Passive Orbital Disconnect Strut (PODS 3) structural test program

NASA Technical Reports Server (NTRS)

Parmley, R. T.

1985-01-01

A passive orbital disconnect strut (PODS-3) was analyzed structurally and thermally. Development tests on a graphite/epoxy orbit tube and S glass epoxy launch tube provided the needed data to finalize the design. A detailed assembly procedure was prepared. One strut was fabricated. Shorting loads in both the axial and lateral direction (vs. load angle and location) were measured. The strut was taken to design limit loads at both ambient and 78 K (cold end only). One million fatigue cycles were performed at predicted STS loads (half in tension, half in compression) with the cold end at 78 K. The fatigue test was repeated at design limit loads. Six struts were then fabricated and tested as a system. Axial loads, side loads, and simulated asymmetric loads due to temperature gradients around the vacuum shell were applied. Shorting loads were measured for all tests.

Efficient field testing for load rating railroad bridges

NASA Astrophysics Data System (ADS)

Schulz, Jeffrey L.; Brett C., Commander

1995-06-01

As the condition of our infrastructure continues to deteriorate, and the loads carried by our bridges continue to increase, an ever growing number of railroad and highway bridges require load limits. With safety and transportation costs at both ends of the spectrum. the need for accurate load rating is paramount. This paper describes a method that has been developed for efficient load testing and evaluation of short- and medium-span bridges. Through the use of a specially-designed structural testing system and efficient load test procedures, a typical bridge can be instrumented and tested at 64 points in less than one working day and with minimum impact on rail traffic. Various techniques are available to evaluate structural properties and obtain a realistic model. With field data, a simple finite element model is 'calibrated' and its accuracy is verified. Appropriate design and rating loads are applied to the resulting model and stress predictions are made. This technique has been performed on numerous structures to address specific problems and to provide accurate load ratings. The merits and limitations of this approach are discussed in the context of actual examples of both rail and highway bridges that were tested and evaluated.

Loading tests of a wing structure for a hypersonic aircraft

NASA Technical Reports Server (NTRS)

Fields, R. A.; Reardon, L. F.; Siegel, W. H.

1980-01-01

Room-temperature loading tests were conducted on a wing structure designed with a beaded panel concept for a Mach 8 hypersonic research airplane. Strain, stress, and deflection data were compared with the results of three finite-element structural analysis computer programs and with design data. The test program data were used to evaluate the structural concept and the methods of analysis used in the design. A force stiffness technique was utilized in conjunction with load conditions which produced various combinations of panel shear and compression loading to determine the failure envelope of the buckling critical beaded panels The force-stiffness data did not result in any predictions of buckling failure. It was, therefore, concluded that the panels were conservatively designed as a result of design constraints and assumptions of panel eccentricities. The analysis programs calculated strains and stresses competently. Comparisons between calculated and measured structural deflections showed good agreement. The test program offered a positive demonstration of the beaded panel concept subjected to room-temperature load conditions.

Highly Loaded Composite Strut Test Development

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey; Phelps, James E.; McKenney, Martin J.; Jegley, Dawn C.

2011-01-01

Highly loaded composite struts, representative of structural elements of a proposed truss-based lunar lander descent stage concept, were selected for design, development, fabrication and testing under NASA s Advanced Composites Technology program. The focus of this paper is the development of a capability for experimental evaluation of the structural performance of these struts. Strut lengths range from 60 to over 120 inches, and compressive launch and ascent loads can exceed -100,000 lbs, or approximately two times the corresponding tensile loads. Allowing all possible compressive structural responses, including elastic buckling, were primary considerations for designing the test hardware.

Static and dynamic pile testing of reinforced concrete piles with structure integrated fibre optic strain sensors

NASA Astrophysics Data System (ADS)

Schilder, Constanze; Kohlhoff, Harald; Hofmann, Detlef; Basedau, Frank; Habel, Wolfgang R.; Baeßler, Matthias; Niederleithinger, Ernst; Georgi, Steven; Herten, Markus

2013-05-01

Static and dynamic pile tests are carried out to determine the load bearing capacity and the quality of reinforced concrete piles. As part of a round robin test to evaluate dynamic load tests, structure integrated fibre optic strain sensors were used to receive more detailed information about the strains along the pile length compared to conventional measurements at the pile head. This paper shows the instrumentation of the pile with extrinsic Fabry-Perot interferometers sensors and fibre Bragg gratings sensors together with the results of the conducted static load test as well as the dynamic load tests and pile integrity tests.

Structural Benchmark Tests of Composite Combustion Chamber Support Completed

NASA Technical Reports Server (NTRS)

Krause, David L.; Thesken, John C.; Shin, E. Eugene; Sutter, James K.

2005-01-01

A series of mechanical load tests was completed on several novel design concepts for extremely lightweight combustion chamber support structures at the NASA Glenn Research Center (http://www.nasa.gov/glenn/). The tests included compliance evaluation, preliminary proof loadings, high-strain cyclic testing, and finally residual strength testing of each design (see the photograph on the left). Loads were applied with single rollers (see the photograph on the right) or pressure plates (not shown) located midspan on each side to minimize the influence of contact stresses on corner deformation measurements. Where rollers alone were used, a more severe structural loading was produced than the corresponding equal-force pressure loading: the maximum transverse shear force existed over the entire length of each side, and the corner bending moments were greater than for a distributed (pressure) loading. Failure modes initiating at the corner only provided a qualitative indication of the performance limitations since the stress state was not identical to internal pressure. Configurations were tested at both room and elevated temperatures. Experimental results were used to evaluate analytical prediction tools and finite-element methodologies for future work, and they were essential to provide insight into the deformation at the corners. The tests also were used to assess fabrication and bonding details for the complicated structures. They will be used to further optimize the design of the support structures for weight performance and the efficacy of corner reinforcement.

Overview Of Structural Behavior and Occupant Responses from Crash Test of a Composite Airplane

NASA Technical Reports Server (NTRS)

Jones, Lisa E.; Carden, Huey D.

1995-01-01

As part of NASA's composite structures crash dynamics research, a general aviation aircraft with composite wing, fuselage and empennage (but with metal subfloor structure) was crash tested at the NASA Langley Research Center Impact Research Facility. The test was conducted to determine composite aircraft structural behavior for crash loading conditions and to provide a baseline for a similar aircraft test with a modified subfloor. Structural integrity and cabin volume were maintained. Lumbar loads for dummy occupants in energy absorbing seats wer substantially lower than those in standard aircraft seats; however, loads in the standard seats were much higher that those recorded under similar conditions for an all-metallic aircraft.

Theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains

NASA Astrophysics Data System (ADS)

Zhu, Ning; Sun, Shou-Guang; Li, Qiang; Zou, Hua

2014-12-01

One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions. This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains. The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames. Moreover, a force-measuring frame is designed and manufactured based on the quasi-static load series. The load decoupling model of the quasi-static load series is then established via calibration tests. Quasi-static load-time histories, together with online tests and decoupling analysis, are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line. The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm. The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames.

Forward Skirt Structural Testing on the Space Launch System (SLS) Program

NASA Technical Reports Server (NTRS)

Lohrer, Joe; Wright, R. D.

2016-01-01

Introduction: (a) Structural testing was performed to evaluate Space Shuttle heritage forward skirts for use on the Space Launch System (SLS) program, (b) Testing was required because SLS loads are approximately 35% greater than shuttle loads; and (c) Two forwards skirts were tested to failure.

T-Cap Pull-Off and Bending Behavior for Stitched Structure

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.; Leone, Frank A., Jr.

2016-01-01

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is a structural concept that was developed by The Boeing Company to address the complex structural design aspects associated with a pressurized hybrid wing body aircraft configuration. An important design feature required for assembly is the integrally stitched T-cap, which provides connectivity of the corner (orthogonal) joint between adjacent panels. A series of tests were conducted on T-cap test articles, with and without a rod stiffener penetrating the T-cap web, under tension (pull-off) and bending loads. Three designs were tested, including the baseline design used in largescale test articles. The baseline had only the manufacturing stitch row adjacent to the fillet at the base of the T-cap web. Two new designs added stitching rows to the T-cap web at either 0.5- or 1.0-inch spacing along the height of the web. Testing was conducted at NASA Langley Research Center to determine the behavior of the T-cap region resulting from the applied loading. Results show that stitching arrests the initial delamination failures so that the maximum strength capability exceeds the load at which the initial delaminations develop. However, it was seen that the added web stitching had very little effect on the initial delamination failure load, but actually decreased the initial delamination failure load for tension loading of test articles without a stiffener passing through the web. Additionally, the added web stitching only increased the maximum load capability by between 1% and 12.5%. The presence of the stiffener, however, did increase the initial and maximum loads for both tension and bending loading as compared to the stringerless baseline design. Based on the results of the few samples tested, the additional stitching in the T-cap web showed little advantage over the baseline design in terms of structural failure at the T-cap web/skin junction for the current test articles.

Compression After Impact Testing of Sandwich Structures Using the Four Point Bend Test

NASA Technical Reports Server (NTRS)

Nettles, Alan T.; Gregory, Elizabeth; Jackson, Justin; Kenworthy, Devon

2008-01-01

For many composite laminated structures, the design is driven by data obtained from Compression after Impact (CAI) testing. There currently is no standard for CAI testing of sandwich structures although there is one for solid laminates of a certain thickness and lay-up configuration. Most sandwich CAI testing has followed the basic technique of this standard where the loaded ends are precision machined and placed between two platens and compressed until failure. If little or no damage is present during the compression tests, the loaded ends may need to be potted to prevent end brooming. By putting a sandwich beam in a four point bend configuration, the region between the inner supports is put under a compressive load and a sandwich laminate with damage can be tested in this manner without the need for precision machining. Also, specimens with no damage can be taken to failure so direct comparisons between damaged and undamaged strength can be made. Data is presented that demonstrates the four point bend CAI test and is compared with end loaded compression tests of the same sandwich structure.

Influence of Axial Load on Electromechanical Impedance (EMI) of Embedded Piezoceramic Transducers in Steel Fiber Concrete.

PubMed

Wang, Zhijie; Chen, Dongdong; Zheng, Liqiong; Huo, Linsheng; Song, Gangbing

2018-06-01

With the advantages of high tensile, bending, and shear strength, steel fiber concrete structures have been widely used in civil engineering. The health monitoring of concrete structures, including steel fiber concrete structures, receives increasing attention, and the Electromechanical Impedance (EMI)-based method is commonly used. Structures are often subject to changing axial load and ignoring the effect of axial forces may introduce error to Structural Health Monitoring (SHM), including the EMI-based method. However, many of the concrete structure monitoring algorithms do not consider the effects of axial loading. To investigate the influence of axial load on the EMI of a steel fiber concrete structure, concrete specimens with different steel fiber content (0, 30, 60, 90, 120) (kg/m³) were casted and the Lead Zirconate Titanate (PZT)-based Smart Aggregate (SA) was used as the EMI sensor. During tests, the step-by-step loading procedure was applied on different steel fiber content specimens, and the electromechanical impedance values were measured. The Normalized root-mean-square deviation Index (NI) was developed to analyze the EMI information and evaluate the test results. The results show that the normalized root-mean-square deviation index increases with the increase of the axial load, which clearly demonstrates the influence of axial load on the EMI values for steel fiber concrete and this influence should be considered during a monitoring or damage detection procedure if the axial load changes. In addition, testing results clearly reveal that the steel fiber content, often at low mass and volume percentage, has no obvious influence on the PZT's EMI values. Furthermore, experiments to test the repeatability of the proposed method were conducted. The repeating test results show that the EMI-based indices are repeatable and there is a great linearity between the NI and the applied loading.

The SLS Stages Intertank Structural Test Assembly (STA) arrives at MSFC

NASA Image and Video Library

2018-03-06

The SLS Stages Intertank Structural Test Assembly (STA) is rolling off the NASA Pegasus Barge at the MSFC Dock enroute to the MSFC 4619 Load Test Annex test facility for qualification testing. Members of MSFC Logistics Office and Move Team members gather for last minute instructions and safety briefing before off-loading STA hardware.

Structural Performance of a Hybrid FRP-Aluminum Modular Triangular Truss System Subjected to Various Loading Conditions

PubMed Central

Zhang, Dongdong; Huang, Yaxin; Zhao, Qilin; Li, Fei; Gao, Yifeng

2014-01-01

A novel hybrid FRP-aluminum truss system has been employed in a two-rut modular bridge superstructure composed of twin inverted triangular trusses. The actual flexural behavior of a one-rut truss has been previously investigated under the on-axis loading test; however, the structural performance of the one-rut truss subjected to an off-axis load is still not fully understood. In this paper, a geometrical linear finite element model is introduced and validated by the on-axis loading test; the structural performance of the one-rut truss subjected to off-axis load was numerically obtained; the dissimilarities of the structural performance between the two different loading cases are investigated in detail. The results indicated that (1) the structural behavior of the off-axis load differs from that of the on-axis load, and the off-axis load is the critical loading condition controlling the structural performance of the triangular truss; (2) under the off-axis load, the FRP trussed members and connectors bear certain out-of-plane bending moments and are subjected to a complicated stress state; and (3) the stress state of these members does not match that of the initial design, and optimization for the redesign of these members is needed, especially for the pretightened teeth connectors. PMID:25254254

Safety envelope for load tolerance of structural element design based on multi-stage testing

DOE PAGES

Park, Chanyoung; Kim, Nam H.

2016-09-06

Structural elements, such as stiffened panels and lap joints, are basic components of aircraft structures. For aircraft structural design, designers select predesigned elements satisfying the design load requirement based on their load-carrying capabilities. Therefore, estimation of safety envelope of structural elements for load tolerances would be a good investment for design purpose. In this article, a method of estimating safety envelope is presented using probabilistic classification, which can estimate a specific level of failure probability under both aleatory and epistemic uncertainties. An important contribution of this article is that the calculation uncertainty is reflected in building a safety envelope usingmore » Gaussian process, and the effect of element test data on reducing the calculation uncertainty is incorporated by updating the Gaussian process model with the element test data. It is shown that even one element test can significantly reduce the calculation uncertainty due to lacking knowledge of actual physics, so that conservativeness in a safety envelope is significantly reduced. The proposed approach was demonstrated with a cantilever beam example, which represents a structural element. The example shows that calculation uncertainty provides about 93% conservativeness against the uncertainty due to a few element tests. As a result, it is shown that even a single element test can increase the load tolerance modeled with the safety envelope by 20%.« less

Analysis of a Hybrid Wing Body Center Section Test Article

NASA Technical Reports Server (NTRS)

Wu, Hsi-Yung T.; Shaw, Peter; Przekop, Adam

2013-01-01

The hybrid wing body center section test article is an all-composite structure made of crown, floor, keel, bulkhead, and rib panels utilizing the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) design concept. The primary goal of this test article is to prove that PRSEUS components are capable of carrying combined loads that are representative of a hybrid wing body pressure cabin design regime. This paper summarizes the analytical approach, analysis results, and failure predictions of the test article. A global finite element model of composite panels, metallic fittings, mechanical fasteners, and the Combined Loads Test System (COLTS) test fixture was used to conduct linear structural strength and stability analyses to validate the specimen under the most critical combination of bending and pressure loading conditions found in the hybrid wing body pressure cabin. Local detail analyses were also performed at locations with high stress concentrations, at Tee-cap noodle interfaces with surrounding laminates, and at fastener locations with high bearing/bypass loads. Failure predictions for different composite and metallic failure modes were made, and nonlinear analyses were also performed to study the structural response of the test article under combined bending and pressure loading. This large-scale specimen test will be conducted at the COLTS facility at the NASA Langley Research Center.

Forward Skirt Structural Testing on the Space Launch System (SLS) Program

NASA Technical Reports Server (NTRS)

Lohrer, J. D.; Wright, R. D.

2016-01-01

Structural testing was performed to evaluate heritage forward skirts from the Space Shuttle program for use on the Space Launch System (SLS) program. One forward skirt is located in each solid rocket booster. Heritage forward skirts are aluminum 2219 welded structures. Loads are applied at the forward skirt thrust post and ball assembly. Testing was needed because SLS ascent loads are roughly 40% higher than Space Shuttle loads. Testing objectives were to determine margins of safety, demonstrate reliability, and validate analytical models. Two forward skirts were structurally tested using the test configuration. The test stand applied loads to the thrust post. Four hydraulic actuators were used to apply axial load and two hydraulic actuators were used to apply radial and tangential loads. The first test was referred to as FSTA-1 (Forward Skirt Structural Test Article) and was performed in April/May 2014. The purpose of FSTA-1 was to verify the ultimate capability of the forward skirt subjected to ascent ultimate loads. Testing consisted of two liftoff load cases taken to 100% limit load followed by an ascent load case taken to 110% limit load. The forward skirt was unloaded to no load after each test case. Lastly, the forward skirt was tested to 140% limit and then to failure using the ascent loads. The second test was referred to as FSTA-2 and performed in July/August of 2014. The purpose of FSTA-2 was to verify the ultimate capability of the forward skirt subjected to liftoff ultimate loads. Testing consisted of six liftoff load cases taken to 100% limit load followed by the six liftoff cases taken to 140% limit load. Two ascent load cases were then tested to 100% limit load. The forward skirt was unloaded to no load after each test case. Lastly, the forward skirt was tested to 140% limit and then to failure using the ascent loads. The forward skirts on FSTA-1 and FSTA-2 successfully carried all applied liftoff and ascent load cases. Both FSTA-1 and FSTA-2 were tested to failure by increasing the ascent loads. Failure occurred in the forward skirt thrust post radius. The forward skirts on FSTA-1 and FSTA-2 had nearly identical failure modes. FSTA-1 failed at 1.72 times limit load and FSTA-2 failed at 1.62 times limit load. This difference is primarily attributed to variation in material properties in the thrust post region. Test data were obtained from strain gages, deflection gages, ARAMIS digital strain measurement, acoustic emissions, and high-speed video. Strain gage data and ARAMIS strain were compared to finite element (FE) analysis predictions. Both the forward skirt and tooling were modeled. This allows the analysis to simulate the loading as close as possible to actual test configuration. FSTA-1 and FSTA-2 were instrumented with over 200 strain gages to ensure all possible failure modes could be captured. However, it turned out that three gages provided critical strain data. One was located in the post bore and two on the post radius. More gages were not specified due to space limitations and the desire to not interfere with the use of the ARAMIS system on the post radius. Measured strains were compared to analysis results for the load cycle to failure. Note that FSTA-1 gages were lost before failure was reached. FSTA-2 gages made it to the failure load but one of the radius gages was lost before testing began. This gage was not replaced because of the time and cost associated with disassembly of the test structure. Correlation to analysis was excellent for FSTA-1. FSTA-2 was not quite as good because there was more residual strain from previous load cycles. FSTA-2 was loaded and unloaded with 12 liftoff cases and two ascent cases before taking the skirt to failure. FSTA-1 only had two liftoff cases and one ascent case before taking the skirt to failure. The ARAMIS system was used to determine strain at the post radius by processing digital images of a speckled paint pattern. Digital cameras recorded images of the speckled paint pattern. ARAMIS strain results for FSTA-2 just prior to failure. Note a high strain location develops near the left side. This high strain compares well to analysis prediction for both FSTA-1 and FSTA-2. The strain at this location was also plotted versus limit load. Both FSTA-1 and FSTA-2 had excellent correlation between ARAMIS and analysis strains. Acoustic emission (AE) sensors were used to monitor for damage formation that may occur during testing (e.g., crack formation and growth or propagation). AE was very important because after disassembly of FSTA-1, a crack was observed in the ball fitting radius. The ball fitting did not crack on FSTA-2. AE data was used to reconstruct when the crack occurred. The AE energy versus time plot for FSTA. The energy increased considerably at 850 seconds (152% limit load), indicating a crack could have formed at this point. The only visual evidence found that could have corresponded to this was the crack that initiated in the ball fitting. The cracks in the forward skirt aluminum structures would likely have been lower energy due to a lower modulus and all that were found after failure correlated to occurring after the initial crack in the post radius. This was verified by high-speed cameras used to record the failure.

Testing Machine for Biaxial Loading

NASA Technical Reports Server (NTRS)

Demonet, R. J.; Reeves, R. D.

1985-01-01

Standard tensile-testing machine applies bending and tension simultaneously. Biaxial-loading test machine created by adding two test fixtures to commercial tensile-testing machine. Bending moment applied by substrate-deformation fixture comprising yoke and anvil block. Pneumatic tension-load fixture pulls up on bracket attached to top surface of specimen. Tension and deflection measured with transducers. Modified test apparatus originally developed to load-test Space Shuttle surface-insulation tiles and particuarly important for composite structures.

Combined Loads Test Fixture for Thermal-Structural Testing Aerospace Vehicle Panel Concepts

NASA Technical Reports Server (NTRS)

Fields, Roger A.; Richards, W. Lance; DeAngelis, Michael V.

2004-01-01

A structural test requirement of the National Aero-Space Plane (NASP) program has resulted in the design, fabrication, and implementation of a combined loads test fixture. Principal requirements for the fixture are testing a 4- by 4-ft hat-stiffened panel with combined axial (either tension or compression) and shear load at temperatures ranging from room temperature to 915 F, keeping the test panel stresses caused by the mechanical loads uniform, and thermal stresses caused by non-uniform panel temperatures minimized. The panel represents the side fuselage skin of an experimental aerospace vehicle, and was produced for the NASP program. A comprehensive mechanical loads test program using the new test fixture has been conducted on this panel from room temperature to 500 F. Measured data have been compared with finite-element analyses predictions, verifying that uniform load distributions were achieved by the fixture. The overall correlation of test data with analysis is excellent. The panel stress distributions and temperature distributions are very uniform and fulfill program requirements. This report provides details of an analytical and experimental validation of the combined loads test fixture. Because of its simple design, this unique test fixture can accommodate panels from a variety of aerospace vehicle designs.

Tension and Bending Testing of an Integral T-Cap for Stitched Composite Airframe Joints

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.; Leone, Frank A., Jr.

2016-01-01

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is a structural concept that was developed by The Boeing Company to address the complex structural design aspects associated with a pressurized hybrid wing body aircraft configuration. An important design feature required for assembly is the integrally stitched T-cap, which provides connectivity of the corner (orthogonal) joint between adjacent panels. A series of tests were conducted on T-cap test articles, with and without a rod stiffener penetrating the T-cap web, under tension (pull-off) and bending loads. Three designs were tested, including the baseline design used in large-scale test articles. The baseline had only the manufacturing stitch row adjacent to the fillet at the base of the T-cap web. Two new designs added stitching rows to the T-cap web at either 0.5- or 1.0-inch spacing along the height of the web. Testing was conducted at NASA Langley Research Center to determine the behavior of the T-cap region resulting from the applied loading. Results show that stitching arrests the initial delamination failures so that the maximum strength capability exceeds the load at which the initial delaminations develop. However, it was seen that the added web stitching had very little effect on the initial delamination failure load, but actually decreased the initial delamination failure load for tension loading of test articles without a stiffener passing through the web. Additionally, the added web stitching only increased the maximum load capability by between 1% and 12.5%. The presence of the stiffener, however, did increase the initial and maximum loads for both tension and bending loading as compared to the stringerless baseline design. Based on the results of the few samples tested, the additional stitching in the T-cap web showed little advantage over the baseline design in terms of structural failure at the T-cap web/skin junction for the current test articles.

Design and commission of an experimental test rig to apply a full-scale pressure load on composite sandwich panels representative of an aircraft secondary structure

NASA Astrophysics Data System (ADS)

Crump, D. A.; Dulieu-Barton, J. M.; Savage, J.

2010-01-01

This paper describes the design of a test rig, which is used to apply a representative pressure load to a full-scale composite sandwich secondary aircraft structure. A generic panel was designed with features to represent those in the composite sandwich secondary aircraft structure. To provide full-field strain data from the panels, the test rig was designed for use with optical measurement techniques such as thermoelastic stress analysis (TSA) and digital image correlation (DIC). TSA requires a cyclic load to be applied to a structure for the measurement of the strain state; therefore, the test rig has been designed to be mounted on a standard servo-hydraulic test machine. As both TSA and DIC require an uninterrupted view of the surface of the test panel, an important consideration in the design is facilitating the optical access for the two techniques. To aid the test rig design a finite element (FE) model was produced. The model provides information on the deflections that must be accommodated by the test rig, and ensures that the stress and strain levels developed in the panel when loaded in the test rig would be sufficient for measurement using TSA and DIC. Finally, initial tests using the test rig have shown it to be capable of achieving the required pressure and maintaining a cyclic load. It was also demonstrated that both TSA and DIC data can be collected from the panels under load, which are used to validate the stress and deflection derived from the FE model.

Analysis of Static Load Test of a Masonry Arch Bridge

NASA Astrophysics Data System (ADS)

Shi, Jing-xian; Fang, Tian-tian; Luo, Sheng

2018-03-01

In order to know whether the carrying capacity of the masonry arch bridge built in the 1980s on the shipping channel entering and coming out of the factory of a cement company can meet the current requirements of Level II Load of highway, through the equivalent load distribution of the test vehicle according to the current design specifications, this paper conducted the load test, evaluated the bearing capacity of the in-service stone arch bridge, and made theoretical analysis combined with Midas Civil. The results showed that under the most unfavorable load conditions the measured strain and deflection of the test sections were less than the calculated values, the bridge was in the elastic stage under the design load; the structural strength and stiffness of the bridge had a certain degree of prosperity, and under the in the current conditions of Level II load of highway, the bridge structure was in a safe state.

Analysis and Design of the NASA Langley Cryogenic Pressure Box

NASA Technical Reports Server (NTRS)

Glass, David E.; Stevens, Jonathan C.; Vause, R. Frank; Winn, Peter M.; Maguire, James F.; Driscoll, Glenn C.; Blackburn, Charles L.; Mason, Brian H.

1999-01-01

A cryogenic pressure box was designed and fabricated for use at NASA Langley Research Center (LaRC) to subject 72 in. x 60 in. curved panels to cryogenic temperatures and biaxial tensile loads. The cryogenic pressure box is capable of testing curved panels down to -423 F (20K) with 54 psig maximum pressure on the concave side, and elevated temperatures and atmospheric pressure on the convex surface. The internal surface of the panel is cooled by high pressure helium as that is cooled to -423 F by liquid helium heat exchangers. An array of twelve independently controlled fans circulate the high pressure gaseous helium to provide uniform cooling on the panel surface. The load introduction structure, consisting of four stainless steel load plates and numerous fingers attaching the load plates to the test panel, is designed to introduce loads into the test panel that represent stresses that will he observed in the actual tank structure. The load plates are trace cooled with liquid nitrogen to reduce thermal gradients that may result in bending the load plates, and thus additional stresses in the test panel. The design of the cryogenic systems, load introduction structure, and control system are discussed in this report.

Centaur Standard Shroud (CSS) static limit load structural tests

NASA Technical Reports Server (NTRS)

Eastwood, C.

1975-01-01

The structural capabilities of the jettisonable metal shroud were tested and the interaction of the shroud with the Centaur stage was evaluated. A flight-configured shroud and the assemblies of the associated Centaur stage were tested for applied axial and shear loads to flight limit values. The tests included various thermal, pressure, and load conditions to verify localized strength capabilities, to evaluate subsystem performance, and to determine the aging effect on insulation system properties. The tests series verified the strength capabilities of the shroud and of all associated flight assembles. Shroud deflections were shown to remain within allowable limits so long as load sharing members were connected between the shroud and the Centaur stage.

Structural testing and analysis of a braided, inflatable fabric torus structure

NASA Astrophysics Data System (ADS)

Young, Andrew C.; Davids, William G.; Whitney, Daniel J.; Clapp, Joshua D.; Goupee, Andrew J.

2017-10-01

Inflatable structural members have military, disaster relief, aerospace and other important applications as they possess low mass, can be stored in a relatively small volume and have significant load-carrying capacity once pressurized. Of particular interest to the present research is the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) structure under development by NASA. In order to make predictions about the structural response of the HIAD system, it is necessary to understand the response of individual inflatable tori composing the HIAD structure. These inflatable members present unique challenges to structural testing and modeling due to their internal inflation pressure and relative compliance. Structural testing was performed on a braided, inflatable, toroidal structural member with axial reinforcing cords. The internal inflation pressure, magnitude of enforced displacement and loading methodology were varied. In-plane and out-of-plane experimental results were compared to model predictions using a three dimensional, corotational, flexibility-based fiber-beam finite element model including geometric and material nonlinearities, as well as the effects of inflation pressure. It was found that in order to approximate the load-deformation response observed in experimentation it is necessary to carefully control the test and model boundary conditions and loading scheme.

Characterizing the Response of Composite Panels to a Pyroshock Induced Environment Using Design of Experiments Methodology

NASA Technical Reports Server (NTRS)

Parsons, David S.; Ordway, David; Johnson, Kenneth

2013-01-01

This experimental study seeks to quantify the impact various composite parameters have on the structural response of a composite structure in a pyroshock environment. The prediction of an aerospace structure's response to pyroshock induced loading is largely dependent on empirical databases created from collections of development and flight test data. While there is significant structural response data due to pyroshock induced loading for metallic structures, there is much less data available for composite structures. One challenge of developing a composite pyroshock response database as well as empirical prediction methods for composite structures is the large number of parameters associated with composite materials. This experimental study uses data from a test series planned using design of experiments (DOE) methods. Statistical analysis methods are then used to identify which composite material parameters most greatly influence a flat composite panel's structural response to pyroshock induced loading. The parameters considered are panel thickness, type of ply, ply orientation, and pyroshock level induced into the panel. The results of this test will aid in future large scale testing by eliminating insignificant parameters as well as aid in the development of empirical scaling methods for composite structures' response to pyroshock induced loading.

Characterizing the Response of Composite Panels to a Pyroshock Induced Environment using Design of Experiments Methodology

NASA Technical Reports Server (NTRS)

Parsons, David S.; Ordway, David O.; Johnson, Kenneth L.

2013-01-01

This experimental study seeks to quantify the impact various composite parameters have on the structural response of a composite structure in a pyroshock environment. The prediction of an aerospace structure's response to pyroshock induced loading is largely dependent on empirical databases created from collections of development and flight test data. While there is significant structural response data due to pyroshock induced loading for metallic structures, there is much less data available for composite structures. One challenge of developing a composite pyroshock response database as well as empirical prediction methods for composite structures is the large number of parameters associated with composite materials. This experimental study uses data from a test series planned using design of experiments (DOE) methods. Statistical analysis methods are then used to identify which composite material parameters most greatly influence a flat composite panel's structural response to pyroshock induced loading. The parameters considered are panel thickness, type of ply, ply orientation, and pyroshock level induced into the panel. The results of this test will aid in future large scale testing by eliminating insignificant parameters as well as aid in the development of empirical scaling methods for composite structures' response to pyroshock induced loading.

Shield evaluation and performance testing at the USMB`s Strategic Structures Testing Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barczak, T.M.; Gearhart, D.F.

1996-12-31

Historically, shield performance testing is conducted by the support manufacturers at European facilities. The U.S. Bureau of Mines (USBM) has conducted extensive research in shield Mechanics and is now opening its Strategic Structures Testing (SST) Laboratory to the mining industry for shield performance testing. The SST Laboratory provides unique shield testing capabilities using the Mine Roof Simulator (MRS) load frame. The MRS provides realistic and cost-effective shield evaluation by combining both vertical and horizontal loading into a single load cycle; whereas, several load cycles would be required to obtain this loading in a static frame. In addition to these advantages,more » the USBM acts as an independent research organization to provide an unbiased assessment of shield performance. This paper describes the USBM`s shield testing program that is designed specifically to simulate in-service mining conditions using the unique the capabilities of the SST Laboratory.« less

Locomotive fuel tank structural safety testing program : passenger locomotive fuel tank jackknife derailment load test.

DOT National Transportation Integrated Search

2010-08-01

This report presents the results of a passenger locomotive fuel tank load test simulating jackknife derailment (JD) load. The test is based on FRA requirements for locomotive fuel tanks in the Title 49, Code of Federal Regulations (CFR), Part 238, Ap...

Rate- and duration-of-load behavior of lab-made structural flakeboards

Treesearch

J. D. McNatt

1985-01-01

Tests of structural use panels under different loading conditions provide basic information for establishing design stresses. This paper reports the effects of loading rate in tension and bending and of duration of load in tension on the properties of four lab-made structural flakeboards, (two of which had aligned flakes). The objective was to determine if these panels...

A study of facilities and fixtures for testing of a high speed civil transport wing component

NASA Technical Reports Server (NTRS)

Cerro, J. A.; Vause, R. F.; Bowman, L. M.; Jensen, J. K.; Martin, C. J., Jr.; Stockwell, A. E.; Waters, W. A., Jr.

1996-01-01

A study was performed to determine the feasibility of testing a large-scale High Speed Civil Transport wing component in the Structures and Materials Testing Laboratory in Building 1148 at NASA Langley Research Center. The report includes a survey of the electrical and hydraulic resources and identifies the backing structure and floor hard points which would be available for reacting the test loads. The backing structure analysis uses a new finite element model of the floor and backstop support system in the Structures Laboratory. Information on the data acquisition system and the thermal power requirements is also presented. The study identified the hardware that would be required to test a typical component, including the number and arrangement of hydraulic actuators required to simulate expected flight loads. Load introduction and reaction structure concepts were analyzed to investigate the effects of experimentally induced boundary conditions.

Design and fabrication of Rene 41 advanced structural panels. [their performance under axial compression, shear, and bending loads

NASA Technical Reports Server (NTRS)

Greene, B. E.; Northrup, R. F.

1975-01-01

The efficiency was investigated of curved elements in the design of lightweight structural panels under combined loads of axial compression, inplane shear, and bending. The application is described of technology generated in the initial aluminum program to the design and fabrication of Rene 41 panels for subsequent performance tests at elevated temperature. Optimum designs for two panel configurations are presented. The designs are applicable to hypersonic airplane wing structure, and are designed specifically for testing at elevated temperature in the hypersonic wing test structure located at the NASA Flight Research Center. Fabrication methods developed to produce the Rene panels are described, and test results of smaller structural element specimens are presented to verify the design and fabrication methods used. Predicted strengths of the panels under several proposed elevated temperature test load conditions are presented.

Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.; Valenzuela, Juan G.; Feller, Jerr; Plachta, Dave

2014-01-01

The development of long duration orbital cryogenic storage systems will require the reduction of heat loads into the storage tank. In the case of liquid hydrogen, complete elimination of the heat load at 20 K is currently impractical due to the limitations in lift available on flight cryocoolers. In order to reduce the heat load, without having to remove heat at 20 K, the concept of Reduced Boil-Off uses cooled shields within the insulation system at approximately 90 K. The development of Load-Bearing Multilayer Insulation (LB-MLI) allowed the 90 K shield with tubing and cryocooler attachments to be suspended within the MLI and still be structurally stable. Coupon testing both thermally and structurally were performed to verify that the LB-MLI should work at the tank applied level. Then tank applied thermal and structural (acoustic) testing was performed to demonstrate the functionality of the LB-MLI as a structural insulation system. The LB-MLI showed no degradation of thermal performance due to the acoustic testing and showed excellent thermal performance when integrated with a 90 K class cryocooler on a liquid hydrogen tank.

Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.; Valenzuela, Juan G.; Feller, Jeffrey R.; Plachta, David W.

2014-01-01

The development of long duration orbital cryogenic storage systems will require the reduction of heat loads into the storage tank. In the case of liquid hydrogen, complete elimination of the heat load at 20 K is currently impractical due to the limitations in lift available on flight cryocoolers. In order to reduce the heat load, without having to remove heat at 20 K, the concept of Reduced Boil-Off uses cooled shields within the insulation system at approximately 90 K. The development of Load-Bearing Multilayer Insulation (LB-MLI) allowed the 90 K shield with tubing and cryocooler attachments to be suspended within the MLI and still be structurally stable. Coupon testing, both thermal and structural was performed to verify that the LB-MLI should work at the tank applied level. Then tank applied thermal and structural (acoustic) testing was performed to demonstrate the functionality of the LB-MLI as a structural insulation system. The LB-MLI showed no degradation of thermal performance due to the acoustic testing and showed excellent thermal performance when integrated with a 90 K class cryocooler on a liquid hydrogen tank.

NASA/FAA general aviation crash dynamics program

NASA Technical Reports Server (NTRS)

Thomson, R. G.; Hayduk, R. J.; Carden, H. D.

1981-01-01

The program involves controlled full scale crash testing, nonlinear structural analyses to predict large deflection elastoplastic response, and load attenuating concepts for use in improved seat and subfloor structure. Both analytical and experimental methods are used to develop expertise in these areas. Analyses include simplified procedures for estimating energy dissipating capabilities and comprehensive computerized procedures for predicting airframe response. These analyses are developed to provide designers with methods for predicting accelerations, loads, and displacements on collapsing structure. Tests on typical full scale aircraft and on full and subscale structural components are performed to verify the analyses and to demonstrate load attenuating concepts. A special apparatus was built to test emergency locator transmitters when attached to representative aircraft structure. The apparatus is shown to provide a good simulation of the longitudinal crash pulse observed in full scale aircraft crash tests.

Load control system. [for space shuttle external tank ground tests

NASA Technical Reports Server (NTRS)

Grosse, J. C.

1977-01-01

The load control system developed for the shuttle external structural tests is described. The system consists of a load programming/display module, and a load control module along with the following hydraulic system components: servo valves, dump valves, hydraulic system components, and servo valve manifold blocks. One load programming/display subsystem can support multiple load control subsystem modules.

Full-Scale Test and Analysis Results of a PRSEUS Fuselage Panel to Assess Damage Containment Features

NASA Technical Reports Server (NTRS)

Bergan, Andrew; Bakuckas, John G., Jr.; Lovejoy, Andrew; Jegley, Dawn; Linton, Kim; Neal, Bert; Korkosz, Gregory; Awerbuch, Jonathan; Tan, Tein-Min

2012-01-01

Integrally stitched composite technology is an area that shows promise in enhancing the structural integrity of aircraft and aerospace structures. The most recent generation of this technology is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The goal of the PRSEUS concept relevant to this test is to provide damage containment capability for composite structures while reducing overall structural weight. The National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), and The Boeing Company have partnered in an effort to assess the damage containment features of a full-scale curved PRSEUS panel using the FAA Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility. A single PRSEUS test panel was subjected to axial tension, internal pressure, and combined axial tension and internal pressure loads. The test results showed excellent performance of the PRSEUS concept. No growth of Barely Visible Impact Damage (BVID) was observed after ultimate loads were applied. With a two-bay notch severing the central stringer, damage was contained within the two-bay region well above the required limit load conditions. Catastrophic failure was well above the ultimate load level. Information describing the test panel and procedure has been previously presented, so this paper focuses on the experimental procedure, test results, nondestructive inspection results, and preliminary test and analysis correlation.

Optimal Multi-Type Sensor Placement for Structural Identification by Static-Load Testing

PubMed Central

Papadopoulou, Maria; Vernay, Didier; Smith, Ian F. C.

2017-01-01

Assessing ageing infrastructure is a critical challenge for civil engineers due to the difficulty in the estimation and integration of uncertainties in structural models. Field measurements are increasingly used to improve knowledge of the real behavior of a structure; this activity is called structural identification. Error-domain model falsification (EDMF) is an easy-to-use model-based structural-identification methodology which robustly accommodates systematic uncertainties originating from sources such as boundary conditions, numerical modelling and model fidelity, as well as aleatory uncertainties from sources such as measurement error and material parameter-value estimations. In most practical applications of structural identification, sensors are placed using engineering judgment and experience. However, since sensor placement is fundamental to the success of structural identification, a more rational and systematic method is justified. This study presents a measurement system design methodology to identify the best sensor locations and sensor types using information from static-load tests. More specifically, three static-load tests were studied for the sensor system design using three types of sensors for a performance evaluation of a full-scale bridge in Singapore. Several sensor placement strategies are compared using joint entropy as an information-gain metric. A modified version of the hierarchical algorithm for sensor placement is proposed to take into account mutual information between load tests. It is shown that a carefully-configured measurement strategy that includes multiple sensor types and several load tests maximizes information gain. PMID:29240684

Quantification of loading in biomechanical testing: the influence of dissection sequence.

PubMed

Funabashi, Martha; El-Rich, Marwan; Prasad, Narasimha; Kawchuk, Gregory N

2015-09-18

Sequential dissection is a technique used to investigate loads experienced by articular tissues. When the joint of interest is tested in an unconstrained manner, its kinematics change with each tissue removal. To address this limitation, sufficiently rigid robots are used to constrain joint kinematics. While this approach can quantify loads experienced by each tissue, it does not assure similar results when removal order is changed. Specifically, structure loading is assumed to be independent of removal order if the structure behaves linearly (i.e. principle of superposition applies), but dependent on removal order when response is affected by material and/or geometry nonlinearities and/or viscoelasticiy (e.g. biological tissues). Therefore, this experiment was conducted to evaluate if structure loading created through robotic testing is dependent on the order in which connectors are removed. Six identical models were 3D printed. Each model was composed of 2 rigid bodies and 3 connecting structures with nonlinear time-dependent behavior. To these models, pure rotations were applied about a predefined static center of rotation using a parallel robot. A unique dissection sequence was used for each of the six models and the same movements applied robotically after each dissection. When comparing the moments experienced by each structure between different removal sequences, a statistically significant difference (p<0.05) was observed. These results suggest that even in an optimized environment, the sequence in which nonlinear viscoelastic structures are removed influence model loading. These findings support prior work suggesting that tissue loads obtained from robotic testing are specific to removal order. Copyright © 2015 Elsevier Ltd. All rights reserved.

Full-Field Reconstruction of Structural Deformations and Loads from Measured Strain Data on a Wing Using the Inverse Finite Element Method

NASA Technical Reports Server (NTRS)

Miller, Eric J.; Manalo, Russel; Tessler, Alexander

2016-01-01

A study was undertaken to investigate the measurement of wing deformation and internal loads using measured strain data. Future aerospace vehicle research depends on the ability to accurately measure the deformation and internal loads during ground testing and in flight. The approach uses the inverse Finite Element Method (iFEM). The iFEM is a robust, computationally efficient method that is well suited for real-time measurement of real-time structural deformation and loads. The method has been validated in previous work, but has yet to be applied to a large-scale test article. This work is in preparation for an upcoming loads test of a half-span test wing in the Flight Loads Laboratory at the National Aeronautics and Space Administration Armstrong Flight Research Center (Edwards, California). The method has been implemented into an efficient MATLAB® (The MathWorks, Inc., Natick, Massachusetts) code for testing different sensor configurations. This report discusses formulation and implementation along with the preliminary results from a representative aerospace structure. The end goal is to investigate the modeling and sensor placement approach so that the best practices can be applied to future aerospace projects.

Composite Grids for Reinforcement of Concrete Structures.

DTIC Science & Technology

1998-06-01

to greater compressive loads before induced shear failure occurs. Concrete columns were tested in compression to explore alter- native... columns were tested on the same day as the fiber-reinforced concrete columns . Load /deflection readings were taken with the load cell to determine the...ln) Figure 78. Ultimate load vs toughness for the different beam types tested . USACERLTR-98/81 141 £\\

Thermal coupon testing of Load-Bearing Multilayer Insulation

NASA Astrophysics Data System (ADS)

Johnson, W. L.; Heckle, K. W.; Hurd, J.

2014-01-01

Advanced liquid hydrogen storage concepts being considered for long duration space travel incorporate refrigeration systems and cryocoolers to lower the heat load. Using a refrigeration loop to intercept the energy flowing through MLI to a liquid hydrogen tank at a temperature between the environment and the liquid hydrogen can lower the heat load on the propellant system by as much as 50%. However, the refrigeration loop requires structural integration into the MLI. Use of a more traditional concept of MLI underneath this refrigeration loop requires that a structural system be put in place to support the loop. Such structures, even when thermally optimized, present a relatively large parasitic heat load into the tank. Through NASA small business innovation research funding, Quest Thermal Group and Ball Aerospace have been developing a structural MLI based insulation system. These systems are designed with discrete polymeric spacers between reflective layers instead of either dacron or silk netting. The spacers (or posts) have an intrinsic structural capability that is beyond that of just supporting the internal insulation mechanical loads. This new MLI variant called Load Bearing MLI (LB-MLI) has been developed specifically for the application of supporting thermal shields within the insulation system. Test articles (coupons) of the new LB-MLI product were fabricated for thermal performance testing using liquid nitrogen at Kennedy Space Center (KSC) and using cryocooler based calorimetry at Florida State University. The test results and analysis are presented. Thermal models developed for correlation with the thermal testing results both at KSC and testing that was performed at Florida State University are also discussed.

What limits the achievable areal densities of large aperture space telescopes?

NASA Astrophysics Data System (ADS)

Peterson, Lee D.; Hinkle, Jason D.

2005-08-01

This paper examines requirements trades involving areal density for large space telescope mirrors. A segmented mirror architecture is used to define a quantitative example that leads to relevant insight about the trades. In this architecture, the mirror consists of segments of non-structural optical elements held in place by a structural truss that rests behind the segments. An analysis is presented of the driving design requirements for typical on-orbit loads and ground-test loads. It is shown that the driving on-orbit load would be the resonance of the lowest mode of the mirror by a reaction wheel static unbalance. The driving ground-test load would be dynamics due to ground-induced random vibration. Two general conclusions are derived from these results. First, the areal density that can be allocated to the segments depends on the depth allocated to the structure. More depth in the structure allows the allocation of more mass to the segments. This, however, leads to large structural depth that might be a significant development challenge. Second, the requirement for ground-test-ability results in an order of magnitude or more depth in the structure than is required by the on-orbit loads. This leads to the proposition that avoiding ground test as a driving requirement should be a fundamental technology on par with the provision of deployable depth. Both are important structural challenges for these future systems.

14 CFR 27.681 - Limit load static tests.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Control Systems § 27.681 Limit load... which— (1) The direction of the test loads produces the most severe loading in the control system; and (2) Each fitting, pulley, and bracket used in attaching the system to the main structure is included...

Development of Vehicle Model Test for Road Loading Analysis of Sedan Model

NASA Astrophysics Data System (ADS)

Mohd Nor, M. K.; Noordin, A.; Ruzali, M. F. S.; Hussen, M. H.

2016-11-01

Simple Structural Surfaces (SSS) method is offered as a means of organizing the process for rationalizing the basic vehicle body structure load paths. The application of this simplified approach is highly beneficial in the design development of modern passenger car structure especially during the conceptual stage. In Malaysia, however, there is no real physical model of SSS available to gain considerable insight and understanding into the function of each major subassembly in the whole vehicle structures. Based on this motivation, a physical model of SSS for sedan model with the corresponding model vehicle tests of bending and torsion is proposed in this work. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results show that the proposed vehicle model test is capable to show that satisfactory load paths can give a sufficient structural stiffness within the vehicle structure. It is clearly observed that the global bending stiffness reduce significantly when more panels are removed from a complete SSS model. It is identified that parcel shelf is an important subassembly to sustain bending load. The results also match with the theoretical hypothesis, as the stiffness of the structure in an open section condition is shown weak when subjected to torsion load compared to bending load. The proposed approach can potentially be integrated with FEM to speed up the design process of automotive vehicle.

Load Testing of GFRP Composite U-Shape Footbridge

NASA Astrophysics Data System (ADS)

Pyrzowski, Łukasz; Miśkiewicz, Mikołaj; Chróścielewski, Jacek; Wilde, Krzysztof

2017-10-01

The paper presents the scope of load tests carried out on an innovative shell composite footbridge. The tested footbridge was manufactured in one production cycle and has no components made from materials other than GFRP laminates and PET foam. The load tests, performed on a 14-m long structure, were the final stage of a research program in the Fobridge project carried out in cooperation with: Gdańsk University of Technology (leader), Military University of Technology in Warsaw, and ROMA Co. Ltd.; and co-financed by NCBR. The aim of the tests was to confirm whether the complex U-shape sandwich structure behaves correctly. The design and technological processes involved in constructing this innovative footbridge required the solving of many problems: absence of standards for design of composite footbridges, lack of standardized material data, lack of guidelines for calculation and evaluation of material strength, and no guidelines for infusion of large, thick sandwich elements. Obtaining answers during the design process demanded extensive experimental tests, development of material models, validation of models, updating parameters and extensive numerical parametric studies. The technological aspects of infusion were tested in numerous trials involving the selection of material parameters and control of the infusion parameters. All scientific validation tests were successfully completed and market assessment showed that the proposed product has potential applications; it can be used for overcoming obstacles in rural areas and cities, as well as in regions affected by natural disasters. Load testing included static and dynamic tests. During the former, the span was examined at 117 independent measurement points. The footbridge was loaded with concrete slabs in different configurations. Their total weight ranged from 140 kN up to 202 kN. The applied load at the most heavily loaded structural points caused an effect from 89% to 120%, compared to the load specified by standards (5 kN/m2). Dynamic tests included standard actions (walking, running, synchronous jumps) as well as aggressive tests, all designed to confirm the usability of the footbridge. The performed trials allowed the identification of the modal and damping parameters of the structure. The designated first natural frequency with a value of 7.8 Hz confirmed the correctness of the U-shape cross-section design due to its significant structural rigidity.

Test load verification through strain data analysis

NASA Technical Reports Server (NTRS)

Verderaime, V.; Harrington, F.

1995-01-01

A traditional binding acceptance criterion on polycrystalline structures is the experimental verification of the ultimate factor of safety. At fracture, the induced strain is inelastic and about an order-of-magnitude greater than designed for maximum expected operational limit. At this extreme strained condition, the structure may rotate and displace at the applied verification load such as to unknowingly distort the load transfer into the static test article. Test may result in erroneously accepting a submarginal design or rejecting a reliable one. A technique was developed to identify, monitor, and assess the load transmission error through two back-to-back surface-measured strain data. The technique is programmed for expediency and convenience. Though the method was developed to support affordable aerostructures, the method is also applicable for most high-performance air and surface transportation structural systems.

Design, fabrication and test of Load Bearing multilayer insulation to support a broad area cooled shield

NASA Astrophysics Data System (ADS)

Dye, S. A.; Johnson, W. L.; Plachta, D. W.; Mills, G. L.; Buchanan, L.; Kopelove, A. B.

2014-11-01

Improvements in cryogenic propellant storage are needed to achieve reduced or Zero Boil Off of cryopropellants, critical for long duration missions. Techniques for reducing heat leak into cryotanks include using passive multi-layer insulation (MLI) and vapor cooled or actively cooled thermal shields. Large scale shields cannot be supported by tank structural supports without heat leak through the supports. Traditional MLI also cannot support shield structural loads, and separate shield support mechanisms add significant heat leak. Quest Thermal Group and Ball Aerospace, with NASA SBIR support, have developed a novel Load Bearing multi-layer insulation (LBMLI) capable of self-supporting thermal shields and providing high thermal performance. We report on the development of LBMLI, including design, modeling and analysis, structural testing via vibe and acoustic loading, calorimeter thermal testing, and Reduced Boil-Off (RBO) testing on NASA large scale cryotanks. LBMLI uses the strength of discrete polymer spacers to control interlayer spacing and support the external load of an actively cooled shield and external MLI. Structural testing at NASA Marshall was performed to beyond maximum launch profiles without failure. LBMLI coupons were thermally tested on calorimeters, with superior performance to traditional MLI on a per layer basis. Thermal and structural tests were performed with LBMLI supporting an actively cooled shield, and comparisons are made to the performance of traditional MLI and thermal shield supports. LBMLI provided a 51% reduction in heat leak per layer over a previously tested traditional MLI with tank standoffs, a 38% reduction in mass, and was advanced to TRL5. Active thermal control using LBMLI and a broad area cooled shield offers significant advantages in total system heat flux, mass and structural robustness for future Reduced Boil-Off and Zero Boil-Off cryogenic missions with durations over a few weeks.

The Very Specific Vortex Shedding Test on VEGA Launch Vehicle

NASA Astrophysics Data System (ADS)

Leofanti, Jose Luis; Fotio, Domenico; Grillenbeck, Anton; Dillinger, Stephan; Scaccia, Aldo

2012-07-01

When tall structures are subjected to lateral wind flow, under certain conditions, vortices are shed from alternate sides of the structure inducing periodic cross wind loads on the structure. The periodic loads, in a relatively narrow and stable frequency band, can couple with the structure’s natural frequencies. To avoid this effect the VEGA Launch System (LS) comprised a decoupling device at the launch vehicle (LV) base called Anti Vortex Shedding (AVS). During the LV-Ground Segment combined test campaign in Kourou, the LV mounted on AVS was experimentally verified, including a modal characterization test, a verification under artificial operational loads and finally tested under real wind environment. The paper gives an overview on the particular aspects of test planning, the test setup preparation inside the launch pad gantry, the test performance, test results and the conclusion for the VEGA launch system’s operational readiness.

Buckling behavior of Rene 41 tubular panels for a hypersonic aircraft wing

NASA Technical Reports Server (NTRS)

Ko, W. L.; Fields, R. A.; Shideler, J. L.

1986-01-01

The buckling characteristics of Rene 41 tubular panels for a hypersonic aircraft wing were investigated. The panels were repeatedly tested for buckling characteristics using a hypersonic wing test structure and a universal tension/compression testing machine. The nondestructive buckling tests were carried out under different combined load conditions and in different temperature environments. The force/stiffness technique was used to determine the buckling loads of the panels. In spite of some data scattering resulting from large extrapolations of the data-fitting curve (because of the termination of applied loads at relatively low percentages of the buckling loads), the overall test data correlate fairly well with theoretically predicted buckling interaction curves. Also, the structural efficiency of the tubular panels was found to be slightly higher than that of beaded panels.

Buckling behavior of Rene 41 tubular panels for a hypersonic aircraft wing

NASA Technical Reports Server (NTRS)

Ko, W. L.; Shideler, J. L.; Fields, R. A.

1986-01-01

The buckling characteristics of Rene 41 tubular panels for a hypersonic aircraft wing were investigated. The panels were repeatedly tested for buckling characteristics using a hypersonic wing test structure and a universal tension/compression testing machine. The nondestructive buckling tests were carried out under different combined load conditions and in different temperature environments. The force/stiffness technique was used to determine the buckling loads of the panel. In spite of some data scattering, resulting from large extrapolations of the data fitting curve (because of the termination of applied loads at relatively low percentages of the buckling loads), the overall test data correlate fairly well with theoretically predicted buckling interaction curves. Also, the structural efficiency of the tubular panels was found to be slightly higher than that of beaded panels.

Forward Skirt Structural Testing on the Space Launch System (SLS) Program

NASA Technical Reports Server (NTRS)

Lohrer, J. D.; Wright, R. D.

2016-01-01

Structural testing was performed to evaluate heritage forward skirts from the Space Shuttle program for use on the NASA Space Launch System (SLS) program. Testing was needed because SLS ascent loads are 35% higher than Space Shuttle loads. Objectives of testing were to determine margins of safety, demonstrate reliability, and validate analytical models. Testing combined with analysis was able to show heritage forward skirts were acceptable to use on the SLS program.

Thermal-Mechanical Testing of Hypersonic Vehicle Structures

NASA Technical Reports Server (NTRS)

Hudson, Larry; Stephens, Craig

2007-01-01

A viewgraph presentation describing thermal-mechanical tests on the structures of hypersonic vehicles is shown. The topics include: 1) U.S. Laboratories for Hot Structures Testing; 2) NASA Dryden Flight Loads Laboratory; 3) Hot Structures Test Programs; 4) Typical Sequence for Hot Structures Testing; 5) Current Hot Structures Testing; and 6) Concluding Remarks.

14 CFR 23.785 - Seats, berths, litters, safety belts, and shoulder harnesses.

Code of Federal Regulations, 2014 CFR

2014-01-01

... combination of structural analysis and static load tests to limit load; or (3) Static load tests to ultimate... OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY... resulting from the ultimate static load factors prescribed in § 23.561(b)(2) of this part. Each occupant...

14 CFR 23.785 - Seats, berths, litters, safety belts, and shoulder harnesses.

Code of Federal Regulations, 2011 CFR

2011-01-01

... combination of structural analysis and static load tests to limit load; or (3) Static load tests to ultimate... OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY... resulting from the ultimate static load factors prescribed in § 23.561(b)(2) of this part. Each occupant...

14 CFR 23.785 - Seats, berths, litters, safety belts, and shoulder harnesses.

Code of Federal Regulations, 2010 CFR

2010-01-01

... combination of structural analysis and static load tests to limit load; or (3) Static load tests to ultimate... OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY... resulting from the ultimate static load factors prescribed in § 23.561(b)(2) of this part. Each occupant...

14 CFR 23.785 - Seats, berths, litters, safety belts, and shoulder harnesses.

Code of Federal Regulations, 2012 CFR

2012-01-01

... combination of structural analysis and static load tests to limit load; or (3) Static load tests to ultimate... OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY... resulting from the ultimate static load factors prescribed in § 23.561(b)(2) of this part. Each occupant...

14 CFR 23.785 - Seats, berths, litters, safety belts, and shoulder harnesses.

Code of Federal Regulations, 2013 CFR

2013-01-01

... combination of structural analysis and static load tests to limit load; or (3) Static load tests to ultimate... OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY... resulting from the ultimate static load factors prescribed in § 23.561(b)(2) of this part. Each occupant...

Evaluation of nanostructural, mechanical, and biological properties of collagen-nanotube composites.

PubMed

Tan, Wei; Twomey, John; Guo, Dongjie; Madhavan, Krishna; Li, Min

2010-06-01

Collagen I is an essential structural and mechanical building block of various tissues, and it is often used as tissue-engineering scaffolds. However, collagen-based constructs reconstituted in vitro often lacks robust fiber structure, mechanical stability, and molecule binding capability. To enhance these performances, the present study developed 3-D collagen-nanotube composite constructs with two types of functionalized carbon nanotubes, carboxylated nanotubes and covalently functionalized nanotubes (CFNTs). The influences of nanotube functionalization and loading concentration on the collagen fiber structure, mechanical property, biocompatibility, and molecule binding were examined. Results revealed that surface modification and loading concentration of nanotubes determined the interactions between nanotubes and collagen fibrils, thus altering the structure and property of nanotube-collagen composites. Scanning electron microscopy and confocal microscopy revealed that the incorporation of CFNT in collagen-based constructs was an effective means of restructuring collagen fibrils because CFNT strongly bound to collagen molecules inducing the formation of larger fibril bundles. However, increased nanotube loading concentration caused the formation of denser fibril network and larger aggregates. Static stress-strain tests under compression showed that the addition of nanotube into collagen-based constructs did not significantly increase static compressive moduli. Creep/recovery testing under compression revealed that CFNT-collagen constructs showed improved mechanical stability under continuous loading. Testing with endothelial cells showed that biocompatibility was highly dependent on nanotube loading concentration. At a low loading level, CFNT-collagen showed higher endothelial coverage than the other tested constructs or materials. Additionally, CFNT-collagen showed capability of binding to other biomolecules to enhance the construct functionality. In conclusion, functionalized nanotube-collagen composites, particularly CFNT-collagen composites, could be promising materials, which provide structural support showing bundled fibril structure, biocompatibility, multifunctionality, and mechanical stability, but rigorous control over chemical modification, loading concentration, and nanotube dispersion are needed.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

The Orion Exploration Mission-1 (EM-1) structural test article, secured inside its transport container, is loaded into NASA's Super Guppy aircraft at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. The test article will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Critical Joints in Large Composite Primary Aircraft Structures. Volume 3: Ancillary Test Results

NASA Technical Reports Server (NTRS)

Bunin, Bruce L.; Sagui, R. L.

1985-01-01

A program was conducted to develop the technology for critical structural joints for composite wing structure that meets all the design requirements of a 1990 commercial transport aircraft. The results of a comprehensive ancillary test program are summarized, consisting of single-bolt composite joint specimens tested in a variety of configurations. These tests were conducted to characterize the strength and load deflection properties that are required for multirow joint analysis. The composite material was Toray 300 fiber and Ciba-Geigy 914 resin, in the form of 0.005 and 0.01 inch thick unidirectional tape. Tests were conducted in single and double shear for loaded and unloaded hole configurations under both tensile and compressive loading. Two different layup patterns were examined. All tests were conducted at room temperature. In addition, the results of NASA Standard Toughness Test (NASA RP 1092) are reported, which were conducted for several material systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Alexander; Jernigan, Dann A.; Dodd, Amanda B.

New aircraft are being designed with increasing quantities of composite materials used in their construction. Different from the more traditional metals, composites have a higher propensity to burn. This presents a challenge to transportation safety analyses, as the aircraft structure now represents an additional fuel source involved in the fire scenario. Most of the historical fire testing of composite materials is aime d at studying kinetics, flammability or yield strength under fire conditions. Most of this testing is small - scale. Heterogeneous reactions are often length - scale dependent, and this is thought to be particularly true for composites whichmore » exhibit signific ant microscopic dynamics that can affect macro - scale behavior. We have designed a series of tests to evaluate composite materials under various structural loading conditions with a consistent thermal condition. We have measured mass - loss , heat flux, and temperature throughout the experiments. Several types of panels have been tested, including simple composite panels, and sandwich panels. The main objective of the testing was to understand the importance of the structural loading on a composite to its b ehavior in response to fire - like conditions. During flaming combustion at early times, there are some features of the panel decomposition that are unique to the type of loading imposed on the panels. At load levels tested, fiber reaction rates at later t imes appear to be independent of the initial structural loading.« less

Optimal Control Allocation with Load Sensor Feedback for Active Load Suppression, Flight-Test Performance

NASA Technical Reports Server (NTRS)

Miller, Christopher J.; Goodrick, Dan

2017-01-01

The problem of control command and maneuver induced structural loads is an important aspect of any control system design. The aircraft structure and the control architecture must be designed to achieve desired piloted control responses while limiting the imparted structural loads. The classical approach is to utilize high structural margins, restrict control surface commands to a limited set of analyzed combinations, and train pilots to follow procedural maneuvering limitations. With recent advances in structural sensing and the continued desire to improve safety and vehicle fuel efficiency, it is both possible and desirable to develop control architectures that enable lighter vehicle weights while maintaining and improving protection against structural damage. An optimal control technique has been explored and shown to achieve desirable vehicle control performance while limiting sensed structural loads to specified values. This technique has been implemented and flown on the National Aeronautics and Space Administration Full-scale Advanced Systems Testbed aircraft. The flight tests illustrate that the approach achieves the desired performance and show promising potential benefits. The flights also uncovered some important issues that will need to be addressed for production application.

Innovative design of composite structures: Design, manufacturing, and testing of plates utilizing curvilinear fiber trajectories

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Rust, R. J.; Waters, W. A., Jr.

1994-01-01

As a means of improving structural design, the concept of fabricating flat plates containing holes by incorporating curvilinear fiber trajectories to transmit loads around the hole is studied. In the present discussion this concept is viewed from a structural level, where access holes, windows, doors, and other openings are of significant size. This is opposed to holes sized for mechanical fasteners. Instead of cutting the important load-bearing fibers at the hole edge, as a conventional straightline design does, the curvilinear design preserves the load-bearing fibers by orienting them in smooth trajectories around the holes, their loading not ending abruptly at the hole edge. Though the concept of curvilinear fiber trajectories has been studied before, attempts to manufacture and test such plates have been limited. This report describes a cooperative effort between Cincinnati Milacron Inc., NASA Langley Research Center, and Virginia Polytechnic Institute and State University to design, manufacture, and test plates using the curvilinear fiber trajectory concept. The paper discusses details of the plate design, details of the manufacturing, and a summary of results from testing the plates with inplane compressive buckling loads and tensile loads. Comparisons between the curvilinear and conventional straightline fiber designs based on measurements and observation are made. Failure modes, failure loads, strains, deflections, and other key responses are compared.

Scaling effects in the static and dynamic response of graphite-epoxy beam-columns. Ph.D. Thesis - Virginia Polytechnic Inst. and State Univ.

NASA Technical Reports Server (NTRS)

Jackson, Karen E.

1990-01-01

Scale model technology represents one method of investigating the behavior of advanced, weight-efficient composite structures under a variety of loading conditions. It is necessary, however, to understand the limitations involved in testing scale model structures before the technique can be fully utilized. These limitations, or scaling effects, are characterized. in the large deflection response and failure of composite beams. Scale model beams were loaded with an eccentric axial compressive load designed to produce large bending deflections and global failure. A dimensional analysis was performed on the composite beam-column loading configuration to determine a model law governing the system response. An experimental program was developed to validate the model law under both static and dynamic loading conditions. Laminate stacking sequences including unidirectional, angle ply, cross ply, and quasi-isotropic were tested to examine a diversity of composite response and failure modes. The model beams were loaded under scaled test conditions until catastrophic failure. A large deflection beam solution was developed to compare with the static experimental results and to analyze beam failure. Also, the finite element code DYCAST (DYnamic Crash Analysis of STructure) was used to model both the static and impulsive beam response. Static test results indicate that the unidirectional and cross ply beam responses scale as predicted by the model law, even under severe deformations. In general, failure modes were consistent between scale models within a laminate family; however, a significant scale effect was observed in strength. The scale effect in strength which was evident in the static tests was also observed in the dynamic tests. Scaling of load and strain time histories between the scale model beams and the prototypes was excellent for the unidirectional beams, but inconsistent results were obtained for the angle ply, cross ply, and quasi-isotropic beams. Results show that valuable information can be obtained from testing on scale model composite structures, especially in the linear elastic response region. However, due to scaling effects in the strength behavior of composite laminates, caution must be used in extrapolating data taken from a scale model test when that test involves failure of the structure.

Advanced bridge safety initiative : live load testing and load rating of the Evans Brook Bridge (#5506) and the Hastings Bridge (#5507) in Batchelders Grant, Maine.

DOT National Transportation Integrated Search

2014-01-01

The Advanced Structures and Composites Center at the University of Maine (UMaine) performed live load testing : and rating factor analysis for two bridges (No. 5506 and No. 5507) in Batchelders Grant, Maine. The bridge load : rating performed by cons...

24 CFR 3280.401 - Structural load tests.

Code of Federal Regulations, 2013 CFR

2013-04-01

... sustaining its dead load plus superimposed live loads equal to 1.75 times the required live loads for a... in 1/4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead... load plus dead load has been reached. Assembly failure shall be considered as design live load...

24 CFR 3280.401 - Structural load tests.

Code of Federal Regulations, 2010 CFR

2010-04-01

... sustaining its dead load plus superimposed live loads equal to 1.75 times the required live loads for a... in 1/4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead... load plus dead load has been reached. Assembly failure shall be considered as design live load...

24 CFR 3280.401 - Structural load tests.

Code of Federal Regulations, 2014 CFR

2014-04-01

... sustaining its dead load plus superimposed live loads equal to 1.75 times the required live loads for a... in 1/4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead... load plus dead load has been reached. Assembly failure shall be considered as design live load...

24 CFR 3280.401 - Structural load tests.

Code of Federal Regulations, 2012 CFR

2012-04-01

... sustaining its dead load plus superimposed live loads equal to 1.75 times the required live loads for a... in 1/4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead... load plus dead load has been reached. Assembly failure shall be considered as design live load...

24 CFR 3280.401 - Structural load tests.

Code of Federal Regulations, 2011 CFR

2011-04-01

... sustaining its dead load plus superimposed live loads equal to 1.75 times the required live loads for a... in 1/4 design live load increments at 10-minute intervals until 1.25 times design live load plus dead... load plus dead load has been reached. Assembly failure shall be considered as design live load...

Acoustic emission evaluation of reinforced concrete bridge beam with graphite composite laminate

NASA Astrophysics Data System (ADS)

Johnson, Dan E.; Shen, H. Warren; Finlayson, Richard D.

2001-07-01

A test was recently conducted on August 1, 2000 at the FHwA Non-Destructive Evaluation Validation Center, sponsored by The New York State DOT, to evaluate a graphite composite laminate as an effective form of retrofit for reinforced concrete bridge beam. One portion of this testing utilized Acoustic Emission Monitoring for Evaluation of the beam under test. Loading was applied to this beam using a two-point loading scheme at FHwA's facility. This load was applied in several incremental loadings until the failure of the graphite composite laminate took place. Each loading culminated by either visual crack location or large audible emissions from the beam. Between tests external cracks were located visually and highlighted and the graphite epoxy was checked for delamination. Acoustic Emission data was collected to locate cracking areas of the structure during the loading cycles. To collect this Acoustic Emission data, FHwA and NYSDOT utilized a Local Area Monitor, an Acoustic Emission instrument developed in a cooperative effort between FHwA and Physical Acoustics Corporation. Eight Acoustic Emission sensors were attached to the structure, with four on each side, in a symmetrical fashion. As testing progressed and culminated with beam failure, Acoustic Emission data was gathered and correlated against time and test load. This paper will discuss the analysis of this test data.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

On the tarmac at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, the Orion Exploration Mission-1 (EM-1) structural test article, secured in its transport container, is loaded into the agency's Super Guppy aircraft. The test article will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

The Orion Exploration Mission-1 (EM-1) structural test article, secured inside its transport container, arrives at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. The test article will be loaded into NASA's Super Guppy aircraft, in view at left, and transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Outer planet probe engineering model structural tests

NASA Technical Reports Server (NTRS)

Smittkamp, J. A.; Gustin, W. H.; Griffin, M. W.

1977-01-01

A series of proof of concept structural tests was performed on an engineering model of the Outer Planets Atmospheric Entry Probe. The tests consisted of pyrotechnic shock, dynamic and static loadings. The tests partially verified the structural concept.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Chanyoung; Kim, Nam H.

Structural elements, such as stiffened panels and lap joints, are basic components of aircraft structures. For aircraft structural design, designers select predesigned elements satisfying the design load requirement based on their load-carrying capabilities. Therefore, estimation of safety envelope of structural elements for load tolerances would be a good investment for design purpose. In this article, a method of estimating safety envelope is presented using probabilistic classification, which can estimate a specific level of failure probability under both aleatory and epistemic uncertainties. An important contribution of this article is that the calculation uncertainty is reflected in building a safety envelope usingmore » Gaussian process, and the effect of element test data on reducing the calculation uncertainty is incorporated by updating the Gaussian process model with the element test data. It is shown that even one element test can significantly reduce the calculation uncertainty due to lacking knowledge of actual physics, so that conservativeness in a safety envelope is significantly reduced. The proposed approach was demonstrated with a cantilever beam example, which represents a structural element. The example shows that calculation uncertainty provides about 93% conservativeness against the uncertainty due to a few element tests. As a result, it is shown that even a single element test can increase the load tolerance modeled with the safety envelope by 20%.« less

Validation Tests of Fiber Optic Strain-Based Operational Shape and Load Measurements

NASA Technical Reports Server (NTRS)

Bakalyar, John A.; Jutte, Christine

2012-01-01

Aircraft design has been progressing toward reduced structural weight to improve fuel efficiency, increase performance, and reduce cost. Lightweight aircraft structures are more flexible than conventional designs and require new design considerations. Intelligent sensing allows for enhanced control and monitoring of aircraft, which enables increased structurally efficiency. The NASA Dryden Flight Research Center (DFRC) has developed an instrumentation system and analysis techniques that combine to make distributed structural measurements practical for lightweight vehicles. Dryden's Fiber Optic Strain Sensing (FOSS) technology enables a multitude of lightweight, distributed surface strain measurements. The analysis techniques, referred to as the Displacement Transfer Functions (DTF) and Load Transfer Functions (LTF), use surface strain values to calculate structural deflections and operational loads. The combined system is useful for real-time monitoring of aeroelastic structures, along with many other applications. This paper describes how the capabilities of the measurement system were demonstrated using subscale test articles that represent simple aircraft structures. Empirical FOSS strain data were used within the DTF to calculate the displacement of the article and within the LTF to calculate bending moments due to loads acting on the article. The results of the tests, accuracy of the measurements, and a sensitivity analysis are presented.

Transient Dynamic Response and Failure of Composite Structure Under Cyclic Loading with Fluid Structure Interaction

DTIC Science & Technology

2014-09-01

TERMS fluid structure interaction, composite structures shipbuilding, fatigue loading 15. NUMBER OF PAGES 85 16. PRICE CODE 17. SECURITY...under the three point bending test. All the composites exhibit an initial nonlinear and inelastic deformation trend and end with a catastrophic abrupt

Development of load spectra for Airbus A330/A340 full scale fatigue tests

NASA Technical Reports Server (NTRS)

Schmidt, H.-J.; Nielsen, Thomas

1994-01-01

For substantiation of the recently certified medium range Airbus A330 and long range A340 the full scale fatigue tests are in progress. The airframe structures of both aircraft types are tested by one set of A340 specimens. The development of the fatigue test spectra for the two major test specimens which are the center fuselage and wing test and the rear fuselage test is described. The applied test load spectra allow a realistic simulation of flight, ground and pressurization loads and the finalization of the tests within the pre-defined test period. The paper contains details about the 1 g and incremental flight and ground loads and the establishment of the flight-by-flight test program, i.e., the definition of flight types, distribution of loads within the flights and randomization of flight types in repeated blocks. Special attention is given to procedures applied for acceleration of the tests, e.g. omission of lower spectrum loads and a general increase of all loads by ten percent.

Deflection-Based Aircraft Structural Loads Estimation with Comparison to Flight

NASA Technical Reports Server (NTRS)

Lizotte, Andrew M.; Lokos, William A.

2005-01-01

Traditional techniques in structural load measurement entail the correlation of a known load with strain-gage output from the individual components of a structure or machine. The use of strain gages has proved successful and is considered the standard approach for load measurement. However, remotely measuring aerodynamic loads using deflection measurement systems to determine aeroelastic deformation as a substitute to strain gages may yield lower testing costs while improving aircraft performance through reduced instrumentation weight. With a reliable strain and structural deformation measurement system this technique was examined. The objective of this study was to explore the utility of a deflection-based load estimation, using the active aeroelastic wing F/A-18 aircraft. Calibration data from ground tests performed on the aircraft were used to derive left wing-root and wing-fold bending-moment and torque load equations based on strain gages, however, for this study, point deflections were used to derive deflection-based load equations. Comparisons between the strain-gage and deflection-based methods are presented. Flight data from the phase-1 active aeroelastic wing flight program were used to validate the deflection-based load estimation method. Flight validation revealed a strong bending-moment correlation and slightly weaker torque correlation. Development of current techniques, and future studies are discussed.

Deflection-Based Structural Loads Estimation From the Active Aeroelastic Wing F/A-18 Aircraft

NASA Technical Reports Server (NTRS)

Lizotte, Andrew M.; Lokos, William A.

2005-01-01

Traditional techniques in structural load measurement entail the correlation of a known load with strain-gage output from the individual components of a structure or machine. The use of strain gages has proved successful and is considered the standard approach for load measurement. However, remotely measuring aerodynamic loads using deflection measurement systems to determine aeroelastic deformation as a substitute to strain gages may yield lower testing costs while improving aircraft performance through reduced instrumentation weight. This technique was examined using a reliable strain and structural deformation measurement system. The objective of this study was to explore the utility of a deflection-based load estimation, using the active aeroelastic wing F/A-18 aircraft. Calibration data from ground tests performed on the aircraft were used to derive left wing-root and wing-fold bending-moment and torque load equations based on strain gages, however, for this study, point deflections were used to derive deflection-based load equations. Comparisons between the strain-gage and deflection-based methods are presented. Flight data from the phase-1 active aeroelastic wing flight program were used to validate the deflection-based load estimation method. Flight validation revealed a strong bending-moment correlation and slightly weaker torque correlation. Development of current techniques, and future studies are discussed.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

A view from inside NASA's Super Guppy aircraft at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, as the Orion Exploration Mission-1 (EM-1) structural test article, secured inside its transport container, is loaded into the aircraft. The test article will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Fire development and wall endurance in sandwich and wood-frame structures

Treesearch

Carlton A. Holmes; Herbert W. Eickner; John J. Brenden; Curtis C. Peters; Robert H. White

1980-01-01

Large-scale fire tests were conducted on seven 16- by 24-foot structures. Four of these structures were of sandwich construction with cores of plastic or paper honeycomb and three were of wood-frame construction. The wasss were loaded to a computer design loading, and the fire endurance determined under a fire exposure from a typical building contents loading of 4-1/2...

Structural Dynamic Behavior of Wind Turbines

NASA Technical Reports Server (NTRS)

Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III

2009-01-01

The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).

14 CFR 29.681 - Limit load static tests.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Control Systems § 29.681 Limit... in which— (1) The direction of the test loads produces the most severe loading in the control system; and (2) Each fitting, pulley, and bracket used in attaching the system to the main structure is...

Response of Composite Fuselage Sandwich Side Panels Subjected to Internal Pressure and Axial Tension

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Ambur, Damodar R.; Dopker, Bernard; Shah, Bharat

1998-01-01

The results from an experimental and analytical study of two composite sandwich fuselage side panels for a transport aircraft are presented. Each panel has two window cutouts and three frames and utilizes a distinctly different structural concept. These panels have been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on both panels. One of the sandwich panels was tested with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. A damage tolerance study was conducted on the two-frame panel by cutting a notch in the panel that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. Both the sandwich panel designs successfully satisfied all desired load requirements in the experimental part of the study, and experimental results from the two-frame panel with and without damage are fully explained by the analytical results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in. wide frame spacing to further reduce aircraft fuselage structural weight.

Damage Arresting Composites for Shaped Vehicles - Phase II Final Report

NASA Technical Reports Server (NTRS)

Velicki, Alex; Yovanof, Nicolette; Baraja, Jaime; Linton, Kim; Li, Victor; Hawley, Arthur; Thrash, Patrick; DeCoux, Steve; Pickell, Robert

2011-01-01

This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration. In addition to the analytical studies, a three specimen test program was also completed to assess the concept under axial tension loading, axial compression loading, and internal pressure loading.

X-33 LH2 Tank Failure Investigation Findings

NASA Technical Reports Server (NTRS)

Niedermeyer, Mindy; Clinton, R. G., Jr. (Technical Monitor)

2000-01-01

This presentation focuses on the tank history, test objectives, failure description, investigation and conclusions. The test objectives include verify structural integrity at 105% expected flight load limit varying the following parameters: cryogenic temperature; internal pressure; and mechanical loading. The Failure description includes structural component of the aft body, quad-lobe design, and sandwich - honeycomb graphite epoxy construction.

Calculating Nozzle Side Loads using Acceleration Measurements of Test-Based Models

NASA Technical Reports Server (NTRS)

Brown, Andrew M.; Ruf, Joe

2007-01-01

As part of a NASA/MSFC research program to evaluate the effect of different nozzle contours on the well-known but poorly characterized "side load" phenomena, we attempt to back out the net force on a sub-scale nozzle during cold-flow testing using acceleration measurements. Because modeling the test facility dynamics is problematic, new techniques for creating a "pseudo-model" of the facility and nozzle directly from modal test results are applied. Extensive verification procedures were undertaken, resulting in a loading scale factor necessary for agreement between test and model based frequency response functions. Side loads are then obtained by applying a wide-band random load onto the system model, obtaining nozzle response PSD's, and iterating both the amplitude and frequency of the input until a good comparison of the response with the measured response PSD for a specific time point is obtained. The final calculated loading can be used to compare different nozzle profiles for assessment during rocket engine nozzle development and as a basis for accurate design of the nozzle and engine structure to withstand these loads. The techniques applied within this procedure have extensive applicability to timely and accurate characterization of all test fixtures used for modal test.A viewgraph presentation on a model-test based pseudo-model used to calculate side loads on rocket engine nozzles is included. The topics include: 1) Side Loads in Rocket Nozzles; 2) Present Side Loads Research at NASA/MSFC; 3) Structural Dynamic Model Generation; 4) Pseudo-Model Generation; 5) Implementation; 6) Calibration of Pseudo-Model Response; 7) Pseudo-Model Response Verification; 8) Inverse Force Determination; 9) Results; and 10) Recent Work.

System Identification of Damped Truss-Like Space Structures. Ph.D. Thesis - Cleveland State Univ., Mar. 1994

NASA Technical Reports Server (NTRS)

Armand, Sasan

1995-01-01

A spacecraft payload flown on a launch vehicle experiences dynamic loads. The dynamic loads are caused by various phenomena ranging from the start-up of the launch vehicle engine to wind gusts. A spacecraft payload should be designed to meet launch vehicle dynamic loads. One of the major steps taken towards determining the dynamic loads is to correlate the finite element model of the spacecraft with the test results of a modal survey test. A test-verified finite element model of the spacecraft should possess the same spatial properties (stiffness, mass, and damping) and modal properties (frequencies and mode shapes) as the test hardware representing the spacecraft. The test-verified and correlated finite element model of the spacecraft is then coupled with the finite element model of the launch vehicle for analysis of loads and stress. Modal survey testing, verification of a finite element model, and modification of the finite element model to match the modal survey test results can easily be accomplished if the spacecraft structure is simple. However, this is rarely the case. A simple structure here is defined as a structure where the influence of nonlinearity between force and displacement (uncertainty in a test, for example, with errors in input and output), and the influence of damping (structural, coulomb, and viscous) are not pronounced. The objective of this study is to develop system identification and correlation methods with the focus on the structural systems that possess nonproportional damping. Two approaches to correct the nonproportional damping matrix of a truss structure were studied, and have been implemented on truss-like structures such as the National Aeronautics and Space Administration's space station truss. The results of this study showed nearly 100 percent improvement of the correlated eigensystem over the analytical eigensystem. The first method showed excellent results with up to three modes used in the system identification process. The second method could handle more modes, but required more computer usage time, and the results were less accurate than those of the first method.

Fractographic study of epoxy fractured under mode I loading and mixed mode I/III loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Fei; Wang, Jy-An John; Bertelsen, Williams D.

2011-01-01

Fiber reinforced polymeric composite materials are widely used in structural components such as wind turbine blades, which are typically subject to complicated loading conditions. Thus, material response under mixed mode loading is of great significance to the reliability of these structures. Epoxy is a thermosetting polymer that is currently used in manufacturing wind turbine blades. The fracture behavior of epoxy is relevant to the mechanical integrity of the wind turbine composite materials. In this study, a novel fracture testing methodology, the spiral notch torsion test (SNTT), was applied to study the fracture behavior of an epoxy material. SNTT samples weremore » tested using either monotonic loading or cyclic loading, while both mode I and mixed mode I/III loading conditions were used. Fractographic examination indicated the epoxy samples included in this study were prone to mode I failure even when the samples were subject to mixed mode loading. Different fatigue precracks were observed on mode I and mixed mode samples, i.e. precracks appeared as a uniform band under mode I loading, and a semi-ellipse under mixed mode loading. Fracture toughness was also estimated using quantitative fractography.« less

Quasi-static elastography comparison of hyaline cartilage structures

NASA Astrophysics Data System (ADS)

McCredie, A. J.; Stride, E.; Saffari, N.

2009-11-01

Joint cartilage, a load bearing structure in mammals, has only limited ability for regeneration after damage. For tissue engineers to design functional constructs, better understanding of the properties of healthy tissue is required. Joint cartilage is a specialised structure of hyaline cartilage; a poroviscoelastic solid containing fibril matrix reinforcements. Healthy joint cartilage is layered, which is thought to be important for correct tissue function. However, the behaviour of each layer during loading is poorly understood. Ultrasound elastography provides access to depth-dependent information in real-time for a sample during loading. A 15 MHz focussed transducer provided details from scatterers within a small fixed region in each sample. Quasi-static loading was applied to cartilage samples while ultrasonic signals before and during compressions were recorded. Ultrasonic signals were processed to provide time-shift profiles using a sum-squared difference method and cross-correlation. Two structures of hyaline cartilage have been tested ultrasonically and mechanically to determine method suitability for monitoring internal deformation differences under load and the effect of the layers on the global mechanical material behaviour. Results show differences in both the global mechanical properties and the ultrasonically tested strain distributions between the two structures tested. It was concluded that these differences are caused primarily by the fibril orientations.

Impact Damage and Strain Rate Effects for Toughened Epoxy Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2006-01-01

Structural integrity of composite systems under dynamic impact loading is investigated herein. The GENOA virtual testing software environment is used to implement the effects of dynamic loading on fracture progression and damage tolerance. Combinations of graphite and glass fibers with a toughened epoxy matrix are investigated. The effect of a ceramic coating for the absorption of impact energy is also included. Impact and post impact simulations include verification and prediction of (1) Load and Impact Energy, (2) Impact Damage Size, (3) Maximum Impact Peak Load, (4) Residual Strength, (5) Maximum Displacement, (6) Contribution of Failure Modes to Failure Mechanisms, (7) Prediction of Impact Load Versus Time, and (8) Damage, and Fracture Pattern. A computer model is utilized for the assessment of structural response, progressive fracture, and defect/damage tolerance characteristics. Results show the damage progression sequence and the changes in the structural response characteristics due to dynamic impact. The fundamental premise of computational simulation is that the complete evaluation of composite fracture requires an assessment of ply and subply level damage/fracture processes as the structure is subjected to loads. Simulation results for the graphite/epoxy composite were compared with the impact and tension failure test data, correlation and verification was obtained that included: (1) impact energy, (2) damage size, (3) maximum impact peak load, (4) residual strength, (5) maximum displacement, and (6) failure mechanisms of the composite structure.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

The Orion Exploration Mission-1 (EM-1) structural test article, secured inside its transport container, is lifted up by crane from its transport vehicle at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. The test article will be loaded into NASA's Super Guppy aircraft, in view at left, and transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

On the tarmac at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, NASA and contractor workers review procedures before beginning loading of the Orion Exploration Mission-1 (EM-1) structural test article in its transport container into NASA's Super Guppy aircraft. The test article will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Slow Crack Growth Analysis of Advanced Structural Ceramics Under Combined Loading Conditions: Damage Assessment in Life Prediction Testing

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Gyekenyesi, John P.

2000-01-01

Slow crack growth analysis was performed with three different loading histories including constant stress-rate/constant stress-rate testing (Case 1 loading), constant stress/constant stress-rate testing (Case 2 loading), and cyclic stress/constant stress-rate testing (Case 2 loading). Strength degradation due to slow crack growth and/or damage accumulation was determined numerically as a function of percentage of interruption time between the two loading sequences for a given loading history. The numerical solutions were examined with the experimental data determined at elevated temperatures using four different advanced ceramic materials, two silicon nitrides, one silicon carbide and one alumina for the Case 1 loading history, and alumina for the Case 3 loading history. The numerical solutions were in reasonable agreement with the experimental data, indicating that notwithstanding some degree of creep deformation presented for some test materials slow crack growth was a governing mechanism associated with failure for all the test materials.

Slow Crack Growth Analysis of Advanced Structural Ceramics Under Combined Loading Conditions: Damage Assessment in Life Prediction Testing

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Gyekenyesi, John P.

2000-01-01

Slow crack growth analysis was performed with three different loading histories including constant stress-rate/constant stress-rate testing (Case I loading), constant stress/constant stress-rate testing (Case II loading), and cyclic stress/constant stress-rate testing (Case III loading). Strength degradation due to slow crack growth arid/or damage accumulation was determined numerically as a Function of percentage of interruption time between the two loading sequences for a given loading history. The numerical solutions were examined with the experimental data determined at elevated temperatures using four different advanced ceramic materials, two silicon nitrides, one silicon carbide and one alumina for the Case I loading history, and alumina for the Case II loading history. The numerical solutions were in reasonable agreement with the experimental data, indicating that notwithstanding some degree of creep deformation presented for some test materials slow crack growth was a governing mechanism associated with failure for all the test material&

Performance of pile supported sign structures : final report.

DOT National Transportation Integrated Search

2015-01-01

Foundations for sign structures are subjected primarily to overturning loads, but published methods for designing driven pile groups only address groups subjected either to compression or uplift, not both simultaneously. A lateral load test of two fo...

Sonic-boom-induced building structure responses including damage.

NASA Technical Reports Server (NTRS)

Clarkson, B. L.; Mayes, W. H.

1972-01-01

Concepts of sonic-boom pressure loading of building structures and the associated responses are reviewed, and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic-boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of such other phenomena as three-dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data from laboratory models and full-scale building tests are summarized, and these data are compared, where possible, with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic-boom-induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.

Lateral load performance of SIP walls with full bearing

Treesearch

Boren Yeh; Tom Skaggs; Xiping Wang; Tom Williamson

2018-01-01

The purpose of this study was to develop test data needed to characterize lateral load performance of structural insulated panel (SIP) walls with full bearing (restrained). The research program involved structural testing of 29 full-size SIP walls (8 ft tall by 8 ft long) of various configurations that bracket a range of SIP wall configurations commonly used in the...

Fuel containment and damage tolerance in large composite primary aircraft structures. Phase 2: Testing

NASA Technical Reports Server (NTRS)

Sandifer, J. P.; Denny, A.; Wood, M. A.

1985-01-01

Technical issues associated with fuel containment and damage tolerance of composite wing structures for transport aircraft were investigated. Material evaluation tests were conducted on two toughened resin composites: Celion/HX1504 and Celion/5245. These consisted of impact, tension, compression, edge delamination, and double cantilever beam tests. Another test series was conducted on graphite/epoxy box beams simulating a wing cover to spar cap joint configuration of a pressurized fuel tank. These tests evaluated the effectiveness of sealing methods with various fastener types and spacings under fatigue loading and with pressurized fuel. Another test series evaluated the ability of the selected coatings, film, and materials to prevent fuel leakage through 32-ply AS4/2220-1 laminates at various impact energy levels. To verify the structural integrity of the technology demonstration article structural details, tests were conducted on blade stiffened panels and sections. Compression tests were performed on undamaged and impacted stiffened AS4/2220-1 panels and smaller element tests to evaluate stiffener pull-off, side load and failsafe properties. Compression tests were also performed on panels subjected to Zone 2 lightning strikes. All of these data were integrated into a demonstration article representing a moderately loaded area of a transport wing. This test combined lightning strike, pressurized fuel, impact, impact repair, fatigue and residual strength.

Multipactor Physics, Acceleration, and Breakdown in Dielectric-Loaded Accelerating Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, Richard P.; Gold, Steven H.

2016-07-01

The objective of this 3-year program is to study the physics issues associated with rf acceleration in dielectric-loaded accelerating (DLA) structures, with a focus on the key issue of multipactor loading, which has been found to cause very significant rf power loss in DLA structures whenever the rf pulsewidth exceeds the multipactor risetime (~10 ns). The experiments are carried out in the X-band magnicon laboratory at the Naval Research Laboratory (NRL) in collaboration with Argonne National Laboratory (ANL) and Euclid Techlabs LLC, who develop the test structures with support from the DoE SBIR program. There are two main elements inmore » the research program: (1) high-power tests of DLA structures using the magnicon output (20 MW @11.4 GHz), and (2) tests of electron acceleration in DLA structures using relativistic electrons from a compact X-band accelerator. The work during this period has focused on a study of the use of an axial magnetic field to suppress multipactor in DLA structures, with several new high power tests carried out at NRL, and on preparation of the accelerator for the electron acceleration experiments.« less

3D FSE Cube and VIPR-aTR 3.0 Tesla magnetic resonance imaging predicts canine cranial cruciate ligament structural properties.

PubMed

Racette, Molly; Al saleh, Habib; Waller, Kenneth R; Bleedorn, Jason A; McCabe, Ronald P; Vanderby, Ray; Markel, Mark D; Brounts, Sabrina H; Block, Walter F; Muir, Peter

2016-03-01

Estimation of cranial cruciate ligament (CrCL) structural properties in client-owned dogs with incipient cruciate rupture would be advantageous. The objective of this study was to determine whether magnetic resonance imaging (MRI) measurement of normal CrCL volume in an ex-vivo canine model predicts structural properties. Stifles from eight dogs underwent 3.0 Tesla 3D MRI. CrCL volume and normalized median grayscale values were determined using 3D Fast Spin Echo (FSE) Cube and Vastly under-sampled Isotropic PRojection (VIPR)-alternative repetition time (aTR) sequences. Stifles were then mechanically tested. After joint laxity testing, CrCL structural properties were determined, including displacement at yield, yield load, load to failure, and stiffness. Yield load and load to failure (R(2)=0.56, P <0.01) were correlated with CrCL volume determined by VIPR-aTR. Yield load was also correlated with CrCL volume determined by 3D FSE Cube (R(2)=0.32, P <0.05). Structural properties were not related to median grayscale values. Joint laxity and CrCL stiffness were not related to MRI parameters, but displacement at yield load was related to CrCL volume for both sequences during testing (R(2)>0.57, P <0.005). In conclusion, 3D MRI offers a predictive method for estimating canine CrCL structural properties. 3D MRI may be useful for monitoring CrCL properties in clinical trials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Load reduction test method of similarity theory and BP neural networks of large cranes

NASA Astrophysics Data System (ADS)

Yang, Ruigang; Duan, Zhibin; Lu, Yi; Wang, Lei; Xu, Gening

2016-01-01

Static load tests are an important means of supervising and detecting a crane's lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solve the loading problems of large-tonnage cranes during testing, an equivalency test is proposed based on the similarity theory and BP neural networks. The maximum stress and displacement of a large bridge crane is tested in small loads, combined with the training neural network of a similar structure crane through stress and displacement data which is collected by a physics simulation progressively loaded to a static load test load within the material scope of work. The maximum stress and displacement of a crane under a static load test load can be predicted through the relationship of stress, displacement, and load. By measuring the stress and displacement of small tonnage weights, the stress and displacement of large loads can be predicted, such as the maximum load capacity, which is 1.25 times the rated capacity. Experimental study shows that the load reduction test method can reflect the lift capacity of large bridge cranes. The load shedding predictive analysis for Sanxia 1200 t bridge crane test data indicates that when the load is 1.25 times the rated lifting capacity, the predicted displacement and actual displacement error is zero. The method solves the problem that lifting capacities are difficult to obtain and testing accidents are easily possible when 1.25 times related weight loads are tested for large tonnage cranes.

Fatigue and post-fatigue performance of Fabry-Perot FOS installed on CFRP-strengthened RC-beams

NASA Astrophysics Data System (ADS)

Gheorghiu, Catalin; Labossiere, Pierre; Proulx, Jean

2004-07-01

There is a growing need for built-in monitoring systems for civil engineering infrastructures, due to problems such as increasing traffic loads and rising costs of maintenance and repair. Fibre optic sensors (FOS), capable of reading various parameters are promising candidates for life-long health monitoring of these structures. However, since FOS have only been introduced recently into the field of structural monitoring, their acceptance and widespread implementation will be conditioned by their durability under severe climatic and loading conditions. This paper reports on the performance of strain extrinsic FOS attached to carbon fibre reinforced polymer (CFRP) plates used to strengthen concrete structures. The specimens tested in this project are reinforced concrete (RC) beams with an additional external CFRP reinforcement. The FOS-instrumented beams were first subjected to fatigue loading for various numbers of cycles and load amplitudes. Then, they were tested monotonically to failure under four-point-bending. The test results provide an insight on the fatigue and post-fatigue behaviour of FOS used for monitoring reinforced concrete structures.

Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 2: Structural fatigue, thermal cycling, creep, and residual strength

NASA Technical Reports Server (NTRS)

Blichfeldt, B.; Mccarty, J. E.

1972-01-01

Specimens representative of metal aircraft structural components reinforced with boron filamentary composites were manufactured and tested under cyclic loading, cyclic temperature, or continuously applied loading to evaluate some of the factors that affect structural integrity under cyclic conditions. Bonded, stepped joints were used throughout to provide composite-to-metal transition regions at load introduction points. Honeycomb panels with titanium or aluminum faces reinforced with unidirectional boron composite were fatigue tested at constant amplitude under completely reversed loading. Results indicated that the matrix material was the most fatigue-sensitive part of the design, with debonding initiating in the stepped joints. However, comparisons with equal weight all-metal specimens show a 10 to 50 times improved fatigue life. Fatigue crack propagation and residual strength were studied for several different stiffened panel concepts, and were found to vary considerably depending on the configuration. Composite-reinforced metal specimens were also subjected to creep and thermal cycling tests. Thermal cycling of stepped joint tensile specimens resulted in a ten percent decrease in residual strength after 4000 cycles.

Algorithms for Determining Physical Responses of Structures Under Load

NASA Technical Reports Server (NTRS)

Richards, W. Lance; Ko, William L.

2012-01-01

Ultra-efficient real-time structural monitoring algorithms have been developed to provide extensive information about the physical response of structures under load. These algorithms are driven by actual strain data to measure accurately local strains at multiple locations on the surface of a structure. Through a single point load calibration test, these structural strains are then used to calculate key physical properties of the structure at each measurement location. Such properties include the structure s flexural rigidity (the product of the structure's modulus of elasticity, and its moment of inertia) and the section modulus (the moment of inertia divided by the structure s half-depth). The resulting structural properties at each location can be used to determine the structure s bending moment, shear, and structural loads in real time while the structure is in service. The amount of structural information can be maximized through the use of highly multiplexed fiber Bragg grating technology using optical time domain reflectometry and optical frequency domain reflectometry, which can provide a local strain measurement every 10 mm on a single hair-sized optical fiber. Since local strain is used as input to the algorithms, this system serves multiple purposes of measuring strains and displacements, as well as determining structural bending moment, shear, and loads for assessing real-time structural health. The first step is to install a series of strain sensors on the structure s surface in such a way as to measure bending strains at desired locations. The next step is to perform a simple ground test calibration. For a beam of length l (see example), discretized into n sections and subjected to a tip load of P that places the beam in bending, the flexural rigidity of the beam can be experimentally determined at each measurement location x. The bending moment at each station can then be determined for any general set of loads applied during operation.

Test and Analysis of a Buckling-Critical Large-Scale Sandwich Composite Cylinder

NASA Technical Reports Server (NTRS)

Schultz, Marc R.; Sleight, David W.; Gardner, Nathaniel W.; Rudd, Michelle T.; Hilburger, Mark W.; Palm, Tod E.; Oldfield, Nathan J.

2018-01-01

Structural stability is an important design consideration for launch-vehicle shell structures and it is well known that the buckling response of such shell structures can be very sensitive to small geometric imperfections. As part of an effort to develop new buckling design guidelines for sandwich composite cylindrical shells, an 8-ft-diameter honeycomb-core sandwich composite cylinder was tested under pure axial compression to failure. The results from this test are compared with finite-element-analysis predictions and overall agreement was very good. In particular, the predicted buckling load was within 1% of the test and the character of the response matched well. However, it was found that the agreement could be improved by including composite material nonlinearity in the analysis, and that the predicted buckling initiation site was sensitive to the addition of small bending loads to the primary axial load in analyses.

Evaluating Changes in Tendon Crimp with Fatigue Loading as an ex vivo Structural Assessment of Tendon Damage

PubMed Central

Freedman, Benjamin R.; Zuskov, Andrey; Sarver, Joseph J.; Buckley, Mark R.; Soslowsky, Louis J.

2015-01-01

The complex structure of tendons relates to their mechanical properties. Previous research has associated the waviness of collagen fibers (crimp) during quasi-static tensile loading to tensile mechanics, but less is known about the role of fatigue loading on crimp properties. In this study (IACUC approved), mouse patellar tendons were fatigue loaded while an integrated plane polariscope simultaneously assessed crimp properties. We demonstrate a novel structural mechanism whereby tendon crimp amplitude and frequency are altered with fatigue loading. In particular, fatigue loading increased the crimp amplitude across the tendon width and length, and these structural alterations were shown to be both region and load dependent. The change in crimp amplitude was strongly correlated to mechanical tissue laxity (defined as the ratio of displacement and gauge length relative to the first cycle of fatigue loading assessed at constant load throughout testing), at all loads and regions evaluated. Together, this study highlights the role of fatigue loading on tendon crimp properties as a function of load applied and region evaluated, and offers an additional structural mechanism for mechanical alterations that may lead to ultimate tendon failure. PMID:25773654

Evaluation Criteria and Results of Full Scale Testing of Bridge Abutment Made from Reinforced Soil

NASA Astrophysics Data System (ADS)

Hildebrand, Maciej; Rybak, Jarosław

2017-10-01

Structures made of reinforced soil can be evaluated for their safety based on a load testing. Measurement results are essentially evaluated by displacements of surcharge (mainly in vertical direction) and facing elements (mainly in horizontal direction). Displacements are within several tenths to several millimetres and they can be taken by common geodetic equipment. Due to slow soil consolidation (progress of displacements) under constant load, observations should be made over several days or even weeks or months. A standard procedure of heating of geotextiles, used in laboratory conditions to simulate long term behaviour cannot be used in a natural scale. When the load is removed, the soil unloading occurs. Both the progress of displacements and soil unloading after unloading of the structure are the key presumptions for evaluating its safety (stability). Assessment of measuring results must be preceded by assuming even the simplest model of the structure, so as it could be possible to estimate the expected displacements under controlled load. In view of clearly random nature of soil parameters of retaining structure composed of reinforced soil and due to specific erection technology of reinforced soil structure, the assessment of its condition is largely based on expert’s judgment. It is an essential and difficult task to interpret very small displacements which are often enough disturbed by numerous factors like temperature, insolation, precipitation, vehicles, etc. In the presented paper, the authors tried to establish and juxtapose some criteria for a load test of a bridge abutment and evaluate their suitability for decision making. Final remarks are based on authors experience from a real full scale load test.

Structural Element Tests in Support of the Keyworker Blast Shelter Program

DTIC Science & Technology

1985-10-01

forced concrete -lab with two transverse reinforced concrete floor beams to transfer the interior column loads to the floor slab. Using a roof slab... lateral buck- "-4 ling; however, this could have occurred after a column buckled and the roof collapsed. Since load cell 2 (middle column ) recorded the...ANALYSIS OF FREE-FIELD AND STRUCTURE LOADING DATA ... ........ .. 102 6.1.1 Loading Wave Velocity ........... .................... ... 102 6.1.2 Lateral

Acoustic and Thermal Testing of an Integrated Multilayer Insulation and Broad Area Cooling Shield System

NASA Technical Reports Server (NTRS)

Wood, Jessica J.; Foster, Lee W.

2013-01-01

A Multilayer Insulation (MLI) and Broad Area Cooling (BAC) shield thermal control system shows promise for long-duration storage of cryogenic propellant. The NASA Cryogenic Propellant Storage and Transfer (CPST) project is investigating the thermal and structural performance of this tank-applied integrated system. The MLI/BAC Shield Acoustic and Thermal Test was performed to evaluate the MLI/BAC shield's structural performance by subjecting it to worst-case launch acoustic loads. Identical thermal tests using Liquid Nitrogen (LN2) were performed before and after the acoustic test. The data from these tests was compared to determine if any degradation occurred in the thermal performance of the system as a result of exposure to the acoustic loads. The thermal test series consisted of two primary components: a passive boil-off test to evaluate the MLI performance and an active cooling test to evaluate the integrated MLI/BAC shield system with chilled vapor circulating through the BAC shield tubes. The acoustic test used loads closely matching the worst-case envelope of all launch vehicles currently under consideration for CPST. Acoustic test results yielded reasonable responses for the given load. The thermal test matrix was completed prior to the acoustic test and successfully repeated after the acoustic test. Data was compared and yielded near identical results, indicating that the MLI/BAC shield configuration tested in this series is an option for structurally implementing this thermal control system concept.

Ground/Flight Correlation of Aerodynamic Loads with Structural Response

NASA Technical Reports Server (NTRS)

Mangalam, Arun S.; Davis, Mark C.

2009-01-01

United States Air Force Research Laboratory (AFRL) ground tests at the NASA Transonic Dynamics Tunnel (TDT) and NASA flight tests provide a basis and methodology for in-flight characterization of the aeroelastic performance through the monitoring of the fluid-structure interaction using surface flow sensors. NASA NF-15B flight tests provided a unique opportunity to test the correlation of aerodynamic loads with sectional flow attachment/detachment points, also known as flow bifurcation points (FBPs), as observed in previous wind tunnel tests. The NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. These data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in root-bending strains and hot-film sensor signals near the stagnation region that were highly correlated. For the TDT tests, a flexible wing section developed under the AFRL SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at multiple span stations. The TDT tests provided data showing a gradual phase change between the FBP and the structural mode occurred during a resonant condition as the wings structural modes were excited by the tunnel-generated gusts.

Slow Crack Growth Analysis of Advanced Structural Ceramics Under Combined Loading Conditions: Damage Assessment in Life Prediction Testing

NASA Technical Reports Server (NTRS)

Choi, S. R.; Gyekenyesi, J. P.

2001-01-01

Slow crack growth analysis was performed with three different loading histories including constant stress- rate/constant stress-rate testing (Case I loading), constant stress/constant stress-rate testing (Case II loading), and cyclic stress/constant stress-rate testing (Case III loading). Strength degradation due to slow crack growth and/or damage accumulation was determined numerically as a function of percentage of interruption time between the two loading sequences for a given loading history. The numerical solutions were examined with the experimental data determined at elevated temperatures using four different advanced ceramic materials, two silicon nitrides, one silicon carbide and one alumina for the Case I loading history, and alumina for the Case II loading history. The numerical solutions were in reasonable agreement with the experimental data, indicating that notwithstanding some degree of creep deformation presented for some test materials slow crack growth was a governing mechanism associated with failure for all the rest materials.

Dynamic Breaking Tests of Airplane Parts

NASA Technical Reports Server (NTRS)

Hertel, Heinrich

1933-01-01

The static stresses of airplane parts, the magnitude of which can be determined with the aid of static load assumptions, are mostly superposed by dynamic stresses, the magnitude of which has been but little explored. The object of the present investigation is to show how the strength of airplane parts can best be tested with respect to dynamic stresses with and without superposed static loading, and to what extent the dynamic strength of the parts depends on their structural design. Experimental apparatus and evaluation methods were developed and tried for the execution of vibration-strength tests with entire structural parts both with and without superposed static loading. Altogether ten metal spars and spar pieces and two wooden spars were subjected to vibration breaking tests.

Thermal and Structural Performance of Woven Carbon Cloth For Adaptive Deployable Entry and Placement Technology

NASA Technical Reports Server (NTRS)

Arnold, James O.; Peterson, Keith H.; Yount, Bryan C.; Schneider, Nigel; Chavez-Garcia, Jose

2013-01-01

Arcjet testing and analysis of a three-dimensional (3D) woven carbon fabric has shown that it can be used as a thermal protection system and as a load bearing structural component for a low ballistic coefficient hypersonic decelerator called ADEPT (Adaptive Deployable Entry and Placement Technology). Results of arcjet tests proved that the 3D woven carbon fabric can withstand flight-like heating while under flight-like biaxial mechanical loads representative of those encountered during shallow entry flight path angles into the atmosphere of Venus. Importantly, the arcjet test results have been used to extend a preliminary material thermal response model based on previous testing of the same 3D woven carbon fabric under uni-axial mechanical loading.

Recent Loads Calibration Experience With a Delta Wing Airplane

NASA Technical Reports Server (NTRS)

Jenkins, Jerald M.; Kuhl, Albert E.

1977-01-01

Aircraft which are designed for supersonic and hypersonic flight are evolving with delta wing configurations. An integral part of the evolution of all new aircraft is the flight test phase. Included in the flight test phase is an effort to identify and evaluate the loads environment of the aircraft. The most effective way of examining the loads environment is to utilize calibrated strain gages to provide load magnitudes. Using strain gage data to accomplish this has turned out to be anything but a straightforward task. The delta wing configuration has turned out to be a very difficult type of wing structure to calibrate. Elevated structural temperatures result in thermal effects which contaminate strain gage data being used to deduce flight loads. The concept of thermally calibrating a strain gage system is an approach to solving this problem. This paper will address how these problems were approached on a program directed toward measuring loads on the wing of a large, flexible supersonic aircraft. Structural configurations typical of high-speed delta wing aircraft will be examined. The temperature environment will be examined to see how it induces thermal stresses which subsequently cause errors in loads equations used to deduce the flight loads.

14 CFR 29.307 - Proof of structure.

Code of Federal Regulations, 2010 CFR

2010-01-01

... loading condition accounting for the environment to which the structure will be exposed in operation... measurement tests; (5) Landing gear drop tests; and (6) Any additional tests required for new or unusual...

Flight Test of an Adaptive Controller and Simulated Failure/Damage on the NASA NF-15B

NASA Technical Reports Server (NTRS)

Buschbacher, Mark; Maliska, Heather

2006-01-01

The method of flight-testing the Intelligent Flight Control System (IFCS) Second Generation (Gen-2) project on the NASA NF-15B is herein described. The Gen-2 project objective includes flight-testing a dynamic inversion controller augmented by a direct adaptive neural network to demonstrate performance improvements in the presence of simulated failure/damage. The Gen-2 objectives as implemented on the NASA NF-15B created challenges for software design, structural loading limitations, and flight test operations. Simulated failure/damage is introduced by modifying control surface commands, therefore requiring structural loads measurements. Flight-testing began with the validation of a structural loads model. Flight-testing of the Gen-2 controller continued, using test maneuvers designed in a sequenced approach. Success would clear the new controller with respect to dynamic response, simulated failure/damage, and with adaptation on and off. A handling qualities evaluation was conducted on the capability of the Gen-2 controller to restore aircraft response in the presence of a simulated failure/damage. Control room monitoring of loads sensors, flight dynamics, and controller adaptation, in addition to postflight data comparison to the simulation, ensured a safe methodology of buildup testing. Flight-testing continued without major incident to accomplish the project objectives, successfully uncovering strengths and weaknesses of the Gen-2 control approach in flight.

Effect of Helicopter Blade Dynamics on Blade Aerodynamic and Structural Loads

NASA Technical Reports Server (NTRS)

Heffernan, Ruth M.

1987-01-01

The effect of rotor blade dynamics on aerodynamic and structural loads is examined for a conventional, main- rotor helicopter using both a comprehensive rotorcraft analysis (CAMRAD) and night test data. The impact of blade dynamics on blade section lift-coefficient time histories is studied by comparing predictions from both a rigid blade analysis and an elastic blade analysis with helicopter flight test data. The elastic blade analysis better predicts high-frequency behavior of section lift. In addition, components of the blade angle of attack, such as elastic blade twist, blade nap rate, blade slope velocity, and inflow, are examined as a function of blade mode. Elastic blade motion affects the blade angle of attack by a few tenths of a degree, and up to the sixth rotor harmonic. A similar study of the influence of blade dynamics on bending and torsion moments was also conducted. The modal analysis of the predicted blade structural loads suggested that five elastic bending deg of freedom (four flap and one lag) and three elastic torsion deg of freedom contributed to calculations of the blade structural loads. However, when structural bending load predictions from several elastic blade analyses were compared with flight test data, an elastic blade model consisting of only three elastic bending modes (first and second flap, and first lag), and two elastic torsion modes was found to be sufficient for maximum correlation.

Self-monitoring fiber reinforced polymer strengthening system for civil engineering infrastructures

NASA Astrophysics Data System (ADS)

Jiang, Guoliang; Dawood, Mina; Peters, Kara; Rizkalla, Sami

2008-03-01

Fiber reinforced polymer (FRP) materials are currently used for strengthening civil engineering infrastructures. The strengthening system is dependant on the bond characteristics of the FRP to the external surface of the structure to be effective in resisting the applied loads. This paper presents an innovative self-monitoring FRP strengthening system. The system consists of two components which can be embedded in FRP materials to monitor the global and local behavior of the strengthened structure respectively. The first component of the system is designed to evaluate the applied load acting on a structure based on elongation of the FRP layer along the entire span of the structure. Success of the global system has been demonstrated using a full-scale prestressed concrete bridge girder which was loaded up to failure. The test results indicate that this type of sensor can be used to accurately determine the load prior to failure within 15 percent of the measured value. The second sensor component consists of fiber Bragg grating sensors. The sensors were used to monitor the behavior of steel double-lap shear splices tested under tensile loading up to failure. The measurements were used to identify abnormal structural behavior such as epoxy cracking and FRP debonding. Test results were also compared to numerical values obtained from a three dimensional shear-lag model which was developed to predict the sensor response.

Thermography Inspection for Early Detection of Composite Damage in Structures During Fatigue Loading

NASA Technical Reports Server (NTRS)

Zalameda, Joseph N.; Burke, Eric R.; Parker, F. Raymond; Seebo, Jeffrey P.; Wright, Christopher W.; Bly, James B.

2012-01-01

Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray.

The SLS Stages Intertank Structural Test Assembly (STA) arrives at MSFC.

NASA Image and Video Library

2018-03-06

The SLS Stages Intertank Structural Test Assembly (STA) is rolling off the NASA Pegasus Barge at the MSFC Dock enroute to the MSFC 4619 Load Test Annex test facility for qualification testing. STA emerges from Barge Pegasus.

Substrate Creep on The Fatigue Life of A Model Dental Multilayer Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, J; Huang, M; Niu, X

In this paper, we investigated the effects of substrate creep on the fatigue behavior of a model dental multilayer structure, in which a top glass layer was bonded to a polycarbonate substrate through a dental adhesive. The top glass layers were ground using 120 grit or 600 grit sand papers before bonding to create different sub-surface crack sizes and morphologies. The multilayer structures were tested under cyclic Hertzian contact loading to study crack growth and obtain fatigue life curves. The experiment results showed that the fatigue lives of the multilayer structures were impaired by increasing crack sizes in the sub-surfaces.more » They were also significantly reduced by the substrate creep when tested at relatively low load levels i.e. P{sub m} < 60 N (Pm is the maximum magnitude of cyclic load). But at relatively high load levels i.e. P{sub m} > 65 N, slow crack growth (SCG) was the major failure mechanisms. A modeling study was then carried out to explore the possible failure mechanisms over a range of load levels. It is found that fatigue life at relatively low load levels can be better estimated by considering the substrate creep effect (SCE).« less

14 CFR 27.307 - Proof of structure.

Code of Federal Regulations, 2010 CFR

2010-01-01

... loading condition accounting for the environment to which the structure will be exposed in operation... measurement tests; (5) Landing gear drop tests; and (6) Any additional test required for new or unusual design...

Initial Mechanical Testing of Superalloy Lattice Block Structures Conducted

NASA Technical Reports Server (NTRS)

Krause, David L.; Whittenberger, J. Daniel

2002-01-01

The first mechanical tests of superalloy lattice block structures produced promising results for this exciting new lightweight material system. The testing was performed in-house at NASA Glenn Research Center's Structural Benchmark Test Facility, where small subelement-sized compression and beam specimens were loaded to observe elastic and plastic behavior, component strength levels, and fatigue resistance for hundreds of thousands of load cycles. Current lattice block construction produces a flat panel composed of thin ligaments arranged in a three-dimensional triangulated trusslike structure. Investment casting of lattice block panels has been developed and greatly expands opportunities for using this unique architecture in today's high-performance structures. In addition, advances made in NASA's Ultra-Efficient Engine Technology Program have extended the lattice block concept to superalloy materials. After a series of casting iterations, the nickel-based superalloy Inconel 718 (IN 718, Inco Alloys International, Inc., Huntington, WV) was successfully cast into lattice block panels; this combination offers light weight combined with high strength, high stiffness, and elevated-temperature durability. For tests to evaluate casting quality and configuration merit, small structural compression and bend test specimens were machined from the 5- by 12- by 0.5-in. panels. Linear elastic finite element analyses were completed for several specimen layouts to predict material stresses and deflections under proposed test conditions. The structural specimens were then subjected to room-temperature static and cyclic loads in Glenn's Life Prediction Branch's material test machine. Surprisingly, the test results exceeded analytical predictions: plastic strains greater than 5 percent were obtained, and fatigue lives did not depreciate relative to the base material. These assets were due to the formation of plastic hinges and the redundancies inherent in lattice block construction, which were not considered in the simplified computer models. The fatigue testing proved the value of redundancies since specimen strength was maintained even after the fracture of one or two ligaments. This ongoing test program is planned to continue through high-temperature testing. Also scheduled for testing are IN 718 lattice block panels with integral face sheets, as well as specimens cast from a higher temperature alloy. The initial testing suggests the value of this technology for large panels under low and moderate pressure loadings and for high-risk, damage-tolerant structures. Potential aeropropulsion uses for lattice blocks include turbine-engine actuated panels, exhaust nozzle flaps, and side panel structures.

Effect of remaining coronal structure on the resistance to fracture of crowned endodontically treated maxillary first premolars.

PubMed

Nissan, Joseph; Barnea, Eitan; Bar Hen, Doron; Assif, David

2008-09-01

Endodontically treated maxillary first premolars present a restorative challenge. The objective of the present study was to assess the resistance to fracture of crowned endodontically treated maxillary first premolars under simulated occlusal load, while preserving various degrees of remaining coronal structure. The study consisted of 50 intact maxillary first premolars with bifurcated roots and similar root diameter and length, randomly divided into 5 equal experimental groups. All dowels were luted with Flexi-Flow titanium-reinforced composite resin cement. TiCore titanium-reinforced composite resin was used to fabricate the core. Complete cast crowns were fabricated and cemented with zinc phosphate cement. Forces at fracture and mode of failure were recorded. Statistically significant differences (P < .05) were found among mean failure forces for all tested groups in their resistance to fracture under load with the Kruskal-Wallias test and among all combinations of the 5 groups (Z = -1.56/-2.34; P > .05) with the Mann-Whitney test. This indicates that crowned maxillary first premolars with varying degrees of remaining coronal structure differ significantly in their resistance to fracture under occlusal load. There was increased protection against fracture under occlusal loads with more remaining tooth structure. Within the limitations of this study, remaining coronal structure influenced the fracture resistance of crowned endodontically treated maxillary first premolars. Preservation of tooth structure is important for its protection against fracture under occlusal loads and may influence the tooth prognosis.

Strain Gage Load Calibration of the Wing Interface Fittings for the Adaptive Compliant Trailing Edge Flap Flight Test

NASA Technical Reports Server (NTRS)

Miller, Eric J.; Holguin, Andrew C.; Cruz, Josue; Lokos, William A.

2014-01-01

This is the presentation to follow conference paper of the same name. The adaptive compliant trailing edge (ACTE) flap experiment safety of flight requires that the flap to wing interface loads be sensed and monitored in real time to ensure that the wing structural load limits are not exceeded. This paper discusses the strain gage load calibration testing and load equation derivation methodology for the ACTE interface fittings. Both the left and right wing flap interfaces will be monitored and each contains four uniquely designed and instrumented flap interface fittings. The interface hardware design and instrumentation layout are discussed. Twenty one applied test load cases were developed using the predicted in-flight loads for the ACTE experiment.

Use of the total station for load testing of retrofitted bridges with limited access

NASA Astrophysics Data System (ADS)

Merkle, Wesley J.; Myers, John J.

2004-07-01

As new technologies are increasingly applied to civil infrastructure, the need for structural monitoring systems becomes more critical. Serviceability, or deflection, is very important in monitoring the health of not only a structural system, but also in analyzing the affects of a new technology applied in the field. Traditionally, Linear Variable Displacement Transducers (LVDT"s) are used to measure deflection in many filed load tests. In the field, access can easily become an issue with this instrumentation system that is truly designed for laboratory use. LVDT instrumentation for load testing typically requires several labor intensive hours to prepare for a load test in the field; the system is accompanied by wiring and expensive electronics that may not only become a safety issue but is also very sensitive to the elements. Set up is especially difficult, if not impossible, on tall bridge spans and bridge spans over water. A recent research project required serviceability monitoring through a series of load tests for several retrofitted bridges in Missouri. For these tests, surveying equipment was employed in attempt to make serviceability measurement more practicable. Until recently, surveying equipment would not have produced the accuracy required for structural monitoring use; however, manufacturers of this equipment have developed new technologies to increase the accuracy of the instrumentation. The major component used, the total station, can measure deflection accurate to 0.2 millimeters (0.0079 in.). This monitoring system is much easier to set up and use, reducing labor and time requirements. The system has almost no site restrictions. This paper will compare and contrast the total station to traditional load testing monitoring equipment (LVDT).

A historical perspective of the YF-12A thermal loads and structures program

NASA Technical Reports Server (NTRS)

Jenkins, Jerald M.; Quinn, Robert D.

1996-01-01

Around 1970, the Y-F-12A loads and structures efforts focused on numerous technological issues that needed defining with regard to aircraft that incorporate hot structures in the design. Laboratory structural heating test technology with infrared systems was largely created during this program. The program demonstrated the ability to duplicate the complex flight temperatures of an advanced supersonic airplane in a ground-based laboratory. The ability to heat and load an advanced operational aircraft in a laboratory at high temperatures and return it to flight status without adverse effects was demonstrated. The technology associated with measuring loads with strain gages on a hot structure was demonstrated with a thermal calibration concept. The results demonstrated that the thermal stresses were significant although the airplane was designed to reduce thermal stresses. Considerable modeling detail was required to predict the heat transfer and the corresponding structural characteristics. The overall YF-12A research effort was particularly productive, and a great deal of flight, laboratory, test and computational data were produced and cross-correlated.

NWTC Researchers Field-Test Advanced Control Turbine Systems to Increase Performance, Decrease Structural Loading of Wind Turbines and Plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Researchers at the National Renewable Energy Laboratory's (NREL's) National Wind Technology Center (NWTC) are studying component controls, including new advanced actuators and sensors, for both conventional turbines as well as wind plants. This research will help develop innovative control strategies that reduce aerodynamic structural loads and improve performance. Structural loads can cause damage that increase maintenance costs and shorten the life of a turbine or wind plant.

Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Torus Mechanical Testing

NASA Technical Reports Server (NTRS)

Chen, Tony; Moholt, Matthew R.; Hudson, Larry D.

2017-01-01

The Armstrong Flight Research Center has performed loads testing of a series of developmental atmospheric entry decelerator structural components. Test setup hardware were designed and fabricated. In addition, test plan and checklist were developed for the consistent and efficient execution of the tests. Eight test articles were successfully tested in over one hundred test runs as test objectives were met. Test article buckling shapes and buckling loads were observed. Displacements and strains were also recorded as various load cases were applied. The test data was sent to Langley Research Center to help with the construction of the finite element model of the decelerator assembly.

Experimental Study on Welded Headed Studs Used In Steel Plate-Concrete Composite Structures Compared with Contactless Method of Measuring Displacement

NASA Astrophysics Data System (ADS)

Kisała, Dawid; Tekieli, Marcin

2017-10-01

Steel plate-concrete composite structures are a new innovative design concept in which a thin steel plate is attached to the reinforced concrete beam by means of welded headed studs. The comparison between experimental studies and theoretical analysis of this type of structures shows that their behaviour is dependent on the load-slip relationship of the shear connectors used to ensure sufficient bond between the concrete and steel parts of the structure. The aim of this paper is to describe an experimental study on headed studs used in steel plate-concrete composite structures. Push-out tests were carried out to investigate the behaviour of shear connectors. The test specimens were prepared according to standard push-out tests, however, instead of I-beam, a steel plate 16 mm thick was used to better reflect the conditions in the real structure. The test specimens were produced in two batches using concrete with significantly different compressive strength. The experimental study was carried out on twelve specimens. Besides the traditional measurements based on LVDT sensors, optical measurements based on the digital image correlation method (DIC) and pattern tracking methods were used. DIC is a full-field contactless optical method for measuring displacements in experimental testing, based on the correlation of the digital images taken during test execution. With respect to conventional methods, optical measurements offer a wider scope of results and can give more information about the material or construction behaviour during the test. The ultimate load capacity and load-slip curves obtained from the experiments were compared with the values calculated based on Eurocodes, American and Chinese design specifications. It was observed that the use of the relationships developed for the traditional steel-concrete composite structures is justified in the case of ultimate load capacity of shear connectors in steel plate-concrete composite structures.

BMI Sandwich Wing Box Analysis and Test

NASA Technical Reports Server (NTRS)

Palm, Tod; Mahler, Mary; Shah, Chandu; Rouse, Marshall; Bush, Harold; Wu, Chauncey; Small, William J.

2000-01-01

A composite sandwich single bay wing box test article was developed by Northrop Grumman and tested recently at NASA Langley Research Center. The objectives for the wing box development effort were to provide a demonstration article for manufacturing scale up of structural concepts related to a high speed transport wing, and to validate the structural performance of the design. The box concept consisted of highly loaded composite sandwich wing skins, with moderately loaded composite sandwich spars. The dimensions of the box were chosen to represent a single bay of the main wing box, with a spar spacing of 30 inches, height of 20 inches constant depth, and length of 64 inches. The bismaleimide facesheet laminates and titanium honeycomb core chosen for this task are high temperature materials able to sustain a 300F service temperature. The completed test article is shown in Figure 1. The tests at NASA Langley demonstrated the structures ability to sustain axial tension and compression loads in excess of 20,000 lb/in, and to maintain integrity in the thermal environment. Test procedures, analysis failure predictions, and test results are presented.

Effects of Simulated Functional Loading Conditions on Dentin, Composite, and Laminate Structures

PubMed Central

Walker, Mary P.; Teitelbaum, Heather K.; Eick, J. David; Williams, Karen B.

2008-01-01

Use of composite restorations continues to increase, tempered by more potential problems when placed in posterior dentition. Thus, it is essential to understand how these materials function under stress-bearing clinical conditions. Since mastication is difficult to replicate in the laboratory, cyclic loading is frequently used within in vitro evaluations but often employs traditional fatigue testing, which typically does not simulate occlusal loading because higher stresses and loading frequencies are used, so failure mechanisms may be different. The present investigation utilized relevant parameters (specimen size; loading frequency) to assess the effects of cyclic loading on flexural mechanical properties and fracture morphology of (coronal) dentin, composite, and dentin-adhesive-composite “laminate” structures. Incremental monitoring of flexural modulus on individual beams over 60,000 loading cycles revealed a gradual increase across materials; post-hoc comparisons indicated statistical significance only for 1 versus 60k cycles. Paired specimens were tested (one exposed to 60k loading cycles, one to static loading only), and comparisons of flexural modulus and strength showed statistically significantly higher values for cyclically-loaded specimens across materials, with no observable differences in fracture morphology. Localized reorganization of dentin collagen and polymer chains could have increased flexural modulus and strength during cyclic loading, which may have implications toward the life and failure mechanisms of clinical restorations and underlying tooth structure. PMID:18823019

Testing and Analysis of a Composite Non-Cylindrical Aircraft Fuselage Structure. Part 1; Ultimate Design Loads

NASA Technical Reports Server (NTRS)

Przekop, Adam; Jegley, Dawn C.; Lovejoy, Andrew E.; Rouse, Marshall; Wu, Hsi-Yung T.

2016-01-01

The Environmentally Responsible Aviation Project aimed to develop aircraft technologies enabling significant fuel burn and community noise reductions. Small incremental changes to the conventional metallic alloy-based 'tube and wing' configuration were not sufficient to achieve the desired metrics. One airframe concept identified by the project as having the potential to dramatically improve aircraft performance was a composite-based hybrid wing body configuration. Such a concept, however, presented inherent challenges stemming from, among other factors, the necessity to transfer wing loads through the entire center fuselage section which accommodates a pressurized cabin confined by flat or nearly flat panels. This paper discusses finite element analysis and testing of a large-scale hybrid wing body center section structure developed and constructed to demonstrate that the Pultruded Rod Stitched Efficient Unitized Structure concept can meet these challenging demands of the next generation airframes. Part I of the paper considers the five most critical load conditions, which are internal pressure only and positive and negative g-loads with and without internal pressure. Analysis results are compared with measurements acquired during testing. Performance of the test article is found to be closely aligned with predictions and, consequently, able to support the hybrid wing body design loads in pristine and barely visible impact damage conditions.

Vibration Testing of Electrical Cables to Quantify Loads at Tie-Down Locations

NASA Technical Reports Server (NTRS)

Dutson, Joseph D.

2013-01-01

The standard method for defining static equivalent structural load factors for components is based on Mile s equation. Unless test data is available, 5% critical damping is assumed for all components when calculating loads. Application of this method to electrical cable tie-down hardware often results in high loads, which often exceed the capability of typical tie-down options such as cable ties and P-clamps. Random vibration testing of electrical cables was used to better understand the factors that influence component loads: natural frequency, damping, and mass participation. An initial round of vibration testing successfully identified variables of interest, checked out the test fixture and instrumentation, and provided justification for removing some conservatism in the standard method. Additional testing is planned that will include a larger range of cable sizes for the most significant contributors to load as variables to further refine loads at cable tie-down points. Completed testing has provided justification to reduce loads at cable tie-downs by 45% with additional refinement based on measured cable natural frequencies.

Gravity-Off-loading System for Large-Displacement Ground Testing of Spacecraft Mechanisms

NASA Technical Reports Server (NTRS)

Han, Olyvia; Kienholz, David; Janzen, Paul; Kidney, Scott

2010-01-01

Gravity-off-loading of deployable spacecraft mechanisms during ground testing is a long-standing problem. Deployable structures which are usually too weak to support their own weight under gravity require a means of gravity-off-loading as they unfurl. Conventional solutions to this problem have been helium-filled balloons or mechanical pulley/counterweight systems. These approaches, however, suffer from the deleterious effects of added inertia or friction forces. The changing form factor of the deployable structure itself and the need to track the trajectory of the center of gravity also pose a challenge to these conventional technologies. This paper presents a novel testing apparatus for high-fidelity zero-gravity simulation for special application to deployable space structures such as solar arrays, magnetometer booms, and robotic arms in class 100,000 clean room environments

Thermo-mechanical cyclic testing of carbon-carbon primary structure for an SSTO vehicle

NASA Astrophysics Data System (ADS)

Croop, Harold C.; Leger, Kenneth B.; Lowndes, Holland B.; Hahn, Steven E.; Barthel, Chris A.

1999-01-01

An advanced carbon-carbon structural component is being experimentally evaluated for use as primary load carrying structure for future single-stage-to-orbit (SSTO) vehicles. The component is a wing torque box section featuring an advanced, three-spar design. This design features 3D-woven, angle-interlock skins, 3D integrally woven spar webs and caps, oxidation inhibited matrix, chemical vapor deposited (CVD) oxidation protection coating, and ceramic matrix composite fasteners. The box spar caps are nested into the skins which, when processed together through the carbon-carbon processing cycle, resulted in monolithic box halves. The box half sections were then joined at the spar web intersections using ceramic matrix composite fasteners. This method of fabrication eliminated fasteners through both the upper and lower skins. Development of the carbon-carbon wing box structure was accomplished in a four phase design and fabrication effort, conducted by Boeing, Information, Space and Defense Systems, Seattle, WA, under contract to the Air Force Research Laboratory (AFRL). The box is now set up for testing and will soon begin cyclic loads testing in the AFRL Structural Test Facility at Wright-Patterson Air Force Base (WPAFB), OH. This paper discusses the latest test setup accomplishments and the results of the pre-cyclic loads testing performed to date.

Design, Analysis and Testing of a PRSEUS Pressure Cube to Investigate Assembly Joints

NASA Technical Reports Server (NTRS)

Yovanof, Nicolette; Lovejoy, Andrew E.; Baraja, Jaime; Gould, Kevin

2012-01-01

Due to its potential to significantly increase fuel efficiency, the current focus of NASA's Environmentally Responsible Aviation Program is the hybrid wing body (HWB) aircraft. Due to the complex load condition that exists in HWB structure, as compared to traditional aircraft configurations, light-weight, cost-effective and manufacturable structural concepts are required to enable the HWB. The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept is one such structural concept. A building block approach for technology development of the PRSEUS concept is being conducted. As part of this approach, a PRSEUS pressure cube was developed as a risk reduction test article to examine a new integral cap joint concept. This paper describes the design, analysis and testing of the PRSEUS pressure cube test article. The pressure cube was required to withstand a 2P, 18.4 psi, overpressure load requirement. The pristine pressure cube was tested to 2.2P with no catastrophic failure. After the addition of barely visible impact damage, the cube was pressure loaded to 48 psi where catastrophic failure occurred, meeting the scale-up requirement. Comparison of pretest and posttest analyses with the cube test response agree well, and indicate that current analysis methods can be used to accurately analyze PRSEUS structure for initial failure response.

Characterization of interdigitated electrode piezoelectric fiber composites under high electrical and mechanical loading

NASA Astrophysics Data System (ADS)

Rodgers, John P.; Bent, Aaron A.; Hagood, Nesbitt W.

1996-05-01

The primary objective of this work is to develop a standard methodology for characterizing structural actuation systems intended for operation in high electrical and mechanical loading environments. The designed set of tests evaluates the performance of the active materials system under realistic operating conditions. The tests are also used to characterize piezoelectric fiber composites which have been developed as an alternative to monolithic piezoceramic wafers for structural actuation applications. The performance of this actuator system has been improved using an interdigitated electrode pattern, which orients the primary component of the electric field into the plane of the structure, enabling the use of the primary piezoelectric effect along the active fibers. One possible application of this technology is in the integral twist actuation of helicopter rotor blades for higher harmonic control. This application requires actuators which can withstand the harsh rotor blade operating environment. This includes large numbers of electrical and mechanical cycles with considerable centripetal and bending loads. The characterization tests include standard active material tests as well as application-driven tests which evaluate the performance of the actuators during simulated operation. Test results for several actuator configurations are provided, including S2 glass- reinforced and E-glass laminated actuators. The study concludes that the interdigitated electrode piezoelectric fiber composite actuator has great potential for high loading applications.

Investigation of UH-60A Rotor Structural Loads from Flight and Wind Tunnel Tests

DTIC Science & Technology

2016-05-19

and main rotor blades. A bifilar pendulum -type vibration absorber system was mounted on top of the hub to reduce 3/rev rotating in-plane loads. Main... pendulum weights were not attached (no 3/rev in-plane load absorption). The rotor assembly was mounted on a large test stand with its own fixed system

An analysis of cross-coupling of a multicomponent jet engine test stand using finite element modeling techniques

NASA Technical Reports Server (NTRS)

Schweikhard, W. G.; Singnoi, W. N.

1985-01-01

A two axis thrust measuring system was analyzed by using a finite a element computer program to determine the sensitivities of the thrust vectoring nozzle system to misalignment of the load cells and applied loads, and the stiffness of the structural members. Three models were evaluated: (1) the basic measuring element and its internal calibration load cells; (2) the basic measuring element and its external load calibration equipment; and (3) the basic measuring element, external calibration load frame and the altitude facility support structure. Alignment of calibration loads was the greatest source of error for multiaxis thrust measuring systems. Uniform increases or decreases in stiffness of the members, which might be caused by the selection of the materials, have little effect on the accuracy of the measurements. It is found that the POLO-FINITE program is a viable tool for designing and analyzing multiaxis thrust measurement systems. The response of the test stand to step inputs that might be encountered with thrust vectoring tests was determined. The dynamic analysis show a potential problem for measuring the dynamic response characteristics of thrust vectoring systems because of the inherently light damping of the test stand.

NASA experiments onboard the controlled impact demonstration

NASA Technical Reports Server (NTRS)

Hayduk, R. J.; Alfaro-Bou, E.; Fasanella, E. L.

1985-01-01

The structural crashworthiness tests conducted by NASA on the December 1, 1984 controlled impact demonstration are discussed. The components and locations of the data acquisition and photographic systems developed by NASA to evaluate impact loads throughout the aircraft structure and the transmission of loads into the dummies are described. The effectiveness of the NASA designed absorbing seats and the vertical, longitudinal, and transverse impact loads are measured. Data that is extremely applicable to crash dynamics structural research was obtained by the data acquisition system and very low load levels were measured for the NASA energy absorbing seats.

Sea loads on ships and offshore structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faltinsen, O.

1990-01-01

The book introduces the theory of the structural loading on ships and offshore structures caused by wind, waves and currents, and goes on to describe the applications of this theory in terms of real structures. The main topics described are linear-wave induced motions, loads on floating structures, numerical methods for ascertaining wave induced motions and loads, viscous wave loads and damping, stationkeeping and water impact and entry. The applications of the theoretical principles are introduced with extensive use of exercises and examples. Applications covered include conventional ships, barges, high speed marine vehicles, semisubmersibles, tension leg platforms, moored or dynamic positionedmore » ships, risers, buoys, fishing nets, jacket structures and gravity platforms. One aim of the book is to provide a physical understanding through simplified mathematical models. In this way one can develop analytical tools to evaluate results from test models, full scale trials or computer simulation, and learns which parameters represent the major contributions and influences on sea loads.« less

Rhythmic crowd bobbing on a grandstand simulator

NASA Astrophysics Data System (ADS)

Comer, A. J.; Blakeborough, A.; Williams, M. S.

2013-01-01

It is widely accepted that concerted human activity such as bouncing or bobbing can excite cantilever grandstands. Crowd coordination can be unwitting and may be exacerbated by structural motion caused by resonant structural response. This is an area of uncertainty in the design and analysis of modern grandstands. This paper presents experimental measurement and analysis of rhythmic crowd bobbing loads obtained from tests on a grandstand simulator with two distinct support conditions; (a) rigid, and; (b) flexible. It was found that significant structural vibration at the bobbing frequency did not increase the effective bobbing load. Structural motion at the bobbing frequency caused a reduction in the dynamic load factor (DLF) at the frequency of the second harmonic while those at the first and third harmonics were unaffected. Two plausible reasons for this are: (a) the bobbing group were unable to supply significant energy to the system at the frequency of the second harmonic; (b) the bobbing group altered their bobbing style to reduce the response of the grandstand simulator. It was deduced that the bobbing group did not absorb energy from the dynamic system. Furthermore, dynamic load factors for groups of test subjects bobbing on a rigid structure were typically greater than those of synthesised groups derived from individuals bobbing alone, possibly due to group effects such as audio and visual stimuli from neighbouring test subjects. Last, the vibration levels experienced by the test subjects appear to be below levels likely to cause discomfort. This is to be expected as the test subjects were themselves controlling the magnitude and duration of vibration for the bobbing tests considered.

Observation of creep behavior of cellulose electro-active paper (EAPap) actuator

NASA Astrophysics Data System (ADS)

Kim, Joo-Hyung; Lee, Sang-Woo; Yun, Gyu-Young; Yang, Chulho; Kim, Heung Soo; Kim, Jaehwan

2009-03-01

Understanding of creep effects on actuating mechanisms is important to precisely figure out the behavior of material. Creep behaviors of cellulose based Electro-Active Paper (EAPap) were studied under different constant loading conditions. We found the structural modification of microfibrils in EAPap after creep test. Structural differences of as-prepared and after creep tested samples were compared by SEM measurements. From the measured creep behaviors by different loading conditions, two different regions of induced strain and current were clearly observed as the measurement time increased. It is consider that local defects may occur and becomes micro-dimple or micro-crack formations in lower load cases as localized deformation proceeds, while the shrinkage of diameter of elongated fibers was observed only at the high level of loading. Therefore, cellulose nanofibers may play a role to be against the creep load and prevent the localized structural deformations. The results provide useful creep behavior and mechanism to understand the mechanical behavior of thin visco-elastic EAPap actuator.

Crack growth induced by thermal-mechanical loading

NASA Astrophysics Data System (ADS)

John, R.; Hartman, G. A.; Gallagher, J. P.

1992-06-01

Advanced aerospace structures are often subjected to combined thermal and mechanical loads. The fracture-mechanics behavior of the structures may be altered by the thermal state existing around the crack. Hence, design of critical structural elements requires the knowledge of stress-intensity factors under both thermal and mechanical loads. This paper describes the development of an experimental technique to verify the thermal-stress-intensity factor generated by a temperature gradient around the crack. Thin plate specimens of a model material (AISI-SAE 1095 steel) were used for the heat transfer and thermal-mechanical fracture tests. Rapid thermal loading was achieved using high-intensity focused infrared spot heaters. These heaters were also used to generate controlled temperature rates for heat-transfer verification tests. The experimental results indicate that thermal loads can generate stress-intensity factors large enough to induce crack growth. The proposed thermal-stress-intensity factors appear to have the same effect as the conventional mechanical-stress-intensity factors with respect to fracture.

Considerations in STS payload environmental verification

NASA Technical Reports Server (NTRS)

Keegan, W. B.

1978-01-01

Considerations regarding the Space Transportation System (STS) payload environmental verification are reviewed. It is noted that emphasis is placed on testing at the subassembly level and that the basic objective of structural dynamic payload verification is to ensure reliability in a cost-effective manner. Structural analyses consist of: (1) stress analysis for critical loading conditions, (2) model analysis for launch and orbital configurations, (3) flight loads analysis, (4) test simulation analysis to verify models, (5) kinematic analysis of deployment/retraction sequences, and (6) structural-thermal-optical program analysis. In addition to these approaches, payload verification programs are being developed in the thermal-vacuum area. These include the exposure to extreme temperatures, temperature cycling, thermal-balance testing and thermal-vacuum testing.

Experimental Verification of the Structural Glass Beam-Columns Strength

NASA Astrophysics Data System (ADS)

Pešek, Ondřej; Melcher, Jindřich; Balázs, Ivan

2017-10-01

This paper deals with experimental research of axially and laterally loaded members made of structural (laminated) glass. The purpose of the research is the evaluation of buckling strength and actual behaviour of the beam-columns due to absence of standards for design of glass load-bearing structures. The experimental research follows the previous one focusing on measuring of initial geometrical imperfections of glass members, testing of glass beams and columns. Within the frame of the research 9 specimens were tested. All of them were of the same geometry (length 2000 mm, width 200 mm and thickness 16 mm) but different composition - laminated double glass made of annealed glass or fully tempered glass panes bonded together by PVB or EVASAFE foil. Specimens were at first loaded by axial force and then by constantly increasing bending moment up to failure. During testing lateral deflections, vertical deflection and normal stresses at mid-span were measured. A maximum load achieved during testing has been adopted as flexural-lateral-torsional buckling strength. The results of experiments were statistically evaluated according to the European standard for design of structures EN 1990, appendix D. There are significant differences between specimens made of annealed glass or fully tempered glass. Differences between specimens loaded by axial forces 1 kN and 2 kN are negligible. The next step was to determine the design strength by calculation procedure based on buckling curves approach intended for design of steel columns and develop interaction criterion for glass beams-columns.

Air Vehicle Integration and Technology Research (AVIATR). Delivery Order 0003: Condition-Based Maintenance Plus Structural Integrity (CBM+SI) Demonstration

DTIC Science & Technology

2009-08-01

K/sigma vs a file Selected design load and material Full scale test results IAT Actual Fracture toughness distribution Selected material...update data from 5.3.4 a vs T file Selected design load and material Full scale test results IAT Actual Max stress Gumbel Dist. (loads exceedance... altitude ; Mach number; control surface positions; selected strain measurements; ground loads; aerodynamic excitations; etc. Data shall also be

Finite element simulation of structural performance on flexible pavements with stabilized base/treated subbase materials under accelerated loading.

DOT National Transportation Integrated Search

2011-12-01

Accelerated pavement testing (APT) has been increasingly used by state highway agencies in recent years for evaluating pavement structures and/or materials. However, running an APT experiment is expensive. It requires costly accelerated loading devic...

Embedded data collector (EDC) evaluation, phase II - comparison with instrumented static load tests : [technical summary].

DOT National Transportation Integrated Search

2013-12-01

Monitoring installation of driven pile foundations : is critically important to ensure adequate safety : of structures with piles, such as the many bridges : which are maintained by the Florida Department : of Transportation (FDOT). Dynamic load test...

Interim Report on Fatigue Characteristics of a Typical Metal Wing

NASA Technical Reports Server (NTRS)

Kepert, J L; Payne, A O

1956-01-01

Constant amplitude fatigue tests of seventy-two P-51D "Mustang" wings are reported. The tests were performed by a vibrational loading system and by an hydraulic loading device for conditions with and without varying amounts of pre-load. The results indicate that: (a) the frequency of occurrence of fatigue at any one location is related to the range of the loads applied, (b) the rate of propagation of visible cracks is more or less constant for a large portion of the life of the specimen, (c) the fatigue strength of the structure is similar to that of notched material having a theoretical stress concentration factor of more than 3.0, (d) the frequency distribution of fatigue life is approximately logarithmic normal, (e) the relative increase in fatigue life for a given pre-load depends on the maximum load of the loading cycle only, while the optimum pre-load value is approximately 85 percent of the ultimate failing load, and (f) that normal design procedure will not permit the determination of local stress levels with sufficient accuracy to determine the fatigue strength of an element of a redundant structure.

Pressure Testing of a Minimum Gauge PRSEUS Panel

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew J.; Rouse, Marshall; Linton, Kim A.; Li, Victor P.

2011-01-01

Advanced aircraft configurations that have been developed to increase fuel efficiency require advanced, novel structural concepts capable of handling the unique load conditions that arise. One such concept is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) developed by the Boeing Company. The PRSEUS concept is being investigated by NASA s Environmentally Responsible Aviation (ERA) Program for use in a hybrid-wing body (HWB) aircraft. This paper summarizes the analysis and test of a PRSEUS panel subjected to internal pressure, the first such pressure test for this structural concept. The pressure panel used minimum gauge skin, with stringer and frame configurations consistent with previous PRSEUS tests. Analysis indicated that for the minimum gauge skin panel, the stringer locations exhibit fairly linear response, but the skin bays between the stringers exhibit nonlinear response. Excellent agreement was seen between nonlinear analysis and test results in the critical portion at the center of the panel. The pristine panel was capable of withstanding the required 18.4 psi pressure load condition without exhibiting any damage. The impacted panel was capable of withstanding a pressure load in excess of 28 psi before initial failure occurred at the center stringer, and the panel was capable of sustaining increased pressure load after the initial failure. This successful PRSEUS panel pressure panel test was a critical step in the building block approach for enabling the use of this advanced structural concept on future aircraft, such as the HWB.

Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

NASA Technical Reports Server (NTRS)

Williams, J. G.; Anderson, M. S.; Rhodes, M. D.; Starnes, J. H., Jr.; Stroud, W. J.

1979-01-01

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described.

Damage source identification of reinforced concrete structure using acoustic emission technique.

PubMed

Panjsetooni, Alireza; Bunnori, Norazura Muhamad; Vakili, Amir Hossein

2013-01-01

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures.

Damage Source Identification of Reinforced Concrete Structure Using Acoustic Emission Technique

PubMed Central

Panjsetooni, Alireza; Bunnori, Norazura Muhamad; Vakili, Amir Hossein

2013-01-01

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures. PMID:23997681

Static test induced loads verification beyond elastic limit

NASA Technical Reports Server (NTRS)

Verderaime, V.; Harrington, F.

1996-01-01

Increasing demands for reliable and least-cost high-performance aerostructures are pressing design analyses, materials, and manufacturing processes to new and narrowly experienced performance and verification technologies. This study assessed the adequacy of current experimental verification of the traditional binding ultimate safety factor which covers rare events in which no statistical design data exist. Because large high-performance structures are inherently very flexible, boundary rotations and deflections under externally applied loads approaching fracture may distort their transmission and unknowingly accept submarginal structures or prematurely fracturing reliable ones. A technique was developed, using measured strains from back-to-back surface mounted gauges, to analyze, define, and monitor induced moments and plane forces through progressive material changes from total-elastic to total-inelastic zones within the structural element cross section. Deviations from specified test loads are identified by the consecutively changing ratios of moment-to-axial load.

Static test induced loads verification beyond elastic limit

NASA Technical Reports Server (NTRS)

Verderaime, V.; Harrington, F.

1996-01-01

Increasing demands for reliable and least-cost high performance aerostructures are pressing design analyses, materials, and manufacturing processes to new and narrowly experienced performance and verification technologies. This study assessed the adequacy of current experimental verification of the traditional binding ultimate safety factor which covers rare events in which no statistical design data exist. Because large, high-performance structures are inherently very flexible, boundary rotations and deflections under externally applied loads approaching fracture may distort their transmission and unknowingly accept submarginal structures or prematurely fracturing reliable ones. A technique was developed, using measured strains from back-to-back surface mounted gauges, to analyze, define, and monitor induced moments and plane forces through progressive material changes from total-elastic to total inelastic zones within the structural element cross section. Deviations from specified test loads are identified by the consecutively changing ratios of moment-to-axial load.

Development of a 20 MeV Dielectric-Loaded Test Accelerator

NASA Astrophysics Data System (ADS)

Gold, Steven H.; Kinkead, Allen K.; Gai, Wei; Power, John G.; Konecny, Richard; Jing, Chunguang; Long, Jidong; Tantawi, Sami G.; Nantista, Christopher D.; Bruce, Ralph W.; Fliflet, Arne W.; Lombardi, Marcie; Lewis, David

2006-11-01

This paper presents a progress report on a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC), to develop a dielectric-loaded test accelerator in the magnicon facility at NRL. The accelerator will be powered by an experimental 11.424-GHz magnicon amplifier that presently produces 25 MW of output power in a ˜250-ns pulse at up to 10 Hz. The accelerator will include a 5-MeV electron injector originally developed at the Tsinghua University in Beijing, China, and can incorporate DLA structures up to 0.5 m in length. The DLA structures are being developed by ANL, and shorter test structures fabricated from a variety of dielectric materials have undergone testing at NRL at gradients up to ˜8 MV/m. SLAC has developed components to distribute the power from the two magnicon output arms to the injector and to the DLA accelerating structure with separate control of the power ratio and relative phase. RWBruce Associates, Inc., working with NRL, has investigated means to join short ceramic sections into a continuous accelerator tube by a brazing process using an intense 83-GHz beam. The installation and testing of the first dielectric-loaded test accelerator, including injector, DLA test structure, and spectrometer, should take place within the next year.

Structural tests on a tile/strain isolation pad thermal protection system. [space shuttles

NASA Technical Reports Server (NTRS)

Williams, J. G.

1980-01-01

The aluminum skin of the space shuttle is covered by a thermal protection system (TPS) consisting of a low density ceramic tile bonded to a matted-felt material called strain insulation pad (SIP). The structural characteristics of the TPS were studied experimentally under selected extreme load conditions. Three basic types of loads were imposed: tension, eccentrically applied tension, and combined in-plane force and transverse pressure. For some tests, transverse pressure was applied rapidly to simulate a transient shock wave passing over the tile. The failure mode for all specimens involved separation of the tile from the SIP at the silicone rubber bond interface. An eccentrically applied tension load caused the tile to separate from the SIP at loads lower than experienced at failure for pure tension loading. Moderate in-plane as well as shock loading did not cause a measurable reduction in the TPS ultimate failure strength. A strong coupling, however, was exhibited between in-plane and transverse loads and displacements.

Creep and cracking of concrete hinges: insight from centric and eccentric compression experiments.

PubMed

Schlappal, Thomas; Schweigler, Michael; Gmainer, Susanne; Peyerl, Martin; Pichler, Bernhard

2017-01-01

Existing design guidelines for concrete hinges consider bending-induced tensile cracking, but the structural behavior is oversimplified to be time-independent. This is the motivation to study creep and bending-induced tensile cracking of initially monolithic concrete hinges systematically. Material tests on plain concrete specimens and structural tests on marginally reinforced concrete hinges are performed. The experiments characterize material and structural creep under centric compression as well as bending-induced tensile cracking and the interaction between creep and cracking of concrete hinges. As for the latter two aims, three nominally identical concrete hinges are subjected to short-term and to longer-term eccentric compression tests. Obtained material and structural creep functions referring to centric compression are found to be very similar. The structural creep activity under eccentric compression is significantly larger because of the interaction between creep and cracking, i.e. bending-induced cracks progressively open and propagate under sustained eccentric loading. As for concrete hinges in frame-like integral bridge construction, it is concluded (i) that realistic simulation of variable loads requires consideration of the here-studied time-dependent behavior and (ii) that permanent compressive normal forces shall be limited by 45% of the ultimate load carrying capacity, in order to avoid damage of concrete hinges under sustained loading.

Ultrasonic Nondestructive Evaluation of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) During Large-Scale Load Testing and Rod Push-Out Testing

NASA Technical Reports Server (NTRS)

Johnston, Patrick H.; Juarez, Peter D.

2016-01-01

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is a structural concept developed by the Boeing Company to address the complex structural design aspects associated with a pressurized hybrid wing body (HWB) aircraft configuration. The HWB has long been a focus of NASA's environmentally responsible aviation (ERA) project, following a building block approach to structures development, culminating with the testing of a nearly full-scale multi-bay box (MBB), representing a segment of the pressurized, non-circular fuselage portion of the HWB. PRSEUS is an integral structural concept wherein skins, frames, stringers and tear straps made of variable number of layers of dry warp-knit carbon-fiber stacks are stitched together, then resin-infused and cured in an out-of-autoclave process. The PRSEUS concept has the potential for reducing the weight and cost and increasing the structural efficiency of transport aircraft structures. A key feature of PRSEUS is the damage-arresting nature of the stitches, which enables the use of fail-safe design principles. During the load testing of the MBB, ultrasonic nondestructive evaluation (NDE) was used to monitor several sites of intentional barely-visible impact damage (BVID) as well as to survey the areas surrounding the failure cracks after final loading to catastrophic failure. The damage-arresting ability of PRSEUS was confirmed by the results of NDE. In parallel with the large-scale structural testing of the MBB, mechanical tests were conducted of the PRSEUS rod-to-overwrap bonds, as measured by pushing the rod axially from a short length of stringer.

Structural Qualification Testing of the WindSat Payload Using Sine Bursts Near Structural Resonance

NASA Technical Reports Server (NTRS)

Pontius, Jim; Barnes, Donald; Broduer, Steve (Technical Monitor)

2001-01-01

Sine burst tests are often used for structural qualification of space flight hardware. In most instances, the driving frequency of the shaker is specified far below the structure's first resonant mode, such that the entire test article sees uniform acceleration. For large structures, this limits qualification testing to lower parts of the structure, or else it over-tests the lower structure to achieve qualification of the upper structure. The WindSat payload, a 10.5 foot tall graphite/epoxy, titanium, and aluminum radiometer, experiences accelerations at the six foot diameter reflector nearly four times that at the spacecraft interface. Due to size of the payload, the number of bonded joints, and the lightweight reflector support structure design and construction, using static pull testing to qualify all of the bonded joints in the upper structure would result in large, expensive, and extensive test fixturing. Sine burst testing near the first two structural resonant modes was performed on the WindSat payload to achieve the correct load factor distribution up the stack for structural qualification. In this presentation, how finite element method (FEM) sine burst predictions were used in conjunction with low level random and sine burst tests to achieve correct qualification test load factor distribution on the WindSat payload is discussed. Also presented is the risk mitigation approach for using the uncorrelated FEM in this procedure.

Structural Analysis for the American Airlines Flight 587 Accident Investigation: Global Analysis

NASA Technical Reports Server (NTRS)

Young, Richard D.; Lovejoy, Andrew E.; Hilburger, Mark W.; Moore, David F.

2005-01-01

NASA Langley Research Center (LaRC) supported the National Transportation Safety Board (NTSB) in the American Airlines Flight 587 accident investigation due to LaRC's expertise in high-fidelity structural analysis and testing of composite structures and materials. A Global Analysis Team from LaRC reviewed the manufacturer s design and certification procedures, developed finite element models and conducted structural analyses, and participated jointly with the NTSB and Airbus in subcomponent tests conducted at Airbus in Hamburg, Germany. The Global Analysis Team identified no significant or obvious deficiencies in the Airbus certification and design methods. Analysis results from the LaRC team indicated that the most-likely failure scenario was failure initiation at the right rear main attachment fitting (lug), followed by an unstable progression of failure of all fin-to-fuselage attachments and separation of the VTP from the aircraft. Additionally, analysis results indicated that failure initiates at the final observed maximum fin loading condition in the accident, when the VTP was subjected to loads that were at minimum 1.92 times the design limit load condition for certification. For certification, the VTP is only required to support loads of 1.5 times design limit load without catastrophic failure. The maximum loading during the accident was shown to significantly exceed the certification requirement. Thus, the structure appeared to perform in a manner consistent with its design and certification, and failure is attributed to VTP loads greater than expected.

Development of an Aeroelastic Modeling Capability for Transient Nozzle Side Load Analysis

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2013-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a coupled aeroelastic modeling capability by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed in the framework of modal analysis. Transient aeroelastic nozzle startup analyses of the Block I Space Shuttle Main Engine at sea level were performed. The computed results from the aeroelastic nozzle modeling are presented.

The SLS Stages Intertank Structural Test Assembly (STA) arrives at MSFC

NASA Image and Video Library

2018-03-08

The SLS Stages Intertank Structural Test Assembly (STA) is rolling off the NASA Pegasus Barge at the MSFC Dock enroute to the MSFC 4619 Load Test Annex test facility for qualification testing via MSFC West Test Area. STA approaches Test Stand 4693, SLS LH2 test Stand, on way to Bldg. 4619

Evaluation of a Composite Sandwich Fuselage Side Panel with Damage and Subjected to Internal Pressure

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Ambur, Damodar R.; Bodine, Jerry; Dopker, Bernhard

1997-01-01

The results from an experimental and analytical study of a composite sandwich fuselage side panel for a transport aircraft are presented. The panel has two window cutouts and three frames, and has been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on the graphite-epoxy sandwich panel with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. The two-frame panel was damaged by cutting a notch that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. The two panel configurations successfully satisfied all design load requirements in the experimental part of the study, and the three-frame and two-frame panel responses are fully explained by the analysis results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in.-wide frame spacing to further reduce aircraft fuselage structural weight.

Edgewise Compression Testing of STIPS-0 (Structurally Integrated Thermal Protection System)

NASA Technical Reports Server (NTRS)

Brewer, Amy R.

2011-01-01

The Structurally Integrated Thermal Protection System (SITPS) task was initiated by the NASA Hypersonics Project under the Fundamental Aeronautics Program to develop a structural load-carrying thermal protection system for use in aerospace applications. The initial NASA concept for SITPS consists of high-temperature composite facesheets (outer and inner mold lines) with a light-weight insulated structural core. An edgewise compression test was performed on the SITPS-0 test article at room temperature using conventional instrumentation and methods in order to obtain panel-level mechanical properties and behavior of the panel. Three compression loadings (10, 20 and 37 kips) were applied to the SITPS-0 panel. The panel behavior was monitored using standard techniques and non-destructive evaluation methods such as photogrammetry and acoustic emission. The elastic modulus of the SITPS-0 panel was determined to be 1.146x106 psi with a proportional limit at 1039 psi. Barrel-shaped bending of the panel and partial delamination of the IML occurred under the final loading.

Thermal loading in the laser holography nondestructive testing of a composite structure

NASA Technical Reports Server (NTRS)

Liu, H. K.; Kurtz, R. L.

1975-01-01

A laser holographic interferometry method that has variable sensitivity to surface deformation was applied to the investigation of composite test samples under thermal loading. A successful attempt was made to detect debonds in a fiberglass-epoxy-ceramic plate. Experimental results are presented along with the mathematical analysis of the physical model of the thermal loading and current conduction in the composite material.

KEITH HIGGINBOTHAM AT TEST STAND 4699

NASA Image and Video Library

2016-10-17

KEITH HIGGINBOTHAM, STRUCTURAL TEST LEAD FOR THE SLS SPACECRAFT PAYLOAD INTEGRATION AND EVOLUTION OFFICE, IS SHOWN BESIDE TEST STAND 4699 AT THE MARSHALL SPACE FLIGHT CENTER’S WEST TEST AREA. HIGGINBOTHAM WILL BE LEADING STRUCTURAL LOADS TESTING AT TEST STAND 4699 FOR THE CORE STAGE SIMULATER AND THE LAUNCH VEHICLE STAGE ADAPTER. THE TEST SERIES WILL ENSURE EACH STRUCTURE CAN WITHSTAND THE INCREDIBLE STRESSES OF LAUNCH.

The SLS Stages Intertank Structural Test Assembly (STA) arrives at MSFC

NASA Image and Video Library

2018-03-06

The SLS Stages Intertank Structural Test Assembly (STA) is rolling off the NASA Pegasus Barge at the MSFC Dock enroute to the MSFC 4619 Load Test Annex test facility for qualification testing. STA hardware completely free of barge and flanked by tug boats.

Shock and vibration tests of uranium mononitride fuel pellets for a space power nuclear reactor

NASA Technical Reports Server (NTRS)

Adams, D. W.

1972-01-01

Shock and vibration tests were conducted on cylindrically shaped, depleted, uranium mononitride (UN) fuel pellets. The structural capabilities of the pellets were determined under exposure to shock and vibration loading which a nuclear reactor may encounter during launching into space. Various combinations of diametral and axial clearances between the pellets and their enclosing structures were tested. The results of these tests indicate that for present fabrication of UN pellets, a diametral clearance of 0.254 millimeter and an axial clearance of 0.025 millimeter are tolerable when subjected to launch-induced loads.

Mechanical Response Analysis of Long-life Asphalt Pavement Structure of Yunluo High-speed on the Semi-rigid Base

NASA Astrophysics Data System (ADS)

Liu, Feng; Wu, Chuanhai; Xu, Xinquan; Li, Hao; Wang, Zhixiang

2018-01-01

In order to grasp the rule of the strain change of the semi-rigid asphalt pavement structure under the FWD load and provide a reliable theoretical and practical basis for the design of the pavement structure, based on the test section of Guangdong Yunluo expressway, taking FWD as the loading tool, by using the finite element analysis software ANSYS, the internal variation rules of each pavement structural layer were obtained. Based on the results of the theoretical analysis, the measured strain sensor was set up in the corresponding layer of the pavement structure, and the strain test plan was determined. Based on the analysis of the strain data obtained from several structural layers and field monitoring, the rationality of the type pavement structure and the strain test scheme were verified, so as to provide useful help for the design and the maintenance of the pavement structure.

Structural Dynamic Analyses And Test Predictions For Spacecraft Structures With Non-Linearities

NASA Astrophysics Data System (ADS)

Vergniaud, Jean-Baptiste; Soula, Laurent; Newerla, Alfred

2012-07-01

The overall objective of the mechanical development and verification process is to ensure that the spacecraft structure is able to sustain the mechanical environments encountered during launch. In general the spacecraft structures are a-priori assumed to behave linear, i.e. the responses to a static load or dynamic excitation, respectively, will increase or decrease proportionally to the amplitude of the load or excitation induced. However, past experiences have shown that various non-linearities might exist in spacecraft structures and the consequences of their dynamic effects can significantly affect the development and verification process. Current processes are mainly adapted to linear spacecraft structure behaviour. No clear rules exist for dealing with major structure non-linearities. They are handled outside the process by individual analysis and margin policy, and analyses after tests to justify the CLA coverage. Non-linearities can primarily affect the current spacecraft development and verification process on two aspects. Prediction of flights loads by launcher/satellite coupled loads analyses (CLA): only linear satellite models are delivered for performing CLA and no well-established rules exist how to properly linearize a model when non- linearities are present. The potential impact of the linearization on the results of the CLA has not yet been properly analyzed. There are thus difficulties to assess that CLA results will cover actual flight levels. Management of satellite verification tests: the CLA results generated with a linear satellite FEM are assumed flight representative. If the internal non- linearities are present in the tested satellite then there might be difficulties to determine which input level must be passed to cover satellite internal loads. The non-linear behaviour can also disturb the shaker control, putting the satellite at risk by potentially imposing too high levels. This paper presents the results of a test campaign performed in the frame of an ESA TRP study [1]. A bread-board including typical non-linearities has been designed, manufactured and tested through a typical spacecraft dynamic test campaign. The study has demonstrate the capabilities to perform non-linear dynamic test predictions on a flight representative spacecraft, the good correlation of test results with respect to Finite Elements Model (FEM) prediction and the possibility to identify modal behaviour and to characterize non-linearities characteristics from test results. As a synthesis for this study, overall guidelines have been derived on the mechanical verification process to improve level of expertise on tests involving spacecraft including non-linearity.

Modal Survey of ETM-3, A 5-Segment Derivative of the Space Shuttle Solid Rocket Booster

NASA Technical Reports Server (NTRS)

Nielsen, D.; Townsend, J.; Kappus, K.; Driskill, T.; Torres, I.; Parks, R.

2005-01-01

The complex interactions between internal motor generated pressure oscillations and motor structural vibration modes associated with the static test configuration of a Reusable Solid Rocket Motor have potential to generate significant dynamic thrust loads in the 5-segment configuration (Engineering Test Motor 3). Finite element model load predictions for worst-case conditions were generated based on extrapolation of a previously correlated 4-segment motor model. A modal survey was performed on the largest rocket motor to date, Engineering Test Motor #3 (ETM-3), to provide data for finite element model correlation and validation of model generated design loads. The modal survey preparation included pretest analyses to determine an efficient analysis set selection using the Effective Independence Method and test simulations to assure critical test stand component loads did not exceed design limits. Historical Reusable Solid Rocket Motor modal testing, ETM-3 test analysis model development and pre-test loads analyses, as well as test execution, and a comparison of results to pre-test predictions are discussed.

In Situ Estimation of Applied Biaxial Loads with Lamb Waves (Preprint)

DTIC Science & Technology

2012-07-01

be correct. IV. EXPERIMENTS AND RESULTS Fatigue tests were conducted for an array of six surface-bonded PZT transducers permanently attached to...because of their cumulative effects on the fatigue life of the structures. Waves propagating between array elements are directly affected by applied loads...their cumulative effects on the fatigue life of the structures. Waves propagating between array elements are directly affected by applied loads

Compression Strength of Composite Primary Structural Components

NASA Technical Reports Server (NTRS)

Johnson, Eric R.; Starnes, James H., Jr. (Technical Monitor)

2000-01-01

The focus of research activities under NASA Grant NAG-1-2035 was the response and failure of thin-walled structural components. The research is applicable to the primary load carrying structure of flight vehicles, with particular emphasis on fuselage and wing'structure. Analyses and tests were performed that are applicable to the following structural components an aft pressure bulkhead, or a composite pressure dome, pressure cabin damage containment, and fuselage frames subject to crash-type loads.

On the coherency of dynamic load estimates for vehicles on flexible structures

NASA Astrophysics Data System (ADS)

Mitra, Mainak; Gordon, Timothy

2014-05-01

This paper develops a novel form of a well-known signal processing technique, so as to be applicable to the interaction between a heavy truck and a supporting bridge structure. Motivated by the problem of structural health monitoring of bridges, a new modal coherency function is defined. This relates the input action of moving wheel loads to the dynamic response of the bridge, including the effects of unevenness of the road surface and the vertical dynamics of the truck suspension. The analysis here is specifically aimed at future experimental testing - the validation of axle load estimators obtained from sensors on the truck. It is applicable even when no independent 'ground truth' for the dynamic loads is available. The approach can be more widely used in the analysis of dynamic interactions involving suspended moving loads on deformable structures, e.g. for structural vibrations due to high-speed trains.

Ground/Flight Correlation of Aerodynamic Loads with Structural Response

NASA Technical Reports Server (NTRS)

Mangalam, Arun S.; Davis, Mark C.

2009-01-01

Ground and flight tests provide a basis and methodology for in-flight characterization of the aerodynamic and structural performance through the monitoring of the fluid-structure interaction. The NF-15B flight tests of the Intelligent Flight Control System program provided a unique opportunity to test the correlation of aerodynamic loads with points of flow attaching and detaching from the surface, which are also known as flow bifurcation points, as observed in a previous wind tunnel test performed at the U.S. Air Force Academy (Colorado Springs, Colorado). Moreover, flight tests, along with the subsequent unsteady aerodynamic tests in the NASA Transonic Dynamics Tunnel (TDT), provide a basis using surface flow sensors as means of assessing the aeroelastic performance of flight vehicles. For the flight tests, the NF-15B tail was instrumented with hot-film sensors and strain gages for measuring root-bending strains. This data were gathered via selected sideslip maneuvers performed at level flight and subsonic speeds. The aerodynamic loads generated by the sideslip maneuver resulted in a structural response, which were then compared with the hot-film sensor signals. The hot-film sensor signals near the stagnation region were found to be highly correlated with the root-bending strains. For the TDT tests, a flexible wing section developed under the U.S. Air Force Research Lab SensorCraft program was instrumented with strain gages, accelerometers, and hot-film sensors at two span stations. The TDT tests confirmed the correlation between flow bifurcation points and the wing structural response to tunnel-generated gusts. Furthermore, as the wings structural modes were excited by the gusts, a gradual phase change between the flow bifurcation point and the structural mode occurred during a resonant condition.

Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures

NASA Astrophysics Data System (ADS)

Lares, Alan

Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the previous insert designs. A casting process for manufacturing the v.3 inserts was developed. The developed casting process, when producing more than 13 inserts, becomes more economical than machining. An exploratory study was conducted looking at the effects of dynamic loading on the v.3 insert performance. The results of this study highlighted areas for improving dynamic testing of foam-core sandwich structure inserts. Correlations were developed relating design variables such as face-sheet thickness and insert diameter to a failure load for different load cases. This was done through simulations using Computer Aided Engineering (CAE) software, and experimental testing. The resulting correlations were integrated into a computer program which outputs the required insert dimensions given a set of design parameters, and load values.

Strain Gage Load Calibration of the Wing Interface Fittings for the Adaptive Compliant Trailing Edge Flap Flight Test

NASA Technical Reports Server (NTRS)

Miller, Eric J.; Holguin, Andrew C.; Cruz, Josue; Lokos, William A.

2014-01-01

The safety-of-flight parameters for the Adaptive Compliant Trailing Edge (ACTE) flap experiment require that flap-to-wing interface loads be sensed and monitored in real time to ensure that the structural load limits of the wing are not exceeded. This paper discusses the strain gage load calibration testing and load equation derivation methodology for the ACTE interface fittings. Both the left and right wing flap interfaces were monitored; each contained four uniquely designed and instrumented flap interface fittings. The interface hardware design and instrumentation layout are discussed. Twenty-one applied test load cases were developed using the predicted in-flight loads. Pre-test predictions of strain gage responses were produced using finite element method models of the interface fittings. Predicted and measured test strains are presented. A load testing rig and three hydraulic jacks were used to apply combinations of shear, bending, and axial loads to the interface fittings. Hardware deflections under load were measured using photogrammetry and transducers. Due to deflections in the interface fitting hardware and test rig, finite element model techniques were used to calculate the reaction loads throughout the applied load range, taking into account the elastically-deformed geometry. The primary load equations were selected based on multiple calibration metrics. An independent set of validation cases was used to validate each derived equation. The 2-sigma residual errors for the shear loads were less than eight percent of the full-scale calibration load; the 2-sigma residual errors for the bending moment loads were less than three percent of the full-scale calibration load. The derived load equations for shear, bending, and axial loads are presented, with the calculated errors for both the calibration cases and the independent validation load cases.

Experimental and numerical investigation of a RC wall loaded by snow-like avalanche pressure signal

NASA Astrophysics Data System (ADS)

Ousset, Isabelle; Bertrand, David; Brun, Michaël; Limam, Ali; Naaïm, Mohamed

2013-04-01

Nowadays, civil engineering structures exposed to snow avalanches are mostly designed considering static loadings involving large safety factors. These latters highlight the lack of knowledge about the effects of the loading generated by a snow flow, and generally lead to oversize the civil structure. Indeed, the transient nature of the loading signal and also the composition of the snow flow can generate dynamic phenomena which cannot be taken into account considering only static loadings. The case of the avalanche of the Taconnaz (France), which occurred in 1999 and where important parts of the defense structure were destroyed, showed that static design approaches can lead to underestimate the potential effect of the snow flow. Thus, in order to give some new insights about this issue, the effect of the temporal variations of the snow loading on the mechanical behavior of an idealized defense structure is investigated. Therefore, a reinforced concrete (RC) wall with a L-like shape has been considered which is supposed to represent a part of the defense structure situated in Taconnaz. Static pushover tests, carried out in laboratory conditions on 1/6 scale physical model of the RC structure, allowed obtaining the capacity of the tested structure (Berthet-Rambaud et al. (2007)). Finite Element (FE) models have been developed and calibrated from the previous experimental data. The FE approach allows simulating the dynamic mechanical response of the structure. The effect of the transient nature of the loading of the avalanche has been explored applying out-of-plan dynamic loadings on the RC wall. In order to be as close as possible of a "field" snow avalanche, the imposed time evolution of the loading has been generated from in situ measurements recorded at the French experimental site "le col du Lautaret" (Thibert et al. (2008)). The RC mechanical behaviour has been described by four nonlinear constitutive laws. The four behaviour laws are compared and analyzed for specific loading situations. Next, the influences of typical parameters characterizing the avalanche loading signal are proposed. In particular, a special focused is presented on the effect of the loading rate. Finally, the vulnerability of the RC wall is studied in a reliability framework. Damage index are proposed and the probability of failure of the RC wall is derived. These relations might be useful for risk analysis.

Above-knee prosthesis design based on fatigue life using finite element method and design of experiment.

PubMed

Phanphet, Suwattanarwong; Dechjarern, Surangsee; Jomjanyong, Sermkiat

2017-05-01

The main objective of this work is to improve the standard of the existing design of knee prosthesis developed by Thailand's Prostheses Foundation of Her Royal Highness The Princess Mother. The experimental structural tests, based on the ISO 10328, of the existing design showed that a few components failed due to fatigue under normal cyclic loading below the required number of cycles. The finite element (FE) simulations of structural tests on the knee prosthesis were carried out. Fatigue life predictions of knee component materials were modeled based on the Morrow's approach. The fatigue life prediction based on the FE model result was validated with the corresponding structural test and the results agreed well. The new designs of the failed components were studied using the design of experimental approach and finite element analysis of the ISO 10328 structural test of knee prostheses under two separated loading cases. Under ultimate loading, knee prosthesis peak von Mises stress must be less than the yield strength of knee component's material and the total knee deflection must be lower than 2.5mm. The fatigue life prediction of all knee components must be higher than 3,000,000 cycles under normal cyclic loading. The design parameters are the thickness of joint bars, the diameter of lower connector and the thickness of absorber-stopper. The optimized knee prosthesis design meeting all the requirements was recommended. Experimental ISO 10328 structural test of the fabricated knee prosthesis based on the optimized design confirmed the finite element prediction. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Full-scale hingeless rotor performance and loads

NASA Technical Reports Server (NTRS)

Peterson, Randall L.

1995-01-01

A full-scale BO-105 hingeless rotor system was tested in the NASA Ames 40- by 80-Foot Wind Tunnel on the rotor test apparatus. Rotor performance, rotor loads, and aeroelastic stability as functions of both collective and cyclic pitch, tunnel velocity, and shaft angle were investigated. This test was performed in support of the Rotor Data Correlation Task under the U.S. Army/German Memorandum of Understanding on Cooperative Research in the Field of Helicopter Aeromechanics. The primary objective of this test program was to create a data base for full-scale hingeless rotor performance and structural blade loads. A secondary objective was to investigate the ability to match flight test conditions in the wind tunnel. This data base can be used for the experimental and analytical studies of hingeless rotor systems over large variations in rotor thrust and tunnel velocity. Rotor performance and structural loads for tunnel velocities from hover to 170 knots and thrust coefficients (C(sub T)/sigma) from 0.0 to 0.12 are presented in this report. Thrust sweeps at tunnel velocities of 10, 20, and 30 knots are also included in this data set.

Load deflection characteristics of inflated structures

NASA Technical Reports Server (NTRS)

Baumgarten, J. R.

1983-01-01

A single, closed form relationship to relate load to the deformed dimensions of the horizontal torus was developed. Wall elasticity was included in the analysis, and special care was taken to predict the final footprint area of the loaded structure. The test fixture utilized is shown. The tori used for the bulk of the testing were rubber inner tubes for a 32 and 160 pneumatic tire. The inner tube being tested was plumbed, to a mercury-filled manometer, which had a 50 inch measurement capacity, by use of a special adapter. The adapter fit over the valve stem and allowed air to be added from a shop-air source and to be bled through the standard valve mechanism. In this fashion, tests requiring the maintenance of a constant indication of air pressure could be run with little difficulty.

Crash Test of an MD-500 Helicopter with a Deployable Energy Absorber Concept

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Jackson, Karen E.; Kellas, Sotiris

2010-01-01

On December 2, 2009, a full scale crash test was successfully conducted of a MD-500 helicopter at the NASA Langley Research Center Landing and Impact Research Facility . The purpose of this test was to evaluate a novel composite honeycomb deployable energy absorbing (DEA) concept for attenuation of structural and crew loads during helicopter crashes under realistic crash conditions. The DEA concept is an alternative to external airbags, and absorbs impact energy through crushing. In the test, the helicopter impacted the concrete surface with 11.83 m/s (38.8 ft/s) horizontal, 7.80 m/s (25.6 ft/s) vertical and 0.15 m/s (0.5 ft/s) lateral velocities; corresponding to a resultant velocity of 14.2 m/s (46.5 ft/s). The airframe and skid gear were instrumented with accelerometers and strain gages to determine structural integrity and load attenuation, while the skin of the airframe was covered with targets for use by photogrammetry to record gross vehicle motion before, during, and after the impact. Along with the collection of airframe data, one Hybrid III 50th percentile anthropomorphic test device (ATD), two Hybrid II 50th percentile ATDs and a specialized human surrogate torso model (HSTM) occupant were seated in the airframe and instrumented for the collection of occupant loads. Resultant occupant data showed that by using the DEA, the loads on the Hybrid II and Hybrid III ATDs were in the Low Risk regime for the injury criteria, while structural data showed the airframe retained its structural integrity post crash. Preliminary results show that the DEA is a viable concept for the attenuation of impact loads.

Nonlinear static and dynamic finite element analysis of an eccentrically loaded graphite-epoxy beam

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.; Jones, Lisa E.

1991-01-01

The Dynamic Crash Analysis of Structures (DYCAT) and NIKE3D nonlinear finite element codes were used to model the static and implulsive response of an eccentrically loaded graphite-epoxy beam. A 48-ply unidirectional composite beam was tested under an eccentric axial compressive load until failure. This loading configuration was chosen to highlight the capabilities of two finite element codes for modeling a highly nonlinear, large deflection structural problem which has an exact solution. These codes are currently used to perform dynamic analyses of aircraft structures under impact loads to study crashworthiness and energy absorbing capabilities. Both beam and plate element models were developed to compare with the experimental data using the DYCAST and NIKE3D codes.

Structural equation model of total phosphorus loads in the Red River of the North Basin, USA and Canada

USGS Publications Warehouse

Ryberg, Karen R.

2017-01-01

Attribution of the causes of trends in nutrient loading is often limited to correlation, qualitative reasoning, or references to the work of others. This paper represents efforts to improve causal attribution of water-quality changes. The Red River of the North basin provides a regional test case because of international interest in the reduction of total phosphorus loads and the availability of long-term total phosphorus data and ancillary geospatial data with the potential to explain changes in water quality over time. The objectives of the study are to investigate structural equation modeling methods for application to water-quality problems and to test causal hypotheses related to the drivers of total phosphorus loads over the period 1970 to 2012. Multiple working hypotheses that explain total phosphorus loads and methods for estimating missing ancillary data were developed, and water-quality related challenges to structural equation modeling (including skewed data and scaling issues) were addressed. The model indicates that increased precipitation in season 1 (November–February) or season 2 (March–June) would increase total phosphorus loads in the basin. The effect of agricultural practices on total phosphorus loads was significant, although the effect is about one-third of the effect of season 1 precipitation. The structural equation model representing loads at six sites in the basin shows that climate and agricultural practices explain almost 60% of the annual total phosphorus load in the Red River of the North basin. The modeling process and the unexplained variance highlight the need for better ancillary long-term data for causal assessments.

Buckling characteristics of hypersonic aircraft wing tubular panels

NASA Technical Reports Server (NTRS)

Ko, William L.; Shideler, John L.; Fields, Roger A.

1986-01-01

The buckling characteristics of Rene 41 tubular panels installed as wing panels on a hypersonic wing test structure (HWTS) were determined nondestructively through use of a force/stiffness technique. The nondestructive buckling tests were carried out under different combined load conditions and different temperature environments. Two panels were subsequently tested to buckling failure in a universal tension compression testing machine. In spite of some data scattering because of large extrapolations of data points resulting from termination of the test at a somewhat low applied load, the overall test data correlated fairly well with theoretically predicted buckling interaction curves. The structural efficiency of the tubular panels was slightly higher than that of the beaded panels which they replaced.

Strain Gage Loads Calibration Testing with Airbag Support for the Gulfstream III SubsoniC Research Aircraft Testbed (SCRAT)

NASA Technical Reports Server (NTRS)

Lokos, William; Miller, Eric; Hudson, Larry; Holguin, Andrew; Neufeld, David; Haraguchi, Ronnie

2015-01-01

This paper describes the design and conduct of the strain gage load calibration ground test of the SubsoniC Research Aircraft Testbed, Gulfstream III aircraft, and the subsequent data analysis and its results. The goal of this effort was to create and validate multi-gage load equations for shear force, bending moment, and torque for two wing measurement stations. For some of the testing the aircraft was supported by three air bags in order to isolate the wing structure from extraneous load inputs through the main landing gear. Thirty-two strain gage bridges were installed on the left wing. Hydraulic loads were applied to the wing lower surface through a total of 16 load zones. Some dead weight load cases were applied to the upper wing surface using shot bags. Maximum applied loads reached 54,000 pounds.

MODEL TESTS AND 3D ELASTIC FINITE ELEMENT ANALYSIS FOR STEEL PIPE PILES WITH WINGS IN STALLED IN SOIL CEMENT COLUMN

NASA Astrophysics Data System (ADS)

Tamai, Toshiyuki; Teramoto, Shuntarou; Kimura, Makoto

Steel pipe piles with wings installed in soil cement column is a composite foundation of pile consisting of soil improvement with cement and steel pipe with wings. This type of pile shows higher vertical bearing capacity when compared to steel pipe piles that are installed without soil cement. It is thought the wings contribute to higher bearing capacity of this type of piles. The wings are also thought to play the role of structural unification of pile foundations and load transfer. In this study, model test and 3D elastic finite element analysis was carried out in order to elucidate the effect of wings on the structural unification of pile foundation and the load transfer mechanism. Firstly, the model test was carried out in order to grasp the influence of pile with and without wings, the shape of wings of the pile and the unconfined compression strength of the soil cement on the structural unification of the pile foundation. The numerical analysis of the model test was then carried out on the intermediate part of the pile foundation with wings and mathematical model developed. Finally load tran sfer mechanism was checked for the entire length of the pile through this mathematical model and the load sharing ratio of the wings and stress distribution occurring in the soil cement clarified. In addition, the effect of the wing interval on the structural unification of the pile foundation and load transfer was also checked and clarified.

ATM/cable arch and beam structural test program

NASA Technical Reports Server (NTRS)

Housley, J. A.

1972-01-01

The structural testing is described of an Apollo Telescope Mount (ATM) cable arch and beam assembly, using static loads to simulate the critical conditions expected during transportation and launch of the ATM. All test objectives were met. Stress and deflection data show that the assembly is structurally adequate for use in the ATM.

Experimental validation of solid rocket motor damping models

NASA Astrophysics Data System (ADS)

Riso, Cristina; Fransen, Sebastiaan; Mastroddi, Franco; Coppotelli, Giuliano; Trequattrini, Francesco; De Vivo, Alessio

2017-12-01

In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young's modulus and structural damping coefficient—complex Young's modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young's modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe damping properties of slender launch vehicles in payload/launcher coupled load analysis.

Experimental validation of solid rocket motor damping models

NASA Astrophysics Data System (ADS)

Riso, Cristina; Fransen, Sebastiaan; Mastroddi, Franco; Coppotelli, Giuliano; Trequattrini, Francesco; De Vivo, Alessio

2018-06-01

In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young's modulus and structural damping coefficient—complex Young's modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young's modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe damping properties of slender launch vehicles in payload/launcher coupled load analysis.

Experimental Study of a Hot Structure for a Reentry Vehicle

NASA Technical Reports Server (NTRS)

Pride, Richard A.; Royster, Dick M.; Helms, Bobbie F.

1960-01-01

A large structural model of a reentry vehicle has been built incorporating design concepts applicable to a radiation-cooled vehicle. Thermal-stress alleviating features of the model are discussed. Environmental tests on the model include approximately 100 cycles of loading at room temperature and 33 cycles of combined loading and-heating up to temperatures of 1,6000 F. Measured temperatures are shown for typical parts of the model. Comparisons are made between experimental and calculated deflections and strains. The structure successfully survived the heating and loading environments.

Load Measurement in Structural Members Using Guided Acoustic Waves

NASA Astrophysics Data System (ADS)

Chen, Feng; Wilcox, Paul D.

2006-03-01

A non-destructive technique to measure load in structures such as rails and bridge cables by using guided acoustic waves is investigated both theoretically and experimentally. Robust finite element models for predicting the effect of load on guided wave propagation are developed and example results are presented for rods. Reasonably good agreement of experimental results with modelling prediction is obtained. The measurement technique has been developed to perform tests on larger specimens.

Opening Loads Analyses for Various Disk-Gap-Band Parachutes

NASA Technical Reports Server (NTRS)

Cruz, J. R.; Kandis, M.; Witkowski, A.

2003-01-01

Detailed opening loads data is presented for 18 tests of Disk-Gap-Band (DGB) parachutes of varying geometry with nominal diameters ranging from 43.2 to 50.1 ft. All of the test parachutes were deployed from a mortar. Six of these tests were conducted via drop testing with drop test vehicles weighing approximately 3,000 or 8,000 lb. Twelve tests were conducted in the National Full-Scale Aerodynamics Complex 80- by 120-foot wind tunnel at the NASA Ames Research Center. The purpose of these tests was to structurally qualify the parachute for the Mars Exploration Rover mission. A key requirement of all tests was that peak parachute load had to be reached at full inflation to more closely simulate the load profile encountered during operation at Mars. Peak loads measured during the tests were in the range from 12,889 to 30,027 lb. Of the two test methods, the wind tunnel tests yielded more accurate and repeatable data. Application of an apparent mass model to the opening loads data yielded insights into the nature of these loads. Although the apparent mass model could reconstruct specific tests with reasonable accuracy, the use of this model for predictive analyses was not accurate enough to set test conditions for either the drop or wind tunnel tests. A simpler empirical model was found to be suitable for predicting opening loads for the wind tunnel tests to a satisfactory level of accuracy. However, this simple empirical model is not applicable to the drop tests.

Development of vehicle model test-bending of a simple structural surfaces model for automotive vehicle sedan

NASA Astrophysics Data System (ADS)

Nor, M. K. Mohd; Noordin, A.; Ruzali, M. F. S.; Hussen, M. H.; Mustapa@Othman, N.

2017-04-01

Simple Structural Surfaces (SSS) method is offered as a means of organizing the process for rationalizing the basic vehicle body structure load paths. The application of this simplified approach is highly beneficial in the development of modern passenger car structure design. In Malaysia, the SSS topic has been widely adopted and seems compulsory in various automotive programs related to automotive vehicle structures in many higher education institutions. However, there is no real physical model of SSS available to gain considerable insight and understanding into the function of each major subassembly in the whole vehicle structures. Based on this motivation, a real physical SSS of sedan model and the corresponding model vehicle tests of bending is proposed in this work. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results prove that the proposed vehicle model test is useful to physically demonstrate the importance of providing continuous load path using the necessary structural components within the vehicle structures. It is clearly observed that the global bending stiffness reduce significantly when more panels are removed from the complete SSS model. The analysis shows the front parcel shelf is an important subassembly to sustain bending load.

Trajectory-Based Loads for the Ares I-X Test Flight Vehicle

NASA Technical Reports Server (NTRS)

Vause, Roland F.; Starr, Brett R.

2011-01-01

In trajectory-based loads, the structural engineer treats each point on the trajectory as a load case. Distributed aero, inertial, and propulsion forces are developed for the structural model which are equivalent to the integrated values of the trajectory model. Free-body diagrams are then used to solve for the internal forces, or loads, that keep the applied aero, inertial, and propulsion forces in dynamic equilibrium. There are several advantages to using trajectory-based loads. First, consistency is maintained between the integrated equilibrium equations of the trajectory analysis and the distributed equilibrium equations of the structural analysis. Second, the structural loads equations are tied to the uncertainty model for the trajectory systems analysis model. Atmosphere, aero, propulsion, mass property, and controls uncertainty models all feed into the dispersions that are generated for the trajectory systems analysis model. Changes in any of these input models will affect structural loads response. The trajectory systems model manages these inputs as well as the output from the structural model over thousands of dispersed cases. Large structural models with hundreds of thousands of degrees of freedom would execute too slowly to be an efficient part of several thousand system analyses. Trajectory-based loads provide a means for the structures discipline to be included in the integrated systems analysis. Successful applications of trajectory-based loads methods for the Ares I-X vehicle are covered in this paper. Preliminary design loads were based on 2000 trajectories using Monte Carlo dispersions. Range safety loads were tied to 8423 malfunction turn trajectories. In addition, active control system loads were based on 2000 preflight trajectories using Monte Carlo dispersions.

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; Toso-Pentecôte, Nathalie; Schueler, Dominik

2014-02-01

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93-136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64-86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.

SLS Test Hardware Taken to Redstone Arsenal Airfield for Guppy Loading

NASA Image and Video Library

2017-07-10

A structural test article of the Orion Stage Adapter for NASA’s Space Launch System, built at NASA's Marshall Space Flight Center, is transported and prepared to be loaded onto NASA's Super Guppy aircraft. With integrated structural testing complete at Marshall, the stage adapter will soon be transported to Lockheed Martin in Denver for further testing with NASA's Orion spacecraft. The Guppy -- a plane large enough to carry cargo weighing more than 26 tons -- arrived at the U.S. Army's Redstone Arsenal Airfield July 10 to transport the stage adapter. On SLS's first integrated flight with Orion, the OSA will connect Orion to the Interim Cryogenic Propulsion Stage.

Development of a Dielectric-Loaded Accelerator Test Facility Based on an X-Band Magnicon Amplifier

NASA Astrophysics Data System (ADS)

Gold, S. H.; Kinkead, A. K.; Gai, W.; Power, J. G.; Konecny, R.; Jing, C.; Tantawi, S. G.; Nantista, C. D.; Hu, Y.; Du, X.; Tang, C.; Lin, Y.; Bruce, R. W.; Bruce, R. L.; Fliflet, A. W.; Lewis, D.

2006-01-01

The Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC), are developing a dielectric-loaded accelerator (DLA) test facility powered by the 11.424-GHz magnicon amplifier that was developed jointly by NRL and Omega-P, Inc. Thus far, DLA structures developed by ANL have been tested at the NRL Magnicon Facility without injected electrons, including tests of alumina and magnesium calcium titanate structures at gradients up to ˜8 MV/m. The next step is to inject electrons in order to build a compact DLA test accelerator. The Accelerator Laboratory of Tsinghua University in Beijing, China has developed a 5-MeV electron injector for the accelerator, and SLAC is developing a means to combine the two magnicon output arms, and to drive the injector and an accelerator section with separate control of the power ratio and relative phase. Also, RWBruce Associates, working with NRL, is developing a means to join ceramic tubes to produce long accelerating sections using a microwave brazing process. The installation and commissioning of the first dielectric-loaded test accelerator, including injector, DLA structure, and spectrometer, should take place within the next year.

Smart Textiles for Strengthening of Structures

NASA Astrophysics Data System (ADS)

Górski, Marcin; Krzywoń, Rafał; Dawczyński, Szymon; Szojda, Leszek; Salvado, Rita; Lopes, Catarina; Araujo, Pedro; Velez, Fernando Jose; Castro-Gomes, Joao

2016-11-01

This paper presents results of mechanical tests on a prototype of an innovative structural strengthening in form of self-monitoring fabric. Smart textile employs carbon fibers conductivity for measuring strains while monitoring changes of electric resistance under increasing load. A general solution was tested in a series of calibrating tests on strengthening of small size concrete slabs. Promising results of simple specimen, has encouraged the research team to perform the next tests using mastered carbon fibre reinforced fabric. Main tests were performed on natural scale RC beam. Smart textile proved its efficiency in both: strengthening and monitoring of strains during load increase. New strengthening proposal was given 10% increase of loading capacity and the readings of strain changes were similar to those obtained in classical methods. In order to calibrate the prototype and to define range limits of solution usability, textile sensor was tested in areas of large deformations (timber beam) and aswell as very small strains (bridge bearing block). In both cases, the prototype demonstrated excellent performance in the range of importance for structural engineering. This paper also presents an example of use of the smart strengthening in situ, in a real life conditions.

14 CFR 25.307 - Proof of structure.

Code of Federal Regulations, 2012 CFR

2012-01-01

... load tests may be inadequate. (b)-(c) [Reserved] (d) When static or dynamic tests are used to show... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... condition. Structural analysis may be used only if the structure conforms to that for which experience has...

14 CFR 25.307 - Proof of structure.

Code of Federal Regulations, 2010 CFR

2010-01-01

... load tests may be inadequate. (b)-(c) [Reserved] (d) When static or dynamic tests are used to show... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... condition. Structural analysis may be used only if the structure conforms to that for which experience has...

14 CFR 25.307 - Proof of structure.

Code of Federal Regulations, 2013 CFR

2013-01-01

... load tests may be inadequate. (b)-(c) [Reserved] (d) When static or dynamic tests are used to show... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... condition. Structural analysis may be used only if the structure conforms to that for which experience has...

14 CFR 25.307 - Proof of structure.

Code of Federal Regulations, 2014 CFR

2014-01-01

... load tests may be inadequate. (b)-(c) [Reserved] (d) When static or dynamic tests are used to show... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... condition. Structural analysis may be used only if the structure conforms to that for which experience has...

14 CFR 23.571 - Metallic pressurized cabin structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Structure... the following: (a) A fatigue strength investigation in which the structure is shown by tests, or by analysis supported by test evidence, to be able to withstand the repeated loads of variable magnitude...

14 CFR 25.307 - Proof of structure.

Code of Federal Regulations, 2011 CFR

2011-01-01

... load tests may be inadequate. (b)-(c) [Reserved] (d) When static or dynamic tests are used to show... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... condition. Structural analysis may be used only if the structure conforms to that for which experience has...

Configuration and Sizing of a Test Fixture for Panels Under Combined Loads

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.

2006-01-01

Future air and space structures are expected to utilize composite panels that are subjected to combined mechanical loads, such as bi-axial compression/tension, shear and pressure. Therefore, the ability to accurately predict the buckling and strength failures of such panels is important. While computational analysis can provide tremendous insight into panel response, experimental results are necessary to verify predicted performances of these panels to judge the accuracy of computational methods. However, application of combined loads is an extremely difficult task due to the complex test fixtures and set-up required. Presented herein is a comparison of several test set-ups capable of testing panels under combined loads. Configurations compared include a D-box, a segmented cylinder and a single panel set-up. The study primarily focuses on the preliminary sizing of a single panel test configuration capable of testing flat panels under combined in-plane mechanical loads. This single panel set-up appears to be best suited to the testing of both strength critical and buckling critical panels. Required actuator loads and strokes are provided for various square, flat panels.

The SLS Stages Intertank Structural Test Assembly (STA) arrives at MSFC

NASA Image and Video Library

2018-03-08

The SLS Stages Intertank Structural Test Assembly (STA) is rolling off the NASA Pegasus Barge at the MSFC Dock enroute to the MSFC 4619 Load Test Annex test facility for qualification testing via MSFC West Test Area. Historic Saturn 1-C test stand on far left, blockhouse 4670 on far right, SLS LH2 test stand, 4693, in center.

The SLS Stages Intertank Structural Test Assembly (STA) arrives at MSFC

NASA Image and Video Library

2018-03-08

The SLS Stages Intertank Structural Test Assembly (STA) is rolling off the NASA Pegasus Barge at the MSFC Dock enroute to the MSFC 4619 Load Test Annex test facility for qualification testing via MSFC West Test Area. STA enters West Test Area from intersection of Dodd and Saturn roads. Onlookers take photos with Historic Dynamic Test Stand in background.

Investigation of charge weight and shock factor effect on non-linear transient structural response of rectangular plates subjected to underwater explosion (UNDEX) shock loading

NASA Astrophysics Data System (ADS)

Demir, Ozgur; Sahin, Abdurrahman; Yilmaz, Tamer

2012-09-01

Underwater explosion induced shock loads are capable of causing considerable structural damage. Investigations of the underwater explosion (UNDEX) effects on structures have seen continuous developments because of security risks. Most of the earlier experimental investigations were performed by military since the World War I. Subsequently; Cole [1] established mathematical relations for modeling underwater explosion shock loading, which were the outcome of many experimental investigations This study predicts and establishes the transient responses of a panel structure to underwater explosion shock loads using non-linear finite element code Ls-Dyna. Accordingly, in this study a new MATLAB code has been developed for predicting shock loading profile for different weight of explosive and different shock factors. Numerical analysis was performed for various test conditions and results are compared with Ramajeyathilagam's experimental study [8].

Fatigue tests on big structure assemblies of concorde aircraft

NASA Technical Reports Server (NTRS)

Nguyen, V. P.; Perrais, J. P.

1972-01-01

Fatigue tests on structural assemblies of the Concorde supersonic transport aircraft are reported. Two main sections of the aircraft were subjected to pressure, mechanical load, and thermal static tests. The types of fatigue tests conducted and the results obtained are discussed. It was concluded that on a supersonic aircraft whose structural weight is a significant part of the weight analysis, many fatigue and static strength development tests should be made and fatigue and thermal tests of the structures are absolutely necessary.

Impacting load control of floating supported friction plate and its experimental verification

NASA Astrophysics Data System (ADS)

Ning, Keyan; Wang, Yu; Huang, Dingchuan; Yin, Lei

2017-05-01

Friction plates are key components in automobile transmission system. Unfortunately, due to the tough working condition i.e. high impact, high temperature, fracture and plastic deformation are easily observed in friction plates. In order to reduce the impact load and increase the impact resistance and life span of the friction plate. This paper presents a variable damping design method and structure, by punching holes in the key position of the friction plate and filling it with damping materials, the impact load of the floating support friction plate can be controlled. Simulation is applied to study the effect of the position and number of damping holes on tooth root stress. Furthermore, physic test was designed and conducted to validate the correctness and effectiveness of the proposed method. Test result shows that the impact load of the new structure is reduced by 40% and its fatigue life is 4.7 times larger. The new structure provides a new way for floating supported friction plates design.

Safe structures for future aircraft

NASA Technical Reports Server (NTRS)

Mccomb, H. G., Jr.

1983-01-01

The failure mechanisms, design lessons, and test equipment employed by NASA in establishing the airworthiness and crashworthiness of aircraft components for commercial applications are described. The composites test programs have progressed to medium primary structures such as stabilizers and a vertical fin. The failures encountered to date have been due to the nonyielding nature of composites, which do not diffuse loads like metals, and the presence of eccentricities, irregular shapes, stiffness changes, and discontinuities that cause tension and shear. Testing to failure, which always occurred in first tests before the design loads were reached, helped identify design changes and reinforcements that produced successful products. New materials and NDE techniques are identified, together with aircraft structural design changes that offer greater protection to the passengers, fuel antimisting agents, and landing gear systems.

Active member vibration control for a 4 meter primary reflector support structure

NASA Technical Reports Server (NTRS)

Umland, J. W.; Chen, G.-S.

1992-01-01

The design and testing of a new low voltage piezoelectric active member with integrated load cell and displacement sensor is described. This active member is intended for micron level vibration and structural shape control of the Precision Segmented Reflector test-bed. The test-bed is an erectable 4 meter diameter backup support truss for a 2.4 meter focal length parabolic reflector. Active damping of the test-bed is then demonstrated using the newly developed active members. The control technique used is referred to as bridge feedback. With this technique the internal sensors are used in a local feedback loop to match the active member's input impedance to the structure's load impedance, which then maximizes vibrational energy dissipation. The active damping effectiveness is then evaluated from closed loop frequency responses.

SRM attrition rate study of the aft motor case segments due to water impact cavity collapse loading

NASA Technical Reports Server (NTRS)

Crockett, C. D.

1976-01-01

The attrition assessment of the aft segments of Solid Rocket Motor due to water impact requires the establishment of a correlation between loading occurrences and structural capability. Each discrete load case, as identified by the water impact velocities and angle, varies longitudinally and radially in magnitude and distribution of the external pressure. The distributions are further required to be shifted forward or aft one-fourth the vehicle diameter to assure minimization of the effect of test instrumentation location for the load determinations. The asymmetrical load distributions result in large geometric nonlinearities in structural response. The critical structural response is progressive buckling of the case. Discrete stiffeners have been added to these aft segments to aid in gaining maximum structural capability for minimum weight addition for resisting these loads. This report presents the development of the attrition assessment of the aft segments and includes the rationale for eliminating all assessable conservatisms from this assessment.

Experimental study on Statistical Damage Detection of RC Structures based on Wavelet Packet Analysis

NASA Astrophysics Data System (ADS)

Zhu, X. Q.; Law, S. S.; Jayawardhan, M.

2011-07-01

A novel damage indicator based on wavelet packet transform is developed in this study for structural health monitoring. The response signal of a structure under an impact load is normalized and then decomposed into wavelet packet components. Energies of these wavelet packet components are then calculated to obtain the energy distribution. A statistical indicator is developed to describe the damage extent of the structure. This approach is applied to the test results from simply supported reinforced concrete beams in the laboratory. Cases with single damage are created from static loading, and accelerations of the structure from under impact loads are analyzed. Results show that the method can be used for the damage monitoring and assessment of the structure.

Microstructurally based variations on the dwell fatgue life of titanium alloy IMI 834

NASA Technical Reports Server (NTRS)

Thomsen, Mark L.; Hoeppner, David W.

1994-01-01

An experimental study was undertaken to determine the role of microstructure on the fatigue life reduction observed in titanium alloy IMI 834 under dwell loading conditions. The wave forms compared were a trapezoid with 15 and 30 second hold times at the maximum test load and a baseline, 10 Hertz, haversine. The stress ratio for both loading wave forms was 0.10. The fatigue loading of each specimen was conducted in a vacuum within a scanning electron microscope chamber which minimized the possibility that the laboratory environment would adversely affect the material behavior. Two microstructural conditions were investigated in the experimental program. The first involved standard 'disk' material with equiaxed alpha in a transformed beta matrix. The second material was cut from the same disk forging as the first but was heat treated to obtain a martensitic alpha prime microstructure. Tensile tests were performed prior to the onset of the fatigue loading portion of the study, and it was determined that the yield strengths of the specimens from both material conditions were within ten percent. The maximum fatigue loads were chosen to be 72 percent of the average yield strength for both materials as determined from the tensile tests. It was found that the cycles to failure from the 10 Hertz loading wave form were reduced by a factor of approximately five when the loading was changed to the trapezoidal wave form for the standard 'disk' material. The fatigue life reduction for the martensitic structure under identical test conditions was approximately 1.75. The improvement observed with the martensitic structure also was accompanied by an increase in overall fatigue life for the wave forms tested. This paper will review the results and conclusions of this effort.

Improving Bending Moment Measurements on Wind Turbine Blades

DOE Office of Scientific and Technical Information (OSTI.GOV)

Post, Nathan L.

Full-scale fatigue testing of wind turbine blades is conducted using resonance test techniques where the blade plus additional masses is excited at its first resonance frequency to achieve the target loading amplitude. Because there is not a direct relationship between the force applied by an actuator and the bending moment, the blade is instrumented with strain gauges that are calibrated under static loading conditions to determine the sensitivity or relationship between strain and applied moment. Then, during dynamic loading the applied moment is calculated using the strain response of the structure. A similar procedure is also used in the fieldmore » to measure in-service loads on turbine blades. Because wind turbine blades are complex twisted structures and the deflections are large, there is often significant cross-talk coupling in the sensitivity of strain gauges placed on the structure. Recent work has shown that a sensitivity matrix with nonzero cross terms must be employed to find constant results when a blade is subjected to both flap and lead-lag loading. However, even under controlled laboratory conditions, potential for errors of 3 percent or more in the measured moment exist when using the typical cross-talk matrix approach due to neglecting the influence of large deformations and torsion. This is particularly critical when considering a biaxial load as would be applied on the turbine or during a biaxial fatigue test. This presentation describes these results demonstrating errors made when performing current loads measurement practices on wind turbine blades in the lab and evaluating potential improvements using enhanced cross-talk matrix approaches and calibration procedures.« less

Force Limited Vibration Testing: Computation C2 for Real Load and Probabilistic Source

NASA Astrophysics Data System (ADS)

Wijker, J. J.; de Boer, A.; Ellenbroek, M. H. M.

2014-06-01

To prevent over-testing of the test-item during random vibration testing Scharton proposed and discussed the force limited random vibration testing (FLVT) in a number of publications, in which the factor C2 is besides the random vibration specification, the total mass and the turnover frequency of the load(test item), a very important parameter. A number of computational methods to estimate C2 are described in the literature, i.e. the simple and the complex two degrees of freedom system, STDFS and CTDFS, respectively. Both the STDFS and the CTDFS describe in a very reduced (simplified) manner the load and the source (adjacent structure to test item transferring the excitation forces, i.e. spacecraft supporting an instrument).The motivation of this work is to establish a method for the computation of a realistic value of C2 to perform a representative random vibration test based on force limitation, when the adjacent structure (source) description is more or less unknown. Marchand formulated a conservative estimation of C2 based on maximum modal effective mass and damping of the test item (load) , when no description of the supporting structure (source) is available [13].Marchand discussed the formal description of getting C 2 , using the maximum PSD of the acceleration and maximum PSD of the force, both at the interface between load and source, in combination with the apparent mass and total mass of the the load. This method is very convenient to compute the factor C 2 . However, finite element models are needed to compute the spectra of the PSD of both the acceleration and force at the interface between load and source.Stevens presented the coupled systems modal approach (CSMA), where simplified asparagus patch models (parallel-oscillator representation) of load and source are connected, consisting of modal effective masses and the spring stiffnesses associated with the natural frequencies. When the random acceleration vibration specification is given the CMSA method is suitable to compute the valueof the parameter C 2 .When no mathematical model of the source can be made available, estimations of the value C2 can be find in literature.In this paper a probabilistic mathematical representation of the unknown source is proposed, such that the asparagus patch model of the source can be approximated. The computation of the value C2 can be done in conjunction with the CMSA method, knowing the apparent mass of the load and the random acceleration specification at the interface between load and source, respectively.Strength & stiffness design rules for spacecraft, instrumentation, units, etc. will be practiced, as mentioned in ECSS Standards and Handbooks, Launch Vehicle User's manuals, papers, books , etc. A probabilistic description of the design parameters is foreseen.As an example a simple experiment has been worked out.

Instrumentation for the Characterization of Inflatable Structures

NASA Technical Reports Server (NTRS)

Swanson, Gregory T.; Cassell, Alan M.; Johnson, R. Keith

2012-01-01

Current entry, descent, and landing technologies are not practical for heavy payloads due to mass and volume constraints dictated by limitations imposed by launch vehicle fairings. Therefore, new technologies are now being explored to provide a mass- and volume-efficient solution for heavy payload capabilities, including Inflatable Aerodynamic Decelerators (IAD) [1]. Consideration of IADs for space applications has prompted the development of instrumentation systems for integration with flexible structures to characterize system response to flight-like environment testing. This development opportunity faces many challenges specific to inflatable structures in extreme environments, including but not limited to physical flexibility, packaging, temperature, structural integration and data acquisition [2]. In the spring of 2012, two large scale Hypersonic Inflatable Aerodynamic Decelerators (HIAD) will be tested in the National Full-Scale Aerodynamics Complex s 40 by 80 wind tunnel at NASA Ames Research Center. The test series will characterize the performance of a 3.0 m and 6.0 m HIAD at various angles of attack and levels of inflation during flight-like loading. To analyze the performance of these inflatable test articles as they undergo aerodynamic loading, many instrumentation systems have been researched and developed. These systems will utilize new experimental sensing systems developed by the HIAD ground test campaign instrumentation team, in addition to traditional wind tunnel sensing techniques in an effort to improve test article characterization and model validation. During the 2012 test series the instrumentation systems will target inflatable aeroshell static and dynamic deformation, structural strap loading, surface pressure distribution, localized skin deflection, and torus inflation pressure. This paper will offer an overview of inflatable structure instrumentation, and provide detail into the design and implementation of the sensors systems that will be utilized during the 2012 HIAD ground test campaign.

Sensitivity and Specificity of Eustachian Tube Function Tests in Adults

PubMed Central

Doyle, William J.; Swarts, J. Douglas; Banks, Julianne; Casselbrant, Margaretha L; Mandel, Ellen M; Alper, Cuneyt M.

2013-01-01

Objective Determine if Eustachian Tube (ET) function (ETF) tests can identify ears with physician-diagnosed ET dysfunction (ETD) in a mixed population at high sensitivity and specificity and define the inter-relatedness of ETF test parameters. Methods ETF was evaluated using the Forced-Response, Inflation-Deflation, Valsalva and Sniffing tests in 15 control ears of adult subjects after unilateral myringotomy (Group I) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (Group II). Data were analyzed using logistic regression including each parameter independently and then a step-down Discriminant Analysis including all ETF test parameters to predict group assignment. Factor Analysis operating over all parameters was used to explore relatedness. Results The Discriminant Analysis identified 4 ETF test parameters (Valsalva, ET opening pressure, dilatory efficiency and % positive pressure equilibrated) that together correctly assigned ears to Group II at a sensitivity of 95% and a specificity of 83%. Individual parameters representing the efficiency of ET opening during swallowing showed moderately accurate assignments of ears to their respective groups. Three factors captured approximately 98% of the variance among parameters, the first had negative loadings of the ETF structural parameters, the second had positive loadings of the muscle-assisted ET opening parameters and the third had negative loadings of the muscle-assisted ET opening parameters and positive loadings of the structural parameters. Discussion These results show that ETF tests can correctly assign individual ears to physician-diagnosed ETD with high sensitivity and specificity and that ETF test parameters can be grouped into structural-functional categories. PMID:23868429

Highly Loaded Composite Strut Test Results

NASA Technical Reports Server (NTRS)

Wu, K. C.; Jegley, Dawn C.; Barnard, Ansley; Phelps, James E.; McKeney, Martin J.

2011-01-01

Highly loaded composite struts from a proposed truss-based Altair lunar lander descent stage concept were selected for development under NASA's Advanced Composites Technology program. Predicted compressive member forces during launch and ascent of over -100,000 lbs were much greater than the tensile loads. Therefore, compressive failure modes, including structural stability, were primary design considerations. NASA's industry partner designed and built highly loaded struts that were delivered to NASA for testing. Their design, fabricated on a washout mandrel, had a uniform-diameter composite tube with composite tapered ends. Each tapered end contained a titanium end fitting with facing conical ramps that are overlaid and overwrapped with composite materials. The highly loaded struts were loaded in both tension and compression, with ultimate failure produced in compression. Results for the two struts tested are presented and discussed, along with measured deflections, strains and observed failure mechanisms.

1001518

NASA Image and Video Library

2010-09-01

DEVELOPMENT TESTING BEING CONDUCTED AT THE REQUEST OF THE MSFC DYNAMICS, LOADS, AND STRENGTH BRANCH (EV31) TO STUDY THE FAILURE BEHAVIOR OF FASTENERS SUBJECTED TO COMBINED SHEAR AND TENSION LOADING. THE DATA FROM THIS TESTING WILL BE USED TO DEVELOP APPROPRIATE STRUCTURAL ANALYSIS METHODS AS PART OF A FASTENER STANDARDS EFFORT SPONSORED BY THE NASA ENGINEERING SAFETY CENTER (NESC). THE TEST FIXTURE WAS DESIGNED AND FABRICATED THROUGH THE MSFC MECHANICAL FABRICATION BRANCH (ES23). THE TESTING ORGANIZATION IS THE MSFC MATERIALS TEST BRANCH (EM10).

1001519

NASA Image and Video Library

2010-09-01

DEVELOPMENT TESTING BEING CONDUCTED AT THE REQUEST OF THE MSFC DYNAMICS, LOADS, AND STRENGTH BRANCH (EV31) TO STUDY THE FAILURE BEHAVIOR OF FASTENERS SUBJECTED TO COMBINED SHEAR AND TENSION LOADING. THE DATA FROM THIS TESTING WILL BE USED TO DEVELOP APPROPRIATE STRUCTURAL ANALYSIS METHODS AS PART OF A FASTENER STANDARDS EFFORT SPONSORED BY THE NASA ENGINEERING SAFETY CENTER (NESC). THE TEST FIXTURE WAS DESIGNED AND FABRICATED THROUGH THE MSFC MECHANICAL FABRICATION BRANCH (ES23). THE TESTING ORGANIZATION IS THE MSFC MATERIALS TEST BRANCH (EM10).

1001520

NASA Image and Video Library

2010-09-01

DEVELOPMENT TESTING BEING CONDUCTED AT THE REQUEST OF THE MSFC DYNAMICS, LOADS, AND STRENGTH BRANCH (EV31) TO STUDY THE FAILURE BEHAVIOR OF FASTENERS SUBJECTED TO COMBINED SHEAR AND TENSION LOADING. THE DATA FROM THIS TESTING WILL BE USED TO DEVELOP APPROPRIATE STRUCTURAL ANALYSIS METHODS AS PART OF A FASTENER STANDARDS EFFORT SPONSORED BY THE NASA ENGINEERING SAFETY CENTER (NESC). THE TEST FIXTURE WAS DESIGNED AND FABRICATED THROUGH THE MSFC MECHANICAL FABRICATION BRANCH (ES23). THE TESTING ORGANIZATION IS THE MSFC MATERIALS TEST BRANCH (EM10).

1001521

NASA Image and Video Library

2010-09-01

DEVELOPMENT TESTING BEING CONDUCTED AT THE REQUEST OF THE MSFC DYNAMICS, LOADS, AND STRENGTH BRANCH (EV31) TO STUDY THE FAILURE BEHAVIOR OF FASTENERS SUBJECTED TO COMBINED SHEAR AND TENSION LOADING. THE DATA FROM THIS TESTING WILL BE USED TO DEVELOP APPROPRIATE STRUCTURAL ANALYSIS METHODS AS PART OF A FASTENER STANDARDS EFFORT SPONSORED BY THE NASA ENGINEERING SAFETY CENTER (NESC). THE TEST FIXTURE WAS DESIGNED AND FABRICATED THROUGH THE MSFC MECHANICAL FABRICATION BRANCH (ES23). THE TESTING ORGANIZATION IS THE MSFC MATERIALS TEST BRANCH (EM10).

Test and Analysis Correlation of a Large-Scale, Orthogrid-Stiffened Metallic Cylinder without Weld Lands

NASA Technical Reports Server (NTRS)

Rudd, Michelle T.; Hilburger, Mark W.; Lovejoy, Andrew E.; Lindell, Michael C.; Gardner, Nathaniel W.; Schultz, Marc R.

2018-01-01

The NASA Engineering Safety Center (NESC) Shell Buckling Knockdown Factor Project (SBKF) was established in 2007 by the NESC with the primary objective to develop analysis-based buckling design factors and guidelines for metallic and composite launch-vehicle structures.1 A secondary objective of the project is to advance technologies that have the potential to increase the structural efficiency of launch-vehicles. The SBKF Project has determined that weld-land stiffness discontinuities can significantly reduce the buckling load of a cylinder. In addition, the welding process can introduce localized geometric imperfections that can further exacerbate the inherent buckling imperfection sensitivity of the cylinder. Therefore, single-piece barrel fabrication technologies can improve structural efficiency by eliminating these weld-land issues. As part of this effort, SBKF partnered with the Advanced Materials and Processing Branch (AMPB) at NASA Langley Research Center (LaRC), the Mechanical and Fabrication Branch at NASA Marshall Space Flight Center (MSFC), and ATI Forged Products to design and fabricate an 8-ft-diameter orthogrid-stiffened seamless metallic cylinder. The cylinder was subjected to seven subcritical load sequences (load levels that are not intended to induce test article buckling or material failure) and one load sequence to failure. The purpose of this test effort was to demonstrate the potential benefits of building cylindrical structures with no weld lands using the flow-formed manufacturing process. This seamless barrel is the ninth 8-ft-diameter metallic barrel and the first single-piece metallic structure to be tested under this program.

Design, Fabrication and Testing of a Crushable Energy Absorber for a Passive Earth Entry Vehicle

NASA Technical Reports Server (NTRS)

Kellas, Sotiris; Corliss, James M. (Technical Monitor)

2002-01-01

A conceptual study was performed to investigate the impact response of a crushable energy absorber for a passive Earth entry vehicle. The spherical energy-absorbing concept consisted of a foam-filled composite cellular structure capable of omni-directional impact-load attenuation as well as penetration resistance. Five composite cellular samples of hemispherical geometry were fabricated and tested dynamically with impact speeds varying from 30 to 42 meters per second. Theoretical crush load predictions were obtained with the aid of a generalized theory which accounts for the energy dissipated during the folding deformation of the cell-walls. Excellent correlation was obtained between theoretical predictions and experimental tests on characteristic cell-web intersections. Good correlation of theory with experiment was also found to exist for the more complex spherical cellular structures. All preliminary design requirements were met by the cellular structure concept, which exhibited a near-ideal sustained crush-load and approximately 90% crush stroke.

Dynamic behaviors of historical wrought iron truss bridges: a field testing case study

NASA Astrophysics Data System (ADS)

Dai, Kaoshan; Wang, Ying; Hedric, Andrew; Huang, Zhenhua

2016-04-01

The U.S. transportation infrastructure has many wrought iron truss bridges that are more than a century old and still remain in use. Understanding the structural properties and identifying the health conditions of these historical bridges are essential to deciding the maintenance or rebuild plan of the bridges. This research involved an on-site full-scale system identification test case study on the historical Old Alton Bridge (a wrought iron truss bridge built in 1884 in Denton, Texas) using a wireless sensor network. The study results demonstrate a practical and convenient experimental system identification method for historical bridge structures. The method includes the basic steps of the in-situ experiment and in-house data analysis. Various excitation methods are studied for field testing, including ambient vibration by wind load, forced vibration by human jumping load, and forced vibration by human pulling load. Structural responses of the bridge under these different excitation approaches were analyzed and compared with numerical analysis results.

Postirradiation thermocyclic loading of ferritic-martensitic structural materials

NASA Astrophysics Data System (ADS)

Belyaeva, L.; Orychtchenko, A.; Petersen, C.; Rybin, V.

Thermonuclear fusion reactors of the Tokamak-type will be unique power engineering plants to operate in thermocyclic mode only. Ferritic-martensitic stainless steels are prime candidate structural materials for test blankets of the ITER fusion reactor. Beyond the radiation damage, thermomechanical cyclic loading is considered as the most detrimental lifetime limiting phenomenon for the above structure. With a Russian and a German facility for thermal fatigue testing of neutron irradiated materials a cooperation has been undertaken. Ampule devices to irradiate specimens for postirradiation thermal fatigue tests have been developed by the Russian partner. The irradiation of these ampule devices loaded with specimens of ferritic-martensitic steels, like the European MANET-II, the Russian 05K12N2M and the Japanese Low Activation Material F82H-mod, in a WWR-M-type reactor just started. A description of the irradiation facility, the qualification of the ampule device and the modification of the German thermal fatigue facility will be presented.

29 CFR 1919.29 - Limitations on safe working loads and proof loads.

Code of Federal Regulations, 2013 CFR

2013-07-01

... ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) GEAR CERTIFICATION Certification of Vessels: Tests and Proof... pertinent limitations based on stability and/or on structural competence at particular radii. Safe working...

29 CFR 1919.29 - Limitations on safe working loads and proof loads.

Code of Federal Regulations, 2012 CFR

2012-07-01

... ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) GEAR CERTIFICATION Certification of Vessels: Tests and Proof... pertinent limitations based on stability and/or on structural competence at particular radii. Safe working...

29 CFR 1919.29 - Limitations on safe working loads and proof loads.

Code of Federal Regulations, 2011 CFR

2011-07-01

... ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) GEAR CERTIFICATION Certification of Vessels: Tests and Proof... pertinent limitations based on stability and/or on structural competence at particular radii. Safe working...

29 CFR 1919.29 - Limitations on safe working loads and proof loads.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) GEAR CERTIFICATION Certification of Vessels: Tests and Proof... pertinent limitations based on stability and/or on structural competence at particular radii. Safe working...

29 CFR 1919.29 - Limitations on safe working loads and proof loads.

Code of Federal Regulations, 2014 CFR

2014-07-01

... ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) GEAR CERTIFICATION Certification of Vessels: Tests and Proof... pertinent limitations based on stability and/or on structural competence at particular radii. Safe working...

Environmental Effects on Long Term Displacement Data of Woven Fabric Webbings Under Constant Load for Inflatable Structures

NASA Technical Reports Server (NTRS)

Kenner, WInfred S.; Jones, Thomas C.; Doggett, William R.; Duncan, Quinton; Plant, James

2015-01-01

An experimental study of the effects of environmental temperature and humidity conditions on long-term creep displacement data of high strength Kevlar and VectranTM woven fabric webbings under constant load for inflatable structures is presented. The restraint layer of an inflatable structure for long-duration space exploration missions is designed to bear load and consists of an assembly of high strength webbings. Long-term creep displacement data of webbings can be utilized by designers to validate service life parameters of restraint layers of inflatable structures. Five groups of high-strength webbings were researched over a two year period. Each group had a unique webbing length, load rating, applied load, and test period. The five groups consisted of 1.) 6K Vectran webbings loaded to 49% ultimate tensile strength (UTS), 2.) 6K Vectran webbings loaded to 55% UTS, 3.) 12.5K Vectran webbings loaded to 22% UTS, 4.) 6K Kevlar webbings loaded to 40% and 43% UTS, and 5.) 6K Kevlar webbings loaded to 48% UTS. Results show that all webbing groups exhibit the initial two stages of three of a typical creep curve of an elastic material. Results also show that webbings exhibit unique local wave patterns over the duration of the test period. Data indicate that the local pattern is primarily generated by daily variations in relative humidity values within the test facility. Data indicate that after a three to six month period, where webbings reach a steady-state creep condition, an annual sinusoidal displacement pattern is exhibited, primarily due to variations in annual mean temperature values. Data indicates that variations in daily temperature values and annual mean humidity values have limited secondary effects on creep displacement behavior. Results show that webbings in groups 2 and 5 do not exhibit well defined annual displacement patterns because the magnitude of the applied loads cause large deformations, and data indicate that material yielding within a webbing tends to neutralize the annual sinusoidal displacement pattern. Study indicates that applied load, environmental effects, mechanical strength, coefficient of thermal expansion, and hygroscopic properties of webbings are fundamental requirements for quantifying accurate creep displacements and behaviors over multiple year time periods. Results from a study of the environmental effects on long-term creep displacement data of Kevlar and Vectran woven webbings are presented to increase the knowledge base of webbing materials and to enhance designs of inflatable space structures for long-duration space missions.

Correlation of Structural Analysis and Test Results for the McDonnell Douglas Stitched/RFI All-Composite Wing Stub Box

NASA Technical Reports Server (NTRS)

Wang, John T.; Jegley, Dawn C.; Bush, Harold G.; Hinrichs, Stephen C.

1996-01-01

The analytical and experimental results of an all-composite wing stub box are presented in this report. The wing stub box, which is representative of an inboard portion of a commercial transport high-aspect-ratio wing, was fabricated from stitched graphite-epoxy material with a Resin Film Infusion manufacturing process. The wing stub box was designed and constructed by the McDonnell Douglas Aerospace Company as part of the NASA Advanced Composites Technology program. The test article contained metallic load-introduction structures on the inboard and outboard ends of the graphite-epoxy wing stub box. The root end of the inboard load introduction structure was attached to a vertical reaction structure, and an upward load was applied to the outermost tip of the outboard load introduction structure to induce bending of the wing stub box. A finite element model was created in which the center portion of the wing-stub-box upper cover panel was modeled with a refined mesh. The refined mesh was required to represent properly the geometrically nonlinear structural behavior of the upper cover panel and to predict accurately the strains in the stringer webs of the stiffened upper cover panel. The analytical and experimental results for deflections and strains are in good agreement.

Oriented Scintillation Spectrometer Experiment (OSSE). Revision A. Volume 1

DTIC Science & Technology

1988-05-19

SYSTEM-LEVEL ENVIRONMENTAL TESTS ................... 108 3.5.1 OPERATION REPORT, PROOF MODEL STRUCTURE TESTS.. .108 3.5.1.1 PROOF MODEL MODAL SURVEY...81 3-21 ALIGNMENT ERROR BUDGET, FOV, A4 ................ 82 3-22 ALIGNMENT ERROR BUDGET, ROTATION AXIS, A4 ...... 83 3-23 OSSE PROOF MODEL MODAL SURVEY...PROOF MODEL MODAL SURVEY .................. 112 3-27-1 OSSE PROOF MODEL STATIC LOAD TEST ............. 116 3-27-2 OSSE PROOF MODEL STATIC LOAD TEST

Embedded electronics for intelligent structures

NASA Astrophysics Data System (ADS)

Warkentin, David J.; Crawley, Edward F.

The signal, power, and communications provisions for the distributed control processing, sensing, and actuation of an intelligent structure could benefit from a method of physically embedding some electronic components. The preliminary feasibility of embedding electronic components in load-bearing intelligent composite structures is addressed. A technique for embedding integrated circuits on silicon chips within graphite/epoxy composite structures is presented which addresses the problems of electrical, mechanical, and chemical isolation. The mechanical and chemical isolation of test articles manufactured by this technique are tested by subjecting them to static and cyclic mechanical loads and a temperature/humidity/bias environment. The likely failure modes under these conditions are identified, and suggestions for further improvements in the technique are discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kot, C.A.; Srinivasan, M.G.; Hsieh, B.J.

As part of the Phase II testing at the HDR Test Facility in Kahl/Main, FRG, two series of high-level seismic/vibrational experiments were performed. In the first of these (SHAG) a coast-down shaker, mounted on the reactor operating floor and capable of generating 1000 tonnes of force, was used to investigate full-scale structural response, soil-structure interaction (SSI), and piping/equipment response at load levels equivalent to those of a design basis earthquake. The HDR soil/structure system was tested to incipient failure exhibiting highly nonlinear response. In the load transmission from structure to piping/equipment significant response amplifications and shifts to higher frequencies occurred.more » The performance of various pipe support configurations was evaluated. This latter effort was continued in the second series of tests (SHAM), in which an in-plant piping system was investigated at simulated seismic loads (generated by two servo-hydraulic actuators each capable of generating 40 tonnes of force), that exceeded design levels manifold and resulted in considerable pipe plastification and failure of some supports (snubbers). The evaluation of six different support configurations demonstrated that proper system design (for a given spectrum) rather than number of supports or system stiffness is essential to limiting pipe stresses. Pipe strains at loads exceeding the design level eightfold were still tolerable, indicating that pipe failure even under extreme seismic loads is unlikely inspite of multiple support failures. Conservatively, an excess capacity (margin) of at least four was estimated for the piping system, and the pipe damping was found to be 4%. Comparisons of linear and nonlinear computational results with measurements showed that analytical predictions have wide scatter and do not necessarily yield conservative responses, underpredicting, in particular, peak support forces.« less

Accumulo/Hadoop, MongoDB, and Elasticsearch Performance for Semi Structured Intrusion Detection (IDS) Data

DTIC Science & Technology

2016-11-01

iii Contents List of Figures v 1. Introduction 1 2. Background 1 3. Yahoo ! Cloud Serving Benchmark (YCSB) 2 3.1 Data Loading and Performance...transactional system. 3. Yahoo ! Cloud Serving Benchmark (YCSB) 3.1 Data Loading and Performance Testing Framework When originally setting out to perform the...that referred to a data loading and performance testing framework, Yahoo ! Cloud Serving Benchmark (YCSB).12 This framework is freely available and

Multiaxial and Thermomechanical Fatigue of Materials: A Historical Perspective and Some Future Challenges

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh

2013-01-01

Structural materials used in engineering applications routinely subjected to repetitive mechanical loads in multiple directions under non-isothermal conditions. Over past few decades, several multiaxial fatigue life estimation models (stress- and strain-based) developed for isothermal conditions. Historically, numerous fatigue life prediction models also developed for thermomechanical fatigue (TMF) life prediction, predominantly for uniaxial mechanical loading conditions. Realistic structural components encounter multiaxial loads and non-isothermal loading conditions, which increase potential for interaction of damage modes. A need exists for mechanical testing and development verification of life prediction models under such conditions.

Drones for aerodynamic and structural testing /DAST/ - A status report

NASA Technical Reports Server (NTRS)

Murrow, H. N.; Eckstrom, C. V.

1978-01-01

A program for providing research data on aerodynamic loads and active control systems on wings with supercritical airfoils in the transonic speed range is described. Analytical development, wind tunnel tests, and flight tests are included. A Firebee II target drone vehicle has been modified for use as a flight test facility. The program currently includes flight experiments on two aeroelastic research wings. The primary purpose of the first flight experiment is to demonstrate an active control system for flutter suppression on a transport-type wing. Design and fabrication of the wing are complete and after installing research instrumentation and the flutter suppression system, flight testing is expected to begin in early 1979. The experiment on the second research wing - a fuel-conservative transport type - is to demonstrate multiple active control systems including flutter suppression, maneuver load alleviation, gust load alleviation, and reduce static stability. Of special importance for this second experiment is the development and validation of integrated design methods which include the benefits of active controls in the structural design.

Assessment of Bilateral Thoracic Loading on the Near-Side Occupant Due to Occupant-to-Occupant Interaction in Vehicle Crash Tests.

PubMed

Sunnevång, Cecilia; Pipkorn, Bengt; Boström, Ola

2015-01-01

This study aims, by means of the WorldSID 50th percentile male, to evaluate thoracic loading and injury risk to the near-side occupant due to occupant-to-occupant interaction in combination with loading from an intruding structure. Nine vehicle crash tests were performed with a 50th percentile WorldSID male dummy in the near-side (adjacent to the intruding structure) seat and a THOR or ES2 dummy in the far-side (opposite the intruding structure) seat. The near-side seated WorldSID was equipped with 6 + 6 IR-Traccs (LH and RH) in the thorax/abdomen enabling measurement of bilateral deflection. To differentiate deflection caused by the intrusion, and the deflection caused by the neighboring occupant, time history curves were analyzed. The crash tests were performed with different modern vehicles, equipped with thorax side airbags and inflatable curtains, ranging from a compact car to a large sedan, and in different loading conditions such as car-to-car, barrier, and pole tests. Lateral delta V based on vehicle tunnel acceleration and maximum residual intrusion at occupant position were used as a measurement of crash severity to compare injury measurements. In the 9 vehicle crash tests, thoracic loading, induced by the intruding structure as well as from the far-side occupant, varied due to the size and structural performance of the car as well as the severity of the crash. Peak deflection on the thoracic outboard side occurred during the first 50 ms of the event. Between 70 to 150 ms loading induced by the neighboring occupant occurred and resulted in an inboard-side peak deflection and viscous criterion. In the tests where the target vehicle lateral delta V was below 30 km/h and intrusion less than 200 mm, deflections were low on both the outboard (20-40 mm) and inboard side (10-15 mm). At higher crash severities, delta V 35 km/h and above as well as intrusions larger than 350 mm, the inboard deflections (caused by interaction to the far-side occupant) were of the same magnitude or even higher (30-70 mm) than the outboard deflections (30-50 mm). A WorldSID 50th percentile male equipped with bilateral IR-Traccs can detect loading to the thorax from a neighboring occupant making injury risk assessment feasible for this type of loading. At crash severities resulting in a delta V above 35 km/h and intrusions larger than 350 mm, both the inboard deflection and VC resulted in high risks of Abbreviated Injury Scale (AIS) 3+ injury, especially for a senior occupant.

Carbon-carbon primary structure for SSTO vehicles

NASA Astrophysics Data System (ADS)

Croop, Harold C.; Lowndes, Holland B.

1997-01-01

A hot structures development program is nearing completion to validate use of carbon-carbon composite structure for primary load carrying members in a single-stage-to-orbit, or SSTO, vehicle. A four phase program was pursued which involved design development and fabrication of a full-scale wing torque box demonstration component. The design development included vehicle and component selection, design criteria and approach, design data development, demonstration component design and analysis, test fixture design and analysis, demonstration component test planning, and high temperature test instrumentation development. The fabrication effort encompassed fabrication of structural elements for mechanical property verification as well as fabrication of the demonstration component itself and associated test fixturing. The demonstration component features 3D woven graphite preforms, integral spars, oxidation inhibited matrix, chemical vapor deposited (CVD) SiC oxidation protection coating, and ceramic matrix composite fasteners. The demonstration component has been delivered to the United States Air Force (USAF) for testing in the Wright Laboratory Structural Test Facility, WPAFB, OH. Multiple thermal-mechanical load cycles will be applied simulating two atmospheric cruise missions and one orbital mission. This paper discusses the overall approach to validation testing of the wing box component and presents some preliminary analytical test predictions.

Fluids and Combustion Facility: Combustion Integrated Rack Modal Model Correlation

NASA Technical Reports Server (NTRS)

McNelis, Mark E.; Suarez, Vicente J.; Sullivan, Timothy L.; Otten, Kim D.; Akers, James C.

2005-01-01

The Fluids and Combustion Facility (FCF) is a modular, multi-user, two-rack facility dedicated to combustion and fluids science in the US Laboratory Destiny on the International Space Station. FCF is a permanent facility that is capable of accommodating up to ten combustion and fluid science investigations per year. FCF research in combustion and fluid science supports NASA's Exploration of Space Initiative for on-orbit fire suppression, fire safety, and space system fluids management. The Combustion Integrated Rack (CIR) is one of two racks in the FCF. The CIR major structural elements include the International Standard Payload Rack (ISPR), Experiment Assembly (optics bench and combustion chamber), Air Thermal Control Unit (ATCU), Rack Door, and Lower Structure Assembly (Input/Output Processor and Electrical Power Control Unit). The load path through the rack structure is outlined. The CIR modal survey was conducted to validate the load path predicted by the CIR finite element model (FEM). The modal survey is done by experimentally measuring the CIR frequencies and mode shapes. The CIR model was test correlated by updating the model to represent the test mode shapes. The correlated CIR model delivery is required by NASA JSC at Launch-10.5 months. The test correlated CIR flight FEM is analytically integrated into the Shuttle for a coupled loads analysis of the launch configuration. The analysis frequency range of interest is 0-50 Hz. A coupled loads analysis is the analytical integration of the Shuttle with its cargo element, the Mini Payload Logistics Module (MPLM), in the Shuttle cargo bay. For each Shuttle launch configuration, a verification coupled loads analysis is performed to determine the loads in the cargo bay as part of the structural certification process.

Strain gage selection in loads equations using a genetic algorithm

NASA Technical Reports Server (NTRS)

1994-01-01

Traditionally, structural loads are measured using strain gages. A loads calibration test must be done before loads can be accurately measured. In one measurement method, a series of point loads is applied to the structure, and loads equations are derived via the least squares curve fitting algorithm using the strain gage responses to the applied point loads. However, many research structures are highly instrumented with strain gages, and the number and selection of gages used in a loads equation can be problematic. This paper presents an improved technique using a genetic algorithm to choose the strain gages used in the loads equations. Also presented are a comparison of the genetic algorithm performance with the current T-value technique and a variant known as the Best Step-down technique. Examples are shown using aerospace vehicle wings of high and low aspect ratio. In addition, a significant limitation in the current methods is revealed. The genetic algorithm arrived at a comparable or superior set of gages with significantly less human effort, and could be applied in instances when the current methods could not.

Structural health monitoring of helicopter hard landing using 3D digital image correlation

NASA Astrophysics Data System (ADS)

LeBlanc, Bruce; Niezrecki, Christopher; Avitabile, Peter

2010-03-01

During operation of vehicles and structures, excessive transient loading can lead to reduced fatigue life and even mechanical failure. It has been shown that when a structure undergoes a damaging sequence of events, such as those occurring during a helicopter hard landing, the structural health of a specimen can be severely affected. In order to effectively quantify damage and monitor the structural health of the specimen, experimental data is required across a wide area of the helicopter. Within this paper the use of three-dimensional (3D) digital image correlation (DIC) and dynamic photogrammetry (DP) is examined as a possible method to acquire the necessary data to perform structural health monitoring in a non-obtrusive manner. DIC and DP are a non-contacting measurement techniques that utilizes a stereo pair of digital cameras to track prescribed surface pattern or optical targets placed on the structure. The approaches can provide global information about changes to the structure over the entire field of view. A scale laboratory test is performed on a helicopter to simulate several loading scenarios. The changes in the structural shape and strain field of the model helicopter fuselage as a direct result of the loadings are identified. The tests demonstrate that this technique is a valid way to determine the damage inflicted on the structure due to an excessive applied loading or dynamic maneuver. Practical applications and common limitations of the technique are discussed.

SLS Engine Section Test Article Loaded on Barge Pegasus at NASA's Michoud Assembly Facility

NASA Image and Video Library

2017-04-27

A NASA move team loaded the engine section structural qualification test article for the Space Launch System into the barge Pegasus docked in the harbor at NASA's Michoud Assembly Facility in New Orleans. The rocket's engine section is the bottom of the core stage and houses the four RS-25 engines. The engine section test article was moved from Building 103, Michoud’s 43-acre rocket factory, to the barge where it was loaded for a river trip to NASA’s Marshall Space Flight Center in Huntsville, Alabama. The bottom part of the test article is structurally the same as the engine section that will be flown as part of the SLS core stage. The shiny metal top part simulates the rocket's liquid hydrogen tank, which is the fuel tank that joins to the engine section. The barge Pegasus will travel 1,240 miles by river to Marshall and endure tests that pull, push, and bend it, subjecting it to millions of pounds of force. This ensures the structure can withstand the incredible stresses produced by the 8.8 million pounds of thrust during launch and ascent.

Fatigue Behavior and Deformation Mechanisms in Inconel 718 Superalloy Investigated

NASA Technical Reports Server (NTRS)

2005-01-01

The nickel-base superalloy Inconel 718 (IN 718) is used as a structural material for a variety of components in the space shuttle main engine (SSME) and accounts for more than half of the total weight of this engine. IN 718 is the bill-of-material for the pressure vessels of nickel-hydrogen batteries for the space station. In the case of the space shuttle main engine, structural components are typically subjected to startup and shutdown load transients and occasional overloads in addition to high-frequency vibratory loads from routine operation. The nickel-hydrogen battery cells are prooftested before service and are subjected to fluctuating pressure loads during operation. In both of these applications, the structural material is subjected to a monotonic load initially, which is subsequently followed by fatigue. To assess the life of these structural components, it is necessary to determine the influence of a prior monotonic load on the subsequent fatigue life of the superalloy. An insight into the underlying deformation and damage mechanisms is also required to properly account for the interaction between the prior monotonic load and the subsequent fatigue loading. An experimental investigation was conducted to establish the effect of prior monotonic straining on the subsequent fatigue behavior of wrought, double-aged, IN 718 at room temperature. First, monotonic strain tests and fully-reversed, strain-controlled fatigue tests were conducted on uniform-gage-section IN 718 specimens. Next, fully reversed fatigue tests were conducted under strain control on specimens that were monotonically strained in tension. Results from this investigation indicated that prior monotonic straining reduced the fatigue resistance of the superalloy particularly at the lowest strain range. Some of the tested specimens were sectioned and examined by transmission electron microscopy to reveal typical microstructures as well as the active deformation and damage mechanisms under each of the loading conditions. In monotonically strained specimens, deformation during the subsequent fatigue loading was mainly confined to the deformation bands initiated during the prior monotonic straining. This can cause dislocations to move more readily along the previously activated deformation bands and to pile up near grain boundaries, eventually making the grain boundaries susceptible to fatigue crack initiation. The mechanisms inferred from the microstructural investigation were extremely valuable in interpreting the influence of prior monotonic straining on the subsequent fatigue life of Inconel 718 superalloy.

Design, manufacturing and characterization of aero-elastically scaled wind turbine blades for testing active and passive load alleviation techniques within a ABL wind tunnel

NASA Astrophysics Data System (ADS)

Campagnolo, Filippo; Bottasso, Carlo L.; Bettini, Paolo

2014-06-01

In the research described in this paper, a scaled wind turbine model featuring individual pitch control (IPC) capabilities, and equipped with aero-elastically scaled blades featuring passive load reduction capabilities (bend-twist coupling, BTC), was constructed to investigate, by means of wind tunnel testing, the load alleviation potential of BTC and its synergy with active load reduction techniques. The paper mainly focus on the design of the aero-elastic blades and their dynamic and static structural characterization. The experimental results highlight that manufactured blades show desired bend-twist coupling behavior and are a first milestone toward their testing in the wind tunnel.

Summary of Results of Tests Made by Aluminum Research Laboratories of Spot-welded Joints and Structural Elements

NASA Technical Reports Server (NTRS)

HARTMANN E C; Stickley, G W

1942-01-01

Available information concerning spot welding as a means of joining aluminum-alloy parts has been summarized and comparisons have been made of the relative merits of spot-welded and riveted aluminum-alloy structural elements. The results indicated that spot welding was as satisfactory as riveting insofar as resistance to static loads is concerned. Spot welds showed slightly lower resistance to impact loads but definitely lower resistance to repeated loads than rivets.

A comparison of reliability and conventional estimation of safe fatigue life and safe inspection intervals

NASA Technical Reports Server (NTRS)

Hooke, F. H.

1972-01-01

Both the conventional and reliability analyses for determining safe fatigue life are predicted on a population having a specified (usually log normal) distribution of life to collapse under a fatigue test load. Under a random service load spectrum, random occurrences of load larger than the fatigue test load may confront and cause collapse of structures which are weakened, though not yet to the fatigue test load. These collapses are included in reliability but excluded in conventional analysis. The theory of risk determination by each method is given, and several reasonably typical examples have been worked out, in which it transpires that if one excludes collapse through exceedance of the uncracked strength, the reliability and conventional analyses gave virtually identical probabilities of failure or survival.

Buckling Test Results from the 8-Foot-Diameter Orthogrid-Stiffened Cylinder Test Article TA01. [Test Dates: 19-21 November 2008

NASA Technical Reports Server (NTRS)

Hilburger, Mark W.; Waters, W. Allen, Jr.; Haynie, Waddy T.

2015-01-01

Results from the testing of cylinder test article SBKF-P2-CYLTA01 (referred to herein as TA01) are presented. The testing was conducted at the Marshall Space Flight Center (MSFC), November 19?21, 2008, in support of the Shell Buckling Knockdown Factor (SBKF) Project.i The test was used to verify the performance of a newly constructed buckling test facility at MSFC and to verify the test article design and analysis approach used by the SBKF project researchers. TA01 is an 8-foot-diameter (96-inches), 78.0-inch long, aluminum-lithium (Al-Li), orthogrid-stiffened cylindrical shell similar to those used in current state-of-the-art launch vehicle structures and was designed to exhibit global buckling when subjected to compression loads. Five different load sequences were applied to TA01 during testing and included four sub-critical load sequences, i.e., loading conditions that did not cause buckling or material failure, and one final load sequence to buckling and collapse. The sub-critical load sequences consisted of either uniform axial compression loading or combined axial compression and bending and the final load sequence subjected TA01 to uniform axial compression. Traditional displacement transducers and strain gages were used to monitor the test article response at nearly 300 locations and an advanced digital image correlation system was used to obtain low-speed and high-speed full-field displacement measurements of the outer surface of the test article. Overall, the test facility and test article performed as designed. In particular, the test facility successfully applied all desired load combinations to the test article and was able to test safely into the postbuckling range of loading, and the test article failed by global buckling. In addition, the test results correlated well with initial pretest predictions.

An inventory of aeronautical ground research facilities. Volume 3: Structural

NASA Technical Reports Server (NTRS)

Pirrello, C. J.; Hardin, R. D.; Heckart, M. V.; Brown, K. R.

1971-01-01

An inventory of test facilities for conducting acceleration, environmental, impact, structural shock, load, heat, vibration, and noise tests is presented. The facility is identified with a description of the equipment, the testing capabilities, and cost of operation. Performance data for the facility are presented in charts and tables.

Modelling and Testing of Blast Effect On the Structures

NASA Astrophysics Data System (ADS)

Figuli, Lucia; Jangl, Štefan; Papán, Daniel

2016-10-01

As a blasting agent in the blasting and mining engineering, has been using one of so called new generation of explosives which offer greater flexibility in their range and application, and such explosive is ANFO. It is type of explosive consists of an oxidiser and a fuel (ammonium nitrate and fuel oil). One of such ANFO explosives which are industrially made in Slovakia is POLONIT. The explosive is a mixture of ammonium nitrate, methyl esters of higher fatty acids, vegetable oil and red dye. The paper deals with the analysis of structure subjected to the blast load created by the explosion of POLONIT charge. First part of paper is describing behaviour and characteristic of blast wave generated from the blast (detonation characteristics, physical characteristics, time-history diagram etc.) and the second part presents the behaviour of such loaded structures, because of the analysis of such dynamical loaded structure is required knowing the parameters of blast wave, its effect on structure and the tools for the solution of dynamic analysis. The real field tests of three different weight of charges and two different structures were done. The explosive POLONIT was used together with 25 g of ignition explosive PLNp10. Analytical and numerical model of blast loaded structure is compared with the results obtained from the field tests (is compared with the corresponding experimental accelerations). For the modelling structures were approximated as a one-degree system of freedom (SDOF), where the blast wave was estimated with linear decay and exponential decay using positive and negative phase of blast wave. Numerical solution of the steel beam dynamic response was performed via FEM (Finite Element Method) using standard software Visual FEA.

System level mechanical testing of the Clementine spacecraft

NASA Technical Reports Server (NTRS)

Haughton, James; Hauser, Joseph; Raynor, William; Lynn, Peter

1994-01-01

This paper discusses the system level structural testing that was performed to qualify the Clementine Spacecraft for flight. These tests included spin balance, combined acoustic and axial random vibration, lateral random vibration, quasi-static loads, pyrotechnic shock, modal survey and on-orbit jitter simulation. Some innovative aspects of this effort were: the simultaneously combined acoustic and random vibration test; the mass loaded interface modal survey test; and the techniques used to assess how operating on board mechanisms and thrusters affect sensor vision.

Understanding and Exploiting the Effects of Loading on Ultrasonic Sensing Systems for Structural Health Monitoring

DTIC Science & Technology

2012-02-01

method to image fatigue cracks without requiring damage-free baseline measurements. Load-differential imaging maps changes in ultrasonic signals...caused by a small increase in applied load to an image, which enables detecting and locating fatigue cracks that open under load and thus distinguishing...them from other load-dependent effects. This method was successfully demonstrated in the laboratory during fatigue tests on a variety of aluminum

Optimal design of high-speed loading spindle based on ABAQUS

NASA Astrophysics Data System (ADS)

Yang, Xudong; Dong, Yu; Ge, Qingkuan; Yang, Hai

2017-12-01

The three-dimensional model of high-speed loading spindle is established by using ABAQUS’s modeling module. A finite element analysis model of high-speed loading spindle was established by using spring element to simulate bearing boundary condition. The static and dynamic performance of the spindle structure with different specifications of the rectangular spline and the different diameter neck of axle are studied in depth, and the influence of different spindle span on the static and dynamic performance of the high-speed loading spindle is studied. Finally, the optimal structure of the high-speed loading spindle is obtained. The results provide a theoretical basis for improving the overall performance of the test-bed

Importance of geologic study and load test of log pod mangartom arch bridge

NASA Astrophysics Data System (ADS)

Kamnik, Rok; Meshcheryakova, Tatiana; Kovačič, Boštjan

2017-10-01

Some structures and their relationships, positions in space and shifts represent the structural set of an area, as included within regional units, and smaller or larger portions of the earth’s crust known as the Earth’s plates and micro plates. The most important fact is that tectonic movements are always possible around the locations of considered bridges. Therefore, it is certainly necessary to define in detail their characteristics due to the potential impacts on individual bridges. A recent structural set was made for the Log pod Mangartom. To assess the bridge in micro sense the load test of the bridge was performed.

Model-based active control of a continuous structure subjected to moving loads

NASA Astrophysics Data System (ADS)

Stancioiu, D.; Ouyang, H.

2016-09-01

Modelling of a structure is an important preliminary step of structural control. The main objectives of the modelling, which are almost always antagonistic are accuracy and simplicity of the model. The first part of this study focuses on the experimental and theoretical modelling of a structure subjected to the action of one or two decelerating moving carriages modelled as masses. The aim of this part is to obtain a simple but accurate model which will include not only the structure-moving load interaction but also the actuators dynamics. A small scale rig is designed to represent a four-span continuous metallic bridge structure with miniature guiding rails. A series of tests are run subjecting the structure to the action of one or two minicarriages with different loads that were launched along the structure at different initial speeds. The second part is dedicated to model based control design where a feedback controller is designed and tested against the validated model. The study shows that a positive position feedback is able to improve system dynamics but also shows some of the limitations of state- space methods for this type of system.

Design and Evaluation of Glass/epoxy Composite Blade and Composite Tower Applied to Wind Turbine

NASA Astrophysics Data System (ADS)

Park, Hyunbum

2018-02-01

In the study, the analysis and manufacturing of small class wind turbine blade was performed. In the structural design, firstly the loading conditions are defined through the load case analysis. The proposed structural configuration of blade has a sandwich type composite structure with the E-glass/Epoxy face sheets and the Urethane foam core for lightness, structural stability, low manufacturing cost and easy manufacturing process. And also, this work proposes a design procedure and results of tower for the small scale wind turbine systems. Structural analysis of blade including load cases, stress, deformation, buckling, vibration and fatigue life was performed using the finite element method, the load spectrum analysis and the Miner rule. Moreover, investigation on structural safety of tower was verified through structural analysis by FEM. The manufacturing of blade and tower was performed based on structural design. In order to investigate the designed structure, the structural tests were conducted and its results were compared with the calculated results. It is confirmed that the final proposed blade and tower meet the design requirements.

Improving the Response of a Load Cell by Using Optimal Filtering

PubMed Central

Hernandez, Wilmar

2006-01-01

Load cells are transducers used to measure force or weight. Despite the fact that there is a wide variety of load cells, most of these transducers that are used in the weighing industry are based on strain gauges. In this paper, an s-beam load cell based on strain gauges was suitably assembled to the mechanical structure of several seats of a bus under performance tests and used to measure the resistance of their mechanical structure to tension forces applied horizontally to the seats being tested. The load cell was buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency spectrum and its performance was improved by using a recursive least-squares (RLS) lattice algorithm. The experimental results are satisfactory and a significant improvement in the signal-to-noise ratio at the system output of 27 dB was achieved, which is a good performance factor for judging the quality of the system.

Water impact analysis of space shuttle solid rocket motor by the finite element method

NASA Technical Reports Server (NTRS)

Buyukozturk, O.; Hibbitt, H. D.; Sorensen, E. P.

1974-01-01

Preliminary analysis showed that the doubly curved triangular shell elements were too stiff for these shell structures. The doubly curved quadrilateral shell elements were found to give much improved results. A total of six load cases were analyzed in this study. The load cases were either those resulting from a static test using reaction straps to simulate the drop conditions or under assumed hydrodynamic conditions resulting from a drop test. The latter hydrodynamic conditions were obtained through an emperical fit of available data. Results obtained from a linear analysis were found to be consistent with results obtained elsewhere with NASTRAN and BOSOR. The nonlinear analysis showed that the originally assumed loads would result in failure of the shell structures. The nonlinear analysis also showed that it was useful to apply internal pressure as a stabilizing influence on collapse. A final analysis with an updated estimate of load conditions resulted in linear behavior up to full load.

Review and Recommendations for the Interagency Ship Structure Committee’s Fiscal 1980 Research Program

DTIC Science & Technology

1979-03-01

fracture-toughness tests and material performance in ships. Fracture criteria remains a field that resists satisfactory quantification, yet it is a...identical conditions of temperature, loading rate, and test material . Specimen configurations (e.g. bend and tensile), specimen dimensions, load train...compliance, and material characteristics should be systematically varied. In each test the specimen should be unloaded immediately after pop- in and the

Fatigue Tests with Random Flight Simulation Loading

NASA Technical Reports Server (NTRS)

Schijve, J.

1972-01-01

Crack propagation was studied in a full-scale wing structure under different simulated flight conditions. Omission of low-amplitude gust cycles had a small effect on the crack rate. Truncation of the infrequently occurring high-amplitude gust cycles to a lower level had a noticeably accelerating effect on crack growth. The application of fail-safe load (100 percent limit load) effectively stopped subsequent crack growth under resumed flight-simulation loading. In another flight-simulation test series on sheet specimens, the variables studied are the design stress level and the cyclic frequency of the random gust loading. Inflight mean stresses vary from 5.5 to 10.0 kg/sq mm. The effect of the stress level is larger for the 2024 alloy than for the 7075 alloy. Three frequencies were employed: namely, 10 cps, 1 cps, and 0.1 cps. The frequency effect was small. The advantages and limitations of flight-simulation tests are compared with those of alternative test procedures such as constant-amplitude tests, program tests, and random-load tests. Various testing purposes are considered. The variables of flight-simulation tests are listed and their effects are discussed. A proposal is made for performing systematic flight-simulation tests in such a way that the compiled data may be used as a source of reference.

Load Testing, Finite Element Analysis, and Design of Steel Traffic-Signal Poles

DOT National Transportation Integrated Search

1993-07-01

At request of the Structures Design and Construction Division, the Engineering Research and Development Bureau performed full-scale testing and finite element analysis (FEA) of span-wire traffic-signal poles to evaluate their structural adequacy. Res...

Improving Thermal Insulation Properties for Prefabricated Wall Components Made Of Lightweight Aggregate Concrete with Open Structure

NASA Astrophysics Data System (ADS)

Abramski, Marcin

2017-10-01

Porous concrete is commonly used in civil engineering due to its good thermal insulation properties in comparison with normal concrete and high compression strength in comparison with other building materials. Reducing of the concrete density can be obviously obtained by using lightweight aggregate (e.g. pumice). The concrete density can be further minimized by using specially graded coarse aggregate and little-to-no fine aggregates. In this way a large number of air voids arise. The aggregate particles are coated by a cement paste and bonded together with it just in contact points. Such an extremely porous concrete, called ‘lightweight aggregate concrete with open structure’ (LAC), is used in some German plants to produce prefabricated wall components. They are used mainly in hall buildings, e.g. supermarkets. The need of improving thermal insulation properties was an inspiration for the prefabrication plant managers, engineers and a scientific staff of the Technical University of Kaiserslautern / Germany to realise an interesting project. Its aim was to reduce the heat transfer coefficient for the wall components. Three different wall structure types were designed and compared in full-scale laboratory tests with originally produced wall components in terms of load-carrying capacity and stiffness. The load was applied perpendicularly to the wall plane. As the components are not originally used for load-bearing walls, but for curtain walls only, the wind load is the main load for them. The wall components were tested in horizontal position and the load was applied vertically. Totally twelve wall components 8.00 × 2.00 × 0.25m (three for every series) were produced in the prefabrication plant and tested in the University of Kaiserslautern laboratory. The designed and tested components differed from each other in the amount of expanded polystyrene (EPS), which was placed in the plant inside the wall structure. The minimal amount of it was designed in the original wall component type. Besides, two improved types of prefabricated wall had built-in steel lattice girders. The failure mode was the same for all the tested components: diagonal cracks occurred on the sides of each component due to their insufficient shear-force-capacity. The span deflection was measured during all the tests by means of LVDTs. Load-carrying capacities obtained in the tests were for all wall structure types similar and much higher (many times) than internal forces (i.e. bending moments and shear forces) calculated for a wind load acting on a typical hall building according to the German codes. An increased amount of EPS (up to 30 per cent in volume) did not influence significantly the wall structural strength. The use of the steel lattice girders caused some technological problems and led to a quality loss of the produced components. The future use of the lattice girders would require a change in the production process: it would have to be more labour consuming.

Buckling Response of a Large-Scale, Seamless, Orthogrid-Stiffened Metallic Cylinder

NASA Technical Reports Server (NTRS)

Rudd, Michelle Tillotson; Hilburger, Mark W.; Lovejoy, Andrew E.; Lindell, Michael C.; Gardner, Nathaniel W.; Schultz, Marc R.

2018-01-01

Results from the buckling test of a compression-loaded 8-ft-diameter seamless (i.e., without manufacturing joints), orthogrid-stiffened metallic cylinder are presented. This test was used to assess the buckling response and imperfection sensitivity characteristics of a seamless cylinder. In addition, the test article and test served as a technology demonstration to show the application of the flow forming manufacturing process to build more efficient buckling-critical structures by eliminating the welded joints that are traditionally used in the manufacturing of large metallic barrels. Pretest predictions of the cylinder buckling response were obtained using a finite-element model that included measured geometric imperfections. The buckling load predicted using this model was 697,000 lb, and the test article buckled at 743,000 lb (6% higher). After the test, the model was revised to account for measured variations in skin and stiffener geometry, nonuniform loading, and material properties. The revised model predicted a buckling load of 754,000 lb, which is within 1.5% of the tested buckling load. In addition, it was determined that the load carrying capability of the seamless cylinder is approximately 28% greater than a corresponding cylinder with welded joints.

Performance of a hypersonic hot fuselage structure with a carbon dioxide frost projected, nonintegral cryogenic tank

NASA Technical Reports Server (NTRS)

Sharpe, E. L.; Jackson, L. R.

1975-01-01

A model which consisted of a hot structure and a nonintegral tank protected by a carbon dioxide frost thermal protection system was tested under the following conditions: (1) room temperature loading and (2) heating and loading corresponding to the Mach 8 flight of an air-breathing launch vehicle. In the simulated flight tests, liquid nitrogen inside the tank was withdrawn at the rate fuel would be consumed. Prior to each simulated flight test, carbon dioxide was cryodeposited in the insulation surrounding the tank; during the tests, subliming CO2 frost absorbed heat and provided a purge gas for the space between the tank and the structure. A method of flame spraying the joints between panels with a nickel-aluminum material was developed to prevent excessive leakage of the purge gas through the outer structure. The tests indicated that the hot structure (with a joint repaired by riveting), the nonintegral tank and suspension system, and the carbon dioxide frost thermal protection system provide a workable concept with predictable performance.

Damage Tolerance Testing of a NASA TransHab Derivative Woven Inflatable Module

NASA Technical Reports Server (NTRS)

Edgecombe, John; delaFuente, Horacio; Valle, Gerard

2009-01-01

Current options for Lunar habitat architecture include inflatable habitats and airlocks. Inflatable structures can have mass and volume advantages over conventional structures. However, inflatable structures carry different inherent risks and are at a lower Technical Readiness Level (TRL) than more conventional metallic structures. One of the risks associated with inflatable structures is in understanding the tolerance to induced damage. The Damage Tolerance Test (DTT) is designed to study the structural integrity of an expandable structure. TransHab (Figure 1) was an experimental inflatable module developed at the NASA/Johnson Space Center in the 1990 s. The TransHab design was originally envisioned for use in Mars Transits but was also studied as a potential habitat for the International Space Station (ISS). The design of the TransHab module was based on a woven design using an Aramid fabric. Testing of this design demonstrated a high level of predictability and repeatability with analytical predictions of stresses and deflections. Based on JSC s experience with the design and analysis of woven inflatable structures, the Damage Tolerance Test article was designed and fabricated using a woven design. The DTT article was inflated to 45 psig, representing 25% of the ultimate burst pressure, and one of the one-inch wide longitudinal structural members was severed by initiating a Linear Shaped Charge (LSC). Strain gage measurements, at the interface between the expandable elements (straps) and the nonexpandable metallic elements for pre-selected longitudinal straps, were taken throughout pressurization of the module and strap separation. Strain gage measurements show no change in longitudinal strap loading at the bulkhead interface after strap separation indicating loads in the restraint layer were re-distributed local to the damaged area due to the effects of friction under high internal pressure loading. The test completed all primary objectives with better than expected results. This paper will discuss space inflatable structures, damage tolerance analysis, test results, and applicability to the Lunar architecture.

Testing and Analysis of a Composite Non-Cylindrical Aircraft Fuselage Structure . Part II; Severe Damage

NASA Technical Reports Server (NTRS)

Przekop, Adam; Jegley, Dawn C.; Lovejoy, Andrew E.; Rouse, Marshall; Wu, Hsi-Yung T.

2016-01-01

The Environmentally Responsible Aviation Project aimed to develop aircraft technologies enabling significant fuel burn and community noise reductions. Small incremental changes to the conventional metallic alloy-based 'tube and wing' configuration were not sufficient to achieve the desired metrics. One airframe concept identified by the project as having the potential to dramatically improve aircraft performance was a composite-based hybrid wing body configuration. Such a concept, however, presented inherent challenges stemming from, among other factors, the necessity to transfer wing loads through the entire center fuselage section which accommodates a pressurized cabin confined by flat or nearly flat panels. This paper discusses a finite element analysis and the testing of a large-scale hybrid wing body center section structure developed and constructed to demonstrate that the Pultruded Rod Stitched Efficient Unitized Structure concept can meet these challenging demands of the next generation airframes. Part II of the paper considers the final test to failure of the test article in the presence of an intentionally inflicted severe discrete source damage under the wing up-bending loading condition. Finite element analysis results are compared with measurements acquired during the test and demonstrate that the hybrid wing body test article was able to redistribute and support the required design loads in a severely damaged condition.

Orion EM-1 Crew Module Structural Test Article Move for Transport from Kennedy Space Center to Lockheed Martin in Denver Colorado

NASA Image and Video Library

2017-04-24

The Guppy aircraft arrives at the Shuttle Landing Facility (SLF) at Kennedy Space Center, to transport the Orion EM-1 Crew Module (CM) Structural Test Article (STA) to Lockheed Martin in Denver Colorado. The Orion EM-1 CM STA is loaded onto a transport truck at the Operations & Checking Building (O&C) and moved to the SLF. Following this, workers load the spacecraft hardware onto the Guppy aircraft. The Guppy takes off from the SLF, in route to Denver Colorado.

Heat pipe investigations

NASA Technical Reports Server (NTRS)

Marshburn, J. P.

1972-01-01

The OAO-C spacecraft has three circular heat pipes, each of a different internal design, located in the space between the spacecraft structural tube and the experiment tube, which are designed to isothermalize the structure. Two of the pipes are used to transport high heat loads, and the third is for low heat loads. The test problems deal with the charging of the pipes, modifications, the mobile tilt table, the position indicator, and the heat input mechanisms. The final results showed that the techniques used were adequate for thermal-vacuum testing of heat pipes.

Theoretical, Experimental, and Computational Evaluation of Disk-Loaded Circular Wave Guides

NASA Technical Reports Server (NTRS)

Wallett, Thomas M.; Qureshi, A. Haq

1994-01-01

A disk-loaded circular wave guide structure and test fixture were fabricated. The dispersion characteristics were found by theoretical analysis, experimental testing, and computer simulation using the codes ARGUS and SOS. Interaction impedances were computed based on the corresponding dispersion characteristics. Finally, an equivalent circuit model for one period of the structure was chosen using equivalent circuit models for cylindrical wave guides of different radii. Optimum values for the discrete capacitors and inductors describing discontinuities between cylindrical wave guides were found using the computer code TOUCHSTONE.

Study of foldable elastic tubes for large space structure applications, phase 3

NASA Technical Reports Server (NTRS)

Jones, I. W.; Mitchell, S. O.

1981-01-01

A bi-convex foldable elastic tube, suitable for use in self deploying space structures, was subjected to a series of buckling tests to deterine initial buckling loads, collapse loads, and the buckling mode. The tube is cylindrical with a cross-section that is lenticular-like with flared edges. It is capable of being flattened in the center and folded compactly, storing up strain energy in the process. Upon removal of constraint, it springs back to its original straight configuration, releasing the stored strain energy. The tests showed that this type of tube has good resistance to buckling, with the initial buckling loads all falling within or above the range of those for comparable circular cylindrical tubes.

Composite Bending Box Section Modal Vibration Fault Detection

NASA Technical Reports Server (NTRS)

Werlink, Rudy

2002-01-01

One of the primary concerns with Composite construction in critical structures such as wings and stabilizers is that hidden faults and cracks can develop operationally. In the real world, catastrophic sudden failure can result from these undetected faults in composite structures. Vibration data incorporating a broad frequency modal approach, could detect significant changes prior to failure. The purpose of this report is to investigate the usefulness of frequency mode testing before and after bending and torsion loading on a composite bending Box Test section. This test article is representative of construction techniques being developed for the recent NASA Blended Wing Body Low Speed Vehicle Project. The Box section represents the construction technique on the proposed blended wing aircraft. Modal testing using an impact hammer provides an frequency fingerprint before and after bending and torsional loading. If a significant structural discontinuity develops, the vibration response is expected to change. The limitations of the data will be evaluated for future use as a non-destructive in-situ method of assessing hidden damage in similarly constructed composite wing assemblies. Modal vibration fault detection sensitivity to band-width, location and axis will be investigated. Do the sensor accelerometers need to be near the fault and or in the same axis? The response data used in this report was recorded at 17 locations using tri-axial accelerometers. The modal tests were conducted following 5 independent loading conditions before load to failure and 2 following load to failure over a period of 6 weeks. Redundant data was used to minimize effects from uncontrolled variables which could lead to incorrect interpretations. It will be shown that vibrational modes detected failure at many locations when skin de-bonding failures occurred near the center section. Important considerations are the axis selected and frequency range.

Measured and predicted structural behavior of the HiMAT tailored composite wing

NASA Technical Reports Server (NTRS)

Nelson, Lawrence H.

1987-01-01

A series of load tests was conducted on the HiMAT tailored composite wing. Coupon tests were also run on a series of unbalanced laminates, including the ply configuration of the wing, the purpose of which was to compare the measured and predicted behavior of unbalanced laminates, including - in the case of the wing - a comparison between the behavior of the full scale structure and coupon tests. Both linear and nonlinear finite element (NASTRAN) analyses were carried out on the wing. Both linear and nonlinear point-stress analyses were performed on the coupons. All test articles were instrumented with strain gages, and wing deflections measured. The leading and trailing edges were found to have no effect on the response of the wing to applied loads. A decrease in the stiffness of the wing box was evident over the 27-test program. The measured load-strain behavior of the wing was found to be linear, in contrast to coupon tests of the same laminate, which were nonlinear. A linear NASTRAN analysis of the wing generally correlated more favorably with measurements than did a nonlinear analysis. An examination of the predicted deflections in the wing root region revealed an anomalous behavior of the structural model that cannot be explained. Both hysteresis and creep appear to be less significant in the wing tests than in the corresponding laminate coupon tests.

Test-Free Fracture Toughness

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

2003-01-01

Computational simulation results can give the prediction of damage growth and progression and fracture toughness of composite structures. The experimental data from literature provide environmental effects on the fracture behavior of metallic or fiber composite structures. However, the traditional experimental methods to analyze the influence of the imposed conditions are expensive and time consuming. This research used the CODSTRAN code to model the temperature effects, scaling effects and the loading effects of fiber/braided composite specimens with and without fiber-optic sensors on the damage initiation and energy release rates. The load-displacement relationship and fracture toughness assessment approach is compared with the test results from literature and it is verified that the computational simulation, with the use of established material modeling and finite element modules, adequately tracks the changes of fracture toughness and subsequent fracture propagation for any fiber/braided composite structure due to the change of fiber orientations, presence of large diameter optical fibers, and any loading conditions.

Test-Free Fracture Toughness

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

2003-01-01

Computational simulation results can give the prediction of damage growth and progression and fracture toughness of composite structures. The experimental data from literature provide environmental effects on the fracture behavior of metallic or fiber composite structures. However, the traditional experimental methods to analyze the influence of the imposed conditions are expensive and time consuming. This research used the CODSTRAN code to model the temperature effects, scaling effects and the loading effects of fiberbraided composite specimens with and without fiber-optic sensors on the damage initiation and energy release rates. The load-displacement relationship and fracture toughness assessment approach is compared with the test results from literature and it is verified that the computational simulation, with the use of established material modeling and finite element modules, adequately tracks the changes of fracture toughness and subsequent fracture propagation for any fiberbraided composite structure due to the change of fiber orientations, presence of large diameter optical fibers, and any loading conditions.

Numerical modeling of the load effect on PZT-induced guided wave for load compensation of damage detection

NASA Astrophysics Data System (ADS)

Sun, Hu; Zhang, Aijia; Wang, Yishou; Qing, Xinlin P.

2017-04-01

Guided wave-based structural health monitoring (SHM) has been given considerable attention and widely studied for large-scale aircraft structures. Nevertheless, it is difficult to apply SHM systems on board or online, for which one of the most serious reasons is the environmental influence. Load is one fact that affects not only the host structure, in which guided wave propagates, but also the PZT, by which guided wave is transmitted and received. In this paper, numerical analysis using finite element method is used to study the load effect on guided wave acquired by PZT. The static loads with different grades are considered to analyze its effect on guided wave signals that PZT transmits and receives. Based on the variation trend of guided waves versus load, a load compensation method is developed to eliminate effects of load in the process of damage detection. The probabilistic reconstruction algorithm based on the signal variation of transmitter-receiver path is employed to identify the damage. Numerical tests is conducted to verify the feasibility and effectiveness of the given method.

Numerical Analyses of Subsoil-structure Interaction in Original Non-commercial Software based on FEM

NASA Astrophysics Data System (ADS)

Cajka, R.; Vaskova, J.; Vasek, J.

2018-04-01

For decades attention has been paid to interaction of foundation structures and subsoil and development of interaction models. Given that analytical solutions of subsoil-structure interaction could be deduced only for some simple shapes of load, analytical solutions are increasingly being replaced by numerical solutions (eg. FEM – Finite element method). Numerical analyses provides greater possibilities for taking into account the real factors involved in the subsoil-structure interaction and was also used in this article. This makes it possible to design the foundation structures more efficiently and still reliably and securely. Currently there are several software that, can deal with the interaction of foundations and subsoil. It has been demonstrated that non-commercial software called MKPINTER (created by Cajka) provides appropriately results close to actual measured values. In MKPINTER software stress-strain analysis of elastic half-space by means of Gauss numerical integration and Jacobean of transformation is done. Input data for numerical analysis were observed by experimental loading test of concrete slab. The loading was performed using unique experimental equipment which was constructed in the area Faculty of Civil Engineering, VŠB-TU Ostrava. The purpose of this paper is to compare resulting deformation of the slab with values observed during experimental loading test.

10.2 Thermal-Structural Testing

NASA Technical Reports Server (NTRS)

Hudson, Larry D.

2008-01-01

Objective: Test a C/SiC Ruddervator Subcomponent under relevant thermal, mechanical & dynamic loading a) Thermal-structural mission cycling for re-entry and hypersonic cruise conditions; b) High-temperature modal survey to study the effect of heating on mode shapes, natural frequencies and damping. Supports NASA ARMD Hypersonics Material & Structures Program. Partners: NASA Dryden / Langley / Glenn, Lockheed-Martin, Materials Research & Design, GE CCP Test Phases - Phase 1: Acoustic-Vibration Testing (LaRC) completed - Phase 2: Thermal-Mechanical Testing (DFRC) in assembly - Phase 3: Mechanical Testing (DFRC) in assembly

Test-bed for the remote health monitoring system for bridge structures using FBG sensors

NASA Astrophysics Data System (ADS)

Lee, Chin-Hyung; Park, Ki-Tae; Joo, Bong-Chul; Hwang, Yoon-Koog

2009-05-01

This paper reports on test-bed for the long-term health monitoring system for bridge structures employing fiber Bragg grating (FBG) sensors, which is remotely accessible via the web, to provide real-time quantitative information on a bridge's response to live loading and environmental changes, and fast prediction of the structure's integrity. The sensors are attached on several locations of the structure and connected to a data acquisition system permanently installed onsite. The system can be accessed through remote communication using an optical cable network, through which the evaluation of the bridge behavior under live loading can be allowed at place far away from the field. Live structural data are transmitted continuously to the server computer at the central office. The server computer is connected securely to the internet, where data can be retrieved, processed and stored for the remote web-based health monitoring. Test-bed revealed that the remote health monitoring technology will enable practical, cost-effective, and reliable condition assessment and maintenance of bridge structures.

Reduction of structural loads using maneuver load control on the Advanced Fighter Technology Integration (AFTI)/F-111 mission adaptive wing

NASA Technical Reports Server (NTRS)

Thornton, Stephen V.

1993-01-01

A transonic fighter-bomber aircraft, having a swept supercritical wing with smooth variable-camber flaps was fitted with a maneuver load control (MLC) system that implements a technique to reduce the inboard bending moments in the wing by shifting the spanwise load distribution inboard as load factor increases. The technique modifies the spanwise camber distribution by automatically commanding flap position as a function of flap position, true airspeed, Mach number, dynamic pressure, normal acceleration, and wing sweep position. Flight test structural loads data were obtained for loads in both the wing box and the wing root. Data from uniformly deflected flaps were compared with data from flaps in the MLC configuration where the outboard segment of three flap segments was deflected downward less than the two inboard segments. The changes in the shear loads in the forward wing spar and at the roots of the stabilators also are presented. The camber control system automatically reconfigures the flaps through varied flight conditions. Configurations having both moderate and full trailing-edge flap deflection were tested. Flight test data were collected at Mach numbers of 0.6, 0.7, 0.8, and 0.9 and dynamic pressures of 300, 450, 600, and 800 lb/sq ft. The Reynolds numbers for these flight conditions ranged from 26 x 10(exp 6) to 54 x 10(exp 6) at the mean aerodynamic chord. Load factor increases of up to 1.0 g achieved with no increase in wing root bending moment with the MLC flap configuration.

Estimation of dynamic rotor loads for the rotor systems research aircraft: Methodology development and validation

NASA Technical Reports Server (NTRS)

Duval, R. W.; Bahrami, M.

1985-01-01

The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission systm from the fuselage. A mathematical model relating applied rotor loads and inertial loads of the rotor/transmission system to the load cell response is required to allow the load cells to be used to estimate rotor loads from flight data. Such a model is derived analytically by applying a force and moment balance to the isolated rotor/transmission system. The model is tested by comparing its estimated values of applied rotor loads with measured values obtained from a ground based shake test. Discrepancies in the comparison are used to isolate sources of unmodeled external loads. Once the structure of the mathematical model has been validated by comparison with experimental data, the parameters must be identified. Since the parameters may vary with flight condition it is desirable to identify the parameters directly from the flight data. A Maximum Likelihood identification algorithm is derived for this purpose and tested using a computer simulation of load cell data. The identification is found to converge within 10 samples. The rapid convergence facilitates tracking of time varying parameters of the load cell model in flight.

Accelerated development and flight evaluation of active controls concepts for subsonic transport aircraft. Volume 1: Load alleviation/extended span development and flight tests

NASA Technical Reports Server (NTRS)

Johnston, J. F.

1979-01-01

Active wing load alleviation to extend the wing span by 5.8 percent, giving a 3 percent reduction in cruise drag is covered. The active wing load alleviation used symmetric motions of the outboard ailerons for maneuver load control (MLC) and elastic mode suppression (EMS), and stabilizer motions for gust load alleviation (GLA). Slow maneuvers verified the MLC, and open and closed-loop flight frequency response tests verified the aircraft dynamic response to symmetric aileron and stabilizer drives as well as the active system performance. Flight tests in turbulence verified the effectiveness of the active controls in reducing gust-induced wing loads. It is concluded that active wing load alleviation/extended span is proven in the L-1011 and is ready for application to airline service; it is a very practical way to obtain the increased efficiency of a higher aspect ratio wing with minimum structural impact.

Correlation of residual strength with acoustic emission from impact-damaged composite structures under constant biaxial load

NASA Astrophysics Data System (ADS)

Hamstad, M. A.; Whittaker, J. W.; Brosey, W. D.

1992-01-01

Small, filament-wound, Kevlar/epoxy, biaxial test specimens were subjected to various levels of impact damage. The specimens were pressurized in a proof test cycle to 58 percent of their nominal, undamaged strength and then pressurized to failure. Acoustic emission data were gathered by multiple sensors during a 10 minute hold at peak proof pressure. Post-test filtering of the data was performed to study composite behavior in the damaged region and other areas. The rate and total amount of AE produced depends on the duration of the static load and degree of damage. The concept of the event rate moment is introduced as a method of quantifying a structure's total AE behavior when under static load. Average event rate, total long duration events, and event rate moments provided various degrees of correlation between AE and residual strength.

Static and fatigue testing of full-scale fuselage panels fabricated using a Therm-X(R) process

NASA Technical Reports Server (NTRS)

Dinicola, Albert J.; Kassapoglou, Christos; Chou, Jack C.

1992-01-01

Large, curved, integrally stiffened composite panels representative of an aircraft fuselage structure were fabricated using a Therm-X process, an alternative concept to conventional two-sided hard tooling and contour vacuum bagging. Panels subsequently were tested under pure shear loading in both static and fatigue regimes to assess the adequacy of the manufacturing process, the effectiveness of damage tolerant design features co-cured with the structure, and the accuracy of finite element and closed-form predictions of postbuckling capability and failure load. Test results indicated the process yielded panels of high quality and increased damage tolerance through suppression of common failure modes such as skin-stiffener separation and frame-stiffener corner failure. Finite element analyses generally produced good predictions of postbuckled shape, and a global-local modelling technique yielded failure load predictions that were within 7% of the experimental mean.

Strain Gage Loads Calibration Testing with Airbag Support for the Gulfstream III SubsoniC Research Aircraft Testbed (SCRAT)

NASA Technical Reports Server (NTRS)

Lokos, William A.; Miller, Eric J.; Hudson, Larry D.; Holguin, Andrew C.; Neufeld, David C.; Haraguchi, Ronnie

2015-01-01

This paper describes the design and conduct of the strain-gage load calibration ground test of the SubsoniC Research Aircraft Testbed, Gulfstream III aircraft, and the subsequent data analysis and results. The goal of this effort was to create and validate multi-gage load equations for shear force, bending moment, and torque for two wing measurement stations. For some of the testing the aircraft was supported by three airbags in order to isolate the wing structure from extraneous load inputs through the main landing gear. Thirty-two strain gage bridges were installed on the left wing. Hydraulic loads were applied to the wing lower surface through a total of 16 load zones. Some dead-weight load cases were applied to the upper wing surface using shot bags. Maximum applied loads reached 54,000 lb. Twenty-six load cases were applied with the aircraft resting on its landing gear, and 16 load cases were performed with the aircraft supported by the nose gear and three airbags around the center of gravity. Maximum wing tip deflection reached 17 inches. An assortment of 2, 3, 4, and 5 strain-gage load equations were derived and evaluated against independent check cases. The better load equations had root mean square errors less than 1 percent. Test techniques and lessons learned are discussed.

Sex differences in verbal working memory performance emerge at very high loads of common neuroimaging tasks.

PubMed

Reed, Jessica L; Gallagher, Natalie M; Sullivan, Marie; Callicott, Joseph H; Green, Adam E

2017-04-01

Working memory (WM) supports a broad range of intelligent cognition and has been the subject of rich cognitive and neural characterization. However, the highest ranges of WM have not been fully characterized, especially for verbal information. Tasks developed to test multiple levels of WM demand (load) currently predominate brain-based WM research. These tasks are typically used at loads that allow most healthy participants to perform well, which facilitates neuroimaging data collection. Critically, however, high performance at lower loads may obscure differences that emerge at higher loads. A key question not yet addressed at high loads concerns the effect of sex. Thoroughgoing investigation of high-load verbal WM is thus timely to test for potential hidden effects, and to provide behavioral context for effects of sex observed in WM-related brain structure and function. We tested 111 young adults, matched on genotype for the WM-associated COMT-Val 108/158 Met polymorphism, on three classic WM tasks using verbal information. Each task was tested at four WM loads, including higher loads than those used in previous studies of sex differences. All tasks loaded on a single factor, enabling comparison of verbal WM ability at a construct level. Results indicated sex effects at high loads across tasks and within each task, such that males had higher accuracy, even among groups that were matched for performance at lower loads. Published by Elsevier Inc.

Strength and deformability of concrete beams reinforced by non-metallic fiber and composite rebar

NASA Astrophysics Data System (ADS)

Kudyakov, K. L.; Plevkov, V. S.; Nevskii, A. V.

2015-01-01

Production of durable and high-strength concrete structures with unique properties has always been crucial. Therefore special attention has been paid to non-metallic composite and fiber reinforcement. This article describes the experimental research of strength and deformability of concrete beams with dispersed and core fiber-based reinforcement. As composite reinforcement fiberglass reinforced plastic rods with diameters 6 mm and 10 mm are used. Carbon and basalt fibers are used as dispersed reinforcement. The developed experimental program includes designing and production of flexural structures with different parameters of dispersed fiber and composite rebar reinforcement. The preliminary testing of mechanical properties of these materials has shown their effectiveness. Structures underwent bending testing on a special bench by applying flexural static load up to complete destruction. During the tests vertical displacements were recorded, as well as value of actual load, slippage of rebars in concrete, crack formation. As a result of research were obtained structural failure and crack formation graphs, value of fracture load and maximum displacements of the beams at midspan. Analysis of experimental data showed the effectiveness of using dispersed reinforcement of concrete and the need for prestressing of fiberglass composite rebar.

Engine System Loads Analysis Compared to Hot-Fire Data

NASA Technical Reports Server (NTRS)

Frady, Gregory P.; Jennings, John M.; Mims, Katherine; Brunty, Joseph; Christensen, Eric R.; McConnaughey, Paul R. (Technical Monitor)

2002-01-01

Early implementation of structural dynamics finite element analyses for calculation of design loads is considered common design practice for high volume manufacturing industries such as automotive and aeronautical industries. However with the rarity of rocket engine development programs starts, these tools are relatively new to the design of rocket engines. In the NASA MC-1 engine program, the focus was to reduce the cost-to-weight ratio. The techniques for structural dynamics analysis practices, were tailored in this program to meet both production and structural design goals. Perturbation of rocket engine design parameters resulted in a number of MC-1 load cycles necessary to characterize the impact due to mass and stiffness changes. Evolution of loads and load extraction methodologies, parametric considerations and a discussion of load path sensitivities are important during the design and integration of a new engine system. During the final stages of development, it is important to verify the results of an engine system model to determine the validity of the results. During the final stages of the MC-1 program, hot-fire test results were obtained and compared to the structural design loads calculated by the engine system model. These comparisons are presented in this paper.

A Summary of Numerous Strain-Gage Load Calibrations on Aircraft Wings and Tails in a Technological Format

NASA Technical Reports Server (NTRS)

Jenkins, Jerald M.; DeAngelis, V. Michael

1997-01-01

Fifteen aircraft structures that were calibrated for flight loads using strain gages are examined. The primary purpose of this paper is to document important examples of load calibrations on airplanes during the past four decades. The emphasis is placed on studying the physical procedures of calibrating strain-gaged structures and all the supporting analyses and computational techniques that have been used. The results and experiences obtained from actual data from 14 structures (on 13 airplanes and 1 laboratory test structure) are presented. This group of structures includes fins, tails, and wings with a wide variety of aspect ratios. Straight- wing, swept-wing, and delta-wing configurations are studied. Some of the structures have skin-dominant construction; others are spar-dominant. Anisotropic materials, heat shields, corrugated components, nonorthogonal primary structures, and truss-type structures are particular characteristics that are included.

Load Deflection of Dow Corning SE 1700 Face Centered Tetragonal Direct Ink Write Materials: Effect of Thickness and Filament Spacing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Small, Ward; Pearson, Mark A.; Metz, Tom R.

Dow Corning SE 1700 (reinforced polydimethylsiloxane) porous structures were made by direct ink writing (DIW) in a face centered tetragonal (FCT) configuration. The filament diameter was 250 μm. Structures consisting of 4, 8, or 12 layers were fabricated with center-to-center filament spacing (“road width” (RW)) of 475, 500, 525, 550, or 575 μm. Three compressive load-unload cycles to 2000 kPa were performed on four separate areas of each sample; three samples of each thickness and filament spacing were tested. At a given strain during the third loading phase, stress varied inversely with porosity. At 10% strain, the stress was nearlymore » independent of the number of layers (i.e., thickness). At higher strains (20- 40%), the stress was highest for the 4-layer structure; the 8- and 12-layer structures were nearly equivalent suggesting that the load deflection is independent of number of layers above 8 layers. Intra-and inter-sample variability of the load deflection response was higher for thinner and less porous structures.« less

Comparative study on diagonal equivalent methods of masonry infill panel

NASA Astrophysics Data System (ADS)

Amalia, Aniendhita Rizki; Iranata, Data

2017-06-01

Infrastructure construction in earthquake prone area needs good design process, including modeling a structure in a correct way to reduce damages caused by an earthquake. Earthquakes cause many damages e.g. collapsed buildings that are dangerous. An incorrect modeling in design process certainly affects the structure's ability in responding to load, i.e. an earthquake load, and it needs to be paid attention to in order to reduce damages and fatalities. A correct modeling considers every aspect that affects the strength of a building, including stiffness of resisting lateral loads caused by an earthquake. Most of structural analyses still use open frame method that does not consider the effect of stiffness of masonry panel to the stiffness and strength of the whole structure. Effect of masonry panel is usually not included in design process, but the presence of this panel greatly affects behavior of the building in responding to an earthquake. In worst case scenario, it can even cause the building to collapse as what has been reported after great earthquakes worldwide. Modeling a structure with masonry panel as consideration can be performed by designing the panel as compression brace or shell element. In designing masonry panel as a compression brace, there are fourteen methods popular to be used by structure designers formulated by Saneinejad-Hobbs, Holmes, Stafford-Smith, Mainstones, Mainstones-Weeks, Bazan-Meli, Liauw Kwan, Paulay and Priestley, FEMA 356, Durani Luo, Hendry, Al-Chaar, Papia and Chen-Iranata. Every method has its own equation and parameters to use, therefore the model of every method was compared to results of experimental test to see which one gives closer values. Moreover, those methods also need to be compared to the open frame to see if they can result values within limits. Experimental test that was used in comparing all methods was taken from Mehrabi's research (Fig. 1), which was a prototype of a frame in a structure with 0.5 scale and the ratio of height to width of 1 to 1.5. Load used in the experiment was based on Uniform Building Code (UBC) 1991. Every method compared was calculated first to get equivalent diagonal strut width. The second step was modelling method using structure analysis software as a frame with a diagonal in a linear mode. The linear mode was chosen based on structure analysis commonly used by structure designers. The frame was loaded and for every model, its load and deformation values were identified. The values of load - deformation of every method were compared to those of experimental test specimen by Mehrabi and open frame. From comparative study performed, Holmes' and Bazan-Meli's equations gave results the closest to the experimental test specimen by Mehrabi. Other equations that gave close values within the limit (by comparing it to the open frame) are Saneinejad-Hobbs, Stafford-Smith, Bazan-Meli, Liauw Kwan, Paulay and Priestley, FEMA 356, Durani Luo, Hendry, Papia and Chen-Iranata.

A case study on the structural assessment of fire damaged building

NASA Astrophysics Data System (ADS)

Osman, M. H.; Sarbini, N. N.; Ibrahim, I. S.; Ma, C. K.; Ismail, M.; Mohd, M. F.

2017-11-01

This paper presents a case study on the structural assessment of building damaged by fire and discussed on the site investigations and test results prior to determine the existing condition of the building. The building was on fire for about one hour before it was extinguished. In order to ascertain the integrity of the building, a visual inspection was conducted for all elements (truss, beam, column and wall), followed by non-destructive, load and material tests. The load test was conducted to determine the ability of truss to resist service load, while the material test to determine the residual strength of the material. At the end of the investigation, a structural analysis was carried out to determine the new factor of safety by considering the residual strength. The highlighted was on the truss element due to steel behaviour that is hardly been predicted. Meanwhile, reinforced concrete elements (beam, column and wall) were found externally affected and caused its strength to be considered as sufficient for further used of building. The new factor of safety is equal to 2, considered as the minimum calculated value for the truss member. Therefore, this fire damaged building was found safe and can be used for further application.

16 CFR 1207.3 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... means members providing structural support to the assembled, installed slide. (5) Casual contact means...) Performance test means a test to measure the functional or structural characteristics of the slide and may... measurements of the slide's response to dynamic and static loads. (20) [Reserved] (21) Pinching hazard means...

Recent development in low-constraint fracture toughness testing for structural integrity assessment of pipelines

NASA Astrophysics Data System (ADS)

Kang, Jidong; Gianetto, James A.; Tyson, William R.

2018-03-01

Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edgenotched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.

Next Generation Car — Example of Function Integration at the Light Urban Vehicle (LUV) Vehicle Concept

NASA Astrophysics Data System (ADS)

Kopp, G.; Brückmann, S.; Kriescher, M.; Friedrich, H. E.

In times of climate change vehicle emissions have to be reduced clearly. One possibility is to reduce the mass of the body in white using lightweight sandwich structures. The department `Lightweight and Hybrid Design Methods' of the Institute of Vehicle Concepts develops a vehicle body structure by using sandwiches with aluminum top layers and polyurethane foam as core material. For that the foam and the sandwiches were investigated under different load cases, e.g. pressure loading and in-plane tests. In tests with components the high potential of the sandwich materials were shown. On the dynamic component test facility of the institute, vehicle front structures were tested successfully. The results of all investigations regarding sandwich materials, integration of functions (e.g. crash, thermal) in vehicle structures and the concept LUV are developed under the research program of Next Generation Car of the DLR. We will show the development and results of the LUV.

Thermal Fatigue Study of W/cu Joint

NASA Astrophysics Data System (ADS)

Zhang, Fu; Wu, Jihong; Xu, Zengyu; Xu, Ying

2003-06-01

HHFC mock-ups with a structure of W/Cu/SS were developed by hot isostatic pressing (HIP). The performance of the W/Cu joint under high heat loads was tested using an electron beam. The size of specimens for heat load tests was 25×25 mm and the size of beam spot on the specimen surface was 22 mm in diameter. During heat load test, the specimens were water-cooled. Thermal fatigue test were conducted at power density of 8.7 MW/m2 with pulse duration of 20 seconds and interval of 20 seconds. After 1000 cycles of tests, no cracks and failure were found in the W/Cu joint. The thermal performance was also investigated in the range of 1 ~ 9 MW/m2.

High-Power Testing of 11.424-GHz Dielectric-Loaded Accelerating Structures

NASA Astrophysics Data System (ADS)

Gold, Steven; Gai, Wei

2001-10-01

Argonne National Laboratory has previously described the design, construction, and bench testing of an X-band traveling-wave accelerating structure loaded with a permittivity=20 dielectric (P. Zou et al., Rev. Sci. Instrum. 71, 2301, 2000.). We describe a new program to build a test accelerator using this structure. The accelerator will be powered by the high-power 11.424-GHz radiation from the magnicon facility at the Naval Research Laboratory ( O.A. Nezhevenko et al., Proc. PAC 2001, in press). The magnicon is expected to provide up to 30 MW from each of two WR-90 output waveguide arms in pulses of up to 1 microsecond duration, permitting tests up to a gradient of 40 MV/m. Still higher power pulses (100-500 MW) may be available at the output of an active pulse compressor driven by the magnicon ( A.L. Vikharev et al., Proc. 9th Workshop on Advanced Accelerator Concepts.).

Optimal Design and Damage Tolerance Verification of an Isogrid Structure for Helicopter Application

NASA Technical Reports Server (NTRS)

Baker, Donald J.; Fudge, Jack; Ambur, Damodar R.; Kassapoglou, Christos

2003-01-01

A composite isogrid panel design for application to a rotorcraft fuselage is presented. An optimum panel design for the lower fuselage of the rotorcraft that is subjected to combined in-plane compression and shear loads was generated using a design tool that utilizes a smeared-stiffener theory in conjunction with a genetic algorithm. A design feature was introduced along the edges of the panel that facilitates introduction of loads into the isogrid panel without producing undesirable local bending gradients. A low-cost manufacturing method for the isogrid panel that incorporates these design details is also presented. Axial compression tests were conducted on the undamaged and low-speed impact damaged panels to demonstrate the damage tolerance of this isogrid panel. A combined loading test fixture was designed and utilized that allowed simultaneous application of compression and shear loads to the test specimen. Results from finite element analyses are presented for the isogrid panel designs and these results are compared with experimental results. This study illustrates the isogrid concept to be a viable candidate for application to the helicopter lower fuselage structure.

Structural characterization of a first-generation articulated-truss joint for space crane application

NASA Technical Reports Server (NTRS)

Sutter, Thomas R.; Wu, K. Chauncey; Riutort, Kevin T.; Laufer, Joseph B.; Phelps, James E.

1992-01-01

A first-generation space crane articulated-truss joint was statically and dynamically characterized in a configuration that approximated an operational environment. The articulated-truss joint was integrated into a test-bed for structural characterization. Static characterization was performed by applying known loads and measuring the corresponding deflections to obtain load-deflection curves. Dynamic characterization was performed using modal testing to experimentally determine the first six mode shapes, frequencies, and modal damping values. Static and dynamic characteristics were also determined for a reference truss that served as a characterization baseline. Load-deflection curves and experimental frequency response functions are presented for the reference truss and the articulated-truss joint mounted in the test-bed. The static and dynamic experimental results are compared with analytical predictions obtained from finite element analyses. Load-deflection response is also presented for one of the linear actuators used in the articulated-truss joint. Finally, an assessment is presented for the predictability of the truss hardware used in the reference truss and articulated-truss joint based upon hardware stiffness properties that were previously obtained during the Precision Segmented Reflector (PSR) Technology Development Program.

Characterization of Solid Polymers, Ceramic Gap Filler, and Closed-Cell Polymer Foam Using Low-Load Test Methods

NASA Technical Reports Server (NTRS)

Herring, Helen M.

2008-01-01

Various solid polymers, polymer-based composites, and closed-cell polymer foam are being characterized to determine their mechanical properties, using low-load test methods. The residual mechanical properties of these materials after environmental exposure or extreme usage conditions determines their value in aerospace structural applications. In this experimental study, four separate polymers were evaluated to measure their individual mechanical responses after thermal aging and moisture exposure by dynamic mechanical analysis. A ceramic gap filler, used in the gaps between the tiles on the Space Shuttle, was also tested, using dynamic mechanical analysis to determine material property limits during flight. Closed-cell polymer foam, used for the Space Shuttle External Tank insulation, was tested under low load levels to evaluate how the foam's mechanical properties are affected by various loading and unloading scenarios.

Reliability-based criteria for load and resistance factor design code for wood bridges

Treesearch

Chris Eamon; Andrzej S. Nowak; Michael A. Ritter; Joe Murphy

2000-01-01

Recently AASHTO adopted a load and resistance factor design code for highway bridges. The new code provides a rational basis for the design of steel and concrete structures. However, the calibration was not done for wood bridges. Therefore, there is a need to fill this gap. The development of statistical models for wood bridge structures is discussed. Recent test...

New Tools Being Developed for Engine- Airframe Blade-Out Structural Simulations

NASA Technical Reports Server (NTRS)

Lawrence, Charles

2003-01-01

One of the primary concerns of aircraft structure designers is the accurate simulation of the blade-out event. This is required for the aircraft to pass Federal Aviation Administration (FAA) certification and to ensure that the aircraft is safe for operation. Typically, the most severe blade-out occurs when a first-stage fan blade in a high-bypass gas turbine engine is released. Structural loading results from both the impact of the blade onto the containment ring and the subsequent instantaneous unbalance of the rotating components. Reliable simulations of blade-out are required to ensure structural integrity during flight as well as to guarantee successful blade-out certification testing. The loads generated by these analyses are critical to the design teams for several components of the airplane structures including the engine, nacelle, strut, and wing, as well as the aircraft fuselage. Currently, a collection of simulation tools is used for aircraft structural design. Detailed high-fidelity simulation tools are used to capture the structural loads resulting from blade loss, and then these loads are used as input into an overall system model that includes complete structural models of both the engines and the airframe. The detailed simulation (shown in the figure) includes the time-dependent trajectory of the lost blade and its interactions with the containment structure, and the system simulation includes the lost blade loadings and the interactions between the rotating turbomachinery and the remaining aircraft structural components. General-purpose finite element structural analysis codes are typically used, and special provisions are made to include transient effects from the blade loss and rotational effects resulting from the engine s turbomachinery. To develop and validate these new tools with test data, the NASA Glenn Research Center has teamed with GE Aircraft Engines, Pratt & Whitney, Boeing Commercial Aircraft, Rolls-Royce, and MSC.Software.

Stress Analysis of Columns and Beam Columns by the Photoelastic Method

NASA Technical Reports Server (NTRS)

Ruffner, B F

1946-01-01

Principles of similarity and other factors in the design of models for photoelastic testing are discussed. Some approximate theoretical equations, useful in the analysis of results obtained from photoelastic tests are derived. Examples of the use of photoelastic techniques and the analysis of results as applied to uniform and tapered beam columns, circular rings, and statically indeterminate frames, are given. It is concluded that this method is an effective tool for the analysis of structures in which column action is present, particularly in tapered beam columns, and in statically indeterminate structures in which the distribution of loads in the structures is influenced by bending moments due to axial loads in one or more members.

Analysis and testing of axial compression in imperfect slender truss struts

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Georgiadis, Nicholas

1990-01-01

The axial compression of imperfect slender struts for large space structures is addressed. The load-shortening behavior of struts with initially imperfect shapes and eccentric compressive end loading is analyzed using linear beam-column theory and results are compared with geometrically nonlinear solutions to determine the applicability of linear analysis. A set of developmental aluminum clad graphite/epoxy struts sized for application to the Space Station Freedom truss are measured to determine their initial imperfection magnitude, load eccentricity, and cross sectional area and moment of inertia. Load-shortening curves are determined from axial compression tests of these specimens and are correlated with theoretical curves generated using linear analysis.

Implementation of Fiber Optic Sensing System on Sandwich Composite Cylinder Buckling Test

NASA Technical Reports Server (NTRS)

Pena, Francisco; Richards, W. Lance; Parker, Allen R.; Piazza, Anthony; Schultz, Marc R.; Rudd, Michelle T.; Gardner, Nathaniel W.; Hilburger, Mark W.

2018-01-01

The National Aeronautics and Space Administration (NASA) Engineering and Safety Center Shell Buckling Knockdown Factor Project is a multicenter project tasked with developing new analysis-based shell buckling design guidelines and design factors (i.e., knockdown factors) through high-fidelity buckling simulations and advanced test technologies. To validate these new buckling knockdown factors for future launch vehicles, the Shell Buckling Knockdown Factor Project is carrying out structural testing on a series of large-scale metallic and composite cylindrical shells at the NASA Marshall Space Flight Center (Marshall Space Flight Center, Alabama). A fiber optic sensor system was used to measure strain on a large-scale sandwich composite cylinder that was tested under multiple axial compressive loads up to more than 850,000 lb, and equivalent bending loads over 22 million in-lb. During the structural testing of the composite cylinder, strain data were collected from optical cables containing distributed fiber Bragg gratings using a custom fiber optic sensor system interrogator developed at the NASA Armstrong Flight Research Center. A total of 16 fiber-optic strands, each containing nearly 1,000 fiber Bragg gratings, measuring strain, were installed on the inner and outer cylinder surfaces to monitor the test article global structural response through high-density real-time and post test strain measurements. The distributed sensing system provided evidence of local epoxy failure at the attachment-ring-to-barrel interface that would not have been detected with conventional instrumentation. Results from the fiber optic sensor system were used to further refine and validate structural models for buckling of the large-scale composite structures. This paper discusses the techniques employed for real-time structural monitoring of the composite cylinder for structural load introduction and distributed bending-strain measurements over a large section of the cylinder by utilizing unique sensing capabilities of fiber optic sensors.

Embedded data collector (EDC) phase II load and resistance factor design (LRFD) : [summary].

DOT National Transportation Integrated Search

2015-07-01

Piles that support bridge structures are designed for the specific site characteristics and loads : that the piles are expected to bear. In Florida, driven piles are monitored during installation : (dynamically tested) to assess resistance, com...

Acceleration Testing: A Better, Faster, Cheaper Alternative for Strength Qualification Testing

NASA Technical Reports Server (NTRS)

Mattiello, Carmine F.

1997-01-01

This paper addresses the advantages of utilizing a centrifuge test over the conventional static load test methods to structurally qualify aerospace structures. Three recent test cases are reviewed and used as examples to highlight these benefits. In addition, the overall capability of Goddard's High Capacity Centrifuge (HCC) is outlined along with some unique features that were designed specifically to reduce costs, test turn around time, and increase test item safety.

Acoustic Emission of Large PRSEUS Structures (Pultruded Rod Stitched Efficient Unitized Structure)

NASA Technical Reports Server (NTRS)

Horne, Michael R.; Juarez, Peter D.

2016-01-01

In the role of structural health monitoring (SHM), Acoustic Emission (AE) analysis is being investigated as an effective method for tracking damage development in large composite structures under load. Structures made using Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) for damage tolerant, light, and economical airframe construction are being pursued by The Boeing Company and NASA under the Environmentally Responsible Aircraft initiative (ERA). The failure tests of two PRSEUS substructures based on the Boeing Hybrid Wing Body fuselage concept were conducted during third quarter 2011 and second quarter 2015. One fundamental concern of these tests was determining the effectiveness of the stitched integral stiffeners to inhibit damage progression. By design, severe degradation of load carrying capability should not occur prior to Design Ultimate Load (DUL). While minor damage prior to DUL was anticipated, the integral stitching should not fail since this would allow a stiffener-skin delamination to progress rapidly and alter the transfer of load into the stiffeners. In addition, the stiffeners should not fracture because they are fundamental to structural integrity. Getting the best information from each AE sensor is a primary consideration because a sparse network of sensors is implemented. Sensitivity to stiffener-contiguous degradation is supported by sensors near the stiffeners, which increases the coverage per sensor via AE waveguide actions. Some sensors are located near potentially critical areas or "critical zones" as identified by numerical analyses. The approach is compared with the damage progression monitored by other techniques (e.g. ultrasonic C-scan).

Nonlinear Analysis and Post-Test Correlation for a Curved PRSEUS Panel

NASA Technical Reports Server (NTRS)

Gould, Kevin; Lovejoy, Andrew E.; Jegley, Dawn; Neal, Albert L.; Linton, Kim, A.; Bergan, Andrew C.; Bakuckas, John G., Jr.

2013-01-01

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept, developed by The Boeing Company, has been extensively studied as part of the National Aeronautics and Space Administration's (NASA s) Environmentally Responsible Aviation (ERA) Program. The PRSEUS concept provides a light-weight alternative to aluminum or traditional composite design concepts and is applicable to traditional-shaped fuselage barrels and wings, as well as advanced configurations such as a hybrid wing body or truss braced wings. Therefore, NASA, the Federal Aviation Administration (FAA) and The Boeing Company partnered in an effort to assess the performance and damage arrestments capabilities of a PRSEUS concept panel using a full-scale curved panel in the FAA Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility. Testing was conducted in the FASTER facility by subjecting the panel to axial tension loads applied to the ends of the panel, internal pressure, and combined axial tension and internal pressure loadings. Additionally, reactive hoop loads were applied to the skin and frames of the panel along its edges. The panel successfully supported the required design loads in the pristine condition and with a severed stiffener. The panel also demonstrated that the PRSEUS concept could arrest the progression of damage including crack arrestment and crack turning. This paper presents the nonlinear post-test analysis and correlation with test results for the curved PRSEUS panel. It is shown that nonlinear analysis can accurately calculate the behavior of a PRSEUS panel under tension, pressure and combined loading conditions.

Comparison of structural response and fatigue endurance of aircraft flap-like box structures subjected to acoustic loading

NASA Astrophysics Data System (ADS)

Xiao, Y.; White, R. G.; Aglietti, G. S.

2005-05-01

The results of an extensive test program to characterize the behavior of typical aircraft structures under acoustic loading and to establish their fatigue endurance are presented. The structures tested were the three flap-like box-type of structures. Each structure consisted of one flat (bottom) and one curved (top) stiffener stiffened skin panel, front, and rear spars, and ribs that divided the structures into three bays. The three structures, constructed from three different materials (aircraft standard aluminum alloy, Carbon Fibre Reinforced Plastic, and a Glass Fibre Metal Laminate, i.e., GLARE) had the same size and configuration, with only minor differences due to the use of different materials. A first set of acoustic tests with excitations of intensity ranging from 140 to 160 dB were carried out to obtain detailed data on the dynamic response of the three structures. The FE analysis of the structures is also briefly described and the results compared with the experimental data. The fatigue endurance of the structures was then determined using random acoustic excitation with an overall sound pressure level of 161 dB, and details of crack propagation are reported. .

Load monitoring of aerospace structures utilizing micro-electro-mechanical systems for static and quasi-static loading conditions

NASA Astrophysics Data System (ADS)

Martinez, M.; Rocha, B.; Li, M.; Shi, G.; Beltempo, A.; Rutledge, R.; Yanishevsky, M.

2012-11-01

The National Research Council Canada (NRC) has worked on the development of structural health monitoring (SHM) test platforms for assessing the performance of sensor systems for load monitoring applications. The first SHM platform consists of a 5.5 m cantilever aluminum beam that provides an optimal scenario for evaluating the ability of a load monitoring system to measure bending, torsion and shear loads. The second SHM platform contains an added level of structural complexity, by consisting of aluminum skins with bonded/riveted stringers, typical of an aircraft lower wing structure. These two load monitoring platforms are well characterized and documented, providing loading conditions similar to those encountered during service. In this study, a micro-electro-mechanical system (MEMS) for acquiring data from triads of gyroscopes, accelerometers and magnetometers is described. The system was used to compute changes in angles at discrete stations along the platforms. The angles obtained from the MEMS were used to compute a second, third or fourth order degree polynomial surface from which displacements at every point could be computed. The use of a new Kalman filter was evaluated for angle estimation, from which displacements in the structure were computed. The outputs of the newly developed algorithms were then compared to the displacements obtained from the linear variable displacement transducers connected to the platforms. The displacement curves were subsequently post-processed either analytically, or with the help of a finite element model of the structure, to estimate strains and loads. The estimated strains were compared with baseline strain gauge instrumentation installed on the platforms. This new approach for load monitoring was able to provide accurate estimates of applied strains and shear loads.

Sensitivity and specificity of eustachian tube function tests in adults.

PubMed

Doyle, William J; Swarts, J Douglas; Banks, Julianne; Casselbrant, Margaretha L; Mandel, Ellen M; Alper, Cuneyt M

2013-07-01

The study demonstrates the utility of eustachian tube (ET) function (ETF) test results for accurately assigning ears to disease state. To determine if ETF tests can identify ears with physician-diagnosed ET dysfunction (ETD) in a mixed population at high sensitivity and specificity and to define the interrelatedness of ETF test parameters. Through use of the forced-response, inflation-deflation, Valsalva, and sniffing tests, ETF was evaluated in 15 control ears of adult subjects after unilateral myringotomy (group 1) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (group 2). Data were analyzed using logistic regression including each parameter independently and then a step-down discriminant analysis including all ETF test parameters to predict group assignment. Factor analysis operating over all parameters was used to explore relatedness. ETF testing. ETF parameters for the forced response, inflation-deflation, Valsalva, and sniffing tests measured in 15 control ears of adult subjects after unilateral myringotomy (group 1) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (group 2). The discriminant analysis identified 4 ETF test parameters (Valsalva, ET opening pressure, dilatory efficiency, and percentage of positive pressure equilibrated) that together correctly assigned ears to group 2 at a sensitivity of 95% and a specificity of 83%. Individual parameters representing the efficiency of ET opening during swallowing showed moderately accurate assignments of ears to their respective groups. Three factors captured approximately 98% of the variance among parameters: the first had negative loadings of the ETF structural parameters; the second had positive loadings of the muscle-assisted ET opening parameters; and the third had negative loadings of the muscle-assisted ET opening parameters and positive loadings of the structural parameters. These results show that ETF tests can correctly assign individual ears to physician-diagnosed ETD with high sensitivity and specificity and that ETF test parameters can be grouped into structural-functional categories.

Projection Moire Interferometry for Rotorcraft Applications: Deformation Measurements of Active Twist Rotor Blades

NASA Technical Reports Server (NTRS)

Fleming, Gary A.; Soto, Hector L.; South, Bruce W.

2002-01-01

Projection Moire Interferometry (PMI) has been used during wind tunnel tests to obtain azimuthally dependent blade bending and twist measurements for a 4-bladed Active Twist Rotor (ATR) system in simulated forward flight. The ATR concept offers a means to reduce rotor vibratory loads and noise by using piezoelectric active fiber composite actuators embedded in the blade structure to twist each blade as they rotate throughout the rotor azimuth. The twist imparted on the blades for blade control causes significant changes in blade loading, resulting in complex blade deformation consisting of coupled bending and twist. Measurement of this blade deformation is critical in understanding the overall behavior of the ATR system and the physical mechanisms causing the reduction in rotor loads and noise. PMI is a non-contacting, video-based optical measurement technique capable of obtaining spatially continuous structural deformation measurements over the entire object surface within the PMI system field-of-view. When applied to rotorcraft testing, PMI can be used to measure the azimuth-dependent blade bending and twist along the full span of the rotor blade. This paper presents the PMI technique as applied to rotorcraft testing, and provides results obtained during the ATR tests demonstrating the PMI system performance. PMI measurements acquired at select blade actuation conditions generating minimum and maximum rotor loads are provided to explore the interrelationship between rotor loads, blade bending, and twist.

The design of low cost structures for extensive ground arrays

NASA Technical Reports Server (NTRS)

Franklin, H. A.; Leonard, R. S.

1980-01-01

The development of conceptual designs of solar array support structures and their foundations including considerations of the use of concrete, steel, aluminum, or timber are reported. Some cost trends were examined by varying selected parameters to determine optimum configurations. Detailed civil/structural design criteria were developed. Using these criteria, eight detailed designs for support structures and foundations were developed and cost estimates were made. As a result of the study wind was identified as the major loading experienced by these low height structures, whose arrays are likely to extend over large tracts of land. Proper wind load estimating is considered essential to developing realistic structural designs and achieving minimum cost support structures. Wind tunnel testing of a conceptual array field was undertaken and some of the resulting wind design criteria are presented. The SPS rectenna system designs may be less sensitive to wind load estimates, but consistent design criteria remain important.

Shuttle Program Loads Integration: Going From Concept to Operations and Staying Successful

NASA Technical Reports Server (NTRS)

Bernstein, Karen; James, George; Mackey, alden; Murphy, Neil C.; Brolliar, Steve

2011-01-01

From the beginning of the Shuttle Program to its end, integrated loads and dynamics analyses and tests have been critical in shaping the vehicle design and operational decisions for NASA and its customers. Starting with scaled models and simple mathematical simulations of the structural dynamics, engineers defined the required structural stiffness and predicted the limit loads for each element of the system. Early structural tests provided reasonable confidence that the models and predictions were good. The first launch of the Space Shuttle brought surprises, though, when the ignition overpressure event caused a forward fuel tank support strut to buckle, among several unexpected effects. The launch pad and other ground equipment became an integral part of the system integration, especially where the acoustic and pressure environments of ignition and lift-off were concerned. Following the Challenger accident, operating limits were changed in response to new understandings of how the integrated system performed. Controlling loads while maximizing performance was a key tenet of the Performance Enhancement design process, which enabled construction of the International Space Station. During the return to flight after the Columbia accident, engineers grew to understand that loads during the roll maneuver were also important to the vehicle s structural margin and life. At this point the crawler transport from the Vehicle Assembly Building to the launch pad also became a part of the integrated loads analysis. Even in the last years of the Space Shuttle Program, new data still provided interesting insights into this complicated and fascinating spaceship. This paper will present some examples of the important findings by the team of specialists that supported the Integrated Loads and Dynamics Panel for the Space Shuttle Program.

Use of Flexible Body Coupled Loads in Assessment of Day of Launch Flight Loads

NASA Technical Reports Server (NTRS)

Starr, Brett R.; Yunis, Isam; Olds, Aaron D.

2011-01-01

A Day of Launch flight loads assessment technique that determines running loads calculated from flexible body coupled loads was developed for the Ares I-X Flight Test Vehicle. The technique was developed to quantify DOL flight loads in terms of structural load components rather than the typically used q-alpha metric to provide more insight into the DOL loads. In this technique, running loads in the primary structure are determined from the combination of quasi-static aerodynamic loads and dynamic loads. The aerodynamic loads are calculated as a function of time using trajectory parameters passed from the DOL trajectory simulation and are combined with precalculated dynamic loads using a load combination equation. The potential change in aerodynamic load due to wind variability during the countdown is included in the load combination. In the event of a load limit exceedance, the technique allows the identification of what load component is exceeded, a quantification of how much the load limit is exceeded, and where on the vehicle the exceedance occurs. This technique was used to clear the Ares I-X FTV for launch on October 28, 2009. This paper describes the use of coupled loads in the Ares I-X flight loads assessment and summarizes the Ares I-X load assessment results.

Reliability demonstration test for load-sharing systems with exponential and Weibull components

PubMed Central

Hu, Qingpei; Yu, Dan; Xie, Min

2017-01-01

Conducting a Reliability Demonstration Test (RDT) is a crucial step in production. Products are tested under certain schemes to demonstrate whether their reliability indices reach pre-specified thresholds. Test schemes for RDT have been studied in different situations, e.g., lifetime testing, degradation testing and accelerated testing. Systems designed with several structures are also investigated in many RDT plans. Despite the availability of a range of test plans for different systems, RDT planning for load-sharing systems hasn’t yet received the attention it deserves. In this paper, we propose a demonstration method for two specific types of load-sharing systems with components subject to two distributions: exponential and Weibull. Based on the assumptions and interpretations made in several previous works on such load-sharing systems, we set the mean time to failure (MTTF) of the total system as the demonstration target. We represent the MTTF as a summation of mean time between successive component failures. Next, we introduce generalized test statistics for both the underlying distributions. Finally, RDT plans for the two types of systems are established on the basis of these test statistics. PMID:29284030

Reliability demonstration test for load-sharing systems with exponential and Weibull components.

PubMed

Xu, Jianyu; Hu, Qingpei; Yu, Dan; Xie, Min

2017-01-01

Conducting a Reliability Demonstration Test (RDT) is a crucial step in production. Products are tested under certain schemes to demonstrate whether their reliability indices reach pre-specified thresholds. Test schemes for RDT have been studied in different situations, e.g., lifetime testing, degradation testing and accelerated testing. Systems designed with several structures are also investigated in many RDT plans. Despite the availability of a range of test plans for different systems, RDT planning for load-sharing systems hasn't yet received the attention it deserves. In this paper, we propose a demonstration method for two specific types of load-sharing systems with components subject to two distributions: exponential and Weibull. Based on the assumptions and interpretations made in several previous works on such load-sharing systems, we set the mean time to failure (MTTF) of the total system as the demonstration target. We represent the MTTF as a summation of mean time between successive component failures. Next, we introduce generalized test statistics for both the underlying distributions. Finally, RDT plans for the two types of systems are established on the basis of these test statistics.

Load Diffusion in Composite and Smart Structures

NASA Technical Reports Server (NTRS)

Horgan, C. O.

2003-01-01

The research carried out here builds on our previous NASA supported research on the general topic of edge effects and load diffusion in composite structures. Further fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for the multi-functional large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Some specific problems recently considered were those of end effects in smart materials and structures, study of the stress response of pressurized linear piezoelectric cylinders for both static and steady rotating configurations, an analysis of the effect of pre-stressing and pre-polarization on the decay of end effects in piezoelectric solids and investigation of constitutive models for hardening rubber-like materials. Our goal in the study of load diffusion is the development of readily applicable results for the decay lengths in terms of non-dimensional material and geometric parameters. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses. The decay behavior of stresses and other field quantities provides a significant aid towards this process. The analysis is also amenable to parameter study with a large parameter space and should be useful in structural tailoring studies. Special purpose analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and in assessing results from general purpose finite element analyses. For example, a rational basis is needed in choosing where to use three-dimensional to two-dimensional transition finite elements in analyzing stiffened plates and shells. The decay behavior of stresses and other field quantities furnished by this research provides a significant aid towards this element transition issue. A priori knowledge of the extent of boundary-layers induced by edge effects is also useful in determination of the instrumentation location in structural verification tests or in material characterization tests.

The high velocity impact loading on symmetrical and woven hybrid composite laminates

NASA Astrophysics Data System (ADS)

Jin, Martin; Richardson, Mel; Zhang, Zhong Yi

2007-07-01

Space structures use fibre composite materials, due to their lightweight. This paper examines the impact response of symmetrical and hybrid composite laminates. Special attention is given to the stacking sequences used. The experimental study of structures has always provided a major contribution to our understanding. Even with the formidable growth in the use and capacity of computing power the need for experimental measurement is as compelling as ever. The design of hybrid composite structures is complicated by the number of design variables and the interaction of the constituents is the composite system. Since it is desirable to experimentally test the design and it is not practical to test a full scale model, the structural/material similitude concept is used to create a small scale model with a similar structural response. In the current study, experimental investigations were carried out to determine the response of four different combinations of hybrid laminates to low-velocity impact loading using an instrumented impact testing machine. Hybrid laminates were fabricated with twill weave carbon fabric and plain weave S2-glass fabric using vacuum assisted resin molding process with SC-15 epoxy resin system. Response of carbon/epoxy and glass/epoxy laminates was also investigated to compare with that of hybrid samples. Square laminates of size 100 mm and nominal thickness of 3 mm were subjected to low-velocity impact loading at four energy levels of 10, 20, 30 and 40 J. Results of the study indicate that there is considerable improvement in the load carrying capability of hybrid composites as compared to carbon/epoxy laminates with slight reduction in stiffness.

Structural Finite Element Model Updating Using Vibration Tests and Modal Analysis for NPL footbridge - SHM demonstrator

NASA Astrophysics Data System (ADS)

Barton, E.; Middleton, C.; Koo, K.; Crocker, L.; Brownjohn, J.

2011-07-01

This paper presents the results from collaboration between the National Physical Laboratory (NPL) and the University of Sheffield on an ongoing research project at NPL. A 50 year old reinforced concrete footbridge has been converted to a full scale structural health monitoring (SHM) demonstrator. The structure is monitored using a variety of techniques; however, interrelating results and converting data to knowledge are not possible without a reliable numerical model. During the first stage of the project, the work concentrated on static loading and an FE model of the undamaged bridge was created, and updated, under specified static loading and temperature conditions. This model was found to accurately represent the response under static loading and it was used to identify locations for sensor installation. The next stage involves the evaluation of repair/strengthening patches under both static and dynamic loading. Therefore, before deliberately introducing significant damage, the first set of dynamic tests was conducted and modal properties were estimated. The measured modal properties did not match the modal analysis from the statically updated FE model; it was clear that the existing model required updating. This paper introduces the results of the dynamic testing and model updating. It is shown that the structure exhibits large non-linear, amplitude dependant characteristics. This creates a difficult updating process, but we attempt to produce the best linear representation of the structure. A sensitivity analysis is performed to determine the most sensitive locations for planned damage/repair scenarios and is used to decide whether additional sensors will be necessary.

Threats to Aircraft Structural Safety Including a Compendium of Selected Structural Accidents/Incidents

DTIC Science & Technology

2010-03-01

stressed radius at the speed brake cut-out in the lower wing surface, the KC-135 (Appendix B.2) was fatigue tested to 55,000 cyclic test hours without...A20]. Post accident flight tests revealed that deployment of the speed brakes during landing role produced a horizontal load spectrum, which was

NDE evidence for the damage arrestment performance of PRSEUS composite cube during high-pressure load test

NASA Astrophysics Data System (ADS)

Johnston, Patrick H.; Parker, F. Raymond

2014-02-01

As an approach to light-weight, cost-effective and manufacturable structures required to enable the hybrid wing body aircraft, The Boeing Company, Inc. and NASA have developed the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. A PRSEUS pressure cube was developed as a risk reduction test article to examine a new integral cap joint concept as part of a building block approach for technology development of the PRSEUS concept. The overall specimen strength exceeded the 18.4 psi load requirement as testing resulted in the cube reaching a final pressure load of around 48 psi prior to catastrophic failure. The cube pressure test verified that the joints and structure were capable of sustaining the required loads, and represented the first testing of joined PRSEUS structure. This paper will address the damage arrestment performance of the stitched PRSEUS structure. Following catastrophic failure of the cube, ultrasonic pulse-echo inspection found that the localized damage, surrounding a barely-visible impact damage site, did not change noticeably between just after impact and catastrophic failure of the cube, and did not play a role in the catastrophic failure event. Ultrasonic inspection of the remaining intact cube panels presented three basic types of indications: delaminations between laminae parallel to the face sheets, lying between face sheet and tear strap layers, or between tear strap and flange layers; delaminations above the noodles of stringers, frames or integral caps, lying within face sheet or tear strap layers; and delaminations between the laminae in the inner fillets of the integral caps, where pulloff stresses were expected to be highest. Delaminations of all three types were predominantly contained by the first row of stitches encountered. For the small fraction of delaminations extending beyond the first row of stitches, all were contained by the second stitch row.

Application of inflatable aeroshell structures for Entry Descent and Landing

NASA Astrophysics Data System (ADS)

Jurewicz, David; Lichodziejewski, Leo; Tutt, Ben; Gilles, Brian; Brown, Glen

Future space missions will require improvements in the Entry, Descent, and Landing (EDL) phases of the mission architecture. The focus of this paper is to discuss recent advances in analysis, fabrication techniques, ground testing, and flight testing of a stacked torus Hypersonic Inflatable Aerodynamic Decelerator (HIAD) and its application to the future of EDL. The primary structure of a stacked torus HIAD consists of nested inflatable tori of increasing major diameter bonded and strapped to form a rigid structure after inflation. The underlying structure of the decelerator is covered with a flexible Thermal Protection System (TPS) capable of high heat flux. The inflatable aeroshell and TPS are packed around a centerbody within the launch fairing and deployed prior to atmospheric reentry. Recent fabrication of multiple HIADs between 3 and 6 meters has led to significant advances in process control and validation of the scalability of the technology. Progress has been made in generating and validating LS-DYNA FEA models to replicate flight loading in addition to analytical models of substructures. Coupon and component testing has improved the validation of modeling techniques and assumptions at the subsystem level. A ground testing campaign at the National Full-Scale Aerodynamics Center (NFAC) wind tunnel at NASA Ames Research center generated substantial aerodynamic and loading data to validate full system modeling with comparable dynamic pressures to a hypersonic reentry. The Inflatable Reentry Vehicle - 3 (IRVE-3) sounding rocket flight test was conducted with NASA Langley Research Center in July 2012. The IRVE-3 mission verified the structural and thermal performance of the stacked torus configuration. Further development of the stacked torus configuration is currently being conducted to increase the thermal capability, deceleration loads, and understanding of the interactions and effects of constituent components. The results of this research have expanded the- feasible flight envelope of stacked torus HIAD designs over a range of sizes, loading conditions, and heating.

NDE Evidence for the Damage Arrestment Performance of PRSEUS Composite Cube During High-Pressure Load Test

NASA Technical Reports Server (NTRS)

Johnston, Patrick H.; Parker, F. Raymond

2013-01-01

As an approach to light-weight, cost-effective and manufacturable structures required to enable the hybrid wing body aircraft, The Boeing Company, Inc. and NASA have developed the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. A PRSEUS pressure cube was developed as a risk reduction test article to examine a new integral cap joint concept as part of a building block approach for technology development of the PRSEUS concept. The overall specimen strength exceeded the 18.4 psi load requirement as testing resulted in the cube reaching a final pressure load of around 48 psi prior to catastrophic failure. The cube pressure test verified that the joints and structure were capable of sustaining the required loads, and represented the first testing of joined PRSEUS structure. This paper will address the damage arrestment performance of the stitched PRSEUS structure. Following catastrophic failure of the cube, ultrasonic pulse-echo inspection found that the localized damage, surrounding a barely-visible impact damage site, did not change noticeably between just after impact and catastrophic failure of the cube, and did not play a role in the catastrophic failure event. Ultrasonic inspection of the remaining intact cube panels presented three basic types of indications: delaminations between laminae parallel to the face sheets, lying between face sheet and tear strap layers, or between tear strap and flange layers; delaminations above the noodles of stringers, frames or integral caps, lying within face sheet or tear strap layers; and delaminations between the laminae in the inner fillets of the integral caps, where pulloff stresses were expected to be highest. Delaminations of all three types were predominantly contained by the first row of stitches encountered. For the small fraction of delaminations extending beyond the first row of stitches, all were contained by the second stitch row.

Investigation of the Structural Behavior and Maximum Bending Strength of Six Multiweb Beams with Three Types of Webs

NASA Technical Reports Server (NTRS)

Peterson, James P.; Bruce, Walter E., Jr.

1959-01-01

The results of bending tests on six multiweb beams of optimum weight-strength design are presented. The internal structure of the beams consisted of various combinations of two types of full-depth solid webs and a post-stringer web. The observed structural behavior, buckling load, and failing load of the beams are compared with results obtained by the use of existing methods of analysis and found to be quite predictable.

The development of test methodology for testing glassy materials

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.

1987-01-01

The inherent brittleness of glass invariably leads to a large variability in strength data and a time dependence in strength (i.e., static fatigue). Loading rate plays a large role in strength values. Glass is found to be weaker when supporting loads over long periods as compared to glass which undergoes rapid loading. In this instance the purpose of rapid loading is to fail the glass before any significant crack growth occurs. However, a decrease in strength occurs with a decrease in loading rate, pursuant to substantial crack extension. These properties complicate the structural design allowable for the utilization of glass components in applications such as mirrors for the Space Telescope and AXAF for Spacelab and the space station.

Utilizing Photogrammetry and Strain Gage Measurement to Characterize Pressurization of Inflatable Modules

NASA Technical Reports Server (NTRS)

Mohammed, Anil

2011-01-01

This paper focuses on integrating a large hatch penetration into inflatable modules of various constructions. This paper also compares load predictions with test measurements. The strain was measured by utilizing photogrammetric methods and strain gages mounted to select clevises that interface with the structural webbings. Bench testing showed good correlation between strain data collected from an extensometer and photogrammetric measurements, even when the material transitioned from the low load to high load strain region of the curve. The full-scale torus design module showed mixed results as well in the lower load and high strain regions. After thorough analysis of photogrammetric measurements, strain gage measurements, and predicted load, the photogrammetric measurements seem to be off by a factor of two.

Fracture behavior of single-structure fiber-reinforced composite restorations

PubMed Central

Nagata, Kohji; Garoushi, Sufyan K.; Vallittu, Pekka K.; Wakabayashi, Noriyuki; Takahashi, Hidekazu; Lassila, Lippo V. J.

2016-01-01

Abstract Objective: The applications of single-structure fiber-reinforced composite (FRC) in restorative dentistry have not been well reported. This study aimed to clarify the static mechanical properties of anterior crown restorations prepared using two types of single-structure FRC. Materials and methods : An experimental crown restoration was designed for an upper anterior incisor. The restorations were made from IPS Empress CAD for CEREC (Emp), IPS e.max® CAD (eMx), experimental single-structure all-FRC (a-FRC), Filtek™ Supreme XTE (XTE), and commercially available single-structure short-FRC (everX Posterior™) (n = 8 for each material) (s-FRC). The a-FRC restorations were prepared from an experimental FRC blank using a computer-aided design and manufacturing (CAD/CAM) device. A fracture test was performed to assess the fracture load, toughness, and failure mode. The fracture loads were vertically applied on the restorations. The surface micromorphology of the FRC restorations was observed by scanning electron microscopy (SEM). The data were analyzed by analysis of variance (p = .05) followed by Tukey's test. Results : s-FRC showed the highest mean fracture load (1145.0 ± 89.6 N) and toughness (26.2 ± 5.8 Ncm) among all the groups tested. With regard to the micromorphology of the prosthetic surface, local crushing of the fiberglass was observed in s-FRC, whereas chopped fiberglass was observed in a-FRC. Conclusions : The restorations made of short-FRC showed a higher load-bearing capacity than those made of the experimental all-FRC blanks for CAD/CAM. The brittle-like fractures were exhibited in the recent dental esthetic materials, while local crushing fractures were shown for single-structure FRC restorations. PMID:28642921

Experimental Analysis of Dynamic Effects of FRP Reinforced Masonry Vaults.

PubMed

Corradi, Marco; Borri, Antonio; Castori, Giulio; Coventry, Kathryn

2015-11-27

An increasing interest in the preservation of historic structures has produced a need for new methods for reinforcing curved masonry structures, such as arches and vaults. These structures are generally very ancient, have geometries and materials which are poorly defined and have been exposed to long-term historical movements and actions. Consequently, they are often in need of repair or reinforcement. This article presents the results of an experimental study carried out in the laboratory and during on-site testing to investigate the behaviour of brick masonry vaults under dynamic loading strengthened with FRPs (Fiber Reinforced Polymers). For the laboratory tests, the brick vaults were built with solid sanded clay bricks and weak mortar and were tested under dynamic loading. The experimental tests were designed to facilitate analysis of the dynamic behaviour of undamaged, damaged and reinforced vaulted structures. On-site tests were carried out on an earthquake-damaged thin brick vault of an 18th century aristocratic residence in the city of L'Aquila, Italy. The provision of FRP reinforcement is shown to re-establish elastic behavior previously compromised by time induced damage in the vaults.

Experimental Analysis of Dynamic Effects of FRP Reinforced Masonry Vaults

PubMed Central

Corradi, Marco; Borri, Antonio; Castori, Giulio; Coventry, Kathryn

2015-01-01

An increasing interest in the preservation of historic structures has produced a need for new methods for reinforcing curved masonry structures, such as arches and vaults. These structures are generally very ancient, have geometries and materials which are poorly defined and have been exposed to long-term historical movements and actions. Consequently, they are often in need of repair or reinforcement. This article presents the results of an experimental study carried out in the laboratory and during on-site testing to investigate the behaviour of brick masonry vaults under dynamic loading strengthened with FRPs (Fiber Reinforced Polymers). For the laboratory tests, the brick vaults were built with solid sanded clay bricks and weak mortar and were tested under dynamic loading. The experimental tests were designed to facilitate analysis of the dynamic behaviour of undamaged, damaged and reinforced vaulted structures. On-site tests were carried out on an earthquake-damaged thin brick vault of an 18th century aristocratic residence in the city of L’Aquila, Italy. The provision of FRP reinforcement is shown to re-establish elastic behavior previously compromised by time induced damage in the vaults. PMID:28793697

The failure mode of two reabsorbable fixation systems: Swivelock with Fibertape versus Bio-Corkscrew with Fiberwire in bovine rotator cuff.

PubMed

De Carli, Angelo; Lanzetti, Riccardo Maria; Monaco, Edoardo; Labianca, Luca; Mossa, Luigi; Ferretti, Andrea; Feretti, Andrea

2012-11-01

Despite technical advances in rotator cuff surgery, recurrent or persistent defects in the repaired tendon continue to occur. The improved strength of sutures and suture anchors has shown that the most common site of failure is the suture-tendon interface. The purpose of this study was to compare two different types of repair under both cyclic and load-to-failure conditions. The hypothesis is that the use of a fixation system with knotless anchor and taped suture results in better biomechanical performance, under both cyclic and load-to-failure conditions. Thirty bovine shoulder specimens were randomly assigned to two group tests: the Swivelock 5-mm anchor with Fibertape (Group A) and the Bio-Corkscrew 5 mm with Fiberwire (Group B). We simulated the reconstruction of a rotator cuff tear with a single-row technique, performing a tenodesis with types A and B fixation. Each specimen underwent cyclic testing from 5 to 30 N for 30 cycles, followed by load-to-failure testing, in order to calculate the ultimate failure load (UFL). Load-to-failure tests revealed a significantly higher UFL in Group A than in Group B. Wire fixing failed at the anchor loop whereas tape fixing failed at the sutures, suture-tendon interface, and anchors. Cyclic testing revealed no significantly greater slippage between the two groups. Stiffness values were not statistically significantly different. In all cases, tendons remained intact until the end of the cyclic testing. The tape structure is biomechanically stronger than the wire structure.

Protective Skins for Composite Airliners

NASA Technical Reports Server (NTRS)

Johnson, Vicki S.; Boone, Richard L.; Jones, Shannon; Pendse, Vandana; Hayward, Greg

2014-01-01

Traditional composite aircraft structures are designed for load bearing and then overdesigned for impact damage and hot humid environments. Seeking revolutionary improvement in the performance and weight of composite structures, Cessna Aircraft Company, with sponsorship from the NASA Fundamental Aeronautics Program/Subsonic Fixed Wing Project, has developed and tested a protective skin concept which would allow the primary composite structure to carry only load and would meet the impact, hot and humid, and other requirements through protective skins. A key requirement for the protective skins is to make any impact damage requiring repair visible. Testing from the first generation of skins helped identify the most promising materials which were used in a second generation of test articles. This report summarizes lessons learned from the first generation of protective skins, the design and construction of the second-generation test articles, test results from the second generation for impact, electromagnetic effects, aesthetics and smoothing, thermal, and acoustic (for the first time), and an assessment of the feasibility of the protective skin concept.

39. VIEW OF CHRYSLER WORKERS LOADING A SATURN IB BOOSTER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

39. VIEW OF CHRYSLER WORKERS LOADING A SATURN IB BOOSTER INTO THE EAST POSITION ON THE STATIC TEST TOWER. AS THE MAIN CONTRACTOR OF THE SATURN IB BOOSTER, CHRYSLER TOOK OVER OPERATIONS OF THE EAST POSITION OF THE STATIC TEST TOWER IN 1963. THAT SAME YEAR, THE WEST POSITION OF THE TEST TOWER WAS MODIFIED (AS SEEN IN THE PHOTO) FOR RESEARCH AND DEVELOPMENT TESTS OF THE SATURN V BOOSTER'S ENGINE, THE F-1. MARCH 1963, MSFC PHOTO LAB. - Marshall Space Flight Center, Saturn Propulsion & Structural Test Facility, East Test Area, Huntsville, Madison County, AL

Distributed cable sensors with memory feature for post-disaster damage assessment

NASA Astrophysics Data System (ADS)

Chen, Genda; McDaniel, Ryan D.; Pommerenke, David J.; Sun, Shishuang

2005-05-01

A new design of distributed crack sensors is presented for the condition assessment of reinforced concrete (RC) structures during and immediately after an earthquake event. This study is mainly focused on the performance of cable sensors under dynamic loading, particularly their ability to memorize the crack history of an RC member. This unique memory feature enables the post-earthquake condition assessment of structural members such as RC columns, in which the earthquake-induced cracks are closed immediately after an earthquake event due to gravity loads and they are visually undetectable. Factors affecting the onset of the memory feature were investigated experimentally with small-scale RC beams under cyclic loading. Test results indicated that both crack width and the number of loading cycles were instrumental in the onset of the memory feature of cable sensors. Practical issues related to dynamic acquisition with the sensors were discussed. The sensors were proven to be fatigue resistant from the shake table tests of RC columns. They continued to show useful signal after the columns can no longer support additional loads.

Analysis and Testing of a Metallic Repair Applicable to Pressurized Composite Aircraft Structure

NASA Technical Reports Server (NTRS)

Przekop, Adam; Jegley, Dawn C.; Rouse, Marshall; Lovejoy, Andrew E.

2014-01-01

Development of repair technology is vital to the long-term application of new structural concepts on aircraft structure. The design, analysis, and testing of a repair concept applicable to a stiffened composite panel based on the Pultruded Rod Stitched Efficient Unitized Structure was recently completed. The damage scenario considered was a mid-bay to mid-bay saw-cut with a severed stiffener, flange, and skin. A bolted metallic repair was selected so that it could be easily applied in the operational environment. The present work describes results obtained from tension and pressure panel tests conducted to validate both the repair concept and finite element analysis techniques used in the design effort. Simulation and experimental strain and displacement results show good correlation, indicating that the finite element modeling techniques applied in the effort are an appropriate compromise between required fidelity and computational effort. Static tests under tension and pressure loadings proved that the proposed repair concept is capable of sustaining load levels that are higher than those resulting from the current working stress allowables. Furthermore, the pressure repair panel was subjected to 55,000 pressure load cycles to verify that the design can withstand a life cycle representative for a transport category aircraft. These findings enable upward revision of the stress allowables that had been kept at an overly-conservative level due to concerns associated with repairability of the panels. This conclusion enables more weight efficient structural designs utilizing the composite concept under investigation.

Flat H Redundant Frangible Joint Development

NASA Technical Reports Server (NTRS)

Brown, Chris

2016-01-01

Orion and Commercial Crew Program (CCP) Partners have chosen to use frangible joints for certain separation events. The joints currently available are zero failure tolerant and will be used in mission safety applications. The goal is to further develop a NASA designed redundant frangible joint that will lower flight risk and increase reliability. FY16 testing revealed a successful design in subscale straight test specimens that gained efficiency and supports Orion load requirements. Approach / Innovation A design constraint is that the redundant joint must fit within the current Orion architecture, without the need for additional vehicle modification. This limitation required a design that changed the orientation of the expanding tube assemblies (XTAs), by rotating them 90deg from the standard joint configuration. The change is not trivial and affects the fracture mechanism and structural load paths. To address these changes, the design incorporates cantilevered arms on the break plate. The shock transmission and expansion of the XTA applies force to these arms and creates a prying motion to push the plate walls outward to the point of structural failure at the notched section. The 2014 test design revealed that parts could slip during functioning wasting valuable energy needed to separate the structure with only a single XTA functioning. Dual XTA functioning fully separated the assembly showing a discrepancy can be backed up with redundancy. Work on other fully redundant systems outside NASA is limited to a few patents that have not been subjected to functionality testing Design changes to prevent unwanted slippage (with ICA funding in 2015) showed success with a single XTA. The main goal for FY 2016 was to send the new Flat H RFJ to WSTF where single XTA test failures occurred back in 2014. The plan was to gain efficiency in this design by separating the Flat H RFJ with thicker ligaments with dimensions baselined in 2014. Other modifications included geometry changes to better disperse loads paths and to minimize air gaps. The design additionally added more structural strength to enhance the structural limits in static loads testing. The design also implemented a smoother load line through the assembly. Results / Knowledge Gained The new Flat H RFJ successfully fractured at WSTF with thicker ligaments and lower cord size. Where failure to separate occurred earlier, there is now excessive energy available for structural separation. The new challenge to provide some structural support to prevent secondary fracturing of the break plate remains to be completed. This future work is being funded by the JSC Engineering Directorate in 2017 to elevate the TRL on curved Flat H RFJs that configure with the Orion Service Panel Separation. Additional funding from JSC Engineering will provide new design testing to avoid secondary fracturing.

Experimental Investigations on Axially and Eccentrically Loaded Masonry Walls

NASA Astrophysics Data System (ADS)

Keshava, Mangala; Raghunath, Seshagiri Rao

2017-12-01

In India, un-reinforced masonry walls are often used as main structural components in load bearing structures. Indian code on masonry accounts the reduction in strength of walls by using stress reduction factors in its design philosophy. This code was introduced in 1987 and reaffirmed in 1995. The present study investigates the use of these factors for south Indian masonry. Also, with the gaining popularity in block work construction, the aim of this study was to find out the suitability of these factors given in the Indian code to block work masonry. Normally, the load carrying capacity of masonry walls can be assessed in three ways, namely, (1) tests on masonry constituents, (2) tests on masonry prisms and (3) tests on full-scale wall specimens. Tests on bricks/blocks, cement-sand mortar, brick/block masonry prisms and 14 full-scale brick/block masonry walls formed the experimental investigation. The behavior of the walls was investigated under varying slenderness and eccentricity ratios. Hollow concrete blocks normally used as in-fill masonry can be considered as load bearing elements as its load carrying capacity was found to be high when compared to conventional brick masonry. Higher slenderness and eccentricity ratios drastically reduced the strength capacity of south Indian brick masonry walls. The reduction in strength due to slenderness and eccentricity is presented in the form of stress reduction factors in the Indian code. These factors obtained through experiments on eccentrically loaded brick masonry walls was lower while that of brick/block masonry under axial loads was higher than the values indicated in the Indian code. Also the reduction in strength is different for brick and block work masonry thus indicating the need for separate stress reduction factors for these two masonry materials.

Testing of a Stitched Composite Large-Scale Multi-Bay Pressure Box

NASA Technical Reports Server (NTRS)

Jegley, Dawn; Rouse, Marshall; Przekop, Adam; Lovejoy, Andrew

2016-01-01

NASA has created the Environmentally Responsible Aviation (ERA) Project to develop technologies to reduce aviation's impact on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe to enable the introduction of unconventional aircraft configurations. NASA and The Boeing Company have worked together to develop a structural concept that is lightweight and an advancement beyond state-of-the-art composite structures. The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is an integrally stiffened panel design where elements are stitched together. The PRSEUS concept is designed to maintain residual load carrying capabilities under a variety of damage scenarios. A series of building block tests were evaluated to explore the fundamental assumptions related to the capability and advantages of PRSEUS panels. The final step in the building block series is an 80%-scale pressure box representing a portion of the center section of a Hybrid Wing Body (HWB) transport aircraft. The testing of this article under maneuver load and internal pressure load conditions is the subject of this paper. The experimental evaluation of this article, along with the other building block tests and the accompanying analyses, has demonstrated the viability of a PRSEUS center body for the HWB vehicle. Additionally, much of the development effort is also applicable to traditional tube-and-wing aircraft, advanced aircraft configurations, and other structures where weight and through-the-thickness strength are design considerations.

Structural fire design : wood

Treesearch

E. L. Schaffer

Analytical procedures to predict the fire endurance of structural wood members have been developed worldwide. This research is reviewed for capability to predict the results of tests in North America and what considerations are necessary to apply the information here. Critical research needs suggested include: (1) Investigation of load levels used in reported tests,...

Multiplicity Control in Structural Equation Modeling: Incorporating Parameter Dependencies

ERIC Educational Resources Information Center

Smith, Carrie E.; Cribbie, Robert A.

2013-01-01

When structural equation modeling (SEM) analyses are conducted, significance tests for all important model relationships (parameters including factor loadings, covariances, etc.) are typically conducted at a specified nominal Type I error rate ([alpha]). Despite the fact that many significance tests are often conducted in SEM, rarely is…

Damage and failure behavior of metal matrix composites under biaxial loads

NASA Astrophysics Data System (ADS)

Kirkpatrick, Steven Wayne

Metal matrix composites (MMCs) are being considered for increased use in structures that require the ductility and damage tolerance of the metal matrix and the enhanced strength and creep resistance at elevated temperatures of high performance fibers. Particularly promising for advanced aerospace engines and airframes are SiC fiber/titanium matrix composites (TMCs). A large program was undertaken in the Air Force to characterize the deformation and failure behaviors of TMCs and to develop computational models that can be used for component design. The effort reported here focused on a SiC SCS-6/Timetal 21S composite under biaxial loading conditions. Biaxial loading conditions are important because multiaxial stresses have been shown to influence the strength and ductility of engineering materials and, in general, structural components are subjected to multiaxial loads. The TMC material response, including stress-strain curves and failure surfaces, was measured using a combination of off-axis uniaxial tension and compression tests and biaxial cruciform tests. The off-axis tests produce combinations of in-plane tension, compression, and shear stresses, the mix of which are controlled by the relative angle between the fiber and specimen axes. The biaxial cruciform tests allowed independent control over the tensile or compressive loads in the fiber and transverse directions. The results of these characterization tests were used to develop a microstructural constitutive model and failure criteria. The basis of the micromechanical constitutive model is a representative unit volume of the MMC with a periodic array of fibers. The representative unit volume is divided into a fiber and three matrix cells for which the microstructural equilibrium and compatibility equations can be analyzed. The resulting constitutive model and associated failure criteria can be used to predict the material behavior under general loading conditions.

Test Plan. GCPS Task 4, subtask 4.2 thrust structure development

NASA Astrophysics Data System (ADS)

Greenberg, H. S.

1994-09-01

The Single Stage To Orbit (SSTO) vehicle is designed to lift off from a vertical position, go into orbit, return to earth for a horizontal landing, and be reusable for the next mission. (NASA baseline only) In order to meet its performance goals, the SSTO relies on light weight structure and the use of 8 tri-propellant engines. These engines are mounted to the thrust structure. This test plan addresses selection of the material for this structure, and the integrity of the design through testing of elements and a full-scale subcomponent. This test plan supports the development of the design for an advanced composite thrust structure for a Single Stage to Orbit manned, heavy launch vehicle. The thrust structure is designed to transmit very high thrust loads from the engines to the rest of the vehicle (see Figure 1 ). The thrust structure will also be used for primary attachment of the twin vertical tails and possibly act as the aft attach point for the wing. The combination of high loading, high vibration, long service life and high acoustic environments will need to be evaluated by tests. To minimize design risk, a building block approach will be used. We will first screen materials to determine which materials show the most promise for this application. Factors in this screening will be the suitability of these materials for chosen design concepts, particularly concerning specific strength, environmental compatibility and applicability to fabrication processes. Next we will characterize two material systems that will be used in the design; the characterization will allow us to generate preliminary design data that will be used for the analysis. Element testing will be performed to evaluate critical structural locations under load. Final testing on the full scale test article will be performed to verify the design and to demonstrate predictability of the analysis. Additionally, risks associated with fabricating full scale thrust structures will be reduced through testing activities. One of the major concerns that stems from full scale fabrication is the realities of size and the associated complexities of handling, manufacturing, and assembly. The need exists to fabricate, assemble and test_representative joint specimens to achieve_confidence in the design and manufacturing technologies being proposed.

Test Plan. GCPS Task 4, subtask 4.2 thrust structure development

NASA Technical Reports Server (NTRS)

Greenberg, H. S.

1994-01-01

The Single Stage To Orbit (SSTO) vehicle is designed to lift off from a vertical position, go into orbit, return to earth for a horizontal landing, and be reusable for the next mission. (NASA baseline only) In order to meet its performance goals, the SSTO relies on light weight structure and the use of 8 tri-propellant engines. These engines are mounted to the thrust structure. This test plan addresses selection of the material for this structure, and the integrity of the design through testing of elements and a full-scale subcomponent. This test plan supports the development of the design for an advanced composite thrust structure for a Single Stage to Orbit manned, heavy launch vehicle. The thrust structure is designed to transmit very high thrust loads from the engines to the rest of the vehicle (see Figure 1 ). The thrust structure will also be used for primary attachment of the twin vertical tails and possibly act as the aft attach point for the wing. The combination of high loading, high vibration, long service life and high acoustic environments will need to be evaluated by tests. To minimize design risk, a building block approach will be used. We will first screen materials to determine which materials show the most promise for this application. Factors in this screening will be the suitability of these materials for chosen design concepts, particularly concerning specific strength, environmental compatibility and applicability to fabrication processes. Next we will characterize two material systems that will be used in the design; the characterization will allow us to generate preliminary design data that will be used for the analysis. Element testing will be performed to evaluate critical structural locations under load. Final testing on the full scale test article will be performed to verify the design and to demonstrate predictability of the analysis. Additionally, risks associated with fabricating full scale thrust structures will be reduced through testing activities. One of the major concerns that stems from full scale fabrication is the realities of size and the associated complexities of handling, manufacturing, and assembly. The need exists to fabricate, assemble and test_representative joint specimens to achieve_confidence in the design and manufacturing technologies being proposed.

Fabrication and evaluation of cold/formed/weldbrazed beta-titanium skin-stiffened compression panels

NASA Technical Reports Server (NTRS)

Royster, D. M.; Bales, T. T.; Davis, R. C.; Wiant, H. R.

1983-01-01

The room temperature and elevated temperature buckling behavior of cold formed beta titanium hat shaped stiffeners joined by weld brazing to alpha-beta titanium skins was determined. A preliminary set of single stiffener compression panels were used to develop a data base for material and panel properties. These panels were tested at room temperature and 316 C (600 F). A final set of multistiffener compression panels were fabricated for room temperature tests by the process developed in making the single stiffener panels. The overall geometrical dimensions for the multistiffener panels were determined by the structural sizing computer code PASCO. The data presented from the panel tests include load shortening curves, local buckling strengths, and failure loads. Experimental buckling loads are compared with the buckling loads predicted by the PASCO code. Material property data obtained from tests of ASTM standard dogbone specimens are also presented.

Non-Invasive Tension Measurement Devices for Parachute Cordage

NASA Technical Reports Server (NTRS)

Litteken, Douglas A.; Daum, Jared S.

2016-01-01

The need for lightweight and non-intrusive tension measurements has arisen alongside the development of high-fidelity computer models of textile and fluid dynamics. In order to validate these computer models, data must be gathered in the operational environment without altering the design, construction, or performance of the test article. Current measurement device designs rely on severing a cord and breaking the load path to introduce a load cell. These load cells are very reliable, but introduce an area of high stiffness in the load path, directly affecting the structural response, adding excessive weight, and possibly altering the dynamics of the parachute during a test. To capture the required data for analysis validation without affecting the response of the system, non-invasive measurement devices have been developed and tested by NASA. These tension measurement devices offer minimal impact to the mass, form, fit, and function of the test article, while providing reliable, axial tension measurements for parachute cordage.

Structural Testing at the NWTC Helps Improve Blade Design and Increase System Reliability; NREL (National Renewable Energy Laboratory)

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2015-08-01

Since 1990, the National Renewable Energy Laboratory’s (NREL's) National Wind Technology Center (NWTC) has tested more than 150 wind turbine blades. NWTC researchers can test full-scale and subcomponent articles, conduct data analyses, and provide engineering expertise on best design practices. Structural testing of wind turbine blades enables designers, manufacturers, and owners to validate designs and assess structural performance to specific load conditions. Rigorous structural testing can reveal design and manufacturing problems at an early stage of development that can lead to overall improvements in design and increase system reliability.

Dynamic Response of X-37 Hot Structure Control Surfaces Exposed to Controlled Reverberant Acoustic Excitation

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.; Rizzi, Stephen A.; Rice, Chad E.

2004-01-01

This document represents a compilation of three informal reports from reverberant acoustic tests performed on X-37 hot structure control surfaces in the NASA Langley Research Center Structural Acoustics Loads and Transmission (SALT) facility. The first test was performed on a carbon-silicone carbide flaperon subcomponent on February 24, 2004. The second test was performed on a carbon-carbon ruddervator subcomponent on May 27, 2004. The third test was performed on a carbon-carbon flaperon subcomponent on June 30, 2004.

Moment measurements in dynamic and quasi-static spine segment testing using eccentric compression are susceptible to artifacts based on loading configuration.

PubMed

Van Toen, Carolyn; Carter, Jarrod W; Oxland, Thomas R; Cripton, Peter A

2014-12-01

The tolerance of the spine to bending moments, used for evaluation of injury prevention devices, is often determined through eccentric axial compression experiments using segments of the cadaver spine. Preliminary experiments in our laboratory demonstrated that eccentric axial compression resulted in "unexpected" (artifact) moments. The aim of this study was to evaluate the static and dynamic effects of test configuration on bending moments during eccentric axial compression typical in cadaver spine segment testing. Specific objectives were to create dynamic equilibrium equations for the loads measured inferior to the specimen, experimentally verify these equations, and compare moment responses from various test configurations using synthetic (rubber) and human cadaver specimens. The equilibrium equations were verified by performing quasi-static (5 mm/s) and dynamic experiments (0.4 m/s) on a rubber specimen and comparing calculated shear forces and bending moments to those measured using a six-axis load cell. Moment responses were compared for hinge joint, linear slider and hinge joint, and roller joint configurations tested at quasi-static and dynamic rates. Calculated shear force and bending moment curves had similar shapes to those measured. Calculated values in the first local minima differed from those measured by 3% and 15%, respectively, in the dynamic test, and these occurred within 1.5 ms of those measured. In the rubber specimen experiments, for the hinge joint (translation constrained), quasi-static and dynamic posterior eccentric compression resulted in flexion (unexpected) moments. For the slider and hinge joints and the roller joints (translation unconstrained), extension ("expected") moments were measured quasi-statically and initial flexion (unexpected) moments were measured dynamically. In the cadaver experiments with roller joints, anterior and posterior eccentricities resulted in extension moments, which were unexpected and expected, for those configurations, respectively. The unexpected moments were due to the inertia of the superior mounting structures. This study has shown that eccentric axial compression produces unexpected moments due to translation constraints at all loading rates and due to the inertia of the superior mounting structures in dynamic experiments. It may be incorrect to assume that bending moments are equal to the product of compression force and eccentricity, particularly where the test configuration involves translational constraints and where the experiments are dynamic. In order to reduce inertial moment artifacts, the mass, and moment of inertia of any loading jig structures that rotate with the specimen should be minimized. Also, the distance between these structures and the load cell should be reduced.

Dynamic impact testing with servohydraulic testing machines

NASA Astrophysics Data System (ADS)

Bardenheier, R.; Rogers, G.

2006-08-01

The design concept of “Crashworthiness” requires the information on material behaviour under dynamic impact loading in order to describe and predict the crash behaviour of structures. Especially the transport related industries, like car, railway or aircraft industry, pursue the concept of lightweight design for a while now. The materials' maximum constraint during loading is pushed to permanently increasing figures. This means in terms of crashworthiness that the process of energy absorption in structures and the mechanical behaviour of materials must well understood and can be described appropriately by material models. In close cooperation with experts from various industries and research institutes Instron has developed throughout the past years a new family of servohydraulic testing machines specifically designed to cope with the dynamics of high rate testing. Main development steps are reflected versus their experimental necessities.

Structural tests on space shuttle thermal protection system constructed with nondensified and densified Li 900 and LI 2200 tile

NASA Technical Reports Server (NTRS)

Williams, J. G.

1981-01-01

Structural tests were conducted on thermal protection systems (TPS) LI 900 and LI 2200 tiles and .41 cm and .23 cm thick strain isolation pads. The bond surface of selected tiles was densified to obtain improved strength. Four basic types of experiments were conducted including tension tests, substrate mismatch (initial imperfection) tests, tension loads eccentrically applied, and pressure loads applied rapidly to the tile top surface. A small initial imperfection mismatch (2.29 m spherical radius on the substrate) did not influence significantly the ultimate failure strength. Densification of the tile bond region improved the strength of TPS constructed both of LI 900 tile and of LI 2200 tile. Pressure shock conditions studied did not significantly affect the TPS strength.

NASA GSFC Mechanical Engineering Latest Inputs for Verification Standards (GEVS) Updates

NASA Technical Reports Server (NTRS)

Kaufman, Daniel

2003-01-01

This viewgraph presentation provides information on quality control standards in mechanical engineering. The presentation addresses safety, structural loads, nonmetallic composite structural elements, bonded structural joints, externally induced shock, random vibration, acoustic tests, and mechanical function.

Factor structure of the Hooper Visual Organization Test: a cross-cultural replication and extension.

PubMed

Merten, Thomas

2005-01-01

To investigate construct validity of the Hooper Visual Organization Test (VOT), a principal-axis analysis was performed on the neuropsychological test results of 200 German-speaking neurological patients who received a comprehensive battery, encompassing tests of visuospatial functions, memory, attention, executive functions, naming ability, and vocabulary. A four-factor solution was obtained with substantial loadings of the VOT only on the first factor, interpreted as a global dimension of non-verbal cognitive functions. This factor loaded significantly on numerous measures of visuospatial processing and attention (with particularly high loadings on WAIS-R Block Design, Trails A and B, and Raven's Standard Progressive Matrices). The remaining three factors were interpreted as memory, verbal abilities (vocabulary), and a separate factor of naming abilities.

Performance and rotor loads measurements of the Lynx XZ170 helicopter with rectangular blades

NASA Technical Reports Server (NTRS)

Lau, Benton H.; Louie, Alexander W.; Griffiths, Nicholas; Sotiriou, Costantinos P.

1993-01-01

This report presents the results of a series of flight tests on the Lynx XZ170 helicopter with rectangular blades. The test objectives were to explore the flight envelope and to measure the performance and structural loads of the Lynx main-rotor system. The tests were conducted as part of the British Experimental Rotor Program (BERP) under a contract with the Ministry of Defense in England. Data were acquired for steady-level flights at five weight coefficients. Some flight conditions were tested at beyond the retreating-blade stall boundary, which was defined by a predetermined limit on the pitchlink vibratory load. In addition to documenting the flight conditions and data, this report describes the aircraft, particularly the rotor system, in detail.

Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading

PubMed Central

Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre

2016-01-01

Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted. PMID:28773522

Experimental and Numerical Evaluation of the Mechanical Behavior of Strongly Anisotropic Light-Weight Metallic Fiber Structures under Static and Dynamic Compressive Loading.

PubMed

Andersen, Olaf; Vesenjak, Matej; Fiedler, Thomas; Jehring, Ulrike; Krstulović-Opara, Lovre

2016-05-21

Rigid metallic fiber structures made from a variety of different metals and alloys have been investigated mainly with regard to their functional properties such as heat transfer, pressure drop, or filtration characteristics. With the recent advent of aluminum and magnesium-based fiber structures, the application of such structures in light-weight crash absorbers has become conceivable. The present paper therefore elucidates the mechanical behavior of rigid sintered fiber structures under quasi-static and dynamic loading. Special attention is paid to the strongly anisotropic properties observed for different directions of loading in relation to the main fiber orientation. Basically, the structures show an orthotropic behavior; however, a finite thickness of the fiber slabs results in moderate deviations from a purely orthotropic behavior. The morphology of the tested specimens is examined by computed tomography, and experimental results for different directions of loading as well as different relative densities are presented. Numerical calculations were carried out using real structural data derived from the computed tomography data. Depending on the direction of loading, the fiber structures show a distinctively different deformation behavior both experimentally and numerically. Based on these results, the prevalent modes of deformation are discussed and a first comparison with an established polymer foam and an assessment of the applicability of aluminum fiber structures in crash protection devices is attempted.

Development of a Pressure Box to Evaluate Reusable-Launch-Vehicle Cryogenic-Tank Panels

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Sikora, Joseph; Maguire, James F.; Winn, Peter M.

1996-01-01

A cryogenic pressure-box test machine has been designed and is being developed to test full-scale reusable-launch-vehicle cryogenic-tank panels. This machine is equipped with an internal pressurization system, a cryogenic cooling system, and a heating system to simulate the mechanical and thermal loading conditions that are representative of a reusable-launch-vehicle mission profile. The cryogenic cooling system uses liquid helium and liquid nitrogen to simulate liquid hydrogen and liquid oxygen tank internal temperatures. A quartz lamp heating system is used for heating the external surface of the test panels to simulate cryogenic-tank external surface temperatures during re-entry of the launch vehicle. The pressurization system uses gaseous helium and is designed to be controlled independently of the cooling system. The tensile loads in the axial direction of the test panel are simulated by means of hydraulic actuators and a load control system. The hoop loads in the test panel are reacted by load-calibrated turnbuckles attached to the skin and frame elements of the test panel. The load distribution in the skin and frames can be adjusted to correspond to the tank structure by using these turnbuckles. The seal between the test panel and the cryogenic pressure box is made from a reinforced Teflon material which can withstand pressures greater than 52 psig at cryogenic temperatures. Analytical results and tests on prototype test components indicate that most of the cryogenic-tank loading conditions that occur in flight can be simulated in the cryogenic pressure-box test machine.

Evaluation of Rotor Structural and Aerodynamic Loads using Measured Blade Properties

NASA Technical Reports Server (NTRS)

Jung, Sung N.; You, Young-Hyun; Lau, Benton H.; Johnson, Wayne; Lim, Joon W.

2012-01-01

The structural properties of Higher harmonic Aeroacoustic Rotor Test (HART I) blades have been measured using the original set of blades tested in the wind tunnel in 1994. A comprehensive rotor dynamics analysis is performed to address the effect of the measured blade properties on airloads, blade motions, and structural loads of the rotor. The measurements include bending and torsion stiffness, geometric offsets, and mass and inertia properties of the blade. The measured properties are correlated against the estimated values obtained initially by the manufacturer of the blades. The previously estimated blade properties showed consistently higher stiffnesses, up to 30% for the flap bending in the blade inboard root section. The measured offset between the center of gravity and the elastic axis is larger by about 5% chord length, as compared with the estimated value. The comprehensive rotor dynamics analysis was carried out using the measured blade property set for HART I rotor with and without HHC (Higher Harmonic Control) pitch inputs. A significant improvement on blade motions and structural loads is obtained with the measured blade properties.

Designing, engineering, and testing wood structures

NASA Technical Reports Server (NTRS)

Gorman, Thomas M.

1992-01-01

The objective of this paper is to introduce basic structural engineering concepts in a clear, simple manner while actively involving students. This project emphasizes the fact that a good design uses materials efficiently. The test structure in this experiment can easily be built and has various design options. Even when the structure is loaded to collapsing, only one or two pieces usually break, leaving the remaining pieces intact and reusable.

Structural and Trajectory Control of Variable Geometry Planetary Entry Systems

NASA Technical Reports Server (NTRS)

Quadrelli, Marco; Kwok, Kawai; Pellegrino, Sergio

2009-01-01

The results presented in this paper apply to a generic vehicle entering a planetary atmosphere which makes use of a variable geometry change to modulate the heat, drag, and acceleration loads. Two structural concepts for implementing the cone angle variation, namely a segmented shell and a corrugated shell, are presented. A structural analysis of these proposed structural configuration shows that the stress levels are tolerable during entry. The analytic expressions of the longitudinal aerodynamic coefficients are also derived, and guidance laws that track reference heat flux, drag, and aerodynamic acceleration loads are also proposed. These guidance laws have been tested in an integrated simulation environment, and the results indicate that use of variable geometry is feasible to track specific profiles of dynamic load conditions during reentry.

Spacecraft load, design and test philosophies

NASA Technical Reports Server (NTRS)

Wada, B. K.

1986-01-01

The development of spacecraft loads, design and test philosophies at the Jet Propulsion Laboratory (JPL) during the past 25 years is presented. Examples from the JPL's Viking, Voyager and Galileo spacecraft are used to explain the changes in philosophy necessary to meet the program requirements with a reduction in cost and schedule. Approaches to validate mathematical models of large structures which can't be ground tested as an overall system because of size and/or adverse effects of terrestrial conditions such as gravity are presented.

University Engineering Design Challenge

DTIC Science & Technology

2015-01-02

strength its members provide. Trusses are common load - bearing structures, and are found in many modern-day applications due to their simple, strong, and...we ran simulations on was one of the member arms. We applied a bearing load on the surfaces of the holes on one side and tested it for static stress...73.24 ksi yield strength as shown figures 17 below. Figure 17: von Mises stress under static bearing load of 8750 lb. Under the static bearing load

Aeroelastic Modeling of a Nozzle Startup Transient

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2014-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,

NDT evaluation of long-term bond durability of CFRP-structural systems applied to RC highway bridges

NASA Astrophysics Data System (ADS)

Crawford, Kenneth C.

2016-06-01

The long-term durability of CFRP structural systems applied to reinforced-concrete (RC) highway bridges is a function of the system bond behavior over time. The sustained structural load performance of strengthened bridges depends on the carbon fiber-reinforced polymer (CFRP) laminates remaining 100 % bonded to concrete bridge members. Periodic testing of the CFRP-concrete bond condition is necessary to sustain load performance. The objective of this paper is to present a non-destructive testing (NDT) method designed to evaluate the bond condition and long-term durability of CFRP laminate (plate) systems applied to RC highway bridges. Using the impact-echo principle, a mobile mechanical device using light impact hammers moving along the length of a bonded CFRP plate produces unique acoustic frequencies which are a function of existing CFRP plate-concrete bond conditions. The purpose of this method is to test and locate CFRP plates de-bonded from bridge structural members to identify associated deterioration in bridge load performance. Laboratory tests of this NDT device on a CFRP plate bonded to concrete with staged voids (de-laminations) produced different frequencies for bonded and de-bonded areas of the plate. The spectra (bands) of frequencies obtained in these tests show a correlation to the CFRP-concrete bond condition and identify bonded and de-bonded areas of the plate. The results of these tests indicate that this NDT impact machine, with design improvements, can potentially provide bridge engineers a means to rapidly evaluate long lengths of CFRP laminates applied to multiple highway bridges within a national transportation infrastructure.

Investigation of Unsteady Pressure-Sensitive Paint (uPSP) and a Dynamic Loads Balance to Predict Launch Vehicle Buffet Environments

NASA Technical Reports Server (NTRS)

Schuster, David M.; Panda, Jayanta; Ross, James C.; Roozeboom, Nettie H.; Burnside, Nathan J.; Ngo, Christina L.; Kumagai, Hiro; Sellers, Marvin; Powell, Jessica M.; Sekula, Martin K.;

Damage tolerance certification of a fighter horizontal stabilizer

NASA Astrophysics Data System (ADS)

Huang, Jia-Yen; Tsai, Ming-Yang; Chen, Jong-Sheng; Ong, Ching-Long

1995-05-01

A review of the program for the damage tolerance certification test of a composite horizontal stabilizer (HS) of a fighter is presented. The object of this program is to certify that the fatigue life and damage tolerance strength of a damaged composite horizontal stabilizer meets the design requirements. According to the specification for damage tolerance certification, a test article should be subjected to two design lifetimes of flight-by-flight load spectra simulating the in-service fatigue loading condition for the aircraft. However, considering the effect of environmental change on the composite structure, one additional lifetime test was performed. In addition, to evaluate the possibilities for extending the service life of the structure, one more lifetime test was carried out with the spectrum increased by a factor of 1.4. To assess the feasibility and reliability of repair technology on a composite structure, two damaged areas were repaired after two lifetimes of damage tolerance test. On completion of four lifetimes of the damage tolerance test, the static residual strength was measured to check whether structural strength after repair met the requirements. Stiffness and static strength of the composite HS with and without damage were evaluated and compared.

Impact of measurement uncertainty from experimental load distribution factors on bridge load rating

NASA Astrophysics Data System (ADS)

Gangone, Michael V.; Whelan, Matthew J.

2018-03-01

Load rating and testing of highway bridges is important in determining the capacity of the structure. Experimental load rating utilizes strain transducers placed at critical locations of the superstructure to measure normal strains. These strains are then used in computing diagnostic performance measures (neutral axis of bending, load distribution factor) and ultimately a load rating. However, it has been shown that experimentally obtained strain measurements contain uncertainties associated with the accuracy and precision of the sensor and sensing system. These uncertainties propagate through to the diagnostic indicators that in turn transmit into the load rating calculation. This paper will analyze the effect that measurement uncertainties have on the experimental load rating results of a 3 span multi-girder/stringer steel and concrete bridge. The focus of this paper will be limited to the uncertainty associated with the experimental distribution factor estimate. For the testing discussed, strain readings were gathered at the midspan of each span of both exterior girders and the center girder. Test vehicles of known weight were positioned at specified locations on each span to generate maximum strain response for each of the five girders. The strain uncertainties were used in conjunction with a propagation formula developed by the authors to determine the standard uncertainty in the distribution factor estimates. This distribution factor uncertainty is then introduced into the load rating computation to determine the possible range of the load rating. The results show the importance of understanding measurement uncertainty in experimental load testing.

Acoustic-Structure Interaction in Rocket Engines: Validation Testing

NASA Technical Reports Server (NTRS)

Davis, R. Benjamin; Joji, Scott S.; Parks, Russel A.; Brown, Andrew M.

2009-01-01

While analyzing a rocket engine component, it is often necessary to account for any effects that adjacent fluids (e.g., liquid fuels or oxidizers) might have on the structural dynamics of the component. To better characterize the fully coupled fluid-structure system responses, an analytical approach that models the system as a coupled expansion of rigid wall acoustic modes and in vacuo structural modes has been proposed. The present work seeks to experimentally validate this approach. To experimentally observe well-coupled system modes, the test article and fluid cavities are designed such that the uncoupled structural frequencies are comparable to the uncoupled acoustic frequencies. The test measures the natural frequencies, mode shapes, and forced response of cylindrical test articles in contact with fluid-filled cylindrical and/or annular cavities. The test article is excited with a stinger and the fluid-loaded response is acquired using a laser-doppler vibrometer. The experimentally determined fluid-loaded natural frequencies are compared directly to the results of the analytical model. Due to the geometric configuration of the test article, the analytical model is found to be valid for natural modes with circumferential wave numbers greater than four. In the case of these modes, the natural frequencies predicted by the analytical model demonstrate excellent agreement with the experimentally determined natural frequencies.

Damage Detection of a Concrete Column Subject to Blast Loads Using Embedded Piezoceramic Transducers.

PubMed

Xu, Kai; Deng, Qingshan; Cai, Lujun; Ho, Siuchun; Song, Gangbing

2018-04-28

Some of the most severe structural loadings come in the form of blast loads, which may be caused by severe accidents or even terrorist activities. Most commonly after exposure to explosive forces, a structure will suffer from different degrees of damage, and even progress towards a state of collapse. Therefore, damage detection of a structure subject to explosive loads is of importance. This paper proposes a new approach to damage detection of a concrete column structure subjected to blast loads using embedded piezoceramic smart aggregates (SAs). Since the sensors are embedded in the structure, the proposed active-sensing based approach is more sensitive to internal or through cracks than surface damage. In the active sensing approach, the embedded SAs act as actuators and sensors, that can respectively generate and detect stress waves. If the stress wave propagates across a crack, the energy of the wave attenuates, and the reduction of the energy compared to the healthy baseline is indicative of a damage. With a damage index matrix constructed by signals obtained from an array of SAs, cracks caused by blast loads can be detected throughout the structure. Conventional sensing methods such as the measurement of dynamic strain and acceleration were included in the experiment. Since columns are critical elements needed to prevent structural collapse, knowledge of their integrity and damage conditions is essential for safety after exposure to blast loads. In this research, a concrete column with embedded SAs was chosen as the specimen, and a series of explosive tests were conducted on the column. Experimental results reveal that surface damages, though appear severe, cause minor changes in the damage index, and through cracks result in significant increase of the damage index, demonstrating the effectiveness of the active sensing, enabled by embedded SAs, in damage monitoring of the column under blast loads, and thus providing a reliable indication of structural integrity in the event of blast loads.

Damage Detection of a Concrete Column Subject to Blast Loads Using Embedded Piezoceramic Transducers

PubMed Central

Deng, Qingshan; Cai, Lujun; Ho, Siuchun; Song, Gangbing

2018-01-01

Some of the most severe structural loadings come in the form of blast loads, which may be caused by severe accidents or even terrorist activities. Most commonly after exposure to explosive forces, a structure will suffer from different degrees of damage, and even progress towards a state of collapse. Therefore, damage detection of a structure subject to explosive loads is of importance. This paper proposes a new approach to damage detection of a concrete column structure subjected to blast loads using embedded piezoceramic smart aggregates (SAs). Since the sensors are embedded in the structure, the proposed active-sensing based approach is more sensitive to internal or through cracks than surface damage. In the active sensing approach, the embedded SAs act as actuators and sensors, that can respectively generate and detect stress waves. If the stress wave propagates across a crack, the energy of the wave attenuates, and the reduction of the energy compared to the healthy baseline is indicative of a damage. With a damage index matrix constructed by signals obtained from an array of SAs, cracks caused by blast loads can be detected throughout the structure. Conventional sensing methods such as the measurement of dynamic strain and acceleration were included in the experiment. Since columns are critical elements needed to prevent structural collapse, knowledge of their integrity and damage conditions is essential for safety after exposure to blast loads. In this research, a concrete column with embedded SAs was chosen as the specimen, and a series of explosive tests were conducted on the column. Experimental results reveal that surface damages, though appear severe, cause minor changes in the damage index, and through cracks result in significant increase of the damage index, demonstrating the effectiveness of the active sensing, enabled by embedded SAs, in damage monitoring of the column under blast loads, and thus providing a reliable indication of structural integrity in the event of blast loads. PMID:29710807

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

The Orion Exploration Mission-1 (EM-1) structural test article, inside its transport container, is secured in NASA's Super Guppy aircraft at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. The test article will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Synchronous meteorological satellite system description document, volume 3

NASA Technical Reports Server (NTRS)

Pipkin, F. B.

1971-01-01

The structural design, analysis, and mechanical integration of the synchronous meteorological satellite system are presented. The subjects discussed are: (1) spacecraft configuration, (2) structural design, (3) static load tests, (4) fixed base sinusoidal vibration survey, (5) flight configuration sinusoidal vibration tests, (6) spacecraft acoustic test, and (7) separation and shock test. Descriptions of the auxiliary propulsion subsystem, the apogee boost motor, communications system, and thermal control subsystem are included.

Structural Dynamics of Electronic Systems

NASA Astrophysics Data System (ADS)

Suhir, E.

2013-03-01

The published work on analytical ("mathematical") and computer-aided, primarily finite-element-analysis (FEA) based, predictive modeling of the dynamic response of electronic systems to shocks and vibrations is reviewed. While understanding the physics of and the ability to predict the response of an electronic structure to dynamic loading has been always of significant importance in military, avionic, aeronautic, automotive and maritime electronics, during the last decade this problem has become especially important also in commercial, and, particularly, in portable electronics in connection with accelerated testing of various surface mount technology (SMT) systems on the board level. The emphasis of the review is on the nonlinear shock-excited vibrations of flexible printed circuit boards (PCBs) experiencing shock loading applied to their support contours during drop tests. At the end of the review we provide, as a suitable and useful illustration, the exact solution to a highly nonlinear problem of the dynamic response of a "flexible-and-heavy" PCB to an impact load applied to its support contour during drop testing.

[Research of joint-robotics-based design of biomechanics testing device on human spine].

PubMed

Deng, Guoyong; Tian, Lianfang; Mao, Zongyuan

2009-12-01

This paper introduces the hardware and software of a biomechanical robot-based testing device. The bottom control orders, posture and torque data transmission, and the control algorithms are integrated in a unified visual control platform by Visual C+ +, with easy control and management. By using hybrid force-displacement control method to load the human spine, we can test the organizational structure and the force state of the FSU (Functional spinal unit) well, which overcomes the shortcomings due to the separation of the force and displacement measurement, thus greatly improves the measurement accuracy. Also it is esay to identify the spinal degeneration and the load-bearing impact on the organizational structure of the FSU after various types of surgery.

Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Dexter, Benson H.

1996-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

Blast Load Simulator Experiments for Computational Model Validation: Report 1

DTIC Science & Technology

2016-08-01

involving the inclusion of non-responding box-type structures in a BLS simulated blast environment. The BLS is a highly tunable com- pressed-gas-driven...Blast Load Simulator (BLS) to evaluate its suitability for a future effort involving the inclusion of non-responding box-type structures located in...Recommendations Preliminary testing indicated that inclusion of the grill and diaphragm striker resulted in a decrease in peak pressure of about 12

14 CFR 23.572 - Metallic wing, empennage, and associated structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... principal structural element, and that the remaining structure is able to withstand a static ultimate load... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES... experience: (1) A fatigue strength investigation in which the structure is shown by tests, or by analysis...

14 CFR 23.572 - Metallic wing, empennage, and associated structures.

Code of Federal Regulations, 2013 CFR

2013-01-01

... principal structural element, and that the remaining structure is able to withstand a static ultimate load... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES... experience: (1) A fatigue strength investigation in which the structure is shown by tests, or by analysis...

14 CFR 23.572 - Metallic wing, empennage, and associated structures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... principal structural element, and that the remaining structure is able to withstand a static ultimate load... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES... experience: (1) A fatigue strength investigation in which the structure is shown by tests, or by analysis...

14 CFR 23.572 - Metallic wing, empennage, and associated structures.

Code of Federal Regulations, 2011 CFR

2011-01-01

... principal structural element, and that the remaining structure is able to withstand a static ultimate load... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES... experience: (1) A fatigue strength investigation in which the structure is shown by tests, or by analysis...

14 CFR 23.572 - Metallic wing, empennage, and associated structures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... principal structural element, and that the remaining structure is able to withstand a static ultimate load... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES... experience: (1) A fatigue strength investigation in which the structure is shown by tests, or by analysis...

Carbon Nanotube Coatings as Used in Strain Sensors for Composite Tanks

NASA Technical Reports Server (NTRS)

Trigwell, Steve; Snyder, Sarah; Hatfield, Walt; Dervishi, Enkeleda; Biris, Alexandru S.

2011-01-01

The next generation of cryogenic fuel tanks, crew habitats and other components for future spacecraft will focus on the usc of lightweight carbon fiber composite materials. A critical issue in the design and optimization of such tanks and structures will bc in structural health monitoring, however, current strain sensors have limitations. In this study, a novel carbon nanotube thin film was applied to carbon fiber composites for structural monitoring. Applying a load using a 3-point bend test to simulate bowing of a tank wall, induced significant increases in the film's electrical resistance at small deflections. Upon release of the load, the resistance returned to its approximate start value and was reproducible over multiple tests. The results show that a carbon nanotube thin film has great potential for the health monitoring of composite structures.

New method of determination of spot welding-adhesive joint fatigue life using full field strain evolution

NASA Astrophysics Data System (ADS)

Sadowski, T.; Kneć, M.

2016-04-01

Fatigue tests were conducted since more than two hundred years ago. Despite this long period, as fatigue phenomena are very complex, assessment of fatigue response of standard materials or composites still requires a long time. Quite precise way to estimate fatigue parameters is to test at least 30 standardized specimens for the analysed material and further statistical post processing is required. In case of structural elements analysis like hybrid joints (Figure 1), the situation is much more complex as more factors influence the fatigue load capacity due to much more complicated structure of the joint in comparison to standard materials specimen, i.e. occurrence of: welded hot spots or rivets, adhesive layers, local notches creating the stress concentrations, etc. In order to shorten testing time some rapid methods are known: Locati's method [1] - step by step load increments up to failure, Prot's method [2] - constant increase of the load amplitude up to failure; Lehr's method [2] - seeking for the point during regular fatigue loading when an increase of temperature or strains become non-linear. The present article proposes new method of the fatigue response assessment - combination of the Locati's and Lehr's method.

Imparting Barely Visible Impact Damage to a Stitched Composite Large-Scale Pressure Box

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.; Przekop, Adam

2016-01-01

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is a concept that was developed by The Boeing Company to address the complex structural design aspects associated with a pressurized hybrid wing body (HWB) aircraft configuration, which has been a focus of the NASA Environmentally Responsible Aviation Project. The NASA-Boeing structural development for the HWB aircraft culminated in testing of the multi-bay box, which is an 80%-scale representation of the pressurized center-body section. This structure was tested in the NASA Langley Research Center Combined Loads Test System facility. As part of this testing, barely visible impact damage was imparted to the interior and exterior of the test article to demonstrate compliance with a condition representative of the requirements for Category 1 damaged composite structure as defined by the Federal Aviation Regulations. Interior impacts were imparted using an existing spring-loaded impactor, while the exterior impacts were imparted using a newly designed, gravity-driven impactor. This paper describes the impacts to the test article, and the design of the gravitydriven guided-weight impactor. The guided-weight impactor proved to be a very reliable method to impart barely visible impact damage in locations which are not easily accessible for a traditional drop-weight impactor, while at the same time having the capability to be highly configurable for use on other aircraft structures.

Fluid Structure Interaction in a Cold Flow Test and Transient CFD Analysis of Out-of-Round Nozzles

NASA Technical Reports Server (NTRS)

Ruf, Joseph; Brown, Andrew; McDaniels, David; Wang, Ten-See

2010-01-01

This viewgraph presentation describes two nozzle fluid flow interactions. They include: 1) Cold flow nozzle tests with fluid-structure interaction at nozzle separated flow; and 2) CFD analysis for nozzle flow and side loads of nozzle extensions with various out-of-round cases.

Seismic damage identification for steel structures using distributed fiber optics.

PubMed

Hou, Shuang; Cai, C S; Ou, Jinping

2009-08-01

A distributed fiber optic monitoring methodology based on optic time domain reflectometry technology is developed for seismic damage identification of steel structures. Epoxy with a strength closely associated to a specified structure damage state is used for bonding zigzagged configured optic fibers on the surfaces of the structure. Sensing the local deformation of the structure, the epoxy modulates the signal change within the optic fiber in response to the damage state of the structure. A monotonic loading test is conducted on a steel specimen installed with the proposed sensing system using selected epoxy that will crack at the designated strain level, which indicates the damage of the steel structure. Then, using the selected epoxy, a varying degree of cyclic loading amplitudes, which is associated with different damage states, is applied on a second specimen. The test results show that the specimen's damage can be identified by the optic sensors, and its maximum local deformation can be recorded by the sensing system; moreover, the damage evolution can also be identified.

Determination of Elevator and Rudder Hinge Forces on the Learjet Model 55 Aircraft

NASA Technical Reports Server (NTRS)

Boroughs, R. R.; Padmanabhan, V.

1983-01-01

The empennage structure on the Learjet 55 aircraft was quite similar to the empennage structure on earlier Learjet models. However, due to an important structural change in the vertical fin along with the new loads environment on the 50 series aircraft, a structural test was required on the vertical fin, but the horizontal tail was substantiated by a comparative analysis with previous tests. NASTRAN analysis was used to investigate empennage deflections, stress levels, and control surface hinge forces. The hinge force calculations were made with the control surfaces in the deflected as well as undeflected configurations. A skin panel buckling analysis was also performed, and the non-linear effects of buckling were simulated in the NASTRAN model to more accurately define internal loads and stress levels. Comparisons were then made between the Model 55 and the Model 35/36 stresses and internal forces to determine which components were qualified by previous tests. Some of the methods and techniques used in this analysis are described.

The use of subjective expert opinions in cost optimum design of aerospace structures. [probabilistic failure models

NASA Technical Reports Server (NTRS)

Thomas, J. M.; Hanagud, S.

1975-01-01

The results of two questionnaires sent to engineering experts are statistically analyzed and compared with objective data from Saturn V design and testing. Engineers were asked how likely it was for structural failure to occur at load increments above and below analysts' stress limit predictions. They were requested to estimate the relative probabilities of different failure causes, and of failure at each load increment given a specific cause. Three mathematical models are constructed based on the experts' assessment of causes. The experts' overall assessment of prediction strength fits the Saturn V data better than the models do, but a model test option (T-3) based on the overall assessment gives more design change likelihood to overstrength structures than does an older standard test option. T-3 compares unfavorably with the standard option in a cost optimum structural design problem. The report reflects a need for subjective data when objective data are unavailable.

Nonlinear Inelastic Mechanical Behavior Of Epoxy Resin Polymeric Materials

NASA Astrophysics Data System (ADS)

Yekani Fard, Masoud

Polymer and polymer matrix composites (PMCs) materials are being used extensively in different civil and mechanical engineering applications. The behavior of the epoxy resin polymers under different types of loading conditions has to be understood before the mechanical behavior of Polymer Matrix Composites (PMCs) can be accurately predicted. In many structural applications, PMC structures are subjected to large flexural loadings, examples include repair of structures against earthquake and engine fan cases. Therefore it is important to characterize and model the flexural mechanical behavior of epoxy resin materials. In this thesis, a comprehensive research effort was undertaken combining experiments and theoretical modeling to investigate the mechanical behavior of epoxy resins subject to different loading conditions. Epoxy resin E 863 was tested at different strain rates. Samples with dog-bone geometry were used in the tension tests. Small sized cubic, prismatic, and cylindrical samples were used in compression tests. Flexural tests were conducted on samples with different sizes and loading conditions. Strains were measured using the digital image correlation (DIC) technique, extensometers, strain gauges, and actuators. Effects of triaxiality state of stress were studied. Cubic, prismatic, and cylindrical compression samples undergo stress drop at yield, but it was found that only cubic samples experience strain hardening before failure. Characteristic points of tensile and compressive stress strain relation and load deflection curve in flexure were measured and their variations with strain rate studied. Two different stress strain models were used to investigate the effect of out-of-plane loading on the uniaxial stress strain response of the epoxy resin material. The first model is a strain softening with plastic flow for tension and compression. The influence of softening localization on material behavior was investigated using the DIC system. It was found that compression plastic flow has negligible influence on flexural behavior in epoxy resins, which are stronger in pre-peak and post-peak softening in compression than in tension. The second model was a piecewise-linear stress strain curve simplified in the post-peak response. Beams and plates with different boundary conditions were tested and analytically studied. The flexural over-strength factor for epoxy resin polymeric materials were also evaluated.

Glass Masonry - Experimental Verification of Bed Joint under Shear

NASA Astrophysics Data System (ADS)

Fíla, J.; Eliášová, M.; Sokol, Z.

2017-10-01

Glass is considered as a traditional material for building industry but was mostly used for glazing of the windows. At present, glass is an integral part of contemporary architecture where glass structural elements such as beams, stairs, railing ribs or columns became popular in the last two decades. However, using glass as structural material started at the beginning of 20th century, when masonry from hollow glass blocks were used. Using solid glass brick is very rare and only a few structures with solid glass bricks walls have been built in the last years. Pillars and walls made from solid glass bricks are mainly loaded by compression and/or bending from the eccentricity of vertical load or wind load. Due to high compressive strength of glass, the limiting factor of the glass masonry is the joint between the glass bricks as the smooth surface requires another type of mortar / glue compared to traditional masonry. Shear resistance and failure modes of brick bed joint was determined during series of tests using various mortars, two types of surface treatment and different thickness of the mortar joint. Shear tests were completed by small scale tests for mortar - determination of flexural and compressive strength of hardened mortar.

Reproducibility of structural strength and stiffness for graphite-epoxy aircraft spoilers

NASA Technical Reports Server (NTRS)

Howell, W. E.; Reese, C. D.

1978-01-01

Structural strength reproducibility of graphite epoxy composite spoilers for the Boeing 737 aircraft was evaluated by statically loading fifteen spoilers to failure at conditions simulating aerodynamic loads. Spoiler strength and stiffness data were statistically modeled using a two parameter Weibull distribution function. Shape parameter values calculated for the composite spoiler strength and stiffness were within the range of corresponding shape parameter values calculated for material property data of composite laminates. This agreement showed that reproducibility of full scale component structural properties was within the reproducibility range of data from material property tests.

PRSEUS Acoustic Panel Fabrication

NASA Technical Reports Server (NTRS)

Nicolette, Velicki; Yovanof, Nicolette P.; Baraja, Jaime; Mathur, Gopal; Thrash, Patrick; Pickell, Robert

2011-01-01

This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program.

Analyses and tests of the B-1 aircraft structural mode control system

NASA Technical Reports Server (NTRS)

Wykes, J. H.; Byar, T. R.; Macmiller, C. J.; Greek, D. C.

1980-01-01

Analyses and flight tests of the B-1 structural mode control system (SMCS) are presented. Improvements in the total dynamic response of a flexible aircraft and the benefits to ride qualities, handling qualities, crew efficiency, and reduced dynamic loads on the primary structures, were investigated. The effectiveness and the performance of the SMCS, which uses small aerodynamic surfaces at the vehicle nose to provide damping to the structural modes, were evaluated.

Wind-induced structural response of a large telescope

NASA Astrophysics Data System (ADS)

Smith, David R.; Avitabile, Peter; Gwaltney, Geoff; Cho, Myung; Sheehan, Michael

2004-09-01

In May of 2000, the construction progress of the Gemini South 8m telescope at Cerro Pachon in Chile was such that the telescope and dome were installed and able to move, but the primary mirror had not been installed. This provided a unique opportunity to make extensive tests of the structure in its nearly-completed state, including a modal impact test and simultaneous measurements of wind pressure and structural response. The testing was even more comprehensive because the Gemini dome design allows for a wide range of wind flow configurations, from nearly enclosed to almost fully exposed. In these tests, the operating response of 24 surface pressures on the primary mirror cell, 5 wind velocity channels (each with direction vector information), and more than 70 channels of accelerometers on the telescope structure were measured. The data were taken in a variety of wind loading configurations. While previous analysis efforts have focused on the wind velocity and pressure measurement, this paper investigates the dynamic behavior of the telescope structure itself. Specifically, the discussion includes the participation of the modes measured in the modal impact test as a function of wind loading configuration. Data that indicate the most important frequency ranges in the operating response of the telescope are also presented. Finally, the importance of the response of the enclosure on the structural vibration of the telescope structure is discussed.

Evaluation of flawed composite structural components under static and cyclic loading. [fatigue life of graphite-epoxy composite materials

NASA Technical Reports Server (NTRS)

Porter, T. R.

1979-01-01

The effects of initial defects on the fatigue and fracture response of graphite-epoxy composite laminates are presented. The structural laminates investigated were a typical angle ply laminate, a polar/hoop wound pressure vessel laminate, and a typical engine fan blade laminate. Defects investigated were full and half penetration circular holes, full and half penetration slits, and countersink holes. The effects of the defect size and type on the static fracture strength, fatigue performance, and residual static strength are shown as well as the results of loadings on damage propagation in composite laminates. The data obtained were used to define proof test levels as a qualification procedure in composite structure subjected to cyclic loading.

Quantitative structure-property relationship (QSPR) modeling of drug-loaded polymeric micelles via genetic function approximation.

PubMed

Wu, Wensheng; Zhang, Canyang; Lin, Wenjing; Chen, Quan; Guo, Xindong; Qian, Yu; Zhang, Lijuan

2015-01-01

Self-assembled nano-micelles of amphiphilic polymers represent a novel anticancer drug delivery system. However, their full clinical utilization remains challenging because the quantitative structure-property relationship (QSPR) between the polymer structure and the efficacy of micelles as a drug carrier is poorly understood. Here, we developed a series of QSPR models to account for the drug loading capacity of polymeric micelles using the genetic function approximation (GFA) algorithm. These models were further evaluated by internal and external validation and a Y-randomization test in terms of stability and generalization, yielding an optimization model that is applicable to an expanded materials regime. As confirmed by experimental data, the relationship between microstructure and drug loading capacity can be well-simulated, suggesting that our models are readily applicable to the quantitative evaluation of the drug-loading capacity of polymeric micelles. Our work may offer a pathway to the design of formulation experiments.

Quantitative Structure-Property Relationship (QSPR) Modeling of Drug-Loaded Polymeric Micelles via Genetic Function Approximation

PubMed Central

Lin, Wenjing; Chen, Quan; Guo, Xindong; Qian, Yu; Zhang, Lijuan

2015-01-01

Self-assembled nano-micelles of amphiphilic polymers represent a novel anticancer drug delivery system. However, their full clinical utilization remains challenging because the quantitative structure-property relationship (QSPR) between the polymer structure and the efficacy of micelles as a drug carrier is poorly understood. Here, we developed a series of QSPR models to account for the drug loading capacity of polymeric micelles using the genetic function approximation (GFA) algorithm. These models were further evaluated by internal and external validation and a Y-randomization test in terms of stability and generalization, yielding an optimization model that is applicable to an expanded materials regime. As confirmed by experimental data, the relationship between microstructure and drug loading capacity can be well-simulated, suggesting that our models are readily applicable to the quantitative evaluation of the drug-loading capacity of polymeric micelles. Our work may offer a pathway to the design of formulation experiments. PMID:25780923

Strength Investigations in Aircraft Construction Under Repeated Application of the Load

NASA Technical Reports Server (NTRS)

Gassner, E.

1946-01-01

In the calculation of the dimensions of modern machines and building constructions, account is taken of the frequency of the occurrence of the anticipated loads. It is generally assumed that these loads will be repeated an infinite number, or at any rate some millions, of times during the total working life of the construction, When calculating the dimensions of the structural parts of aircraft, on the contrary, a consideration only of those frequencies in the appearance of the loads which actually come into play in the various states of stress is allowable. This is because in aircraft construction it is absolutely essential not only to ensure adequate structural strength but also to keep down the structural weight to the lowest possible limit, Strength tests in which this requirement is directly taken into account have recently been carried out by the DVL Material Strength Department.

Thermal Structures Technology Development for Reusable Launch Vehicle Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Johnson, Theodore F.; Natividad, Roderick; Rivers, H. Kevin; Smith, Russell

1998-01-01

Analytical and experimental studies conducted at the NASA Langley Research Center for investigating integrated cryogenic propellant tank systems for a Reusable Launch Vehicle are described. The cryogenic tanks are investigated as an integrated tank system. An integrated tank system includes the tank wall, cryogenic insulation, Thermal Protection System (TPS) attachment sub-structure, and TPS. Analysis codes are used to size the thicknesses of cryogenic insulation and TPS insulation for thermal loads, and to predict tank buckling strengths at various ring frame spacings. The unique test facilities developed for the testing of cryogenic tank components are described. Testing at cryogenic and high-temperatures verifies the integrity of materials, design concepts, manufacturing processes, and thermal/structural analyses. Test specimens ranging from the element level to the subcomponent level are subjected to projected vehicle operational mechanical loads and temperatures. The analytical and experimental studies described in this paper provide a portion of the basic information required for the development of light-weight reusable cryogenic propellant tanks.

Thermal Structures Technology Development for Reusable Launch Vehicle Cryogenic Propellant Tanks

NASA Technical Reports Server (NTRS)

Johnson, Theodore F.; Natividad, Roderick; Rivers, H. Kevin; Smith, Russell W.

2005-01-01

Analytical and experimental studies conducted at the NASA, Langley Research Center (LaRC) for investigating integrated cryogenic propellant tank systems for a reusable launch vehicle (RLV) are described. The cryogenic tanks are investigated as an integrated tank system. An integrated tank system includes the tank wall, cryogenic insulation, thermal protection system (TPS) attachment sub-structure, and TPS. Analysis codes are used to size the thicknesses of cryogenic insulation and TPS insulation for thermal loads, and to predict tank buckling strengths at various ring frame spacings. The unique test facilities developed for the testing of cryogenic tank components are described. Testing at cryogenic and high-temperatures verifies the integrity of materials, design concepts, manufacturing processes, and thermal/structural analyses. Test specimens ranging from the element level to the subcomponent level are subjected to projected vehicle operational mechanical loads and temperatures. The analytical and experimental studies described in this paper provide a portion of the basic information required for the development of light-weight reusable cryogenic propellant tanks.

Sensitivity of Space Launch System Buffet Forcing Functions to Buffet Mitigation Options

NASA Technical Reports Server (NTRS)

Piatak, David J.; Sekula, Martin K.; Rausch, Russ D.

2016-01-01

Time-varying buffet forcing functions arise from unsteady aerodynamic pressures and are one of many load environments, which contribute to the overall loading condition of a launch vehicle during ascent through the atmosphere. The buffet environment is typically highest at transonic conditions and can excite the vehicle dynamic modes of vibration. The vehicle response to these buffet forcing functions may cause high structural bending moments and vibratory environments, which can exceed the capabilities of the structure, or of vehicle components such as payloads and avionics. Vehicle configurations, protuberances, payload fairings, and large changes in stage diameter can trigger undesirable buffet environments. The Space Launch System (SLS) multi-body configuration and its structural dynamic characteristics presented challenges to the load cycle design process with respect to buffet-induced loads and responses. An initial wind-tunnel test of a 3-percent scale SLS rigid buffet model was conducted in 2012 and revealed high buffet environments behind the booster forward attachment protuberance, which contributed to reduced vehicle structural margins. Six buffet mitigation options were explored to alleviate the high buffet environments including modified booster nose cones and fences/strakes on the booster and core. These studies led to a second buffet test program that was conducted in 2014 to assess the ability of the buffet mitigation options to reduce buffet environments on the vehicle. This paper will present comparisons of buffet forcing functions from each of the buffet mitigation options tested, with a focus on sectional forcing function rms levels within regions of the vehicle prone to high buffet environments.

Fabrication and evaluation of superplastically formed/weld-brazed corrugated compression panels with beaded webs

NASA Technical Reports Server (NTRS)

Royster, D. M.; Davis, R. C.; Shinn, J. M., Jr.; Bales, T. T.; Wiant, H. R.

1985-01-01

A study was made to investigate the feasibility of superplastically forming corrugated panels with beaded webs and to demonstrate the structural integrity of these panels by testing. The test panels in the study consist of superplastically formed titanium alloy Ti-6Al-4V half-hat elements that are joined by weld-brazing to titanium alloy Ti-6Al-4V caps to form either single-corrugation compression panels or multiple-corrugation compression panels. Stretching and subsequent thinning of the titanium sheet during superplastic forming is reduced by approximately 35 percent with a shallow half-hat die concept instead of a deep die concept and results in a more uniform thickness across the beaded webs. The complete panels are tested in end compression at room temperature and the results compared with analysis. The heavily loaded panels failed at loads approaching the yield strength of the titanium material. At maximum load, the caps wrinkled locally accompanied with separation of the weld-braze joint in the wrinkle. None of the panels tested, however, failed catastrophically in the weld-braze joint. Experimental test results are in good agreement with structural analysis of the panels.

Dispersion and Input Control Capability in European Large Size Reverberant Acoustic Chambers

NASA Astrophysics Data System (ADS)

Yarza, A.; Lopez, J.; Ozores, E.

2012-07-01

The acoustic test in reverberant chamber is one of the load cases to be proved during the environmental test campaign that demonstrates the capability of a space- unit to survive the launch phase. The crucial requirement for the large size structures is often the survival of the acoustic vibration test, and can be defined as the design driver load case in many circumstances. In addition, the commercial market demands lighter structures as an objective to reduce costs. For an efficient optimisation of the product it is very important to have powerful structural analysis tools in order to obtain knowledge of the structural needs and to refine existing methods for the prediction of structural loads experienced during acoustic testing. In the same line, as part of the contributors involved in the test it is important to acquire knowledge of the characteristics of the reverberant chamber itself and the behaviour of the fluid. With this purpose, EADS CASA Espacio (ECE) has used the measured data of the parameters of the fluid extracted from test of the deployable reflectors validated in the past five years, with the final objective to improve and optimise the capability to face up the acoustic test. In this paper experimental data extracted from acoustic tests performed to space-units are presented. Information related to two European large size acoustic chambers are used. The pressure field inside the acoustic chamber has been post-processed with the objective to study the behaviour of the fluid during the test. The diffuseness of the pressure field and the control capability of the acoustic profile are parameters to be considered as contributors for the design of the structures. The homogeneity of the microphones’ measurements is taken into account to describe the dispersion of the pressure inside the reverberant chamber along the frequency domain. Upon of that, the capability of the facilities to control the input profile is analysed from a statistical point of view. The final conclusions allow defining the minimum tolerances to be considered based on the limits imposed by the chamber.

Geographically distributed hybrid testing & collaboration between geotechnical centrifuge and structures laboratories

NASA Astrophysics Data System (ADS)

Ojaghi, Mobin; Martínez, Ignacio Lamata; Dietz, Matt S.; Williams, Martin S.; Blakeborough, Anthony; Crewe, Adam J.; Taylor, Colin A.; Madabhushi, S. P. Gopal; Haigh, Stuart K.

2018-01-01

Distributed Hybrid Testing (DHT) is an experimental technique designed to capitalise on advances in modern networking infrastructure to overcome traditional laboratory capacity limitations. By coupling the heterogeneous test apparatus and computational resources of geographically distributed laboratories, DHT provides the means to take on complex, multi-disciplinary challenges with new forms of communication and collaboration. To introduce the opportunity and practicability afforded by DHT, here an exemplar multi-site test is addressed in which a dedicated fibre network and suite of custom software is used to connect the geotechnical centrifuge at the University of Cambridge with a variety of structural dynamics loading apparatus at the University of Oxford and the University of Bristol. While centrifuge time-scaling prevents real-time rates of loading in this test, such experiments may be used to gain valuable insights into physical phenomena, test procedure and accuracy. These and other related experiments have led to the development of the real-time DHT technique and the creation of a flexible framework that aims to facilitate future distributed tests within the UK and beyond. As a further example, a real-time DHT experiment between structural labs using this framework for testing across the Internet is also presented.

Progressive Damage and Failure Analysis of Composite Laminates

NASA Astrophysics Data System (ADS)

Joseph, Ashith P. K.

Composite materials are widely used in various industries for making structural parts due to higher strength to weight ratio, better fatigue life, corrosion resistance and material property tailorability. To fully exploit the capability of composites, it is required to know the load carrying capacity of the parts made of them. Unlike metals, composites are orthotropic in nature and fails in a complex manner under various loading conditions which makes it a hard problem to analyze. Lack of reliable and efficient failure analysis tools for composites have led industries to rely more on coupon and component level testing to estimate the design space. Due to the complex failure mechanisms, composite materials require a very large number of coupon level tests to fully characterize the behavior. This makes the entire testing process very time consuming and costly. The alternative is to use virtual testing tools which can predict the complex failure mechanisms accurately. This reduces the cost only to it's associated computational expenses making significant savings. Some of the most desired features in a virtual testing tool are - (1) Accurate representation of failure mechanism: Failure progression predicted by the virtual tool must be same as those observed in experiments. A tool has to be assessed based on the mechanisms it can capture. (2) Computational efficiency: The greatest advantages of a virtual tools are the savings in time and money and hence computational efficiency is one of the most needed features. (3) Applicability to a wide range of problems: Structural parts are subjected to a variety of loading conditions including static, dynamic and fatigue conditions. A good virtual testing tool should be able to make good predictions for all these different loading conditions. The aim of this PhD thesis is to develop a computational tool which can model the progressive failure of composite laminates under different quasi-static loading conditions. The analysis tool is validated by comparing the simulations against experiments for a selected number of quasi-static loading cases.

Structural load testing and flexure analysis of the Route 701 Bridge in Louisa County, Virginia : supplemental report.

DOT National Transportation Integrated Search

2006-01-01

A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current 12-ton posted load restriction of the bridge (instituted ...

Finite element simulation of structural performance on flexible pavements with stabilized base/treated sub-base materials under accelerated loading : research project capsule.

DOT National Transportation Integrated Search

2008-12-01

PROBLEM: The full-scale accelerated pavement testing (APT) provides a unique tool for pavement : engineers to directly collect pavement performance and failure data under heavy : wheel loading. However, running a full-scale APT experiment is very exp...

29 CFR 1910.181 - Derricks.

Code of Federal Regulations, 2013 CFR

2013-07-01

... avoid carrying loads over people. (vii) The operator shall test the brakes each time a load approaching... base supported by ropes attached to corner posts or other parts of the structure. The base is at a... safety hazard: (i) All control mechanisms: Inspect daily for adjustment, wear, and lubrication. (ii) All...

29 CFR 1910.181 - Derricks.

Code of Federal Regulations, 2012 CFR

2012-07-01

... avoid carrying loads over people. (vii) The operator shall test the brakes each time a load approaching... base supported by ropes attached to corner posts or other parts of the structure. The base is at a... safety hazard: (i) All control mechanisms: Inspect daily for adjustment, wear, and lubrication. (ii) All...

29 CFR 1910.181 - Derricks.

Code of Federal Regulations, 2014 CFR

2014-07-01

... avoid carrying loads over people. (vii) The operator shall test the brakes each time a load approaching... base supported by ropes attached to corner posts or other parts of the structure. The base is at a... safety hazard: (i) All control mechanisms: Inspect daily for adjustment, wear, and lubrication. (ii) All...

29 CFR 1910.181 - Derricks.

Code of Federal Regulations, 2011 CFR

2011-07-01

... avoid carrying loads over people. (vii) The operator shall test the brakes each time a load approaching... base supported by ropes attached to corner posts or other parts of the structure. The base is at a... safety hazard: (i) All control mechanisms: Inspect daily for adjustment, wear, and lubrication. (ii) All...

Finite element simulation of structural performance on flexible pavements with stabilized base/treated subbase materials under accelerated loading : tech summary.

DOT National Transportation Integrated Search

2011-12-01

Accelerated pavement testing (APT) has been increasingly used by state highway agencies in recent years for evaluating pavement : design and performance through applying a simulative heavy vehicular load to the pavement section under controlled fi el...

Structural load testing and flexure analysis of the Route 701 Bridge in Louisa County, Virginia.

DOT National Transportation Integrated Search

2004-01-01

A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current load rating of the bridge could be raised and to document...

Method and apparatus for testing surface characteristics of a material

NASA Technical Reports Server (NTRS)

Johnson, David L. (Inventor); Kersker, Karl D. (Inventor); Stratton, Troy C. (Inventor); Richardson, David E. (Inventor)

2006-01-01

A method, apparatus and system for testing characteristics of a material sample is provided. The system includes an apparatus configured to house the material test sample while defining a sealed volume against a surface of the material test sample. A source of pressurized fluid is in communication with, and configured to pressurize, the sealed volume. A load applying apparatus is configured to apply a defined load to the material sample while the sealed volume is monitored for leakage of the pressurized fluid. Thus, the inducement of surface defects such as microcracking and crazing may be detected and their effects analyzed for a given material. The material test samples may include laminar structures formed of, for example, carbon cloth phenolic, glass cloth phenolic, silica cloth phenolic materials or carbon-carbon materials. In one embodiment the system may be configured to analyze the material test sample while an across-ply loading is applied thereto.

Damage tolerance of pressurized graphite/epoxy tape cylinders under uniaxial and biaxial loading. M.S. Thesis

NASA Technical Reports Server (NTRS)

Priest, Stacy Marie

1993-01-01

The damage tolerance behavior of internally pressurized, axially slit, graphite/epoxy tape cylinders was investigated. Specifically, the effects of axial stress, structural anisotropy, and subcritical damage were considered. In addition, the limitations of a methodology which uses coupon fracture data to predict cylinder failure were explored. This predictive methodology was previously shown to be valid for quasi-isotropic fabric and tape cylinders but invalid for structurally anisotropic (+/-45/90)(sub s) and (+/-45/0)(sub s) cylinders. The effects of axial stress and structural anisotropy were assessed by testing tape cylinders with (90/0/+/-45)(sub s), (+/-45/90)(sub s), and (+/-45/0)(sub s) layups in a uniaxial test apparatus, specially designed and built for this work, and comparing the results to previous tests conducted in biaxial loading. Structural anisotropy effects were also investigated by testing cylinders with the quasi-isotropic (0/+/-45/90)(sub s) layup which is a stacking sequence variation of the previously tested (90/0/+/-45)(sub s) layup with higher D(sub 16) and D(sub 26) terms but comparable D(sub 16) and D(sub 26) to D(sub 11) ratios. All cylinders tested and used for comparison are made from AS4/3501-6 graphite/epoxy tape and have a diameter of 305 mm. Cylinder slit lengths range from 12.7 to 50.8 mm. Failure pressures are lower for the uniaxially loaded cylinders in all cases. The smallest percent failure pressure decreases are observed for the (+/-45/90)(sub s) cylinders, while the greatest such decreases are observed for the (+/-45/0)(sub s) cylinders. The relative effects of the axial stress on the cylinder failure pressures do not correlate with the degree of structural coupling. The predictive methodology is not applicable for uniaxially loaded (+/-45/90)(sub s) and (+/-45/0)(sub s) cylinders, may be applicable for uniaxially loaded (90/0/+/-45)(sub s) cylinders, and is applicable for the biaxially loaded (90/0/+/-45)(sub s) and (0/+/-45/90)(sub s) cylinders. This indicates that the ratios of D(sub 16) and D(sub 26) to D(sub 11), as opposed to the absolute magnitudes of D(sub 16) and D(sub 26), may be important in the failure of these cylinders and in the applicability of the methodology. Discontinuities observed in the slit tip hoop strains for all the cylinders tested indicate that subcritical damage can play an important role in the failure of tape cylinders. This role varies with layup and loading condition and is likely coupled to the effects of structural anisotropy. Biaxial failure pressures may exceed the uniaxial values because the axial stress contributes to the formation of 0 deg ply splitting (accompanied by delamination) or similar stress-mitigating subcritical damage. The failure behavior of similar cylinders can also vary as a result of differences in the role of subcritical damage as observed for the case of a biaxially loaded (90/0/+/-45)(sub s) cylinder with a 12.7 mm slit. For this case, the methodology is valid when the initial coupon and cylinder fracture modes agree. However, the methodology underpredicts the failure pressure of the cylinder when a circumferential fracture path, suggestive of a 0 deg ply split, occurs at one slit tip. Thus, the failure behavior of some tape cylinders may be highly sensitive to the initial subcritical damage mechanism. Finite element analyses are recommended to determine how structural anisotropy and axial stress modify the slit tip stress states in cylinders from those found in flat plates since similarity of these stress states is a fundamental assumption of the current predictive methodology.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

On the tarmac at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, the agency's Super Guppy aircraft closes after the Orion Exploration Mission-1 (EM-1) structural test article, in its transport container, is secured inside. The test article will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Optimal structural design of a 5-kW CPV tracking system by considering the ISO 4017/4762 standard through structure and flow simulations

NASA Astrophysics Data System (ADS)

Lee, Hyo Geun; Kim, Sang Suk; Kim, Sung Jo; Park, Su-Jin; Yun, Chang-wuk; Im, Gil-pyeong

2015-09-01

Photovoltaic generation systems have disadvantage in that they are usually installed outdoors and are exposed to extreme environments such as wind, snow and rain loadings. The structure of a photovoltaic generation system should be designed to have sufficient stiffness and strength against such loads. Especially, electric power generation by a concentrator photovoltaic(CPV) system can produce enough power if a right angle is main fained between the solar and the CPV panel within 90° ± 1°. To make the CPV tracking system in this study, we designed the structure by calculating the variations in and the strees applied to the structure by the wind load when the CPV tracking was influenced by the wind load. In this study, a 5-kW CPV tracking structure was designed through a structural analysis and a finiteelement analysis for a wind speed of 65 m/s by using ANSYS. The simulation of the structural design showed that the, structure of the 5-kW CPV tracking system corresponded with the ISO4017/ISO4762 standard. Based on this research, we will produce a 5-kW CPV tracking system and proceed to field test.

Simulation Study of Stress and Deformation Behaviour of Debonded Laminated Structure

NASA Astrophysics Data System (ADS)

Hirwani, C. K.; Mittal, H.; Panda, S. K.; Mahapatra, S. S.; Mandal, S. K.; De, A. K.

2017-02-01

The bending strength and deformation characteristics of the debonded laminated plate under the uniformly distributed loading (UDL) have been investigated in this research article. For the simulation study, an internally damaged laminated plate structure model has been developed in ANSYS based on the first-order shear deformable kinematic theory via ANSYS parametric design language (APDL) code. The internal debonding within the laminated structure is incorporated using two sub-laminate approach. Further, the convergence (different mesh densities), as well as the validity (comparing the responses with published results) of the present simulation model, have been performed by solving the deflection responses under the influence of transversely loaded layered structure. Also, to show the coherence of the simulation analysis the results are compared with the experimental bending results of the homemade Glass/Epoxy composite with artificial delamination. For the experimental analysis, Glass/Epoxy laminated composite seeded with delamination at the central mid-plane of the laminate is fabricated using an open mould hand lay-up composites fabrication technique. For the computational purpose, the necessary material properties of fabricated composite plate evaluated experimentally via uniaxial tensile test (Universal Testing Machine INSTRON-1195). Further, the bending (three-point bend test) test is conducted with the help of Universal Testing Machine INSTRON-5967. Finally, the effect different geometrical and material parameters (thickness ratio, modular ratio, constraint conditions) and magnitude of the loading on the static deflection and stress behaviour of the delaminated composite plate are investigated thoroughly by solving different kinds of numerical illustrations and discussed in detail.

Lateral Load Testing of the Advanced Stirling Convertor (ASC-E2) Heater Head

NASA Technical Reports Server (NTRS)

Cornell, Peggy A.; Krause, David L.; Davis, Glen; Robbie, Malcolm G.; Gubics, David A.

2010-01-01

Free-piston Stirling convertors are fundamental to the development of NASA s next generation of radioisotope power system, the Advanced Stirling Radioisotope Generator (ASRG). The ASRG will use General Purpose Heat Source (GPHS) modules as the energy source and Advanced Stirling Convertors (ASCs) to convert heat into electrical energy, and is being developed by Lockheed Martin under contract to the Department of Energy. Achieving flight status mandates that the ASCs satisfy design as well as flight requirements to ensure reliable operation during launch. To meet these launch requirements, GRC performed a series of quasi-static mechanical tests simulating the pressure, thermal, and external loading conditions that will be experienced by an ASC-E2 heater head assembly. These mechanical tests were collectively referred to as "lateral load tests" since a primary external load lateral to the heater head longitudinal axis was applied in combination with the other loading conditions. The heater head was subjected to the operational pressure, axial mounting force, thermal conditions, and axial and lateral launch vehicle acceleration loadings. To permit reliable prediction of the heater head s structural performance, GRC completed Finite Element Analysis (FEA) computer modeling for the stress, strain, and deformation that will result during launch. The heater head lateral load test directly supported evaluation of the analysis and validation of the design to meet launch requirements. This paper provides an overview of each element within the test and presents assessment of the modeling as well as experimental results of this task.

Lateral Load Testing of the Advanced Stirling Convertor (ASC-E2) Heater Head

NASA Technical Reports Server (NTRS)

Cornell, Peggy A.; Krause, David L.; Davis, Glen; Robbie, Malcolm G.; Gubics, David A.

2011-01-01

Free-piston Stirling convertors are fundamental to the development of NASA s next generation of radioisotope power system, the Advanced Stirling Radioisotope Generator (ASRG). The ASRG will use General Purpose Heat Source (GPHS) modules as the energy source and Advanced Stirling Convertors (ASCs) to convert heat into electrical energy, and is being developed by Lockheed Martin under contract to the Department of Energy. Achieving flight status mandates that the ASCs satisfy design as well as flight requirements to ensure reliable operation during launch. To meet these launch requirements, GRC performed a series of quasi-static mechanical tests simulating the pressure, thermal, and external loading conditions that will be experienced by an ASC-E2 heater head assembly. These mechanical tests were collectively referred to as "lateral load tests" since a primary external load lateral to the heater head longitudinal axis was applied in combination with the other loading conditions. The heater head was subjected to the operational pressure, axial mounting force, thermal conditions, and axial and lateral launch vehicle acceleration loadings. To permit reliable prediction of the heater head s structural performance, GRC completed Finite Element Analysis (FEA) computer modeling for the stress, strain, and deformation that will result during launch. The heater head lateral load test directly supported evaluation of the analysis and validation of the design to meet launch requirements. This paper provides an overview of each element within the test and presents assessment of the modeling as well as experimental results of this task.

Lateral Load Testing of the Advanced Stirling Convertor (ASC-E2) Heater Head

NASA Technical Reports Server (NTRS)

Cornell, Peggy A.; Krause, David L.; Davis, Glen; Robbie, Malcolm G.; Gubics, David A.

2010-01-01

Free-piston Stirling convertors are fundamental to the development of NASA s next generation of radioisotope power system, the Advanced Stirling Radioisotope Generator (ASRG). The ASRG will use General Purpose Heat Source (GPHS) modules as the energy source and Advanced Stirling Convertors (ASCs) to convert heat into electrical energy, and is being developed by Lockheed Martin under contract to the Department of Energy. Achieving flight status mandates that the ASCs satisfy design as well as flight requirements to ensure reliable operation during launch. To meet these launch requirements, GRC performed a series of quasi-static mechanical tests simulating the pressure, thermal, and external loading conditions that will be experienced by an ASC E2 heater head assembly. These mechanical tests were collectively referred to as lateral load tests since a primary external load lateral to the heater head longitudinal axis was applied in combination with the other loading conditions. The heater head was subjected to the operational pressure, axial mounting force, thermal conditions, and axial and lateral launch vehicle acceleration loadings. To permit reliable prediction of the heater head s structural performance, GRC completed Finite Element Analysis (FEA) computer modeling for the stress, strain, and deformation that will result during launch. The heater head lateral load test directly supported evaluation of the analysis and validation of the design to meet launch requirements. This paper provides an overview of each element within the test and presents assessment of the modeling as well as experimental results of this task.

Functional testing of space flight induced changes in tonic motor control by using limb-attached excitation and load devices

NASA Astrophysics Data System (ADS)

Gallasch, Eugen; Kozlovskaya, Inessa

2007-02-01

Long term space flights induce atrophy and contractile changes on postural muscles such effecting tonic motor control. Functional testing of tonic motor control structures is a challenge because of the difficulties to deliver appropriate test forces on crew members. In this paper we propose two approaches for functional testing by using limb attached loading devices. The first approach is based on a frequency and amplitude controllable moving magnet exciter to deliver sinusoidal test forces during limb postures. The responding limb deflection is recorded by an embedded accelerometer to obtain limb impedance. The second approach is based on elastic limb loading to evoke self-excited oscillations during arm extensions. Here the contraction force at the oscillation onset provides information about limb stiffness. The rationale for both testing approaches is based on Feldman's λ-model. An arm expander based on the second approach was probed in a 6-month MIR space flight. The results obtained from the load oscillations, confirmed that this device is well suited to capture space flight induced neuromuscular changes.

An Inverse Interpolation Method Utilizing In-Flight Strain Measurements for Determining Loads and Structural Response of Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Shkarayev, S.; Krashantisa, R.; Tessler, A.

2004-01-01

An important and challenging technology aimed at the next generation of aerospace vehicles is that of structural health monitoring. The key problem is to determine accurately, reliably, and in real time the applied loads, stresses, and displacements experienced in flight, with such data establishing an information database for structural health monitoring. The present effort is aimed at developing a finite element-based methodology involving an inverse formulation that employs measured surface strains to recover the applied loads, stresses, and displacements in an aerospace vehicle in real time. The computational procedure uses a standard finite element model (i.e., "direct analysis") of a given airframe, with the subsequent application of the inverse interpolation approach. The inverse interpolation formulation is based on a parametric approximation of the loading and is further constructed through a least-squares minimization of calculated and measured strains. This procedure results in the governing system of linear algebraic equations, providing the unknown coefficients that accurately define the load approximation. Numerical simulations are carried out for problems involving various levels of structural approximation. These include plate-loading examples and an aircraft wing box. Accuracy and computational efficiency of the proposed method are discussed in detail. The experimental validation of the methodology by way of structural testing of an aircraft wing is also discussed.

A servo controlled gradient loading triaxial model test system for deep-buried cavern.

PubMed

Chen, Xu-guang; Zhang, Qiang-yong; Li, Shu-cai

2015-10-01

A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the "real" geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures.

Inverse Force Determination on a Small Scale Launch Vehicle Model Using a Dynamic Balance

NASA Technical Reports Server (NTRS)

Ngo, Christina L.; Powell, Jessica M.; Ross, James C.

2017-01-01

A launch vehicle can experience large unsteady aerodynamic forces in the transonic regime that, while usually only lasting for tens of seconds during launch, could be devastating if structural components and electronic hardware are not designed to account for them. These aerodynamic loads are difficult to experimentally measure and even harder to computationally estimate. The current method for estimating buffet loads is through the use of a few hundred unsteady pressure transducers and wind tunnel test. Even with a large number of point measurements, the computed integrated load is not an accurate enough representation of the total load caused by buffeting. This paper discusses an attempt at using a dynamic balance to experimentally determine buffet loads on a generic scale hammer head launch vehicle model tested at NASA Ames Research Center's 11' x 11' transonic wind tunnel. To use a dynamic balance, the structural characteristics of the model needed to be identified so that the natural modal response could be and removed from the aerodynamic forces. A finite element model was created on a simplified version of the model to evaluate the natural modes of the balance flexures, assist in model design, and to compare to experimental data. Several modal tests were conducted on the model in two different configurations to check for non-linearity, and to estimate the dynamic characteristics of the model. The experimental results were used in an inverse force determination technique with a psuedo inverse frequency response function. Due to the non linearity, the model not being axisymmetric, and inconsistent data between the two shake tests from different mounting configuration, it was difficult to create a frequency response matrix that satisfied all input and output conditions for wind tunnel configuration to accurately predict unsteady aerodynamic loads.

On the torque and wear behavior of selected thin film MOS2 lubricated gimbal bearings

NASA Technical Reports Server (NTRS)

Bohner, John J.; Conley, Peter L.

1988-01-01

During the thermal vacuum test phase of the GOES 7 spacecraft, the primary scan mirror system exhibited unacceptably high drive friction. The observed friction was found to correlate with small misalignments in the mirror structure and unavoidable loads induced by the vehicle spin. An intensive effort to understand and document the performance of the scan mirror bearing system under these loads is described. This effort involved calculation of the bearing loads and expected friction torque, comparison of the computed values to test data, and verification of the lubrication system performance and limitations under external loads. The study culminated in a successful system launch in February of 1987. The system has operated as predicted since that time.

Static and dynamic crush testing and analysis of a rail vehicle corner structural element

DOT National Transportation Integrated Search

1999-11-01

This paper presents the results of an experimental study to establish the strength and energy absorption capability of cab car rail vehicle corner structures built to current strength requirements and for structures modified to carry higher loads and...

Multiseed liposomal drug delivery system using micelle gradient as driving force to improve amphiphilic drug retention and its anti-tumor efficacy.

PubMed

Zhang, Wenli; Li, Caibin; Jin, Ya; Liu, Xinyue; Wang, Zhiyu; Shaw, John P; Baguley, Bruce C; Wu, Zimei; Liu, Jianping

2018-11-01

To improve drug retention in carriers for amphiphilic asulacrine (ASL), a novel active loading method using micelle gradient was developed to fabricate the ASL-loaded multiseed liposomes (ASL-ML). The empty ML were prepared by hydrating a thin film with empty micelles. Then the micelles in liposomal compartment acting as 'micelle pool' drove the drug to be loaded after the outer micelles were removed. Some reasoning studies including critical micelle concentration (CMC) determination, influencing factors tests on entrapment efficiency (EE), structure visualization, and drug release were carried out to explore the mechanism of active loading, ASL location, and the structure of ASL-ML. Comparisons were made between pre-loading and active loading method. Finally, the extended drug retention capacity of ML was evaluated through pharmacokinetic, drug tissue irritancy, and in vivo anti-tumor activity studies. Comprehensive results from fluorescent and transmission electron microscope (TEM) observation, encapsulation efficiency (EE) comparison, and release studies demonstrated the formation of ML-shell structure for ASL-ML without inter-carrier fusion. The location of drug mainly in inner micelles as well as the superiority of post-loading to the pre-loading method , in which drug in micelles shifted onto the bilayer membrane was an additional positive of this delivery system. It was observed that the drug amphiphilicity and interaction of micelles with drug were the two prerequisites for this active loading method. The extended retention capacity of ML has been verified through the prolonged half-life, reduced paw-lick responses in rats, and enhanced tumor inhibition in model mice. In conclusion, ASL-ML prepared by active loading method can effectively load drug into micelles with expected structure and improve drug retention.

Effects of Interlocking and Supporting Conditions on Concrete Block Pavements

NASA Astrophysics Data System (ADS)

Mahapatra, Geetimukta; Kalita, Kuldeep

2018-02-01

Concrete Block Paving (CBP) is widely used as wearing course in flexible pavements, preferably under light and medium vehicular loadings. Construction of CBP at site is quick and easy in quality control. Usually, flexible pavement design philosophy is followed in CBP construction, though it is structurally different in terms of small block elements with high strength concrete and their interlocking aspects, frequent joints and discontinuity, restrained edge etc. Analytical solution for such group action of concrete blocks under loading in a three dimensional multilayer structure is complex and thus, the need of conducting experimental studies is necessitated for extensive understanding of the load—deformation characteristics and behavior of concrete blocks in pavement. The present paper focuses on the experimental studies for load transfer characteristics of CBP under different interlocking and supporting conditions. It is observed that both interlocking and supporting conditions affect significantly on the load transfer behavior in CBP structures. Coro-lock block exhibits better performance in terms of load carrying capacity and distortion behavior under static loads. Plate load tests are performed over subgrade, granular sub-base (GSB), CBP with and without GSB using different block shapes. For an example case, the comparison of CBP with conventional flexible pavement section is also presented and it is found that CBP provides considerable benefit in terms of construction cost of the road structure.

A study on the crushing behavior of basalt fiber reinforced composite structures

NASA Astrophysics Data System (ADS)

Pandian, A.; Veerasimman, A. P.; Vairavan, M.; Francisco, C.; Sultan, M. T. H.

2016-10-01

The crushing behavior and energy absorption capacity of basalt fiber reinforced hollow square structure composites are studied under axial compression. Using the hand layup technique, basalt fiber reinforced composites were fabricated using general purpose (GP) polyester resin with the help of wooden square shaped mould of varying height (100 mm, 150 mm and 200 mm). For comparison, similar specimens of glass fiber reinforced polymer composites were also fabricated and tested. Axial compression load is applied over the top end of the specimen with cross head speed as 2 mm/min using Universal Testing Machine (UTM). From the experimental results, the load-deformation characteristics of both glass fiber and basalt fiber composites were investigated. Crashworthiness and mode of collapse for the composites were determined from load-deformation curve, and they were then compared to each other in terms of their crushing behaviors.

Fracture modes in human teeth.

PubMed

Lee, J J-W; Kwon, J-Y; Chai, H; Lucas, P W; Thompson, V P; Lawn, B R

2009-03-01

The structural integrity of teeth under stress is vital to functional longevity. We tested the hypothesis that this integrity is limited by fracture of the enamel. Experiments were conducted on molar teeth, with a metal rod loaded onto individual cusps. Fracture during testing was tracked with a video camera. Two longitudinal modes of cracking were observed: median cracking from the contact zone, and margin cracking along side walls. Median cracks initiated from plastic damage at the contact site, at first growing slowly and then accelerating to the tooth margin. Margin cracks appeared to originate from the cemento-enamel junction, and traversed the tooth wall adjacent to the loaded cusp from the gingival to the occlusal surface. All cracks remained confined within the enamel shell up to about 550 N. At higher loads, additional crack modes--such as enamel chipping and delamination--began to manifest themselves, leading to more comprehensive failure of the tooth structure.

Study of the fracture kinetics in structural aluminum alloys subjected to a long-term action of a static load and a corrosive medium using specimens of a new type

NASA Astrophysics Data System (ADS)

Kablov, E. N.; Grinevich, A. V.; Lutsenko, A. N.; Erasov, V. S.; Nuzhnyi, G. A.; Gulina, I. V.

2017-04-01

A new type of specimens is proposed to study the fracture kinetics of the metallic materials subjected to a long-term simultaneous action of a tensile load and a corrosive medium. The new design of specimens makes it possible to determine the stress intensity factor at the crack opening fixed by a wedging bolt, to perform investigations in any aggressive medium, and to measure the tensile load on a specimen at any stage of tests. Standard apparatus is used for this purpose. Plate specimens made of structural aluminum alloys 1163T and V95pchT2 are tested. A paradoxical fact of increasing the conventional stress intensity factor of the V95pchT2 alloy during the development of a corrosion crack is revealed.

Analysis of Bearing Capacity Pile Foundation with Using Capwap Software for Testing Pile Driving Analyzer (pda) at Fasfel Development Project Parlimbungan Ketek Sikara-Kara Mandailing Natal District (north Sumatera)

NASA Astrophysics Data System (ADS)

Oberlyn Simanjuntak, Johan; Suita, Diana

2017-12-01

Pile foundation is one type deep foundation that serves to distribute the load of hard soil structure loading which has a high bearing capacity that is located deep enough inside the soil. To determine the bearing capacity of the pile and at the same time control the Calendring results, the Pile Driving Analyzer (PDA) test at 8 pile sections from the 84 point piling section (10% of the number sections), the results were analyzed by CAPWAP SOFTWARE, and the highest bearing capacity of Ru 177 ton and the lowest bearing capacity of 111 tons, is bigger than the plan load which load plans that is 60,9 tons. Finally the PDA safe is bearing bearing capacity of the load planning.

Damage assessment in reinforced concrete using nonlinear vibration techniques

NASA Astrophysics Data System (ADS)

Van Den Abeele, K.; De Visscher, J.

2000-07-01

Reinforced concrete (RC) structures are subject to microcrack initiation and propagation at load levels far below the actual failure load. In this paper, nonlinear vibration techniques are applied to investigate stages of progressive damage in RC beams induced by static loading tests. At different levels of damage, a modal analysis is carried out, assuming the structure to behave linearly. At the same time, measurement of resonant frequencies and damping ratios as function of vibration amplitude are performed using a frequency domain technique as well as a time domain technique. We compare the results of the linear and nonlinear techniques, and value them against the visual damage evaluation.

Mechanical properties and micro-morphology of fiber posts.

PubMed

Zicari, F; Coutinho, E; Scotti, R; Van Meerbeek, B; Naert, I

2013-04-01

To evaluate flexural properties of different fiber posts systems and to morphologically characterize their micro-structure. Six types of translucent fiber posts were selected: RelyX Post (3M ESPE), ParaPost Taper Lux (Colthéne-Whaledent), GC Fiber Post (GC), LuxaPost (DMG), FRC Postec Plus (Ivoclar-Vivadent), D.T. Light-Post (RTD). For each post system and size, ten specimens were subjected to a three-points bending test. Maximum fracture load, flexural strength and flexural modulus were determined using a universal loading device (5848 MicroTester(®), Instron). Besides, for each system, three intact posts of similar dimensions were processed for scanning electron microscopy to morphologically characterize the micro-structure. The following structural characteristics were analyzed: fibers/matrix ratio, density of fibers, diameter of fibers and distribution of fibers. Data were statistically analyzed with ANOVA. Type and diameter of posts were found to significantly affect the fracture load, flexural strength and flexural modulus (p<0.05). Regarding maximum fracture load, it was found to increase with post diameter, in each post system (p<0.001). Regarding flexural strength and flexural modulus, the highest values were recorded for posts with the smallest diameter (p<0.001). Finally, structural characteristics significantly varied among the post systems tested. However, any correlation has been found between flexural strength and structural characteristics. Flexural strength appeared not to be correlated to structural characteristics of fiber posts, but it may rather be affected by mechanical properties of the resin matrix and the interfacial adhesion between fibers and resin matrix. Copyright © 2013. Published by Elsevier Ltd.

Characterizing the Conductivity and Enhancing the Piezoresistivity of Carbon Nanotube-Polymeric Thin Films

PubMed Central

Zhao, Yingjun; Schagerl, Martin; Viechtbauer, Christoph

2017-01-01

The concept of lightweight design is widely employed for designing and constructing aerospace structures that can sustain extreme loads while also being fuel-efficient. Popular lightweight materials such as aluminum alloy and fiber-reinforced polymers (FRPs) possess outstanding mechanical properties, but their structural integrity requires constant assessment to ensure structural safety. Next-generation structural health monitoring systems for aerospace structures should be lightweight and integrated with the structure itself. In this study, a multi-walled carbon nanotube (MWCNT)-based polymer paint was developed to detect distributed damage in lightweight structures. The thin film’s electromechanical properties were characterized via cyclic loading tests. Moreover, the thin film’s bulk conductivity was characterized by finite element modeling. PMID:28773084

DACS II - A distributed thermal/mechanical loads data acquisition and control system

NASA Technical Reports Server (NTRS)

Zamanzadeh, Behzad; Trover, William F.; Anderson, Karl F.

1987-01-01

A distributed data acquisition and control system has been developed for the NASA Flight Loads Research Facility. The DACS II system is composed of seven computer systems and four array processors configured as a main computer system, three satellite computer systems, and 13 analog input/output systems interconnected through three independent data networks. Up to three independent heating and loading tests can be run concurrently on different test articles or the entire system can be used on a single large test such as a full scale hypersonic aircraft. Thermal tests can include up to 512 independent adaptive closed loop control channels. The control system can apply up to 20 MW of heating to a test specimen while simultaneously applying independent mechanical loads. Each thermal control loop is capable of heating a structure at rates of up to 150 F per second over a temperature range of -300 to +2500 F. Up to 64 independent mechanical load profiles can be commanded along with thermal control. Up to 1280 analog inputs monitor temperature, load, displacement and strain on the test specimens with real time data displayed on up to 15 terminals as color plots and tabular data displays. System setup and operation is accomplished with interactive menu-driver displays with extensive facilities to assist the users in all phases of system operation.

Structural Stability of a Stiffened Aluminum Fuselage Panel Subjected to Combined Mechanical and Internal Pressure Loads

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Young, Richard D.; Gehrki, Ralph R.

2003-01-01

Results from an experimental and analytical study of a curved stiffened aluminum panel subjected to combined mechanical and internal pressure loads are presented. The panel loading conditions were simulated using a D-box test fixture. Analytical buckling load results calculated from a finite element analysis are presented and compared to experimental results. Buckling results presented indicate that the buckling load of the fuselage panel is significantly influenced by internal pressure loading. The experimental results suggest that the stress distribution is uniform in the panel prior to buckling. Nonlinear finite element analysis results correlates well with experimental results up to buckling.

Impact tests on fibrous composite sandwich structures

NASA Technical Reports Server (NTRS)

Rhodes, M. D.

1978-01-01

The effect of low velocity impact on the strength of laminates fabricated from graphite/epoxy and Kevlar 49/epoxy composite materials was studied. The test laminates were loaded statically either in uniaxial tension or compression when impact occurred to evaluate the effect of loading on the initiation of damage and/or failure. Typical aircraft service conditions such as runway debris encountered during landing were simulated by impacting 1.27-cm-diameter projectiles normal to the plane of the test laminates at velocities between 5.2 and 48.8 m/s.

Fluid mass and thermal loading effects on the modal characteristics of space shuttle main engine liquid oxygen inlet splitter vanes

NASA Technical Reports Server (NTRS)

Panossian, H. V.; Boehnlein, J. J.

1987-01-01

An analysis and evaluation of experimental modal survey test data on the variations of modal characteristics induced by pressure and thermal loading events are presented. Extensive modal survey tests were carried out on a Space Shuttle Main Engine (SSME) test article using liquid nitrogen under cryogenic temperatures and high pressures. The results suggest that an increase of pressure under constant cryogenic temperature or a decrease of temperature under high pressure induces an upward shift of frequencies of various modes of the structures.

Optimal periodic proof test based on cost-effective and reliability criteria

NASA Technical Reports Server (NTRS)

Yang, J.-N.

1976-01-01

An exploratory study for the optimization of periodic proof tests for fatigue-critical structures is presented. The optimal proof load level and the optimal number of periodic proof tests are determined by minimizing the total expected (statistical average) cost, while the constraint on the allowable level of structural reliability is satisfied. The total expected cost consists of the expected cost of proof tests, the expected cost of structures destroyed by proof tests, and the expected cost of structural failure in service. It is demonstrated by numerical examples that significant cost saving and reliability improvement for fatigue-critical structures can be achieved by the application of the optimal periodic proof test. The present study is relevant to the establishment of optimal maintenance procedures for fatigue-critical structures.

Vibroacoustic Response of Pad Structures to Space Shuttle Launch Acoustic Loads

NASA Technical Reports Server (NTRS)

Margasahayam, R. N.; Caimi, Raoul E.

1995-01-01

This paper presents a deterministic theory for the random vibration problem for predicting the response of structures in the low-frequency range (0 to 20 hertz) of launch transients. Also presented are some innovative ways to characterize noise and highlights of ongoing test-analysis correlation efforts titled the Verification Test Article (VETA) project.

Semiotic Structure and Meaning Making: The Performance of English Language Learners on Mathematics Tests

ERIC Educational Resources Information Center

Solano-Flores, Guillermo; Barnett-Clarke, Carne; Kachchaf, Rachel R.

2013-01-01

We examined the performance of English language learners (ELLs) and non-ELLs on Grade 4 and Grade 5 mathematics content knowledge (CK) and academic language (AL) tests. CK and AL items had different semiotic loads (numbers of different types of semiotic features) and different semiotic structures (relative frequencies of different semiotic…

Foil system fatigue load environments for commercial hydrofoil operation

NASA Technical Reports Server (NTRS)

Graves, D. L.

1979-01-01

The hydrofoil fatigue loads environment in the open sea is examined. The random nature of wave orbital velocities, periods and heights plus boat heading, speed and control system design are considered in the assessment of structural fatigue requirements. Major nonlinear load events such as hull slamming and foil unwetting are included in the fatigue environment. Full scale rough water load tests, field experience plus analytical loads work on the model 929 Jetfoil commercial hydrofoil are discussed. The problem of developing an overall sea environment for design is defined. State of the art analytical approaches are examined.

Comparison of Analysis with Test for Static Loading of Two Hypersonic Inflatable Aerodynamic Decelerator Concepts

NASA Technical Reports Server (NTRS)

Lyle, Karen H.

2015-01-01

Acceptance of new spacecraft structural architectures and concepts requires validated design methods to minimize the expense involved with technology demonstration via flight-testing. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) architectures are attractive for spacecraft deceleration because they are lightweight, store compactly, and utilize the atmosphere to decelerate a spacecraft during entry. However, designers are hesitant to include these inflatable approaches for large payloads or spacecraft because of the lack of flight validation. This publication summarizes results comparing analytical results with test data for two concepts subjected to representative entry, static loading. The level of agreement and ability to predict the load distribution is considered sufficient to enable analytical predictions to be used in the design process.

Advanced Composite Wind Turbine Blade Design Based on Durability and Damage Tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abumeri, Galib; Abdi, Frank

2012-02-16

The objective of the program was to demonstrate and verify Certification-by-Analysis (CBA) capability for wind turbine blades made from advanced lightweight composite materials. The approach integrated durability and damage tolerance analysis with robust design and virtual testing capabilities to deliver superior, durable, low weight, low cost, long life, and reliable wind blade design. The GENOA durability and life prediction software suite was be used as the primary simulation tool. First, a micromechanics-based computational approach was used to assess the durability of composite laminates with ply drop features commonly used in wind turbine applications. Ply drops occur in composite joints andmore » closures of wind turbine blades to reduce skin thicknesses along the blade span. They increase localized stress concentration, which may cause premature delamination failure in composite and reduced fatigue service life. Durability and damage tolerance (D&DT) were evaluated utilizing a multi-scale micro-macro progressive failure analysis (PFA) technique. PFA is finite element based and is capable of detecting all stages of material damage including initiation and propagation of delamination. It assesses multiple failure criteria and includes the effects of manufacturing anomalies (i.e., void, fiber waviness). Two different approaches have been used within PFA. The first approach is Virtual Crack Closure Technique (VCCT) PFA while the second one is strength-based. Constituent stiffness and strength properties for glass and carbon based material systems were reverse engineered for use in D&DT evaluation of coupons with ply drops under static loading. Lamina and laminate properties calculated using manufacturing and composite architecture details matched closely published test data. Similarly, resin properties were determined for fatigue life calculation. The simulation not only reproduced static strength and fatigue life as observed in the test, it also showed composite damage and fracture modes that resemble those reported in the tests. The results show that computational simulation can be relied on to enhance the design of tapered composite structures such as the ones used in turbine wind blades. A computational simulation for durability, damage tolerance (D&DT) and reliability of composite wind turbine blade structures in presence of uncertainties in material properties was performed. A composite turbine blade was first assessed with finite element based multi-scale progressive failure analysis to determine failure modes and locations as well as the fracture load. D&DT analyses were then validated with static test performed at Sandia National Laboratories. The work was followed by detailed weight analysis to identify contribution of various materials to the overall weight of the blade. The methodology ensured that certain types of failure modes, such as delamination progression, are contained to reduce risk to the structure. Probabilistic analysis indicated that composite shear strength has a great influence on the blade ultimate load under static loading. Weight was reduced by 12% with robust design without loss in reliability or D&DT. Structural benefits obtained with the use of enhanced matrix properties through nanoparticles infusion were also assessed. Thin unidirectional fiberglass layers enriched with silica nanoparticles were applied to the outer surfaces of a wind blade to improve its overall structural performance and durability. The wind blade was a 9-meter prototype structure manufactured and tested subject to three saddle static loading at Sandia National Laboratory (SNL). The blade manufacturing did not include the use of any nano-material. With silica nanoparticles in glass composite applied to the exterior surfaces of the blade, the durability and damage tolerance (D&DT) results from multi-scale PFA showed an increase in ultimate load of the blade by 9.2% as compared to baseline structural performance (without nano). The use of nanoparticles lead to a delay in the onset of delamination. Load-displacement relationships obtained from testing of the blade with baseline neat material were compared to the ones from analytical simulation using neat resin and using silica nanoparticles in the resin. Multi-scale PFA results for the neat material construction matched closely those from test for both load displacement and location and type of damage and failure. AlphaSTAR demonstrated that wind blade structures made from advanced composite materials can be certified with multi-scale progressive failure analysis by following building block verification approach.« less

Design and evaluation of a foam-filled hat-stiffened panel concept for aircraft primary structural applications

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.

1993-01-01

Geodesically stiffened structures are very efficient in carrying combined bending, torsion, and pressure loading that is typical of primary aircraft structures. They are also very damage tolerant since there are multiple load paths available to redistribute loads compared to prismatically stiffened structures. Geodesically stiffened structures utilize continuous filament composite materials which make them amenable to automated manufacturing processes to reduce cost. The current practice for geodesically stiffened structures is to use a solid blade construction for the stiffener. This stiffener configuration is not an efficient concept and there is a need to identify other stiffener configurations that are more efficient but utilize the same manufacturing process as the solid blade. This paper describes a foam-filled stiffener cross section that is more efficient than a solid-blade stiffener in the load range corresponding to primary aircraft structures. A prismatic hat-stiffener panel design is then selected for structural evaluation in uni-axial compression with and without impact damage. Experimental results for both single stiffener specimens and multi-stiffener panel specimens are presented. Finite element analysis results are presented that predict the buckling and postbuckling response of the test specimens. Analytical results for both the element and panel specimens are compared with experimental results.

Research study on multi-KW-DC distribution system

NASA Technical Reports Server (NTRS)

Berkery, E. A.; Krausz, A.

1975-01-01

A detailed definition of the HVDC test facility and the equipment required to implement the test program are provided. The basic elements of the test facility are illustrated, and consist of: the power source, conventional and digital supervision and control equipment, power distribution harness and simulated loads. The regulated dc power supplies provide steady-state power up to 36 KW at 120 VDC. Power for simulated line faults will be obtained from two banks of 90 ampere-hour lead-acid batteries. The relative merits of conventional and multiplexed power control will be demonstrated by the Supervision and Monitor Unit (SMU) and the Automatically Controlled Electrical Systems (ACES) hardware. The distribution harness is supported by a metal duct which is bonded to all component structures and functions as the system ground plane. The load banks contain passive resistance and reactance loads, solid state power controllers and active pulse width modulated loads. The HVDC test facility is designed to simulate a power distribution system for large aerospace vehicles.

Survivability characteristics of composite compression structure

NASA Technical Reports Server (NTRS)

Avery, John G.; Allen, M. R.; Sawdy, D.; Avery, S.

1990-01-01

Test and evaluation was performed to determine the compression residual capability of graphite reinforced composite panels following perforation by high-velocity fragments representative of combat threats. Assessments were made of the size of the ballistic damage, the effect of applied compression load at impact, damage growth during cyclic loading and residual static strength. Several fiber/matrix systems were investigated including high-strain fibers, tough epoxies, and APC-2 thermoplastic. Additionally, several laminate configurations were evaluated including hard and soft laminates and the incorporation of buffer strips and stitching for improved damage resistance of tolerance. Both panels (12 x 20-inches) and full scale box-beam components were tested to assure scalability of results. The evaluation generally showed small differences in the responses of the material systems tested. The soft laminate configurations with concentrated reinforcement exhibited the highest residual strength. Ballistic damage did not grow or increase in severity as a result of cyclic loading, and the effects of applied load at impact were not significant under the conditions tested.

Time-Dependent Behavior of High-Strength Kevlar and Vectran Webbing

NASA Technical Reports Server (NTRS)

Jones, Thomas C.; Doggett, William R.

2014-01-01

High-strength Kevlar and Vectran webbings are currently being used by both NASA and industry as the primary load-bearing structure in inflatable space habitation modules. The time-dependent behavior of high-strength webbing architectures is a vital area of research that is providing critical material data to guide a more robust design process for this class of structures. This paper details the results of a series of time-dependent tests on 1-inch wide webbing including an initial set of comparative tests between specimens that underwent realtime and accelerated creep at 65 and 70% of their ultimate tensile strength. Variability in the ultimate tensile strength of the webbings is investigated and compared with variability in the creep life response. Additional testing studied the effects of load and displacement rate, specimen length and the time-dependent effects of preconditioning the webbings. The creep test facilities, instrumentation and test procedures are also detailed. The accelerated creep tests display consistently longer times to failure than their real-time counterparts; however, several factors were identified that may contribute to the observed disparity. Test setup and instrumentation, grip type, loading scheme, thermal environment and accelerated test postprocessing along with material variability are among these factors. Their effects are discussed and future work is detailed for the exploration and elimination of some of these factors in order to achieve a higher fidelity comparison.

Orion EM-1 Crew Module Structural Test Article loaded onto Guppy

NASA Image and Video Library

2017-04-25

NASA's Super Guppy aircraft has been closed and secured at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida. The Orion Exploration Mission-1 (EM-1) structural test article is secured inside the Super Guppy and will be transported to Lockheed Martin's Denver facility for testing. The Orion spacecraft will launch atop NASA’s Space Launch System rocket on EM-1, its first deep space mission.

Fatigue experience from tests carried out with forged beam and frame structures in the development of the Saab aircraft Viggen

NASA Technical Reports Server (NTRS)

Larsson, S. E.

1972-01-01

A part of the lower side of the main wing at the joint of the main spar with the fuselage frame was investigated. This wing beam area was simulated by a test specimen consisting of a spar boom of AZ 74 forging (7075 aluminum alloy modified with 0.3 percent Ag) and a portion of a honeycomb sandwich panel attached to the boom flange with steel bolts. The cross section was reduced to half scale. However, the flange thickness, the panel height, and the bolt size were full scale. Further, left and right portions of the fuselage frame intended to carry over the bending moment of the main wing were tested. Each of these frame halves consisted of a forward and a rear forging (7079 aluminum alloy, overaged) connected by an outer and inner skin (Alclad 7075) creating a box beam. These test specimens were full scale and were constructed principally of ordinary aircraft components. The test load spectrum was common to both types of specimens with regard to percentage levels. It consisted of maneuver and gust loads, touchdown loads, and loads due to ground roughness. A load history of 200 hours of flight with 15,000 load cycles was punched on a tape. The loads were randomized in groups according to the flight-by-flight principle. The highest positive load level was 90 percent of limit load and the largest negative load was -27 percent. A total of 20 load levels were used. Both types of specimens were provided with strain gages and had a nominal stress of about 300 MN/sq m in some local areas. As a result of the tests, steps were taken to reduce the risk of fatigue damage in aircraft. Thus stress levels were lowered, radii were increased, and demands on surface finish were sharpened.

A Teaching Model for Truss Structures

ERIC Educational Resources Information Center

Bigoni, Davide; Dal Corso, Francesco; Misseroni, Diego; Tommasini, Mirko

2012-01-01

A classroom demonstration model has been designed, machined and successfully tested in different learning environments to facilitate understanding of the mechanics of truss structures, in which struts are subject to purely axial load and deformation. Gaining confidence with these structures is crucial for the development of lattice models, which…

Controlling Buffeting Loads by Rudder and Piezo-Actuation

NASA Technical Reports Server (NTRS)

Moses, Robert W.; Pototzky, Anthony S.; Henderson, Douglas A.; Galea, Stephen C.; Manokaran, Donald S.; Zimcik, David G.; Wickramasinghe, Viresh; Pitt, Dale M.; Gamble, Michael A.

2005-01-01

High performance aircraft, especially those with twin vertical tails, encounter unsteady buffet loads when flying at high angles of attack. These stochastic loads result in significant stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. An international collaborative research activity among Australia, Canada and the United States, conducted under the auspices of The Technical Cooperation Program (TTCP) contributed resources toward a program that coalesced a broad range of technical knowledge and expertise into a single investigation to demonstrate the enhanced performance and capability of the advanced active Buffet Load Alleviation ( ) control system in preparation for a flight test demonstration. The research team investigated the use of active structural control to alleviate the damaging structural response to these loads by applying advanced directional piezoelectric actuators, the aircraft rudder, switch mode amplifiers, and advanced control strategies on an F/A-18 aircraft empennage. Some results of the full-scale investigation are presented herein.

PRSEUS Pressure Cube Test Data and Response

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.

2013-01-01

NASA s Environmentally Responsible Aviation (ERA) Program is examining the hybrid wing body (HWB) aircraft, among others, in an effort to increase the fuel efficiency of commercial aircraft. The HWB design combines features of a flying wing with features of conventional transport aircraft, and has the advantage of simultaneously increasing both fuel efficiency and payload. Recent years have seen an increased focus on the structural performance of the HWB. The key structural challenge of a HWB airframe is the ability to create a cost and weight efficient, non-circular, pressurized shell. Conventional round fuselage sections react cabin pressure by hoop tension. However, the structural configuration of the HWB subjects the majority of the structural panels to bi-axial, in-plane loads in addition to the internal cabin pressure, which requires more thorough examination and analysis than conventional transport aircraft components having traditional and less complex load paths. To address this issue, while keeping structural weights low, extensive use of advanced composite materials is made. This report presents the test data and preliminary conclusions for a pressurized cube test article that utilizes Boeing's Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), and which is part of the building block approach used for HWB development.

Laminar flow control perforated wing panel development

NASA Technical Reports Server (NTRS)

Fischler, J. E.

1986-01-01

Many structural concepts for a wing leading edge laminar flow control hybrid panel were analytically investigated. After many small, medium, and large tests, the selected design was verified. New analytic methods were developed to combine porous titanium sheet bonded to a substructure of fiberglass and carbon/epoxy cloth. At -65 and +160 F test conditions, the critical bond of the porous titanium to the composite failed at lower than anticipated test loads. New cure cycles, design improvements, and test improvements significantly improved the strength and reduced the deflections from thermal and lateral loadings. The wave tolerance limits for turbulence were not exceeded. Consideration of the beam column midbay deflections from the combinations of the axial and lateral loadings and thermal bowing at -65 F, room temperature, and +160 F were included. Many lap shear tests were performed at several cure cycles. Results indicate that sufficient verification was obtained to fabricate a demonstration vehicle.

Reduction of stresses on buried rigid highway structures using the imperfect ditch method and expanded polysterene : geofoam.

DOT National Transportation Integrated Search

2009-01-01

This study provides strong evidences from both numerical model analysis and in-situ test data to indicate that geofoam is an ideal elasto-plastic material to reduce vertical load on top of rigid culvert resting on a rigid foundation. The load on the ...

Gamma Radiation Aging Study of a Dow Corning SE 1700 Porous Structure Made by Direct Ink Writing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Small, Ward; Alviso, Cindy T.; Metz, Tom R.

Dow Corning SE 1700 (reinforced polydimethylsiloxane) porous structures were made by direct ink writing (DIW). The specimens (~50% porosity) were subjected to a compressive strain of ~25% while exposed to a gamma radiation dose of 1, 5, or 10 Mrad under vacuum. Compression set and load retention of the aged specimens were measured after a ~24 h relaxation period. Compression set (relative to deflection) increased with radiation dose: 11, 35, and 51% after 1, 5, and 10 Mrad, respectively. Load retention was 96-97% for the doses tested. The SE 1700 compared favorably to M9763 cellular silicone tested under the samemore » conditions.« less

Selected advanced aerodynamics and active controls technology concepts development on a derivative B-747

NASA Technical Reports Server (NTRS)

1980-01-01

The feasibility of applying wing tip extensions, winglets, and active control wing load alleviation to the Boeing 747 is investigated. Winglet aerodynamic design methods and high speed wind tunnel test results of winglets and of symmetrically deflected ailerons are presented. Structural resizing analyses to determine weight and aeroelastic twist increments for all the concepts and flutter model test results for the wing with winglets are included. Control law development, system mechanization/reliability studies, and aileron balance tab trade studies for active wing load alleviation systems are discussed. Results are presented in the form of incremental effects on L/D, structural weight, block fuel savings, stability and control, airplane price, and airline operating economics.

Crash Testing of Helicopter Airframe Fittings

NASA Technical Reports Server (NTRS)

Clarke, Charles W.; Townsend, William; Boitnott, Richard

2004-01-01

As part of the Rotary Wing Structures Technology Demonstration (RWSTD) program, a surrogate RAH-66 seat attachment fitting was dynamically tested to assess its response to transient, crash impact loads. The dynamic response of this composite material fitting was compared to the performance of an identical fitting subjected to quasi-static loads of similar magnitude. Static and dynamic tests were conducted of both smaller bench level and larger full-scale test articles. At the bench level, the seat fitting was supported in a steel fixture, and in the full-scale tests, the fitting was integrated into a surrogate RAH-66 forward fuselage. Based upon the lessons learned, an improved method to design, analyze, and test similar composite material fittings is proposed.

Citizen sensors for SHM: use of accelerometer data from smartphones.

PubMed

Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

2015-01-29

Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications.

Power system security enhancement through direct non-disruptive load control

NASA Astrophysics Data System (ADS)

Ramanathan, Badri Narayanan

The transition to a competitive market structure raises significant concerns regarding reliability of the power grid. A need to build tools for security assessment that produce operating limit boundaries for both static and dynamic contingencies is recognized. Besides, an increase in overall uncertainty in operating conditions makes corrective actions at times ineffective leaving the system vulnerable to instability. The tools that are in place for stability enhancement are mostly corrective and suffer from lack of robustness to operating condition changes. They often pose serious coordination challenges. With deregulation, there have also been ownership and responsibility issues associated with stability controls. However, the changing utility business model and the developments in enabling technologies such as two-way communication, metering, and control open up several new possibilities for power system security enhancement. This research proposes preventive modulation of selected loads through direct control for power system security enhancement. Two main contributions of this research are the following: development of an analysis framework and two conceptually different analysis approaches for load modulation to enhance oscillatory stability, and the development and study of algorithms for real-time modulation of thermostatic loads. The underlying analysis framework is based on the Structured Singular Value (SSV or mu) theory. Based on the above framework, two fundamentally different approaches towards analysis of the amount of load modulation for desired stability performance have been developed. Both the approaches have been tested on two different test systems: CIGRE Nordic test system and an equivalent of the Western Electric Coordinating Council test system. This research also develops algorithms for real-time modulation of thermostatic loads that use the results of the analysis. In line with some recent load management programs executed by utilities, two different algorithms based on dynamic programming are proposed for air-conditioner loads, while a decision-tree based algorithm is proposed for water-heater loads. An optimization framework has been developed employing the above algorithms. Monte Carlo simulations have been performed using this framework with the objective of studying the impact of different parameters and constraints on the effectiveness as well as the effect of control. The conclusions drawn from this research strongly advocate direct load control for stability enhancement from the perspectives of robustness and coordination, as well as economic viability and the developments towards availability of the institutional framework for load participation in providing system reliability services.

Fracture-resistant monolithic dental crowns.

PubMed

Zhang, Yu; Mai, Zhisong; Barani, Amir; Bush, Mark; Lawn, Brian

2016-03-01

To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. Experimental measurements and XFEM predictions were self-consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity. Copyright © 2015 Academy of Dental Materials. All rights reserved.

FRACTURE-RESISTANT MONOLITHIC DENTAL CROWNS

PubMed Central

Zhang, Yu; Mai, Zhisong; Barani, Amir; Bush, Mark; Lawn, Brian

2016-01-01

Objective To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. Methods Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. Results Experimental measurements and XFEM predictions were self consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. Significance The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity. PMID:26792623

Buckling and Post-Buckling Behaviors of a Variable Stiffness Composite Laminated Wing Box Structure

NASA Astrophysics Data System (ADS)

Wang, Peiyan; Huang, Xinting; Wang, Zhongnan; Geng, Xiaoliang; Wang, Yuansheng

2018-04-01

The buckling and post-buckling behaviors of variable stiffness composite laminates (VSCL) with curvilinear fibers were investigated and compared with constant stiffness composite laminates (CSCL) with straight fibers. A VSCL box structure was evaluated under a pure bending moment. The results of the comparative test showed that the critical buckling load of the VSCL box was approximately 3% higher than that of the CSCL box. However, the post-buckling load-bearing capacity was similar due to the layup angle and the immature status of the material processing technology. The properties of the VSCL and CSCL boxes under a pure bending moment were simulated using the Hashin criterion and cohesive interface elements. The simulation results are consistent with the experimental results in stiffness, critical buckling load and failure modes but not in post-buckling load capacity. The results of the experiment, the simulation and laminated plate theory show that VSCL greatly improves the critical buckling load but has little influence on the post-buckling load-bearing capacity.

Load Balancing Strategies for Multiphase Flows on Structured Grids

NASA Astrophysics Data System (ADS)

Olshefski, Kristopher; Owkes, Mark

2017-11-01

The computation time required to perform large simulations of complex systems is currently one of the leading bottlenecks of computational research. Parallelization allows multiple processing cores to perform calculations simultaneously and reduces computational times. However, load imbalances between processors waste computing resources as processors wait for others to complete imbalanced tasks. In multiphase flows, these imbalances arise due to the additional computational effort required at the gas-liquid interface. However, many current load balancing schemes are only designed for unstructured grid applications. The purpose of this research is to develop a load balancing strategy while maintaining the simplicity of a structured grid. Several approaches are investigated including brute force oversubscription, node oversubscription through Message Passing Interface (MPI) commands, and shared memory load balancing using OpenMP. Each of these strategies are tested with a simple one-dimensional model prior to implementation into the three-dimensional NGA code. Current results show load balancing will reduce computational time by at least 30%.

NASA Structural Analysis Report on the American Airlines Flight 587 Accident - Local Analysis of the Right Rear Lug

NASA Technical Reports Server (NTRS)

Raju, Ivatury S; Glaessgen, Edward H.; Mason, Brian H; Krishnamurthy, Thiagarajan; Davila, Carlos G

2005-01-01

A detailed finite element analysis of the right rear lug of the American Airlines Flight 587 - Airbus A300-600R was performed as part of the National Transportation Safety Board s failure investigation of the accident that occurred on November 12, 2001. The loads experienced by the right rear lug are evaluated using global models of the vertical tail, local models near the right rear lug, and a global-local analysis procedure. The right rear lug was analyzed using two modeling approaches. In the first approach, solid-shell type modeling is used, and in the second approach, layered-shell type modeling is used. The solid-shell and the layered-shell modeling approaches were used in progressive failure analyses (PFA) to determine the load, mode, and location of failure in the right rear lug under loading representative of an Airbus certification test conducted in 1985 (the 1985-certification test). Both analyses were in excellent agreement with each other on the predicted failure loads, failure mode, and location of failure. The solid-shell type modeling was then used to analyze both a subcomponent test conducted by Airbus in 2003 (the 2003-subcomponent test) and the accident condition. Excellent agreement was observed between the analyses and the observed failures in both cases. From the analyses conducted and presented in this paper, the following conclusions were drawn. The moment, Mx (moment about the fuselage longitudinal axis), has significant effect on the failure load of the lugs. Higher absolute values of Mx give lower failure loads. The predicted load, mode, and location of the failure of the 1985-certification test, 2003-subcomponent test, and the accident condition are in very good agreement. This agreement suggests that the 1985-certification and 2003- subcomponent tests represent the accident condition accurately. The failure mode of the right rear lug for the 1985-certification test, 2003-subcomponent test, and the accident load case is identified as a cleavage-type failure. For the accident case, the predicted failure load for the right rear lug from the PFA is greater than 1.98 times the limit load of the lugs. I.

Structural Analysis of the Right Rear Lug of American Airlines Flight 587

NASA Technical Reports Server (NTRS)

Raju, Ivatury S.; Glaessgen, Edward H.; Mason, Brian H.; Krishnamurthy, Thiagarajan; Davila, Carlos G.

2006-01-01

A detailed finite element analysis of the right rear lug of the American Airlines Flight 587 - Airbus A300-600R was performed as part of the National Transportation Safety Board s failure investigation of the accident that occurred on November 12, 2001. The loads experienced by the right rear lug are evaluated using global models of the vertical tail, local models near the right rear lug, and a global-local analysis procedure. The right rear lug was analyzed using two modeling approaches. In the first approach, solid-shell type modeling is used, and in the second approach, layered-shell type modeling is used. The solid-shell and the layered-shell modeling approaches were used in progressive failure analyses (PFA) to determine the load, mode, and location of failure in the right rear lug under loading representative of an Airbus certification test conducted in 1985 (the 1985-certification test). Both analyses were in excellent agreement with each other on the predicted failure loads, failure mode, and location of failure. The solid-shell type modeling was then used to analyze both a subcomponent test conducted by Airbus in 2003 (the 2003-subcomponent test) and the accident condition. Excellent agreement was observed between the analyses and the observed failures in both cases. The moment, Mx (moment about the fuselage longitudinal axis), has significant effect on the failure load of the lugs. Higher absolute values of Mx give lower failure loads. The predicted load, mode, and location of the failure of the 1985- certification test, 2003-subcomponent test, and the accident condition are in very good agreement. This agreement suggests that the 1985-certification and 2003-subcomponent tests represent the accident condition accurately. The failure mode of the right rear lug for the 1985-certification test, 2003-subcomponent test, and the accident load case is identified as a cleavage-type failure. For the accident case, the predicted failure load for the right rear lug from the PFA is greater than 1.98 times the limit load of the lugs.

14 CFR 29.307 - Proof of structure.

Code of Federal Regulations, 2011 CFR

2011-01-01

... system, including control surfaces; (3) Operation tests of the control system; (4) Flight stress... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... loading condition accounting for the environment to which the structure will be exposed in operation...

14 CFR 27.307 - Proof of structure.

Code of Federal Regulations, 2012 CFR

2012-01-01

... system, including control surfaces; (3) Operation tests of the control system; (4) Flight stress... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... loading condition accounting for the environment to which the structure will be exposed in operation...