A Preliminary Assessment of an FBG-Based Hard Landing Monitoring System

In aeronautics, hard landing is a critical condition as the aircraft approaches the runway with a vertical velocity that exceeds 2 m/s. Beyond that level, the energy that should be then absorbed by the whole structure could cause severe damage to the landing gear and the whole structural system. This document reports on the set-up, execution and results of a preparatory test campaign performed on a small landing gear (LG) demonstrator instrumented with a fibre-optic sensor system. In detail, a leaf spring landing gear was released from a drop tower to detect information about the strain state and the related acceleration history of some specific components during the impact. The objective of the present research is the development of a method for assessing whether hard landing is experienced, and to what extent. Deformation measurements through an integrated Fibre-Bragg grating (FBG) network allowed retrieving impact velocity by a devoted, original algorithm. The proposed preliminary methodology is the base for assessing a more complex procedure to correlate structural response to the energy entering the structure during the touchdown event.

Crashworthiness Study of Composite Fuselage Section

Crashworthiness is one of the requirements for design of aircraft to ensure the safety of passengers on aircraft. With increasing applications of advanced composite in aircraft structures, study on the crashworthiness of composite fuselage is desirable and important. For this purpose, this paper investigates the influence of composites on crashworthiness of fuselage section. Firstly, model of fuselage section of aircraft is established. Skin, frame, stringer and stiffener are made of the composite T800/QY8911 or GLARE. Then, the crash responses subjected to vertical impact velocity of 9.14m/s are analyzed. The acceleration history is recorded for assessment of the crashworthiness. In addition, the deformation process and failure mode of composite fuselage section are analyzed. Results indicate that the frame made of brittle composite may fracture in the crash process, which leads to serious damage to the fuselage. While the frame with good toughness can maintain the integrity of fuselage, thereby protecting passengers.

Identification of the Dynamic Load Supplied on Top Pier of High Speed Railway Bridge

With the development of railway transportation, the traffic load increased continuously and it had the adverse effect on the system of pier-foundation. The quantitative analysis of the load supplied on the top pier is necessary for analyzing the dynamic response of pier-foundation system. Based on the theory of vibration inverse analysis and finite element method, the paper identified the dynamical load supplied on the top pier in vertical and the transverse direction. Combined with the vibration and acceleration history measured by the field test in Xiaolinhe Bridge, the vertical and transverse direction vibration-load history curves were calculated when the train speeds were 153 km/h and 206 km/h respectively. The results indicated that the amplitude of dynamic load increased with the higher speed of train.

The Influences of Complex Impact Conditions on Aircraft Fuselage Crashworthiness

In this paper, a certain B737 aircraft fuselage section was used to research the influence of different impact conditions on fuselage dynamic characteristics. A finite element model of fuselage was built up from FS380 to FS500. The impact responses of fuselage subjected to 9.133m/s vertical velocity were analyzed under the conditions of 0° roll angle, 10° left roll angle and combination acceleration. The differences of transformation and acceleration history curves under different conditions were compared. The research results show that the performances of 10° left roll angle will change fuselage transformation and acceleration of seats location, the appears of combination acceleration will increase transformation of floor and decrease acceleration at the seats location. The crashworthiness of aircraft structure can be effectively improved by selecting the appropriate landing way.

A MONUMENT OF HISTORICAL HERITAGE ‐ VILNIUS ARCHCATHEDRAL BELFRY: THE DYNAMIC INVESTIGATION/VILNIAUS ISTORINIO PAVELDO PAMINKLO − ARKIKATEDROS VARPINĖS − DINAMINIAI TYRIMAI

The dynamic investigation of a monument of historical heritage ‐ Vilnius Archcathedral Belfry ‐ is investigated. In 2002 six new bells were installed in Vilnius Archcathedral Belfry according to a modern location scheme and their ringing order was changed. Evidently, they caused different dynamic loads which were not completely controlled and their effect on historical buildings of the Old Town of Vilnius could hardly be predictable. The paper presents the results of dynamic investigation of the Archcathedral Belfry, subject to the influence of the bell system operation. The dynamic impact was evaluated by measuring the acceleration history under the conditions, when different combinations of bells were used. A contribution of the dynamic effects was assessed in terms of response spectra. The obtained results have been thoroughly analysed and the appropriate findings and conclusions provided. Santrauka Nagrinėjamas Vilniaus arkikatedros varpinės eksperimentinis tyrimas nuo dinaminių apkrovų, sukeltų veikiant varpams. Preliminaraus tyrimo metu varpinės sienų konstrukcijose buvo pastebėta irimo požymių, daugybinių plyšių. Tai sukėlė ilgalaikis statinio eksploatavimas. Tačiau 2002 m. pagal naują schemą varpinėje pakabinus 6 naujus varpus labai pasikeitė jų poveikis statinio konstrukcijoms. Skambant varpams sukeliamos dinaminės apkrovos varpinės konstrukcijoms iki šiol dar nebuvo tyrinėtos. Atliktas dinaminis eksperimentas, kurio metu ištirti varpinės charakteringųjų vietų masių pagreičiai nuo įvairiais režimais skambančių varpų: varpai skamba vienas paskui kitą iš eilės; skamba visi varpai kartu; keturi mažieji varpai skamba kartu; skamba tik du didieji varpai. Dinaminis poveikis statinio konstrukcijoms įvertinamas pagreičių atsako spektrais. Gauti rezultatai kruopščiai apdoroti ir pateiktos išvados.