bluuebunny/crossref_metadata_2025 huggingface dataset:
Visualization of Bubble Dissolution As a Means to Measure Dissolved Nitrogen Concentration
Authors: Sato Taisuke , Yamashita Tatsuya , Ando Keita
Published: November 2019

In ultrasonic cleaning, violent cavitation bubble dynamics causes material damage to cleaning surfaces, which is called cavitation erosion. The control of the dissolved gas concentration in cleaning liquid is effective to avoid cavitation erosion. The dissolved oxygen (DO) concentration is easily measured by a commercial DO meter, but the dissolved nitrogen (DN) concentration in water where multiple gas species are dissolved cannot be accurately measured with a commercially available DN meter. Therefore, it is important to construct a new method of measurement of DN concentration. In this study, we visualize the diffusion driven dissolution of bubble in air-saturated water and degassed water. The Epstein-Plesset theory considering multiple gas species is derived and compared with the experimental result where the DN concentration is treated as a fitting parameter in order to estimate the unknown DN concentration. Results indicates that the DN concentration can be measured by comparison between the theory and the relatively slow dissolution of bubble.
Uncertainty Quantification of Molten Hafnium Infusion Into a B4C Packed-Bed
Authors: Schiaffino Arturo , Kotteda V. M. Krushnarao , Kumar Vinod , Bronson Arturo , Shantha-Kumar Sanjay
Published: November 2019

In the manufacturing of metal matrix composites (MMC), liquid-metal reactive infusion with a solid mesh or particles composed of ceramic or metal may be used. The objective of this study is to determine the uncertainty quantification of the modeling of liquid hafnium infusion to expedite the processing and improve properties of MMCs ultimately. Uncertainty quantification (UQ) characterized the uncertainty scientifically especially for high-performance computing with observed physics and/or chemistry of the phenomena and predicted from estimated parameters. In this work, molten hafnium infusing through a boron carbide packed bed is modeled to optimize the manufacturing of components used for a hypersonic vehicle. The creation of molten matrix composites by the infiltration of molten metal represents a formidable challenge to be accurately modeled. First, the structural randomness associated with porous mediums complicates the prediction of the flow passing through it. Secondly, the properties of the molten metal could vary inside our control volume, since the temperature inside the control volume is not constant. Also, there are several chemical reactions and solidification rates occurring in during the impregnation. Given the recent advances in high-performance computing, an in-house pore network simulator are implemented along with Dakota, an open-source, exascale software, to determine the optimal parameters (e.g., porosity and temperature) and uncertainty quantification for the modeling.
Suppression of Secondary Flows in a Transonic Centrifugal Compressor Impeller Using an Inverse Design Method Based on Meridional Viscous Flow Analysis
Authors: Ito Sasuga , Okada Shin , Kawakami Yuki , Manabe Kaito , Furukawa Masato , Yamada Kazutoyo
Published: November 2019

Secondary flows in transonic centrifugal compressor impellers affect their aerodynamic performance. In open-type impellers, low energy fluids can accumulate on the suction surfaces near the trailing edge tip side since the secondary flows and tip leakage flows interfere each other and complex flow phenomena can be generated around the impellers. Therefore, designers must consider the effect of secondary flows to avoid the aerodynamic performance degradation while designing compressor impellers. In this paper, a novel design concept about suppression of secondary flows in centrifugal compressor impellers to improve their aerodynamic performance. A transonic centrifugal compressor impeller was redesigned with the present design concept by a two-dimensional inverse method based on a meridional viscous flow calculation in this study.

A design concept was introduced in above calculation process. As the design concept, by bending vortex filaments with controlling peak positions of the blade loading distributions, induced velocity due to bound vortices at the blades was generated in radial opposite direction of the secondary flows on the suction surface.

Due to investigate the effect of the design concept in this paper, three-dimensional Reynolds Averaged Navier-Stokes simulations were carried out, and the vortex cores were visualized by a critical point theory and colored by non-dimensional helicity. In the conventional transonic centrifugal compressor impeller, the secondary flow vortices were confirmed and one of the vortices was broken down. In the redesigned impeller, the breakdown of the secondary flow vortices was not observed and the accumulation of the low energy fluids was suppressed compared with the conventional impeller. The total pressure ratio and adiabatic efficiency of the redesign impeller were higher than that of the conventional impeller, and the secondary flows were successfully suppressed in this research.
Experimental Study of Free-Surface Deformation and Cavitation Bubble Dynamics in a Megasonic Cleaning Bath
Authors: Katano Yu , Ando Keita
Published: November 2019

Underwater ultrasound causes various physical phenomena in megasonic cleaning baths, e.g. cavitation inception, bubble translation and free-surface deformation (FSD) due to acoustic radiation pressure. Because FSD is especially noticeable in the case of high frequency ultrasound due to its high directivity, it is essential to investigate the interaction between FSD and bubble translation in megasonic cleaning bath. In our present experiments, we construct a typical setup for megasonic cleaning and irradiate water with 1 MHz ultrasound vertically upwards. We visualize FSD and bubbles and analyze the height of FSD and the translational velocity in frequency space. The bubbles translate in both short and long time scales caused by bubble-bubble interaction and periodic FSD, respectively, and the latter has periodicity. The most dominant frequency component in FSD shows good agreement with that in the translational velocity of the bubbles and does not depend on whether cavitation occurs or not. Therefore, it is suggested that FSD causes periodicity of bubble translation.
Relationship Between Macroscopic Rheological Properties and Microstructure of a Dilute Suspension by a Two-Way Coupling Numerical Scheme
Authors: Fukui Tomohiro , Kawaguchi Misa , Morinishi Koji
Published: November 2019

The rheological properties of a suspension depend on particle shape, spatial arrangement of the particles and hydrodynamic interactions as well as the concentration of the particles. So far, we proposed a two-way coupling numerical scheme to evaluate the effects of particle rotation on the rheological properties. This particle rotation decreases the fluid resistance. However, these studies were conducted on the condition that suspended particles were homogeneously distributed. Therefore, the particles in this study are randomly scattered in a suspension for better practical applications. Pressure-driven suspension flow simulations were conducted to consider the effects of inertia on the relationship between spatial arrangement of the particles and the rheological properties of a suspension. The channel width and axial length were set 400 μm and 1620 μm, respectively, and periodic boundary conditions were applied in the flow direction. The rigid spherical particles whose diameter was 20 μm were randomly scattered in the channel as an initial condition. The concentration of the suspension was set 1.02% for dilute assumption, and the suspension flows with the Reynolds number from 2 to 128 were reproduced in order to investigate the inertial effects of the suspended particles on the rheological properties. The rheological properties of the suspension were evaluated in terms of power-law index (non-Newtonian index). The velocity profile of a suspension for low Reynolds number conditions exhibited almost parabolic. This indicates the suspension behaves as a Newtonian fluid. For higher Reynolds number conditions, on the other hand, the lift force on the particles increased and they migrated toward the equilibrium y-axis position, where the lift force is zero. These changes in the y-axis position of the particles caused a change in microstructure of the suspension, which were followed by a change in macroscopic rheological properties. Owing to these microstructure changes, the non-Newtonian (thixotropic) properties were enhanced as the Reynolds number increased.
The Spike Dynamics Source Model for Ejecta in the FLAG Code
Authors: Harrison Alan K.
Published: November 2019

The Lagrangian hydrocode FLAG employs a subgrid model to represent the ejection of particulate mass (“ejecta”) from a shocked metal surface. With a conforming mesh used in typical simulations, the calculations of ejecta production, properties and launch are carried out independently on each mesh face lying on the surface of the metal. Based on experimental evidence [1] that ejecta production is greatest when the shock releases to the liquid state, the ejection process is modeled as a Richtmyer-Meshkov instability (RMI) of the liquid metal surface, in which the metal spikes that form break up to become ejecta. The model applies to the case in which surface perturbations such as machining grooves can be well approximated as a single-mode sinusoidal perturbation; in this case the RMI spikes are actually sheets.

The FLAG model includes (1) a description of RMI spike and bubble growth rates [2] and (2) the Self-Similar Velocity Distribution (SSVD) model of the velocity field within a spike as varying linearly from zero (in the fluid frame) at the base to a maximum value at the tip [3]. We report here on the improvement of this model by incorporating (3) a spike breakup treatment based on the Taylor Analogy Breakup (TAB) model [5], as extended to apply to sheet breakup [6,7], and (4) a new model for the inflow of metal into the base of the spikes. Combining all these elements allows us to self-consistently reconcile the evolving shape of the spikes (elongation and thinning) with the inflow, and with the corresponding properties of the bubbles, under the assumption of incompressibility. Since the model describes the motion of each fluid element into and along the spike, and subsequent fragmentation of the spike into ejecta, it predicts not only mass ejection rate but also the sizes and velocities of the particles launched in this process. We describe the new self-consistent model and its implementation in FLAG.
Experimental Evaluation of Wind Tunnel Test Apparatus for Active Flow Control
Authors: Pesch Alexander H. , Hess Diana V.
Published: November 2019

Active control of flow dynamics is an ever-increasing field of study. This paper presents details on a new experimental apparatus for the testing of dynamic fluid-structure interaction and the control thereof. Specifically, the experimental apparatus involves an open return wind tunnel with an actuated rigid airfoil. The airfoil is replaceable, but this initial evaluation uses a flat plate as a basic geometry airfoil. The pitch of the airfoil is actively controlled in real-time via an angle sensor, microcontroller, and brushed DC electric motor. For a given PID controller, sine sweeps are performed to identify the closed-loop frequency response at varying wind speeds. The wind creates a destabilizing feedback torque on the airfoil which increases with wind speed and results in a change in the closed-loop frequency response. A model of the system is augmented with a mathematical model for the wind dynamics. The assumed form wind model is manually tuned to match the closed-loop frequency response for all wind speeds. Finally, steady-state tests are conducted in which the setpoint for angle of attack is incrementally changed and the frequency spectrum is found for the angle sensor, in the control loop, and a hotwire behind the airfoil which is not in the control loop. The results from the angle sensor show the system holds steady, with slight variation at low frequencies for high angles of attack. The results from the hotwire show a distinct sheading frequency at low angles of attack, which is replaced by chaotic low frequency flow at high angles of attack characteristic of flow separation.
The Dynamic Measurement of Impinging Sheet Thickness via Partial Coherent Interferometry
Authors: Shang Weixiao , Chen Jun
Published: November 2019

In this work, the thicknesses of a series of impinging sheets formed by two ethanol jets under different jet velocities are measured and compared with the theoretical model via a non-intrusive technique, the partial coherent interferometry. An interferometer with the calibrated partial coherence property is used to record the interference pattern by passing one optical path through the impinging sheet. The thickness is measured by analyzing the change of degree of coherence before and after the sheet insertion. The Reynolds numbers and Weber numbers of this experiment range from 269 to 370 and 35 to 67, respectively. The experimental results show that the jet velocity controls the size of the sheet but not affects the thickness distribution. The measured thicknesses are different from the theoretical predictions and indicate that the velocity inside the sheet may not be a constant along the radial direction.
Wingtip Vortex Stability and Control Using Mean Flow Perturbation
Authors: Bodling Andrew L. , Garmann Daniel J.
Published: November 2019

Wingtip vortices generated by aircraft are the source of induced drag. Therefore, flow control devices such as winglets have been created to reduce the impact of tip vortices and consequently improve the wings performance. To use other flow control devices such as periodic heat-flux sources, the receptivity to the actuator must be fully optimized to be effective. The optimization process includes actuator placement, frequency selection and spatial modulation. The Mean Flow Perturbation (MFP) technique is a linear stability analysis that can be used to understand the receptivity of base flows to small perturbations. Its advantage over other linear stability analyses is that it can be applied fairly easily to complex 3-D flows in a relatively efficient manner, embedded within traditional flow-solver frameworks. This technique can help in gaining a better understanding of the receptivity of a flow control actuator that is used to control a complex 3-D flow. The current study seeks to apply the MFP technique to the author’s previous work on unsteady tip vortices. The aspect-ratio-four, rounded-tip wing has a NACA0012 section and operates at a Reynolds number of Re = 2 × 105 and incidence of α = 12°. The objective is to uncover the least stable mode shapes and frequencies of the structure using MFP in hopes of informing future flow control design techniques. At these conditions, the MFP shows a dominant least stable frequency and mode shape that occurs near the trailing edge of the wingtip. A region near the incipient separation of the vortex also showed with a definitive spatial wavelength that may be susceptible to tailored control.
Numerical Simulations of Turbulent Flow Through a 90° Elbow
Authors: Venters Ravon , Helenbrook Brian , Ahmadi Goodarz
Published: November 2019

Turbulent flow in an elbow has been numerically investigated. The flow was modeled using two approaches; Reynolds Averaged Navier-Stokes (RANS) and Direct Numerical Simulation (DNS) methods. The DNS allows for all the scales of turbulence to be evaluated, providing a detailed depiction of the flow. The RANS simulation, which is typically used in industry, evaluates time-averaged components of the flow. The numerical results are accompanied by experimental data, which was used to validate the two methods. Profiles of the mean and root-mean-square (RMS) fluctuating components were compared at various points along the midplane of the elbow. Upstream of the elbow, the predicted mean and RMS velocities from the RANS and DNS simulations compared well with the experiment, differing slightly near the walls. However, downstream of the elbow, the RANS deviated from the experiment and DNS, showing a longer region of flow re-circulation. This caused the mean and RMS velocities to significantly differ. Examining the cross-section flow field, secondary motion was clearly present. Upstream secondary motion of the first kind was observed which is caused by anisotropy of the reynolds stresses in the turbulent flow. Downstream of the bend, the flow transitions to secondary motion of the second kind which is caused by streamline curvature. Qualitatively, the RANS and DNS showed similar results upstream of the bend, however downstream, the magnitude of the secondary motion differed significantly.
Time-Invariant Deformation of Blood During Necking on an Electrowetting Digital Microfluidic Platform
Authors: Young Curtis , Ramasubramanian Anand K. , Simon Melinda , Lee Sang-Joon John
Published: November 2019

Recent developments in electrowetting-on-dielectric (EWOD) technology have expanded the possibilities for testing methods and investigation of blood. This work evaluated the development of necking geometry of whole blood on an EWOD-based digital microfluidic (DMF) platform. This was achieved by performing tensile tests on whole blood on an EWOD-based device, thereby inducing necking. A time-invariant method was used to evaluate the deformation of the tested dilutions, using minimum neck width and neck radius as two characteristic parameters of the necking geometry. Experiments were performed on blood diluted with phosphate-buffered saline (PBS) at dilutions of 1:20 and 1:10 by volume. Parameter measurements were obtained by recording microscope video of on-chip tensile tests and extracting the necking profile. Neck radius and neck width are obtained from the extracted necking profile and evaluated to compare results. Results from tensile tests on blood at different dilutions showed an exponential decrease in neck radius as neck width decreases. A four-parameter exponential model was fit to the collected data, showing that the 1:20 dilution had a higher neck radius to neck width ratio than the 1:10 dilution over a neck width interval of 0.3 mm to 1.7 mm, suggesting a viscosity effect on the necking geometry. The results demonstrate that the concentration of blood influences the necking profile when deformed under tension that is applied by electrowetting forces.
In-Situ Measurement of Liberation of a Dissolved Gas in Unsteady Cavitating Flow in Water
Authors: Makii Daiki , Sasaki Hirotoshi , Iga Yuka
Published: November 2019

Cavitation is a phenomenon in which phase change occurs in a liquid by pressure decrease due to flow acceleration. The phase change is caused by mainly evaporation of the liquid but sometimes by liberation of dissolved non-condensable gas in the liquid. In particular, unsteady cavitation causes vibration, noise, erosion and performance deterioration, which has been a serious problem in the development of fluid machinery. Therefore, it is important to research the characteristics of cavitation generation and develop methods to suppress or control it.

In the current CFD (computational fluid dynamics) model of cavitating flow, the saturated vapor pressure has been used as a criterion for determining the cavitation generation or disappearance based on the idea of phase equilibrium, however it is well known that these calculation results don’t agree well with experimental results. For example, it is reported that the cavitation inception pressure is higher than its saturated vapor pressure in water. This is predicted to be resulting from the generation of gaseous cavitation which is caused by liberation of dissolved air, however this has not been taken into consideration in the current CFD model. Here, liberation of non-condensable gas is supposed to be treated by MD (molecular dynamics) then it is not suitable for CFD. Thus, in order to develop a more accurate CFD model for cavitating flow, it is necessary to develop a macroscopic and coarse-grained model of liberation should be developed, which may be related to flow dynamic-stimulation of the unsteady flow field with cavitation.

In the present study, we focus attention on relationship between liberation of dissolved gas and unsteadiness of cavitation. Experiment is conducted in high-temperature water cavitation tunnel in which in-situ measurement of the amount of dissolved oxygen can be performed during the operation with cavitation. The variation of dissolved oxygen is used as one of the indexes of liberation of dissolved non-condensable gas during the experiment. The degree of cavitation unsteadiness is judged by calculation based on the FFT (Fast Fourier Transform) of the downstream fluctuation pressure and the RMS (root mean square) of brightness value using images taken with a high-speed camera. In addition, in order to eliminate the factors of dissolved gas liberation other than cavitation unsteadiness, the mainstream pressure, the mainstream temperature and volume of the cavity are made to be equal, respectively. Under the above preconditions, the time evolution of dissolved oxygen amount is measured in several kinds of cavitating flow fields around NACA0015 and NACA16012 hydrofoils.
Automatic Mobility Analysis of Parallel Mechanisms: An Algorithm Approach Based on Position and Orientation Characteristic Equations
Authors: Zhu Xiaorong , Shen Huiping , Wu Chengqi , Chablat Damien , Yang Tingli
Published: November 2019

The determination of the mobility of parallel mechanisms (PM) is a fundamental problem. An automatic and intelligent analysis software will be a significant tool for the design and optimization of mechanical systems. Based on the theory of position and orientation characteristics (POC) equations, a systematic approach to computer-aided mobility analysis of PMs is presented in this paper. First, a digital model for topological structures which has a mapping relationship with position and orientation characteristics of mechanism is proposed. It describes not only the dimension of the motion output, but also gives the mapping relationship between the output characteristic and the axis of the kinematic joints. Secondly, algorithmic rules are established that convert the union and intersection operations of POC into the binary logical operations and the automatic analysis of POC are realized. Then, the algorithm of the automatic mobility analysis of PMs and its implementation with VC++ are written. The mobility and its properties (POC) will also be analyzed and displayed automatically after introducing by users of the data of topological structures representation. Finally, typical examples are provided to show the effectiveness of the software platform.
Torsional Stiffness Model of an Industrial Robotic Joint Using Fractal Theory
Authors: Xu Jingjing , Liu Zhifeng , Zhao Yongsheng , Cheng Qiang , Pei Yanhu , Yang Congbin
Published: November 2019

It is known that mechanical connections have great influence on the dynamic characteristic of the assembly. In existing methods, the torsional stiffness of the robotic joint is calculated only considering the stiffness of components of the system, which largely reduces the prediction accuracy of the joint stiffness. In the paper, to predict the joint stiffness more accurately, a model is proposed considering influences of the stiffness of all connections existed in a joint system. The normal and tangential stiffness of the contact surface of each connection are calculated by combining the equilibrium analysis of the force and the fractal theory. Then the total stiffness of one robotic joint can be modelled by putting the torsional stiffness of all connections and that of the RV reducer and gear pair in parallel. To verify the proposed model, its simulation result is compared to the stiffness based on the previous technique without considering the influence of connections. The comparison result shows that the proposed model can improve the stiffness-prediction accuracy. This study can be extended to the stiffness modeling of other joint systems and provides a theoretical basis for the dynamic analysis of the robotic system.
Prediction of Out-of-Plane Rigid Ring Truck Tire Model Parameters Over Flooded Surface Using FEA-SPH Techniques
Authors: El-Sayegh Zeinab , El-Gindy Moustafa , Johansson Inge , Öijer Fredrik
Published: November 2019

This paper focuses on predicting the out-of-plane rigid ring model parameters of an off-road truck tire running over a flooded surface. The truck tire size 315/80R22.5 used in this study is modeled using Finite Element Analysis (FEA) technique and validated in static and dynamic responses. The flooded surface is modeled using Smoothed-Particle Hydrodynamics (SPH) technique and Murnaghan equation of state. The contact between the truck tire and a flooded surface is defined using node-symmetric node-to segment contact with edge treatment algorithm. The out-of-plane rigid ring tire model parameters include the lateral stiffness, cornering stiffness, self-aligning moment stiffness, and relaxation length. The out-of-plane rigid ring model parameters are computed at different operating conditions including various inflation pressures, vertical loads and water depth. The effect of the previously mentioned operating conditions on the tire-flooded surface interaction is examined and investigated.
Reliability Analysis of Nonlinear Vibratory Systems Under Non-Gaussian Loads Using a Sensitivity-Based Propagation of Moments
Authors: Papadimitriou Dimitrios , Mourelatos Zissimos P. , Patil Santosh , Hu Zhen , Tsianika Vasiliki , Geroulas Vasileios
Published: November 2019

This paper proposes a new methodology for time-dependent reliability analysis of vibratory systems using a combination of a First-Order, Four-Moment (FOFM) method and a Non-Gaussian Karhunen-Loeve (NG-KL) expansion. The vibratory system is nonlinear and it is excited by stationary non-Gaussian input random processes which are characterized by their first four marginal moments and autocorrelation function. The NG-KL expansion expresses each input non-Gaussian process as a linear combination of uncorrelated, non-Gaussian random variables and computes their first four moments. The FOFM method then uses the moments of the NG-KL variables to calculate the moments and autocorrelation function of the output processes based on a first-order Taylor expansion (linearization) of the system equations of motion. Using the output moments and autocorrelation function, another NG-KL expansion expresses the output processes in terms of uncorrelated non-Gaussian variables in the time domain, allowing the generation of output trajectories. The latter are used to estimate the time-dependent probability of failure using Monte Carlo Simulation (MCS). The computational cost of the proposed approach is proportional to the number of NG-KL random variables and is significantly lower than that of other recently developed methodologies which are based on sampling. The accuracy and efficiency of the proposed methodology is demonstrated using a two-degree of freedom nonlinear vibratory system with random coefficients excited by a stationary non-Gaussian random process.
Formalization of Fractional Flow Component in Higher-Order Logic Theorem Proving
Authors: Zhao Chunna , Jiang Murong , Huang Yaqun
Published: November 2019

Fractional calculus is a powerful tool for dealing with complex systems, and fractional flow component can effectively reflect the nonlinear gradual change of rheology in vibration state. Besides, higher-order logic theorem proving is a formal method for specification and verification. This paper, accordingly, presents a higher-order logic formalization of fractional flow component based on fractional calculus Caputo definition. The relationship between fractional order differential and integer order differential is verified according to fractional calculus Caputo definition in higher-order logic theorem proving, where fluid mechanics fractional flow component is then formally analyzed.
A New Approach to Compute Natural Frequencies and Mode Shapes of Non-Uniform Continuous Bar, Circular Shaft and Beam Vibration
Authors: Sinha Alok
Published: November 2019

The wave equation governing longitudinal vibration of a bar and torsional vibration of a circular shaft, and the Euler-Bernoulli equation governing transverse vibration of a beam were developed in the eighteenth century. Natural frequencies and mode shapes are easily obtained for uniform or constant spatial parameters (cross sectional area, material property and mass distribution). But, real engineering structures seldom have constant parameters. For non-uniform continuous structure, a large number of papers have been written for more than 100 years since the publication of Kirchhoff’s memoir in 1882. There are analytical solutions only in few cases, and there are approximate numerical methods to deal with other (almost all) cases, most notably Stodola, Holzer and Myklestad methods in addition to Rayleigh-Ritz and finite element methods. This paper presents a novel approach to compute natural frequencies and mode shapes for arbitrary variations of spatial parameters on the basis of linear time-varying system theory. The advantage of this approach is that now it can be claimed that “almost” closed-form solutions are available to find natural frequencies and mode shapes of any non-uniform, linear and one-dimensional continuous structure.
Non-Contact Vehicle Overload Identification Method Based on Body Vibration Theory
Authors: Ding Yiran , Zhou Daolin , Yu Shimin , Wang Zhenyu , Tan Gangfeng
Published: November 2019

Vehicle overload seriously affects the traffic safety, damages the road infrastructure, and the road service life is reduced. There are many shortcomings in the current detection methods for overloaded vehicles. Traditional static weighing stations are relatively fixed and affect the road traffic efficiency; the cost of weighing in motion station is high, while the precision is not enough; on-board weighing electronic products require the modification of vehicles, which is difficult to promote.

In this paper, a non-contact overload detection method based on body vibration is proposed. After the analyzation of the body vibration response of dynamic vehicles under specific vibrational excitation, the load value data can be obtained combined with standard parameters and mathematical calculation model. Firstly, the body vibration response model under specific excitation is established. Then, roadbed facilities are arranged according to specific requirements, cameras calibration are finished, and the identification environment is built. Machine vision technology is used to identify the vibration track of the characteristic point on the vehicle body in the vertical direction. The vibration response characteristic parameters are extracted using the established response model. Finally, the vehicle load value data can be obtained by resolve the characteristic parameters. Compared with the rated load data in the database, the overload judgment of the vehicle is obtained.

In the experiment part, the road speed-control hump was used as the vibration excitation source. The vehicle experiments were carried out with Dongfeng Aeolus S30 and Yuejin Shangjun X500. The results show that the load identification error can be controlled within 20%–30%. This method above can detect overload vehicles without affecting the traffic efficiency and also has certain guiding significance for the development of intelligent vehicles.
Tooth Root Shape Optimization of Thin-Rimmed Planet Gears
Authors: Chao Chen-Xiang , Bestle Dieter , Krüger David
Published: November 2019

Planetary gearboxes in highly sophisticated applications such as turbofan engines are required to have a high power-to-weight ratio and excellent reliability. Hence, thin-rimmed gear units need to be designed as compact as possible which, however, is usually limited by the tooth root load capacity. In order to come up with the best design, a tooth root shape optimization process is developed for thin-rimmed planet gears.
A Highly Manoeuvrable and Untethered Under-Actuated Legged Piezoelectric Miniature Robot
Authors: Hariri Hassan H. , Soh Gim Song , Foong Shaohui , Wood Kristin L.
Published: November 2019

This paper presents the design of a highly manoeuvrable and untethered under-actuated legged piezoelectric miniature robot called PISCES. It comprises of a piezoelectric patch bonded onto a thin diamond-shaped aluminium plate to form a planar unimorph piezoelectric actuator, with three rigidly attached legs to generate locomotion. Unlike other under-actuated robots found in literature which uses compliant mechanisms, our robot utilizes three different standing wave vibration modes of a thin diamond-shaped aluminium plate and well positioned rigid leg positions to achieve forward, clockwise rotation and anticlockwise rotation motion using a single piezoelectric patch. This approach have the benefit of generating a more predefined motion and thus more controllable.

A finite element analysis approach is proposed to understand the modal vibration of the 2D unimorph actuator and how the geometric placement of the rigid legs together with the robot center of mass can be utilized to achieve under-actuated planar locomotion is described in detail. To verify the proposed locomotion, PISCES of a size of 90 × 60 × 11 mm, weight of 21 g is built. It is able to achieve a linear speed of 203.5 mm/s for forward motion, an angular speeds of 7.7 Revolution Per Minute (RPM) for clockwise rotation and an angular speed of 10.6 RPM for anticlockwise rotation using an input sinusoidal voltage of 100 V amplitude. Under a payload of 100 g, it moves with a linear speed of 110.8 mm/s and angular speeds of 4.1 RPM clockwise and 12.5 RPM anticlockwise. A tether-less remotely driven PISCES featuring a full suite of onboard electronics, and a more detailed experimental verification, analysis and characterization of PISCES are also demonstrated in this paper.
Response Sensitivity in a Nonlinear Planetary Gear Set
Authors: Zhan Zhaobin , Liu Hui , Feeny Brian , Xiang Changle , Han Lijin
Published: November 2019

Due to the wide range of speeds of the vehicle engine, the resonance cannot be completely avoided. Aiming at this problem, the analysis of the dynamic characteristics of the vehicle transmission system is transferred from the analysis of the intrinsic characteristics to the analysis of the dynamic response, and the sensitivity analysis based on the dynamic response is derived. This study investigates dynamic response sensitivity to model parameters in a nonlinear single-stage planetary gear set coupled with lateral and torsional directions. The equations of response sensitivity are deduced with the direct method (DM) and the root mean square (RMS) method. Gear meshing is a main reason for gear vibration, so gear meshing power sensitivity to model parameters is analyzed in this paper. Also the influence of rotation speed is considered in the response sensitivity. The sensitivity characteristics make it possible to provide support for dynamic design optimization.
Localised Pre-Heating to Improve Inter-Layer Delamination Strength in Fused Deposition Modelling
Authors: Aitchison Andrew , Wang Qing
Published: November 2019

Additive manufacture, specifically Fused Deposition Modeling (FDM), is an advancing manufacture method opening up new possibilities in design previously impossible to machine, in a relatively affordable way. However, its use in functional products is limited due to anisotropic strength and reduced strength from injection molded components. This paper aims to increase the tensile strength of Acrylonitrile Butadiene Styrene (ABS) in the weakest direction (Z axis), where poor interlayer fusion and air gaps between extruded trails reduce strength. Extra thermal energy was applied to the top surface layer during the printing process (through hot air) to encourage more polymer chain diffusion across the boundary, and spreading out to fill air gaps. Multiple tensile test samples were printed at a variety of heat levels. The ultimate tensile strength σuts was plotted against these temperatures and a weak positive correlation was found. However, only air temperatures above 81°C increased strength past the control to a maximum of 1.4MPa. Heat application has proven to increase tensile strength, but needs to be applied with a more precise method, to the boundary interface, to allow greater thermal energy transfer without sacrificing print quality.
A Digital Twin-Driven Improved Design Approach of Drawing Bench for Brazing Material
Authors: Hu Bingtao , Feng Yixiong , Gao Yicong , Zheng Hao , Tan Jianrong
Published: November 2019

Brazing materials can be made into different shapes to meet the requirements of different scenarios and the welding rod is a very common form. The rough-processed welding rods must be properly finished by the drawing bench to remove the oxide film on the surface and made into a uniform diameter. However, the continuous welding rod often breaks resulting low production efficiency. To reduce the frequency of workers’ reconnection operation of broken welding rods, we proposed a digital twin-based approach to improve the design of the structure of the drawing bench. First, we established a full life cycle digital twin model for the welding rod from the formulation stage to the finishing stage. The product ontology of the welding rod was built and the key process parameters were collected. Second, based on the product ontology, the key structural parameter of the drawing bench that affects the internal stress of the welding rod was determined by means of analytic hierarchy process. Third, we modified the key structural parameter in the digital twin model and simulated the finishing process. A near-optimal parameter was found. Last, we improved the structure of the actual drawing bench accordingly and carried out some experiments. The results matched well with the simulation prediction and the frequency of welding rod breaking is significantly reduced, which proved the effectiveness of our proposed improved design approach.
Wave Dynamics in Reconfigurable Tristable Mechanical Metamaterials
Authors: Yasuda Hiromi , Korpas Lucia M. , Raney Jordan R.
Published: November 2019

We explore unique wave dynamics in a chain of tristable structures, inspired by multistable origami. We specifically focus on the frequency band structure of the chain, and conduct numerical and theoretical analysis. The band gap of the chain can be controlled by switching the stable state of each tristable structure. We also show that if two regions of the chain have different topological properties then wave localization can occur at the interface of the two regions. Interestingly, this interface mode is observed within the band gap. We demonstrate that the interface mode can be altered by leveraging the reconfigurable nature of the tristable structure. Our findings suggest a new strategy for controlling wave propagation in reconfigurable structures, which could be relevant for engineering applications such as energy harvesting.
Characterization of the Damping Coefficient in the Continuous Contact Model
Authors: Poursina Mohammad , Nikravesh Parviz E.
Published: November 2019

This article presents an analytical formula to characterize the damping coefficient in a continuous force model of the direct central impact. The contact force element consists of a linear damper which is in a parallel connection to a spring with Hertz force-deformation characteristic. Unlike the existing models in which the separation condition is assumed to be at the time at which both zero penetration (deformation) and zero force occur, in this study, zero contact force is considered as the separation condition. To ensure that the continuous contact model obtains the desired restitution, an optimization process is performed to find the damping coefficient. The numerical investigations show that the damping coefficient can be analytically expressed as a function of system’s parameters such as the effective mass, penetration speed just before the impact, Hertz spring constant, and the coefficient of restitution.
Collision-Avoidance Reliability Analysis of Autonomous Vehicle Based on Adaptive Kriging Surrogate Modeling
Authors: Liu Yixuan , Zhao Ying , Hu Zhen , Mourelatos Zissimos P. , Papadimitriou Dimitrios
Published: November 2019

This paper presents a reliability analysis method for automated vehicles equipped with adaptive cruise control (ACC) and autonomous emergency braking (AEB) systems to avoid collision with an obstacle in front of the vehicle. The proposed approach consists of two main elements, namely uncertainty modeling of traffic conditions and model-based reliability analysis. In the uncertainty modeling step, a recently developed Gaussian mixture copula method is employed to accurately represent the uncertainty in the road traffic conditions using the real-world data, and to capture the complicated correlations between different variables. Based on the uncertainty modeling of traffic conditions, an adaptive Kriging surrogate modeling method with an active learning function is then used to efficiently and accurately evaluate the collision-avoidance reliability of an automated vehicle. The application of the proposed method to the Department of Transportation Safety Pilot Model Deployment database and an in-house built Advanced Driver Assist Systems with ACC and AEB controllers demonstrate the effectiveness of the proposed method in evaluating the collision-avoidance reliability.
Probabilistic Modeling of Driver Behaviors at Urban Crossroads
Authors: Liu Yuan-Cheng , Chan Kuei-Yuan
Published: November 2019

Interactions with human drivers is one of the major challenges for autonomous vehicles. In this work we consider urban crossroads without signals where driver interactions have to happen. Crossroad parameters are defined and how drivers passing the crossroad while maintaining a desired speed without collision is studied. A point of action is defined for incoming vehicles from different directions and a probability of stopping for each car is proposed as a function of vehicle speed and the distance-to-action for both vehicles. Driver behaviors with these probability models are also proposed. The method is then analyzed and validated by data collected from human drivers. The result shows a similar maneuver as human drivers while more aspects of evaluation is needed in the future work.
Assessment of Joint Parameters in a Kinect Sensor Based Rehabilitation Game
Authors: Manna Soumya K. , Dubey Venketesh N.
Published: November 2019

A Kinect sensor based basketball game is developed for delivering post-stroke exercises in association with a newly developed elbow exoskeleton. Few interesting features such as audio-visual feedback and scoring have been added to the game platform to enhance patient’s engagement during exercises. After playing the game, the performance score has been calculated based on their reachable points and reaching time to measure their current health conditions. During exercises, joint parameters are measured using the motion capture technique of Kinect sensor. The measurement accuracy of Kinect sensor is validated by two comparative studies where two healthy subjects were asked to move elbow joint in front of Kinect sensor wearing the developed elbow exoskeleton. In the first study, the joint information collected from Kinect sensor was compared with the exoskeleton based sensor. In the next study, the length of upperarm and forearm measured by Kinect were compared with the standard anthropometric data. The measurement errors between Kinect and exoskeleton are turned out to be in the acceptable range; 1% for subject 1 and 0.44% for subject 2 in case of joint angle; 5.55% and 3.58% for subject 1 and subject 2 respectively in case of joint torque. The average errors of Kinect measurement as compared to the anthropometric data of the two subjects are 16.52% for upperarm length and 9.87% for forearm length. It shows that Kinect sensor can measure the activity of joint movement with a minimum margin of error.
Critical Thinking in the Design Classroom: An Analysis of Student Design Reflections
Authors: Evans Emmeline , Menold Jessica , McComb Christopher
Published: November 2019

Within the domain of education, the term “critical thinking” is widely understood to mean the various skills that comprise an individual’s logical and reasoning abilities. It is critical that designers possess these abilities so that they can solve the complex problems of an increasingly interconnected world. In order to better understand patterns in engineering students’ critical thinking, this research applies the classifications of the 2001 revision of Bloom’s Taxonomy to 49 reflections written by first-year engineering students on a two-hour design practicum. Reflections were thematically coded to identify when students operated in different levels of the cognitive process and knowledge dimensions. Using k-means clustering analysis, genres of reflection were then determined. Four unique clusters of responses were identified. Notable trends in clusters included application and evaluation of procedural knowledge. Additionally, a difference was observed between the two largest clusters regarding deviance from the design process. While one cluster of responses generally minimized discussion of deviance, the second largest cluster emphasized this deviance, highlighting it as an opportunity for future growth. This work provides insight into how students learn design and how they communicate their learning, providing insight for instructors hoping to encourage deeper critical thinking in design courses.
Modeling and Stability of Milling Processes With Active Damping
Authors: Lehotzky David , Dombovari Zoltan
Published: November 2019

In the recent decade, active dampers have been introduced to machining for the avoidance of machine tool chatter in milling processes. The tuning strategy for most of these devices is based on models which do not account for the dynamics of control loop within the active dampers, hence neglect the dynamics of actuator and measuring device, and do not consider filtering. However, these simplified models might lead to inaccurate stability predictions which can deteriorate the performance of active dampers. In order to better approximate the real behavior of milling processes controlled by active dampers, this paper develops a new mathematical model which incorporates the dynamics of control loop within these devices. In particular, the inertial actuator is modeled as an electromagnetic proof-mass transducer, while the dynamics of piezoelectric accelerometer and finite-impulse-response filtering are also taken into account. By the computation of stability lobe diagrams, it is shown that, at low-frequency actuation and at high-speed milling, the consideration of control loop dynamics in active dampers can be essential.
System Reliability Analysis With Second Order Saddlepoint Approximation
Authors: Wu Hao , Du Xiaoping
Published: November 2019

The second order saddlepoint approximation (SPA) has been used for component reliability analysis for higher accuracy than the traditional second order reliability method. This work extends the second order SPA to system reliability analysis. The joint distribution of all the component responses is approximated by a multivariate normal distribution. To maintain high accuracy of the approximation, the proposed method employs the second order SPA to accurately generate the marginal distributions of component responses; to simplify computations and achieve high efficiency, the proposed method estimates the covariance matrix of the multivariate normal distribution with the first order approximation to component responses. Examples demonstrate the high effectiveness of the second order SPA method for system reliability analysis.