bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Heat Capacity of Salt Hydrate by In-Situ Formed Nanostructure
Authors: Mostafavi Amirhossein , Suzuki S. , Changla S. , Pinto A. , Ipposhi S. , Shin Donghyun
Published: January 2018

Silica nanoparticles and polyethylene-block-poly were doped in sodium acetate trihydrate to in-situ synthesize stelliform nanostructure to enhance the effective specific heat capacity of sodium acetate trihydrate. Sodium dodecyl sulfate and methanol were also used in the synthesis to help the dispersion. A modulated differential scanning calorimeter was employed to characterize the specific heat capacity of pure sodium acetate trihydrate and their nano samples. The measurement was repeated multiple times on different days to confirm the repeatability of the measurement. The result shows the specific heat capacity was enhanced by 11% in comparison with pure sodium acetate trihydrate. The conventional effective specific heat capacity model was compared with the experimental result.
Dynamic Analysis of Hybrid Gear Trains With Flexible Ring Gear Rim
Authors: Xu Xiangyang , Lai Junbin , Liu Yanfang
Published: January 2018

In this paper, the dynamic behavior of a hybrid gear train (HGT), consists of a single-stage helical planetary gear set and a helical gear pair, is analyzed. A ring gear rim is connected with an internal gear in a helical planetary gear set and an external gear in a helical gear pair. Power flows from the helical gear pair to the helical planetary gear set. Therefore, loads in the external gear would cause additional axial force and radial force, which would lead to unexpected moment and force. As a result, deflections of ring gear rim must be taken into consideration. Under this condition, a three-dimensional dynamic model of a HGT with flexible ring gear rim is developed, in which six degrees of freedom including three translational motions and three rotational motions are employed. Coupling effects of the bearing support stiffness, gear mesh stiffness and time-varying transmission error are taken into consideration. The model also takes flexible supporting shafts and planet carrier into consideration by using finite element method. Then, the equations of motion in matrix form are established and solved to predict the forced vibration response due to the transmission error excitations. Subsequently, effects of positions of the helical gear pair relative to the planetary gear set and the thickness of ring gear rim on dynamic behavior of the HGT are discussed. The results show that the proposed model is potential and can be used to guide the design of hybrid gear trains.
Nanoparticles Infused Mesoporous Material for Water Treatment Processes
Authors: Vu Trinh , Sarpomah Highqueen , Kamen Michael , Deksissa Tolessa , Xu Jiajun
Published: January 2018

In current study, a hybrid mesoporous material infused with metallic oxide nanoparticles, MCM-48 with TiO2 nanoparticles, has been developed for potential application in water treatment. Using this unique hybrid structure, it can combine the advantages of the effective pollutants removal capability of metallic oxide nanoparticles, and the strong yet high permeable structure of mesoporous material. A modified hydrothermal method has been developed to synthesize three hybrid samples with TiO2 nanoparticles of three assorted sizes (15, 50 and 300nm), and their structure have also been characterized. The synthesized samples are tested for its capability of removing organic dye and trace metals using ICP-MS. The results have shown that while all three hybrid materials have shown over 80% adsorption rate for organic dye, the sample synthesized using 300nm TiO2 nanoparticle has shown the highest adsorption rate. Similarly, the highest adsorption rate for most trace metals test here also occurs in the sample made with 300nm TiO2 nanoparticle. Coincidentally, the sample prepared with 300nm TiO2 nanoparticle has a much larger internal surface area and smaller average pore size compared to the two other samples, which may lead to the higher adsorption rate of trace metals and organic dye tested here. This study has presented a hybrid mesoporous material that can be potentially used for pollutants removal of water treatment. Future studies are still needed to fully explore this hybrid material and its capability in water treatment.
Molten Carbonate Fuel Cells for Carbon Capture From a Cogeneration System: A Comparative Analysis of Performance to Other Separation Technologies
Authors: Badami Marco , Cipriano Marco , Kowalski Gregory , Portoraro Armando , Zenouzi Mansour
Published: January 2018

This paper develops a mathematical model for the performance assessment and optimization of a small-scale molten carbonate fuel cell (MCFC) stack for the CO2 capture and liquefaction from the exhausts coming from an Internal Combustion Engine (ICE) cogenerator. An internal heat exchangers network has been developed for enhancing heat recovery, optimizing the efficiency of the global system. The model is innovative because, even though similar studies are reported in literature, they have never focused on a small-scale applications of a cogeneration system or compared the global performance to other means of carbon capture and storage (CCS). The energetic performance of the system has been compared to that of a monoethanolamine (MEA) adsorption system, which today is the most common technology for the carbon capture in large scale power plants. The results of the simulation show a carbon capture percent of about 81.3%, while the electrical output of the MCFC is around 280 kW with a conversion efficiency of 54%. The overall efficiency of the cogenerator and CCS system is about 37%. In the investigated MCFC technology the CCS system has a high carbon capture efficiency and produces a net power output unlike competing technologies.
Fracture Evaluation of Low-Density Porous Materials by Reaction Force Analysis in Ball Indentation Test
Authors: Ishino Takayuki , Sakuma Atsushi
Published: January 2018

An indentation test can easily measure the deformation characteristics of a material, because it does not require a test specimen to be cut from the material being examined. The applicability of this test is usually restricted to evaluating the fundamental characteristics of deformation, such as elasticity and plasticity; however, it is also useful if the test can be applied for the fracture evaluation of materials. Therefore, in this study, the fracture behavior of materials is discussed by performing indentation tests. The evaluation procedure depends on the variation in the indentation force owing to the differences in the deformation behavior. The observed variation is analyzed via the fractography of the material. A simple formulation is derived from the results for the development of a material evaluation method. Finally, the importance of the choice of the indenter diameter is explained in terms of the accuracy of the plateau stress of the porous material.
Experimental Thermal Characterization of DBD Plasma Actuators
Authors: Rodrigues F. F. , Pascoa J. C. , Trancossi M.
Published: January 2018

DBD plasma actuators have several applications within the field of active flow control. Separation control, wake control, aircraft noise reduction, modification of velocity fluctuations or boundary layer control are just some examples of their applications. They present several attractive features such as, their simple construction, very low mass, fast response, low power consumption and robustness. Besides their aerodynamic applications, these devices have also possible applications within the field of heat transfer, for example film cooling applications. However, due to the extremely high electric fields in the plasma region and consequent impossibility of applying intrusive techniques, there is a relative lack of information about DBDs thermal characteristics. In an attempt to contradict this scenario, this work describes the thermal behaviour of DBD plasma actuators. The total power consumed, the fraction of power that is dissipated as heat energy and the dielectric temperature variation due to the plasma operation are some parameters with great interest in any plasma actuator applications. Thus, these parameters were quantified and the results were presented and discussed. Infra-red thermography measurements were performed in order to obtain the temperature distribution of the dielectric layer. During this work we analysed DBD plasma actuators with different dielectric thicknesses and also with different dielectric materials, whose thermal behaviour was not reported in the literature yet. Conclusions were taken in order to extend the fundamental knowledge on the thermal aspects of the DBD plasma actuators.
Springback Analysis in Bilayer Material Bending
Authors: Nikhare Chetan P.
Published: January 2018

Exponential increase in the use of auto vehicles, and thus the fuel consumption, which relates to the air pollution, vehicle industry are in a strict environmental regulation from government. Due to which the innovation related to light-weighting is not only an option anymore but became a mandatory necessity to decrease the fuel consumption. To achieve this target, industry has been looking in fabricating components from high strength to ultra-high strength steels. With the usage of these material the lightweight was achieved by reducing a gage thickness. However due to their high strength property often challenges occurred are higher machine tonnage requirement, sudden fracture, geometric defect, etc. The geometric defect comes from elastic recovery of a material, which is also known as a springback. Springback is commonly known as a manufacturing defect due to the geometric error in the part, which would not be able to fit in the assembly without secondary operation or compensation in the forming process. Due to these many challenges, other research route involved is composite material, where light materials can be used with high strength material to reduce the overall vehicle weight. This generally includes, tailor welded blanks, multi-layer material, mechanical joining of dissimilar material, etc. Due to the substantial use of dissimilar materials, these parts are also called as hybrid components. It was noted that the part weight decreases with the use of hybrid components without compromising the integrity and safety. In this paper, a springback analysis was performed considering bilayer metal. For this two dissimilar materials aluminum and composite was considered as bonded material. This material was then bent in a channel forming set-up. The bilayer springback was compared in different condition like aluminum layer on punch side and then on die side. These results were then compared with the baseline springback of only aluminum thin and thick layer. It was found that the layer, which sees the punch side, matters due to the differences in elastic properties for both material and thus it directly influences the springback.
Effects of Grain Size on Ballistic Response of Copper Materials
Authors: He Ge , Dou Yangqing , Guo Xiang , Liu Yucheng
Published: January 2018

Numerical simulations were conducted to compare ballistic performance and penetration mechanism of copper (Cu) with four representative grain sizes. Ballistic limit velocities for coarse-grained (CG) copper (grain size ≈ 90 μm), regular copper (grain size ≈ 30 μm), fine-grained (FG) copper (grain size ≈ 890 nm), and ultrafine-grained (UG) copper (grain size ≈ 200 nm) were determined for the first time through the simulations. It was found that the copper with reduced grain size would offer higher strength and better ductility, and therefore renders improved ballistic performance then the CG and regular copper. High speed impact and penetration behavior of the FG and UG copper was also compared with the CG coppers strengthened by nanotwinned (NT) regions. The comparison results showed the impact and penetration resistance of UG copper is comparable to the CG copper strengthened by NT regions with the minimum twin spacing. Therefore, besides the NT regions-strengthened copper, the single phase copper with nanoscale grain size could also be a strong candidate material for better ballistic protection. A computational modeling and simulation framework was proposed for this study, in which Johnson-Cook (JC) constitutive material model is used to predict the plastic deformation of Cu and Ni; JC damage model is to capture the penetration and fragmentation behavior of Cu; Bao-Wierzbicki (B-W) failure criterion defines the material’s failure mechanisms; and temperature increase during this adiabatic penetration process is given by the Taylor-Quinney method.
Adhesive Properties Subject to Temperature Testing for Cohesive Zone Modeling
Authors: Aerne Nick , Rawlings Taylor J. , Parmigiani John P.
Published: January 2018

The growth of lightweight components and need for non-destructive fastening techniques leads to the use of adhesives in many industries. Modeling the behavior of adhesives in fastening joints can help in the design process to make an optimized joint, with minimal waste. However, in available material properties provided by manufactures of adhesives there is a gap in what is sufficient to accurately model and predict the behavior of real-world adhesive conditions. An adhesive joint may be loaded in mode I, mode II, mode III, or a combination of these in service. In components with outdoor application the ambient temperature outside in many regions can vary to below freezing to over 40 °C. The environmental conditions at these temperatures may influence the adhesive material properties. This body of research presents the results of adhesive properties subject to temperature testing. The needed material properties to compose an accurate model have been shown to be the mode I cohesive strength, mode I cohesive toughness, mode II cohesive strength, and mode II cohesive toughness. These properties can be measured with a test specimen designed to isolate that loading mode and condition. The specimens used are the Dog Bone Tensile Specimen (DBTS), the Double Cantilever Beam (DCB), Shear Loaded Dual Cantilever Beam (SLDCB), and Double Lap Shear (DLS). The effect of temperature will be tested by testing each specimen at −30°C, 20°C, and 45°C. Triplicates of each specimen at the respective temperature were tested. These results will be used in a cohesive zone model that will be validated with additional testing. The results from the two tested adhesives, Plexus MA832 and Pliogrip 7779/220, indicate these temperature conditions can change the cohesive strength in mode I by −60 to −40 % and mode II by −13 to 2% when at high temperatures (HT). The cohesive toughness in mode I by −40 to −20% and mode II by −40 to −2% when at high temperatures. The cohesive strength in mode I by −50 to 15% and mode II by 8% to 60% when at low temperatures (LT). The cohesive toughness in mode I by −70 to −20% and mode II by 30 to 60% when at low temperatures. As compared with those tested at room temperature (RT). The ranges here represent the response for both adhesives.
A Novel Sensorless Direct Torque Control Technique of Interior Permanent Magnet Synchronous Motor
Authors: Gurung Saita , Wang Xin
Published: January 2018

This paper presents a novel sensorless direct torque control of interior permanent magnet synchronous motor with resilient extended Kalman filter. In comparison to the field-oriented control scheme, direct torque control has advantages due to its simplicity (without Park’s transform or space-vector pulse-width-modulation), excellent transient response, high reliability and robustness. The interior permanent magnet synchronous motors have been extensively used in industrial applications due to their high efficiency, large torque to weight ratio, high performance and high reliability. Traditionally, the rotor position and speed of rotation are directly fed back through encoders or resolvers. In order to provide a more reliable and cost saving approach, the sensorless direct torque control of permanent magnet synchronous motor technique is proposed to eliminate the need of using encoders or resolvers. A novel nonlinear estimator, the resilient extended Kalman filter is proposed, which shows superior estimation accuracy compared with other estimation approaches such as extended Kalman filter. Computer simulation and DSP hardware implementation have been conducted to show the superior performance of the proposed approach.
A Novel Digital Speed Control Design for Brushless DC Motor Drives
Authors: Wu Wei , Wang Xin , Lozowski Andy G.
Published: January 2018

This paper presents a novel robust digital speed control design for brushless DC motors (BLDCs). The speed control can be achieved by regulating the DC link voltage of a six-step inverter. The discrete-time brushless DC motor dynamics is derived through bilinear transform. A robust digital control algorithm is designed to guarantee the closed loop system stability by satisfying the desired phase and gain margin. Computer numerical simulation studies and hardware implementation have demonstrated the effectiveness and robustness of the proposed scheme.
A Need for Functionally Graded Stiffness Femoral Stem for Reduction in Stress Shielding and Promoting Bone Growth: Computational Analysis
Authors: Tarlochan Faris , Mehboob Hassan
Published: January 2018

Total Hip Arthroplasty (THA) is an orthopaedic procedure that is available to reduce pain and restore the functionality of hip joints. THA has been successfully implemented for the last 40 years. However, after more than 40 years of design and implementation, premature loosening of the femoral stem still occurs due to the stress shielding. Stress shielding can be reduced by using implants with lower stiffness. This however, could increase the micromotion and interface debonding between the stem and femur bone. The aim of this study is to investigate stress and micromotion distribution across the length of the stem and to develop a bone in growth simulation model. To achieve this, a bone growth mechano-regulation algorithm based on deviatoric strain was applied to study the tissue differentiation process. The initial outcome of the study indicates that the stiffness of the implant should not be uniform rather graded from the distal to proximal and lateral to medial directions of the implant. With such graded stiffness, bone growth density was possible across the entire length of the stem, hence reducing aseptic loosening due to stress shielding.
Injection Angle Influence of Secondary Holes on the Enhancement of Film Cooling Effectiveness With Horn-Shaped or Cylindrical Primary Holes
Authors: Zhu Rui , Xie Gongnan , Simon Terrence W.
Published: January 2018

Secondary holes to a main film cooling hole are used to improve film cooling performance by creating anti-kidney vortices. The effects of injection angle of the secondary holes on both film cooling effectiveness and surrounding thermal and flow fields are investigated in this numerical study. Two kinds of primary hole shapes are adopted. One is a cylindrical hole, the other is a horn-shaped hole which is designed from a cylindrical hole by expanding the hole in the transverse direction to double the hole size at the exit. Two smaller cylindrical holes, the secondary holes, are located symmetrically about the centerline and downstream of the primary hole. Three compound injection angles (α = 30°, 45° and 60°, β = 30°) of the secondary holes are analyzed while the injection angle of the primary hole is kept at 45°. Cases with various blowing ratios are computed. It is shown from the simulation that cooling effectiveness of secondary holes with a horn-shaped primary hole is better than that with a cylindrical primary hole, especially at high blowing ratios. With a cylindrical primary hole, increasing inclination angle of the secondary holes provides better cooling effectiveness because the anti-kidney vortices created by shallow secondary holes cannot counteract the kidney vortex pairs adequately, enhancing mixing of main flow and coolant. For secondary holes with a horn-shaped primary hole, large secondary hole inclination angles provide better cooling performance at low blowing ratios; but, at high blowing ratios, secondary holes with small inclination angles are more effective, as the film coverage becomes wider in the downstream area.
Period-1 and Period-2 Motions in a Brusselator With a Harmonic Diffusion
Authors: Luo Albert C. J. , Guo Siyu
Published: January 2018

In this paper, the analytical solutions of periodic evolution of Brusselator are investigated through the general harmonic balanced method. Both stable and unstable, period-1 and period-2 solutions of the Brussellator are presented. Stability and bifurcations of the periodic evolution are determined by the eigenvalue analysis. Numerical simulations of stable period-1 and period-2 motions of Brusselator are completed. The harmonic amplitude spectrums show harmonic effects on periodic motions, and the corresponding accuracy of approximate analytical solutions can be prescribed specifically.
Nonlinear Modeling of Cracked Beams for Impedance Based Structural Health Monitoring
Authors: Sepehry Naserodin , Bakhtiari-Nejad Firooz , Shamshirsaz Mahnaz , Zhu Weidong
Published: January 2018

One of the main objectives of the structural health monitoring by piezoelectric wafer active sensor (PWAS) using electromechanical impedance method is continuously damage detection applications. In present work impedance method of beam structure is considered and the effect of early crack using breathing crack modeling is studied. In order to model the effect of a crack in beam, the beam is connected with a rotational spring in crack location. The Rayleigh–Ritz method is used to generate ordinary differential equation of cracked beam. Firstly, only open crack is considered that this is leads to linear system equation. In linear system, time domain system equations are converted to frequency domain, and then impedance of PWAS in frequency domain is calculated. Secondly, the breathing crack is modeled to be fully open or fully closed. This phenomenon leads to the nonlinear system equations. These nonlinear equations are solved using pseudo-arc length continuation scheme and collocation method for any harmonic voltage applied to actuator. Then impedance of PWAS is calculated. Two methods are used to detect early crack using breathing crack modeling on PWAS impedance. At the first, frequency response of breathing crack in the frequency range with its sub-harmonics is calculated. Second, only frequency response of one harmonic is computed with its super-harmonics. Finally, the detection method of linear is compared with nonlinear model.
Investigation of Transport-Reaction Phenomena in Multi-Layered PEFC Cathode Catalyst Layer
Authors: Nakano Rinako , Iguro Takumi , Kim Byunggi , Fushinobu Kazuyoshi
Published: January 2018

Improvement in power generation performance of PEFC (Polymer Electrolyte Fuel Cell) is required for its market supremacy in automotive applications. In particular, it is important to suppress concentration overpotential in high current density operation. The microstructure of CCL (cathode catalyst layer) is known to have a great effect on the power generation performance of PEFC. Also, the requirement for the species transport characteristics should vary with the thickness-wise position in CCL. Therefore, the purpose of this study is to design the microstructure of CCL by using multi-layered cathode catalyst layer and to evaluate oxygen transport properties.

In this research, we fabricated three kinds of multi-layered CCLs which have the difference in I/C (ionomer to carbon) ratio of GDL (gas diffusion layer)-side layer (0.3, 0.5, 0.9). And, we investigated oxygen transport-reaction phenomena by evaluating polarization characteristics, ECA (electrochemical surface area) and RCL (oxygen transport resistance in the CCL) using limiting current measurements. As I/C ratio is decreased from 0.9 to 0.5, RCL is decreased 49%. On the contrary, as I/C ratio is decreased from 0.5 to 0.3, RCL is slightly increased. ECA is monotonically decreased as I/C ratio is decreased from 0.9 to 0.3. These results show that the species transport characteristics alone have optimum condition in the GDL-side CCL at around I/C = 0.50.

In addition, we fabricated four kinds of multi-layered CCLs which have the difference in I/C ratio of GDL-side layer (0.5, 0.9) and mass fraction of platinum (10 wt%, 46 wt%.) Oxygen transport resistance is evaluated in CCL by separating the resistance to two components, Rmacro (by Knudsen diffusion) and Rlocal (by dissolution diffusion in ionomer,) by applying the ladder resistance model in CCL. As I/C ratio is decreased from 0.9 to 0.5, Rmacro is decreased and Rlocal is increased regardless of mass fraction of Pt. These results show that the ionomer amount of micropore in CCL is decreased, the micropore diameter is increased, and dissolution surface area near platinum is decreased as I/C ratio is decreased 0.9 to 0.5.

These results strongly suggest that there is an optimization strategy of I/C ratio of GDL-side layer in CCL.
Real-Time Correction of Nonlinearity Error in Homodyne Phase-Locking Interferometer
Authors: Lu S. , Yang K. M. , Zhu Y. , Wang L. J. , Zhang M.
Published: January 2018

Scanning beam interference lithography (SBIL) technology is applied to produce large-area grating with nanoscale phase accuracy. One of the greatest challenges of SBIL is locking interference fringe to a moving substrate with nanometer spatial phase error, which requires measuring the fringe phase with subnanometer precision. We are developing a novel homodyne phase-locking interferometer (HPLI) to meet the harsh measurement requirements. The HPLI offers high precision phase measurements as well as the direction recognition of the interference fringe drift with a four-orthogonal detection system. However, nonlinearity error impacts the phase measurement accuracy of HPLI with nanometer scale, which is mainly due to polarization mixing. In this paper, we present a method to estimate and compensate nonlinearity error in real time by applying an extended Kalman filter algorithm. The simulation results show that the method can effectively eliminate the nonlinearity error.
Multi-Physics Simulation of Complex Flow and Phase Change Induced by a Localized Laser Irradiation on a Urethane-Coated Stainless Steel Substrate
Authors: Mao Yijin , Afrin Nazia , Chen J. K. , Zhang Yuwen
Published: January 2018

A three-dimensional numerical simulation is conducted for a complex process in a multicomponent-multiphase system, which involves heat and mass transfer in the compressible gaseous phase and chemical reaction during laser irradiation on a urethane paint coated on a stainless steel substrate. A finite volume method (FVM) with a co-located grid mesh that discretizes the entire computational domain is employed to simulate the laser irradiation process. The entire problem is solved within one computational domain that includes two solid regions and one fluid region. To be specific, for the considered solid region, the paint will be decomposed via chemical reaction to gaseous phases then mix into the air and the stainless will involve phase change phenomena, such as melting-solidification and vaporization-condensation, once melting or boiling point is reached. Moreover, the air region is considered as a multi-component phase that has O2, N2, CO2, H2O, NO2, binder vapor and stainless vapor. In this multi-physics simulation, the process of melting, vaporization and chemical reaction and the splash of the melted paint and stainless into the air is observed. In the following sections, details on physical models will be given for each key component of the strategy in solving the entire problem. And the last section will show the results and corresponding discussion. This work is done within the framework of the OpenCFD toolbox OpenFOAM [1].
Investigation of Cohesive Zone Model Parameters for Steel Used in Shipbuilding Structure
Authors: Chaudhari Vikas , Kulkarni D. M. , Rathi Shivam , Sancheti Akshay , Dixit Swadesh
Published: January 2018

Present work deals with the investigation of fracture toughness and modeling parameters need in FEA application for steel use in shipbuilding structure. The investigated steel was 12.5mm thick low carbon high strength steel. Two types of tests were performed, tensile test and fracture test to evaluate mechanical properties and fracture toughness respectively. Cohesive zone model (CZM) was used because it is very computer effective and requires only two parameters, which can be determined in experiments with relative ease. Cohesive zone model with trapezoidal traction law found suitable for the investigated steel. To simulate CZM, bulk section with plane stress elements and bulk section with plane stress with plane strain core scheme are found suitable however bulk section with plane stress with plane strain core scheme gives accurate numerical results.
Analysis of a Liquid Filled Poroelastic Cylinder Exposed to a Time Varying Pressure Load
Authors: Ceste Tyler L. , Santhanam Sridhar , Jones Gerard F.
Published: January 2018

Porous materials are of interest for a number of applications one of them being energy absorption. These materials offer the ability to absorb more energy than a typical metallic solid and thus provide an opportunity to improve the performance of structures that endure blast loads. These structures undergo very large loads in very short periods of time and therefore maximizing energy absorption is paramount. This study seeks to improve the understanding of the response of porous materials by developing both analytical and finite element models for a liquid filled porous cylinder exposed to a dynamic compression loading.

The poroelastic cylinder consists of a porous metallic solid phase and a viscous liquid phase. These two phases provide for two mechanisms of energy dissipation which are that of the deformation of the solid and the viscous flow of the liquid. The theories of elasticity and porous media were used to formulate the governing equations for the liquid filled porous cylinder. These equations describe the coupling between the displacements of the solid cylinder and the pressure distribution of the liquid. Analytical and finite element models were developed to predict the cylinders response in order to determine the amount of energy absorbed when the cylinder is exposed to a dynamic compression load. Analytical models were developed to validate the finite element results. As more complexity is added to this problem an analytical approach becomes unviable and a finite element approach must be used. One such complexity that can be considered is the effect of utilizing a non-constant liquid viscosity, which requires developing a non-linear finite element model to account for the viscositys dependence on strain rate. This added non-linear effect should allow for additional viscous energy to be absorbed and thus can further enhance the performance of the system.
A Micromechanics Model for Electrical Conductivity of Three-Dimensional Open-Cell Metallic Foams
Authors: Li Hanzheng , Li Ke , Gao Xin-Lin
Published: January 2018

A microstructure based model is developed to predict the effective electrical conductivity of open-cell metallic foams. A tetrakaidecahedral cell is adopted as the repeating unit, which comprises of 32 ligaments and 24 joints. Each ligament contains a straight section with a uniform cross section and two identical joint sections. Each joint is formed with four identical joint sections. The geometries of the ligaments are constructed based on the minimum surface energy reached during the foaming process. The electrical conductivity of a joint section is first numerically computed. It is then used, along with that of the straight section of the ligament, to give rise to the conductivity of the ligament for a given relative density. The effective electrical conductivity of the foam is then analytically determined along four typical orientations of the unit cell with the resistor network method and Kirchhoff’s current and voltage laws. The numerical results indicate that the electrical conductivity of 3-D open-cell foams exhibits some degree of anisotropy. The predictions of the foam conductivity along the four identified orientations well encompass the scattering of the experimental measurements reported in the existing studies.
Analysis of Distributed Energy System for a Typical SoCal Residential Home
Authors: Xue Hong , Locke Nathan , Radel Scott
Published: January 2018

This study presents a simulation and cost analysis of a distributed energy system for a typical Southern California residential home. A method of simulating a residentially distributed energy system comprised of a fuel cell, a battery, and photovoltaics has been developed. The simulation was performed by developing solar insolation profiles and diurnal demand profiles from energy statistics, and then using them to determine the performance of the system components and estimate the annual operational costs. The results of this simulation were then used to assess the cost effectiveness of the energy system as household size and system component capacities were varied. The simulation results show that the increasing of the photovoltaic capacity has a significant impact on reducing the payback time as higher capacities reduce operation costs by allowing for more electricity to be sold back to the grid. The results payback period decreases as the number of members in a household increases. However, it is found that variation in the capacity of the battery does not have a significant impact on payback time and tends to reduce system performance or adds unnecessary cost if capacity increases or decreases from an optimal value. The present work plays an important role not only for policy makers and utility companies to promote the renewable energy usage, but also for residents to understand the benefits of distributed energy system in residential applications.
Modeling Convective Heat Propagation in a Fractured Domain With X-FEM and Least Square Method
Authors: Bahmani Bahador , Khoei Amir R.
Published: January 2018

The main goal of the current study is developing an advanced and robust numerical tool for accurate capturing heat front propagation. In some applications such as impermeable medium, Heat transfer in the surrounding domain of fracture acts just as a conduction process but the heat transfer through the fractures appears as a convection process. From a mathematical point of view, a parabolic partial differential equation (PDE) should be solved in the surrounding domain whereas a hyperbolic PDE should be solved in the domain of fractures. In fact, they have completely different treatments and this is one of the complicated problems in this area. In this paper, the presence of fractures and discontinuities are considered with the aim of eXtended Finite Element Method (X-FEM). In the proposed numerical approach, the domain is decomposed into local and global scales. Global and local domains are solved by the X-FEM and Least Square Method (LSM) techniques, respectively. As a final result, it is determined that the treatment of coupling term between two scales is one of the most important factors for system performance. Increasing its effect can significantly improve the efficiency of the whole system.
Effect of Design Parameters on Lubrication Behavior of Spur Gear Pairs
Authors: Liu Yanfang , Liu Qiang , Dong Peng
Published: January 2018

An involute spur gear pair meshing model is firstly provided in this study to achieve relevant data such as rolling velocity, sliding velocity, curvature radius etc. These data are needed in a transient, Newtonian elastohydrodynamic lubrication (EHL) model which is provided later. Based on these two models, the behavior of an engaged spur gear pair during the meshing process is investigated under dynamic conditions, film thickness, pressure, friction coefficient etc. could be achieved through the models. Then, power loss under certain operating condition is calculated. Relationship between power loss and lubrication performance is also analyzed.
Electro-Mechanical Impedance Assessment of a Bolted Circular Plate Element of a Space Structure
Authors: Hunter David , Zagrai Andrei
Published: January 2018

Electro-mechanical impedance diagnostic is one of key structural health monitoring approaches in aerospace structures. Considerable number of studies have demonstrated its efficiency in monitoring bolted joints. This investigation focuses on effect of a bolted boundary on the electro-mechanical impedance response of the space structure. Many space vehicles incorporate cylindrical payloads featuring multiple plates connected with threaded rods. Position of nuts on the threaded rods determine layered structure of the payload. Because of the cylindrical configuration of the payload, internal layers are formed by circular plates bolted to the connection rods. The number of connection rods determines the number of bolted boundary conditions around plate’s circumference. In this case, the boundary of the plate is essentially a mix of bolted and free segments and is not associated with a classical boundary condition. It is suggested that this case may be represented by an elastic boundary conditions with boundary stiffnesses depending on torque applied to each bolted joint. Vibrations of a circular plate with indicated complex boundary conditions were studied in this contribution theoretically and experimentally. As a result of numerical studies, a range of stiffnesses was suggested to model the bolted boundary. An analytical expression for the electro-mechanical impedance of a circular plate was presented and was utilized in the calculation of the response of a circular plate with the complex boundary. Structural damage was modeled as deviation of the stiffness associated with the bolted joint. Experimental studies were carried out to validate results of theoretical investigations. Electro-mechanical impedance signatures of the circular plate with an attached piezoelectric active sensor were collected for different sets of boundary conditions representing theoretical scenarios. Effect of the compromised bolted joint on the electro-mechanical impedance response of the whole circular plate was explored and the analysis of changes due to different conditions of the bolted boundary was provided.
Impact Damage Prediction of Assembly Fiber-Reinforced Thermoplastic Polymer (AFRTP) Structures
Authors: Yang Xudong , Sun Lingyu , Li Lijun , Zhang Cheng
Published: January 2018

Assembly Fiber-Reinforced Thermoplastic Polymer (AFRTP) is a hybrid material manufactured by injection overmolding of short/long fiber-reinforced thermoplastic resin on the back of continuous fiber-reinforced laminate preformed by thermal stamping to achieve both high mechanical properties and complex geometries. This new technique has attracted large attention from industry recently. The difficulty in applying AFRTP is the progressive damage prediction of heterogeneous interface because the difference in mechanical properties result from materials and process may lead to the interface separation when subjected to bending or tension loads that reduce the bending resistance capability of AFRTP plates. In this paper, the interfacial cohesive parameters of AFRTP structure are identified based on the published experimental data. Additionally, the low-speed impact under three-point bending loads is simulated and the interface stress distribution and failure modes reveal the damage mechanisms of AFRTP interface under shear stress.
Analysis of the Cutting Force With Ultrasonic Assisted Manufacturing of Steel (S235JR)
Authors: Zopf Philipp , Haas Franz
Published: January 2018

The manufacturing of hard and refractory materials such as ceramics, glass or carbide poses particular challenges on tools and machines. The Sauer Limited a company of the DMG Mori Corporation has developed ultrasonic tool holders working in a frequency range from 15 to 60 kHz. The ultrasonic vibrations are superimposing the tool movement in the tool axis especially for the application on special materials. This technique causes a structural weakening in the contact area and facilitates the machining. For these special materials, a force reduction, mainly in drilling into carbide with diamond tools, of up to 30 percent is possible. This made the authors try to expand the application range of this method. To achieve evaluable results, the authors decided to start working with existing processes. This also makes it easier to understand the mechanism of the positive influence of the ultrasonic assistance. It is difficult to compare a grinding process of hard and brittle materials to the drilling of steel as these two operations are different in many ways. In the first case of investigation, the authors use tools with geometrically undefined edges, where as in the second case, the edges are geometrically defined. To get valid results of the tests, it has then been decided to investigate drilling. This manufacturing method anticipates the best results. The main target of the investigation is to reduce the cutting force. It is measured with a force measurement platform underneath the workpiece. Concerning the direction of the ultrasonic assistance, the authors expect lower cutting forces, longer endurance of the tool, a reduction of the burr height and a better surface quality in the drilling process. To verify the frequencies and the amplitudes, an FFT-analysis is performed. This analysis shows the increase of the damping. This raise depends on the infeed rate of the tool and thus reduces the amplitude of the cutting force.
Novel Type of Biaxial Wheel-Type Haptic Input Device With MR-Brakes to Control Hydraulic Multi-Axis Manipulators
Authors: Myszkowski Adam , Bartkowiak Tomasz , Staniek Roman
Published: January 2018

In the paper, authors present a design of a novel input device, in which, thanks to two ergonomically placed wheels, the operator can control the multi-axis manipulator with a single hand. The application of rotating elements provides the following benefits: achieving unlimited angular displacement, controlling numerous number of axes thanks to the certain combination of wheels motions, assigning force and position amplification individually, what helps to obtain both high speed and precision. In order to generate feedback force in the joystick, dedicated MR brakes were designed and built. The proposed feedback approach is an example of admittance control [1]. The joystick was built and tested at the Institute of Mechanical Technology of Poznan University of Technology. In the article, a theoretical model of the brake was shown together with analysis and discussion of its parameters. Additionally, it was supplemented with the results of theoretical and simulative studies. The paper also contains the outcome of the initial study focused on the analysis of the functionality, ergonomics and possibility of two-, three- and four axis control. It showed that the control algorithms played an essential role in motion control. They allow a rapid change of the generated resistance force during the change of motion direction. The obtained results validated the assumed design of the joystick with rotary elements and applied MR brakes due to the possibility of precisely control the motion resistance.
Parametric Analysis of the Thermal Components of an Alpha-Stirling Engine for Cogeneration Applications
Authors: Ferreira Ana C. , Teixeira Senhorinha F. C. F. , Teixeira José C. , Barreiros Martins Luís A.
Published: January 2018

Stirling engines efficiency, the increased maintenance interval periods, the variety of energy sources and the relatively low gas emissions makes Stirling technology an interesting choice as prime mover for cogeneration applications. These are some of the reasons that justify the attention received from researchers in the last years, focused in its modelling, optimization and its application in the suppression of buildings energy needs. In this study, an alpha-Stirling engine was numerically modelled. At this configuration, the working fluid flows between expansion and compression spaces by alternate crossing of, a high temperature heat exchanger (heater), a regenerator and a low temperature heat exchanger (cooler). Thus, the engine is considered as a set of five components connected in series. MatLab® environment was used to implement a software-code to model the thermodynamic cycle of the Stirling engine. The modular code allows investigating the influence of different geometrical and thermal parameters of all the engine components that affects its power production and the efficiency, the effectiveness of heat exchangers and the design itself of the power plant. This parametric analysis helps finding some restriction values for geometrical parameters that cannot be solved through the optimization procedures. For instance, at some point, there is a geometrical limit for which the increase in heat transfer is overlapped by the void volume or pumping losses increase. The parametric analysis led to an enhanced configuration of the numerical model, which resulted in the increase of engine thermal efficiency (about 13.4%), with a power production close to 5 kW.
Experimental Investigation on Flow Condensation Heat Transfer in Hydrophobic Annular Metal-Foam Tube
Authors: Zheng GongHang , Shi Juan , Chen ZhenQian , Huang XinPeng
Published: January 2018

The vapor flow condensation heat transfer in tube filled with hydrophobic annular metal foam is experimentally investigated. The surface of annular metal foam is hydroph-obically modified through chemical corrosion and molecular self-assembly technology. The thickness of the metal foam is 2mm and cell size is 10PPI. The thermocouples are welded in groove to measure wall temperature. The effects of vapor mass flow, cooling water temperature and vapor quality are analyzed. The results show that the pressure drop and average heat transfer coefficient of tubes filled with annular metal foam increase with increasing vapor mass flow or vapor quality. According to wall temperature distribution, it is predicted that flow pattern is annular flow at vapor entrance and the stratified flow is located at the distance from 0.5m to 0.9m. The average heat transfer coefficient of hydrophobic annular metal foam tube increases approximately 1.2 times compared to untreated metal foam tube.
Radio Frequency and Microwave Power Absorption in Spherical Shaped Objects
Authors: Collins Timothy M. , Hossan Mohammad Robiul
Published: January 2018

Microwave and radio frequency heating has great promise in many engineering and biomedical applications because of its non-contact, volumetric selective heating. However, the heating patterns and temperature distributions are non-uniform due to non-uniform electromagnetic power absorptions. In this study, we present a closed-form analytic expression of electromagnetic field distribution and power absorption in a spherical shaped object. A simplified Maxwell’s equation that represents plane wave is solved in spherical coordinates using vector potentials and separation of variables. The electromagnetic power absorption is obtained from the electromagnetic field distribution within the object using Poynting theorem. The analytical expressions of the electric field and power generation are evaluated for meat balls of 1.0, 2.0, 3.0 and 5.0 cm radii and two different electromagnetic frequencies. Results show that the strength of the absorbed electromagnetic wave and power absorption is highly dependent on the radius of the dielectric sphere. The presence of local maxima of electric and magnetic field strength due to the constructive interference of the reflection and transmission of electromagnetic wave in the target object are found in all sizes. However numbers of peaks or valleys are more in larger meat balls. The spatial distribution of microwave power absorption follows the trend of electromagnetic field distribution. The positions of local maxima and minima of power absorption and electromagnetic field distributions vary with the radius of the sphere and applied frequencies. It indicates that the uniform and effective electromagnetic power absorption can be facilitated by the proper design of the object of interest and selection of an appropriate frequency.