bluuebunny/crossref_metadata_2025 huggingface dataset:
Sources of Particulate Matter Emissions Variability From a Gasoline Direct Injection Engine
Authors: Ramos Manuel J. M. G. , Wallace James S.
Published: July 2018

Particulate matter (PM) emissions from gasoline direct injection (GDI) engines are a concern due to the health effects associated with ultrafine PM. This experimental study investigated sources of PM emissions measurement variability observed in previous tests and also examined the effect of ethanol content in gasoline on PM emissions. Some engine operating parameters (fuel and oil temperature, positive crankcase ventilation filtration) and test conditions (dilution air conditions) were studied and controlled but could not account for the level of measurement variability observed. Fourier transform infrared spectrometry (FTIR) measurements of gas phase hydrocarbon emissions provided evidence that changes in fuel composition were responsible for the variability. Exhaust emissions of toluene and ethanol were correlated positively with PM emissions, while emissions of isobutylene correlated negatively. Exhaust emissions of toluene and isobutylene were interpreted as markers of gasoline aromatic content and gasoline volatility, respectively. Tests conducted with gasoline containing added toluene (10% v/v) supported this hypothesis and led to the overall conclusion that the PM emissions variability observed can be attributed to changes in the composition of the pump gasoline being used. Tests conducted with gasoline containing added ethanol (10% and 30% v/v) found that increasing ethanol fuel content increased PM emissions at the steady-state operating condition utilized.
Denoising Weighting Beamforming Method Applied to Sound Source Localization With Airflow Using Microphone Array
Authors: Xu Zhongming , Tian Kai , He Yansong , Zhang Zhifei , Li Shu
Published: July 2018

Conventional frequency domain beamforming (FDBF) relies on the measured cross-spectral matrix (CSM). However, in wind tunnel tests, the CSM diagonal is contaminated by the interference of incoherent noise after long-time averaging which leads the source map to poor resolution. Diagonal removal (DR) can suppress the noise in beamforming results via the deletion of CSM diagonal, but this method leads to the underestimation of source levels and some negative powers in source maps. Some advanced methods, such as background subtraction, make use of background noise reference to counteract the effects of contamination; however, the results usually become unreliable, because the background noise is difficult to keep constant in different measurements. Diagonal denoising (DD) beamforming is a recent approach to suppress the contamination effects, but it attenuates the noise suppression performance. To overcome the limitations of the above methods, a new method called denoising weighting beamforming (DWB) is proposed in this study on the basis of CSM DD and an iterative regularization method is applied to solve the acoustical inverse problem. Besides, in order to correct the phase mismatch caused by the influence of flow on sound propagation, the shear flow correction is added before using DWB. Experiments on sound source reconstruction are conducted in the environment with the flow. Acoustics data obtained via this method show the successful removal of incoherent noise and the corrected phase mismatch. Furthermore, the sound source localization results are promising and the proposed method is simple to implement.
Approximate Floquet Analysis of Parametrically Excited Multi-Degree-of-Freedom Systems With Application to Wind Turbines
Authors: Acar Gizem D. , Feeny Brian F.
Published: July 2018

General responses of multi-degrees-of-freedom (MDOF) systems with parametric stiffness are studied. A Floquet-type solution, which is a product between an exponential part and a periodic part, is assumed, and applying harmonic balance, an eigenvalue problem is found. Solving the eigenvalue problem, frequency content of the solution and response to arbitrary initial conditions are determined. Using the eigenvalues and the eigenvectors, the system response is written in terms of “Floquet modes,” which are nonsynchronous, contrary to linear modes. Studying the eigenvalues (i.e., characteristic exponents), stability of the solution is investigated. The approach is applied to MDOF systems, including an example of a three-blade wind turbine, where the equations of motion have parametric stiffness terms due to gravity. The analytical solutions are also compared to numerical simulations for verification.
Active Phase Change Material Cold Storage in Off-Grid Telecommunication Base Stations: Potential Assessment of Primary Energy Savings
Authors: Studniorz Alexander , Wolf Daniel , Christidis Andreas , Tsatsaronis George
Published: July 2018

The global demand for wireless, mobile communication, and data services has grown significantly in the recent years. Consequently, electrical energy consumption to provide these services has increased. The principal contributors to this electricity demand are approximately 7 million telecommunication base stations (TBS) worldwide. They act as access points for mobile networks and have typical electrical loads of 2–3 kW. Whereas for most of the TBS, the electricity is supplied by the grid, approximately 15% are located in remote areas or regions with poor grid accessibility, where diesel generators (DG) supply the required electricity. Based on a dynamic simulation model the application of a latent heat storage (LHS) using phase change material (PCM) in existing off-grid TBS has been analyzed. The LHS unit has been modeled as an air-based storage with phase change temperatures between 20 °C and 30 °C with the PCM being macro-encapsulated in slabs. This paper demonstrates the potential to reduce the primary energy consumption in off-grid TBS through the following methods: optimization of the DG operating point, of the air conditioning unit operation schedule and the utilization of photovoltaic (PV) energy.
Equilibrium and Kinetics of Water Vapor Adsorption on Shale
Authors: Duan Shuo , Li Guodong
Published: July 2018

Water vapor adsorption and desorption isotherms and kinetics studies on three Sichuan Basin shale samples were performed at 298 K by an accurate gravimetric method. The adsorption equilibrium data were fitted using both Dent model and Modified Dent model to estimate the adsorption characteristic of water on the primary and secondary sites. The primary site adsorption is restricted to a monolayer while the secondary site adsorption is associated with multilayer sorption. A positive correlation was found between clay mineral content and monolayer sorption content. The isosteric heats of sorption of water were determined from the equilibrium data and they decreased with the increase of adsorption amount. The adsorption/desorption hysteresis were studied with the pore structure. The kinetics of water vapor adsorption was studied with the unipore model and linear driving force mass transfer (LDF) model. The effective diffusivity and kinetic rate constant varied with the increase of relative pressure, which suggested diffusion of water vapor on shale corresponding to a combination of adsorption on primary sites, adsorption on secondary sites, formation of water clusters, and capillary condensation.
Decline Curve Analysis of Fractured Horizontal Wells Through Segmented Fracture Model
Authors: Qin Jiazheng , Cheng Shiqing , He Youwei , Wang Yang , Feng Dong , Yang Zhonglin , Li Dingyi , Yu Haiyang
Published: July 2018

Nowadays, production performance evaluation of a multifractured horizontal well (MFHW) has attracted great attention. This paper presents a mathematical model of an MFHW with considering segmented fracture (SF) for better evaluation of fracture and reservoir properties. Each SF consists of two parts: fracture segment far from wellbore (FSFW) and fracture segment near to wellbore (FSNW) in segmented fracture model (SFM), which is different from fractures consists of only one segment in common fracture model (CFM). Employing the source function and Green's function, Newman's product method, Duhamel principle, Stehfest inversion algorithm, and Laplace transform, production solution of an MFHW can be obtained using SFM. Total production rate is mostly contributed from FSNW rather than FSFW in many cases; ignoring this phenomenon may lead to obvious erroneous in parameter interpretation. Thus, clear distinctions can be found between CFM and SFM on the compound type curves. By using decline curve analysis (DCA), the influences of sensitive parameters (e.g., dimensionless half-length, dimensionless production rate, conductivity, and distance between SF) on compound type curves are analyzed. The results of sensitivity analysis are benefit of parameter estimation during history matching.
Optimization of Damping Properties of Staggered Composites Through Microstructure Design
Authors: Liu Junjie , Hai Xusheng , Zhu Wenqing , Wei Xiaoding
Published: July 2018

Many natural materials, such as shell and bone, exhibit extraordinary damping properties under dynamic outside excitations. To explore the underlying mechanism of these excellent performances, we carry out the shear-lag analysis on the unit cell in staggered composites. Accordingly, the viscoelastic properties of the composites, including the loss modulus, storage modulus, and loss factor, are derived. The damping properties (particularly, the loss modulus and loss factor) show an optimization with respect to the constituents' properties and morphology. The optimal scheme demands a proper selection of four key factors: the modulus ratio, the characteristic frequency of matrix, aspect ratios of tablets, and matrix. The optimal loss modulus is pointed out to saturate to an upper bound that is proportional to the elastic modulus of tablets when the viscosity of matrix increases. Furthermore, a loss factor even greater than one is achievable through microstructure design. Without the assumption of a uniform shear stress distribution in the matrix, the analysis and formulae reported herein are applicable for a wide range of reinforcement aspect ratios. Further, for low-frequency loading, we give practical formulae of the three indexes of damping properties. The model is verified by finite element analysis (FEA) and gives novel ideas for manufacturing high damping composites.
Stress Concentration in Low-Porosity Periodic Tessellations With Generic Patterns of Elliptical Holes Under Biaxial Strain
Authors: Leng Jiazhen , Reynolds Gerard , Schaenzer Megan , Pham Minh Quan , Bourgeois Genevieve , Shanian Ali , Pasini Damiano
Published: July 2018

Stress concentration in porous materials is one of the most crucial culprits of mechanical failure. This paper focuses on planar porous materials with porosity less than 5%. We present a stress-prediction model of an arbitrarily rotated elliptical hole in a rhombus shaped representative volume element (RVE) that can represent a class of generic planar tessellations, including rectangular, triangular, hexagonal, Kagome, and other patterns. The theoretical model allows the determination of peak stress and distribution of stress generated near the edge of elliptical holes for any arbitrary tiling under displacement loading and periodic boundary conditions. The results show that the alignment of the void with the principal directions minimizes stress concentration. Numerical simulations support the theoretical findings and suggest the observations remain valid for porosity as large as 5%. This work provides a fundamental understanding of stress concentration in low-porosity planar materials with insight that not only complements classical theories on the subject but also provides a practical reference for material design in mechanical, aerospace, and other industry.
An Experimental Study of Fracture Toughness for Nano/Ultrafine Grained Al5052/Cu Multilayered Composite Processed by Accumulative Roll Bonding
Authors: Rahmatabadi D. , Mohammadi B. , Hashemi R. , Shojaee T.
Published: July 2018

In this study, ultrafine grained Al5052/Cu multilayered composite has been produced by accumulative roll bonding (ARB) and fracture properties have been studied using plane stress fracture toughness. The fracture toughness has been investigated for the unprocessed specimens, primary sandwich and first, second, and third cycles of ARB process by ASTM E561 and compact tension (CT) specimens. Also, the microstructure and mechanical properties have been investigated using optical microscopy, scanning electron microscopy, uniaxial tensile tests, and microhardness measurements. The value of plane stress fracture toughness for the ultrafine grained Al5052/Cu composite increased by increasing the number of ARB cycles, continuously from the primary sandwich to end of the third cycle. The maximum value of 59.1 MPa m1/2 has been obtained that it is about 2.77 and 4.05 more than Al5052 and pure Cu (unprocessed specimens). This phenomenon indicated that ARB process and the addition of copper to aluminum alloy could increase the value of fracture toughness to more than three times. The results showed that by increasing the ARB cycles, the thickness of copper layers reduced and after the fifth cycle, the excellent uniformity of Cu layers achieved. By increasing the number of ARB cycles, the microhardness of both aluminum and copper layers have been significantly increased. The tensile strength of the sandwich has been enhanced continually, and the maximum value of 566.5 MPa has been achieved.
Uncertainty and Disturbance Estimator-Based Backstepping Control for Nonlinear Systems With Mismatched Uncertainties and Disturbances
Authors: Dai Jiguo , Ren Beibei , Zhong Qing-Chang
Published: July 2018

This paper proposes an uncertainty and disturbance estimator (UDE)-based controller for nonlinear systems with mismatched uncertainties and disturbances, integrating the UDE-based control and the conventional backstepping scheme. The adoption of the backstepping scheme helps to relax the structural constraint of the UDE-based control. Moreover, the reference model design in the UDE-based control offers a solution to address the “complexity explosion” problem of the backstepping approach. Furthermore, the strict-feedback form condition in the conventional backstepping approach is also relaxed by using the UDE-based control to estimate and compensate “disturbance-like” terms including nonstrict-feedback terms and intermediate system errors. The uniformly ultimate boundedness of the closed-loop system is analyzed. Both numerical and experimental studies are provided.
A Constitutive Model Fitting Methodology for Ductile Metals Using Cold Upsetting Tests and Numeric Optimization Techniques
Authors: Hartlen Devon C. , Doman Darrel A.
Published: July 2018

This work documents the development of a tool to perform automated parameter fitting of constitutive material models. Specific to this work is the fitting of a Swift hardening rule and isotropic linear plasticity model to aluminum 2024-T351, C36000 brass, and C10100 copper. Material characterization was conducted through the use of compressive, cold upsetting tests. A noncontact, optical displacement measurement system was applied to measure the axial and radial deformation of the test specimens. Nonlinear optimization techniques were then applied to tune a finite element model to match experimental results through the optimization of material model parameters as well as frictional coefficient. The result is a system, which can determine constitutive model parameters rapidly and without user interaction. While this tool provided material parameters for each material and model tested, the quality of the fit varied depending on how appropriate the constitutive model was to the material's actual plastic behavior. Aluminum's behavior proved to be an excellent match to the Swift hardening rule while the behavior of brass and copper was described better by the linear plasticity model.
Investigation of Mechanical Properties of Mono- and Multi-layer Alumina and Ceria Films Using Finite Element Modeling and Nanoindentation Experiments
Authors: Cherneva Sabina , Guergova Desislava , Iankov Roumen , Stoychev Dimitar
Published: July 2018

Important from exploitation point of view mechanical properties of single-layer, double-layer, and mixed alumina and ceria films and their stainless steel (SS) substrate were investigated by means of nanoindentation experiments. As a result, we obtained the experimental load–displacement curves and calculated the indentation hardness (HIT) and indentation modulus (EIT), by means of Oliver and Pharr approximation method. Numerical simulations of the process of nanoindentation by means of finite element method were performed as well, in order to obtain more information about the plastic properties of the investigated films. The obtained results show that the mixed Al2O3+Ce2O3 film, obtained at dominant concentration of cerium ions in the working electrolyte, has the highest indentation hardness and modulus, followed by the single Ce2O3-CeO2 film, the mixed Al2O3+Ce2O3 film, obtained at dominant concentration of aluminum ions in the working electrolyte, the double Ce2O3-CeO2/Al2O3 layer, and single Al2O3 layer.
Analysis and Inversion of Contact Stress for the Finite Thickness Neo-Hookean Layer
Authors: Yang Heng , Yao Xue-Feng , Wang Shen , Ke Yu-Chao , Huang Sheng-Hao , Liu Ying-Hua
Published: July 2018

In this paper, the theoretical analysis and the inversion of the contact stress on the finite thickness rubber contact surface with the friction effect are investigated. First, an explicit expression of deformation and stress on the surface of rubber under a rigid spherical indenter is developed by means of theoretical model, dimensional analysis, and nonlinear finite element simulation. Second, the inverse approach for obtaining the contact stress on the finite thickness rubber contact surface is presented and verified theoretically. Also, the displacement, the stress field, and the friction coefficient are obtained by means of three-dimensional digital image correlation (3D DIC) method. Finally, the applicability to other hyperelastic models, general boundary conditions, and loading modes are discussed. The results will provide an important theoretical and experimental basis for evaluating the contact stress on the finite thickness rubber layer.
Distribution of Brain Strain in the Cerebrum for Laboratory Impacts to Ice Hockey Goaltender Masks
Authors: Michio Clark J. , Post Andrew , Blaine Hoshizaki T. , Gilchrist Michael D.
Published: July 2018

Concussions are among the most common injuries sustained by goaltenders. Concussive injuries are characterized by impairment to neurological function which can affect many different brain regions. Understanding how different impact loading conditions (event type and impact site) affect the brain tissue response may help identify what kind of impacts create a high risk of injury to specific brain regions. The purpose of this study was to examine the influence of different impact conditions on the distribution of brain strain for ice hockey goaltender impacts. An instrumented headform was fitted with an ice hockey goaltender mask and impacted under a protocol which was developed using video analysis of real world ice hockey goaltender concussions for three different impact events (collision, puck, and fall). The resulting kinematic response served as input into the University College Dublin Brain Trauma Model (UCDBTM), which calculated maximum principal strain (MPS) in the cerebrum. Strain subsets were then determined and analyzed. Resulting peak strains (0.124–0.328) were found to be within the range for concussion reported in the literature. The results demonstrated that falls and collisions produced larger strain subsets in the cerebrum than puck impacts which is likely a reflection of longer impact duration for falls and collisions than puck impacts. For each impact event, impact site was also found to produce strain subsets of varying size and configuration. The results of this study suggest that the location and number of brain regions which can be damaged depend on the loading conditions of the impact.
Diffusive Phonons in Nongray Nanostructures
Authors: Romano Giuseppe , Kolpak Alexie M.
Published: July 2018

Nanostructured semiconducting materials are promising candidates for thermoelectrics (TEs) due to their potential to suppress phonon transport while preserving electrical properties. Modeling phonon-boundary scattering in complex geometries is crucial for predicting materials with high conversion efficiency. However, the simultaneous presence of ballistic and diffusive phonons challenges the development of models that are both accurate and computationally tractable. Using the recently developed first-principles Boltzmann transport equation (BTE) approach, we investigate diffusive phonons in nanomaterials with wide mean-free-path (MFP) distributions. First, we derive the short MFP limit of the suppression function, showing that it does not necessarily recover the value predicted by standard diffusive transport, challenging previous assumptions. Second, we identify a Robin type boundary condition describing diffuse surfaces within Fourier's law, extending the validity of diffusive heat transport in terms of Knudsen numbers. Finally, we use this result to develop a hybrid Fourier/BTE approach to model realistic materials, obtaining good agreement with experiments. These results provide insight on thermal transport in materials that are within experimental reach and open opportunities for large-scale screening of nanostructured TE materials.
Analytical Topography Simulation of Micro/Nano Textures Generated on Freeform Surfaces in Double-Frequency Elliptical Vibration Cutting Based Diamond Turning
Authors: Zuo Chengming , Zhou Xiaoqin , Liu Qiang , Wang Rongqi , Lin Jieqiong , Xu Pengzi , Zhang Xu
Published: July 2018

The surfaces with textures have been widely used as functional surfaces, and the textures are usually generated on flat or cylindrical surfaces. Textured freeform surfaces will have more potential applications. The authors have proposed the double-frequency elliptical vibration cutting (DFEVC) method to machine freeform surfaces on steel materials. Based on this method, a new diamond turning method is developed, in which the variable-frequency modulations are utilized to control the tool marks left on the machined surface to generate the micro/nano dimple textures with high uniformity on the freeform surface. Different from the conventional surface topography model based on the ideal tool cutting edge with zero cutting edge radius, a new modeling approach based on the tool surface profiles is proposed, in which the rake face, the flank face, and the cutting edge surface with actual non-zero cutting edge radius instead of the ideal cutting edge are included for the tool model, the tool surfaces during the machining process are analytically described as a function of the tool geometry and the machining parameters, and the influences of the tool surface profiles on the topography generation of the machined surface are considered. A typical freeform surface is textured on die steel, and the measured results verify the feasibility of the proposed turning method. Compared with the topography prediction results based on the ideal cutting edge, the results considering the tool surfaces show improved simulation accuracy, and are consistent with the experimental results, which validates the proposed topography prediction approach.
Phenomenological Study of Multivariable Effects on Exit Burr Criteria During Orthogonal Cutting of AlSi Alloys Using Principal Components Analysis
Authors: Régnier Tristan , Fromentin Guillaume , D'Acunto Alain , Outeiro José , Marcon Bertrand , Crolet Arnaud
Published: July 2018

During machining, burrs are produced along a part's edges, which can affect a final product lifetime or its efficiency. Moreover, time-consuming and expensive techniques are needed to be applied to remove such burrs. Therefore, companies attempt to reduce burrs formation during machining by manipulating the cutting conditions. This study aims to analyze and quantify the effect of a wide number of parameters on burr formation, resulting from different mechanisms, during orthogonal cutting of AlSi alloys. A highly developed experimental methodology combining high-speed camera recording, laser scanning, and in situ deburring system is used for this study. A statistical analysis is then applied to evaluate relations between controlled parameters and the occurrence of exit burrs morphologies. The results show that the uncut chip thickness influences burr types distribution along the exit edge and chamfer geometry. Among the cutting parameters and tool geometry, tool rake angle is the main parameter affecting burr height. Finally, it is found that none of the burrs geometrical characteristics ranges are piloted by cutting parameters or tool geometry. The assumption of a possible microstructural influence on these outputs is made.
Experimental Study on the Associations Among Sketches Based on Design Cognition
Authors: Yuan Ping , Li Yan , Chen Jian , Xiong Yan , Liu Longfan
Published: July 2018

This study aimed to investigate the generation mechanism of pairwise associated sketches and different associated types through the experimental analysis of the cognitive processes of the designers in conceptual design process. The verbal protocol analysis (VPA) was carried out on three groups of participants (designers). The first group consisted of eight university students majoring in industrial design, the second consisted of eight university students majoring in mechanical design, and the third consisted of six product designers with degrees in industrial design and over 5 years of work experience. Their cognitive processes revealed by the think-aloud protocol and outcome sketches during a specific design task were recorded. Following a content-oriented encoding scheme, the verbal data were encoded into cognitive actions, and according to the generation sequence of the sketches, the encoding results were postprocessed for the further analysis of associated sketches. First, we identified which cognitive actions played important roles in the generation of associated sketches. Next, based on the encoding results and the analyses of all associated sketches, we found that all associations can be categorized into three types (in order from low to high association levels): shape association, behavior association, and function association. Finally, we found that the differences in major background had no significant effect on the number of associated sketches but did have some influence on the diversity of association types, the differences in experience background mainly influenced the number of associated sketches in each type of association. Meanwhile, by analyzing the key cognitive actions, we also found the advantages and disadvantages of each group in the generation of different types of associations. The findings of this study can help designers with different backgrounds to choose suitable strategies to stimulate the important actions at the right time, conceive appropriate association types, and ultimately generate diverse concept sketches with high quality.
A Versatile 3R Pseudo-Rigid-Body Model for Initially Curved and Straight Compliant Beams of Uniform Cross Section
Authors: Venkiteswaran Venkatasubramanian Kalpathy , Su Hai-Jun
Published: July 2018

Rigid-body discretization of continuum elements was developed as a method for simplifying the kinematics of otherwise complex systems. Recent work on pseudo-rigid-body (PRB) models for compliant mechanisms has opened up the possibility of using similar concepts for synthesis and design, while incorporating various types of flexible elements within the same framework. In this paper, an idea for combining initially curved and straight beams within planar compliant mechanisms is developed to create a set of equations that can be used to analyze various designs and topologies. A PRB model with three revolute joints is derived to approximate the behavior of initially curved compliant beams, while treating straight beams as a special case (zero curvature). The optimized model parameter values are tabled for a range of arc angles. The general kinematic and static equations for a single-loop mechanism are shown, with an example to illustrate accuracy for shape and displacement . Finally, this framework is used for the design of a compliant constant force mechanism to illustrate its application, and comparisons with finite element analysis (FEA) are provided for validation.
The Hexapodopter: A Hybrid Flying Hexapod—Holonomic Flying Analysis
Authors: Soto-Guerrero Daniel , Ramírez-Torres José Gabriel
Published: July 2018

This document introduces the holonomic flying capabilities of the Hexapodopter, a six-legged walking machine capable of vertical take-off and landing. For ground locomotion, each limb has two degrees-of-freedom (2DoF); while the thrust required for flying is provided by six motors mounted close to every knee, so the thrust vector can be reoriented depending on the configuration of each limb. The capacity of reorienting the thrust forces makes the Hexapodopter a true holonomic vehicle, capable of individually controlling its six degrees-of-freedom (6DoF) on the air without reorienting any of the thrust motors nor the body. The main design criteria and validation will be discussed on this paper, as well as a control law for the vehicle.
Modular Manipulators for Cluttered Environments: A Task-Based Configuration Design Approach
Authors: Singh Satwinder , Singla Ashish , Singla Ekta
Published: July 2018

Modular manipulators gained popularity for their implicit feature of “reconfigurability”—that is, the ability to serve multiple applications by adopting different configurations. As reported in the literature, most of the robotic arms with modular architecture used specific values of twist angles, e.g., 0 deg or 90 deg. Further, the number of degrees-of-freedom (DoF) is also kept fixed. These constraints on the design parameters lead to a smaller solution space for the configuration synthesis problems and may result as no-feasible solution in a cluttered work-cell. To work in a realistic environment, the task-based customized design of a manipulator may need a larger solution space. This work deals with the extension of the modular architecture from conventional values to unconventional values of design parameters, keeping the degrees-of-freedom also as variable. This results into an effective utilization of modular designs for highly cluttered environments. A three-phase design strategy is proposed in the current work. The design strategy starts with the decision of optimal number of modules required for the given environment in the first phase, which is followed by task-based “configuration planning” and “optimal assembly” in the second and third phase, respectively. Three types of modules are proposed with same architecture and different sizes—heavy (H), medium (M), and light (L). The configuration planning includes detailed discussion on the type-selection of the modules and their possible combinations. Comparison of all possible n-link combinations is analyzed based upon the optimized results with respect to the minimum torque values. Case studies of a power plant with two different workspaces are included to illustrate the three-phase strategy representing the importance of modularity in nonrepetitive maintenance tasks.
A Three-Dimensional Printed, Nonassembly, Passive Dynamic Walking Toy: Design and Analysis
Authors: Treviño Christian L. , Galloway Joseph D. , Bhounsule Pranav A.
Published: July 2018

In this paper, we present the redesign and analysis of a century old walking toy. Historically, the toy is made up of two wooden pieces including a rear leg and a front leg and body (as a single piece) that are attached to each other by means of a pin joint. When the toy is placed on a ramp and given a slight perturbation, it ambles downhill powered only by gravity. Before the toy can walk successfully, it needs careful tuning of its geometry and mass distribution. The traditional technique of manual wood carving offers very limited flexibility to tune the mass distribution and geometry. We have re-engineered the toy to be three-dimensional (3D) printed as a single integrated assembly that includes a pin joint and the two legs. After 3D printing, we have to manually break-off the weakly held support material to allow movement of the pin joint. It took us 6 iterations to progressively tune the leg geometry, mass distribution, and hinge joint tolerances to create our most successful working prototype. The final 3D printed toy needs minimal postprocessing and walks reliably on a 7.87 deg downhill ramp. Next, we created a computer model of the toy to explain its motion and stability. Parameter studies reveal that the toy exhibits stable walking motion for a fairly wide range of mass distributions. Although 3D printing has been used to create nonassembly articulated kinematic mechanisms, this is the first study that shows that it is possible to create dynamics-based nonassembly mechanisms such as walking toys.
Novel Miniature Tip Design for Enhancing Dexterity in Minimally Invasive Surgery
Authors: Sakes Aimée , Ali Awaz , Janjic Jovana , Breedveld Paul
Published: July 2018

Even though technological advances have increased the application area of minimally invasive surgery (MIS), there are still hurdles to allow for widespread adoption for more complex procedures. The development of steerable instruments, in which the surgeon can alter the tip orientation, has increased the application area of MIS, but they are bulky, which limits their ability to navigate through narrow environments, and complex, which complicates miniaturization. Furthermore, they do not allow for navigating through complex anatomies. In an effort to improve the dexterity of the MIS instruments, while minimizing the outer dimensions, the previously developed cable-ring mechanism was redesigned, resulting in the thinnest, Ø 2 mm (Ø 1 mm lumen), eight degrees-of-freedom (DOF) multisteerable tip for MIS to date. The multisteerable tip consists of four steerable segments of 2DOF stackable elements allowing for ±90 deg articulation, as well the construction of complex shapes, actuated by 16 Ø 0.2 mm stainless steel cables. In a proof-of-principle experiment, an ultrasound transducer and optical shape sensing (OSS) fiber were inserted in the lumen, and the multisteerable tip was used to perform scanning motions in order to reconstruct a wire frame in three-dimensional (3D). This configuration could in future be used to safely navigate through delicate environments and allow for tissue characterization. Therefore, the multisteerable tip has the potential to increase the application area of MIS in future, as it allows for improved dexterity, the ability to guide several tip tools toward the operation area, and the ability to navigate through tight anatomies.
Analysis
of Passive Temperature Control Systems Using Phase Change Materials for Application to Secondary
Batteries Cooling
Authors: Bubbico Roberto , D'Annibale Francesco , Mazzarotta Barbara , Menale Carla
Published: July 2018

Temperature control is one of the most significant factors to improve the performance and extend the cycle life of a battery. It is, therefore, important to design and implement an effective battery thermal management system (TMS). Phase change materials (PCMs) can be used as a cooling means for batteries. In the present paper, a preliminary analysis of the thermal behavior of PCMs used to cool down a heated metal surface was carried out. Tests have shown that pure PCMs are able to limit the temperature increase, but only for relatively low-heat fluxes. At higher values of the heat produced, the thermal conductivity of the PCM was increased by using solid foams characterized by higher thermal conductivity; it was, thus, possible to keep the surface temperature within safe limits for longer times. A computational fluid dynamics (CFD) model of the composite material (PCM + solid foam) was also developed, which allowed to predict the temperature trend within the system under different boundary conditions. However, the average thermal conductivity of the composite system that best fitted the experimental results was found to be much lower than that theoretically predicted by using common semiempirical correlations.
Bridging Length Scales in the Analysis of Transient Tests for Metallic Materials
Authors: Gokhale Aditya , Hariharan Krishnaswamy , Jain Jayant , Prasad Rajesh , Han Heung Nam
Published: July 2018

The transient data obtained during stress relaxation test of polycrystalline materials has broader implications. The test is influenced by the material length scale. Efforts to mathematically bridge data at different length scales is scarce. In the present work, it is attempted to modify a recently proposed stress relaxation model with additional coefficients to accommodate the mechanical behavior at different length scales. The macroscale stress relaxation test was performed using a tensile testing machine, whereas the micro- and nanoscale specimens were tested using indentation technique. Assuming power law rate behavior, a scaling relation is derived initially to correlate the indentation pressure and flow stress.
Comparisons of Shear Stress Transport and Detached Eddy Simulations of the Flow Around Trains
Authors: Li Tian , Hemida Hassan , Zhang Jiye , Rashidi Mohammad , Flynn Dominic
Published: July 2018

Shear stress transport (SST) k–ω model and detached eddy simulation (DES) have been widely applied in crosswind stability simulations for trains in the literature. In the previous research, the influence of the SST and DES approaches on the flow field around trains, which affects the surface pressure and consequently the aerodynamic forces of the train, was not properly investigated in terms of their influence flow field. The SST and improved delayed detached eddy simulation (IDDES) turbulence models have been tested in this study for their ability to predict the flow field around, surface pressure, and aerodynamic forces on a 1/25th scale Class 390 train subjected to crosswinds. Numerical simulation results were validated with experimental data. Results show that both SST and IDDES predict similar trends in the mean flow field around the train. However, there were some slight differences observed in the size of vortices, the position of separation points, and consequently, the separation and attachment lines. The SST results compared more closely to the experimental data than IDDES for pressure coefficient on the leeward surface and roof at certain loops. Slight differences were observed in force coefficients for SST and DES. The side force coefficients calculated using computational fluid dynamics (CFD) sit within the experimental uncertainty, whereas the lift force coefficients deviated greatly due to the omission of some underbody geometrical features. Both SST and IDDES approaches used the linear-upwind stabilized transport (LUST) scheme and were able to predict accurately the time-averaged surface pressure within the margin of the experimental uncertainty.
Active Control of Longitudinal Vibration of a Time-Varying Shafting System With a Dynamic Interpolating Adaptive Method
Authors: Zheng Hongbo , Hu Fang , Qin Hui , Zhang Zhiyi
Published: July 2018

An adaptive control method with dynamic interpolation is proposed for the active longitudinal vibration control of propulsion shafting systems. In such systems, the dynamics of longitudinal vibration change with the speed-dependent stiffness, which can result in a time-varying system as the shaft speed changes with time. A longitudinal vibration model is established for the investigation of the dynamic interpolating adaptive method (DIAM). In this model, the longitudinal vibration is induced by the disturbance exerted on the propeller (the left mass) and the control force is exerted on the thrust bearing (the right mass), which defines the disturbance channel and the control channel. The proposed DIAM is used to suppress longitudinal vibration transmission from the propeller to the thrust bearing by applying an active force on the right mass. The interpolation technique in DIAM updates the parameter-dependent compensator dynamically and eliminates the influence of parameter-dependent dynamics on the stability of control. Simulation results have demonstrated that the proposed DIAM is effective in suppressing longitudinal vibration of the thrust bearing in comparison to conventional adaptive methods.
Performance Analysis of a Centrifugal Compressor Based on Circumferential Flow Distortion Induced by Volute
Authors: Shu Mengying , Yang Mingyang , Deng Kangyao , Zheng Xinqian , Martinez-Botas Ricardo F.
Published: July 2018

A volute is one of the key components in a centrifugal compressor. The aerodynamic stability of the compressor deteriorates remarkably when a volute is employed. This paper investigates the influence of volute-induced circumferential flow distortion on aerodynamic stability of a centrifugal compressor via experimentally validated three-dimensional (3D) numerical simulation method. First, the compressor performance is analyzed based on a newly developed stability parameter. The impeller is confirmed to be the main contributor to the instability of the investigated compressor. Next, the influence of volute on impeller performance is studied by circumferentially distorted boundary conditions at the impeller exit which are extracted from flow field at the volute inlet. Results show that the performance of an impeller passage is determined by not only the back pressure but also the local gradient of pressure distribution in the circumferential direction. Moreover, these passages confronted with pressure reduction in the rotational direction are most unstable, while those confronted with pressure rise have better performance. Consequently, the circumferentially distorted distribution at impeller exit results in a loop of passage performance encapsulating the performance of uniform case. The size of the loop is enhanced by the distortion amplitude. Moreover, the influence of volute-induced distortion on the impeller performance is concluded into two main reasons: the imbalance of the force on flow and the imbalance of tip clearance flow taken by passages. The force imbalance influences the accumulation of secondary flow, while the imbalance of the tip clearance flow results in discrepancies of the low momentum flow in passages.
Addressing Two-Phase Flow Maldistribution in Microchannel Heat and Mass Exchangers
Authors: Hoysall Dhruv C. , Keniar Khoudor , Garimella Srinivas
Published: July 2018

Multiphase flow phenomena in single micro and minichannels have been widely studied. Characteristics of two-phase flow through a large array of microchannels are investigated here. An air–water mixture is used to represent the two phases flowing through a microchannel array representative of those employed in practical applications. Flow distribution of the air and water flow across 52 parallel microchannels of 0.4 mm hydraulic diameter is visually investigated using high-speed photography. Two microchannel configurations are studied and compared, with mixing features incorporated into the second configuration. Slug and annular flow regimes are observed in the channels. Void fractions and interfacial areas are calculated for each channel from these observations. The flow distribution is tracked at various lengths along the microchannel array sheets. Statistical distributions of void fraction and interfacial area along the microchannel array are measured. The design with mixing features yields improved flow distribution. Void fraction and interfacial area change along the length of the second configuration, indicating a change in fluid distribution among the channels. The void fraction and interfacial area results are used to predict the performance of different microchannel array configurations for heat and mass transfer applications. Results from this study can help inform the design of compact thermal-fluid energy systems.
Experimental Study About Performance Analysis of Parallel Connected Ranque–Hilsch Counter Flow Vortex Tubes With Different Nozzle Numbers and Materials
Authors: Kaya Hüseyin , Günver Fahrettin , Uluer Onuralp , Kırmacı Volkan
Published: July 2018

An experimental analysis for parallel connected two identical counter flow Ranque–Hilsch vortex tubes (RHVT) with different nozzle materials and numbers was conducted by using compressed air as a working fluid in this paper. Heating and cooling performance of vortex tube system (circuit) and the results of exergy analysis are researched comprehensively according to different inlet pressure, nozzle numbers, and materials. Nozzles made of polyamide plastic, aluminum, and brass were mounted into the vortex tubes individually for each case of experimental investigation with the numbers of nozzles 2, 3, 4, 5, and 6. The range of operated inlet pressure 150–550 kPa with 50 kPa variation. The ratio of length–diameter (L/D) of each vortex tube in the circuit is 14 and the cold mass fraction is 0.36. Coefficient of performance (COP) values, heating, and cooling capacity of the parallel connected RHVT system were evaluated. Further, an exergy analysis was carried out to evaluate the energy losses and second law efficiency of the vortex tube circuit. The greatest thermal performance was obtained with aluminum-six-nozzle when taking into account all parameters such as temperature difference, COP values, heating and cooling capacity, and exergy analysis.
Advanced Multi-Objective Robust Optimization Under Interval Uncertainty Using Kriging Model and Support Vector Machine
Authors: Xie Tingli , Jiang Ping , Zhou Qi , Shu Leshi , Zhang Yahui , Meng Xiangzheng , Wei Hua
Published: July 2018

There are a large number of real-world engineering design problems that are multi-objective and multiconstrained, having uncertainty in their inputs. Robust optimization is developed to obtain solutions that are optimal and less sensitive to uncertainty. Since most of complex engineering design problems rely on time-consuming simulations, the robust optimization approaches may become computationally intractable. To address this issue, an advanced multi-objective robust optimization approach based on Kriging model and support vector machine (MORO-KS) is proposed in this work. First, the main problem in MORO-KS is iteratively restricted by constraint cuts formed in the subproblem. Second, each objective function is approximated by a Kriging model to predict the response value. Third, a support vector machine (SVM) classifier is constructed to replace all constraint functions classifying design alternatives into two categories: feasible and infeasible. The proposed MORO-KS approach is tested on two numerical examples and the design optimization of a micro-aerial vehicle (MAV) fuselage. Compared with the results obtained from other MORO approaches, the effectiveness and efficiency of the proposed MORO-KS approach are illustrated.