Roozbeh Shad; Mohammad Sa'di Mesgari
Abstract
Nowadays, geospatial information systems (GIS) are widely used to solve different spatial problems based on various types of fundamental data: spatial, temporal, attribute and topological relations. Topological relations are the most important part of GIS which distinguish it from the other kinds of ...
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Nowadays, geospatial information systems (GIS) are widely used to solve different spatial problems based on various types of fundamental data: spatial, temporal, attribute and topological relations. Topological relations are the most important part of GIS which distinguish it from the other kinds of information technologies. One of the important mechanisms for representing topological relations between spatial objects is spatial topology. These mechanisms help users to model spatial analysis on the objects simply and efficiently. Topological relations which used for the analysis are influenced by uncertain resources such as: inaccuracy and error of measurements, vagueness to describe information, incompleteness, inconsistency and impreciseness. Then, the fuzzy set theory as an ideal tool can help to handle these uncertain resources in the topological relations. Our methodology relies on the 3D fuzzy 9-intersection, which is a generalization of the crisp 9-intersection of Egenhofer and co-workers. The similarity between the 3D fuzzy and the crisp 9-intersection enables the decision variables, to be derived. The decision variable includes a semantic part and a quantifier. Since determination of the decision variable depends on the definition of the boundary of the fuzzy regions, we try to present a useful method for computing fuzzy boundaries. For this purpose each point of a Fuzzy region has partial membership degree to Interior, Boundary and Exterior set of a region. In order to derive the topological relations between fuzzy spatial objects, the 9-intersection approach is updated into the 3*3-intersection approach in the crisp fuzzy topological space. The topological relations between simple fuzzy regions can be identified based on the topological invariants in the intersections of the matrices. With respect to this, we try to check and complete our information about how we can define 3D fuzzy topological relations between spatial objects and propose an efficient method for simulating relationships and extracting decision variables. This subject is applied for the application of "determining risk areas of Kuwait oil well air pollutions plumes on the southwestern forest areas of Iran". For this purpose, decision variables are extracted based on 3D fuzzy topological relations between air pollution plumes and a forest area, then, reasoned using defined proper rules in the knowledge base part of a spatial reasoning system. When smoke plumes move toward a forest area: data extractor extracts the smokes fuzzy areas form remote sensing satellite images, and topological simulator computes the strength and type of topological relationships and sends the extracted information to a designed knowledge based system. The final results show 20% improvement in reasoning results by adding inclusion index and 3D topological rations to the knowledge part of designed system.
Roozbeh Shad; Hamid Ebadi; Mohammad Sa'di Mesgari; Ali Vafaee Nejad
Abstract
Different industrial decision makers and managers in our country, try to select and organize locations for aggregating industrial units, estates and areas with respect to land use planning visions and industrial development strategies. In this regard, considering large quantity of the input data and ...
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Different industrial decision makers and managers in our country, try to select and organize locations for aggregating industrial units, estates and areas with respect to land use planning visions and industrial development strategies. In this regard, considering large quantity of the input data and diverse criteria affecting this application, it is complicated and difficult to optimally make decision. Geographical Information System (GIS) is able to provide the decision-makers with appropriate tools for removing the difficulties and complexities of site selection process. For this purpose, spatial functions allow selecting an optimum site by using input maps through aggregated operators. These functions are categorized into various groups such as Boolean, Index overlay, Fuzzy logic, Genetic and Weighted evidence, with respect to their activities. So, it is essential to determine appropriate aggregated functions for designing and implementing an applied GIS for selecting optimum industrial estate. In this paper, first, conditions and factors influencing industrial estates site selection are determined and made ready for being entered into aggregated functions. Then, different properties of Index overlay, Fuzzy, Genetic and Weighted evidence models are evaluated for functional efficiency and output accuracy results. Finally, considering the results obtained from different stages, the appropriate model is determined and desirable user interface is developed. As a result of implementing, it was found that Index overlay model with 2.2 seconds time ratio and 5 positive efficiency is the best model for aggregating industrial estate site selection parameters as compared to Fuzzy, Genetic and Weighted evidence models.
Shirin Malihi; Hamid Ebadi; Farshid Farnoud Ahmadi; Mehdi Maboudi
Abstract
An important issue in implementation of a GIS system is preparation of data to be entered in GIS. To produce spatial data for GIS using photogrammetric techniques, conventional method is to apply photogrammetric and GIS systems individually (off-line procedure).
This approach is costly, time consuming ...
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An important issue in implementation of a GIS system is preparation of data to be entered in GIS. To produce spatial data for GIS using photogrammetric techniques, conventional method is to apply photogrammetric and GIS systems individually (off-line procedure).
This approach is costly, time consuming and somehow unreliable due to the fact that 3D photogrammetric model is not available at the time of GIS data structuring, To overcome these problems, editing and structuring of spatial data can be carried out simultaneously during feature digitization.
Feature digitizing from photogrammetric models can be performed in an interface CAD environment by real time integration of photogrammetric and CAD systems. Based on this approach, generated data can be saved with standard structure and format defined by CAD environments (e.g., Micro Station)and directly used for GIS without further editing. In this paper, design and development of a software package called Object oriented CAD-Based Photogrammetric System (OCBPS2, version 2) which integrates Photomod and Micro Station systems in an object oriented way, is described. This system carries out real time structuring and editing of spatial data for class of road features by controlling logical relations among road class features and other features.
Abdorreza Safari; Yahya Jamour; Meisam Ghanizadeh
Mohammad Tale'i; Mohammad Sa'di Mesgari; Ali Sharifi
Abstract
This research is aimed at developing a model for measuring and comparison amount of supply and demand for different urban services from quality of life and equity perspectives, in urban built-up areas. This paper explains different steps of implementing the model as a tool for evaluating accessibility ...
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This research is aimed at developing a model for measuring and comparison amount of supply and demand for different urban services from quality of life and equity perspectives, in urban built-up areas. This paper explains different steps of implementing the model as a tool for evaluating accessibility of residents to various services according to two main criteria: Land per capita and distance to services. In developing the model, geographic information system is used as a spatial planning support generator. The model has been tested in an urban area located in 7th regional municipality of Tehran, the capital city of Iran, and its result have been compared with outcomes of traditional techniques such as zoning. The results show that the model is effectively proper to clarify different levels of shortcoming in accessibility to urban land use services and improves accuracy of assessing the amount and location of the shortcomings. Developing such GIS-based micro-level evaluation model and presenting different approach regarding single-facility and multi-facility’s characteristics of urban services are the specific originality of this research.
Seyyed Abdollah Kianejad; Hamid Ebadi; Masoud Varshosaz; Barat Mojarradi
Abstract
By far, many stereo-matching techniques have been successfully proposed and applied in digital aerial photogrammetry. However, due to some problems such as large parallaxes, occlusions, geometric deformations, and repetitive patterns in convergent close range images, these methods may not be applicable ...
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By far, many stereo-matching techniques have been successfully proposed and applied in digital aerial photogrammetry. However, due to some problems such as large parallaxes, occlusions, geometric deformations, and repetitive patterns in convergent close range images, these methods may not be applicable to the same level of success as that of aerial imagery. In order to overcome these shortcomings, in this paper a new hybrid area and feature-based image matching method is proposed. This technique, puts the emphasis on spectral information of color images without the need for prior knowledge about imaging conditions such as overlap and order of images. This method was implemented and tested on real close range images having different convergence angles. The results showed that it succeeds in convergent images with angles about 40-60 degrees giving an accuracy of 2 pixels.
Barat Mojarradi; Mohammad Javad Valadanzouj; Hamid Abrishami
Ali Reza Azmoude Ardalan; Abdorreza Safari; Abbas Ali Jom'egi
Ali Reza Azmoude Ardalan; Abdorreza Safari; Yahya Tavakkoli
Abstract
The methods applied to regularization of the ill-posed problems can be classified under “direct” and “indirect” methods. Practice has shown that the effects of different regularization techniques on an ill-posed problem are not the same, and as such each ill-posed problem requires its own investigation ...
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The methods applied to regularization of the ill-posed problems can be classified under “direct” and “indirect” methods. Practice has shown that the effects of different regularization techniques on an ill-posed problem are not the same, and as such each ill-posed problem requires its own investigation in order to identify its most suitable regularization method. In the geoid computations without applying Stokes formula, the downward continuation based on Abel-Poisson integral is an inverse problem, which requires regularization. Since so far the regularization of this ill-posed problem has been thoroughly studied, in this paper the regularization of the downward continuation problem based on Abel-Poisson integral, is investigated and various techniques falling into the aforementioned classes of regularizations are applied and their efficiency is compared. From the first class Truncated Singular Value Decomposition (TSVD) and Truncated Generalized Singular Value Decomposition (TGSVD) methods and from the second class Generalized Tikhonov (GT) with the norms and semi-norms in Sobolev subspaces , are applied and their capabilities for the regularization of the problem is compared. Our numerical results derived from simulated studies reveal that the GT method with discretized norm of Sobolev subspace gives the best results among the studied methods for the regularization of the downward continuation problem based on the Abel-Poisson integral. On the contrary, the TGSVD method with the discretized second order derivatives has less consistency with the ill-posed problem and yields less accuracy. Finally, the GT method with discretized norm of Sobolev subspace is applied to the downward continuation of real gravity data of the type modulus of gravity acceleration within the geographical region of Iran to derive a geoid model for this region.
Masoume Amighpey; Behzad Vosoughi; Maryam Dehghani
Abstract
An earthquake with the magnitude of 5.9 Mw occurred in Qeshm Island and Hormozgan province in November 27th 2005. 3D co-seismic deformation field caused by the earthquake are determined based on the ascending and descending interferograms and azimuth offsets. The peak to peak estimated displacement is ...
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An earthquake with the magnitude of 5.9 Mw occurred in Qeshm Island and Hormozgan province in November 27th 2005. 3D co-seismic deformation field caused by the earthquake are determined based on the ascending and descending interferograms and azimuth offsets. The peak to peak estimated displacement is about 10 cm in west, 69 cm in north and 22 cm in vertical directions. We apply strain analysis to study coseismic deformation of the earthquake. Finite element method as numerical solutions is applied in order to compute the strain tensors. Furthermore, dilation and shear parameters are derived from computed strain tensor fiel of the area. The maximum expansion and contraction are computed as 0.006 and 0.005, respectively. Moreover, the maximum shears in xy, xz and yz planes obtained by finite element method were 0.2 rad, 0.4 rad and 0.19 rad, respectively. The results represent the changes in direction and maximum expansion and maximum contraction in the direction of faults proposed by aftershock seismicity study of the earthquake. The concentration of the shear and dilation are observed in central part of island along the NW-SE oriented fault passing from central part of island. The numerical results show considerable amounts of shear and dilation in the vicinity of Qeshm fault, as well.
Mehdi Hassanlou; Mohammad Reza Serajian
Abstract
Oceanographic images obtained from environmental satellites by a wide range of sensors allow characterizing natural phenomena through different physical measurements. For instance Sea Surface Temperature (SST) images, altimetry data and ocean color data can be used for characterizing currents and vortex ...
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Oceanographic images obtained from environmental satellites by a wide range of sensors allow characterizing natural phenomena through different physical measurements. For instance Sea Surface Temperature (SST) images, altimetry data and ocean color data can be used for characterizing currents and vortex structures in the ocean. The purpose of this thesis is to derive a relatively complete framework for processing large dynamic oceanographic image sequences in order to detect global displacements such as oceanographic streams and to localize particular structures like motion current and vortices and fronts. These characterizations will help in initializing particular processes in a global monitoring system. Using area-based algorithms, two least squares methods have been used to solve the apparent motion which involves Least Squares Matching (LSM) and Hierarchical least squares Lucas and Kanade (HLK). SST images of Caspian Sea taken by MODIS sensor on board Terra satellite have been used in this study. Three daily SST images with 24 hours time interval are used as input data. The LSM technique, as a flexible technique for most data matching problems, offers an optimum spatial solution for the motion estimation. The algorithm allows for simultaneous local (i.e. template) radiometric correction and local geometrical image orientation estimation. Actually, the correspondence between two image templates is modeled both geometrically and radiometrically. In order to implement weighted least squares fit of local first-order optical flow constraints in each spatial neighborhood, the HLK method has been used. This method locates water current using coarse-to-fine strategy to track motion in Gaussian pyramids of SST images. This method allows the detection of large motion in coarse resolution layer and guides to correct result in finer layers. The method used in this study has presented more efficient and robust solution compared to the traditional motion estimation schemes to extract water currents.
Mohammad Sa'adat Seresht; Nima Zarrin Panje
Mehdi Takaffoli; Aghil Yusefikoma
Abstract
Numerical modeling of machining processes is of significance in the parametric analysis and optimization of their performance. In this paper, a finite element-based model of abrasive waterjet (AWJ) cutting of a ductile material is presented with the help of an explicit, nonlinear finite element method. ...
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Numerical modeling of machining processes is of significance in the parametric analysis and optimization of their performance. In this paper, a finite element-based model of abrasive waterjet (AWJ) cutting of a ductile material is presented with the help of an explicit, nonlinear finite element method. In this model, both solid-solid interaction and fluid-structure interaction are considered. The water is modeled as an Eulerian volume. The Euler-Lagrange coupling algorithm is employed to simulate the interaction of the waterjet with the abrasive particle and the target material. An elastic-plastic behavior is defined for the target material and the abrasive particle is assumed spherical, which behaves like an elastic material. The erosion of the target due to the AWJ impact is simulated using the element deletion approach. The variation of the depth of cut with respect to the waterjet pressure is estimated and compared with experimental results.
Keyvan Hosseini Safari; Mahmoud Mousavi Mashhadi
Abstract
Determination of the optimum loading path (internal pressure- axial feeding) to restrict the Bursting, buckling and wrinkling through tube hydroforming process is necessary to produce an acceptable tube. In this paper, the wrinkling and fracture criteria are implemented to an finite element code devoted ...
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Determination of the optimum loading path (internal pressure- axial feeding) to restrict the Bursting, buckling and wrinkling through tube hydroforming process is necessary to produce an acceptable tube. In this paper, the wrinkling and fracture criteria are implemented to an finite element code devoted to the simulation of tube hydroforming processes. Using the ANSYS parametric design language (APDL), two macros are built to compute the value of bursting and wrinkling indicators through the elements. By determining the indicators values through the step to step solution of the software, it is possible that compares them with critical values and predicts the fracture and wrinkling in tube hydroforming process.
Mohammad Shariyat; Abbas Ganjipour
Abstract
In the present paper, employing a complete model of a passenger car, contribution of various components and assemblies in the frontal crash energy absorption is determined. Thickness of components with more remarkable contribution is increased to improve the occupant safety. Furthermore, effects of substituting ...
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In the present paper, employing a complete model of a passenger car, contribution of various components and assemblies in the frontal crash energy absorption is determined. Thickness of components with more remarkable contribution is increased to improve the occupant safety. Furthermore, effects of substituting the metallic bumper with one fabricated from GMT materials on the frontal crash behavior of the vehicle are investigated. Boundary condition and dynamic parameters are defined in PAM-CRASH software. To increase the accuracy of the results, all sub-assemblies and their joints are precisely modeled. Finally, components with more remarkable contribution in energy absorption are detected and a comparison is made between the crash results of the original design and the crash results obtained after the mentioned modifications.
Ghader Faraji; Mohammad Kazem Besharati Givi; Saeed Yarmohammadi; Mahmoud Mousavi Mashhadi
Abstract
Deep drawing of cylindrical shapes with high limiting drawing ratio (LDR) values is relatively difficult. Annealing is a further operation, which in turn adds costs and consumes significantly time to the forming process. In the present work, cylindrical cups from brass sheet were made with only limited ...
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Deep drawing of cylindrical shapes with high limiting drawing ratio (LDR) values is relatively difficult. Annealing is a further operation, which in turn adds costs and consumes significantly time to the forming process. In the present work, cylindrical cups from brass sheet were made with only limited anneal during few steps, but having LDR of 9 that is about 2 times higher than previous works. Cups having 4 mm IDs and 70 mm heights were made successfully. The process was simulated by ABAQUS/Explicit finite element (FE) code and experimental tests were carried out based on FEM results. Parameters affecting the process were studied with experimental results, as well as FEM. The wall thickness obtained from the approach were compared for several tests, and verified significantly.
Amin Samadi Ghoushchi; Caren Abrinia; Mohammad Kazem Besharati Givi
Abstract
Slab method of analysis has been used for solving metal forming problems for a long time. However it has been restricted to plane strain and axisymmetric problems due to limitations in its formulations. In this paper a new formulation has been proposed so that it could be applied to three dimensional ...
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Slab method of analysis has been used for solving metal forming problems for a long time. However it has been restricted to plane strain and axisymmetric problems due to limitations in its formulations. In this paper a new formulation has been proposed so that it could be applied to three dimensional problems in metal forming. A parametric slab has been considered in this analysis and the force balance on the slab was carried to obtain equilibrium equations in terms of these parameters. The parameters in fact are related to the geometry of the final extruded shape, the die and the material flow regime assumed in the formulation. In this way most of the limitations encountered in previous formulations were surpassed. The effect of reduction of area, frictional conditions and other process parameters on the extrusion pressure was investigated. The theoretical results obtained in this paper were compared with the results of finite element method and a good agreement was observed between them.
Farshad Kowsari; Seyyed Morteza Azimi
Abstract
In this paper the optimal control of boundary heat flux in a 2-D solid body with an arbitrary shape is performed in order to achieve the desired temperature distribution at a given time interval. The boundary of the body is subdivided into a number of components. On each component a time-dependent heat ...
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In this paper the optimal control of boundary heat flux in a 2-D solid body with an arbitrary shape is performed in order to achieve the desired temperature distribution at a given time interval. The boundary of the body is subdivided into a number of components. On each component a time-dependent heat flux is applied which is independent of the others. Since the thermophysical properties are temperature-dependent, the problem is treated as a nonlinear inverse heat conduction problem. Conjugate gradient method (CGM) along with adjoint problem is utilized in order to solve the inverse problem. Optimization process is employed for the heat flux imposed on each of the boundary component individually which was previously shown to be more efficient than optimizing the entire heat flux array simultaneously. Three versions of CGM; that is, the Fletcher-Reeves (FR), Polak-Ribiere (PR) and Powell-Beale are utilized for comparison. As a test case, heating of an Aluminum bar with a square cross section and temperature-dependent thermo-physical properties is considered. Results show that for large time-steps the Powell-Beale version with normalized search direction, and for small time-steps the Polak-Ribiere version are the most efficient method with the least error in the estimated temperature field. Moreover, for large time step size results show that addition of regularization term to the Error Function reduces the amplitude of oscillations in the estimated heat flux.
Seyyed Masoud Marandi; Mehdi Tajdari; Khosro Rahmani
Abstract
Foreign object damage (FOD) occurs when hard, millimeter-sized objects such as gravel or sand and even the pieces of the engine components are ingested into aircraft jet engines. Particles impacting blades produce small indentation craters which can become sites for fatigue crack initiation, severely ...
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Foreign object damage (FOD) occurs when hard, millimeter-sized objects such as gravel or sand and even the pieces of the engine components are ingested into aircraft jet engines. Particles impacting blades produce small indentation craters which can become sites for fatigue crack initiation, severely limiting the lifetime of the blade. In this study, the impact on the edge of a thin plate is investigated by using the finite element method. Then residual stresses are compared between the quasi-static indentation and fully dynamic impact for three critical locations where the residual hoop stresses are tensile. At the end, experimental stress analysis is performed for investigating the stress concentration factor at the crater base and comparing with data from the finite element method. The comparison shows that the finite element method result agrees well with experimental data at the crater base.
Abdorrasoul Mayyahi; Aghil Yousefikoma; Ali Rangin Kaman; Hesam Maleki
Abstract
An autonomous underwater vehicle (AUV) with less noise and vortices as well as efficient power consumption, is pursued in this research by inspiration of shark swimming. Design, hydrodynamic analysis, modeling, fabrication, navigation, and control of this novel AUV is the main goal of this research. ...
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An autonomous underwater vehicle (AUV) with less noise and vortices as well as efficient power consumption, is pursued in this research by inspiration of shark swimming. Design, hydrodynamic analysis, modeling, fabrication, navigation, and control of this novel AUV is the main goal of this research. Detailed explanation of the test and experiment with a brief overview on fabrication are provided. The transfer function of the system has been extracted from the experimental data. The transfer function is then employed for dynamic analysis and control system development. Zigler-Nickols method is used to predetermine the PID control coefficients. Consequently, small modifications have been done by trial and error. Trajectory control in a 10 cm off the wall and in a 20 cm band in a large swimming pool has been examined by a 3 DOF AUV.
Ali Naserian; Masoud Tahani
Abstract
The Levy-type analytical solution is employed for the problem of bending of cross-ply and antisymmetric angle-ply piezoelectric hybrid laminated plates with at least two simply supported opposite edges. The governing equations of equilibrium are derived in the framework of the first-order shear deformation ...
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The Levy-type analytical solution is employed for the problem of bending of cross-ply and antisymmetric angle-ply piezoelectric hybrid laminated plates with at least two simply supported opposite edges. The governing equations of equilibrium are derived in the framework of the first-order shear deformation plate theory. The equations are classified according to the crystallography type of piezoelectric layers and a comprehensive discussion on limitations of the method for the analysis of this kind of structures is performs. Finally, the governing equations of equilibrium are solved analytically with the aid of the state-space approach. We concluded that during the analysis of piezoelectric hybrid laminated plates with Levy-type method, simultaneous applying of all electrical forces and moments is not possible (depending on type of lay-up, crystallography of piezoelectric layers, and expansion of electrical potential, some of electrical forces and moments may not be considered). In order to study the accuracy and convergence rate of the proposed method, several numerical examples are examined. The numerical results are compared with those obtained by the Navier method and those presented in the other published articles. It is found that the present results have very good agreements with those obtained by other methods.
Vahid Norouzifard; Aghil Yousefikoma
Abstract
The built up layer thickness in secondary deformation zone is one of the important parameters in metal cutting process. The built up layer (BUL) is formed in second deformation zone near the tool-chip interface in the back of the chip. This parameter influences the tool life and machined surface quality. ...
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The built up layer thickness in secondary deformation zone is one of the important parameters in metal cutting process. The built up layer (BUL) is formed in second deformation zone near the tool-chip interface in the back of the chip. This parameter influences the tool life and machined surface quality. This BUL should not be confused with the built up edge (BUE). The deformation of the BUL in the secondary shear zone is a stable and continues process; leading to an uniform thickness of the BUL along the chip's back but the deformation of the BUE is an unstable process in front of the tool edge. Numerical simulation is a suitable method for determination of temperature, stress and strain distribution in metal cutting since it dose not suffer the analytical methods limitations and experimental methods cost. In this paper a new method is presented to calculate the built up layer thickness in secondary deformation zone using finite element simulation of orthogonal metal cutting process. There are two main concepts about chip separation mechanisms from work piece, i. e. crack propagation and pour deformation without crack. In the present work chip formation process is assumed as a pour plastic deformation, considering second chip separation mechanism. There is no separation criterion in the simulations based on pour deformation, but Adaptive remeshing is performed during simulation to avoid the difficulties associated with deformation-induced element distortion. An updated Lagrangian finite element model of two-dimensional orthogonal cutting process is developed. This model is meshed using 4-node plain strain elements. Thermo-mechanical coupled analysis, with adaptive remeshing is performed by LS-DYNA finite element code. Johnson-Cook material model is used for determination of the work piece material flow stress and the cutting tool is assumed as a rigid body. An updated coulomb friction law is used to describe friction condition in tool-chip interface. The temperature and equivalent strain distribution diagrams in cutting zone are shown at various cutting speeds. The built up layer thickness in various cutting speed are also calculated by equivalent strain gradient in second deformation zone. The numerical calculated tool average temperatures and the built up layer thicknesses in various cutting speeds are compared with the experimental data given in literature and good agreement is observed between them.
