The Conversion of Plastic Work to Heat around a Dynamically Propagating Crack in Metals

Investigations of the temperature rise at a dynamically propagating crack tip using an infrared detector array are reported. Also, a measurement of the fraction of plastic work converted to heat using a split hopkinson bar apparatus in conjunction with an infrared detector array is summarized. For 4340 steel it is seen that ≈85% of the plastic work is converted to heat leading to a temperature rise of 300°C at a crack tip propagating 600 m/s in steel. This results is compared to earlier studies that report a 450°C temperature rise at a crack tip propagating 900 m/s in steel. In a titanium alloy the temperature rise is higher than that in steel for equal plastic work rate densities. The conditions at the crack tip are shown to be adiabatic, and, as a result, this effect is due to the difference in density, heat capacity and crack tip speed. Thermal conductivity has no effect.