bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quaternion-Based Control of Acrobatic Quadrotor With Trajectory Following
Authors: Liu Haowen , Yang Bingen 
Published: February 2021

Abstract
For an unmanned aerial vehicle (UAV), its navigation in terrains can be quite challenging. To reach the destination within the required time, the maneuver of the quadrotor must behave aggressively. During this aggressive maneuvering, the quadrotor can experience singularities in the yaw-direction rotation. Thus, it is essentially important to develop a mathematical model and control method that can avoid singularities while enabling such an aggressive maneuver. In our previous effort, we demonstrated a vertical loop aggressive maneuver performed by a quadrotor UAV, which utilizes the controlled loop path following (CLPF) method. As found in this work, conventional modeling and tracking control method may not be good enough if specific requirements, such as fast coasting speed and sharp turns, are imposed. The numerical simulation by singularity-free modeling and the CLPF method enables a quadrotor to be operated in aggressive maneuverability with features like automatic flipping and precise trajectory following. The current research extends the maneuverability of a quadrotor by using a different and more capable control approach. More complex trajectories are used to test this new control method.
In this paper, a quadrotor is used to demonstrate the capability of the proposed control method in delivering an aggressive and singularity-free maneuver. A quaternion-based mathematical model of the quadrotor is derived to avoid the singularities of rotation during the aggressive maneuvers. At the same time, a new control method, namely the full quaternion differential flatness (FQDF) method, is developed for quadrotors to combat the requirement of a fast maneuver in three-dimensional space. The FQDF method, which makes use of full quaternion modeling and differential flatness, enables the quadrotor to react to the reference trajectory timely and to exhibit aggressive rotation without any singularity. Also, the singularities resulting from the heading direction can be resolved by a new algorithm. The FQDF method is compared with the reference literature’s methods and is tested in different trajectories from the ones in the previous studies. The numerical simulation demonstrates the aggressive maneuverability and computational efficiency of the proposed control method.
Parametric Resonance of a Beam Structure Induced by Groups of Oscillators in Periodic Movement
Authors: Gao Hao , Yang Bingen 
Published: February 2021

Abstract
Flexible structures carrying moving subsystems have various engineering applications, including cable transport, fast transit systems, and weapon systems. In some applications, the vibration of the supporting structure induced by successively moving subsystems can become significant and develop into parametric resonance. In study of the parametric resonance caused by moving subsystems, a conventional approach is to model subsystems as moving concentrated external loads, which leads to traditional resonance due to periodic excitation. In this paper, with consideration of the inertia effect and flexible coupling of subsystems, parametric resonance of a beam structure induced by groups of oscillators moving over it is investigated. Through a special formulation of sequential state equations, dynamic stability of the beam structure is predicted by eigenvalues of a time-domain mapping matrix. From numerical simulation, it shows that apart from the speed of oscillators that directly determines the characteristic period, the inertia and stiffness of the oscillators can also alter the parametric resonance conditions. This phenomenon cannot be captured with the conventional moving load assumption.
A Perspective on Tribology and Design
Authors: Suh Nam Pyo 
Published: February 2021

Abstract
Tribology — the science and engineering of friction, wear, and lubrication — enables the design of engineered systems with moving parts to achieve its intended functions. Many systems are so well designed already that they work as expected without requiring much attention, most of the time. However, when a system fails because of tribological problems, we may have a major disaster that may bring down the entire system, such as vehicles, engines, machinery, and even factories. Fortunately, the field of tribology has so far advanced, though often empirically, that many systems usually perform well. For instance, commercial airplanes are airborne for days without maintenance; windmills in the middle of the sea produce electricity for years; the tires of automobiles now last much longer than they used to, and machine tools make products for many months with minimal maintenance. Yet, there are still many unsolved tribology problems that require solutions. The ultimate goal of a tribological system is a life-time operation without any failure.
The quality of design determines the performance of tribological systems. Tribological failures of the system may be avoided through rational and creative design. In that sense, there is a symbiotic relationship between tribology and design. Many tribology problems encountered are often the result of poor system design. By properly designing the tribological system, potential failures caused by friction and wear can be avoided or minimized. Continuous testing of poorly designed tribological systems, which occurs in some cases, can be costly and with no noticeable improvements in the system performance. Since well-designed products yield immense benefits, the creation of tribological systems based on rational design should be pursued. The biggest source of tribological problems is the coupling of the functional requirements (FRs) that are introduced in the early stages of design. Attempts should be made to eliminate coupled tribological systems to improve their performance.
Reduced Order Model for Efficient Engineering Analysis
Authors: Zhong Allan X. , Zhang Haoyue 
Published: February 2021

Abstract
Engineering analysis of complex structures or mechanical systems typically involves contact with multiple components, large deformation, and material nonlinearity, which requires the application of nonlinear finite element methods. Despite the advancement of commercial software for finite element analysis (FEA), nonlinear FEA of a multi-component mechanical assembly will take hours to days, and even weeks to complete. It is highly desired to develop a reduced-order model for a family of complex structures that can reduce an original problems’ complexity and degree of freedom but has a reasonably small discrepancy with the full model and significantly reduces the computation time.
The typical approach to construct a reduced model includes 1) the response surface method via numerical design of experiments and, 2) the simplified physics approach. In this paper, it is proposed to develop a reduced model through the combination of simplified physics, dimensional analysis [1], and numerical design of experiments. The approach is applied to the construction of a reduced model for the analysis of a downhole plug [2]. The developed reduced model is verified by full-scale FEA models and validated through physical tests. The reduced model is implemented in a spreadsheet and takes only seconds to complete a calculation in contrast to hours using a full FEA model, enabling engineers’ quick evaluation of the corresponding designs.
Biomechanical Analysis of the Sensitivity of Brain Tissue Responses to FE Head Models in the Study of Impact-Induced TBI
Authors: Moghaddam Hesam S. , Rezaei Asghar , Ziejewski Mariusz , Karami Ghodrat 
Published: February 2021

Abstract
A numerical investigation is conducted on the injury-related biomechanical parameters of the human head under blunt impacts. The objective of this research is twofold; first to understand the role of the employed finite element (FE) head model — with its specific components, shape, size, material properties, and mesh size — in predicting tissue responses of the brain, and second to investigate the fidelity of pressure response in validating FE head models. Accordingly, two independently established and validated FE head models are impacted in two directions under two impact severities and their predicted responses in terms of intracranial pressure (ICP) and shear stress are compared. The coup-counter ICP peak values are less sensitive to head model, mesh size, and the brain material. In all cases, maximum ICPs occur on the outer surface, vanishing linearly toward the center of the brain. Hence, it is concluded that different head models may simply reproduce the results of ICP variations due to impact. Shear stress prediction, however, is mainly affected by the head model, direction and severity of impact, and the brain material.
Medium Frequency Vibration Analysis of Beam Structures Modeled by the Timoshenko Beam Theory
Authors: Zhang Yichi , Yang Bingen 
Published: February 2021

Abstract
Vibration analysis of complex structures at medium frequencies plays an important role in automotive engineering. Flexible beam structures modeled by the classical Euler-Bernoulli beam theory have been widely used in many engineering problems. A kinematic hypothesis in the Euler-Bernoulli beam theory is that plane sections of a beam normal to its neutral axis remain normal when the beam experiences bending deformation, which neglects the shear deformation of the beam. However, as observed by researchers, the shear deformation of a beam component becomes noticeable in high-frequency vibrations. In this sense, the Timoshenko beam theory, which describes both bending deformation and shear deformation, may be more suitable for medium-frequency vibration analysis of beam structures.
This paper presents an analytical method for medium-frequency vibration analysis of beam structures, with components modeled by the Timoshenko beam theory. The proposed method is developed based on the augmented Distributed Transfer Function Method (DTFM), which has been shown to be useful in various vibration problems. The proposed method models a Timoshenko beam structure by a spatial state-space formulation in the s-domain, without any discretization. With the state-space formulation, the frequency response of a beam structure, in any frequency region (from low to very high frequencies), can be obtained in an exact and analytical form. One advantage of the proposed method is that the local information of a beam structure, such as displacements, bending moment and shear force at any location, can be directly obtained from the space-state formulation, which otherwise would be very difficult with energy-based methods. The medium-frequency analysis by the augmented DTFM is validated with the FEA in numerical examples, where the efficiency and accuracy of the proposed method is present. Also, the effects of shear deformation on the dynamic behaviors of a beam structure at medium frequencies are illustrated through comparison of the Timoshenko beam theory and the Euler-Bernoulli beam theory.
A Proposed Method for Generating Lifetime Failure Data for Manufacturing Equipment: Validation With Bearings
Authors: Wescoat Ethan , Mears Laine 
Published: February 2021

Abstract
Digitization of manufacturing allows modeling and diagnosis of equipment failure, but training such systems is difficult without observations of failed states. This paper presents a method whereby failure data, from the baseline to the destruction case, is methodically generated to train machine health models. Creating failure classifiers and predictive models of manufacturing equipment suffer from two problems: training-data accuracy and data representation of lifetime machine failure modes of both components and systems. The Purposeful Failure Method aims to generate defect training data at both the component and system level, from initial defect to final destruction. Bearings are a validation case and are monitored from a healthy baseline state to a maximum-damage state by applying artificial damage. Bearings are used for validating the method, due to prior knowledge of failure progression, as well as their prevalent use. The generated data were analyzed to see if they matched expected failure phenomena. Preliminary results with the Purposeful Failure Method show promise for generating failure data for machine health models; continued work on validating the method on other components is justified.
Crash Analysis and Characterization of Bio Organic Fillers in the BFRP/Epoxy Composites
Authors: Velukkudi Santhanam Senthil Kumar , Sukumar Pullayikodi Srinil , Sampath Prakash , Doraiswamy Viswanathan , Manickam Dhanashekar 
Published: February 2021

Abstract
Basalt fiber/polymer composites have extensive applications in automotive, aerospace, defense, and sports goods. Addition of ash fillers has enhanced the properties of the composite material. Two types of bio-ash fillers namely, rice husk ash (RHA) and coconut fiber ash (CFA) particles were used. Ashes obtained from rice husk and coconut fiber are a good source of silica which when heated at higher temperature make them good fillers. Hand lay-up technique was used to fabricate composites in rectangular column shapes.
Characterization study of ash particles incorporated polymer composites were made by subjecting it to X-ray diffraction (XRD) measurement. The presence of filler particles reduces the voids ratio and enhances the strength of the composites. The load vs. displacement relations of the composite specimens were obtained from low velocity compression tests. Crashworthiness parameters like maximum force, average force and energy absorption were derived from the compression test results. Properties of plain basalt fiber composites were compared with that of BFRP/Epoxy composites with RHA and CFA fillers incorporated composites. The conclusion drawn from the test results was that the addition of ash filler particles in the composite have an improvement in crashworthiness of BFRP/Epoxy composite.
Developing a Thermally Actuated Soft Robot for Finger Rehabilitation
Authors: Taylor Mark , Westra Kees , Han Yen-Lin 
Published: February 2021

Abstract
As more Americans suffered from mobility impairments, rehabilitation becomes more and more important. Using robots for rehabilitation could potentially lower the barriers of rehabilitation for patients in need and increase the effectiveness of rehabilitation. This paper presented a proof-of-concept soft robot that could be used for finger rehabilitation. This soft robot can bend with heat-induced actuation without many external components. In this soft robot design, a phase changing material (PCM) is sealed in reservoirs inside an elastomer structure. As heat applied, the PCM begins to change phase from solid to liquid and the pressure inside the sealed reservoirs increases and “pushes” the elastomer structure to a different shape to create a “movement” of the robot. Depending on the locations of the reservoirs and methods the heat applied, the movements of the soft robot can be controlled with precision. Preliminary results successfully demonstrated a basic bending motion of this soft robot that mimics the human finger movement.
Effect of Thickness on Tube Deformation Mechanics During Low Pressure Tube Hydroforming Process Sequence Variation
Authors: Nikhare Chetan P. 
Published: February 2021

Abstract
A rapid increase in fuel consumption has been seen due to a sudden increase in the usage of automotive vehicles. This results in an increase in air pollution. Due to which a stricter regulation applied by the federal government to decrease air pollution. To escape from the pollution penalty innovations are been pushed. The industry has been looking at many innovative manufacturing processes like electric assisted manufacturing, single point incremental forming, high-speed forming, and many. All these innovative processes promise more uniform deformation and increases formability in the part. One such process is tube hydroforming for tubular parts. Tube hydroforming is the successful manufacturing process to create a variety of shapes using fluid pressure. The fluid medium can be water with preventive additives, oil, or viscous liquid. In this process, the tube was filled with the fluid medium and further pressurized to deform to various shapes. Tube hydroforming is categorized into three types: high pressure, pressure sequencing and low-pressure tube hydroforming. Ferrous and non-ferrous metals are formed using these processes. Due to uniform thinning in the formed part, the parts can be lower weight and thus proven to be the technology to create light-weight parts for automotive and aerospace industries to increase the fuel economy. Tube hydroforming has gained popularity due to its many advantages such as part consolidation, quality of the formed part and the possibility of unique shapes with indents or angles. This paper focuses on low-pressure tube hydroforming. In low-pressure tube hydroforming, during the closing of the die the tube is marginally pressurized to a fixed volume. The previous study which was published in IMECE2019 was focused on investigating the deformation mechanics of the tube due to variation in the process sequence during low-pressure tube hydroforming. In the second part of this research focus on how the thickness of the tube affect the deformation mechanics in the variation of the process sequence during low-pressure tube hydroforming. The circular tube was formed in a square shape. The four sides of die edges were considered as individual edges and the motion of these edges will be varied to achieve the final shape. The deformation mechanics in each condition was presented and analyzed. The relative thickness and strain distribution were studied. The change of tube profile pattern from the start to the end of the process were presented and compared. It was found that the deformation mechanics was mostly influenced by the variation of movement by punch and die side with no internal pressure case. The buckling in the tube wall also depended on which side of the die moves to deform the tube.
A Numerical Study of Laminar and Intermittently Turbulent Boundary Layer on an Oscillating Flat Plate Using Pseudo-Compressible RANS Model
Authors: Srivastava Shivank , Taravella Brandon M. , Akyuzlu Kazim M. 
Published: February 2021

Abstract
A numerical study was conducted to study the unsteady characteristics of incompressible boundary layer flows over an oscillating flat plate under laminar and intermittently turbulent flow conditions using pseudo-compressible Reynolds Averaged Navier-Stokes (RANS) model. The numerical study is carried out using an in-house code and a commercial CFD package (Fluent). Two equation (k-ε) turbulence closure model, modified near the wall, is used along with RANS equations to simulate intermittently turbulent flows. Fully Explicit-Finite Difference technique (FEFD) is employed to solve the governing differential equations. For validation purposes, the velocity fields predicted by the in-house code and commercial CFD package are compared to the one given by analytical solution to Stokes’ second problem for an oscillating flat plate. Numerical experiments were conducted for unsteady cases for Stokes’ Reynolds number corresponding to laminar and intermittently turbulent flows, respectively. Time dependent velocity profiles, shear stress distribution, turbulence properties during the accelerating and decelerating stages of oscillations are predicted. The above predictions are then compared to ones predicted by commercial CFD code. The velocity magnitudes predicted by the in-house code and commercial CFD code are within acceptable range for laminar and intermittently turbulent flow conditions.
A Finite-Element Based Framework for Transient Rotor Dynamic Simulations
Authors: Rajagopal Anurag , Mandal Dilip K. 
Published: February 2021

Abstract
Transient simulations play a key role in the analysis and subsequent design of structural components with one or more rotating parts. A framework is proposed to this effect, centered around the finite-element solver OptiStruct, consisting of a time integration scheme built on the Newmark family with an appropriate adaptive time-step control. The process accounts for a computationally efficient handling of nonlinearities that might arise through bearings and casings. This solution is detailed starting from the governing equations for transient rotor dynamics to the nuances of the time marching scheme, and this process is applied to a test case from which conclusions are drawn that might be of interest to practicing engineers. These conclusions include insights into enforced motion, operation at or near critical speeds, rotor damping and contact. This work is aimed at producing a user-friendly and robust tool and process for the practicing engineer to perform complex rotor dynamic analysis.
Unreinforced Flat Oval Duct Deformation Testing and Modeling
Authors: Paruchuri Avinash , Liu Jane , Idem Stephen 
Published: February 2021

Abstract
Unreinforced 12 in. × 23 in. (305 mm × 584 mm) galvanized steel flat oval ducts were tested to measure deformations when internal static gauge pressures were applied. The experiments were performed on spiral seam non-corrugated duct. Finite element models with discrete ring seams and an average wall thickness approach were utilized to represent the continuous spiral seam, and therein predict duct deflections at prescribed locations along the duct wall. Predicted deflections from the finite element models were tabulated and compared to experimental data. Satisfactory agreement between model predictions and test data were obtained from a non-linear finite element analysis that employed a simplified average wall thickness to characterize the spiral seam and duct wall. It is straightforward to implement the average wall thickness methodology in finite element modeling of duct deformation.
Design of a Compliant Jumping Robot With Passive Stabilizer
Authors: Hooper Joshua , Garcia Martin , Pena Paul , Tekes Ayse 
Published: February 2021

Abstract
This study presents the design and development of a compliant multi-link hopping mechanism actuated by a single DC motor. Two main design goals are to have a single piece designed main body for the jumping robot and a passive stabilizer to allow consecutive jumps. Mechanism consists of monolithically designed large deflecting main body incorporating the gears and initially curved flexure hinge. Due to the limitations of the design goal, revolute motion between top and bottom legs on the main body are realized by a compliant link which replaces the need of ball bearings. Also, continuous energy store and release during jumping is ensured by the same flexure hinges. Passive self-righting cage is attached to the bottom of the main body to maintain upright position both in landing and takeoff. The cage allows the center of mass to stay in the vertical plane to prevent tilting. During landing, cage absorbs the impact and allows the main body to roll to its initial configuration so that the robot can complete jumping. Mechanism parts including the cage are 3D printed using PETG. Design optimization of the body parts including the rigid legs and flexure hinges are analyzed both experimentally and analytically. Finite element analysis is performed to calculate the equivalent stiffness and natural frequency of the jumping robot and simplified mathematical model is derived using rigid body dynamics.