The current development of digital image correlation, whose displacement uncertainty is well below the pixel value, enables one to better characterise the behaviour of materials and the response of structures to external loads. A general presentation of the extraction of displacement fields from the knowledge of pictures taken at different instants of an experiment is given. Different strategies can be followed to achieve a sub-pixel uncertainty. From these measurements, new identification procedures are devised making use of full-field measures. A priori or a posteriori routes can be followed. They are illustrated on the analysis of a Brazilian test.

Digital Image Correlation: From Displacement Measurement to Identification of Elastic Properties - A Review

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Digital Image Correlation: from Displacement Measurement to Identification of Elastic Properties – a Review

When polyethylene (PE) is deformed to large strains, the stress originates from both the viscous forces associated with the plastic deformation of the crystallites by slip and fragmentation processes and the entropic elastic forces arising from the stretching of the entangled amorphous regions. Relative weights of the different processes change with the crystallinity. The dependencies were analyzed in a comprehensive study on a series of samples encompassing a large range of crystallinities:  PE, low-density PE (LDPE), and ethylene−vinylacetate copolymers. The comparison was based on measured true stress−strain curves for constant strain rates. For the samples with higher crystallinity, which show a necking, this was achieved by employing a video-controlled tensile testing machine. Recovery properties of the sample were studied in step-cycle runs, where the load was applied stepwise and interrupted after each step by an unloading−reloading loop. Simultaneous with the mechanical testing, the related textur...

Network Stretching, Slip Processes, and Fragmentation of Crystallites during Uniaxial Drawing of Polyethylene and Related Copolymers. A Comparative Study

Poly (lactic acid) blends: Processing, properties and applications.

Radical Polymerization and Copper(0) Mediated Polymerization): From Fundamentals to Bioapplications Cyrille Boyer,*,†,‡ Nathaniel Alan Corrigan,‡ Kenward Jung,‡ Diep Nguyen,‡ Thuy-Khanh Nguyen,‡ Nik Nik M. Adnan,†,‡ Susan Oliver,†,‡ Sivaprakash Shanmugam,‡ and Jonathan Yeow†,‡ †Australian Centre for Nanomedicine, and ‡Centre for Advanced Macromolecular Design (CAMD), School of Chemical Engineering, University of New South Wales, Sydney 2052, Australia

Copper-Mediated Living Radical Polymerization (Atom Transfer Radical Polymerization and Copper(0) Mediated Polymerization): From Fundamentals to Bioapplications

A novel technique has been developed to record the intrinsic plastic behaviour of ductile materials by monitoring the effective strain and the effective stress in the mid-plane of hour-glass-shaped tensile specimens. The method utilizes a computer-aided video extensometer which analyses the sample profile in real time. The effective strain is computed automatically from the minimum diameter, and the effective stress is deduced from the applied load by taking into account the stress triaxiality corresponding to the local radius of curvature of the sample profile. Furthermore, a digital closed-loop system controls the ram speed of the hydraulic tensile testing machine in such a way that the local effective strain rate is maintained at a constant value. It is shown that most polymeric and metallic materials are entitled to be investigated by this method, which gives access in real time to the constitutive plastic equation, up to strains far beyond the necking point. The capabilities of the technique are illustrated and discussed critically, with more details for two polymers of different structures: polyethylene and polycarbonate.

J.M. Hiver

Papers

Video-controlled tensile testing of polymers and metals beyond the necking point

Experimental characterization of deformation damage in solid polymers under tension, and its interrelation with necking

Characterization of volume strain at large deformation under uniaxial tension in high-density polyethylene

Deformation and damage upon stretching of degradable polymers (PLA and PCL)

Microstructures and mechanical properties of polypropylene/polyamide 6/polyethelene-octene elastomer blends