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friction
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Study of the effect of pipe friction reduction by polymer friction reduction factor (DRA) in hydrocarbon fluid transfer system
, Article Journal of Advanced Research in Dynamical and Control Systems ; Volume 10, Issue 7 Special Issue , 2018 , Pages 72-78 ; 1943023X (ISSN) ; Radb, M ; Sharif University of Technology
Institute of Advanced Scientific Research, Inc
2018
Abstract
The phenomenon of friction reduction was investigated by using a polymeric injection of a residual stream of turbulent flow known as the tomes phenomenon for a smooth flow without a roughness effect in 1975 by Virk. In the following years, by investigating the development of studies to reduce the friction in the turbulent stream by individuals such as torgeir, the effect of molecular weight, concentration and polymer thermodynamic conditions on friction reduction were investigated, and it was shown that by increasing the polystyrene concentration in the Toluene for turbulent flow, Reduced friction increases. Also, Fernandes and Mowal studied the effect of the polymer on friction reduction in...
Improved passivity criterion in haptic rendering: influence of coulomb and viscous friction [electronic resource]
, Article Advanced Robotics ; 2014 Volume 28, Issue 10 ; R. Bozorgmehry, R ; Nahvi, A ; Meghdari, A ; Asgari, P ; Sharif University of Technology
Abstract
In this paper, a new criterion for passivity of haptic devices is obtained. This criterion creates a relationship between Coulomb friction coefficient, viscous friction coefficient, sampling rate, and the maximum simulated stiffness. The process of derivation of the passivity criterion is described in detail. This criterion is improved compared with other existing criteria and predicts passivity in haptic rendering more accurately. In particular, for speeds of less than 5 cm/s, the new passivity criterion should replace the previous criteria to avoid unwanted vibrations of stiff virtual walls. Analytical and numerical investigations are presented to validate the new criterion. A specific...
Seismic retrofit of existing structures using friction dampers
, Article Asian Journal of Civil Engineering ; Volume 11, Issue 4 , 2010 , Pages 509-520 ; 15630854 (ISSN) ; Ebrahimian, H ; Sharif University of Technology
2010
Abstract
Conventional methods of seismic rehabilitation with concrete shear walls or steel bracing are not considered suitable for some buildings as upgrades with these methods would have required expensive and time consuming foundation work. Supplemental damping in conjunction with appropriate stiffness offered an innovative and attractive solution for the seismic rehabilitation of such structures. This paper deals with the use of friction damper as a passive dissipative device in order to seismic retrofit of existing structures and discusses the design criteria and seismic analysis of a building. The structure is modeled using the finite element program Sap2000 and is analysed using both non-linear...
Dynamic analysis of an a-shaped piezo-actuated walking microrobot
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010, Vancouver, BC ; Volume 10 , 2010 , Pages 161-170 ; 9780791844472 (ISBN) ; Vossoughi, G ; Sharif University of Technology
2010
Abstract
In this paper, a novel, A-shaped microrobot with nanometric resolution for precision positioning applications is addressed. The locomotion concept of the mechanism is founded on the "friction drive principle". To achieve the translational motion, a stack piezoelectric actuates the microrobot near its natural frequency. The dynamic modeling of the mechanism is based on the assumptions of linear behavior of piezo stack actuator and Coulomb friction model at contact points. The suitability of three simple, friction-based locomotion modes for implementation on the proposed device is presented. Influences of different friction coefficients on the behavior of the microrobot, with respect to...
Dynamic recrystallization phenomena during laser-assisted friction stir processing of a precipitation hardened nickel base superalloy
, Article Journal of Alloys and Compounds ; Volume 685 , 2016 , Pages 806-811 ; 09258388 (ISSN) ; Pouranvari, M ; Malek Ghaini, F ; Fujii, H ; Sun, Y. F ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Laser-assisted friction stir processing was used to modify the microstructure of an as-cast gamma prime strengthened nickel base superalloy. The grain structure of top region of the stir zone, where full dissolution of gamma prime precipitates occurred during heating, is controlled by discontinuous dynamic recrystallization mechanism and the pinning effect of refined carbides and cooling gamma prime precipitates. In the bottom of the stir zone, the partial dissolved gamma prime precipitates play important role in grain structure development by their pinning effect in retarding grain growth during cooling as well as by a continuous recrystallization mechanism
Numerical simulation of turbulent boundary layers of surfaces covered with foul release and antifouling coatings
, Article Journal of Naval Architecture and Marine Engineering ; Volume 13, Issue 1 , 2016 , Pages 17-26 ; 18138535 (ISSN) ; Ansarifard, N ; Sharif University of Technology
Department of Naval Architecture and Marine Engineering
2016
Abstract
In order to compare the frictional resistance of three kinds of ship’s hull coatings (foul release, SPC copper, SPC TBT) in the unfouled conditions, the numerical studies have been made. Simulations have been carried out for different Reynolds numbers in the range of 2.85 × 106-5.5 × 106 based on the plate length and flow velocity. Antifouling coatings have larger mean roughness than foul release. The results have indicated that frictional resistance coefficient of foul release test plate is lower than SPC copper and SPC TBT test plates. The total resistance obtained by computational fluid dynamics has been compared with the experimental data and its good agreement has proven the ability of...
Laser-assisted friction stir processing of IN738LC nickel-based superalloy:stir processing of IN738LC nickel-based superalloy: Stir zone characteristics.tir zone characteristics
, Article Science and Technology of Welding and Joining ; Volume 21, Issue 5 , 2016 , Pages 374-380 ; 13621718 (ISSN) ; Pouranvari, M ; Ghaini, F. M ; Fujii, H ; Chung, Y. D ; Sharif University of Technology
Taylor and Francis Ltd
Abstract
Friction stir processing (FSP) of high softening-temperature materials such as nickel-based superalloys is considered to be difficult. Laser heating of a localised area ahead of the FSP tool was used to provide sufficient plasticity during the FSP of IN738LC nickel-based superalloy. The stir zone (SZ) microstructure of the friction stir processed and laser-assisted friction stir processed were characterised. Laser-assisted friction stir processing (LAFSP) produced a defect-free pass, but FSP resulted in generation of a discontinuity in the SZ. Both lower volume fraction of partially dissolved γ′ precipitates and coarser grain structure of SZ in LAFSP led to more ductility of the SZ material...
Experimental optimization of geometrical parameters on heat transfer and pressure drop inside sinusoidal wavy channels
, Article Thermal Science and Engineering Progress ; Volume 9 , 2019 , Pages 121-131 ; 24519049 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The response surface methodology (RSM) is firstly employed to investigate the geometric and flow parameters on heat transfer, pressure drop and thermal performance of sinusoidal wavy channels with different phase shifts. The investigated flow and geometric parameters are axial Reynolds number 1106
Numerical modeling of MDOF structures with sliding supports using rigid-plastic link
, Article Earthquake Engineering and Structural Dynamics ; Volume 30, Issue 1 , 2001 , Pages 27-42 ; 00988847 (ISSN) ; Hamidi, M ; Ahmadi, G ; Sharif University of Technology
2001
Abstract
In this paper, the responses of multi-degree-of-freedom (MDOF) structures on sliding supports subjected to harmonic or random base motions are investigated. Modeling of the friction force under the foundation raft is accomplished by using a fictitious rigid link which has a rigid-perfectly plastic material. This will result in identical equations of motion for the sliding structure, both in the sliding and non-sliding (stick) phases which greatly simplifies the implementation of the method into a numerical algorithm. In this model the phase transition times are determined with high accuracy. This has two advantages: first, it prevents the so-called high-frequency oscillation of the relative...
The effect of dead metal zone formation on strain and extrusion force during equal channel angular extrusion
, Article Computational Materials Science ; Volume 42, Issue 1 , 2008 , Pages 14-20 ; 09270256 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2008
Abstract
In this research, deformation of material during equal channel angular extrusion (ECAE) is analyzed using an upper bound model. The model considers the effect of die angle and friction between the sample and the die walls on the geometry of dead metal zone and total strain. The relationship between the friction coefficient, the extent of dead metal zone and total strain is derived. It is found that strain decreases with increasing die angle and friction coefficient. Moreover, a critical value for friction coefficient is determined that when the friction coefficient is more than the critical, deformation zone and therefore, the dead metal zone forms which consequently total strain decreases....
Implementation of the eXtended finite element method (X-FEM) in frictional contact problems
, Article MATERIALS PROCESSING AND DESIGN; Modeling, Simulation and Applications - NUMIFORM '07: 9th International Conference on Numerical Methods in Industrial Forming Processes, Porto, 17 June 2007 through 21 June 2007 ; Volume 908 , 2007 , Pages 1573-1578 ; 0094243X (ISSN) ; Anahid, M ; Yadegaran, I ; Nikbakht, M ; Sharif University of Technology
2007
Abstract
Numerical modeling of engineering contact problems is one of the most difficult and demanding tasks in computational mechanics. In this paper, the extended finite element method is employed to simulate the presence of discontinuities caused by frictional contact based on the penalty approach. The FEM approximation is enriched by applying additional terms to simulate the frictional behavior of contact between two bodies. The penalty method, which is one of the most commonly used techniques for contact problems, is used to model the penetration between two contacting boundaries and the normal contact force is related to the penetration by a penalty parameter. Finally, numerical examples are...
An upper bound solution of ECAE process with outer curved corner
, Article Journal of Materials Processing Technology ; Volume 182, Issue 1-3 , 2007 , Pages 555-563 ; 09240136 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2007
Abstract
In this research, deformation of material in equal channel angular extrusion (ECAE) process with outer curved corner is analyzed using an upper bound solution. The effects of die angle, friction between the sample and the die walls, and the angle of the outer curved corner, on the extrusion pressure are all considered in the analysis. It is found that the extrusion pressure decreases with increasing both the die angle and the outer curved corner angle and increases with increasing the friction coefficient. Moreover, a good agreement is found between the predicted and experimental results of extrusion pressure relating to two dies of different outer curved corner angles used in ECAE tests of...
Mechanical and microstructural characterization of A1-5083/St-12 lap joints made by friction stir welding
, Article Procedia Engineering, 5 June 2011 through 9 June 2011 ; Volume 10 , June , 2011 , Pages 3297-3303 ; 18777058 (ISSN) ; Kokabi, A. H ; Seyed Reihani, S. M ; Najafi, H ; Sharif University of Technology
2011
Abstract
Al-5083 and St-12 alloys sheets were friction stir lap welded at various travel and rotation speeds of the welding tool. Microscopic examinations indicate that the joint strength is due to the macroscopic and microscopic mechanical lockings and also atomic diffusion. The reaction zone of the welded joints consists of mixed layers of ultra-fine grains and the intermetallic compounds. The microhardness and nano indentation results prove that the intermetallic phase layer is more brittle in comparison to base metals and ultra-fine grain region. The fracture surfaces are a combination of brittle and ductile fractures. The fracture loads show that the joint strength improves significantly by...
Projection friction stir spot welding: a pathway to produce strong keyhole-free welds
, Article Science and Technology of Welding and Joining ; 2018 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This paper introduces a novel facile method, called projection friction stir spot welding, to produce a keyhole-free friction stir welds based on a pinless tool method involving using a specially designed projection on the surface of the backing anvil. The projection plays two key roles contributing to the bonding mechanism and the joint strength: (i) encouraging the material flow perpendicular to the joint interface and (ii) bending the joint interface at the edge of the projection. The process enables pathway to produce keyhole-free welds with superior mechanical performance in steel sheets compared to the other spot welding techniques. © 2018, © 2018 Institute of Materials, Minerals and...
Projection friction stir spot welding: a pathway to produce strong keyhole-free welds
, Article Science and Technology of Welding and Joining ; Volume 24, Issue 3 , 2019 , Pages 256-262 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
This paper introduces a novel facile method, called projection friction stir spot welding, to produce a keyhole-free friction stir welds based on a pinless tool method involving using a specially designed projection on the surface of the backing anvil. The projection plays two key roles contributing to the bonding mechanism and the joint strength: (i) encouraging the material flow perpendicular to the joint interface and (ii) bending the joint interface at the edge of the projection. The process enables pathway to produce keyhole-free welds with superior mechanical performance in steel sheets compared to the other spot welding techniques. © 2018, © 2018 Institute of Materials, Minerals and...
Modeling of large deformation frictional contact in powder compaction processes
, Article Applied Mathematical Modelling ; Volume 32, Issue 5 , 2008 , Pages 775-801 ; 0307904X (ISSN) ; Keshavarz, Sh ; Khaloo, A. R ; Sharif University of Technology
2008
Abstract
In this paper, the computational aspects of large deformation frictional contact are presented in powder forming processes. The influence of powder-tool friction on the mechanical properties of the final product is investigated in pressing metal powders. A general formulation of continuum model is developed for frictional contact and the computational algorithm is presented for analyzing the phenomena. It is particularly concerned with the numerical modeling of frictional contact between a rigid tool and a deformable material. The finite element approach adopted is characterized by the use of penalty approach in which a plasticity theory of friction is incorporated to simulate sliding...
Contact friction simulation in powder compaction process based on the penalty approach
, Article Materials and Design ; Volume 29, Issue 6 , 2008 , Pages 1199-1211 ; 02613069 (ISSN) ; Khoei, A. R ; Khaloo, A. R ; Sharif University of Technology
Elsevier Ltd
2008
Abstract
In this paper, the influence of powder-tool friction on the mechanical properties of the final product is investigated in pressing metal powders. A computational algorithm is presented for simulation of frictional contact in the compaction process of powder. The large deformation finite element (FE) formulation is characterized by the use of penalty approach in which a plasticity theory of friction is incorporated to simulate sliding resistance at the powder-tool interface. The constitutive relations for friction are derived from a Coulomb friction law. A double-surface cap plasticity model is employed together with the nonlinear contact friction behavior in numerical simulation of powder...
Evaluation of microstructure and mechanical properties in friction stir welded A356 + 15%SiCp cast composite
, Article Materials Letters ; Volume 60, Issue 4 , 2006 , Pages 565-568 ; 0167577X (ISSN) ; Kokabi, A. H ; Gharacheh, M. A ; Sarrafi, R ; Shalchi, B ; Azizieh, M ; Sharif University of Technology
2006
Abstract
Friction Stir Welding (FSW) is a novel solid state welding process for joining materials. In this process a high speed tool is introduced into the weld seam and due to localized frictional heat, plastic deformation and transverse movement along the weld seam, joining is accomplished. In this study aluminum matrix composite A356 + 15%SiCp is chosen for friction stir welding. Fragmentation of SiC particles and silicon needles existing in eutectic phase as well as their homogenous distribution as a result of stirring with high plastic strains, improve mechanical properties such as modulus of elasticity, yield and ultimate strength, elongation and hardness in the weld zone compared to that of...
Contact friction modeling with the extended finite element method (X-FEM)
, Article Journal of Materials Processing Technology ; Volume 177, Issue 1-3 , 2006 , Pages 58-62 ; 09240136 (ISSN) ; Nikbakht, M ; Sharif University of Technology
2006
Abstract
In this paper, the extended finite element method (X-FEM) is developed for modeling of frictional contact problems. In order to model the frictional contact behavior within the standard finite element framework, the special functions are included in standard FE method to simulate discontinuity without considering the boundary conditions in meshing the domain. The classical finite element approximation is therefore enriched by applying additional terms to simulate the frictional behavior of contact between two bodies. These terms, which are included for enrichment of nodal displacements, depend on the contact condition between two surfaces. The partition of unity method is applied to...
Effects of post-annealing on the microstructure and mechanical properties of friction stir processed Al–Mg–TiO2 nanocomposites [electronic resource]
, Article Journal of Materials & Design ; November 2014, Volume 63, Pages 30–41 ; Simchi, A. (Abdolreza) ; Kokabi, A. H ; Gerlich, A. P ; Nosko, M ; Sharif University of Technology
Abstract
Aluminum matrix nanocomposites were fabricated via friction stir processing of an Al–Mg alloy with pre-inserted TiO2 nanoparticles at different volume fractions of 3%, 5% and 6%. The nanocomposites were annealed at 300–500 °C for 1–5 h in air to study the effect of annealing on the microstructural changes and mechanical properties. Microstructural studies by scanning and transmission electron microscopy showed that new phases were formed during friction stir processing due to chemical reactions at the interface of TiO2 with the aluminum matrix alloy. Reactive annealing completed the solid-state reactions, which led to a significant improvement in the ductility of the nanocomposites (more...