Notch crack

Determine tool Joint outside diameter. Tool Joint box should have sufficient OD and tool Joint pin sufficient ID to withstand the same torsional loading as the pipe body. When tool Joints are eccentrically worn, determine the minimum shoulder width acceptable for tool Joint class in Table 4-101. Check the inside and outside surfaces for presence of cracks, notches and severe pitting. 

Brittle Failure (8). Brittleness is a principal consideration in selecting construction materials for liquid hydrogen service. Brittle fracture can result in the essentially instantaneous release of a vessel s contents, the hazard being a combined one of PV energy release and the possibility of fire and/or explosion. Three conditions must exist for a brittle fracture to occur 1) a stress riser, a crack, notch, or other discontinuity, 2) a section where the actual stress exceeds the yield stress of the material, and 3) a temperature below which failure occurs without appreciable plastic deformation. Metals that are satisfactory for liquid hydrogen service include aluminum, stainless steels, brass, and copper. Carbon steel is not suitable. 

Cracks may be real cracks (such as fatigue cracks) or simulated cracks notches). If notches are used, they must be narrow and have well defined, rounded tips. 

Crazing requires the presence of dUatational component in the stress tensor and may be inhibited by hydrostatic pressure. On the other hand, it is enhanced by the presence of triaxial tensile stress (Kinloch and Young 1983). Unfortunately, such a stress state exists ahead of large flaws or notches in relative thick specimens (plane-strain conditions). Therefore, the presence of sharp cracks, notches, or defects in thick specimens wUl favor craze initiation leading to brittle fracture, which is opposite to a bulk shear yielding mechanism that leads usually to ductile behavior. 

A localized stress field exists immediately In front of a crack, notch, or defect. 

Becker et al. (11) have performed extensive experiments on surface-breaking cracks, tilting both the cracks or the back-side. The cracks are like a half ellipse, but could presumably be reasonably approximated by a strip-like crack. Figure 3 shows a comparison between the experiments and UTDefect for a 2.54 mm crack with varying tilt. The thickness of the plate with the crack is 15.24 ram. The probe is a circular 45 SV probe with frequency 2.25 MHz and diameter 12.7 mm. The experiments are calibrated with a notch but this is presently not... 

Shear Horizontal (SH) waves generated by Electromagnetic Acoustic Transducer (EMAT) have been used for sizing fatigue cracks and machined notches in steels by Time-of-Flight Diffraction (TOED) method. The used EMATs have been Phased Array-Probes and have been operated by State-of-the-art PC based phased array systems. Test and system parameters have been optimised to maximise defect detection and signal processing methods have been applied to improve accuracy in the transit time measurements. 

Rice J.R. (1968) A path-independent integral and the approximate analysis of strain concentration by notches and cracks. J. Appl. Mech. 35, 379-386. 

Stress-corrosion cracks tend to branch along the metal surfaces. Typically, evidence of corrosion, such as accumulations of corrosion products, is not observed, although stains in the cracked region may be apparent. Stress-corrosion cracks tend to originate at physical discontinuities, such as pits, notches, and corners. Areas that may possess high-residual stresses, such as welds or arc strikes, are also susceptible. 

General description. In incomplete fusion, complete melting and fusion between the base metal and the weld metal or between individual weld beads does not occur (Fig. 15.8). Incomplete fusion that produces crevices or notches at surfaces can combine with environmental factors to induce corrosion fatigue (Chap. 10), stress-corrosion cracking (Chap. 9), or crevice corrosion (Chap. 2). See Fig. 15.9. 

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