Trends in the Development of Machinery and Associated Technology ” TMT 2010 , Mediterranean Cruise , 11-18 September 2010 EXPERIMENTAL DETERMINATION OF FORMING LIMIT DIAGRAM
Forming limit diagrams (FLDs) are a convenient and often used tool for the classification of the formability and for the evaluation of the forming process of sheet materials. Forming limits of sheet metal are represented in the forming limit diagram (FLD) occurring by various deformation states. The paper introduces a experiment method for determination of forming limit curve for whole range of the FLD for sheet metal.
PREDICTION OF MATERIAL NECKING IN DIGITAL ENVIRONMENT
Modern production which is based on metal forming tends to the increased analysis of forming processes in digital environment before the actual production set-up. For all these activities, the quality input data of used material is necessary. Simulations of sheet metal forming demand the input data of friction between the analysed objects, flow curve, yield point, material's anisotropy as well as the level and the course of a forming limit curve. Some aspects of predicting the forming limit diagrams in digital environment are discussed in this paper in order to omit expensive and time consuming experimental work. Improved method of numerical determination of FLD’s in digital environment based on the spatial and time determination of material necking is presented. Influential parameters of Marciniak testing procedure such as the coefficient of friction, mesh size and sampling rate of data acquisition in digital environment have been analysed as well.
The role of dissolved oxygen in supercritical water in the oxidation of ferritic–martensitic steel
Abstract To assess the role of dissolved oxygen in supercritical water on the growth processes of oxide scales, a marker experiment of ferritic–martensitic steel was performed by exposing to supercritical water (H 2 16 O) containing marked 18 O 2 at 600 °C under 25 MPa. The oxide scale was analysed by using Secondary Ion Mass Spectrometry (SIMS). The oxygen isotope profile shows that dissolved oxygen and supercritical water react with metals simultaneously. Dissolved oxygen changes the oxidation/reduction potential of supercritical water leading to an increase in the oxidation rate. The oxidation rate increases with increase in dissolved oxygen content in supercritical water. The mechanism of the effect of dissolved oxygen on oxidation is discussed.