1,720,969 research outputs found
A Novel Approach for the Investigation of Low Energy Ice Impacts
Get PDFSoft body impacts are one of the main sources of damage for aircraft during flight due to the high relative velocities. However, a hailstone can also hit a structure at low velocity (e.g. during parking, taxi and terminal flight phases) causing barely visible damages. In this research work, a new approach is proposed for the investigation of low energy ice impacts. A drop tower apparatus was modified to accommodate specifically developed ice impactors. High-speed Digital Image Correlation was employed to measure the targets out-of-plane deformations and in-plane strain fields. Different ice impactors geometries, target materials and energy levels were considered. From results, it has been demonstrated that this methodology is able to capture the effect of ice impacting at low speed on targets
Foam Application on Railway Transports
No full textEvery year lots of accidents happened along streets involving cars, motorcyclists, public railway transports and human beings, especially pedestrian of any ages. Studying this kind of impact dynamic is extremely important to ensure safety in everyday life, reducing risks to people and limiting heavy consequence for them. In this work, a composite structure made of different foam was applied to the frontal body of a public transport vehicles running on rails (commonly called tram) in order to reduce risks for pedestrian impacting against it. Experimental tests were performed to study different sacrificial material configurations and numerical simulations were used to define the foam material model throughout an optimization process. Some final considerations are here shown
Study of Bird Impact Against a Tilted Target Structure
No full textThe impact of birds against aircrafts and helicopters is not a so remote eventuality, especially during take-off and landing phase and it is one of the biggest economic damage to companies today. To evaluate the effects of this kind of events many experimental tests and numerical models of the phenomenon have been carried out in the last years. The aim of this research work is to numerically analyse the bird impact against oblique target structures. Two case studies are here shown: the impact against a simple plate and against a more complex structure. Different bird models, impact angles and impact velocities were considered. Some considerations on results are finally presented as prescriptions for future works
Experimental and Numerical Assessment of the Crash Performance of a CFRP Racing Car Nosecone
No full textSoft Body Impact Against Aeronautical Structures
Get PDFStatistics show that impacts of soft body against aeronautical structure are not so rare events. The damage caused by the impact of hailstones or of birds can sometimes be so heavy to compromise the service life of the vehicle. Companies, research centers and universities are interested in the evaluation of the effects of this kind of events and lots of researching works have been recently developed in this field. In this paper, an overview of the last studies performed at the Laboratory for the Safety in Transports (LaST – Crash Lab.) of Politecnico of Milan are presented throughout experimental tests and numerical finite element models. The validity of the correlation results method to prevent possible heavy consequence caused by these events is shown
Assessment of Fracture Mechanics of Metallic Materials for Aerospace Field
No full textIn aerospace applications, products must comply with the highest standards and quality or performance under extreme conditions. The modern aerospace industry demands the most innovative and high quality metals able to maintain the integrity of the structure and to be resistant to corrosion or high temperature oxidation. Because of the high costs of tests, it is essential to limit their number preferring sophisticated numerical models necessary to predict the behavior of the real structure. In this research work, experimental tests and numerical models on High strength steel grades have been performed to increase the reliability of virtual testing used for the development of new industrial solutions. High strength steels increase the cost-effectiveness of the designed solutions providing more competitiveness when compared to other materials. In fact, High strength steels have tight controlled mechanical properties that enable better energy absorption in the event of a crash and guarantee high performance of the product, with a significant reduction of structure weight. A campaign of experimental tests on specimens with different shapes has been carried out, focused on the determination of the needed parameters to define the triaxiality stress factor. A numerical calibration and regularization process has been required in order to provide a more precise hardening curve after necking, investigating an engineering method to eliminate mesh size effect in solid elements
FE-to-SPH Approach Applied to the Analysis of Soft Body Impact: Bird Strike and Hail Impact
Get PDFThe soft body impact might be considered as one of the greatest problems for aeronautical structure. To numerically investigate this kind of events both Lagrangian and Smoothed Particles Hydrodynamics (SPH) approaches are generally adopted, but both of them suffer some problems concerning distortion, in Lagrangian elements, and the treatment of essential boundary condition, for SPH approach. The possibility to apply a finite element to SPH transition (FEtoSPH) is here considered. A numerical investigation on hail impact and bird strike phenomenon was performed at the Laboratory for the Safety in Transports (LaST) of Politecnico di Milano. Each of these three approaches was considered for different mesh definitions and impact velocities. A case study concerning the hail impact against an engine inlet was investigated to evaluate the effect of the use of this innovative approach on possible real impact events
Threaded inserts pull-through behaviour in carbon-epoxy thick laminates
Get PDFAim of this work, is the experimental assessment of the mechanical behaviour of threaded inserts, commonly used in racing cars. Tests have been performed, both in tension and in torsion, as a function of the installation technique in composite materials. Different type of inserts have been considered to evaluate the influence of materials on the strength of the inserts. From results has been proved that the installation technique influences very little the pull through strength, whilst it mostly affects the torsion strength. In particular, the failure torque is heavily influenced whether a bonding adhesive is used or not during the insert installation. Numerical models have also been made to simulate the inserts pull-through, using the commercial code LS-Dyna®, an explicit finite element code especially used in crashworthy problems. Due to the thick composite structure, a thick shell numerical laminate has been modeled. The plies have been tied each other with a failure contact model. Numerical results show a good correlation with experimental data both in force-displacement curve and in material local damage
- …
