Key Engineering Materials Vol. 518

Abstract: Periodic rail and guide wear evaluation is essential for their reliability and safety. By regular measurement it is possible to determine whether certain rail or guide fragments need urgent replacement reducing the risk of accidents. In the paper at first we present the measurement system, which is intended to operate in small rail systems such as trams, light rail, narrow gauge rail, mine rail. It can be adopted to operate in two modes: manual pulled along the rail or guide or automatic attached to a measurement car. The measuring system is flexible enabling the measurement of different features of rail or guide geometry depending on the needs. By simplifying the design, the system can be operated by an unqualified personnel, however final wear evaluation has to be done by a qualified engineer. Finally we present the exemplary results of measurements performed on a selected rail section and the full data processing path. The method of relative calibration and synchronizing data from several measurement modules is also reported.

Abstract: In the paper the new type of mobile sensor based on optical coherence tomography is presented. For increasing the measurement range the special dynamic focusing system which moves imaging plane during axial scanning process is used. Therefore developed system allows focusing on measured layer. Additionally, for image analysis the special type of CMOS matrix (called smart-pixel camera), synchronized with a reference mirror transducer, is applied. Due to hardware realization of a fringe contrast analysis simultaneously in each pixel with high frequency, the time of measurement decreases significantly. These advantages together with a compact design allow the sensor to be used as the mobile device for measurements of surface topography, thickness of surface layers and subsurface defects detection in laboratory, workshop and out-door conditions. Calibration of the designed sensor and its application to the technological measurements of the sticker label layers are presented and discussed.

Abstract: A railway bridge has been the object of investigation since mid 2007 as a response to increasing interest in structural health monitoring (SHM) from Polish Railways. It is a typical 40 m long, steel truss structure spanning a channel in Nieporet near Warsaw. There is over 1500 similar bridges in the railway network in Poland. The integrated system consists of two components weigh in motion (WIM) part for identification of train load and SHM part for assessing the state of the bridge. Two aspects of wireless transmission are considered short range (in the vicinity of the bridge, 2.4GHz) and far range (from the bridge to the data analysis center, GSM). The system is designed to be energetically self-sufficient, batteries are recharged by solar panels. Both the subsystems use piezoelectric strain sensors. Numerical model of the bridge corresponds well to the experimental data and provides a good starting point for considering different scenarios of simulated damage in the structure.

Abstract: The phenomenon of vibration of buildings and other structures induced by different sources of vibrations is well known. Some of these sources are vibrohammers used to press in sheet piling, pile drivers with hydraulic hammer to drive in reinforced concrete pre-cast piles and vibroflots suspended to mobile cranes which are used to strengthen subsoil by vibroflotation technology.

Abstract: In this paper the results of modal analysis of a four storey building are presented. To excite the investigated structure, impact excitation was applied in two different points located on pillars supporting the building. In order to extract dynamic parameters of the structure, experimental modal analysis was applied. The parameters of vibration resulting from this excitation were measured by a scanning laser vibrometer; additionally piezoelectric accelerometers were utilized. To compare the results and monitor the state of the building a finite element model (FE) was built. It seems that a reliable identification of the state of building structures using a laser scanning vibrometer is feasible and relevant from a practical point of view. To monitor local changes additional piezoelectric accelerometers should be used. Moreover, it is applicable for damage detection to refine theoretical and experimental modal models for each natural frequency and to calculate the stress distribution for each refined model. Consequently, the sum of these particular stresses conveys information for building engineers and enables comparison with their in situ observations. The analysed building is situated on the terrain of underground coal mine exploitation so the aim of the research is not only to observe the state of the building but also to analyse possible changes during the process of excavation and after it was completed.

Abstract: In the paper there are discussed the most interesting methods dedicated to frescos structural health monitoring. In the further part two methods and devices for fresco delamination detection developed by authors are presented. In order to enable future automation of developed measurement techniques and autonomic detection of fresco structural defects, the novel measures quantifying the probability of critical condition appearance (the lack of adhesive force) were introduced. Finally, the results of measurements of dynamic characteristics of healthy and delaminated structures are presented.

Abstract: Accurate knowledge regarding the ongoing condition of an aircraft’s structural condition together with future life predictions enable optimal use of material, hence reducing mass, cost and environmental effects. Previous work by the authors has demonstrated the potential for using energy harvested from vibrating aircraft panels to power a self contained health monitoring system based on the use of wireless sensor nodes for an aircraft structure. However the system proposed was far from optimal. Research is being undertaken to investigate the various factors affecting the power output of such a system, including the design of the harvesters used (length, width, number of layers), their positioning and their orientation. The work presented in this paper enables the determination of the optimised positions for a series of harvesters on a representative aircraft panel, based on the use of shape functions for the various modes of vibration over the expected frequency range, to derive a function related to power output which is then optimised. A series of recommendations are made.

Abstract: The paper presents structural health monitoring (SHM) system, dedicated to marine structures. The considered system is based on the fibre optic technique with Fibre Bragg Grating (FBG) sensors. The aim of this research is recognition of possible practical applications of the fibre optic techniques in selected elements of marine structures. SHM and damage detection techniques have a great importance (economical, human safety and environment protection) in the wide range of marine structures, especially for ships and offshore platforms. In the paper monitoring system of the Horyzont II and Dar Młodzieży ships and offshore oil platform is presented. Practical implementation of safety system based on optical sensors meets several difficulties. There has been installed the FBG system and its measurement results have been compared with classical techniques, e.g. piezoelectric accelerometers. The investigations have been performed for undamaged and damaged structure. Different types of failures have been modelled and tested. Damage detection ability has been specifying on the base of static and dynamic structural characteristics.

Abstract: The improvement of traveller comfort and safety, in parallel to an increase of passenger train speed, is a reason to implement monitoring systems. These systems are more often used to monitor components of railway infrastructure and vehicles. Studies in this area must be preceded by identification and a complex analysis of the railway vehicle - track system. This allows us to recognise the dynamic properties of the system and then select the appropriate place to install sensors on board the vehicle. This paper presents the results of model studies and a prototype monitoring system which is installed on a passenger electric traction unit. This system is aimed, inter alia, at monitoring the state of train suspension and the detection of some particular track geometric irregularities.

Abstract: The active safety issue of rail vehicles is important for providing regular transportation services and minimizing the risk of accidents. One of the solutions to the problem of assuring high level of active safety is applying the condition monitoring of suspension system. Suspension, as a part of running gear, is crucial for providing proper running behavior stability. The increasing demands on improving safety of railway transport has led to development of prototype of rail vehicles' suspension monitoring system at Monitoring of Technical State of Construction and Evaluation of its Lifespan Project (MONIT). The idea of the system is qualitative assessment of suspension condition based on acceleration signals measured on bogie frames, wheels and body. The monitoring system prototype has been tested on passenger and freight cars in two states of suspension condition: nominal and damaged. Experimental tests have been performed on experimental track near Zmigrod in Poland. This paper presents analysis of the results obtained from the tests of the rail vehicles' suspension monitoring system prototype.