bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Behavior of Octahedral and Octet Structures Produced From CLIP Technology
Authors: Calise Gian J. , Saigal Anil
Published: January 2019

This research concerns the production of mechanical metamaterials by a new means of additive manufacturing (AM). Mechanical metamaterials are man-made materials in which the mechanical properties are defined mainly by their structures rather than the properties of each material component. They are typically cellular lattice structures consisting of various arrangements of interconnected webs and struts. These metamaterials have a wide range of applications, but due to a recent breakthrough technology in the field of AM developed by Carbon, called Continuous Liquid Interface Production (CLIP), they can now be produced with ease at substantially higher speeds on a large scale. Using the CLIP process, Adidas is now utilizing these metamaterials in the midsoles of their new athletic shoes. More information about the mechanical response of parts produced by CLIP was needed to assess their relevance in this application.

The goal of this research was to quantitatively determine the isotropy of octahedral and octet lattice structures produced from CLIP technology. Carbon claims that CLIP technology, unlike most other AM processes, produces parts that are isotropic. This means parts will have the same mechanical properties regardless of the direction of applied load. This claim has yet to be proven on lattice structures like the octahedral and octet structures. Those particular lattice structures are popular in the field of mechanical metamaterials because they are more structurally efficient than foams that are made of the same material with similar densities. The degree of isotropy of samples was measured by comparing values of various mechanical properties. These properties include Young’s modulus, a common measure of elasticity, and peak stress, a common measure of strength. Results indicated relatively isotropic behavior because mechanical properties varied based on the axis of compression by 6.5%, on average. The physical responses and failure mechanisms were also consistent.
Economical and Non-Invasive Residential Human Presence Sensing via Temperature Measurement
Authors: Wang Chenli , Lee Hohyun
Published: January 2019

Heating, ventilation and cooling (HVAC) is the largest source of residential energy consumption in United States, encompassing about 25% of total residential energy usage. A significant portion of energy is wasted by unnecessary operation, such as overheating/overcooling or operation without occupants. Wasteful behaviors will consume twice the amount of energy compared to energy conscious behaviors. Many market programmable thermostats exist to address this problem, however, difficulties in persistent programming of such products and lack of understanding of underlying physics prevent users from achieving tangible impact. Hence, fully autonomous energy control system is desirable to engage as many people into energy conscious behaviors as possible. Occupancy measurement is necessary components to enable fully autonomous control. Occupancy information can save energy by automatically turn off the HVAC system when the building is not occupied, or floats to a more energy-efficient setback temperature when the activity level is low. A number of existing sensor solutions available on the market include Passive Infrared (PIR), ultrasonic, Bluetooth/GPS, and CO2 sensors, but these are either too expensive, not user-friendly, or limited in detection scope. These sensors are also incapable of detecting whether or not the occupant is an animal or a human. The work in this paper proposes an economical, reliable, non-invasive package to both detect human presence in a residence of a wide variety of geometries at the time and predict future occupancy pattern, by utilizing temperature sensors. To accomplish this, thermal sensors will be attached to both ends of door handles to collect the temperature data. This data will allow us to create a schedule to identify human activity leaving and exiting the space. At the same time, we will be collecting the skin temperature to determine the human activity level for better identification of the thermal comfort zone for occupants. The prediction model for occupancy pattern will be developed from previous data by using machine learning algorithm. For verification, experimental setup was built to verify our model by comparing actual human presence data from a house with the measured and predicted occupancy pattern from the temperature sensors. Future steps include implementing a data fusion scheme into the model to combine information from multiple types of sensors.
Optimization of the Composite Airplane Fuselage for an Optimum Structural Integrity
Authors: Nagesh Athreya , Rashwan Ola , Abu-Ayyad Ma’moun
Published: January 2019

The newly developed airplanes are using composite laminates to replace the metal alloys for different components, such as the fuselage and the wings. The major advantage of the composite materials is to reduce structural weight which results in reducing the fuel consumption. The aim of this project is to investigate the structural integrity of an airplane fuselage, which uses various types of carbon composite laminates under the static loading of the cabin pressurization. The research is performed using the finite element method and the HYPERMESH commercial software with a composite tool to change the thickness and the orientation of carbon fiber laminates used in the facesheet of the sandwich structure. Three different orientations/stacking sequence of the HexPly 8552 AS4 carbon fibers with two honeycomb cores: Hexagonal Al and Nomex. The results show that the composite material using the HexPly 8552 carbon fiber oriented at angle 30 and angle 45 and the Nomex Honeycomb core of a total laminate thickness of 15.875mm outperform all other thicknesses and orientations in regards to the static loading failure.
A Generalized Approach to Improve Approximation of Inverse Langevin Function
Authors: Morovati Vahid , Mohammadi Hamid , Dargazany Roozbeh
Published: January 2019

The inverse Langevin function has a crucial role in different research fields, such as polymer physics, para- or superpara-magnetism materials, molecular dynamics simulations, turbulence modeling, and solar energy conversion. The inverse Langevin function cannot be explicitly derived and thus, its inverse function is usually approximated using rational functions. Here, a generalized approach is proposed that can provide multiple approximation functions with a different degree of complexity/accuracy for the inverse Langevin function. While some special cases of our approach have already been proposed as approximation function, a generic approach to provide a family of solutions to a wide range of accuracy/complexity trade-off problems has not been available so far. By coupling a recurrent procedure with current estimation functions, a hybrid function with adjustable accuracy and complexity is developed. Four different estimation families based four estimation functions are presented here and their relative error is calculated with respect to the exact inverse Langevin function. The level of error for these simple and easy-to-use formulas can be reduced as low as 0.1%.
Developing Activated Carbon From Date Seeds and Carbon Fiber for Use in Liver Support Devices
Authors: Hilal-Alnaqbi Ali , Mwafy Asel , Seyedzadeh Ameereh , Ahmed Waleed Khalil , Hilal Alnaqbi Aisha
Published: January 2019

This work aims at utilizing natural resources and recycling materials from aircraft industries to enable their usage in medical and purification applications. The main application for which the materials are tested is the adsorption of bilirubin toxin from the liver of end stage liver failure patients. The two materials of concern are date seeds and carbon fiber reinforced polymers (CFRP). Samples of the materials will be treated to produce activated carbon (AC). Following the preparation of the ACs and chitosan coated ACs, tests are carried out to compare uncoated ACs with chitosan coated ACs. FTIR spectroscopy, TGA, DSC and a Spectrophotometer are utilized in order to characterize the samples obtained. From the data acquired, it is concluded that the chitosan coated ACs have better adsorption than the uncoated ACs. The activated carbon fibers showed the highest efficiency for the adsorption of bilirubin toxin. At an adsorbent dose of 0.8 gm, findings show that 98.4% of bilirubin toxin is adsorbed in samples where ACF is used as the adsorbent while 96.5% remained in samples where DPAC was used as the adsorbent.
Analyzing the Shear Heating Effects in Modeling the Hydrodynamic Lubrication of High Torque Low Speed Diesel Engine by Considering Different Viscosity-Grade Lubricants
Authors: Naseer Saqib , Qasim Syed Adnan , Azim Raja Amer , Malik Kishwat Ijaz
Published: January 2019

Journal bearings of high torque diesel engines are used to cater for high combustion loads which are applied intermittently. A lubrication layer is provided between journal (crankshaft) and bearing to avoid contact between them. The relative velocity between crankshaft and journal bearing results in viscous shear heating among the different layers of lubricating oil. The shear heating reduces the viscosity of the lubricant that ultimately reduces the load carrying ability of the journal bearing. It offers a physical contact and reduces the designed life of crankshaft. In this study the 2-D transient numerical lubrication model is developed by employing the Reynolds equation to calculate the pressure and film thickness profiles as a function of crankshaft speed. The shear heating effects are determined by coupling the energy equation with lubrication model. The finite difference method is used and an appropriate numerical scheme is employed to simulate the conduction and convection based thermal energy transfer in transient and steady state journal bearing lubrication model. The lateral displacement of crankshaft is incorporated in the thermal model to analyze the effect of secondary dynamics of crankshaft. The viscosity and temperature relationship are used to ascertain its variation with temperature. The characteristic of three different viscosity-grade lubricates are incorporated separately in the model to carry out the comprehensive comparative analysis. The results are simulated for particular application where low operating speed and length to width ratio of journal bearing is fixed and analyzed the results for complete 720 degrees of crankshaft in its two revolutions. The results show that the oil with high viscosity produces high hydrodynamic pressures as compared to the oil that have low viscosity. The viscous shearing temperature reduces the hydrodynamic pressures but still the high viscosity lubricating oil have enough pressures to uplift the shaft after incorporating the shear heating effects. This study determines the hydrodynamic pressure, and variation of density, viscosity and thermal-conductivity with temperature for three different lubricating oils. These analyses will facilities towards the selection of appropriate lubricant for high torque low speed diesel engine in order to enhance the life of crankshaft.
A Consistent Approach to Problem Solving in Mechanical Vibrations
Authors: Danesh-Yazdi Amir H. , Wu Yi , Onipede Oladipo
Published: January 2019

A consistent approach to solving problems in an undergraduate vibrations course in Mechanical Engineering is presented in this paper. The traditional approach of solving vibration problems involves several steps such as classifying the system according to degrees of freedom, free or forced vibrations and with or without damping. Based on the classification, an appropriate solution technique is applied and the results are obtained. Since the mathematical solution technique is strictly tied to the classification, students have to learn and apply a variety of solution methods based on the particular form of the mathematical model. The course was literally more like a math course rather than an engineering course. By introducing students to the state-space solution method early in the course and using it as the main/dominant solution method, students can focus more on learning both the physical modeling and mathematical modeling of the vibration systems as well as interpreting results in the engineering context. Since state-space computational solvers are readily available to students (MATLAB, Mathcad, etc.) and they can be applied to solve most (but not all) vibration problems including free or forced SDOF, 2DOF, MDOF systems with or without damping, it allows for consistency when teaching students how to solve vibration problems. State-space solvers can solve for either the time or the frequency response and provides a graphical solution. The students can go from modeling to visually exploring and interpreting results. The students’ response to this approach is also discussed.
Increasing Energy Efficiency in Vehicles by Harvesting Wasted Engine Heat
Authors: Celik Emrah , Aljaghtham Mutabe
Published: January 2019

Nearly 75% of energy produced by fuel is eventually rejected to the environment and ultimately goes unused in terms of waste heat in motor vehicles. A promising method of reclaiming energy waste is to use thermoelectric (TE) energy harvesters which are multi-material solid-state devices that convert a thermal gradient directly into electric potential. In current automotive applications, waste heat recovery systems using TE are only limited to integration on exhaust pipes to convert hot exhaust gases into electricity. In this study, we explored the use of TE materials in the shape of a car oil pan to utilize the temperature difference of hot engine oil and cool outside air and convert this temperature gradient into electricity. In this study, we performed finite element simulations to optimize the geometry and the quantity of thermoelectric modules. This optimization was performed to achieve maximum thermoelectric power under the constraints of manufacturability. Using these optimum design parameters, we determined that 2.3 kW output power can be recovered from the flat plate oil pan and 2.6 kW from the oil pan with a single step due to the enhanced surface area. These power amounts were found to be higher than those previously obtained from thermoelectric systems integrated to exhaust pipes.
Internet of Things in Manufacturing: An Overview
Authors: Alothman Hussam Ali , Khasawneh Mohammad T. , Nagarur Nagen N.
Published: January 2019

Internet of things or IoT represents an emerging concept where the objects and humans are identifiable, connected and can communicate over the internet or the wireless world. With IoT, everything can communicate anytime and at anyplace. IoT has many applications and one of the most important applications is the manufacturing. The IoT in industry sector, sometimes referred to as IIoT, is considered to be a very important factor in the introduction of the fourth industrial revolution. Major manufacturing powers around the world are already trying to adopt IoT in their production systems and lead the way in this new era of advanced manufacturing. A huge number of IoT devices are already being used and connected and it is expected that the number of these applications and devices will increase dramatically in the next few years. In this work, an overview of IoT in manufacturing will be presented. This includes a discussion of some of the advantages and benefits of adopting IoT in manufacturing in addition to the issues and challenges that accompany this IoT application. The discussion will also include the concept of smart manufacturing, how production processes and other related activities can be connected in real time and how this can be achieved by adopting IoT in manufacturing. Furthermore, the enabling technologies needed to realize IoT (whether it is to be applied in a new plant or in already existing machines that don’t have IoT capabilities) are shown along with the different layers or phases needed for this IoT adoption. Finally, some real life examples of factories that adopted IoT are shown.
Deposition Control of a FDM 3D Printer Based Direct Writing System for Hydrogel Molding in Microfluidic Devices Fabrication
Authors: Boyle Jacob , Petersen Kristi , Yan Karen Chang
Published: January 2019

Microfabrication-free methods such as wax printing and hydrogel molding have been developed in recent years for fabricating microfluidic devices to enable the applications of microfluidic devices to a broader range. A process has been developed to fabricate electrospun fiber embedded microfluidic devices by integrating hydrogel molding (HGM) and electrospinning (ES), and the feasibility of this integrated method has been demonstrated through our initial study. In particular, agarose gels with various concentrations have been used to generate the channel molds inside PDMS. Recently, a 3D printer kit based on Fuse-deposition method (FDM) was modified to directly deposit hydrogel mold. The current study focuses on how to control the dispensing rate and the extruder motion of the 3D printer for this application. The paper presents a characterization process for determining optimal work ranges in terms of dispensing rate and the moving rate of the x-y table. Specifically, for a given hydrogel material and needle gauge, consistent dispensing volume rate was determined via varying the flow rate of syringe pump and analyzing recorded images. The ranges of the moving rate of the x-y table and the extrusion rate were then determined to generate the previous determined volume rate based on the experimental measurements. As the printer kit is controlled via open source software, the developed method will be applicable to characterization of depositing different material system.
Enhancement of Thermoelectric Figure of Merit of Bi2Te3 Using Carbon Dots
Authors: Celik Emrah , Oztan Cagri , Zhou Yiqun , LeBlanc Roger , Genc Oguz , Ballikaya Sedat
Published: January 2019

Thermoelectric (TE) energy harvesters are multi-material solid-state devices that convert heat (i.e. a thermal gradient) directly into electric potential. Currently, the biggest challenge limiting the applications of thermoelectric devices is the low conversion efficiency (< 10%). To achieve higher thermoelectric efficiency, electrical conductivity and Seebeck coefficient of thermoelectric materials must be maximized allowing the flow of charge carriers and thermal conductivity must be minimized keeping high temperature gradient between hot and cold sides. These properties are strongly coupled to each other. In other words, improving one property deteriorates the other. In nanoscale however, manipulation of matter at the atomic level can decouple these properties. Nanoengineering is therefore considered to be the only remedy for the low conversion efficiency of thermoelectric materials. Current nanomanipulation techniques focus only on reducing thermal conductivity by scattering heat carrying phonons with nanoscale artifacts. We have observed that doping thermoelectric material with carbon quantum dots (size < 5 nm) tremendously increased electrical conductivity and thermoelectric power. In the control experiments using carbon powder (same chemical arrangement but larger scale, < 100 nm), we did not observe any increase in thermal power density evidencing the nanomanipulation of material properties using carbon quantum dots. Doping thermoelectric materials with carbon quantum dots has high potential due to the quantum enhancement effects on electrical properties of and needs to be further investigated for the design of novel nanocomposite materials with superior thermoelectrical properties.
Using Forecasted Daily Maximum Temperatures to Control a Chiller Thermal Storage System
Authors: Baldwin Christopher , Cruickshank Cynthia A.
Published: January 2019

Residential buildings in Canada and the United States are responsible for approximately 20% of secondary energy consumption. Over the past 25 years, air conditioning has seen the single largest increase of any residential end use. This load currently places a significant peak load on the electrical grid during later afternoon periods during the cooling season. One method to reduce or eliminate this peak load being placed in the grid is the use of a chiller coupled with a thermal storage system. The chiller operates during off-peak periods, predominately over-night to charge the thermal storage tank, and the stored cooling potential is realized to meet the cooling loads during peak periods. In previous studies, the use of a chiller has seen a reduction in annual operating costs, however a significant increase in energy occurs as a result of decreased performance of the chiller. To improve system performance, a new control scheme was developed, which uses the forecasted daily high for the next day to predict the cooling load for the day during peak periods for the day. The predicted cooling load is then used as the set-point for the cold thermal storage tank, allowing the peak cooling load to be met using stored cooling potential. This control scheme was implemented into a modelled house located in each of the 7 major ASHRAE zones, with a storage tank with a previously found optimal tank volume. Across each of the locations, a reduction in annual utility costs and overall energy required to meet the building loads observed, with the total cost savings between 0.3% and 1.5% and total electricity required to meet the cooling demand decreasing by as much as 10.2%.
Scanning Electron Microscopy and Optical Profilometry of Electropolished Additively Manufactured 316 Steel Components
Authors: Tyagi Pawan , Goulet Tobias , Brent Denikka , Klein Kate , Garcia-Moreno Francisco
Published: January 2019

Additive manufacturing (AM) can produce highly complex engineering components that are either extremely challenging for the conventional subtractive manufacturing route or not possible otherwise. High surface roughness can make an AM component highly vulnerable to premature failure during fatigue loading. Post-processing aiming to reduce surface roughness is essential to make as produced AM parts functional. We have explored electropolishing route to achieve optimum surface roughness and surface chemistry. We have performed electropolishing treatment on the steel AM parts around 70 °C in an electrolyte comprising the phosphoric acid and sulfuric acid. Profilometry and scanning electron microscopy were performed to study the electropolished and unpolished areas. Optical profilometry study showed that one needs to remove nearly ∼200 μm material from the surface to achieve very smooth surface. Electropolishing was effective in reducing the surface Ra roughness from ∼2 μm rms to ∼0.07 μm rms. Such low rms roughness makes an AM component suitable for almost every engineering application for which a smooth surface is required. Scanning electron microscopy revealed that electropolished area on AM component possessed distinctively different microstructure as compared to the untreated surface of an AM component. We also conducted the compositional analysis of the electropolished area to investigate the possibility of residual contamination from the electropolishing process. Our study revealed that electropolishing is a highly promising route for improving the surface finishing of AM components.
Computational Human Torso Model Validation for Frontal Blunt Trauma
Authors: Hampton Carolyn E. , Kleinberger Michael
Published: January 2019

Recent research on behind-armor blunt trauma (BABT) has focused on the personal protection offered by lightweight armor. A finite element analysis was performed to improve the biofidelity of the US Army Research Laboratory (ARL) human torso model to prepare for simulating blunt chest impacts and BABT. The overly stiff linear elastic material models for the torso were replaced with material characterizations drawn from current literature. FE torso biofidelity was determined by comparing peak force, force-compression, peak compression, and energy absorption data with cadaver responses to a 23.5 kg pendulum impacting at the sternum at 6.7 m/s. Nonlinear foam, viscous foam, soft rubbers, fibrous hyperelastic rubbers, and low moduli elastic material were considered as material models for the flesh, organs, and bones. Simulations modifying one tissue type revealed that the flesh characterization was most crucial for predicting compression and force, followed closely by the organs characterizations. Combining multiple tissue modifications allowed the FE torso to mimic the cadaveric torsos by reducing peak force and increasing chest compression and energy absorption. Limitations imposed by the Lagrangian finite element approach are discussed with potential workarounds described. Proposed future work is split between considering additional impact scenarios accounting for position and biomaterial variability.
A Crack Detection and Evaluation Method for Self-Piercing Riveting
Authors: Wang Xuyang , Fang Yudong , Zhan Zhenfei
Published: January 2019

Self-piercing riveting (SPR) is a key joining technique for lightweight materials, and it has been widely used in the automobile manufacturing. However, complex process parameters and huge configurations of substrate materials can cause potential button cracks, which bring significant challenges for quality inspection. This paper presents a failure crack detection and evaluation method based on image processing. Firstly, the SPR rivet cracks image is preprocessed through gray-scale transformation and interested area selection; next, the binary crack image is utilized to identify the crack parameters; finally, a crack evaluation method is developed to evaluate the rivet crack quality with quantized scores. In addition, subject matter experts (SME)’ knowledge is incorporated to verify the crack detection and quality evaluation, and case study is conducted to demonstrate feasibility of the proposed method.
Brain Tissue Material and Damage Properties for Blast Trauma
Authors: Assari Soroush , Darvish Kurosh
Published: January 2019

The aim of this study was to develop a test method to characterize the material behavior of bovine brain samples in large shear deformations and high strain rates relevant to blast-induced neurotrauma (BINT) and evaluate tissue damage. A novel shear test setup was designed and built capable of applying strain rates ranging from 300 to 1000 s−1. Based on the shear force time history and propagation of shear waves, it was found that the instantaneous shear modulus (about 6 kPa) was more than 3 times higher than the values previously reported in the literature. The shear wave velocity was found to be strain path dependent which is an indication of tissue damage at strains greater than 10%. The results of this study can help in improving finite element models of the brain for simulating tissue injury during BINT.
Theoretical Study of Electronic Band Structure of Dumbbell-Shape Graphene Nanoribbons for Highly-Sensitive Strain Sensors
Authors: Zhang Qinqiang , Kudo Takuya , Suzuki Ken
Published: January 2019

The authors have proposed the formation of dumbbell-shape graphene nanoribbon (GNR) for developing various semi-conductive materials with metallic electrode at both ends. The novel dumbbell-shape structure, which has a center narrow part and wide parts to sandwich the narrow part, can be considered as a composite structure consisting of two single GNRs with different ribbon width. In this study, the electronic band structure of this dumbbell-shape GNR was analyzed by using the first principle calculation method. All the first-principles calculations were performed using DFT. Throughout these calculations, the electronic band structures, densities of states, and orbital distributions of the new dumbbell-shape structure GNR were examined to describe the electronic properties of dumbbell-shape GNRs and predict the performance of strain sensors. The band gap of dumbbell-shape GNRs is different to that of single GNRs. The magnitude of the band gap of the dumbbell-shape GNR depends on the combination of the single GNRs and the difference in the width of narrow part and wide parts. The main change to the band gap is attributed to a change in the orbital distributions of the lowest unoccupied molecular orbitals (LUMO) and the highest occupied molecular orbitals (HOMO). In addition, when a dumbbell-shape GNR undergoes a uniaxial tensile strain, its band gap showed high strain sensitivity as was expected. Therefore, the GNR material with a dumbbell-shape structure has great potential for use in highly sensitive strain sensors.
Front Dynamics in Miscible Displacement Flow in a Curved Pipe
Authors: Yavari Mohammadreza , Bagherizadeh Elaheh , Bazargan Majid
Published: January 2019

Miscible displacement flow in a curved pipe with two fluids of equal viscosity and in the regime of low Atwood number is studied experimentally at different Reynolds and Atwood numbers. By using a curved pipe the effect of curvature on miscible displacement flow is studied. Curvature may be present in many displacement flow processes in nature or industry which underlines the necessity of studying its effect on displacement flow. As the flow is controlled by gravity as the main driving force, only low to moderate Reynolds numbers are considered and Atwood number is varied by adding NaCl salt to fresh water. This makes it possible to create different values of Atwood numbers which can be varied continuously. The position of the leading front is carefully recorded using a digital camera and is used as a measure of displacement efficiency. It is observed that the ratio of the front velocity to the mean velocity approaches a certain value as Reynolds number increases. The effect of Atwood number on flow dynamics is also studied based on experimental results and is interpreted following the conventions employed in some of the previous researches.
Couple Diffusion-Thermo-Mechanical Model for Life Prediction of a Turbine Engine Blade
Authors: Naboulsi Samir (Sam)
Published: January 2019

The failure of engines on jet aircrafts during the past few years has prompted the National Transportation Safety Board (NTSB) to issue an “urgent” recommendation to increase inspections of the engines on U.S. aircraft. Such uncontained engine failures are particularly dangerous, because flying engine parts could puncture fuel or hydraulic lines, damage flight surfaces or even penetrate the fuselage and injure passengers. At issue is older engines found on small number of jets, and the safety and economic impact damage and fracture risk can have on aircraft engines. For example, high-pressure turbine blades are commonly removed from commercial aircraft engines that had been commercially flown by airlines. These engines were brought to the maintenance shop for refurbishment or overhaul. The blades were removed and inspected for damage. The damage was cataloged into three modes of failure, which are thermal-mechanical fatigue (TMF), Oxidation/Erosion (O/E), and Other (O). These show the complexity of damage in turbine engines and the different mechanisms associated with cause of damage. Hence, life prediction of turbine engine is crucial part of the management and sustainment plan to aircraft jet engine. Fretting is often the root cause of nucleation of cracks at attachment of structural components at or in the vicinity of the contact surfaces. Previous effort presented a model to predict fretting fatigue in turbine engine, which is one of the primary phenomena that leads to damage or failure of blade-disk attachments. The influence of thermal effect and temperature fluctuation during engine operation on fretting fatigue damage were investigated. Leveraging these existing capabilities, the present effort focuses on modeling another important damage mechanism in turbine engine blades, which is erosion at high temperatures. Thus a reaction-diffusion model is implemented in addition to the thermo-mechanical one. The model provides a mean to investigate erosion initiation and propagation in turbine engine blades.
Student Presentation Based Teaching (SPET) Approach for Classes With Higher Enrollment
Authors: Tyagi Pawan
Published: January 2019

Recently student presentation based effective teaching (SPET) approach was designed for elective courses or senior level courses with less than ten students. SPET approach is mainly designed for research active, busy faculty who are interested in active student teaching but have very less time to prepare for the class activities. SPET is based on the student making 10–20 minutes presentation in the class to address the conceptual questions that are assigned 1–2 weeks before the presentation day. However, SPET approach becomes impractical for large class size due to the reason that during one class period all the students can not present. To make sure that all the students are well prepared through their self-study about the conceptual questions an instructor has to design different assignments for the student presenters and non-presenters. Such makeshift arrangement makes SPET cumbersome to practice for large class size. To address the limitations of SPET approach we recently developed a new strategy to establish SPET relevancy for the large class size. The modified SPET focused on group presentations. A group of 3–4 students were assigned conceptual questions and topics to cover in the group presentation before the day of class discussion. However, the number of questions assigned per group were intentionally kept high so that each student group divide the presentation preparation load. However, each group member was expected to understand the whole presentation. To test student mastery, some content and application related questions were asked by the instructor. This modified SPET approach has opened new student active learning through collaboration. The instructor can directly provide the feedback during the in-class presentation. This presentation will highlight the results of students’ feedback and data about student learning from the modified SPET approach. To date modified SPET has been tested on 26 senior level mechanical engineering students and 24 high school students attending freshman-level Introduction to Engineering course at University of the District of Columbia.
CFD Analysis of a Cross-Flow Turbine for Wind and Hydrokinetic Applications
Authors: Hosseini Arian , Goudarzi Navid
Published: January 2019

Tidal current and wind energies have become dominant sources of renewable energies in the modern culture. In this work, the aerodynamic characteristics of a novel hybrid vertical axis turbine (VAT) have been studied in flow fields of water and air using CFD analyses. A parametric study was conducted on the hybrid rotor design with the goal of optimizing the solidity ratio to cover a wide operation range, increase initial torque and maintain high coefficient of power values. The hybrid turbine design with a solidity ratio of 0.5 demonstrated improvements to the self-startup feature and achieved the highest coefficient of power (Cp) values of 44.5% and 50% in air and water flows, respectively. The results were in favor of utilizing this design in flow fields of water and air as an enhancement to previous literature. Further studies are required to assess the aerodynamic properties of the model in 3D CFD analyses.
Experimental Study of Bio-Polymer Knee Implant
Authors: Ramos Gonzalez Maria , O’Toole Brendan , Wang Zhiyong
Published: January 2019

This study tests a custom-designed knee implant made of an FDA approved biomaterial, Chronoflex AR. The implant is designed to cushion the damaged cartilage at the distal end of the femur to reduce knee pain without the removal of cartilage and bone. A patient’s MRI scan was used to render a 3D computer graphic design of the knee. The manufacturing of the implant is conducted by 3D printing the shape of the distal end of the femur and coating it with the biomaterial. This is a preliminary fabrication method. Ultimately, the implant material will be 3D printed or cast in 3D printed molds. A successful implementation of this sort of custom-designed implant would reduce the invasiveness of knee correcting procedures, enable the patient to retain the shape of his or her femoral and tibial anatomy, and reduce the possibility of revision surgeries. A custom knee implant testing machine was designed and fabricated to measure the force, elastic deformation, plastic deformation, wear and fatigue of the component after performing lab tests simulating a normal walking pattern while adhering to ISO standards.
Exergoeconomic Analysis of Intercooled, Reheated and Recuperated Gas Turbine Cycles With Air Film Blade Cooling
Authors: El-Damaty Waleed , Gadalla Mohamed
Published: January 2019

For many years, thermodynamic analysis was considered to be the principal tool that is used to predict the performance of a power plant. Recently, the environmental effect and the cost of power plants have been considered as important as the thermodynamic performance in design of power plants. Thus, researchers started to adopt a relevantly new approach called the exergoeconomic analysis which combines the thermodynamic technicalities as well as the economic analysis to design power plants. The exergoeconomic analysis provides crucial information that helps in foreseeing not only the thermodynamic performance but also all economic variables related to power plants. Increasing the efficiency of the power plant has been the major concern in power plants. Thus, the global approach of reaching high turbine inlet temperatures to improve the efficiency of power plants, has exposed the turbine blades to some serious problems. Thereby, cooling the turbine blades has become an important aspect that needs to be taken care of during the power plant operation. In this paper, a cooled gas turbine with intercooler, recuperator and reheater is adopted where it is incorporated with a cooling system. An exergoeconomic analysis accompanied by a sensitivity analysis was performed on the gas turbine cycle to determine the exergo-economic factor and the relative cost difference in addition to study the effect of different variables on the gas turbine thermal and exergetic efficiency, net specific work and the total cost rate. Average cost theory approach was adopted from various thermo-economic methodologies to determine the cost calculation during this investigation. The results showed a reduction in the total coolant mass flow rate in the base case where no cooling systems are integrated from 3.349 kg/s to 3.01 kg/s, 2.995 kg/s and 2.977 kg/s in the case of integrating the cooling systems triple stage Maisotsenko desiccant, triple stage precooling Maisotsenko desiccant and triple stage extra cooling Maisotsenko desiccant, respectively. Accordingly, the thermal efficiency has increased to reach 52.69%, 52.89% and 53.12% by the integration of TS-MD, TS-PMD and TS-EMD cooling systems, respectively.
Exergy Analysis of a Machining Operation Using Finite Element (FE) Assisted Simulations
Authors: Pervaiz Salman , Gadalla Mohamed
Published: January 2019

Energy security and resource depletion have been emerged as major threats when sustainability of manufacturing sector is considered. The rapid growth and development in the manufacturing sector also requires manufacturing companies to improve their performance towards energy and resource consumption. As manufacturing system deals with different input resources and output waste streams, it is useful to implement any thermodynamic tool for the assessment. Exergy analysis has been identified as one of the practical thermodynamic tools to analyze system’s useful energy associated behavior. Exergy efficiency and exergy destruction can provide very useful indications towards the behavior of a manufacturing system. On the other hand, finite element (FE) analysis has been utilized extensively in the literature when it comes to the machining performance assessment of any operation. Using FE simulations, expensive experimentation can be avoided, and cost optimization can be achieved. The FE machining simulations are capable to predict the machining performance accurately, and at the same time process parameters such as cutting conditions and tool geometry related effects can be simulated virtually. The current study provides a novel methodology of using FE simulation as a collaborative tool when conducting an exergy analysis of a machining process. The study provides cost saving opportunities and process level parameters can be incorporated effectively when conducting an exergy analysis.
Supply Air Temperature Prediction in an Air-Handling Unit Using Artificial Neural Network
Authors: Sukthankar Nikita , Walekar Abhishek , Agonafer Dereje
Published: January 2019

Continuous provision of quality supply air to data center’s IT pod room is a key parameter in ensuring effective data center operation without any down time. Due to number of possible operating conditions and non-linear relations between operating parameters make the working mechanism of data center difficult to optimize energy use. At present industries are using computational fluid dynamics (CFD) to simulate thermal behaviour for all types of operating conditions. The focus of this study is to predict Supply Air Temperature using Artificial Neural Network (ANN) which can overcome limitations of CFD such as high cost, need of an expertise and large computation time.

For developing ANN, input parameters, number of neurons and hidden layers, activation function and the period of training data set were studied. A commercial CFD software package 6sigma room is used to develop a modular data center consisting of an IT pod room and an air-handling unit. CFD analysis is carried out for different outside air conditions. Historical weather data of 1 year was considered as an input for CFD analysis. The ANN model is “trained” using data generated from these CFD results. The predictions of ANN model and the results of CFD analysis for a set of example scenarios were compared to measure the agreement between the two.

The results show that the prediction of ANN model is much faster than full computational fluid dynamics simulations with good prediction accuracy. This demonstrates that ANN is an effective way for predicting the performance of an air handling unit.
Accelerated Degradation Testing of Rigid Wet Cooling Media to Analyse the Impact of Calcium Scaling
Authors: Dakshinamurthy Hemanth N. , Siddarth Ashwin , Guhe Abhishek , Kasukurthy Rajesh , Hoverson James , Agonafer Dereje
Published: January 2019

Rigid wet cooling media is a key component of direct and indirect evaporative cooling systems. Evaporation is the process of a substance in a liquid state changing to a gaseous state. When water evaporates only water molecules get evaporated and the other chemicals in the water are left behind on the surface as residue. Many studies have been conducted on how the change in air flow velocity, media depth, porosity and water distribution affect performance of the cooling system. The operational efficiency of the cooling media varies over its life cycle and depends primarily on temperature and speed of inlet air, water distribution system, type of pad and dimension of the pad.

Although evaporative cooling when implemented with air-side economization enables efficiency gains, a trade-off between the system maintenance and its operational efficiency exists. In this study, the primary objective is to determine how calcium scale affects the overall performance of the cooling pad and the water system. Areas of the pad that are not wetted effectively allow air to pass through without being cooled and the edges between wetted and dry surface establish sites for scale formation. An Accelerated Degradation Testing (ADT) by rapid wetting and drying on the media pads at elevated levels of calcium is designed and conducted on the cellulose wet cooling media pad. This research focuses on monitoring the degradation that occurs over its usage and establish a key maintenance parameter for water used in media pad.

As a novel study, preliminary tests were mandatory because there were no established standards for media pad degradation testing. Sump water conductivity is identified as the key maintenance parameter for monitoring sump replenishing and draining cycles which will result in reduced water usage. The average water conductivity in the sump during wetting cycles increases monotonically when ADT was performed on a new media pad. An empirical relationship between sump water conductivity and number of wetting cycles is proposed. This information will be very helpful for the manufacturers to guide their customers for maintenance of the media pad and sump water drain cycles.
Failure Mechanism of Cementitious Nanocomposites Reinforced by Multi-Walled and Single-Walled Carbon Nanotubes Under Splitting Tensile Test
Authors: Jazaei Robabeh , Karakouzian Moses , O’Toole Brendan , Moon Jaeyun , Gharehdaghi Samad
Published: January 2019

Sudden concrete failure is due to inelastic deformations of concrete subjected to tension. However, synthesizing nanomaterials reinforcements has significant impact on cement-based composites failure mechanism. Nanomaterials morphology bridges cement crystals as homogeneous and ductile matrix.

In this experiment, cement matrix with water to cement ratio of 0.5 reinforced by 0.2–0.6 wt% of functionalized (COOH group) multi-walled and single-walled carbon nanotubes were used. After sonication of carbon nanotubes in water solution for an hour, the cementitious nanocomposites were casted in cylindrical molds (25 mm diameter and 50 mm height). Failure mechanism of cementitious nanocomposite showed considerable ductility throughout splitting tensile test compared to cement mortar. Additionally, the failure pattern after developing the initial crack provided additional time before ultimate failure occurred in cement-based nanocomposites. The evolution of crack propagation was assessed until ultimate specimen failure during splitting-tensile test on cementitious nanocomposite surface. The deformation of cross section from circle to oval shape augmented tensile strength by 50% in cementitious nanocomposite compared to conventional cement mortar.
Modal Identification and Nonlinear Vibration of Flexible Manipulator With Revolute Pair Incorporating Generic Payload
Authors: Kumar Pravesh , Pratiher Barun
Published: January 2019

The effect of all-inclusive generic offset payload characteristics on the modes of vibration and nonlinear characteristics of a rotating flexible manipulator with a revolute pair has been accomplished in the present article. A brief dynamic modelling and free vibration analysis to obtain the eigenspectrums of the system, whereafter nonlinear analysis of a manipulator with a general offset payload undergoing overall motion has been accomplished. Dynamic equation of motion and associated boundary conditions have been developed where the payload is considered as a mass whose center of gravity doesn’t coincide with the point of attachment with the manipulator. The effect of various system parameters such as offset mass, offset inertia, offset length, hub mass, actuated inertia and hub stiffness on eigenfrequency is well tabulated and the same effect on eigenspectrums is presented graphically. Further, MMS is employed to investigate the effect of parametric variation on the nonlinear behaviour and associated bifurcation of the rotating single-link flexible manipulator being harmonically driven at the joint under primary resonance considering the centrifugal forces acting on the link and payload as well. The present analysis indicated the pronounced effect of system mass, inertia, stiffness and rotating speed on the eigencharacteristics and bifurcations of a flexible manipulator with a rotating joint.