Institute of Fundamental Technological Research

The so-called Adaptive Impact Absorption (AIA) is a research area of safety engineering devoted to problems of shock absorption in various unpredictable scenarios of collisions. It makes use of smart technologies (systems equipped with sensors, controllable dissipaters and specialised tools for signal processing). Examples of engineering applications for AIA systems are protective road barriers, automotive bumpers or adaptive landing gears. One of the most challenging problems for AIA systems is on-line identification of impact loads, which is crucial for introducing the optimum real-time strategy of adaptive impact absorption. This paper presents the concept of an impactometer and develops the methodology able to perform real-time impact load identification. Considered dynamic excitation is generated by a mass M1 impacting with initial velocity V0. An analytical formulation of the problem, supported with numerical simulations and experimental verifications is presented. Two identification algorithms based on measured response of the impacted structure are proposed and discussed. Finally, a concept of the AIA device utilizing the idea of impactometer is briefly presented.

Impact load identification, Adaptive Impact Absorption, adaptive structures, real-time systems, impact tests

A railway bridge has been the object of investigation in the context of structural health monitoring (SHM). The current work is focused on utilization of experimental data for refining a numerical model of the structure as well as on tests of dynamic excitations using a controlled hydraulic shaker and passing trains. The numerical model has been matched to experimental measurements using experimental modal analysis - classical and operational. The tailored SHM system for monitoring of the bridge consists of 15 piezoelectric strain sensors taking advantage of wireless communication for data transfer. Experimental responses of the bridge collected by the SHM system are confronted with the ones produced by the FE numerical model of the bridge. The long-term objective of the investigation is to elaborate a method for assessment of structural condition and prediction of remaining lifetime of the bridge.

Bridge Monitoring, Experimental Measurements, Modal Analysis, Wireless SHM

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.

SHM, Piezo sensors, Wireless transmission, Bridge dynamics, Railway infrastructure

The paper presents some results of research on the Weight-in-motion (WIM) system. The device is used for identification of loads on the road surface generated by traveling vehicles. The proposed approach utilizes the piezoelectric measurement techniques to monitor strain development in a deformable body and eventually these measurements are used for tire- pavement load identification. An advantage of the proposed concept is that no additional limitation for a vehicle velocity and direction is required in order to make the measurement feasible. The device allow to identify many parameters which can be stored for statistical and planning purposes. When an overload or an exceed in speed limit is detected the data can be sent for penalization purposes. The research includes a computer simulation of the bending plate detector using the Finite Element Method (FEM). Its objective is to validate the concept as well as to test some factors which are important with respect to the proposed load identification methodology. An experimental research involved field tests on the WIM system using a bending plate detector and inductive loops to detect a vehicle.

Weigh-in-Motion, Load identification, Piezoelectric sensors, Sensitivity analysis

This paper presents results of in situ investigation of a railway truss bridge in the context of structural health monitoring (SHM). Three experimental methods are examined. Dynamic responses of the bridge recorded by strain gauges are confronted with alternative ways of acquisition using piezoelectric patch sensors and ultrasonic probeheads. All types of sensors produce similar output. Also the corresponding responses of the numerical model of the bridge match experimental data.

Prawidłowe funkcjonowanie sieci kolejowej wymaga poznania stanu wyeksploatowanego toru oraz podtorza. Diagnozowanie sieci kolejowej wymaga m. in. Budowy poprawnego modelu numerycznego, symulującego możliwie wiernie badany układ, zachowując przy tym rozsądny czas obliczeń. W pracy przedstawiono wyniki eksperymentów zrealizowanych na doświadczalnym stanowisku polowym. W pomiarach wykorzystano czujniki piezoelektryczne wykonane w formie płytek o prostokątnym kształcie. Otrzymane wyniki porównano z rezultatami obliczeń numerycznych wykonanych metodą elementów czasoprzestrzennych. Wykazano skuteczność symulacji komputerowych w opisie dynamiki rzeczywistych torów kolejowych.

W pracy zaprezentowano wstępną ocenę nowej metodologii stosowanej do identyfikacji obciążeń wywieranych przez przejeżdżające pojazdy na nawierzchnię drogi. Proponowane rozwiązanie opiera się na pomiarze lokalnych odkształceń powstałych na powierzchni detektora nacisku. Celem jest rozwój koncepcji oraz sprawdzenie nowego typu dynamicznej wagi drogowej oraz algorytmu rozwiązania zagadnienia odwrotnego. Przyjętą koncepcję wstępnie sprawdzono wykorzystując metodę elementów skończonych. Przeprowadzono też testy laboratoryjne proponowanego urządzenia. Uzyskano dzięki temu wstępne dane do kalibracji urządzenia. Ważnym zagadnieniem było sprawdzenie czynników wpływających na identyfikację obciążeń. Skuteczność rozwiązania sprawdzono w badaniach doświadczalnych wstępnej wersji urządzenia w warunkach drogowych.

ważenie pojazdów w ruchu, identyfikacja obciążeń, czujniki piezoelektryczne, badania eksperymentalne

The contribution describes three innovative external airbag systems developed by the
authors for the protection of flying objects during emergency landings. The first one is the
AdBag system dedicated for small drones, which is designed to protect the carried equipment
and prevent damages to objects or injuries to people at the crash location. The second system
is external airbag designed for ultralight aircraft Skyleader 600, which provides significant
reduction of touchdown velocity and deceleration levels during emergency landings, thereby
improving protection of the pilot and the passengers. Finally, the last presented solution is the
Spring-Drop system with specialized airbag deployment technique, which is dedicated for
specialised airdrop operations where the touchdown conditions can be extremely harsh and
unexpected, while protection of transported cargo is of crucial importance. Both conceptual
studies, numerical simulations and experimental tests of the three proposed systems are
presented and discussed.

External airbags, adaptive system, emergency landing, human safety

This contribution proposes a decentralized closed-loop control algorithm for semi-active mitigation of free vibrations in frame structures. The control uses dedicated dissipative devices, which consist of two controllable structural nodes placed pairwise in both ends of selected structural beams. The nodes are capable of a controlled transition between the standard frame mode of operation (full moment-bearing ability) and the truss mode in which they do not bear any moments and constitute in fact structural hinges. Synchronous switching is equivalent to reconfiguration of the global structure by (dis)allowing the involved beams to transmit moments and to accumulate vibration energy in the form of their bending strain. Upon switching to the truss mode, the accumulated energy is released into high-frequency local vibrations, which undergo quick dissipation by standard mechanisms of material damping. The approach is illustrated in a numerical example and verified in a preliminary experimental test.

Mitigation of vibrations, Semi-active control, Decentralized control, Structural reconfiguration

This paper presents results of experimental tests of a demonstrator structure equipped with variable stiffness nodes for suppression of free vibrations. So called Prestress Accumulation-Release (PAR) strategy for on-off control of these nodes is utilized. The obtained system is semi-active. The core of the controllable nodes are linear piezo-actuators.

Adaptive Structures, On-Off Control, Variable Stiffness Joint

The so-called Adaptive Impact Absorption (AIA) is a research area of safety engineering devoted to problems of shock absorption in various unpredictable scenarios of collisions. It makes use of smart technologies including systems equipped with sensors, controllable dissipaters and specialized tools for signal processing. One of the most challenging problems for AIA systems is on-line identification of impact lo ads, which is crucial for introducing optimum real-time strategy of adaptive impact absorption. This paper presents development of methodology which enables real-time impact load identification. In considered problem a dynamic excitation is generated by a mass M 1 impacting with initial velocity V 0. An analytical formulation of the problem, corresponding numerical simulations and experimental tests are presented. Two identification algorithms based on measured response of the impacted structure are proposed and thoroughly discussed. Finally, a concept of the AIA device utilizing the idea of detecting device (the so called “impactometer”) is briefly described.

Impact Load Identification, Adaptive Impact Absorption, Real-time Systems

In the last years one can observe an increasing interest in structural health monitoring (SHM) from Polish Railways. There are several hundreds of steel truss bridges of various spans and similar topologies in Polish railway infrastructure. One of them, located over a canal in Nieporęt near Warsaw with span of 40m became an object of investigation and implementation of an integrated SHM system. The system consists of two components – weigh in motion (WIM) part for identification of train load and SHM part for assessing the bridge state. The WIM module supplies load data required for SHM inverse analyses, however it can operate as an independent system for monitoring of railway traffic providing information about axle loads and rolling stock identification. Many in-situ installations of SHM systems suffer from a troublesome and time- consuming way of data acquisition via standard cables. In order to facilitate data collection related with this way of acquisition, an alternative solution of wireless transmission of the measured data from the field to analysis centre is proposed. Two aspects of wireless transmission are considered – short range (in the vicinity of the bridge) and far range (from the bridge to the centre of analysis). This paper takes up the practical issue of design and implementation of the integrated SHM system for truss steel railway bridge with a special insight into the monitoring of railway traffic.

Structural Health Monitoring, monitoring of steel railway bridges

In the last years one can observe an increasing interest in structural health monitoring (SHM) from Polish Railways. There are several hundreds of steel truss bridges of various spans and similar topologies in Polish railway infrastructure. One of them, located over a canal in Nieporęt near Warsaw with span of 40m became an object of investigation and implementation of an integrated SHM system.
The system consists of two components – weigh in motion (WIM) part for identification of train load and SHM part for assessing the bridge state. The WIM module supplies load data required for SHM inverse analyses, however it can operate as an independent system for monitoring of railway traffic providing information about axle loads and rolling stock identification.
Many in-situ installations of SHM systems suffer from a troublesome and time-consuming way of data acquisition via standard cables. In order to facilitate data collection related with this way of acquisition, an alternative solution of wireless transmission of the measured data from the field to analysis centre is proposed. Two aspects of wireless transmission are considered – short range (in the vicinity of the bridge) and far range (from the bridge to the centre of analysis).
This paper takes up the practical issue of design and implementation of the integrated SHM system for truss steel railway bridge with a special insight into the monitoring of railway traffic.

SHM systems, monitoring of railway bridges

The paper presents results of in-situ investigation of a railway truss bridge in the context of SHM. Three experimental methods are examined. Dynamic responses of the bridge recorded by strain gauges are confronted with alternative ways of acquisition using piezoelectric sensors and ultrasonic probeheads. Numerical model corresponds to experimental data.

Kompozytowe podwozie samolotu Skyleader GP ONE poddane zostało obciążeniom symulującym warunki przyziemienia podczas lądowania samolotu, a także próbie niszczącej. Zweryfikowano możliwość wskazania lokalizacji obszarów maksymalnej koncentracji naprężeń zredukowanych przy zastosowaniu uproszczonego modelowania, wykonanego przy założeniu izotropowości materiału podwozia. Do przeprowadzenia testów laboratoryjnych posłużyło unikalne stanowisko z wieżą zrzutową, posiadające pionowy i poziomy układ łożysk liniowych.

zrzutownik, podwozie samolotu ultralekkiego, model izotropowy

The problem of safe, impact loads absorption is present in a wide class of applications, and particularly where direction of the object's movement is well-defined, for example: precise docking systems, rail car buffers or landing gear shock absorbers. In those applications the objective is to absorb gradually impact energy, minimizing the deceleration peak. For safety reasons, the class of drop-caps (eg. in delivery business) or bigger airdrops from airplanes or from stratospheric airships (space debris) becomes a challenge for next decades. However, knowing the dropping mass and estimating the touchdown velocity, our SAI shock-absorbers (cf. [1]) made of multi-layered, "delaminable" panels, can be adapted to the expected impact. Therefore, let us concentrate on the SAI concept based on the following steps: -- design a multi-layer structure capable of semi-active "delamination" control along the contact infrastructure (slipping lines). -- apply an actuator realizing the on/off type of semi-active control for slipping lines' activation, playing the role of structural clutch (cf. the actuator in the so-called PAR vibration suppression technique, [2-3]), -- apply various characteristics for the contact interfaces (friction coefficient), -- apply various control strategies for the slipping lines activation (and releasing of the pre-stress effect), depend on the case study and identified on-line impact parameters. The effectiveness of the proposed, adaptive approach to impact absorption (so-called Depress Dampers) will be compared versus traditional shock-absorbers, based on passive honeycomb panels (cf. also adaptive pneumatic shock-absorber concept).

adaptive inflathigh performance valves, adaptive inflatable structures