Search

The main topic of the paper is the definition of the optimal design of an aeronautical seat, in terms of maximization of occupants’ safety level and of prediction capability of a FE/MB coupled numerical procedure, based on TNO Madymo® MB software and LSTC LS-Dyna® FE software. The proposed numerical procedure can support the physical prototype development and the experimental phase of the current design approach by using design of experiments methods. In particular, the paper deals with the simulation of an experimental seat sled test against the aircraft front fuselage bulkhead (Figure 1). The FE model has been analysed by using LSTC-LsDyna® code; the multibody model has been analysed by considering TNO-Madymo code.Parameters evaluated during the tests are the acceleration of the head, with the relative calculation of HIC, and the loads transmitted to the lower limbs of the dummy. To approach the development phase, it may result very effective to take into account previous experiences, before entering the cumbersome development of the detailed finite element model. The implementation of simplified multibody (MB) structural models, together with design of experiment (DOE) may simplify the definition of the crashworthy scenario for a new seat. Though the adoption of an integrated MB and DOE approach will not eliminate the need for a detailed FE impact model and its experimental validation, it will surely help in identifying the most sensitive parameters to be complying with the applicable regulation (from the numerical simulation point of view) and in reducing the number of tests needed to reach the certification requirements. The paper presents the initial attempt in applying such development strategy, highlighting the importance of previous experience and how to take advantage from it through dedicated self- developed computer tools.

Over the years, air traffic has been constantly increasing: in 2013, over 3 billion passengers were carried by the world’s airlines; according to a recent Airbus’ global market forecast, air traffic will double in the next 15 years, showing 4.7% annual growth between 2013 and 2034 (Airbus, 2016). Despite the growing demand, airlines are still one of the lowest-scoring industries in the American Customer Satisfaction Index (ACSI) and seat comfort is the most unsatisfying aspect of flying (ACSI, 2016). As a matter of fact, improving seat comfort can provide an opportunity to gain competitive edge in aircraft industry. This paper focuses on the assessment of aircraft seating (dis)comfort via a statistical-experimental approach. Seating (dis)comfort data (both objective and subjective) were collected during an experiment involving 18 volunteers (9 males and 9 females) who tested two aircraft seats in upright and upright/reclined configuration, respectively. Data were collected under controlled experimental conditions. In order to minimize experimental uncertainty due to well-known noise factors (i.e. patterns of discomfort during the work week and during the workday, evalua-tion sequence, inter-individual variability), experimental trials were performed according to a crossover de-sign. The whole experiment consisted of 54 experimental sessions; the duration of each session was approxi-mately 40 minutes. In each test run, the participant performed a fixed task so as to minimize differences in postures and control the effect of body posture upon pressure distribution at seat-interface. Statistical data analysis aimed at: 1) investigating gender–based differences in seating (dis)comfort; 2) identifying critical discomfort body areas; 3) analyzing time-variation in seating (dis)comfort. The experimental results are in line with the acknowledged hypotheses that males and females are exposed to different loading patterns and experience different discomfort pathways, due to fundamental biomechanical differences in their sitting pos-ture and anthropometric peculiarities. Moreover, results pinpoint that perceived discomfort increases signifi-cantly over time in several body areas.

OBJECTIVE: Synovial B cells play a critical role in rheumatoid arthritis (RA) being involved in autoantibody synthesis T cell activation and cytokine production. CXCL13 is a B cell chemoattractant that is instrumental in synovial B cell organization; the regulatory determinants of CXCL13 in inflammation are poorly characterized. This study was undertaken to investigate the functional involvement of synovial T cells in the ectopic expression of CXCL13 in RA. METHODS: CXCL13 production and regulation were addressed using immunohistochemistry in situ hybridization quantitative polymerase chain reaction multicolor flow cytometry and enzyme linked immunosorbent assay by in situ ex vivo analysis and in vitro functional assays with rheumatoid synovial tissue and primary cells. RESULTS: CXCL13 messenger RNA and protein expression and spontaneous CXCL13 secretion were detected in RA synovial fluid T cells but were not detected (or were detected only occasionally) in peripheral blood T cells. Analysis of tissue expression confirmed cytoplasm localization of CXCL13 in T lymphocytes infiltrating B cell follicles and small perivascular aggregates. Multicolor characterizations in synovial fluid demonstrated CXCL13 expression in antigen experienced T helper cells frequently characterized by terminal differentiation and the lack of the follicular helper T cell markers CXCR5 and BCL6 protein. In vitro functional assays revealed the enhancing effect of T cell receptor CD28 engagement on CXCL13 production and secretion in primary cells. CONCLUSION: Our findings define a new functional property of synovial T cells demonstrating their active involvement in the local production of B cell chemoattractants and support a direct contribution of the adaptive immune system and antigen dependent signals in the mechanisms of B cell localization in RA.

BACKGROUND: Aircraft seating comfort has a significant impact on passenger on-board experience. Its assessment requires the adoption of well-designed strategies for data collection as well as appropriate data analysis methods in order to obtain accurate and reliable results. OBJECTIVES: This paper focuses on the assessment of aircraft seating comfort based on subjective comfort responses collected during laboratory experiments and taking into account seat features and passenger characteristics. METHODS: The subjective comfort evaluations have been analyzed using a model-based approach to investigate the relationship between overall seating comfort and specific seat/user characteristics. RESULTS: The results show that the overall seating comfort perception is significantly influenced by the thickness of the seat pan, the backrest position (upright or reclined), the age of the passenger and the passenger perception of being comfortably supported at the lumbar region. CONCLUSIONS: The adopted model-based approach allows the analysis of subjective seating comfort data taking into account their ordinal nature as well as the dependency between evaluations provided by the same subject.

This paper deals with the development of an established hybrid finite element multibody (FE-MB) model for the simulation of an experimental sled test of a single row of a double passenger seat placed in front of a fuselage bulkhead, by considering a single anthropomorphic Hybrid II 50th dummy arranged on one of the seat places. The numerical investigation has been carried out by focusing on the passenger passive safety. Specifically, the occupant injury assessment has been quantitatively monitored by means of the head injury criterion (HIC), which, based on the average value of the dummy head acceleration during a crash event, should not exceed, according to the standards, the value of 1000. Numerical results provided by the hybrid model have been compared with the experimental ones provided by the Geven S.p.A. company and with the results carried out by a full FE model. The hybrid model simulates with a good level of accuracy the experimental test and allows reducing significantly the computing time with respect to the full FE one.

This paper deals with the redesign of an aircraft passenger seat, placed at the first seat row, which was not compliant with Federal Aviation Regulations FAR 25.562 “Emergency landing dynamic conditions” regulation (due to a high value for the Head Injury Criterion (HIC)) and related guidelines. Starting from an accurate analysis of some results obtained via an experimental seat sled test, a numerical procedure was developed in order to improve the passenger safety with respect to head injury. Specifically, the proposed numerical procedure, using the advantages of a Finite Element (FE) model and a Design of Experiment (DoE) approach for simulation modeling, was aimed at identifying a new design solution to avoid the impact between the passenger’s head and the bulkhead. The redesign of the passenger seat was validated against an experimental test carried out at Geven S.p.A. Company by demonstrating, consequently, the compliance of the modified seat-belt system with the regulations.

This paper shows that an eco-friendly electrospinning process allows us to produce water resistant sound absorbers with reduced thickness and excellent sound-absorption properties in the low and medium frequency range (250&ndash, 1600 Hz) for which which human sensitivity is high and traditional materials struggle to match, that also pass the fire tests which are mandatory in many engineering areas. The structure and composition were studied through Scanning Electron Microscopy (SEM), Fourier Transform InfraRed (FTIR) Spectroscopy and ThermoGravimetric Analysis (TGA). The density, porosity and flow resistivity were measured. Preliminary investigation of the thermal conductivity through Differential Scanning Calorimetry (DSC) shows that they have perspectives also for thermal insulation. The experimental results indicate that the achievements are to be ascribed to the chemical nature of Polyvinylpyrrolidone (PVP). PVP is, in fact, a polymeric lactam with a side polar group that may be easily released by a thermooxidative process. The side polar groups allow for using ethanol for electrospinning than relying on a good dispersion of silica gel particles. The silica particles dimensionally stabilize the mats upon thermal treatments and confer water resistance while strongly contributing to the self-extinguishing property of the materials.

The certification of aircraft seats involves the investigation of the structural performance of their components under emergency landing conditions. . The paper reports the activities related to an experimental sled-test of a single row of two seats placed in front of a stiff fuselage bulkhead, by considering a single anthropomorphic dummy arranged on one of the seats. Tests have been developed at the facility equipped with a sled decelerator testing system compliant with certification requirements from FAR25 for TSO C127a regulations. Four different numerical models have been developed in order to simulate the experimental test: a full-FE modelby LSTC-LsDyna® code, a full-MB modeland a hybrid FE/MB developed using by TNO-Madymo® code and a Coupled FE/MB model. Numerical results achieved by these models have been compared with experimental ones, in order to assess their use for CBA (certification by analysis) purposeto be applied since the preliminary design phase of the seat.