MEASUREMENT AND FE-MODELING OF THE EFFECTS OF STRESS TRIAXIALITY ON THE NECK INITIATION AND FAILURE OF HIGH-DENSITY POLYETHYLENE

This study analyses the tensile deformation of neck i.e localization initiation, propagation and failure of injection-moulded polymer composed of high-density polyethylene (HDPE) as a function of initial stress triaxiality. Three different specimen geometries namely i) Simple tension, ii) Plane strain and iii) Shear specimens were punched from injection-moulded HDPE plates and tested experimentally in uniaxial tension to induced different stress triaxialities. Based on the major-minor strain paths from digital image correlation (DIC) measurements stress triaxiality has been calculated. It is challenging to follow the stochastic pattern at larger local strain in DIC and hence the strain at failure has been measured using orthogonal grid lines on the specimen surface. Strains at neck-initiation and failure at three different stress triaxialities for injection-moulded HDPE in two material orientations were implemented in finite lement model. ISIGHT with Abaqus was used for calibration of hardening behaviour, triaxiality dependent neck initiation and failure.
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