170 research outputs found
Wear surface damage of a Stainless Steel EN 3358 aeronautical component subjected to sliding
Get PDFThe present paper describes the failure analysis of an aircraft component subjected to several episodes of in service failure, resulted in loss of the aircraft safety. Modern aircrafts are provided with mechanical systems which have the task to open not pressurized hatches during landing. The components of such systems are subject to considerable mechanical stresses in harsh environment (presence of moisture and pollutants, significant and sudden temperature variations). The system is constituted by a sliding piston, a related nipple and by a locking system consisting of 4 steel spheres which are forced into a countersink machined on the piston when the hatches is open. The whole system is activated by a preloaded spring. The machined parts, nipple and piston, are made of EN3358 steel (X3CrNiMo13-8-2), a precipitation hardening stainless steel with very low content of carbon often used in the aerospace. The samples provided by the manufacturer present different types of damage all referable to phenomena relative to the sliding of the piston inside the nipple. The present paper describes the different damage observed and the microstructure of the material, then are reported the results obtained from the characterization of the material of the samples by means of optical and electronic microscopy, carried out to define the mechanisms involved in the system seizure. In order to define the primary cause of failure and to propose solutions to be adopted, also analyzing the criticality of using this PH stainless steel for this application, the results of different tests were compared with system design and working data
Materials and techniques of Art Nouveau architecture in Italy and Portugal: a first insight for an European route to consistent restoration
Get PDFThe results of the investigations on building materials and techniques of Casa Major Pessoa, a typical Art
Nouveau construction in Aveiro (Portugal), and two coeval Art Nouveau buildings in Bologna (Italy) are presented
as a methodological contribution to the restoration of this kind of buildings. This is the first step to
ascertain the existence of a common thread between local materials, technologies and architecture in European
countries at the same period. A holistic approach was adopted: materials were investigated along with
architectural, structural and technological features, in order to achieve a first insight into the Art Nouveau
architecture in Europe in particular for its consistent restoration without loss of historical memory
Surface treatment on breadboards of LARES satellite
No full textLARES satellite was launched on the 13th of February 2012 using the new European Space Agency (ESA) launcher VEGA from Kourou Spaceport in French Guyana. LARES is a passive satellite of the Italian Space Agency (ASI) devised and designed by the University of Salento and Sapienza to measure with high accuracy the effect of the Earth angular momentum on the spacetime geometry and on the orbital motion of a satellite. This effect is called frame-dragging or Lense-Thirring effect and was published in 1918 using Einstein’s equations soon after the publication of general relativity. Because of its design, optimized to minimize the non gravitational perturbations, LARES is the known single object orbiting in the solar system with the highest mean density. The LARES experiment is indeed performed also with two more satellites LAGEOS (NASA) and LAGEOS 2 (NASA and ASI). Before the launch it was studied the possibility either to depose a thin film or to paint the satellite in such a way to perform a passive temperature control of the satellite. In the paper all the different options considered and the actual final choice decided for LARES surface treatment will be described
Detecting Attomolar Concentrations of Interleukin IL-17A via Pollen-Based Nanoplasmonic Biochips
No full textInterleukins are involved in several diseases and cancers, and their detection and monitoring are of great interest. Their low abundance and short half-lives suggest the need to develop rapid, specific, and highly sensitive detection platforms, easily integrable in point-of-care (POC) systems. Among the other interleukins, interleukin IL-17A is associated with inflammations, neurodegenerative diseases, and cancers, and no biosensors have been previously reported for its detection. In this work, for the detection of IL-17A, a highly sensitive nanoplasmonic sensor based on natural nanostructures like pollen shells, covered by a gold film and a bio-receptor layer, is presented. Hybrid plasmonic modes are exploited to reach high sensitivity without using costly techniques to fabricate periodic nanostructures, such as electron beam lithography. A transparent amino-modified glass substrate is functionalized with carboxylic activated pollen via carbodiimide chemistry. Then, the pollen-based nanostructures are covered by a gold film and derivatized by an immuno-layer specific to IL-17A recognition. The developed IL-17A biosensor is monitored via a simple, small-sized, and low-cost experimental setup, demonstrating high selectivity, a fast response time of about five minutes, and sensitivity with a limit of detection in the ag/mL concentration range. The biosensor allows for the detection of IL-17A in complex solutions thanks to the possibility of high dilution, an advantageous aspect to POC systems
Bastone per migliorare la mobilità delle persone con deficit di memoria
No full textbastone da passeggio con navigatore gps e comunicatore vocale integrat
TITAFORM - Precision Hot Forming, development of innovative hot-forming processes of aeronautical components in Ti-alloy with low buy/fly ratio: an Italian example of co-operation between academy and industry
No full textIn the paper the description of the project TITAFORM is provided. The project has been financed on the call "PON Linea 1" of the Italian government and represents an effective example of cooperation between academy and industry. The project is focused on the beta forging and hot stretch forming operations of titanium alloys. �� 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
SURFACE DAMAGE OF STAINLESS STEEL EN3358 SUBJECT TO FRICTION, IMPULSIVE ACCELERATION AND CORROSIVE ENVIRONMENT
No full textThe present paper describe the failure analysis of an aircraft component subjected to several episodes of in service failure, resulted in loss of the aircraft safety. Modern aircrafts are provided with mechanical systems which have the task to open not pressurized hatches during landing. The components of such systems are subject to considerable mechanical stresses in harsh environment (presence of moisture and pollutants, significant and sudden temperature variations). The system is constituted by a sliding piston, and related nipple, assisted in the movement by 4 steel balls which act as a ball bearing, the whole system is activated by a preloaded spring. The machined parts, nipple and piston, are made of N3358 steel (X3CrNiMo13-8-2), an austenitic stainless steel with very low content of carbon often used in the aerospace. The samples provided by the manufacturer present different types of damage all referable to phenomena relative to the sliding of the piston inside the nipple. Particularly, on the cylindrical sample (piston) were detected circular impressions -probably due to the ball-bearing- and various kinds of longitudinal and helicoidal grooves, due both to the original machining and to the spring. The nipple presented longitudinal grooves and residual of lubricant containing metal residues resulting from the relative sliding. The present paper describes the different damage observed and the microstructure of the material, then are reported the results obtained from the characterization of the material of the samples by means of optical and electronic microscopy, carried out to define the mechanisms involved in the system seizure. In order to define the primary cause of failure and to propose solutions to be adopted, the results of different tests were compared with system design and working data
QUALIFICATION OF THE SPECULAR POINT-LIKE QUICK REFERENCE EQUIPMENT AND ACCEPTANCE TESTS FOR INSTALLATION ON THE INTERNATIONAL SPACE STATION
No full textOn February the 28th the Specular Point-like Quick Reference (SPQR) equipment was launched on board the 17P Progress flight to the International Space Station (ISS). The equipment was installed after a few days on a ISS win-dow and the experiment was successfully performed in March-May 2005, in the frame of the Italian Soyouz Mission “Eneide” (ISM).
The Columbia disaster showed how critical manned missions are and how useful would be a device for imaging low Earth orbit manned satellites with a resolution of 20 cm (which would have probably been sufficient to detect the damage on the Columbia surface). Unfortunately, the Earth atmosphere blurs the images thus preventing from achieving sharp photographs of satellites. The aim of SPQR experiment is to test a procedure suitable to overcome this problem and to improve the imaging resolution to about 20 cm or less. This can be done by providing in the pic-ture a point-like light source with a high signal to noise ratio, which has been subjected to the same atmospheric dis-tortion as the target spacecraft. The point spread function of this reference can be used to process the image for ob-taining a sharp image.
The SPQR equipment consists of a glass Cube Corner Reflector (CCR) inserted in a mounting designed to interface the CCR with an ISS window. The window, during the experiment allocated time, has been oriented in the nadir di-rection. The CCR has been illuminated by a ground based laser. The laser beam has been retro-reflected to the ground station by the CCR. Hence, the ground station telescope devoted to take images of the ISS, has also seen the “point-like reference” consisting of the laser beam reflected by the “specular” CCR.
Although the SPQR equipment is completely passive (it is just a reflector), for uploading it on the ISS a number of issues arised, essentially due to safety considerations related with the crew presence in the ISS cabin. For this reason, some tests have been required by Rocket and Space Corporation – Energia (the company managing the ISM for the Russian Space Agency) and by the European Space Agency (ESA, managing the mission for the sponsoring institu-tions and providing additional services). The paper illustrates the tests the SPQR flight models have been submitted to as well as the relevant results. The tests, performed in January 2005, are as follows:
1. Vibration and shock tests, to simulate the vibration environment. The following tests were performed (on each axis):
Vibration test of the Flight Model (FM) inside its Transportation Bag (TB) simulating the Progress launch conditions;
Vibration test of the FM inside its TB simulating the Progress insertion conditions, i.e. the boosting phases while the Progress approaches the ISS orbit;
Shock test of the FM inside its TB simulating the Progress docking to the ISS;
Vibration test of the FM, hard mounted on the interface with the shaker, as it would have been mounted on the ISS window. This test simulated the ISS orbit conditions, i.e. the ISS re-orbiting boosting phases.
2. Interferometric test of the CCR, to verify that the vibration and shock tests did not cause any damage to the CCR glass. This test was requested by ESA safety and structures experts to have a greater safety factor about the CCR glass: in fact this is a major concern from a safety standpoint, since small glass particle in a micro-gravity environment can be lethal for the crew due to the ease of ingestion and breathing.
3. Non-destructive test of the SPQR aluminium interface, to verify the absence of cracks.
4. Off-gassing test, to prove that the SPQR equipment non-metallic materials would not have produced gases dangerous for the astronauts or affecting their capabilities.
5. Flammability tests, to verify the flame propagation on some SPQR materials.
After a short description of the SPQR experiment and equipment, the paper depicts the test purposes, performances and results
TECHNOLOGICAL CHALLENGES FOR MANUFACTURING LARES SATELLITE
No full textLARES is a passive satellite designed to measure the gravitomagnetic field of Earth predicted by Einstein general relativity. The technique used to accurately measure the satellite position is the laser ranging technique. The satellite is uniformly covered with 92 cube corner reflectors that sends back to the ground station the laser pulses. Launch is foreseen in 2010 with the new VEGA launch vehicle. The material selected for building the satellite is a tungsten alloy. Due to this peculiar alloy used for LARES satellite, some concerns arise about the machinability of the material. Although several producers can provide several types of tungsten alloys, and there are applications that use bulk tungsten material, to our knowledge this material, very seldom used in space, was never machined with tight manufacturing tolerances and severe surface finish. Consequently some tests for machinability have been performed. Particular care has been adopted for manufacturing spherical cavities that are used to interface the separation system. Also the screws and the retainer rings for the cube corner reflector mounting system are difficult items to be manufactured in tungsten alloy, being the screw body and the ring thickness very small. All those technological challenges have been faced on several breadboards (full scale prototypes of critical small parts of the satellite)
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