton college in 1980 and got A's in both classes. Funny thing was, I don't remember taking either one of those classes. I don't remember drinking that much back then either

[Martin Glaeser]

This is a bit off topic but I have reccently written a maintenance learing module that covers among other things fatigue cracking. Would it be possible to have copyright permission to use the photo in the opening post please. Many thanks

Martin

[NutmegCarrera]

Looks to me like there was some inclusion in the base metal. Center of picture, and there appears to be a "path" leading to it from somewhere around the 5:00 position in the photo.

A crack can only propogate if there is a void. Usually they start on the outside, unless there was a flaw in the material such as this example has.

We had a very important shaft fail in my first job. Caused a paper machine roll to break under operation. Similar material. About 12" diameter. Under a LOT of tensile pre-load to counteract bending of the body of the roll. Long story short - lots of pieces of roll body material throughout the rest of the machine. Machine down for about 3 weeks to repair damage. Root cause of failure was a similar inclusion - however, ours was on the outside of the shaft.

[M.D. Holloway]

Originally Posted by Martin Glaeser

This is a bit off topic but I have reccently written a maintenance learing module that covers among other things fatigue cracking. Would it be possible to have copyright permission to use the photo in the opening post please. Many thanks

Martin

send me a PM and we can work sump'n out!

[Geary]

Mike .. could you possibly tell us the dimensions, application, and an opinion of this shafts material? It just seems like quite a large keyway on a relatively small diameter shaft.

I have to wonder whether core strength was compromised in just the short keyway portion of the shaft during the heat treatment process, due to the irregular cross sectional shape. That's kinda what the photo looks like to me .. a large hard zone around the keyway, stealing uniformity from a core that's skewed off-center. Copper coating the keyway prior to heat treatment is a probable solution .. or replacing the key with splines. .. (just a layman rambling) ..

[red-beard]

In 1987, I saw guy wearing a pocket protector and thought it was pretty neat! Then I got better...

[javadog]

We ever going to learn all about this failure?

It's been 4 1/2 months and we're not going to get any smarter, so new guesses may not be forthcoming.

JR

[livi]

Thats an easy one, Lube.

You see its all to do with (doing my best Rowan Atkinson impression here) electro-magnetic orientation of the adjacent strata of atoms in relation to the inclination degree perpendicular to the direction of the force.

[svandamme]

Originally Posted by livi

Thats an easy one, Lube.

You see its all to do with (doing my best Rowan Atkinson impression here) electro-magnetic orientation of the adjacent strata of atoms in relation to the inclination degree perpendicular to the direction of the force.

In other words, it went tits up

[livi]

Well.. yes.

[Por_sha911]

Interesting street sign...

[Martin Glaeser]

Originally Posted by LubeMaster77

send me a PM and we can work sump'n out!

You can email me at martin.glaeser@openpolytechnic.ac.nz

Cheers

[svandamme]

You must really love getting spammed to post your email adres in a public forum.

[futuresoptions]

I might not be the smartest man in the world, but I know what love is Jennay...

[sammyg2]

Originally Posted by javadog

We ever going to learn all about this failure?

It's been 4 1/2 months and we're not going to get any smarter, so new guesses may not be forthcoming.

JR

Using a keyway like that to transmit torque is a big no-no under most circumstances.
An interference fit between the hub and the shaft would be optimum so the keyway would not see any shearing forces.
Also I'm guessing the keyway was cut with a standard end mill, leaving sharp edges. Stress riser city.

Design the hub with a taper lock or standard interference fit of .001" per inch of dia. up to 2", then additional .0005" per inch after.
If it's belt driven, make sure proper tension is maintained. Too loose can do that more than too tight, snapping a string like.
Have em cut the keyway in a way that eliminates the sharp edges.

If it's direct drive tell em to use a good laser alignment system to get the alignment just right to reduce vibration.

Don't have enough info to recommend a material upgrade.

[Martin Glaeser]

Hi, any chance of a reply to the request to use the photo? We could probably buy a copy of your book.

[Bob Kontak]

Originally Posted by svandamme

In other words, it went tits up

Tits up in the ditch!