Maria Carolina dos Santos Freitas

Densification Behaviour Modelling for Metallic Powders

Powder forming involves fabrication of a preform by conventional press-and-sinter processing, followed by various forming processes, citing as examples, rolling, compaction, forging, extrusion, among others, of the porous preform into a final shape through substantial densification. This work makes a finite element analysis for porous metals. The finite element model was applied to simulating the case of compaction of nanocristalline copper under uniaxial compression conditions in order investigate the densification behavior. The model was simulated using explicit integration method as applied to the evolution variation of the relative density and the dislocation density of the compact. Finite element analysis program used was Abaqus. Finite element calculations were compared with literature data. The agreements between finite element model and literature results for densification of nanocristalline copper were good.

Experimental analysis and theoretical predictions of the limit strains of a hot-dip galvanized interstitial-free steel sheet

In this work, the formability of a hot-dip galvanized interstitial-free (IF) steel sheet was evaluated by means of uniaxial tensile and Forming Limit Curve (FLC) tests. The FLC was defined using the flat-bottomed Marciniaks punch technique, where the strain analysis was made using a digital image correlation software. A plastic localization model was also proposed wherein the governing equations are solved with the help of the Newtons method. The investigated hot-dip galvanized IF steel sheet presented a very good formability level in the deep-drawing range consistent with the measured Lankford values. The predicted limit strains were found to be in good agreement with the experimental data of the hot-dip galvanized IF steel sheet owing to the definition of the localization model geometrical imperfection as a function of the experimental surface roughness evolution and, in particular, to the yield surface flattening near to the plane-strain stress state authorized by the adopted yield criterion.

Elasto-Plastic Modeling of the Limit Strains in Metallic Sheets

In this work, the model of Marciniak and Kuczynski, hereafter referred to as the M-K model, was extended to account for the elastic strains to forecast the Forming Limit Curve (FLC) of metallic sheets. The return mapping algorithm is adopted where an elastic predictor step is performed with the generalized Hooke’s law and the plastic correction step is performed assuming the isotropic work-hardening together with the associated flow rule. The current M-K model predicted quite well both experimental and rigid-plastic results obtained for an IF steel sheet. Also, the principal stresses predicted by the elasto-plastic M-K model provided a good agreement with the experimental Forming Limit Stress Diagram (FLSD) of a Bake-Hardening steel sheet. Therefore, the elastic strains should be taken into account in the modeling of limit strains in metallic sheets, especially in the case of advanced high strength steels for which the Young modulus decreases with the plastic strain.

Deformations Limits Analysis of Sheet Metal Manufatured through the Incremental Forming Process

The present study is primarily engaged in the implementation of the incremental stamping process in a computerized numeric control This paper presents two different approaches to this forming process, an experimental and other numerical. Experimental used by the computer numerical control to perform the printing process and performs numerical simulations of the process using the finite element method. Some parameters are analyzed in both approaches, such as product geometry effects, tool geometry, tool speed, tool path, contact conditions and mechanical properties of the materials.

A Finite Element Analysis for an Iron Ore Pellet Compression Test

The increasing global demand for iron ore pellets has made the pelletizing companies to step up their investments. The mechanical strength of the pellets, as well as its wear resistance are important factors to characterize the mechanical behavior. These properties are influenced by the type and nature of the ore or concentrate, the additives and the subsequent heat treatment used. This paper develops a numerical finite element model in order to characterize the mechanical behavior of iron ore pellets. The main objective of this study was to establish a valid finite element model that is able to simulate the mechanical behavior of iron ore pellets. The uniaxial compression test was made to evaluate the mechanical properties of the pellets. Furthermore, modeling and simulations are done using the software ABAQUS CAE® for uniaxial compression using the material properties obtained by the test. Lastly, in order to validate the model, the experimental data is crossed with the simulation results to discuss its correlation and particularities.

Analysis of the Iron Ore Pellet Mechanical Behavior under Biaxial Compression

The increasing global demand for iron ore pellets has made the pelletizing companies to step up their investments. The mechanical strength of the pellets, as well as its wear resistance are important factors to characterize the mechanical behavior. These properties are influenced by the type and nature of the ore or concentrate, the additives and the subsequent heat treatment used. This paper develops a numerical finite element model in order to characterize the mechanical behavior of iron ore pellets. The biaxial compressive stress was analyzed in this study. The results show that the pellet subjected to biaxial stress supports higher levels of stress and strain when compared to uniaxial efforts. Accuracy increase of the simulation results can be obtained with the implementation of a failure criterion for brittle materials in the numerical model. Finally, could be seen that the pellet had higher levels of deformation under biaxial symmetric strain, when compared with the uniaxial compression results.

Evolution of Sintering of Particles that Compose Iron Ore Agglomerates

The increasing demand for new technologies in the ironmaking/steelmaking field has been motivating several studies towards pelletizing process improvement. Within this context, evaluate the reduction of iron ore pellets using the dilatometer technique constitutes a promising approach for optimizing this process. This paper aims the metallurgical characterization through the sintering of particles in iron ore pellets. With this purpose, some experimental procedures are of concern as follows. Firstly, the kinetic densification of the iron ore pellets is measured using a dilatometer, which heats the samples up at 30 K/min until high temperatures about 1473 K and an isotherm at 10 minutes have been done. Then, the sample is cooled back to room temperature and undergoes a microstructural characterization, with the aid of a scanning electron microscope. At last, the density of the pellets is evaluated, using an Arquimedes Principle and consequently the porosity of the agglomerates. The results indicate the sintering progress of the particles that comprise the pellets as well as reduction the porosity. This behavior is due to the fact that the heat arising from gas induces the partial liquid phase formation and involves the agglomerate particles aiding in the sintering process.

Forming limit strains of interstitial free-IF steel sheet

Present work examines mathematical models to predict the onset of localized necking in sheet metal forming of interstitial free steel, such as biaxial stretching and deep drawing. Forming Limit Curve, FLC, which is an essential material parameter necessary to numerical simulation by FEM, of IF steel sheet was assessed experimentally by Nakajima testing and ASAME software. The “Map of Principal Surface Limit Strains - MPLS”, shows the experimental FLC which is the plot of principal true strains in the sheet metal surface (e1, e2), occurring at critical points obtained in laboratory formability tests or in the fabrication process of parts. Two types of undesirable rupture mechanisms can occur in sheet metal forming products: localized necking and rupture by induced shear stress. Therefore, two kinds of limit strain curves can be plotted in the forming map: the local necking limit curve FLC-N and the shear stress rupture limit curve FLC-S. Localized necking is theoretically anticipated to occur by two mathem...

Influence of Heat Treatment on Values of a Strain of Interstitial Free Steel

This study aimed to investigate how the heat treatment can influence the strain values of an IF steel observing the different values of the tensile, rupture and drain that were recorded during the tensile test. We analyzed five samples of the specimen (CP) using different combinations of heat treatments to enable evaluation of the behavior of material deformation by tensile test. The evaluation was performed using the deformation calculation of the ratio between the axial and radial deformations (anisotropy parameter). The results indicate how different types of thermal treatments influenced in their initial properties, generating materials with different characteristics.

Cold Rolled Superfine Steel

Aiming to meet new market demands for flat steel, steel companies have been developing new products with special features that allow various adjustments to your application. Our paper is a new product, the superfine steels, its applications, development feasibility and economic aspects. The market for steel furniture for domestic purposes has a great demand for cold-rolled steels, distributed in thick bands, currently between 0.40 mm and 0.70 mm. This segment showed continuous growth in recent years, like the white line, with special focus on the increased consumption presented by the classes C and D, driven by the reduction in Excise Tax (IPI), granted by the federal government in 2009. The proposal is to produce cold-rolled steel with thickness reaching up to 0.25 mm, maintaining the function of the final component to quality and stiffness required. Thinning is a thick white line trend of the world, due to the direct impact on reducing the final cost of the piece, reflecting the competitiveness of customers across the market, and there is a clear need to develop new applications for these materials, not only to the white line, as well as for the mobile industry and metal packaging. Keywords: ColdRolled Superfine Steel, reducingthickwhite line