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At least 289 records · Page 16

All sources NASA NTRS DOE OSTI

NASA NTRS1989

Development of a dual strain gage balance system for measuring light loads

A strain-gage-balance (SGB) force-measurement system is described which was designed to meet light-load requirements for an airfoil model tested in the NASA Langley low-turbulence pressure tunnel (LTPT). This system was developed to obtain direct force data needed to verify calculated pressure/force correlations used in previous aerodynamic tests. The three-component force-measurement system was designed so that the SGBs would simultaneously support and measure the following loads: weight of the airfoil (approximately 3.0 lbf); 8.0 lbf of lift; 0.5 lbf of drag; and 16.0 in. lbf of pitching moment. In addition to these design loads, the system was required to withstand 100-percent overload on all three components. The system comprises an airfoil, two SGBs, a thermal flexure, and a mounting plate. The installation of the system in the LTPT is also discussed.

Roberts, Paul W.↗

NASA NTRS2024

Evaluation, Analysis, and Application of Internal Strain-Gage Balance Data

Experimental processes, analytical methods, and numerical algorithms are described that may be used to predict the forces and moments of an internal strain–gage balance during a wind tunnel test. First, the control volume model of a strain–gage balance and the concepts of load state, load space, and output space are introduced. These important abstractions provide a better understanding of fundamental characteristics of different balance load prediction approaches. Then, the description of strain–gage balance data and the definition of the primary bridge sensitivity are discussed. Afterwards, basic elements of the calibration of a typical six–component balance are reviewed. Two fundamentally different balance load prediction methods, the processing of check loads, and related topics are also discussed. Three real–world balance data examples are reviewed in great detail to illustrate typical analysis results for a variety of strain–gage balance designs. Finally, important observations are summarized and recommendations are provided. – Additional information and detailed mathematical derivations can be found in the appendices of the document. They include the following topics: balance terminology, definitions of important statistical metrics, balance axis system conventions, balance load transformations, the combined load diagram, electrical output format options, bi–directional output characteristics, determination of the natural zeros, derivation of two balance load prediction methods, description of two tare load iteration algorithms, modeling of balance temperature effects, basics of three–component moment balances, definition of the percent contribution, detection of linear and near–linear dependencies in balance calibration data, a regression model search algorithm, balance interactions, and other related information.

strain-gage balance↗

NASA NTRS1955

Flight Measurements of Horizontal-Tail Loads on the Bell X-5 Research Airplane at a Sweep Angle of 58.7 Deg

A flight investigation was made at altitudes of 40,000, 25,000 and 15,000 feet to determine the horizontal-tail loads of the Bell X-5 research airplane at a sweep angle of 58.7 deg over the lift range of the airplane for Mach numbers from 0.61 to 1.00. The horizontal-tail loads were found to be nonlinear with lift throughout the lift ranges tested at all Mach numbers except at a Mach number of 1.00. The balancing tail loads reflected the changes which occur in the wing characteristics with increasing angle of attack. The nonlinearities were, in general, more pronounced at the higher angles of attack near the pitch-up where the balancing tail loads indicate that the wing-fuselage combination becomes unstable. No apparent effects of altitude on the balancing tail loads were evident over the comparable lift ranges of these tests at altitudes from 40,000 feet to 15,000 feet. Comparisons of balancing tail loads obtained from flight and windtunnel tests indicated discrepancies in absolute magnitudes, but the general trends of the data agree. Some differences in absolute magnitude may be accounted for by the tail load carried inboard of the strain-gage station and the load induced on the fuselage by the presence of the tail. These loads were not measured in flight.

Reed, Robert D↗

NASA NTRS2021

Evaluation, Analysis, and Application of Internal Strain-Gage Balance Data

Experimental processes, analytical methods, and numerical algorithms are described that may be used to predict the forces and moments of an internal strain-gage balance during a wind tunnel test. First, the control volume model of a strain-gage balance and the concepts of load state, load space, and output space are introduced. These important abstractions provide a better understanding of fundamental characteristics of different balance load prediction approaches. Then, the description of strain-gage balance data and the definition of the primary gage sensitivity is discussed. Afterwards, basic elements of the calibration of a typical six-component balance are reviewed. Two fundamentally different balance load prediction methods, the processing of check loads, and related topics are also discussed. Three real-world balance data examples are reviewed in great detail to illustrate typical analysis results for a variety of strain-gage balance designs. Finally, important observations are summarized and recommendations are provided. Additional information and detailed mathematical derivations can be found in the appendices of the document. They include the following topics: balance terminology, definitions of important statistical metrics, balance axis system conventions, balance load transformations, the combined load diagram, electrical output format options, bi-directional gage output characteristics, determination of the natural zeros, derivation of two balance load prediction methods, description of two tare load iteration algorithms, modeling of balance temperature effects, basics of three-component moment balances, definition of the percent contribution, detection of linear and near-linear dependencies in balance calibration data, a regression model term selection algorithm, and other related topics.

wind tunnel test↗

NASA NTRSDate not supplied

Application of the Concepts of Load State, Load Space, and Output Space to Strain-Gage Balances

The concepts of load state, load space, and output space are used to describe elements of the development of a load prediction process for a six–component strain–gage balance. The use of these terms adds clarity during the selection of the independent and dependent variables for the development of the load prediction process. First, the control volume model of a strain–gage balance is reviewed as it helps better understand the role of loads, outputs, and state variables during the load prediction. Then, the description of the absolute load datum in both the load space and the output space is discussed. It is concluded that the use of the difference between a raw output and the natural zero of a balance gage has a key advantage for the definition of the output space. In that case, the origin of the output space will also describe the absolute load datum of the balance. Finally, details of the application of the concepts of load state, load space, and output space to two commonly used balance load prediction methods are discussed.

strain-gage balance↗

NASA NTRS1989

SSME alternate turbopump (pump section) axial load analysis

A flow balancing computer program constructed to calculate the axial loads on the Space Shuttle Main Engine (SSME) alternate turbopumps (ATs) pump sections are described. The loads are used in turn to determine load balancing piston design requirements. The application of the program to the inlet section, inducer/impeller/stage, bearings, seals, labyrinth, damper, piston, face and corner, and stationary/rotating surfaces is indicated. Design analysis results are reported which show that the balancing piston's designs are adequate and that performance and life will not be degraded by the turbopump's axial load characteristics.

Crease, G. A.↗

NASA NTRS1964

Self-balancing beam permits safe, easy load handling under overhang

The use of a self-balancing I-beam with a counterweight and motor simplifies moving heavy loads that are inaccessible for cranes. The beam cannot be overloaded, as the counterweight will not balance the load, and thus acts as an automatic safety device.

Edwards, O. H.↗

NASA NTRS2009

Analysis of Sting Balance Calibration Data Using Optimized Regression Models

Calibration data of a wind tunnel sting balance was processed using a search algorithm that identifies an optimized regression model for the data analysis. The selected sting balance had two moment gages that were mounted forward and aft of the balance moment center. The difference and the sum of the two gage outputs were fitted in the least squares sense using the normal force and the pitching moment at the balance moment center as independent variables. The regression model search algorithm predicted that the difference of the gage outputs should be modeled using the intercept and the normal force. The sum of the two gage outputs, on the other hand, should be modeled using the intercept, the pitching moment, and the square of the pitching moment. Equations of the deflection of a cantilever beam are used to show that the search algorithm s two recommended math models can also be obtained after performing a rigorous theoretical analysis of the deflection of the sting balance under load. The analysis of the sting balance calibration data set is a rare example of a situation when regression models of balance calibration data can directly be derived from first principles of physics and engineering. In addition, it is interesting to see that the search algorithm recommended the same regression models for the data analysis using only a set of statistical quality metrics.

Ulbrich, Norbert↗

NASA NTRS1989

Monitoring dynamic loads on wind tunnel force balances

Two devices have been developed at NASA Langley to monitor the dynamic loads incurred during wind-tunnel testing. The Balance Dynamic Display Unit (BDDU), displays and monitors the combined static and dynamic forces and moments in the orthogonal axes. The Balance Critical Point Analyzer scales and sums each normalized signal from the BDDU to obtain combined dynamic and static signals that represent the dynamic loads at predefined high-stress points. The display of each instrument is a multiplex of six analog signals in a way that each channel is displayed sequentially as one-sixth of the horizontal axis on a single oscilloscope trace. Thus this display format permits the operator to quickly and easily monitor the combined static and dynamic level of up to six channels at the same time.

Ferris, Alice T.↗

NASA NTRS2011

A Human-in-the-Loop Evaluation of Multi-Sector Planning in Mixed Equipage Airspace (MSP III)

A human-in-the-loop (HITL) simulation was conducted in May 2010 to determine the feasibility and value 01 conducting multi-sector planning (MSP) operations in a mixed equipage environment. Aircraft were categorized as equipped or unequipped based on the presence or absence of an air-ground data communications (Data Comm) capability for receiving auto-loadable clearances and transfer of communication messages from the air navigation service provider (ANSP). The purpose of the study was to determine the feasibility and possible benefits of introducing multi-sector planning in a mixed equipage context, or whether Data Comm equipage was required for MSP operations. Each test scenario presented one of three different equipage levels to the controllers (10%, 50% or 90% equipped aircraft), so that the operational impact of different equipage levels could be observed. Operational feasibility assessment addressed two related questions: (1) are MSP operations feasible for unequipped aircraft, and (2) are they feasible in a mixed equipage context. Similarly, two categories of potential benefits were explored: (1) system performance improvements (e.g., throughput, workload) associated with MSP at different equipage levels, and (2) the possibility of providing differential service for equipage through MSP operations. Tool requirements (for both planning and controller stations), as well as planning and coordination procedures - within facility (traffic management unit/operational area) and within sector (R-Side/D-Side) - were two other topics addressed in the study. Overall, results suggested that MSP operations were feasible in a mixed equipage environment and that the tools were effective with both equipped and unequipped aircraft. Using the MSP tools, traffic management coordinators were able to manage controller task load, effectively balancing throughput with complexity and controller task load at each of the three equipage levels tested.

Smith, Nancy↗

NASA NTRSDate not supplied

Load Schedule Design Improvements for the Calibration of NASA's Semi-span Balances

Improvements of the load schedule design for the calibration of NASA's semi-span balances are discussed. These improvements became possible after a minor hardware change was made to Calspan's Large Load Rig. This change moves normal and axial force load points 12 inches closer to the balance moment center. Resulting data quality improvements are significant because Calspan's Large Load Rig cannot currently apply forces at the balance moment center of a semi-span balance. Now, the supported set of rolling and yawing moment arms is 28, 38, and 48 inches. Consequently, the new load schedule design better supports expected normal and axial force locations on semi-span models that are tested in the NASA Ames 11-ft Transonic Wind Tunnel. In addition, estimates of the primary sensitivities of the normal force, axial force, rolling moment, and yawing moment have become more accurate as the applied normal and axial forces have moved closer to the balance moment center. Fundamental moment arm range requirements and Calspan's hardware updates are discussed. In addition, calibration and check load analysis results of NASA's ARC30K semi-span balance are presented to illustrate benefits of the hardware changes.

wind tunnel test↗

NASA NTRS1987

Strain-gage balance calibration of a magnetic suspension and balance system

A load calibration of the NASA 13-in magnetic suspension and balance system (MSBS) is described. The calibration procedure was originally intended to establish the empirical relationship between the coil currents and the external loads (forces and moments) applied to a magnetically suspended calibrator. However, it was discovered that the performance of a strain-gage balance is not affected when subjected to the magnetic environment of the MSBS. The use of strain-gage balances greatly reduces the effort required to perform a current-vs.-load calibration as external loads can be directly inferred from the balance outputs while a calibrator is suspended in MSBS. It is conceivable that in the future such a calibration could become unnecessary, since an even more important application for the use of a strain-gage balance in MSBS environment is the acquisition of precision aerodynamic force and moment data by telemetering the balance outputs from a suspended model/core/balance during wind tunnel tests.

Roberts, Paul W.↗

NASA NTRSDate not supplied

Load Schedule Design Improvements for the Calibration of NASA's Semi-span Balances

Improvements of the load schedule design for the calibration of NASA's semi-span balances are discussed. These improvements became possible after a minor hardware change was made to Calspan's Large Load Rig. This change moves normal and axial force load points 12 inches closer to the balance moment center. Resulting data quality improvements are significant because Calspan's Large Load Rig cannot currently apply forces at the balance moment center of a semi-span balance. Now, the supported set of rolling and yawing moment arms is 28 inches, 38 inches, and 48 inches. Consequently, the new load schedule design better supports expected normal and axial force locations on semi-span models that are tested in the NASA Ames 11-ft Transonic Wind Tunnel. In addition, estimates of the primary sensitivities of the normal force, axial force, rolling moment, and yawing moment have become more accurate as the applied normal and axial forces have moved closer to the balance moment center. Fundamental moment arm range requirements and Calspan's hardware updates are discussed in detail. In addition, calibration analysis results of NASA's ARC30K semi-span balance are presented to illustrate benefits of the hardware changes.

wind tunnel test↗

NASA NTRS1987

Visual display and alarm system for wind tunnel static and dynamic loads

A wind tunnel balance monitor and alarm system developed at NASA Ames Research Center will produce several beneficial results. The costs of wind tunnel delays because of inadvertent balance damage and the costs of balance repair or replacement can be greatly reduced or eliminated with better real-time information on the balance static and dynamic loading. The wind tunnel itself will have enhanced utility with the elimination of overly cautious limits on test conditions. The microprocessor-based system features automatic scaling and 16 multicolored LED bargraphs to indicate both static and dynamic components of the signals from eight individual channels. Five individually programmable alarm levels are available with relay closures for internal or external visual and audible warning devices and other functions such as automatic activation of external recording devices, model positioning mechanisms, or tunnel shutdown.

Hanly, Richard D.↗

NASA NTRS1987

Visual display and alarm system for wind tunnel static and dynamic loads

Hanly, Richard D.↗

NASA NTRS1999

Strain Gauge Balance Calibration and Data Reduction at NASA Langley Research Center

This paper will cover the standard force balance calibration and data reduction techniques used at Langley Research Center. It will cover balance axes definition, balance type, calibration instrumentation, traceability of standards to NIST, calibration loading procedures, balance calibration mathematical model, calibration data reduction techniques, balance accuracy reporting, and calibration frequency.

Ferris, A. T. Judy↗

NASA NTRS1993

Dynamic programming on a shared-memory multiprocessor

Three new algorithms for solving dynamic programming problems on a shared-memory parallel computer are described. All three algorithms attempt to balance work load, while keeping synchronization cost low. In particular, for a multiprocessor having p processors, an analysis of the best algorithm shows that the arithmetic cost is O(n-cubed/6p) and that the synchronization cost is O(absolute value of log sub C n) if p much less than n, where C = (2p-1)/(2p + 1) and n is the size of the problem. The low synchronization cost is important for machines where synchronization is expensive. Analysis and experiments show that the best algorithm is effective in balancing the work load and producing high efficiency.

Edmonds, Phil↗

NASA NTRSDate not supplied

Comparison of Two Load Prediction Methods for Strain-Gage Balances

Data from a five-component semi-span balance is used to perform a systematic comparison of the load prediction accuracy of two load prediction methods. Both methods independently obtain the load prediction equations from multivariate least squares fits of balance calibration data. The first method is called the Non-Iterative Method. This approach directly uses regression models of the individual load components of a balance for the load prediction. The second method is called the Iterative Method. This alternate approach uses a load iteration equation for the load prediction that is constructed from the regression coefficients of the gage outputs of the balance. Basic characteristics of the two methods are reviewed. Afterwards, both methods are applied to calibration, check load, and wind tunnel test data of a five-component semi-span balance. Selected analysis results are compared. These comparisons confirm that the accuracy of the two methods is the same for all practical purposes.

strain-gage balance↗