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At least 1,567 records · Page 87

Composite Load Spectra for Select Space Propulsion Structural Components

Generic load models are described with multiple levels of progressive sophistication to simulate the composite (combined) load spectra (CLS) that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades and liquid oxygen (LOX) posts. These generic (coupled) models combine the deterministic models for composite load dynamic, acoustic, high-pressure and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients are then determined using advanced probabilistic simulation methods with and without strategically selected experimental data. The entire simulation process is included in a CLS computer code. Applications of the computer code to various components in conjunction with the PSAM (Probabilistic Structural Analysis Method) to perform probabilistic load evaluation and life prediction evaluations are also described to illustrate the effectiveness of the coupled model approach.

Ho, Hing W.↗

Next Generation Exercise Device (NGED): Advancing Exercise Capabilities for Future Space Missions Through Biomechanical Modeling

BACKGROUND As space exploration extends to long-duration missions on the Moon and Mars, maintaining astronaut health and fitness becomes increasingly critical. The Next Generation Exercise Device (NGED), developed and tested by the HumanWorks Lab in NASA Johnson Space Center's (JSC) Software, Robotics, and Simulation Division, aims to address this challenge through innovative approaches. This study presents the development and evaluation of an NGED system, focusing on its adaptability to various mission scenarios, including prospective use in a Lunar Pressurized Rover (LPR). Central to this project is the application of biomechanical modeling to optimize exercise efficacy and safety in microgravity and partial gravity environments. The project is a collaborative effort with the Human Health and Performance group at Johnson Space Center, ensuring a comprehensive approach to astronaut well-being that integrates biomechanical principles with practical exercise solutions. The NGED represents the next generation of exercise capabilities for missions in space, on the Moon and Mars, with a specific focus on applications such as the LPR. METHODS AND RESULTS Data collection for NGED development was conducted with two motor-driven Beyond Power Voltra I [1] systems and a custom test structure to allow placement of the cable-based devices on the ground, at shoulder height, and overhead. The collection was performed in JSC’s Prototype Immersive Technology (PIT) Lab, utilizing an OptiTrack motion capture system and AMTI force platform, to enable detailed biomechanical analysis via OpenSim [2,3]. Motion capture data were collected for three subjects representing different body types and statures. The marker set used was an enhanced version of the full-body Plug-in Gait marker set [4], with additional markers strategically placed for the primary objective of informing exercise volume requirements. Subjects performed a series of 17 exercises, carefully selected to engage various muscle groups, including novel spaceflight exercises such as skiing (ergometer style), lateral pulldowns, wood chops, triceps extensions, and flies, with load variations ranging from 10 to 90 pounds to maintain kinematic form. This comprehensive approach allowed for a thorough evaluation of the NGED's performance across a wide range of motions and loads. The biomechanical modeling and analysis were conducted using a modified OpenSim Full Body Rajagopal Model [4,5] and also scaled to the maximum and minimum anthropometry provided in NASA-STD-3001 [6]. Volumetric convex hulls were generated based on model marker trajectories and aggregated into geometric assemblies. These can be placed in models of vehicle designs to assess fit to protect for exercise as well as to adapt NGED exercise to fit available space. Preliminary findings from the collection indicate that the NGED prototype demonstrates significant adaptability across varying user anthropometrics and exercise types. The device showed consistent performance in load-bearing exercises, with subjects able to perform exercises effectively while maintaining proper biomechanical form. CONCLUSION NGED represents a forward-looking advancement in exercise capabilities for future space missions. In the future, this system can be used to capture valuable metrics (e.g., isometric mid-thigh pull for force output measurements, assessments of postural muscle strength, overall isometric strength). Its versatility in accommodating various exercises and user physiques, coupled with the ability to provide targeted biomechanical loading, makes it a promising approach for maintaining astronaut health during long-duration missions to the Moon and Mars. Future work will focus on refining the NGED based on initial biomechanical findings, leveraging the detailed insights provided by motion capture and analysis techniques. Particular emphasis will be placed on optimizing its use within the confined spaces of a LPR and other space habitats. This work contributes significantly to NASA's goals of supporting human health and performance in deep space exploration, paving the way for sustainable long-term presence beyond Low Earth Orbit through advanced, biomechanically-informed exercise solutions.

C Wang↗

Static aeroelastic analysis of composite wing

A static aeroelastic analysis capability that can predict aerodynamic loads for the deformed shape of the composite wing has been developed. The finite element method (FEM) was used for composite plate structural analysis, and the linear vortex lattice method (VLM) was used for steady aerodynamic analysis. The final deformed shape of the wing due to applied forces is determined by iterative manner using FEM and VLM. FEM and VLM analysis are related by a surface spline interpolation procedure. The wing with Gr/Ep composite material has been investigated to see the wing deformation effect. Aerodynamic load change due to wing flexibility has been investigated. Also, the effect of fiber orientation and sweep angle on the deformation pattern and aerodynamic coefficients are examined. For a certain fiber orientation, the deflection and aerodynamic loading of the composite wing is very much reduced. The swept forward wing has more significant effect of wing flexibility on aerodynamic coefficient than the swept back wing does.

Lee, IN↗

Comparison of Electrical Output Format Options for the Analysis of Strain-Gage Balance Calibration Data

Fundamental characteristics of three gage output formats are discussed that may be used to both interpret and analyze wind tunnel strain-gage balance data. The first output format uses raw outputs, i.e., absolute voltage measurements, for the analysis. This choice requires an intercept term in the regression model of the outputs if the Iterative Method is chosen for the load prediction. Raw outputs can be used for the analysis of all known output characteristics as long as the Iterative Method is applied. However, raw outputs cannot be used to analyze data of a balance with bi-directional outputs if the Non-Iterative Method is chosen for the analysis. The second output format, i.e., difference type 1, uses the difference between raw outputs and the natural zeros of the balance gages for the analysis. In this case, the use of the intercept term becomes optional. Analysis results for difference type 1 will exactly match analysis results obtained by using raw outputs as long as identical math models are used for the regression analysis. In addition, difference type 1 may be used to analyze data of a balance with bi directional outputs if an analyst prefers to process data using the Non-Iterative Method. The third output format, i.e., difference type 2, uses the difference between raw outputs and the outputs of the zero load point of a load series for the data analysis. The application of this format is only recommended if the maximum magnitude of all tare loads of a given balance calibration data set is less than two percent of capacity. Data from the calibration of a force balance is used to illustrate the application of the three gage output formats.

Wind Tunnel Strain-Gage Balance↗

Optimizing the performance of Ice-storage Systems in Electricity Load Management through a credit mechanism. An analytical work for Jiangsu, China

Ice-storage air-conditioning is a technique that uses ice for thermal energy storage. Replacing existing air conditioning systems with ice storage has the advantage of shifting the load from on-peak times to off-peak times that often have excess generation. However, increasing the use of ice-storage faces significant challenges in China. One major barrier is the inefficiency in the current electricity tariff structure. There is a lack of effective incentive mechanism that induces ice-storage systems from achieving optimal load-shifting results. This study presents an analysis that compares the potential impacts of ice-storage systems on load-shifting under a new credit-based incentive scheme and the existing incentive arrangement in Jiangsu, China. The study indicates that by changing how ice-storage systems are incentivized in Jiangsu, load-shifting results can be improved.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Density profile sensitivity study of ASDEX Upgrade ICRF Antennas with the TOPICA code

During operation of the ASDEX Upgrade (AUG) ion cyclotron radio frequency (ICRF) system, Tungsten (W)-coated poloidal limiters and structures connected along magnetic field lines to the antenna can be sources of W, which is attributed to sputtering by ions accelerated in radio frequency (RF) sheaths. In order to analyze and optimize the ICRF antenna performance, accurate and efficient simulation tools are necessary. TOPICA code was developed for analysis of ICRF antenna systems with plasma loading conditions modeled with ID FELICE code. This paper presents an initial comparative analysis of two AUG ICRF antennas for a set of model plasma density profiles (with varying density gradient and antenna cut-off distance). The antennas are presently installed in AUG and differ in that one was partially optimized using HFSS code to reduce E{sub ||} near fields. Power transferred to plasma and sheath driving RF potentials are computed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Instability analysis of torispherical pressure vessel heads with triangular thin-shell finite elements

The elastic instability of an internally-pressurized cylindrical tank with a torispherical head is investigated using a triangular, doubly curved, thin-shell finite element. The formulation of the finite element, which is based upon cubic displacement functions and a modified principle of potential energy, is first described. Then, the element is verified by comparing numerical results for the linear, stable analysis to alternative solutions for the same problem. The subsequent instability investigation includes the solution of the linearized problem of equilibrium bifurcation, that is, of the classical eigenvalue problem, and a general nonlinear analysis, based on tracing the nonlinear load-displacement path. The critical pressure, obtained with use of the general nonlinear analysis, agrees closely with an experimental result as well as with a numerical solution stemming from an axisymmetric formulation.

Kanodia, V. L.↗

A doublet lattice method for the determination of rotor induced empennage vibration airloads. Analysis description and program documentation

An efficient state-of-the-art method was developed to determine the unteady vibratory airloads produced by the interaction of the main rotor wake with a helicopter empennage. This method was incorporated into a computer program, Rotor Induced Empennage Vibration Analysis (RIEVA). The program requires the main rotor wake position and the strength of the vortices locates near the empennage surfaces. A nonlinear lifting surface analysis is utilized to predict the aerodynamic loads on the empennage surfaces in the presence of these concentrated vortices. The analysis was formulated to include all pertinent effects such as suction of the interacting vortices and the shed vorticity behind the empennage surfaces. The analysis employs a time domain solution. The output of the program consists of chordwise and spanwise airload distributions on the empennage surfaces. The airload distributions are harmonically analyzed and formulated for input into the Coupled Rotor/Airframe Vibration Analysis.

Gangwani, S. T.↗

Stress analysis of 27% scale model of AH-64 main rotor hub

Stress analysis of an AH-64 27% scale model rotor hub was performed. Component loads and stresses were calculated based upon blade root loads and motions. The static and fatigue analysis indicates positive margins of safety in all components checked. Using the format developed here, the hub can be stress checked for future application.

Hodges, R. V.↗

Coupled Aerodynamic and Structural Sensitivity Analysis of a High-Speed Civil Transport

An objective of the High Performance Computing and Communication Program at the NASA Langley Research Center is to demonstrate multidisciplinary shape and sizing optimization of a complete aerospace vehicle configuration by using high-fidelity, finite-element structural analysis and computational fluid dynamics aerodynamic analysis. In a previous study, a multi-disciplinary analysis system for a high-speed civil transport was formulated to integrate a set of existing discipline analysis codes, some of them computationally intensive, This paper is an extension of the previous study, in which the sensitivity analysis for the coupled aerodynamic and structural analysis problem is formulated and implemented. Uncoupled stress sensitivities computed with a constant load vector in a commercial finite element analysis code are compared to coupled aeroelastic sensitivities computed by finite differences. The computational expense of these sensitivity calculation methods is discussed.

Mason, B. H.↗

SLS Trade Study 0058: Day of Launch (DOL) Wind Biasing

SLS heritage hardware and legacy designs have shown load exceedances at several locations during Design Analysis Cycles (DAC): MPCV Z bending moments; ICPS Electro-Mechanical Actuator (EMA) loads; Core Stage loads just downstream of Booster forward interface. SLS Buffet Loads Mitigation Task Team (BLMTT) tasked to study issue. Identified low frequency buffet load responses are a function of the vehicle's total angle of attack (AlphaTotal). SLS DOL Wind Biasing Trade team to analyze DOL wind biasing methods to limit maximum AlphaTotal in the M0.8 - 2.0 altitude region for EM-1 and EM-2 missions through investigating: Trajectory design process; Wind wavelength filtering options; Launch availability; DOL process to achieve shorter processing/uplink timeline. Trade Team consisted of personnel supporting SLS, MPCV, GSDO programs.

Decker, Ryan K.↗

Physics and Engineering Assessmetns of the K-DEMO Magnet Configuration

Increased attention is being given now to studies of next-step fusion facilities with nuclear missions. Among these, South Korea's K DEMO is unique in its focus on a high toroidal magnetic field, large major radius, steady-state tokamak design for the core of a facility to test fusion nuclear components in Phase I and, after upgrades, produce 500 MW of electricity in a Phase II. Innovative features of the K DEMO magnet set include the use of two toroidal field (TF) coil winding packs with conductor grading and a machine configuration designed for vertical maintenance. The magnet arrangement features large TF coils and widely spaced poloidal field (PF) coils to accommodate removal of in-vessel components as large modules. Physics and engineering assessments of the pre-conceptual K-DEMO magnet configuration are reported, including: 1) design point and operating space assessment, 2) conductor assessment, and 3) structural assessment. It is found that a reference design point at 6.8 m major radius and 7.4 T toroidal field provides sufficient operating margins for the 500 MWe Phase II mission. Analyses of candidate cable-in-conduit conductors provide predictions of critical current degradation, both in the initial load cycle and an additionally with cyclic loading. A first-pass global analysis of the magnet system found minimal out-of-plane deformations of the TF coil, but an overstress condition in the inner leg of the TF coil. However an analysis taking into account elastic-plastic behavior, frictional sliding, and displacement shows that the structure can safely carry the load. Although the design evolution is still at an early stage, these assessments support the design point choices to date and the expectation that a feasible solution for the high-field K DEMO magnet system can be found.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Acoustic emission characteristics of copper alloys under low-cycle fatigue conditions

The acoustic emission (AE) characteristics of pure copper, zirconium-copper, and several copper alloys were determined to develop nondestructive evaluation schemes of thrust chambers through AE techniques. The AE counts rms voltages, frequency spectrum, and amplitude distribution analysis evaluated AE behavior under fatigue loading conditions. The results were interpreted with the evaluation of wave forms, crack propagation characteristics, as well as scanning electron fractographs of fatigue-tested samples. AE signals at the beginning of a fatigue test were produced by a sample of annealed alloys. A sample of zirconium-containing alloys annealed repeatedly after each fatigue loading cycle showed numerous surface cracks during the subsequent fatigue cycle, emitting strong-burst AE signals. Amplitude distribution analysis exhibits responses that are characteristic of certain types of AE signals.

Krampfner, Y.↗

Experimental and finite element study of a standing torus under normal and tangential loads

The effect of a combined external load consisting of a normal component and a tangential braking force applied to an inflated torus is addressed. Experimental results obtained by photographic study of the contact area between the torus and load plate are presented as well as measurements of the vertical and horizontal displacement of the torus under load. A numerical procedure for displacement analysis is developed in which the finite element program STAGS (Structural Analysis of General Shells) is used in an iterative manner to produce a flat, horizontal footprint surface under force loading. The redistributed force distribution obtained by the iterative process is displayed along with computed meridional and circumferential stresses. Finally, an extension of the iterative method is introduced which eliminates the need to experimentally determine the footprint area.

Flugrad, D. R.↗

Probabilistic structural analysis methods development for SSME

The development of probabilistic structural analysis methods is a major part of the SSME Structural Durability Program and consists of three program elements: composite load spectra, probabilistic finite element structural analysis, and probabilistic structural analysis applications. Recent progress includes: (1) the effects of the uncertainties of several factors on the HPFP blade temperature pressure and torque, (2) the evaluation of the cumulative distribution function of structural response variables based on assumed uncertainties on primitive structural variables, and (3) evaluation of the failure probability. Collectively, the results obtained demonstrate that the structural durability of critical SSME components can be probabilistically evaluated.

Chamis, C. C.↗

Split torque transmission load sharing

Split torque transmissions are attractive alternatives to conventional planetary designs for helicopter transmissions. The split torque designs can offer lighter weight and fewer parts but have not been used extensively for lack of experience, especially with obtaining proper load sharing. Two split torque designs that use different load sharing methods have been studied. Precise indexing and alignment of the geartrain to produce acceptable load sharing has been demonstrated. An elastomeric torque splitter that has large torsional compliance and damping produces even better load sharing while reducing dynamic transmission error and noise. However, the elastomeric torque splitter as now configured is not capable over the full range of operating conditions of a fielded system. A thrust balancing load sharing device was evaluated. Friction forces that oppose the motion of the balance mechanism are significant. A static analysis suggests increasing the helix angle of the input pinion of the thrust balancing design. Also, dynamic analysis of this design predicts good load sharing and significant torsional response to accumulative pitch errors of the gears.

Krantz, T. L.↗

Wake-Induced Aerodynamics on a Trailing Aircraft

NASA conducted flight tests to measure the exhaust products from alternative fuels using a DC-8 transport aircraft and a Falcon business jet. An independent analysis of the maximum vortex-induced loads on the Falcon in the DC-8 wake was conducted for pre-flight safety analysis and to define safe trail distances for the flight tests. Static and dynamic vortex-induced aerodynamic loads on the Falcon were predicted at a matrix of locations aft of the DC-8 under flight-test conditions, and the maximum loads were compared with design limit loads to assess aircraft safety. Trajectory simulations for the Falcon during close encounters with the DC-8 wake were made to study the vortex-induced loads during traverses of the DC-8 primary trailing vortex. A parametric study of flight traverses through the trailing vortex was conducted to assess Falcon flight behavior and motion characteristics.

Mendenhall, Michael R.↗

Combining Thermal And Structural Analyses

Computer code makes programs compatible so stresses and deformations calculated. Paper describes computer code combining thermal analysis with structural analysis. Called SNIP (for SINDA-NASTRAN Interfacing Program), code provides interface between finite-difference thermal model of system and finite-element structural model when no node-to-element correlation between models. Eliminates much manual work in converting temperature results of SINDA (Systems Improved Numerical Differencing Analyzer) program into thermal loads for NASTRAN (NASA Structural Analysis) program. Used to analyze concentrating reflectors for solar generation of electric power. Large thermal and structural models needed to predict distortion of surface shapes, and SNIP saves considerable time and effort in combining models.

Winegar, Steven R.↗