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Chapter 21 Application of Fracture Mechanics 399
21.8 Examples
Example 21.1: Maximum Tolerable Defect Size in Butt Weld
Problem: A butt-welded plat thickness of 150mm, yield stress of 5OOMPa. There is a surface
crack with an aspect ratio c/a=l. Its minimum critical CTOD is 0.00036m. The weld is loaded
in uniaxial tension perpendicular to the crack plane, and the stress in the weldment is less than
or equal to 0.60 of the yield stress. What is maximum allowable crack width?
Solution:
a= 6, = 0.00036 =- 0.0259
2a~,a, 500 amax
2a-
2.OE5
The following relation exists:
0.0259
E
CD =- - 0.25 = -
E, amax
and therefore, the maximum half-width is am =O.O74m
21.9 References
1. Almar-Naess, A. (1 989, “Fatigue Handbook, Oflshore Steel Structures”, Tapir, Norway.
1. API 1104 (1994), “Alternate Standards for Acceptability for Girth Welds. Appendix A,
Standards for Welding Pipelines and Related Facilities”, 18” edition, American
Petroleum Institute.
2. MI 579 (2001), “Recommended Practice for Fitness for Service”, American Petroleum
Institute.
3. ASME (1989), “ASME Boiler and Pressure Vessel Code, Section X, Rules for In-service
Inspection of Nuclear Plant Components”, American Society of Mechanical Engineers.
4. ASME (1 99 1, 1992, 1994) “Risk-Based Inspection - Development of Guidelines, Vol.
20. I (1991): General Guidelines, V01.20.2 (1992): Light Water Reactor Nuclear Power
Plant Components, Vo1.20.3 (I 994): Fossil Fuel-Fired Electric Power Generating
Station Applications ”, American Society of Mechanical Engineers.
5. Andersen, T.L., (1 991), “Fracture Mechanics - Fundamentals and Application”, CRC
Press.
6. BSI. (1980), “PD 6493 - Guidance on Some Methods for the Derivation of Acceptance
Levels for Defects in Fusion Welded Joints”, London: BSI.
7. BSI (1999) “BS7910-Guidance on Methods for Assessing the Acceptability of Flows in
Fusion Welded Structures”.
8. Burdekin, F.M., and Dawes, M.G. (1971), “Practical Use of Linear Elastic and Yielding
Fracture Mechanics with Particular Reference to Pressure Vessels”, pp. 28-37 in
