bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of Scoop Effect on Film Cooling for Cylindrical Inclined Hole
Authors: Ji Yongbin , Singh Prashant , Ekkad Srinath V. , Zhang Shusheng
Published: January 2018

Film cooling behavior of a single cylindrical hole inclined at an angle of 35° with respect to a flat surface is numerically predicted in this study. Adiabatic film cooling effectiveness has been presented to evaluate the influence of the scoop placed on the coolant entry side. The effect of blowing ratio (0.65, 1, 1.5 and 2) and the length-to-diameter ratio (1.7 and 4.4) are examined. Three-dimensional Reynolds-averaged Navier-Stokes analysis with SST turbulence model is used for the computations. It has been found that both centerline and laterally averaged adiabatic film cooling effectiveness are enhanced by the scoop and the enhancement increases with the blowing ratio in the investigated range of variables. The scoop was more effective for the higher length-to-diameter ratio cases (L/D = 4.4) because of better velocity distribution at the film hole exit, which makes coolant reattach at a more upstream location after blowing off from the wall.
New Insights Into Slip-Stick Vibrations From Compact, Closed-Form Analysis
Authors: Fowler Deborah , Peters David
Published: January 2018

A mechanical system sliding on a moving surface with Coulomb friction is a rich area for study. Despite much past work, there is still something to be gleaned by closed-form expressions for the system behavior. Consider a spring-mass-damper system (K, M, C) with deflection x, base moving in the +x direction at velocity V, sliding friction F, and sticking friction Fs. An initial condition of x0 at rest can be considered general because all possible motions will follow. Two dimensionless schemes are used. For the abstract, we focus on the scheme normalized by x0 with variable z = x/x0, τ = (ωnt, ωn = [K/M]1/2, ζ = c/[2(KM)1/2], ν̄ = V / (ωnx0), f = F/(Kx0), and fs = Fs/(Kx0). Since the solution is piecewise linear, this allows closed-form results.

For this abstract, we consider C = 0, Fs = F. (Other cases are in the paper.) There are three critical ground speeds. The first, ν̄d, is when sticking first occurs (at z = f). At the second speed, ν̄c, sticking has moved to z = −f. Thereafter, the sticking point again increases, reaching z = f at the third speed, ν̄b. For higher ν̄, there is no sticking.

In this paper, closed form expressions are presented for the three critical speeds:(1)ν¯d=[(1+3f)(1−5f)]12,ν¯c=[(1+f)(1−3f)]12,ν¯b=1−f

These formulas are verified by numerical simulation. The insight is that there is a limited range of f for which certain critical points can be reached. Thus, 0 < f < 1/5 has different dynamics than 1/5 < f < 1/3.

Formulas are also derived for the second maximum of z, which gives an indication of decay or growth of the system. For example, with f = fs and C = 0, the second maximum z with f < 1/5 is:(2)zmax=f+((1−f)2−ν¯2−4f)2+ν¯2ν¯d<ν¯<ν¯czmax=ν¯+fν¯c<ν¯<ν¯bzmax=1ν¯>ν¯c

Formulas will also be given for the times at which the maximum occurs and the times at which a transition occurs from static to sliding for all cases.
Experimental Study of Mass Burning Rate of Liquid Pool Fires Under Dynamic Pressure in an Altitude Chamber
Authors: Tao Zhenxiang , Yang Rui , Li Cong , Yao Yina , Wang Wei
Published: January 2018

To study the influence of dynamic pressure on the liquid combustion characteristics, two kind sizes of pool fires were studied under varied pressure rates, namely 100Pa/s, 200Pa/s, 300Pa/s from 90kPa to 38kPa in an altitude chamber which size is 2m*3m*4.65m. Combustion characteristics of n-heptane pool fires, such as mass burning rate, flame temperature, chamber pressure were measured in this research. Experiment results show that the mass burning rate of 20cm pool fires, decreases when the ambient pressure reduces, and the variation trend become more sharply when the dynamic pressure rate is increased, while 30cm pool fires at the beginning of the combustion stage almost remain constant, this is because fire heat feedback have a great influence on it. The results also show that compared to the radiation model, pressure model could be linear fitting better in a double logarithm coordinate, and oil pool fires under 300Pa/s of 20cm, 100Pa/s of 30cm the value of α obtained by the fitted curves were more closer to fixed pressure ones.
Study of Electrostatic-Induced Jumping Droplets on Superhydrophobic Surfaces
Authors: Traipattanakul B. , Tso C. Y. , Chao Christopher Y. H.
Published: January 2018

Condensation of water vapor is an important process utilized in energy/thermal/fluid systems. When droplets coalesce on the non-wetting surface, excess surface energy converts to kinetic energy leading to self-propelled jumping of merged droplets. This coalescing-jumping-droplet condensation can better enhance heat transfer compared to classical dropwise condensation and filmwise condensation. However, the resistance force can cause droplets to return to the surface. These returning droplets can either coalesce with neighboring droplets and jump again, or adhere to the surface. As time passes, these adhering droplets can become larger leading to progressive flooding on the surface, limiting heat transfer performance. However, an electric field is known to be one of the effective methods to prevent droplet return and to address the progressive flooding issue. Therefore, in this study, an experiment is set up to investigate the effects of applied electrical voltages between two parallel copper plates on the jumping height with respect to the droplet radius and to determine the average charge of coalescing-jumping-droplets. Moreover, the gravitational force, the drag force, the inertia force and the electrostatic force as a function of the droplet radius are also discussed. The gap width of 7.5 mm and the electrical voltages of 50 V, 100 V and 150 V are experimentally investigated. Droplet motions are captured with a high-speed camera and analyzed in sequential frames. The results of the study show that the applied electrical voltage between the two plates can reduce the resistance force due to the droplet’s inertia and can increase the effects of the electrostatic force. This results in greater jumping heights and the jumping phenomenon of some bigger-sized droplets. With the same droplet radius, the greater the applied electrical voltage, the higher the coalescing droplet can jump. This work can be utilized in several applications such as self-cleaning, thermal diodes, anti-icing and condensation heat transfer enhancement.
Enhancing Interpretation of Learned Concepts Through an Online Tensile Strength Simulation
Authors: Seely Brian J. , Kapp Karl M. , Kapka Larraine A. , Wendel Steven
Published: January 2018

This NSF funded project was a collaborative research effort that focused on the development and implementation of an open source, online virtual tensile strength testing simulation. The simulation was designed to emphasize the equations used as part of tensile testing rather than solely on the use of the tensile testing equipment. The resulting simulator was utilized by engineering technology and engineering students in higher education as well as pre-engineering high school students in the Project Lead The Way network. The research tested whether or not an online learning simulation can be effective for tensile testing instruction. The developed simulation was designed to focus on and exploit concepts to enhance student ability of interpreting the resultant stress-strain curve by applying mathematical concepts of graphing, predicting and applied knowledge of material properties. Further, the open source tool was developed with a prepare, practice, perform framework allowing students with different knowledge sets to choose the most appropriate level of scaffolding to match their comfort level, enhancing self-efficacy. Analysis of the gathered results of each learner for the pre- and post-test showed a significant improvement after the experience, the pre-test mean score was 53.16 points, while the post-test mean was 72.42 (out of 80), suggesting the online learning simulation had a positive effect on learning. This project has since expanded tensile testing to include hardness and impact testing. Final results will be presented for all three testing methods using both high school and college students as test subjects comparing pre- and post-test results.
Sabatier Based Cycle for CO2 Methanation: Exergy and Thermo-Economic Analysis
Authors: Re Fabiana , Toro Claudia , Sciubba Enrico
Published: January 2018

Growing concerns about global climate change have increased attention on various approaches to reduce emissions of CO2 and other GHGs. Several scale carbon capture and sequestration (CCS) approaches are currently in development and demonstration stages. Currently, CCS still faces several technical, legal, and economic challenges.

In the past decades, researchers have discussed potential use of Sabatier reaction in reducing CO2 emissions. This process converts CO2 and H2 into CH4 reacting over a metal catalyst. Turning waste CO2 into an efficient and easy-to-use fuel can be attractive for the transport sector and industries.

Object of this paper is the modelling, process design and simulation of a CO2 methanation plant based on the Sabatier reaction. The benefits of the plant in terms of reduced dependence on conventional fuels and lower risks to security of supply are described and evaluated in the medium and long term.

A thermoeconomic analysis is presented to evaluate the exergetic performance of the proposed system and the final cost of products and to compare it with other current carbon capture and energy storage technologies considering the effect of the main plant parameters.
Compatibility of Passenger Vehicles and Cable Median Barrier Systems
Authors: Stolle Cody S. , Reid John D.
Published: January 2018

Cross-median crashes are one of the most severe type of highway crashes. Many state Departments of Transportation (DOTs) install median barriers, such as cable median barriers (CMBs), to reduce the rate of cross-median crashes. Nonetheless, these barriers are not always successful.

Approximately 20,000 cable barrier crashes throughout the United States spanning between 1999 and 2010 were examined, and detailed data was sufficient to determine the prevailing causes of 182 penetration crashes (i.e., barrier was breached). Penetration crashes involving CMBs were affected by: (1) impact conditions; (2) barrier placement and design; and (3) vehicle factors, including geometry and inertial properties.

In general, CMB crashes occur at higher CG trajectory angles than with other roadside features. The 85th percentile CG trajectory angle for cable barriers was 39 degrees, compared to 25 degrees when all roadside features are considered. Approximately 2.2% of all CMB crashes were severe, although penetrations were between two and thirteen times more likely to be severe than non-penetration crashes.

Vehicle factors such as weight and geometrical profile affected the likelihood of CMB penetrations. Headlights or taillights fractured or were damaged in approximately 80% of non-penetration crashes, but were damaged or fractured in less than 60% of penetration crashes, often by additional unrelated impacts. Lastly, heavier vehicles with more kinetic energy were more likely than similar, lighter vehicles to penetrate CMBs. Through better understanding of all of the complicating factors affecting CMB performance, better designs and guidelines can be prepared to maximize CMB effectiveness.
Interface Analysis of a Combined Electroosmotic/Pressure Driven Flow of Three Viscoelastic Immiscible Fluids in a Microchannel
Authors: Escandón Juan P. , Gómez Juan R. , Hernández Clara G.
Published: January 2018

This paper presents the analytical solution of a combined electroosmotic/pressure driven flow of three viscoelastic immiscible fluids in a parallel flat plate microchannel. The mathematical model is based in the Poisson-Boltzmann equation and Cauchy momentum conservation equation. In the steady state analysis, we consider that the three fluids are electric conductors and obey to the simplified Phan-Thien-Tanner rheological model; therefore, different conditions at the interface between the fluids as electric slip, surface charge density and electro-viscous stresses balance are discussed in detail. Results show the transport phenomena coupled in the description of the velocity profiles, by the analyzing of the dimensionless parameters obtained, such as: the electric slips, the electric permittivities ratios, the surface charge densities, the zeta potentials at the walls, the interfaces positions, the viscosity ratios, the viscoelastic and electrokinetic parameters, and the term involving the external pressure gradient. Here, the presence of a net electric charges balance at the interface, breaks the continuity of shear viscous stresses, modifying the flow field; hence, for the established electric conditions at the interface through the values of the electric slips and the surface charge densities, play a role like a switch on the flow behavior. This investigation extends the knowledge about the techniques on the control of immiscible non-Newtonian fluids in microescale.
Study on a Photovoltaic Lunar Dust Removal System Based on the Photovoltaic Effect of PLZT
Authors: Jiang Jing , Zhao Hong-Yue , Ding Jin-Cheng , Yue Hong-Hao , Hou Xu-Yan
Published: January 2018

The deposition of lunar dust on the surface of solar panels and optical elements is one of the most important problems need to be solved in lunar exploration. This paper will propose an initiative lunar dust removal system based on the photovoltaic effect of PbLaZrTi (PLZT), which is activated by the ultraviolet light extracted from sun light at the lunar surface. When ultraviolet light with a wavelength near 365nm illuminates on polarized PLZT materials, high voltages of several kilovolt per centimeter can be generated between two electrodes of PLZT. When two electrodes of PLZT are connected to a lunar dust collector (LDC) and the ITO film of protected surface respectively, an electrostatic field forms between LDC and the protected surface. Coulomb forces over particles will overcome gravitational force and surface forces, so the particles can be absorbed to LDC and removed by LDC finally. Based on the equivalent electrical model, mathematical model of electrostatic force is derived when the lunar removal electric field is acted either by single piece PLZT or by multi-pieces PLZT which are connected in parallel. Experimental platform is set up to prove the feasibility of this lunar dust removal system. In order to improve the removal efficiency, a novel configuration design of LDC based on multi-PLZT patched is proposed and its removal efficiency is evaluated by experiments.
Information Theoretic Tools for Parameter Estimation and Model Order Reduction for Mechanical Systems
Authors: Elinger Jared D. , Rogers Jonathan D.
Published: January 2018

Parameter estimation and model order reduction (MOR) are important techniques used in the development of mechanical system models. A variety of classical parameter estimation and MOR methods are available for nonlinear systems but performance generally suffers when little is known about the system model a priori. Recent advancements in information theory have yielded a quantity called causation entropy, which is a measure of the influence between multivariate time series. In parameter estimation problems involving dynamic systems, causation entropy can be used to identify which functions in a discrete-time model are important in driving the subsequent state values. This paper extends on previous works’ use of a Causation Entropy Matrix to nonlinear systems modeled from the real world. This work explores the conversion of continuous systems to a discrete model and applies the causation entropy matrix to the system. Results show that model structure can be estimated by the causation entropy matrix. This work extends the previous work by showing that the method can be applied to general nonlinear systems. Previously shown examples were toy, additively separable nonlinear problems. This work shows that the methodology can be extended to any nonlinear system, including time varying systems, which provides a framework to examine parameter estimation for general nonlinear systems.
Position Control of a Floating Ball in a Vertical Air Stream
Authors: Nudehi Shahin S. , Dehmlow Shaffer , Clark Devin
Published: January 2018

Quantitative Feedback Theory (QFT) control theory was used to design a control loop in order to provide stability and tracking ability for a ball floating in a jet stream of air. Due to nonlinearity of the system governing equations, a set of linear transfer functions was derived to capture the dynamics of the system. Using this set, a controller and a prefilter were designed that met the stability and tracking performances. The feedback loop was also implemented in an experimental setup consisting of a DC motor, an axial fan, an expansion tank, and a nozzle. The experimental data showed some differences with the simulation results, but the closed-loop system response was satisfactory and the design criteria were met.
A Tool to Identify Damping During Large Amplitude Vibrations of Viscoelastic Structures
Authors: Balasubramanian Prabakaran , Ferrari Giovanni , Amabili Marco
Published: January 2018

Various damping models are available to describe the dissipation energy present in structures. Among them, viscous and viscoelastic damping models are widely used to describe the damping in viscoelastic structures. Recent studies show that both viscous and viscoelastic damping of a structure varies as it experiences large amplitude vibrations. This makes it necessary to adjust the damping values with respect to the maximum vibration amplitude. The knowledge of damping values allows engineers to estimate the maximum vibration amplitude of a structure under various operating scenarios, thus improving the estimate of the safety margin and the efficiency of design.

However, the variation of hysteretic damping during large amplitude vibrations was not addressed yet. Hysteretic damping is defined as dissipation energy due to the internal friction between the internal planes of the material and is independent on frequency. Hysteretic damping is well defined in linear vibrations as the ratio of loss and storage energies. The concept is here extended and hysteretic damping is identified during nonlinear vibrations.

This paper presents the experimental data measured on a clamped-clamped rubber square plate under harmonic excitation at various force levels. A tool based on temporal method was developed to identify the nonlinear parameters and to calculate the hysteretic damping from the experimental data. The results show that hysteretic damping decreases with excitation frequency.
Explicit Finite Element Study of Liquid Sloshing Behavior in Fluid-Structure Interaction Condition
Authors: Yang Shuo , Yee Raymond K.
Published: January 2018

As a common phenomenon in liquid motions, sloshing usually happens in a partially filled liquid tank of moving vehicle or structure. The objectives of this paper are to study sloshing behavior in rigid tank and deformable tank, and to develop a better performance baffle design in the tank under seismic excitations. The tank is surged with a sinusoidal oscillation about horizontal x-direction. The hydro-elasticity effect of sloshing pressure on the tank wall was taken into consideration due to the fluid-structure interaction between impact pressures and tank structures. ABAQUS finite element program using Coupled Eulerian-Lagrangian (CEL) technique was employed to simulate fluid sloshing. The sloshing phenomenon was studied in rigid tank and deformable tank models with three different water levels, and the effect of wall thickness of the deformable tank on sloshing behavior was discussed. One way to minimize the effect of sloshing in a tank, baffles are used and installed in the middle of the tank, and then various heights and material types of baffle were evaluated. The simulation results show that higher water level case creates greater pressure impact on the tank wall than lower water level case, and the elasticity of the tank structure would reduce the impact pressure of the wall. For the simulation tank model with size of 1m (H) × 1m (W) × 0.2m (D), better performance baffle was found to be the one with the height of 0.35m and was made of acrylic material. Moreover, the conclusion of this study can be extrapolated to other dimensions of the model based on similarity theory. This paper also can serve as an aid in further studying sloshing phenomenon. The findings of this study can be applied to restrain or minimize sloshing motions inside a tank.
Effects of Velocity on Elastic Deformation in Ball Screw Drives and its Compensation
Authors: Li Fuhua , Li Tiemin , Jiang Yao , Li Fengchun
Published: January 2018

Ball screw drives are widely used in machine tools to provide accurate linear motion. Elastic deformation is one of the major error sources for ball screw drives in achieving high accuracy motion, and changes greatly when velocity varies. The influence of velocity on the elastic deformation can be estimated and it can be compensated by means of dynamic modeling and servo control method. This paper presents a dynamic model considering torque transmission between the ball screw and the nut. And stiffness is identified by a method of combining theoretical calculation and experimental tests on a constructed test bench, which has two novel symmetrical loading mechanisms. In order to analyze the influence of moving velocity on the elastic deformation, simulation and experiments are conducted when two trajectories which have velocity jumps are input. And the simulated elastic deformations are compared with experimental results to evaluate the accuracy of the model. The results show that the simulated results fit the experimental results with high accuracy. The relationship between the elastic deformation of ball screw drives and the velocity is linear based on the experimental results. Then the simulation results are used to compensate the elastic deformation based on the feed-forward compensation method. The results show that the differences between the actual compensation values and actual elastic deformation are small and most of the elastic deformation of the ball screw drives can be compensated. Therefore, the proposed dynamic model and compensation method can be used to improve the tracking accuracy of ball screw drives.
Mechanical Behavior of As-Fabricated and UV-Cured Lattice Structures Printed Using the CLIP Technology
Authors: Saigal Anil , Tumbleston John R. , Vogel Hendric
Published: January 2018

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral and octet lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. Five different octahedral structures and seven different octet structures with relative densities ranging from approximately 0.07 to 0.35 were fabricated by changing the strut diameter. The minimum diameter of the strut elements is 0.50 mm and 0.35 mm for the octahedral and octet structures, respectively. The different relative density structures were tested in compression in the as-fabricated state and after they were UV cured. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, and plastic strain hardening to a peak in strength, followed by a drop in flow stress. It was found that the stiffness and strength of octahedral lattice structures is greater than the stiffness and strength of octet lattice structures at all relative densities for both as printed/fabricated and UV cured parts, and the ratio of stiffness and strength of UV cured parts to as fabricated parts decreases as the relative density increases. However, the ratio of stiffness and strength of UV cured parts to as fabricated parts for octet lattice structures in general is greater than that for octahedral structures. This can be attributed to the relative diameter of the struts and the depth of UV curing.
Condition Monitoring Technology for Connecting Part and Sliding Part of Reciprocating Compressor
Authors: Mori Yoshifumi , Saito Takashi , Mizobe Yu
Published: January 2018

We focused on vibration characteristics of reciprocating compressors and constructed the mathematical model to calculate the natural frequencies and modes for crank angles and proposed a method to estimate the degree and the suspicious portion of failure by difference of temporal parameter values obtained using measuring data in operation and the mathematical model. In this paper, according to the proposed method, a case study is carried out using the field data, where the data were acquired before and after the failures occurred in the connecting parts of connecting rod, to prospect the difference between each parameter value for two operating states. Inspecting resonant characteristics each in the frequency response data relating to the natural frequencies for bending modes of the piston rod, we determined two resonant frequencies, which could correspond to the 1st and 2nd mode about bending of the piston rod. To equate the calculated each natural frequency from eigen value analysis based on the proposed model with each resonant frequency, we define the error function for the identified problem, namely optimum problem. In the identified results, it is found that some parameter values have much difference and the corresponding failure could occur around the connecting rod. We could show the possibility to detect both the change of the parameter values and the deterioration parts for two different kinds of the operating states by our proposed method.
Parametric Influences on the Nonlinear Dynamic Responses of a Rotor-Bearing-Foundation-Labyrinth Seal System
Authors: Zhang Enjie , Jiao Yinghou , Chen Zhaobo , Mo Wenchao , Wang Shuai
Published: January 2018

The modern engineering industries rely heavily on the reliable operation of rotating machinery, e.g., steam turbine and gas turbine. These rotating machineries are inevitable to be excited by the unbalance mass forces, the oil film forces and seal forces. Moreover, the turbines installed in an aircraft as well as vessel are also excited by the base vibration. In order to retain the healthy operation and prolong the interval between overhauls, an enormous amount of experimental and theoretical investigations have been focused on the dynamic behaviors of the rotor system. The dynamic characteristics of the rotor system influenced by the single source of vibration, such as unbalance, flowing lubricating oil, sealing medium etc., and combined sources of vibration have also been thoroughly researched. However, the dynamic responses of the rotor-bearing-foundation system subjected to labyrinth seal forces have seldom been studied. Furthermore, the previous analyses of the rotor dynamics mostly were linear. In fact, the fluid film forces are strongly nonlinear functions of the displacement and velocity of the rotor. As a result, the rotordynamics of the turbine is highly nonlinear. It is not accurate enough to be considered from a linear point of view. Applying the energy method, this paper established a dynamic model of the rotor-bearing-foundation-labyrinth seal system. The influences of the geometrical parameters and operating conditions, such as mass eccentricities, inlet pressure and rotational speed etc., on the nonlinear dynamic behaviors of the rotor system are numerically studied. The responses of the same system excited by one side of and both sides of base movement are also comparatively analyzed by means of spectrum cascades, bifurcation diagrams and whirl orbits as well as Poincaré maps.
High-Sensitivity MEMS Resonant Biosensor for Monitoring Water Toxicity
Authors: Lee Kun-Lin , Ng Simon , Li Fang , Voiculescu Ioana
Published: January 2018

This paper presents the use of a piezoelectric resonator, which can be applied to investigate live cells activity in water-based toxic solution. We perform toxicity tests using commercial quartz crystal microbalance (QCM). The QCM used in this research has the resonant frequency of 10 MHz and consists in an AT-cut crystal with gold electrodes on both sides. This QCM was transformed into a functional biosensor by integrating with polydimethylsiloxane (PDMS) culturing chambers. Rainbow trout gill epithelial cells (RTgill-W1) were cultured on the resonators as sensorial layer. The fluctuation of the resonant frequency, due to the change of cell morphology and adhesion, is an indicator of water toxicity. The shift of resonant frequency will provide information about the cells viability after exposure to toxicants. Experiment setup, fabrication process, and sensor sensitivity testing are addressed. The toxicity result shows distinct responses for different ammonia concentrations.
Development of Multi-Scale Thermo-Crystal Plasticity Finite Element Method to Analyze Plastic Deformation of Magnesium Alloy
Authors: Kashiwagi Sayuki , Tomita Yoshihiro , Yamaguchi Toshihiko , Yamamoto Koji , Morita Yusuke , Nakamachi Eiji
Published: January 2018

To clarify the deformation induced crystal texture evolution of rolled and drawn magnesium alloy sheets with strong basal texture, we developed a multi-scale finite element (FE) analysis code based on the homogenization theory, which combines the microscopic poly-crystal structure and the macroscopic continuum.

In our crystal plasticity constitutive equation of magnesium alloys, the plastic work induced temperature rise and twinning in the crystal slip systems was implemented into our multi-scale FE analysis code. To validate our numerical code to correctly predict macro and micro deformations including the crystal texture evolution, the tension and compression along normal direction (ND) and rolling direction (RD) at the room temperature 300K and the high temperature 673K were numerically investigated.

It is confirmed that numerical results showed the similar tendency to experimentally obtained results including the strengthening the basal texuture in compression along ND, the twinning, the polarity of twinning and the temperature-dependency that twinning is hardly appear at high temperature. Finaly, we concluded that our numerical code can predict the plastic strain induced texture evolution of magnesium alloys.
Numerical Simulation of Radioactive Material Around Opening-Windows Construction
Authors: Wang Yuyu , Yang Rui , Tao Zhenxiang , Li Cong
Published: January 2018

The diffusion of radioactive material in the atmosphere is vital for environmental assessment. Many researches have focused on the diffusion and deposition outside the construction, whereas less attention was paid on the law of the diffusion from the outside into the room. In this paper, three-dimensional numerical simulation was carried out by using OpenFOAM, an open source software for CFD. The incompressible steady flow around the construction with opening windows was investigated. The influence of inflow wind velocity and windows distribution was considered. The results show that as the inflow wind velocity increases, the diffusion is more significant. The vortexes is related to the windows distribution. When windows are perpendicular to the direction of the inflow wind, the concentration inside the construction is higher than that outside. Besides, the radioactive material gathers in the vicinity of the indoor downstream wall. When windows are parallel to the direction of the inflow wind, the concentration of indoors and outdoors is opposite, and the indoor radioactive material is distributed evenly. This study can provide theoretical support for the emergency evacuation around the construction.
Utilizing the Generic Design Analysis (GDA) Process Model Within an Extended Set of Design Analysis Contexts
Authors: Eriksson Martin , Petersson Håkan , Motte Damien , Bjärnemo Robert
Published: January 2018

In most industrial product development projects, computer-based design analysis, or simply design analysis, is frequently utilized. Several design analysis process models exist in the literature for the planning, execution and follow-up of such design analysis tasks. Most of these process models deal explicitly with design analysis tasks within two specific contexts: the context of design evaluation, and the context of design optimization. There are, however, several more contexts within which design analysis tasks are executed. Originating from industrial practice, four contexts were found to represent a significant part of all design analysis tasks in industry. These are:

1. Explorative analysis, aiming at the determination of important design parameters associated with an existing or predefined design solution (of which design optimization is a part).

2. Evaluation, aiming at giving quantitative information on specific design parameters in support of further design decisions.

3. Physical testing, aiming at validating design analysis models through physical testing, that is, determining the degree to which models are accurate representations of the real world from the perspective of the intended uses of the models.

4. Method development, that is the development, verification and validation of specific guidelines, procedures or templates for the design analyst and/or the engineering designer to follow when performing a design analysis task.

A design analysis process model needs to be able to deal with at least these four. In this work, a process model named the generic design analysis (GDA) process model, is applied to these four contexts. The principles for the adaptation of the GDA process model to different contexts are described. The use of the GDA process model in these contexts is exemplified with industrial cases: explorative analysis of design parameters of a bumper beam system, the final physical acceptance tests of a device transportation system (collision test, drop test, vibration test), and the method development of a template for analyzing a valve in a combustion engine. The “Evaluation” context is not exemplified as it is the most common one in industry.

The GDA process model has been successfully used for the four contexts. Using the adaptation principles and industrial cases, the adaptation of the GDA process model to additional contexts is also possible.
Heat Transfer Performance of a Parabolic Trough Receiver Using SWCNTs-Therminol®VP-1 Nanofluids
Authors: Mwesigye Aggrey , Meyer Josua P.
Published: January 2018

In this paper, the potential for improved thermal performance of a high concentration ratio parabolic trough solar energy system working with high thermal conductivity single-walled carbon nanotubes (SWCNTs) and Therminol®VP-1 nanofluid is numerically investigated. In the numerical analysis, the practical heat flux profiles expected for parabolic trough receivers were obtained using Monte-Carlo ray tracing and coupled with a computational fluid dynamics tool using user defined functions to investigate the thermal performance of the parabolic trough solar energy system. A parabolic trough system with a concentration ratio of 113 was considered in this study and heat transfer fluid inlet temperatures between 400 K and 650 K were used. The volume fraction of SWCNTs in the base fluid was in the range 0% to 2.5% and the flow rates used were in the range 0.82 to 69.41 m3/h. Results show improvements in the convective heat transfer performance and receiver thermal efficiency as well as a considerable reduction of the receiver thermal losses with increasing volume fractions. The heat transfer performance increases up to 64% while the thermal efficiency increases by about 4.4%. Higher increments are observed at low flow rates and inlet temperatures. The receiver thermodynamic performance also increases significantly with the use of nanofluids. Entropy generation rates reduce by about 30% for the range of parameters considered.
Variation Analysis of Accumulative Stresses in Multistep Assembly Processes Using Output Transformation Matrices
Authors: Lin Jia , Jin Sun , Zheng Cheng , Yang Fuyong , Ding Siyi
Published: January 2018

Geometric variation produces gaps or interferences between the mating features of parts when assembling them. To accomplish the operation, forces need to be applied to deform the parts; while as a price, stresses arise around the structure and accumulate as the assembly process proceeds, which could impair the structural reliability. A tool modeling and analyzing the accumulation of assembly stresses can help us predict and control it. Associated with geometric variation, the levels of assembly stresses are variables as well, thus variation analysis of them is required rather than a single case analysis; however, research on assembly variation analysis has focused mainly on the geometric variation itself. In a previous study, we developed a compliant assembly variation analysis method which is based on a Finite Element (FE) model condensation technique of substructuring (Lin J, et al. “Compliant assembly variation analysis of aeronautical panels using unified substructures with consideration of identical parts.” Computer-Aided Design, 2014.). In this paper, by introducing Output Transformation Matrices (OTMs) into the unified substructure system, we add the analysis of assembly stresses onto that of assembly deviations: no extra modeling work is needed, but the assembly stresses within a part are recovered from its assembly deviations by OTMs. Though these OTMs need to be generated in advance, this one-off effort will be relatively small when the assembly process to be analyzed involves multiple steps. A case study on an aeronautical panel assembly is presented to illustrate the proposed method and investigate the characteristics of assembly stresses.
Automotive Premium Quality Improvement by High-End-Visualization
Authors: Striegel Serena , Schleich Benjamin , Zielinski Daniel , Wartzack Sandro
Published: January 2018

Volatile markets, tough customer expectations, and short product life cycles are just some of the challenges the automotive industry has to deal with. In this context, important quality features are expressed as key product characteristics (KPC). The process of defining and reviewing such KPCs concerns each department of an automobile company.

This paper presents a method for an intersubjective problem understanding of inter-divisional working groups and a common product KPC’s definition. The scientific contribution lies in the field of quality assessment for the premium-segment automotive industry, while the novelty can be found in providing the opportunity to take quality decisions based on variation simulations and on high-end-visualizations. The proposed method aims to realize and implement a higher premium quality standard and, at the same time, to reduce the number of physical prototypes, to shorten development times and to facilitate an intersubjective problem understanding. In relation to the developed method, an industrial application and its results are presented.
Finite Element Heat Transfer Analysis of a Cylindrical Body in an Enclosed Volume Subjected to Solar Radiation
Authors: Özçatalbaş Mustafa , Kütükçeken Emre , Acar Bülent
Published: January 2018

In aerospace industry, temperature of structures protected in an enclosed volume that are subjected to solar radiation should be known for critical applications. For instance, temperature of solid rocket engines (SRE) before they are ignited is critical for their operations. Therefore, numerical and experimental methods have been used to determine temperature of the SREs. In this study, a novel methodology, which gives the accurate temperature data of bodies placed in enclosed volumes like SREs in terms of hours instead of performing computational fluid dynamics (CFD) for days, was developed. The study included transient uncoupled heat transfer analysis with finite element (FE) method to predict the temperature distribution on a hollow cylindrical body located in a rectangular prism volume and the FE results were compared with a field test. Hourly solar radiation on a horizontal surface and hourly temperature values were measured by pyranometer to obtain the inputs for FE heat transfer analysis. For the tilted surfaces, solar radiation values were calculated by using the data obtained from pyranometer measurements. Absorptivity of enclosed volume was taken into account to determine the actual heat flow in the areas exposed directly to sunlight. Also, ground properties were selected identical to test condition to represent proper ground reflected radiation. Thermal conductance between the inner surfaces of enclosed volume and outer surfaces of cylindrical body has been defined to enable heat transfer mechanism between two separate components. In consequence of having accurate thermal conduction interactions between the inner surfaces of the FE model, CFD calculations of natural convection which was taken place inside the enclosed volume was eliminated. When the FE analysis-test comparison was concluded, it was observed that the calculated temperature values were found to be close agreement with measured temperatures and maximum error was within 10%. Furthermore, computation time was significantly reduced.
Analytical Prediction of Heat Transfer in Tape Generated Swirl Flow
Authors: Yadav R. J. , Kore Sandeep , Riabhole V. N.
Published: January 2018

Heat transfer and pressure drop characteristics in a circular tube with twisted tapes have been investigated experimentally and numerically using different working fluids by many researchers for wide range of Reynolds number. The swirl was generated by tape inserts of various twist ratios. The various twist ratios are considered Many researchers formed generalized correlations to predict friction factors and convective heat transfer coefficients with twisted tapes in a tube for a wide range of Reynolds numbers and Prandtl numbers. Satisfactory agreement was obtained between the present correlations and the data of others validate the proposed correlations. The experimental or numerical predictions were compared with earlier correlations revealing good agreement between them. From the literature review it is observed that most studies are mainly focused on the heat transfer enhancement using twisted tape by experimental or numerical solution. An investigation with analytical approach is rarely reported. Therefore, the main aim of the present work is to form a correlation from theoretical approach for Nusselt number for circular tube with twisted tape. Application of dimensional analysis to heat transfer in tape generated swirl flow is carried out.
Evaluation of Ride Comfort in a Railway Passenger Vehicle With Integrated Vehicle and Human Body Bond Graph Model
Authors: Pradhan Smitirupa , Samantaray Arun Kumar , Bhattarcharyya Ranjan
Published: January 2018

Ride comfort is the level of comfort sensed by the passengers when they are continuously exposed to the vibration and noise. To diminish the vibration level, air springs are used in the secondary suspension system instead of coil springs, especially in the modern railway vehicles. This article focuses on the modeling of Nishimura air spring with non-linear damper and human biodynamic (bio-mechanical) model by using multi-energy domain modeling approach, bond graph. The car body of the railway vehicle is treated as a beam and the first five modes including three flexible modes are considered in the model. We use International Organization for Standardization 2631 for evaluating ride comfort for different durations of the travel time (1 h, 2.5 h, 4 h and 8 h) on flexible and irregular tracks.
Numerical and Experimental Aerodynamic Evaluation of a Solar Vehicle
Authors: De Kock J. P. , Laubscher R. F. , Kruger Sunita , Janse van Rensburg N.
Published: January 2018

Solar car racing has created a competitive platform for research into alternative energy solutions and aids development in the green engineering space. The University of Johannesburg’s Solar Racing team developed a vehicle (Ilanga II) to compete in the 2014 South African Solar Car Challenge. This paper describes the numerical optimization of the vehicle’s body shape, utilizing Computational Fluid Dynamics (CFD) and finally compares the simulated results with the actual performance during the race. Motor control data is used to determine the aerodynamic drag coefficient of the vehicle. This work builds on the paper submitted in 2014 [1], which postulated the use of the Hermite cubic function in conjunction with the shape function analysis as a holistic design tool. By analyzing the motor control data it is possible to comment on the effectiveness of the shape function analysis technique. The final optimized design predicted a straight-line ACd 0.078. A yaw angle characterization study of ±25° degrees, in conjunction with historic weather data were used to fully characterize the vehicle with an average drag area coefficient of 0.119. The final comparative results of the simulated data and the race data show that the vehicle’s straight-line (Zero yaw) ACd was 11.2% higher than the simulated results, whereas the average aerodynamic characteristic ACd was 2.43% lower than the simulated results.
Process Parameter Optimization of Friction Crush Welding (FCW) of AISI 304 Stainless Steel
Authors: Brar Gurinder Singh , Singh Manpreet , Jamwal Ajay Singh
Published: January 2018

AISI 304 stainless steel is one of the grades of steel widely used in engineering applications particularly in chemical equipments, food processing, pressure vessels and paper industry. Friction crush welding (FCW) is type of friction welding, where there is a relative motion between the tool and work-piece. In FCW process, the edges of the work-piece to be joined are prepared with flanged edges and then placed against each other. A non-consumable friction disc tool will transverse with a constant feed rate along the edges of the work-piece, which leads to welding. The joint is formed by the action of crushing a certain amount of additional flanged material into the gap formed by the contacting material. The novelty of present work is that FCW removes the limitations of friction stir welding and Steel work pieces can be economically welded by FCW. Taguchi method of Design of Experiments (DOE) is used to find optimal process parameters of Friction Crush Welding (FCW). A L9 Orthogonal Array, Signal to Noise ratio (S/N) and Analysis of Variance are applied to analyze the effect of welding parameters (welding speed, RPM, tool profile) on the weld properties like bond strength. Grain refinement takes place in friction crush welding as is seen in friction stir welding. Friction crush welding process also has added advantage in reducing distortion and residual stresses.