bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Vibration of Rolling Element Bearing With Localized Defect Considering the Impact Force
Authors: Huang Wentao , Dong Zhenzhen , Kong Fanchao , Fu Qiang
Published: March 2016

In this paper, a vibration model considering the impact force is developed based on Hertz contact theory. The model considered both structural parameters and kinematic parameters. In this model, the contact areas between balls and races are simulated as linear springs, and the contact areas between the inner race and shaft and the contact areas between the outer race and housing are considered as spring-damper systems. Unlike previous studies, in which the stiffness was simply calculated in one direction, the stiffness parameters were calculated separately in the horizontal and vertical directions in the present study. In this model, the impact process between rolling elements and defective races, which is affected by velocity, was studied in detail. The solution of the vibration equation was obtained using the Runge-Kutta method. The numerical results for 6204 deep groove type ball bearings with outer race defects have been obtained and compared with the experimental results, which validated the effectiveness of this model in both the fault mechanism analysis of rolling element bearings and fault diagnosis.
Resonance-Based Sparse Signal Decomposition Based on Genetic Optimization and its Application to Composite Fault Diagnosis of Rolling Bearings
Authors: Huang Wentao , Fu Qiang , Dou Hongyin , Dong Zhenzhen
Published: March 2016

The selection of approximate values for the weight coefficients of the objective function in the existing RSSD with large subjective randomness reduces the advantages of this method for mechanical fault diagnosis. To solve this deficiency, a new method, objective function optimization based on a genetic algorithm and the split augmented Lagrangian shrinkage algorithm applied to RSSD, is proposed. This method utilizes the global optimization ability of genetic algorithms to adaptively optimize each element value of the weight coefficient matrices of the objective function of RSSD and achieve the optimal value of the objective function in the range of the desirable weight coefficients. Thus, this method adaptively realizes a sparse decomposition of the high- and low-resonance components according to the input signal and minimizes the information leakage in the process of signal decomposition. Finally, the proposed method was applied to diagnose a rolling bearing with composite faults of the inner and outer races and used to effectively extract the composite fault characteristics of the rolling bearing vibration signal. Accurate diagnosis of the early composite fault validated the practicability of the proposed method.
A New Approach to the Synthesis of Carbon Nanotube-Polyhedral Oligomeric Silsesquioxane (POSS) Nanohybrids
Authors: Sabet Seyed Morteza , Mahfuz Hassan , Terentis Andrew C. , Hashemi Javad
Published: March 2016

To date, the functionalization of carbon nanotubes (CNTs) with Polyhedral Oligomeric Silsesquioxanes (POSS) has become one of the most intensively explored methods to produce CNT-based nanostructure composite materials. In this study, a simple and effective synthesizing method has been reported to prepare a nanohybrid material consisting of multi-walled carbon nanotubes (MWCNT) and aminopropylisobutyl-POSS. The approach is based on covalent bonding between CNTs and POSS molecules. Characterization of the as-received materials as well as the POSS-treated CNTs has been performed. Raman and Fourier transform infrared spectroscopic analyses verify the covalent grafting of POSS onto CNT walls through the formation of amide bonds. TEM studies reveal the attachment of relatively high amount of POSS to the CNT walls in POSS-treated product. TGA observations suggest that the presence of relatively high amount of POSS in MWCNT-POSS product is responsible for the thermal stability of CNTs at temperature range of RT–200 °C. The resulting nanohybrids with improved functionality and thermal stability would be good candidates as reinforcing materials for compatible polymer matrices.
Thermo-Structural Design of the HEXAFLY-INT Experimental Flight Test Vehicle (EFTV)
Authors: Scigliano Roberto , Carandente Valerio , Favaloro Nunzia , Cardone Salvatore , Steelant Johan
Published: March 2016

The Hexafly-INT project intends to test in free-flight conditions an innovative gliding vehicle with several breakthrough technologies on-board. This approach will create the basis to gradually increase the readiness level of a consistent number of technologies suitable for high-speed flying systems.

This paper presents a Finite Element thermal analysis of the Experimental Flight Test Vehicle, combining information coming from the flight trajectory, the structural layout, the vehicle aerothermodynamics and the thermal behavior of the preliminarily selected materials in high temperature conditions. Numerical results show the thermal performances of the selected high temperature resistant materials in moderate enthalpy flow conditions and provide fundamental information on the thermal loads to be considered for structural analyses.
Fluid Structure Interaction for Nonlinear Response of Aorta Replacement
Authors: Tubaldi Eleonora , Amabili Marco , Paidoussis Michael P.
Published: March 2016

Vascular prostheses used for repairing and replacing damaged and diseased the thoracic aorta in cases of aneurysm, dissection or coarctation have distinctly different mechanical properties than the native aorta. Very little is known about the dynamic behavior of vascular prostheses that can cause unwanted hemodynamic effects leading to their failure. In this study, a Dacron reconstitution of the aorta is modelled as an isotropic cylindrical shell by means of nonlinear Novozhilov shell theory. A numerical bifurcation analysis employs a refined reduced order model to investigate the dynamic behavior of a pressurized Dacron aortic replacement conveying blood flow. A pulsatile time-dependent blood flow model is considered in order to study the effect of pressurization by applying physiological waveforms of velocity and pressure during the heart beating period. Stresses due to pressurization are evaluated and included in the model. The fluid is modeled as a Newtonian pulsatile flow and it is formulated using a hybrid model that contains the unsteady effects obtained from the linear potential flow theory and the pulsatile viscous effects obtained from the unsteady time-averaged Navier-Stokes equations. Geometrically non-linear vibration response to pulsatile flow is here presented via frequency-response curves and time histories. This study provides a fully coupled fluid-structure interaction model and it allows deep insights in the mechanical loading condition of the aortic replacements; this insight has potential to aid in vascular prostheses design and implementation.
Double-Acting Sleeve Muscle: Concept and Example Application in Powered Prostheses
Authors: Wu Molei , Zheng Hao , Shen Xiangrong
Published: March 2016

Pneumatic muscle actuator is a type of muscle-like actuator that mimics human skeletal muscle action through an airtight elastic tube. This unique type of actuator is able to generate a large output force with a very lightweight structure, and thus has been used in various robotic systems. In this paper, the authors further expand the performance and functionality of pneumatic actuator by introducing a unique modification to the actuator structure. Specifically, a telescoping insert is integrated to the center of the actuator. This insert serves dual purposes. First, by eliminating the central space in the pneumatic muscle, this structural change increases the force output and reduces the energy consumption of the actuator. Second, the insert incorporates an additional pneumatic chamber at the center of the actuator, which enables the actuator to generate an extension force and become a double-acting actuator. Comparative experimental results demonstrated the advantages of the new actuator over the traditional pneumatic muscle with respect to the actuation force over the entire range of motion. Furthermore, a design example, knee actuation mechanism in a powered leg prosthesis, is presented to illustrate the application of the new actuator. To provide the desired performance, a double-acting sleeve muscle drives the knee joint through an inverted crank-slider mechanism. A graphic comparison shows that the actuation system is able to provide sufficient torque to support a 75 kg user’s level walking and stair climbing.
Non-Linear Dynamic Response of Thorax to Impulsive Loading of Cardiopulmonary Resuscitation (CPR)
Authors: Borse Rajan , Al-Smadi Yahia M.
Published: March 2016

The purpose of this paper is, to provide the non-linear biodynamic response of thorax through the analytical and numerical simulation methods. Adult thorax data considering sagittal and coronal stiffness in addition to soft and hard tissue material properties will undergo CPR impulsive loading. The numerical simulation is conducted using finite element analysis (FEA) software for modeling biomechanical correct Thorax model to CPR transient loading. AMTI force plate was utilized to record the CPR forces, it accounts for realistic load evaluation during CPR procedure. A dynamic model for numerical simulation includes resonance frequency, damping coefficient, stiffness constant and extinction time for a different kind of physique. The model deflections and forces were analyzed. The maximum deflection obtained from mathematical modelling and ANSYS is found closely related. The result strongly depends on the modeling of the thorax which is used in the numerical simulation. This indicates the necessity of the correlation of the results with the experimental data if available.
Micromechanical Background of Random Structure Thermoperistatic Composites
Authors: Buryachenko Valeriy A.
Published: March 2016

In contrast to the classical local and nonlocal theories, the peridynamic equation of motion introduced by Silling (J. Mech. Phys. Solids 2000; 48: 175–209) is free of any spatial derivatives of displacement. The new general integral equations (GIE) connecting the displacement fields in the point being considered and the surrounding points of random structure composite materials (CMs) is proposed. For statistically homogemneous thermoperistatic media subjected to homogeneous volumetric boundary loading, one proved that the effective behaviour of this media is governing by conventional effective constitutive equation which is intrinsic to the local thermoelasticity theory. It was made by the most exploitation of the popular tools and concepts used in conventional thermoelasticity of CMs and adapted to thermoperistatics. The general results establishing the links between the effective properties (effective elastic moduli, effective thermal expansion) and the corresponding mechanical and transformation influence functions are obtained by the use of decomposition of local fields into the load and residual fields similarly to the locally elastic CMs. This similarity opens a way for straightforward expansion of analytical micromechanics tools for locally elastic CMs to the new area of random structure peridynamic CMs. Detailed numerical examples for 1D case are considered.
Stability Analysis of Input-Output Linearization Control With LuGre Friction Model Using Lyapunov Exponents
Authors: Sun Yun-Hsiang , Wu Christine Qiong
Published: March 2016

This work performs stability analysis on a control system partially modeled by LuGre friction model. Such a friction model has been proved sufficient to account for many features of friction. However, two parameters in the friction model, σ0 and σ1, are extremely difficult to be identified in real-world applications and the parameter errors (disturbances) coming from the measurements are therefore expected. In this work, we present a systematic methodology to rigorously analyze the effect of the disturbances mentioned above on the control system stability. The obtained analysis result clearly shows the robustness of the selected control law (input-output linearization control law). Lyapunov exponents calculated for two disturbed systems and our stability analysis result are in good agreement. The proposed methodology can be applied to other control laws of interest to examine their robustness.
Initial Fracture Behavior of Intra CF/GF Woven Fabric Composites
Authors: Xu Zhilan , Ichikawa Daiki , Yang Yuqiu
Published: March 2016

In this paper, carbon/glass intra-hybrid woven fabric as reinforcement and vinyl ester resin as matrix, CF/GF composite was manufactured through hand lay-up method. Then, the investigation on the mechanical property and initial fracture behavior was carried out. Initial fracture stress or knee point stress was the main factor of initial damage which discussed with AE characteristics during mechanical test. Scanning electron microscope observation was also carried out to observe the fracture of materials after testing. Besides, model of the woven fabric was built by finite element analysis method (FEM) and then the fracture mechanism was simulated by the software Marc. By combining the experimental results and finite element analysis, stress-strain curve and initial behavior of fracture progress in resin hybrid composite materials were predicted.
Study on Mechanical and Wear Characteristics of In-Situ Processed ZrB2/Aluminum Alloy Composites Processed by Salt-Melt Reaction
Authors: John Xavier Raj Jenix Rino , Rajkumar Monish Chakravarty , Kalyanasundharam Rajakumaran , Kalyanakumar Naveenkrishnan , Shanmugavel Balasivanandha Prabu , Ratnam Paskaramoorthy
Published: March 2016

In the present work, ZrB2/Al alloy composites were processed through the salt-melt reaction technique. Aluminum alloy (LM4) was taken as a matrix material. The ZrB2 reinforcement particles were formed in-situ by the reaction of precursor salts K2ZrF6 and KBF4 within the aluminum melt. Relative to the parent alloy, the hardness of the composites reinforced with 2.5, 5 and 7.5 wt.% ZrB2 showed an increase of 8.24%, 17.64% and 33.77%, respectively. The tensile strength also improved initially but decreased when the amount of reinforcement exceeded 5-wt.%. The elongation varied in the same fashion as the tensile strength. The microstructure of the composites showed moderately uniform distribution of particles. However, agglomeration of reinforcement particles became a problem at the highest amount of reinforcement. Wear experiments to determine the influence of load, sliding velocity, sliding distance and the amount of reinforcement on the wear rate of composites were designed in accordance with the Taguchi model. The results revealed that both load and sliding velocity have the highest influence.
Comparative Study of DC Motor Speed Control Using Neural Networks and Fuzzy Logic Controller
Authors: Batayneh Wafa , Nawafleh Nash’at
Published: March 2016

This paper demonstrates the importance of the intelligent controllers over the conventional methods. A speed control of the DC motor is developed using both Neural Networks and Fuzzy logic controller in MATLAB environment as intelligent controllers. In addition a conventional PID controller is developed for comparison purposes. Both intelligent controllers are designed based on the simulation results of the nonlinear equations in addition to the expert pre knowledge of the system. The output response of the system is obtained using the two types of the intelligent controllers, in addition to the conventional PID controller. The performance of the designed Neural Networks, Fuzzy logic controller and the PID controller is compared and investigated. Finally, the results show that the neural network has minimum overshoot, and minimum steady state parameters. This shows more efficiency of the intelligent controllers over the conventional PID controller. Also it shows that Neural Networks is better than Fuzzy logic controller in terms of over shoot and rising time. At the end of this paper an implementation of Graphical User Interface (GUI) method is developed. The main purpose of the GUI is to give the users a chance to use the program in a simple way without the need to understand the program languages.
Development of a Miniaturized, Electromagnetically Actuated Punch
Authors: Ahrens Markus , Hasselbusch Tobias , Dagen Matthias , Behrens Bernd-Arno , Ortmaier Tobias
Published: March 2016

The production of micro-components in high quantities by means of cutting plays a central role in the area of metal forming. Generally, these components are manufactured with mechanical high speed presses with modified drive kinematics which provide stroke rates of up to 4,000 strokes per minute (spm) and punching forces of up to 2,000 kN. Depending on the application, this may result in a significant oversizing both in terms of maximum cutting force and size of the punching machine. This leads to higher production costs due to increased space and energy consumption which could be improved by a better adaptability of the machine to the process. To fulfill both requirements, a prototype of an electromagnetically driven punch machine with highly efficient resonance drive and miniaturization potential is proposed in this paper. Electromagnetic actuators induce oscillations of a mass-spring system at its resonance frequency by storing potential energy in the system’s springs. An advantage of the resonance propulsion is that only magnets with low nominal force are needed, since only small forces are necessary during the swing-up. The resulting oscillation frequency can be adjusted for the given task by using a modular concept with exchangeable springs. After discussing the concept and essentials, the requirements and constraints are pointed out. Subsequently, a model of the system is created and an energy based bang-bang control concept is implemented utilizing model based filter techniques. Based on the simulation results a test rig was built and obtained measurements were compared to the simulation data. The test rig provides stroke rates up to 2,000 spm and cutting forces up to 20 kN. A prototype, which will be able to achieve higher stroke rates and cutting forces will be part of future work.
Statistical Comparison of Feature Sets for Time Series Classification of Dynamical System Response
Authors: Banerjee Amit , Quiroz Juan C. , Abu-Mahfouz Issam
Published: March 2016

The use of classification techniques for machine health monitoring and fault diagnosis has been popular in recent years. System response in form of time series data can be used to identify type of defect, severity of defect etc. However, a central issue with time series classification is that of identifying appropriate features for classification. In this paper, we explore a new feature set based on a delay differential equations (DDEs). DDEs have been used recently for extracting features for classification but have never been used to classify system responses. The Duffing oscillator and Van der Pol–Duffing (VDP-D) oscillator are used as dynamic systems, and the responses are classified into self-similar groups. Responses with the same period should belong to the same group. Misclassification rate is used as an indicator of the efficacy of the feature set. The proposed feature set is compared to a statistical feature set, a power spectral coefficient feature set and a wavelet coefficient feature set. In work described in this paper, a density estimation algorithm called DBSCAN is used as the classification algorithm. The proposed DDE-based feature set is found to be significantly better than the other feature sets for the classifying responses generated by the Duffing system. The wavelet and the power spectral coefficient data sets are not found to be significantly better than the statistical feature set for the Duffing system. None of the feature sets tested are discerning enough on the VDP-D system.
Multivariate Analysis of Orthogonal Tube Cutting Forces With 3-D Tool Wear Analysis of AISI 1020 Alloy Steel Using Cold Compressed Air Versus Liquid Nitrogen as Metal Working Fluids
Authors: Chandrasekaran Vishnu Vardhan , Payton Lewis N. , Hunko Wesley S.
Published: March 2016

The growing cost associated with insurance, handling and disposing of conventional metal working fluids (oil and water based) continues to drive a need for alternative metal working fluids.

An orthogonal tube turning machining experiment on AISI 1020 alloy steel was conducted to study the performance of High Speed Steel (HSS) tool inserts and carbide tool inserts utilizing cold compressed air and liquid nitrogen environments as the metal working fluid of choice The use of both high speed steel and carbide inserts allowed for direct comparison of geometrically identical inserts in customized tool holders that were used to present the tools with the geometrically identical tool rake angle alpha. Tool holder stiffness was therefore common to all tool rake angles compared.

AISI 1020 steel was used because of its commercially dominant availability and usage. Cold cryogenic cooling was selected because of its growing usage in high performance machining applications. The use of cold compressed air has been much less studied in the machining of metals than in the machining of plastics and composites where it is quite commonly used. The comparisons between these two methods represent the first published values comparing the current extremes of gaseous metal working fluid applications in a commercial steel.

This statistically designed experiment produced a large amount of comparative data that focused on the wear of the tools in two different cutting environments allowing for multivariate analysis of variance and regressive curve fitting. The orthogonal tube turning was set up on a conventional two axis HAAS TL-2 CNC tool room lathe. Forces were collected utilizing a standard Kistler force dynamometer to record the force data in X, Y and Z axes. Two levels of uncut chip thickness, 0.002 and 0.004” per revolution were maintained with a constant feed and depth of cut of 0.125” at different tool rake angles of 0°, 7° and 15°, with no chip breaker installed in the tool. Tool rake angles and depth of cuts were selected to ensure maximum statistical power/decisiveness of the experiment. The experiment was carried out for duration of 1 minute while the force data was collected for the entire duration of cut. New tool insert was used for each factor level combination. The traditional force analysis results are provided for an orthogonal tube turning experiment. In addition, all tools were analyzed for 3-dimensional rake face wear using an innovative Keyence white light microscope. Surprisingly, the inexpensive, simple cold compressed air produced less wear than the more expensive liquid nitrogen for all cutting factor level combinations.
Handy-Device Development of Softness Measurement by Indentation Imitating Palpation for Evaluation of Elasticity and Visco-Elasiticity
Authors: Sakuma Atsushi
Published: March 2016

Spherical indentation testing is studied to evaluate the viscoelasticity of soft materials like human body. Here, the Hertzian contact theory is functionally extended to evaluate indentations for the thin tissues. In the expansions, the technique used for evaluating the thickness of finite specimens is first explained by analyzing the experimental results of indentations. Then, the viscoelasticity of soft materials with finite thickness is theoretically derived by defining an equivalent indentation strain for the analysis of the indentation process. The expansions are examined to evaluate its reliability by applying them to measure the viscoelasticity of some soft materials. Furthermore, this technology is applied to the elasticity investigation of the human body. Especially, the measurement results of viscoelastic characteristics of the body of human body are shown and the availability of developed device is discussed to reveal the deformation mechanics of human body in this report.
Damage Detection in Laminated Composite Plates and Shells Using Second Derivatives of Mode Shape Data Through Dynamic Analysis of These Structures
Authors: Govindasamy Mahendran , Kesavan Chandrasekaran , Santkumar Malhotra
Published: March 2016

The main objective of this study is to evaluate the dynamics-based techniques for damage detection in laminated composite cantilevered rectangular plates and cylindrical shells with damages in the form of surface macro-level cracks using finite element analysis (FEA). However, the quantitative change in global vibration characteristics is not sufficiently sensitive to local structural damages especially to small size damages. Hence certain parameters called damage indicators based on mode shape curvature, which are the second derivatives of the vibration characteristics (mode shapes), are used in this study to detect the location and size of even small damages accurately in laminated composite structures. The commercial FEA package ANSYS is used for the theoretical modal analysis to generate the natural frequencies and normalized mode shapes of the intact and damaged structures. Experimental investigations are carried out on the laminated plate and shell structural elements to provide a validation of the analysis. Experimental investigations are carried out on the laminated composite (E-glass unidirectional fibers reinforced epoxy resin) cantilevered plate and shell structural elements to provide a validation of the analysis. The effectiveness of these methods is clearly demonstrated by the results obtained.
Analysis and Control of Aeromechanical Instabilities in Helicopters
Authors: Nair Salini S. , Mohan Ranjith
Published: March 2016

The paper focuses on analysis of aeromechanical instabilities, specifically ground resonance in helicopters and active control methods for improving the existing stability margins. First, a simplified model of coupled rotor-fuselage system with translational fuselage degrees of freedom and blade lead-lag degree of freedom is considered. Anisotropy is introduced through stiffness variation between blades. Depending on the configuration, appropriate methods are used for stability analysis and to determine frequency coalescence. Second, similar analysis is extended to a model with fuselage pitch, roll and blade flap, lag degrees of freedom and incorporates wake model. The analysis brings out effects of collective pitch and lock number on aeromechanical instabilities with the inclusion of wake model. Active control strategy using pole placement technique and Linear Quadratic Regulator (LQR) is applied to the periodic system. Stabilization is done by increasing the aerodynamic damping through control input given either as cyclic or collective pitch.
A Novel Computational Framework for the Oxidation of C/C Composites Under Thermal Shock
Authors: Leanos Alma L. , Prabhakar Pavana
Published: March 2016

In this paper, the influence of thermal shock conditions on both, the extent of carbon materials decomposition and the through-thickness compressive stiffness degradation of 2D woven C/C composites is predicted by computational efforts and validated against experimental results. The proposed computational framework consists of two main steps: a) A radiation heat transfer analysis on a meso-scale C/C composite model exposed to thermal shock conditions accounting for the heat flux in the form of gas due to carbon material decomposition within the meso-scale model; b) A stress analysis to model the carbon stiffness degradation due to oxidation observed in the previous step. This is followed by a through-thickness compressive analysis on the meso-scale model to determine its compressive stiffness. The predicted oxidation behavior and compressive responses of the meso-scale model under various thermal shock conditions are compared with previously published experimental results, resulting in good agreement. In conclusion, the proposed computational framework can be used to aid in the design of C/C composites and protection systems. This computational model has the potential of extension to other C/C composites by changing the fiber architecture, weave pattern and/or fiber volume fraction.
Bluetooth Based Stair Climbing Robot Control Using Cell Phone
Authors: Batayneh Wafa , AL-Smadi Eyad , Al-Zghoul Abdullah , Alshaggah Ghaith
Published: March 2016

In this paper a tracked stair climbing robot will be developed. The robot can be controlled using any smart cell phone through Bluetooth. When designing the robot, the main constraints taken into consideration are the ability to climb the stairs in addition to the optimal size and weight; the robot needs to be small and light enough to get into places inaccessible by human. It needs also to be large enough to climb obstacles commonly found in any areas, such as rough terrains and stairs. Finally, it will be equipped with digital humidity and temperature sensor (DHT). A prototype of the stair climbing robot is designed and implemented, this robot is capable of moving on rough terrains and climbing a stair, it is portable due to the light material used in manufacturing. This robot will be controlled using two modes; the first one will use Arduino communicating by Bluetooth Module that can be connected with any smart mobile phone. The second mode (autonomous) will use the feedback from an ultrasonic sensor installed at the top of the robot and is able to rotate using a servo motor. The prototype is tested on different rough and inclined terrains, on grassy ground and on stairs. The overall system works successfully and it performs very well. Video of the working prototype is provided.
Multilevel Metal Flow-Fill Analysis of Centrifugal Casting for Indirect Additive Manufacturing of Lattice Structures
Authors: Mun Jiwon , Busse Matthew , Ju Jaehyung , Thurman James
Published: March 2016

The centrifugal casting is a classical manufacturing method and it has been widely studied. However, when it comes to manufacture thin walled lattice materials with complex three-dimensional meso-structures, a multiscale flow-fill analysis may be needed for macro-filling at the sprue system and micro-filling at lattice structures. On the micro-filing analysis for a thin walled lattice structure, the surface tension of molten metal appears to be an important factor. On the other hand, flow inertia may affect the flow-filling process more than the surface tension of molten metal does. Our hypothesis is that there exist a range of ratios of cell wall thickness to length that are primarily affected by surface tension or density. From comparison with two different molten metals — aluminum and copper alloys, we can estimate the characteristic of flow, which will be of benefit when designing lattice structures and selecting materials for the manufacturing process. The objective of this study is to test the hypothesis by constructing an analytical model on flow filling of molten metals (aluminum alloy and copper alloy) associated with manufacturing lattice structures. The Naiver-Stokes equation with surface tension is considered for modeling of the flow of molten metal along the micro-channel of lattice structures and is numerically implemented with MATLAB. Temperature dependent properties of the liquid metals; e.g., density, viscosity, and conductivity, are considered for building the analytical model. Numerical simulations with a commercial code, ANSYS are conducted using a user defined function. Experimental validation is followed to manufacture a cubic truss lattice structure with a varying wall thickness; 0.5–1mm. Two molten metals — aluminum alloy and copper alloy are used for filling the mold at the centrifugal casting system. The mold is prepared by removing sacrificial lattice patterns made by a polyjet 3D printer. The preliminary result shows that the final lattice structures with an aluminum alloy through the 3D printing of sacrificial pattern followed by centrifugal casting have relatively good flow filling property at thin wall thickness (∼0.5mm) due to low surface tension of aluminum alloy. On the other hand, the high surface tension of a copper alloy prevents flow-fill to micro-channel mold cavity, resulting in early solidification. The indirect additive manufacturing based casting shows an excellent surface quality, which can be used for manufacturing cellular structures. A coupled flow and heat transfer of molten metal successfully simulate flow-fill and solidification and is compared with the experiment. Faster filling-time and faster solidification for the temperature-dependent material properties were shown.
Use of Conceptual Questions With Prompt Feedback in Engineering Thermodynamics
Authors: Manteufel Randall D.
Published: March 2016

An effective strategy to promote deep understanding in engineering thermodynamics is to increase the use of conceptual questions during lectures coupled with prompt assessment of student responses. A key is to collect responses from all students and provide prompt feedback explaining the correct response. It has been found that conceptual questions are more effective than numerical. Good questions explore if a quantity will increase, decrease or remain unchanged in response to a change in the system. In previous semesters, an instructor would pose conceptual questions during lecture and discuss with those students who participated with the instructor. Using an electronic collection system for student responses, all student responses can be collected and assesses. Results show that (1) it is rare that the entire class is correct even for the simplest of questions, (2) a nearly identical question can be repeated in a subsequent lecture and there will continue to be a incorrect responses, and (3) repeating questions throughout the semester is effective at addressing common conceptual misunderstandings and improving long-term student learning in engineering thermodynamics.
Mechanical and Microstructural Properties of Selective Laser Melted 17-4 PH Stainless Steel
Authors: Yadollahi Aref , Shamsaei Nima , Thompson Scott M. , Elwany Alaa , Bian Linkan
Published: March 2016

The present article focuses on the mechanical properties and microstructural features of Selective Laser Melted (SLM) 17-4 precipitation hardening (PH) stainless steel (SS) as well as their comparison to conventionally built materials. The topics investigated are the effects of different building orientations and post-fabrication heat treatment (solution annealing and aging) on the mechanical and microstructural characteristics of samples fabricated by SLM. Yield and ultimate tensile strengths of SLM-produced 17-4 PH SS were found to be lower than those of wrought materials (H900 condition). In addition, building orientations showed a noticeable effect on tensile properties. Presence of defects, such as pores resulting from entrapped gas, un-melted regions, and powder particles resulting from lack of fusion were the main reasons for lower elongation to failure of SLM-produced 17-4PH SS in this study.
A Theoretical and Numerical Study of the Dzhanibekov and Tennis Racket Phenomena
Authors: Murakami Hidenori , Rios Oscar , Impelluso Thomas J.
Published: March 2016

In this paper, we present complete explanation of the Dzhanibekov phenomenon demonstrated in a space station (www.youtube.com/watch?v=L2o9eBl_Gzw) and the tennis racket phenomenon (www.youtube.com/watch?v=4dqCQqI-Gis). These phenomena are described by Euler’s equation of an unconstrained rigid body that has three distinct values of moments of inertia. In the two phenomena, the rotations of a body about the principal axes that correspond to the largest and the smallest moments of inertia are stable. However, the rotation about the axis corresponding to the intermediate principal moment of inertia becomes unstable, leading to the unexpected rotations that are the basis of the phenomena. If this unexpected rotation is not explained from a complete perspective which accounts for the relevant physical and mathematical aspects, one might misconstrue the phenomena as a violation of the conservation of angular momenta. To address this, especially for students, we investigate the phenomena using more precise mathematical and graphical tools than those employed previously.

Following Élie Cartan [1], we explicitly write the vector basis of a body-attached, moving coordinate system. Using this moving frame method, we describe the Newton and Euler equations. The adoption of the moving coordinate frame expresses the rotation of the body more clearly and allows us to use the Lie group theory of special orthogonal group SO(3).

We integrate the torque-free Euler equation using the fourth-order Runge-Kutta method. Then we apply a recovery equation to obtain the rotation matrix for the body. By combining the geometrical solutions with numerical simulations, we demonstrate that the unexpected rotations observed in the Dzhanibekov and the tennis racket experiments preserve the conservation of angular momentum.
Effect of Solid Solution Temperature on Material Properties and Microstructure of Inconel 718/TiC Composites by Selective Laser Melting
Authors: Shi Jing , Wang Yachao , Lu Shiqiang , Wang Yun
Published: March 2016

Selective laser melting (SLM) is an important additive manufacturing process. It applies focused laser energy to quickly melt and solidify material powders, and a controlled layered operation can result in a free form build that is often out of reach for machining processes. As such, it has attracted much attention in recent years. However, metal components produced by this process often have inferior mechanical properties, as compared with the counterparts by the traditional manufacturing processes. To strengthen the metal components by SLM, adding reinforcement particles and applying post treatment are regarded as the two effective ways. Although adding reinforcement particles to create metal matrix composites has been studied by researchers in literature, much fewer has been done to use post treatment processes to further improve the properties and performance of the metal matrix composites from SLM.

In this study, a nano-TiC reinforced Inconel 718 composite is prepared using SLM technique. The material has 0.5 wt.% nano-TiC addition. Solid solution treatments at three levels of temperature (940, 980, 1020 °C) are carried out to evaluate the effect of the heat treatment methods on the microstructure and resulted mechanical properties of the composite material. The results of samples with and without heat treatment are also compared. SEM observations are carried out to analyze the microstructure of the composite and understand the reinforcing mechanism. Tensile tests are conducted to evaluate the mechanical properties of the formed composites. It is discovered that compared with the pure Inconel 718 by SLM, the Inconel 718-TiC composite exhibits improved ultimate tensile strength. Microscopy observation of as-built samples indicates that the dendritic structures of Inconel 718 is remarkably refined by the TiC particles. Suspected laves phase particles are observed in as-built Inconel-TiC composite, and they partially transform to large amount of needle-like δ phase during the solid solution treatment.
In Situ AFM Characterization of Deformation Behavior of Nano TiC Reinforced Inconel 718 Superalloy Prepared by Selective Laser Melting
Authors: Wang Yachao , Shi Jing , Wang Xinnan , Wang Yun
Published: March 2016

Laser assisted additive manufacturing (LAAM) is regarded as a complementary method to traditional manufacturing processes and it has drawn significant attention from both industry and academia. Improving the performance of components fabricated by LAAM has been an important research task in recent years due to the inevitable negative effects introduced by in the LAAM process, such as porosity, inhomogeneity, and tensile residual stress. In this study, to obtain high-performance metal components by LAAM, nano-TiC particles are adopted to reinforce Inconel 718 and the mixed powders of TiC and Inconel 718 are processed by selective laser melting (SLM). To investigate the effect of TiC concentration on the property and performance of the metal matrix composite, samples with three levels of nano-TiC addition (0, 0.25, 0.5 wt.%) are prepared, in which the SLM process parameters are kept the same for all cases. Three-point bending tests are performed to determine the optimum nano TiC addition. It is found that the material of 0.5 wt.% TiC addition results in the highest bending modulus. Compared with pure Inconel 718, the composite with 0.5 wt.% nano-TiC shows 38% increase in flexural modulus. In addition, to better understand the reinforcing mechanism of nano TiC particles, the SLM processed samples are characterized using a self-designed micro/nano three-point bending tester that is incorporated with an atomic force microscope (AFM) to in situ observe the nanoparticles movement on the sample surface under loading. The sample surface is scanned by AFM at 0%, 2%, 4% and 6% strain condition during the test, and the migration of individual nano particles at the sample surface is tracked at each strain condition. The AFM observations show that the dispersion of TiC nanoparticles is overall random and uniform in the Inconel 718 matrix, and localized agglomeration of TiC particles exists. The interfaces between nanoparticles and the matrix are generally continuous and free of any deleterious micro cracks, indicating a favorable metallurgical bonding feature. The surface morphologies obtained by AFM at different strain conditions are processed by digital image correlation technique to obtain the strain fields during the deformation process. The results show that the agglomerated TiC particles serve as defects in the material, leading to relative sliding of particles with respect to the matrix. This is believed to be the main factor that limits the performance of the composites made by SLM.
Effects of Inhalation Transience on Particle Transport Through a CT-Based Human Airway Geometry
Authors: Gruetzemacher Richard , Arabshahi Abi , Pankajakshan Ramesh
Published: March 2016

The effects of inhalation transience on particle transport through the lungs were examined using numerical simulation. Physiologically appropriate, regional ventilation was induced through a computed tomography (CT) based human airway geometry for steady and transient inhalation using lobar-specific boundary conditions. Transient inhalation and the analogous steady cases were simulated for two breathing rates. Particle transport was modeled for a range of particle sizes and Stokes numbers. The deposition fractions of particles were analyzed and comparisons were made between the results for steady and transient inhalation. Deposition fractions for particles released during transient inhalation were substantially less than those released during steady inhalation for all but the largest particle sizes. Future work is suggested.
Simulation and Experimental Analysis of Magnetorheological Dampers Under Impact and Shock Loading
Authors: Ouyang Q. , Wang J. , Zheng J. J. , Wang X. J. , Xi Y.
Published: March 2016

Magnetorheological (MR) fluids contain suspensions that exhibit a rapid, reversible and tunable transition from a free-flowing state to a semi-solid state upon the application of an external magnetic field. This behavior has attracted significant attention in the development of dampers, shock absorption system, military and defence system and safety devices in aerospace engineering. However, many of the issues pertaining to MR damper behavior in impact and shock applications are relatively unknown. This study provides an experimental analysis and simulation analysis by using COMSOL multyphysics of MR dampers when they are subjected to impact and shock loading. To this end, a novel MR damper with a four-stage piston and independent input currents is designed and analyzed. In this paper, two-dimension symmetrical Computational Fluid Dynamics (CFDs) simulation for the laminar flow of an incompressible MR fluid in the annular gap in the presence of a varying magnetic field. The purpose of this research is to study the couple effect of electromagnetic field and the fluid flow field and magnitude of damping force in a macroscopic view. The governing differential equations describing the magnetic field and fluid flow in the annular gap are solved numerically by COMSOL Multiphysics. Through the electromagnetic analysis and flow field analysis, the coupling effect of the magnetic field between the coil and the multiphysics coupling effect of novel MR was be found. For the each coil has an independent power supply, so it can provide a wider range damping force by combining the electromagnetic field of coils.
Thermal Recovery of Cutaneous Neoplasm During Cryosurgery
Authors: Ibarra-Prieto Maria-Fernanda , Luna Jose-Manuel , Hernandez-Guerrero Abel , Luviano-Ortiz Jose-Luis
Published: March 2016

Cryotherapy, also called cryosurgery, cryoablation or targeted cryoablation therapy, is a minimum invasive treatment that uses extreme cold temperatures to freeze and destroy damage tissue, like tumors or cancer cells. During cryotherapy, a refrigerant as liquid nitrogen or argon gas is forced to flow inside a probe. This probe is similar to a needle and it is called cryoprobe. Once the refrigerant is inside this cryoprobe the temperature decreases below zero Celsius in a given time, creating an intense cold that contacts the diseased tissue. Physicians use image guidance techniques to monitor the cryoprobe, such as ultrasound, computed tomography (CT) or magnetic resonance imaging (MRI). To destroy diseased tissue located outside the body, liquid nitrogen is applied directly to the infected zone with a cotton swab or spray. For tumors located below the skin surface and depth in the body, the medical image guidance to insert one or more cryoprobes is used. Living tissue, whether healthy or sick, cannot tolerate extremely low temperatures. For this reason cryotherapy involves a series of steps leading to cell death. Tumors are repeatedly frozen and thaw, typically two freeze – thaw cycles are used. Once the cells have been destroyed, white blood cells of the immune system remove dead tissue.

The present work is a 3D simulation. The skin is modeled with a regular geometry, divided into three layers: epidermis, thinner and superficial part of the skin; dermis, 40 times thicker than the epidermis (also this layer has a thermoregulatory function because of the blood flow, which also contributes to vasoconstriction and vasodilatation of the skin), and finally the last layer is the hypodermis or subcutaneous fat layer (which mainly stores fat). For a transient analysis of this three layers of the skin, the bio-heat transfer equation of Pennes is used, since it contains terms that involve energy released during metabolism, blood perfusion, body core temperature and certain physical properties such as density, specific heat, thermal conductivity, latent heat of phase change and heat capacity ratio. The malignant tumor, melanoma, is modeled as an irregular symmetric geometry. Three different melanoma Clark levels are analyzed, Clark II, III and IV. Each level is analyzed with three size variations. These levels are chosen because most people who are diagnosed with melanoma have Clark II level. Clark V level was not considered because when melanoma reaches subcutaneous cellular tissue the metastasis process begins. In this work a thermal recovery analysis of the skin during certain periods of time in the freezing-thaw cycles is carried out. Each of this time periods vary according to the type of refrigerant, liquid nitrogen or argon gas. The analysis contemplates the phase change suffered by the skin.