Neural Network Analysis www.msm.cam.ac.uk/phase-trans CSIRO

critical stress intensity Charpy fatigue tensile critical stress intensity corrosion

Axioms All properties can be measured. Measurements can be used in safe design. Measurements can be used in control. Self evident truth, statement which commands general belief, an unverifiable although widely accepted fact

Dogma Given a comprehensive description of material, process and structure, it is not yet possible to predict most properties. Dogma - statement of belief

hardness

Variables C, Mn, Si, Ni, Cr, Mo, V, Co, B, N, O….. Thermomechanical processing of steel Welding consumable Welding parameters Subsequent heat treatment

Conclusions There are useful ways of expressing hardness Limited models relating hardness to microstructure No method for predicting hardness in general Dogma - statement of belief

large numbers of variables uncertainties exploit large knowledge base Solution non-linear functions large numbers of variables uncertainties exploit large knowledge base Dogma - statement of belief

Empirical Equations y = a + b (%C) +c (%Mn) + d (%Ni) .... 1223

y = a + b (%C) +c (%Mn) + d(%C x %Mn)

y = a + b (%C) +c (%Mn) + d(%C x %Mn) y = sin (%C) + tanh (%Mn)

Hyperbolic Tangents

non-linear functions

y A B x

Brun, Robson, Narayan, MacKay & Bhadeshia, 1998

Components of Creep Strength, 2.25Cr1Mo iron + microstructure 550 °C solid solution 600 °C precipitates Murugananth & Bhadeshia, 2001

Cole & Bhadeshia, 1999

GTA weld at 823 K (data from Nippon Steel) 600 500 400 300 200 100 20000 30000 40000 Life / hours Cole & Bhadeshia, 1999

Cole & Bhadeshia, 1999

Cool, 1996

Cool, 1996

600 °C As-welded 700 °C 650 °C Cool, 1996

Siemens Mitsui Babcock Nippon Steel ABB

Nickel base alloy FT750dc wt%

Tancret & Bhadeshia, 2002 1000 800 600 Yield stress / MPa 400 200 200 400 600 800 1000 1200 Temperature / °C