Adaptive Remeshing Technique Research Articles

Finite Element Analysis and Simulation about Microgrinding of SiC

The application of silicon carbide (SiC) is often limited due to its low machining efficiency and unpredictability about the results of the grinding process. The aim of this paper is to set up finite element analysis models (FEM) about microgrinding process of SiC, to study the change processes about tangential and normal grinding force which can lead to stress and strain inside SiC material under different grinding parameters, and to predict the results before the grinding process. Adaptive remeshing technique is used to minimize the computational time without sacrificing the accuracy of the results in the simulation of SiC grinding process. The research results can be used to choose reasonable grinding parameters based on the required surface quality.

Three-Dimensional Finite Element Analysis in Plunge Milling for Stainless Steel

The three-dimensional finite element modeling and experimental validation of plunge milling of stainless steel (1Cr13) are presented. The commercial software Deform 3D applied for the finite element modeling is studied the effect of feed rate per tooth (fz) on the cutting forces and the temperature fields. The formation of chip in the finite element model is formed by local adaptive remeshing technique. The feed rate per tooth (fz) significantly affects the cutting forces, but slightly influences the maximum temperature of the chip.

Effect of Mesh Parameters in Finite Element Simulation of Single Point Incremental Sheet Forming Process

This paper investigates the effect of element size and adaptive re-meshing technique in numerical simulation of incremental sheet forming (ISF) process. In ISF a hemispherical headed tool moves along the specified trajectory to deform the sheet in to required shape. This tool path is generally very long and thus increases the computational time. Therefore, in this work adaptive re- meshing technique has been used to minimize the computational time without sacrificing the accuracy of the results. For this a varying wall angle conical frustum was simulated using shell elements with different element edge lengths and adaptive mesh. Effects of these mesh parameters on plastic strain, punch force and form accuracy of deformed geometry has been studied. The necessary simulations for this study are performed using explicit finite element code LS-DYNA.

Crack growth simulation for arbitrarily shaped cracks based on the virtual crack closure technique

In this paper, crack growth simulation for arbitrarily shaped cracks was investigated based on the virtual crack closure technique. During simulations, the crack front was represented by an approximated zigzag line which had the same general shape as the given crack. For this approximated zigzag crack front, a modified approach was developed to determine the required nodal forces, virtually closed area and displacement opening. After the strain energy release rate G was calculated, crack growth was governed by the fracture criterion G/GC = 1 at all the crack tip nodes. The important features of the proposed approach are that (i) a simple stationary finite element mesh can be used for arbitrarily shaped cracks and (ii) adaptive re-meshing technique is avoided in studying crack growth. Three cases having different initial crack shapes are presented to assess the validity of this approach and to evaluate the ease of use in tracking crack growth. Reasonable agreement between the present study and other approaches are obtained. The shape changes during crack propagation can also be tracked with ease.

Simulation of Thermal and Mechanical Response of (Zr,W)B<sub>2 </sub>Ceramic after Oxidation

This study relates to a micromechanics based finite element model of the effect of oxidation on heat transfer and mechanical behavior of a (Zr,W)B2ceramic at high temperature. An adaptive remeshing technique is employed in both heat transfer and thermal stress analysis models. A global-local modeling technique is used to combine finite elements with infinite elements for thermal stress analysis. Temperature and thermal stress distributions in the ceramic and the oxides are presented.

5th International Conference OTEH 2012 - defense technology (Proceedings review)

This article gives an overview of all papers and events at the Fifth International ScientificConference on Defense Technologies OTEH 2012 held in Belgrade, in the Military Technical Institute (VTI), from 18 th to 19 th September 2012. The paper review presents the Conference Sections by subjects and guest-lectureres as well as the institutions of all authors who actively participated at the Conference. About the Conference The Fifth International Scientific Conference on Defense Technologies OTEH 2012 was held in Belgrade in the Military Technical Institute in Žarkovo, from 18 th to 19 th September 2012.. The Conference program was organized in two plenary sessions and a working part which took place in four halls. In the plenary session, two key lectures were held by eminent experts from abroad. The first lecture entitled „An adaptive remeshing technique for 3D crack growth simulations”, was given by Dr Vincent Chiaruttini (ONERA Institute, Paris, France). The second one, „New Technologies for Advanced Defence Systems”, was held by Dr Filippo Neri (Virtualabs Company, Rome, Italy). Fifteen sessions were organised at the Conference. The authors presented their works in open discussions answering questions from the audience. The average number of attendees at each session was about 40. The papers were sorted by topic areas: Aerodynamics and flight dynamics: 12 papers Aircraft: 23 papers Weapon systems, ammunition, energy materials, combat vehicles: 29 papers Integrated sensor systems and robotic systems: 16 papers Telecommunication and information systems: 18 papers Materials and technologies: 34 papers Quality, standardization, metrology, maintenance and exploitation: 11 papers Out of 163 submitted papers for this Conference, 145 papers were accepted and distributed in an electronic form on CDs to the present authors, co-authors, guests and invitees to the Conference. The number of participants with authors and co-authors was impressive - 243. The authors (either of their own or plenary papers) from 15 countries were present at the Conference. It should be noted that at this conference, unlike the previous one also held in the VTI, Belgrade, in 2011, there was a significantly higher number of younger researchers. There was a general impression that many reseach results communicated at the Conference deserved to be published in reference journals on the SCR list. A number of papers from this Conference will be considered for publication in the Scientific Technical Review. It should be noted that the MO-VTI organizing committee largely contributed to the Conference to be evaluated as a well-organized event. From a total number of papers (145), there were 32 (or 22.06% ) from abroad. Once again, the Conference justified the purpose of this type of conferences. The other works of authors and co-authors were from the following institutions in Serbia: The Ministry of Education and Science and Technological Development, Military Technical Institute (VTI), Military Academy (MA), the Army of Serbia (SAF), the Ministry of Defence (MOD), Department of Defense Technology (MDT), University of Defence (UD) Military Institution Dedinje, Military Archives, Technical Test Center (TTC), Technical Overhaul Institute Cacak (TRZ), the Central Logistics Base, Institute of Strategic Studies, Criminal Police College, GOSA Institute, Institute of Engineering, Faculties of Mathematics, Mechanical Engineering, Electrical Engineering, Metropolitan University, Faculty of Technology and metallurgy, College of Project Management, UTVA Aircraft Industry Pancevo, Intel Communications, IHATEM, Vlata com, Iritel, Peripolis-Electronics, Computer Engineering, Thermo Electric, HK Krusik Valjevo. Conclusion The Conference had a truly international character. As in previous years, the participation of the Army of Serbia in this important event is fully justified, and the goal is reached. In addition to the communication of the research results, there was a fruitful discussion in which the problems were reviewed, opinions and experiences exchanged and possibilities to solve presented problems discussed. It was again confirmed that communicating work at such events with the participation of scientists and relevant institutions from the country and abroad certainly has a positive impact on the scientific and professional level of work in the Army. It also has a positive impact on professional and scientific training of researchers in experimental centers and institutes as well as teachers, thus raising the quality of teaching in undergraduate and postgraduate studies at the Military Academy. It can be concluded that the cooperation of the Army with the members of other institutions in solving and researching problems of organizations and scientific-technical approach confirms the openness of the Army for the involvement of other individuals and institutions in solving problems in the field of defense as well as the willingness and ability of the members of the defense system to engage in solving problems in civil institutions.

Dramatic Speed-Up in FEM Simulations of Various Incremental Forming Processes Thanks to Multi-Mesh Implementation in Forge®

Improvements in parallel computing and adaptive remeshing have permitted to simulate a wide range of metal forming processes within few hours or days on modern multi-core workstations. However, they do not tackle the issues encountered in incremental forming processes, making them very challenging. Multi-mesh methods opens very interesting doors in this domain, making possible to take advantage of adaptive remeshing techniques (optimizing the ratio precision/cost) without its usual drawbacks (loss of information and diffusion issues).We present in this article a fully parallel Dual-Mesh implementation in the commercial FEA software FORGE®, compatible with a wide range of other FEM facilities. Speed-up larger than 4 are common for incremental forming simulations, and speed-up larger than 10 can be reached in favorable cases. Parallel efficiency is the same than for our standard computations (>80% for more than 2000 nodes per core).

Study on the Effect of Tool Geometrical Parameters on Cutting Forces Based on Finite Element Method

Based on finite element software DEFORM-3D, a three-dimensional oblique cutting model for aerospace aluminum alloy was built. The material’s flow stress behavior was described with Johnson-Cook constitutive equation. The separation of the chips with the workpiece was realized by the combination of adaptive remeshing technique and separation criterion. The material’s failure was defined by adopting Cockcroft & Latham fracture criterion. The tool-chip friction model was the combination of a Coulomb friction model and shear (sticking) friction model. To validate the finite element model, cutting tests were conducted. The effects of tool geometrical parameters such as flank wear, cutting edge inclination and corner radius on cutting forces were analyzed by three-dimensional oblique finite element model.

Three-Dimensional Finite Element Analysis on Heavy Cutting for High Strength Steel

The finite element modeling and experimental validation of three-dimensional heavy cutting of high strength steel (2.25Cr-1Mo-0.25V) are presented. The commercial software Deform 3D applied for the finite element modeling is studied the effect of feed rate on the principal cutting forces and the temperature fields. The friction between the tool and the chip is assumed to follow a shear model and the local adaptive remeshing technique is used for the formation of chip. The feed rate significantly affects the cutting forces, but slightly influences the maximum temperature of the chip. The simulation results are compared with experimental data and found to be in good agreement.

Predictions of tool forces in friction stir welding of AZ91 magnesium alloy

Adaptive remeshing technique based finite element model of friction stir welding was used for the investigation of tool forces in the welding processes. Results indicate that the maximum tool forces occur at the initial time in the translational stage. In the tool forces in the three directions, the axial force is the maximum. The tool force in the direction perpendicular to the welding line is the minimum. The tool forces in the three directions are all increased with the increase in transverse speed and decreased with the increase in angular velocity.

A consistent mixed finite element formulation for hydro-mechanical processes in saturated porous media at large strains based on a generalized material description

Abstract This paper presents the theoretical background of a phenomenological biphasic model at large strains based on a generalized material description of the theory of porous media, and its numerical realization within the context of a mixed finite element formulation. The study is aimed at the simulation of coupled hydro-mechanical (HM) problems with special focus on geo- and biomechanics. If, in the sense of an initial approximation, the materials of interest can be considered as a mixture of two immiscible components (solid and fluid phases), they can be modeled as saturated porous media. For the numerical treatment of according problems within a finite element approach, the weak formulation of the balance equations of mass and linear momentum of the overall continuum are developed. Within this context, a generalized material approach is preferred assuming the initial configuration of the solid phase as reference configuration of the overall continuum. The transient problem results in a weak formulation with respect to the displacement and pore pressure fields as well as their time derivatives. Following, time discretization is performed using a generalized single step approach, and a linearization technique based on Taylor series representation is applied. After the usual spatial discretization, a global system for the incremental solution of the initial-boundary value problem within the framework of a stable mixed u/p-c finite element approach is defined. This algorithmic proceeding comprises some different conceptual aspects compared to the known literature, and is characterized by a consistent and comprehensive representation. The presented numerical model was implemented into a scientific in-house finite element code based on hierarchical structures, which support the straightforward use of an iterative solver with hierarchical preconditioning, local adaptive remeshing techniques, and parallelized programming features. The accuracy and the efficiency of the numerical algorithms are demonstrated on typical examples. Therewith, the importance of the consideration of large strains in a consistent and proper way is demonstrated as well as the differences compared to models based on small strains.

Numerical simulation of electromagnetic sheet bulging based on FEM

A sequential coupling method has been used to analyze the electromagnetic sheet bulging. The adaptive remeshing technique is used in air meshes to make it change regularly according to the deformation result of the sheet. The deformed sheet is imported into electromagnetic model to calculate the magnetic force in next time step. Therefore, the method solves the problem of electromagnetic–structure coupling analysis. According to the research results, with the increase of the sheet deflection, the effects of the radial component of the magnetic force on sheet deformation increase gradually. The optimum value of the time step is found, which corresponds to the better simulation result and less computational time. The simulative deflections at the center and 20 mm from the center with time are good in agreement with the experimental ones.

Analysis of Shear Droop on Cut Surface of High-Tensile-Strength Steel in Fine-Blanking Process

The fine-blanking process is used in the production of automobile parts and other metal components. Although the fine-blanking process can produce sheared surfaces with higher precision than the punching process, shear droops on cut surfaces are also formed, as in the punching process. It is important to determine the causes of the formation of shear droops, but the mechanism is difficult to determine experimentally. Here, the finite element method (FEM) is adopted to study the causes of the formation of shear droops. The cut surfaces in the present experiments have fine sheared surfaces but no fracture surfaces. Although a combination of the fracture criterion and element-kill method is used for many simulations of the fine-blanking process, fine sheared surfaces cannot be evaluated by the combination of these methods. In the present calculations, an adaptive remeshing technique for FEM is used to create fine sheared surfaces. The shear droop is associated with the initial compression by and the subsequent clearance of the punches and dies. Results are obtained for various clearances and initial compressions in the fine-blanking process for high-strength steel, and the experimental and calculation results are compared. In the present paper, we show that the shear droops are affected by the clearance of and initial compression by the punches and die. [doi:10.2320/matertrans.P-M2010828]

A modified zigzag approach to approximate moving crack front with arbitrary shape

Abstract This paper proposed a modified zigzag approach to approximate crack front with arbitrary shape based on virtual crack closure-integral technique. The important features of this approach are that: (i) more detailed consideration to determine the required virtually closed area and displacement opening were presented and (ii) adaptive re-meshing technique was avoid in studying crack growth. Three cases were presented to assess the validity of this approach by comparison to the results obtained from other approaches. Reasonable agreement between the present study and the analytical solutions were obtained. Also, the shape changes during crack propagation can be tracked with ease.

Basic function method

A new numerical method-basic function method is proposed. This method can directly discrete differential operators on unstructured grids. By using the expansion of basic function to approach the exact function, the central and upwind schemes of derivative are constructed. By using the polynomial as basic function, applying the technique of flux splitting method and the combination of central and upwind schemes, the non-physical fluctuation near the shock wave is suppressed. The first-order basic function scheme of polynomial type for solving inviscid compressible flow numerically is constructed in this paper. Several numerical results of many typical examples for one-, two- and three-dimensional inviscid compressible steady flow illustrate that it is a new scheme with high accuracy and high resolution for shock wave. Especially, combining with the adaptive remeshing technique, the satisfactory results can be obtained by these schemes.

Basic function scheme of polynomial type

A new numerical method named as basic function method is proposed. It can directly discretize differential operators on unstructured grids. By expanding the basic function to approach the exact function, the central and upwind schemes of derivative are constructed. By using the second-order polynomial as a basic function and applying the flux splitting method and the combination of central and upwind schemes to suppress non-physical fluctuation near shock waves, a second-order basic function scheme of polynomial type is proposed to solve inviscid compressible flows numerically. Numerical results of typical examples for two-dimensional inviscid compressible transonic and supersonic steady flows indicate that the new scheme has high accuracy and high resolution for shock waves. Combined with the adaptive remeshing technique, satisfactory results can be obtained.

Streamline upwind finite element method using 6-node triangular element with adaptive remeshing technique for convective-diffusion problems

A streamline upwind finite element method using 6-node triangular element is presented. The method is applied to the convection term of the governing transport equation directly along local streamlines. Several convective-diffusion examples are used to evaluate efficiency of the method. Results show that the method is monotonic and does not produce any oscillation. In addition, an adaptive meshing technique is combined with the method to further increase accuracy of the solution, and at the same time, to minimize computational time and computer memory requirement.

An Adaptive Remeshing Technique Ensuring High Quality Meshes

This paper deals with adaptive remeshing techniques. The traditional methods for remeshing are presented, raising the problem of quality. The bubble meshing technique that ensures high-quality meshes is exposed, and improvements brought to the technique are also presented. The procedure that consists in using this technique for generating high-quality meshes during the refinement iterations is showed. Some results for both the bubble meshing technique and its use for meshes refinement are presented. The whole study has been completed in 2-D and is extensible to 3-D.

Improving numerical simulation of metal forming processes using adaptive remeshing technique

Numerical simulation by finite element of forming processes requires ductile damage. In this context, problems of meshing and remeshing often impede the convergence of the processes and frequent remeshing must be performed in order to avoid severe mesh distortions while adapting the mesh size to the solution (plasticity, damage, temperature). Solutions to this problems are proposed in this paper. Geometrically and physically error estimators have also been developed in order to locate areas where a remeshing is needed. This adaptive scheme has been coupled to ABAQUS/Explicit solver.

J-integral calculation by domain integral technique using adaptive finite element method

An adaptive finite element method for analyzing two-dimensional and axisymmetric nonlinear elastic fracture mechanics problems with cracks is presented. The J-integral is used as a parameter to characterize the severity of stresses and deformation near crack tips. The domain integral technique, for which all relevant quantities are integrated over any arbitrary element areas around the crack tips, is utilized as the J-integral solution scheme with 9-node degenerated crack tip elements. The solution accuracy is further improved by incorporating an error estimation procedure onto a remeshing algorithm with a solution mapping scheme to resume the analysis at a particular load level after the adaptive remeshing technique has been applied. Several benchmark problems are analyzed to evaluate the efficiency of the combined domain integral technique and the adaptive finite element method.