bluuebunny/crossref_metadata_2025 huggingface dataset:
An Accurate Unstructured Finite Volume Discrete Boltzmann Method
Authors: Chen Leitao , Schaefer Laura , Cai Xiaofeng
Published: January 2019

Unlike the conventional lattice Boltzmann method (LBM), the discrete Boltzmann method (DBM) is Eulerian in nature and decouples the discretization of particle velocity space from configuration space and time space, which allows the use of an unstructured grid to exactly capture complex boundary geometries. A discrete Boltzmann model that solves the discrete Boltzmann equation (DBE) with the finite volume method (FVM) on a triangular unstructured grid is developed. The accuracy of the model is improved with the proposed high-order flux schemes and interpolation scheme. The boundary treatment for commonly used boundary conditions is also formulated. A series of problems with both periodic and non-periodic boundaries are simulated. The results show that the new model can significantly reduce numerical viscosity.
Combined Computational and Experimental Analysis of Cooldown of a Surrogate Engine Mount Assembly
Authors: Verma Navni N. , Iacob Andrei , Mazumder Sandip , Selamet Ahmet
Published: January 2019

A combined computational/ experimental analysis is conducted to investigate the cooldown behavior of a surrogate engine mount assembly. The engine mount in an automobile is often in the close proximity of the catalytic converter, and may heat up significantly during operation of the vehicle. When the vehicle is parked after operation, the mount cools due to heat loss by natural convection and radiation. The objective of this study is to develop a model that is capable of accurately predicting the spatio-temporal evolution of the mount temperature during this cooldown process. Carefully controlled experiments were first conducted, during which temperatures were recorded at 41 different locations. A Computational Fluid Dynamics (CFD) model that includes natural convection and radiation was next developed to simulate the same experiments. The simulations were conducted using roughly 5–6 million control volume (cells). The mesh was generated using ANSA™ and parallel computations of the governing equations were conducted using Ansys-Fluent™. The CFD results were found to agree with the measured temperatures to within a few tens of degrees. The discrepancies may be attributed to differences in initial conditions (measured versus numerical) and due to the fact that thermal contact resistances were neglected. However, the study revealed that to obtain reasonably close agreement, one must use very small time step sizes — small enough to sufficiently resolve the rapidly changing unsteady natural convection patterns — making such computations extremely time-consuming.
Efficiency Variation on a 4-Stage Low Speed Research Compressor With a Redesigned Cantilevered Stator
Authors: Ju Zhenzhou , Teng Jinfang , Fan Lin , Zhong Yongjian , Qiang Xiaoqing
Published: January 2019

Numerical simulations with the steady 3D RANS were performed on a 4-stage low speed research compressor (LSRC) with two typical configurations (a shrouded and a redesigned cantilevered stator of the third stator). The shrouded stator (SS) with 0.67% labyrinth seal clearance of the blade height is the prototype, and the cantilevered stator (CS) with 1.2% hub clearance of the blade height is the redesigned cantilevered stator. The fourth rotor that follows after the cantilevered stator was redesigned (RE) according to blade load and inlet flow angle changed based on the redesigned cantilevered stator. The overall performance of the 4-stage LSRC and the distribution of aerodynamic parameters along the blade height were compared between the prototype and the redesigned third stator. Flow characteristics of the third stator and fourth rotor were analyzed in detail. The results indicate that the flow characteristics below the 35% blade height are very different between the prototype and the redesigned due to the effect of leakage flow from seal cavity and hub gap, respectively. The stall margin of CS is 57% higher than SS. The efficiency of CS at the design point is 0.82% higher than SS. Through the redesigned process of R4, the stall margin of RE is 45% higher than CS and the efficiency of R4 is 0.6% higher on average over the entire operating range.
A Novel Air-Air Heat Exchanger Design and Experimental Validation for Aero-Engines
Authors: Liu Yinlong , Fu Yanchen , Huang Haoran , Wen Jie , Xu Guoqiang
Published: January 2019

To meet the demand of thermal protection in aero engines, this paper presents a novel compact cross-flow air-air heat exchanger based on the Cooled Cooling Air (CCA) technology. This novel air-air heat exchanger consisting of 4 × 10 serpentine tubes (4.4 mm I.D., 5.0 mm O.D., stainless steel type 321) was designed using the classic Logarithmic Mean Temperature Difference (LMTD) method. Experimental verification has been done to research the hydraulic and heat transfer performance of the heat exchanger. The results show that the 1.48 kg serpentine tube air-air heat exchanger can cool the high pressure compressor bleeding air by 200 K at the mass flow rate of 0.05 kg/s using bypass duct cold air. Comparisons between calculated and experimental data have been done and good agreement between them was obtained in both flow resistance and heat transfer characteristics. Thus, the LMTD method could be well adopted in designing compact air-air heat exchanger for aero-engines. A new empirical heat transfer coefficient correlation for the tube outside is obtained using Wilson plot method, and it can be helpful designing heat exchanger with similar structures. This research is a great proof of CCA’s feasibility in terms of theory and practice.
A Small-Scale Robotic Spill Detection and Cleaning Method
Authors: Alsaif Hussain F. , Antar Houssam , Tandon Ashmita , Baker Demitri , Manning Jack , Ma Guohua , McCusker James
Published: January 2019

Small-scale spill detection and removal represents a fundamental concern for a wide variety of industries such as food production plants. Often these spills are detected and cleaned manually resulting in slower operations and less productivity. In this design project, a robotic solution, including detection of the spill and removal of it, is presented to maintain high productivity and operations standards in a given organization. The design consists of a plastic structure including acrylic and polylactide (PLA), a vacuum motor, spill detection electronics using image processing and control apparatus. For initial testing purposes, the robotic attachment was mounted to iRobot Create 2 as a movement platform. Testing methods consisted of rounds of spill cleaning for a variety of materials including oil and syrup. As a result of those tests, the design can be scaled to different industries such as Oil and Gas, Energy, Supermarket and Warehouses. Results show improved spill detection and removal compared to manual methods.
Problem Based Learning: Generating a 3D Educational Brain Model to Engage Undergraduate Engineering Honors Students
Authors: Gomez Connie , Nasir Sheema
Published: January 2019

Engineering courses offered through the Honors Program allow students to conduct both research and design during their time at a community college, which is extremely valuable due to the limited number of research opportunities when compared to a four-year institution. Additionally, community college engineering courses normally serve students seeking to enter a wide range of engineering disciplines.

Therefore, any research or design experience with lasting impact must also encompass a wide range of topics while also fostering communication, teamwork, creativity and life-long learning. This paper describes an engineering graphics honors course that engaged students in the development of a CAD model and prototype of a 3D brain model for use by Anatomy and Physiology students. This project allowed students to engage in the areas of personalized learning, reverse engineering the brain, manufacturing as well a computer-aided design. This paper discusses the development of technical and soft skill competencies through student performance and student perception via questionnaires. Finally, this paper sets forth recommendations for other community colleges interested in developing problem-based learning opportunities throughout their engineering curriculum.
Evaluation of Soft Material Fracture Behavior via Indentation Testing With a Needle-Like Indenter
Authors: Ishino Takayuki , Sakuma Atsushi
Published: January 2019

Because the fracture behaviors of soft materials are complex, high-precision technology is needed to perform the detailed analysis necessary to produce more effective materials. Indentation methods exist to characterize the fracture behavior of soft materials, with fractures varying in accordance with the shape of the indenter. Thus, it is important to clarify the relationship between indenter shape and the fracture behaviors of soft materials, and necessary to consider the complicated deformation patterns induced by the mechanical nonlinearity of the materials. To this end, various needle-like indenter shapes are modeled via a finite element method (FEM). In this study, we employ a cone-shaped reference needle. Then, the shape is changed to have the tip form a curvilinear indentation, resembling a steep mountain ridgeline. In addition, shear strain is set as the fracture criterion for soft material in the FE analysis since the shear force resulting from penetration primarily damages the soft materials. Regarding the force applied to the needle, there is a tendency for the force to become smaller as it more resembles a cone shape. There are three fracture types: holing, opening, and slitting. Holing is generated by the cone needle, and the fracture of soft material appears along the shape of the needle. Opening fractures are generated by the needle with a curvilinearly spreading tip, forming a small slit on the surface of the soft material. Lastly, slitting fractures are also generated by the needle with a curvilinearly spreading tip, but the resulting slit is deepened without damaging the tissue surrounding the needling. These fracture types can also be classified according to the fracture area of the soft material surface, with slitting resulting in the smallest fracture area.
Band Gaps for Elastic Wave Propagation in a Periodic Composite Beam Structure Incorporating Surface Energy, Transverse Shear and Rotational Inertia Effects
Authors: Gao R. Z. , Zhang G. Y. , Ioppolo T.
Published: January 2019

A new model for determining band gaps for elastic wave propagation in a periodic composite beam structure is developed using a non-classical Timoshenko beam model that incorporates the surface energy, transverse shear and rotational inertia effects. The Bloch theorem and transfer matrix method for periodic structures are employed in the formulation. The new model reduces to the classical elasticity-based model when the surface energy effect is not considered. It is shown that the band gaps predicted by the current model depend on the surface elastic constants of each constituent material, beam thickness, unit cell size, and volume fraction. The numerical results reveal that the band gap based on the current non-classical model is always larger than that given by the classical model when the beam thickness is very small, but the difference is diminishing as the thickness becomes large. Also, it is found that the first frequency for producing the band gap and the band gap size decrease with the increase of the unit cell length according to both the current and classical models. In addition, it is observed that the volume fraction has a significant effect on the band gap size, and large band gaps can be obtained by tailoring the volume fraction and material parameters.
Different Definitions of Entropy for Statistical Energy Analysis
Authors: Sotoudeh Zahra
Published: January 2019

This paper explores several definitions of entropy that stem from the fields of statistical mechanics and thermodynamics for vibrating structures. This paper shows that these definitions are equivalent in the context of mechanically vibrating systems. However, one is more suitable for statistical energy analysis. This work is motivated by the usefulness of the entropy concept towards developing a framework for the statistical treatment of vibroacoustic systems. Specifically, entropy provides a thermodynamic framework to justify the methodology of statistical energy analysis.
Deep Convolutional Neural Network for Early Disk Crack Diagnosis Under Variable Speed
Authors: Liu Ruonan , Yan Ruqiang , Ma Meng , Chen Xuefeng
Published: January 2019

Aero engine is essentially the heart of an airplane. However, the high temperature and high pressure working environment of the aero engine can easily lead to fatigue cracks in turbine disks, and result in serious accidents. Therefore, early disk crack diagnosis is very important to guarantee safe flight of the airplane and reduce its maintenance cost, which, however, is challenging due to the difficulty in building a complex physical model under variable operating speeds. To tackle this problem, a novel deep convolutional neural network (CNN)-based method is proposed for early disk crack diagnosis. CNN, as one of the deep learning structures, can learn deep-seated features directly and automatically from the raw data without the need of physical model or prior knowledge. It shows the potential to deal with the challenge of early disk crack diagnosis. Since the proposed diagnosis method is signal-level, the collected vibration signals can be input into the CNN architecture directly without the need of feature extractor. In this paper, the vibration signals at both the beginning and the end of the test are used for training the CNN model, then the rest signals are input into the trained model as test data to diagnose when the incipient disk crack is generated. Experimental study conducted on the fatigue test of a real turbine disk has proved the effectiveness and robustness of the proposed method for early disk crack diagnosis. Meanwhile, comparison study with some state-of-the-art methods is also performed, and further highlights the superiority of the proposed method.
Numerical Study on Influencing Factors of Film Cooling on Turbine Blade Leading Edge Under Rotating State
Authors: Ma Yiwen , Li Haiwang , Yang Meisong , Wu Min , Zhou Huimin
Published: January 2019

Engine turbine blades operate at a high speed of rotation and are subjected to high temperature and pressure prevailing gas from the combustion chamber, making the working condition very harsh. In particular, the leading edge of the blade, which is directly subjected to high-temperature gas impacts, is the hottest part of the turbine. Therefore, it is of great importance to improve the protection of the blade leading edge and enhance the understanding of this part of the flow field and temperature field. This paper will focus on the phenomenon of wake deflection and study the film cooling characteristics of the turbine blade under rotating condition. The characteristics of pressure surface and suction surface of the blade are verified by numerical simulation. The contents cover the influence of the film hole diameter, pitch, blowing ratio, rotation number and the development process, the film cooling efficiency on the outflow of coolant film. The result shows that Coriolis force, centrifugal force and secondary flow induced by rotation will change the mainstream flow along the blade, which will lead to changes of pattern concerning the development of the film on the blade surface. In the process of wake development, deflection occurs in different directions at different positions, and the greater the rotation number is, the more obvious the degree of deflection will be.

Studying the model with film holes on the leading edge of the blade, these phenomena can be observed along the downstream on the pressure and suction surfaces. Also, models with film holes independently set on the pressure and suction surfaces can be used as proof of these features. At the same time, this paper studies the flow and heat transfer characteristics of the leading-edge gas film under rotating condition and focuses on the influence of rotation on the outflow and the development processes of the wake. The gas film cooling models in rotating state of different film hole diameters and film hole radial spacing will also be compared to further understand the flow and heat transfer characteristics of film cooling on the leading edge of the blade.
A Modular Test Platform for Micromechanical Tensile Testing of Soft Biomaterials
Authors: Eng Wilson , Kim Max , Ramasubramanian Anand , Lee Sang-Joon John
Published: January 2019

Mechanical properties of biomaterials are difficult to characterize experimentally because many relevant biomaterials such as hydrogels are very pliable and viscoelastic. Furthermore, test specimens such as blood clots retrieved from patients tend to be small in size, requiring fine positioning and sensitive force measurement. Mechanobiological studies require fast data recording, preferably under simultaneous microscope imaging, in order to monitor events such as structural remodeling or localized rupture while strain is being applied. A low-profile tensile tester that applies prescribed displacement up to several millimeters and measures forces with resolution on the order of micronewtons has been designed and tested, using alginate as a representative soft biomaterial. 1.5% alginate (cross-linked with 0.1 M and 0.2 M calcium chloride) has been chosen as a reference material because of its extensive use in tissue engineering and other biomedical applications. Prescribed displacement control with rates between 20 μm/s and 60 μm/s were applied using a commercial low-noise nanopositioner. Force data were recorded using data acquisition and signal conditioning hardware with sampling rates as high as 1 kHz. Elongation up to approximately 10 mm and force in the range of 250 mN were measured. The data were used to extract elastic and viscoelastic parameters for alginate specimens. Another biomaterial, 2% agarose, was also tested to show versatility of the apparatus for slightly stiffer materials. The apparatus is modular such that different load cells ranging in capacity from hundreds of millinewtons to tens of newtons can be used. The apparatus furthermore is compatible with real-time microscope imaging, particle tracing, and programmable positioning sequences.
Finite Element Analysis of Dynamics of Human Muscle Compressed by Fabric Sleeve
Authors: Ueda Shodai , Sakuma Atsushi
Published: January 2019

Recently, compression wear has become the preferred performance material for many athletes, where it has the effect of reducing the burden on the body by suppressing muscle vibrations and improves athletic performance by providing the body with suitable moderate pressure. This study concerns thigh sleeves formed of compression wear. The optimal level of compression is studied in order to improve athletic performance and reduce muscular strain. Subsequently, the mechanics of the thigh compression sleeve are discussed. Here, the optimal tensile rigidity of the sleeve, which is calculated using the Young’s modulus of the sleeve in the circumferential direction, is discussed with the aim of reducing muscular strain. The finite element method model is adopted to represent the thigh, which commonly experiences muscle strain during running. The model is constructed using a semi-circular shape, which represents the thigh cut in the transverse plane. The model consists of two solid components, which reflect the muscle (outer) and femur (inner), as well as a shell that covers the thigh. The model generates sinusoidal vibrations, which reflect human behavior when running in a uniaxial direction. The maximum shear strain is approximately half of the tensile rigidity of the sleeve. Indeed, the muscle is sufficiently soft that the tensile rigidity of the sleeve is generally smaller when there is little shear strain on the muscle. From these results, it is concluded that the maximum shear strain of the muscle decreases by almost half when covered by the thigh compression sleeve compared to when no thigh compression sleeve is worn. Furthermore, the shear strain of the muscle can be reduced by varying the tensile rigidity of the sleeve when the human is running. Finally, the tensile rigidity of the sleeve can be decreased to reduce the shear strain of the muscle as it softens.
Design of a Ducted Cross-Flow Turbine for Marine Current Energy Extraction
Authors: Goundar Jai N. , Prasad Deepak D. , Ahmed Mohammed Rafiuddin
Published: January 2019

Marine current energy is a clean energy source and is a solution to the problems faced by burning fossil fuels such as global warming and climate change. Once tapped, the useful shaft power can be converted into electrical energy. To make this practical, the designed energy converter should be capable of operating at low marine current velocities, it should be suitable for installation at locations that have low water depths and should have lower manufacturing, installation and maintenance costs. A ducted cross-flow turbine has all the above features and it will be suitable for Pacific Island countries (PICs) for extracting marine current energy. The ducted cross-flow turbine was designed, modelled and analyzed in commercial Computational Fluid dynamic (CFD) code ANSYS-CFX. The inlet and outlet duct sizes were optimized for maximum output. Before the analysis of full model, the CFD results were validated with experimental results. Simulations for the 1:10 ducted cross-flow turbine (having a diameter of 150 mm) were performed with 400,000 nodes, as increase in the grid size did not make much difference other than increasing the simulation time significantly. The maximum difference in the power coefficient between CFD and experimental results was 6%. Simulations were then performed for the full-scale prototype, which has a duct (nozzle) inlet of 3.5 m × 3.5 m and a turbine diameter of 1.5 m, at three freestream velocities of 0.65 m/s, 1.95 m/s and 3.25 m/s. Analysis of the prototype performance showed that the ducted cross-flow turbine can reach a maximum efficiency of 56% and can produce 21.5 kW of power at a current speed of 1.95 m/s and 103.6 kW at 3.25 m/s. The designed cut-off speed was 4 m/s.
Heat Transfer Augmentation From Extended Surface Using Dimples
Authors: Mehta Jay D. , Colah Fay N. , Rao Anurag P. , Pendse Vineeta P. , Bagal Vyankatesh U. , Ajmera Kevin P.
Published: January 2019

This paper concentrates on comparing dimples to improve the heat transfer rate from extended surfaces under forced convection conditions. Dimples are milled on the surface of the fins while keeping the exposed surface area between the various designs as constant. Spherical dimples, ellipsoidal dimples, cylindrical dimples, and pyramidal dimples are selected as part of the paper. Experimental results are compared with results obtained from simulation. The paper concludes that surface modifications improve the heat transfer rates. The paper also compares the thermal performance of various shapes of dimples.
A Study of a Mechanism of Cell Proliferation Promotion of Cultured Osteoblasts by Mechanical Vibration
Authors: Shiraishi Toshihiko , Nishijima Akitoshi
Published: January 2019

This paper describes a mechanism of cell proliferation promotion of cultured osteoblasts by mechanical vibration focusing on β-catenin. 12.5 Hz and 0.5 G mechanical vibration was reported to promote the cell proliferation of cultured osteoblasts in plane culture. That is because the mechanical vibration weakens cell-cell adhesion, promotes to pile up cells, and allows cells to form multilayer structure. However, it has not been clarified why cells continue cell division after their monolayer confluent state. Here we show that mechanical vibration not only weakens cell-cell adhesion bound by β-catenin but also promotes to move β-catenin from the cytoplasm to the nuclei, where β-catenin associates with DNA-binding members of the Tcf/LEF family and other associated transcription factors including cell division. After osteoblastic cells were cultured under 12.5 Hz and 0.5 G mechanical vibration, cells were fractionated into nuclear and cytoplasmic fractions using a centrifugation method. β-catenin in each fraction was detected by a western blot experiment. The protein bands from western blot films were quantified with an image processing and analysis software, ImageJ. As a result, the vibration group gave higher expression of β-catenin in nuclear fraction than the non-vibration group just after the vibration group reached the saturated cell density. It indicates that 12.5 Hz and 0.5 G mechanical vibration may promote to move β-catenin into the nuclei and the cell division.
Effect of Rake Angle and Feed Rate on the Surface Quality While Turning In Situ TiB2/7050 Al Metal Matrix Composites
Authors: Lin Kunyang , Wang Wenhu , Jiang Ruisong , Xiong Yifeng
Published: January 2019

In situ TiB2/7050 Al metal matrix composites are processed by mixed-salt reaction method to improve the interfacial reactions and enhance the material properties. However, the lack of research on its machinability limits its wide application in the industry. In the present study, the effects of rake angle and feed rate on the surface quality while turning in situ TiB2/7050 Al metal matrix composites have been investigated. Three types of polycrystalline diamond (PCD) tools with 0° ∼ 5° ∼ 10° rake angles were utilized in this work. The surface roughness, surface topography and residual stress profile developed in TiB2/7050 Al composites by cylindrical turning were evaluated. The experimental results reveal that feed rate has more significant impact for surface roughness than rake angle. The smooth surface topography without void and defects indicates that the chips are formed in ductile mode. Unlike other metallic alloys, the surface residual stress of TiB2/7050 Al composites are always in compressive state. In addition, the increase of feed rate contributes to deeper residual stress penetration layer. Through the discussion in this study, the role of TiB2 reinforcement particles on the machinability of TiB2/7050 Al composites can be better understood.
Simulating Eddy Current Sensors in Blade Tip Timing Application: Modeling and Experimental Validation
Authors: Jamia Nidhal , Friswell Michael I. , El-Borgi Sami , Rajendran Prakash
Published: January 2019

In gas turbines, the blade vibration caused by aerodynamic excitation or by self-excited vibration and flutter leads to high cycle fatigue that represents the main cause of damage in turbomachinery. Turbine operators have resorted to assess the blade vibrations using non-contact systems. One of the well-known non-contact methods is Blade Tip Timing (BTT). BTT is based on monitoring the time history of the passing of each blade tip by stationary sensors mounted in a casing around the blades. The BTT method evaluates the blade time of arrival (ToA) in order to estimate the vibration. To perform the BTT technique, optical sensors were widely used by industry due to their high accuracy and performance under high temperatures, but the main drawback of these systems is their low tolerance to the presence of contaminants. To mitigate this downside, Eddy Current Sensors (ECS) are a good alternative for health monitoring application in gas turbines due to their immunity to contaminants and debris. This type of sensor was used by many researches, predominantly on the experimental side. The focus was to extract response frequencies and therefore the accuracy of the timing measurement was ignored due to the lack of modeling. This paper fills the gap between experiments and modeling by simulating a BTT application where detailed finite element modeling of active and passive ECS outputs was performed. A test rig composed of a bladed disk with 12 blades clamped to a rotating shaft was designed and manufactured in order to validate the proposed models with experimental measurements. Finally, a comparison between these different types of sensor output is presented to show the effect of the blade tip clearance and rotational speed on the accuracy of the BTT measurement.
Study on Dependency of Dynamic Properties in a Rolling Roller on Fine Coal Upon the Running Velocity
Authors: Oshiro Kentaro , Kobayashi Akira , Watanabe Kazuhiro , Ohno Emi , Echizenya Makoto , Fujita Katsuhide , Saito Takashi
Published: January 2019

In previous study, the relation between dynamic behavior of the system and powder characteristic during rolling the roller on the fine coal spread over a table were investigated with the experimental equipment which consist of an elastic support roller system. In this study, we decreased rigidity of supporting part of experimental equipment to decrease natural frequency. These changes of structure enable us to specify a vibration during rolling the roller. We investigated rotating speed variation which is caused by roller slipping and horizontal vibration acceleration. In addition, we investigated relation between these experimental data and travel speed of the experimental equipment. As a result, both rotating speed variation and horizontal vibration acceleration increased with increasing of travel speed of the experimental equipment. After taking maximum value, both rotating speed variation and horizontal vibration acceleration decreased. To clear up the causes of the phenomenon, we investigated dependency of apparent friction coefficient upon slip ratio. However, noticeable dependency wasn’t represented. In addition, we calculated both horizontal vibration acceleration and RMS with frequency band limiting which is same range as natural frequency of the experimental equipment. As a result, it is found that natural frequency of the low level is excited as a main component and the excited frequency component changed to high level with increasing of travel speed of the experimental equipment.
Phantom-Element Technique for Periodic Deformation Analysis of Plain Fabrics Using LS-DYNA
Authors: Miyaki Hikaru , Sakuma Atsushi
Published: January 2019

Unit-cell modelling is one of the useful methods to analyze deformation in periodic structures like honeycombs, perforated boards, and woven fabrics. The initial state of the structures is considered to be stress-free in ordinal deformation analysis, but in actual practice, the analysis is difficult, because initial stresses like assembly stress and residual stress need to be considered, as they are known to affect the results. In this study, a technique of taking into account the initial-stress state in woven fabrics is discussed, which has resulted in the establishment of a precise design method for textiles. LS-DYNA, which is a general-purpose finite element (FE) software, has been utilized to simulate the complex deformations in woven fabrics. In this software, a function of the global constraint on boundary conditions facilitates the analysis of periodic structures, but causes difficulties in computing the initial stress states in woven fabrics, as the conditions of mechanical equilibrium have to be satisfied in the governing equations. In particular, duplicated definitions of forced displacement and periodic deformation make the computation impossible, hence, a phantom-element has been introduced to ease the FE analysis by defining these quantities. A unit-cell of the woven fabric is identified and the initial states in stressed conditions can be estimated for periodic structures of plain-woven fabrics by a periodic-analysis technique of LS-DYNA coupled with the phantom-element, which yields a weaving motion of the yarn in plain-woven fabrics.
Post-Failure Recovery Strategies for Metrorail Transit Networks With Washington D.C. As a Case Study
Authors: Saadat Yalda , Zhang Yanjie , Zhang Dongming , Ayyub Bilal M. , Huang Hongwei
Published: January 2019

Metro-Rail transit systems are large-scale networks in numerous modern urban areas that play prominent direct and supportive roles in providing efficient mobility for sustaining communities and local economies. Any event leading to failure of a metro-rail network could have serious societal consequences, such as dramatic effect on the safety and wellbeing of commuters in addition to direct and indirect costs from its diminished performance that lead to resilience loss. Potential performance losses might exhibit complexity and pose a challenge for measurement and prediction. Hence, measuring the resilience of such a network enables its efficient enhancement in a cost-effective manner. Enhancing resilience highly depends on identifying recovery strategies with special attention not only to restoring connectedness but also on reducing associated failure and recovery costs. An effective recovery strategy must demonstrate rapid optimal restoration of a disrupted system while minimizing the cost of the disruption. The objective of this paper is to identify effective recovery strategies to reduce the performance loss and to minimize the total cost of a network during and after a disruptive event, using Washington D.C. Metro with its 91 stations and 140 links as a case study. Method of measuring performance loss in this paper, illustrates that the best recovery sequence typically reflects the order of components ranked based on their degree of vulnerability in the network. Also, the proposed cost model provides a basis to decision makers to identify an optimal recovery strategy according to both paramount recovery sequence and minimum cost consideration.
Numerical Research on Machining Stability Subject to Delayed PID Control
Authors: Li Mingjie , Zhang Xiaojian , Xie Yakun
Published: January 2019

Machining stability analysis is important for chatter avoiding and production efficiency improvement. This paper conducts the numerical research on machining stability subject to delayed PID active control which is used to avoid chatter in machine milling. This control strategy is introduced into a two-degree-of-freedom milling system for illustration, the resulting hybrid system with both regenerative and feedback delays is represented as a delay-differential equation with time-periodic coefficients. From the comparison of stability region, it is found that the delayed PID control with proper parameters can lift the stability boundary largely compared with the case without control. To evaluate the stabilizability of the controlled system in cutting, the sensitivity of the stability boundary with respect to the PID parameters is analyzed. The numerical simulation of critical axial depth to PID parameters indicate that the milling stability critical boundary varies drastically with the derivative parameter. It also demonstrates that the stability critical boundary is strongly influenced by the proportional parameter, but it is less effected by the integral parameter. Hence, the stability domain can be expanded drastically with appropriate PID parameters based on the analysis above.
Traditional, Active and Problem-Based Learning Methods Used to Improve an Undergraduate Biomechanics Course
Authors: Shady Sally Fouad
Published: January 2019

Biomechanics is a core curriculum course taught in many biomedical engineering programs. Biomechanical analysis has become a necessary tool for both industry and research when developing a medical device. Despite its significance both inside and outside of the classroom, most students have demonstrated challenges in effectively mastering biomechanical concepts. Biomechanics requires adaptive skill sets needed to solve a multitude of problems from various disciplines and physiological systems. Many students taking biomechanics have not taken foundational courses that are necessary for in-depth learning and mastery of biomechanics. Consequently, limiting their ability to solve complex problems requiring strong foundations in statics, dynamics, fluid mechanics, and physiology. Active (AL) and problem-based learning (PBL) are techniques that has been widely used in medical education and allow faculty to implement engineering concepts into the context of disease solving real-world medical problems. This study investigates using both traditional and problem-based learning teaching pedagogy to enhance student learning in a senior level undergraduate biomechanics course. Results of this technique have shown an increase in student performance and self-assessments.
Optimized Vibration Suppression of Structural Floor Using Passive TMD
Authors: Chini Zaman , Zhang Haifeng
Published: January 2019

Vibration suppression has been implemented for many years as a way for a building’s occupants to feel more comfortable in structures prone to horizontal swaying or vertical oscillation. Suppression of a structure’s natural vibrations becomes even more important when delicate work, like surgeries, will be performed within. The purpose of this experiment was to confirm the validity of a passive vibration suppression unit to reduce the vibration in a portable shelter floor where surgeries would take place. Impact tests were done to determine the natural frequency of the floor, and along with the weight of the floor, were used to calculate operating parameters for a tuned mass damper, or TMD. A TMD was then assembled and vibration suppression effects were tested at 4% of total floor mass, to confirm the viability of the design. Additionally, TMDs of 2%, 3%, 4%, and 5% of the mass of the floor and shaker combined were made so frequency sweep tests could be done. Finally, a cantilever beam TMD was made, to test effectiveness of an easily adjustable TMD variant. The produced TMDs are expected to reduce the time the floor is vibrating and reduce vibration of the floor by up to 60%, bringing oscillations within comfortable levels even at the floor’s natural frequency.
A Numerical Approach for the Evaluation of the Energy Efficiency in Ventilated Façade
Authors: Milani Massimo , Montorsi Luca , Venturelli Matteo
Published: January 2019

The paper studies the ventilated façade as a potential alternative to conventional coating technologies for the thermal insulation of building’s external walls. The ventilated façade is modeled by means of a CFD approach that accounts for the full 3D-geometry of the building, the walls thickness and materials’ thermal properties. The effects of the windows on the heat losses and in the performance of the ventilated façade are modeled in order to accurately characterize the thermal behavior of the system. The solar radiative heat transfer during two representative days of the year is considered in the analysis and a multiband thermal radiation is adopted to capture the different nature of radiative heat exchange according to the light wavelengths.

The numerical approach enables to estimate the thermo-fluid dynamic behavior of the system and the temperature distribution and the velocity flow field within the air gap between the walls are addressed and their influence on the heat transfer through the building’s external walls is determined. The CFD analysis is employed to compare different configurations of the ventilated façade for improving the thermal insulation of the building; the performance of each scenario is determined in terms of electric energy and fuel consumption for the air conditioning and the heating system. Thus, the potential saving of the energy cost for ambient thermal conditioning is evaluated.

The analysis investigates the effects on the energy efficiency of different geometrical features of the system such as the height of the building and the air gap thickness and theoretical correlations are derived in order to estimate the best tradeoff between the energy efficiency of the building and the investment of the ventilated façade configuration.
Sommerfeld Effect and Passive Energy Reallocation in a Self-Synchronizing System
Authors: Sinha Anubhab , Bharti Saurabh Kumar , Samantaray Arun Kumar , Bhattacharyya Ranjan
Published: January 2019

Two eccentric rotors are mounted rigidly on a common vibrating base structure. Each of these rotors are separately driven by two motors, which are by nature non-ideal. Although power input for both rotors are different, the two rotors acquire the same speed via communication through the energized vibrating base. The phenomena is known as ‘self-synchronization’. Additionally, the presence of two non-ideal drives within the vibrating system also lead to the onset of the nonlinear jump phenomena (formally known as the Sommerfeld effect). Numerical simulations are carried out on a model developed on MSC Adams. From the generated responses, an overview of ‘self-synchronization’ as well as the various modes of synchronization are studied adjacent to the nature of Sommerfeld effect inherent within this system. The aim is to reduce the structural vibrations, mainly by virtue of self-synchronization. Henceforth, the behavior of the synchronized system is also examined in the presence of two secondary vibration reducing devices — a tuned Dynamic Vibration Absorber (DVA) and a Nonlinear Energy Sink (NES). Both are designed to passively absorb the excess vibrating energy from the synchronized system, at the onset of resonance.
Finite Element Analysis (FEA) for Optimization the Design of a Baja SAE Chassis
Authors: Maradey Lázaro Jessica Gissella , Esteban Villegas Helio Sneyder , Blanco Caballero Braulio José
Published: January 2019

The chassis is one of the main components of the vehicle, which provides not only support and stiffness but also gives the vehicle its shape. Its design is a challenge for the mechanical engineer: to achieve an optimum resistance-weight ratio which can ensure the safety of the pilot. To optimize its design, engineers can rely on the Finite Element Analysis (FEA) an ideal method to predict the behavior of the chassis to the different loads (Mechanical Effort, fatigue, movement) and effects (Vibration, heat, fluid flow, transfer of heat) given in real environments. This analysis is able to describe if a product may break, wear out or, otherwise, it will work as expected. Additionally, it allows the variation of the geometry and materials used so that the most suitable one can be selected for the application in study.

This article aims to show the preliminary design of the chassis (Simplified 3D model using CAD) taking into account the rules of the SAE competition and its optimization by using the FEA analysis and also taking into account its geometry. Static load analysis will start by selecting the appropriate mesh size and having as criteria that Von Mises stress should be less than the yield point of the selected material. Likewise, the deformation of the members that make up the chassis should not put at risk the safety of the pilot. Moreover, a Modal Analysis of the chassis to verify the natural frequencies and vibration modes is also made.

The result of this research provides a design approach for the validation (theory vs simulation) and optimization of the chassis to ensure better performance as well as to facilitate the manufacture of its parts and assembly.
Efficiency Improvement in Small Internal Combustion Engine Using Exhaust Heat Recovery System
Authors: Rai Shashank , Arslan Selin , Jawad Badih
Published: January 2019

Strict regulations are set up in various parts of the world with respect to vehicular emissions by their respective government bodies forcing automakers to design fuel-efficient vehicles. Fuel economy and carbon emission are the main factors affecting these regulations. In this competitive industry to make fuel efficient vehicles and reduce Green House Gas (GHG) emissions in internal combustions has led to various developments. Exhaust Heat Recovery System (EHRS) plays a vital role in improving powertrain efficiency. In this system, heat rejected by the engine is reused to heat the vehicle fluids faster (like engine coolant, engine oil, etc) also reducing harmful gases emitted. In internal combustion engines, generally only 25% of the fuel energy is converted into useful power output and approximately 40% of it is lost in exhaust heat. Certain studies show that by using the EHRS, the power output can be increased to 40% and the heat loss can be reduced to as much as 25%. The purpose of this study is to make use of this lost energy and convert most of it into useful energy. The thermodynamic properties and fuel consumed during the warmup period were analyzed to measure the improvement in the engine efficiency. The design was implemented on a Briggs and Stratton Junior 206cc engine. This system includes the use of heat exchangers. The main goal of this study is to develop a robust EHRS design and compare it with the baseline engine configuration to see the thermal and fuel economy improvement.
Energy Mix Forecasting in Abu Dhabi Using Mixed Integer Linear Program
Authors: Al Naimi Moza Salim , Hassan Ali Mohamed I. , Mogi Gento
Published: January 2019

Sustainable energy transition requires a critical prediction for the long-term evolvement of energy systems around the world. It is affected by several factors: the changes in the oil economy, the climate change, and the development of renewable energy supply technologies. The aim of this research is to compare and analyze Abu Dhabi’s generation sector in its transition from complete conventional gas to a mix of conventional and Photovoltaic (PV) energy systems. Employing a Mixed Integer Linear Program (MILP) and PLEXOS software, two capacity expansion scenarios of Abu Dhabi’s generation sector for five years are optimized, analyzed, and compared using a real data from the generation and demand sides. This research means to highlight, to the UAE government, the effect of introducing more renewable energy and to evaluate the performance of the generation side in meeting the forecasted demand. Furthermore, this work opens the doors wide for further development and optimization in the GCC area.