Commercially pure (99 per cent) aluminium has been subjected to high-strain low-endurance torsional fatigue under conditions of constant strain rate. (In this paper 'strain' and 'strain rate' refer to conditions at the surface of the specimen and therefore apply to the zones in which cracks are initiated.) Tests were performed at 20'C (0.315TM) and were controlled between constant torque limits of equal but reversed magnitudes.Below a critical strain rate, pCrl,, the fatigue life obeys the law for a constant torque range. When p exceeds ycrlt there is no significant strain-rate effect on fatigue endurance.It is suggested that cyclically activated creep mechanisms cause significant damage at strain rates less than Ycrit.A relaxation behaviour was observed after the first quarter cycle when torque ranges were greater than a critical level of 2T,,,,. A similar phenomenon was observed at ranges less than 2Tc,,, with straining rates less than P~,~~ but only when the specimens were close to failure and the initial cyclic hardening had been removed by cyclic softening. In consequence fatigue endurances were found to be less sensitive to torque at ranges greater than 2T,,,,.Cumulative strain (cyclically induced creep) occurred at all torque ranges and straining rates. Minimum cumulative strains occurred at a torque range of 2TCr1, with the value of TcrIt having a minimal dependence on the straining rate. The ratio of time to cyclic-dependent processes that contribute to failure is itself dependent on both the torque range and the straining rate. However, a single curve suffices to represent all results if a total strain path to failure criterion is adopted.

To study the potential alternative hosts to Potato virus Y (PVY), thirteen different plant species/cultivars, Solanum tuberosum cv. Spounta L., S. tuberosum cv.

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