bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Elasticity Evaluation and its Design Technique for Soft Materials by Using Ball Indentation Test
Authors: Nagai Asuka , Takayama Etsuko , Sakuma Atsushi
Published: January 2018

In order to design the products made from soft materials, it is important to quantify the deformation characteristics of them for the quality and reliability of their design. But the quantification is ordinary difficult because of large deformation due to its softness even if the tensile test which is one of the fundamental technique is easily applied to the quantification for hard materials. Here, usefulness of indentation test is reported for soft materials by extending the Hertzian contact theory. Then the indentation technique based on the contact theory is adopted for quantification in this paper. This theory is commonly used to evaluate elastic materials, but it is found that inelastic behaviors of solid materials like viscosity and fracture can be quantified by the extension of the theory. In this paper, an evaluating equation is formulated and applied to quantify in-elasticity of various materials and it is known that an equation can analyze the variation of soft materials objectively, and the analyzed results has high compatibility to uniaxial test like the fundamental Hertzian contact theory.
Variation Simulation Considering Welding Distortion Applied in High-Speed Trains
Authors: Li Zhimin , Yao Limin , Li Baowang
Published: January 2018

The high-speed trains are currently considered one of the most significant technological breakthroughs in passenger transportation for providing lower time-consuming and higher quality improvement services. Nevertheless, the manufacturing quality of high speed train is related to driving safety and riding comfort. It needs to be emphasized that the control of dimensional variation plays a crucial and irreplaceable role in today’s manufacturing processing which affect the quality of manufacturing. In this study, a variation simulation method considering both tolerance analysis with rigid assumption and welding distortion is developed to predict dimensional variation of the side wall of high-speed train during the assembly process. Firstly, the tolerance analysis with rigid assumption method is employed to simulate the dimensional variation when the parts of side wall are assembled together. Then, the finite element method (FEM) based on inherent strain is used to predict welding distortion including longitudinal shrinkage, transverse shrinkage and angular distortion. Finally, the results combining both tolerance analysis with rigid assumption and welding distortion are compared with actually measured results to identify the effectiveness of this method.
Minimizing Power-Consumption of a Generalized Convective Law Multistage Heat Pump System via Hamilton-Jacobi-Bellman Equations and Dynamic Programming
Authors: Xia Shaojun , Chen Lingen
Published: January 2018

A multistage endoreversible Carnot heat pump (CHP) system with a finite heat sink and generalized convective heat transfer law (HTL) [q ∝ (AT)m] is investigated. For the given initial sink temperature, the minimum power consumption (MPC) is chosen to be optimization objective, the sink temperature is the control variable, and the corresponding continuous Hamilton-Jacobi-Bellman (HJB) equation is established. The detailed expressions of the MPC and the corresponding heat sink temperature for Newtonian HTL (m = 1) are further obtained based on the universal results. While for the cases with other HTLs (m ≠ 1), there exists no analytical solution, so numerical algorithm of dynamic programming (DP) is used, and the difference between the MPC optimization of the multistage endoreversible CHP system and the maximum power output (MPO) of the multistage endoreversible Carnot heat engine (CHE) system is also indicated. The obtained results in this paper could help an engineer in better evaluation of energy limits in practical power-consumption processes.
Investigation of Composite Hydrodynamic Thrust Bearing Operating Temperature Under Varying Axial Loads
Authors: Myers Kyle , Fais Collier , Zacharias Matthew , Ali Muhammad , Alam Khairul
Published: January 2018

The purpose of this experiment was to explore the operational behavior of hydrodynamic thrust bearings machined from various composite materials (PTFE-Filled Delrin Acetal Resin and MDS-Filled Nylon) and general Aluminum under a set of different axial loading conditions. Since thrust bearings allow mechanical components subjected to axial loads to rotate more freely, they must counter a great deal of friction which can cause bearing failure in order to maintain proper movement. In order to reduce friction and weight, this research posits that thrust bearings machined from composite materials of lower friction coefficients and densities to that of conventionally used materials such as aluminum may provide some advantages. This hypothesis was tested by machining three thrust bearings, all to the same geometric specifications (two composites and one Aluminum) and subjecting them to thrust loads of 25, 50, 75, and 100 pounds while rotating them at a constant rotational speed of 3050 RPM for 10 minutes at each load using a customized test rig. A thermocouple implanted into the bearings themselves recorded the operation temperatures at a sampling rate of 20 Hz. Based on the average temperatures recorded at the 100 pound axial/thrust load, the experiments suggest that the PTFE-Filled Delrin Acetal maintains the lowest average operating temperature of 29.5 °C, followed by the MDS-Filled Nylon at 41.6 °C and lastly the Aluminum at 54.4 °C — a trend that is observed at each axial load albeit less pronounced. These results suggest that composite materials such as PTFE-Filled Acetal and MDS-Filled Nylon to be used in lieu of conventional metals and operate at lower temperatures and lower friction.
Heat Mitigation for Underground Coal Mine Refuge Alternatives Using Cryogenic Air or Borehole Air Supplies
Authors: Yan Lincan , Yantek David , Lutz Timothy , Yonkey Jeffrey , Srednicki Justin
Published: January 2018

In case of an emergency in an underground coal mine, miners who fail to escape from the mine can enter a refuge alternative (RA) for protection from adverse conditions, such as high carbon monoxide levels. One of the main concerns with the use of both portable and built-in-place (BIP) RAs, especially for hot or deep mines, is the interior temperature rise due to the occupants’ metabolic heat and the heat released by devices such as the carbon dioxide (CO2) scrubbing system. The humidity within the RA will also increase through occupants’ respiration and perspiration, and from the chemical reaction within the CO2 scrubbing system. Heat and humidity buildup can subject the occupants to hazardous thermal conditions. To protect RA occupants, Mine Safety and Health Administration regulations mandate a maximum apparent temperature of 95°F within an occupied RA.

The National Institute for Occupational Safety and Health (NIOSH) tested both an air conditioned borehole air supply (BAS) and a cryogenic air supply for RAs in the NIOSH Experimental Mine in Bruceton, PA. The BAS was tested on a 60-person BIP RA, while the cryogenic air supply was tested on a 30-person BIP RA and a portable 23-person tent-type RA. Multiple tests were conducted with both air supplies to assess their ability to cool RAs. The test results show that the BAS and the cryogenic air supply were able to maintain the apparent temperature within the tested RAs under the 95°F limit. The BAS and the cryogenic air supply are potential RA heat mitigation strategies that mines could use to prevent heat/humidity buildup within RAs.
Study of Linear and Non-Linear Instabilities in a Multiple Jet Flow Configuration
Authors: Natarajan Hareshram , Jacobs Gustaaf B.
Published: January 2018

The linear and non-linear growth of instabilities in a two dimensional parallel three jet flow configuration is carried out using DNS. A method is presented that enables the study of growth of instability modes using a combination of LSA and DNS. The linear growth of spatial and temporal LSA modes for a single shear layer is verified using DNS. Then DNS is used to study the transition from linear growth to non-linear instabilities. In test, the growth rate of temporal modes found using DNS matches with growth rate predicted by LSA for viscous and inviscid flows. DNS of a non-parallel flow with a spatially growing viscous LSA mode is found to create absolute instability and match between DNS and LSA is not possible. In a temporal analysis, it is found for a multiple shear layer case it is found that the growth of the temporal mode increases with increasing the strength of the additional shear layer for both inviscid and viscous flows. Longer DNS runs show that presence of a stronger shear layer enhances vortex shedding and vortex pairing mechanism of a shear layer. This enhanced mixing in the non-linear region is to be linked with the growth of perturbation in the linear region.
Experimental Study of Shell-Side Fogging Condensation of a Mixture
Authors: Gu Hongfang , Guo Haiyang , Wang Haijun , Gu Yuqiang
Published: January 2018

Fog formation occurs if the vapor pressure in the gas-phase is higher than the saturated vapor pressure and the bulk temperature is lower than its saturation temperature (supersaturated) for condensation in the presence of non-condensable gases. Generally, fogging is formation of entrained small droplets mixing in the vapor-gas stream, and the vapor condenses at the mist-flow and share-controlled flow regime. The phenomenon and mechanism of fogging need to be considered for determining condensation rate and separation of the condensate from vapor-gas phase for the down-stream process.

The experimental study of shell-side condensation using steam mixing with non-condensable air was conducted in a shell-side horizontal baffled tube bundle. Experimental data has been obtained including visualization findings using high-speed photograph. The characteristics of fog formation related to the heat and mas transfer performance are analyzed based on experimental data and observation. The general equation for determining fog formation (degree of supersaturation) is evaluated with experimental data. Results confirm that the transition band of fogging formation is in the range of S = 1.0 to 1.75. This paper presents experimental data and visualization findings on fogging characteristics and heat transfer performance for condensation in the presence of non-condensable gas.
Modeling and Performance Simulation of a Reformer and Fuel Cell System for Electricity Generation From Digester Gas Using PEM Fuel Cells
Authors: Roa Prada Sebastian , Rueda Sanchez Oscar Eduardo
Published: January 2018

Wastewater treatment plants help removing organic matter from wastewater, and at the same time, generate digester gas as a useful byproduct. Digester gas is rich in methane, which can be used to generate electricity. Fuel cell systems are the cleanest technology for power recovery from digester gas, since all other technologies generate electricity by burning all the digester gas. The most commonly used type of fuel cell for power generation from digester gas in wastewater treatment plants is the molten carbonate fuel cell. This type of fuel cell can tolerate the impurities usually found in digester gas, such as CO2 and H2S; however, this kind of fuel cell systems is more suitable for large wastewater treatment plants. This prevents the use of fuel cells for power generation from digester gas in wastewater treatment plants serving medium and small size cities, or even farms. This research attempts to explore solutions to make fuel cell technologies technically and economically feasible for medium and small size wastewater treatment plants. The most suitable type of fuel cells for small applications is the Proton Exchange Membrane, PEM, fuel cell. The main challenge in using PEM fuel cells for power recovery from digester gas is that they are highly sensitive to impurities in its hydrogen gas supply. Therefore, in order to use PEM fuel cells in this application, energy must be spent in cleaning the digester gas before it enters the PEM fuel cell and reformer system. Energy is also required in the form of heat by the reformer system to produce the hydrogen needed by the fuel cell. Both the energy used in the cleaning of the digester gas and the hydrogen generation process comes from burning part of the digester gas. This reduces the amount of digester gas available for hydrogen production and electricity generation, respectively. The approach followed in this investigation seeks to develop a Simulink® model of the reformer and fuel cell so that the modeling tools of Matlab® can be used to simulate the performance of the system under different operating conditions. A sensitivity analysis is carried out to identify critical operating parameters affecting the performance of the overall system. The results obtained in this work provide guidelines for future studies of performance optimization and optimal control using the tools available in Matlab®, in order to get maximum electricity generation from digester gas using PEM fuel cell systems.
Hysteresis Modeling and Control of Piezoelectric Actuator
Authors: Wang Shuai , Chen Zhaobo , Jiao Yinghou , Mo Wenchao , Liu Xiaoxiang
Published: January 2018

The hysteresis characteristic is a common property of intelligent materials, such as shape memory alloy, giant magnetostrictive material and piezoelectric material. It cannot be neglected when the accuracy requirement is at the range of micro meter or smaller. Therefore, it’s essential and important to eliminate the hysteresis with some measures as far as possible. In this paper, an experiment is conducted to obtain the hysteresis characteristic of a piezoelectric actuator (PEA) which is designed and fabricated. The relationship between the output displacement and input voltage is established by combining the RBF neural network (RBFNN) and hysteresis operator. In order to compensate the hysteresis of PEA, an inverse model is built by using RBFNN and an inverse hysteresis operator served as feedforward compensation. Then a PI feedback controller is adopted to eliminate the influence the modeling error of feedforward loop. An experiment based on real time control system is conducted to let the output displacement tracking a desired curve. The test results indicate that the hybrid control system is effective in compensating hysteresis of PEA and makes the output displacement controllable.
Free Vibration Analysis of Uniform and Asymmetric Composite Pretwisted Rotating Thin Walled Beam
Authors: Farsadi Touraj , Şener Özgün , Kayran Altan
Published: January 2018

Composite pretwisted rotating thin walled beams (TWB) can be used as the structural model for composite helicopter and wind turbine blades for the study of aeroelastic response of the blades. In the present study, semi-analytical solution is performed for the free vibration analysis of uniform and asymmetric composite pretwisted rotating TWB. The approximation of the Green-Lagrange strain tensor is adopted to derive the strain field of the system. The Euler–Lagrange governing equations of the dynamic system and the related boundary conditions are derived via Hamilton’s principle. In order to solve the governing set of equations, the Extended Galerkin’s Method (EGM) is employed. For this purpose, the structural variables are separated in space and time and the assumed mode shapes are defined to satisfy the essential boundary conditions. For the purpose of validating the TWB model developed, the commercial finite element analysis tool, MSC Nastran is used to compare the results of modal analysis obtained by the present structural model with the finite element solution. With the results obtained in this paper, it is aimed to ascertain the effect of various coupling in circumferentially asymmetric stiffness (CAS) and circumferentially uniform stiffness CUS configurations, pretwist, angular velocity and fibre orientation, on the natural frequencies and the mode shapes of the rotating thin-walled composite beams. The results are expected to propose better predictions of the vibrational behavior of thin walled structures in general, and in the design of rotor blades of turbomachinery, rotorcraft and wind turbine systems, in particular.
Elasticities and Layer-Thickness Identification of a Layered Material by Indentation Test
Authors: Kaneko Sayumi , Seo Jungmi , Sakuma Atsushi
Published: January 2018

Many industries, such as the biotechnology, food, and beauty industries, require noninvasive methods for quantifying material stiffness. One such method is the indentation test, which is particularly useful in evaluating the mechanical characteristics of soft materials. However, it is difficult to identify mechanical characteristics of the distinct layers of layered materials such as human skin due to their physical integration with one another. There is particular interest in evaluating the softness of the stratum corneum (the outermost layer of skin) in the cosmetics industry, where the effect of cosmetics should be restricted to this outermost layer. The purpose of this study was to develop a method to determine the elasticities and thicknesses of discrete layers in a layered material by using an indentation test. This paper discusses the results of this indentation test derived via the finite element method (FEM). Here, the finite element (FE) model is constructed by a layered structure of flat surfaces with given Young’s moduli. The FEM results suggest the existence of a law among the elasticities and layer thicknesses of a layered material.
3D Simulation of Flow in a Vortex Cell Using RANS and Hybrid RANS-LES Turbulence Models
Authors: Jamal Tausif , Walters D. Keith , Chitta Varun
Published: January 2018

A vortex cell is a cylindrical aerodynamic cavity that traps separated vortices to prevent the formation of large-scale vortex shedding. Due to the presence of complex vortical structures, regions with varying turbulent intensities, and rotation-curvature effects on turbulent structure; the flow inside a vortex cell is a valuable test case for newly proposed turbulence models and numerical schemes. In the present study, numerical simulations were carried using a Reynolds-averaged Navier-Stokes (RANS) turbulence model and two hybrid RANS/large-eddy-simulation (LES) models. The computational domain consists of a cylindrical cavity with an incoming transitional boundary layer and a Reynolds number of 9.4 × 104 based on the diameter of the cavity. Results indicate that the RANS model provides general information about the flow characteristics, while the hybrid RANS-LES models predict the flow characteristics with more accuracy but suffer inaccuracies due to the details of the RANS to LES transition. Most significantly, the dynamic hybrid RANS-LES (DHRL) model in combination with a low-dissipation numerical scheme overpredicts the turbulent mixing in the vortex cell and fails to provide an accurate representation of the physics of the trapped vortex. It is concluded that the hybrid RANS-LES models used in this study need further work to be able to fully and accurately predict the flow in a vortex cell.
Validation of a Full Porcine Finite Element Model for Blast Induced TBI Using a Coupled Eulerian-Lagrangian Approach
Authors: Tan X. Gary , Saunders Robert N. , Bagchi Amit
Published: January 2018

Current understanding of blast induced traumatic brain injury (TBI) mechanisms is incomplete and limits the development of protective and therapeutic measures. Animal testing has been used as a surrogate for human testing. The correlation of animals to human responses is not well understood with a limited set of experimental data, because of ethical concerns and cost of live animal tests. The validated computational animal models can be used to supplement and improve the granularity of available data at a significantly reduced cost.

A whole-body porcine high-fidelity computational model was developed based on the image data. The hyper-viscoelastic model was used for soft tissues to capture the rate dependence and large strain nonlinearity of the material. The shock wave interaction with a porcine subject in a shock tube was simulated using computational fluid dynamics (CFD) models, via a combination of 1-D, 2-D and 3-D numerical techniques. The shock wave loads were applied to the exterior of the porcine finite element (FE) model to simulate the pressure wave transmission through the body and capture its biomechanical response. The CFD and FE problems are solved using the explicit Eulerian and Lagrangian solvers, respectively, in the DoD Open Source code CoBi.

The computational models were validated by comparing the simulation results with experimental data at specific instrumented locations. The predicted brain tissue stress-strain fields were used to determine the areas susceptible to blast induced TBI by using published mechanical injury thresholds. The validated porcine model can be used to better understand TBI and how injury in animals corresponds to injury in humans. The coupled Eurlerian and Lagrangian approaches developed in this paper can be extended to other simulations to improve the solution accuracy.
Investigation of Structure-Property Relationships Between Crystal Orientation and Dielectric Behavior in Liquid Crystalline Polymers
Authors: Sullivan Anthony , Saigal Anil , Zimmerman Michael A.
Published: January 2018

Liquid crystalline polymers (LCP’s) make up a class of high performance materials, which derive favorable mechanical, chemical, and electrical characteristics from their long-range molecular order. The unique LCP microstructure gives rise to anisotropic bulk behavior and an understanding of the driving forces behind this morphology is essential to the design of manufacturing processes for isotropic material production. In this investigation, the crystalline orientation in injection molded LCP plaque samples was measured using 2D wide-angle x-ray scattering (WAXS). The direction of preferred alignment was observed from the WAXS scattering patterns and the degree of orientation in the material was quantified using an order parameter and an anisotropy factor. In addition, the dielectric constant was measured with respect to the mold direction (MD) and transverse direction (TD). To investigate the effects of processing on hierarchal structure in the material, and the resulting macroscopic properties, plaques of two different thicknesses were analyzed, both as-injection molded and with the skin layer mechanically removed. It is shown that preferred orientation along the shear direction in the LCP samples corresponds to dielectric anisotropy, and increasing sample thickness, or conversely, mechanically removing the shear aligned layer, results in a more isotropic dielectric response.
Method for Producing Three-Dimensional Designs in Film Insert Molding
Authors: Fujii Shoko , Aoyama Hideki , Mori Yukio , Azagami Youichi , Harada Syouji
Published: January 2018

Plastic is an important material in product design because it easily transforms, is very light, and has multifarious structural characteristics. Nevertheless, it gives the customer the impression of a cheap product. Therefore, decorative techniques are often applied to plastic products. Decorative techniques can improve the appearance of a plastic product while making use of its beneficial characteristics. At present, film insert molding method is predominantly used in decorating plastic products.

In general, a designer creates a three-dimensional design but the film insert molding method uses a two-dimensional pattern. Thus, it is difficult to reproduce a three-dimensional design with a two-dimensional film; no study has been conducted on the reproduction of three-dimensional design using film insert molding method to-date.

The objective of this study is to develop a design generation method to reproduce a three-dimensional design with a two-dimensional film pattern. The effectiveness of the proposed method is experimentally validated.
Developing a Borehole Miner Extendible-Nozzle Sluicer for Radioactive Waste Dislodging and Retrieval From Underground Storage Tanks
Authors: Bamberger Judith Ann , Pease Leonard F. , Enderlin Carl W.
Published: January 2018

Radioactive waste resulting from production of weapons is stored at five U.S. Department of Energy (DOE) locations. The waste characteristics range from fluid to sludge to granular salts with radiation levels exceeding 10,000 rad/h.

Innovative tools are used to remotely remove the solidified radioactive waste from underground storage tanks. When available, commercial systems are evaluated for waste dislodging and retrieval applications. A waste dislodging and sluicing system developed to dislodge and fracture deposits of ore in underground mining, called a borehole miner, was evaluated by Pacific Northwest National Laboratory (PNNL) and Waterjet Technology, Inc., for removing solidified nuclear waste stored in underground tanks. This compact system may be installed in tanks via small diameter risers and has the capability to both dislodge and retrieve in a single unit. The borehole miner arm includes an extendible nozzle that operates at high pressure using either water or slurry as the dislodging fluid, while providing a focused high-pressure jet to dislodge solidified material. The sluicer nozzle is attached to a retractable arm that can extend and angle to enhance dislodging in specific areas of the tank by changing the standoff distance.

This paper describes the borehole miner system and presents results of experiments to evaluate its ability to dislodge solidified saltcake and sludge materials. Tests were conducted with a stationary jet to evaluate the potential to develop an extendible-nozzle borehole miner system for deployment to dislodge radioactive saltcake and sludge wastes stored in underground storage tanks. The tests were successful and identified ranges of parameters for jet diameter and standoff distance applicable for waste remediation. For saltcake simulants, erosion models were developed that represent the data.
Frequency Effects on Dynamic Characteristics of Tilting-Pad Journal Bearings due to Pivot Flexibility
Authors: Jiale Tian , Lie Yu , Jian Zhou
Published: January 2018

The stable working condition of high speed, heavy loaded rotating machinery depends strongly on the stability provided by the journal bearing. Tilting pad journal bearings (TPJB) are widely used under such situation due to their inherent stability performance. However, because of the complexity of the TPJB structure, obtaining a reliable prediction of the journal bearing’s dynamic characteristics has always been a challenging task. In this paper, a theoretical analysis has been done to investigate the dynamic performance of a 4 pad TPJB with ball-in-socket pivot, emphasizing on the frequency dependency due to pivot flexibility. The analytical model containing the complete set of dynamic coefficients of the TPJB is built and the pivot stiffness is calculated and used to evaluate the equivalent dynamic coefficients of the bearing. In general, at lower perturbation frequency, the equivalent stiffness and damping increase with frequency. While for higher perturbation frequency, the dynamic coefficients are nearly independent of the frequency. Moreover, the results also show the limit value of the dynamic characteristics of the TPJB when the perturbation frequency is set to 0+ and ∞.
Causal Factors of Collision Accidents Involving Underground Coal Mobile Equipment
Authors: Noll James , DeGennaro Cory , Carr Jacob , DuCarme Joseph , Homce Gerald
Published: January 2018

From 2000–2015, thirty-two fatalities occurred due to collisions involving mobile equipment in underground coal mining in the United States. Studies have shown that proximity detection systems (PDS) can be a potential mitigation strategy for this type of accident. However, the effectiveness of this approach for mobile equipment has yet to be fully studied or validated. Researchers at the National Institute for Occupational Safety and Health (NIOSH) evaluated the causal factors of this type of fatality. Fatal accident reports from the Mine Safety and Health Administration (MSHA) accident report database provided details to analyze and determine causal factors and to evaluate whether a PDS may have been a preventive factor in each accident. NIOSH researchers concluded that PDSs used in underground coal mines on mobile equipment which are designed to detect a miner, provide warning to the operator and other miners, and automatically stop the machine before a miner is hit may have helped to prevent 25 of the 32 or 78% of the accidents.
Proposal of Indexes to Support Diagnosis of Epilepsy Symptom Using a Duffing Oscillator
Authors: Saito Takashi , Ogawa Tomomi , Yoshida Takumi , Uehara Kenyu , Kadowaki Hiroko , Mori Koji
Published: January 2018

The misdiagnosis rate of epilepsy is said to keep high from 5% to 30% because of dependency upon an individual judgment by each medical doctor in diagnosis and a quantitative index seems necessary to manage diagnosis uncertainty. To detect some change appearing in brain waves, we focus on introducing a Duffing oscillator model, which could provide reasonably good predictions for the dynamics of neuronal groups. The aim of this paper is to discuss indexes for epilepsy diagnosis by representing characteristics of electroencephalogram (EEG) quantitatively using a Duffing oscillator model. The model parameters are directly identified to adapt the characteristics of the temporal EEG variation to dynamical properties of the model quantitatively. Therefore, in animal experiments, we obtained time histories of the EEG data changed from normal EEG to the epileptic EEG. As a result, it is found that the parameter values related to non-linearity are extremely reduced as the epileptic EEG progresses with time. On the other hand, the input signal strength in epileptic EEG is much bigger than that of normal as expected. Moreover, the directly identified exciting frequency and the eigenfrequency determined by the identified parameter exist in wider band than that of normal as the epileptic EEG progresses with time. The change of the EEG due to epileptic seizure could reflect on the model parameters and it is shown that the model parameters have the possibility to use as supporting index of diagnosis about epilepsy. As a result, the proposed method could be used to support the decline of misdiagnosis rate of epilepsy.
Statistical Linearization of Nonlinear Stiffness Matrix of Planetary Gear Train
Authors: Taheri Kahnamouei Jalal , Yang Jianming
Published: January 2018

Stochastic dynamic analysis of the planetary gear train is complicated and it becomes more challenging when the nonlinear term is considered in the equation. A backlash between gears’ teeth is one of the nonlinearity sources in the gearbox which changes the equation of random vibration to nonlinear. In this paper, the linearization of the random vibration of multi-degrees of freedom (MDOF) with nonlinear stiffness is examined for planetary gear trains. The method used to treat nonlinearity is the statistical linearization method (SL). At first, to achieve adequate accuracy, the time domain is divided into very small time intervals then SL is utilized in each time step. For each time step an equivalent linear stiffness matrix is calculated and replacs the nonlinear stiffness matrix. The comparison between equivalent stiffness and linear stiffness at each step has shown a good agreement.
Periodic Motions in a 2-DOF Self-Excited Duffing Oscillator
Authors: Xu Yeyin , Luo Albert C. J.
Published: January 2018

In this paper, analytical solutions of periodic motions in a 2-DOF self-excited Duffing oscillator are investigated through a semi-analytical method. The semi-analytical method discretizes the self-excited Duffing oscillator for the discrete implicit mappings. Through the implicit mapping, period-1 motion varying with excitation frequency are presented, and the corresponding stability and bifurcation are discussed via the eigenvalues analysis. The Neimark and saddle-node bifurcations of the periodic motion are obtained. Initial conditions for numerical simulations are from analytical solutions. Numerical and analytical solutions of periodic motions are illustrated for comparison.
Flow Resistance Characteristics of a Specific Fuel RP-3 in Helical Tubes at Supercritical Pressure With Uniform Heat Flux
Authors: Zhang Nan , Fu Yanchen , Huang Haoran , Wen Jie , Te Nigeer
Published: January 2018

The flow resistance characteristics of aviation kerosene RP-3 in horizontal helical tubes at the supercritical pressure under heating condition are investigated. Both pressure drop and friction factor were examined under uniform heat flux of 50kW/m2−300kW/m2, mass flux from 786kg/m2s to 1375kg/m2s, and helical diameter from 20mm to 40mm. The influence of viscous factors on the resistance is analyzed to explore flow characteristics in a helical tube and provide a reference for the design of heat exchangers.

Friction factor decreases with the increase of heat flux at low inlet temperatures 323K and 423K. It is explained that the viscosity changes more dramatically than the density. When the fluid inlet temperature is 523K and the fluid mean temperature Tb is close to pseudo-critical temperature, frictional flow resistance becomes significantly larger Tpc due to huge variations in thermal properties in the radical direction. The effect of centrifugal force makes the friction factor decline slowly. The friction factor goes up with the enlargement of mass flux when Tb>0.81Tpc. This phenomenon is caused by the larger radial velocity gradient under the large mass flux. Different helical diameters play the leading roles for the bending flow in the tubes.
Evaluating Forced Versus Natural Convection for Solar Concentrating Hybrid Photovoltaic-Thermoelectric Power Systems Made From Small Up-Cycled Satellite Dishes
Authors: Alamri Said , Alamri Turki , Almutairi Saud , Akbar Muhammad K. , Hadi Fatemeh , Traum Matthew J.
Published: January 2018

Design processes and analytical modeling are presented showing creation of a low-cost concentrating photovoltaic-thermoelectric (PV/TE) hybrid power system for research and laboratory teaching built using a small upcycled satellite dish. Today, concentrated solar hybrid PV/TE systems are drawing significant research attention and funding investment. However, the literature lacks examples of how this cutting-edge energy technology can be made accessible at low cost for STEAEM education at universities, vocational institutions, and high schools. By applying Energy Engineering Laboratory Module (EELM™) design principles and pedagogy, a process is presented to make this technology easily accessible at low cost.

The concentrating solar hybrid PV/TE system presented here is divided into four subsystems: 1) a concentrator, 2) a PV/TE generator, 3) data acquisition, and 4) a cooling system. The key engineering decisions governing the design for each sub-system are described. In addition, a thermodynamic analysis is presented to predict the on-sun steady-state temperature profile of the PV/TE generator at the focus of the concentrator and to determine how much electrical power it will produce.

The concentrator used is a salvaged miniature satellite dish, which is coated with mirrored tape to reflect sunlight upon a focal point. Scavenged at no cost, the satellite dish is a sectioned paraboloid of rotation offset from the vertex and the axis of symmetry. However, which paraboloid section the dish represents is unknown. A technique is presented to find the focal point and to use this information to correctly position a shadow-casting gnomon to ensure proper on-sun alignment. A method to experimentally confirm the focal location and size the PV is also provided.

A key research question for solar concentrating hybrid PV/TE power systems at this size scale is whether it is better to actively cool the TE cold side via forced convection or simply allow cooling via natural convection. The thermodynamic heat balance analysis presented to address this question finds that while forced convection does better cool the PV module, increasing its efficiency and power output, the parasitic energy expenditure of the cooling fan far exceeds the additional power produced. It is therefore more beneficial to rely on natural convection on the TE cold side to maximize power production of the overall PV/TE module.

Two experimental apparatuses were built consisting of a PV module backed by TE generators and instrumented with thermocouples to determine the internal temperature gradient while multi-meters read steady-state PV and TE power output. A halogen lamp placed at various distances from this array approximates concentrated sunlight, which is measured via pyranometer. These experiments validate conclusions drawn from the theoretical model.
Tunable Triangular Cellular Structures by Pneumatic Control of Dual Channel Actuators
Authors: Yuan Zhihao , Ju Jaehyung
Published: January 2018

Programmable matter, a material whose properties can be programmed to achieve desired density with volume change, shapes or structural properties (stiffness, strength, Poisson’s ratio, etc.) upon command, is an important technology for intelligent materials. Recently emerging soft robotics-based pneumatic control can be potentially used for the design of programmable matter due to its several advantages — quick response for actuation, stiffening effect with internal air pressure, easy to manufacture, inexpensive materials, etc. The objective of this work is to construct programmable two-dimensional (2D) cellular structures with pneumatic actuators, investigating the effect of local deformation of the pneumatic actuators on the macroscopic pattern generation and mechanical properties of cellular structures. We synthesize 2D soft triangular structures with pneumatic actuators embedding dual air channels wrapped with fiber reinforcement. The local deformation modes provide different macroscopic deformations of cellular structures. We build an analytical model integrating the deformation of a single actuating member with nonlinear deformation of cellular structures. Finite element based simulations and experimental validation are followed. This study integrates soft robotics with cellular structures for intelligent materials design, expanding the design space of materials with programming. The fast response of the tunable soft cellular structures may be an ideal for the application of acoustic metamaterials with tunable band gaps.
A Comparative Study of Mass Based Vibration Dampers
Authors: Gharib Mohamed , Karkoub Mansour
Published: January 2018

Undesired vibrations in structures, buildings, and machines lead to reduction in the life of the system and greatly affects the safety of the occupying or operating personnel. In addition, economic and time losses could result from needed repairs or reconstruction. Many control techniques, active and passive, have been devised over the years to reduce/eliminate the vibrations in the aforementioned systems. Passive vibration control techniques are favorable over the active ones due to their simplicity, ease of implementation, cost, and power consumption. In dynamic structures, such as large buildings, passive control techniques are favored over their active counterparts. The most common types of passive control devices are tuned mass and impact dampers. The advocates of each of these devices boasts advantages of the others; however, there have been no systematic studies to compare and quantify the effectiveness of each of these types of devices as well as their suitability for specific applications. In this paper, a comparative study between the tuned mass dampers and impact dampers is conducted. A one-story structure is used to show the effectiveness of each of these devices in absorbing the vibrations of the structure. The coupled systems are modeled and simulated under free vibrations. The time responses are acquired using the same geometric parameters, excitation, and initial conditions. The comparisons are based on the settling time and amplitude decay rates of the primary system using each damper type. The numerical results show that both dampers can produce similar dampening effects if the parameters are optimized; however, correlating the dampers parameters is a challenging problem in the field of vibration and control.
Computational Study of Reverse Osmosis Desalination Process: Hollow Fiber Module
Authors: Usta Mustafa , Anqi Ali E. , Morabito Michael , Hakim Alaa , Alrehili Mohammed , Oztekin Alparslan
Published: January 2018

Reverse Osmosis (RO) is a process whereby solutes are removed from a solution by means of a semipermeable membrane. Providing access to clean water is one of our generation’s grand engineering challenges, and RO processes are taking center stage in the global implementation of water purification technologies. In this work, computational fluid dynamics simulations are performed to elucidate the steady state phenomena associated with the mass transport of solution through cylindrical hollow fiber membranes in hopes of optimizing RO technologies. The Navier-Stokes and mass transport equations are solved numerically to determine the flow field and solute concentration distribution in the hollow fiber membrane bank, which is a portion of the three-dimensional feed channel containing a small collection of fibers. The k-ω Shear Stress Transport turbulence model is employed to characterize the flow field. Special attention is given to the prediction of water passage through hollow fiber membranes by the use of the solution-diffusion model, which couples the salt gradient, water flux, and local pressure at the membrane surface. This work probes hollow fiber membrane arrangement in the feed channel by considering inline and staggered alignments. Feed flow rates for Reynolds number values ranging between 400 and 1000 are considered. Increased momentum mixing within the feed channel solution can substantially enhance the system efficiency, and hollow fiber membrane arrangements and feed flow rates dictate the momentum mixing intensity. Velocity and vorticity iso-surfaces of the flow domain are presented in order to assess the momentum mixing achieved with various hollow fiber membrane arrangements and flow rates. The total water permeation rate per hour is calculated to compare system efficiencies, and the coefficient of performance is calculated to compare membrane performance relative to the necessary power input, both for the various hollow fiber membrane arrangements and feed flow rates.
Numerical Analysis of the Prediction of the Two-Phase Flow Rate by Measuring Vibration of Pipelines
Authors: Elmekawy Ahmed M. Nagib , Shabara Mohamed A. , Elgamal Hassan , El-Souhily Bassuny
Published: January 2018

Multi-phase flow is encountered in multiple industrial disciplines including oil and gas industry starting from the reservoirs, production tubes, well heads, separators and transportation systems comprehending risers & onshore/offshore transportation pipelines. The complex nature & instability of slug flow where pressure, temperature, velocities and flow rates oscillate lead to high fatigue loads on mechanical elements in pipelines. The prediction of the two-phase flow pattern inside pipelines is crucial in extending the life of the pipeline. This paper proposes the first numerical approach for predicting the vibration of a three-dimensional pipeline with an elbow due to two-phase flow using one-way fluid-structure interaction technique using the commercial software ANSYS. The unsteady Reynolds-averaged Navier-Stokes equations with three turbulent models are used to model the fluid domain. The finite element analysis is used to model the pipeline by using shell elements. The two-phase mixture superfacial velocities inside the pipeline were identified by measuring the acceleration response of the surface of the pipe. Modal analysis is performed to check the variation of the pipeline natural frequency with the water content in the flow. The simulation results were validated with experimental data. Based on the simulation results, a numerical method for the measuring of the two-phase flow rates is proposed.
Nonlinear Sensitivity Analysis of Twin Non-Symmetric Micro-Cantilever Beams
Authors: Changizi M. Amin , Stiharu Ion , Hajheidari Peyman , Erdem Sahin Davut
Published: January 2018

In this paper, the dynamic performance of two parallel micro-cantilever beams is investigated and the results are presented. The dynamic response is of high interest in MEMS structures as it is related to the performance of the micro-devices. The micro-cantilever beams can be easily fabricated and yield high sensitivity to variations of physical quantities. In this work, the dynamic response of two parallel flexible cantilever beams subjected to a difference of potential is analyzed. This configuration was modeled as mass-damper spring systems with two degrees of freedom. Such a system can be used to measure the viscosity of liquids. This viscosity is related to damping between two masses representing the two beams in the discrete system model. The fabrication of two identical beams using MEMS fabrication processes may be difficult as the fabrication process may yield some variabilities. Thus, the two beams may be slightly different which will be reflected in their mass and stiffness. This condition was assumed in the proposed model. As the system is sensitive to the applied difference of potential such that the pull-in voltage represents a good indicator of the sensitivity performance. The dynamic analysis was carried out at potentials close to the pull-in value. Stability of the system was evaluated and the responses of the beams were calculated at a potential close to the pull-in voltage. The sensitivity of the system was calculated for different viscosities of liquid between two beams. It was found that an increase of the viscosity yields higher nonlinearity and consequently loose of accuracy while assuming linear stiffness for the beams. In this research, the stiffness of micro-cantilever beams was calculated from small deflection theory of beams. However, there are other methods that could be considered to evaluate the stiffness of the beams. One of this different methods was considered and the sensitivity of the modeled stiffness is discussed. Since the stiff nonlinear differential equations cannot be solved analytically, the numerical approach was exploited. In this work ISODE method from Maple software was used to solve the model described by the two differential equations.
Modeling and Analysis of Weld Geometries, Size and Gap on Weld-Induced Thermal Stresses in a Solid Round-on-Flat Plate Fillet Weld
Authors: Ghosh Suhash , Sahay Chittaranjan , Al-Mamoury Haider
Published: January 2018

In this paper a finite element model is presented which describes the effects of fillet weld geometry on the thermal stresses. In a separate research, development of a finite element model for simulating welding-induced thermal stresses is discussed. This nonlinear FE model employs fully coupled three-dimensional thermo-mechanical formulation, including interfacial element to simulate the weaker solidified molten weld pool. Due to the nature of the welding process, heat generation from moving heat source, rapid heating and cooling gives rise to high stresses in the weld. This research investigates the effect of weld shape & size, weld gap, (l/d ratio) depth of weld to size ratio on the generated thermal stresses. The size of the round and flat stocks has been varied to investigate their effects of the stresses as well as to determine the thick-to-thin geometry limits based on acceptable design limits of thermal stresses.