Structural Health Monitoring Approach to the Aerospace Structures
In the article only selected information regarding the SHM applications has been presented. These applications are associated with damage detection and damage growth monitoring. That approach has got crucial influence on the aircraft maintenance procedures. SHM ensures higher reliability and safety of the structures as well as repair monitoring. Right now in the AFIT, there is being conducted research work focused on the application of the SHM system for the integration with the aerospace structures for periodical and on-line monitoring.
In-Service Flaw Detection and Quantification in the Composite Structures of Aircraft
Taking into consideration the increased usage of composites for aircraft structures there is a necessity for gathering information about structural integrity of such components. During the manufacturing of composites as well as during in service and maintenance procedures there is a possibility for damage occurrence. There is a large number of failure modes which can happen in such structures. These failure modes affect structural integrity and durability. In this work modern approach for detection of composites damage detection such as: delaminations, disbonds, foreign object inclusion and core damage has been presented. This detection is possible with the use of advanced P-C aided Non Destructive Testing methods. In the article nondestructive testing results for the composite vertical tail skins on MiG-29 aircraft will be delivered as well as some results of F-16 horizontal stabilizer and W-3 helicopter main rotor blades. Moreover some results of the composite honeycomb and sandwich structures will be presented based on the materials used in the construction of gliders and small aircraft. Factors affecting structural integrity and durability of the composites will be highlighted as well as necessity of the inspection with the use of modern NDT techniques. At the end some effort with Structural Health Monitoring connected with possibility of condition monitoring of composites will be presented.
Analysis of the Possibility to Assess the Occurrence of Hidden Corrosion in Lap Joints Using Active Thermography
The article details the NDT technique of pulse thermography used for objective diagnosis of riveted lap joints construction. The degradation of materials manifesting in corrosion is inherent in the process of aircraft operation. One type of corrosion is galvanic corrosion occurring in the overlap joints (known as hidden corrosion). As a result of the potential difference between the two layers of the aluminum alloy skin, there occurs the phenomenon of oxidation of the material, producing corrosion products in the form of oxide compounds characterized by heat properties different than those of the base material. Active thermography techniques allow observing infrared energy, which changes due to the difference of thermal properties of the tested materials.
Following the damage tolerance philosophy in aircraft design and operation, one of the most significant stages of maintenance is non-destructive testing of structures. It is, therefore, essential to use testing methods sensitive to particular damage types occurring in aircraft structures during operation. In this paper, the authors present a study on selection and comparison of methods of information fusion applied to testing the results of inspection of composite structures used in aircraft elements, obtained using various ultrasonic methods. The presented approach of fusion of ultrasonic scans allows for enhancement of damage detection and identification due to the presence of different parts of information about detected damage obtained from different initial information sources in a single resulting set. Such an approach can be helpful at the decision-making stage during inspection of aircraft elements and structures. Besides the methodology, the GUI-based software for performing fusion of various types of ultrasonic data is presented.
The article presents the impact of welding imperfections on the strength and microhardness of AW 5754 aluminium alloy welded joints executed with the TIG method. It presents the results of tomographic tests of welds. The results of strength and microhardness tests involving welds executed under various welding process parameters were shown. The impact of welding imperfections on the strength and microhardness of a welded joint was analysed. Based on analysing the relations between the r Pearson coefficient values and multiple correlation, significant relationships between strength, hardness and weld defects were evidenced. Furthermore, a very strong relation between the welding process parameters, welding imperfections, and weld strength and microhardness was shown.
The paper presents the problems arising in the process of repairs of aircraft (AC) components made of aluminium alloys during arc welding with the TIG (tungsten inert gas) method. The paper provides information on the rules applicable in the welding process qualification. The procedure algorithm when qualifying the welding process was presented in accordance with PN-EN ISO 15614-2. The main causes and factors affecting the formation of defects and welding imperfections were described and classified. The principles of preparing the components for welding and selection of a binder were discussed. The issue of effect of the welding parameters on the formation of defects and welding imperfections in relation to PN-L-01426 standard was raised. The application of computed tomography in assessment of the welded joints was described and tomograms from tests of butt welds of aluminium alloys made of the AW 5754 grade aluminium alloy were presented. On the example of the tomograms, the welding imperfections and defects formed in the tested joints were discussed. The usefulness of computed tomography in assessment of the welds’ quality was shown.
This article presents preparation of the Full Scale Fatigue Test of the PZL-130 "Orlik" TC-II. After completing the flight load acquisition stage  a load block representing 200 Simulated Flight Hours in 194 flights was developed. This load block was further modified in order to introduce fatigue markers on the crack surface  visible during Quantitative Fractography, planned to take place during the Teardown Inspection of the structure after completion of the test. Meanwhile, the test rig along with the loading system and the test specimen were prepared at Výzkumný a Zkušební Letecký Ústav (VZLU, Prague, Czech Republic). The test specimen, consisting of the overhauled fuselage, modernized wings and the landing gear, was instrumented with the identical strain gauge measuring system as presented in , which was calibrated before the commencement of fatigue testing. Finally, some preliminary issues encountered during the fatigue test startup were highlighted and the outline for future work was described
SHM is a monitoring system which uses sensors, actuators and data transmission, acquisition and analysis, permanently integrated with the inspected object. The objective of SHM is to detect, localize, identify and predict development of fatigue fractures, increasing safety and reliability. This paper presents an assessment of sensor technologies used in aircraft SHM system. Due to the fact that most of these measurement methods are relatively new and still under development the present appraisal focuses on a number of parameters with reference to each method, including a sensor’s installation issues, reliability, power consumption, sensor infrastructure, sensitivity and cost and availability. The work is predominantly focused on the assessment ofpermanently bonded sensors, such as foil strain gages, Comparative Vacuum Monitoring (CVM), Piezo sensors (PZT), Eddy-Current Transducers (ECT). Finally, all these methods are briefly discussed.
Barely visible impact damage is one of the problems commonly occurring in composite elements during an aircraft operation. The authors described the mechanisms of impact damage formation and propagation in composite structures. The paper presents a performed analysis of an influence of impact parameters on the resulting damage, i.e. its detectability by means of visual observation as well as its extent determined based on ultrasonic tests results. The tests were conducted on the CFRP specimens with a wide range of impact damage cases obtained with combinations of variable impact energy and shapes of impactors. Additionally, an algorithm based on image processing and image analysis methods is proposed for the purpose of the effective evaluation of the ultrasonic data obtained.