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In the manipulator transmission system, there are many nonlinear inducements, such as flexibility and friction torque. It is easy to lead to fluctuations of the output rotation speed of the system, and even cause serious resonance. Therefore, PI control strategy based on fuzzy theory is proposed to solve this trouble. Firstly, the dynamic equations of the transmission system of the double flexible manipulator was established. Then, the effects of friction torque and mode order on the output characteristics of the system are analyzed. Based on the fuzzy rules, the controller parameters change constantly to reduce the oscillation of the servo system output rotation speed. Finally, numerical simulation analysis and control experiment verify the effectiveness of the control strategy described in this paper. The results are that the proposed control method can decrease the average value of the load rotation angle tracking error by 13.8 %. [ABSTRACT FROM AUTHOR]

In order to solve the problem of fluid accumulation in horizontal gas wells and improve the fluid-carrying capacity and recovery efficiency of gas wells, this paper simulates three internal vortex tools using the commercial software ANSYS FLUENT, and analyzes the drainage recovery efficiency of the three vortex structures and the vortex characteristics of the downstream section vortex field. The results show that the axial velocity of the three-bladed spiral tube in the cyclonic field rotates quasi-periodically with the flow field compared with the internal vortex tube and the rifled tube, and the axial velocity, tangential velocity and vortex intensity of the three-bladed vortex tube guided flow field are the highest; meanwhile, the axial velocity, tangential velocity and vortex intensity of the three-bladed spiral tube guided flow field decay the fastest, and the line rifled tube decays the slowest. The liquid phase in the cyclonic field exhibits obvious spiral motion and maintains a long-distance cyclonic flow state under the action of cyclonic flow. The enhancement of the vortex intensity easily leads to the increase of liquid volume fraction and liquid film thickness at the tube wall. Through the analysis of the energy efficiency of the three structures, it is found that the three-leaf spiral tube is more suitable for the initial phase of drainage transport, while the internal vortex tube is more favorable for the stable phase of transport. The study of the gas-liquid swirl flow of the three swirl tools demonstrated the feasibility of the internal swirl tool for application in horizontal wells. It can provide theoretical guidance and practical basis for effective liquid filling with internal vortex tools in the future. [ABSTRACT FROM AUTHOR]

In this paper, the noise radiation characteristics of hermetic reciprocating compressor (HRC) are studied. Compressor noise is difficult to investigate because various excitation sources are simultaneously applied. Thus, numerical analysis is performed to identify excitation sources generated by the compression process. Finite element models of HRC are constructed by considering the acoustic-structure interaction. Acoustic propagation can be identified visually by applying each excitation source to the configured finite element models. The analysis and experimental results are compared to confirm the computational simulation methodology. From the analysis results, the HRC noise generation mechanism is verified. In addition, it is possible to investigate the acoustic characteristics of each noise source, which is difficult to identify using experimental methods. [ABSTRACT FROM AUTHOR]

In this paper, the parameter optimization and error analysis of the rack and pinion steering mechanism are carried out on the basis of considering the influence of kingpin parameters. The steering characteristic equation describing the motion of the steering mechanism is calculated by analyzing the spatial geometrical relationship between the wheel and kingpin and unifying the projection relation between the kingpin and the equivalent steering trapezoid. The ideal Ackermann equation is modified by the Ackermann rate and the kingpin parameters. The modified Ackermann equation is used as the objective function. The segmented fitness function and the evaluation function with weighted factors are designed. A genetic algorithm containing the three functions is used to optimize the parameters of the steering characteristic equation. The error analysis of the numerical example shows that the accuracy of steering trapezoid structure parameters, steering characteristic equation, and Ackermann equation is improved compared with that before optimization. [ABSTRACT FROM AUTHOR]

This paper adopts the standard k-ε model and mixture model of the FLUENT code to numerically analyze the components characteristics of the gravity separator. It intends to involve several combinations of four types of rectifiers and two types of coalescers of corrugated plates to optimize the structure of the components. Numerical simulation analysis is carried out on the synergistic effect of the reflective inlet component, the rectifier of square grids, and the coalescer of perforated corrugated plates under variable working conditions. The results illustrate that when the distance between the rectifier and the separator's head is L1 = 3/4 D, the width L2 = 1/4 D, and the plate spacing L3 = 1/10 D, the separation effect gets improved. Additionally, the perforated corrugated plates prove better effects of rectification and coalescence. And when the distance between the coalescer and the head is L4 = 25/183 L and the elevation angle α = 2.5°, the separation performance will be further improved. What's more, the influence of the Reynolds number (Rei, from 5640 through 8297 in the inlet component) and the volume fraction of the dispersed phase (from 5 % through 30 %) on the separation effects of various combination conditions of the internal components has also been investigated. As the former increases, the combined of reflective inlet component, rectifier and coalescer will perform the best separation effects. As the latter increases, the separation efficiency of low-oil ratio of oil-water mixture of the jointly structured separator will increase the most. [ABSTRACT FROM AUTHOR]

This paper proposes a nautilus-inspired bionic volute for a multiblade centrifugal fan. Analysis of the noises generated by the fan is presented. This is made possible by a model that integrates a steady-state equation using the Reynolds-averaged Navier-Stokes (RANS) model and an unsteady-state estimation using the large-eddy simulation (LES) model and the Ffowcs Williams-Hawkings aerodynamic noise model, and by numerical solution to the model. Our computational model is validated on the sound pressure level with the help of the measurements on a physical system. The validation suggests that the proposed bionic volute significantly increases the aerodynamic performance particularly in terms of transformation between the pressure and flow rate under the rated power. The noise associated to the bionic volute is found to be predominantly tonal noise, and this is the primary source of the noise of the fan. Another finding is that the large expansion profile of the proposed volute contributes to the attenuation of the tonal noise associated to the periodic jet impingement at the impeller outlet. [ABSTRACT FROM AUTHOR]

This paper is concerned with the numerical buckling analysis of sandwich plates with functionally graded CNT-reinforced composite (FG-CNTRC) layers. The core is isotropic metallic material while two face-sheets are made of polymer reinforced with CNTs. For an accurate and effective buckling analysis of advanced sandwich structures, a new numerical method is developed by making use of hierarchical models and 2-D natural element method (NEM). The hierarchical models are based on 3-D elasticity theory, in which the displacement field is interpolated as a product of 2-D in-plane unknown functions and 1-D assumed thickness monomials. The model level is adjusted by controlling the maximum orders of thickness monomials, and the 2-D in-plane functions are approximated by NEM. The numerical method is compared with the advanced plate theories, from which the numerical accuracy has been justified. Using the proposed natural element hierarchical models (NEHM), the buckling load parameters of FG-CNTRC sandwich plates are parametrically investigated. Through the parametric numerical experiments, the effects of major design parameters were profoundly investigated, and which provide the useful guideline for the buckling-resisting design of FG-CNTRC sandwich plates. [ABSTRACT FROM AUTHOR]

This paper presents the theoretical derivation and the implementation of a foot-ground contact dynamics system for legged robot physical simulation. The physical simulation imposes high requirements on the contact dynamics for fidelity and accuracy. Thus, we explored the contact mechanism and developed a contact model. We theoretically analyzed the ground reaction force (GRF) by the kinetic equation with constraints first. Considering the limitation of the numerical analysis method, we propose a new contact model based on Hertz theory and clarify the fundamental differences between the model and reality. Due to these differences, we optimized some key parameters by the genetic algorithm. Then, we expanded the contact model to nonhorizontal and nonstationary surface contact. At last, we simulated several cases to present the usefulness of this contact model and analyzed the dynamic contact behavior. The contact force based on this model highly accords with the results of theoretical analysis and includes all phenomena that may occur during a locomotion cycle. [ABSTRACT FROM AUTHOR]

This paper studies automatic balancing of a flexible supported rotor with two disks by two ball balancers. Firstly, reduced dynamic descriptions of different components in the rotor are derived using a special method according to Lagrangian equation, based on which a general vibration model of the rotor system is then constructed. Secondly, equations governing frequency responses of the rotor are derived and working principles of the balls in the rotor are illustrated based on basic dynamic phenomena. Thirdly, an autonomous model of the rotor system is built with equations governing movement of the balls derived. Three equilibrium solutions are discovered whose dynamic characteristics are then studied using numerical bifurcation analysis method. Finally, locations of the balls at the steady state are observed using a high speed camera, and the capability of the two balancers for automatic balancing under different conditions is validated. [ABSTRACT FROM AUTHOR]

Penetration analyses are needed to improve the survivability of combat vehicles. The penetration analysis can be achieved by numerical analysis or experiments. Because excessive time is required to obtain results in both cases, it is needed to derive a penetration equation using numerical analysis. But, the constants for the penetration equation are hardly found in the literature. Therefore, in this paper, the penetration equation is derived using the following steps: (1) Setting up a numerical analysis model and proving it with experimental data, and (2) determining the constants of the penetration equations for various target materials and impact conditions using the numerical analysis model. This procedure can be used to predict penetration when there are no sufficient penetration experimental data for a given material and impact conditions. In this paper, ANSYS Explicit Dynamics was used for creating the simulated penetration data to estimate the parameters of the penetration equation. The penetration numerical analysis was performed for a high-velocity collision between a 7.62 mm AP (armor piercing) bullet and the targets, which include RHA (rolled homogeneous armor) steel and 7075 aluminum. As a result, the error rate between the results of the numerical analysis and penetration experiments is approximately 5 %, which verifies the accuracy of the numerical analysis. The constants of the penetration equation for RHA steel and 7075 aluminum were determined using the numerical analysis model. In vulnerability analyses, penetration equation with the constant that was identified using our methodology can replace the numerical penetration analysis, which requires excessive calculation time. [ABSTRACT FROM AUTHOR]

Dynamics of a long beam on the elastic foundation subjected to moving loads is studied in the present paper. The sliding window technique is used to dynamically truncate the long beam and a reduced time-varying beam system is obtained. The Hamilton’s principle is employed to establish the equations of motion of the reduced system. The variable separation method is adopted to solve dynamical responses of the reduced system. Examples of a long simply supported Timoshenko beam on the nonlinear foundation subjected to a single moving load and multiple loads are included. Numerical results of the reduced model compared with the ones obtained from the moving element model adapted in literature are carried out to show the validity and the good efficiency of the method proposed in the present paper. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic characteristics of the in-arm type hydropneumatic suspension unit (ISU) of armed tracked vehicle are theoretically analyzed and numerically investigated. Accurate spring and damping models are introduced and combined to secure the analysis reliability. One is the Benedict-Webb-Rubin equation of state which is adopted to model the spring behavior of real nitrogen gas in ISU system. The other describes the behavior of a damper during four distinct ISU motions; jounce-loading, jounce-unloading, reboundloading and rebound-unloading. For the comparison purpose, the numerical results of the dynamic behavior of ISU system using a real gas model and two ideal gas models are presented and compared. [ABSTRACT FROM AUTHOR]

The pump is a machine that receives power through a rotating shaft and converts the mechanical energy into pressure and kinetic energy of fluid. Therefore, it is widely used in various industrial fields, and many studies have been conducted to improve the performance of pumps. In this paper, the effect of the gap between the impeller and the volute tongue on the performance and pressure fluctuation of the double suction pump was investigated. Numerical analysis was conducted using the commercial code ANSYS CFX ver. 18.1. Three different values of gap between the impeller and the volute tongue, 0.067%, 0.145% and 0.224% of the impeller diameter were considered. [ABSTRACT FROM AUTHOR]

A numerical simulation analysis of mechanical chip morphology and residual stress for Ti6Al4V alloy was conducted under different cutting speed and feed rate. Johnson-Cook constitutive model and shear failure model were selected in the simulation procedure. The correlations between the mechanical chip morphology and surface residual stress were detailed. The results show that the chip morphology characterized with the degree of serration Gs and the serrated frequency f has a direct impact on residual stress distribution. With the increase of the degree of serration Gs, the maximum residual tensile stress decreases, while with the increase of the serrated frequency f, the maximum residual compressive stress increases on the surface. The research of the present paper provides a new way to understand and evaluate residual stress distribution for titanium alloy mechanical process. [ABSTRACT FROM AUTHOR]

This paper addresses the simultaneously existence problem of both hydrodynamic and hydrostatic pressure components in the oil lubrication film in case of internal gear motor and pump. Reynolds equation with concerning hybrid parameter is developed to calculate the hybrid pressure profile. Finite difference method with appropriate boundary condition is then used to solve the Reynolds equation to obtain 2D hybrid pressure distribution. The percentage of hydrodynamic and hydrostatic components corresponding to the change of the working pressure and rotating speed are analyzed. Experimental setup is then designed and built to verify the individual effect of hydrodynamic and hydrostatic action on the performance of the internal gear motor and pump under different working conditions. The numerical and experimental results pointed out that the eccentricity ratio optimal for good hybrid force is from 0.46 to 0.75. The hydrodynamic action increases with the increase of the rotating speed whilst the hydrostatic action increases with the increase of operating pressure. As the rotating speed at maximum value and working pressure at minimum value, the proportion percentage of hydrodynamic component gets the largest value. Whilst the hydrostatic component has the largest proportion percentage at minimum rotating speed and maximum working pressure. [ABSTRACT FROM AUTHOR]

At the conceptual design stage, utilizing the detailed model to determine the rollover crashworthiness of bus structure would need long design cycle. Currently, rectangular thin-walled beams (RTWBs) are extensively used to create the real bus because of the excellent manufacturability. Remarkably, dual rectangular thin-walled beams (DRTWBs) can generate higher bending resistance. Therefore, this paper presents a rollover crashworthiness analysis and optimization method of bus frame using the RTWBs and DRTWBs. The bus frame with tire, suspension and platform structures is created in the CarFrame software. Analysis numerical example verifies that the frame model, which reduces the modeling and computational costs, is in excellent agreements with the detailed model, and optimization numerical example verifies that the frame model can obtain high rollover crashworthiness and lightweight bus structure. Therefore, the frame model can effectively replace the detailed model for the rollover crashworthiness analysis and optimization. [ABSTRACT FROM AUTHOR]

In this study, a numerical analysis was carried out to investigate the effects of blade thickness on hydraulic performance and cavitation phenomenon of a mixed-flow pump. The three-dimensional Reynolds-averaged Navier-Stokes equation, which was discretized using the finite volume method, was applied to solve a steady-state analysis. For cavitation analysis, the Rayleigh-Plesset equation was applied to calculate the transition between liquid and vapor phases. The hydraulic performance of a mixed-flow pump changes depending on the blade thickness and was systematically analyzed under various operating conditions. Blade thickness was defined as a blockage, and the cavitation coefficient was considered to express the suction performance. Cavitation characteristics were analyzed for each blockage in relation to the vapor volume fraction. The amount and pattern of vapor were different for each blade thickness case. Furthermore, in this paper, detailed flow analyses that consider the angle of incidence are presented and discussed. To verify the numerical analysis results, an experimental test was conducted at specific points. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid algorithm for topology optimization of lightweight cellular materials and structures simultaneously by combining solid isotropic material with penalization (SIMP) and bi-directional evolutionary structural optimization (BESO). Microstructure of the lightweight cellular material is assumed unique in the structure to make the proposed method feasible. A new sensitivity analysis formula with respect to the discrete variable is derived by a principal submatrix stiffness matrix, by which the material can be effectively removed from or added to cellular. Moreover, the validity of the proposed method is then demonstrated through two numerical examples (a simple supported beam and a cantilever beam), which can be easily applied in a variety of practical situations. [ABSTRACT FROM AUTHOR]

As research works of the transient statistical energy analysis (TSEA) and transient local energy approach (TLEA) mostly focus on simple structures, TSEA and TLEA are adopted to quantify the transient response of a complex vibro-acoustic system at the mid-high frequency range in this paper. Numerical examples of a coupled oscillator system, an L-shaped plate, and a launch vehicle fairing model are conducted to demonstrate the effectiveness and accuracy of TSEA and TLEA. The computational precision of TSEA and TLEA is verified by the analytical solution and finite element method. Furtherly, the transient energy responses of subsystems with different coupling ratios between subsystems are investigated. Results show that TLEA has a better performance than TSEA. With the increasing coupling ratio between subsystems, the rise time and peak energy of transient energy response of subsystems decrease gradually. Both ratios of rise time and peak energy predicted by TLEA to these of the TSEA increase as the rising of the coupling ratio. [ABSTRACT FROM AUTHOR]

This paper presents an in-depth investigation into the transient impulsive pressure of an arc-curved water jet impacting a solid surface. The emphasis of this study is on the variations of the surface shape, which are classified into four types: The flat surface, the concave surface, the convex surface and the inclined surface. The numerical tool of arbitrary Lagrangian-Eulerian formulations is used to model the arc-curved jet impacting these different solid surface types. Elaborately designed experiments were conducted to test the impulsive pressure profile; the experimental results are found to be in approximate agreement with the numerical results. The impulsive pressure profiles of water jet impacting the flat and inclined solid surface are observed to exhibit two quintessential stages, in line with the traditional pressure profile; however, a double/multiple-peaked pressure structure is observed for the cases of the water jet impacting the concave and convex solid surfaces. Additionally, the value of the peak pressure is found to be a quadratic representation with the jet velocity, and the duration of the peak pressure is found to be an exponential representation with the jet velocity. The compression degrees of the liquid jet impacting the different surfaces are validated to be the root cause for the discrepancy of the impulsive pressure. [ABSTRACT FROM AUTHOR]

In this paper two different steels, low carbon steel and 304 stainless steel are lap joined to tubular 6063 aluminium by using high velocity electromagnetic force and the joint behaviour is evaluated for mechanical strength, microstructure and leakage proof. Analytical model is used to set the input energy needed to accomplish the welding. Numerical model is used for the analysis of the impact velocity along the length of electromagnetic coil. Aluminum joint with low carbon steel rod has a characteristic waviness at the joint interface whereas aluminum with 304 stainless steel has flat interface under identical electromagnetic force. Mechanical pull test confirmed that joint strength is acceptable for both the steels as failure took place in the base aluminium metal. Helium leak proof tests are found to be satisfactory in both the cases. Fair agreement is observed between experimental results, analytical and numerical analyses. [ABSTRACT FROM AUTHOR]

This paper presents the influence of circular front and back shroud fences on the performance of a backward swept centrifugal fan impeller handling air. The analysis is carried out to determine the main characteristics of the fan i.e. the variation of head and theoretical efficiency for various flow coefficients. The circular fence size is optimized parametrically by varying its diameter and the location on the shroud surface. The effect of the shroud fences on the flow field was analyzed for the fences placed on both front and back shroud surfaces of the impeller separately. The numerical simulation is carried out using an appropriate k - ε turbulence model. The relative flow inside the impeller passages is modeled using the standard sliding mesh technique. The numerical results for the base model (i.e. without the fence) are validated against experimental results obtained from the test rig built specially for validation study and are found to have good agreement. It is found from the analysis that the average percentage increase in head coefficient is significant and is about 2 % higher as compared to the base model for the optimized geometrical configuration of diameter ratio and radial fence location as determined in the study. The optimized geometrical configuration also yields a higher theoretical efficiency of about 2.3 % corroborating the improvement in head coefficient with respect to the base model. Hence the efficacy of optimally placed circular fence on the performance of centrifugal fan is established in this numerical study. [ABSTRACT FROM AUTHOR]

In the present work, numerical investigation of heat and mass transfer analogy on a simulated turbine blade endwall is conducted. For similar geometrical configurations, the experimental boundary conditions of heat and mass transfer are equivalent from the physical point of view, i.e. constant wall temperature in heat transfer and constant wall concentration in mass transfer, but they are numerically modeled in different ways in this study. The three-dimensional Reynolds averaged Navier-Stokes equations (RANS) are solved using a commercial CFD-tool within the blade passage in an attempt to predict the flow physics. The main purpose of this paper is the validation of heat and mass transfer numerical simulation with respect to experimental data and the analysis of the analogy factor between heat and mass transfer using only computed results. [ABSTRACT FROM AUTHOR]

In this paper, effects of bi-stable stiffness and hardening stiffness on the performance of a Vortex induced vibration (VIV) energy converter are theoretically and experimentally studied through a wake oscillator model and a computer-based force-feedback testing platform. Based on the simulation and experimental results, it is found that the bi-stable stiffness is potential to allow the system to operate at low velocity water flows, while the hardening stiffness will extend the operating range at high velocity flows. Subsequently, in order to take the advantages of both types of stiffness, a combined nonlinear stiffness is proposed and verified experimentally to demonstrate its capability in improving the overall operating range of the VIV energy converter. [ABSTRACT FROM AUTHOR]

Resistance spot welding (RSW) is a process in which contacting metal surfaces are joined by the pressure and heat obtained from resistance to electric current flow. It is widely accepted in the industry due to its advantages in high speed and suitability for automation. The RSW process is extremely important to quality in automotive industry because approximately 6000 spot welds were used in automotive body. In addition, the RSW process is a complicated process that includes electrical, thermal and mechanical phenomena. For this reason, it is necessary that researchers should perform electric field, heat transfer and thermo-elastic-plastic analysis, and consider phase change, contact conditions and temperature dependence of material properties in order to simulate a realistic RSW process. There were lots of previous studies for RSW simulation by using Finite element method (FEM), but most of studies have performed qualitative analysis which predicts the shape of weld nugget fatigue life and residual stress. Therefore, this study defines the contents which mentioned above based on the theoretical background and reproduces a 3D DC RSW process through using ABAQUS, commercial FEM program. It also obtains the reliability in terms of simulation results through quantitative approach by comparing between the nugget shape and the actual experimental results. The error percentage of nugget width between simulation and experiment shows outstanding results that from 0.44 % to 3.80 %. Based on the simulation results through these theoretical backgrounds, it is possible to effectively trace the weld nugget shape of all steels, provided the temperature dependent material properties are available. An illustration of such a simulation to predict the nugget shape and size of resistance spot welded SPRC 340 steel is presented in the paper. [ABSTRACT FROM AUTHOR]

This paper proposes an approximate model to predict the spread and surface profile of cross sections of material in a Kocks mill that a string of mills driven by three-roll is lined-up in tandem. The spread at the exit of roll gap is expressed as a function of the effective roll diameter, area fraction of the cross section of incoming material intersecting the roll groove shape, and contact length at the interface of the roll and material. The surface profile of a material is assumed to be a second-order polynomial function; additionally, the shape of the function was determined by the shape of the cross section of the incoming material, roll gap geometry, maximum width, and the reduction ratio. We then evaluated the possibility of 3D FE analysis, which is generally used for predicting the surface profile of materials in a three-roll rolling system, being superseded by the model proposed in this study. The generality and robustness of the model proposed in this study was verified by comparing the approximate model-predictions with FE analysis. Difference in terms of the maximum width, B1, was in the range of 0.05~0.76 % and those in terms of the surface profile radius, R, ranged from 0.54 to 1.23 %. [ABSTRACT FROM AUTHOR]

In this paper a general methodology for the modeling of material composite multilayered shell structures is proposed using a Hex-shell finite element modeling. The first part of the paper is devoted to the general FE formulation of the present composite 8-node Hex-shell element called SCH8, based only on displacement degrees of freedom. A particular attention is given to alleviate shear, trapezoidal and thickness locking, without resorting to the classical plane-stress assumption. The anisotropic material behavior of layered shells is modeled using a fully three dimensional elastic orthotropic material law in each layer, including the thickness stress component. Applications to laminate thick shell structures are studied to validate the methodology, and good results have been obtained in comparison with ABAQUS© commercial code. [ABSTRACT FROM AUTHOR]

Vibrational behavior of harmonically excited MDOF oscillators subjected to multiple contact constraints is investigated in this paper using the combination of the Newmark integration scheme and the Linear complementarity problem (LCP) formulation. An oscillator with gap-activated non-smooth spring constraints exhibits various complex behavior such as sub-harmonic resonances, bifurcations and chaos, which are effectively predicted using the proposed method. Numerical results were obtained and presented for SDOF and 5-DOF systems with frequency and stiffness parameters varying in wide ranges to validate the Newmark-LCP method and to demonstrate its effectiveness in dealing with MDOF systems with multiple contact constraints. [ABSTRACT FROM AUTHOR]

This paper studies the buckling behavior of simply-simply supported Single-walled Carbon nanotubes (SWCNTs) with and without defects. The buckling of carbon nanotubes without defects was investigated using the Finite element method (FEM) and analytical treatment and that of carbon nanotubes with defects was studied only by FEM. The carbon nanotubes were modeled as beams and shells. Computations showed that beam elements in the given form provided varying results as shells in their numerical or analytical manner for a small aspect ratio. The defects resulted from the removal of randomly determined carbon atoms and beam elements connected to the nodes. The increasing number of defects decreased the critical buckling force of SWCNTs. The decrease in the critical buckling force was almost the same for SWCNTs with the same diameter but with different chirality. [ABSTRACT FROM AUTHOR]

The roller profile plays a key role in the overall performance of roller bearings. In traditional profile design for roller bearings, the roller profile was often analyzed in terms of the bearing performance, particularly the fatigue life. However, the bearing dynamic stiffness and fatigue life were seldom considered simultaneously in the design of Tapered roller bearings (TRBs). Among the available roller profiles, the partially crowned roller profile has been acknowledged as one of the best from the viewpoint of the bearing fatigue life and stiffness characteristics. This paper presented a design optimization for the partially crowned roller profile to improve the performance of TRBs. Two profile parameters of rollers employed for TRBs including the central flat length and crown radius were investigated. The optimal design parameters for the roller profile were obtained in consideration of both bearing fatigue life and stiffness. The proposed design approach was useful and applicable for further geometrical optimization, manufacturing, and engineering application of rolling bearings. [ABSTRACT FROM AUTHOR]

The dual-mode scramjet is a prime candidate for air-breathing propulsion engines given its broad speed range and high efficiency. The detailed structure of the pseudo-shock wave in the isolator is worth investigating. Therefore, the present study investigates the effect of isolator length on the pseudo-shock wave. We replicate the experimental work of the reference paper with a two-dimensional numerical model. Pressure distribution on the body surface is applied in the numerical validation. The numerical result is in good agreement with that of the existing experimental work. We simulate the thermal choking condition with a throttling device. As the throat area of throttling device decreases, the back pressure continues increasing and the pseudo-shock wave moves upstream. Avoiding unstart phenomenon is a key objective in the operation of dual-mode scramjet. Therefore, we investigate the critical condition shortly before unstart phenomenon occurs. The pseudo-shock wave structure is described by pressure distribution. Our main objective is to explore the effect of isolator length on the dual-mode scramjet. The optimal isolator length depends on the maximum back pressure and total pressure loss in the critical condition shortly before the unstart phenomenon occurs. The maximum back pressure in the critical condition is higher when the isolator length ranges from 8.7 to 20.7. The total pressure loss in the critical condition decreases at the beginning and then increases when the isolator length ranges from 8.7 to 20.7. [ABSTRACT FROM AUTHOR]

A two-dimensional numerical study is carried out to analyze the drag reduction and vortex shedding suppression behind a square cylinder in presence of splitter plate arranged in upstream, downstream and both upstream and downstream location at low Reynolds number (Re = 160). Computations are performed using a Single relaxation time lattice Boltzmann method (SRT-LBM). Firstly, the code is validated for flow past a single square cylinder. The obtained results are compared to those available in literature and found to be in good agreement. Numerical simulations are performed in the ranges of 1 ≤ L ≤ 4 and 0 ≤ g ≤ 7, where L and g are the length of splitter plate and gap spacing between the splitter plate and main square cylinder, respectively. The effect of these parameters on the vortex shedding frequency, time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualization and force exerted on the cylinder are quantified together with the observed flow patterns around the main cylinder and within the gap spacings. The observed results are also compared with a single square cylinder without splitter plate. We found that at some combinations of L and g, the mean drag coefficient and Strouhal number reach either its maximum or minimum value. It is found that the drag is reduced up to 62.2 %, 13.3 % and 70.2 % for upstream, downstream and dual splitter plates, respectively as compared to a single square cylinder (without splitter plate). In addition, in this paper we also discussed the applications of SRT-LBM for suppression of vortex shedding and reduction of the drag coefficients. [ABSTRACT FROM AUTHOR]

Although previously developed Dielectrophoresis activated cell sorters (DACSes) have achieved high separation efficiency, limitations still exist with respect to the low throughput. In this paper, therefore, a numerical analysis is presented for a novel DACS to achieve not only high efficiency but also high throughput. Additionally, experimental validation is performed based on the results of a numerical simulation. First, streamlines in the channel are investigated according to various flow rate ratios in each outlet. After cells are deflected by a sufficient amount of dielectrophoretic force, they arrive at the tip of the last electrode pair. Their movement is then determined by hydrodynamic force. Therefore, it is important to confirm whether or not the streamline at the tip of the last electrode pair connects to the target area. Based on the streamline analysis results, the particle trajectory under various AC electric fields is investigated using a three-dimensional analysis. Accordingly, an input voltage condition (7 Vp-p at 10 kHz) is selected to confirm the influence of dielectrophoretic force. Conclusively, optimal flow rates under the determined input voltage condition are selected as 10 μl/min and 20 μl/min in outlet A (target area) and outlet B (non-target area), respectively. In order to validate the feasibility of the selected flow rates, a separation test is performed employing a K562 cell-bone marrow cancer cell-as a target cell. In the experiment, the proposed DACS achieves a high throughput of 45000 cells/min as well as a separation efficiency of 96.5% and recovery rate of 47.25%. [ABSTRACT FROM AUTHOR]

This paper studies the thermal behavior of a wireless powered micropump operated using thermo-pneumatic actuation. Numerical analysis was performed to investigate the temporal conduction of the planar inductor-capacitor ( LC) wireless heater and the heating chamber. The result shows that the temperature at the heating chamber reaches steady state temperature of 46.7°C within 40 seconds. The finding was further verified with experimental works through the fabrication of the planar LC heater (RF sensitive actuator) and micropump device using MEMS fabrication technique. The fabricated device delivers a minimum volume of 0.096 μL at the temperature of 29°C after being thermally activated for 10 s. The volume dispensed from the micropump device can precisely controlled by an increase of the electrical heating power within the cut-off input power of 0.22 W. Beyond the power, the heat transfer to the heating chamber exhibits non-linear behavior. In addition, wireless operation of the fabricated device shows successful release of color dye when the micropump is immersed in DI-water containing dish and excited by tuning the RF power. [ABSTRACT FROM AUTHOR]

Double-row Tapered roller bearings (TRBs) are mechanical devices that are designed to support high axial, radial and torque loads. This combination of loads produces high contact stresses on the bearing raceways that are difficult to predict and validate experimentally, and can cause defects like pitting and fatigue spalling. In response, theoretical models have been proposed by many researchers to calculate the approximate distribution of contact stresses over the bearing raceways. More recently, numerical methods that are based on the Finite element method (FEM) have been used to obtain the contact stresses, although this method requires that the mesh size first be adjusted. This paper shows a process for adjusting a double-row TRB Finite element (FE) model. It is based on generating successive nonlinear FE submodels to calculate the distribution of contact stresses. A theoretical model and contact pressure sensors were used to adjust and validate the Finite element (FE) model. [ABSTRACT FROM AUTHOR]

Usage of linear compressors is on the rise due to their high efficiency. In this paper, leakage of a linear compressor has been studied through numerical analysis and experiments. First, nitrogen leakage for a stagnant piston with fixed cylinder pressure as well as for a moving piston with fixed cylinder pressure was analyzed to verify the validity of the two-phase flow analysis model. Next, refrigerant leakage of a linear compressor in operation was finally predicted through 3-dimensional unsteady, two phase flow CFD (Computational fluid dynamics). According to the research results, the numerical analyses for the fixed cylinder pressure models were in good agreement with the experimental results. The refrigerant leakage of the linear compressor in operation mainly occurred through the oil exit and the leakage became negligible after about 0.4s following operation where the leakage became lower than 2.0x10 kg/s. [ABSTRACT FROM AUTHOR]

Contamination in a cleanroom may appear even more complicated by the effect of complicated manufacturing processes and indoor equipment. For this reason, detailed information about the concentration of pollutant particles in the cleanroom is needed to control the level of contamination financially and efficiently without any problem in manufacturing process. Allocation method has been developed as one of main ideas to fulfill a function of controlling contamination under the situation. By using this method, weighting factor can be predicted based on cleanliness on sampling spots and the values based on numerical analysis. In this point, the weighting factor indicates how each of contaminant sources influences the concentration of pollutant in the cleanroom. In this paper, when applied allocation method, we propose zoning method to accelerate the calculation time. And it was applied to cleanliness the actual improvement of the turbulent type clean room. As a result, we could estimate quantitatively the amount of contamination generated from the pollution sources. And was proved by experiments that it is possible to improve the level of cleanliness of the cleanrooms by using these results. [ABSTRACT FROM AUTHOR]

The paper deals with multiphysical modeling of phenomena connected with micro-cracks present in pipelines for transmitting chemical substances in temperature below minus 100°C. In the numerical model, the effect of the pressure and negative temperature of the gas transported in the pipe was taken into consideration. The simulation tests were carried out in the steady and unsteady state to determine the impact of the crack geometrical factors, i.e. type, shape and orientation on the results obtained, with the model parameter values, such as the temperature and pressure of the gas transported inside the pipe remained constant. Based on the achieved analyses results it was stated that the values of all parameters considered depend on all regarded factors: the shape, orientation and location of the crack in the pipe structure. [ABSTRACT FROM AUTHOR]

This paper describes a method for the prediction of behavior of a floating-type structure using an experiment and numerical analysis according to the various marine conditions. The sloshing simulation is considered to verify the behavior of fluid. The fluid is expressed by a set of particles, the motion of fluid is calculated by using SPH (Smoothed particle hydrodynamics). Numerical results are compared with experiments. A wave tank and linear shaker are used in order to express the sloshing environment. Monaghan boundary force is employed to calculate the interacting force between fluid and boundary. Four wave periods are used to consider the various marine conditions in the fluid-structure interacting simulation. The longitudinal motion of a floating body is compared to each other. As a result, the solution of numerical analysis shows the similar tendency compared to the experiment results. [ABSTRACT FROM AUTHOR]

The purpose of this study is to propose a coupled train model with a multibody system considering three-dimensional wheel/rail contact geometry and to assess the safety of high-speed railway vehicles. Railway vehicles are becoming lighter and are running at increased speeds, so it is necessary to discuss their safety when subjected to a crosswind. In this paper, we use the proposed model in a situation presupposing strong crosswinds in order to analyze the behavior of coupled trains under this condition. We discuss the modeling and formulation of a coupled train as well as wheel unloading ratios. Our results show that vibration of a car body is largest in the wheel unloading ratios of the car body when the frequency of the car body is close to the second-mode natural frequency of the vehicle system. [ABSTRACT FROM AUTHOR]

Roll-to-roll (R2R) systems have been mainly designed and developed based on expert experience. There are some important issues in the numerical analysis for R2R systems with the winding web that are included in most general R2R systems. We propose numerical modeling improvements for R2R system analysis to make the numerical methods more efficient. The first is the approximated winding length estimation (AWLE) algorithm, which can calculate the length of the flexible web that is wound around a rotating roller. The winder is approximated with line and arc segments in this algorithm. The second is the contact algorithm between the web and rollers. This contact algorithm has to be stable and fast. This paper proposes an efficient R2R system analysis method. [ABSTRACT FROM AUTHOR]

This paper presents a numerical analysis of interaction between non-gray radiation and laminar forced convection flow in a duct with an expansion. Distributions of absorption coefficients across the spectrum (50 cm < η < 20000 cm) are obtained from the HITRAN2008 database. The full spectrum k-distribution method (FSK) is used to deal with the non-gray part of the problem, while the gray radiation calculations are carried out using the Planck mean absorption coefficient. In addition, the results of non-gray medium are compared with the gray results in order to judge if the differences between these two approaches are significant enough to justify the usage of non-gray models. Results show that for air mixtures with different mole fractions of CO and HO, use of gray model for the radiative properties may leads to considerable errors and should be eschewed. [ABSTRACT FROM AUTHOR]

Manipulators used for the transportation of large panel-shape payloads often adopt long and slender links (or forks) with translational joins to carry the payloads. As the size of the payload increases, the length of the links also increases to hold the payload securely. The increased length of the link inevitably amplifies the effect of the flexure in the link. Intuitively, the translational motion of the link in its longitudinal direction should have no effect on the lateral vibration of the link because of the orthogonality between the direction of the translational motion and the lateral vibration. If, however, the link was flexible and translated horizontally (perpendicular to the gravitational field) the asymmetric deflection of the link caused by gravity would break the orthogonality between the two directions, and the longitudinal motion of the link would excite lateral motion in the link. In this paper, the lateral oscillatory motion of the flexible link in a large-scale solar cell panel handling robot is investigated where the links carry the panel in its longitudinal direction. The Newtonian approach in conjunction with the assumed modes method is used for derivation of the equation of motion for the flexible forks where non-zero control force is applied at the base of the link. The analysis illustrates the effect of longitudinal motion on the lateral vibration and dynamic stiffening effect (variation of the natural frequency) of the link due to the translational velocity. Lateral vibration behavior is simulated using the derived equations of the motion. A robust vibration control scheme, the input shaping filter technique, is implemented on the model and the effectiveness of the scheme is verified numerically. [ABSTRACT FROM AUTHOR]

In this paper, we describe a numerical study about the performance improvement of a mixed-flow pump by optimizing the design of the impeller and diffuser using a commercial computational fluid dynamics (CFD) code and design-of-experiments (DOE). The design variables of impeller and diffuser in the vane plane development were defined with a fixed meridional plane. The design variables were defined by the vane plane development, which indicates the blade-angle distributions and length of the impeller and diffuser. The vane plane development was controlled using the blade-angle in a fixed meridional plane. The blade shape of the impeller and diffuser were designed using a traditional method in which the inlet and exit angles are connected smoothly. First, the impeller optimum design was performed with impeller design variables. The diffuser optimum design was performed with diffuser design variables while the optimally designed impeller shape was fixed. The importance of the impeller and diffuser design variables was analyzed using 2 factorial designs, and the design optimization of the impeller and diffuser design variables was determined using the response surface method (RSM). The objective functions were defined as the total head (Ht) and the total efficiency (?t) at the design flow rate. The optimally designed model was verified using numerical analysis, and the numerical analysis results for both the optimum model and the reference model were compared to determine the reasons for the improved pump performance. A pump performance test was carried out for the optimum model, and its reliability was proved by a comparative analysis of the results of the numerical analysis and an experiment using the optimum model. [ABSTRACT FROM AUTHOR]

A novel beam-elastic substrate element with inclusion of microstructure and surface energy effects is proposed in this paper. The modified couple stress theory is employed to account for the microstructure-dependent effect of the beam bulk material while Gurtin-Murdoch surface theory is used to capture the surface energy-dependent size effect. Interaction mechanism between the beam and the surrounding substrate medium is represented by the Winkler foundation model. The governing differential equilibrium and compatibility equations of the beam-elastic substrate system are consistently derived based on virtual displacement and virtual force principles, respectively. Both essential and natural boundary conditions of the system are also obtained. Two modified Tonti's diagrams are presented to provide the big picture of both displacement-based and force-based formulations of the system. Due to similarity between the current problem and the one related to the beam on Winkler-Pasternak foundation, the so-called 'natural' beam-Winkler-Pasternak foundation element coined by the authors is employed to perform two numerical simulations to study the characteristics and behaviors of a beam-substrate system with inclusion of microstructure and surface effects. [ABSTRACT FROM AUTHOR]

Kriging model is one of popular spatial/temporal interpolation models in engineering field since it could reduce the time resources for the expensive analysis. But generation of the Kriging model is hardly a sinecure because internal semi-variogram structure of the Kriging often reveals numerically unstable or erratic behaviors. In present study, the issues in the maximum likelihood estimation which are the vital-parts of the construction of the Kriging model, is investigated. These issues are divided into two aspects; Issue I is for the erratic response of likelihood function itself, and Issue II is for numerically unstable behaviors in the correlation matrix. For both issues, studies for specific circumstances which might raise the issue, and the reason of that are conducted. Some practical ways further are suggested to cope with them. Furthermore, the issue is studied for practical problem; aerodynamic performance coefficients of two-dimensional airfoil predicted by CFD analysis. Result shows that such erratic behavior of Kriging surrogate model can be effectively resolved by proposed solution. In conclusion, it is expected this paper could be helpful to prevent such an erratic and unstable behavior. [ABSTRACT FROM AUTHOR]

The effects of channel curvature on the performance of viscous micro-pumps with a circular channel were numerically investigated using the Navier-Stokes equations. Channel curvature was defined as the reciprocal of the radius of a circular arc along the centerline of the channel. The performance of viscous micro-pumps was studied in terms of the dimensionless mass flow rate and dimensionless driving power. To study the effects of channel curvature, various pumps were simulated by varying the radius and height of the channel, and the eccentricity of the rotor. Numerical results show that the channel curvature plays a significant role in the performance of viscous micro-pumps. The effects of channel curvature become more significant as the channel height increases and/or the clearance gap decreases. For a given pump geometry and operation conditions, there is an optimal channel height that results in a maximum dimensionless mass flow rate. The value of optimal channel height is shown to be quite dependent on the magnitude of channel curvature and the pressure load. The dimensionless driving power decreases monotonically with channel curvature; thus a viscous micro-pump with a circular channel is more efficient than a corresponding pump with a straight channel. A circular channel viscous micro-pump exhibits a larger mass flow rate than a corresponding pump with a straight channel for all the Reynolds numbers simulated in this paper. [ABSTRACT FROM AUTHOR]

This paper reports on the kinematics of a translational parallel manipulator whose topology is close to the architecture of the famous Delta robot. The displacement analysis is presented in closed-form solution by applying a new strategy based on the unknown coordinates of a point embedded to the moving platform. The input-output equations of velocity and acceleration of the robot are systematically obtained by resorting to reciprocal-screw theory. The singularities of the mechanism are explained through the input-output equation of velocity. Finally, a numerical example is provided to show the application of the method. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the nonlinear dynamics of a thin-plate workpiece during milling process with cutting force nonlinearities. By modeling the thin-plate workpiece as a cantilevered thin plate and applying the Hamilton's principle, the equations of motion of the thin-plate workpiece are derived based on the Kirchhoff-plate theory and the von Karman strain-displacement relations. Using the Galerkin's approach, the equations of motion are reduced to a two-degree-freedom nonlinear system. The method of Asymptotic Perturbation is utilized to obtain the averaged equations in the case of 1:1 internal resonance and foundational resonance. Numerical methods are used to find the periodic and chaotic oscillations of the cantilevered thin-plate workpiece. The results show that the cantilevered thin-plate workpiece demonstrate complex dynamic behaviors under time-delay effects, the external and parametric excitations. [ABSTRACT FROM AUTHOR]

The sabot discard process of an armor-piercing, fin-stabilized discarding sabot (APFSDS) is crucial for the flight stability of the projectile. In this paper, the sabot discard behavior after projectile ejection from the muzzle is investigated at Mach number 4.0 and angle of attack of 0°. 3D compressible equations implemented with a dynamic unstructured tetrahedral mesh are numerically solved with a commercial computational fluid dynamics (CFD) code (FLUENT 12.0). Six-degrees-of-freedom (6DOF) rigid-body motion equations is solved with the CFD results through a user-defined function to update the sabot trajectory at every time step. A combination of springbased smoothing and local re-meshing is employed to regenerate the meshes around the sabot and describe its movement at each time step. Computational results show three different separation processes during the sabot discard process. Furthermore, the aerodynamic forces of APFSDS are calculated, and the trajectories of the three sabots are illustrated through the numerical solution of 6DOF equations. The results of the present study agree well with typical experimental results and provide detailed parameters that are important for analyzing the stability of the projectile. The present computations confirm that the numerical solution of the governing equations of aerodynamics and 6DOF rigid-body equations are a feasible method to study the sabot discard processes of APFSDS. [ABSTRACT FROM AUTHOR]