load simulator tests: Topics by Science.gov

Sample records for load simulator tests

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.
Analysis of Glenoid Fixation with Anatomic Total Shoulder Arthroplasty in an Extreme Cyclic Loading Scenario.

PubMed

Roche, Christopher P; Staunch, Cameron; Hahn, William; Grey, Sean G; Flurin, Pierre-Henri; Wright, Thomas W; Zuckerman, Joseph D

2015-12-01

ASTM F2028-14 was adopted to recom mend a cyclic eccentric glenoid edge loading test that simulates the rocking horse loading mechanism beleived to cause aTSA glenoid loosening. While this method accurately simulates that failure mechanism, the recommended 750 N load may not be sufficient to simulate worst-case loading magnitudes, and the recommended 100,000 cycles may not be sufficient to simulate device fatigue-related failure modes. Finally, if greater loading magnitude or a larger number of cycles is performed, the recommended substrate density may not be sufficiently strong to support the elevated loads and cycles. To this end, a new test method is proposed to supplement ASTM F2028-14. A series of cyclic tests were performed to evaluate the long-term fixation strength of two different hybrid glenoid designs in both low (15 pcf) and high (30 pcf) density polyurethane blocks at elevated loads relative to ASTM F2028-14. To simulate a worst case clinical condition in which the humeral head is superiorly migrated, a cyclic load was applied to the superior glenoid rim to induce a maximum torque on the fixation pegs for three different cyclic loading tests: 1. 1,250 N load for 0.75 M cycles in a 15 pcf block, 2. 1,250 N load for 1.5 M cycles in a 30 pcf block, and 3. 2,000 N load for 0.65 M cycles in a 30 pcf block. All devices completed cyclic loading without failure, fracture, or loss of fixation regardless of glenoid design, polyurethane density, loading magnitude, or cycle length. No significant difference in post-cyclic displacement was noted between designs in any of the three tests. Post-cyclic radiographs demonstrated that each device maintained fixa - tion with the metal pegs within the bone-substitute blocks with no fatigue related failures. These results demonstrate that both cemented hybrid glenoids maintained fixation when tested according to each cyclic loading scenario, with no difference in post-cyclic displacement observed between designs. The lack of fatigue-related failures in these elevated load and high cycle test scenarios are promising, as are the relatively low displacements given the extreme nature of each test. This cyclic loading method is intended to supplement the ASTM F2028-14 standard that adequately simulates the rocking horse loading mechanism but may not adequately simulate the fatigue-related failure modes.
On the road performance tests of electric test vehicle for correlation with road load simulator

NASA Technical Reports Server (NTRS)

Dustin, M. O.; Slavik, R. J.

1982-01-01

A dynamometer (road load simulator) is used to test and evaluate electric vehicle propulsion systems. To improve correlation between system tests on the road load simulator and on the road, similar performance tests are conducted using the same vehicle. The results of track tests on the electric propulsion system test vehicle are described. The tests include range at constant speeds and over SAE J227a driving cycles, maximum accelerations, maximum gradability, and tire rolling resistance determination. Road power requirements and energy consumption were also determined from coast down tests.
Three Dimensional Constraint Effects on the Estimated (Delta)CTOD during the Numerical Simulation of Different Fatigue Threshold Testing Techniques

NASA Technical Reports Server (NTRS)

Seshadri, Banavara R.; Smith, Stephen W.

2007-01-01

Variation in constraint through the thickness of a specimen effects the cyclic crack-tip-opening displacement (DELTA CTOD). DELTA CTOD is a valuable measure of crack growth behavior, indicating closure development, constraint variations and load history effects. Fatigue loading with a continual load reduction was used to simulate the load history associated with fatigue crack growth threshold measurements. The constraint effect on the estimated DELTA CTOD is studied by carrying out three-dimensional elastic-plastic finite element simulations. The analysis involves numerical simulation of different standard fatigue threshold test schemes to determine how each test scheme affects DELTA CTOD. The American Society for Testing and Materials (ASTM) prescribes standard load reduction procedures for threshold testing using either the constant stress ratio (R) or constant maximum stress intensity (K(sub max)) methods. Different specimen types defined in the standard, namely the compact tension, C(T), and middle cracked tension, M(T), specimens were used in this simulation. The threshold simulations were conducted with different initial K(sub max) values to study its effect on estimated DELTA CTOD. During each simulation, the DELTA CTOD was estimated at every load increment during the load reduction procedure. Previous numerical simulation results indicate that the constant R load reduction method generates a plastic wake resulting in remote crack closure during unloading. Upon reloading, this remote contact location was observed to remain in contact well after the crack tip was fully open. The final region to open is located at the point at which the load reduction was initiated and at the free surface of the specimen. However, simulations carried out using the constant Kmax load reduction procedure did not indicate remote crack closure. Previous analysis results using various starting K(sub max) values and different load reduction rates have indicated DELTA CTOD is independent of specimen size. A study of the effect of specimen thickness and geometry on the measured DELTA CTOD for various load reduction procedures and its implication in the estimation of fatigue crack growth threshold values is discussed.
Evaluation of wheelchair back support crashworthiness: combination wheelchair back support surfaces and attachment hardware.

PubMed

Ha, D; Bertocci, G; Deemer, E; van Roosmalen, L; Karg, P

2000-01-01

Automotive seats are tested for compliance with federal motor vehicle safety standards (FMVSS) to assure safety during impact. Many wheelchair users rely upon their wheelchairs to serve as vehicle seats. However, the crashworthiness of these wheelchairs during impact is often unknown. This study evaluated the crashworthiness of five combinations of wheelchair back support surfaces and attachment hardware using a static test procedure simulating crash loading conditions. The crashworthiness was tested by applying a simulated rearward load to each seat-back system. The magnitude of the applied load was established through computer simulation and biodynamic calculations. None of the five tested wheelchair back supports withstood the simulated crash loads. All failures were associated with attachment hardware.
Reconstruction of Orion Engineering Development Unit (EDU) Parachute Inflation Loads

NASA Technical Reports Server (NTRS)

Ray, Eric S.

2013-01-01

The process of reconstructing inflation loads of Capsule Parachute Assembly System (CPAS) has been updated as the program transitioned to testing Engineering Development Unit (EDU) hardware. The equations used to reduce the test data have been re-derived based on the same physical assumptions made by simulations. Due to instrumentation challenges, individual parachute loads are determined from complementary accelerometer and load cell measurements. Cluster inflations are now simulated by modeling each parachute individually to better represent different inflation times and non-synchronous disreefing. The reconstruction procedure is tailored to either infinite mass or finite mass events based on measurable characteristics from the test data. Inflation parameters are determined from an automated optimization routine to reduce subjectivity. Infinite mass inflation parameters have been re-defined to avoid unrealistic interactions in Monte Carlo simulations. Sample cases demonstrate how best-fit inflation parameters are used to generate simulated drag areas and loads which favorably agree with test data.
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.
A piezoelectric shock-loading response simulator for piezoelectric-based device developers

NASA Astrophysics Data System (ADS)

Rastegar, J.; Feng, Z.

2017-04-01

Pulsed loading of piezoelectric transducers occurs in many applications, such as those in munitions firing, or when a mechanical system is subjected to impact type loading. In this paper, an electronic simulator that can be programmed to generate electrical charges that a piezoelectric transducer generates as it is subjected to various shock loading profiles is presented. The piezoelectric output simulator can provide close to realistic outputs so that the circuit designer can use it to test the developed system under close to realistic conditions without the need for the costly and time consuming process of performing actual tests. The design of the electronic simulator and results of its testing are presented.
Flight Test Identification and Simulation of a UH-60A Helicopter and Slung Load

NASA Technical Reports Server (NTRS)

Cicolani, Luigi S.; Sahai, Ranjana; Tucker, George E.; McCoy, Allen H.; Tyson, Peter H.; Tischler, Mark B.; Rosen, Aviv

2001-01-01

Helicopter slung-load operations are common in both military and civil contexts. Helicopters and loads are often qualified for these operations by means of flight tests, which can be expensive and time consuming. There is significant potential to reduce such costs both through revisions in flight-test methods and by using validated simulation models. To these ends, flight tests were conducted at Moffett Field to demonstrate the identification of key dynamic parameters during flight tests (aircraft stability margins and handling-qualities parameters, and load pendulum stability), and to accumulate a data base for simulation development and validation. The test aircraft was a UH-60A Black Hawk, and the primary test load was an instrumented 8- by 6- by 6-ft cargo container. Tests were focused on the lateral and longitudinal axes, which are the axes most affected by the load pendulum modes in the frequency range of interest for handling qualities; tests were conducted at airspeeds from hover to 80 knots. Using telemetered data, the dynamic parameters were evaluated in near real time after each test airspeed and before clearing the aircraft to the next test point. These computations were completed in under 1 min. A simulation model was implemented by integrating an advanced model of the UH-60A aerodynamics, dynamic equations for the two-body slung-load system, and load static aerodynamics obtained from wind-tunnel measurements. Comparisons with flight data for the helicopter alone and with a slung load showed good overall agreement for all parameters and test points; however, unmodeled secondary dynamic losses around 2 Hz were found in the helicopter model and they resulted in conservative stability margin estimates.
Evaluation of a new methodology to simulate damage and wear of polyethylene hip replacements subjected to edge loading in hip simulator testing.

PubMed

Partridge, Susan; Tipper, Joanne L; Al-Hajjar, Mazen; Isaac, Graham H; Fisher, John; Williams, Sophie

2018-05-01

Wear and fatigue of polyethylene acetabular cups have been reported to play a role in the failure of total hip replacements. Hip simulator testing under a wide range of clinically relevant loading conditions is important. Edge loading of hip replacements can occur following impingement under extreme activities and can also occur during normal gait, where there is an offset deficiency and/or joint laxity. This study evaluated a hip simulator method that assessed wear and damage in polyethylene acetabular liners that were subjected to edge loading. The liners tested to evaluate the method were a currently manufactured crosslinked polyethylene acetabular liner and an aged conventional polyethylene acetabular liner. The acetabular liners were tested for 5 million standard walking cycles and following this 5 million walking cycles with edge loading. Edge loading conditions represented a separation of the centers of rotation of the femoral head and the acetabular liner during the swing phase, leading to loading of the liner rim on heel strike. Rim damage and cracking was observed in the aged conventional polyethylene liner. Steady-state wear rates assessed gravimetrically were lower under edge loading compared to standard loading. This study supports previous clinical findings that edge loading may cause rim cracking in liners, where component positioning is suboptimal or where material degradation is present. The simulation method developed has the potential to be used in the future to test the effect of aging and different levels of severity of edge loading on a range of cross-linked polyethylene materials. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1456-1462, 2018. © 2017 Wiley Periodicals, Inc.
Modular, high power, variable R dynamic electrical load simulator

NASA Technical Reports Server (NTRS)

Joncas, K. P.

1974-01-01

The design of a previously developed basic variable R load simulator was entended to increase its power dissipation and transient handling capabilities. The delivered units satisfy all design requirements, and provides for a high power, modular simulation capability uniquely suited to the simulation of complex load responses. In addition to presenting conclusions and recommendations and pertinent background information, the report covers program accomplishments; describes the simulator basic circuits, transfer characteristic, protective features, assembly, and specifications; indicates the results of simulator evaluation, including burn-in and acceptance testing; provides acceptance test data; and summarizes the monthly progress reports.
Fracture load and failure analysis of zirconia single crowns veneered with pressed and layered ceramics after chewing simulation.

PubMed

Stawarczyk, Bogna; Ozcan, Mutlu; Roos, Malgorzata; Trottmann, Albert; Hämmerle, Christoph H F

2011-01-01

This study determined the fracture load of zirconia crowns veneered with four overpressed and four layered ceramics after chewing simulation. The veneered zirconia crowns were cemented and subjected to chewing cycling. Subsequently, the specimens were loaded at an angle of 45° in a Universal Testing Machine to determine the fracture load. One-way ANOVA, followed by a post-hoc Scheffé test, t-test and Weibull statistic were performed. Overpressed crowns showed significantly lower fracture load (543-577 N) compared to layered ones (805-1067 N). No statistical difference was found between the fracture loads within the overpressed group. Within the layered groups, LV (1067 N) presented significantly higher results compared to LC (805 N). The mean values of all other groups were not significantly different. Single zirconia crowns veneered with overpressed ceramics exhibited lower fracture load than those of the layered ones after chewing simulation.
Definition and evaluation of testing scenarios for knee wear simulation under conditions of highly demanding daily activities.

PubMed

Schwiesau, Jens; Schilling, Carolin; Kaddick, Christian; Utzschneider, Sandra; Jansson, Volkmar; Fritz, Bernhard; Blömer, Wilhelm; Grupp, Thomas M

2013-05-01

The objective of our study was the definition of testing scenarios for knee wear simulation under various highly demanding daily activities of patients after total knee arthroplasty. This was mainly based on a review of published data on knee kinematics and kinetics followed by the evaluation of the accuracy and precision of a new experimental setup. We combined tibio-femoral load and kinematic data reported in the literature to develop deep squatting loading profiles for simulator input. A servo-hydraulic knee wear simulator was customised with a capability of a maximum flexion of 120°, a tibio-femoral load of 5000N, an anterior-posterior (AP) shear force of ±1000N and an internal-external (IE) rotational torque of ±50Nm to simulate highly demanding patient activities. During the evaluation of the newly configurated simulator the ability of the test machine to apply the required load and torque profiles and the flexion kinematics in a precise manner was examined by nominal-actual profile comparisons monitored periodically during subsequent knee wear simulation. For the flexion kinematics under displacement control a delayed actuator response of approximately 0.05s was inevitable due to the inertia of masses in movement of the coupled knee wear stations 1-3 during all applied activities. The axial load and IE torque is applied in an effective manner without substantial deviations between nominal and actual load and torque profiles. During the first third of the motion cycle a marked deviation between nominal and actual AP shear load profiles has to be noticed but without any expected measurable effect on the latter wear simulation due to the fact that the load values are well within the peak magnitude of the nominal load amplitude. In conclusion the described testing method will be an important tool to have more realistic knee wear simulations based on load conditions of the knee joint during activities of daily living. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.
A Hybrid Demand Response Simulator Version 1.0

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

2012-05-02

A hybrid demand response simulator is developed to test different control algorithms for centralized and distributed demand response (DR) programs in a small distribution power grid. The HDRS is designed to model a wide variety of DR services such as peak having, load shifting, arbitrage, spinning reserves, load following, regulation, emergency load shedding, etc. The HDRS does not model the dynamic behaviors of the loads, rather, it simulates the load scheduling and dispatch process. The load models include TCAs (water heaters, air conditioners, refrigerators, freezers, etc) and non-TCAs (lighting, washer, dishwasher, etc.) The ambient temperature changes, thermal resistance, capacitance, andmore » the unit control logics can be modeled for TCA loads. The use patterns of the non-TCA can be modeled by probability of use and probabilistic durations. Some of the communication network characteristics, such as delays and errors, can also be modeled. Most importantly, because the simulator is modular and greatly simplified the thermal models for TCA loads, it is very easy and fast to be used to test and validate different control algorithms in a simulated environment.« less
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.
Active tower damping and pitch balancing - design, simulation and field test

NASA Astrophysics Data System (ADS)

Duckwitz, Daniel; Shan, Martin

2014-12-01

The tower is one of the major components in wind turbines with a contribution to the cost of energy of 8 to 12% [1]. In this overview the load situation of the tower will be described in terms of sources of loads, load components and fatigue contribution. Then two load reduction control schemes are described along with simulation and field test results. Pitch Balancing is described as a method to reduce aerodynamic asymmetry and the resulting fatigue loads. Active Tower Damping is reducing the tower oscillations by applying appropiate pitch angle changes. A field test was conducted on an Areva M5000 wind turbine.
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
Performance of Rehabilitated Lightweight Aggregate Asphalt Concrete Pavements Under Wet and Heated Model Mobile Load Simulator Trafficking: A Comparative Study with the TxMLS

DOT National Transportation Integrated Search

2000-03-01

One-third-scale Model Mobile Load Simulator Mk3 (MMLS3) tests were conducted on US 281 in Jacksboro, Texas, adjacent to the full-scale Texas Mobile Load Simulator (TxMLS). The objectives were to investigate the moisture susceptibility and relative pe...
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...
Comparative analysis of international standards for the fatigue testing of posterior spinal fixation systems.

PubMed

Villa, Tomaso; La Barbera, Luigi; Galbusera, Fabio

2014-04-01

Preclinical evaluation of the long-term reliability of devices for lumbar fixation is a mandatory activity before they are put into market. The experimental setups are described in two different standards edited by the International Organization for Standardization (ISO) and the American Society for Testing Materials (ASTM), but the evaluation of the suitability of such tests to simulate the actual loading with in vivo situations has never been performed. To calculate through finite element (FE) simulations the stress in the rods of the fixator when subjected to ASTM and ISO standards. To compare the calculated stresses arising in the same fixator once it has been virtually mounted in a physiological environment and loaded with physiological forces and moments. FE simulations and validation experimental tests. FE models of the ISO and ASTM setups were created to conduct simulations of the tests prescribed by standards and calculate stresses in the rods. Validation of the simulations were performed through experimental tests; the same fixator was virtually mounted in an L2-L4 FE model of the lumbar spine and stresses in the rods were calculated when the spine was subjected to physiological forces and moments. The comparison between FE simulations and experimental tests showed good agreement between results obtained using the two methodologies, thus confirming the suitability of the FE method to evaluate stresses in the device in different loading situations. The usage of a physiological load with ASTM standard is impossible due to the extreme severity of the ASTM configuration; in this circumstance, the presence of an anterior support is suggested. Also, ISO prescriptions, although the choice of the setup correctly simulates the mechanical contribution of the discs, seem to overstress the device as compared with a physiological loading condition. Some daily activities, other than walking, can induce a further state of stress in the device that should be taken into account in setting up new experimental procedures. ISO standard loading prescriptions seems to be more severe than the expected physiological ones. The ASTM standard should be completed by including some anterior supporting device and declaring the value of the load to be imposed. Moreover, a further enhancement of standards would be simulating other movements representative of daily activities different from walking. Copyright © 2014 Elsevier Inc. All rights reserved.

Space Shuttle Projects

NASA Image and Video Library

1987-07-01

A forward segment is being lowered into the Transient Pressure Test Article (TPTA) test stand at the Marshall Space Flight Center (MSFC) east test area. The TPTA test stand, 14-feet wide, 27-feet long, and 33-feet high, was built in 1987 to provide data to verify the sealing capability of the redesign solid rocket motor (SRM) field and nozzle joints. The test facility applies pressure, temperature, and external loads to a short stack of solid rocket motor hardware. The simulated SRM ignition pressure and temperature transients are achieved by firing a small amount of specially configured solid propellant. The pressure transient is synchronized with external programmable dynamic loads that simulate lift off loads at the external tank attach points. Approximately one million pounds of dead weight on top of the test article simulates the weight of the other Shuttle elements.
Space Shuttle Projects

NASA Image and Video Library

1987-07-01

A forward segment is being lowered into the Transient Pressure Test Article (TPTA) test stand at thw Marshall Space Flight Center (MSFC) east test area. The TPTA test stand, 14-feet wide, 27-feet long, and 33-feet high, was built in 1987 to provide data to verify the sealing capability of the redesign solid rocket motor (SRM) field and nozzle joints. The test facility applies pressure, temperature, and external loads to a short stack of solid rocket motor hardware. The simulated SRM ignition pressure and temperature transients are achieved by firing a small amount of specially configured solid propellant. The pressure transient is synchronized with external programmable dynamic loads that simulate lift off loads at the external tank attach points. Approximately one million pounds of dead weight on top of the test article simulates the weight of the other Shuttle elements.
Parallel processing methods for space based power systems

NASA Technical Reports Server (NTRS)

Berry, F. C.

1993-01-01

This report presents a method for doing load-flow analysis of a power system by using a decomposition approach. The power system for the Space Shuttle is used as a basis to build a model for the load-flow analysis. To test the decomposition method for doing load-flow analysis, simulations were performed on power systems of 16, 25, 34, 43, 52, 61, 70, and 79 nodes. Each of the power systems was divided into subsystems and simulated under steady-state conditions. The results from these tests have been found to be as accurate as tests performed using a standard serial simulator. The division of the power systems into different subsystems was done by assigning a processor to each area. There were 13 transputers available, therefore, up to 13 different subsystems could be simulated at the same time. This report has preliminary results for a load-flow analysis using a decomposition principal. The report shows that the decomposition algorithm for load-flow analysis is well suited for parallel processing and provides increases in the speed of execution.
Track-train dynamic analysis and test program, truck static test

NASA Technical Reports Server (NTRS)

Nemes, A. G.

1974-01-01

A series of tests were conducted to define the characteristics of an ASF 11 Ride Truck Assembly including joint slop, friction and stiffness. Loading to the truck assembly included vertical load to simulate the car/pool loading combined with lateral or moment loading that resulted in desired truck deflections for the various phases of testing. All seven test conditions were successfully completed with load and deflection data being collected. No attempt is made to reduce the applicable data other than to provide computer plots.
Biomechanical analysis of tension band fixation for olecranon fracture treatment.

PubMed

Kozin, S H; Berglund, L J; Cooney, W P; Morrey, B F; An, K N

1996-01-01

This study assessed the strength of various tension band fixation methods with wire and cable applied to simulated olecranon fractures to compare stability and potential failure or complications between the two. Transverse olecranon fractures were simulated by osteotomy. The fracture was anatomically reduced, and various tension band fixation techniques were applied with monofilament wire or multifilament cable. With a material testing machine load displacement curves were obtained and statistical relevance determined by analysis of variance. Two loading modes were tested: loading on the posterior surface of olecranon to simulate triceps pull and loading on the anterior olecranon tip to recreate a potential compressive loading on the fragment during the resistive flexion. All fixation methods were more resistant to posterior loading than to an anterior load. Individual comparative analysis for various loading conditions concluded that tension band fixation is more resilient to tensile forces exerted by the triceps than compressive forces on the anterior olecranon tip. Neither wire passage anterior to the K-wires nor the multifilament cable provided statistically significant increased stability.
Impact analysis of air gap motion with respect to parameters of mooring system for floating platform

NASA Astrophysics Data System (ADS)

Shen, Zhong-xiang; Huo, Fa-li; Nie, Yan; Liu, Yin-dong

2017-04-01

In this paper, the impact analysis of air gap concerning the parameters of mooring system for the semi-submersible platform is conducted. It is challenging to simulate the wave, current and wind loads of a platform based on a model test simultaneously. Furthermore, the dynamic equivalence between the truncated and full-depth mooring system is still a tuff work. However, the wind and current loads can be tested accurately in wind tunnel model. Furthermore, the wave can be simulated accurately in wave tank test. The full-scale mooring system and the all environment loads can be simulated accurately by using the numerical model based on the model tests simultaneously. In this paper, the air gap response of a floating platform is calculated based on the results of tunnel test and wave tank. Meanwhile, full-scale mooring system, the wind, wave and current load can be considered simultaneously. In addition, a numerical model of the platform is tuned and validated by ANSYS AQWA according to the model test results. With the support of the tuned numerical model, seventeen simulation cases about the presented platform are considered to study the wave, wind, and current loads simultaneously. Then, the impact analysis studies of air gap motion regarding the length, elasticity, and type of the mooring line are performed in the time domain under the beam wave, head wave, and oblique wave conditions.
JT9D performance deterioration results from a simulated aerodynamic load test

NASA Technical Reports Server (NTRS)

Stakolich, E. G.; Stromberg, W. J.

1981-01-01

The results of testing to identify the effects of simulated aerodynamic flight loads on JT9D engine performance are presented. The test results were also used to refine previous analytical studies on the impact of aerodynamic flight loads on performance losses. To accomplish these objectives, a JT9D-7AH engine was assembled with average production clearances and new seals as well as extensive instrumentation to monitor engine performance, case temperatures, and blade tip clearance changes. A special loading device was designed and constructed to permit application of known moments and shear forces to the engine by the use of cables placed around the flight inlet. The test was conducted in the Pratt & Whitney Aircraft X-Ray Test Facility to permit the use of X-ray techniques in conjunction with laser blade tip proximity probes to monitor important engine clearance changes. Upon completion of the test program, the test engine was disassembled, and the condition of gas path parts and final clearances were documented. The test results indicate that the engine lost 1.1 percent in thrust specific fuel consumption (TSFC), as measured under sea level static conditions, due to increased operating clearances caused by simulated flight loads. This compares with 0.9 percent predicted by the analytical model and previous study efforts.
NCHRP project 20-07/task 361 : hamburg wheel-track test equipment requirements and improvements to AASHTO T 324 : research project capsule.

DOT National Transportation Integrated Search

2015-02-01

The Loaded Wheel Test (LWT) is a laboratory-controlled rut depth test that uses loaded wheel(s) : to apply a moving load on hot-mix and warm-mix asphalt (HMA and WMA) specimens to simulate : tra c load applied on asphalt pavements. In the 1970s He...
Dynamic tests of composite panels of an aircraft wing

NASA Astrophysics Data System (ADS)

Splichal, Jan; Pistek, Antonin; Hlinka, Jiri

2015-10-01

The paper describes the analysis of aerospace composite structures under dynamic loading. Today, it is common to use design procedures based on assumption of static loading only, and dynamic loading is rarely assumed and applied in design and certification of aerospace structures. The paper describes the application of dynamic loading for the design of aircraft structures, and the validation of the procedure on a selected structure. The goal is to verify the possibility of reducing the weight through improved design/modelling processes using dynamic loading instead of static loading. The research activity focuses on the modelling and testing of a composite panel representing a local segment of an aircraft wing section, investigating in particular the buckling behavior under dynamic loading. Finite Elements simulation tools are discussed, as well as the advantages of using a digital optical measurement system for the evaluation of the tests. The comparison of the finite element simulations with the results of the tests is presented.
Wear Scar Similarities between Retrieved and Simulator-Tested Polyethylene TKR Components: An Artificial Neural Network Approach

PubMed Central

2016-01-01

The aim of this study was to determine how representative wear scars of simulator-tested polyethylene (PE) inserts compare with retrieved PE inserts from total knee replacement (TKR). By means of a nonparametric self-organizing feature map (SOFM), wear scar images of 21 postmortem- and 54 revision-retrieved components were compared with six simulator-tested components that were tested either in displacement or in load control according to ISO protocols. The SOFM network was then trained with the wear scar images of postmortem-retrieved components since those are considered well-functioning at the time of retrieval. Based on this training process, eleven clusters were established, suggesting considerable variability among wear scars despite an uncomplicated loading history inside their hosts. The remaining components (revision-retrieved and simulator-tested) were then assigned to these established clusters. Six out of five simulator components were clustered together, suggesting that the network was able to identify similarities in loading history. However, the simulator-tested components ended up in a cluster at the fringe of the map containing only 10.8% of retrieved components. This may suggest that current ISO testing protocols were not fully representative of this TKR population, and protocols that better resemble patients' gait after TKR containing activities other than walking may be warranted. PMID:27597955
A novel dynamic mechanical testing technique for reverse shoulder replacements.

PubMed

Dabirrahmani, Danè; Bokor, Desmond; Appleyard, Richard

2014-04-01

In vitro mechanical testing of orthopedic implants provides information regarding their mechanical performance under simulated biomechanical conditions. Current in vitro component stability testing methods for reverse shoulder implants are based on anatomical shoulder designs, which do not capture the dynamic nature of these loads. With glenoid component loosening as one of the most prevalent modes of failure in reverse shoulder replacements, it is important to establish a testing protocol with a more realistic loading regime. This paper introduces a novel method of mechanically testing reverse shoulder implants, using more realistic load magnitudes and vectors, than is currently practiced. Using a custom made jig setup within an Instron mechanical testing system, it is possible to simulate the change in magnitude and direction of the joint load during arm abduction. This method is a step towards a more realistic testing protocol for measuring reverse shoulder implant stability.
Proposed Framework for Determining Added Mass of Orion Drogue Parachutes

NASA Technical Reports Server (NTRS)

Fraire, Usbaldo, Jr.; Dearman, James; Morris, Aaron

2011-01-01

The Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS) project is executing a program to qualify a parachute system for a next generation human spacecraft. Part of the qualification process involves predicting parachute riser tension during system descent with flight simulations. Human rating the CPAS hardware requires a high degree of confidence in the simulation models used to predict parachute loads. However, uncertainty exists in the heritage added mass models used for loads predictions due to a lack of supporting documentation and data. Even though CPAS anchors flight simulation loads predictions to flight tests, extrapolation of these models outside the test regime carries the risk of producing non-bounding loads. A set of equations based on empirically derived functions of skirt radius is recommended as the simplest and most viable method to test and derive an enhanced added mass model for an inflating parachute. This will increase confidence in the capability to predict parachute loads. The selected equations are based on those published in A Simplified Dynamic Model of Parachute Inflation by Dean Wolf. An Ames 80x120 wind tunnel test campaign is recommended to acquire the reefing line tension and canopy photogrammetric data needed to quantify the terms in the Wolf equations and reduce uncertainties in parachute loads predictions. Once the campaign is completed, the Wolf equations can be used to predict loads in a typical CPAS Drogue Flight test. Comprehensive descriptions of added mass test techniques from the Apollo Era to the current CPAS project are included for reference.
Full-scale locomotive dynamic crash testing and correlations : C-39 type locomotive colliding with a loaded hopper car (test 7).

DOT National Transportation Integrated Search

2011-09-01

This report presents the results of a locomotive and three loaded hopper car consist traveling at 29 miles per hour colliding with a stationary consist of 35 loaded hopper cars. The details of test instrumentation, LS-DYNA finite element simulation, ...
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.
40 CFR 86.229-94 - Road load force, test weight, and inertia weight class determination.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Road load force, test weight, and... § 86.229-94 Road load force, test weight, and inertia weight class determination. (a) Flywheels, electrical forces, or other means of simulating test weight as shown in the table in this paragraph shall be...
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.
Fatigue testing of energy storing prosthetic feet.

PubMed

Toh, S L; Goh, J C; Tan, P H; Tay, T E

1993-12-01

This paper describes a simple approach to the fatigue testing of prosthetic feet. A fatigue testing machine for prosthetic feet was designed as part of the programme to develop an energy storing prosthetic foot (ESPF). The fatigue tester does not simulate the loading pattern on the foot during normal walking. However, cyclic vertical loads are applied to the heel and forefoot during heel-strike and toe-off respectively, for 500,000 cycles. The maximum load applied was chosen to be 1.5 times that applied by the bodyweight of the amputee and the test frequency was chosen to be 2 Hz to shorten the test duration. Four prosthetic feet were tested: two Lambda feet (a newly developed ESPF), a Kingsley SACH foot and a Proteor SACH foot. It was found that the Lambda feet have very good fatigue properties. The Kingsley SACH foot performed better than the Proteor model, with no signs of wear at the heel. The results obtained using the simple approach was found to be comparable to the results from more complex fatigue machines which simulate the load pattern during normal walking. This suggests that simple load simulating machines, which are less costly and require less maintenance, are useful substitutes in studying the fatigue properties of prosthetic feet.
Simulation of the transient processes of load rejection under different accident conditions in a hydroelectric generating set

NASA Astrophysics Data System (ADS)

Guo, W. C.; Yang, J. D.; Chen, J. P.; Peng, Z. Y.; Zhang, Y.; Chen, C. C.

2016-11-01

Load rejection test is one of the essential tests that carried out before the hydroelectric generating set is put into operation formally. The test aims at inspecting the rationality of the design of the water diversion and power generation system of hydropower station, reliability of the equipment of generating set and the dynamic characteristics of hydroturbine governing system. Proceeding from different accident conditions of hydroelectric generating set, this paper presents the transient processes of load rejection corresponding to different accident conditions, and elaborates the characteristics of different types of load rejection. Then the numerical simulation method of different types of load rejection is established. An engineering project is calculated to verify the validity of the method. Finally, based on the numerical simulation results, the relationship among the different types of load rejection and their functions on the design of hydropower station and the operation of load rejection test are pointed out. The results indicate that: The load rejection caused by the accident within the hydroelectric generating set is realized by emergency distributing valve, and it is the basis of the optimization for the closing law of guide vane and the calculation of regulation and guarantee. The load rejection caused by the accident outside the hydroelectric generating set is realized by the governor. It is the most efficient measure to inspect the dynamic characteristics of hydro-turbine governing system, and its closure rate of guide vane set in the governor depends on the optimization result in the former type load rejection.
Method and apparatus for transfer function simulator for testing complex systems

NASA Technical Reports Server (NTRS)

Kavaya, M. J. (Inventor)

1985-01-01

A method and apparatus for testing the operation of a complex stabilization circuit in a closed loop system is presented. The method is comprised of a programmed analog or digital computing system for implementing the transfer function of a load thereby providing a predictable load. The digital computing system employs a table stored in a microprocessor in which precomputed values of the load transfer function are stored for values of input signal from the stabilization circuit over the range of interest. This technique may be used not only for isolating faults in the stabilization circuit, but also for analyzing a fault in a faulty load by so varying parameters of the computing system as to simulate operation of the actual load with the fault.
Comparison of road load simulator test results with track tests on electric vehicle propulsion system

NASA Technical Reports Server (NTRS)

Dustin, M. O.

1983-01-01

A special-purpose dynamometer, the road load simulator (RLS), is being used at NASA's Lewis Research Center to test and evaluate electric vehicle propulsion systems developed under DOE's Electric and Hybrid Vehicle Program. To improve correlation between system tests on the RLS and track tests, similar tests were conducted on the same propulsion system on the RLS and on a test track. These tests are compared in this report. Battery current to maintain a constant vehicle speed with a fixed throttle was used for the comparison. Scatter in the data was greater in the track test results. This is attributable to variations in tire rolling resistance and wind effects in the track data. It also appeared that the RLS road load, determined by coastdown tests on the track, was lower than that of the vehicle on the track. These differences may be due to differences in tire temperature.

Quantifying the Influence of Lightning Strike Pressure Loading on Composite Specimen Damage

NASA Astrophysics Data System (ADS)

Foster, P.; Abdelal, G.; Murphy, A.

2018-04-01

Experimental work has shown that a component of lightning strike damage is caused by a mechanical loading. As the profile of the pressure loading is unknown a number of authors propose different pressure loads, varying in form, application area and magnitude. The objective of this paper is to investigate the potential contribution of pressure loading to composite specimen damage. This is achieved through a simulation study using an established modelling approach for composite damage prediction. The study examines the proposed shockwave loads from the literature. The simulation results are compared with measured test specimen damage examining the form and scale of damage. The results for the first time quantify the significance of pressure loading, demonstrating that although a pressure load can cause damage consistent with that measured experimentally, it has a negligible contribution to the overall scale of damage. Moreover the requirements for a pressure to create the damage behaviours typically witnessed in testing requires that the pressure load be within a very precise window of magnitude and loading area.
Wear simulation of total knee prostheses using load and kinematics waveforms from stair climbing.

PubMed

Abdel-Jaber, Sami; Belvedere, Claudio; Leardini, Alberto; Affatato, Saverio

2015-11-05

Knee wear simulators are meant to perform load cycles on knee implants under physiological conditions, matching exactly, if possible, those experienced at the replaced joint during daily living activities. Unfortunately, only conditions of low demanding level walking, specified in ISO-14243, are used conventionally during such tests. A recent study has provided a consistent knee kinematic and load data-set measured during stair climbing in patients implanted with a specific modern total knee prosthesis design. In the present study, wear simulation tests were performed for the first time using this data-set on the same prosthesis design. It was hypothesised that more demanding tasks would result in wear rates that differ from those observed in retrievals. Four prostheses for total knee arthroplasty were tested using a displacement-controlled knee wear simulator for two million cycles at 1.1 Hz, under kinematics and load conditions typical of stair climbing. After simulation, the corresponding damage scars on the bearings were qualified and compared with equivalent explanted prostheses. An average mass loss of 20.2±1.5 mg was found. Scanning digital microscopy revealed similar features, though the explant had a greater variety of damage modes, including a high prevalence of adhesive wear damage and burnishing in the overall articulating surface. This study confirmed that the results from wear simulation machines are strongly affected by kinematics and loads applied during simulations. Based on the present results for the full understanding of the current clinical failure of knee implants, a more comprehensive series of conditions are necessary for equivalent simulations in vitro. Copyright © 2015 Elsevier Ltd. All rights reserved.
Tire-rim interface pressure of a commercial vehicle wheel under radial loads: theory and experiment

NASA Astrophysics Data System (ADS)

Wan, Xiaofei; Shan, Yingchun; Liu, Xiandong; He, Tian; Wang, Jiegong

2017-11-01

The simulation of the radial fatigue test of a wheel has been a necessary tool to improve the design of the wheel and calculate its fatigue life. The simulation model, including the strong nonlinearity of the tire structure and material, may produce accurate results, but often leads to a divergence in calculation. Thus, a simplified simulation model in which the complicated tire model is replaced with a tire-wheel contact pressure model is used extensively in the industry. In this paper, a simplified tire-rim interface pressure model of a wheel under a radial load is established, and the pressure of the wheel under different radial loads is tested. The tire-rim contact behavior affected by the radial load is studied and analyzed according to the test result, and the tire-rim interface pressure extracted from the test result is used to evaluate the simplified pressure model and the traditional cosine function model. The results show that the proposed model may provide a more accurate prediction of the wheel radial fatigue life than the traditional cosine function model.
A review of the analytical simulation of aircraft crash dynamics

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Carden, Huey D.; Boitnott, Richard L.; Hayduk, Robert J.

1990-01-01

A large number of full scale tests of general aviation aircraft, helicopters, and one unique air-to-ground controlled impact of a transport aircraft were performed. Additionally, research was also conducted on seat dynamic performance, load-limiting seats, load limiting subfloor designs, and emergency-locator-transmitters (ELTs). Computer programs were developed to provide designers with methods for predicting accelerations, velocities, and displacements of collapsing structure and for estimating the human response to crash loads. The results of full scale aircraft and component tests were used to verify and guide the development of analytical simulation tools and to demonstrate impact load attenuating concepts. Analytical simulation of metal and composite aircraft crash dynamics are addressed. Finite element models are examined to determine their degree of corroboration by experimental data and to reveal deficiencies requiring further development.
Dynamic load simulator

NASA Technical Reports Server (NTRS)

Joncas, K. P.

1972-01-01

Concepts and techniques for identifying and simulating both the steady state and dynamic characteristics of electrical loads for use during integrated system test and evaluation are discussed. The investigations showed that it is feasible to design and develop interrogation and simulation equipment to perform the desired functions. During the evaluation, actual spacecraft loads were interrogated by stimulating the loads with their normal input voltage and measuring the resultant voltage and current time histories. Elements of the circuits were optimized by an iterative process of selecting element values and comparing the time-domain response of the model with those obtained from the real equipment during interrogation.
Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Form Domes

NASA Technical Reports Server (NTRS)

Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

2010-01-01

Damage tolerance testing development was required to help qualify a new spin forming dome fabrication process for the Ares 1 program at Marshall Space Flight Center (MSFC). One challenge of the testing was due to the compound curvature of the dome. The testing was developed on a sub-scale dome with a diameter of approximately 40 inches. The simulated service testing performed was based on the EQTP1102 Rev L 2195 Aluminum Lot Acceptance Simulated Service Test and Analysis Procedure generated by Lockheed Martin for the Space Shuttle External Fuel Tank. This testing is performed on a specimen with an induced flaw of elliptical shape generated by Electrical Discharge Machining (EDM) and subsequent fatigue cycling for crack propagation to a predetermined length and depth. The specimen is then loaded in tension at a constant rate of displacement at room temperature until fracture occurs while recording load and strain. An identical specimen with a similar flaw is then proof tested at room temperature to imminent failure based on the critical offset strain achieved by the previous fracture test. If the specimen survives the proof, it is then subjected to cryogenic cycling with loads that are a percentage of the proof load performed at room temperature. If all cryogenic cycles are successful, the specimen is loaded in tension to failure at the end of the test. This standard was generated for flat plate, so a method of translating this to a specimen of compound curvature was required. This was accomplished by fabricating a fixture that maintained the curvature of the specimen rigidly with the exception of approximately one-half inch in the center of the specimen containing the induced flaw. This in conjunction with placing the center of the specimen in the center of the load train allowed for successful testing with a minimal amount of bending introduced into the system. Stress corrosion cracking (SCC) tests were performed using the typical double beam assembly and with 4-point loaded specimens under alternate immersion conditions in a 3.5% NaCl environment for 90 days. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K1SCC) of Al-Li 2195 which to our knowledge has not been determined previously. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication.
Performance deterioration based on simulated aerodynamic loads test, JT9D jet engine diagnostics program

NASA Technical Reports Server (NTRS)

Stromberg, W. J.

1981-01-01

An engine was specially prepared with extensive instrumentation to monitor performance, case temperatures, and clearance changes. A special loading device was used to apply known loads on the engine by the use of cables placed around the flight inlet. These loads simulated the estimated aerodynamic pressure distributions that occur on the inlet in various segments of a typical airplane flight. Test results indicate that the engine lost 1.3 percent in take-off thrust specific fuel consumption (TSFC) during the course of the test effort. Permanent clearance changes due to the loads accounted for 1.1 percent; increase in low pressure compressor airfoil roughness and thermal distortion in the high pressure turbine accounted for 0.2 percent. Pretest predicted performance loss due to clearance changes was 0.9 percent in TSFC. Therefore, the agreement between measurement and prediction is considered to be excellent.
Modeling and Simulation of a Helicopter Slung Load Stabilization Device

NASA Technical Reports Server (NTRS)

Cicolani, Luigi S.; Ehlers, George E.

2002-01-01

This paper addresses the problem of simulation and stabilization of the yaw motions of a cargo container slung load. The study configuration is a UH-60 helicopter carrying a 6ft x 6 ft x 8 ft CONEX container. This load is limited to 60 KIAS in operations and flight testing indicates that it starts spinning in hover and that spin rate increases with airspeed. The simulation reproduced the load yaw motions seen in the flight data after augmenting the load model with terms representing unsteady load yaw moment effects acting to reinforce load oscillations, and augmenting the hook model to include yaw resistance at the hook. The use of a vertical fin to stabilize the load is considered. Results indicate that the CONEX airspeed can be extended to 110 kts using a 3x5 ft fin.
Isolating Added Mass Load Components of CPAS Main Clusters

NASA Technical Reports Server (NTRS)

Ray, Eric S.

2017-01-01

The current simulation for the Capsule Parachute Assembly System (CPAS) lacks fidelity in representing added mass for the 116 ft Do ringsail Main parachute. The availability of 3-D models of inflating Main canopies allowed for better estimation the enclosed air volume as a function of time. This was combined with trajectory state information to estimate the components making up measured axial loads. A proof-of-concept for an alternate simulation algorithm was developed based on enclosed volume as the primary independent variable rather than drag area growth. Databases of volume growth and parachute drag area vs. volume were developed for several flight tests. Other state information was read directly from test data, rather than numerically propagated. The resulting simulated peak loads were close in timing and magnitude to the measured loads data. However, results are very sensitive to data curve fitting and may not be suitable for Monte Carlo simulations. It was assumed that apparent mass was either negligible or a small fraction of enclosed mass, with little difference in results.
Booster Interface Loads

NASA Technical Reports Server (NTRS)

Gentz, Steve; Wood, Bill; Nettles, Mindy

2015-01-01

The interaction between shock waves and the wake shed from the forward booster/core attach hardware results in unsteady pressure fluctuations, which can lead to large buffeting loads on the vehicle. This task investigates whether computational tools can adequately predict these flows, and whether alternative booster nose shapes can reduce these loads. Results from wind tunnel tests will be used to validate the computations and provide design information for future Space Launch System (SLS) configurations. The current work combines numerical simulations with wind tunnel testing to predict buffeting loads caused by the boosters. Variations in nosecone shape, similar to the Ariane 5 design (fig. 1), are being evaluated with regard to lowering the buffet loads. The task will provide design information for the mitigation of buffet loads for SLS, along with validated simulation tools to be used to assess future SLS designs.
Progressive Damage and Fracture in Composites Under Dynamic Loading

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

1994-01-01

A computational simulation tool is used to evaluate the various stages of damage progression in composite materials during losipescu shear testing. Unidirectional composite specimens with either the major or minor material axis in the load direction are considered. Damage progression characteristics are described for each specimen using two types of boundary conditions. A procedure is outlined regarding the use of computational simulation in the testing of composite materials.
Design and Modeling of a Test Bench for Dual-Motor Electric Drive Tracked Vehicles Based on a Dynamic Load Emulation Method.

PubMed

Wang, Zhe; Lv, Haoliang; Zhou, Xiaojun; Chen, Zhaomeng; Yang, Yong

2018-06-21

Dual-motor Electric Drive Tracked Vehicles (DDTVs) have attracted increasing attention due to their high transmission efficiency and economical fuel consumption. A test bench for the development and validation of new DDTV technologies is necessary and urgent. How to load the vehicle on a DDTV test bench exactly the same as on a real road is a crucial issue when designing the bench. This paper proposes a novel dynamic load emulation method to address this problem. The method adopts dual dynamometers to simulate both the road load and the inertia load that are imposed on the dual independent drive systems. The vehicle’s total inertia equivalent to the drive wheels is calculated with separate consideration of vehicle body, tracks and road wheels to obtain a more accurate inertia load. A speed tracking control strategy with feedforward compensation is implemented to control the dual dynamometers, so as to make the real-time dynamic load emulation possible. Additionally, a MATLAB/Simulink model of the test bench is built based on a dynamics analysis of the platform. Experiments are finally carried out on this test bench under different test conditions. The outcomes show that the proposed load emulation method is effective, and has good robustness and adaptability to complex driving conditions. Besides, the accuracy of the established test bench model is also demonstrated by comparing the results obtained from the simulation model and experiments.
A laboratory facility for electric vehicle propulsion system testing

NASA Technical Reports Server (NTRS)

Sargent, N. B.

1980-01-01

The road load simulator facility located at the NASA Lewis Research Center enables a propulsion system or any of its components to be evaluated under a realistic vehicle inertia and road loads. The load is applied to the system under test according to the road load equation: F(net)=K1F1+K2F2V+K3 sq V+K4(dv/dt)+K5 sin theta. The coefficient of each term in the equation can be varied over a wide range with vehicle inertial representative of vehicles up to 7500 pounds simulated by means of flywheels. The required torque is applied by the flywheels, a hydroviscous absorber and clutch, and a drive motor integrated by a closed loop control system to produce a smooth, continuous load up to 150 horsepower.
In vitro evaluation of translating and rotating plates using a robot testing system under follower load.

PubMed

Yan, Y; Bell, K M; Hartman, R A; Hu, J; Wang, W; Kang, J D; Lee, J Y

2017-01-01

Various modifications to standard "rigid" anterior cervical plate designs (constrained plate) have been developed that allow for some degree of axial translation and/or rotation of the plate (semi-constrained plate)-theoretically promoting proper load sharing with the graft and improved fusion rates. However, previous studies about rigid and dynamic plates have not examined the influence of simulated muscle loading. The objective of this study was to compare rigid, translating, and rotating plates for single-level corpectomy procedures using a robot testing system with follower load. In-vitro biomechanical test. N = 15 fresh-frozen human (C3-7) cervical specimens were biomechanically tested. The follower load was applied to the specimens at the neutral position from 0 to 100 N. Specimens were randomized into a rigid plate group, a translating plate group and a rotating plate group and then tested in flexion, extension, lateral bending and axial rotation to a pure moment target of 2.0 Nm under 100N of follower load. Range of motion, load sharing, and adjacent level effects were analyzed using a repeated measures analysis of variance (ANOVA). No significant differences were observed between the translating plate and the rigid plate on load sharing at neutral position and C4-6 ROM, but the translating plate was able to maintain load through the graft at a desired level during flexion. The rotating plate shared less load than rigid and translating plates in the neutral position, but cannot maintain the graft load during flexion. This study demonstrated that, in the presence of simulated muscle loading (follower load), the translating plate demonstrated superior performance for load sharing compared to the rigid and rotating plates.
A New Experimental Design for Bacterial Microleakage Investigation at the Implant-Abutment Interface: An In Vitro Study.

PubMed

Zipprich, Holger; Miatke, Sven; Hmaidouch, Rim; Lauer, Hans-Christoph

2016-01-01

This study aimed to test bacterial microleakage at the implant-abutment interface (IAI) before and after dynamic loading using a new chewing simulation. Fourteen implant systems (n = 5 samples of each) were divided into two groups: (1) systems with conical implant-abutment connections (IACs), and (2) systems with flat IACs. For collecting samples without abutment disconnection, channels (Ø = 0.3 mm) were drilled into implants perpendicularly to their axes, and stainless-steel cannulas were adhesively glued inside these channels to allow a sterilized rinsing solution to enter the implant interior and to exit with potential contaminants for testing. Implants were embedded in epoxy resin matrices, which were supported by titanium cylinders with lateral openings for inward and outward cannulas. Abutments were tightened and then provided with vertically adjustable, threaded titanium balls, which were cemented using composite cement. Specimens were immersed in a bacterial liquid and after a contact time of 15 minutes, the implant interior was rinsed prior to chewing simulation (0 N ≘ static seal testing). Specimens were exposed to a Frankfurt chewing simulator. Two hundred twenty force cycles per power level (110 in ± X-axis) were applied to simulate a daily masticatory load of 660 chewing cycles (equivalent to 1,200,000 cycles/5 years). The applied load was gradually increased from 0 N to a maximum load of 200 N in 25-N increments. The implant interior was rinsed to obtain samples before each new power level. All samples were tested using fluorescence microscopy; invading microorganisms could be counted and evaluated. No bacterial contamination was detected under static loading conditions in both groups. After loading, bacterial contamination was detected in one sample from one specimen in group 1 and in two samples from two specimens in group 2. Controlled dynamic loading applied in this study simulated a clinical situation and enabled time-dependent analysis regarding the bacterial seal of different implant systems. Conical IACs offer a better bacterial seal compared with flat IACs, which showed increased microleakage after dynamic loading. IAC design plays a crucial role in terms of bacterial colonization. Taking samples of the implant interior without abutment disconnection eliminates an error source.
Measuring Permeability of Composite Cryotank Laminants

NASA Technical Reports Server (NTRS)

Oliver, Stanley T.; Selvidge, Shawn; Watwood, Michael C.

2004-01-01

This paper describes a test method developed to identify whether certain materials and material systems are suitable candidates for large pressurized reusable cryogenic tanks intended for use in current and future manned launch systems. It provides a quick way to screen numerous candidate materials for permeability under anticipated loading environments consistent with flight conditions, as well as addressing reusability issues. cryogenic tank, where the major design issue was hydrogen permeability. It was successfully used to evaluate samples subjected to biaxial loading while maintaining test temperatures near liquid hydrogen. After each sample was thermally preconditioned, a cyclic pressure load was applied to simulate the in-plane strain. First permeability was measured while a sample was under load. Then the sample was unloaded and allowed to return to ambient temperature. The test was repeated to simulate reusability, in order to evaluate its effects on material permeability.
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.
Development of Electronic Load Controllers for Free-Piston Stirling Convertors Aided by Stirling Simulation Model

NASA Technical Reports Server (NTRS)

Regan, Timothy F.

2004-01-01

The free-piston Stirling convertor end-to-end modeling effort at the NASA Glenn Research Center has produced a software-based test bed in which free-piston Stirling convertors can be simulated and evaluated. The simulation model includes all the components of the convertor: the Stirling cycle engine, heat source, linear alternator, controller, and load. So far, it has been used in evaluating the performance of electronic controller designs. Three different controller design concepts were simulated using the model: 1) Controllers with parasitic direct current loading. 2) Controllers with parasitic alternating current loading. 3) Controllers that maintain a reference current. The free-piston Stirling convertor is an electromechanical device that operates at resonance. It is the function of the electronic load controller to ensure that the electrical load seen by the machine is always great enough to keep the amplitude of the piston and alternator oscillation at the rated value. This is done by regulating the load on the output bus. The controller monitors the instantaneous voltage, regulating it by switching loads called parasitic loads onto the bus whenever the bus voltage is too high and removing them whenever the voltage is too low. In the first type of controller, the monitor-ing and switching are done on the direct-current (dc) bus. In the second type, the alternating current bus is used. The model allows designers to test a controller concept before investing time in hardware. The simulation code used to develop the model also offers detailed models of digital and analog electronic components so that the resulting designs are realistic enough to translate directly into hardware circuits.
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.
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...

14 CFR 25.305 - Strength and deformation.

Code of Federal Regulations, 2013 CFR

2013-01-01

... strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation....305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT...
14 CFR 25.305 - Strength and deformation.

Code of Federal Regulations, 2012 CFR

2012-01-01

... strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation....305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT...
14 CFR 25.305 - Strength and deformation.

Code of Federal Regulations, 2014 CFR

2014-01-01

... strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation....305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT...
14 CFR 25.305 - Strength and deformation.

Code of Federal Regulations, 2010 CFR

2010-01-01

... strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation....305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT...
14 CFR 25.305 - Strength and deformation.

Code of Federal Regulations, 2011 CFR

2011-01-01

... strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not apply. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation....305 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT...
Determination of elastomeric foam parameters for simulations of complex loading.

PubMed

Petre, M T; Erdemir, A; Cavanagh, P R

2006-08-01

Finite element (FE) analysis has shown promise for the evaluation of elastomeric foam personal protection devices. Although appropriate representation of foam materials is necessary in order to obtain realistic simulation results, material definitions used in the literature vary widely and often fail to account for the multi-mode loading experienced by these devices. This study aims to provide a library of elastomeric foam material parameters that can be used in FE simulations of complex loading scenarios. Twelve foam materials used in footwear were tested in uni-axial compression, simple shear and volumetric compression. For each material, parameters for a common compressible hyperelastic material model used in FE analysis were determined using: (a) compression; (b) compression and shear data; and (c) data from all three tests. Material parameters and Drucker stability limits for the best fits are provided with their associated errors. The material model was able to reproduce deformation modes for which data was provided during parameter determination but was unable to predict behavior in other deformation modes. Simulation results were found to be highly dependent on the extent of the test data used to determine the parameters in the material definition. This finding calls into question the many published results of simulations of complex loading that use foam material parameters obtained from a single mode of testing. The library of foam parameters developed here presents associated errors in three deformation modes that should provide for a more informed selection of material parameters.
Flight Testing and Real-Time System Identification Analysis of a UH-60A Black Hawk Helicopter with an Instrumented External Sling Load

NASA Technical Reports Server (NTRS)

McCoy, Allen H.

1998-01-01

Helicopter external air transportation plays an important role in today's world. For both military and civilian helicopters, external sling load operations offer an efficient and expedient method of handling heavy, oversized cargo. With the ability to reach areas otherwise inaccessible by ground transportation, helicopter external load operations are conducted in industries such as logging, construction, and fire fighting, as well as in support of military tactical transport missions. Historically, helicopter and load combinations have been qualified through flight testing, requiring considerable time and cost. With advancements in simulation and flight test techniques there is potential to substantially reduce costs and increase the safety of helicopter sling load certification. Validated simulation tools make possible accurate prediction of operational flight characteristics before initial flight tests. Real time analysis of test data improves the safety and efficiency of the testing programs. To advance these concepts, the U.S. Army and NASA, in cooperation with the Israeli Air Force and Technion, under a Memorandum of Agreement, seek to develop and validate a numerical model of the UH-60 with sling load and demonstrate a method of near real time flight test analysis. This thesis presents results from flight tests of a U.S. Army Black Hawk helicopter with various external loads. Tests were conducted as the U.S. first phase of this MOA task. The primary load was a container express box (CONEX) which contained a compact instrumentation package. The flights covered the airspeed range from hover to 70 knots. Primary maneuvers were pitch and roll frequency sweeps, steps, and doublets. Results of the test determined the effect of the suspended load on both the aircraft's handling qualities and its control system's stability margins. Included were calculations of the stability characteristics of the load's pendular motion. Utilizing CIFER(R) software, a method for near-real time system identification was also demonstrated during the flight test program.
Effects of forming history on crash simulation of a vehicle

NASA Astrophysics Data System (ADS)

Gökler, M. İ.; Doğan, U. Ç.; Darendeliler, H.

2016-08-01

The effects of forming on the crash simulation of a vehicle have been investigated by considering the load paths produced by sheet metal forming process. The frontal crash analysis has been performed by the finite element method, firstly without considering the forming history, to find out the load paths that absorb the highest energy. The sheet metal forming simulations have been realized for each structural component of the load paths and the frontal crash analysis has been repeated by including forming history. The results of the simulations with and without forming effects have been compared with the physical crash test results available in literature.
Dynamic Response of Reinforced Soil Systems. Volume 2. Appendices

DTIC Science & Technology

1993-03-01

by a burster slab. These protection measures are costly, time consuming to construct, and sensitive to multiple strikes. Soil has been used to...load--deflection behavior of the reinforced soi I Dynamic puilout tests were then performed using the same parameters as the static tests. A standard...system was capable cf loading the sample in just a few micro-seconds to simulate a blast load. Dynamic load-deflection behavior was characterized and
Synthesized multi-station tribo-test system for bio-tribological evaluation in vitro

NASA Astrophysics Data System (ADS)

Wu, Tonghai; Du, Ying; Li, Yang; Wang, Shuo; Zhang, Zhinan

2016-07-01

Tribological tests play an important role on the evaluation of long-term bio-tribological performances of prosthetic materials for commercial fabrication. Those tests focus on the motion simulation of a real joint in vitro with only normal loads and constant velocities, which are far from the real friction behavior of human joints characterized with variable loads and multiple directions. In order to accurately obtain the bio-tribological performances of artificial joint materials, a tribological tester with a miniature four-station tribological system is proposed with four distinctive features. Firstly, comparability and repeatability of a test are ensured by four equal stations of the tester. Secondly, cross-linked scratch between tribo-pairs of human joints can be simulated by using a gear-rack meshing mechanism to produce composite motions. With this mechanism, the friction tracks can be designed by varying reciprocating and rotating speeds. Thirdly, variable loading system is realized by using a ball-screw mechanism driven by a stepper motor, by which loads under different gaits during walking are simulated. Fourthly, dynamic friction force and normal load can be measured simultaneously. The verifications of the performances of the developed tester show that the variable frictional tracks can produce different wear debris compared with one-directional tracks, and the accuracy of loading and friction force is within ±5%. Thus the high consistency among different stations can be obtained. Practically, the proposed tester system could provide more comprehensive and accurate bio-tribological evaluations for prosthetic materials.
Performance of the Boeing LRV wheels in a lunar soil simulant. Report 2: Effects of speed, Wheel load, and soil

NASA Technical Reports Server (NTRS)

Melzer, K.

1971-01-01

Two nearly identical Boeing-GM wire-mesh Lunar Roving Vehicle (LRV) wheels were laboratory tested in a lunar soil simulant to determine the influence of wheel speed and acceleration, wheel load, presence of a fender, travel direction, and soil strength on the wheel performance. Constant-slip and three types of programmed-slip tests were conducted with a single-wheel dynamometer system. Test results indicated that performance of single LRV wheels in terms of pull coefficient, power number, and efficiency were not influenced by wheel speed and acceleration, travel direction, the presence of a fender, or wheel load. Of these variables, only load influenced sinkage, which increased with increasing load. For a given slip, the pull coefficient and power number increased with increasing soil strength. However, for a given pull coefficient or slope, slip was less in firmer soil; thus, the power number decreased and efficiency increased with increasing soil strength.
The use of solar simulation systems for producing artificial global radiation for the purpose of determining the heat load of rooms

NASA Technical Reports Server (NTRS)

Kalt, A. C.

1975-01-01

Certain climatic tests which require solar and sky radiation were carried out in the laboratory by using simulated global radiation. The advantages of such a method of measurement and the possibilities and limitations resulting from the simulation of global radiation are described. Experiments concerning the thermal load in rooms were conducted in order to test the procedure. In particular, the heat gain through a window with sunshade is discussed, a venetian blind between the panes of a double-glazed window being used in most cases.
Investigation in Simulated Vertical Descent of the Characteristics of a Cargo-Dropping Device having Extensible Rotating Blades

NASA Technical Reports Server (NTRS)

Stone, Ralph W., Jr.; Hultz, Burton E.

1949-01-01

The characteristics of a cargo-dropping device having extensible rotating blades as load-carrying surfaces have been studied in simulated vertical descent in the Langley 20-foot free-spinning tunnel. The investigation included tests to determine the variation in vertical sinking speed with load. A study of the blade characteristics and of the test results indicated a method of dynamically balancing the blades to permit proper functioning of the device.
Fatigue-test acceleration with flight-by-flight loading and heating to simulate supersonic-transport operation

NASA Technical Reports Server (NTRS)

Imig, L. A.; Garrett, L. E.

1973-01-01

Possibilities for reducing fatigue-test time for supersonic-transport materials and structures were studied in tests with simulated flight-by-flight loading. In order to determine whether short-time tests were feasible, the results of accelerated tests (2 sec per flight) were compared with the results of real-time tests (96 min per flight). The effects of design mean stress, the stress range for ground-air-ground cycles, simulated thermal stress, the number of stress cycles in each flight, and salt corrosion were studied. The flight-by-flight stress sequences were applied to notched sheet specimens of Ti-8Al-1Mo-1V and Ti-6Al-4V titanium alloys. A linear cumulative-damage analysis accounted for large changes in stress range of the simulated flights but did not account for the differences between real-time and accelerated tests. The fatigue lives from accelerated tests were generally within a factor of two of the lives from real-time tests; thus, within the scope of the investigation, accelerated testing seems feasible.
Space station common module thermal management: Design and construction of a test bed

NASA Technical Reports Server (NTRS)

Barile, R. G.

1986-01-01

In this project, a thermal test bed was designed, simulated, and planned for construction. The thermal system features interior and exterior thermal loads and interfacing with the central-radiator thermal bus. Components of the test bed include body mounted radiator loop with interface heat exchangers (600 Btu/hr); an internal loop with cabin air-conditioning and cold plates (3400 Btu/hr); interface heat exchangers to the central bus (13,000 Btu/hr); and provisions for new technology including advanced radiators, thermal storage, and refrigeration. The apparatus will be mounted in a chamber, heated with lamps, and tested in a vacuum chamber with LN2-cooled walls. Simulation of the test bed was accomplished using a DEC PRO 350 computer and the software package TK! olver. Key input variables were absorbed solar radiation and cold plate loads. The results indicate temperatures on the two loops will be nominal when the radiation and cold plate loads are in the range of 25% to 75% of peak loads. If all loads fall to zero, except the cabin air system which was fixed, the radiator fluid will drop below -100 F and may cause excessive pressure drop. If all loads reach 100%, the cabin air temperature could rise to 96 F.
Study on Roadheader Cutting Load at Different Properties of Coal and Rock

PubMed Central

2013-01-01

The mechanism of cutting process of roadheader with cutting head was researched, and the influences of properties of coal and rock on cutting load were deeply analyzed. Aimed at the defects of traditional calculation method of cutting load on fully expressing the complex cutting process of cutting head, the method of finite element simulation was proposed to simulate the dynamic cutting process. Aimed at the characteristics of coal and rock which affect the cutting load, several simulations with different firmness coefficient were taken repeatedly, and the relationship between three-axis force and firmness coefficient was derived. A comparative analysis of cutting pick load between simulation results and theoretical formula was carried out, and a consistency was achieved. Then cutting process with a total cutting head was carried out on this basis. The results show that the simulation analysis not only provides a reliable guarantee for the accurate calculation of the cutting head load and improves the efficiency of the cutting head cutting test but also offers a basis for selection of cutting head with different geological conditions of coal or rock. PMID:24302866
Joint Live Fire (JLF) Final Report for Instrumentation for Local Accelerative Loading

DTIC Science & Technology

2016-07-22

Comparison with Pretest Prediction ................................................................................... 60 d. Lessons Learned...test designs and results prior to full-scale testing. Correlating simulation to test data can aid in increasing confidence in the models to further...test and test-to-simulation with the current instrumentation used during testing. Recent advances in accelerometer design must be evaluated and
Design and development of data acquisition system for the Louisiana accelerated loading device : final report.

DOT National Transportation Integrated Search

1992-09-01

The Louisiana Transportation Research Center has established a Pavement Research Facility (PRF). The core of the PRF is a testing machine that is capable of conducting full-scale simulated and accelerated load testing of pavement materials, construct...
An Experimental Study of Shear-Dominated Failure in the 2013 Sandia Fracture Challenge Specimen

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

Corona, Edmundo; Deibler, Lisa Anne; Reedlunn, Benjamin

2015-04-01

This report presents an experimental study motivated by results obtained during the 2013 Sandia Fracture Challenge. The challenge involved A286 steel, shear-dominated compression specimens whose load-deflection response contained a load maximum fol- lowed by significant displacement under decreasing load, ending with a catastrophic fracture. Blind numerical simulations deviated from the experiments well before the maximum load and did not predict the failure displacement. A series of new tests were conducted on specimens machined from the original A286 steel stock to learn more about the deformation and failure processes in the specimen and potentially improve future numerical simulations. The study consistedmore » of several uniaxial tension tests to explore anisotropy in the material, and a set of new tests on the compression speci- men. In some compression specimen tests, stereo digital image correlation (DIC) was used to measure the surface strain fields local to the region of interest. In others, the compression specimen was loaded to a given displacement prior to failure, unloaded, sectioned, and imaged under the microscope to determine when material damage first appeared and how it spread. The experiments brought the following observations to light. The tensile tests revealed that the plastic response of the material is anisotropic. DIC during the shear- dominated compression tests showed that all three in-plane surface strain components had maxima in the order of 50% at the maximum load. Sectioning of the specimens revealed no signs of material damage at the point where simulations deviated from the experiments. Cracks and other damage did start to form approximately when the max- imum load was reached, and they grew as the load decreased, eventually culminating in catastrophic failure of the specimens. In addition to the steel specimens, a similar study was carried out for aluminum 7075-T651 specimens. These specimens achieved much lower loads and displacements, and failure occurred very close to the maximum in the load-deflection response. No material damage was observed in these specimens, even when failure was imminent. In the future, we plan to use these experimental results to improve numerical simu- lations of the A286 steel experiments, and to improve plasticity and failure models for the Al 7075 stock. The ultimate goal of our efforts is to increase our confidence in the results of numerical simulations of elastic-plastic structural behavior and failure.« less
Comparison of Building Energy Modeling Programs: Building Loads

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

Zhu, Dandan; Hong, Tianzhen; Yan, Da

This technical report presented the methodologies, processes, and results of comparing three Building Energy Modeling Programs (BEMPs) for load calculations: EnergyPlus, DeST and DOE-2.1E. This joint effort, between Lawrence Berkeley National Laboratory, USA and Tsinghua University, China, was part of research projects under the US-China Clean Energy Research Center on Building Energy Efficiency (CERC-BEE). Energy Foundation, an industrial partner of CERC-BEE, was the co-sponsor of this study work. It is widely known that large discrepancies in simulation results can exist between different BEMPs. The result is a lack of confidence in building simulation amongst many users and stakeholders. In themore » fields of building energy code development and energy labeling programs where building simulation plays a key role, there are also confusing and misleading claims that some BEMPs are better than others. In order to address these problems, it is essential to identify and understand differences between widely-used BEMPs, and the impact of these differences on load simulation results, by detailed comparisons of these BEMPs from source code to results. The primary goal of this work was to research methods and processes that would allow a thorough scientific comparison of the BEMPs. The secondary goal was to provide a list of strengths and weaknesses for each BEMP, based on in-depth understandings of their modeling capabilities, mathematical algorithms, advantages and limitations. This is to guide the use of BEMPs in the design and retrofit of buildings, especially to support China’s building energy standard development and energy labeling program. The research findings could also serve as a good reference to improve the modeling capabilities and applications of the three BEMPs. The methodologies, processes, and analyses employed in the comparison work could also be used to compare other programs. The load calculation method of each program was analyzed and compared to identify the differences in solution algorithms, modeling assumptions and simplifications. Identifying inputs of each program and their default values or algorithms for load simulation was a critical step. These tend to be overlooked by users, but can lead to large discrepancies in simulation results. As weather data was an important input, weather file formats and weather variables used by each program were summarized. Some common mistakes in the weather data conversion process were discussed. ASHRAE Standard 140-2007 tests were carried out to test the fundamental modeling capabilities of the load calculations of the three BEMPs, where inputs for each test case were strictly defined and specified. The tests indicated that the cooling and heating load results of the three BEMPs fell mostly within the range of spread of results from other programs. Based on ASHRAE 140-2007 test results, the finer differences between DeST and EnergyPlus were further analyzed by designing and conducting additional tests. Potential key influencing factors (such as internal gains, air infiltration, convection coefficients of windows and opaque surfaces) were added one at a time to a simple base case with an analytical solution, to compare their relative impacts on load calculation results. Finally, special tests were designed and conducted aiming to ascertain the potential limitations of each program to perform accurate load calculations. The heat balance module was tested for both single and double zone cases. Furthermore, cooling and heating load calculations were compared between the three programs by varying the heat transfer between adjacent zones, the occupancy of the building, and the air-conditioning schedule.« less

Crash Test of Three Cessna 172 Aircraft at NASA Langley Research Center's Landing and Impact Research Facility

NASA Technical Reports Server (NTRS)

Littell, Justin D.

2015-01-01

During the summer of 2015, three Cessna 172 aircraft were crash tested at the Landing and Impact Research Facility (LandIR) at NASA Langley Research Center (LaRC). The three tests simulated three different crash scenarios. The first simulated a flare-to-stall emergency or hard landing onto a rigid surface such as a road or runway, the second simulated a controlled flight into terrain with a nose down pitch on the aircraft, and the third simulated a controlled flight into terrain with an attempt to unsuccessfully recover the aircraft immediately prior to impact, resulting in a tail strike condition. An on-board data acquisition system captured 64 channels of airframe acceleration, along with acceleration and load in two onboard Hybrid II 50th percentile Anthropomorphic Test Devices, representing the pilot and co-pilot. Each test contained different airframe loading conditions and results show large differences in airframe performance. This paper presents test methods used to conduct the crash tests and will summarize the airframe results from the test series.
Effects of ventilation behaviour on indoor heat load based on test reference years.

PubMed

Rosenfelder, Madeleine; Koppe, Christina; Pfafferott, Jens; Matzarakis, Andreas

2016-02-01

Since 2003, most European countries established heat health warning systems to alert the population to heat load. Heat health warning systems are based on predicted meteorological conditions outdoors. But the majority of the European population spends a substantial amount of time indoors, and indoor thermal conditions can differ substantially from outdoor conditions. The German Meteorological Service (Deutscher Wetterdienst, DWD) extended the existing heat health warning system (HHWS) with a thermal building simulation model to consider heat load indoors. In this study, the thermal building simulation model is used to simulate a standardized building representing a modern nursing home, because elderly and sick people are most sensitive to heat stress. Different types of natural ventilation were simulated. Based on current and future test reference years, changes in the future heat load indoors were analyzed. Results show differences between the various ventilation options and the possibility to minimize the thermal heat stress during summer by using an appropriate ventilation method. Nighttime ventilation for indoor thermal comfort is most important. A fully opened window at nighttime and the 2-h ventilation in the morning and evening are more sufficient to avoid heat stress than a tilted window at nighttime and the 1-h ventilation in the morning and the evening. Especially the ventilation in the morning seems to be effective to keep the heat load indoors low. Comparing the results for the current and the future test reference years, an increase of heat stress on all ventilation types can be recognized.
Effects of ventilation behaviour on indoor heat load based on test reference years

NASA Astrophysics Data System (ADS)

Rosenfelder, Madeleine; Koppe, Christina; Pfafferott, Jens; Matzarakis, Andreas

2016-02-01

Since 2003, most European countries established heat health warning systems to alert the population to heat load. Heat health warning systems are based on predicted meteorological conditions outdoors. But the majority of the European population spends a substantial amount of time indoors, and indoor thermal conditions can differ substantially from outdoor conditions. The German Meteorological Service (Deutscher Wetterdienst, DWD) extended the existing heat health warning system (HHWS) with a thermal building simulation model to consider heat load indoors. In this study, the thermal building simulation model is used to simulate a standardized building representing a modern nursing home, because elderly and sick people are most sensitive to heat stress. Different types of natural ventilation were simulated. Based on current and future test reference years, changes in the future heat load indoors were analyzed. Results show differences between the various ventilation options and the possibility to minimize the thermal heat stress during summer by using an appropriate ventilation method. Nighttime ventilation for indoor thermal comfort is most important. A fully opened window at nighttime and the 2-h ventilation in the morning and evening are more sufficient to avoid heat stress than a tilted window at nighttime and the 1-h ventilation in the morning and the evening. Especially the ventilation in the morning seems to be effective to keep the heat load indoors low. Comparing the results for the current and the future test reference years, an increase of heat stress on all ventilation types can be recognized.
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
Predicting Failure Progression and Failure Loads in Composite Open-Hole Tension Coupons

NASA Technical Reports Server (NTRS)

Arunkumar, Satyanarayana; Przekop, Adam

2010-01-01

Failure types and failure loads in carbon-epoxy [45n/90n/-45n/0n]ms laminate coupons with central circular holes subjected to tensile load are simulated using progressive failure analysis (PFA) methodology. The progressive failure methodology is implemented using VUMAT subroutine within the ABAQUS(TradeMark)/Explicit nonlinear finite element code. The degradation model adopted in the present PFA methodology uses an instantaneous complete stress reduction (COSTR) approach to simulate damage at a material point when failure occurs. In-plane modeling parameters such as element size and shape are held constant in the finite element models, irrespective of laminate thickness and hole size, to predict failure loads and failure progression. Comparison to published test data indicates that this methodology accurately simulates brittle, pull-out and delamination failure types. The sensitivity of the failure progression and the failure load to analytical loading rates and solvers precision is demonstrated.
Head and neck response of a finite element anthropomorphic test device and human body model during a simulated rotary-wing aircraft impact.

PubMed

White, Nicholas A; Danelson, Kerry A; Gayzik, F Scott; Stitzel, Joel D

2014-11-01

A finite element (FE) simulation environment has been developed to investigate aviator head and neck response during a simulated rotary-wing aircraft impact using both an FE anthropomorphic test device (ATD) and an FE human body model. The head and neck response of the ATD simulation was successfully validated against an experimental sled test. The majority of the head and neck transducer time histories received a CORrelation and analysis (CORA) rating of 0.7 or higher, indicating good overall correlation. The human body model simulation produced a more biofidelic head and neck response than the ATD experimental test and simulation, including change in neck curvature. While only the upper and lower neck loading can be measured in the ATD, the shear force, axial force, and bending moment were reported for each level of the cervical spine in the human body model using a novel technique involving cross sections. This loading distribution provides further insight into the biomechanical response of the neck during a rotary-wing aircraft impact.
Advanced thermal energy management: A thermal test bed and heat pipe simulation

NASA Technical Reports Server (NTRS)

Barile, Ronald G.

1986-01-01

Work initiated on a common-module thermal test simulation was continued, and a second project on heat pipe simulation was begun. The test bed, constructed from surplus Skylab equipment, was modeled and solved for various thermal load and flow conditions. Low thermal load caused the radiator fluid, Coolanol 25, to thicken due to its temperature avoided by using a regenerator-heat-exchanger. Other possible solutions modeled include a radiator heater and shunting heat from the central thermal bus to the radiator. Also, module air temperature can become excessive with high avionics load. A second preoject concerning advanced heat pipe concepts was initiated. A program was written which calculates fluid physical properties, liquid and vapor pressure in the evaporator and condenser, fluid flow rates, and thermal flux. The program is directed to evaluating newer heat pipe wicks and geometries, especially water in an artery surrounded by six vapor channels. Effects of temperature, groove and slot dimensions, and wick properties are reported.
Open Architecture Data System for NASA Langley Combined Loads Test System

NASA Technical Reports Server (NTRS)

Lightfoot, Michael C.; Ambur, Damodar R.

1998-01-01

The Combined Loads Test System (COLTS) is a new structures test complex that is being developed at NASA Langley Research Center (LaRC) to test large curved panels and cylindrical shell structures. These structural components are representative of aircraft fuselage sections of subsonic and supersonic transport aircraft and cryogenic tank structures of reusable launch vehicles. Test structures are subjected to combined loading conditions that simulate realistic flight load conditions. The facility consists of two pressure-box test machines and one combined loads test machine. Each test machine possesses a unique set of requirements or research data acquisition and real-time data display. Given the complex nature of the mechanical and thermal loads to be applied to the various research test articles, each data system has been designed with connectivity attributes that support both data acquisition and data management functions. This paper addresses the research driven data acquisition requirements for each test machine and demonstrates how an open architecture data system design not only meets those needs but provides robust data sharing between data systems including the various control systems which apply spectra of mechanical and thermal loading profiles.
Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

NASA Technical Reports Server (NTRS)

Braman, Kalen; Ruf, Joseph

2015-01-01

Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and with four different versions of the TIC nozzle model geometry, each of which was created with a different simplification to the test article geometry.
The NASA landing gear test airplane

NASA Technical Reports Server (NTRS)

Carter, John F.; Nagy, Christopher J.

1995-01-01

A tire and landing gear test facility has been developed and incorporated into a Convair 990 aircraft. The system can simulate tire vertical load profiles to 250,000 lb, sideslip angles to 15 degrees, and wheel braking on actual runways. Onboard computers control the preprogrammed test profiles through a feedback loop and also record three axis loads, tire slip angle, and tire condition. The aircraft to date has provided tire force and wear data for the Shuttle Orbiter tire on three different runways and at east and west coast landing sites. This report discusses the role of this facility in complementing existing ground tire and landing gear test facilities, and how this facility can simultaneously simulate the vertical load, tire slip, velocity, and surface for an entire aircraft landing. A description is given of the aircraft as well as the test system. An example of a typical test sequence is presented. Data collection and reduction from this facility are discussed, as well as accuracies of calculated parameters. Validation of the facility through ground and flight tests is presented. Tests to date have shown that this facility can operate at remote sites and gather complete data sets of load, slip, and velocity on actual runway surfaces. The ground and flight tests have led to a successful validation of this test facility.
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.
Digital data processing system dynamic loading analysis

NASA Technical Reports Server (NTRS)

Lagas, J. J.; Peterka, J. J.; Tucker, A. E.

1976-01-01

Simulation and analysis of the Space Shuttle Orbiter Digital Data Processing System (DDPS) are reported. The mated flight and postseparation flight phases of the space shuttle's approach and landing test configuration were modeled utilizing the Information Management System Interpretative Model (IMSIM) in a computerized simulation modeling of the ALT hardware, software, and workload. System requirements simulated for the ALT configuration were defined. Sensitivity analyses determined areas of potential data flow problems in DDPS operation. Based on the defined system requirements and the sensitivity analyses, a test design is described for adapting, parameterizing, and executing the IMSIM. Varying load and stress conditions for the model execution are given. The analyses of the computer simulation runs were documented as results, conclusions, and recommendations for DDPS improvements.
Space shuttle orbiter digital data processing system timing sensitivity analysis OFT ascent phase

NASA Technical Reports Server (NTRS)

Lagas, J. J.; Peterka, J. J.; Becker, D. A.

1977-01-01

Dynamic loads were investigated to provide simulation and analysis of the space shuttle orbiter digital data processing system (DDPS). Segments of the ascent test (OFT) configuration were modeled utilizing the information management system interpretive model (IMSIM) in a computerized simulation modeling of the OFT hardware and software workload. System requirements for simulation of the OFT configuration were defined, and sensitivity analyses determined areas of potential data flow problems in DDPS operation. Based on the defined system requirements and these sensitivity analyses, a test design was developed for adapting, parameterizing, and executing IMSIM, using varying load and stress conditions for model execution. Analyses of the computer simulation runs are documented, including results, conclusions, and recommendations for DDPS improvements.
Reinforcing effect of glass-fiber mesh on complete dentures in a test model with a simulated oral mucosa.

PubMed

Yu, Sang-Hui; Oh, Seunghan; Cho, Hye-Won; Bae, Ji-Myung

2017-11-01

Studies that evaluated the strength of complete dentures reinforced with glass-fiber mesh or metal mesh on a cast with a simulated oral mucosa are lacking. The purpose of this in vitro study was to compare the mechanical properties of maxillary complete dentures reinforced with glass-fiber mesh with those of metal mesh in a new test model, using a simulated oral mucosa. Complete dentures reinforced with 2 types of glass-fiber mesh, SES mesh (SES) and glass cloth (GC) and metal mesh (metal) were fabricated. Complete dentures without any reinforcement were prepared as a control (n=10). The complete dentures were located on a cast with a simulated oral mucosa, and a load was applied on the posterior artificial teeth bilaterally. The fracture load, elastic modulus, and toughness of a complete denture were measured using a universal testing machine at a crosshead speed of 5 mm/min. The fracture load and elastic modulus were analyzed using 1-way analysis of variance, and the toughness was analyzed with the Kruskal-Wallis test (α=.05). The Tukey multiple range test was used as a post hoc test. The fracture load and toughness of the SES group was significantly higher than that of the metal and control groups (P<.05) but not significantly different from that of the GC group. The elastic modulus of the metal group was significantly higher than that of the control group (P<.05), and no significant differences were observed in the SES and GC groups. Compared with the control group, the fracture load and toughness of the SES and GC groups were higher, while those of the metal group were not significantly different. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Fracture resistance of implant- supported monolithic crowns cemented to zirconia hybrid-abutments: zirconia-based crowns vs. lithium disilicate crowns

PubMed Central

Nawafleh, Noor; Öchsner, Andreas; George, Roy

2018-01-01

PURPOSE The aim of this in vitro study was to investigate the fracture resistance under chewing simulation of implant-supported posterior restorations (crowns cemented to hybrid-abutments) made of different all-ceramic materials. MATERIALS AND METHODS Monolithic zirconia (MZr) and monolithic lithium disilicate (MLD) crowns for mandibular first molar were fabricated using computer-aided design/computer-aided manufacturing technology and then cemented to zirconia hybrid-abutments (Ti-based). Each group was divided into two subgroups (n=10): (A) control group, crowns were subjected to single load to fracture; (B) test group, crowns underwent chewing simulation using multiple loads for 1.2 million cycles at 1.2 Hz with simultaneous thermocycling between 5℃ and 55℃. Data was statistically analyzed with one-way ANOVA and a Post-Hoc test. RESULTS All tested crowns survived chewing simulation resulting in 100% survival rate. However, wear facets were observed on all the crowns at the occlusal contact point. Fracture load of monolithic lithium disilicate crowns was statistically significantly lower than that of monolithic zirconia crowns. Also, fracture load was significantly reduced in both of the all-ceramic materials after exposure to chewing simulation and thermocycling. Crowns of all test groups exhibited cohesive fracture within the monolithic crown structure only, and no abutment fractures or screw loosening were observed. CONCLUSION When supported by implants, monolithic zirconia restorations cemented to hybrid abutments withstand masticatory forces. Also, fatigue loading accompanied by simultaneous thermocycling significantly reduces the strength of both of the all-ceramic materials. Moreover, further research is needed to define potentials, limits, and long-term serviceability of the materials and hybrid abutments. PMID:29503716
Environmental Test Program for the Mars Exploration Rover Project

NASA Technical Reports Server (NTRS)

Fisher, Terry C.; VanVelzer, Paul L.

2004-01-01

On June 10 and July 7, 2003 the National Aeronautics and Space Administration (NASA) launched two spacecraft from Cape Canaveral, Florida for a six (6) months flight to the Red Planet, Mars. The two Mars Exploration Rover spacecraft landed safely on the planet in January 2004. Prior to the successful launch, both of the spacecraft were involved in a comprehensive test campaign that included development, qualification, and protoflight test programs. Testing was performed to simulate the environments associated with launch, inter-planetary cruise, landing on the planet and Mars surface operations. Unique test requirements included operating the spacecraft while the chamber pressure was controlled to simulate the decent to the planet from deep space, high impact landing loads and rover operations on the surface of the planet at 8 Torr and -130 C. This paper will present an overview of the test program that included vibration, pyro-shock, landing loads, acoustic noise, thermal vacuum and solar simulation testing at the Jet Propulsion Laboratory (JPL) Environmental Test Laboratory facilities in Pasadena, California.
Fixed Equipment in the Energy Systems Integration Facility | Energy Systems

Science.gov Websites

dynamic simulation of future energy systems. Photo of a robot used to test hydrogen coupling hardware. At test chambers (rated up to 60Â°C) for testing HVAC systems under simulated loading conditions Two bench performance Test stand for measuring performance of receiver tubes for concentrating solar power applications
Metallized Gelled Propellants Combustion Experiments in a Pulse Detonation Engine

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan; Jurns, John; Breisacher, Kevin; Kearns, Kim

2006-01-01

A series of combustion tests were performed with metallized gelled JP 8/aluminum fuels in a Pulse Detonation Engine (PDE). Nanoparticles of aluminum were used in the 60 to 100 nanometer diameter. Gellants were also of a nanoparticulate type composed of hydrocarbon alkoxide materials. Using simulated air (a nitrogen-oxygen mixture), the ignition potential of metallized gelled fuels with nanoparticle aluminum was investigated. Ignition of the JP 8/aluminum was possible with less than or equal to a 23-wt% oxygen loading in the simulated air. JP 8 fuel alone was unable to ignite with less than 30 percent oxygen loaded simulated air. The tests were single shot tests of the metallized gelled fuel to demonstrate the capability of the fuel to improve fuel detonability. The tests were conducted at ambient temperatures and with maximal detonation pressures of 1340 psia.
Nanoindentation cannot accurately predict the tensile strength of graphene or other 2D materials

NASA Astrophysics Data System (ADS)

Han, Jihoon; Pugno, Nicola M.; Ryu, Seunghwa

2015-09-01

Due to the difficulty of performing uniaxial tensile testing, the strengths of graphene and its grain boundaries have been measured in experiments by nanoindentation testing. From a series of molecular dynamics simulations, we find that the strength measured in uniaxial simulation and the strength estimated from the nanoindentation fracture force can differ significantly. Fracture in tensile loading occurs simultaneously with the onset of crack nucleation near 5-7 defects, while the graphene sheets often sustain the indentation loads after the crack initiation because the sharply concentrated stress near the tip does not give rise to enough driving force for further crack propagation. Due to the concentrated stress, strength estimation is sensitive to the indenter tip position along the grain boundaries. Also, it approaches the strength of pristine graphene if the tip is located slightly away from the grain boundary line. Our findings reveal the limitations of nanoindentation testing in quantifying the strength of graphene, and show that the loading-mode-specific failure mechanism must be taken into account in designing reliable devices from graphene and other technologically important 2D materials.Due to the difficulty of performing uniaxial tensile testing, the strengths of graphene and its grain boundaries have been measured in experiments by nanoindentation testing. From a series of molecular dynamics simulations, we find that the strength measured in uniaxial simulation and the strength estimated from the nanoindentation fracture force can differ significantly. Fracture in tensile loading occurs simultaneously with the onset of crack nucleation near 5-7 defects, while the graphene sheets often sustain the indentation loads after the crack initiation because the sharply concentrated stress near the tip does not give rise to enough driving force for further crack propagation. Due to the concentrated stress, strength estimation is sensitive to the indenter tip position along the grain boundaries. Also, it approaches the strength of pristine graphene if the tip is located slightly away from the grain boundary line. Our findings reveal the limitations of nanoindentation testing in quantifying the strength of graphene, and show that the loading-mode-specific failure mechanism must be taken into account in designing reliable devices from graphene and other technologically important 2D materials. Electronic ESI (ESI) available: Modelling of polycrystalline graphene, verification of loading speed, biaxial tensile simulations, comparison of stress distribution, size effects of indenter radius, force-deflection curves, and stability analysis of crack propagation. See DOI: 10.1039/c5nr04134a
LRFD Resistance Factor Calibration for Axially Loaded Drilled Shafts in the Las Vegas Valley

DOT National Transportation Integrated Search

2016-07-19

Resistance factors for LRFD of axially loaded drilled shafts in the Las Vegas Valley are calibrated using data from 41 field load tests. In addition to the traditional implementation of Monte Carlo (MC) simulations for calibration, a more robust tech...

CFD simulations of transient load change on a high head Francis turbine

NASA Astrophysics Data System (ADS)

Jakobsen, Ken-Robert G.; Aasved Holst, Martin

2017-01-01

Motivated by the importance of better understanding the structural integrity of high-head hydraulic turbines operating at intermittent conditions, complete 360º steady-state and transient simulations of a Francis turbine are presented in this paper. The main target of the work has been to investigate different numerical approaches such as mesh deformation for different operating conditions. Steady-state simulations were performed at the best efficiency point (BEP) and used as initial conditions for the transient simulations considering load rejection from BEP to part load (BEP2PL) and during load acceptance from BEP to high load (BEP2HL). Simulation results were compared with experimental data available for the Francis-99 project where close agreement was found for the mesh independent solution. The transient load analyses showed general trends in accordance with the measurement reports, especially for the pressure in vaneless space that is of high importance regarding RSI effects. Some deviations were identified for the net head at load rejection for which further investigations will be conducted. All CFD simulations were performed at model scale with ANSYS CFX v. 17 at either 96 or 120 cores (2.60 GHz). The immersed boundary technique was tested during the initial stages of the project, but had to be abandoned due to severe memory requirements. Pressure amplitudes and other instantaneous results were not considered.
Finite element analyses of continuous filament ties for masonry applications : final report for the Arquin Corporation.

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

Quinones, Armando, Sr.; Bibeau, Tiffany A.; Ho, Clifford Kuofei

2008-08-01

Finite-element analyses were performed to simulate the response of a hypothetical vertical masonry wall subject to different lateral loads with and without continuous horizontal filament ties laid between rows of concrete blocks. A static loading analysis and cost comparison were also performed to evaluate optimal materials and designs for the spacers affixed to the filaments. Results showed that polypropylene, ABS, and polyethylene (high density) were suitable materials for the spacers based on performance and cost, and the short T-spacer design was optimal based on its performance and functionality. Simulations of vertical walls subject to static loads representing 100 mph windsmore » (0.2 psi) and a seismic event (0.66 psi) showed that the simulated walls performed similarly and adequately when subject to these loads with and without the ties. Additional simulations and tests are required to assess the performance of actual walls with and without the ties under greater loads and more realistic conditions (e.g., cracks, non-linear response).« less
Analyses of the dynamic docking test system for advanced mission docking system test programs. [Apollo Soyuz Test Project

NASA Technical Reports Server (NTRS)

Gates, R. M.; Williams, J. E.

1974-01-01

Results are given of analytical studies performed in support of the design, implementation, checkout and use of NASA's dynamic docking test system (DDTS). Included are analyses of simulator components, a list of detailed operational test procedures, a summary of simulator performance, and an analysis and comparison of docking dynamics and loads obtained by test and analysis.
Effect of Abdominal Loading Location on Liver Motion: Experimental Assessment using Ultrafast Ultrasound Imaging and Simulation with a Human Body Model.

PubMed

Le Ruyet, Anicet; Berthet, Fabien; Rongiéras, Frédéric; Beillas, Philippe

2016-11-01

A protocol based on ultrafast ultrasound imaging was applied to study the in situ motion of the liver while the abdomen was subjected to compressive loading at 3 m/s by a hemispherical impactor or a seatbelt. The loading was applied to various locations between the lower abdomen and the mid thorax while feature points inside the liver were followed on the ultrasound movie (2000 frames per second). Based on tests performed on five post mortem human surrogates (including four tested in the current study), trends were found between the loading location and feature point trajectory parameters such as the initial angle of motion or the peak displacement in the direction of impact. The impactor tests were then simulated using the GHBMC M50 human body model that was globally scaled to the dimensions of each surrogate. Some of the experimental trends observed could be reproduced in the simulations (e.g. initial angle) while others differed more widely (e.g. final caudal motion). The causes for the discrepancies need to be further investigated. The liver strain energy density predicted by the model was also widely affected by the impact location. Experimental and simulation results both highlight the importance of the liver position with respect to the impactor when studying its response in situ.
Aerosol Filter Loading Data for a Simulated Jet Engine Test Cell Aerosol.

DTIC Science & Technology

1979-08-01

media. M SECTION II TEST PROGRAM I. TESTING PROCEDURE Sheets of the filter media were obtained from Owens - Corning Fiberglas Corporation. Ten centimeter...loading cycle. 2. TEST FILTERS The four following glass fiber filter medias were obtained from Owens - Corning Fiberglas Corporation (OCF) and tested both...shown in Table 22. Filters were washed from the back side. 5. ONCLUSIONS Four glass fiber filters, specified in the contract, were obtained from Owens
Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

NASA Technical Reports Server (NTRS)

Johnson, R., Jr.; Killpatrick, D. H.

1973-01-01

The work reported constitutes the first phase of a two-phase program. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr material characteristics are reviewed and compared with TD Ni-20Cr produced in previous development efforts; cyclic load, temperature, and pressure effects on TD Ni-20Cr sheet material are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded, diffusion-bonded, or seam-welded joints are evaluated through tests of simple lap-shear joint samples; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full-scale subsize heat shield panels are described. Tests of full-scale subsize panels included simulated meteoroid impact tests; simulated entry flight aerodynamic heating in an arc-heated plasma stream; programmed differential pressure loads and temperatures simulating mission conditions; and acoustic tests simulating sound levels experienced by heat shields during about boost flight. Test results are described, and the performances of two heat shield designs are compared and evaluated.
Hydro turbine governor’s power control of hydroelectric unit with sloping ceiling tailrace tunnel

NASA Astrophysics Data System (ADS)

Fu, Liang; Wu, Changli; Tang, Weiping

2018-02-01

The primary frequency regulation and load regulation transient process when the hydro turbine governor is under the power mode of hydropower unit with sloping ceiling tailrace are analysed by field test and numerical simulation in this paper. A simulation method based on “three-zone model” to simulate small fluctuation transient process of the sloping ceiling tailrace is proposed. The simulation model of hydraulic turbine governor power mode is established by governor’s PLC program identification and parameter measurement, and the simulation model is verified by the test. The slow-fast-slow “three-stage regulation” method which can improve the dynamic quality of hydro turbine governor power mode is proposed. The power regulation strategy and parameters are optimized by numerical simulation, the performance of primary frequency regulation and load regulation transient process when the hydro turbine governor is under power mode are improved significantly.
Modeling a constant power load for nickel-hydrogen battery testing using SPICE

NASA Technical Reports Server (NTRS)

Bearden, Douglas B.; Lollar, Louis F.; Nelms, R. M.

1990-01-01

The effort to design and model a constant power load for the HST (Hubble Space Telescope) nickel-hydrogen battery tests is described. The constant power load was designed for three different simulations on the batteries: life cycling, reconditioning, and capacity testing. A dc-dc boost converter was designed to act as this constant power load. A boost converter design was chosen because of the low test battery voltage (4 to 6 VDC) generated and the relatively high power requirement of 60 to 70 W. The SPICE model was shown to consistently predict variations in the actual circuit as various designs were attempted. It is concluded that the confidence established in the SPICE model of the constant power load ensures its extensive utilization in future efforts to improve performance in the actual load circuit.
Nozzle Side Load Testing and Analysis at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ruf, Joseph H.; McDaniels, David M.; Brown, Andrew M.

2009-01-01

Realistic estimates of nozzle side loads, the off-axis forces that develop during engine start and shutdown, are important in the design cycle of a rocket engine. The estimated magnitude of the nozzle side loads has a large impact on the design of the nozzle shell and the engine s thrust vector control system. In 2004 Marshall Space Flight Center (MSFC) began developing a capability to quantify the relative magnitude of side loads caused by different types of nozzle contours. The MSFC Nozzle Test Facility was modified to measure nozzle side loads during simulated nozzle start. Side load results from cold flow tests on two nozzle test articles, one with a truncated ideal contour and one with a parabolic contour are provided. The experimental approach, nozzle contour designs and wall static pressures are also discussed
Testing and Modeling of a 3-MW Wind Turbine Using Fully Coupled Simulation Codes (Poster)

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

LaCava, W.; Guo, Y.; Van Dam, J.

This poster describes the NREL/Alstom Wind testing and model verification of the Alstom 3-MW wind turbine located at NREL's National Wind Technology Center. NREL,in collaboration with ALSTOM Wind, is studying a 3-MW wind turbine installed at the National Wind Technology Center(NWTC). The project analyzes the turbine design using a state-of-the-art simulation code validated with detailed test data. This poster describes the testing and the model validation effort, and provides conclusions about the performance of the unique drive train configuration used in this wind turbine. The 3-MW machine has been operating at the NWTC since March 2011, and drive train measurementsmore » will be collected through the spring of 2012. The NWTC testing site has particularly turbulent wind patterns that allow for the measurement of large transient loads and the resulting turbine response. This poster describes the 3-MW turbine test project, the instrumentation installed, and the load cases captured. The design of a reliable wind turbine drive train increasingly relies on the use of advanced simulation to predict structural responses in a varying wind field. This poster presents a fully coupled, aero-elastic and dynamic model of the wind turbine. It also shows the methodology used to validate the model, including the use of measured tower modes, model-to-model comparisons of the power curve, and mainshaft bending predictions for various load cases. The drivetrain is designed to only transmit torque to the gearbox, eliminating non-torque moments that are known to cause gear misalignment. Preliminary results show that the drivetrain is able to divert bending loads in extreme loading cases, and that a significantly smaller bending moment is induced on the mainshaft compared to a three-point mounting design.« less
Re-entry simulation chamber for thermo-mechanical characterisation of space materials

NASA Astrophysics Data System (ADS)

Liedtke, Volker

2003-09-01

During re-entry, materials and components are subject to very high thermal and mechanical loads. Any failure may cause loss of mission. Therefore, materials and components have to be tested under most rigid conditions to verify the suitability of the material and to verify the design of the components. The Re-Entry Simulation Chamber (RESiC) at ARC Seibersdorf research (ARCS) allows simulating the high thermal loads as well as complex mechanical load profiles that may occur during a re-entry; additionally, the influence of chemical reactions of materials with gaseous components of the atmosphere can be studied. The high vacuum chamber (better than 1×10-6 mbar) has a diameter of 650 mm and allows a sample height of 500 mm, or 1000 mm with extension flange. The gas dosing system is designed to emulate the increasing atmospheric pressure during the re-entry trajectory of a vehicle. Heating is performed by a 30 kW induction generator that allows a sufficiently rapid heating of larger components; electrically conductive materials such as metals or carbon fibre reinforced ceramics are directly heated, while for electrical insulators, susceptor plates or tubes will be employed. The uniaxial servo-hydraulic testing machine has a maximum load of 70 kN, either static or with a frequency of up to 70 Hz, with any given load profile (sinus, rectangular, triangular, ...). Strain measurements will be done by non-contacting laser speckle system for maximum flexibility and minimum instrumentation time effort (currently under application testing), or by strain gauges. All relevant process parameters are controlled and recorded by microcomputer. The highly sophisticated control software allows a convenient and reliable multi-channel data acquisition, e.g. temperatures at various positions of the test piece, pressure, loads, strains, and any other test data according to customer specifications; the data format is suitable for any further data processing. During the set-up and operation testing, the device has successfully been employed for thermal shock testing, thermal cycling and gas cycling tests, thermomechanical tests and combinations thereof, e.g. sintering or hot-pressing. During the current final test series, the device will be completed, further optimised and shall be fully operational in summer 2003.
Effect of Cyclic Loading on Micromotion at the Implant-Abutment Interface.

PubMed

Karl, Matthias; Taylor, Thomas D

2016-01-01

Cyclic loading may cause settling of abutments mounted on dental implants, potentially affecting screw joint stability and implant-abutment micromotion. It was the goal of this in vitro study to compare micromotion of implant-abutment assemblies before and after masticatory simulation. Six groups of abutments (n = 5) for a specific tissue-level implant system with an internal octagon were subject to micromotion measurements. The implant-abutment assemblies were loaded in a universal testing machine, and an apparatus and extensometers were used to record displacement. This was done twice, in the condition in which they were received from the abutment manufacturer and after simulated loading (100,000 cycles; 100 N). Statistical analysis was based on analysis of variance, two-sample t tests (Welch tests), and Pearson product moment correlation (α = .05). The mean values for micromotion ranged from 33.15 to 63.41 μm and from 30.03 to 42.40 μm before and after load cycling. The general trend toward reduced micromotion following load cycling was statistically significant only for CAD/CAM zirconia abutments (P = .036) and for one type of clone abutment (P = .012), with no significant correlation between values measured before and after cyclic loading (Pearson product moment correlation; P = .104). While significant differences in micromotion were found prior to load cycling, no significant difference among any of the abutment types tested could be observed afterward (P > .05 in all cases). A quantifiable settling effect at the implant-abutment interface seems to result from cyclic loading, leading to a decrease in micromotion. This effect seems to be more pronounced in low-quality abutments. For the implant system tested in this study, retightening of abutment screws is recommended after an initial period of clinical use.
Unsteady hydraulic simulation of the cavitating part load vortex rope in Francis turbines

NASA Astrophysics Data System (ADS)

Brammer, J.; Segoufin, C.; Duparchy, F.; Lowys, P. Y.; Favrel, A.; Avellan, F.

2017-04-01

For Francis turbines at part load operation a helical vortex rope is formed due to the swirling nature of the flow exiting the runner. This vortex creates pressure fluctuations which can lead to power swings, and the unsteady loading can lead to fatigue damage of the runner. In the case that the vortex rope cavitates there is the additional risk that hydro-acoustic resonance can occur. It is therefore important to be able to accurately simulate this phenomenon to address these issues. In this paper an unsteady, multi-phase CFD model was used to simulate two part-load operating points, for two different cavitation conditions. The simulation results were validated with test-rig data, and showed very good agreement. These results also served as an input for FEA calculations and fatigue analysis, which are presented in a separate study.
Transonic pressure and load distributions for a group of simulated launch vehicles. [Langley 8-foot transonic pressure tunnel

NASA Technical Reports Server (NTRS)

Kelly, T. C.

1980-01-01

Pressure and load distributions for a related group of simulated launch vehicle configurations are presented. The configurations were selected so that the nose cone and interstage transition flare components were relatively close to one another and subject to mutual interference effects. Tests extended over a Mach number range from 0.40 to 1.20 at angles of attack from 0 deg to about 10 deg. The test Reynolds numbers, based on main stage diameter, were of the order of 0.00000098.
Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

NASA Technical Reports Server (NTRS)

Johnson, R., Jr.; Killpatrick, D. H.

1976-01-01

The results obtained in a program to evaluate dispersion-strengthened nickel-base alloys for use in a metallic radiative thermal protection system operating at surface temperatures to 1477 K for the space shuttle were presented. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr characteristics of material used in the current study are compared with previous results; cyclic load, temperature, and pressure effects on sheet material residual strength are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded joints are evaluated; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full scale subsize heat shield panels in two configurations are described. Initial tests of full scale subsize panels included simulated meteoroid impact tests, simulated entry flight aerodynamic heating, programmed differential pressure loads and temperatures simulating mission conditions, and acoustic tests simulating sound levels experienced during boost flight.
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.
Flight-Time Identification of a UH-60A Helicopter and Slung Load

NASA Technical Reports Server (NTRS)

Cicolani, Luigi S.; McCoy, Allen H.; Tischler, Mark B.; Tucker, George E.; Gatenio, Pinhas; Marmar, Dani

1998-01-01

This paper describes a flight test demonstration of a system for identification of the stability and handling qualities parameters of a helicopter-slung load configuration simultaneously with flight testing, and the results obtained.Tests were conducted with a UH-60A Black Hawk at speeds from hover to 80 kts. The principal test load was an instrumented 8 x 6 x 6 ft cargo container. The identification used frequency domain analysis in the frequency range to 2 Hz, and focussed on the longitudinal and lateral control axes since these are the axes most affected by the load pendulum modes in the frequency range of interest for handling qualities. Results were computed for stability margins, handling qualities parameters and load pendulum stability. The computations took an average of 4 minutes before clearing the aircraft to the next test point. Important reductions in handling qualities were computed in some cases, depending, on control axis and load-slung combination. A database, including load dynamics measurements, was accumulated for subsequent simulation development and validation.
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.
Structural Integrity of Water Reactor Pressure Boundary Components.

DTIC Science & Technology

1981-02-20

environment, and load waveform parameters . A theory of the influence of dissolved oxygen content on the fatigue crack growth results in simulated PWR ...simulated PWR coolant is - (Continues ) DD IJN7 1473 EDITION OF I NOV S ..OSL- -C 2 S/ 0102-LF-014-6601 S1ECURITY CLASSI1FICATION OF THIS PAGE (When...not seem to influence the data, which was produced for a load ratio of 0.2 and a simulated PWR coolant environment. Test results for A106 Grade C piping
40 CFR 86.162-00 - Approval of alternative air conditioning test simulations and descriptions of AC1 and AC2.

Code of Federal Regulations, 2010 CFR

2010-07-01

... exhaust emission results of air conditioning operation in an environmental test cell by adding additional... conditioning operation in an environmental test cell by adding a heat load to the passenger compartment. The... the simulation matches environmental cell test data for the range of vehicles to be covered by the...

Robotic application of a dynamic resultant force vector using real-time load-control: simulation of an ideal follower load on Cadaveric L4-L5 segments.

PubMed

Bennett, Charles R; Kelly, Brian P

2013-08-09

Standard in-vitro spine testing methods have focused on application of isolated and/or constant load components while the in-vivo spine is subject to multiple components that can be resolved into resultant dynamic load vectors. To advance towards more in-vivo like simulations the objective of the current study was to develop a methodology to apply robotically-controlled, non-zero, real-time dynamic resultant forces during flexion-extension on human lumbar motion segment units (MSU) with initial application towards simulation of an ideal follower load (FL) force vector. A proportional-integral-derivative (PID) controller with custom algorithms coordinated the motion of a Cartesian serial manipulator comprised of six axes each capable of position- or load-control. Six lumbar MSUs (L4-L5) were tested with continuously increasing sagittal plane bending to 8 Nm while force components were dynamically programmed to deliver a resultant 400 N FL that remained normal to the moving midline of the intervertebral disc. Mean absolute load-control tracking errors between commanded and experimental loads were computed. Global spinal ranges of motion and sagittal plane inter-body translations were compared to previously published values for non-robotic applications. Mean TEs for zero-commanded force and moment axes were 0.7 ± 0.4N and 0.03 ± 0.02 Nm, respectively. For non-zero force axes mean TEs were 0.8 ± 0.8 N, 1.3 ± 1.6 Nm, and 1.3 ± 1.6N for Fx, Fz, and the resolved ideal follower load vector FL(R), respectively. Mean extension and flexion ranges of motion were 2.6° ± 1.2° and 5.0° ± 1.7°, respectively. Relative vertebral body translations and rotations were very comparable to data collected with non-robotic systems in the literature. The robotically coordinated Cartesian load controlled testing system demonstrated robust real-time load-control that permitted application of a real-time dynamic non-zero load vector during flexion-extension. For single MSU investigations the methodology has potential to overcome conventional follower load limitations, most notably via application outside the sagittal plane. This methodology holds promise for future work aimed at reducing the gap between current in-vitro testing and in-vivo circumstances. Copyright © 2013 Elsevier Ltd. All rights reserved.
A Model for Simulating the Response of Aluminum Honeycomb Structure to Transverse Loading

NASA Technical Reports Server (NTRS)

Ratcliffe, James G.; Czabaj, Michael W.; Jackson, Wade C.

2012-01-01

A 1-dimensional material model was developed for simulating the transverse (thickness-direction) loading and unloading response of aluminum honeycomb structure. The model was implemented as a user-defined material subroutine (UMAT) in the commercial finite element analysis code, ABAQUS(Registered TradeMark)/Standard. The UMAT has been applied to analyses for simulating quasi-static indentation tests on aluminum honeycomb-based sandwich plates. Comparison of analysis results with data from these experiments shows overall good agreement. Specifically, analyses of quasi-static indentation tests yielded accurate global specimen responses. Predicted residual indentation was also in reasonable agreement with measured values. Overall, this simple model does not involve a significant computational burden, which makes it more tractable to simulate other damage mechanisms in the same analysis.
A prediction model for lift-fan simulator performance. M.S. Thesis - Cleveland State Univ.

NASA Technical Reports Server (NTRS)

Yuska, J. A.

1972-01-01

The performance characteristics of a model VTOL lift-fan simulator installed in a two-dimensional wing are presented. The lift-fan simulator consisted of a 15-inch diameter fan driven by a turbine contained in the fan hub. The performance of the lift-fan simulator was measured in two ways: (1) the calculated momentum thrust of the fan and turbine (total thrust loading), and (2) the axial-force measured on a load cell force balance (axial-force loading). Tests were conducted over a wide range of crossflow velocities, corrected tip speeds, and wing angle of attack. A prediction modeling technique was developed to help in analyzing the performance characteristics of lift-fan simulators. A multiple linear regression analysis technique is presented which calculates prediction model equations for the dependent variables.
Hardware-in-the-Loop Simulation of a Distribution System with Air Conditioners under Model Predictive Control: Preprint

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

Sparn, Bethany F; Ruth, Mark F; Krishnamurthy, Dheepak

Many have proposed that responsive load provided by distributed energy resources (DERs) and demand response (DR) are an option to provide flexibility to the grid and especially to distribution feeders. However, because responsive load involves a complex interplay between tariffs and DER and DR technologies, it is challenging to test and evaluate options without negatively impacting customers. This paper describes a hardware-in-the-loop (HIL) simulation system that has been developed to reduce the cost of evaluating the impact of advanced controllers (e.g., model predictive controllers) and technologies (e.g., responsive appliances). The HIL simulation system combines large-scale software simulation with a smallmore » set of representative building equipment hardware. It is used to perform HIL simulation of a distribution feeder and the loads on it under various tariff structures. In the reported HIL simulation, loads include many simulated air conditioners and one physical air conditioner. Independent model predictive controllers manage operations of all air conditioners under a time-of-use tariff. Results from this HIL simulation and a discussion of future development work of the system are presented.« less
Static Load Test on Instrumented Pile - Field Data and Numerical Simulations

NASA Astrophysics Data System (ADS)

Krasiński, Adam; Wiszniewski, Mateusz

2017-09-01

Static load tests on foundation piles are generally carried out in order to determine load - the displacement characteristic of the pile head. For standard (basic) engineering practices this type of test usually provides enough information. However, the knowledge of force distribution along the pile core and its division into the friction along the shaft and the resistance under the base can be very useful. Such information can be obtained by strain gage pile instrumentation [1]. Significant investigations have been completed on this technology, proving its utility and correctness [8], [10], [12]. The results of static tests on instrumented piles are not easy to interpret. There are many factors and processes affecting the final outcome. In order to understand better the whole testing process and soil-structure behavior some investigations and numerical analyses were done. In the paper, real data from a field load test on instrumented piles is discussed and compared with numerical simulation of such a test in similar conditions. Differences and difficulties in the results interpretation with their possible reasons are discussed. Moreover, the authors used their own analytical solution for more reliable determination of force distribution along the pile. The work was presented at the XVII French-Polish Colloquium of Soil and Rock Mechanics, Łódź, 28-30 November 2016.
Extraction-Separation Performance and Dynamic Modeling of Orion Test Vehicles with Adams Simulation: 3rd Edition

NASA Technical Reports Server (NTRS)

Varela, Jose G.; Reddy, Satish; Moeller, Enrique; Anderson, Keith

2017-01-01

NASA's Orion Capsule Parachute Assembly System (CPAS) Project is now in the qualification phase of testing, and the Adams simulation has continued to evolve to model the complex dynamics experienced during the test article extraction and separation phases of flight. The ability to initiate tests near the upper altitude limit of the Orion parachute deployment envelope requires extractions from the aircraft at 35,000 ft-MSL. Engineering development phase testing of the Parachute Test Vehicle (PTV) carried by the Carriage Platform Separation System (CPSS) at altitude resulted in test support equipment hardware failures due to increased energy caused by higher true airspeeds. As a result, hardware modifications became a necessity requiring ground static testing of the textile components to be conducted and a new ground dynamic test of the extraction system to be devised. Force-displacement curves from static tests were incorporated into the Adams simulations, allowing prediction of loads, velocities and margins encountered during both flight and ground dynamic tests. The Adams simulation was then further refined by fine tuning the damping terms to match the peak loads recorded in the ground dynamic tests. The failure observed in flight testing was successfully replicated in ground testing and true safety margins of the textile components were revealed. A multi-loop energy modulator was then incorporated into the system level Adams simulation model and the effect on improving test margins be properly evaluated leading to high confidence ground verification testing of the final design solution.
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.
Intraoperative Noise Increases Perceived Task Load and Fatigue in Anesthesiology Residents: A Simulation-Based Study.

PubMed

McNeer, Richard R; Bennett, Christopher L; Dudaryk, Roman

2016-02-01

Operating rooms are identified as being one of the noisiest of clinical environments, and intraoperative noise is associated with adverse effects on staff and patient safety. Simulation-based experiments would offer controllable and safe venues for investigating this noise problem. However, realistic simulation of the clinical auditory environment is rare in current simulators. Therefore, we retrofitted our operating room simulator to be able to produce immersive auditory simulations with the use of typical sound sources encountered during surgeries. Then, we tested the hypothesis that anesthesia residents would perceive greater task load and fatigue while being given simulated lunch breaks in noisy environments rather than in quiet ones. As a secondary objective, we proposed and tested the plausibility of a novel psychometric instrument for the assessment of stress. In this simulation-based, randomized, repeated-measures, crossover study, 2 validated psychometric survey instruments, the NASA Task Load Index (NASA-TLX), composed of 6 items, and the Swedish Occupational Fatigue Inventory (SOFI), composed of 5 items, were used to assess perceived task load and fatigue, respectively, in first-year anesthesia residents. Residents completed the psychometric instruments after being given lunch breaks in quiet and noisy intraoperative environments (soundscapes). The effects of soundscape grouping on the psychometric instruments and their comprising items were analyzed with a split-plot analysis. A model for a new psychometric instrument for measuring stress that combines the NASA-TLX and SOFI instruments was proposed, and a factor analysis was performed on the collected data to determine the model's plausibility. Twenty residents participated in this study. Multivariate analysis of variance showed an effect of soundscape grouping on the combined NASA-TLX and SOFI instrument items (P = 0.003) and the comparisons of univariate item reached significance for the NASA Temporal Demand item (P = 0.0004) and the SOFI Lack of Energy item (P = 0.001). Factor analysis extracted 4 factors, which were assigned the following construct names for model development: Psychological Task Load, Psychological Fatigue, Acute Physical Load, and Performance-Chronic Physical Load. Six of the 7 fit tests used in the partial confirmatory factor analysis were positive when we fitted the data to the proposed model, suggesting that further validation is warranted. This study provides evidence that noise during surgery can increase feelings of stress, as measured by perceived task load and fatigue levels, in anesthesiologists and adds to the growing literature pointing to an overall adverse impact of clinical noise on caregivers and patient safety. The psychometric model proposed in this study for assessing perceived stress is plausible based on factor analysis and will be useful for characterizing the impact of the clinical environment on subject stress levels in future investigations.
Surrogate fuel assembly multi-axis shaker tests to simulate normal conditions of rail and truck transport

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

McConnell, Paul E.; Koenig, Greg John; Uncapher, William Leonard

2016-05-01

This report describes the third set of tests (the “DCLa shaker tests”) of an instrumented surrogate PWR fuel assembly. The purpose of this set of tests was to measure strains and accelerations on Zircaloy-4 fuel rods when the PWR assembly was subjected to rail and truck loadings simulating normal conditions of transport when affixed to a multi-axis shaker. This is the first set of tests of the assembly simulating rail normal conditions of transport.
Surrogate fuel assembly multi-axis shaker tests to simulate normal conditions of rail and truck transport

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

McConnell, Paul E.; Koenig, Greg John; Uncapher, William Leonard

2016-05-12

This report describes the third set of tests (the “DCL a shaker tests”) of an instrumented surrogate PWR fuel assembly. The purpose of this set of tests was to measure strains and accelerations on Zircaloy-4 fuel rods when the PWR assembly was subjected to rail and truck loadings simulating normal conditions of transport when affixed to a multi-axis shaker. This is the first set of tests of the assembly simulating rail normal conditions of transport.
Partial depth precast concrete deck panels on curved bridges : finite element analytical model of PCPs.

DOT National Transportation Integrated Search

2017-03-01

A number of full-scale tests have been carried out in the laboratory focused on the shear : performance of simulated precast concrete deck panels (PCP). Shear tests were carried out to : simulate the type of loading that will be applied to the deck p...
Development of a personal computer-based secondary task procedure as a surrogate for a driving simulator

DOT National Transportation Integrated Search

2007-08-01

This research was conducted to develop and test a personal computer-based study procedure (PCSP) with secondary task loading for use in human factors laboratory experiments in lieu of a driving simulator to test reading time and understanding of traf...
Effect of Surface Impulsive Thermal Loads on Fatigue Behavior of Constant Volume Propulsion Engine Combustor Materials

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Fox, Dennis S.; Miller, Robert A.; Ghosn, Louis J.; Kalluri, Sreeramesh

2004-01-01

The development of advanced high performance constant-volume-combustion-cycle engines (CVCCE) requires robust design of the engine components that are capable of enduring harsh combustion environments under high frequency thermal and mechanical fatigue conditions. In this study, a simulated engine test rig has been established to evaluate thermal fatigue behavior of a candidate engine combustor material, Haynes 188, under superimposed CO2 laser surface impulsive thermal loads (30 to 100 Hz) in conjunction with the mechanical fatigue loads (10 Hz). The mechanical high cycle fatigue (HCF) testing of some laser pre-exposed specimens has also been conducted under a frequency of 100 Hz to determine the laser surface damage effect. The test results have indicated that material surface oxidation and creep-enhanced fatigue is an important mechanism for the surface crack initiation and propagation under the simulated CVCCE engine conditions.
Full-scale testing and numerical modeling of a multistory masonry structure subjected to internal blast loading

NASA Astrophysics Data System (ADS)

Zapata, Brian Jarvis

As military and diplomatic representatives of the United States are deployed throughout the world, they must frequently make use of local, existing facilities; it is inevitable that some of these will be load bearing unreinforced masonry (URM) structures. Although generally suitable for conventional design loads, load bearing URM presents a unique hazard, with respect to collapse, when exposed to blast loading. There is therefore a need to study the blast resistance of load bearing URM construction in order to better protect US citizens assigned to dangerous locales. To address this, the Department of Civil and Environmental Engineering at the University of North Carolina at Charlotte conducted three blast tests inside a decommissioned, coal-fired, power plant prior to its scheduled demolition. The power plant's walls were constructed of URM and provided an excellent opportunity to study the response of URM walls in-situ. Post-test analytical studies investigated the ability of existing blast load prediction methodologies to model the case of a cylindrical charge with a low height of burst. It was found that even for the relatively simple blast chamber geometries of these tests, simplified analysis methods predicted blast impulses with an average net error of 22%. The study suggested that existing simplified analysis methods would benefit from additional development to better predict blast loads from cylinders detonated near the ground's surface. A hydrocode, CTH, was also used to perform two and three-dimensional simulations of the blast events. In order to use the hydrocode, Jones Wilkins Lee (JWL) equation of state (EOS) coefficients were developed for the experiment's Unimax dynamite charges; a novel energy-scaling technique was developed which permits the derivation of new JWL coefficients from an existing coefficient set. The hydrocode simulations were able to simulate blast impulses with an average absolute error of 34.5%. Moreover, the hydrocode simulations provided highly resolved spatio-temporal blast loading data for subsequent structural simulations. Equivalent single-degree-of-freedom (ESDOF) structural response models were then used to predict the out-of-plane deflections of blast chamber walls. A new resistance function was developed which permits a URM wall to crack at any height; numerical methodologies were also developed to compute transformation factors required for use in the ESDOF method. When combined with the CTH derived blast loading predictions, the ESDOF models were able to predict out-of-plane deflections with reasonable accuracy. Further investigations were performed using finite element models constructed in LS-DYNA; the models used elastic elements combined with contacts possessing a tension/shear cutoff and the ability to simulate fracture energy release. Using the CTH predicted blast loads and carefully selected constitutive parameters, the LS-DYNA models were able to both qualitatively and quantitatively predict blast chamber wall deflections and damage patterns. Moreover, the finite element models suggested several modes of response which cannot be modeled by current ESDOF methods; the effect of these response modes on the accuracy of ESDOF predictions warrants further study.
Simulated Lunar Testing of Metabolic Heat Regenerated Temperature Swing Adsorption

NASA Technical Reports Server (NTRS)

Padilla, Sebastian A.; Bower, Chad E.; Iacomini, Christie S.; Paul, Heather L.

2012-01-01

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. An Engineering Development Unit (EDU) of the MTSA Subassembly (MTSAS) was designed and assembled for optimized Martian operations, but also meets system requirements for lunar operations. For lunar operations the MTSA sorption cycle is driven via a vacuum swing between suit ventilation loop pressure and lunar vacuum. The focus of this effort was testing in a simulated lunar environment. This environment was simulated in Paragon's EHF vacuum chamber. The objective of the testing was to evaluate the full cycle performance of the MTSA Subassembly EDU, and to assess CO2 loading and pressure drop of the wash coated aluminum reticulated foam sorbent bed. Lunar environment testing proved out the feasibility of pure vacuum swing operation, making MTSA a technology that can be tested and used on the Moon prior to going to Mars. Testing demonstrated better than expected CO2 Nomenclature loading on the sorbent and nearly replicates the equilibrium data from the sorbent manufacturer. This exceeded any of the previous sorbent loading tests performed by Paragon. Subsequently, the increased performance of the sorbent bed design indicates future designs will require less mass and volume than the current EDU rendering MTSA as very competitive for Martian PLSS applications.
Simulated Lunar Testing of Metabolic Heat Regenerated Temperature Swing Adsorption Technology

NASA Technical Reports Server (NTRS)

Padilla, Sebastian A.; Bower, Chad; Iacomini, Christie S.; Paul, H.

2011-01-01

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. An Engineering Development Unit (EDU) of the MTSA subassembly was designed and assembled for optimized Martian operations, but also meets system requirements for lunar operations. For lunar operations the MTSA sorption cycle is driven via a vacuum swing between suit ventilation loop pressure and lunar vacuum. The focus of this effort is operations and testing in a simulated lunar environment. This environment was simulated in Paragon s EHF vacuum chamber. The objective of this testing was to evaluate the full cycle performance of the MTSA Subassembly EDU, and to assess CO2 loading and pressure drop of the wash coated aluminum reticulated foam sorbent bed. The lunar testing proved out the feasibility of pure vacuum swing operation, making MTSA a technology that can be tested and used on the Moon prior to going to Mars. Testing demonstrated better than expected CO2 loading on the sorbent and nearly replicates the equilibrium data from the sorbent manufacturer. This had not been achieved in any of the previous sorbent loading tests performed by Paragon. Subsequently, the increased performance of the sorbent bed design indicates future designs will require less mass and volume than the current EDU rendering MTSA as very competitive for Martian PLSS applications.
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.
Fatigue limits of monolithic Y-TZP three-unit-fixed dental prostheses: effect of grinding at the gingival zone of the connector

PubMed Central

Amaral, Marina; Rocha, Regina FV; Melo, Renata Marques; Pereira, Gabriel KR; Zhang, Yu; Valandro, Luiz Felipe; Bottino, Marco Antonio

2017-01-01

Objectives To determine the fatigue limits of three-unit monolithic zirconia FDPs before and after grinding of the gingival areas of connectors with diamond burs. Material and Methods FDPs were milled from pre-sintered blocks of zirconia simulating the absence of the first mandibular molar. Half of the specimens were subjected to grinding, simulating clinical adjustment, and all of them were subjected to glazing procedure. Additional specimens were manufactured for roughness analysis. FDPs were adhesively cemented onto glass-fiber reinforced epoxy resin abutments. Fatigue limits and standard deviations were obtained using a staircase fatigue method (n = 20, 100,000 loading cycles/5 Hz). The initial test load was 70% of the mean load-to-fracture (n = 3) and load increments were 5% of the initial test load for both the control and ground specimens. Data were compared by Student’s T-test (α ≤ 0.05). Results Both the control and ground groups exhibited similar values of load-to-fracture and fatigue limits. Neither the surface treatments nor ageing affected the surface roughness of the specimens. Conclusions The damage induced by grinding with fine-grit diamond bur in the gingival area of the connectors did not decrease the fatigue limit of the three-unit monolithic zirconia FDP. PMID:28494273
Accelerated fatigue testing of dentin-composite bond with continuously increasing load.

PubMed

Li, Kai; Guo, Jiawen; Li, Yuping; Heo, Young Cheul; Chen, Jihua; Xin, Haitao; Fok, Alex

2017-06-01

The aim of this study was to evaluate an accelerated fatigue test method that used a continuously increasing load for testing the dentin-composite bond strength. Dentin-composite disks (ϕ5mm×2mm) made from bovine incisor roots were subjected to cyclic diametral compression with a continuously increasingly load amplitude. Two different load profiles, linear and nonlinear with respect to the number of cycles, were considered. The data were then analyzed by using a probabilistic failure model based on the Weakest-Link Theory and the classical stress-life function, before being transformed to simulate clinical data of direct restorations. All the experimental data could be well fitted with a 2-parameter Weibull function. However, a calibration was required for the effective stress amplitude to account for the difference between static and cyclic loading. Good agreement was then obtained between theory and experiments for both load profiles. The in vitro model also successfully simulated the clinical data. The method presented will allow tooth-composite interfacial fatigue parameters to be determined more efficiently. With suitable calibration, the in vitro model can also be used to assess composite systems in a more clinically relevant manner. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
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

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.
Modeling of light dynamic cone penetration test - Panda 3 ® in granular material by using 3D Discrete element method

NASA Astrophysics Data System (ADS)

Tran, Quoc Anh; Chevalier, Bastien; Benz, Miguel; Breul, Pierre; Gourvès, Roland

2017-06-01

The recent technological developments made on the light dynamic penetration test Panda 3 ® provide a dynamic load-penetration curve σp - sp for each impact. This curve is influenced by the mechanical and physical properties of the investigated granular media. In order to analyze and exploit the load-penetration curve, a numerical model of penetration test using 3D Discrete Element Method is proposed for reproducing tests in dynamic conditions in granular media. All parameters of impact used in this model have at first been calibrated by respecting mechanical and geometrical properties of the hammer and the rod. There is a good agreement between experimental results and the ones obtained from simulations in 2D or 3D. After creating a sample, we will simulate the Panda 3 ®. It is possible to measure directly the dynamic load-penetration curve occurring at the tip for each impact. Using the force and acceleration measured in the top part of the rod, it is possible to separate the incident and reflected waves and then calculate the tip's load-penetration curve. The load-penetration curve obtained is qualitatively similar with that obtained by experimental tests. In addition, the frequency analysis of the measured signals present also a good compliance with that measured in reality when the tip resistance is qualitatively similar.
Research and Development for Robotic Transportable Waste to Energy System (TWES)

DTIC Science & Technology

2012-01-01

Engineers, April 2003. NFESC UG-2039-ENV, Qualified Recycling Program (QRP) Guide; July 2000 (NOTAL) Paisley, M.A., Anson, D., “ Biomass Gasification ...Full Load Biomass Simulation .............................19 Figure 9. Spreadsheet-Based Heat and Mass Balance—Diesel Operation at 5:00 p.m...diesel fuel. Based on simulation of full-load biomass operation, the diesel-fueled test was expected to demonstrate a 75% net fuel-to-steam efficiency
Computational knee ligament modeling using experimentally determined zero-load lengths.

PubMed

Bloemker, Katherine H; Guess, Trent M; Maletsky, Lorin; Dodd, Kevin

2012-01-01

This study presents a subject-specific method of determining the zero-load lengths of the cruciate and collateral ligaments in computational knee modeling. Three cadaver knees were tested in a dynamic knee simulator. The cadaver knees also underwent manual envelope of motion testing to find their passive range of motion in order to determine the zero-load lengths for each ligament bundle. Computational multibody knee models were created for each knee and model kinematics were compared to experimental kinematics for a simulated walk cycle. One-dimensional non-linear spring damper elements were used to represent cruciate and collateral ligament bundles in the knee models. This study found that knee kinematics were highly sensitive to altering of the zero-load length. The results also suggest optimal methods for defining each of the ligament bundle zero-load lengths, regardless of the subject. These results verify the importance of the zero-load length when modeling the knee joint and verify that manual envelope of motion measurements can be used to determine the passive range of motion of the knee joint. It is also believed that the method described here for determining zero-load length can be used for in vitro or in vivo subject-specific computational models.
Mechanical environmental test program for the Communications Technology Satellite

NASA Technical Reports Server (NTRS)

Buckingham, R.; Sharp, G. R.

1974-01-01

This paper describes the spacecraft and subsystem level mechanical environmental test program which was developed for the Communications Technology Satellite (CTS). At the spacecraft level it includes sine and random vibration, static loading, centrifuge loading, pyrotechnic and separation shock simulation and (tentatively) acoustics. At the subsystem level it entails the same type of environmental exposure as applicable. Matrices of system and subsystem tests are presented showing type, level and hardware status for each major test.
40 CFR 1066.410 - Dynamometer test procedure.

Code of Federal Regulations, 2012 CFR

2012-07-01

... configuration that allows for proper simulation of vehicle cooling during in-use operation, subject to our... simulation of the actual normal forces that the tire and dynamometer roll interface would see if a loaded...
40 CFR 1066.410 - Dynamometer test procedure.

Code of Federal Regulations, 2013 CFR

2013-07-01

... configuration that allows for proper simulation of vehicle cooling during in-use operation, subject to our... simulation of the actual normal forces that the tire and dynamometer roll interface would see if a loaded...
Measuring cognitive load: mixed results from a handover simulation for medical students.

PubMed

Young, John Q; Irby, David M; Barilla-LaBarca, Maria-Louise; Ten Cate, Olle; O'Sullivan, Patricia S

2016-02-01

The application of cognitive load theory to workplace-based activities such as patient handovers is hindered by the absence of a measure of the different load types. This exploratory study tests a method for measuring cognitive load during handovers. The authors developed the Cognitive Load Inventory for Handoffs (CLI4H) with items for intrinsic, extraneous, and germane load. Medical students completed the measure after participating in a simulated handover. Exploratory factor and correlation analyses were performed to collect evidence for validity. Results yielded a two-factor solution for intrinsic and germane load that explained 50 % of the variance. The extraneous load items performed poorly and were removed from the model. The score for intrinsic load correlated with the Paas Cognitive Load scale (r = 0.31, p = 0.004) and was lower for students with more prior handover training (p = 0.036). Intrinsic load did not, however, correlate with performance. Germane load did not correlate with the Paas Cognitive Load scale but did correlate as expected with performance (r = 0.30, p = 0.005) and was lower for those students with more prior handover training (p = 0.03). The CLI4H yielded mixed results with some evidence for validity of the score from the intrinsic load items. The extraneous load items performed poorly and the use of only a single item for germane load limits conclusions. The instrument requires further development and testing. Study results and limitations provide guidance to future efforts to measure cognitive load during workplace-based activities, such as handovers.
Simulation of flow and water quality of the Arroyo Colorado, Texas, 1989-99

USGS Publications Warehouse

Raines, Timothy H.; Miranda, Roger M.

2002-01-01

A model parameter set for use with the Hydrological Simulation Program—FORTRAN watershed model was developed to simulate flow and water quality for selected properties and constituents for the Arroyo Colorado from the city of Mission to the Laguna Madre, Texas. The model simulates flow, selected water-quality properties, and constituent concentrations. The model can be used to estimate a total maximum daily load for selected properties and constituents in the Arroyo Colorado. The model was calibrated and tested for flow with data measured during 1989–99 at three streamflow-gaging stations. The errors for total flow volume ranged from -0.1 to 29.0 percent, and the errors for total storm volume ranged from -15.6 to 8.4 percent. The model was calibrated and tested for water quality for seven properties and constituents with 1989–99 data. The model was calibrated sequentially for suspended sediment, water temperature, biochemical oxygen demand, dissolved oxygen, nitrate nitrogen, ammonia nitrogen, and orthophosphate. The simulated concentrations of the selected properties and constituents generally matched the measured concentrations available for the calibration and testing periods. The model was used to simulate total point- and nonpoint-source loads for selected properties and constituents for 1989–99 for urban, natural, and agricultural land-use types. About one-third to one-half of the biochemical oxygen demand and nutrient loads are from urban point and nonpoint sources, although only 13 percent of the total land use in the basin is urban.
Model predictive control of a wind turbine modelled in Simpack

NASA Astrophysics Data System (ADS)

Jassmann, U.; Berroth, J.; Matzke, D.; Schelenz, R.; Reiter, M.; Jacobs, G.; Abel, D.

2014-06-01

Wind turbines (WT) are steadily growing in size to increase their power production, which also causes increasing loads acting on the turbine's components. At the same time large structures, such as the blades and the tower get more flexible. To minimize this impact, the classical control loops for keeping the power production in an optimum state are more and more extended by load alleviation strategies. These additional control loops can be unified by a multiple-input multiple-output (MIMO) controller to achieve better balancing of tuning parameters. An example for MIMO control, which has been paid more attention to recently by wind industry, is Model Predictive Control (MPC). In a MPC framework a simplified model of the WT is used to predict its controlled outputs. Based on a user-defined cost function an online optimization calculates the optimal control sequence. Thereby MPC can intrinsically incorporate constraints e.g. of actuators. Turbine models used for calculation within the MPC are typically simplified. For testing and verification usually multi body simulations, such as FAST, BLADED or FLEX5 are used to model system dynamics, but they are still limited in the number of degrees of freedom (DOF). Detailed information about load distribution (e.g. inside the gearbox) cannot be provided by such models. In this paper a Model Predictive Controller is presented and tested in a co-simulation with SlMPACK, a multi body system (MBS) simulation framework used for detailed load analysis. The analysis are performed on the basis of the IME6.0 MBS WT model, described in this paper. It is based on the rotor of the NREL 5MW WT and consists of a detailed representation of the drive train. This takes into account a flexible main shaft and its main bearings with a planetary gearbox, where all components are modelled flexible, as well as a supporting flexible main frame. The wind loads are simulated using the NREL AERODYN v13 code which has been implemented as a routine to SlMPACK. This modeling approach allows to investigate the nonlinear behavior of wind loads and nonlinear drive train dynamics. Thereby the MPC's impact on specific loads and effects not covered by standard simulation tools can be assessed and investigated. Keywords. wind turbine simulation, model predictive control, multi body simulation, MIMO, load alleviation
Evaluation of wheelchair sling seat and sling back crashworthiness.

PubMed

Ha, D; Bertocci, G; Karg, P; Deemer, E

2002-07-01

Many wheelchairs are used as vehicle seats by those who cannot transfer to a vehicle seat. Although ANSI/RESNA WC-19 has been recently adopted as a standard to evaluate crashworthiness of the wheelchairs used as motor vehicle seats, replacement or after-market seats may not be tested to this standard. This study evaluated the crashworthiness of two specimens each of three unique sling backs and three unique sling seats using a static test procedure intended to simulate crash loading conditions. To pass the test, a sling back is required to withstand a 2290 lb load, and a sling seat should be capable of withstanding a 3750 lb load. All, but two sling back specimens which failed at 1567 lb and 1787 lb, withstood the test criterion load. Two of six tested sling seats failed to pass the test: one failed at 3123 lb and the other failed to sustain the load for 5 s although it reached the test criterion load. Most of the failures occurred at the seams of the side openings of upholsteries where the wheelchair frame inserts for attachment.
A New Tribological Test for Candidate Brush Seal Materials Evaluation

NASA Technical Reports Server (NTRS)

Fellenstein, James A.; Dellacorte, Christopher

1994-01-01

A new tribological test for candidate brush seal materials evaluation has been developed. The sliding contact between the brush seal wires and their mating counterface journal is simulated by testing a small tuft of wire against the outside diameter of a high speed rotating shaft. The test configuration is similar to a standard block on ring geometry. The new tester provides the capability to measure both the friction and wear of candidate wire and counterface materials under controlled loading conditions in the gram to kilogram range. A wide test condition latitude of speeds (1 to 27 m/s), temperatures (25 to 700 C), and loads (0.5 to 10 N) enables the simulation of many of the important tribological parameters found in turbine engine brush seals. This paper describes the new test rig and specimen configuration and presents initial data for candidate seal materials comparing tuft test results and wear surface morphology to field tested seal components.
Application for managing model-based material properties for simulation-based engineering

DOEpatents

Hoffman, Edward L [Alameda, CA

2009-03-03

An application for generating a property set associated with a constitutive model of a material includes a first program module adapted to receive test data associated with the material and to extract loading conditions from the test data. A material model driver is adapted to receive the loading conditions and a property set and operable in response to the loading conditions and the property set to generate a model response for the material. A numerical optimization module is adapted to receive the test data and the model response and operable in response to the test data and the model response to generate the property set.
The effects of simulated bone loss on the implant-abutment assembly and likelihood of fracture: an in vitro study.

PubMed

Manzoor, Behzad; Suleiman, Mahmood; Palmer, Richard M

2013-01-01

The crestal bone level around a dental implant may influence its strength characteristics by offering protection against mechanical failures. Therefore, the present study investigated the effect of simulated bone loss on modes, loads, and cycles to failure in an in vitro model. Different amounts of bone loss were simulated: 0, 1.5, 3.0, and 4.5 mm from the implant head. Forty narrow-diameter (3.0-mm) implant-abutment assemblies were tested using compressive bending and cyclic fatigue testing. Weibull and accelerated life testing analysis were used to assess reliability and functional life. Statistical analyses were performed using the Fisher-Exact test and the Spearman ranked correlation. Compressive bending tests showed that the level of bone loss influenced the load-bearing capacity of implant-abutment assemblies. Fatigue testing showed that the modes, loads, and cycles to failure had a statistically significant relationship with the level of bone loss. All 16 samples with bone loss of 3.0 mm or more experienced horizontal implant body fractures. In contrast, 14 of 16 samples with 0 and 1.5 mm of bone loss showed abutment and screw fractures. Weibull and accelerated life testing analysis indicated a two-group distribution: the 0- and 1.5-mm bone loss samples had better functional life and reliability than the 3.0- and 4.5-mm samples. Progressive bone loss had a significant effect on modes, loads, and cycles to failure. In addition, bone loss influenced the functional life and reliability of the implant-abutment assemblies. Maintaining crestal bone levels is important in ensuring biomechanical sustainability and predictable long-term function of dental implant assemblies.
ATD Occupant Responses from Three Full-Scale General Aviation Crash Tests

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Annett, Martin S.

2016-01-01

During the summer of 2015, three Cessna 172 General Aviation (GA) aircraft were crash tested at the Landing and Impact Research (LandIR) Facility at NASA Langley Research Center (LaRC). Three different crash scenarios were represented. The first test simulated a flare-to-stall emergency or hard landing onto a rigid surface such as a road or runway. The second test simulated a controlled flight into terrain with a nose down pitch of the aircraft, and the third test simulated a controlled flight into terrain with an attempt to unsuccessfully recover the aircraft immediately prior to impact, resulting in a tail strike condition. An on-board data acquisition system (DAS) captured 64 channels of airframe acceleration, along with accelerations and loads in two onboard Hybrid II 50th percentile Anthropomorphic Test Devices (ATDs) representing the pilot and copilot. Each of the three tests contained different airframe loading conditions and different types of restraints for both the pilot and co-pilot ATDs. The results show large differences in occupant response and restraint performance with varying likelihoods of occupant injury.
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.
Masonry Vaults Subjected To Horizontal Loads: Experimental and Numerical Investigations to Evaluate the Effectiveness of A GFRM Reinforcement

NASA Astrophysics Data System (ADS)

Gattesco, Natalino; Boem, Ingrid

2017-10-01

The paper investigates the effectiveness of a modern reinforcement technique based on a Glass Fiber-Reinforced Mortar (GFRM) for the enhancement of the performances of existing masonry vaults subjected to horizontal seismic actions. In fact, the authors recently evidenced, through numerical simulations, that the typical simplified loading patterns generally adopted in the literature for the experimental tests, based on concentrated vertical loads at 1/4 of the span, are not reliable for such a purpose, due to an unrealistic stress distribution. Thus, experimental quasi-static cyclic tests on full-scale masonry vaults based on a specific setup, designed to apply a horizontal load pattern proportional to the mass, were performed. Three samples were tested: an unreinforced vault, a vault reinforced at the extrados and a vault reinforced at the intrados. The experimental results demonstrated the technique effectiveness in both strength and ductility. Moreover, numerical simulations were performed by adopting a simplified FE, smear-crack model, evidencing the good reliability of the prediction by comparison with the experimental results.
Simulation of a Lunar Surface Base Power Distribution Network for the Constellation Lunar Surface Systems

NASA Technical Reports Server (NTRS)

Mintz, Toby; Maslowski, Edward A.; Colozza, Anthony; McFarland, Willard; Prokopius, Kevin P.; George, Patrick J.; Hussey, Sam W.

2010-01-01

The Lunar Surface Power Distribution Network Study team worked to define, breadboard, build and test an electrical power distribution system consistent with NASA's goal of providing electrical power to sustain life and power equipment used to explore the lunar surface. A testbed was set up to simulate the connection of different power sources and loads together to form a mini-grid and gain an understanding of how the power systems would interact. Within the power distribution scheme, each power source contributes to the grid in an independent manner without communication among the power sources and without a master-slave scenario. The grid consisted of four separate power sources and the accompanying power conditioning equipment. Overall system design and testing was performed. The tests were performed to observe the output and interaction of the different power sources as some sources are added and others are removed from the grid connection. The loads on the system were also varied from no load to maximum load to observe the power source interactions.
Dynamic simulations for preparing the acceptance test of JT-60SA cryogenic system

NASA Astrophysics Data System (ADS)

Cirillo, R.; Hoa, C.; Michel, F.; Poncet, J. M.; Rousset, B.

2016-12-01

Power generation in the future could be provided by thermo-nuclear fusion reactors like tokamaks. There inside, the fusion reaction takes place thanks to the generation of plasmas at hundreds of millions of degrees that must be confined magnetically with superconductive coils, cooled down to around 4.5 K. Within this frame, an experimental tokamak device, JT-60SA is currently under construction in Naka (Japan). The plasma works cyclically and the coil system is subject to pulsed heat loads. In order to size the refrigerator close to the average power and hence optimizing investment and operational costs, measures have to be taken to smooth the heat load. Here we present a dynamic model of the JT-60SA's Auxiliary Cold box (ACB) for preparing the acceptance tests of the refrigeration system planned in 2016 in Naka. The aim of this study is to simulate the pulsed load scenarios using different process controls. All the simulations have been performed with EcosimPro® and the associated cryogenic library: CRYOLIB.
SMR Re-Scaling and Modeling for Load Following Studies

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

Hoover, K.; Wu, Q.; Bragg-Sitton, S.

2016-11-01

This study investigates the creation of a new set of scaling parameters for the Oregon State University Multi-Application Small Light Water Reactor (MASLWR) scaled thermal hydraulic test facility. As part of a study being undertaken by Idaho National Lab involving nuclear reactor load following characteristics, full power operations need to be simulated, and therefore properly scaled. Presented here is the scaling analysis and plans for RELAP5-3D simulation.

Low cognitive load and reduced arousal impede practice effects on executive functioning, metacognitive confidence and decision making.

PubMed

Jackson, Simon A; Kleitman, Sabina; Aidman, Eugene

2014-01-01

The present study investigated the effects of low cognitive workload and the absence of arousal induced via external physical stimulation (motion) on practice-related improvements in executive (inhibitory) control, short-term memory, metacognitive monitoring and decision making. A total of 70 office workers performed low and moderately engaging passenger tasks in two successive 20-minute simulated drives and repeated a battery of decision making and inhibitory control tests three times—before, between and after these drives. For half the participants, visual simulation was synchronised with (moderately arousing) motion generated through LAnd Motion Platform, with vibration levels corresponding to a well-maintained unsealed road. The other half performed the same simulated drive without motion. Participants' performance significantly improved over the three test blocks, which is indicative of typical practice effects. The magnitude of these improvements was the highest when both motion and moderate cognitive load were present. The same effects declined either in the absence of motion (low arousal) or following a low cognitive workload task, thus suggesting two distinct pathways through which practice-related improvements in cognitive performance may be hampered. Practice, however, degraded certain aspects of metacognitive performance, as participants became less likely to detect incorrect decisions in the decision-making test with each subsequent test block. Implications include consideration of low cognitive load and arousal as factors responsible for performance decline and targets for the development of interventions/strategies in low load/arousal conditions such as autonomous vehicle operations and highway driving.
A PVDF-Based Sensor for Internal Stress Monitoring of a Concrete-Filled Steel Tubular (CFST) Column Subject to Impact Loads.

PubMed

Du, Guofeng; Li, Zhao; Song, Gangbing

2018-05-23

Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force⁻time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads.
Evaluation of Approaches for Managing Nitrate Loading from On-Site Wastewater Systems near La Pine, Oregon

USGS Publications Warehouse

Morgan, David S.; Hinkle, Stephen R.; Weick, Rodney J.

2007-01-01

This report presents the results of a study by the U.S. Geological Survey, done in cooperation with the Oregon Department of Environmental Quality and Deschutes County, to develop a better understanding of the effects of nitrogen from on-site wastewater disposal systems on the quality of ground water near La Pine in southern Deschutes County and northern Klamath County, Oregon. Simulation models were used to test the conceptual understanding of the system and were coupled with optimization methods to develop the Nitrate Loading Management Model, a decision-support tool that can be used to efficiently evaluate alternative approaches for managing nitrate loading from on-site wastewater systems. The conceptual model of the system is based on geologic, hydrologic, and geochemical data collected for this study, as well as previous hydrogeologic and water quality studies and field testing of on-site wastewater systems in the area by other agencies. On-site wastewater systems are the only significant source of anthropogenic nitrogen to shallow ground water in the study area. Between 1960 and 2005 estimated nitrate loading from on-site wastewater systems increased from 3,900 to 91,000 pounds of nitrogen per year. When all remaining lots are developed (in 2019 at current building rates), nitrate loading is projected to reach nearly 150,000 pounds of nitrogen per year. Low recharge rates (2-3 inches per year) and ground-water flow velocities generally have limited the extent of nitrate occurrence to discrete plumes within 20-30 feet of the water table; however, hydraulic-gradient and age data indicate that, given sufficient time and additional loading, nitrate will migrate to depths where many domestic wells currently obtain water. In 2000, nitrate concentrations greater than 4 milligrams nitrogen per liter (mg N/L) were detected in 10 percent of domestic wells sampled by Oregon Department of Environmental Quality. Numerical simulation models were constructed at transect (2.4 square miles) and study-area (247 square miles) scales to test the conceptual model and evaluate processes controlling nitrate concentrations in ground water and potential ground-water discharge of nitrate to streams. Simulation of water-quality conditions for a projected future build-out (base) scenario in which all existing lots are developed using conventional on-site wastewater systems indicates that, at equilibrium, average nitrate concentrations near the water table will exceed 10 mg N/L over areas totaling 9,400 acres. Other scenarios were simulated where future nitrate loading was reduced using advanced treatment on-site systems and a development transfer program. Seven other scenarios were simulated with total nitrate loading reductions ranging from 15 to 94 percent; simulated reductions in the area where average nitrate concentrations near the water table exceed 10 mg N/L range from 22 to 99 percent at equilibrium. Simulations also show that the ground-water system responds slowly to changes in nitrate loading due to low recharge rates and ground-water flow velocity. Consequently, reductions in nitrate loading will not immediately reduce average nitrate concentrations and the average concentration in the aquifer will continue to increase for 25-50 years depending on the level and timing of loading reduction. The capacity of the ground-water system to receive on-site wastewater system effluent, which is related to the density of homes, presence of upgradient residential development, ground-water recharge rate, ground-water flow velocity, and thickness of the oxic part of the aquifer, varies within the study area. Optimization capability was added to the study-area simulation model and the combined simulation-optimization model was used to evaluate alternative approaches to management of nitrate loading from on-site wastewater systems to the shallow alluvial aquifer. The Nitrate Loading Management Model (NLMM) was formulated to find the minimum red
Fracture strength of lithium disilicate crowns compared to polymer-infiltrated ceramic-network and zirconia reinforced lithium silicate crowns.

PubMed

Sieper, Kim; Wille, Sebastian; Kern, Matthias

2017-10-01

The aim of this study was to evaluate the fracture strength of crowns made from current CAD/CAM materials. In addition the influence of crown thickness and chewing simulation on the fracture strength was evaluated. Crowns were fabricated from lithium disilicate, zirconia reinforced lithium silicate (ZLS-ceramic) and a polymer-infiltrated ceramic-network (PICN) with an occlusal thickness of 1.0mm or 1.5mm, respectively (n=16). Crowns were cemented on composite dies. Subgroups of eight specimens were loaded with 5kg in a chewing simulator for 1,200,000 cycles with thermal cycling. Finally, all specimens were loaded until fracture in a universal testing machine. Three-way ANOVA was used to detect statistical interaction. Differences regarding the materials were tested with two-way ANOVA, following one-way ANOVA and a post-hoc Tukey's-Test. All crowns survived the chewing simulation. The material had a significant influence on the fracture resistance (p≤0.05). Lithium disilicate achieved the highest values of fracture strength in almost all groups followed by ZLS-ceramic. PICN achieved the lowest values of fracture strength. Chewing simulation increased the fracture strength of thick lithium disilicate crown significantly. Greater occlusal thickness of all crown materials resulted in higher crown fracture strength before chewing simulation. After chewing simulation occlusal thickness of lithium disilicate and PICN crowns had no significant influence on the fracture strength. All crowns revealed fracture strength above the clinically expected loading forces. Therefore the durability of the tested CAD/CAM materials seems promising also in an occlusal thickness of 1.0mm. Copyright © 2017 Elsevier Ltd. All rights reserved.
Effects of laboratory heating, cyclic pore pressure, and cyclic loading on fracture properties of asphalt mixture.

DOT National Transportation Integrated Search

2012-04-01

This study involved the identification and evaluation of laboratory conditioning methods and testing protocols considering heat oxidation, moisture, and load that more effectively simulate asphalt mixture aging in the field, and thereby help to prope...
Steady-state and dynamic evaluation of the electric propulsion system test bed vehicle on a road load simulator

NASA Technical Reports Server (NTRS)

Dustin, M. O.

1983-01-01

The propulsion system of the Lewis Research Center's electric propulsion system test bed vehicle was tested on the road load simulator under the DOE Electric and Hybrid Vehicle Program. This propulsion system, consisting of a series-wound dc motor controlled by an infinitely variable SCR chopper and an 84-V battery pack, is typical of those used in electric vehicles made in 1976. Steady-state tests were conducted over a wide range of differential output torques and vehicle speeds. Efficiencies of all of the components were determined. Effects of temperature and voltage variations on the motor and the effect of voltage changes on the controller were examined. Energy consumption and energy efficiency for the system were determined over the B and C driving schedules of the SAE J227a test procedure.
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.
Comparison of the quasi-static method and the dynamic method for simulating fracture processes in concrete

NASA Astrophysics Data System (ADS)

Liu, J. X.; Deng, S. C.; Liang, N. G.

2008-02-01

Concrete is heterogeneous and usually described as a three-phase material, where matrix, aggregate and interface are distinguished. To take this heterogeneity into consideration, the Generalized Beam (GB) lattice model is adopted. The GB lattice model is much more computationally efficient than the beam lattice model. Numerical procedures of both quasi-static method and dynamic method are developed to simulate fracture processes in uniaxial tensile tests conducted on a concrete panel. Cases of different loading rates are compared with the quasi-static case. It is found that the inertia effect due to load increasing becomes less important and can be ignored with the loading rate decreasing, but the inertia effect due to unstable crack propagation remains considerable no matter how low the loading rate is. Therefore, an unrealistic result will be obtained if a fracture process including unstable cracking is simulated by the quasi-static procedure.
Simulation of streamflow and estimation of streamflow constituent loads in the San Antonio River watershed, Bexar County, Texas, 1997-2001

USGS Publications Warehouse

Ockerman, Darwin J.; McNamara, Kenna C.

2003-01-01

The U.S. Geological Survey developed watershed models (Hydrological Simulation Program—FORTRAN) to simulate streamflow and estimate streamflow constituent loads from five basins that compose the San Antonio River watershed in Bexar County, Texas. Rainfall and streamflow data collected during 1997–2001 were used to calibrate and test the model. The model was configured so that runoff from various land uses and discharges from other sources (such as wastewater recycling facilities) could be accounted for to indicate sources of streamflow. Simulated streamflow volumes were used with land-use-specific, water-quality data to compute streamflow loads of selected constituents from the various streamflow sources.Model simulations for 1997–2001 indicate that inflow from the upper Medina River (originating outside Bexar County) represents about 22 percent of total streamflow. Recycled wastewater discharges account for about 20 percent and base flow (ground-water inflow to streams) about 18 percent. Storm runoff from various land uses represents about 33 percent. Estimates of sources of streamflow constituent loads indicate recycled wastewater as the largest source of dissolved solids and nitrate plus nitrite nitrogen (about 38 and 66 percent, respectively, of the total loads) during 1997–2001. Stormwater runoff from urban land produced about 49 percent of the 1997–2001 total suspended solids load. Stormwater runoff from residential and commercial land (about 23 percent of the land area) produced about 70 percent of the total lead streamflow load during 1997–2001.
Numerical-experimental investigation of load paths in DP800 dual phase steel during Nakajima test

NASA Astrophysics Data System (ADS)

Bergs, Thomas; Nick, Matthias; Feuerhack, Andreas; Trauth, Daniel; Klocke, Fritz

2018-05-01

Fuel efficiency requirements demand lightweight construction of vehicle body parts. The usage of advanced high strength steels permits a reduction of sheet thickness while still maintaining the overall strength required for crash safety. However, damage, internal defects (voids, inclusions, micro fractures), microstructural defects (varying grain size distribution, precipitates on grain boundaries, anisotropy) and surface defects (micro fractures, grooves) act as a concentration point for stress and consequently as an initiation point for failure both during deep drawing and in service. Considering damage evolution in the design of car body deep drawing processes allows for a further reduction in material usage and therefore body weight. Preliminary research has shown that a modification of load paths in forming processes can help mitigate the effects of damage on the material. This paper investigates the load paths in Nakajima tests of a DP800 dual phase steel to research damage in deep drawing processes. Investigation is done via a finite element model using experimentally validated material data for a DP800 dual phase steel. Numerical simulation allows for the investigation of load paths with respect to stress states, strain rates and temperature evolution, which cannot be easily observed in physical experiments. Stress triaxiality and the Lode parameter are used to describe the stress states. Their evolution during the Nakajima tests serves as an indicator for damage evolution. The large variety of sheet metal forming specific load paths in Nakajima tests allows a comprehensive evaluation of damage for deep drawing. The results of the numerical simulation conducted in this project and further physical experiments will later be used to calibrate a damage model for simulation of deep drawing processes.
Design of an Orthodontic Torque Simulator for Measurement of Bracket Deformation

NASA Astrophysics Data System (ADS)

Melenka, G. W.; Nobes, D. S.; Major, P. W.; Carey, J. P.

2013-12-01

The design and testing of an orthodontic torque simulator that reproduces the effect of archwire rotation on orthodontic brackets is described. This unique device is capable of simultaneously measuring the deformation and loads applied to an orthodontic bracket due to archwire rotation. Archwire rotation is used by orthodontists to correct the inclination of teeth within the mouth. This orthodontic torque simulator will provide knowledge of the deformation and loads applied to orthodontic bracket that will aide clinicians by describing the effect of archwire rotation on brackets. This will also impact that design on new archwirebracket systems by providing an assessment of performance. Deformation of the orthodontic bracket tie wings is measured using a digital image correlation process to measure elastic and plastic deformation. The magnitude of force and moments applied to the bracket though the archwire is also measured using a six-axis load cell. Initial tests have been performed on two orthodontic brackets of varying geometry to demonstrate the measurement capability of the orthodontic torque simulator. The demonstration experiment shows that a Damon Q bracket had a final plastic deformation after a single loading of 0.022 mm while the Speed bracket deformed 0.071 mm. This indicates that the Speed bracket plastically deforms 3.2 times more than the Damon Q bracket for similar magnitude of applied moment. The demonstration experiment demonstrates that bracket geometry affect the deformation of orthodontic brackets and this difference can be detected using the orthodontic torque simulator.
Road load simulator tests of the Gould phase 1 functional model silicon controlled rectifier ac motor controller for electric vehicles

NASA Astrophysics Data System (ADS)

Gourash, F.

1984-02-01

The test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator are presented. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.
Road load simulator tests of the Gould phase 1 functional model silicon controlled rectifier ac motor controller for electric vehicles

NASA Technical Reports Server (NTRS)

Gourash, F.

1984-01-01

The test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator are presented. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.
Field Test of Driven Pile Group under Lateral Loading

NASA Astrophysics Data System (ADS)

Gorska, Karolina; Rybak, Jaroslaw; Wyjadlowski, Marek

2017-12-01

All the geotechnical works need to be tested because the diversity of soil parameters is much higher than in other fields of construction. Horizontal load tests are necessary to determine the lateral capacity of driven piles subject to lateral load. Various load tests were carried out altogether on the test field in Kutno (Poland). While selecting the piles for load tests, different load combinations were taken into account. The piles with diverse length were chosen, on the basis of the previous tests of their length and integrity. The subsoil around the piles consisted of mineral soils: clays and medium compacted sands with the density index ID>0.50. The pile heads were free. The points of support of the “base” to which the dial gauges (displacement sensors) were fastened were located at the distance of 0.7 m from the side surface of the pile loaded laterally. In order to assure the independence of measurement, additional control (verifying) geodetic survey of the displacement of the piles subject to the load tests was carried out (by means of the alignment method). The trial load was imposed in stages by means of a hydraulic jack. The oil pressure in the actuator was corrected by means of a manual pump in order to ensure the constant value of the load in the on-going process of the displacement of the pile under test. On the basis of the obtained results it is possible to verify the numerical simulations of the behaviour of piles loaded by a lateral force.
Atomic Oxygen Durability Testing of an International Space Station Solar Array Validation Coupon

NASA Technical Reports Server (NTRS)

Forkapa, Mark J.; Stidham, Curtis; Banks, Bruce A.; Rutledge, Sharon K.; Ma, David H.; Sechkar, Edward A.

1996-01-01

An International Space Station solar array validation coupon was exposed in a directed atomic oxygen beam for space environment durability testing at the NASA Lewis Research Center. Exposure to atomic oxygen and intermittent tensioning of the solar array were conducted to verify the solar array#s durability to low Earth orbital atomic oxygen and to the docking threat of plume loading both of which are anticipated over its expected mission life of fifteen years. The validation coupon was mounted on a specially designed rotisserie. The rotisserie mounting enabled the solar and anti-solar facing side of the array to be exposed to directed atomic oxygen in a sweeping arrival process replicating space exposure. The rotisserie mounting also enabled tensioning, in order to examine the durability of the array and its hinge to simulated plume loads. Flash testing to verify electrical performance of the solar array was performed with a solar simulator before and after the exposure to atomic oxygen and tensile loading. Results of the flash testing indicated little or no degradation in the solar array#s performance. Photographs were also taken of the array before and after the durability testing and are included along with comparisons and discussions in this report. The amount of atomic oxygen damage appeared minor with the exception of a very few isolated defects. There were also no indications that the simulated plume loadings had weakened or damaged the array, even though there was some erosion of Kapton due to atomic oxygen attack. Based on the results of this testing, it is apparent that the International Space Station#s solar arrays should survive the low Earth orbital atomic oxygen environment and docking threats which are anticipated over its expected mission life.
Cyclic Cryogenic Thermal-Mechanical Testing of an X-33/RLV Liquid Oxygen Tank Concept

NASA Technical Reports Server (NTRS)

Rivers, H. Kevin

1999-01-01

An important step in developing a cost-effective, reusable, launch vehicle is the development of durable, lightweight, insulated, cryogenic propellant tanks. Current cryogenic tanks are expendable so most of the existing technology is not directly applicable to future launch vehicles. As part of the X-33/Reusable Launch Vehicle (RLV) Program, an experimental apparatus developed at the NASA Langley Research Center for evaluating the effects of combined, cyclic, thermal and mechanical loading on cryogenic tank concepts was used to evaluate cryogenic propellant tank concepts for Lockheed-Martin Michoud Space Systems. An aluminum-lithium (Al 2195) liquid oxygen tank concept, insulated with SS-1171 and PDL-1034 cryogenic insulation, is tested under simulated mission conditions, and the results of those tests are reported. The tests consists of twenty-five simulated Launch/Abort missions and twenty-five simulated flight missions with temperatures ranging from -320 F to 350 F and a maximum mechanical load of 71,300 lb. in tension.
Mechanical testing and finite element analysis of orthodontic teardrop loop.

PubMed

Coimbra, Maria Elisa Rodrigues; Penedo, Norman Duque; de Gouvêa, Jayme Pereira; Elias, Carlos Nelson; de Souza Araújo, Mônica Tirre; Coelho, Paulo Guilherme

2008-02-01

Understanding how teeth move in response to mechanical loads is an important aspect of orthodontic treatment. Treatment planning should include consideration of the appliances that will meet the desired loading of the teeth to result in optimized treatment outcomes. The purpose of this study was to evaluate the use of computer simulation to predict the force and the torsion obtained after the activation of tear drop loops of 3 heights. Seventy-five retraction loops were divided into 3 groups according to height (6, 7, and 8 mm). The loops were subjected to tensile load through displacements of 0.5, 1.0, 1.5, and 2.0 mm, and the resulting forces and torques were recorded. The loops were designed in AutoCAD software(2005; Autodesk Systems, Alpharetta, GA), and finite element analysis was performed with Ansys software(version 7.0; Swanson Analysis System, Canonsburg, PA). Statistical analysis of the mechanical experiment results was obtained by ANOVA and the Tukey post-hoc test (P < .01). The correlation test and the paired t test (P < .05) were used to compare the computer simulation with the mechanical experiment. The computer simulation accurately predicted the experimentally determined mechanical behavior of tear drop loops of different heights and should be considered an alternative for designing orthodontic appliances before treatment.
Report on the First Jacksboro MMLS Tests

DOT National Transportation Integrated Search

1999-12-01

This report outlines the two accelerated pavement tests completed in Jacksboro, Texas, using the 1/3-scale Model Mobile Load Simulator (MMLS3).The MMLS3 tests were initially commissioned to investigate the stripping phenomenon evident under conventio...
Testing the feasibility of using a conveyor belt to load weanling and nursery pigs for transportation

USDA-ARS?s Scientific Manuscript database

Transportation is known to be a multi-faceted stressor, with the process of loading being one of the most significant factors impacting the stress to which animals are exposed. This project was designed to determine if using a conveyor to load pigs into the top deck of a simulated straight deck trai...
Damage accumulation in titanium matrix composites under generic hypersonic vehicle flight simulation and sustained loads

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

Johnson, W.S.; Mirdamadi, M.; Bakuckas, J.G. Jr.

1996-12-31

Titanium matrix composites (TMC), such as Ti-15V-3Cr-3Al-3Sn (Ti-15-3) reinforced with continuous silicon-carbide fibers (SCS-6), are being evaluated for use in hypersonic vehicles and advanced gas turbine engines where high strength-to-weight and high stiffness-to-weight ratios at elevated temperatures are critical. Such applications expose the composite to mechanical fatigue loading as well as thermally induced cycles. The damage accumulation behavior of a [0/90]2s laminate made of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) reinforced with continuous silicon-carbide fibers (SCS-6) subjected to a simulated generic hypersonic flight profile, portions of the flight profile, and sustained loads was evaluated experimentally. Portions of the flight profile were used separately tomore » isolate combinations of load and time at temperature that influenced the fatigue behavior of the composite. Sustained load tests were also conducted and the results were compared with the fatigue results under the flight profile and its portions. The test results indicated that the fatigue strength of this materials system is considerably reduced by a combination of load and time at temperature.« less

40 CFR 86.161-00 - Air conditioning environmental test facility ambient requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... heat loading. (1)(i) Acceptable types of radiant energy emitters that may be used for simulating solar... this section. (3) Radiant energy specifications. (i) Simulated solar radiant energy intensity is... time major changes in the solar simulation hardware occur. (vi) The radiant energy intensity...
40 CFR 86.161-00 - Air conditioning environmental test facility ambient requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... heat loading. (1)(i) Acceptable types of radiant energy emitters that may be used for simulating solar... this section. (3) Radiant energy specifications. (i) Simulated solar radiant energy intensity is... time major changes in the solar simulation hardware occur. (vi) The radiant energy intensity...
40 CFR 86.161-00 - Air conditioning environmental test facility ambient requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... heat loading. (1)(i) Acceptable types of radiant energy emitters that may be used for simulating solar... this section. (3) Radiant energy specifications. (i) Simulated solar radiant energy intensity is... time major changes in the solar simulation hardware occur. (vi) The radiant energy intensity...
40 CFR 86.161-00 - Air conditioning environmental test facility ambient requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... heat loading. (1)(i) Acceptable types of radiant energy emitters that may be used for simulating solar... this section. (3) Radiant energy specifications. (i) Simulated solar radiant energy intensity is... time major changes in the solar simulation hardware occur. (vi) The radiant energy intensity...
A study on special test stand of automatic and manual descent control in presence of simulated g-load effect

NASA Astrophysics Data System (ADS)

Glazkov, Yury; Artjuchin, Yury; Astakhov, Alexander; Vas'kov, Alexander; Malyshev, Veniamin; Mitroshin, Edward; Glinsky, Valery; Moiseenko, Vasily; Makovlev, Vyacheslav

The development of aircraft-type reusable space vehicles (RSV) involves the problem of complete compatibility of automatic, director and manual control. Task decision is complicated, in particular, due to considerable quantitative and qualitative changes of vehicle dynamic characteristics, little stability margins (and even of unstability) of the RSV, and stringent requirements to control accuracy at some flight phases. Besides, during control a pilot is affected by g-loads which hamper motor activity and deteriorate its accuracy, alter the functional status of the visual analyser, and influence higher nervous activity. A study of g-load effects on the control efficiency, especially in manual and director modes, is of primary importance. The main tools for study of a rational selection of manual and director vehicle control systems and as an aid in formulating recommendations for optimum crew-automatic control system interactions are special complex and functional flight simulator test stands. The proposed simulator stand includes a powerful digital computer complex combined with the control system of the centrifuge. The interior of a pilot's vehicle cabin is imitated. A situation image system, pyscho-physical monitoring system, physician, centrifuge operator, and instructor stations are linked with the test stand.
Tribological measurements on a Charnley-type artificial hip joint

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.

1983-01-01

A total hip simulator was used to determine the friction and wear properties of Charnley-type (316L stainless steel balls and sterile ultrahigh molecular weight polyethylene cups) hip prostheses. Three different sets of specimens were tested to 395,000, 101,500 and 233,000 walking cycles, respectively. All tests were run unlubricated, at ambient conditions (22 to 26 C, 30 to 50 percent relative humidity), at 30 walking cycles per minute, under a dynamic load simulating walking. Polyethylene cup wear rates ranged from 1.4 to 39 ten billions cu m which corresponds to dimensional losses of 4.0 to 11 microns per year. Although these wear rates are lower than those obtained from other hip simulators and from in vivo X-ray measurements, they are comparable when taking run-in and plastic deformation into account. Maximum tangential friction forces ranged from 93 to 129 N under variable load (267 to 3090 N range) and from 93 to 143 N under a static load of 3090 N. A portion of one test 250,000 walking cycles) run under dry air ( 1 percent relative humidity) yielded a wear rate almost 6 times greater than that obtained under wet air ( 70 percent relative humidity) conditions.
Fatigue limit of monolithic Y-TZP three-unit-fixed dental prostheses: Effect of grinding at the gingival zone of the connector.

PubMed

Amaral, Marina; Villefort, Regina F; Melo, Renata Marques; Pereira, Gabriel K R; Zhang, Yu; Valandro, Luiz Felipe; Bottino, Marco Antonio

2017-08-01

To determine the fatigue limits of three-unit monolithic zirconia fixed dental prosthesis (FDPs) before and after grinding of the gingival areas of connectors with diamond burs. FDPs were milled from pre-sintered blocks of zirconia simulating the absence of the first mandibular molar. Half of the specimens were subjected to grinding, simulating clinical adjustment, and all of them were subjected to glazing procedure. Additional specimens were manufactured for roughness analysis. FDPs were adhesively cemented onto glass-fiber reinforced epoxy resin abutments. Fatigue limits and standard deviations were obtained using a staircase fatigue method (n=20, 100,000 loading cycles/5Hz). The initial test load was 70% of the mean load-to-fracture (n=3) and load increments were 5% of the initial test load for both the control and ground specimens. Data were compared by Student's T-test (α≤0.05). Both the control and ground groups exhibited similar values of load-to-fracture and fatigue limits. Neither the surface treatments nor ageing affected the surface roughness of the specimens. The damage induced by grinding with fine-grit diamond bur in the gingival area of the connectors did not decrease the fatigue limit of the three-unit monolithic zirconia FDP. Copyright © 2017 Elsevier Ltd. All rights reserved.
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...
Autonomous Cryogenics Loading Operations Simulation Software: Knowledgebase Autonomous Test Engineer

NASA Technical Reports Server (NTRS)

Wehner, Walter S.

2012-01-01

The Simulation Software, KATE (Knowledgebase Autonomous Test Engineer), is used to demonstrate the automatic identification of faults in a system. The ACLO (Autonomous Cryogenics Loading Operation) project uses KATE to monitor and find faults in the loading of the cryogenics int o a vehicle fuel tank. The KATE software interfaces with the IHM (Integrated Health Management) systems bus to communicate with other systems that are part of ACLO. One system that KATE uses the IHM bus to communicate with is AIS (Advanced Inspection System). KATE will send messages to AIS when there is a detected anomaly. These messages include visual inspection of specific valves, pressure gauges and control messages to have AIS open or close manual valves. My goals include implementing the connection to the IHM bus within KATE and for the AIS project. I will also be working on implementing changes to KATE's Ul and implementing the physics objects in KATE that will model portions of the cryogenics loading operation.
Voltage-Load Sensitivity Matrix Based Demand Response for Voltage Control in High Solar Penetration Distribution Feeders

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

Zhu, Xiangqi; Wang, Jiyu; Mulcahy, David

This paper presents a voltage-load sensitivity matrix (VLSM) based voltage control method to deploy demand response resources for controlling voltage in high solar penetration distribution feeders. The IEEE 123-bus system in OpenDSS is used for testing the performance of the preliminary VLSM-based voltage control approach. A load disaggregation process is applied to disaggregate the total load profile at the feeder head to each load nodes along the feeder so that loads are modeled at residential house level. Measured solar generation profiles are used in the simulation to model the impact of solar power on distribution feeder voltage profiles. Different casemore » studies involving various PV penetration levels and installation locations have been performed. Simulation results show that the VLSM algorithm performance meets the voltage control requirements and is an effective voltage control strategy.« less
A laboratory comparison of individual Targis/Vectris posts with standard fiberglass posts.

PubMed

Corsalini, Massimo; Genovese, Katia; Lamberti, Luciano; Pappalettere, Carmine; Carella, Mauro; Carossa, Stefano

2007-01-01

This article presents an in vitro analysis of a specific occlusal loading test on endodontically treated teeth restored with 2 different composite post materials. Individual, customized posts (IFPs) were compared to standard fiberglass posts (SFPs). The selected IFPs (standard cylindric Targis/Vectris posts) were compared to SFPs (Conic 6% Post, Ghimas). The posts were first subjected to a 3-point bending test to compare their flexural elastic properties. They were then used to restore 22 endodontically treated artificial maxillary central incisors and subjected to a specific occlusal loading simulation test. The loading test showed that IFP restorations performed better than SFP restorations. A clinical evaluation of this laboratory observation is suggested.
Mechanical Properties of a Unidirectional Basalt-Fiber-Reinforced Plastic Under a Loading Simulating Operation Conditions

NASA Astrophysics Data System (ADS)

Lobanov, D. S.; Slovikov, S. V.

2017-01-01

The results of experimental investigations of unidirectional composites based on basalt fibers and different marks of epoxy resins are presented. Uniaxial tensile tests were carried out using a specimen fixation technique simulating the operation conditions of structures. The mechanical properties of the basalt-fiber-reinforced plastics (BFRPs) were determined. The diagrams of loading and deformation of BFRP specimens were obtain. The formulations of the composites with the highest mechanical properties were revealed.
Evaluation of wheelchair seating system crashworthiness: "drop hook"-type seat attachment hardware.

PubMed

Bertocci, G; Ha, D; Deemer, E; Karg, P

2001-04-01

To evaluate the crashworthiness of commercially available hardware that attaches seat surfaces to the wheelchair frame. A low cost static crashworthiness test procedure that simulates a frontal impact motor vehicle crash. Safety testing laboratory. Eleven unique sets of drop-hook hardware made of carbon steel (4), stainless steel (4), and aluminum (3). Replicated seat-loading conditions associated with a 20g/48 kph frontal impact. Test criterion for seat loading was 16,680 N (3750 lb). Failure load and deflection of seat surface. None of the hardware sets tested met the crashworthiness test criterion. All failed at less than 50% of the load that seating hardware could be exposed to in a 20g/48 kph frontal impact. The primary failure mode was excessive deformation, leading to an unstable seat support surface. Results suggest that commercially available seating drop hooks may be unable to withstand loading associated with a frontal crash and may not be the best option for use with transport wheelchairs.
Load-bearing capacity of all-ceramic posterior inlay-retained fixed dental prostheses.

PubMed

Puschmann, Djamila; Wolfart, Stefan; Ludwig, Klaus; Kern, Matthias

2009-06-01

The purpose of this in vitro study was to compare the quasi-static load-bearing capacity of all-ceramic resin-bonded three-unit inlay-retained fixed dental prostheses (IRFDPs) made from computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) frameworks with two different connector dimensions, with and without fatigue loading. Twelve IRFDPs each were made with connector dimensions 3 x 3 mm(2) (width x height) (control group) and 3 x 2 mm(2) (test group). Inlay-retained fixed dental prostheses were adhesively cemented on identical metal-models using composite resin cement. Subgroups of six specimens each were fatigued with maximal 1,200,000 loading cycles in a chewing simulator with a weight load of 25 kg and a load frequency of 1.5 Hz. The load-bearing capacity was tested in a universal testing machine for IRFDPs without fatigue loading and for IRFDPs that had not already fractured during fatigue loading. During fatigue testing one IRFDP (17%) of the test group failed. Under both loading conditions, IRFDPs of the control group exhibited statistically significantly higher load-bearing capacities than the test group. Fatigue loading reduced the load-bearing capacity in both groups. Considering the maximum chewing forces in the molar region, it seems possible to use zirconia ceramic as a core material for IRFDPs with a minimum connector dimension of 9 mm(2). A further reduction of the connector dimensions to 6 mm(2) results in a significant reduction of the load-bearing capacity.
Ares I-X First Stage Separation Loads and Dynamics Reconstruction

NASA Technical Reports Server (NTRS)

Demory, Lee; Rooker, BIll; Jarmulowicz, Marc; Glaese, John

2011-01-01

The Ares I-X flight test provided NASA with the opportunity to test hardware and gather critical data to ensure the success of future Ares I flights. One of the primary test flight objectives was to evaluate the environment during First Stage separation to better understand the conditions that the J-2X second stage engine will experience at ignition [1]. A secondary objective was to evaluate the effectiveness of the stage separation motors. The Ares I-X flight test vehicle was successfully launched on October 29, 2009, achieving most of its primary and secondary test objectives. Ground based video camera recordings of the separation event appeared to show recontact of the First Stage and the Upper Stage Simulator followed by an unconventional tumbling of the Upper Stage Simulator. Closer inspection of the videos and flight test data showed that recontact did not occur. Also, the motion during staging was as predicted through CFD analysis performed during the Ares I-X development. This paper describes the efforts to reconstruct the vehicle dynamics and loads through the staging event by means of a time integrated simulation developed in TREETOPS, a multi-body dynamics software tool developed at NASA [2]. The simulation was built around vehicle mass and geometry properties at the time of staging and thrust profiles for the first stage solid rocket motor as well as for the booster deceleration motors and booster tumble motors. Aerodynamic forces were determined by models created from a combination of wind tunnel testing and CFD. The initial conditions such as position, velocity, and attitude were obtained from the Best Estimated Trajectory (BET), which is compiled from multiple ground based and vehicle mounted instruments. Dynamic loads were calculated by subtracting the inertial forces from the applied forces. The simulation results were compared to the Best Estimated Trajectory, accelerometer flight data, and to ground based video.
Computational Knee Ligament Modeling Using Experimentally Determined Zero-Load Lengths

PubMed Central

Bloemker, Katherine H; Guess, Trent M; Maletsky, Lorin; Dodd, Kevin

2012-01-01

This study presents a subject-specific method of determining the zero-load lengths of the cruciate and collateral ligaments in computational knee modeling. Three cadaver knees were tested in a dynamic knee simulator. The cadaver knees also underwent manual envelope of motion testing to find their passive range of motion in order to determine the zero-load lengths for each ligament bundle. Computational multibody knee models were created for each knee and model kinematics were compared to experimental kinematics for a simulated walk cycle. One-dimensional non-linear spring damper elements were used to represent cruciate and collateral ligament bundles in the knee models. This study found that knee kinematics were highly sensitive to altering of the zero-load length. The results also suggest optimal methods for defining each of the ligament bundle zero-load lengths, regardless of the subject. These results verify the importance of the zero-load length when modeling the knee joint and verify that manual envelope of motion measurements can be used to determine the passive range of motion of the knee joint. It is also believed that the method described here for determining zero-load length can be used for in vitro or in vivo subject-specific computational models. PMID:22523522
Shear test on viscoelastic granular material using Contact Dynamics simulations

NASA Astrophysics Data System (ADS)

Quezada, Juan Carlos; Sagnol, Loba; Chazallon, Cyrille

2017-06-01

By means of 3D contact dynamic simulations, the behavior of a viscoelastic granular material under shear loading is investigated. A viscoelastic fluid phase surrounding the solid particles is simulated by a contact model acting between them. This contact law was implemented in the LMGC90 software, based on the Burgers model. This model is able to simulate also the effect of creep relaxation. To validate the proposed contact model, several direct shear tests were performed, experimentally and numerically using the Leutner device. The numerical samples were created using spheres with two particle size distribution, each one identified for two layers from a road structure. Our results show a reasonable agreement between experimental and numerical data regarding the strain-stress evolution curves and the stress levels measured at failure. The proposed model can be used to simulate the mechanical behavior of multi-layer road structure and to study the influence of traffic on road deformation, cracking and particles pull-out induced by traffic loading.
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.
Design and testing of coring bits on drilling lunar rock simulant

NASA Astrophysics Data System (ADS)

Li, Peng; Jiang, Shengyuan; Tang, Dewei; Xu, Bo; Ma, Chao; Zhang, Hui; Qin, Hongwei; Deng, Zongquan

2017-02-01

Coring bits are widely utilized in the sampling of celestial bodies, and their drilling behaviors directly affect the sampling results and drilling security. This paper introduces a lunar regolith coring bit (LRCB), which is a key component of sampling tools for lunar rock breaking during the lunar soil sampling process. We establish the interaction model between the drill bit and rock at a small cutting depth, and the two main influential parameters (forward and outward rake angles) of LRCB on drilling loads are determined. We perform the parameter screening task of LRCB with the aim to minimize the weight on bit (WOB). We verify the drilling load performances of LRCB after optimization, and the higher penetrations per revolution (PPR) are, the larger drilling loads we gained. Besides, we perform lunar soil drilling simulations to estimate the efficiency on chip conveying and sample coring of LRCB. The results of the simulation and test are basically consistent on coring efficiency, and the chip removal efficiency of LRCB is slightly lower than HIT-H bit from simulation. This work proposes a method for the design of coring bits in subsequent extraterrestrial explorations.
Development of a residuum/socket interface simulator for lower limb prosthetics.

PubMed

McGrath, Michael Paul; Gao, Jianliang; Tang, Jinghua; Laszczak, Piotr; Jiang, Liudi; Bader, Dan; Moser, David; Zahedi, Saeed

2017-03-01

Mechanical coupling at the interface between lower limb residua and prosthetic sockets plays an important role in assessing socket fitting and tissue health. However, most research lab-based lower limb prosthetic simulators to-date have implemented a rigid socket coupling. This study describes the fabrication and implementation of a lower limb residuum/socket interface simulator, designed to reproduce the forces and moments present during the key loading phases of amputee walking. An artificial residuum made with model bones encased in silicone was used, mimicking the compliant mechanical loading of a real residuum/socket interface. A 6-degree-of-freedom load cell measured the overall kinetics, having previously been incorporated into an amputee's prosthesis to collect reference data. The developed simulator was compared to a setup where a rigid pylon replaced the artificial residuum. A maximum uniaxial load of 850 N was applied, comparable to the peak vertical ground reaction force component during amputee walking. Load cell outputs from both pylon and residuum setups were compared. During weight acceptance, when including the artificial residuum, compression decreased by 10%, while during push off, sagittal bending and anterior-posterior shear showed a 25% increase and 34% decrease, respectively. Such notable difference by including a compliant residuum further highlighted the need for such an interface simulator. Subsequently, the simulator was adjusted to produce key load cell outputs briefly aligning with those from amputee walking. Force sensing resistors were deployed at load bearing anatomic locations on the residuum/socket interface to measure pressures and were compared to those cited in the literature for similar locations. The development of such a novel simulator provides an objective adjunct, using commonly available mechanical test machines. It could potentially be used to provide further insight into socket design, fit and the complex load transfer mechanics at the residuum/socket interface, as well as to evaluate the structural performance of prostheses.

Biotribological evaluation of artificial disc arthroplasty devices: influence of loading and kinematic patterns during in vitro wear simulation.

PubMed

Grupp, Thomas M; Yue, James J; Garcia, Rolando; Basson, Janet; Schwiesau, Jens; Fritz, Bernhard; Blömer, Wilhelm

2009-01-01

Wear simulation is an essential pre-clinical method to predict the mid- and long-term clinical wear behavior of newly introduced devices for total disc arthroplasty. The main requirement of a suitable method for spinal wear simulation has to be the ability to distinguish between design concepts and allow for a direct comparison of predicate devices. The objective of our study was to investigate the influence of loading and kinematic patterns based on two different protocols for spinal wear simulation (ISO/FDIS 18192-1 (2006) and ASTM F2423-05). In vitro wear simulation was performed with six activ L lumbar artificial disc devices (Aesculap Tuttlingen, Germany). The applied kinematic pattern of movement was multidirectional for ISO (elliptic track) and unidirectional with a curvilinear shape for ASTM. Testing was done for 10 million cycles in the ISO loading mode and afterwards with the same specimens for 5 million cycles according to the ASTM protocol with a customized six-station servohydraulic spinal wear simulator (EndoLab Thansau, Germany). Gravimetrical and geometrical wear assessment, a slide track analysis correlated to an optical surface characterization, and an estimation of particle size and morphology were performed. The gravimetric wear rate for the first 10 million cycles was ISO(initial) = 2.7 +/- 0.3 mg/million cycles. During the ASTM test period (10-15 million cycles) a gravimetric wear rate of 0.14 +/- 0.06 mg/million cycles was estimated. The wear rates between the ISO and ASTM driven simulations differ substantially (approximately 20-fold) and statistical analysis demonstrates a significant difference (p < 0.001) between the test groups. The main explanation of divergency between ISO and ASTM driven wear simulations is the multidirectional pattern of movement described in the ISO document resulting in a cross-shear stress on the polyethylene material. Due to previous retrieval observations, it seems to be very unlikely that a lumbar artificial disc is loaded with a linear wear path.Testing according to ASTM F2423-05 with pure unidirectional motion does not reflect the kinematics of TDA patients' daily activities. Based on our findings it seems to be more reliable to predict the clinical wear behavior of an artificial disc replacement using the ISO/FDIS 18192-1 method.
Biotribological evaluation of artificial disc arthroplasty devices: influence of loading and kinematic patterns during in vitro wear simulation

PubMed Central

Yue, James J.; Garcia, Rolando; Basson, Janet; Schwiesau, Jens; Fritz, Bernhard; Blömer, Wilhelm

2008-01-01

Wear simulation is an essential pre-clinical method to predict the mid- and long-term clinical wear behavior of newly introduced devices for total disc arthroplasty. The main requirement of a suitable method for spinal wear simulation has to be the ability to distinguish between design concepts and allow for a direct comparison of predicate devices. The objective of our study was to investigate the influence of loading and kinematic patterns based on two different protocols for spinal wear simulation (ISO/FDIS 18192-1 (2006) and ASTM F2423-05). In vitro wear simulation was performed with six activ® L lumbar artificial disc devices (Aesculap Tuttlingen, Germany). The applied kinematic pattern of movement was multidirectional for ISO (elliptic track) and unidirectional with a curvilinear shape for ASTM. Testing was done for 10 million cycles in the ISO loading mode and afterwards with the same specimens for 5 million cycles according to the ASTM protocol with a customized six-station servohydraulic spinal wear simulator (EndoLab Thansau, Germany). Gravimetrical and geometrical wear assessment, a slide track analysis correlated to an optical surface characterization, and an estimation of particle size and morphology were performed. The gravimetric wear rate for the first 10 million cycles was ISOinitial = 2.7 ± 0.3 mg/million cycles. During the ASTM test period (10–15 million cycles) a gravimetric wear rate of 0.14 ± 0.06 mg/million cycles was estimated. The wear rates between the ISO and ASTM driven simulations differ substantially (approximately 20-fold) and statistical analysis demonstrates a significant difference (p < 0.001) between the test groups. The main explanation of divergency between ISO and ASTM driven wear simulations is the multidirectional pattern of movement described in the ISO document resulting in a cross-shear stress on the polyethylene material. Due to previous retrieval observations, it seems to be very unlikely that a lumbar artificial disc is loaded with a linear wear path.Testing according to ASTM F2423-05 with pure unidirectional motion does not reflect the kinematics of TDA patients‘ daily activities. Based on our findings it seems to be more reliable to predict the clinical wear behavior of an artificial disc replacement using the ISO/FDIS 18192-1 method. PMID:19050942
Design and fabrication of brazed Rene 41 honeycomb sandwich structural panels for advanced space transportation systems

NASA Technical Reports Server (NTRS)

Hepler, A. K.; Swegle, A. R.

1981-01-01

The design and fabrication of two large brazed Rene 41 honeycomb panels, the establishment of a test plan, the design and fabrication of a test fixture to subject the panels to cyclic thermal gradients and mechanical loads equivalent to those imposed on an advanced space transportation vehicle during its boost and entry trajectories are discussed. The panels will be supported at four points, creating three spans. The outer spans are 45.7 cm (18 in.) and the center span 76.2 cm (30 in). Specimen width is 30.5 cm (12 in.). The panels were primarily designed by boost conditions simulated by subjecting the panels to liquid nitrogen, 77K (-320 F) on one side and 455K (360 F) on the other side and by mechanically imposing loads representing vehicle fuel pressure loads. Entry conditions were simulated by radiant heating to 1034K (1400 F). The test program subjected the panels to 500 boost thermal conditions. Results are presented.
Numerical simulation of unmanned aerial vehicle under centrifugal load and optimization of milling and planing

NASA Astrophysics Data System (ADS)

Chen, Yunsheng; Lu, Xinghua

2018-05-01

The mechanical parts of the fuselage surface of the UAV are easily fractured by the action of the centrifugal load. In order to improve the compressive strength of UAV and guide the milling and planing of mechanical parts, a numerical simulation method of UAV fuselage compression under centrifugal load based on discrete element analysis method is proposed. The three-dimensional discrete element method is used to establish the splitting tensile force analysis model of the UAV fuselage under centrifugal loading. The micro-contact connection parameters of the UAV fuselage are calculated, and the yield tensile model of the mechanical components is established. The dynamic and static mechanical model of the aircraft fuselage milling is analyzed by the axial amplitude vibration frequency combined method. The correlation parameters of the cutting depth on the tool wear are obtained. The centrifugal load stress spectrum of the surface of the UAV is calculated. The meshing and finite element simulation of the rotor blade of the unmanned aerial vehicle is carried out to optimize the milling process. The test results show that the accuracy of the anti - compression numerical test of the UAV is higher by adopting the method, and the anti - fatigue damage capability of the unmanned aerial vehicle body is improved through the milling and processing optimization, and the mechanical strength of the unmanned aerial vehicle can be effectively improved.
Small Wind Research Turbine: Final Report

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

Corbus, D.; Meadors, M.

2005-10-01

The Small Wind Research Turbine (SWRT) project was initiated to provide reliable test data for model validation of furling wind turbines and to help understand small wind turbine loads. This report will familiarize the user with the scope of the SWRT test and support the use of these data. In addition to describing all the testing details and results, the report presents an analysis of the test data and compares the SWRT test data to simulation results from the FAST aeroelastic simulation model.
Biaxial Testing of 2219-T87 Aluminum Alloy Using Cruciform Specimens

NASA Technical Reports Server (NTRS)

Dawicke, D. S.; Pollock, W. D.

1997-01-01

A cruciform biaxial test specimen was designed and seven biaxial tensile tests were conducted on 2219-T87 aluminum alloy. An elastic-plastic finite element analysis was used to simulate each tests and predict the yield stresses. The elastic-plastic finite analysis accurately simulated the measured load-strain behavior for each test. The yield stresses predicted by the finite element analyses indicated that the yield behavior of the 2219-T87 aluminum alloy agrees with the von Mises yield criterion.
A Model Stitching Architecture for Continuous Full Flight-Envelope Simulation of Fixed-Wing Aircraft and Rotorcraft from Discrete Point Linear Models

DTIC Science & Technology

2016-04-01

incorporated with nonlinear elements to produce a continuous, quasi -nonlinear simulation model. Extrapolation methods within the model stitching architecture...Simulation Model, Quasi -Nonlinear, Piloted Simulation, Flight-Test Implications, System Identification, Off-Nominal Loading Extrapolation, Stability...incorporated with nonlinear elements to produce a continuous, quasi -nonlinear simulation model. Extrapolation methods within the model stitching
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
Space shuttle L-tube radiator testing

NASA Technical Reports Server (NTRS)

Phillips, M. A.

1976-01-01

A series of tests were conducted to support the development of the Orbiter Heat Rejection System. The details of the baseline radiator were defined by designing, fabricating, and testing representative hardware. The tests were performed in the Space Environmental Simulation Laboratory Chamber A. An IR source was used to simulate total solar and infrared environmental loads on the flowing shuttle radiators panel. The thermal and mechanical performance of L tube space radiators and their thermal coating were established.
Limit analysis, rammed earth material and Casagrande test

NASA Astrophysics Data System (ADS)

El-Nabouch, Ranime; Pastor, Joseph; Bui, Quoc-Bao; Plé, Olivier

2018-02-01

The present paper is concerned with the simulation of the Casagrande test carried out on a rammed earth material for wall-type structures in the framework of Limit Analysis (LA). In a preliminary study, the material is considered as a homogeneous Coulomb material, and existing LA static and kinematic codes are used for the simulation of the test. In each loading case, static and kinematic bounds coincide; the corresponding exact solution is a two-rigid-block mechanism together with a quasi-constant stress vector and a velocity jump also constant along the interface, for the three loading cases. In a second study, to take into account the influence of compressive loadings related to the porosity of the material, an elliptic criterion (denoted Cohesive Cam-Clay, CCC) is defined based on recent homogenization results about the hollow sphere model for porous Coulomb materials. Finally, original finite element formulations of the static and mixed kinematic methods for the CCC material are developed and applied to the Casagrande test. The results are the same than above, except that this time the velocity jump depends on the compressive loading, which is more realistic but not satisfying fully the experimental observations. Therefore, the possible extensions of this work towards non-standard direct methods are analyzed in the conclusion section.
Details of Side Load Test Data and Analysis for a Truncated Ideal Contour Nozzle and a Parabolic Contour Nozzle

NASA Technical Reports Server (NTRS)

Ruf, Joseph H.; McDaniels, David M.; Brown, Andrew M.

2010-01-01

Two cold flow subscale nozzles were tested for side load characteristics during simulated nozzle start transients. The two test article contours were a truncated ideal and a parabolic. The current paper is an extension of a 2009 AIAA JPC paper on the test results for the same two nozzle test articles. The side load moments were measured with the strain tube approach in MSFC s Nozzle Test Facility. The processing techniques implemented to convert the strain gage signals into side load moment data are explained. Nozzle wall pressure profiles for separated nozzle flow at many NPRs are presented and discussed in detail. The effect of the test cell diffuser inlet on the parabolic nozzle s wall pressure profiles for separated flow is shown. The maximum measured side load moments for the two contours are compared. The truncated ideal contour s peak side load moment was 45% of that of the parabolic contour. The calculated side load moments, via mean-plus-three-standard-deviations at each nozzle pressure ratio, reproduced the characteristics and absolute values of measured maximums for both contours. The effect of facility vibration on the measured side load moments is quantified and the effect on uncertainty is calculated. The nozzle contour designs are discussed and the impact of a minor fabrication flaw in the nozzle contours is explained.
Modeling the biomechanical and injury response of human liver parenchyma under tensile loading.

PubMed

Untaroiu, Costin D; Lu, Yuan-Chiao; Siripurapu, Sundeep K; Kemper, Andrew R

2015-01-01

The rapid advancement in computational power has made human finite element (FE) models one of the most efficient tools for assessing the risk of abdominal injuries in a crash event. In this study, specimen-specific FE models were employed to quantify material and failure properties of human liver parenchyma using a FE optimization approach. Uniaxial tensile tests were performed on 34 parenchyma coupon specimens prepared from two fresh human livers. Each specimen was tested to failure at one of four loading rates (0.01s(-1), 0.1s(-1), 1s(-1), and 10s(-1)) to investigate the effects of rate dependency on the biomechanical and failure response of liver parenchyma. Each test was simulated by prescribing the end displacements of specimen-specific FE models based on the corresponding test data. The parameters of a first-order Ogden material model were identified for each specimen by a FE optimization approach while simulating the pre-tear loading region. The mean material model parameters were then determined for each loading rate from the characteristic averages of the stress-strain curves, and a stochastic optimization approach was utilized to determine the standard deviations of the material model parameters. A hyperelastic material model using a tabulated formulation for rate effects showed good predictions in terms of tensile material properties of human liver parenchyma. Furthermore, the tissue tearing was numerically simulated using a cohesive zone modeling (CZM) approach. A layer of cohesive elements was added at the failure location, and the CZM parameters were identified by fitting the post-tear force-time history recorded in each test. The results show that the proposed approach is able to capture both the biomechanical and failure response, and accurately model the overall force-deflection response of liver parenchyma over a large range of tensile loadings rates. Copyright © 2014 Elsevier Ltd. All rights reserved.
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.
On the dynamic behavior of three readily available soft tissue simulants

NASA Astrophysics Data System (ADS)

Appleby-Thomas, G. J.; Hazell, P. J.; Wilgeroth, J. M.; Shepherd, C. J.; Wood, D. C.; Roberts, A.

2011-04-01

Plate-impact experiments have been employed to investigate the dynamic response of three readily available tissue simulants for ballistic purposes: gelatin, ballistic soap (both subdermal tissue simulants), and lard (adipose layers). All three materials exhibited linear Hugoniot equations-of-state in the US-uP plane. While gelatin behaved hydrodynamically under shock, soap and lard appeared to strengthen under increased loading. Interestingly, the simulants under test appeared to strengthen in a material-independent manner on shock arrival (tentatively attributed to a rearrangement of the amorphous molecular chains under loading). However, material-specific behavior was apparent behind the shock. This behavior appeared to correlate with microstructural complexity, suggesting a steric hindrance effect.
Preliminary Assessment of Seals for Dust Mitigation of Mechanical Components for Lunar Surface Systems

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Handschuh, Michael J.

2010-01-01

Component tests were conducted on spring-loaded Teflon seals to determine their performance in keeping lunar simulant out of mechanical component gearbox, motor, and bearing housings. Baseline tests were run in a dry-room without simulant for 10,000 cycles to determine wear effects of the seal against either anodized aluminum or stainless steel shafts. Repeat tests were conducted using lunar simulants JSC-1A and LHT-2M. Finally, tests were conducted with and without simulant in vacuum at ambient temperature. Preliminary results indicate minimal seal and shaft wear through 10,000 cycles, and more importantly, no simulant was observed to pass through the seal-shaft interface. Future endurance tests are planned at relevant NASA Lunar Surface System architecture shaft sizes and operating conditions.
Draft Plan to Develop Non-Intrusive Load Monitoring Test Protocols

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

Mayhorn, Ebony T.; Sullivan, Greg P.; Petersen, Joseph M.

2015-09-29

This document presents a Draft Plan proposed to develop a common test protocol that can be used to evaluate the performance requirements of Non-Intrusive Load Monitoring. Development on the test protocol will be focused on providing a consistent method that can be used to quantify and compare the performance characteristics of NILM products. Elements of the protocols include specifications for appliances to be used, metrics, instrumentation, and a procedure to simulate appliance behavior during tests. In addition, three priority use cases for NILM will be identified and their performance requirements will specified.
Model-based framework for multi-axial real-time hybrid simulation testing

NASA Astrophysics Data System (ADS)

Fermandois, Gaston A.; Spencer, Billie F.

2017-10-01

Real-time hybrid simulation is an efficient and cost-effective dynamic testing technique for performance evaluation of structural systems subjected to earthquake loading with rate-dependent behavior. A loading assembly with multiple actuators is required to impose realistic boundary conditions on physical specimens. However, such a testing system is expected to exhibit significant dynamic coupling of the actuators and suffer from time lags that are associated with the dynamics of the servo-hydraulic system, as well as control-structure interaction (CSI). One approach to reducing experimental errors considers a multi-input, multi-output (MIMO) controller design, yielding accurate reference tracking and noise rejection. In this paper, a framework for multi-axial real-time hybrid simulation (maRTHS) testing is presented. The methodology employs a real-time feedback-feedforward controller for multiple actuators commanded in Cartesian coordinates. Kinematic transformations between actuator space and Cartesian space are derived for all six-degrees-offreedom of the moving platform. Then, a frequency domain identification technique is used to develop an accurate MIMO transfer function of the system. Further, a Cartesian-domain model-based feedforward-feedback controller is implemented for time lag compensation and to increase the robustness of the reference tracking for given model uncertainty. The framework is implemented using the 1/5th-scale Load and Boundary Condition Box (LBCB) located at the University of Illinois at Urbana- Champaign. To demonstrate the efficacy of the proposed methodology, a single-story frame subjected to earthquake loading is tested. One of the columns in the frame is represented physically in the laboratory as a cantilevered steel column. For realtime execution, the numerical substructure, kinematic transformations, and controllers are implemented on a digital signal processor. Results show excellent performance of the maRTHS framework when six-degrees-of-freedom are controlled at the interface between substructures.
Skylab Rescue Space Vehicle OAT No. 1 Plugs in Test

NASA Technical Reports Server (NTRS)

Jevitt, S. J.

1973-01-01

A test is described which demonstrates the compatibility of the Skylab Rescue Space Vehicle systems, the ground support equipment, and off-site support facilities by proceeding through a simulated launch countdown, liftoff, and flight. The functions of propellant loading, umbilical ejection, holddown arm release, service arm retraction, liftoff, and inflight separation are simulated. An external power source supplies transfer power to internal, and instrument unit commands are simulated by the digital command system. The test outline is presented along with a list of references, intercommunications information, radio frequency matrix, and interface control chart.
Low Cognitive Load and Reduced Arousal Impede Practice Effects on Executive Functioning, Metacognitive Confidence and Decision Making

PubMed Central

Jackson, Simon A.; Kleitman, Sabina; Aidman, Eugene

2014-01-01

The present study investigated the effects of low cognitive workload and the absence of arousal induced via external physical stimulation (motion) on practice-related improvements in executive (inhibitory) control, short-term memory, metacognitive monitoring and decision making. A total of 70 office workers performed low and moderately engaging passenger tasks in two successive 20-minute simulated drives and repeated a battery of decision making and inhibitory control tests three times – before, between and after these drives. For half the participants, visual simulation was synchronised with (moderately arousing) motion generated through LAnd Motion Platform, with vibration levels corresponding to a well-maintained unsealed road. The other half performed the same simulated drive without motion. Participants’ performance significantly improved over the three test blocks, which is indicative of typical practice effects. The magnitude of these improvements was the highest when both motion and moderate cognitive load were present. The same effects declined either in the absence of motion (low arousal) or following a low cognitive workload task, thus suggesting two distinct pathways through which practice-related improvements in cognitive performance may be hampered. Practice, however, degraded certain aspects of metacognitive performance, as participants became less likely to detect incorrect decisions in the decision-making test with each subsequent test block. Implications include consideration of low cognitive load and arousal as factors responsible for performance decline and targets for the development of interventions/strategies in low load/arousal conditions such as autonomous vehicle operations and highway driving. PMID:25549327
Residual Strength Predictions with Crack Buckling

NASA Technical Reports Server (NTRS)

Dawicke, D. S.; Gullerud, A. S.; Dodds, R. H., Jr.; Hampton, R. W.

1999-01-01

Fracture tests were conducted on middle crack tension, M(T), and compact tension, C(T), specimens of varying widths, constructed from 0.063 inch thick sheets of 2024-T3 aluminum alloy. Guide plates were used to restrict out-of-plane displacements in about half of the tests. Analyses using the three-dimensional, elastic-plastic finite element code WARP3D simulated the tests with and without guide plates using a critical CTOA fracture criterion. The experimental results indicate that crack buckling reduced the failure loads by up to 40%. Using a critical CTOA value of 5.5 deg., the WARP3D analyses predicted the failure loads for the tests with guide plates within +/- 10% of the experimentally measured values. For the M(T) tests without guide plates, the WARP3D analyses predicted the failure loads for the 12 and 24 inch tests within 10%, while over predicting the failure loads for the 40 inch wide tests by about 20%.

Contact angle and surface free energy of experimental resin-based dental restorative materials after chewing simulation.

PubMed

Rüttermann, Stefan; Beikler, Thomas; Janda, Ralf

2014-06-01

To investigate contact angle and surface free energy of experimental dental resin composites containing novel delivery systems of polymeric hollow beads and low-surface tension agents after chewing simulation test. A delivery system of novel polymeric hollow beads differently loaded with two low-surface tension agents was used in different amounts to modify commonly formulated experimental dental resin composites. The non-modified resin was used as standard. Surface roughness Ra, contact angle Θ, total surface free energy γS, its apolar γS(LW), polar γS(AB), Lewis acid γS(+) and base γS(-) terms were determined and the results prior to and after chewing simulation test were compared. Significance was p<0.05. After chewing simulation Ra increased, Θ decreased, Ra increased for two test materials and γS decreased or remained constant for the standard or the test materials after chewing simulation. Ra of one test material was higher than of the standard, Θ and γS of the test materials remained lower than of the standard and, indicating their highly hydrophobic character (Θ≈60-75°, γS≈30mJm(-2)). γS(LW), and γS(-) of the test materials were lower than of the standard. Some of the test materials had lower γS(AB) and γS(+) than of the standard. Delivery systems based on novel polymeric hollow beads highly loaded with low-surface tension agents were found to significantly increase contact angle and thus to reduce surface free energy of experimental dental resin composites prior to and after chewing simulation test. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Experimental strength of restorations with fibre posts at different stages, with and without using a simulated ligament.

PubMed

Pérez-González, A; González-Lluch, C; Sancho-Bru, J L; Rodríguez-Cervantes, P J; Barjau-Escribano, A; Forner-Navarro, L

2012-03-01

The aim of this study was to analyse the strength and failure mode of teeth restored with fibre posts under retention and flexural-compressive loads at different stages of the restoration and to analyse whether including a simulated ligament in the experimental setup has any effect on the strength or the failure mode. Thirty human maxillary central incisors were distributed in three different groups to be restored with simulation of different restoration stages (1: only post, 2: post and core, 3: post-core and crown), using Rebilda fibre posts. The specimens were inserted in resin blocks and loaded by means of a universal testing machine until failure under tension (stage 1) and 50º flexion (stages 2-3). Half the specimens in each group were restored using a simulated ligament between root dentine and resin block and the other half did not use this element. Failure in stage 1 always occurred at the post-dentine interface, with a mean failure load of 191·2 N. Failure in stage 2 was located mainly in the core or coronal dentine (mean failure load of 505·9 N). Failure in stage 3 was observed in the coronal dentine (mean failure load 397·4 N). Failure loads registered were greater than expected masticatory loads. Fracture modes were mostly reparable, thus indicating that this post is clinically valid at the different stages of restoration studied. The inclusion of the simulated ligament in the experimental system did not show a statistically significant effect on the failure load or the failure mode. © 2011 Blackwell Publishing Ltd.
Boeing's Dart and Starliner Parachute System Test

NASA Image and Video Library

2018-02-22

Boeing conducted the first in a series of reliability tests of its CST-100 Starliner flight drogue and main parachute system by releasing a long, dart-shaped test vehicle from a C-17 aircraft over Yuma, Arizona. Two more tests are planned using the dart module, as well as three similar reliability tests using a high fidelity capsule simulator designed to simulate the CST-100 Starliner capsule’s exact shape and mass. In both the dart and capsule simulator tests, the test spacecraft are released at various altitudes to test the parachute system at different deployment speeds, aerodynamic loads, and or weight demands. Data collected from each test is fed into computer models to more accurately predict parachute performance and to verify consistency from test to test.
Simulation of streamflow and water quality in the Leon Creek watershed, Bexar County, Texas, 1997-2004

USGS Publications Warehouse

Ockerman, Darwin J.; Roussel, Meghan C.

2009-01-01

The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers and the San Antonio River Authority, configured, calibrated, and tested a Hydrological Simulation Program ? FORTRAN watershed model for the approximately 238-square-mile Leon Creek watershed in Bexar County, Texas, and used the model to simulate streamflow and water quality (focusing on loads and yields of selected constituents). Streamflow in the model was calibrated and tested with available data from five U.S. Geological Survey streamflow-gaging stations for 1997-2004. Simulated streamflow volumes closely matched measured streamflow volumes at all streamflow-gaging stations. Total simulated streamflow volumes were within 10 percent of measured values. Streamflow volumes are greatly influenced by large storms. Two months that included major floods accounted for about 50 percent of all the streamflow measured at the most downstream gaging station during 1997-2004. Water-quality properties and constituents (water temperature, dissolved oxygen, suspended sediment, dissolved ammonia nitrogen, dissolved nitrate nitrogen, and dissolved and total lead and zinc) in the model were calibrated using available data from 13 sites in and near the Leon Creek watershed for varying periods of record during 1992-2005. Average simulated daily mean water temperature and dissolved oxygen at the most downstream gaging station during 1997-2000 were within 1 percent of average measured daily mean water temperature and dissolved oxygen. Simulated suspended-sediment load at the most downstream gaging station during 2001-04 (excluding July 2002 because of major storms) was 77,700 tons compared with 74,600 tons estimated from a streamflow-load regression relation (coefficient of determination = .869). Simulated concentrations of dissolved ammonia nitrogen and dissolved nitrate nitrogen closely matched measured concentrations after calibration. At the most downstream gaging station, average simulated monthly mean concentrations of dissolved ammonia and nitrate concentrations during 1997-2004 were 0.03 and 0.37 milligram per liter, respectively. For the most downstream station, the measured and simulated concentrations of dissolved and total lead and zinc for stormflows during 1993-97 after calibration do not match particularly closely. For base-flow conditions during 1997-2004 at the most downstream station, the simulated/measured match is better. For example, median simulated concentration of total lead (for 2,041 days) was 0.96 microgram per liter, and median measured concentration (for nine samples) of total lead was 1.0 microgram per liter. To demonstrate an application of the Leon Creek watershed model, streamflow constituent loads and yields for suspended sediment, dissolved nitrate nitrogen, and total lead were simulated at the mouth of Leon Creek (outlet of the watershed) for 1997-2004. The average suspended-sediment load was 51,800 tons per year. The average suspended-sediment yield was 0.34 ton per acre per year. The average load of dissolved nitrate at the outlet of the watershed was 802 tons per year. The corresponding yield was 10.5 pounds per acre per year. The average load of lead at the outlet was 3,900 pounds per year. The average lead yield was 0.026 pound per acre per year. The degree to which available rainfall data represent actual rainfall is potentially the most serious source of measurement error associated with the Leon Creek model. Major storms contribute most of the streamflow loads for certain constituents. For example, the three largest stormflows contributed about 64 percent of the entire suspended-sediment load at the most downstream station during 1997-2004.
40 CFR 86.000-2 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... with air conditioning operating in an environmental test cell by adding the air conditioning compressor... simulates testing with air conditioning operating in an environmental test cell by adding a heat load to the... appendix I, paragraph (a), of this part. Environmental test cell means a test cell capable of wind-speed...
40 CFR 86.000-2 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... with air conditioning operating in an environmental test cell by adding the air conditioning compressor... simulates testing with air conditioning operating in an environmental test cell by adding a heat load to the... appendix I, paragraph (a), of this part. Environmental test cell means a test cell capable of wind-speed...
40 CFR 86.000-2 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... with air conditioning operating in an environmental test cell by adding the air conditioning compressor... simulates testing with air conditioning operating in an environmental test cell by adding a heat load to the... appendix I, paragraph (a), of this part. Environmental test cell means a test cell capable of wind-speed...
Effect of Variation of Speed Limits on Intercity Bus Fuel Consumption, Coach and Driver Utilization, and Corporate Profitability

DOT National Transportation Integrated Search

1975-11-01

The effect of speed limit and passenger load on fuel consumption was determined using actual intercity buses with simulated passenger loads over different types of terrain. In addition to road tests, laboratory type measurements were made on four int...
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...
HiL simulation in biomechanics: a new approach for testing total joint replacements.

PubMed

Herrmann, Sven; Kaehler, Michael; Souffrant, Robert; Rachholz, Roman; Zierath, János; Kluess, Daniel; Mittelmeier, Wolfram; Woernle, Christoph; Bader, Rainer

2012-02-01

Instability of artificial joints is still one of the most prevalent reasons for revision surgery caused by various influencing factors. In order to investigate instability mechanisms such as dislocation under reproducible, physiologically realistic boundary conditions, a novel test approach is introduced by means of a hardware-in-the-loop (HiL) simulation involving a highly flexible mechatronic test system. In this work, the underlying concept and implementation of all required units is presented enabling comparable investigations of different total hip and knee replacements, respectively. The HiL joint simulator consists of two units: a physical setup composed of a six-axes industrial robot and a numerical multibody model running in real-time. Within the multibody model, the anatomical environment of the considered joint is represented such that the soft tissue response is accounted for during an instability event. Hence, the robot loads and moves the real implant components according to the information provided by the multibody model while transferring back the position and resisting moment recorded. Functionality of the simulator is proved by testing the underlying control principles, and verified by reproducing the dislocation process of a standard total hip replacement. HiL simulations provide a new biomechanical testing tool for analyzing different joint replacement systems with respect to their instability behavior under realistic movements and physiological load conditions. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.
Quasi-Static Indentation Analysis of Carbon-Fiber Laminates.

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

Briggs, Timothy; English, Shawn Allen; Nelson, Stacy Michelle

2015-12-01

A series of quasi - static indentation experiments are conducted on carbon fiber reinforced polymer laminates with a systematic variation of thicknesses and fixture boundary conditions. Different deformation mechanisms and their resulting damage mechanisms are activated b y changing the thickn ess and boundary conditions. The quasi - static indentation experiments have been shown to achieve damage mechanisms similar to impact and penetration, however without strain rate effects. The low rate allows for the detailed analysis on the load response. Moreover, interrupted tests allow for the incremental analysis of various damage mechanisms and pr ogressions. The experimentally tested specimens aremore » non - destructively evaluated (NDE) with optical imaging, ultrasonics and computed tomography. The load displacement responses and the NDE are then utilized in numerical simulations for the purpose of model validation and vetting. The accompanying numerical simulation work serves two purposes. First, the results further reveal the time sequence of events and the meaning behind load dro ps not clear from NDE . Second, the simulations demonstrate insufficiencies in the code and can then direct future efforts for development.« less
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.
Evaluation of shuttle solid rocket booster case materials. Corrosion and stress corrosion susceptibility of several high temperature materials

NASA Technical Reports Server (NTRS)

Pionke, L. J.; Garland, K. C.

1973-01-01

Candidate alloys for the Shuttle Solid Rocket Booster (SRB) case were tested under simulated service conditions to define subcritical flaw growth behavior under both sustained and cyclic loading conditions. The materials evaluated were D6AC and 18 Ni maraging steel, both heat treated to a nominal yield strength of 1380 MN/sq m (200 ksi). The sustained load tests were conducted by exposing precracked, stressed specimens of both alloys to alternate immersion in synthetic sea water. It was found that the corrosion and stress corrosion resistance of the 18 Ni maraging steel were superior to that of the D6AC steel under these test conditions. It was also found that austenitizing temperature had little influence on the threshold stress intensity of the D6AC. The cyclic tests were conducted by subjecting precracked surface-flawed specimens of both alloys to repeated load/thermal/environmental profiles which were selected to simulate the SRB missions. It was found that linear removal operations that involve heating to 589 K (600 F) cause a decrease in cyclic life of D6AC steel relative to those tests conducted with no thermal cycling.
Wake-Induced Aerodynamics on a Trailing Aircraft

NASA Technical Reports Server (NTRS)

Mendenhall, Michael R.; Lesieutre, Daniel J.; Kelly, Michael J.

2016-01-01

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

NASA Astrophysics Data System (ADS)

Resnyansky, A. D.; Brown, E. N.; Trujillo, C. P.; Gray, G. T.

2017-01-01

Use of polymers in defense, aerospace and industrial applications under extreme loading conditions makes prediction of the behavior of these materials very important. Crucial to this is knowledge of the physical damage response in association with phase transformations during loading and the ability to predict this via multi-phase simulation accounting for thermodynamical non-equilibrium and strain rate sensitivity. The current work analyzes Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) experiments on polytetrafluoroethylene (PTFE). In particular, the phase transition during loading and subsequent tension are analyzed using a two-phase rate sensitive material model implemented in the CTH hydrocode. The calculations are compared with experimental high-speed photography. Deformation patterns and their link with changing loading modes are analyzed numerically and correlated to the test observations. It is concluded that the phase transformation is not as critical to the response of PTFE under Dyn-Ten-Ext loading as it is during the Taylor rod impact testing.
Zero-Gravity Locomotion Simulators: New Ground-Based Analogs for Microgravity Exercise Simulation

NASA Technical Reports Server (NTRS)

Perusek, Gail P.; DeWitt, John K.; Cavanagh, Peter R.; Grodsinsky, Carlos M.; Gilkey, Kelly M.

2007-01-01

Maintaining health and fitness in crewmembers during space missions is essential for preserving performance for mission-critical tasks. NASA's Exercise Countermeasures Project (ECP) provides space exploration exercise hardware and monitoring requirements that lead to devices that are reliable, meet medical, vehicle, and habitat constraints, and use minimal vehicle and crew resources. ECP will also develop and validate efficient exercise prescriptions that minimize daily time needed for completion of exercise yet maximize performance for mission activities. In meeting these mission goals, NASA Glenn Research Center (Cleveland, OH, USA), in collaboration with the Cleveland Clinic (Cleveland, Ohio, USA), has developed a suite of zero-gravity locomotion simulators and associated technologies to address the need for ground-based test analog capability for simulating in-flight (microgravity) and surface (partial-gravity) exercise to advance the health and safety of astronaut crews and the next generation of space explorers. Various research areas can be explored. These include improving crew comfort during exercise, and understanding joint kinematics and muscle activation pattern differences relative to external loading mechanisms. In addition, exercise protocol and hardware optimization can be investigated, along with characterizing system dynamic response and the physiological demand associated with advanced exercise device concepts and performance of critical mission tasks for Exploration class missions. Three zero-gravity locomotion simulators are currently in use and the research focus for each will be presented. All of the devices are based on a supine subject suspension system, which simulates a reduced gravity environment by completely or partially offloading the weight of the exercising test subject s body. A platform for mounting treadmill is positioned perpendicularly to the test subject. The Cleveland Clinic Zero-g Locomotion Simulator (ZLS) utilizes a pneumatic subject load device to apply a near constant gravity-replacement load to the test subject during exercise, and is currently used in conjunction with the General Clinical Research Center for evaluating exercise protocols using a bedrest analog. The enhanced ZLS (eZLS) at NASA Glenn Research Center features an offloaded treadmill that floats on a thin film of air and interfaces to a force reaction frame via variably-compliant isolators, or vibration isolation system. The isolators can be configured to simulate compliant interfaces to the vehicle, which affects mechanical loading to crewmembers during exercise, and has been used to validate system dynamic models for new countermeasures equipment designs, such as the second International Space Station treadmill slated for use in 2010. In the eZLS, the test subject and exercise device can be pitched at the appropriate angle for partial gravity simulations, such as lunar gravity (1/6th earth gravity). On both the eZLS and the NASA-Johnson Space Center standalone ZLS installed at the University of Texas Medical Branch in Galveston, Texas, USA, the subject's body weight relative to the treadmill is controlled via a linear motor subject load device (LM-SLD). The LM-SLD employs a force-feedback closed-loop control system to provide a relatively constant force to the test subject during locomotion, and is set and verified for subject safety prior to each session. Locomotion data were collected during parabolic flight and on the eZLS. The purpose was to determine the similarities and differences between locomotion in actual and simulated microgravity. Subjects attained greater amounts of hip flexion during walking and running during parabolic flight. During running, subjects had greater hip range of motion. Trunk motion was significantly less on the eZLS than during parabolic flight. Peak impact forces, loading rate, and impulse were greater on the eZLS than during parabolic while walking with a low external load (EL) and rning with a high EL. Activation timing differences existed between locations in all muscles except for the rectus femoris. The tibialis anterior and gluteus maximus were active for longer durations on the eZLS than in parabolic flight during walking. Ground reaction forces were greater with the LM-SLD than with bungees during eZLS locomotion. While the eZLS serves as a ground-based analog, researchers should be aware that subtle, but measurable, differences in kinematics and leg musculature activities exist between the environments. Aside from space applications, zero-gravity locomotion simulators may help medical researchers in the future with development of rehabilitative or therapeutic protocols for injured or ill patients. Zero-gravity locomotion simulators may be used as a ground-based test bed to support future missions for space exploration, and eventually may be used to simulate planetary locomotion in partial gravity environments, including the Moon and Mars. Figure: Zero-gravity Locomotion Simulator at the Cleveland Clinic, Cleveland, Ohio, USA
Simulated hail impact testing of photovoltaic solar panels

NASA Technical Reports Server (NTRS)

Moore, D.; Wilson, A.; Ross, R.

1978-01-01

Techniques used to simulate and study the effect of hail on photovoltaic solar panels are described. Simulated hail stones (frozen ice spheres projected at terminal velocity) or steel balls were applied by air guns, gravity drop, or static loading. Tests with simulated hail and steel balls yielded different results. The impact strength of 10 commercially available flat-plate photovoltaic modules was tested. It was found that none of the six panel designs incorporating clear potting silicone material as the outermost layer remained undamaged by 1-in. simulated hailstones, while a photovoltaic module equipped with a 0.188-in.-thick acrylic cover sheet would be able to withstand the impact of a 2-in.-diameter hailstone.
Cryogenic properties of dispersion strengthened copper for high magnetic fields

NASA Astrophysics Data System (ADS)

Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

2014-01-01

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.
Hydrogen loading system development and evaluation of tritiated substrates to optimize performance in tritium based betavoltaics

NASA Astrophysics Data System (ADS)

Adams, Thomas E.

State-of-the-art hydrogen loading system onto thin metallic films based on differential pressure in calibrated chambers has been developed for conditions pressures and temperatures up to 69 bar and 500°C, respectively. Experiments on hydrogen loading on to palladium films of thickness 50 and 250 nm were conducted at pressure ranging from 0.2 bar to 10 bar at temperature 310°C. For first time film hydrogen loading was carried out at 1 bar and at room temperature which temperature. Beta flux exiting surface of metal tritide films has been modeled with MC-SET (Monte Carlo Simulation of Electron Trajectories in solids). Surface beta flux simulations have been improved to account for density changes from tritium loading and decay. Simulation results indicate a 300 nm slab of MgT2 has a surface flux three times higher than in ScT2, and six times higher than in TiT2. Commercial betavoltaic cells were tested at different temperature environment for their evaluation and characterization.

A seat cushion to provide realistic acceleration cues for aircraft simulators

NASA Technical Reports Server (NTRS)

Ashworth, B. R.

1976-01-01

A seat cushion to provide acceleration cues for aircraft simulator pilots was built, performance tested, and evaluated. The four cell seat, using a thin air cushion with highly responsive pressure control, attempts to reproduce the same events which occur in an aircraft seat under acceleration loading. The pressure controller provides seat cushion responses which are considered adequate for current high performance aircraft simulations. The initial tests of the seat cushions have resulted in excellent pilot opinion of the cushion's ability to provide realistic and useful cues to the simulator pilot.
Power Hardware-in-the-Loop (PHIL) Testing Facility for Distributed Energy Storage (Poster)

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

Neubauer.J.; Lundstrom, B.; Simpson, M.

2014-06-01

The growing deployment of distributed, variable generation and evolving end-user load profiles presents a unique set of challenges to grid operators responsible for providing reliable and high quality electrical service. Mass deployment of distributed energy storage systems (DESS) has the potential to solve many of the associated integration issues while offering reliability and energy security benefits other solutions cannot. However, tools to develop, optimize, and validate DESS control strategies and hardware are in short supply. To fill this gap, NREL has constructed a power hardware-in-the-loop (PHIL) test facility that connects DESS, grid simulator, and load bank hardware to a distributionmore » feeder simulation.« less
Nuclear fuel management optimization using genetic algorithms

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

DeChaine, M.D.; Feltus, M.A.

1995-07-01

The code independent genetic algorithm reactor optimization (CIGARO) system has been developed to optimize nuclear reactor loading patterns. It uses genetic algorithms (GAs) and a code-independent interface, so any reactor physics code (e.g., CASMO-3/SIMULATE-3) can be used to evaluate the loading patterns. The system is compared to other GA-based loading pattern optimizers. Tests were carried out to maximize the beginning of cycle k{sub eff} for a pressurized water reactor core loading with a penalty function to limit power peaking. The CIGARO system performed well, increasing the k{sub eff} after lowering the peak power. Tests of a prototype parallel evaluation methodmore » showed the potential for a significant speedup.« less
Analysis, testing and verification of the behavior of composite pavements under Florida conditions using a heavy vehicle simulator

NASA Astrophysics Data System (ADS)

Tapia Gutierrez, Patricio Enrique

Whitetopping (WT) is a rehabilitation method to resurface deteriorated asphalt pavements. While some of these composite pavements have performed very well carrying heavy load, other have shown poor performance with early cracking. With the objective of analyzing the applicability of WT pavements under Florida conditions, a total of nine full-scale WT test sections were constructed and tested using a Heavy Vehicle Simulator (HVS) in the APT facility at the FDOT Material Research Park. The test sections were instrumented to monitor both strain and temperature. A 3-D finite element model was developed to analyze the WT test sections. The model was calibrated and verified using measured FWD deflections and HVS load-induced strains from the test sections. The model was then used to evaluate the potential performance of these test sections under critical temperature-load condition in Florida. Six of the WT pavement test sections had a bonded concrete-asphalt interface by milling, cleaning and spraying with water the asphalt surface. This method produced excellent bonding at the interface, with shear strength of 195 to 220 psi. Three of the test sections were intended to have an unbonded concrete-asphalt interface by applying a debonding agent in the asphalt surface. However, shear strengths between 119 and 135 psi and a careful analysis of the strain and the temperature data indicated a partial bond condition. The computer model was able to satisfactorily model the behavior of the composite pavement by mainly considering material properties from standard laboratory tests and calibrating the spring elements used to model the interface. Reasonable matches between the measured and the calculated strains were achieved when a temperature-dependent AC elastic modulus was included in the analytical model. The expected numbers of repetitions of the 24-kip single axle loads at critical thermal condition were computed for the nine test sections based on maximum tensile stresses and fatigue theory. The results showed that 4" slabs can be used for heavy loads only for low-volume traffic. To withstand the critical load without fear of fatigue failure, 6" slabs and 8" slabs would be needed for joint spacings of 4' and 6', respectively.
Predicting the Effects of Powder Feeding Rates on Particle Impact Conditions and Cold Spray Deposited Coatings

NASA Astrophysics Data System (ADS)

Ozdemir, Ozan C.; Widener, Christian A.; Carter, Michael J.; Johnson, Kyle W.

2017-10-01

As the industrial application of the cold spray technology grows, the need to optimize both the cost and the quality of the process grows with it. Parameter selection techniques available today require the use of a coupled system of equations to be solved to involve the losses due to particle loading in the gas stream. Such analyses cause a significant increase in the computational time in comparison with calculations with isentropic flow assumptions. In cold spray operations, engineers and operators may, therefore, neglect the effects of particle loading to simplify the multiparameter optimization process. In this study, two-way coupled (particle-fluid) quasi-one-dimensional fluid dynamics simulations are used to test the particle loading effects under many potential cold spray scenarios. Output of the simulations is statistically analyzed to build regression models that estimate the changes in particle impact velocity and temperature due to particle loading. This approach eases particle loading optimization for more complete analysis on deposition cost and time. The model was validated both numerically and experimentally. Further numerical analyses were completed to test the particle loading capacity and limitations of a nozzle with a commonly used throat size. Additional experimentation helped document the physical limitations to high-rate deposition.
The effects of individual differences, prior experience and cognitive load on the transfer of dynamic decision-making performance.

PubMed

Nicholson, Brad; O'Hare, David

2014-01-01

Situational awareness is recognised as an important factor in the performance of individuals and teams in dynamic decision-making (DDM) environments (Salmon et al. 2014 ). The present study was designed to investigate whether the scores on the WOMBAT™ Situational Awareness and Stress Tolerance Test (Roscoe and North 1980 ) would predict the transfer of DDM performance from training under different levels of cognitive load to a novel situation. Participants practised a simulated firefighting task under either low or high conditions of cognitive load and then performed a (transfer) test in an alternative firefighting environment under an intermediate level of cognitive load. WOMBAT™ test scores were a better predictor of DDM performance than scores on the Raven Matrices. Participants with high WOMBAT™ scores performed better regardless of their training condition. Participants with recent gaming experience who practised under low cognitive load showed better practice phase performance but worse transfer performance than those who practised under high cognitive load. The relationship between task experience, situational awareness ability, cognitive load and the transfer of dynamic decision-making (DDM) performance was investigated. Results showed that the WOMBAT™ test predicted transfer of DDM performance regardless of task cognitive load. The effects of cognitive load on performance varied according to previous task-relevant experience.
Testing and Analysis of Composite Skin/Stringer Debonding Under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Cvitkovich, Michael K.; OBrien, T. Kevin; Minguet, Pierre J.

1999-01-01

Damage mechanisms in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out- of-plane) loading conditions were examined. Specimens consisted of a tapered composite flange bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending . For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. The observations showed that, for all three load cases, failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from the skin. A two-dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, principal stresses exceeded the transverse strength of the material in the flange area. Additionally, delaminations of various lengths were simulated in two locations where delaminations were observed. The analyses showed that unstable delamination propagation is likely to occur in one location at the loads corresponding to matrix ply crack initiation for all three load cases.
Evaluation of wheelchair drop seat crashworthiness.

PubMed

Bertocci, G; Ha, D; van Roosmalen, L; Karg, P; Deemer, E

2001-05-01

Wheelchair seating crash performance is critical to protecting wheelchair users who remain seated in their wheelchairs during transportation. Relying upon computer simulation and sled testing seat loads associated with a 20 g/48 kph (20 g/30 mph) frontal impact and 50th percentile male occupant were estimated to develop test criteria. Using a static test setup we evaluated the performance of various types of commercially available drop seats against the loading test criteria. Five different types of drop seats (two specimens each) constructed of various materials (i.e. plastics, plywood, metal) were evaluated. Two types of drop seats (three of the total 10 specimens) met the 16650 N (3750 lb) frontal impact test criteria. While additional validation of the test protocol is necessary, this study suggests that some drop seat designs may be incapable of withstanding crash level loads.
Electrolyzers Enhancing Flexibility in Electric Grids

DOE PAGES

Mohanpurkar, Manish; Luo, Yusheng; Terlip, Danny; ...

2017-11-10

This paper presents a real-time simulation with a hardware-in-the-loop (HIL)-based approach for verifying the performance of electrolyzer systems in providing grid support. Hydrogen refueling stations may use electrolyzer systems to generate hydrogen and are proposed to have the potential of becoming smarter loads that can proactively provide grid services. On the basis of experimental findings, electrolyzer systems with balance of plant are observed to have a high level of controllability and hence can add flexibility to the grid from the demand side. A generic front end controller (FEC) is proposed, which enables an optimal operation of the load on themore » basis of market and grid conditions. This controller has been simulated and tested in a real-time environment with electrolyzer hardware for a performance assessment. It can optimize the operation of electrolyzer systems on the basis of the information collected by a communication module. Real-time simulation tests are performed to verify the performance of the FEC-driven electrolyzers to provide grid support that enables flexibility, greater economic revenue, and grid support for hydrogen producers under dynamic conditions. In conclusion, the FEC proposed in this paper is tested with electrolyzers, however, it is proposed as a generic control topology that is applicable to any load.« less
A flight-test and simulation evaluation of the longitudinal final approach and landing performance of an automatic system for a light wing loading STOL aircraft

NASA Technical Reports Server (NTRS)

Brown, S. C.; Hardy, G. H.; Hindson, W. S.

1983-01-01

As part of a comprehensive flight-test program of STOL operating systems for the terminal area, an automatic landing system was developed and evaluated for a light wing loading turboprop aircraft. The aircraft utilized an onboard advanced digital avionics system. Flight tests were conducted at a facility that included a STOL runway site with a microwave landing system. Longitudinal flight-test results were presented and compared with available (basically CTOL) criteria. These comparisons were augmented by results from a comprehensive simulation of the controlled aircraft which included representations of navigation errors that were encountered in flight and atmospheric disturbances. Acceptable performance on final approach and at touchdown was achieved by the autoland (automatic landing) system for the moderate winds and turbulence conditions encountered in flight. However, some touchdown performance goals were marginally achieved, and simulation results suggested that difficulties could be encountered in the presence of more extreme atmospheric conditions. Suggestions were made for improving performance under those more extreme conditions.
Installation of TVC Actuators in a Two Axis Inertial Load Simulator Test Stand

NASA Technical Reports Server (NTRS)

Dziubanek, Adam

2013-01-01

This paper is about the installation of Space Shuttle Main Engines (SSME) actuators in the new Two Axis Inertial Load Simulator (ILS) at MSFC. The new test stand will support the core stage of the Space Launch System (SLS). Because of the unique geometry of the new test stand standard actuator installation procedures will not work. I have been asked to develop a design on how to install the actuators into the new test stand. After speaking with the engineers and technicians I have created a possible design solution. Using Pro Engineer design software and running my own stress calculations I have proven my design is feasible. I have learned how to calculate the stresses my design will see from this task. From the calculations I have learned I have over built the apparatus. I have also expanded my knowledge of Pro Engineer and was able to create a model of my idea.
Testing a Regenerative Carbon Dioxide and Moisture Removal Technology

NASA Technical Reports Server (NTRS)

Barta, Daniel J.; Button, Amy; Sweterlitsch, Jeffrey J.; Curley, Suzanne

2010-01-01

The National Aeronautics and Space Administration supported the development of a new vacuum-desorbed regenerative carbon dioxide and humidity control technology for use in short duration human spacecraft. The technology was baselined for use in the Orion Crew Exploration Vehicle s Environmental Control and Life Support System (ECLSS). Termed the Carbon Dioxide And Moisture Removal Amine Swing-bed (CAMRAS), the unit was developed by Hamilton Sundstrand and has undergone extensive testing at Johnson Space Center. The tests were performed to evaluate performance characteristics under range of operating conditions and human loads expected in future spacecraft applications, as part of maturation to increase its readiness for flight. Early tests, conducted at nominal atmospheric pressure, used human metabolic simulators to generate loads, with later tests making us of human test subjects. During these tests many different test cases were performed, involving from 1 to 6 test subjects, with different activity profiles (sleep, nominal and exercise). These tests were conducted within the airlock portion of a human rated test chamber sized to simulate the Orion cabin free air volume. More recently, a test was completed that integrated the CAMRAS with a simulated suit loop using prototype umbilicals and was conducted at reduced atmospheric pressure and elevated oxygen levels. This paper will describe the facilities and procedures used to conduct these and future tests, and provide a summary of findings.
Engineering of a multi-station shoulder simulator.

PubMed

Smith, Simon L; Li, Lisa; Joyce, Thomas J

2016-05-01

This work aimed to engineer a multi-station shoulder simulator in order to wear test shoulder prostheses using recognized shoulder activities of daily living. A bespoke simulator was designed, built and subject to commissioning trials before a first wear test was conducted. Five JRI Orthopaedics Reverse Shoulder VAIOS 42 mm prostheses were tested for 2.0 million cycles and a mean wear rate and standard deviation of 14.2 ± 2.1 mm(3)/10(6) cycles measured for the polymeric glenoid components. This result when adjusted for prostheses diameters and test conditions showed excellent agreement with results from hip simulator studies of similar materials in a lubricant of bovine serum. The Newcastle Shoulder Simulator is the first multi-station shoulder simulator capable of applying physiological motion and loading for typical activities of daily living. © IMechE 2016.
Sex-Based Differences in Knee Kinetics With Anterior Cruciate Ligament Strain on Cadaveric Impact Simulations

PubMed Central

Schilaty, Nathan D.; Bates, Nathaniel A.; Nagelli, Christopher; Krych, Aaron J.; Hewett, Timothy E.

2018-01-01

Background: Females are at an increased risk of sustaining noncontact knee ligament injuries as compared with their male counterparts. The kinetics that load the anterior cruciate ligament (ACL) are still under dispute in the literature. Purpose/Hypothesis: The purpose of this study was to determine whether there are differences in knee kinetics between the sexes that lead to greater ACL strain in females when similar external loads are applied during a simulated drop vertical jump landing task. It was hypothesized that female limbs would demonstrate significant differences in knee abduction moment that predispose females to ACL injury when compared with males. Study Design: Controlled laboratory study. Methods: Motion analysis data of 67 athletes who performed a drop vertical jump were collected. The kinematic and kinetic data were used to categorize tertiles of relative risk, and these values were input into a cadaveric impact simulator to assess ligamentous loads during the simulated landing task. Uni- and multiaxial load cells and differential variable reluctance transducer strain sensors were utilized to collect kinetic data and maximum ACL strain for analysis. Conditions of external loads applied to the cadaveric limbs were systematically varied and randomized. Data were analyzed with 2-way repeated-measures analysis of variance and the Fisher exact test. Results: Five kinetic parameters were evaluated. Of the 5 kinetic variables, only knee abduction moment (KAM) demonstrated significant differences in females as compared with males (F 1,136 = 4.398, P = .038). When normalized to height and weight, this difference between males and females increased in significance (F 1,136 = 7.155, P = .008). Compared with males, females exhibited a 10.3-N·m increased knee abduction torque at 66 milliseconds postimpact and a 22.3-N·m increased abduction torque at 100 milliseconds postimpact. For loading condition, the condition of “maximum ACL strain” demonstrated a maximum difference of 54.3-N·m increased abduction torque and 74.5-N·m increased abduction torque at 66 milliseconds postimpact. Conclusion: Under the tested conditions, increased external loads led to increased medial knee translation force, knee abduction moment, and external knee moment. Females exhibited greater forces and moments at the knee, especially at KAM, when loaded in similar conditions. As these KAM loads are associated with increased load and strain on the ACL, the sex-based differences observed in the present study may account for a portion of the underlying mechanics that predispose females to ACL injury as compared with males in a controlled simulated athletic task. Clinical Relevance: KAM increases strain to the ACL under clinically representative loading. Additionally, this work establishes the biomechanical characteristics of knee loading between sexes. PMID:29568787
Sex-Based Differences in Knee Kinetics With Anterior Cruciate Ligament Strain on Cadaveric Impact Simulations.

PubMed

Schilaty, Nathan D; Bates, Nathaniel A; Nagelli, Christopher; Krych, Aaron J; Hewett, Timothy E

2018-03-01

Females are at an increased risk of sustaining noncontact knee ligament injuries as compared with their male counterparts. The kinetics that load the anterior cruciate ligament (ACL) are still under dispute in the literature. The purpose of this study was to determine whether there are differences in knee kinetics between the sexes that lead to greater ACL strain in females when similar external loads are applied during a simulated drop vertical jump landing task. It was hypothesized that female limbs would demonstrate significant differences in knee abduction moment that predispose females to ACL injury when compared with males. Controlled laboratory study. Motion analysis data of 67 athletes who performed a drop vertical jump were collected. The kinematic and kinetic data were used to categorize tertiles of relative risk, and these values were input into a cadaveric impact simulator to assess ligamentous loads during the simulated landing task. Uni- and multiaxial load cells and differential variable reluctance transducer strain sensors were utilized to collect kinetic data and maximum ACL strain for analysis. Conditions of external loads applied to the cadaveric limbs were systematically varied and randomized. Data were analyzed with 2-way repeated-measures analysis of variance and the Fisher exact test. Five kinetic parameters were evaluated. Of the 5 kinetic variables, only knee abduction moment (KAM) demonstrated significant differences in females as compared with males ( F 1,136 = 4.398, P = .038). When normalized to height and weight, this difference between males and females increased in significance ( F 1,136 = 7.155, P = .008). Compared with males, females exhibited a 10.3-N·m increased knee abduction torque at 66 milliseconds postimpact and a 22.3-N·m increased abduction torque at 100 milliseconds postimpact. For loading condition, the condition of "maximum ACL strain" demonstrated a maximum difference of 54.3-N·m increased abduction torque and 74.5-N·m increased abduction torque at 66 milliseconds postimpact. Under the tested conditions, increased external loads led to increased medial knee translation force, knee abduction moment, and external knee moment. Females exhibited greater forces and moments at the knee, especially at KAM, when loaded in similar conditions. As these KAM loads are associated with increased load and strain on the ACL, the sex-based differences observed in the present study may account for a portion of the underlying mechanics that predispose females to ACL injury as compared with males in a controlled simulated athletic task. KAM increases strain to the ACL under clinically representative loading. Additionally, this work establishes the biomechanical characteristics of knee loading between sexes.
40 CFR 1066.805 - Road-load power, test weight, and inertia weight class determination.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... (a) Simulate a vehicle's test weight on the dynamometer using the appropriate equivalent test weight shown in Table 1 of this section. Equivalent test weights are established according to each vehicle's... weight class corresponding to each equivalent test weight; the inertia weight class allows for grouping...
In vitro digestion of curcuminoid-loaded lipid nanoparticles

NASA Astrophysics Data System (ADS)

Noack, Andreas; Oidtmann, Johannes; Kutza, Johannes; Mäder, Karsten

2012-09-01

Curcuminoid-loaded lipid nanoparticles were produced by melt homogenization. The used lipid matrices were medium chain triglycerides, trimyristin (TM), and tristearin. The mean particle size of the preparations was between 130 and 180 nm. The incorporated curcuminoids revealed a good stability over a period of 12 months. The curcuminoid-loaded lipid nanoparticles were intended for the oral delivery of curcuminoids. Therefore, the fate of the triglyceride matrix in simulated gastric and simulated intestinal media under the influence of pepsin and pancreatin, respectively, was assessed. The degradation of the triglycerides was monitored by the pH-stat method and with high performance thin layer chromatography in connection with spectrodensitometry to quantify the different lipid fractions. The TM nanoparticles were not degraded in simulated gastric fluid (SGF), but the decomposition of the triglyceride matrix was rapid in the intestinal media. The digestion process was faster in the simulated fed state medium compared to the simulated fasted state medium. Additionally, the stability of the incorporated drug was tested in the respective physiological media. The curcuminoids showed an overall good stability in the different test media. The release of the curcuminoids from the lipid nanoparticles was determined by fluorescence imaging techniques. A slow release of the drug was found in phosphate buffer. In contrast, a more distinct release of the curcuminoids was verifiable in SGF and in simulated intestinal fluids. Overall, it was considered that the transfer of the drug into the outer media was mainly triggered by the lipid degradation and not by drug release.
Finite element analysis of the lateral load test on battered pile group at I-10 twin span bridge : research project capsule.

DOT National Transportation Integrated Search

2016-04-01

The objectives of this research study are to develop a three-dimensional FE : model for simulating the behavior of a battered pile group foundation subjected : to lateral loading, and to verify the model using results from a unique static : lateral l...
40 CFR 1065.110 - Work inputs and outputs, accessory work, and operator demand.

Code of Federal Regulations, 2013 CFR

2013-07-01

...-current and water-brake dynamometers for any testing that does not involve engine motoring, which is... resistor load bank to simulate electrical loads. (3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the type and capacity installed in use. Use working fluids that are of...
40 CFR 1065.110 - Work inputs and outputs, accessory work, and operator demand.

Code of Federal Regulations, 2014 CFR

2014-07-01

...-current and water-brake dynamometers for any testing that does not involve engine motoring, which is... resistor load bank to simulate electrical loads. (3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the type and capacity installed in use. Use working fluids that are of...

40 CFR 1065.110 - Work inputs and outputs, accessory work, and operator demand.

Code of Federal Regulations, 2012 CFR

2012-07-01

...-current and water-brake dynamometers for any testing that does not involve engine motoring, which is... resistor load bank to simulate electrical loads. (3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the type and capacity installed in use. Use working fluids that are of...
40 CFR 1065.110 - Work inputs and outputs, accessory work, and operator demand.

Code of Federal Regulations, 2011 CFR

2011-07-01

...-current and water-brake dynamometers for any testing that does not involve engine motoring, which is... resistor load bank to simulate electrical loads. (3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the type and capacity installed in use. Use working fluids that are of...
40 CFR 1065.110 - Work inputs and outputs, accessory work, and operator demand.

Code of Federal Regulations, 2010 CFR

2010-07-01

...-current and water-brake dynamometers for any testing that does not involve engine motoring, which is... resistor load bank to simulate electrical loads. (3) Pump, compressor, and turbine work. Use pumps, compressors, and turbines that are of the type and capacity installed in use. Use working fluids that are of...
The influence of simulated clinical use on the flexibility of rotary ProTaper Universal, K3 and EndoSequence nickel-titanium instruments.

PubMed

Viana, A C D; Pereira, E S J; Bahia, M G A; Buono, V T L

2013-09-01

To investigate the influence of cyclic flexural and torsional loading on the flexibility of ProTaper Universal, K3 and EndoSequence nickel-titanium instruments, in view of the hypothesis that these types of loading would decrease the flexibility of the selected NiTi rotary files. The instruments evaluated were S2 and F1 ProTaper Universal, sizes 20 and 25, .06 taper K3, and sizes 20 and 25, .06 taper EndoSequence. Flexibility was determined by 45° bending tests according to ISO 3630-1 specification. Values of the bending moment (MB ) obtained with new instruments were considered as the control group (CG). Bending tests were then conducted in instruments previously fatigued to one-fourth and three-fourths of their average fatigue life (fatigue groups, FG¼ and FG¾), as well as after cyclic torsional loading (torsional group, TG). Fatigue tests were carried out in a bench device that allowed the files to rotate freely inside an artificial canal with an angle of curvature of 45° and a radius of 5 mm. Cyclic torsional loading tests were performed that entailed rotating the instrument from zero angular deflection to 180° and then returning to zero applied torque in 20 cycles. Data were analysed using one-way analysis of variance at a significance level of 5%. Simulated clinical use by means of flexural fatigue tests did not affect the flexibility of the instruments, except for a significant increase in flexibility observed in a few instruments (P < 0.05). In addition, comparative statistical analyses between the values of MB measured in new instruments and after cyclic torsional loading showed no significant differences between them (P > 0.05). The flexibility of rotary ProTaper Universal, K3 and EndoSequence NiTi instruments, measured in bending tests, was not adversely affected by simulated clinical use in curved root canals. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.
The effect of implementing cognitive load theory-based design principles in virtual reality simulation training of surgical skills: a randomized controlled trial.

PubMed

Andersen, Steven Arild Wuyts; Mikkelsen, Peter Trier; Konge, Lars; Cayé-Thomasen, Per; Sørensen, Mads Sølvsten

2016-01-01

Cognitive overload can inhibit learning, and cognitive load theory-based instructional design principles can be used to optimize learning situations. This study aims to investigate the effect of implementing cognitive load theory-based design principles in virtual reality simulation training of mastoidectomy. Eighteen novice medical students received 1 h of self-directed virtual reality simulation training of the mastoidectomy procedure randomized for standard instructions (control) or cognitive load theory-based instructions with a worked example followed by a problem completion exercise (intervention). Participants then completed two post-training virtual procedures for assessment and comparison. Cognitive load during the post-training procedures was estimated by reaction time testing on an integrated secondary task. Final-product analysis by two blinded expert raters was used to assess the virtual mastoidectomy performances. Participants in the intervention group had a significantly increased cognitive load during the post-training procedures compared with the control group (52 vs. 41 %, p = 0.02). This was also reflected in the final-product performance: the intervention group had a significantly lower final-product score than the control group (13.0 vs. 15.4, p < 0.005). Initial instruction using worked examples followed by a problem completion exercise did not reduce the cognitive load or improve the performance of the following procedures in novices. Increased cognitive load when part tasks needed to be integrated in the post-training procedures could be a possible explanation for this. Other instructional designs and methods are needed to lower the cognitive load and improve the performance in virtual reality surgical simulation training of novices.
Development of sensitized pick coal interface detector system

NASA Technical Reports Server (NTRS)

Burchill, R. F.

1982-01-01

One approach for detection of the coal interface is measurement of pick cutting loads and shock through the use of pick strain gage load cells and accelerometers. The cutting drum of a long wall mining machine contains a number of cutting picks. In order to measure pick loads and shocks, one pick was instrumented and telemetry used to transmit the signals from the drum to an instrument-type tape recorder. A data system using FM telemetry was designed to transfer cutting bit load and shock information from the drum of a longwall shearer coal mining machine to a chassis mounted data recorder. The design of components in the test data system were finalized, the required instruments were assembled, the instrument system was evaluated in an above-ground simulation test, and an underground test series to obtain tape recorded sensor data was conducted.
Testing and Life Prediction for Composite Rotor Hub Flexbeams

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.

2004-01-01

A summary of several studies of delamination in tapered composite laminates with internal ply-drops is presented. Initial studies used 2D FE models to calculate interlaminar stresses at the ply-ending locations in linear tapered laminates under tension loading. Strain energy release rates for delamination in these laminates indicated that delamination would likely start at the juncture of the tapered and thin regions and grow unstably in both directions. Tests of glass/epoxy and graphite/epoxy linear tapered laminates under axial tension delaminated as predicted. Nonlinear tapered specimens were cut from a full-size helicopter rotor hub and were tested under combined constant axial tension and cyclic transverse bending loading to simulate the loading experienced by a rotorhub flexbeam in flight. For all the tested specimens, delamination began at the tip of the outermost dropped ply group and grew first toward the tapered region. A 2D FE model was created that duplicated the test flexbeam layup, geometry, and loading. Surface strains calculated by the model agreed very closely with the measured surface strains in the specimens. The delamination patterns observed in the tests were simulated in the model by releasing pairs of MPCs along those interfaces. Strain energy release rates associated with the delamination growth were calculated for several configurations and using two different FE analysis codes. Calculations from the codes agreed very closely. The strain energy release rate results were used with material characterization data to predict fatigue delamination onset lives for nonlinear tapered flexbeams with two different ply-dropping schemes. The predicted curves agreed well with the test data for each case studied.
Exploratory Studies in Generalized Predictive Control for Active Gust Load Alleviation

NASA Technical Reports Server (NTRS)

Kvaternik, Raymond G.; Eure, Kenneth W.; Juang, Jer-Nan

2006-01-01

The results of numerical simulations aimed at assessing the efficacy of Generalized Predictive Control (GPC) for active gust load alleviation using trailing- and leading-edge control surfaces are presented. The equations underlying the method are presented and discussed, including system identification, calculation of control law matrices, and calculation of commands applied to the control effectors. Both embedded and explicit feedforward paths for inclusion of disturbance effects are addressed. Results from two types of simulations are shown. The first used a 3-DOF math model of a mass-spring-dashpot system subject to user-defined external disturbances. The second used open-loop data from a wind-tunnel test in which a wing model was excited by sinusoidal vertical gusts; closed-loop behavior was simulated in post-test calculations. Results obtained from these simulations have been decidedly positive. In particular, results of closed-loop simulations for the wing model showed reductions in root moments by factors as high as 1000, depending on whether the excitation is from a constant- or variable-frequency gust and on the direction of the response.
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.
Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

NASA Technical Reports Server (NTRS)

Braman, K. E.; Ruf, J. H.

2015-01-01

Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated using RANS and URANS for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and for four approximations of the supersonic film injection geometry, each of which was created with a different simplification of the test article geometry. The results show that although a reasonable match to experiment can be obtained with varying levels of geometric fidelity, the modeling choices made do not fully represent the physics of flow separation in a TIC nozzle with film cooling.
Space Suit Environment Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Lin, Amy; Sweterlitsch, Jeffrey; Cox, Marlon

2009-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by Hamilton Sundstrand and baselined for the Orion Atmosphere Revitalization System (ARS). In two previous years at this conference, reports were presented on extensive Johnson Space Center (JSC) testing of this technology in a sea-level pressure environment with simulated human metabolic loads. Another paper at this year s conference discusses similar testing with real human metabolic loads, including some closed-loop testing with emergency breathing masks. The Orion ARS is designed to also support extravehicular activity operations from a depressurized cabin. The next step in developmental testing at JSC was, therefore, to test this ARS technology in a typical closed space suit loop environment with low-pressure pure oxygen inside the process loop and vacuum outside the loop. This was the first instance of low-pressure oxygen loop testing of a new Orion ARS technology, and was conducted with simulated human metabolic loads in December 2008. The test investigated pressure drops through two different styles of prototype suit umbilical connectors and general swing-bed performance with both umbilical configurations as well as with a short jumper line installed in place of the umbilicals. Other interesting results include observations on the thermal effects of swing-bed operation in a vacuum environment and a recommendation of cycle time to maintain acceptable atmospheric CO2 and moisture levels.
Fuel cladding behavior under rapid loading conditions

NASA Astrophysics Data System (ADS)

Yueh, K.; Karlsson, J.; Stjärnsäter, J.; Schrire, D.; Ledergerber, G.; Munoz-Reja, C.; Hallstadius, L.

2016-02-01

A modified burst test (MBT) was used in an extensive test program to characterize fuel cladding failure behavior under rapid loading conditions. The MBT differs from a normal burst test with the use of a driver tube to simulate the expansion of a fuel pellet, thereby producing a partial strain driven deformation condition similar to that of a fuel pellet expansion in a reactivity insertion accident (RIA). A piston/cylinder assembly was used to pressurize the driver tube. By controlling the speed and distance the piston travels the loading rate and degree of sample deformation could be controlled. The use of a driver tube with a machined gauge section localizes deformation and allows for continuous monitoring of the test sample diameter change at the location of maximum hoop strain, during each test. Cladding samples from five irradiated fuel rods were tested between 296 and 553 K and loading rates from 1.5 to 3.5/s. The test rods included variations of Zircaloy-2 with different liners and ZIRLO, ranging in burn-up from 41 to 74 GWd/MTU. The test results show cladding ductility is strongly temperature and loading rate dependent. Zircaloy-2 cladding ductility degradation due to operational hydrogen pickup started to recover at approximately 358 K for test condition used in the study. This recovery temperature is strongly loading rate dependent. At 373 K, ductility recovery was small for loading rates less than 8 ms equivalent RIA pulse width, but longer than 8 ms the ductility recovery increased exponentially with increasing pulse width, consistent with literature observations of loading rate dependent brittle-to-ductile (BTD) transition temperature. The cladding ductility was also observed to be strongly loading rate/pulse width dependent for BWR cladding below the BTD temperature and Pressurized Water Reactor (PWR) cladding at both 296 and 553 K.
Damage progression in Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

1996-01-01

A computational simulation tool is used to evaluate the various stages of damage progression in composite materials during Iosipescu sheat testing. Unidirectional composite specimens with either the major or minor material axis in the load direction are considered. Damage progression characteristics are described for each specimen using two types of boundary conditions. A procedure is outlined regarding the use of computational simulation in composites testing. Iosipescu shear testing using the V-notched beam specimen is a convenient method to measure both shear strength and shear stiffness simultaneously. The evaluation of composite test response can be made more productive and informative via computational simulation of progressive damage and fracture. Computational simulation performs a complete evaluation of laminated composite fracture via assessment of ply and subply level damage/fracture processes.
A technique for measuring dynamic friction coefficient under impact loading

NASA Astrophysics Data System (ADS)

Lin, Y. L.; Qin, J. G.; Chen, R.; Zhao, P. D.; Lu, F. Y.

2014-09-01

We develop a novel setup based on the split Hopkinson pressure bar technique to test the dynamic friction coefficient under impact loading. In the setup, the major improvement is that the end of the incident bar near the specimen is wedge-shaped, which results in a combined compressive and shear loading applied to the specimen. In fact, the shear loading is caused by the interfacial friction between specimen and bars. Therefore, when the two loading force histories are measured, the friction coefficient histories can be calculated without any assumptions and theoretical derivations. The geometry of the friction pairs is simple, and can be either cuboid or cylindrical. Regarding the measurements, two quartz transducers are used to directly record the force histories, and an optical apparatus is designed to test the interfacial slip movement. By using the setup, the dynamic friction coefficient of PTFE/aluminum 7075 friction pairs was tested. The time resolved dynamic friction coefficient and slip movement histories were achieved. The results show that the friction coefficient changes during the loading process, the average data of the relatively stable flat plateau section of the friction coefficient curves is 0.137, the maximum normal pressure is 52 MPa, the maximum relative slip velocity is 1.5 m/s, and the acceleration is 8400 m2/s. Furthermore, the friction test was simulated using an explicit FEM code LS-DYNA. The simulation results showed that the constant pressure and slip velocity can both be obtained with a wide flat plateau incident pulse. For some special friction pairs, normal pressure up to a few hundred MPa, interfacial slip velocities up to 10 m/s, and slip movement up to centimeter-level can be expected.
A technique for measuring dynamic friction coefficient under impact loading.

PubMed

Lin, Y L; Qin, J G; Chen, R; Zhao, P D; Lu, F Y

2014-09-01

We develop a novel setup based on the split Hopkinson pressure bar technique to test the dynamic friction coefficient under impact loading. In the setup, the major improvement is that the end of the incident bar near the specimen is wedge-shaped, which results in a combined compressive and shear loading applied to the specimen. In fact, the shear loading is caused by the interfacial friction between specimen and bars. Therefore, when the two loading force histories are measured, the friction coefficient histories can be calculated without any assumptions and theoretical derivations. The geometry of the friction pairs is simple, and can be either cuboid or cylindrical. Regarding the measurements, two quartz transducers are used to directly record the force histories, and an optical apparatus is designed to test the interfacial slip movement. By using the setup, the dynamic friction coefficient of PTFE/aluminum 7075 friction pairs was tested. The time resolved dynamic friction coefficient and slip movement histories were achieved. The results show that the friction coefficient changes during the loading process, the average data of the relatively stable flat plateau section of the friction coefficient curves is 0.137, the maximum normal pressure is 52 MPa, the maximum relative slip velocity is 1.5 m/s, and the acceleration is 8400 m(2)/s. Furthermore, the friction test was simulated using an explicit FEM code LS-DYNA. The simulation results showed that the constant pressure and slip velocity can both be obtained with a wide flat plateau incident pulse. For some special friction pairs, normal pressure up to a few hundred MPa, interfacial slip velocities up to 10 m/s, and slip movement up to centimeter-level can be expected.
Simulation of the Load-Unload Paths Experienced by Rock in the Vicinity of Buried Explosions.

DTIC Science & Technology

1977-12-01

Y99QAXSB04903 H2590D. 19. KEY WORDS (Continue on revere. aide if necessary end Identify by block number) Kayenta Sandstone Strain and Stress Paths Buried...These calculations are used to define loading and unloading paths in static laboratory tests on Kayenta sandstone. The data presented hsreithus...spherical explosions in an infinite medium. The material tested in the experimental program is Kayenta sandstone. 5 STRESS PATH DETERMINATION FROM FINITE
Precursor Evolution and Stress Corrosion Cracking Initiation of Cold-Worked Alloy 690 in Simulated Pressurized Water Reactor Primary Water

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

Zhai, Ziqing; Toloczko, Mychailo; Kruska, Karen

Stress corrosion crack initiation of two thermally-treated, cold-worked (CW) alloy 690 (UNS N06690) materials was investigated in 360oC simulated PWR primary water using constant load tensile (CLT) tests and blunt notch compact tension (BNCT) tests equipped with direct current potential drop (DCPD) for in-situ detection of cracking. SCC initiation was not detected by DCPD for either the 21% or 31%CW CLT specimens loaded at their yield stress after ~9,220 hours, however intergranular (IG) precursor damage and isolated surface cracks were observed on the specimens. The two 31%CW BNCT specimens loaded at moderate stress intensity after several cyclic loading ramps showedmore » DCPD-indicated crack initiation after 10,400 hours of exposure at constant stress intensity, which was resulted from significant growth of IG cracks. The 21%CW BNCT specimens only exhibited isolated small IG surface cracks and showed no apparent DCPD change throughout the test. Post-test cross-section examinations revealed many grain boundary (GB) nano-cavities in the bulk of all the CLT and BNCT specimens particularly for the 31%CW materials. Cavities were also found along GBs extending to the surface suggesting an important role in crack nucleation. This paper provides an overview of the evolution of GB cavities and discusses their effects on crack initiation in CW alloy 690.« less
Wind Turbine Control Design to Reduce Capital Costs: 7 January 2009 - 31 August 2009

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

Darrow, P. J.

2010-01-01

This report first discusses and identifies which wind turbine components can benefit from advanced control algorithms and also presents results from a preliminary loads case analysis using a baseline controller. Next, it describes the design, implementation, and simulation-based testing of an advanced controller to reduce loads on those components. The case-by-case loads analysis and advanced controller design will help guide future control research.
The dynamic properties behavior of high strength concrete under different strain rate

NASA Astrophysics Data System (ADS)

Abdullah, Hasballah; Husin, Saiful; Umar, Hamdani; Rizal, Samsul

2005-04-01

This paper present a number experimental data and numerical technique used in the dynamic behavior of high strength concrete. A testing device is presented for the experimental study of dynamic behavior material under high strain rates. The specimen is loaded by means of a high carbon steel Hopkinson pressure bar (40 mm diameter, 3000 mm long input bar and 1500 mm long out put bar) allowing for the testing of specimen diameter is large enough in relation to the size of aggregates. The other method also proposed for measuring tensile strength, the measurement method based on the superposition and concentration of tensile stress wave reflected both from the free-free ends of striking bar and the specimen bar. The compression Hopkinson bar test, the impact tensile test of high strength concrete bars are performed, together with compression static strength test. In addition, the relation between break position under finite element simulation and impact tensile strength are examined. The three-dimensional simulation of the specimen under transient loading are presented and comparisons between the experimental and numerical simulation on strain rate effects of constitutive law use in experimental are study.
Mechanics of Ballast Compaction. Volume 4 : Lab. Invest. the Effects of Field Compaction Mechanisms

DOT National Transportation Integrated Search

1982-03-01

This report describes a preliminary series of laboratory tests which attempt to simulate some of the effects of maintenance procedures and traffic on the physical state of ballast as measured by the ballast density test, plate load test, and lateral ...

Design and Testing of CPAS Main Deployment Bag Energy Modulator

NASA Technical Reports Server (NTRS)

Mollmann, Catherine

2017-01-01

During the developmental testing program for CPAS (Capsule Parachute Assembly System), the parachute system for the NASA Orion Crew Module, simulation revealed that high loads may be experienced by the pilot risers during the most devere deployment conditions. As the role of the pilot parachutes is to deploy the main parachutes, these high loads introduced the possibility of main deployment failure. In order to mitigate these high loads, a set of energy modulators was incorporated between the pilot riser and the main deployment bag. An extensive developmental program was implemented to ensure the adequacy of these energy modulators. After initial design comparisons, the energy modulator design was validated through slow-speed joint tests as well as through high-speed bungee tests. This paper documents the design, development, and results of multiple tests completed on the final design.
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.
Influence of the preparation design and artificial aging on the fracture resistance of monolithic zirconia crowns.

PubMed

Mitov, Gergo; Anastassova-Yoshida, Yana; Nothdurft, Frank Phillip; von See, Constantin; Pospiech, Peter

2016-02-01

The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method. An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling 5℃-55℃ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at 137℃, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture. The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly. The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns.
Analysis of non-destructive current simulators of flux compression generators.

PubMed

O'Connor, K A; Curry, R D

2014-06-01

Development and evaluation of power conditioning systems and high power microwave components often used with flux compression generators (FCGs) requires repeated testing and characterization. In an effort to minimize the cost and time required for testing with explosive generators, non-destructive simulators of an FCG's output current have been developed. Flux compression generators and simulators of FCGs are unique pulsed power sources in that the current waveform exhibits a quasi-exponential increasing rate at which the current rises. Accurately reproducing the quasi-exponential current waveform of a FCG can be important in designing electroexplosive opening switches and other power conditioning components that are dependent on the integral of current action and the rate of energy dissipation. Three versions of FCG simulators have been developed that include an inductive network with decreasing impedance in time. A primary difference between these simulators is the voltage source driving them. It is shown that a capacitor-inductor-capacitor network driving a constant or decreasing inductive load can produce the desired high-order derivatives of the load current to replicate a quasi-exponential waveform. The operation of the FCG simulators is reviewed and described mathematically for the first time to aid in the design of new simulators. Experimental and calculated results of two recent simulators are reported with recommendations for future designs.
Dynamic Brazilian Test of Rock Under Intermediate Strain Rate: Pendulum Hammer-Driven SHPB Test and Numerical Simulation

NASA Astrophysics Data System (ADS)

Zhu, W. C.; Niu, L. L.; Li, S. H.; Xu, Z. H.

2015-09-01

The tensile strength of rock subjected to dynamic loading constitutes many engineering applications such as rock drilling and blasting. The dynamic Brazilian test of rock specimens was conducted with the split Hopkinson pressure bar (SHPB) driven by pendulum hammer, in order to determine the indirect tensile strength of rock under an intermediate strain rate ranging from 5.2 to 12.9 s-1, which is achieved when the incident bar is impacted by pendulum hammer with different velocities. The incident wave excited by pendulum hammer is triangular in shape, featuring a long rising time, and it is considered to be helpful for achieving a constant strain rate in the rock specimen. The dynamic indirect tensile strength of rock increases with strain rate. Then, the numerical simulator RFPA-Dynamics, a well-recognized software for simulating the rock failure under dynamic loading, is validated by reproducing the Brazilian test of rock when the incident stress wave retrieved at the incident bar is input as the boundary condition, and then it is employed to study the Brazilian test of rock under the higher strain rate. Based on the numerical simulation, the strain-rate dependency of tensile strength and failure pattern of the Brazilian disc specimen under the intermediate strain rate are numerically simulated, and the associated failure mechanism is clarified. It is deemed that the material heterogeneity should be a reason for the strain-rate dependency of rock.
A Model of BGA Thermal Fatigue Life Prediction Considering Load Sequence Effects

PubMed Central

Hu, Weiwei; Li, Yaqiu; Sun, Yufeng; Mosleh, Ali

2016-01-01

Accurate testing history data is necessary for all fatigue life prediction approaches, but such data is always deficient especially for the microelectronic devices. Additionally, the sequence of the individual load cycle plays an important role in physical fatigue damage. However, most of the existing models based on the linear damage accumulation rule ignore the sequence effects. This paper proposes a thermal fatigue life prediction model for ball grid array (BGA) packages to take into consideration the load sequence effects. For the purpose of improving the availability and accessibility of testing data, a new failure criterion is discussed and verified by simulation and experimentation. The consequences for the fatigue underlying sequence load conditions are shown. PMID:28773980
Probabilistic load simulation: Code development status

NASA Astrophysics Data System (ADS)

Newell, J. F.; Ho, H.

1991-05-01

The objective of the Composite Load Spectra (CLS) project is to develop generic load models to simulate the composite load spectra that are included in space propulsion system components. The probabilistic loads thus generated are part of the probabilistic design analysis (PDA) of a space propulsion system that also includes probabilistic structural analyses, reliability, and risk evaluations. Probabilistic load simulation for space propulsion systems demands sophisticated probabilistic methodology and requires large amounts of load information and engineering data. The CLS approach is to implement a knowledge based system coupled with a probabilistic load simulation module. The knowledge base manages and furnishes load information and expertise and sets up the simulation runs. The load simulation module performs the numerical computation to generate the probabilistic loads with load information supplied from the CLS knowledge base.
Validation of the solar heating and cooling high speed performance (HISPER) computer code

NASA Technical Reports Server (NTRS)

Wallace, D. B.

1980-01-01

Developed to give a quick and accurate predictions HISPER, a simplification of the TRNSYS program, achieves its computational speed by not simulating detailed system operations or performing detailed load computations. In order to validate the HISPER computer for air systems the simulation was compared to the actual performance of an operational test site. Solar insolation, ambient temperature, water usage rate, and water main temperatures from the data tapes for an office building in Huntsville, Alabama were used as input. The HISPER program was found to predict the heating loads and solar fraction of the loads with errors of less than ten percent. Good correlation was found on both a seasonal basis and a monthly basis. Several parameters (such as infiltration rate and the outside ambient temperature above which heating is not required) were found to require careful selection for accurate simulation.
A Novel Mobile Testing Equipment for Rock Cuttability Assessment: Vertical Rock Cutting Rig (VRCR)

NASA Astrophysics Data System (ADS)

Yasar, Serdar; Yilmaz, Ali Osman

2017-04-01

In this study, a new mobile rock cutting testing apparatus was designed and produced for rock cuttability assessment called vertical rock cutting rig (VRCR) which was designed specially to fit into hydraulic press testing equipment which are available in almost every rock mechanics laboratory. Rock cutting trials were initiated just after the production of VRCR along with calibration of the measuring load cell with an external load cell to validate the recorded force data. Then, controlled rock cutting tests with both relieved and unrelieved cutting modes were implemented on five different volcanic rock samples with a standard simple-shaped wedge tool. Additionally, core cutting test which is an important approach for roadheader performance prediction was simulated with VRCR. Mini disc cutters and point attack tools were used for execution of experimental trials. Results clearly showed that rock cutting tests were successfully realized and measuring system is delicate to rock strength, cutting depth and other variables. Core cutting test was successfully simulated, and it was also shown that rock cutting tests with mini disc cutters and point attack tools are also successful with VRCR.
Testing activities at the National Battery Test Laboratory

NASA Astrophysics Data System (ADS)

Hornstra, F.; Deluca, W. H.; Mulcahey, T. P.

The National Battery Test Laboratory (NBTL) is an Argonne National Laboratory facility for testing, evaluating, and studying advanced electric storage batteries. The facility tests batteries developed under Department of Energy programs and from private industry. These include batteries intended for future electric vehicle (EV) propulsion, electric utility load leveling (LL), and solar energy storage. Since becoming operational, the NBTL has evaluated well over 1400 cells (generally in the form of three- to six-cell modules, but up to 140-cell batteries) of various technologies. Performance characterization assessments are conducted under a series of charge/discharge cycles with constant current, constant power, peak power, and computer simulated dynamic load profile conditions. Flexible charging algorithms are provided to accommodate the specific needs of each battery under test. Special studies are conducted to explore and optimize charge procedures, to investigate the impact of unique load demands on battery performance, and to analyze the thermal management requirements of battery systems.
Effects of running with backpack loads during simulated gravitational transitions: Improvements in postural control

NASA Astrophysics Data System (ADS)

Brewer, Jeffrey David

The National Aeronautics and Space Administration is planning for long-duration manned missions to the Moon and Mars. For feasible long-duration space travel, improvements in exercise countermeasures are necessary to maintain cardiovascular fitness, bone mass throughout the body and the ability to perform coordinated movements in a constant gravitational environment that is six orders of magnitude higher than the "near weightlessness" condition experienced during transit to and/or orbit of the Moon, Mars, and Earth. In such gravitational transitions feedback and feedforward postural control strategies must be recalibrated to ensure optimal locomotion performance. In order to investigate methods of improving postural control adaptation during these gravitational transitions, a treadmill based precision stepping task was developed to reveal changes in neuromuscular control of locomotion following both simulated partial gravity exposure and post-simulation exercise countermeasures designed to speed lower extremity impedance adjustment mechanisms. The exercise countermeasures included a short period of running with or without backpack loads immediately after partial gravity running. A novel suspension type partial gravity simulator incorporating spring balancers and a motor-driven treadmill was developed to facilitate body weight off loading and various gait patterns in both simulated partial and full gravitational environments. Studies have provided evidence that suggests: the environmental simulator constructed for this thesis effort does induce locomotor adaptations following partial gravity running; the precision stepping task may be a helpful test for illuminating these adaptations; and musculoskeletal loading in the form of running with or without backpack loads may improve the locomotor adaptation process.
Influence of artificial aging on the load-bearing capability of straight or angulated zirconia abutments in implant/tooth-supported fixed partial dentures.

PubMed

Nothdurft, Frank P; Doppler, Klaus E; Erdelt, Kurt J; Knauber, Andreas W; Pospiech, Peter R

2010-01-01

The aim of the study was to evaluate the influence of artificial aging on the fracture behavior of straight and angulated zirconia implant abutments used in ZirDesign (Astra Tech) implant/tooth-supported fixed partial dentures (FPDs) in the maxilla. Four different test groups (n = 8) representing anterior implant/tooth-supported FPDs were prepared. Groups 1 and 2 simulated a clinical situation with an ideal implant position (maxillary left central incisor) from a prosthetic point of view, which allowed for the use of a straight, prefabricated zirconia abutment. Groups 3 and 4 simulated a situation with a compromised implant position that required an angulated (20-degree) abutment. OsseoSpeed implants (4.5 3 13 mm, Astra Tech) as well as metal tooth analogs (maxillary right lateral incisor) with simulated periodontal mobility were mounted in polymethyl methacrylate. The FPDs (chromium-cobalt alloy) were cemented with glass ionomer. Groups 2 and 4 were thermomechanically loaded and subjected to static loading until failure. Statistical analysis of force data at the fracture site was performed using nonparametric tests. All samples survived thermomechanical loading. Artificial aging did not lead to a significant decrease in load-bearing capacity in either the straight abutments or the angulated abutments. The restorations that used angulated abutments exhibited higher fracture loads than the restorations with straight abutments (group 1: 209.13 ± 39.11 N; group 2: 233.63 ± 30.68 N; group 3: 324.62 ± 108.07 N; group 4: 361.75 ± 73.82 N). This difference in load-bearing performance was statistically significant, both with and without artificial aging. All abutment fractures occurred below the implant shoulder. Compensation for angulated implant positions with an angulated zirconia abutment is possible without reducing the load-bearing capacity of implant/tooth-supported anterior FPDs.
Automated Seat Cushion for Pressure Ulcer Prevention Using Real-Time Mapping, Offloading, and Redistribution of Interface Pressure

DTIC Science & Technology

2016-10-01

testing as well as finite element simulation. Automation and control testing has been completed on a 5x5 array of bubble actuators to verify pressure...mechanical behavior at varying loads and internal pressures both by experimental testing as well as finite element simulation. Automation and control...A finite element (FE) model of the bubble actuator was developed in the commercial software ANSYS in order to determine the deformation of the
Comparison Virtual Landing Gear Drop Test for Commuter Aircraft Utilize MSC ADAMS And Solidworks Motion Analysis

NASA Astrophysics Data System (ADS)

Hidayat, Dony; Istiyanto, Jos; Agus Sumarsono, Danardono

2018-04-01

Loads at main landing gear while touchdown impact is function of aircraft weight and ground reaction load factor. In regulation states ground reaction load factor at Vsink = 3.05 m/s is below 3. Contact/impact force from simulation using MSC ADAMS is 94680 N, while using Solidworks Motion Analysis is 97691 N. The difference between MSC ADAMS and Solidworks Motion Analysis is 3.08%. The ground reaction load factor in MSC ADAMS is 2.78 while in Solidworks Motion Analysis is 2.87.
Evaluation for Loss of Lubrication Performance of Black Oxide, Superfinished, and As-Ground Surfaces for Use in Rotorcraft Transmissions

DTIC Science & Technology

2016-09-01

2.3.2 Loss -of-Lubrication Protocol 5 2.3.3 Friction Mapping Protocol 7 2.4 Test Matrices 9 3. Results and Discussion 10 3.1 Load Capacity 10...protocols used to simulate relevant contact conditions are the load capacity (LC), loss -of-lubrication (LoL), and mapping protocols. 2.3.1 Load ...Entrainment velocity (m/s) Slip (%) Skew (°) Load (N) Contact stress (GPa) LoL 16 –100 0 100 1.29 2.3.2.2 Low-Speed Loss -of-Lubrication
Modeling and Assessment of Alternative Cooling Methods of the Combat Operation Center

DTIC Science & Technology

2012-12-01

through the employment of a measure designed to remove heat load at a lower rate of power consumption than an ECU. 3. The Simulation To test the...24 G. PROCEDURE FOR TESTING PROPOSED SOLUTIONS .....................25 1. The Model...ASSUMPTIONS .............................................................................................28 1. July 2010 COC (v2) test
Mission Information and Test Systems Summary of Accomplishments, 2011

NASA Technical Reports Server (NTRS)

McMorrow, Sean E.; Sherrard, Roberta B.

2013-01-01

This annual report covers the activities of the NASA DRFC Mission Information and Test Systems, which includes the Western Aeronautical Test Range, the Simulation Engineering Branch, the Information Services and the Dryden Technical Laboratory (Flight Loads Lab). This report contains highlights, current projects and various awards achieved during in 2011
Behavior of Brazed W/Cu Mockup Under High Heat Flux Loads

NASA Astrophysics Data System (ADS)

Chen, Lei; Lian, Youyun; Liu, Xiang

2014-03-01

In order to transfer the heat from the armor to the coolant, tungsten has to be connected with a copper heat sink. The joint technology is the most critical issue for manufacturing plasma facing components. Consequently, the reliability of the joints should be verified by a great number of high-heat-flux (HHF) tests to simulate the real load conditions. W/Cu brazed joint technology with sliver free filler metal CuMnNi has been developed at Southwestern Institute of Physics (SWIP). Screening and thermal fatigue tests of one small-scale flat tile W/CuCrZr mockup were performed on a 60 kW electron-beam Material testing scenario (EMS-60) constructed recently at SWIP. The module successfully survived screening test with the absorbed power density (Pabs) of 2 MW/m2 to 10 MW/m2 and the following 1000 cycles at Pabs of 7.2 MW/m2 without hot spots and overheating zones during the whole test campaign. Metallurgy and SEM observations did not find any cracks at both sides and the interface, indicating a good bonding of W and CuCrZr alloy. In addition, finite element simulations by ANSYS 12.0 under experimental load conditions were performed and compared with experimental results.
A study of ignition and simulation circuits for arcjet thrusters, part 1. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Stuart, Thomas A.; King, Roger J.; Altenburger, Gene P.

1991-01-01

A 1 kW electronic load was programmed to simulate the nonlinear i-v (volt-ampere) characteristics of an arcjet, both ignited and unignited. The simulator was tested and found to closely resemble an arcjet both for large transients and small perturbances up to about 40 kHz. No attempt was made to simulate the ignition process itself. The dynamic behavior of the arcjet (and the simulator) was shown to differ significantly from that of a resistor bank. Previous research led to the design and construction of a 1 kW arcjet power supply. A high voltage ignition circuit was added to this hardware, and tests on a 1 kW arcjet were performed at NASA-Lewis. All tests were successful and no ignition failures were observed. Circuit documentation and test results are included.
Debonding in Composite Skin/Stringer Configurations Under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Cvitkovich, Michael K.; Krueger, Ronald; OBrien, T.; Minguet, Pierre J.

2004-01-01

The objective of this work was to investigate the damage mechanisms in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out-of-plane) loading conditions as typically experienced by aircraft crown fuselage panels. The specimens for all tests were identical and consisted of a tapered composite flange, representing a stringer or frame, bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending to evaluate the debonding mechanisms between the skin and the bonded stringer. For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both loads simultaneously. Microscopic investigations of the specimen edges were used to document the damage occurrence and to identify typical damage patterns. The observations showed that, for all three load cases, failure initiated in the flange near the flange tip causing the flange to almost fully debond from the skin. A two-dimensional plain-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, principal stresses exceeded the transverse strength of the material in the flange area. Additionally, delaminations of various lengths were simulated in the locations where delaminations were experimentally observed. The analyses showed that unstable delamination propagation is likely to occur at the loads corresponding to matrix ply crack initiation for all three loadings.

Trailing Vortex-Induced Loads During Close Encounters in Cruise

NASA Technical Reports Server (NTRS)

Mendenhall, Michael R.; Lesieutre, Daniel J; Kelly, Michael J.

2015-01-01

The trailing vortex induced aerodynamic loads on a Falcon 20G business jet flying in the wake of a DC-8 are predicted to provide a preflight estimate of safe trail distances during flight test measurements in the wake. Static and dynamic loads on the airframe flying in the near wake are shown at a matrix of locations, and the dynamic motion of the Falcon 20G during traverses of the DC-8 primary trailing vortex is simulated. Safe trailing distances for the test flights are determined, and optimum vortex traverse schemes are identified to moderate the motion of the trailing aircraft during close encounters with the vortex wake.
SUV Rollover Test

NASA Technical Reports Server (NTRS)

Chambers, William V.

2004-01-01

The National Highway Traffic Safety Administration (NHTSA) approached NASA to evaluate vehicle rollover resistance using the High Capacity Centrifuge Facility. Testing was planned for six different sport utility vehicles. Previous methods for simulating the rollover conditions were considered to be not indicative of the true driving conditions. A more realistic gradual application of side loading could be achieved by using a centrifuge facility. A unique load measuring lower support system was designed to measure tire loading on the inboard tires and to indicate tire liftoff. This lower support system was designed to more closely emulate the actual rollover conditions. Additional design features were provided to mitigate potential safety hazards.
Input Device Characteristics Contribute to Performance during Training to Operate a Simulated Micro-Unmanned Aerial Vehicle

DTIC Science & Technology

2010-10-01

mission, participants were given the NASA Task Load Index ( NASA TLX ) to measure subjective workload. Additional performance measures included mission...16 NASA TLX Workload Analyses...worksheet (See Appendix C), the Hidden Patterns Test (ETS, 1976), and an electronic form of the NASA Task Load Index ( TLX ; Hart & Staveland, 1988). The
Fitted hyperelastic parameters for Human brain tissue from reported tension, compression, and shear tests.

PubMed

Moran, Richard; Smith, Joshua H; García, José J

2014-11-28

The mechanical properties of human brain tissue are the subject of interest because of their use in understanding brain trauma and in developing therapeutic treatments and procedures. To represent the behavior of the tissue, we have developed hyperelastic mechanical models whose parameters are fitted in accordance with experimental test results. However, most studies available in the literature have fitted parameters with data of a single type of loading, such as tension, compression, or shear. Recently, Jin et al. (Journal of Biomechanics 46:2795-2801, 2013) reported data from ex vivo tests of human brain tissue under tension, compression, and shear loading using four strain rates and four different brain regions. However, they do not report parameters of energy functions that can be readily used in finite element simulations. To represent the tissue behavior for the quasi-static loading conditions, we aimed to determine the best fit of the hyperelastic parameters of the hyperfoam, Ogden, and polynomial strain energy functions available in ABAQUS for the low strain rate data, while simultaneously considering all three loading modes. We used an optimization process conducted in MATLAB, calling iteratively three finite element models developed in ABAQUS that represent the three loadings. Results showed a relatively good fit to experimental data in all loading modes using two terms in the energy functions. Values for the shear modulus obtained in this analysis (897-1653Pa) are in the range of those presented in other studies. These energy-function parameters can be used in brain tissue simulations using finite element models. Copyright © 2014 Elsevier Ltd. All rights reserved.
Shock-induced mechanochemistry in heterogeneous reactive powder mixtures

NASA Astrophysics Data System (ADS)

Gonzales, Manny; Gurumurthy, Ashok; Kennedy, Gregory; Neel, Christopher; Gokhale, Arun; Thadhani, Naresh

The bulk response of compacted powder mixtures subjected to high-strain-rate loading conditions in various configurations is manifested from behavior at the meso-scale. Simulations at the meso-scale can provide an additional confirmation of the possible origins of the observed response. This work investigates the bulk dynamic response of Ti +B +Al reactive powder mixtures under two extreme loading configurations - uniaxial stress and strain loading - leveraging highly-resolved in-situ measurements and meso-scale simulations. Modified rod-on-anvil impact tests on a reactive pellet demonstrate an optimized stoichiometry promoting reaction in Ti +B +Al. Encapsulated powders subjected to shock compression via flyer plate tests provide possible evidence of a shock-induced reaction at high pressures. Meso-scale simulations of the direct experimental configurations employing highly-resolved microstructural features of the Ti +B compacted mixture show complex inhomogeneous deformation responses and reveal the importance of meso-scale features such as particle size and morphology and their effects on the measured response. Funding is generously provided by DTRA through Grant No. HDTRA1-10-1-0038 (Dr. Su Peiris - Program Manager) and by the SMART (AFRL Wright Patterson AFB) and NDSEG fellowships (High Performance Computing and Modernization Office).
U. S. Army Engineer Research and Development Center: Rapid Repair of Levee Breaches

DTIC Science & Technology

2011-06-01

tensile loads while allowing rigid (nonfabric) structural elements to bear the compressive loads, as shown in Figure 2.2. In Figure 2.2(a), the...Report 81000-01 2.7.3 Small-Scale Modeling Flume Tests An 80 ft long tilting flume was used to provide a simulated levee breach and flow for...somewhat peripheral to the main thrust of the DHS-SERRI funding in this project, only a cursory description of the technology and testing results will
Investigation of the Loads on a Conventional Front and Rear Sliding Canopy

NASA Technical Reports Server (NTRS)

Dexter, Howard E.; Rickey, Edward A.

1947-01-01

As one phase of a comprehensive canopy load investigation, conventional front and rear sliding canopies which are typified by installation on the SB2C-4E airplane, were tested in the Langley full-scale tunnel to determine the pressure distributions and the aerodynamic loads on the canopies. A preliminary analysis of the results of these tests is presented in this report. Plots are presented that show the distribution of pressure at four longitudinal stations through each canopy for a range of conditions selected to determine the effects of varying canopy position, yaw, lift coefficient, and power. The results indicate that the maximum loads, based on the external-internal pressure differential, for the front and rear canopies were obtained with the airplane simulating the high speed flight condition. The highest loading on the front canopy was in the exploding direction for the configuration with the front and rear canopies closed. The highest loads on the rear canopy were in the crushing direction with the front canopy open and the rear canopy closed. For most of the simulated flight conditions, the highest loads on the front canopy, per unit area, were over twice as great as the highest loads on the rear canopy when the comparison was made for the most critical canopy configuration in each case. The external pressure distribution over the front and rear canopies, which were fairly symmetrical to 0 degree angle of yaw, were greatly distorted at other yaw attitudes, particularly for the propeller operating conditions. These distorted pressure distributions resulted in local exploding and crushing loads on both canopies which were often considerably higher than the average canopy loads.
The application of the Luus-Jaakola direct search method to the optimization of a hybrid renewable energy system

NASA Astrophysics Data System (ADS)

Jatzeck, Bernhard Michael

2000-10-01

The application of the Luus-Jaakola direct search method to the optimization of stand-alone hybrid energy systems consisting of wind turbine generators (WTG's), photovoltaic (PV) modules, batteries, and an auxiliary generator was examined. The loads for these systems were for agricultural applications, with the optimization conducted on the basis of minimum capital, operating, and maintenance costs. Five systems were considered: two near Edmonton, Alberta, and one each near Lethbridge, Alberta, Victoria, British Columbia, and Delta, British Columbia. The optimization algorithm used hourly data for the load demand, WTG output power/area, and PV module output power. These hourly data were in two sets: seasonal (summer and winter values separated) and total (summer and winter values combined). The costs for the WTG's, PV modules, batteries, and auxiliary generator fuel were full market values. To examine the effects of price discounts or tax incentives, these values were lowered to 25% of the full costs for the energy sources and two-thirds of the full cost for agricultural fuel. Annual costs for a renewable energy system depended upon the load, location, component costs, and which data set (seasonal or total) was used. For one Edmonton load, the cost for a renewable energy system consisting of 27.01 m2 of WTG area, 14 PV modules, and 18 batteries (full price, total data set) was 6873/year. For Lethbridge, a system with 22.85 m2 of WTG area, 47 PV modules, and 5 batteries (reduced prices, seasonal data set) cost 2913/year. The performance of renewable energy systems based on the obtained results was tested in a simulation using load and weather data for selected days. Test results for one Edmonton load showed that the simulations for most of the systems examined ran for at least 17 hours per day before failing due to either an excessive load on the auxiliary generator or a battery constraint being violated. Additional testing indicated that increasing the generator capacity and reducing the maximum allowed battery charge current during the time of the day at which these failures occurred allowed the simulation to successfully operate.
Malaligned dynamic anterior cervical plate: a biomechanical analysis of effectiveness.

PubMed

Lawrence, Brandon D; Patel, Alpesh A; Guss, Andrew; Ryan Spiker, W; Brodke, Darrel S

2014-12-01

Biomechanical evaluation. To evaluate the kinematic and load-sharing differences of dynamic anterior cervical plates when placed in-line at 0° and off-axis at 20°. The use of dynamic anterior cervical plating systems has recently gained popularity due to the theoretical benefit of improved load sharing with graft subsidence. Occasionally, due to anatomical restraints, the anterior cervical plate may be placed off-axis in the coronal plane. This may potentially decrease the dynamization capability of the plate, leading to less load sharing and potentially decreased fusion rates. The purpose of this study was to comprehensively evaluate the kinematic and load-sharing differences of a dynamic plate placed in-line versus off-axis in the coronal plane. Thirteen fresh-frozen human cadaveric cervical spines (C2-T1) were used. Nondestructive range-of-motion testing was performed with a pneumatically controlled spine simulator in flexion/extension, lateral bending, and axial rotation using the OptoTrak motion measurement system. A C5 corpectomy was performed, and a custom interbody spacer with an integrated load cell collected load-sharing data under axial compression at varying loads. A dynamic anterior cervical plate was placed in-line at 0° and then off-axis at 20°. Testing conditions ensued using a full-length spacer, followed by simulated subsidence by removing 10% of the height of the original spacer. There were no kinematic differences noted in the in-line model versus the off-axis model. After simulated subsidence, the small decreases in stiffness and increases in motion were similar whether the plate was placed in-line or off-axis in all 3 planes of motion. There were also no significant differences in the load-sharing characteristics of the in-line plate versus the off-axis plate in either the full-length model or the subsided interbody model. This study suggests that off-axis dynamic plate positioning does not significantly impact construct kinematics or graft load sharing. As such, we do not recommend removal or repositioning of an off-axis placed dynamic plate because the kinematic and load-sharing biomechanical properties are similar. N/A.
How oral environment simulation affects ceramic failure behavior.

PubMed

Lodi, Ediléia; Weber, Kátia R; Benetti, Paula; Corazza, Pedro H; Della Bona, Álvaro; Borba, Márcia

2018-05-01

Investigating the mechanical behavior of ceramics in a clinically simulated scenario contributes to the development of new and tougher materials, improving the clinical performance of restorations. The optimal in vitro environment for testing is unclear. The purpose of this in vitro study was to investigate the failure behavior of a leucite-reinforced glass-ceramic under compression loading and fatigue in different simulated oral environment conditions. Fifty-three plate-shaped ceramic specimens were produced from computer-aided design and computer-aided manufactured (CAD-CAM) blocks and adhesively cemented onto a dentin analog substrate. For the monotonic test (n=23), a gradual compressive load (0.5 mm/min) was applied to the center of the specimens, immersed in 37ºC water, using a universal testing machine. The initial crack was detected with an acoustic system. The fatigue test was performed in a mechanical cycling machine (37ºC water, 2 Hz) using the boundary technique (n=30). Two lifetimes were evaluated (1×10 6 and 2×10 6 cycles). Failure analysis was performed using transillumination. Weibull distribution was used to evaluate compressive load data. A cumulative damage model with an inverse power law (IPL) lifetime-stress relationship was used to fit the fatigue data. A characteristic failure load of 1615 N and a Weibull modulus of 5 were obtained with the monotonic test. The estimated probability of failure (P f ) for 1×10 6 cycles at 100 N was 31%, at 150 N it was 55%, and at 200 N it was 75%. For 2×10 6 cycles, the P f increased approximately 20% in comparison with the values predicted for 1×10 6 cycles, which was not significant. The most frequent failure mode was a radial crack from the intaglio surface. For fatigue, combined failure modes were also found (radial crack combined with cone crack or chipping). Fatigue affects the fracture load and failure mode of leucite-reinforced glass-ceramic. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Tests of an alternating current propulsion subsystem for electric vehicles on a road load simulator

NASA Astrophysics Data System (ADS)

Stenger, F. J.

1982-12-01

The test results of a breadboard version of an ac electric-vehicle propulsion subsystem are presented. The breadboard was installed in the NASA Lewis Research Center Road Load Simulator facility and tested under steady-state and transient conditions. Steady-state tests were run to characterize the system and component efficiencies over the complete speed-torque range within the capability of the propulsion subsystem in the motoring mode of operation. Transient tests were performed to determine the energy consumption of the breadboard over the acceleration and cruise portions of SAE J227 and driving schedules B, C, and D. Tests in the regenerative mode were limited to the low-gear-speed range of the two speed transaxle used in the subsystem. The maximum steady-state subsystem efficiency observed for the breadboard was 81.5 percent in the high-gear-speed range in the motoring mode, and 76 percent in the regenerative braking mode (low gear). The subsystem energy efficiency during the transient tests ranged from 49.2 percent for schedule B to 68.4 percent for Schedule D.
Tests of an alternating current propulsion subsystem for electric vehicles on a road load simulator

NASA Technical Reports Server (NTRS)

Stenger, F. J.

1982-01-01

The test results of a breadboard version of an ac electric-vehicle propulsion subsystem are presented. The breadboard was installed in the NASA Lewis Research Center Road Load Simulator facility and tested under steady-state and transient conditions. Steady-state tests were run to characterize the system and component efficiencies over the complete speed-torque range within the capability of the propulsion subsystem in the motoring mode of operation. Transient tests were performed to determine the energy consumption of the breadboard over the acceleration and cruise portions of SAE J227 and driving schedules B, C, and D. Tests in the regenerative mode were limited to the low-gear-speed range of the two speed transaxle used in the subsystem. The maximum steady-state subsystem efficiency observed for the breadboard was 81.5 percent in the high-gear-speed range in the motoring mode, and 76 percent in the regenerative braking mode (low gear). The subsystem energy efficiency during the transient tests ranged from 49.2 percent for schedule B to 68.4 percent for Schedule D.
Wind-tunnel evaluation of an advanced main-rotor blade design for a utility-class helicopter

NASA Technical Reports Server (NTRS)

Yeager, William T., Jr.; Mantay, Wayne R.; Wilbur, Matthew L.; Cramer, Robert G., Jr.; Singleton, Jeffrey D.

1987-01-01

An investigation was conducted in the Langley Transonic Dynamics Tunnel to evaluate differences between an existing utility-class main-rotor blade and an advanced-design main-rotor blade. The two rotor blade designs were compared with regard to rotor performance oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Tests were conducted in hover and over a range of simulated full-scale gross weights and density altitude conditions at advance ratios from 0.15 to 0.40. Results indicate that the advanced blade design offers performance improvements over the baseline blade in both hover and forward flight. Pitch-link oscillatory loads for the baseline rotor were more sensitive to the test conditions than those of the advanced rotor. The 4-per-rev vertical fixed-system load produced by the advanced blade was larger than that produced by the baseline blade at all test conditions.
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.
Implementation of a Biaxial Resonant Fatigue Test Method on a Large Wind Turbine Blade

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

Snowberg, D.; Dana, S.; Hughes, S.

2014-09-01

A biaxial resonant test method was utilized to simultaneously fatigue test a wind turbine blade in the flap and edge (lead-lag) direction. Biaxial resonant blade fatigue testing is an accelerated life test method utilizing oscillating masses on the blade; each mass is independently oscillated at the respective flap and edge blade resonant frequency. The flap and edge resonant frequency were not controlled, nor were they constant for this demonstrated test method. This biaxial resonant test method presented surmountable challenges in test setup simulation, control and data processing. Biaxial resonant testing has the potential to complete test projects faster than single-axismore » testing. The load modulation during a biaxial resonant test may necessitate periodic load application above targets or higher applied test cycles.« less
COMPUTER INTERFACED TOXICITY TESTING SYSTEM FOR SIMULATING VARIABLE EFFLUENT LOADING

EPA Science Inventory

Water quality criteria and standards are based primarily on toxicity tests carried out with single chemicals whose concentration is as nearly constant as possible. In the 'real world', however, organisms are exposed to mixtures of chemicals which usually have markedly fluctuating...
Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

NASA Astrophysics Data System (ADS)

Chen, Rong; Li, Kang; Xia, Kaiwen; Lin, Yuliang; Yao, Wei; Lu, Fangyun

2016-10-01

A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m1/2 s-1. The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data.
PDCI Wide-Area Damping Control: PSLF Simulations of the 2016 Open and Closed Loop Test Plan

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

Wilches Bernal, Felipe; Pierre, Brian Joseph; Elliott, Ryan Thomas

To demonstrate and validate the performance of the wide-are a damping control system, the project plans to conduct closed-loop tests on the PDCI in summer/fall 2016. A test plan details the open and closed loop tests to be conducted on the P DCI using the wide-area damping control system. To ensure the appropriate level of preparedness, simulations were performed in order to predict and evaluate any possible unsafe operations before hardware experiments are attempted. This report contains the result s from these simulations using the power system dynamics software PSLF (Power System Load Flow, trademark of GE). The simulations usemore » the WECC (Western Electricity Coordinating Council) 2016 light summer and heavy summer base cases.« less
Possibilities of rock constitutive modelling and simulations

NASA Astrophysics Data System (ADS)

Baranowski, Paweł; Małachowski, Jerzy

2018-01-01

The paper deals with a problem of rock finite element modelling and simulation. The main intention of authors was to present possibilities of different approaches in case of rock constitutive modelling. For this purpose granite rock was selected, due to its wide mechanical properties recognition and prevalence in literature. Two significantly different constitutive material models were implemented to simulate the granite fracture in various configurations: Johnson - Holmquist ceramic model which is very often used for predicting rock and other brittle materials behavior, and a simple linear elastic model with a brittle failure which can be used for simulating glass fracturing. Four cases with different loading conditions were chosen to compare the aforementioned constitutive models: uniaxial compression test, notched three-point-bending test, copper ball impacting a block test and small scale blasting test.
Analysis of hardening behavior of sheet metals by a new simple shear test method taking into account the Bauschinger effect

NASA Astrophysics Data System (ADS)

Bang, Sungsik; Rickhey, Felix; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo

2013-12-01

In this study we establish a process to predict hardening behavior considering the Bauschinger effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Bauschinger effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with FEA. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.

Binaural Simulation Experiments in the NASA Langley Structural Acoustics Loads and Transmission Facility

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.; Silcox, Richard (Technical Monitor)

2001-01-01

A location and positioning system was developed and implemented in the anechoic chamber of the Structural Acoustics Loads and Transmission (SALT) facility to accurately determine the coordinates of points in three-dimensional space. Transfer functions were measured between a shaker source at two different panel locations and the vibrational response distributed over the panel surface using a scanning laser vibrometer. The binaural simulation test matrix included test runs for several locations of the measuring microphones, various attitudes of the mannequin, two locations of the shaker excitation and three different shaker inputs including pulse, broadband random, and pseudo-random. Transfer functions, auto spectra, and coherence functions were acquired for the pseudo-random excitation. Time histories were acquired for the pulse and broadband random input to the shaker. The tests were repeated with a reflective surface installed. Binary data files were converted to universal format and archived on compact disk.
In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants.

PubMed

García-Roncero, Herminio; Caballé-Serrano, Jordi; Cano-Batalla, Jordi; Cabratosa-Termes, Josep; Figueras-Álvarez, Oscar

2015-04-01

In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants.
Thin tube experiments and numerical simulations of micromechanical multivariant constitutive modeling in superelastic Nitinol

NASA Astrophysics Data System (ADS)

Jung, Youngjean

This dissertation concerns the constitutive description of superelasticity in NiTi alloys and the finite element analysis of a corresponding material model at large strains. Constitutive laws for shape-memory alloys subject to biaxial loading, which are based on direct experimental observations, are generally not available. A reliable constitutive model for shape-memory alloys is important for various applications because Nitinol is now widely used in biotechnology devices such as endovascular stents, vena cava filters, dental files, archwires and guidewires, etc. As part of a broader project, tension-torsion tests are conducted on thin-walled tubes (thickness/radius ratio of 1:10) of the polycrystalline superelastic Nitinol using various loading/unloading paths under isothermal conditions. This biaxial loading/unloading test was carefully designed to avoid torsional buckling and strain non-uniformities. A micromechanical constitutive model, algorithmic implementation and numerical simulation of polycrystalline superelastic alloys under biaxial loading are developed. The constitutive model is based on the micromechanical structure of Ni-Ti crystals and accounts for the physical observation of solid-solid phase transformations through the minimization of the Helmholtz energy with dissipation. The model is formulated in finite deformations and incorporates the effect of texture which is of profound significance in the mechanical response of polycrystalline Nitinol tubes. The numerical implementation is based on the constrained minimization of a functional corresponding to the Helmholtz energy with dissipation. Special treatment of loading/unloading conditions is also developed to distinguish between forward/reverse transformation state. Simulations are conducted for thin tubes of Nitinol under tension-torsion, as well as for a simplified model of a biomedical stent.
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.
Constitutive Modeling of a Glass Fiber-Reinforced PTFE Gasketed-Joint Under a Re-torque

NASA Astrophysics Data System (ADS)

Williams, James; Gordon, Ali P.

Joints gasketed with viscoelastic seals often receive an application of a secondary torque, i.e., retorque, in order to ensure joint tightness and proper sealing. The motivation of this study is to characterize and analytically model the load and deflection re-torque response of a single 25% glass-fiber reinforced polytetrafluorethylene (PTFE) gasket-bolted joint with serrated flange detail. The Burger-type viscoelastic modeling constants of the material are obtained through isolating the gasket from the bolt by performing a gasket creep test via a MTS electromechanical test frame. The re-load creep response is also investigated by re-loading the gasket after a period of initial creep to observe the response. The modeling constants obtained from the creep tests are used with a Burger-type viscoelastic model to predict the re-torque response of a single bolt-gasket test fixture in order to validate the ability of the model to simulate the re-torque response under various loading conditions and flange detail.
High Load Ratio Fatigue Strength and Mean Stress Evolution of Quenched and Tempered 42CrMo4 Steel

NASA Astrophysics Data System (ADS)

Bertini, Leonardo; Le Bone, Luca; Santus, Ciro; Chiesi, Francesco; Tognarelli, Leonardo

2017-08-01

The fatigue strength at a high number of cycles with initial elastic-plastic behavior was experimentally investigated on quenched and tempered 42CrMo4 steel. Fatigue tests on unnotched specimens were performed both under load and strain controls, by imposing various levels of amplitude and with several high load ratios. Different ratcheting and relaxation trends, with significant effects on fatigue, are observed and discussed, and then reported in the Haigh diagram, highlighting a clear correlation with the Smith-Watson-Topper model. High load ratio tests were also conducted on notched specimens with C (blunt) and V (sharp) geometries. A Chaboche model with three parameter couples was proposed by fitting plain specimen cyclic and relaxation tests, and then finite element analyses were performed to simulate the notched specimen test results. A significant stress relaxation at the notch root became clearly evident by reporting the numerical results in the Haigh diagram, thus explaining the low mean stress sensitivity of the notched specimens.
Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams

NASA Technical Reports Server (NTRS)

urri, Gretchen B.; Schaff, Jeffery R.

2006-01-01

Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.
Sex-Based Differences of Medial Collateral Ligament and Anterior Cruciate Ligament Strains With Cadaveric Impact Simulations.

PubMed

Schilaty, Nathan D; Bates, Nathaniel A; Nagelli, Christopher V; Krych, Aaron J; Hewett, Timothy E

2018-04-01

Female patients sustain noncontact knee ligament injuries at a greater rate compared with their male counterparts. The cause of these differences in the injury rate and the movements that load the ligaments until failure are still under dispute in the literature. This study was designed to determine differences in anterior cruciate ligament (ACL) and medial collateral ligament (MCL) strains between male and female cadaveric specimens during a simulated athletic task. The primary hypothesis tested was that female limbs would demonstrate significantly greater ACL strain compared with male limbs under similar loading conditions. A secondary hypothesis was that MCL strain would not differ between sexes. Controlled laboratory study. Motion analysis of 67 athletes performing a drop vertical jump was conducted. Kinetic data were used to categorize injury risk according to tertiles, and these values were input into a cadaveric impact simulator to assess ligamentous strain during a simulated landing task. Uniaxial and multiaxial load cells and differential variable reluctance transducer strain sensors were utilized to collect mechanical data for analysis. Conditions of external loads applied to the cadaveric limbs (knee abduction moment, anterior tibial shear, and internal tibial rotation) were varied and randomized. Data were analyzed using 1-way analysis of variance (ANOVA), 2-way repeated-measures ANOVA, and the Fisher exact test. There were no significant differences ( P = .184) in maximum ACL strain between male (13.2% ± 8.1%) and female (16.7% ± 8.3%) specimens. Two-way ANOVA demonstrated that across all controlled external load conditions, female specimens consistently attained at least 3.5% increased maximum ACL strain compared with male specimens ( F 1,100 = 4.188, P = .043); however, when normalized to initial contact, no significant difference was found. There were no significant differences in MCL strain between sexes for similar parameters. When compared with baseline, female specimens exhibited greater values of ACL strain at maximum, initial contact, and after impact (33, 66, and 100 milliseconds, respectively) than male specimens during similar loading conditions, with a maximum strain difference of at least 3.5%. During these same loading conditions, there were no differences in MCL loading between sexes, and only a minimal increase of MCL loading occurred during the impact forces. Our results indicate that female patients are at an increased risk for ACL strain across all similar conditions compared with male patients. These data demonstrate that female specimens, when loaded similarly to male specimens, experience additional strain on the ACL. As the mechanical environment was similar for both sexes with these simulations, the greater ACL strain of female specimens must be attributed to ligament biology, anatomic differences, or muscular stiffness.
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.
A comparison of hand grasp breakaway strengths and bare-handed grip strengths of the astronauts, SML 3 test subjects, and the subjects from the general population

NASA Technical Reports Server (NTRS)

Rajulu, Sudhakar L.; Klute, Glenn K.

1993-01-01

Astronauts have the task of retrieving and deploying satellites and handling massive objects in a around the payload bay. Concerns were raised that manual handling of such massive objects might induce loads to the shuttle suits exceeding the design-certified loads. The Crew and Thermal Division of NASA JSC simulated the satellite handling tasks (Satellite Manload Tests 1 and 3) and determined the maximum possible load that a suited member could impart onto the suit. In addition, the tests revealed that the load to the suit by an astronaut could be calculated from the astronaut's maximum hand grasp breakaway strength. Thus, this study was conducted to document that hand grasp breakaway strengths of the astronauts who were scheduled to perform EVA during the upcoming missions. In addition, this study verified whether the SML 3 test results were sufficient for documenting the maximum possible load. An attempt was made to predict grasp strength from grip strength and hand anthropometry. Based on the results from this study, the SML 3 test results were deemed sufficient to document the maximum possible load on the suit. Finally, prediction of grasp strength from grip strength was not as accurate as expected. Hence, it was recommended that grasp strength be collected from the astronauts in order to obtain accurate load estimation.
Do European Standard Disinfectant tests truly simulate in-use microbial and organic soiling conditions on food preparation surfaces?

PubMed

Meyer, B; Morin, V N; Rödger, H-J; Holah, J; Bird, C

2010-04-01

The results from European standard disinfectant tests are used as one basis to approve the use of disinfectants in Europe. The design of these laboratory-based tests should thus simulate as closely as possible the practical conditions and challenges that the disinfectants would encounter in use. No evidence is available that the organic and microbial loading in these tests simulates actual levels in the food service sector. Total organic carbon (TOC) and total viable count (TVC) were determined on 17 visibly clean and 45 visibly dirty surfaces in two restaurants and the food preparation surfaces of a large retail store. These values were compared to reference values recovered from surfaces soiled with the organic and microbial loading, following the standard conditions of the European Surface Test for bactericidal efficacy, EN 13697. The TOC reference values for clean and dirty conditions were higher than the data from practice, but cannot be regarded as statistical outliers. This was considered as a conservative assessment; however, as additional nine TOC samples from visibly dirty surfaces were discarded from the analysis, as their loading made them impossible to process. Similarly, the recovery of test organisms from surfaces contaminated according to EN 13697 was higher than the TVC from visibly dirty surfaces in practice; though they could not be regarded as statistical outliers of the whole data field. No correlation was found between TVC and TOC in the sampled data, which re-emphasizes the potential presence of micro-organisms on visibly clean surfaces and thus the need for the same degree of disinfection as visibly dirty surfaces. The organic soil and the microbial burden used in EN disinfectant standards represent a realistic worst-case scenario for disinfectants used in the food service and food-processing areas.
Reliability of Triaxial Accelerometry for Measuring Load in Men's Collegiate Ice Hockey.

PubMed

Van Iterson, Erik H; Fitzgerald, John S; Dietz, Calvin C; Snyder, Eric M; Peterson, Ben J

2017-05-01

Van Iterson, EH, Fitzgerald, JS, Dietz, CC, Snyder, EM, and Peterson, BJ. Reliability of triaxial accelerometry for measuring load in men's collegiate ice hockey. J Strength Cond Res 31(5): 1305-1312, 2017-Wearable microsensor technology incorporating triaxial accelerometry is used to quantify an index of mechanical stress associated with sport-specific movements termed PlayerLoad. The test-retest reliability of PlayerLoad in the environmental setting of ice hockey is unknown. The primary aim of this study was to quantify the test-retest reliability of PlayerLoad in ice hockey players during performance of tasks simulating game conditions. Division I collegiate male ice hockey players (N = 8) wore Catapult Optimeye S5 monitors during repeat performance of 9 ice hockey tasks simulating game conditions. Ordered ice hockey tasks during repeated bouts included acceleration (forward or backward), 60% top-speed, top-speed (forward or backward), repeated shift circuit, ice coasting, slap shot, and bench sitting. Coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimum difference (MD) were used to assess PlayerLoad reliability. Test-retest CVs and ICCs of PlayerLoad were as follows: 8.6% and 0.54 for forward acceleration, 13.8% and 0.78 for backward acceleration, 2.2% and 0.96 for 60% top-speed, 7.5% and 0.79 for forward top-speed, 2.8% and 0.96 for backward top-speed, 26.6% and 0.95 for repeated shift test, 3.9% and 0.68 for slap shot, 3.7% and 0.98 for coasting, and 4.1% and 0.98 for bench sitting, respectively. Raw differences between bouts were not significant for ice hockey tasks (p > 0.05). For each task, between-bout raw differences were lower vs. MD: 0.06 vs. 0.35 (forward acceleration), 0.07 vs. 0.36 (backward acceleration), 0.00 vs. 0.06 (60% top-speed), 0.03 vs. 0.20 (forward top-speed), 0.02 vs. 0.09 (backward top-speed), 0.18 vs. 0.64 (repeated shift test), 0.02 vs. 0.10 (slap shot), 0.00 vs. 0.10 (coasting), and 0.01 vs. 0.11 (bench sitting), respectively. These data suggest that PlayerLoad demonstrates moderate-to-large test-retest reliability in the environmental setting of male Division I collegiate ice hockey. Without previously testing reliability, these data are important as PlayerLoad is routinely quantified in male collegiate ice hockey to assess on ice physical activity.
SMA texture and reorientation: simulations and neutron diffraction studies

NASA Astrophysics Data System (ADS)

Gao, Xiujie; Brown, Donald W.; Brinson, L. Catherine

2005-05-01

With increased usage of shape memory alloys (SMA) for applications in various fields, it is important to understand how the material behavior is affected by factors such as texture, stress state and loading history, especially for complex multiaxial loading states. Using the in-situ neutron diffraction loading facility (SMARTS diffractometer) and ex situ inverse pole figure measurement facility (HIPPO diffractometer) at the Los Alamos Neutron Science Center (LANCE), the macroscopic mechanical behavior and texture evolution of Nickel-Titanium (Nitinol) SMAs under sequential compression in alternating directions were studied. The simplified multivariant model developed at Northwestern University was then used to simulate the macroscopic behavior and the microstructural change of Nitinol under this sequential loading. Pole figures were obtained via post-processing of the multivariant results for volume fraction evolution and compared quantitatively well to the experimental results. The experimental results can also be used to test or verify other SMA constitutive models.
S-190 exposure verification flight test. [photographic emulsions and film

NASA Technical Reports Server (NTRS)

Perry, L.

1973-01-01

A flight test was conducted to determine the optimum exposures for the Skylab S-190A experiment. An aircraft multispectral photographic system (AMPS) which is installed in the NASA Earth Resources aircraft NP3A was used to simulate the S-190A system. The same film emulsions to be used for S-190A were used in the flight test. These rolls were on factory-loaded spools for use in the AMPS camera system. It was found that some variation is to be expected between these rolls and the S-190A flight loads.
Development of a biaxial compression device for biological samples: preliminary experimental results for a closed cell foam.

PubMed

Little, J P; Tevelen, G; Adam, C J; Evans, J H; Pearcy, M J

2009-07-01

Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological samples. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the sample along one axis with an equilibrating tensile pressure. Thus a state of equibiaxial compression was created perpendicular to the long axis of a rectangular sample. For the purpose of calibration and commissioning of the vessel, rectangular samples of closed cell ethylene vinyl acetate (EVA) foam were tested. Each sample was subjected to repeated loading, and nine separate biaxial experiments were carried out to a maximum pressure of 204 kPa (30 psi), with a relaxation time of two hours between them. Calibration testing demonstrated the force applied to the samples had a maximum error of 0.026 N (0.423% of maximum applied force). Under repeated loading, the foam sample demonstrated lower stiffness during the first load cycle. Following this cycle, an increased stiffness, repeatable response was observed with successive loading. While the experimental protocol was developed for EVA foam, preliminary results on this material suggest that this device may be capable of providing test data for biological tissue samples. The load response of the foam was characteristic of closed cell foams, with consolidation during the early loading cycles, then a repeatable load-displacement response upon repeated loading. The repeatability of the test results demonstrated the ability of the test device to provide reproducible test data and the low experimental error in the force demonstrated the reliability of the test data.
Direct model reference adaptive control of robotic arms

NASA Technical Reports Server (NTRS)

Kaufman, Howard; Swift, David C.; Cummings, Steven T.; Shankey, Jeffrey R.

1993-01-01

The results of controlling A PUMA 560 Robotic Manipulator and the NASA shuttle Remote Manipulator System (RMS) using a Command Generator Tracker (CGT) based Model Reference Adaptive Controller (DMRAC) are presented. Initially, the DMRAC algorithm was run in simulation using a detailed dynamic model of the PUMA 560. The algorithm was tuned on the simulation and then used to control the manipulator using minimum jerk trajectories as the desired reference inputs. The ability to track a trajectory in the presence of load changes was also investigated in the simulation. Satisfactory performance was achieved in both simulation and on the actual robot. The obtained responses showed that the algorithm was robust in the presence of sudden load changes. Because these results indicate that the DMRAC algorithm can indeed be successfully applied to the control of robotic manipulators, additional testing was performed to validate the applicability of DMRAC to simulated dynamics of the shuttle RMS.
25th Space Simulation Conference. Environmental Testing: The Earth-Space Connection

NASA Technical Reports Server (NTRS)

Packard, Edward

2008-01-01

Topics covered include: Methods of Helium Injection and Removal for Heat Transfer Augmentation; The ESA Large Space Simulator Mechanical Ground Support Equipment for Spacecraft Testing; Temperature Stability and Control Requirements for Thermal Vacuum/Thermal Balance Testing of the Aquarius Radiometer; The Liquid Nitrogen System for Chamber A: A Change from Original Forced Flow Design to a Natural Flow (Thermo Siphon) System; Return to Mercury: A Comparison of Solar Simulation and Flight Data for the MESSENGER Spacecraft; Floating Pressure Conversion and Equipment Upgrades of Two 3.5kw, 20k, Helium Refrigerators; Affect of Air Leakage into a Thermal-Vacuum Chamber on Helium Refrigeration Heat Load; Special ISO Class 6 Cleanroom for the Lunar Reconnaissance Orbiter (LRO) Project; A State-of-the-Art Contamination Effects Research and Test Facility Martian Dust Simulator; Cleanroom Design Practices and Their Influence on Particle Counts; Extra Terrestrial Environmental Chamber Design; Contamination Sources Effects Analysis (CSEA) - A Tool to Balance Cost/Schedule While Managing Facility Availability; SES and Acoustics at GSFC; HST Super Lightweight Interchangeable Carrier (SLIC) Static Test; Virtual Shaker Testing: Simulation Technology Improves Vibration Test Performance; Estimating Shock Spectra: Extensions beyond GEVS; Structural Dynamic Analysis of a Spacecraft Multi-DOF Shaker Table; Direct Field Acoustic Testing; Manufacture of Cryoshroud Surfaces for Space Simulation Chambers; The New LOTIS Test Facility; Thermal Vacuum Control Systems Options for Test Facilities; Extremely High Vacuum Chamber for Low Outgassing Processing at NASA Goddard; Precision Cleaning - Path to Premier; The New Anechoic Shielded Chambers Designed for Space and Commercial Applications at LIT; Extraction of Thermal Performance Values from Samples in the Lunar Dust Adhesion Bell Jar; Thermal (Silicon Diode) Data Acquisition System; Aquarius's Instrument Science Data System (ISDS) Automated to Acquire, Process, Trend Data and Produce Radiometric System Assessment Reports; Exhaustive Thresholds and Resistance Checkpoints; Reconfigurable HIL Testing of Earth Satellites; FPGA Control System for the Automated Test of MicroShutters; Ongoing Capabilities and Developments of Re-Entry Plasma Ground Tests at EADS-ASTRIUM; Operationally Responsive Space Standard Bus Battery Thermal Balance Testing and Heat Dissipation Analysis; Galileo - The Serial-Production AIT Challenge; The Space Systems Environmental Test Facility Database (SSETFD), Website Development Status; Simulated Reentry Heating by Torching; Micro-Vibration Measurements on Thermally Loaded Multi-Layer Insulation Samples in Vacuum; High Temperature Life Testing of 80Ni-20Cr Wire in a Simulated Mars Atmosphere for the Sample Analysis at Mars (SAM) Instrument Suit Gas Processing System (GPS) Carbon Dioxide Scrubber; The Planning and Implementation of Test Facility Improvements; and Development of a Silicon Carbide Molecular Beam Nozzle for Simulation Planetary Flybys and Low-Earth Orbit.
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.
Application of Watershed Scale Models to Predict Nitrogen Loading From Coastal Plain Watersheds

Treesearch

George M. Chescheir; Glenn P Fernandez; R. Wayne Skaggs; Devendra M. Amatya

2004-01-01

DRAINMOD-based watershed models have been developed and tested using data collected from an intensively instrumented research site on Kendricks Creek watershed near Plymouth. NC. These models were applied to simulate the hydrology and nitrate nitrogen (NO3-N) loading from two other watersheds in the Coastal Plain of North Carolina, the 11600 ha Chicod Creek watershed...
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.
Influence of upper-body external loading on anaerobic exercise performance.

PubMed

Inacio, Mario; Dipietro, Loretta; Visek, Amanda J; Miller, Todd A

2011-04-01

The purpose of this study was to assess the threshold where simulated adipose tissue weight gain significantly affects performance in common anaerobic tasks and determine whether differences exist between men and women. Forty-six subjects (men = 21; women = 25) were tested for vertical jump, 20- and 40-yd dash, and 20-yd shuttle tests under 6 different loading conditions (0, 2, 4, 6, 8, and 10% of added body weight). Results were compared to each subject's baseline values (0% loading condition). Results demonstrate significant decrements in performance, starting at the 2% loading condition, for both genders, in every performance test (p < 0.05). On average, subjects jumped 4.91 ± 0.29 to 9.83 ± 0.30 cm less, increased agility test times from 5.49 ± 0.56 to 5.86 ± 0.61 seconds, and increased sprint times from 7.80 ± 0.96 to 8.39 ± 1.07 seconds (2-10%, respectively; p < 0.05). When lower-body power was corrected for total body mass, men exerted significantly more power than women did in every loading condition. Conversely, when lower-body power was corrected for lean body mass, men exerted significantly more power than did women only at the 2% loading condition. This study demonstrates that for the specific anaerobic performance tests performed, increases in external loading as low as 2% of body weight results in significant decreases in performance. Moreover, for these specific tests, men and women tend to express the same threshold in performance decrements.
Time dependent voiding mechanisms in polyamide 6 submitted to high stress triaxiality: experimental characterisation and finite element modelling

NASA Astrophysics Data System (ADS)

Selles, Nathan; King, Andrew; Proudhon, Henry; Saintier, Nicolas; Laiarinandrasana, Lucien

2017-08-01

Double notched round bars made of semi-crystalline polymer polyamide 6 (PA6) were submitted to monotonic tensile and creep tests. The two notches had a root radius of 0.45 mm, which imposes a multiaxial stress state and a state of high triaxiality in the net (minimal) section of the specimens. Tests were carried out until the failure occurred from one of the notches. The other one, unbroken but deformed under steady strain rate or steady load, was inspected using the Synchrotron Radiation Computed Tomography (SRCT) technique. These 3D through thickness inspections allowed the study of microstructural evolution at the peak stress for the monotonic tensile test and at the beginning of the tertiary creep for the creep tests. Cavitation features were assessed with a micrometre resolution within the notched region. Spatial distributions of void volume fraction ( Vf) and void morphology were studied. Voiding mechanisms were similar under steady strain rates and steady loads. The maximum values of Vf were located between the axis of revolution of the specimens and the notch surface and voids were considered as flat cylinders with a circular basis perpendicular to the loading direction. A model, based on porous plasticity, was used to simulate the mechanical response of this PA6 material under high stress triaxiality. Both macroscopic behaviour (loading curves) and voiding micro-mechanisms (radial distributions of void volume fraction) were accurately predicted using finite element simulations.
The BepiColombo Spacecraft: The Mercury Transfer Module Structure Qualification Test Campaign Description

NASA Astrophysics Data System (ADS)

Martin Zurdo, M. J.

2012-07-01

The BepiColombo is a space mission to Mercury (ESA in cooperation with Japan Aerospace Exploration Agency). The spacecraft consist of three different structures: two orbiters responsible for the scientific mission (MPO and MMO) and one service module, Mercury Transfer Module (MTM), which provides propulsion and services during the journey to Mercury. Taking into account only the MTM structure, the companies involved are ASTRIUM GERMANY acting as the prime contractor and ASTRIUM UK acting as the co- prime contractor company. EADS CASA Espacio (ECE) in Spain is the company responsible for the final design, manufacturing and qualification of the MTM structure. The test campaign specimen is the MTM core structure, which corresponds to the central cone with the structure floors, shear panels and tank support structure. This test campaign qualifies the primary load path and its primary interfaces; the rest of the MTM structure is qualified by system level vibration test. In order to qualify the MTM structure, three different kinds of qualification tests have been performed: stiffness test, global strength test and local tests in different specific areas. The most relevant test during the campaign is the global strength test case, in which several external loads are introduced (different interfaces) simulating the load introduction for a selected critical flight case. There are two important items in the qualification test campaign: 1. The instrumentation of the structure, with two main functions: to control the specimen under test loads, and to demonstrate the qualification of the structure. 2. The set-up structure, designed by ECE to allow the correct load introduction on each testing case during the whole test campaign. This paper describes the MTM structure test campaign from the definition of the loads applied in each test to the qualification of the complete structure.
Numerical Investigations of Interactions between the Knee-Thigh-Hip Complex with Vehicle Interior Structures.

PubMed

Kim, Yong Sun; Choi, Hyeong Ho; Cho, Young Nam; Park, Yong Jae; Lee, Jong B; Yang, King H; King, Albert I

2005-11-01

Although biomechanical studies on the knee-thigh-hip (KTH) complex have been extensive, interactions between the KTH and various vehicular interior design parameters in frontal automotive crashes for newer models have not been reported in the open literature to the best of our knowledge. A 3D finite element (FE) model of a 50(th) percentile male KTH complex, which includes explicit representations of the iliac wing, acetabulum, pubic rami, sacrum, articular cartilage, femoral head, femoral neck, femoral condyles, patella, and patella tendon, has been developed to simulate injuries such as fracture of the patella, femoral neck, acetabulum, and pubic rami of the KTH complex. Model results compared favorably against regional component test data including a three-point bending test of the femur, axial loading of the isolated knee-patella, axial loading of the KTH complex, axial loading of the femoral head, and lateral loading of the isolated pelvis. The model was further integrated into a Wayne State University upper torso model and validated against data obtained from whole body sled tests. The model was validated against these experimental data over a range of impact speeds, impactor masses and boundary conditions. Using Design Of Experiment (DOE) methods based on Taguchi's approach and the developed FE model of the whole body, including the KTH complex, eight vehicular interior design parameters, namely the load limiter force, seat belt elongation, pretensioner inlet amount, knee-knee bolster distance, knee bolster angle, knee bolster stiffness, toe board angle and impact speed, each with either two or three design levels, were simulated to predict their respective effects on the potential of KTH injury in frontal impacts. Simulation results proposed best design levels for vehicular interior design parameters to reduce the injury potential of the KTH complex due to frontal automotive crashes. This study is limited by the fact that prediction of bony fracture was based on an element elimination method available in the LS-DYNA code. No validation study was conducted to determine if this method is suitable when simulating fractures of biological tissues. More work is still needed to further validate the FE model of the KTH complex to increase its reliability in the assessment of various impact loading conditions associated with vehicular crash scenarios.
Testing of an Amine-Based Pressure-Swing System for Carbon Dioxide and Humidity Control

NASA Technical Reports Server (NTRS)

Lin, Amy; Smith, Frederick; Sweterlitsch, Jeffrey; Graf, John; Nalette, Tim; Papale, William; Campbell, Melissa; Lu, Sao-Dung

2007-01-01

In a crewed spacecraft environment, atmospheric carbon dioxide (CO2) and moisture control is crucial. Hamilton Sundstrand has developed a stable and efficient amine-based CO2 and water vapor sorbent, SA9T, that is well-suited for use in a spacecraft environment. The sorbent is efficiently packaged in pressure-swing regenerable beds that are thermally linked to improve removal efficiency and minimize vehicle thermal loads. Flows are all controlled with a single spool valve. This technology has been baselined for the new Orion spacecraft. However, more data was needed on the operational characteristics of the package in a simulated spacecraft environment. A unit was therefore tested with simulated metabolic loads in a closed chamber at Johnson Space Center during the last third of 2006. Tests were run at a variety of cabin temperatures and with a range of operating conditions varying cycle time, vacuum pressure, air flow rate, and crew activity levels. Results of this testing are presented and potential flight operational strategies discussed.
Experimental Characterization of the Energy Absorption of Functionally Graded Foam Filled Tubes Under Axial Crushing Loads

NASA Astrophysics Data System (ADS)

Ebrahimi, Saeed; Vahdatazad, Nader; Liaghat, Gholamhossein

2018-03-01

This paper deals with the energy absorption characterization of functionally graded foam (FGF) filled tubes under axial crushing loads by experimental method. The FGF tubes are filled axially by gradient layers of polyurethane foams with different densities. The mechanical properties of the polyurethane foams are firstly obtained from axial compressive tests. Then, the quasi-static compressive tests are carried out for empty tubes, uniform foam filled tubes and FGF filled tubes. Before to present the experimental test results, a nonlinear FEM simulation of the FGF filled tube is carried out in ABAQUS software to gain more insight into the crush deformation patterns, as well as the energy absorption capability of the FGF filled tube. A good agreement between the experimental and simulation results is observed. Finally, the results of experimental test show that an FGF filled tube has excellent energy absorption capacity compared to the ordinary uniform foam-filled tube with the same weight.
Subject specific finite element modeling of periprosthetic femoral fracture using element deactivation to simulate bone failure.

PubMed

Miles, Brad; Kolos, Elizabeth; Walter, William L; Appleyard, Richard; Shi, Angela; Li, Qing; Ruys, Andrew J

2015-06-01

Subject-specific finite element (FE) modeling methodology could predict peri-prosthetic femoral fracture (PFF) for cementless hip arthoplasty in the early postoperative period. This study develops methodology for subject-specific finite element modeling by using the element deactivation technique to simulate bone failure and validate with experimental testing, thereby predicting peri-prosthetic femoral fracture in the early postoperative period. Material assignments for biphasic and triphasic models were undertaken. Failure modeling with the element deactivation feature available in ABAQUS 6.9 was used to simulate a crack initiation and propagation in the bony tissue based upon a threshold of fracture strain. The crack mode for the biphasic models was very similar to the experimental testing crack mode, with a similar shape and path of the crack. The fracture load is sensitive to the friction coefficient at the implant-bony interface. The development of a novel technique to simulate bone failure by element deactivation of subject-specific finite element models could aid prediction of fracture load in addition to fracture risk characterization for PFF. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.
Influence of the preparation design and artificial aging on the fracture resistance of monolithic zirconia crowns

PubMed Central

Anastassova-Yoshida, Yana; Nothdurft, Frank Phillip; von See, Constantin; Pospiech, Peter

2016-01-01

PURPOSE The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method. MATERIALS AND METHODS An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling 5℃–55℃ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at 137℃, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture. RESULTS The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly. CONCLUSION The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns. PMID:26949485
Simulations and Experiments of the Nonisothermal Forging Process of a Ti-6Al-4V Impeller

NASA Astrophysics Data System (ADS)

Prabhu, T. Ram

2016-09-01

In the present study, a nonisothermal precision forging process of a Ti-6Al-4V first-stage impeller for the gas turbine engine was simulated using the finite element software. The simulation results such as load requirements, damage, velocity field, stress, strain, and temperature distributions are discussed in detail. Simulations predicted the maximum load requirement of about 80 MN. The maximum temperature loss was observed at the contour surface regions. The center and contour regions are the high-strained regions in the part. To validate the model, forging experiments mimicking simulations were performed in the α + β phases region (930 °C). The selected locations of the part were characterized for tensile properties at 27 and 200 °C, hardness, microstructure, grain size, and the amount of primary α phase based on the strain distribution results. The soundness of the forged part was verified using fluorescent penetrant test (Mil Std 2175 Grade A) and ultrasonic test (AMS 2630 class A1). From the experimental results, it was found that the variations in the hardness, tensile properties at room, and elevated temperature are not significant. The microstructure, grain size, and primary α phase content are nearly same.
Reduced Pressure Cabin Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Button, Amy B.; Sweterlitsch, Jeffrey J.

2013-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by United Technologies Corp. Aerospace Systems (UTAS, formerly Hamilton Sundstrand) and baselined for the Atmosphere Revitalization System for moderate duration missions of the Orion Multipurpose Crew Vehicle (MPCV). In previous years at this conference, reports were presented on extensive Johnson Space Center testing of this technology in a sea-level pressure environment with simulated and actual human metabolic loads in both open and closed-loop configurations. In 2011, the technology was tested in an open cabin-loop configuration at ambient and two sub-ambient pressures to compare the performance of the system to the results of previous tests at ambient pressure. The testing used a human metabolic simulator with a different type of water vapor generation than previously used, which added some unique challenges in the data analysis. This paper summarizes the results of: baseline and some matrix testing at all three cabin pressures, increased vacuum regeneration line pressure testing with a high metabolic load, a set of tests studying CO2 and water vapor co-adsorption effects relative to model-predicted performance, and validation tests of flight project computer model predictions with specific operating conditions.
Finite element analysis of 2-Station hip himulator

NASA Astrophysics Data System (ADS)

Fazli, M. I. M.; Yahya, A.; Shahrom, A.; Nawawi, S. W.; Zainudin, M. R.; Nazarudin, M. S.

2017-10-01

This paper presented the analysis of materials and design architecture of 2-station hip simulator. Hip simulator is a machine used to conduct the joint and wear test of hip prosthetic. In earlier work, the hip simulator was modified and some improvement were made by using SolidWorks software. The simulator consists of 3DOF which controlled by separate stepper motor and a static load that set up by manual method in each station. In this work, finite element analysis (FEA) of hip simulator was implemented to analyse the structure of the design and selected materials used for simulator component. The analysis is completed based on two categories which are safety factor and stress tests. Both design drawing and FEA was done using SolidWorks software. The study of the two categories is performed by applying the peak load up to 4000N on the main frame that is embedded with metal-on-metal hip prosthesis. From FEA, the value of safety factor and degree of stress formation are successfully obtained. All the components exceed the value of 2 for safety factor analysis while the degree of stress formation shows higher value compare to the yield strength of the material. With this results, it provides information regarding part of simulator which are susceptible to destruct. Besides, the results could be used for design improvement and certify the stability of the hip simulator in real application.
Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle.

PubMed

Celegatti Filho, Tóride Sebastião; Rodrigues, Danillo Costa; Lauria, Andrezza; Moreira, Roger William Fernandes; Consani, Simonides

2015-01-01

To develop Y-shaped plates with different thicknesses to be used in simulated fractures of the mandibular condyle. Ten plates were developed in Y shape, containing eight holes, and 30 synthetic polyurethane mandible replicas were developed for the study. The load test was performed on an Instron Model 4411 universal testing machine, applying load in the mediolateral and anterior-posterior positions on the head of the condyle. Two-way ANOVA with Tukey testing with a 5% significance level was used. It was observed that when the load was applied in the medial-lateral plate of greater thickness (1.5 mm), it gave the highest strength, while in the anteroposterior direction, the plate with the highest resistance was of the lesser thickness (0.6 mm). A plate with a thickness of 1.5 mm was the one with the highest average value for all displacements. In the anteroposterior direction, the highest values of resistance were seen in the displacement of 15 mm. After comparing the values of the biomechanical testing found in the scientific literature, it is suggested that the use of Y plates are suitable for use in subcondylar fractures within the limitations of the study. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Large scale centrifuge test of a geomembrane-lined landfill subject to waste settlement and seismic loading.

PubMed

Kavazanjian, Edward; Gutierrez, Angel

2017-10-01

A large scale centrifuge test of a geomembrane-lined landfill subject to waste settlement and seismic loading was conducted to help validate a numerical model for performance based design of geomembrane liner systems. The test was conducted using the 240g-ton centrifuge at the University of California at Davis under the U.S. National Science Foundation Network for Earthquake Engineering Simulation Research (NEESR) program. A 0.05mm thin film membrane was used to model the liner. The waste was modeled using a peat-sand mixture. The side slope membrane was underlain by lubricated low density polyethylene to maximize the difference between the interface shear strength on the top and bottom of the geomembrane and the induced tension in it. Instrumentation included thin film strain gages to monitor geomembrane strains and accelerometers to monitor seismic excitation. The model was subjected to an input design motion intended to simulate strong ground motion from the 1994 Hyogo-ken Nanbu earthquake. Results indicate that downdrag waste settlement and seismic loading together, and possibly each phenomenon individually, can induce potentially damaging tensile strains in geomembrane liners. The data collected from this test is publically available and can be used to validate numerical models for the performance of geomembrane liner systems. Published by Elsevier Ltd.
Prediction of Frequency for Simulation of Asphalt Mix Fatigue Tests Using MARS and ANN

PubMed Central

Fakhri, Mansour

2014-01-01

Fatigue life of asphalt mixes in laboratory tests is commonly determined by applying a sinusoidal or haversine waveform with specific frequency. The pavement structure and loading conditions affect the shape and the frequency of tensile response pulses at the bottom of asphalt layer. This paper introduces two methods for predicting the loading frequency in laboratory asphalt fatigue tests for better simulation of field conditions. Five thousand (5000) four-layered pavement sections were analyzed and stress and strain response pulses in both longitudinal and transverse directions was determined. After fitting the haversine function to the response pulses by the concept of equal-energy pulse, the effective length of the response pulses were determined. Two methods including Multivariate Adaptive Regression Splines (MARS) and Artificial Neural Network (ANN) methods were then employed to predict the effective length (i.e., frequency) of tensile stress and strain pulses in longitudinal and transverse directions based on haversine waveform. It is indicated that, under controlled stress and strain modes, both methods (MARS and ANN) are capable of predicting the frequency of loading in HMA fatigue tests with very good accuracy. The accuracy of ANN method is, however, more than MARS method. It is furthermore shown that the results of the present study can be generalized to sinusoidal waveform by a simple equation. PMID:24688400
Prediction of frequency for simulation of asphalt mix fatigue tests using MARS and ANN.

PubMed

Ghanizadeh, Ali Reza; Fakhri, Mansour

2014-01-01

Fatigue life of asphalt mixes in laboratory tests is commonly determined by applying a sinusoidal or haversine waveform with specific frequency. The pavement structure and loading conditions affect the shape and the frequency of tensile response pulses at the bottom of asphalt layer. This paper introduces two methods for predicting the loading frequency in laboratory asphalt fatigue tests for better simulation of field conditions. Five thousand (5000) four-layered pavement sections were analyzed and stress and strain response pulses in both longitudinal and transverse directions was determined. After fitting the haversine function to the response pulses by the concept of equal-energy pulse, the effective length of the response pulses were determined. Two methods including Multivariate Adaptive Regression Splines (MARS) and Artificial Neural Network (ANN) methods were then employed to predict the effective length (i.e., frequency) of tensile stress and strain pulses in longitudinal and transverse directions based on haversine waveform. It is indicated that, under controlled stress and strain modes, both methods (MARS and ANN) are capable of predicting the frequency of loading in HMA fatigue tests with very good accuracy. The accuracy of ANN method is, however, more than MARS method. It is furthermore shown that the results of the present study can be generalized to sinusoidal waveform by a simple equation.
Full-Scale System for Quantifying Loads and Leak Rates of Seals for Space Applications

NASA Technical Reports Server (NTRS)

Dunlap, Patrick H., Jr.; Steinetz, Bruce M.; Daniels, Christopher C.; Wasowski, Janice L.; Robbie, Malcolm G.; Erker, Arthur H.; Drlik, Gary J.; Mayer, John J.

2010-01-01

NASA is developing advanced space-rated vacuum seals in support of future space exploration missions to low-Earth orbit and other destinations. These seals may be 50 to 60 in. (127 to 152 cm) in diameter and must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions to the International Space Station or the Moon. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them during docking or mating, and seal adhesion forces must be low to allow two mated systems to separate when required. NASA Glenn Research Center has developed a new test apparatus to measure leak rates and compression and adhesion loads of candidate full-scale seals under simulated thermal, vacuum, and engagement conditions. Tests can be performed in seal-on-seal or seal-on-flange configurations at temperatures from -76 to 140 F (-60 to 60 C) under operational pressure gradients. Nominal and off-nominal mating conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features of the test apparatus as well as techniques used to overcome some of the design challenges.
Modelling of Dynamic Rock Fracture Process with a Rate-Dependent Combined Continuum Damage-Embedded Discontinuity Model Incorporating Microstructure

NASA Astrophysics Data System (ADS)

Saksala, Timo

2016-10-01

This paper deals with numerical modelling of rock fracture under dynamic loading. For this end, a combined continuum damage-embedded discontinuity model is applied in finite element modelling of crack propagation in rock. In this model, the strong loading rate sensitivity of rock is captured by the rate-dependent continuum scalar damage model that controls the pre-peak nonlinear hardening part of rock behaviour. The post-peak exponential softening part of the rock behaviour is governed by the embedded displacement discontinuity model describing the mode I, mode II and mixed mode fracture of rock. Rock heterogeneity is incorporated in the present approach by random description of the rock mineral texture based on the Voronoi tessellation. The model performance is demonstrated in numerical examples where the uniaxial tension and compression tests on rock are simulated. Finally, the dynamic three-point bending test of a semicircular disc is simulated in order to show that the model correctly predicts the strain rate-dependent tensile strengths as well as the failure modes of rock in this test. Special emphasis is laid on modelling the loading rate sensitivity of tensile strength of Laurentian granite.
Experimental and numerical study of Bondura® 6.6 PIN joints

NASA Astrophysics Data System (ADS)

Berkani, I.; Karlsen, Ø.; Lemu, H. G.

2017-12-01

Pin joints are widely used in heavy-duty machinery such as aircrafts, cranes and offshore drilling equipment to transfer multi-dimensional shear forces. Their strength and service life depend on the clamping force in the contact region that is provided by interference fits. Though the interference fits provide full contact at the pin-hole interface under pretension loads, the contact interface reduces when the pin is subjected to an external load and hence a smaller contact surface leads to dramatic increase of the contact stress. The PIN joint of Bondura® Technology, investigated in this study, is an innovative solution intended to reduce the slack at the contact surface of the pin joint of heavy-duty machinery by using tapered sleeves on each end of the PIN. The study is aimed to better understand the contact pressure build-up and stress distribution in the supporting contact surface under pre-loading of the joint and the influence of temperature difference between part assembly and operation conditions. Numerical simulation using finite element method and diverse experimental tests were conducted. The numerical simulation and the test results, particularly the tests conducted with lubricated joints, show good conformance.

Results of the ETV-1 breadboard tests under steady-state and transient conditions. [conducted in the NASA-LeRC Road Load Simulator

NASA Technical Reports Server (NTRS)

Sargent, N. B.; Dustin, M. O.

1981-01-01

Steady state tests were run to characterize the system and component efficiencies over the complete speed-torque capabilities of the propulsion system in both motoring and regenerative modes of operation. The steady state data were obtained using a battery simulator to separate the effects on efficiency caused by changing battery state-of-charge and component temperature. Transient tests were performed to determine the energy profiles of the propulsion system operating over the SAE J227a driving schedules.
Development of a Continuum Damage Mechanics Material Model of a Graphite-Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Littell, Justin D.

2017-01-01

This paper describes the development of input properties for a continuum damage mechanics based material model, Mat 58, within LS-DYNA(Registered Trademark) to simulate the response of a graphite-Kevlar(Registered Trademark) hybrid plain weave fabric. A limited set of material characterization tests were performed on the hybrid graphite-Kevlar(Registered Trademark) fabric. Simple finite element models were executed in LS-DYNA(Registered Trademark) to simulate the material characterization tests and to verify the Mat 58 material model. Once verified, the Mat 58 model was used in finite element models of two composite energy absorbers: a conical-shaped design, designated the "conusoid," fabricated of four layers of hybrid graphite-Kevlar(Registered Trademark) fabric; and, a sinusoidal-shaped foam sandwich design, designated the "sinusoid," fabricated of the same hybrid fabric face sheets with a foam core. Dynamic crush tests were performed on components of the two energy absorbers, which were designed to limit average vertical accelerations to 25- to 40-g, to minimize peak crush loads, and to generate relatively long crush stroke values under dynamic loading conditions. Finite element models of the two energy absorbers utilized the Mat 58 model that had been verified through material characterization testing. Excellent predictions of the dynamic crushing response were obtained.
A new class of high-G and long-duration shock testing machines

NASA Astrophysics Data System (ADS)

Rastegar, Jahangir

2018-03-01

Currently available methods and systems for testing components for survival and performance under shock loading suffer from several shortcomings for use to simulate high-G acceleration events with relatively long duration. Such events include most munitions firing and target impact, vehicular accidents, drops from relatively high heights, air drops, impact between machine components, and other similar events. In this paper, a new class of shock testing machines are presented that can be used to subject components to be tested to high-G acceleration pulses of prescribed amplitudes and relatively long durations. The machines provide for highly repeatable testing of components. The components are mounted on an open platform for ease of instrumentation and video recording of their dynamic behavior during shock loading tests.
RMS active damping augmentation

NASA Technical Reports Server (NTRS)

Gilbert, Michael G.; Scott, Michael A.; Demeo, Martha E.

1992-01-01

The topics are presented in viewgraph form and include: RMS active damping augmentation; potential space station assembly benefits to CSI; LaRC/JSC bridge program; control law design process; draper RMS simulator; MIMO acceleration control laws improve damping; potential load reduction benefit; DRS modified to model distributed accelerations; accelerometer location; Space Shuttle aft cockpit simulator; simulated shuttle video displays; SES test goals and objectives; and SES modifications to support RMS active damping augmentation.
Reduced Pressure Cabin Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Button, Amy; Sweterlitsch, Jeffrey

2011-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by Hamilton Sundstrand and baselined for the Atmosphere Revitalization System for moderate duration missions of the Orion Multipurpose Crew Vehicle. In previous years at this conference, reports were presented on extensive Johnson Space Center testing of this technology in a sea-level pressure environment with simulated and actual human metabolic loads in both open and closed-loop configurations. In 2011, the technology was tested in an open cabin-loop configuration at ambient and two sub-ambient pressures to compare the performance of the system to the results of previous tests at ambient pressure. The testing used a human metabolic simulator with a different type of water vapor generation than previously used, which added some unique challenges in the data analysis. This paper summarizes the results of: baseline and some matrix testing at all three cabin pressures, increased vacuum regeneration line pressure with a high metabolic load, a set of tests studying CO2 and water vapor co-adsorption effects relative to model-predicted performance, and validation tests of flight program computer model predictions with specific operating conditions.
Reduced Pressure Cabin Testing of the Orion Atmosphere Revitalization Technology

NASA Technical Reports Server (NTRS)

Button, Amy; Sweterlisch, Jeffery J.

2013-01-01

An amine-based carbon dioxide (CO2) and water vapor sorbent in pressure-swing regenerable beds has been developed by Hamilton Sundstrand and baselined for the Atmosphere Revitalization System for moderate duration missions of the Orion Multipurpose Crew Vehicle. In previous years at this conference, reports were presented on extensive Johnson Space Center testing of this technology in a sea-level pressure environment with simulated and actual human metabolic loads in both open and closed-loop configurations. In 2011, the technology was tested in an open cabin-loop configuration at ambient and two sub-ambient pressures to compare the performance of the system to the results of previous tests at ambient pressure. The testing used a human metabolic simulator with a different type of water vapor generation than previously used, which added some unique challenges in the data analysis. This paper summarizes the results of: baseline and some matrix testing at all three cabin pressures, increased vacuum regeneration line pressure with a high metabolic load, a set of tests studying CO2 and water vapor co-adsorption effects relative to model-predicted performance, and validation tests of flight program computer model predictions with specific operating conditions.
Development flight tests of the Viking decelerator system.

NASA Technical Reports Server (NTRS)

Murrow, H. N.; Eckstrom, C. V.; Henke, D. W.

1973-01-01

Significant aspects of a low altitude flight test phase of the overall Viking decelerator system development are given. This test series included nine aircraft drop tests that were conducted at the Joint Parachute Test Facility, El Centro, California, between September 1971 and May 1972. The test technique and analytical planning method utilized to best simulate loading conditions in a low density environment are presented and some test results are shown to assess their adequacy. Performance effects relating to suspension line lengths of 1.7 D sub o with different canopy loadings are noted. System hardware developments are described, in particular the utilization of a fabric deployment mortar cover which remained attached to the parachute canopy. Finally, the contribution of this test series to the overall program is assessed.
Numerical modeling of the fracture process in a three-unit all-ceramic fixed partial denture.

PubMed

Kou, Wen; Kou, Shaoquan; Liu, Hongyuan; Sjögren, Göran

2007-08-01

The main objectives were to examine the fracture mechanism and process of a ceramic fixed partial denture (FPD) framework under simulated mechanical loading using a recently developed numerical modeling code, the R-T(2D) code, and also to evaluate the suitability of R-T(2D) code as a tool for this purpose. Using the recently developed R-T(2D) code the fracture mechanism and process of a 3U yttria-tetragonal zirconia polycrystal ceramic (Y-TZP) FPD framework was simulated under static loading. In addition, the fracture pattern obtained using the numerical simulation was compared with the fracture pattern obtained in a previous laboratory test. The result revealed that the framework fracture pattern obtained using the numerical simulation agreed with that observed in a previous laboratory test. Quasi-photoelastic stress fringe pattern and acoustic emission showed that the fracture mechanism was tensile failure and that the crack started at the lower boundary of the framework. The fracture process could be followed both in step-by-step and step-in-step. Based on the findings in the current study, the R-T(2D) code seems suitable for use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture processes in ceramic FPD frameworks.
Computational fluid dynamic (CFD) investigation of thermal uniformity in a thermal cycling based calibration chamber for MEMS

NASA Astrophysics Data System (ADS)

Gui, Xulong; Luo, Xiaobing; Wang, Xiaoping; Liu, Sheng

2015-12-01

Micro-electrical-mechanical system (MEMS) has become important for many industries such as automotive, home appliance, portable electronics, especially with the emergence of Internet of Things. Volume testing with temperature compensation has been essential in order to provide MEMS based sensors with repeatability, consistency, reliability, and durability, but low cost. Particularly, in the temperature calibration test, temperature uniformity of thermal cycling based calibration chamber becomes more important for obtaining precision sensors, as each sensor is different before the calibration. When sensor samples are loaded into the chamber, we usually open the door of the chamber, then place fixtures into chamber and mount the samples on the fixtures. These operations may affect temperature uniformity in the chamber. In order to study the influencing factors of sample-loading on the temperature uniformity in the chamber during calibration testing, numerical simulation work was conducted first. Temperature field and flow field were simulated in empty chamber, chamber with open door, chamber with samples, and chamber with fixtures, respectively. By simulation, it was found that opening chamber door, sample size and number of fixture layers all have effects on flow field and temperature field. By experimental validation, it was found that the measured temperature value was consistent with the simulated temperature value.
Evaluation of fracture resistance in simulated immature teeth using Resilon and Ribbond as root reinforcements--an in vitro study.

PubMed

Hemalatha, Hiremath; Sandeep, Metgud; Kulkarni, Sadanand; Yakub, Shoeb Sheikh

2009-08-01

To compare the reinforcement and strengthening ability of resilon, gutta-percha, and ribbond in endodontically treated roots of immature teeth. Sixty five freshly extracted human maxillary anterior teeth were prepared with a Peeso no. 6 to simulate immature teeth (Cvek's stage 3 root development). After instrumentation, each root was irrigated with sodium hypochlorite and with ethylene diamino tetra acetic acid to remove the smear layer. To simulate single visit apexification technique a 4-5 mm white Pro Root mineral trioxide aggregate plug was placed apically using schilder carrier. The teeth were divided into three experimental groups and one control group. Group I--control group (root canals instrumented but not filled); Group II--backfilled with thermoplastisized gutta-percha using AH plus sealer; Group III--reinforced with Resilon using epiphany sealer; Group IV--reinforced with Ribbond fibers using Panavia F luting cement. A Universal Testing Machine was used to apply a load, at the level of the lingual cementoenamel junction with a chisel-shaped tip The peak load to fracture was recorded and statistical analysis was completed using student's t-test. Values of peak load to fracture were 1320.8, 1604.88, 1620, and 1851 newtons for Group I to Group IV respectively. The results of student's t-test, revealed no significant difference (P > 0.05,) between Group II and Group III. Comparison between Group IV and Group III and between Group IV and Group II revealed highly significant difference (P > 0.001). Teeth reinforced with Ribbond fibers using Panavia F luting cement showed the highest resistance to fracture. Resilon could not strengthen the roots and showed no statistically significant difference when compared with thermoplastisized gutta-percha in reinforcing immature tooth when tested with universal testing machine in an experimental model of immature tooth.
Investigation of the Loads on a Conventional Front and Rear Sliding Canopy

DTIC Science & Technology

1947-07-09

requirements used in the design of oanopies and their oom.ponents :tll.fl1 .’ ’ ............ -...... -.. - not be adequate. As the current load...oanopy’ ’. internal r rear of the oanopy " 3 The Curtiss,S:S20-4E airplane :is a a1.ngle-engtne" "two-pl.aoe~ low-rlilg sOoUt end dive bomber for use ...range of power conditions employed in these tests. Thrust coefficients" used in the tests to Simulate constant militar,y power operation in flight for
Failure Behavior of Elbows with Local Wall Thinning

NASA Astrophysics Data System (ADS)

Lee, Sung-Ho; Lee, Jeong-Keun; Park, Jai-Hak

Wall thinning defect due to corrosion is one of major aging phenomena in carbon steel pipes in most plant industries, and it results in reducing load carrying capacity of the piping components. A failure test system was set up for real scale elbows containing various simulated wall thinning defects, and monotonic in-plane bending tests were performed under internal pressure to find out the failure behavior of them. The failure behavior of wall-thinned elbows was characterized by the circumferential angle of thinned region and the loading conditions to the piping system.
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.
Modeling the Blast Load Simulator Airblast Environment using First Principles Codes. Report 1, Blast Load Simulator Environment

DTIC Science & Technology

2016-11-01

ER D C/ G SL T R- 16 -3 1 Modeling the Blast Load Simulator Airblast Environment Using First Principles Codes Report 1, Blast Load...Simulator Airblast Environment using First Principles Codes Report 1, Blast Load Simulator Environment Gregory C. Bessette, James L. O’Daniel...evaluate several first principles codes (FPCs) for modeling airblast environments typical of those encountered in the BLS. The FPCs considered were
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.
Advanced Stirling Convertor Dual Convertor Controller Testing at NASA Glenn Research Center in the Radioisotope Power Systems System Integration Laboratory

NASA Technical Reports Server (NTRS)

Dugala, Gina M.; Taylor, Linda M.; Bell, Mark E.; Dolce, James L.; Fraeman, Martin; Frankford, David P.

2015-01-01

NASA Glenn Research Center developed a nonnuclear representation of a Radioisotope Power System (RPS) consisting of a pair of Advanced Stirling Convertors (ASCs), Dual Convertor Controller (DCC) EMs (engineering models) 2 and 3, and associated support equipment, which were tested in the Radioisotope Power Systems System Integration Laboratory (RSIL). The DCC was designed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to actively control a pair of ASCs. The first phase of testing included a Dual Advanced Stirling Convertor Simulator (DASCS), which was developed by JHU/APL and simulates the operation and electrical behavior of a pair of ASCs in real time via a combination of hardware and software. RSIL provides insight into the electrical interactions between a representative radioisotope power generator, its associated control schemes, and realistic electric system loads. The first phase of integration testing included the following spacecraft bus configurations: capacitive, battery, and super-capacitor. A load profile, created based on data from several missions, tested the RPS's and RSIL's ability to maintain operation during load demands above and below the power provided by the RPS. The integration testing also confirmed the DCC's ability to disconnect from the spacecraft when the bus voltage dipped below 22 volts or exceeded 36 volts. Once operation was verified with the DASCS, the tests were repeated with actual operating ASCs. The goal of this integration testing was to verify operation of the DCC when connected to a spacecraft and to verify the functionality of the newly designed RSIL. The results of these tests are presented in this paper.
Design and implementation of an air-conditioning system with storage tank for load shifting

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

Hsu, Y.Y.; Wu, C.J.; Liou, K.L.

1987-11-01

The experience with the design, simulation and implementation of an air-conditioning system with chilled water storage tank is presented in this paper. The system is used to shift air-conditioning load of residential and commercial buildings from on-peak to off-peak period. Demand-side load management can thus be achieved if many buildings are equipped with such storage devices. In the design of this system, a lumped-parameter circuit model is first employed to simulate the heat transfer within the air-conditioned building such that the required capacity of the storage tank can be figured out. Then, a set of desirable parameters for the temperaturemore » controller of the system are determined using the parameter plane method and the root locus method. The validity of the proposed mathematical model and design approach is verified by comparing the results obtained from field tests with those from the computer simulations. Cost-benefit analysis of the system is also discussed.« less
Ares I-X Upper Stage Simulator Structural Analyses Supporting the NESC Critical Initial Flaw Size Assessment

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Phillips, Dawn R.; Raju, Ivatury S.

2008-01-01

The structural analyses described in the present report were performed in support of the NASA Engineering and Safety Center (NESC) Critical Initial Flaw Size (CIFS) assessment for the ARES I-X Upper Stage Simulator (USS) common shell segment. The structural analysis effort for the NESC assessment had three thrusts: shell buckling analyses, detailed stress analyses of the single-bolt joint test; and stress analyses of two-segment 10 degree-wedge models for the peak axial tensile running load. Elasto-plastic, large-deformation simulations were performed. Stress analysis results indicated that the stress levels were well below the material yield stress for the bounding axial tensile design load. This report also summarizes the analyses and results from parametric studies on modeling the shell-to-gusset weld, flange-surface mismatch, bolt preload, and washer-bearing-surface modeling. These analyses models were used to generate the stress levels specified for the fatigue crack growth assessment using the design load with a factor of safety.
Influence of Asymmetric Cyclic Loading on Structural Evolution and Deformation Behavior of Cu-5 at.% Zr Alloy: An Atomistic Simulation-Based Study

NASA Astrophysics Data System (ADS)

Meraj, Md.; Dutta, Krishna; Bhardwaj, Ravindra; Yedla, Natraj; Karthik, V.; Pal, Snehanshu

2017-11-01

Molecular dynamics (MD) simulation-based studies of tensile test and structural evolution of Cu-5 at.% Zr alloy under asymmetric cyclic loading (i.e., ratcheting behavior) considering various stress ratios such as - 0.2, - 0.4 and - 0.6 for different temperatures, viz.≈ 100, 300 and 500 K have been performed using embedded atom model Finnis-Sinclair potential. According to obtained stress-strain response from MD calculation, Cu-5 at.% Zr alloy specimen is pristine in nature as sudden drop in stress just after yield stress and subsequent elastic type deformation are observed for this alloy. Predicted ratcheting strain by MD simulation for Cu-5 at.% Zr alloy varies from 4.5 to 5%. Significant increase in ratcheting strain has been observed with the increase in temperature. Slight reduction in crystallinity is identified at the middle of the each loading cycle from the performed radial distribution function analysis and cluster analysis.
Advanced Ground Systems Maintenance Cryogenics Test Lab Control System Upgrade Project

NASA Technical Reports Server (NTRS)

Harp, Janice Leshay

2014-01-01

This project will outfit the Simulated Propellant Loading System (SPLS) at KSC's Cryogenics Test Laboratory with a new programmable logic control system. The control system upgrade enables the Advanced Ground Systems Maintenace Element Integration Team and other users of the SPLS to conduct testing in a controls environment similar to that used at the launch pad.

Transient Pressure Test Article Test Program

NASA Technical Reports Server (NTRS)

Vibbart, Charles M.

1989-01-01

The Transient Pressure Test Article (TPTA) test program is being conducted at a new test facility located in the East Test Area at the National Aeronautics and Space Administration's (NASA's) Marshall Space Flight Center (MSFC) in Huntsville, Alabama. This facility, along with the special test equipment (STE) required for facility support, was constructed specifically to test and verify the sealing capability of the Redesigned Solid Rocket Motor (RSRM) field, igniter, and nozzle joints. The test article consists of full scale RSRM hardware loaded with inert propellant and assembled in a short stack configuration. The TPTA is pressurized by igniting a propellant cartridge capable of inducing a pressure rise rate which stimulates the ignition transient that occurs during launch. Dynamic loads are applied during the pressure cycle to simulate external tank attach (ETA) strut loads present on the ETA ring. Sealing ability of the redesigned joints is evaluated under joint movement conditions produced by these combined loads since joint sealing ability depends on seal resilience velocity being greater than gap opening velocity. Also, maximum flight dynamic loads are applied to the test article which is either pressurized to 600 psia using gaseous nitrogen (GN2) or applied to the test article as the pressure decays inside the test article on the down cycle after the ignition transient cycle. This new test facility is examined with respect to its capabilities. In addition, both the topic of test effectiveness versus space vehicle flight performance and new aerospace test techniques, as well as a comparison between the old SRM design and the RSRM are presented.
Modeling of the UAE Wind Turbine for Refinement of FAST{_}AD

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

Jonkman, J. M.

The Unsteady Aerodynamics Experiment (UAE) research wind turbine was modeled both aerodynamically and structurally in the FAST{_}AD wind turbine design code, and its response to wind inflows was simulated for a sample of test cases. A study was conducted to determine why wind turbine load magnitude discrepancies-inconsistencies in aerodynamic force coefficients, rotor shaft torque, and out-of-plane bending moments at the blade root across a range of operating conditions-exist between load predictions made by FAST{_}AD and other modeling tools and measured loads taken from the actual UAE wind turbine during the NASA-Ames wind tunnel tests. The acquired experimental test data representmore » the finest, most accurate set of wind turbine aerodynamic and induced flow field data available today. A sample of the FAST{_}AD model input parameters most critical to the aerodynamics computations was also systematically perturbed to determine their effect on load and performance predictions. Attention was focused on the simpler upwind rotor configuration, zero yaw error test cases. Inconsistencies in input file parameters, such as aerodynamic performance characteristics, explain a noteworthy fraction of the load prediction discrepancies of the various modeling tools.« less
Biomechanical analysis of fixation of middle third fractures of the clavicle.

PubMed

Drosdowech, Darren S; Manwell, Stuart E E; Ferreira, Louis M; Goel, Danny P; Faber, Kenneth J; Johnson, James A

2011-01-01

This biomechanical study compares four different techniques of fixation of middle third clavicular fractures. Twenty fresh-frozen clavicles were randomized into four groups. Each group used a different fixation device (3.5 Synthes reconstruction plate, 3.5 Synthes limited contact dynamic compression plate, 3.5 Synthes locking compression plate, and 4.5 DePuy Rockwood clavicular pin). All constructs were mechanically tested in bending and torque modes both with and without a simulated inferior cortical defect. Bending load to failure was also conducted. The four groups were compared using an analysis of variance test. The plate constructs were stiffer than the pin during both pure bending and torque loads with or without an inferior cortical defect. Bending load to failure with an inferior cortical defect revealed that the reconstruction plate was weaker compared with the other three groups. The limited contact and locking plates were stiffer than the reconstruction plate but demonstrated statistical significance only with the cortical defect. As hypothesized, the 3.5 limited contact dynamic compression plate and 3.5 locking compression plate demonstrated the greatest resistance to bending and torque loads, especially in the presence of simulated comminution of a middle third clavicular fracture. The reconstruction plate demonstrated lower stiffness and strength values compared with the other plates, especially with a cortical defect, whereas the pin showed poor resistance to bending and torque loads in all modes of testing. This information may help surgeons to choose the most appropriate method of fixation when treating fractures of the middle third of the clavicle.
Force Measurement on the GLAST Delta II Flight

NASA Technical Reports Server (NTRS)

Gordon, Scott; Kaufman, Daniel

2009-01-01

This viewgraph presentation reviews the interface force measurement at spacecraft separation of GLAST Delta II. The contents include: 1) Flight Force Measurement (FFM) Background; 2) Team Members; 3) GLAST Mission Overview; 4) Methodology Development; 5) Ground Test Validation; 6) Flight Data; 7) Coupled Loads Simulation (VCLA & Reconstruction); 8) Basedrive Simulation; 9) Findings; and 10) Summary and Conclusions.
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.
The SSM/PMAD automated test bed project

NASA Technical Reports Server (NTRS)

Lollar, Louis F.

1991-01-01

The Space Station Module/Power Management and Distribution (SSM/PMAD) autonomous subsystem project was initiated in 1984. The project's goal has been to design and develop an autonomous, user-supportive PMAD test bed simulating the SSF Hab/Lab module(s). An eighteen kilowatt SSM/PMAD test bed model with a high degree of automated operation has been developed. This advanced automation test bed contains three expert/knowledge based systems that interact with one another and with other more conventional software residing in up to eight distributed 386-based microcomputers to perform the necessary tasks of real-time and near real-time load scheduling, dynamic load prioritizing, and fault detection, isolation, and recovery (FDIR).
Simulation of launch and re-entry acceleration profiles for testing of shuttle and unmanned microgravity research payloads

NASA Astrophysics Data System (ADS)

Cassanto, J. M.; Ziserman, H. I.; Chapman, D. K.; Korszun, Z. R.; Todd, P.

Microgravity experiments designed for execution in Get-Away Special canisters, Hitchhiker modules, and Reusable Re-entry Satellites will be subjected to launch and re-entry accelerations. Crew-dependent provisions for preventing acceleration damage to equipment or products will not be available for these payloads during flight; therefore, the effects of launch and re-entry accelerations on all aspects of such payloads must be evaluated prior to flight. A procedure was developed for conveniently simulating the launch and re-entry acceleration profiles of the Space Shuttle (3.3 and 1.7 × g maximum, respectively) and of two versions of NASA's proposed materials research Re-usable Re-entry Satellite (8 × g maximum in one case and 4 × g in the other). By using the 7 m centrifuge of the Gravitational Plant Physiology Laboratory in Philadelphia it was found possible to simulate the time dependence of these 5 different acceleration episodes for payload masses up to 59 kg. A commercial low-cost payload device, the “Materials Dispersion Apparatus” of Instrumentation Technology Associates was tested for (1) integrity of mechanical function, (2) retention of fluid in its compartments, and (3) integrity of products under simulated re-entry g-loads. In particular, the sharp rise from 1 g to maximum g-loading that occurs during re-entry in various unmanned vehicles was successfully simulated, conditions were established for reliable functioning of the MDA, and crystals of 5 proteins suspended in compartments filled with mother liquor were subjected to this acceleration load.
Climate Control Load Reduction Strategies for Electric Drive Vehicles in Warm Weather

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

Jeffers, M. A.; Chaney, L.; Rugh, J. P.

Passenger compartment climate control is one of the largest auxiliary loads on a vehicle. Like conventional vehicles, electric vehicles (EVs) require climate control to maintain occupant comfort and safety, but cabin heating and air conditioning have a negative impact on driving range for all electric vehicles. Range reduction caused by climate control and other factors is a barrier to widespread adoption of EVs. Reducing the thermal loads on the climate control system will extend driving range, thereby reducing consumer range anxiety and increasing the market penetration of EVs. Researchers at the National Renewable Energy Laboratory have investigated strategies for vehiclemore » climate control load reduction, with special attention toward EVs. Outdoor vehicle thermal testing was conducted on two 2012 Ford Focus Electric vehicles to evaluate thermal management strategies for warm weather, including solar load reduction and cabin pre-ventilation. An advanced thermal test manikin was used to assess a zonal approach to climate control. In addition, vehicle thermal analysis was used to support testing by exploring thermal load reduction strategies, evaluating occupant thermal comfort, and calculating EV range impacts. Through stationary cooling tests and vehicle simulations, a zonal cooling configuration demonstrated range improvement of 6%-15%, depending on the drive cycle. A combined cooling configuration that incorporated thermal load reduction and zonal cooling strategies showed up to 33% improvement in EV range.« less
In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants

PubMed Central

2015-01-01

PURPOSE In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants. PMID:25932315
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.
Comparison of analysis and experiment for dynamics of low-contact-ratio spur gears

NASA Technical Reports Server (NTRS)

Oswald, Fred B.; Rebbechi, Brian; Zakrajsek, James J.; Townsend, Dennis P.; Lin, Hsiang Hsi

1991-01-01

Low-contact-ratio spur gears were tested in NASA gear-noise-rig to study gear dynamics including dynamic load, tooth bending stress, vibration, and noise. The experimental results were compared with a NASA gear dynamics code to validate the code as a design tool for predicting transmission vibration and noise. Analytical predictions and experimental data for gear-tooth dynamic loads and tooth-root bending stress were compared at 28 operating conditions. Strain gage data were used to compute the normal load between meshing teeth and the bending stress at the tooth root for direct comparison with the analysis. The computed and measured waveforms for dynamic load and stress were compared for several test conditions. These are very similar in shape, which means the analysis successfully simulates the physical behavior of the test gears. The predicted peak value of the dynamic load agrees with the measurement results within an average error of 4.9 percent except at low-torque, high-speed conditions. Predictions of peak dynamic root stress are generally within 10 to 15 percent of the measured values.
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
Dynamics modeling and loads analysis of an offshore floating wind turbine

NASA Astrophysics Data System (ADS)

Jonkman, Jason Mark

The vast deepwater wind resource represents a potential to use offshore floating wind turbines to power much of the world with renewable energy. Many floating wind turbine concepts have been proposed, but dynamics models, which account for the wind inflow, aerodynamics, elasticity, and controls of the wind turbine, along with the incident waves, sea current, hydrodynamics, and platform and mooring dynamics of the floater, were needed to determine their technical and economic feasibility. This work presents the development of a comprehensive simulation tool for modeling the coupled dynamic response of offshore floating wind turbines, the verification of the simulation tool through model-to-model comparisons, and the application of the simulation tool to an integrated loads analysis for one of the promising system concepts. A fully coupled aero-hydro-servo-elastic simulation tool was developed with enough sophistication to address the limitations of previous frequency- and time-domain studies and to have the features required to perform loads analyses for a variety of wind turbine, support platform, and mooring system configurations. The simulation capability was tested using model-to-model comparisons. The favorable results of all of the verification exercises provided confidence to perform more thorough analyses. The simulation tool was then applied in a preliminary loads analysis of a wind turbine supported by a barge with catenary moorings. A barge platform was chosen because of its simplicity in design, fabrication, and installation. The loads analysis aimed to characterize the dynamic response and to identify potential loads and instabilities resulting from the dynamic couplings between the turbine and the floating barge in the presence of combined wind and wave excitation. The coupling between the wind turbine response and the barge-pitch motion, in particular, produced larger extreme loads in the floating turbine than experienced by an equivalent land-based turbine. Instabilities were also found in the system. The influence of conventional wind turbine blade-pitch control actions on the pitch damping of the floating turbine was also assessed. Design modifications for reducing the platform motions, improving the turbine response, and eliminating the instabilities are suggested. These suggestions are aimed at obtaining cost-effective designs that achieve favorable performance while maintaining structural integrity.
Dynamic Load Predictions for Launchers Using Extra-Large Eddy Simulations X-Les

NASA Astrophysics Data System (ADS)

Maseland, J. E. J.; Soemarwoto, B. I.; Kok, J. C.

2005-02-01

Flow-induced unsteady loads can have a strong impact on performance and flight characteristics of aerospace vehicles and therefore play a crucial role in their design and operation. Complementary to costly flight tests and delicate wind-tunnel experiments, unsteady loads can be calculated using time-accurate Computational Fluid Dynamics. A capability to accurately predict the dynamic loads on aerospace structures at flight Reynolds numbers can be of great value for the design and analysis of aerospace vehicles. Advanced space launchers are subject to dynamic loads in the base region during the ascent to space. In particular the engine and nozzle experience aerodynamic pressure fluctuations resulting from massive flow separations. Understanding these phenomena is essential for performance enhancements for future launchers which operate a larger nozzle. A new hybrid RANS-LES turbulence modelling approach termed eXtra-Large Eddy Simulations (X-LES) holds the promise to capture the flow structures associated with massive separations and enables the prediction of the broad-band spectrum of dynamic loads. This type of method has become a focal point, reducing the cost of full LES, driven by the demand for their applicability in an industrial environment. The industrial feasibility of X-LES simulations is demonstrated by computing the unsteady aerodynamic loads on the main-engine nozzle of a generic space launcher configuration. The potential to calculate the dynamic loads is qualitatively assessed for transonic flow conditions in a comparison to wind-tunnel experiments. In terms of turn-around-times, X-LES computations are already feasible within the time-frames of the development process to support the structural design. Key words: massive separated flows; buffet loads; nozzle vibrations; space launchers; time-accurate CFD; composite RANS-LES formulation.
Dynamic Load Measurement of Ballistic Gelatin Impact Using an Instrumented Tube

NASA Technical Reports Server (NTRS)

Seidt, J. D.; Periira, J. M.; Hammer, J. T.; Gilat, A.; Ruggeri, C. R.

2012-01-01

Bird strikes are a common problem for the aerospace industry and can cause serious damage to an aircraft. Ballistic gelatin is frequently used as a surrogate for actual bird carcasses in bird strike tests. Numerical simulations of these tests are used to supplement experimental data, therefore it is necessary to use numerical modeling techniques that can accurately capture the dynamic response of ballistic gelatin. An experimental technique is introduced to validate these modeling techniques. A ballistic gelatin projectile is fired into a strike plate attached to a 36 in. long sensor tube. Dynamic load is measured at two locations relative to the strike plate using strain gages configured in a full Wheatstone bridge. Data from these experiments are used to validate a gelatin constitutive model. Simulations of the apparatus are analyzed to investigate its performance.
Autonomous Cryogenics Loading Operations Simulation Software: Knowledgebase Autonomous Test Engineer

NASA Technical Reports Server (NTRS)

Wehner, Walter S., Jr.

2013-01-01

Working on the ACLO (Autonomous Cryogenics Loading Operations) project I have had the opportunity to add functionality to the physics simulation software known as KATE (Knowledgebase Autonomous Test Engineer), create a new application allowing WYSIWYG (what-you-see-is-what-you-get) creation of KATE schematic files and begin a preliminary design and implementation of a new subsystem that will provide vision services on the IHM (Integrated Health Management) bus. The functionality I added to KATE over the past few months includes a dynamic visual representation of the fluid height in a pipe based on number of gallons of fluid in the pipe and implementing the IHM bus connection within KATE. I also fixed a broken feature in the system called the Browser Display, implemented many bug fixes and made changes to the GUI (Graphical User Interface).
Experimental and Computational Study of Ductile Fracture in Small Punch Tests

PubMed Central

Bargmann, Swantje; Hähner, Peter

2017-01-01

A unified experimental-computational study on ductile fracture initiation and propagation during small punch testing is presented. Tests are carried out at room temperature with unnotched disks of different thicknesses where large-scale yielding prevails. In thinner specimens, the fracture occurs with severe necking under membrane tension, whereas for thicker ones a through thickness shearing mode prevails changing the crack orientation relative to the loading direction. Computational studies involve finite element simulations using a shear modified Gurson-Tvergaard-Needleman porous plasticity model with an integral-type nonlocal formulation. The predicted punch load-displacement curves and deformed profiles are in good agreement with the experimental results. PMID:29039748
Experimental and Computational Study of Ductile Fracture in Small Punch Tests.

PubMed

Gülçimen Çakan, Betül; Soyarslan, Celal; Bargmann, Swantje; Hähner, Peter

2017-10-17

A unified experimental-computational study on ductile fracture initiation and propagation during small punch testing is presented. Tests are carried out at room temperature with unnotched disks of different thicknesses where large-scale yielding prevails. In thinner specimens, the fracture occurs with severe necking under membrane tension, whereas for thicker ones a through thickness shearing mode prevails changing the crack orientation relative to the loading direction. Computational studies involve finite element simulations using a shear modified Gurson-Tvergaard-Needleman porous plasticity model with an integral-type nonlocal formulation. The predicted punch load-displacement curves and deformed profiles are in good agreement with the experimental results.
Characterization of the Tribological Behavior of Oxide-Based NanoMaterials: Final CRADA Report

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

Fenske, George

2017-01-04

Under the Argonne/Pixelligent cooperative research and development agreement (CRADA – C1200801), Argonne performed labscale tribological tests on proprietary nano-sized ZrO 2 material developed by Pixelligent. Pixelligent utilized their proprietary process to prepare variants with different surfactants at different loadings in different carrier fluids for testing and evaluation at Argonne. Argonne applied a range of benchtop tribological test rigs to evaluate friction and wear under a range of conditions (contact geometry, loads, speeds, and temperature) that simulated a broad range of conditions experienced in engines and driveline components. Post-test analysis of worn surfaces provided information on the structure and chemistry ofmore » the tribofilms produced during the tests.« less
Method for Estimating Thread Strength Reduction of Damaged Parent Holes with Inserts

NASA Technical Reports Server (NTRS)

Johnson, David L.; Stratton, Troy C.

2005-01-01

During normal assembly and disassembly of bolted-joint components, thread damage and/or deformation may occur. If threads are overloaded, thread damage/deformation can also be anticipated. Typical inspection techniques (e.g. using GO-NO GO gages) may not provide adequate visibility of the extent of thread damage. More detailed inspection techniques have provided actual pitch-diameter profiles of damaged-hardware holes. A method to predict the reduction in thread shear-out capacity of damaged threaded holes has been developed. This method was based on testing and analytical modeling. Test samples were machined to simulate damaged holes in the hardware of interest. Test samples containing pristine parent-holes were also manufactured from the same bar-stock material to provide baseline results for comparison purposes. After the particular parent-hole thread profile was machined into each sample a helical insert was installed into the threaded hole. These samples were tested in a specially designed fixture to determine the maximum load required to shear out the parent threads. It was determined from the pristine-hole samples that, for the specific material tested, each individual thread could resist an average load of 3980 pounds. The shear-out loads of the holes having modified pitch diameters were compared to the ultimate loads of the specimens with pristine holes. An equivalent number of missing helical coil threads was then determined based on the ratio of shear-out loads for each thread configuration. These data were compared with the results from a finite element model (FEM). The model gave insights into the ability of the thread loads to redistribute for both pristine and simulated damage configurations. In this case, it was determined that the overall potential reduction in thread load-carrying capability in the hardware of interest was equal to having up to three fewer threads in the hole that bolt threads could engage. One- half of this potential reduction was due to local pitch-diameter variations and the other half was due to overall pitch-diameter enlargement beyond Class 2 fit. This result was important in that the thread shear capacity for this particular hardware design was the limiting structural capability. The details of the method development, including the supporting testing, data reduction and analytical model results comparison will be discussed hereafter.

Response of shallow geothermal energy pile from laboratory model tests

NASA Astrophysics Data System (ADS)

Marto, A.; Amaludin, A.

2015-09-01

In shallow geothermal energy pile systems, the thermal loads from the pile, transferred and stored in the soil will cause thermally induced settlement. This factor must be considered in the geotechnical design process to avoid unexpected hazards. Series of laboratory model tests were carried out to study the behaviour of energy piles installed in kaolin soil, subjected to thermal loads and a combination of axial and thermal loads (henceforth known as thermo-axial loads). Six tests which included two thermal load tests (35°C and 40°C) and four thermo-axial load tests (100 N and 200 N, combined with 35°C and 40°C thermal loads) were conducted. To simulate the behaviour of geothermal energy piles during its operation, the thermo-axial tests were carried out by applying an axial load to the model pile head, and a subsequent application of thermal load. The model soil was compacted at 90% maximum dry density and had an undrained shear strength of 37 kPa, thus classified as having a firm soil consistency. The behaviour of model pile, having the ultimate load capacity of 460 N, was monitored using a linear variable displacement transducer, load cell and wire thermocouple, to measure the pile head settlement, applied axial load and model pile temperature. The acquired data from this study was used to define the thermo-axial response characteristics of the energy pile model. In this study, the limiting settlement was defined as 10% of the model pile diameter. For thermal load tests, higher thermal loads induced higher values of thermal settlement. At 40°C thermal load an irreversible settlement was observed after the heating and cooling cycle was applied to the model pile. Meanwhile, the pile response to thermo-axial loads were attributed to soil consistency and the magnitude of both the axial and thermal loads applied to the pile. The higher the thermoaxial loads, the higher the settlements occurred. A slight hazard on the model pile was detected, since the settlement occurred was greater than the limiting value when the pile was loaded with thermo-axial loads of 40°C and 200 N. It is therefore recommended that the global factor of safety to be applied for energy pile installed in firm soil should be more than 2.3 to prevent any hazard to occur in the future, should the pile also be subjected to thermal load of 40°C or greater.
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
Research on the Fatigue Flexural Performance of RC Beams Attacked by Salt Spray

NASA Astrophysics Data System (ADS)

Mao, Jiang-hong; Xu, Fang-yuan; Jin, Wei-liang; Zhang, Jun; Wu, Xi-xi; Chen, Cai-sheng

2018-04-01

The fatigue flexural performance of RC beams attacked by salt spray was studied. A testing method involving electro osmosis, electrical accelerated corrosion and salt spray was proposed. This corrosion process method effectively simulates real-world salt spray and fatigue loading exerted by RC components on sea bridges. Four RC beams that have different stress amplitudes were tested. It is found that deterioration by corrosion and fatigue loading reduces the fatigue life of the RC and decreases the ability of deformation. The fatigue life and deflection ability could be reduced by increasing the stress amplitude and the corrosion duration time. The test result demonstrates that this experimental method can couple corrosion deterioration and fatigue loading reasonably. This procedure may be applied to evaluate the fatigue life and concrete durability of RC components located in a natural salt spray environment.
Algorithm for loading shot noise microbunching in multi-dimensional, free-electron laser simulation codes

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

Fawley, William M.

We discuss the underlying reasoning behind and the details of the numerical algorithm used in the GINGER free-electron laser(FEL) simulation code to load the initial shot noise microbunching on the electron beam. In particular, we point out that there are some additional subtleties which must be followed for multi-dimensional codes which are not necessary for one-dimensional formulations. Moreover, requiring that the higher harmonics of the microbunching also be properly initialized with the correct statistics leads to additional complexities. We present some numerical results including the predicted incoherent, spontaneous emission as tests of the shot noise algorithm's correctness.
Fiber pushout test: A three-dimensional finite element computational simulation

NASA Technical Reports Server (NTRS)

Mital, Subodh K.; Chamis, Christos C.

1990-01-01

A fiber pushthrough process was computationally simulated using three-dimensional finite element method. The interface material is replaced by an anisotropic material with greatly reduced shear modulus in order to simulate the fiber pushthrough process using a linear analysis. Such a procedure is easily implemented and is computationally very effective. It can be used to predict fiber pushthrough load for a composite system at any temperature. The average interface shear strength obtained from pushthrough load can easily be separated into its two components: one that comes from frictional stresses and the other that comes from chemical adhesion between fiber and the matrix and mechanical interlocking that develops due to shrinkage of the composite because of phase change during the processing. Step-by-step procedures are described to perform the computational simulation, to establish bounds on interfacial bond strength and to interpret interfacial bond quality.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Wei-Yang

Foam materials are used to protect sensitive components from impact loading. In order to predict and simulate the foam performance under various loading conditions, a validated foam model is needed and the mechanical properties of foams need to be characterized. Uniaxial compression and tension tests were conducted for different densities of foams under various temperatures and loading rates. Crush stress, tensile strength, and elastic modulus were obtained. A newly developed confined compression experiment provided data for investigating the foam flow direction. A biaxial tension experiment was also developed to explore the damage surface of a rigid polyurethane foam.
Learning and Control Model of the Arm for Loading

NASA Astrophysics Data System (ADS)

Kim, Kyoungsik; Kambara, Hiroyuki; Shin, Duk; Koike, Yasuharu

We propose a learning and control model of the arm for a loading task in which an object is loaded onto one hand with the other hand, in the sagittal plane. Postural control during object interactions provides important points to motor control theories in terms of how humans handle dynamics changes and use the information of prediction and sensory feedback. For the learning and control model, we coupled a feedback-error-learning scheme with an Actor-Critic method used as a feedback controller. To overcome sensory delays, a feedforward dynamics model (FDM) was used in the sensory feedback path. We tested the proposed model in simulation using a two-joint arm with six muscles, each with time delays in muscle force generation. By applying the proposed model to the loading task, we showed that motor commands started increasing, before an object was loaded on, to stabilize arm posture. We also found that the FDM contributes to the stabilization by predicting how the hand changes based on contexts of the object and efferent signals. For comparison with other computational models, we present the simulation results of a minimum-variance model.
Rubber Impact on 3D Textile Composites

NASA Astrophysics Data System (ADS)

Heimbs, Sebastian; Van Den Broucke, Björn; Duplessis Kergomard, Yann; Dau, Frederic; Malherbe, Benoit

2012-06-01

A low velocity impact study of aircraft tire rubber on 3D textile-reinforced composite plates was performed experimentally and numerically. In contrast to regular unidirectional composite laminates, no delaminations occur in such a 3D textile composite. Yarn decohesions, matrix cracks and yarn ruptures have been identified as the major damage mechanisms under impact load. An increase in the number of 3D warp yarns is proposed to improve the impact damage resistance. The characteristic of a rubber impact is the high amount of elastic energy stored in the impactor during impact, which was more than 90% of the initial kinetic energy. This large geometrical deformation of the rubber during impact leads to a less localised loading of the target structure and poses great challenges for the numerical modelling. A hyperelastic Mooney-Rivlin constitutive law was used in Abaqus/Explicit based on a step-by-step validation with static rubber compression tests and low velocity impact tests on aluminium plates. Simulation models of the textile weave were developed on the meso- and macro-scale. The final correlation between impact simulation results on 3D textile-reinforced composite plates and impact test data was promising, highlighting the potential of such numerical simulation tools.
A flight-test and simulation evaluation of the longitudinal final approach and landing performance of an automatic system for a light wing loading STOL aircraft equipped with wing spoilers

NASA Technical Reports Server (NTRS)

Brown, S. C.; Hardy, G. H.; Hindson, W. S.

1984-01-01

As part of a comprehensive flight-test investigation of short takeoff and landing (STOL) operating systems for the terminal systems for the terminal area, an automatic landing system has been developed and evaluated for a light wing-loading turboprop-powered aircraft. An advanced digital avionics system performed display, navigation, guidance, and control functions for the test aircraft. Control signals were generated in order to command powered actuators for all conventional controls and for a set of symmetrically driven wing spoilers. This report describes effects of the spoiler control on longitudinal autoland (automatic landing) performance. Flight-test results, with and without spoiler control, are presented and compared with available (basically, conventional takeoff and landing) performance criteria. These comparisons are augmented by results from a comprehensive simulation of the controlled aircraft that included representations of the microwave landing system navigation errors that were encountered in flight as well as expected variations in atmospheric turbulence and wind shear. Flight-test results show that the addition of spoiler control improves the touchdown performance of the automatic landing system. Spoilers improve longitudinal touchdown and landing pitch-attitude performance, particularly in tailwind conditions. Furthermore, simulation results indicate that performance would probably be satisfactory for a wider range of atmospheric disturbances than those encountered in flight. Flight results also indicate that the addition of spoiler control during the final approach does not result in any measurable change in glidepath track performance, and results in a very small deterioration in airspeed tracking. This difference contrasts with simulations results, which indicate some improvement in glidepath tracking and no appreciable change in airspeed tracking. The modeling problem in the simulation that contributed to this discrepancy with flight was not resolved.
Composite load spectra for select space propulsion structural components

NASA Technical Reports Server (NTRS)

Newell, J. F.; Kurth, R. E.; Ho, H.

1991-01-01

The objective of this program is to develop generic load models with multiple levels of progressive sophistication to simulate the composite (combined) load spectra that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades, and liquid oxygen posts and system ducting. The first approach will consist of using state of the art probabilistic methods to describe the individual loading conditions and combinations of these loading conditions to synthesize the composite load spectra simulation. The second approach will consist of developing coupled models for composite load spectra simulation which combine the deterministic models for composite load dynamic, acoustic, high pressure, and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients will then be determined using advanced probabilistic simulation methods with and without strategically selected experimental data.
Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge®2) before and after cyclic mechanical loading.

PubMed

Dittmer, Marc Philipp; Nensa, Moritz; Stiesch, Meike; Kohorst, Philipp

2013-01-01

Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. The load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo depends on additional aspects. Further studies are needed to address these aspects.
Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge®2) before and after cyclic mechanical loading

PubMed Central

DITTMER, Marc Philipp; NENSA, Moritz; STIESCH, Meike; KOHORST, Philipp

2013-01-01

Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. Objective The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. Material and Methods Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). Results All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. Conclusion The load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo depends on additional aspects. Further studies are needed to address these aspects. PMID:24037068
FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment.

PubMed

Zhang, Tao; Jiang, Feng; Yan, Lan; Xu, Xipeng

2017-12-26

The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM) model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE) simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature.
FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment

PubMed Central

Zhang, Tao; Jiang, Feng; Yan, Lan; Xu, Xipeng

2017-01-01

The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM) model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE) simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature. PMID:29278398
Development and mechanical properties of construction materials from lunar simulants

NASA Technical Reports Server (NTRS)

Desai, Chandra S.

1990-01-01

The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. Currently, this research involves two aspects: (1) liquefaction of lunar simulants with various additives in a furnace so as to produce a construction material like an intermediate ceramic; and (2) cyclic loading of simulant with different initial vacuums and densities with respect to the theoretical maximum densities (TMD). In both cases, bending, triaxial compression, extension, and hydrostatic tests will be performed to define the stress-strain strength response of the resulting materials. In the case of the intermediate ceramic, bending and available multiaxial test devices will be used, while for the compacted case, tests will be performed directly in the new device. The tests will be performed by simulating in situ confining conditions. A preliminary review of high-purity metal is also conducted.
Molecular Simulations of Adsorption and Diffusion in Silicalite.

NASA Astrophysics Data System (ADS)

Snurr, Randall Quentin

The adsorption and diffusion of hydrocarbons in the zeolite silicalite have been studied using molecular simulations. The simulations use an atomistic description of zeolite/sorbate interactions and are based on principles of statistical mechanics. Emphasis was placed on developing new simulation techniques to allow complex systems relevant to industrial applications in catalysis and separations processes to be studied. Adsorption isotherms and heats of sorption for methane in silicalite were calculated from grand canonical Monte Carlo (GCMC) simulations and also from molecular dynamics (MD) simulations accompanied by Widom test particle insertions. Good agreement with experimental data from the literature was found. The adsorption thermodynamics of aromatic species in silicalite at low loading was predicted by direct evaluation of the configurational integrals. Good agreement with experiment was obtained for the Henry's constants and the heats of adsorption. Molecules were predicted to be localized in the channel intersections at low loading. At higher loading, conventional GCMC simulations were found to be infeasible. Several variations of the GCMC technique were developed incorporating biased insertion moves. These new techniques are much more efficient than conventional GCMC and allow for the prediction of adsorption isotherms of tightly-fitting aromatic molecules in silicalite. Our simulations when combined with experimental evidence of a phase change in the zeolite structure at intermediate loading provide an explanation of the characteristic steps seen in the experimental isotherms. A hierarchical atomistic/lattice model for studying these systems was also developed. The hierarchical model is more than an order of magnitude more efficient computationally than direct atomistic simulation. Diffusion of benzene in silicalite was studied using transition-state theory (TST). Such an approach overcomes the time-scale limitations of using MD simulations for studying sorbate dynamics. Predicted diffusion coefficients were found to be too low compared to experiment. This was attributed to the assumption of a rigid zeolite structure in the calculations and the use of a harmonic approximation for calculating the TST rate constants. Details of sorbate motion were also investigated.
Simulation of beam-induced plasma in gas-filled rf cavities

DOE PAGES

Yu, Kwangmin; Samulyak, Roman; Yonehara, Katsuya; ...

2017-03-07

Processes occurring in a radio-frequency (rf) cavity, filled with high pressure gas and interacting with proton beams, have been studied via advanced numerical simulations. Simulations support the experimental program on the hydrogen gas-filled rf cavity in the Mucool Test Area (MTA) at Fermilab, and broader research on the design of muon cooling devices. space, a 3D electromagnetic particle-in-cell (EM-PIC) code with atomic physics support, was used in simulation studies. Plasma dynamics in the rf cavity, including the process of neutral gas ionization by proton beams, plasma loading of the rf cavity, and atomic processes in plasma such as electron-ion andmore » ion-ion recombination and electron attachment to dopant molecules, have been studied. Here, through comparison with experiments in the MTA, simulations quantified several uncertain values of plasma properties such as effective recombination rates and the attachment time of electrons to dopant molecules. Simulations have achieved very good agreement with experiments on plasma loading and related processes. Lastly, the experimentally validated code space is capable of predictive simulations of muon cooling devices.« less
Man-rated flight software for the F-8 DFBW program

NASA Technical Reports Server (NTRS)

Bairnsfather, R. R.

1975-01-01

The design, implementation, and verification of the flight control software used in the F-8 DFBW program are discussed. Since the DFBW utilizes an Apollo computer and hardware, the procedures, controls, and basic management techniques employed are based on those developed for the Apollo software system. Program Assembly Control, simulator configuration control, erasable-memory load generation, change procedures and anomaly reporting are discussed. The primary verification tools--the all-digital simulator, the hybrid simulator, and the Iron Bird simulator--are described, as well as the program test plans and their implementation on the various simulators. Failure-effects analysis and the creation of special failure-generating software for testing purposes are described. The quality of the end product is evidenced by the F-8 DFBW flight test program in which 42 flights, totaling 58 hours of flight time, were successfully made without any DFCS inflight software, or hardware, failures.
Grain boundary damage evolution and SCC initiation of cold-worked alloy 690 in simulated PWR primary water

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

Zhai, Ziqing; Toloczko, Mychailo B.; Kruska, Karen

Long-term grain boundary (GB) damage evolution and stress corrosion crack initiation in alloy 690 are being investigated by constant load tensile testing in high-temperature, simulated PWR primary water. Six commercial alloy 690 heats are being tested in various cold work conditions loaded at their yield stress. This paper reviews the basic test approach and detailed characterizations performed on selected specimens after an exposure time of ~1 year. Intergranular crack nucleation was observed under constant stress in certain highly cold-worked (CW) alloy 690 heats and was found to be associated with the formation of GB cavities. Somewhat surprisingly, the heats mostmore » susceptible to cavity formation and crack nucleation were thermally treated materials with most uniform coverage of small GB carbides. Microstructure, % cold work and applied stress comparisons are made among the alloy 690 heats to better understand the factors influencing GB cavity formation and crack initiation.« less
Manned maneuvering unit latching mechanism

NASA Technical Reports Server (NTRS)

Allton, C. S.

1980-01-01

The astronaut/Manned Maneuvering Unit interface, which presented a challenging set of requirements for a latching mechanism, is described. A spring loaded cam segment with variable ratio pulley release actuator was developed to meet the requirements. To preclude jamming of the mechanism, special precautions were taken such as spring loaded bearing points and careful selection of materials to resist cold welding. The mechanism successfully passed a number of tests which partially simulated orbital conditions.

Indoor test for thermal performance evaluation on the Sunworks (air) solar collector

NASA Technical Reports Server (NTRS)

1978-01-01

The test procedure used and the results obtained from an evaluation test program conducted to obtain thermal performance data on a Sunworks single glazed air solar collector under simulated conditions are described. A time constant test and incident angle modifier test were conducted to determine the transient effect and the incident angle effect on the collector. These results and the results of the collector load test are also discussed.
Technical Feasibility Evaluation on The Use of A Peltier Thermoelectric Module to Recover Automobile Exhaust Heat

NASA Astrophysics Data System (ADS)

Sugiartha, N.; Sastra Negara, P.

2018-01-01

A thermoelectric module composes of integrated p-n semiconductors as hot and cold side junctions and uses Seebeck effect between them to function as a thermoelectric generator (TEG) to directly convert heat into electrical power. Exhaust heat from engines as otherwise wasted to the atmosphere is one of the heat sources freely available to drive the TEG. This paper evaluates technical feasibility on the use of a Peltier thermoelectric module for energy recovery application of such kind of waste heat. An experimental apparatus has been setup to simulate real conditions of automobile engine exhaust piping system. It includes a square section aluminium ducting, an aluminium fin heat sink and a TEC1 12706 thermoelectric module. A heater and a cooling fan are employed to simulate hot exhaust gas and ambient air flows, respectively. Electrical loading is controlled by resistors. Dependent variables measured during the test are cold and hot side temperatures, open and loaded circuit output voltages and electrical current. The test results revealed a promising application of the Peltier thermoelectric module for the engine exhaust heat recovery, though the loaded output power produced and loaded output voltage are still far lower than the commercially thermoelectric module originally purposed for the TEG application.
Experiment and numerical simulation for laser ultrasonic measurement of residual stress.

PubMed

Zhan, Yu; Liu, Changsheng; Kong, Xiangwei; Lin, Zhongya

2017-01-01

Laser ultrasonic is a most promising method for non-destructive evaluation of residual stress. The residual stress of thin steel plate is measured by laser ultrasonic technique. The pre-stress loading device is designed which can easily realize the condition of the specimen being laser ultrasonic tested at the same time in the known stress state. By the method of pre-stress loading, the acoustoelastic constants are obtained and the effect of different test directions on the results of surface wave velocity measurement is discussed. On the basis of known acoustoelastic constants, the longitudinal and transverse welding residual stresses are measured by the laser ultrasonic technique. The finite element method is used to simulate the process of surface wave detection of welding residual stress. The pulsed laser is equivalent to the surface load and the relationship between the physical parameters of the laser and the load is established by the correction coefficient. The welding residual stress of the specimen is realized by the ABAQUS function module of predefined field. The results of finite element analysis are in good agreement with the experimental method. The simple and effective numerical and experimental methods for laser ultrasonic measurement of residual stress are demonstrated. Copyright © 2016. Published by Elsevier B.V.
Evaluation of a numerical model's ability to predict bed load transport observed in braided river experiments

NASA Astrophysics Data System (ADS)

Javernick, Luke; Redolfi, Marco; Bertoldi, Walter

2018-05-01

New data collection techniques offer numerical modelers the ability to gather and utilize high quality data sets with high spatial and temporal resolution. Such data sets are currently needed for calibration, verification, and to fuel future model development, particularly morphological simulations. This study explores the use of high quality spatial and temporal data sets of observed bed load transport in braided river flume experiments to evaluate the ability of a two-dimensional model, Delft3D, to predict bed load transport. This study uses a fixed bed model configuration and examines the model's shear stress calculations, which are the foundation to predict the sediment fluxes necessary for morphological simulations. The evaluation is conducted for three flow rates, and model setup used highly accurate Structure-from-Motion (SfM) topography and discharge boundary conditions. The model was hydraulically calibrated using bed roughness, and performance was evaluated based on depth and inundation agreement. Model bed load performance was evaluated in terms of critical shear stress exceedance area compared to maps of observed bed mobility in a flume. Following the standard hydraulic calibration, bed load performance was tested for sensitivity to horizontal eddy viscosity parameterization and bed morphology updating. Simulations produced depth errors equal to the SfM inherent errors, inundation agreement of 77-85%, and critical shear stress exceedance in agreement with 49-68% of the observed active area. This study provides insight into the ability of physically based, two-dimensional simulations to accurately predict bed load as well as the effects of horizontal eddy viscosity and bed updating. Further, this study highlights how using high spatial and temporal data to capture the physical processes at work during flume experiments can help to improve morphological modeling.
Effects of noise and task loading on a communication task loading on a communication task

NASA Astrophysics Data System (ADS)

Orrell, Dean H., II

Previous research had shown the effect of noise on a single communication task. This research has been criticized as not being representative of a real world situation since subjects allocated all of their attention to only one task. In the present study, the effect of adding a loading task to a standard noise-communication paradigm was investigated. Subjects performed both a communication task (Modified Rhyme Test; House et al. 1965) and a short term memory task (Sternberg, 1969) in simulated levels of aircraft noise (95, 105 and 115 dB overall sound pressure level (OASPL)). Task loading was varied with Sternberg's task by requiring subjects to memorize one, four, or six alphanumeric characters. Simulated aircraft noise was varied between levels of 95, 105 and 115 dB OASPL using a pink noise source. Results show that the addition of Sternberg's task and little effect on the intelligibility of the communication task while response time for the communication task increased.
Indoor test and long-term weathering effects on the thermal performance of the solar energy system (liquid) solar collector. [Marshall Space Flight Center solar test facility and solar simulator

NASA Technical Reports Server (NTRS)

1979-01-01

The procedures used and the results obtained during the evaluation test program on a liquid solar collector are presented. The narrow flat plate collector with reflective concentrating mirrors uses water as the working fluid. The double-covered collector weighs 137 pounds and has overall dimensions of about 35" by 77" by 6.75". The test program was conducted to obtain the following information: thermal performance data under simulated conditions, structural behavior under static load, and the effects of long term exposure to natural weathering.
Analytical and Experimental Assessment of Seismic Vulnerability of Beam-Column Joints without Transverse Reinforcement in Concrete Buildings

NASA Astrophysics Data System (ADS)

Hassan, Wael Mohammed

Beam-column joints in concrete buildings are key components to ensure structural integrity of building performance under seismic loading. Earthquake reconnaissance has reported the substantial damage that can result from inadequate beam-column joints. In some cases, failure of older-type corner joints appears to have led to building collapse. Since the 1960s, many advances have been made to improve seismic performance of building components, including beam-column joints. New design and detailing approaches are expected to produce new construction that will perform satisfactorily during strong earthquake shaking. Much less attention has been focused on beam-column joints of older construction that may be seismically vulnerable. Concrete buildings constructed prior to developing details for ductility in the 1970s normally lack joint transverse reinforcement. The available literature concerning the performance of such joints is relatively limited, but concerns about performance exist. The current study aimed to improve understanding and assessment of seismic performance of unconfined exterior and corner beam-column joints in existing buildings. An extensive literature survey was performed, leading to development of a database of about a hundred tests. Study of the data enabled identification of the most important parameters and the effect of each parameter on the seismic performance. The available analytical models and guidelines for strength and deformability assessment of unconfined joints were surveyed and evaluated. In particular, The ASCE 41 existing building document proved to be substantially conservative in joint shear strength estimation. Upon identifying deficiencies in these models, two new joint shear strength models, a bond capacity model, and two axial capacity models designed and tailored specifically for unconfined beam-column joints were developed. The proposed models strongly correlated with previous test results. In the laboratory testing phase of the current study, four full-scale corner beam-column joint subassemblies, with slab included, were designed, built, instrumented, tested, and analyzed. The specimens were tested under unidirectional and bidirectional displacement-controlled quasi-static loading that incorporated varying axial loads that simulated overturning seismic moment effects. The axial loads varied between tension and high compression loads reaching about 50% of the column axial capacity. The test parameters were axial load level, loading history, joint aspect ratio, and beam reinforcement ratio. The test results proved that high axial load increases joint shear strength and decreases the deformability of joints failing in pure shear failure mode without beam yielding. On the contrary, high axial load did not affect the strength of joints failing in shear after significant beam yielding; however, it substantially increased their displacement ductility. Joint aspect ratio proved to be instrumental in deciding joint shear strength; that is the deeper the joint the lower the shear strength. Bidirectional loading reduced the apparent strength of the joint in the uniaxial principal axes. However, circular shear strength interaction is an appropriate approximation to predict the biaxial strength. The developed shear strength models predicted successfully the strength of test specimens. Based on the literature database investigation, the shear and axial capacity models developed and the test results of the current study, an analytical finite element component model based on a proposed joint shear stress-rotation backbone constitutive curve was developed to represent the behavior of unconfined beam-column joints in computer numerical simulations of concrete frame buildings. The proposed finite element model included the effect of axial load, mode of joint failure, joint aspect ratio and axial capacity of joint. The proposed backbone curve along with the developed joint element exhibited high accuracy in simulating the test response of the current test specimens as well as previous test joints. Finally, a parametric study was conducted to assess the axial failure vulnerability of unconfined beam-column joints based on the developed shear and axial capacity models. This parametric study compared the axial failure potential of unconfined beam-column joint with that of shear critical columns to provide a preliminary insight into the axial collapse vulnerability of older-type buildings during intense ground shaking.
Stress Corrosion Cracking Behavior of Hardening-Treated 13Cr Stainless Steel

NASA Astrophysics Data System (ADS)

Niu, Li-Bin; Ishitake, Hisamitsu; Izumi, Sakae; Shiokawa, Kunio; Yamashita, Mitsuo; Sakai, Yoshihiro

2018-03-01

Stress corrosion cracking (SCC) behavior of the hardening-treated materials of 13Cr stainless steel was examined with SSRT tests and constant load tests. In the simulated geothermal water and even in the test water without addition of impurities, the hardening-treated materials showed a brittle intergranular fracture due to the sensitization, which was caused by the present hardening-treatments.
Tapered Roller Bearing Damage Detection Using Decision Fusion Analysis

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Kreider, Gary; Fichter, Thomas

2006-01-01

A diagnostic tool was developed for detecting fatigue damage of tapered roller bearings. Tapered roller bearings are used in helicopter transmissions and have potential for use in high bypass advanced gas turbine aircraft engines. A diagnostic tool was developed and evaluated experimentally by collecting oil debris data from failure progression tests conducted using health monitoring hardware. Failure progression tests were performed with tapered roller bearings under simulated engine load conditions. Tests were performed on one healthy bearing and three pre-damaged bearings. During each test, data from an on-line, in-line, inductance type oil debris sensor and three accelerometers were monitored and recorded for the occurrence of bearing failure. The bearing was removed and inspected periodically for damage progression throughout testing. Using data fusion techniques, two different monitoring technologies, oil debris analysis and vibration, were integrated into a health monitoring system for detecting bearing surface fatigue pitting damage. The data fusion diagnostic tool was evaluated during bearing failure progression tests under simulated engine load conditions. This integrated system showed improved detection of fatigue damage and health assessment of the tapered roller bearings as compared to using individual health monitoring technologies.
Influence of filler loading on the two-body wear of a dental composite.

PubMed

Hu, X; Marquis, P M; Shortall, A C

2003-07-01

The purpose of the study was to explore the fundamental wear behaviour of a dental composite with different filler loadings under two-body wear conditions. The parent resin and filler components were mixed according to different weight ratios to produce experimental composites with filler loadings ranging from 20 to 87.5% by weight. A two-body wear test was conducted on the experimental composites using a wear-testing machine. The machine was designed to simulate the impact of the direct cyclic masticatory loading that occurs in the occlusal contact area in vivo. The results showed that there was little increase in the rate of wear with filler loadings below 60 wt%, but a sharp increase between 80 and 87.5 wt% in filler loading. Wide striations and bulk loss of material were apparent on the wear surfaces at higher filler loadings. Coefficients of friction increased with filler loading and followed the increase in rate of wear loss closely. It was concluded that, under two-body wear conditions, addition of high levels of filler particles into the resin matrix could reduce the wear resistance of dental composites. This finding may help when designing future dental composites for use in particular clinical settings.
Time-Accurate Unsteady Pressure Loads Simulated for the Space Launch System at Wind Tunnel Conditions

NASA Technical Reports Server (NTRS)

Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, William L.; Glass, Christopher E.; Streett, Craig L.; Schuster, David M.

2015-01-01

A transonic flow field about a Space Launch System (SLS) configuration was simulated with the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics (CFD) code at wind tunnel conditions. Unsteady, time-accurate computations were performed using second-order Delayed Detached Eddy Simulation (DDES) for up to 1.5 physical seconds. The surface pressure time history was collected at 619 locations, 169 of which matched locations on a 2.5 percent wind tunnel model that was tested in the 11 ft. x 11 ft. test section of the NASA Ames Research Center's Unitary Plan Wind Tunnel. Comparisons between computation and experiment showed that the peak surface pressure RMS level occurs behind the forward attach hardware, and good agreement for frequency and power was obtained in this region. Computational domain, grid resolution, and time step sensitivity studies were performed. These included an investigation of pseudo-time sub-iteration convergence. Using these sensitivity studies and experimental data comparisons, a set of best practices to date have been established for FUN3D simulations for SLS launch vehicle analysis. To the author's knowledge, this is the first time DDES has been used in a systematic approach and establish simulation time needed, to analyze unsteady pressure loads on a space launch vehicle such as the NASA SLS.
Small-scale multi-axial hybrid simulation of a shear-critical reinforced concrete frame

NASA Astrophysics Data System (ADS)

Sadeghian, Vahid; Kwon, Oh-Sung; Vecchio, Frank

2017-10-01

This study presents a numerical multi-scale simulation framework which is extended to accommodate hybrid simulation (numerical-experimental integration). The framework is enhanced with a standardized data exchange format and connected to a generalized controller interface program which facilitates communication with various types of laboratory equipment and testing configurations. A small-scale experimental program was conducted using a six degree-of-freedom hydraulic testing equipment to verify the proposed framework and provide additional data for small-scale testing of shearcritical reinforced concrete structures. The specimens were tested in a multi-axial hybrid simulation manner under a reversed cyclic loading condition simulating earthquake forces. The physical models were 1/3.23-scale representations of a beam and two columns. A mixed-type modelling technique was employed to analyze the remainder of the structures. The hybrid simulation results were compared against those obtained from a large-scale test and finite element analyses. The study found that if precautions are taken in preparing model materials and if the shear-related mechanisms are accurately considered in the numerical model, small-scale hybrid simulations can adequately simulate the behaviour of shear-critical structures. Although the findings of the study are promising, to draw general conclusions additional test data are required.
Peeling behavior and spalling resistance of CFRP sheets bonded to bent concrete surfaces

NASA Astrophysics Data System (ADS)

Yuan, Hong; Li, Faping

2010-05-01

In this paper, the peeling behavior and the spalling resistance effect of carbon fiber reinforced polymer (CFRP) sheets externally bonded to bent concrete surfaces are firstly investigated experimentally. Twenty one curved specimens and seven plane specimens are studied in the paper, in which curved specimens with bonded CFRP sheets can simulate the concrete spalling in tunnel, culvert, arch bridge etc., whereas plane specimens with bonded CFRP sheets can simulate the concrete spalling in beam bridge, slab bridge and pedestrian bridge. Three kinds of curved specimens with different radii of curvature are chosen by referring to practical tunnel structures, and plane specimens are used for comparison with curved ones. A peeling load is applied on the FRP sheet by loading a circular steel tube placed into the central notch of beam to debond CFRP sheets from the bent concrete surface, meanwhile full-range load-deflection curves are recorded by a MTS 831.10 Elastomer Test System. Based on the experimental results, a theoretical analysis is also conducted for the specimens. Both theoretical and experimental results show that only two material parameters, the interfacial fracture energy of CFRP-concrete interface and the tensile stiffness of CFRP sheets, are needed for describing the interfacial spalling behavior. It is found that the radius of curvature has remarkable influence on peeling load-deflection curves. The test methods and test results given in the paper are helpful and available for reference to the designer of tunnel strengthening.
On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle

NASA Astrophysics Data System (ADS)

Weingart, Robert

This thesis is about the validation of a computational fluid dynamics simulation of a ground vehicle by means of a low-budget coast-down test. The vehicle is built to the standards of the 2014 Formula SAE rules. It is equipped with large wings in the front and rear of the car; the vertical loads on the tires are measured by specifically calibrated shock potentiometers. The coast-down test was performed on a runway of a local airport and is used to determine vehicle specific coefficients such as drag, downforce, aerodynamic balance, and rolling resistance for different aerodynamic setups. The test results are then compared to the respective simulated results. The drag deviates about 5% from the simulated to the measured results. The downforce numbers show a deviation up to 18% respectively. Moreover, a sensitivity analysis of inlet velocities, ride heights, and pitch angles was performed with the help of the computational simulation.
Explicit Nonlinear Finite Element Geometric Analysis of Parabolic Leaf Springs under Various Loads

PubMed Central

Kong, Y. S.; Omar, M. Z.; Chua, L. B.; Abdullah, S.

2013-01-01

This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE) method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability. PMID:24298209
Explicit nonlinear finite element geometric analysis of parabolic leaf springs under various loads.

PubMed

Kong, Y S; Omar, M Z; Chua, L B; Abdullah, S

2013-01-01

This study describes the effects of bounce, brake, and roll behavior of a bus toward its leaf spring suspension systems. Parabolic leaf springs are designed based on vertical deflection and stress; however, loads are practically derived from various modes especially under harsh road drives or emergency braking. Parabolic leaf springs must sustain these loads without failing to ensure bus and passenger safety. In this study, the explicit nonlinear dynamic finite element (FE) method is implemented because of the complexity of experimental testing A series of load cases; namely, vertical push, wind-up, and suspension roll are introduced for the simulations. The vertical stiffness of the parabolic leaf springs is related to the vehicle load-carrying capability, whereas the wind-up stiffness is associated with vehicle braking. The roll stiffness of the parabolic leaf springs is correlated with the vehicle roll stability. To obtain a better bus performance, two new parabolic leaf spring designs are proposed and simulated. The stress level during the loadings is observed and compared with its design limit. Results indicate that the newly designed high vertical stiffness parabolic spring provides the bus a greater roll stability and a lower stress value compared with the original design. Bus safety and stability is promoted, as well as the load carrying capability.
Centaur engine gimbal friction characteristics under simulated thrust load

NASA Technical Reports Server (NTRS)

Askew, J. W.

1986-01-01

An investigation was performed to determine the friction characteristics of the engine gimbal system of the Centaur upper stage rocket. Because the Centaur requires low-gain autopilots in order to meet all stability requirements for some configurations, control performance (response to transients and limit-cycle amplitudes) depends highly on these friction characteristics. Forces required to rotate the Centaur engine gimbal system were measured under a simulated thrust load of 66,723 N (15,000 lb) and in an altitude/thermal environment. A series of tests was performed at three test conditions; ambient temperature and pressure, ambient temperature and vacuum, and cryogenic temperature and vacuum. Gimbal rotation was controlled, and tests were performed in which rotation amplitude and frequency were varied by using triangular and sinusoidal waveforms. Test data revealed an elastic characteristic of the gimbal, independent of the input signal, which was evident prior to true gimbal sliding. The torque required to initiate gimbal sliding was found to decrease when both pressure and temperature decreased. Results from the low amplitude and low frequency data are currently being used in mathematically modeling the gimbal friction characteristics for Centaur autopilot performance studies.
Centaur engine gimbal friction characteristics under simulated thrust load

NASA Astrophysics Data System (ADS)

Askew, J. W.

1986-09-01

An investigation was performed to determine the friction characteristics of the engine gimbal system of the Centaur upper stage rocket. Because the Centaur requires low-gain autopilots in order to meet all stability requirements for some configurations, control performance (response to transients and limit-cycle amplitudes) depends highly on these friction characteristics. Forces required to rotate the Centaur engine gimbal system were measured under a simulated thrust load of 66,723 N (15,000 lb) and in an altitude/thermal environment. A series of tests was performed at three test conditions; ambient temperature and pressure, ambient temperature and vacuum, and cryogenic temperature and vacuum. Gimbal rotation was controlled, and tests were performed in which rotation amplitude and frequency were varied by using triangular and sinusoidal waveforms. Test data revealed an elastic characteristic of the gimbal, independent of the input signal, which was evident prior to true gimbal sliding. The torque required to initiate gimbal sliding was found to decrease when both pressure and temperature decreased. Results from the low amplitude and low frequency data are currently being used in mathematically modeling the gimbal friction characteristics for Centaur autopilot performance studies.
Mechanical characterization of human brain tissue.

PubMed

Budday, S; Sommer, G; Birkl, C; Langkammer, C; Haybaeck, J; Kohnert, J; Bauer, M; Paulsen, F; Steinmann, P; Kuhl, E; Holzapfel, G A

2017-01-15

Mechanics are increasingly recognized to play an important role in modulating brain form and function. Computational simulations are a powerful tool to predict the mechanical behavior of the human brain in health and disease. The success of these simulations depends critically on the underlying constitutive model and on the reliable identification of its material parameters. Thus, there is an urgent need to thoroughly characterize the mechanical behavior of brain tissue and to identify mathematical models that capture the tissue response under arbitrary loading conditions. However, most constitutive models have only been calibrated for a single loading mode. Here, we perform a sequence of multiple loading modes on the same human brain specimen - simple shear in two orthogonal directions, compression, and tension - and characterize the loading-mode specific regional and directional behavior. We complement these three individual tests by combined multiaxial compression/tension-shear tests and discuss effects of conditioning and hysteresis. To explore to which extent the macrostructural response is a result of the underlying microstructural architecture, we supplement our biomechanical tests with diffusion tensor imaging and histology. We show that the heterogeneous microstructure leads to a regional but not directional dependence of the mechanical properties. Our experiments confirm that human brain tissue is nonlinear and viscoelastic, with a pronounced compression-tension asymmetry. Using our measurements, we compare the performance of five common constitutive models, neo-Hookean, Mooney-Rivlin, Demiray, Gent, and Ogden, and show that only the isotropic modified one-term Ogden model is capable of representing the hyperelastic behavior under combined shear, compression, and tension loadings: with a shear modulus of 0.4-1.4kPa and a negative nonlinearity parameter it captures the compression-tension asymmetry and the increase in shear stress under superimposed compression but not tension. Our results demonstrate that material parameters identified for a single loading mode fail to predict the response under arbitrary loading conditions. Our systematic characterization of human brain tissue will lead to more accurate computational simulations, which will allow us to determine criteria for injury, to develop smart protection systems, and to predict brain development and disease progression. There is a pressing need to characterize the mechanical behavior of human brain tissue under multiple loading conditions, and to identify constitutive models that are able to capture the tissue response under these conditions. We perform a sequence of experimental tests on the same brain specimen to characterize the regional and directional behavior, and we supplement our tests with DTI and histology to explore to which extent the macrostructural response is a result of the underlying microstructure. Results demonstrate that human brain tissue is nonlinear and viscoelastic, with a pronounced compression-tension asymmetry, and we show that the multiaxial data can best be captured by a modified version of the one-term Ogden model. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Transient Three-Dimensional Side Load Analysis of Out-of-Round Film Cooled Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Lin, Jeff; Ruf, Joe; Guidos, Mike

2010-01-01

The objective of this study is to investigate the effect of nozzle out-of-roundness on the transient startup side loads. The out-of-roundness could be the result of asymmetric loads induced by hardware attached to the nozzle, asymmetric internal stresses induced by previous tests and/or deformation, such as creep, from previous tests. The rocket engine studied encompasses a regeneratively cooled thrust chamber and a film cooled nozzle extension with film coolant distributed from a turbine exhaust manifold. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Transient startup computations were performed with the out-of-roundness achieved by four degrees of ovalization of the nozzle: one perfectly round, one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The computed side load physics caused by the nozzle out-of-roundness and its effect on nozzle side load are reported and discussed.

Verification of the numerical model of insert-type joint of scaffolding in relation to experimental research

NASA Astrophysics Data System (ADS)

Pieńko, Michał; Błazik-Borowa, Ewa

2018-01-01

This paper presents the problem of comparing the results of computer simulations with the results of laboratory tests. The subject of the study was the insert-type joint of scaffolding loaded with a bending moment. The research was carried out on the real elements of the scaffolding. Due to the complexity of the connection different friction coefficients and depths of wedge insertion were taken into account in the analysis. The aim of conducting the series of analyses was to determine the sensitivity of the model to the mentioned characteristics. Since laboratory tests were carried out on the real samples, there were no preparations of surface involved in the load transfer. This approach caused many problems with the clear definition of the nature of work of individual node elements during the load. The analysis consist of two stages: the stage in which the connection is defined (the wedge is inserted into the rosette), and the loading stage (the node is loaded by the bending moment).
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.
Finite element modelling of creep crack growth in 316 stainless and 9Cr-1Mo steels

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

Krishnaswamy, P.; Brust, F.W.

1994-09-01

The failure behavior of steels under sustained and cyclic loads has been addressed. The constitutive behavior of the two steels have been represented by the conventional strain-hardening law and the Murakami-Ohno model for reversed and cyclic loads. The laws have been implemented into the research finite element code FVP. Post processors for FVP to calculate various path independent integral fracture parameters have been written. Compact tension C(T) specimens have been tested under sustained and cyclic loads with both the load point displacement and crack growth monitored during the tests. FE models with extremely refined meshes for the C(T) specimens weremore » prepared and the experiment simulated numerically. Results from this analysis focus on the differences between the various constitutive models as well as the fracture parameters in characterizing the creep crack growth of the two steels.« less
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.
Parametric investigation of scalable tactile sensors

NASA Astrophysics Data System (ADS)

Saadatzi, Mohammad Nasser; Yang, Zhong; Baptist, Joshua R.; Sahasrabuddhe, Ritvij R.; Wijayasinghe, Indika B.; Popa, Dan O.

2017-05-01

In the near future, robots and humans will share the same environment and perform tasks cooperatively. For intuitive, safe, and reliable physical human-robot interaction (pHRI), sensorized robot skins for tactile measurements of contact are necessary. In a previous study, we presented skins consisting of strain gauge arrays encased in silicone encapsulants. Although these structures could measure normal forces applied directly onto the sensing elements, they also exhibited blind spots and response asymmetry to certain loading patterns. This study presents a parametric investigation of piezoresistive polymeric strain gauge that exhibits a symmetric omniaxial response thanks to its novel star-shaped structure. This strain gauge relies on the use of gold micro-patterned star-shaped structures with a thin layer of PEDOT:PSS which is a flexible polymer with piezoresistive properties. In this paper, the sensor is first modeled and comprehensively analyzed in the finite-element simulation environment COMSOL. Simulations include stress-strain loading for a variety of structure parameters such as gauge lengths, widths, and spacing, as well as multiple load locations relative to the gauge. Subsequently, sensors with optimized configurations obtained through simulations were fabricated using cleanroom photolithographic and spin-coating processes, and then experimentally tested. Results show a trend-wise agreement between experiments and simulations.
System reliability of randomly vibrating structures: Computational modeling and laboratory testing

NASA Astrophysics Data System (ADS)

Sundar, V. S.; Ammanagi, S.; Manohar, C. S.

2015-09-01

The problem of determination of system reliability of randomly vibrating structures arises in many application areas of engineering. We discuss in this paper approaches based on Monte Carlo simulations and laboratory testing to tackle problems of time variant system reliability estimation. The strategy we adopt is based on the application of Girsanov's transformation to the governing stochastic differential equations which enables estimation of probability of failure with significantly reduced number of samples than what is needed in a direct simulation study. Notably, we show that the ideas from Girsanov's transformation based Monte Carlo simulations can be extended to conduct laboratory testing to assess system reliability of engineering structures with reduced number of samples and hence with reduced testing times. Illustrative examples include computational studies on a 10-degree of freedom nonlinear system model and laboratory/computational investigations on road load response of an automotive system tested on a four-post test rig.
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
Fracture simulation of elastomer blended polypropylene based on elastoviscoplastic constitutive equation with craze and tensile softening law

NASA Astrophysics Data System (ADS)

Mae, H.

2006-08-01

The strong strain-rate dependence, neck propagation and craze evolution characterize the large plastic deformation and fracture behavior of polymer. In the latest study, Kobayashi, Tomii and Shizawa suggested the elastoviscoplastic constitutive equation based on craze evolution and annihilation and then applied it to the plane strain issue of polymer. In the previous study, the author applied their suggested elastoviscoplastic constitutive equation with craze effect to the three dimensional shell and then showed that the load displacement history was in good agreement with the experimental result including only microscopic crack such as crazes. For the future industrial applications, the macroscopic crack has to be taken into account. Thus, the main objective of this study is to propose the tensile softening equation and then add it to the elastoviscoplastic constitutive equation with craze effect so that the load displacement history can be roughly simulated during the macroscopic crack propagation. The tested material in this study is the elastomer blended polypropylene used in the interior and exterior of automobiles. First, the material properties are obtained based on the tensile test results at wide range of strain rates: 10 - 4-102 (1/sec). Next, the compact tension test is conducted and then the tensile softening parameters are fixed. Then, the dart impact test is carried out in order to obtain the load displacement history and also observe the macroscopic crack propagation at high strain rate. Finally, the fracture behavior is simulated and then compared with the experimental results. It is shown that the predictions of the constitutive equation with the proposed tensile softening equation are in good agreement with the experimental results for the future industrial applications.
Airborne Turbulence Detection System Certification Tool Set

NASA Technical Reports Server (NTRS)

Hamilton, David W.; Proctor, Fred H.

2006-01-01

A methodology and a corresponding set of simulation tools for testing and evaluating turbulence detection sensors has been presented. The tool set is available to industry and the FAA for certification of radar based airborne turbulence detection systems. The tool set consists of simulated data sets representing convectively induced turbulence, an airborne radar simulation system, hazard tables to convert the radar observable to an aircraft load, documentation, a hazard metric "truth" algorithm, and criteria for scoring the predictions. Analysis indicates that flight test data supports spatial buffers for scoring detections. Also, flight data and demonstrations with the tool set suggest the need for a magnitude buffer.
Effect of ACL Transection on Internal Tibial Rotation in an in Vitro Simulated Pivot Landing

PubMed Central

Oh, Youkeun K.; Kreinbrink, Jennifer L.; Ashton-Miller, James A.; Wojtys, Edward M.

2011-01-01

Background: The amount of resistance provided by the ACL (anterior cruciate ligament) to axial tibial rotation remains controversial. The goal of this study was to test the primary hypotheses that ACL transection would not significantly affect tibial rotation under the large impulsive loads associated with a simulated pivot landing but would increase anterior tibial translation. Methods: Twelve cadaveric knees (mean age of donors [and standard deviation] at the time of death, 65.0 ± 10.5 years) were mounted in a custom testing apparatus to simulate a single-leg pivot landing. A compound impulsive load was applied to the distal part of the tibia with compression (∼800 N), flexion moment (∼40 N-m), and axial tibial torque (∼17 N-m) in the presence of five trans-knee muscle forces. A differential variable reluctance transducer mounted on the anteromedial aspect of the ACL measured relative strain. With the knee initially in 15° of flexion, and after five combined compression and flexion moment (baseline) loading trials, six trials were conducted with the addition of either internal or external tibial torque (internal or external loading), and then six baseline trials were performed. The ACL was then sectioned, six baseline trials were repeated, and then six trials of either the internal or the external loading condition, whichever had initially resulted in the larger relative ACL strain, were carried out. Tibiofemoral kinematics were measured optoelectronically. The results were analyzed with a nonparametric Wilcoxon signed-rank test. Results: Following ACL transection, the increase in the normalized internal tibial rotation was significant but small (0.7°/N-m ± 0.3°/N-m to 0.8°/N-m ± 0.3°/N-m, p = 0.012), while anterior tibial translation increased significantly (3.8 ± 2.9 to 7.0 ± 2.9 mm, p = 0.017). Conclusions: ACL transection leads to a small increase in internal tibial rotation, equivalent to a 13% decrease in the dynamic rotational resistance, under the large forces associated with a simulated pivot landing, but it leads to a significant increase in anterior tibial translation. Clinical Relevance: An ACL reconstruction that restores both ligament orientation and stiffness will provide major resistance to anterior tibial translation while providing minor resistance to axial tibial rotation. PMID:21325589
Application of fiber grating-based acoustic sensor in progressive failure testing of e-glass/vinylester curve composites

NASA Astrophysics Data System (ADS)

Azmi, Asrul Izam; Raju, Raju; Peng, Gang-Ding

2012-02-01

This paper reports an application of phase shifted fiber Bragg grating (PS-FBG) intensity-type acoustic sensor in a continuous and in-situ failure testing of an E-glass/vinylester top hat stiffener (THS). The narrow transmission channel of the PS-FBG is highly sensitive to small perturbation, hence suitable to be used in an effective acoustic emission (AE) assessment technique. The progressive failure of THS was tested under transverse loading to experimentally simulate the actual loading in practice. Our experimental tests have demonstrated, in good agreement with the commercial piezoelectric sensors, that the important failures information of the THS was successfully recorded by the simple intensity-type PS-FBG sensor.
A sandwiched piezoelectric transducer with flex end-caps for energy harvesting in large force environments

NASA Astrophysics Data System (ADS)

Kuang, Yang; Daniels, Alice; Zhu, Meiling

2017-08-01

This paper presents a sandwiched piezoelectric transducer (SPT) for energy harvesting in large force environments with increased load capacity and electric power output. The SPT uses (1) flex end-caps to amplify the applied load force so as to increase its power output and (2) a sandwiched piezoelectric-substrate structure to reduce the stress concentration in the piezoelectric material so as to increase the load capacity. A coupled piezoelectric-circuit finite element model (CPC-FEM) was developed, which is able to directly predict the electric power output of the SPT connected to a load resistor. The CPC-FEM was used to study the effects of various parameters of the SPT on the performance to obtain an optimal design. These parameters included the substrate thickness, the end-cap material and thickness, the electrode length, the joint length, the end-cap internal angle and the PZT thickness. A prototype with optimised parameters was tested on a loading machine, and the experimental results were compared with simulation. A good agreement was observed between simulation and experiment. When subjected to a 1 kN 2 Hz sinusoidal force applied by the loading machine, the SPT produced an average power of 4.68 mW. The application of the SPT as a footwear energy harvester was demonstrated by fitting the SPT into a boot and performing the tests on a treadmill, and the SPT generated an average power of 2.5 mW at a walking speed of 4.8 km h-1.
Effects of land-use changes and stormflow-detention basins on flooding and nonpoint-source pollution, in Irondequoit Creek basin, Monroe and Ontario counties, New York--application of a precipitation-runoff model

USGS Publications Warehouse

Coon, William F.; Johnson, Mark S.

2005-01-01

Urbanization of the 150-square-mile Irondequoit Creek basin in Monroe and Ontario Counties, N.Y., continues to spread southward and eastward from the City of Rochester, on the shore of Lake Ontario. Conversion of forested land to other uses over the past 40 years has increased to the extent that more than 50 percent of the basin is now developed. This expansion has increased flooding and impaired stream-water quality in the northern (downstream) half of the basin. A precipitation-runoff model of the Irondequoit Creek basin was developed with the model code HSPF (Hydrological Simulation Program--FORTRAN) to simulate the effects of land-use changes and stormflow-detention basins on flooding and nonpoint-source pollution on the basin. Model performance was evaluated through a combination of graphical comparisons and statistical tests, and indicated 'very good' agreement (mean error less than 10 percent) between observed and simulated daily and monthly streamflows, between observed and simulated monthly water temperatures, and between observed total suspended solids loads and simulated sediment loads. Agreement between monthly observed and simulated nutrient loads was 'very good' (mean error less than 15 percent) or 'good' (mean error between 15 and 25 percent). Results of model simulations indicated that peak flows and loads of sediment and total phosphorus would increase in a rural subbasin, where 10 percent of the basin was converted from forest and grassland to pervious and impervious developed areas. Subsequent simulation of a stormflow-detention basin at the mouth of this subbasin indicated that peak flows and constituent loads would decrease below those that were generated by the land-use-change scenario, and, in some cases, below those that were simulated by the original land-use scenario. Other results from model simulations of peak flows over a 30-year period (1970-2000), with and without simulation of 50-percent flow reductions at one existing and nine hypothetical stormflow-detention basins, indicated that stormflow-detention basins would likely decrease peak flows 14 to 17 percent on Allen Creek and 17 to 18 percent on Irondequoit Creek at Blossom Road. The model is intended as a management tool that water-resource managers can use to guide decisions regarding future development in the basin. The model and associated files are designed to permit (1) creation of scenarios that represent planned or hypothetical development in the basin, and (2) assessment of the flooding and chemical loads that are likely to result. Instream stormflow-detention basins can be simulated in separate scenarios to assess their effect on flooding and chemical loads. This report (1) provides examples of how the model can be applied to address these issues, (2) discusses the model revisions required to simulate land-use changes and detention basins, and (3) describes the analytical steps necessary to evaluate the model results.
Advanced Stirling Convertor Dual Convertor Controller Testing at NASA Glenn Research Center in the Radioisotope Power Systems System Integration Laboratory

NASA Technical Reports Server (NTRS)

Dugala, Gina M.; Taylor, Linda M.; Bell, Mark E.; Dolce, James L.; Fraeman, Martin; Frankford, David P.

2015-01-01

NASA Glenn Research Center (GRC) developed a non-nuclear representation of a Radioisotope Power System (RPS) consisting of a pair of Advanced Stirling Convertors (ASC), a Dual Convertor Controller (DCC) EM (engineering model) 2 & 3, and associated support equipment, which were tested in the Radioisotope Power Systems System Integration Laboratory (RSIL). The DCC was designed by the Johns Hopkins University/Applied Physics Laboratory (JHU/APL) to actively control a pair of Advanced Stirling Convertors (ASC). The first phase of testing included a Dual Advanced Stirling Convertor Simulator (DASCS) which was developed by JHU/APL and simulates the operation and electrical behavior of a pair of ASC's in real time via a combination of hardware and software. RSIL provides insight into the electrical interactions between a representative radioisotope power generator, its associated control schemes, and realistic electric system loads. The first phase of integration testing included the following spacecraft bus configurations: capacitive, battery, and supercapacitor. A load profile, created based on data from several missions, tested the RPS and RSIL ability to maintain operation during load demands above and below the power provided by the RPS. The integration testing also confirmed the DCC's ability to disconnect from the spacecraft when the bus voltage dipped below 22 V or exceeded 36 V. Once operation was verified with the DASCS, the tests were repeated with actual operating ASC's. The goal of this integration testing was to verify operation of the DCC when connected to a spacecraft and to verify the functionality of the newly designed RSIL. The results of these tests are presented in this paper.
Development of implant loading device for animal study about various loading protocol: a pilot study

PubMed Central

Yoon, Joon-Ho; Park, Young-Bum; Cho, Yuna; Kim, Chang-Sung; Choi, Seong-Ho; Moon, Hong-Seok; Lee, Keun-Woo

2012-01-01

PURPOSE The aims of this pilot study were to introduce implant loading devices designed for animal study and to evaluate the validity of the load transmission ability of the loading devices. MATERIALS AND METHODS Implant loading devices were specially designed and fabricated with two implant abutments and cast metal bars, and orthodontic expansion screw. In six Beagles, all premolars were extracted and two implants were placed in each side of the mandibles. The loading device was inserted two weeks after the implant placement. According to the loading protocol, the load was applied to the implants with different time and method,simulating early, progressive, and delayed loading. The implants were clinically evaluated and the loading devices were removed and replaced to the master cast, followed by stress-strain analysis. Descriptive statistics of remained strain (µε) was evaluated after repeating three cycles of the loading device activation. Statistic analysis was performed using nonparametric, independent t-test with 5% significance level and Friedman's test was also used for verification. RESULTS The loading devices were in good action. However, four implants in three Beagles showed loss of osseointegration. In stress-strain analysis, loading devices showed similar amount of increase in the remained strain after applying 1-unit load for three times. CONCLUSION Specialized design of the implant loading device was introduced. The loading device applied similar amount of loads near the implant after each 1-unit loading. However, the direction of the loads was not parallel to the long axis of the implants as predicted before the study. PMID:23236575
Failure Simulation Testing of the Z-1 Spacesuit Titanium Bearing Assemblies

NASA Technical Reports Server (NTRS)

de Baca, Richard C.; Juarez, Alfredo; Peralta, Stephen; Tylka, Jonathan; Rhodes, Richard

2016-01-01

The Z-2 is a candidate for NASA's next generation spacesuit, designed for a range of possible missions with enhanced mobility for spacewalks both on planetary surfaces and in microgravity. Increased mobility was accomplished through innovations in shoulder and hip joints, using a number of new bearings to allow spacesuit wearers to dip, walk, and bend with ease; all important tasks for a planetary explorer collecting samples or traveling over rough terrain. The Advanced Spacesuit Development Team of NASA Johnson Space Center requested that the NASA White Sands Test Facility (WSTF) perform a series failure simulation tests on three titanium bearing assemblies, an elemental part of the joint construction used in new spacesuit designs. This testing simulated two undetected failures within the bearings and as a result the objective of this test program was to evaluate whether a failed or failing bearing could result in ignition of the titanium race material due to friction. The first failure was an inner seal leak sufficient to pressurize the race with +99 percent oxygen. The second failure was an improperly installed or mismatched ball port that created a protrusion in the ball bearing race, partially obstructing the nominal rolling path of each ball bearing. When the spacesuit bearings are assembled, bearing balls are loaded into the assembly via a ball port. The ball port is specific and unique to each bearing assembly (matched pair). The simulated mismatched ball port is a significant source of friction, which would be caused by an assembly error. To evaluate this risk, the bearings were cycled in a simulated worst-case scenario environment, with operational loads, and potential flaw conditions. During test the amount of actuation torque required and heat generated through continuous operation were measured and the bearings were observed for sparks or burning events. This paper provides detailed descriptions of the test hardware, methodology, and results.
A sealed capsule system for biological and liquid shock-recovery experiments.

PubMed

Leighs, James A; Appleby-Thomas, Gareth J; Stennett, Chris; Hameed, Amer; Wilgeroth, James M; Hazell, Paul J

2012-11-01

This paper presents an experimental method designed to one-dimensionally shock load and subsequently recover liquid samples. Resultant loading profiles have been interrogated via hydrocode simulation as the nature of the target did not allow for direct application of the diagnostics typically employed in shock physics (e.g., manganin stress gauges or Heterodyne velocimeter (Het-V)). The target setup has been experimentally tested using aluminium flyer plates accelerated by a 50-mm bore single-stage gas-gun reaching projectile impact velocities of up to ~500 ms(-1) (corresponding to peak pressures of up to ca. 4 GPa being experienced by fluid samples). Recovered capsules survived well showing only minor signs of damage. Modelled gauge traces have been validated through the use of a (slightly modified) experiment in which a Het-V facing the rear of the inner capsule was employed. In these tests, good correlation between simulated and experimental traces was observed.
A sealed capsule system for biological and liquid shock-recovery experiments

NASA Astrophysics Data System (ADS)

Leighs, James A.; Appleby-Thomas, Gareth J.; Stennett, Chris; Hameed, Amer; Wilgeroth, James M.; Hazell, Paul J.

2012-11-01

This paper presents an experimental method designed to one-dimensionally shock load and subsequently recover liquid samples. Resultant loading profiles have been interrogated via hydrocode simulation as the nature of the target did not allow for direct application of the diagnostics typically employed in shock physics (e.g., manganin stress gauges or Heterodyne velocimeter (Het-V)). The target setup has been experimentally tested using aluminium flyer plates accelerated by a 50-mm bore single-stage gas-gun reaching projectile impact velocities of up to ˜500 ms-1 (corresponding to peak pressures of up to ca. 4 GPa being experienced by fluid samples). Recovered capsules survived well showing only minor signs of damage. Modelled gauge traces have been validated through the use of a (slightly modified) experiment in which a Het-V facing the rear of the inner capsule was employed. In these tests, good correlation between simulated and experimental traces was observed.
Mechanical characteristics and comparisons of cerclage wires: introduction of the double-wrap and loop/twist tying methods.

PubMed

Roe, S C

1997-01-01

Evaluate the mechanical properties of twist, loop, double loop, double-wrap and loop/twist cerclage. The initial tension generated by 18 cerclage of each type was determined using a materials testing machine after tying around a testing jig. Six wires from each type were distracted and the initial stiffness and yield load were determined. Yield behavior was further investigated in six wires of each type by determining the load required to reduce cerclage tension below 30 Newton (N) following and incremental (50 N) stepwise load and unload regimen. The amount of collapse of the simulated bone fragments that resulted in the reduction of initial tension to 30 N was measured for the final six wires of each group. Data were analyzed by analysis of variance and a multiple comparison test. Twist type cerclage generated less tension than loop-type cerclage. The yield load of these two types was similar. Double-loop and double-wrap cerclage generated superior tension and resisted a greater load before loosening. Loop/twist cerclage had an intermediate initial tension but had the greatest resistance to loading. In the collapse test, the greater the initial tension, the more collapse could occur before the wire was loose. For all types of cerclage wire fixation, a reduction of diameter of the testing jig of more than 1% caused loosening. Double-loop and double-wrap cerclage provide greater compression of fragments and resist loads associated with weight-bearing better than the twist and loop methods. Loop/twist cerclage may have advantages because of their superior resistance to loading. All cerclage will loosen if fracture fragments collapse.
Failure Behavior Characterization of Mo-Modified Ti Surface by Impact Test and Finite Element Analysis

NASA Astrophysics Data System (ADS)

Ma, Yong; Qin, Jianfeng; Zhang, Xiangyu; Lin, Naiming; Huang, Xiaobo; Tang, Bin

2015-07-01

Using the impact test and finite element simulation, the failure behavior of the Mo-modified layer on pure Ti was investigated. In the impact test, four loads of 100, 300, 500, and 700 N and 104 impacts were adopted. The three-dimensional residual impact dents were examined using an optical microscope (Olympus-DSX500i), indicating that the impact resistance of the Ti surface was improved. Two failure modes cohesive and wearing were elucidated by electron backscatter diffraction and energy-dispersive spectrometer performed in a field-emission scanning electron microscope. Through finite element forward analysis performed at a typical impact load of 300 N, stress-strain distributions in the Mo-modified Ti were quantitatively determined. In addition, the failure behavior of the Mo-modified layer was determined and an ideal failure model was proposed for high-load impact, based on the experimental and finite element forward analysis results.

Evaluation of graphite composite materials for bearingless helicopter rotor application

NASA Technical Reports Server (NTRS)

Ulitchny, M. G.; Lucas, J. J.

1974-01-01

Small scale combined load fatigue tests were conducted on twelve unidirectional graphite-glass scrim-epoxy composite specimens. The specimens were 1 in. (2.54 cm) wide by 0.1 in. (.25 cm) thick by 5 in. (12.70 cm) long. The fatigue data was developed for the preliminary design of the spar for a bearingless helicopter main rotor. Three loading conditions were tested. Combinations of steady axial, vibratory torsion, and vibratory bending stresses were chosen to simulate the calculated stresses which exist at the root and at the outboard end of the pitch change section of the spar. Calculated loads for 150 knots (77.1 m/sec) level flight were chosen as the baseline condition. Test stresses were varied up to 4.4 times the baseline stress levels. Damage resulted in reduced stiffness; however, in no case was complete fracture of the specimen experienced.
Characterization for elastic constants of fused deposition modelling-fabricated materials based on the virtual fields method and digital image correlation

NASA Astrophysics Data System (ADS)

Cao, Quankun; Xie, Huimin

2017-12-01

Fused deposition modelling (FDM), a widely used rapid prototyping process, is a promising technique in manufacturing engineering. In this work, a method for characterizing elastic constants of FDM-fabricated materials is proposed. First of all, according to the manufacturing process of FDM, orthotropic constitutive model is used to describe the mechanical behavior. Then the virtual fields method (VFM) is applied to characterize all the mechanical parameters (Q_{11}, Q_{22}, Q_{12}, Q_{66}) using the full-field strain, which is measured by digital image correlation (DIC). Since the principal axis of the FDM-fabricated structure is sometimes unknown due to the complexity of the manufacturing process, a disk in diametrical compression is used as the load configuration so that the loading angle can be changed conveniently. To verify the feasibility of the proposed method, finite element method (FEM) simulation is conducted to obtain the strain field of the disk. The simulation results show that higher accuracy can be achieved when the loading angle is close to 30°. Finally, a disk fabricated by FDM was used for the experiment. By rotating the disk, several tests with different loading angles were conducted. To determine the position of the principal axis in each test, two groups of parameters (Q_{11}, Q_{22}, Q_{12}, Q_{66}) are calculated by two different groups of virtual fields. Then the corresponding loading angle can be determined by minimizing the deviation between two groups of the parameters. After that, the four constants (Q_{11}, Q_{22}, Q_{12}, Q_{66}) were determined from the test with an angle of 27°.
Mechanical Analysis of W78/88-1 Life Extension Program Warhead Design Options

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

Spencer, Nathan

2014-09-01

Life Extension Program (LEP) is a program to repair/replace components of nuclear weapons to ensure the ability to meet military requirements. The W78/88-1 LEP encompasses the modernization of two major nuclear weapon reentry systems into an interoperable warhead. Several design concepts exist to provide different options for robust safety and security themes, maximum non-nuclear commonality, and cost. Simulation is one capability used to evaluate the mechanical performance of the designs in various operational environments, plan for system and component qualification efforts, and provide insight into the survivability of the warhead in environments that are not currently testable. The simulation effortsmore » use several Sandia-developed tools through the Advanced Simulation and Computing program, including Cubit for mesh generation, the DART Model Manager, SIERRA codes running on the HPC TLCC2 platforms, DAKOTA, and ParaView. Several programmatic objectives were met using the simulation capability including: (1) providing early environmental specification estimates that may be used by component designers to understand the severity of the loads their components will need to survive, (2) providing guidance for load levels and configurations for subassembly tests intended to represent operational environments, and (3) recommending design options including modified geometry and material properties. These objectives were accomplished through regular interactions with component, system, and test engineers while using the laboratory's computational infrastructure to effectively perform ensembles of simulations. Because NNSA has decided to defer the LEP program, simulation results are being documented and models are being archived for future reference. However, some advanced and exploratory efforts will continue to mature key technologies, using the results from these and ongoing simulations for design insights, test planning, and model validation.« less
Staged-Fault Testing of Distance Protection Relay Settings

NASA Astrophysics Data System (ADS)

Havelka, J.; Malarić, R.; Frlan, K.

2012-01-01

In order to analyze the operation of the protection system during induced fault testing in the Croatian power system, a simulation using the CAPE software has been performed. The CAPE software (Computer-Aided Protection Engineering) is expert software intended primarily for relay protection engineers, which calculates current and voltage values during faults in the power system, so that relay protection devices can be properly set up. Once the accuracy of the simulation model had been confirmed, a series of simulations were performed in order to obtain the optimal fault location to test the protection system. The simulation results were used to specify the test sequence definitions for the end-to-end relay testing using advanced testing equipment with GPS synchronization for secondary injection in protection schemes based on communication. The objective of the end-to-end testing was to perform field validation of the protection settings, including verification of the circuit breaker operation, telecommunication channel time and the effectiveness of the relay algorithms. Once the end-to-end secondary injection testing had been completed, the induced fault testing was performed with three-end lines loaded and in service. This paper describes and analyses the test procedure, consisting of CAPE simulations, end-to-end test with advanced secondary equipment and staged-fault test of a three-end power line in the Croatian transmission system.
Simulation-based Testing of Control Software

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

Ozmen, Ozgur; Nutaro, James J.; Sanyal, Jibonananda

It is impossible to adequately test complex software by examining its operation in a physical prototype of the system monitored. Adequate test coverage can require millions of test cases, and the cost of equipment prototypes combined with the real-time constraints of testing with them makes it infeasible to sample more than a small number of these tests. Model based testing seeks to avoid this problem by allowing for large numbers of relatively inexpensive virtual prototypes that operate in simulation time at a speed limited only by the available computing resources. In this report, we describe how a computer system emulatormore » can be used as part of a model based testing environment; specifically, we show that a complete software stack including operating system and application software - can be deployed within a simulated environment, and that these simulations can proceed as fast as possible. To illustrate this approach to model based testing, we describe how it is being used to test several building control systems that act to coordinate air conditioning loads for the purpose of reducing peak demand. These tests involve the use of ADEVS (A Discrete Event System Simulator) and QEMU (Quick Emulator) to host the operational software within the simulation, and a building model developed with the MODELICA programming language using Buildings Library and packaged as an FMU (Functional Mock-up Unit) that serves as the virtual test environment.« less
Upper and Lower Neck Loads in Belted Human Surrogates in Frontal Impacts

PubMed Central

Yoganandan, Narayan; Pintar, Frank A.; Moore, Jason; Rinaldi, James; Schlick, Michael; Maiman, Dennis J.

2012-01-01

The upper and lower neck loads in the restrained Hybrid III dummy and Test Device for Human Occupant Restraint (THOR) were computed in simulated frontal impact sled tests at low, medium, and high velocities; repeatability performance of the two dummies were evaluated at all energy inputs; peak forces and moments were compared with computed loads at the occipital condyles and cervical-thoracic junctions from tests using post mortem human surrogates (PMHS). A custom sled buck was used to position the surrogates. Repeated tests were conducted at each velocity for each dummy and sufficient time was allowed to elapse between the two experiments. The upper and lower neck forces and moments were determined from load cell measures and its locations with respect to the ends of the neck. Both dummies showed good repeatability for axial and shear forces and bending moments at all changes in velocity inputs. Morphological characteristics in the neck loading responses were similar in all surrogates, although the peak magnitudes of the variables differed. In general, the THOR better mimicked the PMHS response than the Hybrid III dummy, and factors such as neck design and chest compliance were attributed to the observed variations. While both dummies were not designed for use at the two extremes of the tested velocities, results from the present study indicate that, currently the THOR may be the preferred anthropomorphic testing device in crashworthiness research studies and full-scale vehicle tests at all velocities. PMID:23169123
Cognitive load, emotion, and performance in high-fidelity simulation among beginning nursing students: a pilot study.

PubMed

Schlairet, Maura C; Schlairet, Timothy James; Sauls, Denise H; Bellflowers, Lois

2015-03-01

Establishing the impact of the high-fidelity simulation environment on student performance, as well as identifying factors that could predict learning, would refine simulation outcome expectations among educators. The purpose of this quasi-experimental pilot study was to explore the impact of simulation on emotion and cognitive load among beginning nursing students. Forty baccalaureate nursing students participated in teaching simulations, rated their emotional state and cognitive load, and completed evaluation simulations. Two principal components of emotion were identified representing the pleasant activation and pleasant deactivation components of affect. Mean rating of cognitive load following simulation was high. Linear regression identiffed slight but statistically nonsignificant positive associations between principal components of emotion and cognitive load. Logistic regression identified a negative but statistically nonsignificant effect of cognitive load on assessment performance. Among lower ability students, a more pronounced effect of cognitive load on assessment performance was observed; this also was statistically non-significant. Copyright 2015, SLACK Incorporated.
Knee Joint Loads and Surrounding Muscle Forces during Stair Ascent in Patients with Total Knee Replacement

PubMed Central

Rasnick, Robert; Standifird, Tyler; Reinbolt, Jeffrey A.; Cates, Harold E.

2016-01-01

Total knee replacement (TKR) is commonly used to correct end-stage knee osteoarthritis. Unfortunately, difficulty with stair climbing often persists and prolongs the challenges of TKR patents. Complete understanding of loading at the knee is of great interest in order to aid patient populations, implant manufacturers, rehabilitation, and future healthcare research. Musculoskeletal modeling and simulation approximates joint loading and corresponding muscle forces during a movement. The purpose of this study was to determine if knee joint loadings following TKR are recovered to the level of healthy individuals, and determine the differences in muscle forces causing those loadings. Data from five healthy and five TKR patients were selected for musculoskeletal simulation. Variables of interest included knee joint reaction forces (JRF) and the corresponding muscle forces. A paired samples t-test was used to detect differences between groups for each variable of interest (p<0.05). No differences were observed for peak joint compressive forces between groups. Some muscle force compensatory strategies appear to be present in both the loading and push-off phases. Evidence from knee extension moment and muscle forces during the loading response phase indicates the presence of deficits in TKR in quadriceps muscle force production during stair ascent. This result combined with greater flexor muscle forces resulted in similar compressive JRF during loading response between groups. PMID:27258086
Wind Energy System Time-domain (WEST) analyzers using hybrid simulation techniques

NASA Technical Reports Server (NTRS)

Hoffman, J. A.

1979-01-01

Two stand-alone analyzers constructed for real time simulation of the complex dynamic characteristics of horizontal-axis wind energy systems are described. Mathematical models for an aeroelastic rotor, including nonlinear aerodynamic and elastic loads, are implemented with high speed digital and analog circuitry. Models for elastic supports, a power train, a control system, and a rotor gimbal system are also included. Limited correlation efforts show good comparisons between results produced by the analyzers and results produced by a large digital simulation. The digital simulation results correlate well with test data.
Development of an aeroelastic methodology for surface morphing rotors

NASA Astrophysics Data System (ADS)

Cook, James R.

Helicopter performance capabilities are limited by maximum lift characteristics and vibratory loading. In high speed forward flight, dynamic stall and transonic flow greatly increase the amplitude of vibratory loads. Experiments and computational simulations alike have indicated that a variety of active rotor control devices are capable of reducing vibratory loads. For example, periodic blade twist and flap excitation have been optimized to reduce vibratory loads in various rotors. Airfoil geometry can also be modified in order to increase lift coefficient, delay stall, or weaken transonic effects. To explore the potential benefits of active controls, computational methods are being developed for aeroelastic rotor evaluation, including coupling between computational fluid dynamics (CFD) and computational structural dynamics (CSD) solvers. In many contemporary CFD/CSD coupling methods it is assumed that the airfoil is rigid to reduce the interface by single dimension. Some methods retain the conventional one-dimensional beam model while prescribing an airfoil shape to simulate active chord deformation. However, to simulate the actual response of a compliant airfoil it is necessary to include deformations that originate not only from control devices (such as piezoelectric actuators), but also inertial forces, elastic stresses, and aerodynamic pressures. An accurate representation of the physics requires an interaction with a more complete representation of loads and geometry. A CFD/CSD coupling methodology capable of communicating three-dimensional structural deformations and a distribution of aerodynamic forces over the wetted blade surface has not yet been developed. In this research an interface is created within the Fully Unstructured Navier-Stokes (FUN3D) solver that communicates aerodynamic forces on the blade surface to University of Michigan's Nonlinear Active Beam Solver (UM/NLABS -- referred to as NLABS in this thesis). Interface routines are developed for transmission of force and deflection information to achieve an aeroelastic coupling updated at each time step. The method is validated first by comparing the integrated aerodynamic work at CFD and CSD nodes to verify work conservation across the interface. Second, the method is verified by comparing the sectional blade loads and deflections of a rotor in hover and in forward flight with experimental data. Finally, stability analyses for pitch/plunge flutter and camber flutter are performed with comprehensive CSD/low-order-aerodynamics and tightly coupled CFD/CSD simulations and compared to analytical solutions of Peters' thin airfoil theory to verify proper aeroelastic behavior. The effects of simple harmonic camber actuation are examined and compared to the response predicted by Peters' finite-state (F-S) theory. In anticipation of active rotor experiments inside enclosed facilities, computational simulations are performed to evaluate the capability of CFD for accurately simulating flow inside enclosed volumes. A computational methodology for accurately simulating a rotor inside a test chamber is developed to determine the influence of test facility components and turbulence modeling and performance predictions. A number of factors that influence the physical accuracy of the simulation, such as temporal resolution, grid resolution, and aeroelasticity are also evaluated.
Cardiac data increase association between self-report and both expert ratings of task load and task performance in flight simulator tasks: An exploratory study.

PubMed

Lehrer, Paul; Karavidas, Maria; Lu, Shou-En; Vaschillo, Evgeny; Vaschillo, Bronya; Cheng, Andrew

2010-05-01

Seven professional airplane pilots participated in a one-session test in a Boeing 737-800 simulator. Mental workload for 18 flight tasks was rated by experienced test pilots (hereinafter called "expert ratings") and by study participants' self-report on NASA's Task Load Index (TLX) scale. Pilot performance was rated by a check pilot. The standard deviation of R-R intervals (SDNN) significantly added 3.7% improvement over the TLX in distinguishing high from moderate-load tasks and 2.3% improvement in distinguishing high from combined moderate and low-load tasks. Minimum RRI in the task significantly discriminated high- from medium- and low-load tasks, but did not add significant predictive variance to the TLX. The low-frequency/high-frequency (LF:HF) RRI ratio based on spectral analysis of R-R intervals, and ventricular relaxation time were each negatively related to pilot performance ratings independently of TLX values, while minimum and average RRI were positively related, showing added contribution of these cardiac measures for predicting performance. Cardiac results were not affected by controlling either for respiration rate or motor activity assessed by accelerometry. The results suggest that cardiac assessment can be a useful addition to self-report measures for determining flight task mental workload and risk for performance decrements. Replication on a larger sample is needed to confirm and extend the results. Copyright 2010 Elsevier B.V. All rights reserved.
The influence of pre-existing rib fractures on Global Human Body Models Consortium thorax response in frontal and oblique impact.

PubMed

Zaseck, Lauren Wood; Chen, Cong; Hu, Jingwen; Reed, Matthew P; Rupp, Jonathan

2018-03-01

Many post-mortem human subjects (PMHS) considered for use in biomechanical impact tests have pre-existing rib fractures (PERFs), usually resulting from cardiopulmonary resuscitation. These specimens are typically excluded from impact studies with the assumption that the fractures will alter the thoracic response to loading. We previously used the Global Human Body Models Consortium 50th percentile whole-body finite element model (GHBMC M50-O) to demonstrate that up to three lateral or bilateral PERFs do not meaningfully influence the response of the GHBMC thorax to lateral loading. This current study used the GHBMC M50-O to explore the influence of PERFs on thorax response in frontal and oblique loading. Up to six PERFs were simulated on the anterior or lateral rib regions, and the model was subjected to frontal or oblique cylindrical impactor, frontal seatbelt, or frontal seatbelt + airbag loading. Changes in thorax force-compression responses due to PERFs were generally minor, with the greatest alterations seen in models with six PERFs on one side of the ribcage. The observed changes, however, were small relative to mid-size male corridors for the loading conditions simulated. PERFs altered rib strain patterns, but the changes did not translate to changes in global thoracic response. Within the limits of model fidelity, the results suggest that PMHS with up to six PERFs may be appropriate for use in frontal or oblique impact testing. Copyright © 2018 Elsevier Ltd. All rights reserved.
Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

PubMed

Kishen, A; Vedantam, S

2007-10-01

This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.
Automatic Detection of Electric Power Troubles (ADEPT)

NASA Technical Reports Server (NTRS)

Wang, Caroline; Zeanah, Hugh; Anderson, Audie; Patrick, Clint; Brady, Mike; Ford, Donnie

1988-01-01

ADEPT is an expert system that integrates knowledge from three different suppliers to offer an advanced fault-detection system, and is designed for two modes of operation: real-time fault isolation and simulated modeling. Real time fault isolation of components is accomplished on a power system breadboard through the Fault Isolation Expert System (FIES II) interface with a rule system developed in-house. Faults are quickly detected and displayed and the rules and chain of reasoning optionally provided on a Laser printer. This system consists of a simulated Space Station power module using direct-current power supplies for Solar arrays on three power busses. For tests of the system's ability to locate faults inserted via switches, loads are configured by an INTEL microcomputer and the Symbolics artificial intelligence development system. As these loads are resistive in nature, Ohm's Law is used as the basis for rules by which faults are located. The three-bus system can correct faults automatically where there is a surplus of power available on any of the three busses. Techniques developed and used can be applied readily to other control systems requiring rapid intelligent decisions. Simulated modelling, used for theoretical studies, is implemented using a modified version of Kennedy Space Center's KATE (Knowledge-Based Automatic Test Equipment), FIES II windowing, and an ADEPT knowledge base. A load scheduler and a fault recovery system are currently under development to support both modes of operation.
Indoor test for thermal performance evaluation of the Solaron (air) solar collector

NASA Technical Reports Server (NTRS)

1978-01-01

The test procedure used and the results obtained from an evaluation test program, conducted to obtain thermal performance data on a Solaron double glazed air solar collector under simulated conditions in a solar simulator are described. A time constant test and incident angle modifier test were also conducted to determine the transient effect and the incident angle effect on the collector. These results and the results of the collector load test are also discussed. The Solaron collector absorber plate is made of 24-gage steel, the coating is baked-on black paint, the cover consists of two sheets of 1/8-inch low-iron tempered glass, and the insulation is one thickness of 3 5/8-inch fiberglass batting.
Failure analysis of pinch-torsion tests as a thermal runaway risk evaluation method of Li-ion cells

NASA Astrophysics Data System (ADS)

Xia, Yuzhi; Li, Tianlei; Ren, Fei; Gao, Yanfei; Wang, Hsin

2014-11-01

Recently a pinch-torsion test is developed for safety testing of Li-ion batteries. It has been demonstrated that this test can generate small internal short-circuit spots in the separator in a controllable and repeatable manner. In the current research, the failure mechanism is examined by numerical simulations and comparisons to experimental observations. Finite element models are developed to evaluate the deformation of the separators under both pure pinch and pinch-torsion loading conditions. It is discovered that the addition of the torsion component significantly increased the maximum first principal strain, which is believed to induce the internal short circuit. In addition, the applied load in the pinch-torsion test is significantly less than in the pure pinch test, thus dramatically improving the applicability of this method to ultra-thick batteries which otherwise require heavy load in excess of machine capability. It is further found that the separator failure is achieved in the early stage of torsion (within a few degree of rotation). Effect of coefficient of friction on the maximum first principal strain is also examined.
Simulating the Response of a Composite Honeycomb Energy Absorber. Part 2; Full-Scale Impact Testing

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Annett, Martin S.; Jackson, Karen E.; Polanco, Michael A.

2012-01-01

NASA has sponsored research to evaluate an externally deployable composite honeycomb designed to attenuate loads in the event of a helicopter crash. The concept, designated the Deployable Energy Absorber (DEA), is an expandable Kevlar(Registered TradeMark) honeycomb. The DEA has a flexible hinge that allows the honeycomb to be stowed collapsed until needed during an emergency. Evaluation of the DEA began with material characterization of the Kevlar(Registered TradeMark)-129 fabric/epoxy, and ended with a full-scale crash test of a retrofitted MD-500 helicopter. During each evaluation phase, finite element models of the test articles were developed and simulations were performed using the dynamic finite element code, LS-DYNA(Registered TradeMark). The paper will focus on simulations of two full-scale impact tests involving the DEA, a mass-simulator and a full-scale crash of an instrumented MD-500 helicopter. Isotropic (MAT24) and composite (MAT58) material models, which were assigned to DEA shell elements, were compared. Based on simulations results, the MAT58 model showed better agreement with test.
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.
Cervical total disc replacement exhibits similar stiffness to intact cervical functional spinal units tested on a dynamic pendulum testing system.

PubMed

Esmende, Sean M; Daniels, Alan H; Paller, David J; Koruprolu, Sarath; Palumbo, Mark A; Crisco, Joseph J

2015-01-01

The pendulum testing system is capable of applying physiologic compressive loads without constraining the motion of functional spinal units (FSUs). The number of cycles to equilibrium observed under pendulum testing is a measure of the energy absorbed by the FSU. To examine the dynamic bending stiffness and energy absorption of the cervical spine, with and without implanted cervical total disc replacement (TDR) under simulated physiologic motion. A biomechanical cadaver investigation. Nine unembalmed, frozen human cervical FSUs from levels C3-C4 and C5-C6 were tested on the pendulum system with axial compressive loads of 25, 50, and 100 N before and after TDR implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5°, resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and the bending stiffness (Newton-meter/°) was calculated and compared for each testing mode. In flexion/extension, with increasing compressive loading from 25 to 100 N, the average number of cycles to equilibrium for the intact FSUs increased from 6.6 to 19.1, compared with 4.1 to 12.7 after TDR implantation (p<.05 for loads of 50 and 100 N). In flexion, with increasing compressive loading from 25 to 100 N, the bending stiffness of the intact FSUs increased from 0.27 to 0.59 Nm/°, compared with 0.21 to 0.57 Nm/° after TDR implantation. No significant differences were found in stiffness between the intact FSU and the TDR in flexion/extension and lateral bending at any load (p<.05). Cervical FSUs with implanted TDR were found to have similar stiffness, but had greater energy absorption than intact FSUs during cyclic loading with an unconstrained pendulum system. These results provide further insight into the biomechanical behavior of cervical TDR under approximated physiologic loading conditions. Copyright © 2015 Elsevier Inc. All rights reserved.
Testing and Analysis of Composite Skin/Stringer Debonding Under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Cvitkovich, Michael K.; O'Brien, T. Kevin; Minguet, Pierre J.

2000-01-01

A consistent step-wise approach is presented to investigate the damage mechanism in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out-of-plane) loading conditions. The approach uses experiments to detect the failure mechanism, computational stress analysis to determine the location of first matrix cracking and computational fracture mechanics to investigate the potential for delamination growth. In a first step, tests were performed on specimens, which consisted of a tapered composite flange, representing a stringer or frame, bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending to evaluate the debonding mechanisms between the skin and the bonded stringer. For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. For all three load cases, observed failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from skin. In a second step, a two dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, computed principal stresses exceeded the transverse strength of the material in those areas of the flange where the matrix cracks had developed during the tests. In a third step, delaminations of various lengths were simulated in two locations where delaminations were observed during the tests. The analyses showed that at the loads corresponding to matrix ply crack initiation computed strain energy release rates exceeded the values obtained from a mixed mode failure criterion in one location, Hence. Unstable delamination propagation is likely to occur as observed in the experiments.

Testing and Analysis of Composite Skin/Stringer Debonding under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Krueger, Ronald; Cvitkovich, Michael; OBrien, Kevin; Minguet, Pierre J.

2000-01-01

A consistent step-wise approach is presented to investigate the damage mechanism in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out-of-plane) loading conditions. The approach uses experiments to detect the failure mechanism, computational stress analysis to determine the location of first matrix cracking and computational fracture mechanics to investigate the potential for delamination growth. In a first step, tests were performed on specimens, which consisted of a tapered composite flange, representing a stringer or frame, bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending to evaluate the debonding mechanisms between the skin and the bonded stringer. For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. For all three load cases, observed failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from the skin. In a second step, a two-dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, computed principal stresses exceeded the transverse strength of the material in those areas of the flange where the matrix cracks had developed during the tests. In a third step, delaminations of various lengths were simulated in two locations where delaminations were observed during the tests. The analyses showed that at the loads corresponding to matrix ply crack initiation computed strain energy release rates exceeded the values obtained from a mixed mode failure criterion in one location. Hence, unstable delamination propagation is likely to occur as observed in the experiments.
Implementation and Simulation Results using Autonomous Aerobraking Development Software

NASA Technical Reports Server (NTRS)

Maddock, Robert W.; DwyerCianciolo, Alicia M.; Bowes, Angela; Prince, Jill L. H.; Powell, Richard W.

2011-01-01

An Autonomous Aerobraking software system is currently under development with support from the NASA Engineering and Safety Center (NESC) that would move typically ground-based operations functions to onboard an aerobraking spacecraft, reducing mission risk and mission cost. The suite of software that will enable autonomous aerobraking is the Autonomous Aerobraking Development Software (AADS) and consists of an ephemeris model, onboard atmosphere estimator, temperature and loads prediction, and a maneuver calculation. The software calculates the maneuver time, magnitude and direction commands to maintain the spacecraft periapsis parameters within design structural load and/or thermal constraints. The AADS is currently tested in simulations at Mars, with plans to also evaluate feasibility and performance at Venus and Titan.
Computer simulation of a cruise missile using brushless dc motor fin control

NASA Astrophysics Data System (ADS)

Franklin, G. C.

1985-03-01

This thesis describes a computer simulation developed in order to provide a method of establishing the potential of brushless dc motors for applications to tactical cruise missile control surface positioning. In particular, an altitude hold controller has been developed that provides an operational load test condition for the evaluation of the electromechanical actuator. A proportional integral control scheme in conjunction with tachometer feedback provides the position control for the missile tailfin surfaces. The fin control system is further imbedded in a cruise missile model to allow altitude control of the missile. The load on the fin is developed from the dynamic fluid environment that the missile will be operating in and is proportional to such factors as fin size and air density. The program written in CSMP language is suitable for parametric studies including motor and torque load characteristics, and missile and control system parameters.
Numerical Modelling of Glass Fibre Reinforced Laminates Subjected to a Low Velocity Impact

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

Fan, J. Y.; Guana, Z. W.; Cantwell, W. J.

2010-05-21

This paper presents a series of numerical predictions of the perforation behaviour of glass fibre laminates subjected to quasi-static and low-velocity impact loading. Both shear and tensile failure criteria were used in the finite element models to simulate the post-failure processes via an automatic element removal procedure. The appropriate material properties, obtained through a series of uniaxial tension and bending tests on the composites, were used in the numerical models. Four, eight and sixteen ply glass fibre laminates panels were perforated at quasi-static rates and under low-velocity impact loading. Reasonably good correlation was obtained between the numerical simulations and themore » experimental results, both in terms of the failure modes and the load-deflection relationships before and during the penetration phase. The predicted impact energies of the GFRP panels were compared with the experimental data and reasonable agreement was observed.« less
Experimental model: dye penetration of extensive interim restorations used during endodontic treatment while under load in a multiple axis chewing simulator.

PubMed

Jensen, Arna-Lee; Abbott, Paul V

2007-10-01

The purpose of this study was to design an experimental model that allowed extensive endodontic interim restorations to be tested for dye penetration while under simulated masticatory load. Extracted premolar teeth had standardized mesio-occluso-distal cavities prepared, and the root canals were instrumented. A cotton wool pellet was placed in the pulp chamber, and the cavities were restored with Cavit, IRM, Ketac-Fil Plus, Ketac-Silver, or composite resin (Z100). They were subjected to the equivalent of 3 months of clinical load while exposed to methylene blue dye. Results of this study could not support IRM as a suitable interim endodontic restorative material to use in extensive cavities. The dye penetration in the Ketac-Fil Plus and Ketac-Silver specimens was not predictable, and the results suggested Cavit and Z100 composite resin require further investigations as potentially useful materials for this purpose.
A Large Motion Suspension System for Simulation of Orbital Deployment

NASA Technical Reports Server (NTRS)

Straube, T. M.; Peterson, L. D.

1994-01-01

This paper describes the design and implementation of a vertical degree of freedom suspension system which provides a constant force off-load condition to counter gravity over large displacements. By accommodating motions up to one meter for structures weighing up to 100 pounds, the system is useful for experiments which simulate the on-orbit deployment of spacecraft components. A unique aspect of this system is the combination of a large stroke passive off-load device augmented by electromotive torque actuated force feedback. The active force feedback has the effect of reducing breakaway friction by an order of magnitude over the passive system alone. The paper describes the development of the suspension hardware and the feedback control algorithm. Experiments were performed to verify the suspensions system's ability to provide a gravity off-load as well as its effect on the modal characteristics of a test article.
Gear Mesh Loss-of-Lubrication Experiments and Analytical Simulation

NASA Technical Reports Server (NTRS)

Handschuh, Robert F.; Polly, Joseph; Morales, Wilfredo

2011-01-01

An experimental program to determine the loss-of-lubrication (LOL) characteristics of spur gears in an aerospace simulation test facility has been completed. Tests were conducted using two different emergency lubricant types: (1) an oil mist system (two different misted lubricants) and (2) a grease injection system (two different grease types). Tests were conducted using a NASA Glenn test facility normally used for conducting contact fatigue. Tests were run at rotational speeds up to 10000 rpm using two different gear designs and two different gear materials. For the tests conducted using an air-oil misting system, a minimum lubricant injection rate was determined to permit the gear mesh to operate without failure for at least 1 hr. The tests allowed an elevated steady state temperature to be established. A basic 2-D heat transfer simulation has been developed to investigate temperatures of a simulated gear as a function of frictional behavior. The friction (heat generation source) between the meshing surfaces is related to the position in the meshing cycle, the load applied, and the amount of lubricant in the contact. Experimental conditions will be compared to those from the 2-D simulation.
Constitutive Modeling of the Dynamic-Tensile-Extrusion Test of PTFE

NASA Astrophysics Data System (ADS)

Resnyansky, Anatoly; Brown, Eric; Trujillo, Carl; Gray, George

2015-06-01

Use of polymers in the defence, aerospace and industrial application at extreme conditions makes prediction of behaviour of these materials very important. Crucial to this is knowledge of the physical damage response in association with the phase transformations during the loading and the ability to predict this via multi-phase simulation taking the thermodynamical non-equilibrium and strain rate sensitivity into account. The current work analyses Dynamic-Tensile-Extrusion (DTE) experiments on polytetrafluoroethylene (PTFE). In particular, the phase transition during the loading with subsequent tension are analysed using a two-phase rate sensitive material model implemented in the CTH hydrocode and the calculations are compared with experimental high-speed photography. The damage patterns and their link with the change of loading modes are analysed numerically and are correlated to the test observations.
Parallel processing for nonlinear dynamics simulations of structures including rotating bladed-disk assemblies

NASA Technical Reports Server (NTRS)

Hsieh, Shang-Hsien

1993-01-01

The principal objective of this research is to develop, test, and implement coarse-grained, parallel-processing strategies for nonlinear dynamic simulations of practical structural problems. There are contributions to four main areas: finite element modeling and analysis of rotational dynamics, numerical algorithms for parallel nonlinear solutions, automatic partitioning techniques to effect load-balancing among processors, and an integrated parallel analysis system.
Effects of flexor-pronator muscle loading on valgus stability of the elbow with an intact, stretched, and resected medial ulnar collateral ligament.

PubMed

Udall, John H; Fitzpatrick, Michael J; McGarry, Michelle H; Leba, Thu-Ba; Lee, Thay Q

2009-01-01

The medial ulnar collateral ligament (MUCL) is an important passive stabilizer to the valgus stresses that athletes experience during overhead throwing motion. However, the role of the flexor-pronator muscles as active stabilizers to valgus stress is not well defined in the literature. The objectives of this study were to quantify the relative contribution of the individual flexor-pronator muscles to valgus stability of the elbow and how this relationship was affected by ligament status. A custom elbow testing system and Microscribe 3DLX were used for biomechanical testing. Flexor-pronator muscles were loaded to simulate contraction, and the valgus angle of the elbow was measured in eight cadaveric specimens at 30 degrees , 60 degrees , and 90 degrees of elbow flexion with 3 different valgus torques applied to the forearm. Loads based on muscle cross-sectional area were applied to the flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), and pronator teres (PT). The effect of each muscle was evaluated by unloading the individual muscle while the other 2 remained loaded, resulting in 5 loading conditions: no muscles loaded, all muscles loaded, unloaded FCU, unloaded FDS, and unloaded PT. Valgus angle was measured for 3 MUCL ligament conditions: intact, stretched, and cut. The effect of muscle loading on valgus angle was similar for each ligament condition. Loading the flexor-pronator muscles significantly decreased valgus angle of the elbow in all testing conditions (P < .01). Unloading the FDS significantly increased valgus angle compared to all muscles loaded in all testing conditions (P < .016). Unloading the FCU and PT significantly increased valgus angle in less than half of the testing conditions. The FDS, PT, and FCU are all active stabilizers of the elbow to valgus stress. The FDS is the biggest contributor amongst the flexor-pronator muscles.
Used fuel rail shock and vibration testing options analysis

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

Ross, Steven B.; Best, Ralph E.; Klymyshyn, Nicholas A.

2014-09-25

The objective of the rail shock and vibration tests is to complete the framework needed to quantify loads of fuel assembly components that are necessary to guide materials research and establish a technical basis for review organizations such as the U.S. Nuclear Regulatory Commission (NRC). A significant body of experimental and numerical modeling data exists to quantify loads and failure limits applicable to normal conditions of transport (NCT) rail transport, but the data are based on assumptions that can only be verified through experimental testing. The test options presented in this report represent possible paths for acquiring the data thatmore » are needed to confirm the assumptions of previous work, validate modeling methods that will be needed for evaluating transported fuel on a case-by-case basis, and inform material test campaigns on the anticipated range of fuel loading. The ultimate goal of this testing is to close all of the existing knowledge gaps related to the loading of used fuel under NCT conditions and inform the experiments and analysis program on specific endpoints for their research. The options include tests that would use an actual railcar, surrogate assemblies, and real or simulated rail transportation casks. The railcar carrying the cradle, cask, and surrogate fuel assembly payload would be moved in a train operating over rail track modified or selected to impart shock and vibration forces that occur during normal rail transportation. Computer modeling would be used to help design surrogates that may be needed for a rail cask, a cask’s internal basket, and a transport cradle. The objective of the design of surrogate components would be to provide a test platform that effectively simulates responses to rail shock and vibration loads that would be exhibited by state-of-the-art rail cask, basket, and/or cradle structures. The computer models would also be used to help determine the placement of instrumentation (accelerometers and strain gauges) on the surrogate fuel assemblies, cask and cradle structures, and the railcar so that forces and deflections that would result in the greatest potential for damage to high burnup and long-cooled UNF can be determined. For purposes of this report we consider testing on controlled track when we have control of the track and speed to facilitate modeling.« less
TARDEC 30-Year Strategy Value Stream Analysis

DTIC Science & Technology

2015-07-01

reduce gun barrel weights and recoil loads, while maintaining or improving energy-on-target metrics. iv. Continue to invest in efforts to...capability, including steels , stainless steel and titanium alloys, among others. Physical Simulation & Test (PS&T) Mark Brudnak
Analysis of flexural strength and contact pressure after simulated chairside adjustment of pressed lithium disilicate glass-ceramic.

PubMed

Ramadhan, Ali; Thompson, Geoffrey A; Maroulakos, Georgios; Berzins, David

2018-04-30

Research evaluating load-to-failure of pressed lithium disilicate glass-ceramic (LDGC) with a clinically validated test after adjustment and repair procedures is scarce. The purpose of this in vitro study was to investigate the effect of the simulated chairside adjustment of the intaglio surface of monolithic pressed LDGC and procedures intended to repair damage. A total of 423 IPS e.max Press (Ivoclar Vivadent AG) disks (15 mm diameter, 1 mm height) were used in the study. The material was tested by using an equibiaxial loading arrangement (n≥30/group) and a contact pressure test (n≥20/group). Specimens were assigned to 1 of 14 groups. One-half was assigned to the equibiaxial load test and the other half underwent contact pressure testing. Testing was performed in 2 parts, before glazing and after glazing. Before-glazing specimens were devested and entered in the test protocol, while after-glazing specimens were devested and glazed before entering the test protocol. Equibiaxial flexure test specimens were placed on a ring-on-ring apparatus and loaded until failure. Contact pressure specimens were cemented to epoxy resin blocks with a resin cement and loaded with a 50-mm diameter hemisphere until failure. Tests were performed on a universal testing machine with a crosshead speed of 0.5 mm/min. Weibull statistics and likelihood ratio contour plots determined intergroup differences (95% confidence bounds). Before glazing, the equibiaxial flexural strength test and the Weibull and likelihood ratio contour plots demonstrated a significantly higher failure strength for 1EC (188 MPa) than that of the damaged and/or repaired groups. Glazing following diamond-adjustment (1EGG) was the most beneficial post-damage procedure (176 MPa). Regarding the contact pressure test, the Weibull and likelihood ratio contour plots revealed no significant difference between the 1PC (98 MPa) and 1PGG (98 MPa) groups. Diamond-adjustment, without glazing (1EG and 1PG), resulted in the next-to-lowest equibiaxial flexure strength and the lowest contact pressure. After glazing, the strength of all the groups, when subjected to glazing following devesting, increased in comparison with corresponding groups in the before-glazing part of the study. A glazing treatment improved the mechanical properties of diamond-adjusted IPS e.max Press disks when evaluated by equibiaxial flexure and contact pressure tests. Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint

PubMed Central

Jang, Andrew T.; Lin, Jeremy D.; Seo, Youngho; Etchin, Sergey; Merkle, Arno; Fahey, Kevin; Ho, Sunita P.

2014-01-01

This study demonstrates a novel biomechanics testing protocol. The advantage of this protocol includes the use of an in situ loading device coupled to a high resolution X-ray microscope, thus enabling visualization of internal structural elements under simulated physiological loads and wet conditions. Experimental specimens will include intact bone-periodontal ligament (PDL)-tooth fibrous joints. Results will illustrate three important features of the protocol as they can be applied to organ level biomechanics: 1) reactionary force vs. displacement: tooth displacement within the alveolar socket and its reactionary response to loading, 2) three-dimensional (3D) spatial configuration and morphometrics: geometric relationship of the tooth with the alveolar socket, and 3) changes in readouts 1 and 2 due to a change in loading axis, i.e. from concentric to eccentric loads. Efficacy of the proposed protocol will be evaluated by coupling mechanical testing readouts to 3D morphometrics and overall biomechanics of the joint. In addition, this technique will emphasize on the need to equilibrate experimental conditions, specifically reactionary loads prior to acquiring tomograms of fibrous joints. It should be noted that the proposed protocol is limited to testing specimens under ex vivo conditions, and that use of contrast agents to visualize soft tissue mechanical response could lead to erroneous conclusions about tissue and organ-level biomechanics. PMID:24638035
Transient Three-Dimensional Startup Side Load Analysis of a Regeneratively Cooled Nozzle

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2008-01-01

The objective of this effort is to develop a computational methodology to capture the startup side load physics and to anchor the computed aerodynamic side loads with the available data from a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, a transient 5 s inlet history based on an engine system simulation, and a wall temperature distribution to reflect the effect of regenerative cooling. To understand the effect of regenerative wall cooling, two transient computations were performed using the boundary conditions of adiabatic and cooled walls, respectively. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with the pulsation of shocks across the lip, although the combustion wave is commonly eliminated with the sparklers during actual test. The test measured two side load events: a secondary and lower side load, followed by a primary and peak side load. Results from both wall boundary conditions captured the free-shock separation to restricted-shock separation transition with computed side loads matching the measured secondary side load. For the primary side load, the cooled wall transient produced restricted-shock pulsation across the nozzle lip with peak side load matching that of the test, while the adiabatic wall transient captured shock transitions and free-shock pulsation across the lip with computed peak side load 50% lower than that of the measurement. The computed dominant pulsation frequency of the cooled wall nozzle agrees with that of a separate test, while that of the adiabatic wall nozzle is more than 50% lower than that of the measurement. The computed teepee-like formation and the tangential motion of the shocks during lip pulsation also qualitatively agree with those of test observations. Moreover, a third transient computation was performed with a proportionately shortened 1 s sequence, and lower side loads were obtained with the higher ramp rate.
Development of a clinically validated bulk failure test for ceramic crowns.

PubMed

Kelly, J Robert; Rungruanganunt, Patchnee; Hunter, Ben; Vailati, Francesca

2010-10-01

Traditional testing of ceramic crowns creates a stress state and damage modes that differ greatly from those seen clinically. There is a need to develop and communicate an in vitro testing protocol that is clinically valid. The purpose of this study was to develop an in vitro failure test for ceramic single-unit prostheses that duplicates the failure mechanism and stress state observed in clinically failed prostheses. This article first compares characteristics of traditional load-to-failure tests of ceramic crowns with the growing body of evidence regarding failure origins and stress states at failure from the examination of clinically failed crowns, finite element analysis (FEA), and data from clinical studies. Based on this analysis, an experimental technique was systematically developed and test materials were identified to recreate key aspects of clinical failure in vitro. One potential dentin analog material (an epoxy filled with woven glass fibers; NEMA grade G10) was evaluated for elastic modulus in blunt contact and for bond strength to resin cement as compared to hydrated dentin. Two bases with different elastic moduli (nickel chrome and resin-based composite) were tested for influence on failure loads. The influence of water during storage and loading (both monotonic and cyclic) was examined. Loading piston materials (G10, aluminum, stainless steel) and piston designs were varied to eliminate Hertzian cracking and to improve performance. Testing was extended from a monolayer ceramic (leucite-filled glass) to a bilayer ceramic system (glass-infiltrated alumina). The influence of cyclic rate on mean failure loads was examined (2 Hz, 10 Hz, 20 Hz) with the extremes compared statistically (t test; α=.05). Failure loads were highly influenced by base elastic modulus (t test; P<.001). Cyclic loading while in water significantly decreased mean failure loads (1-way ANOVA; P=.003) versus wet storage/dry cycling (350 N vs. 1270 N). G10 was not significantly different from hydrated dentin in terms of blunt contact elastic behavior or resin cement bond strength. Testing was successful with the bilayered ceramic, and the cycling rate altered mean failure loads only slightly (approximately 5%). Test methods and materials were developed to validly simulate many aspects of clinical failure. Copyright © 2010 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.
A Hybrid Parachute Simulation Environment for the Orion Parachute Development Project

NASA Technical Reports Server (NTRS)

Moore, James W.

2011-01-01

A parachute simulation environment (PSE) has been developed that aims to take advantage of legacy parachute simulation codes and modern object-oriented programming techniques. This hybrid simulation environment provides the parachute analyst with a natural and intuitive way to construct simulation tasks while preserving the pedigree and authority of established parachute simulations. NASA currently employs four simulation tools for developing and analyzing air-drop tests performed by the CEV Parachute Assembly System (CPAS) Project. These tools were developed at different times, in different languages, and with different capabilities in mind. As a result, each tool has a distinct interface and set of inputs and outputs. However, regardless of the simulation code that is most appropriate for the type of test, engineers typically perform similar tasks for each drop test such as prediction of loads, assessment of altitude, and sequencing of disreefs or cut-aways. An object-oriented approach to simulation configuration allows the analyst to choose models of real physical test articles (parachutes, vehicles, etc.) and sequence them to achieve the desired test conditions. Once configured, these objects are translated into traditional input lists and processed by the legacy simulation codes. This approach minimizes the number of sim inputs that the engineer must track while configuring an input file. An object oriented approach to simulation output allows a common set of post-processing functions to perform routine tasks such as plotting and timeline generation with minimal sensitivity to the simulation that generated the data. Flight test data may also be translated into the common output class to simplify test reconstruction and analysis.
A three-dimensional finite element study on the stress distribution pattern of two prosthetic abutments for external hexagon implants.

PubMed

Moreira, Wagner; Hermann, Caio; Pereira, Jucélio Tomás; Balbinoti, Jean Anacleto; Tiossi, Rodrigo

2013-10-01

The purpose of this study was to evaluate the mechanical behavior of two different straight prosthetic abutments (one- and two-piece) for external hex butt-joint connection implants using three-dimensional finite element analysis (3D-FEA). Two 3D-FEA models were designed, one for the two-piece prosthetic abutment (2 mm in height, two-piece mini-conical abutment, Neodent) and another one for the one-piece abutment (2 mm in height, Slim Fit one-piece mini-conical abutment, Neodent), with their corresponding screws and implants (Titamax Ti, 3.75 diameter by 13 mm in length, Neodent). The model simulated the single restoration of a lower premolar using data from a computerized tomography of a mandible. The preload (20 N) after torque application for installation of the abutment and an occlusal loading were simulated. The occlusal load was simulated using average physiological bite force and direction (114.6 N in the axial direction, 17.1 N in the lingual direction and 23.4 N toward the mesial at an angle of 75° to the occlusal plan). The regions with the highest von Mises stress results were at the bottom of the initial two threads of both prosthetic abutments that were tested. The one-piece prosthetic abutment presented a more homogeneous behavior of stress distribution when compared with the two-piece abutment. Under the simulated chewing loads, the von Mises stresses for both tested prosthetic-abutments were within the tensile strength values of the materials analyzed which thus supports the clinical use of both prosthetic abutments.
A Distributed Dynamic Programming-Based Solution for Load Management in Smart Grids

NASA Astrophysics Data System (ADS)

Zhang, Wei; Xu, Yinliang; Li, Sisi; Zhou, MengChu; Liu, Wenxin; Xu, Ying

2018-03-01

Load management is being recognized as an important option for active user participation in the energy market. Traditional load management methods usually require a centralized powerful control center and a two-way communication network between the system operators and energy end-users. The increasing user participation in smart grids may limit their applications. In this paper, a distributed solution for load management in emerging smart grids is proposed. The load management problem is formulated as a constrained optimization problem aiming at maximizing the overall utility of users while meeting the requirement for load reduction requested by the system operator, and is solved by using a distributed dynamic programming algorithm. The algorithm is implemented via a distributed framework and thus can deliver a highly desired distributed solution. It avoids the required use of a centralized coordinator or control center, and can achieve satisfactory outcomes for load management. Simulation results with various test systems demonstrate its effectiveness.
In-process, non-destructive multimodal dynamic testing of high-speed composite rotors

NASA Astrophysics Data System (ADS)

Kuschmierz, Robert; Filippatos, Angelos; Langkamp, Albert; Hufenbach, Werner; Czarske, Jürgern W.; Fischer, Andreas

2014-03-01

Fibre reinforced plastic (FRP) rotors are lightweight and offer great perspectives in high-speed applications such as turbo machinery. Currently, novel rotor structures and materials are investigated for the purpose of increasing machine efficiency, lifetime and loading limits. Due to complex rotor structures, high anisotropy and non-linear behavior of FRP under dynamic loads, an in-process measurement system is necessary to monitor and to investigate the evolution of damages under real operation conditions. A non-invasive, optical laser Doppler distance sensor measurement system is applied to determine the biaxial deformation of a bladed FRP rotor with micron uncertainty as well as the tangential blade vibrations at surface speeds above 300 m/s. The laser Doppler distance sensor is applicable under vacuum conditions. Measurements at varying loading conditions are used to determine elastic and plastic deformations. Furthermore they allow to determine hysteresis, fatigue, Eigenfrequency shifts and loading limits. The deformation measurements show a highly anisotropic and nonlinear behavior and offer a deeper understanding of the damage evolution in FRP rotors. The experimental results are used to validate and to calibrate a simulation model of the deformation. The simulation combines finite element analysis and a damage mechanics model. The combination of simulation and measurement system enables the monitoring and prediction of damage evolutions of FRP rotors in process.

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