Ni Li, Paolo Arguelles, Kevin Chaput, Stephen L. Kenan, Salla Kim, Donglin Li, Yosuar Vazquez, Dennis Viveros, T. Nye, K. Salinas
Solar sailing is a new satellite propulsion technology using radiation pressure exerted by sunlight on a large mirrored surface. Since it does not need propellants, it is increasingly being considered by both the European Space Agency and the National Aeronautics and Space Administration for future science missions. An attitude control system is essential for a sail craft to maintain a desired orientation. IKAROS, launched in 2010, practically proved the possibility of using a solar sail as a propulsion system. However, it also showed the current sail orientation system could change the attitude very slowly, about 1 degree per day. In contrast to the existing single solar sail design, a new distributed four-sail configuration is proposed in this paper and the coordinated motion of the four sails is used to control the attitude pointing of a satellite. The feasibility and efficiency of this proposed design were assessed and concluded that it is possible to steer a CubeSat up to 1 degree in 60 seconds for either the roll or pitch axes.
{"title":"A Novel Approach for Satellite Attitude Control by Using Solar Sailing","authors":"Ni Li, Paolo Arguelles, Kevin Chaput, Stephen L. Kenan, Salla Kim, Donglin Li, Yosuar Vazquez, Dennis Viveros, T. Nye, K. Salinas","doi":"10.1115/IMECE2018-88311","DOIUrl":"https://doi.org/10.1115/IMECE2018-88311","url":null,"abstract":"Solar sailing is a new satellite propulsion technology using radiation pressure exerted by sunlight on a large mirrored surface. Since it does not need propellants, it is increasingly being considered by both the European Space Agency and the National Aeronautics and Space Administration for future science missions. An attitude control system is essential for a sail craft to maintain a desired orientation. IKAROS, launched in 2010, practically proved the possibility of using a solar sail as a propulsion system. However, it also showed the current sail orientation system could change the attitude very slowly, about 1 degree per day. In contrast to the existing single solar sail design, a new distributed four-sail configuration is proposed in this paper and the coordinated motion of the four sails is used to control the attitude pointing of a satellite. The feasibility and efficiency of this proposed design were assessed and concluded that it is possible to steer a CubeSat up to 1 degree in 60 seconds for either the roll or pitch axes.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122002663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Damage precursor in composites can lead to large structural damages, such as delamination, in carbon fiber reinforced plastic (CFRP) composites due to complex load conditions and environmental effects. In addition, multiple types of damage precursors including micro-scale matrix cracks, fiber pull-out from matrix, and fiber breakages, are extremely difficult to detect due to the limitation of resolution of current non-destructive evaluation (NDE) technologies. This paper presents a photo-acoustic based non-contact NDE system for the detection of damage precursors with extremely high resolution up to one hundred micrometers. This system consists of three major components: picoseconds pulsed laser based ultrasonic actuator, ultrasound receiver, and data processing and computing subsystem. Picoseconds pulsed laser is used to generate ultrasonic propagations in composites during the NDE process, and the ultrasound signals are recorded by the ultrasound receiver. Three-dimensional microstructure of the individual composites grid within the composite is able to be reconstructed for further analysis. The size and position of the damage precursors are evaluated with high accuracy up to 100 μm. The experimental results demonstrate that this imaging system is able to provide a novel non-contact approach with extremely high resolution for damage detection of CFRP composites. In addition, the developed NDE system has a wide industrial application in aerospace, automobile, civil, mechanical, and other key industries.
{"title":"Photo-Acoustic Based Non-Contact and Non-Destructive Evaluation for Detection of Damage Precursors in Composites","authors":"Siqi Wang, L. Xiang, Yingtao Liu, Hong Liu","doi":"10.1115/IMECE2018-86148","DOIUrl":"https://doi.org/10.1115/IMECE2018-86148","url":null,"abstract":"Damage precursor in composites can lead to large structural damages, such as delamination, in carbon fiber reinforced plastic (CFRP) composites due to complex load conditions and environmental effects. In addition, multiple types of damage precursors including micro-scale matrix cracks, fiber pull-out from matrix, and fiber breakages, are extremely difficult to detect due to the limitation of resolution of current non-destructive evaluation (NDE) technologies.\u0000 This paper presents a photo-acoustic based non-contact NDE system for the detection of damage precursors with extremely high resolution up to one hundred micrometers. This system consists of three major components: picoseconds pulsed laser based ultrasonic actuator, ultrasound receiver, and data processing and computing subsystem. Picoseconds pulsed laser is used to generate ultrasonic propagations in composites during the NDE process, and the ultrasound signals are recorded by the ultrasound receiver. Three-dimensional microstructure of the individual composites grid within the composite is able to be reconstructed for further analysis. The size and position of the damage precursors are evaluated with high accuracy up to 100 μm. The experimental results demonstrate that this imaging system is able to provide a novel non-contact approach with extremely high resolution for damage detection of CFRP composites. In addition, the developed NDE system has a wide industrial application in aerospace, automobile, civil, mechanical, and other key industries.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128390086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
One considers linear thermoelastic composite media, which consist of a homogeneous matrix containing a statistically homogeneous random set of aligned homogeneous heterogeneities of non-canonical (i.e. non-ellipsoidal) shape. The representations of the effective properties (effective moduli, thermal expansion, and stored energy) are expressed through the statistical averages of the interface polarization tensors (generalizing the initial concepts, see e.g. [1] and [2]) introduced apparently for the first time. The new general integral equations connecting the stress and strain fields in the point being considered with the stress and strain fields in the surrounding points are obtained for the random fields of heterogeneities. The method is based on a recently developed centering procedure where the notion of a perturbator is introduced in terms of boundary interface integrals estimated by the method of fundamental solution for a single inclusion inside the infinite matrix. This enables one to reconsider basic concepts of micromechanics such as effective field hypothesis, quasi-crystalline approximation, and the hypothesis of ellipsoidal symmetry. The results of this reconsideration are quantitatively estimated for some modeled composite reinforced by aligned homogeneous heterogeneities of non canonical shape. Some new effects are detected that are impossible in the framework of a classical background of micromechanics.
{"title":"Method of Fundamental Solution in Thermoelasticity of Random Structure Matrix Composites","authors":"V. Buryachenko","doi":"10.1115/IMECE2018-86515","DOIUrl":"https://doi.org/10.1115/IMECE2018-86515","url":null,"abstract":"One considers linear thermoelastic composite media, which consist of a homogeneous matrix containing a statistically homogeneous random set of aligned homogeneous heterogeneities of non-canonical (i.e. non-ellipsoidal) shape. The representations of the effective properties (effective moduli, thermal expansion, and stored energy) are expressed through the statistical averages of the interface polarization tensors (generalizing the initial concepts, see e.g. [1] and [2]) introduced apparently for the first time. The new general integral equations connecting the stress and strain fields in the point being considered with the stress and strain fields in the surrounding points are obtained for the random fields of heterogeneities. The method is based on a recently developed centering procedure where the notion of a perturbator is introduced in terms of boundary interface integrals estimated by the method of fundamental solution for a single inclusion inside the infinite matrix. This enables one to reconsider basic concepts of micromechanics such as effective field hypothesis, quasi-crystalline approximation, and the hypothesis of ellipsoidal symmetry. The results of this reconsideration are quantitatively estimated for some modeled composite reinforced by aligned homogeneous heterogeneities of non canonical shape. Some new effects are detected that are impossible in the framework of a classical background of micromechanics.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125354076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, a comparative study is presented on the post-buckling load redistribution in stiffened aircraft panels modeled with and without material nonlinearity. In the first part of the study, a baseline stiffened panel is generated for further investigation of the material nonlinearity on the post-buckling behavior and on the effective width of the stiffened panel. In this respect, a stiffener section which provides classical clamped edge condition is designed by matching the compression buckling coefficient determined by the finite element analysis closely with the analytically determined buckling coefficient of the clamped edge panel. Post-buckling analysis of the stiffened panel is then performed utilizing linear and nonlinear material models in the finite element analysis and the effect of material plasticity on the post-buckling behavior of the panel is ascertained. The load distribution in the stiffened panel is investigated just before the buckling of the panel and before the collapse of the panel in the post-buckled stage. The effective widths of the panel are calculated before the collapse of the panel using the load distributions determined by the finite element analyses of the panel models with and without material nonlinearity and comparisons are made with the effective width calculated by the classical effective width formulation. It is shown that material nonlinearity accounts for higher effective width and in general the classical empirical approach gives the smallest effective width.
{"title":"Comparative Study of Post-Buckling Load Redistribution in Stiffened Aircraft Panel With and Without Material Nonlinearity","authors":"Enes Aydin, A. Kayran","doi":"10.1115/IMECE2018-86346","DOIUrl":"https://doi.org/10.1115/IMECE2018-86346","url":null,"abstract":"In this article, a comparative study is presented on the post-buckling load redistribution in stiffened aircraft panels modeled with and without material nonlinearity. In the first part of the study, a baseline stiffened panel is generated for further investigation of the material nonlinearity on the post-buckling behavior and on the effective width of the stiffened panel. In this respect, a stiffener section which provides classical clamped edge condition is designed by matching the compression buckling coefficient determined by the finite element analysis closely with the analytically determined buckling coefficient of the clamped edge panel. Post-buckling analysis of the stiffened panel is then performed utilizing linear and nonlinear material models in the finite element analysis and the effect of material plasticity on the post-buckling behavior of the panel is ascertained. The load distribution in the stiffened panel is investigated just before the buckling of the panel and before the collapse of the panel in the post-buckled stage. The effective widths of the panel are calculated before the collapse of the panel using the load distributions determined by the finite element analyses of the panel models with and without material nonlinearity and comparisons are made with the effective width calculated by the classical effective width formulation. It is shown that material nonlinearity accounts for higher effective width and in general the classical empirical approach gives the smallest effective width.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133480516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present paper presents an innovative approach to connect one-/two-dimensional models using a unified formulation with node-dependent kinematic capabilities. These models can use a different kinematics approximation at each node of the element. Carrera Unified Formulation has been used to derive the governing equations in a compact and general form. The possibility to connect one- and two-dimensional elements, and eventually to refine the kinematic model locally, has lead to a general reduction of the computational costs guaranteeing the same numerical accuracy.
{"title":"Mixed One-/Two-Dimensional Models With Node Dependent Kinematic Capabilities for the Analysis of Metallic and Composite Structures","authors":"E. Zappino, E. Carrera","doi":"10.1115/IMECE2018-87490","DOIUrl":"https://doi.org/10.1115/IMECE2018-87490","url":null,"abstract":"The present paper presents an innovative approach to connect one-/two-dimensional models using a unified formulation with node-dependent kinematic capabilities. These models can use a different kinematics approximation at each node of the element. Carrera Unified Formulation has been used to derive the governing equations in a compact and general form. The possibility to connect one- and two-dimensional elements, and eventually to refine the kinematic model locally, has lead to a general reduction of the computational costs guaranteeing the same numerical accuracy.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121586464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dielectric Barrier Discharge plasma actuators are simple devices with great potential for active flow control applications. They have very interesting features which have made them a topic of interest for many researchers, for instance they present very low mass, fast response time, low cost, easy implementation and they are fully electronic with no moving parts. The dielectric material used in the construction of these devices present an important role in their performance. The variety of dielectrics studied in the literature is very restrict and the majority of the authors make use of Kapton, Teflon, Macor ceramic or PMMA. Furthermore, several authors reported difficulties in the durability of the dielectric layer when actuators operate at high levels of voltage and frequency. Considering this background, the present study focus on the experimental testing of alternative dielectric materials which can be used for DBD plasma actuators fabrication. Considering this, plasma actuators with dielectric layers made of Poly-Isobutylene rubber, Poly-Lactic acid and Acetoxy Silicon were experimentally tested. Although these dielectric materials are not commonly used in plasma actuators, their values of dielectric strength and dielectric permittivity indicate they can be good solutions. The plasma actuators facbricated with these alternative dielectric materials were experimentally analysed in terms of electrical characteristics and induced flow velocity, and the obtained results were compared with an actuator made of Kapton which is, currently, the most common dielectric material for plasma actuators. The effectiveness of the actuators was estimated and the advantages and disadvantages of the use of each dielectric material were discussed.
{"title":"Experimental Analysis of Alternative Dielectric Materials for DBD Plasma Actuators","authors":"F. Rodrigues, José C. Páscoa, M. Trancossi","doi":"10.1115/IMECE2018-87455","DOIUrl":"https://doi.org/10.1115/IMECE2018-87455","url":null,"abstract":"Dielectric Barrier Discharge plasma actuators are simple devices with great potential for active flow control applications. They have very interesting features which have made them a topic of interest for many researchers, for instance they present very low mass, fast response time, low cost, easy implementation and they are fully electronic with no moving parts. The dielectric material used in the construction of these devices present an important role in their performance. The variety of dielectrics studied in the literature is very restrict and the majority of the authors make use of Kapton, Teflon, Macor ceramic or PMMA. Furthermore, several authors reported difficulties in the durability of the dielectric layer when actuators operate at high levels of voltage and frequency. Considering this background, the present study focus on the experimental testing of alternative dielectric materials which can be used for DBD plasma actuators fabrication. Considering this, plasma actuators with dielectric layers made of Poly-Isobutylene rubber, Poly-Lactic acid and Acetoxy Silicon were experimentally tested. Although these dielectric materials are not commonly used in plasma actuators, their values of dielectric strength and dielectric permittivity indicate they can be good solutions. The plasma actuators facbricated with these alternative dielectric materials were experimentally analysed in terms of electrical characteristics and induced flow velocity, and the obtained results were compared with an actuator made of Kapton which is, currently, the most common dielectric material for plasma actuators. The effectiveness of the actuators was estimated and the advantages and disadvantages of the use of each dielectric material were discussed.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126489980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Sagar, A. Priyadarshini, A. Gupta, Sidharth Kumar Shukla
Tungsten Heavy Alloys (WHA) are used in counterbalance and ballast weights for aerodynamic balancing in fixed and rotary wing aircraft. Manufacturing these components for closer tolerances using machining is a challenging task. The present work aims to develop a 2D Finite Element (FE) model to simulate the chip formation process during machining of WHA using Johnson Cook Material Model (JCMM). The model constants for 95%WHA are determined based on the high strain rate test data using least square method. The calculated values are further optimized using Genetic Algorithm (GA) and Artificial Bee Colony (ABC) algorithm, which are then used as material inputs for FE simulation of machining WHA. The predicted results such as cutting force, chip geometry, shear stress, shear angle are presented and compared with the experimental results under similar cutting conditions. It has been observed that the constants obtained from ABC algorithm show minimum error in the cutting performance measures for all the experimental results.
{"title":"Determination of Johnson Cook Material Model Constants and Their Influence on Machining Simulations of Tungsten Heavy Alloy","authors":"C. Sagar, A. Priyadarshini, A. Gupta, Sidharth Kumar Shukla","doi":"10.1115/IMECE2018-88270","DOIUrl":"https://doi.org/10.1115/IMECE2018-88270","url":null,"abstract":"Tungsten Heavy Alloys (WHA) are used in counterbalance and ballast weights for aerodynamic balancing in fixed and rotary wing aircraft. Manufacturing these components for closer tolerances using machining is a challenging task. The present work aims to develop a 2D Finite Element (FE) model to simulate the chip formation process during machining of WHA using Johnson Cook Material Model (JCMM). The model constants for 95%WHA are determined based on the high strain rate test data using least square method. The calculated values are further optimized using Genetic Algorithm (GA) and Artificial Bee Colony (ABC) algorithm, which are then used as material inputs for FE simulation of machining WHA. The predicted results such as cutting force, chip geometry, shear stress, shear angle are presented and compared with the experimental results under similar cutting conditions. It has been observed that the constants obtained from ABC algorithm show minimum error in the cutting performance measures for all the experimental results.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124113028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carbon fiber reinforced composites are very much imperative to future-generation aircraft structures. However, lightning strike protection (LSP) and electromagnetic interference (EMI) are main concerns. Carbon fibers have very good mechanical properties with the best strength-to-weight ratio, but they are very poor conductors of electricity. These fibers must be reinvented to increase the surface conductance to provide high electrical conductivity to the aircraft structure. The present study deals with preparing composite sandwich structures of carbon fibers used for commercial nacelle applications subject to lightning strike effects with different metallic nanofilm of gold (Au) and silver (Ag) measuring approximately 100 nm. These metallic nanofibers were co-cured on the top layers of composite panels during vacuum curing process. In our laboratory, lightning strike results for a composite sandwich structure using nanofilms were obtained to observe lightning strike damage and structural tolerance necessary to observe the damage tolerance capability. Resistance of composite panels with metallic nanofilm under various strains was studied. It was found that resistance of the metallic nanofilm increased under strain. The voltage was found to be low; hence, an increase in current would help to reduce the damage on composite panels due to lightning strikes, and the same theory would be applicable to EMI. No EMI was absorbed or reflected in the nanofilm using the P-static test. When lightning strikes were applied to composite coupons, the resulting damage from the currents was reduced on those with metallic nanofilms.
{"title":"Lightning Strike Protection and EMI Shielding of Fiber Reinforced Composite Using Gold and Silver Nanofilms","authors":"P. K. Bollavaram, M. M. Rahman, R. Asmatulu","doi":"10.1115/IMECE2018-88639","DOIUrl":"https://doi.org/10.1115/IMECE2018-88639","url":null,"abstract":"Carbon fiber reinforced composites are very much imperative to future-generation aircraft structures. However, lightning strike protection (LSP) and electromagnetic interference (EMI) are main concerns. Carbon fibers have very good mechanical properties with the best strength-to-weight ratio, but they are very poor conductors of electricity. These fibers must be reinvented to increase the surface conductance to provide high electrical conductivity to the aircraft structure. The present study deals with preparing composite sandwich structures of carbon fibers used for commercial nacelle applications subject to lightning strike effects with different metallic nanofilm of gold (Au) and silver (Ag) measuring approximately 100 nm. These metallic nanofibers were co-cured on the top layers of composite panels during vacuum curing process. In our laboratory, lightning strike results for a composite sandwich structure using nanofilms were obtained to observe lightning strike damage and structural tolerance necessary to observe the damage tolerance capability. Resistance of composite panels with metallic nanofilm under various strains was studied. It was found that resistance of the metallic nanofilm increased under strain. The voltage was found to be low; hence, an increase in current would help to reduce the damage on composite panels due to lightning strikes, and the same theory would be applicable to EMI. No EMI was absorbed or reflected in the nanofilm using the P-static test. When lightning strikes were applied to composite coupons, the resulting damage from the currents was reduced on those with metallic nanofilms.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129201352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rotary wing aircrafts in any flight conditions suffer from excessive vibration which makes the passengers feel uncomfortable and causes fatigue failure in the structure. The main sources of vibration are the rotor harmonic airloads which originate primarily from the rapid variation of flow around the blade due to the vortex wake. Unlike fixed wing aircrafts, helicopter wake consists of helical vortex sheets trailed behind each blade and remains under the rotor disk which induces vertical downwash velocities at chordwise and spanwise stations of the blade. In this study, a mathematical model is developed for rotor blades to compute the harmonic loads induced velocity at rotor blades for two flight conditions-vertical takeoff and landing, and forward flight. This method is useful for the performance analysis of rotor blade and selection of airfoils for the blade. The sectional lift, drag, and pitching moment are computed at a radial blade station for both flight conditions. The numerical integration of Biot-Savart relation are done for all the trailing and shed vortices to calculate the downwash through the rotor disc. The airloads are calculated using the relation between harmonic and inflow coefficients. The lift at a particular radial station is computed considering trailing and shed vortices and summing over each blade. Lifting-surface and lifting-line theories are applied to near wake and far wake, respectively, to calculate the downwash and inflow through the rotor disc. The results for lift are compared to the experimental flight-test data.
{"title":"An Analysis of Harmonic Airloads Acting on Helicopter Rotor Blades","authors":"Iftekhar A. Riyad, U. Chakravarty","doi":"10.1115/IMECE2018-86625","DOIUrl":"https://doi.org/10.1115/IMECE2018-86625","url":null,"abstract":"Rotary wing aircrafts in any flight conditions suffer from excessive vibration which makes the passengers feel uncomfortable and causes fatigue failure in the structure. The main sources of vibration are the rotor harmonic airloads which originate primarily from the rapid variation of flow around the blade due to the vortex wake. Unlike fixed wing aircrafts, helicopter wake consists of helical vortex sheets trailed behind each blade and remains under the rotor disk which induces vertical downwash velocities at chordwise and spanwise stations of the blade. In this study, a mathematical model is developed for rotor blades to compute the harmonic loads induced velocity at rotor blades for two flight conditions-vertical takeoff and landing, and forward flight. This method is useful for the performance analysis of rotor blade and selection of airfoils for the blade. The sectional lift, drag, and pitching moment are computed at a radial blade station for both flight conditions. The numerical integration of Biot-Savart relation are done for all the trailing and shed vortices to calculate the downwash through the rotor disc. The airloads are calculated using the relation between harmonic and inflow coefficients. The lift at a particular radial station is computed considering trailing and shed vortices and summing over each blade. Lifting-surface and lifting-line theories are applied to near wake and far wake, respectively, to calculate the downwash and inflow through the rotor disc. The results for lift are compared to the experimental flight-test data.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116061357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. S. Rahman, P. Schilling, P. Herrington, U. Chakravarty
Selective Laser Melting (SLM) and Electron Beam Additive Manufacturing (EBAM) are two of the most promising additive manufacturing technologies that can make full density metallic components using layer-by-layer fabrication methods. In this study, three-dimensional computational fluid dynamics models with Ti-6Al-4V powder were developed to conduct numerical simulations of both the SLM and EBAM processes. A moving conical volumetric heat source with Gaussian distribution and temperature-dependent thermal properties were incorporated in the thermal modeling of both processes. The melt-pool geometry and its thermal behavior were investigated numerically and results for temperature profile, cooling rate, variation in specific heat, density, thermal conductivity, and enthalpy were obtained with similar heat source specifications. Results obtained from the two models at the same maximum temperature of the melt pool were then compared to describe their deterministic features to be considered for industrial applications. Validation of the modeling was performed by comparing the EBAM simulation results with the EBAM experimental results for melt pool geometry.
{"title":"A Comparative Study Between Selective Laser Melting and Electron Beam Additive Manufacturing Based on Thermal Modeling","authors":"M. S. Rahman, P. Schilling, P. Herrington, U. Chakravarty","doi":"10.1115/IMECE2018-86428","DOIUrl":"https://doi.org/10.1115/IMECE2018-86428","url":null,"abstract":"Selective Laser Melting (SLM) and Electron Beam Additive Manufacturing (EBAM) are two of the most promising additive manufacturing technologies that can make full density metallic components using layer-by-layer fabrication methods. In this study, three-dimensional computational fluid dynamics models with Ti-6Al-4V powder were developed to conduct numerical simulations of both the SLM and EBAM processes. A moving conical volumetric heat source with Gaussian distribution and temperature-dependent thermal properties were incorporated in the thermal modeling of both processes. The melt-pool geometry and its thermal behavior were investigated numerically and results for temperature profile, cooling rate, variation in specific heat, density, thermal conductivity, and enthalpy were obtained with similar heat source specifications. Results obtained from the two models at the same maximum temperature of the melt pool were then compared to describe their deterministic features to be considered for industrial applications. Validation of the modeling was performed by comparing the EBAM simulation results with the EBAM experimental results for melt pool geometry.","PeriodicalId":119220,"journal":{"name":"Volume 1: Advances in Aerospace Technology","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116263959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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