Strain cracking

W. F. Brown and J. E. Strawley, Plane Strain Crack Toughness Testing of High Strength Metallic Materials , ASTM STP 410, American Society for Testing and Materials, Philadelphia, 1966, pp. 1-65. 

Also, heating might cause decomposition of sensitive components of the device. In addition, any mismatch in thermal expansion between the NLO film and its package can lead to strain, cracking, and delamination during cooling from high temperature. 

The matrix fracture behavior can also be described by using stress intensity factors, K. This approach is more convenient than the /-integral in some cases particularly for short cracks and for fatigue.31,84 To apply this approach, it is first necessary to specify the contribution to the crack opening induced by the applied stress, as well as that provided by the bridging fibers. For a plane strain crack of length 2a in an infinite plate, the contribution due to the applied stress is85... 

A comparison of Figures 7a and 7b shows that the resistance to craze initiation is lowered more than the resistance to plane strain crack initiation (i.ecraze breakdown) by introducing silicone blocks into BPA polycarbonate. 

WF Brown, JE Srawley. Plane-strain crack toughness testing of high strength metallic materials. ASTM, STP 410, 1966, p 12. 

Fig. 9. A plane strain crack, semi-infinite in length, propagates along the interface of two linearly identical elastic half spaces with a steady state velocity of a under small-scale yielding conditions. The interface is reinforced by polymer chains, (x, y) is the cartesian coordinate frame attached to the moving crack tip. The pullout zone is defined as the region directly ahead of the crack tip in which interface opening is greater than zero but less than the critical value l, i.e. I > 6 (x, t) > 0.

In this case, the crack size is much larger than the plane strain crack-tip plastic zone size. As such the effective crack length 2a = 2ao + 2rjy would be effectively equal to the initial (or physical) size of the crack 2ao. The load-displacement trace would be essentially hnear up to the point at which the specimen fractures abruptly (see Fig. 4.5a). The plane strain fracture toughness Kic can be computed directly from the maximum load Pmax or stress a ax i e., the load or stress at fracture) and the initial crack size ao using Eqn. (4.7). 

Clearly, there would be a minimum thickness to ensure the onset of (or momentary) plane strain crack growth at the midthickness region of a specimen, i.e., the occurrence of pop-in. Because the rehef of constraint is associated with plastic deformation near the specimen surface, the thickness requirement is expected to be a function of the plastic zone size and must be established experimentally ie.,... 

Krafft, J. M., Correlation of Plane Strain Crack Toughness with Strain Hardening Characteristics of a Low, a Medium, and a High Strength Steel, Applied Materials Research (1964), 88. 

Grades of PE have been specially developed for the gas pressure pipe market. Eirst-generation HDPEs were not used in the UK. The second generation of MDPE copolymers has superior creep rupture resistance at the pipe design lifetime of 50 years (Fig. 14.5). The data falls on one or more lines lines of shallow slope are associated with ductile failure and lines of steeper slope with brittle plane strain crack growth (Fig. 14.3). The... 

ASTM (2013d), Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, Kia, of Ferritic Steels, E1221, Annual Book of ASTM Standards, Vol. 03.01, ASTM International, West Conshohocken, PA. 

Backface strain (BFS) measurement is a technique that can be used for the in-situ monitoring for SHM of crack initiation and propagation in adhesively bonded composite joints. Zhang et al., [39] assessed the use of the BFS technique in bonded joints. Their work with single lap joint (SLJ) allowed for finding out that by detecting the switch in the direction of the backface strain crack initiation can be monitored. 

Figure 3.34. SEM images of fracture surfaces in the vicinity of initial crack tip of ME, 15% (a) plane-stress, and (b) plane-strain. Crack propagation direction is from top to bottom. Each scale bar represents 100 im. The circled areas are schematically illustrated in Eigure 3.35 for clarity [37]...

At low strains for both Widmanstatten + grain boimdary and equiaxed a structures, crack initiation took place at a-P interfaces and in the aged P matrix. In Widmanstatten -i- grain boundary a structures, profuse extrusion formation was noted as well. At higher strains, cracking was more predominant at sHp bands within a. 

Figure 4 Schematic oxidation charge density-time relationship for a strained crack tip and unstrained crack sides. (From Ref. 11.)...

Enhanced oxidation (dissolution and oxide reformation) at the strained crack tip. 

Most of these techniques have been applied in the study of enviroiunentally assisted cracking. The experimental difficulties with these techniques have been reviewed [45,107,108], along with the interpretations of the atomistics of the reaction rate [45] as a strained crack tip. These topics will not be covered further in this chapter. 

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