Stress relaxation mechanism

These stresses can reach values as high as flow stress values, and then induce some stress relaxation mechanisms which can include plasticity and/or spontaneous cracking. Meanwhile, if the internal stress levels are lower, any external stress can be critical, and promote a damage mechanism, similar to those previously described. 

In order to design the optimum structure of FGM for stress-relaxation, mechanical and thermal property data of each layer at the practical used temperature are greatly needed, but in the recent work on FGM of PSZ/IN 100, most of such data are obtained only at room temperature. ... 

Theoretical studies of the dynamics of self-assemblies of wormlike surfactant micelles have been reported by a number of investigators, such as Cates and coworkers [Turner and Cates, 1991 Marques et al 1994]. Since they are subject to reversible scission and recombination, they are called living polymers. The continuous breaking and repair of the micellar chains provides more complex solution behavior than do reptating polymer chains that is, their stress relaxation mechanisms are a combination of reptation and breaking followed by reassembly. At low frequencies, linear viscoelastic (Maxwell) behavior is predicted and observed for some surfactant systems. However, non-Maxwell behavior was observed in Cole-Cole plots of a number of cationic surfactant systems [Lu, 1997 Lin, 2000]. 

In conclusion, the experimental results favor a stress-relaxation mechanism in semicrystalline PTMT which occurs primarily by slippage ptxxesses of chain aments thereby homogenizing the transformation of forces between the OTstallites by the intercrystalline segments with only a small contribution from the reversal of extended structural units to the crumpled a-form in the region of the critical stress. 

Viscoelasticity is a phenomenon observed in most of the polymers since they possess elastic and viscous characteristics when deformed. The properties such as creep, stress relaxation, mechanical damping, vibration absorption and hysteresis are included in viscoelasticity. If a material shows linear variation of strain upon the application of stress on it, its behavior is said to be linear viscoelastic. Elastomers and soft biological tissues undergo large deformations and exhibit time dependent stress strain behavior and are nonlinear viscoelastic materials. The non-linear viscoelastic properties of solid polymers are often based on creep and stress-... 

Guo, Y. and Bradshaw, R.D. Isothermal physical aging characterization of polyether-ether-ketone (PEEK) and polyphenylene sulfide (PPS) films by creep and stress relaxation, Mechanics of Time-Dependent Materials, 2007, 11(1), p. 61-89. 

Several rheological studies showed that solutions of telechelic polymers submitted to oscillatory shear exhibit a Maxwellian behavior (single relaxation time). ° ° This behavior was explained by assuming that the main stress relaxation mechanism is the exit of one hydrophobe from the... 

Stress relaxation describes the time-dependent deformation behavior of a material under constant displacement, which is evaluated by measuring the stress reduction with time. The evaluation of the stress relaxation process is necessary in order to assess the eflect of hold periods in the thermomechanical fatigue behavior of solder joints. Understanding of the stress relaxation mechanisms is important because the deformation processes involved in stress relaxation are fairly representative of the stress history experienced by solder joints at the temperature extremes of thermal cycling experienced in service. Thus the stress relaxation behavior may be a better... 

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