bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics Characterization of Paquitop: A Novel Platform for Robotized Domestic Applications
Authors: Carbonari Luca , Botta Andrea , Cavallone Paride , Tagliavini Luigi , Quaglia Giuseppe
Published: February 2021

In the last decades, an unprecedented decrease in fertility and mortality rates in industrialized countries yielded a general ageing of the population. Such phenomenon affected the everyday life of individuals as well as organizations, either government or private, to the point that they are nowadays seeking the solution to the increasing demand of health care, housing, care-giving, and social security. In this scenario, this piece of research aims to fulfil a design task, specifically oriented towards the field of assistance machines. The functionalities which should be guaranteed are mainly two: to follow and monitor reduced mobility subjects, to maintain a constant view contact with its targets, and to accomplish such duties in a non-structured and possibly peopled environment. In particular, the paper analyses the dynamics of Paquitop, a novel over-actuated mobile platform, aiming for a proper design strategy for its suspensions system. The main peculiarity of the robot is that of owning an innovative architecture expressly conceived to enhance the performance offered by the present-day solutions for omni-directional planar motions. Given its purpose, the robot architecture was thought for guaranteeing an effective fulfilment of its primary tasks. This arises a set of uncharted challenges, under both mechanical and control points of view.
Friction Surfacing From Radial Surface of A6063 Aluminum Alloy Consumable Tool Onto A36 Carbon Steel
Authors: Seidi Ebrahim , Miller Scott F.
Published: February 2021

Friction surfacing is an advanced technique to create solid-state deposition of wide range of materials onto a similar or dissimilar material substrate. This paper describes the study of a novel method to deposit material onto a substrate by friction surfacing. In the friction surfacing technique, the heat is generated entirely by friction. This metallic deposition technique consists of a rotating consumable tool that rubs against the surface of the substrate, and due to the frictional heat and forging generated between the tool and substrate, material is deposited onto the substrate. The material transferred from the consumable tool to the substrate occurs from the side of the tool, while in the conventional friction surfacing method, the material transfer happens from the end of the tool. In this investigation, the single and double-pass deposition of A6063 aluminum alloy onto an A36 carbon steel substrate was successfully carried out. To study the influence of the process parameters on the friction depositions, the substrate was divided into three sections, while the applying forces were varied in each section. Process parameters such as tool rotational speeds, table traverse speeds and normal force were experimented. A customized JET JMD-18 milling machine was used to carry out the experiments. The influence of process parameters on the material deposition was characterized by means of roughness tester and optical microscope. The results of the study reveal that this novel method is capable to create an ultra-thin and smooth metallic deposition with excellent coverage. The material consumption during the single and double-pass deposition was evaluated, and the coating cross-section was assessed using the optical microscope.
Edge Forces in Metal Cutting: Fundamental Analysis and Experimental Verification
Authors: Al Aridi Rimah S. , Baydoun Ahmad M. R. , Hamade Ramsey F.
Published: February 2021

In metal cutting, some of the generated forces do not contribute to chip formation. These forces are referred to as plowing forces and are induced mainly as result of the finite sharpness of the tool (cutting edge radius) and the tool’s land (flank). Determining the magnitude of these forces is essential to developing a better understanding of the mechanics and physics of applications that involve cutting at minimal feed values (e.g., micro-machining and vibration-assisted-micro-machining. It is well recognized that plowing forces increase with tool wear. This research estimates these forces by employing analytical and numerical simulations. An extensive experimental analysis is utilized to verify the simulated values of the plowing forces. The experimental verification is designed to measure these forces as a function of several cutting parameters. The developed methodology relates the plowing forces to geometric factors and process parameters such as cutting-edge radius, tool feed, and cutting speed.
A Spectral Correlation Based Nonlinear Ultrasonic Resonance Technique for Fatigue Crack Detection
Authors: Wang Junzhen , Shen Yanfeng
Published: February 2021

This paper presents a spectral correlation based nonlinear ultrasonic resonance technique for fatigue crack detection. A reduced-order nonlinear oscillator model is initially constructed to illuminate the Contact Acoustic Nonlinearity (CAN) and nonlinear resonance phenomenon. The tailored analytical model considers the rough surface condition of the fatigue cracks, with a crack open-close transition range for the effective modeling of the variable-stiffness CAN. Multiple damage indices (DIs) associated with the degree of nonlinearity of the interrogated materials are then proposed by correlating the ultrasonic resonance spectra. The frequency sweeping signals serve as the excitation waveform to obtain the structural dynamic features. The nonlinear resonance procedure is numerically solved using the central difference method. Short time Fourier transform (STFT) is utilized to extract the resonance spectroscopy. In this study, pristine, linear wave damage interaction case (an open notch case), and nonlinear wave damage interaction case (a fatigue crack case) with various damage severities are considered. Subsequently, three case studies taking advantage of different nonlinear oscillation phenomena are conducted based on the spectral correlation algorithm to detect and monitor the fatigue crack growth: time-history dependence, amplitude dependence, and breakage of superposition. Each of these three nonlinear behaviors can either work individually or collaborate synthetically to detect the nucleation and growth of the fatigue cracks. The proposed nonlinear ultrasonic resonance technique possesses great application potential for fatigue crack detection and quantification. This paper finishes with summary, concluding remarks, and suggestions for future work.
Effect of End Rubber Gasket on the Performance of Parabolic Leaf Spring
Authors: Zhang Junhong , Long Feiqi , Jia Hongjie , Lin Jiewei
Published: February 2021

Leaf springs play an important role in the handling stability and ride comfort of vehicle. End rubber gaskets are widely used to reduce the friction between leaves, but they also have considerable effect on the stiffness of the suspension assembly. The ride comfort may deteriorate with the stiffness of leaf spring changes. In this paper the influence of the end rubber gasket on the static stiffness performance of a parabolic leaf spring is studied. A finite element model of the leaf spring is developed and verified against the static stiffness test. Effects of the end rubber gasket parameters on the static stiffness of the leaf spring are analyzed based on an orthogonal experiment. The sensitivities of the five parameters are identified including the width, the length, the end thickness, the tail thickness and the distance to the end of the middle leaf. It is found that the contributions can be ranked in descending order as the tail thickness, the end thickness, the distance from end rubber gasket to the end of Leaf 2, and the width and length. The first two factors are considered of significant effects on the leaf spring stiffness. According to single-factor analysis, it is found that under the same load, as the tail thickness and the end thickness increase, the maximum deformation of the rubber gasket decreases, the stiffness of the rubber gasket increases, and the stiffness of the leaf spring increases, which provides a reference for the forward design of the end rubber gasket and the stiffness matching of leaf springs.
Squeak and Rattle Prevention by Geometric Variation Management Using a Two-Stage Evolutionary Optimisation Approach
Authors: Bayani Mohsen , Wickman Casper , Lindkvist Lars , Söderberg Rikard
Published: February 2021

Squeak and rattle are annoying sounds that often are regarded as the indicators for defects and quality issues by the automotive customers. Among the major causes for the generation of squeak and rattle sounds, geometric variation or tolerance stack-up is a key contributor. In the assembly process, the dimensional variation in critical interfaces for generating squeak and rattle events can be magnified due to tolerance stack-up. One provision to manage the tolerance stack-up in these critical interfaces is to optimise the location of connectors between parts in an assembly. Hence, the focus of this work is to prevent squeak and rattle by introducing a geometric variation management approach to be used in the design phase in the automotive industry. The objective is to identify connection configurations that result in minimum variation and deviation in selected measure points from the critical interfaces for squeak and rattle. In this study, a two-stage evolutionary optimisation scheme, based on the genetic algorithm employing the elitism pool, is introduced to fine-tune the connectors’ configuration in an assembly. The objective function was defined as the variation and the deviation in the normal direction and the squeak plane. In the first stage, the location of one-dimensional connectors was found by minimising the objective function in the rattle direction. In the second stage, the best combination of some of the connectors from the first stage was found to define planar fasteners to optimise the objective function both in the rattle direction and the squeak plane. It was shown that by using the proposed two-stage optimisation scheme, the variation and deviation results in critical interfaces for squeak and rattle improved compared to the baseline results.
Research on Fire Resistance of Stainless Steel Car Body Floor Structure in Urban Rail Vehicles
Authors: Jia Na , Zhang Haifeng , Liu Xiaofang , Cai Mingjun
Published: February 2021

At present, the fire performance of vehicles is highly concerned in domestic and international rail transit market projects [1], where the fire performance of the vehicle’s underframe is a crucial factor that restricts the fire safety of the entire rail vehicle. How to improve the fire resistance of vehicle underframe structure has become the focus and difficulty of vehicle fire engineering [2]. This article introduces main international fireproof standards applicable for urban rail vehicles. Then, based on the typical underframe structures of urban rail vehicles stainless steel body, three refractory structure models on different underframe structures are established by using different fireproof insulation materials as underframe fillers. Moreover, fire resistance tests are conducted on samples of three underframe models to verify the effectiveness of those fire performance. As per the fire test results, the crucial indexes such as heat insulation, fire resistance, temperature rise curve, fire resistance time and material cost of different filler insulation materials are compared and summarized. Finally, the standardized and modular design specification is suggested on refractory underframe structures in urban rail vehicles.
A Compound Recoil-Compensated Chamber Design for Free-Fall Absolute Gravimeters
Authors: Wen Yi , Wu Kang , Guo Meiying , Wang Lijun
Published: February 2021

The ballistic free-fall absolute gravimeters are most commonly-used instruments for high-precision absolute gravity measurements in many fields, such as scientific research, resource survey, geophysics and so on. The instrumental recoil vibrations generated by the release of the test mass can cause troublesome systematic bias, because these vibrations are highly reproducible from drop to drop with coherent phase. A compound counterbalanced design of chamber using both belt-driven mechanism and cam-driven structure is proposed in this paper. This structure is designed to achieve excellent recoil compensation as well as long freefall length for high precision measurements. Simulation results show that the recoil vibration amplitude of the compound recoil-compensated structure during the drop is about 1/4 of that with only belt-driven counterbalanced structure. This confirms the feasibility and superiority of the new design. And it is believed that the absolute gravimeter based on this newly proposed chamber design is expected to obtain more precise gravity measurement results in the future.
Second Modified Student Presentation Based Effective Teaching (SPET) Method Tested in COVID-19 Affected Senior Level Mechanical Engineering Course
Authors: Tyagi Pawan
Published: February 2021

Student presentation based effective teaching (SPET) approach was designed to engage students with different mindsets and academic preparation levels meaningfully and meet several ABET student learning outcomes. SPET method requires that students prepare themselves by guided self-study before coming to the class and make presentations to teach the whole class by (a) presenting complex concepts and systems appealingly and engagingly, and most importantly (b) serving as the discussion platform for the instructor to emphasize on complex concepts from multiple angles during different presentations. In class, SPET presentations address the conceptual questions that are assigned 1–2 weeks before the presentation day. However, the SPET approach becomes impractical for large class sizes because (i) during one class period all the students can not present, (ii) many students do not make their sincere efforts. This paper focuses on the second modification of SPET to make it practical for large classes. The method reported in this paper was tested on MECH 462 Design of Energy System Course. Unlike the first modified approach, all the students were expected to submit the response to the preassigned questions before coming to the class. In class, SPET group presentations were prepared by the group of 3–6 students, who prepared themselves by doing SPET conceptual questions individually. Students communicated with each other to make a cohesive presentation for ∼30 min. In two classes per week, we covered 5–6 group presentations to do enough discussions and repetition of the core concepts for a more in-depth understanding of the content. During the presentation, each student was evaluated for (a) their depth of understanding, (b) understanding other parts of the presentation covered by other teammates, and (c) quality of presentation and content. The student who appeared unprepared in the class group presentation were provided direct feedback and resources to address concerning areas. SPET approach was applied in the online mode during the campus shut down due to COVID-19. SPET was immensely effective and helped to complete the course learning outcomes without interruptions. SPET could be customized for the online version without any additional preparation on the instructor part.
Nanoscale Interphase Characterization of Porous CNT Buckypaper Composites in Correlation to Interlaminar Mode I Fracture
Authors: Yekani Fard Masoud , Mester Jack , Pensky Alek
Published: February 2021

In this conference paper, nanoscale material property data and ASTM mode I interlaminar fracture results for three-phase buckypaper samples are presented and analyzed. Vacuum filtration and surfactant-free methods were used to manufacture buckypaper membranes. Epoxy infused buckypaper membranes were placed in front of the crack tip in a stitch bonded carbon fiber polymer matrix composite. Peak Force Quantitative Nanomechanical Mapping (PFQNM), using probes with nominal tip radius in the range of 5–8 nm were used. PFQNM characterized the interphase region between a three-phase sample of carbon monofilament, epoxy resin, and multi-walled carbon nanotube (MWCNT) buckypaper. This experiment captured reproducible nanoscale morphological, viscoelastic, elastic and energy properties of porous MWCNT buckypaper samples. An enlarged interphase region surrounding the CNT buckypaper was found. The buckypaper and epoxy interphase thickness was found to be 50nm, higher than the 10–40nm reported for epoxy and carbon monofilaments. The observed MWCNT structure provides explanation of the increased surface roughness compared to the smooth carbon monofilaments. The increased surface roughness likely improves mechanical interlocking with the epoxy of adjacent lamina. The nanoscale interphase and subsurface characterization data provide explanation for a change in crack propagation toughness. Buckypaper exhibited inhomogeneous properties at micrometer length scales.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Implementing a Novel Framework to Create Tacit Knowledge Models to Support Human-Robot Interactions
Authors: Guerra-Zubiaga David A. , Nasajpour-Esfahani Navid , Siddiqui Basma , Kamperman Kevin
Published: February 2021

While it is not only important to synthesize instruments, controls, and robotics, it is also essential to connect these elements to people to achieve the future of automation. Whether in an operating room with surgical robots or in an earthquake disaster zone where an operator is aided by search and rescue drones, interaction between machines and humans is becoming central to increasing productivity. Industry 4.0 trends such as Internet of Things (IoT) and digital manufacturing are the early adopters of human-machine interfaces that support manufacturing automation. Such models must consider various aspects of process implementation such as explicit, implicit, and tacit knowledge to properly mimic a human’s performance. However, most inquiries in this field use expressed information instead of tacit knowledge due to an unfulfilled need for an industrial tacit knowledge framework. Tacit knowledge is difficult to learn and transfer if an operator’s logic is never revealed. In response, this research provides a knowledge model to structure, categorize, and reuse tacit knowledge for advanced manufacturing operations. The model is implemented in a human-robot interaction by capturing valuable experiences using digital tools such as Tecnomatix for further reuse in a variety of industrial applications.
Estimation of High-Frequency Vibration Loads in Deep Drilling Systems Using Augmented Kalman Filters
Authors: Ichaoui Mohamed , Ostermeyer Georg-Peter , Tergeist Mathias , Hohl Andreas
Published: February 2021

Deep drilling operations are primarily used to produce oil, gas, and geothermal heat from reservoirs in the earth’s crust. A drill string built of thread-connected components is used to transfer mechanical energy from a drill rig on the surface to a drill bit at the bottom end. The lowest part of a drill string, which is called bottom-hole assembly (BHA), contains sophisticated sub-assemblies for process and trajectory control, formation evaluation, surface communication, power generation, and system diagnostics.

The BHA can experience critical vibrations without indication further up to the string. These vibrations need to be closely monitored for process control, fatigue management, and design feedback. However, the number of sensors is too small to provide reliable indication of loads on all critical components of the drill string. Adding sensors to each component is currently neither economically nor technically viable.

This paper presents an application of existing Kalman Filters, merging information from available sensors and dynamic models to obtain state estimates for all components of the BHA. The expected accuracy and limitations are discussed. The results of load extrapolation are confirmed by comparison with measurements proving the concept under inaccurately defined interaction with a downhole environment.
Impact Analysis of Honeycomb Core Sandwich Panels
Authors: Alam Shah , Khanal Damodar
Published: February 2021

The goal of this paper is to analyze the impact behavior among geometrically different sandwich panels shown upon impact velocities. Initially, composite model with aluminum honeycomb core and Kevlar (K29) face sheets is developed in ABAQUS/Explicit and different impact velocities are applied. Keeping other parameters constant, model is simulated with T800S/epoxy face sheets. Residual velocities, energy absorption (%), and maximum deformation depth is calculated for sandwich panel for both models at five different velocities by executing finite element analysis. Once the better material is found for face sheets, process is extended by varying the ratio of front face sheet thickness to back face sheet thickness keeping other geometrical parameters constant to find the better geometry. Also, comparison of impact responses of sandwich composite panel on different ratio of front face sheet thickness to back face sheet thickness is done and validated with other results available in literature.
Modeling and Design Optimization of Robotic Hoses for 3D Printing of Cement
Authors: Sterckx Peter , Walker Ian D.
Published: February 2021

Modeling tendon tensions for applications of tendon-actuated continuum robots under significant loading is necessary for sizing motors, tendons, and other components to ensure that the robot can safely support its mass during operation. While models exist that express tendon tensions as a function of continuum robot configuration, previously proposed models do not consider the effects of gravity on tendon tensions. In this paper, we discuss the addition of gravity to a static model previously developed for low-mass tendon-actuated continuum robots. Using the Euler-Lagrange methodology, the potential energy due to gravity is incorporated into the formulation of the equations that describe tendon tensions as a function of robot configuration. Preliminary experimental results reveal the potential of this nonzero-gravity tendon-tension model.
Heat Transfer and Melt-Pool Evolution During Powder-Bed Fusion of Ti-6Al-4V Parts Under Various Laser Irradiation Conditions
Authors: Rahman M. Shafiqur , Schilling Paul J. , Herrington Paul D. , Chakravarty Uttam K.
Published: February 2021

Laser Powder-bed Fusion (L-PBF) is a promising additive manufacturing (AM) process that is capable of speedily fabricating functional components typically used for aerospace, automotive, microelectronics, and biomedical applications. In this study, a 3-D computational fluid dynamics model with Ti-6Al-4V powder-bed is developed incorporating a moving conical volumetric heat source and thermophysical properties of Ti-6Al-4V alloy to conduct the simulations of the L-PBF process. The melt-pool dynamics and its thermal behavior are investigated numerically and results for temperature profile, cooling rate, variation in density, thermal conductivity, specific heat capacity, and enthalpy are obtained for different laser irradiation conditions. Simulation results show that the maximum temperature, dimensions, and liquid lifetime of the melt pool increase with the increase of the laser power and decrease of the scanning speed. A custom ytterbium fiber laser system is applied to perform laser melting experiments with a solid Ti-6Al-4V specimen. The microstructures of the cross-sectional areas are examined by a scanning electron microscope to observe the melt-pool dimensions and the heat-affected zones. Finally, the simulation results for melt-pool geometry are compared with the experimental results to validate the numerical model for the L-PBF process.