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surface-hardening
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Statistical Analysis of Surface Hardness for Determination of Residual Stresses
, M.Sc. Thesis Sharif University of Technology ; Hossein Farrahi, Gholam (Supervisor) ; Faghidian, Ali (Co-Advisor)
Abstract
Residual stresses are stress fields that exist in the absence of any external loads. All mechanical processes can cause deformation that may lead to residual stresses. It is well established that virtually no material, no component and no structure of technical importance exists free of residual stresses. However, in practice, the knowledge of the true distribution of exiting residual stress is rare. The residual stress fields are very challenging to evaluate, independent of the measurement techniques. The important aspect about the residual stress determination is that often true distribution is unknown in the engineering specimen. A simple and non-destructive method to measure residual...
Wear Behavior of Cast Rods Manufactured for Hard Surfacing Iron Based Alloy
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
Wear of parts during service is one of the main factors of damage to the industrial parts. From among various kinds of wear, abrasive wear has the most role in damage of industrial parts. Hard surfacing is a useful and cost effective method for improving the surface properties of parts. This method is made through coherent layer sediment from the alloys resistant to abrasion, oxidation and wear by welding or spray. Determining the appropriate alloy for hard surfacing operations need knowing of working conditions of the part and the type of occurred abrasion. Ordinarily, the alloys which are prepared for hard work by welding, are in the form of cored wire or electrodes. In this research die...
Application of corotational rates of the logarithmic strain in constitutive modeling of hardening materials at finite deformations
, Article International Journal of Plasticity ; Volume 21, Issue 8 , 2005 , Pages 1546-1567 ; 07496419 (ISSN) ; Yeganeh, M ; Saidi, A. R ; Sharif University of Technology
2005
Abstract
In this paper a finite deformation constitutive model for rigid plastic hardening materials based on the logarithmic strain tensor is introduced. The flow rule of this constitutive model relates the corotational rate of the logarithmic strain tensor to the difference of the deviatoric Cauchy stress and the back stress tensors. The evolution equation for the kinematic hardening of this model relates the corotational rate of the back stress tensor to the corotational rate of the logarithmic strain tensor. Using Jaumann, Green-Naghdi, Eulerian and logarithmic corotational rates in the proposed constitutive model, stress-strain responses and subsequent yield surfaces are determined for rigid...
Failure Analysis of Torsion bar and Improvement of Manufacturing Processes
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
In order to improve the fatigue performance of torsion bar, induction surface hardening is performed. The aim of the present study is failure analysis of torsion bar and improvement of manufacturing process. Induction hardening was simulated using finite element method. As a result temperature history and residual stresses were obtained. Temperature and residual stress distributions are affected by the component geometry, the material behavior and the induction treatment parameters. Based on the residual stress distribution and the external fatigue loads, cracks can nucleate from the surface or below the hardened layer. Therefore, it is very important to determine the residual stress...
Thermal analysis of laser hardening for different moving patterns
, Article International Journal of Engineering, Transactions A: Basics ; Volume 22, Issue 2 , 2009 , Pages 169-180 ; 17281431 (ISSN) ; Sistaninia, M ; Sharif University of Technology
Materials and Energy Research Center
2009
Abstract
Transient thermal field in laser surface hardening treatment of medium carbon steel was analyzed by employing both three-dimensional analytical model and finite element model. In finite element model the laser beam was considered as a moving plane heat flux to establish the temperature rise distribution in the work-piece, while in analytical model laser beam was considered as an internal heat source. The numerical results were compared with the analytical results. In laser heat treatment of steel some methods are used to produce a wider and nearly uniform average irradiance profile. It may be achieved by rotating the beam optically, thereby producing an overlapping spiral track, or by...
Residual stress analyses of re-autofrettaged thick-walled tubes
, Article International Journal of Pressure Vessels and Piping ; Volume 98 , 2012 , Pages 57-64 ; 03080161 (ISSN) ; Voyiadjis, G. Z ; Hoseini, S. H ; Hosseinian, E ; Sharif University of Technology
Elsevier
2012
Abstract
In this paper the effect of the re-autofrettage process on the residual stress distribution at the wall of a thick-walled tube is considered. For accurate material behavior modeling, it is assumed that the yield surface is a function of all the stress invariants. Also for estimating the behavior of the material under loading-unloading process, a modified Chaboche's hardening model is applied. For evaluation of this unloading behavior model a series of loading-unloading tests are conducted on specimens that are made of the high strength steel, DIN1.6959. In addition the finite element simulations are implemented to simulate the re-autofrettage process and to estimate the residual stresses....
The effect of dynamic strain aging on room temperature mechanical properties of high martensite dual phase (HMDP) steel
, Article Materials Science and Engineering A ; Volume 550 , 2012 , Pages 325-332 ; 09215093 (ISSN) ; Koohbor, B ; Ahadi, K ; Ekrami, A ; Khakian Qomi, M ; Izadyar, T ; Sharif University of Technology
Elsevier
2012
Abstract
AISI 4340 steel bars were heated at 900 °C for one hour, annealed at 738 °C for different durations and oil-quenched in order to obtain dual phase steels with different ferrite volume fractions. A 3% prestrain at the temperature range of 150-450 °C was then imposed to the samples, and room temperature tensile tests were carried out, afterwards. Results indicate that the maximum values for both yield and ultimate tensile strength would exist for the samples pre-strained at the temperature range of 250-300 °C. Also, a sudden drop of the ductility was observed at the mentioned temperature range. The observed behavior might be attributed to the occurrence of dynamic strain aging taken place at...
Numerical simulation of induction hardening of torsion bar
, Article Proceedings of the World Congress on Engineering 2011, WCE 2011, 6 July 2011 through 8 July 2011 ; Volume 3 , July , 2011 , Pages 2080-2083 ; 9789881925152 (ISBN) ; Farrahi, G. H ; Sharif University of Technology
2011
Abstract
In order to improve the fatigue performance of torsion bar, induction surface hardening is performed. The aim of the present study is to compare the experimental residual stress fields measured by X-ray diffraction with those predicted from finite element modeling of the whole induction surface hardening process. Temperature and residual stress distributions are affected by the component geometry, the material behavior and the induction treatment parameters. Based on the residual stress distribution and the fatigue loading, cracks can nucleate from the surface or below the hardened layer. Therefore, it is very important to determine the residual stress distribution and optimize the process,...