Abstract
Methods have been developed for the measurement of macro- and micro-stresses in commercially pure titanium (IMI.130) and macrostresses in 6%Al-4%V titanium alloy (IMI.318A). Macro-stresses we re measured by the X-ray line shift technique, using both the film and diffractometer methods. Micro-stresses were measured by the X-ray line broadening technique, using a diffractometer, and 'line' profiles were analysed by the integral breadth method. The accuracy of macro- and microstress measurement is discussed. Good agreement was obtained in the measurement of macro-stresses in IMI.130 and IMI.318A deformed unidirectionally in four point loading, with X-ray diffraction methods, strain gauges and bending theory. The residual macro-stresses only occur in titanium after it has been plastically deformed and are intimately connected with the X-ray limit of proportionality The effect of deformation in unidirectional and uniaxial tension on the applied and residual macro-stresses in IMI.130 is discussed in the light of current theories and a hypothesis is put forward regarding the existence and measurement of residual lattice strains. The effects of grinding, machining or shot peening on the residual macro- and micro-stresses in IMI.130 and macro-stresses in IMI.318A. are discussed. It is concluded that the deformation processes give rise to both residual macro- and micro-stresses. The various deformation processes produce different patterns of macro- and micro-stress distribution, thus show ing the importance of measuring both types of stresses. Comparison is made between the modes of deformation in shot peened, machined surfaces and in plastically deformed specimens in uniaxial tension. Recommendations for future work are stated.