Ductility, factors affecting

M.F. Horstemeyer, S. Ramaswamy On factors affecting localization and void growth in ductile metals a parametric study. Int. J. Damage Mech. 9, 6-28 (2000)... 

PA-66 (100-80) / EPDM-g-MA (0-20) TSE / mechanical properties / SAXS / SEM / TEM / effects of rubber level and functionality / factors affecting ductile-brittle transition temperature / analysis of fracture surfaces Muratoglu et al., 1995 a, b... 

The influence of chemical and physical structure on the brittle-ductile transition can be analysed by considering how these factors affect the brittle stress curve and the yield stress curve, respectively. As will be appreciated, this approach b3Ttasses the relevance of fracture mechanics to brittle failure. If, however, we consider fracture initiation (as distinct from propagation of a crack) as governed by a... 

As discussed in Young and Lovell (1991) it is hard to believe that general correlations can be derived between the brittle-ductile transition and molecular relaxations (e.g., Tg data obtained by DSC). Molecular relaxations are detected at low strains, whereas T d is measured at high strains and depends on factors such as the presence of notches, which do not affect molecular relaxations. 

There is, however, no generally accepted theory for predicting the brittle-ductile transition or relating it to other properties of the polymer, although for some polymers it is closely related to the glass transition. The type of failure is also affected by geometrical factors and the precise nature of the stresses applied. Plane-strain conditions, under which one of the principal strains is zero, which are often found with thick samples, favour brittle fracture. Plane-stress conditions, xmder which one of the principal stresses is zero, which are often found with thin samples, favour ductile fracture. The type of starting crack or notch often deliberately introduced when fracture behaviour is examined can also have an important effect ... 

We compare the three different types of solutions in order to develop a complementary insight into crack blunting and its meaning for understanding the factors that affect ductile crack growth, particularly in polymers. 

A typical and much studied example of ductility in single crystals is MgO. Parker et al. [6] were the first to suggest that single crystals of MgO could be deformed at RT. Ever since the probability of RT ductility was confirmed, much attention has been given to evaluate the factors that affect such ductility and the mechanical properties of this structure. In addition to the other effects, crystal orientation also affects the deformation of single crystals. Figure 2.33 relates... 

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