Using Digital Image Correlation (DIC) in Dynamic Punch Tests

A dynamic punch test in which three dimensional digital image correlation (DIC) is used to measure the deformation of the rear surface of a disk specimen is introduced. Flat, round Ti-6Al-4V disk specimens are clamped to a custom die fixture that is attached to the transmitter bar of a compression split-Hopkinson bar (SHB) apparatus. A tungsten carbide punch is attached to the incident bar and positioned such that it is in contact with the disk. During a test, a compression wave is introduced into the incident bar which causes the punch to penetrate into the specimen. The die fixture is slotted on both sides such that the rear surface of the disk specimen is visible to two high speed cameras. This provides a stereographic view of the specimen that is used to measure full-field displacement directly on the specimen with three dimensional DIC. The contact force between the punch and the disk is determined from the wave in the transmitter bar. Quasi-static tests using the same fixtures are conducted on a servo-hydraulic load frame. Results from tests with punches of various geometries show that the punch geometry greatly influences the punching force and the failure mode. Forces in the dynamic tests are higher than in the quasi-static tests. The 3D DIC measurements provide data that can be used to construct and validate deformation failure models.