bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Algorithm Based Topology Optimization of Heat Exchanger Fins Used in Aerospace Applications
Authors: Mekki Bashir S. , Langer Joshua , Lynch Stephen
Published: January 2020

Topology Optimization (TO) in the design of structural components is commonly used and well explored. However, its usage in the design of complex thermo-fluid equipment used in aerospace applications is limited and relatively new. This is because the coupling between the fluid dynamics, heat transfer, and the shape is complex and nonlinear. Furthermore, the resulting geometry from a TO analysis is often very complex and difficult to manufacture due to the free forms that can occur. With the advent of Additive Manufacturing (AM), however, it has become possible to directly manufacture complex geometries. This study develops a new Genetic Algorithm (GA) based TO combined with Computational Fluid Dynamics (CFD) to produce optimized fin shapes for heat exchangers used in aerospace applications. To implement this approach, a rectangular shaped baseline fin geometry was created using voxel representation. An initial population is generated by mutating the baseline fin a random number of times. The CFD package OpenFOAM is then used to evaluate the performance of each design, after which the optimization algorithm is applied. The GA sorts the designs using a composite fitness function that is comprised of the overall heat transfer and pressure drop, and generates new generations based on mutation and carryover of top performing designs. The study also explores the sensitivity of the GA to the various GA parameters as well as the effect of varying flow Reynolds number. In general, as Reynolds number increases, the percent improvement in the optimum relative to the baseline increases, with potentially a 60% performance improvement. Overall, the approach enables generation of novel freeform designs that may open new performance space for heat transfer applications.
Joining Techniques for Novel Metal Polymer Hybrid Heat Exchangers
Authors: Kuntumalla Gowtham , Meng Yuquan , Rajagopal Manjunath , Toro Ricardo , Zhao Hanyang , Chang Ho Chan , Sundar Sreenath , Salapaka Srinivasa , Miljkovic Nenad , Shao Chenhui , Ferreira Placid , Sinha Sanjiv
Published: January 2020

In the United States, over 50% of the unrecovered energy from industrial processes is in the form of low-grade heat (< 220°C). Materials and maintenance costs of common heat exchangers are typically too high to justify their usage. Polymers, though more affordable, are usually unsuitable for HX applications due to their low thermal conductivity (∼0.2 W/mK). Here, we show that metal-polymer hybrids may be attractive from both performance and cost perspectives. The use of polymers further increases the resistance to corrosion by sulfuric and carbonic acids often present in flue gases. An ongoing work explores different configurations of layered polyimide-copper macroscale hybrids for heat exchanger applications using numerical simulations. This paper explores a manufacturing pathway for producing such layered hybrid tubes that involves directly rolling and bonding tapes made of polymer and copper foil into tubes. A critical problem in the fabrication process is the bonding of metal and polymers. We explore approaches involving adhesives (epoxy, acrylic and silicone) for metal/polymer interfaces and direct welding (ultrasonic) for metal/metal interfaces that can be integrated into the manufacturing process. We report characterizations of the thermomechanical properties of these joining processes. This work paves the way for realizing cost-effective manufacturing of heat exchangers for low grade waste heat recovery.
Assessment of Parkinson’s Disease Tremor and Correlation Analysis With Applied Signal Processing
Authors: Zhu Na , Miller Nathaniel S.
Published: January 2020

Accurate measurement and assessment of Parkinson’s disease (PD) tremor is important for patients, clinicians, and researchers to track changes in disease progression and the effectiveness of therapeutic interventions. This study measured resting, postural, and kinetic tremor from patient’s most-affected hand with accelerometers and gyrometers, thus the linear and rotational motions in the x, y, z directions were obtained. Data were collected when patients were both ON and OFF their anti-PD medications. A bandpass filter was applied to extract raw tremor information and several signal processing algorithms were used to analyze the data in both time and frequency domains, including the correlations between motions at different directions. The results of medication effectiveness on PD tremor and the correlational analyses will be discussed.
Simulation of Body Force Impact on the Assembly Process of Aircraft Parts
Authors: Lupuleac Sergey , Smirnov Aleksandr , Churilova Maria , Shinder Julia , Zaitseva Nadezhda , Bonhomme Elodie
Published: January 2020

The manufacturing technology of some aircraft parts involves rotation of parts in assembly jig during the integration process. As the jig rotates, the gravity acting on the parts changes its direction. It can affect the residual gap between parts joined with temporary fasteners and lead to eccentricity of drilled holes for rivets. A numerical approach for simulation of airframe assembly process with account of this effect is discussed in the paper. The approach is based on reformulation of contact problem in terms of quadratic programming and introduction of special correction terms in the force vector. The developed approach is applied to evaluation of effect of assembly rotation on the contact quality.
Tribological Properties of Ammonium Protic Ionic Liquids As Additives in Polyalphaolefin for Steel-Steel Contact
Authors: Guo Hong , Iglesias Patricia
Published: January 2020

Around 23% of the world’s energy consumption results from rubbing contacts, in which 20% is used to overcome friction and 3% is due to wear and the consequent failure. The implementation of lubricants and effective lubricant additives are indispensable to reduce friction and wear of rubbing materials. Protic Ionic Liquids (PILs), which are easily obtained by proton transfer from a Brønsted acid to a Brønsted base, have shown great potential to be used as lubricants due to their structures and tunable properties. In this study, two kinds of novel PILs, bis(2-hydroxyethylammonium) succinate (DSu) and tri-[bis(2-hydroxyethylammonium)] citrate (DCi), were synthesized and tested as lubricant additives. The tribological behavior of the two PILs is studied as additives in 1 wt. % to a base synthetic lubricant (PAO) for steel-steel contact under different temperatures (room temperature and 100°C) and normal loads (3 N and 4 N) using a ball-on-flat reciprocating tribometer. When 1 wt. % of any PILs is added into PAO, friction is reduced compared to that with neat PAO at all temperatures and loads studied, and good anti-wear performance is also obtained under the higher temperature studied. Particularly, 1 wt. % DCi +PAO shows the best high-temperature tribological behavior under 4N, with friction and wear reductions of 33% and 35%, respectively.
Comparison of Dummy and Human Body Models in Automotive Side Impact Collisions According to the Regulatory Standards
Authors: Koppisetty D. V. Suresh , Hawaldar S. S. Akhil , Lankarani Hamid M.
Published: January 2020

Side-Impact car accidents are the second leading cause of fatalities in the United States. Regulatory standards have been developed for occupant protection in side impact car accidents using dummies or Anthropomorphic Test Devices (ATDs). Although the regulations are based on the use of ATDs, there might be differences between an actual human crash performance and that of a dummy crash performance. In recent years, technology has improved in such a way that crash scenarios can be modeled in various computational software. The human dynamic responses can be examined using active human body models including a combination of rigid bodies, finite elements, and kinematic joints, thus making them versatile to use in all crash test scenarios. In this study, the nearside occupants are considered as per regulatory standards set by National Highway Traffic Safety Administration (NHTSA). Vehicle side-impact crash simulations are carried out using LS-DYNA finite element (FE) software, and the occupant response simulations are obtained using MADYMO. Because the simulation of an entire FE model of a car and occupant is quite time-consuming and computationally expensive, a prescribed structural motion (PSM) technique has been utilized in this study and applied to the side-door panel with an occupant positioned in the driver seat of the car in MADYMO. Regular side-impact deformable barrier and pole test simulations are performed with belted and unbelted occupant models considering two different target vehicles namely — a mid-size sedan and a small compact car. Responses from the dummy and the human body models are compared in order to quantify differences between the two in side impacts. The results from this study indicate that human body model behavior is generally similar to that of dummy model in terms of kinematic responses. However, the corresponding injury parameters of the human model are typically higher than that of the dummy model.
Contact Analysis of Gear Trains Using Linear Complementarity Based Compliant Contact Model
Authors: Pathak Mangesh , Rakshit Sourav
Published: January 2020

The current computation models for gear contact analysis and wear prediction are mostly based on finite element analysis which consumes much computation time and effort. In this work, we adopt an alternative approach for gear contact analysis using linear complementarity. This approach was successfully applied to a pair of rigid spur gears and a planetary gear train (gears are considered as rigid bodies) in our previous work. In this paper, we extend our linear complementarity model to consider local deformation caused due to contact between gear teeth in mesh. Thus obtained linear complementarity model is applied to a pair of spur gears and a planetary gear train. A linear complementarity solver computes the contact forces between meshing teeth of gears. From the contact forces, sliding wear in gear teeth is predicted. Archard’s wear model is used for the wear prediction. Using this model, the contact forces are uniquely determined for the examples considered. The results of linear complementarity and finite element model for a pair of spur gears are compared. The linear complementarity model consumes much less computation time than the finite element model.
Developing of a Simscape Multibody Contact Library for Gothic Arc Ball Screws: A Three-Dimensional Model for Internal Sphere/Grooves Interactions
Authors: Bertolino Antonio Carlo , Jacazio Giovanni , Mauro Stefano , Sorli Massimo
Published: January 2020

The Simscape Multibody software is a set of libraries and mechanical modeling and simulation tools for use with Simulink®. For what concerns the contact library, currently it contains only the models to describe impacts between simple geometries, such as spheres, cylinders and planes. When this environment is intended to be used to simulate the 3D dynamics of a system with a complex geometry, such as a ball screw, the built-in blocks are not sufficient. This paper presents a new contact library, containing blocks specifically designed to handle the contacts between a sphere and the two gothic arc helical grooves of a ball screw, as well as the interaction between adjacent spheres. The developed blocks are exploited to create a first case study dynamic model of a single nut not preloaded ball screw in presence of internal backlash. The results highlight the superiority of this multibody approach with respect to the quasi-static or lumped parameters models in terms of extracted information and understanding of the internal mechanics.
Effect of Pore Density on Jet Impingement Onto Thin Metal Foams Under Intermediate Crossflow Scheme
Authors: Madhavan Srivatsan , Sambamurthy Vivek Subramaniam , Singh Prashant , Ekkad Srinath
Published: January 2020

Array jet impingement heat transfer onto thin metal foams of different pore densities has been experimentally investigated in the current study. Aluminum foams with high porosity (93%) and different pore densities of 5, 20 and 40 ppi are subjected to array jet impingement under an intermediate crossflow exit scheme. The jets are arranged such that the streamwise jet-to-jet spacing is x/dj = 8 and spanwise jet-to-jet spacing is y/dj = 4. Jet to target plate spacing was maintained at z/dj = 6 where ‘z’ is the distance between the jet plate and the target surface on which metal foams were installed. A steady state heat transfer technique has been used to obtain local heat transfer coefficients along the streamwise direction. It is observed that heat transfer enhancement levels increase as pore density increases. An enhancement of 50–100% over the baseline case of impingement onto smooth surface is obtained over the flow range tested (3000 < Redj < 12000). At a constant pumping power of 40 W, an enhancement of 26–33% is obtained for the different pore densities tested.
High Voltage Energy Harvesting From Embedded PVDF Harvester Inspired From Metamaterial Design
Authors: Saadatzi Mohammadsadegh , Saadatzi Mohammad Nasser , Banerjee Sourav
Published: January 2020

In the current study, a novel multi-frequency, vibration-based Energy Harvester (EH) is proposed, numerically verified, and experimentally validated. The structural design of the proposed EH is inspired from an inner-ear, snail-shaped structure. In the past decade, scavenging power from environmental sources of vibration has attracted a lot of researchers to the field of energy harvesting. High demands for cleaner and renewable energy sources, limited sources of electrical energy, high depletion rates of nonrenewable sources of energy, and environmental concerns have urged researchers to investigate new structures called Metamaterial energy harvesters to harness electrical potential. The proposed EH is a metamaterial structure which has a Polyvinylidene Difluoride (PVDF) structure incapsulated in an aluminum frame and follows the physics of a mass-in-mass Phononic crystal structure. The PVDF snail-shaped structure is encapsulated inside a silicone matrix with a specific material property. This EH reacts to the environmental vibrations and the encapsulating silicone entraps the kinetic energy within its structure. The EH unit cell behaves as a negative mass in the vicinity of its resonance frequencies. In this paper, the dynamic behavior of the proposed EH is numerically modeled in COMSOL Multiphysics and, subsequently, validated experimentally using a unit cell fabricated in-house.
Synthesis of Flexure Based Translational Springs
Authors: Chattopadhyay Abhijit Ashish , Zhou Hong
Published: January 2020

Translational springs are employed to generate desired force-displacement relationships. Conventional translational springs utilize elastic deformations of coiled spring strips to fulfill their functions. The one-dimensional motion of a conventional translational spring is produced by the three-dimensional deformation of its coiled spring strip, which is bending plus twisting of the coiled spring strip. Different from conventional translational springs, flexure based translational springs usually have simple planar monolithic structures, and are convenient to manufacture and maintain. The translation of a flexure based translational spring is from the two-dimensional elastic or recoverable deformations of its planar flexible members. The flexure based translational springs synthesized in this research are required to endure large input translations. Because of large deformation and geometric nonlinearity, flexure based translational springs face difficulties that include parasitic drift, spring stiffness deviation, and high stress in the deformed springs. The research of this paper is motivated by surmounting these difficulties. Flexure based translational springs with different arrangements are synthesized to eliminate parasitic drifts and have desired spring rates and reasonable maximum stress.
Automatic Design in Matlab Using PDE Toolbox for Shape and Topology Optimization
Authors: Sun Yilun , Xu Lingji , Yang Jingru , Lueth Tim C.
Published: January 2020

In this paper, we present a novel concept of using Matlab’s Partial Differential Equation (PDE) Toolbox to achieve shape and topology optimization during the automatic mechanical design process. In our institute, we are developing a toolbox called Solid Geometry (SG) Library in Matlab to achieve automatic design of medical robots and mechanisms. The entire design process is performed in one developing environment without additional data input and output. And those robots and mechanisms can be quickly manufactured by different kinds of 3D printers. Recently, we have also integrated the shape and topology optimization techniques into our automatic design process by using the PDE Toolbox of Matlab for finite element analysis because of its high efficiency and compactness. For optimization algorithms, we have already implemented two bionic structural optimization methods called Computer Aided Optimization (CAO) and Soft Kill Option (SKO) to optimize the stress distribution in the structure. Since the complicated material layout in the optimization results can be easily realized by the 3D printing technology, the mechanical performance of our medical robots and mechanisms can be greatly improved with the work presented in this paper.
Design and Development of Flexible Systems Load Deflection Tester
Authors: Tekes Ayse , Mayeed Mohammed , McFall Kevin
Published: January 2020

This study presents the design and development of a novel, low-cost load-deflection test setup providing the testing of flexible links and compliant mechanisms. Test bench consists of two stepper motors, lead screw, rail system, two carts, two clamps, bearings and a force sensor. Clamps are designed in a way to attach various types of compliant members such as pinned-pinned buckling beam, fixed-fixed beam and 3D printed links. Mechanism enables to calculate the stiffness of compliant and 3D printed flexible systems. Sliders are displaced quasi-statically to slowly stretch or compress the flexible members attached in between two clamps. Displacement of the carts and deflection of the midpoint of the buckling beams are captured using machine vision measurement. Force applied from one of the carts to the end of the attached link is recorded using the force sensor. Stiffness of 3D printed flexible translational vibratory mechanisms is obtained using the displacement of the carts and load deflection curve of buckling beams are obtained using deflection curve and load data. Experimental results are compared with the same simulations performed by FEA analysis.
Decentralized Multi-Robot Motion Planning Applicable to Dynamic Environment
Authors: Wu Bin , Suh C. Steve
Published: January 2020

Multi-robots navigation in dynamic environment is a promising topic in intelligent robotics with motion planning being one of the fundamental problems. However, in practicel, multi-robots motion planning is challenging with traditional centralized approach since computational demand makes it less practical and robust for the motion planning of a large number of robots. In this paper, a decentralized distribute robots motion planning framework (DDRMPF) is discussed which addresses the specific issue. DDRMPF directly maps raw sensor data to steering command to generate optimal paths for each constituent robot. Unlike centralized method which needs a complete observation along with a center agent which processes heavy data collected from all the robots, DDRMPF allows each agent to generate an optimal local path needing only partial observation, thus rendering motion planning involving large numbers of robots more practical and robust. DDRMPF trains the policy for each robot in the complex and dynamic environment simultaneously based on the reinforcement algorithm.
Analysis of Ablation Volume Produced During Microwave Ablation of Breast Cancerous Lesion Using Fourier and Non-Fourier Models
Authors: Satish Vellavalapalli , Kumar Jatin , Repaka Ramjee
Published: January 2020

The present article aims to compare the change in the temperature and ablation volume during Microwave ablation procedure. The microwave ablation process is carried out using Fourier and non-Fourier bioheat transfer models in the computational domain of breast tumor. The above models have been considered with the relaxation time known as thermal delay during ablation procedure at constant power and frequency. The above objective has been carried out on a heterogeneous three compartment Breast model using COMSOL-Multiphysics software, with inbuilt bioheat transfer and electromagnetic waves Physics interfaces. The simulation results show that the ablation volume is slightly greater while using Fourier bioheat transfer model as compared to the non-Fourier bioheat transfer model. Further, the temperature distribution also shows that there is a slight variation initially at the start of the ablation, i.e., Fourier heat transfer model shows nearly 2°C more temperature as compared to the non Fourier model and becomes equal as the time increases. The present study helps in establishing the better clinical procedure of Microwave Ablation technique.
Effect of the Die Hole Structure and Distribution on the Strength of Ring Die in Pelletizing Equipment
Authors: Li Junhong , Sun Yu , Wu Kai , Wang Yu
Published: January 2020

The short life and high cost of ring die restrict the development of pelletizing technology severely. To solve the problem, this paper focuses on the effect of die hole structure and distribution on the die strength by finite element analysis. At first, a parametric model with one random hole surrounded by six same holes is established. Through ANSYS Design Exploration, the significant design parameters affecting the deformation and stress of the die were clarified. Furthermore, the effects of the significant parameters on the total deformation and equivalent stress were obtained by response surface analysis. In addition, the empirical equations between deformation/stress and the significant parameters were developed and the interactions of any two parameters were investigated. The results show that the equations reach a high degree of significance and the coefficient of determination R2 is 0.9803, which means it can predict the total deformation and equivalent stress correctly. Moreover, the optimal combination of the parameters was achieved. When the smallest deformation and equivalent stress of ring die are obtained in the range of parameters value, the cone angle of die hole inlet is 14.67°, the effective diameter is 2.7mm, the radial vertical distance between two adjacent die holes is 10mm and the angle is 2.7°. Using the multi-objective optimization method based on the finite element to study the influence of design parameters on the ring die strength provides an effective method and idea for the design of ring die.
Equilibrium Equations of Incremental Forces and its Application in Assembly Variation Analysis of Compliant Structures
Authors: Niu Zhihua , Li Zhimin , Jin Sun , Li Xinxin
Published: January 2020

Assembly variation analysis is used to handle the tradeoff between product performance and manufacturing cost. Traditionally, the assembly variation analysis of compliant structures is achieved by combining finite element analysis (FEA) and Monte Carlo simulation. Although the distribution of assembly dimensions can be obtained by such a process, the internal relationships between component deviations and assembly precisions are hidden in the reduplicative computational process. This study aims to shed light on the internal relationships between component deviations and assembly deformations of compliant mechanisms by Equilibrium Equations of Incremental Forces (EEIF). Dimensional deviation is an additional part to theoretical dimension, so does incremental force is to theoretical assembly load. EEIF is the bridge between dimensional deviations and incremental forces. This paper extends the application area of EEIF from compliant joints to compliant beams. The beginning of this paper reviews mainstream assembly variation analysis methods and the application of compliant mechanisms. Following is the basic conceptions about Equilibrium Equations of Incremental Forces. In the theory development part, compliant joints and compliant beams are discussed respectively. Precision of the method is verified by comparing it with an ADAMS/Flex model. Then, the output sensitivity coefficient matrix is used to conduct statistical assembly variation analysis for compliant mechanisms.
Micro-Hydrokinetic Turbine Operating in the Vicinity of a Free Surface: Multiphase Large Eddy Simulations
Authors: Attiya Bashar , Altimemy Muhannad , Daskiran Cosan , Liu I-Han , Oztekin Alparslan
Published: January 2020

Large Eddy Simulation (LES) turbulence and multiphase Volume of Fluid (VOF) model are employed to predict the spatial and temporal characteristics of the turbulent flow structures near micro-hydrokinetic turbine operating in the proximity of a free surface. The turbine power performance and the free surface dynamics, and its interaction with the turbine are characterized by examining the results of both single-phase and multiphase flow simulations. Simulations are conducted at the turbine’s best efficiency point at a tip speed ratio of 1.86 with the rotation rate of 150 rpm and the free stream water velocity of 2.25 m/s. The multiphase flow simulation is carried out at Froude number of 1.06. The results indicate slight interaction between the deformed free surface and the turbine wake structures. Acceleration in the flow velocity is observed near the free surface due to the physical confinement. The results indicate that turbine power generation is reduced by about 2.0%, and the thrust coefficient is reduced by 1.60%. It is demonstrated that the turbine performance at this Froude number is hardly influenced by the presence of the free surface.
Surgical Bone Drilling: A Review
Authors: Samarasinghe Chandana , Uddin Mohammad , Bari Saiful , Xian Cory
Published: January 2020

Bone drilling is an important step in orthopedic surgeries for the reconstruction and repair of fractured bones. The main concern in bone drilling is to create holes without causing minimum damage to the bone tissues. It is well reported that high temperature and high force in drilling cause bone thermal necrosis leading to the delayed bone healing and implant failure. In the past, a significant amount of research has been conducted to understand and mitigate the issues in bone drilling. However, the current practice in bone drilling is that medical surgeons still rely on their own experience and feeling, which often causes unwanted damage to the bone. The present paper aims to provide a comprehensive review of surgical bone drilling and impending factors affecting drilling and biological performance of the bone. Current protocols and practices in tackling issues around drilling are discussed and assessed in terms of results obtained in both experimental and computational domains. This pragmatic discussion will signify the importance and challenges ahead in empowering medical surgeons to enable improved surgical outcome. Furthermore, the findings of this extensive review are expected to drive further exploration of new opportunities for developing advanced bone drilling system integrated with intelligent sensors and control technology.
Rate Controlled Constrained-Equilibrium Simulation of Ethanol Combustion Using SVD Derived Constraints
Authors: Roy Shrabanti , Hadi Fatemeh , Askari Omid
Published: January 2020

In this study, the fully automatable Approximate Singular Value Decomposition of the Actual Degrees of Disequilibrium (ASVDADD) method is used for combustion modeling of ethanol. Due to the importance of ethanol as one of the most common type of biofuels, modeling its reaction kinetics and chemical composition evolution during combustion is necessary. The detailed kinetic mechanism (DKM) considered here is generated by authors using reaction mechanism generator (RMG) technique and it consists of 66 species and 1031 reactions. Tracking this number of species and chemical reactions in computational fluid dynamic (CFD) analysis of engineering problems is prohibitive. To alleviate this issue, Rate-Controlled Constrained-Equilibrium (RCCE) model reduction scheme for chemical kinetics is employed. It describes the evolution of a complex chemical system with acceptable accuracy with a number of rates controlling constraints on the associated constrained-equilibrium states of the system, much lower than the number of species in the underlying DKM. Successful approximation of the constrained equilibrium states requires accurate identification of the constraints. One promising procedure is the ASVDADD method that is capable of identifying the best constraints for a given range of thermodynamic conditions and a required level of approximation. ASVDADD is based on simple algebraic analysis of the results of the underlying DKM simulation and is focused on the behavior of the degrees of disequilibrium (DoD) of the individual chemical reactions. In this paper, ASVDADD is used to derive the RCCE constraints and ethanol combustion is modeled using both DKM and RCCE. Comparison of RCCE results with those of DKM shows the effectiveness of the ASVDADD derived constraints which demonstrates the potential of the RCCE method for combustion modeling of heavy and complex fuels.
Motorcycle No Fall Over Kickstand
Authors: Salman Muhammad
Published: January 2020

Motorcycles have been a mode of transportation since 1894, when the first batch of motorcycles were manufactured for consumer use by Hildebrand & Wolfmüller. Motorcycles provide a fast and cost effective, specifically fuel economy, way to commute. They are also used in recreational settings such as motocross and performance racing activities. Over the years, there have been many different design generations for the various manufactures and custom shops. The customer demand for motorcycles is always increasing as well. However, the biggest drawback to someone owning and operating a motorcycle has always been safety concerns. One of these safety concerns is the motorcycle falling over and being damaged while being parked. Fall overs occur for a multitude number of reasons, the most common occurrences due to being parked on an uneven level or someone pushing the motorcycle over. Current safety devices to prevent this from occurring are crash bars and center stands. However, these devices are either not applicable to all motorcycle makes and models or do not appeal to the motorcycles look per the owner’s discretion. A “no fall over” automated mechanical kickstand would solve both of these problems and, at the same time, prevent fall over accidents.
Singular Perturbation Solution for a Two-Phase Stefan Problem in Outward Solidification
Authors: Xu Minghan , Akhtar Saad , Alzoubi Mahmoud A. , Sasmito Agus P.
Published: January 2020

Mathematical modeling of phase change process in porous media can help ensure the efficient design and operation of thermal energy storage and pipe freezing. Numerical methods generally require high computational power to be applicable in practice. Therefore, it is of great interest to develop accurate and reliable analytical frameworks. This study proposes a singular perturbation solution for a two-phase Stefan problem that describes outward solidification in a finite annular space. The problem solves cylindrical heat conduction equations for both solid and liquid phases, with consideration of a moving boundary condition. Perturbation method takes the advantages of small Stefan number as the perturbation parameter, which intrinsically occurs in porous media. Furthermore, a boundary-fixing technique is used to remove nonlinearity in the moving boundary condition. Two different time scales are separately expanded and evaluated to facilitate the construction of a composite asymptotic solution. The analytical solution is verified against a general numerical model using enthalpy method and local volume-averaged thermal properties. The results indicate that the temperature profile of both phases can be well modeled by singular perturbation theory. The analytical solution is found to have similar conclusions to the numerical analysis with much lesser computational cost.
Influence of Vibration Characteristics of Agricultural Tire on Transfer Characteristics of Lug Excitation Force and Shaft Force
Authors: Fujita Katsuhide , Saito Takashi , Kaneko Mitsugu
Published: January 2020

The objective of this study is to clarify the vibration generation mechanism of agricultural machinery caused by the interaction between the tire lugs and the road surface. It is important to investigate the lug excitation force occurring on a rolling agricultural tire in order to clarify the vibration generation mechanism. In our previous study, we modelled the agricultural tire as a three-dimensional rigid ring model (SWIFT model). Further, the frequency equations of SWIFT model are derived and the model parameters are identified by minimizing the difference between measured and calculated natural frequencies. In order to identify lug excitation force, shaft displacement and shaft force during rolling motion are measured three-dimensionally by rolling test and lug excitation force in longitudinal, vertical and lateral direction are identified. From the obtained results, shaft force characteristics and lug excitation force characteristics are investigated. As a result, there is a correlation between shaft force and lug excitation force and it has been confirmed that both characteristics are influenced by the vibration characteristics of the tire. However, the transfer characteristics between lug excitation force (as input) and shaft force (as output) are not investigated.

In this study, amplitude magnification and phase difference are analyzed as the transfer characteristics of lug excitation force and shaft force. From the obtained results, the influence of vibration characteristics of the tire on transfer characteristics are investigated.
Biomechanical Structural Effect of Pinball Region Contact Applied to a Finite Element Model of Human Foot
Authors: Vidal-Lesso Agustín , Lara-Velázquez Carlos , Bayod-López Javier , Becerro de Bengoa Vallejo Ricardo , Mancera Campos Natali
Published: January 2020

Developing a finite element model of the human foot to analyze the numerical effect of the contact between its bones can also help to understand the complex biomechanics of this member.

Therefore, in this work, a three-dimensional model of finite elements of the foot is developed, in order to determine the contact radius between each pair of bones, which help to achieve an adequate distribution of body weight and be able to perform a correct characterization of the biomechanical effect of the foot. In the finite element model developed in this work, the cartilage was replaced by the pair of contact between two bodies (bones) and was simplified to the bony and ligamentous system. It was observed that the radius of the contact sphere of the pinball region has a great impact on the distribution of reactions with the ground (GRF) and the general behavior of the simulation. By varying the contact parameters, it was possible to reduce the error of the results obtained by the simulation with respect to those obtained experimentally up to a value of less than 5%; emphasizing the importance of checking the contact parameters before continuing with a simulation of finite elements.
The Highly Turbulent Flow and Heat Transfer in Semi-Closed Rotating Disc Cavity
Authors: Luo Guohu , Yao Zhenqiang , Wang Shengde , Shen Hong
Published: January 2020

The highly turbulent flow and heat-transfer in a semi-closed rotating disk cavity is numerically simulated based on a hybrid RANS/LES turbulence model. The superimposed radial outflow, which enters into the cavity from the inlet and exits the cavity from the discharge holes, results in the three flow region formed in the disk cavity. The effects of rotating Reynolds’ number and cavity aspect ratio on the pumping mass flow, local momentum coefficient as well as radial heat-transfer coefficient are fully examined. And the corresponding correlations are established with respect to rotating Reynolds’ number and aspect ratio. It is revealed that the radial heat-transfer from the periphery of the cavity to discharge hole is highly correlated to the secondary flow pumped by the rotating disk. Based on those prediction models, an equivalent thermal network for the radial heat-transfer is proposed, which can efficiently predict the radial temperature distribution in the semi-closed disk cavity, and estimate the effects of viscous-heating as well as temperature-viscosity correction.
Evolution of Liquid and Gas Phase Functional Groups During the Distillation Process of an Aviation Fuel
Authors: Luo Lei , Chen Shuqing , Liu Yu Cheng
Published: January 2020

Some surrogate fuel models have been formulated based on gaseous combustion properties. While development of surrogate fuel for spray combustion is still in an exploratory stage, it is in a great demand to develop methods to validate the volatility performance and corresponding combustion properties of a surrogate fuel mixture based on real fuel’s behavior. Distillation experiment of Chinese aviation fuel RP-3 was carried out to reveal evolution of components and chemical functional groups during the vaporization process of a real fuel. Both liquid and vapor samples were analyzed using GC-MS and NMR. The variation of functional groups and volatility performance of surrogate were also investigated using a well-validated numerical model. The experimental results show that the chemical functional groups almost have no change and that the average carbon number in the gas phase increases throughout the distillation. On contrary, the functional groups of some existing surrogates varied greatly during their distillation processes in spite that their distillation curves match well with real fuel’s. A 24-component mixture is formulated to demonstrated possibility to match both distillation behavior and combustion properties during vaporization. This study provides some potential directions for developing a surrogate with its vaporization truthfully representing the vaporization of the target real fuel.
Performance Analysis of the Impeller of a Centrifugal Air Compressor
Authors: Jebieshia T. R. , Raman S. K. , Kim H. D.
Published: January 2020

The present study focuses on the aerodynamic performance and structural analysis of the centrifugal compressor impeller. Performance characteristics of the impeller are analyzed with and without splitter blades by varying the total number of main and splitter blades. The operating conditions of the compressor under centrifugal force and pressure load from the aerodynamic analysis were applied to the impeller blade and hub to perform the one-way Fluid-Structure Interaction (FSI). For the stress assessment, maximum equivalent von-Mises stresses in the impeller blades are compared with the maximum allowable stress of the impeller material. The effects of varying pressure field on the deformation and stress of the impeller is also calculated. The aerodynamic and structural performance of the centrifugal compressor at 73000 rpm are investigated in terms of the efficiency, pressure ratio, equivalent von-Mises stress, and total deformation of the impeller.
Experimental Investigation of Spontaneous Buckling-Driven Delamination of Thin Films on Soft Spherical Substrate
Authors: Saito Yusaku , Yoshioka Shuhei , Emori Kanako , Teoh Rui Ern Brenda , Yonezu Akio
Published: January 2020

This study develops a new experimental system to investigate surface buckling patterns that emerge due to the biaxial compression of elastomeric bilayer spherical shell. The sample used in this study is a thick PDMS (polydimethylsiloxane) substrate and a thin PDMS film. In order to induce biaxial strain to the surface of PDMS substrate, air pressured device like bulge test is first developed. This system enables a flat PDMS plate to isotropically expand and become a hemisphere due to air pressure. In other words, the surface of PDMS substrate is stretched and subjected to biaxial loading. Subsequently, a thin PDMS film is covered on the hemisphere substrate. By releasing the air pressure, the pre-stretch in the substrate is released gradually and the outer film is subjected to biaxial compression. During the biaxial compression, various film buckling patterns are observed. It is found that the surface buckling patterns are wrinkle formation that is associated with film delamination. This formation pattern is dependent on the surface strain distribution, i.e. radial strain and circumferential strain. In order to control the pattern of buckling-delamination, we systematically changed the material parameters, such as the film thickness, Young’s modulus, interfacial fracture toughness, etc. Our experiment is capable in reproducing various wrinkle patterns with film delamination on an elastomeric bilayer spherical shell.
Evaluation of Interfacial Fatigue Strength of Hard Coating by Using Repeated Laser Shock Adhesion Test
Authors: Kanamori Kohei , Saito Yusaku , Yonezu Akio
Published: January 2020

This study aims to evaluate the adhesion strength and durability of hard coatings in a non-contact manner by using Laser Shock Adhesion Test (LaSAT). Both heat-treated and as-plated (non-heat-treated) Ni-P coatings deposited on carbon steel substrate by electroless plating method were prepared as specimens for this study. LaSAT uses strong elastic waves induced by pulsed laser irradiation in order to apply tensile stress to the coating/substrate interface so that interface delamination occurs. The out-of-plane displacement is also measured simultaneously by using a laser ultrasonic interferometer, and the interface delamination is detected by the change of the out-of-plane displacement waveform. Furthermore, computation of the elastic wave propagation using Finite Difference Time Domain (FDTD) is carried out to estimate the interfacial tensile stress. In addition, the adhesion durability is investigated by repetitive pulsed laser irradiation, and the relationship between the adhesion strength and the number of laser irradiation cycles until delamination was obtained. Finally, we discussed the effects of heat treatment on the adhesion strength and durability. This method of LaSAT is a quick measurement for the adhesion durability, and then it may shed some light on quality control of surface coating.
Numerical Analysis of the Performance of an Adjustable Thermoacoustically-Driven Thermo-Acoustic Refrigerator
Authors: Alcock A. C. , Balonji S. , Tartibu L. K.
Published: January 2020

Thermo-acoustic refrigeration could potentially become an alternative option to current traditional refrigeration systems provided that the issue related to its efficiency is addressed. One of the incentives for developing this technology is the opportunity it establishes with respect to the use of a sustainable heat source to induce cooling. Many existing works have pointed out the relationship between the geometrical configuration of the device and its performance. Mainly, the stack geometry and position have been the focus of these previous works. In this work, a standing-wave ThermoAcoustically-Driven Thermo-Acoustic Refrigerator with an adjustable resonator has been developed. Hence the device is made of two portions, joined with an adjustable duct, namely a simple standing-wave thermo-acoustic engine that converts heat into a sound wave and a simple thermo-acoustic refrigerator where heat pumping takes place. The Design Environment for Low-amplitude ThermoAcoustic Energy Conversion (DELTAEC) was used to model and analyze the influence of the adjustment of the resonator on the cooling performance. Parameters like the temperature difference across the stack, the frequency of the acoustic sound wave generated, the cooling power and the coefficient of performance have been studied. The initial results reported in this study show the possibility to change the performance of practical TADTAR by adjusting the resonator length.
Predictive Shimming of Frame-Panel Assemblies Using FEM and Laser Scanning
Authors: Ospina-Aldana Gustavo , Hassan Ali Mohamed I. , Odendaal Hendrik , Abusafieh Abdelqader A. , Woon Wei
Published: January 2020

This paper presents a predictive shimming methodology based on finite element analysis modeling (FEM) and laser scanning metrology. The aim of the predictive shimming methodology is to provide the geometry of the necessary shims for an assembly beforehand, so the shims can be manufactured in advance and placed on the exact location reducing ergonomic harmful conditions for plant personnel, improving accuracy, reducing the components assembly time and lowering manufacturing cost.

The case study for the predictive shimming method is an aircraft torque box assembly (TBA). The interface of interest is the mating surface of the skin and the rib shear ties. A FEM model of the skin was developed to calculate the skin deformation under prescribed displacements at the shimming locations. The FEM model was successfully verified and validated. Using the FEM deformation data, the geometry of the shims needed for an assembly can be calculated. Laser scanning metrology is used to get a point cloud of the assembly, fine-tuning the shims geometry.
How Variations in Downstream Computational Fluid Dynamics Turbulence Studies Can Be Impacted When Employing Commonly Used Initial Set-Up Configuration Parameters for Airfoils
Authors: Al-Qarishey Hussein , Fletcher Robert
Published: January 2020

Upstream wind turbine turbulence can negatively impact the aerodynamic performance of downstream wind turbines. It is important to understand and evaluate the characteristic nature of this inflowing turbulence. Computational Fluid Dynamics (CFD) is a foundational analytical tool used to help predict and describe both boundary layer behavior and the resulting downstream turbulence for both these upstream turbines and the impacted downstream turbines. Increasing the predication accuracy of turbulence models, particularly at the higher Reynolds number regimes, commonly encountered at the outer radius of wind turbine blades, remains a fundamental consideration in such CFD analysis.

The work discussed here focuses on understanding how CFD simulations can be impacted by basic CFD approaches and configurations. Commonly use unstructured grids and incremental positive angles of attack around the well-studied NACA0012 airfoil were used to assess how these basic set-up parameters can influence CFD turbulence results. Navier-Stokes equations were solved for incompressible flow to assess downstream turbulence using the SST k-ω (two equation) turbulence model within ANSYS Fluent (SIMPLE solution method). Two airfoil configurations with respect to angle of attack (α) were of interested and studied, with one configuration defined as “fixed-position” and the second configuration defined as “changed-position”. Fixed-position refers to a single common airfoil/grid configuration and changing incoming ux, vy velocity vectors to yield different angle of attack (α) values. Changed-position refers to a utilizing a single ux velocity vector and physically rotating the impacted airfoil in the computational field to yield different angles of attack.

A two-dimensional unsteady state SST k-ω turbulence model was used at a Reynolds of 3.0 × 106. The resulting data from the system setup models studied here (fixed and changed-positions) were successfully validated by comparing the computed lift and drag coefficients at these varying α values to common values found in literature. Downstream pressure contours, along with Ux and Vy, and net-velocity contours at various distances from 1.5 cord lengths up to 12.0 cord lengths from the leading edge of the airfoil at incremental angles of attack were studied. The authors review how such variations in rudimentary approaches impact the CFD downstream output results.