John G. Harris
Robert E. Johnson
Dept. of Theor. and Appl. Mech., Univ. of Illinois at Urbana-Champaign, 216 Talbot Lab., 104 S. Wright St., Urbana, IL 61801
A model is proposed in this report to describe the potential growth of an existing crack in the structural component caused by collapsing bubbles during ultrasonic cleaning. A local pressure rise is generated by the collapse of a single bubble and the momentum of the collapse is described by the Kelvin impulse I(t). By assuming a uniform pressure distribution and using dynamic fracture mechanics, we obtain a simple relation that expresses the dynamic stress intensity factor K(t) as a function of the Kelvin impulse. Further simplification is achieved by assuming spherical bubble deformation in the description of the Kelvin impulse, as suggested by Blake and Gibson [Ann. Rev. Fluid Mech. 19, 99--123 (1987)], and this leads to a relation between the dynamics of a single bubble and the stress intensity factor K(t). The time history of K(t) is discussed for a completely collapsed bubble obeying the Rayleigh equation. Once the dynamical stress intensity factor exceeds the fracture toughness K[sub IC] crack will start to grow. Repeated action of collapsing bubbles eventually leads to the failure of the component. [Work supported by the Manufacturing Research Center of the University of Illinois.]
All posters will be on display from 8:00 a.m. to 12:00 noon. To allow contributors an opportunity to see other posters, contributors of odd-numbered papers will be at their posters from 8:00 to 10:00 a.m. and contributors of even-numbered papers will be at their posters from 10:00 a.m. to 12:00 noon. Posters will remain on display until 5:00 p.m.