Product Code: ICAL05_1207

Active Stressing and the Control of Macro-Scale Damage in Unsupported Ceramics During Laser Machining
Authors:
Albert Segall, The Penn State Univ.; University Park PA USA
Guodong Cai, Penn State; University Park PA USA
Paul Brugan, Penn State; University Park PA USA
Ravindra Akarapu, Penn State; University Park PA USA
Stephanie Pullford, The Penn State Univ.; University Park PA USA
Presented at ICALEO 2005

The low-force signature of lasers makes them very attractive for the machining of ceramics. Unfortunately, unwanted damage ranging from micro-cracks to macro-scale fracture including chips and burrs still plagues the practice, especially during unsupported machining. Because this damage is costly, studies on the use of simultaneous C02 beams to help control and/or avoid fracture are under way. As demonstrated by the research, the use of a lower-power beam to create shallow grooves or prescores to control fracture was very successful, even under exaggerated mixed-mode conditions typical of unsupported cutting. In addition, the use of prescores was also shown to increase cutting-rates without fracture almost 2x for thicker ceramics. Studies have also focused on a reduced power prescore that can no longer melt/ablate the surface, but is capable of inducing advantageous compressive thermoelastic-stresses to delay/control fracture. Finite-element modeling using a customized algorithm and probabilistic fracture mechanics has revealed safe beam-spacing and the parameters necessary for successful prescoring and active stressing.