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1
Content available Numerical analysis of residual stress distribution in riveted lap joint under tension
Wronicz W.
Journal of KONES
|
2018
|
Vol. 25, No. 4
455--462
EN
Riveted joints are a common location of fatigue cracks in aircraft metal structures. Fatigue life of such joints as well as a place of cracks nucleation is strongly influence by a stress distribution in sheets, which is a result of residual stresses (mainly after riveting) and stresses induced by external loads. Stress distribution in two-row lap joint was investigated with the use of Finite Element Method. The joint consist of two 1.5 mm sheets and two protruding rivets with diameter equal to 4 mm, made of 2024 T3 (sheets) and 2117 T4 (rivets) aluminium alloys. The simulations covered a riveting process and tensile stages. The 3D models of joint with the universal rivets and with the brazier, rivets with a compensator were prepared. Elastoplastic material properties as well as geometric nonlinearity and contact phenomena were included. The results of simulations show that the residual stress distribution after release of tensile loading varies significantly from the distribution after riveting only. This fact should therefore be taken into account in a fatigue life estimation of such joints performed based on a FE calculation. The paper presents also the influence of the analysed rivet geometry on the stress distribution at the sheets faying surfaces.
2
Content available Experimental Validation of Riveting Process Fe Simulation
Wronicz W.
Fatigue of Aircraft Structures
|
2018
|
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.
3
Content available Experimental and Numerical Study of NACA and Conventional Riveting Procedure
Wronicz W., Kaniowski J., Malicki M., Kucio P., Klewicki R.
Fatigue of Aircraft Structures
|
2017
|
Iss. 9
157--170
EN
Fatigue behaviour is one of the most important properties of modern airplanes and rivets influence it strongly. According to the literature, the NACA riveting offers a multiple increase in the fatigue life of joints. The aim of this paper is to investigate the benefits offered by the NACA riveting procedure with respect to the residual stress and strain distribution after riveting as well as rivet hole expansion. Experimental and numerical approaches were adopted. The conventional riveting with both the universal and countersunk rivets was compared with the NACA riveting. The countersunk angle and depth in the case of the NACA riveting was modified somewhat relative to the values met in the literature. For these three cases, strain gauge measurements during riveting, hole expansion measurements and FE calculations were performed. The hole expansion measurement with the use of Computer Tomography(CT) was proposed. Only the FE calculations unambiguously indicate better fatigue properties of the NACA riveting. The proposed method of hole expansion measurement requires further research to increase its accuracy.
4
Content available The In-Depth Stress Distribution for 1H13 Specimen after Cutting
Gadalińska E., Wronicz W., Malicki M.
Fatigue of Aircraft Structures
|
2016
|
Iss. 8
73--79
EN
Measuring the in-depth stress state is of vital importance for materials scientists. Strain gauges methods are capable of yielding information only about the surface stress state. Diffraction methods using synchrotron or neutron radiation, which allow totally non-destructive stress measurements inside the material, are not widely available. In this context, the best widely available method combines the X-ray diffraction stress measurements and gradual removal of the outer layer by means of electropolishing. Here, this method was applied to the specimen made of 1H13 stainless steel cut with under water on a corundum cut-off wheel. The idea was to investigate how deeply an additional stress state resulting from cutting was introduced and whether the technique of combining of X-ray diffractometry and electropolishing can be used widely for determining the stress state inside the specimen.
5
Content available Electropolishing Procedure Dedicated to In-Depth Stress Measurements with X-Ray Diffractometry
Gadalińska E., Wronicz W.
Fatigue of Aircraft Structures
|
2016
|
Iss. 8
65--72
EN
Electropolishing is the sole reliable method of removing the outer layer of the specimen without changing its stress state. This feature of the electropolishing procedure allows researchers to investigate the in-depth stress distribution. Developing of the method in a diffraction laboratory is crucial because there is no universal theory for the electropolishing procedure allowing the removal of the layers of different thickness. This is due to the multiplicity of different factors affecting the electropolishing results. A factor of vital importance from the point of view of indepth stress measurements is the thickness of the electropolishing layer. Hence the importance of the procedures for the electropolishing of a layer of a precisely defined thickness. This work deals with the problem of the selection of the parameters in the electropolishing process for two types of materials: stainless steel and aluminium alloy. The tests of mutual correlation of current intensity, voltage applied and time of the procedure and its results are presented in the paper.
6
Content available Comparison of Residual Stress State on Sheets Faying Surface after Standard and NACA Riveting-Numerical Approach
Wronicz W.
Fatigue of Aircraft Structures
|
2016
|
Iss. 8
116--126
EN
One crucial characteristic of the aircraft structure are fatigue properties and rivets are usually critical areas in metal airframes due to fatigue cracks nucleation. According to literature, the NACA riveting method offers a huge increase in fatigue life of riveted lap joints. This paper presents FE simulations of quasi-static riveting on a press for standard countersunk rivets and the NACA riveting in two configurations: with a normal brazier rivet and a brazier rivet with a compensator. The analyzed configurations have been compared based on the stress courses on the sheets faying surfaces after riveting process. Due to a lack of data, the rivet length and the squeezing force value were assumed for NACA riveting based on FE simulations. The results indicated beneficial influence of the NACA riveting in the outer sheet (with a countersunk) and disadvantageous influence in the inner sheet. This effect was stronger in the case of the rivet with a compensator.
7
Zjawiska lokalne w procesie nitowania a trwałość zmęczeniowa połączeń
Kaniowski J., Wronicz W., Pietrzak K.
Przegląd Mechaniczny
|
2015
|
nr 9
23--28
PL
W artykule zaprezentowano wybrane badania zjawisk lokalnych występujących w procesie nitowania. Na początku przedstawiono wybrane wyniki badań dostępne w literaturze, dotyczące wpływu parametrów nitowania na trwałość zmęczeniową trzyrzędowych zakładkowych połączeń nitowych. Analiza przytoczonych badań prowadzi do wniosku, że zmiana trwałości połączeń nitowych związana ze zmianą siły nitowania jest tak duża, że prawdopodobnie nie jest tylko wynikiem korzystnych naprężeń własnych (zmiana ilościowa), ale powodem jest nowe zjawisko występujące w złączu nitowym (zmiana jakościowa). Sformułowano hipotezę, że podczas procesu nitowania powstają połączenia adhezyjne zwane zgrzaniem (spojeniem) na zimno na powierzchni styku nitu i blach. W celu weryfikacji tej hipotezy wykonano kilka serii badań strukturalnych. Badania te obejmowały nitowanie próbek dla różnych warunków. Wycięte fragmenty połączeń zostały zainkludowane w żywicy Następnie wykonano zgłady i badano je z wykorzystaniem mikroskopii świetlnej i skaningowej. Dla kilku próbek stwierdzono występowanie połączeń punktowych i liniowych pomiędzy trzonem nitu i blachami.
EN
The paper presents the selected investigations of local phenomena during the riveting process. At the beginning some results from the literature, concerning the riveting process influence on fatigue of the three-row lap joint were shown. The analysis of these results leads to the conclusion that the increase in fatigue life caused by a higher riveting force is so high that the more beneficial residual stress cannot be the only explanation, but the new phenomena in riveting process occurs and it is a reason of huge increase in the fatigue life. The working hypothesis has been assumed that during the riveting process adhesive joint (called cold welding) was formed between the rivet shank and the sheets. Several structural tests were conducted in order to verify this hypothesis. The tests include riveting the specimens for various configurations and analyses of the microsection of selected specimens with the use of optical and scanning electron microscope. In the case of several specimens the punctual and linear welding between the rivet shank and sheets were observed.
8
Content available Preparation of Samples used in Fatigue Testing of Aircraft Materials
Manaj W., Wronicz W., Michałowski A.
Fatigue of Aircraft Structures
|
2015
|
Iss. 7
66--68
EN
The application of a new type of alloy requires the evaluation of its properties, which is typically achieved with destructive methods. For this purpose, among others, static and fatigue mechanical tests are performed. Tests are performed on standardized samples in a way which reflects the level of stress occurring in real elements. These tests should limit random errors associated with sample preparation. For this reason the proper preparation of samples is crucial, not only in terms of their geometric dimensions but also in terms of the residual stress level. A sample preparation process was developed, involving checking samples’ surface for cracks, scratches, roughness, and the state of stress. The measurements are performed with nondestructive methods so as not to affect the proceeding research. In this study, the residual stress and features of a mechanically prepared surface were characterized. The specimens were subjected to various surface finishes mainly, lathe turning and grinding surface conditions. The effects of residual surface stress (measured by XRD) were studied after machining and polishing.
9
Content available The Analysis of the Influence of Riveting Parameters Specified in Selected Riveting Instructions on Residual Stresses
Wronicz W., Kaniowski J.
Fatigue of Aircraft Structures
|
2014
|
Iss. 6
63--71
EN
The riveting parameters strongly affect residual stresses induced during riveting, which in turn have an impact on the fatigue life of riveted joints. Since rivets are established as critical from the fatigue point of view, the fatigue life of riveted joints often determines the life of the whole structure. The authors were able to become acquainted with three riveting instructions (process specifications) used by the aerospace companies from western Europe. This work presents the analysis of the riveting parameters' influence on residual stresses around the rivets. The impact of the clearance between a rivet shank and a hole as well as driven head dimensions and a rivet length were investigated based on the numerical simulations. The aim of the analysis was to determine the range of stresses variation when the requirements of the riveting instructions are fulfilled. For the purposes of comparison, the calculations were performed also with the parameters as specified in the Polish industry standards. For all calculations, the geometry of the universal rivet MS20470 was used. The results show that residual stresses can vary strongly depending on the parameters in the instructions and standard requirements.
10
Content available 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.
11
Content available Analysis of the Quasi-Static Riveting Process for 90° Countersunk Rivet
Kaniowski J., Wronicz W.
Fatigue of Aircraft Structures
|
2012
|
Iss. 4
141--156
EN
Riveting is the most commonly used method of joining sheet metal components of the aircraft structure. The riveted joints are critical areas of the aircraft structure due to severe stress concentrations and effects such as fretting and secondary bending. The most spectacular and wellknown evident of this was the accident of Boeing B737 of Aloha Airline in 1988, when during the flight at altitude of 7300 m a large part of fuselage skin was removed due to explosive decompression. The investigation showed that the reason for this accident was widespread fatigue damage of riveted joints. This accident was an impulse for establishing many research programs around the world focused on fatigue of riveted joints.
12
Content available Experimental and Numerical Study of Strain Progress During and After Riveting Process for Brazier Rivet and Rivet with Compensator - Squeezing Force and Rivet Type Effect
Wronicz W., Kaniowski J.
Fatigue of Aircraft Structures
|
2011
|
Iss. 3
166--190
EN
The paper presents the experimental and numerical investigation of the stress and strain field around the rivet after the riveting process. The measurements were carried out with the X-ray diffractometer and strain gauges on the sheet surface near the driven head. The axisymmetric and 3D FEM analyses of the riveting process were performed. The article presents experimental and numerical results for two types of the brazier rivets used in the Polish aerospace industry; the normal rivet (BN-70/1121-06) and the rivet with a compensator (OST 1 34040-79 1). Bare sheets made from 2024 T3 aluminium alloy with the nominal thickness of 1,27 mm and rivets with the diameter of 3 mm and 3,5 mm made from Polish aluminium alloy PA25 were used. The measurements were compared with the FEM calculations. The influence of squeezing force as well as the rivet type on stress and the strain system was investigated.
13
Content available Numerical Analysis of Riveted Lap Joint Used in Aircraft Structures
Wronicz W., Kaniowski J.
Fatigue of Aircraft Structures
|
2010
|
Iss. 2
106--116
EN
The paper presents the results of FEM analysis of two rivet lap joints loaded with tension. The joint consists of two sheets with dimensions of 125x60 mm and nominal thickness of 1.2 mm made of 2024-T3 clad alloy ASNA 3012 and two rivets (fig. 1).The countersunk rivets made of PA25 alloy were used. The diameter of the rivets was 3,5 mm and angle 120º, according to the BN- 70/1121-05 standard. Due to its symmetry, only a half of the joint was analysed. Nonlinear material models were used and contact phenomena between sheets, rivets and tools were taken into account. The analysis involved the riveting process as well as tensile loading of the joint. MSC MARC software was used. The article presents the numerical analysis of the joint. The work of a rivet was studied. The results obtained up to date were discussed as well as the difficulties encountered. Experimental verification of the calculation with strain gauges is planned.
14
Content available Calculation and Experimental Verification of Residual Stresses in Riveted Joints Used in an Airframe
Gadalinska E., Wronicz W., Kaniowski J., Korzeniowski B.
Fatigue of Aircraft Structures
|
2010
|
Iss. 2
23--36
EN
This paper presents diffraction measurements of residual stresses around the rivet, formed during the riveting process. The measurements were made with the XSTRESS-3000 diffractometer, manufactured by Stresstech Oy. The measurements were carried out on specimens made of bare sheet 2024-T3 alloy, (standard AMS-QQ-250 / 4). The measurement results were compared with the FEM simulation results. The work was performed under the EUREKA IMPERIA project E! 3496.
15
Content available Porównanie modelowania MES z wykorzystaniem elementów bryłowych i osiowosymetrycznych na przykładzie zamykania nitu na prasie
Gadalińska E., Kaniowski J., Wronicz W.
Biuletyn Wojskowej Akademii Technicznej
|
2010
|
Vol. 59, nr 4
379-398
PL
W pracy porównano dwa sposoby modelowania zamykania nitu na prasie: z wykorzystaniem elementów bryłowych oraz osiowosymetrycznych. Celem pracy jest określenie, jaki jest wpływ ww. sposobów modelowania na wyniki oraz jakie posiadają one wady i zalety. Analizowano modele używane podczas aktualnie prowadzonych prac. Analizowano modele z różną gęstością siatki, przy czym dla danej gęstości siatka w modelu osiowosymetrycznym odpowiada siatce w przekroju modelu bryłowego, w płaszczyznach symetrii. Uwzględniono nieliniowe własności materiałów oraz zjawiska kontaktowe. Obliczenia prowadzono przy użyciu oprogramowania MSC MARC. Porównano uzyskane wyniki oraz czasy obliczeń dla poszczególnych modeli i wielkość plików wynikowych. Wyniki obliczeń porównano z wynikami pomiaru naprężeń wokół nitu metodą dyfrakcji rentgenowskiej.
EN
The paper presents comparison of FEM modelling of press riveting with solid and axisymmetric elements. The aim of the work was to determine the influence of mentioned techniques on results as well as their advantages and disadvantages. Models used in current works were analysed. Models with different mesh density were studied. For particular density, the mesh in the axisymmetric model corresponds to the mesh in a cross section of the solid model in its symmetry plane. Nonlinear material properties were taken into account as well as contact phenomena. Calculations were performed with the MSC MARC software. Results obtained for various models were compared as well as time of calculations and size of result files. Results of FEM calculations were compared with x-ray diffractometry measurements around rivets.
16
Content available Modele globalne i lokalne MES w analizie struktur lotniczych na przykładzie fragmentu skrzydła samolotu PZL M28 Skytruck
Jachimowicz J., Szymczyk E., Sławiński G., Derewońko A., Wronicz W.
Biuletyn Wojskowej Akademii Technicznej
|
2010
|
Vol. 59, nr 1
35-59
PL
W niniejszym artykule na wstępie przedstawiono globalne analizy statyczne MES struktury fragmentu skrzydła samolotu PZL M28 Skytruck. W dalszej części pracy zamieszczono kolejno modele lokalne o różnym stopniu szczegółowości, umożliwiające analizy MES obszarów konstrukcji skrzydła z uwzględnieniem połączeń nitowych, analizy poszczególnych szwów nitowych, a w końcu analizy pojedynczych nitów. Omawiane modele lokalne poza warunkami brzegowymi wynikającymi z modeli globalnych i obciążeniami ogólnymi samolotu uwzględniają wybrane czynniki materiałowe i technologiczne oraz ich wpływ na stan przemieszczeń i naprężeń wokół nitu. Na końcu artykułu przedstawiono symulację procesu nitowania nitu grzybkowego w wyniku której uzyskano rozkład naprężeń resztkowych wokół nitu.W analizach wykorzystano systemy MSC Nastran, Marc i Ansys, a zakres analiz obejmował materiały sprężysto-plastyczne oraz sformułowania dużych przemieszczeń i odkształceń, a także wielopłaszczyznowy kontakt powierzchniowy.
EN
The paper deals with the analysis of residual stress and strain fields in a riveted joint. This stage of study concerns improving the fatigue performance of riveted joints in an airframe. Riveting, particularly in aviation, is a traditional but still commonly used method of joining sheet metal components. Aircraft structures are thin-walled ones, with coverings made of thin sheets stiffened by stringers, frames or ribs. Sheets are typically assembled by multiple rivet or bolt joints. Rivets and bolts are also used to joint sheets and stiffeners. Therefore fatigue resistance of the aircraft structure depends on tens of thousands or even hundreds of thousands rivet joints, which are used to build it. Global and local numerical models of the joint are considered with regard to the aim introduced in the paper. Numerical FE simulations of upsetting process are carried out using the NASTRAN and MARC code. Three-dimensional numerical models are used to determine the resulting stress and strain fields at the mushroom rivet and around the hole. This type of a problem requires the use of contact between the elements assembled and non-linear geometric and elasto-plastic multilinear material models to simulate behaviour of the rivet and sheets. The influence of the squeezing force on strain and stress states is studied. A certain solution to the problem connected with non-uniform stress distribution in the rivet hole is proposed and analysed.
17
Content available Methods for Global and Local FEM Analysis of Riveted Joint on the Example of the PZL M28 Skytruck Aircraft
Wronicz W., Kaniowski J., Jachimowicz J.
Fatigue of Aircraft Structures
|
2009
|
Iss. 1
212--225
EN
The paper considers some aspects of FEM modeling of riveted joints with application of shell elements and submodeling technique. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints. The project assumed FEM modeling of the operating aircraft’s structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various rivet models were presented and usefulness of them was discussed. Influence of the following simplification was analyzed; • neglecting of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglecting of contact phenomenon • neglecting of secondary bending. The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analyzed as well. In the second part, the example of analysis of riveted joint on a lower skin of the PZL M28 Skytruck aircraft wing was presented. A submodeling technique was used there. At first, part of the wing model, was built. It includes 7 ribs and 6 bulkheads between them. Boundary conditions were taken on a basis of operation data. Presence of rivets was neglected. The Linear material model was used. The purpose of this calculation was to gain accurate boundary conditions for the model of riveted joint on the middle rib. Next a shell model of chosen area was build. Boundary conditions were set on a basis of result from previous analysis. Because of large stiffness difference between part models (part of wing and riveted joint) forces, instead of displacements, were used, as boundary conditions. The nonlinear model of material was used. A contact effect, secondary bending and residual stresses were taken into account. Results from this analysis are planned to be used as boundary conditions in a calculation of single rivet with solid detailed model. The presented method allows analyzing phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN and NASTRAN software.
18
Wybrane problemy modelowania nitowanych, lotniczych struktur cienkościennych
Jachimowicz J., Wronicz W.
Przegląd Mechaniczny
|
2008
|
nr 5
25-34
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