Surface of Metal as an Indicator of Fatigue Damage (original) (raw)
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Extrusion/intrusion structures as quantitative indicators of accumulated fatigue damage
International Journal of Fatigue, 2012
a b s t r a c t Two approaches to aircraft fatigue monitoring by the computer-aided analysis of surface structures are described: (a) application of fatigue indicators attached to the aircraft unit; (b) the direct observation of the alclad aluminium alloys surface. The evolution of aluminium surface state has been monitored at various fatigue loading regimes. Some parameters have been used for the quantitative analysis of surface structures: (a) density of slip lines for single-crystals; (b) intensity and fractal dimensions of the deformation relief for polycrystalline aluminium. The possibility of a fatigue process prediction both at crack initiation stage and fatigue crack propagation stage is shown.
2013
CITATIONS 3 READS 65 4 authors, including: Some of the authors of this publication are also working on these related projects: Surface relief as an indicator of accumulated fatigue damage View project Abstract: The possibility of fatigue damage analysis by the extrusion/intrusion structures on the surface of aluminium alloy is shown. Quantitative characteristics of the extrusion/intrusion structures and the methods for their monitoring are substantiated. Two approaches for fatigue analysis are presented: a) direct inspection of the aircraft components, b) application of fatigue sensors.
Skin Surface Extrusion/Intrusion Structure as an Indicator of Aging Aircraft Fatigue
Problems of Friction and Wear
A new method for fatigue damage detection is proposed. The new method extends earlier proposed and verified approach for fatigue damage assessment based on the quantitative analysis of surface deformation relief on aluminium and some of its alloys. It will be shown that the fundamental property of hidden persistent slip bands to be revealed after secondary cyclical loading can be used for the fatigue analysis of aging aircraft.
2012
It is shown that the deformation pattern is formed under cyclic loads and develops on the surface of the cladding layer of a structural aluminum alloy. The quantitative parameters of the deformation pattern, namely, the saturation, roughness, and plastic strains on the surface, serve as indicators of damage to the material. The experimental dependences of the analyzed parameters on the operating time (number of loading cycles) can be used for the creation of new methods aimed at the prediction of the limit state of structural elements of the aircraft structures. Keywords: deformation pattern, interference profilometry, fatigue, parameters of the deformation pattern. The processes of fatigue damage in metals connected with the formation and evolution of the dislocation structure, plastic loosening, and microfracture are localized in the surface layer. More intense plastic deformation of the surface as compared with the bulk of the material enables us to interpret the surface layer as...
Possibility of fatigue damage detection by non-destructive measurement of the surface hardness
Procedia structural integrity, 2017
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
An Evaluation Study on Fatigue Life of U-shape Aluminium and Structural Steel Fatigue Sensor
2016
Fatigue is the most widely recognized reason for failure in metal structures. Fatigue is not a new phenomenon, it has confounded researcher for more than 200 years. The issue with fatigue makes attention with the applications of metal in various structures. In recent years, impressive efforts have been made for the development of analytical and additionally numerical models for the better estimation of fatigue life for critical component structures. Developing a fatigue damage detection sensor to monitor the structural damage accumulation of critical mechanical or structural components working under cyclic loads before any fatigue failure occurs. The practice of designing structures to take into account fatigue is highly abstruse since the actual loading history of the structure is not known and cannot be accurately predicted. In this way, there is a requirement for a device which would monitor fatigue damage and provide a reliable estimate of remaining fatigue life of a specific st...
e-Journal of Nondestructive Testing, 2023
Strength hardened aluminum alloys as 7075-T6 al are widely used in aeronautical industry due to their low density and high mechanical properties. Their specific microstructural composition makes them sensitive to corrosion damage at intermetallic particles. Aeronautical parts are often submitted to corrosive environments and fatigue loadings. For safety and economic matters, it is important to be able to monitor the development of damages during application. In this context, Acoustic Emission (AE) is a useful tool to monitor the state of material damage and predict its remaining useful lifetime. This work, which is part of a larger European project (Early detection and progress monitoring and prediction of corrosion in aeronautic Al alloys through calibrated Ultrasonic-CorROSion Sensor application), has for main objective to understand, identify and quantify, via AE, how corrosion defects impact the fatigue behaviour of aluminum alloy 7075-T6 specimens and covered with different types of coatings (top coat, primer and a conversion coating obtained by anodizing process). Therefore, tensile-tensile fatigue tests (R = 0.1) monitored with AE are performed at room temperature on non-corroded samples and on corroded samples. Precorrosion defects are generated by the complete immersion of the samples in an NaCl bath (3.5% wt). Pre-corrosion defects tend to decrease the fatigue lifetime of the material tested and create damage in the substrate and coatings generating new AE sources. For all types of coated specimens, damage indicators based on the AE activity are studied in order to find characteristic damage times giving information on the remaining useful lifetime of the material during fatigue tests. Characteristic times linked to damage initiation in the substrate and propagation the main fatigue crack in the material are defined.
Structural and Fractographic Analysis of Aluminum Alloy before and After Fatigue Loading
Manufacturing Technology
The article is focused on the analysis of the structure and fracture surface of aluminum alloy specimens. Aluminum alloy AlMg9 was mainly used as an experimental material. The material from which specimens were made was supplied as cast without heat treatment, and specifically the material was produced by the continuous casting method. The structure of the test material was examined using a Neophot 32 optical microscope, and the fracture surface of the test specimen was examined using a scanning electron microscope (SEM). The fatigue life of the aluminum alloy was tested by method of a three-point bending cyclic loading using the parameters-frequency f = 100 Hz, temperature T = 22 ± 5 ℃ and stress ratio R = 0.11. The analysis showed that cast aluminum alloys are very sensitive to casting defects, such as porosity or the content and distribution of intermetallic phases. If large pores or phases are present on or near the surface of the sample, this can be the dominant cause of fatigue crack initiation and reduction of the fatigue lifetime. Aluminum Alloy Fracture Surface Structure Fatigue Bending Loading
To test the fatigue resistance of aluminum components
To test the fatigue resistance of aluminum components: a new patented equipment Over the last few years it has become tighter the fight for the lightening of all devices and components of machines are characterized, in their operation, by a high level of mobility, as well as of all the means of transport for public and private use , and this is because the efficiency of those machines generates a positive effect in terms of reducing consumption and therefore operating costs, as well as the lower environmental impact than is accompanied by that reduction. In this process we observe the increasing introduction of elements in aluminum alloys within the moving parts of machinery and systems for logistics (continuous movement) or for CNC machining of materials (high acceleration), and the use aluminum frame structures for vehicles for transporting people and \ or goods (Image 1). Since the elements mentioned above mostly are made by assembling components with linear geometry, i.e. beams, one can understand the prevailing use of semi-finished extruded, in the light of other technical and economic potential that this technology can provide to aluminum. In the route of identifying the optimal solutions for the customer, nowadays it is also necessary the contribution of knowledge and experience from suppliers of basic semi-finished, in that process called co-design increasingly widespread that when well-developed can produce examples of the products considered best practises for the sector they belong to. For applications of mechanics and transportation vehicles, it is crucial, given the specific
Fatigue damage and sensor development for aircraft structural health monitoring
Theoretical and Applied Fracture Mechanics, 2013
It was shown by tests conducted at the National Aviation University (Kiev, Ukraine) that fatigue damage of metal structures may be estimated by sensors with the surface relief pattern to indicate the accumulated fatigue damage. The nature of the deformation relief has been investigated by the light, scan and transmission microscopy, as well as by a new nano-interferometer, developed at the National Aviation University. Fractal analysis of the surface patterns based on box-counting method has proved the efficiency of fractal geometry application for additional quantitative description of such surface structures. The evolution of deformation relief parameters on the sensors surface is determined by the process of the sensor and construction fatigue damage accumulation.