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Cyclic deformations of polypropylene with a strain‐controlled program
Author(s) -
Drozdov A.D.,
Dusunceli N.
Publication year - 2012
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.23188
Subject(s) - materials science , viscoelasticity , composite material , tacticity , polypropylene , viscoplasticity , stress (linguistics) , logarithmic scale , hysteresis , strain (injury) , softening , polymer , constitutive equation , structural engineering , finite element method , polymerization , medicine , linguistics , philosophy , physics , acoustics , quantum mechanics , engineering
Experimental data are reported on isotactic polypropylene in uniaxial tensile cyclic tests with a strain‐controlled program (oscillations between fixed minimum and maximum strains). The following characteristic features of stress–strain diagrams are observed: (i) logarithmic decay in maximum and minimum stresses with number of cycles (cyclic softening), (ii) more pronounced reduction in minimum stress than in maximum stress (cyclic strengthening), (iii) independence of rates of decrease in maximum and minimum stresses of strain rate, (iv) decrease in hysteresis energy with number of cycles. To rationalize these observations, a constitutive model is derived in cyclic viscoelasticity and viscoplasticity of semicrystalline polymers. Numerical simulation demonstrates that the model correctly describes experimental stress–strain curves and quantitatively predicts evolution of maximum and minimum stresses with number of cycles. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers