09:50   Poster pitches day 1 Chair: Marcel Bos 09:50 0 mins Virtual flight test tool for aircraft aerodynamics simulations with buffeting Manoj Rajanna, Ming-Chen Hsu, Ning Liu, Jim Lua, Nam Phan Abstract: Extensive and costly flight and ground tests have to be performed during the design and certification of air vehicles. Given the limited time and resource, a subset of critical tests has to be performed in an attempt to cover each point in the sky for the operation of the air vehicle. For a given aircraft geometry and an operational condition, high-energy vortices can be generated and become unstable and burst. The frequency content of the vortex can be shifted from very high-frequency ranges to relatively low frequencies to excite the vibration mode of a critical structural component. The high dynamic response resulting from the buffeting effect damages the impacted structural surfaces and shortens their fatigue life. The primary goal of our study is to investigate and validate a recently proposed stabilized finite element framework for 3D compressible viscous flows for the simulation of an aircraft for an arbitrary operational profile. A strongly-coupled Fluid Structure Interaction (FSI) formulation for compressible flows that is developed based on an augmented Lagrangian approach. The method is suitable for handling problems that involve non-matching fluid–structure interface discretizations. In this work, the fluid is modeled using a stabilized finite element method for the Navier–Stokes equations of compressible flows and is coupled to the structure, which is formulated using isogeometric Kirchhoff–Love shells. The combination of finite elements for fluid and the isogeometric analysis (IGA)-based Kirchhoff-Love shell for structures allows greater modeling flexibility and provides a suitable balance between speed, robustness, and accuracy for FSI simulations. The strongly-coupled system is solved using a block-iterative technique. Three examples are used based on a case with unsteady flow around an airfoil undergoing pitch oscillation, a shock wave impacting an elastic panel, and a buffeting response of a representative aircraft during pitch maneuvering. The buffet simulation results indicate that the unsteady dynamic flow behind the wing region can lead to nonlinear oscillations of the horizontal tail. 09:50 0 mins Multi-objective sensor placement optimization in helicopter main rotor blade considering the number of sensors and mode shape interpolation Felipe Mello, João Pereira, Guilherme Gomes Abstract: Sensor location optimization plays a key role in the application and development of structural integrity monitoring methodologies, especially in large mechanical structures. Given the existence of an effective damage detection and identification procedure, the problem arises of how many and how the acquisition points (sensors) should be placed so that the efficiency is maximum in the monitoring system. In this study, an innovative methodology is proposed in order to maximize the quality of modal information and minimize the number of sensors in SHM system. On maximizing the quality of modal information, it considered the reconstruction of mode shapes using kriging interpolation. The study was carried out on plate-type composite material structures for initial validation and later applied and validated on a main rotor blade of the AS-350 helicopter. The initial modal information (modal deformation) was obtained through the finite element method and the multi-objective Lichtenberg algorithm was used in the complex optimization process. The proposed method presented in this work allows distributing a minimum and sufficient amount of acquisition points in a structure in the best possible way in order to obtain more modal information for a better modal reconstruction from a kriging interpolation of these minimum points. Numerical examples and test results show that the proposed method is robust and effective to distribute a reduced number of sensors in a structure and at the same time guarantee the quality of the information obtained. The results also indicate that the modal configuration obtained by multi-objective optimization does not become trivial when a set of modes is used in the construction of the objective function. This strategy is an advantage in experimental modal analysis tests, as it is only necessary to acquire signals at a limited number of points, saving time and operating costs in vibration-based processes. 09:50 0 mins Study on bonding degradation of PZT sensor based on guided wave structure health monitoring Xiaguang Wang Abstract: Piezoelectric guided wave health monitoring based on bonded PZT sensors has received more and more attention in engineering applications. However, the environmental conditions (temperature, load, calendar life) in engineering have a serious impact on the bonding properties of PZT. The degradation of bonding property directly affects the quality of piezoelectric guided wave signal, thus affecting the monitoring effect. The bonding layer of PZT sensor is difficult to be directly detected, so PZT sensor bonding is required for evaluation. In this study, guided wave, impedance and strain data of PZT sensor under static and fatigue loads are studied through element level tests. It is found that the degradation of adhesive layer can cause the changes of guided wave, impedance and strain at the same time. With the degradation of the adhesive layer, the amplitude of the guided wave decreases, the amplitude of the real part of the impedance increases and the corresponding frequency decreases, and the strain transmissivity also changes, which indicates that the degradation of the PZT adhesive layer can be perceived. In practical engineering, the bonding performance of the sensor can be evaluated by impedance, strain and other parameters to determine whether the PZT sensor needs to be reinstalled, thus strengthening the effect of PZT piezoelectric guided wave health monitoring. This method has a good guiding significance for the effectiveness evaluation of PZT sensors in engineering service. 09:50 0 mins A prognostics and health management approach for aircraft control surface free-play Michael J. Scott, Michael J. Candon, Wim J.C. Verhagen, Oleg Levinski, Pier Marzocca Abstract: The proposed paper describes the use of a machine learning approach for fault diagnostics and prognostics of aircraft control surface free-play using on-board sensors. The significance of this research is in detecting and tracking the aircraft control surface free-play on an all-movable horizontal tail. This will progress proactive condition-based maintenance of free-play through the development of a data-driven Prognostics and Health Management (PHM) framework. Free-play requires labour-intensive maintenance, limits aircraft performance, and can induce aeroelastic asymmetries (i.e., limit cycle oscillations), reducing component life and is therefore costly to operators. The aim of this work is to predict free-play using aircraft on-board sensors; the detailed research questions are outlined by the future work in the authors’ recent paper [1]. The research method utilises time- and frequency-domain signal processing of control surface actuator loads, generating 17 features (e.g., peak frequency, peak amplitude, standard deviation, skewness, kurtosis, etc.), which are labelled “high” or “low” in severity based on measured free-play values. Subsequently, a supervised machine learning model is used to diagnose free-play severity, while prognostics estimate Remaining Useful Life (RUL) for free-play using an optimised exponential degradation model. Preliminary results show good agreement with exact free-play measurements, with a K-Nearest Neighbours (KNN) binary classification model generating an accuracy of 88.6%. The prognostics degradation model produces good early to mid-life prediction for the piece-wise linear RUL target. However, the overall RUL prediction has a root-mean-square-error value of 37.47 samples, which is impacted by over-estimation near the nominal failure threshold later in the degradation life. Nonetheless, this is an important step towards predicting free-play on an aircraft stabilator using on-board sensors. The final manuscript will incorporate more representative flight data and maintenance interventions, as well as increased complexity in diagnostic and prognostic models to handle the non-linearities and behaviour of control surface free-play, further fine-tuning prognostics model parameters. [1] M. J. Candon, M. Scott, S. Koschel, O. Levinski, and P. Marzocca, ‘A Data-Driven Signal Processing Framework for Enhanced Freeplay Diagnostics in NextGen Structural Health Monitoring Systems’, in AIAA SCITECH 2022 Forum, American Institute of Aeronautics and Astronautics, 2021. doi: 10.2514/6.2022-2131. 09:50 0 mins Numerical analysis on random load spectrum enhancement of the crack propagation of the metal structure Fangli Wang, Kai Liu, Qiang Zhu, Mingbo Tong Abstract: Based on enhanced test of crack extended about random load spectrum, the stress intensity factor, critical crack length, fast calculation of crack growth life and load spectrum enhanced factoraccurate selection of two panels under different enhanced factors are analyzed systematically by numerical simulation and random load spectrum crack enhanced program calculation. The results show that in a small range of elastoplasticity, the stress intensity factor after enhanced is the enhanced multiple of the original load spectrum stress intensity factor. If it is in the high load plastic deformation area, the effective value of the stress intensity factor is obtained by subtracting the threshold value after the increase of the multiple. The critical crack length of two panels decreases with the increase of load spectrum enhanced coefficient, and the decrease speed of large panel is faster than that of small panel. When the enhanced coefficient is small„ the enhanced spectrum life / original spectrum life ratio curves of different load spectrum and sizes are all consistent after normalization treatment, and a formula is proposed. According to this conclusion, the crack growth life of the original load spectrum can be calculated quickly or the enhanced factor can be selected quickly when the shortening time of fatigue accelerated test is known; it can also be applied to the prediction of the relevant pa-rameters required for the random spectrum of large samples based on the calculation of constant amplitude spectrum of small samples and the test results, so as to reduce the cost and time of test. 09:50 0 mins Robotic-based laser ultrasonic non-destructive testing of 3D-printed continuous fiber reinforced flight control surface Kyu Jin Lee, Jung Ryul Lee Abstract: Rapid and groundbreaking advancements in 3D printing technology have led to a printing technology using continuous fibers. In the process of continuous fiber 3D printing, inherent defects are inevitable due to the setting of the printing path and the behavior of the continuous fiber itself. Such manufacturing defects can deteriorate structural performance, and methods for visualizing and evaluation are needed. In this study, laser ultrasonic testing (LUT) was mainly used to detect defects that occur when the flight control surface is fabricated by continuous fiber 3D printing. To ensure the precise detection and localization of defects that are key factors for non-destructive testing, a six-degree-of-freedom (DOF) robot arm was used to control the position of the target to be inspected. All of the surfaces of the control surface were inspected based on the scan points calculated through coordinate transformation and spatial rotation using quaternion. Thus a constant stand-off distance was maintained while the sensing laser was vertically incident on the target surface to acquire a high signal-to-noise ratio (SNR) of the ultrasonic signals. From the inspection results, it was verified that the inspection technique we proposed is suitable for the detection of defects in complex-shaped 3D-printed structures. 09:50 0 mins Fatigue fracture mechanics of selective laser PBF titanium alloy Ryo Omura, Shinya Suzukake, Sayaka Maruta, Yuta Imai, Hiroshi Ishikawa, Akiko Kasami Abstract: The strength properties of AM materials are greatly changed by defects and microstructure. Especially, titanium alloy is easy to change surface and internal defect and microstructure by the difference of quality of the powder, molding equipment, molding parameter, type of heat treatment, and the mechanical property greatly changes by it. Therefore, the purpose of this study was to clarify experimentally the effects of defects and microstructure on the strength properties of AM titanium alloy formed by laser Powder Bed Fusion. The microstructure and internal and/or surface defects of additive manufactured titanium alloy Ti-6Al-4V are highly rely on the post heat treatment conditions including HIP and they have a strong relationship with fatigue properties. The relationship between internal defects and microstructure and role of defects in additive manufactured Ti-6Al-4V was evaluated by fatigue test and also detailed investigation based on fracture mechanics were conducted. 09:50 0 mins High fidelity digital twin autoclave tool for quality informed composite fabrication Jim Lua, Kalyan Shrestha, Ze Zhao, Jinhui Yan, Nam Phan Abstract: Variations in the cure cycle, sometimes even apparently minor variations, can harm the laminate properties. Advances in autoclave technology, including modern control systems and new duct and heater configurations, lead to overall composite quality improvements. Given the costly and time-consuming process, there is a strong need to cure the maximum number of parts in the shortest possible time without compromising quality. This study is focused on the development of a versatile, user-friendly, and computationally efficient toolkit for virtual simulation of local environmental conditions in an autoclave with multiple parts to maximize the throughput with the correct cure profile of each part. A coupled immersogeometric thermal CFD and aerodynamics-aided heat transfer module with a consistent LES turbulence model (without ad hoc viscosity) is developed to capture the turbulence-induced local boundary conditions and the resulting thermal and pressurization response of multiple parts in an autoclave. A hybrid shell and solid element modeling approach in CFD and its associated immersogeometric modeling is implemented to greatly enhance the computational efficiency. The predicted time history of the surface temperature of the tool and the associated composite part were used in the user-defined Abaqus heat transfer (UMATHT) and stress analysis module (UMAT) to determine the distortion, thermal shrinkage-induced surface wrinkling, and residual stress. Due to the exothermic nature of the resin curing process, internal heat generation is included in the developed heat transfer analysis module that incorporates a resin cure kinetics model in UMATHT. The resulting SMARTCLAVE toolkit is validated first by using data collected at coupon and component levels. The use of the digital twin autoclave tool is demonstrated to achieve improved fabrication quality. 09:50 0 mins Research on application of cae visualization technology in virtual static strength test of aeronautical structure xiaohui Wang, xiangyan xu, liang chang, xiaohua nie Abstract: As one of the main auxiliary means of aircraft physical test, aircraft structure static strength virtual test can realize real-time monitoring and early warning of the test by comprehensively using the virtual test and physical test result data in the pre test and formal test stages, and can display the test status and response in a highly realistic virtual way, which can provide technical support for test command decision-making, thus reducing the test risk. With the drive of digital technology and the change of computer information technology, digital engineering technology is changing the traditional aircraft design process. Virtual test technology shows a trend of digitalization, intelligence and automation. Among them, the deep integration of CAE technology into virtual test process has become one of the most extensive technical practices in engineering applications. In combination with the requirements of aviation equipment test design and analysis, China Aircraft Strength Research Institute has carried out research on virtual display technology that can support physical tests of aircraft structures. It has independently designed related CAE graphic visualization algorithms and advanced data processing algorithms. It has broken through the test data monitoring and processing technology based on Qt multithreading and the rapid display technology of three-dimensional cloud images based on high-precision interpolation of test data, and is based on the independent CAE graphic engine SABRE Visual has realized the integrated research and development of the virtual display module for the static strength test of aircraft structures, and has been applied in the field of aviation model test, with remarkable results. This technology realizes the good combination of CAE technology and engineering application, innovates the new test mode of virtual reality integration, and also provides technical reference for virtual display and evaluation of multi discipline strength test in the future. 09:50 0 mins A mobile robotic non-destructive inspection system based on ultrasonic propagation and optical images Min-Ji Im, Jung-Ryul Lee Abstract: With the development of the aerospace industry, demand for maintenance and repair technologies for large structures such as aircraft, unmanned aerial vehicle, and reusable rocket is increasing. Damage to large structures can result in structural destruction due to acceleration of damage caused by impact and vibration of structures. To prevent this, studies such as structural health monitoring and non-destructive evaluation are being actively conducted. Fast and efficient evaluation technology is required due to the increase in demand and size of the aerospace industry. Most of the existing measurement methodologies rely on manual inspection, and the accuracy and efficiency are unsatisfactory. This paper introduces a mobile robotic non-destructive inspection system of large-scale and inaccessible components. This inspection system is capable of inspecting internal defects on large structures, aircraft lower parts, curved structures. Damage existing inside the structure was visualized by using an ultrasonic wave imaging system. The beam match between excitation and sensing laser was implemented based on vision. Current position and posture estimation were implemented with SLAM. In addition, it is possible to automate non-destructive inspection by transmitting the desired inspection place using Wi-Fi-based wireless communication. The proposed measurement system and method are verified by measuring a 2 m long aircraft wing model. 09:50 0 mins Numerical and experimental analyses of the stress field ahead of fatigue cracks in laser-treated AA2198-T851 alloy Cauê Carvalho, João Paulo Pascon, Milton Sergio Lima, Carlos Antonio Baptista Abstract: Regarding fatigue life extension, techniques such as shot peening, cold expansion and laser shock peening are well-known in the aircraft industry as residual-stress-based approaches. Compared with the latter, laser heating is a less expensive technique, because it can be applied with continuous wave laser equipment; and has been successful in reducing fatigue crack propagation rates in laboratory specimens. Although this effect is usually related to the original residual stress field, it is known that cyclic loading and crack growth can cause relaxation and redistribution of residual stresses. In this work, M(T) specimens made of 2.0 mm thick AA2198-T851 alloy sheets with L-T and T-L crack orientations were treated with a fiber laser (power 200 W, displacement speed 1 mm/s) to produce two heating lines ahead of each of the crack fronts, on one of each specimens’ face. The specimens with and without laser treatment were tested under constant-amplitude loading at a ratio of R = 0. Electrical resistance strain gages bonded along the crack path right next to the first heating line on the treated specimens and in a similar position on the non-treated ones were employed to register the deformation behaviour ahead of the approaching crack tip. A numerical model for the stress-strain state ahead of the fatigue crack considering an elastoplastic material with strain hardening behaviour was developed. From the symmetry condition, half of the specimen was discretized with plane quadrilateral finite elements of linear order. The constitutive model included plane-strain conditions, linear elastic response, the anisotropic Gurson-Tvergaard-Needleman (GTN) yield criterion coupled with damage, associative plastic flow rule and nonlinear isotropic hardening Swift model. The mesh refinement was concentrated around the crack-tip and strain gauge regions. Numerical simulations were successful in describing the measured strain behaviour in the as-received specimens. The experimental results showed significant fatigue crack growth retardation experienced by the laser-treated specimens; this effect was more pronounced in the L-T orientation. Thereafter, the model was calibrated with imposed average compressive stresses in order to reproduce the experimental deformation behaviour ahead of the crack tip, qualitatively showing how crack extension affects the residual stress field. 09:50 0 mins On the theory of aerocraft structural operational integrity control Yuting He, Rui Bao Abstract: ABSTRACT After the concept of aircraft structural integrity was first proposed in 1954, it has been developed and improved gradually. In 2021, The Welding Institute stated that structural integrity is an engineering field that helps ensure that either a structure or structural component is fit for purpose under normal operational conditions and is safe even should conditions exceed that of the original design [1]. From the view of life cycle time, structural integrity can be categorized into structural manufacturing integrity, structural storage integrity and structural operational integrity. Structural operational integrity concerns the overall quality of structure in its whole operational process and can be used to characterize the general quality characteristic of structure more comprehensively[2]. Correspondingly, aerocraft structural operational integrity(ASOI), as the attribute which exists when aerocraft structure is sound and unimpaired in service or operational processes, shows the general quality characteristic of aerocraft structure more comprehensively. As a more comprehensive general quality characteristic of aerocraft structure, ASOI can be controlled from manufacture to operation. In this paper, ASOI is introduced briefly, including the concept, categorization and characterization, i.e. the inherent readiness rate of aerocraft structures, Rs, inherent health degree of a aerocraft structure, Hs(t), and aerocraft structural operational integrity degree, Iso. Then, something about aerocraft structural operational integrity control (ASOIC) is focused on. The concept of ASOIC is given, which is a series of activities carried out in the process of aerocraft structural design, manufacture and usage to achieve the established ASOI objectives by the trade-off of expected aerocraft structural durability, supportability, safety, performance, survivability and recoverability. The essence here is the adjustment and control process of ASOI. Consequently, the connotation of ASOIC is analyzed, which can be expressed by means of the control activity-loop of ASOI formed by design/establishment, manufacture/achievement, evaluation/validation, monitoring/sustaining, recovery/increasement and inspection/exploitation activities of ASOI. Furthermore, the basic modes of ASOIC are shown here, which include open-loop control, coordinated control and balanced control of ASOI. Finally, aerocraft structural operational integrity control strategy(ASOICS) was discussed briefly, which is to establish and apply an aerocraft structural operational integrity program(ASOIP) to all aerocraft structures. Using ASOIC , structures with more better comprehensive general quality characteristics could be gained for performing and completing the expected functions and missions. References [1] The Welding Institute (TWI). What Is Structural Integrity and Why Is It Important? [EB/OL]. 2021: https://www.twi-global.com/technical-knowledge/faqs/structural-integrity [2] Yuting He. Structural Operational Integrity - The More Comprehensive General Quality Characteristic of Structure [C]. The 12th International Conference on Quality, Reliability, Risk, Maintenance, and Safety Engineering, July27-30, 2022, Emei, Sichuan, China. 09:50 0 mins Virtual testing of low-velocity impact response of a composite laminate – from analytical to high-fidelity modeling Lucy Li, Peyman Shabani, Jeremy Laliberte, Qi Gang Abstract: The primary strategy to ensure structural integrity of composite structures for aircraft design and certification is based on costly experimental campaigns, to account for design, loading cases, manufacturing and testing variabilities, scaling effects and so on. Virtual testing tools including low and high order analytical and numerical tools, as well as artificial intelligence and machine learning can accelerate materials screening and design processes, bringing in transformational changes in aircraft development and certification. The analytical solutions can be used in preliminary designs allowing extensive trade-off studies and layup optimization, while high-fidelity finite element models can be employed to accurately predict the impact response and damage areas in a limited number of scenarios. This study aims to quantify the trade-off between the accuracy and the computational costs of these methods. Using the analytical solution proposed by Esrail and Kassapoglou [1], the stress distribution at peak load along with the resultant delamination was predicted in a composite laminate subjected to a low-velocity impact (LVI) event using an energy minimization and Hertzian contact formulation. A 3-D high-fidelity finite element model for the same LVI damage prediction was developed that took into account failure modes of fibre and matrix such as fibre breakage, splitting and kinking, intelaminar and intralaminar matrix cracking, delamition, as well as the interactions of the different failure modes. The FEM model employed the LaRC05 failure criteria with an efficient search algorithm to find the matrix fracture plane and the fibre kink-band angle. Delamination and its interaction with intra-laminar matrix cracks were also predicted by using inter- and intra-laminar cohesive elements. The damage areas predicted by the high-fidelity model and the analytical solution were compared with experimental results of LVI tests on quasi-isotropic carbon/epoxy (IM7/799-3) laminates. This study offers a case study of the strategies between quick- and efficient analytical solutions, lower-order FEM, and high-fidelity FEM prediction in terms of the trade-off between prediction accuracy and computational time. The study offers an assessment of strategies for aircraft designers, operators and maintenance facilities to make an informed decisions related to aircraft design, certification and maintenance. 09:50 0 mins CREATING A DIGITAL-TWIN FRAMEWORK FOR THE LIFE PREDICTION OF COMPOSITE MATERIALS Jordy Schönthaler, Bojana Rosic, Dario Di Maio Abstract: In the transition to a climate-neutral economy, composite materials can play a big role due to their high strength-to-weight ratio. However, reliable fatigue evaluation methods must be found to ensure long-term integrity of the designs. In aid, a digital-twin framework will be built to predict the residual lifetime of composite materials subjected to vibration fatigue. Previous research [1],[2] has shown applications of near-resonance fatigue testing. This shows a phase degradation up to a critical event, causing a sudden stiffness drop. This sudden stiffness drop can be used for two important parameters. The first parameter is the crack propagation throughout the composite material for the phase degradation up to the sudden stiffness drop, and the second parameter is a failure criterion at the point of the sudden stiffness drop. The crack propagation can be used to create Paris’ Law, containing material parameters. This can be combined with the critical event to create an SN-curve for the material, where the rapid delamination indicates failure. The experimental results obtained from the near-resonance testing will be used as input parameters for the digital-twin framework that will be created. This framework will consist of a loop that contains the following steps: First, a modal analysis will be performed to extract natural frequencies. This will be used for a steady-state analysis at the natural frequency to get the deflection shapes of the material. This will be used in a static analysis to determine the stresses near the crack tip in the material. Then, a heat transfer analysis will be performed to simulate the heat generation in the material during vibration. Finally, the crack growth in the material will be updated. With a new crack length, the loop will be repeated to get the new natural frequency with the degraded stiffness. This framework can be used to predict the residual life of composite materials that are subjected to vibration fatigue. This can significantly speed up conventional fatigue testing methods for composite materials. [1] Magi et al., Composites Sci. & Tech., 132 (2016) 47-56. [2] Di Maio et al., I. J. Fatigue, 155(2022)106617.

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