Cylindrical test samples were compressed statically and dynamically at temperatures ranging from +100 to -195°C and the yield stress, form of yield and surface markings observed. A Hopkinson bar and throw -off rod and electric resistance strain gauges were used for stress determinations under dynamic loads. The stress necessary to in intiate yield rises steeply with fall in temperature and is accompanied by a change in mechanism of deformation from normal slip to the formation of Neumann lamellae at a critical temperature. The critical temperature is higher under dynamic loading, but there appears to be a critical stress for the formation of Neumann lamellae, whether caused by high rates of loading or low temperatures.
A History of the development at Cambridge of a notch tensile test for the investigation of brittlencss in structural mild-steel is described. The test procedure and the methods of assessing the temperature limit at which the material becomes brittle are outlined in Part I. Investigations of material from an oil storage tank and from ships which fractured in service show that this notch tensile test gives good correlation with these casualties whatever the nominal stress in the plates at the time of the fracture. The results of Charpy V-notch and Izod tests are given for comparison, and it is shown that the energy absorption criterion used in these tests may be misleading (Fart II). In Part III experiments are described in which the tensile test has been used to predict performance in test-pieces of more complicated geometric form. Criticisms of the notch tensile test are dealt with in Part IV. In the conclusions, attention is drawn to the fact that the designer of orthodox fabricated structures must be provided with material which is ductile at all operating temperatures and at all stress levels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.