Two new mathematical models to predict the flow stress at hot deformation

Based on both linear and non-linear estimations of work hardening rate versus strain curves, two mathematical models have been developed to predict the flow curves under hot working conditions up to the peak. The models were tested for a mechanically alloyed Al6063/0.75Al2O3/0.75Y2O3 nanocomposite under different hot forming conditions. The predicted results from both models are found to be in accord with the experimental flow stress curves. However, the linear model (with an average error of 0.81%) predicted the flow stress more accurate than the non-linear model (with an average error of 1.94%).Comment: Written in spring of 2012, as an independent work. 19 Pages, 13 Figures, 3 Appendice

Flow curve approximation using Avitzur's model for barreling compression test

The combination of the Cylindrical Profile Model (CPM) and Avitzur's model is commonly used to determine flow stress curves in material testing using compression test. In this process, stress is corrected for friction using Avitzur's model and the average strain is calculated from CPM. This study proposes a method for estimating strain based on Avitzur's model. The presented case studies demonstrate the impact of this strain correction on the flow curves. The results show that increasing friction leads to higher strain values at the center of the sample due to barreling. The proposed method provides a more accurate interpretation of compression test results

Evaluation of coefficient of friction in bulk metal forming

In this study an upper bound analysis for cylindrical "Barrel Compression Test" (BCT) is developed. BCT method is a very simple method which can be utilized in order to evaluate quantitatively the coefficient of friction by means of just one cylindrical specimen in an upsetting test. The method is checked by a series of finite element method (FEM) simulations and by means of the results of FEM simulations the method is modified.Comment: A self report. 20 Pages, 2 Tables, 2 Figure

Revisiting the Common Practice of Sellars and Tegart’s Hyperbolic Sine Constitutive Model

The Sellars and Tegart’s hyperbolic sine constitutive model is widely practiced in describing stress–strain curves of metals in hot deformation processes. The acceptance of this phenomenological model is owed to its versatility (working for a wide range of stress values) and simplicity (being only a function of strain, strain rate, and temperature). The common practices of this model are revisited in this work, with a few suggestions to improve its results. Moreover, it is discussed that, with the progress of data-driven models, the main reason for using the Sellars and Tegart’s model should be to identify reliable activation energies, and not the stress–strain curves. Furthermore, a piece of code (Hot Deformation Fitting Tool) has been created to automate the analysis of stress–strain curves with various models.</p

Indexing Profile of English-Language Journals of the University of Tehran Based on Indexing Criteria of International Citation Databases

Objective: This study aims to determine the feasibility and possibility of indexing English-language journals published by the University of Tehran in international citation indexes (e.g. Web of Science and Scopus). It would also help to find out the reasons why the majority of these journals are not yet indexed in international citation indexes. This study also provides some strategies to increase the international visibility and accessibility of these journals. Materials and Methods: This descriptive survey examined English-language journals published by Scientific Journals Database of Tehran University, available at https://journals.ut.ac.ir. We have used a combination of qualitative and quantitative measures such as journal citation analysis and a checklist. Citation analysis data was collected from Scopus and Google Scholar, and the checklist was designed upon indexing criteria of Web of Science Core Collection Journal Selection Process and Scopus Content Advisory Board. Results: Findings indicate that the total number of citations per journal was low and therefore only 15 percent of these journals were indexed in international databases and there were only two journals comply with all of the minimum acceptance criteria. Some reasons why they are not yet indexed by international citation databases are the irregularity in publishing, lack of description of the peer-review process and lack of publication ethics and malpractice statement. However, the strong points of these journals are proper publication archive, accessibility, and readability of the content to international readerships. Conclusion: This study helps publishers, editors and decision-makers to improve the quality of international journals and give them the rank and the position of being welcomed by a wider scholar community and accepted by international citation databases