IHS ESDU Fatigue crack propagation rates and threshold stress intensity factor ranges for titanium alloy plate, bar and forgings. 82015

Constant amplitude fatigue crack propagation rate (da/dN) data are provided for several titanium alloys commonly used in the aerospace industry. The data have been derived from tests conducted in air at room temperature with, in most cases, uncontrolled humidity. The loading frequencies were generally in the range 0.1 to 100 Hz though some data were obtained from tests conducted at 1000 Hz. Generally measurements of crack length were made using either optical methods or potential drop techniques. Mean da/dN curves are presented in terms of the stress intensity factor range and the stress ratio. Where possible the upper limit of scatter of the data is also provided. The range of da/dN covered is from 1E-4 m/cycle (3.9E-3 in/cycle) down to 1E-11 m/cycle (3.9E-10 in/cycle). The data analysed to calculate the threshold stress intensity factor range were obtained from tests that provide low crack propagation rates (in the range 1E-8 m/cycle (3.9E-7 in/cycle) to 1E-11 m/cycle. The effects of variations in the stress ratio, specimen thickness, grain flow, environment, heat treatment and microstructure are discussed. There are particular references to the effects of texture, grain size and dwell time. Details of all the alloys and types of test specimens are tabulated and summary da/dN curves that compare the performance of the different alloys are given. Curves showing the effect of variations in the value of stress ratio at threshold for the various alloys are also presented.