1. Neural Network Analysis
CSIRO

2. critical stress intensity
Charpy
fatigue
tensile
critical stress intensity
corrosion

3. 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

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

5. hardness

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

7. 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

8. 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

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

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

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

13. Hyperbolic Tangents

16. non-linear functions

21. y A B x

22. Brun, Robson, Narayan,
MacKay & Bhadeshia, 1998

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

24. Cole & Bhadeshia, 1999

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

26. Cole & Bhadeshia, 1999

28. Cool, 1996

29. Cool, 1996

30. 600 °C
As-welded
700 °C
650 °C
Cool, 1996

31. Siemens
Mitsui Babcock
Nippon Steel
ABB

32. Nickel base alloy FT750dc
wt%

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