Fatigue failure mystery, need help
Fatigue failure mystery, need help
(OP)
Hey guys,
I am not a material engineer. I need some help here,
Test condition 1
Engine part made out of high silicone Aluminum is subjected to X MPa of stress for 5 hours until it failed.
Test condition 2
Same engine part, subjected to 0.8X MPa of stress for 60 hours. Once the 60 hours of running time is done, the test continues with X MPa of stress up to its failure. Time will be recorded.
My question is, will it take less than 5 hours to fail the engine part if it is subjected to X MPa of stress?
I have referred to my old material eng. book, goodman diagram is handy but i still cannot relate the accumulation of different stress level in contributing to the final failure. Any help is highly appreciated cause I am not an expert in this field.
I am not a material engineer. I need some help here,
Test condition 1
Engine part made out of high silicone Aluminum is subjected to X MPa of stress for 5 hours until it failed.
Test condition 2
Same engine part, subjected to 0.8X MPa of stress for 60 hours. Once the 60 hours of running time is done, the test continues with X MPa of stress up to its failure. Time will be recorded.
My question is, will it take less than 5 hours to fail the engine part if it is subjected to X MPa of stress?
I have referred to my old material eng. book, goodman diagram is handy but i still cannot relate the accumulation of different stress level in contributing to the final failure. Any help is highly appreciated cause I am not an expert in this field.





RE: Fatigue failure mystery, need help
Summation of n(1)/N(1) + n(2)/N(2) +.... = 1
n(1) refers to number of cycles at a particular stress level
N(1) refers to number of cycles to failure at stress level n(1).
Most material engineering text books should have a section on fatigue damage along with a brief explanation of Miner's Law. If you need more information, consult a materials engineer.
RE: Fatigue failure mystery, need help
I dont have any access to a material engineer at this moment. Anyhow, based on this Miner's law, will it fail sooner than 5 hours for the test condition 2?
RE: Fatigue failure mystery, need help
RE: Fatigue failure mystery, need help
RE: Fatigue failure mystery, need help
RE: Fatigue failure mystery, need help
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Fatigue failure mystery, need help
RE: Fatigue failure mystery, need help
Anyhow, I think Corypad has answered my question. Thanks buddy.