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fatigue-tests
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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...
A simple relation in elastic contact problems
, Article Tribology International ; Volume 41, Issue 5 , 2008 , Pages 341-347 ; 0301679X (ISSN) ; Sharafbafi, F ; Sharif University of Technology
2008
Abstract
In this paper, a new relation is introduced that simplifies the determination of the Muskhelishvili's potential function in plane contact problems. The relation is Φ (z) = 1 / 2 [p (z) - i q (z)], which is correct for all uncoupled contact problems. The new 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 new relation simplifies the solution of contact problems and analytical calculation of the stress and displacement fields, which may lead to the design of...
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
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...
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...
Crack-based healing master curve derived from linear amplitude sweep tests: a cohesive healing indicator for asphalt binders
, Article Materials and Structures/Materiaux et Constructions ; Volume 54, Issue 4 , 2021 ; 13595997 (ISSN) ; Tabatabaee, N ; Hajj, R ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
This investigation employed an interrupted torsion fatigue test using the linear amplitude sweep procedure to assess the intrinsic self-healing potential of unaged, aged, rejuvenated, and re-aged asphalt binders. Continuous oscillatory shear strain loading at different damage levels were interrupted with a single rest period of different durations. An index based on the decrease in crack length following the rest period (Ha) has been defined to accurately reflect the occurrence of healing. The results indicate that Ha is higher at lower damage levels and for longer rest-period durations. The amount of irreversible crack growth increased with an increase in crack propagation and aging level....
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...
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...
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...
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 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...
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...
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...
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 two- and three-dimensional graphene-based nanomaterials on the fatigue behavior of epoxy nanocomposites
, Article Materials Today Communications ; Volume 24 , September , 2020 ; Adibnazari, S ; Imam, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Epoxy resins and their derivatives, such as composites and epoxy adhesives, are widely used in various industries. However, epoxy resins have low performance against dynamic loading and crack propagation. Graphene-based nanomaterials can improve the mechanical performance of polymeric composites because of their appropriate mechanical properties and high surface area. This study aimed to investigate the effect of Two-Dimensional Graphene Oxide (2DGO) and Three-Dimensional Nitrogen-Doped Graphene (3D(N)G) nanomaterials on the fatigue behavior of epoxy resin. 2DGO was produced by the modified Hummer's method and 3D(N)G was synthesised by hydrothermal process, followed by freeze-drying....
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...
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...
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...
Contact of an asymmetrical rounded apex wedge with a half plane
, Article International Journal of Engineering Science ; Volume 50, Issue 1 , January , 2012 , Pages 192-197 ; 00207225 (ISSN) ; Sharafbafi, F ; Ghanati, P ; Sharif University of Technology
Abstract
Two-dimensional elastic contact problem of an asymmetrical rounded apex wedge with a half plane is considered and an analytical solution is presented for vertical and horizontal external loading in the presence of coulomb friction. The pressure and shear distribution functions are found in closed form under partial slip condition. Further by utilizing a new relation Muskhelishvili's potential function is obtained and results are analyzed. Designing better cutting tools, selecting fretting fatigue test pads and deeper lap joint analyzing are several practical applications of the outcomes