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The amount of strain in the stable neck is called the natural draw ratio [6] because it is determined by the material's hardening characteristics, not the amount of drawing imposed on the material. Ductile polymers often exhibit stable necks because molecular orientation provides a mechanism for hardening that predominates at large strains. [7]
A number of different methods are used to evaluate a polymer's resistance to environmental stress cracking. A common method in the polymer industry is use of the Bergen jig, which subjects the sample to variable strain during a single test. The results of this test indicate the critical strain to cracking, using only one sample. [5]
A sample is mounted on the grips and the environmental chamber can slide over to enclose the sample. Polymers composed of long molecular chains have unique viscoelastic properties, which combine the characteristics of elastic solids and Newtonian fluids. The classical theory of elasticity describes the mechanical properties of elastic solids ...
A sample of objects that have an inconsistent size, shape and mass distribution is called non-uniform. The objects can be in any form of chemical dispersion, such as particles in a colloid, droplets in a cloud, [1] crystals in a rock, [2] or polymer macromolecules in a solution or a solid polymer mass. [3]
The stresses in a structure can be determined by making a model of the structure from such a photoelastic material. Dynamic mechanical analysis (DMA) is a technique used to study and characterize viscoelastic materials, particularly polymers. The viscoelastic property of a polymer is studied by dynamic mechanical analysis where a sinusoidal ...
This movement or rearrangement is called creep. Polymers remain a solid material even when these parts of their chains are rearranging in order to accommodate the stress, and as this occurs, it creates a back stress in the material. When the back stress is the same magnitude as the applied stress, the material no longer creeps.
Poisson's ratio of a material defines the ratio of transverse strain (x direction) to the axial strain (y direction)In materials science and solid mechanics, Poisson's ratio (symbol: ν ()) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading.
An oscillating force is applied to a polymer sample and the sample’s response is recorded. DMA documents the lag between force applied and deformation recovery in the sample. Viscoelastic samples exhibit a sinusoidal modulus called the dynamic modulus. Both energy recovered and lost are considered during each deformation and described ...