<abstract><title style='display:none'>Abstract</title>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.</abstract>

Comparison of Selected Rivet and Riveting Instructions

<abstract><title style='display:none'>Abstract</title>Lightning strikes are a serious problem during operation of aircraft due to the increasing applicability of polymeric composites in aircraft structures and the weak electrical conducting properties of such structures. In composite structures, lightning strikes may cause extended damage sites which require to be appropriately maintained and repaired leading to increased operational costs. In order to overcome this problem various lightning strike protection solutions have been developed. Some of them are based on the immersion of metallic elements and particles while others use novel solutions such as intrinsically conductive polymers or other types of highly conductive particles including carbon nanotubes and graphene. The concept of fully organic electrically conductive composites based on intrinsically conductive polymers is currently being developed at the Silesian University of Technology. The results obtained in numerous tests, including concerning electrical conductivity and the capability to carry on high-magnitude electrical charges as well as certain operating properties need to be compared with existing solutions in lightning strike protection of aircraft. The following study presents the properties of the material developed for lightning strike protection and a comparative study with other solutions.</abstract>

Lightning Strike Protection of Aircraft Composite Structures: Analysis and Comparative Study

<abstract><title style='display:none'>Abstract</title>The paper presents a summary of non-destructive testing and evaluation (NDT&amp;E) methods applied in inspections of structural aircraft components. This brief review covers the most commonly applied methods such as visual and penetrant inspections, tap-testing, eddy current inspections, shearography, thermography, acoustic emission testing, radiographic and tomographic inspections, and ultrasonic inspections. The general operating principles of these methods as well as their main advantages, limitations and application areas are described below.</abstract>

A Brief Review on NDT&amp;E Methods For Structural Aircraft Components

<abstract><title style='display:none'>Abstract</title> The paper presents investigations undertaken in order to support developing the UAV airworthiness requirements, in particular those concerning fatigue aspects. Knowledge about UAVs load spectra is of vital importance for fatigue issues. The results of preliminary research are presented in this paper. A description of the load spectrum processing is given, starting from filtering the input-data, and then either counting the load signal transfers or implementing the Rainflow Counting algorithm and presenting the results in the form of a transfer array or halfcycles array. This description is illustrated by three examples of flight tests of 4-meter class UAVs, designed at Warsaw University of Technology. They concern flights controlled in a manual and automatic way in order to show differences between the LSs for such control modes. Besides the LS processing, a method for statistical analysis of load spectra from several flights is also presented to address the important problem of LS dispersion. Finally, there are shown selected tests of the UAV structure elements for which load spectra may have a crucial importance</abstract>

Airworthiness Tests of the UAV Structure − Fatigue Issues

<abstract xml:lang="en"><title style='display:none'>Thermal Fatigue Problems of Turbine Casing</title>This paper presents numerical stress analysis of the turbine casing of an aero-engine. To solve the problem, the geometrically complicated numerical model was created. The finite element method was used in computations. In results of nonlinear static analyses performed for both mechanical and thermal load occurred under operating condition of engine, the stress and deformation contours were generated. High thermal stress gradients were found at the region of casing where fatigue cracks were detected during engine operation.</abstract>

Thermal Fatigue Problems of Turbine Casing

<abstract xml:lang="en"><title style='display:none'>Experimental Crack Propagation Analysis of the Compressor Blades Working in High Cycle Fatigue Condition</title>This paper presents results of experimental vibration tests of the helicopter turbo-engine compressor blades. The blades used in investigation were retired from maintenance under technical inspection of engine. Investigations were conducted for selected undamaged blades, without existence of preliminary cracks or corrosion pits. The blades during experiment were entered into transverse vibration. The crack propagation process was conducted in resonance condition. During the fatigue test, the growth of crack was monitored. In the second part of work, a nonlinear finite element method was utilized to determine the stress state of the blade during vibration. In this analysis a first mode of transverse vibration were considered. High maximum principal stress zone was found at the region of blade where the crack occurred.</abstract>

Experimental Crack Propagation Analysis of the Compressor Blades Working in High Cycle Fatigue Condition

<abstract>
<title style='display:none'>Abstract</title>
This study focuses on the application and improvement of diffraction measurement methodologies for the optimization of manufacturing parameters of CoCr alloy components made by additive manufacturing (AM) – particularly for Mediloy S-Co alloy specimens made using Laser Powder Bed Fusion (LPBF) additive manufacturing. We measured the phase composition of specimens obtained in AM processes, the measurement of residual stresses resulting from the manufacture of these printed parts, as well as the effectiveness of stress relaxation through the use of heat treatments dedicated to this type of material. Findings reveal several insights into how printing strategies affect the porosity and residual stresses in additive manufacturing. Specimens with higher porosity, particularly those created using specific strategies that resulted in lower energy densities, exhibited lower residual stresses. Notably, printing direction and energy density were found to significantly affect the mechanical stresses within the specimens, with directional choices playing a critical role in the final properties of the parts. Additionally, our findings underscore the complex relationship between various printing parameters and the development of mechanical stresses, highlighting the impact of adjustments in printing strategy on the properties of printed components.
</abstract>

elzbieta.gadalinska@ilot.lukasiewicz.gov.pl

Development of Diffraction Research Methodologies for Mediloy S-CO Alloy Speciments Made Using LPBF Additive Manufacturing

<abstract>
<title style='display:none'>Abstract</title>
The currently accepted rules that are applied to the aircraft cable-control systems’ operational use are based on the reactive maintenance idea and the comparative tests, inspections, and diagnostics performed at the mandatory intervals. Fatigue tests of the aviation cables are commonly conducted by bending in the range of ± 90° with constant load. Aircraft cable-control systems are subject to a number of random loads and deformations. Additionally, forces and their values are modified by the wear and tear of cable-pulley raceways, elastic deformations, and changes caused by temperature. The actual values of tension of aviation cable-control systems are relatively low, and bending usually does not exceed the maximum of ± 35°. Moreover, the forces characteristic of the control cables are nonlinear functions of the control surface deflection. This means that the typical fatigue tests we employ help with only comparative estimations and acceptance tests. It is not possible to estimate the operational durability of the systems and forecast inspections and diagnoses intervals based on the mentioned results. The present article utilizes the operational profiles of selected aircraft categories to determine the stochastic load-related deflection spectra for the preparation of cable fatigue-testing programs. Operation profiles are built considering a group of aircraft belonging to the same category, performing similar missions, for example, training missions, photogrammetric missions, aircraft towing, e.q., and having a similar share in the total resource. The special stands for the selected cable fatigue tests have been proposed. The cable test stand ensures the real stochastic loads for the cable use and other actual conditions of load. The proposed stand enables the simultaneous testing of more than one cable at different deformation parameters, for example, wrap angles. The results of the proposed method and tests can be used to estimate the operational durability of aviation-control systems as well as for inspection and diagnosis intervals as well.
</abstract>

Some Comments Concerning the Preparation of and Fatigue Testing of the Aircraft’s Cable-Control System

<abstract>
<title style='display:none'>Abstract</title>
The present article discusses the three-dimensional (3D) printing process in the fused deposition modeling (FDM) or the fused filament fabrication (FFF) technique using the author’s own philosophy of shaping the printing head path. The main requirements are the possibility of eliminating supports and reducing or even eliminating the need for the mechanical processing of 3D prints before their final assembly. The presented methodology was implemented in a computer program written by the author and was used to print typical parts used in aviation. Individual methods of shaping parts typical for the construction of small flying models, such as wings and fuselages, and methods of strengthening and connecting them have been discussed. The proposed solutions are illustrated with photos of readymade prints. This article also discusses the issues that printing high-quality parts may encounter and how to avoid them. Some attention has also been paid to the materials used for printing and their suitability in the construction of aircraft and their fatigue strength.
</abstract>

krzysztof.szafran@ilot.lukasiewicz.gov.pl

Using Own Algorithms to Increase the Quality and Fatigue Resistance of FDM Printing for Use in Drones and Small Aircraft

<abstract>
<title style='display:none'>Abstract</title>
This paper evaluates the efficacy of a patented grip for high-temperature fatigue testing by establishing the S-N curve for full-scale nickel-based turbine blades under simulated environmental conditions. Initially, a bending test assessed the stress-displacement characteristics of the component. This was followed by a series of fatigue tests at 950°C, using cyclic bending with force amplitudes from 5.2 kN to 6.6 kN and a constant frequency of 10 Hz. The setup, integrating the grip into a standard testing machine, proved effective for high-temperature tests and successfully determined the service life of full-scale components.
</abstract>

High-Temperature Fatigue Testing of Turbine Blades

<abstract>
<title style='display:none'>Abstract</title>
In response to the steady rise in global demand for energy resources such as gas and oil, there is a pressing need to enhance the efficiency and safety of pipeline transportation systems. These systems, integral for transferring vast amounts of energy, must operate under increasingly higher pressures and larger diameters without compromising reliability. This study focuses on utilizing finite element analysis (FEA) to investigate the influence of crack orientation and the presence of defects on the fatigue life of pipelines. By simulating internal pressure scenarios and examining various defect characteristics with the AFGROW software, this research applies damage tolerance principles to offer insights into the fatigue behavior of pipelines. The findings can be applied to extend the operational life and ensure the integrity of these critical infrastructures, thereby supporting the sustainable and safe transport of energy resources.
</abstract>

Investigating the Effects of Crack Orientation and Defects on Pipeline Fatigue Life Through Finite Element Analysis

<abstract>
<title style='display:none'>Abstract</title>
In this work, cast steel G17CrMoV5-10 was investigated. The material subject to investigation as part of this study is commonly used to manufacture steam turbine casings. Modern steam turbines operate under elevated temperature and complex oscillated loads. Thus, the focus of this study was to investigate material under behavior during low cycle fatigue (LCF) test performance at 500°C with and without hold time in tension. During all types of test, cyclic softening of cast steel was noticed. Increasing of total strain rate and applying hold time significantly reduce fatigue life. During hold time, due to temperature and tension the material creep what is confirmed by increasing inelastic stain accommodation.
</abstract>

Effect of Strain Range and Hold Time on High Temperature Fatigue Life of G17CrMoV5-10 Cast Alloy Steel

<abstract><title style='display:none'>Abstract</title>From the safety point of view, one of the most important issues regarding aircraft operations is ensuring the durability of the structural components. Corrosion processes can have a significant effect on the integrity of structural materials and are usually associated with aircraft aging. Due to the variety of materials used, environments and loads impacting the planes, a wide range of different types of corrosion may occur in aircraft structures. The main aim of this study is to present some theoretical knowledge related to corrosion processes as well as problems of aircraft structures associated with corrosion occurrence. Firstly, the paper presents a brief overview of what corrosion is and what different types of corrosion are. Secondly, some selected aircraft failures caused by corrosion are shortly presented and discussed.</abstract>

Aircraft Corrosion – Review of Corrosion Processes and its Effects in Selected Cases

<abstract><title style='display:none'>Abstract</title>This article presents a concept of the full scale fatigue test of a Su-22 fighter bomber. The authors define the general concept and goals of the test as well as the tasks to be accomplished in the preparation stage. The current work status is summarized and future tasks are defined.</abstract>

The Concept of a Full Scale Fatigue Test of a Su-22 Fighter Bomber

<abstract><title style='display:none'>Abstract</title>Seat cushion inserts in military helicopters crew seats, as suggested by the helicopters manufacturers, are made of traditional polyurethane foams.Elastic polyurethane auxetic foams are materials that exhibit different utility properties compared to traditionally used polyurethane foams, such as polyether or polystyrene foams. All the differences result from the primary physical property of elastic polyurethane auxetic foams which is a negative Poisson’s ratio. Auxetic materials are characterized by better utility properties than conventional foam materials – they can potentially increase safety in the event of a crash and offer higher comfort during regular use. Application of auxetic materials as seat cushion inserts would also decrease harmful health effects of vibrations.This paper presents the results of the fatigue tests carried out on different foam samples by pressing an indenter into the foams' surface that was much larger than the indenter’s surface. A maximum value of the load used during the test was within a defined range in every fatigue cycle.In order to test 150×150×50 mm foam samples a special indenter was designed and manufactured according to the PN-EN ISO 3385 and PN-EN ISO 2439 standards. The indenter’s dimensions were consistent with the standards in relation to the tested foams' size.The fatigue tests of both conventional and auxetic foams were carried out according to the above given standards by applying 80,000 load cycles at 70 cycle/min frequency. Tests of viscoelastic foam and multilayer foam specimens, for which the upper layer was made of viscoelastic foam, were carried out according to the ASTM D 3574 standard applying 12,000 load cycles at 10 cycle/min frequency. All the tests were carried out using the MTS 370.10 strength testing machine.Changes in thickness and density were determined throughout the tests. Moreover, the influence of the volumetric compression ratio on the fatigue properties of auxetic foam samples and the dependence of foam deflection on the number of cycles were examined. Finally, the test results obtained for conventional and auxetic foams were compared and discussed.</abstract>

Fatigue Properties of Polyurethane Foams, with Special Emphasis on Auxetic Foams, Used for Helicopter Pilot Seat Cushion Inserts

<abstract><title style='display:none'>Abstract</title>This paper presents two techniques of active thermography i.e. the pulsed thermography technique and the step heating technique. The aim of this article is to compare these two techniques and present the possibilities, advantages and limitations of their use in the context of non-destructive testing of composite materials. The experimental section presents the results of tests carried out on samples of the polymer composites reinforced with glass fiber.</abstract>

Comparison of Pulse Thermography (PT) and Step Heating (SH) Thermography in Non-Destructive Testing of Unidirectional GFRP Composites

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Fatigue of Aircraft Structures

The Journal of Institute of Aviation

 Print ISSN - 2081-7738Online ISSN - 2300-7591   The primary version of the journal is the online one.   Based on the decision of the Minister...

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 Print ISSN - 2081-7738Online ISSN - 2300-7591   The primary version of the journal is the online one. ...