strange tensile results
strange tensile results
(OP)
Hello, can anyone advise me on the following problem?
We have bought some components from a machine shop. Tubular forgings. It's offshore equipment. The material spec is a F22 (90ksi Yield) forging. The material certs from the foundry state the material meets all yeild, UTS, NACE (hardness) and charpy requirements. We perform a lot of FEA here and as part of the input to that, we decided to get the true stress - true strain curve measured to ASTM A370. The results that came back showed that at midwall (t/2) the material had a low yield strength and inconsistency between results. The tech who performed the test said that the tensile test specimend failed in a strange way. That is instead of following the usual pattern of the crack in the specimen growing orthogonal to the direction of loading, significant cracking was observed in the direction of load. with the final crack being in the expected direction. also the final fracture faces had a strange surface crack emminating in three places ( a bit like a mercedes-benz symbol). Anyway being a Mechanical I am looking for any opinions before I go back to the Foundry. Please let me know if you can't see the pictures. We got 9 samples tested. all exhibited similar failure modes (tri-laminar tearing with no classic cup and cone failures). Anyone seen this before?
during the test
Link
Link
showing the fracture face
Link
Link
Link
showing the two halfs after fracture
Link
Thanks in advance
Derek
We have bought some components from a machine shop. Tubular forgings. It's offshore equipment. The material spec is a F22 (90ksi Yield) forging. The material certs from the foundry state the material meets all yeild, UTS, NACE (hardness) and charpy requirements. We perform a lot of FEA here and as part of the input to that, we decided to get the true stress - true strain curve measured to ASTM A370. The results that came back showed that at midwall (t/2) the material had a low yield strength and inconsistency between results. The tech who performed the test said that the tensile test specimend failed in a strange way. That is instead of following the usual pattern of the crack in the specimen growing orthogonal to the direction of loading, significant cracking was observed in the direction of load. with the final crack being in the expected direction. also the final fracture faces had a strange surface crack emminating in three places ( a bit like a mercedes-benz symbol). Anyway being a Mechanical I am looking for any opinions before I go back to the Foundry. Please let me know if you can't see the pictures. We got 9 samples tested. all exhibited similar failure modes (tri-laminar tearing with no classic cup and cone failures). Anyone seen this before?
during the test
Link
Link
showing the fracture face
Link
Link
Link
showing the two halfs after fracture
Link
Thanks in advance
Derek





RE: strange tensile results
Have you had any samples sent to a metallurgical lab to confirm the chemistry and most important hardness and microstructure?
RE: strange tensile results
...banding or segregation occurred from either the original heat of material or forming...
RE: strange tensile results
Agree with metengr's comments.It will be interesting to see the microstructure at the fractured surfaceThere is an inconsistency in quality caused by segregation.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: strange tensile results
RE: strange tensile results
thanks
Derek
www.priamengineering.co.uk
RE: strange tensile results
RE: strange tensile results
RE: strange tensile results
RE: strange tensile results
www.priamengineering.co.uk
RE: strange tensile results
"Microstructure consisting of tempered martensite with some grains indicative of low carbon martensite and probably some bainite"
is this what you would expect from a correctly normalized, hardened and tempered carbon steel (0.1% -0.2% by weight).
Thanks in advance
www.priamengineering.co.uk
RE: strange tensile results