From Finite Element Method Research Articles

Phase Dependent Tool Wear in Turning Ti-6Al-4V Using Polycrystalline Diamond and Carbide Inserts

Tool wear of polycrystalline diamond inserts was analyzed in turning experiments on Ti-6Al-4V. Evidence of phase transformation in turning titanium work material is presented and its impact on tool wear is discussed. Confocal laser scanning microscopy was used to analyze the rake face of the turning inserts. At cutting speed of 61 m/min, the rake face exhibited scalloped-shaped, fractured wear, characteristic of typical attrition wear. At cutting speed of 122 m/min, a smooth crater was observed, which is a typical characteristic of diffusion/dissolution wear. At the cutting speed of 91 m/min, the wear features were a combination of those observed at speeds of 61 m/min and 122 m/min. A comparison of the wear on the polycrystalline diamond (PCD) tools to that of WC-6Co from our earlier work is also discussed. Microstructural analysis of the of both the undeformed work material and the chip using electron-backscatter diffraction provided evidence to support the phase transformation. Temperature estimates on the rake face of the tool previously extracted from Finite Element Method (FEM) support the possibility of phase transformation at the high cutting speed tested. The difference in the wear pattern was also linked to the extent of recrystallization in the titanium work material. At 61 m/min there was more alpha phase in the work material without much recrystallization, which generated uneven scalloped wear. At 122 m/min, phase transformation of the existing alpha phase to the beta phase in the work material and recrystallization increased the dissolution/diffusion wear process.

Post-buckling finite strip analysis of thick functionally graded plates

In this paper, a novel semi-energy finite strip method (FSM) is developed based on the concept of first order shear deformation theory (FSDT) in order to attempt the post-buckling solution for thin and relatively thick functionally graded (FG) plates under uniform end-shortening. In order to study the effects of through-the-thickness shear stresses on the post-buckling behavior of FG plates, two previously developed finite strip methods, i.e., semi-energy FSM based on the concept of classical laminated plate theory (CLPT) and a CLPT full-energy FSM, are also implemented. Moreover, the effects of aspect ratio on initial post-buckling stiffness of FG rectangular plates are studied. It has been shown that the variation of the ratio of initial post-buckling stiffness to pre-buckling stiffness (S * /S) with respect to aspects ratios is quite independent of volume fractions of constituents in thin FG plates. It has also been seen that the universal curve representing the variation of (S * /S) with aspect ratio of a FG plate demonstrate a saw shape curve. Moreover, it is revealed that for the thin FG plates in contrast to relatively thick plates, the variations of non- dimensional load versus end-shortening is independent of ceramic-metal volume fraction index. This means that the post-buckling behavior of thin FG plates and the thin pure isotropic plates is similar. The results are discussed in detail and compared with those obtained from finite element method (FEM) of analysis. The study of the results may have a great influence in design of FG plates encountering post-buckling behavior.

A novel simulation of AC magnetic contactor based on electromagnetic transients program

AbstractThis paper proposes a new simulation approach for the AC magnetic contactor using the electromagnetic transients program (EMTP). The duality transformation technique is applied to convert a magnetic model into an electrical model. The great advantages of the proposed model are its capability of being directly simulated with other electrical components using EMTP and, therefore, its minimum level of complexity. To enhance the precision of the proposed model, the saturation of magnetic core and the fringing flux effects are taken into account. The performance and accuracy of the proposed model are verified by comparing them with those from finite element method (FEM) simulations and experiments. The results confirm that the proposed model has very good performance and the technique can be further applied to other magnetic components. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Neuro evolutionary model for weld residual stress prediction

Welding is an efficient reliable metal joining process in which the coalescence of metals is achieved by fusion. Localized heating during welding, followed by rapid cooling, induce residual stresses in the weld and in the base metal. Determination of magnitude and distribution of welding residual stresses is essential and important. Data sets from finite element method (FEM) model are used to train the developed neural network model trained with genetic algorithm and particle swarm optimization (NN–GA–PSO model). The performance of the developed NN–GA–PSO model is compared neural network model trained with genetic algorithm (NN–GA) and neural network model trained with particle swarm optimization (NN–PSO) model. Among the developed models, performance of NN–GA–PSO model is superior in terms of computational speed and accuracy. Confirmatory experiments are performed using X-ray diffraction method to confirm the accuracy of the developed models. These developed models can be used to set the initial weld process parameters in shop floor welding environment.

A high-precision segmented Paul trap with minimized micromotion for an optical multiple-ion clock

We present an experiment to characterize our new linear ion trap designed for the operation of a many-ion optical clock using 115-In^+ as clock ions. For the characterization of the trap as well as the sympathetic cooling of the clock ions we use 172-Yb^+. The trap design has been derived from finite element method (FEM) calculations and a first prototype based on glass-reinforced thermoset laminates was built. This paper details on the trap manufacturing process and micromotion measurement. Excess micromotion is measured using photon-correlation spectroscopy with a resolution of 1.1nm in motional amplitude, and residual axial rf fields in this trap are compared to FEM calculations. With this method, we demonstrate a sensitivity to systematic clock shifts due to excess micromotion of |({\Delta}{\nu}/{\nu})| = 8.5x10^-20. Based on the measurement of axial rf fields of our trap, we estimate a number of twelve ions that can be stored per trapping segment and used as an optical frequency standard with a fractional inaccuracy of \leq 1x10^-18 due to micromotion.

Experimental investigation of spur gear tooth mesh stiffness in the presence of crack using photoelasticity technique

Gear mesh stiffness plays a very important role in gear dynamics and it varies in the presence of gear fault such as crack. The measurement of stress intensity factor can lead to the determination of gear tooth mesh stiffness variation in the presence of crack in a spur gear system. In this paper, the technique of conventional photoelasticity has been revisited to explore the possibility of using it as a supplementary technique to experimentally measure the variation of gear mesh stiffness. An attempt has been made to calculate the variation of mesh stiffness for a pinion having a cracked tooth and a gear tooth with no crack of a spur gear pair. An analytical methodology based on elastic strain energy method in conjunction with total potential energy model has been adopted and implemented within the mesh stiffness calculations. To visualize the state of stress in a structure using finite element and other currently available methods, photoelasticity is considered to be one of the oldest and most developed experimental technique. An experimental methodology based on conventional photo-elasticity technique for computing stress intensity factor (SIF) for cracked spur gear tooth is presented for different single tooth contact position and crack length. The relation between contact position, crack length, crack configuration, SIF and the variation of total effective mesh stiffness have been quantified. Finally, a comparison has been made and the results obtained from finite element method (FEM) based on linear elastic fracture mechanics (LEFM), analytical method and proposed experimental method has been outlined.

Analysis of lobed gas lubricated bearing using neural networks

Purpose – The purpose of this paper is to investigate the performance of noncircular five lobe gas lubricated bearings, making use of the efficiency and simplicity of artificial neural networks (ANNs). The effects of different parameters such as compressibility number, mount and tilt angle on static and dynamic characteristics of such bearings are studied.Design/methodology/approach – For this purpose, various three‐layer neural network models, using Levenberg‐Marquardt method, are selected for training.Findings – The results obtained as neural network outputs compared with those reported results from finite element method (FEM) for two, three and four lobe journal bearings, are very close. The results for five lobe journal bearing show that the effect of tilt and mount angles on the stability of the bearing system are marginal, while low compressibility number can have more influence on the performance of such bearing systems.Originality/value – The paper shows that for the performance analysis of gas lu...

Study on Superalloy Tube Extrusion Process Using Finite Volume Method

In this paper, complexity of the process of high temperature alloy tubing extrusion is studied using the Finite Volume Method (FVM). We establish mathematical model of high temperature alloy tube extrusion process by using the Finite Volume Method. We develop the simulation program by the control equation of the Finite Volume Method and numerical simulation of the key technologies of the axisymmetric problem in cylindrical coordinates. Inconel690 high temperature alloy tubing extrusion process, for example, we got the squeeze pressure in the steady-state extrusion, Velocity field and the corresponding equivalent strain rate field. By comparing the results obtained by the finite volume method and simulation results from Finite Element Method (FEM) software on DEFORM-2D, we find our mathematical model on high temperature alloy tubing extrusion process is reasonable and correct.

An elasto-plastic constitutive model incorporating strain softening and dilatancy for interface thin-layer element and its verification

The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under condition of mixed soil slurry (bentonite mixed with cement grout). For comparison, the interfaces both without slurry and with bentonite slurry were analyzed. The experimental results show that different slurries exert much influence on the strength and deformation of soil/structure interface. Under mixed soil slurry, strain softening and shear dilatation are observed, while shear dilatation appears under the small normal stress of the interface without slurry, and shear contraction is significant under the condition of the bentonite slurry. The thickness of the interface was determined by analyzing the disturbed height of the sample with both simple shear test and particle flow code (PFC). An elasto-plastic constitutive model incorporating strain softening and dilatancy for thin layer element of interface was formulated in the framework of generalized potential theory. The relation curves of shear stress and shear strain, as well as the relation curves of normal strain and shear strain, were fitted by a piecewise function composed by hyperbolic functions and resembling normal functions. The entire model parameters can be identified by tests. The new model is verified by comparing the measured data of indoor cut-off wall model tests with the predictions from finite element method (FEM). The FEM results indicate that the stress of wall calculated by using Goodman element is too large, and the maximum deviation between the test data and prediction is about 45%. While the prediction from the proposed model is close to the measured data, and the error is generally less than 10%.

A Primary Permanent-Magnet Linear Motor for Urban Rail Transit

In this paper, a new permanent-magnet (PM) linear motor is proposed, in which both the magnets and armature windings are placed in the short mover, while the long stator consists of iron core only. Hence, this new PM linear motor can be called a primary permanent-magnet linear motor. It exhibits the advantages of robustness, low cost, high efficiency, high power factor, and high thrust force density. It is especially suitable for long stator applications such as urban rail transit. In this paper, the topology and operation principle of this motor are discussed in detail. The steady-state characteristics including field distributions, flux-linkage, back-EMF, phase inductance and thrust force are investigated. In addition, the technique of skewing stator teeth is adopted to improve the electromagnetic performance. Results from finite element method (FEM) verified the theoretical analysis results.

A novel semi energy finite strip method for post-buckling analysis of relatively thick anti-symmetric laminated plates

In the current paper, a novel semi-energy FSM is developed based on the concept of first order shear deformation theory (FSDT) in order to attempt the post-buckling solution for thin and relatively thick anti-symmetric angle-ply composite laminates subjected to uniform end-shortening. The laminated plates are assumed to be simply supported at their boundaries. The results are discussed in detail and compared with those obtained from finite element method (FEM) of analysis. The study of the results has provided confidence in the validity and capability of the developed FSM in handling the post buckling problem of anti-symmetric angle-ply laminates.

Analysis of Temperature Distribution in Power Converter for Switched Reluctance Motor Drive

This paper presents a thermal model of power converter used in switched reluctance motor (SRM) drive under constant convective heat transfer. The distribution of the system temperature rise is derived based on the average heating power measured as SRM is running steadily, and the temperature rise is independent of ambient temperature which is proved in this paper. The accuracy of the thermal model is verified by comparing experimental data with the results derived from finite-element method (FEM) simulation. Furthermore, this study achieves optimization in heat sink geometry and the placement of power components with the present model.

Large Deflection Behavior of Composite Laminated Plates under End-Shortening and Normal Pressure Loading Using a Semi-Energy Finite Strip Method

In this paper, the application of previously the semi energy finite strip method (FSM) for the non-linear post-buckling analysis of rectangular anti-symmetric laminates is extended to include the effects of normal pressure loading in addition to the progressive end-shortening. One of the main advantages of the semi-energy FSM is that it is based on the closed form solution of von Kármán’s compatibility equation. The developed finite strip method is applied to analyze the large deflection behavior of anti-symmetric angle ply composite laminated plates with simply supported boundary conditions at its loaded ends. To validate the results, they are compared with those obtained from finite element method (FEM) of analysis.

A Semi-Energy Finite Strip Method for Post-Buckling Analysis of Relatively Thick Anti-Symmetric Cross-Ply Laminates

In the current paper, a new semi-energy finite strip method is developed based on the concept of first order shear deformation theory (FSDT) in order to attempt the post-buckling solution for relatively thick composite plates subjected to uniform end-shortening. The main advantage of the semi-energy finite strip method (FSM) is that it is based on the closed form solution of von Karman’s compatibility equation in order to derive the analytical shape functions for the in-plane displacements fields. The developed finite strip method is applied to analyze the post buckling behavior of a relatively thick anti-symmetric cross-ply composite plate with clamped out-of-plane boundary conditions at its loaded ends. The results are discussed in detail and compared with those obtained from finite element method (FEM) of analysis. The study of the results has provided confidence in the validity and capability of the developed finite strip in handling post-buckling problem of relatively thick laminated plates.

Force Balance and Stability of Toroidal Helical Coil with Circular Cross Section

Stability and force equilibrium of toroidal helical coil with circular cross section were investigated. In this paper, we derived and calculated equations for equilibrium of toroidal helical coil based on an axisymmetric surface current model. The helical coil, which is modulated in such a way that a magnetic surface coincides with the coil surface, can reduce overturning force generated by electromagnetic forces. We analyzed the stability of the toroidally modulated helical coil and confirmed that this modulated configuration is held in equilibrium while it is unstable. This condition means the minimum inductance condition. Moreover, we formulated the relationships between electromagnetic forces and stresses acting on toroidal helical coil with circular cross section, and we compared the stress distributions calculated by the equations with those from finite element method (FEM) analysis.

Case study of an evaluation of a Stacker Boom Luffing Pulley by Irwin's model and under BS 7910 guidance

A case study on evaluation of a heavy–duty Stacker Boom Luffing Pulley was presented. Irwin's fracture toughness method and the British Standard were used to help in the decision–making process. Using inspection, discontinuities were found at the first look in the cylinder cross–section at the region of welding of the cylinder ends. A more detailed analysis was conducted by ultrasonic mapping, crossing the cylinder transverse thickness and longitudinal to its length. The final decision took into account accurate analysis of the stress σ1 (Principal Stress) from Finite Element Method (FEM) and σref based on British Standard, and comparing the defect real size and the critical crack size calculated by Irwin equation.

Modeling of Switching Ripple Currents (SRCs) for magnetic bearings including eddy current effects

In magnetic thrust bearings (MTBs), eddy currents induced in the solid stator and thrust disk not only result in performance degrading of the bearing, but also influence the SRC of the coil when driven by a switching power amplifier. In this paper, a fractional differential equation (FDE) model of the SRC considering the effects of eddy current is proposed and a numerical solution can be obtained from it by a predictor-corrector algorithm. Results from finite element method (FEM) and experiments show its validity. The presented model can be applied to the studies of self-sensing of non-laminated magnetic bearings.

Specimen diameter and “side artifacts” in cancellous bone evaluated using end-constrained elastic tension

In cancellous bone testing of cored samples, side artifacts are the underestimation of the true (i.e. in situ) mechanical properties due to the severing of the trabecular network during specimen preparation. Although other researchers have suggested correction factors derived from finite element method (FEM) models, it is proposed that side effects can be minimized by increasing the specimen diameter. Six different diameter specimens (3.1–10.6 mm), from two different anatomic sites (bovine femoral condyle and bovine lumbar vertebrae), were mechanically tested in elastic tension using an epoxy endcap protocol to eliminate end artifacts. Elastic modulus was found to be significantly affected by diameter in both sites. For example, the 5.1 mm samples underestimated the elastic modulus of the 10.6 mm samples by an average of roughly 20%. Yet no statistical difference was detected between the 8.3 and 10.6 mm samples in either anatomic site, suggesting that 8.3 mm diameter specimens were sufficiently large to avoid side artifacts. FEM models created from micro-CT images reveal that modulus approaches an asymptotic value with increasing diameter, and demonstrate an architecture-dependent drop in modulus at decreasing diameters. These results confirm, both experimentally and numerically, that side effects can be ignored given a suitably large specimen diameter and that this minimum diameter will be dependent on the cancellous architecture. An important implication of the latter result is that specimen diameters must be chosen appropriately when comparing test groups with different architectures (e.g. normal versus osteoporotic) to ensure that the magnitude of side artifacts does not confound the true differences between the groups.

A Numerical Elastic–Plastic Contact Model for Rough Surfaces

Elastic-plastic contacts were analyzed by means of a three-dimensional numerical model based on minimization of complementary energy, in which the effect of plastic deformation is included by superimposing the plastic residual displacement on the geometry of contacting surface. The plastic strain increments are determined through the radial return method and J 2 flow theory, which are integrated with the conjugate gradient method (CGM) algorithm and the fast Fourier transform (FFT) technique for improving numerical efficiency. The results from the present numerical model were compared to those from finite element method (FEM) for three typical contacts—i.e., those of a smooth elastic-plastic ball in contact with a rigid body of different geometry: a smooth plane, a plane superposed with a single asperity, and a sinusoidal wave on the plane—which showed persistent good agreement between our model and FEM. Then, three-dimensional elastic-plastic contacts of real engineering surfaces produced by a grinding process were analyzed. Due to roughness effect, the maximum von Mises stress and plastic region were found at the locations closer to the surface. In elastic-plastic contacts, the pressure decreases at the peaks and increases at the valleys if compared to the results from purely elastic model. Moreover, plastic flow makes the rough surface flatten or become less fluctuating.

Calculation of Characteristics of Axial-Gap Motor with Skew Based on Analysis with Three-dimensional Reluctance Network

Axial-gap motors have higher torque density than those with conventional radial gaps because they are able to reduce the thickness of the motor and increase the number of poles with a relatively smaller radius. Therefore, axial-gap motors are expected to be applied to various fields such as home electrical appliances and the in-wheel motors for electric vehicles. The establishment of an optimal method of design for axial-gap motors is required, but it generally takes a long time to calculate the characteristics of these motors since it is necessary to analyze the three-dimensional electromagnetic field. To overcome this problem, this paper presents a method of calculating the characteristics of axial-gap motors with skew based on reluctance network analysis (RNA). The validity of the proposed method is tested and proved by comparing the measurements with the results from finite element method (FEM) analysis.