Cavitation mechanism

Generation Spontaneous generation of gas bubbles within a homogeneous liquid is theoreticaUy impossible (Bikerman, Foams Theoiy and Industrial Applications, Reinhold, New York, 1953, p. 10). The appearance of a bubble requires a gas nucleus as avoid in the liquid. The nucleus may be in the form of a small bubble or of a solid carrying adsorbed gas, examples of the latter being dust particles, boiling chips, and a solid wall. A void can result from cavitation, mechan-ic ly or acoustically induced. Blander and Katz [AlChE J., 21, 833 (1975)] have thoroughly reviewed bubble nucleation in liquids. 

Localized deterioration Corrosion (especially pitting and intergranular attack), erosion, cavitation, mechanical wear, and so on (see Case History 9.8). 

Alex CCT, Goh NN, Chia LS (1995) Effects of particle size morphology on ultrasound induced cavitational mechanism in heterogeneous systems. J Chem Soc Chem Commun 2 201-201... 

While the surface modification is not effective to suppress cavitation, Yee and coworkers performed an experiment to suppress the cavitation mechanically in a rubber-modified epoxy network. They applied hydrostatic pressure during mechanical testing of rubber toughened epoxies [160]. At pressures above BOSS MPa the rubber particles are unable to cavitate and consequently no massive shear yielding is observed, resulting in poor mechanical properties just like with the unmodified matrix. These experiments proved that cavitation is a necessary condition for effective toughening. 

A threshold of interfacial adhesion between both phases is needed to (a) promote the cavitation mechanism and (b) activate the crack-bridging mechanism. For rubbery particles, the former contributes much more than the latter to the total fracture energy. Adhesion is achieved by the use of functionalized rubbers that become covalently bonded to the matrix. Higher toughness values have been reported by the use of functionalized rubbers (Kinloch, 1989 Huang et al., 1993b). However, these experimental results also reflect the effect of other changes (particle size distribution,... 

The Effect of Physical Aging on the Cavitation Mechanism of Craze... 

Table 2). The Code F material exhibits craze growth by the systematic cavitation mechanism whereas the Code G materials has switched to the interface convolution mechanism which has growth rates over a decade lower, as Fig. 9b shows. This slower growth rate manifests itself in the higher flow stresses for the Code G material. 

In the previous section it was pointed out that thermal stresses, arising from the thermal expansion coefficient mismatch between PS and PB, play a significant role in determining the rate of craze growth for the case of the cavitation mechanism. DiCorleto and Cohen made a detailed examination of the extent... 

Figure 19.34 Schematic presentation of different cavitation mechanisms. (From Reference 12 with permission from Elsevier Inc.)...

Transition from the intact system to a system in which either (a) at, or (b) very near, the interface, either the cavitation mechanism or the Argon "Taylor instability" mechanism has functioned, and voids have formed. Other than void formation, there has been little polymer deformation. 

Keywords Cavitation Mechanical effects Mechanotransduction Self-assembly Streaming Ultrasound-responsive systems... 

Knapp, R.T. (1952). Cavitation mechanics and its relation to the design of hydraulic equipment. 

The cavitation mechanism within the modifier particles begins with microvoid formation and fibrillation in the butyl acrylate shell, as shown in higher magnification in Figure 10b. The fibrillated shells with the internal PMMA cores resemble spiders. The fibrils are connected by the PMMA cores, and the cavities in... 

Pioneering works on the micromechanical deformation mechanisms in block copolymers date back to the mid-eighties when cavitation mechanism in styrene-butadiene (SB) diblock copolymers containing PB cylinders in a PS matrix was proposed (52,53). Based mainly on tern investigations, a two-step craze growth mechanism was proposed ... 

The major theories used to interpret the toughening mechanisms of rubber-modified PP are multiple-crazing, damage competition, shear yielding theories, and microvoid and cavitation mechanisms. The rubber particles in a PP matrix have to be uniform in size, and the interfacial adhesion and morphological structure between the matrix and filler have to be excellent. 

Toughening epoxy matrices using liquid reactive rubbers (such as carboxyl-terminated butadiene acrylonitrile, CTBN, or the amine-terminated equivalent, ATBN) has been widely reported in the literature. Spherical rubber particles of a proper size distribution (usually 1-5 pm) can effectively enhance the toughness through crack blunting or cavitation mechanisms. However, rubber modification of epoxies becomes... 

The cavitation mechanism within the modifier partides begins with microvoid formation and fibrillation in the butyl acrylate shell, as shown in higher... 

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