bluuebunny/crossref_metadata_2025 huggingface dataset:
High Cycle Fatigue Behavior of Recycled Additive Manufactured Electron Beam Melted Titanium Ti6Al4V
Authors: Mojib Melody , Pahuja Rishi , Ramulu M. , Arola Dwayne
Published: February 2021

Metal Additive Manufacturing (AM) has become a popular method for producing complex and unique geometries, especially gaining traction in the aerospace and medical industries. With the increase in adoption of AM and the high cost of powder, it is critical to understand the effects of powder recycling on part performance to move towards material qualification and certification of affordable printed components. Due to the limitations of the Electron Beam Melting (EBM) process, current as-printed components are susceptible to failure at limits far below wrought metals and further understanding of the material properties and fatigue life is required. In this study, a high strength Titanium alloy, Ti-6Al-4V, is recycled over time and used to print fatigue specimens using the EBM process. Uniaxial High Cycle Fatigue tests have been performed on as-printed and polished cylindrical specimens and the locations of crack initiation and propagation have been determined through the use of a scanning electron microscope. This investigation has shown that the rough surface exterior is far more detrimental to performance life than the powder degradation occurring due to powder reuse. In addition, the effects of the rough surface exterior as a stress concentration is evaluated using the Arola-Ramulu. The following is a preliminary study of the effects powder recycling and surface treatments on EBM Ti-6Al4V fatigue life.
Uncertainty Quantification in Predicting Behaviour of Rubber-Like Materials in Uni-Axial Loading
Authors: Ghaderi Aref , Morovati Vahid , Nasiri Pouyan , Dargazany Roozbeh
Published: February 2021

Material parameters related to deterministic models can have different values due to variation of experiments outcome. From a mathematical point of view, probabilistic modeling can improve this problem. It means that material parameters of constitutive models can be characterized as random variables with a probability distribution. To this end, we propose a constitutive models of rubber-like materials based on uncertainty quantification (UQ) approach. UQ reduces uncertainties in both computational and real-world applications. Constitutive models in elastomers play a crucial role in both science and industry due to their unique hyper-elastic behavior under different loading conditions (uni-axial extension, biaxial, or pure shear). Here our goal is to model the uncertainty in constitutive models of elastomers, and accordingly, identify sensitive parameters that we highly contribute to model uncertainty and error. Modern UQ models can be implemented to use the physics of the problem compared to black-box machine learning approaches that uses data only. In this research, we propagate uncertainty through the model, characterize sensitivity of material behavior to show the importance of each parameter for uncertainty reduction. To this end, we utilized Bayesian rules to develop a model considering uncertainty in the mechanical response of elastomers. As an important assumption, we believe that our measurements are around the model prediction, but it is contaminated by Gaussian noise. We can make the noise by maximizing the posterior. The uni-axial extension experimental data set is used to calibrate the model and propagate uncertainty in this research.
Design of a Simple Experimental Setup for P-I-D Control Testing
Authors: Ilhan Zeki Okan , Loveland William , Baker Justiz
Published: February 2021

This work aims to demonstrate the use of a simple experimental setup for accurate position control, which will be used to supplement the senior level “Control Systems” class taught in McCoy School of Engineering at Midwestern State University. The experimental setup is an unstable, doubleintegrator system, which consists of a ping-pong ball rolling on a pivoted beam. The control task is to stabilize the ball at the center of the beam by systematically changing the angle of rotation of the beam through the servomotor. The experimental setup is built out of 3D-printed parts, and simple electronics are used for controls. A control-oriented dynamic model is first obtained based on the standard Lagrangian approach and the model is linearized to simplify the control design. Proportional Integral Derivative (PID) controller is then designed based on the system transfer function, and the performance of the PID controller is tested in closed-loop numerical simulations in MATLAB-SIMULINK environment. Finally, the proposed PID algorithm is implemented in the actual setup using the ARDUINO microcontroller platform. Performance of the PID controller is discussed based on the initial results and possible improvement areas are addressed.
Rapid Configuration and Launch of a UAS Swarm for Post-Nuclear Blast Response
Authors: Renard Michael , Anderson Matthew , Rose Luke , Johnston Murray , Walter William , Kopeikin Andrew
Published: February 2021

A multi-disciplinary team of West Point cadets developed an Unmanned Aircraft System (UAS) swarm to provide automated remote sensing of radiation sources and hazards following a nuclear blast. The swarm employs autonomous and adaptive distributed control algorithms to survey (1) a radiation fallout plume to map its contour, and (2) a road network to visually identify obstacles to ground travel. To effectively conduct these missions USMA designed modifications to a fleet of Tarot 650 drones to interface with an existing swarming infrastructure, and to enable rapid tool-free integration of the required sensor suite. In addition, a rapid deployment launcher was designed to safely transport, power, and remotely launch the UAS from the back of a HMMWV. This paper describes considerations and analyses that supported the integrated mechanical and electrical designs, as well as a description of the resulting product. Flight testing was conducted to demonstrate the functionality of most of the designed components. Following the COVID-19 shutdown, the team pivoted to remote subcomponent testing, and computer simulation to demonstrate the remaining functions.
Development of Analytical Force Model for End Milling of Magnesium Matrix Composites
Authors: Anandan Nishita , Ramulu M.
Published: February 2021

An analytical approach to predict the cutting forces in end milling of magnesium metal matrix composite is presented in this study. The model was developed by identifying three events that occur when the cutting edge encounters the composite, when an element of the cutting edge encounters just the particles, it may fracture the particle, when the element encounters pure ductile matrix, plastic deformation occurs and when the element is in contact with both the particle and matrix, particle debonding occurs due to mismatch in coefficient of thermal expansion. The probability of these events was estimated using the particle concentration and the distribution in the matrix. A cutting force model is developed by considering the stresses and forces experienced by the cutting edge contributed by these events. The predicted feed forces and the measured forces are in good agreement for most of the cutting conditions. While, the predictive thrust forces were found to diverge at higher feed of 1 mm/rev.
Chemical Kinetic Study on Reaction Pathway of Anisole Oxidation at Various Operating Condition
Authors: Roy Shrabanti , Askari Omid
Published: February 2021

Biofuels are considered as an alternative source of energy which can decrease the growing consumption of fossil fuel, hence decreasing pollution. Anisole (methoxybenzene) is a potential source of biofuel produced from cellulose base compounds. It is mostly available as a surrogate of phenolic rich compound. Because of the attractive properties of this fuel in combustion, it is important to do detail kinetic study on oxidation of anisole. In this study a detail chemical mechanism is developed to capture the chemical kinetics of anisole oxidation. The mechanism is developed using an automatic reaction mechanism generator (RMG). To generate the mechanism, RMG uses some known set of species and initial conditions such as temperature, pressure, and mole fractions. Proper thermodynamic and reaction library is used to capture the aromaticity of anisole. The generated mechanism has 340 species and 2532 reactions. Laminar burning speed (LBS) calculated through constant volume combustion chamber (CVCC) at temperature ranges from 460–550 K, pressure of 2–3 atm and equivalence ratio of 0.8–1.4 is used to validate the generated mechanism. Some deviation with experimental result is observed with the newly generated mechanism. Important reaction responsible for LBS calculation, is selected through sensitivity analysis. Rate coefficient of sensitive reactions are collected from literature to modify and improve the mechanism with experimental result. The generated mechanism is further validated with available ignition delay time (IDT) results ranging from 10–20 atm pressure, 0.5–1 equivalence ratio and 870–1600 K temperature. A good agreement of results is observed at different operating ranges. Oxidation of anisole at stoichiometric condition and atmospheric pressure in jet stirred reactor is also used to compare the species concentration of the mechanism. This newly generated mechanism is considered as a good addition for further study of anisole kinetics.
Convective Air Drying of Stationary and Moving Moist Porous Medium With Slot Jet Reattachment Nozzle: A Numerical Study
Authors: Farzad Milad , Yagoobi Jamal
Published: February 2021

Drying is an omnipresent operation present in various industrial sectors such as food and agriculture, forestry products, chemicals, and pharmaceuticals. Convective hot air drying with conventional impinging jet nozzles is among the widely used techniques in drying of moist porous materials. However, this method is generally inefficient in drying of fragile materials as a low air flow rate is required to avoid potential damage to the product due to the exerted force by impinging jet. To improve the drying efficiency and enhance the product quality, slot jet reattachment (SJR) nozzle has been developed as an alternative technology to the common in-line jet nozzle, slot jet (SJ) nozzle, and perforated plate. SJR nozzle allows for the control of the exerted impingement force by simply changing its exit angle.

This paper numerically investigates the convective air-drying characteristics of an SJR nozzle and compares it to those of a common SJ nozzle for a moist porous medium. The comparison is made under identical air mass flow rate criterion. The results are presented for stationary and moving reattachment surface under a laminar flow condition. The governing transport equations within a moist porous medium are coupled with the governing equations of the resultant air flow. The results indicate a much higher drying rates with SJR nozzle compared to SJ nozzle.
Nonlinear Dynamics of a Dielectric Elastomer Membrane Under Compressive Loading
Authors: Lowe Robert L. , Cooley Christopher G.
Published: February 2021

This paper investigates the nonlinear dynamics of square dielectric elastomer membranes under time-dependent, through-thickness compressive loading. The dielectric elastomer is modeled as an isotropic ideal dielectric, with mechanical stiffening at large strains captured using the Gent hyperelastic constitutive model. The equation of motion for the in-plane membrane stretch is derived using Hamilton’s principle. The static response of the membrane is first investigated, with equilibrium stretches calculated numerically for a wide range of compressive pre-loads and applied voltages. Snap-through instabilities are observed, with the critical snap-through voltage decreasing with increasing compressive pre-load. The dynamic response of the membrane is then investigated under forced harmonic excitation. Frequency response plots characterizing the steady-state vibration reveal primary, subharmonic, and superharmonic resonances. Near these resonances, two stable vibration states are possible, corresponding to upper and lower branches in the frequency response. Significant and practically meaningful differences in the dynamic response are observed when the system vibrates at a fixed frequency about the upper and lower branches, a feature not discussed in previous research.
Design and Performance of Nonlinear Control for an Electrohydraulic Actuator Used on Shaker Table
Authors: Borrás Pinilla Carlos , Quintero Edwin Ferney
Published: February 2021

Hydraulic actuators are widely used in industrial applications due to their excellent power-size relation, their capacity to apply high forces indefinitely, and their high response. Hydraulic servo systems combine the advantages of hydraulic actuators with the versatility of electronics to give the most powerful actuators in modern industrial applications like robotics, aerospace industry, mining, testing equipment, and production lines.

Hydraulic dynamic systems are usually described by linear or linearized models around operating points. In this work a nonlinear dynamic and mathematic model for the position control of a double rod hydraulic servo actuator was developed.

Three control strategies were implemented: optimal control (LQR), control by Feedback Linearization, and Sliding Mode Control. For the optimal control (LQR) strategy a linearized model of the hydraulic actuator was developed around a specific operating point, contrary to the Feedback Linearization and Sliding Mode control that have a wide operation range and the nonlinear model was used. The Sliding Mode control was designed using a scheduling switch to change between two sliding mode controls and to avoid the chattering problem a solution base in the limit region was used.

Furthermore, it was obtained that depending on the industrial application and the requirements of the position control of a hydraulic actuator, engineers can decide which control strategy to apply. Scheduling sliding mode control is better for industrial applications where it is important to have a rapid and accurate response, low control effort, low energy consumption, and robustness in the presence of disturbances. Feedback linearization control is also an excellent control strategy with rapid response and low control effort. But in certain applications, where there is no fast response, nor extreme precision needed, the LQR control is a great option.
A Directional Damage Constitutive Model for Stress-Softening in Solid Propellant
Authors: Chen Yang , Morovati Vahid , Dargazany Roozbeh
Published: February 2021

Solid propellants are particulate composite with a light cross-linked elastomeric binder filled with a high concentration of energetic, solid aggregates. Solid propellants are often considered as highly nonlinear elastomeric materials, with elastic behavior resulted from its binder and plastic behavior from its energetic particles. The study of the micro-structure and mechanical properties of solid propellant is crucial for its design, safety evaluation, and lifetime prediction of solid fuel carriers. The constitutive model proposed for rubber-like material can often be generalized to predict the nonlinear behavior of solid propellant due to the dependency on the mechanical behavior of solid propellant on its elastomeric binder material. This paper focuses on developing a model that predicts the stress softening and strain-residual mechanism of the solid propellant. This micro-mechanical model for solid propellant was proposed based on the network evolution theory. The motivation of this study is the lack of a micro-mechanical model that can describe both the stress softening effect and strain residual in the quasi-static behavior of propellants. The simplified network-evolution model with only five parameters is a simple micro-mechanical model that captures both the stress softening effect and strain residual. Besides the simplicity and reduced fitting procedure, the model was validated against several experimental data and illustrated good agreement in small and large deformations, making the proposed model a suitable option for commercial and other applications.
Enhanced Wickability of Thin Non-Uniform Sintered Particle Wicks Using Lattice Boltzmann Method
Authors: Borumand Mohammad , Lee Taehun , Hwang Gisuk
Published: February 2021

Thin non-uniform particle size wicks are essential to improve the maximum heat flux of two-phase thermal management systems by improving the wickability. To understand the enhanced wickability, we examine a pore-scale capillary flow within the thin sintered particle wick using a free-energy-based, single-component, two-phase Lattice Boltzmann Method (LBM) with a minimal parasitic current. The developed LBM approach is validated through the rate-of-rise in the two-parallel plates with parallel plates spacing of W = 48 against analytical Bosanquet equation, achieving the RMS error below 10%. The LBM predicts the rate-of-rise through the uniform and non-uniform particle-size wicks between two-parallel plate, including the capillary meniscus front and dynamic capillary filling. At the same plate spacing and porosity, i.e., W = 48 lu and ε = 0.75, the non-uniform particle size wick achieves enhanced wickability by providing the selective flow pathway through pore networks formed in the smaller pores between the small/large particles, which is in qualitative agreement with previous experimental results. The enhancement of the maximum and minimum dimensionless liquid height and the liquid-filled pore ratio of non-uniform particle size wick is found to be up to 11.1, 27.47, and 26.11%, respectively. The simulation results provide insights into the optimal wick structures for high heat flux two-phase thermal management system by enhancing the wickability through the non-uniform particle (or pore) sizes.
Repeatability of a Topology Optimized Tapered Box Beam Additively Manufactured With Electron Beam Melted Ti-6Al-4V
Authors: Bol Eric , Ramulu M.
Published: February 2021

In order for metal additive manufacturing to fully break into the commercial aircraft industry the process has to be stable and repeatable. The product safety of high-quality serial production components is directly related to manufacturing repeatability. In this study a tapered box beam resembling a scaled down commercial aircraft engine pylon forward strut box is designed for additive manufacturing using 3D topology optimization as a guide. The topology optimization algorithm initially sized the structure for maximum stiffness, then the resulting CAD model was redesigned and analyzed for maximum principal stress to reduce the weight. The final design had an asymmetric organic-like truss structure that was manufactured in two halves out of titanium using an Arcam A2X electron beam powder bed fusion machine. A trial build helped to determine the proper support strategy to achieve quality specimens with tight tolerances that would facilitate assembly. To test the manufacturing repeatability a series of three builds was executed to produce six beam specimens for follow-on analysis and strength testing. This paper describes the design, analysis, and manufacturing process for a topology optimized taped box beam that is intended for future ultimate strength testing and analysis.
Analysis on RAMS Information for Metro Vehicles Using Natural Language Processing Algorithm: Evidence From China
Authors: Luo Min , Yu Luman , Yao Yimiao
Published: February 2021

The RAMS information of rail vehicles is an important data for the operation and maintenance of rail transit, and is the key to improving the performance and reliability level of rail vehicle equipment. At present, there are a large number of colloquial, hybridized and subjective data records in the RAMS information of metro trains; especially in the vehicle fault record, this phenomenon is widespread, which brings great difficulties to subsequent data analysis. Therefore, how to convert these irregular fault records into computer-readable fault texts is of great significance. This paper proposes the RAMS information structuring algorithm based on the Jieba word segmentation and Doc2Vec technology. Besides, we compile a professional dictionary of metro vehicles and a standard fault statement library for metro vehicles.
Computational Modelling and Simulation of Pedestrian Subsystem Impactor With Sedan Vehicle and Truck Model
Authors: Mohammed Obaidur Rahman , Suresh D. V. , Lankarani Hamid M.
Published: February 2021

The increase in public transportation in the last decade has resulted in a larger pedestrian population and hence a larger number of pedestrian collisions. In the past, car-pedestrian accident prevention had been a challenge for automotive and transport safety members. Recent reports in car-pedestrian accidents have influenced many improvements to prioritize pedestrian protection for automotive industries. The number of pedestrian fatalities in U.S has raised in last decade proportionally, Car manufacturers, and transport investigation teams are implementing new product designs and adding new development methods to reduce the risk of pedestrian collisions. In this study, adult headform and upper legform is tested with a finite element vehicle model to examine the simulation results and injury behavior during impact. All finite element simulation tests are produced under Euro-NCAP Committee regulations. Finite element models are configured as per the regulation’s and testing criteria. Both upper legform impactor and adult headform finite simulation results are tested with assessing criteria limits. Finite simulation tests are carried on the LS-DYNA – Code platform. This comparative study between sedan and pickup finite vehicle models gives an injury risk prediction of pedestrian safety and assesses design parameters of automotive industries.
Design and Fabrication of Mount Plate for Integration of Multiple Cameras in UAV Using 3D Printing and Traditional Manufacturing Method
Authors: Davis Madelyn , Ball John , Liu Yucheng , Stone Tonya
Published: February 2021

In this project, custom mount plates were designed and fabricated to secure cameras to unmanned aerial vehicles (UAVs) for data collection. An engineering design approach was followed to design the mount plates. Two types of mount plate were fabricated using different methods. One mount plate was cut from G10 fiberglass sheets following a traditional subtractive manufacturing process while the other one was made from 3D printing with polylactic acid (PLA). The two manufacture methods were compared in terms of manufacturing cost, time, and simplicity. Performance of these two plates including compatibility, weight, and strength were also discussed. Results of this project will facilitate researcher’s decision making for choosing the appropriate approach to make such apparatus.
Experimental Study on Flow Boiling of HFE-7100 in Wavy Copper Microchannels
Authors: Cui Peilin , Liu Zhenyu
Published: February 2021

This study experimentally investigated the flow boiling of HFE-7100 in wavy copper microchannel heat sink (20 mm × 10 mm), which was fabricated with the ultrafast laser micromachining approach, consisting of 20 wavy microchannels with wavelength of 2000 μm and wave amplitude of 100 μm with triangular cross section (200 μm × 573 μm). The experiment was conducted with the mass fluxes of 330.07–550.11 kg/(m2·s) and heat flux of 14.5–411.3 kW/m2 at an inlet temperature of 15°C. Four flow patterns including bubbly flow, slug flow, churn flow and annular flow were captured with the visualization technique. Several confined bubbles with irregular shape were observed. In the low heat flux region, the dominant flow regime of heat transfer in the microchannels is the nucleate boiling and the heat transfer coefficient increases with increasing heat flux. With the nucleate boiling suppressed gradually, the evaporation of thin liquid film begins to dominate and the heat transfer coefficient decreases with the increase of heat flux. The heat flux has a significant effect on heat transfer coefficient compared with the mass flux and vapor quality.
Universal Weight Function Method on the Probabilistic Surface Damage Tolerance Assessment of Aeroengine Rotors
Authors: Zhou Huimin , Ding Shuiting , Li Guo
Published: February 2021

The methodology referred as probabilistic surface damage tolerance for aeroengine rotors is used to evaluate the risk of fractures induced by low-cycle failure problems, and fracture mechanical models are usually used to carry out the analysis, in which stress intensity factors (SIFs) need to be calculated. Weight function method (WFM) can help improve the probabilistic surface damage tolerance methodology. The WFM offers remarkable computational efficiency in calculating SIFs for cracks in aeroengine rotors with complex stress gradients that are mainly induced by a local stress concentration or multiple loads, including centrifugal, thermal, and residual stresses. In this case, the universal weight functions (mode I) for surface cracks in three-dimensional finite plates, including flat plates and plates with holes, are presented. The critical step of WFM is to obtain certain coefficients in the universal weight function. Response surface method (RSM) can effectively derive the coefficients determined by multiple geometric parameters, including the length and thickness of a flat plate and the length, thickness, radius of a plate with a hole. Errors between the WFM results and the finite element results are less than 5MPam within the application scope. Furthermore, a surface damage tolerance analysis of the hole features in the aeroengine rotors based on the abovementioned two types of WFM is conducted. The selection of the weight function influences the SIF results, and the probability of failure (POF) calculated by the applied weight function of the plate with a hole is 2.02% higher than that of the flat plate. The relevant difference, which is determined by the fracture threshold crack size, has a negative relationship with the magnitude of stress distributed on the crack surface.
Adaptive Iterative Learning Control of Fluidic Muscle Driven Parallel Manipulators for Force Control With Sliding Mode Technique
Authors: Zhang Xinxin , Li Min , Ding Huafeng
Published: February 2021

In this paper, an adaptive iterative learning control (AILC) method combined with sliding mode technique is proposed to improve the force control performance for repeating tasks of fluidic muscle (FM) driven parallel manipulators. Different from the traditional iterative learning control method, the proposed AILC is to learn the controller time-varying parameters rather than to learn the control signals. Since the AILC is sensitive to non-repetitive disturbances, the sliding mode technique is introduced to enhance the robustness. Since no model information involved in the controller design, the proposed method is a complete data-driven method. Hence, the difficulty of obtaining accurate model is avoided. Simulation studies are performed on a two degrees of freedom FM driven parallel manipulator. Simulation results demonstrate that the proposed method can achieve high force tracking performance and robustness.
Prediction of Blood Flow Distribution in Liver Radioembolization Using Convolutional Neural Networks
Authors: Taebi Amirtahà , Vu Catherine T. , Roncali Emilie
Published: February 2021

We have developed a new dosimetry approach, called CFDose, for liver cancer radioembolization based on computational fluid dynamics (CFD) simulation in the hepatic arterial tree. Although CFDose overcomes some of the limitations of the current dosimetry methods such as the unrealistic assumption of homogeneous distribution of yttrium-90 in the liver, it suffers from the expensive computational cost of CFD simulations. To accelerate CFDose, we introduce a deep learning model to predict the blood flow distribution between the liver segments in a patient with hepatocellular carcinoma. The model was trained with the results of CFD simulations under different outlet boundary conditions. The model consisted of convolutional, average pooling and transposed convolution layers. A regression layer with a mean-squared-error loss function was utilized at the network output to estimate the arterial outlet blood flow. The mean-squared error and prediction accuracy were calculated to measure model performance. Results showed that the average difference between the CFD results and predicted flow data was less than 2.45% for all the samples in the test dataset. The proposed model thus estimated the blood flow distribution with high accuracy significantly faster than a CFD simulation. The network output can be used to estimate the yttrium-90 dose distribution in the liver in future studies.
Effect of Leg Topology on the Energy Conversion Performance of Thermoelectric Generators Systems
Authors: Aljaghtham Mutabe , Celik Emrah
Published: February 2021

Thermoelectric generators (TEGs) convert temperature gradient into electrical power. The shape (or topology) of thermoelectric (TE) leg has a significant impact which can directly affect TEG performance. The conventional uniform, rectangular TE leg configurations were employed widely in TEGs to evaluate the performance of the TE devices. Different leg geometries have been proposed in the past by researchers to enhance thermoelectric efficiency. However, there is no consensus, nor a systematic study exists to find out the ideal leg geometry and maximize the energy conversion efficiency in thermoelectric systems. The current study investigates various configurations of TE legs such as trapezoidal leg, zig-zag leg, butterfly leg, vertical and horizontal cross-shaped leg, X-leg, Y-leg, I-leg based on their individual shape construction. 3-dimensional finite element simulations are conducted to investigate the thermoelectric output power and conversion efficiency of these configurations and compared to (conventional) rectangular TE leg shape geometries. The reliability and accuracy of the used finite element based numerical model are validated with analytical and numerical results. From the study, results indicate that the vertical cross-shaped and butterfly generate more TE output power compared to all other configurations. The (conventional) rectangular TE leg generates around 1.46 Watts which is around 34% and 25% TE power lower than vertical cross-shaped and butterfly configurations, respectively.
Text Writing Using Air Gestures for People With Limited Hand Motor Skills
Authors: Ermidoro Michele , Vitali Andrea , Previdi Fabio , Rizzi Caterina
Published: February 2021

Mobile devices and laptops are the main ICT tools to exchange information among people in the world. All the applications are designed by following a specific interaction style based either touchscreen or mouse and keyboard, which can be performed only with detailed movements of hands and fingers. Traditional interaction becomes difficult for elderly who have diseases limiting the hand motor skills, such as arthritis and brain stroke.

The use of simple air gestures can be adopted as alternative interaction style to interact with smartphones, tablets and laptops. The aim of this research work is the development of an application that allows text writing using air gestures for people with limited hand motor skills. The application embeds several computer vision algorithms and convolutional neural networks software modules to detect and drawn alphanumeric characters and recognizing them using both mobile devices and laptops. The preliminary results obtained show that the approach is robust, and it can easily detect the alphanumeric characters written with the movement of the wrist.
Analysis of Laser Cutting of 1.2mm Thick Austenitic Stainless Steel
Authors: Atayo Asonganyi Ateh , Bashir Mahmood , Rahman Muhammad Mustafizur , Nair Rajeev
Published: February 2021

Stainless steel 304 is one of the most commonly used steel types for corrosion resistance applications, but higher melting point is a limitation in industries from a manufacturing point of view. The non-conventional and subtractive manufacturing technique of laser cutting — a beam directed method, is suitable for these applications. A Gaussian laser beam is directed at the material that melts, burns, vaporizes, or is blown away by a jet of gas, leaving a fine edge with good surface finish. In this study, a numerical study was performed to study the multi-physical fluid processes of laser cutting. Towards this, modeling was performed using 1.2 mm thick austenitic stainless-steel coupons that was cut using a continuous width neodymium-doped yttrium aluminum garnet (CW Nd: YAG) laser. The results showed smoother surface cut, little dross formation, lower temperature rise in heat affected zones, and less finish time at a cutting speed of 8m/min, higher laser power above 1000 W, gas pressure of 11 bars, and focus distance of −1.0 mm. It was observed that an increase in laser power at a faster cutting speed led to an increase in kerf width, reduction in dross formation, lower temperature rises in heat affected zones and a reduced finish time. The simulation results were compared with published experimental data and found to be well within a maximum difference of 15%.
A New Meshless “Fragile Points Method (FPM)” Based on a Galerkin Weak-Form for 2D Flexoelectric Analysis
Authors: Guan Yue , Dong Leiting , Atluri Satya N.
Published: February 2021

A meshless Fragile Points Method (FPM) is presented for analyzing 2D flexoelectric problems. Local, simple, polynomial and discontinuous trial and test functions are generated with the help of a local meshless differential quadrature approximation of the first three derivatives. Interior Penalty Numerical Fluxes are employed to ensure the consistency of the method. Based on a Galerkin weak-form formulation, the present FPM leads to symmetric and sparse matrices, and avoids the difficulties of numerical integration in the previous meshfree methods. Numerical examples including isotropic and anisotropic materials with flexoelectric and piezoelectric effects are provided as validations. The present method is much simpler than the Finite Element Method, or the Element-Free Galerkin (EFG) and Meshless Local Petrov-Galerkin (MLPG) methods, and the numerical integration of the weak form is trivially simple.
Low Wear Debris Compliant Mechanism Cervical Disc Prosthesis
Authors: Brehm Samuel
Published: February 2021

The device outlined in this paper is 3D printable cervical disc prosthesis that uses a compliant mechanism to behave biomechanically like a natural cervical intervertebral disc. The device is DMLS printed out of biocompatible titanium as a single part, and can be manufactured to the custom length, width, height, and lordotic angle desired for the patient. The device has 6 degrees of freedom for flexion, extension, and lateral bending. The device has 0.83 mm of max compression with a compressive stiffness of 473.1 N/mm. The device consists of compliant mechanism with two plates fused on the top and bottom. The mechanism is essentially two perpendicular beams fused at their midpoints. The beams act as rotational as well as compressive springs. This allows the rotational and compressive range of motion. This design is intended to minimize the production of wear debris, which is a problem with prosthetics. It also provides the ability for a disc prosthesis to be easily custom manufactured for the patient.
Investigation of Contact Conditions During Stamping of a Thin Plate
Authors: Shahare Harshal Y. , Rajput Rohan , Tandon Puneet
Published: February 2021

Stamping is one of the most used manufacturing processes, where real-time monitoring is quite difficult due to high speed of the mechanical press, which leads to deterioration of the accuracy of the products In the present work, a method is developed to model elastic waves propagation in solids to measure contact conditions between die and workpiece during stamping. A two-dimensional model is developed that reduces the wave propagation equations to two-dimensional equations. To simulate the wave propagation inside the die-workpiece model, the finite difference time domain (FDTD) method and modified Yee algorithm has been employed. The numerical stability of the wave propagation model is achieved through courant stability condition, i.e., Courant-Friedrichs-Lewy (CFL) number. Two cases, i.e., flat die-workpiece interface and inclined die-workpiece interface, are investigated in the present work. The elastic wave propagation is simulated with a two-dimension (2D) model of the die and workpiece using reflecting boundary conditions for different material properties. The experimental and simulation-based results of reflected and transmitted wave characteristics are compared for different materials in terms of reflected and transmitted wave height ratio and material properties such as acoustic impedance. It is found that the numerical simulation results are in good agreement with the experimental results.
Improved Vibration-Model-Based Analysis for Estimation of Arterial Parameters From Noninvasively Measured Arterial Pulse Signals
Authors: Rahman Md Mahfuzur , Sultana Najmin Ara , Vahala Linda , Reynolds Leryn , Hao Zhili
Published: February 2021

With the goal of achieving consistence in interpretation of an arterial pulse signal between its vibration model and its hemodynamic relations and improving its physiological implications in our previous study, this paper presents an improved vibration-model-based analysis for estimation of arterial parameters: elasticity (E), viscosity (η), and radius (r0) at diastolic blood pressure (DBP) of the arterial wall, from a noninvasively measured arterial pulse signal. The arterial wall is modeled as a unit-mass vibration model, and its spring stiffness (K) and damping coefficient (D) are related to arterial parameters. Key features of a measured pulse signal and its first-order and second-order derivatives are utilized to estimate the values of K and D. These key features are then utilized in hemodynamic relations, where their interpretation is consistent with the vibration model, to estimate the value of r0 from K and D. Consequently, E, η, and pulse wave velocity (PWV) are also estimated from K and D. The improved vibration-model-based analysis was conducted on pulse signals of a few healthy subjects measured under two conditions: at-rest and immediately post-exercise. With E, r0, and PWV at-rest as baseline, their changes immediately post-exercise were found to be consistent with the related findings in the literature. Thus, this improved vibration-model-based analysis is validated and contributes to estimation of arterial parameters with better physiological implications, as compared with its previous counterpart.
Generalized Method of Effective Field in Linear Peridynamic Micromechanics of Random Structure Composites
Authors: Buryachenko Valeriy A.
Published: February 2021

A statistically homogeneous random matrix medium with the bond-based peridynamic properties of constituents is considered. For the media subjected to remote homogeneous volumetric boundary loading, one proved that the effective behavior of this media is governing by conventional effective constitutive equation which is the same as for the local elasticity theory. The average is performed over the surface of the extended inclusion phase rather than over an entire space. Any spatial derivatives of displacement fields are not required. The basic hypotheses of locally elastic micromechanics are generalized to their peri-static counterparts. In particular, in the generalized method of effective field proposed, the effective field is evaluated from self-consistent estimations by the use of closing of a corresponding integral equation in the framework of the quasi-crystalline approximation. In so doing, the classical effective field hypothesis is relaxed, and the hypothesis of the ellipsoidal symmetry of the random structure of CMs is not used. One demonstrates some similarity and difference with respect to other methods (the dilute approximation and Mori-Tanaka approach) proposed before in peridynamic micromechanics of CMs. Comparative numerical analyses of these methods are performed for 1D case.
Automating Aircraft Exterior Inspection With Robotics and Machine Learning Technologies
Authors: Sun Yufeng , Ma Ou
Published: February 2021

Most aircraft exterior inspections require human workers to visually detect defects such as dents, cracks, leaking, broken or missing parts, etc., and manually measure the parameters of the identified defects, which is a time-consuming process and it is also error-prone if the human inspector is not fully focused. This situation can be alleviated by the advance in computer vision and robotics for saving time and relieving human workers from such repetitive and stressful tasks. However, the challenge of automated robotic inspection for aircraft exterior remains due to the very large inspected area, full-coverage requirement and sometimes insufficient digital model available for planning the inspection path. This paper presents a two-stage approach to automate visual inspection of aircraft exterior surface in a static environment such as a MRO shop by a mobile manipulator equipped with a consumer-grade RGB-D camera following an optimal inspection trajectory learned from a low-resolution point cloud model of the aircraft when a proper CAD model of the aircraft is unavailable. In the first stage, a low-cost RGB-D camera is used to acquire a coarse point cloud model of the whole or interested area of the aircraft. In the second stage, a full coverage inspection path is learned based on the coarse model using a reinforcement learning process, which is our focus of this work.
Optimization of Chessboard Scanning Strategy Using Genetic Algorithm in Multi-Laser Additive Manufacturing Process
Authors: Malekipour Ehsan , Valladares Homero , Shin Yung , El-Mounayri Hazim
Published: February 2021

Residual stress and manufacturing time are two serious challenges that hinder the widespread industry adoption and implementation of the powder-bed fusion (PBF) process. Commercial Multi-Laser PBF (ML-PBF) systems have been developed by several vendors in recent years, which dramatically increase the production rate by employing more heat sources (up to 4 laser beams). Although numerous research works conducted toward mitigation of the effects of residual stress on printed parts in the Single Laser PBF (SL-PBF) process, no research work on this topic has been reported for the ML-PBF process to date.

One of the most efficient real-time approaches to mitigate the influence of residual stress and as such the process lead time effectively is to improve the scanning strategy. This approach can be also implemented effectively in the ML-PBF process. In this work, we extend the previously developed GAMP (Genetic Algorithm Maximum Path) strategy for optimizing the scanning path in ML-PBF. The E-GAMP (the Extended GAMP) strategy manipulates the printing topology of the islands and generates more thermally efficient scanning patterns for the chessboard scanning strategy in ML-PBF. This strategy extends the single thermal heat source to multiple ones (2 as well as 3 lasers). To validate the effectiveness of the proposed strategy, we simulate the thermal distribution throughout a simple rectangular layer by ABAQUS for both the traditional successive scanning strategy and the E-GAMP strategy. The results demonstrate that the E-GAMP strategy considerably decreases the manufacturing time while it reduces the maximum temperature gradient, or in other words, generates a more uniform temperature distribution throughout the exposure layer.
Corrosion Evaluation of a Navy MK50 Weapon Station Friction Brake Assembly
Authors: Romsland Ruby , McDonald Kenneth J.
Published: February 2021

The presence of corrosion on or within structures is of major concern as corrosion reduces the integrity of the materials which could potentially result in large-scale failures of structures and equipment.1 The United States Navy is an organization that actively works to prevent large equipment failure due to corrosion. One such problem is the corrosion of the friction brake assembly on the MK50 Weapon Station, which has recently been experiencing corrosion between the friction brake and its set screw preventing it from operating correctly. The friction brake was known to be stainless steel; however, the set screw was of unknown composition. Through elemental analysis it was determined that the MK50 Weapons Station friction brake set screw was similar in composition to commonly available black oxide coated steel screws. Electrochemical polarization measurements of the friction brake assembly components revealed that the set screw and the friction brake were electrochemically dissimilar metals which resulted in the galvanic corrosion of the assembly when out at sea. The electrochemical polarization measurements of a stainless steel screw showed a corrosion potential similar to that of the friction brake; therefore, replacing the current set screw with a stainless steel screw would decrease the galvanic potential difference between the set screw and the friction brake. This proposed solution is expected to slow or prevent further corrosion of the MK50 Weapon Station ensuring the combat readiness of the equipment.
Effect of Alloying Elements Concentration and Processing Parameters on the Structural and Mechanical Properties of Lightweight Magnesium Alloys
Authors: Rawles Jessica , Fialkova Svitlana , Xu Zhigang , Sankar Jagannathan
Published: February 2021

Magnesium is utilized as a light-weight metal in the aerospace and automotive industries, and recently draws a lot of attention in biomedical research due to its biodegradable and biocompatible properties [1–3]. With Zinc being a biocompatible element, magnesium-zinc alloys have been very attractive for such applications.

Mechanical properties including yield strength, tensile strength and hardness values of magnesium alloys are reported to be improved with the adding of alloying elements such as Zn, Zr, Al, Y and some rare earth elements.

In our study we observe the improvement of mechanical properties Vicker’s Hardness (VH) for Mg-Zn-Ca alloys with a fixed content of calcium and varying amounts of zinc alloying elements.

Potential Outcome:

Potentially new developed alloys could be used for lightweight materials for aerospace, automotive, and biomedical application.
Conceptual Design of an In-Pipe Displacement System Applicable for Oil Well Production Column
Authors: Figliuolo Saulo Queiroz , Beal Valter Estevão , Mascarenhas Luis Alberto Breda , Romero Albino Juan Carlos , Santos Hugo Francisco Lisboa
Published: February 2021

Oil well production rate should be maintained during its lifecycle and maintenance interventions are necessary to reach this goal. Production engineer teams work on different ways to make the production stable and to enhance the oil recovery from the reservoirs. However, interventions are necessary to maintain or recover the production rate. Some problems that cause maintenance are malfunctioning/wear of equipment, clogging/obstruction and operational mistakes. These maintenances are required using expensive equipment, especially on offshore operations.

In order to reduce the overall cost of interventions, robotic systems have been proposed. In this work, a conceptual development for a robotic production column well intervention system is proposed. This equipment should be strong enough to resist oil well environmental characteristics. Nowadays, the challenge involves high pressure and high temperature wells, high flow rates, a long/deep well and other very hostile features. Even though, this device has to be very slim and lightweight because it will be responsible for carrying on other systems (measurement / inspection tools, completion tools, etc.) displacing into the oil well production column. On the other hand, it needs to have highly efficient power consumption since the power availability is usually limited in the actuation environment of this autonomous equipment.

In order to guarantee the achievement of the desirable requirements, the design team followed the best practices of the product development process aided by a design for lifecycle guidelines.