12/14/17: Prof. Lee gives an invited talk at Stanford ME Department


Microscopic high-strain-rate mechanical characterization using laser-propelled particles

Precise techniques applying mechanical deformation at the micro-scale, such as an atomic force microscope, nanoindenters, or micromanipulators, have become more conventional in a wide range of disciplines. Due to the quasi-static nature of these techniques, the object being deformed stays near equilibrium. As a deformation speed becomes comparable to the speed of sound of constituent materials, however, corresponding mechanical responses cannot simply be extrapolated from those at the quasi-static conditions, due to various dynamic and nonlinear effects.

My group has worked with a microscopic ballistic technique called Advanced Laser-Induced Projectile Impact Test (α-LIPIT) to provide the high-strain-rate mechanical characteristics of various materials ranging from conventional materials to novel nanomaterials. In this talk, I will introduce our recent progress on the high-strain-rate study using α-LIPIT with metals, ceramics, polymers, and nanomaterials. Highly-controlled single micro-projectile impact experiments are carried out and the ultrafast optical microscopy, which utilizes femtosecond laser pulses, enables precise quantification of the micro-projectile’s motion during the high-speed collision events. Based on the tracking of the projectile motion, the real-time force applied by the projectile can also be defined explicitly.