First pics of broken shaft....
10-09-2002, 12:15 PM
#1
Le Mans Master
Thread Starter
First pics of broken shaft....
Notice the clean break. :eek: I drilled/tapped the shaft to remove it.
I am goign to try and remove the rest of the shaft from the differential tonight. I have about 15 pics at home on my camera of tearing the rear out and diff apart. Enjoy.
Phillip
[Modified by Phil97SVT, 4:16 PM 10/9/2002]
I am goign to try and remove the rest of the shaft from the differential tonight. I have about 15 pics at home on my camera of tearing the rear out and diff apart. Enjoy.
Phillip
[Modified by Phil97SVT, 4:16 PM 10/9/2002]
10-09-2002, 12:46 PM
#2
Burning Brakes
Re: First pics of broken shaft.... (Phil97SVT)
Do you have any closer up high definition pictures of the fracture surface? To me, this looks like a fatigue failure rather than a pure overload failure. Fatigue failures generally are very flat, smooth, and planar with the fracture surface oriented perpendicular to the longitudinal axis. They generally occur in the area of highest stress concentration (at a section change, section interface, imperfection, or notch). It would be interesting to see if there are any beach marks or rachet marks on the fracture surface generated by a growing crack front. A torsional overload in a shaft or pipe will generally have an almost helical fracture at about 45 degrees (plane of maximum shear stress).
10-09-2002, 12:59 PM
#3
Le Mans Master
Thread Starter
Re: First pics of broken shaft.... (R6_C5_ML430)
The surface that broke is VERY smooth. No fracture marks ect. What are your thoughts?
Phillip
Phillip
10-09-2002, 01:29 PM
#4
Race Director
Re: First pics of broken shaft.... (Phil97SVT)
With out looking at it closer, it could have been a pre-existing defect in the original bar stock or a stress riser due to poor manufacturing.
Do you know anything about material or heat treatment?
Do you know anything about material or heat treatment?
10-09-2002, 01:45 PM
#5
Burning Brakes
Re: First pics of broken shaft.... (Phil97SVT)
I would have to see some good high-definition close ups of the fracture surface to say for sure. You say that there are no marks on the surface, but a lot of times you cannot readily see them (beach marks, rachet marks) at 1X magnification (naked eye). The surface is definitely is not indicative of a torsional overload. Fatigue is cumulative and irreversible damage. You likely have a lot of launches and burn-outs on that shaft. These are all stress cycles on the shaft which accumulate fatigue damage over time. Small cracks form and grow with each new stress cycle. Eventually these cracks will merge to form larger cracks. At some point, the remaining uncracked material's cross-sectional area becomes too small to withstand the applied load, and a catastrophic failure (overload) occurs. The amount of area that can remain before a failure occurs will vary depending on the shaft's material properties. Very hard materials (low fracture toughness) will generally fail faster in a brittle nature (even with only a small crack present), whereas softer, more ductile marterials can resist crack propagation, withstand larger cracks, and last longer under identical environmental conditions.
The main point of consideration is that if it IS fatigue, installing a shaft made of a harder material can make the problem worse, not better. Harder materials usually have a lower fracture toughness than relatively softer (more ductile) materials and, therefore, are not as resistant to crack formation and propagation. The trick (as there is a relationship between material hardness and material yield strength) is to get a shaft made of a material with a minimum yield strength and ultimate tensile strength high enough to withstand the high torsional loads being applied (prevent overload failures), yet ductile enough to resist notch effects and other stress concentrations (inhibit fatigue failures). Having the next shaft you install shot peened / bead blasted will impart a compressive residual stress in the shaft's outer fibers which will help prevent the formation and initial propagaion of a fatigue crack (fatigue cracks cannot grow if the crack tip is in compression).
I would be interested to know what the MYS, UTS, HRC, % Elongation, %ROA, Charpy V-notch Impact, grain size, microstructure, and chemical composition by weight is for the stock shaft versus hardened output shafts.
The main point of consideration is that if it IS fatigue, installing a shaft made of a harder material can make the problem worse, not better. Harder materials usually have a lower fracture toughness than relatively softer (more ductile) materials and, therefore, are not as resistant to crack formation and propagation. The trick (as there is a relationship between material hardness and material yield strength) is to get a shaft made of a material with a minimum yield strength and ultimate tensile strength high enough to withstand the high torsional loads being applied (prevent overload failures), yet ductile enough to resist notch effects and other stress concentrations (inhibit fatigue failures). Having the next shaft you install shot peened / bead blasted will impart a compressive residual stress in the shaft's outer fibers which will help prevent the formation and initial propagaion of a fatigue crack (fatigue cracks cannot grow if the crack tip is in compression).
I would be interested to know what the MYS, UTS, HRC, % Elongation, %ROA, Charpy V-notch Impact, grain size, microstructure, and chemical composition by weight is for the stock shaft versus hardened output shafts.
10-09-2002, 02:18 PM
#7
Team Owner
Re: First pics of broken shaft.... (R6_C5_ML430)
To sum up what Sean said...and this you already know...youhave a broken shaft!!! Damn...that is some explanation!!! :eek: :eek: :cheers: :cheers:
10-09-2002, 04:02 PM
#8
Le Mans Master
Re: First pics of broken shaft.... (Phil97SVT)
Ouch! :eek: :eek: :eek:
Bummer dude. :(
That’s why I never wanna put on slicks or even DRs on my car :nonod:
Just because you make it run better numbers at the track doesn’t make the car itselfany faster :nono:
I know some of you guys are into this game though, so I guess you have to pay to play….
Good luck with the repairs!
Bummer dude. :(
That’s why I never wanna put on slicks or even DRs on my car :nonod:
Just because you make it run better numbers at the track doesn’t make the car itselfany faster :nono:
I know some of you guys are into this game though, so I guess you have to pay to play….
Good luck with the repairs!
10-09-2002, 04:16 PM
#9
Le Mans Master
Thread Starter
Re: First pics of broken shaft.... (EuG)
Cost of repairs so far: $50 and 4 hours of labor. :yesnod: I am having a new shaft made to replace the factory one. The one I am replacing it with is a OEM replacement that is cyrogenic treated. Hopefully this will hold for more than 10 passes.
Phillip
Phillip
10-09-2002, 07:12 PM
#10
Former Vendor
Member Since: Nov 2000
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Re: First pics of broken shaft.... (R6_C5_ML430)
I would have to see some good high-definition close ups of the fracture surface to say for sure. You say that there are no marks on the surface, but a lot of times you cannot readily see them (beach marks, rachet marks) at 1X magnification (naked eye). The surface is definitely is not indicative of a torsional overload. Fatigue is cumulative and irreversible damage. You likely have a lot of launches and burn-outs on that shaft. These are all stress cycles on the shaft which accumulate fatigue damage over time. Small cracks form and grow with each new stress cycle. Eventually these cracks will merge to form larger cracks. At some point, the remaining uncracked material's cross-sectional area becomes too small to withstand the applied load, and a catastrophic failure (overload) occurs. The amount of area that can remain before a failure occurs will vary depending on the shaft's material properties. Very hard materials (low fracture toughness) will generally fail faster in a brittle nature (even with only a small crack present), whereas softer, more ductile marterials can resist crack propagation, withstand larger cracks, and last longer under identical environmental conditions.
The main point of consideration is that if it IS fatigue, installing a shaft made of a harder material can make the problem worse, not better. Harder materials usually have a lower fracture toughness than relatively softer (more ductile) materials and, therefore, are not as resistant to crack formation and propagation. The trick (as there is a relationship between material hardness and material yield strength) is to get a shaft made of a material with a minimum yield strength and ultimate tensile strength high enough to withstand the high torsional loads being applied (prevent overload failures), yet ductile enough to resist notch effects and other stress concentrations (inhibit fatigue failures). Having the next shaft you install shot peened / bead blasted will impart a compressive residual stress in the shaft's outer fibers which will help prevent the formation and initial propagaion of a fatigue crack (fatigue cracks cannot grow if the crack tip is in compression).
I would be interested to know what the MYS, UTS, HRC, % Elongation, %ROA, Charpy V-notch Impact, grain size, microstructure, and chemical composition by weight is for the stock shaft versus hardened output shafts.
The main point of consideration is that if it IS fatigue, installing a shaft made of a harder material can make the problem worse, not better. Harder materials usually have a lower fracture toughness than relatively softer (more ductile) materials and, therefore, are not as resistant to crack formation and propagation. The trick (as there is a relationship between material hardness and material yield strength) is to get a shaft made of a material with a minimum yield strength and ultimate tensile strength high enough to withstand the high torsional loads being applied (prevent overload failures), yet ductile enough to resist notch effects and other stress concentrations (inhibit fatigue failures). Having the next shaft you install shot peened / bead blasted will impart a compressive residual stress in the shaft's outer fibers which will help prevent the formation and initial propagaion of a fatigue crack (fatigue cracks cannot grow if the crack tip is in compression).
I would be interested to know what the MYS, UTS, HRC, % Elongation, %ROA, Charpy V-notch Impact, grain size, microstructure, and chemical composition by weight is for the stock shaft versus hardened output shafts.
10-09-2002, 08:36 PM
#12
Melting Slicks
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Re: First pics of broken shaft.... (R6_C5_ML430)
I would have to see some good high-definition close ups of the fracture surface to say for sure. You say that there are no marks on the surface, but a lot of times you cannot readily see them (beach marks, rachet marks) at 1X magnification (naked eye). The surface is definitely is not indicative of a torsional overload. Fatigue is cumulative and irreversible damage. You likely have a lot of launches and burn-outs on that shaft. These are all stress cycles on the shaft which accumulate fatigue damage over time. Small cracks form and grow with each new stress cycle. Eventually these cracks will merge to form larger cracks. At some point, the remaining uncracked material's cross-sectional area becomes too small to withstand the applied load, and a catastrophic failure (overload) occurs. The amount of area that can remain before a failure occurs will vary depending on the shaft's material properties. Very hard materials (low fracture toughness) will generally fail faster in a brittle nature (even with only a small crack present), whereas softer, more ductile marterials can resist crack propagation, withstand larger cracks, and last longer under identical environmental conditions.
The main point of consideration is that if it IS fatigue, installing a shaft made of a harder material can make the problem worse, not better. Harder materials usually have a lower fracture toughness than relatively softer (more ductile) materials and, therefore, are not as resistant to crack formation and propagation. The trick (as there is a relationship between material hardness and material yield strength) is to get a shaft made of a material with a minimum yield strength and ultimate tensile strength high enough to withstand the high torsional loads being applied (prevent overload failures), yet ductile enough to resist notch effects and other stress concentrations (inhibit fatigue failures). Having the next shaft you install shot peened / bead blasted will impart a compressive residual stress in the shaft's outer fibers which will help prevent the formation and initial propagaion of a fatigue crack (fatigue cracks cannot grow if the crack tip is in compression).
I would be interested to know what the MYS, UTS, HRC, % Elongation, %ROA, Charpy V-notch Impact, grain size, microstructure, and chemical composition by weight is for the stock shaft versus hardened output shafts.
The main point of consideration is that if it IS fatigue, installing a shaft made of a harder material can make the problem worse, not better. Harder materials usually have a lower fracture toughness than relatively softer (more ductile) materials and, therefore, are not as resistant to crack formation and propagation. The trick (as there is a relationship between material hardness and material yield strength) is to get a shaft made of a material with a minimum yield strength and ultimate tensile strength high enough to withstand the high torsional loads being applied (prevent overload failures), yet ductile enough to resist notch effects and other stress concentrations (inhibit fatigue failures). Having the next shaft you install shot peened / bead blasted will impart a compressive residual stress in the shaft's outer fibers which will help prevent the formation and initial propagaion of a fatigue crack (fatigue cracks cannot grow if the crack tip is in compression).
I would be interested to know what the MYS, UTS, HRC, % Elongation, %ROA, Charpy V-notch Impact, grain size, microstructure, and chemical composition by weight is for the stock shaft versus hardened output shafts.
But, what do you expect from an engineer. :D
