LOCAL HEATING BY PLASTIC DEFORMATION AT A CRACK TIP.

Abstract : This paper presents calculations of the temperature elevations accompanying rapid plastic deformation near a crack tip. Solutions for the stress and strain distribution in non-hardening materials are employed as a basis for the heating rate distribution. Results are approximate in that temperature independent mechanical and thermal properties are assumed and thermal stressing is neglected. Two cases are considered: a stationary crack under increasing load, and a running crack with locally constant speed and plastic zone size. Numerical results are presented as based on properties of 2024 aluminum alloy, 6Al-4V titanium alloy, and mild steel. Temperature rises predicted for test conditions on these metals seldom exceed 100C. This may, nevertheless, be large enough to influence fracture and to account for the observed rise in roughness at very fast rates. Consequences are examined for the assumption that the localized tip temperature elevation alone governs fracture toughness at very fast rates. (Author)