bluuebunny/crossref_metadata_2025 huggingface dataset:
A Control Oriented Soot Prediction Model for Diesel Engines Using an Integrated Approach
Authors: Shewale Mahesh S. , Razban Ali
Published: January 2022

Diesel engines have been used in many vehicles and power generation units since a long time due to their less fuel consumption and high trustworthiness. With reference to upcoming emission norms, various engine out emissions have proved to be causing adverse effect on human health and environment. Soot, or particulate matter is one of the major pollutants in diesel engine out emissions and causes various lung related issues. There have been efforts to reduce the amount of soot generated using after-treatment devices like diesel particulate filter (DPF) to filter out particles and get clean tailpipe emissions. These technologies increase load on the system and involves additional maintenance. Also, deposition-based soot sensors have been found to be inoperative in certain scenarios like cold start conditions. In this research work, an effort has been made to develop a phenomenological model that predicts soot mass generated in a Cummins 6.7L diesel engine. The model uses in-cylinder conditions such as pressure, bulk mean temperature, fuel mass flow rate and injector orifice diameter. The difference between soot mass formed and oxidized yields the net amount of soot generated at engine out end. Furthermore, the generated soot mass is compared with benchmark results for specific load conditions and appropriate controller is designed to minimize this tradeoff. The control parameter being used here is fuel rail pressure, which controls the lift-off length, and ultimately equivalence ratio, which predicts mass of soot, generated in formation phase. The presented method shows a prediction error ranging from 5–20%, which is significantly reduced to 2% using a PID controller. The approach presented in this research work is generic and can be operated as stand-alone system or an integrated subsystem in a higher order control architecture.
On the Use of Probabilistic Risk Assessment for the Protection of Small Modular Reactors Against Terrorist Attacks
Authors: Polat Burak , Diaconeasa Mihai A.
Published: January 2022

Safety and security are two of the most important requirements of the nuclear industry. In the event of a potential problem, the consequences can have serious implications for the public and the environment. Measures should be taken against various hazards and threats by analyzing possible realistic scenarios. Therefore, probabilistic risk assessment is one of the necessary technologies to achieving safe and secure nuclear facilities. In the study, a limited scope probabilistic risk assessment was made for a possible terrorist attack against a generic small modular reactor (SMR). A possible attack threat was selected to develop scenarios by following a probabilistic risk assessment approach.

In the scenarios created, terrorists have to pass all physical barriers that security guards protect. Thus, the decisions and actions of the security guards directly affect the result of the attack. To analyze these events, a human reliability assessment (HRA) was employed. In the first study, each security guard’s decision-making process was analyzed using the Standardized Plant Analysis Risk Human Reliability Assessment (SPAR-H) method. The purpose of its use in this study is to verify the SPAR-H method’s applicability for security applications.

In this paper, we give the likelihoods of each security guard making a decision and taking action to prevent terrorists from passing obtained using the SPAR-H method. Besides, event tree and fault tree analyses were performed using the SAPHIRE PRA software.

Finally, since the current HRA methods were designed for control room operators, we introduce a new model-based HRA methodology applicable for security guards to be used in physical security PRAs.
Study of Flexural Strength and Fracture of Additive Manufactured Parts With Stiffeners
Authors: Regalla Srinivasa Prakash , Shyam P. V. , Mylavarapu Sampath , Irigineni Sai Harshini , Shrivastava Prakash Narayan
Published: January 2022

The authors have developed trans-tibial prosthetic sockets using additive manufacturing. These sockets made with mono-material thermoplastics such as Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) at lower thicknesses were found to fracture within a few days of use by the amputees. The fracture was repeatedly found to occur at specific locations such as the lobe corners and the socket’s lower one-third zone. The most probable causes of crack initiation are lack of fusion (LOF) sites and voids. The causes of crack propagation are the lower interlayer bond strength compared to intra-layer bond strength. However, no scientific work exists that clearly explains these phenomena and methods to prevent such potential crack initiation sites and arrest the propagation of such fracture in additively manufactured polymeric structures. Therefore, in the present work, the investigation was carried out into possible enhancement in the resistance to fracture by different strength-enhancing post-processing techniques. In the first technique, the placement of stiffener features at selected locations on the socket was investigated. Three-point bending tests were carried out on D790 standard ABS specimens with different stiffeners introduced on the bottom face. The study focused on fracture characteristics in the stiffener-based topologically optimized geometric design of plate structures made by Fused Deposition Modeling (FDM) under flexural loading. The D790 three-point bending specimens were provided with differently shaped stiffeners, namely, triangular, prismatic, cuboidal, and pyramidal, extending all along the specimen’s length and spread with differential gaps in the width direction. In the second method, thermosetting epoxy resin coatings were applied on the three-point bending specimens of ABS, and the effect of the coating on the flexural strength was investigated. Bending tests were done on three specimens, the first specimen without any coating, the second specimen with only the epoxy resin coating, and the third specimen with two different coating layers. The first of the two coating layers on the third specimen was with primer and the second layer was with epoxy resin. Scanning electron microscope (SEM) and energy dispersion spectroscopy (EDS) scanning analyses were conducted on the fractured specimens. The scanning images indicated that both the primer and resin materials showed a tendency to diffuse into the substrate of ABS, thereby weakening the extreme fibers of material on the specimen’s tension side, resulting in premature crack initiation and propagation. Significant gain in the flexural strength was observed in both the strength enhancement techniques compared to plain specimens.
An Analytical Model for Predicting the Deflection of Hollow Surgical Needle in Soft Tissue
Authors: Al-Safadi Samer , Hutapea Parsaoran
Published: January 2022

Considerable research efforts have been devoted for studying the interaction between surgical needles and soft tissues which can be used to evaluate the deflection of a bevel-tip needle inside a tissue. The development of an analytical model to predict the steering behavior of the needle during needle-tissue interactions could improve the performance of many percutaneous needle-based procedures. In this study, Euler-Bernoulli beam elastic foundation theory was utilized to model the needle as a cantilever beam moving along its longitudinal axis and undergoing various external loads. The external loads are the result of the interaction between the tissue and the needle during insertion, they can be modeled as a concentrated tissue cutting force acting at the needle bevel, and needle-tissue interaction forces acting along the needle length and tangent to the needle shaft. The accuracy of the analytical predictions offered by the model are verified by comparing them to the experimental data. Due to the assumption of the elastic tissue material, the difference between the analytical model and the experimental results was between 15% to 33%. Current work is ongoing to consider tissue viscoelastic properties to improve the analytical prediction.
Double Curved Panel Forming With Bespoke Slits
Authors: Mertens Jonas , Troi Valentine , Maleczek Rupert
Published: January 2022

In this publication, the authors show and discuss a method, that allows the forming of flat sheets of material to a wished three-dimensional state, based on bespoke slits cut into the sheet.

Especially a method known as Kerf is investigated. As current methods are using a grid of slits from border to border in linear or orthogonal crossing configuration, the authors are presenting a method with slits based on surface curvature. The bespoke slits can be straight or curved and must not be from border to border of the sheet-material. Depending on the curvature, the slits can cross. The method is applicable for developable and with strong limitations for non-developable surfaces.

The authors will explain their method that analyses a given target surface’s curvature and generates a slit pattern of smooth planar curves on a 2D development of Surfaces. The pattern relates a physical slit, that will be closed until the upper gap is closed. The Angle of the closed gap defines a target angle. In this paper the described slits have a constant angle and a constant depth. but can have different cross sections namely a V- and U-shaped one. The paper focuses on the geometric generation of the slits and will show and analyze some results.

As the investigation is done in the context of architecture, the authors are mainly considering a pure geometric approach that is not taking into account different physical material properties.
Heat Transfer Enhancement of Counter Flow Heat Exchanger With Pin Fins
Authors: Molham Ibrahim Daadoua Mohammed , Alnaimat Fadi , Ziauddin Mohammed
Published: January 2022

Heat exchangers with microchannel/mini-channel configurations have wide applications including aerospace, air-conditioning, process/power industries, gas turbine cooling, etc. Heat sinks are effective due to the main feature of having fins, however, there are limitations with respect to their applications. The main objective of this study is to observe the changes in the performance of the heat exchanger by calculating effectiveness with respect to Reynolds number, pin fins (two types: circular and square), and operating conditions. The current study is conducted through Computational Fluid Dynamics (CFD) analysis using ANSYS Fluent solver platform. The CFD geometric model consisted of a top channel with hot fluid (air), the bottom channel (water), and the middle part, aluminum block. Overall, it is noted that the heat transfer is enhanced by adding pin fins along the mini-channel of the heat exchanger. The findings indicated that square fins perform slightly better than circular fins.
Non-Intrusive Parametric Reduced Order Models For The Prediction Of Internal And External Flow Fields Over Automobile Geometries
Authors: Rezaian Elnaz , Biswas Rajarshi , Duraisamy Karthik
Published: January 2022

In many-query applications such as design, optimization, and model-predictive control, reduced order models (ROMs) have the potential to significantly decrease the computational cost. In contrast to intrusive projection-based ROMs which require direct access to the high-fidelity model (HFM) operators, non-intrusive ROMs can be constructed in a data-driven fashion using the input-output data generated by the HFM. When used in the prediction of the system response in unseen parameter regimes, however, generalization capabilities have to be carefully assessed. In this study, we pursue a two-step approach to construct non-intrusive parametric ROMs: The first step involves the extraction of low-dimensional latent spaces using proper-orthogonal decomposition (POD) and convolutional neural network-based autoencoders (CNN-AE); and the second step uses regression for the latent variables in parameter space. We adapt a unique decomposition approach named Split-POD to enrich the low-dimensional subspace of the parametric ROM. The proposed methods are used to predict the flow field over a vehicle geometry as a function of vehicle speed and internal fan speed. Through orders of magnitude reduction in the degrees of freedom, the non-intrusive ROMs enable flow field prediction in real-time and bypass hours of computations by the HFM. The results show that the nonlinear encoding in CNN-AE can enhance ROM predictions given adequate data. POD-based ROMs are more robust and efficient, and in particular more accurate than CNN-AE in under-sampled regions of the parameter space. We further enhance the utility of non-intrusive ROMs by formulating a training process that minimizes the required number of high-fidelity simulations using Gaussian process regression to adaptively sample the input parameter space and optimize the estimated variance of the predictions.
Application of Oxygen-Enriched Combustion in an Industrial Reheating Furnace Using CFD
Authors: Worl Bethany , Martinez Francisco , Li Xiang , Silaen Armin K. , Johnson Kurt , Fabina Larry , Tian Kelly , Maiolo Joe , Zhou Chenn
Published: January 2022

The most energy intensive part of a hot rolling mill is the reheat furnace, where the steel products, the products are heated to target temperature using the combustion of natural gas. The energy consumption of the reheat furnace in a typical integrated steel mill is the second highest after blast furnace. Any improvement to energy efficiency of the reheat furnace can have significant impact on the overall energy efficiency of the steel plant. Oxygen enrichment of the combustion air beyond 21 vol% oxygen can be used to improve the furnace energy efficiency. The molar fraction of oxygen is increased, replacing nitrogen in the combustion air. In this study, computational fluid dynamics modeling of various burner configurations was conducted to investigate the application of oxygen enrichment or oxy-fuel to reduce fuel usage while maintain a given slab heating rate. The applications of medium oxygen enrichment (46 vol% O2) and oxy-fuel (100 vol% O2) in the preheating zone, which has the highest fuel usage of the three furnace zones, were investigated.
Investigation of Microstructure and Mechanical Properties of Additive Manufactured AISI - 420 Martensitic Steel Developed by Directed Energy Deposition Method
Authors: Hassan Md Mehadi , Radhakrishnan Madhavan , Otazu David , Lienert Thomas , Anderoglu Osman
Published: January 2022

The traditional manufacturing approach to produce engineering components can have a high energy cost, high material waste, longer delivery times, and specific geometries that may be unattainable. The recent developments in additive manufacturing might provide the opportunity to produce complex engineering components, reduced manufacturing costs, and reduced delivery times. Direct Energy Deposition (DED) offers excellent possibilities such as fabrication of metal components with complex geometries, repair of high-value equipment, development of functionally graded materials, and large-scale additive fabrication or repair. This work focuses on the fabrication of AISI 420 martensitic steel using DED for the application of the aerospace, automotive, and medical industries. AISI 420 martensitic steel (12.7%Cr, 0.4%C in wt.%) was successfully deposited onto 316L substrate by a Laser Engineered Net Shaping (LENS®) process carried out in an open atmosphere. The cross-sectional examination by electron microscopy and XRD confirms the dual-phase microstructure of martensitic needles in random orientation and approximately 22 wt. % of austenite lamellar phase by Rietveld refinement and quantitative phase analysis. There are no cracks observed throughout the materials. However, the area fraction of porosity was found to be 0.4%, with the max size of 2μm. Preliminary mechanical characterization by micro-Vickers hardness tests shows uniform hardness about 725 (HV) trend across the build. The microstructure, the chemical composition of the phases, and the mechanical properties of the steel could be affected by the post-heat treatment, which is very sensitive. The team investigates to optimize the heat-treating method to improve the microstructure and mechanical properties.
Investigating the Flow Field Physics Within Unsteady Compressible Flows
Authors: Feng Dehua , Gao Yang , Thompson Larry , Ferguson Frederick
Published: January 2022

Computational Fluid Dynamics (CFD) continues to play a critical role in the solution of complex fluid dynamics flows. This computational tool allows us to investigate complex flow patterns that would otherwise be impossible to investigate and has greatly aided in the development of our knowledgebase. At the Heart of successful CFD tools are creative numerical schemes that are developed and used in an attempt to capture ‘real world’ flow physics. One such creative numerical scheme in the Integro-Differential Scheme (IDS) has be created. In previous studies, the IDS Scheme has demonstrated that it has achieved adequate dispersion and dissipation capabilities in the smooth flow field regions along with very robust shock-capturing capabilities in the vicinity of discontinuities. In this proposed paper, the IDS Scheme will focus on unsteady fluid motion like Rayleigh-Taylor Instability problem as an example with 2nd order accuracy in space and 3rd order of accuracy in time. Initial perturbations will lead to bubbles and mushroom-shaped spikes due to the release of potential energy, which is from a linear growth phase into a non-linear growth phase. The Total Variation Diminishing Runge-Kutta (TVD-RK3) Scheme will be applied in IDS Scheme and shows incredible results. The detail of how eddies are formatting and interact will be proposed in this paper. Also, IDS Scheme shows its capability to capture more eddies which WENO 5th order is not shown with same computational grids. The IDS simulations are governed by the full set of Navier-Stokes Equations (NES) and focus on the basic flow structure and their interaction which lead to complex flow phenomena. The numerical form of the IDS to be used for solving these compressible flow field problems will consist of the coupled 3rd order Runge-Kutta explicit time marching method and an explicit spatial integral method for the control volume convective flux evaluation. The accuracy and resolution of the unsteady IDS scheme will be tested by its simulations of several benchmark unsteady compressible test cases. Already, evidence of the IDS capability is demonstrated in its simulating solution of the unsteady Rayleigh-Taylor problem.
Evaluation of Wave Energy on the Willamette River
Authors: Poor C. J. , Anderson Rachel , Dillon H. E.
Published: January 2022

The trend of using larger boats for wake surfing in river systems has caused concern for dock stability, bank erosion, safety of other boaters, and natural resource conservation. This study evaluates the wave energy due to boat traffic in the Newberg Pool of the Willamette River using budget conscious equipment and involving community stakeholders. Low-cost motion activated game cameras were used to record videos of waves when boats passed.

The video processing was completed using image analysis in the computational tool Matlab. For each image a high-contrast point of reference was used for the tracking, often tape on a dock piling. As the wave or dock moved, the reference point in the image was tracked in Matlab using the maximum or minimum grayscale pixel in a specific part of the image. This calculation allowed the research team to approximate the change in vertical direction in pixels.

A computational analysis tool was used at 4 sites, 2 in wake surfing zones, 1 in a wake zone, and 1 in a no wake zone, to quantify wave height and period. A total of 8567 videos were collected from the four sites, and 1227 were analyzed. For the wake surfing zone, the average and maximum wave heights were 0.026 m and 0.149 m, respectively, and average and maximum wave energies were 0.905 W/m and 19.2 W/m, respectively. In the wake zone, the average and maximum wave heights were 0.031 m and 0.137 m, respectively, and average and maximum wave energies were 1.405 W/m and 5.74 W/m, respectively. The average wave energy was higher in the wake zone, however, the maximum wave height and the number of boat-caused waves recorded were higher (2984 in the wake surfing zone compared to 1117 in the wake zone) in the wake surfing zone. Cameras were attached to dock pilings which may have resulted in lower values due to the dampening of the dock. Wake surfing was also observed in wake zones, where it is not allowed. This study indicates that the large boats used for wake surfing create larger waves that can potentially cause damage to property along the river and natural resources.

The processes and procedures used within this research would not have been possible without citizen involvement. The citizens partaking in the research allowed for their property to be used as a heavily monitored site or a self-monitored site. The self-monitored sites were a useful tool in collecting more data.
Numerical Study of the Percussive Riveting Process: Analysis Validation
Authors: Krovvidi Sai C. , Ramulu M. , Reinhall Per G.
Published: January 2022

This effort represents the continuation of percussive riveting work that has been performed by this University of Washington research group and presented at this event in the past. Percussive riveting is an assembly method that is used ubiquitously in the aerospace industry, especially in the fuselage final assembly phase. It is a dynamic assembly process that requires two entities operating simultaneously in order to form a rivet. One entity operates with a riveting gun on the exterior of the fuselage. The rivet gun provides the energy input to carry out the assembly process. The other entity operates with a bucking bar on the interior of the fuselage. This entity is responsible for forming the rivet from the shank end. In previous work undertaken by this research group, an axisymmetric thermomechanical finite element model (FEM) framework implementing actual boundary conditions was developed to understand the effect of geometric factors on the residual stress and strain distributions within the riveting stackup. A countersunk rivet and two skins are part of the riveting stackup. The countersunk rivet is widely used in the aerospace industry because of flushness requirements. Because no further joint finishing processes are required after the countersunk rivet has been formed, it is an economically viable final assembly method. Residual stress and strain distributions within the rivet stackup affect the fatigue performance of the assembled joint. The percussive riveting process is different from the conventional squeeze riveting process because of the dynamic and adiabatic nature of the percussive riveting process. Strain rate effects and thermal effects are negligible in the squeeze riveting process because of the low velocities and strain rates involved. But these two effects along with large strain magnitude play an influential role in the percussive riveting process. Because of the dynamic nature of the percussive assembly process, framework validation is important. A three-dimensional FEM (3DFEM) was constructed with asymmetric motion of the bucking bar, also known as the forming tool. The results of the 3DFEM simulation are compared with previously presented axisymmetric FEM and are presented in this study. Analysis validation of the axisymmetric FEM was performed and analysis results were compared with FEM results.
Applications of High-Dimensional Data Analytics in Structural Health Monitoring and Non-Destructive Evaluation: Thermal Videos Processing Using Tensor-Based Analysis
Authors: Momeni Hamed , Ebrahimkhanlou Arvin
Published: January 2022

This study reviews existing and potential applications of high-dimensional data analytics in the fields of structural health monitoring and non-destructive evaluation. Contrary to the high potential of these methods, the implemented applications in structural health monitoring and non-destructive evaluation topics are limited. In addition, with the ever-increasing development of measurement equipment, the necessity of using these methods is enhancing. In this paper, videos captured by different non-destructive evaluation techniques are studied as an example of high-dimensional data. Thermal videos are used for automatic damage detection and localization. Particularly, thermal cameras are employed to find delamination zones in composite plates, commonly used in aircraft wings. Due to the high-dimensional intrinsic of videos, using conventional statistical methods raise theoretical and practical challenges. One of the solutions to overcome these challenges is implementing tensor-based data analysis to analyze videos. Two tensor factorization methods are presented and employed to localize the damage automatically. The results show that the recorded video can be represented by a few vectors, which easily extract the time variation and extent of the damage.
On the Dynamic and Control for a Three Degree-of-Freedom Robotic Arm Used for Rehabilitation Purposes in Medicine
Authors: Grandas Franco Jean Carlo , Borrás Pinilla Carlos
Published: January 2022

The usage of “robotic arms” for passive rehabilitation of post-stroke patients has been gaining relevance, considering how it can assist medical personal to carry out their tasks properly. However, when it comes to controlling these kinds of devices, it normally must deal with non-linearities issues resulting from the mathematical model of robotic arms, which is the case for three degrees of freedom (3DoF) articulated arm. Besides, uncertainties and constraints must be considered, as well as proper reduction of error signals, to assist real patients.

For the given case of study, two control strategies were developed and implemented: PID and Sliding Mode Control with LQG. For both cases, the nonlinear mathematical model was developed and implemented as the system to be controlled. The PID controller was developed as a performance reference and comparison, and the Sliding Mode Controller with Extended Kalman Filter (LQG) design was proposed to increase robustness and stability on tracking trajectories to the rehabilitation of patients.

The mathematical model of the 3DOF robotic arm was derived from the Euler-Lagrange formulation which is based on energy equations. For both control strategies, the system was implemented in Matlab© and Simulink© environments. While both show good performance in terms of settling time, SMC delivers the best results in terms of energy costs, noise rejection, and uncertainties, which can be easily set up with a combination of LQG control strategies. Since weight compensation was considered for the plant “robotic arm” design, the control could be applied for a real robot prototype, and it is scalable in terms of physical parameters and the required compensation forces.
Holmquist-Johnson-Cook Constitutive Model Validation and Experimental Study on the Impact Response of Cellular Concrete
Authors: Collard Jack , Lanham Jake , Davis Brad G.
Published: January 2022

In a previous study by Davis and Dequenne, a Holmquist-Johnson-Cook (HJC) constitutive model for a cellular concrete with a nominal density of 1442 kg/m3 was developed from existing direct tension, uniaxial strain, and triaxial shear testing conducted at the United States Army Corps of Engineers Engineer Research and Development Center (ERDC) and Sandia National Laboratory (SNL). The resulting constitutive model was compared to depth of penetration results from testing conducted by Goodman at the Aberdeen Test Center with promising results. This study seeks to build on this previous work by producing depth of penetration and perforation experiments using non-deforming projectiles into a similar cellular concrete for validation of the fit HJC model. Depth of penetration experiments were conducted by firing into a 305 mm thick panel over a velocity range of 200–800 m/s with the strike velocity and depth of penetration recorded for each experiment. Perforation experiments were conducted over a range of 200–800 m/s against panels with thicknesses of 38 mm, 76 mm, and 114 mm with the strike velocity, residual velocity, and crater characteristics recorded for each experiment. 2D numerical simulations were conducted for each experiment and the results were compared for initial model validation, but additional experimental testing and simulation is required. There is error between the experimental and numerical results and a sensitivity analysis should be conducted to determine where additional testing is appropriate to improve the model’s correlation with experimental results.
Implementing a Discrete Element Method for Fused Deposition Modeling Additive Manufacturing Thermal Modeling
Authors: Menezes Chelsea , Turner Cameron J.
Published: January 2022

One of the challenges of additively manufactured parts is that additive manufacturing processes can lead to anisotropic material properties. For this research, we focus on fused deposition modeling (FDM) which is a common consumer grade process that also is often used for early prototyping due to its low investment and processing cost. In FDM, a semimolten filament is extruded. Within the filament (the intrafilament bonds), the material properties are essentially that of a bulk material that has been injection molded. However, because of the differences in temperature when adjacent filaments are deposited, the material properties between filaments within a layer (the intralayer bonds) are generally less than that of the intrafilament bonds leading to an anisotropic behavior within a layer. Similarly, the temperature difference between layers leads to yet another different material bonding strength (interlayer) that is also less than that of the intralayer or intrafilament bonds.

Our hypothesis is that these anisotropic property differences can be predicted using Discrete Element Models (DEM) to model the process of printing the part filament by filament and layer by layer and the subsequent cooling process. A DEM approach discretizes the filament into discrete elements that are treated as a lumped parameter elements connected to adjacent elements through a set of heat transfer boundary conditions. Elements with external part surfaces are therefore connected to the external environment, or in the case of elements in the base layer of the part, are connected to the print bed which is often heated to encourage bonding between filaments.

The DEM model is validated by comparing the predictions of the model against observed behaviors in FDM printing. For instance, the exposed surfaces of an FDM print will cool faster than elements in the core of the print, or elements that are in contact with the heated printing bed.

This paper describes the process of developing a thermal DEM model in MatLAB, including the assumptions underlying the element level heat transfer model. In addition, discussion of the model results is included to demonstrate the validity of the model as well as the comparisons made to available simulation and experimental data which allows us to validate the underlying behavior of the model. As a result of this research, there are several avenues available for future work including the estimation of bond strength between fibers and layers, the incorporation of viscosity effects, mechanical loading, and the possibilities for process optimization based on intelligent filament path planning, reheating technologies and adaptively controlling the build plate and environmental temperatures.
Utilizing the NASA Human Exploration Rover Challenge Project at the University of the District of Columbia (UDC) to Enhance the Engineering Experience for the Diverse Population of Underrepresented Students
Authors: Harrigan Voss , Xu Jiajun , Haghani Sasan
Published: January 2022

For several years, the University of the District of Columbia (UDC), the only public university in the nation’s capital and a land-grant university, has participated in the NASA Human Exploration Rover Challenge. The Rover Challenge participants are tasked with designing and fabricating a two-person human-powered rover capable of traversing a course designed by NASA to simulate various terrain. Based on the success over the years, a team was once again formed in 2020 to improve the previous design and develop students’ areas of proficiency in additive manufacturing and sensor integration. This was done by leveraging UDC’s new NASA-funded Center for Advanced Manufacturing in Space Technology & Applied Research (CAM-STAR) and its additive manufacturing facilities. In this paper, the authors will introduce the rover competition for 2020, new changes for the competition, and UDC team’s news design, AM produced parts for the rover, and lesson learned and plan forward. This paper will also discuss how a diverse population of students were engaged and their feedback on this experiential learning experience. Lastly, this paper will also discuss the impact of infusing cutting-edge technology (i.e., Additive Manufacturing) in STEM project and how it has helped attract students and increase their career readiness.
Dynamics of Droplets in Core Gas Flow Superimposed With Acoustic Pressure Waves
Authors: Mortazavi Mehdi , Pedley Taylor
Published: January 2022

During the operation of a proton exchange membrane fuel cell, water is produced in the cathode electrode. Accumulation of produced water in the flow channel can block the transport of reactants, which ultimately lowers the performance of the cell. The water content in the flow channel can be efficiently removed from the channel with an external excitation. Previously, the author reported utilization of acoustic pressure waves in order to remove the water content from the flow channel [1]. However, the dynamics of liquid water droplets during this removal process were not investigated. The current study investigates dynamics of water droplets on the surface of the gas diffusion layer (GDL) when acoustic pressure waves are superimposed on the core gas flow. Two different modes of superimposition were implemented; (i) continuous, and (ii) on demand. Study of droplet dynamics was achieved by visualizing the droplet from the side-view with a high-speed camera. When the superimposition was done in the continuous mode at 20 Hz, the droplet went through the rocking motion on the surface of the GDL. For 60 and 80 Hz of superimposition, in addition to the rocking motion, droplets underwent the prolate mode of oscillation, which was characterized by vertical oscillations. For higher frequencies of acoustic pressure waves, in addition to rocking and prolate modes of oscillation, droplets underwent the oblate mode of oscillation, which featured horizontal oscillations. The on on demand experiments demonstrated that the liquid water droplet detached from the surface of the GDL only when the droplet size was large enough.
On Structural Damping Characteristics in the Electro-Mechanical Impedance Method
Authors: Misla Aaron , Zagrai Andrei
Published: January 2022

The electro-mechanical impedance method is a useful tool for structural health assessment in a broad range of applications. In the past, the electro-mechanical impedance method was utilized for assessment of metallic aerospace structures. However, advancements in materials engineering have led to the emergence of composite materials as the preferred choice for many aerospace applications. Limited work exists on application of the electro-mechanical impedance method to composite materials. To evaluate the behavioral differences between metallic and composite materials, a study into the impedance response of one dimensional beam structures with surface-bonded thin piezoelectric wafer sensors was conducted. Euler-Bernoulli beam theory is incorporated in the development of an analytical solution, along with viscous and strain-rate damping models, to evaluate the interaction between the piezoelectric wafer and the resulting bending moment and axial force in the beam. Modeling results were compared to experimental observations. Experimentally obtained damping characteristics were utilized to update analytical and numerical electro-mechanical impedance models. The sensitivity of the electromechanical impedance method to detect damage at various distances from a piezoelectric sensor was evaluated in composite and metallic materials using beams of different lengths. Using the results from these studies and evaluation of the effects of attenuation and structural geometry suggestions for structural evaluation using the electro-mechanical impedance method are presented.
Chemical Structure Analysis of Carbon-Doped Silicon Oxide Thin Films by Plasma-Enhanced Chemical Vapor Deposition of Tetrakis(Trimethylsilyloxy)Silane Precursor
Authors: Comeaux Jacob , Wirth William B. , Courville Justin , Luo Lingyiqian , Yan Hui , Jang Seonhee
Published: January 2022

Carbon-doped silicon oxide (CDO) thin films as low dielectric constant materials were deposited on both n-type silicon (Si) (100) and indium tin oxide coated polyethylene naphthalate (ITO/PEN) substrates, using the plasma-enhanced chemical vapor deposition of tetrakis(trimethylsilyoxy)silane (TTMSS) precursor. Chemical structures of the CDO films were analyzed by using FTIR (Fourier transformation infrared) spectroscopy and XPS (X-ray photoelectron spectroscopy). The chemical bonds related with hydrocarbon and Si–O were the main characteristics of the CDO films. The prominent peaks from the FTIR spectra included Si–O–Si stretching, Si–CH3 bending, Si–(CH3)x stretching, and CHx stretching modes. XPS spectra composed of the O1s, C1s, and Si2p electron orbitals were used to quantitatively analyze the elemental composition of the CDO films. The growth mechanisms of CDO films were dependent on the substrate type. For the ITO/PEN substrate, the lack of Si atoms on the ITO surface made difficulty in forming initial Si–O bonds, resulting in insufficient Si–O–Si structure. In comparison, the CDO films could grow easily on Si substrates due to pre-existing Si–O bonds on the surface. The chemical structures of the CDO films are expected to affect electrical and mechanical performances.
Micro Fin Array Configuration in Heat Transfer Enhancement in Mini-Channels
Authors: Carbajal Gerardo , Frear Colton , Clarke Charisma , Romero-Ramirez Edwar
Published: January 2022

An experimental study was conducted on a novel cooling device that consists of a rectangular micro-fins array placed inside the cooling device. A unique cover was designed and fabricated to allow the mass flow rate in and out and for measuring the temperature and pressure of the fluid. Scanning electronic microscope measurements showed that the average hydraulic diameter of the mini channel is 155 microns. The novel mini channels were tested with different volume flow rates and heat inputs. Two thermocouples and two pressure transducer sensors installed at the inlet and outlet recorded the pressure drop and temperature difference for the different flow conditions. A similar experiment was conducted on a dummy finless device to compare its performance with the minichannels. The experimental results showed an improvement in the heat transfer rate of the novel device compared with the dummy device. According to the experimental results, this study revealed an improvement in the cooling process by having rectangular micro-fins inside the device. For constant flow rates, the novel microchannel design was able to remove 5.6 times as much heat as the finless plate. It is expected that this novel device may increase the heat transfer rate significantly in aerospace and electronic cooling applications.
Effects of Geometrical Configuration on the Aerodynamic Performance of the Joined Wings
Authors: Alam M. D. , Soeimanikutanaei Soheil
Published: January 2022

Joined wing holds promises for future generation airplane application. It might provide a superior lift to drag ratio by reducing the effect of the wing vortex as well as the reduced drag. Moreover, it has higher structural rigidity, therefore, provides a lighter aircraft design facility. In this paper, the aerodynamic performance of a joined wing with a different sweep angle of the front and aft wings has been studied numerically. The Reynolds-averaged Navier–Stokes (RANS) equations were solved by the SST model to study the fully developed turbulence flow over the wing. The solution of the flow obtained by commercial software Ansys Fluent. The lift, drag and lift to drag ratio for the various angle of attacks have been calculated and plotted for the different specified geometries. The simulation result shows that the lift, drag coefficient increase with the increase of angle of attack whereas, the lift to drag coefficient increase first then gradually decreases for different joined wing configurations. In some cases, irregular behavior was observed, the vortex shedding behind the front wing could highly affect the aft wing so it might be the reason for this irregularity. The study findings emphasize that the aerodynamic wing performance for joined wing depends on the specification of each wing as well as also the mutual interaction between them.
Empirical Modeling of Launch-to-LEO Accelerations for Mechanical Characterization of Organoids
Authors: Violante Peter , Blischak Nicholas , McLamb William , Clements Twyman , Viirre Erik , Ghazinejad Maziar
Published: January 2022

The commercialization of orbital launch services and the resulting drop in payload cost are allowing more research to be conducted in microgravity. Biological experiments in this field require sealed enclosures with controlled onboard environmental conditions and complex ancillary circuits, sensors, microfluidics, etc. In order to successfully conduct experiments in microgravity, the research platform and its test subjects must survive the violent accelerations encountered while being launched on a rocket into Low Earth Orbit (LEO).

Developing detailed mechanical models to predict the physical behavior of biological subjects under complex launch forces is exceedingly difficult. Moreover, biological materials are transient by nature, presenting further hurdles to establishing accurate models. For these reasons, numerical dynamic simulations typically used in engineering against failure in high- or variable-g environments will not suffice; a means of empirical simulation is necessary.

The following is a review of the existing efforts to meet this need. Further, the design and analysis of a dynamic simulation platform to empirically test the effects of high-acceleration launch regimes on LEO-bound research platforms will be discussed. The research and design work towards BLAST (BOARDS Launch Acceleration Simulation Tool) seeks to achieve the stated goal using a 7-foot beam centrifuge with a swing-bucket design. Rotation will be controlled such that the resultant acceleration experienced by its payload will closely mimic what the payload would experience during launch to LEO.
Modeling the Biomechanics Parameters on Achilles Tendon Using OpenSim Simulations and Validating the Sensor Accuracy
Authors: Salman Muhammad , Contois Zachary , Tanveer M. Hassan
Published: January 2022

OpenSim is a free software platform that enables the user to preform interaction and movement simulations with human, animal, and robotic models. The software is accompanied by a vast user database of simulations and models which is available on the online community. By utilizing the resources available an accurate model can be created to represent any musculoskeletal configuration that happens in day-to-day activities. Forces and moments are calculated experimentally and verified by the OpenSim models for the Achilles Tendon. In this study, the muscle actuation of the Achilles Tendon is collected from multiple subjects and analyzed. Five subjects were tested for the data collection. Data was collected while the participant completed a concentric motion to ensure Achilles Tendon activation. The testing setup utilizes 3 miniature PCB accelerometers, a PCB 4-channel signal conditioner, a DAQ chassis, and a Modally Hand Impact Hammer in tandem with NI signal view express and MATLAB. Once the results from the study were analyzed, a virtual model was setup in the same configuration in OpenSim and the results from the simulation were compared to the results from the testing. The mechanical forces on the Achilles Tendon will be analyzed using the OpenSim software in order to better understand the muscle actuation at various loading levels. The proposed methods offer a non-invasive approach for studying in vivo muscle-tendon mechanics.
Characterization of the Compressive Properties of Triply Periodic Minimal Surface PCL Scaffolds for Bone Tissue Engineering
Authors: Klemstine Cole , Abdelgaber Yousef , Lawrence Logan , Day James B. , Claudio Pier Paolo , Salary Roozbeh (Ross)
Published: January 2022

Pneumatic micro-extrusion (PME) is a high-resolution direct-write additive manufacturing method, which has been widely utilized for the fabrication of biological tissues, structures, and organs. The PME process allows for non-contact, multi-material deposition of a wide range of functional bio-inks for tissue engineering applications. However, the PME process is inherently complex, governed by complex multi-physics phenomena. Consequently, investigation of the effects of significant process parameters and their interactions on scaffold functional properties would be inevitable.

The overarching goal of this research work is to fabricate biocompatible, biodegradable, and porous bone scaffolds for the treatment of large osseous fractures. In pursuit of this goal, the objective of the work is to investigate the compressive properties of triply periodic minimal surface (TPMS) bone scaffolds, composed of polycaprolactone (PCL) and fabricated using the PME additive manufacturing process. In this study, the experimental characterization of TPMS bone scaffolds was on the basis of a designed experiment. The compressive properties of the fabricated bone scaffolds were measured using a compression testing machine. Diamond as well as Icosahedron designs led to fabricated bone scaffolds having relatively high compression moduli. The results of this study pave the way for optimal fabrication of complex bone scaffolds for the treatment of bone fractures and defects.