Ultrasonically damaged surface

However, as shown in Example 11-6, it is possible to avoid the complication of shedding of horn metal into the product, even with direct contact. This is accomplished by (1) controlling power density at the horn surface (watts/cm ) and (2) providing proper maintenance of the horns, including periodic inspection of the probe(s) and machining away tip erosion. Erosion on an ultrasonic horn occurs more rapidly on an already damaged surface. 

The ultrasonic excitation causes small bubbles to form in the liquid the collapse of these bubbles causes abrasion of the surface. The hardened regions are not damaged as much as the surrounding matrix (in contrast to the chemical method described above ) and thus become visible because of differences in light reflectivity. This method is especially effective in removing... 

The development of damage in the form of matrix cracks within 1-D CMCs subject to tensile loading has been traced by direct optical observations on specimens with carefully polished surfaces, and by acoustic emission detection,7 9 62,79-81 as well as by ultrasonic velocity measurements.82 Interrupted tests, in conjunction with sectioning and SEM observations, have also been used. Analysis of the matrix damage found in 1-D CMCs provides the... 

The most common technique involves abrading the substrate surface with hard powders (preferably diamond), or ultrasonic treatment in a slurry of an abrasive powder (preferably diamond grit) in an organic liquid for a prolonged period. This type of pretreatment leads to embedding of the abrasive particulates into the surface as well as mechanical damage to the substrate, both of which are believed to enhance the nucleation density. The maximum nucleation enhancement is observed when diamond grit is used, and this has been attributed to implantation of diamond particles... 

Acoustic energy is mechanical by its nature. Cavitation bubbles are formed, provided that the intensity of ultrasonic field is sufficiently high. Cavitation close to the liquid-solid interface differs from that in pure liquid. Different mechanisms for the effects of cavitation in the vicinity of the surfaces have been proposed microiet imnact and shockwave damage f3. 4V Heterogeneous catalvsis involving... 

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