bluuebunny/crossref_metadata_2025 huggingface dataset:
Retracted: “Numerical Studies of Extreme High-Speed Laser Material Deposition Processes at Powder-Scale” [ASME 2019 International Mechanical Engineering Congress and Exposition, Volume 2A: Advanced Manufacturing, Salt Lake City, Utah, USA, November 11–14, 2019, Conference Sponsors: ASME, ISBN: 978-0-7918-5937-7, Copyright © 2019 by ASME. Paper No. IMECE2019-10730, pp. V02AT02A045; 10 pages; doi: 10.1115/IMECE2019-10730]
Authors: ASME
Published: January 2020

The above referenced paper has been removed from publication. (April 21, 2020)

Copyright © 2020 by ASME
A Constitutive Material Model With Strain-Rate Dependency for Brain Tissue
Authors: Hosseini Farid Mohammad , Ramzanpour Mohammadreza , Ziejewski Mariusz , Karami Ghodrat
Published: January 2020

In almost all scenarios of traumatic brain injuries (TBIs), the brain tissue goes under mechanical loading at high strain rates. In experimental works, it has also shown that brain tissue behavior is highly rate-dependent. We are presenting here the results of a study on mechanical properties of bovine brain tissue under unconfined compression tests at different rates. The tissue specimens are compressed with deformation rates of 10, 100, and 1000 mm/sec, respectively. We observed the tissue is showing a viscoelastic behavior and become stiffer under increasing strain rates. We developed a nonlinear viscoelastic rate-dependent constitutive model to be calibrated with the test results. The material parameters for this constitutive model have been validated for the above tested results. The model was examined against other rates and agrees well. The study will provide new insight into a better understanding of the rate-dependency behavior of the brain tissue under dynamic conditions. The work is a step forward in understanding the material characteristics of brain tissue for TBI analysis and prediction under loading or high kinematical motions.
Functionally Graded Cellular Core Cross Tube: Finite Element Study
Authors: Jenson Sean , Ohioma Eboreime , Ali Muhammad , Alam Khairul
Published: January 2020

Thin wall structures are primarily deployed in automotive chassis to increase the energy absorption capacity of the automobiles in the event of an accident. Researchers have delved into developing lighter structures for improving automobiles’ fuel efficiency with a challenge of maintaining or preferably exceeding the energy absorption properties of the structure. In this study, the work presented is a continuation of research conducted on exploring the effects of the introduction of cellular core in tubular structures under axial compressive loading. The crushing response of cellular core cross tube was numerically studied using ABAQUS/Explicit module. The characteristics such as deformation or collapsing modes, crushing/ reactive force, locking strain, energy curves, and specific energy absorbed were studied. The cellular core cross tube shows significant potential for reducing the weight of automobile structure while giving positive indication towards enhancing the specific energy absorption capacity.
Thermal-Kinetic-Mechanical Modeling of Laser Powder Deposition Process for Rail Repair
Authors: Mortazavian Ershad , Wang Zhiyong , Teng Hualiang
Published: January 2020

The study established a three-dimensional, thermal-kinetic-mechanical finite element (FE) model to simulate an additive manufacturing process with a laser powder deposition (LPD) approach for repairing a 75-lb rail that is broadly used for light rail transportation in the US. A worn rail specimen is repaired using 304L stainless steel powders as the deposition material for lab tests. The researchers incorporated an element-birth-and-kill technique to activate the deposition elements step-by-step, according to the build-up strategy along which the laser heat source is translated simultaneously. The laser power attenuation and solid-state transformation expressions are described using external user-defined subroutines for thermal and kinetic analysis, respectively. A set of equations for calculation of hardness for both of the rail and deposition materials are also defined and developed in the FE model. The microstructure distribution coming from kinetic analysis output is employed for hardness calculation. The estimation of the width and depth of the dilution zone in thermal analysis is compared with the experimental results of the repaired specimen to validate the thermal model. Scanning Electron Microscope (SEM) and Optical Microscope (OM) analyses, along with a Rockwell B-scale hardness test are performed to validate the outgoing microstructure and hardness results of the FE model. Mechanical analysis results showed that residual thermal stresses can significantly reduce the safety margin against shearing off the deposition part under a dynamic train load. The validated model demonstrated great potential for investigating the effects of the variation of different LPD process parameters on the final mechanical and metallurgical properties of the repaired rail.
Estimating Traction Forces for Pneumatic Tires on Soft Soils With Application to BAJA SAE Vehicles
Authors: Saunders Amanda M. , White Darris
Published: January 2020

BAJA SAE is an engineering competition that tasks team with designing single-seat all-terrain vehicles that partake in a variety of events, predominantly on soft soils. Events range from (off-road) land maneuverability, hill climb, tractor pull, and timed acceleration. Tire-terrain interaction strongly influences the performance of off-road vehicles. Tire terrain traction is limited by the mechanical properties for soft soils; therefore, understanding tire-terrain traction forces is important for assessing vehicle performance. Using the stress integration method (SIM) initiated by Bekker and developed by Wong, this paper analyzes the performance of BAJA SAE tires using Bekker’s defined terrain measurements for soft soils. The relative rigidity of the tire versus the soil, in terms of pressure, was compared for operating conditions and used to determine the tire state (rigid wheel or pneumatic tire). Tire state determines shape of the tire-terrain interface, and integration limits. Based on the operating conditions, the tire sinkage into the soil was calculated and used to determine compaction resistance, tire hysteresis, and normal pressures along the tire-terrain interface. Using the SIM, the longitudinal and lateral tractive forces vs the slip ratio and slip angle, respectively, were calculated for a range of operation conditions. The tire-terrain traction forces were evaluated for different tire diameters and tire pressure for a range of soil types. The described process can be used to predict performance for BAJA SAE teams participating in specific events and the results can be used as a basis for selecting tires and tire pressure for dynamic events.
Light Weighting Solutions for Additively Manufactured Aviation Components
Authors: Medikonda Sandeep , Sridharan Sriraghav , Acharya Sunil , Doyle John
Published: January 2020

Recently, additive manufacturing methods have gained popularity for their ability to produce complex mechanical parts where conventional manufacturing methods are not suitable. Such methods not only offer a great sense of freedom to engineers but when combined with topology optimization tools can be used to simulate structures with complex shapes which satisfy the real-world loading constraints while requiring as little material as possible. Hence, combining topology optimization and additive production procedures offers a promising approach for obtaining optimized mechanical parts. This article presents a complete workflow for studying complex topology optimized parts that can be printed using additive manufacturing.

We focus on topologically optimized design approach for additive manufacturing with case studies on lightweight design of aviation safety-critical parts. The complete workflow of such a setup is discussed. The Topology Optimization of these parts has been carried out using the Solid Isotropic Material with Penalization (SIMP) algorithm [1], where a discrete optimization problem is converted to a continuous problem. The primary objective of the optimization studies is to maximize the stiffness of the chosen parts while minimizing their mass at the same time. We also investigate the effect of design constraints to account for feasible manufacturing of the part while maintaining the structural response to performance loads.

These optimized parts are then analyzed using a lumped layer approach to simulate powder bed fusion (PBF) [2] as a coupled thermal-structural analysis within ANSYS®, where the areas of maximum deformation and stress resulting from additive printing are predicted. The influence that the orientation of a part’s build direction has on the end results is investigated using a parametric study. Effect of a cartesian mesh vs a tetrahedron mesh on the results have been analyzed and best practices while working with coupled topology optimization and additive simulations have also been discussed.
Influence Study of Gas Pressure on the Volume Measurement of Engine Combustion Chamber by Using Helmholtz Resonance
Authors: Chen Kun , Jin Sun , Liu Shun , Tian Ang , Mo Wei
Published: January 2020

The combustion chamber of automobile engine is a place where gasoline is burned to provide power for automobile driving and its size has a great influence on engine performance. However, because of the irregularity of the combustion chamber, it is difficult to measure it accurately and efficiently. The principle of Helmholtz resonance reveals the functional relationship between the volume and the resonant frequency of the closed cavity. Having used the Helmholtz resonance principle, the equipment for measuring the combustion chamber of automobile engine accurately and efficiently has been built. The conditions under which the cavity is stimulated to produce resonance are explored, the relationship between volume and the pressure is deduced. Experiments are designed to verify the correctness and accuracy of the measurement. The measuring instrument is improved and the accuracy of the volume measurement is increased. The application of the high precision and high efficiency of non-contact acoustic principle in cavity volume dynamic measurement has been realized.
A Challenge to Adaptability: Learning From the Octopus
Authors: Fukuda Shuichi
Published: January 2020

Our World is expanding very rapidly, and unpredictable changes occur frequently and extensively. Yesterday, our world was small and closed with boundaries. So, we could use past experience as knowledge and solve the problems. But today, our world is an open world without boundaries. And the environment and situations change in an unpredictable manner. So, knowledge does not work anymore. The octopus does not transfer knowledge from generation to generation. They live on their own instinct alone. But they are known to adapt to the unpredictable environments and situations very well. They demonstrate the importance of direct interaction with the outside world. Movement is taken up, because movement is essential for machines and humans. Machines only move as instructed, but in the case of humans, they need to coordinate and balance many body parts to move as they wish. So, they have to proceed by trial and error. This is indeed what the octopus is doing.In this paper, a new performance indicator is proposed. It combines Mahanalobis Distance with movement patterns. This approach provides us with a movement performance measure in a unitless and quantitative manner in a very simple way. Thus, we can understand if we are doing better or worse so we can adapt to the changing situations more reasonably and in shorter time.
Dynamic Impact Properties of a Novel Auxetic Metamaterial
Authors: Chen Zeyao , Wang Zhe , Wu Xian , Shao Jianwang , Zhou Shiwei
Published: January 2020

A novel auxetic metamaterial which is organized in the lattice is presented in this paper. Dynamic uniaxial impact behavior of the auxetic lattice using experiment and finite element simulation is investigated. The corresponding results have proved that the plastic beam-based finite element model has good agreement with the experiment. To explore the rate sensitivity of the auxetic lattice metamaterial, impact simulations of auxetic metamaterials at 13.07% relative density are firstly conducted under six velocities range from 1 to 100m/s. The comparison of deformation exhibits that deformation pattern depends on impact velocities. The shock wave effect can be obviously observed in the impact procedure which results in the loss of negative Poisson’s ratio effect at high velocity. The effective impact indices including plateau stress and densification strain can be extracted from the stress-strain curves. The simplified theory model based on the rigid, perfectly-plastic, locking model is utilized to fit data from the simulation. Furthermore, the effect of relative density on impact mechanical properties is investigated. The basic theoretical model is developed by considering the relative density which accords with simulation data well in four relative densities respectively 7.35%, 13.07%, 20.42%, 29.41%. Finally, the formula of plateau stress with respect to impact velocity and relative density can be obtained. The researches herein are aiming to reveal the dynamic properties of the auxetic lattice metamaterial and provide a constitutive model for potential application.
Selective Lamb Mode Transmission Enabled by Local Resonance Based Ultrasonic Metamaterial
Authors: Tian Yiran , Shen Yanfeng
Published: January 2020

In this study, a kind of elastic metamaterial substructure was designed for the selective mode filtering and transmission of symmetric and antisymmetric elastic waves. It is composed of double-sided aluminum-lead composite cylinders arranged in a periodic pattern bounded on an aluminum plate. The band structure of elastic metamaterial unit cell is numerically investigated using the modal analysis of a finite element model (FEM) by treating a unit microstructural cell with the Bloch-Floquet boundary condition. Through analyzing the vibration modes of the unit cell, a complete antisymmetric wave bandgap and a complete symmetric wave bandgap can be formed in different frequency ranges. Considering the geometric complexity of the designed substructure, the dynamic effective mass density of the proposed metamaterial unit cell is calculated by considering the structure as a homogeneous medium under the sub-wavelength requirement. The negative effective mass density behavior for in-plane and out-of-plane plate modes will be presented to verify the bandgap effect of different wave modes. A FEM harmonic analysis is further conducted to obtain the spectral response of a chain model and explore the mode filtering efficiency. Finally, a coupled field transient dynamic FEM is carried out to acquire the dynamic response of the structure. The frequency-wavenumber analysis demonstrates the successful achievement of model filtering behavior. The proposed selective mode transmission control methodology possesses great potential in future SHM and NDE applications. A case study for S0 mode conversion to SH0 mode using a different metamaterial unit cell is exhibited to illustrate other wave control capabilities. The paper finishes with summary, concluding remarks, and suggestions for future work.
An Inertial / Altimetric / Infrared / Geomagnetic Integrated Navigation Method for Unmanned Aerial Vehicles
Authors: He Zilu , Bu Xiongzhu , Cao Yihan , Xu Miaomiao
Published: January 2020

Unmanned aerial vehicle (UAV), is an unmanned aircraft operated by radio remote control equipment and self-contained program control device. When Unmanned Aerial Vehicle is on mission, its location information needs to be acquired to navigate it. Based on the research background of Unmanned Aerial Vehicle navigation information measurement, a passive integrated navigation mode of Inertial / Altimeter / Infrared / Geomagnetism Navigation method is designed in this paper. Firstly, several methods for Unmanned Aerial Vehicle navigation, including geomagnetic navigation, infrared navigation, inertial navigation and altimeter measurement, are introduced, and the advantages and disadvantages of various navigation methods are presented. Secondly, aiming at the problem that the output of barometric altimeter is affected by temperature and pressure, a temperature and pressure compensation model of barometric altimeter is established. Then, the attitude angle, velocity and position measurement models of inertial, infrared and geomagnetic navigation are established respectively. Finally, the data information of inertial / altimeter / infrared / geomagnetism measurement model is fused by extended Kalman filter and Unscented Kalman filter, and the signals processed by the two filters are compared. The reliability of the integrated navigation method is verified by simulation. This method has remarkable effect on improving the navigation accuracy of UAV and can make UAV suitable for many applications. It is simple and effective, and has wide application prospects.
Experimental Verification of Rubber Clutch Spring Damper Torque Behavior in Time-Dependent Manner and System Optimization Using Simulated Annealing Algorithm Integrated With 1-D Modeling
Authors: Genç Mehmet Onur , Kaya Necmettin , Konakçı Süleyman
Published: January 2020

Automobile components are subjected to high dynamic loads and vibrations under operational conditions which needs detailed system analysis for work properly. The torque generated in the engine creates oscillations, and this case occurred at different levels of frequencies. Clutch is one of the important part of automobile powertrain system with torque transmission controlling and vibration damping properties. Metallic helical springs are widely preferred within the clutch discs with their durable mechanic properties against dynamic variables on an automobile. This study develops the novel approach on the time-based investigation of rubber clutch springs, and system optimization for torsional vibration damping using the simulated annealing algorithm method. In this purpose, the torque behavior of the rubber spring instead of the helical spring was investigated by experimentally in time-dependent manner. Rubbers consist of polymer chains which are highly sensitive to dynamic variables such as operation time, frequency and thermal load. The clutch disc which includes rubber damper spring made of NBR (Nitril rubber) is experimentally tested with functional torque measurement at different compression cycle times to observe rubber damper spring viscoelastic time-based behavior. As the next step, 1-D modeling of powertrain system, including rubber clutch damper springs, were subjected to vibration optimization with simulated annealing (SA) algorithm. Thus, the simulated annealing (SA) algorithm was developed, and integrated run is provided with 1-D modeling for optimization in Python script. This methodology accelerates the powertrain system optimization using both rubber and metallic damper types with eliminating many of real vehicle testing and saving cost and time before the production phase. Also, results give an idea on the importance of 1-D simulation before design modeling of rubber clutch damper system based on time-dependent conditions.
Artificial Intelligence Based Architecture to Support Dementia Patients
Authors: Luís-Ferreira Fernando , Sarraipa João , Calado Jorge , Andrade Joana , Rodrigues Daniel , Jardim Goncalves Ricardo
Published: January 2020

Artificial Intelligence is driving a revolution in the most diverse domains of computational services and user interaction. Data collected in large quantities is becoming useful for feeding intelligent systems that analyse, learn and provide insights and help decision support systems. Machine learning and the usage of algorithms are of most importance to extract features, reason over collected data so it becomes useful and preventive, exposing discoveries augmenting knowledge about systems and processes. Human driven applications, as those related with physiological assessment and user experience, are possible especially in the health domain and especially in supporting patients and the community. The work hereby described refers to different aspects where the Artificial Intelligence can help citizens and wraps a series devices and services that where developed and tested for the benefit of a special kind of citizens. The target population are those under some kind of Dementia, but the proposed solutions are also applicable to other elder citizens or even children that need to be assisted and prevented from risks.
Dynamic Simulation of Planetary Gearbox With Tooth Root Crack Based on a Rigid-Flexible Coupled Model
Authors: Dai Jianchuan , Niu Hang , Hou Chenggang , Zhang Xiaodong
Published: January 2020

Tooth root crack is one of the most common failures in the gearbox which can lead to the failure of the whole transmission system. However, it is difficult to simulate the gear fault impact in practical work. To solve this problem and to study the relationship between tooth crack propagation and vibration features, various dynamic models have been built. However, the crack propagation path and the bearings are simplified in most of the models, which leads to obvious deviation in the dynamic response. In this paper, a rigid-flexible coupled model of a single-stage planetary gearbox in normal and fault conditions are built by ADAMS software. The crack propagation path is considered a parabolic curve and the thickness of the crack decreases along the path. As a reference, a rigid-body model has also been built to prove that the rigid-flexible coupled model can be more accurate and suitable for analyzing the response of the planetary gearbox with fault. Afterward, the effects of gear tooth root crack size on the gear dynamics are simulated and the corresponding changes in statistical indicators are investigated. By studying the torsional vibration signal of the planetary gearbox with varying severity of the damage, the fault characteristics and damage evolution mechanics can be analyzed and by comparing the fault sensitivity of these indicators, the critical and sensitive fault indicators are screened out.
Study of Two-Dimensional Flow-Boiling Morphological Characteristics in the Micro Gap With Surface Wettability on Hot Spot
Authors: Karim Anwarul , Kim Jong-Hoon
Published: January 2020

Thermal management is one of the most challenging problems of electronic devices today. As technology becomes increasingly miniaturized, extremely localized heat dissipation leads to the challenge of keeping devices away from overheating. Flow-boiling microchannel heat-sinks exploit the highly efficient thermal energy transport of phase change from liquid to vapor. However, the excessive consumption of liquid-phase by highly localized heat source causes the two-phase flow maldistribution, leading to greatly reduced heat transfer coefficient, high-pressure loss, and limited flow rate. In this study, we investigate two-dimensional flow-boiling morphological characteristics in a microgap with hydrophilic coating on hot-spot. The experiments are carried out on a Stainless Steel plate having a micro gap depth of 254 μm using deionized water with inlet at room temperature. A partial hydrophilic surface is created on the hot-spot (surface above the heater) which forms a wettability difference along the metal plate. A wide range of mass flux and heat flux are considered to quantify heat transfer coefficient. In addition, high-speed flow visualizations are performed to characterize the nucleation and bubble dynamics in flow boiling.
Beautiful Music in the Classroom: Marimba As a Lab Experiment for Teaching Vibration Measurement
Authors: Schaefer Mathew
Published: January 2020

A marimba bar makes a rich and vibrant sound when played by a skilled musician. When that same marimba bar is played by the typical mechanical engineering junior, it’s a different story. Then, that same marimba key provides a complex set of vibration modes that are a useful subject for a lab experiment in their Measurements & Instrumentation course. This paper will describe development of “The Marimba Experiment”, which is part of a junior-level engineering course in measurements at Milwaukee School of Engineering. Learning outcomes for this course include “provide students with hands-on experience: using various sensors, performing data collection, and interpretation of experimental results.” In this experiment, students measure vibrations using a piezoelectric accelerometer, charge amplifier and analog-to-digital conversion. Results can be viewed in two ways. First, it may be interpreted as a general example of a vibrating structural component. It has several natural frequencies and mode shapes (transverse bending, lateral bending, torsional), which are simultaneously active. The signal represents an example of a complex periodic signal. It may be analyzed by looking at the acceleration versus time response and by examining the Fourier transform of the data, which shows results in the frequency domain. Second, results may be interpreted in musical terms. The lowest frequency is what we recognize as “the note” and the higher modes represent the higher harmonics. The distribution of frequency ratios and the relative amplitudes of the higher frequencies are what gives a musical instrument its unique character. In other words, what makes middle-C on a marimba sound different than middle-C on a clarinet or violin? A well-designed engineering experiment can give students an immediate application example. In this case, it is an example which they spontaneously want to explore because they all enjoy music and want to understand how it is created.
Predicting the Risk of Twist-Off for Rotary Shouldered Threaded Connections With a Statistical Approach
Authors: Zhang Haitao , Li Ke
Published: January 2020

Fatigue is one of the most frequently encountered failure modes of rotary shouldered connections (RSC) used in drill strings. Once initiated, a fatigue crack tends to grow and ultimately lead to a twist-off, which is catastrophic and often results in lengthy non-producing time and expensive fishing operations. The complexity of the fatigue mechanism, the variabilities of material properties, and the nonlinear contact interactions of the pin and the box elements of an RSC pose a substantial challenge to accurately predicting the fatigue life of the RSC. This would require considerable conservatism to be exercised to prevent a twist-off, which causes premature retirement of drilling assets. Using a statistical approach to predict the risk of twist-off (ROTO) of each RSC on the drill string could be a more economically viable solution as it would enable quantified risk assessment and scientifically calculated tradeoffs between performance, cost, and risk of failures.

In this study, a methodology for statistical prediction of the ROTO of rotary shouldered threaded connections was developed. First, static material properties, including yield strength, tensile strength, elongation, and reduction in area, were extracted from a wealth of available material certificates. Feature engineering was carried out to arrive at two independent properties, tensile strength and reduction in area. Fatigue properties were then generated with the retrieved static material data and earlier established correlations between static and fatigue properties. Afterwards, elasto-plastic finite element analyses were performed on RSCs made of the same material but with different properties to determine critical fatigue indicators, stress and strain states as respective functions of the tensile strength. Finally, Monte-Carlo simulations were conducted with respect to statistical distributions of the two independent material variables to predict the ROTO as a function of fatigue life. The predictions were found to be favorable agreement with the available full-scale fatigue test data of an API connection type.
Robust Weed Recognition Through Color Based Image Segmentation and Convolution Neural Network Based Classification
Authors: Khan M. Nazmuzzaman , Anwar Sohel
Published: January 2020

Current image classification techniques for weed detection (classic vision techniques and deep-neural net) provide encouraging results under controlled environment. But most of the algorithms are not robust enough for real-world application. Different lighting conditions and shadows directly impact vegetation color. Varying outdoor lighting conditions create different colors, noise levels, contrast and brightness. High component of illumination causes sensor (industrial camera) saturation. As a result, threshold-based classification algorithms usually fail. To overcome this shortfall, we used visible spectral-index based segmentation to segment the weeds from background. Mean, variance, kurtosis, and skewness are calculated for each input image and image quality (good or bad) is determined. Bad quality image is converted to good-quality image using contrast limited adaptive histogram equalization (CLAHE) before segmentation. A convolution neural network (CNN) based classifier is then trained to classify three different types of weed (Ragweed, Pigweed and Cocklebur) common in a corn field. The main objective of this work is to construct a robust classifier, capable of classifying between three weed species in the presence of occlusion, noise, illumination variation, and motion blurring. Proposed histogram statistics-based image enhancement process solved weed mis-segmentation under extreme lighting condition. CNN based classifier shows accurate, robust classification under low-to-mid level motion blurring and various levels of noise.
Gas Fuel Variability Using Buffer Volume in Aeroderivative Gas Turbines
Authors: Yerram Ravinder , Ponnuraj Balakrishnan
Published: January 2020

General Electric (GE) DLE gas turbines typically use a Gas Chromatograph (GC) and/or a Wobbe Index Meter (WIM) to monitor changing fuel properties during operation. These conventional fuel sensors experience a significant time lag during operation, so a patented buffer volume device and a software algorithm is used to compensate for this lag and to ensure that the control system including metering valves can react to rapid fuel changes. Computational Fluid Dynamics (CFD) was used to design and analyze the buffer volume device that increases the time and distance taken by the gas to the metering valve. This delay provides the control system time to adjust the metering valves when the fuel transitions at the combustor to maintain gas turbine combustor stability and operation during rapid gas property changes that could otherwise result in a trip or flame-out condition. In GE’s Aeroderivative Gas Turbine Gas Fuel transfer system, the innovative buffer volume was the critical component, and this paper describes its performance in detail.
Analysis of Symmetric Angle-Ply Laminated Composite Skew Plates Using Hybrid Trefftz Finite Element
Authors: Dwibedi Subhasankar
Published: January 2020

Analysis of symmetric angle-ply skew laminated composite plates has been presented in the study using a newly developed hybrid Trefftz finite element (hTFE). Mindlin’s plate theory has been used to develop the present hTFE. The forms of displacement are assumed such that governing partial differential equations are satisfied a priori inside the element domain. Particular solutions of the governing equations have been ignored and Trefftz functions are derived using the homogenous solutions only. Inter-element continuity has been established by employing another displacement field along the edges of the hTFEs. The transverse shear stresses have been ignored at the top and bottom surfaces of the laminate. The angle of inclination of the width of the plate with the y-axis has been taken as the skew angle and different forms of skew plates are obtained by varying the skew angle. Sinusoidally distributed load (SDL), uniformly distributed load (UDL), and point load (PL) have been subjected to the top surface of the laminate and the non-dimensionalized center point deflection have been evaluated to assess the performance of the present hTFE. The observation from the present study further reinforce the versatility of the hTFE method for analysis of composite structures with complex shapes or geometries.
First Principle Analysis of the Effect of Strain on Electronic Transport Properties of Dumbbell-Shape Graphene Nanoribbons
Authors: Kudo Takuya , Zhang Qinqiang , Suzuki Ken , Miura Hideo
Published: January 2020

Graphene nanoribbons (GNRs), nano scale strips of graphene which consists of carbon hexagonal unit cell, are expected as next generation materials for high performance devices because of its unique super-conductive properties. When the strip width of graphene is cut into nano-scale, thinner than 70 nm, however, band gap starts to appear in the thin GNRs at room temperature, and thus, they show semiconductive properties. Previous studies have shown that the bad gap of GNR is highly sensitive to strain, which indicates that GNRs are candidates for a detective element of highly sensitive strain sensors. In practical applications, ohmic contact between a metallic electrode and a semiconductive detective element is indispensable for these sensors. By considering the effect of the width of GNRs on their electronic properties, dumbbell-shape GNRs (DS-GNRs) structures have been proposed for the basic structure of the GNR-base strain sensors, which consisted of GNRs with two different widths. Center portion of the DS-GNR is narrower than 70 nm and GNRs wider than 70 nm are attached at the both ends of the center GNR as electrode. Both semiconductive and metallic portions of a strain sensor consist of only carbon atoms using this DS-GNR structure. Even though this structure consists of one material, the effect of the interaction between two metallic and semiconductive GNRs must be clarified to realize the strain sensor with high performance. In this study, first principle calculations were applied to the analysis of the electronic band structure of the DS-GNR based on density functional theory (DFT). It was found that the local distribution of energy states of electrons and charges varied drastically as strong functions of the length of GNRs and the magnitude of the applied strain. The current through the DS-GNR structure was converged as the length of the semiconductive portion increased. In the models with enough length, transport property of the DS-GNR showed high sensitivity to strain. Thus, the effective resistivity of the structure varied from metallic to semiconductive, and therefore, this structure is appropriate for the next-generation highly sensitive and deformable strain sensors.
Dynamic Modelling of an Elephant Trunk Like Flexible Bionic Manipulator
Authors: Mishra Mrunal Kanti , Samantaray Arun Kumar , Chakraborty Goutam , Jain Aditya , Pathak Pushparaj Mani , Merzouki Rochdi
Published: January 2020

In this paper, an attempt is made to model and study the planar and spatial dynamics of flexible elephant trunk-like manipulator by using multi-body dynamics software MSC-ADAMS. The flexible manipulator is modelled for bending with variable curvature. The entire manipulator length is divided into two sub-sections with associated lumped mass, damping and stiffness for the dynamic analysis. In this model, each section has three pressure actuated bellow tubes, which are modelled as simple spring-damper with the net mass distributed at the ends. Besides, a torsional spring-damper system is also incorporated in each section model to resist the bending about the transverse axes when the pressures in the bellow tubes are unequal. The manipulator is so designed that due to different actuation forces (corresponding to different bellows), the resultant action is finally a bending moment at the tip of each section. The effect of the gravitational force is also included. The change in behaviour of the end-effector position and orientation with respect to time is studied along with the elongation of bellow tubes. The nature of the velocity profile of the end-effector is also determined to study the behaviour of the manipulator.
Ride Index for Metro Coaches: Experimental Evaluation and Vehicle Dynamics Results
Authors: Singh Sudhir Kumar , Danawe Hrishikesh Gajanan , Racherla Vikranth , Singh Sanjay R. , Prasad Arun
Published: January 2020

Instrumented field studies during oscillation trials for a new metro line and metro coaches were used to obtain Sperling’s ride index for the same. Ride index was also evaluated using a SIMPACK model. Actual coach, track, and speed information were used in the SIMPACK model. Ride index was seen to be influenced by track, velocity, and acceleration profiles. Ride indices were seen to be different in different directions (vertical, lateral and longitudinal). In the absence of track irregularities in SIMPACK, match between oscillation trail and SIMPACK results is best for longitudinal and worst for vertical ride indices.
Load Capacity of Support Structures for Direct Machining of Selective Laser Melted Parts
Authors: Höller Christian , Zopf Philipp , Schwemberger Philipp , Pichler Rudolf , Haas Franz
Published: January 2020

Selective Laser Melting (SLM), as a fast-growing metal-based Additive Manufacturing technology, allows to produce high strength parts with complex geometries. However, limited part properties in the as-built condition require effortful post-processing tasks (e.g. milling, drilling, polishing) to meet technical specifications and tolerances. This significantly increases the manufacturing costs of SLM parts. To address this problem, the concept of Direct Machining is presented. Direct Machining is defined as the post-processing of SLM parts via machining without prior removal of the parts from the build platform to achieve economic benefits. For this, the support structures have to withstand the occurring cutting forces during machining — a task for which they were not initially designed.

The aim of this study is to investigate the load capacity of 316L SLM support structures. For this, machining experiments on a five-axis milling machine were conducted. Cutting parameters, support geometries and support volume were varied and the cutting forces were measured to investigate their influence on the stability of the support structures. Results show, that deliberate SLM support structures allow precise machining directly on the build platform. Furthermore, a theoretical load model of Direct Machining is developed. Based on this, further optimization of the support structures regarding cutting force absorption and material volume are presented.
Investigation on the Condition Evaluation Method Based on NSET Model of the Propulsion System in Large Scale Ship
Authors: Zhao Jinxin , Zhou Jian , Shang Peng , Zhang Yinxun
Published: January 2020

The condition of the propulsion system in large scale ship directly affects the quality and safety of the ship’s operation, so it is important to evaluate the condition of the propulsion system. The Nonlinear State Estimation Technology (NSET) method is a nonparametric modeling method, which is mostly used in nuclear power plant sensor calibration, equipment monitoring, and electronic product life prediction. In this paper, the nonlinear state estimation technology (NSET) method is applied to the condition evaluation of the propulsion system. According to the operating characteristics and state parameters of the propulsion system, this paper first performs data preprocessing, and then uses the prepossessed data to perform condition evaluation by the NSET method. The model method can be connected with the database system. It has the advantages of faster evaluation speed and higher precision, and can detect possible failures of equipment system in time. This method has a wide range of adaptability.
The Effect of Creep-Fatigue Interactions on Thermo-Mechanical Fatigue Life and Reliability Estimates for a Typical Gas Turbine Engine Component
Authors: Muthu Shanmugam Esakki , Prakash Raghu V.
Published: January 2020

The low cycle fatigue-creep damage is the main parameter for the failures of gas turbine components under high temperature and cyclic loading. In this work, different combinations of Creep-Fatigue damage are introduced and checked for its impact on the Turbine life and its reliability. Linear and Non-Linear Creep-Fatigue combinations were considered as part of this work. The Turbine rotor under present study is made out of Nimonic-90 nickel base alloy forging. Weibull distribution method was used to study the reliability. It was found that, the reliability reduces from 99% to 25% when creep damage component is increased from 20% to 40% for a fixed Turbine life. The damage factor was found more in above linear Creep-Fatigue curve and less in below linear Creep-Fatigue curve.
Grain Boundary Cracking of Nickel-Based Alloy 625 Under Creep Loadings at Elevated Temperatures
Authors: Liang Yan , Luo Yifan , Suzuki Ken , Miura Hideo
Published: January 2020

Since the operating condition of thermal power plants has become harsher for minimizing the emission of CO2, Ni-based superalloys, such as Alloy 617 and 625, have been used in the plants to replace the conventional ferritic materials. Unfortunately, the increase of coefficient of thermal expansion compared with conventional steels is a concern. In addition, Ni-based superalloys have to suffer creep-fatigue random loading because thermal power plants have to compensate the random output of various renewable energies. It was found that the lifetime of Ni-based superalloys under creep-fatigue loading was much shorter than that under simple fatigue or creep loading. Thus, it has become very important to clarify the crack mechanism and establish the quantitative theory for estimating their lifetime under various loading conditions at elevated temperatures.

Thus, the elucidation of the initial damage mechanism of Alloy 625 under various loading is indispensable. Hence, the initial cracking mechanism of Alloy 625 at grain boundaries under creep loading was investigated experimentally. The creep test was applied to small specimens in Argon atmosphere. The change of the micro texture during the creep test was observed by using SEM. It was confirmed that all the initial cracks appeared at certain grain boundaries. The change of the crystallinity was observed by EBSD (Electron Back-Scatter Diffraction) analysis quantitatively. It was found that the local accumulation of dislocations at the cracked grain boundaries caused the initial cracks at those grain boundaries. The initiation of cracks appeared clearly between two grains which had difference of KAM (Kernel Average Misorientation) values larger than 0.2. Therefore, dislocations were accumulated at one side of the grain boundary. By measuring the KAM values near grain boundaries, the appearance of initial cracks can be predicted approximately.
Noncoaxial Vibration of Electrostatically Actuated DWCNT: Frequency Response of Primary Resonance
Authors: Caruntu Dumitru I. , Juarez Ezequiel
Published: January 2020

In this paper, the Method of Multiple Scales (MMS) is used to investigate the influences of the nonlinear intertube van der Waals coefficient, dimensionless damping, and voltage on the amplitude-frequency response of an electrostatically actuated double-walled carbon nanotube (DWCNT). The forces responsible for the nonlinearities in the vibrational behavior are intertube van der Waals and electrostatic forces. For perturbation, a small viscous damping and soft AC actuation are assumed for numerical simulation. For the first time in literature, forced vibration of the noncoaxial (out-of-phase) case is investigated. In this mode of vibration, the outer and inner carbon nanotubes move at ultra-high frequency in opposite direction, i.e., negative amplitude ratio. The DWCNT structure is modelled as a cantilever beam with Euler-Bernoulli beam assumptions since the DWCNT is assumed to have a high length-diameter ratio. The results shown assume steady-state solutions in the second-order MMS solution. The importance of the results in this paper are the effect of the strong nonlinearity of the van der Waals coefficient, damping, and voltage on the the DWCNT vibration.
Data-Driven Feedforward Tuning Approach for LPV Motion Systems
Authors: Huang Weicai , Yang Kaiming , Zhu Yu , Lu Sen
Published: January 2020

This paper aims to develop a new data-driven feedforward tuning approach to achieve high performance for linear parameter varying (LPV) motion systems. In the proposed approach, the feedforward controller is linearly parameterized with polynomial basis functions and parameter varying coefficients. Gauss-Newton Method is exploited to solve the corresponding parameter optimization problem. Parameter perturbing experiments are employed to estimate the gradient. The truncated singular value decomposition (SVD) method is adopted to deal with the ill-conditioned matrix inversion problem. No parametric model is required throughout the tuning process. Simulations are conducted to test the performance of the proposed approach. And the results indicate that the parameter varying dynamics of the plant are well compensated by the proposed approach.
Improving Packing Efficiency and Component Handling Reliability in Logistics With a Novel CAD Approach
Authors: Chekurov Sergei , Mäkelä Ismo
Published: January 2020

This paper presents a novel method of designing logistic separators based on existing 3D models of components. The proposed method is used to create horizontal sheet separators with cavities that conform to the geometry of the component. Because the method allows the components to be packed closer to one another, and because they can be made to overlap in the vertical direction, it increases the number of components that can be transported per logistic box. Additionally, because the components are constrained by cavities based on their geometry, a predefined grasping orientation for robotic arms can be guaranteed. The paper presents two methods to create separators that allow packing in three dimensions: manual and automatic.

The automatic method presented in the paper generates sheets without manual input after setting the components in a three-dimensional space. As there are several technical solutions to performing the method, the paper describes the approach on a general level, while pointing out significant hurdles that can be encountered in development.

The paper describes each step of the workflow of creating the separators in detail by using an example component. The presented method works with practically any component that has a 3D model. However, the extent of the improvement in packing efficiency is highly dependent on their complexity. The paper discusses the factors that contribute to the complexity and gives recommendations on what type of components benefit most from the concept.