High strain rate compression and tension response of high hard tool steel

The cores of armor piercing (APM2) bullets are generally made of high hard (Rc ≈ 60-62) 1070 steel. Tool steel of type AISI O1 is very similar in composition to 1070 steel and can be heat-treated to Rc 60-61. We are conducting a study to generate material model data to numerically simulate the penetration of .30 and .50 caliber M2AP bullets into a variety of ceramic/aluminum/steel ballistic targets. Compression and tension properties of heat treated tool steel are to be presented. The compressive and tensile behavior of AISI O1 tool steel is studied through quasi-static tests, Hopkinson bar experiments and Taylor impact tests. Compressive strength of the heat-treated tool steel increases by a factor of 3 compared to untreated tool steel. Furthermore, experimental data suggest that hard tool steel is strain rate insensitive in tension as well as in compression. However, measured compressive strength (3.5 GPa) and tensile strength (2.5 GPa) at high strain rates (103/s) are different, suggesting that the material behaves almost like a ceramic. A constitutive model for the material is developed based on the experimental data and is used to simulate ballistic penetration into 6061-T6 aluminum and alumina ceramic/aluminum targets

Development of Procedure for Low-Constraint Toughness Test-ing Using a Single-Specimen Technique

both used in common the use of a clamped single-specimen of similar geometry and relied on the unloading compliance technique for crack size estimation. In the former case, a single clip gauge is attached to the integral knife edge and the crack-tip opening displacement (CTOD) is estimated by means of a J-integral-to-CTOD conversion, similar to the procedure of ASTM E1820-11. The latter uses a pair of clip gauges mounted on an attachable raised set of knife edges to estimate CTOD at the original crack tip position by a triangulation rule. Consolidating these two sets of clip gauges in a specimen makes direct comparisons of two SE(T) methods under identical test conditions: material, specimen geometry, equipment, test temperature, and operator (Weeks et al., 2013, "Fracture Toughness Instrumentation Techniques for Single-Specimen Clamped SE(T) Tests on X100 Linepipe Steel: Experimental Setup," 6th Pipeline Technology Conference, Ostend, Belgium). In this study, SE(T) testing employing these two SE(T) methods on a single specimen was conducted on B Â B shallowcracked (a/W $ 0.35) specimens of two X70 pipeline girth welds. This paper discusses details of the two SE(T) methods and techniques on the same specimen