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1

Displacements of shell in soil-steel bridge subjected to moving load: determination using strain gauge measurements and numerical simulation

Machelski Czesław, Sobótka Maciej, Grosel Szczepan

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 1

26--37

EN

This paper analyses displacements of a shell in a soil-steel bridge subjected to quasi-static moving loads. The considerations relate to a large span structure located in Ostróda, Poland. In particular, shell displacements during a loading cycle consisting of consecutive passages of a pair of trucks over the bridge are investigated. The results of a full-scale test, that is, the readings from a system of strain gauges arranged along the shell circumferential section, are the basis for determination of shell displacements. The proposed algorithm makes it possible to calculate any component of the displacement using just a simple model of the shell in the form of a linear elastic curvilinear beam. The approach uses real measurements, and thus, it yields results of displacements reflecting the actual mechanical behaviour of the entire composite structure including not only the shell, but also the backfill, the pavement, etc. The calculated state of displacement sets the basis for calibration of the numerical model. Finite element (FE) analyses include staged construction, that is, backfilling the shell by placing successive soil layers, as well as the loading test with the vehicles moving over the bridge. It is demonstrated that the ballasting of the shell during backfilling contributes to the improvement of the simulated behaviour of the object at the stage of operation, that is, when subjected to moving truck load. Thus, the calibration of the FE model is successfully carried out using the results of strain gauge measurements.

2

Contact interactions between soil and a corrugated metal sheet in soil-shell structures under construction

Machelski Czesław

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 1

1--12

EN

During the construction of soil-shell objects, large deformations of the shell, which is made of corrugated metal sheet, occur. This enables geodetic techniques to be used when monitoring such objects. On this basis, displacements of selected points of the shell are determined, and it is then possible to obtain bending moments, as shown in this paper. Based on measurements using strain gauges in the circumferential band of the shell, internal forces in steel are estimated. The algorithm given in the paper enables the impact of soil on the shell in the examined objects to be analysed. The proposed method of analysing forces in the contact layer becomes especially useful when the static conditions of the model of a shell, which is considered as a bar submerged unilaterally in the soil medium, are met. The paper indicates the possibility of using both measuring techniques. Calculations include a smaller share of axial forces on the contact impact during the laying phase of the backfill. The paper provides examples of the analysis of built shells and record-breaking objects, with an assessment of the effectiveness of the proposed algorithm. Good mapping of contact forces, which were calculated on the basis of bending moments, was indicated even when there was not a dense grid of measuring points. An important advantage of the algorithm involves reduction of the circumferential band that is separated from the soil-shell system to the bar, which is an element resulting from the division of the structure into subsystems.

3

Experimental determination of forces through measurements of strains in the side frame of the bogie

Boronenko Yuriy, Rahimov Rustam

Transport Problems

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2021

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T. 16, z. 3

199--211

EN

This paper investigates the influence of longitudinal and lateral forces on the accuracy of measurements of vertical forces for three-piece bogies. Theoretical studies of the loading of the bogie side frame have been carried out using the finite element method under the action of forces from a wheelset. The places of installation of strain gauges and the method of processing the received signals are determined. A method has been developed for measuring the vertical and lateral forces, which makes it possible to increase the accuracy of measurements of the vertical force, with the help of which the safety of movement is assessed during running dynamic tests and to ensure the simultaneous measurement of vertical and lateral (frame) forces transmitted to the boogie side frame, which will allow to reduce the number of strain gauges for measuring the considered forces during tests.

4

Insight Into Vibration Sources in Turbines

Moneta Grzegorz, Jachimowicz Jerzy, Pietrzakowski Marek, Doligalski Adam, Szwedowicz Jarosław

Fatigue of Aircraft Structures

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2021

|

Iss. 13

40--53

EN

Despite of nearly 100 years of turbine engine development and design, blade vibrations remain a great engineering challenge. The rotating turbine blades’ vibrations lead to cyclic oscillations, which result in alternating stress and strain in harsh environments of high temperature and pressure. In modern aeroengines, high hot flow velocities might generate erosion and corrosion pitting on the metal surfaces, that leverage remarkably mean stresses. The combination of both mean and alternating stresses can lead to unexpected engine failures, especially under resonance conditions. Then, alternating stress amplitudes can exceed the safety endurance limit, what accelerates the high cyclic fatigue leading quickly to catastrophic failure of the blade. Concerning the existing state-of-the-art and new market demands, this paper revises forced vibrations with respect to excitation mechanisms related to three design levels: (i) a component like the blade design, (ii) turbine stage design consisting of vanes and blades and (iii) a system design of a combustor and turbine. This work reviews the best practices for preventing the crotating turbine and compressor blades from High Cyclic Fatigue in the design process. Finally, an engine commissioning is briefly weighed up all the pros and cons to the experimental validations and needed measuring equipment.

5

Skalowanie czujnika tensometrycznego za pomocą funkcji nieliniowej z wymuszeniem w wybranym punkcie jego charakterystyki

Filipowski Ryszard, Arasimowicz Anna, Lechniak Zbigniew, Zawora Józef

Obróbka Metalu

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2020

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nr 3

36--41

PL

Do oceny jakości obróbki zrealizowanej w procesach wytwórczych niezbędne są pomiary wielkości, które mogą stanowić kryteria oceny. Dokładność tych pomiarów zależy, m.in. od dokładności skalowania. W artykule przedstawiono nową, oryginalną procedurę skalowania czujnika tensometrycznego umożliwiającego precyzyjne określenie wartości naprężeń jakie zostają w warstwie wierzchniej po obróbce. Przeprowadzona weryfikacja doświadczalna wykazała poprawność procedury oraz pełną jej przydatność w badaniach technologicznych.

EN

For the evaluation of quality of machining realized in manufacturing processes measurements of quantities which may constitute evaluation criteria are necessary. The accuracy of these measurements depends on, among other from scaling accuracy of sensor. In this paper a new, original procedure for scaling a strain gauge sensor is described. It allows precise determination of values of stresses that remain in surface layer after machining. The experimental verification carried out showed the correctness of the procedure and its full usefulness in technological investigations.

6

Modular Test Stand for Fatigue Testing of Aeronautical Structures - Verification of Assumptions

Leski Andrzej, Wronicz Wojciech, Kowalczyk Piotr, Szmidt Michał, Klewicki Robert, Włodarczyk Karol, Uliński Grzegorz

Fatigue of Aircraft Structures

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2020

|

Iss. 12

78--91

EN

The Modular Test Stand was developed and manufactured to decrease the cost of fatigue testing and reduce the time of its completion as well as to enable testing specimens under more complex load conditions. The stand consists of three connected sections, similar to a wing box, all being loaded in the same way. Thanks to that, several specimens can be tested simultaneously. This configuration requires that stress and strain distribution should be reasonably uniform, as assumed in the design stage. The structure can be loaded with bending or torsion. A whole section, selected structural node or a specimen mounted in the structure as well as a repair or a sensor can be a test object. Two stands, one for bending and one for torsion were prepared. This paper presents the verification of the assumed strain and stress distributions on the skin panels. The measurements were performed with the use of Digital Image Correlation (DIC) as well as strain gauges. DIC measurements were performed on one skin panel of the central section. Five strain gauge rosettes were installed on both panels of the one section. In addition, one rosette was applied to one skin panel in each of two other sections. Measurements were performed on the stand for torsion as well as on the stand for bending. The results of DIC analysis and strain gauge measurement during torsion show uniform shearing strain distributions on the panels. During bending, on the tensioned side, the strains obtained indicate quite uniform strain distributions. On the compressed side, local buckling of the skin panels results in high strain gradients. Strain levels obtained with the use of a DIC analysis and strain gauge measurements were similar. Moreover, horizontal displacements of markers in the spar axis during bending was determined based on a series of photographic. The deflection line obtained in this way has a shape similar to arc, which is characteristic of the constant bending moment. The stand was tested with torsional and bending loads in order to verify the design assumptions. The results of strain distributions on the skin panels with the use of DIC and strain gauges as well as the deflection line of the spar axis indicate that the Modular Test Stand performs as assumed and can be used for tests.

7

Development of a low-cost measurement system to determine 3-dimensional pedal loads during in-situ cycling

Dieltiens Sien, d’Hondt Jordi, Juwet Marc, Versteyhe Mark

Transport Problems

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2019

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T. 14, z. 4

151--159

EN

As increasingly more bicycles are equipped with electrically powered pedal assistance, they can become the solution for the continuous congestion that threatens Europe. Pedal assistance decreases the effort, though cyclists often experience sores that occur at the low back, knees and bottom area. The risk of injuries is predominantly determined by the pedal technique, which is highly dependent of bicycle design, seat type and cycling posture. The optimal cycling technique and the relation to the bicycle characteristics needs to be discovered to create guidelines for bicycle construction and usage. This paper presents the design of a low-cost measurement system to analyse three-dimensional pedal loads in function of the pedal cycle by an instrumented pedal and an absolute encoder fixated on the crank. The pedal proposed is a combination of a unique steel sensor with twelve sensor regions, organized in four full Wheatstone bridges, installed on a standard pedal spindle. The pedals are calibrated with the Global Regression method acquiring a calibration matrix with a standard error percentage of full scale of maximum 0.5%. The instrumented pedal distinguishes itself from state-of-the-art techniques through (i) compatibility: it fits on every conventional bicycle, (ii) compactness: not influencing the cycling kinematics, (iii) broad applicability: it is applicable for in-situ measurements with extreme manoeuvres and (iv) accuracy: it delivers a relative high accuracy in relation to the production precision and production costs.

8

Integrated strain gauge printing in a CFRP structure

Misch Sandra, Welzel Florian, Möhring Hans-Christian

Journal of Machine Engineering

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2019

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Vol. 19, No. 3

74--81

EN

Our approach is to integrate printed strain gauges into a structure of laminated carbon fibre reinforced plastics (CFRP). This can provide minimizing disturbances caused by an additional sensor weight. Another point is to reduce the occurrence of pre-damage, as a printed structure is integrated directly into the CFRP. Due to the printing, no additional masses are applied to the CFRP by cables. To this end, the boundary conditions for the print are first explained. Subsequently, the strain gages were printed. For this purpose, studies were carried out regarding the orientation of the strain gage printing direction, the influence of repeated printing, the overlapping during printing and the subsequent lamination in CFRP plates. The sensors are to be used in the structure of the CFRP plate in a machine tool.

9

Design and modeling of an exoskeleton torque sensor

Herbin P.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2017

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nr 51 (123)

89--94

EN

Controlling the upper limb with force feedback requires the continuous measurement of multiple values, so it is necessary to use a specific measuring system. The position of the joints and the torque produced by the drives are the basic feedbacks necessary for control. Measurement of the joint positions does not cause complications, while measurement of the driving torque is much more complex. This article describes the methods of implementing an exoskeleton drive system through a closed loop conduit system based on Bowden cables, and the integration of a torque sensor within the wheel of the exoskeleton. The integration of the sensor within a mechanical part of the construction of the exoskeleton is the main advantage of the developed sensor because it does not affect the dynamics of the exoskeleton. This article presents the process of designing, calibrating and validating the proposed link wheel torque sensor.

10

Zastosowanie monitoringu tensometryczno-parasejsmicznego w pomiarach wpływów dynamicznych wzbudzonych detonacją materiału wybuchowego

Biessikirski A.

Przegląd Górniczy

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2017

|

T. 73, nr 3

42--49

PL

W pracy przedstawiono zastosowanie spójnego systemu parasejsmiczno-tensometrycznego do pomiaru wpływów dynamicznych wzbudzanych robotami strzałowymi w zakresie niższych wartości częstotliwości. Przedstawiono opracowaną metodykę pomiaru oraz uzyskane przebiegi drgań i naprężeń w warunkach laboratoryjnych. Na podstawie analiz Matching Pursuit (MP) przeprowadzono badania struktury czasowo-częstotliwościowej, których celem było określenie czasów występowania PPV, maksymalnego naprężenia chwilowego oraz uzyskanych wartości energii dla każdej ze składowych. Na podstawie uzyskanych wyników zaobserwowano zależność pomiędzy przebiegami prędkości drgań a wyznaczonymi naprężeniami w całej dziedzinie czasu. Ponadto, otrzymane rezultaty dla analiz czasowo-częstotliwościowych przeprowadzonych na podstawie zarejestrowanych wartości drgań oraz odkształceń wzbudzonych detonacją materiału wybuchowego w skali laboratoryjnej potwierdziły bezpośrednią zależność pomiędzy PPV a maksymalnymi naprężeniami chwilowymi na każdej ze składowych.

EN

This paper presents the combine ground borne vibration and stress analysis measurement system. The methodology and results of the research were included. A detailed analysis in the time-frequency domain was obtained by the Matching Pursuit (MP) analysis. The MP methodology allowed to determine the occurrence of PPV and the maximum stress energy in time domain on each axis. Based on the obtained results the relation between ground – borne vibration velocity and induced stress in the concrete structure was observed in the whole time domain. Furthermore, the results of the analysis in the time – frequency domain obtained from the measured ground – borne vibration velocity and strains which were induced by blasting works on a laboratory scale, confirmed the direct relation between PPV and maximum stress at each axis.

11

Wytrzymałość cięgien nośnych górniczego naczynia wydobywczego

Wolny S., Badura S.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2017

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z. 64, nr 2/I

149--158

PL

Analiza okresowych badań skipów i klatek eksploatowanych w szybach jednej z kopalń wykazała że większość zarejestrowanych uszkodzeń elementów nośnych naczyń wydobywczych to pęknięcia o charakterze zmęczeniowym. Celem wyeliminowania przyczyn powstawania uszkodzeń oraz zwiększenia trwałości naczyń wydobywczych, niezbędnym będzie prawdopodobnie wykonanie rekonstrukcji tych fragmentów naczyń, w których uszkodzenia te występują. Aby rekonstrukcja przyniosła oczekiwane rezultaty niezbędne jest poznanie przyczyn będących źródłem powstających pęknięć. Dlatego postanowiono przeprowadzić pomiary, których wyniki umożliwiłyby wyznaczenia wartości obciążeń cięgien, a w dalszej kolejności ocenę ich wytrzymałości i trwałości. Wykonana analiza trwałości zmęczeniowej cięgien naczynia wydobywczego, wskazuje na możliwość rozwoju pęknięć zmęczeniowych w najbardziej wytężonych obszarach konstrukcji, w krótkiej perspektywie czasowej.

EN

Analysis of periodic tests conveyances and cage operated shafts in one of the mines revealed that most of the failures recorded in load-bearing elements in conveyances, is fatigue cracks. In order to eliminate the causes formation of damage and increased durability in conveyances, necessary will probably perform the reconstruction of the fragments conveyances in which the damage they are. To reconstruction brought the expected results, it is necessary to know the reasons being the source of emerging cracks. Therefore it was decided to carry out measurements the results of which allow you to determine the values of loads and a further assessment of their strength and durability. The analysis of fatigue life rods-bearing elements in conveyances it indicates the possibility of the development of fatigue cracks in the most intensive areas of the construction, in the short term.

12

Strain distribution of aircraft engine compressor blade surface applying numerical and experimental methods

Setkowicz A., Obrocki W., Sieniawski J., Ziaja W.

Advances in Manufacturing Science and Technology

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2017

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Vol. 41, nr 2

43--52

EN

Paper contains an analysis of the 1st stage compressor blade strain distribution. Boundary conditions analysis was presumed for blade clamped in the fatigue holder. Strain distribution verification was performed for blade fundamental frequency. Numerical method results were verified with experimental (strain gauge) method.

PL

Artykuł przedstawia analizę rozkładu wartości odkształceń łopatki 1. stopnia wirnika sprężarki. Warunki brzegowe dla prowadzonej analizy przyjęto dla przypadku zamocowania łopatki w uchwycie maszyny wytrzymałościowej w próbie zmęczeniowej. Weryfikację rozkładu wartości odkształcenia wykonano dla pierwszej postaci drgań własnych łopatki. Wyniki analizy odkształceń metodą numeryczną weryfikowano w badaniach eksperymentalnych.

13

Investigations of the vibration effect in a measurement system for air flow phenomena in large pipelines

Kabaciński M., Pawliczek R.

Measurement Automation Monitoring

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2016

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Vol. 62, No. 3

96--99

EN

A measuring system for investigation of the air flow phenomena in large tubes is presented in this paper. The main goal is to measure and analyze the vibration effect of a sensing element used for air velocity and air stream measurement. It was observed that some vibrations occurred and involved damage effect in the flow sensor. The measuring system is based on the strain gauge technology with the use of a virtual instrument in the laboratory equipment. The presented system allows measuring, identifying and analyzing vibrations of the sensor in time and frequency domains. It was created as a virtual instrument, very easy to implement into the entire control system of the stand. It was found that the load of the sensing element was asymmetric and the mean load value, compared to variable loads, arose from disturbances of the air flow around the sensor. It was observed for the examined velocities of the air stream in the range up to 35 m/s.

14

Pomiar momentu obrotowego w warunkach przemysłowych

Decner A., Iskierski L.

Napędy i Sterowanie

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2015

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R. 17, nr 7/8

139--143

PL

W artykule przedstawiono budowę systemu pomiarowego zastosowanego podczas prac badawczych prowadzonych na terenie KGHM Polska Miedź SA przez Instytut Napędów i Maszyn Elektrycznych KOMEL. Zaprezentowano możliwości zastosowania systemu oraz wyniki rejestracji i pomiarów w oparciu o wybrany przykład. System umożliwia przeprowadzenie pomiaru momentu obrotowego w czasie normalnej pracy układu napędowego. Możliwe jest wyznaczenie charakterystyk obciążenia (wyznaczenie sprawności), rejestracji momentu na wale podczas rozruchu itp. Zastosowany system nie powoduje konieczności wprowadzenia zmian konstrukcyjnych układu mechanicznego ani nie zakłóca normalnej pracy napędu.

EN

The paper presents the construction of the measurement system used during the research work carried out in the KGHM Polish Copper SA by the Institute of Electrical Machines and Drives KOMEL. The possibilities of application of the system and the results of the registration and measurements based on the selected example are presented. The system allows to measure torque during normal operation of the drive. It is possible to determine the load characteristics (determination of efficiency), registration of the torque on the shaft during start-up, etc. Used system does not involve structural changes of the mechanical system or interfere with the normal operation.

15

Zależność pomiędzy oporem elektrycznym a odkształceniem przy ściskaniu kompozytów cementowych zbrojonych włóknami stalowymi

Teomete E., Kocyigit O. I.

Cement Wapno Beton

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2015

|

R. 20/82, nr 4

244--252

PL

Inteligentne materiały konstrukcyjne umożliwiają kontrolę stanu konstrukcji betonowych przy stosunkowo małych kosztach, zapewniając dużą czułość. W pracy przygotowano kompozyty cementowe zbrojone włóknami stalowymi, a ich badania wykazały, że opór elektryczny próbek betonowych rośnie z czasem hydratacji. Zbadano właściwości czujnika tensometrycznego złożonego z betonu z włóknami stalowymi, a mianowicie współczynnik czujnika [czułość], liniowość oraz granicę odkształcenia. Współczynnik czujnika w przypadku komercyjnych czujników metalowych wynosi K=2, podczas gdy dla kompozytów cementowych zbrojonych włóknami stalowymi współczynnik ten jest bardzo duży i wynosi K=156. Tak więc, czujniki betonowe są bardziej czułe na odkształcenie niż komercyjne metalowe czujniki tensometryczne. Nawet w przypadku zastosowania powtórnych obciążeń przy znacznych poziomach naprężeń, współczynnik czujnika betonowego pozostaje wysoki, co wskazuje na możliwość ich stosowania jako inteligentnych materiałów konstrukcyjnych.

EN

The smart structural materials are enable to health monitoring of concrete with reduced expenses and high sensitivity. In this study, steel fibre concretes were produced and their examination was showing that their electrical resistance is increasing with the curing age. The measurements possibilities of these sensors, which are gage factor (sensitivity), linearity and strain limit were determined. The gage factor of the commercial metal strain gages is K=2 while gage factor of steel fibre concrete was high, equal K=156. Thus, the steel fibre concretes are much more sensitive to strain than commercial metal strain gages. Even after the repeated loading of concrete samples to considerable stress levels, the gag e factor remains high which shows that the cement composite can be used as a smart structural material.

16

Static and Dynamic Tests Performed on a Flat Wagon

Sandu N., Zaharia N. L.

Problemy Kolejnictwa

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2014

|

Z. 163

67--77

EN

Today, a wide range of freight wagons is used by railway operators. During the last century, the gondola wagon was the back bone of each freight railway operator due the versatility of such type of wagon. But in the last years because of intermodal necessity a flat wagons are more often used because a 20', 30' or 40' container with goods can be used on ships between containents, on flat wagons from the seaport to a railway station (on main land) and from the railway station to a hypermarket (or end user) with the help of truck. This paper present some of the tests performed at a four axle flat wagon. Based on testing report the wagon was certified (homologated) and putted in service on Romanian Railways.

PL

Operatorzy kolejowi korzystają z wagonów towarowych różnego typu. W ostatnim stuleciu podstawowym typem taboru kolejowego każdego operatora przewozów towarowych był wagon odkryty, cechujący się wszechstronnością zastosowań. W ostatnich latach, coraz szerszym użyciu są wagony – platformy, które spełniają wymagania transportu intermodalnego. Na takich wagonach w morskim transporcie międzykontynentalnym prze-wozi się dwudziesto, trzydziesto i czterdziesto stopowe kontenery towarowe, które po wyładowaniu w porcie są dostarczane do stacji kolejowych na lądzie i samochodami ciężarowymi do placówek handlowych lub innych odbiorców końcowych. W artykule przedstawiono wyniki badań czteroosiowego wagonu platformy. Na podstawie wyników tych badań wagon był certyfikowany (homologowany) i przekazany do eksploatacji na Koleje Rumuńskie.

17

Application of Strain Gauges in Measurements of Strain Distribution in Complex Objects

Tutak P.

Journal of Applied Computer Science Methods

|

2014

|

Vol. 6 No. 2

135--145

EN

This article presents an application of strain gauges in measurements of strain which occurs in charge air cooler during the thermal cycle test. The work shows the main idea of measuring system based on strain gauges and important aspects that should be considered when performing measurement. In this article there has been also presented construction and principle operation of a strain gauge measurement system.

18

Multimode polymer optical fiber strain gauge based on speckle correlation

Varyshchuk V, Bobitski Y., Poisel H.

International Journal of Microelectronics and Computer Science

|

2014

|

Vol. 5, nr 3

111--115

EN

In this paper, we proposed an optical ﬁber strain gauge where the fiber elongation originates from a spatial change in a random intensity pattern which is measured through a correlation coefficient of two speckle image. The optical scheme and the operation principle of strain gauge based on multimode polymer optical fiber is investigated. The possibility of measuring of the relative strain by processing of speckle patterns at the exit face of multimode fiber is studied theoretically and experimentally. The algorithm of correlation processing of speckle pattern is developed too. The sensing technique presented in this paper is simple, effective and low-cost solutions to the problem of small strain monitoring. The proposed method can be used to structural health-monitoring of the elements of buildings and industrial objects.

19

Nieinwazyjne metody kontrolno-pomiarowe w zastosowaniach przemysłowych

Rybak G., Chaniecki Z., Grudzień K., Romanowski A., Sankowski D.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2014

|

nr 3

41--45

PL

Systemy kontrolno-pomiarowe stanowią istotną grupę narzędzi diagnostycznych wykorzystywanych w przemyśle. Prawidłowo dobrane do charakteru procesu pozwalają na wczesne wykrywanie niepożądanych stanów procesu, dzięki czemu możliwe jest np. zapobieganie katastrofom przemysłowym. Nieustanny rozwój tych systemów powoduje, że są one coraz bardziej precyzyjne i efektywne, jednak od dokładności urządzeń często ważniejsze jest zgłębianie stanu wiedzy na temat natury badanych procesów. Na podstawie procesu grawitacyjnego przepływu substancji sypkich opisany został system pomiarowo-kontrolny, w skład którego wchodzą takie narzędzia jak: tensometry, akcelerometry oraz tomograficzne czujniki pojemnościowe. Wstępne wyniki przeprowadzonych eksperymentów potwierdzają skuteczność proponowanego systemu w odniesieniu do monitorowania przemysłowej instalacji przechowywania i rozładowywania materiałów sypkich, znajdującej się w Laboratorium Tomografii Procesowej im. T. Dyakowskiego Instytutu Informatyki Stosowanej.

EN

Monitoring and control systems constitute an important group of diagnostic tools used in the industry. When selected properly, they allow for the early detection of adverse conditions of the process, making it possible to prevent catastrophes. While these systems are becoming more precise and effective it is essential to exploring the state of knowledge about the nature of the processes that are the domains of their proper execution. Based on a process of gravitational flow of solids proposed measuring and control system is described, which includes tools such as strain gauges, accelerometers and capacitance tomography sensors. Preliminary results of conducted tests confirmed the efficiency of the proposed system for the monitoring of an installation for storage and unloading of bulk solids. The flow rig is located in the Tom Dyakowski Process Tomography Lab at the Institute of Applied Computer Science.

20

Local Phenomena During Riveting Process

Kaniowski J., Wronicz W.

Fatigue of Aircraft Structures

|

2013

|

Iss. 5

66--78

EN

The paper presents experimental and numerical study of the local phenomena during the riveting process. It is commonly accepted that technological factors of the riveting process has a strong influence on the fatigue life of riveted joints. The authors analysed the papers concerned the experimental researches of the riveting force influence on fatigue life. The magnitude of the life increase caused by the riveting force increase suggests the authors that this is not only the result of beneficial stress system but the change of the joint formation mechanism has taken place. This was an inspiration to undertake more detailed researches of the riveting process. The strain progress during the riveting process has been experimentally investigated for four types of aluminium rivets used in airframes. Measurements confirm very high strains near the driven head. For some types of rivets the reversal strain signal has been recorded. Several FE model has been use to investigate the riveting process. The axisymmetric and solid models were used. The agreement of experimental and numerical results in some cases were good, in other cases the numerical models demand further development. In any calculations, the reversal strain effect has not been obtained, This suggest that it is result of the phenomenon which has not been taken into account in numerical modelling. The working hypothesis has been assumed that during the riveting process adhesive joints (called cold welding) were formed and destroyed during the process, what was the reason of the observed reversal strain signal. The authors are going to continue this investigation.