A gas gun based technique for studying the role of temperature in dynamic fracture and fragmentation

Presented in this work is a new experimental technique to facilitate studies of materials under uniform radial expansion at rates of strain typically seen in ballistic and impact studies (10³ to 10⁵ s ^-1) at temperatures around 100-1000 K. Previous work places a right-cylinder polymer insert in a sample cylinder, into which a matching polymer projectile is launched using a gas gun. The impact and resulting deformation of the polymers imparts radial momentum to the cylinder. This work replaces the polymer insert with a steel ogive. A polycarbonate projectile deforms around the insert and drives radial expansion. The uniform radial expansion created has a less complex interface than previous work as only one material is driving the cylinder wall. As deformation of the insert is no longer necessary, the opportunity to heat or cool the cylinder prior to expansion is now available for studies into the effect of temperature on fracture and fragmentation behavior. This paper describes the design of this new impact configuration alongside how strain rate and expansion profile can be controlled. Validation experiment results with 6061-T6 aluminum and Ti-6Al-4V cylinders using a variety of diagnostics are compared with numerical modelling, where the benefits of this technique in assisting development of material strength and failure models are discussed with methods to control the sample temperature.