Browse Topic: Fabrication
This organizational process survey provides insight into the technical aspects of approved airworthy aircraft modifications applied in government organization vertical lift flight test. The publication reviews processes applied by the National Research Council of Canada's Flight Research Laboratory (NRC-FRL) and its Airworthiness Control System to enable research flight testing. Dominated by the need for integrating experimental payloads, the NRC-FRL embeds a Design and Fabrication Service organization for modification of internal and external client projects and flight test aircraft. In context of experimental flight testing, this work reviews technical information on process, facilities, and methodology for airworthy integration of flight test payloads. Information is used to synthesize recommendations in experimental vertical lift flight testing that satisfy both formal (regulated compliance) and informal (compliance intent) airworthiness requirements.
Blade–wake interaction (BWI) is a significant source of broadband noise and is often dominant in rotors with high blade counts. Accurately capturing the resulting unsteady blade loading is computationally expensive and, therefore, drives the cost of BWI noise calculation. To address this challenge, a low-fidelity BWI noise prediction tool was developed using aerodynamic data from the blade element momentum theory (BEMT) and the lattice Boltzmann method (LBM) for a series of rotor configurations with medium to high solidity. Starting from a six-bladed baseline rotor, 13 additional configurations were generated by varying blade twist, taper, root collective, solidity, and blade count. The relationship between vortex miss distance and blade loading unsteadiness was quantified to construct a semi-empirical BWI noise model. The model predicted BWI noise with a root mean square error of 3.9 dBA and a mean absolute percentage error of 1%. It was subsequently integrated into a BEMT framework to produce aerodynamic and acoustic data for training a tandem neural network (TNN) that was employed to optimize two rotor geometries. The optimized designs achieved up to a 7% reduction in BWI noise and a 7% improvement in performance. Additional geometric modifications—including blade tip anhedral, forward sweep, and a mixed configuration—were also assessed using LBM, each demonstrating notable noise reduction.
In the proposed article, the authors will focus on two manufacturing method FUSED FILAMENT FABRICATION (FFF) and FUSED DEPOSITION MODELING (FDM) showing examples of application in aviation production and the resulting benefits.
The Autoclave processing is commonly used in manufacturing high-performance fibre-reinforced thermoset composite components in the aerospace industry. Variations in the cure cycle, sometimes even apparently minor deviations from the prescribed cure cycle, can harm the laminate properties. Given the costly and time-consuming autoclave manufacturing process, there is a strong need to cure the maximum number of parts in the shortest possible time without compromising quality. In order to achieve high-rate automated manufacturing with the optimized autoclave process, it is important to construct a digital twin modelling approach to mirror the physical composite curing process in the virtual domain based on the integration of high-fidelity multi-physics models. The resulting digital twin includes a thermal CFD model, a thermo-chemo-mechanical module, and an efficient and accurate block coupling between these two modules. The customized Abaqus driven by local and spatial variation of the turbulence-induced heat transfer coefficient (HTC) imposed through one-way coupling determines the thermo-mechanical response in composite parts. Using the developed digital twin tool (SMARTCLAVE), HTC's spatial and temporal variation can be generated digitally without invoking an expensive and time-consuming experimental approach. The predicted local boundary conditions are used in SMARTCLAVE to determine the cure kinetics, temperature distribution, and thermal-mechanical response that drives the residual stress and distortion of composite parts after curing. The accuracy of the digital twin for autoclaving is demonstrated first using a benchmark problem followed by the capability demonstration with a single-part L-beam assembly. The benefits of using the digital twin tool are illustrated via the optimal placement of multiple parts in an autoclave to balance the throughput and quality.
Over 4 decades of research works on the nutating, now pericyclic, mechanical transmission have studied its capability to achieve high power density, low noise, and amplified single-stage reduction ratios of up to 100:1. These analytical efforts have culminated into the fabrication of a 50 HP and 32:1 reduction ratio pericyclic transmission prototype. This work introduces the prototype with highlights of the assembly and alignment procedures validated by static testing evaluation. Then, discussion of the dynamic test stand integration, instrumentation, and lubrication components lay out the framework of the high-speed testing plan. Power transmission data validated the pericyclic reduction ratio model. Accelerometer data demonstrated the transmission's capability to operate at low vibration, with peak amplitudes of 1.2 and 2.5 inches per second on the pericyclic gear train and output shaft respectively. Acoustic emission data captured the first 5 harmonics of the shaft speed as well as gear mesh frequencies. The thermal profile showed the shaft bearings remained below 180°F throughout testing, implying safe operating conditions. Finally, strain and vibration data showed the pericyclic gear train maintained load sharing throughout the entire operating envelope, further validating static testing and assembly procedures. The results of the experiments demonstrate the technological readiness of pericyclic mechanical transmission.
ABSTRACT
ABSTRACT
Additive Manufacturing (AM) and/or 3-D printing has been used for decades for fabrication of prototyping parts to validate design, geometries and kinematics. The ability to rapidly "grow" one-off and low-volume parts for evaluation and iterative design development is a perfect use of AM processes. As AM materials and machines advance, the repeatability, reproducibility and quality are maturing. Today, AM parts are moving into limited production applications with opportunity for future design features, competitive pricing, lower weight through design optimization, and potential for "on-demand" deliveries. The vast majority of AM parts remain limited to development and prototype phases of a program. As production ramps up, production part fabrications transition to more traditional processes. The higher quantities and schedule demand of production as well as conformity with certified materials and processes still favor traditional manufacturing methods. However, as production ends and the product moves fully into a sustainment phase, the demand for parts plummets (as shown in Figure 1) and subsequent fabrication schedules are dependent on forecasts that are often overwhelmed by "surprise" spares orders. In the latter part of the product life cycle, high rate, production-driven manufacturing processes may no longer be optimal and an alternative that permits a transition back to prototyping methods and one-off "on-demand" fabrication is needed.
Bismaleimide (BMI) resins are commonly used in advanced carbon composites for their high service temperature and excellent mechanical properties. In this study, two different BMI resins were compared: 1) formula RS-8HT, a high-cure temperature resin requiring pressurized consolidation, and 2) formula BMI-2, a lower cure temperature resin compatible with vacuum bag only fabrication. The objective was to identify a suitable high-temperature resin system for hybrid aerospace gear application, however, these materials are applicable to a variety of hot-zone parts. Laminates were fabricated from each resin type and characterized by their fiber volume fraction, compression strength vs. temperature, and glass transition temperature (Tg). Optical microscopy was performed to verify laminate quality. It was found that the carbon/RS-8HT laminates were prone to thermally-induced cracking, especially during post-cure. Carbon/BMI-2 laminates were found to attain a high degree of cure and high Tg from a realtively low temperature cure, without crack development. Additionally, the fiber volume fraction of the carbon/BMI-2 laminates, which were fabricated by a vacuum bag only process, were similar to that of the autoclave-processed carbon/RS-8HT laminates.
An optimized design, fabrication and testing solution is presented for flexible drive systems. A single piece welded drive shaft as well as a system consisting of sub and supercritical shafts, couplings and bearing hangers (for Tail Drive System in Helicopters and Interconnect Drive Systems in Tiltrotors) are included. This solution facilitates the qualification for flight of the drive shaft in airframes with reduced iron bird and expensive flight testing on the airframe. This solution also provides opportunities for improvements during the prototype phase such that potential deficiencies are identified and corrected before the drive shaft is put into service. An important part of the testing is accelerated testing, not in terms of operational life, but in terms of reliability. Theoretical Life of a flexible drive shaft is 'infinite' by design. 2.0
The field called System Safety evolved to satisfy the demand for an organized approach to safety management of complex new aerospace systems being developed in the 1960s. As technology has advanced and complexity has increased, its application spread to aviation, rail transportation, weapons, nuclear power, medical devices, oil and gas production, and almost every area of life where complex systems could lead to events having high consequences. System Safety is often defined as the application of engineering and management principles, criteria, and techniques to achieve acceptable mishap risks within the constraints of operational effectiveness, time, and cost throughout all phases of the system life cycle. The International System Safety Society states that for almost any system, product, or service, the most effective means of limiting product liability and accident risks is to implement an organized system safety function beginning in the conceptual design phase, and continuing through to its development, fabrication, testing, production, use, and ultimate disposal.
This paper describes the features, specifications, and instrumentation of a new tiltrotor test rig at the University of Maryland, the Maryland Tiltrotor Rig (MTR). The MTR is a semi-span, floor-mounted, optionally-powered rig with a static rotor tilt mechanism, capable of testing proprotors of up to 4.75-ft diameter in the Glenn L. Martin wind tunnel (7.75- by 11-ft section with 200 kt maximum speed). It supports interchangeable hubs (gimballed and hingeless), interchangeable blades (straight and swept tip), and interchangeable spars, to allow a systematic variation of components important for tiltrotor flutter and loads. The baseline rig dimensions are 1/5.26 scale XV-15 or 1/8 scale V-22. The principal objectives are to measure tiltrotor instabilities in cruise and vibratory loads in conversion. Additional objectives are airloads, drive system loads, rotor-wing aerodynamic interactions, and closed-loop control of loads and instabilities. The baseline rig is a gimballed hub. It is complete, all components fabricated (Calspan), parts assembled, sensors integrated, and statically calibrated. The objective of this paper is to describe this baseline rig. The vision behind the rig is to conduct research on future high-speed tiltrotors with an envisioned flutter-free cruise up to 400 kt, enabled by thin wings, and light-weight, low-vibration, high-performance rotors. the features, specifications, and instrumentation of this rig. The purpose of the MTR is to provide a testbed for 1 Introduction basic research on aeromechanics of high-speed tiltrotors. A vision for the next generation of these aircraft is 400 kt A new tiltrotor test facility at the University flutter-free cruise with a turboprop-like thin wing (14% of Maryland has continued to make progress on the thickness to chord ratio) and a lightweight, low-vibration, Maryland Tiltrotor Rig (MTR). The design of the rig high-performance proprotor. The objective of MTR was outlined in Ref. [1]. The fabrication of the baseline is to enable this vision through systematic parametric gimballed hub rig is now complete. This paper describes variation of blades, hub, and wing spar. MTR is a research rig, not a scaled-down version of a particular
Magnetic gearing is being investigated at NASA as a replacement to conventional mechanical gearing in aerospace applications. Some potential benefits of magnetic gears over mechanical gearing are torque transmission without mechanical contact, decreased transmission noise, and no required lubrication. However, in order to be a viable alternative for aerospace applications, magnetic gearing must be shown to provide high enough specific torque (torque per unit mass). NASA's second magnetic gearing prototype (PT-2) was able to achieve promising specific torque on par with low torque mechanical gearboxes. This work will briefly review the electromagnetic and structural design of PT-2, provide detailed information on fabrication and assembly, examine build errors, walk through rebuild efforts to improve operation, and conclude with remarks on build difficulties and opportunities for improvement in future prototypes.
Metal additive manufacturing (AM) has become increasingly popular to fabricate complex, light-weight, and high- efficiency components for use in the aerospace industry; however, there are inherent limitations in existing AM processes that have delayed widespread implementation for aviation applications. Porosity is just one example of the key characteristics that can impact the mechanical strength of an AM part. This research focuses on a real-time feedback system to detect and correct defects during the powder bed fusion process of aluminum alloys. In this study, AlSi10Mg coupons were built using various AM parameters. The build process was continuously monitored via a high-frequency in-situ infrared camera which had been integrated into a commercial metal powder bed fusion machine. Porosity information (pore location and size) of the as-built AM coupons were characterized using x-ray computed tomography. The monitoring results were post processed and correlated with porosity location, indicating a strong relationship between abnormal sensing signal and pore formation. This demonstrates that the real-time abnormal sensing signal can be a good indicator for identifying pore formation during the AM process. Additionally, Sentient Science Corporation (Sentient) used its advanced modeling technique to simulate the AM build process regarding the melt pool geometry, porosity, and microstructure. Prediction of porosity level at different AM parameters aligned well with the experimental results. Advanced modeling results showed that careful selection of AM settings is required to correct in-process defects. Repair parameters must be tailored to achieve satisfactory correction of individual defects. Combining the in-situ defect monitoring and advanced simulation capabilities enables the creation of a closed-loop feedback control system that provides automatic defect detection and correction action in powder bed additive manufacturing process.
Additive manufacturing (AM) is a novel process of fabricating components in a layer-by-layer method under the control of computer-aided design (CAD) information, rather than by the traditional use of casting molds and forming dies. By allowing for net-shape fabrication of highly complex geometries without molds or machining, this process offers the potential to reduce material usage, energy consumption, component cost, and fabrication time. While AM presents the unique opportunity to manufacture single components quickly, it also provides for the potential to examine the effects of individual design alterations on overall system performance. QuesTek has utilized its proven Integrated Computational Materials Engineering (ICME) methodology to adapt Ferrium® C64® steel for additive manufacturing, where the market availability of AM gear steels is very limited. QuesTek has demonstrated success in AM-processing of C64 using a laser-based powder bed technique, from procurement of powder through final test part fabrication. This production route is demonstrating the ability to fabricate a near-net shaped part at a reduced cost and significantly reduced lead time relative to conventional manufacturing routes, making it especially useful for rapid prototyping of new components.
Based on component level and system level design analysis tools developed in the past years, an internally-driven torque sharing, twin configuration, Pericyclic drive concept has been developed to operate within allowable operating conditions of the NASA Glenn Transmission Test rig. In this work, design refinements and additional features required for successful fabrication, assembly, and testing of the prototype transmission are described. Thereafter, the weights and inertia of the components are updated in the design analysis to predict performance characteristics of the test article such as efficiency, bearing loads and life, tooth loads, lubrication requirements, and component stiffness. Some of these results will be validated from test runs of the prototype scheduled for near future. The current status of design and fabrication of rotating and static components is also reported.
Items per page:
50
1 – 50 of 918