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Dave has worked in the petrochemical, nuclear and power industries over the last 16 years. Dave’s specialties include finite element analysis (FEA - heat transfer/thermal-stress, creep, fracture and shock and vibration), fatigue, fracture and creep modeling, as well as computational fluid dynamics (CFD) and multiphysics problems. 

He is a long time member of ASME (Sections I, III and VIII) and API committees, as well as AWS (weld residual stress modeling).  Dave lives in the Cleveland, Ohio area. where he works out of the Medina, Ohio office.

Grade 91 Steel - How Did We Get Here? Part 3

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Read Part 1 or Read Part 2 Part 3: Allowable Stresses While inspectability has been at the center of recent concerns, other issues such as chemistry control, ductility and excessive oxidation have also come under scrutiny.  Perhaps most interesting is that while all of the preceding concerns have been debated, it has also been found that existing ASME allowable stresses for Grade 91 are not conservative relative to newer data techniques.  This is beautifully illustrated in Figure 5 from [2], where the continual drop in allowable stress is plotted as more and more short term test data is removed from the analysis.  The good news is that “new” material is not worse than older material (at least from a statistical and data analysis perspective).  The bad news, as discussed in [2] and can be seen in Figure 6, is that even more modern techniques like “region-splitting” do not capture the apparent...
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