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Andrzej Leski

Numerical Calculation of the Aircraft Skin with Multi-Site Damage

The presence of the multi-site damage (MSD) in an aircraft structure can result in catastrophic damage when the residual strength is not sufficient to sustain operational loads. In this paper the influence of the MSD crack size on the residual strength was examined. As a crack criterion the crack tip opening angle (CTOA) was applied in the numerical simulation of the stable tearing. The CTOA criterion was implemented in the commercial software, the MSC.Marc, by means of additional user subroutines. The verification of this implementation was carried out and the obtained results are consistent with those presented in literature. The influence of the MSD crack size was determined for two crack scenarios: with a leading crack and without one.

Open access

Andrzej Leski

Service Life Assessment Program of PZL-130 Orlik TCII Structure

The following paper concerns the structural integrity program (SEWST) for the PZL-130 Orlik TCII trainer aircraft. The origin of the program is defined as well as the most important tasks necessary to fulfill the assumed goal.

Open access

Andrzej Leski

Abstract

An acoustic holography and its practical applications in engineering began to develop at the end of the 20th century. Currently, this technique is being commonly used to locate sound sources. This paper presents the use of an acoustic camera to locate sound sources during the Full Scale Fatigue Test of the MiG-29 stabilizer. During fatigue tests, the tested structure issues a series of sounds in the form of glitches, creaks or beats. These sounds are typical for a structure subjected to dynamic loading, but they can also be a source of diagnostic information about places of fatigue failures. The paper presents the results of measurements made during the fatigue test. Thanks to the analysis of the measurement results, it was possible to identify areas that are the basic source of sounds.

Open access

Andrzej Leski

Obliczenia Numeryczne Wytrzymałości Resztkowej Poszycia Statków Powietrznych z Uszkodzeniem Wielomiejscowym

Obecność wielomiejscowego uszkodzenia w strukturze statku powietrznego może doprowadzić do uszkodzenia katastroficznego, gdy wytrzymałość resztkowa struktury będzie niewystarczająca do przeniesienia obciążeń działających na konstrukcję. W prezentowanej pracy badano wpływ długości pęknięć MSD na wytrzymałość resztkową. Do symulacji numerycznych procesu rozdzierania wykorzystano kąt rozwarcia szczeliny pęknięcia (CTOA) jako kryterium pękania. Kryterium CTOA zostało zaimplementowane w programie komercyjnym MSC.Marc w postaci dodatkowych procedur użytkownika. Przeprowadzono weryfikację tej implementacji, a otrzymane wyniki są zgodne z prezentowanymi w literaturze. Wpływ długości pęknięć MSD wyznaczono dla dwóch konfiguracji pęknięć: z obecnością i bez obecności pęknięcia wiodącego.

Open access

Piotr Reymer and Andrzej Leski

Flight Loads Acquisition for PZL-130 Orlik TCII Full Scale Fatigue Test

The following article presents the research conducted under a complex structure integrity program for PZL-130 "Orlik" TC-II trainer aircraft. The aim of the research was to obtain the actual flight loads characteristic for the Polish Air Force which further on will be used to determine characteristic load spectrum for the Full Scale Fatigue Test purpose. This paper presents the methodology as well as a brief discussion of the obtained results.

Open access

Piotr Reymer and Andrzej Leski

Fatigue Life Estimation of the Tail Boom and Vertical Stabilizer of MI-24 Helicopter

The aim of this work was to estimate fatigue life of the Mi-24 helicopter tail boom and vertical stabilizer sheathing. The analysis was based on a numerical model of the helicopter airframe crucial to obtain stress fields under defined loads and to estimate fatigue life.

In order to do so, the load spectrum, specific for Polish army helicopters, was obtained by means of strain gauge measurements during a series of experimental flights. Data collected during flights was post-processed to create a characteristic ten hour spectrum that would statistically represent the flight profile for Polish Army Mi-24 helicopters.

The third crucial element of the analysis was the safe S-N curve that was created on the basis of 2024-T3 aluminum S-N curve. Two factors were introduced in order to change the curve in a way that would guarantee a higher level of certainty that the outcome is not overrated.

As a result of this analysis the total fatigue life was estimated including the list of critical locations in which fatigue damage is prone to occur. These regions are going to be carefully examined during scheduled inspections.

Open access

Andrzej Leski and Lukasz Obrycki

Representative Load Sequence for the PZL-130 Orlik

Open access

Marcin Kurdelski and Andrzej Leski

Crack Growth Analysis of the Landing Gear Pull Rod of the Fighter Jet Aircraft

This paper describes the problem of searching for the causes of damage in the form of rupture of a strength member of the main landing gear. There have been two incidents noted which both occurred during hangar storage. It should be pointed out that the two occurrences mentioned concern a particular aircraft currently in operation, and that these incidents occurred a few days after the last flight.

This article presents part of the investigation process needed to determine the causes of cracks in the test item. The crack growth analysis of the pull rod was performed using the NASGRO software. In order to perform the calculations, the information was gathered during previously conducted material studies and flight tests.

Open access

Andrzej Leski, Sławomir Klimaszewski and Marcin Kurdelski

The Fatigue Life Assessment of PZL-130 Orlik Structures Based on Historical Usage Data

Material fatigue is the basic factor limiting aircraft's durability. It comes from the fact that changing loads affect aircraft structure as well as from the fact that aircraft's mass restrictions do not allow for diminishing stress to the level when material fatigue does not occur. Estimating fatigue durability of a particular structure as well as its actual fatigue damage degree is possible when the history of loads affecting the structure is known.

Accuracy of loads monitoring influences the accuracy of indicated fatigue wear. In case of older structures, which have been maintained according to safe life principle, the number of hours have been commonly used as a fatigue wear indicator. After aircraft structure reaches flying time estimated by the produces, it is considered as fatigue wear and it is no longer in service. In case of a lack of results of loads spectrum measurements, results of tests conducted for other aircraft (of similar structure and assignment) can be used. For this purpose, average loads spectrum has been elaborated for particular aircraft groups, for example, HELIX, FELIX, FALSTAFF, ENSTAFF, TWIST(10). In the case of small aircraft, the data from FAA (2) report have been often used.

This article describes the way of fatigue wear estimation for PZL-130 Orlik aircraft on the basis of historical data from flight recorders.

Open access

Robert Baraniecki, Małgorzata Kaniewska and Andrzej Leski

Fatigue Life Assessment of Selected Structural Elements of MI-24 Helicopter

In order to ensure the integrity of the structure, it is important to determine the actual loads that act on individual elements and their influence on fatigue life. The article demonstrates how to determine the fatigue life of selected elements of the Mi-24 helicopter. In addition, the work indicates the potential location of damage. In calculations, the actual levels of loads acting on the elements during the flight were used. The entire test was performed using the numerical analysis, which greatly helped reduce the time of the project. Fatigue life was determined using the MSC. FATIGUE program with the Palmgren - Miner linear damage accumulation rule.