|SPACECRAFT STRUCTURES AND MECHANISMS||ING-IND/04||LEZIONI||120|
The student who successfully completes the course will be able to demonstrate a good knowledge of both mechanical and technological aspects that refer to the space structures and to the mechanisms; will be aware of fatigue and fracture mechanics of metallic materials; will be able to solve problems of mechanics and will be able to prepare a technical report at the end of a project exercise. The evaluation is based for a 50% on the verification executed during the examination (written and oral). The other 50% is based on the evaluation of the project report that a single student or a group of students will produce at the end of the course before the examination phase.
The evaluation is based primarily on the verification of the basic knowledge necessary for the design of aerospace structures and mechanisms (strenght analysis, fatigue, fracture mechanics, joints, bearings, gears). The uncertainty of these skills is not allowed. The student must demonstrate the ability to put into practice and to execute, with critical awareness, the design methods and the verification procedures illustrated during the course. For this reason the discussion of the project report will take an important part of the examination phase.
The examination is based on the solution of written exercises and on a subsequent discussion of the results.
basic skills for the mathematical formulation (modeling of) of physical and/or technical problems
basic skills in planning of a spacecraft (space vehicle) design process
basic skills for problem solving in the field of aerospace engineering
during the lesson period the teacher suggests that students solve some simple structural dynamics problems and fatigue and/or fracture mechanics of metallic materials
the periodic meetings, which take place during the development of each project, provide good opportunities to increase the technical preparation of students and to define concrete training objectives
at the same time, the development and preparation of the project report allows the teacher to highlights personal preparation and/or personal gaps of each student
it is suggested to the students to follow the lessons with assiduity both in the first period and in the second period
the experience of the teacher allows to identify the students who have shown little commitment during the lessons and to define a preliminary framework for the assessment of the preparation of each student
statics of mechanical systems
theory of beams - basic knowledge on the theory of plates and shells
computation of characteristics (forces and moments)
basic knowledge on the stress analysis
basic knowledge on buckling phenomena
basic knowledge on kinematics and dynamics of discrete systems
basic knowledge on the dynamics of mechanical systems
basic knwoldge on thermal analysis
basic knowledge on the materials technology
use of standard software for solving mathematical problems
basic knowledge on the use of a CAD software
knowledge on stress analysis methodology and verification procedures
knowledge on kinematics and dynamics of discrete and continuous systems
knowledge on dynamics of mechanical systems (discrete and continuous)
knowledge on random analyses (stresses, acoustics and/or random vibrations)
basic knowledge and practical use of a commercial Finite Element software/or code
basic knowledge for the preliminary design of a spacecraft
basic knowledge of standard codes and/or rules for the preliminary design of a spacecraft
Theoretical lessons and, in the second period, use of personal computer for the preparation of Finite Element models by Ansys Workbench environment.
periodic meetings during the development of the project work (in general each project will be produced by a team of students two-three)
( I ) October-December
Notes about the design process of a spacecraft.
The launch phase: preliminary examination of acoustic and vibration loading conditions
Random vibrations analysis.
Vibro-acoustic Response Analysis.
Reliability of components and structures: basic definitions and applications.
Strength analysis: definition of the limit loading condition and ultimate loading condition (yielding and collapse of structures).
( II ) February-April
Computer Lab (ANSYS Workbench)
The Goodman diagram for ductile materials.
Effect of the stress concentration.
Fatigue crack growth: basic notes on fracture mechanics.
( III ) May
Computer Lab (ANSYS Workbench)
Contact stresses: discussion of results of the Hertz theory.
Springs (basic notes)
Gear trains (basic notes)
Rotating shaft dynamics: critical speeds computation.
Recommended reading includes the following books and/or technical documentation:
T.P. Sarafin "Spacecraft Structures and Mechanisms - From Concept to Launch"
R.C. Juvinall & K.M. Marshek "Fundamentals of Machine Component Design"
ESA Spacecraft mechanical loads analysis handbook - ECSS-E-HB-32-26A, 19 February 2013
ESA Buckling - ECSS-HB-32-24A, 24 March 2010
NASA TM-X-73305 - Astronautic Structures Manual - Vol I - Vol II - Vol III, 1975
NASA-HDBK-7008 - SPACECRAFT DYNAMIC ENVIRONMENTS TESTING, 2014
Jacob Job Wijker - Spacecraft Structures, Springer, 2008
Lectures of Spacecraft Structures and Mechanisms (notes) - M. Chiarelli (e-learning)
Please visit the website www.ecss.nl to consult all the technical documentation produced by ESA
the missed attendance of the lessons can cause considerable difficulties in the development of the preparation itself, in the understanding and development of the simple mechanical exercises proposed during the year and finally in the preparation and development of the project work
The exam concerns:
a) during the exam the teacher performs the revision of the project report and a suitable discussion of methods, results, technical solutions provided in the report can be part of the exam itself (50%-60% of total score)
b) students must solve at least two technical exercises (possible topics: spacecraft environments, deterministic or random dynamics of discrete and/or continuous system, statistical approach for the definition of loads and strength requirements, simple applications of stress analysis and verification criteria for mechanical systems, bolted joints, welded joints, fatigue of metallic materials, fracture mechanics of metallic materials, contact stress theory, basic notes on gear analysis, critical speeds of rotating shafts (40%-50% of total score)
in general the exam has a duration of two or three hours