Khalil Sherafatnia's research while affiliated with Sharif University of Technology and other places

Publications (15)

Article
Shot peening is the most common surface treatment employed to enhance the fatigue performance of structural metallic materials and often carried out after other surface treatments. This paper mainly focuses on the effects of initial conditions of surface such as initial stress filed and hardness profile on shot peening residual stress field. The re...
Article
The experimental observations indicate that the mechanical behavior of micro and nano scale structures is size-dependent. In this study, employing the modified couple stress theory the size-dependent strain energy release rate of notched Euler-Bernoulli beams made of functionally graded material (FGM) is formulated. The normalized energy release ra...
Chapter
Full-text available
Mechanical failures in most cases originate from the exterior layers of the components. It is considerably effective to apply methods and treatments capable to improve the mechanical properties on component’s surface. Surface nanocrystallization produced by severe plastic deformation (SPD) processes such as severe shot peening (SSP) is increasingly...
Article
This paper presents an analytical model to predict the residual stress distribution induced by Shot peening. The analytical approach is based on the work of Shen and Atluri [S. Shen, S.N. Atluri, An analytical model for shot-peening induced residual stresses, Comput. Mater. Con. 4 (2006) 75-85] with some modifications. The modifications are related...
Article
Full-text available
Shot peening is a process of cold working a part that increase its resistance to metal fatigue and some forms of stress corrosion. Shot peening causes plastic deformation in the surface of the peened part and leads some changes in mechanical and metallurgical properties of it. Artificial intelligence (AI) systems such as artificial neural netw...
Conference Paper
Full-text available
The present study investigates the micro-structural size effect on the strain energy release rate of notched beams made of functionally graded material (FGM) under three-point bending condition. Using the modified couple stress theory, a non-classical continuum theory capable of capturing the size effect, the normalized energy release rate of a Tim...
Article
Shot peening is one of the most effective surface strengthening treatment technologies in which compressive residual stresses are induced beneath the specimen surface. Effects of various factors on the distribution of residual stress profile induced by shot peening have been investigated by many researchers. However, initial residual stresses are o...
Article
Full-text available
In this paper, effect of the internal viscous damping on the frequency shift and damping ratios of a microbeam made of functionally graded materials is investigated for different boundary conditions. To achieve this goal the FGM microbeam is modeled by an Euler-Bernoulli beam and utilizing Hamilton principle the governing partial differential eq...
Conference Paper
Severe shot peening (SSP) as one of the severe plastic deformation (SPD) techniques is widely used to make the surface layer microstructure to nano scale in the last decade. Surface nanocrystallization (NC) causes considerable improvement in mechanical properties of the surface. Mathematical modeling methods such as artificial neural networks (ANNs...
Conference Paper
Full-text available
In this paper, effect of the internal viscous damping on the frequency shift and damping ratios of a microbeam made of functionally graded materials is investigated for different boundary conditions. To achieve this goal the FGM microbeam is modeled by an Euler-Bernoulli beam and utilizing Hamilton principle the governing partial differential equat...
Conference Paper
Full-text available
Shot peening is a process of cold working a part that increase its resistance to metal fatigue and some forms of stress corrosion. Shot peening causes plastic deformation in the surface of the peened part and leads some changes in mechanical and metallurgical properties of it. Artificial intelligence (AI) systems such as artificial neural networks...
Conference Paper
Mechanical failures in most cases originate from the exterior layers of the components. It is considerably effective to apply methods and treatments capable to improve the mechanical properties on component’s surface. Surface nanocrystallization produced by severe plastic deformation (SPD) processes such as severe shot peening (SSP) is considerable...
Conference Paper
The experimental observations have shown that the mechanical properties in nano length scales are dependent on the internal microstructure and the geometry as well. Internal viscous damping is associated to the viscosity of the structural material and is proportional to velocity. In this study, the modified couple stress theory is employed to inves...
Article
The modified couple stress theory is employed in this paper in order to formulate the size-dependent strain energy release rate of Euler-Bernoulli and Timoshenko notched beams. As a case study, the normalized energy release rate of the aforementioned beams has been developed for three-point bending as a function of the ratio of material length scal...
Article
Fatigue failure of holding U-bolt of a cooling fan blade is analyzed. Fractography of the fracture surface reveals the characteristics of a fatigue fracture. Finite element modeling is used for stress analyzing. Analysis of the loading conditions indicates that the bolts are under multiaxial fatigue. Effective alternating and mean stresses are obta...

Citations

... Mechanical, chemical polishing, electropolishing with mixture of mineral acids, and laser surface treatment techniques have been reported as posttreatment processes for laser-built components to reduce the surface roughness of the resulting parts. e postprocessing techniques include short peening [7], low plasticity burnishing [8], laser shock processing [9], surface laser remelting [10], and deep cryogenic treatment [11]. All these techniques are complex and require computer-aided designs. ...
... Thai et al. [23] introduced a robust numerical model to take size effect into mechanical properties of FGM microplates via the modified strain gradient elasticity theory and isogeometric analysis. Maleki et al. [24] examined the size-dependent strain energy rate release rate for FGM Euler-Bernoulli nanobeams modeled via the modified couple stress theory of elasticity. Acierno et al. [25] studied polypropylene fibers containing singlewalled carbon nanotubes in terms of the experimental mechanical properties as well as numerical nonlocal models. ...
... The results predicted from the neural network are in good agreement with the experimental results. The researchers indicated that with the shot peening process, the residual stress and surface hardness increased due to the creation of severe plastic deformation, nanostructure, micro-strains, and grain refinement on the surface [18]. In another study, Atal Pathak et al. studied the effect of shot peening parameters on the residual stress generated on the PMG Al 2024 alloy surface, applying the experimental design and Taguchi L16 array. ...
... Based on the results reported by Elangovan et al. [45] and Maleki et el. [37,46,47], attaining values of R 2 more than 0.99 are much acceptable for this criterion. The methodology used in the current study is shown in Fig. 3. ...
... Shot peening is one of the methods of dynamic burnishing. In this cold working process, the component surface is bombarded by small spherical particles which are propelled by a stream of compressed air [23][24][25]. The basic parameters influencing the efficiency of the shot peening process include: processing time, ball diameter, compressed air pressure, total number of balls in the working chamber and nozzle structure [26]. ...
... These also accords with our earlier results using finite element analysis [45]. The depth of the area insensitive to initial residual stress is primarily influenced by the mechanical properties of the materials and the shot peening parameters [48,49]. This is important to realize because micro-pitting occurs on the ...
... In the implementation of ANN, there are many parameters that changing them causes alteration of the operation method, speed and accuracy of the network [42]. The number of ANN layers, the number of each layer neurons and rate of network training are some of these parameters [43]. Number of ANN layers and neurons of each layer are important parameters in deployment of ANN, since they are so effective in its operation. ...
... The modified couple stress theory (MCST) possesses only one length-scale parameter which relates the couple stresses of a continuum to its curvature. This theory was used to present size-dependent mechanical models of bending (Ma et al., 2008), vibration (Kong et al., 2008), buckling (Akgöz and Civalek, 2011), and energy release rate (Sherafatnia et al., 2014) of small-scale structures. ...
... Pipeline systems are regarded as a fundamental section of the industry infrastructure due to their undeniable role in the supply and transportation of fluids [1]. Various failures are occurring in pipelines such as corrosion [2], creep [3], fatigue [4], and other fracture types leading to failure of equipment. Failure in pipelines is generally described as the occurrence of bursts along a pipe or several other pipes in a network [5][6][7], whereas some other researchers [8,9] claim that pipe break or even leakage should be introduced as a form of failure. ...