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Probabilistic fatigue crack growth analyses for critical structural details

AIAA JOURNAL 2000年第5期38卷 882-892页

作者： Wang, GS Aeronaut Res Inst Sweden Struct Div S-16111 Bromma Sweden

The damage tolerance method requires the assumption that cracks preexist at the critical structural details and that subsequent fatigue crack propagation could cover at least twice the design life before failure occurs. If fatigue crack propagation cannot meet these requirements, an inspection could be arranged to detect cracks at half of the Fatigue life to prevent catastrophic failure. Fatigue tests using from coupons up to the whole structure should be performed to complement the damage tolerance analyses. Nevertheless, the damage tolerance method can still not guarantee an economical airframe due to uncertainties in initial fatigue quality, material, usage, and maintenance, Probabilistic analyses are needed to cover major sources of these uncertainties. A procedure is presented based on several novel probabilistic fracture mechanics solutions for the analyses of fatigue crack propagation. A practical example is used in the discussion to illustrate the procedure and to address important issues when uncertainties are considered. It is shown that different consequences may appear if analyses of the fatigue life are based on the probabilistic consideration.

关键词： Fatigue Cracking Probabilistic Fracture Mechanics Damage Tolerance Fatigue Test Catastrophic Failure Airframes Fracture Toughness Aspect Ratio Structural Reliability geometry functions

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Assessing the Usability of Two Declarative Programming Languages to Model Geometric Events

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2023年第9期20卷 546-554页

作者： Llopis, Marcel Franch, Xavier Soria, Manel CALTECH Flight Software & Av Syst Sect Jet Prop Lab Pasadena CA 91109 USA Univ Politecn Cataluna Software & Serv Engn Grp Barcelona 08034 Spain Univ Politecn Cataluna Aerosp Engn Div Barcelona 08034 Spain

When space missions plan scientific actions for robotic spacecraft to execute, they frequently do so within a geometric context called an opportunity. Although there are geometric software libraries that let users write code to search for opportunities, they require knowledge of algorithms and imperative programming languages, which is a condition that might exclude a potentially large population of scientists. Additionally, there might be more user-friendly software systems for scientists to model and search for opportunities, but those might exclude other missions due to export concerns or an inability to maintain such software due to lack of staff or funding. To address these concerns, we designed two different computer languages to model opportunities. In this paper, we present these two languages, our study to evaluate their relative readability and usability, and results obtained in our research along with an interpretation of the same. The metric for this study has been a questionnaire with active exercises, statements with corresponding responses on a Likert scale, and open-ended questions to elicit qualitative responses. The study's quantitative results provide us with relative and absolute quantification of the usability and readability of each language, while the study's qualitative results help us direct future language design decisions.

关键词： Space Missions Software Systems Integrated Development Environments Aerospace Engineering Human Computer Interaction geometry functions Mission Planning and Design Space Science and Technology Software Evaluation Ground Software Systems

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Kinematic Batch Estimator for Angular Velocity and Associated Uncertainty

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2024年第6期47卷 1039-1054页

作者： Kaki, Siddarth Akella, Maruthi R. Univ Texas Austin Dept Aerosp Engn & Engn Mech Austin TX 78705 USA Univ Texas Austin Dept Aerosp Engn & Engn Mech Engn 19 Austin TX 78705 USA

Estimating the relative pose and angular velocity of an uncooperative space object is a critical component for many applications such as on-orbit assembly, inspection, and servicing. This paper presents new mathematical insights that permit a kinematic batch filter formulation for angular velocity estimation using quaternion measurements for relative orientation, thereby eliminating the need to know the moment of inertia of the target. In particular, a novel batch approach to computing the associated uncertainties for the angular velocity magnitude, spin-axis direction, and overall angular velocity vector estimates is presented and compared against previous recursive methodologies. Finally, a realistic use-case scenario is demonstrated in real-time on flightlike hardware.

关键词： geometry functions Probability Distribution functions Unscented Kalman Filter Monte Carlo Experiment Quaternion Regression Algorithm Attitude Kinematics Optimization Algorithm Angular Velocity Quaternions

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An experimental and numerical study of the fracture behaviour of tubular specimens in a pin-loading-tension set-up

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE 2010年第C1期224卷 1-12页

作者： Samal, M. K. Sanyal, G. Chakravartty, J. K. Bhabha Atom Res Ctr Reactor Safety Div Bombay 400085 Maharashtra India Bhabha Atom Res Ctr Mech Met Sect Bombay 400085 Maharashtra India

Evaluation of a valid crack Lip loading parameter using standard ASTM practice may not be feasible in many situations, e.g. in thin tubular specimens with diametrically opposite axial through-wall cracks (loaded in opening mode) that are obtained from zircaloy fuel Pills Of nuclear reactors. Recently, a pin-loading-tension (PLT) experimental set-Lip has evolved for this purpose. However, the required geometry functions (which should be obtained from a three-dimensional (3D) finite-element (FE) analysis procedure) for evaluation of the stress intensity factor (SIF) for such a set-LIP is not available in the literature. In this work, a detailed 3D FE analysis of the PLT set-Lip has been carried Out where both the pin and the mandrel have been modelled. Analysis has been carried Out for the full loading path (i.e. for applied displacements beyond the limit load of the specimen) in order to demonstrate the effectiveness of the model and the results have been compared with those of the experiment. in addition, the SIFs (and geometry functions) of the PLT set-up (with different initial crack lengths) have been evaluated from the FE results using extrapolation techniques and were compared with the results from two different analytical techniques.

关键词： zircaloy fuel pin fuel clad material pin-loading-tension set-up stress intensity factor geometry functions

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Multibody-Dynamics Approach to Study the Deformation and Aerodynamics of an Insect Wing

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AIAA JOURNAL 2023年第6期61卷 2500-2516页

作者： Le, Vu Dan Thanh Nguyen, Anh Tuan Dang, Ngoc Thanh Le Quy Don Tech Univ Fac Aerosp Engn Hanoi 100000 Vietnam

In this study, a multibody-dynamics simulation approach was developed for a hawkmoth flexible wing. The wing structure is modeled as a chain of rigid bodies connected by elastic springs, and the aerodynamic force is measured by the extended unsteady vortex-lattice method. The multibody-dynamics and aerodynamic solvers are combined by an implicit coupling approach, and the quasi-Newtonian method is adopted to solve the system of nonlinear differential equations of motion. For validation, numerical results were compared with measurement data from a robotic wing and a living insect. A parametric analysis was conducted to study the effects of several kinematic parameters on the deformation and aerodynamic performance of the wing in hover. In most cases, using a flexible wing is far more efficient in terms of force production in comparison with its rigid counterpart. In general, wing deformation may cause considerable differences between the wing-tip and wing-base kinematic parameters. In particular, elevation motion as observed in living insects may be due to the passive oscillations of elastic elements, as opposed to a deliberate motion.

关键词： Aerodynamic Characteristics Multibody Dynamics Aircraft Wing Design Aircraft Wing Components Aerodynamic Performance Computational Fluid Dynamics Wing Configurations Finite Element Modeling Vortex Dynamics geometry functions

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Distribution of points on a sphere with application to star catalogs

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2000年第1期23卷 130-137页

作者： Bauer, R Bauer Engn Enterprises Langhorne PA 19047 USA

A new framework is introduced to analyze the spatial distribution of stars in a catalog, namely, the Voronoi diagram/Delaunay triangulation. The Voronoi diagram is a subdivision of the celestial sphere into polygonal cells, one for each star, so that the cell for star P consists of the region on the sphere closer to P than to any other star. The Delaunay triangulation is the topological dual with the important property that each spherical cap circumscribing a triangle contains no stars in its interior. Measures of the uniformity in star density and geometric arrangement based on the Voronoi diagram/Delaunay triangulation are presented and compared with existing measures, Methods to generate uniformly distributed points on the sphere, which serve as useful test cases for stellar attitude determination analysis, are formulated and compared. One such method, based on a spherical spiral, is easy to implement and yields a very uniform distribution of points. Finally, the Voronoi density reduction method is introduced to select stars for an onboard catalog from a larger candidate set. The candidate with the smallest Voronoi cell is removed, and the Voronoi diagram of the reduced set is constructed. This process is repeated until the desired number of stars remains.

关键词： Space Shuttle Attitude Determination Algorithms Spacecraft Attitude Data Structures Satellites Earth Space Shuttle Missions Numerical Algorithms geometry functions Computer Memory

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Transient analysis of forced convection along a wavy surface in micropolar fluids

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2000年第3期14卷 340-347页

作者： Chen, CK Wang, CC Natl Cheng Kung Univ Dept Mech Engn Tainan 701 Taiwan

Numerical results for transient laminar-forced convection along a wavy surface In micropolar fluids are presented. A simple coordinate transformation is employed to transform the complex wavy surface to a hat plate, and the obtained nonsimilarity boundary layer equation is solved numerically by the spline alternating-direction implicit method. The effects of micropolar parameter and wavy geometry on the velocity and temperature fields are examined, The transient skin friction and transient local and averaged heat-transfer rates decrease with time. Their axial distributions have a frequency equal to the frequency of the wavy surface, but their crests and troughs do not occur just at the crests and troughs of the wavy surface. The amplitudes of the transient local skin-friction coefficient and the transient local Nusselt number tend to increase as the wavy length and the wavy amplitude-wavelength ratio increases. Furthermore, the transient Nusselt number of a micropolar fluid is smaller than that of a Newtonian fluid everywhere, whereas the transient local skin-friction coefficient of a micropolar fluid is larger than that of a Newtonian fluid just near the leading edge.

关键词： Forced Convection Convection Heat Transfer Skin Friction Prandtl's Transposition Theorem Viscosity Freestream Velocity Vortices Thermal Conductivity geometry functions Solar Collectors

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Fundamentals Of High Accuracy Inertial Navigation 1st

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丛书名： Progress in Astronautics and Aeronautics

1997年

作者： Averil B. Chatfield

ISBN: (数字)9781600866463

ISBN: (纸本)9781563472435

The primary focus of Fundamentals of High Accuracy Inertial Navigation is on the physical and mathematical principles forming the basis for inertial navigation. It differs from other books on the subject by treating aspects of the blend of inertial navigation technology and geodesy. Accuracy criteria and evaluation are also discussed. Fundamentals of High Accuracy Inertial Navigation is divided into three parts: inertial navigation, inertial navigation with aids, and accuracy analysis. The first two parts are designed to give the reader an understanding of the fundamentals without requiring knowledge of the statistical analysis techniques involved in determining the effects of errors on accuracy. The third part defines the criteria for determining accuracy and then leads the reader through the complex process of that determination. This book is intended for the third- or fourth-year engineering student, as well as professional engineers or scientists trained in mathematics, control theory, analytical mechanics, geodesy, or physics, who have a need for understanding the basic principles of inertial navigation technology.

关键词： Aerodynamics Aeronautical Engineering Aeronautics Air Navigation Aircraft Navigation Systems Altitudes in Aviation Applied Mathematics Astronomy Avionics Avionics Computers Bearings (Mechanical) Celestial Mechanics Classical Mechanics Computational Fluid Dynamics Computer Programming and Language Computing and Informatics Computing, Information, and Communication Control Systems Control Theory Coordinate System Doppler Effect Earth Observation Satellite Earth Sciences Electrodynamics Electromagnetic Radiation Electromagnetism Elementary Algebra Fault Detection and Isolation Feedback Control Finite Element Method Fluid Dynamics Fluid Flow Properties Fluid Mechanics General Physics geometry functions Geophysics Global Positioning System Guidance, Navigation, and Control Systems Gyroscopes Hydraulic Fluid Hydraulics Kalman Filter Mathematical Analysis Mechanical and Structural Vibrations Monte Carlo Method Navigational Guidance Newton's Laws of Motion Numerical Analysis Planetary Atmospheres Planetary Science and Exploration Planets Satellite Navigation Systems Satellites Sensors Signal Processing Solar Physics Solar Wind Space Flight Tracking and Data Network Space Science and Technology Space Systems and Vehicles Spacecraft Guidance and Control Spacecrafts Structural Analysis Structural Design and Development Structural Engineering Structural Kinematics and Dynamics Structures, Design and Test Torsional Vibration Transducers Tribology and Bearing Design Vibration Measuring Instruments

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Advanced Dynamics Har/Dskt

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丛书名： AIAA Education Series

1997年

作者： Shuh-Jing (Benjamin) Ying

ISBN: (数字)9781600861307

ISBN: (纸本)9781563472244

Advanced Dynamics is recognized as an important subject of study for all engineering students and professionals in competitive university programs and throughout the industry. This textbook adeptly explains the fundamental laws of motion, but goes a step beyond by covering new topics such as gyroscopic effects, missile trajectories, interplanetary missions, multistage rockets, and use of numerical methods. In addition, theories such as the rotation operator are taken to a new degree and developed further, far surpassing comparable *** book balances theory and application and relates all subjects to practical problems, real-world situations, and recent advances that affect everyday life. This text distinguishes itself with a more complete introduction to recent developments in dynamics, new and practical applications to help the reader remember key theories and uses, and an appreciation that the subject matter is riddled with ongoing problems that need new solutions. These distinguishing features make Advanced Dynamics more complete, interesting, and understandable than existing textbooks and resource materials. Problems appear at the end of each chapter, and a complimentary solutions manual is available for professors. Advanced Dynamics is also written for those engineers who want to update their knowledge and stay current on changes in the field, but do not have the opportunity to attend formal classes. The reader will take away a thorough understanding of the foundation of mechanical engineering, which is necessary to read and assimilate scholarly papers and leading articles published in journals and peer-reviewed magazines.

关键词： Aerodynamics Aeronautical Engineering Aeronautics Aircraft Operations Aircraft Operations and Technology Aircraft Stability and Control Aircrafts Applied Mathematics Beam (Structures) Classical Mechanics Computational Fluid Dynamics Computer Programming and Language Computing and Informatics Computing, Information, and Communication Coordinate System Earth Observation Satellite Elementary Algebra Energy Energy Forms Energy Forms, Production and Conversion Energy Storage and Batteries Finite Element Method Flexible and Active Structures Flight Control Surfaces Fluid Dynamics Fluid Flow Properties Fluid Mechanics General Physics geometry functions Gyroscopes Launch Vehicles Material Properties Materials and Structural Mechanics Mathematical Analysis Mechanical and Structural Vibrations Multistage Rocket Newton's Laws of Motion Numerical Analysis Planetary Science and Exploration Planets Rotor Dynamics Runge-Kutta Methods Satellites Shell Structures Solid Mechanics Space Launch Systems Space Missions Space Probe Space Science and Technology Space Systems Space Systems and Vehicles Space Vehicle Spacecrafts Stress-Strain Analysis Structural Analysis Structural Design and Development Structural Engineering Structural Kinematics and Dynamics Structural Mechanics Structures, Design and Test Uncrewed Spacecraft Vibration Measuring Instruments Weather Satellite

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Partial derivatives of the lambert problem

Partial derivatives of the lambert problem

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AIAA/AAS Astrodynamics Specialist Conference 2014

作者： Arora, Nitin Russell, Ryan P. Strange, Nathan Jet Propulsion Laboratory California Institute of Technology United States Department of Aerospace Engineering and Engineering Mechanics University of Texas at Austin United States

ISBN: (数字)9781624103087

ISBN: (纸本)9781624103087

A procedure for deriving analytic partial derivatives of the Lambert problem is presented. Using the universal, cosine based Lambert formulation;first order partial derivatives of the velocities with respect to the positions and times are developed. Taking advantage of inherent symmetries and intermediate variables, the derivatives are expressed in a computationally efficient form. The added cost of computing these partials is found to be ~10% to ~60% of the Lambert compute cost. The availability of analytic partial derivatives increases optimization speed, efficiency and allows for trajectory optimization formulations that implicitly enforce continuity constraints via embedded Lambert problems.

关键词： Lambert's Problem Computing Trajectory Optimization Orbit Determination Finite Difference Method Space Flight Mechanics Boundary Value Problems geometry functions Linear Programming Computing Cost

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