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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After the rise of the automotive industry, aluminum wheels have superseded steel counterparts due to their numerous advantages.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...
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...
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...
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...
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...
The effect of shot peening on fatigue life of welded tubular joint in offshore structure
, Article Materials and Design ; Volume 36 , 2012 , Pages 250-257 ; 02641275 (ISSN) ; H-Gangaraj, S. M ; Farrahi, G. H ; Majzoobi, G. H ; Mahmoudi, A. H ; Daghigh, M ; Yari, A ; Moridi, A ; Sharif University of Technology
2012
Abstract
An offshore structure is exposed to environmental loading and cyclic stress variations throughout its life. This would result in the possibility of fatigue cracking in its members. Cracks in these structures usually initiate around welded areas, then grow progressively from the heat-affected zone to base metal through the thickness of the tubular members. Therefore, fatigue life improvement of offshore structures is of great importance. In this paper, structural analysis of an offshore platform is carried out and the critical joint is specified. The welding process is simulated and the residual stresses due to the welding are determined. Experimental residual stress measurement is carried...
The effect of pre-straining at intermediate temperatures on the mechanical behavior of high-bainite dual phase (HBDP) steels
, Article Materials Science and Engineering A ; Volume 543 , May , 2012 , Pages 224-230 ; 09215093 (ISSN) ; Haghshenas Fatmehsari, D ; Ekrami, A ; Sharif University of Technology
Abstract
High-bainite dual phase (HBDP) steels with 34. vol.% ferrite were subjected to tensile strains of 1%, 3%, and 5% at intermediate temperatures (150-450. °C). Mechanical behavior of pre-deformed steels was then investigated at room temperature. A maximum value for both yield stress and ultimate tensile strength was observed for pre-deformed steels. A minimum elongation was also found in the same pre-deformed specimens at the range of 250-350. °C. It was found that dynamic strain aging (DSA) plays the major role in mechanical properties of pre-strained HBDP steels. The DSA indicator parameter (DSAP) was introduced to evaluate DSA mechanism. Maxima of DSAP were likewise observed at the range of...
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...
The effect of bainite morphology on the mechanical properties of a high bainite dual phase (HBDP) steel
, Article Materials Science and Engineering A ; Volume 525, Issue 1-2 , 2009 , Pages 159-165 ; 09215093 (ISSN) ; Ekrami, A ; Sharif University of Technology
2009
Abstract
4340 steel bars were austenitized at 850 °C for 1 h followed by heating at 700 °C for 90 min and quenching into a salt bath at the temperature range of 300-450 °C for 1 h to obtain dual structures with 34 vol.% fraction ferrite and various bainite morphologies. SEM studies showed that by increasing the austempering temperature, bainite morphology varies from lower to upper bainite. Tensile, impact and hardness tests revealed that increasing the austempering temperature from 300 to 400 °C leads to a reduction in yield and ultimate tensile strength, hardness, uniform and total elongation and impact energy. But in dual phase steel produced by austempering at 450 °C, yield and tensile strength...
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...
Stress–strain time-dependent behavior of A356.0 aluminum alloy subjected to cyclic thermal and mechanical loadings
, Article Mechanics of Time-Dependent Materials ; Vol. 18, issue. 3 , 2014 , p. 475-491 ; Ghodrati, M ; Azadi, M ; Rezvani Rad, M ; Sharif University of Technology
Abstract
This article presents the cyclic behavior of the A356.0 aluminum alloy under low-cycle fatigue (or isothermal) and thermo-mechanical fatigue loadings. Since the thermo-mechanical fatigue (TMF) test is time consuming and has high costs in comparison to low-cycle fatigue (LCF) tests, the purpose of this research is to use LCF test results to predict the TMF behavior of the material. A time-independent model, considering the combined nonlinear isotropic/kinematic hardening law, was used to predict the TMF behavior of the material. Material constants of this model were calibrated based on room-temperature and high-temperature low-cycle fatigue tests. The nonlinear isotropic/kinematic hardening...
Simultaneous effects of cutting depth and tool overhang on the vibration behavior of cutting tool and high-cycle fatigue behavior of product: experimental research on the turning machine
, Article International Journal of Advanced Manufacturing Technology ; Volume 122, Issue 5-6 , 2022 , Pages 2361-2378 ; 02683768 (ISSN) ; Borisovna, K. D ; Ghorbani, S ; Reza Kashyzadeh, K ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
One of the major challenges in the manufacturing parts, especially metals, is turning with good/excellent surface quality, which has a significant effect on the fatigue strength of the industrial components. Selecting incorrect or unsuitable values of machining parameters leads to vibration instability in the cutting tool and as a result, excessive roughness is created on the product’s surface. Therefore, one of the ways to reduce the roughness factor and increase the product fatigue life is to control the relative slip and vibration between the cutting tool and the workpiece. To achieve this goal, the authors attempted to investigate the simultaneous effects of tool overhang and cutting...
Prediction by Genetic Algorithm and measurement by center hole drilling of residual stresses of MAG weldment
, Article Advanced Materials Research, 2 November 2008 through 5 November 2008 ; Volume 83-86 , 2010 , Pages 738-745 ; 10226680 (ISSN) ; 0878492976 (ISBN); 9780878492978 (ISBN) ; Majzoobi, G. H ; Fadaee, A ; Sharif University of Technology
Abstract
In the present work, specimens were cut out from St-37 plates with 19 mm thickness. The thickness of plates was reduced to 12.5 mm by milling and grinding operations. Then a standard V-shaped fillet was made on one edge of the plates. Two plates were butt-welded by standard metal arc gas (MAG) welding process. Residual stresses induced by welding were measured on 20 specimens by centre hole drilling. Load controlled axial fatigue tests were carried out to determine the fatigue life of specimens. Crack growth rates were obtained from experiment. Fractography of specimens was performed. Genetic Algorithm (GA) was employed for prediction of residual stress value in weldments using the crack...
Optimization of air plasma sprayed thermal barrier coating parameters in diesel engine applications
, Article Journal of Materials Engineering and Performance ; Volume 22, Issue 11 , 2013 , Pages 3530-3538 ; 10599495 (ISSN) ; Farrahi, G. H ; Moridi, A ; Sharif University of Technology
2013
Abstract
In the present paper, an optimization of thermal barrier coating parameters is performed for diesel engine applications. The substrate is A356.0-T7, a cast aluminum alloy which has a vast application in diesel engines, and the alloy is coated by plasma sprayed ZrO2-8 wt.% Y2O3. Parameters including the feed rate of coating powders, the nozzle distance to specimen surfaces, and the coating thickness are optimized by thermal shock fatigue tests and bending tests. Optimum values of the feed rate and the nozzle distance are 30 g/min and 80 mm, respectively, when the objective is considered as maximizing the bending strength. Thermal shock tests demonstrate that lower thickness of coating layers...
Numerical simulations of cyclic behaviors in light alloys under isothermal and thermo-mechanical fatigue loadings
, Article Materials and Design ; Vol. 56 , April , 2014 , pp. 245-253 ; ISSN: 02641275 ; Shamloo, A ; Felfeli, M ; Azadi, M ; Sharif University of Technology
Abstract
In this article, numerical simulations of cyclic behaviors in light alloys are conducted under isothermal and thermo-mechanical fatigue loadings. For this purpose, an aluminum alloy (A356) which is widely used in cylinder heads and a magnesium alloy (AZ91) which can be applicable in cylinder heads are considered to study their stress-strain hysteresis loops. Two plasticity approaches including the Chaboche's hardening model and the Nagode's spring-slider model are applied to simulate cyclic behaviors. To validate obtained results, strain-controlled fatigue tests are performed under low cycle and thermo-mechanical fatigue loadings. Numerical results demonstrate a good agreement with...
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...
Mechanical and electrochemical behaviors of butt-welded high temperature steel pipes
, Article Engineering Failure Analysis ; 2016 ; 13506307 (ISSN) ; Vanini, S. A. S ; Fereiduni, E ; Rokni, M. H ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this study, fatigue, corrosion fatigue and electrochemical behaviors of butt-welded A106-B steel pipes were investigated. These pipes were subjected to mechanical and thermal cyclic stresses due to the internal pressure fluctuations and cooling-heating cycles. Residual stress measurements were carried out for three different depths through the thickness and were correlated to the microstructural observations and microhardness measurements. Results showed that the maximum tensile residual stresses existed at the boundary of weld metal and base metal because of the contraction-expansion effects resulting from phase transformations and cooling rate differences. Fatigue fractures occurred at...
Influence of residual stress on fatigue life of st-37 butt-mag weldment
, Article 12th International Conference on Metal Forming, METAL FORMING 2008, Krakow, 21 September 2008 through 24 September 2008 ; Volume 79, Issue 2 , 2008 , Pages 280-287 ; 16113683 (ISSN) ; Majzoobi, G. H ; Fadaee, A ; Sharif University of Technology
Wiley-VCH Verlag
2008
Abstract
In this paper residual stresses induced by butt metal arc gas welding (MAGW), in accordance with ASTM E837, are determined by hole drilling. The results are analyzed by probabilistic methods. Also, the effect of fatigue life on relaxation of welding residual stress is investigated. The specimens are tested to measure fatigue life and crack growth rates in accordance with ASTM E466 for force controlled amplitude axial fatigue testing. © 2008 Verlag Stahleisen GmbH, Düsseldorf
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....