Nucleation and Growth of Cracks in CVD ZnS Under Particle Impact.
Abstract
This research program was undertaken to identify and evaluate material properties governing fracture damage development in a laser window material under hard particle impact. The approach was to determine the sequential development of fracture damage in a ceramic in the vicinity of a particle impact site, to quantitatively assess the population of radial cracks, and to deduce crack nucleationand growth expressions and properties by correlating the damage with an appropriate load parameter. Individual 800-micrometers-diameter tungsten carbide (WC) spheres were accelerated in a pneumatic gun to velocities up to 80 m/s and made to impact polished surfaces of chemical-vapor-deposited zinc sulfide (CVD ZnS) to produce various levels of impact damage in the form of a plastic impression anda population of cracks. The size distributions of radial cracks were determinedas a function of plastic impression radius (see Figure 7). The shapes of the crack size distribution curves suggest that the size distribution of inherent flaws is exponential, consistent with the results of probability theory. These curves further suggest that the growth law for radical cracks is similar in form to expressions derived from elastic energy balances.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1979
- Accession Number
- ADA069528
Entities
People
- D. A. Shockey
- Damian Curran
- K. C. Dao
Organizations
- SRI International