Embrittlement history

The cracking susceptibility of a micro-alloyed HSLA-100 steel was examined and compared to that of a HY-100 steel in the as-received condition and after heat treatment to simulate the thermal history of a single pass weld. Slow strain rate tensile tests were conducted on samples of these alloys with these thermal histories in an inert environment and in an aqueous solution during continuous cathodic charging at different potentials with respect to a reference electrode. Both alloys exhibited reduced ductilities at cathodic potentials indicating susceptibility to hydrogen embrittlement. The results of these experiments will be presented and discussed in relation to the observed microstructures and fractography. 

The inplane shear stress-strain tests reported here have been well demonstrated to be a reliable test for matrix-dominated properties in composites 141). For the selected mechanical properties that were monitored, their sensitivity to the thermal history was well demonstrated. In particular, the embrittlement process during the sub-Tg annealing or physical aging has been clearly observed. This decrease in molecular mobility, which gives rise to an increase in relaxation time and hence a decrease in toughness, can be rationalized as a decrease in free volume in an approach towards the equilibrium glassy state. 

Nineteen archaeological pre-Columbian textile specimens from the collections of the American Museum of Natural History and the Metropolitan Museum of Art were examined. The textiles (Huari/Tiahuanaco, lea, Paracas-Caver-nas, and Paracas-Necropolis) are described. Elemental analyses for archaeological textile and modern wool samples (C, H, N, S, and ash) are reported. Elemental analyses for samples treated with distilled H20 and CClk are compared with analyses of modern wool samples similarly treated. An unambiguous direct correlation between loss of sulfur and embrittlement could not be made. The possibilities of dating and provenance determination by technical means are discussed. 

While it may be true that many materials will become severely embrittled or discolored before Stage III is far advanced, some special situations exist in which a polymeric system can be regarded as being in Stage IV. For example, in the life history of polymers that tend to crosslink when exposed to near ultraviolet radiation, the conservator may have to remove them or at least have a sound understanding of their swelling properties in solvents under conditions in which the films are in Stage IV with respect to the formation of insoluble matter (27). In a similar sense,... 

The second condition to validate the scheme B is that embrittlement must correspond to a critical morphological state that is the only approach to explain its sudden character. The extensive and careful work of Kennedy et al. (//) on relationships between fracture behavior, molar mass and lamellar morphology, shows that this condition is fulfilled in the case of PE. Comparing various samples of different molar masses with different thermal histories, they found that the thickness of the amorphous layer (la) separating two adjacent lamellae is the key parameter (Fig. 6). As a matter of fact, there is a critical value lac of the order of 6-7 nm. For la > lac the samples are always ductile whatever their molar mass, whereas for U < laC the samples are consistently brittle. As a result, lac appears to be independent of the molar mass. Indeed, there is a specific molar mass, probably close to 70 kg.mof for PE below which crystallization is so fast that it is impossible to have la values higher than lac whatever the processing conditions. 

Consequently inter-laboratory comparisons of uv stability of polymers and the effects of uv stabilisers is normally difficult if not impossible. There is evidence that in some cases the role of photostabilisers has been confused with that of thermal stabilisers since the two are mechanistically related (11). Just how important can be the prior thermal history of polyethylene on its uv stability is shown in Figure 1 which relates the processing time under standard conditions to the time to embrittlement in a standard sunlamp / blacklamp (S/B) environmental simulator. Figure 1 also shows the... 

Changes in the residual elongation at break for four filaments of varying draw history are shown in Figure 6. From Figure 6a, which is based on the time taken to halve the initial elongation at break, it is obvious that photosensitivity as measured by embrittlement increases in the sequence highly oriented (hot drawn X6 at 180°), << undrawn partially oriented (hot drawn X2.5 at 180°) << cold drawn (X3 at 25°C). 

Abstract An embrittlement correlation method is a technique to calcnlate the expected amonnt of neutron irradiation embrittlement for the material of interest at a given time using the information on the material chemistry, irradiation conditions, etc. The first embrittlement correlation method was developed in the 1970s. Since then, different methods have been developed worldwide based on improved nnderstanding of the mechanisms of embrittlement and also on the enhanced snrveillance databases compiled in different countries. In this chapter, the history of the development of embrittlement correlation methods is reviewed first, followed by detailed descriptions of the representative methods together with their background. 

In this chapter, the history of embrittlement correlation methods will be reviewed hrst, followed by descriptions of the representative embrittlement correlation methods in different countries. In particular, the embrittlement correlation methods developed over the last several years are explained in detail. 

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