bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measuring the Impact of a New Mechanical Engineering Sophomore Design Course on Students’ Systems Thinking Skills
Authors: Degen Cassandra M. , Muci-Küchler Karim H. , Bedillion Mark D. , Huang Shaobo , Ellingsen Marius 
Published: January 2019

As the complexity of cutting edge products increases with advances in technology, there is a need to include activities in the undergraduate curriculum that allow students to learn basic systems engineering concepts, that promote the development of their systems thinking skills, and that allow them to practice these skills. To this end, the aim of this work was to impact students’ systems thinking skills at an early stage of their mechanical engineering curriculum, develop assessment tools to measure sophomore-level mechanical engineering students’ system thinking skills, and observe trends in measured systems thinking skills both before and after exposure to a new sophomore design course.
This paper provides an overview of the new course, gives details about an Engineering Systems Thinking Survey (ESTS) that was developed to assess systems thinking skills in specific areas, and presents the results of the ESTS from implementation of the course during two separate semesters. The specific areas that were targeted were identification of customer needs, setting target product specifications, concept generation, and systems architecture. The survey results showed that the course was successful in improving students’ self-efficacy on each of the four topics, particularly in setting target specifications and systems architecture. In addition, comparisons of pre- and post-ESTS results showed improvements in student answers on the technical questions related to identification of customer needs, setting target product specifications, and concept generation, with a slight decrease in the area of systems architecture.
While the newly developed course was successful in the dissemination of fundamental systems thinking and systems engineering concepts among students, the survey results indicated the need to strengthen students’ awareness of concept implementation. Future work will explore how to improve the course activities to help students learn how to apply the concepts, particularly for the topics of setting target specifications and systems architecture.
The Physics of Deep Surge in an Automotive Turbocharger Centrifugal Compression System
Authors: Dehner Rick , Selamet Ahmet 
Published: January 2019

Deep surge is a violent fluid instability that occurs within turbomachinery compression systems and limits the low-flow operating range. It is characterized by large amplitude pressure and flow rate fluctuations, where the cross-sectional averaged flow direction alternates between forward and reverse. When a compressor transitions into deep surge, the time-averaged compressor outlet pressure and temperature decrease and increase, respectively, along with a drastic rise in narrowband, low-frequency noise.
The present study includes both measurements and predictions from a turbocharger centrifugal compressor installed on a gas stand. The compressor breathes air from ambient through an inlet duct with a bellmouth opening. The downstream compression system consists of a compressor outlet duct attached to a plenum with increased cross-sectional area, and an additional duct that connects the plenum outlet to a control valve. A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of this compression system was constructed to carry out unsteady surge predictions. The results included here capture the transition from mild to deep surge, as the flow rate at the outlet boundary (valve) is reduced. During this transition, the amplitude of pressure and flow rate fluctuations greatly increase until they reach a repeating cyclic structure characteristic of deep surge. During the deep surge portion of the prediction, pressure fluctuations are compared with measurements at the corresponding compressor inlet and outlet transducer locations, where the amplitudes and frequency exhibit excellent agreement.
The predicted flow-field throughout the compression system is studied in detail during operation in deep surge, in order to characterize the unsteady and highly 3D structures present within the impeller, diffuser, and compressor inlet duct. Key observations include a core flow region near the center of the inlet duct, where the flow remains in the forward direction throughout the deep surge cycle. The dominant noise generation occurs at the fundamental surge frequency, which is near the Helmholtz resonance of the compression system, along with harmonics at integer multiples of this fundamental frequency.
Finite Element Analysis of the Passenger Rail Equipment Workstation Table Sled Test
Authors: Eshraghi Shaun , Severson Kristine , Hynd David , Perlman A. Benjamin 
Published: January 2019

Fixed workstation tables in passenger rail coaches can pose a potential injury hazard for passengers seated at them during an accident. Tables designed to absorb impact energy while minimizing contact forces can reduce the risk of serious injury, while helping to compartmentalize occupants during a train collision. The Rail Safety and Standards Board (RSSB) in the U.K. issued safety requirement GM/RT2100, Issue 5 [1] and the American Public Transportation Association (APTA) in the U.S. issued safety standard APTA PR-CS-S-018-13, Rev. 1 [2] with the goals of setting design and performance requirements for energy-absorbing workstation tables.
The U.S. Department of Transportation, Federal Railroad Administration (FRA) Office of Research, Development and Technology directed the Volpe National Transportation Systems Center (Volpe Center) to evaluate the performance of the Hybrid-III Rail Safety (H3-RS) anthropomorphic test device (ATD), also known as a test dummy, in the APTA sled test in order to incorporate a reference to the H3-RS in the safety standard. The Volpe Center contracted with the manufacturer of the H3-RS, Transport Research Laboratory (TRL), in the U.K. to conduct a series of sled tests [3] with energy-absorbing tables, donated by various table manufacturers. The tables were either already compliant with the RSSB table standard or were being developed to comply with the APTA table standard.
The sled test specified in Option A of the APTA table standard involves the use of two different 50th percentile male frontal impact ATDs. The H3-RS and the standard Hybrid-III (H3-50M) ATDs performed as expected. The H3-RS, which features bilateral deflection sensors in the chest and abdomen, was able to measure abdomen deflections while the H3-50M, which features a single sensor measuring chest compression, was not equipped to measure abdomen deflection.
This study attempts to validate a finite element (FE) model of the APTA 8G sled test with respect to the thorax response of the H3-RS and H3-50M. The model uses a simplified rigid body-spring representation of one of the energy absorbing tables tested by TRL. The FE models of the H3-RS ATD and the H3-50M ATD were provided by TRL and LSTC, respectively. Results from the sled tests and FE simulations are compared using data obtained from the chest accelerometer, the chest and abdomen deflection sensors, and the femur load cells. Using video analysis, the gross motion of the dummies and table are also compared. Technical challenges related to model validation of the 8G sled test are also discussed.
This study builds on previous analyses conducted to validate the abdomen response of the H3-RS FE model, which are presented in a companion paper [4].
Comparison of Experimental, Thermoelastohydrodynamic (TEHD) and Thermal, Non-Deforming Computational Fluid Dynamics (CFD) Results for Thrust Bearings: Part II
Authors: Deng Xin , Watson Cori , He Minhui , Fittro Roger , Wood Houston 
Published: January 2019

A thrust bearing is a particular type of rotary bearing permitting rotation between parts but designed to support a predominately axial load. Part I of this study was submitted to ASME 5th Joint US-European Fluids Engineering Summer Meeting. It compared the experimental, TEHD and CFD results for a thrust bearing. Reasonable relative errors between these three results were observed. The outlet oil film thickness at low speeds and the inlet oil film thickness at high speeds as calculated using TEHD were found to be more accurate than their counterparts. Isothermal, non-deforming CFD was found to predict outlet film thickness accurately as thermal deformation has a lower impact in the outlet region. Isothermal and non-deforming CFD was also found to produce a qualitatively accurate film thickness and pressure distribution.
Experimental data from a second paper reported by the same authors in Part I, provides temperature measurements in two different pads and showed some variation of temperature from pad to pad. A thermal CFD, different from isothermal CFD in Part I, was performed in this Part II. Different data analysis methods will be included in Part II including a comparison of leading edge, mid-plane and trailing edge temperature at two loads, two speeds. 24 different speed-load combination TEHD cases and 12 CFD cases were run in Part II in addition to the 32 TEHD cases and 8 CFD cases in Part I.
Both TEHD and CFD underpredict the slope between temperature and shaft speeds. TEHD also underpredicts the slope between temperature and bearing loads while CFD can get an accurate slope between temperature and bearing loads. An improved inlet temperature model would fix the error between temperature and bearing load in CFD, and also can enable CFD to have the same accuracy as TEHD analysis for the temperature versus shaft speed relation. The inlet film thickness from both TEHD and CFD is underestimated. TEHD is more accurate than CFD in outlet film thickness, or minimum film thickness, which is a critical performance characteristic in fluid film thrust bearings. While CFD is more accurate than TEHD in inlet film thickness and power loss.
Optimization of Design Process of Fused Filament Fabrication (FFF) 3D Printing
Authors: Kim Jaeyoon , Kang Bruce S. 
Published: January 2019

Fused Filament Fabrication (FFF) is one of the most common Additive Manufacturing (AM) technologies for thermoplastic materials. PLA, ABS, and nylon have generally been used for prototype development. With the development of carbon fiber reinforced polymer (CFRP) filament for FFF, AM parts with improved strength and functionality can be realized. While mechanical properties of various CFRP have been well studied, design methodology for structural optimization of CFRP parts remains an active research area. In this paper, a systematic optimization of design process of FFF 3D printing methodology is proposed for CFRP. Starting with standard coupon specimen tests including tensile, bending, and creep tests to obtain mechanical properties of CFRP. Finite element analyses (FEA) are conducted to find principal directions of the AM part and computed principal directions are utilized as fiber orientations. Then, the connecting lines of principal directions are used to develop a customized tool-path in FFF 3D printing to extrude fibers aligned with principal directions. Since currently available infill-patterns in 3D printing cannot precisely draw customized lines, a specific tool-path algorithm has been developed to distribute fibers with the desired orientations. To predict/assess mechanical behavior of the AM part, 3D printing process was simulated followed by FEA to obtain the anisotropic structural behavior induced by the customized tool-path. To demonstrate the design/manufacturing methodology, spur gears of a ball milling machine were selected as a case study and carbon fiber reinforced nylon filament was chosen as the AM materials. Relevant compression tests were conducted to assess their performance compared with those printed at regular tool-path patterns.
Preliminary results show that CFRP gear printed by customized tool-path has about 8% higher stiffness than those printed by regular patterns. Also, flow distribution of printed fibers was verified using scanning electron microscope (SEM). SEM images showed that approximately 91% of fibers were oriented as intended. In summary, assisted by FEA, a customized 3D printing tool-path for CFRP has been developed with a case study to verify the proposed AM design methodology.
Computational Modeling of Blunt Impact to Head and Correlation of Biomechanical Measures With Medical Images
Authors: Tan X. Gary , D’Souza Maria M. , Khushu Subhash , Gupta Raj K. , DeGiorgi Virginia G. , Singh Ajay K. , Bagchi Amit 
Published: January 2019

Mild traumatic brain injury (TBI) is a very common injury to service members in recent conflicts. Computational models can offer insights in understanding the underlying mechanism of brain injury, which can aid in the development of effective personal protective equipment. This paper attempts to correlate simulation results with clinical data from advanced techniques such as magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), functional MRI (fMRI), MR spectroscopy and susceptibility weighted imaging (SWI), to identify TBI related subtle alterations in brain morphology, function and metabolism.
High-resolution image data were obtained from the MRI scan of a young adult male, from a concussive head injury caused by a road traffic accident. The falling accident of human was modeled by combing high-resolution human head model with an articulated human body model. This mixed, multi-fidelity computational modeling approach can efficiently investigate such accident-related TBI. A high-fidelity computational head model was used to accurately reproduce the complex structures of the head. For most soft materials, the hyper-viscoelastic model was used to captures the strain rate dependence and finite strain nonlinearity. Stiffer materials, such as bony structure were simulated using an elasto-plastic material model to capture the permanent deformation. We used the enhanced linear tetrahedral elements to remove the parasitic locking problem in modeling such incompressible biological tissues. The bio-fidelity of human head model was validated from human cadaver tests.
The accidental fall was reconstructed using such multi-fidelity models. The localized large deformation in the head was simulated and compared with the MRI images. The shear stress and shear strain were used to correlate with the post-accident medical images with respect to the injury location and severity in the brain. The correspondence between model results and MRI findings further validates the human head models and enhances our understanding of the mechanism, extent and impact of TBI.
A Numerical Study of Solder Paste Rolling Process for PCB Printing
Authors: Oliveira Ricardo F. , Rodrigues Nelson , Teixeira José Carlos , Santos Duarte , Soares Delfim , Cerqueira Maria F. , Teixeira Senhorinha F. C. F. 
Published: January 2019

The increasing demand for electronic devices associated with the increasing competitiveness between enterprises, pushes towards process automation to decrease production costs. The reflow soldering has proven to be effective in this regard. This is composed by a series of steps or processes, such as: (a) stencil printing, (b) component placement and (c) reflow oven soldering. Each process has its specific traits that contribute to the overall process efficiency.
The present study is directed towards process (a), which includes the rolling of the solder paste over the stencil surface, followed by the subsequent filling of the stencil apertures. Several parameters influence the solder paste behaviour and thus the effectiveness of the rolling process. This work focuses on the solder paste non-Newtonian viscosity properties, with the solder paste presenting a thixotropic behaviour, necessary for the filling of the stencil apertures. Although the increase in the squeegee velocity causes extra shear in the solder paste and consequently lower viscosity, the excess of velocity may cause defects in the aperture filling process. In addition, during the rolling process, air may become entrapped in the solder paste.
The complexity of this process is addressed by numerical simulation, in particular, using the work-package ANSYS to study the solder paste progress, during the rolling process, as well as the parameters influencing it. The fluid flow simulation is solved using the solver FLUENT®, a simplified 2D domain with real case dimensions, a transient prediction of the viscosity, which is a function of the solder paste solicitation, and finally by using the Volume of Fluid (VOF) method to track the solder-air interface boundary. Dynamic meshing methods are also employed to replicate the movement of the squeegee wall, in its task to push the solder paste tumble over the stencil.
This study enlightens the role played by the printing velocity in the stencil aperture filling, a logarithm correlation can be found between them. It was found that lower print velocities provide better results than higher speeds.
It was observed that the back tip of the squeegee blade causes a partial removal of the solder paste from the aperture, which is higher for faster print processes.
An analysis of the filling process over time concluded that, independently of the printing velocity, 90% of the filling occurs in the first quarter of the process.
Modeling Heat Regulation With a Structured Mesh, Finite Volume Approach in a Voxelized Domain
Authors: Amare Rohan , Bahadori Amir A. , Eckels Steven 
Published: January 2019

Modeling human thermal behavior is important for applications involving medical device design, non-ionizing radiation dosimetry, and human comfort. Most thermal models use the finite element method (FEM) to represent the complicated domain structure. With the FEM, challenges in mesh and equation derivation limit rapid implementation. Finite difference (FDM) and finite volume (FVM) methods are alternatives to the FEM but have their own limitations. The FDM faces challenges in discontinuous domains at the boundaries. The FVM provides a possible solution to problems faced with FDM and FEM use.
In a computational human phantom generated from medical imaging data, the finite volume structure is readily available in the form of two-dimensional pixels and three-dimensional voxels. However, geometric characteristics of rectangular prisms prevent acceptable surface-area convergence for curved surfaces, introducing an error that substantially impacts boundaries between regions such as a convection interface.
The present work focuses on developing surface-area corrections for a domain generated from computed tomography scans. These geometric corrections are coupled with an FVM heat-transfer solution on a structured mesh. Solutions are demonstrated for thermoregulation in a domain similar to a section of the human forearm. The ultimate goal of this work is to evaluate human body temperature distributions under the influence of external stimuli and internal heat generation.
Energy and Exergy Analysis of a Biomass Based Ceramic Plant
Authors: Esteves Diogo , Vilarinho Cândida , Ferreira Manuel Eduardo , Carvalho Joana , Araújo Jorge , Teixeira José 
Published: January 2019

The manufacture of relatively low commercial value ceramic products for construction is an energy intensive industry. It is important to improve and optimize the energy equation of the plant operation while simultaneously introducing renewable primary energy sources for the heat supply.
The present paper concerns the analysis of the energy usage in a brick plant. This unit operates continuously on a 3 shift schedule. The overall annual production of five types of bricks is over 62 kton and the main energy consumption unit is the furnace. For this unit, the thermal load is supplied mainly by biomass coupled with fuel oil (80%–20% split, respectively) which yield a maximum temperature of 950 °C. The process is controlled by adjusting the air mixing in the kiln. A secondary furnace provides the heat for a rotating dryer for biomass drying which is supplied to the main furnace.
The fuel is a mixture of various sources and its characteristics were determined by means of an elemental analysis, ash content and the measurement of the heat value. Measurements of mass fluxes along with the operating temperature on critical elements of the plant and chemical composition of the flue gases were used to calculate the energy balances to the plant. Because of the diversity of the product mix the production was normalized using the mass/surface area ratio of the various types of bricks. From the results, the energy intensity is 44 kg of oil equivalent per ton.
The exergy analysis of the plant shows that most of the energy degradation occurs in the kiln. The analysis also enabled to assess the influence of the replacing fossil fuel by biomass on the increase of exergy efficiency of the plant.
Combustion Modelling of a 20 kW Pellet Boiler
Authors: Silva João , Fraga Lelis , Ferreira Manuel Eduardo , Chapela Sergio , Porteiro Jacobo , Teixeira Senhorinha F. C. F. , Teixeira José 
Published: January 2019

In a domestic boiler that uses pellets as fuel, it is important to control the efficiency of the combustion process. The combustion process in the boiler is a complex process that involves several and simultaneous phenomena such as fluid flow, physical and chemical reactions and heat and mass transfer. Computational Fluid Dynamics (CFD) modeling in combination with detailed sub-models for the solid fuel conversion is a useful tool to study the combustion performance and to study, for instance, the pollutant emissions.
This paper presents the CFD simulation of the combustion in a 20 kW pellet boiler using the ANSYS Fluent software with a fully integrated packed-bed model. Furthermore, an experimental test was performed to contrast the results obtained. The CFD results were able to predict the arrangement of the particles on the grate, temperature profile of the particles and, the main gas species concentration inside of the boiler with reasonable accuracy when compared with the experimental measurements.
Mechanical Performance Analysis of ULTEM 9085 in a Heated, Irradiated Environment
Authors: Ng Matthew B. , Brennan Sean N. 
Published: January 2019

This paper investigates the thermal and radiation performance of 3D-printed ULTEM materials following ASTM standard D638. ULTEM is a thermoplastic in the polyetherimide (PEI) family that is regularly used as a high-grade material for 3D printing. This material has similar properties to polyether ether ketone (PEEK), which is another thermoplastic that has strong mechanical properties at elevated temperature conditions. While PEEK has stronger mechanical properties, ULTEM is significantly more cost efficient to acquire and process via 3D printing. Also, most 3D printers are unable to utilize PEEK because of the significantly higher temperature requirements this material imposes on a 3D printer.
This work is motivated by the need to rapidly deploy robotic inspection systems within a nuclear canister environment, which exposes the material to temperatures up to 170°C (340°F), and radiation levels of 270 Gy/hr (27 krad/hr), which are significantly beyond that of conventional 3D-printed parts. The design analysis was performed via an experiment consisting of three treatment groups of dogbone ULTEM test pieces. After tensile testing all of the pieces, the material properties were compared to those of the control group.
These results allow manufacturers to select a more cost-effective material to build parts to operate in such a harsh high-temperature, high-radiation environment, which could include applications in both space systems and nuclear inspection robotics. Specifically, the results were used to guide the development of a robust robotic inspection system for the Nuclear Energy University Program (NEUP) by replacing complex parts with easily-fabricated 3D-printed ULTEM pieces.