Metallurgy training advertisement

vyv_cox

vyv_cox

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You may have noticed a banner advertisement about failure diagnosis at the top of the main page of ybw.com. Of course, I could not resist opening it. The diagnosis of the fastener is particularly well done and worth watching. This is exactly the stuff I used to do, although I was never fortunate enough to present my findings by video.
 
vyv_cox said:
You may have noticed a banner advertisement about failure diagnosis at the top of the main page of ybw.com. Of course, I could not resist opening it. The diagnosis of the fastener is particularly well done and worth watching. This is exactly the stuff I used to do, although I was never fortunate enough to present my findings by video.
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Session
IIRC the banner advert is generated by your browsing habits so nobody sees the same.
 
vyv_cox said:
That explains why I could not find it on Jill's iPad to show her. The link to the failure diagnosis video is https://www.imetllc.com/training-lesson/metal-fastener-failure-analysis/
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Interesting video, but the banner ad I see is for mobility bathrooms with easy access baths and showers :(

Esprit-BS-Esprit-22_RT1_new_39L.jpg
 
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I'm relieved to advise I get the same banner ad as Vyv, so there is no jingoism. But it was lost on me - I mentally filter out all the ads completely. Maybe I should look more closely at the ads - now that I know what I'm missing.

Thanks for the heads up!

Jonathan
 
Dougal Tolan said:
That's a bloody long winded version of "shoulda used bigger screws"
Now I can hear the cries of the screw was big enough but it's manufacture was to blame. But how much strength was lost and shouldn't the job tolerance exceed that?
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I think the example is a bit on the Mickey Mouse side but I have been involved in similar investigations on far larger equipment. I assume there was a large batch of these screws: it would hardly be worthwhile carrying out such a costly investigation on just one failure. Unless it was a result of his own DIY and he did it for fun!

The area of final fracture (dimpled appearance) will always tell you how strong the component was, as this represents its UTS. Measure the hardness, (why do Americans insist on using the ridiculous Rockwell scale?) convert to strength as there is a direct relationship with Brinell or Vickers, then you know exactly what force was being applied when it broke. In this case it looks as though the intergranular part, which effectively has no strength, was something like 50% of the total CSA.
 
Found it intersting that at the beginning of the advert, it was referred to as "Metal Fastener Failure" by the end it was a "screw"!! I am reaching out to them??
 
VicS said:
Interesting video, but the banner ad I see is for mobility bathrooms with easy access baths and showers :( .....
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Very funny! Maybe not from your perspective :-(
 
vyv_cox said:
I think the example is a bit on the Mickey Mouse side but I have been involved in similar investigations on far larger equipment. I assume there was a large batch of these screws: it would hardly be worthwhile carrying out such a costly investigation on just one failure. Unless it was a result of his own DIY and he did it for fun!

The area of final fracture (dimpled appearance) will always tell you how strong the component was, as this represents its UTS. Measure the hardness, (why do Americans insist on using the ridiculous Rockwell scale?) convert to strength as there is a direct relationship with Brinell or Vickers, then you know exactly what force was being applied when it broke. In this case it looks as though the intergranular part, which effectively has no strength, was something like 50% of the total CSA.
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My guess is it was an example he had to hand.

There have been a number of cases of identical cause of failure, hydrogen embrittlement, with bolts used in construction. A bridge in Melbourne, a good few years ago, and more recently a bridge being built in San Francisco. I have this idea Australia does not make high tensile bolts any more, they are all imported, and the same may be true of other countries. India and China seem to be common sources. Nothing wrong with sourcing from either - but the suggestion was that no-one checked the quality - and took the specification and certification of the manufacturer as gospel.

it would have been more dramatic in this video if he had been able to say the failure caused $x million worth of damage - but we should not need dramatics to illustrate the point.

A well known range of shackles have had their specification changed - because the importer had not checked the specifications - and they were found out. Think of the bendy shank debacle. Some tests are cheap to conduct - the test in the video utilised some expensive kit - though they could simply have tested the screw for strength and rejected it - without determining the underlying cause.

We take on trust that suppliers are doing the right thing - personally I think our trust for some items is misplaced.

Jonathan
 
Neeves said:
We take on trust that suppliers are doing the right thing - personally I think our trust for some items is misplaced.
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To some extent this example is a case in point. There are many causes of intergranular fracture, several of which are shown on my website. His conclusion that the cause of failure was hydrogen was a huge leap from his findings, and completely unproven. There are tests for hydrogen embrittlement but I doubt they can be used unless the item has been made very recently, which he does not say. I am guessing that this investigation was far wider than he says, with input from the manufacturers.
 
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