PD 6493:1991

Committees responsible
Foreword
Section 1. General
0 Introduction
1 Scope
2 References
3 Notation
4 Types of flaw
5 Modes of failure
6 Information required for assessment
Section 2. Assessment for fracture
7 General
8 Data required for assessment
9 Parameters required for different assessment levels
    (and methods)
10 Level 1, preliminary assessment
11 Level 2, normal assessment
12 Level 3, advanced assessment
13 Fracture assessment for non-planar flaws, imperfect
    shape and fillet welds
Section 3. Assessment for fatigue
14 Assessment procedures
15 Data required for assessment
16 Probability of survival
17 General procedure for fracture mechanics assessment
    of planar flaws
18 Basis of procedure for assessing flaws using quality
    categories
19 Assessment of planar flaws using quality categories
20 Assessment of embedded non-planar flaws using
    quality categories
21 Assessment of shape imperfection using quality
    categories
22 Estimation of tolerable sizes of flaws
Section 4. Assessment for other modes of failure
23 Yielding due to overloading of remaining cross
    section
24 Leakage in pressure, liquid or vacuum containing
    equipment
25 Environmental effects
26 Instability (buckling)
27 Creep
Appendices
A Safety factors, number of tests and treatment of
    variability in input data for fracture assessment
B Use of Charpy tests to indicate fracture toughness
    levels
C Assessment of pop-in crack extensions
D Stress due to misalignment
E Stress intensity factor solutions for cracks in
    welded joints
F Formulae for effective net section stress
G Examples of level 3 assessment diagrams
H Approximate numerical integration methods
J References
Tables
1 Limits for slag inclusions and porosity
2 Stress ranges used in fatigue assessments
3 Details of quality category S-N curves
4 Minimum values of delta sigma j for assessing non-
    planar flaws and shape imperfections
5 Limits for non-planar flaws in as-welded steel and
    aluminium alloy weldments
6 Limits for non-planar flaws in steel weldments
    stress relieved by post-weld heat treatment
7 Acceptance levels for misalignment expressed in
    terms of stress magnification factor, Km
8 Acceptance levels for weld toe undercut in material
    thicknesses from 10 mm to 25 mm
9 Procedure for assessment of known flaws
10 Temperature below which creep is negligible in
    200 000 h
11 Equivalent fracture toughness values to the minimum
    of three results
12 Definitions of failure consequences
13 Partial safety factors for fracture assessments at
    level 2
14 Formulae for calculating the secondary bending
    stress due to misalignment in butt joints
15 Formulae for calculating the secondary bending
    stress due to misalignment in cruciform joints
16 Values of v and w for axial and bending loading
Figures
1 Schematic representation of stress distributions
    across section
2 Alternative procedure for resolving flaws normal to
    principal stress
3 Linearization of stress distributions
4 Typical distributions of residual stresses at welds
5 Flaw dimensions
6 Planar flaw interactions
7 Elliptical integral phi as a function of a/c used
    for calculation of K1 for surface and embedded flaws
8 Stress intensity magnification factor Mm for
    embedded flaws in tension (at point nearest material
    surface)
9 Stress intensity magnification factor Mm for surface
    flaws in tension
10 Stress intensity magnification factor Mb for
    embedded flaws in bending
11 Stress intensity magnification factor Mb for surface
    flaws in bending
12 Calculation of rho, the plasticity correction
    factor, using above equations and rho1 from graph
13 Failure assessment diagrams
14 Relationship between actual flaw dimensions and the
    parameter a for surface flaws
15 Relationship between actual flaw dimensions and the
    parameter a for embedded flaws
16 Values of constant C for different loading
    condition (level 1)
17 Stress/endurance relationship
18 Assessment of surface flaws in axially-loaded
    material for simplified procedure
19 Assessment of surface flaws in flat material in
    bending for simplified procedure
20 Assessment of embedded flaws in axially-loaded
    joints for simplified procedure
21 Assessment of weld toe flaws in axially-loaded
    joints for simplified procedure
22 Assessment of weld toe flaws in joints in bending
    for simplified procedure
23 Interaction criteria for slag inclusions
24 Schematic diagrams of typical relationships between
    crack velocity and stress intensity factor during
    stress corrosion cracking
25 Types of corrosion fatigue crack growth behaviour
26 Determination of the temperature To at which 0.2 %
    creep strain is accumulated at a stress level equal
    to the 'proof strength'
27 Determination of the time t(T) to achieve an
    accumulated creep strain of 0.2 % at a stress level
    equal to the 'proof strength'
28 Procedure for obtaining lower bound Klc toughness
    estimates from Charpy impact test
29 Load/clip gauge displacement diagram for fracture
    tests showing behaviour to be assessed for pop-in
30 Crack and welded joint geometries
31 Transverse load-carrying cruciform joint
32 Example of level 3 assessment diagram for carbon
    steel having stated stress/strain curves
33 Example of level 3 assessment diagram for quenched
    and tempered steel having stated stress/strain
    curves
34 Example of level 3 assessment diagram for austenitic
    stainless steel having stated stress/strain curves

Simplified treatment of use of fracture mechanics methods to establish acceptance levels based on fitness for purpose. Applies basically to fusion welded joints in ferritic steels, austenitic steels and aluminium alloys.