bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability Optimization Allocation Method for Multifunction Systems Based on Goal Oriented Methodology
Authors: Yi Xiaojian , Dhillon B. S. , Shi Jian , Mu Hui-na , Hou Peng
Published: February 2017

This paper proposes a new reliability optimization allocation for multifunction systems based on GO methodology. First, two constraints functions are proposed, which are unit reliability constraint function and system reliability constraint function, respectively. The unit reliability constraint function consists of allocated reliability index of unit and the range of reliability index for unit. And the system reliability constraint function consists of the target reliability index of system, and the predicted reliability index of system obtained by using GO method and allocated reliability index of unit. Then, the objective function of optimization allocation problem is established to describe the system cost minimization taking into consideration costs of unit redesigned and unit selected versions. Based on above, the mathematic model of reliability optimization allocation problem for complex multifunction systems is established. In addition, an improved genetic algorithm is presented to solve this mathematic model. Furthermore, the process of the new reliability optimization allocation method for complex multifunction systems is formulated. Finally, the new method is applied in reliability optimization allocation of Power-shift Steering Transmission whose goal is to minimize the system cost. The results analysis shows that the system costs for different operation times turn to a relatively stable value, and the allocated reliability indexes of unit are satisfied with engineering requirements. All in all, this new optimization allocation method can not only obtain the reasonable allocation results quickly and effectively, but it also can overcome the disadvantages of existing reliability optimization allocation methods for complex multifunction systems efficiently. In addition, the analysis process shows that the reliability optimization allocation method based on GO method can provide a new approach for the reliability optimization allocation of multifunction systems.
Reliability Prediction Approach Based on Non-Probabilistic Interval Analysis: Case Study of Transmission System
Authors: Yi XiaoJian , Shi Jian , Dhillon B. S. , Dong Hai-ping , Lai Yue-hua
Published: February 2017

This paper presents a reliability prediction approach based on non-probabilistic interval analysis. First, the interval reliability prediction model is presented from the aspects of interval stress-strength interference model, and interval reliability criteria. Then, the process of reliability prediction approach based on non-probabilistic interval analysis is formulated. Furthermore, the reliabilities of Planetary Gear Drive Mechanism at different confidence coefficients are obtained by using the non-probabilistic interval analysis. Finally, the result of the non-probabilistic interval analysis is compared with the results of non-probabilistic convex model and the probabilistic method in order to illustrate the characteristics, advantage and engineering practicality of the non-probabilistic interval analysis. In addition, the consistent relationship between reliability by using probabilistic method and the reliability by using non-probabilistic method is preliminarily discussed. All in all, this paper not only takes planetary gear drive mechanism as a case to provide guidance for mechanisms by using the reliability prediction approach based on non-probabilistic interval analysis, but also it points out the direction for future research of the reliability prediction approach based on non-probabilistic interval analysis.
Thermal Drift and Dynamic Response of Micro Flow Sensors for Smart VP Shunts
Authors: Enikov Eniko T. , Édes Gergő , Anton Rein
Published: February 2017

This paper describes the development of a highly sensitive microfluidics flow sensor using MTJ magnetic sensors to detect motion of slow-moving fluids. A motivating application for the proposed device is the development of an implantable flow sensor, capable of monitoring the amount of cerebral spinal fluid drained from the ventricles of the brain. Micro-fabricated ferromagnetic flaps are used to detect motion of the surrounding fluid. The deflection of the flaps is detected by an ultra-sensitive MTJ magnetic field sensor placed outside of the lumen of the catheter. Previous studies have presented a working device with a resolution of up to 1.4 mL/hr. This paper presents the improvements made to the device in terms of sensitivity, thermal noise rejection, and dynamic response. Upon investigation of possible noise sources, a thermally induced sensor drift was found to be the most significant factor affecting the sensors response. A static temperature compensation reduced this drift to less than 120 mL per 12-hr period. Further improvements to the design of the ferromagnetic transducers resulted in a 4.5-fold increase in sensitivity over the previous designs. Results from dynamic testing of the sensor revealed a time constant of 0.4 seconds, which was found adequate for the envisioned application.
Parametric Analysis of Factors Influencing Stiffness and Crashworthiness of a Ladder Frame
Authors: Shammy Devaraj , Prakash Raghu V.
Published: February 2017

During a vehicle crash, a major portion of the energy is absorbed by the frame structure. In general, stiffness and durability are considered as the primary criteria for design; but, not the crashworthiness of a frame structure. The purpose of this study is to evaluate the crash worthiness of a ladder frame structure. The effect of variation of bending stiffness and torsion stiffness of the ladder frame on the crashworthiness, specific energy absorption (SEA) and the peak load is investigated. Numerical analysis for frontal crash and stiffness of the ladder frame is done using LS DYNA® and CATIA®-Structural analysis software respectively. The numerical model for the frame frontal crash is validated by benchmarking the results obtained in this work with literature data. The height and the thickness of the frame side member (FSM) which absorbs most of the energy are taken as the design variables. The cross section of the FSM and cross members are taken as rectangular tubes with 90 mm height and 2 mm thickness as the base model dimension. The optimization is done to maximize the SEA of the frame with stiffness as the constraint. An optimized combination of design variables is identified using the response surface method. It is seen that the optimal point is found to be with the maximum height and minimum thickness; it is inferred that the crashworthiness parameters are bounded by the stiffness target set for the frame. Parametric analysis is done to investigate the influence of the design variables on the crash performance of ladder frame. The results show that increase in height by 50% from the base model will result in 4% increase in SEA and 60% reduction in peak loads when compared to a case with 50% increase in thickness. Torsion and bending stiffness was found to be 8% lesser and 62% higher respectively in case of 50% increase in height.
Flow Architectures for Ground-Coupled Heat Pumps
Authors: Lorente S. , Bejan A.
Published: February 2017

In this paper we report the main advances made by our research group on the heat transfer performance of complex stream architectures embedded in a conducting solid. The immediate application of this review work deals with ground-coupled heat pumps. Various configurations are considered: U-shaped with varying spacing between the parallel portions of the U, serpentines with three elbows, and trees with T- and Y-shaped bifurcations. In each case the volume ratio of fluid to soil is fixed. We determine the critical geometric features that allow the heat transfer density of the stream-solid configuration to be the highest that it can be. In the case of U-tubes and serpentines, the best spacing between parallel portions is discovered, whereas the vascular designs morph into bifurcations and angles of connection that provide progressively greater heat transfer rate per unit volume. Next we move to more complex underground structures, connecting several heat pumps to the same fluid loop. We conclude by comparing the merits of the two options.
Rub-Impact Detection of Rotor Systems Using Time-Frequency Techniques
Authors: Yang Laihao , Chen Xuefeng , Wang Shibin , Zuo Hao
Published: February 2017

Since increasing demands for high efficiency of high speed rotating machines in recent years, the clearance between rotor and stator becomes smaller and smaller. Consequently, rub-impact fault is more likely to occur. It has become one of the most common and serious malfunctions for rotor system in practical engineering. Because the rub-impact severely induces the rotor dynamic instability, it will finally result in catastrophic failures and great economic loss if undetected in time. The occurrence of the rub-impact leads to a contact force between rotating shaft and stator which can be regarded as an additional support on the rotor system. The contact force will further result in the stiffening effect. As a result, some fast time-varying phenomena of vibration responses including the fast time-varying transient stiffness and the fast oscillated instantaneous frequency (IF) may appear. These phenomena may offer abundant characteristics to diagnose the rub-impact fault of rotor system. In this paper, an effective method based on the fast oscillated characteristics of IF for vibration responses is proposed to detect rub-impact fault of rotor bearing system. First of all, the fast time-varying transient stiffness of rub-impact rotor system is qualitatively formulated based on the Jeffcott rotor model and the fast oscillated characteristics of IF is presented and theoretically analyzed. Second, a time-frequency technique called nonlinear squeezing time-frequency transform (NSTFT) is introduced to extract the fast oscillated IF resulting from the rub-impact fault of rotor systems. Numerical simulations are respectively conducted on the Jeffcott rotor system with linear stiffness and oil film bearings. And then the oscillated characteristics of the IF are analyzed. The analysis results suggest that the IF of the vibration responses remains constant at the rotating frequency if there is no rub-impact fault. However, if rub-impact fault occurs, the IF of the vibration responses will oscillate periodically around the basic harmonic frequency. Furthermore, the oscillation law of the IF of vibration responses for rub-impact rotor systems is also numerically investigated. It is found that the oscillation frequency is the 1/k (k = 1, 2, 3, ...) of the rotating frequency if the rotor system operates at periodic-k motion. Finally, rub-impact fault experiments are performed under different operating regimes. The experimental results are consistent with the numerical results, thus demonstrating the validity and the practicability of the proposed method.
Optimizing Dynamic Performance of High-Speed Road Vehicles Using Aerodynamic Aids
Authors: Sikder Tushita , Kapoor Saurabh , He Yuping
Published: February 2017

This paper focuses on the effects of aerodynamic aids on the lateral and longitudinal dynamics of high-speed road vehicles. Aerodynamic aids, such as spoilers, can reduce drag to improve vehicle’s fuel economy and acceleration performance. On the other hand, aerodynamic aids can be utilized to enhance the lateral stability of the vehicle at high speeds by generating downforce or negative lift. However, the co-existence of drag and lift creates a paradox, that is, the downforce generated to improve car’s high-speed stability acts as a parasitic force on the car-body and slows down the vehicle forward speed. This paper will illustrate the juxtaposed effects of the aerodynamic forces on the lateral stability of the vehicle. Airfoils in the role of external aerodynamic aids will be examined based on their shapes, geometrical configurations, and at varying relative positions using the CFD technique. Moreover, the effects of attack angles, change in Reynold’s numbers (air stream velocities), and varying ground clearance on the lateral dynamics of the vehicle will be analyzed using numerical simulations with ANSYS FLUENT software package. The results and reliability of CFD simulations has a high dependency on the size of the grid, thus the aim of this paper will be to ensure that the results are independent of the grid size. Selection of the optimum design will be based on performance parameters like drag and lift coefficients. The challenge posed here is to ensure the lateral stability of the vehicle while achieving high average speed. Therefore, the main goal of the study is to enhance handling capabilities of the road vehicles at high speeds while minimizing the drag.
Investigation of Two Mechanisms Governing Cloud Cavitation Shedding: Experimental Study and Numerical Highlight
Authors: Croci Kilian , Tomov Petar , Ravelet Florent , Danlos Amélie , Khelladi Sofiane , Robinet Jean-Christophe
Published: February 2017

Cavitation is a phenomenon of classical interest which can be observed in various applications. It consists in a transition of phase due to a pressure drop under the saturation pressure of a liquid. The unsteady behavior of this phenomenon leads to generate some issues such as erosion, noise or vibrations: as a result the comprehension of the cavity dynamics remains of crucial importance. Unsteady cavitation has been investigated in numerous studies and a mechanism of re-entrant jet has been firstly identified as responsible of the cavity shedding process. Recently, a second shedding mechanism, induced by a shock wave propagation due to the condensation of vapor structures, has been experimentally highlighted with X-ray measurements [1]. The present paper focuses on the experimental detection, with a wavelet method, of these two shedding features on 2D image sequences recorded with a high-speed camera about a double transparent horizontal Venturi nozzle with 18°/8° convergent/divergent angles respectively. A compressible two-phase flow numerical 3D model is performed in complement in order to illustrate some phenomena hardly perceptible experimentally.
Simplified Spur Gear Design
Authors: Osakue Edward E.
Published: February 2017

A simplified design method (SDM) for spur gears is presented. The Hertz contact stress and Lewis root bending stress capacity models for spur gears have been reformulated and formatted into simplified forms. A scheme is suggested for estimating the AGMA J-factor in Lewis root bending stress for spur gears from a single curve for both pinion and gear instead of the conventional two curves. A service load factor is introduced in gear design that accounts for different conventional rated load modifier factors. It represents a magnification factor for the rated load in a gear design problem.

Two design examples are considered for applications of the stress capacity models. In Example 1, the Hertz contact stress of the SDM deviates from AGMA value by 1.95%. The variance in Example 2 between the contact stress of the SDM and FEM is 1.184% while that between SDM and AGMA is 0.09%. The root bending stress of AGMA and SDM for the pinion in Example 1 differs by 1.44% and that for the gear by 6.59%. The difference between the root bending stress of AGMA and SDM for pinion and gear in Example 2 is 0.18%. These examples suggest that the new simplified method gives results that compare very favorably with both AGMA and FEM solutions. The simplified method developed is recommended mainly for preliminary design when quick but reliable solutions are sought.
Optimized Modular Design for Energy Efficiency: The Case of an Innovative Electric Hybrid Vehicle Design
Authors: Trancossi Michele , Pascoa Jose C.
Published: February 2017

Modular Design has made an important contribution to the industrial evolution, increase of quality of products and goods and to economic development. It has produced an important evolution in design (technical modularity), in the organization of production and of companies. It allowed going beyond vertical integration, by fostering vertical specialization in both manufacturing and innovation. Several authors are appointing important question on the modular approach. They move observations of different nature concluding that the enthusiasm for modularity has gone too far. One of the critical positions sustains that modular design has imposed technical choices that conflicts with energy efficiency in vehicle design such as a gradual increase of weight over time and the consequent reduction of potential gains in terms of energy consumption and environmental footprint of vehicles. This paper agrees with some arguments of the revisionist literature in cautioning against errors that can be produced by a pervasive modularity. But it moves from an energetic analysis and has not the objective of defining an alternative theory. More modestly, it aims to present a possible way for coupling modular design with energy optimization in the case of an electric vehicle. The initial inspiration can be of this case study is Bejan’s preliminary modular definition of constructal optimization, which can fit perfectly with industrial modular design. Even if this modular optimization does not have the ambition of defining the best possible solution to a complex design problem, such as Multidisciplinary Design Optimization has, it allows defining configuration that can simply evolve over time by mean of a step by step optimization of the critical components that influences the behavior of a complex industrial system. It reveals then to be applicable to the concept of vehicle platform that is today widely in use. The specific test case is the design of an electric city vehicle which has been optimized by a step applying this modular optimization approach. This paper has also a romantic value because it ha taken the move from the emotion that has been caused by the stop to the production of an extraordinary myth, such as Land Rover Defender. 70 years of production without important changes means that Defender has been not only the most successful British vehicle, but also that it has been a fundamental part of our way of living. This extraordinary longevity is an extraordinary technical and cultural heritage to our time. This decision forces the authors to try to analyze the conceptual modular design of a vehicle that can compete with Defender in terms of use and performances. Results have been surprising demonstrating that the use of industrial grade components and their accurate choice will allow defining new vehicle platforms that can radically improve energy efficiency of vehicles.
Viscoelastic Flow in Teardrop-Shaped Tubes: Transversal Field
Authors: Letelier Mario F. , Siginer Dennis A. , Gutiérrez Sebastian , Arratia Pablo , González Amaru
Published: February 2017

We present an analytical study of secondary flows in tubes of teardrop shape for a viscoelastic fluid described by the Phan-Thien-Tanner (PPT) model. The analytical development is based on a one-to-one mapping (shape function) to describe the teardrop contour and the expansion of field variables into asymptotic series in terms of the Weissenberg number Wi. Secondary flows and the temperature field are determined solving the hierarchical set of equations resulting from the asymptotic series expansions.
Theoretical Prediction of Laminar Burning Speed and Ignition Delay of Gas to Liquid Fuel
Authors: Yu Guangying , Askari Omid , Hadi Fatemeh , Wang Ziyu , Metghalchi Hameed , Kannaiyan Kumaran , Sadr Reza
Published: February 2017

Gas to Liquid (GTL), an alternative synthetic jet fuel derived from natural gas has gained significant attention recently due to its cleaner combustion characteristics when compared to conventional counterparts. The effect of chemical composition on key performance aspects such as ignition delay time, laminar burning speed, and emission characteristics have been experimentally studied. However, the development of chemical kinetics mechanism to predict those parameters for GTL fuel is still in its early stage. In this work, a detailed kinetics model (DKM) has been developed based on the chemical kinetics reported for GTL surrogate fuels. The DKM is applied to the chemical kinetic mechanism of 597 species and 3853 reactions. The DKM is employed in a constant internal energy and constant volume reactor to predict the ignition delay times for GTL and its three surrogates over a wide range of initial temperature, pressure and equivalence ratio. The ignition delay times predicted using DKM are validated with those reported in the literature. Furthermore, the CANTERA freely propagating 1D flame code is used in conjunction with the chemical kinetic mechanism to predict the laminar burning speeds for GTL fuel over a wide range of operating conditions.
Thermal Analysis of Offshore Buried Pipelines Through Experimental Investigations and Numerical Analysis
Authors: Chakraborty Suvra , Talimi Vandad , Haghighi Mohammad , Muzychka Yuri , McAffee Rodney
Published: February 2017

Modeling of heat loss from offshore buried pipelines is one of the prime concerns for Oil and Gas industries. Offshore Oil and Gas production and thermal modeling of buried pipelines in arctic regions are challenging tasks due to environmental conditions and hazards. Flow properties of Oil and Gas flowing through the pipelines in arctic regions are also affected due to freezing around pipelines. Solid formation in the production path can have serious implications on production. Heavy components of crude oil start to precipitate as wax crystal when the fluid temperature drops. Gas hydrates also form when natural gas combines with free water at high pressure and low temperature. Pipeline burial and trenching in some offshore developments are now one of the prime methods to avoid ice gouge, ice cover, icebergs, and other threats. Long pipelines require more thermal management to deliver production to the sea surface. Significant heat loss may occur from offshore buried pipelines in the forms of heat conduction and natural convection through the seabed. The later can become more prominent where the backfill soil is loose or sandy. The aim of this paper is to provide an insight of modeling and conducting the experiments using different parameters with numerical analysis results support to investigate the heat loss from offshore buried pipelines. This paper also provides validation of the outputs from benchmark tests with analytical models available for theoretical shape factor at constant temperature and constant heat flux boundary conditions. These theoretical models have limitations such as the assumption of uniform soil properties around the buried pipeline, isothermal outer surface of the buried pipeline and soil surface. Degree of saturation of surrounding medium can play a significant role in the thermal behavior of fluid travelling through the backfill soil. This paper presents several steady states and transient response analysis describing some influential geotechnical parameters along with test procedures and numerical simulations using CFD to model the heat loss for different parameters such as burial depth, backfill soil, trench geometries etc. This paper also shows the transient response for several shutdown (cooldown) tests performed in the saturated sand medium. The statistical and uncertainty analysis performed from the experimental outputs also ensure the legitimacy of the experimental model. The outcomes of this research will provide valuable experimental data and numerical predictions for offshore pipeline design, heat loss from buried pipelines in offshore conditions, and efficient model to mitigate the flow assurance issues e.g. wax and hydrates.
Risk Management for Rail Safety: Post Lac Megantic
Authors: Raghunathan Vijay , Mitchell Ron , Pitblado Robin , Wu Hong
Published: February 2017

Following several recent serious rail accidents in North America, changes in regulation and increased public awareness is driving the need to address gaps in rail safety. The industry and regulators have numerous safety initiatives; however prescriptive standards in combination with a performance based approach could be a powerful tool for understanding and mitigating risk in a cost effective way.

This paper reviews the principles of safety risk management that can be applied to safe transportation of flammable hydrocarbons by Rail. FRA’s proposed rulemaking on Risk reduction program and its potential impact on the industry are also addressed.

The approach proposed in this paper focuses on existing and new proposed safeguards/barriers and how they could be monitored and managed. The paper aims to set the path forward for structured risk based thinking in managing rail safety. The first part of the paper explains the barrier based risk assessment approach using the Lac Megantic accident as an example. A bow-tie is developed to deconstruct the incident timeline and to capture the safeguards that existed at that time and their working status. This diagram cross references Transport Canada’s Investigation findings.

The second part of the paper evaluates the new mitigation measures proposed by FRA HM 251 rulemaking (“Enhanced Tank Car Standards and Operational Controls for High-Hazard Flammable Trains” Final Rulemaking”) as potential safeguards and their impact on the overall risk of transportation. A baseline risk is first established for transporting crude by rail assuming some common safeguards in place. A simple Quantitative Risk Assessment methodology including likelihood and consequence was then used to estimate the base case risk. Risk mitigation and effect of any additional new measures like Changes in Rail Tank Car design, Oil Conditioning, Enhanced Braking to Mitigate Damage in Derailments, Speed Limit changes, Positive train control, Train manning when loading are assessed.
Preventing Upper Airway Collapse Using CPAP With and Without Pressure Oscillations
Authors: Ashaat Sherif , Al-Jumaily Ahmed M. , Huang Loulin
Published: February 2017

During respiration, upper airway collapse occurs when the forces generated from the airway negative pressures become greater than the forces of the airway wall muscles. For patients diagnosed with moderate to severe obstructive sleep apnea (OSA), Continuous Positive Airway Pressure (CPAP) is the most effective non-invasive treatment. The CPAP provides a continuous humidified and pressurized air to prevent airway collapse. The use of the CPAP has been reported to be associated with some side effects including nasal congestion and dry nose. Also stroke symptoms were recorded for cardiovascular disease patients due to the high operating pressure. Using MRI scans, this paper investigates the effects of using the pressure oscillations superimposed on the CPAP to keep the airway open at lower pressure distributions inside the upper airway and consequently increase the patients’ comfort and reduce their rejection to the CPAP.
A Kinetic Formulation of Reacting Molecular Dynamics
Authors: Bass Joseph L. , Fahrenthold Eric P.
Published: February 2017

Macroscale, mesoscale, and ab initio models of reacting shock physics are based, in their most general forms, on rate law descriptions of the chemical processes of interest. Reacting molecular dynamics simulations, by contrast, typically employ potential functions to model chemical reactions. An alternative reacting molecular dynamics formulation, employing nonholonomic Hamiltonian methods, models bonding-debonding as a kinetic process. Simulation results using this method are compared with experiment, for energy release and detonation products in HMX. The molecular dynamics simulations may be used to develop a macroscale, adiabatic model of the detonation chemistry.
Analytical Model for Lattice Thermal Conductivity Predictions of Periodic Nanoporous Structures
Authors: Hao Qing , Xiao Yue , Zhao Hongbo
Published: February 2017

Phonon transport within nanoporous bulk materials or thin films is of importance to applications in thermoelectrics, gas sensors, and thermal insulation materials. Considering classical phonon size effects, the lattice thermal conductivity KL can be predicted assuming diffusive pore-edge scattering of phonons and bulk phonon mean free paths. In the kinetic relationship, kL can be computed by modifying the phonon mean free paths with the characteristic length ΛPore of the porous structure. Despite some efforts using the Monte Carlo ray tracing method to extract ΛPore, the resulting KL often diverges from that predicted by phonon Monte Carlo simulations. In this work, the effective ΛPore is extracted by directly comparing the predictions by the kinetic relationship and phonon Monte Carlo simulations. The investigation covers a wide range of period sizes and volumetric porosities. In practice, these ΛPore values can be used for thermal analysis of general nanoporous materials.
A Kinematics Velocity Reliability Analyzing Method for Complex Planar Linkage Mechanism Based on Equal-Effective Mechanics Model
Authors: Liu Jingyi , Zhang Yugang , Guo Wei , Sun Cong
Published: February 2017

The planar linkage mechanism (PLM) is a kind of familiar mechanism. The accuracy of its kinematic parameters, such as displacement or velocity, is crucial to accomplish its function. The parameters are not always precise due to the indeterminacy of some influencing factors. This paper proposes a methodology to analyze the velocity reliability of PLM based on the equal-effective mechanics model (EMM), with the effect of joint clearance, component size randomness and applied force randomness considered. More specifically, how these factors would influence the EMM is studied and then the motion law and risk velocity point of certain part can be obtained. To model the joint clearance exactly, the concept of effective length is recommend. The Response Surface Method (RSM) is used to express the relationship between input parameters and output parameter (velocity), based on which the reliability analysis is conducted. The sensitivities of the parameters are expressed by Sobol variance analyzing method. Finally a certain aircraft cabin door retractable mechanism (one sort of complex planar linkage mechanism) is selected as an example, showing that the approach proposed this article has a great value to be used for engineering object.
Aerodynamics Simulation Method for Swept Wind Turbine Blades Based on Improved Vortex Lattice Method
Authors: Wu Guangxing , Zhang Lei
Published: February 2017

Recent advances in blade design involve the development of backward swept blades, which can increase energy capture that minimizes an increase in the turbine loads by bend-twist coupling deformation. Most of the aerodynamics simulation modules in aeroelastic analyses are based on Blade Element Momentum Theory, which is limited to straight blades and does not account for sweep. The goal of this work is to develop higher fidelity aerodynamic simulation method for swept wind turbine. The vortex lattice method (VLM) with lower computational cost can consider the effects of spanwise flow, dynamic inflow and wake. A VLM code was obtained and validated for an elliptical planform wing with analytical solutions. Unfortunately, the VLM dose not consider viscous effects such as skin friction and form drag due to inherently assumption of potential flow; therefore, it is limited to be applied to wind turbine blades with thick airfoils. A numerical methodology named viscous correction method (VCM) considering viscosity was developed for predicting the aerodynamic force of wind turbine blades. Experimental results that include viscous terms are brought in the iteration of VLM to modify the vortex strength of all the vortex lattices, so that skin friction and form drag can be included. Lots of wind tunnel experimental results on NREL phase VI rotor with two straight blades have been published, which were chosen to validate the VCM. Good qualitative agreement is obtained between computated and experimental results when VCM is introduced into VLM. To apply VCM to swept blade, it is still high-cost work to conduct lots of experiments on the swept blade strips with different sweep angles and airfoils. Furthermore, one correction model was also developed to compute the aerodynamic force of swept blade from experimental results of straight blade, which is named sweep correction model (SCM). The SCM is obtained by theoretical derivation and validated by CFD method. Finally, the vortex lattice method with VCM and SCM was applied to NREL 5MW rotor with two swept blade designs and baseline blade. The effects of sweep on power and load are minor if the effects of structure deformation are not involved.
Observations on the Residual Martensite Phase of NiTi Shape Memory Alloy Micro-Tubes Under Uniaxial and Multiaxial Fatigue-Loadings
Authors: Song Di , Kang Guozheng , Kan Qianhua , Yu Chao
Published: February 2017

NiTi shape memory alloys (SMAs) are widely used in astronautics and bio-medical fields due to their shape memory property, superelasticity and excellent biological compatibility. In such applications, the NiTi SMA devices are often subjected to a kind of strain- or stress-controlled cyclic loading, leading to the fatigue failure of NiTi SMAs is a key issue that should be investigated. Meanwhile, with the ambient temperature higher than austenite transformation finish temperature (Af), the NiTi SMAs can transform into martensite phase during loading process and recover their austenite phase during unloading, the unique martensite transformation and its reverse of NiTi SMAs indicates their fatigue failure characters much different from ordinary metals. Thus, besides cyclic-loading experiments, the micro-structure observations on the morphology of residual martensite on fracture surfaces is also an important component of investigating the damage mechanisms of NiTi SMAs, which should be taken into considered as well. This paper aims at the micro-structure observations on the fractured NiTi micro-tubes after both uniaxial and multiaxial stress-controlled fatigue loadings, in which the morphology of residual martensite affected by different stress levels and loading paths are compared and analyzed. The results show that the bigger-sized residual martensite phase is inclined to appear in the loading cases with higher stress level or multiaxial paths, corresponding to the higher residue deformations in the fatigue-loading tests. Meanwhile, in multiaxial loadings, due to the effect of gradually increased shear stress along the radial direction, it leads to the size of residual martensite near the outer surface of the NiTi micro-tubes much bigger than that near the inner surface, whereas in uniaxial loadings, the distribution of martensite phase are nearly uniform on the cross section of NiTi specimens. It can be also found that the locations near the internal defects tend to produce bigger sized martensite phase as well, which indicates the stress-concentration effect induced therein. Moreover, the morphology of mutually hindered martensite phase in different directions can be also observed in the fractured specimens, it implies the propagation of the micro-cracks which caused by the transformation induced plasticity between the interface of austenite and martensite will be further prevented, leading to the relatively slower crack propagation rate of NiTi SMAs than ordinary metals. The findings can provide experimental support to investigating the damage mechanisms of NiTi SMAs in microscopic field, and it is also the foundation of establishing the reasonable damage evolution model and life prediction model of NiTi SMAs, describing their distinctive fatigue characters in both uniaxial and multiaxial loading conditions.
Understanding Progressive Buckling in Extruded Square Tubes Using Multiple Measurement Techniques
Authors: Sethy Girija Kumari , Prakash Raghu V.
Published: February 2017

Thin walled structures are widely used as energy absorbing devices during accidents, collisions in various transportation systems. Designing an energy absorbing device requires proper combination of geometry and material. The deformation behavior and collapse modes of these structures are complex. Simple geometries with square, polygonal or circular cross section deform with various collapse modes for energy absorption in these structures. In the present work, square extruded Aluminum tubes are axially compressed under quasistatic loading. Infra-red thermal imaging is done to measure the rise in surface temperature during axial compression of the square tube. Post experimental investigations have been conducted using Scanning Electron Microscope (SEM) and Computerized Tomography (CT) scan to understand the deformation behavior at micro level. The out of plane displacement after progressive buckling is measured using a Coordinate Measuring Machine (CMM). Full field 3D Digital image correlation (DIC) technique has been used to measure the surface strain. The results indicate a good correlation between displacements measured by DIC technique and CMM. Strain field developed during progressive buckling suggests large strains at crumple zones. SEM investigations suggest material pile-up at severely compressed regions with thinning on tensile deformation edges.
Experimental Characterization and Finite Element Modeling of Film Capacitors for Automotive Applications
Authors: Croccolo D. , Brugo T. M. , De Agostinis M. , Fini S. , Olmi G.
Published: February 2017

As electronics keeps on its trend towards miniaturization, increased functionality and connectivity, the need for improved reliability capacitors is growing rapidly in several industrial compartments, such as automotive, medical, aerospace and military. Particularly, recent developments of the automotive compartment, mostly due to changes in standards and regulations, are challenging the capabilities of capacitors in general, and especially film capacitors. Among the required features for a modern capacitor are the following: (i) high reliability under mechanical shock, (ii) wide working temperature range, (iii) high insulation resistance, (iv) small dimensions, (v) long expected life time and (vi) high peak withstanding voltage. This work aims at analyzing the key features that characterize the mechanical response of the capacitor towards temperature changes. Firstly, all the key components of the capacitor have been characterized, in terms of strength and stiffness, as a function of temperature. These objectives have been accomplished by means of several strain analysis methods, such as strain gauges, digital image correlation (DIC) or dynamic mechanical analysis (DMA). All the materials used to manufacture the capacitor, have been characterized, at least, with respect to their Young’s modulus and Poisson’s ratio. Then, a three-dimensional finite element model of the whole capacitor has been set up using the ANSYS code. Based on all the previously collected rehological data, the numerical model allowed to simulate the response in terms of stress and strain of each of the capacitor components when a steady state thermal load is applied. Due to noticeable differences between the thermal expansion coefficients of the capacitor components, stresses and strains build up, especially at the interface between different components, when thermal loads are applied to the assembly. Therefore, the final aim of these numerical analyses is to allow the design engineer to define structural optimization strategies, aimed at reducing the mechanical stresses on the capacitor components when thermal loads are applied.
Mechanical Properties of Biomimetic Leaf Composite
Authors: Nayeb Hashemi Hamid , Liu Gongdai , Vaziri Ashkan , Olia Masoud , Ghosh Ranajay
Published: February 2017

In this paper, we mimic the venous morphology of a typical plant leaf into a fiber composite structure where the veins are replaced by stiff fibers and the rest of the leaf is idealized as an elastic perfectly plastic polymeric matrix. The variegated venations found in nature are idealized into three principal fibers — the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary veins of a typical leaf. The tertiary fibers do not interconnect the secondary fibers in our present study. We carry out finite element (FE) based computational investigation of the mechanical properties such as Young’s moduli, Poisson’s ratio and yield stress under uniaxial loading of the resultant composite structures and study the effect of different fiber architectures. To this end, we use two broad types of architectures both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions are kept constant and a comparative parametric study is carried out by varying the inclination of the secondary fibers. We find significant effect of fiber inclination on the overall mechanical properties of the composites with higher fiber angles transitioning the composite increasingly into a matrix-dominated response. We also find that in general, composites with only secondary fibers are stiffer with closed cell architecture of the secondary fibers. The closed cell architecture also arrested the yield stress decrease and Poisson’s ratio increase at higher fiber angles thereby mitigating the transition into the matrix dominated mode. The addition of tertiary fibers also had a pronounced effect in arresting this transition into the matrix dominated mode. However, it was found that indiscriminate addition of tertiary fibers may not provide desired additional stiffness for fixed volume fraction of constituents. In conclusion, introducing a leaf-mimicking topology in fiber architecture can provide significant additional degrees of tunability in design of these composite structures.
Handling Uncertainty in the Remnant Fatigue Life Assessment of Offshore Process Pipework
Authors: Keprate Arvind , Ratnayake R. M. Chandima
Published: February 2017

A typical procedure for a remnant fatigue life (RFL) assessment is stated in the BS-7910 standard. The aforementioned standard provides two different methodologies for estimating RFL; these are: the S-N curve approach and the crack growth laws (i.e. using Linear Elastic Fracture Mechanics (LEFM) principles) approach. Due to its higher accuracy, the latter approach is more commonly used for RFL assessment in the offshore industry. Nevertheless, accurate prediction of RFL using the deterministic LEFM approach (stated in BS-7910) is a challenging task, as RFL prediction is afflicted with a high number of uncertainties. Furthermore, BS-7910 does not provide any recommendation in regard to handling the uncertainty in the deterministic RFL assessment process. The most common way of dealing with the aforementioned uncertainty is to employ Probabilistic Crack Growth (PCG) models for estimating the RFL. This manuscript explains the procedure for addressing the uncertainty in the RFL assessment of process piping with the help of a numerical example. The numerically obtained RFL estimate is used to demonstrate a calculation of inspection interval.
Experimental and Simulation of a Cam and Translated Roller Follower Over a Range of Speeds
Authors: Yousuf Louay S. , Marghitu Dan B.
Published: February 2017

In this study a cam and follower mechanism is analyzed. There is a clearance between the follower and the guide. The mechanism is analyzed using SolidWorks simulations taking into account the impact and the friction between the roller follower and the guide. Four different follower guide’s clearances have been used in the simulations like 0.5, 1, 1.5, and 2 mm. An experimental set up is developed to capture the general planar motion of the cam and follower. The measures of the cam and the follower positions are obtained through high-resolution optical encoders (markers). The effect of follower guide’s clearance is investigated for different cam rotational speeds such as 100, 200, 300, 400, 500, 600, 700 and 800 R.P.M. Impact with friction is considered in our study to calculate the Lyapunov exponent. The largest Lyapunov exponents for the simulated and experimental data are analyzed and selected.
Motion Analysis of Robot Arm With Movement Restriction
Authors: Poley Celeste Colberg , Balachandran Balakumar
Published: February 2017

Medical robots are increasingly being used to assist surgeons during procedures requiring precision. As reported in the literature, surgeons have been opting for minimally invasive surgery, as it reduces patient complications, overall patient recovery time, and hospital time for the patient. Robotic manipulators can be used to overcome natural limitations related to vision and human dexterity, and allow surgeons to transcend these limitations without having to sacrifice improvement in patient outcome. A desirable attribute of surgical robots is maneuverability similar to the human arm. The KUKA DLR Lightweight Robot Arm (LWR), with seven degrees of freedom, retains many of these human-like dexterity traits. Due to the KUKA robot arms maneuverability and flexibility, it is well-suited for intricate tasks based upon motion analyses and modeling of the compliance to path trajectory in addition to the overall smoothness of the path. This robot may be further programmed to be effective and precise for surgical applications. In the studies reported here, a unique Rapidly exploring Randomized Tree (RRT) based path-planning algorithm is developed and this algorithm is used to generate path plans between an initial state and a goal state for simulated models of robotic manipulator arms. Along with constraints, the RRT algorithm has been implemented to find paths for the chosen kinematic or dynamic robotic manipulator arm. Similar techniques are to be used to analyze the KUKA LWR IV+ system. Motion analyses have been carried out with consideration of motion trajectories and all possible locations of the end effector with unique constraints applied to the system. In these simulations, the Denavit-Hartenberg parameters were recorded, with special attention to movement restrictions. The results of the RRT paths generation, analysis of the manipulator arm trajectories, and simulations allow one to better determine the location of the end-effector at any given point in time and location. From this foundation, the generation of path-planning restrictions for the KUKA robots path programming is expected to take into account surgically restricted dangerous or undesirable zones. In future work, the trajectories of the KUKA robot and other manipulator arms are to be compared with the data available in the literature. This work holds promising implications for the improved use of such robot systems in surgical applications. For example, precise pre-programmed robotic movements are expected to be particularly helpful for surgeries in tight, anatomically restricted sites, with adjacent delicate tissues. Ultimately, it is expected that this type of novel robotic application will greatly aid surgeons in improving the precision and safety of surgical procedures, by reducing potential complications and minimizing potential nicks and tears, and working towards giving the surgeons the same ease that they have with traditional surgery.
Modeling of a Small Remotely Operated Underwater Vehicle for Autonomous Navigation and Control
Authors: Rustrian Wilmer , Shankar Praveen
Published: February 2017

Autonomous control of a remotely operated underwater vehicle requires a high fidelity simulation model to be developed. In this paper, we present a simulation model of a commercially available Mini Observant Class ROV that is developed based on first principles and validated by empirical data. Open-loop testing conducted on the underwater vehicle is utilized to validate the pitch attitude behavior and fine-tune the physical parameters in the simulation model. In addition, three autopilot systems is designed using classical control theory to enable autonomous control over the attitudes and depth of the underwater vehicle.