Methods of modeling the operating conditions during thermal life tests of supersonic aircraft lanterns

2019 ◽  
Author(s):  
V. K. Belov ◽  
N. V. Pystovoi ◽  
D. A. Shinkarev
Keyword(s):  
Operating Conditions ◽  
Supersonic Aircraft ◽  
Life Tests ◽  
Thermal Life

Life Prediction of Directionally Solidified Air Cooled HPT Gas Turbine Blade Used in a Supersonic Aircraft Using FEM

2013 ◽  
Author(s):  
S. Esakki Muthu ◽  
S. Dileep ◽  
S. Saji Kumar ◽  
D. K. Girish
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Operating Conditions ◽  
Test Facility ◽  
Time To Failure ◽  
Generation Process ◽  
Gas Turbine Blade ◽  
Directionally Solidified ◽  
Life Estimation ◽  
Supersonic Aircraft

Life estimation of Directionally Solidified (DS) MARM-247 HPT gas turbine blade used in a turbofan engine of a supersonic aircraft is presented. These blades were drafted into the engine as a replacement for the polycrystal (NIMONIC) blades since a more efficient, reliable and durable material with high strength and temperature resistance was required to further enhance the life of the turbine blade and the efficiency of the power generation process. The supersonic aircraft is having a repeated mission cycle of a fast acceleration from idle, a 1hr cruise at Mach 1.5 and a fast deceleration to idle. The mission cycle which is a repetition of acceleration, cruise and deceleration cycles can produce wide variety of complex loading conditions which can result in HCF, LCF and creep damage of the turbine blade. Empirical equation of the universal slope developed by Manson was used to estimate the damage component due to LCF. The cumulative stresses and strains due to creep as a function of time was determined using Time hardening rule. Creep data for MARM-247 was correlated using LMP to predict the lives to 1% of creep strain at worst possible combination of temperature and stress value. Damage due to creep per mission cycle was determined using Life fraction Rule proposed by Robinson and Taira. The vibration characteristics of the turbine blade were predicted using Modal analysis. Campbell diagram was plotted to ascertain whether any nozzle passing frequency fall within the working range of the blade. Harmonic analysis was carried out to evaluate the magnitude of the alternating stresses resulting from the blade vibrations at resonance during the acceleration and deceleration cycle. HCF life of the turbine blade was assessed using Goodman diagram. The total damage of the turbine blade per mission cycle due to the above loading was assumed as the combination of the individual damage due to fatigue and creep. Time to failure under combined creep and fatigue damage was estimated using linear damage rule. Non linear features of FEA tool ANSYS12.0 was exploited to calculate the stress distribution, creep, plastic and the total strain encountered by the turbine blade as a function of mission cycle time. The loading spectrum associated with the mission cycle which includes the temperature, gas pressure and the speed profiles were obtained from a sophisticated engine ground test facility which was configured to simulate actual engine operating conditions. The proposed method of cyclic life estimation using FEM was validated by performing various component and engine level tests. A good agreement was observed between the calculated and observed blade lives.

scholarly journals Reliability of X7R Multilayer Ceramic Capacitors During High Accelerated Life Testing (HALT)

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1900 ◽  
Author(s):  
Ana Hernández-López ◽  
Juan Aguilar-Garib ◽  
Sophie Guillemet-Fritsch ◽  
Roman Nava-Quintero ◽  
Pascal Dufour ◽  
...  
Keyword(s):  
Operating Conditions ◽  
Time To Failure ◽  
Multilayer Ceramic Capacitors ◽  
Thermal Failure ◽  
Accelerated Life Tests ◽  
Accelerated Life ◽  
Essential Components ◽  
Ceramic Capacitors ◽  
Life Tests ◽  
Multilayer Ceramic

Multilayer ceramic capacitors (MLCC) are essential components for determining the reliability of electronic components in terms of time to failure. It is known that the reliability of MLCCs depends on their composition, processing, and operating conditions. In this present work, we analyzed the lifetime of three similar X7R type MLCCs based on BaTiO3 by conducting High Accelerated Life Tests (HALT) at temperatures up to 200 °C at 400 V and 600 V. The results were adjusted to an Arrhenius equation, which is a function of the activation energy (Ea) and a voltage stress exponent (n), in order to predict their time to failure. The values of Ea are in the range of 1–1.45 eV, which has been reported for the thermal failure and dielectric wear out of BaTiO3-based dielectric capacitors. The stress voltage exponent value was in the range of 4–5. Although the Ea can be associated with a failure mechanism, n only gives an indication of the effect of voltage in the tests. It was possible to associate those values with each type of tested MLCC so that their expected life could be estimated in the range of 400–600 V.

Life Testing and Reliability Behavior of Gan/Ingan/Aigan Light-Emitting Diodes

1998 ◽  
Vol 531 ◽  
Author(s):  
M. Osinski ◽  
D. L. Barton ◽  
C. J. Helms ◽  
N. H. Berg ◽  
C. H. Seager
Keyword(s):  
Room Temperature ◽  
Operating Conditions ◽  
Degradation Mechanisms ◽  
Final Temperature ◽  
Light Emitting ◽  
Electrical Pulses ◽  
Life Tests ◽  
Metal Migration ◽  
Device Lifetime ◽  
Temperature Test

AbstractOur studies of device lifetime and the main degradation mechanisms in Nichia blue LEDs date back to Spring 1994. Following the initial studies of rapid failures under high current electrical pulses, where metal migration was identified as the cause of degradation, we have placed a number of Nichia NLPB-500 LEDs on a series of life tests. The first test ran for 1000 hours under normal operating conditions (20 mA at 23 °C). As no noticeable degradation was observed, the second room temperature test was performed with the same devices but with a range of currents between 20 and 70 mA. After 1600 hours, some degradation in output intensity was observed in devices driven at 60 and 70 mA, but it was still less than 20%. The subsequent tests included stepping up the temperature by 10 °C in 500 h intervals up to a final temperature of 95 °C using the same currents applied in the second test. This work reviews the failure analysis that was performed on the degraded devices and the degradation mechanisms that were identified.

Bearing life prognosis under environmental effects based on accelerated life testing

2002 ◽  
Vol 216 (5) ◽  
pp. 509-516 ◽  
Author(s):  
C Zhang ◽  
M T Le ◽  
B B Seth ◽  
S Y Liang
Keyword(s):  
Operating Conditions ◽  
Accelerated Life Testing ◽  
Model Verification ◽  
Accelerated Life Test ◽  
Experimental Result ◽  
Life Testing ◽  
Accelerated Life ◽  
Bearing Life ◽  
Stress Levels ◽  
Life Tests

The reliability of a bearing is typically estabilished by repeated life testing which provides valuable information on the fatigue mechanisms from crack initiation, crack propagation to flake or spall. Under nominal operating conditions, life testing often consumes a significant amount of time and resources, due to the comparatively high bearing mean lifetime before failure (MTBF), rendering the procedures expensive and impractical. Therefore, the technology of accelerated life testing (ALT), which is widely used in manufacturing practice, offers the attractive benefit of requiring relatively less investment in terms of time and resources. Data from tests at high stress levels (e.g. temperature, voltage, pressure, corrosive media, etc.) can be extrapolated, through a physically reasonable statistical model, to obtain life estimates at lower, normal stress levels. In this study, a methodology to predict bearing lifetime under a corrosive environment has been developed based on accelerated life testing data and the application of the inverse power law. Bearing life tests under various corrosion stress levels were performed for model identification followed by additional independent bearing life tests conducted for model verification. The experimental result shows that the accelerated life test model can effectively assess the life probability of a bearing based on accelerated environmental testing, even with extrapolation to untested stress levels.

OPTIMAL DESIGN OF SIMPLE STEP-STRESS ACCELERATED LIFE TESTS FOR ONE-SHOT DEVICES UNDER EXPONENTIAL DISTRIBUTIONS

2018 ◽  
Vol 33 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Man Ho Ling
Keyword(s):  
Optimal Design ◽  
Asymptotic Variance ◽  
Operating Conditions ◽  
Model Parameters ◽  
Normal Operating ◽  
Accelerated Life Tests ◽  
Accelerated Life ◽  
Decision Variables ◽  
Simple Step ◽  
Life Tests

This paper considers simple step-stress accelerated life tests (SSALTs) for one-shot devices. The one-shot device is an item that cannot be used again after the test, for instance, munitions, rockets, and automobile air-bags. Either left-or right-censored data are collected instead of actual lifetimes of the devices under test. An expectation-maximization algorithm is developed here to find the maximum likelihood estimates of the model parameters based on one-shot device testing data collected from simple SSALTs. Furthermore, the asymptotic variance of the mean lifetime under normal operating conditions is determined under the expectation-maximization framework. On the other hand, the optimal design that minimizes the asymptotic variance of the estimate of the mean lifetime under normal operating conditions in terms of three decision variables, including stress levels, inspection times, and sample allocation is discussed. A procedure then is presented to determine the decision variables when a range of stress levels and the termination time of the test as well as normal operating conditions of the devices are given. The properties of the optimal design and the effects of errors in pre-specified planning values of the model parameters are also investigated. Comprehensive simulation studies show that the procedure is quite reliable for the design of simple SSALTs.

Stator Life of a Positive Displacement Downhole Drilling Motor

1999 ◽  
Vol 121 (2) ◽  
pp. 110-116 ◽  
Author(s):  
M. S. Delpassand
Keyword(s):  
Drilling Fluid ◽  
Operating Conditions ◽  
Motor Speed ◽  
Element Analysis ◽  
Factors Affecting ◽  
Positive Displacement ◽  
Accelerated Life Tests ◽  
Accelerated Life ◽  
Life Tests ◽  
Downhole Temperature

The power section of a positive displacement drill motor (PDM) consists of a steel rotor and a tube with a molded elastomeric lining (stator). Power section failures are typically due to the failure of the stator elastomer. Stator life depends on many factors such as design, materials of construction, and downhole operating conditions. This paper focuses on the stator failure mechanisms and factors affecting stator life. An analytical method for predicting the effect of various design and operating parameters on the strain state and heat build-up within elastomers is discussed. The effect of parameters such as rotor/stator design, downhole temperature, drilling fluid, stator elastomer properties, motor speed, and motor differential pressure on the stator life is discussed. Nonlinear finite element analysis is used to perform thermal and structural analysis on the stator elastomer. Data from laboratory accelerated life tests on power section stators is presented to demonstrate the effect of operating conditions on stator life.

scholarly journals Failure Mechanism of Solid Tantalum Capacitors

1976 ◽  
Vol 3 (3) ◽  
pp. 171-179 ◽  
Author(s):  
B. Goudswaard ◽  
F. J. J. Driesens
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Alternative Hypothesis ◽  
Tantalum Oxide ◽  
Operating Conditions ◽  
Thermal Migration ◽  
Accelerated Life Tests ◽  
Accelerated Life ◽  
Life Tests ◽  
Scanning Electron

It has been suggested that failure of solid tantalum capacitors is due to thermal migration of impurities from the tantalum anode to flaws in the oxide layer. This implies, however, that leakage current gradually increases under normal operating conditions, an effect which has not been observed. An alternative hypothesis advanced here is that failure is due to crystallization of tantalum oxide under the influence of the electric field. Scanning electron microscopy of specially cleaned anodized tantalum sheet on which thin gold electrodes have been deposited clearly shows the occurrence of crystallization after 17 hours at an applied voltage of 75 V and a temperature of 65℃. Results of accelerated life tests on solid tantalum capacitors at temperatures of 85℃ and 125℃, and at up to 2,5 times rated voltage also accord better with a field crystallization hypothesis than with a thermal migration failure hypothesis.

Paper 6: Lubrication of Bearings and Gears for Operation in a Space Environment

1968 ◽  
Vol 183 (9) ◽  
pp. 39-49
Author(s):  
C. L. Harris ◽  
M. G. Warwick
Keyword(s):  
Prolonged Exposure ◽  
High Vacuum ◽  
Film Coating ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Space Environment ◽  
Special Effects ◽  
Space Instruments ◽  
Hardened Tool Steel ◽  
Life Tests

The lubrication of moving mechanical parts in the environment of space presents problems not ordinarily encountered in conventional operating conditions on earth. The special effects to be considered include those of weighlessness, radiation, temperature extremes, and prolonged exposure to hard vacuum. Of these, the last probably represents the most fundamental obstacle to the application of conventional designs, lubricants, and techniques. The high degree of reliability required in mechanisms for use in space instruments or vehicles necessitates the use of test chambers which have an ultra-high vacuum capability in the range 10-7–10-10 torr. The paper will describe the techniques used and the results obtained from a large number of such tests, conducted in this laboratory, on miniature ball bearings, gears, and jewel bearings. Lubricants studied include low vapour pressure oils and greases, lamellar solids, soft metals, and composites. Basic materials range from plastics to hardened tool-steel. Over 200 vacuum life tests have been performed on pairs of bearings mounted in specially designed eddy-current motors operating at 3000 rev/min. With certain oils and greases, up to two years' continuous life has been demonstrated. The most successful performance, in terms of life and reliability, has been obtained by the application of the soft metal, lead, as a thin film coating. The longest running test motor has completed in excess of 30 000 h continuous operation at 3000 rev/min in vacuum of 10-10 torr.

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

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