1. Complex Weldment Properties: Trends in Predictive Power

2. Colleagues
H. S. Lalam, M. Murugananth, T. Sourmail, D. J. C. MacKay, T. Cool
E. A. Metzbower, D. Moon
L. Karlsson
L.-E. Svensson
E. Keehan, H.-O. Andren

3. Goldak’s (1990) grand challenges for the year 2000
residual stress
microstructure
use of fracture mechanics
use of continuum damage mechanics
weld pool
arc models
multipass welds
distortion during repairs
hydrogen cracking
hot cracking

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

5. 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

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

7. hardness

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

9. MULTIPASS ARC WELD
Weld macro
L.-E. SVENSSON

10. Loureiro & Fernandes, 1994

11. Ion, Easterling and Ashby, 1984

12. Ion, Easterling and Ashby, 1984

13. Ion, Easterling and Ashby, 1984

14. Ion, Easterling and Ashby, 1984

15. 100 µm

16. Fe-1Mn-C wt % manual metal arc welds
0.2
0.4
0.6
0.8
1.0
Allotriomorphic
Volume fraction
Widmanstatten
Acicular
0.11
0.09
0.07
0.05
0.03
Carbon / wt %

18. Young & Bhadeshia, 1994

20. Tempering
Bhadeshia & Downs, 2002

21. Bhadeshia & Downs, 2002

22. Bhadeshia & Downs, 2002

23. 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

24. 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

25. non-linear functions

26. (Bayesian inference)
Dogma - statement of belief

27. Bayesian inference
Dogma - statement of belief

28. prior beliefs

29. the data

30. Baye’s rule
likelihood
prior

31. Baye’s rule

32. y x

34. Benefits
Quantitative prediction of mechanical properties, minimal dangers of extrapolation
New science
New products
New industries
Dogma - statement of belief

35. Murugananth & Bhadeshia, 2002

36. Moon, Murugananth & Bhadeshia, 2002

37. Progress on material properties
yield strength
UTS
reduction of area
elongation
Charpy
fatigue
creep rupture
creep ductility
ductile tear
microstructure
complex deformation
……………………...

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

39. elements in solution
Murugananth & Bhadeshia, 2001

40. integrated model
Summerfield et al., 1995

41. Siemens
Mitsui Babcock
Nippon Steel
ABB

42. Remove gaussian assumption. Use method to define experiments.
Reverse predictions
Dogma - statement of belief

43. Recommendation
Model mechanical properties with non-linear methods, large numbers of variables, within a Bayesian framework, exploiting all available data