Mfg1080 Failure Research1

8/11/2019 Mfg1080 Failure Research1

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Terra Community College

Research Assignment #1

Submitted for

Course Number: MFG1!

Course Title: Materials"nstructor: Michelle hite

$y:

%aniel Sic&les

Clyde' ()

*+,+-1.


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The /orld0s deadliest train /rec& has been attributed to a fatigue crac& in one of the train

car0s /heels and ultimately leads to derailment "t has been called 2schede train disaster and

too& 3lace 4une .' 1*!! in 2schede' Germany A33ro5imately 11 3eo3le /ere &illed and !!

3eo3le in6ured in this horrific e7ent "t /as re3orted that a steel /heel on the first railcar bro&e

and 3ortions of the /heel 3unctured the car floor and remained embedded "t is unclear if there

/ere any /arning signs 3rior to the /heel0s failure' ho/e7er' 3assengers and the conductor

noticed 7ibrations soon after and /ithin minutes the chain reaction of derailment e7ents

occurred

The original design of the 2schede train /heel consisted of /hat is &no/n as monobloc

design A monobloc is a single cast /heel much li&e /hat is seen on railcars today 8(9Connor'

-; The do/nside of this /heel is that loud 7ibrations caused discomfort for 3assengers The

noise le7el of the 7ibrations as /ell as the mo7ement in the dining cars for e5am3le' caused

glass/are to /al& off the table and 3ro7ed to be an issue

Management instructed engineers to de7elo3 a solution to this 3roblem and they came u3

/ith a ne/ design called the /heel


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load it is carrying The /heel must /ithstand constant abuse from stresses caused by such factors

as bra&ing friction and hea7y loading This leads to thermal 3ressure not only from bra&ing but

from friction of the /heel riding on the trac& The t/o surfaces are constantly heating and

cooling /hich o7er time /ill e7entually result in stress crac&s in the /heel Steel is the 3rimary

material used and is generally cast

There is another 3rocess of manufacturing that ta&es 3lace by forming a solid bloc& of

metal and then a series of machines 3ress the steel into sha3e /ith immense 3ressure This

3rocess is &no/n as forging The forging 3rocess is able to 3roduce 3roducts that are stronger in

com3arison to a cast 3roduct The deformation due to com3ressi7e force im3ro7es the strength

uniformly throughout the entire structure of the /heel 8Channel' -*;

Fatigue failure is defined as the tendency of a material to fracture by means of

3rogressi7e brittle crac&ing under re3eated alternating or cyclic stress of an intensity

considerably belo/ the normal strength 8metalinfo' --; Fatigue for these rail /heels may ta&e

some time before failure occurs and only an estimate of /hen this /ill occur can be based

loosely on intensity and fre=uency of a material that is sub6ected to re3eat loading and unloading

Any solid material can be tested for fatigue Stress analysis allo/s engineers to determine the

stress in materials and structures sub6ected to static or dynamic forces or loads

"t /as soon a33arent that dynamic re3etiti7e forces had not been accounted for in the

statistical failure modeling done during the design 3hase' and the resulting design lac&ed

an ade=uate margin of safety The follo/ing factors' o7erloo&ed during design' /ere

noted: The tires /ere flattened into an elli3se as the /heel turned through each re7olution

8a33ro5imately >' times during a ty3ical day in ser7ice on an "C2 train;' /ith


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corres3onding fatigue effects "n contrast to the monobloc& /heel design' crac&s could

also form on the inside of the tire As the tire became thinner due to /ear' the dynamic

forces /ere e5aggerated' resulting in crac& gro/th Flat s3ots and ridges or s/ells in the

tire dramatically increased the dynamic forces on the assembly and greatly accelerated

/ear 8(9Connor' -;

The maintenance de3artment had re3orted that the 3rocedure for e5amination include

only the use of standard flashlights to 7isually ins3ect the /heels for 3otential 3roblems instead

of using metal fatigue detection e=ui3ment ?re7iously' the use of more technical e=ui3ment /as

thought to ha7e sho/n false 3ositi7es and /as discarded as a reliable test 8(9Connor' -;

%etection of material failure needs to be more than 6ust 7isual ins3ection /ith flashlights

$y the time a 7isible failure is 3resent the material has already been com3romised and there

really /asn0t any 3re7entati7e action 3rior to the ob7ious A ne/ found /ay to 3redict material

fatigue has been re7ealed in the study of using 3olymer com3osites as a filler material

"t is difficult to detect the failure of a material inside' such as stress crac&s' by loo&ing at

the outside of the material There may be no e7idence 7isible to indicate any 3roblem The use of

luminescent @inc o5ide tetra3od fillers ma&e inner damages 7isible by using ultra7iolet light

hen the material is loo&ed at under B light' there are ob7ious changes in color to the

com3osite filler based on stress le7el e53osure The result is clear indication that a failure

3rediction can be made based on this ne/ internal 7isual indicator

The luminescent features of @inc o5ide tetra3od crystals are /ell established According

to our /or& hy3othesis' these characteristics sho/ed 3ronounced 7ariations under a

mechanical load' and /e realised that it could hel3 to detect internal damages of


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com3osite materials' says %r Dogendra Mishra of Eiel ni7ersity9s Technical Faculty

"n one e53eriment' the scientists added @inc o5ide tetra3od sha3ed crystals to a silicone

83olydimethylsilo5ane; 3olymer and tested its general 3ro3erties They found that the

resulting com3osite material is on the one hand stronger than silicon and on the other

hand emits light in different colours /hen e53osed to B light hen the material is

sub6ected to mechanical stress and ultra7iolet light' the intensities of the emitted lights

and thus the colour changes The micro


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References

Channel, S. (Director). (2009). How it's made, train wheels [Motion Picture].

metalinfo. (2002). metalinfo. Retrieved Set !, 20"#, from metalinfo.com

$%Connor, &. (200', Ma '). *chede +rain Di*a*ter. Leadership ViTS, . "-.

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Mfg1080 Failure Research1