Complex Weldment Properties: Trends in Predictive Power

1
Complex Weldment PropertiesTrends in Predictive
Power
www.msm.cam.ac.uk/phase-trans
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
Goldaks (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
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.

6
Dogma

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

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
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
Allotriomorphic
Volume fraction
Widmanstatten
Acicular
Carbon / wt
17
(No Transcript)
18
Young Bhadeshia, 1994
19
(No Transcript)
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

24
Solution

• non-linear functions
• large numbers of variables
• uncertainties
• exploit large knowledge base

25
non-linear functions
26
(Bayesian inference)
27
Bayesian inference
28
prior beliefs
29
the data
30
Bayes rule
prior
likelihood
31
Bayes rule
32
y
x
33
(No Transcript)
34
Benefits

• Quantitative prediction of mechanical properties,
  minimal dangers of extrapolation
• New science
• New products
• New industries

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

43
Recommendation

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

www.msm.cam.ac.uk/phase-trans