Michał Stefaniuk

Structural Load Monitoring Systems for Military Aircraft in the Polish Armed Forces with Examples of Selected Activities

Airplanes and helicopters currently operated by the Polish Armed Forces have been introduced into service without any load monitoring systems. The only exception is the F-16 and its Aircraft Structural Integrity Program.

Compressor Blade Fatigue Diagnostics and Modelling with the Use of Modal Analysis

Compressor Blade Fatigue Diagnostics and Modelling with the Use of Modal Analysis This paper investigates the diagnostic and research aspects of the compressor blade fatigue. The authors have reviewed the characteristics of different modes of metal blade fatigue (LCF, HCF, VHCF). The polycrystalline defects and impurities influencing the fatigue, along with their related surface finish techniques, have been taken into account. The experimental methods of structural health assessment have been considered. The Tip Timing (TTM), Experimental Modal Analysis (EMA) and Metal Magnetic Memory (MMM) provide information on the damage of the diagnosed object (compressor blade). It has been proven that the shape of resonance characteristics gives an ability to determinate if fatigue or a blade crack is concerned. Early damage symptoms, i.e. modal properties of material strengthening and weakening phases have been described. The experimental verification of the FEM model is presented based on a large body of experimental data collected by the author.

Use of a composite repair patches to repair the upper air intake flap for the MiG-29 aircraft engine

Abstract The Composite Patch Bonded Repair (CPBR) is one of the most cost-efficient types of aircraft structure repair. In the CPBR, the damaged structure is reinforced by applying a composite patch. The boron-epoxy composite (BFRP) is a popular choice for these types of repair. The BFRP was utilized to repair the cracked resistance welding joints in the upper flap of the MiG-29’s RD-33 engine intake. In the present paper, the numerical results are shown, along with the comparative tests of the undamaged inlet flap, the damaged inlet flap and of the CPBR repaired inlet flap.

Approach to Critical Crack Opening Displacement Modeling of Damage in Metal Sheets after Composite Patch Bonded Repair

Abstract The paper proposes a method of calculating the maximum displacement in the aircraft metal structure repaired by CPBR (bonded composite patch repair). The calculations were made based on specimens. The specimens were prepared according to the current requirements used in aviation. The 2024-T3 alloy metal sheet was a structure. To repair the structure used the boron-epoxy composite patch in prepreg technology was used. The metal structure was modeled as an isotropic elastic body. The metal structure coated with the composite patch was modeled as an orthotropic structure. Based on this, the stress was determined in the metal structure. The size opening displacement in the metal structure was determined based on the model of linear elastic fracture mechanics for the plane stress state. The calculation results were verified by measuring the displacement in laboratory conditions. The laboratory tests made it possible to demonstrate the accuracy of the proposed approach.

The Verification of the Technical Conditions of a Combat-Trainer Jet’s Airframe

Abstract The combat-trainer jet aircraft is an important element in the process of fighter pilot training. This type of aircraft provides a means of transition from basic training on low-speed propeller trainers to piloting high-speed and highly maneuverable fighter aircraft. Nowadays, in Poland, the PZL TS-11 “ISKRA” jet trainers, designed in 1960s, are employed for training purposes. Because of financial considerations this trainer hasn’t been yet replaced by modern aircraft that conforms to current specifications and needs. As is the case with other aircraft in service of the PLAF, the TS-11 fleet has a large reserve of remaining Hourly Service Life (HSL). This opens an opportunity to extend the Calendar Service Life (CSL), so as it matches the HSL. To this end, a series of technical and research activities needed to be undertaken. The Air Force Institute of Technology is conducting the necessary verification of airframe structural conditions in cooperation with the Military Aviation Works No. 1 J.S.C. (branch in Dęblin) responsible for the overhaul and repair operations. The AFIT’s activities in this program include: deformation analysis of the selected surface areas of the wing and the fuselage; assessment of hidden corrosion in riveted joints; non-destructive testing of selected riveted joints. This paper describes the deformation analysis. As of today, the first stage of the deformation inspection has been completed. At this stage, baseline surface measurements were obtained. Further inspections shall be performed cyclically. The future measurements will be used to establish the areas that deform due to the aircraft operation.

Monitoring of Crack Growth in a Structure Under a Composite Patch

Monitoring of Crack Growth in a Structure Under a Composite Patch In civil as well as in military aviation, boron, carbon and aramid fiber reinforced composites are employed for the repair of metal structures. After such composite bonded repairs, the monitoring of the repaired structure along with the composite patch and its bond is necessary. The paper describes the possibilities of utilizing NDT methods for periodical check-ups and examinations. Also, a novel approach to continuous monitoring of the repaired structure is presented.