bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-Dimensional Strain-Based Model for the Severity Characterization of Dented Pipelines
Authors: Okoloekwe Chike , Kainat Muntaseer , Langer Doug , Hassanien Sherif , Roger Cheng J.J. , Adeeb Samer
Published: July 2018

Oil and gas pipelines traverse long distances and are often subjected to mechanical forces that result in permanent distortion of its geometric cross section in the form of dents. In order to prioritize the repair of dents in pipelines, dents need to be ranked in order of severity. Numerical modeling via finite element analysis (FEA) to rank the dents based on the accumulated localized strain is one approach that is considered to be computationally demanding. In order to reduce the computation time with minimal effect to the completeness of the strain analysis, an approach to the analytical evaluation of strains in dented pipes based on the geometry of the deformed pipe is presented in this study. This procedure employs the use of B-spline functions, which are equipped with second-order continuity to generate displacement functions, which define the surface of the dent. The strains associated with the deformation can be determined by evaluating the derivatives of the displacement functions. The proposed technique will allow pipeline operators to rapidly determine the severity of a dent with flexibility in the choice of strain measure. The strain distribution predicted using the mathematical model proposed is benchmarked against the strains predicted by nonlinear FEA. A good correlation is observed in the strain contours predicted by the analytical and numerical models in terms of magnitude and location. A direct implication of the observed agreement is the possibility of performing concise strain analysis on dented pipes with algorithms relatively easy to implement and not as computationally demanding as FEA.
Data-Driven Damage Model Based on Nondestructive Evaluation
Authors: Baxevanakis Konstantinos P. , Wisner Brian , Schlenker Sara , Baid Harsh , Kontsos Antonios
Published: July 2018

A computational damage model, which is driven by material, mechanical behavior, and nondestructive evaluation (NDE) data, is presented in this study. To collect material and mechanical behavior damage data, an aerospace grade precipitate-hardened aluminum alloy was mechanically loaded under monotonic conditions inside a scanning electron microscope, while acoustic and optical methods were used to track the damage accumulation process. In addition, to obtain experimental information about damage accumulation at the laboratory scale, a set of cyclic loading experiments was completed using three-point bending specimens made out of the same aluminum alloy and by employing the same nondestructive methods. The ensemble of recorded data for both cases was then used in a postprocessing scheme based on outlier analysis to form damage progression curves, which were subsequently used as custom damage laws in finite element (FE) simulations. Specifically, a plasticity model coupled with stiffness degradation triggered by the experimentally defined damage curves was used in custom subroutines. The results highlight the effect of the data-driven damage model on the simulated mechanical response of the geometries considered and provide an information workflow that is capable of coupling experiments with simulations that can be used for remaining useful life (RUL) estimations.
Nonlinear Analysis of a Torsional Vibration of a Multidegrees-of-Freedom System With Centrifugal Pendulum Vibration Absorbers and Its Suppression
Authors: Kadoi Keiyu , Inoue Tsuyoshi , Kawano Junichi , Kondo Masahiko
Published: July 2018

Centrifugal pendulum vibration absorber (CPVA) has been used as a torsional vibration suppression device. Recently, downsizing turbotechnology is widespread and it causes a torsional vibration in the drivetrains of automobiles, and CPVA is used for torsional vibration suppression. In such cases of vibration suppression of the drive-train shaft, it should be modeled as a multi degrees-of-freedom system and considered the suppression of its multiple modes. However, most of researches on CPVA so far have focused on a one degree-of-freedom system, and the vibration analysis and its suppression of the torsional vibration caused in the multi degrees-of-freedom system has been hardly investigated. In this paper, the dynamical characteristic of torsional vibration of the multi degrees-of-freedom system with CPVAs is investigated both theoretically and experimentally. Vibration suppression mechanism of CPVA on the torsional vibration of the multi degrees-of-freedom system is studied by the eigenvalue analysis. The vibration suppression effect of CPVA on the harmonic resonances, and the occurrence of superharmonic resonances in multiple modes are observed by the numerical simulation. Then, nonlinear theoretical analyses of harmonic resonances and superharmonic resonances are performed and the vibration suppression effects of CPVA are explained. These obtained theoretical results are confirmed by experiments.
Effect of Residual Stresses on Microstructural Evolution Due to Rolling Contact Fatigue
Authors: Morris Dallin , Sadeghi Farshid , Chen Yong-Ching , Wang Chinpei , Wang Ben
Published: July 2018

Rolling contact fatigue (RCF) induces a complex subsurface stress state, which produces significant microstructural alterations within bearing steels. A novel modeling approach is presented in this paper, which investigates the effects of microstructural deterioration, phase transformations, and residual stress (RS) formation occurring within bearing steels subject to RCF. The continuum damage mechanics approach was implemented to capture microstructural decay. State and dissipation functions corresponding to the damage mechanics process were used via an energy criterion to predict the phase transformations of retained austenite (RA). Experimental measurements for RA decomposition and corresponding RS were combined to produce a function providing RS formation as a function of RA decomposition and stress history within the material. Microstructural decay, phase transformations, and internal stresses were implemented within a two-dimensional (2D) finite element analysis (FEA) line contact model to investigate variation in microstructural alterations due to RSs present within the material. In order to verify the model developed for this investigation, initial simulations were performed implementing conditions of previously published experimental work and directly comparing to observed RA decomposition and RS formation in 52100 steel deep groove ball bearings. The finite element model developed was then used to implement various RS profiles commonly observed due to manufacturing processes such as laser-shot peening and carburizing. It was found that some RS profiles are beneficial in altering RA decomposition patterns and increasing life while others proved less advantageous.
The Application of Polyvinylpyrrolidone as a Modifier of Tribological Properties of Lubricating Greases Based on Linseed Oil
Authors: Kozdrach Rafał , Skowroński Jarosław
Published: July 2018

The paper presents the research results on the relations between additive content and tribological, rheological, and oxidizing properties of lubricating greases. The greases were based on linseed oil, thickened with amorphous silica Aerosil® and modified with different concentration of polyvinylpyrrolidone. The greases were tested tribologically according to the test on T-02 testing machine and referred to the unmodified control. The evaluation of tribological properties was based on the following parameters: welding load, scuffing load, limiting load of wear, limiting load of scuffing, and limiting pressure of seizure. The results of tribological research revealed the most promising impact of the 3% addition of polyvinylpyrrolidone. All of the crucial parameters were improved in comparison to the unmodified control grease. The spectral analyses revealed that some of the components undergo oxidation during mechanical forces, leading to the formation of the oxidized organic compounds. These substances generated a layer, counteracting the wear of lubricated tribosystem. The improved resistance to oxidation of the tested lubricants with polyvinylpyrrolidone can be explained by the presence of highly hydrophilic pyrrolidone groups and hydrophobic alkyl group in polyvinylpyrrolidone (PVP) molecule. These compounds combine with hydrocarbon chains of linseed oil and act synergistically with the silicon dioxide molecules. The introduction of polyvinylpyrrolidone caused the improvement in dynamic viscosity at lower shear rates and a significant change of viscosity in low temperatures. An increased value of the yield point of the tested lubricating compositions after introduction of the additive was also observed.
A Comparative Study of Genetic and Particle Swarm Optimization Algorithms and Their Hybrid Method in Water Flooding Optimization
Authors: Siavashi Majid , Yazdani Mohsen
Published: July 2018

Optimization of oil production from petroleum reservoirs is an interesting and complex problem which can be done by optimal control of well parameters such as their flow rates and pressure. Different optimization techniques have been developed yet, and metaheuristic algorithms are commonly employed to enhance oil recovery projects. Among different metaheuristic techniques, the genetic algorithm (GA) and the particle swarm optimization (PSO) have received more attention in engineering problems. These methods require a population and many objective function calls to approach more the global optimal solution. However, for a water flooding project in a reservoir, each function call requires a long time reservoir simulation. Hence, it is necessary to reduce the number of required function evaluations to increase the rate of convergence of optimization techniques. In this study, performance of GA and PSO are compared with each other in an enhanced oil recovery (EOR) project, and Newton method is linked with PSO to improve its convergence speed. Furthermore, hybrid genetic algorithm-particle swarm optimization (GA-PSO) as the third optimization technique is introduced and all of these techniques are implemented to EOR in a water injection project with 13 decision variables. Results indicate that PSO with Newton method (NPSO) is remarkably faster than the standard PSO (SPSO). Also, the hybrid GA-PSO method is more capable of finding the optimal solution with respect to GA and PSO. In addition, GA-PSO, NPSO, and GA-NPSO methods are compared and, respectively, GA-NPSO and NPSO showed excellence over GA-PSO.
Multidimensional Numerical Simulations of Knocking Combustion in a Cooperative Fuel Research Engine
Authors: Pal Pinaki , Wu Yunchao , Lu Tianfeng , Som Sibendu , See Yee Chee , Le Moine Alexandra
Published: July 2018

A numerical approach was developed based on multidimensional computational fluid dynamics (CFD) to predict knocking combustion in a cooperative fuel research (CFR) engine. G-equation model was employed to track the turbulent flame front and a multizone model was used to capture auto-ignition in the end-gas. Furthermore, a novel methodology was developed wherein a lookup table generated from a chemical kinetic mechanism could be employed to provide laminar flame speed as an input to the G-equation model, instead of using empirical correlations. To account for fuel chemistry effects accurately and lower the computational cost, a compact 121-species primary reference fuel (PRF) skeletal mechanism was developed from a detailed gasoline surrogate mechanism using the directed relation graph (DRG) assisted sensitivity analysis (DRGASA) reduction technique. Extensive validation of the skeletal mechanism was performed against experimental data available from the literature on both homogeneous ignition delay and laminar flame speed. The skeletal mechanism was used to generate lookup tables for laminar flame speed as a function of pressure, temperature, and equivalence ratio. The numerical model incorporating the skeletal mechanism was employed to perform simulations under research octane number (RON) and motor octane number (MON) conditions for two different PRFs. Parametric tests were conducted at different compression ratios (CR) and the predicted values of critical CR, delineating the boundary between “no knock” and “knock,” were found to be in good agreement with available experimental data. The virtual CFR engine model was, therefore, demonstrated to be capable of adequately capturing the sensitivity of knock propensity to fuel chemistry.
Thermal and Optical Efficiency Analysis of the Linear Fresnel Concentrator Compound Parabolic Collector Receiver
Authors: Ajdad H. , Filali Baba Y. , Al Mers A. , Merroun O. , Bouatem A. , Boutammachte N. , El Alj S. , Benyakhlef S.
Published: July 2018

A solar heating compound parabolic collector (CPC) using air and palm oil as heat carrier fluid is proposed and analyzed within this study via heat transfer and ray tracing simulations. The system is a linear focusing solar system intended to be used for applications across a broad range of industrial sectors for generating medium temperature heat up to 250 °C. The Monte Carlo ray tracing method was used to predict the optical performances of the receiver. We have developed a simplified thermal model to investigate and analyze the thermal performances of the receiver under different conditions. It has been demonstrated that the investigated receiver satisfactorily matches the heat demand by producing low and medium temperature heat with an annual system efficiency of 45%.
Numerical Analysis of Heat Transfer Enhancement in a Parabolic Trough Collector Based on Geometry Modifications and Working Fluid Usage
Authors: Okonkwo Eric C. , Abid Muhammad , Ratlamwala Tahir A. H.
Published: July 2018

The parabolic trough collector (PTC) is one of the most widely deployed concentrating solar power technology in the world. This study aims at improving the operational efficiency of the commercially available LS-2 solar collector by increasing the convective heat transfer coefficient inside the receiver tube. The two main factors affecting this parameter are the properties of the working fluid and the inner geometry of the receiver tube. An investigation was carried out on six different working fluids: pressurized water, supercritical CO2, Therminol VP-1, and the addition of CuO, Fe3O4, and Al2O3 nanoparticles to Therminol VP-1. Furthermore, the influence of a converging-diverging tube with sine geometry is investigated because this geometry increases the heat transfer surface and enhances turbulent flow within the receiver. The results showed that of all the fluids investigated, the Al2O3/Oil nanofluid provides the best improvement of 0.22% to thermal efficiency, while the modified geometry accounted for a 1.13% increase in efficiency. Other parameters investigated include the exergy efficiency, heat transfer coefficient, outlet temperatures, and pressure drop. The analysis and modeling of a parabolic trough receiver are implemented in engineering equation solver (EES).
Thermalizing and Damping in Structural Dynamics
Authors: Louhghalam Arghavan , Pellenq Roland J.-M. , Ulm Franz-Josef
Published: July 2018

Structural damping, that is the presence of a velocity dependent dissipative term in the equation of motion, is rationalized as a thermalization process between a structure (here a beam) and an outside bath (understood in a broad sense as a system property). This is achieved via the introduction of the kinetic temperature of structures and formalized by means of an extended Lagrangian formulation of a structure in contact with an outside bath at a given temperature. Using the Nosé–Hoover thermostat, the heat exchange rate between structure and bath is identified as a mass damping coefficient, which evolves in time in function of the kinetic energy/temperature history exhibited by the structure. By way of application to a simple beam structure subjected to eigen-vibrations and dynamic buckling, commonality and differences of the Nosé–Hoover beam theory with constant mass damping models are shown, which permit a handshake between classical damping models and statistical mechanics–based thermalization models. The solid foundation of these thermalization models in statistical physics provides new insights into stability and instability for engineering structures. Specifically, since two systems are considered in (thermodynamic) equilibrium when they have the same temperature, we show in the case of dynamic buckling that a persistent steady-state difference in kinetic temperature between structure and bath is but indicative of the instability of the system. This shows that the kinetic temperature can serve as a structural order parameter to identify and comprehend failure of structures, possibly well beyond the elastic stability considered here.
Analytical Modeling and Experimental Validation of Cutting Forces Considering Edge Effects and Size Effects With Round Chamfered Ceramic Tools
Authors: Zhuang Kejia , Weng Jian , Zhu Dahu , Ding Han
Published: July 2018

The cutting force is one of the key factors for planning and optimizing the machining operation in material removal processes. An analytical cutting force prediction model that takes into consideration both edge effects and size effects based on the oblique cutting theory is developed and analyzed in this study. A detailed analysis of the cutting geometry is presented based on the coordinate system transformation and uncut chip thickness (UCT), which is evaluated on the rake plane instead of the reference plane. Then, the developed Johnson–Cook constitutive model of the workpiece that takes into consideration the size effects is then applied to the prediction of edge forces coefficients and cutting forces coefficients. The edge forces are predicted using the edge coefficients prediction model with the regularity found in the orthogonal simulations, which reflect the influences of chamfered length and chamfered angle. The developed model is validated using the turning operations of super alloys with round chamfered inserts. Finally, the effects of the cutter edge, cutting parameters, and UCT on the cutting forces are investigated using the developed model. The reasonableness and effectiveness of the proposed model is demonstrated through the comparison of the measured and predicted cutting forces for various chamfer characteristics.
Experimental Investigation and Constitutive Modeling for Hot Deformation Behavior of 2219 Al-Alloy Microalloyed With Silver
Authors: Mandal Purnendu Kumar , Robi P. S.
Published: July 2018

2219Al and 2219Al + 0.1 wt % Ag alloys were processed by casting route. The hot compression tests were carried out at constant true strain rates and temperatures in the range of 10−3 to 101 s−1 and 300–500 °C, respectively. Flow stress of the alloy decreases with the addition of silver. The flow stress of both alloys increases with the decrease in deformation temperature and the increase in strain rates. Constitutive models correlating the peak flow stress with deformation temperature and strain rates for the two alloys were developed using hyperbolic–sine relationship. The activation energy for hot deformation of 2219 Al alloy decreases with the addition of silver. Comparison of the predicted and experimental values of peak flow stress reveals that 92% of the data could be predicted within a deviation error of ±10% indicating good predictive capability for the developed constitutive relationships.
A Study on Long-Term In Vitro Reliability of Intracochlear Lead-Zirconate-Titanate Microactuators
Authors: Liu Yifeng , Luo Chuan , Cao G. Z. , Hume Clifford R. , Shen I. Y.
Published: July 2018

An intracochlear lead-zirconate-titanate (PZT) microactuator integrated with a cochlear implant electrode array could be a feasible strategy to implement combined electric and acoustic stimulation inside the cochlea. The purpose of this paper is to characterize in vitro a prototype PZT microactuator for intracochlear applications, including service life, failure mechanisms, and lead leaching. PZT microactuators were driven sinusoidally to failure in air and in artificial perilymph. Frequency response functions (FRFs) and electrical impedance were monitored. After the PZT microactuators failed, the amount of leached lead was measured via inductive coupled plasma mass spectrometry (ICP-MS). Two failure mechanisms are identified: electrical breakdown and structural failure. The electrical breakdown, possibly from loss of parylene encapsulation, is evidenced by a sudden and significant drop of the actuators' electrical resistance. The structural failure, possibly from electrode delamination, is evidenced by a sudden and significant drop of FRFs. The amount of lead leached from the PZT microactuator is well below published safety guidelines from federal agencies.
Effect of Long-Term Room Temperature Aging on the Fatigue Properties of SnAgCu Solder Joint
Authors: Su Sinan , Fu Nianjun , John Akkara Francy , Hamasha Sa'd
Published: July 2018

Solder joints in electronic assemblies are subjected to mechanical and thermal cycling. These cyclic loadings lead to the fatigue failure of solder joints involving damage accumulation, crack initiation, crack propagation, and failure. Aging leads to significant changes on the microstructure and mechanical behavior of solder joints. While the effect of thermal aging on solder behavior has been examined, no prior studies have focused on the effect of long-term room temperature aging (25 °C) on the solder failure and fatigue behavior. In this paper, the effects of long-term room temperature aging on the fatigue behavior of five common lead-free solder alloys, i.e., SAC305, SAC105, SAC-Ni, SAC-X-Plus, and Innolot, have been investigated. Several individual lead-free solder joints on printed circuited boards with two aging conditions (no aging and 4 years of aging) have been prepared and subjected to shear cyclic stress–strain loadings until the complete failure. Fatigue life was recorded for each solder alloy. From the stress–strain hysteresis loop, inelastic work and plastic strain ranges were measured and empirically modeled with the fatigue life. The results indicated that 4 years of room temperature aging significantly decreases the fatigue life of the solder joints. Also, inelastic work per cycle and plastic strain range are increased after 4 years of room temperature aging. The fatigue life degradation for the solder alloys with doped elements (Ni, Bi, Sb) was relatively less compared to the traditional SAC105 and SAC305.
Effects of Compressor Fouling and Compressor Turbine Degradation on Engine Creep Life Consumption
Authors: Saturday Ebigenibo Genuine , Isaiah Thank-God
Published: July 2018

The effect of engine degradation in the form of compressor fouling and compressor turbine degradation on the creep life consumption of the high-pressure (HP) turbine blades of an LM2500+ industrial gas turbine engine is investigated in this work. The degradations are flow capacity degradation and isentropic efficiency degradation. An engine model was created in Cranfield gas turbine performance and diagnostics software, pythia. Blade thermal and stress models were developed together with the Larson–Miller parameter (LMP) method for creep life analysis. The percentage decreases in creep life due to each effect were examined. For the engine considered, compressor degradation has more impact on engine creep life toward peak power operation, while HP turbine degradation has more impact on creep life at lower power levels. The results of this work will give engine operators an idea of how engine components creep life is consumed and make reasonable decisions concerning operating at part loads.
A Recipe for Optimum Mixing of Polymer Drag Reducers
Authors: Rowin Wagih Abu , Sean Sanders R. , Ghaemi Sina
Published: July 2018

Preparation of large-scale homogeneous solutions of drag reducing polymers requires an appropriate mixing procedure to ensure full disentanglement of the polymer chains without chain scission due to over-mixing. The latter is known as mechanical degradation and reduces the performance of drag reducing polymers. The dominant large-scale mixing parameters including time, impeller type, impeller speed, and impeller-to-tank diameter ratio are investigated to obtain a recipe for maximum mixing with minimum polymer degradation. Three water-based solutions of 100 ppm Superfloc A-110 (flexible structure), Magnafloc 5250 (flexible structure), and Xanthan Gum (XG) (rigid structure) are considered. The performance of the mixing parameters for each polymer is evaluated based on the solution viscosity in comparison with the highest viscosity (i.e., optimum mixing) obtained by 2 h of low-shear mixing of a small-scale polymer solution using a magnetic stirrer. The results demonstrate that optimum large-scale mixing is obtained at mean and maximum shear rates of ∼17 s−1 and ∼930 s−1, respectively, after 2–2.5 h of mixing for each of the polymers. This shear rate is obtained here using a three-blade marine impeller operating at 75 rpm and at impeller-to-tank diameter ratio of 0.5. The resulting polymer solution has the highest viscosity, which is an indication of minimal degradation while achieving complete mixing. It is also confirmed that chemical degradation due to contact with a stainless steel impeller is negligible.
Development and Testing of a Multitransducer System for Measuring Height of Condensed Water in Steam Pipes With Steady-State and Turbulent Flow Conditions
Authors: Lih Shyh-Shiuh , Jae Lee Hyeong , Bar-Cohen Yoseph , Badescu Mircea
Published: July 2018

A system consisting of a multiplexer and multiple ultrasonic probes was developed for in situ monitoring of the water condensation height in steam pipes under steady-state and turbulent flow conditions. The measurement method, the signal processing techniques, the experimental setup, and the test results are presented in this paper. The feasibility and efficiency of the developed multitransducers and signal processing algorithms were demonstrated. The measured water height and wave pattern in dynamic surface conditions inside the pipe were verified through the snapshot of the recorded video images. The developed methodology built the framework for the use of multiple transducers array ultrasonic system for practical application to in situ monitor the water height in steam pipes.
Dynamic Force Coefficients of Hydrostatic Gas Films for Recessed Flat Plates: Experimental Identification and Numerical Predictions
Authors: Delgado Adolfo , Ertas Bugra
Published: July 2018

The following paper focuses on an experimental and analytical study aimed at identifying the dynamic force coefficients of hydrostatic gas films for recessed flat plates. The motivation for the effort was brought upon by the necessity of generating more accurate models for hydrostatic gas films found in hybrid gas bearings. Pressurized air at room temperature up to 120 psi was used to test different recess geometries on a flat plate test rig, capable of characterizing the stiffness and damping force coefficients for varying supply pressures, gas film thickness values, excitation frequencies, and vibration amplitudes. The test rig design and operation is described. Experimental results include frequency-dependent stiffness and damping coefficients, and leakage. The test results show that using external pressurization can generate large stiffness values while exhibiting small leakage. However, the results also show that the majority of the test configurations portray high negative damping values. An analytical model is presented and numerical predictions are compared to experimental results. Example damping trends as a function of frequency, pressure, and film thickness are presented in addition to force coefficient plots as functions of pressure ratio.
Modeling Flow in Porous Media With Double Porosity/Permeability: Mathematical Model, Properties, and Analytical Solutions
Authors: Nakshatrala Kalyana B. , Joodat Seyedeh Hanie S. , Ballarini Roberto
Published: July 2018

Geomaterials such as vuggy carbonates are known to exhibit multiple spatial scales. A common manifestation of spatial scales is the presence of (at least) two different scales of pores with different hydromechanical properties. Moreover, these pore-networks are connected through fissures and conduits. Although some models are available in the literature to describe flows in such media, they lack a strong theoretical basis. This paper aims to fill this gap in knowledge by providing the theoretical foundation for the flow of incompressible single-phase fluids in rigid porous media that exhibit double porosity/permeability. We first obtain a mathematical model by combining the theory of interacting continua and the maximization of rate of dissipation (MRD) hypothesis, and thereby provide a firm thermodynamic underpinning. The governing equations of the model are a system of elliptic partial differential equations (PDEs) under a steady-state response and a system of parabolic PDEs under a transient response. We then present, along with mathematical proofs, several important mathematical properties that the solutions to the model satisfy. We also present several canonical problems with analytical solutions which are used to gain insights into the velocity and pressure profiles, and the mass transfer across the two pore-networks. In particular, we highlight how the solutions under the double porosity/permeability differ from the corresponding ones under Darcy equations.
An Approach to Calculate the Elastic Interaction Energy of Inhomogeneous Precipitates: Application to γ′-Ni3Ti in A-286 Steel
Authors: Shmulevitsh Mati , Shneck Roni Z.
Published: July 2018

The elastic interaction energy between several precipitates is of interest since it may induce ordering of precipitates in many metallurgical systems. Most of the works on this subject assumed homogeneous systems, namely, the elastic constants of the matrix and the precipitates are identical. In this study, the elastic fields, and self and interaction energies of inhomogeneous anisotropic precipitates have been solved and assessed, based on a new iterative approach using the quasi-analytic Fourier transform method. This approach allows good approximation for problems of several inhomogeneous precipitates in solid matrix. We illustrate the calculation approach on γ′-Ni3Ti precipitates in A-286 steel and demonstrate that the influence of elastic inhomogeneity is in some incidences only quantitative, while in others it has essential effect. Assuming homogeneous system, disk shape precipitate is associated with minimum elastic energy. Only by taking into account different elastic constants of the precipitate, the minimum self-energy is found to be associated with spherical shape, and indeed, this is the observed shape of the precipitates in A-286 steel. The elastic interaction energy between two precipitates was calculated for several configurations. Significant differences between the interactions in homogeneous and inhomogeneous were found for disk shape morphologies. Only quantitative differences (9% higher interaction between inhomogeneous precipitates) were found between two spherical precipitates, which are the actual shape.
Water Leakage Detection for Complex Pipe Systems Using Hybrid Learning Algorithm Based on ANFIS Method
Authors: Yalçın Barış Can , Demir Cihan , Gökçe Murat , Koyun Ahmet
Published: July 2018

In most city water distribution systems, a considerable amount of water is lost because of leaks occurring in pipes. Moreover, an unobservable fluid leakage fault that may occur in a hazardous industrial system, such as nuclear power plant cooling process or chemical waste disposal, can cause both environmental and economical disasters. This situation generates crucial interest for industry and academia due to the financial cost related with public health risks, environmental responsibility, and energy efficiency. In this paper, to find a reliable and economic solution for this problem, adaptive neuro fuzzy inference system (ANFIS) method which consists of backpropagation and least-squares learning algorithms is proposed for estimating leakage locations in a complex water distribution system. The hybrid algorithm is trained with acceleration, pressure, and flow rate data measured through the sensors located on some specific points of the complex water distribution system. The effectiveness of the proposed method is discussed comparing the results with the current methods popularly used in this area.
The Design Process of Additively Manufactured Mesoscale Lattice Structures: A Review
Authors: Tamburrino Francesco , Graziosi Serena , Bordegoni Monica
Published: July 2018

This review focuses on the design process of additively manufactured mesoscale lattice structures (MSLSs). They are arrays of three-dimensional (3D) printed trussed unit cells, whose dimensions span from 0.1 to 10.0 mm. This study intends to detail the phases of the MSLSs design process (with a particular focus on MSLSs whose unit cells are made up of a network of struts and nodes), proposing an integrated and holistic view of it, which is currently lacking in the literature. It aims at guiding designers' decisions with respect to the settled functional requirements and the manufacturing constraints. It also aims to provide an overview for software developers and researchers concerning the design approaches and strategies currently available. A further objective of this review is to stimulate researchers in exploring new MSLSs functionalities, consciously considering the impact of each design phase on the whole process, and on the manufactured product.
A Complete Geometric Singular Characterization of the 6/6 Stewart Platform
Authors: Slavutin Michael , Sheffer Avshalom , Shai Offer , Reich Yoram
Published: July 2018

This paper introduces the three-dimensional (3D) dual Kennedy theorem in statics, and demonstrates its application to characterize the singular configuration of the 6/6 Stewart Platform (6/6 SP). The proposed characterization is articulated as a simple geometric relation that is easy to apply and check. We find two lines that cross four of the six legs of the platform. Each one of these two lines has a parallel line that crosses the remaining two legs. Each pair of parallel lines defines a plane. The 6/6 SP is in a singular position if the intersection of these two planes is perpendicular to the common normal of the remaining two legs. The method developed for the singular characterization is also used for the analysis of the mobility and forces of the SP. Finally, the proposed method is compared to some known singular configurations, such as Hunt's and Fichter's singular configurations and the 3/6 Stewart Platform (3/6 SP) singularity. The relation between the reported characterizations of the 6/6 SP and other reported works is highlighted. Moreover, it is shown that the known 3/6 SP characterization is a special case of the results reported in the paper. Finally, a characterization of a platform that does not appear in the literature, 5/6 SP, is developed based on the new approach to demonstrate its utility.
Fabrication
of a Cell Culture Plate With a Three-Dimensional Printed Mold and Thermal Analysis of PDMS-Based
Casting Process
Authors: Min
Zaw Myo , Hedrich William
D. , Munuhe Timothy , Hossein
Banazadeh Mohamad , Wang Hongbing , Andrew
Gadsden S. , Zhu Liang , Ma Ronghui
Published: July 2018

Polydimethylsiloxane (PDMS)-based casting method was used to fabricate PDMS cell culture platforms with molds printed by a fused deposition modeling (FDM) printer. Cell viability study indicated that the produced plates have the suitable biocompatibility, surface properties, and transparency for cell culture purposes. The molds printed from acrylonitrile-butadiene-syrene (ABS) were reusable after curing at 65 °C, but were damaged at 75 °C. To understand thermal damage to the mold at elevated temperatures, the temperature distribution in an ABS mold during the curing process was predicted using a model that considers conduction, convection, and radiation in the oven. The simulated temperature distribution was consistent with the observed mold deformation. As the maximum temperature difference in the mold did not change appreciably with the curing temperature, we consider that the thermal damage is due to the porous structure that increases the thermal expansion coefficient of the printed material. Our study demonstrated that FDM, an affordable and accessible three-dimensional (3D) printer, has great potential for rapid prototyping of custom-designed cell culture devices for biomedical research.
An Analytical Model of Tumors With Higher Permeability Than Surrounding Tissues for Ultrasound Elastography Imaging
Authors: Islam Md Tauhidul , Chaudhry Anuj , Unnikrishnan Ginu , Reddy J. N. , Righetti Raffaella
Published: July 2018

Cancerous tissues are known to possess different poroelastic properties with respect to normal tissues. Interstitial permeability is one of these properties, and it has been shown to be of diagnostic relevance for the detection of soft tissue cancers and for assessment of their treatment. In some cases, interstitial permeability of cancers has been reported to be lower than the surrounding tissue, while in other cases interstitial permeability of cancers has been reported to be higher than the surrounding tissue. We have previously reported an analytical model of a cylindrical tumor embedded in a more permeable background. In this paper, we present and analyze a poroelastic mathematical model of a tumor tissue in cylindrical coordinate system, where the permeability of the tumor tissue is assumed to be higher than the surrounding normal tissue. A full set of analytical expressions are obtained for radial displacement, strain, and fluid pressure under stress relaxation testing conditions. The results obtained with the proposed analytical model are compared with corresponding finite element analysis results for a broad range of mechanical parameters of the tumor. The results indicate that the proposed model is accurate and closely resembles the finite element analysis. The availability of this model and its solutions can be helpful for ultrasound elastography applications such as for extracting the mechanical parameters of the tumor and normal tissue and, in general, to study the impact of poroelastic material properties in the assessment of tumors.
Ambient Temperature and Self-Heating Scaling Laws for Materials With Temperature-Dependent Thermal Conductivity
Authors: Ditri John
Published: July 2018

Two of the primary variables affecting junction temperature of semiconductor devices are the self-heating due to internal power dissipation within the device and the device's base (or ambient) temperature. For materials with temperature-independent material properties, the junction temperature is a linear function of these two variables, which allows for simple “scaling” of the junction temperature for arbitrary dissipation and/or base temperatures. In materials with temperature-dependent material properties, however, the relationship between junction temperature and either variable is nonlinear. The scaling law between junction temperature and dissipated power and base temperature for materials with temperature-dependent material properties are developed in this work. This scaling law allows for fast computation of junction temperature for any values of power dissipation and/or base temperature given the junction temperature for one specific instance of power dissipation and base temperature and hence may find applicability in fast electrothermal solvers.
Thermally Developing Heat Transfer With Nonlinear Viscoelastic and Newtonian Fluids With Pressure-Dependent Viscosity
Authors: Siginer Dennis A. , Talay Akyildiz F. , Boutaous Mhamed
Published: July 2018

A semi-analytical solution of the thermal entrance problem with constant wall temperature for channel flow of Maxwell type viscoelastic fluids and Newtonian fluids, both with pressure dependent viscosity, is derived. A Fourier–Gauss pseudo-spectral scheme is developed and used to solve the variable coefficient parabolic partial differential energy equation. The dependence of the Nusselt number and the bulk temperature on the pressure coefficient is investigated for the Newtonian case including viscous dissipation. These effects are found to be closely interactive. The effect of the Weissenberg number on the local Nusselt number is explored for the Maxwell fluid with pressure-dependent viscosity. Local Nusselt number decreases with increasing pressure coefficient for both fluids. The local Nusselt number Nu for Newtonian fluid with pressure-dependent viscosity is always greater than Nu related to the viscoelastic Maxwell fluid with pressure-dependent viscosity.
Tribological Properties of Three-Dimensionally Printed Ti–6Al–4V Material Via Electron Beam Melting Process Tested Against 100Cr6 Steel Without and With Hank's Solution
Authors: Khun N. W. , Toh W. Q. , Tan X. P. , Liu E. , Tor S. B.
Published: July 2018

Three-dimensionally (3D) printed Ti–6Al–4V (Ti64) samples via an electron beam melting (EBM) process were developed to investigate their microstructure and mechanical and tribological properties in comparison with those of commercial Ti64 samples. The 3D-printed Ti64 samples had a heavily twinned and acicular martensitic structure that was responsible for their higher surface hardness than that of the commercial Ti64 samples. The 3D-printed Ti64 samples tested against a 100Cr6 steel counter ball without and with Hank's solution had a higher wear resistance associated with their higher surface hardness than the commercial Ti64 samples. The use of Hank's solution during sliding reduced the wear of the both Ti64 samples as a result of the lubricating effect of the solution. It could be concluded that the 3D-printed Ti64 samples in this study had comparable mechanical and tribological properties to those of the commercial Ti64 samples.
A Method for Mode Coupling Chatter Detection and Suppression in Robotic Milling
Authors: Cen Lejun , Melkote Shreyes N. , Castle James , Appelman Howard
Published: July 2018

A new method for online chatter detection and suppression in robotic milling is presented. To compute the chatter stability of robotic milling along a curvilinear tool path characterized by significant variation in robot arm configuration and cutting conditions, the tool path is partitioned into small sections such that the dynamic stability characteristics of the robot can be assumed to be constant within each section. A methodology to determine the appropriate section length is proposed. The instantaneous cutting force-induced dynamic strain signal is measured using a wireless piezoelectric thin-film polymer (polyvinyldene fluoride (PVDF))-based sensor system, and a discrete wavelet transform (DWT)-based online chatter detection algorithm and chatter suppression strategy are developed and experimentally evaluated. The proposed chatter detection algorithm is shown to be capable of recognizing the onset of chatter while the chatter suppression strategy is found to be effective in minimizing chatter during robotic milling.
Synergetic Effect of Cryorolling and Postroll Aging on Simultaneous Increase in Wear Resistance and Mechanical Properties of an Al–Cu Alloy
Authors: Jaseem I. , Immanuel R. J. , Rao P. N. , Khan F. , Sahoo B. N. , Panigrahi S. K. , Kamaraj M.
Published: July 2018

Aluminum–copper alloy system is extensively used in structural and aerospace applications for its high strength-to-weight ratio, good mechanical and tribological properties. Improving the properties of these alloys would likely widen their application area. In the present work, an attempt has been made to simultaneously enhance the wear resistance and mechanical properties of an Al–Cu alloy, AA2014 by imparting different levels of cryorolling strains and postroll aging treatment. The wear behavior of the material is studied under dry sliding condition by pin-on-disk experiments and mechanical properties are assessed by tensile test. Formation of high fraction of dislocation density and significant refinement of microstructure during cryorolling and nucleation of fine coherent Guinier–Preston (GP) zones of Al2Cu precipitates during postcryoroll aging has led to about 100% increment in the wear resistance of the material. Tensile test results proved that the synergetic effect of cryorolling and aging treatment led to 53% increment in strength (557 MPa) without compromising the material's ductility (22.5%). A detailed investigation on the various mechanisms responsible for the enhanced wear resistance and improved mechanical performance is presented based on the microstructural evidence.
Implementation of Design Rules for Perception Into a Tool for Three-Dimensional Shape Generation Using a Shape Grammar and a Parametric Model
Authors: Mata Marta Perez , Ahmed-Kristensen Saeema , Shea Kristina
Published: July 2018

The user experience of a product is recognized as having an increasing importance in particular in consumer products. Current approaches to designing user experiences are not easily translated to languages that a computer can understand. This paper examines a particular aspect of user experience, namely perception of the aesthetics of a product, to formalize this to rules, which are embedded into a tool to generate design. Investigating the perception of consumers is key to designing for their aesthetic preferences. Previous research has shown that consumers and designers often perceive the same products differently. This paper aims to embed rules on perception into a tool to support designers during design synthesis. Aesthetic design rules connecting perceptions with aesthetic features were integrated into a set grammar and a parametric modeling tool, and applied to the particular case of vases. The generated tool targeted the creation of vases with the perception of beautiful, elegant, and exciting. Results show that it is possible to generate beautiful, elegant, and exciting vases following the three aesthetic design rules, i.e., tall, simple, and curvy. The main contribution of this paper is the method used to incorporate information on perception into the set grammar and the parametric model. The tool is additionally proposed for supporting designers during design synthesis of shapes. The results are valid for vases but the method can be applied to other perceptions and product categories.
Design and Treadmill Test of a Broadband Energy Harvesting Backpack With a Mechanical Motion Rectifier
Authors: Yuan Yue , Liu Mingyi , Tai Wei-Che , Zuo Lei
Published: July 2018

The energy harvesting backpack that converts the kinetic energy produced by the vertical oscillatory motion of suspended loads to electricity during normal walking is a promising solution to fulfill the ever-rising need of electrical power for the use of electronic devices in civilians and military. An energy harvesting backpack that is based on mechanical motion rectification (MMR) is developed in this paper. Unlike the conventional rack-pinion mechanism used in the conventional energy harvesting backpacks, the rack-pinion mechanism used in the MMR backpack has two pinions that are mounted on a generator shaft via two one-way bearings in a way that the bidirectional oscillatory motion of the suspended load is converted into unidirectional rotation of the generator. Due to engagement and disengagement between the pinions and the generator shaft, the MMR backpack has broader bandwidths than the conventional energy harvesting backpacks; thus, the electrical power generated is less sensitive to change in walking speed. Two male subjects were recruited to test the MMR backpack and its non-MMR counterpart at three different walking speeds. For both subjects, the MMR backpack for most of the time generated more power than the non-MMR counterpart. When compared with literature, the MMR backpack had nearly sixfold improvement in bandwidth. Finally, the MMR backpack generated nearly 3.3 W of electrical power with a 13.6 kg load and showed nearly two- to tenfold increases in specific power when compared with a conventional energy harvesting backpack.