Browse Topic: Advanced manufacturing
Hybrid additive manufacturing (AM) and subtractive manufacturing (SM) processes utilize the combination of AM (e.g., LPBF and DED) and SM (e.g., milling and turning operations) to produce the final part. Due to the poor surface roughness resulting from the uneven melting of powders in AM, the subtractive process is a necessary finishing operation to improve the surface roughness of the AM part. The hybrid AM/SM technology combines the benefits of AM and SM processes to create complex geometry while introducing good surface finish and compressive stress to prevent crack initiation. However, the relationship between large process parameter space and the residual stress/distortion in the part is not well understood, which impedes the adoption of hybrid AM/SM to minimize the residual stress in the final product. To expedite the process optimization, we establish a pipeline for the sequential modeling of additive manufacturing (AM) and subtractive manufacturing (SM) processes. Key accomplishments achieved under this study include (1) development of thermal abstraction technique for the AM process to speed up the macroscale level heat transfer analysis based on the manufacturing factors including scanning vector, laser power, dwelling time, etc.; (2) development of the sequentially coupled thermal-mechanical model to predict the residual stress and distortion after AM process by passing the temperature history obtained from heat transfer analysis to the mechanical analysis at each time point; (3) validation of the thermal-mechanical model for AM using thin-wall structure from literature and cantilever beam structure from UNT’s experiments data; (4) conduction of the parametric study on the chamber temperature and part design in the AM process to demonstrate how the temperature gradient and supporting structure affect the residual stress and distortion; (5) exploration of macro and micro scale models to predict the bulk and surface residual stress after cutting; (6) applying the developed modeling framework to tailoring the hybrid AM/SM process. To support model verification and demonstration, we print cantilever beam structure with different supporting structure designs and cutting strategies to study how these factors affect the final part residual stress and distortion. The data collected in the printing and cutting process is used to examine the applicability of the developed simulation tool.
Helicopter pilots are exposed to a wide range of vibration frequencies, primarily generated by engine and rotor dynamics. These vibrations, particularly within the 0.5–80 Hz range, pose significant risks to pilot health, including musculoskeletal injuries and fatigue. To mitigate these effects, vibration isolators are employed, with passive and active isolation systems offering different advantages. This study investigates the initial design and performance of a novel metal additive manufactured vibration isolator, optimized for placement under the pilot's seat in a rotorcraft simulator. The isolator was designed with key structural parameters including stiffness, coil dimensions, and material properties while maintaining a lightweight and durable form, with a primary goal of validating the additive manufacturing of a metallic isolator. Experimental corroboration was conducted by incorporating modifications to the Gannon Biomechanics Flight Simulator test stand (GBFS), comparing the novel isolator to an elastomeric isolator. Results demonstrate the successful fabrication of the initial additive isolator design. The additive isolator displayed a similar performance to the rubber isolator after being installed in the GBFS, though limitations on the current test rig and sensing configuration did not allow accurate characterization of the transmissibility. This research sets the groundwork for further development of a novel additive isolator and test facility.
Maintaining the operational readiness of military helicopters demands repair solutions that are fast, reliable, and adaptable. This paper presents the integration of Gamma Alloys' advanced metal matrix composites (MMCs) into additive manufacturing (AM) techniques - specifically Cold Spray and Friction Stir Additive Manufacturing (FSAM) - as a transformative approach to helicopter repair and replace for the US Army.
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.
This paper presents the design and development of a swashplateless micro helicopter with a target endurance of more than 30 minutes using an optimized direct drive rotor connected to a unique rotor hub that has blades with a flap hinge and proprietary skewed-lag hinge with pitch-lag kinematic coupling. This obviates the need for conventional swashplate based cyclic pitch control, as the cyclic variation in control angle is achieved by cyclically varying the motor RPM. UP12 underactuated propulsion system developed by VertiQ is used for the baseline design. The blades in this propulsion system are optimized using Blade Element Momentum Theory (BEMT) analysis with lookup table to enhance its performance. BEMT is validated using experimental measurements and then used to optimize the geometry of the rotor. The optimized blades offer better performance and are 30% lighter than the original 3D-printed plastic blades. The prototyping of the Micro Aerial Vehicle (MAV) is completed by fabricating the airframe and using off-the-shelf electronic components. Tabletop tests are carried out using a yawing test stand to tune the yaw attitude gains for the MAV. A coupled flap-lag rotor dynamics is combined with the motor angular speed dynamics to simulate the dynamics of the system to carry out fundamental understanding of the control power being generated by the swashplateless system. The swashplateless rotor design is able to generate significant propulsive and side forces, however it is unable to generate control moments which may be inadequate for aggressive maneuvering warranted by small agile MAV.
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.
The use of additive manufacturing to produce rotorcraft components is challenging due to demanding material property performance requirements. The need to contend with high cycle fatigue, fretting, and vibratory loading conditions has driven our industry to use high pedigree materials that are fully characterized and with well established and understood processes to transform them into parts. No additive manufacturing processes or materials approach this level of understanding today, making it difficult to utilize the technology to manufacture components designed to be produced using conventional methods. This has limited consideration of the technology in the sustainment segment of our business. Customers have a quite different perspective. Additive manufacturing has been identified by the Department of Defense as a critical technology for the sustainment of their vehicles and weapons systems. Each branch of the military and the Defense Logistics Agency has resources and facilities established to support the proliferation of 3D printing capability. They have all experienced success producing shop aides, tools, prototypes, and surrogate parts to address real time, point of use challenges in depots and in some cases, at or near the battlefield. This success has prompted the DoD to challenge our industry to find ways to utilize this technology to address component shortages due to obsolescence, lost tooling, or a lack of qualified sources. This paper presents Sikorsky's activities and programs that have been initiated to meet this challenge. This will include approaches for component characterization and business case analysis used to evaluate the practicality of using additively manufactured surrogate parts in legacy vehicles.
A concept of operations (CONOPS) is proposed for providing U.S. Marine Corps squads with mission-tailored small unmanned aerial systems (SUASs) using additive manufacturing. This is done on a tactically relevant timescale, ensuring that design improvements can be fielded far faster than with a traditional acquisition process. The CONOPS includes the following stages: mission planning and UAS selection/allocation/modification, order production and transmission, additive manufacturing, assembly and quality control, packaging and delivery, field assembly, field training and guidance, pre-mission checks, and mission use. The stages were developed through extensive discussions and interviews with Marine end users and iterated through several rounds of realistic wargaming. A comprehensive one-week training session was created that equipped Marines to demonstrate all design, manufacturing, and operational skills outlined in the CONOPS.
Sikorsky has developed a specification outlining the use of three casting technologies: simulation, additive manufacturing of the mold and low pressure casting. This specification has been used in the past on new development projects with positive results, reducing lead times and number of pours to produce a useable part. When the S-92 program needed to develop a second source for a casting, they worked with Magellan Aerospace to implement the specification. The project proceeded on time with all castings able to be used. Some elements of the specification were modified to work with a legacy part design, including the use of statistical process controls to reduce variability in crucible pouring.
For high end composite manufacturing in a rapid development environment, the long lead item is often the hard tooling, in particular the cure mold. A traditional metal mold takes in the neighborhood of four to nine months to design, fabricate and validate. With high temperature capable print materials, and larger and faster printers, Additive Manufacturing (AM) appears to have high potential in this area of advanced composites manufacturing. Sikorsky has used AM very successfully on a scale up to approximately 3'x3' and cure temperatures of 350°F. Though long-term durability is still to be determined; the materials, technologies, and techniques Sikorsky has employed for AM autoclave cure molds on this scale have consistently exceeded expectations. AM tools along the scale of main rotor blades could be leveraged to realize even more significant cost and schedule gains from AM autoclave tooling, and in this area, there are still more questions than answers when it comes to a dependable tooling solution. Rotorcraft development, in particular Future Vertical Lift (FVL), programs offer an opportunity to realize the significant schedule and cost benefits AM can provide for composite tooling.
The rapid growth of small-size rotorcraft such as Unmanned Aerial Vehicles (UAV's) creates new missions with a new range of issues. Rotor noise is an inevitable consequence of rotary wing flight and can lead to the annoyance or dissatisfaction of customers. This paper presents the experimental work to explore possible acoustic and aerodynamic performance benefits from a proposed anti-phase rotor technology developed previously by NASA Ames and team. The anti-phase alternating pattern from blade to blade aims to prevent harmonic reinforcement of the blade vortex structure that could theoretically lead to an acoustic reduction. A modified NACA-4412 rotor with a NACA-E63 root was used as the baseline rotor for acoustics and aerodynamic performance comparisons. Six 8inch rotors (two sets per design) were manufactured using 3D printing technology. Testing was conducted in the Open Jet Flow-through Anechoic Chamber on the UAV Rotor Test System at Penn State. A semi-circular array that has a radius of 104 cm and held 15 microphones was used to measure the far-field rotor noise. Three flight conditions, hovering and advancing side edgewise flight 9.7 m/s and retreating side edgewise flight at 9.7 m/s, were tested. A total of nine cases for Matching RPM (MR) and nine cases for Matching Thrust (MT) cases were conducted. Possible uncertainties in the study were identified. Recirculation effects of testing in a closed anechoic chamber was acknowledged. A single rotor hover test at Penn State determined that peaks of Sound Pressure Level (SPL) within 2,000-4,000 Hz showed similar values within 10% difference when the test was in the chamber and outside free from recirculation. This range was taken as the range of interest of this study. The repeatability of data between the three runs in each case, showed variations below 10 % in acoustic performance metrics and below 5 % in aerodynamic performance metrics deeming each case repeatable at the point of testing. Physical differences in the advancing and retreating side rotors of the same design caused by uncertainties in manufacturing were identified to have caused discrepancies in the OASPL readings at the compared microphones of up to 2.3 dB. These discrepancy values can be taken as the possible acoustic error value in this study. In hover the modified rotors showed decreased aerodynamic performance and no significant increase in acoustic performance compared to the baseline rotor. In MR cases, the asymmetric and symmetric design had 10 % and 11 % more thrust but required 12.8 % and 8.4 % more torque and had negative values for percentage 1 / Power Loading (1 / PL) respectively. Overall Sound Pressure Level (OASPL) acoustic delta values were up to +1.3 dB louder. For the advancing side of the edgewise flight cases, the asymmetric design had a -5.1% decrease in torque and 8.4 % 1 / PL value, making it a better design for aerodynamic performance as compared to the symmetric design and the baseline rotor. There were also no significant acoustic performance benefits from either modified rotor. The retreating side showed the most significant aerodynamic performance benefits for both modified rotors. In the MR cases, the asymmetric design had a -22.1 % reduction in torque and a percentage 1 / PL value of 27.1 %. At 3,000 Hz, both the symmetric and asymmetric designs demonstrated significant acoustic advantages over the baseline rotor in the MR case. The symmetric design was 4 to 5 dB quieter and the asymmetric design was 3 to 4 dB quieter. This initial experimental exploration of the anti-phase blade concepts showed promising aerodynamic performance and SPL Spectrum at 3,000 Hz acoustic benefits.
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