Mechanical Response of M30, XM39, and JA2 Propellants at Strain Rates from OneOne-hundredth to 250 per second

摘要

The mechanical response of M30, XM39, and JA2 gun propellants at strain rates from .01 to 250/sec is characterized using the BRL's new Hi-Rate Servohydraulic test apparatus. At axial strain rates of 250/sec, there is good experimental agreement between the compressive moduli determined on the drop weight and servohydraulic apparatuses, yet the post-yield responses vary because of differing displacement history inputs. All three propellants deformed in a ductile fashion and sustained over 40% shortening. The M30 and XM39 propellants deformed by macroscopic fracture and work-softened after reaching maximum stress. The JA2 propellant deformed by macroscopic flow and work-hardened throughout the deformation history. The absorbed strain energy density per unit volume at 30% shortening and strain rate of 250/sec, is 16 and 23 MPa for the XM39 and M30 propellants, respectively. In contrast, the absorbed strain energy density for the JA2 propellant is only 8 MPa and is due to the relatively low flow stress sustained by the material during deformation. A viscoelastic characterization reveals that the secant and relaxation moduli for these propellants can be represented by a power law in time with nonlinear behavior in the time range from .01 to .0001 millisecs.