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1

Experimental Validation of Riveting Process Fe Simulation

Wronicz W.

Fatigue of Aircraft Structures

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2018

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Iss. 10

63--72

EN

Rivets are critical areas in metal airframes from the fatigue point of view. Fatigue behaviour of riveted joints depends strongly on the residual stress system around the rivet holes. The both most convenient and most common method of determining these stresses is the Finite Element (FE) analyses. The validation of models used is necessary to ensure the reliability of results. This paper presents the validation process of the riveting FE simulations for the universal and the countersunk rivets. At first, the material model of the rivets was validated with the use of the force-displacement curves of the press stamp obtained experimentally. Because of the displacement measurement method, it was necessary to take into account the flexibility of the stand. After that, good correlation between the numerical simulations and the experiment was obtained for both rivet types. At the second stage, strains around driven heads measured with the use of strip gauge patterns were compared with the results of the FE simulations. Quite good correlation was obtained for the countersunk rivet. In the case of the universal rivet, the numerical results are significantly higher values than the measured ones. Differences in correlation of the experiments and FE simulations for the analysed rivet types probably result from material differences of the rivets.

2

Analiza procesu odkształcenia cienkościennych belek skrzynkowych, łączonych różnymi metodami, pod wpływem trójpunktowego zginania

Sadowski T., Nowicki M., Pietras D., Golewski P.

Rudy i Metale Nieżelazne Recykling

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2015

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R. 60, nr 12

694--699

PL

Przedstawiona praca zawiera wyniki badań laboratoryjnych oraz analiz numerycznych trójpunktowego zginania aluminiowych belek skrzynkowych. Analizowane elementy, o przekroju poprzecznym omega zostały połączone na kilka różnych sposobów z płaskimi płytkami tworząc przekroje zamknięte. Łączniki j akie zostały tu u żyte to k leje z g rupy L octite o raz nity zrywalne o średnicy 4 mm, a także kombinacje tych połączeń. Belki o wymiarach 84 × 36 × 300 mm poddano quasi statycznemu obciążeniu w dwóch położeniach: profil omega w górnej lub dolnej pozycji. Dla każdej z tych pozycji wykonano taką samą liczbę analiz i testów. Ponadto praca zawiera wyniki analiz numerycznych dla profili jednolitych. Przedstawione wyniki prezentują charakter odkształcenia profilu w zależności od jego położenia względem obciążenia oraz od rodzaju użytego łącznika. Można tu także wyraźnie zaobserwować rozkłady naprężeń w elementach oraz poziom delaminacji łączonych warstw w różnych przypadkach obciążenia.

EN

This paper presents results of laboratory tests and numerical analyzes of three-point bending of aluminum box beams. The analyzed omega profiles are combined in different ways with the flat plates to form a closed profile. Various combinations of made of Loctite adhesives and rivets having a diameter of 4 mm were applied to get different types of connections. Specimens of dimensions 84 × 36 × 300 mm were subjected to quasi-static loading in two positions: omega profile on the top or bottom position. The experimental tests were modeled numerically with application of the ABAQUS program. Moreover, the work contains also numerical analyzes of uniform profiles made of pure aluminium material. The results represent modes of the deformation profile, depending on its position relative to load and on type of connectors. Distributions of stresses in the elements and the level of delamination of the adhesive layers combined in various cases of the thinwalled box beams were presented.

3

Comparison of selected contact materials used in low-voltage relays

Książkiewicz A.

Poznan University of Technology Academic Journals. Electrical Engineering

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2015

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No. 82

207--212

EN

Low-voltage relays are widely used in many areas of electrical applications. There are used for such applications as protection, signalization or control of electrical installations. There all are similar in many ways were it comes to construction and operating principles. However for different applications different contact materials must be used. There are many materials used for contacts in electrical appliances. In this paper contact materials used especially in low-voltage electromechanical relays are described. Their electrical and mechanical properties are characterised.

4

Contact materials used in low voltage electrical relays

Książkiewicz A.

Computer Applications in Electrical Engineering

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2015

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Vol. 13

300--309

EN

Low-voltage relays are widely used in many areas of electrical applications. There are used for such applications as protection, signalization or control of electrical installations. There all are similar in many ways were it comes to construction and operating principles. However for different applications different contact materials must be used. There are many materials used for contacts in electrical appliances. In this paper contact materials used especially in low-voltage electromechanical relays are described. Their electrical and mechanical properties are characterised.

5

Comparison of Selected Rivet and Riveting Instructions

Kaniowski J.

Fatigue of Aircraft Structures

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2014

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Iss. 6

39--62

EN

Sheet metal parts are widely used in airframes. Most sheet metal parts used in aircraft assembly are joined using rivets. A number of riveting parameters directly influence fatigue properties of a structure. These include a rivet length, driven head diameter, tolerance of a rivet hole and a rivet shank diameter, and a protective layer among others. Unfavourable selection or change of these parameters can lead to stress concentrations and early crack nucleation. Crack growth can cause failure of a whole structure. The selection of the riveting process parameters is usually described in a company’s internal instruction (process specifications). Some parameters can be defined in an aircraft's technical specifications. Riveting instructions among other production documentation are part of a company's closely guarded know-how. The author obtained access to two riveting instructions used in Poland and three such documents used in western Europe. The author was permitted to publish the comparison of the parameters from these documents but he is not supposed to reveal any other information. For the reasons stated above, the following cryptonyms were used in the article: Poland-1, Poland-2, West-1, West-2 and West-3. The quality of a joint also depends on rivets parameters that are defined in rivets standards. For this reason, selected rivets defined in the Polish and Russian industry standards as well as western standards are compared in this paper. Tolerances of a rivet and a hole diameter, clearances between a rivet and a hole, rivet lengths anticipated for driven head formation as well as driven head dimensions are taken into account.

6

The Influence of The Degree of the Rivet Hole Sizing on the Fatigue Life

Lipski A.

Fatigue of Aircraft Structures

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2012

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Iss. 4

64--69

EN

The paper presents the results of fatigue tests of specimens with sized rivet holes. Samples for tests were made of 0.05'' (1.27 mm) thick non-clad plates of aluminium grade 2024-T3. Rivet holes were prepared assuming that they shall be used for 3 mm nominal diameter snap head rivets for aviation-related purposes. Different sizing degrees were achieved by drilling holes of different diameters in the samples followed by the sizing process using a sizing mandrel of the same diameter of 3.15 mm. Holes in the test samples were drilled using special device ensuring appropriate quality and repeatability of the holes. Five different sizing degrees were achieved be means of five drills of different diameters. Samples with holes of varying degrees of sizing were tested under constant amplitude sinusoidal loading conditions (cycle asymmetry coefficient R = 0) at the load frequency of 5 Hz. The study was conducted at three levels of maximum stress in the cycle. Fatigue life test results were presented in the form of fatigue diagrams (regression lines) determined in the bi-logarithmic coordinate system log N, log Smax. The results of the fatigue life tests received for the drilled as well as drilled and reamed holes were also presentedfor comparison. The results obtained lead to the conclusion that that the lowest fatigue life characterises samples with drilled holes and drilled and reamed holes. Fatigue life of specimens with holes for rivets improved (by 50% to 74%, depending on load level), even as a result of the hole surface polishing only (minimum sizing degree), whilst the two-fold growth of fatigue life was achieved for holes of a slight sizing degree. A further significant increase in fatigue life was achieved by the cold work of the hole's surface. Based on the location of the fatigue diagrams and the fatigue life tests results, it may be concluded that the higher a sizing degree, the higher the fatigue life growth. The growth is also proportional to the specimen load level: the lower the load level, the higher the fatigue life growth. Fatigue diagrams obtained from tests were divided into three groups: diagrams for drilled holes and drilled and reamed holes, diagrams for holes with a low degree of sizing and diagrams for holes with a high degree of sizing. This division was confirmed by statistical tests of regression lines parallelism by the “peer-to-peer” method.