bluuebunny/crossref_metadata_2025 huggingface dataset:
The Modeling and Prediction of Gravity Deformation in Precision Machine Tool Assembly
Authors: Guo Junkang , Hong Jun , Wu Xiaopan , Wang Mengxi , Feng Yan
Published: April 2014

The variation propagation in mechanical assembly is an important topic in several research fields, such as computer aided tolerancing (CAT) and product quality control. Mathematical models and analysis methods have been developed to solve this practical problem. Tolerance analysis which is based on the rigid hypothesis can be used to simulate the mass manufacturing and assembly. The state space model and stream of variation theory are mainly applied in flexible part assembly. However, in precision machine tool assembly, both tolerance design and process planning critically impact the accuracy performance, mainly because of the fact that the gravity deformation, including the part deformation and the variation in the joint of two connecting parts, cannot be ignored in variation propagation analysis. In this paper, based on the new generation GPS (Geometrical Product Specification and Verification) standards, the verification and modeling of key characteristics variation due to gravity deformation of single part and adjacent parts are discussed. The accurate evaluation of position and orientation variation taking into account form errors and gravity deformation can be solved from this model by FEM. A mathematical model considering rail error, stiffness of bearings is introduced to simulate the motion error in gravity effect. Based on this work to more accurately calculate the variation propagation considering gravity impact, a state space model describing the assembly process of machine tools is proposed. Then, in any assembly process, the final accuracy can be predicted to find out whether the accuracy is out of design requirement. The validity of this method is verified by a simulation of the assembly of a precision horizontal machining center.
Laminar Mixed Convection Boundary Layer Flow Over Two Dimensional and Axisymmetric Bodies
Authors: Aliu Sufianu A. , Fagbenle Richard O.
Published: April 2014

Simple and familiar perturbation parameters have been employed in applying the corrected Merk series of Chao and Fagbenle to the laminar mixed convection flow over two dimensional or axisymmetric bodies. The governing ordinary differential equations for the first five sets of the resulting universal functions for the velocity and temperature have been given. Numerical solutions were subsequently obtained and the relevant universal functions tabulated with respect to the ‘wedge parameter’ for mixed convection two dimensional flows and with respect to both the ‘wedge parameter’ and ‘shape parameter’ for the axisymmetric case. Using the wall derivatives of these universal functions, friction and heat transfer in mixed convection flows over two dimensional or axisymmetric bodies have been obtained and used in evaluation of skin friction and surface heat transfer.
Hydrodynamic Modeling of the Helical Membrane Modules
Authors: Liu Fengxia , Wei Wei , Wang Guan , Xu Xiaofei , Liu Zhijun , Liu Lifen , Yang Fenglin
Published: April 2014

Membrane fouling and concentration polarization can be greatly mitigated by using the helical membrane modules to enhance the mass transport process. In this study, experiments and computational fluid dynamics were used to investigate the transport phenomena in a helical membrane filter with several helical membrane modules. A model is constructed with a square filter which has three helical membrane modules embedded as not only turbulence promoters but also filtering elements. Direct numerical simulations based on the Navier-Stokes equations are performed over a range of characteristic parameters of membrane and aeration flux. The distributions of local parameters such as velocity, shear stress and turbulent kinetic energy on the membrane surface were obtained by numerical simulations with different helical angle and aeration flux. These parameters are directly related to mass transport enhancement. Results show that both wall shear stress and turbulent kinetic energy obtained from helical membrane modules are larger than those from flat membrane modules, and they increase with an increase of the helical angle. The average shear stress on the membrane surface increases from 0.097 Pa to 0.217 Pa as the helical angle changes from 0° to 360°. In addition, the flow field was analyzed by means of noncontact measuring and visualization device-Particle Image Velocimetry (PIV), and the vorticity as well as the turbulent kinetic energy were obtained from the velocity distribution. The measured data are in agreement with the numerical results. From the research, we can see that the helical membrane modules can enhance the transfer efficiently compared to the flat membrane modules, which means the concentration polarization and membrane fouling can be alleviated efficaciously, it can be concluded that the helical membrane modules can play an important role in government actions membrane separation engineering and its application prospect in industry is very broad.
Analysis and Simulation of an Oil Lubrication Pump for the Internal Combustion Engine
Authors: Senatore Adolfo , Buono Dario , Frosina Emma , Santato Luca
Published: April 2014

This paper presents the simulation model of an oil lubrication gerotor pump for the internal combustion engine.

The model was constructed by using a mono-dimensional commercial code taking into account all the phenomena that occur during the revolution of the pump shaft. First of all, several geometric considerations and theoretical observation are presented.

An experimental campaign was also performed to validate the simulation model. In these experimental tests particular attention was regarded to the behavior of the pressure oscillations during the pump shaft revolutions.

The final aim of this activity is to obtain an instrument that allows in-depth analysis of pump and lubrication circuit functioning and that can be coupled with other models (e.g. VVA, VVT, etc.) in order to take into account different problems of the hydraulic components of engines.
Implementation of a Nonlinear Torsional Vibration Absorber for Suppression of Vibrations in Rotating Machinery
Authors: Tahir Ammaar Bin , Shiryayev Oleg , Vahdati Nader , Karki Hamad
Published: April 2014

Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is tuned for a specific resonant frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies. Vibrations dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system.

Experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, we carry out the design optimization of the nonlinear torsional vibration absorber using an equivalent 2-DOF modal model. A linear vibration absorber is developed in parallel. Subsequently, both absorbers will be manufactured, assembled and mounted on the system to evaluate their vibration suppression capabilities.
Effect of Polyurethane Surface Treatment on Basalt Fiber Composite
Authors: Yang Ting , Liao Mengyuan , Cui Zhenjin , Yang Yuqiu
Published: April 2014

Nowadays, Basalt fiber is obtained increasing attention worldwide as a kind of promising reinforced fiber in composite field, which has the excellent mechanical properties, chemical resistance, comparative low cost, easily processing and abundance resource. In this paper, polyurethane dispersion (PUD) was employed as the surface treatment for the basalt fiber-woven fabric. Basalt woven fabric was washed by acetone solution following by different pick-up ratio PUD treating. Treated BFRP and virgin one were tested by tensile test with AE equipment, comparison and analysis have been carried out in order to discuss the change of mechanical property by changing the PUD treatment’s pick-up ratio and improved mechanical and thermal properties compared with virgin one.
Dynamic Response of Corrugated Sandwich Plates Under Shock Tube Loading
Authors: Kim Jeong-Ho , Zhang Linhui , Wright Jefferson T. , Hebert Rainer , Shukla Arun
Published: April 2014

This paper addresses three-dimensional dynamic finite element analysis and validations for strain-rate dependent elastic-plastic sandwich steel plate with various corrugated core arrangements subjected to dynamic air pressure loads. The sandwich steel plate consists of top and bottom flat substrates of Steel 1018 and corrugated core layers of Steel 1008. The developed model is validated with a set of shock tube experiments. Various corrugated core arrangements are taken into consideration for optimizing core design parameters in order to maximize mitigation of blast load effects onto the structure.
Optimization of Heat-Sink Fin Features by FEA Simulation
Authors: Wen Jing Heng , Neely Michael J.
Published: April 2014

Heat sinks are frequently used when heat exchange is required for electric circuits. In cases where the heat generation is evenly distributed, the height and spacing of fins are uniform. However, when heat generation is locally concentrated, uniform fin distribution is not the most efficient design.

The original battery-charger heat-sink for a particular model of electric golf car featured a uniform fin design that had been in use for a long time. When re-tooling was required, the design team decided to investigate the heat-sink design for potential improvement.

The project began by analyzing the heat-flow distribution of the baseline design. It was found that approximately 70% of the total heat flow was concentrated at a local area. The efficiency of the heat sink was based on material thermal property, fin height, fin spacing and etc. ANSYS thermal and structure were used to optimize these features.

In order to understand how fin height and spacing influenced heat exchange, a three-step optimization process was used, including fin spacing optimization, fin height optimization and a combining analysis. The working environment was assumed to be non-forced convective cooling. The final design featured a highly non-uniform fin distribution that improved heat exchange by approximately 10% with a material reduction of about 15% compared with the baseline design. A US patent is pending for the improved heat-sink design.
Flow Analysis on Piping Networks Using the Finite Element Method
Authors: Moreno Carlos Luis
Published: April 2014

The objective of this work is to apply the Finite Element Methodology (F.E.M.) to several piping systems, using an incompressible working fluid, in order to calculate the volumetric flow on each element and the piezometric load on each node of the network. To accomplish this goal a computational code was designed using Fortran Computational Language. Such a code consists of a main program and six subroutines. The input variables are general data of the network including the number of pipes, the number of nodes, the piezometric load values on nodes where they are constant (tanks for example), demanding flows in those nodes where the fluid is removed from the system, a connectivity table indicating the assumed flow direction in each pipe, and the number of pumps with respective parabolic curve coefficients. Program data also included both the maximum number of iterations and tolerance allowed. Fluid properties such as kinematic viscosity, density and pipe features such as length, diameter and absolute rugosity are also required. The output data include pipe volumetric flows and piezometric load on variable static pressure nodes.

In this work, three different network systems were analyzed: 51-, 63- and 65-element networks. All were examples taken from the bibliography. The Finite Element Methodology results were first validated with real data, and then compared with the other results coming from the Hardy-Cross, Newton-Raphson and Linear Methods. The comparison was based on convergence speed and numerical stability. It is concluded that the methodology called Finite Element Methodology requires a smaller number of iterations than the Hardy-Cross, Linear and Newton-Raphson Methods. Another advantage of the Finite Element Methodology is that there is no need to assign the flow initial values that satisfy the Continuity Equation on each node of the piping network before running the program. Also, no loops establishing is needed. In addition, the designed code permits calculations for networks that present both booster and feed pumps. The importance of this work rests on the fact that nowadays it is necessary for piping network flow analysis to use computational simulation in order to design systems more efficiently and economically. Furthermore, this work is important for network construction as well as the satisfaction of consumer demand on a local community level, taking into account prevailing normative requirements. This paper, consequently, aims to contribute to progress in these areas.
Design and Structure Analysis of Wheeled Chassis With Self-Balancing Rocker of Rescue Engineering Machinery
Authors: Xu Guoyan , Wang Xiaopo , Gao Feng , Xie Xiaolin , Ding Nenggen
Published: April 2014

A wheeled chassis with self-balancing rocker is developed for rescue engineering machinery. This chassis has better ground adaptability compared with traditional ones because of the automatically adjustable ground clearance and body posture, non-trapezium steering mechanism, independent four-wheel steering, and “X”-type radiation legs.

Finite element analysis on the chassis structure is done with two mechanical models and under typical finite element working conditions. HyperWorks software is used to analyze different parts of the chassis, and the results are used for structure optimization. The rocker plate thickness and rocker frame topology are optimized using Optistruct. The results demonstrate the effectiveness and feasibility of proposed optimization methods.
A Simple Flexible Plate for Usage as Force Sensor Element With Constant Stiffness
Authors: Ottnad Thomas , Lüßmann Henrik , Lueth Tim C.
Published: April 2014

Control of pressure is one of the most decisive parameters influencing the quality and reproducibility of products when dealing with plastics producing techniques such as injection molding, extrusion, and related techniques. For that purpose different types of pressure sensors for specific tasks come into action. Different tasks can be different working pressure ranges, static or dynamic pressure, working temperatures and requirements concerning the environment. Therefore different types of pressure sensors are commonly used which most often transform mechanical deformation into electrical signals and these in turn are converted into the value of pressure. This in turn can mean extensive effort for installation and insulation of the pressure sensors.

An approach to design a pressure sensor based solely on its mechanical deformation is basic idea of the present work. The pressure sensor consists of a flexible element which is in fact a thin plate with a ram on its outer side and can be clamped easily at any desired area on a melt channel. When being applied to pressure the working pressure causes a deflection of the flexible element. Measuring this deflection and knowing the mechanical behavior of the flexible element allows the calculation of the value of pressure.

To get to know to the mechanical behavior, especially the stiffness, of the flexible element a test rig was designed and refined. In the test rig as substitution of the pressure variable but defined load can be applied using a piezo-electrical actuator with integrated position sensor. Measuring the applied force using a force sensor and measuring the resulting deflection of the flexible element using a length gauge allows to calculate the stiffness of the flexible element. Regarding the flexible element as Kirchhoff plate a constant stiffness is expected and this could be proven taking measurements.

When taking a look at the deflection of the piezo-electrical actuator and the flexible element there is a difference due to the elasticity of the test rig itself. When determining the stiffness of the test rig a non-constant stiffness was detected which was not expected. Reason for that is the non-constant stiffness of the used force sensor though stated other by the manufacturer. This could be proven substituting the force sensor with the flexible element. With that the flexible element showed to be appropriate to be used as force sensor with a constant stiffness.
Cellular Materials With Extremely High Negative and Positive Poisson’s Ratios: A Mechanism Based Material Design
Authors: Kim Kwangwon , Ju Jaehyung , Kim Doo-Man
Published: April 2014

In an effort to tailor functional materials with customized anisotropic properties — stiffness and yield strain, we propose porous materials consisting of flexible mesostructures designed from the deformation of a re-entrant auxetic honeycomb and compliant mechanisms. Using an analogy between compliant mechanisms and a cellular material’s deformation, we can tailor in-plane properties of mesostructures; low stiffness and high strain in one direction and high stiffness and low strain in the other direction. Two mesostructures based on hexagonal honeycombs with positive and negative cell angles are generated. An analytical model is developed to obtain effective moduli and yield strains of the porous materials by combining the kinematics of a rigid link mechanism and deformation of flexure hinges. A numerical technique is implemented to the analytical model for nonlinear constitutive relations of the mesostructures and their strain dependent Poisson’s ratios. A Finite Element Analysis (FEA) is used to validate the analytical and numerical model. The moduli and yield strain of a porous aluminum alloy are about 6.3GPa and 0.26% in one direction and about 2.8MPa and 12% in the other direction. The mesostructures have extremely high positive and negative Poisson’s ratios, νxy* (∼ ±40) due to the large rotation of the link member in the transverse direction caused by the input displacement in the longitudinal direction. The mesostructures also show higher moduli for compressive loading due to the contact of slit edges at the center region. This paper demonstrates that compliant mesostructures can be used for a next generation material design in terms of tailoring mechanical properties; moduli, strength, strain, and Poisson’s ratios. The proposed mesostructures can also be easily manufactured using a conventional cutting method.
Development of Mass-Conservative Phase-Change Model for Convective Boiling Simulations
Authors: Sato Yohei , Lal Sreeyuth , Niceno Bojan
Published: April 2014

A numerical method based on Computational Fluid Dynamics (CFD) has been developed to simulate convective nucleate boiling flows in laminar and turbulent flow regimes. A single set of Navier-Stokes equations is solved based on a staggered finite-volume algorithm on Cartesian grids using Smagorinsky model for sub-grid scale turbulence. A color function is used for the two-phase flow model with a local sharpening scheme [1] to prevent the smearing of the color function, and Brackbill’s Continuum Surface Force (CSF) model [2] is used for the surface tension and the wall adhesion force. A sharp-interface mass-conservative phase change model [3], which can capture the velocity jump accurately, is used for the mass transfer model. A micro-region model developed by Stephan [4] is used to model the mass transfer at the vapor-liquid-solid triple point, and the mass transfer rate and the surface tension force in the micro-region is introduced to the Navier-Stokes solver. The developed scheme is validated against the experiments of convective boiling flows in the horizontal and vertical flow directions [5]. The validation cases considered in this paper are based on a single nucleation site and single bubble growth, in the same approach as Li and Dhir [6], and several assumptions are used for the initial and boundary conditions to complement the limited measured data. Thus, the comparison between the simulation and the experiment may not have the true meaning of validation, but the computed bubble liftoff diameter and time show agreement with experiments under the given conditions, and the applicability of the developed method to the simulation of convective boiling flows is demonstrated.
Computational Optimization of Arc Welding Parameters Using Coupled Genetic Algorithms and Finite Element Method
Authors: Islam Mohammad R. , Rohbrecht Jens , Buijk Arjaan , Namazi Ehsan , Liu Bing , Motoyama Keiichi
Published: April 2014

An effective and rigorous approach to determine optimum welding process parameters is implementation of advanced computer aided engineering (CAE) tool that integrates efficient optimization techniques and numerical welding simulation. In this paper, an automated computational methodology to determine optimum arc welding process control parameters is proposed. It is a coupled Genetic Algorithms (GA) and Finite Element (FE) based optimization method where GA directly utilizes output responses of FE based welding simulations for iterative optimization. Effectiveness of the method has been demonstrated by predicting optimum parameters of a lap joint specimen of two thin steel plates for minimum distortion. Three dimensional FE model has been developed to simulate the arc welding process and validated by experimental results. Subsequently, it is used by GA as the evaluation model for optimization. The optimization results show that such a CAE based method can predict optimum parameters successfully with limited effort and cost.
Collaborative Design in DARPA’s FANG I Challenge
Authors: Myers Michael R. , Gregory Richard E. , Hite Joseph E. , Neema Sandeep , Bapty Ted
Published: April 2014

The Defense Advanced Research Projects Agency (DARPA) created the Fast, Adaptable, Next-Generation Ground Vehicle (FANG) program to design and develop a new heavy, amphibious infantry fighting vehicle (IFV). DARPA, through the FANG program, is undertaking a radically novel approach to the design and manufacture of complex defense systems, and is hosting a series of prize-based design competitions. These are called the FANG Challenges, and their products will be progressively more complex vehicle subsystems, culminating in the design of a full IFV. They leverage the META design tools and the VehicleFORGE collaboration environment to significantly change the design experience and widen the aperture for design innovation. The META tool suite is a set of free, open source tools for compositional design synthesis at multiple levels of abstraction, design trade space exploration, metrics assessment, and probabilistic verification of system correctness. VehicleFORGE is an open source development collaboration environment for the creation of large, complex systems by numerous unaffiliated designers with the goal of democratizing the design innovation process by engaging several orders of magnitude more talent than the current industry model. This work summarizes the results from the first FANG challenge through analysis of participants, team structures, and the designs created.
A Numerical Study of Conjugate Heat Transfer by Natural Convection and Surface Radiation in a Square Enclosure With Thick Adiabatic Walls
Authors: Hadim H. , Blecker K.
Published: April 2014

A numerical solution of heat transfer by combined natural convection and surface radiation in a square enclosure with thick adiabatic top and bottom walls and isothermal vertical walls is presented. The present model was used to obtain new results with the addition of thermal conduction at the thick top and bottom walls for a thermal conductivity ratio, K = ksolid/kfluid, that ranges from 0 to 10, emissivity of the adiabatic walls that ranges from 0 to 1, and the Rayleigh Number that ranges from 103 to 106. The model was validated by comparing the results to a benchmark solution and other solutions found in the literature. The results showed that with an increase in thermal conductivity ratio, the flow circulation decreases while the average Nusselt Number increases indicating increased heat transfer across the thick walls and the fluid in the corners. The results indicate that while past studies have shown negligible impact of the emissivity of the adiabatic walls on characteristics of the flow and heat transfer within the cavity, when a wall with moderate heat capacity and conductivity is considered, the resulting flow velocity and temperature distribution within the cavity are found to be significantly influenced by the thick wall emissivity. As the conductivity ratio increases this discrepancy between thin and thick walls becomes greater, there is further need for a more complex and accurate model including the thick walls. The results also showed that an increase in the emissivity of the adiabatic walls results in a slight decrease in the average Nusselt Number.
Stability Analysis of a Complex Geared Rotor-Bearing System in a Turbine Reduction Gearbox
Authors: Guan Yuanhong , Sieveking Edward W. , Sampathkumar Varad
Published: April 2014

It is well known that the rotor system will meet several critical speeds or unstable regions as its rotation speed increases, especially when the rotor system is supported by journal bearings, since there exists a strong fluid-structure coupling which is rather prone to stability issues. Stability analysis of rotor-bearing systems (such as turbine-compressor) has been extensively studied in the literatures over the past 50 years. However, few studies have been performed on geared rotor-bearing systems, especially for complex multi-stage gear train systems. In this paper, the abnormal noise/vibration problem on a high speed 2 stage epicyclic reduction gearbox of a turbine-generator system is studied. This gearbox showed abnormal low frequency vibrations at low speed cranking and high speed partial load conditions. Further detailed probe testing showed that the gear bodies which were supported by 6 journal bearings had quite large sub-synchronized vibrations and shaft whirls were developed when the abnormal noise was present. In order to better understand the root cause and to fully eliminate such low frequency noise/vibration, a detailed finite element model for the whole turbine-gearbox-generator was developed under different speed / load conditions. The linearized journal bearing stiffness and damping matrix were calculated using a separate tool and then plugged into the above FE model. The gears are modeled as rigid bodies and connected by gear mesh stiffness. Gyroscopic force terms have also been included in the model. The stability of the whole system was evaluated by a complex eigenvalue analysis and the stability margin evaluated by the corresponding damping factor (or log decrement). The model predicts a range of instability regions and has good correlation with testing data. The root cause of this abnormal noise/vibration is due to the strong torsional-lateral coupling of gear systems, and further coupling with the fluid dynamics of the journal bearings under certain speed/load conditions. Some sensitivity studies are also performed in order to increase the stability margin and eliminate the sub-synchronized vibrations.
Rapidly Deployable Lightweight Shelters for Austere Environments
Authors: Jayson Eric M. , Mathy Gregory R.
Published: April 2014

An innovative solution for a rapidly deployable shelter for use in austere environments is presented in this paper. The design incorporates a self-erecting dome structure and a compressible, high R-value thermal barrier to enable rapid in-theatre deployment of personnel in harsh environmental conditions.

The design concept presented in the paper was originally developed in response to the Army branch of the small business innovative research (SBIR) solicitation topic A11-099. The proposed 400 ft2 shelter meets the design goals of deployment by two people in 20 minutes, capability of withstanding 100 mph winds, and an R value of at least 15. These objectives have been proven via test, analysis, and mechanical demonstration of the key design components and systems.

The primary structure consists of eight composite tubes. The tubes are slip-fit into a central hub; each member is similar to a spoke extending outward radially from the hub. A tension cable is run around the outer perimeter of the radial spokes, passing through a fitting at the tip of each spoke, and a protective skin is draped over the structural members. The structure is then elastically deformed via buckling into a dome-shaped structure by tensioning the cable. This allows quick, easy shelter erection from a single location by one person using a winch. The protective skin is then tensioned to the shelter base with adjustable straps. Stakes are not required to support the structure. A scale model of the primary structure was built to demonstrate the controlled buckling of the members to form the main structural components, and the scale model successfully demonstrated deployment in minimal time.

A cellular fabric blanket, which uses entrapped air to provide a thermal barrier, is hung from the inside of the structure and is mechanically expanded to maintain the desired cell size. It can then be packed to 1/20th of its deployed volume for transportation. Simulations and tests were used to optimize the cell size and aspect ratio for weight, manufacturability, and R value. Analytical predictions and component-level testing have demonstrated that a system-level R value of 15 is achievable.
Microscopic Tool Wear in Machining Aluminum 6061 T6 (Cold Compressed Air, Nitrogen and Dry Environments
Authors: Chandrasekaran Vishnu Vardhan , Payton Lewis N.
Published: April 2014

The current study is a statistically designed experiment to evaluate different cutting environments that can be used in machining aluminum 6061 T6. High speed steel inserts were used along with different levels of uncut chip thickness in a classic orthogonal tube turning experiment. The cutting fluids used in this study are nitrogen and cold compressed “shop” air that are compared to the results obtained from dry machining. The force data (cutting force and the thrust force) were collected using a Kistler force dynamometer and processed using Labview software. The tools are subjected to 1 minute of cutting at two different feed rates of 0.002″/rev. and 0.004″/rev at a constant depth of cut of 0.125″ and at a constant speed. The tool inserts after 1 minute of cutting are studied for tool wear using a Keyance microscope. The surface finish of the work piece surface (average surface roughness) after one minute of cutting is examined under a Dektak 150 contact type surface profilometer. Alternative metal working fluid options are discussed.
Microstructural Response of High Aluminum Steels to Quenching and Partitioning Treatment
Authors: Nyyssönen Tuomo , Somani Mahesh , Peura Pasi , Kuokkala Veli-Tapani
Published: April 2014

Quenching and Partitioning (Q&P) is a novel heat treatment process that is able to produce steels with a microstructure consisting of controlled amounts of finely divided retained austenite in a martensitic or ferritic-martensitic matrix. Following quenching to a temperature in the Ms-Mf range, the steel is subjected to partitioning treatment that concerns the diffusion of carbon atoms from supersaturated martensite phase to the austenite phase, resulting in the possibility of stabilizing it down to room temperature. Competing reactions such as cementite and/or transition carbide precipitation must be suppressed by suitably alloying with certain elements, conventionally silicon. In this study, aluminum was used as the main precipitation suppressor. Three Nb-microalloyed experimental steels with aluminum at different levels in the range 2–3%, with or without additions of Si, Ni and Cu were subjected to Q&P treatments. The microstructures and phase compositions of the quenched and partitioned steels were characterized with optical and scanning electron microscopy combined with EBSD phase mapping and X-ray diffraction measurements. The mechanical properties of the steels were studied with microhardness and tensile testing. The preliminary experiments suggest that aluminum-bearing steels can retain significant amounts of austenite after partitioning in a ferritic-martensitic microstructure. Promising strength-ductility ratios were also found in tensile testing. Based on the encouraging results, future work will be directed to produce microstructures with higher martensite fractions to impart higher strengths in steels combined with good ductility and formability.
Objective Assessment of Minimally Invasive Surgical Skills
Authors: Keshavarz Panahi Ali , Cho Sohyung
Published: April 2014

Minimally invasive surgery (MIS) is known to be a difficult procedure to master due to its complexity, compared to traditional open surgery. Therefore, an objective and quantitative assessment tool is highly required in MIS, which can be used for determining surgeon’s skills, evaluating educational programs and providing subjects with unbiased feedback. The goal of this paper is to review various assessment methods, summarize capabilities of the methods, and suggest future possible improvements. Specifically, this paper categorize existing methods into two groups: the first and the most well known group focuses on the analysis of surgical motions, and the other group uses force and torque as a key metric. Specifically, motion analysis includes tracking the body, tool, or hand motions of a surgeon, either from teleoperated robotic systems or surgical simulators using different sensors like wireless or electromagnetic motion tracking sensors, video-glove-based input devices, optical tracking system, or magnetic tracking technologies. Sometimes data explored form this method is synchronized with eye-gaze data (what a surgeon looks at while operating), or videographic data. Using motion analysis actually the number of movements, rate of movements, total path length, movement variability, time taken to complete the operation, average or peak velocity are considered for assessing surgical skills. On the other hand, the methods in the second group assess the skills based on force and toque data that surgeons apply through surgical instruments. More specifically, these methods use different kind of sensors placed on the grasper. Different force and torque measurement systems, hidden-Markov-model-based analysis, simulated models with criteria, and Virtual reality have been developed, allowing for the quantification of the performance of surgeons.

Although, each method has its own advantageous, and according to the kind of surgical task and evaluation, these methods can be used successfully to assess surgical skills, to provide predictive validity for each of these methods more study is needed. Also, future works should improve the efficiency of each method and move toward automated, low-cost and real time assessment methods.
Contactless Superconducting Magnetic Instrument for Precise Positioning in Cryogenic Environments
Authors: Perez-Diaz J. L. , Valiente-Blanco I. , Diez-Jimenez E. , Sanchez-Garcia-Casarrubios J. , Alvarez-Valenzuela M. A. , Cristache C. , Serrano J. , Romera-Juarez F. , Gonzalez-de-Maria D. , Lamesans M. , Argelaguet-Vilaseca H.
Published: April 2014

There is an increasing demand of nanotechnology and nano-devices in microelectronics, optics, biomedical and precision engineering industries. In this context, a wide range of applications require micrometer/nanometer positioning within a long range. Ultra precision manufacturing and inspection systems in micro-automating semiconductor fabrication, nanopositioning and nanomeasuring machines (NPM-Machine), development of MEMS and NEMS, copying machines, stepper stages for photolithography, small-scale measuring machines (CMMs) for large area scanning or surface imaging in scanning probe microscopy (SPM) are a few examples of these applications. In some applications, cryogenic environments (temperatures below 120 K) are a desirable or mandatory condition. The sensitivity of a large number of sensors is greatly increased when they are at cryogenics temperatures, like for example, those required for far infrared interferometer spectroscopy. The operating conditions in these environments include very low temperatures but also high vacuum. In this context, it is challenging for mechanisms to overcome all the tribological problems associated with these conditions. In addition very low energy consumption is also desirable in cryogenic environments. The invention here presented is a contactless linear slider that gets benefit of superconducting magnetic levitation to obtain a nanometer resolution within a long stroke (∼ 15 mm), minimizing run-outs of the slider (in the micron scale). Moreover, due to self-stable levitation and guidance of the slider, the complexity of the control is significantly reduced and the power consumption minimized (of the order of mW). The linear slider can be divided in two subsystems: the guidance system and the actuating system. The guidance system is composed of a static guideline, made of two superconducting disks and a slider composed of a long permanent magnet. Due to the high translational symmetry of the magnetic field generated by the PM, a contactless sliding kinematic pair is established between the PM and the superconductors in the sliding DoF. Thus, the slider is able to be moved in the sliding direction with very low resistance. However, greater restoring forces appear if the PM is moved in any other direction. Due to the lack of contact between the moving parts is also suitable for operation in clean-room applications, like in semiconductor manufacturing industry. Ultimately, the device was designed, built and tested in a relevant cryogenic environment (15 K and high vacuum) and the results introduced and discussed.
Numerical Modeling of Pulsating Inflow to the Pulmonary Arteries in TCPC Morphology Using FSI Approach
Authors: Rajabzadeh Hamid Reza , Firoozabadi Bahar , Saidi Mohammad Said , Sohrabi Salman , Nemati Mehr Seyyed Mahdi
Published: April 2014

The Fontan surgery is performed on patients with a single ventricle heart defect to prevent the combination of highly-oxygenated and poorly-oxygenated blood. Blood flow in total cavopulmonary connection (TCPC) which culminates an ordinary Fontan operation is practically steady-state but this flow is not appropriate for respiratory systems. This article investigates an approach in Fontan surgery that has been recently proposed in order to make the pulmonary blood flow pulsating. Moreover, for investigating the compliance of vessels and its effects on blood flow in TCPC, we have used the FSI (Fluid Structure Interaction) method as well as rigid wall assumption for comparison purposes. Our TCPC model structure has obtained from CT Angiography (CTA) scan of a single ventricle patient who has undergone a normal Fontan surgery. In this new procedure, pulmonary stenosis (PS), containing high pressure and pulsating flow, has been added to the original geometry for pulsating the main flow and then its effect on the general flow in left and right pulmonary arteries has been studied by increasing the inlet velocity to PS. In overall, our results show that this new approach increases the pulsations of pulmonary flow.
Modeling and Simulation of Shoulder-Humerus Complex via Multibody Dynamics
Authors: Harrington Nicholas D. , Duan Shanzhong (Shawn)
Published: April 2014

In this paper, a multibody dynamics model of the shoulder-upper arm complex is presented. Three major bones clavicle, scapula, and humerus in the shoulder-upper arm complex are represented by rigid bodies. The soft tissues such as tendons, ligaments, and muscles are modeled as springs and dampers respectively attached to the rigid bodies. The joints between the bones are expressed as ideal kinematic joints. Kane’s equations are then used to derive equations of motion of this multibody system.

Based on the model, a person’s stand-up motion, aided by shoulder-upper arm complex force for lifting his/her upper body weight is analyzed. Commercial computer software is used to create the multibody shoulder-upper arm complex computational model and then carry out simulation. The model may be utilized in motion analysis of elderly people and sports medicine to study fatigue mechanism and prevent injuries of the shoulder-upper arm complex.
Hydrodynamic Loads on Vibrating Cantilevers Under a Free Surface in Viscous Fluids With SPH
Authors: Tafuni Angelantonio , Sahin Iskender
Published: April 2014

Smoothed Particle Hydrodynamics (SPH) based simulations are implemented to study finite amplitude vibrations of a submerged cantilever beam in viscous fluids under a free surface. The cross section of a thin beam is modelled as a rectangular 2D oscillating rigid lamina, around which fluid field properties are computed. The study is carried out using non-dimensional frequency, amplitude of oscillations and depth of submergence. The total hydrodynamic force on the vibrating beam is extracted via SPH analysis, together with the contours of fluid field properties. Comparison is made between the results obtained with and without the free surface. We find that the presence of the free surface strongly influences the flow physics around the lamina, giving rise to non-harmonic velocity profiles and non-periodic force responses, coupled with phase lags and non-zero mean force during periodic oscillations.
Stratification in Isothermal Ice-Slurry Pipe Flow
Authors: Onokoko Charles Landa , Galanis Nicolas
Published: April 2014

A single-phase 3D model for isothermal laminar and turbulent flow of an ice slurry in a horizontal pipe is used to investigate the effects of the uniform inlet velocity and ice concentration on their axial evolution. The slurry is modeled as a Newtonian fluid with effective local properties depending on the local ice concentration. Despite the relative simplicity of this model (compared to the two-phase models used elsewhere) its numerical solution gives results which correctly reflect experimental observations. Specifically, these results show that as the fluid moves downstream the ice concentration increases in the upper part of the pipe and it decreases in the lower part. The velocity profile is principally influenced by the boundary layer growth close to the inlet but further downstream it becomes asymmetrical with respect to the horizontal symmetry plane with higher velocities in the lower part of the pipe. The differences between the values in the upper and lower parts of the pipe are much more important in the case of laminar flow. The results are analyzed by considering the phenomena influencing the ice particle movement (buoyancy and diffusion) and the relation between ice concentration and the thermophysical properties of the slurry.
Effect of Rider Position on Bicycle Stability
Authors: Lipp Genevieve M. , Hall Kenneth C. , Mann Brian P.
Published: April 2014

Bicycle stability has been of interest to dynamicists and athletes since before J. W. Whipple described the canonical model for bicycle motion in 1899. Since then, the subject has fascinated many who sought to find a simple way to describe the essence of stability for a hands free bicycle at a prescribed forward speed. Caster and gyroscopic effects have been shown to be helpful, but not necessary for there to exist a stable range of forward speeds. This work focuses on showing how using the eigenvalues of the linearized equations for roll and steer (with and without a steering torque) can illuminate the stabilizing and destabilizing effects of changing bicycle geometry and rider position. Of particular interest is the mathematical demonstration of the decreased stability a cyclist on a time trial bike experiences when in the aerodynamic position, as opposed to riding with hands on the brake hoods or bull horns.
Rotordynamics of a Trans-Rotary Magnetic Gear Rotor
Authors: Heikkinen Janne E. , Pakdelian Siavash
Published: April 2014

Trans-Rotary Magnetic Gear (TROMAG) has recently been introduced as a reliable and efficient way of converting low-speed, high-force translation into high-speed, low-torque rotation, or vice versa. The gear can be used in any high force linear motion application; specifically, it would be a strong contender for wave energy harvesting. The TROMAG consists of two main parts: a rotor and a translator, both of which are formed by furnishing tubular ferromagnetic iron cores with helically-disposed permanent magnets. In this paper, the dynamics of the rotor is studied by employing the Finite Element Method (FEM) and using a simplified model where a flexible rotor is spinning on the flexible isotropic bearings. The rotor system has non-idealities that may excite the system to vibrate. In addition, the non-idealities in geometry cause uneven magnetic pulling force that is considered as an external force. The transient response of the rotor-bearing system is studied by varying the eccentricity of the rotor with respect to the translator. The vibration characteristics of the rotor-bearing system of the TROMAG are evaluated and presented in this paper.
Time Transient Analysis of Horizontal Rigid Rotor Supported With O-Ring Sealed Squeeze Film Damper
Authors: Dousti Saeid , Dimond Timothy W. , Allaire Paul E. , Wood Houston E.
Published: April 2014

This study addresses the nonlinear dynamic behavior of O-ring seals as the retaining spring in squeeze film dampers (SFDs). An analytical model is developed to predict the restoring and hysteresis forces of elastomer O-rings based on experimental and numerical data. This model takes into account the temperature softening and excitation frequency hardening effects in O-rings as well as the installation conditions in the form of radial and vertical preloads, σ and γ, respectively. Long bearing assumption is adopted for the solution of Reynolds equation. The equations of motion of horizontal unbalanced rigid rotor are derived, and a dimensional analysis is conducted on them. The numerical results substantiates the synchronizing effects of bearing parameter, B and vertical preload, γ, and the asynchronizing effects of O-ring parameter, O and radial preload, σ. It is shown that the variation of temperature and rotational speed as operating conditions influence the rotor response significantly.