http://hdl.handle.net/10316/19948 2020-03-07T13:37:04Z 2020-03-07T13:37:04Z Prates, Pedro Marques, Armando Oliveira, Marta Fernandes, José Valdemar http://hdl.handle.net/10316/87511 2019-09-10T20:31:48Z 2019-01-01T00:00:00Z

Title: Comparing Metamodeling Techniques For Variability Analysis In Sheet Metal Forming Processes Authors: Prates, Pedro; Marques, Armando; Oliveira, Marta; Fernandes, José Valdemar Abstract: This study presents a systematic comparison on the performance of different metamodeling techniques in the analysis of variability in sheet metal forming processes. For this purpose, three steel grades (DC06, DP600 and HSLA340) are selected as reference materials and two sheet metal forming processes are considered: the U-Channel and the Square Cup forming processes. The sources of variability selected for this study are the Young’s modulus, the isotropic hardening law parameters, the anisotropy coefficients and the initial thickness of the sheet metal; the variability is described for all of them by a probabilistic normal distribution. The process outputs selected for analysis are the springback and maximum thinning, in case of the U-Channel forming process, and the maximum equivalent plastic strain and maximum thinning, in case of the Square Cup deep-drawing. Firstly, a number of random simulations is performed for each material and forming process. Then, metamodeling techniques based on 2nd degree polynomial RSM and three Kriging methods (Simple, Ordinary and Universal Kriging) are established, and their performance is evaluated. The results show that the performance of Kriging metamodels is generally better than RSM; also, the performance of RSM metamodels is strongly dependent on the number of design (training) points, which is not the case for Kriging metamodels.

2019-01-01T00:00:00Z Marques, Armando Prates, Pedro Pereira, André Oliveira, Marta Fernandes, José http://hdl.handle.net/10316/87510 2019-09-10T20:31:47Z 2019-01-01T00:00:00Z

Title: Hole Expansion Tests of Metal Sheets: Numerical Study Authors: Marques, Armando; Prates, Pedro; Pereira, André; Oliveira, Marta; Fernandes, José Abstract: A numerical analysis of the hole expansion test is presented. It focuses on the impact that different values of initial blank hole diameter have on the maximum values achieved for the principal strains, during the test. This analysis considers a case in full conformity with the ISO 16630 standard. The remaining cases studied differ from this, changing only the initial value of the blank hole. The results show that a smaller blank hole allows the test to reach higher values of major strain.

2019-01-01T00:00:00Z Marques, Armando Prates, Pedro Oliveira, Marta Fernandes, José Valdemar http://hdl.handle.net/10316/87509 2019-09-10T20:31:47Z 2019-01-01T00:00:00Z

Title: NUMERICAL STUDY ON HOLE EXPANSION TESTS OF METAL SHEETS Authors: Marques, Armando; Prates, Pedro; Oliveira, Marta; Fernandes, José Valdemar Abstract: In this work, a numerical analysis of the hole expansion test is presented. This analysis focuses on the impact that certain geometric and material features have on the strain path and maximum values achieved for the principal strains, during the test. The features analysed are the die diameter, the sheet thickness and the material hardening behaviour. In order to study the impact of each feature individually, a reference study case was defined, which strictly follows the ISO 16630 standard, to serve as a basis of comparison. Then, other study cases were created from the reference one, by changing each feature in study. The results show that a uniaxial tension strain path is observed at the outer edge of the blank hole, which is not significantly changed with the variation of the features under study.

2019-01-01T00:00:00Z