Stress intensity factors and fatigue life of beams in reversed bending
AbstractTwo problems concerning the propagation of transverse cracks through beams are studied with a crack modelled as a distribution of dislocations. The first consists of a surface breaking normal crack present in reversing bending, where it is shown that for deep cracks two cycles of loading are experienced for each cycle of applied load. The second is an initially buried normal crack, where stress intensity factors affecting propagation both towards the surface and into the beam are evaluated. The effect on the life of each of these components is then considered for a representative material.
We study the relaxational dynamics of the one-spin facilitated Ising model introduced by Fredrickson and Andersen. We show the existence of a critical time which separates an initial regime in which the relaxation is exponentially fast and aging is absent from a regime in which relaxation becomes slow and aging effects are present. The presence of this fast exponential process and its associated critical time is in agreement with some recent experimental results on fragile glasses. @S0163-1829~96!04426-8#