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This paper deals with finite element analysis of fundamental deformation of robot soft finger. The aim of this paper is to develop a simple contact static model of cylindrical soft flexible finger for effective power grasping. In this paper, the geometrical relation connecting different contact parameter, for example, distortion, flexible contact width, and contact angle of developed soft finger are derived. Formula for total force on fundamental deformation has been analyzed using simple mathematics. Selection of appropriate soft elastic material required for modelling of flexible finger is based on fundamental deformation and change in contact width with respect to applied normal load ranges from 0 to 100 N. Experiment is performed for 3 different nonlinear hyper soft elastic materials: Neoprene W, Viton E-60C and Silicone R401/70. Furthermore, deformation of cylindrical finger was determined by performing compression testing for each finger with load step 10 N. Contact width was determined by measuring vivid print observed above the recording paper. Additionally, coefficient of friction (COF) flanked by soft finger and target was measured by performing inclined test. Further, experimental result was successfully validated with finite element simulation performed on ANSYS software. [ABSTRACT FROM AUTHOR]

The equations of the combined model of phase and structural deformation of shape memory alloys (SMA) express the increments of deformations in terms of the increments of stresses, martensite volume part parameter and temperature, stresses themselves, deformations, and the temperature. However, to solve the stability problems of long-or thin-walled elements from SMA, as well as to formulate the tangent stiffness matrix of the finite element method for SMA, it is necessary to have an explicit expression of stress increments in terms of stresses, deformations, strain increments, temperature increments, and temperature. The paper presents an analytical method for obtaining such inverting. [ABSTRACT FROM AUTHOR]

Numerous empirical and numerical studies have been carried out on the mechanical characterization of ductile materials. The application of digital image correlation (DIC) equipped with three-dimensional measurement analysis was used to examine the mechanical characteristics of aluminum alloy (AL 7075). Then, the DIC outcome with finite element simulation results will be compared with the experimental results to measure the performance of the DIC. A tensile specimen of AL 7075 is tested under constant loading with a 2 mm/min displacement rate until fracture. Strain gauge and extensometer are used along with DIC monitoring technique to capture the structural deformation of the specimens. The specimen and test are simulated in ABAQUS software, in which the results are compared with experiment and DIC data, indicating a good correlation between the results. Limited data in the form of average deformation and strain of the experiments are not applicable to the plastic and necking process. In this respect, the 3D DIC results are used to analyze the strain field throughout the test, including specimen necking, and predict fracture location. Moreover, the outcome of DIC and finite element simulation are employed to examine the characteristics of AL 7075 about the large plastic deformation and mechanical behavior. The proposed 3D DIC methodology in providing insight into the characteristic mechanical behavior of ductile materials is highlighted in this paper. [ABSTRACT FROM AUTHOR]

Rollovers are complex road accidents causing a big deal of fatalities. FE model for rollover study will costtoo much time due to its long duration. A new multi-body modeling method is proposed in this paper which can save a lot of time and has high-fidelity meanwhile. Following works were carried out to validate this new method. First, a small van was tested following the FMVSS 208 protocol for the validation of the proposed modeling method. Second, a MADYMO model of this small van was reconstructed. The vehicle body was divided into two main parts, the deformable upper body and the rigid lower body, modeled by different waysbased on an FE model. The specific method of modeling is offered in this paper. Finally, the trajectories of the vehicle from test and simulation were compared and the match was very good. Acceleration of left B pillar was taken into consideration, which turned out fitting the test result well in the time of event. The final deformation status of the vehicle in test and simulation showed similar trend. This validated model provides a reliable way for further research in occupant injuries during rollovers. [ABSTRACT FROM AUTHOR]

Identification of parameters of laser beams is important in all applications of lasers. In this paper, results of numerical verification are presented for identification of parameters of pulsed, high-power laser beam based on displacement fields of the target body. It is considered how laser power as well as spatial and temporal characteristics of the beam may be recovered based on measurements of thermally-caused deformation of thin aluminum plate. Mechanical displacement of the plate surface was calculated using Finite Element Method (FEM), for selected time instants, based on solutions of the unsteady thermal problem obtained with Finite Volume Method (FVM). Sensitivity of measured displacements to changes of recovered laser pulse parameters is discussed. Preliminary results of parameter estimation based solely on measurements of the Z-component of displacement field were compared with results of estimations based on measurements of temperatures. The comparison was made for inverse problems solved using Levenberg-Marquardt method applying synthetic measurement data instead of physical one. It was found that solutions of the inverse problem based on temperatures are better than those based on mechanical analysis. [ABSTRACT FROM AUTHOR]

The paper presents the innovative process with possibility of predict the state of deformation and stresses in a two-stage metal forming process. In the first stage, regular surface roughness with arched outlines are embossed. In the second stage, these inequalities are flat burnished to obtain the required dimensions, roughness of the surface, and state of deformation and stresses in the surface layer of the workpiece. The process are considered as a geometrical and physical non-linear boundary and initial value problem, with unknown boundary conditions in the contact zone. The applications were developed in the Ansys/LS-Dyna system, which makes possible a complex time analysis of the states of displacements, strains and stresses, in the workpiece in the two-stage cold metal forming processes. Application of this method were showed for examples the modelling and the analysis of the regular asperities with arched outlines. In the simulations, the material as well as the geometrical parameters of surface asperities were changed. The simulation results were verified experimentally. [ABSTRACT FROM AUTHOR]

One of the main problems in control is that the overwhelming number of physical quantities cannot be measured directly. Hence, there arise so-called inverse problems on the determination of physical quantities from the results of their manifestations. In the mechanics of a deformable solid there is a problem of obtaining material properties at all stages of deformation and especially at the overcritical stage. In this paper, we formulate and solve the inverse problem of finding the tensile diagram of a material element from the diagram of the dependence of the bending moment on the curvature of a rectangular beam under pure bending. [ABSTRACT FROM AUTHOR]

Computer simulation is widely used in the design and development of technical products. Multiscale nature of deformation and fracture of novel materials requires to use for this purpose not only the conventional finite element method but particle methods at different spatial scales as well. This paper presents a computer code aimed for discrete-continuum simulation of friction based on coupling finite elements (as a continuum method) with movable cellular automata (discrete particle method). Two computer codes based on finite elements and written in different programming languages are used: commercial and in-house. Peculiarities of the application program interfaces of the particle code for coupling with both finite element codes are described and analyzed. It is shown that the code developed takes the advantages of both cases and promises to be very efficient for simulating various contact problems including friction. [ABSTRACT FROM AUTHOR]

In this paper, a fully adaptive 3D numerical methodology based on a tetrahedral element was proposed in order to improve the finite element simulation of any metal forming process. This automatic methodology was implemented in a computational platform which integrates a finite element solver, 3D mesh generation and a field transfer algorithm. The proposed remeshing method was developed in order to solve problems associated with the severe distortion of elements subject to large deformations, to concentrate the elements where the error is large and to coarsen the mesh where the error is small. This leads to a significant reduction in the computation times while maintaining simulation accuracy. In addition, in order to enhance the contact conditions, this method has been coupled with a specific operator to maintain the initial contact between the workpiece nodes and the rigid tool after each remeshing step. In this paper special attention is paid to the data transfer methods and the necessary adaptive remeshing steps are given. Finally, a numerical example is detailed to demonstrate the efficiency of the approach and to compare the results for the different field transfer strategies. [ABSTRACT FROM AUTHOR]

Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. In this process two different deformations occur in order to reduce the width and the height of a preform hollow ring; as results a diameter expansion is obtained. In order to guarantee a uniform deformation, the preform is forced toward the Driver Roll whose aim is to transmit the rotation to the ring. The ring rotational speed selection is fundamental because the higher is the speed the higher will be the axial symmetry of the deformation process. However, it is important to underline that the rotational speed will affect not only the final ring geometry but also the loads and energy needed to produce it. Despite this importance in industrial environment, usually, a constant value for the Driver Roll angular velocity is set so to result in a decreasing trend law for the ring rotational speed. The main risk due to this approach is not fulfilling the axial symmetric constrain (due to the diameter expansion) and to generate a high localized ring section deformation. In order to improve the knowledge about this topic in the present paper three different ring rotational speed trends (constant, linearly increasing and linearly decreasing) were investigated by FEM approach. Results were compared in terms of geometrical and dimensional analysis, loads and energies required. [ABSTRACT FROM AUTHOR]

This paper concerns the numerical modeling of deformation behavior taking into account the pores shape of porous materials. In the research were used porous sintered 316L stainless steel. These types of materials have wide application, among others, in the automotive, aerospace and medical industries, e.g. for the production of bone substitutes. The production process of sinters causes heterogeneous distribution of pores in different directions. This results in the occurrence of anisotropy in a deformed porous material. The use of X-ray computed microtomography allowed to the mapping of the real shape of pores in mesoscopic scale. Based on the obtained microtomographic images were generated three-dimensional geometrical models of porous mesostructures. The micro-CT device has a limited measurement accuracy, which results in a lack of mapping of small pores and fissures of porous structures. For this reason, in the study used two methods for compensating the influence of the measurement inaccuracies on numerical calculations. Received geometrical models were used for numerical calculation using the finite element method (FEM). Based on the numerical results, was determined the influence of the material inhomogeneity on its mechanical properties are and how the sintering process effects on the anisotropic deformation behavior. [ABSTRACT FROM AUTHOR]

The paper determines the actual stress-strain state of a vertical steel tank RVS-20000's bottom considering the subsoil base inhomogeneity zones of various sizes. Using the ANSYS software a finite element model of the RVS-20000's bottom has been developed. A design scheme proposed in the article takes into account the impact of the out-contour space. Analysis of the test calculation results has shown that the area of maximum stress acting on the vertical steel tank bottom is located along the perimeter of the base subsidence area. There are dependences that characterize tank bottom sags at maximum operating stress occurring in the metalwork of the tank bottom and concentrated on the border of the subsidence area out-contour zone in the paper end. It is found that Russian regulatory documents require harmonization with international standards. [ABSTRACT FROM AUTHOR]

In this paper, considering the process of deepwater SCR installation with the limitations of small deformation theory of beam and catenary theory, a mechanical model of deepwater SCR installation is given based on large deformation beam model. In the following model, getting the relation of the length of the riser, bending stiffness and the unit weight by dimensional analysis, the simple approximate analytical expressions are obtained by using Homotopy Analysis Method. In the same condition, the calculated results are compared with the proposed approximate analytical expressions, the catenary theory or the commercial software of nonlinear finite element program ORCAFLEX. Hopefully, a convenient and effective method for mechanical model of deepwater SCR installation is provided. [ABSTRACT FROM AUTHOR]

This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study which has smaller density from the steel. A two-dimensional finite element computational method is implemented to describe the dynamic behavior of the riser. The governing equation of motion was based on Hamilton's principle, consists of the strain energy due to bending and axial deformation, kinetic energy due to both riser and internal fluid movement and also external force from currents and waves. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The natural frequency and damping ratio are presented for each mode. Dynamic response of riser is shown in time-domain and the numerical results are discussed. Several parameter effects are used to investigate dynamic responses and the results show an agreement with the theory. Vortex shedding phenomenon also has been discussed in this paper. As a conclusion, the simulation results have successfully shown the vortex induced vibration responses for GRP pipeline. [ABSTRACT FROM AUTHOR]

In this paper the authors outline a constitutive model, implemented within finite element analyses, which was developed for large deformation, high temperature multi-axial stretching of polypropylenes. The model has been generalised to a fully 3-dimensional thermally coupled form. The paper describes how model parameters were characterised using constant width, biaxial and sequential stretching of polypropylenes at elevated temperature using a custom built flexible biaxial stretching machine developed at Queen's University Belfast. The paper presents results of finite element model predictions of material stretching behaviour compared to range of physical experiments. The results presented in the paper confirm that this model is very effective in predicting the complex thermo-mechanical behaviours of polypropylenes at elevated temperatures. [ABSTRACT FROM AUTHOR]

A heartbeat is the consequence of cardiac tissue deforming in response to tension generated in cardiac fibres. This tension is a result of biochemical reactions that occur as part of cardiac electrophysiology. This coupled electro-mechanical system is usually modelled by coupling a model of tissue deformation with a tissue level model of cardiac electrophysiology such as the bidomain equations [1]. One difficulty with computing a numerical solution of this coupled system is numerical stability [3, 7]. In this paper we describe how numerical stability may be attained by embedding the model of generation of active tension within the tissue deformation model. [ABSTRACT FROM AUTHOR]

Finite element analyses of rolling processes have been carried out for many years. Most of the simulations focus on deformation of metal plates/sheets without taking into consideration flexibility of rolls and the machine frame. In our paper, we present a unique approach to simulation of rolling of thick plates where compliance of rolls and the complete structure of a roll leveler is taken into account. This approach makes it possible to accurately predict shape distortion of steel plates and gives valuable, practical information on how to prevent shape defects in a rolled product. In this paper, roll leveling of steel plates after continuous casting, is analyzed. Our approach is universal and can be applied to other types of rolling processes. As a simulation tool, we used a non-linear FEM code. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Among forging processes, incremental processes are those where the work piece undergoes several thermal and deformation steps with small increment of deformation. They offer high flexibility in terms of the work piece size since they allow shaping wide range of parts from small to large size. Since thermal treatment is essential to obtain the required shape and quality, this paper presents the thermal modeling of incremental processes. The finite element discretization, spatial and temporal, is exposed. Simulation is performed using commercial software Forge 3. Results show the thermal behavior at the beginning and at the end of the process. [ABSTRACT FROM AUTHOR]

This paper concerns the application of variational methods for the formulation of object motion equations as well as generation heat and its transfer formulated in the updated Lagrange description. These physical phenomena occur in the processing of metals in which there are thermal, plastic viscous and phase deformations. The obtained incremental variation equation of the object's motion and the incremental variation of the heat conduction equation were discretized by the Finite Element Method to obtain discrete systems of equations. These equations are solved by known methods for given boundary and initial conditions. As a result, a column vector of the displacement increment and a column vector of the temperature increment in the object nodes are obtained at each time step. Examples of the use of these methods for the burnishing rolling process with electric current are shown. [ABSTRACT FROM AUTHOR]

B-Pillars are specifically designed to absorb substantial energy with a minimum amount of deformation to limit its intrusion in the passenger compartment during an event of side impact. In this paper, the B-pillar has been developed using composite materials, with the main objective is to improve crashworthiness performance at a lesser weight, as a replacement for steel. The three-point bending test simulations of the composite B-pillar model were modelled, which applied various parameters of materials, number of ply and additional reinforcement. The composite B-pillar design parameter that scored the highest performance to weight ratio in the numerical simulation was then fabricated using vacuum bagging method. Subsequently, the B-pillar was tested under three-point bending experimental work. The force and central displacement results were compared to simulation data and a good agreement was obtained, where B-pillar made of carbon fibre reinforced polymer (CFRP) performed better than glass fibre reinforced polymer (GFRP). The simulation and experimental results indicated errors ranging between 6 and 15%. With the additional reinforcement at the critical area, the energy absorption of CFRP B-pillar was considerably improved by 18%. The weight of the fabricated composite B-pillar was 58% lighter compared to the original steel B-pillar. These results confirmed that the novel composite material holds a high strength, and has lightweight potential to substitute steel as car B-pillar material. [ABSTRACT FROM AUTHOR]

Beam-to-column end-plate bolted connections are usually used as moment-resistant connections in steel framed structures. For this joint type, the deformability is governed by the deformation capacity of the column flange and end-plate under tension and elongation of the bolts. All these elements around the beam tension flange form the tension region of the joint, which can be modeled by means of equivalent T-stubs. In this paper a beam-to-column end-plate bolted connection is substituted with a T-stub of appropriate effective length and it is analyzed using the commercially available finite element software ABAQUS. The performance of the model is validated by comparing the behavior of the T-stub from the numerical simulation with the behavior of the connection as a whole. The moment-rotation curve of the T-stub obtained from the numerical simulation is compared with the behavior of the whole extended end-plate connection, obtained by numerical simulation, experimental tests and analytical approach. [ABSTRACT FROM AUTHOR]

This paper deals with the development and approbation of a computational model of damage accumulation in a vertical steel tank at the non-uniform foundation subsidence. The object of research is structure behavior at the survivability stage, namely, the character and sequence of damage initiation and accumulation (elastic-plastic strain, bottom and wall buckling) in the tank structure. [ABSTRACT FROM AUTHOR]

Influence of solar radiation and Earth’s radiation, as well as heat radiation of devices and on-board equipment on the deformation of the primary structure of the small spacecraft Aist-2D on the orbital flight stage is considered in this paper. The thermoelasticity problem is solved by the finite element method in the ANSYS® software. The results of the analysis are presented in the form of graphs of variation over time of the relative rotation angles of the sensors of the orientation system and optical equipment. [ABSTRACT FROM AUTHOR]

The lobule is the structural unit of the liver. In this paper a multi-physical model of blood flow in the liver lobule is considered. The proposed model is built on the basis of a double porosity model for the process of blood flow which is coupled with linear elasticity for deformations. The computational algorithm is based on finite-element approximation in space and explicit-implicit approximation in time which is a splitting scheme by physical processes. Results of numerical experiments are demonstrated. [ABSTRACT FROM AUTHOR]

In aircraft gas turbine engine, the rotating turbine disc is highly stressed component. The demand of high strength to weight ratio for each component of aeroengine makes the disc, a critical component from design point of view. Burst of rotor disc is one of the catastrophic failure mode of gas turbine engine. The present paper, therefore, deliberates the burst of rotating turbine disc due to overspeed. A typical gas turbine disc is modeled and elastic-plastic analysis is carried out by linearly increasing the speed. Finite element technique has been used for the analysis. The burst criteria is proposed based on the deformation taking place in the disc. A safe permissible speed between burst rotation speed and maximum allowable speed of the turbine disc is also identified as per federal aviation regulations. [ABSTRACT FROM AUTHOR]

Traffic accidents are terrible scourge that occurs in many countries, for developing countries where transportation problems seem like a tangled yarn. Besides its function as an engine compartment cover, the hood of modern compact SUV can also help to manage the impact energy of pedestrian's head in a vehicle-pedestrian impact. This paper presents a compact SUV's outer hood design that has a potential to improve hood ability and also to absorb the impact energy of a pedestrian's head. The developed methodology for the design of a hood configuration aims to provide a compatible design and stress distribution for the left side impact position at WAD 1000 with three different thicknesses (1.25 mm, 1.30 mm and 1.50 mm) of outer hood panel of local compact SUV, taking into consideration the limited space available for deformation. Finite Element Modeling (FEM) software was used in this research to simulate the ANCAP for child pedestrian head impact testing procedures. The results show that the minimum deformation space and meet the requirement for stress (von Mises) value are required to obtain a sturdy design. Moreover, the hood thickness and materials are the main factors that influence stress and deformation value. Finally, 1.25 thickness aluminum alloy is recommended for vehicle hood component and the pedestrian safety. [ABSTRACT FROM AUTHOR]

The study of springback analysis of 440MPa high strength steel is investigated in this paper. Because of the springback phenomenon is related to the material properties and the deformation mechanism during the forming process, the material properties of 440MPa high strength steel are studied at first. The material properties of 440MPa high strength steel are obtained by conducting cyclic uniaxial tension-compression tests with different strain ranges. In order to apply the material properties obtained from the experiments to the finite element analysis, the material constants required in the Yoshida-Uemori model (Y-U model) with the Bauschinger effect considered are established. For realizing the springback characteristics of 440MPa high strength steel, the U-hat draw-bending and V-shape bending are examined by the finite element analysis. From the simulation results, it finds that the side wall curl phenomenon occurs in the U-hat drawbending and the springback phenomenon appears in the V-shape bending. Moreover, it also shows that the side wall curl phenomenon and springback phenomenon are more obvious in the finite element simulations with the Bauschinger effect considered. Finally, the validation of springback prediction is performed by stamping an engine hood reinforcement with 440MPa high strength steel sheet. From the stamping results, it shows that the simulation results of springback prediction are in a well agreement to the production part data. It also finds that the springback predictions are more accurate by the finite element simulations with the use of the Y-U model. It is also found that for a stamping part which is subjected to a reversed tension-compression deformation in the forming process, the occurrence of the Bauschinger effect is obvious. It is also concluded that the accuracy of springback prediction can be much improved by the use of material model with the Bauschinger effect considered. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) is applied to analyze closed extruding fine blanking gear. The reason of engendering corner collapse is the friction between blank and die. Meanwhile, this paper analyzes effects of various counterpunch forces on the flow characteristics, obtains the fiber distribution on different sections of the gear. The effects of counterpunch forces on material flow characteristics in deformation zone and the swirling flow in scrap are also obtained. [ABSTRACT FROM AUTHOR]

The aim of this paper is to introduce a method to reduce the weight in structures which are subjected to multiple restrictions like deformation, max allowable stress, natural frequency, etc.... The method is shown through the analysis of an aluminum bracket, whose maximum stress and deformation is well defined. The analysis is done using the Structural and Design of Experiments modules of Ansys Workbench v12.1. As result of the method a weight reduction of 50,2% is achieved. [ABSTRACT FROM AUTHOR]

Modeling of collision processes of colliding bodies with different properties is of particular theoretical and practical interest e.g. for modeling of plastic deformation processes. Best results regarding the parameters of the collision processes (forces, stress, strain, duration of contact, etc.) are obtained using the finite elements method (FEM). This paper presents the results of FEM modeling of the collision process after a free fall of a sphere on an elastic-plastic plate of specific dimensions under the additional application of an external force. Two cases are described: the application of an external force during the time of contact of the colliding bodies, and without application of an external force. Correlations were obtained for the change of the strength of the impact, the stress and strain as function of time for the sphere and the plate. The strain of the plate were defined for various values of the external force. These results allow us to define the conditions, necessary to perform the so called 'Combined Impact' leading to significant change of the deformation processes conditions. [ABSTRACT FROM AUTHOR]

For middle-high rise buildings, vibration controlled structures to reduce the damage of main frames are recently becoming general in Japan. A steel material damper is low price and excellent in the energy absorption efficiency at a large earthquake. Though the exchange of the dampers are necessary when an excessive accumulation of plasticity deformation occurs, a steel material damping system, which received an excessive accumulation of plasticity deformation after a large earthquake, can recover a seismic-proof performance and property value of the building after the replacement. In the paper, shear yielding steel panel dampers installed in the web of a beam connected with high tension bolt joint is introduced. This damper is made of low-yield point steel, and the advantages of this system are low cost, easy-production and easy-replacement. For this steel panel damper, the finite element method (FEM) analysis using the shell element model adjusted to 1/2 of 6.4 m beam span is executed to make the design most effective. Yielding property of the beam installing this damper, shape of the splice plate and the bolt orientation for the connecting are examined in this analysis. As a result, we found that the plastic strain extends uniformly to the entire damping panel when making the splice plate a trapezoidal shape. The basic performance confirmation examination was also done using the real scale examination model besides the FEM analysis, and the performance of the system was confirmed. In addition, design of a high rise building in which the steel shear-yielding panel dampers and oil dampers were adopted without disturbing an architectural plan is also introduced [ABSTRACT FROM AUTHOR]

In this paper, a new computational technique is presented based on the eXtended Arbitrary Lagrangian-Eulerian Finite Element Model (X-ALE-FEM) in large plasticity deformations. An arbitrary Lagrangian-Eulerian (ALE) technique is employed to capture the advantages of both Lagrangian and Eulerian methods and alleviate the drawbacks of the mesh distortion in Lagrangian formulation. In order to remove the limitation of the mesh conforming to the boundary conditions in the simulation, the extended finite element method (X-FEM) is implemented by incorporating discontinuous fields through a partition of unity method. The implementation of X-FEM technique in the framework of ALE model is finally presented in modeling of free-die pressing with flexible central core. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

A parallel computational environment for modeling the resin transfer molding manufacturing process has been developed at the U.S. Army Research Laboratory. This environment utilizes an implicit numerical method for modeling resin flow, a thermal model for analyzing convection and conduction, and a resin kinetics model to compute the heat generated and degree of resin cure during the curing process. The computing environment also includes a multiscale thermal residual stress model for computing the distortions and residual stresses in the composite component caused by the manufacturing process. All of these models have been tied together within a parallel object-oriented programming framework. This paper will discuss the computing environment in detail and its utility to real world applications. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The critical issue during finite element analysis of tailor welded blank is the handling of the weld region — either the weld may be treated just as a weld line (without imposing mechanical properties) or as a weld zone (by imposing separate mechanical properties to the weld zone). The formability of TWB will be affected not only by the weld characteristics but also by the relative mechanical properties of the weld zone and the base metal. The above effects will be discussed in this paper by considering the tensile and Limiting Dome Height (LDH) testing of the TWB. Tensile testing will be modeled using standard tensile specimen. In LDH simulations, samples deforming near plane strain and balanced biaxial stretching will be modeled. Load-progression behavior will be monitored. Throughout this study , simulations will be performed by finite element analysis. By analyzing the simulation results, the specific conditions where the weld zone assumption should be followed will be identified. It is found from the analysis that modeling weld region as weld line is not accurate for all the weld conditions. Also the domain of weld conditions wherein weld line assumption breaks down depends on the deformation mode or part shape. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

One of the most important methods for improving the flexibility of sheet metal forming process is the deformation with discrete surfaces. The method developed by Hardt, consists in a spatial discretization of the continuous active elements surfaces with a number of pins. As the spatial positions of the pins are of a great importance, in the paper is developed, based on surface generation method, a mathematical model for pins coordinates determination. Then using the finite element code DYNAFORM, it was modeled the process of deformation for obtaining two types of parts geometries namely: a simple curved geometry and a double curved geometry. Finally, as a result of simulation it was point out the advantages and disadvantages of using this type of deformation. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper the reliability assessment of buckling resistance of steel beam is presented. A number of parameters such as: the boundary conditions, the section height to width ratio, the thickness and the span are considered. The examples are solved using FEM procedures and formulas proposed in the literature and standards. In the case of the numerical models the following parameters are investigated: support conditions, mesh size, load conditions, steel grade. The numerical results are compared with approximate solutions calculated according to the standard formulas. It was observed that for high slenderness section the deformation of the cross-section had to be described by the following modes: longitudinal and transverse displacement, warping, rotation and distortion of the cross section shape. In this case we face interactive buckling problem. Unfortunately, neither the EN Standards nor the subject literature give close-form formulas to solve these problems. For this reason the reliability of the critical bending moment calculations is discussed. [ABSTRACT FROM AUTHOR]

Over the past 60 years, the finite element method has been very successful in modelling deformation in engineering structures. However the method requires the definition of constitutive models that represent the response of the material to applied loads. There are two issues. Firstly, the models are often difficult to define. Secondly, there is often no physical connection between the models and the mechanisms that accommodate deformation. In this paper, we present a potentially disruptive two-level strategy which couples the finite element method at the macroscale with cellular automata at the mesoscale. The cellular automata are used to simulate mechanisms, such as crack propagation. The stress-strain relationship emerges as a continuum mechanics scale interpretation of changes at the micro- and meso-scales. Iterative two-way updating between the cellular automata and finite elements drives the simulation forward as the material undergoes progressive damage at high strain rates. The strategy is particularly attractive on large-scale computing platforms as both methods scale well on tens of thousands of CPUs. [ABSTRACT FROM AUTHOR]

The paper deals with the problem of identification of microstructure evolution model on the basis of two-step compression test. This test is characterized by non-uniform fields of strains, stresses and temperatures in the deformation zone. Therefore, the inverse approach with finite element model for the experiment - direct problem, was applied to eliminate the influence of these inhomogeneities. Inverse solution for two-step compression test is time consuming. Thus, sensitivity analysis was performed and an influence of the parameters of the microstructure model on the goal function defined in the inverse solution was evaluated. Data generated for sensitivity analysis was reused in the inverse approach to reduce the computation costs of identification. [ABSTRACT FROM AUTHOR]

The application of laminated sandwich composite in machine structures is attractive due to the low specific and tailorable properties of the composites. As such a study on the parametric instability that often occurs in machine structures should be crucially conducted on composite plates. In this paper, finite element method (FEM) has been used to model laminated composite plate subjected to periodic compressive loading for the parametric instability analysis. The FEM formulation is based on the first order shear deformation theory. Eight noded serendipity element that requires 5 degrees of freedom per node is used in this study. The developed Mathieu-Hill type equation that represents the parametric instability of the composite plate has been solved using the Bolotin's method that reduces the Mathieu-Hill equation to a couple of eigen-value problems. The FEM source codes have been developed to determine the instability charts for several configurations of composite plates. While the formulation and codes have been found to give results that agree well with past results, it has been also been found that as the static load factor is increased, the frequency center for dynamic instability region is shifted to the left while the degree of instability is increased. [ABSTRACT FROM AUTHOR]

This paper presents a simplified finite element method called "Pseudo Inverse Approach" (PIA) for tool shape design and optimization in multi-step cold forging processes. The approach is based on the knowledge of the final part shape. Some intermediate configurations are introduced and corrected by using a free surface method to consider the deformation paths without contact treatment. A robust direct algorithm of plasticity is implemented by using the equivalent stress notion and tensile curve. Numerical tests have shown that the PIA is very fast compared to the incremental approach. The PIA is used in an optimization procedure to automatically design the shapes of the preform tools. Our objective is to find the optimal preforms which minimize the equivalent plastic strain and punch force. The preform shapes are defined by B-Spline curves. A simulated annealing algorithm is adopted for the optimization procedure. The forging results obtained by the PIA are compared to those obtained by the incremental approach to show the efficiency and accuracy of the PIA. [ABSTRACT FROM AUTHOR]

To control thinning is a challenge in traditional flaring process of thin-walled tubes. Electromagnetic forming provides a new way to expand the tubes end with uniform wall thickness, as it can produce a uniform distribution of magnetic force on tubes and easily form by one step based on adjusting the discharge parameters. In this paper, a 3D asymmetric finite element model of electromagnetic flaring of thin-walled copper tubes based on the magnetic vector potential is developed for calculating magnetic field and magnetic forces, and Newmark integration method is used to calculate the dynamic plastic deformation of tubes in the mechanical model. A sequential-coupled simulation approach is developed to analyze the deformation behaviors and the influences of different discharge parameters on deformation behaviors for electromagnetic tube flaring. The deformation height and thinning rate of thin-walled copper tubes show a positive correlation with the charge voltage and capacitance, and deformation zone maintains uniform thickness resulting in smaller thinning rate so as to reduce the trend of crack. Subsequently, some experiments are used to verify the simulation results. A comparison of simulation results and experimental results for final tubes shows a good agreement, and the measured hardness of deformation zone significantly improved after electromagnetic tube flaring. [ABSTRACT FROM AUTHOR]

In this paper residual stresses and radial deformation of the hub of a shaft-hub-connection manufactured by lateral extrusion is examined within different methods. Beside FEA (finite-element analysis) the radial deformation of the external hub contour is determined by using a 3D coordinate measurement device. Residual stresses are examined also by FEA and by application of strain gauges to the external hub contour at the area of minimum and maximum hub thickness. A P3G polygon profile according to DIN 32711-1 [1] and DIN 3711-2 [2] showing a nominal diameter of 25 mm and a profile eccentricity of 1.12 mm is used as hub profile. [ABSTRACT FROM AUTHOR]

In the paper, the micro deformation of oxide scale in hot strip rolling has been investigated with considering the friction effect. The finite element simulation of the micro deformation of oxide scale has been successfully conducted, and the calculated surface roughness is compared with the measured value, which shows a good agreement. A crystal plasticity finite element method (CPFEM) model was also successfully developed to analyse the surface roughness transfer during metal manufacturing. The simulation results show a good agreement with the experimental results in the flattening of surface asperity, and the surface roughness decreases significantly with an increase of reduction. This study also indicates that the lubrication can delay surface asperity flattening. [ABSTRACT FROM AUTHOR]

A novel flexible roll forming method is proposed for manufacturing of large curved metal plates. By adjusting the position of three rows of staggered arranged rollers, a large curved metal plate is formed in an incremental way. In this paper, FE (finite element) model is established to analyze the stress-strain distribution of the deformed plates in the forming process. Based on the numerical simulation, the influence of the relative position between upper rollers and lower rollers on the dimensional accuracy of the large curved metal plate is studied. Comparison results show that roller arrangement has great influence on the dimensional accuracy of deformed plates, and process with staggered arranged rollers has the best dimensional accuracy. [ABSTRACT FROM AUTHOR]

Hydroforming has been selected as a technique for the seamless fabrication of multicell superconducting radiofrequency (SRF) cavities. For the successful application of this technique to cavity fabrication, it is essential to understand deformation behavior of tubes under hydroforming conditions. Input to the finite-element modeling (FEM) which generally precedes the actual hydroforming process requires the constitutive properties of the tube material. This information may be obtained from the results of hydraulic bulge testing. The present paper provides an example of this activity. In order to verify the steps to be taken in analyzing future bulge-test data a circular argument recovers the original constitutive properties from the results of an FEM-based "virtual bulge test". [ABSTRACT FROM AUTHOR]

One critical factor affecting the performance of Lamb wave based damage detection and characterization techniques is the angular amplitude distribution of the interrogating wave scattered at defects and structural features. Analytical solutions for this problem do not exist for composite laminates due to the anisotropic nature and multilayer characteristics of the material. In this paper the scattering characteristics of the fundamental anti-symmetric Lamb wave at delaminations and structural features in composite laminates is considered. Experimental measurements and finite element simulations are employed to quantify the A0 mode Lamb wave scattering characteristics at delaminations and through holes. Good agreement is found between the simulations and experimental measurements. Extended parameter studies provide improved physical insight into the phenomena and show that the angular distributions of the scattered wave amplitudes depend on the defect size to wavelength ratio, the stacking sequence of the laminate and, in the case of delamination damage, the through thickness location of the delamination. [ABSTRACT FROM AUTHOR]

The paper presents an approach that combines the simulation of technological processes on two levels. One of them is the finite element model that predicts material flow and temperature distribution in the workpiece during any multi-stage deformation where forming steps can be separated by heating/cooling of the billet. The second level is a semi-empirical microstructural model that simulates static and dynamic recrystallisation and grain growth during deformation or dwelling time. The background of the microstructural model is Sellars formulation. The model parameters are derived by parameterization of the experiments done with the material specimens for a wide range of strain, strain-rate, temperature variation and pause time. This model has been integrated in QForm3D software and tested for several practical cases of open and closed die forging. The case studies have shown good agreement between the simulation results and practice that have opened the way for its implementation in industry. [ABSTRACT FROM AUTHOR]

Machining is the most common manufacturing process. A good behaviour law is necessary in the simulation of machining processes (analytical and finite element modeling). Usually, commonly used behaviour laws such as Jonhson-Cook can bring unsatisfactory results especially for high strain and large deformation processes. Significant differences can appear between experimental and simulation results. The aim of this paper is to present the choices made regarding the behaviour law in this context. This study develops a large deformation strain-gradient theoretical framework with hypothesis linked to metal cutting processes. The theoretical framework has the potential of expressing moments at the tool tip as they were observed in experiments. It will be shown that the theory has the capability of interpreting the complex phenomena found in machining and more particularly in high speed machining. [ABSTRACT FROM AUTHOR]

The paper is focused on application of multi-scale 2D method. Model approach consists of Cellular Automata (CA) model of microstructure development and the finite element code to solve thermo-mechanical problem. Dynamic recrystallization phenomenon is taken into account in 2D CA model which takes advantage of explicit representation of microstructure, including individual grains and grain boundaries. Flow stress is the main material parameter in mechanical part of FE and is calculated on the basis of average dislocation density obtained from CA model. The results attained from the model were validated with the experimental data. In the present study, austenitic steel X3CrNi18-10 was investigated. The examination of microstructure for the initial and final microstructures was carried out, using light microscopy and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

The paper deals with the development of the technique for J-integral computation using the vector fields obtained by digital image correlation method. The proposed computing algorithm includes several steps following each other: (i) construction of displacement vector field; (ii) calculation of deformations and stresses; (iii) calculation of the J-integral value. A comparative study of the results obtained by the proposed technique and by finite element simulation was carried out. The errors of the data modeled in the ANSYS from the computed J-integral values were estimated at various tensile loads. [ABSTRACT FROM AUTHOR]