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fatigue-testing
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Effect of Different Defects of Spot Welded Joint in Automotive Body on Fatigue Strength: Experimental and Numerical Investigation
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor) ; Mehmanparast, Ali (Supervisor) ; Reza Kashyzadeh, Kazem (Co-Supervisor)
Abstract
On average there are to resistance spot welding connections per vehicle. The quality of these welding directly affects the quality of the finished product and the strength of the vehicle against various loads, including road roughness, different maneuvers and even sudden impacts from accidents. During the spot welding process, unintentional failures occur due to the wrong choice of current, force and time. The aim of this study is to investigate the fatigue strength of three-sheets welding joints in numerical and laboratory methods, considering the defects of (Undersize weld, Stick, edge of sheet metal and Edge of sheet metal-SECANT) . For this purpose, a healthy spot welding model was first...
Geometrical Optimization of Aluminum Alloy Wheels for High Fatigue and Impact Strength
, M.Sc. Thesis Sharif University of Technology ; Khayyat, Ali Akbar (Supervisor) ; Pasharavesh, Abdolreza (Supervisor)
Abstract
After the rise of the automotive industry, aluminum wheels have superseded steel counterparts due to their numerous advantages. Foremost among these benefits is their reduced weight, leading to fuel savings and diminished environmental impact. Moreover, aluminum wheels offer enhanced aesthetics and greater strength in comparison to steel alternatives. This thesis focuses on the geometrical optimization of an aluminum wheel model conforming to the standards set by Iran's Department of Standards, aiming to achieve a higher strength-to-weight ratio. While prior research works have mainly focused on weight reduction while maintaining strength within approved standards, this thesis aims at the...
The Evaluation of Different Parameters on Fatigue Life of Carbon / Epoxy and Carbon / Phenolic Polymer Composite Rods under Tensile-pressure Loads
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkheili, Ali (Supervisor)
Abstract
The aim of this dissertation is to analyze the tensile-stress fatigue of composite rods made of a combination of carbon-epoxy resin as well as carbon chopped-phenolic resin and to investigate the effect of different parameters on their fatigue life. The curing process is completely different in carbon / epoxy and carbon / phenolic composites, Carbon / Epoxy is a thermo-plastic composite, but carbon / phenolic is a thermo- set composite. Therefore, differences in the curing process, raw materials, changes in the volume percentage of resin and fibers, the effects of different loading during the production and curing process of the composite, cooling and heating rates during production can...
Experimental and Finite Element Analysis of Vehicle Steering Knuckle Fatigue Life under Road Driving Test
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Steering Knuckle is a mechanical part in an automobile which connects the break, suspension system, hub, and steering system to the chassis. In the recent years due to the variant imposing forces on the steering knuckle this part’s fatigue life has attracted engineers and designers’ attention. The considered steering knuckle in this project is a steering knuckle from an Iranian car. The goal of this project is to determine the fatigue life of a steering knuckle under street loads. The fatigue life of a steering knuckle has been investigated with both experimental and finite element methods. In order to perform the fatigue test a test fixture was designed. The finite element analysis consists...
Fatigue properties of machinable austempered ductile iron
, Article 16th International Metallurgical and Materials Conference, METAL 2007, 22 May 2007 through 24 May 2007 ; 2007 ; Baghersaee, N ; Varahram, N ; Hanumantha Rao, M ; Sharif University of Technology
TANGER spol. s r.o
2007
Abstract
MADI is new engineering material with very desirable properties such as higher strength at the same hardness compared to regular ductile iron, significantly better fatigue performance than regular ductile iron or austempered ductile iron, better machinability than regular austempered ductile iron and similar to as cast ductile iron. In this study,fatigue properties of Machinable Austempering Ductile was investigated using rotary -bend fatigue testing device. Chemical composition of sample was selected on the base of previous work which results in good mechanical properties and low hardness after austempering process. The results of this study,indicates that for an austempered ductile iron...
Multiple stress creep and recovery and time sweep fatigue tests: Crumb rubber modified binder and mixture performance
, Article Transportation Research Record ; Issue 2180 , 2010 , Pages 67-74 ; 03611981 (ISSN) ; Tabatabaee, H. A ; Sharif University of Technology
2010
Abstract
Crumb rubber modification (CRM) is an effective means of improving neat asphalt performance. Numerous studies have investigated the effects of CRM using the current Superpave® laboratory tests. Recent studies have shown that the assumption of linear viscoelastic behavior or employing insufficient stress or strain levels makes current tests inadequate for properly assessing the performance of binders, especially when modified. This problem has resulted in the development of improved test methods such as the time sweep binder fatigue test and the multiple stress creep and recovery (MSCR) test for permanent deformation. The present study assesses the performance of binders modified with a wide...
Tensile and fatigue fracture of nanometric alumina reinforced copper with bimodal grain size distribution
, Article Materials Science and Engineering A ; Volume 507, Issue 1-2 , 2009 , Pages 200-206 ; 09215093 (ISSN) ; Simchi, A ; Sharif University of Technology
2009
Abstract
Alumina dispersion-strengthened copper was produced by an internal oxidation process and hot powder extrusion method. The microstructure of the composite consisted of fine-grained region with an average grain size of 1.1 ± 0.1 μm, coarse-grained region with an average grain size of 5.6 ± 0.1 μm, nanometric alumina particles (γ-type) with an average diameter of 30 nm, and coarse alumina particles (350 nm) at the boundaries of the large grains. The tensile and fatigue fracture of the composite was studied in the extruded condition and after 11% cold working. The low cycle fatigue behavior was examined in strain control mode (ε = 0.5%) under fully reverse tension-compression cycle at 1 Hz up to...
Determination of potential function in contact problems
, Article 8th International Conference on Computer Methods and Experimental Measurements for Surface and Contact Mechanics, CONTACT/SURFACE 2007, 16 May 2007 through 18 May 2007 ; Volume 55 , 2007 , Pages 227-236 ; 17433533 (ISSN); 9781845640736 (ISBN) ; Adibnazari, S ; Sharif University of Technology
2007
Abstract
In this paper, a relation is introduced that simplifies the determination of the Muskhelishvilis potential function in plane contact problems. The relation is (z)=1/2[p(z)iq(z)], which is correct for all uncoupled-elastic contact problems. This relation is proved in a mathematical way and utilized to obtain the potential function in several contact problems. A complete agreement has been observed between our results and the potential functions that have been obtained from complicated methods in the past. Utilization of the relation simplifies the solution of contact problems and analytical calculation of the stress and displacement fields, which is helpful in the analytical studies of...
Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; 2021 ; 09544062 (ISSN) ; Adibnazari, S ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The...
Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 236, Issue 7 , 2022 , Pages 3623-3635 ; 09544062 (ISSN) ; Adibnazari, S ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The...
Fatigue fracture of friction-stir processed Al-Al3Ti-MgO hybrid nanocomposites
, Article International Journal of Fatigue ; Volume 87 , 2016 , Pages 266-278 ; 01421123 (ISSN) ; Khodabakhshi, F ; Simchi, A ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
Abstract
This paper presents experimental results on the fatigue properties of Al-matrix nanocomposites prepared by the friction stir processing (FSP) technique. An Al-Mg alloy (AA5052) with different amounts (∼2 and 3.5 vol%) of pre-placed TiO2 nanoparticles were FSPed up to 6 passes to attain homogenous dispersion of nano-metric inclusions. Microstructural studies by electron microscopic and electron back scattering diffraction (EBSD) techniques showed that nano-metric Al3Ti (50 nm), TiO2 (30 nm), and MgO (50 nm) particles were distributed throughout a fine-grained Al matrix (<2 μm). Consequently, a significant improvement in the tensile strength and hardness was attained. Uniaxial...
Effectiveness of linear amplitude sweep (LAS) asphalt binder test in predicting asphalt mixtures fatigue performance
, Article Construction and Building Materials ; Volume 171 , May , 2018 , Pages 281-290 ; 09500618 (ISSN) ; Mirzaeian, D ; Moniri, A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this research, Linear Amplitude Sweep (LAS) test was conducted on several asphalt binders modified by different percentages of gilsonite and Styrene-Butadiene-Styrene (SBS) polymer. Asphalt mixtures were also made from some of the study binders and tested for fatigue resistance using Four-point Bending Beam (FBB) fatigue test. The results showed that a strong correlation exists between LAS and FBB rankings at all the tested strain levels. Also, SHRP binder fatigue index (G∗sinδ), as a traditional binder fatigue index, was evaluated which did not show a strong correlation with either LAS or FBB tests. It was concluded that LAS test seems to be an effective binder fatigue test in predicting...
Thermo-mechanical stress analysis of thermal barrier coating system considering thickness and roughness effects
, Article Surface and Coatings Technology ; Vol. 243 , 2014 , pp. 91-99 ; ISSN: 02578972 ; Azadi, M ; Farrahi, G. H ; Sharif University of Technology
Abstract
Cast aluminium-silicon alloy, A356.0, is widely used in automotive and aerospace industries because of its outstanding mechanical, physical, and casting properties. Thermal barrier coatings can be applied to combustion chamber to reduce fuel consumption and pollutions and also improve fatigue life of components. The purpose of the present work is to simulate stress distribution of A356.0 under thermo-mechanical cyclic loadings, using a two-layer elastic-visco-plastic model of ABAQUS. The results of stress-strain hysteresis loop are validated by an out of phase thermo-mechanical fatigue test. Different thicknesses from 300 to 800. μm of top coat and also roughness of the interfaces are...
Coating thickness and roughness effect on stress distribution of A356.0 under thermo-mechanical loadings
, Article Procedia Engineering, 5 June 2011 through 9 June 2011 ; Volume 10 , June , 2011 , Pages 1372-1377 ; 18777058 (ISSN) ; Azadi, M ; Farrahi, G. H ; Sharif University of Technology
2011
Abstract
Cast aluminium-silicon alloy, A356.0, is widely used in automotive components such as diesel engine cylinder heads and also in aerospace industries because of its outstanding mechanical, physical, and casting properties. Thermal barrier coatings are applied to combustion chamber in order to reduce fuel consumption and pollutions and also improve fatigue life of components. However, studies on behaviour of A356.0 with thermal barrier coating are still rare. The purpose of the present work is to simulate stress distribution of A356.0 under thermo-mechanical cyclic loadings, using a two-layer elastic-visco-plastic model of ABAQUS software. The results of stress-strain hysteresis loop are...
The effect of dynamic strain aging on fatigue properties of dual phase steels with different martensite morphology
, Article Materials Science and Engineering A ; Volume 527, Issue 1-2 , 2009 , Pages 235-238 ; 09215093 (ISSN) ; Ekrami, A ; Sharif University of Technology
Abstract
Dual phase (DP) steels with network and fibrous martensite were produced by intercritical annealing heat treatment cycles. Some of these steels were deformed at dynamic strain aging temperatures. Room temperature tensile tests of specimens deformed at 300 °C showed that both yield and ultimate tensile strengths for both morphologies increased, while total elongation decreased. Fatigue test results before and after high temperature deformation showed that dynamic strain aging has a stronger effect on fatigue properties of dual phase steels with fibrous martensite. Cracks in DP steels with fibrous martensite propagate in a tortuous path in soft ferrite phase, while they pass of both hard and...
Improvement of high temperature fatigue lifetime in AZ91 magnesium alloy by heat treatment
, Article Materials Science and Engineering A ; Volume 588 , December , 2013 , Pages 357-365 ; 09215093 (ISSN) ; Azadi, M ; Hossein Farrahi, G ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2013
Abstract
In the present paper, an improvement in high temperature fatigue properties of the AZ91 magnesium alloy with rare earth elements has been obtained by a typical heat treatment, denoted by T6. For this objective, out-of-phase thermo-mechanical fatigue, room temperature and high temperature low cycle fatigue tests are performed to compare lifetimes. Several rare earth elements are initially added to the AZ91 alloy during a gravity casting process in permanent molds. Also, the type of the heat treatment is examined. Results of specimens with only the solution (the T4 heat treatment) and the solution with the ageing process (the T6 heat treatment) are compared under isothermal fatigue loadings....
The effects of combination of severe plastic deformation and Shot Peening surface treatment on fatigue behavior of 6082 aluminum alloy
, Article Russian Journal of Non-Ferrous Metals ; Volume 56, Issue 2 , 2015 , Pages 206-211 ; 10678212 (ISSN) ; Irani, M ; Karimi Taheri, A ; Sharif University of Technology
Abstract
In this paper, the effects of Equal Channel Angular Pressing process (ECAP) followed by Shot Peening process (SP) on the fatigue properties of 6082 aluminum alloy are investigated. Several samples of the alloy are ECAPed and SPed and then their mechanical behavior are characterized using tensile, micro-hardness, and fatigue tests. The results indicate that shot peening and then polishing the specimen after one-pass ECAP is an effective method to improve the fatigue life of the alloy. Moreover, by increasing the number of ECAP passes before shot peening, a local work softening occurs at the subsurface layer, leading to a significant decrease in the fatigue life of the alloy. The results of...
Effects of the hardened nickel coating on the fatigue behavior of CK45 steel: experimental, finite element method, and artificial neural network modeling
, Article Iranian Journal of Materials Science and Engineering ; Volume 14, Issue 4 , 2017 , Pages 81-99 ; 17350808 (ISSN) ; Kashyzadeh, K. R ; Sharif University of Technology
Abstract
Hardened nickel coating is widely used in many industrial applications and manufacturing processes because of its benefits in improving the corrosion fatigue life. It is clear that increasing the coating thickness provides good protection against corrosion. However, it reduces the fatigue life. Thus, applying a thin layer of coated nickel might give an acceptable corrosion protection with minimum loss of the fatigue life. In the present study, the effects of hardened nickel coating with different thicknesses on the fatigue behavior of CK45 mild steel were experimentally investigated. After conducting the experimental tests, we carried out two different modeling approaches of finite element...
Effects of conventional, severe, over, and re-shot peening processes on the fatigue behavior of mild carbon steel
, Article Surface and Coatings Technology ; Volume 344 , 25 June , 2018 , Pages 62-74 ; 02578972 (ISSN) ; Unal, O ; Kashyzadeh, K. R ; Sharif University of Technology
Elsevier B.V
2018
Abstract
The present study investigates experimentally the effects of different shot peening treatments, including conventional, severe, over, and re-shot peening on microstructure, mechanical properties, and fatigue behavior of AISI 1050 mild carbon steel. Different shot peening treatments were performed using various effective parameters by considering the influences of increasing Almen intensity and coverage. Optical microscopy and field emission scanning electron microscopy observations and X-Ray diffraction measurements were carried out to analyze grains refinement in each shot peening treatment. Microhardness and residual stress measurements were taken from shot peened surfaces to the core...
Effects of conventional and severe shot peening on residual stress and fatigue strength of steel aisi 1060 and residual stress relaxation due to fatigue loading: experimental and numerical simulation
, Article Metals and Materials International ; Volume 27, Issue 8 , 2021 , Pages 2575-2591 ; 15989623 (ISSN) ; Farrahi, G. H ; Reza Kashyzadeh, K ; Unal, O ; Gugaliano, M ; Bagherifard, S ; Sharif University of Technology
Korean Institute of Metals and Materials
2021
Abstract
Abstract: This study investigates and compares the effects of different shot peening treatments including conventional and severe shot peening on microstructure, mechanical properties, fatigue behavior, and residual stress relaxation of AISI 1060 steel. Shot peening treatments were applied with two Almen intensities of 17 and 21 A and a wide ranges of coverage (100%–1500%). Various microstructural observations were carried out to analyze the evolution of microstructure. Microhardness, residual stress and surface roughness measurements and also axial fatigue test were performed. Moreover, the extent of the residual stress relaxation during cyclic loading was investigated by means of XRD...