An analytical method for predicting elastic–plastic stress distribution in a cylindrical pressure vessel has been presented. The vessel material was a ceramic/metal functionally graded material, i.e. a particle–reinforcement composite. It was assumed that the material’s plastic deformation follows an isotropic strain-hardening rule based on the von-Mises yield criterion, and that the vessel was under plane-stress conditions. The mechanical properties of the graded layer were modelled by the modified rule of mixtures. By assuming small strains, Hencky’s stress–strain relation was used to obtain the governing differential equations for the plastic region. A numerical method for solving those differential equations was then proposed that enabledthe prediction of stress state within the structure. Selected finite element results were also presented to establish supporting evidence for the validation of the proposed analytical modelling approach. Similar analyses were performed and solutions for spherical pressure made of FGMs were also provided. پرونده مقاله

In this paper the capability of Gurson-Tvergaard-Needleman (GTN) model in the prediction of ductile damage in 7075-T651 aluminum alloy is investigated. For this purpose, three types of specimens were tested: Standard tensile bars, Round notched bar (RNB) specimens and compact tension (C(T)) specimens. Standard tensile bar tests were used to obtain the mechanical properties of the material and to calibrate the independent parameters of GTN model. RNB and C(T) specimen test results were used for validation of the calibrated parameters. Finite element analyses were carried out using ABAQUS commercial software for two purposes; calibration of the GTN model parameters and validation of the model predictions. The comparison between the finite element analyses and the test results suggested that the GTN model is capable of damage prediction in notched specimens, but not a good in cracked specimens. Finally, To show the applicability of the model in industry-level problems, the model is used for damage predictions of internal pressure vessels made of 7075-t651 aluminum alloy. پرونده مقاله

Electro Discharge Machining (EDM) is a very efficient machining process widely used in manufacturing components of complicated geometry. Based on its nature, i.e. material removal by electric discharge, the process induces thermal stresses that in turn result in generation of wide spread micro-cracks on the surface of the machined part. In this paper the influence of EDM characteristic parameters on the surface microstructure in CK45 alloy steel which is suitable for manufacturing of forging dies has been extensively investigated. An extensive experimental programme has been carried out to explore the role of various EDM parameters on the quality of the machined surface. The relation of EDM parameters has been evaluated quantitatively using the test results and regression analysis. Predicting the impact of EDM parameters on the surface quality as the outcome of this study provides means to appropriately decide on the adjustment of parameters to their optimum values and achieve the desired die surface quality at reasonable manufacturing time and cost. پرونده مقاله