Critical plastic energy density

An alternative criterion which includes adhesive plasticity is to use a value of critical plastic energy density. Harris and Adams [10] included a small degree... 

The elasticity of the skin shell of the pore is always higher than the bulk interior because the elasticity is proportional to the energy density though the total energy stored in the shell may be lower than the entire sphere beyond the critical size. For plastic deformation, the hollow sphere could be tougher than the ideal bulk because of the long-distance effect in the indentation measurement. On the other hand, the thermal stability of the hollow sphere is always lower than the solid sphere [71]. 

Thermal vibration of the atoms, hence the thermal energy of the polymer, increases with absolute temperature T (for gas molecules the thermal energy is 3/2RT where R is the gas constant 8.3JK mol ). When the thermal energy exceeds a critical value (at Tg), free volume is available for molecular motion. It is likely that the free volume is non-uniformly distributed in the melt, and that a number of lower density regions move rapidly through the melt (rather as dislocations move through a crystal lattice to allow plastic deformation). 

The strain energy release critical rate Gj, characterizing polymer local plasticity level (see the Eq. (5.13)), is coupled with material structure. The higher entanglements cluster network density v, is the more intensively shear local deformation mechanism is realized [13], and the larger Gj is. This means, that growth should result to Gj reduction. Actually, for PASF considered samples such correlation was obtained and it can be approximated by the following relationship [1] ... 

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