Fracture surface in cases of proportional and non proportional stresses
Fracture surface in cases of proportional and non proportional stresses
(OP)
Hi all
Does anyone know whether the fracture surface changes if the stresses applied in the cycles change from proportional (desired) to non proportional ?
Does anyone know whether the fracture surface changes if the stresses applied in the cycles change from proportional (desired) to non proportional ?





RE: Fracture surface in cases of proportional and non proportional stresses
If you want a response you need to better define your question. Non-proportional to me is variable amplitude loads but this could be different to what you intended.
RE: Fracture surface in cases of proportional and non proportional stresses
RE: Fracture surface in cases of proportional and non proportional stresses
The fracture surface would change only if the nature of the fracture changes, i.e. ductile to brittle or vice versa. If the original stresses were producing fatigue leading to a ductile fracture, a change over to non-proportional stresses may well produce a fatigue leading to a brittle fracture!
RE: Fracture surface in cases of proportional and non proportional stresses
RE: Fracture surface in cases of proportional and non proportional stresses
Flaw initiation/detection/characterization can be affected/driven by many complicated factors... but 'where-you-start' affects total crack-growth and fracture toughness.
For the X-material in question: Characterize the unique crack-growth [KI], critical crack length [fracture toughness, KIc] and stress corrosion cracking [SCC] parameters... bare minimum... using standard ASTM tests.
Geometry VS loading SS crack(s) orientations can affects crack growth dramatically.
The surface of the part can grossly affect fracture: rough/smooth [see ASME B46.1], porous [cast, pitted/corroded, scratched/scored/gouged], brittle [hard anodized, abusively plated, abusively machined, etc], shot-peened [properly or poorly], etc...
Service environment affects crack growth: Corrosives, chemical exposures, extreme heat, extreme cold
Regards, Wil Taylor
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RE: Fracture surface in cases of proportional and non proportional stresses
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."