bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Life Prediction Using Strain Intensity Factor and Equivalent Initial Flaw Size
Authors: Zhang Wei , Liu Huili , Wang Qiang , Jiang Shan
Published: February 2017

In this paper, an effective approach is developed to evaluate fatigue life of smooth specimens of 316 austenitic stainless steel under the fully reversed loading condition based on strain intensity factor and the equivalent initial flaw size (EIFS) concept. The strain intensity factor is indicated to be a better driving parameter to correlate with the fatigue crack growth rate, especially for the fully reversed load condition and the low cycle fatigue region. EIFS is an effective approach to account for complex process of the crack initiation and small crack propagation, which can be calculated by correlating the fatigue limit strain with fatigue threshold strain intensity factor. The fatigue limit strain is obtained from experimental data by analyzing the asymptotic behavior of the fatigue life curve. The driving force of crack growth is expressed in strain intensity factor. Then the fatigue life could be calculated by integrating the crack growth rate from integral lower limit EIFS to integral upper limit critical crack length ac. The experimental data of 316 austenitic stainless steel are employed to validate the proposed model. The good agreements are observed. It has shown that strain-intensity-factor-based approach could be a good method for fatigue life evaluation.
Improving the Computational Efficiency of Stability Prediction in Milling Employing the Two-Dimensional Bisection Method
Authors: Xie Yakun , Zhang Xiaojian , Yan Sijie , Ding Han
Published: February 2017

This paper presents an effective method to improve the computational efficiency of stability prediction in milling based on the two-dimensional bisection method. Contrasted with the traditional semi-analytical time-domain methods, the proposed method for stability prediction only checks the eigenvalues of less nodes on the parameter plane with the two-dimensional bisection method, so that, the computational efficiency of stability can be improved. The novel method for milling stability calculation is comprised of the bisection method in two dimensions and the numerical integration method [NIM], its validity is testified by the comparison of the stability diagram and computation time in contrast to the NIM. The computation demonstrates that the calculated stability diagram by using the presented method agrees well with the result of NIM, while the computation time of the stability diagram can reduce to 1/4 to 3/4 compared with the original methods.
Application of Infrared Imaging Technology in Fatigue Failure Prediction of Vehicle Wheel in Wheel Bending Fatigue Test
Authors: Chai W. H. , Liu X. D. , Shan Y. C. , Wang J. G.
Published: February 2017

Bending fatigue test of vehicle wheel is the main test to verify the mechanics performance of spoke. The wheel is fastened to the bending fatigue test platform with bolts in the bending fatigue test. A cyclic bending moment is applied to the wheel, and after some number of cycles, fatigue failure will happen. In this paper, the bending fatigue test is carried out on a steel wheel and a wheel made of long glass fiber reinforced thermoplastic (LGFT) wheel, and infrared imager is used to monitor the temperature distribution and variation of wheels under bending loads in the test process. After the test, it is found that there are cracks at the highest-temperature spots. In addition, because some cracks of LGFT wheel are too tiny to be found, it’s convenient to search those cracks according to the high-temperature areas in infrared images. All above indicate that it is practicable to predict fatigue failure area by monitoring temperature distribution and variation in wheel bending fatigue test. A method for real-time prediction of fatigue failure area in wheel bending fatigue test is described in this paper, which is also helpful to real-time prediction of fatigue failure area in fatigue tests of other products.
Variation Simulation of Dissimilar Materials Using Clip Fasteners
Authors: Wärmefjord Kristina , Söderberg Rikard , Lindkvist Lars
Published: February 2017

The use, and the joining process, of dissimilar materials have recently been highlighted. Joining of dissimilar materials can however be problematic, due to different material properties. Different materials respond differently to temperature changes and this might lead to deformations and stress in the final assembly. The joining methods differ also often from the one used to join similar material.

Variation simulation is used to predict the geometrical variation of a subassembly or a final product. In variation simulation of dissimilar materials it is important to include material properties in order to achieve an accurate result. Also the effects form joining method must be included in the simulation. To join dissimilar materials like plastic and sheet metal parts, clip fasteners are often used.

This paper presents a method for variation simulation of dissimilar materials with a focus on how to model clip fasteners. The method allows effects of temperature changes on holding forces and geometrical variation in the final assembly to be evaluated. Holding force refers to the force a clip fastener must withstand after the parts are joined. The method proposed can be used to support the design and selection of clip fasteners.
MATLAB Simulation of Autonomous Servo Driven Oil-Hydraulic Power Unit
Authors: Seabra Eurico , Costa Jorge , Puga Hélder , Leão Celina
Published: February 2017

Servo driven hydraulic power units have been implemented in some sectors of industry in order to counteract rising energy costs and reduce our ecological footprint. The advantages associated with the use of these technologies has motivated us to research a new control approach that allows its use independently, with reduced implementation costs and high efficiency.

This investigation develops new solutions to concurrently implement and improve volumetric control methodology for oil-hydraulic power units, which aims to produce and provide strictly necessary hydraulic power to the actuators. The approach used is based on a balance of flows present in a hydraulic circuit, reducing the pressure ripple generated by the pumps, valves and actuators, using a hydraulic accumulator.

The work begins with the mathematical modeling of a volumetric oil-hydraulic power unit, designed to demonstrate the concepts of the project, its components and the associated advantages. The definitions of the models presented are intended to exemplify the new control strategy and infer about the possibilities that arise from the use of this new methodology for power oil-hydraulic units.

In order to carry out the research and conclude about the results of the simulations, two simulations were performed using MATLAB Simulink software for two distinct hydraulic circuits and their control strategy: resistive control and volume control with the use of a servo motor.

In the resistive control, an internal gear pump driven by an induction motor with constant speed uses a pressure regulating valve to derive the excess of the flow to the reservoir. Despite their low efficiency, this type of assembly has very low costs and has a very good dynamic compared with traditional volumetric drive systems, avoiding the use of dedicated engineering.

The volumetric control makes use of an internal gear pump (to allow direct comparisons with the resistive control method), a servo motor, a hydraulic accumulator and a directional valve which prevent the flow from de accumulator draining into the reservoir during the downtimes. The controller allows you to establish a direct relationship between the accumulator volume and pressure of the hydraulic circuit.

The control methodology discussed throughout this work reveals an alternative volumetric control solution to consider, whether in new equipment or in retrofitting even with the different objectives of existing technologies available in the market.

The simulations allow us to conclude on energy-saving and environmental advantages of the volumetric control system presented, comparing it with existing systems on the market.
Investigation of Cryogenic Cooling of Micro EDM Drilling Process on AISI 304 Stainless Steel
Authors: Raja Manivannan , Murugasen Pradeep Kumar , Periannapillai Hariharan
Published: February 2017

In this experimental work, the cryogenic cooling of the Micro-EDM (μEDM) drilling process for improving the performance and quality of micro holes. The controllable parameters such as the current (Ip), pulse on time (Ton), Pulse off time (Toff) and gap voltage (Vg) were chosen for further investigation. The Taguchi L27 orthogonal array is preferred to achieve the best experimental runs. Case hardened AISI 304 stainless steel is selected to perform the experiments. The overall machining performances of geometrical characterization such as taper angle, Overcut, Circularity at the entry and exit and the performance evaluation such as the material removal rate and electrode wear rate are analyzed. It is found that the taper angle improved by 91%, overcut improved by 17 to 66%, Circularity improved up to 70% and 68% respectively, material removal rate increased from 9 to 70% and electrode wear rate reduced up to 76%. It is found that pulse off time plays a vital role in the quality of micro holes drilled in both conventional and cryogenic micro-EDM (CμEDM) processes.
Strength and Hardness Assessment of Copper and Copper Alloy Coatings on Stainless Steel Substrates
Authors: Ibrahim Mohamed , Al-Athel Khaled , Arif Abul Fazal M.
Published: February 2017

Coatings are extensively used in many areas including industrial and medical fields to serve various functions as corrosion resistance, wear resistance and antibacterial purposes. Copper and copper alloys are among the most widely applied coating materials for several industrial and medical applications. One of their widely used copper coating applications is in the antibacterial coating area. Most of the research done in this field focuses on the antibacterial behavior with no comprehensive assessment regarding their mechanical properties, such as hardness and adhesion strength. In this work, mechanical assessment of strength and hardness of pure copper and several copper alloys including Cu Sn5% P0.6%, Cu Ni18 Zn14 (German silver), and Cu Al9 Fe1 are studied experimentally and numerically. All coatings are deposited on stainless steel substrate disks of 25mm diameter by wire-arc thermal spraying at the center of advanced coating technologies, University of Toronto. All coatings are 150 microns in thickness, with two additional thicknesses up to 350 microns for Cu Ni18 Zn14 (German silver) and Cu Al9 Fe1. The effect of the coating thickness and composition on the mechanical properties is studied for all the copper and copper alloy samples with the varying thicknesses between 150 and 350 microns.

Scanning Electron Microscope (SEM) is used to study the surface as well as the cross-sectional microstructure of the coatings. Vickers micro-indentation tests are used to evaluate hardness at various locations on the cross-section of the coating and the substrate. This is used to evaluate the effect of the deposition of the coating material, and the subsequent solidification, on the hardness of the coating layer as well as the substrate near the coating interface. Pull-off adhesion tests are performed to evaluate the effect of the coating composition and thickness on the strength of the coatings. Tests are carried out to compute the pull-off failure stress that causes the delamination between the coating and the substrate. Computational analysis will be used to calibrate the experimental data when available by means of finite element analysis.

The preliminary pull-off tests show interesting results as the samples with lower coating thicknesses exhibit delamination at higher strengths. This is due to the increase in residual stresses in higher thicknesses building up during the deposition process. Some of the samples did not even fail at lower thicknesses of 150 microns. A comprehensive analysis between the adhesion strength and hardness will be very useful in understanding the effect of coating composition and thickness on the mechanical properties of the coating.
Investigation of Riveting Parameters Influence on the Riveted Joints Deformation During Slug Rivet Installation
Authors: Chang Zhengping , Wang Zhongqi , Zhang Jinming , Yang Yuan , Kang Yonggang
Published: February 2017

Slug rivet is widely used in aircraft assembly due to the higher interference fit level and the longer fatigue life. However, the inhomogeneity of riveting interference value along the thickness direction of the aircraft panels always leads to inevitable deformation, which significantly degrades the dimensional accuracy of the final products. In this study, a quantitative model is established to describe the relationship between several riveting parameters (i.e. squeezing force, buck cavity, upsetting rise time, upsetting dwell time and clamping force between sheets) and the deformation of a formed slug rivet joint. Then the coefficient of variance (CV) is introduced to evaluate the homogeneity of deformation. Subsequently, an optimized combination of the presented parameters is obtained by using finite element method (FEM) simulation so as to generate more uniform deformation. Finally, the FEM model is validated by a series of orthogonal experiments conducted in G86 fully automated C-frame riveting machine and the results show that the squeezing force and the buck cavity are the main significant factors and contributors to the riveted joints deformation, and the sequence of this effect from the high to low are: upsetting dwell time, clamping force, and upsetting rise time. The results also indicate that the developed FE model can be used for further analysis, including the prediction of large component riveting deformation and the mechanical properties of riveted joint.
Motion Reliability Analysis of a 3-RRR Parallel Manipulator With Random and Interval Variables
Authors: Zhan Zhenhui , Zhang Xianmin
Published: February 2017

A general methodology for motion error and motion reliability analysis of planar parallel manipulators (PPMs) with random and interval variables is presented. The inherent uncertainties of the manipulator, including tolerances in manufactures, errors in inputs as well as joint clearances are taken into account. The error model of a 3-RRR parallel manipulator is built and the global sensitivity coefficients of motion errors to variations are defined and obtained. The joint clearances are treated as interval variables while the others are treated as random variables. As a result, the motion error of the manipulator could turn out to be the mixture of a random variable and an interval variable. A new motion reliability analysis method based on the First Order Second Moment (FOSM) method and the Monte Carlo simulation (MCS) method is developed for the manipulator with random and interval variables. This paper provides a new idea to better understand the motion reliability affected by the inherent uncertainties of PPMs.
On Wind-Driven Land Vehicles
Authors: Reina G. , Foglia M. M.
Published: February 2017

This paper deals with the study of a land-yacht, that is a ground vehicle propelled by wind energy. There is a large interest in exploring alternative source of energy for propulsion and wind energy could be a feasible solution being totally green, available and free. The idea envisaged by a land-yacht is that of using one or several flexible or rigid vertical wing-sails to produce a thrust-force, which can eventually generate a higher travel velocity than its prevailing wind. A model of a three-wheel land-yacht is presented capturing the main dynamic and aerodynamic aspects of the system behaviour. Simulations are included showing how environment conditions, i.e. wind intensity and direction, influence the vehicle response and performance. In view of a robotic embodiment of the vehicle, a controller of the sail trim angle and front wheel steer angle is also discussed for autonomous navigation.
Deformation and Failure Mechanisms of Austenitic Piping Under the Influence of Oxyhydrogen Reactions
Authors: Offermanns Stefan , Weihe Stefan
Published: February 2017

The present paper deals with the deformation and failure mechanisms of austenitic piping under the influence of oxyhydrogen reactions for the safety evaluation of incident scenarios in technical installations based on previous work of the author [1–5].

For the characterization of the processes, detonation tests performed at the Materials Testing Institute University of Stuttgart (MPA Stuttgart) have been used. The aim of these experiments was to study the detonation processes in head spray cooling piping of boiling water reactors. The experiments were performed on austenitic pipes with an outer diameter of O. D. = 114.3 mm and various wall thicknesses. Oxyhydrogen was used in its stoichiometric ratio of 2H2+O2 mixed with various amounts of an inert gas component. These tests have shown that less amounts of reactive gas may result in a stronger reaction of the pipe structure. This observation is attributed to the influence of the so-called overdriven detonation.

Depending on the ratio of oxyhydrogen to the inert gas component and the pipe-wall thickness, adiabatic shear bands can occur in the piping structure. Adiabatic shear bands are very narrow zones with intense localized shear deformations due to the conversion of a significant portion of strain energy into heat.

In order to describe this phenomenon numerically, a strain-based failure model was used which can reflect material damage over a wide range of different stress states. However, it has shown that damage of the studied material depends significantly on the Lode angle. Furthermore, no clear dependence of the failure limit on the loading rate has been found for the studied material.

For the constitutive description of the material behavior under the occurring loading rates and temperatures suitable material models were selected and the required parameters have been evaluated experimentally and verified by numerical methods. With the aid of this constitutive description of the material behavior and the failure model numerical simulations of the detonation tests were carried out.
Characteristic Variation of Self-Excited Vibration in the Vertical Rotor System due to the Flexible Support of the Journal Bearing
Authors: Nishimura Atsushi , Inoue Tsuyoshi , Watanabe Yusuke
Published: February 2017

Various vibration problems occur in rotating machinery. Specifically, the amplitude of shaft motion can be large in the case of vertical pump using a journal bearing. In such case, rotor motion such as self-excited vibration is not able to be predicted accurately without considering both rotordynamic fluid force and contact phenomena to the bearing surfaces or boundary lubrication condition. Moreover, in an actual vertical pump, the stationary side structure that supports the pump shaft may be relatively flexible. However, the vibration characteristics in such situations have not been so far explained simply. The purpose of this paper is a development of the simple and quantitative method for evaluating vibration characteristics of a vertical rotating shaft with journal bearing. In this study, the rotor system flexibly supported by a journal bearing at the axial center is considered. Eigenvalue analysis is demonstrated for the linearized system, and steady-state vibration analysis of the self-excited vibration is carried out for the nonlinear system. As a result, the effect on the vibration characteristics of the system by changing fluid viscosity, radial clearance, stiffness and damping of the support is clarified. Moreover, the obtained experimental results correspond to the theoretical results of the self-excited vibration qualitatively.
Performance Evaluation of Concentrated Photovoltaic System Using a Microchannel Heat Sink
Authors: Radwan Ali , Ahmed Mahmoud , Ookawara Shinichi
Published: February 2017

The high incident heat flux on the concentrated photovoltaic (CPV) system causes a significant increase in the cell temperature and thus reduces the system efficiency. Therefore, using an efficient cooling technique is of great importance for those systems. In the present study, a new technology for concentrated photovoltaic systems is introduced using a truncated-double layer microchannel heat sink. A comprehensive three-dimensional thermo-fluid model for the photovoltaic layers integrated with a microchannel heat sink was developed. The proposed model was simulated numerically to estimate the solar cell temperature, temperature uniformity, cooling system pumping power, electrical efficiency and thermal efficiency of the CPV system. The numerical results were validated with the available experimental, analytical and numerical results in the literature. In the designed heat sink, various design parameters are investigated such as the truncation length, cooling mass flow rate, concentration ratio, and converging width ratio of the flow channel. Results indicate that increasing the truncated length leads to an increase of solar cell temperature at a constant coolant mass flow rate. The cell temperature varies between 80.1°C and 146.5°C as the truncation length ratio increases from 0 (i.e. single layer microchannel) to 1 respectively at a concentration ratio (CR) of 40 and a cooling mass flow rate (ṁ) of 26.6 g/min. Using the double layer microchannel reduces the consumed pumping power at the same total mass flow rate compared to the single layer microchannel. The Double layer configuration with a truncation length ratio (l/lsc) equal to unity achieves a lower pumping power and solar cell temperature uniformity in comparison to the single layer microchannel.
Characterization of Adhesive Materials Under High Strain Rate Loading
Authors: Gollins Kenneth , Chiu Jack , Shaffren Daniel , Delale Feridun , Elvin Niell , Liaw Benjamin
Published: February 2017

Adhesive materials present two potential opportunities for light weighting current and future vehicles including military vehicles: use of an adhesive may reduce the number of bolts and weldments needed for mechanically joined components, and adhesives may open the possibility for multi-material joints allowing for the incorporation of lighter-weight materials. To meet these opportunities, prospective adhesive materials would need to perform satisfactorily in high strain rate loading situations such as impact. Since little is known about the dynamic failure of adhesive materials, this study investigates the behavior and failure modes of adhesive materials and joints subjected to ballistic impact. The critical failure speed, defined as the projectile speed at which the adhesive or interface fails is determined experimentally. Furthermore, the energy absorption characteristics of the adhesive are determined experimentally and numerically using finite element analysis.
Arterial Pulse Signal Monitoring During the Valsalva Maneuver via a Flexible Microfluidic-Based Sensor
Authors: Wang Dan , Stamenkovich Andrew , Zemlin Christian , Hao Zhili
Published: February 2017

In light of the need to diagnose and monitor the heart condition of a heart failure patient, this paper presents a preliminary investigation on the application of a flexible microfluidic-based sensor for measuring the arterial pulse signal during the Valsalva Maneuver (VM), which allows assessment of the patient’s volume status. The core of the sensor is a polydimethylsiloxane (PDMS) microstructure embedded with a 5x1 electrolyte-enabled resistive transducer array. As a time-varying load, an arterial pulse signal acting on the microstructure gives rise to the distributed sensor deflection along the microstructure length and further registers as the resistance changes by the transducer array. The radial pulse signals of four healthy subjects during the VM are measured and are further expressed in terms of the absolute resistance and the sensor deflection. The pulse amplitude change in absolute resistance captures the expected hemodynamic response of a healthy subject to the VM, but the sensor deflection does not manifest such response, due to baseline drift. The corresponding pulse signals of the four subjects at-rest are also measured, verifying that the pulse amplitude change in absolute resistance does not arise from baseline drift. In the future, this sensor will be used to measure the arterial pulse signals of heart failure patients during the VM.
Study on Bonding and Shear Flow Phenomena of Shear Probe Test for BGA Solder Joint in Nano-Scale Analysis
Authors: Liu Bao-Hsin , Chen Yu-Liang , Hsu Quang-Cherng
Published: February 2017

This study investigates bonding and shear flow phenomena for nanoscale BGA (Ball Grid Array) solder joint in electronic package pads with or without intermetallic compounds (IMC). Three types of solder joints have been studied, such as Sn100%, Sn44%-Cu56% and Sn92.5%-Ag3.5%-Cu4%. The IMC layer composes of Cu6Sn5 and Cu3Sn materials. The above materials are arranged according to the single crystal structure. The molecular dynamics method and the embedded atom potential are used to understand the internal micro structure, interface layer and the bonding strength differences for welded joints. The total energy of the simulated system includes the molecular potential energy, kinetic energy and electromagnetic coupling moments. An aging process at 453K for solder joint without IMC layer has been conducted to understand the aging effect.
Towards a Safer Design of Helmets: Finite Element and Experimental Assessment
Authors: Kassar Sari , Siblini Sarah , Wehbi Bilal , Abro Omar , Shehadeh Mutasem
Published: February 2017

Motorcycle helmets are vital to protect from recurrent road accidents as they prove crucial in reducing brain trauma. This research piece presents a new and plausible bio-inspired design affined to the foam liner material and structure in helmets. The proposed liner design is inspired from animal horn micro-structure and tubule arrangement. An innovative drop-testing apparatus is presented with a spring-ratchet mechanism for experimental testing. The aim is to validate the new design by meeting the ECE 22.05 standard for motorbike helmets using peak linear acceleration and HIC criteria. Experimental results are partly verified against FEA simulations for two proposed samples. Further samples call for more complex simulations at a later stage to best describe material properties and structures.
Design and Development of a Small Scale Ocean Current and Wave Energy Converter
Authors: Johnson Tyler , Phillips Benjamin , Ringuette Scott , Zenouzi Mansour , McCusker James
Published: February 2017

The inability to tie into the electrical power grid drives mariners to search for alternative energy sources. One such alternative energy source is to harness the vast supply of kinetic and potential energies associated with ocean currents and waves. In the Ocean Current and Wave Energy Converter, a tandem system of an underwater turbine and a wave energy buoy is designed to provide power to a standard 12 volt marine battery. Subsurface energy in the form of current flow is harvested by a helical cross-flow Gorlov turbine. Kinetic surface wave energy is harnessed through an inertial mass system. This system utilizes a 360°, bidirectional, rotating mass enclosed in a spherical buoy that converts the pitching motion into rotational motion. Both subsystems are integrated together through the charging circuit. The charging system is designed to integrate multiple energy sources to maximize the total energy harnessed. Through testing and analysis, design improvements are identified and it is determined that the design of a small scale current flow and wave energy conversion system is a feasible solution to providing power from the ocean.
Parameter Estimation for HVAC System Models From Standard Test Data
Authors: Luthman Hannah , Gardner John F.
Published: February 2017

Nearly all cooling systems, and an increasing proportion of heating systems, utilize the vapor compression cycle (VCC) to provide and remove heat from conditioned spaces. Even though the application of VCC’s throughout the built environment is ubiquitous, effective and accessible models of the performance of these systems remains elusive. Such models could be important tools for equipment and building designers, and building energy managers and those who are attempting to optimize building energy performance through the use of model-based control systems. A quasi-steady state, spreadsheet-based model has been developed which requires knowledge of 10 system-specific parameters. A method utilizing manufacturer’s test conditions to derive these values is presented.

The model is applied to three commercially available units and a subset of test conditions is used to identify the model parameters. The model is validated over the entire range of conditions with modeling errors ranging from 2 to 4%.
An Investigation Into Acoustic Dipole Source Calibration Methods for Turbomachinery Sound Radiation in Reverberant Fields
Authors: Jonson Michael L. , Young Steven D.
Published: February 2017

In-situ calibration methods using a single spherical-shaped transmitting hydrophone (idealized as a monopole acoustic source) have traditionally been used for radiated sound measurements of turbomachinery performed in the Garfield Thomas 1.22-m diameter water tunnel located at The Pennsylvania State University’s Applied Research Laboratory (ARL Penn State). In this reverberant field, the monopole source containing known transmitting characteristics was used to calibrate acoustic sensors that were either near or far from the source. This method typically works well when the type of source is monopole in nature; however, many acoustics sources can be dipole or quadrupole in nature. In this study we investigated the applicability of using dipole sources in a space such as a well-characterized reverberant tank, and we found through a virtual dipole method that the radiation still appears monopole in the reverberant field. The method was extended for the vibration of a panel (a known dipole source) and once again the monopole assumption for the in-situ calibration for a near-field hydrophone and conventional reverberant hydrophones remained consistent.
The Strength of Dissimilar Fractal Joints
Authors: Monsef Khoshhesab Mona , Li Yaning
Published: February 2017

In this investigation, the influences of fractal geometry and material properties on the strength of dissimilar joints were studied. The fractal geometry explored was an iterative Koch curve. The interfacial layer joining two different materials was designed to be a Koch layer with three different numbers of iteration. The mechanical behaviors of the fractal dissimilar joints under both normal tensile traction and shear traction were simulated via finite element (FE) method.

In the three-phase FE models, isotropic elasto-perfect-plastic material models with different stiffness and yielding strength were used for all three phases. By varying the stiffness and strength ratio of the Koch layer and the dissimilar materials, fractal dissimilar joints with both perfect bonding and imperfect bonding were simulated and compared. It was found that the fractal geometry plays a very important role in enhancing both the tensile and shearing strength of dissimilar joints, especially for the cases with imperfect bonding.
Nonlinear Boundary Condition Effects for Piping System in the Dynamic Analysis
Authors: Abou El-Ella Mohamed I. , Papadopoulos Anestis
Published: February 2017

Piping system in thermal power plants usually include nonlinear boundary condition (e.g. Single acting and gap supports) to eliminate the high thermal stresses since those systems are operating in high temperature range with large thermal displacement. Using this kind of non-linear supports may include error due to the linear approximation when it comes to study the response of the piping system in the dynamic analysis. Most of the common pipe stress analysis programs such as CAESAR II [1].cannot perform a dynamic analysis for nonlinear systems. This paper is investigating the effect on maximum reaction forces when modelling nonlinear boundary condition using the dynamic analysis module in ANSYS program [2]. The aim of of this paper is to estimate the impact of gaps and to study the effect of different pipe support stiffness. The dynamic analysis is performed for a range of different gap and stiffness support arrangements. The results from the nonlinear analysis are compared with regular linear analysis (supports with zero gaps) and a correlation is established indicating that large spikes in dynamic force are expected when large gaps are included in dynamic analysis. The results of the paper shows that the design engineer must be very caution in using linear dynamic analysis when large gaps are included and that the nonlinear analysis is required when dynamic amplification is significant.
Strategies to Improve Solar Fraction in an Adsorption Cooling System Based on Metal Organic Frameworks in Humid and Dry Climates: A Case Study for Southeast and Southwest Texas
Authors: Demirocak Dervis Emre , Kumar Bharath , Kolatkar Yashada
Published: February 2017

In this study, the performance of a solar-thermal powered adsorption cooling system based on HKUST-1-water (a type of metal organic framework) working pair for a detached single story family house located in two geographically diverse areas of South Texas was investigated. Using TRNSYS, the optimal system parameters such as collector area and chiller loop mass flow rate were determined to maximize the solar fraction of the cooling system. Based on the simulation results, it is possible to obtain monthly average solar fraction value of 0.7 or above during most of the cooling season (i.e., Apr to Nov) in both locations. For the same operating parameters, solar fraction in Kingsville, TX is slightly higher than the El Paso, TX.
Sustainability Index of Community Energy Systems for Benchmarking and Multi-Criteria Decision Analysis
Authors: Moslehi Salim , Reddy T. Agami
Published: February 2017

Sustainable development of energy infrastructure systems is critical for a sustainable future. Planners are adopting a variety of tools from diverse domains to design, assess, operate and plan for sustainable energy systems. The purpose of this study is to propose a quantitative sustainability assessment framework, adopting a bottom-up approach suitable to energy infrastructure systems. We have extended many of the well-accepted processes and analysis methods applicable to individual buildings to a community involving numerous buildings and centralized energy systems. We propose a simple framework which allows determining a measure called SICES, Sustainability Index of Community Energy Systems, that recognizes the three important pillars of sustainability. Willingness to pay, captured by environmental externalities, is considered to be the social value which enables quantifying the impacts of energy systems on the environment, economy, and society. Well-developed tools and methods, such as building stock modeling, Life Cycle Assessment (LCA), and Life Cycle Costing (LCC), are used in conjunction with additional indices, i.e. Reliability, Robustness, and Resilience (RRR) to evaluate the sustainable performance of community energy systems. SICES explicitly considers environmental, health, and energy cost impacts of on-site energy systems (solar photovoltaics, combined heat and power systems, boilers, chillers, etc.) as well as those of the upstream systems, i.e. natural gas production and utility power generation facilities, accounting for location-specific and temporal variation in fuel mix. We present the results of a case study analysis of applying this framework to an actual campus with more than 280 buildings and numerous solar PV systems using year-long monitored data of hourly cooling, heating and electricity demands to compute the SICES index. How different energy mixes and application of energy conservation measures would alter the current SICES index of the campus is also illustrated and discussed. A new type of diagram called the “Sustainability Compass” is proposed which allows one to track the directional change and magnitude in SICES of different energy scenarios compared to a baseline scenario.
Energy and Exergy Analysis of a Biomass Power Plant
Authors: Silva João , Teixeira Senhorinha F. , Preziati Simone , Teixeira José Carlos
Published: February 2017

The fulfilment of energy targets regarding the use of renewable energy has been a strong incentive to the development of dedicated power plants using biomass. Because these facilities operate with low value residues, this orientation has also received a strong incentive by the quest to reduce the amount of fuel in the woods and lowering the risk of fire. This issue is a major problem in dry climates. Although the number of plants planned for Portugal was very large, the actual number of units in operation is small. The first plant to enter production in Portugal was the thermal power plant of Mortágua. In this paper the energy and exergy analysis in this plant is presented. The objective of this work is to develop an analysis for the energy conversion in the plant. This is based on parameters that were retrieved during its normal operation and include: biomass and air flow rate, temperature measurements of the flue gases throughout the facility including the economizer, the two superheaters and flue gas composition. The elemental analysis of the biomass resulting from a blend of various sources was measured in addition to its moisture (ranging between 20 and 45% depending on the sources). The analysis was carried out for a fuel batch with a moisture of 35%.

The plant was operated at three loads (full load, 80% and 65% load) and from the energy/mass balances the overall efficiency was calculated to be approximately 26%. The data were also used to perform a second law analysis of the plant which enables the calculation of the exergy destruction in the various components of the facility, including the external irreversibility. It was observed that the combustion chamber is the prime contributor to the overall loss of efficiency. The exergy efficiency was found approximately 22%.
Reduced Order Modeling and Experimental Investigation of Acoustic Particle Manipulation in Complex 3D Geometries
Authors: Binkley Michael , Ledbetter Andrew , Shahan Stefanie , Meacham J. Mark
Published: February 2017

A reduced order computational model and imaging experiments are presented as a combined method to investigate migration and trapping of microscale particles within an ultrasonic droplet generator. Use of two-dimensional (2D) cross-sectional representations of the three-dimensional (3D) device enables observation of acoustic focusing phenomena that are otherwise visually inaccessible. Our approach establishes relationships between system operating parameters and particle retention due to acoustic radiation forces that arise during atomization of heterogeneous particle suspensions. The droplet generator consists of a piezoelectric transducer for ultrasonic actuation, a resonant fluid-filled chamber, and an array of microscopic pyramidal nozzles. 2D visualization chips were produced through anodic bonding of glass to microfluidic reservoirs deep reactive ion etched in silicon. Open nozzle orifices of the 3D microarray were sealed in its 2D representation to facilitate filling and testing. Finite element analysis was used to model the harmonic response of the 2D assembly from 500 kHz to 2 MHz. The average nozzle tip pressure amplitude across the 2D array was then used to identify operating frequencies that correspond to optimal droplet ejection from the 3D device (ejection modes). The pressure field at these resonant frequencies predicts the equilibrium distribution of polymeric beads suspended in the reservoirs of the 2D chips. To qualitatively assess the accuracy of the model results, visualization experiments were performed at the first three ejection modes of the system (fn1 ≈ 620–680 kHz, fn2 ≈ 1.14 MHz, and fn3 ≈ 1.63 MHz) using 10 μm polystyrene beads. The model demonstrates a remarkable ability to capture the overall shape, as well as specific details of the terminal particle distributions, defined as the state with no further movement toward a pressure node or antinode. Finally, time course trials of acoustic focusing of heterogeneous particle suspensions were used to observe the influence of particle volume on the magnitude of the acoustic radiation force. A mixture of 5 μm and 20 μm diameter polystyrene beads was subjected to a standing acoustic field in the 2D chips. Particle position was recorded at 5 ms intervals until an equilibrium distribution was achieved. As expected, the larger beads focused much more rapidly than smaller beads, acquiring their final positions in seconds (versus 10s of seconds for the 5 μm particles). The method and results reported here serve as building blocks toward translation of an existing ultrasonic droplet generator into a high-throughput particle separation and isolation platform.
The Effects of In-Service Induced Reduction of Bonding Quality on the Mode I, II, and I-II Fracture Toughness of CNT Nanocomposites
Authors: Yekani Fard Masoud , Raji Brian , Woodward John M. , Chattopadhyay Aditi
Published: February 2017

Tests were carried out to determine the interlaminar fracture toughness of stitch-bonded biaxial polymer matrix carbon nanotube nanocomposites for mode I, II, and I-II including durability effects. Analysis of the test specimens in terms of mode I energy release rates showed good agreement among Modified Beam Theory, Compliance Calibration, and Modified Compliance Calibration methods. End-Notched Flexure (ENF) and four point End-Notched Flexure (4ENF) tests gave very consistent crack initiation and propagation results for mode II fracture. The results show that the critical mode I energy release rate for delamination decreases monotonically with increasing mode II loading. The effects of accelerated aging (60°C and 90% Rh) on fracture properties were studied. Early accelerated aging (0–12 months) has the dominant diminishing effect on energy release rate initiation and propagation in composites and nanocomposites.
Programming Over AutoCAD for the Proficiency of Disabled Users Using Webcam Based Eye-Tracker
Authors: Luís-Ferreira Fernando , Sarraipa João , Jardim-Goncalves Ricardo
Published: February 2017

Mechanical project is a task that requires knowledge about materials and technologies. The need for those skills is supported by mathematical knowledge associated with such technologies. Disabled people can have tremendous skills in terms of calculation and conception of mechanical devices but they may lack on proper access to handle tools that represent parts or mechanisms in terms of graphical design. The present research aims at deploying a setup that can help on such task by allowing drafting in AutoCAD using the eyes. The proposed approach makes use of a laptop camera to act as an eye-tracker, thus avoiding additional hardware costs. The authors envisage new opportunities from this work to future work, including the possibility of disabled people to build 3D real models from the generation of STL models to export to 3D printing devices.
Characterization of Tissue Thermal Conductivity During a Tissue Joining Process
Authors: Yang Che-Hao , Liu Yang , Li Wei , Chen Roland K.
Published: February 2017

Electrosurgical vessel sealing, a tissue joining process, has been widely used in surgical procedures, such as prostatectomies for bleeding control. The heat generated during the process may cause thermal damages to the surrounding tissues which can lead to detrimental postoperative problems. Having better understanding about the thermal spread helps to minimize these undesired thermal damages. The purpose of this study is to investigate the changes of tissue thermal conductivity during the joining process. We propose a hybrid method combining experimental measurement with inverse heat transfer analysis to determine thermal conductivity of thin tissue sample. Instead of self-heating the tissue by the thermistor, we apply an external cold boundary on the other side of the tissue sample to stimulate a higher temperature gradient without denaturing the tissue in comparison to the heated method. The inverse heat transfer technique was then applied to determine the tissue thermal conductivity. Tissue thermal conductivity at different levels (0%, 25%, 50%, 75%, and 100%) of the joining process was measured. The results show a decreasing trend in tissue thermal conductivity with increasing joining level. When the tissue is fully joined, an average of 60% reduction in tissue thermal conductivity was found.
Characterization of Interlaminar Fracture Properties of Advanced Polymer Matrix Composites Interleaved With Buckypaper
Authors: Yekani Fard Masoud , Woodward John M. , Datta Siddhant , Raji Brian , Chattopadhyay Aditi
Published: February 2017

Recently a novel high-speed/high-yield surfactant-free manufacturing method has been developed for manufacturing of large size buckypaper. In spite of this development, there is no data on the effects of microstructural characteristics on the structural properties of surfactant-free buckypaper based nanocomposites. This investigation examines the effects of the proposed manufacturing procedure on the resultant interlaminar fracture properties of buckypaper based nanocomposites. Buckypaper samples were fabricated using the novel surfactant-free technique. Buckypaper based nanocomposite samples were subjected to mode I, II, and I-II fracture testing in Double Cantilever Beam (DCB ), End Notched Flexure (ENF) and 4-point End Notched Flexure (4ENF), and Mixed Mode Bending (MMB) configurations, respectively. Analysis of the test specimens in terms of mode I energy release rates showed good agreement among Modified Beam Theory, Compliance Calibration, and Modified Compliance Calibration methods. ENF and 4ENF tests gave very consistent crack initiation and propagation results for mode II fracture. The fracture envelope function of the composite and the nanocomposites was developed as a design guideline for nanocomposite materials.
Control of an Aerial Manipulator With an On-Board Balancing Mechanism
Authors: Lee Jameson Y. , Cook Zachary , Barzilov Alexander , Yim Woosoon
Published: February 2017

Multirotor Unmanned Aerial Systems (UAS) are highly mobile in flight and possess stable hovering capabilities. Because of their unique flight characteristics, the utilization of the platform for active tasks such as aerial manipulation is highly attractive. Much work has been done in recent years towards the implementation of multirotor for aerial manipulation, however, progress in the field has been slow due to the many challenges involved in the implementation of robust rotor control. In an attempt to reduce the effects of the manipulator, a technique for disturbance rejection using a novel balancing mechanism is proposed. In this paper, the dynamic equations of a coupled multirotor and manipulator are analyzed as a single body for use in the attitude control of the platform. By mounting the mechanism, the platform effectively gains marginal control over the positioning of its center of gravity relative to a body fixed frame. It can be shown that the increased mobility can be utilized to reduce rotor saturation for any given flight condition and improve the effectiveness of previously developed rotor control methods.