Loading...
Search for:
strain-rate
0.008 seconds
Total 200 records
A study on kinetics of static and metadynamic recrystallization during hot rolling
, Article Materials Science and Engineering A ; Volume 448, Issue 1-2 , 2007 , Pages 146-153 ; 09215093 (ISSN) ; Sharif University of Technology
2007
Abstract
A model has been developed for evaluation of recrystallization kinetics during hot rolling of a low carbon steel. For doing so, the finite difference and the finite element methods have been coupled to consider the interconnections among temperature, strain rate, strain and the kinetics of recrystallization within the steel under non-isothermal hot rolling conditions. To verify the model predictions, hot rolling experiments are carried out and the roll forces and microstructure of the rolled metal are compared with the predicted results. The comparison between the two sets of data shows a good agreement. © 2006 Elsevier B.V. All rights reserved
Elastic solids with high concentration of arbitrarily oriented multiphase particles
, Article Acta Mechanica ; Volume 189, Issue 3-4 , 2007 , Pages 125-139 ; 00015970 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Springer-Verlag Wien
2007
Abstract
The effective properties of elastic solids are strongly linked to their interacting micro-constituent phases. For materials containing dilute distributions of single-phase inhomogeneities, the overall behavior can be estimated in a straightforward manner. But in the non-dilute case, due to the complex inter-particle and particle-matrix interactions the treatment is rather involved. When the particles are heterogeneous, not only become the mentioned interactions more complex, but must properly account for the intra-particle interactions as well. The present work addresses an analytical approach to determine the overall moduli of elastic solids containing random distributions of arbitrarily...
An investigation on the sintering behavior of 316L and 17-4PH stainless steel powders for graded composites
, Article Materials Science and Engineering A ; Volume 424, Issue 1-2 , 2006 , Pages 282-289 ; 09215093 (ISSN) ; Rota, A ; Imgrund, P ; Sharif University of Technology
2006
Abstract
This paper presents the densification and microstructure of bilayer structures made from 316L and 17-4PH stainless steels powders during sintering. The requirements for such objects could be magnetic properties at one area of the part and non-magnetic properties at another area of the object. A pressureless solid state sintering method in conjunction with a powder layering technique was used. The sintering was carried out at temperatures ranging from 1100 to 1340 °C for 120 min in hydrogen and vacuum atmospheres. Non-isothermal sintering behavior was also examined by dilatometric analysis. It was found that the strain rate of 17-4PH stainless steel powder is higher than that of 316L during...
Effective parameters modeling in compression of an austenitic stainless steel using artificial neural network
, Article Computational Materials Science ; Volume 34, Issue 4 , 2005 , Pages 335-341 ; 09270256 (ISSN) ; Mousavi Anijdan, S. H ; Madaah Hosseini, H. R ; Shafyei, A ; Narimani, R ; Sharif University of Technology
2005
Abstract
In this study, the prediction of flow stress in 304 stainless steel using artificial neural networks (ANN) has been investigated. Experimental data earlier deduced-by [S. Venugopal et al., Optimization of cold and warm workability in 304 stainless steel using instability maps, Metall. Trans. A 27A (1996) 126-199]-were collected to obtain training and test data. Temperature, strain-rate and strain were used as input layer, while the output was flow stress. The back propagation learning algorithm with three different variants and logistic sigmoid transfer function were used in the network. The results of this investigation shows that the R2 values for the test and training data set are about...
Modelling dynamic softening processes during hot working
, Article Materials Science and Engineering A ; Volume 404, Issue 1-2 , 2005 , Pages 130-137 ; 09215093 (ISSN) ; Sharif University of Technology
2005
Abstract
This paper models the kinetics of dynamic recovery and recrystallization under hot working conditions. For doing so, the first-order kinetics equation is coupled with a thermo-viscoplastic finite element analysis to determine the kinetics of dynamic softening processes at different points of deforming metal. The proposed model can consider the effects of macro parameters, such as temperature and strain rate variations as well as the influences of microparameters as initial grain size on the rate of dynamic softening processes. © 2005 Elsevier B.V. All rights reserved
A rate-dependent constitutive equation for 5052 aluminum diaphragms
, Article Materials and Design ; Vol. 60, Issue 1 , 2014 , pp. 13-20 ; ISSN: 02613069 ; Ashrafian, M. M ; Toozandehjani, H ; Sharif University of Technology
Abstract
In this article, both experimental and numerical approaches are conducted to present a constitutive equation for 5052 aluminum diaphragms under quasi-static strain rate loadings. For this purpose the stress-strain curves at different strain rates are obtained using tensile tests. Brittle behavior during tensile tests is observed due to samples thin thicknesses. Employing Johnson-Cook constitutive equation no yields in reasonable agreement with these tensile tests results. Therefore, developing a more suitable constitutive equation for aluminum diaphragms is taken into consideration. This equation is then implemented into the commercial finite element software, ABAQUS, via a developed user...
Dislocation density and flow stress modeling of nanostructured Al-SiC p composite during accumulative roll bonding
, Article Computational Materials Science ; Volume 67 , February , 2013 , Pages 359-363 ; 09270256 (ISSN) ; Saei, M ; Kazeminezhad, M ; Sharif University of Technology
2013
Abstract
In order to investigate the dislocation structure and flow stress evolution of Al-SiCp composite during ARB process, a comprehensive model which describes the evolution of dislocation density is needed. Dislocation density, microstructure and flow stress evolution of Al-SiCp composite are predicted considering the ETMB model, strain and strain rate achieved from the mechanical model of ARB process and shear modulus calculated from the composite model. In addition, models' parameters such as dislocation generation parameters are modified due to the effect of SiC particles. The predicted results are in good agreement with experimental data
Effects of strain rate and mean strain on cyclic behavior of aluminum alloys under isothermal and thermo-mechanical fatigue loadings
, Article International Journal of Fatigue ; Volume 47 , 2013 , Pages 148-153 ; 01421123 (ISSN) ; Sharif University of Technology
2013
Abstract
In this paper, effects of strain rate and mean strain on the cyclic behavior and the lifetime of aluminum-silicon alloys are investigated under thermo-mechanical and isothermal fatigue loadings. To achieve these goals, low cycle fatigue tests are accomplished at evaluated temperatures under various strain rates (by changing the loading frequency) and different strain ratios (minimum to maximum strain). Thermo-mechanical fatigue experiments are performed in an out-of-phase condition where the temperature varies between 50 and 250 °C. Various heating/cooling rates are taken into account to assess the strain rate effect and different starting temperatures are considered to study the mean strain...
Investigating the effect of rolling strain on fracture behavior of roll bonded Al6061 laminates under quasi-static and dynamic loading
, Article Materials Science and Engineering A ; Volume 558 , 2012 , Pages 82-89 ; 09215093 (ISSN) ; Bagheri, R ; Seyed Reihani, S. M ; Sharif University of Technology
2012
Abstract
Damage tolerance improvement has been reported by laminating aluminum alloys and composites by researchers. Three-layer laminates comprising Al6061 outer layers and Al1050 interlayer have been roll bonded in this research. While most of the works done have focused on fracture properties of roll bonded Al laminates in crack arrester geometry, this study explores their behavior in crack divider configuration. Rolling strain is varied to control the interfacial bonding in laminates. The fracture behavior of laminates and the constituent material was examined via three-point bending and impact tests. This study presents significant improvement in damage tolerance of laminates compared to their...
The effect of deformation heating on restoration and constitutive equation of a wrought equiatomic NiTi alloy
, Article Journal of Materials Engineering and Performance ; Volume 21, Issue 4 , April , 2012 , Pages 516-523 ; 10599495 (ISSN) ; Karimi Taheri, A ; Karimi Taheri, K ; Sarraf, I. S ; Abbasi, S. M ; Sharif University of Technology
Abstract
In this study, a set of constitutive equation corrected for deformation heating is proposed for a near equiatomic NiTi shape memory alloy using isothermal hot compression tests in temperature range of 700 to 1000 °C and strain rate of 0.001 to 1 s -1. In order to determine the temperature rise due to deformation heating, Abaqus simulation was employed and varied thermal properties were considered in the simulation. The results of hot compression tests showed that at low pre-set temperatures and high strain rates the flow curves exhibit a softening, while after correction of deformation heating the softening is vanished. Using the corrected flow curves, the power-law constitutive equation of...
Experimental and numerical investigation of pulse-shaped split Hopkinson pressure bar test
, Article Materials Science and Engineering A ; Volume 539 , 2012 , Pages 285-293 ; 09215093 (ISSN) ; Ashrafi, M. J ; Arghavani, J ; Sharif University of Technology
Abstract
Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-hardening materials. Also, for...
Strain rate sensitivity and fracture behavior of severely deformed Al-Mn alloy sheets
, Article Materials Science and Engineering A ; Volume 532 , January , 2012 , Pages 26-30 ; 09215093 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2012
Abstract
Wrought sheets of an Al-Mn alloy are subjected to severe plastic deformation using constrained groove pressing (CGP) method. After applying CGP passes on the sheets, tensile tests at different strain rates are carried out and the strain rate sensitivity values are calculated. Results show that strain rate sensitivity is increased from 0.0081 in annealed sheets to 0.019 after three passes of constrained groove pressing. This arises from intrinsic decrease in grain size due to severe straining. Experimental results reveal that after three CGP passes, the rate of increasing in strain rate sensitivity is decreased. Fracture surfaces of the tensile samples are observed using scanning electron...
Constitutive modeling of temperature and strain rate dependent elastoplastic hardening materials using a corotational rate associated with the plastic deformation
, Article International Journal of Plasticity ; Volume 27, Issue 9 , 2011 , Pages 1445-1455 ; 07496419 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
Abstract
In this paper, a constitutive model with a temperature and strain rate dependent flow stress (Bergstrom hardening rule) and modified Armstrong-Frederick kinematic evolution equation for elastoplastic hardening materials is introduced. Based on the multiplicative decomposition of the deformation gradient,new kinematic relations for the elastic and plastic left stretch tensors as well as the plastic deformation-dependent spin tensor are proposed. Also, a closed-form solution has been obtained for the elastic and plastic left stretch tensors for the simple shear problem.To evaluate model validity, results are compared with known experimental data for SUS 304 stainless steel, which shows a good...
Investigation into characteristics of Portevin-Le Chatelier effect of an Al-Mg Alloy
, Article Journal of Materials Engineering and Performance ; Volume 19, Issue 9 , 2010 , Pages 1264-1267 ; 10599495 (ISSN) ; Sharif University of Technology
Abstract
In this study, the plastic instabilities associated with the Portevin-Le Chatelier (PLC) and their effects on the mechanical properties and the fracture surfaces have been investigated for AA 5083. Tensile tests were performed at various temperatures and strain rates in order to do so. Then, serrated and smooth yielding domains were determined in Ln ε̇-1/T diagram. The stress-strain curves related to the serrated domain show the values of flow stress decreases by increasing the strain rate at a constant temperature. In addition, the plot of critical strain versus imposed strain rate indicates an inverse manner at very low strain rates. It is confirmed that the type of PLC bands alters the...
Experimental and numerical study on choosing proper pulse shapers for testing concrete specimens by split hopkinson pressure bar apparatus
, Article Construction and Building Materials ; Volume 125 , 2016 , Pages 326-336 ; 09500618 (ISSN) ; Naghdabadi, R ; Ashrafi, M. J ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Dynamic behavior of concrete specimens is investigated experimentally and numerically by split Hopkinson pressure bar (SHPB) tests. In order to accurately determine dynamic properties of brittle materials such as concrete, specimens should be subjected to particular pulse loading that can be generated by using pulse shapers. Choosing proper pulse shaper dimensions helps to obtain dynamic stress equilibrium, achieve constant strain rate and minimize pulse oscillation in the concrete specimens. To this end, SHPB tests are performed for concrete specimens and effective parameters on shaping pulses such as striker bar velocity, diameter and thickness of the pulse shaper are studied...
An upper-bound finite element solution for rolling of stainless steel 304L under warm and hot deformation conditions
, Article Multidiscipline Modeling in Materials and Structures ; Volume 12, Issue 3 , 2016 , Pages 514-533 ; 15736105 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
Emerald Group Publishing Ltd
Abstract
Purpose: The purpose of this paper is to investigate the thermomechanical behavior of stainless steel AISI 304L during rolling at elevated temperatures. Design/methodology/approach: Two-dimensional finite element analysis together with the upperbound solution were used for predicting temperature field and required power in warm and hot rolling operations. The required power and heat of deformation were estimated employing an upper-bound solution based on cylindrical velocity field and at the same time, temperature distributions within the rolling steel and the work rolls were determined by means of a thermal finite element analysis. To consider the effect of flow stress and its dependence on...
Parametric study of strain rate effects on nanoparticle-reinforced polymer composites
, Article Journal of Nanomaterials ; Volume 2016 , 2016 ; 16874110 (ISSN) ; Haji Gholami, I ; Masajedian, S ; Mertiny, P ; Sameoto, D ; Taheri, F ; Sharif University of Technology
Hindawi Publishing Corporation
2016
Abstract
Crashworthiness, energy absorption capacity, and safety are important factors in the design of lightweight vehicles made of fiber-reinforced polymer composite (FRP) components. The relatively recent emergence of the nanotechnology industry has presented a novel means to augment the mechanical properties of various materials. As a result, recent attempts have contemplated the use of nanoparticles to further improve the resiliency of resins, especially when resins are used for mating FRP components. Therefore, a comprehensive understanding of the response of nanoreinforced polymer composites, subjected to various rates of loading, is of paramount importance for developing reliable structures....
Effect of silicon carbide nanoparticles on hot deformation of ultrafine-grained aluminium nanocomposites prepared by hot powder extrusion process
, Article Powder Metallurgy ; Volume 59, Issue 4 , 2016 , Pages 262-270 ; 00325899 (ISSN) ; Simchi, A ; Sharif University of Technology
Taylor and Francis Ltd
Abstract
The flow behaviour of Al–SiC nanocomposites prepared by mechanical milling and hot powder extrusion methods was studied at different temperatures (350–500°C) and strain rates (0.005–0.5 s−1). The flow of the Powder metallurgy nanocomposites exhibited a peak stress followed by a dynamic flow softening behaviour. It was shown that mechanical milling increased high-temperature strain rate sensitivity of ultrafine-grained (UFG) aluminium while decreasing its flow dependence to temperature. Constitutive analysis of the hot deformation process by Zener–Hollomon parameter (Z) also indicated a remarkable increase in the deformation activation energy (about 40%). Likewise, SiC nanoparticles (up to...
Development of equations for strain rate sensitivity of UFG aluminum as a function of strain rate
, Article International Journal of Plasticity ; Volume 90 , 2017 , Pages 167-176 ; 07496419 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
Abstract
Strain rate sensitivity (m-value) of ultrafine grain (UFG) AA 1050 and AA 5052 sheets processed by accumulative roll-bonding is investigated versus strain rate by stress relaxation (SR) test at ambient temperature. The results show a weak viscous nature of deformation for AA 5052 specimens as compared to AA 1050 ones. So that much less stress relaxation and negligible strain rate sensitivity are obtained for this material due to dislocation and grain boundary mobility limitation caused by Mg solute atoms. In order to formulate strain rate sensitivity of UFG aluminum as a function of strain rate, three phenomenological and two empirical models are developed and assessed by the experimental...
Development of a molecular dynamic based cohesive zone model for prediction of an equivalent material behavior for Al/Al2O3 composite
, Article Materials Science and Engineering A ; Volume 679 , 2017 , Pages 116-122 ; 09215093 (ISSN) ; Movahhedy, M. R ; Mahnama, M ; Sohrabpour, S ; Sharif University of Technology
Abstract
The interfacial behavior of composites is often simulated using a cohesive zone model (CZM). In this approach, a traction-separation (T-S) relation between the matrix and reinforcement particles, which is often obtained from experimental results, is employed. However, since the determination of this relation from experimental results is difficult, the molecular dynamics (MD) simulation may be used as a virtual environment to obtain this relation. In this study, MD simulations under the normal and shear loadings are used to obtain the interface behavior of Al/Al2O3 composite material and to derive the T-S relation. For better agreement with Al/Al2O3 interfacial behavior, the exponential form...