Abstract: A detailed interpretation of load distribution in composite single-lap bolted joints is presented based on theoretical, experimental and numerical investigations. Modified instrumented bolts (MIBs) were used to measure bolt shear loads consisting of the bolt bearing load and the friction force between the laminate and nut. The bolt-load carrying mechanism in single-bolt joints and the load transfer mechanism in multi-bolt joints with various tightening torques and bolt-hole clearances were revealed based on theoretical and numerical analyses and validated against experimental results. The load transferred by each bolt in a multi-bolt joint was determined with greater fidelity, and the load distributions obtained using a three-dimensional finite element (FE) model and a spring-based method were compared. The load distributions obtained from the established 3D FE model were found to be identical to those obtained using the spring-based method; the bolt-hole clearances significantly impacted the load distributions, but the effects of the bolt tightening torques on the load distributions could be ignored.

Abstract: A multiscale analysis strategy with physical modified-micromechanics of failure (MMF3) criterion was proposed to analyze the failure behaviors of carbon fiber reinforced plastic (CFRP) laminates. The quantitative relationship between the macro- and micro- stresses was determined considering two typical fiber distributions. Thermal residual stress was taken into account in the stress transformation. The failures were defined and the properties of damaged elements were degraded at the constituent level. The back-calculation method based on the iteration algorithm was proposed to determine the micro strength with macro mechanical tests. A series of off-axis loading tests were conducted to verify the established multiscale models. The predicted strength was also compared with the results using micromechanics of failure (MMF) criterion to present accuracy improvements. Thermal residual stress was found to affect the strength by contributing to the matrix damage status. Meanwhile, sensitivity analysis was provided for the matrix-dominant micro strength to investigate its physical meaning. Results suggest that the micro tensile and compressive strength of the matrix influenced the off-axis tensile and compressive strengths respectively, with relative large off-axis angles, while the micro shear strength of the matrix dominated when the off-axis angles were relative small.

Abstract: Besides the influence of aircraft noise and emissions on the local air quality, the impact of greenhouse gas emissions on the global climate achieves more and more attention recently. The engine is...

Abstract: This paper discusses the effects of different space vector modulation (SVM) hexagon partition on common mode voltage suppression at high modulation index and presents an improved capacitor voltage balance strategy for multilevel matrix converter. Matrix converter is a compact designed converter which allows direct AC–AC power transfer without an intermediate DC link. Multilevel matrix converters, which utilises a multilevel structure on a traditional matrix converter, expand these characters to high-voltage and high-power situations. This paper is concerned with SVM of three-level matrix converter and concentrates on the comparison between different hexagon partitions; the improved balancing strategy is employed to improve the performance of flying capacitor voltage control. Simulation from Matlab/Simulink and results from a small-scale experimental prototype are presented to validate the theoretical results.

Abstract: In avionics domain, there have been many efforts in recent years to build a MBSE methodology with tooling support. The main purpose is often to improve quality and efficiency of system definition, architecture and integration. Sometimes there is also an additional objective to ease system verification and validation. This paper introduces an additional challenge with the support of an agile development cycle to ease impact analysis and incorporation of late and changing requirements at different times. It presents key principles and requirements of an agile MBSE approach and presents associated modeling activities with illustration on an avionics case study.

Abstract: Compared with conventional monolithic material, an aluminum-polymer sandwich sheet possesses advantageous strength/stiffness versus weight ratio and has received increasing attention in aeronautical, automotive, marine, and civil engineering industries. In the present study, limiting draw ratio (LDR) and other cylindrical cup-drawing characteristics of aluminum-polymer sandwich sheets were investigated by experiments and numerical simulations. Deformation behaviors of skin layer and core polymer layer were analyzed respectively. It was demonstrated that the deformation mode of exterior sheet tends to biaxial tension state and that of interior sheet tend to compression state. The LDR of aluminum-polyethylene sandwich sheet was well predicted, and influences of core layer thickness and mechanical properties of skin sheet on the LDR of sandwich sheet were analyzed. Research results show that the drawability of the aluminum-polymer sandwich sheet becomes poor with increasing the thickness of the polymeric core and the strength of core polymer. The LDR of the sandwich sheet mainly depends on the drawability of the skin sheet.

Abstract: This study was a phase I double-blind, randomized, placebo-controlled trial to evaluate the safety and immunogenicity of a Serbian-produced seasonal trivalent split, inactivated influenza vaccine in healthy adults. The vaccine was manufactured in eggs by the Torlak Institute of Virology, Vaccines and Sera, Belgrade, Serbia and contained A/H1N1, A/H3N2 and B viruses. The clinical trial took place at the Clinical Center of Serbia in Belgrade. Sixty healthy volunteers, aged 18-45 years, were enrolled in the trial. On the day of immunization, volunteers were randomly assigned to receive either a single dose of the trivalent seasonal influenza vaccine (15 μg of hemagglutinin per strain) or placebo (phosphate-buffered saline). Subjects were monitored for adverse events through a clinical history and physical examination, and blood was taken for testing at screening and on day 8 to assess vaccine safety. Serum samples obtained before and 21 days after immunization were tested for influenza antibody titers using hemagglutination-inhibition (HAI) and microneutralization (MN) tests. No serious adverse events were reported. Pain and tenderness at the injection site were the most commonly reported symptoms in both vaccine and placebo groups. Overall, serum HAI responses of fourfold or greater magnitude were observed to H1, H3, and B antigen in 80%, 75%, and 70% of subjects, respectively. Seroprotection rates as measured by HAI were also high (100%, 100% and 86.67%, respectively, for H1, H3 and B). Thus, Torlak's seasonal trivalent influenza vaccine was not associated with adverse events, was well-tolerated and immunogenic. It should be further evaluated in clinical trials to provide sufficient safety and immunogenicity data for licensing in Serbia.

Abstract: System safety analysis, as a powerful technology to verify and ensure the safety of system, has been applied throughout the entire process of system design and operation. The Traffic Collision Avoidance System (TCAS) significantly ensures flight safety. Understanding the factors which can influence the decision of TCAS, is critical to improve the safety design of next generation airborne avionic system. In this paper, the control process of TCAS is constructed via Systems Theoretic Accident Model and Process (STAMP) theory, and the unsafe causal factors are analyzed based on a normative analysis process. A standard scenario of crossing flight level is simulated to specify the potential hazards of current TCAS. Then, a safety verification model is constructed to verify the validity of the hazard-analysis system through Simulink.

Abstract: A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding (VARTM). Two modified preforms were prepared under 0.1 and 0.6 MPa in an autoclave and then were used to fabricate the laminates via VARTM. Permeability and thickness distribution of the laminates were obtained by using a special device. Moreover, the tensile and compressive strengths of the obtained laminates were studied and compared with the unmodified ones. Results show that the tackified laminates present a maximum and minimum thickness under 0.1 and 0.6 MPa, respectively. The thicknesses and in-plane permeability of the tackified laminates, with better thickness uniformity, are significantly decreased compared with that of the unmodified cases, while the tensile and compressive strengths of the tackified laminates are improved obviously. Results show that the mechanical property of the tackified laminates prepared by hotpressing at 0.1 MPa is better than that processed at 0.6 MPa.

Abstract: More electric aircraft (MEA) is a developing trend in modern aerospace engineering aiming for a reduction of the aircraft weight, operation cost and environmental impact through putting more emphasis on the utilisation of electrical power. It has many advantages, but also increases the complexity of the aircraft. Therefore, the requirements of prognostic and health management for MEA are needed. The method that using sequential importance re-sampling (SIR) particle filtering state estimation and smoothed residual to diagnose fault for typical components is discussed. The simulation results show that this method can locate faults accurately and quickly.

Abstract: This study presents a kind of feedback between smooth and discontinuous feedback control method for electromechanical servo system. First, the construction and working principle of electromechanical servo systems was introduced on the basis of their structure characteristic. Then with the building of the electromechanical servo system structure, some research on the control strategy of permanent-magnet synchronous motors has been developed control in the light of their control characteristics. Combined with the theory of the field oriented control and the structure features and performance metrics of the mechanical and electrical servo system, a simulation model for the mechanical and electrical servo system was built. The simulation result shows the reliability of this method.

Abstract: By analysing the structure and working principle of hybrid actuation system (HAS) which consists of a servo-hydraulic actuator (SHA) and an electro-hydrostatic actuator (EHA), the overall mathematical model with dissimilar redundancy conforms is established, which considers various influencing factors, such as air load and attachment stiffness. Furthermore, the mechanism of dynamic force fighting is expounded. In addition, a new control strategy which uses the trajectory generator and weight coefficient theory is proposed to restrain the force fighting. The modelling and simulation analysis between the new control strategy and a conventional proportional–integral–derivative control strategy is carried out as well. Based on the above researches, quantitative analysis is carried out on the procedure of operating mode switching, which is from active/active mode to active/passive mode. The results indicate that the position/velocity trade-off control strategy has a good control performance, and effectively restrains the static force fighting as well as dynamic force fighting. Besides that, it can also shorten the system response time. The HAS can still meet the actuating requirements after the operating mode switches to active/passive mode. The actuator in passive state generates a certain static error by the reason of tracking the position of the control surface.

Abstract: High-voltage direct current (HVDC) electric power system (EPS) is a promising architecture for more electric aircraft (MEA). With more electric power used, a higher voltage is necessary to make aircrafts more efficient and less weighted. However, there are no standards can be followed to evaluate the power quality of HVDC EPS, especially for 540 VDC system. In this study, a potential HVDC EPS is proposed and power quality is studied by simulation. Behavioural models of the system are established in detail from source to load. Three kinds of typical loads of MEA are defined and their impacts on power quality are analysed including resistances, power electronic converters, and motors. Some suggestions are provided for design and integration of the EPS for MEA.

Abstract: The rapid development of the additive manufacturing technology (3D printing) has brought much greater optimization space for the structural innovation design. The combination of topology optimization design and additive manufacturing technology can further reduce the structural weight, thus improving the bearing efficiency of the structure. The main purpose of this paper is to explore the feasibility of reducing weight for civil aircraft structure by means of optimization design. The structural topology optimization design of typical hinge structure for civil aircraft is carried out. Compared with the traditional structure, the topology optimization structure achieves a weight reduction of 25% and a structural stiffness increasing of 75.7% under the condition that the strength requirement is satisfied, which reaches the expected goals.

Abstract: An Exhaled Breath Temperature (EBT) monitor for the measurement of portions of exhaled respiratory gas temperature during a single exhalation, the monitor comprising: An inlet channel for receiving a stream of exhaled respiratory gas, a plurality of measurement chambers, temperature sensors located within more than one measurement chamber adapted for measuring the temperature of exhaled respiratory gas, a plurality of valves intermediate the air channel and each measurement chamber, configured to selectively pass portions of the gas stream in to each chamber and a control unit, configured to operate the valves and record the measurements of the temperature sensor

Abstract: The matrix converter (MC) is a kind of universal power transformation topology. It merits in unit power factor operation; no intermediate storage link, bidirectional power conversion etc. Compared to traditional MC, three-level MC can achieve multilevel high-voltage output, high-power conversion, improved power quality etc. An interesting space vector modulation (SVM) of the MCs has been reported for the common mode voltage (CMV) suppression recently. However, the CMV suppression method on three-level MCs is seldom mentioned due to its complicated SVM. The CMV suppression of a capacitor clamped three-level MC is introduced in this paper. Aiming at reduce the CMV on three-level MC, the contribution of this article is determined an improved SVM with minimised CMV on the proposed three-level MC, this SVM chooses the different modulation strategy based on the different modulation index.

Abstract: Isolation distance is an important consideration in aircraft wiring for coupling effect. according to electrical wiring interconnect system (EWIS) isolation requirements specified in SAE 50881D and airworthiness regulations CCAR 25.1707, explicit isolation distances are not specified. Aircraft wiring is complex or diverse. In order to evaluate coupling effects between the main feeder and signal wire, the three-phase-seven-wire main feeder with 230 VAC, 250 kVA was chosen as the simulation object. The impedance model of three-phase feeder is given with which the coupling effects can be analysed in theory at first. The coupling voltage amplitude is the main evaluation index. In the simulation process, the following cases are chosen: different distances between signal wire and main feeder; signal wire lies in the different phase of the main feeder; isolation distance analysis with types of loads; there exits arc faults on main feeder. Based on the analysis of the simulation results, proposed methods to reduce the coupling effects between wires are given. Through the work in this study, it has some guiding significance for wire or cable laying.

Abstract: PIO (Pilot-Induced-Oscillation) is due to the mutual influence between abnormal aircraft response and pilot’s dynamic characteristic which causes the phenomenon that aircraft-pilot closed loop is instable. Therefore, airworthiness regulations (FAA25 CS25 CCAR25) 143 (a) (b) have given specific requirements for these. At the preliminary design stage of control law design, PIO tendency shall be analyzed by engineering prediction methods which will confirm whether the design of the FBW control law is suitable. In the detailed design stage, PIO tendency will be analyzed by means of simulator test with pilot in loop. During verification of worthiness compliance, evaluation criteria of PIO shall be determined according to recommended methods of AC25-7C and verify airworthiness compliance through MOC6 and MOC8. Finally, the data of flight test and/or simulator test with pilot comments show that there is no PIO tendency which meets the requirements of airworthiness regulations.

Abstract: In the initial stage of design, capturing user's purposes/needs and transforming them into functions is crucial for wider range selection of design solutions. However, few researchers have distinguished the concepts of purpose and function. The purpose to function transition is still largely an experience‐based process by designers in early design stage and there is still lack of formal approaches or any standard in this field. Therefore, this paper firstly provides a philosophical understanding of purpose and function, tries to clarify their differences, and then proposes a scenario‐based systematic approach to facilitate their transition. In this approach, the transition is conceptualized as a stepwise process and scenarios are integrated in such process for elaborating the initial needs. A case study will also be discussed to demonstrate the proposed approach.

Abstract: The application of touch screen in the cockpit of civil aircraft is a trend for the development of wide-body aircraft. So this paper analyses those elements that should be considered when the touch screen is introduced into the civil aircraft cockpit for application. The paper firstly combs the requirements of the current aerospace standard or specifications for touch screen design, then points out the design requirements of the characteristics of touch screen itself, the human-machine interface, system integration, and environment factors which should be considered when the touch screen is applied to the cockpit. Finally, the ergonomics requirements caused by the touch screen in cockpit application are also analysed based on the human factor handbook, human factor reports and the characteristics of the touch screen. The paper aims to provide a design reference for the application of the touch screen in civil aircraft cockpit.