Wyniki wyszukiwania - Biblioteka Nauki

1

Metodyka interpretowania wyników badań zmęczeniowych w oparciu o analizy fraktograficzne - na przykładzie skrzydła samolotu PZL I-22 Iryda

100%

Dorn E. , Kaniowski J.

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tom nr 4 (159)

11-17

PL

W artykule przedstawiono wycinek cyklu prac badawczo-konstrukcyjnych dotyczących wytrzymałości zmęczeniowej układu nośnego samolotu. Przedmiotem badań była mała próbka pokrycia dolnego skrzydła, którą poddano próbom zmęczeniowym. W pracy prześledzono proces i kolejność niszczenia poszczególnych elementów próbki, tzn. podłużnic, podkładki, pokrycia i półki żebra oraz nitów i wkrętów. Zniszczone elementy zostały poddane obserwacjom fraktograficznym w mikroskopie świetlnym, skankingowym mikroskopie elektronowym (SEM) oraz wykonano repliki biodenowo-węglowe, które poddano obserwacjom w transmisyjnym mikroskopie elektronowym (TEM). Analiza wyników badań makro i mikrofraktograficznych pozwoliła na wyróżnienie sześciu geometrycznych cech konstrukcyjnych mających wpływ na trwałość próbki. Były to: - rozstaw nitów w podłużnicach najbliższych linii podziału pokryć, - grubość półki żebra, - sposób ustawienia nitów w połączeniu pokrycia z podkładką, - stopniowanie podatności pakietu w połączeniu podkładki z pokryciem, - średnica wkrętów łączących pokrycie z podkładką i półką żebra, - średnica nitów łączących pokrycie z podkładką.

EN

The paper presents a part of a long scheduled investigation to determine fatigue life of the wing of a jet combat trainer aircraft. A small specimen of a skin panel modelling a lower part of the wing has been tested. There was investigated a process of damaging and the sequence of the damage regarding particular components of the specimen- i.e. the stringers, strap, the skin, and the joints (rivets and bolts). Fractographic investigations regarding the damaged components have been provided by using a light microscope (SEM), and transmission microscope (TEM). These investigations pointed out six different hot spots of the design: distance between two rivets indicated in Fig. 3 as "1" and "2"; rib shelf thickness; pitch and gage in the rivet spacing for strap splicing; resilience distribution in the strap splicing; diameter of the bolts connecting the skin, the strap and rib shelf; diameter of the rivets connecting the skin and the strap.

2

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

100%

Wronicz W. , Kaniowski J.

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2011

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tom 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.

3

Methods for Global and Local FEM Analysis of Riveted Joint on the Example of the PZL M28 Skytruck Aircraft

80%

Wronicz W. , Kaniowski J. , Jachimowicz J.

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2009

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tom 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.

4

Fretting w konstrukcjach lotniczych

80%

Jachimowicz J. , Kajka R. , Kaniowski J. , Karliński W.

Tribologia

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2005

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tom nr 3

97-108

PL

Zmęczenie cierne często jest przyczyną przedwczesnego zniszczenia zmęczeniowego konstrukcji. W artykule omówiono typowe rozwiązania konstrukcyjne, w których może wystąpić fretting. Dla ilustracji tego zjawiska wybrano przykłady obiektów lotniczych, których trwałość została istotnie zmniejszona z powodu wystąpienia efektu frettingu: skrzydło samolotu i wirnik silnika lotniczego.

EN

Fretting fatigue proceeds when a pair of structural elements are in contact and cyclic stress and relative displacement occur along their contact surfaces. These fretting conditions are observed in bolted and riveted joints, in shrink-fitted shaft couplings, in the blade-dovetail regions of turbomachinery and in the coil wedges of turbine generator rotors as shown in Tab. 1. Under these fretting conditions the fatigue strength decreases less than one-third of that under non fretting conditions. The strength is reduced because of the concentration of contact stresses such as contact pressure and tangential stress at the contact edge, where the fretting fatigue crack forms and propagates.