Foreign Object Damage Research Articles

Time-Lapse Photography of Runway Reconstruction for Education and Training

Airfield construction projects have unique construction challenges because of their close proximity to aircraft operations. During these projects, communication, safety areas, airspace protection zones, and foreign object damage are emphasized. Incursions and incidents are of significant concern to FAA, the airport operator, and the contractor. This paper discusses and illustrates how time-lapse photography can be used to develop training and educational material pertaining to the construction practices on airfields. This proposed idea is illustrated through case studies documenting runway reconstruction at two airports in Indiana. The paper is supplemented by several images and with links to YouTube videos to illustrate these concepts. This material is beneficial for training construction workers in airfield awareness, and it provides an overall understanding of the complexities of airside construction. Although this paper focuses on general aviation airports, the material can be of value to all sizes and types of airports. With some modifications and support, the proposed techniques could be applied to larger airports.

The Future of Conventional Aircraft Ground Propulsion Systems in Relation to Fuel Consumption and CO2 Emission

Aircraft spends a minimum of 20 minutes using its main engine to taxi from the airport terminal gate to the runway, where the aircraft takes-off and similarly to the terminal gate after landing. During taxi operation, aircraft burns a lot of fuel, generates large quantity of emissions and the engine in the process of taxiing is exposed to damage due to Foreign Object Damage (FOD). This results in huge operational and maintenance cost as well as carbon emission tax which are all at the expense of the airline. EGTS is a recent technology designed to prevent aircraft from using its main engine for taxi operation and this in turn reduces the rate of fuel consumption, slashes carbon emissions and minimises operational and maintenance cost. This paper examines the viability of using EGTS in single engines for taxi operation rather than the aircraft engine. Block fuel savings was calculated for two engine, single engine and hybrid aircraft and it was observed that two engine aircraft using EGTS saved 110kg block fuel, single engine saved 74kg and for hybrid engine the block fuel savings was 50kg. Block fuel savings was calculated for aircraft such as airbus A320, airbus A380, Cessna 172 and A600ST and it was observed that EGTS is more compatible with airbus A320 but was not recommended for A600ST and A380 due to extra weight implication and for Cessna 172, EGTS was not necessary because the aircraft weight is low and consumes less fuel already. It was observed that the higher the aircraft weight including the extra weight of EGTS, the higher the fuel consumption emission as well as the torque required to overcome drag force when the aircraft operates in air. CO2 emission was also calculated for aircraft with EGTS and aircraft without installation, the result for aircraft with EGTS showed 797.56kg reduction of CO2 emission when compared to aircraft without EGTS. Comparably, EGTS was proven to be viable in terms of fuel savings, CO2 emissions, operational and maintenance cost than its contemporary Ground Propulsion Systems (GPS) for single aircraft engines and therefore, was recommended for aircraft in airbus A320 category to help minimise global warming which results from CO2 emission during taxing operations.

A study of foreign object damage (FOD) and prevention method at the airport and aircraft maintenance area

Foreign object damage (FOD) is common risk for aviation industry since long time ago and it has contributed to many terrible incidents and fatalities. The cost of FOD cases every year is very high, which is around RM 1.2 billion. Therefore, a proper technique and strategy has to be taken by the designated organizations including airlines to further eliminate the FOD occurrences. It is not easy to control FOD due to some circumstances such as inappropriate working behaviour, poor working environment, insufficient technology and also disorganized housekeeping system. The main purpose of this research is to discuss and explain further about FOD and the techniques to prevent FOD. FOD is a universal concern in aviation industry and it is one of the reasons that contribute to aircraft failure and unwanted damages such as fatalities and causalities. Throughout this research, many information related to FOD problems and their impact on aviation industry are gathered and presented.

Foreign Object Damage in an Oxide/Oxide Ceramic Matrix Composite Under Prescribed Tensile Loading

Foreign object damage (FOD) behavior of an N720/alumina oxide/oxide ceramic matrix composite (CMC) was characterized at ambient temperature by using spherical projectiles impacted at velocities ranging from 100 to 350 m/s. The CMC targets were subject to ballistic impact at a normal incidence angle while being loaded under different levels of tensile loading in order to simulate conditions of rotating aeroengine airfoils. The impact damage of frontal and back surfaces was assessed with respect to impact velocity and load factor. Subsequent postimpact residual strength was also estimated to determine quantitatively the severity of impact damage. Impact force was predicted based on the principles of energy conservation.

WEIGHT OPTIMIZATION OF FTAC SECONDARY STRUCTURE OF AN AIRCRAFT

The Fuel Tank Access Covers (FTAC) primary function is to provide the aerodynamic surface on the lower wing at the Fuel Tank Access Manholes. These manholes are used in maintenance to access the inside of the wing box. The FTACs also provide sealing of the fuel bays. Fuel Tank Access Cover area include wings, control surfaces, aero engine nacelles, fan casings, etc. These are all safety critical components which may be subjected to high velocity impacts due to bird strike or foreign object damage (FOD). Typically on wing leading edges, nacelles, or on fan blades causing fan blade debris to impact fan casings and wing or fuselage structures. Analysis tools, such as finite element (FE) codes for predicting structural stiffness and strength of the structures under quasistatic loading with relevant materials data. The aim of the present work is to optimize the Fuel tank Access Cover. As the weight optimization of each component in the Aircraft plays as a significant role in the performance of the aircraft. The 3D modeling of fuel tank access plate is designing using PRO-E and FEA analysis especially structural analysis was done using ANSYS. The structural strength of the Inner Cover, Outer Cover, and Fasteners are validated. Objectives  To study about the FTAC design.  To study various conditions which can be replicated to get the most approximate results?  To demonstrate a CAD model of FTAC by using predominant software PRO (E).  To develop a Finite Element Model of Fuel Tank Access Cover accurately to the dimensions with the limited information available as any company does not release all the designs data. To determine the structural behavior of Fuel Tank Access Cover with different boundary conditions by using ANSYS software.

Compressors for ultra-high-pressure-ratio aero-engines

A highly efficient, robust compression system is a key part of any high-performance core engine that is to be developed for meeting future low emission requirements, i.e., for significant reductions in CO2, NOx, and other gaseous emissions. Not only does the compression system has to deliver the increased OPR demanded by the thermal cycle. It has to do so more efficiently to avoid excessive increases in cycle temperatures and weight to avoid reducing the benefit from the new cycle. This challenge is made harder, as OPR is increased up to 70:1, as core-engine size will reduce introducing greater threats to efficiency and compressor stability margin through: (1) lower Reynolds numbers that will result in higher blade losses; (2) tip and shroud/seal clearances increasing due to physical size limitations; (3) if manufacturing tolerances are maintained, blade and vane leading edges, maximum thickness, and fillets radii will be relatively larger; (4) the threat of inclement weather, deterioration, and foreign object damage (FOD) will be greater as compressors get smaller; (5) high aspect ratio blade design will be applied to limit the relative weight and length increase due to required pressure ratio increase of the compression system; (6) higher OPR compression systems will require more stability improvement features, such as VSVs, bleeds, and rotor tip treatments. This paper gives an overview of the above issues and how the FP7 integrated project LEMCOTEC is addressing them through CFD simulations, low- and high-speed rig tests, and innovative designs.

Characterization of Damage Induced by Impacting Objects in Udimet-500 Alloy

Foreign object damage (FOD) is one of the common mechanisms in turbine blade failures which reduces high cycle fatigue life and contributes significantly to premature failure. Therefore, this study experimentally simulated FOD on the first stage blade of a gas turbine. Foreign objects with two parameters of object nose shape (spherical, conical, and flat) and impact angle (90° and 45° relative to the blade surface) were impacted on the surface of flat specimens of Udimet-500 at a temperature of 733°C with velocity of 300 m/s (same as working condition of blades). In order to evaluate the impact site morphologies, induced craters were first studied by scanning electron microscopy (SEM). Then samples were sectioned symmetrically, and by using image analysis tool software, the depth of each crater was measured. Finally, based on the results, it was found that maximum and minimum stress concentration factors and induced microcracks, respectively, are regarding to flat projectiles with impact angel of 45° and spherical at impact angle of 90°.

Experimental Fatigue Analysis of Compressor Blades with Preliminary Defects

This work presents results of the experimental fatigue analysis of the compressor blades. In the investigations the blade with the V-notch (which simulates the foreign object damage) was considered. The notch was created by machining. The blades during the fatigue test were entered into transverse vibration. The crack propagation process was conducted in resonance conditions. During investigations both the amplitude of the blade tip displacement and also the crack length were monitored. As the results of presented investigations both the number of load cycles to crack initiation and also the crack growth dynamics in the compressor blade subjected to resonant vibrations were determined. In the work the influence of crack size on the resonant frequency was also investigated.

Explicit Finite Element Modelling as a Development Tool for New Ultrasound Testing Methodologies for Detection and Characterization of Porosity and Defects in Composites

Abstract Composite components frequently contain porosity or defects, which might, in some circumstances, be deemed benign. Other defects could lead to progressive or sudden failure in service; hence reliable and accurate material condition monitoring and health assessment is an important prerequisite for further design for the use of composite materials in high duty and life sensitive engineering components. The objective of this paper was to demonstrate the use of explicit finite element as an effective development tool in the development of ultrasound testing methodologies for the characterization of porosity in composites – a virtual ultrasound vibration laboratory. This would enable an improved inspection sentencing capability for as-manufactured composite structural components. It would also be of benefit in sentencing components subject to foreign object damage (FOD) in order to determine whether the component can continue in service, possibly with in-service monitoring or cosmetic repair, or must be condemned. In this work, finite element models simulating damage and porosity were presented. The models were compared with ultrasound tests on real specimens with practically relevant defects. Experimental tests, making use of wave superposition from two piezo-electric vibration sources, were shown to detect energy absorbing damage in the specimen, such as might have been created by impact or crush loads. The same piezo-electric vibration system was also used to measure the dissipated energy. Computational analysis, using simple material model variations, was able to replicate the Lamb wave generation and evolve a wave form resembling a “standing wave.” The computational material model was modified to represent porosity in composites.

Influence of Foreign Object Damage on High Cycle Fatigue of Ti–6Al–4V Alloy

The influence of foreign object damage (FOD) on high cycle fatigue (HCF) of Ti–6Al–4V alloy has been investigated. FOD was induced by shooting 3.2 mm diameter steel spheres at a velocity of 300 m/s on the centre of flat plate specimens using a compressed air gun facility. Both normal and 60° angular impacts were carried out. In order to assess debit in the fatigue strength due to notch effect, machined notches of the same notch profile (radii and depth dimensions) as those observed in high velocity impact were also tested. The tests were conducted at room temperature and at two R ratios of 0.1 and 0.5. Fatigue life was found to be reduced in FOD impacted samples and the debit in fatigue life was much larger than that for machined notch specimens. This might be attributed to the effect of residual stresses. Further, the role of residual stresses were also brought out by comparing results of HCF tests at R = 0.1 and R = 0.5. As expected, a larger debit in fatigue life was found to occur at low R values where residual stresses were not expected to be relaxed. No significant differences in fatigue life between the normal and angular impacted samples was noticed. Optical and SEM investigations were carried out to examine the shape of the indents and micro-structural features.

Microstructural change and impact toughness property of Inconel 738LC after 12years of service

The Domestic and Foreign Object Damage (DOD & FOD) are knownas serious problems for many heavy duty (or high temperature) device such as compressor, different turbine sections of jet engines and gas turbine, therefore the impact resistance study plays an important role to prevent any catastrophic failures. In this study a V94.2 Siemens gas turbine blade was used, which has been exposed to hot gases, heating the material to a temperature of 800–900°C in 105,120 operating hours. Initial metallographic investigation confirmed microstructural damage in the airfoil compared with the root of turbine blade.Charpy V-Notch tests were made according to the specification ASTM-E23 in ambient and service temperature (900°C). The fracture surfaces of the Charpy specimens were analyzed with the scanning electron microscopy,in order to identify the fracture mechanisms. The results showed that, with increasing the test temperature from 25 to 900°C, the impact energy of the root in both temperatures were relatively equal and far from airfoil. The microstructural investigation confirmed that the microstructure of airfoil was damaged due to the long operation at high temperature. Also, rafting behavior is observed in airfoil section.Fractographic investigations showed fracture mechanism of transgranular cleavage and dimples in the airfoil and root specimens in both temperatures.

Progress update on failure mechanisms of advanced thermal barrier coatings: A review

Abstract Thermal barrier coatings (TBCs) have proved to be a key technology in thermal stability and their use to achieve surface temperature reduction of the underlying super alloys surpass all other achievements in the field of material technologies that have taken place in last three decades. The technological advances in TBCs also make them suitable for wider engineering and defense applications. The performance of these multi-layered and multi-material systems, tailored for high temperature applications is closely linked to their microstructure evolution. The article presents a comprehensive review of various degradation mechanisms to which the TBC system is subjected during service life viz. hot corrosion, CMAS attack, oxidation, erosion, foreign object damage, sintering and phase transformations. Strategies to mitigate the adverse impact of the degradation mechanisms and the recent advances toward reduction in the thermal conductivity of TBCs have also been discussed. The emphasis of this review is on the relationship between the properties and the microstructure of TBCs for better understanding of their life limiting mechanisms to assist developments in advanced and novel TBCs for engineering applications.

Fatigue analysis of compressor blade with simulated foreign object damage

In this work the fatigue analysis of aero engine compressor blade subjected to resonant vibration was performed. In experimental investigations the blade with V-notch which simulates the foreign object damage (FOD) was considered. The notch located on the leading edge of the blade was created by machining. Mechanical defect (FOD) causes a considerable decrease of the fatigue life of blade working in resonance conditions. The main assumption of experimental investigations was to maintain the constant vibration amplitude during the blade fracture. As a result of performed investigations both the number of load cycles to crack initiation and also the crack growth dynamics were determined. In the last part of the work the finite element method (FEM) was used in order to determine the stress field in the blade with V-notch, subjected to resonant vibration.

Finite Element Modelling and Investigation of the Process Parameters in Deep Rolling of AISI 4140 Steel

The application of beneficial residual stresses in components is often used to increase their fatigue life and resistance to FOD (Foreign object damage). There are several production processes having the main aim to induce beneficial compressive residual stresses at the surface and on the sub-surface level in components. As examples can be mentioned the shot peening, autofrettage, laser shock peening, ultrasonic impact treatment and DR (Deep rolling) processes. The prediction and measurement of the induced residual stresses is always difficult and a time-consuming and therefore, the employment of the FEA (Finite element analysis) to model such processes can be very profitable. In this article the explicit module of the FE-Code ABAQUS 6.13 was applied to model the DR process on a plane geometry. The input parameters applied force, number of overturns and percentage of overlapping are varied and their influence on the resulted depth profile of residual stresses is commented on.

Multi-length-scale derivation of the room-temperature material constitutive model for SiC/SiC ceramic-matrix composites

In the present work, multi-length-scale physical and numerical analyses are used to derive a SiC/SiC ceramic matrix composite (CMC) material model suitable for use in a general room-temperature, finite element-based, structural/damage analysis of gas turbine engine components. Due to its multi-length-scale character, the material model incorporates the effects of fiber/tow (e.g. the volume fraction of the filaments, thickness of the filament coatings, decohesion properties of the coating/matrix interfaces, quality, as quantified by the Weibull distribution parameters, of the filament, coating, and matrix materials, etc.) and ply/lamina (e.g. the 0°/90° cross-ply vs. plain-weave architectures, the extent of tow crimping in the case of the plain-weave plies, cohesive properties of the inter-ply boundaries, etc.) length-scale microstructural/architectural parameters on the mechanical response of the CMCs. To identify and quantify the contribution of the aforementioned parameters on the material response, detailed numerical procedures involving the representative volume elements and the virtual mechanical tests are developed and utilized. The resulting homogenized turbine-engine component-level material model is next integrated into a user-material subroutine and used, in conjunction with a commercial finite element program, to analyze the foreign object damage experienced by a toboggan-shaped turbine shroud segment. The results obtained clearly revealed the role different fiber/tow and ply/lamina microstructural parameters play in the structural/damage response of the gas-turbine CMC components.

Computational investigation of foreign object damage sustained by environmental barrier coatings (EBCs) and SiC/SiC ceramic-matrix composites (CMCs)

Purpose – The purpose of this paper is to prevent their recession caused through chemical reaction with high-temperature water vapor, SiC-fiber/SiC-matrix ceramic-matrix composite (CMC) components used in gas-turbine engines are commonly protected with so-called environmental barrier coatings (EBCs). EBCs typically consist of three layers: a top thermal and mechanical protection coat; an intermediate layer which provides environmental protection; and a bond coat which assures good EBC/CMC adhesion. The materials used in different layers and their thicknesses are selected in such a way that the coating performance is optimized for the gas-turbine component in question. Design/methodology/approach – Gas-turbine engines, while in service, often tend to ingest various foreign objects of different sizes. Such objects, entrained within the gas flow, can be accelerated to velocities as high as 600 m/s and, on impact, cause substantial damage to the EBC and SiC/SiC CMC substrate, compromising the component integrity and service life. The problem of foreign object damage (FOD) is addressed in the present work computationally using a series of transient non-linear dynamics finite-element analyses. Before such analyses could be conducted, a major effort had to be invested toward developing, parameterizing and validating the constitutive models for all attendant materials. Findings – The computed FOD results are compared with their experimental counterparts in order to validate the numerical methodology employed. Originality/value – To the authors’ knowledge, the present work is the first reported study dealing with the computational analysis of the FOD sustained by CMCs protected with EBCs.

Quantification of Foreign Object Damage and Electrical Resistivity for Ceramic Matrix Composites and Tensile Residual Strength Prediction

SiC-based ceramic matrix composites (CMC) in turbine engine applications must sustain certain foreign object impacts (FOIs) that might occur in services. Experiments and nondestructive evaluation (NDE) have illustrated good correlations between impact energy and foreign object damage (FOD) assessed using electrical resistivity (ER), acoustic emission (AE), and microscopy. A progressive failure dynamic analysis (PFDA) method is explored in understanding and predicting the damage states, ER, and residual strength after impact of CMCs. To accurately correlate the damage state with ER, the PFDA tool has been improved to incorporate the physical damage mechanisms in CMCs, which are matrix microcrack density due to both longitudinal and transverse tensile loads and the fiber breakage due to probabilistic fiber strength distribution. The predicted damage states and ER are correlated with the measurement of FOD and validated with tension after impact tests using high temperature ER. The PFDA tool has demonstrated a great potential for CMCs' FOD and residual strength predictions.

Investigation of Flame Blow-Out in a Low Bypass Military Turbofan Engine

Flame blow-out is a serious concern for military gas turbine engines, and maintaining a reliable and stable flame in engine throughout the mission is a great challenge. A low bypass military turbo fan engine is investigated for flame blow-out. The history of the engine and its accessories were reviewed. Flight data were analyzed to confirm the blow-out incident. Air flow passages and engine modules were examined for possible foreign object damages or internal damages and found satisfactory. Analysis of atomizer characteristics showed the shifting of spray cone angle and fuel flow rate close to the lower limits. Blockage of atomizer flow passages and liner front end flares could contribute to flame blow-out. One of the filters in the fuel line found damaged. Significant amount of debris were found inside the fuel control valve. From the investigations and evidences, it was concluded that the engine flame blow-out was due to blockage of fuel flow when the air flow was almost steady. Assessment and control of debris in fuel accessories, the periodicity of inspection, and cleaning are very important for maintaining a stable flame throughout the mission. Also understanding the blow-out mechanism in an aero gas turbine engine during maneuvers is necessary to address blow-out issues.

Mechanism of Foreign Object Damage and Investigating Effect of Particle Parameters on Erosion Rate of a Rough Surface Using Experimental and Numerical Methods

In many industrial applications, we deal with the impact of micron-scale particles onto a target surface. So, a large number of studies have been conducted to perceive damage mechanism and identify effective parameters of this phenomenon at micron scale. In all of these studies, target surface has been considered as ideally smooth. However, it is very obvious, the ideally smooth surface is not imaginable at this micron level and a few works have been performed on rough surface. In this paper, single impact of micron-scale particle onto a small area of rough surface was simulated using ABAQUS/Explicit Version 6-11. In our experimental study, damage mechanism of rough surface due to multiple particle impact on a large area of a real turbine blade surface was studied and the created zones were characterized. Also, permanent impression was expressed for the damage mechanism. The experimental results were implicated from the simulated model in order to validate the present numerical study. Effects of the particle parameters including particle shape, impact location, and impact angle on erosion rate were separately investigated. For each of them, a simple power relation in terms of erosion rate was reported using finite element model calculation.

Performance of Grooved Warm-Mix Asphalt Pavement Surfaces under Heavy Aircraft Load and High Tire Pressure

This paper presents an evaluation of the performance of grooved warm-mix asphalt (WMA) under heavy aircraft loading compared with that of grooved hot-mix asphalt (HMA). Runway surface grooving is often required to provide high skid resistance for aircraft braking, particularly in wet conditions where hydroplaning must be minimized. An area of potential concern with the use of WMA on the surface of airfield runway pavements is the material response to surface grooving. If the asphalt binder in WMA is softer than that of comparable HMA because of reduced binder aging during production and placement, the WMA mixture may be more likely to experience groove closure or collapse. This condition could result in hydroplaning issues because of the reduction in water discharge and also in chipping of aggregate from the groove edges, which could increase the potential for foreign object damage. A full-scale experiment was designed to evaluate two pavement curing conditions and three WMA mixtures. Traffic was applied to the pavements with an F-15 load cart, and testing occurred during the summer of 2013. The performance of WMA, measured as the percentage of groove closure, was compared with that of comparative HMA. It was concluded that WMA could perform as well as HMA under different pavement curing conditions. This result indicates that WMA runway surface pavement that is properly cured before grooving should not exhibit groove closure under normal aircraft traffic conditions.