1,720,990 research outputs found
DYNAMIC ANALYSIS OF VARIABLE THICKNESS SHELLS IN AEROSPACE APPLICATIONS VIA CUF ADAPTIVE FINITE ELEMENTS
No full textNew technologies and tools lead to design structures with increasingly more complex and disruptive geometries. In the field of thin structures, such as plates and shells, it is necessary to have numerical analysis tools that take into account these innovations and the use of advanced materials, such as composites, metamaterials or sandwich plates, or in general muti-layer materials. Within the Carrera’s Unified Formulation (CUF) framework, this article proposes a formulation based on adaptive finite elements that can study complex geometries, as variable thickness plates or with edges not orthogonal to the midsurface, while retaining the advantages of CUF theories for the study of multi-layer structures, both in terms of accuracy and reduced computational cost. The adaptability of these new elements concerns both the geometry and the possibility of using different structural models within the same element. Two case studies are presented in the following paper in order to demonstrate the new formulation: a plate with a topology optimized thickness and a semi-cylinder with a sinusoidal thickness
Vibroacoustic analysis of an innovative windowless cabin with metamaterial trim panels in regional turboprops
No full textThe purpose of this work is to study the possible noise reduction, in terms of sound pressure level, in the passenger cabin of a regional turboprop aircraft under multiple tonal and broadband noise components characterizing the noise generated by the engines during cruise flight conditions. In particular, we want to show the acoustic performances of innovative passive noise and vibration technologies, such as acoustic metamaterials applied to the trim panel of the cabin, in the low-frequency range, from 100 to 300 Hz. Moreover, the removal of windows from the passenger cabin is evaluated, in acoustic terms. Analyses are performed using a numerical tool, Actran, a finite element based software, and a numerical model of a regional aircraft fuselage. According to the results, metamaterials seem to have significant acoustic performances that lead to a reduction in noise and therefore an increase in passenger comfort
Vibroacoustic analysis of an innovative windowless cabin with metamaterial trim panels in regional turboprops
Full text linkThe purpose of this work is to study the possible noise reduction, in terms of sound pressure level, in the passenger cabin of a regional turboprop aircraft under multiple tonal and broadband noise components characterizing the noise generated by the engines during cruise flight conditions. In particular, we want to show the acoustic performances of innovative passive noise and vibration technologies, such as acoustic metamaterials applied to the trim panel of the cabin, in the low-frequency range, from 100 to 300 Hz. Moreover, the removal of windows from the passenger cabin is evaluated, in acoustic terms. Analyses are performed using a numerical tool, Actran, a finite element based software, and a numerical model of a regional aircraft fuselage. According to the results, metamaterials seem to have significant acoustic performances that lead to a reduction in noise and therefore an increase in passenger comfort
Transmission loss investigation of acoustic metamaterials via Adaptive Finite Elements
No full textThis work develops the integration of the Rayleigh’s integral method for calculating transmission loss into a new class of 2D finite elements, the adaptive finite elements. These
elements, recently developed within Carrera’s Unified Formulation framework, allow 2D
structures to be studied independently of expansion along the thickness, allowing for increased
computational efficiency over traditional solid elements. In this paper, they are used to calculate
the transmission loss on a panel of sandwich material. The aim is to demonstrate their efficiency
within a future core geometry optimisation process. These elements make studying different
thickness geometries accurate and fast, always based on the same 2D mesh. The article briefly
presents the formulation of the adaptive finite elements and Rayleigh’s integral method. Then,
the implementation is validated, and a series of geometries chosen as examples are studied by
calculating their transmission loss
VIBRO-ACOUSTIC ANALYSIS OF MULTI-LAYER CYLINDRICAL SHELL-CAVITY SYSTEMS VIA CUF FINITE ELEMENTS
No full textThe understanding of the vibro-acoustic behaviour of the aircraft structure is an important step in order to reduce the noise and vibration (N&V) of aircraft itself. A powerful tool is the well-known Finite Element Method (FEM), which allows to study the vibro-acoustic problem in the low frequency range. The FEM applied to vibro-acoustic has a limitation: to increase the frequency range, it is necessary to decrease the size of the elements. Therefore, in order to study complex model as an aircraft structure, the maximum frequency is often too low to have useful results. Moreover, the exploitation in the aeronautical field of multi-layer and sandwich materials with visco-elastic core, leads to the decrease of accuracy of classical shell elements and the need to often adopt solid elements, further increasing the size of the FEM problem. In this work we exploit a powerful notation for shells, the Carrera's unified formulation (CUF), to reduce the size of the vibro-acoustic problem. Curvilinear shell elements are applied to a cylindrical structure, similar to a fuselage, to study different materials, without increasing the size of the problem or losing accuracy in the solution. In this way it will be possible to reach higher frequency in the vibro-acoustic analysis, still describing the behaviour of sandwich and composite structures with the same accuracy of the solid elements
DESIGN AND DEVELOPMENT OF THE VISUAL AND AUDITORY LAYER FOR DIFFERENT CABIN/COCKPIT LAYOUT
No full textThis study, part of the Italian PRIN project TWINCRAFT - Digital Twin for Human-Centred Design of Future Aircraft, explores the enhancement of acoustic comfort for passengers and pilots through noise reduction in aircraft using advanced acoustic metamaterials. We assess comfort via a human-centered design approach, integrating noise auralization in eXtended Reality (XR) within the passenger cabin. This novel method utilizes augmented and virtual reality technologies alongside physical flight simulators to evaluate the efficacy of noise reduction strategies. The acoustic field, i.e., noise, calculated using accurate numerical analyses, is integrated into a digital mock-up of an aircraft through auralization. In this way, by combining the auditory layer and visual layer defined in previous works, it is possible to create an immersive experience for the user. The paper details the auralization process, from vibro-acoustic analysis of a section of an aircraft fuselage to the creation of an acoustic digital twin, thereby optimizing the aircraft design process
Vibro-acoustic analysis of composite plate-cavity systems via CUF finite elements
No full textThe vibro-acoustic problem of a plate made of an advanced material, like a composite one, backed to a fluid filled cavity represents an important issue for the automotive and the aerospace sector. In fact, the noise and the vibrations prediction and then mitigation leads to an essential increase in the structural safety of the system and in the passenger comfort. Over the last thirty years, a large amount of studies has been published about the vibratory characteristics of the structure-cavity systems and, thanks to these researches, the physical phenomena linked to the reduction of noise at low frequencies is well known. Although, there is a lack of accurate numerical models, valid for innovative materials, able to describe the complex kinematic behavior of new materials and so the structural response in the low frequency range. The aim of the this work is to develop reliable finite element models for vibro-acoustic analysis of structures made of advanced materials, coupled with fluid filled cavities. The structure is described according to the Carrera’s Unified Formulation (CUF), in order to enhance a wide class of powerful refined 2D plate theories with a unique formulation. The fluid cavity is described with a standard pressure-based finite element formulation of the acoustic field. The numerical results are presented for the case of a plate backed to a fluid filled cavity. Different plate layouts, in terms of materials, are considered, and also different fluids for the cavity, in order to consider both the weak and the strong coupling interaction. The results are compared with the solutions obtained by Actran®, a commercial software based on finite element method
The video endoscopy inguinal lymphadenectomy for vulvar cancer: A pilot study
Full text linkObjective This prospective pilot study aims to validate feasibility, efficacy and safeness of the innovative technique of video endoscopy inguinal lymphadenectomy (VEIL) and compare it to open inguinal lymphadenectomy (OIL) in the staging and treatment of vulvar cancer (VC). Material and methods All patients affected by VC suitable for bilateral inguinal-femoral lymphadenectomy were prospectively enrolled and submitted to VEIL on one side and OIL contralaterally, sparing the saphenous vein. The surgical and post-surgical data were collected. Univariate analysis included chi square analysis or Fisher's exact test, when appropriate for categorical variables, and the Student t test and Mann–Whitney test when appropriate for continuous variables. Results Between October 2014 and June 2015 fifteen patients were valuable for the study. Although nodal retrieval was comparable for both procedures, operative time was higher after VEIL. No intraoperative complications were observed in both techniques. Postoperative complications were observed in 3 and 2 cases for OIL and VEIL respectively. One patient needed reoperation after OIL for wound necrosis and infection. According to Campisi's stage, lymphedema resulted significantly to be lower after VEIL (p = 0.024). Conclusions Waiting for larger series and longer follow-up data, the VEIL seems to be feasible allowing a radical removal of inguinal lymph nodes as well as OIL with lower morbidity
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