bluuebunny/crossref_metadata_2025 huggingface dataset:
Updating of Non-Conservative Systems Using Inverse Methods
Authors: Starek Ladislav , Musil Milos , Inman Daniel J.
Published: February 2021

Several incompatibilities exist between analytical models and experimentally obtained data for many systems. In particular finite element analysis (FEA) modeling often produces analytical modal data that does not agree with measured modal data from experimental modal analysis (EMA). These two methods account for the majority of activity in vibration modeling used in industry. The existence of these discrepancies has spanned the discipline of model updating as summarized in the review articles by Inman (1990), Imregun (1991), and Friswell (1995). In this situation the analytical model is characterized by a large number of degrees of freedom (and hence modes), ad hoc damping mechanisms and real eigenvectors (mode shapes). The FEM model produces a mass, damping and stiffness matrix which is numerically solved for modal data consisting of natural frequencies, mode shapes and damping ratios. Common practice is to compare this analytically generated modal data with natural frequencies, mode shapes and damping ratios obtained from EMA. The EMA data is characterized by a small number of modes, incomplete and complex mode shapes and non proportional damping. It is very common in practice for this experimentally obtained modal data to be in minor disagreement with the analytically derived modal data. The point of view taken is that the analytical model is in error and must be refined or corrected based on experimented data.

The approach proposed here is to use the results of inverse eigenvalue problems to develop methods for model updating for damped systems. The inverse problem has been addressed by Lancaster and Maroulas (1987), Starek and Inman (1992,1993,1994,1997) and is summarized for undamped systems in the text by Gladwell (1986).

There are many sophisticated model updating methods available. The purpose of this paper is to introduce using inverse eigenvalues calculated as a possible approach to solving the model updating problem. The approach is new and as such many of the practical and important issues of noise, incomplete data, etc. are not yet resolved. Hence, the method introduced here is only useful for low order lumped parameter models of the type used for machines rather than structures. In particular, it will be assumed that the entries and geometry of the lumped components is also known.
Absolute Nodal Coordinate Formulation
Authors: Shabana Ahmed A. , Hussien Hussien A. , Escalona José L.
Published: February 2021

There are three basic finite element formulations, which are used in multibody dynamics. These are the floating frame reference approach, the incremental method and the large rotation vector approach. In the floating frame of reference and incremental formulations, the slopes are assumed small in order to define infinitesimal rotations that can be treated and transformed as vectors. This description, however, limits the use of some important elements such as beams and plates in a wide range of large displacement applications. As demonstrated in some recent publications, if infinitesimal rotations are used as nodal coordinates, the use of the finite element incremental formulation in the large reference displacement analysis does not lead to exact modeling of the rigid body inertia when the structures rotate as rigid bodies.

In this paper, a new and simple finite element procedure that employs the mathematical definition of the slope and uses it to define the element coordinates instead of the infinitesimal and finite rotations is developed for large rotation and deformation problems. By using this description and by defining the element coordinates in the global system, not only the need for performing coordinate transformation is avoided, but also a simple expression for the inertia forces is obtained. Furthermore, the resulting mass matrix is constant and it is the same matrix that appears in linear structural dynamics.

It is demonstrated in this paper, that this coordinate description leads to exact modeling of the rigid body inertia when the structure rotate as rigid bodies. Nonetheless, the stiffness matrix becomes nonlinear function of time even in the case of small displacements.

The method presented in this paper differs from previous large rotation vector formulations in the sense that the inertia forces, the kinetic energy, and the strain energy are not expressed in terms of any orientation coordinates, and therefore, the method does not require interpolation of finite rotations. While the use of the formulation is demonstrated using a simple planar beam element, the generalization of the method to other element types and to the three dimensional case is straightforward. Using the finite element procedure presented in this paper, beams and plates can be treated as isoparametric elements.
Energy Recovery Unit Using Phase Change Materials
Authors: Elsharafi Mahmoud , Elmozughi Ali , Vidal Kelton , Thomas Rumelia , Almutairi Saleh , Senevirathne Thilanka , Lambright Joshua
Published: February 2021

Energy recovery can benefit from phase change materials. A phase change material is a substance with a high heat of fusion, melting, and solidifying at a certain temperature, which is capable of storing and releasing large amounts of energy. The objective of this research is to enhance the efficiency of a system by performing experiments with corrugated plates within the recovery unit and paraffin as the PCM (Phase Change Material). This research focuses on understanding Thermal Energy Storage (TES) at melting temperature for heating. This research used corrugated plates as an advanced material and channels of media which carry the thermal fluid (water) to the back plate of the unit which was occupied with the PCM or in this case paraffin. The experiment measured the temperature in and out from the unit to estimate how much kWh (power) that unit can save in the molten wax and also, monitor the temperature inside the PCM using implanted thermocouples. The approach of this work is to collect temperature as a function of time to find how much energy units are used to reach the charging point and reverse the flow to retrieve energy from the unit.
Extraordinary Enhancement of Forced Convective Heat Transfer in Dilute Oil-in-Water Emulsions
Authors: Liu Fang
Published: February 2021

In this study, flow and heat transfer characteristics of the dilute oil-in-water emulsions containing micrometer-sized dimethyl silicone oil droplets with different concentrations are investigated experimentally in a helically coiled tube. Forced convective heat transfer of emulsions can be enhanced significantly by low-concentration oil droplets although thermal conductivity of oil is much lower than that of water. Pressure drop of low-concentration emulsions can be lower than that of the water base fluid in laminar flow region. Early onset of transition to turbulence for oil-in-water emulsions occurs compared to pure water in a heated tube. The largest thermal performance factor is 1.044 at oil mass fraction of 0.5% and at Re around 3500. This study could be helpful for exploring a new heat transfer media with large heat transfer enhancement at a slight or even negative increase of pumping energy consumption by adding low-concentration oil droplets.
Compact Design of High-Contact-Ratio Spur Gears
Authors: Nguyen Tuan H.
Published: February 2021

This study presents a computer simulation for the dynamic design of compact high-contact-ratio spur gear transmissions.

High contact ratio gears have the potential to produce lower dynamic tooth loads and minimum root stress but they can be sensitive to tooth profile errors. The analysis presented in this work was performed by using the NASA gear dynamics code DANST (Dynamic Analysis of Spur Gear Transmissions). In the analysis, the addendum ratio (addendum/diametral pitch) was varied over the range 1.30 to 1.40 to obtain a contact ratio of 2.00 or higher. The constraints of bending stress limit and involute interference provide the main criteria for this investigation. Compact design of high-contact-ratio gears with different gear ratios and pressure angles was investigated. Comparison of compact design between low-contact-ratio and high-contact-ratio gears was conducted. With the same operating parameters, high-contact-ratio gears appear to have much more compact design than low-contact-ratio gears. For compact design of high-contact-ratio gears, a diametral pitch of 6.00 appears to be the best choice for an optimal gear set.
Experimental Methods for Road Tankers: A Critical Review
Authors: Otremba Frank , Romero Navarrete José A. , Lozano Guzmán Alejandro A.
Published: February 2021

The transportation of liquids involves several situations derived from the curved shape of the cargo containers, including a comparatively high center of gravity, which negatively shifts when the container is partially loaded, and the vehicle is subjected to steering or braking accelerations. Aiming at reducing these effects several experimental approaches have been applied, involving different tank shapes and the use of baffles, tested under laboratory or field conditions, at full scale or at a down-scale. However, the scope of such approaches has been limited, mainly because the potential effect of other components of the vehicle on the road tanker behavior, has been neglected. In this paper, a critical review is presented of the experimental approaches considered so far, identifying specific experimental needs to improve the performance of the vehicles, from both the road safety and the environmental perspective.
Comparison of Flexoelectric and Piezoelectric Actuating of Beams
Authors: Fan Mu
Published: February 2021

The flexoelectric and piezoelectric effect on the actuating of a cantilever beam are compared in this study to explore how the size-dependent effect could affect the application of the flexoelectric effect. An AFM (atomic force microscopy) probe is used to generate the electric field in the flexoelectric patch, significant electric field gradient is induced. The electric field, distribution of control moment, induced modal force and the vibration control efficiency in terms of transverse displacements are analyzed in case studies. Analytical results show that the control moment of flexoelectric effect highly concentrates at the location of the AFM probe due to the inhomogeneous electric field, which shrink the effect area of flexoelectric patch size. The distribution of the flexoelectric control moment is an impulse function and the distribution of the piezoelectric control moment is a step function, which results to the flexoelectric modal force strongly affected by the electric field gradient while the piezoelectric modal force highly depends on the patch size. For the flexoelectric actuating, decreasing the AFM probe radius can increase the electric field gradient and induce larger modal force. The thickness effect of flexoelectric patch depends on the electric field gradient and the control moment arm, and in the current study, increasing the patch size, the induced flexoelectric modal force increases slightly. Case studies on vibration control show that both the flexoelectric actuating and piezoelectric actuating could generate larger transverse tip displacement with increasing the patch size. This study proves that the flexoelectric actuating can provide effectively actuating and control effect to engineering structures when the size decreases.
A Pseudo S-Plane Mapping of Z-Plane Root Locus
Authors: Noury Keyvan , Yang Bingen
Published: February 2021

In this paper, inspired by the geometric inversion transformation, a novel transformation of the z-plane root locus to a pseudo s-plane is proposed. In the z-plane, the stability of a discrete closed-loop system (a sampled-data control system) requires that all the system poles lie within the unit circle. In root locus analysis, the unit circle region seems congested, compared to the stability region of a continuous system, which is the left half of the s-plane. In the case of fast sampling, the poles of a discrete system can really be in a small neighborhood, thus making the control implementation difficult. The geometric transformation developed in this work helps widen or enlarge the space for the system poles and preserves most of the features of z-plane root loci, including marginal stability and root loci branching off at vertical angles. The usefulness of the new transformation in design of discrete control systems is demonstrated in a numerical example.
Preparation and Characterisation of Graphene Nanofluid: To Be Used As Coolant
Authors: Velukkudi Santhanam Senthil Kumar , Austen Thomas Dolly , Michael Duke Mystica Augustine , Doraiswamy Viswanathan
Published: February 2021

In the recent years, nanofluids embarked as a new class of fluids with improved thermophysical properties such as thermal conductivity, thermal diffusivity, viscosity, and convective heat transfer coefficients thus promoting better heat transfer. Nanofluids consists of two-phase system where the nano sized solid phase (nanoparticles) is dispersed into a base fluid. Graphene is a material which has two-dimensional planar geometry with thermal conductivity of the order of 5000 W/mK. Nanoparticles in the form of thin flakes as small as 50 nm, 100 nm has been used in this study. Two step technique is the used method for preparing nanofluids. Inclusion of additives in small quantity, enhance the durability of the nano particles inside the conventional base fluids. The stability of the solid nano particles inside the conventional base fluid is increased by using surfactants. The heat transfer capacity and stability of the fluids are considered as the basic properties for investigation. The nanofluids characterization studies were drawn from the SEM, XRD and thermal conductivity results. Hot wire method was used to determine the thermal conductivity of the nanofluids. The preparation and properties of graphene based nanofluids which can be used as coolant are studied in this work.
On Calculation of Leakage Flow in Screw Compressor Elements
Authors: Stosic Nikola
Published: February 2021

The computation of the gas velocity in leaking paths which may contain labyrinth elements of screw compressors is developed from the continuity, energy and momentum equations. It accounts for the effects of the local loss of flow kinetic energy and line fluid-wall friction by assuming that the fluid is an ideal gas at constant temperature to eliminate gas density.

This is straightforward situation if the clearance leakage flow is considered to happen in a single leakage gap element, however, if a series of leakage elements are applied, as for example, it happens in a labyrinth seal components, there will be a pressure drop in each groove which in sum will give the overall pressure drop.

A sensitivity analysis of the compressor design parameters that influence such a sequence of the labyrinth seal performance upon that the leakage flow strongly depends upon the gap clearance and only weakly depends on the clearance length and the number of labyrinth grooves. The influence of the number of grooves becomes even weaker if the entire kinetic energy of the leakage flow is not fully dissipated in the labyrinth grooves.
On the Manufacturing Defects of Thermoplastic Carbon/Epoxy Composites Manufactured by Automated Tape Placement
Authors: Sebaey Tamer A. , O’Dowd Noel
Published: February 2021

Thermoplastic composites are highly recommended for structural application, not only for their superior characteristics derived from the fiber and matrix materials but also for their recycling possibilities, which is a major issue in the today’s engineering practice. The manufacturing techniques for thermoplastics are different from those for the well-established thermoset composites. This paper addresses the quality of the thermoplastic composites by assessing the distribution of the fiber, the void contents and the waviness of the fibers, compared to the thermoset composites. IM7/PEEK and AS4/PA12 are the two thermoplastic composite systems used for this study, whereas, IM7/8552 is the thermoset composite used as reference. The specimens were examined using optical microscopy and computed tomography (CT) and the results were statistically treated using circular statistics. Compared to the IM7/8552 composite, the analysis reveals that the IM7/PEEK and AS4/PA12 composites, manufactured by ATP result in a higher volume of voids. On the other hand, ATP processing improves the alignment of the fibers, as the solidification process occurs while the fibers are in tension. The microscopy studies also show that the ATP manufactured composites have an area in between the different layers of tape with a low number of fibers, compared to the other areas.
Autologous Ear Reconstruction: A Semi-Automatic Procedure for Patient-Specific Surgical Guides
Authors: Mussi Elisa , Furferi Rocco , Servi Michaela , Volpe Yary , Facchini Flavio
Published: February 2021

Autologous ear reconstruction, i.e. the reconstruction of the outer ear from autologous cartilage tissue, is a very important surgery considering the psychosocial repercussions of an individual affected by microtia (i.e. the total or partial absence of the outer ear). The execution of this surgery can be very complex due to the unique characteristics of this anatomical region. In order to help the surgeon in the process of cutting and suturing, innovative surgical guides were designed that can transmit information about the shape and size of the anatomy to be reconstructed. This work lays the foundation for the creation of a semi-automatic and easy-to-use tool for the modeling of surgical guides. The goal is to make the hospital staff autonomous in the creation of instruments that can be used in pre-surgical simulation and during surgery.
An Evaluation of Mode Tracking Methods for Practical Rotor Dynamic Analysis
Authors: Rajagopal Anurag , Mandal Dilip K.
Published: February 2021

An important precursor to the dynamic analysis of rotating machinery, in either frequency or time domain, is the extraction of its mode shapes and corresponding frequencies. This is often presented as a Campbell diagram, which plots the frequency of each mode as a function of the rotor speed. A typical Campbell diagram has several backward whirl, linear and forward whirl modes leading to numerous intersections. Therefore augmenting the eigenvalue solution with a mode tracking algorithm to output the Campbell diagram is of essential interest to a practicing engineer. This paper presents an evaluation of several mode tracking approaches for rotor dynamic simulations, starting from their theoretical foundations to practical applications using several test cases. These tracking algorithms are implemented in the structural solver, OptiStruct, part of Altair Engineering’s CAE framework. Finally, the conclusions drawn from this exercise offer engineers studying rotating machinery several key insights.
Modeling of Compliant Mechanisms in MATLAB Simscape
Authors: Pena Paul , Garcia Martin , Tekes Ayse
Published: February 2021

This paper presents the informative process of modeling of compliant mechanisms using MATLAB Simscape. Simscape is the modeling environment analyzing both rigid and flexible systems using either the blocks provided in the library or the CAD models imported from modeling software. We present the modeling of four compliant mechanisms: dwell, five bar, translational and hopping mechanisms. Once the cad model of a system is imported into Simscape, the flexible links or flexure segment on each example system is replaced by its equivalent lumped parameter block. Compliant dwell mechanism is comprised of a rail, two pinned-pinned flexible links, slider, rigid crank and a DC motor. The second mechanism is a fully compliant five bar mechanism incorporating large deflecting flexures and actuated by two servo motors. The objective is to control the trajectory of the tip position. Third example models a bio-inspired translational compliant mechanism driven by servo motors and comprised of three sliders connected by single piece designed 2 rigid arm-flexure hinge linkages mimicking the motion of a caterpillar. The last example is the modeling of a compliant hopping robot consisting of two pairs of gears; one pair is attached to the motor and the other pair allows the bottom links to rotate at same angular velocity in opposite directions.
Effects of Rapid Microwave-Curing on Mechanical and Piezoresistive Sensing Properties of Elastomeric Nanocomposites
Authors: Herren Blake , Saha Mrinal C. , Altan M. Cengiz , Liu Yingtao
Published: February 2021

Carbon nanotubes (CNTs) have the unique ability to absorb microwave radiation and efficiently transfer the energy into substantial heat. When adequately dispersed in a thermoset polymer, such as polydimethylsiloxane (PDMS), the nanocomposite can be fully cured in seconds in a microwave oven rather than in hours in a convection oven. In this paper, cylindrical PDMS nanocomposites containing well-dispersed CNTs are fabricated by either microwave-curing or conventional thermal-curing. The mechanical, electrical, and piezoresistive properties of the fabricated samples are compared to understand the effects of different curing methods. Microwave-cured nanocomposites exhibit a significantly reduced compressive modulus for different CNT loadings. In addition, the electrical conductivity of microwave-cured nanocomposites is significantly enhanced over the thermally-cured counterparts. Experimental results demonstrate that the one-step microwave-curing procedure can improve the electrical conductivity of 1 wt% nanocomposites by almost 150 % over thermal-curing. However, their piezoresistive sensitivity remains remarkably similar, showing the potential for microwave-curing to replace thermal-curing for the manufacturing of highly flexible CNT-based nanocomposites.
Quantifying the Accuracy of a Motion Detecting Neural Prosthesis
Authors: Tanaka Martin L. , Subbukutti Premkumar , Hudson David , Hudson Kimberly , Valenzuela Pablo , Yanik Paul
Published: February 2021

The neural prosthesis under development is designed to improve gait in people with muscle weakness. The strategy is to augment impaired or damaged neural connections between the brain and the muscles that control walking. This third-generation neural prosthesis contains triaxial inertial measurement units (IMUs - accelerometers, gyroscopes, and processing chip) to measure body segment position and force sensitive resistors placed under the feet to detect ground contact. A study was conducted to compare the accuracy of the neural prosthesis using a traditional camera motion capture system as a reference. The IMUs were found to accurately represent the amplitude of the gait cycle components and generally track the motion. However, there are some differences in phase, with the IMUs lagging the actual motion. Phase lagged by about 10 degrees in the ankle and by about 5 degrees in the knee. Error of the neural prosthesis varied over the gait cycle. The average error for the ankle, knee and hip were 6°, 8°, and 9°, respectively. Testing showed that the neural prosthesis was able to capture the general shape of the joint angle curves when compared to a commercial camera motion capture system. In the future, measures will be taken to reduce lag in the gyroscope and reduce jitter in the accelerometer so that data from both sensors can be combination to obtain more accurate readings.
Advanced Data Center Cold Aisle Airflow Organization Optimization Using an Adjustable Fan Unit
Authors: Song Zhihang , Zhang Qian
Published: February 2021

The real-time smart data center cooling has become a key to maintenance and operation of energy-efficient data centers, primarily including the server inlet airflow/thermal domains. Here, the cold-aisle airflow phenomena in a widely-used cold/hot aisle data center configuration was under parametric investigation, This concern is mainly because of the airflow separation and recirculation from the stream emerging from the server outlet and returning to the computer room air-conditioning unit. In order to achieve a better understanding and to correspondingly eliminate the negative effects of the hot air over-tack recirculation towards a satisfied effectiveness, an addition of a rack-level adjustable fan unit (AFU), which is placed inside the cold aisle, was considered at an early stage and the model prototype was numerically analyzed with respects to differently predefined parameters. The cooling performance consequence, consisting of the server-neighbored inflow rates and maximum server inlet temperatures explored by computational fluid dynamics (CFD) observation panel and sensors, demonstrates that the over-rack air recirculation and its resulting hot spot, in comparison with the case in absence of the AFU, can be suppressed. The results additionally concludes the extents to which the optimized airflow organization and temperature drop of the rack-level region (e.g., from the bottom towards the top of the rack unit) can be achieved with/without the AFU addition.
Sustainability Benefits Analysis of Cyber-Manufacturing Systems
Authors: Song Zhengyi , Moon Young
Published: February 2021

Cyber-Manufacturing System (CMS) is a vision for the factory of the future, where manufacturing processes and physical components are seamlessly integrated with computational processes to provide agile, adaptive, and scalable manufacturing services. Functional elements of CMS are digitized, registered, and shared with users and stakeholders through various computer networks and the Internet. CMS incorporates recent advances in the Internet of Things, Cloud Computing, Cyber-Physical System, Service-Oriented Technologies, Modeling and Simulation, Sensor Networks, Machine Learning, Data Analytics, and Advanced Manufacturing Processes. CMS possesses intelligence such as self-monitoring, self-adjustment, self-prediction, self-allocation, self-configuration, self-scalability, self-remediating, and self-reusing.

Such intelligent capabilities enable CMS to contribute to manufacturing sustainability. However, prior studies are limited in addressing a narrow scope of CMS or in covering only a subset of sustainability dimensions. This paper addresses the research gap by developing a holistic CMS infrastructure and adopting a Distance-to-Target based sustainability assessment approach to measure the sustainability benefits of CMS. To illustrate how the infrastructure and metrics are used to analyze the sustainability benefits of CMS, an example case is presented. The results show that CMS can deliver substantial sustainability benefits through increased productivity, profitability & energy efficiencies, and reduction of working-in-process (WIP) inventory levels & logistics costs.
The Influence of a Non-Aligned Semi-Elliptical Embedded Crack on the Stress Intensity Factor Distribution Along the Front of a Quarter-Circle Corner Crack in a Semi-Infinite Plate Under Pure Bending
Authors: Levy Cesar , Ma Qin , Perl Mordechai
Published: February 2021

Fitness-for-Service codes require whether non-aligned cracks be treated as coalesced or separate multiple cracks. The authors previously reported on the effect between an corner and an embedded parallel crack in 2-D and in 3-D scenarios subject to tensile loading. Since realistic crack configurations detected using non-destructive methods are generally 3-D in nature, the study of 3-D effect under different loading types is deemed necessary in order to obtain more practical guidance. In this study, we investigate stress intensity factors (SIFs) along the crack front of a quarter-circle corner crack when affected by a semi-elliptic surface crack in a semi-infinite large solid under pure bending. While keeping constant the geometry of the quarter-circle corner crack, the SIFs along its front are studied for a wide range of geometrical configurations of the surface crack by varying its ellipticity b1/a1 = 0.1∼1; the relative crack size of the two parallel cracks a1/a2 = 1/3∼2; the normalized vertical gap, H/a2 = 0.4∼2; and the normalized horizontal gap, S/a2 = −0.5∼2 between the two cracks on using linear elastic fracture mechanics (LEFM). The results from this study are collectively significant to the understanding of the correlation between the criteria and standards in Fitness-for-Service community and the consequence of their usage in engineering practice.
Effect of Cutting Environments on Drilling Induced Damage in GFRP Nanocomposites
Authors: Kishore Kumar Panchagnula , Jayaprakash Sharma Panchagnula
Published: February 2021

Drilling is most commonly used secondary machining process for structural joining of Glass Fiber Reinforced Plastic (GFRP) composites. Performing drilling operations on GFRPs/Multi-Walled CarbonNanoTubes (MWCNTs) reinforced GFRPs is really a challenging task due to their non-homogeneity and anisotropic behavior, which directs to generation of material damages. The prime focus of current work is to identify the suitable process parameters for enhancing the performance of drilling of GFRP nanocomposites. In this study, the drilling experiments are conducted on 0.3wt.% MWCNT-GFRP nanocomposites with solid carbide, TiCN and TiAlN coated drills (6mm diameter) under dry and chilled air cutting environments. The dry drilling experiments are conducted without any assistance of cooling fluid in ambient condition. The chilled air at a temperature of 3°C was supplied from the vortex tube. Experimental data is used for ANOVA (balanced) analysis. The cutting parameters such as feed rate, cutting speed and tool type (coating) are considered as input and the measured thrust force, delamination factor and AE RMS signal are treated as output responses. From ANOVA results, it is observed that the influence of feed rate is more on thrust force as compared to cutting speed. The coefficients of determination (R2) shows good fit between thrust force and cutting parameters and the corresponding confidence levels are above 98% for all cutting environments. Similarly, R2 values of delamination factor and AE RMS signals are above 90% and 96% respectively. The minimum thrust force and torque values are noted as 12.61 N and 0.152 N-m respectively at lower feed rate (10 mm/min) and higher cutting speed (1500 RPM) using TiCN coated drill under chilled air cutting environment. The delamination factor is also low (1.025) under the same cutting conditions of minimum cutting forces. A good correlation exists between the thrust force vs. delamination factor (> 0.85) and the delamination factor vs. AE RMS signal (> 0.80) for the selected cutting environments. The recommended range of RMS voltage is 0.083 to 0.121 volts for producing the delamination free holes on GFRP nanocomposites.
A Novelty Detection Approach to Compressor Valve Fault Detection and Localization
Authors: Scott Colton M. , Kolodziej Jason R.
Published: February 2021

Presented in this paper is the development of a vibration-based novelty detection algorithm for locating and identifying valve wear within industrial reciprocating compressors through the combined use of time-frequency analysis, image-based pattern recognition, and one-class support vector machines. A commonly reported cause of valve wear-related machine downtime is wear in the valve seat, causing a change in flow profile into and out of the compression chamber. Seeded faults are introduced into the valve manifolds of the ESH-1 industrial compressor and vibration data collected and separated into individual crank cycles before being analyzed using time-frequency analysis. The result is processed as an image and features used for classification are extracted using 1st and 2nd order images statistics and shape factors. A one-class support vector machine learning algorithm is then trained using data collected during healthy operation and then used to both detect and locate anomalous valve behavior with a greater than 82% success rate.
Ultrasonic Phased Array Technique for Defect Detection and Sizing in Heavy-Walled Cast Components
Authors: Hossain Md Shahjahan , Krenek Russell , Taheri Hossein , Dababneh Fadwa
Published: February 2021

Cast metal parts are extensively found in many engineering products such as pump casing and engines. Thermal effects exhibited during metal casting processes, such as solidification can generate defects in the cast components. Effective nondestructive testing (NDT) for detection and sizing of defects in cast parts prevents extra cost and time associated with repair and maintenance. Surface-breaking cracks and porosity are among the common types of defects in large cast components. There are several limitations in using conventional NDT methods for as built cast parts due to surface conditions, coarse-grain structure, and characteristics of potential defects. Ultrasonic adaptive imaging based on the Phased Array Ultrasonic Testing (PAUT) technology is proposed for coarse-grain heavy-walled cast material inspection. The capability of aperture focusing in PAUT provides the opportunity for better imaging results. A comprehensive understanding about the ultrasonic beam focusing and the selection of an appropriate transducer and wedges is necessary for successful defect characterization. Cast aluminum and iron samples having on-purpose made defects were successfully inspected using the PAUT. Unlike conventional techniques, the results indicated that the PAUT is a promising method for inspecting as-built cast parts with rough surface finish conditions. The proposed method helps to decrease the inspection time, machining requirements, and preparation costs. Moreover, the enhanced defect sizing approach provides useful information for repair and maintenance decision making such as amount of material grinding and post-welding procedure.
Bioinspired Monolithically Designed Compliant Swimming Robots
Authors: Hooper Joshua , Houghton Andy , Tekes Ayse
Published: February 2021

As technology advances and enables us to design and realize complex systems using new materials and manufacturing methods, biologically inspired robots in every aspect of engineering have attracted much attention in the last few decades. This paper presents the design and motion analysis of monolithically designed two compliant swimming robots that are actuated and controlled by single motor. Each design incorporates large deflecting compliant members and rigid levers to transfer the input torque to the different parts on the mechanism. While the first design integrates flexible tail to perform swimming motion, the second design adopts snapping type motion for the same action. Both mechanisms are 3D printed and tested for forward motion. The first robot has a constant speed of 0.68 BL/s while the second has an average speed of 0.6 BL/s. Kinematic model using pseudo rigid body modeling (PRBM) is derived to calculate the load-deflection curves of the flexible tail for Design I, finite element analysis for deflection analysis are performed for Design II.
A Model for Sustainable Orthopedic Care in Low and Middle Income Countries
Authors: Gillard Joel , Smith Terry
Published: February 2021

This paper describes a scalable and sustainable patient care model for low and middle-income countries (LMICs) that can improve the standard of care for hospitals with scarce resources and an ever growing backlog of patients. SIGN Fracture Care International (SIGN), a non-profit, humanitarian medical device organization, has developed technical solutions over the last 20 years, to address the yearly increasing number of patients affected by upper and lower extremity trauma, using a three-pronged approach. The model includes effective training of in-country local surgeons on current orthopaedic techniques; providing an on-going supply of appropriately designed surgical implants and instruments manufactured to ISO 13485 and FDA standards; and evaluating patient outcomes until healing occurs to validate the model is truly benefiting patients and the hospital throughput. By providing equal access to technology, knowledge, and timely feedback, LMIC surgeons can provide vital orthopedic care to their local communities and sustainably respond to the daily trauma cases they encounter and enable patients to return to work, school, keep families on the path out of poverty, and improve the lives of future generations. The model is describe in detail in the hopes that other entities can utilize the principles for additional healthcare specialties around the world.
Computational Analysis of the Dynamics Flow in the Duct System of an Continuous Positive Airways Pressure Device
Authors: Vuong Tung Xuan , Al-Jumaily Ahmed , Paxton Robert
Published: February 2021

In this paper, 3-D duct models of Continuous Positive Airway Pressure (CPAP) device are developed to investigate the internal airflow behaviours and to identify potential noise source locations. The Computational Aeroacoustics (CAA) with a hybrid approach is conducted in the ANSYS software environment. CFD simulations were used to investigate the internal flow behaviours of the duct systems. The predicted results have shown the internal flow characteristics as circulation and separation behaviours. Those behaviours were found at several locations such as 90-degree corners, restricted cross-sectional areas, etc. High levels of turbulent energy are also found in those locations indicated they are likely to have a high level of noise. Further investigation to predict the noise generated from the duct system to validate the findings in CFD simulations. The results showed that there is a high level of noise generated at the identified locations in the CFD simulations. The noise experiments were also conducted to compare with the predicted noise results. It was found the predicted models can be used to evaluate the flow behaviours inside the duct system.

In summary, the CAA with a hybrid approach is used to investigate the internal flow behaviours and the potential noise source locations of the duct systems in the studied CPAP device. The predicted results have explained and identified some potential noise source locations. These findings will be used as guidelines to optimize the internal flow and therefore improve the noise generated from ducts. The broadband noise source models are potential tools that can be used to determine the loudness at the source locations in the early product development process for reducing noise level and better sound quality as well as a cost-effective tool for noise prediction.
Energy Absorption Characteristics of Axially Compressed Double Wall Foam Filled and Empty Square Tubes
Authors: Prakash Raghu V. , Toshniwal Sanjay
Published: February 2021

Occupant safety has become increasingly important in the recent times. At the instance of an accident or collision, structures with high energy absorption can provide better occupant safety. Thin-walled tubes are widely used as energy absorbers in automobiles and other structures. In the present work, crashworthiness characteristics of double wall empty and double wall foam filled tubes are investigated. Thin wall extruded aluminum square tubes are used in this study. Polymer foam of three different densities, viz., 40 kg/m3, 80 kg/m3, 140 kg/m3 was used as filler material between the two tubes to fabricate a double wall foam filled tube. Both parallel and diamond configurations were considered for double walled empty and foam filled configurations. All the specimens were compressed at a displacement rate of 100 mm/min. Crushing of different configurations was numerically analyzed using nonlinear finite element tool LS-Dyna®. In double wall empty configuration, diamond arrangement absorbed more energy compared to parallel due to the interaction between inner and outer tubes. Results indicate that energy absorption increases with the filling of foam. Compared to double wall tubes, the maximum increase in energy absorption of ∼ 50% is observed in foam filled tubes. Using Computed Tomography (CT) scan of specimens, it is observed that foam filling alters the crushing behavior of the inner and outer tubes.
XFEM Fracture Analysis of 2-D Plastically Graded Domain With Thermo-Mechanical J-Integral
Authors: Gajjar Margi , Pathak Himanshu
Published: February 2021

Many engineering components fail in the presence of service loads like thermal residual stresses and thermomechanical loading. An accurate evaluation of the fracture parameter (J-integral) at the crack tip is essential for the safe design of structures.

In this work, a novel computational method called the Extended Finite Element Method (XFEM) has been implemented to analyze the plastically graded material (PGM) subjected to thermal and thermo-mechanical loading. For crack discontinuity modeling, a partition of unity enrichment concept can be employed with additional mathematical functions like Heaviside and branch enrichment for crack discontinuity and stress field gradient, respectively. The modeling of the stressstrain relationship of material has been done using the Ramberg-Osgood material model. The isotropic hardening and Von-Mises yield criteria have been considered to check the plasticity condition. The variation in plasticity properties for PGM has been modeled by exponential law. Further, the nonlinear discrete equation has been numerically solved using a Newton-Rhapson iterative scheme.
Less Conservative Stability Constraint for Data-Based Feedback Tuning
Authors: Huang Weicai , Yang Kaiming , Zhu Yu , Lu Sen , Li Min
Published: February 2021

It is necessary to keep the closed-loop system stable in data-driven feedback tuning. A widely-used strategy is using stability criterions as the constraint while parameter updating. In this strategy, the conservatism of the stability constraint has great influence on the achievable convergence performance. In this paper, a less conservative stability constraint is proposed to improve the convergence rate of data-driven feedback tuning methods. Specifically, the proposed stability constraint is developed based on small gain theorem (SGT). The conservatism is reduced through extension of SGT and further reduced using the properties of H∞ norm. Besides, an unbiased data-driven estimation method of H∞ norm is employed to estimate the proposed stability constraint accurately. Simulations are conducted to test the performance of the proposed stability constraint. The results demonstrate that the proposed stability constraint is less conservative and contributes to higher convergence rate.
Nanomechanical Characterization of Additive Manufactured GRCop-42 Alloy Developed by Directed Energy Deposition Methods
Authors: Suresh Trupti , Landes Scott , Letcher Todd , Prasad Anamika , Gradl Paul , Ellis David
Published: February 2021

Propulsion applications such as combustion chambers and nozzles for liquid rocket engines require the use of unique materials with superior mechanical and thermal properties. GRCop-42 (Cu-4 wt.% Cr-2 wt.% Nb) is one such candidate material developed by NASA and is now being manufactured using additive manufacturing (AM) techniques. AM offers a unique processing environment different from traditional metal fabrication processes. This study characterized the mechanical and structural properties of as-deposited and heat-treated GRCop-42 manufactured with Blown Powder Directed Energy Deposition (BPD) based on preliminary testing. The materials were characterized using several techniques including surface profiling by laser microscopy, mechanical stiffness by instrumented indentation, crystal structure, residual stress measurements using XRD and residual XRD, and chemical composition and microstructural evaluation using SEM with EBSD. The results of the study are compared using the BPD techniques for samples in the as-deposited and heat-treated conditions.
Wind Harvesting on Mars: Study and Approach
Authors: Qomsiya Mohanad , Fletcher Robert W.
Published: February 2021

Sustainable energy utilization on Mars is fundamental for the success of habitation on Mars. The two sustainable energy sources for In-Situ Resource Utilization (ISRU) with the highest potential for implementation on Mars are solar and wind. Unfortunately, the former cannot provide a reliable continuous source of energy for multiple reasons. Accordingly, wind energy is presented as a viable solution, or as a strong potential complement to solar energy.

The authors investigate different sites on Mars by evaluating the available wind resources to select the most feasible location in terms of energy yield and other critical habitability criteria. This work is conducted by applying the General Circulation Model (GCM) simulation, this particular analysis of wind harvesting feasibility on Mars will be studied by employing the Mars Climate Database (MCD) model.

In addition, this novel research provides a systematic approach for future energy harvesting projects on Mars. Moreover, it evaluates different potential wind turbine design concepts applicable for the Martian ISRU. The results of this research lay the foundation for future energy utilization necessary for habitation to thrive, as well as it will be a key for future exploration missions. Ultimately, this will enrich our understanding of wind turbine systems.
Bayesian Information Fusion of Multmodality Nondestructive Measurements for Probabilistic Mechanical Property Estimation
Authors: Chen Jie , Liu Yongming
Published: February 2021

Missing data occur when no data value is available for the variable in an observation. In this research, Bayesian data augmentation method is adopted and implemented for prediction with missing data. The data augmentation process is conducted through Bayesian inference with missing data assuming the multivariate normal distribution. Gibbs sampling is used to draw posterior simulations of the joint distribution of unknown parameters and unobserved quantities. The missing elements of the data are sampled conditional on the observed elements. The distribution of model parameters and variables with missing data can be obtained for reliability analysis. Two examples are given to illustrate the engineering application of Bayesian inference with missing data. The first example is to predict the yield strength of aging pipeline by fusing the incomplete surface information with missing data. The predictive performance is compared among direct surface indentation technique, linear regression with complete data and Bayesian inference with missing data. The second example is to predict the fatigue life of corroded steel reinforcing bar from the incomplete input dataset. The predicted fatigue lives are compared with experimental data. Both examples demonstrate that the Bayesian method can deal with missing data problem properly and show good predictive performance.
Effect of Freeze Pipe Eccentricity in Artificial Ground Freezing Applications
Authors: Zueter Ahmad F. , Xu Minghan , Alzoubi Mahmoud A. , Sasmito Agus P.
Published: February 2021

Building concentric tubes is one of biggest practical challenges in the construction of freeze-pipes of artificial ground freezing (AGF) applications for deep underground mines. In this study, the influence of tubes eccentricity on phase-front expansion (i.e., expansion of the frozen body) and energy consumption of AGF systems is analyzed. A 1+1D semi-conjugate model that solves two-phase transient energy conservation equation is derived. The model is firstly validated against experimental data and then verified with a fully-conjugate model from the literature. After that, the model is extended to a field scale of typical deep underground mines to study freeze-pipe eccentricity. The results show that an eccentric freeze pipe can reduce the phase-front expansion by around 25%, as compared with a concentric one. Also, the geometrical profile of the phase-front is significantly influenced by the freeze-pipe eccentricity. Furthermore, in the passive zone, where AGF coolants are isolated from the ground to reduce energy consumption, freeze pipe eccentricity can increase the coolant heat gain by 10%. This percentage can increase up to 200% if radiation heat transfer is minimized.