bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tensile and Fatigue Properties of Ti-6Al-4V Alloy Fabricated by Laser Powder-Bed Fusion Process
Authors: Rahman M. Shafiqur , Chakravarty Uttam K. 
Published: February 2021

Abstract
The tensile and fatigue properties of laser-powder-bed-fusion (L-PBF) processed Ti-6Al-4V specimens are investigated at different loading conditions. Two types of as-built and post-machined L-PBF processed dogbone specimens are considered for the study, one is an ASTME8M round specimen and the other one is a customized small-scale flat structure. The tensile and fatigue behavior of the specimens are investigated numerically using the finite element (FE) method. The FE modeling considers both low cycle fatigue (LCF) and high cycle fatigue (HCF) test conditions by applying cyclic loads in fully-reversed and stress ratio R = 0.1 conditions. The FE results for the von Mises stress, strain, total deformation, fatigue life, factor of safety, and fatigue limit of the Ti-6Al-4V specimens are obtained at room temperature (295 K). Results obtained from the model show that the fatigue life decreases as the load increases. It is also found that fatigue life does not vary with the change of the test frequency under a specific fatigue load. The comparison of mechanical properties of the L-PBF processed specimens with conventionally manufactured Ti-6Al-4V parts is also shown to understand the differences in the tensile and fatigue behavior. The validation of the FE model is performed by comparing the numerical results for the yield stress and fatigue limit with the experimental results found from the literature. The overall study contains a detailed analysis of the tensile and fatigue behavior of additively manufactured Ti-6Al-4V parts and provides a guide to investigating the similar properties for other functional materials used in the L-PBF process.
A Multiband RF Energy Harvesting System for Efficient Power Conversion
Authors: Rahman M. Shafiqur , Chakravarty Uttam K. 
Published: February 2021

Abstract
This paper presents a radio frequency (RF) energy harvesting (RFEH) system with a multiband antenna configuration that can simultaneously harvest energy from the sub-6 GHz and 5G millimeter-wave (mm-Wave) frequency bands. The performance of the RFEH system is studied from −25 dBm to 5 dBm input power levels underlying the maximization of the overall efficiency and possible optimization strategies. The maximum achievable power conversion efficiency (PCE) is formulated as a mathematical programming problem and solved by optimizing the design factors including antenna geometry, operational frequencies, rectifier topologies, and rectifier parameters. An array of broadband high gain patch antennas with reconfigurable rectifiers, an impedance matching network, and a voltage-multiplier circuit are employed in the system to maximize the PCE. The voltage standing wave ratio (VSWR) and reflection coefficient (S11) of the antenna are estimated and optimized by numerical method. Simulations are conducted to evaluate the performances of the rectenna and the voltage-multiplier circuit. Results for radiation pattern, wave absorption, input impedance, voltage, and power across the load resistance as a function of frequency are obtained for the optimized configuration. The overall efficiency of the optimized RFEH system is measured at various power inputs and load resistances.
Fatigue Life Law Based on Inelastic Strain Energy Density of Solder Alloys and its Simple Prediction Method
Authors: Fumikura Tomoya , Kato Mitsuaki , Omori Takahiro 
Published: February 2021

Abstract
In recent years, a fatigue life law based on inelastic strain energy density as proposed by Morrow has been applied to solder materials. In this study, the effectiveness of the fatigue life law based on inelastic strain energy density was compared with the conventional law based on inelastic strain range.
First, the fatigue properties of Sn-Ag-Cu solder alloy were investigated by a torsional fatigue test with strain control. It was found that the stress–strain hysteresis loop arising from inelastic deformation occurred even under a low strain load with a fatigue life of about 1 million cycles. Therefore, as an extension of the low-cycle fatigue test, evaluation was performed using inelastic strain range and inelastic strain energy density. Experimental results show that when fatigue life was evaluated using inelastic strain energy density, a single power law was found over a wide range from the low-cycle region to the high-cycle region, and the validity of the fatigue life law based on inelastic strain energy density was confirmed.
Next, a simple prediction method for the fatigue life law based on inelastic strain energy density was examined, taking the physical background into account. Two material constants of the fatigue life law based on the inelastic strain energy density were estimated from the stress–strain curve for a monotonic load and shown to be close to the actual fatigue test results.
Emotional Tools Design: A Project to Increase Empathy, Engagement and Interest in Industrial Design Students
Authors: Rojas Juan-Carlos , Muniz Gerardo , Higuera-Trujillo Juan Luis 
Published: February 2021

Abstract
Empathy is the ability of people to identify emotional aspects of others. A fundamental aspect to teaching in design education must be empathy. This paper presents the design process of an emotional tools using emoticons or emojis for evaluated products as educational exercise. The dynamics behind of the tool is the empathy experimented during the develop of the emojis characters. The project was implemented in the second period of the second year, with an execution time of 5 weeks. A series of surveys were conducted to assess perception of aspects such as utility, novelty, sensitivity and relevance of the project, in addition to knowing the progress of empathy evoked by the students dynamic. The results revealed the following findings: The opinion of 25 students describe their wide acceptance of this project methodology. Students considered the relevance of assessment processes, their recommendation to use those processes, and invited other students to develop it. Also, student’s positive perception about utility, novelty, sensibility and relevance of project dynamics are not determined by acceptance of this type of project. The preliminary results suggest that this educational exercise has the potential to cultivate or train empathy and other skills in design and engineering students.
Damage Mechanism of the Acceleration of Intergranular Cracking of Stainless Steel SUS316LN Under Creep Loading at Elevated Temperatures
Authors: Gu Chongzhe , Takahashi Yukako , Miura Hideo 
Published: February 2021

Abstract
In this study, the simple creep test and intermittent creep test of SUS316LN, which has become a preferred materials for the structural components used in Boiling Water Reactors and Sodium Cooled-fast Reactors, were carried out to investigate the damage evolution. The effect of doping nitrogen into conventionally used SUS316L on the creep and fatigue strength has been proved in the comparison experiment between SUS316L and SUS316LN. At elevated temperatures, however, intergranular cracking still appeared under the application of low tensile stress. The mechanism of intergranular cracking at elevated temperatures, however, has not been clarified quantitatively yet. Therefore, in this research, EBSD method was applied to investigate the degradation process of the crystallinity around grain boundaries in this alloy from the viewpoint of the change of micro texture and atom arrangement. IQ (Image Quality) values, which indicates the average sharpness of the obtained diffraction pattern, were used for the evaluation of the local total density of defects. KAM (Kernel Average Misorientation) value was used for the evaluation of local plastic deformation in this study. In the creep test, the crystallinity decreased monotonically with the increase of creep damage. Combined with ΔKAM value, it was concluded that the accumulation of dislocations along specific grain boundaries and the difference of the magnitude of plastic deformation between two nearby grains were the dominant factors of intergranular cracking. Large difference of the magnitude of plastic deformation between two grains accelerated the accumulation of dislocations around the grain boundary. Therefore, the large difference of Schmid Factor between nearby grain is the dominant factor which determines the place where intergranular cracking starts to occur.
Numerical Simulation of Ampacity in Advanced Electrical Conductors
Authors: Khanbolouki Pouria , Tehrani Mehran 
Published: February 2021

Abstract
Elevated temperature performance of advanced conductors are investigated with a one-dimensional joule heating model. Step-by-step development and validation of the ampacity prediction model are discussed and results from case studies are provided. A potential advantage of advanced electrical conductors is their relatively low density. Copper — as reference — is compared with carbon-based conductors and copper nanocomposites, on the basis of equivalent volume and equivalent weight. It is shown that while doped carbon nanotube (CNT) conductors may potentially result in an improved conductor compared with copper on a weight basis, ultra-conductive copper (UCC) can outperform copper on both volume and weight bases.
Dynamics of Piezo-Embedded Negative Stiffness Mechanical Metamaterials: A Study on Electromechanical Bandgaps
Authors: Dwivedi Ankur , Banerjee Arnab , Bhattacharya Bishakh 
Published: February 2021

Abstract
Dynamics of periodic materials and structures have a profound historic background starting from Newton’s first effort to find sound propagation in the air to Rayleigh’s exploration of continuous periodic structures. This field of interest has received another surge from the early 21st century. Elastic mechanical metamaterials are the exemplars of periodic structures that exhibit interesting frequency-dependent properties like negative Young’s modulus, negative mass and negative Poisson’s ratio in a specific frequency band due to additional feature of local resonance. In this research, we present the modeling of piezo-embedded negative stiffness metamaterials by considering a shunted inductor energy harvesting circuit. For a chain of a finite number of metamaterial units, the coupled equation of motion of the system is deduced using generalized Bloch’s theorem. Successively, the backward substitution method is applied to compute harvested power and the transmissibility of the system. Additionally, through the extensive non-dimensional study of this system, the proposed metamaterial band structure is investigated to perceive locally resonant mechanical and electromechanical bandgaps. The results explicate that the insertion of the piezoelectric material in the resonating unit provides better tun-ability for vibration attenuation and harvested energy.
Nonlinear Model Predictive Control of a Stewart Platform Motion Stabilizer
Authors: Ono Takeyuki , Eto Ryosuke , Yamakawa Junya , Murakami Hidenori 
Published: February 2021

Abstract
In an operating room of a hospital ship, to remotely perform surgery on a patient laid on an operating table utilizing the surgical manipulators attached to the table, the rotation and translation of the operating table must be properly isolated from the wave-induced motion of the floor. Similarly, on a moving vehicle, when a sensitive equipment is transported or a manipulator is utilized to perform precise positioning tasks, it becomes necessary to isolate them from undesirable motion of the vehicle.
In response to the need for a motion stabilizer, which isolates a manipulator from undesirable ship or vehicle motion, we present a nonlinear model predictive control (NMPC) of a six degrees-of-freedom, base-moving Stewart platform. Analytical nonlinear equations of motion are utilized for nonlinear model predictive control, wherein an optimization problem in a finite time horizon at each time step is solved adopting C/GMRES algorithm. To predict the future motion caused by a ship or a moving vehicle, we employ an auto regressive moving average model which forecasts future behavior based on past behavior. Furthermore, to incorporate prediction errors as disturbance at each time step, we endow NMPC with the robustness. As a result, even if prediction errors exist, the set of all possible output states are predicted using the equations of motion in a finite time, while the system kinematic constraints are precisely satisfied.
In order to assess the performance of the proposed controller, numerical simulations are presented for a base-moving Stewart platform.
Dynamic Characteristics of Infants Riding on Stroller
Authors: Okajima Hiroyuki , Ota Shinichiro , Ota Ryo 
Published: February 2021

Abstract
When a stroller with an infant ride over protrusions or irregularities, vibrations are transmitted from the infant’s lower limb to the upper limb through the tire-frame-cushion. To reduce the load on the infant, the challenge is to reduce the vibration at each part of the infant’s body. To design an equipment for reducing such vibration, it is important to understand the vibration characteristics of infants. Therefore, the purpose of this study was to clarify the vibration characteristics of infants. Transient and frequency response characteristics of the infant–stroller system were investigated by riding over protrusions and irregularities, respectively.
In the transient response obtained by both wheels riding over the protrusion, the vibration of the head and chest is a mixture of the primary secondary vibration modes. In the transient response obtained with one wheel riding over the protrusion, the primary vibration mode becomes prominent when the vibration transmitted to the stroller seat is small, and the secondary vibration mode becomes prominent when the vibration transmitted to the stroller seat is large. The frequency response shows some resonance frequencies between 1 Hz and 6 Hz. Vibrations over 8 Hz have small effects on the infants because the acceleration ratio is low at values below 1.
Crystallinity Dependence of Grain and Grain Boundary Strength of a Bicrystal Structure of Copper
Authors: Suzuki Ken , Fan Yiqing , Luo Yifan 
Published: February 2021

Abstract
Electroplated copper thin films often contain porous grain boundaries and the volume ratio of porous grain boundaries in the copper thin films is much larger than that in bulk copper. Thus, the lifetime of the interconnection components fabricated by electroplating is strongly dominated by the strength of grain boundaries because final fracture caused by the acceleration of atomic diffusion during electromigration (EM) occurs at grain boundaries in polycrystalline interconnections. It is important, therefore, to quantitatively evaluate the grain boundary strength of electroplated copper films for estimating the lifetime of the interconnection in order to assure the product reliability. In this study, relationship between the strength and crystallinity of electroplated copper thin films was investigated experimentally and theoretically. In order to investigate the relationship between the strength and grain boundary quality, molecular dynamics (MD) simulations were applied to analyze the deformation behavior of a bicrystal sample and its strength. The variation of the strength and deformation property were attributed to the higher defect density around grain boundaries.
Automation CAE Toolkit Method for Ram BOP Design
Authors: Wang Yaou , Nault Chris , Givens Matthew , Threadgill Micah , Berry Seth , Zhang Haitao , Li Ke 
Published: February 2021

Abstract
A Blowout Preventer (BOP) serves as a safety valve in the drilling process in the oil and gas industry. It will be closed if an influx of formation fluids occurs and threatens the rig. A Ram BOP is one type of widely used BOP. It is composed of two ram blades, which will move towards each other to shear the drilling pipe and to close the valve. To ensure the shearing process be completed on the rig, lab tests are often run to evaluate the BOP’s capability and the required shearing pressure. The paper presents a new automation CAE (Computer-Aided Engineering) toolkit method recently developed to simulate the Ram BOP pipe shearing process. The toolkit method automates and integrates the process from computer aided design (CAD) to computer aided simulation for the Ram shearing process. It significantly simplifies the modeling effort and facilitates the design optimization process.
Traction Separation Laws of Hydrogenated Grain Boundaries of Graphene
Authors: Elapolu Mohan S. R. , Tabarraei Alireza 
Published: February 2021

Abstract
Molecular dynamic simulations are conducted to understand the fracture properties of bicrystalline graphene sheets containing high angle grain boundaries. In our simulations, hydrogen atoms are adsorbed at the Stone–Wales defect on the grain boundaries. Hydrogenation of these defects alters the properties of grain boundaries. Using molecular dynamic modeling, the traction-separation laws of grain boundaries before and after hydrogenation are extracted. Our results show that the hydrogen adsorption site and hydrogen concentration are two factors which can significantly impact fracture toughness and strength of grain boundaries. Generally speaking, by increase in hydrogen concentration at the grain boundaries the fracture toughness and strength of the grain boundaries are reduced.
Lattice Boltzmann Model Simulation of Bubble Deformation and Breakup Induced by Micro-Scale Couette Flow
Authors: Atykhan Magzhan , Kabdenova (Dauyeshova) Bagdagul , Rojas-Solorzano Luis , Monaco Ernesto 
Published: February 2021

Abstract
Understanding the morphology of transformation of a single bubble immersed in a liquid undergoing a shear flow is essential in predicting bubble deformation and breakup phenomena commonly found in applications involving complex liquid-gas multiphase flow. In this study, the deformation and breakup of a single bubble released in a fully developed laminar Couette flow in a micro-scale domain are evaluated under different spanwise positions, as well as under different initial diameters. The simulation is carried out using a multiphase Shan-Chen Lattice Boltzmann Model (SC-LBM). The transition between deformation and breakup experienced by the bubble is described under different Capillary (Ca) numbers, viscosity ratios and relative initial spanwise positions with respect to the channel centreline. A critical Ca number, Cac = 0.31, was found at the onset of breakup, with bubble centroid location varying as a function of the remaining parameters. The results obtained with the SC-LBM are in excellent agreement with those published in the literature.
A Hybrid Methodology for Model-Based Probabilistic Resilience Evaluation of Dynamic Systems
Authors: Morozov Andrey , Diaconeasa Mihai A. , Steurer Mikael 
Published: February 2021

Abstract
Advanced classical Probabilistic Risk Assessment (PRA) effectively combines various methods for quantitative risk evaluation, such as event trees, fault trees, and Bayesian networks. PRA methods and tools provide the means for the qualitative reliability evaluation (e.g., cut sets) and the computation of quantitative reliability metrics (e.g., end states probabilities). Modern safety-critical systems from various industrial domains tend toward a high level of autonomy and demand not only reliability but also resilience, the ability to recover from degraded or failed states. The numerical resilience analysis of such dynamic systems requires more flexible methods. These methods shall enable the analysis of the systems with sophisticated software parts and dynamic feedback loops. A suitable candidate is the Dual-graph Error Propagation Model (DEPM) that can capture nontrivial failure scenarios and dynamic fault-tolerance mechanisms. The DEPM exploits the method for the automatic generation of Markov chain models and the application of probabilistic model checking techniques. Moreover, the DEPM enables the analysis of highly-customizable system resilience metrics, e.g., “the probability of system recovery to a particular state after a specified system failure during a defined time interval.” In this paper, we show how DEPM-based resilience analysis can be integrated with the general PRA methodology for resilience evaluations. The proposed methodology is demonstrated on a safety-critical autonomous UAV system.
Algorithm-Based Support for the Redesign of Product Variants
Authors: Redeker Julian , Gebhardt Philipp , Vietor Thomas 
Published: February 2021

Abstract
Incremental Manufacturing is a novel manufacturing approach where product variants are manufactured based on a finalization of pre-produced parts through additive and subtractive manufacturing processes. This approach allows a multi-scale production with the possibility to scale product variants as well as the production volume. In order to ensure high economic efficiency of the manufacturing concept, there is a need for pre-produced parts that come as close as possible to the final variant geometries to ensure that only variant-specific features need to be added by additive or subtractive manufacturing steps. Furthermore, to ensure high economies of scale, a high degree of commonality should be ensured for the pre-produced parts manufactured in mass production. In this context, a graph-based method is developed that enables an automated analysis of product families, based on physical and functional attributes, for standardization potentials. The method thus provides support for the strategic definition of pre-produced parts and is embedded in an overall approach for the redesign of products for Incremental Manufacturing. For the demonstration of the approach, which is based on 3D Shape and Graph Matching methods, a first case study is carried out using a guiding bush product family as an example.
Analysis of Lithium-Ion Battery Cap Structure and Characterization of Venting Parameters
Authors: Li Weisi , Crompton K. R. , Hacker Christopher , Ostanek Jason 
Published: February 2021

Abstract
Lithium-ion batteries are a proven energy storage device which continue to gain market share across a wide range of applications. However, the safety of these devices is still a major factor in many applications. In failures which result in thermal runaway, a series of chemical reactions are initiated which produce a large quantity of gas and heat. The pressure and temperature inside the battery rise sharply and may cause fire or explosion. The lithium-ion battery vent cap is a key safety device used in 18650 format cells to prevent an energetic failure of the metal casing. In this paper, the cap structure and venting parameters of three cap designs are analyzed. The venting parameters investigated were the open flow area and discharge coefficient. Open flow area through different components of the cap assembly were measured using 3D x-ray scans. A new experimental apparatus was used to measure mass flowrate and pressure ratio across the battery cap, which allowed calculation of discharge coefficient. Results indicate that discharge coefficients follow the same trend as a sharp-edged orifice, albeit at a reduced magnitude due to the more tortuous flow path. A semi-empirical model is proposed to simulate mass flow through the battery cap.