The Experts below are selected from a list of 40242 Experts worldwide ranked by ideXlab platform
Ali Nazari - One of the best experts on this subject based on the ideXlab platform.
-
Artificial neural network to predict the effect of heat treatments on Vickers microhardness of low-carbon Nb microalloyed steels
Neural Computing and Applications, 2013Co-Authors: Gholamreza Khalaj, Ali Reza Khodabandeh, Hossein Yoozbashizadeh, Ali NazariAbstract:In the present study, an artificial neural networks-based model (ANNs) was developed to predict the Vickers microhardness of low-carbon Nb microalloyed steels. Fourteen parameters affecting the Vickers microhardness were considered as inputs, including the austenitizing temperature, cooling rate, initial austenite grain size, different chemical compositions and Nb in solution. The network was then trained to predict the Vickers microhardness amounts as outputs. A Multilayer feed-forward back-propagation network was developed and trained using experimental data form literatures. Five low-carbon Nb microalloyed steels and one low-carbon steel without Nb were investigated. The effects of austenitizing temperature (900–1,100°C) and subsequent cooling rate (0.15–227°C/s) and initial austenite grain size (5–130 μm) on the Vickers microhardness of steels were modeled by ANNs as well. The predicted values are in very good agreement with the measured ones, indicating that the developed model is very accurate and has the great ability for predicting the Vickers microhardness.
-
retraction note to artificial neural network to predict the effect of heat treatments on Vickers microhardness of low carbon nb microalloyed steels
Neural Computing and Applications, 2013Co-Authors: Gholamreza Khalaj, Ali Reza Khodabandeh, Hossein Yoozbashizadeh, Ali NazariAbstract:In the present study, an artificial neural networks-based model (ANNs) was developed to predict the Vickers microhardness of low-carbon Nb microalloyed steels. Fourteen parameters affecting the Vickers microhardness were considered as inputs, including the austenitizing temperature, cooling rate, initial austenite grain size, different chemical compositions and Nb in solution. The network was then trained to predict the Vickers microhardness amounts as outputs. A Multilayer feed-forward back-propagation network was developed and trained using experimental data form literatures. Five low-carbon Nb microalloyed steels and one low-carbon steel without Nb were investigated. The effects of austenitizing temperature (900–1,100°C) and subsequent cooling rate (0.15–227°C/s) and initial austenite grain size (5–130 μm) on the Vickers microhardness of steels were modeled by ANNs as well. The predicted values are in very good agreement with the measured ones, indicating that the developed model is very accurate and has the great ability for predicting the Vickers microhardness.
-
application of artificial neural networks for analytical modeling of charpy impact energy of functionally graded steels
Neural Computing and Applications, 2013Co-Authors: Ali NazariAbstract:In the present study, the Charpy impact energy of ferritic and austenitic functionally graded steel produced by electroslag remelting has been modeled in crack divider configuration. To produce functionally graded steels, two slices of plain carbon steel and austenitic stainless steels were spot welded and used as electroslag remelting electrode. Functionally graded steel containing graded layers of ferrite and austenite may be fabricated via diffusion of alloying elements during remelting stage. Vickers microhardness profile of the specimen has been obtained experimentally and modeled with artificial neural networks. To build the model for graded ferritic and austenitic steels, training, testing and validation using, respectively, 174 and 120 experimental data were conducted. According to the input parameters, in the neural networks model, the Vickers microhardness of each layer was predicted. A good fit equation that correlates the Vickers microhardness of each layer to its corresponding chemical composition was achieved by the optimized network for both ferritic and austenitic graded steels. Afterward, the Vickers microhardness of each layer in functionally graded steels was related to the yield stress of the corresponding layer and by assuming Holloman relation for stress–strain curve of each layer, the area under each stress–strain curve was acquired. Finally, by applying the rule of mixtures, Charpy impact energy of functionally graded steels in crack divider configuration was found through numerical method. The obtained results from the proposed model are in good agreement with those acquired from the experiments.
-
microhardness profile prediction of a graded steel by strain gradient plasticity theory
Computational Materials Science, 2011Co-Authors: Ali Nazari, Jamshid Aghazadeh Mohandesi, Saeed TavarehAbstract:In the present study, the Vickers microhardness profile of functionally graded steel austenitic steel produced by electroslag remelting process has been investigated. To produce functionally graded steels, two different slices from plain carbon steel and austenitic stainless steels were spot welded and used as electroslag remelting electrode. Functionally graded steel containing graded layers of austenite may be fabricated via diffusion of alloying elements during remelting stage. Vickers microhardness profile of the specimen has been obtained experimentally and modeled with mechanism-based strain gradient plasticity theory. In this regard, the density of the statistically stored dislocations and that of geometrically necessary dislocations was related to the Vickers microhardness profile of each layer. The experimental results are in good agreement with those obtained from the theory.
Dongil Kwon - One of the best experts on this subject based on the ideXlab platform.
-
effect of contact angle on contact morphology and Vickers hardness measurement in instrumented indentation testing
International Journal of Mechanical Sciences, 2014Co-Authors: Seungkyun Kang, Dongil KwonAbstract:Abstract We derive a general contact-depth function for the Vickers indenter by modifying a scaling relation between yield strain and indentation depth ratio, which is comprised of indenter angle, plastic constraint factor, and indentation depth ratio. The validity of this function is demonstrated by using various indenters of different angles. A method for calibrating the actual contact area of an imperfectly shaped Vickers indenter is suggested that yields a better evaluation of Vickers hardness in the instrumented indentation test.
-
conventional Vickers and true instrumented indentation hardness determined by instrumented indentation tests
Journal of Materials Research, 2010Co-Authors: Seungkyun Kang, Chanpyoung Park, Dongil KwonAbstract:We evaluate Vickers hardness and true instrumented indentation test (IIT) hardness of 24 metals over a wide range of mechanical properties using just IIT parameters by taking into account the real contact morphology beneath the Vickers indenter. Correlating the conventional Vickers hardness, indentation contact morphology, and IIT parameters for the 24 metals reveals relationships between contact depths and apparent material properties. We report the conventional Vickers and true IIT hardnesses measured only from IIT contact depths; these agree well with directly measured hardnesses within ±6% for Vickers hardness and ±10% for true IIT hardness.
Seungkyun Kang - One of the best experts on this subject based on the ideXlab platform.
-
effect of contact angle on contact morphology and Vickers hardness measurement in instrumented indentation testing
International Journal of Mechanical Sciences, 2014Co-Authors: Seungkyun Kang, Dongil KwonAbstract:Abstract We derive a general contact-depth function for the Vickers indenter by modifying a scaling relation between yield strain and indentation depth ratio, which is comprised of indenter angle, plastic constraint factor, and indentation depth ratio. The validity of this function is demonstrated by using various indenters of different angles. A method for calibrating the actual contact area of an imperfectly shaped Vickers indenter is suggested that yields a better evaluation of Vickers hardness in the instrumented indentation test.
-
conventional Vickers and true instrumented indentation hardness determined by instrumented indentation tests
Journal of Materials Research, 2010Co-Authors: Seungkyun Kang, Chanpyoung Park, Dongil KwonAbstract:We evaluate Vickers hardness and true instrumented indentation test (IIT) hardness of 24 metals over a wide range of mechanical properties using just IIT parameters by taking into account the real contact morphology beneath the Vickers indenter. Correlating the conventional Vickers hardness, indentation contact morphology, and IIT parameters for the 24 metals reveals relationships between contact depths and apparent material properties. We report the conventional Vickers and true IIT hardnesses measured only from IIT contact depths; these agree well with directly measured hardnesses within ±6% for Vickers hardness and ±10% for true IIT hardness.
R Caram - One of the best experts on this subject based on the ideXlab platform.
-
ise and fracture toughness evaluation by Vickers hardness testing of an al3nb nb2al alnbni in situ composite
Journal of Alloys and Compounds, 2009Co-Authors: C T Rios, A A Coelho, W W Batista, Maria Do Carmo Goncalves, R CaramAbstract:Abstract The aim of this work is to present correlations between Vickers indentation cracks and fracture toughness of an Al 3 Nb + Nb 2 Al + AlNbNi in situ composite. Correlations between the resulting crack parameters and indentation load suggested that the radial-median model resulted in a better fit to the experimental data. The hardness value was found to change according to the indentation load applied. Low indentation loads resulted in high hardness values, while the application of higher loads decreased the hardness. Experimental results indicate that Vickers hardness varied from 8.6 to 9.5 GPa, which is due to the indentation size effect (ISE). Fracture toughness was calculated based on several models and the results were found to vary in a broad range of values. The fracture toughness obtained from Vickers indentation was in the order of 1.65–2.26 MPa m 1/2 .
Richard C Bradt - One of the best experts on this subject based on the ideXlab platform.
-
on the Vickers indentation fracture toughness test
Journal of the American Ceramic Society, 2007Co-Authors: George D Quinn, Richard C BradtAbstract:The Vickers indentation fracture toughness test, or VIF, is addressed by considering its origins and the numerous equations that have been applied along with the technique to estimate the fracture resistance, or the KIc of ceramics. Initiation and propagation of cracks during the VIF test are described and contrasted with the pre-cracking and crack growth for internationally standardized fracture toughness tests. It is concluded that the VIF test technique is fundamentally different than standard fracture toughness tests. The VIF test has a complex three-dimensional crack system with substantial deformation residual stresses and damage around the cracks. The VIF test relates to an ill-defined crack arrest condition as opposed to the rapid crack propagation of the standardized fracture toughness tests. Previously published fracture toughness results employing the VIF technique are reviewed. These reveal serious discrepancies in reported VIF fracture toughness values. Finally, recent fracture resistance measurements by the VIF technique for the Standard Reference Material SRM 2100 are presented. These are compared with standardized test results for the same material. It is concluded that the VIF technique is not reliable as a fracture toughness test for ceramics or for other brittle materials. What the VIF actually measures in terms of fracture resistance cannot be readily defined. It is recommended that the VIF technique no longer be acceptable for the fracture toughness testing of ceramic materials.
