Fatigue in Welds

Figure 28 Corrosion fatigue in welded angle samples made of P355N (StE 335, 1.0545, cf. UNS KOI 600) in air and synthetic seawater, crack initialisation and crack propagation at maximum collective stress of 150 N/mm (load collective derived from North Sea wave statistics) [73]...

Figure 15.18 Examples of crack patterns due to stress-corrosion cracking and corrosion fatigue in butt welds. (Reprinted with permission from Helmut Thielsch, Defects and Failures in Pressure Vessels and Piping, New York, Van Nostrand Reinhold, 1965.)...

The toughness of wood is important in design for exactly the same reasons that that of steel is it determines whether a structure (a frame building, a pit prop, the mast of a yacht) will fail suddenly and unexpectedly by the propagation of a fast crack. In a steel structure the initial crack is that of a defective weld, or is formed by corrosion or fatigue in a wooden structure the initial defect may be a knot, or a saw cut, or cell damage caused by severe mishandling. 

Fig. 19.24 (o) Rig for a laboratory study of the corrosion fatigue of welded joints in sea-water and (b) view of test-pieces showing welded joint (after Jarman et olP )... 

D. Hornbach, M. Mahoney, P. Prevey, D. Waldron, and J. Cammett, Low Plasticity Burnishing of Friction Stir Welds in 2219 Aluminum to Increase Corrosion Fatigue Life, Sixth International Trends in Welding Research Conf. Proceedings, April 15-19, 2002 (Pine Mountain, GA), ASM International, Materials Park, OH, 2003, p 302-306... 

Fig. 6. Rate of fatigue crack propagation in welded Al-Mg plate.

Many cases of cracks in piping have occurred (especially in welds, although almost all have been discovered before the pipes have broken). The most common causes are inter-granular stress corrosion cracking, and thermal fatigue from the movement of variable temperature fluids. 

If the project involves demolition and refurbishment, then information on the occupancy of the premises or nearby premises needs to be ascertained. A structural survey should be made of the building to investigate the types of structural defect that may be apparent during a visual inspection and explain the causes of those defects. Typical defects include corrosion of steelwork, cracking due to fatigue in structural steel and welds, cracked brickwork and concrete, concrete degradation (flaking), dropped lintels and... 

A useful method of calculation for the crack propagation rate da/dN of welded steel samples under seawater conditions that provides a basis for predictions of fatigue behaviour, is described in [77]. As the results in Figure 29 make dear, use of this Paris equation results in a suffidendy accurate estimation of crack propagation in welded angle samples under temporally variable load amplitudes (ECSC sequence) based on crack propagation data obtained under constant load amplitude. 

FATIGUE OF WELDED STEEL IN SEA WATER AS APPLICABLE TO OFFSHORE STRUCTURES... 

W. H. Hartt, Fatigue of Welded Structural Steel in Sea Water", Proc. Second Int l Conf. on Environ. Degradation of Engr. Matls., Ed. M. R. Louthan, R. P. McNitt and R. D. Sisson, Va., Tech. Printing Dept., Blacksburg, Va., 1981, p. 97. 

W. H. Hartt, "Fatigue of Welded Structural Steel in Sea Water", Proc. Thirteenth Ann. Offshore Tech., Conf., 1981, p. 87. 

R. Holmes and G. S. Booth, "Fatigue and Corrosion Fatigue of Welded Joints under Narrow Band Random Loading", paper no. 7.2 presented at Int l. Conf. on Steel in Marine Structures, Paris, Oct. 5-8, 1981. 

Cisilino, A.P., Aliabadi, M.H. Three-dimensional BEM analysis for fatigue crack growth in welded components. Int. J. for Pressure Vessel and Piping 70, 135-144 (1997)... 

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