Proportional mean remaining life model

1991 ◽  
Vol 29 (1-2) ◽  
pp. 221-228 ◽  
Author(s):  
Hassan Zahedi
Keyword(s):  
Remaining Life ◽  
Life Model

On Remaining Life Analysis of Turbine Disks Subjected to High Thermal Stresses

2011 ◽  
Author(s):  
Vishwas Iyengar ◽  
Stephen James ◽  
Harold Simmons
Keyword(s):  
Thermal Stresses ◽  
Turbine Disk ◽  
Operating Conditions ◽  
Creep Model ◽  
Remaining Life ◽  
Creep Life ◽  
High Rotational Speed ◽  
Life Model ◽  
Turbine Disks ◽  
Life Analysis

Disk failures can be caused by a number of mechanisms under the turbine operating conditions of high rotational speed at elevated temperatures. It is not uncommon for highly stressed turbine blades and disks to operate at temperatures in excess of 1,000°F, where increased exposure can affect their life. In the past, it has been adequate to analyze the life of these high temperature components using methods which calculate creep life and low cycle fatigue life independently in predicting service hours. More often than not, the parameters included in the creep life model are based on empirical data. Here, a practical methodology is presented to predict the remaining life of a turbine disk that utilizes a combination of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and a creep model. A full three-dimensional CFD analysis is performed on the turbine disks at design and off-design conditions, in order to accurately capture the thermal loads. A detailed FEA is performed on the turbine disk. The stress inputs for the creep life model are based on the stresses obtained from the FEA. A case study is presented that utilizes the proposed methodology. It is found that the methodology is beneficial for the remaining life analysis on highly loaded turbine disks. The accuracy of the methodology is somewhat dictated by the amount of historical operating data that is available.

scholarly journals Fatigue Stress-Life Model of RC Beams Based on an Accelerated Fatigue Method

2019 ◽  
Vol 4 (2) ◽  
pp. 16
Author(s):  
Eljufout ◽  
Toutanji ◽  
Al-Qaralleh
Keyword(s):  
Cyclic Loading ◽  
Fatigue Testing ◽  
Three Dimensional ◽  
Rc Beam ◽  
Rc Beams ◽  
Testing Methods ◽  
Load Range ◽  
Fatigue Stress ◽  
Life Model ◽  
Prediction Band

Several standard fatigue testing methods are used to determine the fatigue stress-life prediction model (S-N curve) and the endurance limit of Reinforced Concrete (RC) beams, including the application of constant cyclic tension-tension loads at different stress or strain ranges. The standard fatigue testing methods are time-consuming and expensive to perform, as a large number of specimens is needed to obtain valid results. The purpose of this paper is to examine a fatigue stress-life predication model of RC beams that are developed with an accelerated fatigue approach. This approach is based on the hypothesis of linear accumulative damage of the Palmgren–Miner rule, whereby the applied cyclic load range is linearly increased with respect to the number of cycles until the specimen fails. A three-dimensional RC beam was modeled and validated using ANSYS software. Numerical simulations were performed for the RC beam under linearly increased cyclic loading with different initial loading conditions. A fatigue stress-life model was developed that was based on the analyzed data of three specimens. The accelerated fatigue approach has a higher rate of damage accumulations than the standard testing approach. All of the analyzed specimens failed due to an unstable cracking of concrete. The developed fatigue stress-life model fits the upper 95% prediction band of RC beams that were tested under constant amplitude cyclic loading.

scholarly journals Patterns of Weight Change in Aging and Dying

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 491-491
Author(s):  
Stephen Thielke
Keyword(s):  
Older Adults ◽  
Weight Loss ◽  
Risk Factor ◽  
Weight Change ◽  
Population Level ◽  
Chronological Age ◽  
Average Weight ◽  
Remaining Life ◽  
Entire Cohort ◽  
History Of

Abstract Little research has characterized the natural history of weight change in older adults. Different changes may occur during aging and dying. We analyzed 18 years of weight measures from a cohort of 736,361 Veterans, all of whom had died at age 70 or older. We produced summary measures that accounted for both chronological age and number of years before death. Several clear population-level trends appeared. (1) The average weight of the sample declined across all ages at a rate of about 0.18 BMI points per year. (2) Starting about seven years before death, the amount of loss began to accelerate, reaching a decline of 0.75 BMI points in the year before death. (3) Changes in weight relative to years of remaining life were independent of chronologic age. People who died at age 70 experienced, on average, the same type and duration of terminal decline as did those who died at age 95. (4) The dying process involved a cumulative loss of about 1.3 BMI points. (5) The distribution of weights during advancing age both declined and narrowed. (6) Disproportionate deaths occurred at the lower BMI ranges (below a BMI of 24), and especially below 18, regardless of age. (7) The finding in #5 is explained by the entire cohort losing weight, with death of the thinnest members. These findings argue for examining survival time in studies of weight change. They indicate that weight loss may be a natural part of dying, rather than a risk factor for it.

The Value of Life at the End of Life: A Critical Assessment of Hope and other Factors

2011 ◽  
Vol 39 (2) ◽  
pp. 215-223 ◽  
Author(s):  
Paul T. Menzel
Keyword(s):  
End Of Life ◽  
Value Of Life ◽  
Critical Assessment ◽  
Remaining Life ◽  
Brute Fact ◽  
Inherent Part

“The thing about life is that one day you’ll be dead.” Indeed. But even total and honest acceptance of this brute fact about our relationship to death does not diminish the value we see in short remaining life at the end of life. Few just “give in” and no more fight for life because death is seen as an inherent part of life. They still invest small amounts of additional life with huge value. How high may that value plausibly be? What is the value of a relatively short extension of life when death is inevitably near?

The Effect of the EHD Pressure Spike on Rolling Bearing Fatigue

1987 ◽  
Vol 109 (3) ◽  
pp. 444-450 ◽  
Author(s):  
L. Houpert ◽  
E. Ioannides ◽  
J. C. Kuypers ◽  
J. Tripp
Keyword(s):  
Pressure Distribution ◽  
High Stress ◽  
Surface Damage ◽  
Rolling Bearing ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Surface Layers ◽  
Rolling Bearings ◽  
Life Model ◽  
Pressure Spike

A recently proposed fatigue life model for rolling bearings has been applied to the study of lifetime reduction under conditions conducive to microspalling. The presence of a spike in the EHD pressure distribution produces large shear stresses localized very close to the surface which may account for early failure. This paper describes a parametric study of the effect of such spikes. Accurate stress fields in the volume are calculated for simulated pressure spikes of different height, width and position relative to a Hertzian pressure distribution, as well as for different lubricant traction coefficients and film thicknesses. Despite the high stress concentrations in the surface layers, reductions in life predicted by the model are modest. Typically, the pressure spike may halve the life, with the implication that subsurface fatigue still dominates. In corroboration of this prediction, preliminary experimental work designed to reproduce microspalling conditions shows that microindents due to overrolling particles are a much more common form of surface damage than microspalling.

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