Necking

About: Necking is a research topic. Over the lifetime, 5280 publications have been published within this topic receiving 113945 citations.

Identification of the constitutive equation by the indentation technique using plural indenters with different apex angles

Abstract: This paper describes a novel technique for determining the constitutive equation of elastic–plastic materials by the indentation technique using plural indenters with different apex angles. Finite element method (FEM) analyses were carried out to evaluate the effects of yield stress, work hardening coefficient, work hardening exponent, and the apex angle of indenter on the load–depth curve obtained from the indentation test. As a result, the characterized curves describing the relationship among the yield stress, work hardening coefficient, and the work hardening exponent were established. Identification of the constants of a constitutive equation was made on the basis of the relationship between the characterized curves and the hardness given by the load–depth curve. This technique was validated through experiments on Inconel 600 and aluminum alloy. The determined constitutive equation was applied to the FEM analyses to simulate the deformation including necking behavior under uniaxial tension. The analytical results are in good agreement with experimental results.

Strain localization and damage development during bending of Al–Mg alloy sheets

Abstract: The mechanism triggering failure during deformation in Al–Mg alloys often includes localization of the plastic flow into narrow and intense transgranular shear bands propagating through the microstructure with little evidence of damage prior to the final fracture event. The cracks initiate in the sheared zones and propagate by conventional ductile mechanism of fracture, including nucleation of voids at second-phase particles, followed by their growth and ultimate coalescence. In an attempt to fully understand the mechanism of damage in continuous cast (CC) AA5754 aluminium alloy sheet, a methodology for characterization of the microscopic fracture strain distribution during bending was adopted in this work. A batch of digital images representing the deformation history of the samples bent during in situ V-bending tests performed in a scanning electron microscope (SEM) was recorded and later used as an input to a digital image correlation system (DIC) for strain calculations. Local strain maps of the tensile through-thickness cross-section of the bent sheets were built. The results clearly reveal development of spatial inhomogeneity of the strain at microscopic level. The strain concentration inside the formed intensive shear bands, which were the predecessors of the subsequent crack propagation, was found to be considerably larger than the macro-strains typically suggested by the forming limit diagrams for aluminium sheet materials. The presented results are consistent with previously published results on the general forming characteristics of continuous cast AA5754 aluminium alloy sheet materials.