INVESTIGADORES
PETTARIN Valeria
congresos y reuniones científicas
Título:
Multiaxial deformation of propylene polymers
Autor/es:
LAURA FASCE; CLAUDIA MARANO; VALERIA PETTARIN; MARTA RINK; PATRICIA FRONTINI
Lugar:
Los Cocos, Córdoba, Argentina
Reunión:
Simposio; III Simposio Argentino-Chileno de Polímeros ARCHIPOL III; 2005
Resumen:
Engineering components may be subjected to complex loading in tension, compression, bending, torsion, or pressure, or combinations of these. If sufficiently severe, such combined stresses can act together to cause the material to yield or fracture. Predicting the safety limits of a material under combined stresses requires the application of a failure criterion. The yield behavior of polymer solids, unlike most metals, depends upon the mean normal stress as well as the deviatoric components of the applied state of stress (Quinson, 1996). This means that deformation behavior in polymers is very sensitive to hydrostatic pressure (Caddell, 1974). Yield criteria modified to account for the effect of hydrostatic pressure Modified Von Mises and Modified Tresca- are usually employed to describe yielding behaviour of polymers.
The modified Von Mises criterion can be written as:
(1)
in which toct and P are the octahedral shear stress and pressure respectively, which can be expressed in terms of the principal stresses, as :
(2)
(3)
The modified Tresca criterion can be formulated as:
(4)
in which tT , the maximum shear stress, can be expressed in terms of the principal stresses as:
(5)
The parameters tooct and tT are the limiting octahedral shear stress and shear yield stress under zero pressure, respectively. The pressure coefficients mVM and mT quantify the yield stress sensitivity to pressure.
In this work, several polypropylene polymers were subjected to different stress states in order to find an appropiatte criterion which predicts their failure limits by yielding under multiaxial loading conditions.
