A model for the axisymmetric growth and coalescence of small internal voids in elastoplastic solids is proposed and assessed using void cell computations. Two contributions existing in the literature have been integrated into the enhanced model. The first is the model of Gologanu-Leblond-Devaux, extending the Gurson model to void shape effects. The second is the approach of Thomason for the onset of void coalescence. Each of these has been extended heuristically to account for strain hardening. In addition, a micromechanically-based simple constitutive model for the void coalescence stage is proposed to supplement the criterion for the onset of coalescence. The fully enhanced Gurson model depends on the flow properties of the material and the dimensional ratios of the void-cell representative volume element. Phenomenological parameters such as critical porosities are not employed in the enhanced model. It incorporates the effect of void shape, relative void spacing, strain hardening, and porosity. The effect of the relative void spacing on void coalescence, which has not yet been carefully addressed in the literature. has received special attention. Using cell model computations, accurate predictions through final fracture have been obtained for a wide range of porosity, void spacing, initial void shape, strain hardening, and stress triaxiality. These predictions have been used to assess the enhanced model. (C) 2000 Elsevier Science Ltd. All rights reserved.

An extended model for void growth and coalescence - application to anisotropic ductile fracture

http://www.iust.ac.ir/files/mech/javanrodi_819ec/experimental_and_numerical_evaluation_of_forming_limit_diagram_for_ti6al4v.pdf

Experimental and numerical evaluation of forming limit diagram for Ti6Al4V titanium and Al6061-T6 aluminum alloys sheets

Mechanical and anisotropic behaviors of 7075 aluminum alloy sheets

http://www.mate.tue.nl/mate/pdfs/10983.pdf

Experimental analysis of strain path dependent ductile damage mechanics and forming limits

Development of experimental and theoretical forming limit diagrams for warm forming of austenitic stainless steel 316

This article presents an experimental work and investigation on electrical discharge machining (EDM) of Inconel 718 and 625 superalloys. These superalloys are used for making parts like turbine blades, marine components, and nuclear reactor components. The precise components made up of superalloys which have cylindrical, square, and hexagonal machined features are required regular estimations of cylindricity, circularity, perpendicularity, and parallelism. In this work, EDM of the above said superalloys was carried out and form tolerances were analyzed. The significance of input parameters namely peak current, pulse-on time (T on), and pulse-off time (T off) on the form tolerances were investigated. In addition to these, the influence of individual parameters were also analyzed by analysis of variance (ANOVA) technique.

Analysis of Form Tolerances in Electrical Discharge Machining Process for Inconel 718 and 625

Optimization of EDM process parameters in machining Si 3 N 4 –TiN conductive ceramic composites to improve form and orientation tolerances

The dominance of the spark eroding process in complex ceramic components has promoted a significant growth analysis in the ceramic composites domain in modern manufacturing industries. The latest developments in ceramic components are concentrated on both the enhancement of the mechanical properties and the machinability of complex 3D parts while using spark EDM. The current (I), pulse on time (Ton), pulse off time (Toff), and dielectric flushing pressure (DP) are considered sparking parameters for the machining of a Si3N4–TiN ceramic composite. These composites find their application in high-temperature environments, viz. metal forming, extrusion dies, turbine blade, and non-ferrous molten metal handling components. Taguchi's orthogonal array (OA), L18, has been used to design the experiments. The optimal machining inputs are determined by the grey relational grade (GRG), which is attained from the grey relation analysis (GRA) for various response characteristics, such as the material removal rate (MRR),...

Optimization of EDM Parameters on Machining Si3N4–TiN Composite for Improving Circularity, Cylindricity, and Perpendicularity

In this work, forming limit diagrams with fracture limit have been evaluated for various steel sheets namely interstitial free (IF) steel with thickness 0.6, 0.85, 0.9, 1.2 and 1.6 mm, 0.85 mm noncoated and 0.85 mm coated, high strength low alloy (HSLA) steel with thickness 1.6 mm, extra deep drawing quality (EDDQ) steel with thickness of 1.2 mm and stainless steel 430 grade of 1.2 mm. The fractography of the sheets were taken using scanning electron microscope for the above said steel sheets under various conditions namely tension–tension strain condition, plane strain condition and tension–compression strain condition. Using the fractography, the average size of voids developed at fracture under the above said conditions were measured. The average size of voids for various sheets mentioned above were correlated with various shear strains, the ratio of mean strain to effective strain and other factors involving various shear strains, strain hardening exponent and normal anisotropy values. The ratio of height of the dome to punch radius (H/R) for various sheets mentioned above was correlated with the mean strain and also with the ratio of mean strain to effective strain. The average void sizes were also correlated with the ratio of Mohr's circle shear strain ɛ31 to effective strain.

C. Sathiya Narayanan

Papers

Analysis of Form Tolerances in Electrical Discharge Machining Process for Inconel 718 and 625

Optimization of EDM process parameters in machining Si 3 N 4 –TiN conductive ceramic composites to improve form and orientation tolerances

Optimization of EDM Parameters on Machining Si3N4–TiN Composite for Improving Circularity, Cylindricity, and Perpendicularity

Some aspects on fracture limit diagram developed for different steel sheets

Modelling of forming limit diagram of perforated commercial pure aluminium sheets using artificial neural network