Wedging mechanism

The buckling stress, Equation (8.14), increases as the square of the film thickness such that, for thick films, buckling might not be feasible. In this case, shear cracks can form in the film and, if Equation (8.13) is satisfied, lead to scale spallation by a wedging mechanism , which is shown schematically in Figure 8.4(b). 

Figure 15.12 Bilinear failure surface (double-wedge mechanism).

Figure 15.13 Calculation of maximum required force with a double-wedge mechanism. Modified from Rimoldi, P., 2000. II progetto di pendii ripidi rinforzati con Geosintetici di rinforzo. In Prontuario di Ingegneria Edile e Stmtturale, Ed. UTET, Torino (in Italian).

The properties of the piezocomposite material mentioned above offer special benefits when the transducer is coupled to a material of low acoustic impedance. This especially applies to probes having plastic delay lines or wedges and to immersion and medical probes. These probes with piezocomposite elements can be designed to have not only a high sensitivity but also at the same time an excellent resolution and, in addition, the effort required for the probe s mechanical damping can be reduced. 

Mechanical sensitivity can be divided into two categories—mechanical friction and mechanical shock. Mechanical friction can be defined as mechanical energy imposed by materials being wedged between surfaces and mechanical shock can be defined as mechanical energy imposed by materials undergoing an impact. Several tests for measuring the sensitivity to friction and the impact of materials are detailed in CCPS G-13. 

The proximity of the anodes to structures is also important. For example, if the sacrificial anodes are placed on, or very close to, steel pipework in soil then the output from the face of the anodes next to the steelwork can be severely limited. Alternatively, in high conductivity environments, corrosion products may build up and wedge between the anode and the structure. The resulting stresses can lead to mechanical failure of the anode. On the other hand, when anodes are located at an appreciable distance from the steelwork, part of the potential difference will be consumed in overcoming the environmental resistance between the anode and cathode. 

In order to supplement micro-mechanical investigations and advance knowledge of the fracture process, micro-mechanical measurements in the deformation zone are required to determine local stresses and strains. In TPs, craze zones can develop that are important microscopic features around a crack tip governing strength behavior. For certain plastics fracture is preceded by the formation of a craze zone that is a wedge shaped region spanned by oriented micro-fibrils. Methods of craze zone measurements include optical emission spectroscopy, diffraction... 

Dahlen, F. A., Suppe, J., and Davis, D. (1984). Mechanics of fold-and-thrust belts and accretionary wedges Cohesive Coulomb theory. /. Geophys. Res. 89,10087-10101. 

Mechanism of sediment transfer—implications for the temperature of the wedge ... 

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