Exploiting internal pressurisation to enhance structural properties

The thesis investigates ways to use internal pressure in a favourable way. It focuses on the structural effects of internal pressurisation of mechanical components. The buckling phenomenon of shell structures is analysed in depth and the conducted work confirms the long known beneficial influence of the internal pressure on buckling and suggests how to exploit this to the utmost extent. Changes in failure modes, stiffness and dynamic response due to pressurisation are also considered. Given the nature of the problem, Finite Element Analysis (FEA) is an essential part of the PhD project. The state-of-the-art FEA techniques are described and employed. Geometric imperfections are introduced in the FE models and, to this regard, a novel FEA technique ensuring high-accuracy simulations is developed. Parametric studies on thin-walled structures are carried out. The studies concern both straight and curved cylindrical shells, as well as more complex geometries. These were subjected to different combinations of loads including bending loads, compressive loads and internal pressure. Among the main findings, it is found that internal pressurisation can change the failure mechanism of the structure and, for a given geometry and material, an optimal value of internal pressure exist. This value allows to fully exploit the material capabilities and to maximise the mechanical performance of the structure. Moreover, it is found that internal pressurisation, as well as pipe curvature, modifies the stiffness and this is significant for structures wherein deflections must be kept to a minimum. Exploitation of internal pressurisation is especially attractive in applications wherein weight minimisation is a key objective. Therefore the content of the thesis is particularly relevant to the aerospace sector. A possible application consisting in the use of pressurised members within aircraft wings is here proposed. With regard to the above application, a prototype of a UAV wing with an internal pressurised structure was built. The structure is made of composite material for performance maximisation and its manufacturing process and related considerations are described. Experimental tests were performed with the aim of measuring the effects of internal pressurisation in the component stiff-ness and natural vibrational frequencies. Experimental results were compared to numerical results. Results confirms the potential of internal pressurisation to enhance mechanical properties

Optimal internal pressurisation of cylindrical shells for maximising their critical bending load

AbstractThe paper studies the influence of internal pressure on circular thin-walled pipes (D/t>150) subjected to pure bending. Both straight pipes and curved pipes are analysed. Both yield and buckling failures are considered. It is shown that internal pressure decreases the limiting load for yield but increases the limiting load for buckling.The study is mainly FEA-based. A formula to predict critical moment given by linear buckling analysis is proposed. Comments on difference between linear and non-linear analysis results are given. It is shown that a pipe curvature opposite to the bending moment can increase the critical load. It is shown that cylindrical thin-walled shells have an optimal value of internal pressure to which limiting load for yield and critical buckling moment are equal, corresponding to an optimal use of material

Novel stiffeners exploiting internal pressurisation to enhance buckling behaviour under bending loads

The paper proposes a novel type of stiffener designed to bear bending loads by exploiting internal pressure effects. The stiffener is made of two adjacent thin-walled pipes (r/t≥50) jointed with a connecting strip. Such a structure is shown to have higher performance against buckling failure compared to a single pipe and its geometry allows for good exploitation of internal pressurisation. The study is conducted by using the FEA software ANSYS and the analysis technique is the linear perturbation buckling analysis. Internal pressure ranges from 0 to 1.4 MPa. The buckling mechanisms are observed for a set of models with different values of length, wall thickness and geometric variation of the cross-section. It is shown that two different buckling modes can take place. However, for a given geometry, the level of pressure can alter the behaviour and lead to one mode rather than the other one. Potential of the presented structure is maximised by the use of high performance materials and a possible aerospace engineering application is presented

Reducing weight and fuel consumption of civil aircraft by electromagnetic launch

Electromagnetic launch systems have been proposed for military applications to accelerate jet planes on aircraft carriers. This paper proposes the implementation of similar technology to aid civil aircraft take-off, which can provide significant economic, environmental and technical benefits. Assisted launch has the potential of reducing on ground noise and emissions near airports and improving overall aircraft efficiency through reducing engine thrust requirements. This paper presents a take-off performance analysis for an Airbus A320-200 taking off with and without the assistance of the electromagnetic catapult. Assisted take-off allows for a significant reduction in take-off field length, giving more capacity with existing airport footprints and reducing the necessary footprint of new airports, which will both reduce costs and increase the number of suitable sites. The electromagnetic catapult may allow the installation of smaller engines with lower rated thrust. The consequent fuel consumption and operational cost reduction is estimated. The potential of reducing the aircraft operational costs and the runway length required make electromagnetic launch system an attractive solution to the air traffic growth in busy airports

The Gamma-Flash data acquisition system for observation of terrestrial gamma-ray flashes

Gamma-Flash is an Italian project funded by the Italian Space Agency (ASI) and led by the National Institute for Astrophysics (INAF), devoted to the observation and study of high-energy phenomena, such as terrestrial gamma-ray flashes and gamma-ray glows produced in the Earth's atmosphere during thunderstorms. The project's detectors and the data acquisition and control system (DACS) are placed at the "O. Vittori" observatory on the top of Mt. Cimone (Italy). Another payload will be placed on an aircraft for observations of thunderstorms in the air. This work presents the architecture of the data acquisition and control system and the data flow.Comment: 4 pages, 1 figure, Astronomical Data Analysis Software and System XXXII (2022

CAESAR: Space Weather archive prototype for ASPIS

The project CAESAR (Comprehensive spAce wEather Studies for the ASPIS prototype Realization) is aimed to tackle all the relevant aspects of Space Weather (SWE) and realize the prototype of the scientific data centre for Space Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather InfraStructure). This contribution is meant to bring attention upon the first steps in the development of the CAESAR prototype for ASPIS and will focus on the activities of the Node 2000 of CAESAR, the set of Work Packages dedicated to the technical design and implementation of the CAESAR ASPIS archive prototype. The product specifications of the intended resources that will form the archive, functional and system requirements gathered as first steps to seed the design of the prototype infrastructure, and evaluation of existing frameworks, tools and standards, will be presented as well as the status of the project in its initial stage.Comment: 4 pages, 2 figures, ADASS XXXII (2022) Proceeding

Enabling planetary science across light-years. Ariel Definition Study Report

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution

Goodbye Hartmann trial: a prospective, international, multicenter, observational study on the current use of a surgical procedure developed a century ago

Background: Literature suggests colonic resection and primary anastomosis (RPA) instead of Hartmann's procedure (HP) for the treatment of left-sided colonic emergencies. We aim to evaluate the surgical options globally used to treat patients with acute left-sided colonic emergencies and the factors that leading to the choice of treatment, comparing HP and RPA. Methods: This is a prospective, international, multicenter, observational study registered on ClinicalTrials.gov. A total 1215 patients with left-sided colonic emergencies who required surgery were included from 204 centers during the period of March 1, 2020, to May 31, 2020. with a 1-year follow-up. Results: 564 patients (43.1%) were females. The mean age was 65.9 ± 15.6 years. HP was performed in 697 (57.3%) patients and RPA in 384 (31.6%) cases. Complicated acute diverticulitis was the most common cause of left-sided colonic emergencies (40.2%), followed by colorectal malignancy (36.6%). Severe complications (Clavien-Dindo ≥ 3b) were higher in the HP group (P < 0.001). 30-day mortality was higher in HP patients (13.7%), especially in case of bowel perforation and diffused peritonitis. 1-year follow-up showed no differences on ostomy reversal rate between HP and RPA. (P = 0.127). A backward likelihood logistic regression model showed that RPA was preferred in younger patients, having low ASA score (≤ 3), in case of large bowel obstruction, absence of colonic ischemia, longer time from admission to surgery, operating early at the day working hours, by a surgeon who performed more than 50 colorectal resections. Conclusions: After 100 years since the first Hartmann's procedure, HP remains the most common treatment for left-sided colorectal emergencies. Treatment's choice depends on patient characteristics, the time of surgery and the experience of the surgeon. RPA should be considered as the gold standard for surgery, with HP being an exception

Exploiting internal pressurisation to enhance structural properties

The thesis investigates ways to use internal pressure in a favourable way. It focuses on the structural effects of internal pressurisation of mechanical components. The buckling phenomenon of shell structures is analysed in depth and the conducted work confirms the long known beneficial influence of the internal pressure on buckling and suggests how to exploit this to the utmost extent. Changes in failure modes, stiffness and dynamic response due to pressurisation are also considered. Given the nature of the problem, Finite Element Analysis (FEA) is an essential part of the PhD project. The state-of-the-art FEA techniques are described and employed. Geometric imperfections are introduced in the FE models and, to this regard, a novel FEA technique ensuring high-accuracy simulations is developed. Parametric studies on thin-walled structures are carried out. The studies concern both straight and curved cylindrical shells, as well as more complex geometries. These were subjected to different combinations of loads including bending loads, compressive loads and internal pressure. Among the main findings, it is found that internal pressurisation can change the failure mechanism of the structure and, for a given geometry and material, an optimal value of internal pressure exist. This value allows to fully exploit the material capabilities and to maximise the mechanical performance of the structure. Moreover, it is found that internal pressurisation, as well as pipe curvature, modifies the stiffness and this is significant for structures wherein deflections must be kept to a minimum. Exploitation of internal pressurisation is especially attractive in applications wherein weight minimisation is a key objective. Therefore the content of the thesis is particularly relevant to the aerospace sector. A possible application consisting in the use of pressurised members within aircraft wings is here proposed. With regard to the above application, a prototype of a UAV wing with an internal pressurised structure was built. The structure is made of composite material for performance maximisation and its manufacturing process and related considerations are described. Experimental tests were performed with the aim of measuring the effects of internal pressurisation in the component stiff-ness and natural vibrational frequencies. Experimental results were compared to numerical results. Results confirms the potential of internal pressurisation to enhance mechanical properties

Reducing weight and fuel consumption of civil aircraft by electromagnetic launch

Electromagnetic launch systems have been proposed for military applications to accelerate jet planes on aircraft carriers. This paper proposes the implementation of similar technology to aid civil aircraft take-off, which can provide significant economic, environmental and technical benefits. Assisted launch has the potential of reducing on ground noise and emissions near airports and improving overall aircraft efficiency through reducing engine thrust requirements. This paper presents a take-off performance analysis for an Airbus A320-200 taking off with and without the assistance of the electromagnetic catapult. Assisted take-off allows for a significant reduction in take-off field length, giving more capacity with existing airport footprints and reducing the necessary footprint of new airports, which will both reduce costs and increase the number of suitable sites. The electromagnetic catapult may allow the installation of smaller engines with lower rated thrust. The consequent fuel consumption and operational cost reduction is estimated. The potential of reducing the aircraft operational costs and the runway length required make electromagnetic launch system an attractive solution to the air traffic growth in busy airports