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 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.

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.

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.

scholarly journals Leveraging Label Information in a Knowledge-Driven Approach for Rolling-Element Bearings Remaining Useful Life Prediction

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2163
Author(s):  
Tarek Berghout ◽  
Mohamed Benbouzid ◽  
Leïla-Hayet Mouss
Keyword(s):  
Transfer Learning ◽  
Short Term Memory ◽  
Remaining Useful Life ◽  
Accelerated Life Tests ◽  
Learning Path ◽  
Accelerated Life ◽  
Unseen Data ◽  
Label Information ◽  
Life Tests ◽  
Ill Posed

Since bearing deterioration patterns are difficult to collect from real, long lifetime scenarios, data-driven research has been directed towards recovering them by imposing accelerated life tests. Consequently, insufficiently recovered features due to rapid damage propagation seem more likely to lead to poorly generalized learning machines. Knowledge-driven learning comes as a solution by providing prior assumptions from transfer learning. Likewise, the absence of true labels was able to create inconsistency related problems between samples, and teacher-given label behaviors led to more ill-posed predictors. Therefore, in an attempt to overcome the incomplete, unlabeled data drawbacks, a new autoencoder has been designed as an additional source that could correlate inputs and labels by exploiting label information in a completely unsupervised learning scheme. Additionally, its stacked denoising version seems to more robustly be able to recover them for new unseen data. Due to the non-stationary and sequentially driven nature of samples, recovered representations have been fed into a transfer learning, convolutional, long–short-term memory neural network for further meaningful learning representations. The assessment procedures were benchmarked against recent methods under different training datasets. The obtained results led to more efficiency confirming the strength of the new learning path.

scholarly journals Increased Surface Fatigue Lives of Spur Gears by Application of a Coating

2004 ◽  
Vol 126 (6) ◽  
pp. 1047-1054 ◽  
Author(s):  
Timothy Krantz ◽  
Clark Cooper ◽  
Dennis Townsend ◽  
Bruce Hansen
Keyword(s):  
Magnetron Sputtering ◽  
Fatigue Failure ◽  
Hard Coatings ◽  
Spur Gears ◽  
Surface Fatigue ◽  
Accelerated Life Tests ◽  
Accelerated Life ◽  
Life Tests ◽  
Carbon Based

Hard coatings have potential for increasing gear surface fatigue lives. Experiments were conducted using gears both with and without a metal-containing, carbon-based coating. The gears were case-carburized AISI 9310 steel spur gears. Some gears were provided with the coating by magnetron sputtering. Lives were evaluated by accelerated life tests. For uncoated gears, all of 15 tests resulted in fatigue failure before completing 275 million revolutions. For coated gears, 11 of the 14 tests were suspended with no fatigue failure after 275 million revolutions. The improved life owing to the coating, approximately a sixfold increase, was a statistically significant result.

PLANNING FOR ACCELERATED LIFE TESTS

1999 ◽  
Vol 06 (03) ◽  
pp. 265-275 ◽  
Author(s):  
LOON-CHING TANG
Keyword(s):  
Acceleration Factor ◽  
Test Time ◽  
Initial Sample ◽  
Lower Stress ◽  
Nonlinear Programs ◽  
Accelerated Life Tests ◽  
Accelerated Life ◽  
Stress Levels ◽  
Life Tests ◽  
Sample Allocation

We present two alternative perspectives to the current way of planning for constant-stress accelerated life tests (CSALTs) and step-stress ALT (SSALT). In 3-stress CSALT, we consider test plans that not only optimize the stress levels but also optimize the sample allocation. The resulting allocations also limit the chances of inconsistency when data are plotted on a probability plot. For SSALT, we consider test plans that not only optimize both stress levels and holding times, but also achieve a target acceleration factor that meets the test time constraint with the desirable fraction of failure. The results for both problems suggest that the statistically optimal way to increase acceleration factor in an ALT is to increase lower stress levels and; in the case of CSALT, to decrease their initial sample allocations; in the case of SSALT, to reduce their initial hold times. Both problems are formulated as constrained nonlinear programs.

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