Tuesday, 12 October 2004 - 4:45 PM

This presentation is part of : Thermalelasticity and Thermal Shock

Preordained Fracture Paths and Tailored Thermoelastic Stress-States to Control/Repair Damage during Dual-Beam Laser Machining of Ceramics

Albert Segall, Guodong Cai, Ravindra Arakrapu, Stephanie Pullford, and Paul Brugan. Penn State University, University Park, PA 16802

During unsupported laser-machining, premature fractures and damage such as chips, burrs, and cracks (micro- to macro-scale) can result. While thermal stresses play a role in this damage, significant biaxial stresses also arise from the bending and twisting moments from the attached scrap. Even if the scrap weight remains relatively constant, mixed-mode fracture is all but inevitable since the supporting section is diminishing as the cut progresses. Given the nature of the resulting biaxial stresses and fracture, it is conceivable that intentionally induced compressive stresses on the surface might be used to control or delay such fractures. In addition, a shallow groove placed ahead of the cut could provide a straight fracture path and avoid damage. This study therefore explores the use of a tailored laser-heating scenario ahead of a progressing cut to “actively” induce compressive thermal-stresses to control fracture. In addition, the use of a simultaneous prescore beam to create shallow grooves that will guide fracture and avoid mixed-mode fractures was also investigated. Finally, the use of a second beam that is both trailing and offset from the main cutting beam was explored as a means to heal damage induced by the cutting process. Finite-element simulations involving melting and ablation were used with probabilistic fracture mechanics to quantify the time and nature of fracture. The effect of important parameters such as laser beam diameter, incident power density, positioning of the laser with respect to cut, as well as timing were then studied.

Back to Thermalelasticity and Thermal Shock
Back to SES Abstracts

Back to The 41st Annual SES Technical Meeting